US1715732A - House electric - Google Patents

Description

June 4, 1929. v ZWORYKIN' 1,715,732

TELEVISION SYSTEM Filed Sept. 25, 1927 3 Sheets-Sheet 1 INVENTOR V/adl'mar/f. Zworyhn.

ATT oRNEY June 4, 1929. v. K. ZWORYKIN 1,715,732

TELEVIS ION SYSTEM Filed Sept. 23, 1927 3 Sheets-Sheet 2 3:0 a: .NVENTOR l/iadlmar K. Z wary/fin.

ATTORNEY June 1929. v. K. ZWORYKIN 1,715,732

TELEVISION SYSTEM Filed Sept. 1927 3 Sheets-Sheet 5 Fig. 3.

AITTORNEY Patented June 4, 1929.

UNITED. STATES PATENT OFFICE.

'V'LADIMIR K. ZWORYKIN, OF SWISSVALE, PENNSYLVANIA,

ASSIGNOR TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VAN TELEVISION SYSTEM.

Application filed September 23, 1927. Serial No. 221,441

. visual signals at a distance, there is an apparatus at the sending station which is affected successively by the brightness of the several points in the object, view or picture to be sent. Some moving member, usually an optical device, traces a path in the scene, and

the points of the scene are effective in succession, in the order in which, they occur alongflsuch path. I

At the receiving station, another moving member, usually an optical device, causes a source of light to illuminate successive points upon a surface, such as a projection screen or a photographic plate. The brightness of the source of light or the degree of transparency of the path over which the light travels are controlled, moment-by-moment, by the device at the sending apparatus which is controlled by the brightness of the points in the view.

In order that the reproduction of the picture shall be faithful, the change in-bri htness of the illumination must occur at t e correct places on the screen. To accomplish thls,

' the movement of the moving part which determines what point in the view is acting upon the device responsive. to the brightness of,the points must correspond exactly to the movement of the moving part in the receiving device which determines what point upon the screen shall have the corresponding illumination. The correspondence between these two movements must-be exact to a very high degree. A very slight departure from strictly correct phase relation between these movements is suflicient to render the reproduced picture unsatisfactory, and a very slightlv greater departure from the correct phase relation will often render the reproduction unrecognizable.

It is an object of this invention to provide a synchronizing device ,which shall produce a suflicient degree of exactness in the correlation of the movements synchronized to meet the needs of picture transmission.

It is a further object of this invention to associate with the moving part at the send ing station a means for generating an electromotive force,o to associate with the moving part at the receiving" station a device for generating another electromotive force and to control the phase relation of the two movements by means of the phase relation between drawirigsfln which Figure 1 is a view, in sectional elevation, of the optical and mechanical portions of the sending device,

Fig. 2 is a view, in sectional elevation, of the like parts of the receiving device,

Fig. 3 is a circuit diagram illustrating the arrangements at the sending station, and Fig. 4 is a similar diagram for the receivmg station.

The picture, object or landscape which constitutes the visual signal to be transmitted is received by the sending apparatus shown in Fig. 1 throughthe lens. 1, which has the usual provision, illustrated at 2, for adjustment for focusing. An additional lens shown at 3. assists in producing, upon the plate 4, an image of the view or object toward which the lens 1 is directed. The plate 4 is additional moveprovided with an orifice 5 through which i the photo-electric cell 6 is illuminated.

In order that the image upon the plate 4 may move, causing the orifice 5 to trace a path therein, a moving optical system is provided. The action of this moving optical system is explained at greaterlength in my U. S. Patent Nod1,689,847, patented Oct. 30,

to the Westinghouse Electhe rotor 11 of an though, as drawn, the source is a direct-current source and themotor a direct-current motor, an alternating or, particularly, a polyphase source may be utilized and the motorselected accordingly. In the form illustrated, the source 21 is connected, through a voltage stabilizing device 22', to the field 13, and a shunt connection through the brushes 23 and 24 is provided to energize the rotor 11.

