JPS59127346A - Color picture tube electron gun - Google Patents

Abstract

PURPOSE:To surely correct horizontal astigmatism while being able to set an interval of plates small so as to effectively check invasion of electric potential by providing plates connecting with a screening cup top and bottom of its opening and projecting into the inside of G4 electrode. CONSTITUTION:Plates 26 and 26' for correcting potential are provided top and bottom of the central beam outlet of G4 electrode 12. Namely, a screening cup 13 consists of cup-shaped electrodes while the base thereof, that is to say, the opposing surface to G4 electrode 12 is provided with the openings 30, 31 and 32 which three beams pass through respectively. And G4 electrode, the screening cup 13 and the plates 26 and 26' are electrically connected while being equipotentially impressed. The curves 27, 27' and 28, 28' in the figure are both showing the equipotential lines of the equipotential invading the inside of G4 electrode. The invasion of the equipotential lines in the vertical direction can strongly be checked by providing the plates 26, 26' while strengthening a divergent lens in the vertical direction thus extending beams in the vertical detection. Accordingly, horizontal astigmatism can surely be corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electron gun for a color picture tube, and more particularly to an electrode constituting a main lens.

[Prior art]

FIG. 1 is a sectional view of a color picture tube equipped with a conventional electron gun. On the inner wall of the face plate portion 2 of the glass envelope 1, a phosphor surface 3 is supported, in which phosphors of three colors are coated alternately in stripes. central axis 15 of cathodes 6, 7, 8;
16.17 is an opening corresponding to the cathode of the G1 electrode 9 and the G2 electrode 10 which together with the cathode constitute the triode part, the G3 electrode 11 and the shielding cup 13 which constitute the main lens, and the opening of the G3 electrode. They coincide with the central axes of the inner cylinders 20, 21, 22 that connect with the openings, and are arranged substantially parallel to each other in a common plane.

G4 electrode 12, which is the other electrode that constitutes the main lens
The central aperture and the central axis of the inner cylinder 24 that connects it coincide with the center @16, but the central axes of both outer apertures and the inner cylinder 23 and 25 that connect them coincide with 18.19 are the corresponding centers 'H1]15
, 17, and is slightly displaced outward. The inner diameter of each inner cylinder matches the diameter of the corresponding aperture. The three electron beams emitted from each cathode have central axes of 15 and 16 degrees.
7 from the triode to the main lens.

The G3 electrode 11 is set to a lower potential than the G4 electrode 12,
The high-potential 04 electrode 12 has the same potential as the shielding cup 13 and the conductive film 5 provided on the inner wall of the glass envelope l. G3,04 Opening in the center of both electrodes and inner cylinder 21.24
are coaxial, and since the inner cylinder cancels out the influence from the non-axisymmetric electrode outer periphery, the main lens formed in the center is axisymmetric, and the central beam is focused by the main lens. After that, it moves straight along the trajectory along the axis. On the other hand, the outer apertures of both electrodes, the inner cylinders 20, 22, and 23.
Since the axes of the lens elements 25 are shifted from each other, a non-axisymmetric main lens is formed on the outside. Therefore, the outer beam passes through a part of the main lens area that is deviated from the lens center axis in the direction of the center beam in the diverging lens area formed on the G4 electrode side, and at the same time the main lens focuses the outer beam. Gain concentration in a direction. In this way, the three electron beams form images on the shadow mask 4 and at the same time are concentrated so as to overlap each other. The operation of concentrating each beam in this manner is called static convergence (hereinafter abbreviated as STC). Furthermore, each electron beam is exposed to a shadow mask 4.
Only the components that excite the phosphor of the color corresponding to each beam and cause it to emit light pass through the apertures of the shadow master 4 and reach the phosphor surface 3. Further, an external magnetic deflection yoke 14 is provided to scan the electron beam on the fluorescent surface.

In recent color picture tubes, by using a self-focusing yoke as the magnetic deflection yoke, it is possible to maintain the beam concentration even when scanning over the entire fluorescent surface as long as there is a quiet convergence at the center of the fluorescent surface. Therefore, adjustment is very easy.

