US2777088A - Tri-color cathode ray image reproducing tube - Google Patents

Description

Jan. 8, 1957 J. M. LAFFERTY 2,777,083

TRI-COLOR CATHODE RAY IMAGE REPRODUCING TUBE Filed Feb. 5. 1952. 4 Sheets-Sheet 1 Fig.3.

y/n d I N Inventor".

James M. Laffertg,

9c b5 $14 M 0 His Attorney.

TRI-COLOR CATHODE RAY IMAGE REPRODUCING TUBE Filed Feb. 5. 1952 Jan. 8, 1957 J. M. LAFFERTY 4 Sheets-Sheet 2 Fi g4. O

@ QD on FigJO.

Inventor: Jam es M. Laffertg, by Z 4 7 His Attorney.

J. M. LAFFERTY 2,777,088

TRI-COLOR CATHODE RAY IMAGE REPRODUCING TUBE Jan. 8 1957 4 Sheets-Sheet 4 Filed Feb. 5, 1952 Figll.

FiglZ.

Inventor: James M. Laffevtg, b5 )QJ a. 7 7

His Attorney.

REPRODUCIN G TUBE James M. Lafierty, Schenectady, N, Y., assignorto General Electric Company, a corp ra ion of New Yo k Application February 5, 1952, Serial No. 269,978

Claims. Cl. 315-21 The present invention relates to a tri-color, cathoderay image reproducing tube that is particularly Well suited for use in a color television receiving system.

M Pa ti ularly, the invention relates to a trircolor, cathode-ray image reproducing tube of the reflecting type, and to a new and improved tri-color image reproducing eleetro'de structure for such tube, and thernethod of making such structure.v i i A tri-color cathode-ray image reproducing tube of the reflecting-type comprises generally a vacuum sealed envelope having an electron gun disposed therein, and a first," apertured, image reproducing electrode member supportedctherein which has a plurality of symmetrically arranged different colored phosphorescent materials se The first apertured elec cured to one of its surfaces. trode member is supported in the envelope with the phos-' phorescent material coated surfacethereof adapted to be viewed through the face of the tube,and with the electron gun disposed on the side-thereof opposite the phosphorescent material coated surface in a manner such that the electron beam emitted by the electron gun must pass hrou h e pe u in th m m r e r mp n ing on the different colored phosphorescent material. Disposed between the phosphorescent material coated surface of the electrode member and the tube face is a second, transparent, electrically conductive, reflecting electrode mem-. her to which is applied a reflecting electric potential that coacts with an electric potential applied to the apertured electrode member to produce a retarding electric field between the two members that causes the electron beam passing through the apertures in the first electrode mem; her to be reflected back, and to impinge on a desired colored phosphorescent material. Thus, as the electron beam emitted by the electron gun is caused to sweep out a desired image by properly positioned vertical and horizontal electron beam displacing means disposed adjacent the electron beam path, the image thereby reproduced can be caused to have a desired color by controlling the particular color phosphorescent material upon which the reflected electron beam impinges. The particular color phosphorescent material excited by the reflected electron v fi i tgdlstates Patent ice effects as arcing between the two spaced-apart different potential electrode members; vibration of the first aperturcd electrode member (which results in varying the spacing between the two different potential members and thereby affects the point of return of the reflected electron image reproducing tube that is particularly suitable'for use in a color television receiving system.

Another object of the invention is to provide an image reproducing tube of the above type which is relatively simple and cheap to construct, and wherein activation of the desired color sequences can be obtained without requiring use of complicated circuitry or mechanical structure.

Still another object of the invention is to provide an improved structure for supporting in spaced-apart relation, twlo'elements of an image reproducing tube which are maintained at diflerent electric potentials.

A further object of the invention is to provide an improved supporting frame construction for a cathode-ray tube image reproducing electrode member that includes a vibration damping means for reducing to a minimum any tendency of the electrode member to vibrate.

A still further object of the invention is to provide a new and improved method of forming apertured members from relatively thin sheet material, which method is particularly suitable for producing thin apertured electrode members designed for use in cathode-ray image reproducing tubes in that the members thus produced can reduce to a minimum any shading'efi'ect that the member might have on the'intensity of an electron beam as the beam passes through the apertures thereof.

One feature of the present invention is the provision of an image reproducing electrode for a cathode-ray tube Which comprises a planar'backing member having a plurality of concentrically arranged arcuate rows of phosphorescent material secured to one of its surfaces. In

a particular embodiment of the image reproducing elecnode, the planar backing member is electrically, co n-v ducti've and has a plurality of concentrically arranged arcuate rows of spaced-apart apertures formed therein,

1 and a plurality of concentrically and symmetrically arbear will of course be determined by the point at which the electron beam impinges on the first apertured electrode member, and this in turnis determined by a number of factors including the spacing of the two electrode mern hers, their relative electric potentials, and the a gleolj incidence ofthe electron beam with respect/to the plane of the apertured electrode member. factors can be controlled in one manner or another so that a desired color image can be reproduced by a catty de- 73v imag rep d i tu on t d in; he above described manner; however, difiiculties have been e neren ed with e p n ly known. tubes of thisttype which have prohibited their. widestpead adoption. in! cluded among thesedifiiculties are the provision of a suff ciently satisfactory, cheap and simple methodof eolor control, n t e ab lity t el minate or reduce. s ch ranged 'arcuate rows of dilferent color producing phosphorescent materials are secured to one surface thereof intermediate ,the rows of apertures. In this embodiment of the image reproducing electrode, the position of the concentric rows of apertures and phosphorescent material are, established by varying length radii having thesame centerpoint, and'rotated through respective angular dis tan'ces determined by the dimensions of the imagereproducing area of the electrode.

Another feature of the invention is the provisionof an electrode structure for a cathode-ray tube whichcomprises a first electrically conductive electrode member maintained at a predetermined electric potential, and a second electrically con'ductivemeiriber spaced from the v first member, and maintained at an electric potential dif- All of the above ferent than the electric potential of the first member, the first and second members being maintainedin the abovedescribed spaced-apart relation by a plurality of spacer elements having a relatively high resistivity to the flowof e1ectric urrent' i c A further featuretof the invention; is the provision of an electrode structure for a cathode-ray tube which comprises a supporting frame, a relatively thin planar'con ductive riember adapted to be disposed in the electron beam of a cathode .ray tube and having the outer edges' thereof secured to the frame in a drumhead fashion, and

vibration damping means cooperating with therelatively thin electrode member to reduce vibrations thereof.

A still further feature of the invention is the provision of an electrode for a cathode-ray image reproducing tube which comprises a relatively thin sheet of material having a plurality of apertures therein, the opposing edges of the relatively thin sheet of material defining desired ones of the apertures being formed at predetermined angles with respect to the surface of the member.

In its preferred form, the invention provides a new and improved, reflecting-type, tri-color, cathode-ray image reproducing tube incorporating all of the above set forth novel features of construction.

