Color television tube incorporating correction of coma defects of small amplitude

A color tube of the automatic convergence kind comprises three coplanar electron beams, with magnetic coma defect correction elements situated to the rear of the deflector unit. For the case where these defects are of small size, of the order of 1 mm or less in each direction, and of opposite sense in the horizontal and vertical directions, the correcting elements are formed by four plates of rectangular shape and whose plane is perpendicular to the axis of the tube. The plates are situated above and below each of the lateral beams and one dimension of each of the plates affects the amplitude of the correction in one direction, and the other dimension affects the coma correction in the other direction.