Surveillance arrangement including a television system and infrared

Abstract

The invention provides a surveillance arrangement, and in particular an airborne surveillance arrangement, in which a television display of a scene is brightened up, by means of infra-red detectors, to emphasize heat emitting targets. In one example of airborne surveillance system, a linear array of infra-red detectors is arranged to view part of a scene viewed by a television camera, with the same horizontal field of view at a desired target range. In front of the array of detectors a light chopper is provided so that the output of each detector is a modulated carrier. The output of each detector is applied to a store, via individual impedance transformers, narrow bandpass filters and demodulators. Between each demodulator and the store, individual sharp out-off low pass filters and threshold detectors may be provided to provide a degree of discrimination against spurious responses. The store is read-out under the control of a sequence timing unit which is synchronized with the synchronizing signal generator of the television camera and the video output of the latter is mixed with the output from the store prior to application to a display unit so that the display provided is a scene of an area towards which the aircraft is flying with heat emitting targets highlighted.