Apparatus for compensating for image rotation in a CRT display

Claim 1

A video display unit for displaying an image on a screen, said unit being subject to an external magnetic field, said external magnetic field causing a rotation of said image with respect to said screen, said unit comprising: A. cathode ray tube means, said tube means including an electron gun and a screen, said gun for emitting an electron beam along a path toward said screen, said beam for forming an image on said screen; B. deflection yoke means, said yoke means being disposed between said electron gun and said screen, said yoke means operating to deflect said electron beam, thereby forming said image, said yoke means having a first end juxtaposed with said screen and a second end juxtaposed with said electron gun, said first end including a recessed area, 1. said yoke means further including a conductive winding having first and second ends, said winding being substantially disposed in said recessed area, said winding oriented substantially transverse to said path; and C. control means, said control means coupled to said first and second ends of said winding, said control means for producing a compensation current which is conducted through said winding, said compensation current producing a compensating magnetic field for substantially canceling said external magnetic field.