JPH07249387A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To reduce deterioration in image quality on image rotating correction by arranging a plurality of correcting coils in a tube Axial direction on the outside of a cathode ray tube and generating a magnetic field reverse to an outside magnetic field. CONSTITUTION:Image rotating correction coils 16A, 16B having the same shape, each generates a magnet field in the opposite direction to an outside magnetic field in the vertical direction to each tube surface are arranged on the outside of a tube body, especially in the position on a fluorescent screen side of a deflecting yoke 6 and in the position on an electron gun side. The coils 16A, 16B are arranged so that the coil surfaces are parallel to the panel surface and d.c. current passes so as to generate a magnetic field in the same direction. Thereby, the magnetic field in the direction opposite to a magnetic field in the vertical direction to a tube surface. The magnetic field acts an opposite force to a force generated by a geomagnetism on an electron beam and image rotation is retarded. A magnetic field vertical to a tube surface is superposed on magnetic fields 18A, 18B generated by the coils 16A, 16B to form a synthetic magnetic field 19. The magnetic field 19 uniform in a tube axial direction in a region containing a beam deflection center can be generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube provided with measures against an external magnetic field such as earth magnetism.

[0002]

2. Description of the Related Art In a color cathode ray tube, as shown in FIG. 12, a fluorescent surface 2 is formed on the inner surface of the panel of a tube body 1, and a color selection electrode (for example, an aperture grill, a shadow mask, etc.) is formed facing the fluorescent surface 2. ) 3 is arranged, and the electron gun 4 is arranged at the neck portion. The electron beam 5 emitted from the electron gun 4 is deflected in a horizontal direction and a vertical direction at a predetermined cycle by a deflection yoke 6, and is irradiated onto the phosphor screen 2 to emit light.

Here, the electron beam 5 deflected by the deflection yoke 6 receives various forces due to the magnetic field generated in the tube body 1 by the geomagnetism before reaching the phosphor screen 2, and deviates from the regular trajectory. I will end up. For example, when the color cathode ray tube is used in the north-south direction, the orbit of the electron beam 5 is deviated due to the horizontal component of the geomagnetism in the north-south direction (the component in the direction perpendicular to the tube surface). When the amount of change in the electron beam trajectory is large, it is represented as a phenomenon (referred to as image rotation) in which the entire screen 10 rotates on the screen, as shown in FIG.

Conventionally, in order to suppress the influence of the horizontal geomagnetic component, the outer circumference of the panel and the funnel of the cathode ray tube is surrounded by an external magnetic shield (OMS) to magnetically shield them, or an annular shape is formed in the tube 1. Internal magnetic shield (IM
S) is arranged to provide magnetic shielding. Furthermore, a degaussing coil is arranged on a part outside the tube body,
The magnetic material inside and outside the tube is demagnetized.

By the way, the current color cathode ray tube is progressing in the direction of removing the external magnetic shield body due to the increase in size and size. However, the inner magnetic shield body is inferior to the outer magnetic shield body in the shield property with respect to the horizontal geomagnetic component which largely contributes to the image rotation.

[0006]

On the other hand, in order to improve the above-mentioned problems, as shown in FIG. One image rotation correction coil 8 to be generated is connected to the deflection yoke 6
Alternatively, a method of mounting on the outside of the pipe has been proposed. Figure 7A
And B show the shape of the image rotation correction coil 8,
For example, it is formed in a perfect circle shape.

The magnetic field 9 generated by the image rotation correction coil 8 in the tube axis direction, that is, the beam axis direction has a Gaussian distribution shown in FIG. The correction of the image rotation is performed by the correction coil 8. However, at the time of the image rotation correction, the magnetic field 9 by the correction coil 8 has the magnetic field distribution shown in FIG. It causes deterioration of image quality such as convergence and mislanding. And these quantities cannot be ignored.

In particular, the problem is image distortion (see FIG. 9) caused by different image rotation correction amounts in the vertical and horizontal directions,
Corner bow type vertical misconvergence (CBV) (Fig. 1
0), twist-shaped mislanding of the axial and corners (see FIG. 11), and the like. The solid line 11 in FIG.
Corresponds to the red beam, and the broken line 12 corresponds to the blue beam. See also FIG.
In 1, the solid line 13 indicates mislanding and the chain line 14 indicates just landing.

In view of the above points, the present invention provides a cathode ray tube capable of reducing the deterioration of image quality caused at the time of image rotation correction.

[0010]

According to a first aspect of the present invention, a plurality of correction coils 16 for generating a magnetic field opposite to an external magnetic field perpendicular to the tube surface are arranged outside the cathode ray tube along the tube axis direction. Configure.

A second aspect of the invention is the cathode ray tube of the first aspect of the invention, in which a plurality of correction coils 16 are attached to the deflection yoke 6 at predetermined intervals.

According to a third invention, in the cathode ray tube according to the first or second invention, the plurality of correction coils 16 include correction coils having different diameters.

[0013]

In the first aspect of the invention, a plurality of correction coils 16 for generating a magnetic field in the direction opposite to the external magnetic field (so-called horizontal geomagnetic component) perpendicular to the tube surface are arranged outside the cathode ray tube along the tube axis direction. This plural correction coils 1
The magnetic field uniformity in the tube axis direction is improved by the combined magnetic field generated in 6, and the image rotation can be corrected while reducing the deterioration of image quality.

In the second aspect of the invention, the plurality of correction coils 16 are attached to the deflection yoke 6 at a predetermined interval so that the combined magnetic field produced by the correction coils 16 is formed in the region including the deflection center. Therefore, it is possible to efficiently correct the image rotation and reduce the image quality deterioration.

