HK1168458B - Improvements to particle detectors - Google Patents

Description

Improvements in particle detectors

Technical Field

The present invention relates to aspects of particle detectors. By way of example, embodiments are described that relate to a beam detector adapted to detect smoke (smoke). In one aspect, the invention relates more broadly to battery powered devices, although the illustrated embodiments will be described with respect to a beam detector.

Background

Various methods are known for detecting particles in air. One method involves projecting a light beam through a monitored area and measuring the attenuation of the light beam. Such detectors are commonly referred to as "obscuration detectors", or simply "beam detectors".

Some beam detectors employ co-located transmitters and receivers and remote reflectors, while others employ separate transmitter and receiver units located on opposite sides of the open space being monitored.

Fig. 1 shows a typical conventional beam detector. The detector 10 includes a light source and detector 12 and a reflector 14 located on either side of a monitored area 16. Incident light 18 from the light source and detector 12 is projected toward the reflector 14. Reflector 14 reflects incident light 18 and reflected light 20 back to source and detector 12. If particulate matter enters the monitored area 16, it will attenuate the incident 18 and reflected 20 light and cause a reduction in the amount of light received at the source and detector 12. An alternative beam detector separates the light source from the detector, omits the reflector, and illuminates the detector directly with the light source through the area 16 being monitored. Other geometries are possible.

Although the smoke detection mechanism employed by beam detectors is good, beam detectors often suffer from several problems.

First, the beam detector may generate type I (false positive) errors in which foreign objects or other particulate matter (e.g., dust) enter the monitored area and obscure the beam. Beam detectors generally cannot resolve the obscuration caused by target particles (e.g., smoke) from the obscuration caused by the presence of non-target foreign objects (e.g., bugs flying into the beam).

Second, the beam detector may require careful alignment during installation. The purpose of this alignment is to ensure that the beam enters the sensor in a normal state without particles so as to capture the vast majority of the emitted beam, thereby maximizing sensitivity to darkness. This calibration process is slow and therefore costly to perform. Furthermore, repeated calibrations may be required as the physical environment changes (e.g., due to slight movement of the structure to which the beam detector is attached). In some cases, such misalignment may also cause false alarms if the intensity of the incident light on the detector diminishes rapidly.

In australian provisional patent application 2008902909 in the name of xtricires technologies Ltd, filed on 10.6.2008, and international patent application PCT/AU 2009/000727, the inventors have proposed a system that overcomes some of these disadvantages. The exemplary embodiment described therein and reproduced herein by fig. 2 includes a light source 32, a receiver 34 and a target 36 which together detect particles in a monitored area 38. The target 36 (e.g., a corner cube) reflects the incident light 40 such that the reflected light 42 returns to the receiver 34. In a preferred embodiment, receiver 34 is preferably a video camera or other receiver having an array of light sensors, such as one or more CCD (charge coupled device) image sensors or CMOS (complementary metal oxide semiconductor) image sensors, or virtually any device capable of recording and reporting light intensity at multiple points across its field of view.

In this system, the receiver 34 receives all of the light in its field of view 40 and includes imaging optics to form an image of its field of view 40 (including the target 36) on its image sensor. The receiver 34 records the intensity of light in its field of view in the form of data representing the image intensity at a series of locations throughout the field of view. A portion of this data corresponds at least in part to the reflected light 42. The microcontroller 54 analyzes the image data and determines which portion of the data provides the best judgment of the reflected light 42. Because the receiver 34 has a wide field of view and the ability to measure light independently at a wide range of points within that field of view, the light source 32 does not have to be carefully aligned with the target 36 or receiver 34, since the effect of the misalignment is simply to measure the reflected light 42 using different data portions corresponding to different pixels within the field of view. Thus, as long as the field of view of the receiver includes the target 36, one or more target areas in the image will include measurements of the reflected light 42.

If smoke or other particulate matter enters the monitored area 38, it will obscure or scatter incident light 40 or reflected light 42. This shadowing or scattering will be detected as a drop in the intensity of the received reflected light 42 measured in the image area determined by the microcontroller.

To include the reflected light 42, pixels beyond the selected area of the microcontroller may be ignored because the light received by these pixels does not correspond to the reflected light 42.

As the accumulated movement or other factors change the geometry of the system over time, the target 36 will still be in the field of view of the receiver 34, however the image of the target 36 will appear at a different point of the image detector of the receiver 34. To account for this movement, the microcontroller can be adapted to track the image of the target 36 on its light sensor over time so that smoke detection can be performed on the correct image area over time.

In some embodiments described therein, target 36 is encoded by two (or more) wavelengths λ₁And λ₂(e.g., Infrared (IR) and Ultraviolet (UV) wavelengths) emitted by corresponding light sources (or a common light source) along two substantially collinear paths.

The wavelengths are chosen such that they exhibit different behavior in the presence of particles to be detected, such as smoke particles. In this way, the relative changes in the received light at the two (or more) wavelengths can be used to give an indication of what caused the beam to be attenuated.

Further, the applicant's earlier application describes an embodiment that is capable of monitoring multiple targets simultaneously. According to this embodiment (shown in fig. 3 herein), the detector 50 includes a light source 52, a receiver 54, a first target 56 and a second target 57, which together detect smoke in a monitored area 58. The target 56 reflects the incident light 62 causing reflected light 64 to return to the receiver 54. Target 57 reflects incident light 65 causing reflected light 67 to return to receiver 54. As with the previous embodiment, the receiver 54 transmits the image data to the microcontroller 74. The microcontroller 74 analyzes the data and determines which portion of the data contains the most relevant information to the reflected light 64 and reflected light 67, respectively. When this decision process is complete, the microcontroller 74 will select two portions of data, corresponding to respective individual pixels or respective groups of pixels read from the image sensor, that can be most reliably used to measure the intensity of the reflected light 64 and the reflected light 67. Thus, the system 50 can perform the function of two beam detectors by simply adding yet another target or light source.

Using such a system, the present inventors have previously proposed a particle detection system that addresses the seemingly contradictory requirements (i.e., the requirement for high sensitivity and the requirement for a wide angular operating range in a beam detection system). However, these limitations, as well as the limitation on the intensity of the light source that can be used as an emitter, mean that there is still a need to further improve the particle detection system in these respects.

In a beam detector, the intensity of the emitted light may be limited. For example, there may be budget considerations which mean that low power light emitters have to be selected in the product. Furthermore, in some cases a limited power supply is available, especially if the transmitter unit is powered by a power supply. Eye safety is also a factor limiting the emitted power of the light source because of the potentially damaging effects of visible light from the emitter. For any of these reasons, a relatively low transmitted signal power may be used for the beam detector. Thus, the signal-to-noise ratio of the system may be affected.

In order to keep the transmitted power as low as possible while operating satisfactorily, it is advantageous from a sensitivity standpoint to keep the polar transmission pattern of the transmitter and the viewing angle of the receiver as narrow as possible. However, from mounting and alignment considerations, it is advantageous to keep the same angle as wide as possible. Thus, there are problems with retaining these seemingly contradictory requirements of the system.

Another problem that may arise in such systems is that the reflective surface may provide one or more unintended optical paths between the transmitter and receiver and thus interfere with the identification of a straight optical path or produce an uncontrolled and unintended contribution to the received signal, or both. This effect is exacerbated if the reflecting surface is subjected to any change, such as movement with temperature or wind loads that accumulate over time, or movement of a person or vehicle that causes the contribution reflected by the reflecting surface to change over time.

Such unwanted reflections may be common because the components of the beam detector are typically mounted just below a substantially flat ceiling. The inventors have realised that to cause such problems, the coating of the reflective surface need not be substantially reflective or mirror-like, and that even a common matt-painted surface may provide a relatively strong specular reflection at narrow angles of incidence, as would typically occur, for example, in a beam detector having a long wing mounted near the surface. Although mirror-like or glossy coatings are extreme, even very rough surfaces can cause sufficiently specular reflection, creating these problems.

Adjacent walls, especially glazed walls, also create similar problems with the added difficulty that blinds or openable windows may be used at different times. However, this problem does not occur very often, as it is seldom necessary to direct the light beam close to the wall.

For this and other reasons, beam detectors often require careful alignment at installation. The purpose of this alignment is to ensure that the beam enters the sensor in a normal state without particles so as to capture the vast majority of the emitted beam, thereby maximizing sensitivity to darkness. This calibration process is slow and therefore costly to perform. Furthermore, repeated calibrations may be required as the physical environment changes (e.g., due to slight movement of the structure to which the beam detector is attached). In some cases, such misalignment may also cause false alarms if the intensity of the incident light on the detector diminishes rapidly.

Because the beam detector is typically mounted to a wall or similar flat surface, it is generally not possible to use an array of sight-type alignment devices behind the detector. Furthermore, because the detectors are typically mounted at high and inaccessible locations, the problems of obtaining precise alignment and the hassle caused by misalignment are even more pronounced.

As discussed with reference to fig. 1, some beam detectors employ co-located transmitters and receivers and remotely located reflectors. Another arrangement, as shown in FIG. 9, uses a light source 1102 that is remote from the receiver 1104. The separate transmitter 1102 may be battery powered to avoid the need for expensive wiring. Furthermore, in embodiments powered by a fire alarm loop, the detector unit 1104 (or the combined light source and detector 102 of FIG. 1) may also use a battery as a backup power source during periods of high power consumption (beyond the specific limits on the capabilities of the wired loop power supply).

In order to obtain the required service life and comply with safety regulations, it is desirable that battery powered units should not be powered during transport or long term storage.

Conventionally, battery powered devices are typically activated using a manual switch, either by removing an insulated spacer or by inserting a battery. The inventors have identified that these methods have some drawbacks, especially in the case of beam detection systems. Conventional systems for powering up battery-powered devices are not automatic and therefore may be ignored when installing the beam detection system. In a beam detection system, the wavelengths used for the light sources 102, 202 are typically invisible to the human eye. This makes it difficult to confirm that the light sources 102, 202 are active at installation. In addition, the beam detection system is typically mounted high, requiring scaffolding or a vehicle lift to access the components of the system. Therefore, it is time consuming and costly to approach and adjust a unit that has been inadvertently inoperable.

Some conventional techniques for activating a battery-powered unit also hinder the common requirement (i.e. the beam detection system should avoid some means of causing penetration of the main housing of the unit). It is often the case that the emitter is designed to be sealed against the ingress of dust and moisture, and the use of a manual switch may make such isolation more difficult and costly to achieve.

Another problem that may arise with beam detectors is that their exposed optical surfaces may become contaminated with dirt over time. This will gradually weaken the received signal and there is a possibility of false alarms being generated. Methods are known for avoiding and removing dirt that accumulates on optical surfaces, and these are particularly common in the field of closed circuit television security surveillance equipment, such as anti-fouling coatings on viewing windows, guard rings, scrubbing mechanisms and other similar devices.

Furthermore, as described in PCT/AU2008/001697 in the name of eletricis technologies, there are other mechanical methods for cleaning or avoiding the accumulation of dirt on optical surfaces, including methods that use filtered clean air as a barrier or electrostatic protection area to prevent window contamination. Such methods may be used advantageously in beam detectors, either alone or in combination with other aspects of the invention, and each constitutes an aspect of the invention.

With the dual wavelength system described with reference to fig. 2 and 3, it is possible to allow the absolute intensity of the received light to vary to some extent, since a differential measure is used to detect particles in the beam, but relative variations between wavelengths may cause malfunctions or, more seriously, false alarms; in particular, the relative attenuation of the signal received from the ultraviolet beam compared to the infrared beam may be mistaken for smoke. Thus, any wavelength-selective accumulation of dirt on the optical surface can be a problem.

This is a problem in the field of video surveillance and other similar fields having remotely located optics, such as cameras, where insects or other foreign objects may occasionally land on exposed surfaces of the optics of the system and partially or completely obscure the field of view of the optics. Similar problems may also occur in particle detection systems (e.g., beam detectors) that are exposed to insects and other foreign objects. Thus, there is a need to protect the components of a particle detection system (e.g. a beam detector) and thereby avoid or minimize false alarms caused by such conditions.

As described above, some embodiments of the invention may include separate emitters in the emitter that are configured to emit light in different wavelength bands. Most preferably, the light emitter is an LED. Over time, the output of an LED may vary in absolute or relative intensity, or both. By means of the dual wavelength system, a certain variation of the absolute intensity may be allowed, as long as the relative measurement of the intensity used by the system for detecting particles remains substantially constant. However, a relative change in the output intensity of the two lights may produce a fault or false alarm. This is particularly true when the output signal from the ultraviolet LED is attenuated relative to the output of the infrared LED.

It is known to monitor large areas by using beams that pass through a length of, for example, 150 meters, or to monitor a relatively restricted space using beams that require only a length of, for example, 3 meters. In conventional beam detector systems, the same light source and receiver can be used for these two very different applications (i.e. 150 meter separation or 3 meter separation). This is possible by adjusting the gain of the receiver or by reducing the power of the transmitter, depending on the separation distance between the transmitter and the receiver.

However, the applicant's previous application discussed above, and the example of fig. 3, shows that the beam detector may comprise more than one emitter per receiver. This has its own particular problem in that multiple transmitters may be placed at very different distances from the receiver. For example, consider a room of the type shown in FIG. 57. The room 5700 is generally L-shaped and has a receiver 5702 mounted at the outer apex of the L-shape. 3 emitters 5704, 5706, 5708 are positioned around the room 5700. A first emitter 5704 is positioned along one arm of L. The second transmitter 5706 is located at 90 to the first receiver 5704, at the end of the other arm of the L. A third transmitter 5708 is mounted from the receiver 5702 through the apex of the L-shape. It will be appreciated that the distance between the transmitters 5704, 5706 and the receiver 5702 is much greater than the distance between the transmitters 5708 and the receiver 5702. Thus, the brightness of the light received from each emitter will be very different. In addition, the transmitter 5708 may be so close to the receiver as to saturate its light receiving elements.

Other disadvantages may also arise, such as the possibility of the installer to use the reliability of the beam detector from time to time, installing the system outside the manufacturer's specifications. For example, although beam detectors typically operate with a transmitter and receiver separated by a distance, the installer may extend the distance to establish a range outside of what the manufacturer's recommendations or regulations allow. In some cases, the installer of the particle detector may not be aware of the operational limitations of the receiver provided for the light source.

In such a case, the installed particle detector may operate satisfactorily during initial installation, but no longer operate properly at some point after installation. This may occur, for example, if the particle detector is initially installed close to but beyond its design limits. Over time, the equipment and environment may change, gradually changing the intensity of the received signal for reasons other than the presence of particles in the beam. These changes may be caused by, for example, component aging, shifts in coarse alignment, or contamination on the optical surfaces. Such system drift will typically be handled by the system if it has been built within design limits. However, when the system is set up outside these limits, the deterioration of performance and consequent fault conditions may occur prematurely or repeatedly.

It is also desirable to be able to calibrate and/or test such beam detectors by simulating the presence of smoke using a solid object. Such testing is a requirement for standard body testing of beam detectors. For example, the standard EN 54-12 for "fire detection and fire alarm systems, smoke detectors, linear detectors using optical beams".

In prior art testing methods, the beam detector test employs a filter that partially obscures the projected beam to simulate the smoke effect. The filters used are typically composed of a fiber mesh, or a dye-loaded plate or a clear film with printed features that obscure in a repeatable manner all visible and near visible wavelengths in substantially the same amount. The present inventors have realised that such filters may not be suitable for use with beam detectors of the type described above.

In a preferred embodiment of the system shown in fig. 1 to 3, the light source is arranged to comprise a plurality of luminaires, wherein each luminaire is adapted to generate light of a specific wavelength band. Further, the separate light sources are arranged to emit light at different timings, so that a monochrome imaging element can be used. The direct result of using separate emitters is that there is a certain separation between two emitters in the light source, whereby the light will traverse a somewhat different (although very close) light path through the space between the light source and the receiver. The potential for this is that small objects (e.g. insects) on the transmitter will affect one path more than the other and therefore the reading of the receiver. This would include false alarms or unnecessary fault conditions.

Conventional beam detectors require careful alignment during installation. The purpose of this alignment is to ensure that the beam enters the sensor in a normal state without particles so as to capture the vast majority of the emitted beam, thereby maximizing sensitivity to darkness. This calibration process is slow and therefore costly to perform. Furthermore, repeated calibrations may be required as the physical environment changes (e.g., due to slight movement of the structure to which the beam detector is attached). As mentioned above, the inventors have previously proposed in PCT/AU2008/001697 in the name of eletricius technologies, filed on 10.6.2009, the specification of which is incorporated herein by reference in its entirety, a particle detector comprising a receiver having a photosensor comprising an array of photosensor elements, such as a CCD (charge coupled device) image sensor chip or a CMOS (complementary metal oxide semiconductor) image sensor in a video camera, or other receiver capable of receiving and reporting light intensity at a plurality of points across its field of view. Each sensor element in the receiver produces a signal related to the intensity of light it receives. These signals are transmitted to a controller where a particle detection algorithm is applied to the received image data. The receiver in the particle detector has a wider field of view and lower noise than a single sensor receiver, and has the ability to measure light independently at a wider range of points within the field of view.

Because each sensor element has an inherent noise level, the overall signal-to-noise ratio of the system can be improved by focusing the target (e.g., beam image) on a single sensor element. However, this does not produce the desired results.

Sensors of the above type (for example CCD or other types) sometimes suffer from a phenomenon, known as stair stepping, in which adjacent pixels or groups of adjacent pixels have significantly different values, resulting from the image processing algorithms used by the receiver. The physical structure of the sensor also has non-inductive "gaps" between the sensor elements, which do not generate a signal. Due to these effects, any change in the alignment of the smoke detector components will likely result in a large change in the measured light intensity level.

For example, due to the small size of the target being focused, very small movements of the receiver or transmitter may cause the target to move onto a completely different sensor element that has a very different inherent noise level or response than the previous pixel on which the target was focused. The target may also fall into a position where all or a valuable portion of the received beam falls into one of the aforementioned "gaps". Thus, the resulting change in image intensity determined by the controller will likely cause the controller to falsely detect smoke.

To partially solve this problem, the detector can be adapted to track the target on the light sensor over time, so that smoke detection can be performed on the signal from the correct sensor over time. However, to correctly determine the image intensity, the controller will be required to determine the inherent characteristics of the different light sensors used over time. This depends on system resources such as processing cycles and power. Further, the controller may not always make this determination.

Another problem that may arise in beam detectors is interference from ambient light within the volume being monitored. The ambient light may come from sunlight illuminating the volume or artificial lighting for illuminating the space. Thus, the beam detector needs a mechanism for reducing the influence of such light as much as possible. The problem is made worse by the conflicting requirements that the light source of the beam detector should be relatively low power, so as to minimize power consumption, be eye safe and not cause visible damage. In prior art beam detectors using a single wavelength, optical filters are typically used to attenuate the signal from ambient light. In the case of infrared beam detectors, the filter is typically a low pass filter that removes substantially all visible and ultraviolet light. However, this is not appropriate for the multi-wavelength system described herein.

In a preferred embodiment of the above system, the particle detector is powered directly by the fire alarm loop at the receiver. This reduces the installation costs of the device as much as possible, since it avoids the need for special wiring for power supply or communication with the detector. However, fire alarm circuits typically provide only a small amount of dc power to the detector. For example, for such detectors, a normal power consumption of about 50mW is available. However, with current technology, the power consumed during video capture and processing may be much higher than the 50mW available to the loop. To address this problem, a separate power supply may be used, but this is expensive because of the wide variety of standards for fire protection equipment, such as battery-backed power supplies and fixed mains that they require to be fully approved and supervised.

The limited power supply also limits the optical power output of the transmitter. The limited optical power output in turn limits the signal-to-noise ratio of the measured signal. If the signal-to-noise ratio of the system is severely degraded, the system may experience frequent or sustained false alarms.

In some systems, the signal-to-noise ratio can be improved by using a long accumulation time or averaging time at the receiver. However, if long integration times are used, the system response time (typically between 1O second and 60 seconds) must be increased to a higher level. This is not desirable.

In addition to using beam detectors for smoke detection, it is often desirable to use other sensor mechanisms for detecting additional or alternative environmental conditions or hazards, such as CO₂Gas detection or temperature detection. These detectors conventionally use wired or wireless communication links to send an alarm or fault condition to a fire alarm control panel or similar monitoring system. These connections themselves add considerable cost and potential reliability problems to the alarm system.

In some systems, the inventors have determined that it is beneficial to have at least some of the components (most advantageously the transmitter) operate on batteries. Exemplary components are described in applicants' co-pending patent application PCT/AU 2009/000727 (filed on 26.6.2008), the contents of which are incorporated herein by reference in their entirety.

However, a problem that will arise in a battery-powered component of a particle detector is that over time the battery of that component is exhausted and eventually fails. Such failure would likely require unscheduled maintenance of the equipment to be put into service again. This is particularly problematic in smoke detection applications, as the equipment functions to ensure life safety and requires prompt troubleshooting. This problem can be solved by performing preventive maintenance, but eventually it becomes unnecessary to overhaul and replace the unit, which still has a lot of electricity, and it causes high cost and waste of materials.

Unfortunately, variations in individual battery performance and environmental conditions make simple periodic replacement cycles unreliable and potentially uneconomical. An obvious solution to this problem is to provide the component with an indicator of the battery status, however this has the disadvantage of increasing the cost and the indicator itself consumes power, further reducing battery life. Furthermore, it is necessary to regularly check the indicators on the components directly, which is particularly inconvenient in the case of a beam detector.

One problem that may arise in some beam detectors, such as the one described with reference to fig. 3 (i.e., where multiple beam detectors are formed by corresponding transmitter and receiver pairs such that two or more beams intersect or pass close enough to each other through a common air region such that their intersection points may be mapped to addresses in the monitored area) is that any one subsystem may be affected by environmental conditions or system problems that do not affect the other subsystems. Such problems often force the achievable sensitivity to be reduced or increase the rate of unwanted false alarms.

The reference to any prior art is not (and should not be taken as) an acknowledgement or any form of suggestion that prior art forms part of the common general knowledge in australia or any other jurisdiction or that an acknowledgement or suggestion may warrant that the prior art is fully expected to be ascertained, understood and regarded as relevant by a person skilled in the art.

Disclosure of Invention

In a first aspect, the present invention provides a beam detector arrangement comprising a transmitter and a receiver, the transmitter being a transmitter adapted to transmit one or more beams of light having a predetermined characteristic over an illumination range, the receiver having a receiver field of view and being adapted to receive the beams transmitted by the transmitter;

the beam detector is mounted to protect a monitored volume, the volume including a structure having one or more reflective surfaces within an illumination area of the transmitter and a field of view of the receiver;

the beam detector comprises a processor adapted to determine whether the light beam received at the receiver has one or more predetermined light characteristics.

Where provided, the processor can be adapted to determine that a light beam from the transmitter is received. In the event that the received light beam does not have the one or more characteristics, the processor can determine that the light beam from the emitter was not received. Alternatively, the processor can determine that the received light beam is a reflected light beam of the emitted light beam.

The beam detector arrangement may comprise a signal arrangement adapted to signal a fault condition in the event that the processor determines that the beam from the emitter is not received and/or that a reflected beam is received.

In a second aspect, the present invention provides a method for determining whether a beam of light received by a receiver of a beam detector is a direct emitted beam or a reflected beam. The method includes receiving the light beam at a receiver and measuring one or more predetermined characteristics of the light beam, and determining whether the received light beam is a direct emitted light beam or a reflected light beam based on the extent to which the predetermined characteristics are present in the light beam. In the event that one or more characteristics of the received light beam do not substantially match one or more characteristics of the emitted light beam, the method may include determining that the received light beam is a reflected light beam. The characteristics of the light beam may include relative intensities of two or more wavelength components in the received light beam and/or polarization characteristics of the received light beam.

In another aspect, the invention provides a receiver for a beam detector, the receiver comprising a plurality of image sensors, each image sensor comprising a plurality of sensor elements, the image sensors being arranged to have at least partially overlapping fields of view. The receiver may additionally comprise optical means adapted to form an image on each of the two sensors. The receiver may additionally comprise image analysis means to analyse images from more than one of the plurality of image sensors to determine the angular position of the image component in the field of view of the plurality of sensors. The image component may be one or more light beams emitted by a light source of a beam detector.

In a further aspect, the present invention provides a receiver for a beam detector, the receiver comprising:

one or more sensors comprising a plurality of sensor elements to receive the light beam from the emitter;

processing means in data communication with the one or more sensors for receiving and processing image data from the sensors; and

an input device adapted to receive an input representative of a plurality of light beams to be received from one or more emitters of the beam detector.

Preferably, the input means may comprise one or more switches (e.g. DIP switches) or by providing a data input interface (e.g. a serial port or similar) through which data may be provided to the processor means or a memory associated therewith.

In yet another aspect, the present invention provides a beam detector comprising: one or more light sources adapted to emit said light beams through a monitored area; one or more receivers arranged relative to the emitter and the monitored volume such that light from the emitter reaches the receivers after passing through at least a portion of the monitored volume.

In certain embodiments of the present invention, the beam detector system may include one or more light-blocking baffles arranged relative to the monitored volume and the emitter and/or receiver such that no reflected light from the illuminated area of the light source and the surface within the field of view of the light receiver of the beam detector reaches the receiver.

In a preferred embodiment of the beam detector, the light receiver is manufactured according to one aspect of the invention described herein.

In some embodiments of the invention, the emitter of the beam detector is manufactured according to embodiments of any one of the aspects of the invention.

In one aspect, the present invention provides an emitter for a beam detector emitter that includes one or more light sources adapted to generate light in spatially distinct beam patterns. Preferably, the spatially resolved beam pattern is not symmetrical in at least one plane. The spatially resolved beam patterns may comprise patterns of individual beams having resolvable characteristics. The characteristics may include wavelength characteristics, polarization characteristics, or modulation characteristics that can be resolved from each other. Other characteristics may also be used. For example, in a preferred form, the distinguishable pattern may comprise a pair of distinguishable beams. A single light source may be used for some embodiments of the emitter. In this case, the image of the light beam formed by the receiver must be such that the shape of the light source can be directly resolved. For example, the image of the light source may be "L" shaped so that up and down and left and right can be discerned from the image of the light source.

In a beam detector including an emitter of the above type, the present invention also provides in a further aspect a method of determining whether a beam of light received at a receiver is emitted in a direct or reflected path, the method comprising:

arranging the light source and the receiver such that the light beam emitted by the light source is received at the receiver; and

the light source is oriented relative to an adjacent surface within the illumination area of the light source and the field of view of the receiver such that a direct image of the light source is resolvable at the receiver with a mirror image of the reflection of the light source from the surface.

This alignment step may include aligning the light source such that its image is not symmetrical in the direct and reflected images.

In yet another aspect, the invention provides a method of distinguishing a directly received light beam from a reflected light beam in a beam detector system, the method comprising receiving an image comprising two image segments potentially corresponding to a light beam emitted by a particle detector;

determining the brightness of each received light beam; and

it is determined that the brightest of the received light beams is the directly received light beam.

