JP3655708B2 - Color cathode ray tube - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color cathode ray tube, and particularly to an inline type color cathode ray tube having a good resolution.
[0002]
[Prior art]
In general, a color cathode ray tube has an envelope consisting of a panel and a funnel, and deflects three electron beams emitted from an electron gun disposed in the neck of the funnel by horizontal and vertical deflection magnetic fields generated by a deflecting device. The phosphor screen provided on the inner surface of the panel is horizontally and vertically scanned through a shadow mask to display a color image.
[0003]
In such a color cathode ray tube, in particular, the electron gun is an in-line type electron gun that emits three electron beams arranged in a row consisting of a center beam and a pair of side beams that pass on the same horizontal plane, and the horizontal deflection magnetic field generated by the deflection device is pinned. A self-convergence in-line type color cathode ray tube that self-concentrates the three electron beams arranged in a row is widely used as a cushion type and a non-uniform magnetic field having a vertical deflection magnetic field as a barrel type.
[0004]
There are various types of electron guns that emit three electron beams arranged in a row, and one of them is an electron gun called a BPF (Bi Potential Focus) type double focus method. As shown in FIG. 5, this BPF type double focus type electron gun has three cathodes K arranged in a row in the horizontal direction (H-axis direction), and a control arranged sequentially from these cathodes K in the phosphor screen direction. It has a grid G1, a screen grid G2, first and second focus grids G31 and G32, and a final acceleration grid G4. Each of the grids G1, G2, G31, G32, and G4 has an integral structure, and three electron beam passage holes are formed in a line corresponding to the three cathodes K, respectively.
[0005]
In this electron gun, a voltage of about 120 V is applied to each cathode K, the control grid G1 is grounded, the screen grid G2 is about 500-600 V, the first focus grid G31 is about 6-7 kV, the second A dynamic voltage in which a parabolic voltage increasing in synchronism with the deflection amount of the electron beam is applied to a voltage of about 6 to 7 kV is applied to the focus grid G32, and a voltage of about 26 to 27 kV is applied to the final acceleration grid G4. The high voltage is applied.
[0006]
By applying the voltage, in this electron gun, the cathode K, the control grid G1, and the screen grid G2 form a triode portion that generates an electron beam and forms an object point with respect to the main lens portion described below. The main lens portion is formed by the grid G32 to the final acceleration grid G4.
[0007]
When the electron beam is directed toward the center of the phosphor screen without being deflected, the dynamic voltage applied to the second focus grid G32 is the lowest, and between the first and second focus grids G31 and G32. An electron lens (quadrupole lens) is not formed, and the electron beam from the triode is focused on the phosphor screen by the main lens formed by the second focus grid G32 to the final acceleration grid electrode G4. On the other hand, when the electron beam is deflected to the periphery of the phosphor screen, the dynamic voltage applied to the second focus grid G32 gradually increases (maximum when going to the diagonal end of the phosphor screen). As the voltage of the second focus grid G32 changes, the main lens formed by the second focus grid G32 and the final acceleration grid G4 becomes weaker. At the same time, a quadrupole lens is formed between the first and second focus grids G31 and G32, and the strength of the quadrupole lens is increased. As a result, the distance from the electron gun to the phosphor screen is increased, the lens magnification is changed in response to the image point becoming far away, the horizontal deflection magnetic field generated by the deflection device is a pincushion type, and the vertical deflection magnetic field is barreled. This compensates for the deflection aberration caused by the shape.
[0008]
However, with this electron gun, the beam spot on the phosphor screen is crushed horizontally at the end of the horizontal and diagonal axes, causing moiré due to interference with the electron beam passage hole of the shadow mask, and displaying characters on the screen. There is a problem that it becomes difficult to see.
