CN1088355A - The electron gun of dynamic focusing - Google Patents

Abstract

In the dynamic focus electron gun, the horizontal dynamic focus voltage varies according to the position where the electron beam reaches on the phosphor screen, and the peak-to-peak value of the horizontal dynamic focus voltage in one horizontal deflection period in the upper and lower regions of the phosphor screen is larger than that in the center of the phosphor screen. Peak-to-peak, resulting in a uniform electron beam spot across the screen.

Description

This invention relates to dynamically focused electron guns for color cathode ray tubes (CRT). More particularly, the present invention relates to a dynamically focused electron gun capable of forming a high resolution electron beam spot across a phosphor screen.

The resolution of a color CRT depends on the size and shape of the electron beam spot formed on the phosphor screen. In order to obtain high-resolution images, the electron beam spot should be as small as possible and its shape should be distorted as little as possible. However, ordinary color CRTs use the so-called self-converging method and a deflection coil. In this method, three beams of electrons pass through a final accelerating lens of the electron gun to electrodes on the back of the fluorescent screen. The deflection coil can form a pincushion-shaped A horizontal deflection magnetic field and a barrel-shaped vertical deflection magnetic field are used as means for deflecting the electron beams. With this structure, the deflection angle of the electron beams directed to the edge of the phosphor screen is relatively large, and thus the electron beams pass through the non-uniform vertical and horizontal deflection magnetic fields. Therefore, the electron beam passing through the non-uniform magnetic field is under-focused in the horizontal direction and over-focused in the vertical direction, and the electron beam spot formed by the electron beam reaching the edge of the fluorescent screen is horizontally elongated so that a considerable gap is formed around the spot. halo. Therefore, the portion of the image formed at the edge of the screen is distorted to some extent compared with the image formed at the center of the screen.

In order to avoid the above-mentioned edge image distortion, a method has been proposed in which the focus of electron beams is dynamically controlled according to the area of the phosphor screen using a dynamic electric field to form a uniform spot on the entire phosphor screen. This method is used in a so-called dynamic focus electron gun, various modifications of which are disclosed in US Pat.

With reference to Fig. 1, common dynamic focus electron gun comprises cathode 2, control pole 3 and screen pole 4, and they constitute three poles that are used to generate electron beam; Also comprise a static focus electrode 5a, dynamic focus electrode 5b and final stage acceleration Electrodes 6, which constitute a main lens system for forming a static focus lens and a dynamic focus lens.

When a screen voltage of 200-1200 volts is applied to the screen electrode 4, the control electrode 3 is kept at a potential of 0 volts. The static focus voltage Vs and the dynamic focus voltage Vd are applied to the static focus electrode 5a and the dynamic focus electrode 5b, respectively. An accelerating voltage Va of 20-35 kV is applied to the accelerating electrode 6 . The waveform of the dynamic focus voltage Vd is usually parabolic and synchronized with the deflection signal applied to the deflection coil. Its peak voltage is 600 to 800 volts higher than the static focus voltage. The range of the static focus voltage Vs is 20-35% of the acceleration voltage Va.

The waveform of the dynamic focus voltage applied to such a dynamic focus electron gun is generally as shown in FIG. 2 . In particular, the static focus voltage Vs applied to the static focus electrode 5a is maintained at a preset value. Thus, the parabolic dynamic focus voltage Vd applied to the dynamic focus electrode 5b varies in accordance with the area of the phosphor screen where the electron beams will land, and is repeated every horizontal deflection period (1H).

The minimum voltage of each parabolic waveform of a horizontal deflection period may be higher than, equal to or lower than the static focus voltage, and compared with the electron beam reaching the center of any scanning line, when the electron beam reaches the end of any scanning line, This minimum voltage is relatively high. This difference in the minimum voltage changes regularly in one vertical period (1V) per frame.

