JPS62131449A - Electromagnetic deflectional distortion corrector - Google Patents

Abstract

PURPOSE:To prevent the deterioration in the quality of an image, by disposing a non-ferromagnetic material of a negative temperature coefficient for the saturated magnetic flux density, near a distortion correcting permanent magnet. CONSTITUTION:A distortion correcting permanent magnet 2 is attached to a support frame 8 by screw securing or the like. The magnet 2 is made of a magnetic material of high coercive force and residual magnetic flux density and stable structure, preferably made of a barium ferrite. A non-ferromagnetic material 4 is disposed near the magnet 2 nearly in parallel therewith. The material 4 is preferably a non-ferromagnetic steel such as an Ni-Zn ferrite and an Ni-Fe alloy. As a result, the magnetic flux phix in a space is made constant regardless of the change in the temperature, to enhance the quality of an image.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a deflection distortion correction device for a cathode ray tube (CRT) display device, and more particularly to a deflection distortion correction device using a permanent magnet.

[Prior art]

In a CRT display device, a deflection yoke is attached to the neck of the cathode ray tube, and the electron beam generated from the electron gun is deflected by the deflection yoke.

The deflected electron beam causes a fluorescent surface on the inner surface of a CRT (cathode ray tube) tube wall to emit light. Horizontal and vertical deflection coils are wound around the deflection yoke, and a deflection magnetic field generated by passing current through the horizontal and vertical deflection coils deflects the electron beam. In order to achieve compatibility between deflection magnetic field resolution and deflection distortion, there are many cases in which a distorted magnetic field is generated. If the deflection magnetic field is not uniform,
The electron beam is deflected in different directions at different locations. Therefore, distortion of the screen (raster) occurs. Also color C
In the case of RT, each electron gun is angled with respect to the tube axis of the CRT so that the electron beams generated from the three electron guns are properly focused at the center of the fluorescent surface. Therefore, each electron beam is incident on the deflection magnetic field at a different angle. Since each electron beam is incident on the deflecting magnetic field at a different angle, each electron beam is deflected differently, causing a color shift in the phosphor plane. This type of screen distortion and color shift is also caused by, for example, a shift between the center of deflection and the center of curvature of the screen.

In order to remove these distortions, it is necessary to correct the electron beam, and two types of methods are used. One is the electronic circuit method, which is horizontal.

The current flowing through the vertical deflection coil is adjusted to the optimum value for each coordinate position in the vertical and horizontal directions of the screen.

The other method is a permanent magnet method, in which a distortion correction permanent magnet is placed near the deflection yoke, and distortion is corrected by the magnetic field generated in the space. Particularly when performing highly accurate distortion correction, two combination methods are used. The present invention relates to this permanent magnet system.

Problems with the permanent magnet system will be explained with reference to FIGS. 5 to 7 and FIG. 3, which illustrates the effects of the present invention.

FIG. 5 is a sectional view showing the neck portion of a cathode ray tube of a conventional CRT display device. Further, FIG. 6 is a sectional view showing the entire CRT. Electron beam 4 generated from an electron gun
4 is deflected and scanned by the deflection yoke 46, and the CRTWq
40 fluorescent surfaces are made to emit light. As mentioned above, this electron beam 44 tends to be distorted around the fluorescent surface due to the non-uniformity of the deflection magnetic field. Therefore, the screen is distorted into a pincushion shape, as shown in FIG. 7(a), for example. In order to obtain a screen like that shown in FIG. 7 (color), it is necessary to correct the electron beam 44, and this is done using the distortion correction permanent magnet 34 shown in FIG. However, with this distortion-corrected permanent magnet method,
For example, when using a CRT display device for a long time, the screen may change from the shape shown in Figure 7Cb) to the original
There was a problem in that it was distorted into the pincushion shape shown in Figure (a). For this situation, please refer to FIG. 3(a) which shows the effect of the present invention. Currently, as the definition of CRT display devices becomes higher, there is a demand for higher image quality, and this type of screen distortion cannot be tolerated.

[Purpose of the invention]

Therefore, a primary objective of the present invention is to prevent deterioration of the picture quality of a CRT display device.

Another object of the present invention is to provide a single-mode magnetic deflection distortion correction system capable of achieving the above objects.

[Summary of the invention]

The present inventor obtained the knowledge that this type of image quality deterioration is caused by temperature changes in the magnetic field generated from the distortion correction permanent magnet, and created the present invention based on this knowledge. The present invention will be described in detail with reference to FIG. 1 showing an embodiment of the invention and FIG. 4 showing the principle of the invention.

Referring to FIG. 1(a), a sectional view of the upper half of the neck of a cathode ray tube of a CRT display device is shown. The same goes for the lower half. A deflection yoke 12 is attached to this neck portion via a support frame 8.