In yet another aspect of the present invention, there is provided a method of determining which of a plurality of received light beams are received directly from a light source and which are received by surface reflection, the method comprising:

Determining which of the received light beams is received by the sensor element of the light sensor of the receiver of the beam detector that is furthest away from the reflecting surface perpendicularly; and

the determined beam image is designated as a direct beam image.

In a first aspect, there is provided a beam detector comprising:

a light source adapted to emit a light beam with a first polarization state;

a light receiver adapted to receive light of a second polarization state and to output a received light level; and

a controller adapted to analyze the received light levels and apply alarm and/or fault logic and take action if a predetermined fault condition exists.

In one embodiment, the first and second polarization states are parallel.

In another embodiment, the first and second polarization states are non-coincident with each other. They may be orthogonal.

The beam detector may comprise a light source adapted to emit a second light beam with a third polarization state. The first and third states of polarization are preferably different. Most preferably, they are orthogonal. The first and second light sources may be a common light source. The third and second polarization states may be the same.

The beam detector may further comprise an optical receiver adapted to receive light of a fourth polarization state.

The second and fourth polarization states are preferably different. Most preferably, they are orthogonal. The fourth and first polarization states may be the same.

One or both of the optical receiver and transmitter may include a polarizing filter, or a plurality of interchangeable filters.

A component of a beam detector system, comprising:

at least one electro-optical device arranged to emit or receive light in a first spatial distribution; and

an optical subsystem arranged relative to the electro-optical device such that the first spatial distribution is adjusted to form a second spatial distribution, wherein

The relative extent of the first spatial distribution along two non-parallel axes is different from the relative extent of the second spatial distribution along the same axis.

Preferably, the axes are orthogonal to each other. Most preferably, one axis is interrupted into a vertical axis and the other axis is a horizontal axis.

Preferably, the second spatial distribution is relatively wider in the horizontal direction than in the vertical direction compared to the first spatial distribution.

The optical subsystem may include anamorphic lenses, or other "wide screen" optical systems.

The electro-optical device may be an image sensor. The electro-optical device may be a light emitter, e.g. an LED, a laser diode.

Yet another aspect of the invention provides a light source for a particle detector, comprising:

at least one light emitter for generating a light beam; and

an optical subsystem for controlling the angular dispersion of a light beam, wherein the optical subsystem is adapted to shape the light beam to have a greater angular dispersion along one axis than along another axis.

Preferably, the shape of the beam is wider than it is tall. The beam may be shaped to have a horizontal angular dispersion of between 5 and 25 degrees. And most preferably between about 10 and 15 degrees.

The vertical dispersion may be between 0 and 10 degrees. Most preferably between about 3 degrees and 5 degrees.

In another aspect, the present invention provides a receiver for a beam detector, comprising:

a light sensor capable of providing an output representative of light levels detected at a plurality of locations on the sensor; and

an optical subsystem adapted to receive light having a first shape in a field of view and direct it onto the light sensor in an image of a second, different shape.

Preferably, the optical subsystem comprises an anamorphic lens. The field of view of the optical subsystem is preferably wider in one direction than in the other. Preferably, its width is greater than its height.

The field of view of the optical subsystem may be defined by the largest acceptable light angle in one direction and the largest acceptable light angle in the other direction.

Preferably, the maximum horizontal acceptable angle is 90 degrees or less. But may be larger in some cases.

Preferably, the maximum vertically acceptable angle is 10 degrees or less.

Another aspect of the invention relates generally to the set-up of a particle detection apparatus, wherein a visual alignment apparatus incorporated with or attached to the particle detection apparatus is pointed at a target and used to accurately align with the apparatus at the time of installation or when alignment adjustments need to be made. The visual alignment device and the optical elements in the particle detector will have a fixed alignment relationship with respect to each other. The visual alignment apparatus may include a visible beam generator that projects a visually observable beam toward the remote surface, or may include a video camera that receives an image of the remote surface and displays the image of the surface on a display screen.

One aspect of the invention provides an assembly of a smoke detector comprising:

an optical module comprising one or more light sources and/or one or more light receivers;

Mounting means for mounting the optical module to a support surface;

an articulating connection between the mounting device and the optical module; and

a visual alignment apparatus fixed for movement with said optical module for assisting in aligning said light source and/or said receiver relative to a target.

Optionally, the visual alignment apparatus comprises one or more sockets in the optical module into which an alignment beam generator (alignment beam generator) can be inserted.

The articulated connection may comprise one or more locking means for locking the orientation of the optical module relative to the mounting means. The articulation may comprise a ball and socket joint capable of allowing the optical module to tilt through a relatively large arc of tilt relative to the mounting means, the locking means being adapted to lock said ball with said socket in a selected orientation. The locking means may comprise a screw member which engages in a threaded bore in the socket and contacts a surface of the ball to lock the ball and socket together. Alternatively, the screws can be accessed via a visual alignment device.

In an alternative arrangement, the present invention provides an assembly of smoke detectors comprising:

an optical module comprising one or more light sources and/or one or more light receivers;

a fixed mounting device for mounting the optical module to a support surface;

an articulating mount located between the optical module and one or more light sources or light receivers; and

a visual alignment apparatus fixed for movement with said light source and/or said receiver for assisting in aligning said light source and/or said receiver relative to a target.

Optionally, the visual alignment apparatus comprises one or more sockets in the articulated mounting arrangement into which the alignment beam generator can be inserted.

The articulated connection may comprise one or more locking means for locking the orientation of the optical module relative to the articulated mounting means. The articulation may comprise a ball and socket joint capable of allowing the optical module to tilt through a relatively large arc of tilt relative to the mounting means, the locking means being adapted to lock said ball with said socket in a selected orientation. The locking means may comprise a screw member which engages in a threaded bore in the socket and contacts a surface of the ball to lock the ball and socket together. Alternatively, the screws can be accessed via a visual alignment device. Alternatively, a rotatable mounting may be used.

The visual alignment device may include a laser housed in or mounted on a cylindrical tube or shaft that is sized to slip fit with the beam alignment device. Optionally, the laser forms part of a means for locking the articulated connection. The laser may blink to aid in visual identification.

Alternatively, the visual alignment apparatus may comprise a video camera mounted for movement with the housing and capable of producing an image of the target, the image comprising aiming means which, when aligned with the target, will indicate that the optics are operatively aligned. The housing may include a video camera mount that aligns the camera with the housing when the camera is mounted to the camera mount such that the camera has a field of view aligned in a known direction relative to the light source. Optionally, the known direction is axially aligned with light emitted from the light source.

The component may be, for example, a transmitter, receiver or target for a particle detector (e.g. a beam detector).

Another aspect of the invention provides a method of aligning components of a smoke detector, comprising:

Mounting an assembly to a support surface in an initial orientation, the assembly including a visual alignment apparatus;

determining the orientation of the assembly by visually observing the output of the visual alignment device;

adjusting the orientation of the assembly by monitoring the visual alignment apparatus until the assembly is in the selected working orientation; and

the assembly is secured in the operating orientation.

The method may include removing the visual alignment apparatus from the assembly.

The orientation of the assembly can be determined by observing the position of an alignment beam emitted from a visual alignment apparatus located remotely from the support surface, or by observing an image of the remote surface produced by a camera of the visual alignment apparatus.

Yet another aspect of the invention provides an alignment tool comprising:

a shaft having a handle;

a drive device actuatable by the handle;

a visual alignment apparatus in a fixed or known orientation relative to the drive means; and

a shaft and a handle.

It is further provided that the visual alignment apparatus includes a laser located in a cartridge, with the handle having a socket therein shaped to receive the cartridge. The laser will typically be battery powered and the laser may be turned off when not in use by turning on/off a switch. The shaft may be straight or may have an elbow therein, depending on the configuration of the device in which the tool is to be used. Alternatively, the visual alignment apparatus may comprise a video camera.

One aspect of the present invention provides a visual alignment tool comprising:

an engagement means for engaging with said visual alignment tool and aligning said visual alignment tool relative to the particle detector assembly; and

a visual aiming device for providing a visual indication of alignment of the particle detector assembly after said engagement.

The visual aiming means may be a camera, but is preferably a means for projecting visible light. The visible light may be a simple beam as in a laser pointer, or a more complex pattern, such as cross hairs. The means for projecting may flash to aid visual identification. The visual aiming device is preferably battery powered, but may include an on/off switch so that it can be turned off when not in use.

The engagement means is preferably an elongate projection which is receivable in a recess in the particle detector assembly. Preferably, the visual aiming means is coaxially aligned with the engagement means.

The visual alignment tool means preferably comprises an elongate handle and a shaft extending from one end of said handle and coaxially aligned therewith, wherein at least a portion of said shaft forms the engagement means. The shaft and the recess may be cylindrical and dimensioned to slip fit into each other.

The visual aiming means is preferably arranged at the other end of the handle. Optionally, the visual aiming device is removable from the handle.

The visual alignment tool may include a drive means for engaging and actuating the locking means of the particle detector assembly.

The drive means is preferably formed at an end of the shaft remote from the handle and is rotatable about the axis of the shaft to actuate the locking means. The drive means may be, for example, an allen wrench (hex), phillips head or other suitable shape (e.g. triangular). Ideally, the drive means is shaped for engagement with the locking means in only a single relative rotational direction, for example, the drive means may be a non-equilateral triangular projection receivable in a complementary recess so that the rotational direction of the visual alignment tool indicates the state of the locking means. Visible markings may be provided on the tool to assist in the indication.

In this aspect, the invention also provides a particle detector assembly;

the assembly includes a mounting portion, an optical module, and a locking device;

the mounting portion is fixedly attachable to a mounting surface;

said optical module being articulated with respect to said mounting portion for alignment with respect to a target and said optical module comprising means for producing a visual indication of said alignment; and is

The locking device is activatable to lock the optical module in a selected alignment relative to the mounting portion.

The term "target" as used herein should be broadly construed and may include a real target mounted remotely for reflecting light from a light source back to a receiver. However, the target may also simply indicate the distant surface (if light reflected from the distant surface is monitored by the receiver) or even a desired point to which a component should be aimed (e.g. for a light source, the receiver may be a target, or vice versa).

The means for producing a visual indication may be a visual aiming device comprising an electro-optical device, such as a camera or a laser pointer, but is preferably an engagement member for cooperation with a visual alignment tool containing the visual aiming device.

Preferably, the optical module comprises an elongated recess forming the engagement member. The recess preferably has at least one open end and is arranged such that the axis of the recess projects towards a target when the optical component is aligned with the target. The recess may extend in a direction parallel to the boundary of the operating region of the optical module or be in some other known physical relationship with the spatial optical properties of the optical module.

The locking means is preferably activatable by a visual alignment tool. The locking means preferably comprises a driven member located within the recess and engageable with a drive means of the visual alignment tool to actuate the locking means. Preferably it is adapted to be rotationally driven about the axis of the recess into a selected direction to actuate the locking means. The driven member is preferably shaped for engagement with the drive means of the visual alignment tool in only a single relative rotational direction, for example the drive means may be a protrusion of a non-equilateral triangle capable of being received in a complementary recess formed in the driven member such that the visual alignment tool indicates the state of the locking means. A marker may be placed on the component to assist in the indication.

Preferably one of said optical module and said mounting portion (most preferably said optical module) is captured in the other portion, said articulated connection being effected by a spherical sliding fit between the optical module and the mounting portion. The driven member may be a grub screw located in one of the optical module and the mounting portion and rotatable to engage the other of the optical module and the mounting portion. Preferably, however, the optical module includes a stop and a cam, wherein the cam is arranged to be driven by the driven member and in turn to drive the stop to frictionally or otherwise engage the mounting portion and thereby lock the optical module relative to the mounting portion. The cam may be attached to or integrally formed with the driven member. The brake pads may be biased towards a retracted non-braking position.

The optical module may comprise simple optical elements such as lenses or mirrors. For example, a mirror can be aligned to redirect the light beam to or from a fixedly mounted electro-optical element. In this case, the mirror and the electro-optical element may be mounted in a housing.

Preferably, the particle detector assembly is arranged to operatively connect an electrical circuit to a power supply to effect operation of the electro-optical element when the locking means is activated. To this end, a switch may be associated with the driven member. For example, the driven member may carry a magnet at a point on a radius from its axis, the magnet being arranged to act on a reed switch when the driven member is rotated to a selected direction.

This aspect of the invention also provides a combination of a particle detector assembly and a visual alignment tool, and a method of mounting and aligning a particle detector assembly.

There is provided a method of aligning a particle detector assembly, the particle detector comprising an optical module, a mounting portion and a locking device, the method comprising:

articulating the optical module relative to the mounting portion to align a visual indication of orientation with a target.

Preferably, the method comprises actuating the locking device to lock the optical module in the alignment direction.

Preferably, the method further comprises engaging an optical module of a particle detector assembly with a visual alignment tool to provide said visual indication of the orientation of said optical module; and

disengaging the visual alignment tool.

The activation preferably comprises rotating the visual indication means and most preferably while connecting the electro-optical device to a power source.

A method of installing a particle detector assembly includes:

fixedly mounting a mounting portion of a particle detector assembly to a mounting surface; and

the particle detector assembly is aligned according to the method described above.

In a preferred form, there is included the step of locking the optical module and connecting the electro-optic device to a power supply.

In another aspect, the invention provides a smoke detector assembly:

the assembly comprises a mounting portion, an optical module, a locking device and an actuating device;

the mounting portion is fixedly attachable to a mounting surface;

the optical module includes an electro-optical element and is articulated with respect to the mounting portion for alignment with respect to a target;

The locking device being actuable in response to intervention by an installer to lock the optical module in a selected alignment direction relative to the mounting portion; and

the activation device is configured to operatively connect the electro-optical element to the power source in response to intervention by an installer.

In a further aspect, the present invention provides an assembly of a particle detector comprising an electro-optical device adapted to at least emit or receive optical signals in an angular range, and an optical assembly adapted to redirect the optical signals, the optical assembly and the electro-optical device being mounted relative to each other such that the electro-optical device receives or emits the optical signals via the optical assembly, wherein: the orientation of the optical assembly can be adjusted relative to the electro-optic device to enable the direction of optical signals emitted or received by the assembly to be changed.

Preferably, the assembly comprises a housing in which the electro-optical device and the optical assembly are mounted and an aperture through which an optical signal can pass.

The mounting means may be adapted to rotatably mount the optical assembly relative to the housing. The mounting means preferably frictionally engages a recess in the housing. The mounting means preferably includes engagement means engageable by an actuating tool to allow rotation of the optical assembly. The engagement means can be adapted to engage with an activation tool as described herein.

The optical assembly may include a mirror to reflect the optical signal.

The electro-optical device may be a light sensor comprising a plurality of sensor elements. The light sensor is preferably a camera adapted to capture a series of images.

According to an aspect of the invention, there is provided a particle detector assembly comprising a first module having an actuator and a second module arranged to be mounted to the first module. The second module comprises an electro-optical system for a beam detection system and a power supply capable of supplying power to the electro-optical system. The second module also includes a switch that reacts to the actuator. The actuator causes the switch to operatively connect the power source to the electro-optic system when the second module is mounted to the first module.

In one arrangement, the actuator is a magnet and, after assembly of the two modules, the proximity of the magnet is detected using a reed switch.

In a broad concept, one aspect of the present invention can improve system performance where contamination of the optical surface has substantially the same effect on both wavelengths. In this respect, the gradual attenuation of the received signal is compensated by an increase in the effective overall receiver gain of the two channels, and uses a time constant selected to be much greater than the time that a real fire may be missed, for example, a week.

Thus in one aspect, the invention includes detecting a long-term drift in the light level received in the particle detection system; and increasing the gain of the detection circuit to compensate for the drift. In a system with multiple illuminations, e.g., multiple illuminations at different wavelengths, the wavelength dependent gain can be increased.

The concept can be extended such that in the case where contamination of the optical surfaces has a greater effect on shorter wavelengths than on longer wavelengths (as may occur when the contamination contains mainly small particles (e.g. as a result of smoke contamination)), the very slow decay of the received signal is compensated for individually by increasing the effective overall receiver gain of each signal channel, again using a selected time constant that is selected to be much greater than the time at which a real fire may be missed, for example a week.

In a first aspect, the present invention provides a light source for a particle detection system, the light source being adapted to emit: a first light beam in a first wavelength band; a second light beam in a second wavelength band; and a third optical beam in a third wavelength band, wherein the first and second wavelength bands are substantially the same and different from the third wavelength band.

The first and second bands may be in the ultraviolet portion of the electromagnetic spectrum. The third wavelength may be in the infrared portion of the electromagnetic spectrum.

The position at which the first light beam is emitted away from the light source may be separated from the position at which the second light beam is emitted away from the light source. The separation distance may be about 50 mm.

The light source may further comprise a first light emitter for emitting the first and second light beams and a second light emitter for emitting the third light source. In this case, the light source may further include a beam splitter for splitting the light beam emitted from the first light emitter into the first and second light beams. Optionally, the light source comprises a first light emitter for emitting the first light beam, a second light emitter for emitting the second light beam and a third light emitter for emitting the third light beam. The first, second and/or third light emitters are light emitting diodes.

The light source may further comprise a controller arranged to generate the first, second and third light beams in a repeated sequence. Preferably, the repeated sequence comprises a rotation of the first, second and/or third light emitters.

In yet another aspect, the present invention provides a light source for a particle detection system, the light source comprising: a first light emitter for emitting a first light beam; a second light emitter for emitting a second light beam; and an optical system comprising a transmissive region from which light from the first and second light emitters is emitted from the light source, wherein the optical system is arranged such that obstruction of the transmissive region causes substantially the same obstruction to the first and second light beams.

The first and second light emitters are semiconductor dies. Preferably, they are semiconductor dies housed within a single optical package.

The optical system may further include a light guide for guiding the first and second light beams from the first and second light emitters to the transmissive region.

The light guide is selected from the group including, but not limited to: convex lenses, fresnel lenses and mirrors. Other optical devices or combinations of the foregoing may be used.

Wherein the transmissive region preferably forms at least a part of an externally accessible optical surface of the optical system. Such as the outer surface of a lens, mirror, window, LED package, or other similar optical device.

The optical system may comprise beam shaping optics adapted to change the beam shape of one or both of the first and second beams.

The beam shaping optics may provide a divergence angle of about 10 degrees to light emitted from the light source.

In this case, the beam shaping optics may alter the beam shape of one or both of the beams to extend further in one direction than in the other, e.g. greater in the horizontal direction than in the vertical direction.

The beam shaping optics may also alter the first and second beams so that they have different beam shapes from each other. The beam shaping optics may alter the first beam to have a wider beam shape than the second beam.

The beam shaping optics may comprise one or more beam intensity adjusting elements arranged to adjust the spatial intensity of the beam. The beam intensity adjusting element is selected from the group including, but not limited to: optical surface coatings, frosted glass diffusers, and etched glass diffusers.

The first light emitter may emit an ultraviolet light beam and the second light emitter may emit an infrared light beam.

The light guide and the beam shaping optics may be combined into a single optical element or comprise an optical device with multiple optical elements. The optical element may be a transmissive or reflective element.

In a further aspect, the invention provides a particle detection system comprising a light source, a receiver, the light source being a light source according to one or more of the above aspects.

A light source for a particle detector, comprising: one or more light emitters adapted to produce at least one light beam having a first apparent size as viewed from a remote viewpoint; an optical system arranged to receive the at least one light beam and to emit the at least one light beam and adapted such that the emitted light beam has a second apparent size, viewed from the remote viewpoint, which is larger than the first apparent size.

The optical system preferably comprises a beam diffuser. The diffuser may be a dedicated optic (e.g., a piece of etched glass) or formed by a surface treatment on the optic for another purpose.

In another aspect, there is provided a light source for a particle detector, comprising: one or more light emitters adapted to produce at least one light beam having components in at least two wavelength bands; and an optional optical system through which the one or more light beams pass; the light emitter and/or the optical system are arranged such that light in one of the at least two wavelength bands has a different spatial intensity distribution than light in the other wavelength band.

Preferably, the beam width of light in one wavelength band is wider than the beam width of light in another wavelength band. Preferably, light in a wavelength band having a longer wavelength has a narrower beam width than light in a wavelength band having a shorter wavelength. Preferably, the shorter wavelength band may include light in the blue, violet or ultraviolet portion of the electromagnetic spectrum.

In another aspect, the present invention provides a luminophore which can be used in a particle detector, the luminophore comprising: a housing including a window portion through which light is emitted; means for generating light in a plurality of wavelength bands; and a light sensitive element disposed in the housing and configured to receive a portion of the light in at least one or more wavelength bands emitted by the light generating means; one or more electrical connections for making electrical connections between the light generating means, the light sensitive element and an electrical circuit.

Preferably, the light emitter comprises a plurality of light emitting elements adapted to emit light within a corresponding wavelength band.

The photosensitive element may be a photodiode or other photosensitive circuit element.

Most preferably, the light emitting element is an LED die. Preferably, the window portion of the housing can be adapted to control the shape of the emitted light beam.

The housing may be an LED package.

In one form the light emitter comprises a plurality of light emitters for emitting light in one or more wavelength bands. The plurality of luminous bodies may be arranged in the housing to obtain a predetermined beam characteristic. In one example, the luminophores corresponding to one wavelength band may be arranged around one or more luminophores corresponding to another wavelength band.

In a preferred form, the housing may include means for reducing as much as possible ambient light reaching the photosensitive element. For example, the device may include one or more filters that attenuate light outside of the wavelength band emitted by the light-emitting elements. Alternatively, it may comprise one or more baffles or walls in the housing to substantially shield the photosensitive element from direct reception of light from outside the housing.

In yet another aspect, the present invention provides a method of determining the output intensity of a light-emitting element of a light source in a particle detector. The method includes illuminating the light emitting elements according to a modulation pattern, the modulation pattern including an "on period" during which the light is emitting and an "off period" during which the light is not emitting; detecting an output of the light emitting element during one or more on periods and one or more off periods; the light output detected during one or more on periods is adjusted in accordance with the light level measured during the one or more off periods. For example, the adjusting may include subtracting the measurement of the off period from the measurement of the adjacent on period. Alternatively, the on or off periods may be accumulated or averaged over a predetermined number of corresponding on or off periods to determine the light output level.

In another aspect, the present invention provides a light source for a particle detector, the light source comprising at least one luminophore of the type described herein.

The light source may comprise a modulation circuit assembly adapted to control the manner of illumination of the light source and a feedback circuit assembly electrically connected to the light sensitive element and adapted to receive an input from the light sensitive element and to output a control signal to the modulation circuit.

Depending on the level or variation of the received feedback signal, the modulation circuit may be adapted to vary one or more of:

the duration of the illumination;

the intensity of the illumination;

a voltage applied to the light emitter; or

A current applied to the light emitter.

In yet another aspect, the present invention provides a method for a light source of a particle detector, the method comprising: illuminating at least one light of the light source according to a first modulation pattern, the modulation pattern comprising a plurality of illumination pulses; receiving a feedback signal; adjusting the modulation pattern in response to the feedback signal.

The method may comprise adjusting at least one of:

the duration of the illumination;

the intensity of the illumination;

a voltage applied to the light emitter;

a current applied to the light emitter.

Preferably, the feedback signal is generated by a light sensitive element arranged to monitor the light output of at least one light emitting element of the light source.

The feedback signal may be a signal adapted to compensate for a predetermined characteristic of at least one luminaire of the light source. The predetermined characteristic may be a temperature response of the luminaire.

In an embodiment of the invention, the step of adjusting the modulation pattern in response to the feedback signal may comprise adjusting the modulation pattern to encode data relating to the output intensity of the at least one light of the light source. For example, one or more modulation pulses may be inserted, or adjusted, into the modulation pattern to transmit the output data of the luminaire to a receiver of the light output.

In another aspect of the invention, there is provided an assembly for a beam detector, comprising:

a housing having a sidewall defining at least one interior volume, the at least one sidewall including an optically transparent wall through which light can enter and exit the housing;

an electro-optic system located in the interior volume adapted to emit and/or receive light through the optically transparent wall of the housing;

a foreign object detection system adapted to detect a foreign object on or near an outer surface of the optically transparent wall and comprising a light source adapted to illuminate the outer surface and a foreign object on or near the outer surface;

a light receiver to receive light scattered from the foreign object and generate an output signal in a case where the foreign object is illuminated;

a controller adapted to analyze the output signal and apply fault logic to determine the presence of a foreign object and take action if one or more criteria are met.

The optical receiver may be any one of the following:

a photodiode; and

a portion of a photosensor array for detecting particles in use.

The light source may be mounted within the interior volume. Alternatively, it may be mounted on the outside of the housing.

In a first aspect, the present invention provides a method for a particle detection system comprising one or more light sources and a receiver arranged such that light from the one or more light sources passes through an area to be monitored for smoke and is received by the receiver, and a controller programmed to monitor for the occurrence of one or more predetermined alarm and/or fault conditions based on at least one received light intensity threshold; the method comprises the following steps: providing at least one initial received light intensity threshold for use by the controller during operation (comuting period); and providing at least one first operable received light intensity threshold for use during operation subsequent to the run-time period.

Preferably, the received light intensity thresholds provided during said operation comprise the lowest received light intensity threshold below which a fault condition is indicated.

The received light intensity thresholds provided during the operation may comprise a lowest received light intensity threshold below which a fault condition or alarm condition is indicated.

The lowest received light intensity threshold during said operation may be higher than the lowest received light intensity threshold during at least a part of said operation.

The method may further comprise: after the delay period has elapsed, providing at least one second operable light intensity threshold for use during at least a portion of the period of operation following said delay period.

The second operable light intensity threshold may be based on one or more measurements of intensity received during the delay period.

The second operable light intensity threshold is preferably higher than the at least one first operable light intensity threshold. The second operable intensity threshold may be lower than the at least one initial intensity threshold.

The method further comprises: it is determined that the delay period has elapsed. The step of determining that the delay period has elapsed may be performed automatically by the controller and/or upon receipt of a command informing of the expiration of the delay period.

If the received light includes multiple wavelength components, the method includes: the occurrence of at least one predetermined alarm condition is determined based on the received light intensities at the two or more wavelengths. The method may include determining the occurrence of one or more predetermined alarm conditions based on a combination of the received light intensities at the two or more wavelengths.

The method may further comprise initiating the operational period after the operational period. Starting the operation may be performed automatically (e.g., based on a timer) or upon receiving a start command.

In a further aspect, the present invention provides a controller for a particle detection system comprising one or more light sources and a receiver arranged such that light from the one or more light sources passes through an area to be monitored for smoke and is received by the receiver, the controller being programmed to monitor for the occurrence of one or more predetermined alarm and/or fault conditions based on at least one received light intensity threshold; the controller is adapted to perform the method described herein.

The controller may take action upon the occurrence of one or more predetermined alarm and/or fault conditions. For example, the action may be the generation of an alarm or error signal.

The invention also provides a particle detection system comprising such a controller. The particle detection system may further comprise a receiver for receiving light; one or more light sources arranged to emit light at one or more wavelengths such that light from the one or more light sources passes through an area to be monitored for smoke and is received by a receiver. Preferably, each light source is a light emitting diode. The receiver may comprise an array of light sensor elements, for example the receiver may be a video camera.

