EP0517320B1 - Tube d'affichage en couleurs avec correction de coma - Google Patents

Tube d'affichage en couleurs avec correction de coma Download PDF

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Publication number
EP0517320B1
EP0517320B1 EP19920201573 EP92201573A EP0517320B1 EP 0517320 B1 EP0517320 B1 EP 0517320B1 EP 19920201573 EP19920201573 EP 19920201573 EP 92201573 A EP92201573 A EP 92201573A EP 0517320 B1 EP0517320 B1 EP 0517320B1
Authority
EP
European Patent Office
Prior art keywords
field
coma
deflection
display tube
shaped
Prior art date
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Expired - Lifetime
Application number
EP19920201573
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German (de)
English (en)
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EP0517320A3 (en
EP0517320A2 (fr
Inventor
Albertus Aemilius Seyno Sluyterman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips Electronics NV
Philips Electronics NV
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Publication date
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Priority to EP19920201573 priority Critical patent/EP0517320B1/fr
Publication of EP0517320A2 publication Critical patent/EP0517320A2/fr
Publication of EP0517320A3 publication Critical patent/EP0517320A3/en
Application granted granted Critical
Publication of EP0517320B1 publication Critical patent/EP0517320B1/fr
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/70—Arrangements for deflecting ray or beam
    • H01J29/701—Systems for correcting deviation or convergence of a plurality of beams by means of magnetic fields at least
    • H01J29/702—Convergence correction arrangements therefor
    • H01J29/703—Static convergence systems

