Electron gun assembly of color ray tube

A color cathode ray tube assembly having a horizontal plane and a vertical plane normal to the horizontal plane comprising:

• a phosphor screen;
• quadra-potential electron gun means for generating and directing three electron, beams toward the phosphor screen, said electron gun means including:
• (a) cathode means, comprised of three cathodes which are arranged in a line, for emitting the three electron beams in the horizontal plane;
• (b) first electrode means, comprised of first, second and third grid electrodes separated from each other, for forming prefocus lenses to accelerate and control the electron beams emitted from said cathode means, respectively, by a constant amount;
• (c) second electrode means, comprised of a fourth grid assembly which includes first, second and third electrode segments separated from each other and closely arranged, for forming asymmetrical lenses each having a lens power to converge the accelerated and controlled electron beams in the horizontal plane and diverge the accelerated and controlled electron beams in the vertical plane, respectively and for forming first symmetrical sublenses with said first electrode means for converging the electron beams, each having a lens power which is dynamically changed in accordance with the deflection amount of the electron beam on one said side of said asymmetrical lenses closer to said cathode means;
• and
• (d) third electrode means, comprised of fifth sixth grid electrodes separated from each other, for forming symmetrical main lenses to focus the electron beams passing through said second electrode means onto the phosphor screen by a constant focusing amount, respectively and for forming second symmetrical sublenses with said second electrode means on another side of said asymmetrical lenses farther from said cathode means for converging the electron beam, each having a lens power which is dynamically changed in accordance with the deflection of the electron beam;
• first connecting means for connecting the third grid electrode to the fifth grid electrode;
• second connecting means for connecting the first segment to the third segment;
• first voltage applying means for applying a high voltage through said first connecting means to the third and fifth grid electrodes to maintain the third and fifth grid electrodes at a same potential level;
• second voltage applying means for applying a D.C. constant potential to the second electrode segment;
• and
• third voltage applying means for applying a dynamic voltage through said second electrode segment to the first and third electrode segments, having a dynamic level which is lower than the high potential level applied to said third and fifth grid electrodes when a deflection amount of the electron beams is other than zero, and is varied in accordance with the deflection amount of the electron beams,
• wherein the first and second symmetrical sublenses dynamically focus the electron beams onto the phosphor screen, and the lens power of the asymmetrical electron lenses formed in said second electrode means is dynamically changed in accordance with the deflection of the electron beams so that each of the electron beams is vertically elongated to have an elliptical shape.