JPH10294067A - Cathode-ray tube and electron gun for cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the resolution of the whole of a screen by making each beam spot at the peripheral part and center of the screen round with the lateral distortion of each side beam corrected. SOLUTION: A quadrupole lens can be formed of an electrostatic electrode such as a convergence deflector comprising a convergence plate CP and convergence shield plate CS of a cathode-ray tube capable of forming a quadrupole lens with dynamic focus voltage applied to the main lens of an electron gun 5 while being synchronized with deflection so as to allow the electrostatic electrode to be interposed between the main lens and a deflection yoke. In this case, the electrostatic electrode is formed while being approached to the quadrupole lens side introduced by the deflection yoke as much as possible such that quadrupole electromagnetic fields introduced by the deflection electromagnetic field of the deflection yoke, are canceled by the quadrupole electromagnetic fields introduced by the quadrupole lens of the electrostatic electrode, and concurrently, the asymmetric distortion of each side beam is corrected by the electrostatic electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an electron gun for a cathode ray tube, and more particularly to a cathode ray tube and an electron gun capable of obtaining a high resolution over the entire area of a face panel screen.

[0002]

2. Description of the Related Art Various improvements have been made to CRTs and electron guns in order to project a high-resolution screen over the entire face panel of a cathode ray tube (hereinafter referred to as CRT).

A general color CRT is shown in FIG.
The tube 2 includes an electron gun 5 and a deflection yoke 6 disposed in the neck 2 c of the tube 2.

The tube 2 comprises a panel 2a, a funnel-shaped funnel 2b and a neck 2c.
A phosphor of three primary colors is applied to the inner surface to form a phosphor screen 3, and a color selection electrode (not shown) is provided.
The primary color beam is irradiated on predetermined three primary color stripes of the fluorescent screen 3.

The neck 2c and the funnel 2b of the tube 2
A saddle-type deflection yoke 6 is provided outside the vicinity of the boundary.

FIGS. 7 and 8 show the inside of the neck portion 2c of the tube 2. FIG.
The electron gun 5 is provided as shown in FIG.
(Red), G (green), B (blue) cathodes RK, GK, B
K, a first grid G ₁ and a second grid G ₂ forming a prefocus unit, a third grid G ₃ , a fourth grid G ₄ and a fifth grid G ₅ forming a main lens, and a concentrated deflection for electrostatic use. Devices 33 are sequentially arranged, and the centralized deflector 33
Is composed of a convergence plate (hereinafter referred to as CP) and a convergence shield plate (hereinafter referred to as CS).

These electron guns 5 are integrally insulated and held by upper and lower (Y-axis) bead glasses 8U and 8D, and are fixed to a stem base 9. In FIG. 8, reference numeral 10 denotes an exhaust glass tube for exhausting the inside of the tube 2 for vacuuming, and 11 denotes an internal resistance dividing plate (hereinafter referred to as IBR) for dividing the anode voltage by about 5% and supplying the CP. Is written).

The centralized deflector 3 comprising the above-mentioned CP and CS
3 will be described with reference to FIGS. 9 and 10. FIG. 9 is a sectional view taken along the line AA 'of FIG. 8, and FIG. 10 is a view taken along the line BB' of FIG.
It is an arrow direction sectional view.

In FIG. 9 and FIG. 10, the side beam 7 emitted from the cathode RK for R and the cathode BK for B
S is passed to the side of CS to which a high anode voltage is applied, passes between CP and CS, and is then focused on the phosphor screen 3 and emitted from the G cathode GK.
C directly enters the phosphor screen without being electrostatically deflected through between the two CPs.

[0010] As shown in FIG. 10, both the CP and CS are formed by bending two metal plates into a U-shape to form a rectangular shape, and a tongue piece obtained by bending the U-shaped bent end vertically at a right angle. Bead glass 8U so that 12 do not touch each other,
8D is welded. Further, as shown in FIG. 9, the length of CP in the Z-axis direction is formed shorter than that of CS. That is, CS protrudes toward the fluorescent screen 3 side of the CRT.

