EP1024465A1 - Passive infrared detector - Google Patents

Abstract

The detector has at least two heat sensitive sensor (S,S',S) and focussing devices (R,R',R) for focussing the thermal radiation onto the sensors such that each region being monitored can be identified by determining which sensors are subjected to thermal radiation. The outputs of the sensors may be combined into an encoded sensor signal that indicates which sensors are subjected to radiation and which are not, each monitored region having a corresponding sensor signal.

Description

The present invention relates to a passive infrared detector with a heat sensitive Sensor and with a focusing means for bundling the different radial Monitoring areas on the detector heat rays falling on the sensor.

Passive infrared detectors of this type have been known and widely used for years. You serve in particular to determine the presence or intrusion of unauthorized persons in a surveillance room by proof of the emitted by these people typical infrared radiation, which is directed onto the sensor by the focusing means becomes. Either Fresnel lenses are used as focusing means, which in the Integrated entrance windows for the infrared radiation are arranged on the front of the detector housing are (see, for example, EP-A-0 559 110), or an inside the detector housing arranged mirror, which consists of individual reflectors (see for example EP-A-0 303 913).

Both the Fresnel lenses and the mirrors are designed so that the one to be monitored Room covered with monitoring areas starting from the detector in a fan shape is. As soon as an object emitting heat radiation enters a surveillance area penetrates, the sensor detects the heat radiation emitted by this object, the detection being safest when the object is across the surveillance area emotional.

Today's passive infrared detectors detect intruders inside of the effective range of the detector is very reliable, but does not provide any information about the position of the burglar in the effective range. That is for common, conventional Applications not required, but could for certain new applications be desired.

Such a new application would be a passive infrared detector, for example individual monitoring zones optionally, for example by an internal switch, active or inactive can be set. With such detectors one could have certain during the day Monitoring zones for visitor disruption or alarm, i.e. active, and the remaining zones switch inactive. Another application would be to monitor one Room, for example the counter room of a bank, with video cameras, the cameras save the images if the image processing requires it. Since the cameras are used Surveillance of a room must be known to have a large opening angle and therefore the picture quality is generally poor, it would be desirable to get one Use a camera with a narrow viewing angle and thus higher resolution and use this Align the signal of an infrared detector to the area of interest to be able to.

The invention is now to provide a passive infrared detector, which not only detection but also localization of an intruder in its effective area enables.

According to the invention, this object is achieved in that the detector has at least two Has heat-sensitive sensors, and that the focusing means so constructed and is arranged that each surveillance area based on the number and number of sensors exposed to heat radiation can be clearly identified.

A first preferred embodiment of the detector according to the invention is characterized in that that the output signals from the sensors into a single, encoded sensor signal are summarized, which is the exposure of each sensor or has no sign indicating heat radiation, and that Such a coded sensor signal is assigned to each monitoring area.

A second preferred embodiment of the passive infrared detector according to the invention is characterized in that the focusing means consists of a number of focusing elements is built up, the number of which is greater than that of the monitoring areas, and that between the focusing elements and the monitoring areas there is clear mutual correlation.

If the detector has n sensors, this gives 2 ⁿ -1 possible combinations with clear identification of the intruder's azimuth; with acceptable n = 3 sensors, these are m = 7 monitoring areas and this is a common size in today's passive infrared detectors. As is easy to see, one needs for the unambiguous assignment between focusing elements and monitoring areas with three sensors and seven monitoring areas (3 * 1) + (3 * 2) + (1 * 3), i.e. a total of 12 focusing elements, which is compared to that for the same number of surveillance areas required 7 focusing elements of a conventional passive infrared detector means an increase of about 70%.

According to a third preferred embodiment of the passive infrared detector according to the invention is the focusing means by a mirror arrangement or by a Fresnel lens formed. The mirror arrangement is preferably by a single one Focusing elements forming reflectors, mirrors formed.

If you take into account that a mirror common in today's detectors, for example is just under 50 mm wide, then the mirror for the passive infrared detector according to the invention about 85 mm wide, which should still be acceptable for many applications.

Another preferred embodiment of the passive infrared detector according to the invention is characterized in that the focusing means is designed such that a given coverage pattern of the monitoring areas to a fraction the partial area corresponding to the original opening angle is compressed and up to is repeated to achieve the original opening angle.

