Detection device

Abstract

Reflective means comprising substrates, selectively reflects electromagnetic radiation whose frequency lies between 3×10Hz and 10Hz, and includes, for example, a layer of high resistivity silicon, on which the radiation is arranged to be incident, and means for selectively generating charge carriers in the layer to reflect the radiation, for example, by illuminating a face of the substrate with electromagnetic radiation whose wavelength lies between 5 μm and 100 mn in order to generate the charge carriers. The reflective means may form part of an imaging device in which a scene to be imaged is illuminated by radiation which passes through the reflective means in a coaxial arrangement, the reflected radiation being received by the reflective element while the reflective region is scanned over its entire surface, to produce a stream of radiation reflected from the scene which can be detected and used to drive a display. Noise produced by reflection from areas of the reflective means other than the scanned spot may be reduced by crossed polarizers, and the substrates may be grooved to form the polarizers, as well as to simplify the scanning arrangement. Other applications are for chemical signature detection.