Photometric circuit for camera

Details Photometric circuit for camera Photometric circuit for camera

1979-06-19

1981-01-27

Gellner, Michael L.

Optics: measuring and testing

Range or remote distance finding

With photodetection

354 60R, 356223, G03B 7083

Patent

active

042471869

ABSTRACT:
A photometric circuit for a camera including a first operational amplifier with a photo-electric element connected between its inverted and non-inverted input terminals and, a logarithmic compression diode connected between the output terminal and the inverted input terminal of the first operational amplifier, thus providing a voltage corresponding to the logarithmic value of the brightness of an object to be photographed at the output terminal of the first operational amplifier.A second operational amplifier has a plurality of temperature compensating commonly polarized diodes connected in parallel between its inverted input terminal and the output terminal. A first constant voltage is applied to the non-inverted input terminal of the second operational amplifier while a second constant voltage is applied through a resistor to the inverted input terminal of the second operatonal amplifier, thereby providing temperature-compensation of the output voltage of said first operational amplifier.

REFERENCES:
patent: 4072962 (1978-02-01), Maida
patent: 4200374 (1980-04-01), Shimizu et al.

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