EXTERNAL MAGNETIC FIELD COMPENSATOR FOR A CRT

摘要

DOCKET H4207.01 FRA:1hw EXTERNAL MAGNETIC FIELD COMPENSATOR FOR A CRT Light sensors with red filters are located at four corners of a CRT out of view of the operator. A red raster is generated in the corners of the CRT, the pattern of the raster corresponding to the area covered by the sensors. A pair of coils is located about the face of the CRT in a Helmholtz configuration and are driven by a current generator in response to the sensor output to maximize sensor output, thereby generating a compensating magnetic field which cancels external axial fields affecting the CRT.