In this embodiment, by appropriately shaping the focusing means, e.g. with a mirror by appropriate resolution in partial mirror with simultaneous Downsizing of the focusing elements, the overlap pattern from an opening angle compressed from, for example, 90 ° to 15 ° or 30 ° and then correspondingly six or repeated three times. This creates an extremely dense coverage of the interstitial space achieved, which is especially true for the so-called presence monitoring is attractive. Especially when using an array of heat sensitive sensors an extremely dense coverage of the interstitial space can be achieved.

Another preferred embodiment of the passive infrared detector according to the invention is characterized in that tracking is based on the coded sensor signals the movement of an intruder through the various surveillance areas he follows.

The movement of an intruder is preferably between in the alarm decision the surveillance areas, whereby the criterion is that a Intruder from one surveillance area directly into an immediately adjacent one Surveillance area can move. In this way, malfunctions, the monitoring areas infested in any order as eliminated as not relevant. It also opens up the possibility of recognizing from the movement pattern that there is more than one intruder in the surveillance room, Police are of great interest.

Fig. 1

eine schematische Darstellung der Fokussiermittel eines erfindungsgemässen Passiv-Infrarotmelders; und

Fig. 2

eine schematische Darstellung des mit den Fokussiermitteln von Fig. 1 erzeugten Überdeckungsmusters.

The invention is explained in more detail below on the basis of an exemplary embodiment illustrated in the drawings; it shows:

Fig. 1

a schematic representation of the focusing means of a passive infrared detector according to the invention; and

Fig. 2

is a schematic representation of the overlap pattern generated with the focusing means of FIG. 1.

The focusing means of a passive infrared detector shown in Fig. 1 are by three (generally: several) conventional mirrors R, R ', R "formed, each of which a number of reflectors. Every mirror is a heat sensitive sensor for example a pyrosensor S, S 'or S "or a thermopile sensor (see European Patent Application No. 98 115 476) assigned. If in the description below Pyrosensor is mentioned, then this should not be understood as restrictive become. Of course, a Fresnel lens can also be used instead of the mirror R, R ', R " can be used, which is usually the case due to space and cost reasons becomes. The representation with the mirrors has been made for reasons of better comprehensibility chosen.

As described, for example, in EP-A-0 303 913, the individual reflectors are each individual mirror designed so that the area to be monitored is also from the detector outgoing surveillance areas is covered in a fan shape, with corresponding to at different distances from the detector several such "subject areas" or surveillance zones are provided. There are four monitoring zones, for example, a far zone, a middle zone, a near zone and a so-called look-down Zone covered by four rows of reflectors offset vertically are.

In the case of the mirror R, these rows are the row containing the reflectors A _n for the far zone, the row containing the reflectors B _m for the middle zone, the row containing the reflectors C _k for the near zone and the row containing the reflector D for the look zone. Down zone. The fan-shaped coverage is achieved by mutually displacing the reflectors of each row in the horizontal direction, the number of reflectors per row increasing with the distance of the respective monitoring zone from the detector in order to achieve an approximately uniform coverage pattern.

Each reflector "looks" into a certain solid angle of a certain zone, receives the incident heat radiation from this solid angle and focuses it on the assigned pyrosensor S. As soon as an object emitting heat radiation into a Penetrates the monitoring area, the sensor detects the one emitted by this object Heat radiation, whereupon the detector emits an alarm signal. This alarm signal indicates that an object, such as an intruder, is in the surveillance room, but does not allow any conclusions to be drawn about the exact position of the intruder in the surveillance room to.

The previous information and considerations also apply to a passive infrared detector a single mirror R, R 'or R "or with such a mirror corresponding Fresnel lens. If now several, as shown three, mirrors R, R 'and R "with several, as shown three, assigned pyro sensors S, S 'and S "used a determination of the position of an intruder (so-called "tracking") possible if you combine the reflectors of the individual mirrors and the pyro sensors in such a way that an intruder's azimuth can be clearly identified.

A detector M is symbolically drawn in FIG. 2 and contains a mirror arrangement of the type shown in FIG. 1. The detector M is mounted, for example, in a corner of a room to be monitored and covers the monitoring areas of the far zone designated with Ü1 to Ü7 (row with the reflectors A). The surveillance areas of the other zones are not shown; in this connection reference is made to EP-A-0 303 913, in particular to FIG. 3 thereof. The reflectors A _n , A _n 'and A _n "with n = 1 to 7 are arranged and designed such that a reflector with the index 1 receives heat radiation from the monitoring area Ü1, one with the index 2 heat radiation from the monitoring area Ü2, and In the aforementioned EP-A-0 303 913 it is shown that the reflectors B1 and B5 are directed towards the monitoring areas U1 and U7 (if not towards the far zone, but towards the middle zone) and the reflectors B3, C2 and D on the surveillance area Ü4.