Other objects, features, and many of the attendant'advantages of this invention will be appreciated more readily as the same becomes more fully understood by reference to the following detailed description, when considered in connection with the accompanying drawings, wherein like parts in each of the several figures are identified by the same reference character, and wherein: Fig. 1 is a sectional view of a reflecting type, .tri-color, cathoderay image reproducing tube constructed in accordance with the invention; Fig. 2 is a diagrammaticview of the physical relationship of a pair of spaced-apart electrode members comprising the image reproducing electrode structure of the cathode-ray tube shown in Fig. l, and illustrates the path of movement of an electron projected into the space between the two, electrode I members; Fig. 3 is a diagrammatic sketch illustrating the preferred geometrical relationship between the image reproducing electrode member and the electron gun, of the reflecting type tri-color tube illustrated in Fig. 1; Fig. 4 is a plan view'of an apertured, tri-color, image reproducing electrode member and of the supporting frame therefor showing the manner in which the electrode member is supported; Fig. 5 is an enlarged plan view of a fragmentary portion of the electrode member shown in Fig. 4; Fig.6 is a diagrammatic view illustrating the geometrical relationship between "the various apertures of the apertured electrode member shown in Fig. 4, and illustrating the manner in which each one of one particular series of concentric rows of apertures is located on the apertured electrode member; Fig. 7 is a serie's'of views illustrating the various steps in forming the apertures in the apertured electrode member shown in Fig. 4; Fig. 81s a series of fragmentary sectional views showing the various kinds of apertures that can be formed in the apertured electrode member of Fig. 4; Fig. 9 is a fragmentary section View illustrating the manner in which the two spaced-apart electrode members of I the tube shown in Fig. 1, and illustrated diagrammatically in Fig.

has an electron gun, indicated at 14, disposed therein.

The electrons emitted by electron gun 14 are focused into a relatively sharp beam by a focusing coil 15 arranged around a portion of conical neck portion 13, and the beam of electrons thus formed are caused to scan over the area of a reflecting type, tri-color, image reproducing electrode structure, indicated at 16, by a set of vertical deflection coils 17 and horizontal deflection coils 18, in a manner such that the electron beam appears to be emitted from a point source of origin 19.

The reflecting type, tri-color, image reproducing electrode structure 16 is in manyrespects similar to the electrode structure of the tri-color, reflecting type, image reproducing tube disclosed in my United States patent application Serial No. 208,875, Color Television Apparatus and Method, filed February 1, 1951, now Patent No. 2,741,720, but differs therefrom in a manner to be pointed out hereinafter. The electrode structure 16 includes a first planar backing member 21 which, as is best seen in Fig. 2 of the drawing, has a plurality of apertures 22 formed therein, and a plurality of difierent colored phosphorescent materials secured thereto, comprising a blue light emitting phosphorescent material 23, a green light emitting phosphorescent material 24, and a red light emitting phosphorescent material 25, which are symmetrically arranged intermediate the apertures. Spaced from and parallel to the first electrode member 21 is a second, transparent, electrically conductive reflecting electrode member 26 disposed between first electrode member 21 and the transparent face portion 12 of the tube, and maintained at some electric potential Vc, different from an electric potentiol V0 applied to first aper tured electrode member 21. The potential V0 is the potential difference existing between first, apertured electrode member 21 and the electron gun cathode, assumed to be at zero reference potential. It is also the potential applied to the accelerating electrode of the electron gun" so that it is therefore the potential which acts upon the electron beam emitted by the electron gun cathode to accelerate the electrons in the beam toward the member 21. As the electron beam is scanned over the area of member 21, this electron beam is intermittently disposed over one of the apertures 22, in which event the electron 2, are maintained in spacedapart relationship; Fig. 10 is a side view of the supporting frame for the electrode member shown in Fig. 4; Fig. 11 is a side view of a mounting block adapted to be secured to the supporting frame shown in 10, and comprising a part of the vibration damping means incorporated into the tube structure illustrated in Fig. 1 to reduce vibration of the thin image reproducing electrode member thereof; and

Fig. 12 is a plan view of the mounting block shown in Fig. 11.

beam passes through the aperture, and enters into the area between electrode members 21 and 26. Because the potential Vc of reflecting electrode member 26 is considerably less than the potential V0 of electrode member 21, the two potentials coact to produce a uniform retarding electric field throughout the area between the two members' The electrons passing through the apertures in first electrode member 21 then, enter this retarding field, are reflected thereby so that they describe a more or less parabolic path, indicated at 27, and impinge upon one of the different colored phosphorescent materials 2325. By this arrangement, with the perpendicular distance d between the electrode members held at a fixed value, the electron beam entering the retarding field may strike, say the green light emitting phosphorescent material 24 in the manner shown for one set of values of V0 and V0. .If the retarding field is' then increased in magnitude by decreasing the reflector voltage Vc for example, the electron beam follows a slightly different trajectory and strikes the blue light emitting phosphorescent material23. Similarly, by decreasing the magnitude of the retarding field, the electron beam may be made to strike the red light emitting phosphorescent material 25. With a fixed value of a retarding field, and by proper distribution of the phosphorescent materials and the velope 11 for enclosing the various elements of the tube v apertures on the electrode member 21, then, it is possible to excite only a desired color phosphorescent material as the electron beam is scanned back and forth over electrode member 21 in tracing out an image. Hence, the image to be displayed on the electrode member 21 can be reproduced in either red, green, or blue by utilization of the proper apertured electrode memberreflector Geometrical layout of apertured electrode member In order to determine the voltagesrequired, the geometrical layout'of apertured electrode, member 21, and

other pertinent characteristics of the electrode structure diagrammatically illustrated in Fig. 2, it is necessary to determine 'the various mathematical relations that exist between'the electron motion, the applied voltages and the tube geometry, and, particularly, the geometry of the reflecting, tri -color electrode structure with respect tothe point source of electrons 19. For the purpose of convenience in this discussion, the plane of apertured electrode member 21 in Fig. 2, is arranged to define the X-axis of a set of Cartesian coordinates, and a perpendicular to the plane of electrode member 21 defines the Y-axis, with the origin. of the coordinates located in the center: of any one vof'the apertures 22 in member 21. With the reflector electrode member 26 spaced parallel to apertured electrode member 21, and at a fixed distance d from it, the voltages V and Vc produce a uniform retarding field in the enclosed area which is given by the expression: r i i The, mathematical expression of the force acting on an, electron when the same enters the retarding field E; can be developed from the classical physical expression of Newtons second law of motion:

where f is the force acting on the electron-to retard the same, m is the mass of the electron, and a is the acceleration of the electron. From elementary electron physics it is known that force acting on an electron having a charge (-e) in an electric, field E, is given by the expression f=(e)E, and; that the acceleration of an electron, or for that matter any body in motion, is equal to to time Thus, Equation 2 may be expressed in the following manner:

Fo mexpression for the trajectory of an electron beam which enters the retarding field E at an angle. of incidence m measured with respect ,to atnormal to the plane of le tro m m r 21, a be ive ro -Equa i n 3 by transposing Equation 3 to separate the two variables dy and dz. The expression thus obtained may be solved by integrating dv between the limits of v and 110 cos a (where v is the y component of the velocity at the variable time t, v0 is the initial velocityof the electron upon enteringthc retarding field at time i=0, and-v0 cos a is the component of the velocity in the direction of the field. at time 21:0), and by integrating dt between the limits of .0 and any variabletime t after the electron has entered theretarding field E. Thisstep results in an expression:

to 005 or V sults; in:

eE i i t in Equation 5, transposing, and integrating the terms containing y between thelimits 0 and y, and the terms containing 2 between the limits (land 23, the following ex- "Bysubstituting the. identity tpressilonmay be obtained:

1/ i fdy=v cos a results in;

Y refe g o 2 t is adi v ppa en thattht component of v in the direction of the x-a-xis (vii) is givenby: I

