US2928981A - Multi-beam convergence apparatus - Google Patents

Description

Marchls, 1960 M. KOLESNIK mL 2,9'8,981

MULTI-BEAM CONVERGENCE APPARATUS Filed May 31, 1955 2 Sheets-Sheet l C il? 5E .5/7/7LL www United States Patent 2,928,981 MULTI-BEAM CONVERGENCE APPARATUS Michael Kolesnik, Haddon Heights, and Charles Ernest Small, Pennsauken, NJ., assignors to Radio Corporation of America, a corporation of Delaware Application May 31, 1955, Serial No. 511,940 '5 Claims. (Cl. 315-13) The invention relates to systems for controlling the dellection of electron beams of cathode ray tubes, or kinescopes, and it particularly pertains to such systems in which a plurality of electron beams are deflected by common deection circuitry.

One type of cathode ray tube with which the invention and fixed capacitance in series resonance at the horizontal line deflection rate provide variable amplitude current sine waves at horizontal deflection rate. The above mentioned current waveforms are then combined to provide the desired convergence waves for application to the pole piece exciting windings of the multi-beam kinescope. Amplitude variation of the sine waves is obtained by adjusting taps on the adjustable resistance elements and phasing is achieved by varyingthe tuning of the adjustable inductance elements.

In Iorder that the practical aspects will be more fully appreciated, an express embodiment of the invention,

given by way of example only, is described hereinafter may be successfully used is a color kinescope of the general typeV described in an article A Three-Gun Shadow-Mask Color Kinescope, by H. D. Law published in the Proceedings of the IRE, volume 39, No. 10, for October 1951 at page 1186. Such a tube has a luminescent screen as part of the target electrode structure, in which screen different phosphor areas produce dilferently colored light when excited by electron beams `impinging from different angles, the angle of impingement determining the particular color of the light produced. For satisfactory operation of such kinescopes, it is neces- Asary to eifect substantial convergence of the different 4electron beams at all points on the raster formed by dellecting the electron beams in two directions perpendicular with respect tol each other. A general discussion of this beam convergence problem will be found in an article entitled Deflection and Convergence in Color Kinescopes, by A. W. Friend, published in the Proceedings of the IRE, volume 39, No. l0, for October 1951 at page 1249. One type of multi-beam kinescope to which the invention particularly pertains includes a pair of magnetic pole pieces located internally of the kinescope envelope for each beam. These internally located pole pieces are energized by the magnetic components externally of the kinescope envelope. These magnetic components may be entirely electromagnetic or they may include some permanent magnetic structure since in general the internally located pole pieces require static as well as dynamic energization. In general it is `desirable to provide such convergence means for kinescopes with the minimum of additional components.

An object of the invention is to provide improved circuitry for effecting convergence of the plurality of electron beams of a multi-beam kinescope.

Another object of the invention is to provide components which are smaller and lighter 'than those of the prior art for exciting the internal pole pieces of a multibeam kinescope.

According to the invention convergence is obtained fwith a simplified circuit using a minimum of components. The circuit features an isolated winding on the vertical `tlellection wave output transformer which in conjunction with an inductance element and adjustable resistance `elements provide variable amplitude parabolic current `waves at the vertical dellection ratewhile other resistance elements connected to other taps on the above mentioned winding provide variable amplitude positive or negative sawt'ooth current waves at the vertical deflection rates for tilting the parabolic waves. i An isolated Vwinding on thehorizontal deflection wave output transformer in conjunction with adjustable resstance elements and aV plu- 'i'ality'of series circuits comprising adjustable inductance with vreference to the accompanying drawing in which: Fig. `1 is a functional diagram of a television receiving apparatus in which the invention may be incorporated;

Fig. 2 is a cross section view of a multi-beam kinescope of the type to which the use of the invention is particularly applicable; and

Fig. 3 is a schematic diagram of an embodiment of the invention.

