US2344736A - Television transmitting system - Google Patents

Description

March 21, 0 H SCHA TELEVISION TRANSMITTING SYSTEM Filed Jan. 51, 1942 6 ESE WEE-3 M AT-T?W Patented Mar. 21, 1944 TELEVISION TRANSMITTING SYSTEM Otto H. Schade, West Caldwell, N. J assignor to Radio Corporation of America, a corporation of Delaware Application January 31, 1942, Serial No. 429,008

Claims.

This invention relates to television transmit ting systems and more particularly to improvements in systems used in connection with storage type television transmitting tubes in which the storage or mosaic electrode is inclined with respect to the axis of the scanning beam electron gun structure.

A television transmitting system must necessarily include some element or device for transferring or converting an optical image into a series of electrical picture signals. One apparatus for effecting such a conversion is the iconoscope which includes an electron gun structure for generating a focused cathode ray beam and a mosaic electrode upon which a charge image is produced in response to the projection of an optical light image on the mosaic. The mosaic electrode is then scanned in bilateral directions in order to remove the charge image and in order to produce electrical potential variations representative of the optical image projected thereon.

In the receiver a television picture reproducing tube is normally employed and such a tube may, for example, be the kinescope. The kinescope or picture reproducing tube also includes an electron gun structure for producing a focused cathode ray beam and additional means are provided for causing the cathode ray beam to be directed against and to scan a target area or fluorescent surface. As the cathode ray beam in the receiving tube is deflected in synchronism with corresponding deflections of the scanning beam in the television transmitting tube, the current intensity of the cathode ray beam in the receiving tube is modulated in order to produce varying efiects on the fluorescent target electrode to reproduce the television image. The modulations of the cathode ray beam in the receiving tube are naturally controlled in accordance with the received picture signals transmitted from the transmitting station. In the receiving tube the target electrode is normally positioned at right angles to the axis of the electron gun structure and the axis of symmetry of the electron gun structure is normally directed at a point near the center of the target electrode. In the transmitting tube and particularly in tubes of the iconoscope type, the mosaic electrode is positioned at an angle with respect to the electron gun structure in order that an optical image may be projected on the surface of the mosa c electrode and in order that the same surface of the mosaic electrode may be scanned by the cathode ray beam generated in the tube.

The commonly termed pin-cushion distortion results in the area scanned not being perfectly square or rectangular. This lack of rectangularity in so far as the scanned area is concerned may be compensated for in the design of the deflecting electrodes or the deflecting yoke.

In the transmitting tube, however, in view of the fact that the target electrode is inclined at an angle with respect to the axis of the electron gun structure, the electrical distortion or lack of rectangularity of the scanned area is not symmetrical or'uniform at all of the edges of the area with the result that complete correction may be accomplished by non-symmetrical design of the deflecting electrodes or the electromagnetic deflecting yoke. Variations in the dimensions of the tube, however, naturally require alterations in the corrections of the deflecting yoke. Most of the distortion or lack of rectangularity in the area scanned by the electron beam in the televi sion transmitting tube is in. the horizontal deflection direction of the cathode ray beam and particularly at that portion of the mosaic electrode most removed from the electron gun structure. Furthermore, after a television transmitting tube has been constructed and by reason of the various processes that the tube must undergo in the steps of manufacturing the tube, the mosaic electrode may in some instances become warped and by reason of this slight possible warping, a slight additional distortion is produced. g

It is therefore one purpose of the present invention to provide a system wherein the scanning cathode ray beam in a television transmitting tube of the iconoscope type may be caused to traverse or scan a perfectly rectangular area.

Another purpose of the present invention resides in the provision of circuit means at the television transmitting tube for causing the scanning cathode ray beam to traverse the mosaic electrode in straight horizontal lines irrespective of the particular portion of the mosaic electrode being traversed.

Still another purpose of the present invention resides in the provision of means in a television transmitter wherein compensating or auxiliary deflecting potentials may be superimposed or combined with the principal or fundamental deflecting voltages in order to compensate for any lack of rectangularity in the area scanned by the cathode ray beam.

Another purpose of the present invention resides in the provision of means whereby the cathode ray beammay be subjected to a slight additional vertical deflection component when the beam is near the middle portion of a scanned line in addition to the deflecting force or fleld to which the beam is subjected when the beam is near either end of the scanned lines.

A still further purpose of the present invention resides in the provision of a relatively simple and effective circuit arrangement whereby the cathode ray beam in a television transmitting tube of the iconoscope type may be caused to scan a substantially rectangular area on the mosaic electrode regardless of slight warped conditions of the mosaic electrode and the circuit also includes means whereby the degree or intensity of the compensating deflection voltages may bev controlled to render the system applicable to any particular tube even though slight differences and variations may exist between various television transmitting tubes.

Still other purposes and advantages of the present invent on will become more apparent to those skilled in the art from the following detailed description of the invention particularly when considered in connection with the drawing wherein:

Figure 1 shows one preferred form of the present invention.

Figure 2 shows in relatively simple detail the construction of a television transmitting tube of the iconoscope type.

Figure 3 represents the area that would be scanned on the surface of the mosaic electrode if no compensatin voltages were incorporated in the deflectin circuit.

Figure 4 shows the area that would be scanned on the surface of the mosaic electrode after electrical keystone correction and pin-cush on distortion correctionsffor the vertical side curvature) have been introduced but without the correct ons accomplished by the present invention.

Figure 5 shows a curve representing one form of voltage variation that may be used to accomplish the purposes of this invent on and p Figure 6 shows a curve representing the voltage variations appearing at one part of the circuit shown in Figure 1.

Referring now to the drawing there is shown in Figure 2 a television transmitt ng tube of the iconoscope type. The tube includes an envelope 2 of glass or ceramic material and inside the tube is positioned a mosaic or target electrode 4. The tube also includes an electron gun structure generally represented at 6 for producing a focused cathode ray beam and for deflecting the focused beam in substantially mutually perpend cular directions a deflecting yoke 8 is provided. A lens system H) is also shown associated with the television transmitting tube by means of which an optical image of an object I2 may be focused upon the surface of the mosaic electrode 4. It will be observed in Figure 2 that the mosaic elec -trode 4 is not positioned normal to the axis of the electron gun structure 6 but is instead positioned at an angle with respect thereto in order not to obstruct light rays which are focused upon the mosaic electrode to produce the optical image. Inasmuch as the cathode ray beam scans the same side of the mosaic electrode upon which the optical image is projected, the gun structure must necessarily be positioned at an angle with respect to the mosaic electrode.

In Figure l is shown partially schematically and partially in detail the circuit arrangement necessary for effecting thedesired deflection of the cathode ray beam in a television transmit television field repetit on rate. frequency voltage variations are then applied to a vertical deflection generator 22 which is deting tube. The system includes a master oscillator it which preferably operates at line deflection or double line deflection frequency. The frequency of operation of the master oscillator therefore depends upon the number of line elements in each television frame together with the number of television frames traversed or transmitted per second. The master oscillator then supplies voltage variations of line or horizontal deflection frequency to a horizontal deflection generator ill. The horizontal deflection gener ator produces voltage variations of the desired wave form to deflect the cathode ray beam at a uniform rate in a horizontal direction. The master oscillator also supplies voltage variations or impulses to a frequency divider 20 which may include counter circuits or frequency divider circuits .for reducing the frequency of the voltage variations. The output from the frequency divider 20, therefore, corresponds to the number of vertical deflections of the cathode ray beam or, in other words, the frequency corresponds to the These reduced signed to produce the required voltage variations for deflecting the cathode ray beam in a vertical direction. Details of .the horizontal and vertical deflection generators i8 and 22 will not be con sidered at this time since any suitable horizontal and vertical deflection generators may be used. Such generators are quite well known to those skilled in the art.

