Television picture tubes having an electron gun with aperture electrode

Abstract

This disclosure depicts a television cathode ray picture tube having a plural-beam electron gun for projecting in superimposition on the picture imaging screen of the tube at least two electron beam spots. The gun includes at least one aperture electrode having an aperture for passage therethrough of each of said beams. The beams are subject to a first-order aberration attributable to the aperture electrode resulting in the astigmatizing, and consequent distortion of, the beam spots. This astigmatizing is due to the coalescing of electric field vectors contiguous to each aperture with the vectors of at least one adjacent aperture. The improvement comprises shielding means interposed between the apertures comprising wall means. The wall means are effective to mutually shield the apertures and isolate the electric field vectors to ameliorate the first order aberration. The wall means introduces, however, higher-order aberrations due to a disordering of the electric field vectors resulting in forms of beam spot distortion other than astigmatic. The improvement further comprises a configuration of the wall means wherein a section of the wall means comprises a cut-out. The cut-out is shaped so as to be effective to re-order the vectors and ameliorate the effect of the higher order aberrations. As a result, the electron gun having aperture electrodes is enabled to project substantially undistorted beam spots.