Deflection yoke with a magnet for reducing sensitivity of convergence to

Abstract

A deflection yoke of the self-converging type uses pincushion-shaped horizontal deflection fields and barrel-shaped vertical deflection fields for converging three in-line electron beams and includes a first pair of magnets disposed near the top and bottom of the beam exit end of the yoke. Each magnet is poled to produce a field having the same polarity as the vertical deflection field during the interval in which the electron beam is deflected towards the magnet. A second pair of magnets is disposed at the top and bottom of the inside of the flared inner surface of the yoke at a generally central position between the beam entrance and beam exit ends of the yoke, each of which is poled for producing a field of a polarity opposite to that of the vertical deflection field when deflecting the beam towards the respective magnet. The first and second magnet pairs coact to correct North-South pincushion distortion without substantial effect on the convergence. A third pair of magnets is disposed at the top and bottom of the inside flare of the yoke between the beam entrance end of the yoke and the second pair of magnets and is poled in the same direction as the first magnet pair. The third magnet pair reduces the sensitivity of the convergence to the position of the deflection yoke relative to the electron beams.