Convergence device for projection type color television system

A convergence device for the projection type color television system wherein a plurality of primary-color images are projected by respectively different cathode-ray tubes to obtain a color picture on a screen comprising:

• a substantially ring-shaped convergence core mounted around a neck of each of said cathode-ray tubes,
• eight pole pieces provided on the inner surface of said core, said eight pole pieces being aligned in pairs along a first axis passing through the center of said ring-shaped core, a second axis perpendicularly intersecting with said first axis, and third and fourth axes each dividing into two halves the angle between said first and second axes, said third and fourth axes intersecting perpendiculary with each other,
• a first two pairs of windings respectively disposed around a first two pairs of pole pieces (P.sub.1 --P.sub.1 ', P.sub.2 --P.sub.2 ') the axes thereof intersecting perpendicularly, said two pairs of windings being adapted upon excitation to produce magnetic fields respectively in directions along the opposing pole pieces (P.sub.1 --P.sub.1 ') and along the other opposing pole pieces (P.sub.2 --P.sub.2 '), and
• a second two pairs of windings respectively disposed around the remaining second two pairs of pole pieces (P.sub.3 --P.sub.3 ', P.sub.4 --P.sub.4 '), said second two pairs of windings being adapted when excited with a current flowing therethrough to produce magnetic fields respectively in the directions along said first two pairs of pole pieces (P.sub.1 --P.sub.1 ', P.sub.2 --P.sub.2 ') the axes thereof intersecting perpendicularly, the strength of said two sets of magnetic fields produced by said first two pairs of windings and said second two pairs of windings being controllable independently from each other along the two orthogonal directions, one of said two sets of magnetic fields being controlled by a static convergence control signal, and the other controlled by a dynamic convergence control signal.