US2000694A - Television system - Google Patents

Description

y 1935- E. H. FELIX 2,000,694

TELEVI S ION SYSTEM Filed March 16, 1932 2 Sheets-Sheet 1 I 0 D D I: U I: D 11 I: U 1 3 c O m [@ari'ifhx E D l 13 c D VENTOR.

T:" n c Q m C U 1 ATTORNEY May 7, 1935. E. H. FELIX TELEVISION SYSTEM Filed March 16, 1932 2 Sheets-Sheet 2 r// Q 2 2mm 0 2 a w 4 A 2 a mam a L 7 m2 5 Z 2 a a a E a 8 Luw a IN V EN TOR.

Patented May 7, 1935 UNITED STATES TELEVISION SYSTEM Edgar H. Felix, Ridgewood, N. J., asslgnor to Radio Inventions, Incorporated, New York, N. Y., a corporation of New York Application March 16, 1932, Serial No. 599,179

10 Claims.

The present invention relates to an improved method of transmission and reception of moving or stationary visual images, whereby the requirements of the transmission channel are very great- 1y reduced.

Motion in the subject of a television transmission is usually confined to a very small number of the elementary areas into which the subject is divided by the scanning operation. Furthermore, only a small fraction of these elementary areas which portray such motion are caused to vary in brilliance during the motion.

In ordinary methods of television transmission, however, each elementary area is transmitted periodically with a repetition frequency exceeding the limit of persistence of vision. This may be of the order of twenty per second, and the resulting current variations in the transmission channel usually assume a relatively inconveniently high frequency. I propose to 'reducethe frequency of these variations by the method of transmitting only those elementary areas of the subject which are changed in brilliance, due to the motion of the subject, during the intervals separating successive scannings. It is evident that a relatively few impulses will be transmitted by this method, hereinafter designated as differential scanning.

The method of my invention lends itself very readily to television transmission of subjects from motion picture film, but can also be applied to "direct pick-up transmission by employing lightstoring means to secure the differential scanning.

The apparatus and method constituting my invention may be more easily'understood by refer-' ence to the drawings forming part of this specification.

Fig. 1 represents a general diagrammatic view of one form of the transmitting apparatus of my invention.

Fig. 2 shows a front elevation of a scanning disc as used in the apparatus of Fig. 1.

Fig. 3 represents diagrammatically one form of apparatus at the receiving location.

Figs. 4 and 5 show a plan view and rear elevation respectively, of a light valve or shutter et ll engaging it. Two light sources l8 and i8 such as projection lamps with appropriate condensers are shown with their optical axes spaced from each other by substantially the height of one frame of film II and projecting beams of light 19 and I9 through adjacent frames of film H. The light beams passing through the film maybe focused upon the lower edge and upper edge, respectively, of two scanning discs 25 and 25 by means of suitable objective lenses 22 and 22', casting rays through screens 23 and 23 provided with apertures 24 and 24' so as to form upon these edges images of adjacent frames of the film. A mask 20 parallel to the film and provided with two relatively wide slits 2i and 2| perpendicular to the direction of motion of the film may be placed near the film to prevent undesired stray light impinging upon the scanning discs 25 and 25 A main shaft 26 is shown with a two-speed clutch at the lower end. This clutch includes driven clutch member 21 with sliding key to shaft 26 and carrying two clutch faces 28. Clutch member 21 may be moved along shaft 26 by controller rod 29 with handle 29 so as to engage either of driving clutch faces 30 or 3! for fast or slow operation respectively. Fast clutch face 30 may be mounted directly upon the shaft 32 of motor 33, which may preferably be of the synchronous type and may be provided with a switch 34 for determining its connection to power lines Slow clutch face 3| may be caused to rotate at a relatively slower speed but in the same direction as fast clutch face 39, through the medium of a reducing gear train 35, 36, 31 and 38, which last gear is'fixed upon shaft 32 of motor 33. All clutch faces may preferably be provided with a large number of double-sloping teeth in order to insure registration'when the clutch is shifted.

In this clutch shifting mechanism the member 21 should be shifted with great rapidity in order that no time should lapse sufiicient to allow a dephasing of. the mechanism during this shift. With this end in View these double sloping teeth are designed so that the probable angle of dephasing which has time to occur during the brief interval when there is no coupling between member 21 and either one of the driving gears thereof, i. e while it is being shifted, shall be less than the angular spacing of these teeth.

Accordingly when a shift is made, the sloping teeth will engage and during the process of forcing the teeth into complete engagement the correct angular relationships will be restored by the force which impels these teeth into engagement bein transformed, in as far as needed into a rotational force, by this above action of the teeth.

Shaft 26 carries affixed thereto a bevel gear 39 Which engages another bevel gear 40 thus rotating a shaft M, which latter carries at its other end bevel gear 42, meshing with another bevel gear 43 fixed upon another shaft. This last shaft carries at its other end bevel gear 45 which meshes with a bevel gear 46 upon the same shaft 45 which carries sprocket Shaft 26 also carries another bevel gear 41 engaging a gear ll upon a shaft'48, upon'which latter is mounted scanning member 25.

The other scanning member 25 is rotated in a contrary direction to the rotation of member 25 by means of a motor 48'. This motor ispreferably synchronous with motor 33 and operated from the same power source through a controlling switch 59, to aid in securing this synchrony. It is also possible to mechanicallycouple member 25' to the same driving sourceas member 25, in

lieu of employing synchronous motor 48 to electrically couple them together, but the electrical coupling is preferred, since the phase of the power lines is likely to change to a lesser degree when a sudden load is thrown upon them, than is the speed and/or angular displacement of a Single rotating member. The effect of this connection to the power lines may be considered equivalent to that obtained by the use of a large electrical fly-wheel in order to maintain stability of the speed of rotating members.

Main shaft 26 may also carry fixed thereon a bevel gear 55, engaging another bevel gear 5| fixed on countershaft 52. A plate cam 53 may also be fixed upon this countershaft, the face of the cam being shaped to move a roll follower 54 with substantial constant velocity of lateral displacement away from the axis of said cam, and then to allow this follower roll to be impelled by a suitable retractile spring 56 acting through intermediary members hereafter described so as to return substantially immediately to its initial position. This cam should preferably rotate one half a revolution during the time that one frame of film I is being scanned.

Roll follower 54 may move a reciprocating arm which may slide in a longitudinal guide (not shown) and be impelled toward cam 53 by a suitable tension spring 56. Arm 55 may carry a wedge shaped member 51 and a suitably insulated contact 58. This contact is so arranged as to momentarily touch another and fixed contact 59 during the longitudinal motion of arm 55. A trigger 58 slides in a mount BI and is urged toward arm 55 by compression spring 62. It also has affixed thereto a limiting stop 63. Mount 6| may move in a guide member 54, and when the mount is in its uppermost position a. trigger Eli] affixed thereto will be in the path of wedge member 57 during the longitudinal transverse of the latter. When mount 6| is moved to its lower position by means of a handle 65, with which it is provided, trigger 80 will not contact wedge member 51.

A suitably insulated contact 86 is affixed to mount SI and makes connection with a fixed contact 61 when mount BI is in its uppermost position.

Controller arm 29 is pivoted upon an axle 68 and carries an insulated contact 69 which makes connection to another fixed contact 10 whenthe controller arm is moved to the high-speed position, i. e., when the portion bearing contact 59 is raised. An electro-magnet 1| is suitable and fixedly mounted and urges controller arm 29 toward its high speed position when the electromagnet is energized, by reason of its action upon an iron armature 12 which is suitably fixed upon the controller arm 29. A spring latch 13 with handle 14 and retractile spring 14 may be provided to lock the controller handle in high speed position until released by actuation of this latch.

A tension spring 15 moves controller handle 29 to the slow speed position and holds it there when no other forces are acting upon it.

The light transmitted through the active aper tures of scanning discs 25 and 25' falls upon "photo- sensitive devices 16 and 16 respectively,

and the resulting-electric currents flowing in the photo-sensitive devices may be fed into suitable amplifiers TI and H, thence into the two primary-windings l8 and 79' of a transformer 19 which may be preferably of the powdered iron coretype or any other type suited for aflwide range of frequencies.

