1982-12-10
1985-04-09
Perkey, William B.
G03B 310
Patent
active
045098417
ABSTRACT:
The disclosed automatic focusing device operates by detecting a motor signal which is produced according to the lens movement and by forming a limit signal when the motor signal is not produced for a period longer than a predetermined time. A reference signal forming circuit produces a reference signal corresponding to the shift in focus per unit time. The motor signal is compared with the reference signal and the lens drive speed is adjusted to reduce the difference between the two signals. The invention avoids a mechanical limit switch and maintains an unvarying shift in focus per unit time for different kinds of lenses.
REFERENCES:
patent: 4200378 (1980-04-01), Shenk
Kawabata Takashi
Sakai Shinji
Canon Kabushiki Kaisha
Perkey William B.
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