INFRARED DETECTOR FOR DETERMINING THE PRESENCE OF AN INTRUDER IN A MONITORED AREA

摘要

INVENTORS: GUSTAV PFISTER and PETER W?GLIINVENTION: INFRARED DETECTOR FOR DETERMINING THE PRESENCEOF AN INTRUDER IN A MONITORED AREAABSTRACTFor reducing the susceptibility to false alarmsand for increasing the detection probability of a passiveinfrared detector the actual signals obtained from a firstsensor element are continuously compared in a correlatorwith reference or set signals stored in a read-only memoryand/or with the actual signals obtained from a second sensorelement monitoring the near region. The correlator deliversan output signal which corresponds to the correlation ofboth signals which are compared with one another. An alarmsignal is triggered when the correlation exceeds apredetermined value, for instance 0.7, and the amplitude hasreached a predetermined threshold. The infrared detectoraffords high security against giving of false alarms and ahigh detection probability, even in the presence of signalspossessing a great amount of noise, but also delivers analarm signal in the event the detector is attempted to besabotaged, for instance by covering the inlet opticalsystem.