[0009]
As a method for solving this problem, Japanese Patent Application Laid-Open No. 3-95835 discloses that a focusing electrode of a BPF type electron gun is divided into four to form positive and negative first quadrupole lenses and second quadrupole lenses. The first quadrupole lens has a function of focusing the electron beam in the horizontal direction and diverging in the vertical direction, and the second quadrupole lens has a function of diverging in the horizontal direction and converging in the vertical direction. A method for reducing the collapse of the beam spot at the periphery of the phosphor screen is shown. However, in such an electron gun, due to the action of the two quadrupole lenses, the horizontal diameter of the electron beam incident on the main lens is increased, and the spherical aberration of the main lens is easily received. As a result, the resolution at the periphery of the phosphor screen is degraded. In particular, the influence of spherical aberration becomes large in a large current region, and the resolution is remarkably deteriorated.
[0010]
As a method for reducing the spherical aberration of the main lens, Japanese Patent Application Laid-Open No. 6-162958 discloses a method in which the main lens is an asymmetric lens and the focusing action in the horizontal direction is weaker than that in the vertical direction. However, in order to make the beam spot around the phosphor screen a perfect circle with such an electron gun, it is necessary to make the diameter of the electron beam when passing through the main lens considerably long. Therefore, it is insufficient to reduce the spherical aberration of the main lens in a large current region.
[0011]
[Problems to be solved by the invention]
In general, in order to improve the resolution of a color cathode ray tube, it is necessary to minimize the influence of spherical aberration and deflection aberration of the main lens of the electron gun as much as possible, and to make the beam spot on the phosphor screen round and small.
[0012]
However, in the conventional electron gun, as described for the BPF type double focus type electron gun, the deflection aberration can be compensated for by the quadrupole lens, but the lateral collapse of the beam spot at the periphery of the phosphor screen is improved. I can't.
[0013]
As a method of solving the lateral collapse of the beam spot, the focus grid of the BPF type electron gun is divided into four to form first and second quadrupole lenses that are positive and negative, and the first quadrupole lens. The electron beam is focused in the horizontal direction and diverged in the vertical direction, and the second quadrupole lens is diverged in the horizontal direction and focused in the vertical direction. An electron gun that reduces lateral collapse is known. However, this electron gun can reduce the lateral collapse of the beam spot at the periphery of the phosphor screen, but the action of the two quadrupole lenses increases the horizontal diameter of the electron beam incident on the main lens. It is easy to receive the spherical aberration. As a result, the resolution at the periphery of the phosphor screen is degraded. In particular, the influence of spherical aberration becomes large in a large current region, and the resolution is remarkably deteriorated.
[0014]
As a method for reducing the spherical aberration of the main lens, an electron gun is known in which the main lens is an asymmetric lens and the focusing action in the horizontal direction is weaker than in the vertical direction. However, with this electron gun, the spherical aberration of the main lens can be reduced, but in order to make the beam spot around the phosphor screen a perfect circle, the electron beam diameter when passing through the main lens is made considerably long. Therefore, it is insufficient to reduce the spherical aberration of the main lens in a large current region.
[0015]
The present invention has been made in view of the above problems, and an object of the present invention is to improve the resolution of a color cathode ray tube by making the beam spot close to a perfect circle and making it small over the entire area of the phosphor screen.
[0016]
[Means for Solving the Problems]
An electron gun that emits three electron beams arranged in a row passing through the same plane is provided, and the electron gun is composed of three cathodes arranged in a row, a control grid sequentially arranged from the cathodes toward the phosphor screen, and a screen grid. And a main lens portion including a plurality of grids for focusing the electron beam emitted from the cathode, and the grid forming the main lens portion is sequentially arranged from the cathode toward the phosphor screen. The first, second, third, and fourth grids and the final accelerating grid are each applied with a voltage that changes in synchronization with the amount of deflection of the electron beam. The first quadrupole lens that diverges the electron beam in the horizontal direction and focuses in the vertical direction is formed by the two grids, and the electron beam is formed by the third and fourth grids. In a color cathode ray tube in which a second quadrupole lens that converges in the horizontal direction and diverges in the vertical direction is formed, a correction grid is disposed between the second and third grids, and electrons are disposed between the second and third grids. The lens has a structure in which the horizontal focusing action on the beam is stronger than the vertical focusing action.
