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Aug. 26 1930.

This invention relates to a television apparatus and process that is it is directed to an apparatus and process for the instantaneous transmission of a scene or moving image of
5 an object located at a distance in which the transmission is by electricity.
Heretofore attempts have been made to
transmit an image of an object by electricity
so that the image of the object will instan-10 taneously appear at a distance. These prior
attempts at television have generally em-
bodied an apparatus and method in which
each particular elementary area of the image
of the object is successively converted into an 15 electrical current the intensity of which is
proiortional to the intensity of the light at
that particular elementary area; all the ele-
mentary areas of the image being covered in
that fraction of a second during which the eye 20 will retain a picture hereafter referred to as the optical period. This is followed by a transmission of such current and a conversion of such current to light corresponding in in-tensity to the intensities of the light of the individual areas of the original image; the reconversion process likewise being per-formed within the optical period so that by a proper coordination of the developed light an image of the object to be transmitted appears as instantly formed at the receiving end of the apparatus and method.
The time during which the human eye will
retain a picture is of si.ich short duration that
the conversion of the light shades of the orig-
inal image of the object to electricity and the
reconversion of said electricity to light and
the proper coordination of such light must be
performed at a. very tremendous speed. All
prior attempts at television have attempted
40 to employ some mechanically moving part
for dissecting the image of the original ob-
ject during the process of forming an elec-
trical current which varies in intensity in ac
cordance with the light . shades of the
45 respective elementary areas of the image.
None of these prior attempts at television
have proven successful. They have resulted
at best in the production of a crude moving
silhouette of the object to be transmitted.
50 This has generally been due to the fact that
the mechanically moving parts of the prior apparatus have not been able to travel at the necessary speed requirements with the synchronism required in a television apparatus
An object of the present invention is to provide a method and apparatus for television which is adapted to transmit electrically a true moving image in full light shades of the object to be transmitted.
Another object of the present invention is to provide a method and apparatus for television in which the conversion and dissecting of the light shades of the object. to be trans mitted to electricity and the reconversion of such electricity to form an image is accomplished in the following manner:
In the process and apparatus of the present invention light from all portions of the object whose image is to be transmitted is focused at one time upon a light sensitive plate of a photo-electrical cell to thereby develop an electronic discharge from said plate in which each portion of the cross section of such electronic discharge will correspond in electrical intensity with the intensity of light imposed on that portion of the sensitive plate from which the electrical discharge originated. Such a discharge is herein termed an electrical image. An electrical shutter is then interposed between said sensitive plate and the anode of the photo-electrical cell the shutter having a small aperture therein so that there can he received upon said anode at one instant only the electrons which originate from one elementary area of the light sensitive plate. There is then imposed upon the electrical discharge a plurality of electrical potentials of different frequencies for causing the electrical discharge to bend in-two directions whereby the electrons from each elementary portion of the sensitive plate are successively directed through said shutter this action taking place so as to completely cover the area of file sensitive plate within the optical period. The scene to be transmitted is thus analyzed or dissected to produce an electrical current or "light" current having 'variations in intensity in accordance with the light shades of the object to be transmitted and this is accomplished within the optical
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period without the necessity of employing any mechanically moving parts.
The produced electrical current or "light" current may be transmitted to the receiving
6 end of the apparatus by either wires or may be superimposed upon a wireless carrier wave. There is also transmitted at the same time and preferably superimposed upon the same carrier wave the two electric potentials of dif-
10 ferent frequencies which are employed in analyzing the image so that such currents may be employed to synchronize the receiving apparatus and process.
At the receiving end of the apparatus and
15 process the "light" current is reconverted to light and the light coordinated to form an image of the object transmitted in accordance with the following apparatus and process.
Preferably a constant source of light is uti-
2o lined which is directed first through a polar-'zing prism and hence through an apparatus or means by which the plane of polarization of the light may be rotated by the "light" current. In this manner an instantaneous
a5 response to the variations of such light cur-rent is obtained in the rotation of the plane of polarization of the light. The light is then directed through a suitable screen capable of shutting oft the light in accordance
15 with the rotation of its plane of polarization. In this manner a beam of light is developed fluctuating in intensity to the variations of intensity of the "light" current transmitted without the necessity of employ ing any mechanically moving parts. This said beam of light is then projected by means of two cooperating oscillographs upon the screen where the image is to be transmitted said oscillographs being operated by the
0 synchronizing frequencies transmitted with the "light" current to correctly coordinate the light upon the screen to form a correct image.
