Beam current control system for image pickup tube

Details Beam current control system for image pickup tube Beam current control system for image pickup tube

1978-12-13

1981-03-31

Konick, Bernard

Facsimile and static presentation processing

Facsimile

Recording apparatus

H04N 316

Patent

active

042596912

ABSTRACT:
A system for controlling beam current in an image pickup tube so as to prevent comet-tailing and blooming of highlights in the imaged scene. The video signal derived from the image pickup tube (12, 14, 16) is fed back to the beam current control circuitry (22, 24, 26) so that the beam current varies with the video signal. A non-linear amplifier (20) included in the feedback loop has low gain for normal video signals and greater gain for highlights in the video signal. This reduces normal beam current overhead and thus extends the useful life of the tube. The feedback signal provided by the amplifier (20) is a current signal in order to simplify the addition of a DC component to it. A resistor (54) and voltage source (56) perform the addition of the DC component. When multiple image pickup tubes (12, 14, 16) are used, a non-additive mixer (18) combines the plural video signals to provide the amplifier (20) with a signal representative of the video signal of greatest intensity. The amplifier (20) then controls the beam currents in all of the tubes in accordance with the non-additively mixed video signal. In one embodiment (FIG. 6) several comparators (184, 200, 206) monitor the level of the video signal and step-up the beam current when highlights are detected.

REFERENCES:
patent: 3975657 (1976-08-01), Sato et al.
patent: 3999011 (1976-12-01), Sato et al.
patent: 4151552 (1979-04-01), Sato et al.

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