Circuit for controlling beam current in a picture tube
AssigneeDeutsche Thomson-Brandt GmbH
InventorsHossein Ahmari, Gerard Rilly
Life of this patent
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Abstract
A circuit for controlling beam current in a picture tube, which circuit calculates current pictures for the R, G, B beam currents in the picture tube, which largely correspond to real beam currents in the color picture tube. The circuit comprises a comparator/integrator which compares a sum of these current pictures with a beam current information item for the purpose of controlling the R, G, B beam currents and/or the picture sharpness. Gamma correction is carried out in the circuit. The circuit may be of analog or digital construction and may advantageously be integrated in a video processor IC. The present circuit is particularly applicable for television sets or computer monitors.
Claims6
Circuit for controlling beam current in a color picture tube which is driven by R, G, B signals, comprising:
- an input connected to a source of R, G, B signals;
- an amplifier for amplifying each of the R, G, B signals individually;
- means for calculating a separate current picture for each of the R, G, B beam currents by weighting each of the amplified R, G, B signals by means of gamma correction;
- a control circuit coupled to the calculating means for monitoring each of the R, G, B, current pictures and regulating picture sharpness in response to the current pictures;
- summing means for generating a weighted sum in response to the calculated current pictures;
- comparator/integrator for comparing the weighted sum of the current pictures with a beam current information item
- and controlling gain of the amplifier in response to the comparison.
Method for controlling the beam current in a colour picture tube that is driven by R, G, B signals, comprising the steps of
- tapping each of the R, G, B signals and separately weighting each of the tapped signals by means of gamma correction for the purpose of calculating a separate current picture for each of the R, G, B beam currents,
- monitoring each of the separate R, G, B current pictures and controlling picture sharpness in response to the current pictures,
- forming a weighted sum from the calculated beam pictures, and
- comparing the weighted sum with a beam current information item in a comparator/integrator and controlling the beam currents in response to the comparison.
Dependencies are inferred from the claim text.