EP0515635B1 - Direction sensitive counting and switching device - Google Patents

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

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

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

According to the state of the art, counting and determining the direction of moving people / objects has 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 for traffic monitoring. For this purpose, induction loops are laid in all lanes. Disadvantages are the high installation costs and the traffic problems that occur during the laying of the induction loops.

Image processing devices are also suitable for detecting 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 directionally 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. Since side by side moving vehicles are not resolved individually, an exact count is not possible here.

Another solution - described in EP-PS 0 245 242 - provides that a plurality of pyroelectric sensor elements are arranged on a spherically parabolically shaped mirror and thus movement and direction-dependent detection is 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 two mutually at least partially enclosing infrared sensors that 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 that does not register people passing the door and only directly on the door approaching people. 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 area of the motion detector. The application of this solution, for example as a light switch in apartments, is not possible, because when a person enters a room, the lighting in it is switched on, but it switches off again after the specified time if the person in the room does not move any further .

With the device described in DE-PS 36 23 792, the use of a plurality of individual infrared sensors, which are arranged one behind the other in the passage direction and transversely to the passage direction, makes it possible to determine the number and direction of people within a room to be monitored or a passage gate. Since the individual sensors have very large fields of view, this device cannot be used in cases where only very narrow or very small fields of vision can be implemented. In addition, this device cannot be miniaturized by using individual sensors.

In public transport, the number of passengers is primarily analyzed using light barriers, pressure sensors and sensitive running boards.

When using light barriers, 2 radiation transmitters and receivers are installed on the doors of public transport. The successive crossing of both light barriers triggers a counting process corresponding to the direction of movement of the passenger. However, since people walking closely next to one another 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 is used to determine their number, the recording is the number of passengers is not very accurate. The pressure sensors cannot be used in trams and trains due to 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.

US-A-4 799 243 describes a similar device.

An overview of (formerly) development lines in two-dimensional IR detectors and the description of a system concept for them can be found in Conference Proceedings Military Microwaves '88, July 5, 1988, London, pages 93 to 98. There are indications of a direction-sensitive count or circuit not here.

The invention has for its object to provide a device of the type mentioned that distinguishes people and / or objects with high accuracy from each other and according to their directions of movement, counts and / or triggers switching operations that is inexpensive to manufacture and unobtrusive and without significant 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 a directionally sensitive object or person detection is then included great accuracy is possible if signals are evaluated which only contain information about changes in the detection range. By using pyroelectric detectors, there is the advantageous possibility of creating a reliable, direction-dependent detector device with a detection double row having a few sensor elements.

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

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 there is a signal sequence that indicates the movement of people and / or objects in the field of view of the directionally selective counting and switching device. The multi-element sensors represent radiation receivers for receiving the thermal radiation 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 makes it possible to focus the incident heat radiation on the multi-element sensors and also to substantially miniaturize the device according to the invention in comparison with 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 shifting 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 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. This allows the movement of a person to be followed with simple means. It is important for the pattern recognition taking place in a signal processor that the constant background does not provide any detectable signals. The detection of 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 environment in the form of a pattern sequence.

• Figur 1 eine schematische Darstellung einer möglichen Anordnung der Mehrelementesensoren eines Ausführungsbeispiels in einer Doppelzeile,
• Figur 2 eine prinzipielle Schnittdarstellung des Ausführungsbeispiels mit den dazugehörigen Gesichtsfeldern,
• Figur 3 eine weitere prinzipielle Schnittdarstellung der Vorrichtung gemäß Figur 2 bei der die Ansicht um 90° gedreht dargestellt ist,
• Figur 4 ein Ausführungsbeispiel für die Verwendung der erfindungsgemäßen Vorrichtung zur Besetzungsgraderfassung in öffentlichen Verkehrsmitteln in Frontalansicht,
• Figur 5 eine weitere günstige Anordnung eines Ausführungsbeispiels eines Mehrelementesensors in mehreren Doppelzeilen,
• Figur 6 ein Ausführungsbeispiel für die Verwendung der erfindungsgemäßen Vorrichtung zur Steuerung einer Lichtsignalanlage an einem Fußgängerübergang,
• Figur 7 ein Prinzipschaltbild eines Ausführungsbeispiels einer erfindungsgemäßen Vorrichtung einschließlich Signalverarbeitung sowie
• Figur 8 eine schematische Darstellung der sich bei der Vorrichtung gemäß Figur 7 ergebenden Eingangssignale.

