EP1158561B1 - Bobine de déviation à shunt asymétrique pour diminuer des défauts symétriques diagonaux - Google Patents

Bobine de déviation à shunt asymétrique pour diminuer des défauts symétriques diagonaux Download PDF

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Publication number
EP1158561B1
EP1158561B1 EP20000111205 EP00111205A EP1158561B1 EP 1158561 B1 EP1158561 B1 EP 1158561B1 EP 20000111205 EP20000111205 EP 20000111205 EP 00111205 A EP00111205 A EP 00111205A EP 1158561 B1 EP1158561 B1 EP 1158561B1
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EP
European Patent Office
Prior art keywords
coils
deflection
conductor assembly
deflection yoke
respect
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP20000111205
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German (de)
English (en)
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EP1158561A1 (fr
Inventor
Nacerdine Azzi
Olivier Masson
Sébastien Volatier
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.)
THOMSON LICENSING
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Thomson Licensing SAS
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Publication date
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Priority to DE2000638006 priority Critical patent/DE60038006T2/de
Priority to EP20000111205 priority patent/EP1158561B1/fr
Publication of EP1158561A1 publication Critical patent/EP1158561A1/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
    • H01J29/72—Arrangements for deflecting ray or beam along one straight line or along two perpendicular straight lines
    • H01J29/76—Deflecting by magnetic fields only
    • H01J29/762—Deflecting by magnetic fields only using saddle coils or printed windings

