JPS59146132A - Inline electron gun - Google Patents

Abstract

PURPOSE:To prevent occurrence of shift caused by astigmatism on scanning picture face, by forming a plurality of thin cuttings around the outside beam pass holes in central and outside beam pass holes made through the bottom of tubular concentrating pole. CONSTITUTION:Central and a pair of outside electron beam pass holes 22-24 are made with same interval through the bottom face 21 of a concentric pole 20 formed into a bottomed tube with non-magnetic stainless steel on X-X axis corresponding with long axis of phosphor face. Thin cuttings 25 are formed in X-X direction and perpendicular direction of said outside electron beam through-holes 23, 24. A field control element made of high permeability material is arranged on the bottom of said pole 20. In other word, a pair of magnetic intensifier element discs 15, 16 are provided while holding the central electron beam through-hole 22 between them on the short axis of phosphor face or vertical axis Y-Y while shielding elements 17, 18 are arranged while surrounding the beam through-holes 23, 24 made on the horizontal axis X-X.

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a cathode ray tube, in which a central electron beam emitted from an in-line electron gun and a pair of both row side electron beams are formed on both sides by a common deflection magnetic field. The present invention relates to a self-convergence type in-line electron gun that can make the size of a raster constant regardless of the horizontal deflection frequency.

Figure 1 shows the conventionally used dynamic convergence [f
FIG. 2 is a longitudinal sectional view of a color cathode ray tube using a so-called self-convergence type in-line electron gun that is not thick. A central electron beam B1 and a pair of peripheral electron beams B2 emitted from the in-line electron gun 1 and located in the same plane. B3 is deflected horizontally and vertically by a deflection device 5 disposed in the funnel-shaped part of the evacuated glass envelope 2, and a reed is placed on the top surface of the glass envelope 20, emitting light in three colors inside. A scanning screen is formed on a phosphor surface 4 on which a plurality of phosphor pixels are deposited through a shadow mask 3 disposed opposite thereto. In order to make this color cathode ray tube a self-convergence system that does not require dynamic convergence correction, the horizontal deflection magnetic field of the deflection device 5 is made to have a strong first-wound distortion, and the vertical deflection magnetic field is made to have a strong barrel distortion as shown in Fig. 2. As shown, a pair of outermost electron beams B2. The comatic aberration of B3 is eliminated to form a matching scanning screen 6 on the fluorescent surface 4. In this case, the scanning screen 7 of the central beam B1 is generally horizontally and vertically spaced from both outer electron beams B2. It is smaller than the scanning screen 6 formed by B3. This misalignment of the scanning screen is due to the comatic aberration of the deflection device 5. In order to remove the comatic aberration and make each scanning screen coincident, the electric field affected by the rear leakage magnetic field of the deflection device 5 is used.
A magnetic field control element made of a magnetic material with high magnetic permeability is disposed on the bottom surface 11 of a concentrated magnetic pole 10 formed in the shape of a cylinder with a bottom and made of a non-magnetic material and attached to the tip of the child gun 1. FIG. 3 shows an example of a magnetic field control element, in which a central electron beam transmission aperture 12 formed in the bottom surface 11 of the concentrated magnetic pole 1o is arranged so as to be sandwiched on the vertical axis YY, which is the short axis of the fluorescent surface 4. A pair of disk-shaped magnetic enhancement elements 15 and 16 are provided, and electron beam transmission apertures 13 on both row sides are bored on the horizontal axis XX, which is the long axis of the fluorescent surface 4.
, 14, an annular magnetic shielding element 17,
It consists of 18. The magnetic enhancement elements 15.16 increase the deflection sensitivity of the horizontal deflection magnetic field FH of the deflection device 5 with respect to the central electron beam B1 compared to the inner and outer electron beams B2 and B3, and the annular magnetic shielding elements 17.18 increase the deflection sensitivity of the horizontal deflection magnetic field FH of the deflection device 5 with respect to the center electron beam B1. Beam B2. B3, the deflection sensitivity of the horizontal and vertical deflection magnetic fields FH9Fv of the deflection device 5 is lowered than that of the central electron beam B1, and the vertical deflection magnetic field Fv is lowered with respect to the central electron beam B1.
Its function is to increase the deflection sensitivity of the inner and outer electron beams.