Primary windings l8 and 18 are wound in opposite directions upon the core 80 so that they electrically oppose each other, and the resultant primary magnet-motive force acting on the core (and therefore the voltage across and direction of flow in the secondary winding 8|) is at any instant dependent on the difference between the currents in primary windings l8 and 18.

This device provides the differential scanning partially described heretofore, so that elementary picture areas of the same density in two adiacent frames of film I do not produce any voltage impulse in secondary winding 8|. However, elementary picture areas of different densities in two adjacent frames of film produce in secondary winding 8| a voltage impulse whose direction and magnitude depend on the relative densities of these elementary areas which determine the primary currents.

Primary winding 18 may be open circuited and made inoperative when the pair of contacts 59 and 70 in one primary lead wire are opened. The secondary winding 8| may be connected to a modulator-amplifier 82 which may serve to modulate a transmitter 83 whose output can be fed to an antenna 84 for radiation to the receiving station, or can be transmitted thereto over suitable physical conducting channels.

A constant frequency oscillator 85 is shown, which may provide a substantially continuous voltage of suitable frequency across its terminals 85 and 81. A relay 88 tuned to the frequency of oscillator 85 as shown, whose construction may be such that it causes to be supplied from power source 88, a suitable current sufficient to operate electro-magnet Tl, which pulls up controller handle 29 when the relay input terminals 89 and 9B are connected to the oscillator 85. The oscillator may be connected simultaneously to the tuned relay 88 and to the input of modulation-amplifier 82 by the closing of the two pairs of series contacts 58, 53, and 61.

Referring now to Fig. 2, a disc 25 of sheet metal, paper or other suitable material is shown with a plurality of equally-spaced radial slits 9| arranged about its periphery. A stationary mask perforated with a narrow cross-slit 24 may be positioned close to the disc or close to the film to delimit elementary scanning area 84 in a radialdimension. Each of the discs 25 and 25 shown in Fig. 1 may be of this construction and identical in size or they may be of different sizes,

' rent.

or may be provided with difi'erent numbers of radial slits 9! if rotated at proper relative speeds. Other scanning constructions may be used, as will be apparent to those skilled in the art. For example, the radial slits and cross slits of Fig. 2 may be replaced by a plurality of equally spaced scanning holes arranged in a circle concentric with the center of the disc.

Radially-slitted discs 25 and 25' may also be replaced by longitudinally-slitted drums. Likewise a plurality of equally spaced scanning holes may be arranged in a spiral about the discs, and the film H of Fig. 1 moved by an intermittent mechanism, in which case the masks 20, 23 and 23' of Fig. 1 should be removed.

Referring to Fig. 3, an antenna 203 is shown for intercepting the signal sent from the transmitter. A radio receiver indicated at 204 is actuated by this signal and operates uponand delivers it to output terminals 214 and 215 as an amplified and pulsating direct current through a suitable shunting resistor 2H5. A coupling condenser 2l1 allows only the alternating component of this pulsating direct current to flow through any load circuit which is in series with the condenser. Alternatively a transformer may serve as a selective device in the place of resistor 216 and condenser 2", so as to transmit only the alternating portion of the output our- A tuned relay 288, electromagnet 211, armature 212, and controller rod 229 may be identical in structure and operation with the corresponding parts similarly numbered in Fig. 1, as may be also mechanical latch 213, spring 213, spring 215, pivot 268, motor 233, a two-speed clutch mechanism and a main driving shaft 266. Motor 233 should preferably be of the synchronous type and operate from the same power supply mains as does motor 33 of Fig. 1 or else be made to operate synchronously therewith.

A variable resistor H9 and switch 234 may be inserted in series with the motor supply leads to allow framing of the scanning device, according to principles well known in the art.

