US2646521A - Color television picture tube - Google Patents

Description

y 1953 J. A. RAJCHMAN 2,646,521

COLOR TELEVISION PICTURE TUBE Filed March 25, 1950 2 Sheets-Sheet 1 .17 Zhwentor f JAN A.RAJEHMAN (Ittorneg July 21, 1953 J. A. RAJCHMAN COLOR TELEVISION PICTURE TUBE 2 Sheets-Sheet 2 Filed March 23, 1950 lllllllllllllIlllllllllllll 'l'illlllllllll' 3nvcntor JAN A. RAJ EHMAN Gttorucg Patented July 21, 1 953 1 2,646,521 COLOR TELEVISION PICTURE TUBE Jan A. Rajchman, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application March 23, 1950, Serial No. 151,397

17 Claims.

This invention relates" tubes.

to television picture More particularly, it relates to an improved picture tube capable of producing full color images.

with respect to the image surface that each jet will necessarily bombard a particular coating and not any other. The different colors in which the coatings in each group fluoresce appear to be The usual color-kinescope comprises an elec- 5 mixed when viewed from a distance. Moreover, tron-gun and an electron-sensitive color screen this is true whether these coatings are energized or target upon which the gunis trained. The simultaneously or in sequence at a high cyclical color screen may comprise a transparent foimdarate. A means is provided whereby each of a tion surface containing many duplicate groups plurality of separate color signals is effective to of two or more sub-elementary areas. The recontrol selectively only jetsiwhich bombard the spective areas of each group are constituted of same kind of coatings. Thus, each color signal diiferent phosphor materials, each of which controls all light emissions of a particular color. emits light of a particular color (e. g., red, green The means for selectively controlling the elecor blue) when struck by the electrons from the tron jets comprises a laminated control assembly gun. In a kinescope of this kind it is difficult of closely-spaced multi-apertured electrodes, into make sure that the beam shall at all times cluding the above-mentioned apertured plate. impinge upon the particular sub-elementary area some of the electrodes are herein referred to as upon which it should impinge. selective retarding. electrodes. The term selec- A first object of the present invention is to tive is used since each of these electrodes effecprovide a color television picture tube the suctively retards only selected jets which cause cessful operation of which does not require unemission of one particular color. And the word usual precision in the scanning of its electron fretarding is used in this manner because these beam. v electrodes do not actually retard but only effec- A further object is to provide a tube of the kind tively do so. More specifically, each of these mentioned above whose operation is not easily electrodes absorbs'high-speed jets in certain sedisturbed by stray fields. lected locations on one of its sides and emits low- Still another object is to provide a tube of the speed jets of secondary electrons from correkind mentioned above which is operable with sponding locations on its other side. A control less than the customary amount of deflection electrode is positioned in front of each of these power. retarding electrodes to cover its entire front In general, the above objects are attained as surface. During operation, this electrode is. so follows: As indicated above, the fluorescent biased that a video signal which is applied to screen is made up of a great many very small it is able to influence, 1. e., current-modulate, low sub-elementary coatings. The individual coatspeed jets which pass through its apertures. ings may be dot-like patches of pin-point size Each and every jet into which the beam is subor strips of hair-line thinness. They. are posidivided during every fully-scanned raster gets to tioned in an image surface to form groups havbe retarded at one or another of the retarding ing combined areas corresponding to black-andelectrodes and thereby becomes controllable by white picture elements. The groups in turn the associated control electrode thereof. are positioned in a pattern of parallel lines cor- In the drawing: responding to the image raster. The tube is so Fig. 1 represents an embodiment of the invenarranged that to reach any part of the image tion partly taken in section; surface the electron beam must (in fact or in ef- Fig. 2 is an enlarged sectional view of a portion fect) first pass through an apertured plate. In of the control assembly of Fig. 1; passing through the plate the beam is split into Fig. 3 represents another embodiment of the a number of adjacent parallel jets. The aperinvention, also partly taken in section; tures are small enough and close enough to- Fig. 4 is an enlarged sectional view of a portion gether so that a beam focused as sharply as in of the control assembly of Fig. 3; bla-ck-and-white practice (for an image of equal Fig. 5 is a front view of a control assembly; size) will be split into at least as many jets as Figs. 6, '7, and 8 represent different patterns in the number of sub-elementary coatings in each which sub-elementary coatingsmay be arranged of the groups. There is a different aperture for to form screens suitable for use in the present each sub-elementary coating in each picture invention; and element." Moreover, the apertures are so posi- Fig. 9 is an enlarged sectional view of a portion tioned in the plate and the plate is so positioned of a fluorescent target.

