Digital exposure time indicating circuit for camera

Details Digital exposure time indicating circuit for camera Digital exposure time indicating circuit for camera

1976-11-04

1978-05-09

Adams, Russell E.

354 53, 354 60L, G03B 708

Patent

active

040890120

ABSTRACT:
A digital exposure time indicating system for a camera includes a light meter whose analog output is proportional to exposure time as a function of preset film sensitivity and aperture opening values, and the measured brightness level. The meter output is fed to a comparator, together with an analog signal from a D/A converter coupled to a counter which accumulates the pulses generated by an oscillator. When the converter output reaches the meter output the comparator signal, acting through a logic circuit, causes the counter signals to be set into a latch, whose outputs are fed through a B/D converter to an LED display.
The latching is performed a half cycle after a comparison, whereby transients are allowed to settle out. Provision is also made for over scale and under scale indications when the meter output is outside of the normal comparison range, and a gate circuit causes the LEDs to flicker when the battery is low.

REFERENCES:
patent: 3972626 (1976-08-01), Laskowsi
patent: 3995284 (1976-11-01), Kitaura et al.

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