US2581487A

US2581487A - Color television reproduction tube

Info

Publication number: US2581487A
Application number: US147034A
Authority: US
Inventors: Dietrich A Jenny
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1950-03-01
Filing date: 1950-03-01
Publication date: 1952-01-08
Anticipated expiration: 1969-01-08

Description

Jan. 8, 1952 D, A, JENNY COLOR TELEVISION REPRODUCTION TUBE 2 SHEETS-SI-IEET 1 Filed March 1, 1950 11 in 1 3: is 4.

INVENTOR DIETRICHA. ITENNY QQE b Jan. 8, 1952 JENNY 2,581,487

COLOR TELEVISION REPRODUCTION TUBE Filed March 1, 1950 '2 SHEETS-SHEET 2 i E. v "E. LLLLL WILL;

INVENTQR DIETRICH A. JENNY ATTO R N EY Patented Jan. 8, 1952 COLOR TELEVISION REPRODUCTION TUBE Dietrich A. Jenny, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware- Application March 1, 1950, Serial No. 147,034

This invention is directed to a cathode ray tube and specifically to a singlepicture tube for viewing television pictures in color.

This invention is directed to a television picture tube of the type wherein the electron beam of the tube is caused to approach the target surface from a direction having a slight angle to the normal of the target surface. Picture viewing tubes of this type may have directional type fluorescent screens which luminesce in different colored light depending upon the directional approach of the beam. One specific type of directional screen is that formed of small elemental cells. the inner surfaces of which are coated with phosphor materials. The electron beam is caused to scan over such a cellular target surface and caused to impinge upon the screensurface at an angle and tostrike the phosphor coated inner surfaces of the individual cells. Such screens may be made of two or more phosphor materials each fiuorescing with a different colored light upon impact by the beam. Such a screen structure is shown and described in the co-pending application to Schroeder Serial No. 730,637, filed February 24, 1947, and in the'co-pending application to R. R. Law, Serial No. 143,405, filed February 10, 1950. 1 I

The last cited co-pending application also describes a color television picture. tube usinga single electron gun. The electron beam, is commutated into three portions and each portion is caused to approach the cellular target structure at a different angle. Each beam portion is caused to strikea different phosphor coated inner surface of each screen cell, to produce luminescence in a color corresponding to the direction of approach of the electron beam.

The specific tube described in the above cited co-pending application to R. R. Law involves the use of a first rotating magnetic field for conically scanning the beam in a circle over the surface of an apertured commutator electrode. The portions of the beam penetrating through the aper- 'tured electrode are descanned by a second rotatapertures through which an electron beam passes 8 Claims. (Cl. 3l3-76) at a specific angle to the masking electrode'surface. The beam continues on to strike a phos-" phor on a transparent support plate which emits light of a specific color. When the electron beam passes through the apertures of the mask, at

another predetermined angle to the plane of the mask, the beam will strike a second phosphor,- luminescing with a different colored light. Such tubes may utilize two or more beams, which are formed by individual electron gun structures, or

such tubes may utilize a single electron beam, which is caused to strike through the apertured mask from the several different angular directions successively. Such an electron picture tube is described in the co-pending application Serial No. 762,175, filed July 19, 1947, of Alfred N. Goldsmith.

This last described directional target structure, 1

using a masking electrode, may be combined with the single gun picture tube disclosed in the abovecited co-pending application to R. R. Law, Serial No. 143,405, filed February 10, 1950.

It is an object of this invention to simplify the structure of a cathode ray picture tube using a directional type target electrode.

It is a further object of my invention to simpli fy the structure of a color television picture tube using a single beam, which is rotated about its normal path to bring the beam into the target surface at an angle.

itself to converge to a fine spot at the target sur-. face, but also to direct the deflected beam back to its beam path and at an angle to the normal of the target surface. The successful use of the deflecting and focusing fields depends upon bringing the beam to, a cross-over or point. of focus within the deflecting field, and so that the virtual cross-over point imaged by the focusing field on the target is essentially on the axis of the focusing field.

