Digital display circuit for a photographic exposure meter

Details Digital display circuit for a photographic exposure meter Digital display circuit for a photographic exposure meter

1976-11-24

1978-09-05

Adams, Russell E.

Optics: measuring and testing

Range or remote distance finding

With photodetection

354 53, 354 60R, 354 60L, 356226, G03B 708, G03B 1720

Patent

active

041124391

ABSTRACT:
An analog-to-digital converter circuit for a photographic exposure meter includes a plurality of parallel connected transistors 51, 54, 57 and 60 whose bases are connected to the logarithmic output of a light measuring circuit A. The transistor collectors are driven by constant current sources comprising an equal plurality of transistors 50, 53, 56 and 59 having emitter area ratios of 1:2:4:8, whereby the collector voltages of the transistors represent a digital threshold conversion of the light measuring circuit output.

REFERENCES:
patent: 3858199 (1974-12-01), Neuner et al.
patent: 3964076 (1976-06-01), Ichihashi et al.
patent: 3968486 (1977-07-01), Gerdes
patent: 3984832 (1976-10-01), Henry
patent: 4051491 (1977-09-01), Toyoda

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