CN1053523C

CN1053523C - Electron gun for color CRT

Info

Publication number: CN1053523C
Application number: CN96105248A
Authority: CN
Inventors: 木村正通; 章纾; 王春娣
Original assignee: Matsushita Color CRT Beijing Co Ltd
Current assignee: Matsushita Color CRT Beijing Co Ltd
Priority date: 1996-05-24
Filing date: 1996-05-24
Publication date: 2000-06-14
Anticipated expiration: 2016-05-24
Also published as: CN1166690A

Abstract

The present invention relates to an electron gun for color CRTs. A decelerating electrode for exerting voltage lower than the voltage of a second electrode is arranged between the second electrode and a third electrode of a pre-lens so that emitted electron beams generate secondary intersection; a single-potential prepositive lens is arranged in the position where a distance from the electron beams of secondary intersection to an axial line is larger than a distance from the electron beams of primary intersection to the axial line. The electron gun of the present invention reduces spherical aberration, enhances the resolution, and focuses the electron beams in a small range without the phenomenon of impacting a top cup.

Description

Electron gun for color CRT

The present invention relates to electron gun for color CRT, specifically, relate to the improvement of lens in the described electron gun.

The resolution that improves colored picture tube is to improve an important topic of colored picture tube quality, and for this reason, forefathers have done many effort.Existing electricity rifle be pre-lens, to intersect directive main focusing lens afterwards with electron gun axis near first electrode (G1) from the electron beam of cathode emission, make the electron beam size minimum that on phosphor screen, becomes herein after the focusing.For most colored picture tubes, its electron gun all adopts three rifle types of emission three electron-beam, in narrow neck, to insert three electron guns, so the space that allows every electron gun to occupy is very little, therefore, the size of lens is restricted, the influence of the spherical aberration that lens produce can't further reduce, clearly, the colored picture tube of three rifle types, this problem is very outstanding.

In order to reduce the spherical aberration of main focusing lens, the special fair 1-38345 of Japan Patent has proposed the scheme that a kind of secondary that is used for three rifle formula projection tubes intersects, and this mode is highly effective in projection tube, and its main points are illustrated among the accompanying drawing 1-3.Accompanying drawing 1 (a) has represented not have main focusing lens ML focused beam state diagram under the above-mentioned dysgenic perfect condition, from the electron beam scioptics central portion that sends from main focusing lens point P1 far away through path B1, the electron beam that near point P3 sends then the outer edge of scioptics through path B3, and focus on jointly on the screen 1, P2 focuses on the screen 1 through the B2 path for the point between Jie P1, the P3 point sends electron beam, so just guaranteed that electron beam is small-sized on the screen 1, shown in S1.Fig. 1 (b) is the situation of general electron gun, and its result is different with Fig. 1 (a), and spherical aberration is outstanding, and electron beam becomes very big on the screen 1, shown in S2.Fig. 1 (c) is the situation of secondary interleaved mode, be to make those be equivalent to the electron beam that sends by the P3 point among Fig. 1 (b) at this moment, become the P3 point that is equivalent among Fig. 1 (c) through its position of sending, secondary intersection back, so just approached the perfect condition among Fig. 1 (a).Pre-lens electron beam intersects situation in the prior art that Fig. 2,3 represents respectively once to intersect and secondary intersects.As mentioned above, the size of lens is very limited in the color cathode ray tube, there is following problem here in effective secondary interleaved scheme in the projection tube: shown in Fig. 3 and 6, the electron beam divergence that intersects through secondary is very big, the tangent tg δ of the ray and the axis angle of cut is as being made as 0.09 when with main lens during apart from 32mm, diameter will reach 5.8mm when electron beam reaches main lens, as main lens top cup aperture 3.5mm is arranged, electron beam part greater than this diameter will be intercepted and captured by the top cup, not only this part electronics does not arrive screen 1, the top cup also will be impaired because of the electron beam bump, distortion, Here it is because the electron beam secondary is dispersed the problem that causes greatly after intersecting, reach its diameter 4.5mm of main lens place and only intersect time a time, line focus may compress into 2.6mm, as Fig. 5.

The purpose of this invention is to provide a kind of improved electron gun structure, not only reduce spherical aberration but also can not cause problem because of the electron beam secondary intersects to disperse.

