Method for providing coextensive raster patterns in television CRT in-line electron guns

摘要

A television cathode ray picture tube has an in-line electron gun for generating three coplanar electron beams. The raster pattern projected by the center beam is diminished in vertical height so as to be non-coextensive with the superimposed raster patterns projected by the off-axis beams. The method according to the invention for providing raster coextensiveness comprises embracing each off-axis beam at the point of beam egress from the gun with a pair of inwardly converging but non-intersecting magnetic field enhancer means in symmetrical relationship and defining an opening therebetween. Each member of the enhancer means is oriented at a predetermined convergence angle with respect to the plane of the three beam paths, and located at a predetermined distance from the tube axis. The enhancer means, the predetermined convergence angle and distance, and the separation and length of the enhancer means are such that the enhancer means is effective to divert the flux of the vertical deflection field through the opening between each pair of enhancer means onto the center beam. The height of the raster pattern projected by the center beam is enhanced into coextensiveness with the patterns projected by the off-axis beams.