US3459989A - Electron beam convergence apparatus - Google Patents

Description

Aug. 5, 1969 P. G. M CABE ELECTRON BEAM CONVERGENCE APPARATUS 5 Sheets-Sheet 1 Filed Aug. 5 l963 INVENTOR. a ah/ 4-. 4/ 014;-

l IFWED FROM 50055 END Aug. 5, 1969 P. G. M CABE 3,459,989

E LECTRON BEAM CONVERGENCE APPARATUS Filed Aug. 5. 1965 5 Sheets-Sheet :5

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I I J INYENTOR. r-IF/HOT/HHD 0 1 g y/ (3 United States Patent 015cc 3,459,989 ELECTRON BEAM CONVERGENCE APPARATUS Philip G. McCabe, Indianapolis, Ind., assignor to Radio Corporation of America, a corporation of Delaware Filed Aug. 5, 1963, Ser. No. 299,770 Int. Cl. H01j 29/50 US. Cl. 31513 19 Claims 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 of such a multiple beam display device is a color kinescope. Color kinescopes of the shadow type normally have three electron guns positioned in the neck of the kinescope and a target electrode including an apertured shadow mask located between 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 mask. Static magnetic means are provided for making 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 deflected 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 of 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 means 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 produced from energy derived from the horizontal and vertical deflection circuits and are employed, in conjunction with three convergence electromagnets, to dynamically converge the three beams at all points of the entire scanned area of the kinescope target.

The waveforms employed must have proper shapes and amplitudes 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 deflection, as for example 70 or more, 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 effect 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 deflection, but also considerably more deflecting force (i.e., Wave amplitude) is needed to suitably eifect the desired beam convergence.

Recent trends in the design of color television receivers have been to employ dynamic beam convergence circuits which include no active elements. Such circuits perform essentially the function of providing suitably shaped waves for application to the convergence electromagnets. The energy for these electromagnets consequently must come entirely from the horizontal and vertical deflection circuits. As the angle of beam deflection increases, more 3,459,989 Patented Aug. 5, 1969 Therefore, it is an object of the invention to provide an improved high efliciency circuit by which to effect convergence of a plurality of electron beams of a color kinescope throughout a raster produced by relatively wide angle deflection of said beams.

The present invention reduces the energy demands placed upon the deflection circuits by providing improved wave shaping accomplished by the use of inactive circuit elements in the convergence circuits. At each of the horizontal and vertical deflection frequencies the substantially parabolic convergence current waves through the electromagnet windings are produced by deriving substantially sawtooth voltage waves from the respective deflection circuits. The improved wave shaping is achieved at the vertical deflection rate by clipping the substantially sawtooth voltage wave derived from the vertical deflection circuit during the first part of the deflection cycle and by suitably sloping the clipped portion of the wave. The vertical frequency convergence circuits include wave shaping networks including such clipping facilities so as to provide more symmetrical convergence parabolic current waves with steeper sides than heretofore has been achieved in order to provide better beam convergence at the top and bottom portions of the picture area for a kinescope operating with (or more) beam deflection.

More specifically, the improved wave shaping of the present invention is achieved by means including a series arrangement of a clipping device and a resistor connected effectively in parallel with the convergence electromagnet apparatus operating at the vertical deflection rate.

For a better understanding of the invention together with additional objects, features and advantages thereof, reference now will be made to the following detailed description taken in connection with the accompanying drawings, in which;

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

FIGURE 2 is a fragmentary sectional view of the neck portion of a color kinescope, showing the relationship of the convergence electromagnets and the electron beams controlled thereby;

FIGURE 3 is a schematic ciruit diagram of apparatus embodying the invention for controlling the convergence electromagnets at the vertical deflection frequency;

FIGURES 4 and 5 are fragmentary circuit diagrams of other embodiments of the invention; and

FIGURES 6 and 7 are sets of curves for reference in describing the operation of the invention.

Reference first is made to FIGURE 1 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 (1) video signals representing three component colors of an image to be reproduced and (2) synchronizing signals for controlling beam deflection and for other purposes such as the production of suitable signals by which to eflect convergence of the three electron 'beams at the target electrode of the imagereproducing 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, Ind.

