GB2207241A - A device for varying the angular coverage of an infrared motion indicator - Google Patents

Description

S, 1 A device for varying the angular coverage of an infrared motion

indicator The invention relates to a device f or varying the angular coverage of an infrared motion indicator.

Known entrance windows for the detectors in infrared motion indicators usually have a rectangular outline and a corresponding opening (see e.g. Gebrauchsmuster 85 22 515.0). A monitoring device of this kind has an angular coverage up to 1800, depending on the complexity of the recognition, measurement and evaluation components installed in the motion indicator.

Angular coverages of this size a'ie often undesirable for local space reasons, or a smaller angular coverage may be desirable owing to a change in the original space conditions.

The apparatuses at present on the market and often already installed have the disadvantage that their angular coverage, which is determined by the construction, is invariable and consequently cannot adapt to changes in the guard zone or object zone.

An object of the invention therefore is to design a device which obviates these disadvantages in that it can be used-to adjust the angular coverage of the device to a particular monitoring situation.

In accordance with the invention, the device comprises a shutter having an opening which can be 22072di i 1 i i i 1 1 J i i j i i inserted into an entrance window of an infrared motion indicator for making a first reduction in the angular coverage, and provision for the insertion into the opening of the shutter of narrow and/or wide segments for optionally additionally reducing and/or varying the angular coverage.

The shutter reduces the angular coverage and also can be used for additionally reducing and varying the angular coverage in conjunction with additional segments of varying size which can be inserted individually, in pairs or in combination into the shutter.

In an embodiment, the shutter is'dligned for positive insertion into the entrance window of the infrared motion indicator in that the shutter corresponds in shape to the shape of a segment of the casing of the motion indicator.

In order to lock segments of varying size in the window opening -in the shutter, the segments are formed with grooves and the window opening with cams.

An embodiment of the invention will now be described with reference to the figures.

In the drawings:

Figure 1 shows the front of an infrared motion indicator having an entrance window for detecting infrared Z i rays; Figure 1A diagrammatically shows the corresponding maximum angular coverage; Figure 2 is a view corresponding to Figure 1 but comprising a shutter for reducing the window area; Figure 2A diagrammatically shows the correspondingly reduced angular coverage; Figure 3 is a view corresponding to Figure 2, showing narrow segments inserted into the shutter opening for additionally reducing the angular coverage; Figure 3A diagrammatically shows the correspondingly further reduced angular coverage; Figure 4 is a view showing wide segments inserted into the shutter opening for additionally reducing the angular coverage; Figure 4A diagrammatically shows the correspondingly further reduced angular coverage; Figure 5 is a view showing narrow and wide segments inserted into the shutter opening; Figure 5A diagrammatically shows the reduced and also varied'angular coverage; Figure 6 shows the shutter on a much larger scale, corresponding in segmentary form to the shape of the casing of the motion indicator; Figure 7 is a side view of the shutter corresponding to Figure 6; Figure 8 is a plan view corresponding to Figure 6; Figure 9 shows a wide segment on a much larger scale, corresponding in sementary manner to the shape of the casing of the motion indicator, and Figure 10 shows a narrow segment on a much larger scale, corresponding in segmentary form to the shape of the casing of the infrared motion indicator.

The casing of the infrared motion indicator, shown in a front view only and in projection in Figure 1, comprises e.g. two spherical halves 1. Since only the front of the indicator is relevant to the invention, the complete structure of the indicator is not shov inn the diagrams.

Instead of the casing comprising two spherical halves, other constructions are possible, since the device according to the invention, i.e. a shutter with segments insertable into its opening, can be constructed for any suitable casing.

Figure 1 shows the front side of an infrared motion indicator comprising two spherical halves 1, in which an entrance window 2 is disposed for detecting infrared radiation. The window surface 3 in known manner comprises a plastics moulded sheet and corresponds in segmentary manner to a spherical half 1. The window surface 3, made of plastics moulded sheeting, is set back in window 2 in the direction towards the interior of the casing by an amount equal to the thickness of the spherical half (not i i 1 1 i i 1 separately shown). The angular coverage CY, in Figure 1A diagrammatically shows the size of the area covered for infrared radiation, which can travel through the entrance window 2 of the infrared motion indicator.

