| 摘要 |
PURPOSE:To obtain a quick and stable exposure controller with high accuracy by obtaining an integration output of a video signal, sampling and holding a black level signal preset at a part of the video signal in an image pickup device and generating a reference voltage deciding a proper aperture from the output of sample-and-hold processing. CONSTITUTION:The video signal processed for photometry is integrated by an integration circuit 3 and sample and held by a sampling pulse as shown in Fig. (d) at a sample-and-hold circuit 4. The sampling pulse is a pulse generated at, e.g., one field. The sample and held output is compared with a preset reference voltage Vref by an error amplifier circuit 5, the error signal is amplified, fed to an aperature drive circuit 10 via an electronic switch 14, an aperture motor 11 is driven and the aperture is set to a proper value at a time T5 as shown in Fig. (e).
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