JPH021340B2 - - 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 becomes distorted as the beam deflection angle increases, and the beam spots that appear on the phosphor screen surface, especially at the periphery, have a tendency as shown in Figure 2. distortion is likely to occur. That is, the beam spot 5 that appears at the center of the phosphor screen surface 4 is a perfect circle, whereas the beam spot 6 that appears at the periphery is a high-brightness core section 7 that is elongated in the horizontal direction.
In addition to this, a vertically long low-luminance haze portion 8 is attached, 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 fact that the deflection yoke in the self-focusing method applies 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, a front-stage focusing electrode system 13, and a rear-stage focusing electrode system 14. have.
The pre-focusing system 13 includes first, second and third grid electrodes 1 arranged sequentially along the electron beam path.
5, 16, 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 Figure 4, the first
The third grid electrodes 15, 17 each have three circular electron beam passing holes 18', 18'', 18;
The second grid electrode 16 has rectangular electron beam passing holes 20', 20'', 20 which are elongated in the horizontal direction (hereinafter referred to as horizontally elongated). A constant focusing voltage V _fpc is applied to the first and third grid electrodes 15 and 17,
A dynamic voltage V' _fpc is applied to the second grid electrode 16, which varies depending on the amount of beam deflection. In addition, the latter focusing electrode system 14 includes a grid electrode 2 on the cathode side.
1 and a grid electrode 22 on the phosphor screen surface side.As shown in FIG.
are long in the vertical direction (hereinafter referred to as vertically long)
Rectangular electron beam passing holes 23', 23'', 23
; 24', 24'', 24. A constant focusing voltage is applied to both the grid electrodes 21, 22.
V _fpc and anode voltage V _a are given respectively.

The dynamic voltage V' _fpc applied to the second grid electrode 16 of the front-stage focusing lens system 13 is determined when the deflection current 27 reaches its maximum value or minimum value, as shown by the solid line 25 or the dashed-dotted line 26 in FIG. ,
When the beam spot appears at the periphery of the phosphor screen, it takes the same value as the voltage V _fpc and gradually decreases or increases from the voltage V _fpc as the deflection current increases or decreases. Therefore, when the beam spot appears at the periphery of the phosphor screen surface, the first,
The second and third grid electrodes 15, 16, 17 have the same potential V _fpc , no lens electric field is generated in the front focusing electrode system 13, and the electron beam passing holes 20', 20'' of the second grid electrode 16 , 20 are axially asymmetric, no axially asymmetric lens electric field is generated. Therefore, the electron beam passes through the front-stage focusing electrode system 13 without receiving any focusing effect and reaches the rear-stage focusing electrode system 14. As shown in FIG. 5, a focusing voltage V _fpc and an anode voltage V _a are applied to the grid electrodes 21 and 22 on the cathode side and the phosphor screen side of the latter focusing electrode system 14, respectively, but the electron beam Passing hole 23', 23'', 23;2
Since lenses 4', 24'', and 24 have a vertically long rectangular shape, axially asymmetric lenses 28', 28'', and 28 are generated between the grid electrodes 21 and 22, and the electron beams passing through these lenses are axially asymmetrical. It receives a focusing effect. Like the latter focusing electrode system 14 of this embodiment,
An axially asymmetric lens formed when the electron beam passage hole is formed into a vertically long rectangle or a vertically long ellipse becomes a focusing lens that is strong in the horizontal direction and weak in the vertical direction with respect to the electron beam. Therefore, as shown in FIG. 7, when the electron beam 29 passes through the axially asymmetric lens 28, a strong focusing effect works in the horizontal direction and a weak focusing effect in the vertical direction, and the focus point 30 in the vertical direction becomes the focus point 31 in the horizontal direction. occurs at a point further away than This phenomenon occurs because the electron beam within the deflection magnetic field becomes weaker in the horizontal direction as the amount of beam deflection increases, as described above.
It acts to cancel out the strong focusing in the vertical direction. Therefore, the beam spot of the electron beam that is largely deflected in the horizontal direction can be brought 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.

On the other hand, as the amount of beam deflection decreases, the voltage V′ _fpc increases.
When descending or rising from V _fpc , the first and third grid electrodes 15 and 17 to which a constant focusing voltage V _fpc is applied in the front-stage focusing electrode system 13, and the second
An axially asymmetric lens electric field is generated between the grid electrode 16 and the grid electrode 16 of the lens. When the electron beam passing holes 20', 20'', 20 of the second grid electrode 16 are shaped into a horizontally long rectangle or a horizontally long ellipse as shown in FIG. 3
It exhibits an axially asymmetric focusing effect that is strong in the vertical direction and weak in the horizontal direction with respect to the electron beam. Furthermore, this axially asymmetric focusing action tends to gradually cancel out the axially asymmetric focusing action of the axially asymmetric lenses 28', 28'', and 28 formed in the post-stage focusing electrode system 14 as the beam deflection angle decreases. Therefore, by appropriately selecting the minimum or maximum values of the signal waveforms 25 and 26 of the dynamic voltage V' _fpc , a perfect circle can be obtained even when the deflection current is zero, that is, when the beam spot appears at the center of the phosphor screen surface. You can get a beam spot.

As described above, in the cathode ray tube device implementing the present invention, the dynamic voltage is adjusted according to the amount of beam deflection.
By increasing or decreasing V′ _fpc from the focusing voltage V _fpc ,
A good beam spot with little distortion can be obtained at the center and periphery of the phosphor screen surface. 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.

Note that the horizontally elongated axis-asymmetric electron beam passage hole is
It may be provided on at least one grid electrode of the front-stage focusing electrode system.

[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 color cathode ray tube device, Figure 5 is a perspective view of the rear-stage focusing system, Figure 6 is a signal waveform diagram showing the relationship between deflection current and dynamic voltage, and Figure 7. FIG. 2 is a diagram for explaining a focusing state of an electron beam by an axially asymmetric lens formed in a rear-stage focusing electrode system. 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, V _a ...anode voltage.

Claims (1)

[Claims] 1 Three cathodes arranged in a horizontal line, a control grid electrode, an accelerating electrode system, a front-stage focusing electrode system, and a rear-stage focusing electrode system for generating a main lens are arranged in sequence, and the front-stage focusing electrode system is arranged in sequence. A constant focusing voltage is applied to the first grid electrode and the third grid electrode, which are formed into 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 changes is applied to the second grid electrode, and at least one grid electrode of the pre-focusing electrode system is horizontally A cathode ray tube characterized in that the cathode ray tube has an axially asymmetrical electron beam passing hole that is long in the vertical direction, and the pair of grid electrodes of the latter focusing electrode system has an axially asymmetrical electron beam passing hole that is long in the vertical direction. Device.