GB1125749A - Improvements relating to scanners for image reproduction systems - Google Patents

Abstract

1,125,749. Image reproduction by scanning. CROSFIELD ELECTRONICS Ltd. 14 July, 1967 [14 July, 1966], No. 31638/66. Heading H4F. A cathode-ray tube flying-spot scanner 3, which scans an original image 5 to produce signals by a photo electric cell 7 which modulate a light source 14 exposed to a light sensitive sheet 15 on which a reproduction of the original is reproduced, is periodically varied in focus under control of oscillator 24 so as to cause the output signal of the photo-electric cell to consist of components representative alternately of "unsharp" and "sharp" image scanning. The components are separated to channels 10-11 by a distributor 9 controlled by oscillator 24, the distributor also including means to smooth the components to continuous signals, and then pass to a computer 12 in which the signals are recombined after first inverting the "unsharp" signal so as to bring about "unsharp masking", whereby the apparent definition of the reproduced image is improved. As illustrated, light sensitive sheet 15 is carried by drum 16, the scanning circuits 1 of cathode-ray tube 3 being synchronized with the drum rotation by a photo-electric pulse generator 19-23 associated with the drum shaft. Reference is made however to alternative arrangements which use an oscillating table in place of drum 16 or a cathode-ray tube display and exposing unit. Reference is also made to the application of the invention to colour reproduction where the light from image 5 is split into red, green and blue components which are detected by separate photo-electric cells. In carrying out the invention each cell signal is separated into "sharp" and "unsharp" components by a distributor 9 controlled by oscillator 24.