US2572861A - Deflection system for cathode-ray tubes - Google Patents

Description

Oct. 30, 1951 R G. E. HUTTER 2,572,861

DEFLECTION SYSTEM FOR CATHODE-RAY TUBES Filed June 5, 1947 2 SHEETS SI-IEET 1 GE) m 3 W I E13 I JNVENTOR.

Oct. 30, 1951 R. G. E. HUTTER 2,572,861

DEFLECTION SYSTEM FOR CATHODE-RAY TUBES Filed June 3, 1947 2 SHEETS-SHEET 2 48 INVENTOR.

Rudolf iEf/Yuiier Patented Oct. 30, I95! DEFLECTION SYSTEM FOR CATHODE-RAY TUBES Rudolf G. E. Hutter, Flushing, N. Y., assignor to Sylvania Electric Products, Inc., a corporation of Massachusetts Application June 3, 1947, Serial N 0. 752,157

The present invention relates to cathode-ray tubes and their circuits that provide a variably deflected, point-focused electron beam, and to methods of improving beam focus.

In the typical cathode-ray tube, an electron gun is provided which produces a beam or pencil of electron rays, and these are focused at a point ordinarily in the center of a photoelectric, fluorescent or comparable screen or other target such as one having discrete conductive areas. the electron beam is deflected from the center of the target for scanning or to produce a trace, the focus of the'beam at the target is distorted. This effect is usually more pronounced and objectionable with electrostatic deflection than with magnetic deflection systems, but it is serious in both types where the angl of deflection is wide. Whereas the beam produces a circular spot of small diameter at the center of the screen, there is a serious out-of-round enlargement when the beam is deflected. In television, this not only reduces the sharpness of the image (picked up or displayed) but also decreases its contrast. In applications other than television the loss of sharp focus may similarly impair the result. Accordingly, among the objects of the present invention are: to provide an improvement in the electron optical systems of cathode-ray devices, to provide novel electrical circuits for utilizing the improved cathode-ray devices, and in another aspect to improve the methods of beam focusing and deflection.

In the development of cathode-ray tubes there have been separate improvements in the electron gun, and in the deflection system. The present invention provides an improvement interrelating these two portions in such manner as to yield improved beam formation at all parts of the target, such as is now obtained in the absence of deflection signals.

The distortion of the electron beam caused by a single field or crossed fields has previously been recognized and various attempts have been made to reduce this distortion. According to one line of thought the mean potential of a pair of deflection plates can be varied according to a nonlinear function of the deflection voltage and relative to the last anode of the electron gun in the cathode-ray tube. Such arrangement alters the deflection sensitivity and tends to introduc serious barrel distortion of the image. Some small part of this distortion may be desirable in order to reduce the pin-cushion distortion that is normally characteristic of electrostatic deflection fields. The desired balance between the barrel When l Claims. (01. 315 15),

distortion and the pin-cushion distortion is further affected by the optional inclusion of a post accelerator electrode used. to increase the bril-r liance of the image without requiring excessive sweep voltages. Accordingly a further object of this invention is. to provide a new and useful method and arrangement for correction of spot distortion adapted to control as a variable essentially independent of the image-formation and image-correction systems.

In the drawings there are shown several embodiments of the invention having an electron lens system including cylindrical lens. means to introduce a certain beam distortion in advance of the deflection system which is very nearly equal and opposite to the cylindrical beam distortion caused by a transverse deflection field. .For further improvement, spherical focus adjustment is also introduced. For crossed deflection fields the correction electron lens system and its energization are somewhat more complex but utilizes similar lens elements. The invention will be better understood, together with further features of novelty and objects from the following specific but illustrative disclosure including the drawings in which:

Fig. 1 is a diagrammatic view of an undeflected electron beam focused at the target;

Fig. 2 is a similar view of an electron beam vertically deflected electrostatically;

Fig. 3 is an exploded perspective view of a cathode-ray tube including a single transverse electrostatic deflection field and one form of focus-correction electrode, and a circuit arrangement for beam-distortion correction;

Fig. 4 is a similar view of cathode-ray tube elements incorporating a modified electron lens system;

Fig. 5 is a similar view of a cathode-ray tube and an operating circuit showing another arrangement of focusing and correction electrodes;

Fig. 6 is a similar diagrammatic view of a cathode-ray tube utilizing magnetic deflection in the horizontal direction together with another form of beam-correction system and a circuit for the correction system; and

Fig. 7 is a similar view of'a cathode-ray tube and circuit for crossed electrostatic deflection fields with an electrostatic arrangement for correcting beam distortion.