Yet another aspect of the invention may also provide a method of operating and operating a particle detection system, comprising: arranging one or more light sources and a receiver such that light from the one or more light sources passes through an area to be monitored for smoke before being received by the receiver; and a method of performing an embodiment of the first aspect of the invention.

In yet another aspect, there is also provided a particle detection system for monitoring a volume, the system comprising: at least one emitter adapted to emit one or more light beams; a receiver adapted to receive the one or more light beams from at least one transmitter after passing through a monitored volume; a controller adapted to determine the presence of particles in the volume based on the output of the receiver; and means for determining the light output intensity of the emitter for particle detection.

Means for determining the intensity of the light output of the emitter is associated with the emitter. The means for determining the intensity of the light output of the emitter may comprise one or more filters which can be selectively positioned in the path of the beam of light emitted by the emitter. The emitter may comprise mounting means arranged to receive one or more filter elements to enable the intensity of the light output emitted by the emitter to be set to a predetermined level.

The means for determining the intensity of the light output of the emitter may comprise electronic control means adapted to electronically control the light output of the emitter. The electronic control means may comprise one or more manually controllable switches to select the intensity of the light output of the emitter.

The electronic control means may be in data communication with the receiver and adapted to receive control information from the receiver, the information being related to the received light level from the emitter, and to control the light output of the emitter in response to the control information.

The means for determining the intensity of the light output of the emitter for the particle detector may be associated with the receiver.

The transmitter may be adapted to transmit a plurality of signals at different intensity levels. In this case, the means for determining the light output intensity of the emitter for particle detection may comprise means associated with the receiver for determining the received light intensity levels corresponding to the plurality of signals emitted at different intensity levels, and comparing the received light intensity levels to one or more criteria to determine the light output intensity of the emitter for particle detection.

The transmitter may be adapted to transmit a repeating pattern of signals, including a plurality of signals at different intensity levels; and the receiver may be adapted to selectively receive one or more signals determined to be for particle detection in the repetitive pattern.

The transmitter may comprise means for generating a repetitive pattern of signals (comprising a plurality of signals) arranged to produce different received light levels at the receiver of the detection system.

The particle detection system is most preferably a beam detector.

The repeating pattern of signals may comprise signals emitted at different intensity levels. The repeating pattern of signals may include signals of different durations.

In another aspect, the present invention provides an emitter for a particle detection system, comprising: at least one light source to generate a beam of light at least one wavelength; a housing in which the light source is mounted; one or more filters selectively mountable relative to the light source for selectively attenuating the light beam.

The transmitter may comprise a power source to supply power to the at least one light source.

The transmitter may comprise control circuitry to control the illumination pattern of the at least one light source.

In another aspect, the invention provides a receiver for a particle detection system: at least one light sensor for measuring a light level received from an emitter of the particle detection system; a controller to selectively activate the light sensor to receive a signal. The controller can be adapted to selectively activate the light sensor to receive a predetermined signal emitted by an emitter of the particle detection system.

The predetermined signal emitted by the emitter may be determined from a measured light level received by the sensor at an earlier time.

The test filter comprises at least one lamellar filter element and is arranged to transmit light in a first wavelength band emitted by the particle detector to a different extent than light in a second wavelength band emitted by the particle detector. Preferably, the test filter transmits less light in the shorter wavelengths emitted by the particle detector than in the longer wavelengths emitted by the particle detector.

The test filter may include one or more layers of filter material.

In one embodiment, one or more layers of filter material may be formed of a material that achieves different transmittances for two wavelengths. Alternatively, one or more of the filter elements may be treated or impregnated with a color selective transmissive material. In this case, the material may be a dye.

In a preferred form, the test filter comprises a plurality of filter elements which are combined in such a way that a predetermined transmission characteristic can be obtained. Preferably, the transmission characteristic mimics smoke at a predetermined concentration. The combination of multiple thin layers may provide selectable transmission characteristics.

In one embodiment, one or more layers of material have added particles having a predetermined size range corresponding to particles to be detected by the detector being tested. Most preferably, the particle diameter is between 0.2 and 1.0 microns.

In yet another embodiment, the filter element may have a surface treatment to produce the desired absorption characteristics. In one form, the filter element may include a deformed surface. The deformed surface may be caused by, for example, mechanical abrasion, particle blasting, chemical or laser etching.

In an alternative embodiment, in a third form, the surface is printed with a predetermined number of dots corresponding to a predetermined transmission.

The filter element may reflect or absorb light that is not transmitted. However, absorption is generally more convenient.

In a first aspect, the present invention provides a receiver for a particle detector, the receiver comprising at least one receiver element adapted to receive light and output a signal indicative of the light intensity received at a plurality of spatial locations; and an optical system comprising at least one wavelength selective element arranged to simultaneously receive light at a plurality of wavelengths and to emit light in two or more wavelength bands towards one or more sensor elements, thereby enabling an output signal to be obtained indicative of the intensity of light in the received at least two wavelength bands.

In a preferred form, the receiver is arranged to measure the intensity of light received in a plurality of wavelength bands at a plurality of spatially independent locations substantially simultaneously.

In one form of the invention, the wavelength selective element may comprise one or more filter elements located in the optical path before the receiver. Most preferably, the one or more filter elements comprise a mosaic dye filter. Alternatively, the wavelength selective element may comprise one or more beam splitting elements, such as prisms, diffraction gratings or other elements. In yet another alternative, the light splitting element may be combined with the light sensor element and comprise one multi-layer light sensitive element, wherein a corresponding layer of the multi-layer light sensitive element is arranged to measure the intensity of light in a corresponding wavelength band.

In a preferred form, the wavelength bands of interest include the infrared and ultraviolet bands. In this example, the wavelength selective element may be infrared selective and ultraviolet selective.

In some embodiments of the invention, the wavelength selective element may be adapted to split an incident light beam into individual wavelength components and to direct each wavelength component to a corresponding sensor or subset of elements of the sensor.

In yet another aspect, the present invention provides a receiver for a beam detector comprising a filtering arrangement having a plurality of pass bands. In one form the filtering means may comprise a plurality of band pass interference filters. For example, such a filter may be arranged to selectively emit a long wavelength and one or more harmonics of that wavelength in the first pass band sensor. For example, the filter may be designed to transmit substantially all light at 800 nanometers and 400 nanometers, while blocking a substantial portion of light at other wavelengths. The filtering means may comprise a plurality of filters. For example, the plurality of filters may include more than one interference filter or a plurality of dye filters or other similar filters. The plurality of filters can be arranged in a predetermined spatial pattern such that light in different passbands falls on different portions of the sensor of the receiver.

In a further aspect of the invention there is provided a projected beam particle detector comprising a receiver of the type described above. Preferably, the particle detector comprises a polychromatic light source. Most preferably, the light source may be adapted to emit light of a plurality of wavelength bands simultaneously. In a particularly preferred form, the light sources comprise monochromatic light sources operating simultaneously. However, a polychromatic light source may alternatively be included. The multi-color light source may comprise a xenon pulse tube or a krypton light source. Alternatively, the luminophore may be a combination of a phosphorescent material and a luminophore arranged to illuminate said phosphorescent material. The light may be, for example, an LED.

In yet another aspect of the invention, a transmitter for a beam detector is provided, comprising a light source adapted to emit light in a plurality of wavelength bands corresponding substantially to respective passbands of a filter of a receiver of the beam detector.

In a further aspect of the invention, there is provided a beam detector comprising at least one receiver and transmitter made in accordance with the above aspects of the invention.

According to one aspect of the present invention, there is provided a smoke detector comprising:

an emitter adapted to emit a light beam;

a receiver having a sensor with a plurality of sensor elements for detecting the light beam, each sensor element being adapted to generate a signal related to the intensity of light impinging thereon;

The transmitter and receiver are arranged such that at least a portion of the light beam from the transmitter is received by the receiver;

beam spreading optics located on a propagation path of the light beam to the receiver for forming a spread image of the light beam on the light sensor; and

a controller that processes the electrical signals generated by the plurality of sensor elements to determine the intensity of the received light beam and applies alarm and/or fault logic to the intensity data to determine whether a predetermined condition is met and to take action if the predetermined condition is met.

The beam spreading optics may include a lens that focuses the beam at a point that is not coincident with the sensor. The beam spreading optics may optionally include a diffuser, which may be located between the emitter and the light sensor. A diffuser and a lens may be used together.

The diffuse image of the light beam preferably covers a plurality of sensor elements on the sensor of the receiver. For example, it may cover 2 to 100 elements. Preferably it covers 4 to 20 sensor elements, although this depends more on the density and size of the sensor elements on the sensor. The diffuse image of the light beam is preferably larger than the sharply focused image of the light beam.

The controller is preferably adapted to combine the signals received from the plurality of light sensors to determine the received light level. In a preferred form, the light level measured from the plurality of sensor elements is increased. Before the increase, the signal level of each active sensor element is weighted.

The controller may determine the location of the signal center of the beam image on the corresponding photosensor and weight the signal from each sensor element according to the distance between each sensor and the location of the signal center.

The emitter may emit a light beam having components in two or more wavelength bands.

According to another aspect of the present invention, there is provided a method for detecting particles, comprising:

transmitting a beam of light from a transmitter toward a receiver having a sensor comprising a plurality of sensor elements;

arranging a receiver to receive the light beam;

forming a diffused image of the light beam on the sensor;

generating an electrical signal related to the intensity of the received light level detected by at least those of the plurality of sensor elements illuminated by the light beam;

determining an intensity of the received light beam based on the plurality of signals;

applying alarm and/or fault logic to the received determined strengths; and

If a predetermined alarm and/or fault condition is determined, action is taken.

The step of forming a diffused image of the light beam optionally comprises defocusing the light beam so that it is focused at a location that is not coincident with the light sensor.

Alternatively or additionally, the step of diffusing the light beam may comprise placing a diffuser between the emitter and the receiver.

The step of determining the intensity of the received light beam may comprise combining the received plurality of signals. The signals may be weighted in combination. For example, the method may comprise determining the position of the signal center of the diffuse image of the light beam and weighting the signal according to the distance of the sensor element to which the signal corresponds from the position of the signal center.

In a first aspect, the present invention provides a component for a particle detection system, comprising a first processor adapted to intermittently receive data from an image capture device and process the data, and a second processor communicatively coupled to the first processor and adapted to selectively activate the first processor.

The second processing device may additionally be arranged to perform one or more of the following functions of the particle detection system: communicating with an external data communication system connected to the particle detector; controlling one or more interface components of the system; monitoring the components for fault conditions or other functions.

Preferably, the second processor has a lower power consumption than the first processor.

The assembly also preferably includes an imaging device to receive one or more optical signals from an emitter associated with the particle detection system.

In a second aspect of the invention, a method for a particle detection system is provided. The method includes monitoring a startup period of a first processor using a second processor; activating the first processor in response to a signal from the second processor; and performing one or more data processing steps with the first processor.

The method may include deactivating the first processor after completion of one or more processing tasks.

The first processor is preferably adapted to process video data from a receiver of the particle detection system.

In one aspect, the present invention provides a light source for a particle detector, comprising:

at least one light emitter for emitting at least one beam of light for illuminating a portion of the monitored area;

a battery for providing power to the light source;

a cell monitor for measuring at least one of a voltage of the cell or a current output thereof;

a controller configured to control illumination of at least one light of the light source, receive at least one of a voltage of the battery or a current output thereof, and determine a valve (valid) indicative of an expected battery life remaining. Preferably, the controller is adapted to generate an indication of the expected battery life remaining in the event that the expected battery life remaining is less than a predetermined period of time.

Preferably, the light source includes an environmental monitor to monitor environmental factors, such as temperature, that affect the remaining expected battery life.

The predetermined period of time is preferably longer than a period of time of a regular, recommended or designated service interval for the light source.

In another aspect, the present invention provides an environmental monitoring system comprising:

a beam detector subsystem comprising at least one transmitter adapted to transmit one or more beams of light through a monitored area and at least one receiver adapted to receive at least one beam of light transmitted by the transmitter;

at least one additional environmental monitor adapted to detect an environmental condition associated with the monitored area and to transmit an output to a receiver of the beam detector subsystem via an optical communication channel.

In a preferred form, the optical communication channel may be achieved by modulating the light beam output by one or more emitters of the beam detection subsystem.

Alternatively, the optical communication channel may include a light emitter associated with one or more additional environmental monitors and arranged to be located in the field of view of the receiver of the beam detector subsystem, wherein the light emitter is adapted to be modulated to transmit the condition detected by the associated environmental monitor.

In a particularly preferred form, the light receiver of the particle detection subsystem may comprise one or more sensors comprising detection elements adapted to measure the intensity of received light at a plurality of spatial locations. Such a system may be used to simultaneously monitor the optical communication channel and the particle detection beam of one or more emitters of the beam detector subsystem.

In yet another aspect of the present invention, a beam detection system is provided, comprising a plurality of beam detectors; at least one controller in data communication with the detectors and receiving an output from each of the beam detectors. The controller is adapted to correlate the outputs of at least one pair of beam detectors which are spatially substantially coincident for at least a portion of their beam lengths and which, in the presence of a predetermined related condition, determine that a particle detection event or fault condition has occurred. In one form the correlation comprises a temporal correlation. The correlation may include a particle detection level correlation. In a simple form, the correlation may be performed simply by comparing whether the particle detection levels of two or more of the beam detectors are substantially equal, alternatively the particle detection characteristics for a plurality of beam detectors may be compared with one another to determine the degree of correlation therebetween.

In another aspect of the invention, a method of operating a particle detection system comprising a plurality of beam detectors having beams that can substantially coincide at least one point is provided. The method includes receiving outputs from the plurality of beam detectors, determining whether a correlation condition exists between at least two of the outputs, and if a predetermined correlation condition exists, determining that a particle detection event or a fault alarm event has occurred based on predetermined particle detection and/or fault logic. The alerting may comprise cross-correlating the time-varying particle detection characteristics of the two detectors. It may also or alternatively comprise determining a correlation between particle detection states, i.e. the crossing of alarm levels or alarm thresholds between two or more detectors.

Throughout the specification, the term "beam of light" will be used to refer to the output of a light emitter (e.g. an LED). The beam need not be collimated or confined to a single direction but may be divergent, convergent or any suitable shape. Similarly, "light" should be understood to refer broadly to electromagnetic radiation and is not limited to the visible portion of the electromagnetic spectrum.

In another aspect of the invention, there is provided a particle detection system comprising: at least one light source adapted to illuminate a monitored volume, the illumination comprising a pulse sequence comprising a plurality of pulses, the pulse sequence repeating with a first period; a receiver having a field of view and adapted to receive light from at least one light source after having passed through the volume being monitored and further adapted to generate a signal indicative of the intensity of light received at a region in the field of view of the receiver, the receiver being arranged to receive light from the at least one light source in a series defined by an exposure time and a frame rate of reception; a processor associated with the receiver and adapted to process the signal generated by the receiver, wherein each of the plurality of pulses transmitted in the pulse train has a temporal position associated with a frame rate of reception.

The pulses in the pulse train have a duration of about half the exposure time. Preferably, the repetition period of the pulse sequence is substantially longer than the period between temporally adjacent frames. The frame rate is any one of the following ranges: 100-1500 fps, 900-1100 fps and 500-1200 fps. Most preferably, the frame rate is about 1000 fps.

The duration of the pulse is preferably about 1 to 100 mus. Most preferably, the duration of the pulse is about 50 μ s.

The exposure time is usually 2 to 200. mu.s. Preferably, the exposure time is about 100 μ s.

The pulse sequence may comprise at least one synchronization pulse. Preferably two. The pulse train may comprise at least one pulse of a first wavelength. The pulse train may comprise at least one pulse of the second wavelength. The pulse sequence may comprise at least one data pulse.

The frame rate and the time interval between each of the pulses are chosen such that, at least during a first period, there is a varying phase difference between them. The frame rate and the time interval between each of the pulses are selected such that each pulse in the sequence of pulses falls substantially within a respective exposure time.

In another aspect of the invention, there is provided a method for a particle detection system, the system comprising: at least one light source adapted to illuminate a monitored volume, a receiver having a field of view and adapted to receive said light from the at least one light source after it has passed through the monitored volume, and further adapted to produce a series of frames representing the intensity of light received at regions in said receiver field of view, and a processor associated with the receiver adapted to process signals produced by the receiver and provide an output; the method comprises the following steps: the number of light sources from which the receiver receives light is determined.

The method may further comprise: a number of frames output by the receiver is analyzed to determine a number of light sources.

The method may further comprise: operating the receiver at a high frame rate during the step of determining the number of light sources; and then operating the receiver at a second, lower frame rate.

The method may further comprise: a plurality of frames from the receiver are analyzed to identify regions of relatively large variation in received brightness levels between frames to identify candidate locations in the field of view of the receiver.

The method may further comprise: the change in brightness level received for locations between frames is compared to a threshold.

The method may further comprise: an attempt is made to synchronize the receiver with a predetermined transmission pattern expected for the transmitter and, if synchronization is successful, to determine that the candidate location is receiving light from the transmitter.

The method may further comprise: an attempt is made to synchronize the receiver with a predetermined transmission pattern expected for the transmitter and, without successful synchronization, to determine that the candidate location did not receive light from the transmitter.

The step of attempting to synchronize the receiver with a predetermined transmission pattern expected for the transmitter may include: capturing a plurality of at least partial frames comprising candidate locations; comparing the received frame with an expected pattern of received light corresponding to a pulse sequence emitted by the emitter; synchronization with the received pattern is attempted using a phase locked loop.

The step of comparing the received frame with the received expected pattern of light corresponding to the pulse sequence emitted by the emitter may comprise: determining a reference level of received light, the level representing a time instant at which no pulse is received for a candidate location; the brightness level received from each pulse is compared to the reference level and if the difference exceeds a predetermined threshold, it is determined that a pulse is received.

The step of comparing the received frame with the received expected pattern of light corresponding to the pulse sequence emitted by the emitter may comprise: it is determined whether a series of pulses corresponding to the desired pattern is received.

The method may further comprise comparing the determined number of light sources with a predetermined number of light sources; and repeating the determining step if the determined number does not match the predetermined number; or to signal a fault.

In order to more clearly explain each aspect of the invention and its implementation, it has been described with reference to separate embodiments. Those skilled in the art will readily understand how to combine two or more of such embodiments into an implementation of the present invention. Thus, it should be understood that the invention disclosed and defined in this specification extends to any combination of two or more individual features and aspects thereof as may be apparent from the text and drawings. All of these different combinations constitute various alternative aspects of the present invention.

Throughout the specification, the term "beam of light" will be used to refer to the output of a light emitter (e.g. an LED). The beam need not be collimated or confined to a single direction but may be divergent, convergent or any suitable shape. Similarly, "light" should be understood to refer broadly to electromagnetic radiation and is not limited to the visible portion of the electromagnetic spectrum.

As used herein, the terms "comprises" and variations thereof, such as "comprises," "comprising," and "comprising," are not intended to exclude additional components, integers or steps, unless the content specifically requires otherwise.

Drawings

Illustrative embodiments of the invention will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

FIG. 1 illustrates a conventional beam detector;

FIG. 2 illustrates a beam detector capable of implementing embodiments of the present invention;

FIG. 3 illustrates a beam detector capable of implementing embodiments of the present invention;

FIG. 4 shows a situation where reflections may be caused in the beam detector;

FIG. 5 illustrates a close-up view of a receiver in a beam detector made in accordance with an embodiment of the present invention;

FIG. 6 illustrates a beam detector structure fabricated in accordance with another embodiment of the present invention;

FIG. 7 illustrates a beam detector apparatus made in accordance with another embodiment of the present invention;

FIG. 8 shows another embodiment of a beam detector made in accordance with the present invention;

FIG. 9 schematically illustrates an embodiment of the invention in which the polarization states of the transmitter and receiver are aligned;

FIG. 10 schematically illustrates an embodiment of the invention in which the polarization states at the transmitter and receiver are arranged orthogonally;

FIG. 11 illustrates an embodiment of the present invention in which two orthogonally polarized beams are transmitted to a polarization sensitive receiver;

FIG. 12 illustrates an embodiment of the invention in which a transmitter transmits a single polarized beam to be received by two orthogonally polarized receivers;

FIG. 13 illustrates a plan view of a volume monitored by a particle detection system operating in accordance with an embodiment of the present invention;

FIG. 14 shows a cross-sectional view through the volume of FIG. 13, showing the receiver and one transmitter of the system;

FIG. 15 shows a schematic diagram of an example of a receiver for use in an embodiment of the invention;

FIG. 16 shows a schematic diagram of a transmitter for use in an embodiment of the invention;

Figure 17 schematically illustrates a smoke detector and mounting device according to the present invention;

figure 18 shows a cross-sectional side view of the smoke detector shown in figure 17;

figure 19 shows a side view of another embodiment of a smoke detector device according to the invention;

figure 20 shows a plan view of another embodiment of a smoke detector device according to the invention;

figure 21 shows a schematic view of a further embodiment of a smoke detector device according to the invention;

figure 22 shows a cross-sectional view of a smoke detector assembly made in accordance with an alternative embodiment of the present invention;

figure 23 is a schematic view of a smoke detector assembly having a first module and a second module, which is activated after the two modules are assembled;

FIG. 24 is a perspective view of a transmitter according to an embodiment of the present invention;

FIG. 25 is a close-up perspective view of the brake shoes and shaft of the launcher of FIG. 24;

FIG. 26 is a partial cross-sectional view of the receiver of FIG. 24;

fig. 27 is a perspective view of a receiver according to an embodiment of the invention;

FIG. 28 is a perspective view of the brake pads, lever arm and shaft of the transmitter of FIG. 27;

FIG. 29 shows a plot of two wavelengths of light received in a beam detector according to an embodiment of the invention;

FIG. 30 shows a plot of gain and modified output when a method according to an embodiment of the invention is performed;

FIG. 31 shows brightness levels at two wavelength bands received in an embodiment of the invention;

FIG. 32 shows the corrected output level and the adjusted gain level when the method according to an embodiment of the invention is performed under the conditions shown in FIG. 31;

FIG. 33 shows a particle detection system including a light source according to an embodiment of the invention;

FIG. 34 shows the light source of FIG. 33 when partially occluded by a foreign object;

FIG. 35 shows the light source of FIG. 33 when occluded by smoke;

FIG. 36 illustrates an alternative embodiment of the light source illustrated in FIGS. 33-35;

FIG. 37 shows a particle detection system including a light source according to an alternative embodiment of the invention;

FIG. 38 shows the light source of FIG. 37 when partially occluded by a foreign object;

FIG. 39 illustrates an alternative embodiment of the light source shown in FIGS. 37 and 38;

FIG. 40 illustrates an optical subsystem that can be used in embodiments of the present invention;

FIGS. 41 and 42 illustrate a light source according to yet another embodiment of the present invention;

FIGS. 43 and 44 illustrate the effect of modifying the beam width of a light source used in a particle detection system;

FIGS. 45 and 46 illustrate the advantages of different spatial distributions of different bands of light in the emitted light used in the particle detection system;

fig. 47 shows a luminaire that can be used in a first embodiment of the invention;

FIG. 48 shows further details of a luminaire that can be used in embodiments of the present invention;

fig. 49 shows a further embodiment of a luminaire that can be used in embodiments of the present invention;

FIG. 50 is a schematic block diagram illustrating circuitry that can be used in embodiments of the present invention;

FIG. 51 is a graph illustrating the operation of the circuit of FIG. 50;

FIG. 52 is a schematic block diagram illustrating a second circuit that can be used in embodiments of the present invention;

FIG. 53 is a graph illustrating the operation of the circuit of FIG. 50;

FIG. 54 shows a schematic view of a light source using a beam detector of an embodiment of the invention;

FIG. 55 shows a schematic view of a light source using a beam detector according to an embodiment of the invention;

FIG. 56 shows a schematic view of a light source using a beam detector according to an embodiment of the invention;

FIG. 57 shows a room in which a particle detection system according to an embodiment of the invention is installed;

FIG. 58 is a flow diagram illustrating one embodiment of a process that may be performed to install a beam detector that operates according to an embodiment of the present invention;

FIG. 59 shows a flow chart of one embodiment of a process that may be performed by the controller of the beam detector according to an embodiment of the invention after installation;

FIG. 60 shows a flow chart of another embodiment of a process that may be performed by a controller of a beam detector according to an embodiment of the invention after installation;

FIG. 61 schematically illustrates a portion of a transmitter in accordance with an embodiment of the invention;

FIG. 62 shows a second embodiment of the emitter shown in FIG. 61;

FIG. 63 illustrates an exemplary attenuator that can be used with embodiments of the present invention;

FIG. 64 is a timing diagram illustrating a transmit power diagram and corresponding receiver states illustrating another embodiment of the present invention;

FIG. 65 schematically illustrates a particle detection system employing a test filter according to an aspect of the present invention;

FIG. 66 illustrates an exemplary test filter fabricated in accordance with an embodiment of the present invention;

FIG. 67 is a graph of the transmission spectrum of a filter made according to an embodiment of the invention;

68-75 illustrate various embodiments of optical filters made in accordance with an aspect of the present invention;

FIG. 76 schematically illustrates a particle detection system made in accordance with an embodiment of the invention;

FIG. 77 illustrates an exemplary receiver fabricated in accordance with an embodiment of the present invention;

FIG. 78 shows yet another illustrative embodiment of an optical receiver in accordance with the invention;

FIG. 79 illustrates yet another optical receiver fabricated in accordance with an embodiment of the present invention;

FIG. 80 illustrates a fourth embodiment of an optical receiver made in accordance with embodiments of the present invention;

FIG. 81 is a schematic view of a beam detector using an embodiment of the present invention;

FIG. 82 is a schematic view of the beam detector shown in FIG. 81, showing different emitter positions;

FIG. 83 is a schematic diagram illustrating one embodiment of a diffusing device of an embodiment of the present invention in which the emitters are far enough that the light rays entering the lens are substantially parallel;

FIG. 84 is a schematic view showing another embodiment of the diffusion device of the present invention;

FIG. 85 depicts a further embodiment of an aspect of the present invention;

FIGS. 86-89 illustrate a plurality of wavelength filter devices that can be used with embodiments of the present invention (e.g., the embodiment shown in FIG. 85);

FIG. 90 is a schematic view of a fire alerting system that may be adapted to operate in accordance with an embodiment of the present invention;

FIG. 91 shows a schematic block diagram of a receiver component of a beam detector according to an embodiment of the invention;

FIG. 92 shows an exemplary pulse sequence for an embodiment of the present invention;

FIG. 93 schematically illustrates an environmental monitoring system in accordance with a first embodiment of the present invention;

FIG. 94 shows a second embodiment of an environmental monitoring system in accordance with a second embodiment of the present invention;

FIG. 95 schematically illustrates a light source that can be used with embodiments of the invention;

FIG. 96 illustrates a system made in accordance with yet another embodiment of the invention.

