US2824250A - Cathode ray apparatus utilizing convergence means - Google Patents

Description

Feb. 18,1958

CATHODE RAY Filed May 12, 1955 J. T. M NANEY ET AL 2,824,250

APPARATUS UTILIZING CONVERGENCE MEANS 3 SheetsSheet l IN UT INPUT CHARACTEI? CHARACTER SELfCT/ON POSITION 45 omens/2 4e Dco02 50 4-9 52 5/ j 53 54 Hole/z. VEQT. l-IOQ/Z. V527. 5MNK BLANK saw. 1 SELN. T DEFL'N. fi DEFLN. "A 5g? 'xgg AMP AMP! 7 AMP. AMP. GEN]? GEN? mi [/9 20 2/ I r a I 5 'l i F m P f L m :4 I M 1 "V. I I8 23 2 27 comm/r 2 awe/ mm RfGUlATOR J A A WM} "A a I pow m SUPPLIES F] G 1 INVENTORS.

JOSEPH Z McNANEY OMER F. HAMAA/N y JAMES H-REDMAN Feb. 18, 1958 J, T, MONANEY ET AL 2,824,250

CATHODE RAY APPARATUS UTILIZING CONVERGENCE MEANS Filed May 12, 1955 3 Sheets-Sheet 2 IN VEN TORS. JOSEPH T. McNANEY OMEQ E HAMANN y JAMES H. QEDMAN F 1 1 5 J. T. M NANEY ET AL 2,824,250

CATHODE RAY APPARATUS UTILIZING CONVERGENCE MEANS Filed May 12, 1955 3 Sheets-Sheet 3 IN VEN TORS. JOSEPH T. MCNANE Y OMER F. HAMANN BY JAMES H. REDMAN .shape.

CATHODE RAY APPARATUS UTILIZING CONVERGENCE MEANS Application May 12, 1955, SerialNo. 507,356 6 Claims. (Cl. 313-77) This invention relates generally to cathode ray display tubes and more particularly to an'electron beam convergence means therefor.

A cathode ray display tube, such as exemplified'bya co-pendmg application of J; T. McNaney,

Serial No. 298,603, new U. S. Patent 2,735,956, and assigned to the common assignee hereof, is provided with means for shaping an electron beam into desired character infor- .mation for direct reading visual presentation upon a screen of the tube. The electron beam, emitted at one end of the tube toward the screen or target at the other end .thereof, is caused to select a character opening in amatrix thereby shaping the beam into a cross-sectional corresponding to that of the character opening illuminated. To eflect such selection, the electron beam, which is emitted substantially along the longitudinal axis of the tube, is deflected away from .that axis an amount necessary to illuminate the desired character opening in the matrix providing the beam with a cross-sectional shape corresponding to the character opening illuminated. The beam, being directed away from the axis by the deflection, must be redirected from that path and converged to the axis at 'a focus or. cross over point. This action, which may be referred to as lens .action,.is effected by a convergence means which is, positioned about the axis to effect beam convergence. The convergence means, which may be either electrostatic or electromagnetic, redirects the electron beams path to the. convergence or cross over point on the axis and in. addition to the redirection, effects lens action upon. the bearmso shaped, to eifect a minimal cross-sectional area. of the beam at the cross-overpoint on the axis. Thisproblem is peculiar to the display tube. The electron beanrinthe display tube must be directedfrorn the axis to select. the desired character .opening. for illumination in the. matrix, and the resulting charactershaped beam..must thereafter be returned to the axis of the tubeatminimal cross section thereof, prior to deflection of thebeam onto, the desired screen position. Should the. beam be ofl. axis or of large cross=sectional area at. the point of deflection, deflection of such beam wouldcause undue distortion of the characterimpinged upon .the target thereby rendering such. character partially or totally unintelligible.

