JPH06283112A - Electron gun - Google Patents

Abstract

PURPOSE:To provide an in-line type electron gun capable of improving resolution. CONSTITUTION:Laterally rectangular passing holes 2a are formed on the first grid 2, laterally rectangular passing holes 3a are formed on the first grid 2 side on the second grid 3, and circular passing holes 3b are formed on the opposite side. The object point position in the horizontal direction from a main lens at three pole sections is formed farther than the object point position in the vertical direction, and the emittance in the vertical direction is made smaller than the emittance in the horizontal direction. In order to form the main lens having the focal distance in the horizontal direction longer than the focal distance in the vertical direction, the third grid 4 formed with an elliptic passing hole 4b at the center on one face side and deformed elliptic passing holes 4a, 4c on both sides of it and the fourth grid 5 are provided. Electron beams are extended in the horizontal direction at the deflection center, they are hardly applied with a deflection aberration, they are made almost a completely round, and resolution is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-line type electron gun which emits, for example, three electron beams on one horizontal plane.

[0002]

2. Description of the Related Art FIG. 10 is a schematic view showing a structure of a triode of a cathode ray tube equipped with a conventional in-line type electron gun, and shows only one electron beam. A circular cathode 1, a first grid 12 having a circular passage hole 12a for passing an electron beam emitted from the cathode 1, and a circular electron on the first grid 12 side are arranged along the tube axis of a cathode ray tube (not shown). A second grid 13 in which a beam passage hole 13a is formed and a laterally long rectangular passage hole 13b is formed on the opposite side, and a focus electrode (third grid) 14 for forming a prefocus lens together with the second grid 13. , A focus electrode 14 and a high-voltage electrode (fourth grid) 15 for constituting a main lens are provided in this order, and a fluorescent screen which emits light when a focused electron beam strikes in front of the cathode ray tube. Is provided with a screen 16.

A voltage lower than that of the cathode 1 is applied to the first grid 12, the electron amount is controlled by the potential difference between the cathode 1 and the first grid 12, and an electron beam is emitted. By applying a positive voltage to the second grid 13, the first grid
The electron beam that has passed through the 12 through holes 12a is in the second grid 13
Is sucked into. Further, the electron beam passing through the second grid 13 is further accelerated and focused by the positive voltage applied to the third and fourth grids 14 and 15, and reaches the screen 16 at a predetermined speed.

FIG. 11 is an explanatory view showing trajectories of electron beams in the electron gun having the above-mentioned structure. The electron beam emitted from the cathode surface and passing through the main lens is deflected by, for example, a deflection yoke (not shown) provided outside the cathode ray tube in order to scan each point of the screen on the screen 16. V indicates the outermost electron beam trajectory in the vertical direction, and H indicates the outermost electron beam trajectory in the horizontal direction.

Generally, a conventional electron beam deflection system in a cathode ray tube does not require a dynamic convergence circuit by automatically focusing three electron beams on a screen. For this reason, a self-convergence system is adopted that distorts the horizontal deflection magnetic field in a pincushion shape (pincushion shape) and the vertical deflection magnetic field in a barrel shape (barrel shape). This system has many advantages such as easy adjustment, low cost, and little change in convergence over time, and is widely used at present.

[0006]

FIG. 12 is an explanatory diagram showing the trajectory of the electron beam between the main lens and the screen 16.
Diameter of the electron beam in the main lens DSM (D iameter S
ize in M ain lens) susceptible to the deflection aberration perpendicular diameters DSMv is large, also the resolution is degraded in the center of the screen perpendicular diameters DSv large diameter DS of the electron beam spot (D iameter S ize) in the screen 16. Conventionally, the quadrupole magnetic field component generated due to the nonuniform magnetic field formed by the above-described self-convergence deflection yoke has caused astigmatism in the deflected electron beam. Therefore, the electron beam undergoes a focusing action, that is, deflection aberration (distortion) in the vertical direction, and as a result, the deflected beam spot becomes overfocus in the vertical direction, and a halo (overfocusing portion) that extends vertically in the peripheral portion of the screen As a result, the vertical resolution deteriorates. If, for example, the vertical direction is corrected by adjusting the focus voltage (voltage applied to the focusing electrode) or the like to optimize the vertical focusing, the horizontal direction in which the optimum focus is maintained becomes the underfocus and the horizontal resolution is deteriorated. The problem arises.

