US3548234A - Color cathode ray tube electrode support arrangement - Google Patents

Description

Dec. 15, 1970 SUSUMU og ETAL 3,548,234

COLOR CATHODE RAY TUBE ELECTRODE SUPPORT ARRANGEMENT Filed June 13, 2 Sheets-Shem l SUSUMU YOSHIDA AKIO OHGOSHI SENRI MIYAOKA YOSHIHARU KATAGIRI ATTORNE Y United States Patent U.S. (Tl. 31382 3 Claims ABSTRACT OF THE DISCLOSURE A color picture tube or other cathode ray tube in which a plurality of electron beams eminating from one or more cathodes are made to converge substantially at the optical center of an electrostatic focusing lens which focuses the beams on an electron receiving screen. The grids forming the electron gun are supported by an insulating mem her. The grid in which the electrostatic focusing lens is formed has a diameter greater than the other grids or electrodes in order to permit the focusing lens to have as fiat opposing surfaces as possible, that is, surfaces with a maximum radius. The outer diameter of the support member for the grids is essentially equal to the inner diameter of the neck of the cathode ray tube. This is accomplished by forming the insulating support in two parts with the grid forming the focusing lens extending between the two parts and being supported by each of the insulating members.

This application is a continuation-in-part application of our copending application filed I an. 12, 1968, entitled Cathode Ray Tube and which bears US. Pat. No. 3,448,316.

This invention generally relates to cathode ray tubes and is particularly directed to improvements in color cathode ray tubes of the type in which a single electron gun is provided for emitting a plurality of electron beams in order to produce a color picture such for example as in color television receivers.

Existing color picture tubes are usually of the multi-gun type and include three independent electron guns emitting respective electron beams which are modulated by corresponding color signals and acted upon by a grid system so as to be focused on a collector or electron receiving screen which may be simply a phosphor or luminescence screen or a phosphorus screen with a perforated electrode or shadow mask in front thereof. The three electron guns have to be aligned with respect to each other so that the emitted electron beams converge at the electron receiving screen. Such color picture tubes of the multi-gun type are disadvantageous in that it is difficult to obtain and maintain the precise alignment of the three electron guns required for the convergence of their beams on the electron receiving screen and any misconvergence of the beams causes deterioration of the quality and resolution of the color picture that results.

In an attempt to avoid the above-mentioned disadvantages and limitations of the existing color picture tubes of the multi-gun type, it has been proposed to provide a color picture tube of the single gun plural beam type in which a single electron gun emits three beams from either three respective cathodes or a single cathode and the three electron beams are passed through a lens like focusing system so as to converge at the electron receiving screen. However, in the tubes of the single gun plural beam type heretofore proposed, no more than one of the electron beams passes through the lens like focusing system at the 3,548,234 Patented Dec. 15, 1970 optical axis of the latter and the beams that pass through the focusing system at a distance from the optical axis are subject to coma and spherical aberration. By reason of such coma and spherical aberration and the consequent deterioration of the quality of the color picture that results, color picture tubes of the single gun plural beam type have not enjoyed any wide-spread use.

In my copending patent application filed J an. 12, 1968, and bearing US. Pat. No. 3,448,316 entitled Cathode Ray Tube, there is described a cathode ray tube adapted for use in a color television receiver and which is provided with a single electron gun. This gun includes a cathode structure that emits electrons which are formed into a plurality of electron beams and such beams are made to converge substantially by the optical center of a lens like electrostatic focusing lens which is common to all the beams and focuses the beams on the electron receiving screen whereby the introduction of spherical aberrations is diminished.

In cases where the electron beams are emitted parallel to each other, the convergence of the beams at the optical center of the lens like focusing means is effected by an auxiliary electrostatic lens located between the grid structure which forms the electron beams and the focusing lens. When it is desired that the beams focused on the electron receiving screen be converged at a common point on the screen the beams which diverge from the focusing lens are acted upon by either electrostatic or magnetic deflection means located between the focusing lens and the screen.

In most prior art cathode ray tubes which utilize an electron gun having a plurality of grids, the grids all generally have the same diameter. The electron gun is positioned in the neck of the cathode ray tube and the various grids and electrodes are held in position spaced from each other by an elongated insulating support. This insulating support is made in one piece and is positioned between the grids and the interior surface of the neck of the cathode ray tube. In such prior art cathode ray tubes, the diameter of the respective grids forming the electron gun are limited to a diameter less than the interior diameter of the insulating support member.

The disadvantage with such prior art type of electron guns is that the diameter of the individual grids limits the size of the electrostatic focusing lens which can be formed. It is of course desirable that this focusing lens have as flat a surface as possible, that is, that the surfaces of the electrostatic lens be formed with the maximum radius. The smaller the radius of the electrostatic focusing lens the greater the error that can be introduced due to various spherical aberrations. The radius of the electrostatic focusing lens, however, is limited by the diameter of the grid within which it is formed.

In view of the foregoing, it is the primary object of this invention to provide a cathode ray tube of the single gun plural beam type which is free of the abovementioned disadvantages and which is particularly suited to the formation of an electrostatic focusing lens having opposed surfaces with a large radius.

Another object of this invention is to provide a cathode ray tube of the type in which the electron gun has a plurality of grids and in which the insulating support member for the grids is formed in at least two sections with the two sections being spaced from each other to permit insertion therebetween of the grid within which the electron focusing lens is formed.

In accordance with this invention a cathode ray tube adapted for use as the picture tube in a color television receiver is provided with an electron gun which includes a cathode structure that emits electrons which are formed by a grid structure into a plurality of electron beams. These beams are made to converge substantially at the optical center of a lens like electrostatic focusing lens which is common to all of the beams and focuses the beams on the electron receiving screen. The insulating support for the various grids is made in two sections and the two sections are spaced from each other to permit insertion therebetween of the grid within which the electrostatic focusing lens is formed. This particular grid accordingly has a diameter which can be substantially equal to the inner diameter of the neck of the cathode ray tube. In this manner the electrostatic focusing lens can be formed with opposed surfaces which have an exceptionally large radius to present a relatively flat surface and thereby diminish spherical aberrations.

The above and further objects, features and advantages of the present invention will appear from the following detailed description of a preferred embodiment of the invention which is to be read in conjunction with the accompanying drawings in which:

FIG. 1 is a diagrammatic view illustrating the optical equivalent of a single gun plural beam system in which the beams are converged to substantially the optical center of an electrostatic focusing lens;

FIG. 2 is a schematic longitudinal sectional view of an electron gun illustrating the manner in which the various grids forming the electron gun are supported in a conventional manner by a single insulating support member; and

FIG. 3 is a schematic longitudinal sectional view of an electron gun in accordance with the present invention in which the various grids forming the electron gun are supported by at least two spaced insulating support members between which are positioned the grid within which the electrostatic focusing lens is formed.

Referring now to the figures there is illustrated in FIG. 1 the optical equivalent of a cathode ray tube having a single electron gun that generates a plurality of electron beams that are converged to substantially the optical center of a focusing lens. The single electron gun A includes equivalent beam generating sources K K and K which are located on a straight line in a plane substantially perpendicular to the axis of the electron gun and spaced apart from each other by a distance d These beam generating sources K K and K have been converged to an area of minimum crosssection by means not illustrated such that the area of minimum cross-section of each of the beams is at the position designated K K and K The beam generating sources emit three electron beams B B and B respectively, which are refracted by means of a common auxiliary lens L so as to be converged substantially at the optical center sequently the beams B and B which diverge from the optical axis and from the beam B lying on such axis are deflected toward the center beam B by means of convergence deflectors F and F provided between the electron receiving screen S and the main lens L and spaced from the latter by a distance 1 so that the three beam spots B B and B on the screen are converged or superimposed on each other.

With the arrangements shown in FIG. 1 therefor very small beam spots can be obtained since all three beams B B and B pass through the center of the main focusing lens L and thus the focus beams spots are prevented from being blurred due to various spherical aberrations. Consequently a picture with a high resolution can be produced. Furthermore, utilization of the deflectors F and F advantageously facilitates the dynamic convergence correction with respect to the three beams.

It is to be understood that although FIG. 1 illustrates the beam generating sources K K and K as lying in a straight line and the electron beams being refracted by means of a common auxiliary lens L so as to be converged substantially at the optical center of the main focusing lens L the same thing can be accomplished by arranging the beam generating sources K K and K on a arcuate surface. In this respect FIG. 1 is merely illustrative and not in any way meant to limit the scope of this invention.

In FIG. 2 there is illustrated an electron gun A in which the various grids forming the electron gun are supported in a conventional manner. A cathode K constitutes the electron beam generating source. The first control grid G comprises three grid members which are supported in close opposing relationship to the electron emitting end surface of cathode K. The three grid members have three small apertures arranged on a straight line. The common grid G also has three apertures formed therein in opposing adjacent relationship to the apertures in grid G Arranged in order following the grid G in the direction away from control grid G are successive open end tubular grids or electrodes G G and G The several electrodes 6;, G and G as Well as the grids G G and the cathode K are all assembled together in the illustrated relationship by means of a suitable support 10 of insulating material. The support 10 is positioned adjacent the neck 11 of the cathode ray tube. The electrodes and the grids are attached to the support 10- by means of clips 12 which are attached to or formed integrally with the support 10. As illustrated in FIG. 2, the various grids and electrodes have essentially the same diameter with the maximum diameter being limited by the inner diameter of the support 10. The focusing lens L is formed in the electrode G The height of the focusing lens L is limited by the maximum diameter of the electrode 6.; which in turn is limited by the inner diameter of the support 10.

