Television – Special applications – Simulator
Patent
1992-09-04
1994-06-28
Perkey, William B.
Television
Special applications
Simulator
348353, 348356, G03B 1336
Patent
active
053251466
ABSTRACT:
A differential value of a characteristic curve of a focus distance of a zooming lens versus a position of a focus lens is calculated or found from a table in a contrast or phase difference type auto focus mechanism by detecting a high frequency part of an image signal. A follow-up speed of a focus lens is stepped or continuously changed based on the differential value. A focus position of a focus lens can therefore be changed smoothly corresponding to displacement of a focus distance of a zooming lens. A current brightness and a brightness when the evaluative value is peak is compared. If a brightness difference is large, a peak is not recognized and processing is repeated. Also, a gain of an amplifier is reduced corresponding to a linear-, step- or curve characteristic of a focus position of the focus lens versus a focus distance of the zooming lens when a gain of an AGC circuit is relatively high, so that noise is a high frequency part is reduced. If an iris of the apparatus is relatively closed a gain of the AGC or an amplifier is relatively high, noise increases and the reference value therefore increases to judge a peak of an evaluative value certainly. If the iris is relatively opened, a gain of the AGC and the amplifier is relatively low and noise decreases wherein a peak is rapidly detected without the focus lens passing a focus point.
REFERENCES:
patent: 4735494 (1988-04-01), Makino et al.
patent: 4920369 (1990-04-01), Kaneda et al.
patent: 5055932 (1991-08-01), Hijikata
patent: 5140357 (1992-08-01), Suda et al.
patent: 5157432 (1992-10-01), Fukuoka et al.
Fuji Photo Film Co. , Ltd.
Perkey William B.
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