GB650457A - Improvements in recording images by means of phosphors - Google Patents

Abstract

650,457. Luminescent recording processes. KODAK, Ltd. March 25, 1947, No. 8159. Convention date, March 26, 1946. Drawings to Specification. [Classes 98 (i) and 98 (ii)] [Also in Group XL (a)] A method of delayed-action recording of a short wavelength image comprises projecting the image on to a layer of a phosphor which stores the exciting radiation and releases at least a part of it, when stimulated with longer wavelength radiation such as red or infra-red light, as light of intermediate wavelength, placing the excited phosphor layer in contact with, or if a projection system is interposed, in a plane conjugate to that of the recording layer and stimulating the excited phosphor to form an image on the recording layer. This layer may either be a photographic layer and a permanent image formed by the usual processing steps or merely a layer on which the image can be observed and recorded manually as by tracing. Numerous examples of suitable phosphors are given in the Specification and are included in the list given in Specification 650,455. When making copies of an original, the phosphor is excited image-wise by passing light from an ultra-violet lamp through the orignal or causing such light to pass through the phosphor first, when it then is excited by the light reflected from the more opaque parts of the original. The excited phosphor is then stimulated by uniform illumination with infrared light so as to print on to a light-sensitive sheet contacting the phosphor by means of the light emitted by the latter. If several prints are required from a single excitation of the phosphor the intensity of the stimulating infrared light is progressively increased to maintain the exposure time constant. To increase the sensitivity of the phosphor to the stimulating infra-red, it may be initially either strongly excited with ultra-violet and partially exhausted with infra-red, or partially excited with ultra-violet. In an application to recording galvanometer deflections, ultra-violet light is reflected from the galvanometer mirror and projected on to a continuously moving phosphor band. The faintly luminescent trace may be examined and either obliterated by flooding with red or infra-red light or a permanent record made on stimulating the phosphor with infra-red. Specifications 650,458 and 650,459, [both in Group XL (a)], also are referred to.