JPH0142110B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic focusing cathode ray tube.

Figures 1 to 4 show an example of a so-called in-line magnetic type electromagnetic focusing cathode ray tube in which electron guns are aligned in a straight line and magnets are placed inside the network. 2 is a cross-sectional view of the cathode ray tube neck portion, FIG. 2 is a longitudinal sectional view, FIG. 3 is a sectional view taken along line AA' in FIG. 2, and FIG. 4 is a sectional view taken along line BB' in FIG. In these figures, 1 is the envelope, 2
3 is a cathode, 3 is a first grid electrode, 3a is its electron beam passage hole, 4 is a second grid electrode, 4a is its electron beam passage hole, 5 is a pair of magnetic yokes,
Reference numeral 5a denotes an electron beam passage hole, 6 a plurality of anode conductive pieces, and 7 an anode conductor, which are adhered to the inner wall surface of the envelope 1. A permanent magnet 8 is disposed between the magnetic yokes 5. Reference numeral 9 denotes a plurality of electrode support rods, 10 a deflection yoke disposed outside the envelope 1, and 11 a stem lead-in wire, which is not shown but is connected to an electrode within the envelope 1. 12c and 12s indicate center and side electron beams.

In the electromagnetic focusing cathode ray tube configured in this way, the electron beams 12c, 1 emitted from the cathode 2
2s is a first grid electrode 3, a second grid electrode 4
The electron beam is once converged to form a so-called crossover. Thereafter, the electron beam is accelerated by the magnetic yoke 5 to which an anode voltage is applied from the anode conductor 7 through the anode conduction piece 6, passes through the electron beam passage hole 5a, and reaches a fluorescent surface (not shown).

On the other hand, a magnetic yoke 5 made of a high magnetic permeability magnetic material
absorbs the magnetic field generated by the permanent magnet 9, and a strong focusing magnetic field is generated in the gap portion 5b between the magnetic yokes 5, and this portion serves as a focusing portion. Therefore, the electron beams 12c and 12s passing through this point are focused to connect the crossover object point on the fluorescent surface.

However, in the electromagnetic focusing cathode ray tube having the above configuration, the focusing magnetic field acting on each electron beam 12c, 12s does not have a rotationally symmetrical focusing magnetic field distribution, and forms a magnetic field lens including astigmatism. In other words, the focused magnetic field of the beam passage hole is in the lateral direction (x direction)
is weaker than in the vertical direction (y direction). Therefore, the electron beams 12c and 12s that have passed through this focusing magnetic field and reached the fluorescent surface have a flat beam spot shape as shown in FIGS. It was looming. The reason why the flat direction of the beam is rotated in Figures 5a and 5b is as follows.
This is due to the rotational effect of a focused magnetic field.

FIG. 6 schematically shows the beam trajectory of the electron gun as described above. Since the electron beam after passing through the crossover 14 has a focusing magnetic field in the y direction that is stronger than the x direction, the magnetic field lens 15 For convenience of construction, the y-direction magnetic field lens 15a is shown by a broken line, and the x-direction magnetic field lens 15a is shown by a solid line.
Forming a lens stronger than the directional magnetic field lens 15b,
Therefore, the image point of the y-direction beam shown by the dashed line is connected in front of the fluorescent surface 13, while the image point of the x-direction beam shown by the solid line is connected on the fluorescent surface 13.
As a result, a flat beam spot shape as shown in FIGS. 5a and 5b is obtained.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electromagnetic focusing cathode ray tube which eliminates the above-mentioned drawbacks and has a perfect circular beam spot on the phosphor surface.

In order to achieve this object, the present invention provides means for making the electron beam spot incident on the electromagnetic focusing part non-circular (distorting) at a stage preceding the electromagnetic focusing part. The electromagnetic focusing cathode ray tube according to the present invention will be described in detail below using embodiments shown in the drawings.

7 to 9 show an embodiment of an in-line magnetic type electromagnetic focusing cathode ray tube according to the present invention, and the same parts as in FIGS. 1 to 3 are given the same symbols. . Further, FIG. 10 corresponds to FIG. 6, which schematically shows the trajectory of the electron beam in the electromagnetic focusing cathode ray tube of the present invention.

