EP1089244B1 - Mirrors layout in a passive infrared detector - Google Patents

Description

The present invention relates to a mirror arrangement for passive infrared detectors for monitoring elongated rooms, with a plurality of reflectors for focusing the heat rays falling on the detector from a monitoring room onto a sensor arranged in the detector, each reflector having a monitoring area at a specific radial distance from the mirror arrangement and is assigned by the detector and the monitoring areas cover the monitoring area in a vertical direction.

Such passive infrared detectors for monitoring elongated rooms, which are also referred to as curtain detectors, are used in particular to determine the presence or intrusion of unauthorized persons into the monitoring room by detecting the typical infrared radiation emitted by these persons, which is directed onto the sensor by the mirror arrangement (See, for example, EP-A-0 361 224). The reflectors are usually arranged in horizontally and / or vertically staggered rows, and depending on the distance from the detector, different monitoring zones are distinguished, e.g. Femzone, middle zone, near zone and look-down zone, each of which has at least one surveillance area. Each reflector thus defines a monitoring area with a defined position in the monitoring room. As soon as an object emitting heat radiation enters a monitoring area, the sensor detects the heat radiation emitted by this object.

In the mirror arrangement described in EP-A-0 361 224, a total of 11 reflectors are provided which are offset not only from one another in the horizontal and vertical directions but also in depth, which leads to a graduated design of the reflecting surface of the mirror arrangement. The individual reflectors are sometimes very small, strip-shaped segments that can hardly be touched by hand, which are cut out of a paraboloid, for example.

The mirror arrangement is produced using the injection molding process, the injection molding tool for each reflector having a "tooth" of the width and length of the respective segment and with a curved end face corresponding to the reflecting surface of the segment. The individual teeth are then assembled in such a way that their end faces form the counterpart to the reflecting surface of the mirror arrangement, with gradations being formed between the individual reflectors and accordingly also between the associated teeth are. Apart from the costs for the production of the injection molding tool, its maintenance is also relatively complex and expensive, because corrosion develops over time between the individual teeth, which necessitates regular maintenance. During this maintenance, the injection molding tool must be disassembled and cleaned and then reassembled.

The invention is now to provide a detection-safe mirror arrangement of the type mentioned at the outset, the production and maintenance costs of which are significantly reduced compared to the mirror arrangements used today.

This object is achieved according to the invention in that each reflector consists of a number of segments, so that the monitoring areas are split vertically into subzones with slightly different elevations, the elevation of the sub-elements being selected such that the majority of the monitoring areas have at most a slight overlap of the subzones, the subzones are stacked on top of each other and the layering is selected so that a tight curtain is created and that the individual segments of each reflector each form a continuous, coherent surface.

Splitting each reflector into sub-elements and correspondingly each monitoring area into sub-zones has the advantage that the detection reliability increases markedly because a passive infrared detector equipped with a mirror arrangement according to the invention has a so-called pet immunity. This means that the mirror arrangement according to the invention enables a distinction to be drawn between people and larger pets, so that false alarms caused by pets are almost impossible.

The at most slight overlap of the subzones in most surveillance areas has the advantage that no areas of greater sensitivity arise in which correspondingly stronger signals would necessarily be generated.

The design of the reflectors as continuous, coherent surfaces has the advantage that each injection molding tool provided for a reflector can be manufactured from one piece and no longer has to be assembled from individual teeth. If one assumes that a femzone, a middle zone, a near zone and a look-down zone and accordingly four reflectors are provided, then there is a reduction compared to the mirror arrangement with 11 reflectors described in EP-A-0 361 224 two thirds, but which is at the same time due to the splitting of the reflectors into partial elements by at least the same number of monitoring areas as before.

Passive infrared detectors of the current generation can reliably detect intruders within the effective range of the detector, but they are generally not able to distinguish people from larger pets, such as dogs, and also give an alarm if an animal penetrates , If today's passive infrared detectors already have a pet immunity, this is achieved with a few exceptions by reducing the sensitivity of the detector accordingly, which means an undesirable reduction in detection reliability.

A passive infrared detector is described in US Pat. No. 4,849,635, in which a Fresnel lens arrangement is used instead of the mirror arrangement for focusing the heat radiation onto the sensor. In this detector, pet immunity is achieved in that the lens arrangement has a plurality of differently oriented, non-overlapping visual fields or monitoring areas, which run from the lens arrangement in a fan shape into the monitoring room. These monitoring areas are staggered vertically, with gaps of approximately the same size being formed between the individual areas. An intruder with a certain minimum size will always cross at least one surveillance area and thus always generate a sensor signal, and an intruder below this minimum size will alternately cross surveillance areas and only gaps and in the latter case will not generate a sensor signal. In this way, a human being will generate a steady sensor signal with an approximately constant amplitude when moving in the surveillance space, whereas an animal will trigger a pulse-shaped signal of substantially lower maximum amplitude.