The brushes 23 and 24 and the shunt connection to them are not illustrated in Fig. 1 because needless complication of thedrawing is. thereby avoided. The commutator 25 co-operates with the brushes 23 and 24.

At two points 27 and 28 of the rotor winding, connect-ion is made to the slip rings 29 and 30. The connection from these slip rings is illustrated at the binding posts 31 and 32 in Fig. 1. r

The electromotive force delivered by the rotor winding to'the slip rings is supplied to an amplifier 35 which controls the modulation produced by a modulator 36. A modulation, the phase of which necessarily corresponds to the movement of the rotor 11 is thus impressed upon the energy supplied from the oscillator 37. The modulated oscillations are delivered to an antenna 38 or to any other .suitable transmission system and thus reach the receiving apparatus. 7 1

The receiving apparatus illustrated in Fig. 2 includes a source 40 of light which, by means of an opticalsystem, produces a small and concentrated beam of light. On the drawing, the lens 41 and the diaphragm 42 illustrate one form of optical'system which may be combined with any projection lens or train of projection lenses. I The light beam produces an illuminated spot upon the screen 45 which may be .the

projection screen of an exhibition hall, the".

ground glass to be viewed in a photographicplate.

The spot of light upon the screen 45 must move over the screen and change its intensity as it moves. If the changes in intensity are correctly correlatedto the motion, the picture will be reproduced upon the screen CHIIIEITL 01 21 J 45. This movement of the spot of light is effected by the prisms 46 and 47. These prisms also are each made of two kinds of glass to minimize color effects.

- 'The prism 46 is mounted in 'a tribe 50 which is centered in the rotor 51 of the motor. The stator 52 of the motor is supported in a frame 53 which is mounted for rotation in supports 54. A train 55 of gears is supported in the frame '53 and rotates a second tube 56 which is mounted in alignment with the tube 50, a bearing surface being provided by the telescoping of the tube 50 by the tube 56. The gearing 55 has the same gear-ratio as the gear train 14 and causes the prism 47 to rotate at a different velocity from the prism 46.

The combined effect of the two moving prisms is to produce a movement ofthe spot of light upon the screen 45 which will correspond to the movement of the image upon the screen 4 in Fig. 1, provided the motion of the rotor 11 is strictly synchronous with the motion of the rotor 51.

A source of power 60 supplies the field 52 through a voltage-control device 61. Obviously, an alternating oreven a polyphase source may be used instead of the source 60 if corresponding changes are made in the motor. A shunt through the brushes 62 and 63 supplies power to the rotor 51. An additional winding 64 is provided on this rotor. The midpoint of this winding is connected to the slip ring 65. The two terminals of this winding are connected to the slip rings 66 and 67. The commutator, cooperating with the brushes 62 and 63, is illustrated at 68 in Fig. 2 but the brushes themselves have not been shown in order to avoid unnecessary complications in the drawing.

Upon the exterior of the rotatable frame 53, slip rings 70, 71 and 72 are provided to cooperate with the slip- rings 65, 66 and 67. The connection from the source 60 is through the slip rings 73 and 74 on the exterior of the frame.

The energy transmitted from the sending station is received at the receiving station upon the antenna 80 and being translated by any suitable or familiar receiving set 81, produces a current in the tuned circuit 82, corresponding in frequency and phase to the current delivered from the slip rings 29 and 30 in Fig. 3. This correspondence does not require that the phase in the circuit 82'shall be exactly the same as that in the slip rings in Fig. 3, but, whatever difference of phase exists, must be a constant difference.

The circuit 82 is inductively coupled by a coil 83, to the connection between the filaments of a vacuum tube device and the slip ring 65. This connector includes a C-battery 84. The vacuum-tube device includes two or three electrode tubes 90 and 91, the filaments of which are connected together. The plates of these tubes are also connected together and supplied from a'common B-battery 92. The connection includes a tuned circuit 93 for the tube 90, a tuned circuit 94. for the tube 91, a resistor 95 for the tube 90 and a resistor 96 for the tube 91, the connection to the com- I mon B-battery 92 being between the two reof tubes 100 and 101, the plate circuits of which are supplied by a common B-battery 102 and the filaments of which 'are connected together.

