US2416573A - High-speed facsimile synchronizing system - Google Patents

Description

Feb. 25, 1947. w. e. H. FINCH 2,416,573

-- HIGH SPEED FAGSIMILE YNCHRONIZ ING SYSTEM Fi1 ed Sept. 28, 1945 .2 Sheets-Sheet i sYucmzomzme SIGNAL GENERATOR :AMPLIFlER Tmsmmgj RECEIVER I AND AUDIO RECTIFIER AMPLIFIER INVENTOR. WILL/AM 6 ll, Fl/VCl-l ATTORNEY.

Feb. 25, 1947. w. e. H. FlNCH 2,416,573 HIGH SPEED FACSIMILE SYNCHRONIZING SYSTEM Filed Sept. 28, 1945 2 Shegts-She'et 2 P- PICTURE $|GNAL5*H5YNCH:'P' PICTURE SIGNALS SPEED -i-- .QPICTURE SIGNALS PICTURE SIGNALS SPEED ATTORNEY.

Patented Feb. 25, 1947 HIGH- SPEED FACSIMILE SYN CHRONIZIN G SYSTEM .William G. Finch, Conn. Application September 28, 1% )45, Serial No. 619,167

My present invention relates to the transmission and reception of facsimile by wire'or radio,

and more particularly to novel synchronizing mechanism which will operate eiiiciently at high speed picture transmission.

Heretofore, in the transmission and reception of facsimiles, it has been-necessary, where'abso lute synchronism was desired between the transmitting and receiving apparatus, to transmit the facsimiles at a relatively'slow speed; This relatively slow speed of about one hundred lines per minute hasnevertheless been regarded as a rather high speed; For instance, where a drum was ten inches wide, and one hundred'lines per inch was transmitted, then at this speed a picture ten inches long and having a Width only slightly less than the circumference of 'thedrum, was :transmitted in ten minutes or less. Modern develop. ments have made it possible, however, to transmit facsimiles by photo-recording or chemical recording processes at a much higher speed. Thus, for

instance, it has been found that without any attempt to m'aintain'synchronism, speeds as high 7 four hundred lines per minute became feasible,

and thus the ten-inch picture above described could bejtransmitted in .two. and once-half minutes.

.Heretofore, synchronizing systems have consisted essentially of stop-start mechanisms'of the type specifically described in my Patent No. 2,108,983. The receiving drumwas rotated at, a slightly greater speed than the transmitter, say, in a ratio of 101:100, so that the receivingdrum wouldreach the synchronizing area first. receiving drum was thenbrought. to astop or its rate ofspeed adjusted practically to zero for an extremely short interval pending the receipt of. a synchronizing, signal which would permit the 'receiving drum to start once more. The arrangement of themechanical elements as well as-of the electrical elements used for synchronizing Was such. that at one hundred lines per-minute, the receiving drumcould' readily be brought to astop and started once .more'at 'atratexap-proaching twice per second.

Where higherspeeds -were attemptedthe stopstart method could be adapted by various adjustments to work .properlysat a scanning rate of one hundred twenty lines per minute (exactly 'two stop-start operations in each second), and even slightly higher; but at speeds of four hundred linesrper minute the stop-start, mechanism crethe quality oi the image being recorded, and at times causing the synchronizing'impulse to be skipped entirely, due to the vibration introduced.

Essentially, my invention contemplates varying the speed of -the' transmitterjand receiver-si- The,

he. obtained for the transmission, reception-and .operationof thersynehronizing signal.

ated too much vibration, thusinterferingwith i lwso that agreatertime'interval Wills.

Heretofore, the synchronizing signal was areranged to take place over .about twenty degrees of the rotation-of each'of the drums, thus representing about $5 or /20 ot the .scanning time.

Wherethe transmitterand receiver operated ata rate of :R. P, .M., the scanningoperation took" place approximately slightly lessthan ,twice,,a .second, and the scanning time occurred over; an' interval of about 4 of .a second. Where the op.- eration of the drums is speeded up .to 400 or ,even 500 R. ,P. M., then the scanning time is correspondingly reduced to as little as yoo ofa second. Since the mechanical elements must be stopped and brought into operationwithin that time, and sincethey must Operate with accuracy,

