Magnetic field compensation apparatus.

摘要

A compensating coil (50) for a scanning electron beam display such as a color television tube (20) reduces undesirable deflection of the electron beams due to ambient magnetic fields, in particular the geomagnetic field. A first coil section (52) has at least one winding disposed to encircle the tube neck (32), perpendicular to the Z axis. Upper (62) and lower (64) coil sections are disposed above and below the first coil section (52), each inclined forwardly along the Z axis and having a loop encompassing an area extending in the X and Y directions generally following the surface of an internal magnetic shield (80). The coil sections are coupled in series. The upper (62) and lower (64) coil sections have a wider X axis dimension proceeding forwardly along the Z axis, being keystone shaped. Lateral lengths (66) of the upper and lower coils sections connect to the first coil section (52) at lateral sides, such that the compensating coil (50) is a continuous winding. The first coil section may have two passes for each pass of the upper and lower coil sections. <IMAGE>