MXPA99002355A - Passive infrared detector - Google Patents

Abstract

A passive infrared detection system is described which has a wide angular field of view and a flat or nearly flat front surface. Input optical elements direct and/or focus incident peripheral infrared radiation onto one or more internal Fresnel lens arrays and/or a sensitive area of a detector, including radiation having incident angles of less than about 30°. Because of the absence of protruding elements improved performance and greater functionality can be obtained by employing larger or multiple infrared input windows and/or opto-electronic sections without degrading the aesthetic appearance of the unit.

Description

PAS IVO DETECTOR, OF INFRARED DIAGRAM.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide angle passive infrared system, improved for detecting the presence of an infrared source and / or the presence of an infrared source that enters, exits or it moves within a specific field of view and angular range. 2. Description of the Related Art Motion detectors, alarms, occupancy detectors and other passive infrared radiation detection systems employ an infrared lens detector system with an electrical output signal that varies by a measurable amount according to a radiation source of Infrared enters, exits or moves within its field of view and angular range. The electrical signal coming out of the detector is amplified and used, for example, to activate an alarm, switch or other control system. The lens detector system consists of a one or two dimensional array of Fresnel lenses on a thin strip or sheet each of which focuses the incident infrared radiation in a specific angular range over a sensitive area of a detector. In the prior art, a wide angular field of view is achieved by employing a Fresnel lens array on a strip or sheet protruding from the front surface of the unit. The protruding detectors collect the infrared radiation from the peripheral angles. Figure 1 is a schematic of the configuration of the lens detector system for motion detectors, alarms, occupancy detectors and similar systems according to the prior art. A thin, segmented strip or sheet forming an array 10 covers the entry opening and extends to the exterior of the lens detection system; that is, the exterior of the housing 12. A section of a Fresnel lens 14 is molded or cut in each sector of the strip or sheet. In the diagram, 12 sectors are indicated. Each individual Fresnel lens focuses incident infrared radiation at some angle on one edge of a sensitive area of a detector. For example, the Fresnel lenses 14 focus the indicated infrared radiation beam on a sensitive area 16 of a detector 18. As the angle 20 increases the focal spot moves through the sensitive area 16 of the detector 18 and finally moves out on the opposite bank of the sensitive area 16. The change in the electrical output signal of the detector 18 as a focal spot moves in or out of the sensitive area 16 is interpreted as an infrared source moving through one of the critical angles for which the focal spot is on the edge of the sensitive area 16 of the detector 18. For a single source of infrared rays within the general field of view of the strips or sheets 10 of the lenses there is a multiplicity of focal spots which move through the sensitive area 16 of the detector 18 as the source moves through the total field of view of the system. An example of this is illustrated in the scheme of FIG. 2. The incident infrared radiation of the enclosed angular ranges 22, for example, is focused on the corresponding sensitive area 16 of at least one detector 18 by a sector of the array 10 of the lenses. of Fresnel. Incidental infrared radiation of the open angular ranges 24, for example, does not give rise to a focal spot on a sensitive area of any detector. In this way, the intensity of the radiation in a sensitive area of one of the detectors will vary significantly as the infrared source moves in or out of one of the enclosed angular ranges. The output signal of the resulting detector is processed electronically to activate the alarm, switch or other control system. The configuration of the Fresnel lenses outside the housing allows the prior art radiation detection systems to detect the radiation over a wide range of incidence ranges 20 which includes minor angles such as angles less than about 30 °. The angle of incidence 20 is measured relative to the exposed surface. Until now, this exterior placement of the Fresnel lens may not have an aesthetic appearance, and may also cause suspicion of damage as well as accidents or injuries. For example, a detector placed to detect people may be rubbed or otherwise may have contact with these people, including children. As such, outdoor Fresnel lenses can cause harm to these people. In the prior art, the placement of Fresnel lenses or other internal mechanisms for a housing may be more aesthetic and less susceptible to damage and injury, but these internal configurations thus far reduce the detection range, in which the angles of incidence 20 lower, lower than for example, approximately 30 ° are not detectable.