The color television receiver also includes a threebeam color kinescope 13 serving as a color image-reproducing device such as a shadow mask color kinescope of the RCA type 2lFBP22 or 21FJP22 for example. The red, green and blue representative signals received from the receiver circuits 12 are impressed respectively upon electron guns 14, 15 and 16 of the tricolor kinescope 13. The three electron beams produced by these guns are deflected together over the target screen of the kinescope under the control of a deflection yoke 17. Also, the beams are maintained in convergence with each other by means of a suitably energized beam convergence yoke 18, an illustrative form of which will be described 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 HM and V--V. All of the apparatus of FIG- URE 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 electromagnets of the convergence yoke 18. Signals at the vertical 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. Details of such vertical convergence circuits by which suitable convergence waves are produced will be described subsequently. The horizontal convergence circuits are not part of the present invention and may be of a known type per se such as disclosed in Patent No. 2,903,622, granted Sept. 8, 1959, to I. C. Schopp.

Reference now is made to FIGURE 2 for a description of the physical relationship of the convergence electromagnets and the electron beams controlled respectively thereby as presently embodied in commercial color television receivers such as that disclosed in the referenced RCA service data.

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 convergence electromagnets 30, 31 and 32 respectively mounted externally around the neck of the kinescope. The convergence electromagnets are provided with horizontal frequency energizing windings designated 33G, 33R and 33B and with vertical frequency energizing windings designated 34G, 34R and 34B respectively for the green, red and blue electromagnets 30, 31 and 32. Energization of the electromagnet 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 electromagnet 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 a description of it is not needed for an understanding of this invention, it is not shown.

Reference now is made to FIGURE 3 of the drawings. There is shown a vertical deflection output tube 35 having in its anode circuit a primary winding 36 of an output transformer 37. One of the secondary windings 38 of this transformer is coupled as indicated in the usual manner to the vertical windings of a deflection yoke (not shown) for deflecting the three electron beams of the color kinescope to scan the luminescent screen of the kinesope vertically at the rate of approximately 60 fields per second. It is to be understood that horizontal windings of the yoke also will be energized to deflect the beams to scan the screen horizontally at the rate of approximately 15,750 lines per second in the usual manner. The cathode circuit of the vertical output tube includes a resistor 39 which is bypassed by a capacitor 40, connected between terminal 41 and ground and across which cathode circuit there is developed a substantially sawtooth voltage wave 42 at the vertical deflection frequency.

The cathode of the vertical output tube 35 is coupled by means of a series resistor 43 which is shunted by a capacitor 44 to the vertical frequency windings 34G, 34R and 34B, respectively, of the green, red and blue convergence electromagnets 30, 31 and 32, respectively. By means of the resistor 43 and shunting capacitor 44, the AC and DC components of the saw tooth voltage wave 42 are proportioned in a predetermined ratio. The proportioning is such that the currents which are caused to flow through the vertical frequency windings of the convergence electromagnets always have substantially the same magnitudes at the time that the electron beams are tracing the horizontal lines of the raster at the center of the screen, irrespective of the particular shapes of the convergence currents and their peak-to-peak amplitudes.

The impression of the sawtooth voltage wave 42 upon the convergence apparatus causes an integration of this wave such that the green and red convergence electromagnet windings 34G and 34R are traversed by a substantially parabolic convergence current wave 45. The amplitude of the parabolic current wave for the green and red convergence electromagnet windings 346 and 34R respectively is controlled by a master amplitude control potentiometer 46, the movable contact of which is connected to terminal 47 to which also are connected the green and red electromagnet windings.

The vertical windings 34G and 34R of the green and red convergence electromagnets 30 and 31 respectively are connected in series to the movable contact of a master tilt control potentiometer 48, the resistive element of which is connected across the terminals of another secondary winding 49 of the vertical deflection output transformer 37. The center of this winding is grounded to provide a return path for the currents flowing in the windings of the convergence electromagnets. Pulse voltage waves 50 and 51 of opposite polarity are developed respectively in the coils 49a and 49b of the transformer winding and are available at the terminals of the winding.

' The impression of such pulses upon the convergence apparatus causes an integration of the pulses such that the convergence windings 34G and 34R are traversed by a substantially sawtooth current wave 52, the amplitude and polarity of which are determined by the adjustment of the master tilt control potentiometer 48. The sawtooth current wave 52 is added to the generally parabolic current wave in the usual manner to tilt or phase the parabolic wave to effect substantial beam convergence at most points of the scanned raster, except at those points in areas adjacent to the outer edges of the rastor for which the beams are subjected to relatively wide angle deflection.

