US2757231A

US2757231A - One gun color-dot tube with dynamic beam convergence

Info

Publication number: US2757231A
Application number: US165551A
Authority: US
Inventors: Russell R Law
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1950-06-01
Filing date: 1950-06-01
Publication date: 1956-07-31
Anticipated expiration: 1973-07-31

Description

July 3,1, 1956 R. R. I Aw 2,757,231

ONE: GUN coLoR-DoT TUBE WITH DYNAMIC BEAM coNvERcENcE Filed June l. 1950 2 Sheets-Sheet 1 Qkbwb wl: W N wwwwmm mL m .ESN /mm Qbkuxbwmw N .MASS N A H@ ,w w n@ f Nm .w M w YHQ WGQ .fl mm, Q T M f QR .Ss w Q.nm mm w R S m f m. mw w m (NN f-: i SSG w S. Q mwwmm E e ww |V @SNS k w. NN QN N. m Sw T vm m N Img .mdmx k/ b,

July 31, 1956 R. R. LAW 2,757,231

ONE GUN COLOR-DOT TUBE WITH DYNAMIC BEAM CONVERGENCE Filed June l. 1950 2 Sheets-Sheet 2 INVENTOR Ru el] R.Law

United States Patent O il it.

UNE GUN COLOR-DGT TUBE WITH DYNAIVIIC BEAM CNVERGENCE Russell R. Law, Princeton, N. J., assigner to Radio Corporation of America, a corporation of Delaware Application June 1, 1950, Serial No. 165,551

The terminal years of the term of the patent to be granted has been disclairned 1o Claims. (c1. 17e- 5.4)

This invention relates to electron beam-controlling systems. Though not necessarily limited thereto, it has particular reference to Icontrol systems for effecting electron beam convergence in multi-color kinescopes.

The problem of controlling the convergence of a plurality of electron beam components at substantially all points in the plane of a target electrode over which they are delected to scan a predetermined raster is one which frequently is encountered in television image-reproducing systems. The trend toward providing kinescopes with flatter screens has made the problem of achieving beam convergence more severe. In certain types of kinescopes used in color television systems, the particular problem is to elTect accurate convergence of a plurality of electron beams, or their equivalents, which are directed tov/ard a target electrode from different angles. The different angles of approach of the electron beams are employed for color selection purposes.

A representative multi-color kinescope of the type in which color selection is eected by the angle of approach of an electron beam forms the subject matter of a copending U. S. application of Alfred N. Goldsmith, Serial No. 762,175 filed July 19, 1947, now Patent No. 2,630,542 issued March 3, 1953 and titled Multicolor Television. The Goldsmith tube has a luminescent screen consisting of a multiplicity of phosphor areas of sub-elemental dimensions. The phosphor areas are capable respectively of producing light of diiferent colors when excited by electron beam components. The different screen areas are scanned by electron beams produced by a plurality of guns and projected toward the screen through an apertured masking electrode. The desired color producing phosphor areas are selected by the angle at which the electron beams traverse the apertures of the masking electrode.

Another multi-color kinescope with Which the present invention may be employed successfully forms the subject matter of a copending U. S. application of Russell R. Law, Serial No. 165,552, led .lune 1, 1950 and titled Color Television. The Law tube has luminescent screen and masln'ng electrode structure similar to that embodied in the Goldsmith tube. It also operates on generally the same principles. The chief difference is in the provision of only a single electron gun. The electron beam produced by this gun is caused to approach the masking electrode and the luminescent screen from dilerent angles by imparting a spinning type of movement to the beam. By such means the electron beam is caused to rotate about the center or longitudinal axis of the tube so that, at successive intervals, it occupies substantially the same positions as those occupied by the separate electron beams in the Goldsmith tube.