The present invention together with various objects and advantages thereof will best be understood from a description of a preferred form or example of a process and apparatus for television embodying the invention. For this purpose I have hereinafter
- set forth one form of example of a method and apparatus for producing television in accordance with the present invention . and have illustrated said apparatus and method as it is adapted for television by wireless. It is to be understood however that the invention is capable of various and numerous modifications changes and substitutions and is not necessarily limited to the trans-mission by wireless or radio.
The apparatus and method will best be understood from a description of the accompanying drawings in which :
Figure 1 is a diagrammatic view of a cornplete television transmitter including a cir cuit diagram therefor
Figure 2 is a diagrammatic view of the television receiver
Figure 3 is a circuit diagram of the electrical connections for the television receiver
Figure 4 is an elevation of one of the oscillographs
Figure 5 is a plan view of one of the oscillographs
Figure 6 is a perspective view of the light diverting means 75
Figure 7 is a sectional view of the photo-electric cell -
Figure 8 is a section on the line 8—8 of Figure 7
Figure 9 is a section of the light rotator Figure 10 is an end view thereof
Figure 11 is a representation of the form of electric current of the first oscillator em ployed in developing a potential for the photo-electric cell 86
Figure 12 is a representation of. the form of electric current produced in the second oscillator
Figure 13 is a representation of the resulting straight lined potential
+ igure 14 is a view of the scanning path and also a view of the path of the light beam over the receiving screen
Figure 15 is a perspective view of a bi-axial crystal showing the conical refraction of un 95 polarized light
Figure 16 is a perspective view of a biaxial crystal showing the refraction of polarized light and
Figure 17 is a diagrammatic illustration toe of the path of light through the gratings.
Referring to the drawings 2 represent= an object an image of which is to be transmitted. Said object may be an actual scene
or a photograph a projection of a motion 105 picture film or any other object. The object 2 is preferably illuminated for example by means of an arc light 3 focused thereon by a lens 4. 5 indicates a lens for focusing an image of the object 2 upon the light sensi- 11n Live plate 6 of a photo electric cell 7.
The photo-electric cell is preferably constructed as follows :
The light sensitive plate 6 or cathode of
the cell is preferably made flat and is formed ~10 of a fine mesh screen 8 and said screen 8 is covered or coated with a light sensitive material such as sodium potassium or rubidium. 10 is the anode of the photd-electric cell positioned at the other end of the cell. 1Lo Between the sensitive plate 6 and anode 10 and closely adjacent to anode 10 is placed an electric shutter 11 formed by a metallic plate in which there is a small aperture 12. Between the shutter 11 and light sensitive 1%'5 plate 6 four plates 13 14 15 and 16 are placed at right angles to each other and out-side the path of electrons from the plate '6 to the shutter 11. Each opposed pair of the plates are connected to a source of electrical ==)
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potential of a different frequency. The circuit in resonance with the frequency of the photo-electric cell should be highly evacu- desired circuit. Said oscillator in turn proated such for example as to 10-7 cm. mer- vices a source of potential for a second oscilcury to permit a high potential across the lcting circuit of similar design the second
A cell without ionization. oscillator operating at a higher frequency ;«
The necessity for employing a high po- such for example as 500 kilo-cycles. The tential across the cell arises from the fact second oscillator comprises the tube 32 the that the photo electrons emitted from the plate 33 of which is charged with the oscilcathode 6 have a small emission velocity latory energy of the first oscillator. The first
10 which depends upon the color of the light oscillator is coupled thru the secondary coil 75 causing their emission. This emission 31' to plate 33 the inductance 34 being in-velocity is always small of the order of that eluded in series therewith. The inductance 34 which an electron would acquire by falling may be any suitable radio frequency choke through a volt or two but it may have nearly to prevent the hi eh frequencies in the sec-any direction. This haphazard motion tends and oscillating circuit from being imposed on so to distort the electric image and is only pre- the first oeillating circuit. The plate 33 is vented from doing so by making the poten- connected through the primary 40 of a radio tial between the cathode 6 and the anode frequency transformer and hence through the 10 high enough to insure that the time taken capacity 41 with the grid 42. Capacities 43
20 for an electron to traverse the distance be- and 44 are shunted around all or part of the 85
tween cathode 6 and anode 10 is so small that primary 40 and a lead is connected from their
the small velocity transverse to this path midpoint. to the filament 39 of the tube 32.