Since the distance x, the displacement of the electron along the x-axis from the point at which it enters the field E to the point at which it impinges on the apertured x=tvo sin a From a consideration of electron Physics, it can, be shown that the kinetic energy acquired by an electron at the time it reaches any one of the apertures 22 in e loctrode member 21, and therefore the kinetic energy of an electron when it passes through the origin of the co.- ordinate system under consideration, is given by:

mv V e (:1 1)

Solving Equation 11 to obtain an expression for the velocity .of the electron when the same passes through the origin, in terms of the electric potential applied to elec trode member 21 results in:

Substituting Expression 12in Equation 10 and simplify ing, results in:

4d sin a ("13) 2d sin 2a lf the distance from the apertured electrode member 21 to the zero Potential plane in the retarding field, measured parallel to the y-axis, is denoted do, then and, Equation 14 may be expressed in the following manner:

7 ConsideringEquation 16, it is readily apparent that if the angle of incidence of the electron beam is 45, the displacement of the beam (S) is exactly twice the distance (do) between the apertured electrode member 21, and the zero potential plane. If the angle of incidence is made greater or less than 45 the displacement drops ofi. Consequently at cz=45, S is a maximum, and is equal to 2:10. If this value of S is identified as S0, Equation 16 may be written: I

S=S sin 20c (17) Referring now to Fig. 3 of the drawing, the plane ABCE represents the image reproducing area of the apertured electrode member 21, and the point 0 represents the point source 19 of the electron beam emitted from the electron gun of the reflecting type, tri-color tube arrangement illustrated in Fig. 1. From a consideration of Fig. 3, it is obvious that as the beam .scans over the image reproducing area ABCE of'electrode member 21 along a straight line from left to right or right to left in tracing out an image in the usual manner the angle of incidence or is constantly changing. Consequently, this means that if the distance d, and the ratio Y vo are held constant, the displacement of the beam (S) is constantly changing in accordance with Equation 14. Thus, it can be appreciated that with straight line scanning across the image reproducing area ABCE, it would be impossible to excite a single distinct color over the entire area if the arrangement of apertures and different colored phosphorescent material were symmetrically arranged. Because it is desirable for obvious reasons to have the rows of spaced apart apertures 22, and different colored phosphorescent material symmetrically arranged on electrode member 21, it is essential to work out some method of controlling the particular color phosphorescent material excited by the reflected electron beam, independently of the changes in a due to vertical and horizontal scanning. This could be accomplished'by using a curved reflecting electrode member 26, by modulating the reflecting electrode member voltage Vc, by a combination of both, or by some other means; however, it appears much simpler to keep a constant, and with a fixed value of let S vary with or according to Equation 14. When op- 'erated in this manner, a pattern can bemade out of apertures, and different colored phosphorescent materials in such a way that it is possible to excite only a single desired color while the area ABCE is being scanned. Then, by changing the reflector voltage Vc, or by some other method of color control, it is possible to selectively excite any desired one of the plurality of different colored phosphorescent materials 23, 24, or 25 at any instant during the scanning cycle of the electron beam as the same sweeps out an image on electrode member 21.

In order to accomplish the above result, it is necessary to lay out the pattern. of apertures and difierent colored phosphorescent materials on electrode member 2.1 in the form of concentrically arranged rows, each of which follows an arcuate contour line of constant angle of incidence over the image reproducing area ABCE of the electrode member. This is done by drawing a perpendicular from the point 0 (which represents the point source of the electron beam 19) to a plane containing the plane ABCE (and therefore the plane of the electrode member 21). The point at which this perpendicular intersects the above-referred to plane, identified as O, constitutes a common center point for varying length radii utilized in tracing out the plurality of concentrically arranged arcuate rows, such as LMN by rotation of a particular length radius, such as R, through an angular distance determined by the width of the image reproducing area ABCEof the electrode member 21. When an electron enters the retarding field through an aperture along one of these arcs, for example the arc LMN, it makes a constant angle of incidence a with the apertured electrode member 21 at any point along the length of the arc. It will therefore return to, and impinge upon the electrode member 21 at a constant distance S above the point on the are through which it enters the retarding field, measured along a radial line passing through 0' as a center, and the point where the beam enters the retarding field (assuming d and to be held constant.

Considering now the triangle formed by three intersecting lines comprising the perpendicular distance between the point source of electron beam 0 and the common center point 0 (identified as h), the radius R of any particular arcuate row of apertures or phosphorescent material such as LMN, and the straight line connecting the free end of R and D (identified as Z for the purpose of convenience). Then Substituting the values for sin a and cosine a in the wellknown trigonometric identity (sin 211:2 sin a cos a), and simplifying, it can be shown that 2Rh Ra+h Substituting the value of sin 2a obtained in Expression 18 in Equation 17 and simplifying, results in:

sin 2a= ranged, arcuate rows of apertures can be laid out over the image-reproducing area ABCE of the electrode member 21 with a series of symmetrically and concentrically arranged ditferent colored arcuate rows of phosphorescent material disposed intermediate each row of apertures whereby the electron beam upon passing through any one of the apertures can be reflected back, and made to impinge upon a desired color phosphorescent material. The preferred construction of electrode member 21 utilizing the above set forth structural features, is illustrated in Figs. 4 and 5, wherein it is seen that apertures 22 are formed in concentrically arranged arcuate rows having a common center point in a manner such that the apertures in difierent rows are aligned along a straight line radiating outwardly from the common center point. Disposed intermediate the arcuate rows of apertures are the continuous, unbroken, arcuate different colored lines of phosphorescent material 23, 24, and 25 which are likewise concentrically arranged with respect to the rows of apertures 22, and a common center point.

With regard now to the spacing between each of the arcuate rows of apertures 22, it has been shown that the maximum displacement of the beam (So) occurs when a=, and that the beam displacement (S) drops off enemas for values of or on either side of 45. Hence, it can be seen that as the electron beam is scanned between the upper and lower limits of its vertical sweep, the value of uyaries, for the smallest angle of incidence a which the beam makes with the apertured electrode member 21 will be at the point P in Fig. 3 of the drawings, and the largest angle of incidence will occur at the points A and B. Consequently, the displacement S varies in accordance with Equation 19, and it is therefore necessary that the spacing between the arcuate rows of apertures 23 likewise vary. By proper design of the apertured electrode member 21, it is possible to make the spacing between the arcuate rows of apertures 23 at F approximately equal to the spacing between the rows of apertures 23 at A andB, and thereby simplify somewhat the construction of the apertured electrode member. This can be accomplished by making the value of the beam displacement S at point F, approximately equal to the value of S at points A and B.

