JPH1050233A - Inline type color picture tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cathode-ray tube equipped with an electron gun in which the difference of astigmatism and focal distance resulting from deflection can be eliminated by a comparatively simple construction. SOLUTION: A pre-stage focusing electrode unit composed of one pair of first and second grid electrodes 23, 24 which are successively arranged from the cathode side along an electron beam path between an acceleration electrode unit and a post-stage converging electrode unit, first plate-like protrusion 28 sandwiching the electron beam path in an approximately horizontal direction is provided on either one of the first and the second grid electrodes 23, 24, and second plate-like protrusion 27 sandwiching the electron beam path in an approximately vertical direction is provided on the other grid electrode. Both plate-like protrusions 27, 28 are overlapped in the direction along the electron beam path, and potential difference is applied across both plate-like protrusions 27, 28 so that a nonaxisymmetric quadrupole electric field is generated against an electron beam axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cathode ray tube provided with an electron gun for generating an electron beam in a vacuum vessel and a target for receiving the electron beam.

[0002]

2. Description of the Related Art Such a cathode ray tube is used for a television set and various displays, and is used for an oscilloscope and for recording a television image. There is no surrounding blur,
This is desirable for obtaining good quality images.

For this reason, conventionally, for example, Japanese Patent Application Laid-Open No. 54-856
No. 66, JP-A-54-85667, a non-axisymmetric lens system composed of a first grid and a second grid in an electron gun and correcting astigmatism due to deflection. Has been proposed. However, this improves the beam spot uniformity over the entire target, but increases the beam diameter at the center of the target as compared with the case where an axisymmetric lens system is used.

On the other hand, Japanese Patent Application Laid-Open No. 58-1988 discloses
As shown in Japanese Patent Publication No. 32, a first-stage focusing system provided between an acceleration electrode system and a second-stage focusing electrode system is constituted by first to third grating electrodes, and the first and third grating electrodes are provided between the first and third grating electrodes. There has been proposed a technique in which a constant focusing voltage is applied, and a dynamic voltage that gradually decreases or increases from the focusing voltage as the beam deflection increases is applied to the second grating electrode.

[0005]

However, in this case, although the problem of astigmatism is solved, the problem of the difference in focal length due to the difference in the amount of deflection remains. In other words, in the peripheral portion where the beam deflection amount is larger than before, the focusing voltage is increased, the lens is weakened, the focal length is lengthened, and a device is devised to always focus on the target. More voltage is required. In particular, since the presence of the third grid electrode generally shortens the focal length as compared with the case where the third grid electrode is not provided, consideration must be given to the influence of the third grid electrode.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a cathode ray tube having an electron gun capable of resolving the problems of astigmatism due to deflection and a difference in focal length with a relatively simple structure.

[0007]

For this purpose, the present invention provides at least one pair of a first and a second pair of electrodes arranged sequentially from the cathode side along the electron beam path between the accelerating electrode system and the post-focusing electrode system. And a first plate-shaped projection provided on one of the first and second grid electrodes so as to sandwich the electron beam path in a substantially horizontal direction. Further, a second plate-like projection is provided on the other grid electrode so as to sandwich the electron beam path in a substantially vertical direction, and the first plate-like protrusion and the second plate-like protrusion are provided. Are overlapped in a direction along the electron beam path to provide a potential difference between the first plate-shaped projection and the second plate-shaped projection, and thus, the non-axial symmetry with respect to the electron beam axis. A structure for generating a quadrupole electric field, and applying a constant focusing voltage to the first grid electrode, It is obtained so as to apply a dynamic voltage gradually increases with the fixed focus voltage with respect to the increase in the beam deflection amount to the second grid electrode.

