US1751584A

US1751584A - Picture transmission

Info

Publication number: US1751584A
Application number: US212803A
Authority: US
Inventors: Clarence W Hansell
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1927-08-13
Filing date: 1927-08-13
Publication date: 1930-03-25
Anticipated expiration: 1947-03-25
Also published as: NL26557C; GB295601A

Description

Mrch 25, 1930.

C. W. HANSELL PICTURE TRANSMISSION 3 Sheets-Sheet 1 Filed Aug. 13, 1927 a w n w mnm 50E? 5 m5 INVENTOR CLARENCE W. NISELL Patented Mar. 25, 1930 a This invention relates to picture transmission, and includes methods which may or may not involve the intermediateuse of electrical energy.

' It is an object of my invention to make possible the, transmission of radiant energy, m a curved path, and this I do by employin .a conductor composed of transparent su stance having'a large critical refractionangle, such as quartz, andliending the conductor to follow fliedesired path.

- It is a further object of m invention to control the concentration 0 energization, that is, to make possible a change in intensity as well as a change in direction of radiant energy during its transmission, and this I do by suitably varying the cross section of the quartz conductor.

It is a further object of my invention to :0 make a conductor for radiant energy which shall be relatively flexible, which I do by buildingup a cable out of so many relatively fine strands of quartz that the resultant cable is sufiicientl flexible for the purpose desired. ,Such 9. ca le is not merely suitable for con-' ducting radiant energy but also for transmitting and reproducing radiant energy of varyin intensities, for-each strand 1. 1%"- lated m the adjacent strands, and there'- ac fore the "intensit ""doesnotaverage. In effeet, then, the ca le becomes a icture transfer cable, which may be apphed to .a wide range of uses. For example, such a cable may be used for tra'nsferring' theirjeading. of instruments from inaccessib to accessible locations, as the reading of a gasoline gage .from the gas tank to the dashboard of an automobile. Or it may be used by surgeons for examining inaccessible internal parts of a the body, or by mechanics to examine in- "visible interiors of complicated castings, or in war time as a flexible penscope 'I shall more particularly describe the use of such a cable in connection with picture I45 transmission over reat distances through the intermediate use 0 electrical waves. In such 3 picture transmissionitis customary to have movable means to scan the picture to be reproduced, and the resultant picture cons sts of the of a large a I r I rrcruna'ramsmssron cell has proved troublesome, an

number of such ."uurrsb .sr TEs, PATENT OFFICE CLARENCE 'W. EANSELL, OF ROCKY POINT, NEW YOiK, ASSIGNOB 1'0 RADIO CORPORA- 'lION OF AMERICA, .5. CORPORATION OF DELAWARE Application filed Augult 1a, 1927. Serial No. 212,503.

scanning movements. To transfer the light from the scanning means to a (photo-electric for this purpose my invention is especially a plicable.

The time for transmission 0 a complete picture depends upon the total number of scanning movements necessary to integrate the picture, and to reduce the necessary number of scanning movements is a furtherob-- ject of my invention. This I propose to so do by utilizing a multiple scanning means,

and a plurality of photo-electric cells arranged to control a multiplex transmitter. For simultaneously scanning a pluralit of ad acent pomts in picture transfer cab e is 05 especially useful, or at each end the strands m be separated and an sitioned as desired,

the -flexibility of t e'intermediate cable i I the picture is moved, the cable permits of picture' transmission from closely points to se arated photo-sensitive es s located 'out o the normal direct path of the nor. a

i -To increase the speed of intelligence trans-'1. mission eflorts are being made to employ facsimile reproduction instead of tele aphic code. For this purpose in multip e scan- 59 .nin device is well applica le,'for the ends of t e cable strands mayibe arranged to simul tive secrecy of signalling, fononl stations 05 properly 'uippe will be able to ecode the j transmitte si als. Furthermore, b V the use of my special cable the relative or or of permits movement of the scanning means, or-if the scanning means are stationary and j ad'acent I -'radiant energy, a very convenient man- 75,

the scanning linesmay be mixed up as desired at th' transmitter, and only i the r a 14; :"f'f i Q sensation of heat.

very similarly to the transmitting means except that in place of the photo-electric cells there are light sources independently responsive to the electrical signals received over the various signal channels, and light from each of these sources is impressed upon the separated ends of the strands of a quartz cable. The other end of the cable is formed into a multiple printing means which is placed in transverse juxtaposition to a light sensitive surface on which the facsimile is printed.

