| 摘要 |
PURPOSE:To prevent the appearance of an unnatural monitor video image on the way of focus adjustment by providing a detection means detecting the focus adjustment state and an output means limiting a pass frequency band of a pickup signal and giving an output based on the result of detection. CONSTITUTION:A VCF (voltage controlled filter) 16 is provided, which acts like an LPF eliminating a high frequency component of a luminance signal component from a pickup signal from an image pickup element 12, to a video signal processing circuit 14. A peak hold circuit 20 receives a high frequency component of the said luminance signal, detects its peak value at each field, a detection signal is subject to A/D conversion and sent to a microprocessor (MP) 24. The MP 24 is provided with variables En-2, En-1, En to calculate the differentiation value and the 2nd order differentiation value of the peak value E and variables of the differentiation value DELTAEn and the 2nd order differentiation value DELTA<2>En. Then a motor 28 is driven properly, after peak values En-2, En-1 are obtained, the present peak value En is read and the differentiation value DELTAEn and the 2nd-order differentiation value DELTA<2>NEn are calculated. The control voltage of the VCF 16 is controlled in response to the 2nd order differentiation value DELTA<2>En. Thus, the production of a displeasant picture at out of focus is prevented.
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