GB1399178A - Image display system - Google Patents

Abstract

1399178 Colour television MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 10 April 1973 [12 April 1972] 17210/73 Heading H4F A coloured image relating to the information on a card or film 55 is produced on a flying spot scanner 52 having a coloured filter 53 formed of red, green and blue stripes or dots placed in front of its phosphorescent screen 51, by feeding back the output of photo-detector 56 to control the intensity of the light beam from scanner 52. The fedback signal may be directly or inversely proportional to the output of photo-detector 56. If an inverse signal is fed back, and film 55 is a negative, scanner 52 will reproduce a positive image, e.g. a cyan portion of film 55 will block red light thus causing the points on screen 51 corresponding to red portions of filter 53 to glow more brightly, blue and green light being passed by this portion of the film 55, thus reducing the intensities of points on screen 51 corresponding to blue and green portions of filter 53, thus producing a red portion on the image viewed through filter 53. To reduce flicker without reducing resolution, screen 51 may be formed of a mixture of laminations of two phosphors, one of which has a short persistence time and is not sensed by the human eye, and the other of which has a long persistence time, this phosphor causing a constant D.C. component in the output of photo-detector 56. The signal from photo-detector 56 may also be fed to a separate display from 59 in which case a colour synchronizing signal may be produced by a second photo-detector which is sensitive only to red light. Filter 53 may be provided on the inside of the faceplate of scanner 52( Figs. 9a, 9b, not shown), the fluorescent screen being on the inner side of the filter 53. If positive feed-back is employed a D.C. input may be supplied to photo-detector 56 to ensure a minimum intensity of scanner 52 even if no light is incident on photo.detector 56.