it has been found that with mechanical, systems now known, insuflicient time might be .giyen for thefls'ynchronizing operation. i My invention provides cyclical speed-changin means for the transmitter and receiver, which will slow' up the transmitting and receiver'drums 'just prior to thesync'hroni'zing operation, maintain thisv slower, speed jdllring thev Synchronizing operation, and speed upithe drums durin the secon c c e- T j It has been found that scanning' operations must be performed at extremely high speeds, while the ynchronizing operation nevertheless should be slowed down. By this cyclical. varying 'of th'e speed of the receiving and transmitting drums, the entire; scanning operation may vbe made to take place int of a second rather than the half-second per line scanning operation of prior d'eviceswhile at the same time the speed of the'drums at the time 'ofithe synchronizing ops 'era'tion is maintained at from A to 50 of a sec,-

ond, dependingou the ratio of the cyclical spee'dchanging mechanism which is ,used.

My novel device contemplates essentially the utilization of a quadric' chainv arrangement for cyclical variation ofthe rotational speed of the drums. 'The drivenshaft of the drum has a crank extending therefrom, the driving shaft connected to the motorhas another-crank exetending therefrom, and a link interconnects the ends of the two cranks. The driving shaft connec'ted to the motor, and the driven shaft of the drum, are parallel to each other, but out of axial alignmentr'so that the effective driving radius" varies cyclically.

The primary object of my invention, therefore; is, the provision of novel synchronizing means for high-speed'fa'csimile transmission.

Another object of my-invention is the provision of means for'cyclica llyyarying the speed of rota- "tion of the. transmitting and "receiving drums in 'order-i'to--*proyide sufficie'nt time for the sending, receipt and-operation of synchronizing signals,

,-tu're 'or facsimile systems.

" L yc1 ,$11o-vo1t system. i x 'The drivefrom shaft 3 V while at the same time permitting high-speed scanning to take place.

Still another object of my invention is the utilization of a quadricchain arrahgfemnt to obtain cyclical" variation in speed of operation of the transmitting and receiving apparatus to allow opera suflicient time for the transmission and tion'of the synchronizing signal. v i p The foregoingand many other objects of m invention will become apparent fromthe follow.

ing description thereof and from the accompanying drawings, in which: 7 Figure 1 is a schematic view showing my novel facsimile transmitter with the cyclically variable drive operating thesa'me; I Fig'ure 2 is a schematic view'of my novel face simile receiver withthe cyclically variable drive operating the same;

""Figure'3 is-a schematic view ofthe quadric chain drive arrangement, showing the? angular position of the driving and drivenmechanisms a -"for' the lowfspeed section of the cycle;

- Figure 4 is a view'showing the relative positions ofthe driving and driven elements of the cycli *cally variable driving mechanism during the v high-speed section of the cycle; and

Figure 5 is a graph showing the manner in "which the transmitting and receiving drums are slowedup during the transmission of' the syn& chronizing impulse; and correspondingly speeded ation will take place "the cycle. 7

during the remainder .of

The refracted picture'light beam I5 impinging oniphotoelectricscell I5fproducescorresponding electrical signals which are amplifiedby amplifier 22. quency carrier wave maybe employed with the A light chopper or an audio freamplifier 22 to facilitate transmission of the varying unidirectionalpicture signals, as'is well known in the art. V 1 V H The te'lepicture signals may be directly transmitted to a remote station. over wire lines or may be transmitted'by radio transmission means.

Figure 1 illustrates a transmitter 23 connected to the output of amplifier 22 for converting the audio .frequency telepicture signals intocorresponding radio frequency signals which are radiated by antenna, 24.

Synchronizing signals are cyclically transmitted for effecting synchronization of the trans- 7 mitter scanning apparatus in a manner to be deup' during the transmission of a picture signal.

= "Thefschematic diagramsFigures 1 and 2, of a ftele'picture transmitter and receiver respectively,

are described to more clearlyset forth the function'and relation of the synchronizing mechanismjof'my present invention. Itis to be'understand that the telepicture system and circuits de iscribed are'by'way of example only and that the lsynchronizing mechanism to be hereinafterfde- ;scribed'jin'detai1 is applicable to other telepic:

j Referring to Figure 1,a source of'li ght. lfl 'gen eratesafbeam' H focused to a point by a lens f system l2 upon the picture [3 to be transmitted,

fwhichismouhted on'the'cylindrical'drurnJ4; If

vItliepicture li'sfscannedone hundred lines per inch ".thefdiameterh'f theflig'htspot focused upon the Ipicture sh'duldbe .01 inch. The refracted Ib'eam 15' rromi he'pietureis focused upon the photo electric icell l6 eens system; 11'. The intensity .Of theirefracted beam I5 is proportional tothe shadin g o'f the picture elements which are suc-' c essivly"rnoved past thelight beam ll. 7

' 'The' picture drum I 4 isrotated' byworm l8 and worzn gear [9' which suitably reduce the spee'dof the motor'fZgli. Motor .20 is preferably 1 asynchronous meter connected to a commercial electrical supply linefil for example a sixty- I I!) which carries worm 1" gea lltiotheeMfi on whi hnr 4.

mounted, is through th quadric chain arrange-C mntcomprisin'g the cranks lfil and I02, andgthe link I03.- This drive, as shown in Figures 3 and.