In the CRT having the above-described configuration, an electron beam 7 emitted from the three primary color cathodes RK, GK, and BK in the Z-axis direction of the phosphor screen 3 of the panel 2a is generated on the screen of the phosphor screen 3 by collision. The beam spot must be small in diameter and a perfect circle, but beam spot distortion occurs at the periphery of the screen due to the following two factors. (A) Distortion of the geometric beam spot caused by the difference in image point distance between the electron beam deflected to the periphery of the screen and the center of the screen. (B) Astigmatic distortion of a beam spot due to a quadrupole force of an asymmetric deflection magnetic field from a deflection yoke or the like. And

The cause of the distortion in the above item (a) will be described with reference to FIG. FIG. 11 is an explanatory diagram showing a cause of a beam spot being distorted in a peripheral portion due to a geometric factor. When the optimum focus voltage is selected so that the beam spot size of the electron beam 7 emitted from the deflection center line 13 of the deflection yoke 6 to the center of the fluorescent screen 3 applied to the inner surface of the panel 2a becomes a perfect circle and a small diameter, The focal plane 14 of the electron beam 7 composed of the center beam 7c and the side beam 7s has a radius up to the fluorescent screen 3 centered on the intersection of the center beam 7c orthogonal to the deflection center line 13, and is in the longitudinal direction of the panel 2a (X-axis). Direction) is 8000 to 10000 even if it is formed cylindrically.
Since a large R is formed with R, the peripheral electron beam 7 ′ composed of the center beam 7 c ′ and the side beam 7 s ′ is in an overfocus state in the left and right peripheral portions, and is in a focus state. Due to the difference Δd in image point distance between the surfaces 3, the beam spot in the peripheral portion of the screen of the CRT 1 becomes horizontally long, and a favorable beam spot and resolution cannot be obtained in the peripheral portion.

Next, the cause of the distortion of the beam spot in item (b) will be described with reference to FIG. FIG. 12 illustrates quadrupole astigmatic distortion generated by the electron beam 7 due to an asymmetric magnetic field such as a deflection yoke.

In general, in the in-line type color CRT, the horizontal deflection magnetic field of the deflection yoke 6 is distorted in a pincushion shape in order to obtain a self-convergence effect.
In particular, the electron beam 7 at the peripheral portion of the screen is subjected to the deflection action of the quadrupole magnetic field component 15 in FIG. In the (Y-axis direction), a compressive force such as compression as indicated by an arrow 17 is received. As a result, the electron beam 7 'becomes horizontally long, and the resolution at the periphery of the screen is degraded.

In order to correct such a distortion of two points (a) and (b), the present applicant first described in IEEE 1988 INTERNATIONA.
L DISPLAY RESEARCH CONFERENCE, CH-2678-1 / 88 / 0000-00
13 proposed a CRT as described below.

That is, in order to supplement the above two points (a) and (b), the electron gun is connected to a DQL (DYNAMIC QUADRUPOLE LENS).
This is what we have achieved.

FIG. 13 shows a DQL type electron gun. The fourth grid G ₄ for focusing constituting the main lens shown in FIG. 7 is formed into a large-diameter unipotential lens and divided into three parts. The fourth grid G _4AB, the second fourth grid G _4C, and the third fourth grid G _4DE are formed.

First and third fourth grids G _4AB and G _{4AB
The 4DE} has a bottomed cylindrical shape, an oval aperture 19 is drilled in the bottom, a second fourth grid G _4C is formed in a disk shape, and an elliptical aperture 18 is drilled.

First and third fourth grids G _4AB and G _{4AB
The major} axis of the _4DE aperture 19 is parallel to the X-axis direction as shown in FIG. 14, the major axis length is 11.4φ, and the minor axis length is 9.
0 mm. The major axis of the second fourth grid G _4C is parallel to the Y-axis direction, the major axis length is 11.4φ, and the minor axis length is 9.5 mm.

Further, the second grid G ₂ and the third grid G
G _M grid is disposed between the _3, the G _M grid three apertures in the X-axis direction is formed, the apertures of the central circular, lateral apertures made elliptical, G _M grid and the third grid G ₃ are constitutes three small bipotential lens.

[0021] G _M grid and the second in the electron gun structure of the above
A fixed voltage Fc is supplied to the fourth grid G _4C of
FIG. 1 shows the first and second fourth grids G _4AB and G _4DE .
As shown in FIG. 5, during one vertical period (1 V), a dynamic focus voltage Va having a voltage substantially equal to the fixed voltage Fc for focusing at the center of the screen and a voltage waveform higher than the fixed voltage Fc at the left and right of the screen is applied. 3rd and 5th grid G
₃ and G ₅ are accelerating anode voltage Va is supplied.