The convergencemeans, therefore, permits operation and utilization of the beam. over. a relatively. largevariety of angles of. deflection .ofgthe .beam. and. reconverging he beamtoaxisatitsminim l cross-sectionm minimize character distortion upon the. screen.

Such-..conver gence means may include an electrostatic or electromagneticlens-system, each eliecting redirection and/focusing at minimum cross section of theelectron beam to, and at the: axis-'bytheir respective fields of influence. The; prime, requisite, of the. convergence means, whether electrostatic: or electromagnetic, is the :need for redirecting or converging of the divergent curvature of the-electron path, effecting this in a-smooth-transition havingpredictablecharacteristics, and in" focusing the J 2,824,250 5Q tl d I-fgb. is, was

beam to minimalcrossesectionat the cross .over point on the axis. 7

It .-is..an object .of this invention-to provide .a -.ca.tho.de ray display tube which will present clear'and: undistorted charactersxuponia screen-of the tube. g

It is an objectsof .this invention to provide a cathode ray display tube with means for causing .anelectron beam having. angularity with respecttothe tube axis, t.0 become. coaxial, at. minimum. beam cross section at a point on the .tubeaxis. prior to deflection ofthe-beamto predetermined target locations.

it is .an object of thisvinvention to provide arcathode ray display tube with means for substantially eliminating adverse-effectscaused by deflection of .the electron heam to selectivelyilluminate character openingssin. a matrix.

Itis an .objectof this invention to provide an-improved cathode ray display-.tubewherein'the electron beam may be .projected' at angles with respect to the tube axis and returned toaxisprionto deflection ofthe beam to-a predetermined positiomon the target.

It .isaniobject-cf this invention to provide a cathode ray tube -.for producing and directing an electron beam toward adarget alongipaths which are angular with-respect toitheituhe axis and whereinmeans are providedto .elimi- .nate the adverse effects of nonrlinearities :resulting..from .such irregular :paths.

Objects and advantages other than those set :forth above will be apparent from the following description whenreadin connection with the accompanying: drawings, in which:

portion of:- the electromagnetic :lens;

Figure 3 is a view,.in perspective, ofva' cathode-ray display tube embodying, .anqelectrostatic dens;

.Figure 4 isia diagrammatic. illustration of the convergence-smarts, and its; field :of inflnence on tlre electron beam;

Eigureiisa diagrammatic view showing-thepath of the-electron beam through the convergence means;

Figure: ;.6- is::.a diagrammatic view showing pathof- :a single electron beam through the convergence means.

- The diagram of Figure .lillustratesaan embodiment ".ofi the..-invention: block diagram. form showing a. cathode .ray display-tube 10 connected with electronic-circuitry necessary ito effect its operation. 'portray-ssselected charactershupon its screen in response The display tube '10 to predetermined-"voltages applied to the tube.

Specifically, display tube: 10: comprises: an-evacu'ated container. 11in which. a. target or screen= 1=2 ispositioned substantially along longitudinal. axis .15, oicontainer :11,

toward the-target 12. As the .electron.:heam-.,.13 leaves the cathode .1 4 on itspatlrsaalong, mtis..15-.aud.;tcward target 12,,beam- 13 passes successivelythrough; a control grid 18, anodes 19, 20,, and 21,, thence intermediatea. first deflection means, which may be electrostatic. or electromagnetic .but. are shown .in this embodiment vas electrostatic having vertical. selection. platess22 and. horizontal selection plates. 23. Vertical and horizontal selection. plates 22,.and 23 are of knowngelectrostatic deflection; plate construction and are supplied with selec- 'tively supplied,predetermined operating. potentials'for contra-t thereof-deflecting electron beam toillumi-hate V V 3 r a desired character opening-26 in beam-shaping member or matrix 27. Matrix 27 shapes the electron beam 13 into a cross-sectional shape corresponding to that of the character opening 26 illuminated.