The picture tube It shown in Fig. 1 includes and a window It. Within I neck l2 there is mounted an electron gun Hi. It is directed toward the back of a control assembly l6 which is supported behind window 14 by any suitable means (not shown). A target i1 is mounted on the side of assembly l6 farthest from electron gun l5. Target ll comprises a glass support plate [8, a transparent conductive coating Hi the back thereof, such as a nesa coating, and a great many dot-like or line-like sub-elementary fluorescent coatings R, B, G. In the description which follows (but not in the claims), coating will mean coatings of'the dot type unless they are specifically otherwise designated. Each of the coatings R, B and Geemit light of a different hue in response to electron bombardment. However, if desired, a single uniform fluorescent coating may be used as shown in Fig. 9. Such asingle coating can be used in combination with a multi-sub-element optical filter, for examplea filter made of elementary parts R, B QG' each ofwhich selectively transmits light of a predetermined color. A conductivecoating ZB carried on'the inside of conical portion [3 serves as'an accelerating electrode.

In the operation of tube Ill a beam of electronsfromgun I5 is caused to trace a raster pattern" over the back of assembly l6. Assembly= it has as many individual back-to-front passageways for electron jets as the total number of sub-elementarycoatings R, G and B. Target IT is mounted on the front of assembly lfi in such a position that each of its coatings R, G; andB is in exact alignment with a different passageway. These,passageways and the spacings between them are-so small that at any instant of time, the beam-will strike the backs of several of-them to be'subdivided into an equal number of jets. Each passageway is defined by arow'ofexactlyaligned aperturesformcd in the respective electrodes occurring from the backto the front ofassembly l6;

The-electrode nearest to gun-IE in assembly I6- isa normalizing electrodei l Its use overcomes diflicultiescaused by thefact that the scanning beam from gun I5" doesnot impinge upon all parts-of the back of structure [6 at right angles thereto. Without this electrode, electrons might enter- -some of the-passageways at angles sofar from-normal asnot to be able to go all the way through. Practical tests were made in which the back surfaceof anormalizing-electrode 2| was-bombarded-with fast primary electrons at a variety of angles ofincidence. Under these conditions,- secondary electrons emerged from the-opposite side at such low velocities that with a little forward acceleration they followed normal paths.

Normalizing electrode 24 includesa thin aluminum film (or foil) 23 which is carried on one side of a multi-apertured plate 22 and covers all of its apertures. Thisfilm may be formed by first'wetting the back of plate 22 witha thin solution of organic material, e. g, lacquer, so that its apertures are bridged by minute amounts thereof which are stretched into thin films by surface-tension. After the'solution has dried, the. aluminumfilm 23-is evaporated on top of it. Later, for example inde-gassingof the completed tube, the lacquerwillbe baked out.

Immediately in front of normalizing electrode 2lin-the order named are a back selective retarding electrode 24 and a back .controlelectrode 25. Each comprises an apertured plate having a pattern of apertures exactly like that of plate 22. However, a selected one-third of the apertures of the back retarding electrode 24 are covered by individual secondary-emitter films 26. Each of the covered apertures of electrode 25 is aligned with a different one of the R sub-elementary coatings. (Or, where the coatings are of the strip type, individual rows of the covered apertures are aligned withdifferent R strips.) Thus, where the target I1 is either of the type shown in Fig; 6-or in Fig. '7, the apertures for all of the electrodes should be positioned in parallel horizontal rows and all of the apertures of every third horizontal row should be covered with secondary emitter films 26.

