The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 30, 1999
Filed:
Oct. 17, 1997
Michael W Allen, Shortsville, NY (US);
Paul DeLucia, Baldwinsville, NY (US);
Welch Allyn, Inc., Skaneateles Falls, NY (US);
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.