JP3420778B2 - Color display tube - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises an in-line type electron gun for generating three electron beams in an exhaust container, which has an electron-optical lens field for focusing the electron beams on a display screen of a cathode ray tube. The present invention relates to a color display tube which is provided with first and second lens electrodes for generating the above, and one of the lens electrodes has a correction element for correcting astigmatism of the lens field.

[0002]

Such a color display tube is known from European patent application EP-104674B1. The lens field formed by the lens electrodes and sequentially forming the electro-optical lens becomes astigmatism due to manufacturing errors and other causes. As a result, the electron beam is astigmatically focused on the display screen. That is, when the electron beams are focused in the horizontal direction, for example, the electron beams are defocused in the vertical direction. This causes the electron beam spot on the display screen to be less than optimal. Therefore, the electron beam cannot be sharply focused on the display screen. In order to correct this adverse effect, a correction element is provided on one of the lens electrodes. The correction element has a plate-shaped portion, and forms an elliptical or rectangular aperture through which the electron beam passes.

[0003]

It has been determined that this correction is inadequate for some applications. In particular, in the corners of the display screen it is required to improve the size of the spots, ie the sharp focus.

It is an object of the present invention to provide a color display tube of the kind set forth which at least partly overcomes the problems mentioned above.

[0005]

SUMMARY OF THE INVENTION The present invention has three features in an exhaust container.
An in-line type electron gun for generating two electron beams, each of which is provided with a cup-shaped portion, has a bottom portion through which the electron beam passes, and has first and second lenses having three apertures facing each other. With electrodes,
These electrodes, when activated, generate an electron-optical lens field between the first and second lens electrodes that focuses the electron beam on the display screen, one of the first and second lens electrodes having a cup-like shape. And a correction element for correcting astigmatism in the electron-optical lens field, the correction element being provided apart from the aperture of the part, and having three collinear lines.
In a color display tube having an upper aperture, an outer aperture of the correction element is appropriately formed to generate an electric field having a sextupole component with respect to an outer electron beam during operation, and the first and second lens electrodes are provided. It is characterized in that the interference effect of the 6-pole component of the lens field existing in the outer electron beam is compensated at least locally.

[0006]

The present invention is based on the field of view that a six-pole magnetic field having a disturbing effect on the outer electron beam is generated in the lens field of the electron optical lens. This sextupole field adversely affects the focusing of the outer electron beam in the direction between the vertical and horizontal directions. The disturbance effect of the sextupole magnetic field in the focusing lens can be compensated at least locally by generating a compensating sextupole magnetic field for the outer electron beam in the correction element.

In one example of the color display tube of the present invention, the outer aperture of the correction element has a trapezoidal shape. By making the outer aperture of the correction element trapezoidal, a 6-pole magnetic field can be easily generated in the correction element, and the 6-pole magnetic field at least locally compensates for the disturbance effect of the 6-pole magnetic field component of the lens field. You can The trapezoid referred to here means a plane that is mirror-symmetric with respect to the in-line surface and passes through a point on the in-line surface that is equidistant from the intersection of the in-line surface and the boundary line of the aperture. When dividing the aperture into four virtual portions surrounded by a line extending perpendicular to the line surface and the in-line surface, the center of gravity of the four virtual portions thus formed of the aperture forms a trapezoid. Shall mean a face.

The strength of the hexapole magnetic field is determined by the difference between the long side and the short side of the trapezoid.

[0009]

Embodiments of the present invention will be described with reference to the drawings. In the figure, the same parts are designated by the same reference numerals. FIG. 1 is a sectional view showing a color display tube of the present invention.

The color display tube 1 of the present invention comprises an exhaust container 2, which comprises a display window 3, a conical portion 4 and a neck 5. The neck 5 is provided with an electron gun 6 for generating three electron beams 7, 8 and 9, which can be located in one plane, namely the in-line plane, in this case the plane of the drawing. The display screen 10 is provided inside the display window 3. The display screen 10 comprises a large number of fluorescent elements which emit red, green and blue light. These fluorescent elements can be in the form of dots or stripes, for example. For this display screen 10, the electron beams 7, 8 and 9 are deflected by the deflection unit 11 across the display screen 10,
In addition, the color selection electrode 12 is allowed to pass therethrough. The color selection electrode 12 is arranged on the front surface of the display window 3 and includes a thin metal plate having an aperture.
These three electron beams 7, 8 and 9 pass through the aperture 13 at a slight angle to each other and thus each impinge on the fluorescent element of only one color. Color selection electrode 12
Is suspended by the suspension means 14.