A differential amplitude control potentiometer 53 has its resistive element connected across the series arrangement of the windings 346 and 34R of the green and red convergence electromagnets 30 and 31, respectively. The junction point 54 between the green and red windings 34G and 34R is connected to the center point of still another secondary winding 55 of the vertical deflection output transformer 37. Pulse voltage waves a and 51a of opposite polarity are developed respectively in the coils a and 55b of this secondary winding and are available at the terminals of the winding. The termnials of this secondary winding 55 are connected to the terminals of the resistive component of a differential tilt control potentiometer 56. The movable contacts of the two differential potentiometers 53 and 56 are conected together. The adjustment of the movable contact of the differential amplitude control potentiometer 53 varies distribution of the parabolic current wave 45 through the respective windings 34G and 34R of the green and red convergence electromagnets 30 and 31. The adjustment of the movable contact of the differential tilt control potentiometer 56 determines the distribution between the windings 34G and 34R of the green and red convergence electromagnets 30 and 31 of the sawtooth current wave 52 by controlling the combination with this Wave of another sawtooth current wave resulting from the integration of voltage pulses 50a, 51a by the convergence apparatus.

The vertical frequency winding 34B of the blue convergence electromagnet 32 is energized by a substantially parabolic current wave 45a, the amplitude of which is adjusted by a blue amplitude control potentiometer 57 connected to terminal 58 in common with the winding 34B. This parabolic wave is tilted or phased by means of a suitable sawtooth component 52a, the amplitude and polarity of which is determined by the adjustment of a blue shape control potentiometer 59, the resistive element of which is connected across the terminals of the deflection transformer secondary winding 49.

The green, red and blue convergence electromagnets 30, 31 and 32 also are provided with respective windings 33G, 33R and 33B as previously described and which are energized by suitably shaped waves at the horizontal defiection frequency. These windings may be energized by any suitable means such as that shown in Patent No. 2,903,622, granted Sept. 8, 1959', to J. C. Schopp.

In order to improve the shape of the convergence current wave by which the green and red convergence electromagnets 30 and 31 are energized when relatively large beam deflection angles are employed, there also is provided a series arrangement of a unilaterally conducting device such as a diode 61 and a variable biasing resistor 62 connected from the movable contact of the master amplitude control potentiometer 46 to ground. This series arrangement is thus effectively connected in parallel with the series arrangement of the green and red electromagnet windings 34G and 34R, respectively, the movable tap of potentiometer 48 being substantially at ground. Note the grounded center tap of secondary winding 49.

The improved wave shaping effected by the diode 61 and resistor 62 may better be seen by additional refererence to FIGURE 6. The substantially sawtooth voltage wave 42 appearing at the terminal 41, and impressed across the potentiometer 46, has its negative-going portion clipped by the diode 61 so as to form a modified sawtooth wave 63 for impression upon the electromagnet windings 34G and 34R at terminal 47. This clipping action occurs during the first portion of the vertical scanning interval. The desired slope of the clipped portion 64 of the Wave 63 is controlled by variation of the resistor 62, thereby providing a suitable control of the wave shaping facility to fit the particular convergence needs of the apparatus in which the facility is embodied. The positive-going portion 65 of the modified sawtooth voltage wave 63 is not materially altered by the described wave shaping circuit from its original shape in the wave 42. As a result of the integration of the wave 63 by the convergence apparatus, the substantially parabolic current wave 66 traversing the green and red electromagnet windings 34G and 34R has a more symmetrical shape with steeper sides than it would have without the wave shaping circuit of this invention. Such wave shaping thus, enables the achievement of substantial convergence of the red and green electron beams with the blue electron beam in the top and bottom portions of the raster scanned by these beams.