However, this type of yoke is designed to impart astigmatism to the beam in order to obtain self-focusing characteristics. For this reason, the beam is weakly focused in the alignment direction (hereinafter referred to as the horizontal direction) and strongly focused in the direction perpendicular to it, and the beam spot when deflected on the fluorescent surface is more horizontal than when it is not deflected. As the image is stretched, a low-brightness area called the no-guchi spreads out in the vertical direction, leading to a deterioration in resolution. This is called horizontal astigmatism. The astigmatism described above also arises from other causes. The inner cylinders 20 to 25 are provided with main lenses that focus the three electron beams so that they are axially symmetrical, but when the axial length of the main lenses becomes less than a required value, the external Electrode 11 with an axially symmetrical structure
．． Influenced by 12.

Therefore, the main lens is also non-axially symmetrical, and the electron beam suffers from astigmatism. In particular, the length of the inner cylinders 20 to 22 on the G3 side needs to be longer than the inner cylinders 23 to 25 on the G4 side,
If it is shorter than the required value, a strong focusing force will act in the vertical direction, causing astigmatism in the horizontal direction, similar to a self-focusing yoke.

Furthermore, the STC disclosed in %Application No. 137800/1983
In the electron gun to which this method is applied, the inner cylinders 20, 22 on both sides,
The tips of 23 and 25 are cut diagonally,
Especially on the 03 car pole, the inner cylinder 20°22 is the center inner cylinder 21
Since the central inner cylinder 20 is cut short in the adjacent portion, the same effect occurs as if the central inner cylinder 20 were shortened, and horizontal astigmatism is produced for the central electron beam.

In order to eliminate this astigmatism, it is necessary to intentionally provide vertical astigmatism such that the electron beam shape is stretched in the vertical direction, and to cancel it out with the horizontal astigmatism.

Japanese Patent Application Laid-Open No. 51-118957 discloses a technique in which parallel plates are provided on the left and right or above and below the mutually opposing openings of the G3 and 04 electrodes. However, - the electrode plates provided in this position have the disadvantage that the distance between them cannot be smaller than the diameter of the aperture.

That is, since the diameter of the aperture is made as large as possible in order to improve the resolution, the above-mentioned interval is also large, and therefore the influence on the electron beam is conversely reduced. Moreover, since this electrode plate needs to be provided outside the inner cylinder that connects to the opening, the effect of the electrode plate is shielded by the inner cylinder.
The influence on the electron beam is further reduced. This is no good,
It is difficult to generate vertical astigmatism large enough to cancel out horizontal astigmatism, and it is difficult to reliably correct astigmatism.

In addition, G3. The flatness or parallelism of the G4 electrode facing surface,
There is a problem in that the problem is exacerbated when attaching the electrode plate.

[Purpose of the invention]

An object of the present invention is to provide a color picture tube electron gun that can solve all of the above problems and reliably correct the horizontal astigmatism.

[Summary of the invention]

Generally, in a color picture tube electron gun, a low potential is applied to the G3 electrode and a high potential is applied to the 04'M pole, and a focusing lens is formed inside the G3 electrode and a diverging lens is formed inside the G4 electrode. The main lens is formed by combining the two.

On the G4 electrode side, the low potential of the 03tM pole penetrates, but the deeper the penetration, the weaker the diverging lens becomes, and the shallower the penetration, the stronger it becomes.

Therefore, in the present invention, electrode plates are connected to the shielding cup at the upper and lower portions of the opening thereof and protrude inside the G4 electrode, and the astigmatism in the horizontal direction is corrected by this electrode plate. In other words, the electrode plate added according to the present invention is connected to the G4 electrode and a high potential is applied to it, so the intrusion of low potential is suppressed in the vertical direction, and since there is no plate in the horizontal direction, the intrusion is prevented. I can't control it.

Therefore, only the vertical diverging lens becomes strong, the beam is stretched in the vertical direction, vertical astigmatism occurs, and horizontal astigmatism can be canceled out, so that the above objective can be achieved.

The openings in the shielding cup are generally smaller in diameter than the openings on the opposing surfaces of the 03 and 04m poles, so the spacing between the electrode plates can be set narrower, making it possible to more effectively suppress the intrusion of potential.
Horizontal astigmatism can be reliably corrected. In addition, G3. which has a great influence on focus characteristics and S'J'C characteristics.
Since the machining accuracy of the G4 electrode facing surface does not deteriorate when attaching the electrode plate, the focus characteristics of the main lens, 5TCe
Astigmatism can be corrected without any adverse effect on the image quality.

