Focal controller of camera

Details Focal controller of camera Focal controller of camera

1995-10-25

1997-09-02

Perkey, W. B.

Photography

With exposure objective focusing means, focusing aid, or...

With electronic filtering

396135, 348355, G03B 1336

Patent

active

056642385

ABSTRACT:
In a focal controller of a camera, two brightness components in different frequency bands are obtained by two band pass filters from a video signal obtained by image pickup. Integral values a and b of the respective brightness components are detected by integrating circuits. When both a ratio a/b and a value a calculated by an arithmetic circuit are increased, a CPU judges this increase as an unfocusing position of a focusing lens. In contrast to this, when an increasing degree of the ratio a/b is decreased or tends to be decreased, the CPU judges this decrease as a position near a focusing position of the focusing lens. Thus, the driving speed of a focusing motor is set to a high speed in the unfocusing position and is set to a low speed in the position near the focusing position. For example, a microcomputer obtains a focal evaluation value at an interval of three fields (k+2 after k-1) in the vicinity of a focusing position and compares this focal evaluation value with reference data.

REFERENCES:
patent: 4990947 (1991-02-01), Komiya et al.

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