Contrast-enhancement in Imaging Devices by Selection of Input Photosurface Spectral Response

Publisher Summary This chapter describes the contrast-enhancement in imaging devices by selection of input photosurface spectral response. The low light level performances of four hypothetical imaging devices possessing significantly differing input spectral responses are compared. At the lower light levels the use of image intensification, either direct view or a television technique, is of particular value because, firstly, the efficiency of the input photosurface is normally far greater than that of a photographic emulsion, and, secondly, the brightness of the output display can, in principle, be adjusted to a level suitable for photography or viewing directly . Spectral products obtained for concrete against a vegetation background are shown. If the current density is sufficiently high, a further improvement in the output display contrast could be obtained by including a band-pass optical filter at the input to the imaging system. This filter should be designed to accept wavelengths, either above or below the contrast inversion point at 0.7μm. The integrated responses to reflected night-sky radiation are also elaborated.