JPS58197639A - Cathode-ray tube device - Google Patents

Abstract

PURPOSE:To obtain a good beam spot with few distortion in the central part and peripheral section of a phosphor screen face by increasing and decreasing dynamic voltage from focusing voltage depending upon the beam deflection. CONSTITUTION:An electron gun 9 is provided with three cathodes 10', 10'', and 10''', control electrode 11, acceleration electrode system 12, front stage focusing electrode system 13, and rear stage focusing electrode system 14. The front stage focusing system 13 consists of the first, second, and third grid electrodes 15, 16, and 17 that are arranged sequentially along an electron beam path. Fixed focusing voltage is applied to the first and third grid electrodes 15 and 17 and dynamic voltage that varies depending upon the beam deflection is applied to the second grid electrode 16. Besides, the rear stage focusing electrode system 14 consists of a grid electrode 21 at a cathode side and a grid electrode 22 at a phosphor screen face. When the beam spot appears at the peripheral section of the phosphor screen face, the dynamic voltage applied to the grid electrode 16 of the front stage focusing lens system 13 is equivalent to the value of the focusing voltage and slowly decreases or increases it following the increase and decrease of deflection current.

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. In order to obtain high resolution, the beam spot must be as small as possible and without 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. For those that use
The horizontal deflection magnetic field distribution is shaped like a bottle cushion as shown in Figure 1(a), and the vertical deflection magnetic field distribution is shaped like Figure 1(b).
The three electron beams 1, 2.3 are self-converged by distorting them into a barrel shape as shown in FIG.

However, when such a self-concentration method is adopted, even though the concentration of the three electron beams is good, the cross-sectional shape of the three electron beams becomes distorted as the beam deflection angle increases, causing problems especially in areas on the phosphor screen surface. The beam spot appearing in the peripheral area tends to be distorted as shown in FIG. That is, the beam spot 6 appearing at the center of the phosphor screen surface 4 is a perfect circle, whereas the beam spot 6 bordering the periphery is a high-intensity core center 7 in the shape of a horizontally long ellipse. In addition to this, a vertically long low-luminance haze portion 8 is attached, making it difficult to maintain high resolution, especially at the periphery of the screen.

Note that the above-mentioned distortion of the beam spot shape is caused by the deflection yoke in the self-focusing method applying a non-uniform magnetic field to the three electron beams as shown in FIGS. 1(a) and 1(b). The electron beam within the deflecting magnetic field will weaken the focusing provided in the electron gun in the horizontal direction and strengthen it in the vertical direction.

The present invention has been made to eliminate the drawbacks of the prior art as mentioned above. DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a cathode ray tube device according to the present invention will be explained along with embodiments shown in the drawings.

In FIG. 3, the electron gun 9 includes three cathodes 10' arranged horizontally in a straight line, a 1σ decoration electrode 11, an acceleration electrode system 12, a front-stage focusing electrode system 13, and a rear-stage focusing electrode system. It has 14. The pre-focusing system 13 includes first and second focusing systems sequentially arranged along the electron beam path. It consists of second and third grid electrodes 15, 16, 17, and as shown in FIG.
circular electron beam passing holes 18', 18': 18"'
; 19'.

1cl', 1cl', and the second grid electrode 16 has horizontally long rectangular electron beam passing holes 20', 2
o'', 20''. The first and third grid electrodes 15.17 are provided with a focusing voltage Vfoa.
is applied to the second grating electrode 16, and a dynamic voltage "foa" that changes depending on the amount of beam deflection is applied to the second grating electrode 16.Furthermore, the latter focusing electrode system 14 is connected to the grating electrode 2 on the cathode side.
1 and a lattice basket with a phosphor screen embossed @! , 22, as shown in FIG.
2 f';24',24'',24''. A negative focusing voltage Vfo is applied to both grid electrodes 21 and 22. The dynamic voltage "foa" applied to the second grid electrode 16 of the front-stage focusing lens system 13 is as shown by the solid line 26 or the dashed-dotted line 26 in FIG. When the deflection current 27 reaches its maximum or minimum value, that is, when the beam spot appears at the periphery of the phosphor screen, it takes the same value as the voltage Vfo, and as the deflection current increases or decreases, the voltage Fo .

Gradually descend or rise from Therefore, when the beam spot appears at the periphery of the phosphor screen surface,
1st degree The second and third grid electrodes 15, 16, and 17 have the same potential fo0, no lens electric field is generated in the front-stage focusing electrode system 13, and the electron beam passing hole 20 of the second grid electrode 16 ', 20', 2 d'-7) Despite the five-axis asymmetry, no axis-asymmetric lens electric field is generated fL. Therefore, the electron beam passes through the front-stage focusing electrode system 13 without being subjected to any focusing effect, and reaches the rear-stage focusing electrode system 14. As shown in FIG. 6, a focusing voltage Vfo is applied to the grid electrodes 21 and 22 on the cathode side and the phosphor screen side of the post-focusing electrode system 14. and anode voltage (8) are applied respectively to the electron beam passing holes 23', 2.
3', 23";24',24'.