' The action of the veincat'aaa horizontal selection plates 22. 23 to select the character opening 26. will generally cause the beam 13 to depart, from its initial path along the longitudinal axis 15. which path the beam 13 continues to follow after passing through matrix 27. This path diverges from the longitudinal axis 15. While the beam 13 is following such divergent path. it enters the sphere of influence of a convergence means 28. Convergence means 28 may bean electromagnetic lens 29 or an electrostatic lens 30. as illustrated in Figures 2 and 3.

respectively. The convergencemeans 28 will substantially effect redirection and focusing of the beam. Conwhich action reduces the beam cross section to a minimum at or'substa'ntially adjacent focus point 3]. Focus point 31 lies on the axis 15 substantially adjacent the electromagnetic field or-electrostatic field generated by asecnd deflection means 34. The second deflection means 34 may be electromagnetic as illustrated in "Figure 2a 'by vertic'al and horizontal deflection yokes 35, '36-or 'may be'electrostatic as shown in Figure 3 as vertical and horizontal deflection plates 37, 38. Y The field of influence of the second deflection means 34, whether electromagnetic or electrostatic, is positioned so as to effect deflection of the beam 13 substantially adjacent the predetermined focus point 31. The desired deflection is thereby effected at or substantially adjacent the point 31 and beam 13 has at this point 31 minimal cross-section, therefore, eliminating undesired distortions which may result from deflection of the beam 13 to predetermined locations on the target 12.

The various components of the display tube are supplied with predetermined potentials from a power supply which may be of any known construction incorporating well regulated voltage and current supplies.

V tal deflection means either deflection yokes, 35, 36 or Power supply 42 also supplies the necessary power requirements of decoders, amplifiers and generators shown in Figure 1.

The input signals, which maybe of pulse coded information, such as computer output information, are

presented to inputs 43, 44. Input 43 is connected with a character selection decoder'45. Input 44 is connected with a character'position decoder46: Decoders 45, 46

are generally pulse to binary. code converters and may have various circuitry arrangements for'etfecting such decoding. :A particular circuitry suitable therefor is illustrated in a, co-pending applicationof J; T. McNaney, Serial-No. 340,245, assigned to the common assignee hereof. The character selection decoder 45 reduces the input 43 to predetermined vertical and horizontal selecand'horizon'tal selection plates 23.

' Signals from input 44 aredecoded by character posiamplify them for presentation to the vertical and horizon- .tion voltage signals. These vertical and horizontal selec- 7 'tion voltage signals are amplified by vertical and horizon- V ital selection'amplifiers 49,50 to predetermined amplitudes 7 to energize, respectively, the vertical selection plates, 22

deflection plates 37. 38 as desired. a

The electrostatic lens 30, shown in Figure 3, comprises In addition, a blank-interval pulse generator 53 receives its information from input 44 and character position decoder 46 to effect proper character intervals and de-energize the tube 10 intermediate. characters. Blank-interval pulse generator 53 supplies a blank-unblankvoltage generator 54 with'necessary excitation to effect energizing of control'grid 18 from generator 54 with the predetermined blanking pulsesx l a j 'Convergence means 28, if of an electromagnetic lens 29 construction, will generally be supplied with a constant current regulator 57; if of'an electrostatic lens 30 construction, will generally 'be' supplied'with a constant high voltage source (not shown), buLof a construction familiar to the prior art. 1

During development of the display tube 10 it became apparent that a problem peculiar to this type of character display was that of deflecting the electron beam 13 from the longitudinal axis 15;:an'amount necessary to effect selection of a desired character opening26 in'the matrix 27 andthenredirecting the shaped beam 13 back to the axis 15 at minimum cross-sectional area prior to deflection to predetermined positions on the screen12.

if theshaped beam'l3 were deflected at a time whenthe beam was not on axis 15, or of other than minimal crosssectional area the resulting character distortion on the screen 12 rendered the character distorted in shape and unintelligible. Therefore, it became necessary to return the beam'13to axis 15 with minimal beam cross section, at or substantially adjacent the field of influence exerted upon the beam 13 by the second deflection means 34.