In Fig. 1 an electron beam is shown which converges to a point p at target T. The pencil of electron rays is circular in cross-section before reaching the deflection plates l 0 and I2 as is indicated by the shaded area. Rays a and b repredirection are all deflected because of a potential difference applied between plates l and [2, but

at target T they do not focus'at 'a'lpoint. Electrostatic plates characteristically exert a focus'- ing effect in addition to their primary deflection function. As a consequence the components of the electron beam tend to cross over at various aa'ias'ei scribed herein for illustrative purposes and appear now to be more important, appropriate corrective magnetic electron lenses and combinations of magnetic and electrostatic lenses can be substituted. Thus, with either electrostatically or magnetically. focused electron guns, a magnetic cylindrical-electron lens appears to be superior to a like electrostatic lens .v'vhn the defiection system is magnetic. Purely electrostatic correction appears to be preferable for correction of beam distortion in an electrostatic deflec'tion arrangement.

points before reaching target T, in the manner of a light beam passing through a prism having convex faces. The spot p ontarg'et observed to 'be greatly elongated in thexdirectionof the .deflection '(y) and is also somewhat spread in the a: direction. Thus paths (1' and b intersect at q, some distance away from target T, whereas paths '0 and d intersect at r, considerably closer to target T.

In'orderto maintain aspot of minimum .area, I adjust the focus of the electron rays (their angle of convergence or their lateral separation or both) before the beam enters a deflection field.

No correction is required for .zero deflection in the usual type of cathode-ray system, and a sub- 'stantial correction is required for extreme deflection. The means for disturbing the circular symmetry of the beam includes a cylindrical electron lens which is energized as some function of the deflection field-strength. I also use a variable spherical electron lens,=.energized as a function of the deflection field-strength, for further improvement in the focus correction and for im proved operation 'of the cylindrical lens.

The term cylindrical electron lens is here used to mean any electron-focusing 'field which in effect resembles a cylindrical optical lens, in producing equal increased or decreased conver- 'gence of the electron .paths in spaced parallel planes. This type of 1.electro'n :lens is alternatively referred to as a two-dimensional lens,,and an electrostatic system at least one of the electrodes which establish this lens variously takes the shape of a slit between two transverse equipotential plates or an axially extended space between conductive walls'which 'are directly wired to each other but are different in potential from part of the adjacent electron-optical system. The term spherical electron-lens is here used to mean any focusing field for an electron beam which in effect resembles -a spherical optical lens, in producing equal converging .or diverging efiects in'all planes having a :common intersection coinciding with the axis of the electron-optical system. Spherical electron lenses may vare iously take the form of conductive plates or tubes with circular passages for the electrons,"centered about the beam path, differing in potential from similar adjacent elements. Where the term combined spherical and cylindrical electron lens is used, the =metallic construction in an electrostatic system will usually-include circu- While "electrostatic electron lenses are dc,-

In Fig. 3 there is shown an electrostatically focused 'electrongun, plates for providing a balanced tra'nsverse electrostatic deflection field and,

