US2730651A - Dynamic electron beam control systems - Google Patents

Description

R. w. soNNENFL-:LDT 2,730,651

DYNAMIC ELECTRON BEAM CONTROL SYSTEMS Filed March 51, 1953 2 Sheets-Sheet 1 Jan. 10, 1956 Jan. l0, 1956 R. w. sQNNENFELD-r DYNAMIC ELECTRON BEAM CONTROL SYSTEMS Filed March 3l, 1953 2 Sheets-Sheet 2 INI/ENTOR.

EINNENFELDT /ITTORNEY RICHARD W. El'

UnitedStates Patent "O p DYNAMIC ELECTRON `BEAM CQNTRL SYSTEMS Richard W; Snnnenfeldt, 'Hadamar-1&1, N. J., ns'signor to .,iThisrrinvention relates-to systems for controlling the electron beams' of cathode fray tubefsand in more partic- Lilaiit'yjf, although not necessarily exclusively, to improved means fr permitting the dynamic control of a plurality of electron bea-rn components as employed in cathode faytubsfso s ato rnaintaiugood focusing of the respective .beam `ornponents and also to effect convergence vof said components at all points of `a raster scanned in a' predetermined plane. l

'I'he prsent trend in 'television kinescopes is toward the 'use of Yatter luminescent screens of increasingly greaterrre'as. Also, the tendency is to shorten the tubes as uch fas 'possible 'to permit their employment in home instrument cbine'tsof smaller size. These factors ke the prbble'nof decting an electron beam or a plurality of el, tron beam componentswithin -the cathode-'ray tube 'a i ore ldifficult one.. VDeflection problems become fevfn more ei'riple'it Vwhen the 'size of the kine- 's'cpe 'i`s` 'increased lng'vvtli lthe'p'rovision of specialized tube g'eo'rfetijies aimed 'atf'eiihan'cihg `the electron ybeam fo s` overthe wide 'angles 'of deflection required in s'hrtertubes of large fsr'eeu area.

Ax'representative example ofa ycathode ray tubeof fthe character 'refe'red to i's afmltic'olor `kin`escope formingjthe subject'inatter nf aU. iS. Patent cf'AIfred N. ocmsniitnfNn.2,630,542, fissneajMereh 3, 1953, and entitled -Multifciiiil'oi' Television. The luminescent "screen of 'this tube 'consists'of arnultiplicity of phosphor ar of sub-elemental dimensions. Different sub-elemental tareas are respectiveliy,''capable 'of producing a color 'of light corresponding 'to 'a lditerent one 'of three "component `irjnjagefcolcfrs, when excited by electron bjeain energy. p In this tube 'the different light producing phasph'rscreen areas are 'excited respectively by a plurality of electron beamsfappoaching 'the sceen from different :angles through an yapertured .masking electrode; C'lefr selection ijs Aseeunei lay-controlling Y'the angie at which the "electronbeanis approach the screen.

Another representative Aexample `of the cathode` ray tubeto wh'i'hjjurepresent invention may usefully apply, orfns the subject rnlpatter of afeopending v4U. spate-nt Iapplic'atic'iri'of Russell "R; LawfseriallNo. 130,195, tiled November 30, 1949, fnd entitled Color Television RepdiicingTubes,'now abandoned but continued in part by U. fS. patent application, S, N; 1651552, iiled 'June 51, 1915.0, entitled LColor Tel fr si'n. In general, the L''w tube jis siniila'r in the J'Goldsmith tube. The `chief difference -isithat the -Lawtube employs a single `electron gun by which to produce the plurality 'of electron beamc'rripriett's, whereas; in the Goldsmith tube, an electron gun lis 'providedfto produce each beam. This is accomplished by 'fiiriprlting a s'pinningitype-offmoveme't t6 fthe llfrlV S`0 fth'at lit-'Sld'e 4iiolltltc bblt the centralor longitudinal airis offthe tribe. fIn its :rotation about the tube axis, the ibeam Aoccupies `at successive intervals, ysubstantiall-ywthe same positions -as the vdifterventelectron beams of the Goldsmith tube.

The expression felectron `beam -componentsfas used in this specication and claims, is intended to cover the type of phosphor exciting electronic energy produced by a single or vplurality of electron guns. This energy may be continuous or pulsating asrequired Without departing from the spirit and scope of the presentV invention.

