Automatic exposure time control circuitry for a camera using a p

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Details

354 50, 354 51, 354 60E, G03B 708, G01J 144

Patent

active

039368424

ABSTRACT:
A light measuring circuit for an exposure time control device uses a photodiode to measure the object brightness and a logarithmic compressing diode to provide negative feedback between the output terminal and one input terminal of a differential amplifying circuit. The output of the light measuring circuit is summed with signals representing film sensitivity and diaphragm aperture setting and the resulting exposure time control signal is compensated for changes in temperature. An antilogarithmic converting circuit generates a signal proportional to the logarithmic value of the compensated exposure time control signal. The antilogarithmic converting circuit operates at the same reference potential as the differential amplifying circuit and its output is integrated and then used to terminate exposure.

REFERENCES:
patent: 3625124 (1971-12-01), Miyakawa
patent: 3670637 (1972-06-01), Mori et al.
patent: 3679905 (1972-07-01), Watanabe
patent: 3712192 (1973-01-01), Ono et al.
patent: 3736851 (1973-06-01), Ono et al.
patent: 3781551 (1973-12-01), Mori
patent: 3827066 (1974-07-01), Yanagisawa et al.
patent: 3852774 (1974-12-01), Taguchi et al.
patent: 3877039 (1975-04-01), Ichinohe et al.

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