However, since the distinction between humans and pets is based on the signal form, and since the vertical staggering of the surveillance areas is a constant, the risk is relatively high that large pets cannot be distinguished from small people and vice versa.

The solution according to the invention has the advantage that a pet, however large, as long as its height is smaller than that of a human being, is always distinguished with certainty from a human being. Because an upright person will always cross several subzones of the fem and middle zone, or middle and near zone, etc. and thereby trigger a sensor signal that is several times larger than an animal of lower height. Because this will cross significantly fewer subzones and generate a significantly reduced sensor signal. A dog of normal size will cross a sub-zone or at most two, but only partially, and will thereby trigger a signal reduced by half or one third compared to the detector described in EP-A-0 361 224.

A first preferred embodiment of the mirror arrangement according to the invention is characterized in that the sensitivity to a pet is approximately the same in the individual subzones. This is achieved by avoiding the overlap of the individual subzones.

A second preferred embodiment of the mirror arrangement according to the invention is characterized in that the weighting of the individual segments, in particular their optical aperture and / or area is selected such that an animal of a selectable size that moves transversely to the coverage pattern formed by the surveillance areas delivers an approximately equally small signal from a certain distance from the detector.

A third preferred embodiment of the mirror arrangement according to the invention is characterized in that the reflectors associated with a small radial distance of the monitoring zones from the detector are brighter than those for monitoring zones further away from the detector.

A fourth preferred embodiment is characterized in that a first reflector for a far zone, a second reflector for a central zone, a third reflector for a near zone and a fourth reflector for a look-down zone is provided, and that the third and fourth Reflector are more powerful.

Fig. 1

eine perspektivische Darstellung einer erfindungsgemässen Spiegelanordnung,

Fig. 2

eine Vorderansicht einer Variante der Spiegelanordnung von Fig. 1; und

Fig. 3

eine Darstellung des Überdeckungsmusters der Spiegelanordnung von Fig. 1 in der Elevationsebene.

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

Fig. 1

2 shows a perspective illustration of a mirror arrangement according to the invention,

Fig. 2

a front view of a variant of the mirror arrangement of Fig. 1; and

Fig. 3

a representation of the overlap pattern of the mirror arrangement of FIG. 1 in the elevation plane.

The mirror arrangement 1 shown in FIG. 1 is a further development of the mirror described in EP-A-0 361 224, by means of which the mirror is improved in such a way that it is immune to pets in its effective range on the one hand, and it is more cost-effective to manufacture and maintain. Of course, instead of the mirror arrangement 1, a Fresnel lens arrangement can also be used, in which the individual Fresnel lenses are correspondingly divided into partial lenses, so that the monitoring areas would also be split vertically into subzones.

As described in the aforementioned EP-A-0 361 224, the disclosure of which is hereby expressly incorporated by reference, the mirror arrangement 1 consists of a number of reflectors which are designed in such a way that the monitoring areas assigned to the individual reflectors verticalize the monitoring space Cover direction. The reflectors are arranged in rows, several monitoring zones being provided according to the distance from the detector. A distinction is made between four surveillance zones, a far zone, a middle zone, a near zone and a so-called look-down zone, which are covered by four reflectors or rows of reflectors offset in the vertical direction.

In the mirror arrangement 1, these reflectors are the reflector A for the far zone, the reflector B for the middle zone, the reflector C for the near zone and the reflector D for the look-down zone. Each reflector "looks" into the monitoring room at a certain elevation angle, receives the heat radiation incident from this angle and bundles it on the heat-sensitive sensor, which is formed, for example, by a pyro sensor. This is preferably a so-called standard dual pyrosensor, as used, for example, in the passive infrared detectors of Siemens Building Technologies AG, Cerberus Division, formerly Cerberus AG (see also EP-A-0 303 913). As soon as an object that emits heat radiation penetrates into the monitoring area, the sensor detects the heat radiation emitted by this object, whereupon the detector emits an alarm signal. This alarm signal indicates that an object, such as an intruder, is in the surveillance room.

