JPH09259797A - Beam index type cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a halo ungenerating rectangular beam spot by adopting an electron beam to form a longitudinally long reactangular beam spot cross section, and controlling an orbit of the electron beam by an octpole electron lens means in an electron gun. SOLUTION: When an opening of a first grid G1 being a first control electrode is formed in a small rectangular shape, an electron beam 8 emitted from a cathode K is formed in a longitudinally long rectangular shape, and is accelerated by a second grid G2 being a first accelerating electrode. It receives the focus adjusting action by a third grid G3 being a focus electrode, and is accelerated by a fourth grid G4 being the final accelerating electrode, and is projected on a fluorescent screen 11. An octpole electron lens QP1 is arranged between a main lens part ML and the fluorescent screen 11 in the vicinity of the fourth grid G4. Therefore, a halo ungenerating rectangular beam spot can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam index type cathode ray tube (hereinafter referred to as "beam index tube").

[0002]

[Prior art]

[Explanation of Beam Index Tube] (Comparison with Shadow Mask Tube) The characteristics of the beam index tube according to the present invention are a shadow mask type cathode ray tube (hereinafter, referred to as “shadow mask tube”) which is widely used at present. In order to explain in comparison with, the shadow mask tube will be first outlined.

A shadow mask tube is known as a color cathode ray tube (cathode ray tube) which has been widely put into practical use at present. 7A and 7B are views for explaining the shadow mask tube as a whole, in which FIG. 7A is a horizontal sectional view of the shadow mask tube seen from above, and FIGS. 7B and 7C are views for explaining different types of shadow masks. 7D is a diagram showing the relative relationship between the electron beam, the shadow mask, and the RGB phosphors.

The shadow mask tube will be briefly described. As shown in FIG. 7A, in the shadow mask tube, the three electron beams 53 emitted from the electron gun 51 are parallel to the shadow mask (mechanical color selection mechanism) 55. By utilizing the lux (parallax), the three color phosphors formed on the phosphor screen 57 are selectively stimulated and emitted.

As shown in FIG. 7B, three electron guns 51 are prepared corresponding to the three primary colors R, G, B, and there are two types of shadow masks 55. Generally, a shadow mask having a slot-like opening 55a (see FIG. 7B) is used, but a dot-like one 55b is used depending on the purpose.
(See FIG. 7C) is also used, and the phosphor 59 of the phosphor screen 57 is used.
Each has a stripe shape 59a (see FIG. 7B) or a mosaic shape 59b (see FIG. 7C).

(Index tube) On the other hand, recently,
A beam index tube without a shadow mask (mechanical color selection mechanism) is being developed. FIG. 8 is a view for explaining the beam index tube as a whole, and FIG.
Is a horizontal sectional view of the beam index tube seen from above, FIG. 8B is a view for explaining the relationship between the electron beam, the phosphor and the index phosphor, and FIG. 8C is for explaining the relationship between the beam spot size and the phosphor size. FIG.

As shown in FIG. 8A, in the beam index tube, R, G, and B phosphors 63 are formed on the phosphor screen 61 in stripes extending in the vertical direction of the screen, and further, at regular intervals. And has a phosphor screen formed by forming index phosphors (short afterglow phosphors) 65 in a stripe shape. This fluorescent screen 61 is scanned with one electron beam 67, and at this time, an index signal (for example, ultraviolet ray) 69 emitted from the index fluorescent substance 65 is detected by a sensor (for example, photodiode) 71 and the electron beam 67 is detected.
After the position information is obtained, the color signal switching circuit 73 switches the video signal (color signals of three colors) in synchronization with this to modulate the beam.

This beam index tube has an advantage that the utilization rate of the electron beam 67 is high because a shadow mask (reference numeral 55 in FIG. 7) for trapping the electron beam is unnecessary. As an example, the shadow mask tube has an electron beam utilization rate of about 20%, while the index tube has an electron beam utilization rate of about 70%, which is about 3.5 times higher. Therefore, a high-luminance screen can be realized. In addition to this, the beam index tube has various advantages such as low power consumption, no problem of beam concentration because it is a single beam, little influence of geomagnetism, and simple cathode ray tube structure. ing.

(Fine Beam Spot of Beam Index Tube) In the shadow mask tube described above, the opening dimension of the slot 56 of the shadow mask 55 corresponding to the dimension W1 of the phosphor 59 is fluorescent as shown in FIG. 7D. Since the size of the beam that strikes the surface 57 is determined, the electron beam 53 emitted from the electron gun 51 is emitted from each phosphor 59.
It is possible to use a beam spot having a size slightly larger than the size W1 of.

On the other hand, in the beam index tube related to the present invention, as shown in FIG. 8, since there is no shadow mask, the utilization rate of the electron beam 67 is high, but in principle, the three primary color (RGB) phosphors 63 are used. A fine beam spot having a width equal to or smaller than the width W2 of is required. That is, the beam spot size (beam diameter) is set to the RGB phosphor 6 of the phosphor screen 61.
It is necessary to make it small so as to fit each stripe width W2 of No. 3. When the beam spot becomes large, not only the adjacent phosphors are excited to deteriorate the color purity, but also the index signal width is reduced and an index signal 69 detection error occurs. Therefore, it is necessary to reduce the beam spot size in the horizontal direction from the low current region to the high current region, and also in consideration of the deflection distortion, over the entire phosphor screen.

