Electron gun for color cathode ray tubes with side electron-beam-passing apertures of plurality of circular arcs having different radii of curvature

An in-line electron gun for a color cathode ray tube, which includes an electron beam generating means for generating and directing three electron beams along paths toward a phosphor screen, and a main lens of a large aperture type for focusing the three electron beams radiated from said electron beam generating means, said in-line electron gun for a color cathode ray tube being characterized in that:

• said main lens is formed between a focusing electrode and an accelerating electrode;
• and
• electric field correction plates disposed in each of the focusing electrode and an accelerating electrode in the vertical direction to electron beam passing axes, and have three electron beam passing apertures aligned in line, respectively, said three apertures comprising at least one central electron beam passing aperture of a key-hole shape which is symmetrical with respect to a vertical line to a central electron beam passing axis and which includes two opposite straight lines, and two side electron beam passing apertures each of which is defined by a plurality of circular arcs having different radii of curvature, connected to each other circular arc by a plurality of straight lines including at least two opposite and parallel straight lines and asymmetrical with respect to a vertical line to each side electron beam passing axis.