As indicated by dashed lines in the figure, the reflector A for the far zone consists of five segments A ₁ to A ₅ , the reflector B for the middle zone consists of three segments B ₁ to B ₃ , and the reflector C for the near zone consists of four segments C ₁ to C ₄ and the reflector D for the look-down zone from two segments D ₁ and D ₂ , wherein the segments of each reflector together form a continuous, coherent surface. Of course, the number of the respective segments is only to be understood as an example. The mirror arrangement 1 thus consists of a total of 14 segments which are distributed over four continuous, coherent surfaces. This means that the surveillance areas assigned to the four zones, femzone, middle zone, near zone and look-down zone are divided into subzones with slightly different elevation, the subzones representing surveillance areas.

Since each reflector A, B, C, D forms a continuous, coherent surface, the injection molding tool required for its production can be manufactured in one piece. In practice, this injection molding tool is milled from a single workpiece. In contrast to the mirror arrangement described in EP-A-0 361 224, in which 11 tool inserts are required for the 11 reflectors, only 4 tool inserts are required for the mirror arrangement 1 and nevertheless the end result is 14 subzones, that is 14 monitoring areas. The individual segments and subzones are weighted, i.e. their optical aperture and / or their area are selected such that a dog moving transversely to the covering pattern (FIG. 3) generates a signal which is the same for a distance from the dog to the detector from approximately 5 meters.

The reflectors C and D for the close-up and look-down zones are relatively bright to prevent a fast-moving intruder from going underneath a relatively high-mounted detector (mounting height> 3m). In the case of a high-mounted detector, this intruder would cross only a few subzones, possibly only one, and thus only generate a relatively small signal, which is compensated for by the increased light intensity. A detector with bright reflectors C and D for the near and the look-down zone is absolutely detection-safe for people at an installation height between about 1.6 and 4 meters.

However, it cannot be ruled out that such a detector loses domestic animal immunity. This can be maintained if the increased light intensity of the zones mentioned is reduced again, which can be done according to FIG. 2, for example, by partially covering these zones with a plastic part 2 (hatched). If you make this plastic part resilient, it can simply be pressed into the mirror assembly 1. You can match the pet immunity to the existing pet at the intended installation site if you provide different plastic parts 2 for pets of different weights, for example for animals up to 10 kg, up to 20 kg and up to 30 kg, and so on, of which the appropriate one Installation of the detector is used in this.

FIG. 3 shows the coverage pattern of the mirror arrangement 1 (FIG. 1) in a vertical section in its elevation plane, the course of the heat radiation from the individual subzones in the monitoring room to the mirror arrangement 1 being shown. The subzones are identified by reference numerals A ' ₁ to A' ₅ for the femzone, B 'to B' ₃ , for the central zone, C ' ₁ to C' ₄ for the near zone and D ' ₁ and D' ₂ for the look -down zone. The subzones are stacked on top of each other. They touch each other, but overlap at most very little so that no areas of greater sensitivity arise. In the event of overlaps, heat radiation would be focused simultaneously on the sensor in the overlap area from the two respective monitoring areas, and a correspondingly stronger signal would thereby be generated. The mutual non-overlap does not apply to the sub-zones A ' ₃ to A' _{5 of} the femzone, because an overlap cannot be avoided here due to the flat course of the rays. Since these subzones are at a relatively large distance of more than 15 m in front of the detector, fluctuations in the signal amplitude are not critical here.

The mirror arrangement 1 is at a height of 2.2 m above the floor: the two horizontal lines H and M correspond to a height of 0.6 and 1.8 m, respectively, and thus symbolize the movement of a dog or a person in the surveillance room. As can be seen in FIG. 3, in most cases a dog crosses only one sub-zone fully or two sub-zones partially in the effective range of the detector. In contrast, an upright intruder always crosses several sub-zones from the far and middle zone or middle and near zone or near and look-down zone and thereby generates a signal that is several times larger than that of the dog.

The conditions just described are illustrated in FIG. 3 for three different distances from the detector, E ₁ = 2.5 m, E ₂ = 5 m and E ₃ = 10 m. At a distance E ₁ a person (line M) crosses the subzones C ' ₄ , B' ₁ , B ' ₂ , B' ₃ and A ' ₁ , a dog (line H), however, only crosses the subzones C' ₄ and B ' ₁ , At a distance E ₂ a person crosses the subzones B ' ₂ , B' ₃ , A ' ₁ , A' ₂ and A ' ₃ , a dog crosses the subzones B' ₂ and B ' ₁ 3 At a distance E ₃ a person crosses the subzones A ' ₁ to A' ₅ and a dog the subzones A ' ₁ and A' ₂ .

Practical tests have shown that within an effective range of 12 to 13 m, the sensor signal triggered by a dog of about 30 kg body weight is at most 50% of the detection threshold, so that this dog can certainly not trigger a false alarm. Outside the above-mentioned effective range, the dog's signal rises to just below the detection threshold. If the detector's far zones can "see" beyond the effective range without being limited by a wall, false alarms from large dogs cannot be ruled out.

