Abstract: A CRT device with an electron gun provided therein includes control means for controlling voltages applied to a cathode and a control electrode constituting the electron gun. The control means exerts control on each electrode voltage so that the difference between the cutoff voltage of the cathode and the voltage of the control electrode is greater when the luminance level of a luminance signal separated from picture signal is higher, thereby minimizing a spot diameter.

Abstract: A color picture tube apparatus comprises auxiliary electrodes provided between first and second focusing electrodes, a nonaxisymmetric electrostatic lens is generated between the auxiliary electrodes and a focusing lens is generated between the first focusing electrode and the auxiliary electrode. A dynamic voltage V.sub.d is applied to the first and second focusing electrodes. Consequently, the effect of compensating the astigmatism of the electron beam caused by the deflection magnetic field and the defocus of the electron beam can be increased, the dynamic voltage can be decreased, and as a result, the cost of the circuit can be reduced. As the focusing function of the additional focusing lens is weakened and the electron beam trajectory is expanded, the magnification of the lens both at the center and the periphery of the screen can be equalized substantially and the uniformity of the focus of the electron beam between that at the center of the screen and that at the periphery of the screen becomes high.

Abstract: A color picture tube apparatus comprises cathodes, a control electrode, an accelerating electrode, a first focusing electrode, a second focusing electrode and a final accelerating electrode, a voltage applying means which applies a dynamic voltage which increases with increasing deflection angle to the second focusing electrode, a resistor which is connected between the first and second focusing electrodes. Electron beam through holes that are vertically oblong are provided at the facing sides of the second focusing electrode and the final accelerating electrode. A quadrupole electric field lens is formed wherein a focusing effect is obtained in the horizontal direction and a diverging effect is obtained in the vertical direction when the potential level of the second focusing electrode is higher than that of the first focusing electrode.