The beam index tube sequentially switches one beam 67 so that the electron beam 67 impinges on only one phosphor (color) 63 at a certain time (that is, at a moment). While scanning the R, G, B phosphors 63. Therefore, the horizontal dimension of the beam spot limits the pitch of the R, G, and B phosphors 63.

Therefore, in order to obtain a high-definition (fine pitch) image in which the pitch of the R, G, and B phosphors 63 is small, the horizontal dimension of the beam spot of the electron beam 67 is necessarily made extremely small. It is necessary to make a fine beam spot. Thus, as the image becomes finer in pitch, it is necessary to further reduce the beam spot size corresponding to the smaller phosphor size. But,
Color purity (purity) when the beam spot is reduced
It will be difficult to achieve both securing (coloring) and maintaining brightness.

Further, as shown in FIG. 8C, the R, G, B phosphors 63 on the phosphor screen 61 are separated from each other by a carbon guard band (also called a black stripe or a carbon stripe) 75. It extends in between. Therefore, if the shape of the beam spot can be made relatively small with respect to each phosphor size (dimension between carbon guard bands) W2, a round fine beam spot as shown by reference numeral 77 is preferable. However, as a practical problem, if the electron density of the beam is increased to that extent, the phosphor 63 is saturated and the color does not develop properly. Therefore, under the present circumstances, it is unavoidable to adopt a generally vertical fine beam spot as shown by reference numeral 79.

[0014]

[Problems to be Solved by the Invention]

[Occurrence of Halo of Rectangular Beam Spot] (Elliptical and Rectangular) As such a vertically long fine beam spot, an elliptical or rectangular fine beam spot can be considered. Of these, the elliptical beam spot 81 as shown in FIG. 9A has the same spot area (that is, the same spot area as long as the width direction dimension We is not relatively increased as compared with the rectangular beam spot 81 as shown in FIG. 9B. Beam current) cannot be secured. Therefore, there is no problem when the beam current is small, but when the beam current is increased, the width direction dimension We becomes relatively large and the color purity is deteriorated.

(Generation of Halo of Rectangular Beam Spot) As shown in FIG. 9B, when the beam spot has a generally rectangular shape 83, the width direction dimension Wr is relatively small in order to secure the same beam current. It has the advantage of being completed. Therefore, at present, 0.6 mmH × 0.25 m
A rectangular beam spot of about mW is used.
However, when the beam current is increased even in the rectangular beam spot 83, the halo 85 appears in the diagonal direction of the rectangular shape to cause the adjacent phosphor stripes to emit light, which causes a problem of deterioration in color purity.

[Investigation of Cause of Problems in Prior Art] The present inventor examined the cause of the halo in the beam spot. As a result, by making the beam spot shape rectangular, the orbits of the individual electron beams forming the beam spot differ in the vicinity of the cathode depending on the position of each beam spot cross-sectional direction, which causes the halo. It was determined that 85 occurred.

The structure of the electron gun of the beam index tube will be described later in detail with reference to FIG. 1. Here, the cause of the halo 85 will be briefly described. As shown in FIG. 10A, the structure in the vicinity of the cathode of the electron gun of the beam index tube is composed of the cathode K, the first grid G1 and the second grid G2 arranged in the neck portion of the funnel glass. Here, the cathode K is 0 to
There is a modulation voltage of about 200 [V], and the first grid G
1 is held at 0 [V], and the second grid is held at about 30 [kV]. Note that other grids etc. are omitted. In addition, FIGS. A, B and C respectively show Y in the upper half.
The orbits of the electron beam in the (longitudinal) direction and the D (oblique) direction are shown, and the orbits of the electron beam in the X (horizontal) direction are shown in the lower half.

The thermoelectrons emitted from the cathode K form an electron beam, and the electron beam is formed into a rectangular beam spot by the generally rectangular passage hole of the first grid G1 and is subjected to the focusing action. 2 grid G2
Under the action of other grid electrodes not shown in the figure, the light proceeds toward the phosphor screen (not shown).

At this time, if a beam spot is formed so that the electron beam has a rectangular sectional shape as a whole, the behavior of the individual electron beams forming the rectangular shape near the cathode K is different. . An electron beam (hereinafter, referred to as an electron beam) located at a Y-axis direction (longitudinal direction) end that is a typical position and an electron beam (hereinafter, referred to as an electron beam) located at a D-axis direction (oblique direction) end. And an electron beam located at the end portion in the X-axis direction (transverse direction) (hereinafter referred to as an electron beam), the orbits of these electron beams are as follows. Will be different.

