1985-02-28
1987-10-06
Adams, Russell E.
354437, 354452, G03B 708
Patent
active
046979085
ABSTRACT:
A program shutter has a shutter mechanism comprised of at least one sector movable in opening and closing directions in response to forward and reverse rotation of a step motor to form a lens aperture. A control unit automatically controls the shutter operation and comprises an exposure quantity storage circuit for storing exposure quantity data corresponding to the brightness of a subject being photographed, a motor control data storage circuit for storing step drive number data proportional to the exposure quantity data and interpolation quantity data corresponding to the exposure quantity data, a pulse generator circuit for generating step drive pulses and clock pulses, a first presettable counter preset with the step drive number data before opening of the sector and downcounted to zero by the drive pulses, a second presettable counter preset with the interpolation quantity data and downcounted to zero by the clock pulses beginning at a time after the first counter has downcounted to zero, a reverse drive circuit for detecting when the second counter has counted down to zero and thereafter effecting rotation of the step motor in the reverse direction, and a motor drive circuit for rotationally driving the step motor according to the drive pulses generated by the pulse generator circuit means.
REFERENCES:
patent: 4306786 (1981-12-01), Carcia et al.
patent: 4325614 (1982-04-01), Grimes
patent: 4362372 (1982-12-01), Kiesel
Oda Hajime
Ogihara Masuo
Seki Yoichi
Yamazaki Hiroshi
Adams Bruce L.
Adams Russell E.
Seikosha Co. Ltd.
Wilks Van C.
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