A distortion correction permanent magnet 2 is attached to the deflection yoke 12 around the wall of the cathode ray tube via a holding frame 8 around which horizontal and vertical deflection coils are wound. The present invention is characterized in that a soft magnetic material 4 having a negative temperature coefficient of saturation magnetic flux density is disposed close to the distortion correction permanent magnet 2. The arrangement of the distortion correction permanent magnet 2 and the soft magnetic material 4 is shown in FIG. 1(b) and FIG. 4. As is clear from the figure, the soft magnetic material 4 is disposed close to and substantially parallel to the strain correction permanent magnet 2.

[Detailed description of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to FIGS. 2 to 4.

Materials for strain-correcting permanent magnets are required to have high coercive force, high residual magnetic flux density, and structural stability.

Examples of this type of magnetic material include Ba ferrite (MO-6
Fe203, M=Ba) is desirable (and has been conventionally used). Ba 7 elite is a so-called 7-magnetic material, and emits certain lines of magnetic force into the external space under conditions of constant temperature. The electron beam generated from the electron gun is corrected by the magnetic field created by these lines of magnetic force. However, if the temperature changes, the magnetization state of B & ferrite changes, and as a result, the lines of magnetic force in the outside space change, and the strength of the magnetic field in the outside space changes. Magnetic flux density (unit: Wb/m") is usually used to quantitatively represent lines of magnetic force.
], and if Bo is the magnetic flux density of the lines of magnetic force emitted from the strain-compensated permanent magnet, then the magnetic flux φ generated from the strain-compensated permanent magnet is
□ becomes φ = FmA, TI(Wb) (1).

The inventor of the present invention found that the screen distortion at the end of a CRT display device using a permanent magnet method is caused by a temperature change in the generated magnetic flux φm, and arranged a soft magnetic material close to the distortion correction permanent magnet. The effects, conditions, etc. of the distortion correction permanent magnet 2 and the soft magnetic material 4 will be explained below.

The soft magnetic material 4 can be easily magnetized to magnetic saturation by the magnetic field generated from the strain correction permanent magnet if the magnetic path cross-sectional area is designed to be the minimum required for temperature compensation.

In this case, the magnetic flux density of the soft magnetic material when magnetically saturated is called the saturation magnetic flux density, and is expressed by the symbol Bs (wb/mt). The cross-sectional area of the cross-section 28 of the soft magnetic material 4 is defined as the magnetic path cross-sectional area hmc
m! ] Then, the magnetic flux φ3 absorbed by the soft magnetic material is φ, = nm A @ (W b ) (
It will be 21. Assuming that the magnetic flux in space is φ, as is clear from Figure 4, φ = φ. −φ, (Wb) +31 holds true. The magnetic flux φ in this space corrects the electron beam generated from the electron gun.

As mentioned above, the material for the distortion-correcting permanent magnet is, for example, B.
A7 elite is preferable, and in this case, the magnetic flux generated by the strain-correcting permanent magnet changes as the temperature changes. Figure 2 shows the magnetic flux φ generated from the distortion-correcting permanent magnet. and temperature τ('
C) shows the relationship. As is clear from Fig. 2, the magnetic flux φ generated from the distortion-correcting permanent magnet. decreases as temperature increases. This means that the magnetic flux generated by the strain-correcting permanent magnet has a negative temperature coefficient. Here, if we derive the condition that the magnetic flux φ in the space does not change regardless of the temperature change from equation (3), if we differentiate both sides of equation (3) with respect to temperature T, we get dT dT dT, and dφx/dT on the left side is Since it only needs to be zero, the condition is dT dT. This is because, as described above, the magnetic flux φ□ generated by the distortion correction permanent magnet has a negative temperature coefficient. Formula (5
) and Equation (6), we can also substituting Equation (2) into Equation (by substituting force into dT, the magnetic path cross-sectional area A is a positive number, and if it is constant without depending on temperature, we get the above equation. (5) and equation (9) are the conditions required for soft magnetic materials.Since B is the saturation magnetic flux density of the soft magnetic material, equation (9) is physically speaking the saturation magnetic flux density of the soft magnetic material. The magnetic flux density B must decrease as the temperature increases. This is said to mean that the saturation magnetic flux density of a soft magnetic material has a negative temperature coefficient.

Also, by substituting equation (2) into equation (5), dT dT dB.

=As□ dT dφm/dT on the left side is known depending on the magnetic material used in the distortion correction permanent magnet. The soft magnetic material is determined by the formula αG, and its magnetic path cross-sectional area A is determined by the formula α1.

Description of examples The present invention will be described in detail with reference to FIG.