In rthe operation of multicolor kinescopes of the type referred to above, it is requiredl that the plurality of electron beam components Ybe made to converge substantially in the vplane of the masking electrode of all points in the scanned raster. In view of the .fact that the differed points ofthe target electrode are at different distances from the point or region of 'the electron beam deection it is `necessary 'to provide a field producing means which is variably energized to produce a dynamic convergence control. One Ysuch electronr beam Ycontrol system forms the subject matter 'of a copending U. SQ

patent 'application of Albert Friend, Serial No. 164,444, led May 26, 1950, and entitled Electron Beam Controlling Systems. In the Friend case, an electron optical system is variably energized as .functions of both the horizontal and vertical beam deilec'ti'ons It can be demonstrated that without dynamic convergence control the electron beam components converge at driierent points as they are deilected to scan a raster. Locus of these convergence points is approximately parabolic in form. Accordingly as disclosed in the Friend application referred to, the electron optical system is variably energized as a parabolic function of 'both the horizontal and yerticalbeam deflection waveforms.

Itv has also been found that Iin wide `angle cathode ray beam deiection systems the electron 'beam components tend to become defocused for the same reasons that a plurality -of Ydiscrete electron beams tend Jto Adiverge 'when an attempt was made to converge them on a single point in the target plane. The electron beam convergence problem and the electron Vbeam focusingproblem in wide a'nfgle deflection Systems are respectively discussed in U. -S. patent application by Loren 'R. Kirkwood, entitled Dynamic-Electron Beam Control Systems, tiled November 30, 195'0,Serial No. 198,313, issued August 24, 1954, `as Patent No. 2,687,493. A complete color television receiving system using a parabolic waveform for both beam convergence and beam `focus correction in a multigun lcolor `kin'es'c/ope, '-isA'described in an article entitled Compatible Co'lor TV Receiver, by Kenneth E. Kerr, appearing in 'the January 1953 issue of Electronics, page `9'8.

:In fthe 'Kirkwoodcase and the Electronics article, it is pointed out that the electrical waveform required for electron beam convergence correction as well as focus correction are 'substantially fthe same. Accordingly, throughout "the specification the terms correction signal or correction waveform`will "be mea'ntto include the use `of `a parabolic form vof electrical lsignal to improve the `dynamic beam convergence and/or dynamic beam focus in a cathode ray beam system.

The obtaining'of trulyparabolicwaveforms of suitable amplitude :for `the correctionof dynamic beam convergenceY and focus, withoutresorting to costly circuitry and apparatus, has presented litself as amajorproblem.

i Ideally, the beam convergencel and beam focus correction waveform should be obtained directlyfrom the cathode ray `tube in which beam convergence and beam focus Patented Jan. 10, 1956` Y 3 changes in the values of circuit parameters can be met by complementary and corresponding change in the amplitude of correction waveform. As one attempts to extract energy from a deflection circuit in a parabolic waveform, it is generally found that either linearity and circuit etliciency of the deflection system must be sacrificed or the correction waveform kmust suffer compromise in not representing a true mathematical parabola.

It is, therefore, an object of the present invention to provide an improved and simplified electron beam control system by which it is possible to maintain uniformity of performance in beam detlection'within a cathode ray type tube. Y

It is further an object of the present invention to provide an improved generator circuit 'of electrical waves of complex waveform and high amplitude at a minimum of circuit complexity and expense. v Y Y It is still another object of the present invention to provide an improved and simplified means for deriving para bolic shaped waveforms suitable for cathode ray beam convergence and focus correction from standard forms of cathode ray beam deflection circuits. Y

It is a further object of the present invention to provide an improved and simplified means for deriving a parabolic shaped waveform of high voltage amplitude from a vertical electromagnetic cathode ray deflection circuit of the type used in home instrument television receivers.

Another object of the present invention is to provide an improved means for obtaining proper energization of the beam convergence and focus correctionrmeans of a multigun cathode ray beam color kinescope.

In the realization of the above objects and features of advantage, the present invention in one of its more specific embodiments, contemplates the development of a parabolic waveform by the addition of two signal waveforms derived from a conventional type cathode ray beam deflection circuit. Firstly, a substantially parabolic waveform is extracted from the deflection circuit in such a way that the low frequency components requisite to form a perfect parabola are absent. Secondly, a sawtooth waveform of voltage is developed which is conditionally added to the firstly developed signal to produce an overall waveform having substantially perfect parabolic features.