First, in the first grid G1, these electron beams are subjected to the focusing action. The influence of the focusing action depends on the potential distribution of the vertically long rectangular beam passage holes of the first grid G1. , The electron beam at the lateral end is the strongest, the electron beam at the longitudinal end is the intermediate, and the electron beam at the diagonal end is weakest. As a result, as shown in FIG. 10A, the actual crossover point (point intersecting the Z axis) a3 of the electron beam is formed near the entrance of the first grid G1 closest to the cathode K, and then the actual crossover of the electron beam is performed. The over point a1 is formed at a position slightly moved from a3 toward the phosphor screen, and the actual crossover point a2 of the electron beam is formed at a position near the second grid G2 slightly moved from the farthest a1. That is, as shown in FIG. 10A, the actual crossover points of the electron beams are formed in the order of a3, a1, and a2 from the cathode K side toward the phosphor screen side.

Next, these actual crossover points a3, a
When the electron beam with 1, a2, passes through the second grid G2 which has a diverging lens effect, the electron beam first comes from the farthest actual crossover point a3 from the second grid G2, Since the axial amount (the amount away from the Z axis) is large, that is, the axial amount passes the closest to the second grid G2, it proceeds with the strongest diverging action.
On the other hand, since the electron beam comes from the actual crossover point a2 closest to the second grid, the off-axis amount is small, that is, the electron beam passes in the vicinity of the Z axis far from the second grid G2 and is therefore subjected to a weak diverging action. proceed. The influence of the electron beam is between the electron beam and the electron beam.

The electron beam ,, is the second grid G
A trajectory passing through 2 and proceeding toward a phosphor screen (not shown) is extended toward the cathode K in reverse (shown by a broken line), and Z
A point that intersects the axis is a virtual object point. Electron beam,
The virtual object points of are va3, va1, and va2, respectively.
These virtual object points va3, va1, va2 represent the positions of effective object points viewed from the main lens.

The electron lens of the index tube which influences the electron beam emitted from these virtual object points until it reaches the phosphor screen thereafter, as will be described later in detail, has a convex lens action (focusing action). The lens ML is formed. Therefore, the virtual object points va3, va1, va2 are Z
If it is displaced in the axial direction, a focus shift as shown in FIG. 10B occurs, and the image formation points do not match. As shown in FIG. 10B, va on the Z axis from the cathode K toward the phosphor screen.
Each electron beam emitted from the virtual object point displaced in the order of 3, va2, va1 forms an image plane displaced in the Z-axis direction in the order of f3, f2, f1 by the convex lens action of the electron lens ML. However, defocus occurs.

The inventor of the present invention is concerned with the defocusing in the X and Y directions among these, Japanese Patent Application No. 6-286708 and Japanese Patent Application No. 7-86708.
No. 287527 (all of which have not been published at the time of filing this application), and the like, proposed to adopt a quadrupole electron lens 87 to solve the problem. As shown in FIG. 10C, the outline of the already proposed invention is that a convex lens action is exerted in the Y (longitudinal) direction and a concave lens action is exerted in the X (horizontal) direction in an electron beam focusing region. The quadrupole electron lens 87 is arranged. This allows
For the electron beam (electron beam at the lateral end),
The image forming point f3 is just focused on f0 on the fluorescent screen 61 by the concave lens action of the quadrupole. Similarly, for the electron beam (electron beam at the end in the vertical direction), the image forming point f1 is just focused on f0 on the fluorescent screen by the action of the quadrupole convex lens.

However, even with the technique of the quadrupole electron lens, the problem still remains with respect to the electron beam (electron beam at the end in the oblique direction). That is, before the quadrupole electron lens is arranged, the electron beam has a focal point f2 in front of the phosphor screen as shown in FIG. 10B, and is in an overfocus state. At this time, the quadrupole electron lens 87
Is adopted, the beam spot shape is a vertically long rectangular shape, so the effect of the quadrupole electron lens is that the X direction (horizontal direction)
The factor (convex lens action) in the Y direction is stronger than the factor (concave lens action). As shown in FIG. 10B, the electron beam was in the overfocused state, whereas as shown in FIG. 10C, the convex point action of the quadrupole electron lens 87 further moves the image forming point toward the main lens ML side. The image is moved to the image forming point f4, and the overfocus state is further advanced.

The present invention is a technique developed in order to further solve these problems at the stage of elucidating the behavior of the electron beam in the vicinity of the cathode K, as described above. In the following description of the present invention, the technology of the quadrupole electron lens such as Japanese Patent Application No. 6-286708 already developed has been adopted, and as a result, the Y (longitudinal) direction and the X (horizontal) direction have been adopted.
The description will proceed assuming that the electron beam in the direction is in the just focus state. Further, in the description of the present invention, the description regarding the quadrupole electron lens is omitted for the sake of simplicity and easy understanding.

However, it should be understood that the meaning of the present invention is not necessarily limited to the technique used in combination with the quadrupole electron lens. The present invention is to selectively control the electron beam mainly located in the D (oblique) direction among the individual electron beams forming the electron beam.

SUMMARY OF THE INVENTION Therefore, in view of the above-mentioned problems, the present invention provides a beam index tube equipped with an electron gun capable of forming a beam spot whose horizontal dimension is further reduced.

