GB819576A - Electron focusing structure - Google Patents

Abstract

819,576. Colour television tubes. CHROMATIC TELEVISION LABORATORIES Inc. Oct. 18, 1955 [Oct. 22, 1954], No. 29636/55. Class 39(1). Colour control grids comprise cylindrical lens arrangement made up of two or more sets of linear conductors, the sets being disposed perpendicularly one to the other. In the arrangement of Fig. 3, a grid 21 of metal tapes or wires running parallel to the colour phosphor strips 15 is flanked by electron permeable electrodes 23, 25 which may be tightly stretched parallel fine wires. The grid 21 is preferably of metal tape when a single beam is used, but of wire for three gun control. The conductive layer 17 covering the phosphor strips is at a high positive potential, the two permeable electrodes 23, 25 at positive potentials and the grid 21 at a negative potential. The conductors of electrode 23, may be staggered relatively to those of electrode 25 and the spacing of the conductors 25 greater at the side of the tube than that of the conductor 23 in order to correct aberration. The spacing of the phosphor groups conforms to that of the grid conductors away from the centre of the screen, Figs. 6, 7A and 7B (not shown). In Fig. 4 a positive electrode 37 of fine wire 37 lies between two sets of linear conductors 33, 35 at negative potential running parallel to the phosphor strips and simulating a double convex lens or two plano-convex lenses back to back. In another alternative, a single permeable electrode at positive potential lies on the side of the grid of linear conductors remote from the phosphor screen, Fig. 5 (not shown). Screens comprising three aligned grids of conductors which produce electron optical effects similar to the lenses of the present invention are also disclosed, Figs. 8, 9 and 10 (not shown). The specification discusses the focusing actions and the spacings and aberrations of the various arrangements described. Specification 757,071 is referred to.