Electronic exposure control

Details Electronic exposure control Electronic exposure control

1976-01-20

1979-11-27

Adams, Russell E.

Photocopying

Projection printing and copying cameras

Illumination systems or details

355 71, 355 77, G03B 2774, G03B 2778

Patent

active

041758552

ABSTRACT:
A photographic exposure control for sensing and electrically processing illumination reflected from a moving document. An opto-photoelectric pickup accepts reflected illumination having a selected spectral characteristic. Electronic analog logic; (1) samples and holds the equivalent electrical magnitude of the reflected illumination, (2) provides an electrical timing interval that is the reciprocal of the electrical magnitude, (3) arranges automatically for constant exposure of the film through an adjustable electrical ramp generator, and (4) generates an "exposure stop" signal in a comparator that receives the ramp and the reciprocal timing information. The control signal thereby formulated typically accurately actuates a translational type shutter through a stepper motor to maintain a constant density of the background of images on microfilm for successive documents regardless of the background reflectivity thereof. A "Manual" mode is alternately available for providing a fixed exposure, particularly for documents having unorthodox reflectivity formats.

REFERENCES:
patent: 3426357 (1969-02-01), Paulus
patent: 3512140 (1970-05-01), Yokozawa et al.
patent: 3544214 (1970-12-01), Edgar
patent: 3679905 (1972-07-01), Watanabe
patent: 3732011 (1973-05-01), Hansard
patent: 3734611 (1973-05-01), Knapp et al.
patent: 3746446 (1973-07-01), Sliwkowski
patent: 3795444 (1974-03-01), Glidden et al.
patent: 3795445 (1974-03-01), Hamlin et al.

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