GB591628A - Improvements in or relating to photography - Google Patents

Abstract

591,628. Photographic and radiographic apparatus. SCOPHONY, Ltd., and WIKKENHAUSER, G. May 4, 1944, Nos. 8471/44 and 4820/45. [Class 98 (i)] A method of obtaining increased contrast in dimly ilhuninated parts of photographs and radiographs comprises exposing a photosensitive carrier through a diffraction grating which is so disposed as also to yield an image thereof on the sensitive surface, developing the image and reproducing therefrom in apparatus which forms a positive image only from light diffracted by the grating pattern on the negative film. A photograph of a dimly illuminated object is taken on a photographic plate with a grating in contact with or close to the surface of the plate. The plate is developed and is then placed between a pair of lenses L1, L2. A stop B is placed at the point of the image of a light-source S formed by the lens system L1, L2. A lens L3 is placed behind the stop B and an opaque diaphragm M is associated therewith. The light from S is normally, stopped by B but when the plate P is inserted between the lenses L1, L2, the diffracted light deviates from the stop and the lens L3 forms an image therefrom on the viewing screen XY. Light scattered by the plate will be dispersed over a larger angle and will be arrested by the diaphragm M. The diffraction grating may consists of parallel lines or zones alternately opaque and transparent or of two intersecting sets of parallel lines. In the case of X-rays, a grating of thin narrow slats of wood coated with a thin layer of metal or interspersed with thin narrow strips of metal foil is placed on the X-ray permeable container of the sensitive material and the developed image is viewed in the apparatus described. The thickness of the metal should not exceed .02 inch. A picture of the image may be taken by inserting a light sensitive carrier in the plane of the screen XY.