| 摘要 |
PURPOSE:To attain correct shading correction even with flaw or dirt on a white level calibration plate by providing a circuit comparing a picture data read by plural lines in the subscanning direction with the shading correction data and a secting circuit. CONSTITUTION:A comparing circuit 12 compares a picture data A at the read by plural lines with a shading correction data B read by a shading RAM 11 to decide a white reference level of an image pickup element. Moreover, a selection circuit 13, based on a write control signal, selects either of data A, B which is larger and outputs it as a data C in the RAM 11. Then the next address of the RAM 11 is read and the similar operation as to each bit in the main scanning direction and when all of one lie is finished, the reading of 2-line and 3-line is consecutive. Then a wide sufficiently wide as to a small flaw or dirt on the white level calibration plate is applied and the shading correction is applied accurately even with flaw or dirt on the white calibration plate.
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