Brightness modulator for closed loop compensation of black level

Details Brightness modulator for closed loop compensation of black level Brightness modulator for closed loop compensation of black level

1989-04-18

1990-08-07

Peng, John K.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358168, 358169, 358219, 358183, 358243, H04N 552, H04N 557, H04N 5228, H04N 568

Patent

active

049472534

ABSTRACT:
A contrast control circuit develops a video gain control signal for continuously varying the video gain of a video signal to adjust the contrast of the video signal and limit beam current. The contrast control circuit may comprise an auto contrast control responsive to video signal peaks, a contrast limiter responsive to a beam current control signal related to average picture intensity and a manual control. A brightness modulator is also responsive to the contrast control signal for continuously adjusting the brightness of the video signal inversely with the contrast. The brightness modulation is especially useful as part of a pix-in-pix video control circuit, further comprising video sources for first and second video signals and a selector for alternatively feeding the first and second video signals to a video amplifier to form a primary picture with an inset secondary picture.

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