Abstract: This invention is concerned with a thermal imaging optical system finding utility as an individual weapon sight. The system comprises an infra-red objective lens including a chopper blade together with front and back elements with an adjustable element therebetween. Infra-red radiation is received by the objective lens which also incorporates an internal substantially collimated plane polarized visible light source which illuminates a liquid crystal. The path of the infra-red and visible light which is directed to the liquid crystal cell, is repeatedly interrupted by the chopper blade. Changes in the liquid crystal cell due to the infra-red radiation transmitted by the objective lens are caused to modulate the plane polarized visible light transmitted through the liquid crystal cell to generate a visible image. This image passes through a relay inverting system and is detected by a visible light detector and viewed through an eyepiece.

Abstract: A display system which can be used inside a vehicle such as a military tank to monitor at least part of the surrounding panorama. The display system has a display generator and an optical system for viewing the display. Electronic means are provided to predistort the display to compensate for distortion present in the optical system. The system includes individual display units mounted side-by-side, each having a respective television camera associated therewith so that a substantially continuous picture of at least part of the surrounding panorama can be reconstructed and viewed by an observer without any apparent mismatch between adjacent displays.