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Shading compensation for scanning apparatus

  • US 4,314,281 A
  • Filed: 10/12/1979
  • Issued: 02/02/1982
  • Est. Priority Date: 10/12/1979
  • Status: Expired due to Term
First Claim
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1. A method of compensating for variations in light to which individual image sensors of a scanning array are subjected, the steps comprising:

  • (a) processing image signals output by said sensors when scanning original images to provide multi-bit digital signals representative of the image gray level in a first operating mode;

    (b) processing image signals output by said sensors when scanning original images to provide single bit binary level signals representative of the image in a second operating mode;

    (c) producing a separate test signal from each sensor in said array by scanning a test image of predetermined optical density;

    (d) segregating said sensors into groups each comprised of a preset number of sensors;

    (e) processing said test signals from said sensors in said first operating mode to provide multi-bit test signals;

    (f) averaging the test signals from each of the sensors in said sensor groups to provide composite compensating signals for each of said sensor groups;

    (g) storing said compensating signals; and

    (h) correcting the image signal output of said sensors in both said first and second operating modes with the stored compensating signal for the sensor group within which said sensor is included.

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