In order to solve this problem, in the conventional in-line type electron gun, the action of the prefocus lens is strengthened to narrow down the electron beam, and the diameter of the electron beam in the deflection magnetic field is kept small to be influenced by the deflection aberration. The method of making it difficult is adopted. In particular, in order to reduce the deflection aberration in the vertical direction, as shown in FIG. 12, the electron beam diameter in the main lens is often made horizontally long, and in reality, the shape of the passage hole 3b of the second grid 3 is made to be horizontally long slot. As a method, a method of holding a quadrupole lens action with the third grid 4 is adopted.

However, in the method of narrowing the electron beam by strengthening the action of the prefocus lens as described above, the magnification of the prefocus lens is increased, the virtual object point is enlarged, and the electron beam spot diameter is increased. Therefore, even if the deflection aberration at the periphery of the screen is reduced, the vertical diameter DSv of the electron beam spot at the center of the screen is increased as shown in FIG. 12, and the resolution at the center of the screen is lowered. Fig. 10
There is a limit to the method of using the horizontally long passage hole 3b shown in (1) and then making the electron beam horizontally long only by the action of the quadrupole lens such as the prefocus lens because the electron beam emitted from the cathode 1 is circular.

Even if the electron beam can be made horizontally long at the deflection center, it becomes impossible to obtain a circular electron beam spot (optimal focus) at the center of the screen as shown in FIG. 13, and the resolution of the entire screen is improved. Is difficult to do. The present invention has been made in view of such circumstances, and includes at least a first grid and a first grid.
Distortion due to deflection aberration is reduced by making the grid side passage hole shape longer in the horizontal direction than in the vertical direction,
An object of the present invention is to provide an in-line type electron gun that can obtain high resolution in the center of the screen by providing an electrode having a required stigma (horizontal focus voltage-vertical focus voltage).

[0010]

In the electron gun according to the first aspect of the invention, the horizontal object point of the three-pole portion is formed at a position farther from the main lens side than the vertical object point, and the three-pole portion is vertical. In order to make the emittance in the horizontal direction smaller than the emittance in the horizontal direction, the through holes formed in the first grid and the through holes formed at least on the first grid side of the second grid have a shape in which the horizontal direction is longer than the vertical direction. It is characterized by being done.

In the electron gun according to the second invention, the horizontal object point of the three-pole portion is formed at a position farther from the main lens side than the vertical object point, and the vertical emittance of the three-pole portion is horizontal. In order to reduce the emittance of the first grid and the through holes formed on at least the first grid side of the second grid, the horizontal direction is longer than the vertical direction. Is provided with an electrode forming a main lens whose focal length is equal to or longer than the vertical focal length.

[0012]

With the passage holes of the first grid and the second grid, quadrupole lenses are formed on the cathode side and the second grid side of the first grid, respectively. The quadrupole lens on the cathode side acts on the quality of the electron beam, and the quadrupole lens on the second grid side acts on the focusing of the electron beam, that is, the object point position. Therefore, in the first aspect of the invention, the shape of the passage holes of the first grid and the passage holes of at least the first grid side of the second grid are made longer in the horizontal direction than in the vertical direction, so that the main lens side The horizontal object point of the three-pole portion is formed at a position farther than the vertical object point. As a result, the vertical diameter of the electron beam at the deflection center can be reduced to make it difficult to receive the deflection aberration, and the resolution at the peripheral portion of the screen is increased. Further, since the vertical emittance of the three poles is made smaller than the horizontal emittance due to the shape of the through hole described above, it is possible to reduce the deterioration of the vertical resolution that has occurred in the conventional device.