The novel features which I believe to be char-' acteristic of my invention are set forth with.

particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing, in which:

Fig. 1 is a sectional view of a cathode ray picture tube according to my invention;

Fig. 2 is a partial enlarged view of the tube of Fig. 1;

Figs. 3 and 4 are partial sectional views of the screen structure used in the tube of Fig. 1; and

Fig. 5 is a sectional view of a screen structure which may also be used in the tube of Fig. 1. Figs. 1 and 2 show a cathode ray tube according to my invention. The tube consists of an evacuated envelope in, having both a conical portion l2 and a tubular neck portion i4 coaxially joined together as shown. The conical portion l2 of the envelope is closed by a face plate It and closely spaced from it is a fluorescent target and screen structure l8 to be described below. Mounted coaxially within the tubular envelope portion I4 is an electron gun structure for producing and focusing a beam of electrons 20 on the screen structure la. The electron gun is essentially a conventional design and consists of a cathode cylinder 22 closed, as is shown, at the end facing the target screen l8. The closed end of the cathode cylinder is coated, as is well known in the art, by a mixture of strontium and barium oxides which, when heated to an appropriate temperature, produce a free emission of electrons.

A control grid cylinder 24 coaxially surrounds the electron emitting end of the cathode 22 and has an apertured plate structure closing one end thereof and closely spaced from the coated surface of the cathode. A shield electrode or grid 26 constitutes a short thimble-like electrode having an aperture in the bottom thereof for the passage of electrons therethrough. Spaced along the tubular neck portion l4 and coaxial with the other electron gun parts is a first anode electrode 28 constituting a tubular member, having an enlarged portion at the end facing the fluorescent screen l8. A second anode electrode constitutes a conductive coating 30 on the inner surface of the tubular envelope portion l4 and extends into the conical envelope portion l2 to a point adjacent the fluorescent screen 18. The several electrodes described, which constitute the electron gun structure of the tube, are. during tube operation, connected to a source of direct current potential which may be a voltage divider 32 connected between the positive and negative points of a direct current potential source.

In a tube of the type shown in Fi 1. certain voltage ranges are applied to the several electrodes to form an electron beam from the'thermionic emission of the cathode 22. The following voltages are given as an example of operating potentials, which may be applied to the several electrode and are not meant to be limiting. In a successfully operated tube of the type described. the control grid 24 was operated in a range between and 60 volts below the potential of the cathode electrode. Screen grid electrode 28 was operated in the order of 100 volts positive to cathode potential to provide a positive accelerating field for drawing the thermionic emission from the cathode surface to the negative control grid 24. First anode electrode 28 was operated at around 2,000 volts positive relative to cathode potential, while second anode electrode 30 was maintained at around 12,000 volts positive, relative to cathode potential.

The electrostatic fields produced respectively between electrodes 28 and 28, and 28 and 80, are of a converging nature and cause the electrons to form into a beam having a minimum cross section or cross-over point 56 (Fig. 2) between tubular electrode 28 and screen l8. The electron beam, after passing through this cross-over point 56, tend to diverge before striking the screen l8. In order to redirect the electrons back to a second cross-over point of minimum cross sectional area, a focusing field is used to image the cross-over point 58 on the screen surface l8. Such a focusing field is obtained by the use of a coil 34 mounted on the neck portion l4. A soft iron casing 88 is used, as is .well, known in,.the

art, t enclose coil 34, to restrict and intensify.

the focusing field of coil 34. Casing. 36 hasa, short air gap 38 to concentrate the magnetic focusing field in a small transverse region of the, neck portion l4. As is well known in the. art,- adjustments of the potential of the first. anode electrode 28, as well as adjustments in the strength of the focusing field of coil 30 willbring the electrons of the beam. 20 to a well defined point on the surface of target vl8.