FIGURE 4, to which reference now is made, illustrates another embodiment of a wave shaping circuit including the series arrangement of the diode 61 and the variable resistor 62. In this case the circuit is connected from the junction of resistor 43 and potentiometer 46 to ground so that, as in FINGURE 3, it is effectively in parallel with the series arrangement of the green and red electromagnet windings 34G and 34R. The circuit functions substantially in the same manner as that described with reference to FIGURE 6. It has been found that additional improvement may be made in the shape of the current waveform 66 by the connection of a capacitor 67 of suitable value across the diode 61- This additional improvement is the further steepening of the leading slope of the parabolic current wave 66, whereby better beam convergence is achieved in the top portion of the scanned raster. It should be noted with reference to FIGURE 6 with the arrangement of either FIGURE 3 or FIGURE 4, the clipping action does not continue throughout the entire first half of the vertical scanning cycle, the halfway point of the cycle being indicated by the broken line 68 Still another embodiment of the invention is shown in FIGURE 5. In this case only the AC component of the vertical deflection frequency sawtooth wave 42 appearing at terminal 41 is impressed upon the convergence circuitry connected to terminal 47. The AC component of this wave is impressed upon the convergence apparatus by means of a capacitor 69. The wave shaping circuit including the series arrangement of the diode 61 and the resistor 62 is connected in substantially the same manner as that described with reference to FIGURE 4.

The operation of the wave shaping apparatus shown in FIGURE 5 is illustrated by the curves of FIGURE 7 representing the voltage wave 71 impressed upon the convergence electromagnet windings by which to produce the substantially parabolic current wave 72 through these windings. As in the previously described embodiment of the invention, the diode 61 serve to clip the negative-going portion of the substantially sawtooth voltage wave 42 developed at terminal 41. The clipped portion 73 of the voltage wave 71 extends to substantially the midpoint of the vertical deflection cycle indicated by the broken line 68. This type of operation is achieved by virtue of the fact that the wave shaping circuit operates on only the AC component of the sawtooth wave 42, thereby permitting the clipping action to be effective at approximately the AC axis of the wave rather than at a lower voltage point dependent upon a DC component.

As a result of the extension of the clipping action to substantially the mid point of the vertical deflection cycle, a more symmetrical parabolic current wave 72 is produced than can be obtained by the use of any of the circuit arrangements shown in FIGURES 3 and 4. As in other embodiments of the invention, the variable resistor 62 enables the control of the slope of the clipped portion 73 of the voltage wave 71.

What is claimed is:

1. In a dynamic convergence system for multigun color cathode ray tubes, which convergence system includes a plurality of beam convergence electromagnets having energizing coils and convergence wave generating means for producing energizing current having a parabolic current component, with said energizing coils presenting both series .inductance and series resistance to said energizing current, the combination including means for providing a sawtooth wave having portions extending above and below a reference axis, means for coupling said sawtooth wave to one end of said coils, resistance means connected between said one end of said coils and a reference potential, said resistance means coacting with the series inductance of said coils to integrate said sawtooth wave, with a portion of said sawtooth wave remaining unintegrated depending on the ratio of resistance to inductance of said coils, and clipping circuit means adapted to exclude portions of said sawtooth wave of a given polarity with respect to said reference axis from said coils, with said sawtooth wave thereby modified including components corresponding to the fundamental components of a parabolic wave, whereby additional parabolic components are added to the energizing current of said coils.

2. In a vertical deflection system for a multibeam cathode ray tube, the beam convergence system including in combination, resistor means carrying current of sawtooth waveform at the vertical deflection frequency; a coupling capacitor, a variable resistor, and a convergence inductor connected in a series circuit across said resistor means for energizing said inductor with current of the sawtooth waveform and at selected amplitude; and wave shaping means including a rectifier device and a further resistor connected to said circuit for conducting during a substantial portion of said sawtooth waveform to clip sald sawtooth waveform and establish a voltage reference axis therefor to approximate the reference axis of a wave of parabolic shape.

3. In a vertical deflection system for a multibeam cathode ray tube, the beam convergence system including in combination, resistor means carrying current of sawtooth waveform at the vertical deflection frequency; a coupling capacitor, a variable resistor, and a convergence inductor connected to said resistor means for energizing said inductor with current of selected amplitude and sawtooth waveform; and wave shaping means including a rectifier device connected in circuit with said convergence inductor, said rectifier device being conductive during a substantial portion of said sawtooth waveform to clip said sawtooth waveform and apply to said inductor a wave of parabola-like shape.

4. In a vertical deflection system for a television receiver, a dynamic convergence circuit for a multibeam cathode ray tube including in combination, first resistor means across which appears a sawtooth waveform of vertical deflection frequency, a capacitor and second resistor means connected in series and the combination thereof coupled across said first resistor means, said second resistor means having a variable tap, a convergence coil, means coupling said convergence coil between said variable tap and a fixed point of said second resistor means, and a rectifier diode and third resistor means connected in series and the combination thereof connected in shunt with at least a portion of said second resistor means, said diode being poled with the cathode thereof conductive through said capacitor for clipping a portion of the sawtooth waveform and applying the same to said convergence coil.