an arrangement for introducing the desired corrective distortion for the beam before it enters the deflection region. The arrangement is of use asshown, Where the crossed transverse deflection field is magnetic; and it illustrates the fundamental features that are utilized in correcting b m di o tio cros ele t s ati fie s Pla e l 4 n lfiron v t deflection field system, and are shown with elements IQ of aknoyvn form of cathode-ray gun thatis suitable for providing an ad 1l 2ably focused 161g}? tron nc uded i s 18 are ca h e 1:0, grid Ha i u nse e trod s 8 nd severally in the form of circular-apertured plates and nduct e c l nder 9.u p vi es beam intensity control voltage, as from the ideo amplifier in a television receiver or an adjustable D.+C. supply. v I I Positioned in advance of deflection plates is and i6 is a composite cylindrical and spherical corrective lens 32. The corrective lens in this instance utilizes part of the focusing electrodes of a gun l8 as a spherical corrective component and in addition a pair of parallel-edged plates 35 as part of a predominantly cylindrical electron lens. Plates 3t provide a slit perpendicularto the deflection plane. :This slit contrasts with a circular aperture, and seen to beam aperture that is elongated transverse to the path of the electron beam, and symmetrical about the y vertical and a; horizontalaxes that 'intersectat the center of the slit and perpendicular to the z axis along the electron beam pat h'. liflectrodefi is preferably maintained aticonstant D.-C. potential with respect to the cathode, in order not to disturb the characteristic I of beam-intensity triode 20, 22, 2B. To avoid changing the deflection sensitivity of plates 14 and 16, the potential on the electrode closest to the deflection system should also be held constant. By maintaining the voltage on slit electrode 36 constant at .the mean potential of the system, this condition is satisfied. With no deflection the potential last circular anode 3!} is made the same-as that of slit electrode 36 and the potentials of focusing electrodes 2-6, 28 and 30 are made such as to provide a point focus-at thescreen. The potenf tial-on-last anode =30 can then be lowered-relative vergence primarily in the :vertical plane. This isaccompaniedby-a spherical change-in focus because of changedyoltage gradients at both sides of anode 30. -At-t he same time .the-spherical beam focus is appropriately adjusted by properly changing the potential on electrode 28 in rela: tionito electrodes--26 and 30. The composite-result is a slightly enlarged horizontal beam spread and an appreciably enlarged -vertical spread which aftertraversing the deflectipn field is restor d o o ntiio sy M water thesame time source 38 energizes separate recti fying, wave-shaping, and amplifying voltage supplies 42 and 44. The modified deflection voltage developed in supply 42 is combined with the'D.-C. potential normally applied between cathode 20 and spherical focus electrode 28. The last circular aperture electrode 30 is normally maintained at a constant potential with respect to cathode 20, conveniently the same potential as that of first anode 26, and this voltage is combined with the modified deflection voltage developed in sup ply 44. Plates 36 are connected to each other and, if no effect on the image raster is desired, to the mean potential point of deflection-voltage source 38 as well as to the usual internal conductive coating 46 surrounding the deflection system. The potential of slit electrode 36 can thus be made the same as the mean potential of the balanced deflection system l4, Hi.

In operation of this circuit there is no voltage at the output terminals of unit 38 when there is to be no deflection, and nothing is combined with the D.-C. voltages in units 42 or 44, The potentials on all of the focusing electrodes at this time should be so adjusted as to provide essentially a point focus at target T. Slit electrode 36 will then be at the potential of last electrode 30. Under normal (no deflection) conditions the potential of center aperture 28 is much lower than both first anode 26 and last aperture 30. For correction of th beam in the presence of a deflection voltage, the circuit in the block diagram appropriately adjusts the voltages on electrodes 28 and 38.

. I have found the spot distortion to be a nonlinear function of the deflection, being the same for equal .deflections on opposite sides of the axis for aligned electrodes. Consequently units 42 and 44 will include a rectifier when used in a system producing this type of distortion, and in addition, a wave-shaper,

' In Fig. 4 there is shown an alternativearrangement for achieving substantially the same results as in Fig. 3, a vertical slit being substituted for the horizontal slit of Fig. 3. The electrodes are all unchanged in Fig. 4 as compared with Fig. 3, except that plates 36' are arranged to provide a slit perpendicular to the deflection plates 14 and l6 or otherwise regarded, the slit provided by plates 36' is parallel to the deflection. Using the same circuit as in Fig. 3 but by making the voltage on electrode 38 variably positive relative to the slit electrode it is possible to increase the convergence toward the vertical plane between electrode 30 and slit 36'. Some change in the magnitude and wave-shape of supplies 42 and 44 is also desirable.

This arrangement provides the desired beam the vertical spread of which is suficiently increased to correct for the inherent non-circular focusing or beam-distorting effect of deflection plates l4 and [6. The focus in the horizontal plane of the beam can at the same timebe adjusted to complement the spherical and cylindrical effects of electrodes 30 and 36' in correcting for the tendency of the deflection plates to cause cross-over of the electron paths represented by c and d in Fig. 2.

flFigs. 3 and 4 involve alternative methods of changing the focus of the beam emerging from first electrode 26 of the characteristically electroe static system. The purpose to be achieved is the correction of the spot distortion caused'by a 6. transverse deflection field, without materially affecting the deflection sensitivity, and this is achieved overall by weakening the focus of the beam in a non-circular manner before the beam reaches the deflection field. This shaping of the beam is achieved without affecting its deflection by providing electrodes enabling operation with constant potential on the last electrode adjacentthe deflection system. In order not to affect the: beam intensity it is furthermore desirable to in-- clude a constant-potential anode between the: cathode and the beam focusing and shaping region.