24; Since it has a vertically long rectangular shape, axially asymmetric lenses 28', 28',
The electron beam generated by 28' and passing through it is subjected to an asymmetric focusing action along the n axis. As in the latter stage focusing electrode system 14 of this embodiment, when the electron beam passing hole is formed into a vertically elongated rectangular shape or a vertically elongated elliptical shape, the axis asymmetric lens formed is strongly horizontal and vertical to the electron beam. It becomes a weak focusing lens. Therefore, as shown in FIG. 7, when the electron beam 29 passes through the axially asymmetric lens 28, the focusing force 5 is strong in the horizontal direction and weak in the vertical direction, and the focus point 30 in the vertical direction is the focus point in the horizontal direction. 3.1
occurs at a point further away than This phenomenon acts to cancel out the fact that the electron beam within the deflection magnetic field becomes weakly focused in the horizontal direction and strongly focused in the vertical direction as the amount of beam deflection increases, as described above. Therefore, nf is largely deflected in the horizontal direction.
C. The beam sporatra by the electron beam can be made close to a perfect circle, and the resolution of the phosphor screen surface, especially in the left and right cylinders and in the diagonal area, is increased.

-10,000, as the amount of beam deflection decreases, the voltage "foa" changes to vf
When descending or rising from Oo, a focusing voltage foo of one foot is applied in the front-stage focusing electrode system 13. There is an axial asymmetry between the first and third grid electrodes 15, 17 and the second grid electrode 16. A lens electric field is generated. If the electron beam passing holes 2σ, 20j2fi of the second grid electrode 16 are made into a horizontally long rectangular shape or a horizontally long ellipse shape as shown in FIG.
The n-axis asymmetric lens 32', 31.3 generated here
2' exhibits an axially asymmetric focusing effect that is strong in the vertical direction and weak in the horizontal direction for the three electron beams. Moreover, this axially asymmetric focusing effect tends to gradually cancel out the axially asymmetric focusing effect of the second axially asymmetric lenses 2 B', 28', and 2♂ formed in the subsequent focusing electrode system 14 as the beam deflection angle decreases. Since it is a dynamic voltage “foa”
By appropriately selecting the minimum or maximum value of the signal waveforms 25 and 26, even when the deflection current is zero, that is, the beam spot appears at the center of the phosphor screen surface,
You can get a perfectly round beam sporatra.

As described above, in the cathode ray tube device embodying the present invention, by increasing or decreasing the dynamic voltage V′f0° from the focusing voltage vfoo depending on the amount of beam deflection, distortion occurs in the central and peripheral portions of the phosphor screen surface. A good beam spot with a small number of beams can be obtained. 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.

The embodiments in which the present invention is applied to an in-line color cathode ray tube device have been described above, but the object of the present invention is to improve the shape of the beam spot caused by the electron beam deflected within the asymmetric deflection magnetic field. The point is to correct distortion,
The same can be applied to a cathode ray tube device that operates with one beam or two beams. Further, the axially asymmetric electron beam passage hole may be provided in at least one grid electrode of the front-stage focusing electrode system and at least one grid electrode of the rear-stage focusing electrode system.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are diagrams showing the relationship between the non-uniform deflection magnetic field distribution and three electron beams, and Figure 2 is a diagram showing the relationship between the non-uniform deflection magnetic field distribution and three electron beams, and Figure 2 shows the relationship between the non-uniform deflection magnetic field distribution and the three electron beams. Figure 3 schematically showing shape distortion of a rolling beam spot.
The figure is a side cross-sectional view of the electronic control section of an in-line color cathode ray tube device in which the present invention is implemented, FIG. 6 is a signal waveform diagram showing the relationship between deflection current and dynamic voltage, and FIG. 7 is a diagram for explaining the focusing state of the electron beam by the n-axis asymmetric lens formed in the subsequent focusing electrode system. . 10', 1o11Cf-... cathode, 11...
...Side leg electrode, 12...Acceleration electrode system, 13...
...Front-stage focusing electrode system, 14... Back-stage focusing electrode system, 15... First grid electrode, 16...
...Second grid electrode, 17...Third grid electrode, 18', 18τ1Ef, 19', 19', 11; 20
', 2o': 2bi...electron beam passing hole,
Vfo. Figure 1 (a) Figure 2 Figure 3

Claims (1)

[Claims] The electron beam focusing electrode system includes a front-stage focusing electrode system and a rear-stage focusing electrode system, and the front-stage focusing electrode system has first, second, and third grid electrodes, and the first and third grid electrodes are connected to the first and third grid electrodes. A constant focusing voltage is applied, and a dynamic voltage is applied to the second grid electrode, which gradually decreases or increases from the constant focusing voltage as the amount of beam deflection changes,
At least one grid electrode of the front-stage focusing electrode system and at least one grid electrode of the second-stage focusing electrode system have an axis-asymmetric electron beam passage hole that is long in a direction orthogonal to each other. Cathode ray tube device.