5. In a dynamic convergence system for multigun color cathode ray tubes, which convergence system includes a plurality of beam convergence electromagnets having energizing coils and convergence wave generating means for producing energizing current having a parabolic current component, with said energizing coils presenting both series inductance and series resistance to said energizing current, the combination including means for providing a sawtooth wave having portions extending above and below a reference axis, means for coupling said sawtooth wave to one end of at least one of said coils, variable resistance means connected between said one end of said coil and a reference potential, the series inductance of said coil serving to integrate said sawtooth wave, with a portion of said sawtooth wave remaining unintegrated depending on the ratio of resistance to inductance of said coil, and clipping circuit means adapted to exclude portions of said sawtooth wave of a given polarity with respect to said reference axis in said coil, with said sawtooth wave thereby modified including components corresponding to the fundamental components of a parabolic wave, whereby additional parabolic components are added to the energizing current for said coil.

6. A dynamic convergence system for a multibeam cathode ray tube including in combination, a vertical deflection circuit providing a sawtooth Waveform at the vertical deflection frequency of the electron beams, an inductance winding to produce a magnetic field for converging one beam with respect to another, circuit means coupled between said vertical deflection circuit and said inductance winding to apply the sawtooth waveform to the latter so that said inductance winding tends to integrate said sawtooth wave form for producing a field varying as a function of a parabola, said inductance winding having internal resistance tending to cause incomplete integration of the sawtooth waveform therein, said circuit means including a clipping network comprising impedance means and unidirectionally conductive means, said clipping network clipping a substantial portion of said sawtooth waveform of said vertical deflection circuit so that a clipped sawtooth wave form is applied to said inductance winding to render the field thereof more parabolic.

7. A dynamic convergence system for a multibeam cathode ray tube including in combination, a vertical deflection circuit having a given source impedance and providing a sawtooth waveform at the vertical deflection frequency of the electron beams, an inductance winding to produce a magnetic field for converging one beam with respect to another, circuit means coupled between said vertical deflection circuit and said inductance Winding to apply the sawtooth waveform to the latter so that said inductance winding tends to integrate said sawtooth wave form for producing a filed varying as a function of a parabola, said inductance winding having an internal resistance tending to cause incomplete integration of the sawtooth waveform therein, said circuit means including a clipping network comprising resistor means, capacitor means and unidirectionally conductive means, said clipping network and the source impedance of said deflection circuit having component values chosen to clip a substantial portion of said sawtooth wave form of said vertical deflection circuit so that a clipped sawtooth wave form is applied to said inductance winding to render the field thereof more parabolic.

8. In a television color image display system including a multiple beam color image reproducing device and 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 plurality of respective dynamic convergence electromagnets for said beams, each of said eletcromagnets having an energizing winding;

a source of a sawtooth wave;

means coupling said source to said windings; and

wave-shaping means including a series arrangement of a diode and a resistor connected to said coupling means in parallel with a circuit including a series arrangement of two of said windings to so modify said sawtooth wave that its impression upon said two windings causes to flow through said two windings a current wave having a substantially symmertical parabolic form with relatively steep side portions occuring respectively at the start and finish of each of said trace periods.

9. In a television color image display system including a multiple beam color image reproducing device and deflection means for deflecting said beams in a series of verr tically 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; a source of a sawtooth wave; means coupling said source to said winding; and wave-shaping means including a parallel arrangement of a diode and a capacitor connected in series with a resistor, said wave-shaping means being connected to said coupling means to so modify said sawtooth wave that its impression upon said winding causes to flow through siad winding a current wave having a substantially symmetrical parabolic form with relatively steep side portions occurring respectively at the start and finish of each of said trace periods. 10. In a television color image display system including a multiple beam color image reproducing device and deflection means for deflecting said beams at line and field rates during respective beam trace periods to form a raster,

the combination of converging said beams at all points of said raster comprising;

a dynamic convergence electromagnet having an energizing winding;

a source of a sawtooth wave at one of said deflection rates, said wave having AC and DC components;

means coupling said source to said winding to impress a predetermined ratio of said AC and DC wave components upon said winding; and

wave-shaping means including a series arrangement of a diode and a resistor connected to said coupling means and to said winding to so modify the AC component of said sawtooth wave during the first part of each of one of said trace periods that the impression of said modified sawtooth Wave upon said winding causes to flow through said winding a current wave having a substantially symmetrical parabolic form with relatively steep side portions occurring respectively at the start and finish of each of said trace periods.

