EP0515635A1

EP0515635A1 - Direction sensitive counting and switching device.

Info

Publication number: EP0515635A1
Application number: EP92901333A
Authority: EP
Inventors: Ralf Gast; Andreas Thun; Andre Haufe; Andreas Wermke
Original assignee: Iris GmbH IG Infrared and Intelligent Sensors
Current assignee: Iris GmbH IG Infrared and Intelligent Sensors
Priority date: 1990-12-14
Filing date: 1991-12-16
Publication date: 1992-12-02
Anticipated expiration: 2011-12-16
Also published as: US5313060A; EP0515635B1; JPH05508252A; DE59107554D1; WO1992010812A1; ATE135480T1; DE4040811A1; CA2075899A1

Abstract

A direction sensitive counting and switching device has an optical system which includes a convex lens and a passive infrared detector composed of sensor elements arranged in at least one double row. The detector is disposed on one side of the convex lens for detecting radiation transmitted along a beam path from persons or objects moving through a detection area of the detector located on the other side of the convex lens and producing output signals in response to the detected radiation. A preamplifier is coupled to the detector for producing amplified output signals from the output signals. An evaluation circuit is coupled to the preamplifier for processing the amplified output signals of the sensor elements and, if the amplified output signals permit a conclusion as to directional movement of a person or object in the detection area of the detector, initiates a counting or a switching process which contains information about direction of movement of the respective person or object in the detection area.

Description

Direction-sensitive counting and switching device

Description

The invention relates to a device of the type specified in the preamble of claim 1.

Directional.Selective counting and switching devices are used to count people and / or objects moving or moving in different directions. puts. They provide additional information which provides information about the directions of movement of the persons and / or objects detected.

According to the prior art, counting and determining the direction of moving people / objects has hitherto been implemented as follows:

When using light barriers, at least two radiation transmitters and receivers are installed at the location to be monitored. Accurate detection of moving objects / people is only possible if they pass through them one after the other.

Loop technology is often used in traffic monitoring. For this purpose, induction loops are laid in all lanes. Disadvantages are the high installation costs and the traffic disturbances that occur during the laying of induction loops.

Image processing devices are also suitable for the detection of moving objects in terms of numbers and direction. However, since these devices record the signals of moving and still objects, the computational outlay for image processing is very high and the devices are therefore relatively expensive.

EP-PS 0 287 827 describes a direction-selective pyrodetector which consists of a sensor with at least two sensor elements for different detection directions and is used for the detection and speed measurement of moving objects. Besides- vehicles driving each other cannot be resolved individually, an exact count is not possible here.

Another solution - described in EP-PS 0 245 242 - provides that several pyroelectric sensor elements are arranged in a spherical-parabolic mirror, thus making movement and direction-dependent detection possible. It is disadvantageous that objects moving next to one another are not detected individually, the complicated mirror is too expensive for many applications and does not meet the frequent demand for small, unobtrusive signaling systems.

By means of two mutually at least partially enclosing infrared sensors which have a radiation-sensitive surface corresponding to the shape of the desired field of view, according to DE-PS 3 407 462, for example, a door opener can be realized which does not register people walking past the door and only responds to people directly approaching the door. This means that the door opener is only directionally selective in one direction.

From DE-OS 32 25 264 an infrared motion detector is also known which switches on the lighting of corridors, passageways, etc. for a predetermined time when people move through the detection range of the motion detector. The use of this solution, for example as a light switch in apartments, is not possible since the lighting in the room is switched on when a person enters a room, but switches off again after the predetermined time has expired if the room is in the room Person does not move any further. With the device described in DE-PS 36 23 792, it is possible to determine the number and direction of people within a room to be monitored or a passage lock by using a plurality of individual infrared sensors which are arranged one behind the other in the passage direction and transversely to the passage direction ¬ Lich. Since the individual sensors have very large visual fields, this device cannot be used in cases where only very narrow or very small visual fields can be implemented. In addition, this device cannot be miniaturized by using individual sensors.

In public transport, the volume of passengers is analyzed primarily by means of light barriers, pressure sensors and sensitive footboards.

When using light barriers, 2 radiation transmitters and receivers are installed on the doors of public transport. The successive traversal of both light barriers triggers a counting process corresponding to the direction of movement of the passenger. However, since people walking closely next to each other are not reliably recorded and objects carried by passengers, such as umbrellas and bags, are often counted, it is not possible to determine the exact number of passengers.

The use of pressure sensors on the shock absorbers is known in buses. Since the number of the bus and the passengers determines the number of passengers, the the number of passengers is not very accurate. The pressure sensors cannot be used in trams and trains because of the high weight of the vehicles.

From DE-OS 38 32 428 a device of the type mentioned is known. In this device, however, not only moving objects or people, but also immovable targets in the detection area are evaluated, so that the results are inaccurate.

The invention has for its object to provide a device of the type mentioned that distinguishes people and / or objects from each other and according to their directions of movement with high accuracy, counts and / or triggers switching operations, which is inexpensive to manufacture and inconspicuous and without essential structural changes can be installed.

This object is achieved by the measures described in the characterizing part of claim 1.

The invention includes the knowledge that direction-sensitive object or person detection is possible with great accuracy if signals are evaluated which only contain information about changes in the detection area. By using pyroelectric detectors, ^"there is the advantageous possibility of using a detection matrix having a few sensor elements to create a reliably working, direction-dependent detector device. - 6 -

Such a device can be used particularly advantageously in public transport, even when the number of passengers is high.

The solution according to the invention preferably consists of a passive infrared detector, which is formed from a plurality of pyroelectric elements in the form of one or more double lines, behind a converging lens, as a result of which the field of view of the directionally selective counting and switching device in front of the converging lens, corresponding to the number , Geometry and arrangement of the multi-element sensors is divided into several smaller fields of view, and the evaluation circuit triggers a counting and / or switching process if one, based on the movement of people and / or objects in the field of view of the directionally selective counting and switching device indicating signal sequence is present. The multi-element sensors provide radiation receivers for recording those emitted by people and / or objects. The pyroelectric sensors can also be produced inexpensively and operated without additional cooling.

The preferred use of a converging lens enables the incident heat radiation to be focused on the multiple sensor sensors and also the essential miniaturization of the device according to the invention in comparison to known devices.

The central arrangement of a pinhole in front of the converging lens prevents the incidence of flat rays and scattered light on the lens as well as total reflections within the lens. The fields of view of the directionally selective counting and switching device are preferably dimensioned such that persons and / or objects to be detected are reliably detected. The signals occurring at the multi-element sensors are amplified in the associated preamplifiers, digitized in A / D converters and processed in the evaluation circuit. The direction of movement of the people and / or objects crossing the field of view of the direction-selective counting and switching device is determined from the signal sequence of different lines belonging to multi-element sensors.

Since a defined signal sequence must be present in order to detect a movement in the detection range of the device according to the invention, malfunctions can be excluded with high probability. The use of an interference filter in front of the converging lens also prevents interference radiation, such as radiation from the sun or from car headlights, from falling onto the multi-element sensors.

Applications exist, for example, in the occupancy level detection in public transport, in the analysis of traffic flows, in the control of various building facilities, as door openers and people counters, and in the use of motion-dependent switches.

The invention is preferably implemented by an arrangement consisting of a pyroelectric chip with at least one double line of sensitive elements, analog signal preprocessing, digital signal processing. work for pattern recognition and an optically imaging system, for example a converging lens.

As a result of the pyroelectric sensor principle, only movement of objects when it is combined with a thermal contrast is detected. The course of a person's movement can thus be followed with simple means. For the pattern recognition running in a signal processor, it is important that the constant background does not provide any detectable signals. Detecting a movement of a person or a moving object is thus greatly simplified by suppressing the information about the background, in contrast to a conventional video camera. In the invention described here, the signal processor only has to analyze the signals from moving objects which have a thermal contrast to the surroundings in the form of a pattern sequence.

_"^ Other advantageous developments of the invention are characterized in the subclaims and will be described hereinafter together with the description of the preferred embodiments of the invention with reference to the figures. Show it:

FIG. 1 shows a schematic illustration of a possible arrangement of the multi-element sensors of an exemplary embodiment in a double line,

FIG. 2 shows a basic sectional illustration of the exemplary embodiment with the associated visual fields, FIG. 3 shows a further basic sectional illustration of the device according to FIG. 2, in which the view is shown rotated through 90 °,

FIG. 4 shows an embodiment of the use of the device according to the invention for occupancy level detection in public transport in a frontal view,

FIG. 5 shows a further favorable arrangement of an exemplary embodiment of a multi-element sensor in several double lines,

FIG. 6 shows an exemplary embodiment for the use of the device according to the invention for controlling a light signal system at a pedestrian crossing,

FIG. 7 shows a basic circuit diagram of an exemplary embodiment of a device according to the invention including signal processing and

Figure 8 is a schematic representation of the input signals resulting in the device of Figure 7.