The invention is described more in detail in the following specification which is accompanied by drawingsin which Figure 1 shows a conductor of transparent material characterized by a largecritical angle of refraction;

Figure 2 indicates a cable composed of a large number of strands of such material;

Figure 3 represents the scanning end. of a cable used for facsimile transmission;

Figure 4 is a cross section of such a cable having a flexible core; I Figure 5 is a cross section of a cable as in Fi re 4 wherein each strand is itself a cable;

igure 6 shows how the terminae may be formed into convenient shapes of desired cross section area;

Figure 7 schematically indicates both a scanning arrangement at a transmitter, and

a rinting arrangement at a receiver;

igure 8 is a wiring diagram for a. trans,- mitter;

Figure 9 is a wiring diagram for a receiver;

Figure 10 is a transmitter for frequency modulation; and

Figure 11 is a receiver for frequency modulated signals.

Referring to Figure 1 it is seen that radiant energy from a source 2 is impressed on a transversely cut end of a conductor 6. I This conductor is preferably made of fused quartz but may be made of glass, though with less satisfaction, or of any transparent substance havin a large critical angle of refraction, so

are refracted, somewhat as indicated by t e dotted lines in the figure. If the curvature is not made too shar the radiant energy is entirely confined-an is emitted at the other end 8. Ba-

" w diant heat energy is transferred as well as lighlfiiher an experimentally, the remote end of sue a rod ma be used to ignite paper even though the con uctor is quite cool along its surface, and may be held without any The radiant energy in such a conductor is mixed up and averaged out at the far end. If it is desired to transmit radiant energy of varying intensities and to reproduce equivalent energies at another point a cable may be formed, as is indicated in Figure 2. If the cable is used for picture transfer it is obvious that the fineness of detail will depend upon the cross section area of theindividual strands. The cable may be twisted, but for picture transfer the strands should keep their relative position. Such a cable consti! tutes a simple means for looking around 'cor-' ners and complicated curves, and is very useful when circumstances are such that reflecting prisms or mirrors cannot well be used. hasalready been mentioned, it may be used for transferring the readings of gages, :or for any number of inspection pur ses.

I intend more particularly to emp oy the cable for picture and facsimile transmission. Fi re 3 indicates a cable intended for multipTie scanning where a five channel multiplex signal system is to be used. There is a scannin head 14 within which there are clampe the ends of five parts of the quartz cable 16. a

For increasing flexibility a core of more flexible material may be used as indicated in Figure 4, the quartz conductors 18 being wound upon a core 20. Also each of the conductors 18 may itself be a cable com osed of a lar e number of fine quartz threa s which may e arranged indiscriminately, as indicated by the cables 22 formed upon the core 20 in Figure 5.

In Figure 6 there is shown a conductor the end 10 of which has been formed into a desirable shape for scanning a line of a picture, while the other end 12 has been enlarged to pzrmit the light picked up at the end 10 to impressed uKon a greater area of a photobe ex osed to a fluctuating light source, whilethe light is then greatly intensified and reproduced at as small an area as desired for the photographic printing 1 Referring to Figure 7 t ere is a drum 30 on which a picture 32 is fixed. The drum ma be transparent, and illuminated from wit in. The cable 16 terminates at one end in a scanning head 14 which is reciprocated longtudinally of the drum 30 by a reciprocating carria e 34. Mechanism is provided so that at eac reciprocation of the carriage 34 the drum 30 is rotated a distance equivalent to the spacin between the lines of type, in the case of acsimile transmission, but in the 'case of picture transmission the rotation is equivalentto the effective width of the scannin head 14..

It is t ought not necessary to describe the mechanical details, nor the method of synchronizing the transmitter and the receiver The cable 16 leads to an enclosure 36, within which there are located hoto-electric cells and associated circuits whrch are further described in connection with Figures 8 and 10.

In Figure 8 the five ends of the quartz cable, numbered 22, are suitably enlarged and conyeniently separated, and each is placed m uxtaposition to a photo-electric cell 40.