Definitions

  • the invention relates to a deflection unit for a colour cathode-ray tube, which unit is also called a deflection yoke, which includes a pair of horizontal deflection coils and a pair of vertical deflection coils in the form of a saddle, the particular shape of which makes it possible to minimize the coma, geometry and convergence errors of the beams simultaneously.
  • a deflection yoke which includes a pair of horizontal deflection coils and a pair of vertical deflection coils in the form of a saddle, the particular shape of which makes it possible to minimize the coma, geometry and convergence errors of the beams simultaneously.
  • a cathode-ray tube intended to generate colour images generally comprises an electron gun which emits three coplanar electron beams, each beam being intended to excite a phosphor for a specific primary colour (red, green or blue) on the screen of the tube.
  • the electron beams scan the screen of the tube due to the effect of the deflection fields created by the horizontal and vertical deflection coils of the deflection yoke fixed to the neck of the tube.
  • a separator made of plastic serves to isolate the two pairs of coils and to ensure that the deflection yoke is mechanically rigid.
  • a ring of ferromagnetic material conventionally surrounds the deflection coils so as to concentrate the deflection fields in the appropriate region.
  • the three beams generated by the electron gun must always converge on the screen of the tube on pain of introducing a so-called convergence error which falsifies, in particular, the rendition of the colours.
  • the volume scanned by the electron beams is a pyramid, the apex of which is coincident with the centre of deflection of the deflection yoke and the intersection of which with a non-spherical screen surface exhibits a geometrical defect called pin-cushion distortion.
  • This geometrical distortion of the image is all the greater the larger the radius of curvature of the screen of the tube.
  • Self-converging deflection yokes generate astigmatic deflection fields making it possible to modify the North/South and East/West geometry of the image and, in particular, partially compensate for the North/South pin-cushion distortion.
  • the design of the deflection yoke must also take into account the coma, which is an aberration affecting the lateral beams emanating from an electron gun emitting three beams in line, independently of the astigmatism of the deflection fields and of the curvature of the screen surface of the tube; these lateral beams enter the deflection zone at a low angle with respect to the axis of the tube and undergo a deflection in addition to that of the axial beam.
  • the coma is generally corrected by modifying the distribution of the deflection fields at the point where the beams enter the deflection yoke so that the coma generated compensates for that produced by the distribution of the field which is necessary in order to obtain the desired astigmatism for achieving self-convergence.
  • the field at the rear of the deflection yoke is in the form of a barrel and in the front part in the form of a pin-cushion.
  • the cross-modulation generates geometrical problems in the image created on the screen of the tube by the scanning of the electron beams.
  • These problems are, for example, orthogonality and parallelogram faults.
  • the correction of these faults requires them to be taken into account when designing the deflection yoke, but this process of taking them into account is difficult, or even impossible, since the defects result from manufacturing problems which arise in the first phases of manufacturing the deflection yoke, when the design stage has been completed; it was therefore necessary to remedy these problems either by introducing a new step in the design of the deflection coils or by using electronic control circuits capable of being responsible for the geometrical corrections of the image.
  • EP-A-0 952 604 provides a simple solution to these problems, by modifying the front conductor assembly of a pair of saddle-shaped coils and by introducing a shape asymmetry into said conductor assembly. This modification is introduced into the manufacture by modifying the shape of the coil shaper placed in front of the mould in which the winding takes place, which modification has no effect on the other parameters defined in the design of the coil, such as the convergence of the three electron beams or the coma.
  • Figure 1 shows, in cross-section, a deflection yoke 1 illustrating the invention, placed on the neck 8 of a cathode-ray tube 6.
  • the deflection yoke comprises a pair of vertical deflection coils 4, a horizontal pair of deflection coils 3, the two pairs being insulated from each other by a separator 2 generally made of plastic, and a ring 5 of ferromagnetic material intended to concentrate the magnetic fields created by the coils 3 and 4.
  • These fields deflect the electron beams 12 created by the electron gun 7 so that said beams scan the screen 9 of the tube 6.
  • FIGs 2A and 2B illustrate the state of the art in which the vertical deflection coils 4 are saddle-shaped.
  • Each coil comprises loops of conductors forming a rear conductor assembly 24 lying in the rear zone 32, a front conductor assembly 25 lying in the front zone 30, the two conductor assemblies being connected by lateral conductor bundles 26 in an intermediate zone 31.
  • the plane P of symmetry of each vertical deflection coil is, in the case illustrated in Figures 2A and 2B , the XZ plane.
  • parameters defined in the design stage may be affected by the industrial manufacturing process or by the equipment used for manufacturing said deflection yoke.
  • the cross-modulation causes orthogonality and parallelogram defects. These defects are manifested on the screen of the tube in the following manner:
  • the example not being an embodiment aims to provide a simple solution to these problems without modifying the design of the deflection yoke and therefore without modifying the beam-convergence or coma parameters.
  • the rear conductor assembly 24 and the lateral conductor bundles 26 are not modified and are placed symmetrically with respect to a plane P, this plane being coincident with the plane defined by the main axis Z of the tube and the horizontal axis X in the case of the vertical deflection coils; the front conductor assembly is modified so as to introduce a dissymmetry into the conductor assembly with respect to the plane P, in a zone A of said conductor assembly, this dissymmetry being in the form of a depression or a notch, as illustrated in Figure 4 .
  • Figure 5 shows a depth depression 41 created on the outside of the conductor assembly and the effect of this dissymmetry on the field H created by the current flow in the conductors of said front conductor assembly 25.
  • the field H undergoes a slight rotation with respect to the direction which it would have in the absence of the dissymmetry, and the resulting field H' introduces, in particular, a component H' y .
  • This rotation acting at the front of the deflection yoke, only influences the geometry of the image generated on the screen of the tube; the component H' y compensates for the shift between the direction of the horizontal deflection field and the perpendicular to the vertical deflection field in order to cancel out the effects of said shift.
  • a metal plate 43 is placed close to the front conductor assembly 25 of the vertical deflection coil.
  • the piece 43 which forms a magnetic screen, may either increase or decrease the intensity of the magnetic field acting as the election-beam deflection field, depending on whether the said metal piece 43 is placed above or below the front conductor assembly.
  • Figure 7 shows a metal piece 43 lying below the front conductor assembly 25 of the vertical deflection coil.
  • the metal piece 43 introduces a local modification of the amplitude of the frame field and consequently a proportional modification of the amplitude of the component of the field along the Y axis.
  • This local modification of the component of the field along the Y axis compensates for the shift between the direction of the horizontal deflection field and the perpendicular to the vertical deflection field in order to cancel out the effects of the said shift.
  • the depression 40 located on the front conductor assembly 25 of the vertical deflection coils 4, extends in a radial plane with an angular aperture ⁇ about a mean angle ⁇ m measured with respect to the direction of the plane of separation YZ of the two vertical deflection coils; the same applies to the position of the metal piece 43 locally modifying the deflection field. From experience, it has been shown that the optimum effect was obtained by choosing a mean angle of between 60° and 90° for the vertical deflection coils and between 45° and 90° for the horizontal deflection coils.
  • the depth 41 of the depression created on the conductor assembly will vary, as will the angular aperture ⁇ over which said depression extends.
  • the depression(s) or notch(es) of the front conductor assembly of one of the coils and the depression(s) or notch(es) of the front conductor assembly of the other coil of the same pair of deflection coils are generally arranged symmetrically with respect to the Z axis, if there is no additional correction to be introduced between the two coils of the same pair.
  • the metal plates (43) for modifying the magnetic field which themselves will also be arranged symmetrically with respect to the Z axis.
  • the depressions or notches may be arranged on the outer part of the conductor assembly, as indicated in Figure 5 , or on the inner part of the conductor assembly, as indicated in Figure 6 , depending on the local orientation which it is desired to give to the deflection field.
  • a major advantage of the invention as claimed is that it is easy to implement.
  • the amplitude of the field is locally modified by means of metal plates, it is possible to place those plates, for example, by adhesively bonding them to the plastic body of the deflection yoke seperator; this solution is particularly simple to implement as it avoids any modification of the coils themselves.