The desired pattern of secondary emitter films 26 may be obtained by the use of the masks suitable for forming (in a manner to be described below) the G and B sets of sub-elementary coatings; For example, the retarding electrode 24 is first made to be just like the normalizing electrode 2L. Thereafter, a mask suitable for settling the G set of coatings is placed over the electrode to expose the positions of onethird of the covered apertures. Then a compressed air iet is played over the mask to blow out 7 the parts of the aluminum film in these exposed positions. And .finally, the last two steps may be repeated with a' mask suitable for settling the B set of coatings.

The pattern of films may also be obtained by using a. single mask for causing the evaporated film of aluminum to be deposited only where wanted. The apertures oithi kind of mask are positioned in the pattern desired for the films andthey are-larger than the apertures i'n the electrodes of assembly .l6. Of course, all the apertures of electrode 24=will temporarily be covered with lacquer. However, the ones not covered by films 26 will be openedby heat, e. g., duringde-gassing;

The control electrode 25 comprise simplya smooth plate havingthe same pattern of apertures as plate 22-; i. e., as allof the other electrodes in assembly it. These plates can be made with accuracy and uniformity in anumber of known-ways; For example, they-may be made by a photo-etching process. According to this process an exact replica of the screen is first drawnwith pen and ink, this being done on a scaleyery much larger than one-to-one, if it will be helpful-(for attaining precision); a reduced-facsimile of the replica is photographically produced if necessary; the thin copper sheet is coated with a-photo-sensitive material such as aphoto-sensitive material which contains albumen, whereby it exposure .tolight; a light-image of the'replica is projectedonto the copper sheet; the unhardened portions of the photo-sensitive material are washed away; and. the copper sheet is etched through in-place exposed by' the Washing.

If control electrode 25 is biased at a direct potential slightly below that of retarding electures of retarding electrode 24. In otherwords, they willnot affect any electrons .which reach it. without being retarded by asecondary emitis adapted to harden onjet of secondary electrons from electrode 24.

will see a positive field through an aperture of electrode 25. And, of course, the geometry and intensity of this field will be a function of the potential of this control electrode.

The electrode next ahead of control electrode 25 V is an intermediate retarding electrode 21. From what has preceded and What is to follow, it will be apparent that this next electrode 21 has two functions: a principal one as a retarder of oertain fast jets emitted from normalizing electrode 2|, and a subordinate one as an accelerator for certain slow secondary jets emitted from retarding electrode 24. More specifically, it is a retarder for jets which are directed toward the G coatings, and an accelerator for-jets which are directed toward the R coatings. If desired for any reason, separate electrodes could be used to perform these respective functions.

An intermediate control electrode 28 is positioned in front of retarding electrode 21. These two electrodes co-operate in what may be considered a second stage for the selective control of electron jets according to their positions. Similarly, two more electrodes co-operate in a third stage for selective control. These electrodes, a front retarding electrode 29 and a front control electrode 30, are positioned in front of the intermediate control electrode 28 in the order named.

Since the back, intermediate and front retarding electrodes are at slightly ascending potentials, the electron jets which they respectively retard will have progressively slightly higher energies. This does not present any significant difiiculty. It merely necessitates the use of slightly different values of bias between each retarding electrode and its associated control electrode.

Ahead of front control electrode 30 is a front accelerating electrode 3|. In the operation of tube 10, it provides the positive field required for the proper operation of this control electrode.

Tests have indicated the following to be suitable operating potentials for electrodes 2|, 24, 25, 21, 28, 29, 30 and 3i and the target I! respectively (as related to that of the electron-gun cathode as a reference) +3000 volts; +6000 volts; about +5990 volts; +6200 volts; about +6190 volts; +6400 volts; about +6390 volts; +6600 volts; and +15,000 to +25,000 volts.

When target I! is spaced in front of the front accelerating electrode by as much as .125 to .200 inch, each jet of electrons impinges accurately on a desired predetermined coating R, G, or B if an accelerating voltage of as much as 10,000 volts is established across this space. Moreover, any increase in this voltage permits an increase in this spacing and vice versa. Therefore, this arrangement aifords in tube It! a means for attaining high-level target excitation by post-acceleration. As a result, the beam electrons do not need to attain more than a relatively low range of velocities while still moving through neck I2.

Thereforetube operates satisfactorily with the provision of less deflection power for its yoke 32 than is possible with a tube which does not use post-acceleration but otherwise i similar to tube 10.

The electrodes of control assembly [6 may be assembled in exact registry by th use of 3351111111- ber of sapphire rods 34 as shown in Fig. 2. This is possible because the same pattern of apertures However, since is used for all of the electrodes. target it is not'apertured, its supporting structure, glass plate l8,'must have holes specially drilled for receiving the sapphire rods. Accordingly, a particular order of assembly is suggested for obtaining excellent registry. The holes are drilled somewhat oversize, and rods 34 are set in soft cement in these holes. The rods are positioned accurately (while the cement is still soft) by using an apertured plate as a template They are kept in these positions until the cement 35' hardens. A first settling mask is placed overthe back surface of the plate. It has one-thirda's many apertures asplate 22 and the pattern of its apertures corresponds to the pattern of positions for one of the sets of coatings. This mask is guided to an exact desired position on plate 18 by the sapphire rods 34. The sets of coatingsin question R, G, or B, is then settled (or sprayed, or dusted, or squeegeed) onto plate [6 through the mask. The last two steps are repeated with second and third masks for forming the other two respective sets of coatings.

-Thereafter, a number of ring-shaped mica' washers 36 are placed over the respective rods adjacent plate l3 to fix the distance between accelerating electrode 3| and the back surface of the target ll. Thereafter, electrodes 30, 29, 28, 27, 25, 24 and 2| are slipped over the sapphire rods in the order named with a ring-shaped mica washer 37 fixing the spacing between each pair of adjacent electrodes. The normalizing electrode 2! is cemented to the back ends ofthe rods 34 (as shown at 38) while the elements-ofassem'bly l6 are urged compactlytogether.

Where large-diameter electrodes are'used, small glass balls 39 may be cemented between adjacent electrodes to fix a predetermined minimum spacing between them at diiferent points on their aper' tured central portions. Each ball may be captive between a pair of apertures and further heldin place by cement.

In Fig. 3 there is shown a modification of the tube of Fig. 1. In this embodiment no normalizing electrode tube It the conductive coating 20' and the back selective retarding electrode 24' are polarized at different direct potentials to establish a large diameter electrostatic normalizing lens in the region immediately behind assembly 16.

In addition, this embodiment has no electrode corresponding tothe final accelerating electrode 3| of Figs. 1 and 2, target 11 being relied on to perform its accelerating function. This is not to be preferred, because the very high positive potential at which the target I! is maintained-during great variety of possible patterns as long as they For example, if decorrespond to each other.

sired, the apertures may be rows which intersect each degrees as shown in Fig. 5,

positioned in parallel and the coatings R, G

2| i used. Instead, in operating this proper operation-of control However, the sub-elementary coatings other at so (and is used,. i. e., a target having a Single uniform.

fluorescent coating, this coating is formed of a mixture of material capable of emitting light components extending well over the visible spectrum. Moreover, thesub-elementary parts R, B, G" of the optical filter which is used with such a single coating. are arranged in patterns corresponding in any embodiment to the combination of patterns used for the positions of the films 26 on the several retarding electrodes.

It is not necessary for the secondary emitter films used herein to be coated with activated compounds as is done with an electron multiplier. dynode which emits secondary electrons fromits bombarded side. The one thing that is essential is that the films be thin enough to afford a satisfactory secondary emission ratio (at least a value not much under 1) where bombarded with primary electrons having velocities of the order of two or three thousand volts. Another is that they should not be so thin and/or have so many pinholes'that a substantial per centage of such primary electrons will penetrate entirely through and not be retarded.