It is not necessary for the slit electrode (or' comparable two-dimensional electron-lens component) to follow the spherical electron lens system although the arrangements described above now appear to be preferable. The arrangement in Fig. 5 is an illustration of an alternative in which the correction component precedes the circular focusing elements, retaining the independent control of beam intensity and deflection as in Figs. 3 and 4. Vertical deflection plates 18 and 12 are provided with a properly corrected beam by cathode l4, first anode l6, slit anode 18 and three circularly symmetrical electrodes 80, 82 and 84. The intensity of the beam is controlled by grid 86 between cathode l4 and. first anode I6 by means of a video or adjustable D.-C. sup-' ply 88. D.'-C. supply 89 maintains electrodes 16 and 84 at constant potential to stabilize the characteristic of triode 14, 86 and I6 and the deflection sensitivity. The halves of electrode 18 are wired to each other and to electrode 16. A variable supply 9!] establishes a potential difference between slit and circular electrodes 18 and primarily for spreading the beam in a vertical plane while variable supply 9| and D.-C. supply 92, connected to electrode 82, separately adjust the spherical focus of the beam. The voltages from supplies 90 and 9| are related in appropriate manner as described in connection with Fig. 3 to the deflection voltage source 93 so that the beam distortion caused by the deflection system will be neatly compensated. Because the non-circular correction will evidently be reduced by the spherical electron lenses following, the arrangements of Figs. 3 and 4 are now regarded preferable.

In Fig. 6 an arrangement is shown for correct ing the spot when magnetic deflection is used. The two-section coil 48 is provided for deflecting the beam, ordinarily circular in cross-section, produced by the electron gun comprising cathode 50, intensity-control grid 52, and focusing electrodes 54, 55 and 56. For zero deflection the focus is adjusted for incidence at the target in a spot of minimum size. When coils 48 are energized by deflection supply 68 to produce a deflection field, and the beam is closer to one of the deflection 'coil sections than the other, the

. different transverse portions of the beam will be variously affected by the magnetic deflecting field and its incidence at the target will be enlarged in the direction of the deflection. I

The spot distortion is less with magnetic deflection than with electrostatic deflection, because of greater uniformity of the deflecting field and because there is no change in beam velocity; but image definition can be improved and the length of the tube decreased in a wide-angle deflection system by correcting the beam before it enters the deflection field. Thus, aflat-field coil 58, optionally in two parts as shown, can be arranged toprovide an axial field in advance of the de-" the .dhi Qntiono l h. h ne e o ooiho oe w h. the so ioel 9l i9 li elohtoyield a sho tened C rent th ugh soil SHDPLY '6 991 voltage ese itlod hr ph y hs a d roo iihill .sn oly .69 s he orm l D .c. -vo .taee. oh. anode oyh hiool a d sph rica t u hs- Y s th el c sta c focus o tho h smih-tho io ton gun and compressing it in the y direction upon enere za ioh o co 5. the hoh' ohta elo s tlo of the spo or focus .foroshorto ih that would notmah be caused hr ooh .8 be comhon sato It shou d b n r t d that t e lectros atic o u in el t s own Fi 6 oonhs .repla d by a x al ma n tic oil. and its ur eht or th u re t th ou a upplementa y .9011 can be appropriately varied by a current $0 1,196 like upp y .5 Also, crossed magnetic. e; hsot on fields can e corr c ed o pot .di tor: t on by m tua y erpe di u a axial flahho d coils like 0.0.11 58 and o or more .spheh oal or: motion coils enc rc i the ube neck and enor: sized n part by h d fies 01 su p i aop o: priately revised to de iver wav esh h d content- If one deflect on hold of a cathode-ray tub i electrostatiozand a crossed deflecti n field s as.- net c it. a :he nd e ti e y atis o y to c rect f r the spot dist ti n o th o ootror st ic fie d only, as n F s.- 3 o l o-v ne h lesser ma ne ca y caused :be, -d 1 9. .QIl on: corre tedn the alternative the e trostati deflecti n and c rrec ion a r m nt oi Fies- $.01 .15 m y b use o e honwith a ossed ma netic deflection andcorreotion arrangement as Eie. 6,. However, it is desirabl wh re b th o the crossed fields re eloo ro ta oth t the e he a correspondin correction for both horizontal and vertical distortions .of the beam focus.

