Electric lamp and discharge devices: systems – Cathode ray tube circuits
Patent
1997-10-17
1999-11-30
Pascal, Robert
Electric lamp and discharge devices: systems
Cathode ray tube circuits
315383, 324404, 348379, H04N 568
Patent
active
059948418
ABSTRACT:
A circuit apparatus and method is disclosed for determining the actual beam current of a display device having at least one cathode and that actual beam current is used to both correctly bias a voltage that drives the display device and determine the actual drive voltage according to a desired beam current. At periodic intervals, according to the invention, a series of test voltages in known relation to one another are applied to the display device, and measured cathode currents corresponding to the applied voltages are stored in appropriate memory elements of an correction unit. If at least two of the test voltages is selected to result in a black level, and at least one of the test voltages is selected to result in a white level beam current then the correction unit can precisely determine actual beam current through application of a mathematical relationship between test voltage an measured beam current which takes into account a leakage current between a cathode and a first grid of the display device.
REFERENCES:
patent: 4224640 (1980-09-01), Hovens et al.
patent: 4922328 (1990-05-01), Engel et al.
Allen Michael W.
DeLucia Paul
Bettendorf Justin P.
Pascal Robert
Welch Allyn Inc.
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