Electron gun having an extended field beam focusing and converging lens

Abstract

This disclosure depicts an electron gun for use in a color cathode ray tube of the small neck, shadow mask-type. The gun includes an extended field lens for generating a cluster of electron beams converged and individually focused at the screen of the tube. Three main focus lens means are situated on lens axes which are mutually parallel and parallel to a gun central axis. At least two of the lens axis are off-axis with respect to the gun axis. The focus lens means has for each beam at least three electrodes including a focus electrode for receiving a variable potential for electrically adjusting the focus of the beam. In succession down-beam, there are at least two associated electrodes having potentials thereon which forms in the gaps between adjacent electrodes significant main focus field components. To adjust beam focus, the strength of a first of these components is controlled by adjustment of the voltage received by the focus electrode. The strength of the second of the field components is relatively less than that of the first component. Each of the lens means is characterized by having addressing faces of the associated electrodes which define the second field component being so structured and disposed as to cause the second field component to be asymmetrical and effective to significantly divert the beam from its path in convergence of the beams without any significant distortion of the beam and substantially independently of any beam-focusing adjustments of the first field component.