In Fi 7, a -c.a-.th d :ray tub is showninolud: ing an illustrative ,form of correction vand 11 00115: ing electrode assembly for vcrossed electrostatic fields, Vertical .defieqt cq plates 9. "I? nd horizontal deflection plates .104, 106 constitute the deflection system, While electron gun I08 supplies a focused beam of electrons and correction system H0 ,modifies the normally circular .elec: tron :beam'to correct the vertical or horizontal or both ,beamrdistortion components. The cor; rected beam, after passing through the deflection field, will be excellently focused at target T despite the inherent circularlyasymmetrical focus;

ing-actionlof the deflectin pla s- Electron gun L08 includes cathode H2, :inten; s y-oo trol H fi s anod 1L5, ce ter aperture .8, and last an d L B- Asu to lo los and i tensity Control si nal is po d t rid 4.1 as .from t e vid o sm hfis in elevision .reco v First n d H5 s h d a :hleh 90 .sten ncsitive pot ntial b D- .-.su 1y 12. with respect to the cathode in order that all variations in beam intensity shall be caused under. contml o rid H4 a o e Ce t a ertur llo'ahsllast ape tur electrode 2" are h l hi h posit ve :DQ entialS, but the pot nt on these o sotrodos a e m tl va iable in ac dan e w th modifiosl sleoeetioh vo ta s to he s qrihodt The vol e oh elect od H is n rm l ow r tha oh sst s o t r ltfl, f

menses hoo rootioh system I o-or 1o9tl oh t' he ooos h. osrshs hioh of e1 9 4% o lit i a t s slit electgode 26th; ar.-

d tohtootis 7 su ta isst oh sre r. (1e ection plates prefer o. t e h st ge o thos moss one 12s. ar oth oo tohtoo ehtiol oonv hiehtl that ol ole no, mo the .intsths ohdho fvo oat A. ba anced rt os ome 13. ohd. ho d. h riz ntal d M. h ootod at the o v to t e to th t enorsie ss t 61 f l29l1o I 5 o tt h vol a e sou ces. .13 32 are oonh o .o to re ti yin omb nin also wovo-shopihe on 13;!-

imit ideal y to. Yidos o-ro taeo Y e s as, a tuhotiono the al oomoohootioht a pro imation the. swoeh voltages can oro t fi d ad ed in a e s oi ohit limited to. th pooh valu o i he one nd th ssultahtoon b no th ou h a waves hop s.- elterhs 'vol the two vol a es an b a pli d to; e ara e ba n d mo l tors a in so mi i .3421 6%; relat vel shif ed 1 0 in the w moi-1.1 ls ors and t o uto o t e two m d a rs oah be dd d and t eir mp i utloe o ootoi p o ides. a va in vo a e c rr s o din to the instohtoheonsrad l .deheotioh which. is th n nht th ou h on a n o t ato :wsyo: ape tn an? the alt rnative .a flat resis r hav o central ndu tive ton an a po ioh loonductive rin 1 o. esi. n a small aux i cathode: ay tube as a toltoee divider the movable co tact of which is the deflected electron beam. iho. pa ti l r details .of combinin .u it 135 ha lshsodtforgn no hotter the-pr se t nv n olta .itom nit. 13. co bi d w h the ll-Q- .from source. 1 d applied t spherical ohso ottoo l "1- A r cti y n and .combinin un t l.-7. ;oh.a .shh an wave-shapin the se.p.a.-; rately rectified sweep voltages, variably reduces. the og. potential on last anode l 20. Another te tify he ampl yi an Wave-shaping circuit Q49, energized lpyhorizontal defiectionsource H2} i used t m edu e th D.-.C. pot ntial on s c nd 1 s own-tho si nal out ut-of unit jl tsuho ti woosotl 91E! t ero ifie and w. .ro-..sha1ood .sisha .dere ned n hit 4 8 ;i ao 'oo to lastsh do H In ohos ion thoa a is d e ted othe cents; th so oo th eb o o d le tion s nals d. the .hotoht m o he o o us olo i des H8 and 2. :o o'hl o o o for p e e ns h P te tial o all the sl e sleeso oh isthe m a the hstohoo and a th mesh 'tnedetecmfi system, so that there is' no further chan'g e l f ocusl in traversing those elements: or biital' 'd'flectionybltage rch electrodelzll is llfgra'dient along the elc I elec'trbde I 26 causes" the id oh ayso he beamit h xt marily .m the horizontal direction." The on snlimo t t vs ttis lofi'o tatlelo t ooe 12 though the fiel traversed by theelectron b on sh n 1 team: e t d l2; equal and opposite. This is eliminated wins the whatsom uh 4 roug ut toll ast anode J29. Deflection source I39 at this tim ode hot i .t th ol o' o 1 1 1 shi 4 he s her s1 oousiis ihsted" 3t s sh ssyelta .1- hoes li o. dt' lto tel sl .24- In the ock dia am I34. However there is a change in spherical focus between electrodes H8 and I20 due to the lowering of the voltage on anode I20, and this makes possible the total elimination of variable supply I31 with critical design of the electrode, assembly, provided that the relative dimensions, spacing and D.-C. voltages are carefully designed.