FIG. 2 is a sectional view of an electron gun suitable for the color display tube of the present invention. The electron gun 21 has three electron beams 7, 8.
And three cathodes 22, 23 and 24 which emit 9 and 9, respectively. Further, the electron gun 21 has a first joint electrode 25 and a second joint electrode 2 for three electron beams.
6, a third joint electrode 27 and a fourth joint electrode 28. In operation, electrodes 27 and 28 create an electro-optical magnetic field. This electron-optical magnetic field focuses the electron beam on the display tube screen of the color display tube. Electrode 28 has apertures 30, 31, and 3
Compensation element 29 having two.

FIG. 3 is a top view of the correction element of the electron gun shown in FIG. The apertures 30 and 32 for the outer electron beam generate an electric field having a sextupole field component for the outer electron beam during operation. In this example, this aperture has a trapezoidal shape.

4a to 4d show another example of the correction element of the electron gun suitable for the color display tube of the present invention, and in this case also, the outer aperture of the correction element has a trapezoidal shape. The trapezoid referred to here is the center of gravity 44, 4 of the portions I, II, III and IV, respectively, as shown in the aperture 32 of the electrode 29 in FIG. 4a.
We shall mean shapes such that 5, 46 and 47 form a trapezoid. These moieties I, II, III and IV are 2
It is surrounded by two imaginary planes, namely an in-line plane 42 and a plane 43 extending perpendicularly to this in-line plane and passing through the point A.

FIG. 5 shows the beam diameter (vertical axis) as a function of the beam intensity I (horizontal axis). Line 51 shows the diameter of the beam by an electron gun with a correction element according to the conventional state. Line 52 shows the diameter of the beam when using a correction element suitable for use in the electron gun of the color display tube of the present invention.

FIG. 6 shows the shape of the beam spot when the electron beam is focused to the smallest possible diameter. Line 61 shows the shape of the outer electron beam according to the conventional state. The state of the maximum beam is shown by a chain line 62. In this case, the trapezoidal aperture of the aperture is used for the outer beam, so that the spot of the outer beam can be a substantially circular spot as shown by the line 63. In this case the maximum beam diameter is reduced.

It is thus clear that FIG. 6 shows the effect of a trapezoidal aperture on a nearly circular spot.
In practice, the shape of the spot will vary somewhat across the screen, but the shape of the aperture of the compensator will be chosen appropriately to give the best possible compromise to the size and shape of the spot at the center and corners. To be able to

The present invention is not limited to the above-mentioned examples, and it goes without saying that various modifications and changes can be made without departing from the scope of the invention.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional side view showing the configuration of a color display tube of the present invention.

FIG. 2 is a sectional view showing the structure of an electron gun suitable for the color display tube of the present invention.

FIG. 3 is a cross-sectional view showing a configuration of a correction element for the electron gun shown in FIG.

4A to 4D are cross-sectional views showing the configurations of several examples of correction elements.

FIG. 5 is a characteristic diagram showing the diameter of the beam as a function of the intensity I of the beam.

FIG. 6 is a characteristic diagram showing the shape of beam spots when focusing the beam spots so that they have the smallest possible diameter.

[Explanation of symbols]

1 color display tube 2 exhaust container 3 Display window 4 cone part 5 neck 6 electron gun 7, 8, 9 electron beam 10 Display screen 11 Deflection unit 12 color selection electrodes 13 Aperture 14 Suspension means 21 electron gun 22, 23, 24 electrodes 25, 26, 27, 28 Joint electrode 29 Correction element 30, 31, 32 aperture 42, 43 sides 44, 45, 46, 47 Center of gravity

Front Page Continuation (72) Inventor Erich Eduard Himmelbauer The Netherlands 5621 Beer Eindowen Frühne Bautzwech 1 (56) References JP 60-54143 (JP, A) JP 59-54150 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01J 29/48-29/51

Claims (2)

(57) [Claims] 1. An in-line type electron gun for generating three electron beams in an exhaust container is provided, each of which is provided with a cup-shaped portion, and an electron beam is allowed to pass through the bottom portion of the electron gun. A first and a second lens electrode having two apertures, the electrodes being
An electron-optical lens field for focusing the electron beam on the display screen is generated between the first and second lens electrodes, and one of the first and second lens electrodes is separated from the aperture of each cup-shaped portion thereof. provided Te, the electron - a correction element provided with correcting astigmatism of an optical lens field, the said correction element in a color display tube comprising an aperture on the three collinear, the outer aperture of the compensation element When properly formed, an electric field having a sextupole component with respect to the outer electron beam is generated during operation, and the six-pole component of the lens field generated by the first and second lens electrodes interferes with the outer electron beam. A color display tube characterized in that the effect is compensated at least locally. 2. The color display tube according to claim 1, wherein the outer aperture of the correction element has a trapezoidal shape.