Photocopying – Contact printing – Light monitoring exposure control
Patent
1982-07-23
1984-12-18
Hix, L. T.
Photocopying
Contact printing
Light monitoring exposure control
355 88, G03B 2136, G03B 2778
Patent
active
044888074
ABSTRACT:
A photographic printer light valve/fader control circuit may convert control data for conventional automatic solenoid driven photographic printer light valves to control data for high speed and reliable electronic photographic printer light valves and faders. The circuit is adapted to retrofit printers designed for existing solenoid driven devices and to convert the color and fade control signals received from a conventional paper tape reader to a form useful for electronic control of the angularly adjustable light valve vanes. The vanes adjust the mix of red, green and blue light in the resulting print and control fades, lap dissolves and the like. The color correction signals, received from the paper tape reader in a quasi-binary format, are converted into a conventional binary format and inputted at the proper time to two digital to analog converters which convert these signals into a form useful in controlling the angle of the vanes. The signals from the two digital to analog controllers are multiplied and fed to a servo-amplifier to adjust the vane position in accordance with the desired color mix and fade characteristics. A feedback potentiometer is mounted directly adjacent the motor, on the motor shaft, to minimize backlash. In addition, the light valves are identical and include three position switches to enable them to select information relating to only one of three colors when the valves are sequentially addressed.
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Bell & Howell Company
Hix L. T,.
Lee Douglas S.
LandOfFree
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