GB638937A - Improvements in or relating to television or like systems - Google Patents

Abstract

638,937. Television. CINEMA-TELEVISION, Ltd., and JESTY, L. C. Nov. 6, 1947, No. 29593. [Class 40 (iii)] In a system in which signals derived by scanning a background scene are periodically replaced by those derived by scanning a foreground scene to produce at a receiver the appearance of performers located against a background other than that before which they are in fact located, the foreground and background are illuminated by light of different colours. In Fig. 1, the performers 1 appear before a semi-transparent black backcloth 2 illuminated at the rear by blue or ultra-violet lamps 3 and are themselves illuminated by lamps 4 giving yellow or white light from which the blue or ultra-violet components have been eliminated. One form of scanning apparatus A comprises a television camera 5 in front of which is rotated a two colour filter disc 6 having filters so chosen that signals due to the performers alone and the backcloth alone appear sequentially in the camera output. The signals, applied to circuit A, Fig. 2, are separated in a synchronous blanking generator 10, the performer signals passing to a film recorder 14, and the backcloth signals to a limiter and phase reverser 12. The signals from 12 feed a blanking device 15 which receives over line 16 the picture signals representative of the desired background into which the performers are to be inserted. Device 15 blanks out the background signals over the portions corresponding to the positions of the performers and the resultant signals pass by way of 17 to the film recorder where the performer signals and the partially blanked background signals are recorded successively in pairs on single frames of the film. The background signals can be derived by a direct pick-up camera or telecine film scanner. An alternative scanner B employs two cameras 7 and 8 at right angles and arranged to receive light by way of an optical system formed of a dichroic mirror 9, the arrangement being such that 7 receives light from the performers only and 8, from the backcloth only. In this case the signals appear simultaneously in the camera outputs and are applied to circuit B of Fig. 2, the performer signals passing to the film recorder 21 over line 22 and the backcloth signals to a blanking device 20 by way of line 18 and limiter and phase reverser 19. Device 20 operates in the same manner as device 15 to blank out the background signals received from line 23. Recorder 21 records the performer and background signals simultaneously on each frame of the film. By a suitable combination of colour separation filters with an ultra-violet filter, system A may be applied to a colour-picture system. Infra-red light may be used in place of ultra-violet. Specifications 472,762 and 489,717 are referred to.