JPH0332172B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a triode section consisting of a cathode, a cathode current control electrode, and an anode, and a limiting aperture for controlling the divergence angle of an electron beam taken out through an aperture of the anode. The present invention relates to an electron gun including an accelerating electrode.

Figure 1 is a configuration diagram of a so-called triode gun, which has been widely used in image pickup tubes and picture tubes. 1 is a cathode, 2 is a cathode current control electrode, 3 is an anode, 4 is an accelerating electrode, and 5 is an electron The beam, 6 indicates a crossover section, and 7 indicates an aperture. With this gun,
A cathode lens is generated by keeping the cathode current control electrode (hereinafter abbreviated as _G1 ) 2 at a negative potential with respect to the cathode (hereinafter abbreviated as K) 1, and the crossover part 6 of the electron beam from _K1 is connected to the anode (hereinafter abbreviated as K). below
The electron beam is generated behind the front plate of G ₂ (abbreviated as G ₂ ) 3, and the divergence angle of the electron beam is limited by the aperture 7 of the rear plate of G 2 3. In order to reduce the divergence angle of the electron beam 5, it is necessary to reduce the beam divergence angle from the crossover section, so the anode 3 has a double structure and the apparent crossover section is placed as far away from _K1 as possible. However, it becomes difficult to increase the current density in the apparent crossover section. In order to reduce the divergence angle of the electron beam 5, it is necessary to make the voltage V _G1 of _G12 more negative and move the position of the crossover section 6 to the K1 side, but in this case, the cathode current and the crossover section The solid angle from the aperture to the aperture decreases, and the amount of electron beam 5 obtained is drastically _reduced .

FIG. 2 illustrates the relationship between the electron beam amount _IS and the beam divergence angle α of a triode gun used in a 2/3-inch image pickup tube. It can be seen that if α is set to 1 degree or less, I _S will be less than 1 μA. Furthermore, K ₁ , G ₁ 2, G ₂ 3
If the coaxiality of G 3 and the subsequent coaxiality of the electrode for generating an electron lens (not shown) are not improved, the electron beam 5 from the aperture will deviate from the center axis of G ₃ 4, as shown in an exaggerated manner in Fig. 1. , G ₃ does not pass through the center of the electron lens generating electrode following 4, aberrations due to the electron lens increase, and the performance of the cathode ray tube using this gun deteriorates.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electron gun whose resulting electron beam has a small divergence angle and a large beam current.

FIG. 3A shows an embodiment of the electron gun of the present invention.
In this figure, 1 is a cathode, 2 is a cathode current control electrode having an electron beam distribution hole smaller than the cathode diameter, 3 is a foil-like flat plate anode with a fine aperture, 4 has a potential higher than the anode potential, An accelerating electrode having a limiting aperture for controlling the divergence angle of the electron beam from the aperture, 5 and 5' are electron beams, 6 is a crossover section, 7 is an aperture, and 8 is a limiting aperture. .

This electron gun has an anode (hereinafter abbreviated as G ₂ ) 3
Because it is not a double structure but a foil-like flat plate electrode,
By making the hole diameter φ of the cathode current control electrode (hereinafter abbreviated as G ₁ ) 2 approximately equal to the distance d between G ₁ 2 and G ₂ 3, the position of the crossover part and the position of the aperture can be adjusted. In other words, a high current density crossover section 6 can be created on the aperture 7. However, it is difficult to assemble a foil-like flat plate electrode with a fine aperture of about 10 μm in diameter, so a foil-like flat plate with an aperture is attached to a perforated metal plate as shown in Fig. 3B _. It is necessary to have a structure. In the case of forming _{the G2} structure shown in FIG. According to the structure shown in FIG. 3B, this is not necessary.

By configuring G ₂ 3 with a flat plate electrode as shown in FIG. 3B, the velocity vector of electrons after forming the crossover portion 6 is highly parallel to the axial direction of the electron gun. That is, when the electron velocity vector is decomposed into the axial direction of the electron gun and the direction orthogonal to the axis, the axial component is large and the orthogonal component is distributed in a small range. This means that the electron beams are well aligned in the axial direction.

The reason why such an effect can be obtained will be explained below with reference to FIGS. 3C and 3D.

