| 摘要 |
PROBLEM TO BE SOLVED: To provide a picture reader capable of properly correcting the offset level at any time in a simple constitution without using a clamp circuit. SOLUTION: A detecting means 22 detects the offset level from digital signals at a digital processor 19. A calculating means 23 calculates correction values for a target level. D/A converting means 25e, 25o convert them to analog correction signals. A correcting means 26 corrects the offset level by directly feeding them back to amplifier circuits 17e, 17o in an analog processor 16. This eliminates the need of using a clamp circuit being apt to cause the droop in the prior art, resulting in no change of the offset level due to drooping. Thus, the offset level can be always held constant.
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