JPS6248342B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron gun device suitable for application to a cathode ray tube such as a color television picture tube.

As shown in FIG. 1, cathodes K _R , K _G , and K _B are provided corresponding to red, green, and blue as an electron gun device used in a color television picture tube, for example.
, the first grid G ₁ , the second grid G ₂ , the third grid G ₃ , the fourth grid G ₄ , and the fifth grid
Grid G ₅ is arranged such that the second grid G ₂
A prefocus electron lens is formed between the third grid G ₃ and the third grid G ₃ .
There is a so-called double-beam single electron gun device in which a unipotential type main electron lens is constructed in grid _G4 and fifth grid _G5 .

In this case, the electron beams from each of the cathodes K _R , K _G and K _B are arranged so that they intersect approximately at the center of the main electron lens at a position that satisfies the Franffauer condition, that is, provides a condition where the coma aberration becomes zero. A convergence means C constituted by, for example, an electrostatic deflection plate is provided downstream of the fifth grid _G5 , and thereby each cathode K
Electron beams B _R , B _G and B _B from _R , K _G and K _B
Although not shown, the light is converged (concentrated) on the fluorescent surface.

In an electron gun with such a configuration, by using a common main electron lens for each electron beam, the lens diameter can be increased within the limited neck diameter of the cathode ray tube, resulting in an electron gun with small aberrations. However, even with such a configuration, there is a drawback that as the beam current increases, spherical aberration increases and the beam spot blooms.

Furthermore, considering the unipotential type electron lens with reference to Fig. 2, in this unipotential type electron lens system, the third grid
A high voltage V _A is applied to G ₃ and the fifth grid G ₅ , and a focus voltage V _F is applied to the fourth grid G ₄ to form a main electron lens. Normally, in this kind of unipotential type electron lens, high voltage V _A
The diameter of the electrodes G ₃ and G ₅ to which the focus voltage V _F is applied is selected to be approximately the same as the diameter of the electrode G ₄ to which the focus voltage V F is applied, or the diameter of the high voltage electrodes G ₃ and G ₅ is selected as shown in FIG. is made small in diameter on the side facing the focus electrode G ₄ to shield the path of the electron beam from disturbances in the electric field from the outside, but in any case, the focus electrode
When the diameter of G ₄ is D and the length is l, the value of l/D is selected in the range of 0.5 to 2.0.

When calculating the spherical aberration characteristics when the value of l/D is changed in a unipotential type electron lens in which each electrode G ₃ to _{G 5} is selected to have the same diameter as shown in Fig. 2, the fourth The result will be as shown in the figure. In this figure, the horizontal axis represents the ratio of focal length f to lens aperture D,
The vertical axis represents the spherical aberration coefficient C _S . As is clear from this, if l/D is γ and f/D=ζ, the larger γ is for the same ζ value, the more the spherical aberration coefficient C
_S becomes small. In practice, the lens aperture D is limited by the neck diameter of the cathode ray tube body, so that at a given focal length f, the longer the electrode _G4 is, the smaller the spherical aberration will be. However, on the other hand, when γ=2.0 or more, the aberration phenomenon becomes saturated, so in order to achieve smaller aberrations, it is desirable to reduce the focal length f at the same γ. However, in general, if the length l of the electrode _G4 , ie, γ, is made large, the focal length f cannot be made small. This will be explained with reference to FIG. Now, in a unipotential type electron lens, this is the lens (Lens 1) formed between the third grid _G3 and the fourth grid _G4 , and the lens formed between the fourth grid _G4 and the fifth grid _G5 . We will discuss this separately from the lens (Lens 2). And each lens (Lens
The object focal lengths of 1) and (Lens 2) are f ₁ and f ₂ , the image focal lengths are f ₁ ′ and f ₂ ′, the object focal lengths are F ₁ and F ₂ , and the image focal points are F ₁ ′ and F ₂ '. and,
Distance from the image focus of Lens 1 to the object focus of Lens 2
When F ₁ ′→F ₂ =F ₁ ′F ₂ ≡C, the combined focal length f′ of both lenses is given by f′=f ₁ ′·f ₂ ′/−C (1).

