JPS6138572B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron gun device used in a cathode ray tube.

Generally, an electron gun used in a cathode ray tube is composed of a cylindrical electrode group, and its main electron lens is an axially symmetrical lens and has an accelerating lens structure (relative to the pair of cylindrical electrodes that make up the electron lens). , a structure in which the electrode on the electron emitter side is at a low voltage) causes large aberrations. The aberration of an electron lens becomes larger as the diameter of the electrode becomes smaller. Particularly in electron gun devices that require multiple electron beams, such as color cathode ray tubes, when the diameter of the cathode ray tube is constant, the aperture of the electrode corresponding to each beam becomes smaller, resulting in larger aberrations for the electron beam. .

The present invention provides an electron gun device that uses a secondary lens, a so-called plane symmetric lens, as a main electron lens to reduce aberrations to an electron beam.

Hereinafter, the entire electron gun device according to the present invention will be explained with reference to the drawings.

First, the principle of a plane-symmetric electron lens will be explained using FIG. In the figure, a ₁ , a ₂ , b ₁ and b ₂ each indicate a flat electrode, and each pair of flat electrodes
a ₁ , a ₂ and b ₁ , b ₂ are arranged parallel to each other at a predetermined interval so as to be parallel to the yz plane, and the flat electrodes a ₁ , a ₂ and the flat electrodes b ₁ , b ₂ are arranged in the Z-axis direction with a required gap. In such a configuration, one plate-shaped electrode a ₁ and a ₂ are commonly connected and a voltage V 1 is applied thereto, and the other plate-shaped electrode b ₁ and b ₂ are similarly connected in common and a voltage V ₁ is applied thereto. When a voltage V ₂ is applied to (V ₁ ≠ V ₂ ), a lens effect occurs in the gap between the flat electrodes a ₁ , a ₂ and the flat electrodes b ₁ , b ₂ , that is, based on the potential distribution as shown in the figure. An electronic lens L is created. The nature of this electron lens L is a plane-symmetric electron lens according to the theory of electron optics. That is, this electronic lens L is x
- In the z plane, the potential distribution 1 is as shown in Figure 2A.
The electron beam entering the lens takes the path indicated by the chain line 2, and has a so-called convex lens effect. In this xz plane, a convex lens action occurs regardless of the magnitude relationship between voltages V ₁ and V ₂ . On the other hand, on the yz plane, the focal length is infinite, but because the values of voltages V ₁ and V ₂ are different, the refractive index on both sides is different, and the angular magnification of the electron beam naturally changes. Therefore, when V ₁ > V ₂ , the electron beam entering the potential distribution 1 takes the path indicated by the chain line 2' as shown in FIG. 2B, resulting in a so-called concave lens action.
When V ₁ <V ₂ , the electron beam takes the path indicated by the dashed line 2'' as shown in FIG.

Based on this principle, as shown in Figure 3, 4
Two sets of plane symmetrical electron lenses each consisting of two flat plate electrodes are provided, and these two sets of plane symmetrical electron lenses L ₁ and
L ₂ are arranged by rotating each other by 90° about the Z axis.
That is, the first flat electrode group A [a ₁ , a ₂ , b ₁ and b ₂ ] constituting the electron lens L ₁ and the electron lens
The _second flat electrode group B [a ₁ ′, a ₂ ′,
b ₁ ′ and b ₂ ′] are arranged along the Z-axis direction so that their electrode plate surfaces are perpendicular to each other. For both electrode groups A and B, for example, the inner flat plate electrode
b ₁ , b ₂ and a ₁ ′, a ₂ ′ are commonly connected to each other, a low voltage Va is applied thereto, and the outer flat electrodes a ₁ , a ₂ and
b ₁ ′ and b ₂ ′ are commonly connected to each other and a high voltage Vb is applied thereto. According to such a configuration, each plane-symmetric electron lens L ₁ and L ₂ has a convex lens action in the yz plane and the xz plane, respectively, and the integrated lens system is a so-called axially symmetric electron lens. It will have the same function as . The lens system composed of these two pairs of plane-symmetric lenses L ₁ and L ₂ is a so-called deceleration type because the potential of electrodes a ₁ and a ₂ is lower than that of electrodes b ₁ and b ₂ on the yz plane. Since it is an electronic lens, aberrations are reduced.

