US2925506A

US2925506A - Electrical apparatus

Info

Publication number: US2925506A
Application number: US774661A
Authority: US
Inventors: Henry S Vasilevskis
Original assignee: Philco Ford Corp
Current assignee: Space Systems Loral LLC
Priority date: 1956-05-08
Filing date: 1958-11-18
Publication date: 1960-02-16
Anticipated expiration: 1977-02-16

Description

Feb. 16, 1960 H. s. vAslLEvsKls 2,925,506

ELECTRICAL APPARATUS Feb. 16, 1960 H. s. vAslLEvsKls 2,925,506

ELECTRICAL APPARATUS Original Filed May 8, 1956 5 Sheets-Shes?l 2 Feb. 16, 1960 H. s. vAslLEvsKls 2,925,506

ELECTRICAL APPARATUS Original Filed May 8, 1956 5 Sheets-Sheet F76. 7x. 4 ,57s. 7d.

Feb. 16, 1960 H. s. vAslLEvsKls 2,925,506

ELEcTRIcAL' APPARATUS Original Filed May 8, 1956 5 Sheets-Sheet 4 Feb. 16, 1960 H. s. vAslLEvsKls '2,925,506

ELECTRICAL APPARATUS Original Filed May 8, 1956 A 5 Sheets-Sheet 5 ATTORAEY 2,925,506 Y ELECTRICAL APPARATUS Henry S. Vasilevskis, Ardsley, SPa., assignor to Philco Corporation, Philadelphia, Pa., a corporation of Pennsylvania Original application May 8, 1956, `Serial No. 583,402. Divided and this application November 18, 1958, Serial No. 774,661

6 Claims. (Cl. 313-468) This application is a division of my co-pending application entitled Electrical Systems, Serial'No. 583,402, tiled May 8, 1956. v

This invention relates to apparatus for adjusting the relative positions of the several beams of a plural beam cathode ray tube. In particular the invention relates to apparatus for adjusting the relative positions of the areas of impingement of the several electron beams produced within certain types of cathode ray tubes for reproducing television images. l

Among the various types'of image'reproducing devices used in color television receivers is'one known as the aperture mask or shadow mask tube. Thisv is an image reproducing tube consisting. of a lscreen which contains a plurality of sets of phosphor dotsff the dots of each set being emissive of light of a dierent color as, for example, one of the additive primaries red,'bl'ue and green. These phosphor dots are disposed in a recurrent sequence on the inner surface of the faceplate of the cathode ray tube (or on any other appropriate transparent substrate). They are arranged in triads,*7 i.e., groups each containing a red, a blue anda green color emissive phosphor dot approximately equally spaced from one another. Within the tube there are three electron guns for generating three electron beams, each of which ideally should impinge only upon phosphor dots emissive of only one of the primary colors ywhen deflected over the screen. Accordingly one of the beams (hereinafter known as the blue beam) is modulated in intensity by signals representative of the blue information present in the televised scene, and is arranged so as to impinge only upon phosphor dots emissive of blue light; The other two beams (hereinafter known respectively as the red beam and the green bean1 are modulated in intensity by signals representative of the red and green information in the televised scene and are arranged tol impinge only upon red and green emissive phosphor dots respectively. To assist in insuring that these three beams impinge on the proper phosphor dots, a so-called aperture mask or shadow mask is interposed between the electron guns and the lluorescent screen. The aperture mask has one-third as many perforations or apertures;

therein as there are phosphor dots on the fluorescent screen. Each perforation is alignedwith just one of the Lriads of phosphor dots. The perforations are so 'dise posed that, ifthe beams approach the screen at the proper angles, the unperforated portions of the aperture mask will prevent the beams from striking th'e wrong phosi phor dots. lf it is desired, for example, to produce a white element in the reproduced image, the red, green j center ofthe screen.

tofore been resorted to. K

mask tube, apparatus whichv is mounted external to they with the aperture in which theygconverge'd. ,If the tube is to produce Aa magenta (redfllblu'e) colored image element, the red and b'luebea'iiis (the green beam being cut off) should cros's over in' one of the perforatioiisl of the mask and should then divergebefore striking` the red and blue r'phos' `p'hor dots of the triad associatedwith the latter perforation. Fory proper color -iidelityin `the image, the beams'ljshould cross over in the Vrespective perforations of the aperturev mask aligned with the ,triads which are successively liipiriged `upon as the beams are scanned over all points' ofv the lluorescent screen.- ;It, is relatiely simple to cause the beams to cross over in theaper'tures in any given restricted area of the aperturemask, as for example, in apertures thereof near the However the faceplate `and the aperture mask are 'both somewhat curved, and the radius of curvature is not constant, so thatjthe beams', in the absenceof any correction, do, not cross over in the perfor-ations ofthe aperture mask when ther beams are scanned over parts of thefs'creenfto the left, right, above, or below the center ofthe screen. ',Instead, they cross overy at points 'intermediate the maskandthe electron guns. Because of the factl that they beams. cross over behind the mask it is possiblethat, at a timewhen` it is desiredr that'the beams produce a white image element, the, red and blue beams may passthrough one particularaperture, while the green beanrmay -pass through a different aperture which is lower .than the other aperture.-4 Even if all the beams impinge. on the. right phosphor dots, the phosphor dots struck ,by the red and blue'beamsgbelong to a triad higher than th'eone whose green phosphor'dot is struck yby the green beam.A Thereforethe phosphorsV vof the triad struck byv the red and blue beams Will coi if the red and blue beams, when being swept'lower, also- Y pass through the same perforation). Thus whereV the beams do not cross over one another in one of the perforations, i.e., at the sides and at the top and bottom ofthe raster, the colordelity of the image will be' considerably degraded.

