U.S. Philips Corporation

U.S. Phillips Corporation

Albertus A Sluyterman

Nicolaas G Vink

Gerrit Bosch

Fransiscus M Doomernik

Marinus L Vrinten

Tjebbe R Pasma

Adriaan J Groothoff

Lambert J Stil

Tjerk G Spanjer

Remko Horne

Johannes Penninga

Bernardus H Dekkers

Wilhelmus A Beelaard

Johannes A De Volder

Dik R Overdijk

Antonius J Bolder

Augustinus H Boshouwers

Bernadus H Dekkers

Berend J Ter Weeme

Steven M Wielink

Jacob Van Maastricht

Ronald J DeMan

A color cathode ray tube is provided with a saddle-shaped shadow mask. As a result, the sensitivity to doming and microphonics of the mask is improved. This is advantageous, in particular, for a cathode ray tube having a very flat display window. Preferably, the display device in which the cathode ray tube is employed is provided with two dynamic quadrupoles, for example, in front of the electron gun and in front of a deflection unit.

Color display device comprising a saddle-shaped color selection electrode

A color display device having a color display tube with a display screen, comprising an electron gun for generating three co-planar electron beams, and a deflection system which, in operation, generates deflection fields for scanning the display screen, and an element influencing the landing angle of the outermost beams, for example an element generating, in operation, a 45.degree. magnetic 4-pole field, and comprising a correction device which supplies a signal to the element influencing the landing angle, which signal is derived from the video information (for example a signal which is proportional to the strength of the instantaneous beam current) in order to remedy landing errors caused by space-charge repellence between beams.

Color display device

A method for improving brightness uniformity reduces a decrease of light towards the edges of a display screen (10) of a display tube (1). The extent of the decrease of light particularly depends on an increase of the thickness of the glass of the display screen (10) from the center of the display screen (10) to its edges, and on a transmission of the glass. This decrease of light is corrected by causing the deflection rate to decrease (C1, Cs) from the center of the display screen (10) towards its edges.

Brightness uniformity on a display screen

In a method of reducing a moire phenomenon upon display of a video signal on a display device (4), the video signal is low-pass filtered (2) with a cut-off frequency substantially corresponding to a maximum frequency of a baseband portion of the video signal, to obtain a low-pass filtered video signal. The low-pass filtered video signal is filtered (3) in accordance with a transfer function substantially corresponding to the inverse of the transfer function of the display device, to obtain a filtered signal. Finally, the filtered signal is applied (3a) to the display device (4).

Method and device for reducing moire when displaying a video signal

The display system comprises a colour cathode ray tube. The colour cathode ray tube comprises an in-line electron gun with a distributed main lens (DML). The final electrode (anode) of the DML generates a quadrupole lens field. To a first electrode a static voltage V.sub.foc is applied. Between a second electrode, on which a dynamic voltage V.sub.dyn is applied, and a first intermediate electrode a quadrupole electric field is generated. The value of the dynamic voltage is lower than the static voltage.

Color cathode ray tube display system

A color display tube system having an electron gun producing three co-planar electron beams which are non-convergent, i.e. parallel or divergent. A convergence element located at a distance from the electron gun and coaxial with the tube axis then produces convergence of the electron beams at the display screen by generating a static 45.degree. 4-pole field. This combination reduces growth of the scanning beam spot in the horizontal direction at the ends of the horizontal axis, which is a problem encountered with electron guns which are convergent.

Color display tube system with reduced spot growth

An electromagnetic deflection unit (5) comprising a coil holder (6) with a flange (8) whose inner side supports coils (10a, 10b) for (line) deflection of electron beams. At the flange side of the coil holder (magnetized) preformed elements (14) are arranged within these coils so as to influence the magnetic field of these coils (10a, 10b), thereby reducing spreading errors, caused during manufacture, throughout the display screen. For the purpose of automatic mounting of the preformed elements, an annular support having predetermined locations (in particular from 12 to 36) for accommodating preformed elements is used. The preformed elements (14) are accommodated at a plurality of these predetermined locations and, if made of a permanent magnetic material, produce magnetic fields having magnetic strengths measured at a distance of some mm above the heart of the elements in the range between 1 and 1000 .mu.T. In a special embodiment the elements of permanent magnetic material belong to a limited collection as regards their magnetic field strength.

