KR100310648B1 - Video display device - Google Patents

Abstract

The present invention relates to a video display device having four corner magnets for correcting internal N-S geometric distortion. These four corner magnets 24a, 25a, 24b, 25b are arranged to be symmetrical in four quadrants of the X-Y plane perpendicular to the Z axis of the CRT. Further, the angle that the upper corner magnets 24a and 25a or the lower corner magnets 24b and 25b make with the Y axis is smaller than 45 °, that is, closer to the Y axis than the X axis, The NS axis is arranged parallel to the Z axis. These four corner magnets can further improve image quality by correcting internal N-S geometric distortion or gullwing distortion.

Description

Video display

1 is a side view of a deflection yoke mounted on a cathode ray tube implementing the features of the present invention.

FIG. 2 is a front view of the deflection yoke shown in FIG. 1 as viewed from the display screen side of the cathode ray tube.

3 is a side view of the deflection yoke of FIG.

4 shows a corresponding display pattern on the screen of the cathode ray tube to explain the corresponding beam arrival point error.

5 is a plan view of a corner magnet embodying the features of the present invention for the deflection yoke of FIG.

6A-6D show the harmonic potential distribution function for the deflection yoke of FIG.

* Explanation of symbols for main parts of the drawings

10: cathode ray tube (CRT) 11: screen

15 electron gun assembly 16 deflection yoke

17: core 18V: vertical deflection coil

18H: horizontal deflection coil 24a, 24b, 25a, 25b: corner magnet

The present invention relates to a color water tube (CRT) display device.

Because the surface of the CRT is flat, the lines displayed at the top or bottom of the CRT screen, which should ideally be displayed as a horizontal straight line, exhibit geometric distortion, commonly referred to as outer pincushion North-South geometry distortion. Pray. For example, even if the external pincushion geometric distortion is completely corrected by installing conventional magnets on the top and bottom of the yoke, the inner barrel N-S geometric distortion remains. The inner barrel N-S geometric distortion occurs at the midpoint between the top and center of the CRT screen or at the midpoint between the bottom and center of the CRT screen in the area of the CRT screen. It is desirable to correct the internal N-S geometric distortion so that the overall N-S geometric distortion can be reduced. In addition, because the surface of the CRT is flat, geometric distortion, commonly referred to as gullwing distortion, may appear in the horizontal lines displayed on the CRT screen. It is also desirable to correct this gullwing distortion. Thus, four corner magnets are placed near the electron beam exit of the deflection yoke to implement the features of the present invention. The corner magnets are placed at positions symmetrical to each other in four quadrants of the plane perpendicular to the Z axis of the CRT. The magnetic field generated by the corner magnets corrects the geometric distortion.

A deflection device embodying the features of the present invention includes a cathode ray tube of an inline system having an evacuated glass envelope. The display screen is disposed at one end of the envelope. The electron gun assembly is disposed at the other end of the envelope. The electron gun assembly generates a plurality of electron beams that form a corresponding raster on the screen upon deflection. The deflection yoke includes a vertical deflection coil mounted around the envelope and generating a vertical deflection magnetic field in the cathode ray tube. The deflection yoke also includes a horizontal deflection coil that generates a horizontal deflection magnetic field in the cathode ray tube. The core made of magnetically permeable material is magnetically coupled to the vertical and horizontal deflection coils. In general, corner magnets having an N-S axis parallel to the Z axis of the yoke are arranged closer to the Y axis than the X axis of the yoke near the beam exit.

In FIG. 1, the CRT 10 includes a screen or surface plate 11 on which red, green and blue phosphor groups are repeatedly projected. The CRT 10 is of type A68EET38X110 and has a super-plate surface plate measuring 27V or 68 centimeters. The deflection angle is 108 °. The distance from the yoke reference line, called the throw distance, to the inside of the screen is 275 millimeters. The surface plate 11 is much flatter than a conventional CRT and its height is only half of the normal surface contour height.

The inner surface contour of the surface plate 11 is defined by the following equation.

Here, Z _C is the distance from the plane in contact with the tangent plane of the inner contour. X and Y represent distances from the center in the major axis and minor axis directions, respectively, and A1 to A15 are coefficients according to the diagonal size of the surface plate.

Appropriate coefficients A1 to A15 are shown in Table I for the outer skin surface of the CRT 10 having a diagonal field of view of 68 cm. CRTs having contours defined by these coefficients have good convergence characteristics when using the features of the present invention described below. The magnitudes of X and Y are in millimeters when using the coefficients in Table 1.