COMPENDIUM OF THE INVENTION Wide-angle motion detectors, usurpation alarms, occupancy detectors and other passive infrared radiation detection systems would be aesthetically more comfortable and less intrusive if the face of the unit were flat or nearly flat, allowing at the same time the detection of radiation that has low incidence angles, such as peripheral angles of less than about 30 °. This would greatly improve the value of these units in some facilities. Also, the sensitivity, range, angular field of view, angular resolution and other performance measures can be improved over those of the prior art by using larger or multiple infrared radiation input windows that do not protrude and therefore do not degrade the appearance of the unit or interfere with other functions. A wide-angle passive infrared radiation motion detector with a flat or nearly flat frontal surface can be obtained by inverting the arrangement of the Fresnel lenses through the plane of the entry aperture and / or by using optical input elements to direct and / or or focusing the incident infrared radiation on one or more internal Fresnel lenses or a sensitive area of a detector. The arrangements of the Fresnel lenses are totally inside the unit but nevertheless they collect, or using suitable optical elements of entrance they can be collected, enough infrared radiation from the peripheral angles where they are used. Each internal Fresnel lens array detector focuses a specific angular range of the incident infrared radiation over one or more of the sensitive areas of one or more detectors. To increase the collector power of the system and reduce the necessary width of the unit, it is possible to use unitary curved mirrors, lenses or prisms to direct and / or focus the incident infrared radiation on an internal Fresnel lens array and / or a sensitive area of a detector. In one embodiment of the invention, one or more prisms encompassing all or most of the entry opening are used to direct incident infrared radiation from peripheral angles towards the center of the unit. The orientation of the exit faces of the series of prisms may be chosen to direct and / or focus the infrared radiation on a suitable sector of one or more of the conveniently placed internal Fresnel lens arrays and / or a sensitive area of a detector.

