Closed loop bucking field system

Abstract

A system for improving the operation of a cathode ray tube (CRT) is disclosed whereby interference caused by external magnetic fields is mitigated. The system comprises a CRT having a CRT magnetic shield housing and at least one electromagnetic field sensor disposed adjacent to the inner surface of the CRT housing. Sensors form to generate a reference magnetic field and to generate a sensor output signal in response to the detection of both the reference field and an external field as sensed within the housing. A bucking field coil drive circuit is provided in electrical communication with the field sensor, the drive circuit being operative to generate a bucking field coil drive signal responsive to the field sensor output signal. A bucking field coil is disposed circumferentially about the CRT and is driven by the bucking field coil drive signal. The bucking field coil generates a bucking electromagnetic field in opposition to the sensed external magnetic field, thereby opposing and reducing the degrading effects of the external magnetic field on the CRT display.

Dependencies are inferred from the claim text.