JPH0546656B2 - - 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]

FIG. 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 forming 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, 4b through which G and B pass are circular, and the cross-sectional shape of each electron beam passing through each of these through holes 4r, 4g, 4b is also circular, and the first accelerating electrode
G ₂ circular hole and pre-lens 11R, 11
After passing through G and 11B, the electron beams enter the main lens 12 as electron beams with a circular cross section that are uniformly diverging in each direction, and are converged and impinge on the phosphor screen.
The dashed-dotted lines in FIG. 2 indicate the electron beams R and
The center paths of G and B are shown. Below, electron beam R,
The convergence effect of the main lens 12 will be described with the direction in which G and B are arranged as the X axis, the direction orthogonal 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 with 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.

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

[Means for solving problems]

The electron gun according to the present invention includes a first accelerating electrode having three through holes for passing the electron beam, and an X-axis direction facing the accelerating electrode and in which the electron beams R, G, and B are arranged. In an in-line electron gun having a focusing electrode that is longer than the Y-axis direction and forms a rotationally asymmetric electric field lens common to the electron beams R, G, and B, on the surface of the first accelerating electrode on the focusing electrode side. A recessed portion communicating with the central through-hole is formed in the top.

[Effect]

According to this invention, the recess formed on the surface of the first accelerating electrode on the focusing electrode side and communicating with the central through hole increases the divergence angle of the X-axis component of the electron beam.
Since the crossover point (corresponding to the object point) is moved closer to the cathode than that of the Y-axis component, that is, it is moved away from the main lens common to the three electron beams, the main lens converges the X component (image point).
This produces the effect of bringing the Y-axis component closer to the main lens than the convergence point of the Y-axis component.

Therefore, when the above-mentioned recess is provided only in the central through hole, or when recesses are formed in each of the three through holes, the recesses on both sides have a planar shape that is smaller in the X-axis direction and the Y-axis direction than the central recess. In this case, the convergence point of the electron beam passing through the central through-hole will be closer to the main lens than the convergence point of the electron beam passing through the through-holes on both sides, so the ratio of the size of the central recess and the recesses on both sides should be adjusted appropriately. By setting, the above-mentioned imbalance of the main lens can be corrected.

[Embodiments of the invention]

Figure 1a is a front view of an embodiment of the first accelerating electrode _G2 constituting the main part of the present invention, and Figure 1b is the
-B is a sectional view taken along the arrow. In the figure, 17r,1
7g and 17b are circular through holes 5r and 5g, respectively.
5b is a rectangular recess formed on the surface facing the focusing electrode _G3 , and the dimension Xc in the X-axis direction and the dimension Yc in the Y-axis direction of the central recess 17g are as follows.
Dimension Xs of the recesses 17r and 17b on both sides in the X-axis direction
and Ys in the Y-axis direction, and have the same depth.

Next, the function of the recess will be explained.

A recess formed on the surface communicating with the through hole and facing the focusing electrode _G3 reduces the divergence angle of the electron beam passing through the through hole, and moves its crossover point away from the cathode surface (closer to the main lens). , has the effect of moving the convergence point of the main lens away from the main lens.

This effect becomes stronger as the wall surface formed by the recess approaches the hole, and the longer the hole is, the more
The deeper the recess is (the higher the wall height)
Get stronger.

Therefore, even in the embodiment described above in which recesses are formed in the three through holes 5r, 5g, and 5b, the recesses 17r and 17b on both sides are smaller than the central recess 17g.
has smaller dimensions in the X- and Y-axis directions and is closer to the wall surface, so the convergence points of the electron beams R and B are closer to the main lens 12 than the convergence point of the electron beam G. Therefore, by appropriately setting the ratio of both sizes, the above-mentioned imbalance of the main lens 12 can be corrected.

It should be noted that if the size of each of the recesses 17r, 17g, and 17b is made smaller, the result will be a case where only the central recess 17g is formed, but it is clear that similar effects can be obtained in this case as well.

Further, although the shape of the recessed portion is square in the above embodiment, it may be circular, oval, or oval.

〔Effect of the invention〕

As described above, according to the present invention, the concave portion communicating with the central through hole is formed on the surface of the first accelerating electrode on the focusing electrode side, so that the electron beam passing through the central through hole is focused. This makes it possible to bring the point closer to the main lens than the convergence point of the electron beam passing through the holes on both sides of the main lens. This has the effect of making it possible to correct the spot shape of the electron beam, thereby eliminating deterioration in resolution, contrast, and occurrence of color shift.

[Brief explanation of drawings]

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 showing the main lens as an optical lens, and FIG. 6 is a diagram showing the shape of each electron beam spot on the phosphor screen. DESCRIPTION OF SYMBOLS 1... In-line electron gun, 5... First accelerating electrode G ₂ , 5r, 5g, 5b... Through hole, 6, 7...
...Focusing electrode _G3 , 8, 9...Second accelerating electrode, 1
2...Main lens, 14...Common lens, 17r,
17g, 17b...square recesses. In addition, in each figure,
The same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A first hole having three through holes for electron beam passage.
, and the X-axis direction facing this acceleration electrode and in which the electron beams R, G, and B are arranged is Y.
In an in-line electron gun having a focusing electrode that is longer than the axial direction and forms a rotationally asymmetric electric field lens common to the electron beams R, G, and B, on the surface of the first accelerating electrode on the focusing electrode side. , an in-line electron gun characterized by forming a recess that communicates with a central through hole. 2. Concave portions are formed in communication with each of the three through holes formed in the first accelerating electrode, and the concave portions on both sides are formed in a planar shape smaller than the central concave portion in both the X-axis direction and the Y-axis direction. An in-line electron gun according to claim 1, characterized in that: