US3187218A - Electron dynamic beam convergence apparatus for color receiver - Google Patents

Description

R. R. E'DEL 3,187,218 ELECTRON DYNAMIC BEAM CONVERGENGE 'APPARATUS FOR COLOR RECEIVER June 1, 1965 2 Sheets-Sheet 1 Filed July 5, 1962 2 Sheets-Sheet 2 R. R. E'DEL June l, 1965 ELEcTEoN DYNAMIC BEAM coNvERGENcE APPARATUS EOE coLoR RECEIVER Filed July 5, 1962 ldfil Patented .lime l, i965 ice This invention relates to color image display systems and particularly to means for making a plurality of electron beams of a multiple beam display device converge at all scanned points on the target electrode of said device.

An illustrative example or" such a multiple beam display device is a color liinescope. Color kinescopes of the shadow mask type normally have three electron guns positioned in the neck of the liinescope and a target electrode includinn an apertured shadow mask located bctween the electron guns and a luminescent screen of phosphor dots. The dots are arranged in groups of three in register with respective apertures of the masl. Means are provided for the three electron beams converge at the center of the scanned area of the target electrode. The three beams, after passing through the shadow mask, respectively strike three phosphor dots, each emitting light of a different color. All three beams are eilected by a common horizontal and vertical deflection system so that the beams systematically scan the kinescope target'. The more the three beams are deflected from the center or the target, unless corrective measures are taken, the greater may be the misconvergence of the beams when they reach the shadow mask. It is, therefore, customary to provide dynamic electromagnetic rneans for correcting the misconvergence of the beams as a function of the angular deflection of the beams from the center of the kinescope target. For this purpose, current waveforms of generally parabolic shape are derived from the horizontal and vertical deflection cir cuits and are employed, in conjunction with three convergence eleclromagnets, to dynamically converge the three beams at all points or the entire scanned area of the lrinescope target.

The waveforms employed must have proper shapes in order to achieve good convergence of the three beams at all points of the kinescope target. The waveform requirements may be estimated by observing the unconverged rasters of the three beams. It has been observed that color picture tube systems operating with relatively large angles of deilection, as for example 9i), require more correction at the outer edges of the scanned .area when the undeflected beams are statically converged at the center of the picture area. Because of this requirement, the dynamic waveform must have greater amplitude and precision in order to elect satisfactory convergence throughout the scanned picture area. Not only are the wave-shaping requirements more severe in more recent systems having greater .angles of beam deliection, but also considerably more detiecting force is needed to suitably effect the desired beam convergence.

Therefore, it is an object of the invention to provide an improved high emciency circuit by which to edect convergence of the three electron beams of a tri-color kinescope..

The present invention is embodied in a beam convergence circuit such as that disclosed in Patent No. 2,963,- 622, granted September 8, 1959, te l. Schopp. in such apparatus the convergence electromagnet circuits appear essentially inductive to voltage pulses impresse' thereon from the horizontal deflection circuits. Hence,

these pulses are effectively integrated to form generally sawtooth waves which are impressed upon coils incorporated in the circuits tor exciting the convergence electro- CII magnets. A second integration of these sawtooth waves is effected by the convergence control circuits to produce the substantially parabolic current waves desired for traversal of the electromagnet windings. Circuits such as those disclosed in the Schopp patent include a resistivecapacitive circuit which functions to add a sawtooth component to the current traversin(7 each of the convergence electromagnet windings. Such a component is used because the parabolic current waves produced in the manner described do not always have the proper shape to achieve the desired beam convergence.

The present invention is embodied in such a circuit and one feature of it comprises the connection of a unilateral conducting device (eg. a diode) across the resistive element of the circuit by which the sawtooth wave component is produced. The connection of this unilateral conducting device is such that it is gated on (Le. rendered conductive) during the latter part of each beam trace period. Such operation decreases the losses in the beam convergence circuits suitably to 'improve the wave shape of the current traversing the electromagnet winding and thereby to effect better beam convergence. During the rst part of each beam trace period, the unilateral conducting device is substantially non-conducting so that the resistive element across which it is connected may be adjusted to provide an optimum discharge rate for the capacitive element in the savvtooth wave-forming circuit, thereby improving the beam convergence during the rst part of each beam trace period.