In general, in electronic lens systems, C<0.
f′>0. As mentioned above, in order to reduce the spherical aberration, the length l of the electrode _G4 , therefore,
If the distance L between Lens 1 and 2 is large, |C|
becomes small. Therefore, from equation (1), the composite focal length
f' becomes large. Since the focal length f' becomes large in this way, it is not possible to make l sufficiently large and f sufficiently small to reduce aberrations sufficiently, as explained with reference to FIG. Furthermore, as f becomes larger, the imaging state changes. Therefore, in order to keep f constant, that is, small when l is large, the image focal length f 1 ′ (or) f ₂ ′ of lenses 1 and 2 must be adjusted as is clear from equation ( ₁ ). is required to be made smaller. However, the distance Q of the rear lens Lens 2 to the fluorescent surface of the cathode ray tube
is the focal length of the cathode ray tube from its relationship with the horizontal and vertical deflection means placed at the base of the funnel section.
There is a limit to reducing f ₂ ′. Therefore, it is desirable to reduce the focal length f ₁ ' of the lens 1 at the front stage. And this focal length
As a way to reduce f ₁ ′, the third grid G ₃
There is a method of increasing the ratio V _A /V _F between the anode voltage V _A applied to the fourth grid G ₄ and the focus voltage V _F applied to the fourth grid G ₄ . Applying a high voltage independent of ₅ requires separate high voltage wiring, which causes considerable practical complexity due to the problem of high voltage insulation shielding.

In order to reduce the focal length f ₁ ' of the front lens system without causing such drawbacks, as shown in FIG.
G ₃ and the front electron lens (Lens 1) which is decelerated by the second electrode, i.e., for example, the fourth grid G ₄
The second electrode (fourth grid G ₄ ) and the third electrode, for example, the fifth grid G ₅ , constitute an accelerating type subsequent electron lens (Lens 2). In particular, the front-stage electronic lens (Lens1) and the rear-stage electronic lens (Lens1)
2) Set the length l of electrode _G4 so that each electron lens action area is separated, and also set the lens aperture of the front-stage electron lens (Lens 1) to be smaller than the lens aperture of the rear-stage electron lens (Lens 2). be selected.
That is, the diameter D ₁ of each of the opposite ends of the third grid G ₃ and the fourth grid G ₄ is made smaller than the diameter D ₂ of each of the opposite ends of the fourth grid G ₄ and the fifth grid G ₅ , that is, D When the ratio of _{D 1} and D ₂ , D ₁ /D ₂ , is k, k<1. In addition, as mentioned above, in order to separate the electron lens action areas of the front and rear lenses from each other, the penetration of the electric field by the third grid _G3 and the fifth grid _G5 into the _fourth grid G4 is ₄ ,
Since the opening diameters D ₁ and D ₂ of the portions facing the third and fifth grids G ₃ and G ₅ are approximately equal, the length l of the small diameter portion and the length l ₂ of the large diameter portion are respectively l ₁ > D ₁ , l ₂ >D ₂ and therefore the length l of the fourth grid _G4 is chosen such that l>D ₁ +D ₂ .

Now, FIG. 7 shows an optical system shown by a solid line when the lens diameters of the front stage and the rear stage are made equal (that is, k=1). Suppose that an image is formed above. In the figure, P ₀ is the object point, that is, the cathode image at the crossover point, and P ₁ is the front lens
It shows the virtual image by Lens 1, that is, the object point of the rear lens Lens 2, and P ₂ is the lens imaged on the fluorescent surface S.
The image of Lens 2 is shown. In this state, reduce the aperture D ₁ of the front lens 1 and change its focal length.
In order to avoid a change in the imaging relationship when f ₁ ' is made small, that is, to form an image on the fluorescent surface S, the position of the front lens Lens 1 and the object point P ₀ is indicated by a broken line. Move it the required distance like this. Considering optically how to reduce the diameter of the lens Lens1, the image magnification of the lenses Lens1 and Lens2 is kept constant, so the image formation relationship of the lens Lens1 is reduced by keeping the image magnification constant.
In other words, it can be expected that the amount of aberration caused by Lens 1 will also be reduced by the reduction ratio. Specifically, the aperture _D1 of the front lens Lens1 is made smaller, the distance L between both lenses Lens1 and Lens2 is made larger, and the position of the cathode K is shifted. Now, the magnification M of the entire lens diameter is selected as M=12, and the image point P ₂ is set from the lens Lens2.
When the distance Q to the object point P0 is set as Q=50× _D2 , and the distance from the subsequent lens Lens2 to the object point _P0 is O, then V _F /V _A between this distance O and the distance L is set as constant. The relationship with respect to the aperture ratio k of both lenses at this time is the relationship shown by the solid line and broken line in FIG. In this case, the aperture D ₂ of the rear lens (Lens 2) is 6
In FIG. 8, the vertical axis is expressed in units of this aperture D ₂ , that is, D ₂ =1.