In the application of the present invention to a vertical type cathode ray beam deflection circuit which employs a standard verticaldeflection output transformer', an additional transformer is provided having its primary winding connected in series with the primary winding of the vertical deilection output transformer. The secondary winding of the additional transformer is terminated in a resistance-capacitance load suited for the development'of a high potential signal which approaches a parabolic waveform but is deficient in low frequency components. An auxiliary Winding is then provided on the vertical deflection output transformer which is resistively terminated so as to form a voltage waveform corresponding to the developed sawtooth of a deflection current. This Waveform is added to the firstly developed semi-parabolicwave,A form to provide the desired convergence and focus correction signals.

A more complete understanding of the present invention, as well as other objects and features of advantage Y the basic elements of a dot multiplex type color television system to which the present invention may be advantageously applied. The underlying principles of operation of the dot sequential color television system are treated at some length in an article entitled Analysis of dot sequential color television, appearing in the October 1951, issue of the Proceedings of the'Institute of Radio Engineers, page 1280.

In the arrangement of Figure l, a television signal receiving Vmeans is indicated by block 2. The television receiver amplies signals detected by the antenna 4, demodulates these signals and provides a video signal tothe video signal channel means indicated by block 6. l Suitable color demodulation means are provided in the video signal channel 6 so thatV three separate component color signals are made available on the output buses 8, 10 and 12 respectively connected with gun control electrodes 14, 16 and 18. Average brightness information for each. color channel is developed by the D. C. restorer circuit 20.' The restorer circuit 20 is a three channel device' which permits separate brightness informationY to be applied to the separate electron gun cathodes 22, 24 and 26.

As described in an article entitled A three gunshadow mask color kinescope, by H. B. Law, appearing in Octo` ber 1951, issue of the Proceedings of the Institute of Radio Engineers, pages 1186-1194, the color television picture reproducing kinescope 28, referred Vto sometimes as Va Triniscope, includes three separate cathodeV Aray beam gun structures. The gun control electrodeV and cathodes of these gun structures havebeen described hereinabove. Also shown within the envelope 28 are the respective gun screen electrodes 30, 32 and 34.' The gun screen electrodes are connected in a conventional fashion to a source of positive power supply potential indicated by the block 36. Focus control electrodes are indicated atl38, 40 and 42 for focusing the yrespective electron beams onto the multicolor phosphor dot target 44. A shadow mask for producing selective energiza'tion of predetermined color dots by the respective electron beams sindicated at 46. For purposes of illustration, the direction of approach to the targetV of the 'three electron beams produced by the three electron beam guns, is indicated by the dotted lines 50, 52 and 54. Thus, asdescribed in the above article, A three gun shadow mask color kinescope, the

three beams produced by the respective electronguns passing through a given aperture in the shadow mask 46, will excite respective deposits of phosphor on the target 44. The phosphor deposits on the target 44 are arranged in tangential relationship so that any group of three deposits served by a given aperture in the shadow mask 46, will, when simultaneously excited by properly balanced beam energy, act to produce a resultant whitev light. A

Y beam convergence electrodeSS is provided for insuring the coincidence of the three beams upon any given aperthereof, will be gleaned from a reading of the following ture in the shadow mask 46 for any angle o f beam deflection. Y

The method by which the beam convergence electrode serves to improve coincidence ofthe three. electron rays produced by the three separate electron beam guns is discussed in an article, Deflection and convergence in color kinescopes, by Albert W. Friend, Yappearing inv the Proceedings of the Institute of Radio Engineers for Octo ber 1951, pages 1249-1263. In .this article is pointed out that in order to accomplish a satisfactory degree of beam convergence over very wide angles ofY deflection, the waveform of voltage-applied to the beam convergence electrode 55 vshould be substantially parabolic in shape, and synchronously related to the deflection signal of the system. As brought .out in the above identified U. S. patent application Dynamic Electron Beam Control Systems,. ledNovember 30, 1950, Serial No. 198,313, by Loren R. Kirkwood, issuedV August 24, 1954, as Patent 2,687,493, the dynamic beam convergence's'ignal applied to the beam convergence electrode 545 mayalso'be applied to the gun'focus electrodes 38, 40 and 42 vto improve 'the to inherent characteristics of most commercially available transformers, the lower frequency-components of the Asawtooth current flowing through the primary winding 144 of the transformer means 148 will not find representation in the secondary winding 153. Characteristics of the transformer means 148 will not only impose a loss in low frequency components, but also produce a net shift in the phase of the signal appearing across resistor 156 relative to the beginning and ending of the sawtooth current waveform flowing in the primary circuit. Thus, the signal appearing` across resistor 156 will be the result of removing the lower frequency components from a parabolic waveform signal.