Detailed Description

Fig. 4 shows a beam detector of the type described above. The beam detector 100 includes a transmitter 102 and a receiver 104. A beam detector 100 is established to detect particles in a volume 101, which may be a room, for example. The emitter 102 emits a diverging beam of light covering an illumination area defined by a line 106. The light beam comprises a straight illumination path 108, which reaches the receiver 104 without reflection. Within the illumination area 106 of the emitter 102, some light rays will reach the receiver 104 through a reflected path, such as path 110, which is reflected on a ceiling 112 defining the volume 101. The inventors have determined that the presence of the reflected beam 110 can be ignored if certain conditions are met. For example, if the received beam meets the requirement of minimum received intensity; and in the case where the light beam contains distinguishable characteristics (e.g., wavelength components and/or polarization states) and the received light beam possesses these predetermined characteristics. In some cases it may be relevant whether the beam used for detecting the particles is a direct beam 108 or a reflected beam 110, for example in a multi-wavelength system, it is possible that the surface coating of the ceiling 112 is such that light in one wavelength band will be reflected more completely than light in a second wavelength band. When the wavelength band coincides with the wavelength band emitted by the transmitter 102 for particle detection by the receiver 104, the received differential measure of the light intensity in the two wavelength bands will behave differently in the reflected optical path 110 and the straight optical path 108. Thus, in this case, it is necessary to correctly discriminate the light beam 108 of the straight light path.

Fig. 5 shows a mechanism for determining a direct beam from a reflected beam in such a system. In fig. 5, corresponding parts will be denoted by the same reference numerals as in fig. 4. Fig. 5 shows a close-up view of the receiver 104 of the beam detector 100, showing the reflected beam 110 and the straight beam 108. Fig. 5 also shows details of the sensor 200 of the receiver 104. In this embodiment, the possibility of resolving a direct light beam 108 from the reflected light beam 110 is increased by providing the light receiver 104 with a sensor having a high spatial resolution. As described above, the sensor 200 of the receiver 104 includes a plurality of sensing elements 202, which sensing elements 202 are capable of independently detecting the intensity of received light at different spatial locations. In fig. 5, by providing a high resolution sensor 200, it can be seen that a group of pixels 208 is illuminated by a direct light beam 108, while a group of separate and distinct sensor elements 210 is illuminated by a received reflected light beam 110. If the size of the sensor elements is inherently large, it is not possible to resolve the two received beams into different groups of sensor elements. In a particularly preferred form, the spatial resolution of the light sensor is particularly high in the direction of the plane defined by the direct light beam and the reflected light beam.

In most embodiments, the controller of the beam detector can be arranged to determine which spot (e.g. 210 or 208) has the highest intensity and use the highest intensity beam for particle detection. Typically, the brightest received light beam will correspond to the straight light ray 108. In extreme cases, there may not be a sufficient discernable difference between the intensities of the two received beams. In this case, the light beam that reaches the receiver furthest from the reflecting surface is preferably chosen to be a straight light beam, since the other light beam (i.e. the light beam closer to the reflecting surface) is more likely to be reflected light.

In one exemplary embodiment, the resolution of the image sensor is 640 × 480 pixels.

Fig. 6 shows a further beam detector arrangement according to an embodiment of the invention. In this case, the beam detector 300 includes a transmitter 302 and a receiver 304. The operation of the beam detector is substantially the same as the beam detector described elsewhere. However, the beam detector arrangement also includes two baffles 306 and 308 attached to the reflective surface 310. Baffles 306 and 308 extend outward from reflective surface 310 toward a direct optical path 312 and serve to intercept a reflected optical path that may reach reflector 304. The number and length of baffles may be selected to suit a particular installation and may be positioned to extend almost entirely down toward the straight beam 312. Alternatively, if precise positioning is possible, a relatively short baffle may be used (if the precise position of the reflected beam can be determined). Another option involves a longer baffle having precisely positioned holes such that the straight beam 312 passes through the holes. As will be appreciated, the same effect can be achieved by placing the transmitter and receiver in close proximity to an existing structure that will function as a baffle, for example in a warehouse type installation where the warehouse has a plurality of horizontally extending ceiling-maintained beams (located below the ceiling), the transmitter and receiver may be located slightly below the beams so that the beams operate efficiently, as the baffle prevents interference from reflections from the ceiling surface.

Fig. 7 shows another embodiment of the present invention. This embodiment shows a beam detector arrangement 350 comprising a transmitter 354 and a receiver 356. The emitter 354 emits one or more beams of light covering a predetermined illumination area, and as discussed with reference to previous embodiments, both the direct beam 358 and the reflected beam 360 may reach the receiver 356. In this embodiment, the receiver is arranged so that it has a relatively narrow field of view θ in the direction of reflection and the receiver 356 therefore cannot "see" the reflective surface 362. If the receiver 356 cannot see the reflecting surface 362, the only optical path from the transmitter 354 to the receiver that will produce a strong enough signal to be discernable will be the straight beam 358. Similarly, the illumination area of emitter 354 may be limited so that it does not illuminate reflective surface 362. Typically, in a beam detector installation, the reflective surface will be the ceiling of the room being monitored. In this case, it is desirable to limit the field of view of the receiver 356 and/or the illumination area of the transmitter 354 in the vertical direction. A suitable field of view or illumination area will have a divergence angle between 0 ° and 5 °. However, this requirement will vary depending on the geometry of the system. It is clear that systems with long distances between transmitter and receiver (e.g. 100 meters) will require very narrow beam divergence angles or viewing angles to achieve this result. However, in embodiments with only 3 meters between the transmitter and receiver, a wider illumination angle and field of view is acceptable. The proximity to the reflective surface will also affect the angle required to achieve the aforementioned results.

FIG. 8 illustrates another embodiment of a beam detector in accordance with an aspect of the present invention. In this embodiment, the beam detector 500 includes a transmitter 502 and a receiver 504. Transmitter 502 includes two emitters 502A and 502B. Each emitter 502A and 502B emits one or more beams of light, covering its respective illumination area, and may direct a direct beam 508 and a reflected beam 510 that reach receiver 504. The two emitters 502A and 502B are arranged to be activated in a predetermined illumination sequence so that the source of the received light beam (i.e. from which emitter it came) can be determined by analysing the light received at the receiver 504. In this embodiment, light reaching the receiver 504 via the direct light path 508 will form an image 514A on a receiver sensor (not shown), while light received at the receiver through the reflected light path 510 will form an image, such as that shown at 514B, on the sensor of the receiver 504. As will be appreciated, the images formed on the receiver in both cases (i.e. direct and reflected) differ from each other in that one image is a mirror image of the other. The image 514A formed in a straight manner maintains the relative positions of the two light sources 502A and 502B, while in the image 514B formed in a reflective manner, the positions of the two light sources 502A and 502B are flipped in a plane containing the reflected light beam and the receiver. Thus, by analyzing the received images, it is possible to determine which pair of received light beams corresponds to the direct light path 508 and which pair corresponds to the reflected light path 510. In other embodiments of the present invention, rather than illuminating them with different modulation patterns, the two light sources 502A and 502B may be illuminants with different wavelength or polarization characteristics.

As will be appreciated by those skilled in the art, light arranged in any form may be imaged on the emitter. For example, a two-dimensional ray of some distinguishable illuminant can be incorporated into the emitter to allow determination of a reflected beam that is straight or from any reflective surface arbitrarily oriented with respect to the beam.

Turning now to FIG. 9, a beam detection system 1100 is shown. The beam detection system may be of any of the types described above and includes a transmitter 1102 and a receiver 1104. The emitter may emit any number of light beams in any one or more emission bands. One or more light beams emitted by the transmitter 1102 are received by a receiver 1104. In this embodiment, the emitter is arranged to emit polarized light (e.g. vertically polarized light). The receiver 1104 is only adapted to receive light having the same polarization state as the emitted light.

The polarization of the emitter can be achieved in a number of ways, including using an inherently polarized light source (e.g., a laser diode) or by placing a polarizing filter in the optical path of a randomly (or otherwise) polarized light source. Similarly, the polarization sensitivity of the receiver may be determined by the inherent characteristics of the receiver or by placing one or more polarizing filters in front of the sensor elements of the receiver.

In this example, the disruptive light that is not typically polarized or randomly polarized (e.g., ambient sunlight) will be substantially discarded by the receiver, while all of the emitted light beam (a small portion of which is eliminated by particles and objects between the emitter and receiver) will be received by the receiver 104.

Fig. 10 shows a system similar to that of fig. 9. The system 1200 in fig. 10 includes a transmitter 1202 that transmits a light beam 1206 that is received by a receiver 1204. In this example, the emitter is polarized in a first direction (e.g., polarized in a vertical direction) and emits at least one polarized light beam 1206. The receiver 1204 is arranged to receive light orthogonal to the polarization state of the light beam emitted by the emitter 1202. In this case, the receiver 1204 is adapted to receive horizontally polarized light. Such polarization misalignment presents the benefit that large particles (e.g., dust) can be distinguished from small particles (e.g., smoke) on the beam path 1206. This is because large particles (e.g., dust) tend to transmit scattered light with random polarization and thus increase the cross-polarization component of the light received at the receiver 1204.

A combination of the two embodiments described in fig. 9 and 10 may incorporate a particle detection system. Turning first to fig. 11, a system 1300 includes a transmitter 1302 and a receiver 1304. Emitter 1302 is adapted to emit light beams 1306A and 1306B. A first of the two light beams 1306A is arranged to emit in a first polarization state and a second light beam 1306B emits in an orthogonal polarization state. The receiver 1304 is arranged to receive light of only a single polarization state (e.g. the first polarization state). Thus, as will be appreciated, both techniques described with reference to fig. 9 and 10 may be used with the same receiver. Preferably, the transmitter 1302 is arranged to alternately generate the light beams 1306A and 1306B such that the light beams of the two polarization states reach the receiver 1304 at different times.

Figure 12 shows an alternative system. In this system, the beam detector 1400 includes a transmitter 1402 and a receiver 1404. The emitter 1402 is arranged to emit a vertically polarized light beam 1406. The receiver 1404 is adapted to be capable of splitting the received light into a plurality of polarization states, for example, into a vertical polarization state or a horizontal polarization state. This can be achieved by providing a plurality of adjacent light receiving elements having different polarization characteristics, which operate simultaneously or alternately. In this example, a beam splitting device 1408 is provided before the receiver elements to direct the light beam to each receiver.

As will be appreciated by those skilled in the art, vertical and horizontal polarizations are chosen for illustration purposes only, and any polarization state may be chosen. Further, for ease of description, orthogonal polarization states are chosen to describe the invention. However, the present invention should not be limited to polarization states that are aligned or orthogonal to each other. Other angular offsets between polarizations are also possible. One skilled in the art will be able to determine appropriate calculations to account for this variation.

One way to obtain a change in polarization state for a receiver or transmitter is to provide a mechanical means for placing a polarizing filter in the light path. For example, a solenoid may be used as an actuator to move a reciprocating polarizing filter into and out of the optical path. Alternatively, a rotating filter mechanism may be used having a plurality of filters of different polarization directions surrounding a wheel structure. By rotating the wheel structure through the optical path, different polarization states can be obtained over time. Other mechanisms are possible, for example, the light emitting element of the transmitter 402 may be physically rotated about an axis, as may one or more sensors of the receiver. Other mechanisms will be apparent to those skilled in the art.

Fig. 13 shows a plan view of a room 400A in which a beam detector system 402A according to an embodiment of the invention is installed. The beam detector system comprises a single receiver 404A arranged to monitor 8 transmitters 406A, 406B to 406H. Each of the emitters 406A-406H is adapted to emit light with a horizontal illumination angle of a degrees. It is also adapted to emit a vertical illumination angle with β degrees as shown in fig. 14. Similarly, the field of view of the receiver 404A is all different in its vertical and horizontal extent. In this example, the receiver 404A is adapted to receive light covering a horizontal viewing angle of γ degrees and a vertical viewing angle of degrees. In a preferred form of the invention, the emitters 406A-406H have a wider horizontal illumination angle than their vertical illumination angle β. Similarly, receiver 404A has a horizontal field of view that is wider than its vertical field of view.

The selection of different fields of view and illumination areas for the receiver and transmitter, respectively, takes into account alignment tolerances in a typical installation. For example, in most installations (such as that shown in fig. 13), the transmitters 406A-406H will typically be mounted at the same height as each other, while the receiver 404A will be mounted in a plane parallel to the transmitters 406A-406H. Thus, when images of the emitters 406A-406H are received on the light sensor of the receiver 404A, the images will tend to align on the light sensor. Thus, a relatively narrow field of view in the vertical direction may be allowable for the receiver 404A. However, as is apparent from fig. 4, the receiver 404A requires a very wide horizontal field of view. Similarly, horizontal alignment of the emitters 406A-406H is more difficult to achieve than vertical alignment in most installations. This is generally because the range of movement in a vertical plane is more limited and typically the walls of a building are arranged relatively parallel. For this reason, installers may be reluctant to install transmitters and receivers so that their fields of view are orthogonal to the plane of the surface on which they are mounted, and suitably accurate vertical alignment will be achieved. However, this may not be the case for horizontal alignment, as the illumination angle of the light source and the acceptance angle of the light receiver will differ from the orientation of the surface to which they are mounted due to the geometry of the mounted system. Thus, the ability to provide horizontal alignment is necessary, while the horizontal field of view of the receiver and the horizontal beam width of the transmitter are advantageously relatively wide.

For example, the receiver may be adapted such that the horizontal field of view is close to 90 degrees, while its vertical field of view is only about 10 degrees. Similarly, the transmitter may be arranged such that its horizontal beam width is about 10 degrees, while its vertical beam width may be between 3 and 5 degrees.

To obtain different horizontal and vertical beam divergence angles or viewing angles, the transmitter or receiver may be adapted to fit an optical system comprising an anamorphic lens.

Fig. 15 shows an exemplary structure of the receiver as described with reference to fig. 13.

Receiver 420 includes a multi-segmented light sensor 422 that is coupled to a video readout and processing subsystem 424. The optical receiver 420 includes an optical device 426, the optical device 426 including, for example, a plurality of lenses or other optical devices (e.g., mirrors) for focusing received light on the sensor array 422. In a preferred form, the anamorphic lens is arranged to provide the receiver with substantially different horizontal and vertical fields of view.

Fig. 16 shows an emitter 700 that includes at least one light emitter 702 adapted to emit one or more beams of light in one or more wavelength bands. The transmitter 700 includes a control circuit 704, the control circuit 704 being powered by a power source 706, which power source 706 may be, for example, a battery. The light emitter 702 emits a beam of light 708. This beam of light is shaped into a particular dispersion mode or beam shape by optical device 710. As described above, the optical device 710 may include one or more anamorphic lenses.

As will be appreciated by those skilled in the art, different installations will have different geometric limitations and requirements added thereto. Thus, the present invention should not be limited to the following cases: the beam shape of the transmitter (e.g., 406) or receiver (e.g., 404) is defined by its vertical or horizontal angle. Rather, the invention extends to systems in which either or both of the width of the emitter or the angular extent of the receiver are different in any two directions, whether they are orthogonal to each other or whether they are vertically and horizontally aligned.

Regardless of whether the particle detection system is of the type shown in fig. 1, 2 or 3, or of a different type as disclosed in, for example, PCT/AU2004/000637, PCT/AU2005/001723 or PCT/AU2008/001697, the alignment of the system components (e.g. the reflection of the light source back to the target and of the emitted light beam to the receiver) is important. As mentioned above, there can be a large distance between the light source and the target, and therefore, precise alignment of the light source and the target can be difficult. For this purpose, it is preferred to provide adjustable mounting means which allow the direction of the light source (and/or target if it is not retro-reflective) to be changed at the time of mounting and in the event of movement of the light source and/or target away from its mounting location.

FIG. 17 illustrates one embodiment of a beam alignment apparatus that facilitates alignment of the optics of the particle detector. The device shown in figure 17 is of the type discussed above with reference to figure 2, but the smoke detector may take many different forms. As shown, the smoke detector 2200 includes a light source 2202 and a receiver 2204. In addition, smoke detector 2200 includes a visual alignment device 2230 adapted to produce an alignment beam 2242, alignment beam 2242 being axially aligned with light source 2202 but visually observable. The light beam 2242 will impinge on a target 2206 some distance away from the smoke detector 2200.

The smoke detector 2200 is provided with mounting means in the form of a circular plate 2232, the circular plate 2232 being mounted, in use, to a support surface by screws or the like so as to secure the smoke detector 2200 to said support surface at a suitable height. An articulating joint 2234 is disposed between the mounting plate 2232 and the smoke detector 2200. The articulation may take a variety of forms which will allow the alignment of the detector to be changed, but which can be locked in a selected orientation. May be a friction brake device or some form of screw fixing device may be used.

As shown in fig. 18, the articulating joint 2234 includes a socket 2236 and a ball 2238 that can rotate within the socket. The ball is captively received in the socket to allow the smoke detector 2200 to tilt relative to the support plate 2232, thereby allowing the incident light 2210 to be directed accurately toward the target 2206 at a distance away. Grub screws 2240 are provided for locking the ball relative to the socket. Other ways of locking the ball in the socket are possible including, for example, a friction fit.

As depicted, alignment beam 2242 is used to facilitate alignment of incident light 2210 with a target. Thus, alignment beam 2242 (typically comprising a laser beam) is parallel to incident light 2210. The operator can thus aim alignment beam 2242 at or just near the target, thereby ensuring that incident light 2210 (which is generally invisible) is aimed at the center of the target. Once the incident light 2210 is aligned with the center of the target, the grub screws 2240 will be tightened, thereby locking the ball 2238 in the socket 2236. This will ensure that the smoke detector 2200 is ideally aligned so that the system can be calibrated in the manner described herein.

Figure 19 illustrates the manner in which the smoke detector 2200 is secured in a selected operative position. In this embodiment, a grub screw 2240 for locking the ball 2238 within the socket 2236 can be accessed along a passage 2244, the passage 2244 extending open to the first side 2246 of the probe housing 2200. The passage 2244 is configured to receive the shaft 2248 of the alignment tool 2250. The alignment tool 2250 has a drive 2252 at one end and a handle 2254 at the other end. The handle 2254 has a recess 2256 at its rear end, and the laser 2258 is inserted into the recess 2256. Shaft 2248 is a very small clearance sliding fit (close sliding fit) with passageway 2244, for example, when the shaft is in passageway 2244, laser beam 2242 from laser 2258 is axially aligned with light source 2202 and/or receiver 2204, as described above.

In this embodiment, shaft 2248 and passage 2244 each have a complementary cylindrical shape. Of course, those skilled in the art will appreciate that other arrangements are possible, such as passageways 2244 may have a square profile with side dimensions corresponding to the diameter of shaft 2248.

Thus, the installer uses the tool 2250 shown in fig. 19 to insert the shaft 2248 into the passage 2244 and then operates the housing 2200 while viewing the visible alignment beam 2242 at the remote target. When the housing is properly aligned, the handle 2254 is rotated and the tip 2252 of the drive device engages the grub screw 2240, thereby tightening the grub screw 2240 and locking the socket and ball together. Once locked together in this manner, the technician installing the device will check the laser beam 2242, which is still properly aligned with the target, and if so, will know that the smoke detector is properly oriented. It is clear that at any time in the future (e.g., whenever the equipment is serviced or overhauled), the orientation of the unit can be checked by simply inserting the shaft of the tool 2250 into the passage 2244 and again checking whether the laser beam 2242 is properly aligned with the target at the remote location.

In this embodiment, the drive 2252 is shown as the tip of a screwdriver, but it will be appreciated that if the grub screw had some other form of engagement, such as an Allen key female (Allen key), the drive 2252 would be of a suitably sized Allen key configuration.

Although fig. 19 shows a tool with a laser mounted for alignment purposes, it is of course possible to simply insert the laser 2258 into the passage 2244 to aid in alignment of the housing with respect to a remote target.

Figures 17 to 19 show an arrangement in which the beam is collimated to be parallel to the incident beam, but this is not the only possible arrangement. For example, the housing may have a plurality of laser receiving sockets therein that are angled with respect to the incident beam in a structure that facilitates mounting and orientation of the smoke detector with respect to a remote target or area of interest. For example, where the smoke detector has the form discussed above with reference to figure 3, it may be desirable to have a laser beam that also exhibits the full arc 2622 of source illumination. It will be appreciated that the housing 2200 may include a socket therein at an angle to the incident light beam corresponding to the full arc of illumination of the light source.

Fig. 20 schematically illustrates a housing having 3 receptacles 2249, each adapted to receive a tool 2250 as shown in fig. 19, so that an installation technician can properly align the housing for desired performance. The two lateral sockets 2249 are preferably aligned relative to the arc of visible light that the video camera can detect, while the middle socket will be used to align the center of the video camera with the target 2206 at a remote location.

Fig. 21 shows another embodiment of the present invention. In this embodiment, the visual alignment device 2260 includes a shaft 2262, which in turn is mounted in a socket of the smoke detector housing 2264 and will be aligned in a fixed direction with optics mounted in the housing 2264. A video camera 2266 is mounted on a handle portion 2268 at the end of a shaft 2262. The video camera will preferably be battery powered and adapted to produce images of a target at a location remote from the housing 2264. The video camera is preferably provided with a telescopic lens.

The images viewed by the video camera are preferably transmitted wirelessly to a receiver unit 2270, the receiver unit 2270 including a screen 2272 on which images of distant objects are displayed. The image may also include visual symbols or sights 2274, which may be in the form of cross hairs, or other alignment forms of some auxiliary sight, such as a grid pattern or other pattern.

It is clear that when moving the housing, the field of view of the video camera, and thus the image produced via the video camera, will move over the screen, and the technician performing the alignment of the smoke detector will be able to correctly orient the housing by viewing the image on the screen. Because the video camera is aligned with the optics of the smoke detector in a fixed relative alignment direction, once the image on the screen is properly aligned with the intended target, the skilled person will know that the optics are properly aligned. The receiver unit is preferably a hand-held, battery-powered computer device, such as a PDA or other device, that displays real-time images from the camera. The connection between the camera and the receiver is preferably wireless, but may also be via a cable.

The camera may be provided with a wavelength dependent filter mounted at the target location at the wavelength of the corresponding light source, e.g. an LED or other active or passive light source. The target light source may blink (optionally at a particular rate or manner) so as to be readily discernible by the human eye. The manner of flashing may also be recognized by software in the camera and/or receiver.

The software in the receiver unit and/or the camera may comprise means for generating an enhanced view of the target on the display and may comprise a surround image of the room or surface in which the target is installed. The combination of the receiver unit and the camera preferably comprises means for producing audible and/or voice indications to the operator to assist in the alignment process. These indications may be essentially indications indicating how to move the housing to properly align with the target, and may include words that can be heard, such as "up," "down," "left," "right," "hit," and other words.

It will be appreciated that with a video camera mounted at the end of the shaft 2262, slight movement of the housing about the articulated connection 2274 will cause the video camera at the end of the shaft to move through a relatively wide arc. The shaft thus acts as a lever arm, with a video camera mounted at the distal end of the arm. This increases the sensitivity of the alignment process so that once the video camera and optics are in the correct relative alignment, the optics will be precisely aligned in the desired direction when the video camera is correctly aligned with the target.

Fig. 22 illustrates an alternative housing structure for an optical device manufactured in accordance with an embodiment of the present invention.

In this example, device 2900 includes an electro-optical device (e.g., a camera or light source and its associated circuitry) and an optical device 2904. The electro-optical device 2902 is mounted in a fixed relationship relative to the housing 2906 and is connected to the electronic and data connection 2910 via a fixed wiring 2908.

The housing 2906 includes an aperture 2912, and a beam of light may enter and exit the housing through the aperture 2912. The aperture 2912 may be open or closed by a lens or window. The device 2900 also includes an optical assembly 2914 mounted to the housing 2906. In this case, the optical assembly is a mirror mounted at an angle to the optical axis of the electro-optical systems 2902, 2904. The mirrors are used to redirect the optical signal into and out of the electro-optical systems 2902, 2904 through the aperture 2912.

The mirror 2914 is mounted to the housing 2906 via an articulated mounting device 2916. In this case, the articulation mounting comprises a rotatable shaft mounted in a rotational friction bearing 2918, the rotational friction bearing 2918 being located in a correspondingly shaped recess 2920 of the housing 2906. The articulation mounting device 2916 includes an engagement device 2922 that can be engaged from the exterior of the housing 2906 using an alignment tool. For example, the alignment tool described with reference to the previous embodiments may be used.

In use, a technician installing the optics uses a fixed mounting device to attach the housing in a fixed manner relative to the mounting surface, and then adjusts the external field of view (or illumination area) of the electro-optical device 2902 by adjusting the orientation of the mirror 2914 using the alignment tool. The method of operation of the system is substantially the same as described above, except that the articulating enables the orientation of the optical assembly 2914 to be changed relative to the electro-optic device (which is fixedly mounted with the mounting surface) rather than enabling the entire housing to be realigned relative to the mounting surface.

FIG. 23 shows a beam detector assembly 2300, which may be, for example, a light emitter. The assembly 2300 is comprised of two modules. The module 2302 is a main housing that houses a battery (not shown) and an electro-optical system 2306 for the unit. The electro-optical system 2306 may be mounted on a circuit board 2308. Module 2302 also includes a switch 2310, which in one arrangement, switch 2310 is sensitive to magnetic fields. An example of such a switch is a reed switch having a pair of tabs located on ferrous metal reeds in a sealed glass envelope. The joints are initially separated. In the presence of a magnetic field, the switch is closed. Upon removal of the magnetic field, the stiffness of the leaves causes the tabs to separate.

Other switching devices that are sensitive to magnetic fields, such as hall effect devices, may also be used.

Module 2304 is a mounting base that includes an actuator that can act on switch 2310. For example, the actuator may be a magnet 2312.

Modules 2302 and 2304 are shipped and stored separately from one another or in a package where the actuator is separated from the switch by a sufficient distance to prevent actuation of the switch. Typically when installed, module 2304 is secured to wall 2320 or a mounting surface, while module 2302 is attached to module 2304. It will be appreciated that there are many means by which the module 2302 can be simply and securely mounted to the module 2304. For example, module 2304 may have one or more rails along which module 2302 may slide until encountering an obstruction during assembly. A detent arrangement may be provided to hold the two modules in place. Such an arrangement allows the two modules to be assembled in a predetermined orientation, thereby positioning switch 2310 relative to magnet 2312.

Only when the modules 2302 and 2304 are in the assembled state will the switch 2301 be closed, allowing the onset of significant power consumption from the battery.

In another arrangement, module 2304 includes a plurality of magnets 2312. The configuration of magnet 2312 may be used to represent an item of information, such as identification data about module 2304. This information may include a serial number or a cyclic address associated with the location of module 2304. By providing some form of magnet on the base module 2304, data can be effectively permanently retained where the module 2304 is attached to the wall 2320. Thus, even if module 2302 is replaced, for example, after a failure (e.g., a discarded battery), the identification data is still present.