Further, the present invention provides a beam index tube equipped with an electron gun capable of forming a rectangular beam spot without causing a halo.

Further, the present invention provides a fine (fine pitch)
A beam index tube capable of realizing an image is provided.

[0031]

According to the present invention, in a beam index type cathode ray tube, an electron beam used in the cathode ray tube adopts an electron beam forming a beam spot cross section of a generally elongated rectangular shape when viewed from a screen. The orbit of the electron beam is controlled by the octopole electron lens means.

In one embodiment, the octupole electron lens means is arranged so as to surround the electron beam in the vicinity of the main lens or at a position closer to the fluorescent screen with respect to the main lens, and is obliquely arranged in the beam spot cross section. The orbit of the electron beam located is corrected to be divergent.

Further, in another aspect, the octupole electron lens means is arranged so as to surround the electron beam at a position near the main lens or near the cathode with respect to the main lens, and is oblique in the beam spot cross section. The orbit of the electron beam located in the direction is also corrected to be divergent.

As described above, by adopting the octopole electron lens means, it is possible to selectively control the trajectory of the electron beam positioned in the oblique direction within the beam spot cross section.

Further, the quadrupole electron lens selectively controls the electron beam positioned in the orthogonal direction, and the octopole electron lens selectively controls the electron beam in the oblique direction. With a proper combination of polar electron lenses, the electron beams in the orthogonal axis direction and the oblique direction can be individually and comprehensively controlled.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a beam index tube according to the present invention will be described in detail below with reference to the accompanying drawings.

[First Embodiment] (Structure of First Embodiment) FIG. 1 is a horizontal cross-sectional view of a main part of an index type cathode ray tube according to the first embodiment, as viewed from above. In FIG. 1, the beam index tube is covered with a funnel glass 1 having a high vacuum inside, and the funnel glass 1 includes a neck portion 3 and a funnel portion 4.
And the panel portion 6. An electron gun 5 is incorporated inside the neck portion 3. The electron gun 5 includes a cathode (hot cathode) K which is an electron beam generation source and a first grid (first control electrode) which constitutes an electron lens system. G1, a second grid G2 (first acceleration electrode), a third grid G3 (focus electrode), and a fourth grid (final acceleration electrode) G4 are provided.

The arrangement of these components is determined by the neck portion 3
The cathode K is attached to the stem portion 7 at the rear end with its terminal 9 protruding to the outside, and the first grid G1 and the second grid G are sequentially arranged from the cathode K toward the phosphor screen (not shown).
The second, third grid G3 and fourth grid G4 are arranged.

The voltage applied to each electrode of the electron gun 5 is as follows, for example. -Cathode K ... Modulation in the range of about 0 to 200 [V] -First grid G1 ... 0 [V] -Second grid G2 ... approximately 30 [kV] (anode voltage) -Third grid G3 ... number [kV] (Focus voltage) -Fourth grid G4 ... Approximately 30 [kV] (anode voltage)

Reference numeral DY is a deflection yoke DY (Deflection Yoke) for generating a deflection magnetic field, but the deflection yoke DY is adopted in both the present invention and the prior art, and its lens action and effect are the same. Is. Therefore, in order to simplify the drawings and the description for the sake of clarity, the deflection yoke DY will be described unless otherwise specified.
Items related to are omitted.

As described above, the first control electrode, the first
By forming the opening of the grid G1 into a small rectangular shape, the electron beam 8 emitted from the cathode K is formed into a vertically long rectangular shape (reference numeral 83 in FIG. 9) and is accelerated by the first grid G2 which is the first accelerating electrode. The third grid G3, which is a focus electrode, receives a focus adjustment action, and the fourth grid G4, which is a final accelerating electrode, accelerates and focuses the light on the phosphor screen 11.

Expressed as an optical lens system, a main lens ML having a convex lens function is formed at the third grid G3 by the second to fourth grids G2, G3 and G4, and a light ray (electron beam) is formed at an image forming point ( Focus on the phosphor screen 11. Hereinafter, that position is shown by a broken line as the main lens portion ML.

It should be noted that the index pulse, sensor, color signal switching circuit, etc. described in FIG. 8A, which are not directly related to understanding the present invention, are not shown in the figure or their description is omitted.

For such a beam index tube, an octupole electron lens QP1 is arranged in the vicinity of the fourth grid G4 and between the main lens portion ML and the fluorescent screen 11 in this embodiment. There are mainly two modes of embodying the octupole electron lens QP1, namely the following electrostatic octupole and electromagnetic octupole.

(Electrostatic Octopole) First, the case where the octupole electrode QP1 is formed as an electrostatic octupole will be described. The configuration of the electrostatic quadrupole, which has a smaller number of poles than this, is well known in the art. For details, see Shoji Shirai.
and Masakazu Fukusima, "Quadrupole Lens for Dynam
ic Forcus and Astigmatism Contorol in an Elliptica
l Aperture Lens Gun ", Proceeding SID 87 DIGEST Page
s 162-165, etc.