Main shaft 226 carries fixed thereon a brush arm 265 which receives current through a stationary brush 286 and slip ring 261, and delivers it through wire 269 to the distributing brush 210. This distributing brush makes connection with individual contacts 240 arranged around a circular commutator ring 24!, and each contact may be connected through a wire in a cable 242 to a light valve or light shutter 243 in a scanning rack 244. This scanning rack is diagrammatically indicated, as such light valve devices are well known in the art. The sequence of wiring to the light shutters 243 should be such as to connect distributor brush 210 to the light shutters 243 in the desired scanning order, as brush arm 265 revolves. The alternating current signal supplied through resistor 2l6 and coupling condenser 211 may also be delivered to the tuned relay 288, as well as to the scanning rack 244 through commutator contacts 240.

A fixed light source H8 is shown, which may be for example an incandescent projection lamp with a suitable large condenser lens 245 so as to distribute light substantially uniformly over scanning rack 244. Light passing through the aperturesof this scanning rack may be focused upon viewing screen 246 substantially as an image of optically active portions of the scanning rack, by means of an objective lens 241.

Referring now to Figs. 4 and 5, an individual single light valve or shutter 243 of which a plurality may be used in scanning rack 244 is shown, with polarized (permanent steel magnet) armature' 248, which slides freely along metal guides 249 and 243" except as restrained by the uniform friction of'two end shoes 250 and 250' made of material such as felt. An electro-magnet comprised of an iron core 25!, pole pieces 252 and 252' and coil 253 provides a magnetomotive force when energized, which causes armature 248 to move to positions of greater or less proximity to said pole pieces, depending on the direction, duration, and magnitude of current flow in coil 253. Terminal lugs 254 and 254 may be provided for making current connection to this coil. One lug 254 may be insulated and connected to a single commutator contact 240 of the commutator-ring in Fig. 3, while the other lug 254' may be grounded to the frame of the light valve 243. The individual light valves in scanning rack 244 may be mounted upon vertical metal rods 255 by means of screws, and rods 255 may be supported at each end so that the light valves 243 lie in parallel rows both vertically and horizontally, this forming the elements of the picture being received. This picture will consist of elementary white areas of graded size upon a dark background, the various sizes of white areas delivering the pictorial images to .be reproduced.

A light valve of the character above described.

is able to distinguish not only between currents of different magnitudes but also between currents of equal magnitude with different directions or phases. Currents of opposite phases will cause movements of the light valve armature in opposite directions thus allowing discrimination between changes at the transmitter of light values in the object to be transmitted, i. e., Whether such changes are from light to darkor dark to light.

Referring now to Fig. 6, a short length of moving picture film H is shown as prepared for transmision by the apparatus disclosed herein. It is desirable to provide at the starting end of the film a series of approximately twenty solid black frames l2, interspersed between the successive picture frames l3 for a purpose hereinafter explained. In all other respects the film maybe identical with standard moving picture film.

There are three important functional operations in the performance of the apparatus of my invention, namely (1) erasing any existing image from the receiving screen (2) setting up a new scene and (3) transmitting the action of the scene. These operations may be repeated in the above sequence each time a reel of film is transmitted. It should not be necessary to repeat them during the transmission of a reel if the action of the film story is shifted slowly from one scene to another, i. e., if novery abrupt changes in the scene occur, but they may be repeated whenever necessary. The first and second operations each take up the time of one frame of film run at slow speed, while the third operation may continue for an indefinite number of frames of film run at high speed. In accordance with the principles of this invention a speed change from slow to fast is required between operations(2) and (3), and a speed change from fast to slow between operations (3) and (1). No speed change is required between operations (1) and (2) in the sequence, so that these two operations may be repeated indefinitely for image-framing purposes,,without affecting the general sequence.

