GB769432A - Improvements in or relating to cathode ray tubes for the reproduction of images in colour - Google Patents

Abstract

769,432. Colour television tubes. RAULAND CORPORATION. Oct. 29, 1953 [Oct. 31, 1952], No. 29911/53. Class 39(1). Apparatus for reproducing television images in colour comprises a cathode ray tube containing an electron source 41, Fig. 4, coaxially surrounding but spaced from, or a plurality of electron sources 12, Fig. 1, symmetrically spaced from, the axis of the tube, means 21, 24 for modulating uniformly the electron emission from the source or sources in response to a television signal received by the antenna 20, and for accelerating the electrons towards a plurality of target structures 13, 14, 15, Fig. 1, or 13, 14, 48, Fig. 4, spaced along the axis and adapted to luminesce in different colours when struck by electrons, and focusing means 16, 17 controlled by a colour component of the signal from the colour-control circuits 25 to cause the electrons to converge to a point upon one or other of the target structures. The target structures can comprise conductive mesh electrodes or electron pervious metallic films coated with differently luminescing phosphors. The target structures can lie in parallel planes or can be formed as spherical or cylindrical segments having common centres or axes. The focusing means 16, 17 comprises spaced conductive coatings on the inner surface of the tube envelope. An additional electron permeable mesh focusing electrode 49, Fig. 4, can be provided which may be operated at a constant potential different from those of the target structures and is preferably modulated in synchronism with focusing electrode 17 as by direct connection thereto. Electrodes 13-16, Fig. 1, are connected together and to a movable tap 26 on a potentiometer resistor 27 and focusing electrode 17 is connected through a resistor 29 to a movable tap 28. Colour control voltages may be applied to the target structures in synchronism with the colour switching signal applied to the focusing electrode 17 in such manner as to render the potentials of those target structures from which no response is desired materially lower than that of the target electrode from which the response is elicited as described in U.S.A. Specification 2,461,515. In the construction shown in Fig. 4 a cathode 40 is provided with an annular electron-emissive area 41 having a central non-emissive region 42 and an intensity-control grid 43 is provided with an annular aperture 44 in registration with the annular emissive surface 41. Small connecting wires can extend radially across the annular aperture 44 for centering purposes. A tubular anode 45 is provided with a diaphragm 46 having an annular aperture 47 corresponding to the annular aperture 44. The final target structure is formed as a phosphorcoated transparent plate 48 which may be provided with a transparent conductive coating.