11. In a television color image display system including a multiple beam color image reproducing device and deflection means for deflecting said beams at line and field rates during respective beam trace periods to form a raster,

the combination for converging said means at all points of said raster comprising;

a plurality of respective dynamic convergence electromagnets for said beams, each of said electromagnets having an energizing winding;

a source of a sawtooth wave at one of said deflection rates, said wave having AC and DC components;

means coupling said source to said windings to impress a predetermined ratio of said AC and DC wave components upon said windings; and

wave-shaping means including a series arrangement of a diode and a resistor connected to said coupling means in parallel with a circuit including a series arrangement of two of said windings to so modify the AC component of said sawtooth wave during the first part of each of one of said trace periods that its impression upon said two windings causes to flow through said two windings a current wave having a substantially symmetrical parabolic form with relatively steep side portions occurring respectively at the start and finish of each of said trace periods.

12. In a television color image display system including a multiple beam color image reproducing device and deflection means or deflecting said beams at line and field rates during respective 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;

a source of a sawtooth wave at said field deflection rate,

said wave having AC and DC components;

means coupling said source to said winding to impress only said AC wave component upon said winding; and

wave-shaping means including a diode and a resistor connected to said coupling means to so modify the AC component of said sawtooth wave during substantially the first half of each of said field trace periods that the impression of said modified sawtooth wave upon said winding causes to flow through said Winding a current wave having a substantially symmetrical parabolic form with relatively steep side portions occurring respectively at the start and finish of each of said trace periods.

13. In a television color image display system including a multiple beam color image reproducing device and deflection means for deflecting said beams at line and field rates 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;

a source of a sawtooth wave having alternate trace and retrace periods at said field deflection rate;

means coupling said source to said winding; and

clipping means connected to said coupling means to so modify said sawtooth wave that its impression upon said winding causes to flow through said winding a current wave having a substantially symmetrical parabolic form with relatively steep side portions occurring respectively at the start and finish of each of said trace periods.

14; Ina television color image display system including a multiple beam color image reproducing device and deflection means for deflecting said beams at line and field rates 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;

a source of a sawtooth Wave having alternate trace and retrace periods at said field deflection rate;

means coupling said source to said winding; and

means for clipping said sawtooth wave during a portion of each of said trace periods so as to modify said sawtooth wave such that its impression upon said winding causes to flow through said winding a current Wave having a substantially symmetrical parabolic-form with relatively steep side portions occurring respectively at the start and finish of each of said trace periods.

15. In a television color image display system including a multiple beam color image reproducing device and deflection means for deflecting said beams at line and field rates to form a raster,

circuit means for converging said beams at all points of said raster comprising;

a dynamic convergence electromagnet having an energizing winding;

a source of a sawtooth wave having alternate trace and retrace periods at said field deflection rate;

means coupling said source to said winding; and

Wave-shaping apparatus including diode means for clipping said sawtooth wave during a portion of each of said trace periods and resistor 'means for controlling the slope of the clipped portions of said sawtooth wave, said wave-shaping apparatus being so connected in said convergence circuit means as to modify said sawtooth wave such that its impression upon said winding causes to flow through said winding a current wave having a substantially symmetrical parabolic form with relatively steep side portions occurring respectively at the start and finish of each of said trace periods.

16. In a television color image display system including a three beam color image reproducing device and deflection means for deflecting said beams at line and field rates during respective beam trace periods to form a raster,

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

three respective dynamic convergence electromagnets for said beams, each of said electromagnets having an energizing winding;

a source of a sawtooth wave at said field deflection rate, said wave having AC and DC components; means including an amplitude controlling potentiometer coupling said source to two of said windings to impress a predetermined ratio of said AC and DC wave components upon said two windings; and wave-shaping means including a series arrangement of a diode and a resistor connected in shunt with at least a portion of said potentiometer and to a series arrangement of said two windings to so modify the AC component of said sawtooth wave during the first part of each of said field rate trace periods that its impression upon said two windings causes to flow through said two windings a current wave having a substantially symmetrical parabolic form with relatively steep side portions occurring respectively at the start and finish of each of said field rate trace periods.