BRIEF DESCRIPTION OF THE DRAWINGS The characteristics of the passive infrared detector described will be more readily apparent and better understood with reference to the following detailed description of the illustrative embodiments of the present invention, taken together with the accompanying drawings, in which: Figure 1 represents in a schematic manner the configuration of the arrangement system of the Fresnel-detector lenses according to the prior art. Figure 2 represents schematically an example of the fields of view of each of the detectors of a combination Fresnel-detector lenses in a one-dimensional arrangement of two elements and the intervening angular regions, which are not in the field of view of any of the Fresnel-detector lens combinations. Figure 3 is a schematic drawing of a system employing a combination of the concave, inverted-detector Firesel lens array according to the present invention. Figure 4 is a schematic drawing of an alternative embodiment of the present invention employing a convex, internal Fresnel lens array and mirrors on the sides of the entry aperture. Figure 5 is a schematic drawing of an alternative embodiment of the present invention employing an array of convex, internal Fresnel lenses and prisms on the sides of the inlet opening. Fig. 6 is a schematic drawing of an alternative embodiment of the present invention employing an internal Fresnel lens array, concave and an entry prism that covers the entire entry opening. Figure 7 is a schematic drawing of an alternative embodiment of the present invention employing an entrance window and a lens near the entrance opening. Figure 8 is a schematic drawing of an alternative embodiment of the present invention employing an array of internal Fresnel lenses, an inlet window and a mirror near the inlet opening. Figure 9 is a schematic drawing of an alternative embodiment of the present invention employing an array of internal Fresnel lenses, an inlet window and a prism near the inlet opening. Figure 10 is a schematic drawing illustrating a technique for increasing the angular resolution and functionality of passive infrared radiation detection systems employing multiple opto-electronic sections with overlapping fields of view. Figure 11 is a schematic drawing of a detector that includes an array of Fresnel lenses with a composite configuration. Figure 12 is a schematic drawing of a detector including a stepped window to reduce reflection of radiation. Figure 13 is a schematic drawing of an intruder detection system that includes the level mounted detectors described herein.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Now with regard to the specific details of the drawings, with like reference numbers identifying similar or identical elements, as shown by way of scheme in Figure 3, the present description describes a radiation detection system. Passive infrared including a unit having an array of inverted Fresnel lenses 26, a detector 18 having a sensitivity area 16 and detection circuits 28 placed in a housing 12 in accordance with the present invention. Because the Fresnel lens array 26 is reversed in the manner in which it has been employed in the prior art, ie, the Fresnel lens array 26 is placed internal to the total detector system within the housing 12, the ranges Angles of the infrared radiation processed by each Fresnel lens 30 are reversed from left to right in the scheme, and can also detect peripheral radiation having angles of incidence of less than about 30 °. For example, in contrast to the infrared radiation beam indicated in the scheme of Figure 1 falling in the rightmost sector 14 of the Fresnel lens array 10, a corresponding beam of infrared radiation indicated in the scheme "of the figure 3, falls in the leftmost sector 30 of the Fresnel lens array 26 in FIG. 3. This sector 30 of the Fresnel lens array 26 focuses the incident infrared radiation on the sensitive area 16 of a detector 18. From the In the same way, each sector of the Fresnel lens array 26 focuses a specific angular range of the incident infrared radiation over a sensitive area of a detector, for example, the sector 30 can focus the incident radiation at angles in the range between approximately 5 ° to about 10 ° on the sensitive area 16. It is understood that one skilled in the art can form and / or bend a Fresnel lens to focus the received radiation at a predetermined angle, and also that an array c of the segment or sections of Fresnel lenses can be formed as a sheet or strip in a known way e_? The technique. As shown in the illustrative embodiment of Figure 3, the Fresnel lens array is configured to be generally concave with the curved portion oriented away from the entrance window of the exposed surface. In other embodiments, the Fresnel lens array 26 may have a generally convex configuration. It should be understood that Fresnel lens array sectors can be individually and substantially planar but positioned at angles relative to each other to provide a generally concave or generally convex configuration. It is also contemplated that the Fresnel lens array may have a composite configuration. By the term "composite configuration" is meant that the array of lenses includes at least two different portions that are of different configuration. In this way, for example one portion of the lens array can have a generally concave configuration, while another portion of the lens array is flat or convex. One of these lens arrays with a composite configuration is shown in Figure 11, wherein the central portion 127 of the lens array 126 has a generally convex configuration, while the end portions 129 have a generally concave configuration. As will be appreciated, the convex central portion 127 does not interfere with the detection of low angle radiation by the end portions 129. Figure 4 is a schematic drawing showing an alternative embodiment of a lens-detector unit having a lens array of Fresnel placed in internal