It is desirable that the reproduced image have as high a resolution as possible. One of the ways of accomplishing this is to minimize as much as possible the optical aberrations. Ideally, the focusing lens L should have parallel surfaces in order to eliminate optical aberrations. This of course is impossible and it is, therefore, desired that the opposed surfaces of the focusing lens L have as flat a surface as possible, that is, a surface having a maximum radius. The radius of the opposed surfaces of the focusing lens L are, however, limited by the diameter of the electrode G The manner in which this is accomplished in the present invention is illustrated in FIG. 3. The same parts in FIG. 3 bear the same reference numerals as in FIG. 2. The major difference between the electron gun in FIG. 3 and the electron gun in FIG. 2 is that the electrode G; has been increased in diameter such that it has a diameter substantially equal to the inner diameter of the neck 11 of the cathode ray tube. This is accomplished by forming the support 10 in two sections 13 and 14 with the supports 13 and 14 spaced apart a suificient distance to allow the electrode 6.; to extend therebetween.

The electrode G is formed with end portions 15 and 16 which fit over the end portions of the grid G and the electrode G The end portions 15 and 16 of electrode G are formed with clips or pins 17 for supporting the electrode G in the supports 13 and 14.

As can be seen from an observation of FIGS. 2 and 3, the embodiment illustrated in FIG. 3 permits the grid 6,; to be made much larger in diameter. This accordingly permits the focusing lens L to also be increased along its longitudinal axis. This accordingly permits the opposed surfaces of the focusing lens L to have a much greater radius than the focusing lens L illustrated in FIG. 2. This results in less optical aberrations for the electron beams passing substantially through the center of the focusing lens.

In operating the electron gun illustrated in FIGS. 2

and 3, appropriate voltages are applied to the grids G and G and the electrodes G G and G In this manner an electron lens field is established between grid G and the end electrode G which corresponds to the auxiliary lens L of FIG. 1. In addition, an electron focusing lens field corresponding to the main focusing lens L of FIG. 1 is formed at the axial center of electrode 6,, by the electrodes G G and G In order to cause convergence of the beams B and B which emerge from electrode G along divergent paths, the electron gun of FIGS. 2 and 3 have deflecting means F thus the three beams B B and B emanating from the cathode K are made to pass through grid G and are modulated with three different signals applied between the cathode K and the grid members in grid G The beams B B and B pass through the common auxiliary lens L which is formed mainly by the grid G and the electrode G and cross each other at substantially the center of the main focusing lens L which is constituted mainly by the electrodes G G and G Then the beams B B and B pass through the deflecting means F after leaving the electrode G Accordingly the beams B and B which emerge from the focusing lens L along divergent paths are deflected so that three beams B B and B are made to converge at a point on the electron receiving screen.

It accordingly can be seen that with the present invention the grid G in which the focusing lens L is formed can be made much larger in diameter than with prior art electron guns. This permits the focusing lens L to be increased in height which accordingly permits the opposed surfaces to have a much larger radius. In this manner the amount of optical aberrations is substantially reduced.

In the foregoing description the electron gun embodying this invention has been described as being applied specifically to colored picture tubes in which a single gun is employed to produce three electron beams which are intensity modulated with the usual red, green, and blue color signals. However, it is obvious that an electron gun in accordance with this invention can be used in any other cathode ray tube requiring a plurality of beams which are to be focused at a common spot or at separated spots on an electron receiving screen.

Although illustrative embodiments of electron guns according to this invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments and that various changes and modifications may be made therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.

What is claimed is:

1. A cathode ray tube having a face plate with an electron receiving screen thereon and a neck portion opening in the direction toward said screen, an electron gun disposed within said neck portion and comprising beam generating means for producing a plurality of electron beams originating in a plane including the longitudinal axis of the tube and focusing lens means for focusing said beams on said screen, said focusing lens means including first, second and third tubular electrodes arranged axially with said first and third electrodes spaced from each other and said second electrode interposed between said first and third electrodes and having at least a central portion that fits closely within said neck portion and has a diameter substantially greater than that of said first and third electrodes, and mounting means for locating said gun within said neck portion of the tube, said mounting means comprising axially spaced first and second sets of longitudinal support bars arranged around said first and third elec trodes, respectively, and fitting within said neck portion, said central portion of the second electrode projecting radially between the adjacent end portions of the bars of said first and second sets, support members projecting radially from said first and third electrodes and secured to said support bars of said first and second sets of support bars for mounting said first and third electrodes therefrom, and additional support members extending from said second electrode and secured to said adjacent end portions of the support bars for mounting said second electrode therefrom.

2. A cathode ray tube according to claim 1, in which said second electrode has end portions of reduced diameter, and said additional support members extend radially from said end portions of the second electrode to said adjacent end portions of the support bars.

3. A cathode ray tube according to claim 1, in which said plurality of electron beams intersect each other substantially at the optical center of the lens defined by said focusing lens means.

References Cited UNITED STATES PATENTS 2,792,515 5/1957 Broderick et a1. 313-82 2,859,378 11/1958 Gundert et a1. 2,945,143 7/1960 Shapiro 31382 3,258,627 6/1966 Paull 31382 ROBERT SEGAL, Primary Examiner US. Cl. X.R. 313251

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