INFRARED INTRUSION SENSOR.

摘要

PCT No. PCT/AU93/00093 Sec. 371 Date Sep. 7, 1994 Sec. 102(e) Date Sep. 7, 1994 PCT Filed Mar. 8, 1993 PCT Pub. No. WO93/18492 PCT Pub. Date Sep. 16, 1993.An infrared intrusion sensor includes an array of infrared detectors, infrared collection optics, a focal plane scanning device having a dither adapted to repetitively scan the infrared radiation across the detector array, signal process devices, and local or remote displays. The sensor incorporates heterodyne detection techniques with a local oscillator signal derived from the scanning frequency of the focal plane scanning device. The sensor has a low false alarm rate and enhanced detection range. A method of processing the signals includes analog to digital conversion, integration of the digital signals to produce a background signal, phase sensitive detection of the digital signal producing a target signal, and comparison of the background and target signals producing a difference signal. The difference signal is integrated to produce a background noise signal and processed to become a threshold signal which is finally compared to the difference signal to produce an alarm signal.