The amplitude I of each horizontal deflection period of the parabolic dynamic voltage is the same over the entire phosphor screen regardless of the landing area of the electron beam. The maximum and minimum values of the dynamic focus voltage vary with one vertical period as a period. One horizontal scanning line is formed in one horizontal deflection period and a plurality of horizontal scanning lines are formed in one vertical period to form one frame of image data.

In the curve of Fig. 2, the upper and lower enveloping lines V1 and V2 formed by the connection of the parabolic waveform peaks (positive and negative values respectively) correspond to the change of the dynamic focus voltage peak value of the electron beam falling along any vertical line of the phosphor screen. (Here, the peak of the inclusion line occurs at the endpoint of the line.) This is seen as a hypothetical virtual vertical dynamic focus voltage. In contrast to this, it can be noted that the difference between the vertical and horizontal dynamic focus voltage and the static focus voltage varies in both directions (vertical and horizontal) of the phosphor screen. However, the peak-to-peak value of Vd in one horizontal deflection period 1H at the central portion of the screen is substantially equal to the peak-to-peak value at the upper or lower portion of the screen. The vertical dynamic focus voltage is applied in such a manner that the rate of change at the left and right sides of the screen is the same as that at the center of the screen during the vertical deflection period. Thus, the rates of change of the upper and lower wrap lines V1 and V2 (showing the change of the vertical dynamic focus voltage Vd) are equal.

Figures 3 and 4 show another conventional dynamic focus voltage waveform.

First, referring to Figure 3, when the electron beam lands on the center of the phosphor screen, the minimum value of the dynamic focus voltage Vd is lower than the static focus voltage Vs, and when the electron beam lands on the upper or lower part of the phosphor screen, the dynamic focus voltage Vd is lower than the static focus voltage Vs. The minimum value is relatively high.

Referring to FIG. 4, when the electron beam lands on the center of the phosphor screen, the minimum value of the dynamic focus voltage Vd is substantially equal to the static focus voltage Vs. When the electron beam lands on the upper or lower part of the fluorescent screen, the minimum value of the dynamic focus voltage is relatively high.

The magnitude of the dynamic focus voltage applied to a conventional dynamic focus electron gun remains constant regardless of the landing position of the electron beam on the phosphor screen. However, since the distance from the emission point of the electron beam (from the electron gun) to the phosphor screen varies with the landing position (the phosphor screen is aspherical), and since the electron beam is severely distorted by the deflection coil, it cannot be obtained over the entire phosphor screen. Uniform electron beam spot. Due to the structural limitations of the CRT, high-quality pictures cannot be obtained by the above-mentioned conventional voltage application method.

As shown in FIG. 5, when the focus of the electron beam is adapted to the left and right edges of the phosphor screen 100, that is, at the ends of the horizontal scanning line 110, the core of the electron beam spot located in the center of the scanning line 110 becomes larger, which greatly reduces the formation of The quality of the image in the center of the screen. In addition, as shown in FIG. 6, when the electron beam is focused along the vertical line passing through the center of the fluorescent screen, that is, when it fits in the center of the scanning line 110, the electron beam spot formed at the end of the horizontal scanning line 110 presents a larger halo , and thus cannot obtain high-quality images on the entire fluorescent screen.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a dynamically focusing electron gun which can uniformly focus electron beams over the entire screen to obtain high-quality images on the entire screen.

In order to realize this object of the present invention, the provided dynamic focusing electron gun includes cathode, control electrode and screen electrode, is used for generating electron beam, also includes static focusing electrode, dynamic focusing electrode and last-stage accelerating electrode, applies on the static focusing electrode The static focusing voltage is used to form the main lens for accelerating and converging the electron beam, the dynamic focusing voltage is applied to the dynamic focusing electrode, and the highest accelerating anode voltage is applied to the final accelerating electrode, wherein the dynamic focusing voltage changes with the position of the electron beam on the fluorescent screen, And be applied in such a way that when the electron beam scans to the upper and lower parts of the phosphor screen, the amplitude of the dynamic focus voltage is greater than that when the electron beam scans to the center of the phosphor screen.