FIG. 1 shows the detector 1, consisting of fifteen multiple element sensors 1.1 to 1.15 arranged alternately in a double line. A field of view is assigned to each multi-element sensor. The individual elements are designed as pyroelectric sensor elements and are offset from one another. Each sensor element detects a sub-area of the field of vision and emits a signal if a change occurs here. On In this way, immobile objects or people are hidden without any additional electronic effort when they are captured. Only the output signals of the individual sensor elements have to be amplified and post-processed separately. The geometry and arrangement of the multi-element sensors corresponds to the geometry and arrangement of the desired visual fields, but is also essentially determined by the shape and refractive index of the lens and by the distance of the multi-element sensors from the lens.

FIGS. 2 and 3 show the front and side views of the device according to the invention with its field of view 4. The detection sectors of the individual sensors are arranged in a radiation pattern. The number of sensors arranged transversely to the direction of passage is selected such that the area to be detected is covered, that is to say it depends on the passage width. In contrast, only a few sensors (at least two) are required in the direction of passage, since only the chronological sequence of the changes detected has to be evaluated here. (Preamplifier, multiplexer, analog / digital converter and evaluation circuit are not shown here and are described in more detail below.

The detector 1 is located in the focal plane of a hemispherical lens 2. A perforated diaphragm 3 is arranged centrally in front of the flat side of the lens, which keeps flat rays and scattered light away from the lens and prevents the occurrence of total reflections in the lens. (In a further embodiment of the invention, not shown here, an additional in- Interference filter is provided for reducing interfering light radiation. The entire field of view of the device according to the invention, which comprises an angular range of 120 ° parallel to the double line and an angular range of 16 ° perpendicular to the double line, consists of fifteen small (partial) visual fields 4.1 to 1.15, each with an opening angle of 8 ° have, and alternately on both sides of a plane running through the center of the lens and between the multi-element sensors along the double line, are arranged.

FIG. 4 shows how the device 5 according to the invention for occupancy level detection can be used in a public transport 6.

The direction-selective counting and switching device is installed in the middle above the doors in such a way that the accessible door area is in its field of vision. When passengers get on and off, they cross several fields of view of the device according to the invention and thereby trigger a counting process.

FIG. 5 shows a detector 7 consisting of a plurality of multi-element sensors in the form of a plurality of double lines which completely enclose an area as a visual field, so that it can be detected whether people or objects are entering or leaving the monitored area get this out. Such an arrangement is suitable, for example, for controlling a light signal system.

FIG. 6 shows a pedestrian crossing 8, the light signal system 9 and the one from the field of view 10 that is not shown here. provided device according to the invention enclosed pedestrian detection area 11. By using the direction-selective counting and switching device, the light signal system can be controlled so that it only shows "green" when pedestrians really want to cross the street at this point. In this way, the traffic can be made more fluid, since pedestrians no longer need green phases of the traffic light system.

FIG. 7 shows the flow of information in an exemplary embodiment of the device according to the invention. The infrared radiation is imaged by an object plane 21 by means of a lens 22 onto the pyroelectric matrix 23 located in the focal plane. A voltage signal is generated on the sensitive elements onto which heat radiation changes over time. After an analog signal amplification 24, a multiplexer 25 converts the voltage applied to the individual elements into a serial signal sequence. This sequence of analog signals is converted at the A / D converter 26 into a digitized signal sequence. A gray value pattern is then created in the signal processor 27 by means of software in accordance with the original pixel geometry. This pattern shows in which section of the detection area of the object plane a movement took place in a predetermined time window.

The grayscale pattern recorded, as is available in digitized form after the corresponding signal processing, is shown in FIGS. 8a to d. The patterns shown in FIGS. 8a to d were different times in a time grid, which is adapted to the expected crossing of an object or a person through the detection area. The timing is indicated by the direction of arrow t and corresponds to the order of the figure names.

