Convergence yoke for improving focus characteristics

A convergence yoke for equalizing a deflection field to improve focus characteristics of a cathode ray tube, comprising:

• a cylindrical core having an inner circumference;
• vertical correcting coils wound symmetrically on a first part of the inner circumference of said core so that a central axis thereof is substantially perpendicular to a central axis of the core;
• horizontal correcting coils wound symmetrically on a second part of the inner circumference of said core so that a central axis thereof is substantially perpendicular to the central axis of the core, said first part being displaced from said second part in a direction substantially parallel to the central axis of the core;
• and
• wherein each of said horizontal and vertical correcting coils extend along an arc with respect to the central axis of the core in the range of 100.degree. to 130.degree., said horizontal and vertical correcting coils producing a mutually compensating barrel-shaped deflection field and pincushion-shaped deflection field for improving focus characteristics, and a deflection field which changes from substantially the barrel-shaped deflection field to substantially the pincushion-shaped deflection field along an axial direction of the cathode ray tube as a function of a deflection signal for correcting coma aberration.