;4, is acyclically variable one the fourth link of the quadric chain arrangement being the imaginary, linlrbetween shafts 8- and H2. At. one

1 .langular position of the drive, that shown in Figi 'ure 3,,"a,slowspeedis ob.tainecl.. At the opposite position of the. drive, that shown in Figure 4,

Lia high-speedisobtained; The switchoperating projection 21-of cam 25 willmove into operative 5 v'. jpo'sitio'ri with{.the cam switch 39 during. the 1OW-. E 4; piiie hiijii yc e fiiheg ae i qs r-iscribed in detail. The synchronizing signals have heretofore been transmitted once perscanning operation. When a drum is used as in'the preferred embodiment, the *underlap period'of the rotation cycle is employed to transmit the synchronizing signal.

or otherwise fastened into position onthe drum. A cam 25, is mounted upon the'shaft '26 of the telepicture drum- !4. A projection 21 offthe cam '25 ispositioned angularly corresponding to V the underlap portion of the drum I l. The edge 28" of thepicture sheet l3determines'0ne side of the un'derlap zoneand is gripped by clamping means internal to the drum it in a manner fpr'eferably as described inmy prior'Patent Nop The synchronizing cam switch 38; is cyclically clo'sedby the cam projection 2"! toimpress suitable synchronizing impulses upon'the amplifier 22 from the synchronizing signal generator 3|.

"Synchronizing switch 30 is con'nected in series with the synchronizing signal'generator 3| out- -put to a suitable portion'of the telepicture ampliher 22 schematically indicated in Figure 1. The

synchronizing impulse effective during the underlap period is preferably of intensity somewhat greater than the maximum or white telepicturesignal intensity in" order to readily distinguish the synchronizingsignals from the (telepicture signals at the receiver.

a direct-current-source which produces a unidisi'gnals during the remaining period of the cycle. A preferred embodiment ofsuch a method for .si'gnalgeneration' forms the basis of my prior Patent No. 2,059,061.

Figure 2is a schematic diagram of a telepicture receiver used in conjunction with the transmitter of Figure 1, andiemploying the synchronizing mechanism of my present invention. A radio .receiver andrectifier 32 is'connected to'a'receivgwire line is used, suitable amplifying and line equipment are instead. employed. 7 The output of .thereceiver and rectifierS2-are connected to an 7 audioamplifier .34- v;;' Ihe output, of, audio ampli- 1' 5;

ing antenna 1331 01 receiving the radio transmitted'signals from the radio transmitter 23. If a The .underlap period corre-. sponds to the portion of the picture drum where the ,opposite ends of the picture [3 are gripped "stage 3*5?-36 by aninterstage coupling; transformer 31. The output of the-push-pul-l stage 35-56 isnonnected to the primaryiifl of'the output transformer 39. The output of the secondary 40J of transformer 66 is connected to a photolamp'4l containing a gassuch'as neon, for producing a light beam 42o'utput in accordance with the telepicture signals received. The light output 42 from lamp llv is suitably focused upon the record sheet 49 on the receiving drum 50 by a lens system 42".

' I have here used a neon crater photo-lamp 4| having a control electrode 43 which is connected t.o..one .terminal 44 of the transformer secondary The crater plate 46 of lamp 4| is connected to the. positive terminal of a suitable direct-current source-41, the negative terminal of which is connected to. ground. The other terminal 48 ofthe transformer secondary 4B is connected to the crater plate 46 through avariable resistance The auxiliary or striking electrode 45 is connected toground by lead 52. As is, well known in the art... the auxiliary electrode 45 maintains a striking or discharge condition at the photoelamp crater plate 46, so that it will always be in readinessto respond to telepicture signals introduced between the plate 46 and the control grid 43. A by-pass condenser 53 is connected between the output terminal 48 and ground.