The Schupp patent also discloses the series connection of a diode and a resistor in parallel with each beam convergence clectromagnet for properly proportioning the alternating current (A.C.) and direct current (D.C.) components of the current Waves traversing the convergence electromagnets. Another feature of the present invcntion, which may be used separately or in conjunction with other features, is a parallel arrangement of a diode and a resistor connected in series with the convergence electromagnet. By such an arrangement, less power is used to eilect the desired beam convergence without detracting from the performance of the circuit. Thus, rela-` tively high er'lciency of operation is achieved.

For a better understanding of the invention together With additional objects, features and advantages thereof, reference will be made to the accompanying drawings in which:

FIGURE 1 is a block diagram of a color television receiver in which the present invention is embodied;

EEG/URE 2 is a fragmentary sectional view of the neck portion of a shadow mask color kinescope showing the relationship of the convergence electromagnets and the electron beams respectively controlled thereby;

FIGURE 3 is a circuit diagram, partly in block form and partly in schematic form, of the beam convergence circuits embodying a unilateral conducting device in the sawtooth Wave-developing circuit by which wave shaping is improved;

FIGURE 4 comprises a series of curves for use in describing the operation of the wave-shaping feature of the invention;

FIGURE 5 is a schematic circuit diagram of the corivergence circuit for one electromagnet showing the waveshaping unilateral conducting device in conjunction with the parallel connection to the clectromagnet of a series diode and resistor arrangement for A.C.to-D.C. component proportioning as disclosed in the Schopp patent; and

FIGURE 6 is a schematic circuit diagram of the convergence circuit for one electromagnet showing the waveshaping diode feature of the invention in conjunction with the additional feature of a parallel arrangement of a diode anar/,sie

and resistor for A.C.to-D.C. component proportioning connected in series with the convergence electromagnet.

Reference Vfirst is made to FIGURE l for a general description of a color television receiver embodying the present invention. Radiated signals received by the antenna 11 are processed in the TV receiver circuits 12 in a known manner to produce video signals representing three component colors of image to be reproduced and synchronizing signals for controlling beam deflection and for other purposes such as the production of suitable signals by which to effect convergence of the three electron beams at the target electrode of the image-reproducing color kinescope. The receiver circuits 12 may be of the type disclosed in Color Television Service Data, 1961, No. T6, furnished by RCA Sales Corporation, Indianapolis, Indiana.

The color television receiver also includes a three beam color kinescope 13 serving as a color image-reproducing device such as a shadow mask color kinescope of the RSA type Z-IFBPZ'Z or ZlFJPLZlZ. The red, green aud blue representative signals received from the receiver Vcircuits 12 are impressed respectively upon electron guns 14, 15 and 16 of the tri-color kinescope 13. The three electron beams produced by these guns are deflected together over the target screen o-f the kinescope under the control of a deflection yoke 17. Also the beams are maintained lin convergence with each other by means of a suit-ably energized beam convergence yoke 1S, an illustrative form of which will be descibed subsequently.

Also derived from the receiver circuits 12 are horizontal and vertical synchronizing signals which are impressed upon a synchronizing signal separator 19. The horizontal synchronizing signals are impressed upon the horizontal deflection circuit 21 and the vertical synchronizing signals are impressed upon the vertical deflection circuit 22. The horizontal and vertical deflection circuits are connected to the deflection yoke 17 as indicated by the reference characters H--H and V-V. All of the apparatus of FIGURE 1 described up to this point may be of the same character as that disclosed in the service data previously referred to.

Signals derived from the horizontal deflection circuit 21 at the horizontal deflection rate are impressed upon horizontal convergence circuits 23, the output of which is connected to the convergence electromagnets of the convergence yoke 18. Details of such convergencecircuits by which suitable convergence waves are produced will be described subsequently. Signals at the yvertical deflection rate derived from the vertical deflection circuit 22 are impressed upon the vertical convergence circuits 24 for the production of suitable waves which also are impressed upon the electromagnets of the convergence yoke 18. The vertical convergence circuits are not part of the present invention and may be of a known type such as disclosed in the Schopp patent.

