| 摘要 |
PROBLEM TO BE SOLVED: To provide an image reader that can ensure proper image quality, even if there is dust on a white reference board. SOLUTION: The image reader is provided with a correction coefficient deciding circuit 4 that decides correction coefficient by each bit in the main scanning direction of white data of a read white reference board before reading an original, a correction coefficient correction circuit 5 that outputs a correction coefficient, and a correction coefficient prediction circuit 6, that generates a correction coefficient value on the basis of the correction coefficient value. The correction coefficient correction circuit 5 outputs a correction coefficient as a correction coefficient corrected value, when the absolute value of the difference between the correction coefficient and the correction coefficient predicted value is smaller than a prescribed threshold and outputs the correction coefficient predicted value as the correction coefficient corrected value, when it is larger than the threshold or more. A correction coefficient storage circuit stores the correction coefficient corrected value as shading correction coefficient data. The correction coefficient prediction circuit 6 predicts correction coefficient predicted value in a bit among the bits of white data in the main scanning direction, on the basis of at least a preceding adjacent bit to the bit in the main scanning direction. |