The cell 1s in series with a resistance 42, and

thence, by way of the conductor 44, with a source of constant electromotive force C. As the resistance of the cell is altered according to the light sensitization impressed thereon the otential at a point betweenthe cell 40 and t e' constant resistance 42 fluctuates, and this potential fluctutation is im pressed on the grid of an electron emission tube 46. There are five such tubes, and the anode circuits of these tubes are provided with rela; coils 48 which influence armatures 50 to ma e and break the circuits of the alternating current sources 52, which each have difi'erent frequencies, indicated by f f f,, f., and f,, each representing a separate sign channel. The alternating current sources may be miniature rotary converters, or rotary frequency changersenergized from a single alternating current line.

The complex wave *representing the sum at any instant of the waves of frequenc f,, f,, etc., 1s transferred over a line 54, w 'ch may a long land line leadin from the transmltter to the receiver, in t e case of a wire transmission, or from an urban oflice to a suburban transmission station, in the case of radio transmission.

' At the radio transmitting station there is a source of carrier frequency 56, which preferably 1s crystal-contro1led by a crystal 58. The carrler energy is supplied symmetrically to a push-pull modulator 60, as shown in the wiring diagram, and in consequence of this the carrier 1s ehminated from the output 62, and only the two side bands and the on al modulating frequencies are produced. i filter 64 is arranged preferab y as a high pass filter with cut-off at the carrier frequency, so that the modulating frequencies'and the lower side band are ehminated. The upger side band is amplified b a power amp i er 66, the output'from w ich is radiated by means of an antenna system 68, the exact form of which will depend on considerations The transmitter has been described in such as frequency and directivity.

simple form, and it is clear that the,use of relays such as 48, 50 is probably only for facsimile transmission, because such relays do not reproduce the varying shades of light characteristic of a picture, t either make or break, according as the picture is dark or light. In the case 0 picture transmission it is preferably toobtain modulation rather than make or break,and to do this we may amplify the energy output from each tube 46 and use it to modulate ener of frequencies f etc., or we may use t e simple direct in ulation sch'eme shown in the left hand portion of Figure 10. The modulation of these land line fre uencies will then be reproduced in the si e band at is, they finally transmitted from the antenna sysy tem 68.

Fi ure 9 indicates a receiving circuit in simp e form. The signals are picked up on an antenna and are transferred through a coupling 72 to a rectifying tube 74. A heterod mug current is supplied from a a source 7 6, which preferably is'crystal controlled by a crystal 78, and combined with the incoming wave by means of the coupling 72 and the rectifying tube 74. The heterodyning fre uency may equal the carrier frequenc at t e transmitter, in which case'the beat requencies will equal the frequencies f f etc. To so do is convenient, but not necessary, for if the heterodyne frequency is different the beat frequencies will be f 1 etc., which will differ from each at or by the same amountsas the etc. I

The complex low frequency wave may be amplified by an amplifier 'and then, conveyed over a land line 82 to a reproducing means located wherever convenient. In the case of wire transmission the line will be the line 82, connected to the line 54 in Figure 8. At the end of the line there may be an amlifier 84, the output of which is coupled to Eltersf86 each of whichis adjustedtoselect oneof the frequencies f f etc. The output of the filters 86 may be amplified by amplifiers 88, and then used-eitherindirectly,

frequencies )3, f2,

or directly, as shown, to ener 'ze 1i ht sources 90. These are exposed to e en 22 of a picture transfer cable such as was used at th transmitting station.

is reciprocated by a carriage'34 across a photo sensitive surface 32 mounted upon a drum 30. 1

It is clear that if the reciprocations of carriage 34 at the transmitter and at the receiver occur even relatively crudely in synchronism the facsimile will be reproduced with suflicient fidelity. i r

Another arrangement for transmission is indicated in Figure 10, in which it is seen that the ends 22 of the strands of a light cable are ositioned before light sensitive cells 40, as in igure 8. The cells, instead of being connected in series with a direct current source, are in series with alternating current 70 is coup sources 52,having frequencies f ,f ,etc. Each cell being essentially a variable resistance this arrangement results directly in amplitude modulation of the alternating energies. The modulated signal ener ies are preferably amplified in the am lif ying tubes 102, the output from which is coupled by means of the transformers 104 to a common bus 106 to which a land line 54 is connected.

As so far described this arrangement provides a complex signalling wave the com onent energies of which are modulated rat er than completely cut off, and the land line 54 may be connected to a carrier suppression modulator such as was described in connection with Figure 8. However, in some cases it may be desirable to use frequency modulation, rather than amplitude modulation, and in such a case the signal energy from the land line 54 in either Figure 8 or 10 is led to a frequency Wobbler.

