Sony Corporation

Sony Corporation of America

Shigemasa Kamimura

Toshiyuki Kawashima

Apparatus and method for performing convergence calibration in a system that uses multiple beams to generate a video display on a screen. A photosensor is exposed to first and second distinct convergence test patterns which have illuminated areas that cover approximately first and second halves of the photosensor, respectively. For each beam, first and second output signals are generated by the photosensor when the first and second test patterns are generated, respectively, and alignment is determined on the basis of the output signals. The test patterns are selected in such a manner as to reduce the dynamic range requirement for the A/D converter(s) that digitize photosensor output signals. Optionally, measurement resolution is enhanced by varying test pattern density in accordance with the A/D converter input signal level so as to maintain a generally constant A/D converter input level. This approach optimizes A/D converter resolution, thereby enhancing measurement resolution even when CRT and photosensor characteristics vary. Test pattern density may be reduced by generating a segregated test pattern.

Automatic convergence adjustment system with the capacity to modify test

A predetermined rush current is set by a current setting switch (25). A digital-to-analog (D/A) converter (27) multiplies an attenuation curve signal input thereto from a read-only memory (ROM) (28) and the rush current thus set by the current setting switch (25) with each other and outputs a multiplied output to a D/A converter (29). The D/A converter (29) multiplies a signal input thereto from the D/A converter (27) and a sine wave signal read out from a ROM (30) and output a multiplied output to a field effect transistor (FET) (22) through an operational amplifier (24) to thereby control a degaussing current flowing through a degaussing coil (5). Therefore, a stable degaussing effect can be reproduced.

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Chiba, Japan

Shigemasa Kamimura