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Passive infrared intrusion detector employing correlation analysis

  • US 4,746,910 A
  • Filed: 10/03/1986
  • Issued: 05/24/1988
  • Est. Priority Date: 10/01/1982
  • Status: Expired due to Fees
First Claim
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1. A passive infrared detector for determining the presence of an intruder possessing a temperature differing from the ambient temperature, comprising:

  • at least one sensor element generating an electrical signal as a function of infrared radiation impinging upon said at least one sensor element;

    at least one optical system for focusing the infrared radiation upon said at least one sensor element;

    said at least one optical system imaging infrared radiation upon said at least one sensor element which infrared radiation emanates from a number of predetermined separate fields of view;

    an evaluation circuit operatively connected with said at least one sensor element and delivering an output signal dependent upon changes in the impinging radiation;

    said evaluation circuit comprising;

    a correlator; and

    storage means for storing a predetermined number of reference signals which are representative of typical movement patterns of intruders;

    said correlator correlating by means of a correlation method said electrical signals generated by said at least one sensor element with said reference signals stored in said storage means;

    said correlator delivering an output signal corresponding to the correlation of the electrical signal generated by said at least one sensor element and the reference signals; and

    said evaluation circuit further comprising an alarm stage arranged in circuit after the correlator for delivery an alarm signal when the correlation between the electrical signal generated by said at least one sensor element and at least one of said stored reference signals as well as the amplitude of said electrical signal simultaneously exceed a predetermined value.

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