Module 2302 can include a plurality of switches 2310 or sensors that are sensitive to the magnetic fields present in module 2304. For example, an array or predetermined pattern of reed switches may be provided that are capable of reading the identification data encoded in the magnet form of the module 2304.

In another arrangement, the magnet 2312 form in module 2304 may be provided on a removable device (e.g., a card). A card with a magnet of the form described may, for example, be inserted into the module 2304 when the module 2304 is secured to the wall 2320.

Figures 24 to 26 show an alternative embodiment of the invention. The emitter unit 3000 includes a housing 3200, which forms an optical module. The emitter further comprises a back plate 3010, a back cover 3020 and a front cover 3030, which together form a mounting portion 3180.

The footplate 3010 includes screw holes through which the footplate 3010 may be mounted to a mounting surface (not shown) (e.g., a wall). The footplate 3010 is attached to the back cover 3020 by means of a simple, releasable snap fit.

The rear cover 3020 and the front cover 3030 together define a partially spherical cavity in which the housing 3200 is received. The housing 3200 includes a rear housing 3040 and a front housing 3050. Each of the rear case 3040 and the front case 3050 has a shell-like structure which is obviously a hollow hemisphere.

The rear housing 3040 has a lip around its outer perimeter. The front shell 3050 has a complementary lip inside its outer perimeter. The complementary lips snap-fit together to define a spherical shell 3200. In the vicinity of the snap-fit, a small portion of the rear housing 3040 extends into the front housing 3050 and defines an annular step therearound.

The outer surface of the probe housing 3200 is substantially spherical and is complementary to the spherical cavity defined by the rear cover 3020 and the front cover 3030. There is a very small clearance sliding fit between the complementary spherical surfaces so that housing 3020 can be rotated to a wide range of orientations relative to mounting portion 3180 and loosely frictionally held in alignment during installation.

The front end of the front cover 3030 is open to expose the housing 3200. In this embodiment, the shape and degree of curvature of the opening in the front cover 3030 allows the housing 3200 to articulate about a vertical axis to a wider range of angles than a horizontal axis: typically such transmitters are mounted on the wall, close to the ceiling, as are the corresponding receivers, and therefore typically require less adjustment about the horizontal axis (i.e. up and down).

The front end of the front housing 3050 is truncated to define a circular opening in which the lens 3060 is carried. A circular Printed Circuit Board (PCB)3070 is centrally mounted within the housing 3020 and spans the housing 3020. The PCB 3070 is parallel to the lens 3060 and rests on an annular step defined by the rear housing 3040 that extends into the front housing 3050.

A light source 3080 in the form of an LED is mounted centrally on the front surface of the PCB 3070 and projects, in use, a beam of light, for example in one or more wavelength bands, the obscuration of the beam providing an indication of the presence of particles. The lens 3060 is arranged to collimate the beam projected by the LED 3080. Battery 3090 is carried on the rear surface of PCB 3070.

The illustrated embodiment includes a locking mechanism 3190 that includes a shaft 3240, a cam 3100, and a brake pad 3110, as shown in fig. 25. The shaft 3240 has an outwardly projecting collar 3140 at its axial midpoint.

Each of the rear housing 3040 and the front housing 3050 includes a tubular recess for receiving a respective portion of the spindle 3240. When the rear and front housings are snap-fit together, the collar 3140 is captured between the rear housing 3040 and the front housing 3050. An O-ring seals around the shaft, in the forward and rearward direction of the collar 3140, restricting debris from entering the housing 3200 via the tubular recess.

A hexagonal wrench socket 3160 is formed in a front end surface of the rotation shaft 3240. A cylindrical tubular passageway 3244 passes through the front housing 3050 and may lead to a female head 3160. During installation of the emitter unit, female head 3160 receives an allen key type device from the front of emitter unit 3000 via passageway 3244 so that the installer can rotate spindle 3240 about its axis. As will be described, the rotation causes the housing 3200 to be locked in a selected orientation relative to the mounting portion 3180.

The rear housing 3040 has a rearward aperture in which the brake pad 3110 is carried. The brake pad 3110 has an outer surface 3130, the outer surface 3130 being partially spherical and aligned with the spherical outer surface of the rear housing 3040 when in the retracted "articulated position". The brake pad 3110 is provided with a support 3120 on each side thereof. The support 3120 extends a short lateral (i.e., in a direction perpendicular to the up-down and front-to-back directions) distance. The strut 3120 is received in a complementary recess (not shown) in the rear housing 3040 and thereby defines a pivot about which the brake pad 3110 can be rotated through a range of motion. The range of motion is limited by contact between the braking surface 3130 and the internal spherical surface (defined by the rear cover 3020 and/or the front cover 3030) and also by contact with the cam 3100 described below.

As shown in figure 25, the brake pad 3110 includes a central longitudinal channel separating two wings, each carrying a respective strut 3120. The brake pad 3110 is somewhat compliant such that the brake pad 3110 and the rear housing 3040 can be assembled by compressing the wings to reduce the overall size across the strut 3120 and to mate the brake pad 3110 with the rear housing 3040 such that the strut 3120 is received in a complementary recess (not shown) formed in the rear housing 3040. Once released, the wings return to their uncompressed shape so that the strut 3120 snaps into engagement with the complementary recess.

The cam 3100 is carried by a shaft 3240. Of course, another option is that the cam would be formed integrally with the shaft, as shown in FIG. 28. Cam 3100 comprises a single lobe and is arranged to act downwardly on stop block 3110 at a location forwardly away from strut 3120 (and the pivot axis defined thereby).

During installation of the receiver 3000, after aligning the housing 3200, an installer uses a tool, such as an allen key, to enter the female end 3160 of the shaft 3240 via the passageway 3244. Rotation of the shaft 3240 using a tool such as an allen key rotates the cam 3100 which in turn drives the front portion of the brake pad 3110 downwardly so that the braking surface 3130 frictionally engages the inner spherical surfaces defined by the rear and front covers 3020 and 3030. Thereby, the alignment of the housing 3200 with respect to the mounting portion 3180 is locked.

In this embodiment, the lens 3060 and the LED 3080 are arranged to project light in a direction perpendicular to the plane of the lens 3060. The passageway 3244 is also perpendicular to the plane of the lens 3060. An alignment tool similar to that described above may be used during installation, where the alignment tool has a cylindrical shaft sized to slip fit with the channel 3244 with a very small clearance, and includes a laser pointer arranged to project a beam of light coaxial with the shaft. In this embodiment, the shaft of the alignment tool terminates in an allen key that complementarily fits the female head 3160. During installation, the tool is inserted into the passageway 3244 and engages the female head 3160. After engagement, the alignment tool may be used as a lever and may be manipulated until its projected beam is focused on a target (e.g., a receiver). The pathway 3244 thus provides a convenient means for providing a visual indication of the alignment of the housing 3200. The alignment tool may then simply be rotated about its axis to lock the housing 3200 in the correct alignment.

As noted above, it is desirable that the power source (in this case battery 3090) be connected (to activate the transmitter) only when quickly installed. The collar 3140 of the shaft 3240 carries magnets 3150 at points of its circumference. The relative positions of the magnet 3150 and the lobe of the cam 3100 are selected such that when the stop block 3110 is in the forward "brake" position, the magnet 3150 interacts with a reed switch (not shown) mounted on the rear surface of the PCB 3070 to close the switch and thus connect the power activation receiver 3000. The position of the magnet on the collar 3140 relative to the lobe of the cam 3100 is selected so that when the stop block 3110 is in the retracted "articulated" position, the position of the magnet 3150 does not act on the reed switch, so that the reed switch remains open and the receiver remains deactivated.

The transmitter unit 3000 is easy to install. The receiver 3000 may be provided as a pre-assembled unit-the locking mechanism is in a retracted articulated position so that the battery is not connected and cannot run out. The backing plate to which rear housing 3020 is attached by a simple snap fit is pried up (i.e., not snapped on) and screwed or otherwise secured to a wall or other mounting surface. The rear cover 3020 and the remainder of the receiver 3000 attached thereto are then simply snapped onto the backing plate. The housing is then aligned using the aforementioned alignment tool and then simply and conveniently locked in that alignment position and activated by a single movement of the same tool.

Fig. 27 and 28 show another alternative embodiment of the invention (similar to the embodiment described in fig. 24 to 26). Fig. 28 is similar to fig. 25, however fig. 28 shows a receiver 3000' that can be used in embodiments of the present invention. Receiver 3000 'includes a passageway 3244' through which passage 3244 'may access a shaft 3240', as in the previous embodiments. This embodiment differs from the embodiment of fig. 24 in the details of the locking mechanism. The spool 3240 'includes an integrally formed cam 3100' arranged to act on a pivotally mounted lever arm 3210.

The lever arm 3210 has a length in a lateral direction (i.e., perpendicular to the up-down and front-to-back directions). The post at 3120' extends forward from one end of the lever arm 3210. The support 3120 ' is received in a complementary recess (not shown) defined within the transmitter housing 3200 ', where the lever arm 3210 is pivotally supported in the transmitter housing 3200 '.

A short strut 3230 extends in a fore-aft direction from the other end of the lever arm 3210. The struts 3230 are coaxially aligned. Stop 3110 'comprising an upwardly extending prong means surrounds the other end of the lever arm and engages post 3230 to pivotally connect lever arm 3210 and stop 3110'. The brake pad 3110 'extends downwardly from the lever arm 3210 and has a square cross-section defining a partially spherical braking surface 3130'.

Stop block 3110 'is located in and guided by a tubular bore (not shown) having a complementary square profile located in emitter housing 3200'.

The shaft 3240 'is rotated during installation of the launcher 3000', as in the previous embodiment. As the shaft 3240 ' is rotated, the cam 3100 ' acts to drive the lever arm 3210 downwardly about its pivot axis (defined by the strut 3120 '). The brake pad 3110 'is in turn urged downwardly into frictional engagement with the inner surface of the fixed mounting portion 3180'.

Lever arm 3210 includes an integrally formed finger 3220 that extends downwardly from the end of lever arm 3210 at an acute angle to the body of the lever arm. The fingers 3220 define a curved path having an outer surface that is complementary to the interior of the emitter housing 3200'. Finger 3220 is sized to press against the inner portion and thereby bias lever arm 3210 to rotate upwardly about its pivot axis (defined by post 3120'). The brake pad 3110' is thereby biased against the cam towards a retracted non-braking position.

As mentioned above, contamination of the optical surfaces over time can cause some problems in the beam detector. To solve the problem, the inventors have determined that the system can be adapted to compensate for contamination of the optical system over time. Fig. 29 shows how the true received light level (i.e. the level of light reaching the receiver or light sensor of the system) decreases over time. Fig. 29 shows a plot of the true light level reaching the sensor of the beam detector receiver over time between times t1 and t 2. As can be seen from the figure, the received wavelength is λ ₁And λ₂The light level of the light decreases over time due to the constant accumulation of contamination of the surface of the optical system of the receiver. To compensate for the loss of sensitivity, in one embodiment of the invention, the system gain is correspondingly increased very slowly over time (as shown in FIG. 30), such that the detected intensity λ₁And λ₂Can remain substantially stable over time.

It can be seen that FIG. 31 is similar to FIG. 30, except for the band λ₁And λ₂Is not loweredThe same is true. In this embodiment, λ₂Signal ratio λ of₁The signal at (a) is more affected by contamination of the optics. In such a case, a system using the difference or relative value between the signals received in the two bands, likely as a function of the wavelength λ received₁And λ₂The difference between the signals at (a) increases and a false alarm condition is entered. To address this problem, the gain is adjusted differently for each wavelength, and as shown, when the gain is adjusted, as shown in fig. 30, the long term average output of the system remains substantially constant.

In the example of fig. 31 and 32, the smoke event 3500 occurs approximately midway between times t1 and t 2. In this case, because of λ₁Effectively operating as a reference wavelength, which experiences very little intensity drop, however, the received lambda ₂The signal at (a) undergoes a very significant drop because of lambda₂The tendency to be absorbed by small particles is more intense. It can be seen that because the smoke event has such a short duration compared to the compensation applied to the gain, long term compensation for system contamination is not affected by the occurrence of the smoke event 3500, and the smoke event 3500 is also reliably detected by the system.

Referring to fig. 33 to 35, a light source 3300 according to an embodiment of the present invention is shown. Light source 3300 includes a housing 3302 with a transmissive region 3304 through which light is emitted from light source 3300 to reach a receiver 3306.

In this case, transmissive region 3304 is located outside of housing 3302 and provides points at which light from within housing 3302 is transmitted from light source 3300 toward receiver 3306. For this reason, the transmissive region 3304 is accessible from outside the light source 3300 and may be affected by dust/dirt accumulation, insect/insect activity, and the like. Without limitation, transmissive region 3304 may be any optical surface (or portion of an optical surface), and although for purposes of description, the transmissive region has been shown as protruding from housing 3302, it may naturally also be flush with the walls of housing 3302 or recessed within the walls of housing 3302. The transmissive region 3304 may be integral with the housing 3302, or may be an integral part thereof.

In the present embodiment, the housing 3302 encloses the first, second, and third light emitters 3308, 3310, 3312. Each of the emitters 3308-3312 is an LED and emits a beam of light (3314, 3316, and 3318, respectively) through the transmissive region 3304 to the receiver 3306. The first emitter 3308 and the third emitter 3312 emit electromagnetic radiation in a first spectral band, e.g., ultraviolet light of substantially equal wavelengths (i.e., light in the ultraviolet portion of the electromagnetic spectrum), and therefore should be referred to as ultraviolet emitters. The second emitter 3310 emits electromagnetic radiation in a second spectral band, e.g., infrared light (i.e., light in the infrared portion of the electromagnetic spectrum), and therefore should be referred to as an infrared emitter. Correspondingly, beams 3314 and 3318 are referred to as ultraviolet beams and beam 3316 is referred to as infrared beam.

The light source 3300 further comprises a controller 3320 adapted to control the operation of the first, second and third light emitters 3308-3312. The controller may be housed in the housing 3302, as shown, or may be remote from the housing and remotely control the operation of the lights 3308-3312.

As will be appreciated, the specific manner in which the controller 3320 operates the lights 3308-3312 depends on the programming of the system. In this embodiment, the controller 3320 controls the operation of the light emitters 3308 to 3312 in turn in a repeating alternating sequence. The processing of these beams received by receiver 3306 is discussed in further detail below.

The controller may also be adapted to operate one or more of the lights 3308-3312 to send control signals to the receiver 3306. Such control signals may indicate status information about the light source 3300, e.g., indicating that the light source 3300 is operational, indicating that the light source 3300 is malfunctioning, and/or indicating that the battery of the light source 3300 is depleted. The control signal may be determined by the timing and/or intensity of the light beams 3314, 3316 and/or 3318 emitted by the respective light emitters 3308-3312.

It can be seen that uv emitters 3308 and 3312 are separated from each other, which in turn results in separation of the points at which uv beams 3314 and 3318 exit transmissive region 3304. The ultraviolet emitters (and ultraviolet light beams 3314 and 3318) are separated by a sufficient distance such that if transmissive region 3304 is blocked by foreign object 3322, only one of ultraviolet light beams 3314 or 3318 will be blocked. For this reason, a separation of about 50mm between first light beam 3314 and third light beam 3318 is considered suitable. Thus, the device effectively provides a backup light emitter in the ultraviolet band.

The term "foreign object" is used herein to refer to an object or unwanted particle that is larger than a dust or smoke particle or other particle of interest that may be present in the air. As an example, the foreign object that obscures the transmissive region 3304 may be an insect or bug that crawls through the transmissive region 3304.

Fig. 34 shows an example where a single ultraviolet light beam 3318 is blocked, and the remaining infrared light beams 3314 are not blocked. In this case, receiver 3306 identifies a fault condition rather than an alarm condition because it only receives the desired ultraviolet pulse every other time.

If this condition (i.e., only one of ultraviolet light beams 3314 or 3318 is received at receiver 3306, or one of the received ultraviolet light beams 3314 or 3318 is significantly less bright than the other due to partial occlusion) persists for a significant amount of time (e.g., 1 minute), receiver 3306 may be programmed to interpret this as an error/malfunction of light source 3300 and trigger an appropriate alarm/error message.

Fig. 35 shows the situation where smoke particles 3324 obscure 3 beams 3314 to 3318, compared to the obscuration shown in fig. 34. In this case, smoke 3324 attenuates each of beams 3314 and 3318 by substantially the same amount, and common alarm logic can be applied to determine if an alarm or fault condition exists.

Fig. 36 provides an alternative to the above embodiment. Similar to the previous embodiments, the light source 3600 includes a housing 3602 and a transmissive region (or window) 3604 through which light beams 3614, 3616, and 3618 are emitted to a receiver 3606. The operation of the light source 3600 is controlled by the controller 3620. Ultraviolet light beams 3614 and 3618 are emitted from a single ultraviolet emitter 3626. In this case, the light source 3600 includes a beam splitter 3628 that splits the light beam from the light source 3626 such that the first and third light beams 3614, 3618 are separated from each other by a sufficient distance to exit from the transmissive region 3604, as described above.

Turning to fig. 37-40, another alternative embodiment of a light source 3700 for a particle detection system is provided. The light source 3700 includes a housing 3702 with a transmissive region 3704 through which light is transmitted 3704 from the light source 3700 to the receiver 3706. The transmissive region 3704 is as described above with reference to the transmissive region 3604, however it can be seen that it is much smaller than the transmissive region 3604.

The housing 3702 houses the first and second LED lights 3708 and 3710. Emitter 3708 is an ultraviolet emitter and emits an ultraviolet beam 3712, while emitter 3710 is an infrared emitter and emits an infrared beam 3714. The light source 3700 also includes a controller 3716 adapted to control the operation of the first and second light sources 3708 and 3710. The controller may be housed in the housing 3702, as shown, or may be remote from the housing and remotely control the operation of the lights 3708 and 3710.

As shown, the light source 3700 is positioned (as described below) such that light beams 3712 and 3714 exit the light source from the transmissive region 3704 along substantially the same path. Most preferably, they are collinear. This arrangement provides the feature that if the transmissive region 3704 is blocked by a foreign object 3718, as shown in fig. 38 (again, for example, an insect climbs through the transmissive region), the ultraviolet light beam 3712 and infrared light beam 3714 are blocked to substantially the same extent.

When the foreign object 3718 obstructs the transmissive region 3704, it causes substantially the same obstruction of the first and second light beams 3712 and 3714, and the controller associated with the receiver will apply alarm and/or fault logic to determine the cause of the drop in received light level. The fault and alarm logic may be arranged to interpret the same and simultaneous drop in received intensity in the following manner. In some cases with a small drop in intensity, the system may interpret this as a fault or occlusion. If the condition persists, it can be compensated for in software or elevated fault conditions. A large intensity drop can cause an alarm even if the basic alarm criterion is based on differential attenuation of two bands, as described in our co-pending patent application.

Fig. 37 and 38 provide an embodiment of a light source 3700 that is configured to provide light beams 3712 and 3714 that exit the light source 3726 from the transmissive region 3704 along a substantially collinear path. In this embodiment, light beams 3712 and 3714 do not originate from physically close light sources 3708 and 3710, but are brought close to each other by light guide 3722 before reaching the transmissive region. Light guide 3722 may be any optical device suitable for guiding light, such as a mirror, lens (e.g., convex lens, concave lens, fresnel lens), and/or prism or combination thereof, and may also function to collimate light beams 3712 and 3714.

Fig. 39 provides an alternative embodiment of emitter 3724, which is positioned such that beams 3712 and 3714 exit the source close together from transmissive region 3726. In this embodiment, the first and second light emitters 3728 and 3730 are semiconductor dies housed in a single optical package 3732 (transmissive region 3726 is the point at which emitted light beams 3712 and 3714 exit package 3732). In this embodiment, the proximity of beams 3712 and 3714 is achieved by the physical proximity of semiconductor dies 3728 and 3730 in package 3732 and the release effect (discharging effect) of package 3732.

This may be achieved by using LEDs with multiple semiconductor dies in a common LED package. Fig. 47 to 49 show examples. As is typical with LEDs, the housing is made of a transparent material and is shaped to have a lens effect on the emitted light beam, which generally constrains the light beam in the forward direction.

In another embodiment, and as shown in fig. 41 and 42, the light source 3700 is also provided with beam shaping optics 4102 for adjusting the shape of the light beam emitted from the emitters 3708 and 3710. Although fig. 41 shows a single element, in practice (and as shown in fig. 42), the beam shaping optics 4102 may include multiple beam adjusting elements to adjust the beam width and/or beam shape of the light emitted from the light source 3700 to the receiver 3706 in a variety of ways.

Beams 3712 and 3714 (from emitters 3708 and 3710) pass through beam shaping optics 4202, which optics 4202 function to set desired characteristics for adjusted beam 4104, as described below.

As will be appreciated, the beam will have a spatial intensity distribution or beam profile in a direction transverse to its axis. Using the beam profile, the beam width of the beam between two points of equal intensity (e.g., 3db points on either side of the maximum, etc.) can be defined. One common measure of beam width is the "full width at half maximum (FWHM)" of the beam. For example, modulated beam 4204 in FIG. 42 is shown having a wide cross-section 4212 within which beam 4202 has an intensity above a predetermined threshold (shown in black), beam cross-section 4216 having an intensity below the predetermined threshold forming the periphery of the threshold.

Beam shaping optics 4102 can be selected to obtain a desired beam profile, and calibration element 4208 functions to calibrate beams 3712 and 3714 to a tighter beam shape. The collimating element 4208 may be, for example, a lens (e.g., a fresnel lens or a convex lens) or a reflector.

Beam conditioning optics may also include a diffuser element 4210, selected to "flatten" the beam profile and increase the beam width of beams 3712 and 3714. The diffusing element may be, for example, a ground glass/etched glass/fumed glass diffuser. Alternatively, the diffusing element 4210 may be a coating applied to the transmissive region 3704 or another beam conditioning device.

Fig. 40 shows an exemplary optical element 4000 that shapes and flattens the beam profile. The optical element 4000 includes a fresnel lens 4080 placed back-to-back with a multi-element lens 4801. The fresnel lens collimates the beam and the multivariate lens 4801 efficiently diffuses the beam. Instead of the multi-element lens 4801, another diffuser (e.g., ground glass, fumed glass, or etched glass or surface) may also be used.

Providing a diffuser on the emitter is advantageous because the receiver will "see" an extended spot corresponding to the light source, rather than a point (which would be seen without the diffuser). Thus, any foreign object (e.g., insect) located in the transmissive region 3702 will cover a small portion of the transmissive region and thus have a proportionately smaller effect on the total amount of light received at the receiver 3706. Furthermore, in a multiple beam system, when all of the illuminants (3708 and 3710, i.e., at both the ultraviolet and infrared wavelengths) are diffused through a common element, any foreign object (e.g., insect) on the transmissive region 3702 will have substantially the same degree of influence on each wavelength of light (i.e., both the ultraviolet and infrared).

Furthermore, by providing a larger beam width for the conditioned light beam 4204, alignment of the receiver 3706 with the light source 3700 is simplified. Fig. 43 provides a depiction of a receiver 4350, the receiver 4350 receiving a light beam 4352 from a light source 4354. By having a wide beam width, the rate of change of intensity across the beam width (near its center) is reduced. This means that, for small relative movements, the rate of change of the received intensity near the centre of the beam is reduced compared to a beam with a narrow beam width, due to the drift of the alignment of the beam and the receiver over time.

In this case, beam width 4356 of beam 4352 corresponds to approximately 3 sensor elements on sensor 4350. If the system is designed to average (or sum) the outputs, these 3 pixels are used to determine the intensity of the received beam, a small change in alignment between the receiver and transmitter will require the system to accurately track the beam movement over the sensor surface, or alternatively, cause a large change in the signal intensity measured from these 3 pixels. This problem is solved to the maximum extent by using a wider beam width as shown in fig. 44. In this system, the light surface 4454 emits a light beam 4462 having a width 4456 equal to the size of about 6 sensor elements on the sensor 4450. As will be appreciated, such a system is more tolerant of alignment drift before the middle 3 pixels are outside the middle high intensity beam region.

The specific characteristics of the diffuser used and the beam width provided will depend on the receiver and the emitter. However, using LEDs, a beam width of about 10 degrees has been found to be a suitable compromise between intensity preservation and width of the conditioned beam to accommodate easy alignment of the receiver with the light source and drift of the receiver and/or light source.

Referring to fig. 42, the profile adjustment element 4212 is selected such that the beam profile of the adjusted light beam 4204 extends more in the horizontal direction than in the vertical direction. This serves to maximize the intensity of the modulated light beam 4202 at the receiver, while also taking into account the fact that: the movement that accumulates is generally more variable in the horizontal plane than in the vertical plane.

The light source may comprise a wavelength dependent distribution adjusting element 4212 for providing different intensity distributions for the light beams of different wavelength bands. Further, the beam conditioning elements may be lenses, reflectors, coatings, etc., selected to provide a desired beam distribution at each wavelength.

Distribution adjusting element 4212 has the effect of producing an adjusted beam 4204 having a beam distribution in which the beam width of the ultraviolet light (originating from ultraviolet emitter 3708) is wider than the beam width of the infrared light (originating from infrared emitter 3710). This is illustrated in fig. 45 and 46, the light source 4500 emits a light beam 4502 in which the beam width of the ultraviolet light 4504 is wider than the beam width of the infrared light 4506. This has the advantage that once the light source 4500 or receiver 4508 are moved (e.g., due to accumulated movement) and the alignment between them is broken, the infrared light 4506 (with a narrower beam width) will lose alignment with the receiver 4508 earlier than the ultraviolet light (i.e., reduce the amount of infrared light received at the receiver). This causes a decrease in the intensity of the infrared light at the receiver, followed by a decrease in the intensity of the ultraviolet light, as the alignment becomes progressively worse. This is in contrast to the effect seen when smoke enters the beam, where ultraviolet light falls before infrared light. Thus, misalignment can be distinguished from smoke events by the fault/alarm logic of the controller.

As an alternative to using a distributed tuning element, the light source may employ a plurality of ultraviolet emitters surrounding one or more infrared emitters. In this case, as the alignment of the light source and receiver is broken, the receiver will cease receiving the infrared beam before it ceases receiving the ultraviolet beam, thereby allowing the receiver to interpret this as a fault rather than an alarm event.

In some embodiments, an anomalous intensity distribution may be formed, such as an intensity distribution having a sinc function or similar form. In this case, the controller can determine that the light beam sweeps over a sensor element or a group of sensors of the receiver sensor if the sensor element or the group of sensors detects a change in the intensity of the received light beam that matches the spatial intensity distribution of the emitted light beam. This can be detected by fault logic and signaled that the system is gradually misaligned and needs or is about to need realignment.

