System for detecting radiation in the presence of more intense background radiation

摘要

A system for sensitively discriminating against background radiation which tends to swamp and prevent detection of radiation from a source of interest such as IR (Infra-Red) light radiation as may be found on “low observable” aircraft collision avoidance lighting, utilizes the modulation of such radiation as a mechanism for tracking the radiation and discriminating against the background radiation, for example, from other light energy sources. The radiation is detected and tracked even though the source of interest produces the radiation in bursts or pulses by controlling the sensitivity of the detector inversely with the amplitude of the radiation to which the detector is exposed, translating the electrical signals into a plurality of cycles at the modulation frequency with the aid of a high Q bandpass filter tuned to the modulation frequency and detecting the output of the filter in a phase-locked-loop detector circuit thereby providing an indication of the intensity of the radiation from the source of interest of an acceptable level. An instrument for detecting the radiation of interest may be portable and of the size approximating that of a conventional flashlight.