Reference now is made to FIGURE 2 for a description of thephysical relationship of the convergence electromagnets and the electron beams controlled respectively thereby as presently embodied in commercial color television receivers. This figure is a transverse sectional view of the neck portion of a color kinescope as it appears when viewed from the luminescent screen end of the kinescope. The three electron beams 25 pass respectively between pairs of pole pieces 26, 27 and 28 located internally of the neck 29 of the kinescope 13. These pole pieces extend inwardly from the ends of substantially U- shaped cores of green, red and blue vconvergence electromagnets 31, 32 and 33 respectively mounted externally around the neck of the kinescope. Each of the convergence electromagnets is provided with a horizontal deflection frequency winding and with a vertical deflection frequency winding. The horizontal deflection frequency windings are designated 34S, 34R and 34B respectively for the green, red and blue electromagnets 31, 32 and 33. The vertical deflection frequency windings are designated 35G,

K and 35B respectively for the green, red and blue electromagnets 31, 32 and 33. Energization of the electromagnetl windings produces a magnetic field between the corresponding pole pieces which moves the corresponding electron beam radially. There also may be included as part of the convergence electromagnetic structure some means for effecting a static convergence Of the electron beams 25. The static convergence means may be permanent magnets associated with the respective convergence electromagnets or may comprise windings on the respective electromagnets for energization by direct current of the proper amplitude and polarity to effect the desired static convergence of the electron beams. Such static convergence means is known and, since it forms no part of the present invention and is not needed for an understanding of this invention, it is not shown.

FIGURE 3 illustrates generally the connections of the horizontal convergence circuits 23 and the vertical convergence circuits 24 between the horizontal and vertical deflection circuits 21 and 22 respectively and the windings of the green, red and blue convergence electromagnets 31, 32 and 33 respectively. The horizontal deflection circuit 21 includes a deflection output tube 36 and an output transformer 37. This circuit is connected in a known manner to the horizontal deflection yoke and to the high voltage rectifier circuits as indicated. The output transformer also is provided with a secondary winding 38 in which voltage pulses at the horizontal deflection repetition rate are produced. These pulsesY are impressed upon the green, red and blue horizontal convergence circuits 39, 41 and 42. Each of these convcergence circuits converts the voltage pulses derived from the transformer winding 38 into suitably shaped parabolic current waves for traversal of the associated horizontal deflection frequency electromagnet windings 34G, 34R and 34B.

Also, voltage pulses at the vertical deflection repetition rate derived from the vertical deflection circuit 22 are converted bythe green, red and blue vertical convergence circuits 43, 44 and 45 respectively into suitably shaped parabolic current waves for traversal of the associated vertical deflection frequency electromagnet windings 35G, 35K and 35B respectively.

The present invention relates principally to the horizontal convergence circuits of which the blue horizontal convergence circuit 42 is representative. Hence, only this circuit'will be described in detail. The voltage pulses derived from the secondary winding 38 of the horizontal deflection output transformer 37 are impressed uponla parabola amplitude control coil 46, the inductance of which may be varied as indicated by means such as a ferrite core movable within the coil in a known manner. The coil 46 is connected to one terminaliof the winding 34B of the blue convergence electromagnet'SS, the other terminal of this winding being grounded. Connected in parallel across the winding 34B is a series arrangement of a capacitor 47 and a potentiometer 48 connected as a variable resistor, The blue horizontal frequency convergence electromagnet circuit appears essentially inductive to the voltage pulses developed in the transformer winding 3S principally by reason of the inclusion of the amplitudecontrolling coil 46. Hence, these pulses are effectively integrated to cause a generally sawtooth current wave to traverse the coil 46. A second integration of this sawtooth wave is effected by the convergence control circuit (principally the essentially inductive winding 34B) toproduce the desired substantially parabolic current wave for traversal of theelectromagnet winding 34B. ln order yto shape Vthe parabolic wave to better effect the desired convergence, a sawtooth current wave component is cornbined with the parabolic wave. This additional sawtooth current for tilting or phasing the parabolic current traversingthe electromagnet winding 34B is produced by the series arrangement of the capacitor 4'7 and the variable resistor 48. The amplitudeof this sawtooth wave component and hence the amount of tilting of the parabolic Wave is determined `'oy the adjustment of the variable resistor 48.

It has been found that the shape of the parabolic current Wave traversing the electromagnet Winding 34B for example, is not in all cases entirely adequate for eliecting Ibeam convergence in color picture tube systems operating with relatively large angles of beam deflection. The wave shaping is materially improved by connecting a unilateral conducting device such as a diode 49 in parallel across the variable resistor i8 in the polarity indicated. In prior art circuits, which did not include the diode 49, the best adjustment of the resistor 48 was a compromise between a value which would provide an adequate discharge rate for the capacitor 47 to eiect satisfactory shaping of the substantially parabolic current Wave during the initial portion of a trace period and which would suitably reduce circuit losses in the latter portion of a trace period to effect satisfactory Wave shaping during such latter portion.