Figure 9 shows the calculation results of the relationship between the spherical aberration coefficient C _S and V _F /V _A when the magnification M of the entire lens system is M = -8 and Q = 50 x D ₂ . Curves 10 to 13 in the figure represent the aperture ratio k of the lens, and k
The calculation results are shown when = 1.0, 0.8, 0.6, and 0.4 are selected, respectively. In addition, the numerical value shown in the box about each curve 10-13 shows the value of the distance L in _D2 as a unit. In FIG. 9, the vertical axis is expressed as the ratio of the coefficients C _S and D ₂ .

Figure 10 shows curves of spherical aberration coefficients similar to Figure 9, but in this case, M = -10, Q = 50 x D ₂ , and curves 20 to 24 have k = 1.0, 0.8, respectively.
This is the case of 0.6, 0.4, and 0.3.

As is clear from FIGS. 9 and 10, the smaller the aperture ratio k of the front and rear lens diameters,
That is, it can be seen that the aberrations are improved as the aperture D ₁ of the front-stage lens becomes smaller than the aperture D ₂ of the rear-stage lens.

As mentioned above, when providing a front-stage lens action area and a rear-stage lens action area that are independent of each other and reducing the aperture ratio k between the two, a lens with small spherical aberration can be constructed. Lens1 formed by the action area
The total spherical aberration C _S of the composite lens system consisting of Lens 1 and Lens 2 is the sum of these two lenses Lens 1 and Lens 2.
When the spherical aberration coefficients of C _S ¹ and S _S ² are given by the following equation.

C _S =k・C _S ¹ +1/M ₁ ⁴・(V ₁ /V ₂ ) ^3/2・
C _S ² ...(1) From this, the amount of aberration Δr can be expressed as follows.

Δr=M ₁・M ₂ {k・C _S ¹ (φ ₁ ) +1/M ₁ ⁴ (φ ₁ ) ^3/2 C _S ² (φ ₂ )} (1/φ
₀ ) ^3/2 α ₀₃ ...(3) Here, k is the aperture of each front and rear lens D ₁
and _D2 , and _M1 and _M2 are the magnifications of the front and rear lenses. Also, φ ₀ =V ₁ /V ₃ , φ ₁ =V ₂ /
V ₁ , φ ₂ =V ₂ /V ₃ , where V ₁ , V ₂ and V ₃ are the voltages applied to the first, second and third electrodes.

It can also be seen from equation (3) that in order to effectively reduce the overall amount of aberration, the ratio k between the front lens aperture D ₁ and the rear lens aperture D ₂ is made small.

In this way, two independent lenses Lens1,
The main electron lens formed by combining Lens 2 can improve spherical aberration by selecting a small k value, but this lens has problems with astigmatism and curvature of field. , this becomes a large value. Therefore, such a composite lens system is used as a common main electron lens for a plurality of beams, for example, three, as explained in FIG. Even if the configuration is such that the three beams B _R , B _G and B _B intersect at the position where the aberration becomes zero, the beams B on both sides
The spot size of _R and B _B becomes worse. Therefore,
In the present invention, it is possible to obtain a good spot even with such a side beam.

In the present invention, as described above, there is a front-stage electronic lens Lens 1, that is, a front-stage electron lens action area, and a rear-stage electronic lens Lens separated from this.
2. In other words, the main electron lens is constituted by the latter electron lens action area, and in particular, the former electron lens is provided individually corresponding to each beam from each cathode, and the latter electron lens is is composed of an electron lens with small astigmatism and curvature of field, and is provided commonly to each beam. Then, the lens aperture of each front stage is selected to be smaller than the lens aperture of the rear stage.