In FIGS. 7 to 10, 23 is a first grid electrode, and the first grid electrode 23 has an electron beam passing hole 23a that is non-circular and elliptical, and its long axis is slightly inclined from the y-axis. When the electron beam emitted from the cathode 2 passes through the first grid electrode 23, the y direction receives a weaker convergence effect than the x direction, and the electron beam crossover 14 moves toward the fluorescent surface 13. do. the result,
On the fluorescent surface 13, the image point in the y direction moves toward the fluorescent surface 13, and the image points are focused on the fluorescent surface in both the x and y directions, and the beam spot shape becomes a perfect circle.
Of course, the direction of the ellipse of the first grid electrode must be determined by taking into account the rotation effect of the beam spot due to the focusing magnetic field, but the experimental results show that the direction of the ellipse is 14
High voltage 20KV with 90° deflection color cathode ray tube.
It was found that if the peak value of the focused magnetic field is 1000G, it is sufficient to tilt the device by approximately 20 degrees. Further, the shape of this hole is not limited to the above-mentioned ellipse, but may be any non-circular shape such as a rectangle or a rhombus.

The above explained the first grid electrode, but
Similar effects can be obtained even if the holes in the second grid electrode, third grid, etc. are non-circular.

In addition, in the above description, the electron beam passing hole of the electrode at the stage before the electromagnetic focusing area is made non-circular as a means for distorting the electron beam incident on the electromagnetic focusing area, but the shape of the hole is not limited to the shape, for example, as shown in FIG. The same applies to a structure in which the thickness of the peripheral edge of the hole 33a of the one-grid electrode 33 is changed. In addition, although the in-line array magnetic type electromagnetic focusing cathode ray tube was described above, there are also magnetic type electromagnetic focusing cathode ray tubes outside the in-line array in which the permanent magnet is installed outside the network, and even delta-ray tubes in which the electron gun is arranged in a triangular shape. It is clear that the present invention also applies to array electromagnetic focusing cathode ray tubes. Furthermore, in the above description, the thickness of the periphery of the hole of the first grid electrode was changed, but the thickness of other electric plates such as the second grid electrode may be changed.

As explained above, according to the electromagnetic focusing cathode ray tube according to the present invention, the beam spot shape on the fluorescent surface can be made into a perfect circle, and it can be obtained by a method that is inexpensive and has good mass production. You can get the same effect.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a neck part showing an example of a conventional in-line magnetic type electromagnetic focusing cathode ray tube, Fig. 2 is a longitudinal sectional view thereof, and Fig. 3 is a sectional view taken along line A-A' in Fig. 1. Figure 4 is a sectional view taken along line B-B' in Figure 1, Figure 5 is a beam spot shape on a fluorescent surface according to the prior art, Figure 6 is a diagram showing an electron beam trajectory according to the conventional structure, and Figure 7 is a diagram showing the electron beam trajectory according to the conventional structure. FIG. 8 is a cross-sectional view of a neck portion showing an embodiment of an in-line magnetic electromagnetic focusing cathode ray tube according to the present invention. FIG. 9 is a longitudinal sectional view thereof, FIG. 11 is a diagram showing an electron beam trajectory according to the present invention, and FIG. 11 is a longitudinal sectional view showing another embodiment of the present invention. 3, 23, 33...first grid electrode, 3a,
23a... Electron beam passing hole, 4... Second grid, 4a... Electron beam passing hole, 5... Magnetic yoke, 5b... Electromagnetic focusing section, 8... Permanent magnet, 1
2...Electron beam.

Claims (1)

[Claims] 1. In an electromagnetic focusing cathode ray tube in which a pair of magnetic yokes having a plurality of electron beam passage holes arranged in-line are disposed in the traveling direction of the electron beam, and a permanent magnet for generating a focusing magnetic field is provided in the cathode ray tube neck, the magnetic The electron beam passing hole of at least one electrode closer to the cathode than the body yoke is oval, rectangular,
The electron beam spot incident on the electromagnetic focusing area is distorted by forming the non-circular through hole into a non-circular shape such as a rhombus, and by tilting the long axis of the non-circular passage hole with respect to the in-line arrangement direction and a direction perpendicular to the in-line arrangement direction. An electromagnetic focusing cathode ray tube featuring: