JPH0216541B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetically focused cathode ray tube device having multiple electron beams.

There are both electrostatic focusing methods and magnetic focusing methods as electron beam focusing means, but the magnetic focusing method provides higher resolution. In addition, the magnetic focusing method does not require the supply of a focus voltage, and has associated great advantages such as improved reliability and reduced cost of the cathode ray tube. In particular, in the method using a permanent magnet as the magnetic field generation source, no focusing power is required. FIG. 1 is an example of a magnetically focused cathode ray tube having a plurality of electron beams. 1 is a glass envelope that keeps the inside vacuum; 2 is an envelope neck; 3R, 3G, and 3B are electron gun structures each consisting of a heater, a cathode, and first and second electrodes; 4 is a fluorescent screen; 5 is a color selection electrode;
6 and 6' are soft ferromagnetic magnetic yokes facing each other;
7R, 7G, and 7B are electron gun structures 3R and 3, respectively.
8 is a deflection yoke, and 9 is an electron beam concentrator. A permanent magnet (not shown) for generating a magnetic field is placed within the tube.
The electron beams 7R, 7G, 7B emitted from the electron guns 3R, 3G, 3B are directed to the opposing magnetic yokes 6, 6'.
The smallest beam spot is focused on the screen 4 due to the focusing effect of the magnetic field in the tube axis direction formed between the beams. Furthermore, in order to concentrate the three electron beams, a concentrator 9 is used to deflect the side beams 7R and 7B toward the center beam 7G, thereby implementing three beam concentration. However, in such an electron beam concentration method, the beam spot on the screen 4 becomes vertically elongated, which is not preferable.

The present invention provides a magnetically focused cathode ray tube device that performs self-focusing using a focusing magnetic field. In order to facilitate the explanation of the present invention, a conventional example will be explained in more detail.

Figure 2 shows permanent magnets placed above and below the center beam. Figure 2a shows a cross-sectional shape of a neck, 21R, 21G, and 21B are three electron beam passing holes, and 22 is a permanent magnet whose longitudinal direction is in the tube axis direction, and is placed at a predetermined position above and below the center beam passing hole 21G. Ru. FIGS. 2b and 2c show cross-sectional shapes taken along Y-Y' and X-X' lines in FIG. 2a.
In FIG. 2, the explanation will be made assuming that the Z axis is the tube axis and that the screen is in the Z ₊ direction. The permanent magnet 22 is magnetized so that the end face in the Z _- direction is the N pole and the end face in the Z ₊ direction is the S pole. The magnetic field lines emitted from the north pole in the _vertical cross section of FIG. It is absorbed and returns to the S pole. However, it is difficult to completely shape the magnetic field; in reality, there is a magnetic field that originates from the north pole and goes to an infinite distance in the Z _- direction, and a magnetic field that enters the south pole from an infinite distance in the Z ₊ direction. The same thing happens for horizontal sections. That is, in FIG. 2c, the focused main magnetic field is formed between the magnetic yokes 23 and 23' in the Z ₊ direction, but the magnetic field from the end of the magnetic yoke 23 in the Z _- direction and the Z ₊
There is a magnetic field directed from the magnetic yoke 23' to the magnetic yoke 23'. FIG. 2d schematically shows the magnetic field distribution on the axis of the side beam hole 21R, and Bx is a component that gives a deflection effect to the beam. In FIG. 3A, four permanent magnets 31 are arranged above and below near the side beam passage holes 32B and 32R. In this configuration, the above-mentioned Bx component, that is, the deflection magnetic field component is reduced compared to FIG. 2a.
Furthermore, as shown in FIGS. 3b and 3c, by setting the common yoke 34 surrounding the three beams before and after the permanent magnet 31 to a predetermined length, the above-mentioned deflection component can be significantly reduced. As described above, it is possible to form a magnetic field with almost no deflection component by changing the shape of the magnetic yoke, the arrangement of the permanent magnets, etc.

The present invention further allows three beams to be focused in a magnetic focusing device having almost no deflection magnetic field component as described above.

The present invention will be explained in detail below.

FIG. 4 is a diagram showing the principle of the present invention. electron beam 4
As described above, the beams 1R, 41G, and 41B pass through the insides of the magnetic yokes 42 and 43, which have almost no deflection components, and enter the magnetic yoke gap portion 44. The main magnetic field in the magnetic yoke gap portion 44 is as shown in the figure.
Direction Z ₊ (screen) and 41R, 41B
In the above example, it is made to have a predetermined angle θ with respect to the beam traveling direction and include an outward magnetic field component Bx. Naturally, there is only a magnetic field in the Z ₊ direction on the electron beam 41G.

The force applied to the beam at this time is shown in Figure 4b.
The velocity of the electron beam is only Vz, and due to the above Bx, it is Y _- (down) in 41R and Y ₊ (up) in 41B.
Receives force in the direction. Therefore, after passing through the magnetic yoke gap 44, the electron beam 41R is directed Y _- (downward);
The electron beam 41B has a velocity component in the Y ₊ (upward) direction. Cathode (neck end) side (Z _- )
and yoke 4 placed on the screen side (Z ₊ ) side
2 and 42' have an asymmetrical shape. That is, the cathode side yoke 42 has a sufficient length in the Z direction to obtain a sufficiently uniform magnetic field, and the screen side yoke 42' has a predetermined length. Therefore, in the section aB-B' of FIG. 4, the shielding and shaping of the magnetic field is weak and the Bx component remains. FIG. 4c is an explanatory diagram of the force exerted on the beam at the B-B' cross section.

