Intrusion detector

Abstract

A simple optical system collects and applies radiation from a predetermined field of view onto a thermopile detector. The thermopile detector has a plurality of rows of thermocouples having all active junctions with alternate polarity which are aligned in columns of the same polarity, whereby in response to an object moving across the thermopile an output signal is produced of alternately changing polarity. Logic circuitry is provided for processing the signals from the thermopile in a predetermined polarity sequence to discriminate against false alarms and for indicating the presence of an intruder and sounding an alarm.

I claim: 
     
       1. An intrusion detector for generating alternating signals as a result of thermally varying patterns of objects moving across the field of view of the detector comprising a. a layer of thermal insulating material,   b. a thermopile detector mounted on said layer of insulating material comprised of a plurality of thermocouples of dissimilar metals with all junctions being constantly exposed to the field of view of said detector,   c. said thermocouples being serially connected in rows with adjacent thermocouples in said rows being of alternate polarity   d. said rows of thermocouples being serially interconnected and aligned to form columns of the same polarity thermocouples and adjacent columns of alternate polarity thermocouples, and   e. output terminals connected across said thermopile detector which provides thereat a changing polarity output signal in response to an object moving across said thermopile detector.   
     
     
       2. The structure set forth in claim 1 having optical means for collecting and applying radiation from a predetermined field of view on all junctions of said thermopile detector. 
     
     
       3. The structure set forth in claim 2 wherein said optical means comprises a wide angle lens. 
     
     
       4. The structure set forth in claim 2 wherein said optical means includes a wide angle spherical reflector. 
     
     
       5. The structure set forth in claim 1 including a. optical means for collecting and applying radiation from a predetermined field of view on all junctions of said thermopile detector, and   b. circuit means coupled to the output terminals of said thermopile detector for processing signals from said thermopile detector in a predetermined polarity sequence for indicating the presence of an intruder and discriminating against false alarms.   
     
     
       6. The structure set forth in claim 5 wherein said circuit means includes a plurality of signal processing channels which respond to said predetermined polarity sequence and generate signals of fixed duration, the coincidence of which provides an output indicating the presence of an intruder.