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Optical input arrangement and method of using same

  • US 5,504,501 A
  • Filed: 07/18/1994
  • Issued: 04/02/1996
  • Est. Priority Date: 11/07/1989
  • Status: Expired due to Term
First Claim
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1. In an image projection arrangement including projection means for directing a projected image onto a remote viewing surface, light sensing means for detecting all wavelengths of light in the visible spectrum including the reflected projected image and ambient light, and an optical apparatus for generating a video image, a system for controlling the optical apparatus for generating a video image, comprising:

  • means for generating an optical control image having a predetermined optical wavelength and a given intensity level to modify the projected image;

    means interposed between the remote viewing surface and the light sensing means for passing visible light within a narrow predetermined band of optical wavelengths only including the reflected projected image, ambient light and said optical control image;

    signal means responsive to the light sensing means for generating an electrical signal indicative of the visible light having said narrow band of wavelengths;

    signal modification means responsive to said signal means for determining a black level reference level to help generate a modified electrical signal indicative of the visible light having said narrow band of wavelengths and a peak intensity level substantially equal to the combination of the lowest intensity level of the projected image reflecting from the viewing surface and the highest intensity level of the control image reflecting from the viewing surface;

    reference level means responsive to said modified electrical signal for determining a peak video image reference level, and a peak control image reference level and for establishing a reference level between said peak video image reference level and said peak control image reference level;

    control means responsive to said electrical signal for generating a control signal indicative of a desired modification of the projected image whenever the electrical signal is greater than said reference level, said electrical signal being further indicative of visible light in said narrow band of wavelengths and having a peak intensity level that is at least greater than the highest intensity level of the protected image reflecting from the viewing surface; and

    means for modifying the projected image in response to said control signal.

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