Therefore, the scanning screen 7 of the central electron beam B1 is enlarged both horizontally and vertically by the magnetic field control elements 15.16 and 17.18, and conversely, the scanning screen 6 of the inner and outer electron beams B2 and B3 is enlarged.
is reduced, comatic aberration due to the deflection magnetic field is eliminated, and it becomes possible to perfectly match the scanning planes 6.7.

Recently, so-called display color cathode ray tubes, which are color cathode ray tubes with high resolution characteristics, have been used to display various types of information.
Kanji, charts, etc. are displayed in high density.

To achieve high-density display, the color cathode ray tube must have high resolution and uniform focus characteristics, the video circuit must have a wide frequency band to increase the horizontal resolution of the display screen, and the vertical resolution of the display screen must be increased. This requires a large number of scanning lines.

Normally, in order to increase the number of scanning lines as a means of high-density display, the horizontal deflection frequency fh is increased to more than 15.734 KHz of the current standard color TV system. In this case, the horizontal deflection frequency, l'h=15.734
Scanning screens 6' and 7 formed by the electron beams on both rows and the center due to the horizontal deflection magnetic field, which had no problems at around KHz.
A coma aberration of ' occurs, and as shown in FIG. 4, the scanning screen 6' of the inner and outer electron beams is
is slightly enlarged in the horizontal direction, and the rate of enlargement is different on the left and right sides of the fluorescent surface 4, resulting in an asymmetry in which the enlarged dimension d1 on the left side is larger than the enlarged dimension d2 on the right side. This shift in the scanning screen is a convergence error, which significantly deteriorates the quality of the image received on the fluorescent surface. For example, 20 inches 9
In a 0 degree deflection color cathode ray tube, the horizontal deflection frequency fh=
15.78KHz is doubled to fh = 31.5, and the above-mentioned deviation d1. d2 becomes 5-d1=Q, 7im, d2==0.3ho near the effective fluorescent surface.

The reason why the scanning screens 6' and 7' formed by the inner and outer electron beams and the central electron beam are shifted in the horizontal direction due to coma aberration as the horizontal deflection frequency fh increases is as follows.

First of all, the horizontal deflection magnetic field component guided to the bottom surface 11 of the concentrated magnetic pole 10 and penetrating this surface causes the electron beam transmission apertures 13 on both row sides in which the annular magnetic shielding elements 17 and 18 are arranged.
．． 04 Eddy currents are generated around the annular magnetic shielding element 17.18, which generates a magnetic flux that obstructs the magnetic flux change in the annular magnetic shielding element 17.18, thereby attenuating the magnetic flux and thus reducing the magnetic shielding effect. . The loss of magnetic flux due to this eddy current is due to the conventional horizontal deflection frequency f h=l 5.73KH
It was completely negligible at around Z, but as the frequency increases, the loss of magnetic flux due to eddy currents becomes impossible to ignore, and as shown in Fig. 4, the scanning screen 6' of the inner and outer electron beams becomes the central electron beam scanning screen. This is because it expands in the left and right direction relative to 7'.

The current waveform applied to the horizontal deflection coil of the deflection device f5 to perform horizontal scanning is a sawtooth wave shown in FIG. 5, and the time t1 from point a to point b in the figure is the horizontal scanning. The time t2 from point b to point C is the horizontal retrace time, and t2 is usually set to about 115 of tl. Point a or point C corresponds to the left end of horizontal scanning, and point b corresponds to the right end. In other words, the left end of the horizontal scanning screen corresponds to the end of horizontal blanking time t2, and the right end corresponds to the end of horizontal scanning time t1. During the horizontal retrace period t2, which corresponds to the termination, a magnetic field is generated due to the current that changes about five times faster than during the horizontal scanning period dl, and therefore an annular magnetic field is generated due to the eddy current loss due to the harmonic component magnetic field. The magnetic shielding effect loss of the magnetic shielding elements 17 and 18 is larger on the left side of the fluorescent surface than on the right side, and as shown in FIG. The horizontal expansion width for is dl on the left
becomes larger than dl on the right side, causing asymmetry in comatic aberration in the horizontal direction.