The receiver drum 56 is driven by a synchronous. motor 54 connected to supply lines 2|. The lines 2 l are-, where possible, from the same alternating current supply lines 2| as those of the transmitter, although such condition is not essential. The. synchronous motor 54 drives drum 50- through the schematically indicated synchronizing phase adjusting mechanism 55. The drum phasing mechanism 55 maintainsa driving connection between the shaft 56 which is driven .positively from the; motor shaft 51. through worm .58.:and Worm geariil; and the shaft 66- directly attached to the receiver, drum 5!].

The drive from shaft 2m to shaft 56v is through the quadric chain arrangement 26], 202 263, in which the elements 261 and 26.2 are cranks, re-.- spectively on shafts, 2H! and 56,, and the link, 203 interconnects the ends of. the cranks. The. quadric chain, drive: is identical with the drive forsthe transmitter, described inconnection with Figure Land produces corresponding: variations. in speed.

. The control plate 6! cooperatingwith the phasing mechanism 55 is actuated by thesynchronizing magnet 62 through its armature. 63; Drum iii-is: preferably driven at a slightly faster speed than thezcorresponding transmitterdrum l4, for

examplezin a ratio of 401:400.,

The phasing mechanism 55- is under'the control of'the synchronizing. magnet 62. to maintain the drum. 50 in phase synchronism with the transmitter drum [4. A direct-current potential source 64- supplies the synchronizing magnet 62 through its. relay contacts 65 -66;

The anode potential source 61 for the push-pull amplifier stage 35-56 is supplied-to the center tap 68 of the primary 38 through the synchronizing cam switch 16-4 l. A cam 12 is connected to the shaft 66' adfiacent'the drum 56. The projection l3 of the cam 12 is 'inthe same angular position on shaft 66 as the u-nderlap or dead zone 14 on the drum 56. The cam switch 16--1l isnermally maintained closed during the major portion of the rotation of cam 12, and the anode current from source 61 normally directly flows the receptionof the telepicture signals.

The cam switch 101l is opened by the projection 13' of the cam" 12 during the synchronizing period of thereceiver at an underlap-portion thereof; The anode current fromsource 6.1 is accordingly directed to the amplifier 3536 through the synchronizing relay 15, which relay i5 is otherwise short-circuited by switch l6l I.

The synchronizing signal, as hereinabove described, occurs during an underlap period of the picture transmitter, and is preferably of greater magnitude than the telepicture signals. Synchronizing relay I5 is preferably a marginal relay respondingonly to the increased magnitude signals so as to avoid the possibility of interference of the synchronizing action by any of the telepicture signals. The push-pull amplifier 35-46 rectifies an alternating current synchronizing impulse in the anode lead if such is used, and the actuation of the relay i5 is by rectified or unidirectional current. as will be understood by those skilled in the art.

Although I prefer to use synchronizing signals of" increased intensity, and v a marginal synchronizing relay, I have also successfully employed synchronizing-signals of intensity equal to the maximinnintensity picture signals to operate an ordinary relay. It is also to be understood that the synchronizing magnet 62' may be directly energized by the synchronizing signals, displacing the relay l5.

Thereceiver drum 56- is prepared for the synchronizing signal during its underlap period by cam W. The synchronizing signal will flow through to energize the synchronizing relay 15' which then closes the relay contacts 6566 locally energizing the synchronizing magnet 62'. The synchronizing magnet 62, when energized, will attract the armature 63 away from control plate 6| to permit the phasing mechanism 55 to continue to normally drive the receiver drum 56; i. e., if the drum 50 were in, phase synchronism and in proper phase, the release of armature 63 away from the plate 6| would avoid phasing or angular correction by the mechanism 55.

The control plate 6| of the phase correcting mechanism 65 has a notch 16 on its periphery;

in a manner to be described in detail hereinafter.

By rotating drum 5!] at a slightly faster rate than the transmitter drum l4. for" example in the ratio' of 4611460; the underlap period of the drum 56Wi1l reach the predetermined position corresponding to the-engagement of armature 63 Ofnotchlfi slightly before the normal reception of the synchronizing signal from the transmitter. The cam- 12 will accordingly open cam switch 'I0!I by the projection 13 and permit the ener- "gizatio'n of synchronizing relay 15 by the synchronizing impulse as it isreceived. The ener- 'giza tion of synchronizingrelay 15 by the synchronizing impulse will close relay' 65-:66 to correspondingly energize the synchronizing magnet 62 to attract the armature 63 away from engage- V ment with notch it of control plate 6 I. The con nection between the motor 54 and-drum Ellis continuously maintained and the synchronizing signal in attracting the armature 63 from the control plate 6| permits the drum 50 to continue rotating with the positive driving connection intact and in accurate phase synchronous relation with the transmitter drum.