The individual sensor elements of the matrix are designated by combinations of letters and numbers. The patterns are stored in a correspondingly coded form in the memory of the signal processor. The type of signal processing and memory organization depends on the type of processor used and therefore does not need to be described in more detail here, since it is evident from the corresponding system manuals.

After the successive patterns have been stored in the memory, the pattern analysis is carried out by comparing successive patterns. _^

It can be seen that in the representations according to FIGS. 8a to d, an object has moved from corner AI to corner D4. Moving objects in their direction are now determined by comparing the signal differences in adjacent fields at successive points in time. Each increase or decrease in signals that occurs at a later point in time compared to an adjacent element is evaluated as a movement of the element towards the element in which the change occurred later (for example elements D2 / D3 in FIGS. 8a) and b). There is a message and summary for Adjacent sensors in which signal changes were determined in the vicinity, so that the detection for the object in question only triggers a registration process in a corresponding downstream counter in association with the respective direction. If various smaller objects are detected in the representation according to FIGS. 8a to 8d, registration is carried out in different counters according to the direction of movement. An additional classification according to the object size can also be made.

It can be seen that in the solution according to the invention, only signal changes — that is, moving objects — are detected by using pyroelectric sensor elements, while at the same time, stationary objects located in the detection area do not influence the signal processing. This eliminates a large part of disruptive signals from the outset and does not need to be eliminated in a complex manner in the course of troubleshooting.

As a result of the pattern comparison, the geometric size, the direction and the number of moving objects can be recognized depending on the application.

The invention has created a device which distinguishes, counts and / or triggers people and / or objects from one another and according to their directions of movement with high accuracy, is significantly smaller than known infrared motion detectors, can be manufactured inexpensively and can be installed without significant structural changes . The embodiment of the invention is not limited to the preferred exemplary embodiment specified above. Rather, a number of variants are conceivable which make use of the solution shown, even in the case of fundamentally different types.

Claims

Expectations

1. Direction-sensitive counting and switching device, consisting of an optical system, with a passive infrared detector, which is designed as a multi-element sensor, a preamplifier and a downstream evaluation circuit, which uses the sequence of signals emitted by the elements to generate a counting or triggers a switching process that contains information about the direction of movement of the person concerned,

characterized ,

that the sensor elements of the multi-element sensor are arranged in the form of one or more double lines,

- That the detector is arranged behind a collecting line, and

- That the evaluation circuit only triggers a counting and / or switching operation if there is a signal sequence which indicates a directional movement of a person and / or an object in the detection range of the detector.

2. Device according to claim 1, dadurchge ¬ indicates that a pinhole is provided in the beam path in front of the converging lens.

3. Device according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that an interference filter is provided in the beam path in front of the converging lens.

4. Device according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the converging lens consists of plastic.

5. Device according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the converging lens is designed as a Fresnel lens.

6. Device according to one of the preceding claims, d a d u r c h g e k e n n z e i c h-n e t that the sensor elements consist of pyroelectric material.

7. Device according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that two neighboring sensor elements, which belong to different lines, have a common back electrode.

8. Device according to one of the preceding claims, characterized in that the double-line forming sensor elements are arranged such that their detection areas completely or partially enclose a predetermined geometrical area.

9. Device according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that each sensor element has a separate feed line and is connected electrically separated.

10. The apparatus of claim 9, d a d u r c h g e ¬ k e n n z e i c h n e t that each sensor element is followed by a separate amplifier.

11. Device according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the amplifiers are combined in an integrated assembly.

12. The device as claimed in one of the preceding claims, that the evaluation circuit emits a direction-dependent count signal for registering the passage of a person or an object when output signals of essentially adjacent sensor elements of the multi-element sensor occur at different times.

13. The apparatus according to ^' claim 12, dadurchge ¬ indicates that the evaluation circuit in the sequential succession of the same time offset occurrence of output signals substantially adjacent sensor element of the multi-element sensor inside emits only a single direction-dependent counting signal for registering the passage of a person or an object within a predetermined time window.

14. The apparatus according to claim 1, dadurchge ¬ indicates that the evaluation circuit has a pattern recognition circuit, which consists of a directional dependence of a signal sequence recorded in a time pattern, which forms a pattern and consists of the output signals of the individual sensor elements of the multi-element sensor Outputs a counting signal for registering the passage of a person or an object.

15. Device according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the converging lens (2) is designed as a plano-convex lens whose flat surface forms the continuation of the outer surface of a housing (5) enclosing the components.

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