In order to determine the value of the beam displacement S at points F, A and B, it is first desirable to detera mine the limits on the values of the least angle of incidence ML, and the greatest angle of incidence m that the electron beam makes with the plane of the electrode member 21. To do this, there are certain inherent characteristics of the reflecting type image reproducing electrode structure described herein, which should be considered in arriving at the values of the maximum and minimumangles of incidence 06g and an. The most im portant of' these characteristics is the focusing action of the retarding fieldE in the plane of incidence of the electron beam. A mathematical expression for this phenomena may be obtained by difierentiating Equation 14 with respect to a, and results in the following expression:

It can be shown from elementary trigonometry that electrons traveling in a beam with uniform velocity and diverging from the axis of the beam with an angle doc, assumed to be extremely small, will, after traveling a distance So, be displaced transversely a distance Soda. From this characteristic, when considered in connection with Equation 20, it can be seen that, if 2 cos Zais less than 1, then a focusing action occurs, and, if the quantity 2 cos 2a is greater than 1, a defocusing action occurs. Consequently, it can be shown that the greatest focusing action will occur when the angle of incidence c is 45, and that a defocusing action will occur when or is less than 30, or greater than 60. Thus, if one is to take advantage of the inherent focusing action of the reflecting type image reproducing electrode structure, the limits of the vertical scan should be established so that an equals or is greater than 30, and m is equal to or less than 60. 7 This limi- =2S cos 2a (20) tation 0n the scanning angle is nottoo severe, in view angle of incidence aL from a consideration of the focusing action of retarding field on the beam, as set forth in the preceding paragraph, the least radius R1. can be computed for the first arcuate row of apertures passing through point F on electrode member 21. In making such computation, it would be convenient to obtain an expression which discloses more readily the relationship of a particular radius R, and its associated angle of incidence 0:. For this purpose, consider the are, shown in- Fig. 3,

of radius OA', and drawn from A to A where it inter-- sects the vertical center line 06 passing through the center of theimage-reproducing area ABCE. The pointsO, 0'

I0 and A, then define a rightvtriangle (illustrated in Fig. 6 of the drawings) having one of the right angle legs thereof equal to h, and the remaining right angle leg equal to the maximum radius Rg=O'A'-, The angle ozL=a1 then, is the least angle of incidence that the electron beam makes with the apertured electrode member, and occurs at the point F; and the angle cz=ot1v is the greatest angle of incidence that the electron beam makes with respect to electrode member 21, and occurs at points A and B. The values of Rg=RN,. the maximum radius from point 0' which defines an arc passing through points A and B, and the radius Rr,=R1, the least radius from point 0' which defines an arc passing through the point F, can be found by solving Equation 19 for the ratio This can be done by transposing Equation 19 and simplifying, and results in a quadratic expression that can be, solved by substitution in the quadratic formula to produce the following. equation:

trated in Fig. 6 along with Equation 21, the following expressions relating the values of a; and d1. can be ob- Aft'er values for the ratio and for the dimensions of the image reproducing area have been selected, the value ofRr. (or R1 since Rg=R1). can be computed from Equation 22. Having obtained the value R: for the radius of the first row of arcuate apertures then, from a consideration of Figs. 3-6 of the drawings, it can be seen that an electron which enters the retarding field betweenelectrode members 21 and 26 at any point along the length of the arcuate row of apertures defined by radius R1, will return to the apertured electrode member 21, and impinge thereon at a distance S1 from the aperture through which it centered, measured along a radial line which passes through 0', and the aperture. The distance S1 may be computed from Equation 19 by substituting the value of R1 for R, and by adding R1 S1, the value of the length of the radius R2 of the nextmost, concentrically arranged, arcuate row of apertures in a series of such rows of apertures to be formed in the electrode member 21, can be determined. By substi tution of value R2 for R in Equation 19, the value of S2 can be obtained, and by adding R2 and S2, the value of the length of the radius R3 of the next following arcuate row of apertures in the series in question, can be obtained. From the two preceding operations, it is believed apparent that a general recurrence formula for computing the radius of any desired one of the arcuate rows of apertures comprising a particular series of such apertures, may be obtained, and has the following form:

With Equations 24 and 25, it is possible to lay out a series of arcuate rows of apertures which are arcs of concentric 1 1 circles having varying length radii, and a common center point at O.

With the arrangement so far described, if the ratio were kept constant, electrons which enter the retarding field B through the nth row of apertures in electrode member would pass back out of the retarding field through the (nth-i-l) row of apertures without impinging on the electrode member. However, by modulating the ratio with the received color switching information, the electrons entering through the nth row of apertures can be made to impinge upon any desired one of the different colored rows of phosphorescent material which are disposed adjacent to the apertures,

In order to obtain satisfactory image resolution, it is desirable that about 75% of the image reproducing area of electrode member 21 be occupied by the colored phosphorescent materials 23, 24, and 25, and approximately 25% of the remaining image reproducing area of the electrode member be occupied by apertures. Consequently, it is necessary to interlace additional series of arcuate concentrically arranged rows of apertures, i. e., a number of series, each one comparable to the series of rows of apertures having radii R1, R2, R3, between the series of apertures, R1, R2 Rn where R1t=Rg. The exact number of additional rows of apertures to be interlaced between the arcuate row of apertures having radius R1 and the arcuate row of apertures having a radius of R2, will depend primarily on the width of the individual apertures, and the value of So. Because the positioning of the first arcuate row of apertures in each additional series of apertures to be interlaced between the arcuate rows of apertures ofthe first series (i. e., the particular arcuate row of apertures of the additional series that will be positioned intermediate the arcuate rows of apertures having radii of length R1 and R2 res'pectively), will automatically determine the position of the remaining arcuate rows of apertures in each additional series by virtue of Equation 24, it is desirable to position the additional arcuate rows of apertures inserted between the rows' of apertures having radius R1 and R2, in such a way that the remaining arcuate rows of apertures in each series will be uniformly spaced without abrupt discontinuities in the spacing. To do this, the most satisfactory method used to date, has een to determine the position of the first arcuate row of apertures in each series by means of Newtons interpolation formula:

where it takes on the successive values m m m m m is the total number of additional series of arcuate rows of apertures to be interlaced between the series R1, R2, R3 and the deltas are the tabular difierences between corresponding rows of apertures in the series R1, R2, R3 Rn. The general recurrence formula set forth in Equation 24 may then be used with the values of Ri-j-k computed from Equation 26 to obtain the positions of the remaining arcuate rows of apertures in each additional series.

Method of construction of apertured image reproducing electrode member Having determined the desired geometrical layout of the concentrically arranged arcuate rows of apertures and different colored lines of phosphorescent material for the image reproducing apertured electrode member 21, the next step to be accomplished is the construction of the member. Referring now to Fig. 7 of the drawings, the method steps of the operation to be carried out in forming the desired concentrically arranged arcuate rows of apertures in the member 21 is disclosed. Apertured electrode member 21 is constructed from a flat, relatively broad sheet of electrically conductive material 31 shown in Fig. 7a, in which the desired apertures are formed by etching, punching, or some similar operation. Because the most practical way of forming the desired apertures is to etch the same in the sheet of material 31, the material should also be easily etched. Therefore, one material out of which the apertured electrode member 21 can be formed is copper; however, the most satisfactory results to date have been accomplished with the use of a copper, beryllium and cobalt alloy identified as Trodaloy, and disclosed in any one of United States Patents 1,847,929; 2,225,339; 2,226,284; or 2,283,675. This material is particularly well suited for use in constructing apertured electrode member 21 because of its many desirable characteristics which include a high electrical conductivity, a relatively high Youngs modulus of elasticity, a high service temperature and the ability to be readily etched.

In carrying out the operation of forming apertures, the particular method used is disclosed in United States Patent No. 2,437,228, and includes coating a light sensitive emulsion 32 over one of the surfaces of the sheet of material 31, in the manner shown in Fig. 7a. A mask 33 having a plurality of opaque areas 34 where it is desired that apertures be formed in the sheet of material 31, is then deposited over the light sensitive emulsion 32, and the areas of the emulsion not covered by opaque portions 34 are exposed to a source of illumination 35 as illustrated in Fig. 7b. Mask 33 is then removed, and the emulsion-coated sheet of material 31 subjected to treatment with a developing fluid that removes only those areas of the light sensitive emulsion not exposed to the source of illumination 35, in the manner shown in Fig. 7c. The areas of the light sensitive emulsion 32 that were exposed to source of illumination 35 are unafiected by the developing fluid, and remain on the sheet of backing material 31 to form masks over those portions of the sheet of backing material where it is desired that no apertures be formed.