In order to overcome the eifects of improper cross-' over of the beams certain corrective measures havehere- In recent types of the Vshadow tube has been provided for adjusting and correcting the convergence of the several beams. This apparatus'uin-L cludes a convergence magnet assembly whichisposi- `tioned about the neck of the tube intermediate thev deection yoke and the electron guns. This assembly coirsists of threecoils wound around three respective cores',

and` three adjustable permanentlmagnets, eachofwwhich is situated in spaces providedI therefor in the respectiv i Ycores'. Each coil and core",lv and its associated perman magnet, is sov positioned that itsmagiietic eld ca Y corresponding one' of thebeair'i'sto shift-'in positio only one direction transverseitoz the cetrlrry ofthe beam.- Furr.hermore,thel respective directions' iirvvhich Vthe beams can be movedlare displaced approximately* from one another.

Patented Feb'. 16,y 1,1960

The convergence apparatus, in recent types of shadow mask tubes, also includes a permanent magnet external to the tube placed about its neck between the convergence magnet assembly and the electron guns. This magnet, which is usually known as the blue lateral positioning magnet, enables the blue beam, to be shifted in position in a direction transverse to the direction in which it can be moved by the part of the convergence magnet assembly associated therewith.

In order to direct the magnetic fields created by component parts of the convergence assembly to the area directly in front of the electron gunswhich produce the respective beams whose positions they inuence,. each of the electron guns is flankedby a pair of internal magnetic pole pieces. These pole pieces also help to minimize interaction between the guns. There are also internal pole pieces for guiding the field of the blue lateral positioning magnet so as to influence the position of the blue beam.

The permanent magnets of the convergence magnet assembly and the blue lateral positioning magnet are used to adjust for static convergence of the several beams-that is the adjustment of the positions of the several beams so that, in the absence of any deection, and when modulated by signals corresponding to a white colored object, they will strike the centrally located triads to produce a white spot in the center of the raster.

In order to converge the several beams properlyas they are being deflected, so that, for example, when modulated by signals corresponding to a white! object, they will cause the production of white at all points on the screen, it is customary to apply corrective waveforms to the electromagnetic components of the convergence magnet assembly. 'These waveforms yenergize the electromagnets in such a fashion that the fields produced in response thereto cause the beams to cross over approx mately in the perforations of the shadow mask at all points in the pattern of scanning. In general, as the beams are swept from one side to the other of the screen, the amount of misconvergence is large at the rextreme left, diminishes gradually to a minimum in the center, and increases to a second maximum on the extreme right. A similar condition prevails as the beam is deflected down from the top of the raster to the bottom, i.e., the error is greatest at the top and bottom and decreases gradually to a minimum at the center of the raster measured in a vertical direction. More precisely, it has been found that the deviation of the apertures from an arc of true cross over, when plotted both with respect to the distance from the horizontal axis of the screen and with respect to the vertical axis thereof, results in parabolic curves. It is therefore possible to correct convergence dynamically by energizing the respective electromagnetic components of the convergence magnet assembly with compensatory currents having parabolic waveforms. Usually these parabolic waveforms are derived from the horizontal and vertical deflection circuits and are applied simultaneously to each of the electromagnetic components.

Previously, in order to ascertain Whether convergence, both static and dynamic, was perfect or as nearly so as possible, it was customary to use signal generators which produce signal waves which are applied so as to modulate the intensity of a selected one or ones of the several beams so that the latter produced luminous patterns on the screen comprising small rectangular or square areas known as dots (which shall hereinafter be referred to as test dots in order to distinguish them from the phosphor dots of the fluorescent screen). These test dots are either red, green or blue in color depending upon which beam produces them. Test dots of any one color are produced by turning on, during a number of successive line intervals, one of the beams for a Ishort while at a specified time after the beginning 4 of the scanning of each of the number of successive lines so that phosphor dots of only one color are traversed by the particular beam which is on.

If the test -signals are applied to modulate all the beams simultaneously, each beam will produce a pattern of test dots in a different one of the three primary colors. If the beams are properly converged, the patterns of test dots produced by the several beams will seem to coincide with one another at all points on the raster to produce a single pattern of white test dots. Each white test dot is composed of one red, one green and one blue test dot all of which are substantially in register with one another. Stated in another way, each white test dot comprises a number o'f activated adjacent triads whose respective phosphor dots have been impinged upon by the divergent beams which have crossed over one another in the perforations respectivelyassociated therewith. t l

If the beams do not cross over properly, then at one or more points on the raster the test dots of different colors produced by the respective beams will not coincide but will be either` totally or partially separated from one or more of the others. Where they overlap one another, a color mixture area will be visible. Adjustments are thus required to bring the different colored test dots into substantial registerlwith one another sol that they will merge into a single pattern of white` dots. The adjustments necessary to correct convergence will necessarily depend on the nature of the trouble causing the misconvergence'. It maybe necessary in adjusting convergence of such tubes on the production line, for example, to adjust all theconponents of the convergence magnet assembly and theblue lateral positioning magnet before perfect crossover is achieved. In practice, this may entail high labor costs because' as many as sixteen separate adjustments may be necessary.

Hitherto, when the convergence of the beams of an aperture mask tube` was checked` by using test dot pattems, it was necessary-,for the Vperson testing the tube to be able to interpret the particular test dot pattern correcly before making the "proper adjustments. lf, for example, in the center of the raster a green colored test dot was to the left" and'f'a littlel below the corresponding red test dot, the blue dot being above and to the left of the red dot, the operator either had to know by experience, or had to iind out by experiment, whethelthe red beam should'be moved diagonally down, and if so how far down, or whether to move the green beam down in a different diagonal direction, and if so how far down, or whether to move both4 by a certain amount. When using test dots it is very difficult to tell, in adjusting the position of eitherjtliered or green beam by itself, when that beam isin its correct convergence position, i.e., when it impingeson the'proper phosphor dot of a given triad after having crossed over the other beams in the aperture associated therewith: Usually a trial-anderror method is employed which may necessitate a relatively long convergence adjustment period and higher labor costs as a result thereof.