Other advantageous developments of the invention are characterized in the subclaims or are shown below together with the description of the preferred embodiment 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 another basic sectional illustration of the device according to FIG. 2, in which the view is shown rotated by 90 °,
• FIG. 4 shows an exemplary embodiment for the use of the device according to the invention for determining the degree of occupancy in public transport in a frontal view,
• FIG. 5 shows a further advantageous 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 multi-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 partial area of the field of view 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 need to be amplified and 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 chosen such that the area to be detected is covered, that is to say depends on the passage width. In contrast, only a few sensors (minimum, two) are required in the direction of passage, since only the temporal sequence of the detected changes 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 in front of the flat side of the lens, a pinhole 3 is arranged centrally, 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, there is an additional interference filter in the area of the pinhole The entire field of view of the device according to the invention, which includes 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) fields of view 4.1 to 1.15, each have an opening angle of 8 °, and are arranged alternately on both sides of a plane running through the center of the lens and between the multi-element sensors along the double line.

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 so that the accessible door area is in your 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 ascertained whether people or objects get into or out of the monitored area. 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 that of the field of view 10 of the one not shown here Device enclosed pedestrian detection area 11 according to the invention. By using the direction-selective counting and switching device, the light signal system can be controlled in such a way 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 one 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 into a digitized signal sequence on the A / D converter 26. 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 recorded gray value pattern, 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 became different Times are included in a time grid which is adapted to the anticipated 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 the memory of the signal processor in a correspondingly coded form. The type of signal processing and memory organization depends on the type of processor used and therefore does not need to be described here, since it can be found in the corresponding system manuals.

After the storage of the successive patterns 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 A1 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 signal compared to an adjacent element at a later point in time is interpreted 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 neighboring Sensors in which signal changes were determined in the vicinity of time, 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. Thus, if different smaller objects are detected in the representation according to FIGS. 8a to 8d, registration takes place in different counters according to the direction of movement. An additional classification according to the object size can also take place.

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 differentiates, counts and / or triggers people and / or objects from one another and according to their directions of movement with great accuracy, is significantly smaller than known infrared motion detectors, can be manufactured inexpensively and can be installed without significant structural changes.

In a special embodiment, two adjacent sensor elements that belong to different rows can have a common back electrode. In a further special embodiment, each sensor element that has a separate feed line is connected electrically separately.

The amplifiers downstream of the sensor elements are combined in an appropriate design in an integrated assembly.

Claims (15)

1. A direction-sensitive counting and switching means, comprising an optical system (2,3; 22) with a passive infra-red detector (1; 7; 23), which is arranged at the rear of a collector lens and constructed as a multi-element sensor, a pre-amplifier (24) and an evaluating circuit (26, 27) which is connected thereto and triggers off a counting or switching operation based on the sequence of the signals emitted by the elements, which contains data of the direction of movement of the person surveyed, characterised in that the sensor elements of the multi-element sensor (1; 7; 23) are arranged in the form of one or more twin lines, each sensor element detecting a partial region of the visual field of the multi-element sensor, and in that the evaluation circuit (26, 27) only triggers off a counting and/or switching operation when there is a signal sequence which suggests a directional movement of a person and/or an object within the area of coverage of the detector (1; 7; 23).
2. A device according to Claim 1, characterised in that an apertured partition (3) is provided in the optical path in front of the collector lens.
3. A device according to one of the preceding claims, characterised in that an interference filter is provided in the optical path in front of the collector lens.
4. A device according to one of the preceding claims, characterised in that the collector lens is made of plastics material.
5. A device according to one of the preceding claims, characterised in that the collector lens is constructed as a Fresnel lens.
6. A device according to one of the preceding claims, characterised in that the sensor elements are made of pyroelectric material.
7. A device according to one of the preceding claims, characterised in that two adjacent sensor elements which belong to different rows have a common return electrode.
8. A device according to one of the preceding claims, characterised in that the sensor elements which form double rows are arranged in such a way that their regions of coverage enclose a predetermined geometrical region, either completely or partly.
9. A device according to one of the preceding claims, characterised in that each sensor element has a separate supply line and a separate electrical connection.
10. A device according to Claim 9, characterised in that a separate amplifier (24) is connected to each sensor element.
11. A device according to one of the preceding claims, characterised in that the amplifiers are combined to form an integrated group of components.
12. A device according to one of the preceding claims, characterised in that in the event of a time-staggered occurrence of output signals from substantially adjacent sensor elements of the multi-element sensor, the evaluation circuit emits a direction-dependent counting signal for recording the passing of a person or an object.
13. A device according to Claim 12, characterised in that in the event of a chronological succession of equidirectionally time-staggered output signals from substantially adjacent sensor elements of the multi-element sensor within a predetermined time window, the evaluation circuit emits only a single direction-dependent counting signal for recording the passing of a person or an object.
14. A device according to Claim 1, characterised in that the evaluation circuit comprises a pattern-detecting circuit which emits a direction-dependent counting signal for recording the passing of a person or an object, said counting signal being formed from a signal sequence picked up in a time scan and forming a pattern, and consisting of the output signals of the individual sensor elements of the multi-element sensor.
15. A device according to one of the preceding claims, characterised in that the collector lens (2) is constructed as a plano-convex lens whose planar surface forms the continuation of the outer face of a housing (5) enclosing the components.

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