Brightness control circuit employing a closed control loop

Details Brightness control circuit employing a closed control loop Brightness control circuit employing a closed control loop

1977-05-05

1980-04-08

Griffin, Robert L.

Facsimile and static presentation processing

Static presentation processing

Attribute control

358168, 358172, H04N 516, H04N 514, H04N 518

Patent

active

041975570

ABSTRACT:
Brightness control apparatus for a video signal image reproducing system including a video signal processing channel, a source of reference voltage for establishing a desired level of image brightness, and a keyed comparator circuit. The comparator forms a closed control loop with the signal processing channel, and is keyed during periodic blanking intervals of the video signal to sense the magnitude of the reference voltage and a brightness representative blanking level of the video signal which may vary undesirably. The comparator provides an output control signal indicative of a voltage difference between the reference voltage and the blanking level. The control voltage is applied to the signal channel for translating the blanking level in a direction to minimize the voltage difference, so that a desired relationship between the reference voltage and the blanking level is preserved.

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"Fernsehtechnick"; Schroter, 2nd part, 1963, Springer-Verlag, pp. 29-34.

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