The problem of adjusting the convergence of the beams of such tubes also arises when a new set is to be installed in the home of the ultimate consumer. If conventional test dot patterns are used, the ambiguities and uncertainties inherent in their use unnecessarily prolong the time required to adjust the beam convergence since the serviceman must constantly experiment, adjust and readjust until the 'sixteen possible convergence adjustments have been made so that an optimum convergence condition exists. Similar considerations of time and trouble arise in connection with the replacement of one aperture mask tube by another in the receiver of a customer, or in connection with convergence adjustments made necessary by the effects of the earths magnetic field when the color television receiver `is moved into a different position.

It is, accordingly, an object of` the present` invention-to provide apparatus for adjusting @the .relativefrposition of the several beams `of a pluralfbeam .cathode ray tube of the type aforementioned. e.

Another aim of the invention is to provide apparatus for adjusting the positions of `the several beamsoi` cathode ray tubes of the aperture mask type so4 as-toobtain polychromatic images having good color fidelity-'andimtinted monochromatic images. v l

Still another object of the present invention is to provide systems for expediting the production of color tele- Vision receivers using ltubes of the type describedY herein.,`

Another object of the invention is toprovide=apparatus for expediting the adjustment of convergence ,controlsincident to the installation for `consumer use lofcolor television receivers using cathode ray tubes of the type described. j

Still another object of the invention istto providev apparatus which produces non-ambiguous test I.patterns for adjusting the convergence controls of color television receivers using cathode ray tubes of. the type-described.

My invention of apparatus for use in adjustingfthe, respective positions of the beams of cathode rayV tubesof the type described is based on the factthat if first and second ones of said beams are caused to produce sub-' stantially the same test patterns, comprising configura-YA tions which include portions having axes parallel 'tothe signals which are Aapplieclf..so-as :to -modulatetwo of the beams of aperture maskftubes Vso that they produce substantially Vident-ical..testpatterns comprising a plurality ofilines for.rrcctilineatr'-,figures which are disposed parallel to the direction in which the first of said two beamsy can be moved, 1 The beam-moving :'lpparatus associated ,with

is :in it's correct convergence position. .Two-of the beams" having been adjusted to their proper convergence positions, .thethird beam, whichmay bemovedineither of direction in which the rst beam can be moved bythe beam-moving means associated therewith, adjustment `of the beam-moving means associatedwith said second beam can be made which will bring vthe configuration Vof the test pattern of the second beam into a-` desiredspatial relation to that ofthe first beam, which thereupon indicates that the second beam is in its correcty convergence posi.v tion. Similarly, in order to adjust the position, of 'the first beam, the test patterns produced by the 4two beams must have portions whose axes arev parallel tothe direction in which the second beam can be moved; adjustment of the beam-moving means associated with the first beam can then be made until the latter is in its correct convergence position.

Accordingly, in one form of my invention as applied to obtain the correct convergence of the three beams-of an aperture mask tube having a plurality of beam-moving. means associated therewith as hereinbefore described, my invention comprises apparatus for producing signals which can be applied to modulate two of said beams so that the latter produce substantially the same patterns of configurations shaped substantially like Vs or inverted Vs, the legs of the Vs being respectively parallel to `the directions in which the respective beams can be moved by the beam-moving means associated therewith. With such patterns, the beams of said tube may then be converged properly as taught in my aforesaid co-pending application, say by adjusting the beam-moving means associated with a lirst of said two beams until at least a portion of one of the legs of each of the Vvs produced by said first beam coincides with va portion Vofrthe corresponding leg of one of the Vs produced by a second `of said beams adjusting the beam-movingmeans associated with the second of said two beams -until the Vs producedY thereby coincide with Vs produced by said iirst beam,

applying the same signals to modulat'ethe third beam, and adjusting the beam-moving means associated -therewith until the Vs produced by said third beam coincide with Vs produced by said first and second beams.

In this invention, the apparatus for producing the sig'- nals applied to modulate the respective beams may take several alternative forms. The inverted V-shap'ed con- 'igurations may be printed on the target vof a monoscope, for example, or the desired test patternma-y be `placed on a placard which is televised, or may be made finto `a film transparency which is scanned by a flying` spot-scanner. In another form, apparatus is` provided for producing;

two' directions -which aretransverse to one another, is thenfadjusted to :its proper convergence position. This is accomplished; by 'providing apparatus for producing and applying signals to the beams such that each producesv 'I a test pattern comprising anumberof lines or rectilinear figures-'which are parallel"to'fone of the directionsv in j which the third beamfm'aybemoved. Since the first and second beams havealready fbeen adjusted to their proper convergence positions they`,will ,produce respective patterns whichzare superimposed., 1 Therefo're',.ify the pattern produced by the third beaml is shifted in a direction transverse tto the lines-ofthe test patterns, lthe pat# ternrof'the third beam maybe made to coincidewith the registered patterns :of ythe 1first. andsecond beams. Thiscondition indicates thatthe .thirdbeam has been adjusted in proper position insofarfas one; of its ydegrees ofjfreedom isconcerned. Finally, apparatus is provided v for applying ,signals tf1-.modulate all three beams such that they producesubstantially identical test-,patterns com# prising lines orirectilinear figures parallel to the other direction in whichgthe third beam may` be moved Since the .'irst two beams have already been converged prop-v erly, their test patterns will coincide.- By adjusting the beam-movingmeans associated withpthe third beamuntil the test pattern of thelatter is superimposed'on thej registeredpatterns of the first and second beams, the con-A vergence of the, three beams can then be completed. Although this form of the invention requires apparatus for `producing more than one set .of signals, the testpatterns produced are very simpleand relatively uncomplicated apparatus `is needed .to produce them.

