| 摘要 |
PROBLEM TO BE SOLVED: To provide an image reader that prevents the image quality from being deteriorated due to changeover aging without need for re-shading. SOLUTION: At a point of time when a prescribed period elapses after the start of use, reference data 10 set at initial shading are corrected on the basis of a deteriorated amount of a signal level, and black/white border level 20 of the image is shifted downward according to the reference data 12 obtained as a result. Since shading is implemented once at factory shipment to automatically adjust the black/white border level depending on the deterioration period of elements afterward, the image quality can be kept at a prescribed level without need for re-shading.
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