JPS6324293B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a color picture tube equipped with an in-line three-beam electron gun.
The purpose is to improve the image quality of color picture tubes by improving the focus characteristics.

FIGS. 1A and 1B show an example of a conventional in-line three-beam electron gun, in which:
1 is a first grid arranged on the same plane, 2 is a second grid, 3 is a third grid, and 4 is a fourth grid, and the third grid 3 is a third grid 5 on the main lens side and a third grid on the focus side. It consists of 6.

As shown in FIG. 2, the third grid 5 and fourth grid 4 on the main lens side, which constitute the third grid 3, have a bridge portion w and three circular holes a.
are arranged in a row. Therefore, the third grid 5 and the fourth grid 4 on the main lens side are located on the bottom surface b.
It has a box-like shape with three circular holes a.

In order to eliminate the need for dynamic convergence in the electron gun configured as described above, it is necessary to reduce the electron beam spacing at the deflection center plane to some extent. The pitch of the circular holes a of the 4-grid 4 cannot be set large.

On the other hand, each circular hole a is preferably formed large in order to reduce the spherical aberration of the main lens, so the bridge portion w existing between each circular hole a is It is customary to make each circular hole a large by making it as small as possible.

However, if the circular holes a are made too large, as shown in FIGS. 3A and 3B, the circular holes a are connected, and the equipotential lines at each circular hole a change from being independent to being continuous. As a result, the electron beam 8 passing through the center axis of each circular hole a is subjected to astigmatism more than the spherical aberration is reduced, resulting in poor focusing of the electron beam and poor resolution on the screen.

As an improvement measure, it has been proposed to install an auxiliary electrode plate 9 between the circular holes a as shown in Figures 4A and 4B, but in this case as well, the formation of the equipotential surface is rotated about the central axis. There is a problem that symmetry is poor and astigmatism is not sufficiently alleviated.

This invention was made in view of the above-mentioned conventional points, and consists of two opposing surfaces of the two opposing box-shaped electrodes constituting the main lens, improving the rotational symmetry of the equipotential surface, Another object of the present invention is to provide an in-line three-beam electron gun with reduced astigmatism.

Embodiments of the present invention will be described below with reference to the drawings.

In FIGS. 5A and 5B, three circular holes a forming the main lens and provided on the opposing surfaces of the main lens side third grid 5 and fourth grid 4 are shown.
The diameter is made larger than the hole interval, and each circular hole a is configured so as to be connected, and the diameter is larger than the opposing surface.
A second electrode 9 (see FIG. 6), which has three independent circular holes a, is set at a position that is set back by the same amount.

The three circular holes _a1 of the second electrode 9 are provided concentrically with the three circular holes a that are connected to each other.

With this configuration, the aperture of the main lens is close to the diameter of the circular hole a on the opposing surface, and the second electrode 9 ensures relatively good rotational symmetry on the equipotential surface, eliminating astigmatism. The electrostatic lens has a well-balanced structure in both spherical aberration and spherical aberration.

It is recommended that the distance l between the opposing surface and the second electrode 9 be set to approximately the radius of the circular hole of the second electrode 10.

Although the above embodiment describes the case where there is only one lens, the present invention is not limited to the above embodiment and can be applied to multi-stage lenses.

As explained above, according to the present invention, it is possible to construct an electron lens with small both spherical aberration and astigmatism, and it is possible to improve the focusing degree of the electron beam and improve the resolution on the screen. There are advantages that can be achieved.

[Brief explanation of the drawing]

FIG. 1A is a plan view showing an example of a conventional in-line three-beam electron gun, FIG. 1B is a longitudinal sectional front view of the same,
Fig. 2 is a perspective view showing an example of the third and fourth grids on the main lens side, Fig. 3A is a plan view when the diameter of the circular hole is increased, Fig. 3B is a longitudinal sectional front view of the same, and Fig. 4A 4B is an explanatory diagram of a conventional example configured to alleviate astigmatism, FIG. 5A is a plan view of the third and fourth grids on the main lens side to which the present invention is applied, and FIG. 5B is a longitudinal front view of the same. figure,
FIG. 6 is a plan view of the second electrode. 3...3rd grid, 4...4th grid, 5
...Third grid on the main lens side, 9...Second electrode,
a...Circular hole, _a1 ...Circular hole of the second electrode.

Claims (1)

[Claims] 1. A second electrode is formed by partially connecting three circular holes on the opposing surfaces of the opposing box-shaped electrodes, and a second electrode having three independent circular holes is provided at a position set back from the opposing surface by a predetermined distance, 3 of the box-shaped electrode and the second electrode
An in-line three-beam electron gun characterized in that each of the circular holes is concentric.