Patent
1979-03-09
1980-07-22
Griffin, Donald A.
354 50, 354 60A, 328129, G03B 700, H03K 2136
Patent
active
042136881
ABSTRACT:
An automatic exposure time control apparatus for use with a camera having a shutter is disclosed. The apparatus includes a pulse generating circuit for producing pulses having a frequency corresponding to a base time, a counter for counting the pulses from the pulse generating circuit at the time of the opening of the shutter, a multiplying circuit for multiplying the product of the integral part n with 2.sup.n by the decimal part b of the exposure time value, a shutter driving device and a control circuit. The control circuit detects the existence of the decimal part so as to deliver the shutter closing signal to the shutter driving device when the counter has counted 2.sup.n pulses when the decimal part does not exist and to deliver the shutter closing signal after lapse of the sum of the above-mentioned count time with the time during which one or another counter counts the number corresponding to the output of the multiplying circuit of the pulses of the period corresponding to 1/a of the aforementioned pulses when the decimal part exists.
REFERENCES:
patent: 3037166 (1962-05-01), Alexander
patent: 3868704 (1975-02-01), Yamada et al.
patent: 3995284 (1976-11-01), Kitaura et al.
patent: 4037233 (1977-07-01), Shinoda
Canon Kabushiki Kaisha
Griffin Donald A.
Perkey William B.
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