The electron beam 20 maybe causedwto' scan, over the surface of target l8 in any desired pate tern or raster. However, in tubes ofthistype, the conventional scanning consists of parallel lines from top to the bottom of screen, scanningof the beam is produced by scanning fields established by two pairs of scanning-coilsrepresented, in Figs. 1 and 2,.by neck yoke ,.40. Each pair of coils is connected toappropriate; circuits producing appropriate saw-tooth voltages for providing both line and frame scansion. of the beam". Such circuits and systemsmrQvidlng beam scansion are well known in thelartand are not described further in thiscase.-;,,,.'1hese; systems and circuits do not constitute, apart of this invention. .3

The screen structure used .in the tube shown in Figs. 1 and 2 is similar to that illustrated-and described in the co-pending application Serial No. 762,175, filed July 19, 1947, of Alfred .N. Gold-1. smith, cited above. In Figs. 1, 3 and 4 screen structure I8 is shown as constituting a masking electrode 44 positioned in front of atransparent, phosphor supporting sheet 48. The masking, electrode 44 is formed from thin metallic. foil which is opaque to the electrons of the beam IS. A plurality of apertures 48 are formed through the metal foil of the masking electrode 44 for. the passage therethrough of the electron beam. Supported on the surface of the transparent plate 46 are areas 50 of phosphor coating which are positioned in the path of the beam- 20 passing through apertures 48. 1

It is to be noted in the detailed'drawings of Figs. 3 and 4 that if the electron beam approaches the target from any one of the directions indis cated asX, Y or Z, the electrons of the beam will pass through the apertures of thetarget-and strike those phosphor spots which are-in line-with the beam path coincident with these directions, As for example, in Figs. 2 and 3, it -is showiilby way of illustration, that the beam approaching thetarget surface along a path X which -is at an angle to the target surface; will pass through and strike only those phosphor coated spotsindicated b R, which may, for example, luminesce with'a' red light. In a similar manner;- the electrons of the beam" approaching the target along a path Y" will pass through thea'pertures 48 of the mask 44 and strike only 'those areas indicated by the letters G which may, for examplegluminesce with a green light. If the tube is a three color tube, the electrons of the beam appreaching the target along a path Z will pass thro ah the apertures-44 and strike those phos- D 0 areas indicated by the letter B, which may be thoseluminescing with a blue-colored light.

' Means are provided to produce an electron beam which can be properly controlled and directed to producethe desired color effects on a screen of .the.type described above. As shown in detail in rfiglzrthe electron beam first passes through the aperture .of the control grid 24 and into the aperturedthlmble constituting the screen grid 26. Dueto the configuration of the electrostatic field between the. cathode, the control grid and the scre engrid, the electrons form a beam substantiallyas shown in Fig. 2. The electrons from the cathode surface first form and pass through a point of. minimum cross-sectional area or a crossover point 25 in this region. From the cross-over point'25', the electrons of the beam are essentiallydiverging. The beam passes into the first anode electrode 28', where it strikes two apertured plate portions 52 and 54, which shave off the outer, more divergent. portions of the beam and limit the beam essentially to the less divergent electrons at the center or core of the beam. Passing from the first anode electrode 28, the electrons meet a converging electrostatic lens field between the first anode 28 and the second anode coating 38. ,By adjusting the voltage of electrode 28, it is possible tocause the electrons ofthe beam to reconverge to a cross-over point 56, shown in Figure 2. The beam after passing through the cross-over .point 56 is again divergent. The focusing field of coil 34 is adjusted to converge the paths of the electrons of beam 20, so that the beam is brought a, fine focus-spot on the surface of target l8. 'As is well known in the art, the optics of the several electron lenses described as well as that of coil 34, is analogous to that of light optics. When, by adjustment, the beam is brought to a fine focus point on target l8, actually the cross-over point 55 of the beam is being imaged on the target surface.