Lines from the detector M to the monitoring areas Ü _n indicate which reflector covers the relevant monitoring area, that is to say heat radiation from this monitoring area is applied to it. A solid line symbolizes radiation to a reflector A of the mirror R, a dashed line a radiation to a reflector A 'of the mirror R' and a dash-dotted line shows radiation to a reflector A "of the mirror R".

As shown, the monitoring areas Ü1 to Ü7 are covered as follows: Surveillance area Coverage by reflector (s) Ü1 A1 (+ B1) Ü2 A2 '+ A2 " Ü3 A3 ' Ü4 A4 + A4 '+ A4 "(+ B3 + B3' + B3") (+ C2 + C2 '+ C2 ") (+ D + D' + D") Ü5 A5 + A5 ' Ü6 A6 + A6 " Ü7 A7 "(+ B5")

This list shows that a number of reflectors, namely the reflectors A2, A3, A7, A1 ', A6', A7 ', A1 ", A3" and A5 "is not required. These reflectors, which are hatched in Fig. 1, as well as the corresponding reflectors of the other rows are omitted, which results in a reduction in the width of the Mirror arrangement results in about 40%.

The reflectors for the nearer zones in parentheses in Table 1 indicate that these reflectors can be included in the evaluation, but under Loss of radial resolution. You could also use the remaining reflectors of the closer ones Align zones in the same way as those in the far zones, for example the reflectors B2 and B4 on Ü3 or Ü5 and C1 and C2 on Ü1 or Ü7. This would, as it were, from Detector M curtains curtained to the reception areas Ü1 to Ü7 and you could Detect penetration of each curtain by an intruder.

Since the incident heat radiation is focused by the reflectors of the mirror R onto the pyrosensor S, from the reflectors of the mirror R 'to the pyrosensor S' and from the reflectors of the mirror R "onto the pyrosensor S", this results in the individual monitoring areas the following exposure to the pyro sensors: Surveillance area Pyro sensor (s) Ü1 S Ü2 S '+ S " Ü3 S " Ü4 S + S '+ S " Ü5 S + S ' Ü6 S + S " Ü7 S "

Each monitoring area is therefore only a specific pyro sensor or only a specific one Combination of two or three pyro sensors assigned and you can choose from Number and number of pyro-sensors exposed to heat radiation at the same time unequivocally infer the surveillance area concerned.

In general terms, n pyrosensors 2 ⁿ -1 combination possibilities with unambiguous identification of the azimuth of an intruder, ie with 3 pyrosensors 7, with 4 pyrosensors 15 combination possibilities, and so on. If for some reason the number of pyro sensors is so limited that they are not sufficient for the required combination options, then neighboring surveillance areas can be summarized.

Taking into account that the coverage pattern shown in EP-A-0 303 913 in addition to the seven surveillance areas of the far zone, five surveillance areas in the middle zone and three surveillance areas in the near zone, So has a total of 15 monitoring areas, then you can use of a fourth pyro sensor clearly identify all 15 monitoring areas and receives an additional, albeit rough, radial resolution.

If the 7 monitoring areas shown in FIG. 2 have a too rough coverage of the should result in space to be monitored and a denser coverage is desired then you can see the overlap pattern covering an angle of about 90 ° compress the mirror to, for example, 15 ° or 30 ° by appropriate shaping and then repeat until the original angle of 90 ° is reached is. Compression from 90 ° to 30 ° would mean that each of the pyro sensors S, S 'and S "each have three mirrors R1, R2, R3; R1', R2 ', R3' and R1", R2 ", R3" respectively narrower reflectors would be assigned, the mirror with the index 1 den Angular range from 0 ° to 30 °, the angles with index 2 the angular range from 30 ° up to 60 ° and the mirrors with index 3 cover the angular range from 60 ° to 90 ° would.

