CN1315053A - Color display device having quadrupole convergence coils - Google Patents

Abstract

The invention relates to a color display device comprising an in-line electron gun (5) for generating three electron beams (6,7,8), and a convergence unit (14') to dynamically influence the convergence of the electron beams and deflecting means (51) for deflecting the electron beams (6,7,8). The convergence unit (14') comprises a ring-shaped element (21'), said ring-shaped element comprising two parts, a first part (60) being positioned closer to the in-line gun (5) than a second part (68), and the first and/or the second part having four coils (22') for generating a magnetic quadrupole field.

Description

Color display device with quadrupole converging coils

The invention relates to a color display device comprising an inline electron gun for generating three electron beams and a unit for deflecting the electron beams through a color selection electrode.

Such display devices are known.

A current goal is to make the outer surface of the color display window flatter so that the image displayed on the display window appears flat to the viewer. However, increasing the radius of curvature of the outer surface causes a number of problems. The radius of curvature of the inner surface of the display window and the color selection electrode should also increase, and as the color selection electrode becomes flatter, the mechanical strength of the color selection electrode decreases, thus increasing the possibility of doming and vibration. Another solution to this problem is to make the inner surface of the display window more curved than the outer surface. Thereby, color selection electrodes with relatively small radii of curvature can be used. As a result, vaulting and vibration problems may be reduced, but other problems may arise instead. The edge of the display window is much thicker than the center. As a result, the weight of the display window increases and the brightness of the image decreases substantially towards the edges.

EP0421523 discloses a color cathode ray tube with an in-line electron gun, a pincushion correction yoke and an eyebrow (eyebrow) effect electron-optical distortion correction device comprising two pairs of coils, each pair having a coils on each outer electron beam side. Coil pairs are spaced along the Z axis between the electron gun and the yoke and are driven synchronously with the scanning raster by a sawtooth current with a bow-tie envelope to correct dynamic asymmetric eyebrow effects on the raster that manifest as color purity defects.

WO99/34392 describes a color display device comprising a color cathode ray tube comprising an in-line electron gun producing three electron beams; a color selection electrode; deflection means for deflecting the electron beams located on a deflection plane; dynamically influencing the electron beams First and second influencing means converging to reduce the distance between the electron beams at the deflection plane.

The presence of influencing devices may introduce certain undesired image artifacts. The so-called East/West raster distortion can be influenced, as well as the linearity of the electron beam deflection in the vertical direction. In conventional cathode ray tubes, the deflection in the vertical direction is not a linear function of the deflection current. This non-linearity is corrected electrically. The introduction of the first and second influencing means results in the non-linearity of the cathode ray tube being reduced or overcompensated. These effects are undesirable.

It is an object of the invention to provide an improved color display device. To this end, the invention provides a color display device and a deflection unit as defined in the independent claims. The dependent claims describe preferred embodiments.

These and other objects of the present invention are apparent from the embodiments, and will be explained below with reference to the embodiments.

In the attached picture:

1 is a cross-sectional view of a color display device;

Figures 2A, 2B represent first and second parts of an annular element according to the present invention;

Figure 3 shows a deflection unit according to the invention; and

4A, 4B show an embodiment of the present invention.

The figures are not drawn to scale. In the drawings, like reference numerals generally refer to like parts.

The display device shown in FIG. 1 includes a color cathode ray tube having a vacuum envelope 1 including a display window 2 , a funnel portion 3 and a neck 4 . The neck 4 is provided with an inline electron gun 5 extending in the X direction of the rectangular X-Z coordinate system for generating three electron beams 6, 7 and 8 extending in one plane. In the undeflected state, the central electron beam 7 substantially coincides with the tube axis 9, extending in the Z-axis. The third direction, ie, the Y direction, extends in a direction perpendicular to the inline plane (not shown). Typically, under operating conditions, the pipe is arranged such that the X-Z plane coincides with the horizontal plane, and the Y direction coincides with the vertical direction.

