Abstract: 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.

Abstract: A thermal infrared detector comprising a dielectric pellicle suspended over a cavity in a substrate, the pellicle supporting a detector element comprising a heat sensitive semiconductor layer between a pair of thin fim metallic contracts, these being deposited on the pellicle, the cavity being formed by etching and removal of the substrate material through holes or slots in the surface of the substrate.

Abstract: An infrared radiation detector in which a stable substrate (5) has a hole (10) through it and a pair of bonding pads (9) on two opposite sides of the hole, the hole being covered by a pellicle (6) of insulating or semi-conductor material with supports over the hole, a detector element (7) comprising an ultrathin infrared absorbing film of nickel, palladium, platinum or iridium less than 10 nm thick or a gold film less than 20 nm thick, two sides of the detector element connecting to the bonding pads (9) by thin film contacts (8).