Figure la isi-a schematic representation'ofa cathode I i ray tube of the aperture mask 'type showing various'cony ditions of convergence of the'several beams thereof;

Figures lb and lc arefragmentaryperspective views` of the aperture mask and the screenl of an aperturemask tube which illustrates correct and incorrect convergence of the several beams thereof;

Figure 2a is acombined circuit,v schematic and,block i diagram vshowingvthe circuits associated with the permanent and electromagnetic components of a typical convergencemagnet assembly for an aperture mask tube;

Figure2b is an enlarged and perspective view of one of thepermanent magnets of the convergence magnetY assembly shown in Figure 2a;

Figure 3 shows waveforms of signals used to energize the components of the convergence magnet assemblyv shown in Fig. 2a;

Figure 4 isa schematic and block diagram of a system which employs one formof the invention for converging the beams of arrv .aperture mask type .of cathode ray tube;

erated` in Aone form of my invention which have certain Figures 522; 5b; 5c, 5d, and 5e show test patterns gen-v "f1 e desired characteristics which are used to converge the beams of aperture mask typetubes;

Figure 6 is a schematic diagram of another test pattern constructed in accordance with one form of the invention;

Figures 7a through 7p depict a number of possible conditions of displacements of test patterns generated according to my invention which indicate various forms of beam misconvergence; and

Figures 8a, 8b, 8c, and 8d show test patterns produced in accordance with another form of the invention.

Referring to Figure 1, a shadow mask tube 10 is shown together with some of the conventional components associated therewith. The tube 10 consists of a faceplate 11 on which a screen 12 of fluorescent phosphors is disposed. The aperture mask 17 is a perforated sheet of metal whose curvature corresponds generally to that of the faceplate 11 and is disposed intermediate the screen 12 and the electron guns indicated schematically at

numerals

19, 20 and 21. The screen 12 is shown in enlarged form in Figs. 1b and 1c and comprises a plurality of sets of phosphor dots, the dots or each set being emissive of light of one of the three additive primary colors red, green and blue when impinged upon by-an electron beam. The dots are arranged as shown in Figure 1b, red dot 13, green dot 14 and blue dot 15 being displaced equally from one another and arranged in a group known as a triad which is aligned with aperture 16 of the mask. All other phosphor dots of the screen 12 are similarly arranged in triads, each of which is aligned with one of the apertures of the aperture mask 17. If desired, a reflective coating 18 of a metal such as aluminum may be deposited upon the rear surfaces of the phosphors as indicated. This layer 18 increases the brightness of the image reproduced by the tube and also assists in preventing the discoloration of the phosphor screen known commonly as ion spot.

The electron guns indicated schematically by the

numerals

19, 20 and 21 generate the red beam 22, the green beam 23 and the blue beam 24 respectively. At the center of the faceplate 11 of the tube 10 the red, green, and blue beams may be made to cross over in the aperture 16 as shown in Figs. 1a and 1b. After crossing over in aperture 16 the beams will diverge slightly and impinge upon the corresponding red, green and

blue phosphor dots

13, 14 and 15 which constitute one triad. When the beams are deected from the left side to the right side of the screen, however, the

beams

22, 23 and 24 will not cross over in apertures of the aperture mask 17 but rather at the points in their scanning path indicated by the letters A and B, for example, provided that no dynamic correction of the points of cross over has been made. All cross over points of the three beams when scanning off center will fall on the indicated arc of uncorrected beam cross over 9. After crossing over at some point on arc 9 away from the center of the screen the beams will diverge slightly and pass through one or more of the apertures before striking the screen 12. It may be seen that when the beams nally do strike the screen 12 they are more widely spaced than they would have been had they crossed over in one of the apertures of the aperture mask 17.

The effects of uncorrected beam convergence are shown in the greatly simplified case illustrated in Figure 1c. lt is seen that the beams cross over between the aperture mask 17 and the electron guns rather than in one of the apertures ofthe mask itself. As a result, beams 23 and 24 pass through the aperture 29, whereas the beam 22 passes through the aperture 30. Thus the beams do not impinge on the

phosphor dots

31, 32 and 33 of a single triad, but rather the green beam 23 strikes the green emissive phosphor dot 32 and the red beam 22 strikes the red emissive phosphor dot 31 in one triad, While the blue beam 24 strikes the blue emissive phosphor dot 28 which bclongs to a triad other than the one containing the red and

green phosphor dots

31 and 32. Thus the red and green beams are in'their correct convergence positions whereas the blue beam is not.: Consequently in relatively small detail areas it will be observed that the edges of objects will have fringes of the wrong color due to'the fact that the b lue beam 24 is not in its correct convergence position, since it does not fall on blue phosphor dots. 33 which belong to the same triad as the red and green

emissive phosphor dots

31 and 32.

In orderto adjust the positions of the

beams

22, 23 and 24 so that they will cross over in apertures of the aperture mask 17, .convergence magnet assembly 35 is shown in Fig. la interposed between a conventional color television deflection yoke 36 and a conventional so-called purity magnet 37. This is usually a permanent magnet similar to centering magnets used on conventional black and White receivers, and its eld affects all three beams equally. The eld of this magnet is adjusted for strength and direction such that all the beams pass through their centers of deflection.

The convergence magnet assembly 35 is susceptible of a number of adjustments for moving the positions of the red, green and blue beams in directions which are apart for both static (center of raster) convergence and dynamic (all points on the raster) convergence. One of the beams, usually the blue beam, may also be moved in a direction transverse to the direction in which it can be moved by adjustment of assembly 35, by adjusting the position of the blue beam lateral positioning magnet 3S which is interposed between the Ipurity magnet 37 and the

electron guns

19, 20 and 21.

