Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Patent
1998-09-24
2000-10-31
Hannaher, Constantine
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
2503383, 250DIG1, G08B 1318
Patent
active
061406481
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a compound-eye crime prevention sensor system which comprises two, upper and lower, detection zones which are to be crossed by a trespassing subject to be detected.
BACKGROUND ART
In detectors used in a trespass warning system, the system which has been put to frequent use in recent years comprises two pyroelectric elements made of ferroelectric material horizontally disposed side by side, the outputs thereof being connected in series or parallel to derive a differential output. This is called the twin type pyroelectric elements or twin sensors. Further, a compound-eye crime prevention sensor system, which is called the dual twin type pyroelectric elements, comprising two, upper and lower, twin type pyroelectric elements has already been put to practical use. For this compound-eye crime prevention sensor system, refer to Japanese Patent Publication No. 12,358 of 1991 and Japanese Laid-Open Patent Publication No. 143,873 of 1993.
The compound-eye crime prevention sensor system comprises a pair of detection axes substantially horizontally spaced and extending in substantially the same direction in a predetermined space, another pair of detection axes disposed above or below said pair of detection axes and extending in directions respectively corresponding to said detection axes, a far infrared ray focussing mirror disposed on the side of the device associated with these two pairs of detection axes for focussing radiant energy falling along each axis, and dual twin type pyroelectric elements corresponding to them at the focal point corresponding to said two pairs of detection axes in the focal planes of said far infrared ray focussing mirrors.
In said compound-eye system, the four detection zones formed by the optical unit comprising the dual twin type pyroelectric elements consisting of the two, upper and lower, twin type pyroelectric elements and by one far infrared focussing mirror, extend along said detection axes in substantially the same direction but, stated strictly, they are geometrically not parallel (widening angle being 0.degree.); the four detection zones extend with some amount of widening angle. In the present invention, the wording "substantially parallel" or the like also refers to the case where they extend with some amount of widening angle. The size of the upper and lower twin type pyroelectric elements, and the distance between the upper and lower elements have been preset at particular values. The detection zones respectively associated with the detection axes and extending from the optical unit constituted by the twin type pyroelectric elements of fixed shape and the far infrared ray focussing mirror having a fixed focal length grow thicker as they are further away from the optical unit. In the detector for detecting trespassing subjects, with consideration given to the size of the cross section of the detection zones and the size of human beings who walk across the detection zones, the limit distance beyond which the detection efficiency drops is defined as the farthest point of the trespassing subject detection range.
For example, the size of the cross section of one detection zone in the farthest point in this kind of detector for which the distance to the farthest point of the trespassing subject detection range is set at 12 m, is about 0.3 m wide and about 0.5 m high. There are four detection zones of this size disposed at upper and lower and right and left positions, 0.3 m spaced away from each other, and grouped together to form the detection zone of a compound-eye crime prevention sensor system.
FIG. 1 is a side view showing the layout of a conventional compound-eye crime prevention sensor system. The numeral 1 denotes a detector and L denotes the position which determines the farthest point of the trespassing subject detection range. This detection range is defined by upper and lower detection zones Z1, Z2 extending in substantially the same plane from upper and lower twin elements. The numeral 2 denotes a ceiling surface to which t
REFERENCES:
patent: 4339748 (1982-07-01), Guscott et al.
patent: 4618854 (1986-10-01), Miyake et al.
patent: 4849635 (1989-07-01), Sugimoto
patent: 6037594 (2000-03-01), Claytor et al.
Iriyama Koichi
Tsukamoto Kazuo
Gabor Otilia
Hannaher Constantine
Takenaka Engineering Co. Ltd.
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