JPS5871535A - Electromagnetic focusing picture tube - Google Patents

Abstract

PURPOSE:To enable true-circle side beam spots without almost no halos to be obtained on a fluorescent screen by designating the shape, the dimension and the location of a high-permeability magnetic shielding body used for sheilding horizontal magnetic fields. CONSTITUTION:In an external-magnetic-type in-line-arrangement electromagnetic focusing picture tube, many cylindrical magnetic shielding bodies 14 with different thickness (tmm.) and length (lmm.) are prepared. The installed position of each body 14 is selected so that the halos of side beams 12S1 and 12S2 are prevented with the body 14, and indicated by the length (gmm.) of the exposed part of a neck tube which is the distance between a permanent magnet and the end of the body 14. When the length (l) of above body 14 normalized by the outer diameter of the neck, l/D, and the length (g) normalized by the outer diameter of the neck, g/D, satisfy the relationship given by the equation of g/D=(k1.t)/(l/ D-k2)-k3 (0.1<=k1<=0.5, 0.1<=k2<=0.2 and 0<=k3<=0.2), the effect of the body 14 is exhibited remarkably, a beam spot with an excellent shape is obtained, and an excellent picture quality is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-electron beam electromagnetic focusing picture tube in which the beam spot shape of side beams is improved.

Figure 1.2 shows an example of a conventional so-called in-line non-array magnetic electromagnetic focusing picture tube in which three electron guns are arranged in one plane and an annular permanent magnet for generating a focusing magnetic field is installed outside the neck tube. , FIG. 1 is a cross-sectional view taken along a plane (in-line plane) including the three electron guns of the neck portion, and FIG. 2 is a cross-sectional view taken along a plane including the tube axis and perpendicular to the plane. In these figures, 1 is an envelope (neck tube), 2 is a cathode, 3 is a first grid, 4 is a second grid, 5 is a pair of magnetic yokes,
6 is an anode conductive piece, 7 is an internal conductive film, 8 is a permanent magnet that generates a focusing magnetic field between opposing yokes, 9 is a plurality of electrode support rods, 10 is a deflection yoke, 11 is a stem bin, 12
c is the center (electron) beam, and 1281.1282 are the side beams. Similar to the third grid of an ordinary electrostatic focusing tube, a high anode voltage is applied to the magnetic yoke 5 from an anode terminal (not shown) via the internal conductive film 7 and the anode conduction piece 6. Electron beam 1 emitted from cathode 2
2c, 12s+, 12s2 are first grid 3, second grid
It passes through the grid 4 and is narrowed once near the second grid to form a so-called crossover. Thereafter, the electron beam is accelerated by the magnetic yoke 5 to which an anode voltage is applied, passes through an electron beam passage hole 5a provided in the magnetic yoke 5, and reaches a fluorescent surface (not shown).

The yoke 5 made of a high magnetic permeability magnetic material absorbs the magnetic flux generated by the permanent magnet 8 and generates a strong focusing magnetic field in the gap 5b between the pair of opposing magnetic yokes 5, and the magnetic main lens 13 is attached here. Form.

Therefore, the electron beam 12c1128 that passed through this
1.1282 receives a focusing action and forms a crossover image on the fluorescent surface.

However, in the conventional electromagnetic focusing picture tube mentioned above, the beam spot shape of the side beams 12 sl and 1282 on the fluorescent surface is affected by coma aberration as shown in Fig. 3, and the overall focus characteristic is The reason why the side beam 1281, which had a large adverse effect on the convergence characteristics, is affected by coma aberration will be explained below.

FIG. 4 shows the X direction on the path of the side beam 12B shown in FIG. The results of measuring the magnetic field Bx (which is orthogonal to two directions within the area) are shown. That is, before the side electron beam 12sl emitted from the cathode 2 reaches the magnetic main lens 13 formed in the gap 5b of the magnetic yoke 5, it is affected by the magnetic field indicated by diagonal lines in FIG. Therefore, when the side beam 12s1 enters the magnetic main lens 13, it is shifted in the y direction (perpendicular to the x and z directions) by Δy calculated by the following equation (1).

(e/m is the specific charge of the electron, and vz is the velocity of the electron in two directions.) Inserting the measured value of Bx shown in Figure 4 into equation (1) and calculating it assuming that it is accelerated at an anode voltage of 20 kV, △y
= o, s mm. Although we have explained the side electron beam 12s+ which is 0 or more, which causes comatic aberration because Δy is not zero, resulting in a beam spot with no and low as shown in FIG. 3, the same thing occurs with the side electron beam 12S2. There is. In order to eliminate the beam spot distortion that occurs as described above, the outer periphery of the neck tube from the cathode electrode system to the vicinity of the magnetic field generator (the annular permanent magnet 8 in the illustrated case) is made with high transparency, as shown in Figure 5.6. The present applicant has already filed a patent application in 1973 to cover the shield body 14 made of magnetic material.
It has been filed as No. 4-154594.

However, if the shape, dimensions, and position of this high-permeability magnetic shield are not appropriate, the halo of the beam spot cannot be removed, and in some cases, the halo may even increase. Magnetic field (Bx) By specifying the optimal range of shape, size, and position of the high permeability magnetic material barrier for L-rays, it is possible to obtain a perfectly circular side beam spot with almost no halo on the fluorescent surface. An object of the present invention is to provide a multi-electron beam electromagnetic focusing picture tube.