Referring first to Fig. 1, there is shown a functional diagram of portions of a color television receiver in which the invention is particularly adaptable, and which color television receiver may otherwise comprise entirely conventional circuitry. In such a receiver, color television signals appearing at an antenna are applied to a radio frequency wave amplifying circuit and the output therefrom is Vapplied along with the wave obtained from a local beat oscillation generating circuit to a frequency changing circuit. The output of the frequency changing circuit is applied to an intermediate frequency (L-F.) amplifier which may be one having separate channels for picture and sound signals or one in which both picture and sound signals are amplified, at the same time. A video demodulating circuit`17 is connected at terminal 16 to the I.F. amplifying circuit for deriving a video wave from the television signals. The detected video signals are amplilied in a video frequency (V.F.) amplifying circuit 18. Sound signals are derived from the sound I.F. amplifying circuit, or from the demodulating circuit 17 or from the V.F. circuit 18, for further processing in a sound I.F."amplifying circuit, an aural signal discriminating circuit, an audio frequency (A.F.) amplifying circuit and a transducer, usually in the form of`a loud speaker. The output of the V.F. amplifying circuit is applied to a circuit 19 for converting luminance and chrominance components into proper form for application to the signal input circuitry of an image reproducing device, or kinescope 20. The output of the video frequency amplifying circuit is also applied to'synchronizing pulse separating circuit 28. High voltage and focus voltage generating circuit may be coupled to the horizontal deflection wave amplifying circuit. The vertical deilection wave amplifying circuit 26, the horizontal deflection wave amplifying circuit 28 and the high voltage and focus voltage generating circuit 29 are coupled to the kinescope 20 to supply vertical and horizontal deflection waves to focus and ultor potentials. The vertical deflection wave amplifying circuit 26 and the horizontal deflection wave amplifying circuit 28 are connected to a convergence wave generating circuit 30l for generating convergence waves-for dynamic convergence of individual beams of the multi-gun kine'scope' 20. A low voltage power supply, normally connected to the local A.C. power lines, is arranged to furnish direct energizing potentials to all circuits. An automatic gain control amplifying distributing network is coupled to the synchronizing pulse separating circuit 24 or the video frequency demodulating circuit 17 or to the video amplifying circuit 18 to supply control potentials to the desired ones of the circuits previously mentioned. Normally the radio frequency and intermediate frequency amplifying circuits are at least so supplied.

The kinescope 20 may be of the same general type as that disclosed in the HB. Law paper previously referred to. The kinescope 20 preferably has a luminescent screen provided with a multiplicity of small phosphor areas arranged in groups and capable of producing light of the different component colors when excited by electrons. In back of and spaced from the screen there is an apertured masking electrode having an aperture for and in substantial alignment with each group of phosphor areas. The luminescent screen and the masking electrode may be planar or may have partial spherical surfaces; the invention being equally applicable to either form. of target electrode structure.

The kinescope 2t) also has a plurality of electron beams equal in number to the number of component color in which the image is to be reproduced. Conventionally, three such electron guns, which may be entirely conventional in structure consisting of a cathode, a control electrode and a focusing electrode, are arranged substantially parallel to produce three separate electron beams by which to energize respectively blue, red and green. phosphor areas of the screen of the kinescope. The kinescope 20 also contains a beam accelerating electrode, or ultor, consisting of a conductive Wall coating on the inner surface of the envelope of the kinescope and extending out to the region of the target electrode structure. When these electron beams are properly convergedA at the, target structure, the electrons pass through the apertures of the masking electrode from different directions and impinge on different phosphor areas of each of the groups so as toY produce light in the three component colors. The electrodes of the kinescope 20 may be energized in the conventional manner and the color information signals are applied sov that the electron beams are modulated in intensity in accordance with the information carried by the color-representative video signals derived from the translator circuit 19. The video signal source will not be described further herein since it does not form an essential part of the invention.

Associated with the color kinescope 20 is a deflection system yoke, which may be entirely conventional and in which may be mounted at two pairs of suitably placed windings electrically connected so that when properly energized, electromagnetic fields are produced to effect both horizontal and vertical angular deflections of the electron beams to scan the usual rectangular raster at the target electrode structure. Deflection waves for application to the deflection system windings are obtained from the vertical and horizontal deflection wave amplifying circuits 26 and 28 respectively.

The beam convergence system in accordance with the invention also includes a plurality of electromagnetic field producing elements arranged about the neck of the kinescope adjacent to the predeection paths of the electron beams. An example ofV such construction is shown in Fig. 2 wherein three magnet assemblies 31, 32 and 33 arranged about the neck of a kinescope envelope 35. The precise location of the magnet assemblies is not necessarily indicated in Fig. 2 but it is to be understood that each of the magnet assemblies is located relative to the path of one of the electron beams to influence that one beamte the virtual exclusion of the others. The magnetic fields produced by these magnet assemblies are transverse to theassociated beam paths andin avdirection tomove the associated beam radially relative to the longitudinal axis of the kinescope. The convergence magnet assemblies 31-33 are usually energized by a substantially unidirectional current component to elect an initial convergence of the electron beams substantially at the target electrode structure. Normally convergence is initially made at the center of the screen, however, this initial convergence may be made at any point, for example at one corner of the raster. In order to do this, the unidirectional energizing current component is effected in such a way that the magnet may be individually energized in different magnitudes.

The convergence magnet assemblies 31-33 are also dynamically energized by wave energy derived from suitable generating means so as to effect a variation in the magnitude of the transverse fields produced and to vary the deflection of the individual electron beams as a function ofthe overall deflection of the three beams. In this way suitable variations are made in the convergence angles between the various beam components in the individual beams so as to produce the desired convergence of the beams substantially at all points of the target electrode structure. All of the magnet assemblies being the same only one will be described in detail. The magnet assembly 31 comprises a core, which may be in one piece, but is shown in two pieces 36, 37 having legs 38, 39 ex'- tending at right angles to the main body of the core. If direct current is utilized to afford static convergence, the core might conveniently be in one piece. As shown, however, the core of the magnet assembly 31 is split into two pieces 36, 37 and mounted between the core pieces in suitable recesses formed therein is a substantially cylindrical permanent magnet 40. This magnet is polarized substantially diametrically so as to present north and south poles in the two halves thereof substantially as indicated. The permanent magnet 40 may be provided with suitable adjusting facilities, such as a screw driver slot, formed in one orA both ends. The rotation of the permanent magnet 40 between the core sections 36, 37 enables the strength of the permanent magnetic iield produced to be adjusted in both magnitude and polarity. Windings 41, 42 are mounted on the legs of the core pieces, although alternatively windings may be wound as a unitary structure and mounted on the main body portion of the core. For each of the convergence magnet assemblies there is provided a set of pole pieces 43, 44 internally of the kinescope envelope 35. The internal pole pieces 43, 44 are arranged toA increase the effectiveness of the associated magnet assemblies by decreasing the reluctance of the magnetic circuit and considerably improving the flux distribution of the field produced between the pole pieces. The convergence magnet assemblies therefore produce fields which in the vicinity of the electron beams associated therewith are substantially transverse to the axis of the kinescope and the associated beam may be moved readilyy toward or away from the longitudinal tube axis. The direction and magnitude of such beam movement is controlled by the cnergization of the windings 4l, 42.

The convergence magnet assemblies are energized according to the invention by means of the circuit arrangement shown in Fig. 3, to which reference is made. The convergence magnet assemblies are substantially identical, as stated before, and are therefore energized by substantially identical circuits. Therefore the description will belimited to the particular circuits by which the windings 41 and 42 of the convergence magnet assembly 31 are energized, it being understood that the same description applies equally as well to the circuits illustrated for energizing the other convergence magnet windings.

Sawtooth deection waves of vertical deflection rate are applied at input terminals 51, 52 to a vertical deflectionwave amplifier tube 54. Vertical sawtooth current waves are induced in transformer 56 by the primary winding 5.7 connectedr in the anode circuit of the vertical amplifier tubel 6.4. 'Ihesawtooth deflection wavefappear ing' across the secondary winding 58 is applied to the ver- 'tlcal defiection system winding comprising sections 61, I62 by way of a coupling capacitor 63. If desired, balancing resistors 66 and 67 may be connected as shown to equalize current fiow. No provisions are shown in the circuit for centering, but conventional centering current circuitry may be connected across the coupling capacitor 63 in known manner. Sawtooth waves at horizontal defiection rate are applied at input terminals 71, 72 of the horizontal amplifier tube 74. Sawtooth current waves are induced in the windings of the horizontal defiection wave output transformer 76 by the primary windlng section 77. The sawtooth deflection waves appearing in the output secondary winding 78 are applied by means of the width control selector switch to the horizontal defiection system winding comprising two sections 81, 82, the latter of which is shunted by an anti-ringing capacitor 83. A balancing resistor 86 is preferably connected between the center tap of the secondary winding 78 and the connection between the two horizontal defection system winding portions 81, 82. Again no centering provisions have been shown, but these may be readily supplied by connecting the defiection system winding 82 to an intermediate tap on the series resistor 87 instead of to the junction between the resistor 87 and the wind` ing 78, and connecting a centering choke'between the width control switch 79 and the terminal 88 of the primary winding 77 of the horizontal output transformer 76. A suitable bypass capacitor should be connected across the series resistor 87.

