Infrared image sensor for video camera - includes automatic focussing system overcoming strong temp. dependence of focal position

摘要

The camera includes a focussing objective lens bringing the IR to a focus on a detector which is refrigerated. An automatic focussing system maintains the photodetecting surface in the focal plane of the lens, and a shutter is provided for interrupting radiation entering the lens. A displacement mechanism including a motor moves the photodetecting surface relative to the objective lens within specified limits. An output signal analysing circuit detects the image signal produced in conjunction with a position signal derived from the displacement mechanism, in order to determine when the signal is a min., so that this position may be reproduced by further adjustment. The system is intended to reduce the strong temp. dependence of the focussing of such systems which otherwise rapidly degrades the quality of the image.