JPH0161222B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cathode ray tube device, which is constructed so that good resolution can be obtained over the entire area on the phosphor screen surface.

In general, the resolution of a cathode ray tube device depends on the size and shape of the beam spot (bright spot) produced on the phosphor screen surface, and in order to obtain high resolution, the beam spot must be as small as possible and without distortion. is important. In addition, in color cathode ray tube devices, it is important from the viewpoint of resolution that the beam spots of the three electron beams are correctly concentrated at any one point on the phosphor screen surface, and for this reason, an in-line type color cathode ray tube is used. In this case, three electron beams can be generated by distorting the horizontal deflection magnetic field distribution into a pincushion shape as shown in Figure 1a and the vertical deflection magnetic field distribution into a barrel shape as shown in Figure 1b. 1, 2, and 3 are self-converging. However, if such a self-concentration method is adopted, even if the concentration of the three electron beams is good, the three
The cross-sectional shape of the electron beam is distorted as the beam deflection angle increases, and the beam spots appearing on the phosphor screen surface, particularly in the peripheral area, tend to be distorted as shown in FIG. That is, a beam spot 5 appearing at the center of the phosphor screen surface 4
is a perfect circle, whereas the beam spot 6 that appears at the periphery has a horizontally long elliptical high-brightness core part 7 and a vertically long low-brightness haze part 8, which is especially It becomes difficult to obtain high resolution at the periphery of the screen.

The shape distortion of the beam spot as described above is due to the fact that the deflection yoke in the self-concentration method applies a non-uniform magnetic field to the three electron beams as shown in Figure 1 a and b. The electron beam is defocused in the electron gun in the horizontal direction and strengthened in the vertical direction.

The present invention has been made to eliminate the above-mentioned drawbacks of the conventional art. Next, a cathode ray tube device of the present invention will be described with reference to embodiments shown in the drawings.

In FIG. 3, the electron gun 9 consists of three cathodes 10', 10'', 10, a control electrode 11, an accelerating electrode 12, a focusing electrode system 13, and an anode 14 arranged horizontally in a straight line. 13 consists of flat plate-shaped first and second grid electrodes 15, 16 and a box-shaped main focusing electrode 17 arranged sequentially along the electron beam path. The second grid electrode side end plate portion 17a of the first grid electrode 15 and the main focusing electrode 17 has three circular electron beam passing holes 18', 18'', 18; 19',
19'', 19, and the central second grid electrode 16 has three horizontally elongated rectangular electron beam passing holes 20', 20'', 20. and,
A constant focusing voltage V _fpc is applied to the first grid electrode 15 and the main focusing electrode 17, and the second grid electrode 1
6 is given a dynamic voltage V _fpc ' that changes depending on the amount of beam deflection.

The dynamic voltage V _fpc ′ is shown by the solid line 21 in FIG.
Alternatively, when the deflection current 23 is zero as shown by the dashed line 22, that is, when the beam spot appears at the center of the phosphor screen surface, it takes the same value as the voltage V _fpc , and as the deflection current increases or decreases, it takes on the same value as the voltage V fpc. Voltage V _fpc
Gradually descend or rise from Therefore, when the beam spot appears at the center of the phosphor screen surface, the first and second grid electrodes 15, 16 and the main focusing electrode 17 are all at the same potential V _fpc ;
No lens electric field is generated between each of these electrodes 15, 16, 17, and even though the electron beam passing holes 20', 20'', 20 of the second grid electrode 16 are non-circular, the electron beam On the other hand, no axially asymmetric electric field acts, and a perfectly circular beam spot is obtained at the center of the screen surface.

On the other hand, when the voltage V _fpc ′ falls or rises from V _fpc as the deflection current increases or decreases, that is, the amount of beam deflection increases, the first grid electrode 15 and the second grid to which a constant focusing voltage V _fpc is applied A lens electric field is generated between the electrode 16 and between the second grid electrode 16 and the main focusing electrode 17. This lens electric field is
electron beam passing hole 20' of second grid electrode 16;
Since the holes 20'', 20 are axially asymmetric, the three electron beams passing through them are each subjected to an axially asymmetric focusing effect. , in the case of a horizontally long rectangle or horizontally long ellipse as shown in FIG. 4, the lens electric field gives a strong focusing effect in the vertical direction and a weak focusing effect in the horizontal direction on the electron beam passing through the lens. As a result, the electron beam immediately after exiting the focusing electrode system 13 has a horizontally long elliptical cross-sectional shape, and with this cross-sectional shape, the main lens portions 24' and 24'
4″, 24.