, Each of the tubes 100 and 101 is supplied with two grids. The first grid of the tube 100 is connected, through a condenser 103, to the positive end of the resistor 95. The second grid of the tube 100 is connected to the same point through a C-battery 104. The

first grid is also connected through a resistor 105, to the filament. The resistor 105 is of much greater resistance than the resistor 95, constituting merely a leakage path for the charge upon the first grid of the: tube 100. The tube 101 is similarly connected to the condenser 113, a C-battery 114 and a grid leak 115 corresponding to theelements designated by numerals less by 10 associated with the tube 100.

The plate circuit of the tube 100 includes a field winding 120 for a generator 121 and the platecircuit of the tube 101 contains a field coil 122 for the same generator. The rotor of this generator is driven by any suitable motor, the series motor 123 being chosen merely for illustration.

The current supplied from the generator 12 supplies the rotor of a motor 124 which drives a worm 126 which meshes with a worm wheel 127 on the frame 53. The field of motor 124 is preferably supplied from the same source as the motor 123. Y

In the operation of the device, the movement of the rotor 11 in the sending apparatus, Fig. 1, causes the prisms 8 and 16 to rotate. The action of the prism 8 will be added to that of the prism 16 to produce maximum deviation of the light rays when these prisms are in such position that their diverting action adds. The action of the prism 8 will be more or less completely counteracted by the -action of the prism 16 when they are in a relative position 180 different from that just mentioned. At intermediate relative positions, an intermediate resultant effective diversion of the light rays occurs.

As a consequence of the movement of prisms 8 and 16 relative to each other, the image upon the surface 4 moves radially. As a consequence of the rotation of the prisms 8 and 16, the image rotates. The combination of these two movements of the image causes the orifice 5 to trace a spiral path in the image. The movement of the prisms 46 and 47, in Fig. 2, causes the spot of light upon the screen 15 to trace a similar spiral. The illumination of the photo cell 6 through the orifice 5 at any given instant controls the brightness of the light from the source 40. The means by which this control is effected is not shown or described herein, because it forms no part of the invention covered by this application.

As a result of the, synchronization of the movements and the control of the light, the position and brightness at any moment, of the spot of light upon the screen 45 will produce there a representation of that point in the image on the screen 4 which, at that moment, is at the orifice 5. There will, therefore, be formed on the screen 45 a reproduction of the View toward which the lens 1 is directed. In order that this reproduction may be faithful, it is necessary that; at all times, the position of the prism 46 shall either be like that of the prism 8, or differ therefrom by a constant angle. If the difierence should vary, the picture would either be blurred, distorted or rendered completely unrecognizable. 1

The rotation of the prism 8 is necessarily in the same phase as the movement of the winding of the rotor 11. There is, therefore, a necessarily constant relation between the phase of the electromotive force delivered to the slip rings 29 and 30 and the position of the prism 8.

The phase of the electromotive force delivered to the slip rings 29 and 30 is related, in a constant way, to the phase of the current in the circuit 82. The phase ofthe oscillations impressed upon the antenna 80 maybe different from the phase of the oscillations delivered by the antenna 38 because of changes in atmospheric conditions between these antennae, but this will not alter the phase relation of the modulation of the two oscillations.

Consequently, the phase of the electromotive force impressed by the coupling 82-83 upon the slip ring is a faithful reproduction of the phase of the movement of the prism 8. I

The grid of the tube 90 has impressed upon it the sum of the electromotive force in onehalf of the windingfit and the electromotive tioned upon the rotor 51 that they deliver currents difi'ering slightly in phase, say approxi mately 10. Moreover, the apparatus is so designed that, under normal conditions, these phases equally differ from opposition to the phase introduced by the coupling 8283.

