| 摘要 |
PROBLEM TO BE SOLVED: To prevent the non-uniformity of concentration even when the reflection efficiency of a reflecting board is low. SOLUTION: Concerning this reader, first and second white reference plates 2 and 3 are read, respective read values in the case of making constant a reference voltage Vref of an A/D converter 16 are stored in a memory 17, average values (a) and (b) at the central parts of the first and second white reference plates 2 and 3 in main scanning direction are calculated and using the number of pulses of an SP motor as an address in sub scanning direction, the table of correction values of a primary expression obtd. by connecting the average values (a) and (b) is prepared. When an original is read, the correction values of the table are read out based on the number of pulses of the SP motor and applied to the A/D converter 16 as the reference voltage Vref. In place of the reference voltage Vref of the A/D converter 16, the gain of a gain control amplifier can be controlled as well.
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