Color cathode ray tube with coma reduced

摘要

A color cathode ray tube includes a vacuum envelope formed by a panel, neck and funnel portions. The cathode ray tube includes a phosphor screen, a shadow mask, an electron gun and a deflection device. The cathode ray tube further includes a convergence correction device having a plurality of magnetic pieces positioned on opposite sides of each of the three electron beams in an in-line direction of the electron beams in a magnetic deflection fields generated by the deflection device. The plurality of magnetic pieces include a first pair of magnetic pieces positioned on a neck wall side of each of side electron beams in the in-line direction and a second pair of magnetic pieces positioned on opposite sides of a center electron beam of the three electron beams in the in-line direction. The plurality of magnetic pieces are configured so as to locally modify the magnetic deflection fields to make three rasters formed on the phosphor screen by the three electron beams coincident with each other. The first pair of magnetic pieces have a portion of an axial length greater than an axial length of the second pair of magnetic pieces, where the axial lengths is measured in a plane containing the in-line direction and a longitudinal axis of the cathode ray tube.