In the third aspect of the present invention, by using the correction coils having different diameters as the plurality of correction coils 16, it is possible to further efficiently correct the image rotation and reduce the image quality deterioration.

[0016]

Embodiments of the color cathode ray tube according to the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the present invention. In the figure, reference numeral 1 denotes a cathode ray tube body. In this tube body 1, a color fluorescent screen is formed on the inner surface of the panel as described above, and a color selection electrode (for example, an aperture grill, Shadow mask, etc.) is arranged, and an electron gun is arranged on the neck portion. Reference numeral 6 denotes a deflection yoke for deflecting the electron beam in the horizontal and vertical directions.

In this example, however, an external magnetic field (that is, the external magnetic field) perpendicular to the tube surface is provided outside the tube body 1, particularly on the position of the deflection yoke 6 on the phosphor screen side and the position of the electron gun side. The image rotation correction coils 16 [16A, 16B] having the same shape that generate a magnetic field in the direction opposite to the horizontal geomagnetic component) are arranged such that the coil surface is parallel to the panel surface (so-called screen). The correction coil 11B arranged on the electron gun side can be attached to the back cover of the deflection yoke, for example. As the image rotation correction coil 16 [16A, 16B], in this example, a perfect circular coil as shown in FIGS. 2A and 2B is used.

In such an embodiment, a direct current is applied to the two image rotation correction coils 16A and 16B so as to simultaneously generate magnetic fields in the same direction. As a result, a magnetic field in the direction opposite to the magnetic field in the direction perpendicular to the tube surface (that is, the horizontal geomagnetic component) is generated, and a force opposite to the force exerted by the geomagnetism on the electron beam acts to suppress the image rotation. . At this time, the magnetic field in the direction perpendicular to the tube surface (that is, the beam axis direction) becomes a combined magnetic field 19 in which the magnetic fields 18A and 18B generated by the two correction coils 16A and 16B are superposed, as shown in FIG. A magnetic field that is uniform and close to the earth's magnetism is generated in the tube axis direction on the region including the beam deflection center.

The synthetic magnetic field 19 improves the magnetic field uniformity in the tube axis direction as compared with the magnetic field 9 generated by one conventional correction coil 8. Therefore, there is no adverse effect on others,
It is possible to correct the image rotation due to the geomagnetism. That is,
It is possible to reduce image distortion at the time of image rotation correction, corner bow type vertical misconvergence, twisted mislanding of axial and corners, and the like.

FIG. 4 shows another embodiment of the present invention. Although the two correction coils 16A and 16B are arranged in FIG. 1 described above, if the deflection yoke 6 is large or the magnetic field uniformity is further enhanced, as shown in FIG. In the example, three correction coils 16 [16A, 16B
And 16C].

In this way, three or more correction coils 16 are provided.
By arranging [16A, 16B, 16C], the magnetic field uniformity of the composite magnetic field formed by the coil 16 in the tube axis direction is enhanced, and it is adapted to the formation of a large deflection yoke or a more uniform magnetic field. be able to. Then, the image rotation is corrected, and the image quality deterioration caused at that time can be reduced.

Depending on the mounting position and structure of the magnetic body used in the deflection yoke 6, as shown in FIG.
The efficiency is further improved by changing the coil diameters of the two correction coils 16A and 16B, that is, by making the coil diameter of the correction coil 16B on the electron gun side smaller than the coil diameter of the correction coil 16A on the phosphor screen side. .

[0024]

According to the present invention, it is possible to correct the image rotation due to the external magnetic field in the direction perpendicular to the tube surface, that is, the horizontal geomagnetic component, and at the same time, the image distortion, misconvergence, and the like which occur during the image rotation correction. Image quality deterioration such as mislanding can be reduced. Further, the uniformity of the magnetic field can be controlled by the number of correction coils used.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of a cathode ray tube according to the present invention.

FIG. 2A is a front view showing an example of an image rotation correction coil used in the present invention. B is a side view showing an example of an image rotation correction coil used in the present invention. FIG.

3 is a composite magnetic field distribution diagram formed by the image rotation correction coil of the cathode ray tube of FIG.

FIG. 4 is a configuration diagram showing another example of the cathode ray tube according to the present invention.

FIG. 5 is a configuration diagram showing another example of the cathode ray tube according to the present invention.

FIG. 6 is a configuration diagram showing an example of a conventional cathode ray tube.

7 is a front view of an image rotation correction coil used in the cathode ray tube of FIG. 7B is a side view of the image rotation correction coil used in the cathode ray tube of FIG. 6. FIG.

FIG. 8 is a magnetic field distribution chart formed by the image rotation correction coil of the cathode ray tube of FIG.

FIG. 9 is an explanatory diagram of image distortion.

FIG. 10 is an explanatory diagram of a corner bow type vertical misconvergence.

FIG. 11 is an explanatory diagram of twisted mislanding.

FIG. 12 is a cross-sectional view of a cathode ray tube.

FIG. 13 is an explanatory diagram showing a state of image rotation due to the influence of the geomagnetism of the cathode ray tube.

[Explanation of symbols]

1 Cathode ray tube 2 Phosphor screen 3 Color selection electrode 4 Electron gun 6 Deflection yoke 8, 16 [16A, 16B, 16C] Image rotation correction coil 19 Composite magnetic field

Claims (3)

[Claims] 1. A cathode ray tube comprising a plurality of correction coils arranged outside the cathode ray tube along a tube axis direction for generating a magnetic field in a direction opposite to an external magnetic field perpendicular to the tube surface. 2. The cathode ray tube according to claim 1, wherein the plurality of correction coils are attached to the deflection yoke at predetermined intervals. 3. The cathode ray tube according to claim 1, wherein the plurality of correction coils include correction coils having different diameters.