An example of the present invention will be described with reference to FIG.
In this example, the main electron lens is composed of a front stage electron lens having a deceleration type bipotential electron lens configuration and an acceleration type bipotential electron lens having an electron lens action area separated from the front stage electron lens. This is the case. In this case, for example, cathodes K _R , K _G corresponding to red, green and blue
and K _B are provided, and each of these cathodes K _R , K _G
and K _B , i.e. for each beam B _R , B _G and B _B respectively the first grid G _1R , G _1G and G _1B , the second grid
Grids G _2R , G _2G and G _2B , third grid G _3
R , _G3G and _G3B are arranged in sequence, and a fourth grid _G4 and a fifth grid _G5 are commonly provided to these grids. Each third grid G _3R of the fourth grid G ₄ ,
At the end opposite to G _3G and G _3B , cylindrically branched electrode portions G _4R , G _4G , and G _4B are provided corresponding to the grids G _3R , G _3G , and G _3B , respectively. Then, the voltage V ₁ applied to the third grid G _3R , G _3G and G _3B , the voltage V 2 applied to the fourth grid G ₄ , that is, the respective electrode portions G _4R , G _4G and G _4B , and the voltage V ₂ applied to the fifth grid G ₅ The relationship with the voltage V ₃ applied to V ₂ < V ₁
V ₃ and V ₁ and V ₃ are selected to be, for example, the anode voltage H _V . In this way, each of the electrode sections G _4R , G _4G and G _4B of the fourth grid and the third grid G ₃ constitute a main electron lens for each beam B _R , B _G and B _B individually. Pre-stage deceleration bipotential electronic lenses Lens1R, Lens1G, and Lens1
4th grid G ₄ and 5th grid G ₅
Accordingly, a subsequent accelerating bipotential electron lens is commonly used for each beam B _R , B _G and B _B.
Configure Lens2. Here, the diameter of the end of the fourth grid G ₄ on the third grid side, that is, the electrode part G _4R , G
The ratio of the diameter D ₁ of _4G and G _4B to the diameter D ₂ of the end on the fifth grid side is k=D ₁ /D ₂ , and k<1, and the length of the fourth grid is D ₁ +D. Select a value larger than ₂ , and use the front lenses Lens1R, Lens1G, and Lens
The respective lens action areas of Lens 1B and the rear lens 2 are separated.

Then, each of the beams B _R , B _G , and B _B is made to intersect approximately at the center of the rear lens 2 so as to satisfy the Franchaufer condition.

FIG. 12 shows another example of the device of the present invention, in which the subsequent electron lens Lens 2 has an extended type (extended electric field type) bipotential electron lens configuration. That is, in this case, the rear lens Lens 2 is connected to each of the fourth, fifth, and sixth grids.
Consisting of G ₄ to _{G 6} , the third grid G ₃ (G _3
R , _G3G , _G3B ), the respective applied voltages _V1 to _V4 to the fourth grid _G4 , the fifth grid _G5 , and the _sixth grid G6
For example, the anode voltage is given as V ₁ =V ₄ , and V ₂ /
The relationships are selected such that V ₁ =0.25 to 0.40 and V ₃ /V ₄ =0.4 to 0.6.

In addition, the front lens Lens1R, Lens1G, Lens
1B is not limited to a deceleration type bipotential lens configuration, but can also be an acceleration type, a unipotential type, or an extended (extended electric field) type bipotential electron lens configuration.

According to the above-described configuration of the present invention, the main electron lens is constituted by a small-diameter front lens and a large-diameter rear lens, thereby configuring a main electron lens with small spherical aberration, and the front lens has By adopting a configuration in which each beam is provided individually, and the subsequent lens is provided in common for each beam, the problems of astigmatism and field curvature aberration related to the front lens can be solved, and the subsequent lens is provided in common for each beam. As for the lens, it is possible to use an electron lens with a lens configuration that has small astigmatism and field curvature, and as a result, even though it has a double-beam single electron gun configuration, the side beam astigmatism and image This solves spot distortion caused by surface curvature aberration.

[Brief explanation of the drawing]

FIG. 1 is an electrode layout diagram of a conventional double-beam single electron gun device, FIGS. 2, 3, and 5 are configuration diagrams of an electron lens used to explain the present invention, and FIG. 4 is a diagram showing the focal length and lens. A curve diagram showing the relationship between the ratio to the aperture and the spherical aberration coefficient, Fig. 6 is an electrode configuration diagram used to explain the present invention, Fig. 7 is an explanatory diagram thereof, and Fig. 8 shows the aperture ratio of the front and rear lenses and the relationship between the two. FIGS. 9 and 10 are curve diagrams showing the relationship between distance L and object point distance, FIGS. 9 and 10 are curve diagrams showing spherical aberration, respectively, and FIGS. 11 and 12 are electrode arrangement diagrams of each example of the device of the present invention, respectively. . K _R , K _G and K _B are cathodes; G _1R , G _1G and G _1B are first grids; G _2R , G _2G and G _2B are second grids;
grid, G _3R , G _3G and G _3B are the third grid;
G ₄ to _{G 6} are the 4th to 6th grids, Lens 1R, Lens
1G and Lens 1B are front stage lenses, and Lens 2 is a rear stage lens.

Claims (1)

[Claims] 1. In an electron gun device provided with a plurality of cathodes, the main electron lens is separated into a front-stage electron lens action region and a front-stage electron lens action region provided individually on each path of the electron beam by each of the cathodes, and a rear-stage electron lens action area provided in common on the path of the plurality of beams, the electron lens aperture of the electron lens system by the front-stage action area being smaller than the electron lens aperture of the rear-stage electron lens action area. An electron gun device characterized by: