Color cathode ray tube of the plural beam, single electron gun type

Abstract

A color cathode ray tube preferably of the single gun, plural beam type wherein the beams originate on a horizontal or vertical straight line and are directed into a field produced by a horizontal-vertical electromagnetic deflection yoke at predetermined incident angles to each other so as to converge at a color screen, is provided with a magnetic yoke, for example, secured to the electron beam convergence plates at the end of the electron gun so as to be disposed in the path of the leakage flux produced by the horizontal-vertical electromagnetic deflection yoke, and thereby impart a further vertical or horizontal deflection field to at least one of the plural beams for correcting a deviation between the positions of rasters on the color screen produced by the plural beams.

What is claimed is: 
     
       1. In a color cathode ray tube having means generating plural beams including a central beam and opposite side beams which originate in a common plane and which are directed, at predetermined incident angles to each other for convergence on a screen, through horizontal and vertical deflection fields produced by electromagnetic deflection means and by which said beams are made to scan said screen, the improvement comprising magnetic yoke means disposed .Iadd.in advance of said electromagnetic deflection means to be in advance of all but the leakage flux of at least one field from the same and .Iaddend.wholly within said tube adjacent the paths of said beams through said deflection fields and being operative to collect .Iadd.said .Iaddend.leakage flux from one of said fields and to concentrate the collected leakage flux in a correction field through which only said central beam passes for correcting deviations between the rasters of said plural beams on said screen. 
     
     
       2. A color cathode ray tube according to claim 1, in which said magnetic yoke means includes two spaced apart yoke members disposed at opposite sides of the path of said central beam and being shaped to collect said leakage flux for concentration in the space between said yoke members. 
     
     
       3. A color cathode ray tube according to claim 2, in which each of said yoke members includes a substantially straight portion extending substantially parallel to and in spaced relation to the straight portion of the other yoke member, and end portions at the ends of said straight portion and being directed at substantial angles to the latter in the direction away from said space between the yoke members. 
     
     
       4. A color cathode ray tube according to claim 3, in which said common plane is horizontal and said straight portions of the yoke members extend substantially vertically so that said yoke members collect and concentrate said leakage flux from said vertical deflection field. 
     
     
       5. In a single-gun, plural-beam color picture tube which includes a color screen having arrays of color phosphors and beam selecting means provided with apertures corresponding to said arrays, beam generating means for directing a central electron beam and two side electron beams in a common plane toward said screen for impingement on respective phosphors of each array through the corresponding aperture, lens means for focussing said electron beams on said screen and having an optical center at which said beams are made to cross each other with said side beams emerging from said lens means along paths lying in said plane and which are divergent with respect to the central beam, electron beam convergence deflecting means operative, upon the application of a convergence deflecting voltage thereto, to deflect said side beams emerging along said divergent paths for convergence of all of said beams at an aperture of said beam selecting means, and deflection yoke means having sweep signals applied thereto to provide fields which deflect said beams in directions respectively parallel, and at right angles to said plane for causing said beams to scan said screen; the improvement comprising magnetic yoke means disposed .Iadd.in advance of said deflection yoke means to be in advance of all but the leakage flux of at least one field from the same and .Iaddend.wholly within said tube and collecting .Iadd.said .Iaddend.leakage flux from said field which deflects said beams in said direction at right angles to said plane and concentrating the collected leakage flux in a correction field through which said central beam passes for correcting deviations between the positions of the rasters on the color screen produced by said beams in scanning said screen. 
     
     
       6. A single-gun, plural-beam color picture tube according to claim 5, in which said magnetic yoke means includes spaced apart yoke members arranged at opposite sides of said central beam and each having a substantially straight portion at right angles to said plane between said central beam and one of said side beams and end portions at the ends of said straight portion and being directed at substantial angles to the latter in the direction away from the other yoke member so that said end portions act as pole pieces to collect said leakage flux for concentration in said correction field established between said straight portions of the yoke members. 
     
     
       7. A single-gun, plural-beam color picture tube according to claim 6, in which said yoke members are mounted adjacent the entry end of said convergence deflecting means. .Iadd. 8. In a color cathode ray tube having means generating plural beams including a central beam and opposite side beams which originate in a common horizontal plane and which are directed, at predetermined incident angles to each other for convergence on a screen, through pincushion-shaped horizontal and barrel-shaped vertical deflection fields produced by electromagnetic deflection means and by which said beams are made to scan said screen, the improvement comprising magnetic yoke means disposed in advance of said electromagnetic deflection means wholly within said tube adjacent the paths of said beams through said deflection fields and being operative to collect leakage flux from one of said fields and to concentrate the collected leakage flux in a correction field through which only said central beam passes for correcting deviations between the rasters of said plural beams on said screen without substantially affecting the pincushion and barrel-shapes of said horizontal and vertical deflection fields. .Iaddend..Iadd. 9. In a single-gun, plural-beam color picture tube which includes a color screen having arrays of color phosphors and beam selecting means provided with apertures corresponding to said arrays, beam generating means for directing a central electron beam and two side electron beams in a common plane toward said screen for impingement on respective phosphors of each array through the corresponding aperture, lens means for focusing said electron beams on said screen and having an optical center at which said beams are made to cross each other with said side beams emerging from said lens means along paths lying in said plane and which are divergent with respect to the central beam, electron beam convergence deflecting means operative, upon the application of a convergence deflecting voltage thereto, to deflect said side beams emerging along said divergent paths for convergence of all of said beams at an aperture of said beam selecting means, and deflection yoke means having sweep signals applied thereto to provide pincushion-shaped and barrel-shaped fields which deflect said beams in directions respectively parallel, and at right angles to said plane for causing said beams to scan said screen; the improvement comprising magnetic yoke means disposed in advance of said deflection yoke means wholly within said tube and collecting leakage flux from said field with deflects said beams in said direction at right angles to said plane and concentrating the collected leakage flux in a correction field through which said central beam passes for correcting deviations between the positions of the rasters on the color screen produced by said beams in scanning said screen without substantially affecting the pincushion- and barrel-shapes of said fields provided by said deflection yoke means.