When a difference is given between two kinds of voltages applied to the pair of grid electrodes forming the focusing electrode system, a non-axially symmetric electric field is generated, causing astigmatism. I do. Therefore, by controlling the focusing voltage according to the deflection amount, that is, the position on the target, a uniform and small beam diameter can be obtained over the entire surface of the target.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In general, a color picture tube uses three electron guns arranged in a straight line or in a triangular shape in close proximity to each other. In these electron guns, one or more electrodes are used. Is usually formed integrally with that for an electron gun. For an electron gun equipped with such an electrode,
For example, as described in U.S. Pat. No. 3,772,554, the present invention is useful when applied to a color picture tube having such an integrated electron gun. Hereinafter, such an example will be described.

FIG. 1 is a sectional view of an in-line type color picture tube showing one embodiment of the present invention. Referring to FIG. 1, a glass envelope 1 includes a face plate 2 having a fluorescent surface 12, a funnel portion 3, and a neck portion 4. The neck portion 4 accommodates electron guns 5, 6, and 7. In the three-electron gun, the axes are arranged in a common plane, that is, the plane of the drawing, and the axis of the central electron gun 6 is substantially coincident with the tube axis 11.

Electron beams 8, 9, 10 emitted from each electron gun
The light travels straight toward the fluorescent light surface 12 and is deflected by the deflection coil system 15 in the horizontal direction (in the plane of the drawing) and in the vertical direction (perpendicular to the drawing plane). In front of the fluorescent surface 12, there is a shadow mask 13 having a number of apertures 14. The electron beam is subjected to a color selection action by the apertures to reach the fluorescent surface 12, causing the corresponding phosphor picture elements to emit light. To reproduce a predetermined image.

FIG. 2 shows the configuration of the electron gun. In the figure, an electron gun 17 corresponding to 5, 6, 7 in FIG. 1 has three cathodes 18, 18 ', 18 ", arranged in a horizontal straight line.
It has a first grid 19, a second grid 20, a pre-focusing electrode system 21 and a final electrode 22;
Consists of two grid electrodes 23 and 24 sequentially arranged along the electron beam path. Here, the accelerating electrode system for accelerating and pre-focusing the electron beam emitted from each cathode includes electrodes facing the second grid and the second grid of the preceding focusing electrode system. The second-stage focusing electrode system for mainly focusing the electron beam includes a final electrode and an electrode facing the final electrode of the first-stage focusing electrode system. Further, the grid electrodes 23, 24
Are beam passing holes 25 and 2 as shown in FIG.
5 ', 25 "and 26, 26', 26" and plate-like projections 27, 28 on the opposing surface.

Here, a DC power supply 29 is connected to the grid electrode 23.
Provides a constant focusing voltage Vfoc, and the grid electrode 24
Is supplied with a dynamic focus voltage Vfoc 'which varies according to the amount of beam deflection by superimposing a voltage from the AC power supply 30. That is, the dynamic focus voltage V
foc ', as shown in FIG. 4, when the deflection current shown in FIG. 4A is 0, that is, when the electron beam is located at the center of the fluorescent surface 12, as shown in FIG. It takes the same value as the voltage Vfoc of one lattice electrode 23, and increases from the voltage Vfoc as the deflection current increases or decreases. Therefore, when the beam spot is located at the center of the fluorescent surface, the grid electrode 23,
24 have the same potential, and a lens electric field is not formed between them, so that a perfect circular spot is obtained at the center of the fluorescent surface. On the other hand, as the beam deflection increases, the voltage Vfoc '
Rises, a potential difference is generated between the grid electrodes 23 and 24, and between the two electrodes, as shown in FIG.
A pole field 31 is generated and the beam passing therethrough undergoes a diverging effect in the vertical direction and a focusing effect in the horizontal direction. For this reason, as shown in FIG. 6, an axially symmetric lens 32, 32 ′, 32 ″ formed by an electrode facing the final electrode 22 of the former-stage focusing electrode system 21 and the final electrode 22, and constitutes the former-stage focusing electrode system 21. When the electron beam 34 passes through one of three lenses 33 equivalently combined with the lens formed by the first and second grid electrodes 23 and 24, the focusing action is strong in the horizontal direction and weak in the vertical direction. , Vertical focus 3
5 occurs at a point farther than the horizontal focus 36. As a result, it acts so as to cancel astigmatism due to the quadrupole magnetic field for deflection. That is, FIG. 7 is a diagram showing a state of a beam spot in a general in-line color picture tube.
While the beam spot 37 at the center of the fluorescent surface 12 is a perfect circle, the beam spot that is largely horizontally deflected is
It comprises a horizontally long core 38 and a halo portion 39. By using the electron gun of this embodiment, such a beam shape can be made close to a perfect circle even at the periphery of the screen, and an excellent beam spot shape can be obtained over the entire surface, and a clear reproduced image can be obtained. Obtainable.