At fh = 15.734KHz, which is used in the conventional standard color TV system (NTSC system), tl = approximately 51 to 5.
3μ(6), t2 = 10 to 12μ, the eddy current loss caused by this can be completely ignored, and therefore the above-mentioned coma aberration and its asymmetry could not be found substantially, but as fh increases, the mouth and t2 In order to further increase the effective scanning time 11, the retrace time t2 is set as small as possible, and the asymmetry of the eddy current loss becomes a non-negligible amount, causing the above-mentioned phenomenon.

This invention was made in view of the above-mentioned drawbacks, and as the horizontal deflection frequency of the self-convergence type in-line electron gun increases, coma aberration occurs in the scanning screen formed by the inner and outer electron beams and the central electron beam. This is to prevent the occurrence of distortion caused by

That is, the white outside of the center and both row side beam transmission apertures arranged in-line and bored on the bottom surface of the bottomed cylindrical concentrated magnetic pole made of non-magnetic gold ingot attached to the tip of the electron beam exit side of the in-line electron gun. A plurality of elongated cuts are formed around the electron beam transmission hole. With this configuration, the magnetic field control elements disposed in the child beam transmission apertures on both row sides can prevent the generation of eddy currents due to high-frequency horizontal deflection frequency components passing through the magnetic field control elements. Regardless of the increase in frequency, it is possible to eliminate asymmetric shifts due to coma in the scanning screen formed by the central and inner and outer electron beams, making it possible to make the in-line electron gun an excellent electron gun capable of high-density display.

Hereinafter, embodiments of the invention will be described in detail with reference to the drawings.

FIG. 6 shows a perspective view of a concentrated magnetic pole 20 according to one embodiment of the invention. A bottom surface 21 of a concentrated magnetic pole 20 formed in a cylindrical shape with a bottom and made of non-magnetic stainless steel and attached to the tip of an electron gun.
has a center and a pair of inner and outer electron beam transmission apertures 22, 2.
3.24 are drilled at equal intervals on the same straight line and on the X--X axis corresponding to the long axis of the fluorescent surface. However, in the inner and outer electron beam transmission apertures 23 and 24, elongated incisions 25 are formed in the X-X axis direction and in a direction perpendicular thereto.
As shown in FIG. 7, on the bottom surface of the concentrated magnetic pole 20, a magnetic field control element made of a high permeability magnetic material similar to the conventional one is arranged.

That is, the central electron beam transmission aperture 22 has a pair of disc-shaped magnetic enhancement tabs 15 and 16 facing each other, and a horizontal axis X-. Inner and outer electron beam transmission apertures 23 bored on X
．． 24'(il-surrounding annular magnetic shielding element 17°18
to be placed. These magnetic field control elements 15, 16°17.
The function of the deflection magnetic field 18 is exactly the same as that of the conventional example.

However, even if the horizontal deflection magnetic field is induced to the bottom surface of the concentrated magnetic pole 20 and there is a component that penetrates this surface, a plurality of elongated cuts 25 are formed around the inner and outer electron beam transmission apertures 23 and 24. This prevents the generation of eddy currents in this hole.

This eddy current therefore causes the annular magnetic shielding element 17.1
The generation of magnetic flux that obstructs the magnetic flux change in 8 is extremely small, and its magnetic shielding effect is especially noticeable when the horizontal deflection frequency is fh=
Even if it becomes higher than 15.73KH2, it will not decrease regardless of the frequency.

As a result, even if the horizontal deflection frequency fh increases as in the conventional case, the scanning screen of the inner and outer electron beams is expanded relative to the scanning screen of the central electron beam, or the expansion rate is the difference between the horizontal scanning time and the horizontal retrace time. Therefore, there will be no asymmetry.