The operation of the transmitting apparatus is as follows: After light sources l8 and I 8 are turned on, a reel of film is placed upon idle reel 14 of Fig. 1, and threaded over idle spool l6 and film sprocket ll to take-up reel [5. Start marks on sprocket I! and on the film indicate the proper relative position of these two parts to obtain correct action of cam 53 at a later instant. Handle 65 of trigger mount BI is then pushed down manually, automatically opening contacts 66 and so that the output of oscillator 85 is positively disconnected from the other circuit of the apparatus. Latch I3 is then unlocked manually by means of handle 14, allowing the controller rod 29 to assume the slow speed position under the action of tension spring 15, and also automatically opening contacts 69 and 73 thus preventing any current flow in primary winding 18'. Motor switch 34 and 49 are next closed manually. The film II and disc 25 now operate at slow speed, and disc 25 at high speed, the electrical output of disc 25 being terminated at the open contacts 69 and 10. A slow picture signal is transmitted from photo-sensitive device 75 through amplifier 11 to primary winding 18, secondary winding 8|, modulatoramplifier 82, transmitter 83 and to antenna 94.

The slow speed may be made as slow as desired in order to reduce the frequency of the resulting picture signal; for example, if the slow speed is one twentieth of the high speed, a picture signal frequency approximately one twentieth of that provided in high speed scanning will be obtained.

The operation of the receiving apparatus will now be substantially as follows: The receiver 204,

light source N8, and motor 233 of Fig. 3 are turned on and the latch 273 is unlocked manually by means of handle 214, allowing controller rod 225 to assume the slow speed position under the action of tension spring 215. The signal from the transmitter is received as alternate frames of darkness and picture upon viewing screen 246. Each black frame transmitted causes all of light valves 243 to be completely closed, and each picture frame transmitted causes each light valve 243 to open to the proper aperture for portraying the elementary areas scanned at the instant it is connected to distributor brush 210. However, the resulting slow moving image will usually be out of frame, i. e., not properly timed with respect to the scanning action at the transmitter, and the observer may bring the picture in frame vertically by opening motor switch 234 for a suitable short interval and then closing it again. The observer may also bring the picture in frame horizontally by varying the resistor 219, causing a slight mechanical phase shift or phase rotation of motor shaft 253, or other well known methods of framing may be used.

These adjustments may in practice require from 10 to 20 seconds for their completion. The receiving apparatus is now ready for operation (3) of the sequence heretofore described.

At the transmitter (Fig. 1) when the last black frame of the film has just been. completely scanned by disc 25, the handle 65 of trigger mount 6| may be pushed upward manually, closing contacts 66 and 6'! and bringing trigger 69 into operating position. This should be done at an instant when arm 55 and its wedge member 5'! are just starting on its travel away from cam 53, and at the instant that the first picture frame succeeding the last black frame has been completely scanned by disc 25. Contact 58 will touch contact 59 and momentarily connect oscillator 85 to modulator-amplifier 82 and to tuned relay 88. Contact 58 continues to move with arm 55, breaking its connection with contact 59, and when arm 55 has completed its travel away from cam 53 the trigger 60 engages catch 51 and holds the arm locked.

During the instant that oscillator 85 is connected, tuned relay 88 operates electro-magnet H and the controller handle 29 is drawn quickly to the high speed position, locking in that position by the action of latch 13. At this instant a portion of the energy from oscillator 85 is conveyed to the modulator-transmitter and radiated to the receiving station.

Similarly at the receiving apparatus (Fig. 3) this momentary oscillatory signal is received and causes tuned relay 288 to operate electro-magnet 2H, drawing controller rod 229 to the high speed position where it is automatically locked by latch 213.

The change from slow to high speed operation should preferably occur in the shortest possible interval of time, and without losing synchronlsm between the transmitting and receiving apparatus. Even if the first one of two lines of the received image are distorted or totally lost during the transition, the remainder of the image will not be affected. Those rotating parts which must change in angular velocity during the transition should therefore be of light-weight construction, and motors 33 and 233 at the transmitter and receiver respectively may be provided with flywheels upon their shafts to prevent their dropping behind by one or more poles during the transition period. The rotors of motors 33 and 344 may drop back slightly in angular position during the transition without slipping a'pole.

The contacts 89 and it (Fig. 1) are closed when controller rod 29 is moved to the high speed position, and photo-sensitve device 16' is thereby connected through its amplifier TI to primary winding 18'.

The differential signal now induced in secondary winding 8| and transmitted to the receiver is dependent solely upon the algebraic differences between corresponding elementary areas in successive adjacent frames of film ll, since these corresponding elementary areas are scanned in exact synchrony. Consequently only a comparatively small number of signal impulses are transmitted in depicting the motion of the picture.