When only a vertical deflection voltage ap pears, the potential on last anode I20 is reduced and the beam focus is extended predominantly in the vertical direction as explained in connection with Fig. 3. The spherical focus is also properly changed by changed potential on electrode H8 to perfect the corrective beam-conditioning in advance of the deflection system. Electrode I24 is at this time at the same potential as electrodes I22 and'I26 and therefore does not further affect the beam In the presence of crossed deflection fields, the two crossed components of the beam-focus correction are severally provided as described above. In unit I38 the rectified and shaped signals are added, to reduce the voltage on anode I20 further than on I 24 for proper correction of the crossed cylindrical components. The signal on electrode H8 provides the proper spherical correction.

- The focus-correcting arrangementsdescribed are primarily intended to avoid the spot distortion caused by usual deflection systems; but where the spot distortion is altered by special deflection system designed principally to reduce image distortion or for other purposes, the foregoing arrangements provide an independent control over beam focus. It will be recognized that the improved focus of a variably deflected circular electron beam achieved with my invention, while of-importance primarily in tubes having a photoelectric or a fluorescent screen, is also applicable to other types of tubes having, for example, a target embodying distinct conductive areas. And whereas several embodiments have been illustrated as preferred, it will be recognized that others will occur to those skilled in the art.

What I claim is: v 1. A cathode-ray device having a cathode for providing an electron stream, a target, means for causing transverse deflection of the electron stream across said target, electrodes forming said stream into a beam and additional electrodes establi'shing electrically variable spherical and cylindrical electron lenses providing a substantially fixed straight-line electron path between said cathode and said deflection means and effective when energized to variably control the focus of the beam and to extend the focus in non-circular symmetry as a function of the stream deflection said electrodes including a final electrode dis posed in advance of the deflection means which electrode can be connected to a fixed potential point as others of said electron lens electrodes are varied in potential.

- 2. A cathode-ray device according to claim 1 wherein said cylindrical electron lens is established by electrodes including an electrode having a transversely symmetrical aperture elongated transverse to the electron stream.

3; A cathode-ray device according to claim 1 including in addition an intensity control electrode between said cathode and said stream focusing lenses.

4. Cathode-ray apparatus including a cathoderay device having a cathode, a screen, transverse deflection means and plural beam focusing and shaping elements between said cathode and said deflection means, one of said elements being ircularly asymmetrical, deflection supply means for energizing said deflection means, and wave-shaping circuits interconnecting said deflection supply means and said focusing and beam-shaping elements for variably circularly enlarging the electron beam and for causing circular asymmetry as a function of the deflection, in advance of the deflection field. V

5. A cathode-ray system according to claim 4 wherein a constant potential supply is connected between that element of the focusing and-correcting elements which is closest to said deflection elements and the point of mean potential in said deflection supply means. r

.6. A cathode-ray system according to claim 4 including in addition an intensity control electrode between said cathode and said focusing and beam shaping elements, and a constant voltage supply between said cathode and the first of said focusing and shaping electrodes adjacent said intensity control electrode.

7. Cathode-ray apparatus including a cathoderay device having a cathode, a screen, a transverse deflection system for variably directing an electron stream from said cathode to various portions of said screen, a plurality of electrodes'between said cathode and said deflection system for focusing the electron stream in circular symmetry or asymmetry as a function of the deflection, at least one of said electrodes having a transversely long and narrow aperture, and an intensity control electrode between said cathode and said focusing electrodes, in combination with deflection supply means for said system, constant potential supply means for those focusing electrodes immediately adjacent said intensity con-' trol electrode and adjacent said transverse deflection system, and wave-shaping voltage supplies coupling said deflection supply means to certain of said focusing electrodes.

