JPH0240841A - Color picture tube - Google Patents

Abstract

PURPOSE:To enable the display of a satisfactory picture image by forming the main lens of an electron gun of an electrostatic lens passing three electron beams in common without crossing to each other, and forming the auxiliary lens of three independent electrostatic lenses passing the three electron beams separately. CONSTITUTION:The main lens 21 of an electron gun 16 is formed of one electrostatic lens passing three electron beams in common without crossing to each other. The auxiliary lenses 20a-20c are formed so that they have the action of deflecting a pair of side beams 22a, 22c in the directions separating to each other, as well as the action of preliminarily converging three electron beams 22a-22c, whereby the spherical aberration of the pair of side beams 22a, 22c caused in the main lens 21 can be made to the same level as the spherical aberration of the center beam 22b. As the object point of the pair of side beams 22a, 22c goes ahead, the excessive concentration of the pair of the side beams 22a, 22c is corrected. Hence, a picture image of a satisfactory grade can be displayed.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Field of Application) The present invention relates to a color picture tube, and in particular, to reducing the spot diameter of an electron beam on a phosphor screen and properly controlling three electron beams. The present invention relates to a color picture tube equipped with an electron gun that can concentrate electrons.

(Prior Art) A color picture tube has an envelope consisting of a panel and a funnel-shaped funnel integrally joined to the panel. A phosphor screen consisting of three color phosphor layers is formed on the inner surface. Furthermore, an electron gun that emits three electron beams is installed in the neck of the funnel, and the three electron beams emitted from the electron gun are irradiated onto the phosphor screen to display a color image on the phosphor screen. It is formed in a structure that Therefore, in order to improve the image quality of this color picture tube, it is necessary to reduce the spot diameter of the electron beam on the phosphor screen, and the diameter of the spora 1 is determined by the performance of the electron gun. It is well known that

In general, an electron gun for a cathode ray tube such as a color picture tube has an electron beam generation section consisting of a cathode that generates an electron beam and an electrode that controls the emission of the electron beam from the cathode, and an electron beam from the electron beam generation section. One means of improving electron gun performance is to have an auxiliary lens (prefocus lens) that prefocuses the electron beam, and a main lens that accelerates and focuses the electron beam that has been prefocused by this auxiliary lens toward a phosphor screen. As a result, efforts are being made to improve the performance of the main lens.

The above-mentioned main lens is often an electrostatic lens, and is constructed by arranging a plurality of cylindrical electrodes with electron beam passage holes coaxially on the tube axis and applying a predetermined potential to each electrode. be done. There are several types of electrode configurations for this main lens, but in order to improve the performance of the electron gun in any of them, the distance between the electrodes is basically long and the long-focus electron beam has a gentle potential gradient. It is effective to use a lens, or to make a large-diameter electron lens by increasing the diameter of the electron beam passage hole.

However, since the electron gun of a cathode ray tube is generally placed inside a narrow neck, it is necessary for long focus electron lenses to ensure that the focused electric field formed between the electrodes is not disturbed by charges on the inner surface of the neck. be. Further, in the case of a large-diameter electron lens, the diameter of the electron beam passage hole is physically limited by its narrow neck diameter. In particular, in devices such as color picture tube electron guns that emit three electron beams in a delta array that passes through the vertices of a triangle or in an inline array that passes on the same plane, the smaller the interval between the electron beams, the more the three electron beams are emitted. It is desirable to reduce the electrode spacing because it is easier to concentrate and the deflection power can be reduced.

As a solution to this problem, in particular, for an electron gun that emits three electron beams in an in-line arrangement, the main lens is a large-diameter electron lens through which the three electron beams pass through in common and intersectingly, as disclosed in Japanese Patent Publication No. 49-5591 and This is shown in U.S. Pat. No. 4,528,476. As shown in the optical equivalent diagram in FIG. 5, this electron gun consists of three electron beams (2a), (2b), ( 2c) are three independent auxiliary lenses (3a) and (3b) on the front side.

After being prefocused by (3C), it passes through the center of the main lens (4) consisting of one large-diameter electron lens, and then the pair of side beams (2a) and (2c) are
The beam is strongly deflected by the deflecting means (5a) and (5c) as shown by .degree., and is concentrated on the phosphor screen (6).

Therefore, this electron gun has a pair of side beams (2a
), (2c), a large deflection aberration or coma aberration occurs, and the spot shape on the phosphor screen (6) is different from that of the center beam (2b), making it difficult to fully demonstrate the performance of the large-diameter electron lens. Can not.

In order to eliminate the deflection aberration or coma aberration of the pair of side beams (2a) and (2c), as shown in FIG.
4. :A [t le 3m child t:j-mu (2a), (2b
), (2c) are made parallel, the center beam (2b) hits the center of the lens (4), and the pair of side beams (2a
), (2C) should pass through its periphery, but in such an electron gun, when the center beam (2b) is focused on the phosphor screen (6), a pair of side beams ( 2a) and (2c) are concentrated in front of the phosphor screen (6) due to the strong refraction of the main lens (4), resulting in overfocus. Also, at this time, the spot shape on the phosphor screen (6) is the same (
B) As shown in the figure, for the center beam, (7
(7a) for the pair of side beams (2a) and (2c) while being properly focused as shown in b).
, as shown in (7c), it is in an overfocused state and has coma aberration.

Furthermore, if the lens strength of the main lens (4) is weakened from this state, three electron beams (two
a), (2b), (2c) are phosphor screens (
6) - The focus of the center beam (2b) weakens, and as shown in figure (8), the spot shape (7b) on the phosphor screen (6) becomes underfocused ( (underfocus), and a high-quality image cannot be obtained.

In order to solve these problems, Japanese Unexamined Patent Publication No. 53-69
In the publication, as shown in FIG. 8, a diverging lens (8) is provided between an auxiliary lens (not shown) and a main lens (4) consisting of a large-diameter electron lens, and a -pair of side beams is provided. (2
A pair of side beams (2a) move forward through object points (9a) and (9c) in a) and (2c).

An electron gun is shown in which the electron beam (2C) is passed through the periphery of the main lens (4) to cancel out the coma aberration caused by the diverging lens (8) and the coma aberration received from the main lens (4).

However, an electron gun with such a configuration has a diverging lens (8).
By providing this, the diameter of the pair of side beams (2a), (2(')) after passing through the diverging lens (8) increases as the distance from the axis of the diverging lens (8) increases.Therefore, coma aberration Even if these can be canceled out, the spherical aberration experienced by the main lens (4) will increase, and the spot diameter on the phosphor screen (6) in the high current range will deteriorate compared to a normal electron gun. Now, as mentioned above, a pair of side beams (2a), (2
c) The diameter becomes larger.

For this reason, it suffers from greater deflection aberration than a normal electron gun,
A pair of side beams (2a) at the periphery of the screen.

The spot diameter of (2C) deteriorates. In addition, the main lens (4
), a strong auxiliary lens is required to cancel out the coma aberration received from the side beams (2a),
Concentration of (2c) and each electron beam (2a), (2b)
, It is not easy to achieve both the focusing and (2c).

(Problems to be Solved by the Invention) As mentioned above, in order to improve the image quality of the conventional color picture tube, the main lens of the electron gun that emits three in-line array electron beams is constructed of a large-diameter electron lens. There is. However, in conventional electron guns whose main lens is a large-diameter electron lens, three electron beams cross and pass through this large-diameter electron lens. If so, there is a problem that the pair of side beams are subjected to strong deflection aberration or coma aberration, and the spot shape on the phosphor screen is distorted, making it impossible to fully demonstrate the performance of the large-diameter electron lens. Also,
If three electron beams are made parallel to a large-diameter electron lens, a pair of side beams will be in an overconcentrated state, and at the same time coma aberration will occur. If the lens strength is weakened to eliminate overconcentration of the pair of side beams, although the three electron beams can be concentrated on the phosphor screen, the focus of the center beam will be weakened and the spot shape on the phosphor screen will be reduced. There is a problem in that the image becomes insufficiently focused, making it impossible to obtain a high-quality image.

In general, if a diverging lens is installed in front of a large-diameter electron lens, although it is possible to eliminate coma, spherical aberration increases, and the spot diameter on the phosphor screen in the high current range is smaller than that of a normal electron lens. It deteriorates compared to a gun, and the pair of side beams suffers from stronger deflection aberration than a normal electron gun.
There are problems such as deterioration of the spot diameter of the pair of side beams at the periphery of the screen.

This invention was made in view of the above problems, and
In a color picture tube with an in-line array electron gun that emits three electron beams, the main lens is composed of a large-diameter electron lens, the three electron beams can be properly focused on the phosphor screen, and the coma can be reduced and the phosphor The purpose is to improve the shape of the spot on the screen so that an image with good quality can be obtained.

[Structure of the Invention] (Means for Solving the Problems) In a color picture tube having an electron gun that emits three electron beams consisting of a center beam and a pair of side beams passing on the same plane, the color picture tube is pre-focused by an auxiliary lens. The main lens that accelerates and focuses the three electron beams toward the phosphor screen is composed of one electrostatic lens that allows the three electron beams to pass through in common without crossing each other, and the auxiliary lens that accelerates and focuses the three electron beams toward the phosphor screen. It is composed of three independent electrostatic lenses corresponding to each of the side beams, and the electrostatic lenses corresponding to the pair of side beams are deflected in a direction that separates the pair of side beams from each other, and the coma aberration received from the main lens is It is an electrostatic lens that provides coma aberration to cancel it out.

More specifically, the electrode group constituting the main lens of such an electron gun consists of at least two cylindrical electrodes having one electron beam passage hole through which three electron beams commonly pass, in the tube axis direction. The electrode group, which is arranged in an array and constitutes an auxiliary lens, is composed of electrodes having three independent electron beam passage holes through which three electron beams pass through, and among the electrode groups,
It is constructed by eccentrically centering the side beam passing hole of the electrode located on the main lens side adjacent to this electrode toward the center beam passing hole side with respect to the side beam passing hole of the electrode located on the side of the electron beam generating section.

(Function) As mentioned above, the main lens is composed of one electrostatic lens that allows the three electron beams to pass through in common without crossing each other, and the normal auxiliary lens function that pre-focuses the three electron beams on the auxiliary lens. In addition, if the pair of side beams is deflected in a direction away from each other, the spherical aberration of the pair of side beams caused by the main lens and the spherical aberration of the center beam can be made to the same level. At the same time, for the pair of side beams, the coma aberration that occurs when the main lens focuses the beams can be canceled out by the coma aberration that occurs by deflecting the side beams in a direction away from each other using the auxiliary lens. Furthermore, since the object points of the pair of side beams move forward, overconcentration of the pair of side beams is corrected, thereby making it possible to provide a color picture tube that displays images of good quality.

(Example) Hereinafter, the present invention will be described based on an example with reference to the drawings.

FIG. 4 shows a color picture tube which is an embodiment of the present invention. This color picture tube consists of a panel (10) and this panel (
Funnel-shaped funnel (11) integrally joined to 10)
A shell 1 having an envelope (12) and having a large number of electron beam passing holes arranged inside the panel (10).
7 Opposite the dough mask (13), the above panel (10)
A phosphor screen (14) consisting of three-color phosphor spheres that emit red, blue, and green light is formed on the inner surface. Further, an electron gun (16) that emits three electron beams (described later) is provided in the neck (15) of the funnel (11), and the three electron beams emitted from the electron gun (16) are transferred to the funnel (11). ) is deflected by a deflection yoke (18) attached to the outside of the boundary between the cone part (17) and the neck (15), and the phosphor screen (14) is scanned horizontally and vertically. Phosphor screen (14
) is formed into a structure that displays a color image on top.

The electron gun (16) has an inline array 3 consisting of a center beam and a pair of side beams passing on the same plane.
It is an electron gun that emits an electron beam, and as shown in FIG.
a), (lb), (lc) and each cathode (la).

(lb), (19
), the first to fourth grids (G1) to (G4) of integral M4 structure arranged coaxially on the electron emitting surfaces of each cathode (la), (lb), (lc), and the convergence cup (Fig. (not shown) and an insulating support (not shown)
Accordingly, the heater (19), cathode (la>, (lb),
(lc) and the first to fourth grids (G1) to (G
4) are fixed together, and a convergence cup is attached to the fourth grid (G4).

In the electron gun of this example, the first and second grids (G1>, (G2) are composed of plate-shaped electrodes, and these grids (G1), (G2) have three cathodes arranged in the above-mentioned column. Three independent electron beam passing holes corresponding to (la), (lb), and (lc) are formed coaxially through the plate surface.The third grid (G3) is connected to the second grid (G3).
2) is the bottom surface, and the fourth grid (G4
) side is a cup-shaped electrode with an opening that serves as an electron beam passage hole common to all 3N beams, and its second grid (G2
〉, there are three cathodes (
la).

Three independent electron beam passing holes are formed corresponding to (Ib) and (lc). The electron beam passing hole of this third grid (G3) is slightly larger than the electron beam passing hole of the second grid (G2), and among the three electron beam passing holes, the center beam passing hole is the first and third electron beam passing hole. It is coaxial with that of 2 grids (G1>, (G:2),
The pair of side beam passage holes are eccentric to the center beam passage hole side with respect to the side beam passage holes of the second grid (G2). The fourth grid (G4) is the third grid (
It consists of a cylindrical electrode with a larger diameter than G3) and open at both ends, and a part of it covers the outer surface of the third grid (G3).

Describing this electron gun as a specific example of a 19-inch color picture tube with a neck diameter of 36.5 m, the first and second grids are composed of plate-shaped electrodes with a plate thickness of 0.25 m disposed close to each other. Three electron beam passing holes each having a diameter of 0.628 are formed on the surface at an interval S# of 4.92#. Third
The grid consists of a cup-shaped electrode with a diameter of about 25 mm and a length of about 70 rrm, and three electron beam passing holes each having a diameter of 1.5 mm are formed at an interval S8 of 4.85 # on the bottom surface of the grid. Also, the fourth grid has a diameter of about 28. , consisting of a cup-shaped electrode with a length of 30 m or more, of which at least 30. overlaps and covers the third grid.

In an electron gun having such a structure, in order to make it a pi potential type electron gun, for example, a cathode (la),
A cutoff voltage of about 150V and a video signal are applied to (lb) and (lc), and the first grid (G1) is kept at ground potential. In addition, the second grid (G2)
ov, 3rd Ri') Tsut' (G3) Niha 5-7
kV.

A voltage of 25 to 30 kV is applied to the fourth grid (G4).

With such a potential configuration, the second grid (G2) and the third grid (G3) create three independent lenses (20
a>, (20b), and (20c) are formed, and the third grid (G3) and fourth grid (G4) form a main lens (21) consisting of a large-diameter electron lens. The center beam (22b) emitted from the shadow %1j (1b) is pre-focused by the auxiliary lens (20b) corresponding to this center beam (22b), and then accelerated and focused by the main lens (21). Under the focusing action, it is focused onto the phosphor screen (14).

On the other hand, the pair of side beams (22a) and (22C) emitted from the cathodes (la) and (lc) are similar to the center beam (22b), respectively.
(22c) Compatible auxiliary lens (20a), (20c)
However, at the same time, the third grid (G
The center beam (22b
), that is, in a direction away from each other, and coma aberration occurs.

To explain in detail the effects of the auxiliary lenses (20a) and (20c) on the side beams (22a) and (22C), as shown in FIG.
2) and the third grid (G3) are eccentric, a distorted rotationally asymmetric lens (20) (lens (20a) or (20C)) is formed between them.
) is formed and a side beam (22) is incident on this lens (20) area from the low pressure side (side beam (22)
a) or (22C)) undergoes a component force f1r in the direction of the tube axis (23) perpendicular to the lines of electric force, almost as in the case of a rotationally symmetric lens without distortion, and changes its trajectory as shown by the arrow (24). Turn it in the direction of the tube axis (23). However, this lens (2
0), this rotationally symmetric lens (25) receives a component force f2r in the direction away from the tube axis (23) and passes through the periphery of the lens more than in the case of the rotationally symmetric lens shown in (25). ), the tube axis (23) receives a component force larger than the component force f3r received in the case (fz r > f3r ).
Change the trajectory away from . Moreover, this tube shaft (2
3) The component force f2r in the direction away from the lens (20) is large at the peripheral part of the lens (20), and the off-axis beam receives a large force, so the side beam (22) after passing through the lens (20) is
As shown in the same figure (B), it becomes a distorted shape (26).

As mentioned above, the pair of side beams (22a) are deflected and subjected to coma by the auxiliary lenses (20a) and (20c).
).

(22C) is then accelerated and focused by the main lens (21) formed by the third grid (G3) and the fourth grid (G4). ) and (22c) are deflected in the direction away from each other by the auxiliary lenses (20a) and (20c) as described above, so they do not become overconcentrated.
This pair of side beams (22a) and (22c) are
Since the off-axis beam enters the main lens (21) at a large angle, the coma aberration received from the main lens (21) is offset by the coma aberration received from the auxiliary lenses (20a) and (20c).

The effect on these three electron beams is explained using an optical equivalent diagram as shown in FIG. 3. In this optical equivalent diagram, 3
Individual auxiliary lenses (20a), (20b).

(20c), a pair of side beams (22a),
Auxiliary lens (20a) for (22c), (20c
), they are shown divided into lenses (28a), (28c) for pre-focusing and lenses (29a), (29c) for deflection, respectively.

First, three cathodes (la) arranged in a - column (1b),
Three electron beams (22a) emitted from (1c), (
Among center beams (22b) and (22C),
After being pre-focused by the auxiliary lens (20b), the light beam b) travels straight and is focused by the main lens (21), which is roughly a large-diameter electron lens, and reaches the phosphor screen (14). On the other hand, a pair of side beams (22a), (2
2c) are respectively prefocused by lenses (28a), (28C) and lenses (29a), (29
c) in the direction of separating them from each other. Due to this deflection, the object points (30a) and (30c) of each side beam (22a) and (22c) move forward and are simultaneously subjected to coma aberration. This lens (28a).

After passing through the auxiliary lenses (20a) and (20C) shown in (28C) and (29a) and (29c), the pair of side beams (22a) and (22c) are focused by the main lens (21). phosphor screen (1
4) is reached. In this case, the lens (29a
), (29C) causes a pair of side beams (2
2a), object point (30a) of (22c).

Since (30c) is moving forward, its image point can be moved back to match the image point of the center beam (22b). Furthermore, the coma aberration received from the main lens (21) is offset by the coma aberration generated from the lenses (29a) and (29c). In other words, the lens (29a).

(29c) and the main lens (21), three electron beams (22aL (22b)
, (22c) can be concentrated at one point on the phosphor screen (14) and a spot without coma can be formed.

In the above embodiment, the main lens formed between the third grid and the fourth grid of the pi-potential electron beam is a 1g1 large-diameter electron lens that allows the three electron beams to pass through in common without crossing each other. Although the present invention is not limited to a case in which a pi-potential type lens is used, it is also applicable to a case in which a uni-potential type lens or a compound type lens that is a combination of these lenses is used.
Alternatively, it can also be applied to a combination of individual electron lenses and large-diameter electron lenses.

Further, in the above embodiment, three independent auxiliary lenses are formed between the second grid and the third grid, but the auxiliary lenses can also be formed by dividing the third grid.

[Effect of the invention] Regarding an electron gun that emits three electron beams consisting of a center beam and a pair of side beams that pass on the same plane,
The main lens is composed of one electrostatic lens that allows the three electron beams to pass through in common without crossing each other, and the auxiliary lens is composed of three independent electrostatic lenses that allow the three electron beams to pass through each separately. 3. In addition to the normal auxiliary lens function that pre-focuses the electron beam, if the pair of side beams is deflected in the direction away from each other, the spherical aberration of the pair of side beams caused by the main lens and the center The spherical aberration of the beam can be made to the same level. At the same time, for the pair of side beams, the coma aberration that occurs when the main lens focuses the beams can be canceled out by the coma aberration that occurs by deflecting the side beams in a direction away from each other using the auxiliary lens. Furthermore, since the object points of the pair of side beams move forward, the overconcentration of the pair of side beams is corrected. Therefore, by making full use of the performance of the large-diameter electron lens that constitutes the main lens, we can reduce the spot diameter of the electron beam on the phosphor screen and focus the electron beam appropriately. , it can be a color picture tube that displays good images.

[Brief explanation of the drawing]

1 to 4 are detailed explanatory diagrams of the present invention, in which FIG. 1 is a sectional view showing the structure of an electron gun of a color picture tube according to one embodiment, and FIGS. 2(8) and 2(B) are An explanatory diagram of the action of the auxiliary lens on the pair of side beams and a diagram of the spot shape of the electron beam on the phosphor screen, respectively.
Figure 1 is an optical equivalent diagram of the electron gun shown in Figure 1. Figure 4 is a diagram showing the configuration of an embodiment of a color picture tube. Figure 5 is composed of a large-diameter electron lens through which three electron beams cross and pass through the main lens. Optical equivalent diagram of the conventional electron gun, Figure 6 (^) and (B)
The figures are an optical equivalent diagram of a conventional electron gun in which three electron beams are incident in parallel on a main lens consisting of a large-diameter electron lens, and a spot shape diagram of the electron beams on a phosphor screen, respectively. ) Figures 6 and 8 are an optical equivalent diagram and a spot shape diagram of the electron beam on the phosphor screen when the intensity of the main lens of the electron gun shown in Figure 6 is weakened, respectively.
The figure is an optical equivalent diagram of a conventional electron gun in which a diverging lens is provided between an auxiliary lens and a main lens. la, lb, 1c...cathode 14...phosphor screen 16...electron gun 20a, 20b,
20c...Auxiliary lens 21...Main lens 22a
, 22C...Side beam 22b...Center beam G...First grid G...Second grid G...
・3rd Grid G...4th Grid Agent Patent Attorney Norio Ogo No. 4121 Fig. Fig. Fig.

Claims (2)

[Claims] (1) It has an electron gun that emits three electron beams that pass on the same plane, consisting of a center beam and a pair of side beams, toward the phosphor screen, and this electron gun generates and controls the three electron beams. an auxiliary lens consisting of an electrode group that pre-focuses the three electron beams from the electron beam generator, and directs the three electron beams pre-focused by the auxiliary lens toward the phosphor screen. In a color picture tube equipped with a main lens consisting of a group of electrodes for accelerating and focusing, the main lens consists of one electrostatic lens that allows the three electron beams to pass through in common without crossing each other, and the auxiliary lens includes the three electron beams. Consisting of three independent electrostatic lenses corresponding to each of the electron beams, the electrostatic lenses corresponding to the pair of side beams deflect the pair of side beams in a direction that separates them from each other, and A color picture tube comprising an electrostatic lens that provides coma aberration that offsets coma aberration received from the main lens. (2) The electrode group constituting the main lens is composed of at least two cylindrical electrodes arranged in the tube axis direction, each having one electron beam passage hole through which three electron beams pass in common, and constitutes an auxiliary lens. The electrode group consists of electrodes with three independent electron beam passage holes through which three electron beams pass through, and among the electrode groups that make up this auxiliary lens, the side beam passage of the electrode located on the electron beam generation side is 2. The color picture tube according to claim 1, wherein the side beam passage hole of the electrode located adjacent to the electrode and on the side of the main lens is decentered toward the center beam passage hole with respect to the hole.