The output from the horizontal deflection generator is applied to a horizontal deflection output tube 24. The tube includes a cathode 26, a control electrode 28 and an anode 30. The control electrode 28 is connected to ground by the usual grid or control electrode resistor 32 and the output from the horizontal deflection generator I8 is applied to the control electrode 28 by way of coupling condenser 34. The cathode 26 of the horizontal deflection output tube is connected to ground by way of a: potentiometer 36 and the resistance element of the potentiometer is bypassed by a condenser 38. For maintaining the anode 30 positive with respect to the cathode 26. the anode is connected to a positive terminal 40 by way of the primary of the output transformer $2. The secondary of transformer 42 supplies energy to the horizontal deflecting coils 44, these coils being included in the deflecting yoke 8 shown in Figure 2. The usual horizontal damping tube 46 is shown connected across the secondary of transformer 42 in order to absorb the transient following the high inductive voltage peak produced during the instant of beam return. Furthermore, a potentiometer 48 is also included in the circuit, one endof the resistance element of the potentiometer being connected to ground while the other end of the resistance element of the potentiometer is connected to a source of negative potential. By means of this potentiometer an adjustable direct current component may be caused to flow through the horizontal deflecting coils 44 in order to control the horizontal position of the scanned pattern on the mosaic electrode 4 of the television transmitting tube 2. This method of centering the scanned pattern is well known to those skilled in the art.

The output from the vertical deflection gener ator 22 is applied similarly to a vertical deflection output tube 50. This tube includes a cathode 52, a control electrode 54 and an anode 56. The

control electrode is connected to ground by way of the usual grid resistor 58 while the voltage variations derived from the vertical deflection generator 22 are applied to the control electrode 54 by the way of coupling condenser 60. The cathode 52 is connected to ground by variable resistance 62, the resistance being by-passed to ground by an appropriate condenser 64. For maintaining the anode 56 positive with respect to its cathode 52, the anode is connected, byway of the primary of transformer 68, to terminal 66 to which a positive potential is applied. When voltage variations are applied to the control electrode 54 of the vertical deflection output tube and these voltage variations are amplified they in turn appear at the secondary of transformer 68 and are then applied to the vertical deflecting coils 10. The vertical deflecting coils are also incorporated in the deflecting yoke 8 shown in Figure 2. For centering the scanned area in a vertical direction, a potentiometer I2 is provided, the purpose of the potentiometer being to permit the circulation of a small direct current in the one direction or another through the vertical deflecting coils in a manner well known in the art.

Furthermore, by providing means whereb the cathode resistance 62 may be adjusted the linearity Of the vertical deflection may also becontrolled.

With the system as so far described, the cathode ray beam in a television transmitting tube may be caused to be deflected in substantially mutually perpendicular directions across the surface of the mosaic electrode 4. For indicating the area traversed, reference is now made to Fig ure 3 wherein the dotted rectangle A--BC--D represents the desired area to be scanned. Actually'the area ABE--F will be scanned by the cathode ray beam when the deflecting coils 44 and 10, which are contained in the deflecting yoke 8, are subjected to the voltage variations produced by the system as above described. The arrows shown in Figure 3 represent the direction of scanning and although these directions are exactly opposite to the directions that the picture is reproduced in the receiver, it must be remembered that the optical image on the mosaic electrode is inverted and reversed from left to right. The useful horizontal deflections of the cathode ray beam over the mosaic electrode are thereforefrom left to right while the useful vertical deflections are from the bottom of the mosaic to the top. It will be noticed that the area A--BE-F that is actually scanned is considerably di torted (the distortions are in fact exaggerated in Figure 3 in order to more clearly describe the invention and in order that it may be more clearly understood) and these distortions may be referred to broadly as keystone distortion and pin-cushion distortion. The fact that the top edge of the mosaic is more removed from the electron gun structure than is the bottom edge, a keystone shape pattern or area is traversed. In Figure 3 the horizontal curved line A--B at the top of the picture is considerably longer than the horizontal curvedline E-F at the bottom of the picture. Furthermore, all four of the boundary edges of the scanned area are curved inwardly and this lack of linearity is generally referred to as pin-cushion distortion.

The keystone distortion may be simply and readily compensated for by varying the degree of horizontal deflection in accordance with the vertical position of the cathode ray beam. One simple method for accomplishing this is to modulate the amplitude of the horizontal deflection voltages at vertical deflection frequency. Accordingly, in Figure 1, the vertical deflection generator 22 is shown as supplying energy, by way of conductor 2|, to the horizontal deflection generator 1| 8. ,By this action it is possible to amplitude modulate the horizontal deflection voltage variations at vertical deflection frequency. Since the matter of keystone correction is not the principal purpose of the present invention and since circuits for compensating for keystone distortion'are, well known in the art, a further discussion of the elimination of the inherent keystone distortion is believed unnecessary.

The so called pin-cushion distortion can be considerably reduced or substantially entirely eliminated by designing the electromagnetic, deflection yoke to compensate for this distortion. In fact, if the degree of pin-cushion distortion is uniform at all 'four sides of the scanned area, it is possible .to completely eliminate the pin- -cushion distortion. By reason of the fact, how ever, that the mosaic electrodeis positioned at an angle with respect to the axis of the electron gun structure the pin-cushion distortion is not uniform and, as shown in Figure 3, is considerably reater at the top of the mosaic than itis near the bottom. It may be. seen in Figure 3 that the curvature of the scanned line A.B or the top edge of the scanned area is considerably greater than the curvature of the scanned line along the bottom edge 13-]? of the scanned area.

When keystone correction circuits are included in the deflection generating network and when the deflection yoke has been so designed as to completely remove or compensate for all of the pin-cushion distortion, the cathode ray beam will then traverse an area on the mosaic electrode corresponding to the area bounded by the solid lines between the points G, H, J and K in Figure 4. It will be noticed in Figure 4 that'tbe scanned area is still not perfectly rectangular but extends below the desired boundary between the points G and H and also extends be low the desired boundary (or outside the boundary) between the points J and K. The desiredhorizontal boundaries are represented by the dotted lines in Figure 4. g

'The pin-cushion effect may be eliminated by proper design of the deflection yoke for a tube of given fixed dimensions. Also, it is possible, by proper keystone modulation, to cause the side boundaries between the points G-J'and H-K to' lie substantially along the desired boundaries. Under these conditions and with careful design of the yoke, the cathode ray beam may be caused to scan a perfectly rectangular surface provided, however, that the mosaic electrode is flat and also provided that exact uniformity in the production of the television transmitting tubes may be maintained. Since the production of television transmitting tubes is rather involved and many steps must be included in the process of making the tubes, exact electrical response uniformity and perfectly flat mosaic electrodes are difficult to assure.

Accordingly, in this invention, means have been provided in the beam deflecting circuits for compensating for thepin-cushion and barrel distortion shown in Figure 4 which remains after a certain amount of pin-cushion distortion has been compensated by design of the deflecting yoke and/or by modulated keystone correction circuits. It may be seen by inspecting Figure 4 that during the horizontal deflection of the cathode ray beam the vertical deflection component should be altered so that the path traversed by the cathode ray beam in a horizontal direction will be in a straight line. It is therefore necessary that the cathode ray beam be subjected to a slightly greater deflection voltage when the beam is near the middle of each scanned line than when it is near either end of each scanned line. The distortion between points G and H at the top of the mosaic exceeds the distortion between pointsJ and K at the bottom of the mosaic, but the deflecting force need not be gradually increased as the beam is deflected in a vertical direction because the same additional deflecting force would cause a greater beam deflection at the top of the mosaic because of the greater beam length. The intensity of the vertical deflecting field to which the cathode ray beam is subjected may therefore vary in a manner such as represented by the curve N in Figure 5. If the beam is subjected to a deflection frequency such as represented by the dotted line in Figure 5, then the beam will be deflected in a vertical direction in a perfectly uniform manner and the combination pin-cushion and barrel distortion shown in Figure 4 would not be compensated for. In Figure 5 is shown a curve representing the variation in the vertical deflecting field which should be imposed upon the cathode ray beam to compensate for the distortion shown in Figure 4. For the sake of clarity, the curve shown at N in Figure 5 would apply to a sixline element picture, however it is to be understood that a very much larger number of lines would in fact be used. a

