JPH021341B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cathode ray tube device, which is constructed so that good resolution can be obtained over the entire area on the phosphor screen surface.

In general, the resolution of a cathode ray tube device depends on the size and shape of the beam spot (bright spot) produced on the phosphor screen surface, and in order to obtain high resolution, the beam spot must be as small as possible and free of distortion. is important. In addition, in a color cathode ray tube device, it is important from the viewpoint of resolution that the beam spot of the three electron beams be correctly concentrated at any one point on the phosphor screen surface, and for this reason, an in-line type color cathode tube is used. By distorting the horizontal deflection magnetic field distribution into a pincushion shape as shown in Figure 1a and the vertical deflection magnetic field distribution into a barrel shape as shown in Figure 1b, three electron beams can be generated. , 2 and 3 are self-converging.
However, if we adopt this self-concentration method,
Even if the concentration of the 3-electron beam is good, the cross-sectional shape of the 3-electron beam is distorted as the beam deflection angle increases, resulting in beam spots that appear on the phosphor screen surface, especially at the periphery, as shown in Figure 2. Distortion of trends is likely to occur. That is, while the beam spot 5 appearing at the center of the phosphor screen surface 4 is a perfect circle, the beam spot 6 appearing at the periphery has a vertically long elliptical high-brightness core part 7 as well as a horizontally long elliptical high-brightness core part 7. A long low-luminance haze portion 8 accompanies the screen, making it difficult to obtain high resolution, especially at the periphery of the screen.

The above-mentioned distortion of the beam spot shape is caused by the deflection yoke in the self-concentration method applying an asymmetric magnetic field to the three electron beams as shown in Figure 1 a and b. The electron beam given within the electron gun is weakened in the horizontal direction and strengthened in the vertical direction.

The present invention has been made to eliminate the above-mentioned drawbacks of the conventional art. Next, a cathode ray tube device of the present invention will be described with reference to embodiments shown in the drawings.

In FIG. 3, the electron gun 9 includes three cathodes 10', 10'', 10 arranged horizontally in a straight line, a control grid electrode 11, an accelerating electrode system 12, a front-stage focusing electrode system 13, and a rear-stage focusing electrode system 14. The pre-focusing system 13 includes first, second and third grid electrodes 15, 1 arranged sequentially along the electron beam path.
6 and 17, the first grid electrode 15 is formed in a box shape together with the final electrode plate of the accelerating electrode system 12. As shown in FIG. 4, the first and third grid electrodes 15, 17 each have three circular electron beam passing holes 18', 18'', 18; 19', 19'', 1
9, and the second grid electrode 16 has vertically long (hereinafter referred to as vertically long) rectangular electron beam passing holes 20', 20'', 20. A constant focusing voltage Vfoc is applied to the electrodes 15 and 17, and a dynamic voltage V' _fpc that changes depending on the amount of beam deflection is applied to the second grid electrode 16.

The dynamic voltage V' _fpc is the same as the voltage V fpc when the deflection current 23 is zero, as shown by the solid line 21 or the dashed-dotted line 22 in FIG. 5, that is, when the beam spot appears at the center of the phosphor _screen surface. The voltage V _fpc gradually decreases or increases as the deflection current increases or decreases. Therefore, when the beam spot appears in the center of the phosphor screen surface, the first, second and third grid electrodes 1
5, 16, and 17 have the same potential V _fpc , no lens electric field is generated between these grid electrodes, and the electron beam passing holes 20', 20'', and
Although the electron beam 20 is non-circular, no axially asymmetric electric field acts on the electron beam, and a perfectly circular beam spot is obtained at the center of the screen surface.