According to the second invention, in addition to the effect of the first invention, the focal length in the horizontal direction of the main lens is equal to or longer than the focal length in the vertical direction. By setting the stigma to be 0 to -300 V, the difference in the object point position in the horizontal and vertical directions is corrected, and an electron beam whose vertical diameter is smaller than the horizontal diameter in the main lens is close to a perfect circle on the screen. The spot shape (optimal focus) can be obtained, and the resolution in the central portion of the screen becomes high. As described above, good resolution can be obtained over the entire screen.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a schematic diagram showing the configuration of a three-pole part and a main lens part of an in-line type electron gun (hereinafter referred to as the device of the present invention) according to the present invention. In the case of an electron gun that emits three electron beams, Shows. Along the tube axis of a cathode ray tube (not shown), three circular cathodes 1, 1, 1 arranged inline, and three horizontally elongated rectangles for accelerating and passing the electron beam emitted from the cathodes 1, 1, 1 A first grid 2 having passing holes 2a, 2a, 2a, three horizontally-long rectangular passing holes 3a, 3a, 3a are formed on the first grid 2 side, and three circular passing holes 3b, 3b, on the opposite side. A second grid 3 having 3b formed therein and three circular passage holes 4d, 4d, 4d on the second grid 3 side, and a passage hole having a shape described later on the opposite side.
A third grid 4 which is a track-shaped electrode having 4a, 4b and 4c, and a fourth grid 5 which is a track-shaped electrode having through holes 4a, 4b and 4c on the side of the third grid 4 are provided in this order. Therefore, a prefocus lens is formed by the third grid 4 side of the second grid 3 and the second grid 3 side of the third grid 4, and the fourth grid 5 side of the third grid 4 and the fourth grid 5 side of the fourth grid 5 are formed. The main lens is formed with the 3 grid 4 side. A screen 6 having a fluorescent screen which emits light by an electron beam focused by a main lens is provided on the front surface of the cathode ray tube.

FIG. 2 is a schematic diagram showing the second grid 3. 2A is a sectional view, FIG. 2B is a side view as seen from the first grid 2 side, and FIG. 2C is a side view as seen from the screen side. A laterally long rectangular passage hole 3a is formed on the first grid 2 side of the second grid 3, and a circular passage hole 3b having a smaller diameter than the passage hole 3a is formed on the screen 6 side. With the configuration of the first grid 2 and the second grid 3 as described above, a quadrupole lens is created on each of the cathode 1 side and the second grid 3 side of the first grid 2.

FIG. 3 shows a third grid 4 forming the main lens.
(Or a fourth grid 5) is a schematic view showing one surface side,
3 (a) is a perspective view and FIG. 3 (b) is a front view. In the third grid 4, an elliptical plate 41 having three through holes 4a, 4b, 4c is fitted to one side of a track-shaped electrode 42 having a height Hv forming an opening having the same shape as the plate 41. It is a thing. The passage hole 4b located at the center of the plate 41 has an elliptical shape with a major axis Cv and a minor axis Ch (Cv> Ch). The passage holes 4a and 4c on both sides of the passage hole 4b have the same line-symmetrical shape. The half on the passage hole 4b side is an elliptic arc with the major axis Cv and the minor axis Ch, and the outside half has a radius Sr (Cv>Sr> Ch). ) Has an elliptical shape that is a circular arc. The through holes 4a, 4b, 4c provided in the third grid 4 and the fourth grid 5 are arranged in such a manner that the plate 41 sides face each other at a predetermined distance in the tube axis direction and form a main lens.

On the other surface side of the track-shaped electrode 42 forming the third grid 4, three circular through holes 4d,
Plates having 4d and 4d are fitted, and the other surface side of the track-shaped electrode 42 forming the fourth grid 5 is in an open state. As for the focus characteristics (astigma characteristics) of the main lens, desired characteristics can be obtained by changing the shapes and sizes of the through holes 4a, 4b, 4c and the shapes and depths of the track-shaped electrodes 42. In this embodiment, it is set to obtain 0 to -300V.

In the device of the present invention having the above structure, the electron beam emitted from the cathode 1 is emitted from the first grid 2
Passing through the passage hole of the second grid 3 is sucked and accelerated,
Further, it is accelerated and focused by the prefocus lens and the main lens and reaches the screen 6 at a predetermined speed.

FIG. 4 is an explanatory view showing the trajectory of the electron beam in the device of the present invention, V indicates the outermost electron beam trajectory in the vertical direction, and H indicates the outermost electron beam trajectory in the horizontal direction. 5 is an explanatory diagram showing the trajectory of the electron beam from the cathode 1 to the main lens, FIG. 6 is an explanatory diagram showing the trajectory of the electron beam from the main lens to the screen, and FIG. 7 shows this trajectory using a beam cross section. FIG. By combining the first grid 2, the second grid 3 and the main lens portion as in this embodiment, the DSMv becomes smaller than the conventional one, so that the shape of the electron beam becomes laterally long and it becomes difficult to receive the deflection aberration. As a result, the resolution of the peripheral portion and the central portion of the screen is improved. In addition, since the DSv becomes smaller than in the conventional case and the beam spot shape at the center of the screen becomes closer to a perfect circle, the resolution at the center of the screen becomes higher and a high resolution can be obtained over the entire screen.