The convergence magnet assembly 35 is shown in schematic form in Figure 2a together with representative circuits associated therewith which supply the necessary corrective waveforms thereto for achieving substantially perfect dynamic convergence. Within a mounting member 40 are positioned a number of magnetic cores 41, v42 and 43 around which coils 51, 52 and 53 respectively are wound. The poles of the electromagnets formed by the cores and their associated coils are placed in contact with the neck 44 of the tube 10. In proximity to each of the poles of the electromagnets formed by the coils and the cores are the

internal pole pieces

45, 46 and 47, 48, 49, and 50 which assist in directing the iields produced by the electromagnets onto particular ones of the electron beams produced by the electron guns. For example, pole pieces 45 and 46 direct the magnetic flux emanating from the core 41-coil 51 combination so that it affects the blue beam 24 which is shown as an unlled circle. The other beams indicated by the black circular area 22 and the stippled area 23 respectively are likewise aiected by the fields produced by the electromagnets associated therewith. The respective directionsV in which the

beams

22, 23 and 24 may be moved by adjustment of assembly 35 are indicated by the arrows passing through the respective circular areas representative thereof.

Each of the core-coil combinations is adapted to be energized by currents having appropriate waveforms so that the

beams

22, 23 and 24 are moved up or down as required as they are deected so that they will cross over in the apertures of the aperture mask 17'for proper dynamic convergence.

Also associated with each of the cores 41, 42 and 43 are the permanent magnets 61, 62 and 63 which are disposed in apertures within the respective cores. A typical one of these permanent magnets is shown in enlarged, perspective form in Figure 2b. It consists of an active magnetic portion 65 which comprises a north pole in the form of a half cylinder (indicated by the white portion of the active section 65) in contact with an oppositely magnetized pole also in the form of a half cylinder (indicated by the black portion of the section 65).

To eect changes in the static convergence positions of the three beams, the permanent magnets 61, 62 and 63 may be rotated manually by means of the knurled end spammer Previously it was remarked that,l in ortlertorobtain,`

dynamic convergence of the threeA beams in the Aapertures of the aperture mask 17, corrective waveforms were applied to the coil-'core combinations-.in the'convergence magnet assembly 35. It wasfalso'stated :previously that the corrective currentsY through tle=coils V'1,I

52, and 53 should haveparabolicwaveforms:to correct for the parabolic curve of error: in the `vertical Adirection and for the parabolic curve of error in'the horizontal direction.

In Figure 3 a typical parabolic waveform lA of a current is shown which can be applied: to th'e coils of assembly 35 to compensate for the -error inthe vertical direction. Portions of this parabolic wave'fcorrespond ing to the top, middle and bottom ofv araster lareso indicated. It will be seen by reference to Figurek 1a that, at the top and bottom of the screen, the beams must be made to cross over at points farther from Vthe electron guns than the point alt-Which :they cross over at the center of the screen. Thus, during the scanning of lines toward the top and toward the bottom of the raster, the beams are made to diverge more in the region of the convergence magnet assembly, than when the beams scan the central lines of the raster. ly, if corrective currents having waveform A are applied to the core-coil combinations of the assembly 35, electromagnets having their poles as shown in Fig. 2a will produce magnetic fields which will cause the beams toy move away from one another during intervals corresponding to the scanning of the upper and lower ylines of the raster, and will cause the beams to move toward one another during intervals corresponding to the scanning of the central lines thereof.

The manner in which :the parabolic waveformrequired tofcorrect convergence dynamically in the vertical direction is obtained in thecircuit shown in Fig. 2a will be explained in detail in connection with the yblue .beam 24. In the typical circuit shown in Fig'. 2a a waveform which is parabolic but tilted'to the right is obtained at the cathode of the vertical output tube 70. This tilted waveform results from the partial integration by the circuit including the resistance of tube 70, resistor 65 and condenser 68 of the saw-tooth supplied to the grid of the tube 70. Another integrating circuit comprising resistor 6.4 and condensers 61 and 66 in series, and potentiometer 71 produces the fully integrated Waveform; shown at the junction of potentiometer 7f1 and condenser 66.- Movement of the tap on potentiometer 71 changes the amount of resistance in series ywith vthe capacitors 66 and 61 thus determining the amountI of integration of the unsymmetrical parabola on the-cathode of tube 70. When the tap is at the top of the resistive element a parabola having the greatest possible tilt toward the right is obtained -as shown in waveform B (Fig. 3); when the tap is at the bottom of the element a practically symmetrical parabola is obtained. Waveforms having shapes intermediate these two extremes may be obtained by corresponding adjustment of the tap of potentiometer 71. The amplitudey of the vertical parabola applied to the coil 51 is determined by the setting of the movable arm'on the potentiometer 72 so that` the desired amount of the vertical parabola is applied by the variable inductance 74 to the coil 51 associated with the core 41. Not specifically shown, but indicated by blocks 75 and 76, are essentially similar circuits for applying the vertical corrective waveform from the appropriate sections of the circuits 75 and 76 to the red and fgreen beam-moving means comprising the cores42 and43t1rwith their. respective coils 52 and 53.