It may be noted that not all of the secondary electrons are emitted along normal paths (to be specific, their directions of emission have a dispersion accordin to a cosine law). However, the paths actually taken by these slowmoving electrons soon after they leave the secondary. emitter films are almost entirely forward since the accelerating fields which they encounter are many times greater than their own initial velocities (about 200 to 5).

If desired, tube I of Fig. 1 may be operated in the manner described above with respect to tube ill of Fig. 3. That is, it may be operated so as to establish an electrostatic lens immediately back of control assembly i6. To do this, it. is necessary to sever the direct connection 40 shown in-Fi'g. 1. In such operation, two separate means are acting simultaneously tonormalize the scanning beam. Therefore, optimum results are obtained in this respect.

In Fig. a small part of the electrode nearest to the-front of'a" control assembly, e. g;, a'front acceleratin'g electrode in-aFig. 2 embodiment or a front control electrode in a-Fig; 4' embodiment is represented as seen through a'magnifying" glass. This isdone to emphasizethefact that the aper= tures are so small and so close together that they are not easily seen with-the naked'eye.- Actually, theenlargement represented in Fig.- 5 is grossly exaggerated and is more in accordance with what would beachieved with a microscope. Fig. fi'also shows clearly a number of tabs 4| each of which serves as'a conductive lead for a respective electrode-of the control assembly, Oneof these tabs also'appears in Fig; 2; one terminal pin 42 is sealed-through thecone Win a position opposite-eachof the tabs 4| and its inside vided for connecting eachelectrodeto an 'ex-" ternal circuit element.

In one way, of operatingtube ill the electron beam from gun I5 is scanned over the back-of the controlassembly l6 withoutbeing either 8. current-modulatedor keyed. 'The determination of picture-element values for the respective interlaced monocromatic images is effected at the control electrodes 25, 28, 30. For example, these electrodes may be respectively connected to individual video signal sources 43, 44, 45 each of which provides a train of positive going impulses which are amplitude'modulated to represent the picture-element values of a different monochromatic image. If each of these electrodes is biased a little below cut-on, these impulses eiiect both sequential color switching and selective video modulation.

The color switching may be at either an element sequential, a line sequential or a pulse sequential rate. Moreover, simultaneous operation is also possible because of the subdivision of the beam into several jets, each of which can cause light emissions of a difierent color. For such operation, the separate video signals are not pulsed and the control electrodes are biased for class A density-modulation.

Another manner of operation is illustrated in Fig. 3. Appropriately-phased color-switching signals, such as three-phase sine waves, are applied to the control electrodes 25, 28 and 30 from individual sources 45, 41 and 48. At the same time a multiplex color video signal (1. e., a composite polychromatic video signal) from a common source 49 is applied to gun 15 while it is biased for class A operation;

I claim:

1. A color-television tube comprising an image surface consisting, effectively, of a multiplicity of duplicate groups of sub-elemental areas of diiierent color-response characteristics, a source of beam-electrons directed toward said surface, a control assembly including at least two apertured plates mounted in successive array adjacent to said surface with the apertures or" said plates in register with individual ones of said sub-elemental color-areas, means including one of said apertured plates for dividing said beam into a plurality of sets of electron-jets, each set individual to surface areas of a particular colorresponsecharacteristic, and means including another of' said apertured plates for controlling a predetermined one of said sets of jets.

2.'The invention as set forth in claim 1 and wherein said last-mentioned means comprises a retarding electrode mounted adjacent to said second-mentioned apertured plate, on the side nearest said source, for efiectively retarding the jets of said selected set, and wherein means are provided for applying to said second-mentioned apertured plate a current modulating potential for said effectively retarded jets.

