Exposure control circuit

Details Exposure control circuit Exposure control circuit

1974-04-02

1976-05-04

Smith, Alfred E.

Radiant energy

Photocells; circuits and apparatus

Photocell controlled circuit

250212, H01J 3912

Patent

active

039550818

ABSTRACT:
An exposure control circuit connected with an electrically operated exposure control element such as an electric shutter or an electrically controlled diaphragm includes a bridge circuit. The bridge circuit has four arms and is provided in one arm thereof with a photodetector to receive light from the object to be photographed. A resistor is connected in series with the photodetector to convert the current flowing through the photodetector into a voltage. A transistor is connected with the photodetector to amplify the photocurrent thereof. Another resistor is connected with the transistor to convert the current obtained by amplification of the photocurrent of the photodetector by use of the transistor to a voltage. These two resistors are provided in one arm of the bridge circuit so as to be independently varied of their resistance.

REFERENCES:
patent: 2142940 (1939-01-01), Hackenberg et al.
patent: 2219928 (1940-10-01), Kalmus et al.
patent: 3160759 (1964-12-01), Ward
patent: 3473036 (1969-10-01), Marcus

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