JPH021342B2 - - 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 surface of a phosphor screen.

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 ray 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 such a self-concentration method is adopted, even if the concentration of the three electron beams is good, the three
The cross-sectional shape of the electron beam becomes distorted as the beam deflection angle increases, and the beam spots appearing on the phosphor screen surface, particularly at the periphery, tend to become distorted as shown in FIG. That is, a beam spot 5 appearing at the center of the phosphor screen surface 4
is a perfect circle, whereas the beam spot 6 that appears at the periphery has a horizontally long elliptical high-brightness core part 7 and a vertically long low-brightness haze part 8, which is particularly It becomes difficult to obtain high resolution at the periphery of the screen.

The shape distortion of the beam spot as described above is caused by the deflection yoke in the self-concentration method applying a non-uniform magnetic field to the three electron beams as shown in Figure 1 a and b. The electron beam is defocused in the electron gun 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, and a focusing electrode 13.
and an anode 14, and the accelerating electrode system 12 consists of first and second grid electrodes 15, 16 in the form of flat plates arranged sequentially along the electron beam path. As shown in FIG.
has three circular electron beam passing holes 17', 1
7'', 17, and three oblong rectangular electron beam passing holes 19', 19'', 19.
The second grid electrode 16 has three circular electron beam passing holes 21', 21'', and 21. A constant acceleration voltage V _g2 is applied to the grid electrode 15, and a dynamic voltage that changes depending on the amount of beam deflection is applied to the second grid electrode 16.
V _g2 ′ is applied.

The dynamic voltage V _g2 ' takes the same value as the voltage V _g2 when the deflection current 23 is zero, as shown by the line 22 in FIG. 5, that is, when the beam spot appears at the center of the phosphor screen surface. , which has a waveform that gradually rises as the deflection current increases. Therefore, when the beam spot appears at the center of the phosphor screen surface, the first and second grid electrodes 15, 16 have the same potential V _g2 , and a lens electric field is generated between both grid electrodes 15, 16. Although the electron beam passing holes 19', 19'', and 19 of the electrode plate 20 of the first grid electrode 15 are non-circular, no axially asymmetric electric field acts on the electron beam, and the phosphor A perfectly circular beam spot is obtained at the center of the screen surface.

On the other hand, when the voltage V _g2 ' increases from V _g2 as the deflection current increases or decreases, that is, the amount of beam deflection increases, the first grid electrode 15 and the second grid electrode 16 to which a constant acceleration voltage V _g2 is applied A lens electric field is generated between the two. Since the electron beam passing holes 19', 19'', and 19 of the electrode plate 20 are axially asymmetric, the electron beams passing through the lens electric field are each subjected to an axially asymmetric focusing effect. When the beam passing holes 19', 19'', and 19 are in the shape of a horizontally long rectangle or a horizontally long ellipse as shown in FIG. give effect. Therefore, the electron beam immediately after exiting the accelerating electrode system 12 has a horizontally long elliptical cross-sectional shape, and with this cross-sectional shape, the main lens portion 2
4', 24'', and 24.

As shown in FIG. 6, when an electron beam 25 with a horizontally oblong elliptical cross section enters the main lens section 24, due to the spherical aberration of the lens, a focusing effect is strong in the horizontal direction and weak in the vertical direction, resulting in a focusing effect in the vertical direction. Point 2
6 occurs at a point farther than the focus point 27 in the horizontal direction.

In this way, when the cross-sectional shape of the electron beam that has passed through the accelerating electrode system 12 is distorted into a horizontally elongated ellipse as the amount of beam deflection increases, the main lens portion 24
The focusing effect on the electron beam by It is weak and acts to cancel out the strong focusing in the vertical direction.

Therefore, 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 the left and right sides and in the diagonal area. Since the distortion of the beam spot appearing near the upper middle and lower middle of the phosphor screen surface is originally slight, a very clear reproduced image can be obtained over the entire region on the phosphor screen surface.

The value of the accelerating voltage V _g2 is determined based on the required maximum beam current value, but a relatively low voltage of 1 kV or less is usually sufficient. This means that the variation width of the dynamic voltage V _g2 ' may be relatively small, and the dynamic voltage generating circuit can be constructed compactly and inexpensively.

Furthermore, when the potential of the second grid electrode increases as the amount of beam deflection increases, the potential difference between the second grid electrode and the focusing electrode, which is given a constant potential higher than the second grid electrode, decreases, resulting in the preform generated here. A change occurs in the lens electric field of the cass lens, and dynamic focus operation is obtained by the total lens action with the main lens, making it possible to prevent so-called deflection blur at the periphery of the screen.

The above has described an embodiment in which the present invention is applied to an in-line color cathode ray tube device, but 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.

[Brief explanation of drawings]

Figures 1a and b are diagrams showing the relationship between the nonuniform deflection magnetic field distribution and three electron beams, and Figure 2 is a diagram showing 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 the electron gun section of an in-line color cathode ray tube device embodying the present invention, FIG. 4 is a perspective view of the accelerating electrode system of the same color cathode ray tube device, and FIG. The figure is a signal waveform diagram showing the relationship between deflection current and dynamic voltage, and FIG. 6 is a diagram for explaining the focusing state of an electron beam having a horizontally long elliptical cross section at the main lens section. 11... Control grid electrode, 12... Accelerating electrode system,
13... Focusing electrode, 15... First grid electrode, 1
6...second grid electrode, V _g2 ...constant accelerating voltage, V _g2 '...dynamic voltage.

Claims (1)

[Claims] 1. An accelerating electrode system disposed between a control grid electrode and a focusing electrode to which a constant focusing voltage is applied,
The first grid electrode, to which a constant acceleration voltage is applied, has a circular electron beam passage hole and faces the control grid electrode, and the first grid electrode is axially asymmetrical. and an electrode plate facing the second grid electrode, each having a shaped electron beam passing hole, and a wavy waveform that gradually increases from the constant acceleration voltage as the amount of beam deflection increases. A cathode ray tube device characterized in that the second grid electrode to which a dynamic voltage is applied has a circular electron beam passage hole and faces the focusing electrode.