3. .A color-television tube comprising an evacu ated envelope containing an image surface con sisting, effectively, of: a multiplicity of dupiicate groups of sub-elemental areas of different colorresponse characteristics, an electron gun for pro jecting a beam of electrons toward said surface, I

a control assembly mounted adjacent to said surface between'it' andsaid-gun, said. assembly comprising means including an apertured plate for effectively subdividing a beam from said gun into a plurality of sets of electron jets each individual to surface areas of a particular color-response characteristic; and a plurality of means for current-modulatingsaid sets or" electron jets inde pendently of each other.

jets with respect to a planar reference of said assembly for different angles of approach of said beam towardsaid target from said gun.

, 5. A color television tube comprising an image surface consisting, effectively, of a multiplicity of duplicate groups of sub-elemental areas of different color-response characteristics, a source of electrons directed toward said surface, a control assembly including at least two apertured plates mounted in successive array adjacent to said surface, means including one of said apertured plates for effectively subdividing the supplyof electrons derived from said source into a plurality of sets of electron jets, each individual to surface areas of a particular color-response characteristic, a plurality of means each including another apertured plate for effectively retarding selected of said sets of jets, and means including a control electrode between each retarding electrode and said surface for current-modulating each of said selected sets of retarded jets.

6. A discharge device as in claim 5 which fur ther comprises a target electrode having a conductive surface as a support for said image surface and means ccnnectable to an external source of potential for polarizing said conductive surface at a different direct potential than an of the electrodes of any of said means for controlling selected sets of jets.

'7. A color-television tube comprising an evacuated envelope containing an image surface, consisting effectively of a multiplicity of groups of sub-elemental areas of different color-response characteristics, an electron gun for projecting a beam of electrons toward said surface, a control assembly mounted adjacent'said surface between it and said gun, said assembly comprising means including an apertured plate for effectively subdividing a beam from said gun into a plurality of sets of electron jets, each individual to sub-elemental surface areas of a particular color-response characteristic, a plurality of means for individually controlling selected sets of jets, each of said last-mentioned means including an elec trode for effectively retarding one set of selected jets -,predetermined according to the color-response characteristic of the sub-elemental areas allotted to said set, a control electrode between the retarding electrode and said surface for ourrent-modulating only jets which have been effectively retarded at said retarding electrode, each retarding electrode comprising a plate having a plurality of apertures each of which is aligned with a different aperture of said first mentioned plate and secondary emitter films covering particular ones of its apertures toward each of which selected jets of a different set thereof move from said first-mentioned plate.

8. A color-television picture tube comprising an evacuated envelope containing an image surface, consisting effectively of a multiplicity of duplicate groups of sub-elemental areas of. different color-response characteristics, an electron gun for projecting a beam of electrons toward said surface, a control assembly, at least two parallel apertured plates mounted adjacent to said surface between it and said gun, said assembly comprising means including one apertured plate for effectively subdividing a beam from said gun into aplurality of sets of electron jets, each individual to surface areas of a particular colorresponse characteristic, and a plurality of means each including another apertured plate for individually controlling selected sets of jets predetermined according to the color-response characteristic of the sub-elemental areas allotted to eluding an apertured plate for effectively subdilines corresponding to a raster'to be scanned by said set, means in the path of said beam for normalizing said jets with respect tosaid firstmentioned plate for a variety of angles of approach of said beam toward said plate.

9. A color television'picture tube as in claim 8 in which said means for normalizing comprises a secondary emitter film in the path of electrons tending to pass through each of said apertures and responsive thereto to emit a jet of secondary electrons therethrough from the side of the film facing said image surface.

10. A color television picture tube as in claim 8 in which said means for normalizing comprises at least two juxtaposed electrodes of substantially circular symmetry for producing a large-diamplurality of coatings comprising at least two dis I crete sets thereof inwhich all of the coatings of each set fluoresce in the same color and the coatings of the different sets fluoresce in different colors, said coatings being positioned on said surface in groups, each group including one coating of each set arranged so as to constitute a polychromatic screen element, a control assembly mounted adjacent said surface between it and said gun, said assembly comprising means inviding said beam'into at least as many jets as the number of said coatings in one group, means including said apertured plate for directing each jet toward a particular coating, at least as many jet-current control means as the number of said sets of coatings, each of said last=mentioned means including an electrode for effectively r'etarding a set of jets which are directed toward coatings of the same set thereof, and a control electrode between the retarding electrode and said target electrode for controlling only jets which are effectively retarded by said retarding said beam'in the operation of the tube.