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

Claims (5)

  1. - Déviateur pour tube à rayons cathodiques en couleur, comprenant une paire de bobines de déflexion horizontale (3), une paire de bobine de déflexion verticale (4), destinées à générer des champs magnétiques de déflexion perpendiculaires à un axe principal Z, au moins une de ces deux paires étant constituée de bobines en forme de selle, les fils conducteurs de chacune desdites bobines étant disposés de façon à former un chignon avant (25), un chignon arrière (24), les deux chignons étant reliés l'un à l'autre par des faisceaux latéraux de conducteurs (26), les parties de chacune desdites bobines, formant le chignon arrière et les faisceaux latéraux étant disposés sensiblement symétriquement par rapport à un plan P, caractérisé en ce que le déviateur comporte au moins une plaque métallique placée près du chignon avant pour modifier localement l'amplitude du champ magnétique créé par la circulation du courant dans ledit chignon de façon à ce que, considérant une première zone du chignon avant et une seconde zone symétrique de la première zone par rapport à P, les champs magnétiques créés au niveau de la première et deuxième zone ne sont pas symétriques par rapport à P.
  2. - Déviateur selon l'une des revendications précédentes, caractérisé en ce que les deux bobines en forme de selle sont les bobines de déflexion verticale.
  3. - Déviateur selon la revendication précédente, caractérisé en ce qu'au moins la plaque métallique placée près du chignon avant pour modifier localement l'amplitude du champ magnétique s'étend, dans un plan perpendiculaire à Z, autour d'une direction radiale moyenne comprise entre 60° et 90° mesurée par rapport à la direction du plan de séparation des deux bobines d'une même paire.
  4. - Déviateur suivant au moins l'une des revendications précédentes, caractérisé en ce qu'il comprend deux plaques métalliques disposées sur l'une et l'autre des bobines en forme de selle d'une même paire, dans des positions symétriques par rapport à l'axe Z.
  5. - Tube à rayons cathodiques comportant un déviateur conforme à au moins l'une des revendications précédentes.
EP20000111205 2000-05-24 2000-05-24 Bobine de déviation à shunt asymétrique pour diminuer des défauts symétriques diagonaux Expired - Lifetime EP1158561B1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE2000638006 DE60038006T2 (de) 2000-05-24 2000-05-24 Ablenkjoch mit asymetrischem Shunt zur Verminderung von diagonalen symetrischen Defekten
EP20000111205 EP1158561B1 (fr) 2000-05-24 2000-05-24 Bobine de déviation à shunt asymétrique pour diminuer des défauts symétriques diagonaux

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP20000111205 EP1158561B1 (fr) 2000-05-24 2000-05-24 Bobine de déviation à shunt asymétrique pour diminuer des défauts symétriques diagonaux

Publications (2)

Publication Number Publication Date
EP1158561A1 EP1158561A1 (fr) 2001-11-28
EP1158561B1 true EP1158561B1 (fr) 2008-02-13

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EP20000111205 Expired - Lifetime EP1158561B1 (fr) 2000-05-24 2000-05-24 Bobine de déviation à shunt asymétrique pour diminuer des défauts symétriques diagonaux

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EP (1) EP1158561B1 (fr)
DE (1) DE60038006T2 (fr)

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB709382A (en) * 1951-04-28 1954-05-19 Telefunken Gmbh Improvements relating to means for deflecting the ray of a cathode-ray tube
FR2034201B1 (fr) * 1969-02-21 1973-10-19 Videon Sa
EP0470315B1 (fr) * 1990-08-07 1996-01-10 THOMSON TUBES & DISPLAYS SA Bobine pour un montage à déviation électromagnétique, dispositif et sa méthode de fabrication
FR2778016B1 (fr) * 1998-04-24 2000-06-02 Thomson Tubes & Displays Unite de deflexion pour tubes a rayons cathodiques couleur comportant des bobines asymetriques

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Publication number Publication date
EP1158561A1 (fr) 2001-11-28
DE60038006D1 (de) 2008-03-27
DE60038006T2 (de) 2009-02-05

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