According to the invention a vertical defiection output transformer 56 is provided with an additional winding 90. Aspiked sawtooth wave at the vertical defiection rate appears between terminals 91 and 93 of the secondary winding 90, the latter terminal being maintained at reference potential, shown Vas ground. By means of an inductance enlement 9,6 this spiked vertical sawtooth wave is partially integrated to produce a parabolic wave, the amplitude of which is determined by the position of a tap or arm 98 on a variably tapped resistance element or potentiometer 99 shunted across this portion of the winding 90. By means of a variably tapped resistance element or potentiometer 101 connected across'terminals 102, 104 of the secondary winding 90 positive or negative sawtooth waveforms of vertical defiecton rate maybe obtained by movement of the tap or arm 106 along the resistance element 101. There is an equal number of turns between the terminals 102 -93 and 93-104 of the winding 90. In the central position the potential from the arm 106 to the point of reference potential, shown as ground, is zero and moving to 4either side produces either a'positive or negative sawtoothwave between the tap 106 and ground. The convergence magnet winding sections 41', 42' are connectedbetween the taps or arms 93 and 106. Neglecting forthe moment the effect of the adjustable series inductor 102, there is a parabolic current wave applied tothe convergence system winding sections 41', 42 of amplitude determined by the position of the arm 98 on the potentiometer 99, which wave is tilted, that is efectively shifted so that the minimum amplitude point is either toward the beginning or the end of the wave as determined by the position of the arm 106 on the sawtooth potentiometer 101. For this reason the resistance element 101 is usually termed a tilt control.

By the use of the inductor 96 for integrating the vertical sawtooth, the expense of the large electrolytic capacitors previously used for this purpose has been eliminated and a lower cost inductor used. Also the stability of the circuit has been greatly improved because the electrolytic capacitors when used vin such circuits are not sufficiently stable to prevent drift of the electron beam. Furthermore the integrating inductor 96 has a negligible effect on the vertical deection wave, which means that a less expensive vertical output stage may be used to secure the desired results.

With tri-colored kinescopes of the type described, horizontal convergence is readily obtained with sine wave or modified sine wave current. According to the invention'such waveform is derived at the horizontal rate by means of secondary winding on the horizontal output transformer 76. From this winding a substantially square wave at horizontal deflection rate is derived and applied to a series circuit comprising an adjustable inductor 102'and a capacitor 108 having values providing series resonance at the horizontal deflection frequency. The negative kick-back pulse obtained from the transformer winding 100 is applied to a variably tapped resistance element or potentiometer 110, the tap or arm`111 of which is connected to the capacitor 108. The amplitude of the sine wave component is determined by the position of the arm 111 on the potentiometer 110. The choke or inductor 102 is made adjustable so'that the sine wave can be phased similar to the tilt obtained for the sawtooth wave, by slightly varying the tuning of the inductor 102. The junction between the inductor 102 and the capacitor 108 is connected to the convergance system windings 41', 42 so that the various current waveforms are combined and dynamic convergence of the electron beams is achieved by adjusting the associated potentiometer arms and inductors to the necessary current waveforms through the individual pole piece excited or convergence system windings.

The convergence circuitry of the invention presents high impedance to the vertical and horizontal deliection wave amplifying circuits so that there is not appreciable loading effect on these circuits. Series resonance ofthe reactive elements assures that power is dissipated only in the resistance components of the inductance elements which minimizes `the magnitude of voltage drawn from the horizontal deflection wave amplifying circuit, whereby vacuum tube amplifying circuits are unnecessary in the convergence` circuitry of the television receiver.

The values given below were used for the listed components for an embodiment of the invention as shown in Fig. 3 which provided fully satisfactory operation in a color television receiving circuit arrangement and are suggested as an aid in the practice of the invention.

Rel'. Component Type or Value N o.

54---.- Vertical amplifier tube 6AQ5. 74----- VHorizontal amplifier tube 6CB5. 87.- Series resistor 100 ohms.

Vertical Output Transformer Primarywinding 2.600 turns. Duection secondary 2 turns.

Convergence secondary-- 280 turns; taps at 220 and 250 Volts from 9193=130 V.P.P.

360 mh., 11 ohms.

Integrating inductor Parabolic potentiometer Horizontal convergence w ding-- -70 v.

Tilt potentiometer 100 o.

Ringing inductor.- 45-65 Inh. 25 ohms. Ringing capacitor--- 0.0022 mf.

Sine potentiometer 1,500 ohms.

The power supply delivered 385 volts between the points marked with the plus (-lf) sign and ground and 20 volts between the points marked with the minus sign and ground. Other values of components and voltage will be determined by those skilled in the art for other applications of the invention.

