Digital display circuit for camera exposure meter

Details Digital display circuit for camera exposure meter Digital display circuit for camera exposure meter

1976-11-12

1978-07-11

Rolinec, Rudolph V.

Optics: measuring and testing

Photometers

Photoelectric

324 99D, 324111, 354 24, G01J 142, G01R 1706

Patent

active

040998851

ABSTRACT:
A digital exposure meter display circuit for a camera includes a first oscillator 1 whose output controls the charging of an integrating capacitor 28 from a constant current source 3. When the capacitor charge reaches the level of a reference voltage from source 7, as detected by a first comparator 6, a counter 10 is enabled and begins to register clock pulses from a second oscillator 8 through an AND gate 31. When the capacitor charge subsequently reaches the output level of a light measuring circuit 4, which is proportional to the apex value of the sensed object brightness, a second comparator 5 disables the AND gate and enables an LED display 12 supplied with the decoded counter value.

REFERENCES:
patent: 2582831 (1952-01-01), Hester
patent: 2836356 (1958-05-01), Forrest et al.
patent: 3303493 (1967-02-01), Charbonnier
patent: 3700934 (1972-10-01), Swain
patent: 3760272 (1973-09-01), Battes

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