8. A cathode-ray tube having a cathode for providing an electron stream, a screen at which the stream is to be focused at an area of minimum circular size irrespective of deflection, means between said cathode and said screen for producing neutrally perpendicular symmetrical transverse deflection fields, and a plurality of aligned electrodes between said cathode and said deflecting means for shaping the electron stream into a beam focused at said screen in an area of minimum circular size irrespective of the inherent non-circular focusing effect of the deflection fields, said electrodes including plural circularly symmetric electrodes and an adjacent series of three electrodes, the first two of which have transversely elongated slots parallel to one deflection field and the third having an elongated slot parallel to the other deflection fleld.

9. Cathode ray apparatus including a cathoderay device havinga cathode, a screen, a transverse deflection couple between said cathode and said screen, beam-focusing and focus-correcting.

electrodes between said cathode and said deflect-' ing couple including at least one unipotential electrode having a transversely elongated pas-' sage, a deflection signal source for said deflection couple, and connecting and wave-shaping circuits between said source and said electrodes.

10. A cathode-ray device including a cathoderay tube having a cathode for providing an electron stream, a screen, a pair of mutually perpene dicular deflection couples for determining the traverse of the electron stream over said screen, and electron-focusing and focus-correctingelectrodes embodying circular and transversely elon-' mass-i gated passages positioned between said cathode and said deflection couples, deflection signal supplie for said deflection. couples, a correction signal source connected to a said circularly symmetrical electrode for. providing a voltage varying as functions of the signals from said deflection supplies, and connections. between one of said deflection supplies and another of said focuscorrecting electrodes.

11.. The method of correcting for the defocusing effect of a deflection field in a cathode-ray device causing non-circular enlargement of the normally circular incidence of the beam preferentially at the screen or target, which comprises the steps of providing a normally circular electron beam and spreading the beam in the direction of the deflection as a function of the deflection field. before it enters the deflection field.

12. The method of correcting for the spot distortion of the beam in a cathode-ray device at the screen or target caused by the deflection field, which comprises the steps of adjusting the beam focus three-dimensionally and two-dimensional- 1y before it reaches the deflection field, each as a respective function of the deflection field.

1'3. Themethod of correcting for the distortion. of a normally circular electron beam due to an. electrostatic deflection field, which comprises the step of electrostatically extending the focus of the beam predominantly in one transverse plane in advance of the deflection field and as a function of the field. I

14 The method of correcting for the'non-circular distortion of a normally circular electron beam caused by a magnetic deflection field, whichcomprises the step of magnetically changing the beam focus. predominantly in one transverse direction as a function of the deflection field.

15. The method of correcting for the non-circular defocusing effect of a pair of crossed defiection fields which com-prises the step of extending the beam focus in the separate directions of the deflection fields before enteringthose fields as. functions of the deflection field intensities.

I 16. The method of correcting the focus-distortionof a cathode ray that is incidental to deflection comprising the step of cylindrically adjusting the focus of the electron beam in ad'- vance of the deflection field as a function of the deflection.

17.. Cathode-ray apparatus comprising a oath-- ode-ray tube having a cathode for providing an electron beam, a screen at which the beam is desirably focused at an area of. minimum. circul'ar size irrespective of deflection, a transverse deflection couple between said cathode and said screen. plural accelerating and focusing electrodes between said cathode and said deflection couple, at least one of, said electrodes having a trans versely elongated passage acting with an axially adjacent electrode to modify the focus of the electron beam in the manner of a cylindrical lens, a. source of deflection voltage, and waveshaping and proportioning circuits between said deflection voltage source and at least one of said electrodes for variably adjusting its voltage as a function of the deflection voltage.

18. Cathode-ray apparatus including a cathode-ray tube having a cathode and the first anode for providing a normally circular electron beam, a screen at which the beam is intended to be focused at an area of minimum circular size independent of deflection, a pair of transverse deflection couples mutually perpendicular to eachother, a plural-electrode electron optical system.