This, lens action or focusing action of convergence means 28 effected such a redirecting of'thebeam from its divergent path from the axis 15 and to converge the beam at minimal cross section with axis '15 at focus point 31. The convergence means 28, as previously stated may -be of the type .of electromagnetic lens 29 or electrostatic lens 30. The electromagnetic lens 29, illustrated in Figure 2a, and 2b comprises an electromagnetic convergence coil 58 positioned about the evacuated container 11 in include one or more twindings, and is shown in this embodiment as including the main or center winding 60, trim winding 61,[and,trim winding 62. Center winding 60 effects the ,field' of influence to redirect beam 13 from its.divergent path from the axis 15 to one converging with axis'15 substantially at focus point 31 and focuses the beam to its minimum cross section at focus point 31. However, in so acting uponbeam 13, the

field of influence may cause the beam 13 to rotate as it is converged as isshown in Figure 5. This rotational effect may be controlled to any degree desired by addition of at least one trim winding, which may be aiding or opposing the center winding 60. The preferred embodiment utilizes two. such windings 61, 62 and the rotation is preferably controlled at 90 beam rotation by selective energization and proportioning of currents as between the trim windings 61, 62 and center winding 60.

a plurality of electrostaticelectrodes 66, 67 and 68, having preferably an annular shape, positioned within the -eva cuated container substantially symmetrically spaced from and coaxially about axis 15 intermediate the matrix 27 and the deflection'plates 37, 38. The electrostatic electrodes 66, 67 and 68 present fields of influence which have a converging action anda lens action upon beam 13' similarto that ;of the" electromagnetic lens 29. Elec- -tro'des 66; 67- and 68 converge the divergent beam 13 75.

to focus point 31-v andefiect minimum beam cross sectiqn .perpower consumptionlo'sses of the electromagnetic-lens 29 requires power consumption g re'ater than 'e'le'ctrostatic lens 30-.- The .elect'rosta't'ic lens 30 has very small power requirements and utilizes static potentials to efiect theldesired convergence of'bearn' 13.

. The methodof operation of the convergence" means 28 will be restricted to explanationof the operation'of the electromagnetic lens"- 29. previously explained, the operationof the" field of influence of the: electrostatic lens 30 upo'n t'he'ele'ctron beam 13 wilibe'sirnilarm that of the field of influence of the electromagnetic lens 29.

A representative field pattern 69of the center winding 60'of'ccnvergence coil '58is shown in Figure-4 in a cross-' sectionaLvieWbf coil 58. The field plot of tl're cen't'er winding-60 isgenerally, the'same for-any plane which contains the coil axis since the coil is symmetrically disposed about the longitudinal axis 15 and coaxial therewith. The divergent path of the electron beam 13 is slightly over-exaggerated in-Figure 4 in order to more effectively demonstrate the action of the field upon the beam to'conye'r'ge thesame to the longitudinal axis. In

actual practice the approximate angle 'at which the electron-beam 13 leaves the axis 15 approximates 4, which angle represents a departure of "about $5 of an inch radially away from the axisls ina display tube" having a '19 inch'display screen 12. Thisradial di'st'ance'is rather small in comparison to the'actual diameter of convergence coil 58 which in this embodiment is approximately 2.25 inches. Therefore, the electron beam 13 is influenced chiefly by magnetic field components normal to the direction oi the path of beam 13. The axial field com- '-ponents will exert very slight influence upon the beam 13 'when it enters the field of influence of the coil 58. It is the radial-or normal component of the field 69 which acts upon the beam to effect the convergence necessary to return the beam to the predetermined focus point 31 on the axis 15. This converging action is then utilized to eflfect focusing of the beam to minimum cross-section :at focus point 31. The electron beam 13 will spiral slightly as is illustrated in Figure 5, wherein the beam is rotated approximately 90 clock-wise from its beginning divergent position to its convergent position at the focus point 31. To control this rotation, the previously mentioned at least one of trim windings 61, 62 are utilized to effect predetermined rotational control. As shown in Figure 6, the con ergence means 28 accepts the electron beam from its divergent path and redirects and converges the beam 13 to axis to the focus point 31 substantially adjacent the second deflection means 34 for desired positioning upon the target 12. The beam as shown in Figure 5, is focused by convergence means 28 to minimum cross section at focus point 31.