[Embodiments of the invention]

Figures 2 and 3 are cross-sectional views showing the main part (main lens part) of an embodiment of the present invention, which is made of an electrode structure in which the inner cylinders on both sides are cut diagonally in order to obtain STC. An example in which the present invention is applied to a main lens will be shown.

FIG. 2 shows a horizontal cross section of the main lens portion of the electron gun of the present invention, and FIG. 3 shows a vertical cross section thereof.

In the figure, reference numerals 26 and 26' are electrode plates for potential correction according to the present invention, and other electrode configurations other than these, particularly the shapes of the inner cylinders 20 to 25 and their effects, are described in the above-mentioned Japanese Patent Application No. 55 -137800 in detail,
The explanation will be omitted. In the main lens with such a structure, G3
In the electrode 11, the inner cylinder 20.2 for the side beam
2 is cut at an angle so that it becomes shorter at the portion adjacent to the inner cylinder 21 for the central beam, and as described above, astigmatism occurs that stretches the central beam in the horizontal direction. In order to correct this astigmatism, in this embodiment, G
Pole plates 26 and 26' for potential correction are provided above and below the central beam exit of the four electrodes 12.

That is, the shielding cup 13 is made of a cup-shaped electrode, and the bottom surface thereof, which faces the pG4 electrode, is provided with openings 30, 31, and 32 through which the three beams pass, respectively. - The central axes of these openings coincide with the central axes 15, 16.17 of the cathode 6.7.8. Also, the openings 30, 3
The diameter of 1.32 is the corresponding inner cylinder 23, 24 .
smaller than the inner diameter of 25. The electrode plates 26 and 26' are disposed above and below the aperture 31, symmetrically with respect to a horizontal axis passing through the central axis of the tab aperture 31, and parallel to the horizontal axis, and are arranged on the bottom surface of the shielding cup 13. 1°3 and the plates 26, 26' are electrically connected and the same potential is applied. In the figure, 27.27'.

28 and 28' both indicate equipotential lines of the same potential that penetrate into the G4 electrode. 27.27' is the electrode plate 26,2
The horizontal and vertical equipotential lines when 6' is not present are represented by broken lines, and 28°28' is the polar plate 26, 2.
The equipotential lines in the horizontal and vertical directions when 6' is provided are shown by solid lines. By providing the electrode plates, the invasion of vertical equipotential lines can be strongly suppressed. This strengthens the vertically diverging lens and stretches the beam vertically.

Next, the specific dimensions of this embodiment and its effects will be explained in detail.

G3. Horizontal internal diameter of G4 electrode (outer periphery) 21cm G3.O4 vertical internal diameter of electrode (outer periphery) 9.6cm Inner diameter of inner cylinders 20 to 25 5.5cm Inner cylinder for central beam 21.24 Axial length of 3, Orrrtn Axial length of inner cylinder 20, 22, 23.25 for side beam 25-0.7 Axial length of 04 ton pole (outer circumference) 6. Oran shielding hole opening diameter 4 electrode side) 3. Otran plate 26,
26' horizontal width W 4.0 wnG4 electrode voltage 25.0KV Axial distance from the G4 electrode side end surface of G3 electrode to the fluorescent surface
340 mm, and the axial length of the electrode plates 26, 26' is t as shown in FIG. Similarly, as shown in FIG. 3, the distance from the central axis of the electrode plates 26, 26' (which is the central axis of the electron gun, and corresponds to the central axis 16 in FIG. 1) is h. do.

Here, the horizontal focusing voltage Vfh and the vertical focusing voltage Vfv are defined as follows.

That is, the focusing voltage (G3 electrode voltage) when the focusing position of the electron beam incident on the main lens along the horizontal cross section coincides with the fluorescent surface is the horizontal focusing voltage Vfhs, which is incident on the main lens along the vertical cross section. The focusing voltage when the focusing position of the electron beam coincides with the fluorescent surface is defined as the vertical focusing voltage Vfv.

If Vfh and Vfv match, no astigmatism will occur.

If Vfh<vfv, then in the horizontal direction, Vt h >
If it is Vfv, it means that vertical astigmatism has occurred.