13. A color television picture tube comprising an evacuated envelope containing a target electrode having an image surface, an electron gun for projecting a beam of electrons toward said surface, a fluorescent screen carried onsaid surface, a light filter comprising a plurality of sub elementary parts for filtering light emitted from sub-elementary portions of said coating said-plurality of parts comprising at least two discrete sets thereof in which all of the parts in each set selectively transmit light of the same color and the parts of the different sets selectively transmit light of different colors, said parts being positioned with respect to said image surface in groups, each group including one part of each set arranged so as to constitute an interlaced polychromatic screen element, a control assembly mounted adjacent said surface between it and said gun, said assembly comprising means including an apertured plate for effectively sub dividing said beam into at least as many jets 11 as the number of said filter parts in one group, means including said apertured plate for directing each jet toward an area of said fluorescent coating registered with a particular part of said filter, at least as many individual jet-density control means as the number of said sets of filter parts, each of said last-mentioned means in,- cluding an electrode for effectively retarding a set of jets which are directed toward coating areas registering with filter parts of the same set, and a control electrode between the retarding'electrode and said target electrode for controlling only jets which are effectively retarded by said retarding electrode.

14. A cathode-ray discharge device. comprising a source of electrons, means for deriving a beam of electrons from said source, means for imparting a scanning movement to said beam, a control assembly mounted in the path of scan of said beam, said control assembly comprising means including an apertured plate for effectively dividing said beam. into a plurality of sets of electron jets whose axes are substantially normal to said plate, and a plurality of jet-intensity corn trol means, each including another apertnred plate parallel to said first mentioned plate, for selectively controlling said sets of jets in accordance with the positions of the intersection of their axes with said first mentioned plate.

15. An electron discharge device comprisin an electron-sensitive screen having a foundation surface containing a multiplicity of sub-elementary phosphor areas, astack of mutually insulated foraminous electrodes mounted with their holes in alignment with each other and with individual ones of said phosphor areas to provide a multiplicity of discrete passageways through which electrons may pass to said individual ones of, said phosphor areas, a secondaryelectron emissive means in each of said passageways, and a source of electrons common to said passage.- ways for energizing saidlast means whereby secondary electrons which vare emitted therefrom selectively energize said sub-elementary phosphor areas of said screen.

16. An electron discharge device comprising an evacuated envelope containing a target surface including a number of sub-elementary image.

having a multiplicity of sub-elementary electronsensitive image-areas thereon, means for direct.- ing electrons toward said target surface, an array of foraminous electrodes mounted in mutually insulated relation in the space between said electron source and said target surface, the holes in said foraminous electrodes being disposed in alignment with each other and with individual ones of said image-areas to provide a multiplicity of discrete passageways through which electrons may pass as separate jets to said individual ones of said image-areas, and means for impressing different current-modulating potentials upon respective ones of said mutually insulated foraminous electrodes for selectively controlling different sets of said jets.

17. A television tube comprising a sealed envelope containing an electron-sensitive surface areas, emissive means spaced from said surfiace for providing a flow of electrons toward said image areas, a structure mounted between said emissive means and said surface and having a number of electron passages each providinga respective path from the emissive means to a different sub-elementary area, an apertured plate lying athwart said passages and including retarding means aligned with a predetermined number less than all of said passages for effectively retarding electrons moving therethrough, and a foraminous control electrode adjacent the side of said apertured plate toward said surface.

JAN A. RAJCHMAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,280,191 Hergenrother Apr. 21, 1942 2 7 5 fi iphm n at we Mar 2'1,., 9%5 2,446,440 Swedlund Aug. 3, 1948 2,461,515 Bronwell Feb. 15, 1949 2,513,743 Rajchman July 4, 1950 FOREIGN PATENTS Number Country Date 866,065 France Mar. 3 1, 1941

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