When the electron beam 7 is deflected to the center 21 (see FIG. 16) of the screen of the panel 2a via the deflection yoke 6, the fixed voltage Fc for focusing and the dynamic focus voltage Fv are changed as shown in FIG. Since they are equal, the potentials of the first to third fourth grids G _4AB , G _4C , G _4DE are equal and the third grid G ₃ , the fourth grid G _{4 and} the fifth grid G ₅ operate as a normal _unipotential lens.

Next, when the electron beam is deflected by the deflection yoke 6 to the peripheral portion 20 (see FIG. 16) of the panel 2a, the first and third fourth grids G _4AB and G _4AB
4DE has a higher voltage than the second fourth grid G _4C and the third
The focal length of the grid G ₃ and the first of the fourth grid G _4AB and third fourth grid G _4DE a main lens formed by the fifth grid G ₅ are longer (a) geometric is a disadvantage in terms It becomes possible to correct the geometric distortion.

The first to third fourth grids G _4AB ,
The DQL (quadrupole lens) composed of G _4C and G _4DE generates an electrostatic quadrupole magnetic field around the screen as shown in FIG. It is configured to cancel the magnetic field of the heavy pole.

That is, as described with reference to FIG.
In the X axis direction, a compressive force of 1 compresses the electron beam 7 '.
6 'operates in the quadrupole magnetic field, and an extension force 17' operates in the Y-axis direction.
In contrast to the stretching force 16 and the compressing force 17 in the X and Y directions shown in FIG.
The astigmatism distortion of the term (ii) is corrected.

The electron beam in the central portion 21 of the screen operates as a normal _unipotential lens since the first to third fourth grids G _4AB , G _4C and G _4DE have the same potential and do not generate a quadrupole magnetic field. It will be.

According to the DQL type electron gun shown in FIG. 13, the optical model diagram can be represented as shown in FIG.

In FIG. 17, the main lens 24 is the third lens.
Grid G ₃ and the first of the fourth grid G _4AB and between the third
_Occurs between the fourth grid G _4DE and the fifth grid G ₅ , and in the second fourth grid G _4C , the quadrupole lens (DQL) 2
Yields 4. Numeral 25 indicates the DQL of the deflection magnetic field generated by the deflection yoke 6.

In the model diagram of FIG. 17, the upper side of the center line 26 represents the optical model in the Y-axis direction (vertical direction), and the lower side represents the optical model in the X-axis direction (horizontal direction).

That is, in the Y-axis direction, the main lens 23 and the DQL 25 by the deflecting magnetic field act as a convex lens, exhibiting a converging lens effect, and the DQL 24 of the main lens acts as a concave lens, exhibiting a diverging lens effect.

In the X-axis direction, the main lens 23 and the DQL 24 of the main lens 23 act as a convex lens,
It shows a converging lens effect, and the DQL 25 by the deflection magnetic field acts as a concave lens and shows a diverging lens effect. Therefore, the electron beam 7 emitted from the crossover point 28 is repeatedly focused and diverged as shown by the solid line in FIG. 17, and is irradiated on the phosphor screen 3 of the panel 2a to generate a beam spot 40 or 41 having a predetermined diameter. (See Fig. 18)

In FIG. 17, a tangent line 29 indicated by a broken line along the locus of the electron beam 7 emitted from the crossover point 28 of the electron beam 7 and a broken line along the electron beam 7 also incident on the phosphor screen 3 Intersection 3 of tangent line 29 shown
The distances to the X-axis and Y-axis directions until 0 are ax and bx, respectively.
And ay and by, the imaging magnification M of the beam spot is Mx = bx / ax in the X-axis direction, and My in the Y-axis direction.
= By / ay.

[0033] In general spot size magnification caused spot diameter dx and the diameter enlarged portion D _SC due to lens aberrations
These values largely depend on the imaging magnification M.