produces no appreciable distortion. Hence The grid 42 of the tube is connected through
the vacuum in the photo-electric cell 7 should a suitable leak 45 and negative bias battery
Ed be the highest obtainable. -16 with filament 39. It is understood that 90
The electrical potentials are provided by the second oscillating circuit thus described an oscillator 17 capable of developing two is only one caample of a circuit adapted for different high frequency electrical currents. this pin poet and the various constants of the Said oscillator 17 not only is required to pro- circuit may be of any value suitable for bring-vide a source of oscillating energy but is re- ing the circuit into resonance with the fre- gs quired to provide a form of oscillating en- quency of the oscillations (500 kilo-cycles) ergy the wave form of which is composed desired to be produced therein. of substantially straight lines as will be The voltage of the first oscillator is adjust-
hereinafter pointed out. Such a wave form ecl to be well above the value required for
35 is essential to accomplish a uniform lighting maximum plate current of the second oscil- lae of all portions of the image which is to be lator. Hence since the second oscillator will produced. generate oscillations only when the plate volt-
The oscillator comprises a tri-electrode age is positive the current generated by the valve 20 connected in a circuit acting as an second oscillator will be similar to that shown
40 oscillator to .produce an oscillating energy in Figure 12. Tice harmonic oscillating cur- 105
of low frequency such for example as 10 rent developed by the first oscillator is repre-
cycles per second. It is understood that any stinted in Figure 11. This current when nn-
customary or preferred form of circuit for posed upon the second oscillator develops. a
this purpose may be employed the partial- current such as illustrated in Figure 12 in
45 lar circuit described being provided with a which it will be seen that each positive cy-- 1D!
grid leak 21 connected with the grid 22 of cle of the first harmonic current produces a
the tube 20 and hence through a negative series of harmonic oscillations in the second
bias battery 23 to the filament 24. The fila- oscillator of substantially equal intensity
ment 24 is indicated as heated by a battery while during the negative period of the first
0 25. The plate 26 of the tube is connected harmonic current substantially no oscilla.- iii
through a battery 26' and the choke coil 25' tions are developed in the second oscillator.
to the filament 24. The plate 26 also con- The output from the second oscillator is
netts through an inductance 27 and capacity then imposed upon an audion circuit having
28' with the grid. The inductance 27 is a tube 48 with its grid 49 connected by a line
dt shunted by a fixed capacity 28 and a variable through the grid leak and grid condenser 50 12 capacity 29 in series one end of the series to an inductance 51 inductively coupled to the being connected to the end of the induct- inductance 40. Said secondary 51 is connectance 27 and the other end having. a variable ed to the filament 52 of the au (Eon 48. Shunt-connection with said inductance. Between ed across the secondary 52 is a condenser 53 these capacities 28 and 29 a lead 31 is con- of value suitable. to produce resonance with 12 neeted which connects with the filament 24 the oscillations developed in the second osof the tube 20. (dilator. The plate 54 and the audion 48 is
By this connection the constants of the os- connected by the lead 55 with the plate 15 of cillating circuit may be any value of induc- the photo-electric cell and the opposed plate
63 tance and capacity to bring the oscillating 16 of the photo-electric cell is connected by if
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a lead 56 through the battery 57 to the filament 52. The resistance 58 is shunted across the leads 55 and 56 to provide a potential for the plates 15 and 16.
c The action of the audion circuit including the tube 48 is to produce an alternating cur-rent equal to the frequency developed in the first oscillator but the wave form of said frequency is of substantially straight lines such
to for example as indicated in Figure 13. In producing this wave form the audion tube 48 operates due to the bias of the grid leak and condenser 50 to accumulate a charge during the passage of each wave train indicated in
15 Figure 12 and such accumulated charge leaks off during the interval between successive trains so that the output of the audion 40 into the plate circuit indicated by the leads 55 and 56 (passing to the plates 15 and 16 of the
20 photo-electric cells) assumes the straight line form of Figure 13.
There. is also a duplicate form of audion circuit for supplying a similar wave form of electrical oscillations for the plates 13 and
25 14 of the photo-electric cell said oscillations being however at a higher frequency such for example as 5000 cycles per second. Inasmuch as this circuit is identical except in value of constants to the circuit just described
3o the parts corresponding to those numbered 20 to 54 are numbered 20a to 54a. It is understood that the oscillating tube 20a develbps a harmonic oscillating current of 5000 cycles which will be imposed upon the oscil-
t5 lator including the tube 32a operating at 500 kilo-cycles producing a straight line alternating current in tube 48a of a frequency of 5000 cycles per second. The outputfromtube 48a to the plates 13 and 14 is from filament
o. 52a; through resistance 58a battery 57a and hence through a modulating tube 59 through the plate 60 thereof and to the filament 61. thereof and hence to the plate 54a of the tube 48a. The potential drop across resistance 58a is utilized to pro-vide the potential for plates 13 and 14 through leads 55a and 56a. The modulated tube 59 has its grid 62 connected through the negative bias battery 63 and condenser 64 with lead 56 while the filament 61 is connected to lead 65 with the lead 55. In this way the tube 61 acts to modulate the low frequency from the first oscillator circuit upon the higher frequency of the second oscillating circuit.