s Inzorder toizcorrectgtheconvergence ofthe three beams to account for the errors in the points ofxconvergencev whiclnoccur during the scanning ofieach line from the left to the'rightside Iofl the screen, corrective currents are 'also applied to. the con'vergence'magnet assembly 35, buty the latteri cur-rents have a much higher frequency, i.e., the horizontal linescanning frequency, as shown in waveform C. These corrective waveforms also cause the beams to diverge more (in the region of the magnet assembly 35) when'the left and right sides of the raster' are scanned than when the central portions are scanned. Consequently, toward the left and right sides of the screen the beams will be made to cross over approximately inthe apertures of the aperture mask 17 rather than at points intermediate it and the electron guns asv 51 as;itappearstlookinginto the* coil atV the center tap 70;. This seriesfresonant'circuitis resonant to the horizontall -line scanning` frequency and provides achannell by which-the horizontal parabolic corrective signal is appliedwith'.voltagefandlcurrent in phase `to energize the coil 51. However,v inL the-circuit shown, the parabolicy corrective signal .-is notusedatoeiectthe horizontal con-- vergence. vInstead).asinewave at the horizontal line ScanningffrequencyA is-generated by a resonant circuit comprisingY thcjcoil 51-in parallel with the condenser 92. Thegwaveform -of .the sine `wave l generated `by this parallelresonant :circuit 'isapproximately'ithe same as the desired parabolic.v waveform `andcan. conveniently be usedtoenergize the-convergence coils. `If it is desiredto .apply nalargercorrtive current on the left side of the rasterthanonlthe right; itis necessary lto unbalance the .corrective waveform with respect-to the -center of the scanning'line.. Asimplemethod is .to change the phase .ofthe-correctivesine twave with respect to the'timingoftthe horizontal blanking intervals as` shown in waveformD ofFigJBwhich .is .anf :enlarged view of one cycleofthewaveformHQ It will be notedthat the dashedlinewcycle fhasnbeen .advanced `in phase so that during. theactualimage `scanningperiod there is a lesser corrective current ,applied at the beginning than at the en d..of the scanningzlney Asimple way ofchanging the phaseof .the .corrective `sine wave iszto detune the natural frequeruyY of the :parallelresonant circuit (coil 51-condenser92.). Ihis maybe accomplished by adjusting thehorrizontal .phase variable inductance-f7l` which Vis eiectively in,par,al1el withtheinductance'of the coils 51. When this .is donethe :parallel resonant circuit 51-92 has a naturalfrequency whichv iswdiierent from the driving frequency, .i.e .the frequency -of -the parabolic Waveform applied from .the series 4resonant -circuitl to `the parallel resonantvcircuit. This will produce-the desired shift in phasewith the result vthat the minimumY corrective current is .110, :longer .spaced approximately equally between' the .endlottheprevioushorizontal blanking period and the 'beginningo'f .the next..-horizonta1 Vblanking, 'butis shiftedeitherrtothe left .(.as .shown in Awaveform D) or to :the .right thereof. Ihevertical corrective parabolic current fwave and,the horizontalfsine wave (waveform C) are A,combined 'incoil' 51v to produce a composite Wave which'is shown in waveform E of Figure 3. This composite Wave causes the position of the beam 24 to be shifted gradually from the top of the raster to the bottom, and also causes it to be shifted during the course of each scanning line.

As shown in Figure 2a there are

similar circuits

75, 76, 77 and 78 connected With the coils 52 and 53 for affecting the positions of the

beams

22 and 23 respectively. Thus there are sixteen possible adjustmentsthat can be made (i.e., four adjustments for static convergence, and twelve for dynamic convergence) before all the beams are properly converged. When test dot patterns are used in making convergence adjustments it is very difficult to interpret them in such a way that one can, by adjusting the position of only one of the beams, determine when the adjusted beam is in its correct position for proper earn convergence Without adjusting the position of any other beam.

I have found that if test patterns such as shown in Figures 5a-5e are produced by the several beams, the adjustment of the convergence of the beams is greatly simplified and one can tell, by adjusting the position of only one beam, when that beam is in its correct convergence position. To this end, I provide apparatus, in the form of the invention shown in Figure 4, for generating signals which, when applied to the respective electron guns of an aperture mask tube, result in the production of test patterns of the sort shown in Fig. 5. As shown in Fig. 4, these signals may be generated by a conventional monoscope 80 having an electron beam 81 which is scanned over a target 82 in response to defiection signals supplied to yoke 96 from circuits 94. On target 82 there appears one or more inverted-V- shaped configurations printed in carbon ink on the metallic surface 83 which is composed of aluminum with an oxide coating. The surface 83 is deposited on a backplate 93. When the beam 81 scans the target 82, the number of secondary electrons emitted from the metallic surface 83 differs from the number of secondary electrons emitted from the impinged-upon carbon pattern. The emitted secondary electrons are collected by the anode 84. The differences in emitted secondary electrons give a rise to a modulated secondary emission current on the backplate of the target which is amplified in the preamplifier S5. The amplified secondary emission'current may then be applied by appropriate adjustment of the arm 87 of switch 86 to one or more of the electron guns (not shown) of tube 10. Thus if arm 87 is turned to contact 91, the monoscope signal will be supplied to all three of the electron guns. If the beams from the three guns are properly converged, a pattern of white inverted Vs will appear on the face of tube 10, as shown, produced by the scanning of the screen by the three beams in response to signals applied to yoke 36 from circuits 95. This pattern corresponds substantially to the pattern on the monoscope targets. l If, however, the beams are not properly converged, displaced patterns will be produced in the three primary colors emitted by the different colored phosphors of which the screen of the tube is composed. For example, the portion of the pattern on the face of tube 10 shown in box 92 may appear as shown in Fig. 5a where the colors of the separate V-shaped configurations are as indicated by the key. The red configuration 101 is above and to the right of the blue configuration 100, whereas the green configuration 102 is above both the red and blue configurations, being directly above the blue configuration 100. The broken line X-X drawn through one of the legs of the configuration 101 indicates the direction in which the latter may be moved by adjusting the permanent magnet 62 of the convergence magnet assembly 35. The first step in registering the three

configurations

100, 101, and 102 is to move the magnet 62 by turning the knurled end thereof until a portion of the right leg of red configuration 101 is superimposed upon aportion of the right leg of the green configuration 102 as 12 shown in Fig. 5b. The portion where the red and green configurations overlap indicated at the numeral 103 in Fig. 5b will therefore be yellow, indicating that the red beam 22 has been adjusted to its proper static convergence position.