The above objects and other advantages of the present invention will become more apparent after a detailed description of the preferred embodiment thereof is made with reference to the accompanying drawings. In the attached picture:

Fig. 1 is the schematic sectional view of common dynamic focusing electron gun;

Fig. 2 is a dynamic focusing voltage waveform diagram applied to a conventional focusing electron gun;

Fig. 3 is another dynamic focusing voltage waveform diagram applied to the conventional focusing electron gun;

Fig. 4 is another dynamic focusing voltage waveform diagram applied to the conventional focusing electron gun;

Fig. 5 and Fig. 6 show the distortion of scanning line when adopting conventional dynamic focus voltage application method;

Figure 7 is a schematic perspective view of a dynamically focusing electron gun according to the present invention;

Fig. 8 is a waveform diagram of a dynamic focus voltage applied to a dynamic focus electron gun according to the present invention;

Fig. 9 is a waveform diagram of another dynamic focus voltage applied to the dynamic focus electron gun according to the present invention;

Fig. 10 is a waveform diagram of another dynamic focus voltage applied to the dynamic focus electron gun according to the present invention;

Fig. 11 shows the scanning lines on the fluorescent screen obtained when using the dynamic focusing electron gun according to the present invention.

Referring to Fig. 7, the dynamic focusing electron gun 10 according to the present invention comprises sequentially the cathode 20 of emitting thermions; the control electrode 30 and the screen electrode 40 for controlling thermions to form electron beams; the static focusing electrode 50a, the dynamic focusing electrode 50b and the final acceleration The electrode 60, the electrodes 50a, 50b and 60 constitute the pre-focus lens and the main focus lens of the main lens system for finally converging and accelerating the electron beams. The screen electrode 30, the static focus electrode 50a and the dynamic focus electrode 50b constitute a static pre-focus lens and a dynamic pre-focus lens. The accelerating electrode 60 constitutes a dynamic main focusing lens. Form three vertically elongated electron beam passing holes side by side at the electron beam emitting plane of the static focusing electrode 50a, and form three horizontal electron beam receiving planes side by side at the electron beam receiving plane of the dynamic focusing electrode 50b opposite the emitting plane of the static focusing electrode. The elongated electron beam passes through the aperture. In doing so, a dynamic quadrupole lens is formed between the static focusing electrode and the dynamic focusing electrode.

A voltage of 0 volts is applied to the control electrode 30 and a voltage of 200-1200 volts is applied to the screen electrode 40 in a conventional manner. A static focus voltage Vs is applied to the static focus electrode 50a and a dynamic focus voltage Vd is applied to the dynamic focus electrode 50b. An accelerating voltage Va of 20-35 kV is applied to the accelerating electrode 60 . The range of the static focus voltage Vs is 20-35% of the acceleration voltage Va. The peak voltage of the dynamic focus voltage is 600-800 volts higher than the static focus voltage.

The waveforms of the static and dynamic focus voltages applied to the dynamic focus electron gun of the present invention are generally shown in FIGS. 8 , 9 and 10 . In FIGS. 8, 9 and 10, the static focus voltage Vs applied to the static focus electrode 50a is maintained at a predetermined value. The parabolic dynamic focus voltage Vd applied to the dynamic focus electrode 50b varies in accordance with the position on the phosphor screen where the electron beams arrive, and is repeated every horizontal deflection period. As a feature of the present invention, the amplitude of each horizontal deflection period of the parabolic dynamic voltage varies in accordance with the landing position of the electron beam, and the maximum and minimum values of the dynamic focus voltage vary each vertical deflection period. The minimum voltage of each parabolic waveform of a horizontal deflection period has a value higher than, equal to or lower than the static focus voltage, and compared with the electron beam landing in the middle of each scan line, when the electron beam lands on each scan line For the upper and lower parts of the line, the minimum voltage is relatively high. The difference between the minimum voltages is regularly varied in one vertical period by frame.

