JPS6324294B2 - - 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.

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 the second grid, 3 is the third grid, 4 is the fourth grid
The third grid 3 is composed of a third grid 5 on the main lens side and a third grid 6 on the focus side.

As shown in FIG. 2, the third grid 5 and the fourth grid 4 on the main lens side, which constitute the third grid 3, have three circular holes a in a line, each having a bridge portion w. It is provided. Therefore, the third grid 5 and the fourth grid 4 on the main lens side are formed into a box-like body with three circular holes a in the bottom surface b.

In the electron gun configured as described above, in order to eliminate the need for dynamic convergence, it is necessary to reduce the electron beam spacing at the center plane of deflection to a certain extent. It is not possible to set the pitch to a large value.

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 allowed from the viewpoint of mechanical strength and parts processing. 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, the circular holes a become connected as shown in FIGS. 3A and 3B, and the equipotential lines change from being independent at each circular hole a to being continuous.

As a result, the electron beam 8 passing through the central axis of each circular hole 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 relative to the central axis. There is a problem that rotational symmetry is poor and astigmatism is not sufficiently alleviated.

The present invention has been made in view of the above-mentioned conventional points, and includes three beam passing holes arranged in-line in two opposing box-shaped electrodes constituting an electron lens. The rotational symmetry of the equipotential surface was improved and astigmatism was alleviated by installing an electrode with three independent circular holes arranged in-line facing the continuous circular holes in the box-shaped electrode. The purpose is to provide an in-line three-beam electron gun.

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

FIG. 5A shows a cylindrical electrode 10 in which beam passing holes for passing three electron beams are arranged in a straight line, and each hole has a cylindrical portion. FIG. 5B is an enlarged example of the opening end of FIG. 5A.

In FIGS. 6A and 6B, three circular holes a provided in the opposing surfaces of the third grid 5 and fourth grid 4 on the main lens side, which are opposite to each other to configure the electron lens, have a diameter equal to that of the hole. A cylindrical electrode 10 is set in which the circular holes a are arranged so as to be connected with each other, and three independent circular holes a are provided facing the circular holes a.

The three circular holes _a1 of the cylinder electrode 10 are provided substantially 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 equipotential surface has relatively good rotational symmetry due to the cylindrical electrode 10, which reduces astigmatism and spherical aberration. This results in an electrostatic lens configuration in which both aberrations are well-balanced.

In addition, although the case where there is one lens is explained in the said Example, this invention is not limited to the said Example, but can be applied to a multistage lens.

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, 4A and 4B are explanatory diagrams of a conventional example having a configuration to alleviate astigmatism, FIGS. 5A and 5B are longitudinal sectional front views of the cylinder electrode used in the present invention, and FIGS. Figure A is a plan view of the third and fourth grids on the main lens side to which the present invention is applied, and Figure 6B is a longitudinal sectional front view of the same. 3...3rd grid, 4...4th grid, 5
...Third grid on main lens side, 10... Cylinder electrode, a... Circular hole, a ₁ ... Circular hole of cylinder electrode.

Claims (1)

[Claims] 1. Three circular holes are formed by partially connecting the opposing surfaces of the opposing box-shaped electrodes, and a cylindrical electrode having three independent cylinders is provided behind the opposing surface, An in-line three-beam electron gun characterized in that the circular hole of the box-shaped electrode and the cylinder of the cylinder electrode are concentric circles. 2. The in-line three-beam electron gun according to claim 1, characterized in that the diameter of the opening of the cylinder electrode is enlarged.