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Photographic copier image contrast control

  • US 4,706,131 A
  • Filed: 03/10/1986
  • Issued: 11/10/1987
  • Est. Priority Date: 03/25/1985
  • Status: Expired due to Term
First Claim
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1. In a hard copy recorder, in which light-sensitive paper or film is exposed to an image produced by a cathode ray tube, apparatus for controlling image contrast comprising:

  • a source of video signals;

    first and second controls for separately adjusting image intensity and background shading;

    means, coupled to said first and second controls, for developing a first control signal representative of background shading, and for developing a second control signal representative of image intensity and determining a maximum intensity level established solely by said image intensity control setting;

    means for amplifying video signals produced by said source by a factor determined by said second control setting;

    means for producing a video pedestal signal exhibiting a level determined by said first control signal;

    means for combining said amplified video signals and said video pedestal signal; and

    means for applying said combined signals to said cathode ray tube.

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