The potential impressed uponthe grid of the tube 90 is the vector sum of two nearly op; posed electromotive forces. It is, therefore, a small electromotive force. Similarly, the potential impressed upon the grid of tube 91 is the resultant of two nearly opposed electromotive forces and is, therefore, small. Moreover, the electromotive force upon the gridof tube 90 is normally equal'to that upon the grid of tube 91 and 180 different from it in phase. v

The C-battery 97 brings the average value I of the potentials of the grids of the tubes 90 and 91 to a point on the characteristic curve of these tubes which insures that the alternating potential impressed upon the grids, 'will "cause the average-value of the plate current to increase.-- If this change in the value of the 'plate current is the same in'both tubes, the potentials of the positive terminals of the resistors 95 and 96 will vary in the same direction and no difference will appear.

Because the circuits 90 and 91 are tuned to the frequency of the potential changer delivered over. the slip. rings, no substantial change of this frequency will pccur in the potential of the positive ends of the re-- sistors 95 and 96 but the potentials there will correspond to the average value of the plate current. For this reason, the phase relation between the potential on the grids of the tubes 90 and 91 is unimportant but the relation of the amplitude is of great importance.

When starting the system, the two motors are brought to the same speed by, adjusting the potential of the source 21 or of the source 60. Having reached the correct speed, the correct phase relation is produced by rotating the worm 126 normally. Theaction described beldw will then maintain the correct phase relation.

If, through same acoident, the rotor of the sending apparatus changes its phase relation to the rotor of the receivingapparatus, the

electromotive force impressed upon the slip ring will no longer be as nearly opposed to the electromotive' force in one-half of the winding 64 as to that in the other Consequently, the resultant impressed upon the grid of one of the two tubes 90 and 91 will be greater than the resultant impressed upon the other grid.

This will cause a difference between the potential upon the second grid of thetube 100 and that upon the second grid of the tube 101.

The plate currentsof these two tubes will, therefore',-be no longer equal. The field impressed upon the generator 121 by the coil 120 will no longer be completely counterbalanced by the field impressed thereon by the coil 122. A resultant field will then exist and a current will be generated by the rotation of the, armature of this generator.

The current from generator 121 will flow through the armature of the motor 124 and the motor 124 will rotate. The frame 53 h and, thereby, the stator 52 will thus be rotated.

The energy from-the source60 causes a rotation of the rotor 51 relative to the stator 52.

When the stator itself is moving, the motion of the prism 46 will be the 'resultant of the two movements. If the excess current be in the other one of the coils 120 and 122, the current in the rotor of the motor 124 will be in the opposite direction, and the movement rame 53, and also of the rotor 52,

of the will be reversed. The action of the motor 124 is, therefore, to correct the change in' phase relation in the position of the prisms 8 and 46 which may have arisen.

It is important that the momentum of the frame 53 and stator 52 shall not cause this correction to be excessive because hunting would result from any such excess. In order to avoid this, each of the tubes 100and 101 is provided with an additional grid. The potenti'al upon the first grid of the tube 100 is a determined by the rate of change of the potential of the positive end of the resistor 95.

- The current delivered to the coil 120 is, therefore, proportional not only to the departure from correct phase but to the rate of said departure. V

The motor 124 will, therefore, move the stator 52 rapidly when and only when the change in phase is a rapid one. For a slow,.- a

change in phase, the stator 52 will be moved slowly and, therefpre, will have only a small momentum. Danger of over-correction is thus avoided.

The tuned circuits 93 and 94 remove practically all high-frequency alternating changes of potential. Consequently, the-condensers 103 and 113 transmit to the first grids of the tubes and 101 only the potentials corresponding to the rateof change of phase restead of at each of a number of separated receiving stations. For the purpose of describing this feature, without reference to the direction of transmission, either station may be selected as the standpoint from which the description is to be stated. The station thus selected is properly called the home station, the other then being, of-course, the distant station. a

It will be apparent to those skilled in the art, that many variations in the details of the system illustrated and described, come within the spirit (if this invention. The specific illustration and description of one form of this deviceis not to be construed as a limitation excluding other forms. No limitation is intended except such as is required by the prior art or stated in the claims.