The electrostatic octupole QP1 is arranged inside the fourth grid G4 so as to be orthogonal to the traveling direction of the electron beam, as shown in a perspective view of FIG. 2A and a front view of FIG. 2B, for example. A disk-shaped electrode having a vertical angle in the X and Y directions and a beam-passing hole 15, which is a generally rhombic opening having diagonal sides, is formed inside the electrode.
This electrostatic octupole electrode QP1 is attached to the fourth grid G4 by an appropriate method such as welding,
The same voltage is applied. The "generally rhombus shape" does not necessarily mean only the rhombus shape, but X, Y with respect to the electron beam in the D direction (oblique direction) described later.
A shape that exerts a stronger influence than the electron beam in the direction (orthogonal axis direction) is included. Therefore, the first good G1
The modified rhombus shape and the like are included in correspondence with the rectangular shape and the like.

As shown in FIG. 2B, the electrostatic octupole electrode QP
Since the beam passage hole 15 of No. 1 has a generally rhombic shape, the beam passing hole 15 of No. 1 has an oblique D as compared with four directions of ± X and ± Y directions.
The edges in the four directions of 1, D2, D3 and D4 are positionally closer to the electron beam flow and have a relatively strong influence.
(Here, for the sake of explanation, the shape of the electron beam spot, which is a set of electron beams, is indicated by a broken line circle.) That is, the electrostatic octupole electrode having the diamond-shaped beam passage hole 15 is the fourth grid G4. Since the same voltage (anode voltage of about 30 [kV]) is applied as the above, ± X and ± Y
The electron beam passing in the vicinity of the oblique four directions D1 to D4 receives a stronger attractive force than the electron beam passing in the vicinity of the apex angle in the four directions. If the X and Y directions and the D direction are relatively considered (that is, based on the attractive force received by the electron beams in the X and Y directions as a reference), the electron beam 8 is selectively selected in the four oblique directions D1 to D4. Can be said to be divergent to.

The advantages of using an electrostatic octupole instead of the electromagnetic octupole described below as the octupole electron lens are:
In the electromagnetic octupole, a current generating means for driving the coil must be additionally provided as described later, and therefore the electrostatic quadrupole makes the structure of the electron gun 5 simpler and the manufacturing cost lower. In point.

(Electromagnetic octopole) Next, an octopole electron lens Q
A case where P1 is configured as an electromagnetic octupole will be described. FIG. 3 is a diagram for explaining the details of the electromagnetic octupole QP1, and instead of the electrostatic octupole QP1 of FIG.
This electromagnetic octupole is placed in the −III direction. FIG.
As shown in FIG. 4, four electromagnets 17a, 17b, 17c, 17d are arranged around the neck portion 3 of the funnel glass. The DC power source E is connected to the coil windings sequentially wound around four electromagnets 17a, 17b, 17c and 17d each having a substantially U-shaped core. In this way, the electromagnetic octupole QP1 is composed of the four electromagnets 17a to 17b, and as shown in the drawing, the eight-pole magnetic pole (four-pole magnetic pole pair) N.
1, S1, N2, S2, N3, S3, N4, S4 are formed.

An electron beam is emitted near the center of the neck portion 3 of the funnel glass in a direction perpendicular to the drawing from the front to the back of the paper (from the cathode K to the phosphor screen 11). That is, as shown in the drawing, the beam current flows from the back side of the paper to the front side. For the sake of explanation, the shape of an electron beam spot, which is a set of electron beams, is shown by a broken line circle.

Due to this electromagnetic octupole, in the ± X and ± Y directions, between N4 and S1, between N2 and S3, between N1 and S2, and N3.
Due to the respective magnetic fields between S4, the electron beams affected by these magnetic fields are focused in the central axis direction of the funnel glass tube (inward in the radial direction). On the other hand, diagonal direction D
In the four directions of 1 to D4, between N1 and S1, between N2 and S2, N
The electron beam is diverged radially outward by the magnetic fields between 3-S3 and N4-S4. That is, also in the case of the electromagnetic octupole, as in the case of the electrostatic octopole, when the electron beam is relatively considered (based on the inward focusing force in the X and Y directions), the oblique directions D1 to D4 are obtained. It can be said that it is subjected to divergence in the four directions.

The electromagnets 17a to 17d may be magnetic field generating means, and may be constituted by, for example, permanent magnets.
Specifically, for example, four appropriate band-shaped permanent magnet pieces having flexibility may be attached to the periphery of the neck portion 3 to be formed. Further, a part of the electromagnet shown in FIG. 3 may be configured by a permanent magnet, and a combination of the permanent magnet and the electromagnet may be configured.

The advantage of using an electromagnetic octupole instead of the electrostatic octupole as the octupole QP1 is that the magnetic field strength of the electromagnetic octupole (corresponding to the lens power of the optical lens system) is appropriately adjusted. The divergence of the desired oblique electron beam can be adjusted freely. That is, the magnetic field strength of the electromagnetic octupole QP1 is adjusted by separately providing the DC power source E to be applied to each of the four electromagnets 17a to 17d, or by changing the number of coil windings of the electromagnets 17a to 17d. The electron beams passing through D1, D2, D3 and D4 can be controlled independently. Therefore, even if the divergence angle in each oblique direction differs depending on the index tube, each can be independently adjusted to the just focus state.