Fig. 47 shows an illuminant 4740 that can be used for an emitter of a beam detector according to an embodiment of the invention. The luminaire 4740 includes a body 4742 in which one or more light-emitting elements (not shown) are housed. Emitter 4740 includes a lens or window portion 4744 through which the light beam generated by the light emitting element is emitted. It also includes a plurality of leads 4746 for making electrical connections to the device. Fig. 48 shows a plan view of the same illuminant 4740. The light 4740 includes a plurality of light emitting elements 4748, 4750. In this case, the light emitter is an LED and the light emitting element is two LED bare chips in the form of an ultraviolet LED bare chip 4748 and an infrared LED bare chip 4750, which constitute the light emitting element. The package 4740 also includes a photodiode 4752 in the body 4742. Each of the light emitting elements 4748, 4750 is adapted to emit light through the lens 4744. The photodiode 4752 receives some portion of the light emitted by the light-emitting elements 4748, 4750 and generates an electrical signal that is supplied to a feedback circuit. The output signal of the photodiode is used by a feedback circuit to adjust the output of the light emitting element to maintain proper operation of the light 4740.

Fig. 49 shows a second embodiment of a light source. In this example, luminaire 4955 includes a plurality of light emitting elements arranged in a checkered pattern. In this case, emitter 4955 includes 4 ultraviolet LED die 4958 arranged around a central infrared LED die 4960. As mentioned above, such an arrangement may have particular advantages for preventing false alarms caused by misalignment of a light source and its corresponding receiver. The package 4955 also includes a photodiode 4952.

Fig. 50 shows a schematic block diagram of a circuit of a transmitter that may be used in embodiments of the invention. The circuit 5000 includes 2 luminophores 5002, 5004, e.g. corresponding to infrared and ultraviolet LED dies as described above. It also includes a photodiode 5006. As is apparent from the above description, LEDs 5002, 5004 and photodiode 5006 may be packaged in a single LED package in close proximity to each other. However, they may also be packaged separately in separate components. The light emitters 5002, 5004 are electrically connected to a current source 5008, and the photodiode 5006 is electrically connected to a feedback circuit 5010. The feedback circuit 5010 is in communication with the current source 5008. In use, the output from the photodiode 5006 (which is representative of the output of the LEDs 5002, 5004) is directed to the feedback circuit 5010, which in turn controls the output of the current source 5008 to the luminaires 5002, 5004. As the optical signal received at the photodiode 5006 decreases, for example due to the light output of the LED decreasing over time or the light emission of the light emitters 5002, 5004 decreasing (due to an increase in temperature), the feedback circuit 5010 will produce an output to the current source 5008 that causes the drive current of the light sources 5002, 5004 to increase. In this way, the light output of the luminophores 5002, 5004 can be maintained at a substantially constant brightness. Because the luminaires can have different characteristics, as well as predetermined lighting characteristics required for proper operation of the system, the outputs of the two luminaires 5002, 5004 can be controlled and adjusted individually. This can be achieved by optionally pulsing their illumination and individually determining their light output using the photodiode 5006. Alternatively, a plurality of photodiodes may be used in the following manner: wherein the response of the photodiodes is wavelength selective and tuned to the corresponding luminophores. This may be achieved, for example, by providing a different bandpass filter over each of the photodiodes. In this case, the illuminants 5002, 5004 can be illuminated simultaneously, while their outputs are independently stabilized using the feedback circuitry described herein. Fig. 51 shows the feedback process of the circuit of fig. 50 in stabilizing the light output of one luminaire (continuous illumination). The graph of fig. 51 includes a first portion 5102, the first portion 5102 representing the output of the photodiode over time and the drop in light output from the light source over time. This output is fed back to a feedback circuit that controls the drive current output of the current source 5008. The decrease in photodiode output causes an increase in LED output current as shown by curve 5104.

Fig. 52 shows a second circuit in schematic block diagram form. In this example, instead of controlling the output current of the current source, a feedback circuit is used to control the duration of the output pulse of the light. Thus, fig. 52 includes two light sources 5202, 5204, each of which is connected to a current source 5208. The circuit also includes a photodiode 5206 which is connected to a feedback circuit 5210. The circuit 5200 also includes a drive pulse modulation circuit 5212 that controls the timing and duration of the current pulses provided by the current source 5208 to the lights 5202, 5204. In this example, the feedback circuit 5210 provides a signal to the modulation circuit 5212 when a drop in the light level received by the photodiode 5212 is detected. In response, modulation circuit 5212 increases the length of the pulse generated by current source 5208 that is provided to the LED.

Fig. 53 illustrates a method of operation of the circuit of fig. 52. The upper graph 5302 shows the output of the photodiode, which generally drops over time as can be seen. The lower graph 5304 shows the drive current provided to the emitter. In this case, the output current is provided in the form of square wave pulses (e.g., 5306). As the output of the photodiode decreases, the duration of the pulse gradually increases. By adjusting the pulse duration and maintaining the current at a constant level in this way, the effective intensity of light emitted by the luminophor (integrated over the pulse length) remains substantially constant. Advantageously, it also results in more accurate reception of the pulses at the receiver, since the receiver can act as an integrator and collect more of the transmitted signal, rather than the receiver simply taking a single sample of the light intensity within each pulse.

The graphs of fig. 51 and 53 show the response of the photodiode and the drive circuit current for a single light-emitting element of the emitter. Similar plots may be generated for other light emitting elements.

In another embodiment of the invention, open loop control of the intensity of the LEDs may be provided. This can be achieved at low cost, for example, by providing a current drive circuit that is temperature stable or temperature compensated for the output characteristics of the LED.

In a further embodiment of the invention the output of the light emitting element may be only weakly controlled, for example by driving the output of the light emitting element with a fixed pulse length by means of a very simple current control circuit. In this case, the average output intensity measured by the photodiode may be transmitted to the receiver. The receiver may then be set to compensate for the varying LED output in software. In a preferred form, the averaged LED output may be communicated to the receiver using an optical communication channel or other wireless communication channel. In the case of an optical communication channel, this can be achieved by modulating the output of the luminaires themselves (by inserting or omitting pulses in the sequence of illumination pulses of one or the other, or both, of the two luminaires). This embodiment has the advantage that only a relatively low cost transmitter is required, without the need for complex feedback circuitry. It also makes use of the fact that: the temperature and aging related output drift of the luminaires is likely to be relatively slow and therefore only a low communication bandwidth is required.

Another problem that will exist in the above-described method (measuring and controlling the output intensity of a luminaire using one or more photodiodes) is that ambient light may interfere with the measurement. For example, sunlight may be received by the photodiode and erroneously increase the light level of the light emitting element detected by the photodiode.

To overcome this problem, in one embodiment, effective ambient light can be significantly attenuated by using a bandpass filter in conjunction with a photodiode. For example, photodiodes such as: it can only pass light in the band emitted by its corresponding illuminant, while attenuating all other wavelengths (such as those common in sunlight). Similarly, if artificial illumination, such as fluorescent illumination, is used, the bandpass filter may be adapted to substantially exclude all of the artificial illumination, while still transmitting light in the wavelength band emitted by the respective luminary.

In alternative embodiments, the light absorbing baffle may be located around the photodiode, for example in an LED package, so that only light from the light emitting element can reach the photodiode. By placing a baffle between the photodiode and the lens of the LED package, the photodiode can be shielded from external light.

Another mechanism for correcting the level of background light is to measure from the photodiode when the light is in the "on" and "off" states. In this case, the measurements taken during the "off" period (between pulses of the illuminant) represent background light. The level of background light may be subtracted from the brightness level measured during the subsequent (or previous) "on" period (i.e. the illumination period of the light-emitting element). If it is desired to smooth the level of background light, the background light may be averaged over several "off" frames and a running average of the background light level subtracted from the "on" period data. This may be required, for example, when the level of ambient light varies widely at a frequency equal or substantially equal to the pulse frequency of the light emitters.

FIG. 54 illustrates a light source according to an embodiment of the present invention. The light source 5400 includes a light emitter 5402 electrically connected to a control circuit 5404, the control circuit 5404 being powered by a power supply 5406. Emitter 5402 projects a light beam (or beams) through optical system 5408 toward a receiver. In some embodiments, the optical system 5408 may simply be a transparent window through which the light beam is projected in use, but the optical system 5408 may also be a more complex optical device including, for example, one or more lenses, mirrors, or filters, etc., adapted to impart some particular beam characteristics to the light beam emitted by the light source 5402. As described above, the outer surface of the optical device 5408 is susceptible to temporary shading due to insects or similar objects on the outer surface thereof.

To detect these foreign objects, the light source 5400 is provided with a photodiode 5410 or other light sensitive element connected to the control circuit 5404. In use, the photodiode 5410 is arranged such that it receives light scattered from a foreign object that obscures at least a portion of the outer surface of the optical device 5408. The photodiode 5410 is connected back to the control circuit 5404, and the control circuit 5404 is adapted to determine whether a fault condition exists based on the integrity of the scattered light received by the photodiode 5410. For example, the control circuit 5404 may include a microcontroller 5412 programmed with fault logic (and possibly other logic as well) that compares the feedback signal received from the photodiode 5410 to a predetermined threshold, and if the received intensity is above the threshold, or the feedback signal meets some other intensity and/or time based criteria, the fault logic may be adapted to trigger a fault response in the light source 5400. For example, the microcontroller may cause the illumination pattern of light emitter 5402 to change in response to a fault condition to signal the presence of the fault condition to a receiver of the particle detection system. By encoding a specific signal in the illumination mode, the type of fault can be sent back to the receiver. By modulating the amplitude, duration and/or timing of the emitted light pulses in a predetermined manner, a fault condition may be communicated. This has the advantage that no wires or other wireless communication systems need to be arranged between the transmitter and the receiver of the particle detection system.

Fig. 55 and 56 show an alternative embodiment of this aspect of the invention, and common components are denoted by common reference numerals.

Turning first to FIG. 55, a second embodiment of a light source 5500 made in accordance with an embodiment of the present invention is shown. In this embodiment, the light source 5500 has been provided with an additional light emitting device 5502. The light emitting device is positioned such that it illuminates the lens at a shallow angle of incidence. This increases the chance that particles or foreign objects falling on the outer surface of the optics 5408 will produce sufficient reflections to be detected by the photodiode 5410. In this embodiment, the photodiode can be blocked by a wall or baffle 5504 to prevent direct illumination of the light source 5502.

Fig. 56 shows a light source 5600. This embodiment differs from the light source shown in fig. 54 and 55 in that it includes an externally mounted luminaire 5602. The illuminant 5602 is positioned such that it directly illuminates the outer surface of the optic 5408. This may have additional advantages in correctly identifying the presence of foreign objects, such as insects or other objects on the outer surface.

In some embodiments of the invention, the light source may be provided with an internally mounted feedback photodiode. The feedback photodiode is typically used to monitor the light output of one or more light sources and adjust the emission characteristics of the light sources (e.g., if a drop in the received light level is measured). However, by applying an upper threshold to the signal received by the internal photodiode, which may be determined as a result of a foreign object being located on the outer surface of the optical system 5408, an embodiment of this aspect of the invention may be used with the internal photodiode if the received brightness level is above the upper threshold (and not the result of the increase in light output caused by the controller 5404).

Embodiments of the present invention can also be used with a receiver of a particle detection system. In this embodiment, the receiver may be equipped with a light emitter (such as that shown in fig. 14) and a photodiode, and arranged to perform the method described herein in relation to the light source. By virtue of the receiver, it is clearly advantageous that the light transmission within the receiver housing does not hinder the particle detection performance of the system. Thus, the light source 5502 may be selected such that it emits light outside the receiver's reception band, or the receiver may be provided with a band pass filter that excludes the selected wavelength. Alternatively, if the light source of the particle detector is set to blink according to a predetermined pattern (with "off periods" between blinks), the foreign object detection function may be performed during these "off periods. If foreign object detection during "off" is to be used, then the illuminant (e.g., illuminant 5502) may emit light in the passband of the receiver, and the primary receiver may be used to detect the presence of foreign objects on the outer surface of optics 5408.

As mentioned above, it is important for the particle detector to be properly installed and operated. Proper installation and operation ensures reliable and safe operation of the system. Thus, several processes that can be used for the installation and operation of the particle detection system are now described.

For clarity, the following process description will focus on the particle detector described with reference to fig. 2. However, it will be apparent to those skilled in the relevant art that the process may be performed using the apparatus described with reference to fig. 3 and other apparatuses.

In one embodiment, the process includes two phases, including a run phase and an operate phase. The operational phase is performed when the beam detector is initially installed, and the operational phase is performed after a period of installation.

Fig. 58 shows a process for operating the particle detector. A technician or other suitable installer mounts the light source 32, receiver 34 and target 36 (which are optional in other geometries) in the appropriate locations across the area where the particles (e.g., smoke) are to be monitored (step 5801). As discussed, the installation process may be simple and quick by virtue of using a receiver 34 in the form of a video camera or other suitable device.

After installation, the technician activates the detector by powering the particle detector, step 5802. Initially, the detector explores the presence of light sources within the field of view of the detector to the monitor. As discussed elsewhere in this application and in our co-pending application, the controller identifies the relevant portion of the detector field of view that represents the light from the light source 32, and then measures the intensity of the light signal received from the light source 32 (step 5803). The identification process may be manual, such as by a technician coupling a portable computer to the receiver 34, viewing the image captured by the camera, and pointing out the relevant portion of the field of view using a pointing device or other device. The identification process may alternatively be automated, such as by virtue of the controller 44 being programmed to identify the portion of the screen illuminated by the light source (e.g., ultraviolet and/or infrared light in the case of an ultraviolet or infrared light source).

A detailed description of an exemplary method of target searching and timing discovery may be found elsewhere in the application.

In step 5804, the received light level from each identified light source is compared to a threshold to determine if the received light level is within an acceptable range. If the controller 54 receives light from the light source 32 above the existing threshold, the particle detector is caused to be instructed to operate acceptably (step 5805). The indication of the system status may include a continuously illuminated LED on the receiver 34, although other notification mechanisms may be used, such as generating a sound and/or transmitting a signal to a PDA or computer in communication with the controller 44 for observation by a technician.

The detection system will apply alarm and fault logic to determine if the detection system is operating correctly or if particles are detected. The alarm and fault logic will include alarm criteria based on the intensity of light received at the receiver. The criteria may be based on raw intensity measurements, differences or comparisons at multiple wavelengths, or other quantities known to those skilled in the art. In general, the criteria may be viewed as a comparison of received data to a threshold level. The inventors have realized that the usual alarm thresholds can be ignored to a large extent during the operational phase, since the installation and operation of the particle detection system is governed by the skilled person and the system is not relied upon during operation to provide particle detection or life safety functions. Thus, the threshold applied during the run phase may be set very close to one or more of the alarm or fault thresholds applied during the operational phase.

In a preferred form, the at least one threshold value used during the operational phase will be set to a level substantially above that which would cause the particle detector to generate an alarm, and during the operational phase, other action will be taken to indicate that smoke has been detected or is malfunctioning.

For example, the minimum acceptable brightness of light received during the run-up phase may be set to more than 20% above the brightness level that would result in a fault condition during normal operation. Such thresholds require the installer to ensure that the initial alignment of the system is very accurate, that the optical surfaces are clean and well-behaved, and that the length of the transmission path does not exceed an acceptable range, otherwise the system will not reach relatively stringent light intensity requirements during operation.

If the controller 44 determines during the run-up phase that the received light level is below the preset threshold, the controller 44 causes the particle detector to indicate an error (step 5806). This may, for example, include flashing an LED or transmitting a signal to a technician's PDA or computer. If the identification of the relevant portion of the field of view is automatic, controller 44 may allow the manual identification process to be completed, after which steps 5802 through 5804 are repeated.

Upon receiving the error indication, the technician may take the necessary action to correct the problem. For example, the technician may reposition the light source 32, receiver 34, and/or target 36, for example, to shorten the path length between the light source 32 and receiver 34. In the event that the path length needs to be substantially shortened and the target 36 is used in the initial installation, the technician may remove the target 36 and place the receiver 34 where the target 36 was previously located to halve the path length. Alternatively, the technician may locate the midpoint where the components of the particle detector are mounted.

The controller 44 can be programmed to automatically complete its role in the process shown in fig. 58 upon each start-up. Alternatively, this may be done only on demand, such as by pressing a button associated with the recipient 34, or upon receiving a command via a communication port of the recipient 34.

If the operational phase has been successfully completed, the receiver 34 is in a state to begin operation. Two embodiments of such "phases of operation" are described below, the first with reference to fig. 59 and the second with reference to fig. 60. In the operational phase, the receiver 34 measures the intensity of light received from the light source 32. The data is processed and if the received signal indicates that smoke is present in the light path between the light source 32 and the receiver 34, the controller 44 causes an alarm condition in the particle detector and/or sends a signal to cause another device (e.g., a fire control panel) or system (e.g., an automatic evacuation system) to generate an alarm.

In a preferred embodiment of the invention operating on multiple wavelengths, the master alarm threshold is based on a differential measure of the received light intensity of more than one wavelength, such as the ratio or difference of the received light intensities of the two wavelengths, or the rate of change of such measurements. The second "standby" threshold may be set independently based on the absolute light intensity or the modified light intensity at the received wavelength or wavelengths. The detection of correct operation and fault conditions may also be based on the difference in received light levels or absolute light levels.

Referring to fig. 59, the controller 44 is programmed to again check the received signal strength from the or each light source 32 (if more than one) against an absolute signal strength threshold. The examination may be performed continuously or periodically (e.g., once per day, twice or more per day, or less frequently), depending on the particular needs. It is also possible to check on demand, for example on receiving a command requesting a check of the signal strength received at the communication port of the receiver 34, or on activating a button provided in connection with the receiver 34. If controller 44 determines in step 5907 that no inspection is required, receiver 34 continues to monitor the light path for smoke.

If inspection is required, the controller 44 estimates the signal intensity of the light from the light source 32 in step 5908 and compares it to a threshold in step 5909. The threshold may be the same as that used in step 5803, or alternatively another set value determined to indicate a desired level of operational reliability.

In step 5910, the result of the comparison is evaluated, and if a threshold corresponding to the minimum required intensity is not exceeded, an error is indicated/generated (step 5911), which may be the same or different from the error indicated in step 5806, depending on the particular implementation. For example, the error indicated in step 5911 may be an audible signal generated at the location of the particle detector and/or at a control point (e.g., a secure location of a building) and/or at a remote monitoring station (by transmitting the error over a wired and/or wireless public and/or private network).

If the threshold corresponding to the minimum required intensity is exceeded, then in step 5912 the particle detector indicates acceptable operation (which may be indicated in the same manner as described above in step 5805).

Referring to fig. 60, a flow chart of a process that may be performed by controller 44 to perform alternative operational stages is shown.

After operation (i.e., step 5805), the controller 44 determines whether the delay time has expired at step 6016. The delay time may be, for example, 24 hours, after which time it would be desirable for the particle detector to operate in a steady state. In other embodiments, other non-zero delay times may also be used. Preferably, during the delay time, the detector is not used for basic particle detection purposes, but is merely monitored for proper operation.

When the delay time has expired, the controller 44 resets its threshold (in step 6018). Preferably, the new threshold to be used is based on (or a parameter from) the signal strength measured in (optional step) 6015. Alternatively, it may be based on measurements made after the delay time has expired (step 6017). The operable threshold intensity (operable threshold intensity) may also have a preset minimum value. Alternatively, the acceptable threshold can be determined by observing the performance of the system over the delay time, for example by analyzing the change in light intensity received at one or more wavelengths over the delay time. For example, if the variation in received light intensity over the entire delay time caused by a cause other than the intrusion of the particle of interest into the light beam (e.g., mounting offset, temperature-dependent light output variation of the light source, etc.) is 2%, the acceptable minimum received light level may be set to be 2% lower than the average received light level or some other level. The operable intensity may be a function of the intensity measured at the end of the delay time and a preset minimum value, e.g. determined as the average of the two values. The operational threshold and the preset minimum, if any, may be determined/set for each light path individually (if there is more than one light path).

Next, the controller estimates the intensity of light received from the light source 32 (step 608A) and compares it to the new operational threshold at step 609A.

Using the operational threshold determined in step 689A, steps 600A through 602A may then proceed as previously described herein with reference to FIG. 59.

In the case where there are multiple light sources and/or multiple light paths from a single light source, an error indication may be made when the intensity of light received along any one of the monitored light paths falls below a threshold. Alternatively, there may be different levels of error conditions, where one level indicates when light along one of the optical paths falls below a threshold, and another level indicates when light along more than one or all of the optical paths falls below the threshold. The threshold may be different for each light path, e.g. reflecting the difference in intensity of light generated by the light source 32 for that light path.

In the foregoing description, reference has been made to various optical paths from the light source 32 to the receiver 34. One skilled in the relevant art will appreciate that light may reflect off a variety of structures (e.g., a ceiling) and result in more than one path between a particular point on the light source and the receiver. Implementations are intended to fall within the scope of the present invention where light from a light source is received by a receiver through multiple paths, and where light from one light source is reflected onto a receiver portion that receives light from another light source.

Turning again to fig. 57, in installations such as this, the difference between the intensity of light reaching the receiver 5702 from the emitters 5704, 5706, 5708 can be adjusted, in an embodiment of a further aspect of the invention, by applying an optical attenuator to the optical path of each emitter of the system, or at least those emitters in the system that are located at a distance that may cause the receiver 5702 to saturate. Fig. 61 shows an exemplary housing for implementing this mechanism. Figure 61 shows a cross-sectional view through the emitter housing 6100. A light source (e.g., LED 6102) is located in the housing. Which is connected to a suitable circuit (not shown) and is used to generate a beam of light for particle detection. The light emitted by the light source 6102 may pass through one or more optical elements 6104 for focusing the beam into a suitable shape (e.g., a narrow diverging volume or a wide diverging beam, or some other shape described herein. the transmitter 6100 additionally includes one or more optical attenuators 6108 for attenuating the beam emitted by the transmitter 6100. by using one or more filters 6108 having suitable characteristics, the degree of attenuation may be selected and set at a suitable degree for the spacing between the transmitter and its corresponding receiver. The receiving mechanism enables the selectable optical filter to be attached or removed by an installer during operation of the system. For example, the housing may include a plurality of recesses, such as recesses 6112, each adapted to receive a single filter element.

Fig. 63 illustrates 3 exemplary filter elements that may be used with embodiments of the present invention, such as those illustrated in fig. 61 and 62. The filters 6300, 6301, 6302 are preferably neutral density filters and may be made of an attenuating material, such as a plastic film. Attenuators for different distances may be made by increasing the absorption level of the material (e.g. changing the material properties or increasing the material thickness).

Preferably, each filter has indicia indicative of its intensity. For example, indicia may be printed, embossed, or otherwise displayed on the filter that indicates a preferred distance or range of distances between the emitter and receiver. Alternatively, a fractional decay may be displayed. The information displayed on the filters may be used by the installer to determine the appropriate filter or filter set for the emitter for the particular system geometry being installed.

Alternative (or additional) embodiments of this aspect of the invention will now be described. In this embodiment, the system is adapted such that the receiver can avoid saturation without the use of filters, although filters may be used with this embodiment if necessary. Fig. 64 is a timing diagram illustrating a second scheme for solving the above-described problems according to an aspect of the present invention.

In this aspect of the invention, the transmitter may be arranged to transmit a sequence of pulses of different intensities and to repeat the sequence during operation. The receiver can then determine which pulses received at the receiver fall within the acceptable brightness level and select from that time on to receive only those pulses having the acceptable brightness level.

Turning now to fig. 64, the uppermost plot 6400 is a timing diagram showing the transmit power of a sequence of pulses transmitted by the transmitter over time. The lower graph shows the reception state of the receiver. At a starting period t₁The transmitter gives a number of transmit pulses 6404, 6406 and 6408 with gradually increasing transmit power in one cycle. The sequence being over a time period t₂And t₃Repeated and continued. In a first period t₁The receiver does not know which transmitted pulse will be in a state that will not cause receptionThe device saturates but is still high enough to have a suitable level of satisfactory signal to noise ratio. Thus, for a period t₁The receiver is continuously in the "on" state and is able to receive each of the transmitted pulses 6404, 6406, and 6408. From the measured strength of these 3 received pulses, the receiver is able to determine which pulse should be received therefrom. In this case, the pulse 6408 is determined to have the appropriate strength, and the receiver is set to fire at times 6410 and 6412 corresponding to the firing period of the pulse 6408 in successive firing cycles T2 and T3.

As mentioned above, the receiver and transmitter are not typically coupled to each other, but the transmitter will continue to transmit 3 different levels of pulses during its operation. Alternatively, in embodiments where the receiver may be connected back to the transmitter, the receiver can signal to the transmitter which pulse is to continue to be transmitted and which pulse is to be removed. Such a system will reduce the power consumption of the transmitter as fewer pulses will be transmitted.

The start period of monitoring multiple transmit pulses may be extended beyond a single transmit time period as this is necessary for the receiver to find the way the transmitter is illuminated in several transmit periods.

In a third solution for improving or solving the problem, a further aspect of the invention uses an electronic device to control the transmission power of the transmitter. In this example, DIP switches may be incorporated into the transmitter that is set by the installer during installation to the appropriate transmission level. The setting of the DIP switch can be selected to reduce the current through the LED and thereby dim the LED, or to reduce the duration of the "on period" pulse to avoid receiver saturation. In this case, it may be advantageous to have an installation mode in which the emitters initially emit light at different power levels. During this time period, the receiver may determine the appropriate transmission level and indicate to the installer the appropriate DIP switch setting to be made to set the transmission level to the most preferred value. For example, the receiver may be provided with a display or other interface that may be used to display the setting of the DIP switch for the transmitter. It should also be understood that in a system with multiple transmitters, any process may be repeated for each transmitter.

In yet another embodiment of this aspect of the invention, a system having multiple transmitters may include different types of transmitters therein. Each transmitter type may be optimized for a particular distance or range of distances, and in this case, the installer decides which type of transmitter should be installed.

FIG. 65 illustrates an embodiment of a particle detection system 6500 that is being tested using a test filter according to an embodiment of another aspect of the invention. The particle detection system 6500 includes a light source 6502 and a light receiver 6504. The light source 6502 generates one or more beams of light, including light in a first wavelength band 6506 (centered at λ 1) and a second wavelength band 6508 (centered at λ 2). Preferably, λ 1 is a shorter wavelength band, e.g., in the ultraviolet portion of the electromagnetic spectrum, and λ 2 is a longer wavelength band, e.g., centered in the near infrared region. Light beams 6506 and 6508 pass through test filter 6510, and by rotating light beams 6506 and 6508, test filter 6510 simulates the effect of smoke on the light beams. The operation of the receiver 6504 may then be checked to determine if the receiver 6504 is behaving correctly given the degree of beam attenuation caused by the test filter 6510. Since the light emitted by the light source 6502 contains light in two wavelength bands λ 1 and λ 2, the optical filter 6510 needs to deal with the absorption characteristics of the two wavelength bands in an appropriate manner. In a preferred form of the particle detector 6500, as described above, a differential measure of the intensity of light in the two wavelength bands λ 1 and λ 2 (e.g., the ratio of the intensities measured at each wavelength, or the rate of change of these values, etc.) is used to determine the presence of particles of a predetermined size range in the light beams 6506 and 6508. Most preferably, a particle detection event may be indicated if the proportion of received light intensity varies in a predetermined manner. Thus, in most cases, test filter 6510 does not uniformly attenuate both bands, but must provide differential attenuation in both bands to simulate the effects of smoke. In this example, test filter 6510 absorbs the short wavelength λ 1 significantly more than the long wavelength λ 2. For example, the test filter may absorb significantly more than twice as much light at λ 1 than λ 2, which may be determined to be likely a particular type of particle.

