Electron beam and deflection yoke alignment for producing convergence of plural in-line beams

Abstract

In a color television display system in which a plurality of horizontal in-line electron beams are directed toward color phosphor elements of a color picture tube, substantial convergence of the beams at all points on a scanned raster is achieved by transversely positioning the deflection yoke relative to the picture tube while maintaining substantial parallelism between the central longitudinal axes of the yoke and picture tube.

What is claimed is: 
     
       1. A method of mounting a beam deflection yoke relative to a color picture tube comprising an envelope containing a color phosphor screen, an electron gun assembly for projecting a plurality of electron beams toward said screen and a deflection region for said beams, said method comprising: supporting said tube in a predetermined position;   temporarily supporting said deflection yoke loosely assembled around said picture tube adjacent said deflection region;   operating said tube and yoke to project said beams toward said screen and to scan said beams in separate rasters on said screen, and simultaneously adjusting the transverse position of said yoke relative to said picture tube while maintaining .[.substantial.]. parallelism of the longitudinal axes of said yoke and picture tube to achieve substantial convergence of said beams and coincidence of said rasters on said screen .Iadd.without the use of dynamic convergence correction means.Iaddend.; and   fixedly attaching said yoke to said picture tube in said adjusted position.   
     
     
       2. A method according to claim 1 wherein said electron gun assembly is selected for producing three coplanar in-line beams. 
     
     
       3. A method according to claim 2 wherein said yoke comprises a pair of vertical and a pair of horizontal deflection coils toroidally wound around a core, the conductor winding distribution of said coils being selected for producing positive vertical isotropic astigmatism and negative horizontal isotropic astigmatism. 
     
     
       4. A method according to claim 3 wherein said phosphor screen comprises strips of different color phosphor elements. 
     
     
       5. In a color image display system, the combination comprising: a color picture tube including an envelope containing a screen of different color phosphor elements and an electron gun assembly disposed within a neck portion of said tube envelope for producing a plurality of beams for impinging on said respective color phosphor elements;   a deflection yoke adapted to be energized to cause said beams to scan respective rasters on said phosphor screen, said yoke having a smallest inner diameter larger than the outer diameter of said neck portion of said tube envelope; and   means for mounting said yoke on said picture tube, said means being selected for allowing transverse movement of said yoke relative to said picture tube while maintaining .[.substantial.]. parallelism of the central longitudinal axes of said yoke and said picture tube such that said yoke can be fixedly mounted in a position providing substantial convergence of said beams and coincidence of said rasters .Iadd.without the use of dynamic convergence correction means.Iaddend..   
     
     
       6. A system for converging a plurality of beams in a color television display system, comprising: a color picture tube comprising an envelope containing a color phosphor element screen at one end thereof and an electron gun assembly for producing three horizontal coplanar in-line beams disposed within a neck portion of said envelope remote from said screen; .Iadd.said electron gun assembly including, near that end of the electron gun assembly from which the electron beam exit, at least two adjacent common electrodes, each common electrode having, for each electron beam, a separate aperture, through which the beam passes, so that a selected alignment of the beams relative to one another can be produced; .Iaddend.   a deflection yoke having the conductor winding distribution of horizontal and vertical deflection coils thereof selected for producing negative horizontal isotropic astigmatism and positive vertical isotropic astigamatism, said coils being spaced circumferentially around a core and forming a smallest inside diameter of said yoke larger than the outside diameter of said neck portion of said tube envelope; and   means for mounting said yoke around said picture tube and including means for allowing movement of said entire yoke in directions substantially normal to the central longitudinal axis of said picture tube and for fixedly retaining said yoke in a position providing substantial convergence of said beams .Iadd.without the use of dynamic convergence correction means. .Iaddend.   
     
     
       7. A system for converging a plurality of beams according to claim 6 wherein said deflection yoke produces underconvergence of said beams along the horizontal axis of deflection and overconvergence of said beams along the vertical axis of deflection. 
     
     
       8. A system for converging a plurality of beams according to claim 7 wherein said phosphor screen includes a repeating pattern of red, green and blue vertically extending phosphor strips. .Iadd. 9. A system for converging a plurality of beams in a color television display system, comprising: a color picture tube comprising an envelope containing a color phosphor element screen at one end thereof and an electron gun assembly for producing three horizontal coplanar in-line beams disposed within a neck portion of said envelope remote from said screen; said electron gun assembly including, near that end of the electron gun assembly from which the electron beams exit, at least two adjacent common electrodes, each common electrode having, for each electron beam, a separate aperture, through which the beam passes, the spacing of the apertures of said two adjacent electrodes relative to each other producing a selected alignment of the beams relative to one another;   a deflection yoke having the conductor winding distribution of horizontal and vertical deflection coils thereof selected for producing negative horizontal isotropic astigmatism and positive vertical isotropic astigmatism, said coils being spaced circumferentially around a core and forming a smallest inside diameter of said yoke larger than the outside diameter of said neck portion of said tube envelope; and   means for mounting said yoke around said picture tube and including means for allowing movement of said entire yoke in directions substantially normal to the central longitudinal axis of said picture tube and for fixedly retaining said yoke in a position providing substantial convergence of said beams without the use of dynamic convergence correction means. .Iaddend.