The electric field in the configuration of FIG. 3B is in the state shown in FIG. 3D. In other words, the electric field becomes flat near the anode G ₂ 3, and the electric field becomes flat near the cathode current control electrode G ₁ 2.
A curved electric field is formed so as to be convex to the side. The effect of such an electric field on an electron beam can be approximated by an optical system in which one convex lens is arranged.

The electron beam emitted from the cathode K1 is first focused by a curved electric field. Furthermore, in a flat electric field, it is subjected to a force in a direction perpendicular to the equipotential surface, that is, in the axial direction of the electron gun. Therefore, the velocity energy of the electron beam increases its axial component.

After passing through the crossover section, the electron beam diverges at an angle determined by the velocity component at the crossover section.

On the other hand, an anode that is not a flat plate, that is, FIG.
When using a concave cathode current control electrode G _{1 2} as shown in FIG _.
The electric field is also curved near point 3 (concave toward the cathode). Therefore, it can be approximated to an optical system in which a convex lens and a concave lens are sequentially arranged from the cathode K1 to the anode _G23 .

The electron beam emitted from the cathode K1 is focused by a curved electric field corresponding to a convex lens.
Thereafter, the concave lens equivalent portion receives a force having an outward component in a direction perpendicular to the axis. In other words, the electron beam that has passed through the crossover section is further diverged by the concave lens equivalent section.

As is clear from the above, in the case of Fig. 3E, compared to the case of Fig. 3D, the anode G ₂ 3
In principle, the divergence angle increases when the electron beam reaches , and the current density of the electron beam passing through the aperture 7 therefore decreases.

As mentioned above, since the crossover portion 6 is formed on the aperture 7, both the amount I _S ' of the electron beam 5' from the aperture 7 and its divergence angle α' increase as shown in FIG. Most of the electron beam 5' from is blocked by the accelerating electrode 4,
Since only a small portion of the electron beam 5' from the aperture 7 passes through the limiting aperture 8, the divergence angle of the electron beam 5 from the limiting aperture 8 is controlled, and the electron beam 5 passing through it The divergence angle of can be made small. In this gun, since the aperture 7 is placed at the crossover section 6, which is the position of maximum current density, almost all the electron beams pass through the aperture 7 without being restricted. Therefore, the electron beam 5' reaches the limiting aperture 8 while diverging, but as mentioned above, the current density of the electron beam is extremely high, so the electrons passing through the limiting aperture 8 are Even if the diameter of the limiting aperture 8 is made small in order to limit the divergence angle of the beam 5 to a small value, the beam current can be made sufficiently large.

Furthermore, if only the central axes of the aperture 7 and the limiting aperture 8 are made to coincide with each other with high accuracy, the direction of the electron beam 5 from the aperture 7 may change as shown in FIGS. 3A and 4 for some reason. Even if the limiting aperture 8 is shifted from the center, the direction of _the electron beam 5 passing through it and the divergence angle distribution of the current density hardly change. This can improve the performance of cathode ray tubes using this gun.

The specific structure of the triode portion in the embodiment of the present invention is shown in FIGS. 5A and 5B.

Figure 6 shows the relationship between d and V _G1 by finding the value of d at which the crossover portion 6 is formed on the aperture 7 for each value when V G1 is changed _. It is. Here, d is G ₁ 2 and G ₂ 3
The distance between V _G1 and G 1 is the voltage of G ₁ 2. Also,
V _G2 shown in the figure is the voltage of G ₂ 3, and ΦK' is the diameter of the electron beam passage hole of G ₁ 2.

The three types of curves are obtained under the following conditions: ΦK' = 0.3 mm, V _G2 = 300V, ΦK' = 0.5 mm, V _G2 = 200V, and ΦK' = 0.7 mm, V _G2 = 100V. The results of the measurements carried out are shown.

Here, for V _G2 , at least 100V ~
As long as it is within the range of 300V, changing the value will not substantially affect the value of d at which the crossover portion is formed.

From Figure 6, if d is made equal to ΦK', then
It can be seen that the crossover portion 6 can be formed on the aperture 7 under the condition that V _G1 =0V, that is, K1 and G ₁ 2 are at the same potential.

On the other hand, FIG. 7 shows the relationship between d and I _S ', α' and I _S . Here, I _S ' is the amount of electron beam 5' that passed through aperture 7, α' is the divergence angle of electron beam 5',
_IS is the amount of electron beam 5 that has passed through limiting aperture 8.