The next step in aligning the beams for static convergence is to move the green beam by adjusting the position of the permanent magnet 63 until the green configuration 102 moves down along the axis Y-Y and becomes superimposed on the red configuration 101 as shown in Fig. 5c. The superimposed

configurations

101 and 102 which will be yellow colored, must then be aligned with the configuration to complete the convergence adjustment. Configuration 100 is produced byV the blue beam 24 which, it will be recalled, can be moved both horizontally and vertically. Accordingly, the blue configuration 100 is moved to the right until it is directly under the combined

configurations

101 and 102 as shown in Figure 5d. This is accomplished by adjustment of the blue beam lateral positioning magnet 38.

The final step is to adjust the permanent magnet 61 until the blue configuration 100 is caused to move up and become exactly superimposed upon the combined

configurations

101 and 102, as shown in Fig. 5e, whereupon the composite inverted V-shaped configuration will be totally white indicating that all three of the beams have been correctly converged.

If desired, adjustment of the position of the blue beam to its correct convergence position can be accomplished in a way different from that illustrated in Figs. 5d and 5e. Instead of relying on visual inspection of the inverted Vs for vertical and horizontal alignment thereof as wasthe case in the last two steps of the illustrated process, the blue beam may be correctly converged by applying to all three beams test patterns containing portions whose axes are parallel to the directions of possible movement of the blue beam, i.e., test patterns containing vertical and horizontal lines as shown in Fig. 6 which is a view of a monoscope target containing congurations according to my invention.

Fig. 6 includes a series of inverted Vs along the horizontal axis, and a number of inverted Vs placed along the vertical axis for horizontal and vertical dynamic convergence. Additional horizontal and vertical rows of configurations may be included for checking convergence at other points on the raster. "In the test pattern illustrated there is included a supplemental pattern of dots located at the intersections of a series of equispaced vertical and horizontal lines extending over the entire target area. These dots are used to test the con vergence on the raster at specified points other than those where inverted Vs are to be found. If desired the: test pattern may also be supplemented by the addition of a cross-hatch pattern of regularly spaced vertical and horizontal lines as shown which can be used to 'test linearity of the sweep circuits. Another check on linearity may optionally be provided by the addition of the' circular designs as shown which are well known in conventional black and white test patterns.

Figures 7a-7p indicate how the inverted V-shaped configurations of the test pattern shown in Fig. 6 would appear if the beams are misconverged because of one or more improper adjustments. In Figs. 7a-7p, in order to simplify the illustration and explanation thereof, only the central top and bottom, extreme left and extreme right inverted Vs of the test pattern shown on the face of tube 10 in Fig. 4 are shown. In the adjustment of the convergence of the beams of tube 10 by using this kind of test pattern it becomes possible to correct for any one or combination of the sixteen possible misadjustments of convergence in a minimum amount of time and without substantial experimentation, estimating, or interpretation. Below, in table form, the symptoms of sixteen possible causesY of misconvergence of the beams producing the patterns of Figs. 7a-7p are listed together with a brief statement of the corresponding adjustment required to correct it.

STATIO CONVERGENCE TROUBLES Figure Symptom Analysis Required Adjustment 7a Blue beam too far right A'djust blue beam lateral positioning magnet 38. 7b Blue beam too high Adjust blue beam permanent magnet 61. 7c Red beam too high Adjust red beam permanent magnet 62. 7d Green beam too high Adjust green beam permanent magnet 63.

DYNAMIC CONVERGENOE TROUBLES 7e Blue beam vertical parabola is Adjust potentiometer 72.

symmetrical but needs more` amplitude at top and bottom of raster. 7]'...- Blue beam vertical parabola is Adjust vertical tilt 71.

unsymmetrical. 7g Blue beam horizontal parabola `Adjust potentiometer 73.

is symmetrical `but wrong amplitude at left and right sides oi raster.

Blue beam horizontal parabola is unsymmetrical.

Green beam vertical parabola is symmetrical, but wrong amplitude at top and bottom of raster.

Adjust variable inductance74.

Adjust vertical ampliigde portion of circuit 7] Green beam vertical parabola Adjust vertical tilt poris unsymmetrical. tion of circuit 76. 7k Green beam horizontal parabola Adjust green beam horizontal amplitude circuit 78.

Adjust .horlzcntal phase portion of circuit 76. yAdjust vertical amplitude section of circuit is symmetrical but has wrong, amplitude at lett and right sides of raster.

Green beam horizontal parabola is unsymmetrical.

Red beam vertical parabola is symmetrical but has wrong amplitude.

Red beam vertical parabola is unsymmetrical.

Red beam horizontal parabola ls symmetrical but has wrong itu e. Red beam horizontal parabola is unsymmetrical.

75. Adjust vertical tilt portion of circuit 75. Adjust circuit 77.

Adjust horizontal phase section of circuit 75.

While, as hereinbefore mentioned, the apparatus shown in Fig. 4 for practicing my invention is entirely suitable for use in factory production of television receivers, it is somewhat cumbersome and therefore not readily adapted for field service use. I have found, however, that it is entirely feasible to product suitable test patterns for use in accordance with my invention employing apparatus which is much simpler and more readily portable. I Figs. 8a, 8b, 8c and 8d illustrate test patterns of the type which can be generated by apparatus employing my invention which is useful to service men in initially installing a color television set in the home of a consumer, in adjusting the convergence of a new aperture mask tube which replaces an old one, or in touching up the convergence of an aperture mask tube when it has been thrown out of adjustment because of the effects of the earths magnetic iield thereupon when the receiver has been moved to a new position.