The expression electron beam components as used in vthis specification is intended to cover the type of phosphor-exciting electronic energy produced by a single or a plurality of electron gun. This energy may be continuous or pulsating as required without departing from the scope of this invention.

l i 2,757,231 Patented July 31, V1956r It is necessary for the successful operation of multicolor kinescopes of the type represented by the Goldsmith and Law tubes referred to that the plurality of electron beam components be made to converge substantially in the plane of the masking electrode at all points in the raster or other predetermined pattern scanned thereon by thedeection of the beam components. In order to accomplish this, it is necessary to provide a dynamic convergence control of the electron beam components. One such electron beam control system forms the subject matter of a copending U. S. application of Albert W. Friend, Serial No. 164,444 led May 26, 1950 and titled Electron Beam Controlling System. In this Friend application there is provided an electron-optical system which is variably energized as a function of both the horizontal andl vertical deections of the electron beam components. Further details or dynamic beam convergence system may be found in a paper titled Deection and Convergence in Color Kinescopes by A. W. Friend, published in the Proceedings of the I. R. E., vol. 39, No. 10 at page 1249. The present invention is in the nature of an improvement upon the Friend system, particularly in color television systems of a particular character.

The present invention is particularly adapted for use with a color kinescope embodied in a color television system operating in accordance with the dot or elemental multiplex principle. A system of such a character forms the subject matter of a copending U. S. application of John Evans, Serial No. 111,3 84, tiled August 20, 1949 and titled Color Television. information from each elemental area of the television subject is transmitted bysuccessive video signals; The composite video signal wave which includes all of the color information from all of the elemental areas in succession of an image to be reproduced is sampled at a receiving point. The rate at which the video signal sampling is eiected is equal to a multiple of the rate at which the elemental areas of the image are to be reproduced. The particular multiple depends upon the number of component colors in which the image is to be reproduced. Ordinarily color television systems employ three compo? nent colors. In this case the video signal wave is sampled at the third harmonic of the elemental area repetition frequency.

It is an object of the present invention to provide animproved electron beam control system by which to effeet convergence of a plurality of electron beam compo- The invention is embodied in Van electron-optical sys-y tem for effecting convergence of a plurality of electron beam components. The system is energized variably in4 accordance with the deflection of the beam components.

The energization of the system also is varied at a fre-` quency substantially higher than the horizontal dellection frequency. Preferably, this higher frequency corresponds to the elemental image area repetition frequency. In al color television system, it may be equal to the frequency;

at which a composite multiplex video signal waveis sampled.

The novel features that are. considered characteristic of this invention are set forth with particularity in the appended claims.V The invention itself, however, both'l as to its organization and method of operation as Well In this type of system, the color as additional objects and yadvantages thereof will best be under-stood fromthefollowingV description takerr in- In the drawings: f f

Figure` 1A is` a circuit diagram mostly' inf block. form of' a color television" signal receiver and 'image-reproduc ing@ system embodying the invention; f

f connection` with the accompanying drawings.

4. subjected to the influence of a rotating field produced ,by ai coil- 2'1 surrounding theneck of the tubef substantially. as shown.y y This coil is energized by a constantly changingvoltage of a charactery to yproduce a rotating field by means of ywhich the electron beam is caused. to

f spin or rotatefabout the centraly longitudinal axis. Such Figure 2 isa sectional view of a portion' of 'a` color f kinescope used inthe system of .Figure 1, taken on the lines 2-'-Z of Figure 1'. The present 'figure' shows" the general configuration and relative 'positioning of the com-y ponents1 ofA the electronLoptical; system for effecting dynamic'electron beamV convergence;

kapparatus yis of the same general` type as that shown in yPatent 2,057,773issued October 20; 1936 to W. G. H.

, Finch.,

` Figures r3, 4, and1 5A areviews of thekinescope screen;

f Figure 3 indicatesy the non'-convergen'c'e of the electron beam components inthe absence of any dynamic convergence control;

Figure 4- indicatesarst order improvementy ofelectrolr' beam' convergence byproviding dynamic` beam con yvergencc. control varying as a function of horizontal and vertical beam#- deflections; 'and Figure 5 illustrates a` secondorder improvement of f electron-"beam, convergence in which-.the dynamic con'- vergence control` system is varied further asr a function of' the1 video signal: wave' sampling frequency kin accord`r k a'ncewith this invention;

Reference r'st will be made to Figure ,1' yof"the-'drawrings. The television signal-receiving or image-reproducyingfsystem show-n in block diagramformgenerally iscon-y ventional.' An antenna 11 'iscoupled toy yacompositeL impressed upon a synchronizing signal separator'14; apparatus. also. may be` entirely conventional. Ac-

cordingly, it. will be understood that. it includes `appay ratusz` for( separating the ksynchronizing signalsA fromv the video signals. Also, the horizontal synchronizingfsignas are: separated from the vertical synchronizing signals.