Figure 2 shows the first embodiment for reducing the angular coverage CX To this end the device according to the invention in the form of a shutter 4 is inserted into the entrance window 2. As can be seen from the highly enlarged diagram of shutter 4 in Figures 6 to 8, the shutter in the chosen example likewise corresponds in segmentary form to a spherical half 1 and is shaped so as to fit positively into window 2.

For the purpose of securing in the entrance window of spherical half 1, two opposite narrow sides of shutter 4 are formed with tongues 8 having cams 9 on their outer surfaces. When the shutter is inserted into the entrance window, the tongues press sideways into the casing and their cams 9 lock in corresponding recesses in the inner wall of the casing of spherical half 1. The locking inside the casing is not shown.

Figure 2A diagrammatically shows the angular coverage reduced by the shutter.

In order further to reduce the angular coverage narrow segments 6 (Figure 3) or wide segments 7 (Figure 4) can be inserted into the opening 5 in shutter 4. The corresponding reduced angular coverages 0( for the embodiments in Figures 3 and 4 are shown diagrammatically in Figures 3A and 4A respectively. Owing to the positive inclusion in the overall design, therefore, segments 6 and 7 correspond in segmentary manner to spherical half 1.

For the purpose of securing in opening 5 of shutter 4, segments 6 and 7 (Figures 9 and 10) are formed with grooves 11 of equal size for snapping over cans 10. The distances between cams 10 in opening 5 are such that, depending on the choice of segments 6 or 7 (Figures 3 or 4) or 6 and 7 combined as shown in Figure 5, the grooves 11 correspond to cams 10.

Finally Figure 5 shows a combifiation of a narrow segment 6 and a wide segment 7. This combination can be used both to reduce and to vary the angular coverage Ck - The device described therefore can be used in simple manner, with few manipulations, for monitoring selected object areas and district zones.

:z, i 1 i i -;z 1 j fll- claims 1. An arrangement comprising: an infrared motion indicator having an entrance window via which infrared radiation is received; and a device for varying the angular coverage of the infrared motion indicator; the device includes a shutter having an opening, the shutter being insertable into the entrance window of the indicator for making a first reduction in the angular coverage.

2. An arrangement according to claim 1, further including narrow and/or wide segments insertable into the opening of the shutter for additi6nally reducing or varying the angular coverage.

3. An arrangement according to claim 1 or 2, wherein the shutter and opening correspQnd in shape to a segment of the casing of the indicator.

4. An arrangement according to claim 3, wherein the infrared motion indicator comprises a casing formed of two spherical halves of equal size.

5. An arrangement according to claim 4, wherein the 20 shutter and opening have the shape of a segment of a sphere.

6. An arrangement according to claim 4 or 5 when dependent on 2, wherein the narrow and/or wide segments have the shape of a segment of a sphere.

7. An arrangement according to any one of claims 1 to 6, 0.

1 - 8 wherein the surface of the entrance window is moulded of a plastics sheet.

8. An arrangement according to any one of claims 1 to 7, wherein two opposite sides of the shutter have integral tongues- having projections thereon by means of which the shutter can be inserted and positively locked in the entrance window.

9. An arrangement according to claim 2 or any one of claims 3 to 8 when dependent on claim 2, comprising projections in the shutter for retaining the said wide and/or narrow segments in the opening of-the shutter.

10. An arrangement according to cldim 9, wherein the wide and/or narrow segments have in their edges grooves for cooperating with the projections in the shutter for retaining the segments in the opening in the shutter.

11. An arrangement of an infrared motion detector and a shutter devicesubstantially as hereinbefore described with reference to Figures 1 to 10.

12. A shutter device substantially as hereinbefore 20 described with reference to Figures 1 to 10.

Published 1988 at The Patent Office. State Rouse. 6671 High Holborn, London WC1R 4TP. Further copies may be obtained from The Patent oMce. Sales Branch, St Mary Cray. Orpington. Kent BW 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Con- 1.187.

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