In the present invention, an electrode structure formed by combining two sets of plane-symmetric lenses L ₁ and L ₂ as described above is used as a focus electrode to construct an electron gun device of a cathode ray tube.

When constructing an electron gun using the electrode structure shown in FIG. 3 as a focus electrode, the following conditions must be met in order to obtain a circular beam spot on the fluorescent surface.

First, physical quantities related to the electron lens L ₁ (convex lens action) on the yz plane are defined as shown in FIG. 4A. That is, the focal length is f _A , the size of the object, that is, the diameter of the beam spot at the crossover point on the y-z plane is α, and the object point distance, that is, the distance from the crossover point P ₁ to the center of the lens L ₁ where a _A is the image point distance, that is, the distance from the center of the lens L ₁ to the point P ₂ on the fluorescent surface 3 is b _A (note that if the lens L ₂ were not present, the image would be focused at P ₂ ', but (Because of the lens _L2 , the real image extends to the fluorescent surface 3), and the image magnification is M _A.

Further, physical quantities related to the electron lens L ₂ (convex lens action) on the xz plane are defined as shown in FIG. 4B. The focal length is f _B and the size of the object is x
- The diameter of the beam spot at the crossover point in the z plane is β, and the distance from the objective point, that is, P ₃ to the lens L ₂
The distance to the center of is a _B (in this case, the object point position is equivalently P ₃ and not the crossover point P ₁ ),
Let b _B be the image point distance, that is, the distance from the center of the lens L ₂ to the point P ₂ on the fluorescent surface 3, and M _B be the image magnification.

From the lens formula, for lens L ₁ , 1/a _A + 1/b _A = 1/f _A ...(1) M _A = b _A /a _A ...(2) For lens L ₂ , 1/a _B + 1/ b _B = 1/f _B ……(3) _MB = b _B /a _B ……(4) Therefore, in order to obtain a circular beam spot from this, αM _A = βM _B ……(5) 〓α/β＝a _A・b _B /a _B・b _A ...(6) And, generally speaking, in cathode ray tubes such as television receivers, distance b _A and distance b _B are approximate (b _A 〓b _B )
Therefore, by substituting this condition into the above equation (6), we get α/β=a _A /a _B (7). Two sets of plane-symmetric lenses L ₁ and L ₂ in Fig. 3
In a configuration consisting of a combination of , it is structurally impossible to set a _A = a _B , so α and β are not equal. Therefore, in the electron gun, the beam spot diameter at the crossover point is determined by the objective distance a _A of the two lenses L ₁ and L ₂ .
By forming an ellipse with the ratio of and a _B , a circular beam spot can be obtained on the fluorescent surface 3.

The basic configuration of the present invention has been described above, and by using this principle, it is possible to configure, for example, an electron gun device for a color cathode ray tube that handles a plurality of beams. Next, Figures 5 and 6
An example of an electron gun device for a color cathode ray tube according to the present invention will be described with reference to the drawings.

