JPS6310442A - Electron gun device - Google Patents

Abstract

PURPOSE:To avoid the generation of an electron lens action unnecessary to a cathode prefocus electron lens, by making grids composing the cathode prefocus electron lens parallel with respect to each cathode. CONSTITUTION:An end plate of a second grid G2 in which electron beam transmitting apertures h2 (h2R, h2G, and h2B) are bored, is faced to each first grid G1 with the same separation and arranged in parallel with plain surfaces at each aperture h2. Also in a third grid G3, the center part of the pre-stage side end plate 31, where the central beam transmitting aperture h31G is bored, is pressed by machining to make projection part inserting into the cylindrical part SG2 of the second grid, and each top plate of the both cylindrical parts SG2 and SG3 are faced in parallel with plain surfaces. Therefore, improper troubles such as making curved equi-potential surfaces to produce a lens action can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron gun device suitable for use in cathode ray tubes such as color television picture tubes.

[Summary of the invention]

The present invention provides an electron gun having a plurality of cathodes, in which a center electron beam is generated by the center cathode;
The cross-over positions of the side electron beams caused by the side cathodes are mutually shifted to reduce the difference in focusing voltage for each electron beam and to obtain a good focus state for each beam. The grid that makes up the prefocus electronic lens,
For each cathode, the cathode
This prevents unnecessary electronic lens effects from occurring in the prefocus electronic lens.

[Conventional technology]

As an electron gun device in a cathode ray tube such as a color television picture tube, for example, as shown in FIG. ta%
A common second grid 02%, a third grid G3, a fourth grid G→, a fifth grid G5 are arranged, and a cathode K (KR, Ka
, KB) and the first to third grids 61 to G] form a cathode prefocus electron lens;
! 5th grid G]~G5, high voltage (anode voltage) VH is applied to the third and fifth grids G3 and G5, and the fourth
There is a so-called double-beam single electron gun device in which a focus voltage VF sufficiently lower than this is applied to the grid G4 to form a unipotential type main electron lens L.

In this case, the electron beams from each cathode KR, KO, and KB are arranged so that they intersect approximately at the center of the main electron lens at a position that satisfies the Fraunhofer condition, that is, provides a condition where coma aberration becomes zero. A convergence means C constituted by, for example, an electrostatic deflection plate is provided downstream of the fifth grid G5, thereby converging the electron beams BR from each of the cathodes KR, KO and KB.
.

Although not shown, BG and BB are made to converge (concentrate) on the fluorescent surface of the cathode ray tube.

In an electron gun device with such a configuration, by making the main electron lens common for each electron beam, the lens diameter within the limited neck diameter of the cathode ray tube can be increased, and an electron gun with small aberrations can be created. Can be configured.

However, in such a configuration, the center beam BG that enters the main electron lens L on its axis, and the side beams BR and BB that enter the main electron lens L obliquely,
The focus (convergence) voltage for forming these images well at the same position on the fluorescent surface, so-called just focusing, is different. In other words, if the side beams BR and BB are just focused using a common focus voltage VF, the center beam B will be focused behind the fluorescent surface, which is called underfocus, and the center beam BG will be focused behind the fluorescent surface.
If you just focus the side beams BR and B
B results in overfocus. In order to match the focus voltages for each of these beams, as shown in FIG.
G may be set back from the cathodes KR and KB on both sides to make the distance from the main electron lens L larger than the cathodes KR and KB on both sides. In this case, since the grids after the second grid G2 are common, in order to make the characteristics of the cathode prefocus electron lens constant for each beam, the first grid with respect to the central cathode KG of the second grid G2 is The part facing Gta is made to protrude so that the distance from the first grid Gto is approximately the same as the distance from the first grids GIR and GIB with respect to the other cathodes KR and KB. However, in this case, as shown by the thin line a in FIG. 4, the equipotential surface is curved only with respect to the center beam BG, which produces a focusing lens effect. In other words, an extra lens effect is added to the cathode pre-focusing electron lens only for the center beam, which causes a shift in the crossover point of this beam, causing a deviation in the actual object point position of the entire electron lens system with respect to this beam. If this occurs, the spot may be distorted. In order to avoid such inconvenience, the surface of the third grid G3 facing the second grid G2 is bent parallel to the surface of the second grid G2, and both grids are bent so that a parallel electric field is generated between them. It is conceivable to narrow the distance between G2 and 03, but the third grid G3 has a high voltage V.

is applied, problems such as generation of discharge between the second and third grids arise.