This has been shown in Figure 10, wherein the oscillator 110 has for part of the reactance of its resonant circuit 112 the radio frequency winding of a magnetic Wobbler 114. The land line 54 is connected to the saturation winding of the Wobbler. The frequency F; of the frequency modulated oscillator 110 may be a transmission frequency, or it may be: an intermediate frequency which is then used to modulate energy of a higher frequency F generated in a constant frequency oscil ator 116. The energy from this oscillator is coupled symmetrically through radio frequency condensers to a push-pull modulator stage 120. The frequency modulated energy of intermediate frequency is used to modulate high frequency energy, and of the two resulting side bands the filter 64 selects one, which may then be amplified in a power amplifier 66 and radiated from an antenna system 68.- The side band is constant in amplitude because the intermediate frequency energy is constant i1} amlplitude, while-the mean'frequency F ility of the high frequency oscillator 116, which preferably is crystal controlled.

A receiver for frequency modulated si nals has-been shown in Figure 11, in whic the energy gicked up by the antenna system e to the input circuit of a combining tube 74, to which there is also coupled an oscillator 76. The local oscillator ma supply ener of frequency F in whic case there wil result a beat frequency equal to the transmissionintermediate frequency F but this is not an essential condition. The intermediate frequency energy is amplified i. an amplifier 122, the output from which is coupled to an analyzing circuit 124. This is a resonant circuit the fre uency of which is adjusted to lie to one si e of the operating range of intermediate frequency supplied to is quite uniform because of the sta-' energy is directed towards the ends 22 of a light cable 16, as has already been described in connection with Figure 7.

The systems described are relativel secret because an intercepting receiver wi l have to exactly duplicate the actual receiver employed. Even with'make and break signalling, as is shown in Figure 8, ordinary receivers will be unable to multiplex and unable to decode the equivalent dots and dashes of a single scannin line. The secrecy may be further increase by rearranging the relative order of the scanning lines in a similar manner at both the transmitter and the receiver.

It is clear that the arran ement disclosed herein may be used on lan lines as well as with radio systems. Any convenient number of signal channels may be employed. Any type of multiplex transmitter and receiver may be utilized, whether employing frequency or amplitude'modulation, and I shall therefore use the term modulation broadly, intending it to include both.

I claim: 7 1. In combination, a source of radian energy, a device located out of the normal direct path of said radiant energy for response thereto, and means to convey said energy from the source to the device com rising a flexible quartz conductor ca able 0 being moved relatively thereto, sai conductor having transversely cut ends located in juxtaposition to the source and the device.

2. In combination, a surface to be scanned, scannin means including one end of a relatively exible strand of quartz, means provide by said flexibility for permitting movement 0 said scannin means relative to said surface, hoto-electrlc means responsive to the light intensity of said surface, and means comprising the aforesaid strand of quartz to convey' the light from the surface to the photo-electric means.

3. In combination, a surface to be scanned, scanning means including one endof a relatively flexible quartz cable having a plurality of strands of quartz for scanning a redetermined number of unit areas of sai surface, means provided by said flexibility of Cable for permitting relative motion between said' scanning means and said surface, photo-electric means responsive to the light intensity of said quartz cable to convey t tively flexible quartz cable having a plurality of strands of quartz, means to move said scanning means over said surface, a plurality of photo-electric cells responsive to the light intensity of the portions of said surface scanned by the strands of said cable, and means comprising the aforesaid cable to convey the light from said surface portions to the cells.

5. In combination, a surface to be scanned, scanning means including one end of a relatively flexible quartz cable having a pluralityof strands of quartz, means to move said scanning means over said surface, a plurality of separated photo-electric cells res onsive to the light intensity of the portions 0 said surface scanned by the strands of said cable, and means comprising the aforesaid cable to convey the light from said surface portions to the cells, the strands of said cable being spread apart at one end and positioned separately adjacent the cells.

' 6 A picture transmission system comprising multiple scanning means, a plurality of photo-electric cells, a plurality of quartz conductors for conveying light from the multiple scanning means to the ce Is, a multiplex transmitter having a plurality of signal channels,

. ling on the several channels inaccordance and means controlled by the cells for signalwith the light intensities impressed on the multiple scanning means.