On the other hand, as the amount of beam deflection increases, the voltage V′ _fpc increases.
Constant focusing voltage as it falls or rises from V _fpc
A lens electric field is generated between the first and third grid electrodes 15, 17 and the second grid electrode 16 to which V _fpc is applied. This lens electric field is applied to the electron beam passing holes 20', 20'', 2 of the second grid electrode 16.
Since 0 is axially asymmetric, each of the three electron beams passing through it is subjected to an axially asymmetrical focusing effect. When the electron beam passing holes 20', 20'', and 20 of the second grid grid 16 are vertically rectangular or vertically elliptical as shown in FIG. 4, the three electron beams passing through them are strongly horizontally A weak focusing effect in the vertical direction is provided by lenses 24', 24'', 24. The electron beam is further passed through axially symmetrical focusing lenses 25' and 2 generated by the subsequent focusing electrode system 14.
5'', 25, one of the three lenses is an equivalent combination of axially asymmetrical lenses 24', 24'', 24 and axially symmetrical focusing lenses 25', 25'', 25. As shown in FIG. 6 as a composite lens 26, it is an axially asymmetric lens that is strong in the horizontal direction and weak in the vertical direction.Therefore, when the electron beam 27 passes through the composite lens 26, it is strong in the horizontal direction, It receives a weak focusing effect in the vertical direction,
The vertical focus point 28 occurs at a point farther away than the horizontal focus point 29. This phenomenon is
This acts to cancel out the fact that the electron beam within the deflection magnetic field is focused weakly in the horizontal direction and strongly focused in the vertical direction as the amount of beam deflection increases, as described above.

As a result, even though the beam spot is caused by an electron beam that is largely deflected in the horizontal direction, it is possible to make the beam spot close to a perfect circle, and the resolution of the phosphor screen surface is improved, particularly on both left and right sides and on the diagonal. Since the distortion of the beam spot appearing near the upper middle of the phosphor screen surface is originally slight, a very clear reproduced image can be obtained over the entire area on the phosphor screen surface. Furthermore, since the lens electric field of the composite lens changes as the amount of beam deflection increases, a dynamic focus effect can also be obtained.

The above has described an embodiment in which the present invention is applied to an in-line color cathode ray tube device. However, the purpose of the present invention is to reduce shape distortion of a beam spot due to an electron beam subjected to a deflection action within a non-uniform deflection magnetic field. The present invention is applicable to cathode ray tube devices operating with one beam or two beams in the same manner as described above.

In this example, the electron beam passing hole of the second grating electrode constituting the front-stage focusing lens system has an axially asymmetric shape. The same beam spot distortion correction effect as described above can be obtained even if only the electron beam passing holes in the grating electrode are made in an axially asymmetrical shape and the electron beam passing holes in the other grid electrodes are made circular.

[Brief explanation of drawings]

Figures 1a and b are diagrams showing the relationship between the non-uniform deflection magnetic field distribution and the three electron beams, and Figure 2 shows the shape distortion of the beam spot appearing on the phosphor screen surface of a color cathode ray tube device using the self-concentration method. FIG. 3 is a side sectional view of an electron gun section of an in-line color cathode ray tube device embodying the present invention;
Figure 4 is a perspective view of the front-stage focusing electrode system of the same color cathode ray tube device, Figure 5 is a signal waveform diagram showing the relationship between deflection current and dynamic voltage, and Figure 6 is a composite of the front-stage focusing lens and the rear-stage focusing lens. FIG. 3 is a diagram for explaining the focusing state of an electron beam by a synthetic lens. 10', 10'', 10... cathode, 11... control grid electrode, 12... accelerating electrode system, 13... front focusing electrode system, 14... rear focusing electrode system, 15... first grid electrode, 16... second grid electrode, 17...
...Third grid electrode, 18', 18'', 18, 1
9', 19'', 19, 20', 20'', 20...
Electron beam passage hole, V _fpc ...constant focusing voltage,
V′ _fpc ...dynamic voltage.

Claims (1)

[Claims] 1. A front-stage focusing electrode system comprising three cathodes arranged in a horizontal line and a control grid electrode, and disposed between an acceleration electrode system and a rear-stage focusing electrode system adjacent to the control grid electrode. is composed of first, second, and third grid electrodes, and applies a constant focusing voltage to the first grid electrode and the third grid electrode, which are formed in a box shape together with the final electrode plate of the accelerating electrode system. A dynamic voltage that gradually decreases or increases from the constant focusing voltage as the amount of beam deflection increases is applied to the second grid electrode, and A cathode ray tube device characterized in that at least one of the holes has an axis-asymmetric electron beam passage hole that is long in the vertical direction.