In the present invention, there are three cathodes K _R , K G and _{K B} corresponding to the three electron beams B _R , B _G and B _B along the y-axis as shown in FIGS. 5 and 6.
and these three cathodes K _R , K _G and K _B
Commonly, a first grid G ₁ , a second grid G ₂ , a third grid G ₃ , a fourth grid G 4 and G _{4 '} , and a fifth grid G ₅ are arranged in sequence along the z-axis direction, respectively. Become. The first grid G ₁ and the second grid G ₂ each have a cup shape, and beam transmission holes 4R, 4 are located at positions corresponding to the cathodes K _R , K _G and _KB , respectively.
It has G, 4B and 5R, 5G, 5B. The third grid G ₃ and the fourth grid G ₄ are composed of four parallel flat electrodes 7 a and 7 arranged at a predetermined interval, respectively.
b, 7c, 7d and 8a, 8b, 8c, 8d, and the plate surface of each of these plate electrodes is x-z.
Place it parallel to the plane. In this case, the flat electrodes 7a, 7b, 7c and 7d of grid _G3
and each corresponding flat electrode 8 of grid G ₄
space portions 9R, 9G, 9B and 10R, 10G, 10B are respectively opposed to each other on the z-axis, and partitioned by respective flat electrodes of grids _G3 and _G4 . Cathode K _R ,
It is configured to face K _G and _KB . In addition, in grid G ₃ , the end face on the grid G ₂ side is closed, and beam transmission holes 6R, 6G, and 6B can be formed in the end face at positions corresponding to cathodes K _R , K _G , and _KB . . Grid G ₄ ′ and Grid G ₅
has two flat electrodes 11a, 11b and 12a, 12b that are parallel to each other with a predetermined interval, and each of the flat electrodes 11a, 11b, 12
a and 12b are arranged so that their plate surfaces are perpendicular to the flat electrodes of grids G ₃ and G ₄ ', that is, parallel to the yz plane. In this case, the space 13 formed between the electrodes 11a and 11b and the electrode 12a
The space portion 14 formed between the grid G ₄ ' and 12b commonly faces the space portions 10R, 10G, and 10B of the grid G4'. In addition, each of these grids G ₃ ,
G ₄ , G ₄ ', and G ₅ can be formed by inserting a flat plate into a cylindrical body. In such a configuration, for example, the _first grid G1 is supplied with approximately 0V, the second grid _G2 is supplied with approximately 500V, and the third grid _G3 and fifth grid _G5 are each supplied with approximately 20KV.
If a fixed potential of about 8KV is applied to the fourth grids _G4 and _G4 ', each cathode _KR , _KG and _KB will be connected between the third grid _G3 and the fourth grid _G4 .
Independent first plane-symmetrical lenses L _1R , L _1G and L _1B are constructed corresponding to the respective beams B _R , B _G and B _B , and between the fourth grid G ₄ ' and the fifth grid G ₅ A second plane-symmetric lens _L2 common to each beam B _R , B _G , B _B is configured. Therefore, the cathode K _R ,
Each beam B _R , B _G and B _B from K _G and K _B is
y respectively by the electron lenses L _1R , L _1G and L _1B when passing through the third grid G ₃ and the fourth grid G _{4 respectively} .
- Focused on the z-plane, followed by the fourth grid
When passing through G ₄ ' and the fifth grid G ₅ , the electronic lens L ₂
The beam is focused on the xz plane and reaches the fluorescent surface. Here, the first plane-symmetric lenses L _1R , L _1G
Since the third grid G ₃ on the cathode side has a higher pressure than the fourth grid G ₄ , L _1B becomes a so-called deceleration type lens, and the second plane-symmetric lens L ₂ is connected to the fourth grid G ₄ ' on the cathode side. Since the pressure is lower than that of the fifth grid _G5 , it becomes a so-called accelerating lens.

In addition, in order to make the beam spot shape circular on the fluorescent surface, for example, the first grid G ₁ and the second grid
Beam passing holes 4 and 5 in G ₂ and third grid G ₃
This can be achieved by forming the shape of at least one of the beam passing holes in the ratios obtained by the above equation (7) into an ellipse shape.

Further, the following methods can be considered as means for obtaining static comperience in the electron gun. For example, as shown in Fig. 7, the fourth grid G ₄
The flat electrodes 8a and 8d located on the outside of the grid are shifted outward, and the distance _d1 between the spaces 10R and 10B is changed to the space 9 on the outside of the third grid _G3 that faces this.
Convergence is achieved by making the distance d between R and 9B larger than ₂ , making the lenses _L1R and _L1B on both sides of the first plane-symmetric lens group asymmetric, and deflecting the beams B _R and B _B on both sides toward the center. can be done.
In this case, when the beams B _R and B _B pass through the spaces 10R and 10B, the same potential is applied to the electrodes 8a, 8b, 8c, and 8d, but the beams are deflected toward the electrodes 8b and 8c, which are closer in distance. be done.

