| 摘要 |
PURPOSE:To obtain an optimum luminance level, by comparing the DC level, which was detected by adding the amplified outputs of a plurality detection circuit, with a predetermined level to obtain a difference signal and reversing said difference signal to add the same to the prescribed level of each clamp circuit. CONSTITUTION:The images of the positions 11-1n of objective matter 1 are picked up to be inputted to the detection elements 31-3n of a multielement detection circuit 3. The outputs of the detection elements 31-3n are amplified by amplifying circuits 61-6n to be inputted to a display part 7. THe outputs of the amplifying circuits 61-6n are added by an adder 91 and a DC level is detected by a detector to be compared with reference voltage by comparator 93 and the difference voltage is reversed by a reversal circuit 94 and amplified by an amplifying circuit 95 to be superposed to the DC set voltage of a level setting circuit 8. The voltage signals obtained by superposition are outputted to the clamp circuits 51-5n. The DC level of video signal receives negative feedback to be suppressed in level variation. By this method, an optimum luminance level is always obtained.
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