GB188030A - Improved process for taking photographs and apparatus therefor - Google Patents

Abstract

188,030. Bronk, O. von. July 23, 1921. Negatives, producing by means other than photography; p h o t o - graphs, producing electrically.-Consists in a process for taking photographs wherein a film sensitive to electricity is exposed to the action of an electric current passed through a substance with which it is in contact or coated, and whose electric resistance is varied by the incidence of light upon it. An objective 8 projects an image upon a glass plate 1 coated with thin transparent metal 2 and a thin uniform layer 3 of a substance such as selenium whose electric resistance is affected by light. The metal coating 2 is connected through an electric battery 4 and switch 6 to a metal plate 5 between which and the composite plate 1, 2, 3 is interposed a film 7 carrying a material sensitive to electricity and prepared, for example, like the paper used in chemical copying telegraphs, by moistening paper with a solution of potassium iodide or a cyanide. The photograph is taken by passing the film 7 against the coating 3 by means of the plate 5, and closing the switch 6 for a predetermined length of time. In a modification, the coatings 2, 3 are dispensed with, and a film is employed containing a material sensitive to electricity and also a material whose electric resistance is affected by light. The current is led into this film through a grating of fine wires pressed against the back of the film, alternate members of the grating being connected together to form two series which are connected respectively through a switch to the poles of a battery. The film, being light-insensitive, may be handled in daylight. Salts sensitive to light may be added to the film coating to shorten the time of exposure.