Having completed the above steps on one side of the sheet of material 21, the sheet of material is then turned over, and the identical operations performed on the opposite side of the sheet of material as indicated in Figs. 711, 7c and 7). In the operation carried out on the opposite side of the sheet of material 31, however, the opaque areas 34 of the mask 33 are offset a predetermined amount in a predetermined direction from the center of the first bores 36 in the first treated side of the sheet of material, in the manner shown in Fig. 7e. Upon exposure of the light sensitive emulsion 32 to source of light 35, and removal of the unexposed portions of the light sensitive emulsion 32 by a developing fluid, the sheet of material 31 has the form shown in Fig. 7f. Thereafter the sheet of material is subjected to a suitable etching bath which acts upon the portions of the sheet of material not covered by mask 32 to form a set of first bores 36 in one side thereof, and a set of second bores 37 in the remaining side thereof, in the manner shown in Fig. 7g. Subsequent to this operation, the masking material 32 is removed, and results in the blank apertured electrode member 21'shown in Fig. 711.

Because of the offset given to masking material 32, each one of the set of second bores 37 is offset a predetermined amount from its corresponding first bore 36, and the resulting aperture 22 formed by the juncture 13 9f e o bor asthe id hereo (d fined by the thin ed s of t heet f e a ma essome p d erm n d a le ith' sp e t t e surf of he et, of material. Asis best seeninFigs. 8a, 8b and 8c, the a u that e c esp nding ba es and 3 are fset, generally determines the angle that the sides of the a u e formed y hei ncturef of b es makes it r spect to the surface of the sheet of material, and therefore the angle of incidence that a beamof electrons passing through the aperture, can make with respect to the plane of the sheet of material 31 in order that the maximum cross-sectional area ofthe aperture be exposed to the electron beam whereby no reduction in. the intensity of the beam. will occur due to shading efiects of the edges of the apertures, as the beam. passes through the aperture. t

A better appreciation of the results accomplished by forming angular apertures22 in the electrode member 21-: can be obtained from an inspection of Figs. 3, 8 and 9 of the drawings; Considering the" point P, in the center of image reproducing area ABCE of apertured electrode member 21, it can be appreciated :that the angle of incidence that an electron beam makes with the plane of the electrode member 21 at this point is some value intermediate the least and greatest angles of incidence, for example 45. The apertures 23 formed in the vicinity of. point P therefore should be constructed as shown in Fig. 8a so that substantially the full intensity of an electron beam, indicated at 38, will pass. through the aperture with no shading effects. If, instead of forming the aperture 23 is electrode member 21 at point P in the manner shown in Fig. 8a of the drawing, the aperture was formed with the sides thereof substantially vertical to, the surface of thesheet of material 31, in the manner shown in Fig. 8d of the drawings, the path of the electronv beam 38. would be shaded almost. entirely by the sidesof the apertures which are approximately equal in width to the thickness of sheet of material 31. This could be corrected byfenlarging the apertures 22 in electrode. However, wider aperturedimensions would of course disrupt the beam displacement calculations. aswell as destroy the resolution of an image reproduced on the member, and are therefore impractical. Thus, it is not only desirable but almost necessary that the sides of the aperture form some predetermined angle with respect to the plane of electrode member-21, and, in the manner described with relation to Fig 7, this can be most satise ous unbroken arcuate line that extends over an angular distance determined by the dimensions of the image reproducing, area of the electrode member. In securing the phosphorescent material to the blank apertured member 21, the apertured member first has a vehicle, for example, nitrocellulose or linseed. oil, printed thereon, by means of either a letter press or a lithographing op-. eration. The vehicle is.printed in the form of a first series of concentrically arranged, arcuate lines located on apertured electrode member 21 in the position of the. concentrically arranged arcuate linesof one color phos-. phorescent material, for example the green light emitting phosphorescent material 24. Thereafter, the particular color phosphorescent material to be located in the position of the first printed series of lines is dusted over the entire surface of the apertured electrode member, and adheres to those portions of the electrode member on which the vehicle is printed. The excess phosphorescent material is then blown off in any suitable manner. This operationthen completes depositing of one of the-colored arr-77,089

1'4 phosphorescent materials, on: the electrode. member 21.

Electrode member. 21. is then moved slightly, and again has a. vehicle printed thereon, along a series of con.- eentricallyarranged lines. spaced? slightly fromv the lines previously printed, and located'in the position of the con.- centr-ically arranged arcuate lines of a second, different colored phosphorescent material, for example the, blue light: emitting phosphorescent material 23. The second colored phosphorescent material is then. dusted over the entire screen, and adheres only to the portions of the screen having the exposed vehicle printed thereon. The excess'phosphorescent materialwhichv does not fall upon the exposed, vehicle is then blown off, and. will. include any phosphorescent. material which might have fallen upon the first deposited phosphorescent material.

-After securing the second. colored phosphorescent material to the apertured electrode member, the member is againmoved slightly andthe entire procedure repeatedto deposit the third. colored phosphorescentmaterial along the series of concentricallyarranged arcuate. lines which it is to occupy, in accordance with the calculations set forth in the section covering the geometrical layout of the member. While the particular order in which the different colored. lines are depositedon the electrode member 21 is not too important, is is desirable that the strongest phosphorescent material i. e., the phosphorescent material that is. capable of producing the greatest amount oflight) be deposited first, and the Weakest phosphorescent material be deposited last.

Because of the fact that the diiferent color phosphorescent material. are deposited. on the electrode member 21 in continuous arcuate lines, all areas upon which electrons might; impinge should they drift, sidewise a small amount in'returning tothe electrode member, are covered q with a phosphorescent material. Thus, such electrons are Mechanical construction of tube After construction of the apertured, tri-colored, image reproducing electrode, member 21 in the manner describedin the preceding section, the component parts of the tube structure are ready to be assembled together to form the completed article. One of the first steps in assembling the completed tube is to. support the apertured tri-colored ele trode member 21 in spaced-apart, parallel relationship with the electrically conductive, transparent, reflecting electrode member 26. If desired, this step may be accomplished in a subassembly operation prior to securing the reflecting type electrode structure formed thereby in the tube envelope, in order to simplify construction and speed up manufacture of the completed tube. Prior to this step, however, the apertured tri-colored member 21 is mounted in a drumhead fashion on a substantially annular supporting frame 41, the construction of which is described more fully hereinafter, and the mounted apertured, tri-colored member then supported in spaced-apart, parallel relationship with the transparent reflecting member 26. Transparent electrically conductive reflecting electrode member 26 preferably comprises a plate of electrically conductive glass available on the market commerciallythrough any one of a number of glass manufacturing concerns, such as Corning Glass Works, Pitts,- burgh Plate Glass Company, and others, and as is best shown in Fig. 9, consists essentially ofa pane of plate glass having a relatively thin, electrically conductive, transparent coating 42 on at least one surface thereof. The two electrode members are supported in spaced-apart parallel relationship with conductively coated surface of reflecting electrode member 26 adjacent aperture elec-.

trode member 21, and are maintained at two diflercnt electric potentials, the potential of the reflecting electrode member 26 being less than the potential of the apertured tri-colored electrode member 21 so that a retarding electric fieldexists in the area between the two members.

In order to support the two electrode members 21 and 26 in spaced-apart, parallel relationship, the electrode members are rigidly secured within the jaws of an electrically conductive U-shaped clamp 43, by means of a plurality of spacer elements 44 having a relatively high resistivity to the flow of electric current. The spacer elements 44 preferably comprise a plurality of electrically conductive lead silicate glass blocks having a substantially rectangular cross-section, and having the surface thereof hydrogen-treated so as to produce a very thin conducting layer on the outside surface. The conducting layer thus produced has a surface resistance in the order of some 800 megohms square or more, so that each spacer element acts as a very high resistance, voltage divider between the electrode members 21 and 26. As is best shown in Fig. 9 of the drawings, transparent reflecting electrode member 26 has the electrically conductive surface 42 thereof formed around the edges of the side opposite electrode member 21 so as to provide a contact surface for a spacer element 44 disposed between the electrode member 26 and one jaw of U-shaped clamp 43. Another spacer element 44 is disposed between member 26 and aperture tri-colored electrode member 21, with the supporting frame 41 of electrode member 26 engaging the remaining jaw of U-shaped clamp 43. The entire arrangement is held in rigidly assembled relation by means of an adjusting screw 45 in the end of one of the jaws of U-shaped clamp 43, which coacts with the end of one of the spacer elements 44 to place each of the elements 44, reflecting electrode member 42, and the supporting frame 41 of apertured electrode member 21 under compression between the jaws of U-shaped clamp 43. If desired, a ball bearing point support may be provided between the supporting frame 41 and the end of the jaw of U-shaped clamp 43, and a relatively soft gasket material 46 may be disposed between the end of adjusting screw 45 and the end of the spacer element 44 with which it comes in contact, to prevent breakage of the spacer element. In all, there are a total of four structures'similar to that shown in Fig. 9 spaced about the periphery of the electrode members 21 and 26, one at eachcorner, to rigidly hold the two members in spaced-apart, parallel relationship.

Because of the above-described construction of the spacer elements 44, each of the elements acts as a high resistance, voltage divider between the electrode members 21 and 26. As previously stated a potential gradient exists between the two members by reason of the application of the potential V to the conductive coating 42 of reflecting electrode member 26 by means of a resilient contact arm 47 having a V-shaped contact 48 engaging the rectangular corner of the edge of the electrode member, and the application of an electric potential Vo (which is greater than V0) applied to electrode member 21, supporting frame 41, and existing on U-shaped clamp 43. Due to the fact the spacer elements 44 are electrically conductive, this potential gradient is evenly distributed over the length of the spacer elements in the manner indicated in Fig. 9 so that arcing between the electrode members and the spacers is substantially prevented, yet because the spacer elements have a sufficiently high resistivity to the flow of electric current, sufiicient leakage current does not flow across spacer elements to seriously affect the operation of the tube.

Referring now to Figs. 4 and of the drawings, the construction of the supporting frame 41 for apertured, tri-colored electrode member 21, is illustrated. The supporting frame 41 comprises a substantially annular body portion 5'1, having a generally rectangular cross-section, and a plurality of internally threaded bolt holes 52 spaced about its periphery. Adapted to be secured to the body portion 51 of supporting frame 41 is a face plate portion 53 which may comprise a single integral piece, or a plurality of individual pieces, of strip material shaped to complementarily fit around the annular surface of body portion 51. The apertured tri-colored electrode member 21, which has a plurality of bolt holes 54 formed around its periphery axis best shown in Fig. 4 of the drawings, is secured over body portion 51 with the bolt holes 54 therein aligned over the bolt holes 52 in body portion 51, and the face plate portion 53 is secured thereover with the bolt-receiving apertures thereof also aligned with the bolt holes 52 and 54. The entire assembly is then secured together by means of a plurality of bolts threadably secured to body portion 51 so that the apertured tricolcred electrode member 21 is securely fastened between the body portion and face plate portion 51 and 53, respectively, of supporting frame 41 in a drumhead or stretched membrane fashion. If desired, certain portions of the face plate 53 may be hollowed out as at 57 in order to form a pocket for receiving the ends of the spacer elements 44 upon the supporting frame and apertured electrode member 21 being supported in assembled relation with transparent reflecting electrode member 26.

Because apertured electrode member 21 is of relatively thin construction, upon being stretched across the opening in supporting frame 41 in a drumhead or stretched membrane fashion, the electrode member is highly subject to vibrations in the manner of a drumhead. Such vibrations cannot be tolerated in the present structure, however, and therefore any tendency of the member to vibrate must be eliminated, or at least reduced to a minimum. To accomplish this, vibration damping means are provided which includes a thin, fiat, relatively wide strip 58, best seen in Fig. 1 and ll, having a pair of apertures in each of the ends thereof. Strip 58 is mounted with the plane thereof perpendicular to the plane of electrode member 21, in order that one of the thin edges thereof might engage apertured electrode member 21 to prevent any tendency of the member to vibrate, and is supported in this fashion by a pair of mounting blocks 61 secured to opposite faces of the supporting frame 41, in the manner shown in Fig. 1 of the drawings. As is best seen in Fig. 12 of the drawings, each of the supporting blocks 61 has a slot 62 extending transverse to its length for receiving the end of strip 58, and intercepting a substantially U-shaped groove 65 in the face thereof opposite the slot at substantially a right angle. The mounting blocks 61 are supported on supporting frame 41 with the faces having U-shaped grooves 65 formed therein, engaging the surface of the supporting frame, and have a pair of wire springs 59 supported therein. The wire springs are secured in the apertures in the ends of the strip 58 with their respective ends coacting with a cam surface defined in the mounting blocks by U-shaped grooves 65 to place the strip 58 under tension. By this construction, the strip 58 is maintained under tension with one of the thin edges thereof adjacent to the surface of the electrode member 21, and with the plane thereof at substantially right angles with respect to the plane of electrode member 21. In order to assure against vibration of the electrode member, it is desirable that the edge of strip 58 adjacent apertured electrode member 21 be soldered to the electrode member, as shown in Fig. l, at one or more points 66 along its length. To accomplish this, it is necessary to use a solder, such as indium, which has a relatively low melting point. This requirement is impressed with regard to the solder used, due to the fact that during the bake out portion of the tube sealing operation, the thin electrode member 21 will be caused to expand. Should the solder 66 become set while the electrode member is still in expanded condition, it can be appreciated that crippling or warping of the electrode member would occur. Consequently, a low melting point solder is used to secure the edge of strip 58 to the electrode member, which will remain in the molten state until the electrode member has contracted after bake out" to its normal size. 7

Adverting again to Fig. 4 of the drawings, it can be seen that the apertures 22 in the electrode member 21 17 are disposed along radial lines having a common centerpoint, andconsequently the webbing or sheet material out of which electrode member 21 is constructed intermediate adjacent apertures disposed along the same arcubeam as it sweeps across the apertures adjacent the strip. 7

Thus, one, two, or any number of vibration damping strips 58 may be secured on the supporting frame 41 for substantially preventing microphonic tendencies of the structure, without in any manner affecting electronically the operation of the image reproducing electrode structure.

