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Beam index color television receiver

  • US 4,268,856 A
  • Filed: 09/24/1979
  • Issued: 05/19/1981
  • Est. Priority Date: 09/25/1978
  • Status: Expired due to Term
First Claim
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1. A beam index color television receiver, comprising:

  • a beam index color cathode ray tube including a screen, means for providing an electron beam adapted to scan said screen during scanning intervals, said screen having an image area and a run-in area contiguous to an edge of said image area and which is scanned by said beam during a predetermined period of each of said scanning intervals, a repetitive pattern of a plurality of groups of color phosphor elements arranged side-by-side across said image area with the elements of each of said groups emitting light of a respective color different from the color of light emitted by the elements of each of the other groups when excited by said beam, index elements spaced apart across said run-in and image areas and emitting radiant energy when excited by said beam, and means responsive to said radiant energy to provide index signals;

    means for applying a potential to said color cathode ray tube so as to produce a current in said beam during said predetermined period of each of the scanning intervals;

    means responsive to said index signals for producing a controlled signal of a level dependent on said beam current;

    means responsive to said level of the controlled signal for controlling said potential so as to maintain constant the levels of said controlled signal during the scanning of said run-in area and said image area, respectively;

    means for producing a reference potential which is shifted from the controlled potential in the direction for reducing said beam current; and

    means for applying color signals to said color cathode ray tube with said reference potential as a reference level for the applied color signals during the scanning of said image area.

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