Automatic focusing circuit for automatically matching focus in r

Details Automatic focusing circuit for automatically matching focus in r Automatic focusing circuit for automatically matching focus in r

1987-11-13

1989-06-20

Ng, Jin F.

Facsimile and static presentation processing

Facsimile

Recording apparatus

354404, H04N 5232

Patent

active

048413704

ABSTRACT:
In an automatic focusing circuit of a video camera, automatic focusing operation is performed by a focus evaluating value formed in response to a video signal obtained by an image sensing circuit (4). A first focusing motor control circuit (15) controls the rotation of a focusing motor (3) so that a focusing lens (1) is once fixed in the position where the focus evaluating value takes the maximum value. A second focusing motor control circuit (17) changes the focusing motor (3), by a predetermined very small amount, to determine the slope of the focus evaluating value, which change is repeated until inversion of the slope, that is, the maximal point is detected. As a result, the position of the focusing lens is corrected at the maximal point of the focus evaluating value. When the correction amount exceeds a predetermined value, first automatic focusing operation by the first focusing motor control circuit (15) is resumed.

REFERENCES:
patent: 3617633 (1971-11-01), Barr
patent: 4354204 (1982-10-01), Kimura
patent: 4370038 (1983-01-01), Kimura
patent: 4484806 (1984-11-01), Onishi et al.
patent: 4614975 (1986-09-01), Kaite
patent: 4638364 (1987-01-01), Hiramatsu

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