| 摘要 |
PURPOSE:To attain easy gain control independently of the sort of an original by reading out also a white reference plate arranged adjacently to the original and controlling the A/D conversion of an original reading output in each line. CONSTITUTION:The white reference plate arranged adjacently to an original is read out by a line image sensor 11 together with the original, the output of a W and Ye element string is supplied to an A/D converter 23 through an amplifier 21 and the output of the W element is simultaneously held in a sample holding circuit 25. The held value is converted into a reference voltage through an amplifier 27 and the converter 23 is controlled to automatically adjust gain in a density range. Since the output of G and Cy elements are similarly processed, gain control can be easily executed in each line independently of the sorts of originals, a uniform color image can be obtained and color reproducing can be improved.
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