This problem can be eliminated by using a quadpyro sensor with 4 flakes or sensor elements as sensor S instead of a standard dual pyro sensor (see EP-A-0 303 913). In such a sensor, each pair of sensor elements forms a channel, the two channels effectively corresponding to a vertical splitting of the monitoring areas. Of these two channels, the lower one "looks" into the ground at a distance of about 20 m from the detector, so that the range is limited when a signal is requested in both channels for an alarm. On the other hand, even a large dog will never be able to deliver a signal above the detection threshold in the upper channel, so that even large dogs outside the detector's effective range cannot trigger a false alarm.

A cheaper, but less effective variant compared to the Quadpyrosensor would be to use Longflake-Pyros. With the standard flakes, the image of a medium-sized dog covers significantly more than 50% of the height of the flakes (sensor elements), and the image of an upright person protrudes far beyond the height of the flakes, with the part protruding beyond the flakes contributing nothing to the sensor signal , For example, if you doubled the amount of flakes, the difference between the signals triggered by a dog and a human would be much larger, which would improve the distinguishability. The gain factor (magnification of a human signal) compared to a dual sensor would be about 1.4, for a quad sensor it would be 2.5 to 3.

Claims (9)

1. Mirror arrangement for passive infrared signalling device for surveying elongated spaces, comprising several reflectors (A-D) for concentrating on to a sensor disposed in the signalling device the heat rays falling on to the signalling device from the surveillance space, there being assigned to each reflector (A-D) a surveillance region at a certain radial distance from the mirror arrangement (1) and consequently from the signalling device, and the surveillance regions covering the surveillance space in the vertical direction, characterized in that each reflector (A-D) consists of a number of segments (A₁-A₅; B₁-B₃; C₁-C₄; D₁,D₂), so that the surveillance regions are split vertically into sub-zones (A'₁-A'₅; B'₁-B'₃; C'₁-C'₄; D'₁,D'₂) of slightly different elevations, the elevation of the segments (A₁-A₅; B₁-B₃; C₁-C₄; D₁,D₂)being selected such that, in the case of the majority of the surveillance regions, there is produced, at most, a slight overlapping of the sub-zones (A'₁-A'₅; B'₁-B'₃; C'₁-C'₄; D'₁,D'₂), the sub-zones (A'₁-A'₅; B'₁-B'₃; C'₁-C'₄; D'₁,D'₂) are stacked in strata on one another and the stratification is selected such that a dense curtain is produced, and the individual segments A₁-A₅; B₁-B₃; C₁-C₄; D₁,D₂) of each reflector (A, B, C, D) in each case form a continuous, coherent surface area.
2. Mirror arrangement according to Claim 1, characterized in that the sensitivity to a domestic animal is approximately equal in the individual sub-zones (A'₁-A'₅; B'₁-B'₃; C'₁-C'₄; D'₁,D'₂).
3. Mirror arrangement according to Claim 2, characterized in that the weighting of the individual segments (A₁-A₅; B₁-B₃; C₁-C₄; D₁,D₂), particularly their optical aperture and/or surface area, is selected such that, from a certain distance from the signalling device, an animal of a certain size moving transversely relative to the coverage pattern formed by the surveillance regions delivers a signal of approximately equally small magnitude.
4. Mirror arrangement according to any one of Claims 1 to 3, characterized in that the reflectors (C, D) assigned to a short radial distance of the surveillance zones from the signalling device have a greater light-transmitting capacity than those for surveillance zones at a greater distance from the signalling device.
5. Mirror arrangement according to Claim 4, characterized in that there is provided a first reflector (A) for a remote zone, a second reflector (B) for a middle zone, a third reflector (C) for a near zone and a fourth reflector (D) for a look-down zone, and the third and fourth reflectors (C and D) have a greater light-transmitting capacity.
6. Mirror arrangement according to either of Claims 4 or 5, characterized by a mask which can be attached to the mirror arrangement (1) for the purpose of partially covering the reflectors (C, D) having the greater light-transmitting capacity.
7. Mirror arrangement according to Claim 6, characterized in that the mask consists of a resilient plastic insert (2).
8. Mirror arrangement according to Claim 7, characterized in that the size of the plastic insert (2) is matched to the weight of an animal which, upon entry into the zones assigned to the partially covered reflectors (B, C, D), is not to trigger an alarm.
9. Mirror arrangement according to Claim 8, characterized in that there are provided several plastic inserts (2) which are matched to animals of different weights and may optionally be inserted in the mirror arrangement (1).