GB906150A - Improvements in or relating to photographic printing methods and apparatus - Google Patents

Abstract

906,150. Applications of luminescence. UNITED STATES RADIUM CORPORATION, EUROPE. Dec. 4, 1958 [Oct. 10, 1958], No. 39153/58. Class 39 (1). [Also in Group XX] Apparatus for dodging photographic positive or negative prints comprises a U.V. source 16, a fluorescent layer 15 producing actinic light on excitation by U.V. light, a filter 19 for stopping U.V. light, a photographic negative 12, a lightsensitive emulsion 13 insensitive to I.R. light, a filter 18 passing only I.R. light, and an I.R. light source 17. For producing negative prints the order of the negative 12 and emulsion 13 is reversed. The I.R. light passing through the negative 12 produces a patterned quenching action on the light produced on the fluorescent layer 15 by the U.V. source 16 and thereby regulates the light passing from the layer 15 through the negative 12 to the emulsion 13. The fluorescent layer 15 and the negative 12 can be separated by a distance between a little more than zero, and approximately half an inch, e.g. about one-sixteenth of an inch. The fluorescent layer 15 is formed of material producing strong emission in the range of 4200-4400 Š, e.g. activated zinc sulphide. An exposure timer 20, Fig. 2, having a photo-cell 21 exposed to the output luminescence of the layer 15, is coupled both to the U.V. source 16 and the I.R. source 17. In order that the rays from the fluorescent layer 15 and the I.R. source 17 towards the negative 12 and emulsion 13 should be strictly parallel. A Fresnel lens system or parabolic reflectors can be used.