[0017]
In the above-mentioned color cathode ray tube, when the electron beam is deflected, it is formed between the horizontal diverging action of the first quadrupole lens formed by the first and second grids and the second and third grids. The lens is constructed so as to cancel out the horizontal focusing action of the lens.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0019]
FIG. 3 shows a configuration of an inline type color cathode ray tube which is one form thereof. This color cathode ray tube has an envelope composed of a substantially rectangular panel 1 and a funnel-shaped funnel 2 joined to the panel 1, and emits blue, green and red light on the inner surface of the panel 1. A phosphor screen 3 composed of a dot-like three-color phosphor layer is provided, and a shadow mask 4 is disposed inside the phosphor screen 3 so as to face the phosphor screen 3. On the other hand, in the neck 5 of the funnel 2, the following electron gun 7 is disposed that emits a three-electron beam 6B, 6G, 6R arranged in a row consisting of a center beam 6G passing through the same horizontal plane and a pair of side beams 6B, 6R. ing. Then, the three electron beams 6B, 6G, 6R emitted from the electron gun 7 are deflected by the horizontal and vertical magnetic fields generated by the deflection device 8 mounted outside the funnel 2, so that the phosphor screen 3 is horizontal. A structure for displaying a color image is formed by performing vertical scanning.
[0020]
The electron gun 7 is a BPF type double focus system, and as shown in FIG. 1, three cathodes K arranged in a line in the horizontal direction (H-axis direction), and three each for heating the cathodes K separately. And a control grid G1, a screen grid G2, a focus grid G3, and a final acceleration grid G4, which are sequentially arranged from the cathode K toward the phosphor screen. The focus grid G3 is divided into four parts, and includes first, second, third, and fourth grids G31, G32, G33, and G34 that are sequentially arranged from the screen grid G2 toward the final acceleration grid G4. Further, in this electron gun 7, a correction grid Gs is disposed between the second grid G32 and the third grid G33.
[0021]
Each of the control grid G1 and the screen grid G2 is composed of a plate-like electrode having an integral structure whose major axis is the arrangement direction of the cathodes K. The plate surfaces of these grids G1 and G2 correspond to the three cathodes K, Three electron beam passage holes are formed in a row in the horizontal direction.
[0022]
Each of the first, second, third, and fourth grids G31, G32, G33, and G34 is formed of a single-piece cylindrical electrode having a major axis in the arrangement direction of the cathodes K. On the screen grid G2 side of the first grid G31, three electron beam passage holes are formed in a row in the horizontal direction corresponding to the three cathodes K, and on the second grid G32 side, Non-circular electron beam passage holes such as a rectangle and an ellipse having a major axis in the horizontal direction are formed in a row in the horizontal direction. On the first grid G31 side of the second grid G32, non-circular electron beam passage holes such as a rectangle and an ellipse having a major axis in the vertical direction are arranged in a row corresponding to the three cathodes K in the horizontal direction. In the third grid G33 side, three electron beam passage holes are formed in a row in the horizontal direction. On the second grid G32 side of the third grid G33, three electron beam passage holes are formed in a line in the horizontal direction corresponding to the three cathodes K, and on the fourth grid G34 side. In addition, non-circular electron beam passage holes such as a rectangle and an oval having a major axis in the vertical direction are formed in a row in the horizontal direction. On the third grid G33 side of the fourth grid G34, in correspondence with the three cathodes K, non-circular electron beam passage holes such as a rectangle and an ellipse having a horizontal axis as a major axis are arranged in a row in the horizontal direction. Three electron beam passage holes are formed in a row in the horizontal direction on the final acceleration grid G4 side.
[0023]
The final accelerating grid G4 is composed of a cup-shaped electrode having an integral structure whose major axis is the arrangement direction of the cathode K, and three electrons corresponding to the three cathodes K at the bottom of the fourth grid G34 side. Beam passage holes are formed in a row in the horizontal direction.
[0024]
The correction grid Gs is composed of a plate-like electrode having an integral structure whose major axis is the direction in which the cathodes are arranged. As shown in FIG. 2, the plate surface of the electrode Gs corresponds to the three cathodes in the vertical direction ( Non-circular electron beam passage holes 10 (in the illustrated example, an oval shape) such as a rectangle or an oval having a major axis in the (V-axis direction) are formed in a row in the horizontal direction (H-axis direction).
[0025]
In this electron gun 7, the first grid G31 and the third grid G33 are connected in the tube, and a constant focus voltage Vf is applied to these grids G31 and G33. The second grid G32 and the fourth grid G34 are also connected in the tube, and a parabolic voltage Vd that increases in synchronization with the deflection amount of the electron beam is supplied to the grids G32 and G34 in synchronization with the deflection amount of the electron beam. The superimposed dynamic focus voltage Vf + Vd is applied. The correction grid Gs is connected to the screen grid G2 in the tube, and a constant voltage Vc2 is applied to the grids G2 and Gs.
[0026]
In the electron gun 7 by the application of the voltage, the cathode K, the control grid G1, and the screen grid G2 form a triode that generates an electron beam and forms an object point with respect to the main lens portion described below. The main lens portion is formed by the second, third and fourth grids G31, G32, G33, G34, the correction grid Gs and the final acceleration grid G4. In the main lens portion, a first quadrupole lens that diverges the electron beam in the horizontal direction and focuses it in the vertical direction by the first grid G31 and the second grid G32 is formed. The fourth grid G34 forms a second quadrupole lens that converges in the horizontal direction and diverges in the vertical direction. The second grid G32, the correction grid Gs, and the third grid G33 form a lens in which the horizontal focusing on the electron beam is stronger than the vertical focusing. Further, the fourth lens G34 and the final acceleration grid G4 form a main lens that finally focuses the electron beam on the phosphor screen.
[0027]
FIG. 4 shows the behavior of the electron beam by the electron lens. In this figure, the upper part is in the horizontal direction and the lower part is in the vertical direction across the tube axis (Z axis).
[0028]
When the electron beam 6 is directed toward the center of the phosphor screen 3 without being deflected by the deflecting device, the first and second quadrupoles are respectively provided between the first and second grids and between the third and fourth grids. The lenses QPL1 and QPL2 are not formed, and the lens SL formed by the second grid, the correction grid, and the third grid during the period from the object point 10 to the phosphor screen 3, causes a strong focusing action in the horizontal direction and the vertical direction. Then, the light is focused on the phosphor screen 3 by the main lens ML formed by the fourth grid and the final acceleration grid. As a result, the beam spot on the phosphor screen 3 is as indicated by 13 and is just focused on the phosphor screen 3 in both the horizontal and vertical directions.
[0029]
On the other hand, when the electron beam 6 is deflected in the horizontal direction by the deflecting device, a first quadrupole lens QPL1 is formed between the first and second grids, and the first quadrupole lens QPL1 is formed. The diverging action in the horizontal direction and the focusing action in the vertical direction are dynamically increased in synchronization with the deflection amount. As a result, the object point in the horizontal direction advances toward the phosphor screen 3 as indicated by 12H, the object point in the vertical direction recedes as indicated by 12V, and the object point diameter becomes vertically long. In addition, the lens SL formed by the second grid, the correction grid, and the third grid has a strong horizontal focusing action, cancels the horizontal diverging action of the first quadrupole lens, and provides an electron beam. Reduce the horizontal divergence angle. A second quadrupole lens QPL2 is formed between the third and fourth grids, and the horizontal focusing action and vertical diverging action of the second quadrupole lens QPL2 move in synchronization with the deflection amount. Become stronger. Furthermore, the focusing action of the main lens ML formed by the fourth grid and the final acceleration grid is weakened. Therefore, the electron beam 6 passing through the main lens ML is less susceptible to horizontal spherical aberration. In addition, when passing through the deflection magnetic field, the action of the lens DY of the deflection magnetic field can be canceled out. As a result, the beam spot on the periphery of the phosphor screen indicated by 3a is substantially a perfect circle and can be reduced as indicated by 13a.
[0030]
The same effect can be obtained when the electron beam is deflected in the vertical direction and the diagonal direction. Therefore, by configuring the electron gun 7 as described above, the entire area of the phosphor screen 3 can be made into a perfect circle and reduced to improve the resolution.
[0031]
【The invention's effect】
An electron gun that emits three electron beams arranged in a row passing through the same plane is provided. The electron gun is composed of three cathodes arranged in a row, a control grid arranged sequentially from the cathodes toward the phosphor screen, and a screen grid. At least a first electrode having a triode portion and a main lens portion composed of a plurality of grids for focusing an electron beam emitted from the cathode and sequentially forming the grid forming the main lens portion from the cathode toward the phosphor screen. , Second, third, and fourth grids and a final acceleration grid. A voltage that changes in synchronization with the amount of deflection of the electron beam is applied to the second and fourth grids. The first quadrupole lens that diverges the electron beam in the horizontal direction and focuses it in the vertical direction is formed by the grids of the third and fourth grids. In a color cathode ray tube in which a second quadrupole lens that converges in a flat direction and diverges in a vertical direction is formed, a correction grid is disposed between the second and third grids, and electrons are disposed between the second and third grids. When the electron beam is deflected, the first quadrupole formed by the first and second grids has a structure in which the horizontal focusing action on the beam is stronger than the vertical focusing action. When an electron beam is deflected to the periphery of the phosphor screen when the horizontal diverging action of the lens and the horizontal focusing action of the lens formed between the second and third grids are cancelled. However, there is no horizontal collapse of the beam spot, and it can be made into a perfect circle and small over almost the entire area of the phosphor screen, making it difficult to receive horizontal spherical aberration even in a large current range. It can be a good color CRT resolution.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an electron gun of an inline type color cathode ray tube according to an embodiment of the present invention.
FIG. 2 is a diagram of a correction grid of the electron gun.
FIG. 3 is a diagram showing a configuration of an inline type color cathode ray tube according to an embodiment of the present invention.
FIG. 4 is a diagram for explaining the behavior of an electron beam in the electron gun.
FIG. 5 is a diagram showing a configuration of a conventional electron gun of an inline type color cathode ray tube.
[Explanation of symbols]
3 ... phosphor screens 6B, 6R ... pair of side beams 6G ... center beam 7 ... electron gun 8 ... deflection device G1 ... control grid G2 ... screen grid G3 ... focus grid G31 ... first grid G32 ... second grid G33 ... third grid G34 ... fourth grid G4 ... final acceleration grid Gs ... correction grid K ... cathode DY ... deflection magnetic field lens ML ... main lens QPL1 ... first quadrupole lens QPL2 ... second quadrupole lens SL …lens

Claims (2)

An electron gun that emits three electron beams arranged in a row passing through the same plane is provided, and the electron gun is composed of three cathodes arranged in a row, a control grid sequentially arranged from the cathodes toward the phosphor screen, and a screen grid. A triode and a main lens portion comprising a plurality of grids for focusing the electron beam emitted from the cathode, and the grid forming the main lens portion is sequentially arranged from the cathode toward the phosphor screen. At least a first grid, a second grid, a fourth grid, and a final acceleration grid, and a voltage that changes in synchronization with the deflection amount of the electron beam is applied to the second grid and the fourth grid. First and second grids form a first quadrupole lens that diverges the electron beam in the horizontal direction and focuses it in the vertical direction. Focusing the electron beam in the horizontal direction by de, in a color cathode ray tube in which the second quadrupole lens diverging in the vertical direction is formed,
A correction grid is disposed between the second and third grids, and a lens in which the horizontal focusing action on the electron beam is stronger than the vertical focusing action is formed between the second and third grids. Color cathode ray tube characterized by When the electron beam is deflected, the horizontal divergence action of the first quadrupole lens formed by the first and second grids and the horizontal focusing of the lens formed between the second and third grids. 2. The color cathode ray tube according to claim 1, wherein the actions cancel each other.

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