Electronic exposure timing circuit for photographic cameras

Details Electronic exposure timing circuit for photographic cameras Electronic exposure timing circuit for photographic cameras

1977-03-31

1979-02-20

Wintercorn, Richard A.

354 32, 354149, G03B 708, G03B 1503

Patent

active

041403797

ABSTRACT:
The camera shutter is opened. An electromagnet is energized to keep the shutter open. A first timing circuit includes a photosensitive element exposed to scene light through which a timing capacitor charges. The voltage across the timing capacitor is applied to a threshold circuit which deenergizes the electromagnet when a predetermined capacitor voltage is reached. An auxiliary timing circuit includes an auxiliary capacitor which is charged independently of scene light. An auxiliary threshold circuit produces a control signal when the auxiliary capacitor voltage reaches a predetermined voltage, corresponding to a predetermined time interval. This control signal renders conductive an electronic switch connected across the photosensitive element of the first timing circuit, thereby causing the electromagnet to become deenergized. In this way, if the first timing circuit does not cause the shutter to close within the predetermined time interval, the auxiliary timing circuit does.

REFERENCES:
patent: 3245332 (1966-04-01), Kagan
patent: 3500729 (1970-03-01), Rentschler et al.
patent: 3687027 (1972-08-01), Watanabe et al.
patent: 3978496 (1976-08-01), Matsumoto

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