Photography – With object illumination for exposure – Activated under low light condition
Patent
1999-03-16
2000-05-02
Perkey, W. B.
Photography
With object illumination for exposure
Activated under low light condition
396176, 396205, 250214P, 356218, G03B 1503, G03B 726, H01J 4014, G01J 142
Patent
active
060582707
ABSTRACT:
A low cost, low power photometric circuit suitable for use in a low end camera includes a first counter for counting successive pulses produced by a first oscillator having a substantially constant oscillation frequency and a second counter for counting successive pulses produced by a second oscillator having an oscillation frequency which varies in accordance with ambient brightness. The ambient brightness is judged according to outputs of the counters so that even if the oscillation frequency of the second oscillator varies only slightly due to a change in ambient brightness, the slight variation is easily detectable as an accumulated count value. Accordingly, costly, high-precision components are not needed. The low cost photometric circuit requires no microcomputer, analog/digital converter or comparator and can be fabricated in a single integrated circuit operated at a low voltage of 1V or less, and is thus suitable for incorporation into a low end camera.
REFERENCES:
patent: 3792648 (1974-02-01), Ishiguro
patent: 4472042 (1984-09-01), Iwata et al.
Oda Hajime
Seki Yoichi
Perkey W. B.
Seiko Precision Inc.
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