THERMOGRAPHS (synonym thermal imagers) — the medical diagnostic units working by the principle of optical and mechanical scanning, perceiving and registering a natural caloradiance of a body in an invisible infrared spectral range. In thermal imagers infrared radiation will be transformed to visible.
Basic element of the thermal imager (fig.) — the highly sensitive receiver of infrared radiation — catches energy in the small space angle called by an instant field of vision of the device. Thanks to movement during the scanning of an instant field of vision in space the sequential analysis of the general field of the review is carried out. If this field has heterogeneous temperature, then the size of a flow of the radiation falling on the receiver at this provision of an instant field of vision changes. This change will be transformed by the receiver to an electric signal, to-ry amplifies and reproduced on the screen of the display in the form of the black-and-white or color image — the thermogram. The most important technical characteristics of the thermal imager: the threshold sensitivity characterizing the minimum thermal gradient of an object, distinguishable on the screen of the display; the angular resolving power defining a possibility of separate observation and identification of a form of small details of an object and speed (a heating-up period of one shot of the image).
A recent trend in development of the thermovision equipment is use of the pyroelectric vidicons which are working in the mode of electronic scanning and not demanding use of the cooling system, and also the matrix receivers of infrared radiation allowing to create compact thermal imagers on their basis.
Bibliography: See bibliogr. to St. Termografiya .
R. I. Utyamyshev, Yu. N. Korotkov.