JPH0546655B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an in-line electron gun for a color cathode ray tube, and particularly relates to improvement of its convergence characteristics.

[Conventional technology]

Figure 2 is a longitudinal cross-sectional view of a conventional in-line electron gun 1, where 2 is a heater, 3 is a cathode, and 4 is a control electrode.
G ₁ and 5 are the first accelerating electrodes G ₂ , and 6 and 7 are the focusing electrodes
The first and second members constituting G ₃ , 8 and 9 are the second members
The first and second members constituting the accelerating electrode _G4 , 1
0 is the mounting electrode, 11R, 11G, 11B are the members 6
An electric field lens 12 is formed by the through holes 6r, 6g, and 6b (hereinafter referred to as a pre-lens), and 12 is an electric field lens formed by the members 7 and 8 (hereinafter referred to as a main lens).

FIG. 3a is a front view of the conventional control electrode _G1 , and FIG.
The through holes 4r, 4g, and 4b through which G and B pass are circular, and the cross-sectional shapes of the electron beams R, G, and B that have passed through these through holes 4r, 4g, and 4b are also circular.
After passing through the circular through holes 5r, 5g, 5b of the accelerating electrode G2 and the pre-lenses 11R, 11G, 11B, the electron beams enter the main lens 12 as electron beams with a circular cross section that diverge uniformly in each direction, respectively. It converges and hits the fluorescent screen. The dash-dotted lines in FIG. 2 indicate the center paths of the electron beams R, G, and B, respectively. Hereinafter, the convergence effect of the main lens 12 will be described with the arrangement direction of the electron beams R, G, and B as the X axis, the direction perpendicular to the X axis as the Y axis, and the direction in which each electron beam advances as the z axis.

FIG. 4a shows the members 7 and 8 constituting the main lens 12.
Figure b is a front view of the member 7, taken along line bb. Through holes 7r, 7g, 7
b is an oval wall surface 7 formed at equal intervals on the X axis.
w is formed in a shape surrounding them. Note that the other member 8 constituting the main lens 12 is also formed symmetrically with the member 7. The broken lines in the figure indicate equipotential surfaces, and the main lens 12 forms a rotationally asymmetric electric field lens in which the X-axis direction is longer than the Y-axis direction.

FIG. 5 is a schematic diagram showing the structure of the main lens 12 as an optical lens system, in which 13R, 13G, and 13B are small lenses formed in the through holes 7r, 7g, and 7b, respectively, and 14 is the small lens formed in the parts 7 and 8. Rotationally asymmetric common lenses formed between 15R, 15G, 15B
are small lenses formed in the through holes 8r, 8g, and 8b of the member 8, respectively.

[Problem that the invention seeks to solve]

In the conventional in-line electron gun described above, the common lens 14 is a rotationally asymmetric electric field lens, and therefore the focusing electrode _G3 has the following refractive power imbalance.

The refractive power in the Y-axis direction is stronger than the refractive power in the X-axis direction (astigmatism).

The refractive power in the X-axis direction and the refractive power in the Y-axis direction are stronger on both sides than at the center (spherical aberration).

Regarding the refractive power in the X-axis direction that acts on the electron beams R and B passing through the through holes on both sides, the refractive power in the direction from the outside to the center is stronger than the refractive power in the direction from the center to the outside.

Arrows F ₁ , F ₂ , F ₃ in Fig. 4a and Fig. 5 are
It shows the strength of the refractive power in the X-axis direction acting on each of the electron beams R, G, and B, and for the above reason, the relationship is F ₁ >F ₂ >F ₃ .

FIG. 6 is a diagram showing an example of the spot shape of electron beams R, G, and B converged on a phosphor screen. Due to the above reasons, the spot shape of each electron beam is not circular, and furthermore, the spot shape of each electron beam is not circular. Beams R and B have a halo H in the direction of refractive power F ₁ due to the above reasons.
is added.

Since the spot shape of each electron beam is not circular as described above, there are problems in that resolution is lowered, contrast is lowered, and color shift occurs.

In order to solve these problems, the control electrode
There is a prior art technique that corrects the rotational asymmetry of a common lens by forming an elongated planar concave portion following the through hole in _G1 .

FIG. 7a is a front view thereof, and FIG. 7b is a sectional view taken along line bb. In this example, circular through holes 4r, 4g,
4b, a rectangular recess 1 whose Y-axis direction is longer than the X-axis direction is formed on the surface facing the first accelerating electrode _G2 .
6, respectively.

This concave portion 16 brings the crossover point of the X-axis component of each electron beam closer to the cathode 3 than that of the Y-axis component, and moves the convergence position of the X-axis component by the main lens 12 from the convergence position of the Y-axis component. Since it acts to bring the lens closer to the main lens 12 side, it has the effect of correcting the above-mentioned imbalance.

However, the control electrode G ₁ is connected to the cathode 3 with a narrow gap.
and facing the first accelerating electrode _G2 , and there were also dimensional constraints, which caused problems in that sufficient correction could not be made and machining was difficult.