As mentioned above, the electron beam 41R at this cross section is
Vz and -Vy. On the other hand, the magnetic fields are −Bz and −Bx
have. Therefore, the force exerted on the beam is Fx=-(-
V _Y )×(−Bz), Fx=−(−Vz)×(−Bx),
Receives forces in the X _- and Y ₊ directions. Therefore, the electron beam 41R obtains a velocity in the X _- direction and a velocity in the Y ₊ direction. The Y ₊ direction velocity cancels out the Y _- direction velocity component received at the A-A' cross section, and as a whole, the Y direction velocity component is zero and only the Z _- direction velocity component remains.
Similarly, the beam 41B at the opposite position obtains a velocity component in the X ₊ direction. As described above, both side beams receive a concentration effect in the direction of the center beam.

FIG. 5 is a horizontal sectional view of the magnetic yoke portion of one embodiment of the present invention. 51 is a three-beam common magnetic yoke disposed on the cathode side, 52 and 52' are opposing magnetic yokes according to the present invention, and 51' is a screen side magnetic yoke. The opposing magnetic yokes 52, 52' according to the present invention have three independent cylindrical portions 53, 54 and 53', 54' on their opposing surfaces. In the cathode side magnetic yoke 52, this cylindrical part coincides with the central axis of the three electron guns determined by the cathode and control electrodes, whereas in the screen side magnetic yoke 52', both side cylinders 54' are the cathode and control electrodes. A predetermined value of △ is placed outside the electron gun axis determined by the electrode.
It is off-axis by x.

In the magnetic field shaped by the magnetic yokes 52, 52' having such a shape, the lines of magnetic force advance so that the magnetic resistance is minimized, so that the magnetic field is bent in the direction away from the axis of the screen-side magnetic yokes 52'. As a result, the magnetic field formed between the magnetic yokes 52, 52' has an outward component at the side cylinders 54, 54'. Naturally, if the polarity of the permanent magnet is reversed, the opposite will occur. The cathode side magnetic yoke 51 is not limited to a magnetic yoke common to the three beams, as long as the magnetic field therein is sufficiently uniform and the beam is practically not deflected. Also, the screen side magnetic yoke 5
1' may be of any type as long as its height and shape can control the deflection component of the screen-side leakage magnetic field to a predetermined value.

As described above, the effects of the magnetic yoke applied to the present invention on the three beams are as explained using FIG. 4, and detailed explanation will be omitted. In addition, in the present invention, since the magnetic field inclination angle can be changed appropriately by changing the above-mentioned off-axis amount Δx, the three-beam concentration effect can also be set appropriately, and its versatility is wide and manufacturing is easy. It goes without saying that the same effect can be obtained even when the cylindrical portions are formed inside the opposing magnetic yokes.

As described above, according to the present invention, three beams are concentrated by the magnetic focusing device itself, and a good and highly reliable magnetic focusing cathode ray device can be provided by maximizing the advantages of the magnetic focusing method.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a magnetically focused cathode ray tube device, FIGS. 2a and 3a are cross-sectional views showing an example of the arrangement of permanent magnets in FIG. Figures 3 b to c are side views of the net and schematic diagrams for explaining the magnetic field distribution, and Figures 4 a to c
5 is a side view and a cross-sectional view for explaining the principle of the present invention, and FIG. 5 is a schematic horizontal cross-sectional view showing a magnetic yoke portion according to an embodiment of the present invention. 41R, 41G, 41B...electron beam, 4
2, 42', 43, 43'...Magnetic yoke, 44...
...Magnetic yoke gap part, 51, 51'... Common magnetic yoke, 52, 52'... Opposite magnetic yoke,
53, 53', 54, 54'... Cylindrical portion.

Claims (1)

[Scope of Claims] 1. A glass envelope, an electron gun sealed in the neck portion of the envelope and equipped with control means for emitting and controlling three electron beams arranged in-line, and coating formed on the inner surface of the envelope panel. The cathode ray tube is mainly composed of a fluorescent surface and a shadow mask disposed near the fluorescent surface, and is equipped with a permanent magnet for generating a magnetic field in the tube axis direction and a magnetic yoke for shaping the magnetic field as means for focusing the electron beam. In a magnetically focused cathode ray tube device,
The magnetic yokes facing each other have at least three independent cylindrical parts, and the cylindrical parts are a cathode in the magnetic yoke at the end of the neck part,
A magnetically focused cathode ray tube device, characterized in that the distance between the cylinders on both sides of the screen-side magnetic yoke coincides with the three electron gun axes determined by the control electrodes and is larger than the distance between the electron gun axes. 2 In the area between the pair of opposing magnetic yokes from the cathode that emits the electron beam, the radial magnetic field component on the axis of the side beam is as small as possible, and in the area between the pair of opposing magnetic yokes and the screen, the side beam 2. The magnetically focused cathode ray tube device according to claim 1, wherein the magnetic yoke is asymmetrical in the front and back so that a predetermined radial magnetic field component is formed on the axis.