Figure 4 shows the difference in focusing voltage in the horizontal and vertical directions, Vfh - vf.
The relationship between v and the axial length t of the electrode plates 26, 26' is shown. This is obtained by numerically calculating a three-dimensional electric field distribution using distance as a parameter, and then analyzing the electron beam trajectory within the electric field. Note that the focusing position of the electron beam is 0.0 mm horizontally or vertically from the central axis.
The electron beam emitted at an angle of 5° was focused by the main lens, and the point was determined to intersect the central axis again.

As can be seen from Figure 4, when t = 0, that is, when there is no plate, Hlvfh (Vtv) causes horizontal astigmatism. By extending the plate, vertical astigmatism Astigmatism occurs and cancels out the horizontal astigmatism.''At 1.5m and 7=2.3mm, the horizontal and vertical astigmatism completely cancel each other out. Eliminate, v
fh=■fv, and horizontal astigmatism can be completely corrected.

In this embodiment, the electrode plate has a rectangular shape, but various other shapes can be used, such as a shape in which a part of a cylinder is cut out.

In addition, the shielding cup 13 is pressed, and the electrode plate 26,
By integrally shaping 26', an increase in the number of parts can be suppressed.

5 and 6 show essential parts of other embodiments of the present invention, and are vertical sectional views of an electron gun main lens provided with an electric field correction plate integrated with a shielding cup. Figure 5 shows an example of forming an electrode plate by pressing the beam passage hole portion, and Figure 6
The figure shows an example in which the upper and lower parts of the beam passage hole are pressed to form electrode plates.

Furthermore, it goes without saying that the present invention can be applied not only to the pi-potential type main lens shown in FIG. 1, but also to uni-potential type or other types of main lenses.

However, in the above explanation, the correction electrode plate is placed at 04 of the shielding cup.
- is provided on the pole side end face, but when using an electrode structure that has a closed end face on the electron beam exit side (of course, an electron beam passage hole is also formed) as the G4 electrode, it is necessary to use a correction electrode plate. is provided on this closed end surface.

〔Effect of the invention〕

According to the present invention, by adding a simple plate inside the 04 electrode, it is possible to provide astigmatism that stretches the beam in the vertical direction, thereby reducing horizontal astigmatism. It can be corrected reliably.Moreover, the electrode plate is G
It is provided on the beam exit side of the 4 electrodes, and does not deteriorate the machining accuracy of the surface of the G4 electrode that faces the 03 electrode, so it does not have any negative effect on the focus time and S'I"C characteristics of the main lens. Astigmatism can be corrected.

[Brief explanation of drawings]

FIG. 1 is a sectional view schematically showing an in-line color picture tube, FIG. 2 is a horizontal sectional view showing a main lens according to an embodiment of the present invention, and FIG. 3 is a vertical sectional view showing the main lens. The sectional view, FIG. 4, is a diagram for explaining the present invention in detail,
FIGS. 5 and 6 are vertical sectional views showing main lenses of other embodiments of the present invention, respectively. 1...Glass envelope, 2...Face plate, 3
... Fluorescent surface, 4... Shadow mask, 5... Conductive film, 6°7.8... Cathode, 9... G1 electrode, 10.
... G2 electrode, 11... G3 electrode, 12... G4 electrode, 13... Shielding cup, 14... External porcelain deflection yoke, 15, 16° 17... Central axis, 20, 21, 2
2, 23, 24゜25...Inner cylinder, 26.26'.
... Pole plate for generating vertical astigmatism. Agent: Patent attorney Akio Takahashi. Figure 2 3 Ward'fI4- Ward/ρOρL

Claims (1)

[Scope of Claims] 1. An electron beam generating means for generating three electron beams aligned in parallel in the same plane toward a fluorescent surface; and a passage hole for the electron distribution beam; between the beam generating means and the fluorescent surface; second and third electrodes; and the second electrode and the third electrode.
a pair of electrode plates disposed symmetrically with respect to the plane between the electrodes, the first and second electrodes constituting a lens that focuses the electron beam on the fluorescent surface; A Cassie picture tube electron gun, wherein astigmatism of the electron beam is corrected by the pair of electrode plates. 2. A patent claim characterized in that the third electrode is a cup-shaped electrode having the same potential as the second electrode, and the pair of electrode plates are provided on the bottom surface of the cup-shaped electrode. A color picture tube electron gun according to item 1.