17. In a television color image display system including a three beam color image reproducing device and deflection means for deflecting said beams at line and field rates during respective beam trace periods to form a raster,

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

three respective dynamic convergence electromagnets for said beams, each of said electromagnets having an energizing winding;

means connecting two of said windings in an energizing circuit; a source of a sawtooth wave at said field deflection rate, said wave having AC and DC components;

means including an amplitude controlling potentiometer coupling said source to two of said windings to impress a predetermined ratio of said AC and DC wave components upon said two windings; and

wave-shaping means including a series arrangement of a diode and a resistor connected in shunt with only a portion of said potentiometer and in parallel with said energizing circuit to so modify the AC component of said sawtooth wave during the first part of each of said field rate trace periods that its impression upon said two windings causes to flow through said two windings a current Wave having a substantially symmetrical parabolic form with relatively steep side portions occurring respectively at the start and finish of each of said field rate trace periods.

18. In a television color image display system including a three beam color image reproducing device and deflection means for deflecting said beams at line and field rates during respective beam trace periods to form a raster,

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

three respective dynamic convergence electromagnets for said beams, each of said electromagnets having an energizing winding;

means connecting two of said windings in series in an energizing circuit;

a source of a sawtooth wave at said field deflection rate,

said wave having AC and DC components;

means including an amplitude controlling potentiometer coupling said source to two of said windings to impress a predetermined ratio of said AC and DC wave components upon said two windings; and

wave-shaping means including a series arrangement of a diode and a resistor connected in shunt with said potentiometer and in parallel with said energizing circuit to so modify the AC component of said sawtooth wave during the first part of each of said field rate trace periods that its impression upon said two windings causes to flow through said two windings a current wave having a substantially symmetrical parabolic form with relatively steep side portions occurring respectively at the start and finish of each of said field rate trace periods.

19. In a television color image display system including a three beam color image reproducing device and deflection means for deflecting said beams at line and field rates during respective beam trace periods to form a raster,

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

three respective dynamic convergence electromagnets for said beams, each of said electromagnets having an energizing winding;

means connecting two of said windings in series in an energizing circuit; a source of a sawtooth wave at said field deflection rate, said wave having AC and DC components;

means including an amplitude controlling potentiometer coupling said source to two of said windings to impress a predetermined ratio of said AC and DC wave components upon said two windings; and

wave-shaping means including a series arrangement of a capacitively bypassed diode and a resistor connected in shunt with said potentiometer and in parallel with said energizing circuit to so modify the AC component of said sawtooth wave during the first part of each of said field rate trace periods that its impression upon said two windings causes to flow through said two windings a current wave having a substantially symmetrical parabolic form with relatively steep side portions occurring respectively at the start and finish of each of said field rate trace periods.

No references cited.

RODNEY D. BENNETT, JR., Primary Examiner JOSEPH G. BAXTER, Assistant Examiner US. Cl. X.R. 315-27

Claims (1)

1. IN DYNAMIC CONVERGENCE SYSTEM FOR MULTIGUN COLOR CATHODE RAY TUBES, WHICH CONVERGENCE ELECTROMAGNETS HAVING ENPLURALITY OF BEAM CONVERGENCE ELECTROMAGNETS HAVING ENENERGIZING COILS AND CONVERGENCE WAVE GENERATING MEANS FOR PRODUCING ENERGIZING CURRENT HAVING A PARABOLIC CURRENT COMPONENT, WITH SAID ENERGIZING COILS PRESENTING BOTH SERIES INDUCTANCE AND SERIES RESISTANCE TO SAID ENERGIZING CURRENT, THE COMBINATION INCLUDING MEANS FOR PROVIDING A SAWTOOTH WAVE HAVING PORTIONS EXTENDING ABOVE AND BELOW A REFERENCE AXIS, MEANS FOR COUPLING SAID SAWTOOTH WAVE TO ONE END OF SAID COILS, RESISTANCE MEANS CONNECTED BETWEEN SAID ONE OF SAID COILS AND A REFERENCE POTENTIAL, SAID RESISTANCE MEANS COACTING WITH THE SERIES IN-

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