International projectionist (Jan-Dec 1947)

Simultaneous ALL-ELECTRONIC Color Television The appended article comprises the latest progress report on color television and the first on the new simultaneous all-electronic system, as published in the RCA REVIEW (Dec, 1946). Basic design and operating characteristics are reviewed, and the apparatus for scanning color slides and color motion picture film, together with the receivers, are described. IN October and November, 1946, the Radio Corporation of America gave several demonstrations of color television to press, industry and Government groups. These demonstrations constituted a progress report on the work done in color television, which follows the program announced at the time of earlier demonstrations in December, 1945. In the current demonstration, important advances in color television were shown. The new system is all-electronic, having the potential flexibility inherent in electronic arrangements, and is also simultaneous, all three color images being transmitted continuously. This system has many operating and performance advantages and is compatible with the present black-and-white television. Since each of the three color channels employs the same standards as those now in use for black-and-white transmissions, the green channel is suitable for monochrome presentation. Color television of this type can be introduced at any time it is made ready and can be operated interchangeably with black-and-white television; undesirable obsolescence is not created. The recent demonstrations included television pictures in natural color scanned from Kodachrome slides and from 16-mm color motion picture film. In order to demonstrate interchangeability, pictures in monochrome using signals of present black-and-white standards were shown on the color receivers; pictures in monochrome, using signals of the simultaneous color transmission, were then demonstrated on a current model black-and-white receiver. COLOR FILM SCANNING UNIT SCANNING CATHODERAY TUBE COLOR CHANNELS SIMULTANEOUS COLOR PICTURE PROJECTION COLOR CHANNELS CATHOOE-RAY PROJECTION TUBES FIGURE 1. Block diagram of the simultaneous' allelectronic color television system. Each of the color channels, shown at the right of the upper figure, have the same operating standards as the current blackand-white system. At the receiving end, shown at the left of the lower figure, each' color channel is^slo'ctfited with ' ifS' separate cathode-ray projection tube. FIGURE 2. Stationary picture signal generator. Research work is under way and progress is being made in the radio transmission and reception of simultaneous allelectronic color television and in the building of television cameras for studio and outdoor pickup of this system. This work together with propagation tests and field surveys, is a part of the overall schedule yet to be fully worked out, but already well along. Since simultaneous all-electronic color television is of far-reaching importance, the experimental equipment used during the recent demonstrations is described herein. This includes the apparatus for scanning color slides and color motion picture film together with the television receivers for color. Some of the basic design and operating characteristics are also reviewed. Fig. 1 is a block diagram of the system. Picture Signal Generator One of the primary needs for the development of a simultaneous color television system is a standard source of tricolor video signals on which one may rely for good resolution, good registration, high signal-to-noise ratio, freedom from spurious signals, and good color fidelity. A special slide scanner utilizing a cathode-ray tube as a flying-spot scanner, a beam splitter, and three photoelectric tubes, were developed for this purpose. A photograph of this apparatus with a superimposed phantom view of the kinescope and the light paths is shown in Fig. 2. The raster formed on the screen of the kinescope is imaged on the INTERNATIONAL PROJECTIONIST • February 1947