The present invention has been made to solve these problems, and it is an object of the present invention to provide an electron gun that corrects the above imbalance.

[Means for solving problems]

The electron gun according to the present invention has electron beams R, G,
In an in-line electron gun, the X-axis direction in which the electron beams B are arranged is longer than the Y-axis direction, and the in-line electron gun has a focusing electrode that forms a rotationally asymmetric electric field lens common to the electron beams R, G, and B. The three through holes through which the electron beam passes are each smaller in the X-axis direction than in the Y-axis direction, and the central through-hole is smaller in both the X-axis and Y-axis directions than the through-holes on both sides. It is something.

[Effect]

According to this invention, the closer the inner peripheral surface of the through hole formed in the focusing electrode is to the passing electron beam (the smaller the hole diameter), the stronger the refractive power of the small lens formed by the through hole becomes. , acts to bring the convergence point of the electron beam passing through the through hole closer to the main lens common to the three electron beams.

Therefore, since the X-axis direction of each through-hole is smaller than the Y-axis direction, the X-axis component of the electron beam passing through each through-hole is refracted more strongly than the Y-axis component, so the above-mentioned imperfection of the main lens is Balance can be corrected.

Also, since the center hole is smaller in both the X-axis and Y-axis directions than the holes on both sides, the electron beam passing through the center hole is smaller in the X-axis and Y-axis directions than the electron beam passing through the holes on both sides. Since both lenses receive strong refractive power, the above-mentioned imbalance of the main lens can be corrected.

[Embodiments of the invention]

Figure 1a shows a focusing electrode that constitutes the main part of this invention.
A front view of one member 7 constituting _G3 , and FIG.

In the figure, the central through hole 7g is the same as the through holes 7g on both sides.
It is formed to have a smaller size in both the X-axis direction and the Y-axis direction than r and 7b, and each through hole 7
g, 7r, and 7b are each smaller in the X-axis direction than in the Y-axis direction, and are formed into oval shapes symmetrical to the X- and Y-axes.

In this way, the central through hole 7g is replaced with the through hole 7g on both sides.
When r is smaller than 7b, the refractive power of the small lens 13G formed by the through hole 7g is equal to that of the through hole 7 on both sides.
It is stronger in both the X-axis direction and the Y-axis direction than the small lenses 13R and 13B formed by r and 7b.

Further, the refractive power in the X-axis direction and the refractive power in the Y-axis direction of each through hole is also stronger in the X-axis having a smaller diameter than in the Y-axis.

Therefore, the above-mentioned imbalance of the main lens 12 is corrected by the latter, and the above-mentioned imbalance is corrected by the former.

Note that the above imbalance can be corrected in a well-balanced manner by establishing the following relationship.

Yc／Xc＜Ys／Xs However, Yc: Dimension in the Y-axis direction of the central through-hole Xc: Dimension in the X-axis direction of the central through-hole Ys: Dimension in the Y-axis direction of the through-holes on both sides Dimensions of holes in the X-axis direction In the above embodiments, each through hole has an oval shape, but it may also be an oval shape.

〔Effect of the invention〕

As described above, according to the present invention, the three through holes for electron beam passage in the focusing electrode are each smaller in the X-axis direction than in the Y-axis direction, and the central through-hole is smaller than the through-holes on both sides in the X-axis. Since it is formed to have small dimensions in both the direction and the Y-axis direction, it is possible to correct the imbalance in refractive power between and, which was explained at the beginning as a problem with the focusing electrode G3, thereby improving resolution and contrast. , it is possible to provide an electron gun that does not cause color shift.

[Brief explanation of the drawing]

FIG. 1a is a front view of an embodiment of the first accelerating electrode _G2 which is the essential part of this invention, and FIG.
2 is a longitudinal sectional view of the in-line electron gun, FIG. 3 a is a front view of the conventional control electrode _G1 ,
Figure 4b is a cross-sectional view taken along the line b-b, Figure 4a is an enlarged cross-sectional view of the main lens of the electron gun, and figure b is a cross-sectional view of the electron gun.
5 is a schematic diagram of the main lens represented by an optical lens, FIG. 6 is a diagram showing the shape of each electron beam spot on the phosphor screen, and FIG. 7 a
is a front view of an example of control electrode G ₁ according to the prior art,
Figure b is a sectional view taken along line b-b. 1... In-line electron gun, 6, 7... Focusing electrode G ₃ , 7r, 7g, 7b... Through hole, 8, 9...
Second accelerating electrode, 12... main lens, 14... common lens. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. The X-axis direction in which the electron beams R, G, and B are arranged is longer than the Y-axis direction, and the electron beams R,
In an in-line electron gun that has a focusing electrode that forms a rotationally asymmetric electric field lens common to G and B, the three through holes for electron beam passage formed in the focusing electrode have their X-axis direction aligned with their Y-axis direction. An in-line electron gun characterized in that the central through-hole is smaller in both the X-axis direction and the Y-axis direction than the through-holes on both sides. 2. The in-line electron gun according to claim 1, wherein each of the three through holes has an oval or oval shape symmetrical with the X and Y axes.