In operation or" the blue horizontal convergence circuit d2 of FIGURE 3, the diode i9 is substantially non-conducting during the iirst portion of each horizontal beam trace over the target electrode of the color kines/cope. The variable resistor may be adjusted to an optimum value for eiiecting discharge of the capacitor d? during the initial trace period which produces a material improvement in the shape of the parabolic current Wave traversing the electromagnet Winding 3dB during such period. The diode i9 is cond .cting during the latter portion of each horizontal beam trace period, thereby decreasing the losses in the circuit. The resultant shape of the parabolic current Wave through the electromagnet winding 34B is thereby improved so that better convergence ofthe color lzinescope electron beams is achieved, particularly in those systems using color lcinescopes operating with relatively wide deflection angles.

The improved shape of the parabolic current Wave is illustrated by the curves of FIGURE 4. The solid line curve 5l represents the voltage developed across the convergence electromagnet such as the Winding 3dB of the blue electromagnet 33 in prior art circuits such as that described in the Schopp patent. This curve 5l is substantially linear throughout the entire beam trace period. As a consequence, the solid line curve 52 represents the shape of the current traversing the electromagnet winding during the beam trace period. Although the shape of this curve 52 is substantially parabolic, it has a relatively sharp .peak portion 53 at the middle of the horizon-tal beam trace and sides which do not have suihcient ste-epilees to effect entirely satisfactory beam convergence at the beginning and ending of the beam trace, especially in color kinescopes having relatively wide deilection angles.

The inclusion of the Wave-shaping diode rfi-9 of EEG- URE 3 in the blue horizontal convergence circuit d2 alters the shape of the voltage Wave across the convergence electromagnet Winding as represented by the broken line curve of FiGURE 4. This curve is no longer linear during beam trace intervals, but instead decreases more rapidly during the first part of trace and again more rapidly during the final part of trace. During the central portion of beam trace the voltage curve changes at a slower rate than in the first and unal parts or trace. As a result, the substantially parabolic current Wave which traverses the electromagnet winding has a shape substantially as illustrated by the broken curve line 55. This curve has somewhat steeper sides at both the beginning and ending of beam trace than in the previous case. This steepening results from the greater slope of the voltage Wave 54.- during these portions of the beam trace interval. Also, the curve 55 has a ilatter peak portion during the middle of beam trace which results from the lesser slope of the voltage Wave 541 during this period. The energization of the convergence electromagnet windings by substantially parabolic current Waves having the shape f the curve 5S has been found to produce significantly better dynamic beam convergence over the entire screen of a color kinescope operating with relatively Wide deflection angles.

The novel features of the convergence circuit described with reference to FIGURE 3 also may be used in convergence circuits such as those `disclosed in the Schopp Patent 2,903,622 previously rete red to. FlGURE 5 illustrates such a circuit incorporating the improved Waveshaping feature of the present invention. The blue horizontal convergence circuit 42 includes the amplitudecontrolling coil 46, the sawtooth Wave component circuit including the capacitor 47 and the variable resistor` d8 and the wave-shaping diode 4% previously described. These elements function substantially in the salme manner as described With reference to FIGURE 3. rlhe voltage pulses derived from the secondary Winding 38 of the horizontal deflection output transformer 37 in this case, are impressed upon vthe convergence circuit lby a blocking capacitor el. rlhis circuit also includes a series arrangement of a diode 62 and a resistor 63 connected in parallel with the convergence electrornagnet Winding 34B. The diode 623 and its associated resistor o3 serve to suitab y proportion the A.C. and DC. components of the substantially parabolic current Wave impressed upon the electromagnet Winding as disclosed in the Schopp patent. As disclosed in this patent, the proportioning is such that, at the troughs of the resultant parabolic Wave, the current through the electromagnet winding has the same magnitude irrespective of the particular shape and peak-to-peal amplitude of the Wave. This makes it easier to adjust the circuitry to effect beam convergence over the entire luminescent screen of the kinescope. The blocking capacitor 6l prevents the direct cur-rent flowing through the diode 62 `and the resistor 63 from undesirably traversing the secondary Winding 38 ofthe horizontal output transformer 37 (EEGURE 3). Hence, the moditication of the present invention shown in FIGURE 5 achieves the same results as in the Schopp patent and in addition etiects the improved shaping of the substantially parabolic current wave as described previously with reference to ElGURES 3 and 4.