The particular embodiment of the invention illustrated and described herein is illustrative only and the invention includes such other modifications and equivalents as may readily aooe r to th e skilled in the art, within the scope of the appended claims.

We claim:

1. In an evacuated container having a target at one end and a source of electrons at the other end for projecting a beam of electrons toward the target and substantially along a longitudinal axis of said container, a beam shaping member positioned along said axis for altering 'jecting' 'abeam the 'c'ross'se'ctional shape ofme'beaim in accordancewith a selected portion or me beam-shaping memoer mro'ugn which the electronbeam- 18 projected, said beam eme'r ging tr'o'm said-member onadiver'gent patn rrom said axis, a nrst' deflection 'means suostantiauy symmetrically disposed "about said axis and positioned intermeuiate said source and said'memoerror 'denee'tin'g' tne electron beam along two directions irorn saidaxisand causing the beam to pdss'se'quen'uauy lnrou'gnseiecred pornons 01 me beamsnapmg member, a convergence means capaoie or snobt'anltaiiy redirecting and roe-using the beam, said convergence "means being adapted to cause and beam to no influenced trorn said divergent patn to converge witn tne axis and t'ocustnebeam'scr'oss section at a-pred'etermined'rocus pointon mean Wi'U'FlIllfllinal-Deam cross section atsaid point andasecond'defl'ection means substant ally adjacentsaid predetermmed-focus point-tord'irecnng the shaped -beam toward- -predeterinmed locations on the target; I

z. in an evact'iatedcontainerhavinga target'a't one end ane a sourc'e (if-electrons a't 'tn'e other end for proectron'siow'ard tn'e ta'rget-and substantially along a ngitiidina'l axis of said container, abeamsnal'ping memberpositionedtransverselyof and along said axistoraltering-the*crbSsI-Setidiiiil snape of the beam in accordan'ce wifh a's'el'ect'edportion or the beam-shaping member tnrotigh which the electron beam is projected, said beam emerging from saidfmember on-a divergent pathfrom said axis, a first deflectionmeans substannaily symmetrically disposed about-and along said axis and positioned'intermediate said-source and=said'member for sequentially deflecting the electionbeam-along two directions substantially transvcrse o'f said-'axis to causeme beam to pass through "selected portions of the beamsnaping member, a convergencemeans capable of simultaneously 'redirecting'and focusing the beam, said -con vergence means being adapted to "cause said beam to be influenced from said divergent path to converge-with the'axis and simultaneously-foods the beams'cro's'ssec- .ion at a predetermined focus point-on the axis with minimal beam cross section atsaid point and --a-' second deflection means substantially adjacent said predeter- 'mined focus point fordirecting the shaped bearn toward predetermined locations on the target.

3. ln-anevacuated container having a t'arget at one end'and a source ofel'e'c'trons-at the other end for 'projecting a beam of electrons toward the target and substantially along a longitudinal axis of said container, a beam shaping member positioned along said axis for altering the cross-sectional shape of the beam in accordance with a selected portion of the beam-shaping member through which the electron beam is projected, said beam emerging from said member on a divergent path from said axis, a first deflection means substantially symmetrically disposed about said axis for deflecting the electron beam from said axis along two directions to cause the beam to pass sequentially through selected portions of the beamshaping member, a convergence means capable of substantially simultaneously redirecting and focusing the beam, said convergence means being adapted to cause said beam to be influenced from said divergent path to converge with the axis and simultaneously focus the beams cross section at a predetermined focus point on the axis, said convergence means including an electromagnetic lens symmetrically disposed about the axis, said lens being adapted to efiect electromagnetic redirection of the beam focused to its minimal cross section at said focus point, and a second deflection means disposed about and adjacent said predetermined focus point for directing the shaped beam toward predetermined locations on the target.

