| 摘要 |
A color display device with an improved focus performance. Conventional color display tubes with DAF have an electron gun with a second focusing electrode (25) driven with a dynamic voltage which is varied synchronously with the deflection field. The dynamic quadruple lens formed between the first focusing electrode (23) and the second focusing electrode (25) is designed such that the horizontal lens action, which arises when the voltage on the second focusing electrode is increased, should be compensated by the main lens which becomes weaker when the voltage on the second focusing electrode is increased. In practice, this is not possible in the required range of the dynamic voltage on the second focusing electrode, leading to a deterioration of the focus performance of the color display device. This problem is solved by applying a dynamic voltage to the first focusing electrode so that it is possible to focus the electron spots on the display window (3) in the horizontal and vertical directions, resulting in an optimally focused picture.
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