Thus, the characteristics of the test filter are selected to set the proportion of different wavelength bands of light emitted (or attenuated) and to vary the absolute brightness at which the test filter transmits (or attenuates) light. These two variables can be adapted to produce suitable test filters to simulate different smoke or particle types and different smoke or particle densities.

Fig. 66 shows a first exemplary test filter comprising 3 filter elements 6512, 6514 and 6516. Test filter 6510 is generally a thin layer type of material, consisting of 3 layers of filter material. In this example, the first two filter elements 6512 and 6514 attenuate light in the wavelength band λ 1, while the third filter element 6516 absorbs light in the wavelength band λ 2. In this example, each of the filter elements 6512 to 6516 constituting the test filter 6510 is arranged to provide the same amount of attenuation to light passing therethrough. Thus, test filter 6510 attenuates light in wavelength band λ 1 by twice as much as light in wavelength band λ 2.

Fig. 67 shows the transmission spectrum for test filter 6570. It can be seen that the test filter transmits substantially all light outside of the wavelength bands λ 1 and λ 2, but the attenuation of light in the wavelength band λ 1 is approximately twice that of light in the wavelength band λ 2. In other embodiments, the transmission outside of the bands λ 1 and λ 2 may be of any degree and need not be uniform for all wavelengths.

The above-mentioned absorption properties can be obtained in various ways. Fig. 68 to 75 illustrate a series of these techniques. Other techniques will be apparent to those skilled in the art.

Fig. 68 shows a filter element. The filter element has a front face 6802 to which a number of particles are attached, which particles have substantially the same size distribution as the particles to be detected by the particle detector to be tested by means of the filter element. Such particles may be manufactured using a variety of known processes or selected by screen separation from a powder (e.g., alumina). Fig. 69 shows a variation of this mechanism. The filter element 6900 of fig. 69 comprises particles similar to those used in the embodiment of fig. 68, but distributed over the bulk of the filter element.

Fig. 70 shows a filter element 7000, one or both of its surfaces having been surface treated to introduce defects on the surface of the material. Surface defects may be created by, for example, mechanical abrasion, particle blasting, chemical or laser etching, or the like. Alternatively, defects may be created throughout the bulk of the filter elements in the layout 70 using, for example, 3D laser etching.

Fig. 71 and 72 show another surface treatment that can be performed on the filter elements 7100, 7200 to obtain predetermined attenuation characteristics. In these examples, the filter element is made of a substantially transparent material and is decorated by using surface printing. For example, an ink jet or laser printer may be used to print a pattern on one or both surfaces of the thin layer of filter elements. Preferably, the pattern of dots is printed over the entire surface of the filter element. Most preferably, the dots of uniform size are printed at a predetermined pitch, which is determined by the level of attenuation obtained by the filter element. Fig. 71 and 72 are generally identical except for the number of dots printed on the filter element. It can be seen that the dots printed on fig. 71 will be much less numerous than the dots on fig. 72 and will therefore be less absorptive than the filter element of fig. 15E.

Obviously, other patterns may be used to obtain the predetermined attenuation.

Fig. 73 shows a printed pattern that can be implemented on the surface of the filter element 7300. The filter element 7300 is printed in a bi-color printing process and includes a pattern of dots having dots of a first color 7304 and dots of a second color 7306. It can be seen that the dots of color 7304 are more numerous than the dots of color 7306, and therefore, the filter element will attenuate light in one wavelength more than the other wavelength. Alternatively, a pattern of dots of one colour may be printed on one side of the filter element, while a pattern of dots on the other side may be printed in a second colour.

Fig. 74 shows a test filter with a more complex structure. The test filter element 7408 consists of 5 layers 7410 to 7418. 4 of the 5 layers, 7410 to 7416 attenuate light in the wavelength band λ 1, but transmit light in all other wavelength bands, while the last layer 6818 absorbs the wavelength band λ 2.

Fig. 75 shows another test filter. The test filter has a middle portion 7420 whose properties are selected so as to obtain a predetermined attenuation of light in the wavelength bands λ 1 and λ 2, but which is covered by transparent layers 7422 and 7424 to protect the attenuating layers forming the core 7420. This is particularly advantageous where a surface treatment is used in the attenuating layer (which may be damaged by contact with other objects or substances).

In another embodiment, one or both surfaces of the test filter may be treated with a plurality of thin films to produce predetermined wavelength selective attenuation characteristics. Furthermore, the filter element may be reflective rather than absorptive to obtain the desired attenuation characteristics.

Figure 76 shows a beam detector 7600 which includes an emitter or light source 7602 and a receiver 7604. The emitter 7602 includes one or more emitters 7606 adapted to generate one or more beams of light 7608. At least a portion of the one or more beams of light is received by receiver 7604. Preferably, the light emitter 7606 is adapted to simultaneously generate light in two wavelength bands centered at different wavelengths λ 1 and λ 2 (hereinafter referred to as "wavelength bands λ 1 and λ 2") for emission to the receiver 7604. The receiver 7604 comprises a light sensor 7610 which is adapted to output signals representative of the light intensities in the two wavelength bands received at a plurality of locations on its surface. The outputs in these two bands are communicated to the controller 7612, and the controller 7612 performs an analysis of the output of the optical receiver 7604 and applies alarm and/or fault logic to determine whether action needs to be taken in response to the received signal. The receiver 7604 may additionally include an optical system 7614 for forming an image or controlling the received light beam 7608.

In embodiments of the invention where the emitter 7608 emits in two wavelength bands λ 1 and λ 2 simultaneously, the sensor 7610 of the receiver 7604 is preferably adapted to receive light in each wavelength band simultaneously and resolvable. To this end, the receiver 7604 may be provided with a wavelength selective device adapted to separate light in the wavelength band λ 1 from light in the wavelength band λ 2 and to direct them differently to the sensor 7610 in such a way that the two wavelength components can be measured independently.

Fig. 77 illustrates a first example of a receiver 7750 that enables the techniques to be performed. Receiver 7750 includes window 7752, and beam 7754 enters receiver 7750 through window 7752. The window 7752 may be a flat piece of glass or the like, or alternatively, may be part of an optical device (e.g., a lens or series of lenses) adapted for imaging on or near a light receiver. The receiver 7750 includes a sensor 7756, and the sensor 7756 includes a plurality of sensor elements 7758. The wavelength selective device 7760 is mounted proximate to the front of the light sensor 7756 and comprises, for example, a mosaic dye filter. The dye filter 7760 includes a plurality of elements 7762 and 7764. The element 7762 is adapted to transmit the first wavelength band λ 1 and the element 7764 is adapted to transmit the second wavelength band λ 2. The combination of the mosaic dye filter 7760 and the photosensor array 7756 enables a first set of sensor elements or pixels of the sensor 7756 to receive light in the first wavelength band while other pixels of the sensor 7756 simultaneously receive and record the intensity of light used in the second wavelength band λ 2.

The controller may then be arranged to separate the intensity values in one set (i.e. associated with one wavelength band) from the other, e.g. the output of the sensor elements may be selectively "read out" to obtain signals for both wavelength bands.

Fig. 78 shows an alternative embodiment that achieves similar results. In this embodiment, receiver 7800 is similar to that of fig. 77 in that it includes optics 7802, which optics 7802 may include a window or focusing optics through which light enters receiver housing 7804. After passing through the optics 7802, the light beam enters a wavelength selective prism 7806, the wavelength selective prism 7806 being adapted to divert the light into different directions, depending on the wavelength of the incident light. Thus, light in wavelength band λ 1 is transmitted into first light beam 7808, and light in wavelength band λ 2 is transmitted into second light beam 7810. The light beam in the wavelength band λ 1 falls on the first sensor array 7812, and the light beam in the wavelength band λ 2 falls on the second sensor array 7814. As described above with reference to previous embodiments, the sensor arrays 7812 and 7814 are adapted to simultaneously record the intensity of light at multiple points on their surfaces.

Fig. 79 shows a second embodiment using a prism to split a beam into its wavelength components. In this embodiment, receiver 7820 includes a single sensor array 7822, sensor array 7822 being adapted to receive light via optics 7824 and beam splitting devices 7826. The beam splitting device is adapted to separate light in the first wavelength band from light in the second wavelength band and direct them in different directions. This embodiment differs from fig. 78 in that the beam splitting device 7826 is mounted very close to the sensor array 7822, rather than forming images in each of the wavelength bands λ 1 and λ 2 on separate sensor arrays. Thus, beam splitting occurs very close to the surface of sensor array 7822. Effectively, this provides a separate wavelength-selective beam splitter for a subset of the pixels of the pair of sensor elements 7822.

Fig. 80 shows yet another embodiment of the present invention. This embodiment shows an optical receiver 7850 comprising a housing 7852 with a sensor element 7854 mounted in the housing 7852. Light enters the housing through the optical system 7856 and is transmitted to the light sensor 7854. In this embodiment, the sensor 7854 is a multi-layer sensor and includes n sensor layers 7854.1, 7854.2 through 7854. n. Each sensor layer 7854.1 to 7854.n is adapted to receive light of a different energy. Energy separation may be achieved by utilizing the phenomenon of different depths of penetration of photons of different energies into sensor device 7854. In this case, the sensor device may be a silicon photo-sensing element. In each layer of sensor 7854, spatially distinct measurements of light intensity corresponding to a wavelength may be determined.

In each of the embodiments described above, signals at multiple wavelengths may be processed according to the methods described above to produce particle detection or fault condition outputs.

It should be understood that although the preferred embodiment is described with reference to a dual wavelength system, three or more wavelengths may be used in some embodiments.

Fig. 81 and 82 illustrate an embodiment of the invention comprising a transmitter 8101 for transmitting at least one beam of light 8102 and a receiver 8103 for receiving the beam of light. The receiver 8103 has a photosensor with a plurality of photosensitive elements 8104. An example of a suitable receiver is a video imager, the sensors of which are arranged as a matrix of pixels. Each sensor element produces an electrical signal that is related to (e.g., proportional to) the intensity of light detected by the sensor.

In fig. 81, a transmitter 8101 is shown across a monitored space 8105 from a receiver 8103. It should be understood, however, that the transmitter 8101 may also be otherwise positioned (i.e., not directly such that the transmitted beam is aimed at the receiver 8103) so long as the transmitted beam 8102 passes through the monitored space 8105. The emitted light beam 8102 may be directed to the receiver 8103 by some means, such as an optical reflector.

A diffusing device 8106 is arranged in the path of the emitted light beam 8102 in order to produce an intentional diffused image of the light beam on the sensor 8107A of the receiver. Signals from sensor element 8104 are passed to a controller 8108, such as a processor.

The controller 8108 combines signals from at least some of the sets 8109 of sensor elements (e.g., only those sensor elements onto which the light beam falls) to determine the intensity of the received light beam 8107A. Each sensor element in CCD 8103 may have a different inherent noise level and a different light conversion efficiency. Thus, in its calculations, controller 8108 takes into account information about sensor 8109A (which was initially aligned with beam 8107A). Based on the determined strength, the controller 8108 applies alarm logic and decides whether to take any action, such as issuing an alarm signal, or issuing an alert or message to an administrator or other user. In the aforementioned system, the decision is made based on whether the determined intensity is below a threshold (corresponding to the presence of smoke particles).

In fig. 82, the position of transmitter 8101 is shown slightly displaced from the position shown in fig. 81. This change results in a change in the position of the image 8017B of the diffused beam relative to the receiver 8103. Some of the sensor elements upon which the diverging beam 8107B is incident are outside of a subset 8109 of sensor elements, the signals of which subset 8109 are initially read out by the controller 8108. The controller 8108 is adapted to track the position of the beam image that is swept across the surface of the sensor 8103 and thereby incorporate the light received on the sensor into a new region 8109A. As will be appreciated, the set of sensors in region 8109A is different than that originally used in set 8109, but the two sets (8109, 8109A) include the same number of sensors.

In theory, the sensor elements in the new region 8109A may have a different inherent signal error than the sensor elements in the original region 8109. However, this difference is not significant. In this example, the average noise floor of the 4 newly combined sensor elements is about the same as the average noise floor of the 4 sensor elements that are no longer in use. Furthermore, the spacing between the sensor elements (i.e. the number and size of the gaps) remains substantially constant, so no additional light is lost in the gaps between the sensor elements.

This is in contrast to the case of a sharply focused image, in which case the error related to the received beam intensity will vary significantly as the sharply focused image moves from one sensor element to the next, because the two sensors have different light conversion efficiencies, which difference is not improved by averaging (in the case of a more diffuse beam image). Furthermore, as the focused beam moves from one sensor to the next, it will sweep the spacing between sensor elements, and there will be an intermediate period when a significant amount of optical power will be lost in the spacing between sensors. As described above, these problems can be alleviated by using an out-of-focus image.

The following paragraphs describe embodiments of how the optics used in the receiver (e.g. the imaging system) are arranged so as to produce an intentionally out-of-focus object. In this specification, the term "diffusing device" should be broadly construed as any device or component that produces a diffused image of a light beam on a sensor.

In the embodiment shown in fig. 83, the diffusing device 8301 includes a focusing lens 8302 in the path of the emitted light beam.

The focusing lens 8302 has an associated focal point 8304. The emitted light beam 8303 is emitted by a transmitter (not shown) directly toward the lens 8302 or a reflector (not shown) that reflects the light beam toward the lens 8302. In this embodiment, the relative position of the lens 8302 and the sensor 8305 is where the image 8306 of the focused beam of light is located to bring the sensor out of focus. The sensor 8305 thus receives an image of the beam that is intentionally slightly out of focus. The amount of focusing and the amount of spreading are controlled such that a signal-to-noise ratio (obtained with a more compact focused beam) can be obtained while a relatively stable system (obtained with a spread or blurred image) is obtained (even when there is movement in the system).

In yet another embodiment (fig. 84), the receiver 8310 includes a focusing lens 8311. The light sensor 8312 is positioned at the spot where the focused image is located. The diffusing means in this embodiment includes a diffuser 8313 located somewhere between the lens 8311 and the light sensor 8312 (e.g., directly above the sensor). Thus, the received image is intentionally blurred. The diffuser 8313 may be a piece of ground or etched glass, or simply comprise an etched surface on the sensor itself.

In some cases, the diffusion device 8313 may be located somewhere in the path of the emitted light beam towards the sensor 8312.

In some embodiments, the emitter may output a light beam having two (or more) band components (e.g., infrared and ultraviolet bands), both along substantially collinear paths. The two wavelengths are chosen such that they behave differently in the presence of particles to be detected (e.g. smoke particles). In this way, relative changes in the received light at two (or more) wavelengths can be used to give a cause for attenuation of the light beam.

In some embodiments, a receiver may receive multiple beams, or multiple emitters may emit beams to be received. Together, the multiple beams are used for smoke detection purposes in the space being monitored. As with the previous embodiments, the sensor receives the light beam and sends a signal to the controller. The controller analyzes the signal and determines which portion of the signal contains the most relevant information to the respective beam. In the outcome of this decision process, the controller will select two portions of the signals generated by the respective individual sensors or groups of sensors so that the selected signals can be most reliably used to measure the intensity of the light beam. One way of selecting the sensor whose data can be used most reliably is to observe the image from the receiver as the smoke detector is operated and select the appropriate sensor.

Another mechanism to ensure that the calculated received beam intensity is as close as possible to the received beam intensity may be performed by the controller. The controller may decide whether to use the value corresponding to a certain sensor element (depending on the contribution of that element to the overall image intensity). For example, from the output of the sensor element, the controller can determine the "signal center" position of the light beam. The signal center position is similar to the mass center position except that the signal value contributed by each pixel (i.e., sensor element) is used in the calculation rather than the mass. For example, the following formula may be used:

position vector of signal center (position vector of each pixel × value of each pixel) and/or sum of values of all pixels

After the signal center location is determined, the controller may weigh the signals each sensor element contributes to the received beam intensity value (i.e., the electrical signal generated for each sensor) based on the distance between the sensor element and the signal center location. In this way, the controller determines the sensor elements whose signals are most representative of the target image and least likely to disappear from subsequent measurements due to drift in the beam image position on the sensor.

FIG. 85 illustrates an embodiment of a further aspect of the present invention. In this embodiment, the particle detection system 8500 includes a transmitter 8502 and a receiver 8504. Emitter 8502 includes one or more light sources adapted to emit light including wavelength bands λ 1 and λ 2. The light source 8502 may include a plurality of light emitting elements each adapted to emit light of a different wavelength band or a broadband light source. Emitter 8502 may additionally include one or more optics (e.g., 8506) for forming a light beam with a desired beam profile or dispersion characteristic. The receiver 8504 may also include light directing or imaging optics 8508 adapted to form an image of the light beam on a sensor array 8510 of the receiver 8504. In order to minimize the interference of ambient light with the receiver 8504, the receiver 8504 is further provided with a plurality of pass-band filter means 8512. For example, the plurality of pass-band filters may be interference filters arranged to selectively transmit a first pass-band and a second pass-band (corresponding to the emission band of the light source 8502). Most preferably, the filter devices 8512 are band pass interference filters having a pass band at a long wavelength and one or more harmonics of that wavelength. In such an embodiment, the light source 8502 must be set to emit light at a similar associated harmonic frequency. For example, a single interference filter may be designed to transmit substantially all light at 800 nanometers and 400 nanometers, while blocking a substantial portion of light at other wavelengths. When using such a filter, the light source can be adapted to emit light at 800 nm and 400 nm.

In yet another embodiment of the invention, the filter device 8512 may include more than one interference filter or dye filter or other similar filters used side-by-side. For example, two or more filters corresponding to the number of bands at which the system is set to operate may be placed in a side-by-side relationship in the imaging path of the receiver. Fig. 86 to 89 show examples of such filter devices. In this regard, the filter arrangement of fig. 86 to 89 includes portions adapted to transmit light in a first pass band (the portions being indicated by reference numeral 8602 and shaded in white) and interleaved portions indicated by reference numeral 8604 and shaded in gray, the portions being adapted to transmit light in a second pass band. Fig. 88 is suitable for a 4-wavelength system and therefore additionally includes portions, indicated by reference numerals 8606 and 8608, which are suitable for transmitting light in the third and fourth wavelength bands. In each filter arrangement, the surface of the filter is divided approximately equally between different wavelength components and thereby transmits approximately equal amounts of light in each wavelength band to the receiver. Such an arrangement has the disadvantage of a reduced effective diameter of the receiver lens (e.g., by about half for each wavelength in fig. 86, 87 and 89), thereby reducing the effective signal strength, as compared to the arrangement of the plurality of pass-band filters described above. However, this is partly compensated by the fact that the light source LEDs need not be at harmonics of each other, which can be chosen taking into account other advantages, such as the cost of the goods. Furthermore, in such an arrangement, the cost of the filter may be lower and the centre of the wavelength need not be so accurately determined and therefore less sensitive to variations in the output of the emitter over temperature.

FIG. 90 shows a schematic diagram of a fire alerting system in which embodiments of the present invention may be used. The fire alarm system 9000 includes a fire control panel 9010, to which a fire alarm loop 9012 is connected. The fire alarm loop 9012 transmits power and communication information from the fire control panel to the various fire alarm devices connected to the system 9000. For example, the fire alarm loop 9012 may be used to communicate with and power one or more point detectors 9014 and alarms 9016. It may also be used to communicate with one or more aspirated particle detectors 9018. In addition, the light beam detection system 9020 may also be connected to the fire alarm loop 9012. In the present invention, the beam detection system 9020 may be of the type described herein with reference to any of the embodiments described above, and includes a receiver 9022 at a first end and a transmitter 9024 located remotely from the receiver. Preferably, the transmitter 9024 is a battery-powered device and does not need to draw power from the fire alarm loop 9012. Alternatively, it may be powered by, for example, a separate power grid or loop. The receiver 9022 is connected to a fire alarm loop 9012 from which power is drawn and communicates with the fire control panel 9010 via the loop. The manner of communication is known to those skilled in the art and allows the light beam detector 9020 to indicate a fire or fault condition or other condition to the fire control panel 9010.

The present inventors have realised that because the smoke detector does not require a transient response, acceptable average power consumption can be achieved by intermittently (at periods when processing and capturing is suspended) starting the video capture and/or video processing subsystems of the smoke detector. Thus, the system can enter a "frozen" state in which the system is designed to consume little or no power.

A first way to achieve this solution is to provide the video processing subsystem of the particle detector with a simple timing unit that operates to intermittently start the video capture and processing subsystem.

In a preferred form of system, however, the transmitter 9024 is not powered by the loop or other power grid, but is powered by a battery and is preferably not connected to the receiver 9022 or in high speed communication with the receiver 9022. In such a system, the timing of the transmitted light pulses may not be controlled by the receiver, nor synchronized with any other receiver that may be in communication with the same transmitter 9024.

In addition, during video processor "freeze," the receiver 9022 may still be required to manage other functions, such as processing polling from fire alarm loops, or flashing LEDs or other similar devices. Therefore, using a simple custom mechanism to start the system processor and wake it up from a "frozen" state is not a preferred solution to this problem.

In a preferred form of the invention, the receiver 9022 employs a secondary processor, having much lower power consumption than the primary processor, which is used to start the primary processor and handle other functions that must continue uninterrupted while the primary processor is in its "frozen" state.

Fig. 91 shows a schematic block diagram of a receiver 9100 embodying this aspect of the invention.

The receiver 9100 includes an image chip 9102, such as a CMOS sensor manufactured by Aptina, part number MT9V034, for receiving an optical signal from the transmitter 9024.

It may optionally include an optical system 9104, such as a focusing lens (e.g., a standard 4.5mm, f1.4c-mount lens), for focusing the received electromagnetic radiation onto the image chip in a desired manner.

The image chip 9102 IS in data communication with a controller 9106 and associated memory 9108, the controller 9106 preferably being an Actel M1AGL600-V2 Field Programmable Gate Array (FPGA), the memory 9108 comprising a PC28F256P33 flash ROM (for program storage), two IS61LV51216 high-speed RAMs (for image storage) and two CY621777DV30L (for program execution and data storage). The controller functions to control the image chip 9102 and perform the sequence required for data operations to implement the functions required for the detection system. The control device has a wide variety of additional components that are required for proper operation and are understood by those skilled in the art of digital electronic design.

A second processor 9112 is also provided. The processor 9112 may be a texas instruments MSP430F2122 microcontroller or similar device and performs certain functions, such as checking the health of the control device and, if desired, signaling a fault to an external monitoring device (if the control device fails or is otherwise unable to perform its required tasks for any other reason). It is also responsible for timely power control of the control device and the imaging device in order to minimize power consumption. This is performed by the processor 9112, which is deactivated when the main processor 9106 is not needed, and which is intermittently awakened when needed.

The processor 9112 is also in data communication with an interface apparatus 9114 (e.g., a display or user interface) and is also connected to the fire alarm circuit so as to be capable of data communication with other devices connected to the fire alarm circuit (e.g., a fire control panel).

In a preferred embodiment, interface apparatus 9114 is used to inform an external monitoring device whether an alarm or fault condition exists. If the receiver determines that there is a fault, the interface device informs the monitoring device (e.g., fire control panel 9010 of FIG. 90) by opening a switch and thereby interrupting the flow of current to the monitoring device. In a preferred embodiment, the switch is a solid state device using metal oxide semiconductor field effect transistors, which have the advantage of very low power consumption for activation and deactivation. If the receiver determines that an alarm condition exists, the interface means informs the monitoring device of this by drawing a current from the monitoring device that exceeds a predetermined threshold. In a preferred embodiment, the excess current draw is obtained by providing a bipolar transistor, a current limiting breaker on the interface line from the monitoring device. A current draw of about 50mA is used to indicate an alarm condition. In a preferred embodiment, in a non-alarm condition, power for normal operation is drawn from the connection line to the monitoring device, approximately 3 mA.

In a preferred embodiment of the present invention, transistor 9024 includes a controller to control the illumination pattern, illumination time, sequence, and intensity for each light source (e.g., infrared and ultraviolet light sources). This may be, for example, a texas instruments MSP430F2122 microcontroller. The microcontroller also detects the start-up of the device when first installed. In a preferred embodiment of the transmitter, the power source is a lithium thionyl chloride battery.

In a preferred form of the invention, the main processor 9106 may be programmed to discover the illumination pattern of each light source (e.g., light source 9024 of fig. 90) and determine its activation pattern for a period of preferably a few minutes (e.g., 10 minutes) during operation of the system. This process may be repeated for all light sources associated with the receiver. The low power processor 9112 may use the discovered light source sequencing information to enable the main processor 9106 at the correct time.

As will be appreciated, by using a system of this configuration, the functionality of the system (which must always operate) can be controlled by the very low power processor 9112, while high intensity processing can be performed intermittently by the main video processor 9106, so that the average power can be kept at a relatively low level.

The inventors have determined that there are a number of, and often competing, limitations on practical embodiments that must be handled in selecting the illumination mode of the transmitter and corresponding receiver operation in order to accurately obtain and track the transmitter output. For example, in some systems, it may be desirable to use the rate of change of decay to distinguish a fault condition from a particle detection event. This complicates the long integration time discussed in the background. The preferred embodiment uses an integration period of 10 seconds for normal measurements and a shorter integration period of 1 second for rate of change based fault detection.

Another limitation on system performance is the scene lighting level. For practical systems, it is often necessary to assume that a scene is illuminated by sunlight for at least a portion of its useful life. There may also be limitations (e.g., at least cost limitations) on the ability of wavelength selective filters to be used on the camera. Therefore, it is necessary to use a short exposure to avoid saturation and still leave sufficient head space for the signal. In a preferred implementation of the system, the exposure duration is 100 μ s, but the ideal value will depend on the choice of sensors, filters, lenses, worst case scene lighting, and amount of headroom for the signal.

Means for synchronizing the receiver with the transmitter are also required. Preferably, this is done without the use of additional hardware (e.g., an audio system). Alternatively, in one desirable implementation, the synchronization is achieved optically using the same imaging and processing hardware used for particle detection. However, as will be appreciated by those skilled in the art, the use of the same hardware for particle detection as synchronization ties two concerns in the system, thereby adding additional limitations to these possible solutions.

Another limitation in the system is due to the presence of noise. The main noise sources in the system are camera shot noise and noise from variations in light in the scene. For systems that have to deal with all sunlight, dark noise is usually not a significant component. Scene noise is very effectively handled by the background cancellation methods described in our earlier patent applications. Shot noise cannot be completely eliminated because it is the basis of the quantum detection process. However, shot noise can be reduced by reducing the exposure time and summing up less exposure. In a preferred embodiment, substantially all of the transmitter power is at a very brief flash, with a repetition rate that still allows sufficient system response time.

