| 摘要 |
A method of manufacturing an electron gun (10) for use in a color display tube (1) is described. The electron gun (10) is provided with an additional electrode (44), positioned between the anode electrode (21a) and the centering cup (23). This additional electrode (44) is part of the beaded unit (29) of the electron gun (10), and this enables very accurate positioning of this additional electrode (44) with regard to its distance to the main focusing section (21) as well as its rotation. This makes it possible to use this additional electrode (44) to improve the quality of the main focusing section (21) by considering it as an integral part of the main focusing section (21). For this reason this additional electrode is referred to as Main lens Field Modifier (MFM) (44). It is shown that by varying the vertical dimension of the apertures (52), (53) of the MFM (44) or the spacing between MFM (44) and main focusing section (21), it is possible to increase the effective lens diameter for spherical aberration, while the effective lens diameter for magnification is kept constant. In other words, the spot performance of the electron gun (10) is improved, while the length of the electron gun (10) is kept unaltered. With a view to obtaining the accuracy needed for a main focusing section (21) with a good tolerance behavior, this new method of manufacturing an electron gun (10) is of great importance.
|