In FIGS. 8, 9 and 10, the upper and lower wavy lines V10 and V20 respectively connecting the maximum point and the minimum point of the parabolic waveform show that when the electron beam lands on the vertical line passing through the edge and center of the phosphor screen The change of the dynamic focus voltage during the time. Since they are related to the vertical focus characteristics, they can be regarded as the hypothetical first and second vertical dynamic focus voltages V10 and V20. According to the change of the vertical voltage, it can be seen that the difference between the dynamic focus voltage and the static focus voltage changes in all directions (vertical and horizontal) of the fluorescent screen. Also, according to a feature of the present invention, the amplitude Io in one horizontal deflection period at the upper or lower portion of the screen is different from the amplitude Ic in one horizontal deflection period at the central portion of the screen. During the vertical deflection period of the vertical dynamic focus voltages V10 and V20, the rate of change at the left and right sides of the phosphor screen is also different from the rate of change at the center of the phosphor screen.

Referring to Figure 9, when the electron beam lands on the center of the phosphor screen, the minimum value of the dynamic focus voltage Vd is lower than the static focus voltage Vs, and when the electron beam lands on the edge of the phosphor screen, the minimum value of the dynamic focus voltage is relatively higher.

Referring to FIG. 10, when the electron beam lands on the center of the phosphor screen, the minimum value of the dynamic focus voltage Vd is substantially equal to the static focus voltage Vs. When the electron beam lands on the upper and lower parts of the phosphor screen, the dynamic focus voltage is relatively high.

At this time, the amplitude Io in the horizontal deflection period in the upper and lower regions of the phosphor screen is different from the amplitude Ic in the horizontal deflection period in the central portion of the phosphor screen. During the vertical deflection period, the rate of change of the parabolic wave on the left and right sides of the phosphor screen is greater than that in the center of the phosphor screen. Therefore, the change rate of the assumed first vertical dynamic focus voltage V10 obtained by connecting the maximum value point of the horizontal dynamic focus voltage is different from the change rate of the assumed second vertical dynamic focus voltage V20 obtained by connecting the minimum value point of the horizontal dynamic focus voltage. .

As shown in Figure 9, when the electron beam lands on the center of the phosphor screen, the minimum value of the second vertical dynamic voltage V20 of the dynamic focus voltage Vd is lower than the static focus voltage Vs, while at the upper and lower parts of the phosphor screen, its minimum The value is relatively higher than the static focus voltage Vs. As shown in Figure 10, when the electron beam lands on the center of the phosphor screen, the minimum value of the second vertical dynamic voltage V20 of the dynamic focus voltage Vd is basically the same as the static focus voltage, while at the upper and lower parts of the phosphor screen, its The minimum value is relatively high.

As described above, the electron gun of the present invention is characterized in that the amplitude of the parabolic dynamic focus voltage varies according to the scanning position of the electron beam.

The operation and effect of the embodiment of the dynamic focus electron gun of the present invention will be described below.

The horizontal dynamic focus voltage Vd varies depending on the position of the electron beam on the screen, and is applied such that the amplitude in the horizontal deflection period 1H at the upper and lower parts of the screen is larger than that at the center of the screen. The rate of change of the vertical dynamic focus voltages V10 and V20 at the left and right sides of the phosphor screen is greater than that at the center of the phosphor screen. In Figures 8, 9 and 10, the dynamic voltage of each parabola shows the horizontal focus voltage Vd and shows the variation of the horizontal focus voltage when the electron beam scans horizontally from left to right or from right to left across the center of the fluorescent screen .

Here, according to the characteristics of the present invention, the amplitude of the parabolic wave of the horizontal dynamic focus voltage Vd at the upper and lower portions of the phosphor screen is greater than that at the center of the phosphor screen, thereby obtaining good focusing characteristics in the upper and lower regions of the phosphor screen .