For example, a repetition rate of 1 time per second will meet the requirements of the reflection time, and a flicker duration of less than 1 μ s and an exposure time of 2 μ s (theoretically) may be used. In practice, this would be difficult to synchronize. Furthermore, the emitter LED will need to handle very high peak currents to deliver energy in such a short time, which in turn increases the cost. Another limitation is the dynamic range of the sensor. A flicker that puts the full power at 1 time per second will cause saturation in the sensor.

In view of the above, a preferred embodiment uses an exposure of 100 μ s, a flicker duration of 50 μ s and a period of 9000 ms. An integration length of 3 samples is used for failure detection based on the rate of change. An integrated length of 30 samples was used for smoke measurement.

To perform background cancellation techniques, the receiver also needs to capture images just before and after the flicker, which are used to cancel the contribution from the scene. Ideally, these "off" exposures would occur as close as possible to the "on" exposures to optimize the elimination against a time-varying background. With the receiver system used in the preferred implementation, the maximum practical frame rate is 1000fps, so the "off" exposure is located 1ms either side of the "on" exposure.

In one form, the light output of the emitter consists of a series of short pulses with a very low duty cycle. These pulses are arranged to match the frame rate of the imaging system (e.g. 1000 fps). Fig. 92 shows an exemplary pulse sequence related to the exposure of the sensor in the receiver. In this case, the emitter is adapted to emit light in the infrared and ultraviolet bands. The series of pulses is repeated with a period of 9000 ms.

In the example, there are 5 pulses, as follows:

● Sync 1 (frame 1)110 and Sync 2 (frame 2) 112: the synchronization pulses are used to maintain synchronization between the transmitter and the receiver (discussed in more detail below). These pulses are preferably formed in the most power efficient band. In this case an infrared light source is used, since it causes lower power consumption. Furthermore, long waves are more permeable to smoke and therefore can be kept in synchronism over a wider range of conditions. The sync pulse is 50 mus long.

Ideally, the center of each sync pulse is located in time at the leading edge (sync 1) and the trailing edge (sync 2) of the on period of the shutter of the receiver. This causes their reception strengths to vary with small synchronization errors.

● infrared (frame 5)110 and ultraviolet (frame 7) 116: infrared and ultraviolet pulses are used for signal level measurement (and thus for measuring attenuation and smoke levels). They are 50 mus long, which allows timing errors between transmitter and receiver up to 25 mus without affecting the received strength.

● data (frame 9) 118: the data burst is used to transmit a small amount of data to the receiver. The data is encoded by transmitting or not transmitting data pulses. The data pulses have a reduced amplitude to save power and are for the same reason infrared light. They are 50 mus long. The system provides a 3bps data channel. This data may include serial number, date of manufacture, total run time, battery status, and fault condition. Those skilled in the art will appreciate many alternative ways of transmitting data in the system. These approaches may include pulse position encoding, pulse width encoding, and multi-level encoding schemes. Greater data rates can be readily achieved, however the simple scheme used in the preferred implementation is adequate for small amounts of data.

In fig. 92, data from the receiver during "off" frames (i.e., frames without corresponding transmitter output) is used for the following purposes:

● Frames 0 and 3 are used for background cancellation of synchronization pulses

● Frames 4 and 6 are used for background cancellation of Infrared pulses

● Frames 6 and 8 were used for background elimination of UV pulses

● frames 8 and 10 are used for background removal of data pulses

(a) Spatial search

As described above, the receiver receives each pulse of the transmission in the form of one or more pixels in an image frame.

However, during operation, when the system begins to operate (at least for the first time), the location of the emitters in the image frame must be established. This may be performed by, for example, a manual process involving an operator examining the image and programming in coordinates. However, it is undesirable because of the need for special training, special tools, and long, complicated installation procedures. In a preferred embodiment, determining the location of the emitters in the image frame is automated. The implementation procedure for locating the transmitter operates to:

● the system first captures multiple images at a high frame rate and with sufficient time to ensure that the emitter pulse will be present in one or more of the images (if the emitter is within the field of view of the camera and emits a pulse during capture).

● the system then subtracts each pair of (temporary) adjacent images and takes the modulus of each pixel, then tests each pixel against a threshold to detect the location of large variations where an emitter may be present.

● the system then reduces the list of candidates for emitter locations by merging candidate points that are adjacent or not far apart (e.g., less than 3 pixels apart). A barycentric approach may be used to find the center of a set of candidate points.

● the system then performs an attempted synchronization at each candidate hub (using the procedure described below) to verify that the value received at the candidate hub corresponds to a true transmitter.

● the system then checks for a match of the number of emitters to the expected number of emitters. This number may be set by pre-programming the receiver prior to installation, or by one or more switches installed on or connected to the receiver unit. In a preferred implementation, there is a set of configuration DIP switches incorporated into the receiver unit and accessible only when the system is not mounted to a wall.

The locations of the set of emitters in the image are stored in non-volatile memory. These positions may be cleared by placing the receiver into a particular mode (e.g., by setting a DIP switch to a particular setting and powering the receiver on or off, or by using a special tool such as a laptop computer). This is only required if the transmitter is moved from its original position or the system is to be installed in another position again.

Performance limitations in imaging systems may limit the number of pixels or lines that can be read when operating at high frame rates. In one implementation, up to 30 rows 640 of pixels may be read out in 1 ms. Thus, the first few steps of the above method need to be repeated 16 times to cover the entire 640 x 480 pixel frame. Alternatively, some embodiments use only a portion of the image frame. Similarly, some embodiments use a slower frame rate. However, if a lower frame rate is used, the possibility of sensor saturation in high light conditions typically limits the exposure time, while changes in background light conditions typically introduce more noise.

The frame rate must be selected to ensure that emitter pulses do not always occur during periods when the shutter is off. For example, if the frame rate is exactly 1000fps with an exposure of 100 mus, and the emitter produces a pulse on the exact 1ms boundary, the pulse will all occur when the shutter is closed. The receiver frame rates are chosen such that there is a slight difference, causing a gradual phase shift, ensuring that the pulse will fall sufficiently early and late on the shutter on period.

In some embodiments, processing speed limitations are addressed by not analyzing all pixels, but rather simply subtracting and checking every n (e.g., 4) horizontal and vertical pixels, thereby reducing processing effort (e.g., by a factor of 16). If the received image (i.e. the image of each emitter on the sensor) is spread out over a sufficiently large area (e.g. a spot having a diameter of 5 pixels), the emitter will still be reliably found.

Whenever the system is powered up, a phase search and locking method is used to establish initial synchronization, either with a known set of transmitter positions, or as part of the spatial search described above, with a set of candidate positions.

The method mainly comprises the following steps:

The system captures images (at least part of the images in the desired location) at a high frame rate.

The system waits for the desired pulse pattern to occur at the candidate center position.

The system uses the arrival time of the selected pulse in the desired mode as the starting phase of the phase locked loop.

The system waits for the PLL to settle. If no PLL lock is formed, the position is flagged as false in the case of a test candidate position, or the receiver can continue to try again and declare a fault until successful when synchronization with the known transmitter position is re-established.

As with the spatial search, a small deviation in the frame rate of the receiver is used to cause a gradual phase shift, ensuring that the pulse will fall sufficiently early and late on the shutter on period.

For each frame, the total intensity is calculated in a small area of the image, centered at a known or candidate location. A sequence of intensity values is then calculated for the desired pattern from the emitter.

The test operation for the desired mode is as follows:

after at least 9 frames of intensity values have been collected, these intensity values are tested in the following manner to test for the presence of the desired transmitter pulse sequence.

Given an intensity value I (N), 0 < N < N,

testing for possible transmitter signals received at frame n starting with frame 0

First, the reference level of the "off frame" is calculated

I₀＝(I_R(n+0)+I_R(n+3)+I_R(n+4)+I_R(n+6)+I_R(n +8))/5{ "average of off frames }

Calculating relative intensities

I_R(n+m)＝I(n+m)-I₀0 to 8 for m

Compared with a predetermined threshold to determine the presence or absence of a transmitter pulse in each frame

Found＝{(I_R(n+1)＞I_ON)or I_R(n+2)＞I_ONAnd { sync 1 or sync 2 pulse }

(I_R(n+5)＞I_ON) and { Infrared pulse }

(I_R(n+7)＞I_ON) and { ultraviolet pulse }

(I_R(n+0)＞I_ON) and { off frame }

(I_R(n+3)＞I_ON) and { off frame }

(I_R(n+4)＞I_ON) and { off frame }

(I_R(n+6)＞I_ON) and { off frame }

(I_R(n+8)＞I_ON) and { off frame }

Any one of the synchronization pulses may be completely lost due to a random phase error, and thus "or" is used in the above expression. Alternatively, the test for sync pulses may be omitted entirely and the test for off frames may be reduced. However care must be taken to ensure that the position of the transmitter pulse sequence is not identified by error.

Following positive detection, the time corresponding to frame n is recorded with some variable. The amplitude of the phase pulse can be used to trim the recorded time instant values to more closely represent the start of the sequence. This helps to reduce the initial phase error that the phase locked loop has to deal with and may not be needed if the frequency error is not sufficiently small.

In a preferred implementation, the image capture rate is 1000fps, matching the transmitter timing as described above. Shutter times of 100. mu.s were used.

This completes the initial synchronization. The arrival time of the next set of pulses can now be predicted by simply adding the known emitter period to the time recorded in the previous step.

Although the receiver knows the transmitter period (300 ms in the preferred implementation), there is a small error at each end of the clock frequency. This will inevitably cause the transmitted pulse to be misaligned with the opening time of the shutter of the receiver. Phase-locked loop systems are used to maintain the correct phase or timing. PLL technology is well known and therefore will not be described in detail. In a preferred implementation, the PLL control formula is implemented in software. The phase comparator function is based on measuring the amplitude of the phase pulse. These amplitudes are calculated by subtracting the average of the intensities measured in the nearest neighbor off-frames (frames 0 and 3). The phase error is then calculated with the following equation:

where T is the width of the phase pulse.

In the case of a phase pulse whose amplitude falls below a predetermined threshold value, the phase error is designed to be zero. In this way, noisy data is allowed to enter the PLL, and in practice the system is able to maintain adequate synchronization for at least a few minutes. Thus, high smoke levels do not cause synchronization failures before an alarm can be issued. In the case of an obstacle, this feature allows the system to recover quickly after the obstacle is removed.

The PLL control formula includes proportional and integral terms. It is not necessary to use differential terms. In a preferred implementation, proportional and integral gains of 0.3 and 0.11, respectively, were found to produce acceptable results. In yet another variation, the gain may be initially set to a larger value and decreased after the phase error falls below a predetermined threshold, thereby reducing the overall lock time for a given loop bandwidth.

Phase errors below +/-10 mus may be used to indicate phase lock for the purpose of verifying candidate transmitter locations and for the purpose of allowing normal smoke detection operations to commence.

Fig. 93 shows an environmental monitoring system 9300, suitable for monitoring a region 9302 in a room 9304. The environment monitoring system comprises a beam detection subsystem 9306 comprising a receiver 9308 and 4 transmitters 9310, 9312, 9314, 9316. The beam detection subsystem operates in accordance with an embodiment of any of the systems described above.

Environmental monitoring system 9300 also includes 4 additional environmental monitors 9318, 9320, 9322, 9324. Each of the additional environmental monitors 9318-9324 can be of the same type, but alternatively can be of different types (i.e., detect different environmental conditions or detect the same condition with different mechanisms). The environmental monitor may include, for example, a sensor for carbon dioxide, carbon monoxide, temperature, flame, other gases, or the like. Each of the additional environmental monitors 9318 to 9324 is connected by a communication channel to a transmitter of a nearby beam detection subsystem. For example, an additional environmental monitor 9318 is connected via line 9326 to a corresponding transmitter 9310 of the beam detection subsystem 9306. Similarly, the environmental monitor 9320 is in data communication with the transmitter 9312, the environmental monitor 9322 is in data communication with the transmitter 9314, and the environmental monitor 9324 is in data communication with the transmitter 9316. The data communication channel between each environmental monitor and its respective transmitter may be a hard connection or a communication link via a wireless connection (e.g., wireless, optical, etc.). In most embodiments, the communication link need only be unidirectional, but may be bidirectional in some embodiments. In the unidirectional case, the communication channel is adapted to enable the environmental monitor to issue an alarm and/or fault condition or other output (e.g., raw or processed sensor output) to the beam detection subsystem 9606 that it detects.

As can be appreciated, the environmental sensor may be housed in the transmitter rather than being remotely located and connected by a long wire or communication link.

The transmitter of the beam detection subsystem 9306 is adapted to receive signals from environmental monitors and retransmit these signals back to the receiver 9308 via an optical communication channel, with or without additional encoding. The optical communication channel may be implemented by modulating the particle detection beam or a secondary beam sent by the transmitter to the receiver 9308. The communication channel may be alternately or intermittently transmitted between pulses of particle probe beam generated by the transmitter. Alternatively, it may be illuminated continuously (possibly simultaneously with the particle detection beam). In this case, the wavelength used for the particle detection beam may be different from the wavelength implementing the optical communication channel.

With such a system, a network of environmental monitors can be placed around the monitored region 9302, and environmental conditions detected by these monitors can be transmitted back to the receiver of the beam probing subsystem. The receiver 9308 is in data communication with the fire alarm control panel (e.g., via a fire alarm loop or a dedicated network or other notification system, without requiring a complex dedicated wiring system between the environmental monitor network and the fire alarm system). In a preferred embodiment, the plurality of optical communication channels are differentially encoded so that the receiver of the beam detection subsystem is able to distinguish each optical communication channel from the other. For example, each optical communication channel may be modulated differently, or may be arranged to operate at different times. Thereby, the time division multiplexing device can be effectively used for different optical communication channels. Different wavelengths may also be used for each communication channel.

The system also enables determination of where the environmental condition is detected, since the receiver 9308 can resolve the optical channels from the different emitters, e.g. based on the received signal or the location where the signal arrives on the sensor if the sensor of the receiver is of the multi-sensor element type. Addressing information or channel information may be communicated to a fire alarm control panel and the location of the alarm may be communicated to an operator or fire department.

In the example of fig. 93, each of the transmitter and environmental monitor is preferably battery powered to eliminate the need for wiring.

FIG. 94 illustrates yet another embodiment of this aspect of the invention. In this embodiment, environmental monitoring system 9400 includes a beam detection subsystem 9402 and an environmental monitoring subsystem 9404. The beam detection subsystem includes a receiver 9406 and a transmitter 9408. The transmitter is adapted to transmit one or more beams of light 9410 received by the receiver 9406. The receiver 9406 has a wide field of view with boundaries represented by lines 9409A, 9409B. Two environmental monitors 9412, 9414 are placed in the field of view of receiver 9406. Environmental monitors 9412 and 9414 can be of any of the types described above and additionally include respective light emitters 9416, 9418. Light 9416, 9418 may be a low power LED or similar light and is used to generate an optical signal that is received by receiver 9406. Each of the LEDs 9416, 9418 can be individually modulated to transmit the output of the respective environmental monitor 9412, 9414 back to the receiver 9406. As with the previous embodiments, the optical communication channels may be time or wavelength multiplexed with each other, and the particle detection beam 9410 is transmitted by the transmitter 9408. This embodiment has the additional advantage over the embodiment of fig. 93 of not requiring any wiring or communication channels between the environmental monitors 9412 and 9414 and the transmitter 9408 of the particle detection subsystem. Thereby reducing installation costs as much as possible.

Figure 95 shows components of a particle detection system. Element 9500 is a light source for emitting one or more beams of light through a volume being monitored for particles. Light source 9500 includes one or more light emitters 9502 coupled to circuit 9504, with circuit 9504 providing power to light emitter 9502. The operation of the lights 9502 is controlled by a microcontroller 9506, which causes the lights 9506 to illuminate in a predetermined manner, e.g., flash in a particular sequence. Light source 9500 is powered by battery 9508. The output of the battery is monitored by a monitoring component 9510, and the operating environment condition of the component is monitored by an environmental monitor 9512. Environmental monitor 9512 may be a temperature sensing device, such as a thermocouple. The controller 9506 receives the output of the battery monitor 9510 and the output of the environmental sensor 9512, and determines an expected battery life.

More particularly, the controller receives a signal representative of the temperature of the environment immediately adjacent the battery and a measured output voltage of the battery 9508. The battery output voltage is compared with a threshold voltage corresponding to the measured temperature, and the discharge state of the battery 9508 is determined.

In an alternative embodiment, the battery monitor 9510 is adapted to measure the total current drawn from the battery. For example, the monitor 9510 may be an electricity meter and determines the level of current being drawn from a battery. In this case, the controller is adapted to integrate the measured current over time and to determine the amount of power still available. An indication of an impending discharged state of the battery may be generated when the calculated amount of charge still available is below a predetermined threshold.

In yet another alternative case, an estimate of the total current may be formed. For example, in a preferred embodiment, a majority of the power drawn from the battery will be drawn in pulses for flashing the light 9502. If circuit 9504 is operating at a constant current (which is preferred), the duration of time that the LEDs are operating, multiplied by the constant current, will provide a relatively accurate measure of the total amount of power used by the system over time. In a more crude alternative case, the typical average current draw that the device requires knowledge can be pre-calculated and the length of time that the components are in operation can be used to determine the total current drawn from the battery over time.

In the above-described embodiment, environmental conditions (most advantageously the temperature of the ambient environment in close proximity to the battery) may be monitored over time, and this temperature data may be used by the controller to produce a more accurate estimate of the amount of power still available in the battery 9808. As will be appreciated, the controller may be adapted to calculate an estimate of the battery life that is still available in the prevailing circumstances. The remaining time may be compared to an alarm threshold and if the threshold is exceeded, an indication of a gradual approach to a discharged condition may be generated.

In a preferred embodiment, a predetermined time threshold at which an indication of a gradual near-discharged state of the battery is generated may be selected such that maintenance personnel are allowed to receive an indication of an impending battery discharge in a periodic maintenance event. If an impending battery discharge can be alerted at a sufficiently early stage, i.e., prior to a scheduled maintenance event prior to another scheduled maintenance event (at which time the battery needs to be charged), then no additional unscheduled maintenance events are required. In addition, service personnel can ensure that the required equipment (e.g., the special tool and battery) is acquired prior to a service event (at which time the battery will be charged). For example, where a component has a rated battery life of 5 years and a periodic check per year is arranged, an indication of impending battery failure may occur 13 or 14 months prior to the end of the rated life. Thus, when the system is inspected after about 4 years of operation, the maintenance personnel will find that the battery needs to be charged during the next maintenance period (over the course of a year) and can plan to bring a backup battery at the next annual inspection. It should be appreciated that to avoid system failure, the nominal battery life is set at some safety margin. The 13 or 14 month period is chosen to take into account the scheduling margin for two maintenance periods, i.e. once the maintenance personnel knows the discharge state of the battery and the next time the battery is charged.

In a preferred form of the invention, the light source controller may be adapted to issue a battery status to the receiver when the monitored component is a light source of a particle detector. This may be achieved by modulating the amplitude, duration and/or timing of one or more emitted light pulses in a predetermined manner. The light pulse used for data transmission may be one of a light pulse for particle detection or an additional light pulse added to the light pulse train (generated by the light source for the purpose of data communication from the light source to the receiver). As described above, such an approach avoids the need for wiring between cells. Alternatively, the light source may be equipped with an additional low power LED that may blink to indicate to a person at a distance (not the receiver) the status of their battery.

In a particularly sophisticated embodiment, the controller of the light source may be adapted to generate a battery output signal (e.g. by modulating the light beam to a particular code) thereby indicating the time before the battery is expected to discharge. For example, the output signal may indicate the number of months before the battery power is expected to be insufficient. This allows the service personnel to more accurately schedule the next scheduled service period and determine whether the battery needs to be replaced before the next scheduled inspection. Furthermore, if the exact "time to full discharge" is known, the light source can enter a low power mode, e.g. with its duty cycle reduced from normal, to extend battery life. The receiver may be programmed to detect this low duty cycle mode and indicate a fault if a low duty cycle mode is observed.

FIG. 96 illustrates a system according to yet another embodiment of the invention. A first receiver 9602 is provided in the system 9600, the first receiver 9602 being associated with a pair of transmitters 9604 and 9608. The first emitter 9604 emits a first light beam 9606, while the second emitter 9608 emits a corresponding light beam 9610. Both beams are received by receiver 9602 and particle detection decisions may be made in accordance with embodiments of the invention described herein. The system 9600 also includes a receiver 9612 and an associated transmitter 9614, the transmitter 9614 emitting a beam of light 9616. The light beam 9616 is received by a receiver 9612, and the receiver 9612 may be adapted to determine the presence of particles, as described elsewhere herein. The beam detector arrangement effectively provides 3 beam detectors with simultaneous (or nearly simultaneous) beams in two places. The receivers 9602 and 9612 are each connected to a controller 9618, and the controller 9618 is adapted to apply fault and/or alarm logic to determine the presence of a fault condition and/or a particle detection condition. As will be appreciated, the intersecting beams 9606 and 9616, and 9610 and 9616, enable the system 9600 to determine whether a particle has been detected at the intersection of the beams by correlating the outputs from the receivers 9602 and 9612. Such an arrangement also enables relatively advanced processing to be performed and distinguishes the particle detection algorithm of each of the individual beam detectors from the particle detection algorithm used in a single, stand-alone beam detector. For example, a simple dual alarm system may be implemented in which at least two beams of light must detect particles above a predetermined threshold before an alarm is given. In a preferred form, such a system may reduce the overall false alarm rate, since false alarm conditions are unlikely to occur in two different beams. However, this also allows the use of a lower alarm threshold, thereby enabling more rapid detection of particles, with substantially no effect on the false alarm rate of the system. In such a system, the false alarm probability of the entire system is the same as the individual false alarm probability of the light beam. As will be appreciated, the advantages of the above-described system can all be achieved to some extent by setting alarm thresholds that include a compromise between sensitivity and false alarm rate improvement. In addition, the temporal characteristics of the particle detection output of the various beam detectors may be used to improve particle detection performance or reduce the occurrence of false alarms. In this regard, the time interval of occurrence of suspected smoke events in each beam may be used to improve the likelihood of early detection without increasing false alarms. For example, the time at which each of a pair of light beams enters an alarm, occurring substantially simultaneously, may be used to determine whether the alarm condition is caused by the presence of particulates or a false alarm. Particle detection events may be true if they occur substantially simultaneously in time. On the other hand, if the particle detection events occur at substantially different times, a false alarm may be indicated. In a sophisticated system, time-varying particle detection characteristics may be compared to each of the beam detectors to identify a corresponding particle detection event. This may be achieved, for example, by cross-correlating the outputs of multiple substantially simultaneous beam detectors in the system. Where a pair of outputs are determined to be highly cross-correlated, this may indicate that the outputs of each of the beam detectors have experienced similar conditions, such as the same particle detection event or the same false alarm event. Determination of such events can be accomplished by analyzing characteristics (e.g., duration of occlusion; level of obscuration; rate of change at the onset of observation, etc.) to determine whether the event is caused by the presence of a particle or a foreign object.

It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the present invention.

Claims (20)

1. A beam detector (100) arranged to detect the presence of particles in a monitored space (101), the beam detector (100) comprising:

a light source (4500) adapted to generate at least one light beam (4502) having a composition (4506, 4504) in at least a first and a second wavelength band;

a sensor (4508) arranged relative to the light source (4500) such that the at least one light beam from the light source (4500) is received at the sensor after the at least one light beam passes through the monitored space, the sensor being a light sensor array capable of recording and reporting light intensity across a plurality of points (202) in its field of view; and

processing means arranged to determine that a particle is intruding into the at least one light beam (4502) based at least in part on a relative attenuation of the second wavelength band relative to the first wavelength band in the light intensity received at the sensor;

wherein the light source (4500) is arranged such that: the at least one light beam emitted by the light source has a spatial intensity distribution that is different for the components (4506, 4504) in at least a first band and a second band such that when the light source (4500) is misaligned relative to the sensor (4508), the components (4506) in the first band of light intensities received at the sensor decrease first before the components (4504) in the second band of light intensities received at the sensor decrease, causing a relative change in the received light intensities that is distinguishable from a relative decrease in the second band of light intensities relative to the first band of light intensities caused by particles intruding the at least one light beam in the monitored space.

2. The beam detector (100) of claim 1 wherein the beam width of the component (4504) in the second wavelength band is wider than the beam width of the component (4506) in the first wavelength band.

3. The beam detector (100) of claim 1, wherein the light in the first wavelength band is longer in wavelength than the light in the second wavelength band.

4. The beam detector (100) of claim 1, wherein the first wavelength band comprises the infrared or red portion of the electromagnetic spectrum.

5. The beam detector (100) according to claim 1, wherein the second wavelength band comprises light in the blue, violet or ultraviolet part of the electromagnetic spectrum.

6. The beam detector (100) according to claim 1, wherein the light source comprises:

a first light emitter for emitting a first light beam;

a second light emitter for emitting a second light beam; and

an optical system comprising a transmissive region from which light from the first and second light emitters is emitted from the light source, wherein the optical system is arranged such that obstruction of the transmissive region causes substantially the same obstruction to the first and second light beams.

7. The beam detector (100) of claim 6, wherein the first and second light emitters are semiconductor dies.

8. The beam detector (100) of claim 7, wherein the semiconductor die is housed within a single optical package.

9. The beam detector (100) of claim 6, wherein the optical system further comprises a light guide for guiding the first and second light beams from the first and second light emitters to the transmissive region.

10. The beam detector (100) according to claim 9, wherein the light guiding means is selected from the group consisting of: a convex lens, a fresnel lens and a mirror, or a combination of any two or more of a convex lens, a fresnel lens and a mirror.

11. The beam detector (100) according to claim 6, wherein the transmission region forms at least a part of an externally accessible optical surface of the optical system.

12. The beam detector (100) according to claim 6, wherein the optical system comprises beam shaping optics adapted to change the beam shape of one or both of the first and second beams.

13. The beam detector (100) of claim 12, wherein the beam shaping optics provide a divergence angle of about 10 degrees to the light emitted from the light source.

14. The beam detector (100) of claim 12, wherein the beam shaping optics change the beam shape of one or both of the beams to extend further in one direction than in the other direction.

15. The beam detector (100) according to claim 12, wherein the beam shaping optics modify the first and second beams such that they have different beam shapes from each other.

16. The beam detector (100) of claim 15, wherein the beam shaping optics alters the first beam to have a wider beam shape than the second beam.

17. The beam detector (100) according to claim 12, wherein the beam shaping optics comprise one or more beam intensity adjusting elements arranged to adjust the spatial intensity of the beam.

18. The beam detector (100) of claim 17, wherein the beam intensity adjusting element is selected from the group consisting of:

an optical surface coating is applied to the optical surface,

a frosted glass diffuser, and

the glass diffuser is etched.

19. The beam detector (100) of claim 6, wherein the second light emitter emits an ultraviolet beam and the first light emitter emits an infrared beam.

20. The beam detector (100) according to claim 9, wherein the optical system comprises beam shaping optics adapted to change the beam shape of one or both of the first and second light beams, and the light guiding optics and the beam shaping optics are combined into a single optical element.