Permeable corrector for deflection yokes

In a color television display system comprising a kinescope having a neck and a display screen, an electron gun assembly within said neck for producing three horizontal in-line electron beams including a central beam directed substantially along the longitudinally axis of said neck, and a deflection yoke disposed forwardly of said assembly and having a magnetically permeable core, first deflection coils for deflecting said beam in a horizontal direction, and second deflection coils toroidally-wound about said core and producing an internal field for deflecting said beams in a vertical direction, an external field, and a quantity of magnetic flux within said core;

• a correction apparatus comprising:
• first and second field formers, each of said field formers including:
• first magnetically permeable means disposed and extending substantially parallel to said kinescope neck axis in the vicinity of the beam entrance end of said yoke;
• second magnetically permeable means magnetically coupled to said first field forming means and disposed parallel to said kinescope neck axis, said second magnetically permeable means comprising a pair of rearwardly extending feet disposed in opposition with respect to said axis and terminating in the vicinity of the beam exit end of said assembly;
• third magnetically permeable means disposed at the front of said yoke and comprising field forming crossarms;
• and
• fourth magnetically permeable means, disposed within said external field and adjacent said core and coupled between said first and third magnetically permeable means for channeling magnetic flux from said external field and said core into said first, second and third magnetically permeable means;
• wherein said first and second field formers are disposed in opposition with respect to said neck axis such that said flux is directed by said first magnetically permeable means to form a barrel-shaped field within said kinescope in the vicinity of the beam entrance end of said yoke, and is directed by said second magnetically permeable means to form a pincushion-shaped field within said kinescope neck in the vicinity of the beam exit end of said assembly, and is directed by said third magnetically permeable means to form a pincushion-shaped field within said kinescope in the vicinity of the exit end of said deflection yoke.