With the apertured, tri-colored electrode member secured to supporting frame 41, and mounted in spacedapart parallel relationship with transparent reflecting electrode member 26 in the above-described manner, the sub assembly reflecting type, image reproducing electrode structure formed thereby is secured within hemispherical body portion 11 of the television tube envelope. The hemispherical body portion 11 is constructed of an electrically conductivematerial preferably chrome iron to match the expansion of the glass face portion 12, and has a plurality of electrically conductive supports 67 secured to its inner surface by a number of electrically conductive screws threadably attached to hemispherical body portion 11,.and having the end thereof fused so as to form an air-tight seal around the opening receiving the screw.

Each of the conductive supports 67 has the surface there of engaging hemispherical body portion 11 complementarily shaped to fitithe surface of the hemispherical body portion, and has a plurality of internally threaded bolt holes in one end thereof for receiving bolts adapted to pass through a particular one of a plurality of projecting cars 68, 69 and 71, integral with the face plate portion 53 of supporting frame 41, for securing the supporting frame 41 within hemispherical body portion 11. In this manner, the apertured, tri-colored electrode struc tuer is rigidly secured within the tube envelope in a position such that the point source 19 of the electron beam is located with respect to the plane apertured tri-colored electrode member 21 in the manner illustrated in'Fig. 3 of the drawings. Further, by reason of the above construction, the operating potential V can be supplied to electrode member 21 by connecting the conductive hemispherical body portion ll to the source of potential V0. In order to supply the potential Vc to transparent reflecting electrode member 26, a cup-shaped insulating member 72 (best seen in Fig. 1) is secured to the hemispherical body portion 11 of the tube, which is centrally apertured, and has a conductive post 73 extending therethrough, to which the resilient contact arm 47, described in connection with Fig. 9, is electrically connected. The cup-shaped insulating member 72 is secured to hemispherical body portion 11 with an air-tight connection, and forms an the tight seal around the conductive post 73. Likewise, the conical neck portion 13, and the transparent face portion 12 of the tube are secured to hemispherical body portion 11 with air-tight connections. If desired, transparent face portion 12 may be connected to hemispherical body portion 11 through the medium of a point welded flanged joint, indicated at 74, in order to facilitate manufacture of the tube.

Operation of new and improved reflecting type tri-color tube The synchronizing com-' ponents of the received television signal are supplied to 18 the vertical deflection means 17, and to the horizontal deflection means 18, both of which may be of either of the electromagnetic type or the electrostatic type, and cause the electron beam to vertically and horizontally scan the tri-color apertured image reproducing electrode member 21 along substantially straight lines, in a wellknown manner. Simultaneously, color synchronizing signals are supplied to either the transparent reflecting electrode member 22, or alternatively, to apertured tri-color electrode member 21. Thus, as the electron beam scans back and forth across the apertured electrode member 21 in tracing out an image to be reproduced, it passes through the apertures 22 in the member, is reversed through the action of the retarding field existing between the two electrode members, and impinges upon a particular colored phosphorescent material. The phosphorescent material that the electron beam impinges upon of course determines the color excited in that particular portion of the reproduced image, and is therefore varied by the color synchronizing signals. Hence, the tube may be used to reproduce a color television picture from a received colored television signal which supplies, in addition to the' video signal and the usualline and frame synchronizing signals, a color synchronizing signal. The tube may be used with either a dot sequential, a line sequentiai, a frame sequential, or a simultaneous colored television system; but, in the case of the simultaneous colored television system, however, the received simultaneous color information must be first changed to colored synchronizing signals which can be employed sequentially to operate the tube.

From the foregoing description,.it can be readily appreciated that the invention provides a new and improved, reflection type, tri-color, image reproducing television tube for use in a colored television receiving system, which is relatively simple and cheap to construct, and which does not require the use of complicated and expensive circuitry, or tube structure, in order to achieve activation of desired color sequences. The inventional also provides an improved method and means for supporting in spacedapart relation two elements or electrode members of an image reproducing tube, which are maintained at diiferent electric potentials, in a manner such that arcing is prevented. Further, the invention provides an improved supporting frame construction for the electrode member of a cathode-ray image reproducing tube which includes vibration damping means for reducing to a minimum any tendency of the electrode member to vibrate. In addition to the above, the invention also provides a new and improved method for forming apertures in a relatively thin sheet material in a manner such that the apertured member produced thereby is particularly well suited for use as an electrode member of a cathode-ray image reproducing tube by reason of the fact that the members thus produced have little shading effect on the intensity of an electron beam passing through the apertures therein. Additionally, the invention makes available a reflecting type tri-color reproducing tube having ail of the above desirable characteristics embodied in a single article.

In the light of the above teachings, it is obvious that other modifications and variations of the invention will be suggested to those skilled in the art. It is therefore to be understood that changes may be made herein which are within the full intended scope of the invention, as defined by the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An image reproducing electrode structure for a cathode ray tube comprising a first electrically conductive image reproducing electrode member having a prearranged design of different color phosphorescent materials secured thereto and maintained at a predetermined electric potential, a second electrically conductive planar member spaced from and substantially parallel to said first member and maintained at an electric potential dif' ferent from the electric potential of said first member, a plurality of electrically conductive hydrogen surface treated glass spacer elements having a relatively high resistivity to the flow of electric current and disposed about said members for spacing the same apart, and means for holding said members and said spacer elements in assembled relation.

2. A cathode ray image reproducing tube including an outer envelope, an image reproducing electrode structure supported Within said envelope, said electrode structure comprising a first apertured electrically conductive image reproducing planar electrode member having a plurality of concentrically arranged dilferent color emitting arcuate rows of phosphorescent material secured thereto, and maintained at a predetermined electric potential, a second transparent electrically conductive reflecting electrode member spaced from and parallel to said first member and maintained at an electric potential different from the electric potential of said first member, said first and second members being spaced apart by a plurality of circumferentially spaced spacer elements of insulating material having a treated surface providing a relatively high resistivity conductive coating for establishing a uniform voltage gradient between said electrodes, and an electron gun supported within said envelope in a position relative to said first apertured member such that the electrons produced thereby pass through the apertures in said first member are reflected by said second member and impinge along any selected one of the different colored rows of phosphorescent material on said first member at equal angles of incidence.

3. A cathode ray image reproducing tube including an outer envelope, an image reproducing electrode structure supported within said envelope, said electrode structure comprising a first apertured, electrically conductive image reproducing planar electrode member having a plurality of concentrically and symmetrically arranged different color emitting continuous arcuate lines of phosphorescent material secured thereto, and maintained at a predetermined electric potential, a second transparent electrically conductive reflecting electrode member spaced from and parallel to said first member and maintained at an electric potential different from the electric potential of said first member, said first and second members being spaced apart by a plurality of circumferentially spaced spacer elements of insulating material having 3. treated surface having a relatively high resistivity conductive coating for establishing a uniform voltage gradient between said electrodes, and an electron gun supported within said envelope in a position relative to said apertured electrode member such that the electrons produced thereby pass through the apertures in said member, are reflected by said second member, and impinge upon said first electrode member at equal angles of incidence along any desired color line of phosphorescent material.