The 'potential for the photo-electric cell is provided by a battery 67. The negative terminal of the battery 67 is connected by a line 70 with the light sensitive plate 6 of the photo-electric cell and the positive terminal of the battery 67 is connected through a resistance 69 to a lead 68 connecting with the anode 10 of the photo-electric cell. The battery 67 has preferably a high potential such as the order of 1000 volts and the resistance 69 is of high resistance such for example as
one megohm in order that the drop across such resistance induced by the fluctuations of light in the photo-electric cell may be amplified before being transmitted. The shutter 11 of the photo-electric cell is connected by line 71 to the positive terminal of the battery 67 between the resistance 69 and the battery 67 so that it operates at the same potential as the anode 10. of the cell but its current supply does not pass through the 'resistance 69.
The effect of the potential applied to the plates 13 and 14 is to cause the electric discharge from the light sensitive plate 6 to be bent back and 'forth between the plates 13 and 14 at a frequency corresponding to the frequency of the electric potential imposed on the plates 13 and .14 (for example 10 cycles per second): The effect of the potential applied to the plates 15 and. 16 is to cause the electric discharge from the light sensitive plate to be bent back and forth between the plates 15 and 16 at frequency corresponding to the frequency of the electric potential imposed on the plates 13 and 14 (for exam- go pie 5000 cycles per second). The resulting
effect is the same as if the opening 12 of the shutter 11 was mechanically moved over the. light sensitive plate' in accordance with the. line shown in Figure 14 in which the sub- 95 stantially parallel lines indicate . the movement caused by the potential on the plates 15 and 16. The oscillations of the electric discharge in the direction at right angles to the lines of Figure 14 is caused by the potential Ica on plates 13 and 14 causing the image on the plate 6 to be traversed once every 1/20th of a second with a 10 cycle per second potential. During this period of time the 5000 cycle per second frequency imposed on plates 15 and 16 will have caused five hundred pas-sages across the image as contrasted with the other television attempts which have succeeded in securing only about thirty-five lines across the image. during the optical period. no Moreover it is understood that the frequencies imposed .on the plates; 13 to 16 inclusive mad be increased without limit (up to at least ten thousand kilo-cycles per second) giving any desired number of passages over the im- $15 age within the optical period or to make the optical period as short as desired.
There will now be described the apparatus utilized for amplifying the light current and
for transmitting such current on a wireless 120 carrier wave together with the two analyzing.oscillator currents or potentials employed on the plates 13 to 16 inclusive of the photo-electric cell. The transmitting means comprises the tube 72 said tube operating both 125 as an amplifier of the light current and as a modulator of a further tube 73 it being illustrated as in a Heising modulating-circuit. The tube 73 produces a first carrier wave of suitable frequency such for example as' of 120
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the filament 99. The tube 94 is part of a Heising modulator that has its plate 102 connected by a lead 103 through a radio frequency choke or resistance 104 to the positive terminal of battery 105 the negative terminal
of which is connected with the filament 99. The lead 103 also connects with the radio frequency choke 106 to the plate 107 of the oscillator tube 95. The choke 106 prevents the second carrier wave from being imposed 75 upon the double modulating tube 94 while the choke or resistance 104 fluctuates the potential supply to the plate 107 of the oscillator 95 in accordance with the output of the double modulating tube 94. The plate 107 connects with the lead 108 to an inductance 109 producing the second carrier wave said inductance being connected with the lead 110 through condenser 111 with the grid 112 of the oscillator tube 95. The filament 113 of the tube is connected by lead 114 through a variable condenser 115 to the inductance 109. There is also a condenser 116 between the lead 114 and the grid leak 110. The inductance is also connected with an antenna 117 or other means for radiating the output from the transmitter. The filament 113 is grounded as indicated at 118.
