GB1257011A - - Google Patents

Abstract

1,257,011. Photochromism. BRITISH AIRCRAFT CORP. Ltd. 24 Jan., 1967 [27 Oct., 1965], No. 45518/65. Heading C4S. Optical apparatus, comprising means for focusing an image of a scene at an image plane and detecting means whereby the image may be viewed, has material which is transparent when subjected to radiation of lower intensity but which is rendered more absorptive when subjected to radiation of a higher intensity and which again becomes transparent when the higher intensity radiation is removed, placed at or near the image plane. By this means, the brightness of potential sources of glare within the field of view is reduced but the brightness of areas of low illumination remains unaffected. Objects may thus be viewed angularly closer to a bright source of illumination, e.g. the sun. The detecting means may be for example the eye using a subsidiary lens, a television camera, an image intensifier or an image converter. The glare reducing material may be a sheet of glass or other suitable carrier incorporating lightsensitive particles, e.g. photochromic glass. Binoculars incorporating sensitive glass in the manner outlined above could be used with spectacle frames by motorists to eliminate the hazard of dazzle caused by on-coming traffic.