The deflection yoke 16 is obtained by kneading a pre-sintered powdered magnetic material (for example, ferrite) with a suitable binder, pressurizing and shaping the material, sintering it, and then winding the horizontal and vertical deflection coils 16. The deflection yoke 12 is attached to the neck of the cathode ray tube via the support frame 8. The distortion correction permanent magnet 2 is attached to the support frame 8 by screwing, for example. The material for the strain-correcting permanent magnet 2 is a magnetic material that has high coercive force, high residual magnetic flux density, and is structurally stable, preferably Ba.
7 Eli) (MO・6FetO8, M= B &)
use. A soft magnetic material 4 is placed close to and parallel to the distortion correction permanent magnet 2. The soft magnetic material 4 is preferably Ni-Zn7 (MO-F
@2 o, , M=N i, Zn) or l'Ll-
Fs gold alloy magnetic shunt steel is used. As shown in Fig. 1), the combination member 3 of the strain correction permanent magnet 2 and the soft magnetic material 4 is mounted at approximately symmetrical positions on the upper and lower, left and right sides of the support frame 8. Table 1 shows examples A2 to &4 of combinations of the shapes, constituent materials, and mounting positions of the distortion correction permanent magnet 2 and the soft magnetic material 4. In Table 1, Rin 1 indicates a conventional example for comparison.

[Invention effect]

As explained above, temperature changes in the magnetic flux generated by the distortion-correcting permanent magnet are compensated for by the soft magnetic material, and as a result, the magnetic flux φ in the space remains constant regardless of temperature changes, and the screen distortion changes due to temperature changes. It can be almost eliminated and the image quality of the CRT display device can be improved. Referring to Table 1, the average value of the maximum tension length at the top, bottom, left, and right of the screen is △
In comparing the temperature changes of X and Δy, it will be understood that the examples according to the present invention (42 to black 4) are improved compared to the conventional example (&1).

As explained above, it will be obvious to those skilled in the art that various applications and modifications can be made without departing from the technical bond concept of the present invention. For example, Ni-Zn7 is used as a soft magnetic material.
Although ELITE or magnetic shunt steel is shown as an example, the present invention can also be realized using soft magnetic materials other than those mentioned above whose saturation magnetic flux density B has a negative temperature coefficient. It is also obvious that the shape, VI arrangement, mounting position, number of mounting, etc. of the distortion correction permanent magnet and the soft magnetic material can be changed as necessary.

[Brief explanation of drawings]

FIG. 1 (4m) is a longitudinal sectional view of the electromagnetic deflection distortion correction device according to the present invention. FIG. 1(b) is a cross-sectional view when viewed from the A-A axis in FIG. 1(&). FIG. 2 shows the magnetic flux φ generated by the distortion-correcting permanent magnet in the present invention. It is a graph diagram showing the temperature characteristics of. FIGS. 3(a) and 3(b) show 1! according to the present invention!
It is a change diagram of screen distortion showing the effect of the magnetic deflection distortion correction device. FIG. 4 is a schematic diagram showing the principle of the present invention. FIG. 5 is a sectional view showing the neck portion of a cathode ray tube of a conventional permanent magnet type CRT display device. FIG. 6 is a sectional view showing the entire conventional cathode ray tube. FIG. 7(a) is a conceptual diagram showing a screen distorted into a pincushion shape, and FIG. 7(b) is a conceptual diagram showing a desirable screen shape. The names indicated by each reference number in the figure are listed below. Note that the same reference numbers in the figures indicate the same parts. 2: Distortion correction permanent magnet 4: Soft magnetic material (for temperature guarantee) 8: Support frame 10: Cathode ray tube (CRT) 12: Deflection eye 13: Vertical deflection coil 16: Horizontal deflection coil 24: Distortion correction permanent magnet Magnetic flux generated from φ□ 26: Magnetic flux in space φ work 28: Cross-sectional area of magnetic path of soft magnetic material A3 30: Cross-sectional area of distortion correction permanent cornerstone Am 32: Magnetic flux φ absorbed by soft magnetic material. 54: Distortion correction permanent magnet 38: Support frame 40: Cathode ray tube (CRT) tube wall 42: Cathode ray tube 4A: vL beam 46: Deflection yoke t--). Name of agent: Motohiro Kurauchi; /=-1＼ Hiroshi Kazama ('Figure 1 (a) (b) Figure 2 Figure 3 ((1) (b) ^v1 Figure 4 Figure 5 Figure 7 (Q) (b)

Claims (5)

[Claims] (1) An electromagnetic device consisting of a plurality of permanent magnets placed around the cathode ray tube wall of a CRT display device, and a soft magnetic material that is placed almost parallel to and close to the permanent magnets and has a negative temperature coefficient of saturation magnetic flux density. Deflection distortion correction device. (2) Electromagnetic deflection distortion correction according to claim 1, wherein the product of the temperature coefficient of the saturation magnetic flux density of the soft magnetic material and the magnetic path cross-sectional area of the soft magnetic material is approximately equal to the temperature coefficient of the generated magnetic flux of the permanent magnet. Device. (3) The electromagnetic deflection distortion correction device according to claim 1, wherein the material of the permanent magnet is barium (Ba) ferrite. (4) The soft magnetic material is nickel-zinc (Ni-Zn)
The electromagnetic deflection distortion correction device according to claim 1, which is made of ferrite. (5) The electromagnetic deflection distortion correction device according to claim 1, wherein the soft magnetic material is magnetic shunt steel.