FIGS. 8 and 9 are schematic views showing another embodiment of the shape of the through holes of the first grid 2 and the second grid 3. In FIG. 8, the passage holes of the first grid 2 and the second grid 3 are both horizontally long rectangles. Further, in FIG. 9, the passage holes of the first grid 2 and the second grid 3 have a horizontally long elliptical shape. As shown in FIG. 8 and FIG. 9, at least the first grid 2 and the second grid 3 have at least a first grid side through hole shape having a shape in which the horizontal direction is longer than the vertical direction, such as a rectangle, an ellipse, an oval, and an egg. With the shape, the same effect as that of the above-described embodiment can be obtained. In this embodiment, the case of the bipotential electron gun has been described, but it is needless to say that the present invention can be applied to other electron guns such as a multistage focusing electron gun.

[0021]

As described above, the electron gun according to the present invention forms the electron at the deflection center by forming the horizontal object point of the three-pole part from the main lens side at a position farther than the vertical object point. The vertical diameter of the beam can be reduced to make it less susceptible to deflection aberrations, and the resolution in the peripheral area of the screen is improved. Further, by making the emittance in the vertical direction of the three-pole portion smaller than the emittance in the horizontal direction, deterioration of resolution in the vertical direction can be reduced. In addition, the horizontal focal length of the main lens is equivalent to the vertical focal length or longer than the vertical focal length.
Since the vertical diameter of the electron beam spot on the screen of the electron beam having a small vertical diameter at the deflection center can be reduced, the resolution at the center of the screen is further increased, and good resolution can be obtained over the entire screen. Produce the effect.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a main part of an in-line type electron gun according to the present invention.

FIG. 2 is a schematic diagram showing a second grid in FIG.

3 is a schematic diagram showing a third grid in FIG. 1. FIG.

FIG. 4 is an explanatory diagram showing a trajectory of an electron beam in the electron gun shown in FIG.

5 is an explanatory diagram showing a trajectory of an electron beam in the electron gun shown in FIG.

6 is an explanatory diagram showing the trajectory of an electron beam in the electron gun shown in FIG.

7 is an explanatory view showing the trajectory of an electron beam in the electron gun shown in FIG.

FIG. 8 is a schematic view showing another embodiment of the first and second grids in the present invention.

FIG. 9 is a schematic view showing another embodiment of the first and second grids in the present invention.

FIG. 10 is a schematic diagram showing a configuration of a triode portion of a cathode ray tube including a conventional in-line type electron gun.

11 is an explanatory diagram showing the trajectory of an electron beam in the electron gun shown in FIG.

12 is an explanatory diagram showing the trajectory of an electron beam in the electron gun shown in FIG.

13 is an explanatory diagram showing the trajectory of an electron beam in the electron gun shown in FIG.

[Explanation of symbols]

 1 Cathode 2 1st grid 3 2nd grid 2a, 3a, 3b, 4a, 4b, 4c, 4d through hole 4 3rd grid 5 4th grid 41 plate 42 track electrode 6 screen

Claims (2)

[Claims] 1. A three-pole part composed of a cathode emitting a plurality of electron beams on one plane and first and second grids having passage holes for accelerating and passing the electron beams, and the three-pole part. In an in-line type electron gun including a main lens unit that focuses a plurality of electron beams that have passed through on a screen, a horizontal object point of the three-pole unit is located farther from the main lens side than a vertical object point. In order to make the vertical emittance of the three-pole portion smaller than the horizontal emittance, the through holes formed in the first grid and the second grid are formed at least on the first grid side. An electron gun characterized in that the through hole has a shape in which the horizontal direction is longer than the vertical direction. 2. A three-pole part composed of a cathode emitting a plurality of electron beams on one plane and first and second grids having passage holes for accelerating and passing the electron beams, and the three-pole part. In an in-line type electron gun including a main lens unit that focuses a plurality of electron beams that have passed through on a screen, a horizontal object point of the three-pole unit is located farther from the main lens side than a vertical object point. In order to make the vertical emittance of the three-pole portion smaller than the horizontal emittance, the through holes formed in the first grid and the second grid are formed at least on the first grid side. The through hole has a shape in which the horizontal direction is longer than the vertical direction, and the horizontal focal length is
An electron gun comprising an electrode forming a main lens having a length equal to or longer than a focal length in a vertical direction.