Abstract: An electron gun for a color cathode ray tube includes a triode having a cathode, a control electrode and a screen electrode for producing an electron beam, and first, second, third and fourth focus electrodes and a final accelerating electrode for accelerating and focusing the electron beam. A predetermined static focus voltage is supplied to the first and third focus electrodes, a dynamic focus voltage synchronized with a deflection signal is supplied to the second and fourth focus electrodes, and an anode voltage higher than the highest dynamic focus voltage is supplied to the final accelerating electrode. Thus, by means of a dynamic and axially symmetrical lens, astigmatism of the electron beam spot on the periphery of the screen is improved, thereby forming an almost circular beam spot.

Abstract: An electron gun for a color cathode ray tube having sequentially formed a cathode, a control electrode, a screen electrode, a focus electrode and a final accelerating electrode, wherein the focus electrode is constituted by first and second focus electrodes. The first focus electrode includes an evenly formed electron beam inlet plane and an electron beam outlet plane in which a portion for shaping a central electron beam passing hole is formed convexly in respect to portions for shaping outer electron beam passing holes, while the second focus electrode comprises an evenly formed electron beam outlet plane and an electron beam inlet plane in which a portion for shaping a central electron beam passing hole is formed concavely in respect to portions for shaping outer electron beam passing holes. The quadruple lens formed between outer electron beam passing holes is formed asymmetrically, to improve the convergence characteristic.