Therefore, it is necessary to make the values of the imaging magnifications Mx and My equal in the X and Y axis directions as much as possible. However, according to the configuration of FIG. 17, the horizontal direction M is larger than the vertical direction My described above.
x increases, the vertical and horizontal image magnification difference ΔM = Mx−My increases, and as shown in FIG. 18, the beam spot 4 at the center of the screen projected on the screen 31 of the panel 2a of the CRT.
0 is substantially circular, but beam spot 4 at the periphery of the screen
1 is horizontally long, so that a uniform resolution cannot be obtained for the entire screen.

In order to make such a horizontally long spot in the peripheral portion of the screen as round as possible, the distance between the quadrupole lens 25 caused by the deflection magnetic field generated by the deflection yoke 6 and the quadrupole lens 24 generated by the main lens is required. In order to realize this, a quadrupole lens is generated using the CS of the centralized deflector 33 of the electron gun of the Trinitron (Sony trademark) CRT as shown in FIG. Like

That is, the deflection yoke 6 is connected to the electron gun 5 shown in FIG.
Is located on the panel 2a side of the tubular body 2 from the position of the centralized deflector 33, and as shown in the optical model diagram of the electron gun in FIG.
Since the quadrupole lens 32 of CP and CS can be generated between the lens 5 and the main lens 23, the vertical and horizontal image magnification difference ΔM ′ = Mx′−My ′ can be reduced.

However, since the quadrupole lens formed by the concentrated deflector 33 is fixed irrespective of the deflection, distortion occurs in the center portion 21 of the screen. In order to correct this, the main lens 23
The applicant of the present application has previously proposed to apply the reverse DQL to that described in FIG.

In order to form a quadrupole lens using the above-described concentrated deflector 33, the concentrated deflector 33 is configured as shown in a perspective view of FIG. FIG. 20 shows the centralized deflector 33 viewed from the panel 2a side of the tubular body 2, and FIG.
FIG. 22 is a sectional view taken along the line DD in FIG. 21 and shows a concentrated action area, and FIG. 23 is a sectional view taken along the line EE in FIG. 21 and shows a quadrupole action area. ing.

The central deflector 33 is composed of CP, CS and CS
Is composed of a CS parallel plate 35 added to CP, CS and CS.
Has substantially the same configuration as that of FIG.
The end 36 of the P on the panel 2a side protrudes toward the panel 2a from the end of the CS end 37 of the two plates. Further, a convergence shield parallel plate (CS parallel plate) 35 is disposed at an end 37 on the panel side of the CS at a position vertically sandwiching the center beam 7c and the left and right side beams 7s.

Therefore, as shown in FIG.
And the end 36 of the CP are in the same plane.

An anode voltage Va is applied to CS, and C
A voltage of about 95% of the anode voltage Va is applied to P. As a result, as shown in the schematic view of the sectional view of the concentrated action area in FIG. 22, the side beam 7s sandwiched between CS and CP of the concentrated deflector 33 is bent in the direction of the arrow of the center beam 7c.

On the other hand, as shown in the schematic diagram showing the quadrupole action region of FIG. 23, a quadrupole electric field is formed by the projection 39 of the CP and the CS parallel plate 35.

The quadrupole electric field in the centralized deflector 33 has the function of forming a vertically passing beam as shown by the arrow in FIG. That is, the center beam 7c and the side beams 7s and 7s are vertically elongated in a region surrounded by the protrusion 39 of the CP and the CS parallel plate 35.

When the electron beam collides with the screen center 21 of the panel 2a of the tube 2, a quadrupole electric field formed by the first to third grids G _4AB , G _4C and G _{4DE of} the fourth grid G ₄ . As a result, the electron beam becomes horizontally long, while the electron beam passing through the space surrounded by the projection 39 of the CP of the concentrated deflector 33 and the CS parallel plate 35 becomes vertically long, and as a result, quadrupled by the fourth grid G _4. The polar lens effect and the quadrupole lens effect by the concentrated deflector 33 are canceled out, and the spot shape incident on the central portion of the phosphor screen approaches a perfect circle.
Of course, the deflection yoke 6 does not operate at the center of the screen.