In addition, a magnet is placed around the outer periphery of the neck of the cathode ray tube, and static comperience can be achieved by this magnet. Furthermore, the cathodes K _R and K _B on both sides are tilted toward the central axis, and at the same time, the lenses L _1R and L _1B on both sides of the first plane-symmetric lens group are also tilted by the same amount to obtain static convergence. be able to.

According to the above-mentioned configuration, in the main electron lens system, the first lenses L _1R , L _1G and L _1B are deceleration type lenses in the yz plane, so that the aberration to the beam can be reduced and the x - In the z plane, the second lens L ₂ becomes an accelerating lens, but since it is common to the three beams, the fourth grid
The electrode apertures of the electrodes of G ₄ ' and the fifth grid G ₅ , that is, the distance between the electrodes 11a and 11b and between the electrodes 12a and 12b can be made large, and distortion due to aberration can be sufficiently corrected. Therefore, the aberrations to the beam can be reduced as a whole.

Further, the deflection distortion caused by the deflection yoke due to the use of a plane-symmetric lens can be easily corrected by correction voltages applied independently to the fourth grid G ₄ ' or G ₄ , respectively.

Furthermore, compared to the already proposed Trinitron (registered trademark) type electron gun, the convergence plate is omitted and the electrode structure is simplified.

Incidentally, FIGS. 8 and 9 show other examples of the present invention. In the case of FIG. 8, another set of flat electrodes 15a, 15b is arranged between the fourth grid _G4 and the fourth grid _G4 ' in the same manner as the grid _G4 ' in the configuration shown in FIG. A grid G ₄ '' is provided, and this grid G ₄ '' is provided with the same potential as grids G ₃ and G ₅ . With this configuration, the convex lens made up of grids G ₄ ″ and G ₄ ′ becomes a deceleration type lens in the xz plane, so a beam with fewer aberrations can be obtained compared to the case shown in Figure 6. .

Also, Figure 9 shows the third grid _G3 and the fourth grid.
This is a case where the electrode plate shape of G ₄ is replaced with a flat plate shape and is made into a curved plate shape as shown in the figure. Even in such a shape, a plane symmetric lens is constructed in the same way as described above, and a beam with little aberration can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram of a plane-symmetric lens used in the present invention, FIGS. 2A to C are explanatory diagrams showing the lens action, FIG. 3 is a perspective view showing the principle configuration of an electron gun according to the present invention, and FIG. Figures A and B are y- of Figure 3, respectively.
A plan view seen from the z plane and a plan view seen from the xz plane, and FIGS. 5 and 6 are a perspective view of the main part and an overall plan view, respectively, when the present invention is applied to an electron gun device of a color cathode ray tube. , FIG. 7 is a plan view of the main part showing another example of the present invention, FIG. 8 is a plan view showing another example of the invention, and FIG. 9 is a plan view of the main part showing still another example of the invention. FIG. a ₁ , a ₂ , b ₁ , b ₂ , a ₁ ′, a ₂ ′, b ₁ ′, b ₂ ′ are plate-shaped electrodes, L ₁ is a deceleration type plane symmetric electron lens, and L ₂ is an acceleration type plane symmetric electron lens. The electron lenses _BR , _BG , and _BB are electron beams.

Claims (1)

[Claims] 1. A deceleration type plane symmetric electron lens and an acceleration type plane symmetric electron lens configured by a plate-shaped electrode body in front of the electron emitter are orthogonal to each other, and the deceleration type plane symmetric electron lens is an acceleration type plane symmetric electron lens. An electron gun device arranged so as to be located closer to the electron emitter.