[Problem that the invention seeks to solve]

In the present invention, when the position of the center cathode is moved back from the positions of the cathodes on both sides in a direction in which electrons can be returned from the main electron lens, the electric field is created such that a special lens effect occurs only for the center beam from this position. This solves the problem of curvature.

[Means for solving problems]

The present invention uses an electron gun configuration based on a special electrode configuration and skillfully utilizes its characteristics to solve the above-mentioned problems. An electron gun with this special electrode configuration is disclosed in Japanese Patent Laid-Open Publication No. 19755/1983. First, this will be explained.

According to the electron gun configuration explained in FIG. 3, aberrations can be improved by increasing the aperture of the main electron lens, but even with this configuration, if the beam current becomes large, , the disadvantage is that the spherical aberration becomes large and the beam spot becomes blooming.

Furthermore, considering the unipotential type electron lens with reference to FIG. 5, in this unipotential type electron lens diameter, the third grid G3 and the fifth grid G3 are
A high voltage VA is applied to s, and a focus voltage VF is applied to the fourth grid G4, thereby forming a main electron lens.

Normally, in this type of unipotential electron lens, the diameters of electrodes G3 and G5 to which high voltage ■^ is applied,
The diameter of the electrode G4 to which the focus voltage VF is applied is selected to be approximately the same diameter, or the diameter of the high voltage electrodes G3 and G5 is made small on the side facing the single focus pole G4 as shown in FIG. This is done to shield the path from disturbance of the electric field from the outside, but in any case, when the diameter of the focus electrode G4 is D and the length is β, the value of - is 0.5 to 2. .0 range.

In a unipotential type electron lens in which the electrodes 63 to G5 are selected to have the same diameter as shown in FIG. The result will be as shown in the figure.

In this figure, the horizontal axis represents the ratio of the focal length f to the lens aperture D, and the vertical axis represents the spherical aberration coefficient Cs. As is clear from this, if - is γ and 1 = 1, then the larger γ is for the same ζ value, the smaller the spherical aberration coefficient C5 becomes. In practice, the lens aperture is limited by the neck diameter of the cathode ray tube, so that at a given focal length f, the longer the length l of the electrode G4, the smaller the spherical aberration. However, on the other hand, γ=2.0
In the above case, the aberration phenomenon is saturated, so in order to achieve smaller aberrations, it is desirable to reduce the focal length f at the same γ.However, generally speaking, if the length l of the electrode G4, that is, γ, is increased, the focal length It is only possible to reduce the distance fif.This will be explained with reference to FIG.

Now, in the unipotential type electron lens, this is defined as a lens (Lensl) formed between the third grid G3 and the fourth grid 04, and a lens (Lens2) formed between the fourth grid G4 and the fifth grid 05. Let's consider this separately. The object focal lengths of each lens (Lens 1) and (Lens 2) are set to fl and 2, the image focal lengths are set to 111 and f2', and the object focal lengths are set to F and F.
2. Set the image focal points to F1' and F21. Distance F1 from the image focus F1' of Lens 1 to the object focus of Lens 2
When 'F2=C', the combined focal length f' of both lenses is given by:

Generally, in an electron lens system, since C is 0, f'>0. As mentioned above, the length of the electrode G4 is increased to reduce spherical aberration! , therefore Lens 1 and Le
If the distance between ns 2 is made large, IcI becomes small.

Therefore, according to formula +11, 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 r becomes larger, the imaging state changes. Therefore, when 2 is increased, f is constant,
Ie to keep this small! As is clear from Equation 11, the image focal length f1' of LellJLIJHUν2
(or) it is required to reduce f2'.

However, the distance Q between the rear-stage lens Lens 2 and the fluorescent surface S of the cathode ray tube should be such that its focal length f2' is small due to the relationship with the horizontal and vertical deflection means arranged at the base of the funnel section of the cathode ray tube. There are restrictions on Therefore,
It is desirable to reduce the focal length f,' of the front-stage lens I, ens 1. And this focal path a
As a method of reducing rt', the anode voltage ⑾ applied to the third grid G3 and the focus voltage VF applied to the fourth grid G4 are applied to the third grid G3 and the fifth grid G.
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 (11) of the front lens system without causing such drawbacks, as shown in FIG.
The electrode, for example, the fourth grid G4, constitutes a deceleration-type front-stage electron lens (Lensl), and the second electrode (fourth grid 04) and the third electrode, for example, the fifth grid G5, constitute an acceleration-type rear-stage electron lens. Electronic lens (L
ens2), but in this configuration, the length l of the electrode G4 is particularly set so that the front-stage electron lens (Lensl) and the rear-stage electron lens (Lens2) are separated from each other. Further, the lens aperture of the front-stage electronic lens (Lensl) is set to be smaller than the lens aperture of the rear-stage electronic lens (Lens2). That is, the diameter D1 of each opposing end of the third grid G3 and the fourth grid G4 is made smaller than the diameter D2 of each opposing end of the fourth grid G4 and the fifth grid G5,
Further, as described above, in order to separate the electron lens action areas of the front and rear lenses from each other, the electric field must penetrate into the fourth grid G4 by the third grid G3 and the fifth grid G5.

