Resonant radiation protector

Abstract

In an imaging system employing an array of detectors and an optical system for focusing rays of an image upon the detectors, there is provided a protection system in the form of a cell of gaseous lasing material disposed along a path of the imaging rays. A pair of electrodes and a supply of electric power induces an electric discharge through the lasing medium to heat the medium so as to enhance interaction between intense laser radiation which might inadvertently or deliberately, be directed toward the array of detectors. The laser radiation induces still further heating of the lasing medium with a resultant absorption of a relatively narrow frequency band of radiation, at the lasing frequency, so as to prevent damage to the array of detectors while allowing scene radiation outside of the narrow band to be received by the detectors. A further detector may be located offset from a path of propagation of the laser radiation for decting fluorescent rays produced by interaction of the laser radiation with the lasing medium. If desired, a shutter activated by a signal of the further fluorescent detector may be employed to provide additional protection of the array of detectors from the laser radiation.