On the other hand, an electronic window is
When the beam enters, the fourth grid G _FourBy the quadrupole
The opposite of FIG. 15 as shown in FIG. 24 so that no electrodes are formed
Characteristic dynamic focus voltages Fv 'and Fc'
Is being applied. On the other hand, the protrusion 39 of the CP and the CS parallel plate 3
The electron beam passing through the space surrounded by 5 is vertically long
Since the deflection yoke 6 is operating, the deflection yoke 6
The electron beam passing through 6 becomes horizontally long. The above result
The quadrupole lens effect and the deflection yaw
6 cancels the quadrupole lens effect,
The spot shape of the electron beam colliding with the left and right peripheral parts is a perfect circle
It comes to approach.

[0046]

According to the above-described conventional CRT and the electron gun of the CRT, the DQL function of the centralized deflector 33 is as shown in FIG.
As shown in Fig. 25, only the center beam 7c is vertically elongated as shown in Fig. 25, but the side beams 7s and 7s are not only vertically elongated but also horizontally. There is a problem that the lateral (X-axis direction) asymmetry such that the side beam seeps in the direction remains.

An object of the present invention is to provide a CRT and an electron gun which solve the above-mentioned problems, and correct the lateral asymmetry of the side beam to improve the peripheral area of the screen. The spot is corrected to obtain a uniform resolution over the entire screen.

[0048]

As shown in FIG. 1, the CRT of the present invention is formed by a quadrupole lens generated by a deflection yoke and a main lens electrode portion according to dynamic focus as shown in FIG. This is a cathode ray tube in which a quadrupole lens is generated by a concentrated deflecting unit 33 disposed between quadrupole lenses, and a convergence plate (CP) and a convergence shield plate (CS) constituting the concentrated deflecting unit 33 The horizontal beam components of the quadrupole applied to the passing side beams 7s and 7s are applied in the opposite direction in advance.

As shown in FIG. 1, the electron gun according to the present invention has a structure in which a quadrupole lens can be formed between a third grid G ₃ and a fifth grid G ₅ forming a main lens. A concentrated deflection electrode 33 having a third fourth grid G _4AB , G _4C , G _4DE and forming a quadrupole lens disposed between the deflection yoke and the quadrupole lens formed by the main lens;
The electron gun 5 has a horizontal component of the quadrupole applied to the side beams 7s and 7s passing between the convergence plate CP and the convergence shield plate CS constituting the concentrated deflection electrode 33 in the reverse direction in advance. It is made to apply.

According to the CRT and the electron gun of the present invention, in order to form the side beams 7s and 7s into the same beam shape as the center beam 7c, the horizontal (X-axis direction) of the quadrupole force applied to the side beams is used. The component is applied in the reverse direction in advance to correct the lateral asymmetry in the side beam.

[0051]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A CRT according to the present invention will be described below in detail with reference to FIGS. Note that C shown in FIGS.
Parts corresponding to the RT and the electron gun are denoted by the same reference numerals, and redundant description is omitted.

FIG. 1 is a perspective view of a main part of an electron gun of a CRT according to the present invention, in which a part of an electron gun is cut away. Various grid arrangements are the same as those in FIG. In FIG. 1, the cascades RK, GK, and BK, the first grid G ₁ , and the second grid G ₂ are omitted. Only the points different from FIG. 13 in this example will be described below.

The first and third fourth grids G _4AB and G _4DE of the first to third divided fourth grids G ₄ constituting the main lens are lower at the center of the screen as shown in FIG. A dynamic focus voltage Fv 'equal to the fixed voltage Fc' is supplied around the screen, and the second
Fourth grid G _4C and G _M fixed focus voltage to the grid, i.e. fixed voltage Fc 'is fed, the anode voltage Va for focusing is supplied to the third grid G _3, and the fifth grid G _5. The anode voltage V for CS constituting the concentrating deflector 33 is integrated with the fifth grid G ₅
a is applied. Further, a voltage about 5% lower than the anode voltage is supplied to the CP via the resistor of the IBR 11.

As shown in FIG. 19, the third grid G ₃ , the first fourth grid G _4AB , and the third fourth grid G
_4DE the fifth grid G ₅ with two of the main lens 23 is formed. In this example, the DQL 25 formed by the deflection magnetic field is preferably formed between the DQL 25 formed by the deflection magnetic field of the deflection yoke 6 and the main lens 23 formed by the third fourth grid G _4DE and the fifth grid G _5. On the near side, an electrode for forming a DQL 32 that makes the electron beam vertically long when the electron beam 7 is deflected is disposed at the periphery of the screen.