Since the opening diameters D1 and D2 of the portions facing the third and fifth grids G3 and G5 are approximately equal, the length 11 of the small diameter portion and the length i12 of the large diameter portion are β, >Dt, respectively. 12
>D2, and therefore the length l of the fourth grid G4 is selected to be l>D1+D2.

Now, FIG. 10 shows an optical system shown by a solid line when the lens diameters of the front and rear stages are equal (!p = 1).
At this time, it is assumed that this lens system forms an image on the fluorescent surface S of the cathode ray tube. In Figure 0, Po is the object point, that is, the cathode image at the crossover point of each beam by the cathode-prefocus electron lens. So, Pl is the virtual image due to the front lens (Lensl),
In other words, it indicates the object point of the rear lens (Lens2), and P2
shows the image of the lens (Lens2) formed on the fluorescent surface S.

In this state, when the aperture D1 of the front lens (Lens 1) is made smaller and its focal length r1' is made smaller, the fluorescent surface S is
In order for the image to be formed on the top, the front lens (L
ensl) and the position of the object point Pa are moved by a required distance as shown by the broken line. Considering optically how to reduce the diameter of the lens (Lensl), the lens Lens 1
Since the image magnification of Lens 2 is constant, the image formation relationship of Lens 1 is reduced with 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 rate. Specifically, the aperture D1 of the front-stage lens Lens 1 is made smaller, the distance between both lenses Lens 1 and Lens 2 is increased, and the position of the cathode is shifted. Now, the magnification M of the entire lens diameter is selected as M=12, and the lens
When the distance Q from Lens 2 to the image point P2 is set to Q=50XD2,
The relationship between the aperture ratio k of both lenses and the distance to 0 is shown by the solid line and broken line in FIG. in this case,! & stage lens (Lens2)
The aperture D2 is 6 mm, and in FIG. 11, the σ axis is expressed using the aperture D2 as a unit, that is, D2=1.

Figure 12 shows the calculation results of the relationship between the coefficient Cs and the magnification M of the entire lens (M=-8).
) to (13) are the aperture ratios of both lenses, respectively, and k =
Each calculation result when selecting 1.0.0.8.0.6.0.4 is shown. Note that the numerical values shown in parentheses for each of the curves (10) to (13) indicate the value of the distance ML in units of D2. In FIG. 12, the vertical axis is expressed as the ratio of coefficients C3 and D2.

FIG. 13 shows curves of spherical aberration coefficients similar to those in FIG. 12, but in this case, M=-10 and Q=50×D2, and curves (20) to (24) each have k=1.0. 0.
This is the case when it is set to 8°0.6.0.4.0.3.

As is clear from FIGS. 12 and 13, the smaller the aperture ratio k of the front and rear lens diameters, that is, the smaller the aperture D1 of the front lens diameter is compared to the aperture D2 of the rear lens diameter. , it can be seen that aberrations are improved.

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 of the two, a lens with small spherical aberration can be constructed. The total spherical aberration C3 of the composite lens system consisting of lenses Lens 1 and Lens 2 formed by the lens action area is the spherical aberration coefficient of these two lenses Lens 1 and Lens 2 as C5
1, C52, it is given by the following equation.

・・・・・・・・・(2) As a result, the aberration amount Δr can be expressed as follows.

(3) Here, k is the ratio of the lens aperture D□ and D2 in the front and rear stages, and Mz and M2 are the voltages applied to each of the front and rear stages and the third electrode.

From this equation (3), in order to effectively reduce the overall amount of aberration, the front lens aperture D1 and the rear lens aperture D2 must be
It can be seen that by decreasing the ratio k.

In this way, two independent lenses Lens l, L
The main electron lens formed by the synthesis of ens2 is
Spherical aberration can be improved by selecting a small aperture ratio k, but this lens has large values for astigmatism and curvature of field. Therefore, such a composite lens system can be
As explained in the figure, it is used as a common main electron lens for a plurality of beams, for example, three beams, and the three Beams BR on both sides are configured so that the book beams BR, BG, and BB intersect.
and the BB spot size becomes worse.