Technical program of the present invention lies in: between pre-lens second electrode and third electrode (and main lens is linked to be focusing electrode), retarding electrode is set, apply the voltage lower on it, make the cathode emission electron beam intersection once more take place between described retarding electrode and main lens through for the first time intersecting its Outboard Sections than second electrode; Between electron beam secondary crosspoint and main lens, be positioned at the electron beam that intersects through secondary is provided with a unipotential type from the place of the distance of axis greater than the electron beam through once intersecting from the distance of axis supplementary lens.

According to the solution of the present invention, the electron beam that intersects through secondary will be compressed, and both guarantee that whole electrons emitted bundles focus on enough little scope, thereby high resolution is arranged, and can not clash into the result of top cup again.

Fig. 1 (a) is that expression electron gun electron beam focuses on and do not have a dysgenic perfect condition figure of spherical aberration.

1 (b) is the actual electron gun electron beam focus state figure of explanation.

1 (c) is that explanation improves the figure that electron beam focuses on situation.

Fig. 2 is the electron beam trace schematic diagram that once intersects.

Fig. 3 is the electron beam trace schematic diagram that has secondary to intersect.

Fig. 4 is the electron beam trace figure that retarding electrode is not set.

Fig. 5 is electron beam trace figure in the electron beam intersection electron gun once.

Fig. 6 be the embodiment of the invention oneself the pre-lens area electron beam trace figure of retarding electrode is set.

Fig. 7 is electron beam trace figure in the embodiment of the invention electron gun.

Below will narrate embodiments of the invention.

Fig. 6 is one embodiment of the present of invention electron beam trace figure, its transverse axis is the electron gun axial location, the longitudinal axis is an off-axis position, 2 is pre-lens, wherein 21,22,23 be respectively first, second and third electrode, the common third electrode formation focusing electrode that in fact links to each other in the structure, the 24th, retarding electrode with main focusing lens, be added between second, third electrode, apply the voltage that is lower than second electrode on it.Each line 3 of horizontal direction is electron beam traces among the figure, and each line 4 that vertically distributes is equipotential lines of Electrode Field, owing to be provided with retarding electrode, electron beam forms secondary and intersects.Fig. 7 is electron beam trace figure in the embodiment of the invention electron gun, and 5 is supplementary lens in this example, is the structure member that the present invention sets up, and it is with main lens focusing electrode in the prior art separately, adds a central electrode 51 and forms a kind of unipotential lens structure.Supplementary lens 5 is arranged on the position between electron beam secondary crosspoint and the main lens, the electron beam that secondary intersects on this position is bigger from the distance of axis than the electron beam that intersects once from the distance of axis, promptly in Fig. 3 between B1 line and B3 line intersection point A and the main lens.Electron beam is compressed by supplementary lens, arrive the 5.8mm of main lens its diameter of place (in this example) when not establishing supplementary lens and reduce to approximate existing level, reached purpose of the present invention, both reduced spherical aberration, improved resolution, have the less beam diameter that reaches main lens again, avoided electron beam to be pushed up the phenomenon that cup is intercepted and captured fully.

The central electrode 51 of supplementary lens 5 and retarding electrode 24 voltages all can be set at 0 in this example in addition.Aperture by suitable this supplementary lens of selection and gap make described two electrodes reach voltage and are set at 0, just can finish the electron beam design optimization, the power supply of electron gun is simplified greatly, promptly can increase power supply in addition.

Claims

1. electron gun for color CRT, between second electrode (22) of pre-lens (2) and third electrode (23), retarding electrode (24) is set, on described retarding electrode, apply than the low voltage of described second electrode, make cathode emission its Outboard Sections of electron beam between described retarding electrode and main lens, take place to intersect once more, it is characterized in that between electron beam secondary crosspoint and main lens, being positioned at the electron beam that intersects through secondary is provided with a unipotential type from the place of the distance of axis greater than the electron beam through once intersecting from the distance of axis supplementary lens (5) through intersecting for the first time.

2. electron gun for color CRT according to claim 1 is characterized in that the central electrode (51) of described supplementary lens (5) and described retarding electrode (24) voltage all can be set at 0.