' Means are also provided to cause the electron beam 20 to approach the target 18 from the requisite direction so that the beam will pass through apertures 48 .of screen l8 and strike selected phos- 'phor .spots 50. To provide such an effect, the electron beam 20 is given a rotational movement by a magnetic field established between the first anode electrode 28 and the focusing coil 34. This beam rotating field may be produced, for example. by'tw'o'pairs of coils arranged in a neck yoke structure 50, Each pair of coils will produce a field transverse to the beam path 20 and perpendicular to the tube axis and to the direction of the otherfleld. The two pairs of coils are connected to appropriate voltage sources of a type, for example, which will cause to flow through the tons-' current pulses having a sine wave configuration. The current pulses flowing through one pair of coils are set to be 90 degrees out of phase with the current flow through the other pair. Such a system is well known and will produce a rotational or conical scanningof the electron'jbeam 20. .When theelectron beam passes through, the constantly rotating field of coils 60., it is"'as a dire'ctrix forming a conical surface.) .Figurez discloses an effect of the. rotational field produced'by the coils, in which the beam isdlsplaced upwardly from its normal path along lthe'axis of the tube. The beam in leaving the rotating field of coils 60 passes into the focusing field of the coil 34. As is well known in the art, an electron beam passing through a lens field. is acted upon in a manner to cause all portions of the beam diverging from the field axis to be brought back to a focus point beyond the lens field. Thus, when the beam 20 is given a displacement from the field axis of coil 34, in the direction shown in Figure 2, the beam is redirected back toward the field axis by the field of coil 34. Furthermore, the individual electrons of the beam are acted upon to take paths, which will converge to a point of focus on the field axis. The focusing field of coil 34 thus has two functions, first, that of focusing the individual electrons of the beam to a common focus point on the screen l8; and second, the function of directing the electron beam 20 back to the field axis after it has been displaced from the axis by the rotating fields of coils 60.

Thus, the combined effects of the rotating field of coils 60 and that of the focusing coil 34 results in beam 20 being first displaced from its normal path and then redirected along a new path to strike the surface of target l8 at an angle and sequentially from different directions.

In order that the focusing coil 34 simultaneously perform the two operations described above, and in the manner described, certain conditions are necessary. So that the beam be focused to a fine spot it is necessary that the cross-over point 56 of the beam be imaged on the screen l8. It is obvious that if any other portion of the beam having a larger cross-sectional area than the cross-over point 56 were focused or imaged on screen l8, the image spot would be larger and thus picture resolution of the'tube would be reduced. It is to be noted, however, that, as shown in Figure 2, the crossover point 56 is displaced from the field axis of focusing coil 34 and that during tube operation, the cross-over point 56 will describe a circular path about the field axis. This condition results since the beam takes a curved path from the electron gun axis into the rotating field of coil 60. Due to this curved path, the beam in entering the field of focusing coil 34 appears to come from a virtual cross-over point 62 on the tube axis, as indicated by the dotted projection backward of the beam to point 62. Since the virtual cross-over point 62 is the object point seen-by the field of coil 34 and this point is on the field axis, the beam will then be directed back to the axis at the screen.

Also, because of the fact that the'field of coil 34 images a virtual point 62, it is necessary that the cross-over point 56 be within the rotating field of coils 60 and in a position that the ,virtual cross-over point 62 will remain on. the axis of the focusing field 34. If the cross-over point 56 were not within the field of coils 60, it can be seen that, when beam 20 passes through the rotating field of coils 60, and into the focusing field of coil 34, the virtual cross-over point 62, would not remain on the axis of the field.- Because of this reason, then, the focus spot on target l8 would trace a circle. Thus, the crossover point 56 must lie within the rotating field of coil 60 and thus be displaced from the axis ofthefocusing field 34, in order that the .vir tual crossover point 62 lie on the field axis. As can be seen'from Figure 1, thebeam 20.will always be deflected by the scanning field of coils 40 from points forming an arcuate area about the axis of .tube neck l4. The approximate cenalways form an ter of this area of deflection may be indicated by a point 4|, which can be considered as the center of beam deflection. The beam then will angle with a line N" joining thiscentr of deflection 4| with the point of beam impact on target l8 and as shown in the figure. tual point of beam deflection is always spaced from this center of deflection.