The inner surface of the display window is equipped with a display screen 10 . The display screen 10 includes a large number of fluorescent cells that emit red, green and blue fluorescent light. On its way to the display screen, the electron beam is deflected by the electromagnetic deflection unit 51 through the display screen and passes through the color selection electrode 11 , which is arranged in front of the display window 2 and includes a thin plate with a small hole 12 . The three electron beams 6, 7 and 8 pass through the aperture 12 of the color selection electrode at small angles relative to each other, so that each electron beam bombards phosphors of only one color. In addition to the coil holder 13, the deflection unit 51 comprises deflection coils 13' which deflect the electron beams in two mutually perpendicular directions. Around the deflection yoke 13' is arranged an annular element 21', a so-called yoke ring. The purpose of the yoke ring, which usually includes ferrite, is to "short circuit" the flux lines outside the coil. Without the yoke, the current through the deflection yoke would have to be very high and would also generate disturbing stray magnetic fields. The display device also comprises means for generating a voltage which, during operation, supplies the elements of the electron gun via the feed-in means. The deflection plane 20 and the distance p between the electron beams 6 and 8 in this plane and the distance q between the color selection electrode and the display are shown schematically. The distance q is inversely proportional to the distance p.

The color display device includes two electron beam convergence influencing units 14, 14'. In operation, the first unit 14 is used to dynamically bend the outermost electron beams toward each other, that is, to deflect in this direction, and the second unit 14' Used to bend the outermost electron beams in opposite directions. Unit 14 is used to bend the electron beams towards each other and unit 14' bends the electron beams in the opposite direction. As a result, the distance between the deflected electron beams is smaller than the distance between the undeflected electron beams. Since the distance p is small, the distance q can be increased, which can increase the degree of freedom in the design of the curvature of the color selection electrode. The design freedom is utilized to increase the curvature of the color selection pole with advantages for the strength of the color selection pole while reducing the possibility of doming and vibration.

The two units 14, 14' are arranged at a certain distance from each other. The first unit 14 is arranged closer to the electron gun, hence the name "gun quadrupole", while the second unit 14' is near or located at the deflection unit, hence the name "yoke quadrupole". The unit 14' is conveniently integrated with the deflection unit 51 by winding four coils generating a dynamic electromagnetic quadrupole field on the annular element 21'.

During operation, the units 14, 14' affect the deflection of the electron beams, which can lead to undesired artifacts in the image displayed on the display window 2.

In conventional cathode ray tubes (CRTs), deflection in the vertical (Y) dimension is a nonlinear phenomenon, ie, the displacement of the electron beam is a nonlinear function of the current flowing through the deflection yoke. The deflection of the electron beam at the edge of the display window requires relatively little current. The electronic method of correcting non-linearity, the so-called vertical S correction, is used in televisions using this tube. The deflection of the electron beam is a more linear process due to the effect of the quadrupole of the yoke, which means that the S-correction overcomes the non-linear deflection phenomenon. This is not expected.

Conventional CRTs also correct for so-called east-west pincushion distortion (east and west refer to the two vertical sides of the display window). This means that an image consisting of a rectangular raster of horizontal and vertical lines is displayed on the screen like a distorted mat shape, where the vertical lines near the border of the display window are bent inwards. Clearly, the application of unit 14' adds to the artificiality of the image.

The purpose of the present invention is to reduce the influence of unit 14' on the above-mentioned spurious components of the displayed image. The invention is based on the awareness that the unit 14' has its main influence on the side of the annular element 21' facing the display window 2. It is therefore proposed to split the annular element 21' into two parts (coaxial split) and to wind a quadrupole coil on one of the two parts. Preferably, a quadrupole coil is wound around the portion of the core closest to the electron gun. This method offers the possibility of offsetting the two core sections independently of each other, thereby improving the rastering and converging properties of the tube.

2A and 2B illustrate an embodiment of the present invention. Figure 2A shows the first portion 60 of the annular element 21', which is closest to the in-line electron gun 5. Section 60 is equipped with four coils 22' for generating a quadrupole magnetic field. The coil shown is wound in a toroidal manner on a ring-shaped element. However, this type of winding is not necessary for the present invention. It is also possible to wind a quadrupole coil in a saddle fashion around a ring element. To facilitate the winding process and to hold the respective wires of the coil 22' in the correct position on the first part 60, the first part is provided on its ends with ring members 64, 66 having grooves where the coil windings are located. Figure 2B shows the second part 68 of the ring element 21', which part is closest to the display window 2. When used on pipes, the two parts 60, 68 may be joined to each other by conventional joining means such as glue, tape or the like. For proper performance, it is not necessary to connect these two parts.