The image-reproducing apparatusalso` includes a kine scope which, for illustrativelpurposes, isIof thekind disclosed in. the. copending` Law application referred to. Such. a` kinescope a1so:is;disc1osedV inl a paper titled A- One-Gun Shadow-Mask: Color. Kinescope by R..R. Law; published in the Proceedings of the I. R. E., vol'. 39, No. 10, October 19.5:1 at page' 1194; Essentially, it includesl a. luminescent screen 16, an aperturedf masking electrode 17 and an electron gun 18. The'. luminescent screen- 16 may be formed on'. a substantially flat transparent plate. The phosphors are disposed on thefinsideA surface; ofthe plate in any.` desired pattern'. Preferably, multi-colored phosphors` are in. the formof. sub-elementall areas or, dots. arranged in4 groups.y Each` group of. phos-f phor dots contains at leastr one each of' phosphors` capa.- ble` ofrespectively producing lightl. of the: component image colors. The masking electrode` 11 is. provided; with amultiplicity of apertures. 'Ihese` apertures are provided in the same. patterni as the groups.: of phosphor dots. appearing upon the screen I6. Each. aperture of theelectrode 17 is: in-registrationewitlr one group of phosphor dots.

The` kinescope` 1'5- also. is: provided' with` a deecting yoke 1-9 of substantially conventional'V form'. It' will be understood that the yoke, when; suitably energized, functions todeflect the electron. beam. components over the masking. electrode surface in` accordance withl a predetermined. pattern. or' raster.`

In. this case, the plurality of.' electron beam components is derived from a single electron gun 18. Tliisgun is .mounted in sucli a; mannen thattheelectron'. beam emanating therefrom is" substantially along. the, centralV longitudinal ,axis ofthe kinescope. The electron bea-mis "[le. kinescope, 15- also; is provided with: a magnetic yconvergence coil 22. This coilisenergized to-produce a steady or static iield` of a character to cause the spinning electron beam to impinge upon ya pointofthe maskingy electrode 181 located substantially at the center.` thereof in a the absence of` any energizaticm4 ofthe'deecting yoke 19. Such a coil isfof the same generalr character as a beam focusing coil, an example of which is disclosed in Patent 2,442,975 issuedlune 8, 1948 to G. LGmndrnann. y

The magnetic" convergence coil 22` is ,energizedA from'r a power source,l indicated; yby* a; batteryr 23' throughy a rheo-r stat 24. By suitable' adjustment ofy the rheostat the spinning` electron beam may be made to impingeupon the' center of theY masking electrode 17, irrespective of its radial location relative to" the' central axis of the' tubei kThe color rkinescopey 15j` alsol is kprovided with an elec-` tron-optical systemby kWbichtoy effectV convergence of y rthe electron beam components at substantiallykr all kpoints in the yrastery scanned in-y thej planeof the ,maskingyele'cif trode`17kr As disclosed rherein for illustrative purposes, the` electron-optical ysystem comprisesi-ayvertical dynamic convergencev coil 25 yand' a horizontal;` dynamic converg--Ay ence coil 261. Theshapeofeach of theseitwoK collsis` substantially el1ipn generally ellipticalv so as to provide tical or cylindricalelectron lenses. Further details, of

" such` coils may ,beV foundin the Friend I; R. EL'paper previously referred to,y particularly in-tlie ydescription of Figure 2.1y of that paper., n n

` Thecontrol circuits for the' color kinescope, 15 ralsm includes the usual deflection generators y2.7 coupled 'for-r 'control tothe synchronizingfsignal separator 111;'k The", koutput ofthe deflection' generator, which willl be understood to`- produce substantially sawtootli waves; at horizontal or vertical frequencies respectively, is coupled; to thedetleeting yoke 19. In thisl manner the deectmgfields produced by the yoke causethe electron beam com-` ponents to scantheAv target electrode structure-1n a` pre1- determined pattern.

The sampling of the composite videof signalv wave as.` disclosed herein` is in accordancewith the soacalled-high: levelV samplingI principle. A system of suchsignal sarnplirlg' forms` the subject matter of acopeuding U. Si application of George C. Siklai, Serial No'.` 145,4.20,` filed February 2l, 1950, and titled Color Televislon. Receiving/System A high-level? videosignal sampling systemconsists generally of" asingle video signal. amplier channel in which= the v-ideo' signals representing all of` the component colors are; amplied= simultaneously. rEhe amplified composite video signal is impressed upon oneV of a pair of` electronbeam` intensity control electrodes of the color kinescope; The intensity control electrodes normally are biased relative to one another so thatno electron` beam; isproduced The other intensity control" electrode is keyed concurrently with the reception off successive color' representative video signals; rIhe keying of the electron gun producesA an electron'beam. The intensity of the electron `beamuislcontrolled in accordance'with the amplitude of thevid'eosignal Wave'rcceived` at that instant. lt, therefore, isseen that it is necessary tokey the-electron beanrefi the-colorkinescope at|` a` fre'- quency corresponding totth'e repetition frequency of the video signals. InA a tlireewcolor television system this repetition frequency' is three times tliev frequency; at which' the successive elemental'l areas of the: image' are` reproduced.

Accordingly, thel presenti4 apparatus includes a sampling frequency oscillator 28 coupled for synchronizing control to the synchronizing signal separator 14. The essential requirements of an oscillator by which to control video signal Wave sampling are that it be relatively stable at a frequency equal to the frequency at which the elemental areas of an image are to be reproduced and that it be susceptible of synchronous control from an external source. An oscillator of the character described is disclosed in the book entitled Wave Forms published by McGraw Hill Inc., New York, at page 143 with particular reference to figure 4-45. The output of the oscillator 28 is essentially a sine wave at an elemental dot frequency of the television image. The output circuit of the oscillator 28 is coupled to a frequency multiplier 29. In the case of a three-color television system the frequency multiplier increases the fundamental frequency produced by the oscillator by a factor of three. The frequency multiplier is coupled to the electron gun 18 as indicated to control the keying of the electron beam in the manner described. The sampling frequency oscillator 28 also is coupled to a rotating iield generator 31. This device is coupled to the magnetic convergence coil 21. It is considered that means for producing constantly rotating magnetic fields are so well known generally, as indicated in said Finch Patent 2,057,773, that it is not necessary to disclose a particular one here in order to completely understand this invention. Accordingly, it Will be understood that the generator 31 includes means for producing substantially sinusoidal waves of such a character that, when impressed upon the coil 21, there are produced rotating magnetic fields that are always substantially 180 out of phase with one another.

The electron-optical system including the

coils

25 and 26, by which dynamic convergence of electron beam components is effected, is energized as a substantially parabolic function of the horizontal and vertical deiiection of electron beam components. Accordingly, the vertical dynamic convergence coil 25 is variably energized by a wave produced by a vertical convergence control wave generator 32. It will be understood that this generator 32 includes suitable wave shaping circuits to produce a wave of suitable form to energize the coil 25 in response to signals derived from the deflection generator 27 at the vertical deflecting frequency. A convergence control wave of substantially parabolic form may be produced by a suitable integration of a sawtooth wave as taught in Patent 2,312,054 issued February 23, 1943, to O. H. Schade. In general, the energization of the coil 25 is a minimum when the-electron beam components are directed at points substantially at the center of the vertical scansion of the target electrodes. The energization of the coil 25 increases in suitable polarity as a function of an increase in the angle of deflection'of the beam components from the central vertical portion of the raster.