FIGURE 6 illustrates a blue horizontal convergence circuit 42; which includes both the .improved Wave-shaping feature and an additional feature of the invention which enables the convergence circuit to operate in a manner to properly proportion the A.C. and DC. components `of the substantially parabolic current Wave traversing the electromagnet winding at a considerably higher efficiency than heretofore. As in the'forrn of the invention shown in and described with reference to FIGURE 3, the voltage pulses derived from the horizontal deflection `circuit are impressed directly upon the convergence circuit without the use of a blocking capacitor, such as the capacitor 61 of FIGURE 5. This circuit includes the amplitude-controlling coil do, the sawtooth wave circuit including the capacitor 4-7' and the variable resistor d3, and the wave-shaping diode 49. All of these components are connected and operated substantially as previously described. l

Additionally there is provided a parallel arrangement of a diode 6d and a resistor d5 connected in series between the amplitude-controlling coil le and the convergence electromagnetic winding. The diode ed and the resistor function to properly proportion the AC. and DC. components of the substantially parabolic current wave traversing the electromagnet winding. By virtue of the series connection of these components with the electromagnet Winding, instead of the parallel connection of the diode 62 and resistor 63 of FIGURE 5, a material saving in power is achieved. Thus, the convergence circuit 42" of FIGURE 6 operates in a more eicient manner to achieve dynamic beam convergence in a color ltineseope operating Vwith a relatively Wide deflection angle.

Whatis claimed is:

1. In a color television receiver including, a multiplebeam color kinescope image-reproducing device, and line deection means for deiiectingsaid beams in a series of vertically spaced horizontal lines during successive beam trace periods to form a raster,

the combination for converging said beams at all points of said raster, comprising: a dynamic convergence electromagnet having an energizing winding; l

inductive means connected with said energizing winding to cooperate with said winding in converting voltage pulses derived from said deilection means into a substantially parabolic current Wave for traversal of said winding; v

means including a series arrangement of a capacit-or and a resistor connected in parallel with said energizing winding to produce a sa-wtooth current wave component Ifor traversal of said winding; and

a unilateral conducting device connected only across said resistor in such manner as to be rendered conducting only during the latter portions of lsaid beam trace periods to improve the shape of the substantially parabolic current wave traversing said energizing winding.

2. In a color television receiverV including, a multiple-V beam color kinescope image-reproducing device, yand line deflection means for defleoting said beams in a series of vertically spaced horizontal lines during successive beam trace periods to form a raster,

fthe combination for converging said beams at -all pointsy `of said raster, comprising: a plurality of dynamic convergence electromagents having respective energizing windings; means including a coil connected in series with yone of said energizing windings `to-cooperate with said one winding in convent-ing voltage pulses derived from said deiiection means into a substantially parabolic lcurrent wave for traversal of said one winding;

means including a series arrangement of a capacitor and a resistor connected in parallel with said one energizing winding to produce a sawtooth current' wave component for traversal of saidone winding; and

a unilateral conducting device connected only across said resistor in such manner as to 4be substantially non-conducting during the initial portion of each Y of said beam trace periods and to be substantially non-'conducting during the initial portion of each of "said beam trace periods and to be conducting during the latter portion ol each of said beam trace periods Ito improve the shape of the substantially parabolic current wave traversing said one energizing winding.

3. In a color television receiver including, a multiplebeam color kinescope image-reproducing device, and line deection means for deecting Vsaid beams in a series of f vertically spaced horizontal lines dur-ing successive beam trace periods to tor-m a raster,V Y the combination for converging said beams at all points `of said raster, comprising: a dynamic convergence clectromagnet having an energizing winding, there being one such electro-magnet -for each of said beams; Y means including a coil connected in series with one of said energizing windings to cooper-ate with said one `winding in converting voltage pulses derived from :said deflection means into a substantially parabolic; current wave for traversal of said one winding; means including a series arrangement-oi a capacitorl rand a resistor connected in parallel with said one energizing winding lto yproduce a lsawtooth currentx wave component for traversal of said one winding;-

a unilateral conducting device connected only across said resistor in such manner .as to be rendered conducting only during the latter portion of each oi said beam tra'ce periods to improve the shape of the substantially parabolic current wave traversing said one energizing winding.