Figure 3 shows the two parts 60, 68 according to the invention arranged around the deflection yoke 13' and the coil support 13. The first part 60 is provided with ring members 64, 66 and four coils 22' for generating a quadrupole magnetic field.

4A and 4B represent an embodiment of the invention in which the coil 22' around the first part 60 of the annular element 21 is obtained by an electrically conductive wire which is circularly wound in the winding direction and according to the winding density distribution N(φ) given below :

N(φ)=N ₀ cos(2φ);

where φ is the angle formed by the line between the X direction and the coil unit and the center, the angle is between 0° and 360°; N ₀ is the winding density when φ is equal to 0°, and N(φ) The symbol indicates the winding direction.

This embodiment has the advantage of producing an almost pure quadrupole magnetic field, which greatly suppresses the occurrence of other multiple magnetic fields.

Due to the limited dimensions of the wires, in practice only approximately the aforementioned winding densities can be achieved. This embodiment comprises packages 30 of electrically conductive wires wound annularly around the yoke ring 21' at the above-mentioned winding density:

N(φ)=N ₀ cos(2φ).

In this embodiment, the winding takes place in the grooves 34 of the ring members 64, 66 spaced 15 degrees apart. The winding method is as follows:

18 turns in the groove with φ = 0 degrees (position a),

15 turns in the groove at φ = 15 degrees (position b),

9 turns in the groove at φ = 30 degrees (position c),

There is no winding in the groove at φ = 45 degrees (position d),

There are 9 turns with opposite current directions in the groove of φ=60 degrees (position e),

15 turns in the groove at φ = 75 degrees (position f),

18 turns in the groove with φ = 90 degrees (position g), etc. This is close to the ideal winding density N(φ), yielding good results in practice.

In summary, the invention relates to a color display device comprising an inline electron gun 5 producing three electron beams 6, 7, 8; deflection device 51 . The converging unit 14' comprises an annular element 21', the annular element comprises two parts, the first part 60 is arranged closer to the in-line electron gun 5 than the second part 68, and the first part and/or the second part have a function for generating a quadrupole Four coils 22' of the magnetic field.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude elements or steps other than those stated in a claim. The article "a or an" used before an element does not exclude the presence of a plurality of such elements.

Claims (5)

1. Color display devices, including: An inline electron gun (5) producing three electron beams (6,7,8); deflection means (51) for deflecting the electron beams (6,7,8); and A converging device (14') for dynamically influencing the convergence of the electron beams, the converging device (14') comprising an annular element (21'), characterized in that: The ring element (21') includes two parts (60, 68), the first part (60) is arranged closer to the in-line electron gun (5) than the second part (68), and the first part (60) and/or the second The second part (68) has four coils (22') for generating a quadrupole magnetic field. 2. A color display device as claimed in claim 1, wherein the coil (22') comprises a conductive wire, in the winding direction and according to the winding density distribution N(φ) ring given by N(φ)=N ₀ cos(2φ) winding the conductive wire, wherein φ is the angle formed by the wire in the X direction and the coil unit and the center, the angle is between 0° and 360°; N ₀ is the winding density when φ is equal to 0°, and The symbol of N(φ) indicates the winding direction. 3. A color display device as claimed in claim 1, wherein the coil (22') comprises an envelope (30) of conductive thread, in the winding direction and according to the approximate winding given by N(φ)=N ₀ cos(2φ) A density distribution N(φ) is toroidally wound around the envelope, where φ is the angle formed by the line between the envelope unit and the center in the X direction. 4. deflection unit (51) comprising deflection coils (13, 13') and converging means (14') dynamically influencing the convergence of the electron beams (6, 7, 8), the converging means (14') comprising annular elements (21'), The annular element comprises two parts (60, 68), the first part (60) is arranged closer to the inline electron gun (5) than the second part (68), and the first part (60) and/or the second part (68) ) has four coils (22') for generating a quadrupole magnetic field. 5. Deflection unit (51) as claimed in claim 4, wherein said coil (22') comprises a conductive wire, in the winding direction and according to the winding density distribution N given by N(φ)=N ₀ cos(2φ) (φ) Toroidally wind the conductive wire, where φ is the angle formed by the line between the X direction and the coil element and the center, the angle is between 0° and 360°; N ₀ is when φ is equal to 0° The winding density, and the sign of N(φ) indicate the winding direction.

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