FIELD COMPENSATION SYSTEM AND METHOD FOR MITIGATE THE EFFECTS OF AN EXTERNAL MAGNETIC FIELD ON A VISUAL TUBE.

摘要

A magnetic compensation system discloses a visual CRT 22 to 24, which includes a magnetic shield 30 and a compensation coil 36 for generating a compensation field 58a, 58b. The CRT is placed in the magnetic shield and the latter is derived the transverse component 74 of an external magnetic field 56. An annular metal end plate 34 is attached to the shield at its open end and extending inwardly from the edges shield in a plane substantially parallel to the visual. The compensation coil is disposed on the outer surface of the faceplate and provide a magnetic field compensating for opposing the axial component of the external magnetic field in response to a drive signal 72. A pair of magnetic field detectors 40a and 40b for detecting the difference between the outer fields and compensation are spaced inwardly relative to the coil and opposed to each other. The detectors are positioned substantially perpendicularly to the plane of the end plate on its inner edge 35. A circuit 44 detects the average of the outputs of the detectors and controls the signal ...