TABLE 1

The electron gun assembly 15 is mounted to the neck portion 12 opposite the surface plate of the shell. The electron gun assembly 15 generates three horizontal inline beams R, G and B. The deflection yoke, denoted collectively 16, is mounted by a yoke mount 19 formed of a suitable plastic liner at the periphery of the shell neck or edge portion. The deflection yoke 16 also includes a ferrite core 17 on the flare, a vertical deflection coil 18V and a horizontal deflection coil 18H. The deflection yoke 16 is self-converging.

2 shows in more detail the deflection yoke 16 according to one embodiment of the invention. The same symbols and reference numerals in FIGS. 1 and 2 denote the same components or functions. In FIG. 2 the yoke assembly is viewed from the electron beam exit side. The yoke mount 19 formed of the plastic of FIG. 2 has a pair of saddle-shaped horizontal coils 18H in a proper direction with respect to the flared ferrite core 17 around which the vertical deflection coils 18V are wound. Position it. Thus, the deflection yoke 16 is saddle-toroid (ST) type. In the side view shown in Figure 3, the beam exit end is on the right. The same symbols and reference numerals in FIGS. 1 through 3 represent the same components or functions.

The longitudinal or Z axis of the deflection yoke 16 or CRT 10 of FIG. 1 is defined in a conventional manner. In each face of the deflection yoke 16 determined by the corresponding coordinate Z perpendicular to the Z side, the corresponding Y axis is formed parallel to the vertical or short axis of the screen 11. Also, the corresponding X axis is formed parallel to the horizontal or long axis of the screen 11. In each plane of the deflection yoke 16, the coordinate X = Y = 0 is located on the Z axis.

For example, in the vicinity of the beam inlet end of the deflection yoke 16 of FIG. 1, the vertical deflection magnetic field produced by the vertical deflection coil 18V preferably has a pincushion shape to correct the vertical coma error. In order to reduce overconvergence at 6 and 12 o'clock, the vertical deflection magnetic field produced by the vertical deflection coil 18V is applied to the middle portion of the yoke between the beam inlet end and the outlet end of the deflection yoke 16 of FIG. In barrel shape.

It is desirable to increase the degree of barrel-shaped magnetic field nonuniformity beyond that which can be obtained by the arrangement of the winding distribution of the vertical deflection coil. Thus, a pair of magnetic field generators, i.e. shunts 23a and 23b, made of soft or permeable material, is mounted near the top and bottom of the deflection yoke in the middle portion of the deflection yoke. The magnetic field generators 23a and 23b increase the barrel-shaped magnetic field nonuniformity, and yoke mounts constituting the plastic insulator facing the vertical deflection coil 18V between the vertical deflection winding 18V and the neck portion of the CRT 10 ( It is advantageously mounted on the side of 19).

FIG. 4 shows, for example, the display pattern of the curved horizontal line A1 in the upper portion of the CRT 10 screen 11 as a dotted line. The same symbols and reference numerals in FIGS. 1 through 4 denote the same components or functions. Line A1 in FIG. 4 shows that the curve is curved when the external N-S raster distortion is not corrected. External N-S raster distortion is measured by distance d3 in FIG. 4, which represents the maximum deviation between line A1 and the ideal straight horizontal line A1 '. In order to correct this NS raster distortion, as shown in FIGS. 2 and 3, a pair of magnets 21a, 21b are respectively positioned near the top and bottom of the deflection yoke at the front or beam exit of the deflection yoke. Mount it. The magnets 21a and 21b are fixed in the recesses of the yoke mount 19 to have the polarity shown in the drawing. As shown in FIG. 2, magnets 21a and 21b disposed near the beam exit end of the deflection yoke are used to correct external N-S (upper-lower) pincushion distortion. The magnetic field formed by the magnet 21a provides the maximum deflection force near the center at the top of the raster and the minimum deflection force near the side of the raster. Therefore, the magnetic field of the magnet 21a is suitable for correcting the external N-S pincushion distortion. As a result of the correction, the line A1 in FIG. 4 approaches the ideal horizontal straight line A1 'shown by solid lines on the screen 11. The magnet 21b shown in FIGS. 2 and 3 performs the same function as the magnet 21a when a line is displayed at the bottom of the screen.