The horizontal deflection voltage variations are modulated at vertical deflection frequency to compensate for keystone correction, and accordingly the current flowing in the cathode resistance 36 of tube 24 varies at horizontal or line deflection frequency and is modulated to a small extent at vertical deflection frequency. Figure 6 shows at curve M a wave form representing the potential variations at the cathode 25 of the horizontal deflection output tube 24. These potential variations may be controlled somewhat as to Wave form by proper choice of the size of the condenser 38. This small variation in amplitude, as stated above, is a result of the effects of the keystone correction circuits incorporated in the horizontal deflection generator l8.

The voltage variations of the wave form shown at M in Figure 6 are therefore present at point M in the circuit shown in Figure 1 which corresponds to the movable contact of the potentiometer 38. The movable contact of the potentiometer is then connected to one end of the secondary winding of transformer 68 byway of series resistance 14 and condenser 16'. 'The application of this voltage variation to the secondary of transformer 68 therefore superimposes upon the vertical deflection voltage variations a component of horizontal frequency having a parabolic shape. There therefore results in the circuit including the secondary of transformer 68 and the vertical deflecting coil a current or voltage variation similar to the curve N in Figure 5. When such a deflecting potential is applied to the vertical deflecting coils the cathode ray beam may then be caused to scan a substantially perfectly rectangular area on the surface of the mosaic electrode.

In order to control the intensity of the superimposed voltage variations of parabolic shape and of line frequency, the potentiometer 3B is desirable since by moving the position of the movable contact along the potentiometer the intensity of the superimposed voltage variations may be controlled in order that varying degrees of the combined pin-cushion and barrel distortions shown in Figure 4 may be compensated. Due to possible slight Warping of the mosaic electrode through processing and de-gassing of the television transmitting tube, it is desirable to include the adjustable feature since th amount of warping, if

any, will not be uniform in all tubes.

From the foregoing it may be seen, therefore, that a perfectly rectangular area may be scanned on a mosaic electrode in an iconoscope television transmitting tube even though the mosaic electrode is inclined at an angl with respect to the axis of symmetry of the electron gun structure and even though a slight amount of warping may in fact be present over the surface of the'mosaic electrode. Furthermore, it is possible to vary the intensity of the compensating voltages in order to permit the required amount of compensation to be affected where the television transmitting tubes are not exactly uniform.

Although the present; invention is described as applicable to a standard and conventional iconoscope, it is entirely possible for the invention to be used with tubes of different design. Should the transmitting tube be so constructed as to have the mosaic electrode positioned at an angle to the optical axis and normal with respect to the electron gun structure, the invention could still be used to correct for combination pin-cushion barrel distortion. 7 Furthermore, the invention is also applicable to television transmitting tubes wherein the mosaic electrode is of the double-faced type. that is where the optical image is projected on one side of the mosaic and the scanning cathode ray beam is directed against the other side of the mosaic, the mosaic being positioned normal to both the optical axis and the axis of symmetry of the electron gun structure.

Various. alterations and modifications of the present invention may become apparent to those skilled in the art and it is desirable that any and all such modifications and alterations be considered within the purview of th present invention except as limited by the hereinafter appanded claims.

