JPS5953656B2 - cathode ray tube equipment - 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. 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 spot of the three electron beams be 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, by distorting the horizontal deflection magnetic field distribution into a bottle cushion shape as shown in Figure 1a and the vertical deflection magnetic field distribution into a barrel shape as shown in Figure 1A, three electron beams can be generated. , 2, and 3 are self-converging.

However, when such a self-concentration method is adopted, even though the concentration of the three electron beams is good, the cross-sectional shape of the three electron beams becomes distorted as the beam deflection angle increases, causing problems especially in areas on the phosphor screen surface. The beam spot that appears on the periphery,
This tends to cause distortions as shown in FIG.

That is, the beam spot 5 that appears 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 high-intensity core part 7 that is elongated in the horizontal direction. A vertically long low-luminance haze portion 8 accompanies the screen, making it difficult to obtain high resolution, especially at the periphery of the screen.

The shape distortion of the beam spot as described above is caused by the deflection yoke in the self-concentration method applying a non-uniform magnetic field to the three electron beams as shown in Figure 1 a and l). The electron beam given within the electron gun is weakened 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 includes three cathodes 10', 10", 10'" and a control electrode 11. Accelerating electrode system 12, focusing electrode 13 and anode 1
The accelerating electrode system 12 consists of flat grid electrodes 15.4, second and third grid electrodes 15. 16. It consists of 17.

As shown in FIG. 4, the first and third grid electrodes 15.17 on both sides each have three circular electron beam passing holes 18'.
, 18", 18";19',19",
19'', but the central second grid electrode 16
are three oblong rectangular electron beam passing holes 20', 20''.
, 20''.

A constant accelerating voltage g2 is applied to the first and third grid electrodes 15.17, and a dynamic voltage Vg2 is applied to the second grid electrode 16, which changes depending on the amount of beam deflection.
2' is given.

The dynamic voltage g2' is the same as the voltage Vg2 when the deflection current 23 is zero, as shown by the solid line 21 and the dashed-dotted line 22 in FIG. 5, that is, when the beam spot appears at the center of the phosphor screen surface. As the deflection current increases or decreases, the voltage gradually decreases or increases from g2.

Therefore, when the beam spot appears at the center of the phosphor screen surface, the first to third grid electrodes 15,1
6° 17 are all at the same potential Vg2, and no lens electric field is generated between each of the first, second and third grid electrodes 15, 16, 17, and the electron beam passing hole 20' of the second grid electrode 16 , 20'', and 20'' are non-circular, no axially asymmetric electric field acts on the electron beam, and a perfectly circular beam spot is obtained at the center of the screen surface.

On the other hand, when the voltage Vg2' decreases or increases from vg2 as the deflection current increases or decreases, that is, the amount of beam deflection increases,
The first and third to which a constant acceleration voltage Vg2 is applied.
A lens electric field is generated between the first grid electrode 15,17 and the second grid electrode 16.

Since the electron beam passing holes 20', 20'', and 20''' of the second grid electrode 16 are axially asymmetric, the three electron beams passing through the lens electric field each have an axially asymmetric focusing effect. receive.

Electron beam passing holes 20', 2 of the second grid electrode 16
0", 20"' is a horizontally long rectangle or a horizontally long ellipse as shown in FIG. .

As a result, the electron beam immediately after leaving the accelerating electrode system 12 is
It has a horizontally long elliptical cross-sectional shape, and enters the main lens portions 24', 24'', 24''' with this cross-sectional shape.

The refractive index of the part of the electron beam that passes through the periphery of the lens is larger than that of the part of the electron beam that passes near the center of the lens (due to spherical aberration), so as shown in Figure 6, When an electron beam 25 having a horizontally oblong elliptical cross section enters the main lens section 24, a focus point 26 in the vertical direction on the outer periphery of the beam occurs at a point farther than a focus point 27 in the horizontal direction.

28 indicates the position of the phosphor screen surface.

As described above, when the cross-sectional shape of the electron beam that has passed through the accelerating electrode system 12 is distorted into a long ellipse in the horizontal direction as the amount of beam deflection increases, the outer peripheral portion of the electron beam, which has a large influence on the deflection aberration, becomes distorted. The refractive index becomes larger in the horizontal direction than in the vertical direction, and this phenomenon is caused by the fact that the electron beam within the deflecting magnetic field becomes weaker in the horizontal direction as the amount of beam deflection increases, and weaker in the vertical direction. It acts to cancel out the strong focusing caused by

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, especially on both the left and right sides and on the diagonal, is improved.

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 accelerating electrode system 12, a dynamic voltage vg2
' is applied to the second grid electrode 16, which has a constant voltage g2
is located between the first and third grid electrodes 15, 17 to which the voltage is applied and is electrostatically shielded, so that no undesirable brightness modulation effects occur.

Furthermore, since there is no change in the pre-focusing lens formed between the third grid electrode 17 and the focusing electrode 13, extremely stable operation can be achieved.

Furthermore, since the distance between the first and second grid electrodes 15 and 16 and the distance between the second and third grid electrodes 16 and 17 can be set to small values of about 0.1 mm, the potential difference between each Even if the voltage is small, sufficient electric field strength can be obtained.

The value of the accelerating voltage Vg2 is determined depending on the required maximum beam current value, but a relatively low voltage of 1 kV or less is usually sufficient.

This means that the variation width of the dynamic voltage IF "EVg2' may be relatively small, and the dynamic voltage generation circuit can be constructed compactly and at low cost.

Although the embodiments in which the present invention is applied to an in-line color cathode ray tube device have been described above, the purpose of the present invention is to improve beam deflection by electron beams deflected within an asymmetric deflection magnetic field. The point is to correct shape distortion,
The same can be applied to a cathode ray tube device that operates with one beam or two beams.

[Brief explanation of the drawing]

Figures 1a and l) are diagrams showing the relationship between the non-uniform deflection magnetic field distribution and three electron beams, and Figure 2 is a diagram showing the beam spot appearing on the phosphor screen surface of a color cathode ray tube device that uses the self-focusing method. A diagram schematically showing shape distortion, FIG. 3 is a side sectional view of the electron gun section of an in-line color cathode ray tube device embodying the present invention, and FIG. 4 is a perspective view of the accelerating electrode system of the same color cathode ray tube device. FIG. 5 is a signal waveform diagram showing the relationship between deflection current and dynamic voltage, and FIG. 6 is a diagram illustrating the refraction state of the outer peripheral portion of the electron beam having a horizontally oblong elliptical cross section at the main lens portion. 11... Control electrode, 12... Accelerating electrode system, 13... Focusing electrode, 15... First
grid electrode, 16... second grid electrode, 17.
...Third grid electrode, 18', 18", 18"'
, 19', 19", 19", 20', 20", 20"・
...Electron beam passage hole, vg2...constant acceleration voltage, Vg2'...dynamic voltage.

Claims (1)

[Claims] 1. The accelerating electrode system disposed between the control electrode and the focusing electrode consists of first, second and third grid electrodes, with the first and third grids on both sides to which a constant acceleration voltage is applied. The electrode has a circular electron beam passage hole, and the central second grid electrode is of an axially asymmetrical shape, to which a dynamic voltage is applied that gradually decreases or increases from the constant acceleration voltage as the amount of beam deflection increases. A cathode ray tube device characterized in that it has an electron beam passage hole.