The phosphor screen shown partially in Figures 3 and 4 is one which has been successfully demonstrated in a tube of the type of Figure l. The apertures 48 are circular openings spaced in parallel lines forming a rectangular area or raster on plate 44. The phosphor coatings 50 on the support plate 46 are small dots of phosphor material spaced from the point of intersection of the line N" passing through the center of each aperture with plate 46 and arranged 120 degrees about this point of intersection. For each aperture 48 there are, thus, three phosphor spots 50, arranged as described. The spacing between plates 44 and 4B are determined by the angle of beam approach and the spacing desired between the phosphor spots 50. A tube of the type described for Figures 1 and 2 can be used with any type of simultaneous color television system. in which the video signals, corresponding to different colors, follow each other successively and are applied in sequence to the control grid 24 of the tube to modulate the beam 20.

In the successfully operated tube described above, sequential video signals corresponding to the three primary colors, red, blue and green were applied to the control grid 24 to modulate beam 20. The voltages, applied to coils (in forming the rotating field, were synchronized with the sequence of the incoming video signals so that the beam 20 was modulated for one of the three colors at a point in beam rotation 120 degrees from its position when modulated by the voltages corresponding to the other two colors. That is, for example, in the position of the beam in Figure 2, where the beam is shown to be displaced in an upward direction from the field axis, the beam could be simultaneously modulated with an incoming video signal applied to control grid 24 and corresponding to a particular color to be reproduced as for example, blue.

As the beam continues in its rotational move-- ment, and reaches a point 120 degrees in rotation from its position shown in Figure 2, the beam could be modulated by a video signal corresponding to a second color to be reproduced, as for example, green; while the beam in a third position 120 degrees spaced from the first and second positions could be again modulated by signals corresponding to the color red to be reproduced.

In actual operation, cut all pulses are applied to the cathode 22 to cut off the beam between these three positions, so that the chance of color mixing at the screen is eliminated. The beam thus strikes target iii in a series of short bursts, each of which will pass through the apertures 48 of the masking electrode 44 from a different angle, in order to strike the phosphor. spot 50 corresponding to the color modulation given to the beam. Thus, for example, the beam, in its position shown in Figure 2, where it has been displaced by the rotating field of coil 60 to a path above the field axis, will approach the target at a small angle to the line N which in actual tube operation has been found to be in Thisrresults from the fact that the acthe order oione degree. As shown iii Figure 3, the beam in this position will approach target l8 along the directional path Z and will pass through an aperture and strike ,a phosphor spot represented by B," in order to produce a visible blue luminescence. In a similar manner. the beam approaching the target surface from the two directions Y and X spaced 'degrees apart will pass through the apertures 48 to strike successively phosphor spots giving a green and red luminescent light.

The operation of the tube described, in Fi ures 1 and 3, need not be limited. to a type of beam commutation provided by the cut-off pulses applied to control grid 24, but there may be also used an apertured electrode positioned between the screen 18 and the rotating fields 60 as disclosed in the above-mentioned copending application of R. R. Law. In this modification, the apertured electrode comprises arcuate apertures equally spaced 120 degrees apart from the center of the electrode. The beam then is mechanically cut off between apertures and passes through the apertures as short bursts which are then brought by the field of coil 34 to the target surface from the three different directions.

The operation of the tube described has been that in which sequential color signals are applied to the control grid 24 for modulating the electron beam. The time of the sequential picture signals may be of any appropriate length. For example, in the successfully operated tube described above, the picture signals were applied sequentially for apicture element time, so that, as the beam scanned a line across the target surface, red, green and blue fluorescing dots were activated in succession. The elemental period of time is that determined by the time the beam scans one line across the target divided by the number of also be used with a system providing sequential,

line scanning or sequential frame scanning in which respectively the beam scans across the target in one line and strikes only the phosphor spots luminescing with a single color or scans a whole frame to produce a single color. In any of the above-described systems which are used, it is obvious that the rotating field of coils 60 must be synchronized with the sequential color video signals applied to the control grid, and also if cut off pulses are used, such pulses must correspond in time sequence to the sequential system used.

