1988-12-27
1990-07-31
Adams, Russell E.
354430, 354432, G03B 708
Patent
active
049453785
ABSTRACT:
A circuit for detecting back light comprises a time constant circuit including a capacitor selectively connectable in series with either a resistive element, or one of two CdS photoconductive elements used to measure the central and surrounding portions, respectively, of an object being photographed. Three switches separately conect the resistive element and the two photoconductive elements in series with the capacitor. A circuit generates pulses for a length of time governed by a time constant determined by the time constant circuit, and three separate counters store the pulses the number of which is determined by the time constant. An arithmetic circuit processes the pulses stored in the counters to determine the amount of back light present on the object.
REFERENCES:
patent: 4690536 (1987-09-01), Nakai et al.
patent: 4746949 (1988-05-01), Takei et al.
patent: 4809031 (1989-02-01), Sakaguchi et al.
patent: 4821074 (1989-04-01), Nakai et al.
Nagaoka Shinji
Saito Hiroyuki
Seki Yoichi
Taniwaki Michio
Adams Bruce L.
Adams Russell E.
Seikosha Co. Ltd.
Wilks Van C.
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