In accordance with the present invention, the absence of lower frequency components and the resultant phase shift in the signal appearingracross resistor 156 is cornpensated bythe addition of a sawtooth waveform developed across the resistor 158. Resistor 158 is connected in shunt with the secondaryrwinding 160 of transformer means 146. A tap 162 on the winding 160 is connected with circuit ground. The sawtooth of current developed in the secondary winding 166, will, therefore, cause a sawtooth voltage to appear across resistor 158 in such a way that the tap 166 on resistor 158 may be positioned to display substantially no voltage with respect to ground or it may be adjusted to display. aV positive or negative going sawtooth voltage waveform of an adjustable amplitude. Depending upon the particular characteristics of the transformer 1.48, it is found in the practice of the present inventionthat the tap 166 may be so adjusted that when taken in combination with the voltage developed across resistor 156 a substantially perfect parabola of voltage will appear at terminal 168. This terminal is then capacitively coupled by a capacitor 170 to a focus electrode 172 ofthe .kinescope 152. The static focus supply voltage means 174 has its'negative polarity terminal connected with circuit ground and its positive polarity terminal connected through an isolating resistor 176 to the focus electrode 172. Y The value of the resistor 176 is so chosen as to allow a sufficient amplitude of dynamic focus-control voltage to be developed at-the focus electrode by merit of its coupling viacapacitorY 170 to the parabolic control voltage appearing at terminal 168. l It will be appreciated that the practice of the present invention is inno way limited to the provision of two separate transformer means. Itis evidently quite possible to provide a single transformer means having three secondary windings or threeseparate transformer means, each having'a single secondary winding; In one'of the preferred form of the invention, the arrangement of Figure 2 is desirable since by providing a separate transformer means 148, the primary winding 144 Ymay be resonated by capacitor 178 to supplement the resonant secondary winding 153. In this way, the ,deflection current waveform delivered to the 'deflection yoke 150 is not altered by any circuit change in either the primary or secondary windings of the transformer means 148.

For purposes of considering the application of the embodiment of the present invention in Figure 2, to the circuitry of, Figure 1, it is only necessary to regard theoutput terminal v84 Vof the vertical convergence control wave generator 82 of Figure l, as the equivalent of terminal 168 in Figure 2,. The horizontalpconvergence and focus control generator V'76, illustrated in both Figures 1.V and 2, merely provides the meansfor accomplishing the serial addition of a parabola o f horizontal deflection frequency to the vertical deflection frequency parabola developed by the circuitry of the present. invention.

What is claimed is: v l. In a voltage generating means for developing a sub'- stantially parabolic waveform, the combination of: a

source of sawtooth waveform; integrating means includform source for developing a sawtooth waveform suitable for addition to the waveform produced by said Aintegrating means including said low frequency attenuation means; circuit means connected with said integrating means including said low frequency attenuation means and said sawtooth waveform developing means for linearly combining the output signals from each to provide a single composite waveform of substantially parabolic shape.

2. A `signal waveform system for developing a substantially parabolic waveform signal comprising in combination: a source of sawtooth deflection signal; a signal amplifier tube having atleast an anode and control electrode; signal coupling means connected from said sawtooth deflection signal source and said control electrode; a source of biasing potential for said anode; transformer means having a primary winding connected between said anode and said source of biasing potential; a first secondary winding and a ,second secondary winding included in'said transformer means, said first secondary winding having a predetermined inductance; a capacitor connected in shunt with said first secondaryV winding means to form a 'tuned circuit whose resonance is below the recurrence frequency of sawtooth signal supplied by said sawtooth signal source; resistance means connected in shunt with said second secondary winding; and a connection from a point on said resistance means to said first secondary winding.

,3. A signal waveform system according to claim 2, wherein there exists a predetermined leakage inductance between said secondary means and said transformer pri- Ymary means and wherein there is additionally provided -a capacitor in shunt with at least a portion of said transformer primary winding means, the value of said capacitor being so chosen as to resonate with the value `of leakage inductance at a frequency sufficiently low to minimize leakage inductance ringing in said first secondary winding.

