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AUTOMATIC BRIGHTNESS CONTROL FOR PHOTOGRAPHIC PROJECTORS

  • US 3,833,297 A
  • Filed: 03/13/1972
  • Issued: 09/03/1974
  • Est. Priority Date: 03/13/1972
  • Status: Expired due to Term
First Claim
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1. A photographic projector comprising a. projecting means for projecting an image of a transparency along an optical projection path, said projecting means comprising i. light source means for illuminating a transparency optically aligned with said light source means in said optical projection path, and ii. projection lens means for projecting an image of the transparency, said projection lens means being aligned with said light source means along said optical projection path with the transparency interposed in said optical projection path between said light source means and said projection lens means;

  • b. light intensity sensing means mounted adjacent to and offset from said optical projection path for sensing the intensity of a light image of the transparency projected upon and reflected from at least a portion of a surface of said projection lens means facing the transparency prior to passage of said light image through said projection lens means; and

    c. potential control means operably connected to said light source means and said intensity sensing means for controlling the potential applied to said light source means in accordance with the intensity of the light image projected upon at least said portion of said surface of said projection lens means.

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