Stabilized automatic brightness control network in a video signa

Details Stabilized automatic brightness control network in a video signa Stabilized automatic brightness control network in a video signa

1979-03-26

1980-06-24

Martin, John C.

Facsimile and static presentation processing

Facsimile

Recording apparatus

358 74, 358 39, 358168, H04N 568

Patent

active

042098084

ABSTRACT:
A video signal processing system is disclosed including a sample and hold comparator arranged in a closed control loop with a video channel including a video amplifier for the purpose of providing automatic brightness control, and an automatic kinescope beam current limiter. The beam current limiter is coupled to a first point in the amplifier for controlling the amplifier signal gain to limit excessive beam current demand in a first control mode. In a second control mode, the beam current limiter cooperates with the automatic brightness control network to control the D.C. output level of the video amplifier in the presence of excessive beam current demand. The comparator response time is slow relative to transient variations of the D.C. level at the amplifier output induced by beam limiter action in the first control mode, but is otherwise sufficient to permit compensation of relatively long term variations in the output D.C. level. Compensation of the transient D.C. variations is provided by coupling transient beam limiter control voltages developed in the first control mode to a second point in the amplifier, for opposing transient D.C. level variations which would otherwise appear at the amplifier output in response to beam limiter action.

REFERENCES:
patent: 3873767 (1975-03-01), Okada
patent: 4096518 (1978-06-01), Tuma
patent: 4121252 (1978-10-01), Saiki
patent: 4126884 (1978-10-01), Shanley
patent: 4137552 (1979-01-01), Serafini
patent: 4167025 (1979-09-01), Willis

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