Therefore, the electron gun device disclosed in the above-mentioned Japanese Patent Application Laid-open No. 19755-1983 was proposed as a device that can obtain a good spot even with a side beam. In this electron gun device, as described above, there is a front-stage electron lens Lensl, that is, a front-stage electron lens action area, and a rear-stage electron lens Lensl separated from this.
2. That is, the main electron lens is constituted by the latter electron lens action area, and in particular, the front electron lens is provided individually and individually corresponding to each beam from each cathode,
The rear-stage electron lens is composed of an electron lens with small astigmatism and field curvature, and this is provided in common for each beam, and the aperture of each front-stage lens is selected to be smaller than the rear-stage lens aperture. be.

FIG. 2 shows an electron gun with such a configuration. In this case, each cathode K R1K G and KB corresponding to each color
and the first grid GIR, GIR,
GIG and GIB are provided individually. In common to these, the second grid G2 to the sixth grid G6 are installed in the subsequent stage.
will be established. The third grid G] has a front side end plate (31) facing the second grid G2 and a rear stage I11 end face slope (32) facing the fourth grid G4. An end plate (4
1).

Each end plate (31) of the first grid GIR, GIG, GiB, the second grid G2, and the third grid G3
32), the end plate (41) of the fourth grid G4 has electron beam transmission holes R1 for electron beams BR+ BG, BB taken out from each cathode KR, Ka, KB, respectively.
hia, hIB+ h2R+ h201h2B
, h31R+ hxla +11318 , h3R+
h3G+ h3B+ )14R+ h4G+
h4B are drilled so as to face each other. In such a configuration, for example, the fourth grid G4 and the sixth grid G4
A high voltage, e.g., 28 kV, is applied to G3 and G5, and a low voltage, e.g., 8 kV, corresponding to about 25 to 30% of this voltage, is applied to the third and fifth grids G3 and G5. In addition, each first grid G IR, G IG +G
1B has O~several IQV, 2nd grid G2 has 600
~700 μ is applied to each cathode K (KR, KG.

Ka) and each first grind G1CG1R, Gia,
Gts) and the third grid G3 constitute a cathode prefocus electron lens, and the rear end plate (32) of the third grid G3 and the end plate (41) of the fourth grid G
) between each electron beam transmission hole of the main electron lens, a small diameter front electron lens LenstPL+LenstB, L
ensIB is formed, and separated from this, a large-diameter common rear-stage electron lens Lens 2 of the main electron lens is formed by the fourth to sixth grids 04 to G6.

In this case, the axis of each cathode, each electron beam transmission hole hL
R+ )lIG+ htB+ h2R+ F'
20+ h2B+ fi31R+h 3i Q +
h 31 El is placed on the axis OG that coincides with the central axis of the electron gun, and on the axis 0R100 that intersects this at a required angle, but the front lens Len
For s1R+ Lensla + LenstB, that is, electron beam transmission hole h 3R+ h 3G+
h 3B, h 4R1 h4G + h4B are arranged on mutually parallel axes to simplify manufacturing and improve accuracy. In this case, the electron beams BG on both sides of these lenses LenstRI LensH) , BB are to be incident obliquely, so in this case, the positions of these lenses are set so that the Fraunhofer condition is satisfied.

With the electron gun having such a configuration, aberrations can be improved as is clear from the above, but in the electron gun with this configuration, the third grid G3 facing the second grid G2 has a focus potential, That is, high pressure V, 25 to 3
It has the characteristic that a low voltage corresponding to about 0% is applied.

Therefore, in the present invention, such an electron gun configuration is adopted and its characteristics are utilized to avoid the above-described curvature of the electric field when the central cathode is retracted.

That is, in the present invention, as shown in FIG. 1, a plurality of cathodes K (KR, KO, KB) are provided, and the main electron lens is provided individually on each path of the electron beam by each cathode. The structure consists of an electron lens action area, and a rear electron lens action area that is separated from these preceding electron lens action areas and is provided in common on the path of each beam. The aperture of the electron lens is selected to be smaller than the diameter of the electron lens Lens 20 in the action area of the subsequent electron lens, and the placement position of each cathode is further adjusted to the position of the central cathode KaO main electron lens and the subsequent electron lens Lens.
Lens 2 is selected so that the distance from the latter electron lens Lens 2 is greater than the distance from the rear electron lens Lens 2 of both outer cathodes KR and KB. Then, each cathode, that is, each cathode and grid constituting a cathode prefocus electron lens for each electron beam, is formed such that the facing portions of these cathodes and each grid are parallel and flat.

