Arthur J Draz

US Patent:

47913398, Dec 13, 1988

Filed:

May 5, 1987

Appl. No.:

7/046955

Inventors:

Arthur J. Draz - Tigard OR
Dana E. Whitlow - Aloha OR
Stephen F. Blazo - Portland OR

Assignee:

Tektronix, Inc. - Beaverton OR

International Classification:

H01J 2952
H01J 2956

US Classification:

315386

Abstract:

An electrical circuit compensates for spatial variations in the light transmittance of the target surface (45) of an electron beam-addressed liquid crystal light valve (10). Such variations in light transmittance, which stem in part from the position dependent angle of incidence of the writing beam electrons and position dependent alignment layer variations arising out of manufacturing process limitations, affect the ability to achieve a monotonic gray scale luminance over the display surface. The compensating circuit adjusts the amount of beam current of the writing electron beam by varying the gain and offset voltage of the video signal, which modulates the writing beam current. This is accomplished by applying the X and Y scan position signals to a correction signal generator (102), which produces gain correction and offset correction signals whose magnitudes vary in response to instantaneous scan position of the writing electron beam on the target surface of a particular light valve. The gain correction and offset correction signals alter the character of the video signal, which is then delivered to the Z-axis driver of the writing beam-producing cathode ray tube.