4. A cathode ray image reproducing tube including an outer envelope, an image reproducing electrode structure supported Within said envelope, said electrode structure comprising a first electrically conductive planar electrode member maintained ata predetermined electric potential, said first electrode member having a plurality of concentrically arranged arcuate rows of spaced apart apertures therein, and a plurality of concentrically and symmetrically arranged different colored arcuate rows of phosphorescent material secured thereto intermediate said rows of apertures, the position of said concentric rows of apertures and different color emitting rows of phosphorescent material being established by varying length radii having the same center point and rotated through respective angular distances determined by the dimensions of the image reproducing area of the member, a second transparent electrically conductive planar reflecting electrode member spaced from and parallel to said first member and maintained at an electric potential different from-the electric potential of said first member, said first and second memspaced glass spacer elements having a treated surface to provide a relatively high resistivity conductive coating to provide a uniform voltage gradient between said electrodes, and an electron gun supported Within said envelope in a position along a line perpendicular to the plane containing said first electrode member and passing through the common center point of the concentrically arranged, arcuate rows of apertures and phosphorescent material and on the side thereof opposite said second reflecting electrode member whereby the electrons produced thereby pass through said first electrode member, are reflected by said second reflecting electrode member, and selectively impinge upon said first electrode member at equal angles of incidence along any selected one of said different colored concentrically arranged lines of phosphorescent material.

5. An electrode structure for a cathode ray tube comprising a supporting frame, a relatively thin planar conductive electrode member adapted to be disposed in the electron beam of a cathode ray tube and having the outer edges thereof secured to said frame in a drumhead fashion, and vibration damping means cooperating with said relatively thin electrode member to reduce vibrations thereof, said damping means comprising at least one thin flat relatively wide strip having the ends thereof secured between portions of said frame with one of the thin edges thereof positioned adjacent to and engaging one of the surfaces of said relatively thin member at, at least one point along the length thereof with the plane of said strip at substantially a right angle with respect to the plane of said member.

6. An image reproducing electrode for a cathode ray tube comprising a supporting frame, a relatively thin planar conductive member adapted to be disposed in the electron beam of a cathode ray tube and having the outer edges thereof secured to said frame in a dmmhead fashion, and vibration damping means cooperating with said rela tively thin member to reduce vibrations thereof, said damping means comprising at least one thin flat relatively Wide strip having the ends thereof secured between portions of said frame, and spring biasing means enacting with the ends of said strip and-said frame for maintaining one of the thin edges of said strip adjacent to and ber at, at least one point along the length thereof with the plane of said strip at substantially a right angle with respect to the plane of said member.

7. An image reproducing electrode for a cathode ray tube comprising a supporting frame, a relatively thin planar conductive member adapted to be disposed in the electron beam of a cathode ray tube and having the outer edges thereof secured to said frame in a drumhead fashion, and vibration damping means cooperating with said relatively thin member to reduce vibrations thereof, said damping means comprising at least one thin flat relatively Wide strip having apertures formed in each of the ends thereof, a pair of mounting blocks secured to oppositeportions of said frame, said mounting blocks having slots in the adjacent faces thereof for receiving the ends of said strip and grooves formed in the faces thereof opposite said slotted faces, said grooves defining a cam surface, and wire springs supported in the apertures in the ends of said strip and coacting with the cam surface in said blocks for maintaining said strip under tension with one of the thin edges thereof adjacent to one of the surfaces of said relatively thin electrode member and the plane of said strip at substantially a right angle with respect to the plane of said member, the edge of said strip adjacent said thin member being soldered to said thin member at, at least one point along the length of said strip.

8. A cathode ray image reproducing tube including an envelope, an electrode supported within said envelope,

said electrode comprising a supporting frame, a relatively thin planar conductive member having the outer edges thereof secured to said frame in a drumhead fashion, and vibration damping means cooperating with said relatively thin member to reduce vibrations thereof, said damping means comprising at least one thin flat relatively wide strip having the ends thereof secured between portions of said frame with one of the thin edges thereof adjacent to and engaging one of the surfaces of said relatively thin member at, at least one point along the length thereof with the plane of said strip at substantially a right angle with respect to the plane of said member, and an electron gun supported in said envelope for producing an electron beam adapted to be swept across said relatively thin member in tracing out an image reproduction.

9. A cathode ray image reproducing tube including an outer envelope, an image reproducing electrode structure supported within said envelope, said electrode structure comprising a first electrically conductive thin planar electrode member maintained at a predetermined electric tinuous arcuate linesof phosphorescent material secured thereto intermediate said rows of apertures, the position of said concentric rows of apertures and lines of difierent color rows of phosphorescent material being established by varying length radii having the same center point and rotated through respective angular distances determined by the dimensions of the image reproducing area of the member, desired ones of said apertures being formed by the juncture of corresponding bores etched in opposite sides of said thin electrode member, said corresponding bores being offset a predetermined amount in a predetermined direction whereby the edges of the membr defining the apertures form some predetermined angle with respect to the surface of the member, a second transparent electrically conductive planar reflecting electrode member spaced from and parallel to said first member and maintained at an electric potential difierent from the electric potential of said first member, said first and second members being spaced apart by a plurality of circumferentially spaced glass spacer elements having a treated surface to provide a conductive coating having a relatively high resistivity to the flow of electric current whereby the potential gradient between said members is maintained at a desired level and is evenly distributed over the length of said spacer elements, and an electron gun supported within said envelope in a position along a line perpendicular to the plane containing said first electrode member and passing through the common center point of the concentrically arranged, arcuate rows of apertures and phosphorescent material and on the side thereof opposite said second reflecting electrode member whereby the electrons produced thereby pass through said first electrode member, are reflected by said second reflecting electrode member, and selectively impinge upon said first electrode member at equal angles of incidence along any selected one of said different colored concentrically arranged lines of phosphorescent material, the direction and amount of offset of each of said corresponding pairs of bores forming apertures in said first electrode member being determined by the relative location of the aperture formed by the bores with respect to the electron gun whereby the cross-sectional area of each aperture is a maximum along a substantially straight line defining the path of the electrons emitted by the electron gun and passing through the aperture.

10. The method of constructing apertures in a relatively thin cathode ray tube electrode member with the edges of the member defining the apertures describing predetermined angles with respect to the surface of the member, said method comprising forming a set of first bores in one major surface of said relatively thin member extending into said member in the direction of the thin dimension thereof, forming a set of second bores in the opposite major surface of the relatively thin member extending into the relatively thin member in the direction of the thin dimension thereof, offsetting each one of said second bores during the formation thereof a predetermined amount along a major dimension from a corresponding first bore, and subjecting the member to the forming action for a sulficient period of time to allow said first and second bores to extend through the thickness of the thin member a sufficient distance to join together and form an aperture passing entirely through the thickness of the relatively thin member in a manner such that the edges of the member defining the aperture describe an angle relative to the surface of the member, the angle being determined by the amount and direction of offset between corresponding first and second bores.

References Cited in the file of this patent UNITED STATES PATENTS 393,867 Tompsett Dec. 4, 1888 2,063,610 Linsell Dec. 8, 1936 2,123,636 Schwartz July 12, 1938 2,182,578 Blumlein et a1. Dec. 5, 1939 2,250,528 Gray July 29, 1941 2,466,440 Swedlund Aug. 3, 1948 2,512,655 Kohler June 27, 1950 2,532,339 Schlesinger Dec. 5, 1950 2,543,046 Murray Feb. 27, 1951 2,577,038 Rose Dec. 4, 1951 2,590,764 Forgue Mar. 25, 1952 2,606,303 Bramley Aug. 5, 1952 2,611,100 Faulkner et al Sept. 16, 1952 2,615,087 Rines Oct. 21, 1952 2,635,205 Olson Apr. 14, 1953 2,663,821 Law Dec. 22, 1953 2,728,025 Weimer Dec. 20, 1955 OTHER REFERENCES RCA Review, September 1951, volume XII, Number 3, Part II, pages 503-512.

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