Purity adjusting device for slotted mask in-line color picture tubes

Abstract

Apparatus is provided for performing the purity adjustment in slotted mask color picture tubes of the type having in-line electron guns located in side-by-side relationship along a single plane. The apparatus includes first and second bar magnets located externally of the tube and parallel to the gun-containing plane. Each of the bar magnets is oriented to generate a magnetic field in substantially the same plane, that plane being perpendicular to the gun-containing plane. Means are provided for jointly moving the bar magnets between a first position wherein the net resultant field generated across the gun containing plane is zero, and second position wherein the net resultant field generated by the bar magnets across the gun-containing plane is greater than zero and has a substantially equal effect on each of the guns. In a first embodiment, the moving means comprises a support upon which each of the bar magnets is fixedly mounted. Means are provided for moving the support in a plane substantially perpendicular to the gun-containing plane. In the second embodiment, each of the bar magnets is independently rotatably mounted to the support and means are provided for jointly rotating the bar magnets relative to the support. In each embodiment the movement of the magnets causes a variation in the resultant field generated along the gun-containing plane, thereby causing a correction of the misregistration of the electron beams with the phosphor dots on the tube face.

Dependencies are inferred from the claim text.