In this case, one could choose from number and number of heat radiation simultaneously charged pyro sensors to the number of the relevant monitoring area close without knowing in which of the three angular ranges mentioned this surveillance area is located. The determination of the angular range can but in software, in the following way:

If "1" means that the pyro sensor in question is exposed to thermal radiation, and "0" that it does not receive any thermal radiation, the contents of Table 1 can be written as follows and thus encode the signal of the pyro sensors (the first bit stands for the pyrosensor S, the second bit for the pyrosensor S 'and the third bit for the pyrosensor S "): Surveillance area Coded sensor signal Ü1 100 Ü2 011 Ü3 001 Ü4 111 Ü5 110 Ü6 101 Ü7 001

If the encoded sensor signal is "111", the intruder is in the surveillance area Ü4 and can only move on from there to Ü3 or Ü5. When it moves in the direction from Ü7 to Ü1 through an angular range and on the edge of which reaches the signal "100". If the next signal is "001", then you know that the intruder has entered the next angular range. With the help of the coded sensor signals, the path of an intruder in the track the monitored space, even if the coverage pattern is on compresses a fraction of the original opening angle and accordingly often is repeated. The coded signal also provides clues about the number of possible Burglars, which is of no small interest for the police who are moving out.

If a surveillance camera is installed in the monitored room, it can Align them based on the tracking of the burglar and even if it is tight Angle of view take a picture with good resolution, what with today's applications not possible. This application is especially for banks, museums and the like Interesting.

Another interesting application is the ability to switch certain ones Switch monitoring areas either active or inactive and therefore in rooms to monitor certain zones during the day with visitors. You can also in at night, when the detector is armed, certain problem areas in the monitoring room, in which, for example, fax or air conditioning units are located, switch off. The multiplication of the overlap pattern has particular use of pyro arrays for intrusion detection and presence monitoring a promising one Potential because the immunity to interference is increased considerably.

Claims (10)

Passive infrared detector with a heat-sensitive sensor (S, S ', S ") and with a focusing means (R, R', R") for bundling those falling from different radial monitoring areas (U ₁ - Ü ₇ ) onto the detector (M) Heat rays on the sensor, characterized in that the detector (M) has at least two heat-sensitive sensors (S, S ', S "), and that the focusing means is constructed and arranged in such a way that each monitoring area (Ü ₁ - Ü ₇ ) is based on the number and number of the sensors (S, S ', S ") exposed to heat radiation can be clearly identified. Passive infrared detector according to claim 1, characterized in that the detector (M) has three heat-sensitive sensors (S, S ', S "). Passive infrared detector according to claim 1 or 2, characterized in that the output signals of the sensors (S, S ', S ") are combined to form a single, coded sensor signal, which is a separate one for each sensor (S, S', S") Exposure or non-exposure to heat radiation has a sign indicating that such a coded sensor signal is assigned to each monitoring area (Ü ₁ - Ü ₇ ). Passive infrared detector according to one of claims 1 to 3, characterized in that the focusing means (R, R ', R ") is made up of a number of focusing elements (A, A', A"), the number of which is greater than that Monitoring areas (U ₁ - Ü ₇ ), and that there is a clear mutual association between the focusing elements and the monitoring areas (Ü ₁ - Ü ₇ ). Passive infrared detector according to one of claims 1 to 4, characterized in that the focusing means (R, R ', R ") is formed by a Fresnel lens. Passive infrared detector according to one of claims 1 to 4, characterized in that the focusing means (R, R ', R ") is formed by a mirror arrangement. Passive infrared detector according to claim 6, characterized in that the mirror arrangement by a single reflector forming the focusing elements (A, A ', A ") having, mirror is formed. Passive infrared detector according to one of claims 5 to 7, characterized in that the focusing means (A, A ', A ") is designed such that a given coverage pattern of the monitoring areas (U ₁ - Ü ₇ ) to a fraction of the original opening angle corresponding sub-area is compressed and repeated until the original opening angle is reached. Passive infrared detector according to one of Claims 3 to 8, characterized in that the encoded sensor signals are used to track the movement of an intruder through the various monitoring areas (Ü ₁ - Ü ₇ ). Passive infrared detector according to claim 9, characterized in that the movement of an intruder between the surveillance areas (Ü ₁ - Ü ₇ ) is also taken into account in the alarm decision, the criterion being that an intruder is only in a surveillance area (Ü _n ) can move an immediately adjacent surveillance area (Ü _{n + 1} or Ü _n-1 ).

Images