| 摘要 |
PURPOSE:To improve the quality of a displayed video by providing a reference zero-level correction circuit to the pre-stage of a processing circuit part and preventing the circuit from being clamped to an erroneous reference-zero-level. CONSTITUTION:A video signal AS conducted from an image pickup element 1 to the reference-zero-level correction circuit 10 flows through a switch 11 during a horizontal scanning period, and is supplied to a video amplification circuit 5. The switch 11 comes in a cut-off state during the blanking period of the video signal AS, and a signal at the reference-zero-level position during the blanking period is conducted to a correction circuit main body 12, and the DC level at a prescribed position is sampled by a switch 13. The signal is smoothed by a smoothing capacitor 15 and supplied to the video amplification circuit 15 through a switch 14, and the DC level at the reference-zero-level position of the video signal AS is substituted. Thus a video signal AS' including no level-fluctured component at the reference-zero-level position is supplied to the processing circuit part 7. As a result, a level varied due to noise, etc. is not erroneously clamped.
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