| 摘要 |
PROBLEM TO BE SOLVED: To prevent a read gravity center of each color from being shifted in a subscanning direction due to the difference of the afterglow characteristics of each color phosphor in the case of using a white fluorescent light or the like as the light source of an image reader. SOLUTION: The centers of dimmer control signals to control the light quantity of a fluorescent light or the like are controlled to be arranged not to the top of a Hsync period equivalent to one storage time of an image pickup element but to the center of the period. Thus, the gravity center shift is reduced to d1 compared to the gravity center shift d2 in the former case. Furthermore, the number of accumulated scan times with respect to each light source is measured and the control is conducted on the basis of the result so as to cope with changes in a dimmer control signal by the secular change of the light source.
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