Infrared intrustion detector
First Claim
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1. In a passive infrared detector of the type wherein optical means are arranged to focus infrared radiation on a pyroelectric sensor for detecting changes in infrared radiation and an evaluation circuit coupled to the sensor is arranged to develop signals indicative of detected changes in infrared radiation, a pyroelectric sensor comprising:
- a plurality of elongated radiation sensitive sensor elements, arranged in a pattern of laterally spaced pairs with at least one element of each pair longitudinally spaced from an element of a different pair, comprising a first pair of opposite polarity sensor elements interconnected electrically and a second pair of opposite polarity sensor elements interconnected electrically, said first and second pairs of elements being electrically connected in series;
output means for coupling signals to a single evaluation channel; and
coupling means, comprising first resistive means coupled to said first pair of sensor elements and second resistive means coupled to said second pair of sensor elements, for developing a composite signal in response to signals developed by said sensor elements and coupling said composite signal to said output means;
whereby the operation of said detector benefits from the differential interconnection of each of said pairs of sensor elements in combination with the increased sensitivity provided by the combination of said pairs of elements, while requiring only a single evaluation channel.
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Abstract
A passive infrared intrusion detector provides improved intruder detection while using a single signal evaluation channel. Pyroelectric sensor element configurations include a diamond pattern with differentially opposed pairs of elements of opposite polarization connected in series for increased coverage and sensitivity.
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Citations
17 Claims
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1. In a passive infrared detector of the type wherein optical means are arranged to focus infrared radiation on a pyroelectric sensor for detecting changes in infrared radiation and an evaluation circuit coupled to the sensor is arranged to develop signals indicative of detected changes in infrared radiation, a pyroelectric sensor comprising:
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a plurality of elongated radiation sensitive sensor elements, arranged in a pattern of laterally spaced pairs with at least one element of each pair longitudinally spaced from an element of a different pair, comprising a first pair of opposite polarity sensor elements interconnected electrically and a second pair of opposite polarity sensor elements interconnected electrically, said first and second pairs of elements being electrically connected in series; output means for coupling signals to a single evaluation channel; and coupling means, comprising first resistive means coupled to said first pair of sensor elements and second resistive means coupled to said second pair of sensor elements, for developing a composite signal in response to signals developed by said sensor elements and coupling said composite signal to said output means; whereby the operation of said detector benefits from the differential interconnection of each of said pairs of sensor elements in combination with the increased sensitivity provided by the combination of said pairs of elements, while requiring only a single evaluation channel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A pyroelectric sensor for use in a passive infrared detector, comprising:
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four elongated pyroelectric sensor elements arranged with first and third elements of a first polarization spaced apart in parallel relationship and second and fourth elements of the reverse polarity positioned between and parallel to said first and third elements in end to end relationship; insulative substrate means attached to the back surface of each of said sensor elements for supporting said elements in said spaced relationship; conductor means for connecting said first and second sensor elements as a differentially opposed first pair of elements, connecting said third and fourth sensor elements as a differentially opposed second pair of elements, and connecting said first and second pairs of elements in series; output means for coupling signals to a single evaluation channel; coupling means, comprising first resistive means coupled in parallel with said first pair of sensor elements and second resistive means coupled in parallel with said second pair of sensor elements, for developing a composite signal in response to signals developed by said sensor elements and coupling said composite signal between said output means and a point of common voltage; and support means for supporting the foregoing elements of the sensor; whereby the sensor obtains the operational benefits of the differential interconnection of said sensor elements and increased sensitivity provided by the series combination of pairs of such elements, enabling operation with a single signal evaluation channel. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification