| 摘要 |
PROBLEM TO BE SOLVED: To provide an image reader that can completely separate position shift in the subscanning direction from a position shift in the main scanning direction, so as to quickly correct only the dispersion in the read position in the subscanning direction with high accuracy. SOLUTION: The image reader is provided with a measurement means, that measures a position error by an image signal acquired by the image reader from an original, where patterns expressing the contrast of image and comprising parallel lines that have density which is uniform in the main scanning direction and density which is ununiform in the subscanning direction perpendicular to the main scanning direction and patterns with a uniform density in a direction which is neither horizontal or vertical with respect to the main scanning direction are adjacent to each other, and with a correction means that corrects the image of the image reader, by using the position error.
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