DQL2 generated by the deflection magnetic field of the deflection yoke 6
5 and D for canceling the magnetic field generated by this DQL 25
When the QL 32 is brought as close to the DQL 25 side as possible, the image magnification difference ΔM ′ in the Y-axis direction with respect to the X-axis direction becomes smaller as described above, so that the DQL 32 is generated in the concentrated deflector 33.

The specific configuration of the centralized deflector 33 for generating the DQL 32 will be described in detail with reference to FIGS. Conventional centralized deflector 33 is part attached as in Figure 1 close to the deflection yoke 6 in the distal end of the fifth grid G ₅ as described in FIGS. 20 to 23. Such a centralized deflector 33
FIG. 2 is a perspective view of a main part of the centralized deflector of the present invention, and FIG.
FIG. 4 is an explanatory view of the concentrated action and DQL action area of the present invention in the D section, and FIG. 4 is an explanatory view of the DQL action area of the present invention in the EE section in FIG. 2.

The centralized deflector 33 used in the present invention has the same basic shape as that described with reference to FIGS. 20 to 23 of the conventional configuration. The tongue pieces 12 to be welded to the bead glasses 8U and 8D are bent alternately as shown in FIGS.

[0058] The fifth grid G ₅ side of the CS is formed attachment pieces 43 bent outward so as to perpendicular to the main surface of CS, rectangular hole 42 for electron beam passage with substantially square shape is bored G ₅ mounting plate 4 which is integrated with the fifth grid G ₅
4 is integrated by welding or the like via a mounting piece 43.

The direction of the electron beam emission between CS and CP (Z
The dimensions of the shaft are the same as those described with reference to FIGS. 20 and 21, and the CS parallel plate 35 is welded to the upper and lower surfaces of the front portion of the U-shaped portion. Therefore, the protrusion 39 of the CP and the upper and lower C
4 without changing the arrangement of the quadrupole action area shown in FIG. 4 surrounded by the S parallel plate 35, and changing the shape of the CS of the concentrated action and quadrupole action area shown in FIG. Make it bend to the side.

Two sets of the CP and CS formed as described above are prepared, and the two plates of CS are opposed to each other in a rectangular shape as viewed from the front as shown in FIG. The upper and lower bead glasses 8U and 8D are welded together via the tongue piece 12 so as to face each other so as to form a character and surround the CS.

At the time of this assembling, as shown in FIG.
In the longitudinal direction (Z-axis direction) protruding toward the deflection yoke 6 (or the fluorescent screen 3).

The centralized deflector 33 assembled as described above
The of CS is supplied anode voltage Va applied to the fifth grid G _5, the CP is supplied the anode voltage Va of 5% down through the IBR11.

The C curved outside the centralized deflector 33 described above
By S, as shown in FIG. 3, the side beams 7s and 7s are previously set high between CS and CP so that the force F _{X in the} X-axis direction and the forces F _XU and F _XD from diagonally up and down directions are given. A barrel-shaped equipotential line 46 is formed by CS on the potential side.

In this case, the center beam 7c travels straight between the two main surfaces 45 of the CS with substantially the same beam shape without being affected by the electric field.

Next, when the center beam 7c and the side beams 7s and 7s enter the quadrupole action region of the converging deflector 33 shown in FIG. 4, the center beam 7c rises and falls due to the anode voltage Va of the upper and lower CS parallel plates 35. The forces F _Y and F _{Y in the} (Y-axis) direction act, and the center beam 7c is formed vertically long for the first time.

On the other hand, since the side beams 7s and 7s receive opposite forces in the X-axis direction due to the curved main surface 45 of the CS shown in FIG. 3, the side beams 7s entering the quadrupole action region shown in FIG. And 7s are F _XU and F in the oblique vertical direction
Forces F _XU ′ and F _XU ′ that pull obliquely up and down with respect to _XD
Work, the two beams are canceled each other, and the asymmetry in the X-axis direction is corrected. As shown in FIG. 5, the center beam 7c and the side beams 7s and 7s are vertically elongated to form the centralized deflector 3
3 is emitted.

[0067] Thus, oblong beams by DQL fourth grid G ₄ are when the electron beam incident on the central portion of the phosphor screen as described above becomes a portrait in the intensive deflector 33, as shown in FIG. 6 is canceled each other In the center of the screen 31, the spot 40 becomes a perfect circle.