The first step in converging the beams of a shadow mask tube using test patterns such as those illustrated in Figs. 8a and Sb is to apply to the red and green electron guns signals such as to jroduce the test patterns shown in Fig. 8a. The solid lines represent luminous lines of red and the dashed lines represent lines of green. The red lines are oriented so that they are parallel to the direction in which the red beam may be moved by the beammoving means associated therewith. Since the red lines are thus disposed parallel to the direction in which they are movable, adjustment of the red beam-moving means cannot possibly cause the pattern of red lines to coincide with the green lines. -Only by adjusting the means for moving the green beam can the superimposition of the red and green lines be achieved. Therefore, the means for moving the green beam is adjusted until there appears but one test pattern of yellow lines parallel to the direction in which the red beam may be moved. This the red and4 green electron guns respectively so that the* two 'sets of' red and green lines shown in Figure. 8b appear on the screen of the tube. with respect to the lines of Fig. 8a and both sets of lines are parallel to lthe direction in which the green beam may be moved. Adjustment of the position of the green beam `cannot cause the two sets of lines to coincide. Therefore adjustment ofthe red beam position by the beam-moving means associated therewith is made until the two sets of lines coincide forming a single pattern of yellow lines, which indicates that the red beamis in its proper convergence position.l

Having adjusted the red and green beams to their proper convergence positions it is only necessary to adjustl horizontal lines coincide, whereupon one set of horizontall white lines lis formed. Thisindicat'es that the blue beam is properly positioned insofar as its vertical-component of j movement is.4 concerned.

The finalstep is .'shownin the test pattern of Fig. 8d which is obtained by applying to the4 red, blue and green guns signals which are such asto produce two sets of Vertical lines, one yellow (the red and green beams being properly converged) and one blue. By adjusting the blue beam lateral positioning magnet, the blue lines are shifted laterally until they coincide with the yellow lines, whereupon one single set of white vertical lines is produced indicating that the lateral position of the blue beam is correct for proper beam convergence.

It is possible to produce test patterns such as shown in Figs. 8a and 8b by using apparatus such as shown in Figure 4, or by using a iiying spot scanner, or a televised placard on which the desired lines appear.

It should also be appreciated that, after the red and green beams have been moved into their proper convergence positions by the use of inverted V-shaped configurations, -as explained in connection with Figures 4 and 5, it is not necessary that the signals applied to the blue beam for the adjustment of the position thereof be such as will also produce inverted V-shaped configurations. Since the red and green beams are in their proper convergence position it is only necessary to adjust the blue beam r laterally and vertically. This may be accomplished, for

example, by applying signals to all three electron guns which will produce vertical and horizontal lines as shown in Figs. 8c and 8d.

Similarly, when the red and green beams have been properly adjusted by using line test patterns such as shown in Figs. 8a and 8b, inverted V-shaped test patterns may be used to adjust the position of the blue beam. To this end, appropriate signals may be applied to all three guns and the blue configurations may be shifted horizontally or vertically, by adjustment of the beam-moving means -associated with the blue beam, until they coincide with the yellow inverted V-shaped configurations produced by the properly converged red and green beams.

It is also true that the inverted V-shaped configurations or V-shaped configurations need not actually have two legs which intersect one another. So long as the lines are displaced 120 (or the number of degrees corresponding to the displacement of two electron guns of .a multibeam cathode ray tube) the two beams can easily be adjusted to the proper convergence position.

These lines are inclined While the invention has been described with particular reference to its use in color television image reproducing tubes of the aperture mask type, it may be used in adiusting the areas of impingement of other types of cathode ray tubes in which it is desired that several beams converge on the screen. Also, in other applications, as in so-called dark trace cathode ray tubes having a plurality of beams, the test patterns will be dark traces rather than luminous ones.

It will be understood that still other embodiments and applications of the invention described herein will occur to those skilled in the art. Consequently, I desire the scope of this invention to be limited only by the appended claims.

What I claim is:

l. A target for a monoscope comprising a rst portion and a second portion, said first portion comprising a plurality of congurations of a irst material, each configuration including two lines which are displaced 120 with respect to one another, each of said lines forming an angle of substantially 60 with respect to -a reference line parallel to the vertical axis of said target, said second portion being composed of a material having a secondaryemission ratio differing from that of said first material.

2. A target according to claim 1 wherein said configurations are arranged in mutually perpendicular rows 3. A target according to claim 2 comprising in addition a plurality of parallel vertical and horizontal lines in a cross-hatch pattern, and a plurality of substantially rectanguar areas in a predetermined spatial relation to said cross-hatched lines.

4. A structure for use in producing a test pattern for making beam convergence adjustments to a cathode ray tube in which a plurality of beams are produced which may be moved in `a plurality of respectively different single directions, comprising: an essentially planar body having first and second portions which have respectively different light absorption characteristics, said rst portion being arranged in the form of a plurality of configurations each of which has parts whose axes are substantially parallel to the directions in which said beams can be moved, said second portion constituting the background of the configurations of said irst portion.

5. A structure for use in producing a test pattern for making beam convergence adjustments to a cathode ray tube in which a plurality of beams are produced which may be moved in a plurality of respectively different single directions, comprising: an essential planar body having rst and second portions which have respectively different light absorption characteristics, said rst portion being arranged in the form of a plurality of configurations, each configuration including two lines which are displaced 120 with respect to one another, each of said lines forming an angle of substantially 60 with respect to a reference line parallel to the vertical axis of said structure, said two lines being substantially respectively parallel to the directions in which said beams can be moved, said second portion constituting the background of the conligurations of saidirst portion.

6. The structure according to claim 5 wherein said configurations are arranged in mutually perpendicular rows.

References Cited in the tile of this patent UNITED STATES PATENTS