position 32 in a housing 12 that includes mirrors 34, 36 placed on opposite sides of an entrance opening or access window. In the illustrative mode shown in figure 4, the Fresnel lens array 32 is configured to be convex with the curved portion facing the entrance window of the exposed surface. In other embodiments, the Fresnel lens array 32 may have a concave configuration. The mirrors 34, 36 are used to direct the peripheral infrared radiation, such as radiation incident at less than about 30 °, towards a sector 38 of the internal Fresnel lens array 32 and / or a sensitive area 16 of a detector 18 placed substantially closer to the center of the unit. This reduces the necessary width of the unit that is important in some applications, such as in configurations configured and sized to be placed in standard wall electrical boxes, such as in openings sized to be approximately 2 inches wide by approximately 3 inches. inches high by approximately 2 inches deep. In another alternative embodiment, the mirrors may be curved to focus the incident radiation directly on the sensitive area of a detector, and thus some sectors of the Fresnel lens array or otherwise the entire Fresnel lens array are not employed. For example, multiple detectors (not shown in Figure 4) such as detector 18 can be oriented to receive radiation directed internally to the unit. More than a series of mirrors can also be used to provide sufficient angular coverage to receive the incident radiation. Figure 5 is a schematic of another alternative embodiment of the invention, which employs the prisms 40, 42 to direct and / or focus the incident infrared radiation towards a sector 38 of the Fresnel lens array 32 and from there to an area sensitive 16 of a detector 18 internally placed in a housing 12. Otherwise, the unit can use these prisms 40, 42 to directly focus the incident infrared radiation on the sensitive area 16 of the detector 18 without employing the Fresnel lens array 32 or sectors 38 thereof. Figure 6 is a schematic of an alternative embodiment of the invention having at least one inlet prism 44 that encompasses or almost encompasses the entire inlet opening of the unit. The at least one input prism 44 has at least one output face 46 and collects and directs the peripheral infrared radiation through the at least one output face 46 towards the interior of the unit in which a lens array is placed. Fresnel 26 having at least one sector 30 for directing the infrared radiation towards a sensitive area 16 of a detector 18 positioned within a housing 12. The orientation of the exit faces 46 of the at least one prism 44 determines the direction and amplitude of the infrared beams that emerge from it. Upon passing through the coarse input prism 44, the amplitude of the beam can be amplified or compressed depending on the angle between the input and output faces of the prism 44. This effect can be used to increase or decrease the sensitivity of the system; that is, the angular range over which the source must move so that the focal spot moves through the sensitive area 16 of the detector 18. This effect can be improved or reduced by adjusting the orientation angle of the Fresnel lens sector with relation to the beam that is being processed. As already described for other embodiments, the Fresnel lens array 26 may not be employed. Figure 7 is a schematic showing an example of an alternative embodiment of the invention, which employs one or more lenses 48 placed on or near the input opening of the unit for directing and / or focusing the incident infrared radiation towards a sector of an internal Fresnel lens array (not shown in FIG. 7) and / or a sensitive area 16 of a detector 18 placed inside housing 12 of the unit. An entrance window 50 can also be placed substantially adjacent to the entry opening, as described in detail below. Figure 8 is a schematic presentation of an example of another alternative embodiment of the invention that employs one or more flat or curved mirrors 52 at or near the entry aperture for directing and / or focusing the incident infrared radiation towards a sector 30; of a Fresnel lens array 26 and / or in a sensitive area 16 of a detector 18 positioned in an internal position within a housing 12 of the unit. An entry window 50 can also be positioned substantially adjacent to the entry opening, as described in detail below. Figure 9 is a schematic presentation of an example of another alternative embodiment of the invention employing one or more prisms 54 positioned at or near the entry aperture for directing and / or focusing the incident infrared radiation on a sector 30 of an arrangement of Fresnel lenses 26 and / or a sensitive area 16 of a detector 18 placed in an internal position within a housing 12. An entrance window 50 can also be placed substantially adjacent to the entrance opening or access window, as described in detail below. In each of the embodiments of the invention already shown, the entry opening or access window of the unit can be covered with a thin entry window 50, respectively, having a slightly outward curvature, as indicated, for example , for the dotted lines in figures 7-8. The slightly outward curvature of the input window 50 reduces the Fresnel reflection of the peripheral infrared radiation on the window surfaces. Otherwise, a series of input prisms may be employed as described above with respect to the embodiment illustrated in FIG. 6 to direct and / or focus the incoming infrared radiation towards the interior or center of the unit. It is also contemplated that the hole in the housing may be covered by a stepped access window to avoid reflection of the received radiation at low incident angles. Specifically, as seen in Figure 12, window 150 includes stepped surfaces 154 that are configured to provide a highly angled surface with respect to low angle radiation. In this way, although the low angle radiation making contact with the portions 152 of the window 