[Effect]

According to the above configuration, the cathode and
By making the mutually opposing surfaces constituting the prefocus electron lens parallel and flat, it is possible to avoid unnecessary lens effects that are different from those of other beams with respect to each beam path.

〔Example〕

An example of the apparatus of the present invention will be explained in more detail with reference to FIG. This example corresponds to the electron gun configuration explained in FIG. 2, and in FIG. 1, parts corresponding to those in FIG. compares the cathode Ka in the center with the cathodes KR and KB on both sides, and compares the cathode Ka in the center with the cathodes KR and KB on both sides.
Place it at a greater distance from ens 2, that is, move it backwards. Then, in response to this, the first grid GIG facing this cathode KG is also moved backward, and each cathode K (KR, KO, KB) and the first grid GL
(Gza, G Engineering G, Gxs) are selected almost constant.

In particular, each electron beam transmission hole h of the second grid G2
1 (hIR+hIG+hts) are arranged to face each first grid G1 at approximately the same distance and with parallel flat surfaces at the perforated portion of each through hole h1. Therefore, the central part of the end plate of the second grid G2, where the electron beam transmission hole h20 is formed, is made into a cylinder with a diameter larger than that of the first grid G The shaped part SG2 is squeezed so that the top surface of the cylindrical part SG2 faces the first grid Gia in parallel.

Also, regarding the third grid G3, its front end plate (3
In 1), the center part where the central electron beam transmission hole h3-10 is bored is made to protrude toward the second grid G2 side so as to enter, for example, into the cylindrical part SG2 of the second grid. The cylindrical portion 5C13 is squeezed out so that the top plates of the cylindrical portions SG2 and SG3 are parallel and flat and face each other.

In this way, for each cathode K, the intervals between the first grid G1%, the second grid G2, and the third grid 03 are made uniform, and the characteristics of each cathode and prefocus lens for each beam are made uniform. At the same time,
As for the center beam BG, as shown by the thin line a in FIG. 1, the solenoid potential surface between the second and third grids G2 and 03 can be parallelized and flattened. Inconveniences such as curvature of the potential surface and addition of lens action are avoided.

In this case, the front side end plate (31
) Since the cylindrical part SG3 is provided in the center of the grid G3, the distance to the rear end plate (32) is larger here than in other parts, but both end plates (31) and (32) are of the same grid G3. Since both parts are at the same potential, there is no non-uniformity in the electric field that would cause unnecessary lensing for each beam.

In the above-described example, the lens subsequent to the main electron lens has a unipotential structure, but it can be modified to various structures such as an extended electric field type pipotential structure.

〔Effect of the invention〕

According to the present invention, the central cathode is retracted to match the focus voltages of the electron beams from each cathode, and a special electron gun configuration in which the third grid has a low voltage is used. By the cathode
The spacing between each electrode that makes up the prefocus electron lens is
Since the electric fields involved in each beam are made uniform by allowing the electron beams to approach each other, the generation of unnecessary lenses can be avoided, and an electron gun with excellent characteristics can be constructed.

[Brief explanation of the drawing]

FIG. 1 is an electrode layout configuration diagram of an example of an electron gun device according to the present invention, FIG. 2 is an electrode layout configuration diagram of an electron gun device used for explanation thereof, and FIGS. 3 and 4 are electrode layout diagrams of a conventional device. , 5th
Figures 6, 8, and 9 are configuration diagrams of electronic lenses, Figure 7 is a curve diagram showing the relationship between the ratio of focal length and lens aperture, and the spherical aberration coefficient, and Figure 10 is a diagram of the electron lens. FIG. 11 is a curve diagram showing the relationship between the aperture ratio of the front and rear lenses, the distance between them, and the object distance, and FIGS. 12 and 13 are curve diagrams showing spherical aberration, respectively. KR, KO and KB are cathodes, GIR, G and G
as is the first grid, G2 to CG are the second to sixth grids, LsnsIH, Lensl (3 and 5nsts are the front lenses, and Lens 2 is the rear lens.

Claims (1)

[Scope of Claims] (a) A plurality of cathodes are provided; (b) a main electron lens includes a front-stage electron lens action area individually provided on each path of the electron beam by each of the cathodes; (c) the electron lens aperture of the electron lens system due to the front stage working area is separated from the electron lens working area and is provided in common on the path of the plurality of beams; (d) The position of each of the cathodes is selected such that the distance from the central cathode to the rear electron lens is smaller than the rear electron lens of both outer cathodes. (e) Each cathode and grid constituting the cathode prefocus electron lens for each of the above cathodes are selected such that the mutually opposing parts of these cathodes and grids are parallel and flat surfaces. An electron gun device characterized in that it is formed as follows.