FIG. 8 is a sectional view of an electron gun showing another embodiment of the present invention. That is, the present embodiment is an example using a multi-stage focusing type in-line electron gun. One of the front-stage focusing electrode system 21A including the third grid and one 21B of the front-stage focusing electrode system 21B including the fifth grid are connected to two grid electrodes. 23, 2
4, a pre-focusing electrode system 21 comprising a third grid
A constant focusing voltage Vfoc is applied to A and the first grid electrode 23 by a DC power supply 29, and a voltage from an AC power supply 30 is superimposed on the second grid electrode 24 to change the dynamic focus that varies with the beam deflection amount. Voltage Vfo
c 'is given. Furthermore, two front-stage focusing electrode systems 21
A high voltage is applied by a power supply 41 to the fourth grid 40 and the final electrode 22 arranged between A and 21B.
The fourth grid 40 may be set to the same potential as the second grid 20 without applying a high voltage. Further, the configuration of the two grid electrodes 23 and 24 for generating the non-axisymmetric electric field is not limited to the configuration shown in FIG. 3, and for example, as shown in FIG. A similar effect can be obtained by making the 42 "and 43, 43 ', 43" non-axisymmetric.

By the way, as described above, in a color picture tube, in general, a focus shift caused by a difference in distance from the center of deflection to the fluorescent surface 12 between the center of the screen and the peripheral portion is corrected. However, according to the above-described embodiments, the predetermined deflection coil 1
By appropriately designing the sensitivity of the focusing system to astigmatism with respect to the focus voltage difference with respect to the focus envelope 5 and the glass envelope 1, the above-described dynamic focus voltage Vfoc 'simultaneously causes the focus shift due to the difference in focal length. Can be corrected. That is, astigmatism is determined by the deflection coil 15 and the glass envelope 1,
If the former-stage focusing system is appropriately designed for them, and the dynamic focus voltage Vfoc 'for correcting astigmatism determined by the former is made to coincide with the voltage for correcting defocus due to the difference in focal length, then Can be corrected simultaneously.

Although an example in which the present invention is applied to an in-line type color picture tube has been described above, the present invention is not limited to this. Can correct the astigmatism of the beam spot, and can obtain a uniform and small beam diameter over the entire surface of the target.

[0017]

As described above, according to the present invention,
A front-stage focusing electrode system including at least one pair of first and second grid electrodes is provided between the acceleration electrode system and the rear-stage focusing electrode system, and one of the first and second grid electrodes is provided on one of the first and second grid electrodes. A first plate-like projection that sandwiches the electron beam path in a substantially horizontal direction toward the other grid electrode side opposite thereto is provided, and a second plate that sandwiches the electron beam path in a substantially vertical direction is provided on the other grid electrode. A plate-shaped projection is provided, and the first plate-shaped projection and the second plate-shaped projection are overlapped in a direction along the electron beam path, so that the first plate-shaped projection and the second plate-shaped projection are overlapped. When a potential difference is applied between the first grid electrode and the second grid electrode, a constant focusing voltage is applied to the first grid electrode, and the second grid electrode is applied to the second grid electrode. With respect to the grid electrode, a damper that gradually rises with an increase in the amount of beam deflection with reference to the constant focusing voltage. By applying a natural voltage, the problem of astigmatism due to deflection and the difference in focal length can be eliminated at once with a relatively simple configuration, and good image quality without defocus can be obtained over the entire target. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of an electron gun.

FIG. 3 is a perspective view showing first and second grid electrodes.

FIG. 4 is a waveform chart for explaining a dynamic focus voltage.

FIG. 5 is a diagram showing an electric field formed by a voltage of each grid electrode.

FIG. 6 is a diagram showing a focusing state by a synthetic lens.

FIG. 7 is a diagram showing a beam spot shape in a general color picture tube.

FIG. 8 is a sectional view of an electron gun showing another embodiment of the present invention.

FIG. 9 is a perspective view showing another configuration example of the first and second grid electrodes.

[Explanation of symbols]

18, 18 ', 18 "... cathode, 19 ... first
Grid, 20... Second grid, 21, 21A,
21B ··· front-stage focusing electrode system, 22 ··· final electrode, 23 ··· first grid electrode, 24 ··· second grid electrode, 25, 25 ′, 25 ″, 26, 26 ', 2
6 ", 42, 42 ', 42", 43, 43', 43 "
... Beam passing holes, 27, 28.
9 DC power supply, 30 AC power supply.

Claims (6)

[Claims] 1. An in-line three cathodes for emitting an electron beam, an accelerating electrode system for accelerating and pre-focusing an electron beam emitted from each cathode, and a post-focusing electrode system for main-focusing the electron beam. An in-line type color picture tube provided with an electron gun having at least one pair of first and second pairs arranged sequentially along the electron beam path from the cathode side between the acceleration electrode system and the subsequent focusing electrode system. A first-stage focusing electrode system including a grid electrode is provided, and one of the first and second grid electrodes is disposed substantially parallel to the in-line direction and the first focusing electrode system sandwiches the electron beam path.
A second plate-shaped projection is provided on the other grid electrode so as to be substantially perpendicular to the in-line direction and sandwiches the electron beam path. And the second plate-shaped protrusion overlap each other in a direction along the electron beam path, so that a potential difference is formed between the first plate-shaped protrusion and the second plate-shaped protrusion. , A structure in which a quadrupole electric field which is non-axially symmetric with respect to the electron beam axis is generated, a constant focusing voltage is applied to the first grating electrode, and the constant focusing voltage is applied to the second grating electrode. An in-line type color picture tube characterized by applying a dynamic voltage that gradually rises with an increase in the amount of beam deflection based on the reference. 2. The in-line type color picture tube according to claim 1, wherein a plate-like projection arranged substantially parallel to said in-line direction is provided on said second grid electrode. 3. The device according to claim 2, wherein the bottom surface of the second grid electrode opposite to the surface on which the plate-shaped protrusions are provided is opposed to the final electrode to which a high voltage is applied. In-line color picture tube. 4. The in-line type color picture tube according to claim 2, wherein said electron gun is of a multistage focusing type having a front stage focusing electrode system constituted by a plurality of focusing electrodes. 5. The electron gun according to claim 1, further comprising:
A sixth grid including a grid, a second grid, a third grid, a fourth grid, a fifth grid including a first grid electrode and a second grid electrode, and a sixth grid to which a high voltage is applied.
The in-line color picture tube according to claim 4, wherein the grid and the fourth grid have the same potential, and the first grid electrode and the third grid have the same potential. 6. The electron gun according to claim 1, wherein:
A first grid including a grid, a second grid, a third grid, a fourth grid, a fifth grid including a first grid electrode and a second grid electrode, and a sixth grid to which a high voltage is applied;
The in-line type color picture tube according to claim 4, wherein the grid electrode and the third grid have the same potential, and the fourth grid and the second grid have the same potential.