| 摘要 |
An automatic focusing system for a video camera carries out automatic focusing on the basis of a focus signal extracted from a high-frequency component of a video signal. The automatic focusing system comprises at least one of picture-contents change detecting means for detecting a change, if any, between the contents of pictures of two consecutive picture periods on the basis of the output signal of a low-pass filter to which the video signal is applied, momentary change detecting means for detecting an abrupt change of the focus signal, and reduction-factor change detecting means for detecting a change between the contents of pictures of two consecutive picture periods on the basis of the output signal of a detector detecting the reduction factor of the lens system, so that the automatic focusing operation can be interrupted in response to the output signal of the change detecting means and can be re-started when the output signal is reduced to a level lower than a predetermined level.
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