GB1040263A - Cathode ray tube devices - Google Patents

Abstract

1,040,263. Cathode-ray tubes. TOKYO SHIBAURA ELECTRIC CO. Ltd. Dec. 10, 1963 [Dec. 11,1962 (2); Dec. 29, 1962; Aug. 11, 1963 (3)], No. 48700/63. Heading H1D. In a flat cathode-ray tube, Fig. 3, the fluorescent screen 14 lies on a cylindrical surface of the envelope and the beam deflection centre 22 of the deflection system 17 lies in an extension of the cylindrical surface, the electron beam a being directed by the gun 16 perpendicular to the axis of the cylindrical surface and at an angle to the screen. A magnetic collimating lens 19 has zero field strength at the centre of the lens and increasing field strength, but with opposite sign, in opposite directions away from the lens centre. The lens may be electromagnetic or may consist, Fig. 6, of flexible triangular magnets 31-33 with or without core end plates, and with the triangular shape of the magnets possibly modified to have concave sides or to have asymmetrical configuration, Figs. 11, 12 and 13 (not shown), or with varied intensity of magnetization or varied composition of the magnetic material to compensate for large deflection angles and fringe effects. The apices of the triangular magnets need not abut and need not terminate in points. Deflection errors are eliminated by having non-uniform deflecting fields in the deflecting systems 17, 18, Fig. 3, which may be either magnetic or electrostatic. The fields may be curved or tapered and may be produced by asymmetrically disposed or shaped magnetic coils or polepieces or by electrostatic plates or in the case of coils, by having identical coils carrying currents of different magnitude. The deflecting systems 17, 18 may be superposed upon one another and with suitable fields the collimating lens may be dispensed with. The deflection errors may alternatively be corrected by providing a third fixed field deflecting system, the field being of a barrel-shaped configuration. The fluorescent screen 14, Fig. 3, may comprise a fluorescent film on a transparent conductive film 21 or the fluorescent film may be applied first and then coated with a thin metallic film. The screen may be constructed to be viewed on both sides or on one side only.