The three types of curves are respectively ΦK' = 0.3 mm, V _G2 = 300V, 50 μm between G ₁ and K, ΦK' = 0.5 mm, V _G2 = 200 V, 100 μm between G ₁ and K, and ΦK' _The following shows the results of measurements conducted under the _following conditions:

From FIG. 7, it can be seen that I _S becomes maximum near d=ΦK'. As is clear from comparing this result with the data shown in FIG. 6, with regard to the value of d, the maximum I _S is obtained under the condition that the crossover portion 6 is formed on the aperture 7. I understand that.

By the way, in a triode gun, within the operating condition of V _G1 ≦0,
The amount of electron beam is controlled by changing V _G1 , and as V _G1 becomes more negative, the electrons emitted from the cathode are suppressed by the negative potential, so the amount of electron beam extracted from the cathode is V _G1 = 0.
It is maximum when .

Therefore, under V _G1 = 0, which is the condition for the maximum amount of electron beam with respect to V _G1 , if the above-mentioned d is configured so that the condition that the amount of electron beam is maximum is satisfied, the maximum amount of electron beam will be It turns out that you can get it. In other words, the configuration of the electron gun is G ₁
It can be said that it is best to make the distance d between G 2 and G ₂ 3 equal to the diameter ΦK' of the electron beam passage hole in G ₁ 2. The electron gun of the present invention is constructed according to this condition.

For an actual electron gun that meets the requirements of the present invention as described above, when the divergence angle α of the electron beam from the limiting aperture 8 is limited to 0.8 degrees,
With an aperture diameter of 25μφ, V _G2 = 200, V _G3 = 750V, I _S of approximately 3 μA was obtained. This is approximately compared to the results in Figure 2.
It is 20 times more.

The above-mentioned good results are obtained when φK′=d=0.3~0.7mm, K・G ₁
The voltage was obtained in the range of 50 to 200μ and V _G2 =100 to 300V.

As is clear from the above description, according to the present invention, the anode is formed by attaching a foil plate to the triode side of a thick metal support plate and forming the operating area on the triode side only by the foil plate. By having this configuration,
For the electron beam after the electric field near the anode becomes flat and a crossover region is formed,
It doesn't give you the power to release it. Therefore, the current density of the electron beam after passing through the crossover section is extremely high. Therefore, even if the divergence angle is limited to a small value by the limiting aperture, the amount of electron beam finally obtained is sufficiently large compared to the conventional one.

Furthermore, by making the diameter of the electron beam distribution hole provided in the cathode current control electrode approximately the same as the distance between the electrode and the anode, conditions for obtaining the maximum amount of electron beam can be realized.

As a result, an electron gun with a small divergence angle and an extremely large beam current can be obtained.

[Brief explanation of drawings]

Figure 1 is a schematic side view to explain the triode gun;
Fig. 2 is a characteristic diagram of a triode gun, Fig. 3A is a schematic side view for explaining an embodiment of the electron gun of the present invention, and Figs. 3B and C mainly show the structure of the anode of the electron gun. 3D and E are sectional views showing the operation of the electron gun of the embodiment of the present invention and the conventional example, respectively. FIG. 4 is a beam divergence angle distribution characteristic diagram of the electron gun, and FIG.
Figures A and B are side views showing the structure of the triode part of the electron gun, and Figures 6 and 7 are characteristic diagrams of the electron gun. 1... Cathode, 2... Cathode current control electrode, 3... Anode, 4... Accelerating electrode, 5... Electron beam, 6... Crossover section, 7... Aperture, 8... Limiting aperture .

Claims (1)

[Claims] 1. An accelerating electrode having a triode consisting of a cathode, a cathode current control electrode, and an anode, and a limiting aperture for controlling the divergence angle of an electron beam taken out through the aperture of the anode, In an electron gun used under operating conditions in which the potential of the control electrode is equal to or lower than the potential of the cathode, the diameter of the electron beam distribution hole provided in the cathode current control electrode is approximately the same as the distance between the electrode and the anode. The anode is formed by attaching a foil flat plate to the triode side of a thick metal support plate so that the operating area on the triode side is formed only by the foil flat plate, and the aperture provided on this flat plate is An electron gun characterized by having a fine hole that fits in the crossover part of the electron beam.