150 could be largely reflected, the radiation contacting the portion 154 is transmitted directly to the housing, thereby improving the detection of the radiation that has a low incidence angle. It should be understood that the units shown in Figs. 3-9 may also include detection circuits known in the art that are connected to the respective detectors and placed internal to the respective housing, or otherwise located at remote locations of the respective accommodations. Thus, for example, as shown in Figure 13, the detector may include a wireless transmitter 202 placed within the wall or ceiling in which the detector housing is installed. When the detector detects an intruder, the wireless transmitter 202 is activated and sends a signal to a main control box 205 located at a distance from the detector. The main control box 205 activates an alarm or makes contact with a central monitoring station or the police in a manner known to those skilled in the art. In this way, the detectors described herein eliminate the need for surface mounted detector units. Instead, the current level mounted detectors are installed to replace a room light switch and may require no special wiring to provide an intruder detector. Preferably a limit switch (not shown) is provided to allow manual operation of the light switch or to deactivate the intruder alarm mechanism when desired. In an illustrative embodiment, the present invention may include units having components placed in a respective housing, as shown in FIGS. 3-9, in which the housing can be configured and sized to fit a standard electrical box, or another way in an opening of a wall or ceiling. For example, the respective housing 12 may be approximately 2 inches wide, approximately 3 inches high and approximately 2 inches deep for the placement of the complete lens-detection unit in a wall or ceiling of a construction, such as a residential house as a component of an anti-theft system. As already described, the present invention includes means positioned internally within the housing to direct the radiation received from the substantially planar surface onto the sensitive region of the detector. Accordingly, the directing means is defined herein as the Fresnel lenses mentioned above, the arrangements thereof, mirrors, lenses, prisms, etc., individually or in combinations thereof, such as those respectively described above with reference to figures 3-9. It is understood that other configurations of Fresnel lenses, arrangements thereof, mirrors, lenses, prisms, etc., not shown in Figures 3-9 are also contemplated. As described above for Figures 3-9, since the director means is internally positioned within the housing, the units may have a flat or substantially planar exposed surface, providing minimal external protrusion that prevents accidental injury or damage, and "providing better aesthetic appearance Due to the flat or substantially flat surface of the units described in Figures 3-9 that are exposed outward for which the radiation is incident, larger and / or multiple infrared radiation input windows and combinations Detector lenses can be used without deteriorating the appearance of the unit This allows sensitivity, range, angular field of view, angular resolution and other improved performance measurements on prior art devices due to the greater collector force of the larger windows and / or multiples, in particular, the greater collecting force for the infrared radiation peri This increases the system's raneo in peripheral angles. In addition, multiple lens-detector combinations with overlapping fields of view can be used to increase the angular resolution of the system. This is illustrated in the scheme of Figure 10 with two infrared input sections and the corresponding lens-detector combinations (not shown in Figure 10), which have, for example, a first input section focusing the infrared radiation of the closed angled sectors 56 on a sensitive area 16 of a detector 18. A second input section can then focus the infrared radiation of the closed angular sectors 58, illustrated by the dotted lines in Figure 10, on the sensitive area 16 or, another way over a different sensitive area (not shown in Figure 10) of the detector 18 or otherwise in another detector (not shown in Figure 10). The infrared radiation from the open angular sectors 60 may not be focused on any detector, but the degree or measurement of these open angular sectors 60 can be minimized by the use of multiple lens-detector combinations with overlapping fields of view. If all the angular sectors in Figure 10 are of the same size, the electronic processing of the two detector outputs by a logic circuit, which can be included in the detection circuits, such as the detection circuits 18 shown in FIG. Figures 3-9, produces an angular resolution of, for example, a means of the angular size of any sector. For further explanation, the illustrative embodiments of the described passive infrared detector are presented as individual functional blocks, which may include functional blocks labeled as "detector" and "detection circuits" '. The functions represented by these blocks can be provided through the use of shared or dedicated equipment, which includes, but is not limited to, equipment capable of running software. Although the described passive infrared detector has been particularly shown and described with reference to preferred embodiments, those skilled in the art will understand that various modifications in form and detail may be made herein without departing from the scope and spirit of the invention. For example, lenses, mirrors and mobile or adjustable prisms, with suitable structure or control mechanisms, can be used as the internally placed means to direct the received radiation to the sensitive regions of at least one detector. Accordingly, modifications such as those suggested above, but not limited thereto, should be considered within the scope of the invention.

