| 摘要 |
A CRT system is provided, preventing the resolution on a phosphor screen from degrading due to the characteristic or performance variation and/or deviation of an electron gun. The electron gun has cathodes for emitting R, G, and B electron beams. First and second focusing electrodes focus the electron beams onto a phosphor screen. A drive unit has a power supply for supplying first and second focusing voltages to the first and second focusing electrodes, respectively. The second focusing voltage is an ac voltage with a parabolic waveform. The first focusing voltage is a dc voltage generated by dividing the second focusing voltage with the use of a resistor. A difference between the first and second focusing voltages generates an electrostatic quadruple lens in a space between the first and second focusing electrodes. The difference between the first and second focusing voltages is adjusted by changing the parabolic waveform of the second focusing voltage, thereby controlling the action of the electrostatic quadruple lens to compensate defocusing of the electrostatic quadruple lens.
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