I. A facsimile transmission system comprising a plurality of photo-electric cells, a plurality of strands of quartzone set of ends of which are superposed transversely of a hne of print for scanning the line in a single scanning movementand the other ends of which are conveniently'separated and increased in area for cooperation withthe plurality of photo-electric cells, and amultiplex transmission system the several signal channels of which are independently controlled by said cells: a

8. In combination, a hght sensitive surface to be rinted, printing means including one end 0 a relativel flexible strand of quartz,

end 0 means provided y the flexibility of said quartz strand for permitt ng movement of said printing means over sa1d surface, a lu m1- nous source responsive to received electrical signals, and means comprisin the aforesaid strand of quartz to convey ght from the ,source to the printing means. I 9. In combination, a light sensitive surface to be rinted, printing means including one Fa relatively flexible quartz cable having a plurality of strands of quartz for prlnting a plurality of unit areas on sa1d surface simultaneously, means to move the printing means over and surface and means pro- Y vided by the flexibility of said cable for permitting said movement of thesaid printing means relative to said surface, a luminous source responsive to received electrical sig-' nals, and means comprising the aforesaid 7o quartz cable to convey light from the source to the surface.

10. In combination, a light sensitive surface to be printed, multiple printing means including one end of a relatively flexible quartz cable having a plurality of strands of quartz,.means to move said printing means over said surface, a plurality of luminous sources each independently, responsive to re ceived electrical signals, and means coinprising the .aforesaid cable to independently convey light from each of said sources to the printing means. i

11. In combination, a light sensitive surface to be printed, a relatively flexible quartz 35 cable formed of a plurality of strands separated at one end, printing means including the other ends of the strands of the quartz cable arranged in superposition, means to move said printing means over said surface, a plurality of separated luminous sources each independently responsive to received electrical signals, and means comprising the strands of the aforesaid quartz cable to convey light from each of said sources to the printing means, the separated ends of the strands of said cable being positioned adjacent the separated luminous sources. 7

12. In a picture transmission'system, a reproducer comprising a plurality of variable light sources, a plurality of strands of quartz one set of ends of which are positioned transversely of the direction of printing and the other ends of which are conveniently sep-' arated and increased in area for cooperation with the lurality of variable light sources, and a mu tiplex receiving system for independently controlling the light emission from each of said sources. 13. In a facsimile transmission system, a reproducer comprising a plurality of variab e light sources, a plurality ofstrands 6f quartz one set of ends of which are superposed transversely of the direction of a line of print for photo printing the line in a single passage and the other ends of which are conveniently separated and increased in area for cooperation with the plurality of variable light sources, and a multiplex receivin system for independently controlling the lig t emission fronieach of said sources. 1.4. In combination, a surface to be scanned, a light responsive relay, and a flexible member of greater refractive boundary than the surrounding medium for conveying impressions of the light intensity on said surface to said relay, and means provided by the flexibility of said member for permittin relative motions between said surface an member for vely causing renpon es 13c.

from said relay proportionate to the successive light intensities forming the entirety of said surface.

15. The combination of a source of light, a relatively long flexible light conveying element having a sharp light confining boundary throughout its length for distributing light from said source, a surface res onsive to light and means rovided by the exibility of said element or permittin movement thereof relative to said sur ace for causing said light to influence the same, and means for effecting relative movement of the said cable to said surface.

16. The combination of a source of light, a plurality of flexible conducting rods adjacent said source for pickin up the light therefrom and distributing t e same at a point remote therefrom in a predetermined manner, a light sensitive record surface at the end of said rods remote from said source, and means provided by said flexibility of rods and the plurality thereof for respectively permitting relative motion between said rods and said surface and influencin said light sensitive surface at a plurality 0 points simultaneously.

17. A system for increasing the speed of picture transmission by multiplexing which includes means for simultaneously scanning a pluralit of adjacent points located transversely o the direction of seaming, a plurality of elongated flexible light conveyin elements for conveying the light from eac of said points along predetermined aths, a photo-electric element at the end 0 each of said light conveying elements, means for simultaneously transmitting a plurality of inde endent signals over carriers of different etpuencies, and means provided by said photo-e ectric elements for simultaneously modulating each of said carriers in accordance with the intensity of li ht and shadow conveyed through each of sai light conducting elements for influencing said cells.

CLARENCE W. HANSELL.