Claims (22)

1. A radiation detection system consists of: a housing that includes a surface with a 5 hole peira receive radiation; a Fresnel lens array having a generally concave configuration and positioned internally within the housing; and at least one detector, wherein the arrangement of concave Fresnel lenses 10 directs the received radiation toward the at least one detector.

2. The radiation detection system of claim 1, wherein the arrangement of concave Fresnel lenses is adapted to receive the radiation at an angle of 15 incidence to the surface plane less than about 30 °.

3. The radiation detection system of claim 1, further comprising: "t" at least one prism for directing the received radiation 20 into the housing to the concave Fresnel lens

4. The radiation detection system of claim 3, wherein the at least one prism is placed substantially close to the center of the hole in the 25 accommodation.

5. The radiation detection system of claim 3, wherein the at least one prism encompasses the hole in the housing.

6. The radiation detection system of claim 1 further comprising: at least one lens for directing radiation received into the interior of the concave Fresnel lens.

7. The radiation detection system ale of claim 6, wherein the at least one lens is positioned substantially close to the center of the hole in the housing.

8. The radiation detection system of claim 1 further comprises: at least one mirror for directing radiation received into the interior of the housing toward the concave Fresnel lens.

9. The radiation detection system of claim 8, wherein the at least one mirror is positioned substantially close to the center of the hole in the housing.

10. The radiation detection system of claim 8, wherein the at least one mirror is positioned adjacent to one edge of the hole.

11. A radiation detection system consists of: a housing that includes a surface that has a hole for receiving radiation; at least one detector; and an arrangement of Fresnel lenses placed internally within the housing, wherein the arrangement of Fresnel directs the radiation with an angle of incidence to the plane of the surface less than about 30 ° toward the at least one detector. The radiation detection system of claim 11, wherein the Fresnel lens array is configured to direct the radiation to a sensitive region of the detector as the angle of incidence of the radiation received to the plane of the surface changes from 5. ° to approximately 10 °. 13. A radiation detection system consists of: a housing with a surface having a hole for receiving radiation; the means placed within the housing adjacent the orifice to direct the received radiation into the interior of the housing; at least one detector; and an arrangement of Fresnel lenses placed within the housing and positioned between the means for directing the received radiation and the at least one detector, the arrangement of Fresnel lenses focusing the received radiation on the at least one detector. The radiation detection system of claim 13, wherein the means for directing includes at least one mirror adjacent to one edge of the orifice. 15. The radiation detection system of claim 13, wherein the means for directing includes at least one prism positioned adjacent to one edge of the orifice. 16. The radiation detection system of claim 13, wherein the Fresnel lens array consists of a Fresnel lens array configured in a generally convex orientation. 17. The radiation detection system of claim 13, wherein the Fresnel lenses comprise an array of Fresnel lenses configured in a generally concave orientation. 18. A radiation detection system consists of: a housing that includes a surface that has a hole for receiving radiation; at least one detector; and a lens positioned internally within the housing for directing the received radiation with an angle of incidence to the plane of the surface of less than about 30 ° toward the at least one detector, the lens being oriented to be perpendicular to the plane of the surface. 19. The radiation detection system of claim 18, wherein the lens is positioned substantially close to the center of the hole in the housing. 20. The radiation detection system of claim 1, wherein the at least one detector includes a plurality of regions sensitive to radiation incident thereto to generate corresponding detection signals. 21. A radiation detection system consists of: a housing having a surface with a hole for receiving radiation; a prism that covers the hole in the housing to direct the received radiation into the interior of the housing; at least one detector; and an arrangement of Fresnel lenses placed inside the housing and placed between the prism and the at least one detector, the Fresnel lens focusing the received radiation on the detector means. 22. An intrusion detection system consists of: a detector unit; a wireless transmitter operably connected to the detector unit; and a main control unit responsive to signals from the wireless transmitter, the detector unit including a housing having a surface with a hole for receiving radiation; at least one detector; and an arrangement of Fresnel lenses positioned internally within the housing, wherein the Fresnel lens array directs the radiation having an angle of incidence to the plane of the surface of less than about 30 ° toward the at least one detector, generating the transmitter Wireless signals in response to radiation that makes contact with the detector.