Further, the magnetic field strength of all or an arbitrary part of each magnetic pole of the electromagnetic octupole is dynamically modulated by a current or voltage signal synchronized with the deflection cycle to obtain a fluorescent screen (image).
Without degrading the focus at the center, it is possible to improve and maintain the focus at the periphery of the image, correct the spot shape at each position on the screen, and optimize the beam spot over the entire screen.

As described above, the octupole QP1 can be formed by an electrostatic octupole or an electromagnetic octupole (or a permanent magnet piece or an electromagnet and a permanent magnet are used in common). The mounting position of the octupole electron lens QP1 in the Z direction is as follows:
Any region near L or a focusing region of the electron beam 8 closer to the phosphor screen 11 than the main lens portion ML may be used. Preferably, it is provided near the third grid G3 or the fourth grid G4.

(Principle of Example) FIG. 4 is a schematic diagram when the electron lens system of the beam index tube according to Example 1 is replaced by an optical lens system to explain the principle of this example. Is. In general, the aberration theory of an optical lens system holds almost as is also in the area of an electron lens system in electron optics applied to a cathode ray tube. Here, symbol a indicates an object point near the cathode K, ML indicates a main lens, QP1 indicates an octopole electron lens, and f1 indicates an image forming point on the fluorescent screen 11. Further, the center of the optical axis is the Z axis, and the upper part of the Z axis serves as a lens function in the X and Y directions (orthogonal axis direction), and the lower part is D
It shows the lens action in the direction (oblique direction). As described above, this octupole QP1 is realized by an electrostatic octupole or an electromagnetic octupole (or a permanent magnet).

In reality, the electron beam spot has a small spot shape in the horizontal axis direction due to the opening of the first grid G1. However, for simplification of explanation, the image of the virtual object point and the image formation point will be described as a small point.

In FIG. 4, the schematic diagram of the optical lens system of the beam index tube corresponding to the prior art already proposed corresponds to the case without the octopole QP1, that is, the case with only the main lens ML.

First, the main lens M corresponding to the prior art.
Assuming that only L exists and the octopole QP1 does not exist, in the X and Y directions (orthogonal axis directions), just focus is achieved on the screen by performing the above-mentioned quadrupole correction (f1). On the other hand, in the oblique direction (D), the object point va2 is focused by the convex lens action of the main lens ML and the composite lens action with the above-mentioned quadrupole, and then is imaged at the image forming point f2, which is over. It is in focus.

On the other hand, in the first embodiment, in addition to the main lens ML, the octopole electron lens QP1 is arranged between the main lens ML and the image formation point. The octupole electron lens QP1 has a lens action in which the action in the X and Y directions and the action in the D direction are different from each other. If you think relatively,
The octopole QP1 has a divergent effect only in the oblique direction. As a result, just focus is achieved not only in the X and Y directions but also in the D direction.

As a modification of this embodiment, the octupole electron lens QP1 may be composed of a plurality of octupoles. Specifically, the octupole QP1 may be configured by arranging one or both of two or more electrostatic octupoles and electromagnetic octupoles in the Z direction. As long as the combination of a plurality of octupoles has a substantially similar action as the octupole electron lens QP1 as a whole, that is, a relatively concave lens action in the D direction as compared with the X and Y directions, this embodiment is performed. This is a technology equivalent to the example.

As described above, in the beam index tube (FIG. 1) according to the first embodiment, as compared with the case where the octupole electron lens QP1 of the prior art is not inserted, the X and Y directions (orthogonal axis directions) are Similarly, a just focus state is obtained also in the D direction (oblique direction), and a rectangular beam spot without halo is obtained. Therefore, by adopting the above-described first embodiment, an index type cathode ray tube with higher definition can be realized.

[Second Embodiment] (Structure of Second Embodiment) FIG. 5 is a cross-sectional view of a main portion of an index type cathode ray tube according to the second embodiment, as viewed from above. Compared with the first embodiment (FIG. 1), the difference is that the octopole electron lens QP2 is arranged on the focus electrode G3. In addition, the same reference numerals are given to the same member elements as those in the first embodiment, and the duplicated description will be omitted.

The electron gun 5 includes a cathode (hot cathode) K and a first grid (first control electrode) G which constitutes an electron lens system.
1, a second grid (first acceleration electrode) G2, a third grid (focus electrode) G3, a fourth grid (final acceleration electrode) G4, and an octopole QP2 arranged on the third grid.
And

Expressed as an optical lens system, the main lens ML is formed at the third grid G3 by the second to fourth grids G2 to G4. The octopole QP2 is arranged on the main lens portion ML. Double pole QP2
Can be achieved by either an electrostatic octopole or an electromagnetic octopole, as described in the first embodiment, but the configuration and action are different from those of the first embodiment.