Deflection unit having a ring with field correction elements, and

Color display tube comprising an electron gun system (5) of the 'in-line' type and an electromagnetic deflection unit. This unit is provided with coma correctors 14 and 14' at its gun side, which correctors, viewed from the gun system, provide a pincushion-shaped vertical deflection field component and a barrel-shaped vertical deflection field component. These components are used to reduce the 'green droop' (=anisotropic Y coma) in the corners and at the ends of the display screen axes to an equal extent without the spot shape of the outer beams being influenced detrimentally.

Color display tube with coma correction

Color display tube comprising an electron gun for producing three co-planar electron beams, and including a deflection system which, in operation, generates deflection fields of the self-convergent type, with three consecutive elements influencing convergence being arranged between the electron gun and the display screen, the two outer elements producing, in operation, opposite effects and the central element being energizable for correcting remaining convergence errors.

Color display tube system

Picture display device comprising an in-line color display tube having an elongate display screen with a short axis and a long axis, which screen is provided on an inner surface, and a deflection system. The plane in which the undeflected electron beams are located is parallel to the short axis of the display screen. The deflection system comprises a first system of deflection coils for generating a substantially pincushion-shaped deflection field in the direction of the short axis of the display screen and a second system of deflection coils for generating a substantially barrel-shaped deflection field in the direction of the long axis of the display screen. The deflection system has terminals to be connected to a signal generator for scanning the display screen in a raster having a plurality of lines oriented along the short axis of the display screen.

Picture display device

In-line color display tube with a deflection unit, provided with a twist correction device comprising two permanent magnets which generate magnetic fields with oppositely directed magnetic field components which, at the beginning and the end of a path traversed by each side beam, are transverse to the path of the relevant side beam and are located in the plane of the beams. This provides the possibility of deflecting each side beam once up and once down for compensating twist errors.

Color display tube with twist correction means

Picture display device comprising a display tube, a deflection unit and a compensation coil system for generating a magnetic compensation field which is oppositely directed to the line frequency radiation field of the deflection unit in a space in front of the display screen. The compensation coil system comprises two coils each being wound on a rod-shaped core portion. The core portions are arranged in a V-formation in the y-z plane, symmetrically relative to the x-z plane. Alternatively, the compensation coil system may comprise two pairs of coils arranged in this way and located in planes parallel to the x-y plane and equidistantly therefrom.

Picture display device with core means comprising compensation coils

A color display tube system comprising an electron gun for producing three co-planar electron beams, and including a main deflection system which in operation generates deflection fields of the self-convergent type, and an auxiliary deflection system which in operation generates a 45.degree. magnetic 4-pole field facing the electron gun and moving the outer electron beams away from each other, and a 45.degree. magnetic 4-pole field facing the display screen and moving the outer beams towards each other.

Deflection unit mounted around a display tube for deflecting electron beams across the display screen includes a line deflection coil and a field deflection coil. A compensation coil system for generating a magnetic compensation field oppositely directed to the line frequency radiation field in a space in front of the display screen includes core means of a magnetizable material positioned between the display screen and the deflection unit in a plane parallel to the display screen and two diametrically arranged coils each having at least one turn.

Picture display device with magnetizable core means comprising

A color cathode ray tube system comprising three coplanar electron guns and one deflection unit. A dynamically controlled element driving the outer electron beams away from each other is arranged at the input side of the deflection unit. The underconvergence induced thereby is compensated in that the deflection unit generates deflection fields which cause an overconvergence of the outer beams. This leads to a reduction of the spot growth upon deflection.

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Eindhoven, Netherlands

Albertus A Sluyterman