The horizontal dynamic convergence coil 26 also is energized by a wave derived from a horizontal convergence control wave generator 33. This apparatus, except for values of the circuit components, may be substantially similar to the generator 32 and may follow the teachings of said Schade Patent 2,312,054. In this case, however, it is required to produce waves of suitable substantially parabolic shape at the horizontal deflection frequency. The output of the generator 33 is coupled to the control grid 34 of an electron tube 35. This tube functions as a signal-combining stage by which to develop a composite control wave for impression upon the coil 26. The anode of the tube 35 therefor is coupled to one terminal of the coil 26. The other terminal of the coil is connected to the positive terminal of a power supply indicated at -l-B.

The vertical and horizontal convergence control wave generators 32 and 33 may be of the general type disclosed in greater detail in Figure 20,`and related description thereof, of the previously referred to Friend I. R. E.

6 paper. The outputs of these generators may be coupled to the convergence coils as indicated in Figure 1 of the drawings herein.

In accordance with a special feature of the present invention a wave component having the fundamental frequency of the sampling frequency oscillator 28 is combined with the output from the wave generator 33. For this purpose the output of the oscillator 28 is coupled through a phase adjuster 36 to a primary coil 37. A secondary coil 38 is inductively coupled to the coil 37 and is connected between a source of positive voltage and the screen grid 39 of the tube 35. Manipulation of the phase adjuster 36 results in the impression of a voltage component at image dot frequency upon an input electrode of the tube 35 in suitable phase to combine effectively with the wave derived from the generator 36 so that an improved dynamic convergence of the electron beam components may be effected by the coil 26.

A graphic illustration of the effectiveness of the system embodying the present invention as given in the Figures 3, 4 and 5 to which reference now will be made.

In Figure 3 the color kinescope is provided with no dynamic convergence control. The central trace 41 is one which is made by a spinning electron beam of the character described. By suitable adjustment of the rheostat 24 the magnetic convergence coil 22 may be energized to converge the spinning beam to a point 42 at the luminescent screen 16. It may be seen from an inspection of the figure that, as the electron beam is deilected both vertically and horizontally from the central position, the convergence of the beam components is subject to a relatively wide variation. For example, the trace 43 located at one extreme of a horizontal deliection of an electron beam no longer is substantially a point as it is at the center of the raster.

It may be appreciated that a spinning beam following a path such as indicated by the trace 43 will produce a misregistration of the electron beam components with the different color-producing phosphor areas of the screen 16. The failure of the beam components to converge any better than indicated by the trace 43 will result in such a degradation of the reproduced image which can not be tolerated. It may be seen from Figure 3 that the tendency of the beam components to fail to converge is much greater in a horizontal sense than in a vertical one.

The electron beam traces at different points of the raster as shown in Figure 4 represents the improved operation of a color kinescope when dynamic convergence control means are provided. The dynamic convergence coils 25 and 26 are energized by waves varying in accordance with horizontal and vertical deflection frequencies. However, no energizing component at the dot repetition or sampling frequency is present in the control wave for the dynamic convergence coils. The conditions to produce the results of Figure 4 may be simulated by impressing a constant potential upon the screen grid 39 of the tube 35 of Figure 1.

Figure 5 represents the added improvement in the dynamic convergence of the electron beam components when the sampling frequency component is included in the control wave for the horizontal convergence coil 26.

It will be appreciated that alternatively in accordance with this invention, a sampling frequency component may be introduced in the control wave for the vertical convergence coil 25. Also, it will be understood that the present invention may be used successfully with plural electron gun tubes of the type covered by the Goldsmith application referred to. Furthermore, convergence coils 25 and 26 may be combined into a unitary structure which is not necessarily of elliptical shape without departing from the scope of this invention.

Having thus disclosed the nature of the invention, its scope is set out in the appended claims.

What is claimed is: l. In a cathode ray tube image reproducing system wherein. a plurality of electron: beam components effectively traversingzpaths spaced, respectively,` about a longitudinal axis of the tube are deected horizontally and vertically through substantially equal anglesv to' scan a raster in4 af predetermined plane, said` beam components being differently deflected` at any instant by reason of said traversal of spaced paths, al dynamic convergence system to effect convergence of said beam components at all.` points in` said raster comprising, field-producing means` disposed'.L adjacentl to the'paths of said beam components for producingV a' eld of suchcharacter as to converge saidbeam components, means including a source of a substantially parabolic Wave for energizing said field-producing means in accordance with the angular deflection of said beamv components, and means effectively modifying, said substantially parabolic wave for varying the energizationA of`saidliield p`roducing means-at a frequency higher than. that of said horizontal beam deflection.

