| 摘要 |
PURPOSE:To apply accurate shading correction without making a circuit complicated by obtaining shading correction data averaging image data in the subscanning direction in an image sensor at the scanning time of calibration plate. CONSTITUTION:An optical unit 9 scans in the sub-direction at the scanning time of calibration plate at a speed four times that at original scanning by switching a command speed signal 51 to an optical unit driver 5. The image sensor 1 receives reflected light from an area corresponding to 4 main scanning lines or the calibration plate 7 and stores the light as signal charge. By reading the signal charge, the image data averaged in the subscanning direction is obtained. An A/D converter circuit 2 converts the said image data into a digital signal and stores it in a memory 4 as shading correction data. The correction data stored in the memory 4 is used at the scanning time of original and the image data read by the sensor 1 is corrected by a shading correction circuit 3.
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