I claim:

1. A television transmitter including a tran mitting tube having a mosaic electrode and a cathode ray gun structure adapted to generate a focused beam of'electrons, means to produce an electrostatic charge image on said mosaic electrode, means to scan said mosaic electrode in horizontal and vertical directions at predetermined different rates in order to produce picture signals. said horizontal scanning means including a discharge tube having a cathode, a control electrode and an anode, means including a resistance for connecting the cathode to a point of fixed potential, means including a load circuit for maintaining the anode positive with respect to the cathode, means for applying voltage variations of horizontal scanning frequency to the control electrode of said tube, said vertical scanning means including a second discharge tube having a cathode, a control electrode and an anode, means including a load circuit for maintaining the anode positive with respect to the cathode, means to apply voltage variations of vertical scanning frequency to the control electrode of said last mentioned tube, and means to apply a predetermined percentage of the potential variations present at the cathode of, said first mentioned tube to the anode load circuit of said second mentioned tube in order to compensate for inaccuracies in the pattern scanned by the cathode ray beam.

2. A television transmitter including a transmitting tube having a mosaic electrode and a cathode ray gun structure adapted to generate a focused beam of electrons, means to produce an electrostatic charge image on said mosaic electrode, means to scan said mosaic electrode in horizontal and vertical directions by the generated cathode ray beam at predetermined different rates in order to produce picture signals, said horizontal scanning means including a first electron discharge tube having a cathode, a control electrode and an anode, means including a resistance for connecting the cathode to a point of fixed potential, means including a load circuit for maintaining the anode positive with respect to the cathode, means for applying voltage variations of horizontal scanning frequency to the control electrode of said tube, said vertical scanning means including a second electron discharge tube having a cathode, a control electrode and an anode, means including a load circuit for maintaining the anode positive with respect to the cathode, means to apply voltage variations of vertical scanning frequency to the control electrodev of said last mentioned tube, and mean to apply a predetermined intensity of the potential variations of parabolic ,wave form and of horizontal scanning frequency to the anode load circuit of said second mentioned tube in order to compensate for inaccuracies in the pattern scanned by the cathode ray beam.

3. A television transmitter including a transmitting tube having a light responsive mosaic electrode and a cathode ray gun structure adapted to generate a focused beam of electrons, means for projecting an optical image on the mosaic electrode to produce an electrostatic charge image thereon, means to scan said mosaic electrode in horizontal and vertical directions at predetermined different rates by the generated cathode ray beam in order to produce picture signals, said horizontal scanning means including a first electron discharge tube having a cathode, a control electrode and an anode, means including a resistance for connecting the cathode to a point of fixed potential, means including a load circuit for maintaining the anode positive with respect to the cathode, means for applying voltage variations of horizontal scanning frequency to the control electrode of said tube, said vertical scanning means including a second electron discharge tube having a'cathode, a control electrode and an anode, means including a load circuit for maintaining the anode positive with respect to the cathode, means to apply voltage variations of vertical scanning frequency to the control electrode of said last mentioned tube, and means to to apply a predetermined percentage of the potential variations of parabolic wave form present at the cathode of said first electron discharge tube to the anode load circuit of said second electron discharge tube in order to compensate for inaccuracies in the linearity of deflection of the cathode ray beam in the horizontal direction.

4. A television transmitting system wherein a television transmitting tube is included for converting an optical image into a series of television picture signals, said tube comprising a mosaic of horizontal beam deflection frequency to the electrode and means adapted to generate a focused cathode ray beam, beam deflecting means for causing the generated cathode ray beam to be deflected across the mosaic at a predetermined rate in a horizontal direction, beam deflecting means for causing the generated cathode ray beam to be deflected across the mosaic at a different predetermined rate in a vertical direction, said horizontal beam deflecting means including a first electron discharge tube having a cathode, a control electrode and an anode, means includ ing a resistance for connecting the cathode of said tube to a point of fixed potential, means including a load circuit for maintaining the anode of said tube positive with respect to its associated cathode, means for applying voltage variations control electrode of said tube, said vertical beam deflecting means including a second electron discharge tube having a cathode, a control electrode and an anode, means including a load circuit for maintaining the anode of said second tube positive with respect to its associated cathode, means for applying voltage variations of vertical beam deflecting frequency to the control electrode of said second tube, and means including a series connected resistance and condenser for super-. imposing a predetermined percentage of the voltage variations present at the cathode of said first discharge tube upon the voltage variations present at the anode loadcircuit of said second discharge tube, whereby said cathode ray beam may be caused to scan a rectangular pattern on said mosaic electrode.