The invention claimed is: n

1. A beam convergence circuit arrangement for a multi-beam kinescope the electron beams of which are deflected in two directions normal with respect to each other, including a pairpof adjustably tapped resistance elements connected in series, an adjustable inductor and a. capacitor connected-in series betweenk the tapsgotV said resistance elements, said inductor and capacitor beingiad-v justable to series resonance ata frequency corresponding to beam deflection in one direction, an adjustably tapped resistive element, means to connect convergence system windings individually between the tap of said resistive element and the junction between said series connected inductorand capacitor, means to apply a potential varying; as a function of deflection in one direction across said resistive element, an inductance element connectedftoone adjustably tapped resistance element, means to apply a potential varying as a function of the beam deflection in one direction between the other terminal of said inductance element and the junction between saidseriesconnected adjustable resistance elements, and means to apply a, potential varying as a function of the deflection in the other direction across the remaining resistance element.

2. A beam convergence circuit arrangement for a multi-beam kinescope the electron beams of which are deiiected in two directions normal with respect to each other, including a plurality of pairs of adjustably tapped resistance elements connected in. series, a plurality of series circuits connected individually between the taps ofsaid pairs of resistance elements, each of said circuits comprising an inductor and capacitor adjustable. to series resonance at a frequency corresponding to beam deflection in one direction, a plurality of adjustably tapped resistive elements, means to connect convergence system windings individually between the taps ofV said resistive elements and the junctions between said inductors` and capacitors, means to apply potentials varying as a function of deflection in one direction across said resistive elements, an inductance element connected in common tov one set of adjustably tapped resistance elementsmeans to apply potentials varying as a function of the beam defiection in one direction between the other terminal of said inductance element and thek junctions between said series connected adjustable resistance elementsand means to apply potentials varying as a function of the deflection in the other direction across the remaining resistance elements.

3. A beam convergence circuit arrangement for a multi-beam kinescope, including a deflection wave output transformer having a convergence winding with two intermediate taps, one intermediate tap being electrically at a point of fixed reference potential and midway between tbe other tap and one terminal of said winding, a variably tapped resistive element connected between said one terminal and said other tap, an inductor having one terminal connected to the other terminal of said winding, a variably tapped resistance element connected between the other terminal of said inductor and said one intermediate tap, another deflection wave output transformer having a winding, and adjustably'tapped resistance element connected to said winding on said other transformer, an adjustable inductor and a capacitor connected in series between taps of said resistance elements, and a convergence system winding connected between junctions of said inductor andcapacitor and thetap of said resistivel element.

4. A beam convergence circuit arrangement for a multi-beam kinescope, including a deflection wave output transformer having a convergence winding with two intermediate taps, one. intermediate tap being electrically at a point of fixed reference potential and midway between the other tap and one terminal of said winding, a plurality of variably tapped resistive elements connected between said one terminal and said other tap, an inductor having one terminal connected to the other terminal of said Winding, a plurality of variably tapped resistance ele.- ments connected between the other terminal of said ini-1 ductor and said one intermediate tap, another deflection wave output transformer having a winding, a pluralityk of adjustably tapped resistance elements connected to said winding on said other transformer, an adjustable inductor and a capacitor connected in series individually between the taps of said adjustably and said variably tapped resistance elements, said adjustable inductor and.. said capacitor having values at which the circuit may be tuned to series resonance at a frequency corresponding to the deflection in one direction, and a plurality of convergence system windings connected individually between junctions of each series connection of said inductor and capacitor and the taps of said resistive elements.

5. A beam convergence circuit arrangement for a multi-beam kinescope, including a vertical deflection wave output transformer having a convergence winding with two intermediate taps, one intermediate tap being electrically at a point of fixed reference potential and midway between the other tap andone terminal of said winding, a plurality of variably tapped resistive elements connected between said one terminal and said other tap, an inductor having one terminal connected to the other terminal of said winding, a plurality of variably tapped resistance elements connected between the other terminal of said inductor and said one intermediate tap, a horizontal deflection wave output transformer having a winding, a plurality of adjustably tapped resistance elements connected to said horizontal winding, an adjustable inductor and a capacitor connected in series individually between the taps of said adjustably and variabe tapped resistance elements, said adjustable inductor and said capacitor having values at which the circuit may be tuned to series resonance at the horizontal deflection frequency, and a plurality of convergence system windings connected individually between junctions of each series connection of said inductor and capacitor and the taps of said resisftive elements.

References Cited in the file of this patent UNITED STATES PATENTS 2,672,574 Evans Mar. l6, 2,706,796 Tannenbaum et al. Apr. 19, 2,707,248 Goodrich Apr. 26, 2,737,609 Kelly et al. Mar. 6, 2,880,360 Hauge Mar. 31,

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