2. A- dynamic electron beam' convergence system delined in claim l in which said field-producing means includes an electromagnetic coil system for producing both horizontal and vertical" field components and said energization varying means is of such acharacter that it operates to vary the energization of said field-producing means substantially at the elemental image area repetition frequency.

3. A dynamic electron beamA convergence system asV dened in claim 2 in which, saidenergizingrneans is of such a.` character that it provides energy to vary the horizontal convergence field component at the horizontal beam dellection frequency, and also energy to vary the vertical eld component at the vertical'beam deection frequency.

4: A dynamic electron beam` convergence system as dened in claim 3 in which, said energization varying' means is of such character that it effectively varies only one'of said field components.

5. A dynamic electron beam convergence system asl defined in claim 4 in which, said energization varying means is of such a character that itetfectively varies said horizontal field component.

6. In a color television system, a colorkinescope having a luminescent screen comprising a multiplicity of groups of phosphor dots capable' respectively of producing light of different component colorsof an image when impinged by electrons, anapertured masking electrode spaced behind said screen, said masking electrode having an aperture for, and in substantial registration with, each of saidgroups of phosphor dots, means for directingl toward said screen a video signal-modulated electron beam, means for rotating said beam about a longitudinal axis of said kinescope at a predetermined colorcycle repetition frequency, whereby toY cause components of' said beamto approach said screen from different' angles at successive instants ineach color cycle, means for angularly detlecting said beam to' trace a raster at said screen, said beam components being differently deected by reason of said beam rotation, a dynamic convergence system adjacent to the path of said rotating beam and energizable to effect convergence of saidl beam components at all points of said raster, means including a sourceof a substantially parabolic Wavefor varying the energization of said convergence system-proportional to the angular deection` ofi saidi beam components,- and means eectively modifying said substantially parabolic wave for varying the energization of saidconvergence system proportional to saidcolor cycle repetition frequency.

7, In a color television"` system, a color kinescope having ay luminescent screen'` comprising4 a multiplicity of groups of phosphor dotscapable respectively of producingV light of different component` colors of: an image whenimpinged by electrons, anv apertured mask-ingi electrode spaced behind said screen, said masking electrode" having an aperture for, and in substantial registration with, each of said groups of phosphor dots, meanslfor directing toward'l said screen a video signal-modulated electron beam; means for rotatingsaid beamlabout a longitudinal axisof, said kinescope` at` a predetermined color cycle repetitionfrequency, whereby tocause components of said beam to approach saidscreen through said masking; electrode from different` angles at successive instants in eachf color cycle,.rneans1` for deilecting said beam horizontally and vertically to trace a raster at said screen, said beam components being differently deflected by reason of said beam rotation,` a dynamic electromagnetic convergence system surrounding` the path of said rotatingz beam and` energizable to effect convergence of said beam components at all points of said raster, means including a source of a substantially parabolic wave for varyingthe energization of said convergence system at arate proportional to'the verticaldeflection' frequency, means including a source of a substantially parabolic wave for varying the energization of said` convergence system at a rate proportional to the horizontal deflection frequency, and means effectively modifying` one of' said substantially parabolic Waves for varyingv the energization of said convergence system at a rateproportional tosaid color cycle repetition frequency.