5. A television transmitting system wherein a television transmitting tube is'included for converting an optical image into a series of picture signals, said tube comprising a mosaic electrode and means adapted to generate a'focused cathode ray beam, beam deflecting means for causing'the generated cathode ray beam to be deflected across the mosaic at a predetermined rate in a horizontal direction, beam deflecting means for causing the generated cathode ray beam to bedeflected across the mosaic at a different predetermined rate in a vertical direction, said horizontal beam deflecting means including a first electron discharge tube having a cathode, a control electrode and an anode, means including a resistance for connecting the cathode of said tube to a point of flxed potential, a condenser connected in parallel with said resistance, means including a load circuit for maintaining the anode of said tube positive with respect to its associated cathode, means for applying voltage variations of horizontal beam deflection frequency to the control electrode of said tube,'said vertical beam deflecting means including a second electron discharge tube having a cathode, a control electrode and an anode, means including a load circuit for maintaining the anode of said second tube positive with respect to its associated cathode, means for applying voltage variations of vertical beamdeflecting frequency to the control electrode of said second tube, and means including a series connected impedance and electron storage device for superimposing a predetermined percentage of the voltage variations of parabolic wave form present at the cathode of said first discharge tube upon the voltage variations present in the load circuit of said second discharge tube, to thereby compensate for undesired variations in the pattern scanned by said cathode ray beam on said mosaic electrode.

6. A television transmitting system wherein a television transmitting tube is included for converting an optical image into a series of picture signals, said tube comprising a target electrode and means adapted to generate a focused cathode ray beam, horizontal beam deflecting means for causing the generated cathode ray beam to be deflected horizontally across the mosaic at a predetermined rate, vertical beam deflecting means for causing the generated cathode ray beam to be deflected vertically across the mosaic at a different predetermined rate, said horizontal beam deflecting means including a first electron discharge tube haw'ng a cathode, a control electrode and an anode, means including a resistance for connecting the cathode of said tube to a point of fixed potential, a condenser connected in parallel with said resistance, means including a load circuit for maintaining the anode of said tube positive with respect to its associated cathode, means for applying voltage variations of horizontal beam deflection frequency to the control electrode of said tube, said vertical beam deflecting means including a second electron discharge tube having a cathode, a control electrode and an anode, means including a load circuit for maintaining the anode of said second tube positive with respect to its associated cathode, means for applying voltage variations of vertical beam deflecting frequency to the control electrode of said second tube, and means for amplitude modulating the voltage variations present at the anode of said second discharge tube by the voltage variations of parabolic wave form present at the cathode of said first discharge tube, whereby said cathode ray beam may be caused to be deflected linearly across said mosaic electrode in a horizontal direction.

7. A system for use in a television transmitter for compensating for pin-cushion and barrel distortion comprising a television transmitting tube having a target electrode and means to produce a focused cathode ray beam, a first electron discharge tube having a cathode, a control electrode and an anode, means including a resistance for connecting the cathode to a point of fixed potential, means including a load circuit for maintaining the anode positive with respect to its associated cathode, means to apply voltage variations of one predetermined beam defiection frequency to the control electrode of said discharge tube to produce corresponding voltage variations in the load circuit of said tube, means to utilize the voltage variations of said load circuit to cause the cathode ray beam to be deflected across the target electrode in one predetermined direction, a second electron discharge tube having a cathode, a control electrode and an anode, means including a load circuit for maintaining the anode of said second discharge tube positive with respect to its cathode, means to apply voltage variations of another predetermined beam deflection frequency to' the control electrode of said second discharge tube to produce corresponding voltage variations in the load circuit of said tube, means to utilize the voltage variations of said load circuit to cause the oathode ray beam to be deflected across the target electrode in another predetermined direction to thereby cause the cathodev ray beam to scan a predetermined pattern on said target electrode, and means including a series connected condenser and resistance for superimposing a predetermined percentage of the voltage variations of parabolic wave form present at the cathode of said first electron discharge tube upon the voltage variations present in the load circuit of said second electron discharge tube, whereby the deflection of the produced cathode ray beam at said another predetermined beam deflection frequency will be in part controlled by the voltage Variationsof said first predetermined frequency.