4. In a color television receiver including, amultiplebeam color kinescope image-reproducing device, and line; deilection means vfor deilecting said beams in a series of vertically spaced horizontal lines during successive beam trace periodsrto form a raster,

the combination for converging said beams at all points of said raster, comprising:

a dynamic convergence electromagnet having an energizing winding, there being one such electromaguet for each of said beams;

means including an amplitude-controlling coil com nected in series with at least one of said energizing i windings to cooperate with said one Winding in converting'voltage pulses derived from said deflection means into a substantially `parabolic current wave :for traversal of said one winding; means including a series arrangement of a capacitor and a variable resistor connected in parallel with said one energizing winding to produce Ia sawtooth current wave component for traversal of said one winding, the amplitude of which is determined by said variable resistor; and a diode connected only across .said resistor in such polarity as to be rendered conducting only during :the latter portion of each of said beam trace periods Ito improve the -shape of the substantially parabolic current wave traversing said one energizing winding. 5. In acolor image display system including, a multiplebea'm color' image-reproducing device, and line deflection means for deflecting said beams in a `series of vertically spaced horizontal lines during succe'ss've beam trace periods to form a raster, Y

lthe combination for converging said beams at all points of said raster, comprising: a dynamic convergence electromagnet having an energizing winding; means including a coil corrected in series with said energizing winding to cooperate with said winding in converting voltage pulses derived from said dflection means into a substantially parabolic current Wave for traversal of said winding; means including a rst resistor connected in parallel with said energizing winding to produce a sawtooth Y current wave component for traversal of said winding; Y

-a series arrangement of a diode and a second resistor connected in parallel with said electromagnet wind- 'ing to proportion the direct current and alternating :current components of the substantially.parabolic cur-rent was so that, at the troughs of said wave, the current through said winding always has the same magnitude irrespective of the particular shape and peakto-peak amplitude of said wave; and

a unilateral conducting device connected across said first resistor in such manner as tobe rendered conduct-ing only during the latter Iportion of each of said Ibeam trace periods to improve the shape of the substantially parabolic current Wave traversing said energizing winding.

6. In acolor television receiver including, `a multiple- Y Ibeam color lcinescope imagedreproducing device, and line deflection means for deecting sa'd beams in a series of vertically spaced horizontal lines during successive .beam trace periods to for-m a raster,

the combination for converging said beams at all points of said raster, comprising: a dynamic convergence Velectr-omagnet having an energizing Winding; Y means including a Yseries arrangement of a capacitor i and `a coil connected in series with said energizing winding to cooperate with said winding in converting voltage pulses derived from said deection means 'anemie into a substantially parabolic current wave for traversal of said winding;

means including a series arrangement of a capacitor and a rst resistor connected in parallel with said energizing winding to produce a sawtooth current Wave component for traversal of said winding;

a series arrangement of a diode and a second resistor connected in parallel with said electromagnet winding to proportion the direct current and alternating current components of the substantially parabolic current wave so that, at the troughs of said wave, the current `through said winding always has the isame m-agnitude irrespective of the particular shape yand peak-to-peak amplitude of said wave; and

a kunilateral conducting devi-ce connected across said first resistor in such manner as to be substantially non-conducting during the initial portion of each of said trace periods and to be rendered conducting during the latter portion of each of said beam trace periods to improve the shape of the substantially parabolic cur-rent wave traversing said energizing Winding.

7. In a color television receiver including, a multiplebeam color kinescope image-reproducing device, and line deflection means for deiiecting said beams in a series of vertically spaced horizontal lines during successive beam trace periods to form a raster, Y

the combination for converging said beams at yall points of said raster, comprising:

a dynamic convergence electromagnet having an energizing winding;

means including a series arrangement of a capacitor rand a variable inductance coil connected in series with said energizing winding to cooperate with said winding in converting voltage pulses derived from said deflection means into a substantially parabolic -cunrent wave for traversal of said winding, said coil serving to control the amplitude of said parabolic wave;

means including a series arrangement of a capacitor and a variable resistor connected in parallel with said energizing winding to produce a sawtooth current wave component for traversal of said winding, said resistor serving to control the amplitude of 'said sawtooth wave component;

a eries arrangement of a diode and a resistor connected in parallel `with said electromagnet Iwinding to proportion the direct current and alternating currentk components `of the substantially parabolic current wave so that, at the troughs of said wave, the current through said winding always has the same magnitude irrespective of the particular shape and peakto-peak amplitude of said wave; and

a diode connected across said variable resistor in such polarity as to `be rendered conducting only during fthe latter portion of each of said beam trace periods to improve the shape of the substantially parabolic current wave traversing said energizing windin".

3. in a color image display system including, a multiple-beam color image-reproducing device, and line deiiection means for dellecting said beams in a series of vertically spaced horizontal lines during successive beam trace periods to form a raster,

the combination for converging said beams at all points of said raster, comprising:

a dynamic convergence electromagnet having an energizing winding;

means including a coil connected in series with said energizing winding to cooperate with said winding in converting voltage pulses derived from said deiiection means into a substantially parabolic current wave for traversal of said winding;

means including a first resistor connected in parallel with said energizing winding to produce a sawtooth current Wave component for traversal of said Windins;

a first unilateral conducting device connected across said first resistor in such manner as to be rendered conducting only during the latter portion of each of said beam trace periods to improve the shape of the substantially parabolic current wave traversing said energizing winding; and

a parallel arrangement of `a second unilateral conducting device and a second resistor connected in series with said electromagnet winding to proportion the direct current and alternating current components of the substantially parabolic current wave so that, at the troughs of said wave, the current through said Winding always has the same magnitude irrespective of the particular shape and peak-to-peak amplitude of said Wave, whereby to etect convergence of said beams with a high degree of efficiency over relatively large angles of beam deilection.

9. In a color television receiver including, a multiplebeam color kinescope image-reproducing device, and line deilection means for detiecting said beams in a series of vertically spaced horizontal lines during successive beam trace periods to form a raster,

the combination for converging said of said raster, comprising:

a dynamic convergence electromagnet having an energizing winding;

means including a coil connected in series with said energizing winding to cooperate with said winding in converting voltage pulses derived from said deiection means into a substantially parabolic current wave for traversal of said winding;

means including a series arrangment of a capacitor and a first resistor connected in parallel with said energizing Winding to produce a sawtooth current wave component for traversal of said winding;

a unilateral conducting device connected across said resistor in such manner as to be rendered conducting only during the latter portion of each of said beam trace periods to improve the shape of the substantially parabolic current wave traversing said energizing winding; and

a parallel arrangement of a diode and a second resistor connected in series with said electromagnet winding to proportion the direct current and alternating current components of the substantially parabolic current wave so that, at the troughs of said wave, the current through said winding always has the same magnitude irrespective of the particular shape and peak-to-peak amplitude of said wave, whereby to effect convergence of said beams with a high degree of eciency over relatively large angles of beam deiiection.

It). In a color television receiver including, a multiplebeam color kinescope image-reproducing device, and line deilection means for deilecting said beams in a series of beams at all points vertically spaced horizontal lines during successive beam trace periods to form a raster,

the combination for converging said beams at all points of said raster, comprising:

a dynamic convergence electromagnet having an energizing winding;

means including a variable inductance coil connected in series with said energizing winding to cooperate with said winding in converting voltage pulses derived from said deection means into al substantially parabolic current wave for traversal or" said winding, said coil serving to control the amplitude of said parabolic wave;

means including a series arrangement of a capacitor and a variable resistor connected in parallel with said energizing winding to produce a sav/tooth current wave component for traversal of said winding, said resistor serving to control the amplitude of said sawtooth wave component; a diode connected across said variable resistor in such polarity as to be rendered conducting only during the l latter portion of each of said beam trace periods t improve the shape of the substantially parabolic current Wave traversing said energizing winding; and

a parallel arrangement of a diode and another resistor connected in .series with said electromagnet winding to proportion the direct current and alternating current components of the substantially p-arabolic current Wave so that, at the troughs of said wave, the current through said winding always has the same magnitude irrespective of the particular shape and peak-to-peak amplitude of said wave, whereby to effeet convergence of said beam with a high degree of eilciency over relatively large angles of beam deection.

11. In a color image display system including, a multiple-beam color image-reproducing device, and line delection means for deilecting said beams in a series of vertically spaced horizontal lines during successive beam trace periods to form a raster,

the combination for converging said beams at all points of said raster, comprising:

a dynamic convergence electromagnet having an energizing winding;

means connected with said energizing winding to coopcrate with said winding in converting voltage pulses derived from said deflection means into a substantially parabolic current wave for traversal of said winding; and

'a parallel arrangment of a unilateral conducting device and resistive means connected in series with said electromagnet winding to proportion the direct current and alternating current components of the substantially parabolic current wave so that, at the troughs of said wave, the current through said winding always has the same magnitude irrespective of the particular shape and peakto-peak amplitude of said waves, whereby to eiect convergence of said beams with a high degree of eiliciency.

12. In a color television receiver including, a multiplebeam color kinescope image-reproducing device, and line dellection means for defiecting said beams in a series of vertically spaced horizontal lines during successive beam trace periods to form a raster,

the combination for converging said beams at all points of said raster, comprising: a dynamic convergence electromagnet having an energizing winding;

l2 inductive means connected in series with said energizing winding to cooperate with said winding in converting voltage pulses derived from said deiiection means into a substantially parabolic current wave for traversal of said winding; and

a parallel arrangement of a unilateral conductive device and a resistor connected in series with said electromagnet winding to proportion the direct current and alternating current components of the substantially parabolic current Wave so that, at the troughs of said wave, the current through said Winding always has the same magnitude irrespective of the particular shape and peak-to-peak amplitude of said wave, whereby to eifect convergence of said beams with a high degree of efficiency. 13. In a color television receiver including, a multiplebeam color kinescope image-reproducing device, and line dellection means for deflecting said beams in a series of vertically spaced horizontal lines during successive beam trace periods to form a raster,

the combination for converging said beams at allv points of said raster, comprising: Y

a dynamic convergence electromagnet having an energizing Winding; Y

means including a coil connected in series with said energizing winding to cooperate with said winding in converting voltage pulses derived from said deilection means into a substantially parabolic current .wave for traversal of said winding; and

a parallel arrangement of a diode and a resistor connected in series between said coil and said electromagnet winding to proportion the directcurrent and alternating current components of the substantially parabolic current Wave so that, at the troughs of said wave, the current through said winding always has the same magnitude irrespective of the particular shape and peak-to-peak amplitude of A said wave, whereby tov effect convergence of said beams with a high degree of efliciency.

References Cited by the Examiner RCA Color Television Service Data, 1960, No. T5, p. 33, lune 17,1960.

DAVID G. REDI-NBAUGH, Primary Examiner.

ROBERT SEGAL, Examiner. Y

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No., 3,187,218 A' June l, 1965 Ralph R. E'del It is heteby certified that error appears in the above numbered patent reqiring correction and that the said Letters Patent should read as co;reeted,below.

Column 3, line 20, for "RSA" read RCA column 7, lines 47 to 49, strike out "and to be substantially non-Conducting during the initial portion of each of said beam trace periods" column 8, line 52, fot "was" read wave Signed and sealed this 7th day of December 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER AI testing Officer Commissioner of Patents

Claims (1)

1. IN A COLOR TELEVISION RECEIVER INCLUDING, A MULTIPLEBEAM COLOR KINESCOPE IMAGE-REPRODUCING DEVICE, AND LINE DEFLECTION MEANS FOR DEFLECTING SAID BEAMS IN A SERIES OF VERTICALLY SPACED HORIZONTAL LINES DURING SUCCESSIVE BEAM TRACE PERIODS TO FORM A RASTER, THE COMBINATION FOR CONVERGING SAID BEAMS AT ALL POINTS OF SAID RASTER, COMPRISING: A DYNAMIC CONVERGENCE ELECTROMAGNET HAVING AN ENERGIZING WINDING; INDUCTIVE MEANS CONNECTED WITH SAID ENGAGING WINDING TO COOPERATE WITH SAID WINDING IN CONVERGING VOLTAGE PULSES DERIVED FROM SAID DEFLECTION MEANS INTO A SUBSTANTIALLY PARABOLIC CURRENT WAVE FOR TRAVERSAL OF SAID WINDING; MEANS INCLUDING A SERIES ARRANGEMENT OF A CAPACITOR AND A RESISTOR CONNECTED IN PARALLEL WITH SAID ENERGIZING WINDING TO PRODUCE A SAWTOOTH CURRENT WAVE COMPONENT FOR TRAVERSAL OF SAID WINDING; AND

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