(Electrostatic octopole) FIG. 6A shows a case where the octopole QP2 is composed of an electrostatic octupole. When the electrostatic octopole is used as shown in FIG. 6A, the electrostatic octupole QP2 has four sides having sides in X and Y directions and an apex angle in an oblique direction as shown in the front view of FIG. Is an electrode that forms a rectangular opening, and is an electrode in which a generally rectangular beam passage hole 19 is formed. The electrostatic octupole electrode QP2 is attached to the third grid G3 by an appropriate method such as welding, and the same voltage is applied.

The "generally rectangular shape" does not necessarily mean only a rectangular shape, and is stronger than the electron beam in the X and Y directions (orthogonal axis direction) with respect to the electron beam in the D direction (oblique direction). It shall include the shape that affects it. Therefore, the modified rectangular shape is included corresponding to the rectangular shape of the first good G1 and the like. The electrostatic octupole QP2 in the second embodiment corresponds to a structure obtained by rotating the electrostatic octupole OP1 in the first embodiment by 1/8 rotation (angle 45 degrees).

Since the beam passage hole 19 has a generally rectangular shape, it acts on the electron beam 8 in the opposite manner as compared with the action of the electrostatic octupole QP1 of the first embodiment. That is, the electrostatic octupole electrode Q forming the rectangular beam passage hole 19
Since the same voltage as the third grid G3 (focus voltage of about several kV) is applied to P2, ± X, ± Y
The flow of the electron beam passing near the apex angle in the four directions of the directions (orthogonal axis directions) receives a strong attractive force, whereas the oblique directions (D1 to D4) receive a weaker attractive force. Therefore, if considered relatively (that is, based on the strong attractive forces in the X and Y directions), the electron beam 8 is directed in the oblique direction D.
It can be said that the divergent action is selectively exerted in the four directions of 1 to D4.

The merit of using an electrostatic octopole instead of an electromagnetic octopole as the octopole electron lens is the same as that described in the first embodiment.

The principle of the embodiment in this case is similar to that of the first embodiment, and by making the focusing power of the main lens in the D direction relatively weaker than the focusing power in the XY directions, the imaging position f
1 and f2 can be matched.

As a modification of this embodiment, as described in the first embodiment, the octupole electrode QP2 may be composed of one or both of a plurality of electrostatic octupoles and electromagnetic octupoles. .

As described above, in the beam index tube according to the second embodiment (FIG. 5), the beam spot of the prior art is a rectangular beam spot with no halo, as compared with the case where the octopole OP2 is not inserted. Can be obtained.
Therefore, by adopting the second embodiment described above, an index type cathode ray tube with higher definition can be realized.

[Additional Embodiments] The embodiments according to the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various improvements and modifications that can be made by those skilled in the art can be made. Of course you can get it.

That is, when the beam index tube according to the present invention is expressed as an optical lens system, the electron gun used in this cathode ray tube has a main lens ML and further has an octopole QP to form an image. The beam index tube is characterized in that the oblique direction of the shape of the beam spot at the point f is relatively corrected so that the beam is just focused.

In the above-described first embodiment, the octopole Q for relatively enhancing the focusing force of the electron beam in the oblique direction is provided in the electron beam divergence region between the main lens ML and the image forming point f.
It is realized by arranging P1.

The above-described second embodiment is realized by disposing the octopole QP2 that relatively weakens the focusing power of the electron beam in the oblique direction in the focusing region of the main lens ML.

However, the octupole electron lens QP is used for one or both of the focusing area and the diverging area of the electron beam to selectively correct the electron beam in the D direction (oblique direction) to achieve just focus. What is achieved is equivalent to the present invention as long as its action and effect are substantially the same.

Further, by combining the quadrupole lens disclosed in the prior art with the octupole electron lens QP described above, among the electron beams forming the beam spot, the X and Y directions (orthogonal direction) and the D direction (oblique direction). In order to achieve just focus as a whole by selectively correcting each electron beam in each direction), such an invention is within the technical scope of the present invention as long as its action and effect are substantially the same. included. The technical scope of the present invention is determined based on the description of the claims.

[0079]

According to the present invention, it is possible to provide a beam index tube equipped with an electron gun capable of forming a beam spot whose horizontal dimension is further reduced.

Further, according to the present invention, it is possible to provide a beam index tube equipped with an electron gun capable of forming a rectangular beam spot without causing a halo.

Further, according to the present invention, it is possible to provide a beam index tube capable of realizing a fine (fine pitch) image.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of a first embodiment of a beam index tube according to the present invention.

2A and 2B are a perspective view and a front view for explaining an electrostatic octupole electron lens used in the first embodiment shown in FIG.

FIG. 3 is a diagram for explaining an electromagnetic octupole electron lens used in the first embodiment shown in FIG.

FIG. 4 is a diagram illustrating the principle of the first embodiment shown in FIG.

FIG. 5 is a diagram showing the configuration of a second embodiment of the beam index tube according to the present invention.