As shown in FIG. 6, when an electron beam 25 with a horizontally oblong elliptical cross section enters the main lens section 24, due to the spherical aberration of the lens, a focusing effect is strong in the horizontal direction and weak in the vertical direction, resulting in a focusing effect in the vertical direction. Point 2
6 occurs at a point farther than the focus point 27 in the horizontal direction.

In this way, when the cross-sectional shape of the electron beam that has passed through the focusing electrode system 13 is distorted into a horizontally elongated ellipse as the amount of beam deflection increases, the main lens portion 24
The focusing effect on the electron beam by It is weak and acts to cancel out the strong focusing in the vertical direction.

Therefore, even though the beam spot is caused by an electron beam that is largely deflected in the horizontal direction, it is possible to make the beam spot close to a perfect circle, and the resolution of the phosphor screen surface is improved, particularly on both left and right sides and in diagonal areas. Since the distortion of the beam spot appearing near the upper middle and lower middle of the phosphor screen surface is originally slight, a very clear reproduced image can be obtained over the entire area on the phosphor screen surface.

Further, in the focusing electrode system 13, the second grid electrode 16 to which the dynamic voltage V _fpc ' is applied is located between the first grid electrode 15 to which the constant voltage V _fpc is applied and the main focusing electrode 17. Since it is electrostatically shielded, it does not produce undesirable brightness modulation effects.

Furthermore, the pre-focusing lens generated between the accelerating electrode 12 and the first grid electrode 15 does not change because a constant accelerating voltage and a constant focusing voltage are respectively applied to both electrodes; Since the focusing lens moves the axially asymmetric lens away from the crossover point of the electron beam, the beam correction effect by the axially asymmetric lens works efficiently and stability is also improved.

The above has described an embodiment in which the present invention is applied to an in-line color cathode ray tube device. However, the purpose of the present invention is to reduce shape distortion of a beam spot due to an electron beam subjected to a deflection action within a non-uniform deflection magnetic field. The present invention is applicable to cathode ray tube devices operating with one beam or two beams in the same manner as described above.

[Brief explanation of drawings]

Figures 1a and b are diagrams showing the relationship between the nonuniform deflection magnetic field distribution and three electron beams, and Figure 2 is the shape of the beam spot appearing on the phosphor screen surface of a color cathode ray tube device that uses the self-focusing method. 3 is a side sectional view of the electron gun section of an in-line color cathode ray tube device embodying the present invention; FIG. 4 is a perspective view of the focusing electrode system of the same color cathode ray tube device; FIG. FIG. 5 is a signal waveform diagram showing the relationship between deflection current and dynamic voltage, and FIG. 6 is a diagram illustrating the focusing state of an electron beam having a horizontally long elliptical cross section at the main lens portion. 11...control electrode, 12...acceleration electrode, 13...
...Focusing electrode system, 15...First grid electrode, 16...
...Second grid electrode, 17...Main focusing electrode, 18',
18″, 18, 19′, 19″, 19, 20′,
20″, 20……Electron beam passing hole, V _fpc ……
Constant focusing voltage, V _fpc ′...dynamic voltage.

Claims (1)

[Claims] 1. A focusing electrode system disposed between a flat accelerating electrode to which a constant accelerating voltage is applied and an anode serving as the final accelerating electrode includes a flat accelerating electrode system that forms a preliminary focusing lens between the accelerating electrode and the anode. The first grid electrode is composed of one grid electrode, a flat second grid electrode, and a box-shaped main focusing electrode having an end plate portion on the side of the second grid electrode, and to which a constant focusing voltage is applied. The grid electrode and the end plate portion of the main focusing electrode connected to the grid electrode have a circular electron beam passing hole, and as the amount of beam deflection increases, the focusing voltage gradually decreases or increases from the constant focusing voltage. A cathode ray tube device, wherein the second grid electrode to which a dynamic voltage is applied has an axially asymmetric electron beam passage hole.