8. In a` color television system, av color kinescope having ai luminescent screen comprising` a multiplicity of groups of phosphor dots capable respectively of producing light of different component colors of arrimage when impinged by electrons, an apertured` masking electrode` spaced behind said screen,` said masking electrode having; an aperture for,. and in substantial registration with, each of said groups-.of phosphor dots, means including` an electron gun for. directing toward said' screen a video signal-modulatedelectron` beam, means for rotating` said beamabout a longitudinal axis of said kinescope at a predetermined color cycle repetition: frequency, whereby to cause components of saidbeamto approach said screen through saidv apertured` masking electrode from diiferent angles at successive instants ineach color cycle, means for deflecting. said` beam horizontally and vertically to trace a raster at said screen, said beam components being differently deflected by reason of said beam rotation, a horizontall andvertical dynamic convergence coil system surrounding? the path of said, rotating beam and energizable` tor effect convergence of: said beam componente at alls points ofV said raster,` means including a source of a'. substantiallyl parabolic wave for varying the energization of said? coil system4 as a function of said vertical deiection` frequency, means' including a source of` a` substantially` parabolic` Wave: for varying the energization of saidcoil system as azfunction'of-,said horizontal deection` frequency,` and. means effectively modifyingv one of said: substantially parabolic waves` for additionally varying the energization of saidl coil; system as a function offsaid color cycle.` repetitioni frequency.

9. In a color television system, a color kinescope having a luminescent( screen` comprising a multiplicity of groupsofl phosphor dots capable respectively of producingglight of different component colors of an image when impinged'by electrons,.a\masking electrodespaced behind said screen and; having an aperture for and` inregister with each'` of? said groups of phosphor' dots, means including an-` electron" gun for'directing` toward said screen a videolsignal-modulatedelectron beam, means including al.rotatingeld-producing system for rotating said beam about a.longitudinali axis of said kines'cope at a predetermined colorcycle repetition frequency, whereby to cause componentsof said beamtoapproach said-screenthrough the apertures ofi' said? masking electrode from different anglesat successive instants inV each color cycle, means for deflecting said beam horizontally andi vertically atdifferent frequencies to trace a raster at said screen, said beam". components being differently deected` by reason of said beam rotation, horizontal and vertical dynamic' convergence coils surrounding the path ofi said rotating. beanr and: energizable to effect convergence of said beam components at all points of said raster, means including a first substantially parabolic wave generator for variably energizing said vertical coil at said vertical deflection frequency, means including a second substantially parabolic wave generator for variably energizing said horizontal coil at said horizontal deflection frequency, and means effectively modifying said substantially parabolic wave at horizontal deflection frequency for variably energizing said horizontal coil at said color cycle repeti tion frequency.

10. In a color television system, a color kinescope having a luminescent screen comprising a multiplicity of groups of phosphor dots capable respectively of producing light of dierent component colors of an image when impinged by electrons, a masking electrode spaced behind said screen and having an aperture for and in register with each of said groups of phosphor dots, means including an electron gun for directing toward said screen a video signal-modulated electron beam, means including a rotating field-producing system for rotating said beam about the central longitudinal axis of said kinescope at a predetermined color cycle repetition frequency, whereby to cause components of said beam to approach said screen through successive ones of said apertures from different angles at successive instants in each color cycle, means for deiiecting said beam horizontally and vertically at diierent frequencies to trace a raster at said screen, said beam components being differently deflected by reason of said beam rotation, horizontal and vertical dynamic convergence coils surrounding the path of said rotating beam and energizable to elect convergence of said beam components at all points of said raster, means including a vertical frequency substantially parabolic wave generator for variably energizing said vertical coil, means including a horizontal frequency substantially parabolic wave generator for variably energizing said horizontal coil, and means including an oscillator producing a substantially sinusoidal wave having said color cycle repetition frequency for variably energizing said horizontal coil.

References Cited in the file of this patent UNITED STATES PATENTS 2,077,574 Maloi Apr. 20, 1937 2,093,157 Nakashima et al Sept. 14, 1937 2,123,011 Keyston et al July 5, 1938 2,140,284 Farnsworth Dec. 13, 1938 2,212,640 Hogan Aug. 27, 1940 2,222,934 Blumlein Nov. 26, 1940 2,384,717 Wilson Sept. 11, 1945 2,449,524 Witherby et al Sept. 14, 1948 2,485,569 Coughlin Oct. 25, 1949 2,572,858 Harrison Oct. 30, 1951 2,581,487 Jenny Jan. 8, 1952 2,613,333 vBull Oct. 7, 1952 FOREIGN PATENTS 114,048 Australia Oct. 30, 1941 866,065 France June 16, 1941