In order to achieve the above object, as a result of many experiments, the present inventor determined that the wall thickness of a shielding body made of a high permeability magnetic material for shielding transverse magnetic fields is t, myn, and the length in the tube axis direction is l mrn. When the axial length of the neck exposed part between the end of the jellyfish and the magnetic field generator is gmm, and the outside diameter of the neck tube is l)mm, the following formula holds true, and the numerical values in the formula are 1 + k2 Hk3, respectively.
01≦1≦0.5.0.1≦2≦0.2.0≦3
It was decided to set t, l, and g so that they were within the range of ≦0.2.

A more detailed explanation will be given below with reference to the drawings.

FIG. 7 shows the setting conditions of the cylindrical magnetic barrier body 14, which the inventor obtained from the results of numerous experiments, so that no halo is generated in the side beams 12s1 and 12B2 and an almost perfectly circular beam spot can be obtained. show. That is, the wall thickness j Tnm,
A large number of shielding bodies 14 made of cylindrical magnetic material with various lengths l mm are prepared, and the positions of the shielding bodies 14 are selected so that the halo of the side beams 1281 and 1282 is eliminated by each shielding body 14. At that time, set the installation position to the axial length of the exposed neck tube from the end of the shield body to the permanent magnet, and set the wall thickness tmm to . Figure 7 shows the relationship between A/D and g/D normalized by the outer diameter.As a result, t+ shown in Figure 7
1. When the relational expression between g was determined, it was found that it can be approximated by the following expression (2).

Here, the values of the numbers k, + k21 and k3 are determined depending on the shape and dimensions of the permanent magnet 8, the strength of the magnetic field, and the material of the cylindrical magnetic body;
For the 0 experiment in which 3≦02, ≦ks≦0.5.01≦kz≦02.0≦, for example, the permanent magnet 8 is made of Hitachi Metals m5B-2C and has an inner diameter of 54φmz.

The plate had an outer diameter of 54φ and a thickness of 15 mm, and the material of the cylindrical magnetic barrier body 14 was 8841 mild steel. If the condition of equation (2) is satisfied, what is shown in FIG. 5.6 is an embodiment of the present invention.

It should be noted that the barrier against the transverse magnetic field does not have to be perfectly cylindrical, as shown in Figures 8 and 9 (however, Figure 8 is a cross-sectional view taken from an in-line plane, and Figure 9 is a cross-sectional view taken along line A-A' shown in Figure 8). Almost the same effect can be obtained by using a pair of partially circumferential shields 15B and 15b that cover only a part of the outer periphery of the neck pipe as shown in the cross-sectional diagram (line sectional view), and in this case, the same relationship as in equation (2) is obtained. To establish.

As explained above, according to the present invention, on the outer periphery of the neck tube,
From the cathode electrode system to the vicinity of the focusing magnetic field generator, the effect of the magnetic barrier body installed to suppress the influence of transverse magnetic fields on the side beam is clearly exhibited, resulting in a well-shaped beam spot and a good beam spot. You will be able to get better image quality.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional external magnetic type in-line arrangement electromagnetic focusing picture tube taken along an inline plane, Figure 2 is a cross-sectional view of the same example taken along a plane perpendicular to the inline plane, and Figure 5 is a cross-sectional view of the same example taken from a fluorescent surface. Fig. 4 is a diagram of the X-direction magnetic field distribution on the path of the side beam of the same example, Fig. 5 is a cross-sectional view of an in-line surface of an embodiment of the present invention, and Fig. 6 is a diagram of the side beam spot shape of the same embodiment. Sectional view taken along a plane perpendicular to the inline plane, No. 7
The figure is a diagram of the shape, dimensions, and position of a magnetic barrier body that provides good effects; FIG. 8 is a cross-sectional view taken from an in-line plane of an embodiment using the partially circumferential barrier body of the present invention; and FIG. 9 is a sectional view taken along the line AN shown in FIG. 8. 1... Envelope (neck tube) 5... Yoke 8.
...Annular permanent magnet 12S1.1282...Side beam 15...Magnetic main lens 14, 15a, 15
b...Shiyahei body representative patent attorney Susuki 1) Ri Yukisui 1 figure 3 figures skin 1 place η'5 figure 6 figure 廼wa figure = /p Yu δ figure i○ figure

Claims (1)

[Claims] A pair of yokes made of a magnetic material with high magnetic permeability and having a plurality of electron beam passage holes are arranged facing each other in the direction in which the electron beam travels, and a focusing magnetic field is applied between the pair of yokes along each electron beam path. In a multi-electron beam electromagnetic focusing picture tube in which the generating device is installed outside the neck of the pulp, the outer periphery of the neck from the cathode electrode system to the vicinity of the magnetic field generating device is covered with a high permeability magnetic material barrier. The body thickness is t
mm, the length in the tube axis direction is l mm, the axial length of the neck exposed part between the end of the shayahei body and the magnetic field generator is g, and the outer diameter of the neck is D mm.
Then, the following formula holds true, and the value kt+ in the formula is 2
．． and 3 are respectively 0.1≦1≦05 and 0.1≦2
An electromagnetic focusing picture tube characterized in that the range is within the range of ≦02.0≦ and 3≦02.