GB648823A - Improvements in or relating to cathode-ray or the like apparatus for reproducing television images - Google Patents

Abstract

648,823. Cathode-ray tubes. COMPAGNIE GENERALE DE TELEGRAPHIC SANS FIL. Feb. 7, 1947, No. 3718. Convention date, Feb. 9, 1946. [Class 39 (i)] In a cathode-ray tube for the reproduction of a television image, the electron beam is scanned over a gas-tight diaphragm F, Fig. 6, separating the tube from a compartment V filled with a gas. Such an acceleration is imparted to the beam, and the diaphragm is made of a metallic or semi-insulating material of such thickness that the beam traverses the diaphragm and directly produces a glow by impact on the gas. The gas is at a relatively high pressure, for example exceeding one atmosphere in order that the luminous glow is confined to the point at which the beam penetrates the diaphragm. The diaphragm is realized so as to mechanically withstand the gas pressure. The gas chamber V is provided with a light-transparent glass G. A first electric system L1, L2 gives by scanning through the fields M1, M2 an intermediate image I<SP>1</SP>. The lens system V0, V1 accelerates the electrons to give the final image I2. The diaphragm may be of aluminium or of plastic material reinforced by a metal grid consisting of steel strips or wires. The grid may comprise a mesh or parallel wires. The plane of the bars of the metal grid may be directed towards the axis of the tube, Fig. 3d, so that the beam is not too greatly intercepted as the angle of the beam increases. The diaphragm may be goffered on one or both sides, and may be moulded on to the reinforcing grid so as to cover the grid wires, Fig. 4b. The diaphragm may be metallized on the face directed towards the electron beam or more particularly on the thicker parts of the goffering. The gas may be hydrogen at a pressure of five atmospheres, and examples of the thickness of the diaphragm and dimensions of the reinforcing grid are given. U.S.A. Specification 1,907,507 is referred to in connection with the construction of the diaphragm. For colour television, several cathoderay tubes, each employing a gas luminous with a different colour, may be used by superposing their projections on a common screen. Four gas compartments side by side, may comprise the screen of a single cathode-ray tube.