The receiver of the television apparatus and process is constructed and operates as 95 follows : Preferably there is employed a source of light of constant intensity such as an arc light 120 and to obtain a pencil of light therefrom there is placed a shutter 121 with
a small aperture 122 in front of the arc light. DUe The light from said shutter is then passed through a polarizer 123. The polarizer is indicated as preferably in the form of a Nicol prism. The polarized light from the Nicol prism 123 is then passed through a lens 124 105 which parallels the polarized light and the paralleled light is then passed through a de-vice 125 for rotating the plane of the polarized light. The device 125 may be any de-vice suitable for rotating the plane of the Ho polarized light in accordance with the fluctuations of the light current received at the receiver. The method of receiving and separating this light current from the transmitted wave will be hereinafter pointed out. 115 The preferred form of such device is illustrated as comprising a means for producing a magnetic field fluctuating in accordance with the light current such as the coil 126 surrounding an electrically optically active )20 medium 127 such for example as a thin film of iron cobalt or nickel or carbon disulfide glass or any other material in which. a beam of polarized light rotates considerably when subjected to a magnetic field. I prefer to em- 725 ploy carbon disulfide and said carbon disul-
imposed upon the double modulating grid. fide is held in the core of the coil 126 by glass
The analyzing potentials are imposed upon plates 128.
the grid 96 by a lead 100 which connects across The light from the light rotator 125 is then
;5 the resistance 58a and hence by a lead 101 to passed through a device adapted for restrict- 130
about 500 kilo-cycles. For this purpose the tube is illustrated as having its plate 74 connected by lead 75 with an inductance 76 the opposite end of which is connected through the condenser 77 to the grid 78 of the tube.
' The inductance 76 is tapped in the center by a variable tap 79 which connects to a variable condenser 80 and hence by a line 81 to the filament 82. The condenser 80 and the coil 76 may have any values provided that the condenser 80 and the inductance 76 are adapted to bring the circuit in resonance with the carrier wave to be produced. The line 81 is also connected with the line 77 by a con-denser 82a The grid 78 is also connected with the filament 82 through a grid leak 84 and negative battery 85. The potential for the tube 73 is provided by the battery 91 through the resistance or choke 90. The tube
o 72 acts as a variable resistance across 90 and 91 increasing or decreasing the potential drop and thereby modulating the potential on plate 74 of the tube 73. The tube 72 has its grid 86 connected by a negative bias bat-
5 tery 87 with the resistance 69 across which there is imposed the "light" potential where-by said "light" potential is amplified in the tube 73. The plate 88 of the amplifying and modulating tube 72 is connected by a line
0 89 through a choke or resistance 90 and a battery 91 the negative side of which is connected with the filament 92 of the tube 72 and also with the filament 82 of the oscillating tube 73.
J The choke 90 operates to fluctuate the potential supply to the plate of the oscillating tube in accordance with the amplified light current. In the lead between the choke 90 and plate 74 is provided a choke 92 which
u prevents the carrier wave produced in the oscillator 73 from being imposed upon the amplifying and' modulating tube 72 by the circuit thus described. The carrier wave produced in the oscillator 73 is modulated by
s the amplified light current. This potential is then imposed upon a double modulating tube 94 which operates to modulate an oscillator 95 producing a second carrier wave of higher frequency such for example as 1500
o kilo-cycles or the wave length to be transmitted.
Said double modulator tube 94 not only modulates the second carrier wave with the modulated first carrier wave from oscillator
5 73 but also modulates said carrier wave with the analyzing potentials from the modulator tube 59. The double modulating tube 94 has its grid 96 connected by lead 97 with a coil 98 the coil 98 being connected. to the filament
i9 99 of the double modulating tube. By this means the output from the oscillator 73 is
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passes through perpendicularly to the optic axis of the crystal.
By means of the polarizer 123 light rotator 125 and analyzer comprising the gratings 129 and 130 and. the hi-axial crystal 131 the constant supply of light through arc light 120 is caused to produce. a light of varying in-tensity varying in accordance" with the in-tensity of the light current supplied t& the coil .126. Thereby .without the employment of any mechanical moving apparatus the light current is reconverted into light.
Such light is then passed through a lens 132 by which it is focused upon a pair of cooperating oscillographs 133 and 134. Said co-operating oscillographs 133 and 134 are positioned at right angles one to the other and so that the light from one strikes the other oscillograph. Said oscillographs are operated at different frequencies with the result that the light is by said oscillographs projected in horizontal vibrations which are successively lowered or raised vertically so that the light-can pass through a lens 135 upon a screen 136 and covers successively an entire rectangular area of said screen. The oscillographs 133 and 134 are operated by electrical currents of the frequencies of