A target similar to that indicated in Figures 3 and 4, may also be produced by making the phosphor areas .R, G and 3" as parallel strips extending horizontally across the surface of the target support plate 46. Furthermore, the masking screen may be one in which the apertures 48 are also parallel to each other and to the phosphor strips on the surface of plate 46. If the target 18 is of such a form, it is obvious that the apertures 48 cannot be spaced apart less than the Width of three of the color strips placed on the supporting plate 46. Furthermore, the spacing of th masking foil 44 from support plate 46 as well as the spacing of thecolofstrips themselves from each other are limited by the simple"- -The above described details of the target are by way of illustration of the target structure which can be used with the tube of Figure 1.

Another type of target structure which may be used with tubes similar to that described above and illustrated in Figures 1 through 4 are those, not using a masking electrode, but consisting principally of cellular structure. A screen of this type is shown in Figure 5 in which the elemental portions of the target, which are of picture element size, consist of tubular members having a triangular cross-sectional area. The tubular members 10 are similarly arranged, as shown in Figure 5, in parallel rows, which are preferably positioned within the tube parallel to the line scanning direction of the electron beam. The spaces between the tubular members 10, which do not have the same positioned arrangement, are filled or covered to provide screen portions opaque to the electron beam. The inner surfaces of the triangular tubular members '10 are coated with different phosphors, each inner face of each tubular member being coated with a different phosphor.

The screen structure shown in Figure 5 is used with the tube described in Figures 1 and 2 in which, as described above, the beam is caused to approach the target from a plurality of dif-- ferent directions X, Y and Z. In the tube using the screen of Figure 5, these directions of beam approach to the target are selected so that the beam approaching along any one of the directions will strike only one inner face of each tubular cell 10. As shown in Figure 5, the beam approaching the target screen from the direction X is caused to strike an inner surface of each cell III, which is coated with a phosphor R having a red fluorescence. In like manner, the beam \striking the target from direction Y and Z will strike the inner surfaces of each cell 10 which are respectively coated with phosphors G and B, luminescing respectively with a green and blue light.

The screen of Figure 5 described above has some advantages over that described in Figures 1 through 4 as well as some disadvantages. For example, the screen of Figure 5 does not necessitate the use of a masking electrode so that the phosphor area of the screen is struck by all of the beam, to provide greater luminescence. However, since the phosphor surfaces of the screen of Figure 5 are parallel to the line of vision of an observer, the total light output from the screen can not be fully realized. Thus, screens of the type of Figure 5 have actually shown less brilliance and light response than those of the type shown in Figures 1 through 4.

While certain specific embodiments have been illustrated and described, it will be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. An electron discharge device comprising, an electron gun means for forming a beam of electrons along a normal path, a target electrode positioned transversely to said beam path, means for scanning said beam over a surface of said target, a. phosphor coating on portions of said target surface, each of said coated portions being responsive to specific directions of beam approach, means between said gun and said target electrode for producing a beam deflecting field transverse to said beam path, a first focusing means for bringing the electrons of said beam between said target and said beam deflecting means forimaging said cross-over point on said target surface and for returning said beam to its normal path at an angle thereto.

2. An electron discharge device comprising, an electron gun means including an electron source for forming a beam of electrons along a normal path, a targetelectrode having a portion positioned transversely to said beam path, a phosphor coating on a plurality of areas of said target portion, a first beam focusing means between said electron source and said target electrode for bringing the electrons of said beam to a cross-over point spaced from said target electrode, a second beam focusing means between said first beam focusing means and said target electrode for imaging said cross-over point on said target portion, and means for providing a beam deflecting field in the region of said crossover point for displacing said beam from its normal path, whereby said beam approaches said target from a plurality pf directions, said target electrode including an apertured structure positioned between said target portion and said electron gun to mask each of said phosphor coated target areas from all but one of said plurality of directions of beam approach.

3. An electron discharge device comprising, an electron gun means including an electron source for forming a beam of electrons along a normal path, a target electrode having a portion positioned transversely to said beam path, a phosphor coating on a plurality of areas of said target portion, a first beam focusing means between said electron source and said target electrode for bringing the electrons of said beam to a cross-over point spaced from said target electrode, a second beam focusing means between said first beam focusing means and said target electrode for imaging said cross-over point on said target portion, and field producing means for displacing said beam along a plurality of paths off-set from said normal beam path, whereby said beam approaches said target from a plurality of directions, said target electrode including an apertured structure positioned between said target portion and said electron gun to mask each of said phosphor coated target areas from all but one of said plurality of directions of beam approach.