12 between said first-anode and said. deflection couples the. last electrode of which connected; to the mean potential point of said deflection couples and, through a constant potential source, to said cathode, said electronoptical system including .a circularly symmetrical electrode energized as a function of the combined. deflection fields, and an electrode having a transversely elongated aperture forming part of a cylindrical lens energized as function of said composite fields. I

19. Cathode-rayapparatus including. a cathode-ray tube having. a cathode, a target. atrans of minimum circular size; saidsystem including an axial flat-field electromagnet. V a v 20.. Cathode-ray apparatus including arcathode-ray tube having a cathode and a. first anode for providing. an electron beam normally circular in cross section, a. screengat-which the beam is. intended to be focused at an. area minimum circular size independent of deflection, a pair of transverse. deflection devices between said cathode and saidscreen. disposed to produce transverse deflection fields perpendicular to each other. each. deflection devices having a respective deflection signal supply, a multiple-electrode electron optical system betweensaid: first anode and said deflection devices, the lastelectrode of'said electron optical system beingconnected to the mean point'of the deflectionsignal supply of the deflection device-nearest to said last electrode. said electron optical system including electrodes establishing a variable spherical electron lensand electrodes forming: plural cylindrical. electron lenses effectively extending parallel respectively to the fields of the deflection devices, a. waveshaping circuit between one of said cylindrical lens electrodes and one of. said deflection signal 7 tion field producing means disposed between said cathode and said target, electrodes forming said.

stream into a beam, a beam-intensity control electrode, and electrodes establishing electrically variable spherical and cylindrical electron lenses, all said electrodes being disposed between said cathode and said deflection means, and providing a substantially fixed straight lineelectron beam path, said electron lens electrodes including an electrode having an aperture elongatedtransverse of the electron beampath'which aper-.=

ture. is symmetrical about a pair of mutually perpendicular axes in the plane perpendicular to the electron path, said electrodes including a. final electrode that can be connected to a. fixed potential point separate from others of the electrodes that can be varied in potentiaLsaid spherical and cylindrical lenses being eflective when en.- ergized to variably control the focus of the beam and. 50, extend the focus in. non circular symmetry as a function of the electron beam deflection.

22. A cathode-ray device comprising a screen, means for forming and projecting an electron beam along a certain path toward said screen, beam-deflecting means including beam-deflection power supply means efi'ective to cause the beam to scan substantially the entire screen, an electron lens system including a cylindrical electron lens component and spherlcal electron lens means along said certain path of said beam and both coupled through shaping circuits to said beam-deflection power supply means for energization thereby and efiective to minimize the variation in size of the beam when deflected over the area of the screen.

23. A cathode-ray device comprising a screen, means for forming and projecting an electron beam along a certain path toward said screen, vertical electrostatic deflection means and horizontal electrostatic deflection means positioned along said path, separate beam-deflection power supplies for said vertical deflection means and said horizontal deflection means, a cylindrical electron lens component along said certain beam path, a spherical electron lens component separate from said cylindrical electron lens component along the beam path, and coupling and shaping circuits between both of said electron lenses and both of said power supplies.

24. A cathode-ray device comprising an electron target, means for forming and projecting an electron beam along a certain path toward said target, means for deflecting said beam laterally in a first direction including a deflection power supply, means for deflecting said beam laterally in a direction perpendicular to the first direction and including a separate deflection power supply, said deflecting means intrinsically causing variation in shape of the beam incidental to d fl c n. an a c r ec e e e tron lens system including a cylindrical component and a spherical component both coupled through shaping circuits to both of said beam deflection power supplies.

25. A cathode-ray device comprising a screen, means for projecting an electron beam along a path toward said screen, beam-deflecting means including beam-deflection power supply means effective to cause the beam to scan substantially the entire screen, a cylindrical electron lens distinct from said deflecting means, and spherical electron lens means, said lens and lens means both being coupled through shaping circuits to said beam-deflection power supply means and effective to compensate for the inherent beamdefocusing effect of said deflecting means.

RUDOLF' G. E. HUTTER.

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

UNITED STATES PATENTS Number Name Date 1,779,794 Ackerman Oct. 28, 1930 2,089,692 Drewanz et a1 Aug. 10, 1937 2,101,669 Bruche et a1 Dec. 7, 1937 2,103,645 Schlesinger Dec. 28, 1937 2,114,610 Schlesinger Apr. 19, 1938 2,137,353 Schlesinger Nov. 22, 1938 2,196,838 Rogowski et a1. Apr. 9, 1940 2,212,640 Hogan Aug. 27, 1940 2,217,197 Davisson Oct. 8, 1940 2,227,020 Schlesinger Dec. 31, 1940 2,252,441 Schlesinger Aug. 12, 1941 2,296,102 Gray Sept. 15, 1942 2,332,622 Calbick Oct. 26, 1943 FOREIGN PATENTS Number Country Date 1 1L 1 A stralia V--V---- July 23, 194.0

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