Abstract: The invention relates to a color display device comprising an in-line electron gun (5) for generating three electron beams (6,7,8), and a convergence unit (14′) to dynamically influence the convergence of the electron beams, preferably to decrease a distance (p) between the electron beams. The convergence unit (14′) comprises a ring-shaped element (21′) having four coils (22′). The coils (22′) comprise electrically conductive wires, which have been toroidally wound in a winding direction and according to a winding density distribution N (&phgr;) given by N (&phgr;)=N0 cos (2&phgr;). Here &phgr; is an angle enclosed by the X-direction and a line between an element of the coil and the center, which ranges between 0° and 360°, N0 is the winding density at &phgr; equal to 0°, and the sign of N &phgr; denotes the winding direction.

Abstract: The invention relates to a color display device comprising an in-line electron gun (5) for generating three electron beams (6,7,8), and a convergence unit (14) to dynamically influence the convergence of the electron beams, preferably to decrease a distance (p) between the electron beams. The convergence unit (14) comprises a ring-shaped element (21) having four coils (22) and a longitudinal axis (24). A cross-section of the ring-shaped element (21) with a plane perpendicular to the longitudinal axis (24) is a circle with the longitudinal axis as its center and the ring-shaped element (21) forming the circumference. Each coil extends over the circumference over an angle &phgr; having a value between 50° and 75°.

Abstract: To prevent breakdown of an insulating layer located underneath a gate electrode, the gate electrode is connected to an external terminal via a high-ohmic resistor. The high-ohmic resistor may form part of a resistive network for biasing voltages for a plurality of gate electrodes. The resistive network may be realised partly on the insulating layer.

Abstract: An in-line electron gun includes main lens electrodes, a common aperture and, at a distance from the common aperture, three in-line apertures in a plate-shaped part. The outer apertures extend, viewed in a direction transverse to the plate-shaped part, beyond the common aperture.

Abstract: A color cathode ray tube includes an in-line electron gun having a main lens with recessed apertures. The main lens is formed by two electrodes. These electrodes have outer edges and recessed apertures which allow passage of three in-line electron beams and which are arranged at a distance d1 and d2, respectively, from the outer edges. The outermost apertures are asymmetric. The difference d1-d2 and the asymmetry of the outermost apertures is such that both the beam displacement and the core haze asymmetry are minimal.

Abstract: A display device with a DAF-gun (Dynamic Astigmatism and Focusing) in which the first focusing electrode (G3a) has at the side facing the pre-focusing part of the electron gun three elongated apertures (36, 37, 38). Hereby in operation in the vicinity of the elongated apertures an electron-optical field is generated between the pre-focusing part of the electron gun and the elongated apertures for reduction of the vertical dimension (vertical meaning transverse to the plane of the electron beams) of the beam size of the electron beams in the main lens. This reduction of the electron beam size results in an increase of the vertical dimension of the beam spot on the screen. This reduces Moire effects.

Abstract: 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.

Abstract: A cathode ray tube in which the pre-focusing field, the main lens field, a quadripolar field in the pre-focusing portion of the electron gun and a quadripolar field in the main lens are dynamically varied by means of only one dynamic voltage.

Abstract: Picture display device comprising a display tube with an electron gun having a hollow tubular structure with an inner surface on which a resistance structure of a material having a high electrical resistance is provided, which structure constitutes a focusing lens. The resistance structure is connected to at least two axially spaced electric contacts for connecting an anode voltage and at least one electric contact located in between for applying a focusing voltage. An electrode means of low-ohmic material for controlling the focusing lens by means of a dynamic correction signal is arranged in the region of the connection for the focusing voltage. Upon energization, the low-ohmic electrode means particularly exercises a non-rotationally symmetrical effect on the electron beam.

Abstract: Picture display device comprising a display tube with an electron gun having a tubular structure with an outer surface and an inner surface on which a helical resistance structure is provided in a layer of a material having a high electrical resistance for constituting a focusing lens. In the layer is also formed a coaxial correction element for generating an electric multi-pole field. The outer surface is provided with electrodes of readily electrically conducting material arranged opposite the correction element for capacitively coupling a dynamic correction signal into the correction element.

Abstract: Picture display device comprising a display tube having an electron gun with an electrostatic focusing lens for generating a focusing lens field, which tube further comprises deflection means for generating a deflection field. The focusing lens field partly overlaps the deflection field. The focusing lens comprises a tubular structure having an inner surface on which a helical resistance structure of a material having a high electrical resistance is provided, which tubular structure has a coaxial input portion and a coaxial output portion, the output portion having dimensions which prevent the deflected electron beam from impinging upon the glass of the inner wall. Correction means may be provided for correcting errors caused by the advanced position of the focusing lens.

Abstract: A display tube comprising an electron gun having a beam-shaping part and a focusing structure. The focusing structure comprises an elongate hollow structure with a high-ohmic resistive layer provided on the inner and/or outer surface and comprises means for forming a non-rotationally symmetrical lens element in the area of the focusing structure. This may be a structure generating an electric multipole (for example, dipole or quadrupole) which may be incorporated particularly in the high-ohmic resistive layer.

Abstract: Cathode ray tube having an electron gun positioned in the neck portion, the gun comprising a beam-forming part and a focusing structure and the beam-forming part comprising at least a cathode and a metal electrode plate provided with a central aperture, and the focusing structure comprising a hollow tube of an electrically insulating material with inner and outer surfaces and with a layer of high-ohmic resistive material on at least one of the surfaces. The electrodes of the beam-forming part of the electron gun are secured via metal pins to rods for forming an assembly. The hollow tube is directly secured to the metal electrode plate for the purpose of correct alignment. The tube has a first and a second end face, the first end face in one embodiment having a metal plate with a coaxial aperture, and the said metal plate is fixedly connected to the metal electrode plate of the beam-shaping part of the electron gun in such a way that their apertures are coaxial.

Abstract: The invention relates to a cathode ray tube having an envelope 1 comprising a screen 2 and an electron gun 3 which is situated inside the envelope 1 opposite to the screen and which has three electrodes 4, 5 and 6, which electrodes are provided coaxially on the inner wall of a glass tube 7 in adjoining places having diameters differing for each electrode. In order to obtain, for example, smaller dimensions and a better alignment of the electron gun and a higher resolution, a focusing lens associated with the electron gun 3 is a high-ohmic resistance layer 8 having a spiral shape 9.

Abstract: An electron beam device such as a cathode ray tube in which spherical aberration is reduced by optimising the axial potential distribution in the focusing lens of the electron gun. In one embodiment of the invention the electron gun comprises a beam forming part and a segmented focusing lens (25). The focusing lens (25) comprises a preformed glass tube (22) having a high-ohmic resistive layer (23) on the interior wall thereof, the resistive layer (23) comprises helical segments (33 to 37) alternated with intermediate segments (42 to 47). A focusing voltage is applied to the intermediate section (42) closest to the beam forming part and a higher voltage is applied to the end segment (47). The lengths of the helical segments (33 to 37) increase in a direction from the point of application of the focusing voltage whereas the lengths of the intermediate segments (42 to 46) decrease. The lengths of the helical segments (33 37) are such as to produce the desired axial potential distribution.