4. An electron discharge device comprising, an electron gun means including an electron source for forming a beam of electrons along a normal path, a target electrode having a portion positioned transversely to said beam path, a phosphor coating on a plurality of areas of said target portion, a first beam focusing means between said electron source and said target electrode for bringing the electrons of said beamto a cross-over point spaced from said target electrode, a second beam focusing means between said first beam focusing means and said target electrode for imaging said cross-over point on said target portion, and field producing means for displacing said beam along a plurality of paths off-set at equal angular spacings from said normal beam path, whereby said beam approaches said target from a plurality of directions, said target electrode including structure positioned to mask each of said phosphor coated target areas from all but one of said plurality of directions of beam approach.

5. An electron discharge device comprising, an

electron gun means including an electron source ii for forming a beam of electrons along a normal path, a target electrode having a portion positioned transversely to said beam path, a phosphor coating on a plurality of areas of said'target portion, a, first beam focusing means between said electron source and said target electrode for bringing 'the electrons of said beam to a crossover point spaced from said targetelectrode, a second beam focusing means between said first beam focusing means and said target electrode for imaging said cross-over point on said target portion, and means for providing a rotating field in the region of said cross-over point for displacing said beam along a plurality of paths offq set from said normal beam path, whereby said beamapproaches said target from a plurality of directions, said target electrode including an apertured structure positioned between said target portions and said electron gun to mask each of said phosphor coated target areas from all but one of said plurality of directions of beam approach.

6. An electron discharge device comprising, an electron gun means including an electron source for forming a beam of electrons along a normal path, a target electrode having a portion positioned transversely to said beam path, a phosphor coating on. a plurality of areas of said target portion,

a first beam focusing means between said electron source and said target electrode for bringing the electrons of said beam to a cross-over point spaced from said target electrode, a second beam focusing means between said first beam focusing means and said target electrode for imaging said cross-over point on said target portion, and a coil surrounding said beam path for providing a rotating field in the region of said cross-over point for displacing said beam along a plurality of paths off-set from said normal beam path, whereby said beam approaches said target from a plurality of direc-' tions, said target electrode including an apertured structure positioned between said target portions and said electron gun to mask each of said phosphor coated target areas from all but one of said plurality of directions of beam approach.

7. An electron discharge device comprising. an electron gun means for forming a beam of electrons along a normal path, a target electrode positioned transversely of said'beam path, said target electrode having a plurality of surfaces divided into series with the. surfaces of. each series facing substantially the same direction different from the direction faced by the other series. a first focusing means for bringing the electrons of said beam to a cross-over point spaced from said target electrode, a second focusing means between said first focusing means and said target for impinging said cross-over point on said target and a beam deflecting means between said flrst and second focusing means for displacing said beam from its. normal path, whereby said beam approaches said target from said different directions.

8. An electron discharge device comprising, an electron gun means for forming a beam of electrons along a normal path, a target electrode positioned transversely to said beam path, said target electrode having a plurality of surfaces divided into series with the surfaces of each series facing substantially the same direction different from the direction faced by the other series, a' first focusing means for bringing the electrons of said beam to a cross-over point spaced from said target electrode, a second focusing means between said first focusing means and said target for imaging said cross-over point on said target and means for providing a bearndefleeting field in the region of said cross-over pointfor displacing said beam from its normal path, whereby said beam approaches saidtarget from said diiferent directions. DIETRICH A. JENNY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,197,523 Gabor Apr. 16, 1940 2,446,249 Schroeder Aug. 3, 1948 2,446,440 Swedlund Aug. 3, 1948 2,446,791 Schroeder Aug. 10, 1948 2,480,848 Geer Sept. 6, 1949 2,481,839 Goldsmith Sept. 13, 1949. 2,498,705 Parker Feb. 28, 1950