4. Ina parabolic wave generating system, the combination of: an output transformer means having aprimary winding; a first secondary winding and a second secondary winding; an auxiliary transformer means having a primary winding and a secondary windingg-an inductive load connected across said output transformer first secondary winding; an electron discharge tube having at least an anode and control electrode; a source of biasing potential for said anode; connectionsl between said anode, said auxiliary transformer means primary winding, said output transformer means primary winding and said source of biasing potential for placing said primary windings in series with one another between said anode and said biasingpotential source; a source of driving signal for said electron discharge tube, said driving signal having a waveform of such contour that when amplified by said discharge device results in a substantiallyY linear sawtooth current flow through said inductive load; resistance means connected in shunt with said output transformer means secondary winding; a capacitor connected in shunt with said auxiliary transformer means secondary winding and a connection between said resist- `ance means and said auxiliary transformer means secondary winding such that the voltage appearing between a point on said auxiliary transformer secondary winding and a point on said output transformer second secondary Winding is substantially parabolicI in wave shape.

5. in a parabolic Wave generating system, according to claim 4, wherein said auxiliary transformer means has an inherent leakag'einductance ,between its primary and secondary windings and wherein there is additionally provided aV capacitor connectedV in shunt with said auxiliary transformer means primary winding, thev value-of said capacitor beingso chosen relative to the value of said leakage inductance as to minimize the effect of leakage inductance ringing in said auxiliary transformer means secondary winding. Y j

6. In a parabolic'wavegenerating system, according to Vclaim. 4, wherein said capacitor inshunt with said auxiliary transformer means secondary winding is so chosen relative to the value of the inductnce of said auxiliary transformer means secondary winding as to detine a resonant circuit tuned to a frequency value below the recurrence frequency of the waveform applied to said electron discharge tube control electrode.

7. In a parabolic wave generating system, according to claim 6, wherein there is additionally provided a resistance means connected in shunt with said auxiliary transformer means secondary winding, said resistance means having a variable signal output'tap thereon; and wherein the output transformer second secondary winding is provided with a tap which is established at a signal datum potential; and wherein said resistance means connected in shunt with said output transformer second secondary winding has a variable tap thereon; and wherein said connection from said output transformer resistance means auxiliary transformer means secondary winding is made from said variable tap on said output transformer resistance means.

8. in a cathode ray beam deflection system in which is to bc developed a sawtooth of deflection current and a parabola of control voltage, said parabola of control voltage being suitable for dynamic beam convergence and dynamic beam focus control, the combination of: an electron discharge tube having at least an anode cathode and control electrode; input circuit means connected between said control electrode and said cathode for receivf ing a deection signal; a rst and a second transformer means whose primary windings are connected in series with one another between said electron discharge tube anode and cathode; a rst secondary winding on said Iirst transformer means designated for connection with an electromagnetic deiiection yoke; a second secondary on said rst transformer means having atap thereon; a

signal datum terminal connected with said rst transformer second secondary winding tap; a rst resistance means connected in shunt with said first transformer second secondary winding, said rst resistance means having a variable tap thereon; a secondary winding on said second transformer means having a predetermined inductance; a capacitor vconnected in shunt with said second transformer secondary winding, the value of said capacitor being so chosen as to resonate with the inductance of said second transformer secondary winding at a frequency below the recurrence rate of the deflection signal applied to said electron discharge tube control electrode; a second resistance means connected in shunt with said second transformer secondary winding, said second resistance means having a variable tap thereon whereby there is permitted to exist between said variable tap and. said signal datum terminal a substantially parabolic waveform concomitantly with the existence of sawtooth current iow in said sawtooth transformer said secondary winding.

9. In a cathode ray beam deection system according to claim 8, wherein said cathode ray beam deection system is incorporated in a color television picture reproducing system employing a multi-element electron beam and having a beam convergence electrode and wherein said second transformer secondary winding is connected with said beam convergence electrode.

References Cited in the file of this patent UNITED STATES PATENTS 2,220,303 Tingley Nov. 5, 1940 2,449,524 v Witherby et al Sept. 14, 1948 2,455,373 Lester Dec. 7, 1948 2,651,602 De Cola Sept. 1, 1953

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