FIG. 6 is a diagram for explaining an electrostatic octopole electron lens used in the second embodiment shown in FIG.

FIG. 7 is a diagram illustrating an outline of a conventional shadow mask tube, which is compared with an index type cathode ray tube.

FIG. 8 is a diagram illustrating an outline of an index type cathode ray tube.

FIG. 9 is a diagram for explaining a difference between the elliptical and vertically long rectangular beam spots and the first grid shape on the phosphor screen, and a halo generated in the vertically long rectangular beam spots.

FIG. 10 is a diagram illustrating a cause of a halo that occurs in the vertically long rectangular beam spot shown in FIG. 9; here,
FIG. 10A is a diagram for explaining equipotential surfaces of the holes of the first grid G1 electrode, and FIG. 9B is a diagram showing electrons in the horizontal direction (X), vertical direction (Y), and diagonal direction (D) near the cathode K. It is a figure explaining the track of a beam.

[Explanation of symbols]

1 funnel glass, 3 neck part, 4 funnel part, 5 electron gun, 7 stem part, 8 electron beam, 9 terminal, 11 fluorescent screen (imaging surface), 15 beam passage hole, 1
7, 17a, 17b, 17c, 17d Electromagnet, 19
Beam passing holes 21, 21a, 21b, 21c, 21d
Electromagnets, 24a, 24b, 24c, 24d electromagnets,
51 electron gun, 53 electron beam, 55, 55a, 55
b shadow mask, 57 phosphor screen, 59 phosphor, 6
1 phosphor screen, 63 phosphor, 65 index phosphor, 65 slots, 67 electron beam, 69 index signal, 71 sensor, 73 color signal switching circuit, 7
4 beam passage hole, 75 guard band, black stripe, carbon stripe, 77 round beam spot, 79 vertically elongated beam spot, 81 elliptical beam spot, 83 rectangular beam spot, 8
5 halo, 87 quadrupole electron lens a, a1, a2, a3 object point, a1, a2, a3 real crossover point, va1, va2, va3 virtual object point, D
Diagonal direction, DY deflection yoke, E DC power supply, f, f
1, f2, f3 imaging point, G1 first grid, G2
2nd grid, G3 3rd grid, G4 4th
Grid, ML main lens, QP1, QP2
Octopole electron lens (octupole electrode), K cathode, WE
Width dimension of elliptical beam spot, W1 and W2 phosphor width dimension, X and Y orthogonal axis direction

Claims (10)

[Claims] 1. In a beam index type cathode ray tube, an electron gun used in the cathode ray tube adopts an electron beam which forms a generally vertically elongated rectangular beam spot cross section when viewed from a screen, and the trajectory of the electron beam is changed. A beam index type cathode ray tube characterized by being controlled by an octopole electron lens means. 2. The beam index type cathode ray tube according to claim 1, wherein the generally vertically long rectangular beam spot cross section is formed by a first control electrode having a vertically long electron beam passage hole. tube. 3. The beam index type cathode ray tube according to claim 1, wherein the electron gun comprises at least one or more grids acting as a main lens, and the octupole electron lens means is the main lens. Is arranged so as to surround the electron beam at a position near the fluorescent surface with respect to the main lens or near the main lens, and the trajectory of the electron beam positioned in the oblique direction in the cross section of the beam spot is selectively corrected to be divergent. Beam index type cathode ray tube. 4. The beam index cathode ray tube according to claim 1, wherein the octupole electron lens means comprises an electrostatic octupole having a beam passage hole of generally rhombic or substantially square shape. 5. The beam index type cathode ray tube according to claim 1, wherein the octupole electron lens means is an electromagnetic octupole. 6. The beam index type cathode ray tube according to claim 5, wherein the magnetic field strength of all or any part of each magnetic pole of the electromagnetic octupole is dynamically changed by a current or voltage signal synchronized with a deflection cycle. A beam index cathode ray tube that modulates and maintains the focus in the peripheral area of the image without degrading the focus at the center of the phosphor screen. 7. The beam index type cathode ray tube according to claim 1, wherein the octupole electron lens means comprises a plurality of permanent magnets. 8. The beam index type cathode ray tube according to claim 1, wherein the octupole electron lens means is a combination of an electromagnetic octupole and a permanent magnet. 9. The beam index type cathode ray tube according to claim 1, wherein the electron gun comprises at least one or more grids acting as a main lens, and the octupole electron lens means is the main lens. A beam which is arranged so as to surround the electron beam at a position near the cathode or close to the main lens with respect to the main lens and selectively corrects the trajectory of the electron beam located in the oblique direction in the cross section of the beam spot to a divergent form. Index type cathode ray tube. 10. In a beam index type cathode ray tube, an electron gun used in the cathode ray tube is provided with at least one or more grids acting as main lenses, and positioned at an end portion in a cross section of a beam spot in an orthogonal axial direction. Quadrupole means for selectively correcting the trajectory of the electron beam to be used, and octupole electron lens means for correcting the trajectory of the electron beam located at the diagonal end in the beam spot cross section. Beam index type cathode ray tube.