| 摘要 |
PROBLEM TO BE SOLVED: To read a picture while assuring its quality for a while in spite of the deterioration of the light quantity of a light source by lowering a relative moving speed between a light source for reading the picture and an original according to the extending amount of the storing time of CCD. SOLUTION: Based on information on a set original size, a reading mode, etc., CPU 28 determines a gain adjustment executing timing and a warning level. The gain adjustment executing timing is set at a time just before a timing of original reading when it is predicted that the fluctuation of a light quantity since after the former gain adjustment can no longer be assured concerning a picture quality in a view from the secular change characteristic of the light quantity of a fluorescent lamp 22 housed in EEPROM 46 in advance. Then, in this case, when the output value of CCD 30 is lowered comparing with the level of guaranteeing the picture quality, the storing time of CCD 30 is extended and according to the extending quantity of this storing time, control for lowering the relative moving speed between the light source for reading the picture and the original.
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