Magnets 21a and 21b can reduce the barreling of the vertically deflected magnetic field required to provide proper convergence. To partially recover the barrelization of the vertically deflected magnetic field, a pair of magnets 22a, 22b are disposed close to the inner surface of the flare portion of the deflection yoke at the top and bottom closer to the beam inlet end of the deflection yoke. The magnets 22a and 22b are mounted along the contour of the coil 18H and are arranged between the neck portion of the coil 18H and the CRT 10. The magnets 22a and 22b, like the other shunts 23a and 23b, compensate for the vertical convergence errors that may be caused by the magnets 21a and 21b, respectively. Compensation for convergence error is achieved due to an increase in the barrelization of the vertically deflected magnetic field in the region of the deflected magnetic field further spaced along the Z axis from the screen of the CRT 10 as compared to the magnets 21a and 21b.

Assume that correction for external or external N-S geometrical distortions is made by magnets 21a and 21b. Since the screen 11 of the CRT 10 is flat, it should ideally be a horizontal straight line, but it can exhibit a barrel-shaped geometric distortion like the line A2 of the display pattern shown in dashed lines in FIG. Line A2 is indicated at the intermediate point between the vertical center of FIG. 4 and the upper line A1 or A1 '. This geometric distortion is called the inner or inner N-S geometric distortion and is measured in the same way as the outer N-S geometric distortion. In order to correct this internal N-S geometric distortion, it is desirable to apply a greater deflection force in the vertical direction with respect to the line A2 near the side of the raster than at the center of the raster.

Thus, as shown in FIG. 2, a pair of corner permanent magnets 24a and 25a are mounted on the yoke mount 19 so as to face each other about the upper magnet 21a so as to implement the features of the present invention. The magnets 24a are arranged at an angle of approximately phi = +29 degrees, and the magnets 25a are arranged at an angle of approximately phi = -29 degrees so as to be symmetrical about the corresponding Y axis. Therefore, each of the magnets 24a and 25a is disposed closer to the Y axis than the X axis because φ is smaller than 45 °.

Using the corner magnets 24a and 25a makes it possible to use a weaker N-S magnet 21a than would be required in the absence of the corner magnets. By using the weaker magnet 21a, the aforementioned barrel-shaped inner N-S geometrical distortion is reduced. Therefore, the combination of the corner magnets 24a and 25a and the N-S magnet 21a enables correction for both internal and external N-S geometrical distortions.

The pair of corner magnets 24b and 25b in FIG. 2 are arranged symmetrically with the magnets 24a and 25a with respect to the X axis, respectively. The corner magnets 24b and 25b are arranged to face each other around the magnet 21b. The magnets 24a, 21a, 25a mainly influence the beam spot arrival position when the beam spot is above the vertical center of the CRT screen. Likewise, magnets 24b, 21b, 25b mainly affect the position of beam spot arrival when the beam spot is below the vertical center. 5 is a plan view of the magnets 21a, 24a, and 25a. The same symbols and reference numerals in FIGS. 1 through 5 denote the same components or functions.

In implementing the features of the present invention, the N-S axis of each magnet 24a, 25a, 24b, 25b shown in FIG. 2 has an angle smaller than 45 ° with respect to the Z axis. Thus, this N-S axis is closer to the parallel to the Z axis than to be perpendicular to the Z axis. In the example of FIG. 2, this N-S axis is usually arranged parallel to the Z axis. In contrast, the N-S axis of the magnet 21a is perpendicular to the Z axis. Therefore, the N-S axis 24a1 of the corner magnet 24a is parallel to the Z axis of FIG. Making the NS axis parallel to the Z axis of each of the magnets 24a, 25a, 24b, and 25b in FIG. It is advantageous in that. For example, when the NS axis of each corner magnet 24a, 25a, 24b, 25b shown in FIG. 2 is parallel to the Z axis, the outer NS geometric distortion is measured at -0.15 percent, and the inner NS geometric distortion is- It was measured at 0.5 percent. For comparison, when the N-S axis of each corner magnet was perpendicular to the Z side, the results were +1.9 percent and +0.2 percent, respectively. Thus, the total or average outer / inner N-S distortion is reduced when the corner magnets are arranged in the direction shown in FIG.