In the above explanation, the scanning screen of the central and out-of-plane electron beams uses a magnetic field control element consisting of a pair of magnetic enhancement elements and an annular magnetic shielding element for correcting comatic aberration of the scanning screen with the relationship shown in FIG. However, the invention is not limited to this, and can be applied to the case of correcting various coma aberrations. For example, the top and bottom of the scanning screen on the fluorescent surface 4,
When corrected by the magnetic fields of the left and right distorted sound deflectors, as shown in FIG. Although it is narrower, it can also be applied to a magnetic field control element that completely corrects coma aberration in this case. In this case, as shown in FIG. 9, a pair of U-shaped magnetic field control elements 27 and 28
Electron beam transmission apertures 23 on both row sides are bored in the bottom surface 21 of the
, 24, and a plurality of elongated cuts 25 are formed around the hole.

Furthermore, if the present invention is applied not to the above-mentioned Rask scanning method in which the scanning speed is constant during the effective scanning period in the line sequential manner, but to the random scanning method in which the scanning speed is undefined, coma aberration will not occur in this case as well. As time passes, its effectiveness becomes even more obvious.

Alternatively, according to the invention, it is not necessary to optimize the magnetic field control element disposed on the bottom surface of the concentrated magnetic pole for each horizontal deflection frequency to be used, and the same magnetic field control element can be used in common.

As described above, according to the invention, a plurality of elongated cuts are formed around the electron beam transmission apertures on both row sides of the bottom surface of the concentrated magnetic pole attached to the tip of the self-convergence type in-line electron gun. The dependence of the effect of the magnetic field control element disposed on the horizontal deflection frequency and the difference in effect due to the difference between the horizontal scanning time and the horizontal retrace time can be eliminated. As a result, regardless of the increase in the horizontal deflection frequency, it is possible to eliminate asymmetric shifts based on comatic aberration of the scanning screen formed by the central and out-of-plane electron beams.
The in-line type electron gun can be made into an extremely excellent electron gun capable of high-density display, and its practical value is extremely high.

[Brief explanation of drawings]

Figure 1 is a longitudinal cross-sectional view of a color cathode ray tube that uses a conventional self-convergence type in-line electron gun, and Figure 2 shows the center and both row side electron guns on the fluorescent surface of this color cathode ray tube. FIG. 3 is a diagram showing a scanning screen formed by a magnetic field control element for correcting coma aberration of the scanning screen;
Figure 4 shows the coma aberration of the scanning screen, Figure 5 shows the current waveform flowing through the horizontal deflection coil, Figures 6 and 7 show an example of the invention. A perspective view of a concentrated magnetic pole according to an example and a plan view of a state in which a magnetic field control element is disposed on the bottom surface of the concentrated magnetic pole, FIG. 8 is a diagram showing a coma aberration pattern of another scanning screen to which the invention can be applied, and FIG. FIG. 7 shows plan views of the bottom surfaces of concentrated magnetic poles according to other embodiments in which the invention is applied to a magnetic field control device for correcting coma aberration. DESCRIPTION OF SYMBOLS 1... In-line electron gun, 2... Glass envelope, 4... Fluorescent surface, 5... Deflection device,
6. 6', 60... Scanning screen formed by the out-of-plane electron beam, 7. 'l', 70... Scanning screen formed by the central electron beam, 10.2013-... Concentrated magnetic pole, 12.22... Center electron beam transmission opening on the bottom surface of the concentrated magnetic pole. Hole, 13, 14, 23.
24... Circumferential electron beam transmission aperture on the bottom surface of the concentrated magnetic pole, 15.16... Magnetic enhancement element, 17.18
...Annular magnetic shielding element, 27.28...Magnetic field control element, 25...Elongated notch. 14-

Claims (1)

[Claims] Electron beam transmission apertures in the center and both rows are arranged in-line on the bottom surface of a bottomed cylindrical concentrating pole made of a non-magnetic metal material, which is attached to the tip of the electron beam exit side of an in-line electron gun for color cathode ray tubes. An in-line electron gun characterized in that a plurality of elongated cuts are formed around the aperture in which a magnetic field control element for correcting coma aberration of a scanning screen formed by a deflection magnetic field is disposed.