Patent ID: 6469459
Filing Date: 2002-10-22
Classification: H01J

Abstract:
A cathode ray tube apparatus comprising:an envelope having a screen; and an electron gun assembly constructed by a cathode for emitting an electron beam, and a main lens including a focus electrode, an intermediate electrode, and a final acceleration electrode, to focus the electron beam emitted toward the screen, wherein the intermediate electrode is provided between the focus electrode and the final acceleration electrode, the main lens includes a focusing area positioned in a side of the focus electrode and having a focusing force, and a diverging area positioned in a side of the final acceleration electrode, having a diverging force, and being continuous to the focusing area, the intermediate electrode has at least one hole having a non-circular shape for allowing the electron beam to pass and is provided in the focusing area in the side of the focus electrode, and a focusing force curve expressing a focusing force along a tube-axis direction of the cathode ray tube apparatus in the focusing area has at least two convex parts respectively being at first and second levels, and a concave part provided between the convex parts and being at a third level sufficiently lower than focusing forces of the first and second levels, the third level is set to a lowermost level at which a focusing or diverging force is not substantially effected on the electron beam or a focusing or diverging force is sufficiently small even if it is effected, the intermediate electrode is positioned near an area of the tube-axis that corresponds to the lowermost level of the focusing force curve, and at least one of the electrodes constructing the main lens is applied with a dynamic voltage which changes in synchronization with deflection of the electron beam.