More specifically, when the electron beam emitted by the electron gun scans the middle of each scan line and the applied dynamic voltage is slightly lower or slightly higher than the static focus voltage, then when the electron beam passes through the static focus electrode 50a and the dynamic focus electrode 50b time will be affected by the electric field in between. Thus, what is formed on the phosphor screen is an electron beam spot having a relatively small difference in vertical and horizontal widths. When the dynamic focus voltage is the same as the static focus voltage, since no lens is formed between the static focus electrode 50a and the dynamic focus electrode 50b, the electron beam will not be affected by the lens when passing through. Thus, a circular electron beam spot having almost the same width in the horizontal and vertical directions is formed.

When the electron beam scans at the end of the scanning line, since the applied dynamic focus voltage is higher than the static focus voltage, when the electron beam passes between the static focus electrode 50a and the dynamic focus electrode 50b, the electron beam is formed by the electrode vertically elongated due to the influence of the strong quadrupole lens between electrode 50a and electrode 50b. The degree of vertical elongation of the electron beam deflected toward the edge of the phosphor screen varies according to the scanning position. When the electron beam scans the upper and lower areas of the phosphor screen, the electron beams directed to the four corners of the phosphor screen are vertically elongated to the maximum and the focal length is elongated due to the strong quadrupole lens formed. Since the vertically elongated electron beam is affected by the non-uniform deflection magnetic field, and due to the astigmatism according to the asphericity of the phosphor screen, an almost circular electron beam spot is formed when the electron beam reaches the edge of the phosphor screen.

Through the above method, uniform scanning lines 110 can be obtained on the entire fluorescent screen 100, as shown in FIG. 11 .

In the dynamic focus electron gun according to the present invention, since the amplitude of the applied dynamic focus voltage is varied according to the features of the present invention, both the horizontal focus state and the vertical focus degree can be adjusted.

Such a dynamic focus voltage application method can be used in a dynamic focus electron gun using a low voltage driving method in which the adjustment voltage is lower than the focusing voltage and a high voltage driving method in which the adjustment voltage is higher than the focusing voltage. Voltage.

As described above, in the dynamic focus voltage application method of the dynamic electron gun of the present invention, the horizontal dynamic focus voltage is changed according to the position where the electron beam reaches on the phosphor screen, and after the voltage is applied, the horizontal deflection period in the upper and lower parts of the phosphor screen The amplitude is greater than the value at the center of the phosphor screen. In the vertical dynamic focus voltage, since the rate of change in the vertical deflection period on the left and right sides of the phosphor screen is greater than that in the center of the phosphor screen, the focus state at the center and edge of the phosphor screen is improved, and the deflection coil Due to the distortion of the focus characteristics at the edge of the phosphor screen due to its geometric structure, a high-resolution image is obtained on the entire phosphor screen.

The electron gun according to the present invention can be applied to HDTV as well as ordinary television.

Claims (4)

1, a kind of dynamic focusing electron gun, comprise the negative electrode 20 that produces electron beam, the control utmost point 30 and anode 40, be applied with the static focus electrode 50a of static focus voltage, be applied with the dynamic focus electrode 50b and the final stage accelerating electrode 60 that is applied with accelerating anode voltage of dynamic focus voltage, form the main lens that quickens and assemble electron beam, it is characterized in that the point on the phosphor screen that above-mentioned dynamic focus voltage will arrive according to electron beam changes, this voltage applies like this, and the amplitude the when amplitude when making the electron beam scanning phosphor screen than top with than the bottom is more central than electron beam scanning phosphor screen is big.

2, according to the dynamic focusing electron gun in the claim 1, it is characterized in that when the electron beam land in fluoroscopic when central authorities, the negative peak voltage of a horizontal deflection cycle of above-mentioned dynamic focus voltage is lower than described static focus voltage, when the electron beam land were regional in fluoroscopic upper and lower, negative peak voltage was higher relatively.

3, according to the dynamic focusing electron gun in the claim 1, the minimum value that it is characterized in that described dynamic focus voltage is more than or equal to described static focus voltage.

4,, it is characterized in that the minimum voltage value of a horizontal deflection cycle of described dynamic focus voltage is lower than described static focus voltage according to the dynamic focusing electron gun in the claim 1.

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