I claim as my invention:

1. In a transmitting system for visual signals, a periodically-moving, point-selecting means at a distant station, a reference part at the home station, a point-selecting means at the home station having a periodic movement relative to said reference part, and means controlled by the phase relation between the movement of the point-selecting means for so'moving the reference part at the home station that the combined effect of its movement and of the periodic move ment-of the point-selecting means at the home station will maintain said point-selecting means in synchronism.

2. In an image-transmitting system, a sending deviceincluding a moving part, and means associated therewith for generating an alternating potential synchronized in phase with the position of said part, a receiving device including a moving part and means associated therewith for generating a periodic potential synchronized in phase with the position of said part, means for combining said potentials to produce a resultant otential and means whereby departures rom synchronism of said moving parts are corrected by said resultant potential.

3. In a transmitting system for visual signals, a scanning device including movable parts, a motor for driving said parts and means for producing a periodic electromotive force, the phase of which is permanently correlated with the position of said moving parts and a second device comprising movable parts, a motor for driving said parts and means for producing a periodic electromotive force, the phase of which is permanently correlated with the position of said moving parts of said second device, an adjusting device for'imparting to the last named moving parts a motion in addition to the motion imparted by said second-named motor, and means controlled by the resultant of said phases for controlling the action of said adjusting device.

4. In a transmitting system for visual signals, a sending device including a periodically moving part, a receiving device including a periodically moving part, and means for synchronizing the movements of said parts, said means, including apparatus for producing at the receiving device a periodic current the phase of which is determined by the posi-. tion of the moving part at the sending device, apparatus for producing at the receiving device, a periodic current, the phase of which is determined by the position of the moving part at the receiving device, and means controlled by the resultant of the phases of said currents for correcting the position of one of said moving parts whenever said position departs fromsynchronism.

5. In a synchronizing'system, two stations,

' rotating elements, one at each station, windings, at least one for each rotating element, said windings each forming part of an electro-dynamic machine the movable member of which is constrained to move with the respective rotating element, whereby the phase of the electromotive force across each winding respectively is correlated with the position of the respective rotatingelement, means for producing at a home station an electromotive force corresponding in phase to the electromotive force across one of said windings at a distant statlon, means for combining said corresponding electromotive force with the electromot-ive force from at least one of said windings at said home station and means controlled by the resultant of said electromotive forces for governing the position of the rotating element at said home station.

6. In a transmitting system for visual signals,a scanning device comprising a motor having a stator and a rotor, an optical member mounted in said rotor to rotate therewith, and a second optical member driven by said rotor at a lower speed, the speed ratio of the two optical members in the reproducing device being equal to the speed ratio of the two optical members inthe scanning device, con nections from the rotor of the scanning motor to a radio sending device, means at the reproducingdevice for producing an electromotive force in accordance with that delivered to the sending device, a circuit subjected to said electromotive force, connections from the rotor of the reproducing device to said circuit, and means controlled by said circuit for changing the position of the rotor in the reproducing device.

7. In a transmitting system for visual signals, a scanning device and a reproducing device one of said devices comprising a stator and a rotor mounted to turn therein, and means controlled by the phase relation between said devices for moving said stator in the direction to keep said devices in synchronism. t

8. In a transmitting system for visual signals, a scanning device and a reproducing device, one of said devices comprising a stator and a rotor mounted to turn therein, and means for rotating said stator in accordance with. the departure of said devices from'synchronism, said means including a motor the speed of which is dependent upon both the degree of departure fromsynchronism and the rate of said departure.

In testimony whereof, I'havehereunto subscribed my name this 19th day of September,

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