8. A system for use in a television transmitter for compensating for pin-cushion and barrel distortion comprising a television transmitting tube having a target electrode and means to produce a focused cathode ray beam, a first electron discharge tube having a cathode, a control electrode and an anode, means including a resistance for connecting the cathode to a point of fixed potential, a condenser connected in parallel with said resistance, means including a load circuit for maintaining the anode positive with respect to its associated cathode, means to apply voltage variations of horizontal beam. deflection frequency to the control electrode of said discharge tube to produce corresponding voltage variations in the load circuit of said tube, means to utilize the voltage variations of said load circuit to cause the cathode ray beam'to be deflected across the target electrode in a horizontal direction, a second electron discharge tube having a cathode, a control electrode and an anode, means including a load circuit for maintaining the anode of said second discharge tube positive with respect to its cathode, means to apply voltage variations of vertical beam deflection frequency to the control electrode of'said second discharge tube to produce corresponding voltage variations in the load circuit of said tube, means to utilize the voltage variations of said load circuit to cause the cathode ray beam to be deflected across the target electrode in a vertical direction, and means for superimposing a predetermined percentage of the voltage variations of parabolic wave form present at the cathode of said first electron discharge tube upon the voltage variations present in the load circuit of said second electron discharge tube, whereby the deflection of the produced cathode ray beam in the horizontal direction will be in part controlled by the voltage variations of said first predetermined frequency to cause the cathode ray beam to be deflected linearly horizontally.

9. A system for use in a television system for compensating for pin-cushion and barrel distortion comprising a cathode ray tube having a target electrode and means to produce a focused cathode ray beam, a'first electron discharge tube having a cathode, a control electrode and an anode, means including a resistance for connecting the cathode to a point of fixed potential,

means including a load circuit for maintaining the anode positive with respect to its associated cathode, means to apply voltage variations of one predetermined beam deflection frequency to the control electrode of said discharge tube to produce corresponding voltage variations in the load circuit of said tube, meansto utilize the voltage variations of said load circuit to cause the cathode ray beam to be deflected across the target electrode in one predetermined direction, a. second electron discharge tube having a cathode, a control electrode and an anode, means including a load circuit for maintaining the anode of said second discharge tube positive with respect to its cathode, means to apply voltage variations oi another predetermined beam deflection frequency to the control electrode of said second discharge tube to produce corresponding voltage variations in the load circuit of said tube, means to utilize the voltage variations of said load circuit to cause the cathode ray beam to be deflected across the target electrode in another predetermined direction, and means including a time constant circuit for mixing a predetermined percentage of the voltage variations of substantially parabolic wave form present at the cathode of said first electron discharge tube upon the voltage variations present in the load circuit of said second electron discharge tube, whereby the deflection of the produced cathode ray beam in said another predetermined direction will be partially controlled by the voltage variations of said first predetermined frequency to assure linearity of deflection of the produced cathode ray beam in the last mentioned direction.

10. In a television apparatus wherein a cathode ray beam is controllably deflected and caused to scan a mosaic electrode upon which a light image is projected, including cathoderay beam deflecting means, a pair of electron discharge tubes each having a cathode, a control electrode and an anode, a resistance element for indicause the cathode ray beam to scan a bidimensional pattern on the mosaic electrode, and means to superimpose a predetermined percentage of the voltage variations of parabolic wave form present at the cathode of one of the electron discharge tubes upon the voltage variations present at the anode load circuit of the other electron discharge tubes to compensate for inaccuracies in the pattern scanned by the cathode ray beam.

OTTO H. SCHADE.

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