| 摘要 |
PURPOSE:To prevent an error of the digital data needed for elimination of ghosts by controlling the gain of a variable gain amplifier set at the preceding stage of an A/D converter in response to a dynamic range of the A/D converter or the differential arithmetic result. CONSTITUTION:The video signal containing the ghost signal is applied to an input terminal 1 and amplified by a variable gain amplifier 13. The DC level of the amplified video signal is clamped at the fixed value by a clamping circuit 2. This clamped video signal is converted into the digital value by an A/D converter 3 and stored temporarily to an RAM6. This stored digital signal is read out when necessary for correlative operation. The data read out of the RAM6 is applied to a data-over detector 14 and then to a differential data overflow detector 15 via a differentiator 7. The gain of the amplifier 13 is controlled according to the results of detection of both detectors 14 and 15.
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