U.S. Philips Corporation

Otto Mensies

Jan Gerritsen

Piet G Barten

Display tube such as a projection television display tube or a DGD tube (DGD=Data Graphic Display), including an electron gun (5) in an evacuated envelope (1) for generating an electron beam (6) which is focussed to a spot (8) on a display screen (7) with the aid of an electrostatic focussing lens (27, 30) and which is deflected across the display screen (7) in two mutually perpendicular directions (x, y). If a correction structure (37) consisting of magnetic half-hard material is provided in such a tube in the proximity of the focussing lens (27, 30) and coaxially of the gun axis (20) in which at least one magnetic 2N pole (N.gtoreq.2) is induced for correcting spot shape errors, a high spot quality can be realized with low-cost deep-drawn lens electrodes (27, 30).

Display tube with magnetic correction elements

A display tube comprising an evacuated envelope having a display window, a conical portion and a neck, and an electron gun in the neck for generating an electron beam which is focused to form a spot on a display screen on the display window, the electron beam being deflected over the display screen in mutually perpendicular directions by pin-cushion-shaped deflection fields produced by a system of deflection coils. Field shapers are provided at the gun end of the tube which comprise two mutually perpendicular pairs of flat plates of ferromagnetic sheet material, the respective pairs of plates being arranged coaxially around the electron beam and respectively extending in the respective deflection directions. The plates are supported so that the gun ends thereof are at substantially the same distance from the electron gun, and cause the edge fields of the deflection fields to be barrel-shaped so as to prevent defocusing of the beam by the pin-cushion deflection fields.

Display tube having ferromagnetic field shapers to prevent beam

In a color display tube having an electron gun of the 'in-line' type for generating three electron beams situated with their axes in one plane, the electron gun includes curved field shapers at the end from which the beams exit into frame and line deflection fields. Each field shaper includes two or more plates of ferromagnetic material aligned along a curve and spaced from each other by slots. The plates are arranged symmetrically with respect to the plane and the central beam axis, and a concave side of each field shaper faces the three beam axes. At least the ends of each field shaper which are most remote from the plane have substantially flat plates extending in the direction of the central electron beam axis. By using such field shapers the losses in the line deflection field are small and substantially undistorted, while a desirable pincushion-shaped distortion of the frame deflection field is intensified.

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Eindhoven, Netherlands

Otto Mensies