Definitions

  • the invention relates to a colour display tube comprising an electron gun of the "in-line" type for generating three electron beams whose axes are coplanar, a deflection unit comprising a first and a second deflection rail for generating a first and a second deflection field for deflecting the electron beams in the operating display tube across said display screen in two mutually perpendicular directions, the direction of the first deflection field being parallel to said plane, and convergence correction means which, during deflection, keep the electron beams converged on a display screen arranged on a wall of the envelope and having a short display screen axis and a long display screen axis.
  • deflection units may be used for deflecting the electron beams in colour display tubes.
  • these deflection units are generally self-convergent.
  • conventional deflection units having field deflection coils of the saddle type and field deflection coils of the toroidal type the winding technique used does not permit of rendering the unit entirely self-convergent.
  • coma a certain convergence error remains, which error is commonly referred to as coma.
  • This coma error becomes manifest, for example, in a larger raster (horizontal and vertical) for the outer beams with respect to the central beam.
  • the horizontal and vertical deflection of the central beam is smaller than that of the outer beams.
  • this can be corrected by providing elements (referred to as field shapers) of a material (for example of mu-metal) having a high magnetic permeability around the outer beams at the end of the gun.
  • the peripheral field at the arc of the outer electron beams is shielded to some extent by these elements, so that these beams are deflected to a lesser extent and the coma error is reduced.
  • a first problem is that the shielding means around the outer electron beams detrimentally influence the spot shape of these beams.
  • the correction of the field coma (Y coma) is anisotropic. In other words, the correction in the corners is less than the correction at the end of the field axis (the field axis is the display screen axis which is parallel to the field deflection direction). This is caused by the positive "lens" action of the line deflection coil (approximately quadratically with the line deflection) for vertical beam displacements. (The field deflection coil has a corresponding lens action, but it does not contribute to the relevant anisotropic effect.)
  • a colour display tube of the type described in the opening paragraph is characterized in that the convergence correction means effect a first, or field deflection field which is characterized in that an electron beam entering the field deflection field first passes an area with a barrel-shaped delection field component and next an adjoining area with a pincushion-shaped deflection field component.
  • convergence correction means comprise a first coma corrector which is positioned at the gun side of the first deflection coil and provides the pincushion-shaped field component, and a second coma corrector which, viewed in the direction of propagation of electrons, is positioned upstream of the first coma corrector and provides the barrelshaped field component.
  • the invention is based, inter alia , on the recognition that the problem of the anisotropic Y coma (referred to as "green doop") can be reduced by making suitable use of the Z dependence of the anisotropic Y coma.
  • This dependence implies that as the coma correction takes place at a larger distance (in the Z direction) from the "lens" formed by the line deflection coil, the action of said "lens” becomes more effective so that the coma correction acquires a stronger anisotropic character.
  • the invention utilizes this aspect in that a pincushion-shaped component is realised at the entrance side of the field deflection field, so that coma is corrected, and in that barrel-shaped component is realised upstream of said area, so that the anisotropic character of the correction will be less anisotropic.
  • Field coma errors at the end of the vertical axis and in the corners can be corrected effectively and to an approximately equal extent by effecting particularly a pincushion-shaped component which has a strength which is sufficient to correct the field coma in the corners, but which is more pincushion-shaped than is necessary for coma correction at the ends of the vertical axis, and by effecting a barrel-shaped vertical deflection field component at a location located closer to the electron gun or around the electron gun, which field component corrects the overcompensation at the ends of the vertical axis.
  • the deflection unit can be moved in the axial direction, for example, for colour purity adjustment without this influencing the convergence.
  • the display tube according to the invention is very suitable for use with a field deflection coil of the toroidal type, particularly when the display tube should be free from raster correction.
  • Fig. 1 is a longitudinal section of a display tube according to the invention. It is a colour display tube of the "in-line" type.
  • a glass envelope 1 which is composed of a display window 2, a cone 3 and a neck 4, said neck accommodates an integrated electron gun system 5 which generates three electron beams 6, 7 and 8 whose axes are coplanar prior to deflection.
  • the axis of the central ("green") electron beam 7 coincides with the tube axis 9.
  • the display window 2 has a large number of phosphor element triplets on its inner side. The elements may be rows or dots.
  • Each triplet comprises an element of a blue-luminescing phosphor, an element of a green-luminescing phosphor and an element of a red-luminescing phosphor. All triplets combined constitute the display screen 10.
  • the phosphor rows are substantially perpendicular to said plane through the beam axes.
  • a shadow mask 11 having a very large number of elongate apertures 12 for passing the electron beams 6, 7 and 8 each impinging upon phosphor elements of one colour only is arranged in front of the display screen.
  • the three coplanar electron beams are deflected by a system 13 of deflection coils, which is not completely self converging because of the fact that a field coma error occurs, which system comprises a line deflection coil 16, a yoke ring 15 and a field deflection coil 16'.
  • Coma correction coil 14' produces a (positive) six-pole field by which a pincushion-shaped field distribution is effected so that the green beam is deflected in the direction of deflection of the field deflection coil to a greater extent than the side beams.
  • Correction coil 14 produces a (negative) six-pole field by which a barrel-shaped field distribution is effected, so that the green beam is deflected in the direction of deflection of the vertical deflection coil to a lesser extent than the side beams.
  • Green droop means that the field coma is corrected at the end of the vertical axis but is insufficiently corrected in the corners.
  • Fig. 2a shows a situation where the field coma correction is insufficient
  • Fig. 2b shows the green droop situation.
  • This problem becomes worse as the axial distance between the location of coma correction and the centre of the line deflection coil increases.
  • Use can be made of the axial dependence of the green droop for solving the problem of the green droop.
  • the problem can be solved by overcorrecting the field coma at the entrance side of the field deflection field (see Fig. 2c) and by performing an opposite correction at a location "upstream" (see Fig.
  • the method described in this Application is based on coma correction by means of field-shielding components arranged around the paths of individual electron beams.
  • the drawback of coma correction by partially shielding the beams is that the spot shape of the side beams is detrimentally influenced.
  • the invention provides, inter alia , a solution for correcting field coma and preventing the green droop, while the spot shape of the side beames is minimally influenced.
  • the deflection unit can be moved in the axial direction, for example, for colour purity adjustment without any convergence side effects.
  • Figure 3, 4 and 5 show modifications of embodiments of coma correctors 14' each comprising one or more magnetic cores with such a coil arrangement that a positive six-pole field is generated upon energization.
  • Figures 3, 4 and 5 show, in this order, increasingly simplified embodiments (i.e. magnetic cores provided with fewer coils).
  • the (overcompensated) coma correction can also be performed by means of coma correction means of the type used in the Philips colour display tube systems 30AX, 45AX or as described in PHN 10.667 (USP 4,524,340) or PHN 12.132 (USP 4,874,983).
  • the corrector 14 which works in the opposite way and this enlarges the original coma error to some extent may comprise correctors of the type shown in Figs. 3, 4 and 5, with such an energization of the coils that the field direction is opposite to that shown in Figures 3, 4 and 5. This means that a negative sixpole field is generated.

Landscapes

  • Video Image Reproduction Devices For Color Tv Systems (AREA)

Claims (6)

  1. Tube d'affichage en couleurs comprenant un canon électronique (5) pour générer trois faisceaux d'électrons (6, 7, 8) dont les axes sont coplanaires, une unité de déviation (13) comprenant une première et une deuxième bobines de déviation pour générer un champ de déviation verticale (16) et un champ de déviation horizontale (16') afin de dévier les faisceaux d'électrons dans le tube d'affichage en service, en travers de l'écran d'affichage (10) dans deux directions mutuellement perpendiculaires (x, y), la direction du champ de déviation verticale étant parallèle au plan desdits axes de faisceaux, et des moyens de correction de convergence (14, 14') qui, pendant la déviation, maintiennent les faisceaux d'électrons en convergence sur un écran d'affichage agencé sur une paroi de l'enveloppe et ayant un axe d'écran court et un axe d'écran long, caractérisé en ce que les moyens de correction de convergence aident à former un champ de déviation verticale ayant une distribution telle que les faisceaux d'électrons pénétrant dans le champ de déviation verticale passent d'abord par une zone ayant une composante de champ de déviation en forme de tonneau, puis par une zone ayant une composante de champ de déviation en forme de coussin.
  2. Tube d'affichage en couleurs selon la revendication 1, caractérisé en ce que les moyens de correction de convergence comprennent un premier correcteur de coma (14') qui est disposé du côté canon de la bobine de déviation verticale et fournit la composante de champ en forme de coussin, et un deuxième correcteur de coma (14) qui, vu dans la direction de propagation des électrons, est positionné en amont du premier correcteur de coma et fournit la composante de champ en forme de tonneau.
  3. Tube d'affichage en couleurs selon la revendication 2, caractérisé en ce que le premier correcteur de coma (14') surcompense le coma aux extrémités de l'axe court de l'écran d'affichage et en ce que le deuxième correcteur de coma (14) corrige la surcompensation produite par le premier correcteur de coma.
  4. Tube d'affichage en couleurs selon la revendication 2, caractérisé en ce que le premier correcteur de coma (14') comprend un système de bobines enroulées sur au moins un noyau magnétique, ledit système, lorsqu'il est excité, générant un champ hexapolaire magnétique.
  5. Tube d'affichage en couleurs selon la revendication 2, caractérisé en ce que le deuxième correcteur de coma (14) comprend un système de bobines enroulées sur au moins un noyau magnétique, ledit système, lorsqu'il est excité, générant un champ hexapolaire magnétique.
  6. Tube d'affichage en couleurs selon la revendication 2, caractérisé en ce qu'au moins un des correcteurs de coma comprend au moins deux éléments magnétiques (17, 17') en forme de plaques agencés dans le champ de déviation verticale de manière à réaliser une composante de champ hexapolaire.
EP19920201573 1991-06-05 1992-06-02 Tube d'affichage en couleurs avec correction de coma Expired - Lifetime EP0517320B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP19920201573 EP0517320B1 (fr) 1991-06-05 1992-06-02 Tube d'affichage en couleurs avec correction de coma

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP91201380 1991-06-05
EP91201380 1991-06-05
EP19920201573 EP0517320B1 (fr) 1991-06-05 1992-06-02 Tube d'affichage en couleurs avec correction de coma

Publications (3)

Publication Number Publication Date
EP0517320A2 EP0517320A2 (fr) 1992-12-09
EP0517320A3 EP0517320A3 (en) 1993-11-18
EP0517320B1 true EP0517320B1 (fr) 1996-10-16

Family

ID=26129287

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19920201573 Expired - Lifetime EP0517320B1 (fr) 1991-06-05 1992-06-02 Tube d'affichage en couleurs avec correction de coma

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Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3725831A (en) * 1972-01-14 1973-04-03 Rca Corp Magnetic beam adjusting arrangements
NL8300032A (nl) * 1983-01-06 1984-08-01 Philips Nv Inrichting voor het weergeven van televisiebeelden en afbuigeenheid daarvoor.
NL8301534A (nl) * 1983-05-02 1984-12-03 Philips Nv Inrichting voor het weergeven van televisiebeelden met een afbuigeenheid met comacorrecties.
NL8601003A (nl) * 1986-03-28 1987-10-16 Philips Nv Kleurenbeeldbuis met een afbuigeenheid met beeldbalanscorrectiemiddelen.
NL8701276A (nl) * 1987-05-29 1988-12-16 Philips Nv Beeldweergeefsysteem met afbuigeenheid met dubbel zadelspoelenstelsel.

Also Published As

Publication number Publication date
EP0517320A3 (en) 1993-11-18
EP0517320A2 (fr) 1992-12-09

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