| 摘要 |
PROBLEM TO BE SOLVED: To provide an image reading apparatus preventing deterioration in dust detecting accuracy more than that of the prior arts by decreasing the effect of dirt of a background body even when the background body on a read position gets dirt. SOLUTION: The image reading apparatus includes: a dust detecting binary circuit 504 for binarizing image data read by a CIS (contact image sensor) 110 on the basis of a binary threshold value calculated by a CPU 406; and a dust discriminating binary circuit 507 for discriminating the presence of dirt at an original read position on the basis of data subjected to binary processing by the dust detecting binary circuit 504. The CPU 406 calculates an average of read values in a prescribed area read by the CIS 110 and calculates the binary threshold value by using a value furthermore averaging the average and an average of another prescribed area. COPYRIGHT: (C)2004,JPO&NCIPI
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