In addition, the degree of gull wing distortion correction is improved as compared to the imaginary case where the N-S axis of each corner magnet is perpendicular to the Z axis. Thus, when the NS axes of the magnets 24a, 25a, 24b, 25b are arranged as shown in FIG. 2, for example, at 1:30 time, the maximum external gulling distortion was measured at +0.16 percent and 2A: 30 time. The maximum internal gullwing distortion at the same horizontal coordinate was +0.13 percent. On the other hand, at the same point on the screen, when the N-S axis is perpendicular to the Z axis, the maximum external / internal gulling distortion was measured as -0.3 and +0.16 percent, respectively. By having the same sign for each magnitude of the outer and inner gullwing distortions, it is possible to provide a less troublesome image than when the signs are reversed. This effect is particularly evident in picture-in-picture applications.

6A to 6D show the second, fourth, sixth and eighth order harmonic potential distribution functions relating to the horizontal magnetic field of the first degree configuration in solid lines. The same symbols and reference numerals in FIGS. 1 through 5 and 6a through 6d represent the same components or functions. For comparison only, the corresponding harmonic potential function in each of FIG. 1 is indicated by the dotted line for the situation where the N-S side of each of the corner magnets 24a, 25a, 24b, and 25b of FIG. 2 is perpendicular to the Z axis. By arranging the NS axes of each of the corner magnets 24a, 25a, 24b, and 25b in FIG. 2 in parallel to the Z axis, the respective magnitudes of the secondary and quaternary harmonic potential values are shown in FIGS. 6a and 6b. Increases together. On the other hand, the magnitude of each of the sixth and eighth order harmonic potential values decreases as shown in Figs. 6C and 6D.

Claims (7)

A plurality of electron beams (R, G) formed on a pressure-sensitive glass envelope, a display screen (11) disposed at one end of the envelope, and a raster disposed on the other end of the envelope and forming a corresponding raster on the screen according to deflection. A cathode ray tube 10 of an inline system having an electron gun assembly 15 for generating B), Magnetically coupled to a vertical deflection coil (18V) for generating a vertical deflection magnetic field in the cathode ray tube, a horizontal deflection coil (1 bird) for generating a horizontal deflection magnetic field in the cathode ray tube and the vertical deflection coil and a horizontal deflection coil. A video display device comprising a deflection yoke 16 having a core 17 made of a magnetically permeable material and mounted around the envelope. The deflection yoke 16 has four, quadrally arranged first corner magnets 24a, second corner magnets 24b, and third corner magnets that are XY planes perpendicular to the Z axis of the deflection yoke. 25a) and a fourth corner magnet 25b, wherein the four corner magnets each have an NS axis substantially parallel to the Z axis, and are disposed near the beam exit closer to the Y axis than the X axis of the deflection yoke. Video display device. A plurality of electron beams (R, G) formed on a pressure-sensitive glass envelope, a display surface 11 disposed at one end of the envelope, and a raster disposed on the other end of the envelope, and forming a corresponding raster on the screen according to deflection. (B) a cathode ray tube (10) of an inline system having an electron gun assembly (15) generating all Magnetically coupled to a vertical deflection coil (18V) for generating a vertical deflection magnetic field in the cathode ray tube, a horizontal deflection coil (1 bird) for generating a horizontal deflection magnetic field in the cathode ray tube and the vertical deflection coil and a horizontal deflection coil. A video display device comprising a deflection yoke 16 having a core 17 made of a magnetically permeable material and mounted around the envelope. The deflection yoke 16 has an NS axis closer to the side that is not perpendicular to the Z axis of the deflection yoke and has a corner magnet 24a disposed near the beam outlet closer to the Y axis than the X axis of the deflection yoke. Video display device comprising a. The video display device of claim 2, wherein the N-S axis is substantially parallel to the Z axis. 4. The second corner magnet 25a has an NS axis substantially parallel to the Z axis, and has a first corner with respect to the Y axis, in order to correct both the outer NS geometric distortion and the inner NS geometric distortion. A third magnet 21a symmetrical with magnet 24a and disposed between the first and second corner magnets near the Y side near the beam exit end of the deflection yoke and having an NS axis perpendicular to the Z axis; The video display device further comprises. 5. Video display device according to claim 4, wherein each of the corner magnets (24a, 25a) constitutes a permanent magnet. 6. A video display device according to claim 5, wherein each front end of said first, second and third magnets (24a, 25a, 21a) is disposed in the same X-Y plane as the X-Y plane of said deflection yoke. 5. The method of claim 4, wherein the third magnet 21a corrects external NS geometric distortion, and the corner magnets 24a and 25a correct more internal NS geometric distortion than the third magnet. Video display device.