| 摘要 |
PURPOSE:To prevent density difference at each divided scanning period from being caused by controlling output levels of each division variable amplifier so as to be arranged during scanning period of density reference plate and controlling the variable amplifier synthesizing the output of the division variable amplifier during original reading period. CONSTITUTION:An output of sensors 1, 5 scanning dividedly one line is synthesized serially timewise by a switch SW1 via a variable amplifier comprising resistors R1, R3, variable resistors 2, 6 and amplifiers 3, 7 respectively and amplified by a variable amplifier comprising a resistor R5, a variable resistor 10 and an amplifier 11. The output of the amplifier 11 is subject to A/D conversion 9 and inputted to a shading correction circuit 13. When the input exceeds two reference values (lower/higher limit) to the circuit 13, signals h, i are outputted respectively to a selection circuit 14. The circuit 14 outputs signals n, m alternately from the signal (h) by using a signal (g) of logical ''0'' during the scanning of density reference plate, the resistors 2, 6 are controlled respectively by the amplifiers 15, 16 so as to arrange the output level of the amplifiers 3, 7. The signal (g) goes to logical ''1'' during the scanning of the original, the resistor 10 is controlled via the amplifier 12 by using a signal (l) so as to bring the output of the amplifier 11 close to the reference value.
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