On the other hand, since DQL is not generated in the fourth grid G ₄ in the circumferential portion of the screen 31, the electron beam emitted from the centralized deflector 33 becomes vertically long and the DQ in the deflection yoke 6
L becomes horizontally long and cancels out each other, so that the spot 41 approaches a perfect circle around the screen 31.

In the above-described embodiment, the DQL 32 is formed by using the CP and the CS.
It is obvious that an electrostatic electrode different from the centralized deflector may be provided so as to form a special electrostatic DQL between the DQL 25 and the deflection yoke.

[0070]

According to the CRT of the present invention, it is possible to correct the beam spot at the peripheral portion of the screen and the central portion of the screen to a round state with a very simple structure, and to correct the asymmetric distortion of the side beam in the X-axis direction. It is possible to provide a CRT with a uniform resolution throughout.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an electron gun of a cathode ray tube according to the present invention.

FIG. 2 is a perspective view of a main part of a centralized deflector used for an electron gun of a cathode ray tube according to the present invention.

FIG. 3 is an explanatory view of a concentrated action and quadrupole action area of the present invention.

FIG. 4 is an explanatory view of a quadrupole action region of the present invention.

FIG. 5 is an explanatory diagram of an output beam shape according to the present invention.

FIG. 6 is a spot diagram on a screen according to the present invention.

FIG. 7 is a configuration diagram of a conventional cathode ray tube.

FIG. 8 is a perspective view of a conventional electron gun.

9 is a cross-sectional view of the conventional centralized deflector taken along the line AA 'in FIG.

FIG. 10 is a sectional view taken along the line BB ′ of FIG. 8 of the conventional concentrated deflector.

FIG. 11 is an explanatory diagram of a cause of generation of a conventional geometric distortion.

FIG. 12 is an explanatory diagram of a cause of occurrence of a conventional asymmetric magnetic field distortion.

FIG. 13 is a configuration diagram of a conventional improved electron gun.

FIG. 14 is an explanatory diagram of an aperture of a fourth grid G;

FIG. 15 is a waveform diagram of a conventional dynamic focus voltage.

FIG. 16 is an explanatory diagram of beam spot distortion correction by a conventional DQL.

FIG. 17 is an optical model diagram of a conventional electron gun.

FIG. 18 is a spot view on a conventional screen.

FIG. 19 is an optical model diagram of a conventional electron gun.

FIG. 20 is a perspective view of a conventional centralized deflector.

FIG. 21 is a sectional view taken along the line CC in FIG. 20;

FIG. 22 is an explanatory view of a conventional concentrated action area.

FIG. 23 is an explanatory view of a conventional quadrupole action region.

FIG. 24 is a conventional dynamic focus voltage waveform diagram.

FIG. 25 is an explanatory diagram of a conventional output beam shape.

[Explanation of symbols]

G ₃ third grid, G ₄ fourth grid, G _4AB, G
_4C, G _4DE first to third fourth grid, G ₅ fifth grid, CP convergence plates, CS convergence shield plate, 5 an electron gun, 33 concentrating deflector, 35CS parallel plate, 45 main surface

Claims (3)

[Claims] A quadrupole lens generated by a deflection yoke;
A cathode ray tube comprising a quadrupole lens generated by centralized deflecting means disposed between quadrupole lenses formed in accordance with dynamic focus at a main lens electrode portion, wherein a convergence plate constituting the centralized deflecting means is provided. Wherein a horizontal component force of a quadrupole applied to a side beam passing between the convergence shield plate and the convergence shield plate is applied in a reverse direction in advance. 2. The cathode ray tube according to claim 1, wherein the shape of the two parallel plates of the convergence shield plate is convex so that the distance at the center is larger than at both ends. . 3. A first to a third fourth grid capable of forming a quadrupole lens between a third grid and a fifth grid forming a main lens, and a fourth yoke formed by a deflection yoke and the main lens. An electron gun having a concentrated deflection electrode forming a quadrupole lens disposed between quadrupole lenses, the quadrupole being applied to a side beam passing between a convergence plate and a convergence shield plate constituting the concentrated deflection electrode. An electron gun characterized in that the force of the horizontal component is applied in the reverse direction in advance.