Accession Number : AD0696930

Title :   CONTRAST-ENHANCEMENT IN IMAGING DEVICES BY SELECTION OF INPUT PHOTOSURFACE SPECTRAL RESPONSE,

Corporate Author : SIGNALS RESEARCH AND DEVELOPMENT ESTABLISHMENT CHRISTCHURCH (ENGLAND)

Personal Author(s) : Richards,E. A.

Report Date : JAN 1969

Pagination or Media Count : 20

Abstract : When viewing distant terrain scenes in daylight, improvement in perception-range and contrast can be obtained using near-infrared photography. This is due to the increased reflectivity of vegetation and better haze-penetration at the longer wavelenths. At night-time, however, photographic emulsions are too insensitive and intensification of the image is essential if a record is to be made. Since the spectral distribution of the illumination changes considerably between moonlight and starlight conditions (and terrain materials possess individually different spectral reflectivity characteristics) the apparent contrast and signal-level registered by the image-intensifier also depend on the spectral response of the input photosurface. The performances of four hypothetical imaging systems, each having significantly different input spectral responses (i.e. an S20 photocathode, a caesiated GaAs photocathode, Si and intrinsic Ge photoconductors) are compared when surveying representative terrain materials (a) under full moonlight illumination, and (b) under clear starlight illumination. (Author)

Descriptors :   (*IMAGE TUBES, *PHOTOCATHODES), (*NIGHT VISION, PHOTOCATHODES), INFRARED PHENOMENA, TERRAIN, REFLECTIVITY, GALLIUM ARSENIDES, PHOTOELECTRIC MATERIALS, LOW LIGHT LEVELS, GREAT BRITAIN

Subject Categories : Electrooptical and Optoelectronic Devices

Distribution Statement : APPROVED FOR PUBLIC RELEASE