' At the receiver (Fig; 3) the brush arm 265 now rotates continuously at the synchronous high speed and connects periodically the picture signal to each light valve in the proper scanning order. Any signal impulse received causes the proper light valve or valves 243 to be increased or decreased in aperture according to the amount of the density changes in the corresponding elementary areas at the transmitted film, and reception continues as long as the signal is received. When the end of a film reel is reached, the sequence described above may be again repeated.

Other methods of speed-changing than that above described may be used, such as synchronous motors at the transmitter and receiver, both operated from a power supply whose frequency may be varied gradually for changing from slow to fast operation or vice versa.

While I have described certain apparatus for the operation of a television system according to my invention, I do not limit myself to the specific instrumentalities therein described for the accomplishment of television transmission according to the system of my invention.

Other means will be apparent to those skilled in the art, whereby the purposes of my invention may be carried out and I am accordingly only limited by the scope of the hereunto appended claims.

I claim:

1. Apparatus for transmitting moving images including means for reducing the apparent motion thereof to a degree substantially below the point of persistence of vision, transmitting said image at a similarly slow rate of speed, reproducing said image at a correspondingly slow rate of speed, and then raising the rate of motion of said image to normal, transmitting only the portions of said image which are moving, and altering said first reproduced image in accordance with the portions thereof which are in motion.

2. In television transmitting apparatus, means for scanning successive frames of motion picture film simultaneously, means for translating said scannings into electrical impulses, means for opposing said impulses so that similar ones are cancelled out, and means for transmitting only such impulses as are not cancelled out.

3. Television apparatus including a transmitter operating upon motion picture film first at a speed below the limit of persistence of vision and then at a speed above the limit of persistence of vision, including a speed change device acting to change from the first of said speeds to the second of said speeds and means for transmitting, at the higher speed, only changes occurring in the subject matter of the film transmitted at the slower speed.

4. A television transmitter including means for simultaneously scanning two successive motion picture images, means for differentially combining said scannings and means for transmitting the differential results of said scannings.

5. In television apparatus, the method of reducing the total number of signals required for each single scanning of an image, including transmitting said image at slow speed and then transmitting at higher speed only the portions of said image which change between successive scannings thereof.

6. In television apparatus for scanning motion picture film, means for scanning adjacent frames simultaneously and in identical manner, means for producing thereby simultaneously occurring electrical impulses, means for combining said impulses so that identical impulses are suppressed, and

means for transmitting the resultant of differing impulses.

, 7. In television transmitting apparatus means for scanning at one time an optical image and an optical representation of said image as it existed at a previous instant, means for translating said scannings into electrical impulses, means for opposing said impulses so that similar ones are cancelled out, and means for tran mitting only such impulses as are not cancelled out.

8. Television transmitting apparatus employing the method of transmitting images having the appearance of motion over channels of communication incapable of transmitting frequencies high enough to portray all portions of said images upon each individual reproduction thereof, including means for simultaneously scanning a plurality of frames of motion picture film, means for producing electrical impulses from the picture element scanning, means for balancing out the electrical impulses caused by identical picture elements in said frames and means for transmitting only the electrical impulses caused by nonidentical picture elements in said frames.

9. Television transmitting apparatus comprising two discrete scanning devices driven simultaneously, electro-optical translation means giving rise to electrical impulses correspondant to the picture element scannings, electrical means for combining said electrical impulses so that identical simultaneous impulses are suppressed and a signal is produced corresponding to the difference in the light values presented by the two scanning devices, a single communication channel and means for transferring said differential signal to said channel.

10. Television transmitting apparatus comprising means for simultaneously scanning two motion picture frames, means for deriving electrical signals from said scannings, means for producing a differential signal from said scanning signals, means for combining said differential signals and means for transmitting a signal corresponding to the difference between the light values of the two frames, said scanning means and said differential producing means having operative speeds automatically remaining proportional to one another when a change occurs in one of said speeds.

EDGAR H. FELIX.

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