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Image reading apparatus with black-level and/or white level correction

  • US 5,038,225 A
  • Filed: 04/03/1987
  • Issued: 08/06/1991
  • Est. Priority Date: 04/04/1986
  • Status: Expired due to Term
First Claim
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1. An image reading apparatus comprising:

  • reading means, comprising a plurality of photosensing elements, for reading an image line by line and generating analog image data corresponding to each of said photosensing elements;

    a light source for exposing the image;

    conversion means for converting the analog image data generated by said reading means into digital image data pixel by pixel;

    memory means for storing digital reference data representing a reference black from said conversion means when said light source is off;

    correcting means for correcting the digital image data from said conversion means pixel by pixel on the basis of the digital reference data read out from said memory means when said reading means reads the image exposed by said source; and

    second correcting means for correcting white levels of the digital image data of which the black levels are corrected by said correcting means,wherein said second correcting means corrects white levels of the digital image data on the basis of digital image data output from said conversion means when said reading means reads said reference white image exposed by said light source.

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