Automatic focusing circuit selectively using multiple focus eval

Details Automatic focusing circuit selectively using multiple focus eval Automatic focusing circuit selectively using multiple focus eval

1988-02-16

1989-08-01

Groody, James J.

Facsimile and static presentation processing

Facsimile

Recording apparatus

358225, H04N 5232

Patent

active

048537888

ABSTRACT:
In an automatic focusing circuit of a video camera, an automatic focusing operation is performed in response to a first focus evaluating value which is steeply changed and a second focus evaluating value which is gently changed, in response to the position of a lens, in which the first and second focus evaluation values are generated in response to a video signal obtained in an image sensing circuit 4. When a comparator 28 determines that the first focus evaluating value does not reach a predetermined reference value, a in-focus state detecting circuit 24 and a focusing motor control circuit 10 perform an intermittent automatic focusing operating every other field in response to the second focus evaluating value. When the comparator 28 determines that the first focus evaluating value exceeds the perdetermined reference value, the in-focus state detecting circuit 24 and the focusing motor control circuit 10 perform an automatic focusing operation more frequently every field in response to the first focus evaluating value. The moment a change of an object is detected after the object is in focus, the automatic focusing operation is resumed in response to the second focus evaluating value.

REFERENCES:
patent: 4414575 (1983-11-01), Yamamoto et al.

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