4. In an evacuated container having a target at one end and a source of electrons at the other end for projecting a beam of electrons toward the target and substantially along a longitudinal axis of said container, 61

beam=shaping member positioned along said axis for alteringithe cross-sectional shape of the beam 'in accordance with'aselected-s portion, of' the beam-shaping member through which the electron beam is projected, said beam emerging from said member on atdivergent path from the beam-shaping member, a convergence means capable of substantially simultaneously redirecting and focusing the beam, said convergence means being adapted to cause said beamto be influenced from said divergent path to converge with the axis and simultaneously. focusthe beamscross section, at at, predetermined focus point on the axis,said convergence means, including an electromagne tic lens symmetrically spaced from and coaxially disposed about the axis, ,said lens having a main winding and at least one trim winding, said windings being positioned about said container, said trim winding being'20 disposed adjacent an extremity; ofthe main winding, said .rnain winding effecting rotationalconvergence and focusing of said beam to said focus,point, said,trim winding effecting predetermined control of rotation of said beam,

and a second deflection means substantially adjacent said predetermined focus point for directing the shaped beam toward predetermined locations on the target.

5. In an evacuated container having a target at one end and a source of electrons at theother end for projecting a beam of electrons toward the target and substan-' tially along a longitudinal axis of said container, a beamshaping member positioned along said axis for altering the cross-sectional shape of the beam in accordance with a selected portion of the beam-shaping member through i which the electronbeam is projected, said beam emerging235 from said member on a; divergent path from said axis, a first deflection means substantially symmetrically disposed about said axis for deflecting the electron beam along two directions from said axis and causing the beam to pass sequentially through selected portions of theJAO beam-shaping member, a convergence means capable of substantially simultaneously redirecting and focusing the beam, said convergence means being adapted to cause said beam to beinfluenced from said divergent path to converge with the axis and simultaneously focus the beams cross section at a predetermined focus point on the axis, said. convergence means including an electrostatic lenssymmetrically disposed about the axis within said container and being adapted to effect electrostatic redirection and focusing of. the beam to said focus point .said beam havinga minimum cross section at said focus point, andja second deflection means substantially adjacent said focus point for directing the shaped beam toward predetermined locations on the target.

6. In an evacuated container having a target at one end and a, source of electrons at the other end for projecting'a beam of electrons toward the target and substantially along a longitudinal axis of said container, a beamshaping member positioned transversely of and along said axis for altering the cross-sectional shape of the beam in accordance with a selected portion of the beam-shaping member through which thetelectron beam is projected, said beam emerging from said member on a divergent path from said axis, a first deflection means substantially symmetrically disposed about, and along said axis for deflecting the electron beam along two directions sub-- stantially transverse of said axis and causing the beam to pass sequentially through selected portions of thebeam-shaping member, a convergence means capable of substantially simultaneously redirecting and focusing the beam, said convergence means being adapted to cause said beam to be influenced from said divergent path to converge with the axis and simultaneously focus the beams cross section at a predetermined focus point on the axis, said convergence means including an electrostatic lens within said container symmetrically disposed about the axis and being adapted to effect electrostatic redirection and focusing of the beam, said lens having a plurality of annular, electrodes disposed in spaced relation about and along the axis, said electrodes effecting References cream the file of this patent UNITED STATES PATENTS 2,379,880 Burgess July 10, 1945 2,735,956 McNaney Feb. 21, 1956 2,769,116 Koda, et a1. Oct. 30, 1956

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