By the means herein described, therefore, the utilization of the'quadric chain arrangement between the driven and driving elements of both the receiver and transmitter, produces the speed variations which slow up the operating elements during sending of synchronizing impulses and the operations attendant thereon, and correspond-V ingly speedup the apparatus during the picture signal section.

The synchronizing impulse in prior art types of synchronizing mechanisms operated over about twenty degrees ofthe arc of the drum, and in the case of scanning at 100 lines per minute, oper ated at about /400f a second, and the operation was there effected. By my novelmeans, I may step up the speed of the drums to 400 R, P. M., or even higher, and make the slow-speed portion of the cycle of the order of 100 R. P. M., 50 that the synchronizing time will be of the same duration, but the spacing between synchronizing impulses for the transmission and recording of the picture image will be relatively small.

In Figure I have shown an approximation of the speed variation which is obtained. Various lengthsrof link and crank, and various proportions between the cranks and links will produce different curves. The optimum curve is one which is substantially flat or both the picture signal and the synchronizing signal transmission, with almost vertical connection between the two flat areas. 'Even violent variations of even as'much as 4:1 or 5.21 during the'picture signal section will not be of any substantial effect, since the recording paper, where it is photographic or even chemical, may have sufiicient latitude or contrast to compensate for this. While I have described my invention in connection with the use of drum-type transmission for photoelectric recording, it will be obvious that the same kind of drive can be used for stylus recording. It will also be obvious that my novel synchronizing system is adapted for continuous sheet recording and for oscillating armrecording as in prior Patent 'No. 2,296,274, "and for spiral or lawn-mower type scanners.

Since many variations and modifications of my invention will now be obvious to those skilled in the art, and since I have illustrated my invention solely in connection with an illustrative embodiment thereof, I prefer notto be bound by the specific disclosures herein contained, but only by the appended claims.

I claim: 1. In a high-speed facsimile system comprising a high-speed facsimile transmitter and a highspeed facsimile receiver; said transmitter and receiver each comprising cyclically moving members and means for operating the same; meansv at the transmitter for generating a synchronizing signal at a predetermined point in each cycle;

means at the receiver for receiving said synchrcnizing signaland responsivethereto; and ad- 'clitionalmeans at the receiver for varying the speed of the cyclically movable member during each cycle of movement thereof; said speed-vary ing means imparting a relatively slow speed tothe cyclically movable member at the receiverfduring the portion of the cycle immediatelyibe'fore and after the receipt of the synchronizing signal, and a relatively high speed thereto during the remainder of the cycle, said cyclical speed-varying means comprising a crank connected to the driving means at the receiver; a crank connected to the cyclically moving member at the receiver; the centers of rotation at the cranks being out of alignment with each other and non-coaxial; and a link connecting the outer ends of said cranks.

2. In a high-speed facsimile system comprising a high-speed facsimile transmitter and a highspeed facsimile receiver; said transmitter and re ceiver each comprising cyclically moving members and means for operating the same; means at the transmitter for generating a synchronizfing signal at a predetermined point in each cycle; I

means at the receiver for receiving. said synchronizing signal and responsive thereto; and additional means at the receiver for varying the speed of the cyclically movable member during each cycle of movement thereof; said speed-varying means imparting a relatively slow speed to the cyclically movable member-at the receiver during the portion of the cycle immedi-ately'before'and after the receipt of the synchronizing signal, and a relatively high speed thereto during the remain der of the cycle, said cyclical speed varying means comprising a crank connected to the driving means at the receiver; a crank connected to the cyclically moving member at the receiver; 'the centers of rotation at the cranks being out "of alignment with each other and non-coaxial; and a link connecting the outer endsof said cranks; said cranks and link comprising a quadric chain arrangement.

3. In a high-speed facsimile system comprising a high-speed facsimile transmitter and a high' speed of the cyclically movable member during each cycle of movement thereof; said speedvarying means imparting a relatively slow speed to the cyclically movable member at the receiver during the portion of the cycle immediately before and after. the receipt of the synchronizing signal, andarelatively highspeed thereto ,uring the remainderv of the cycle, said cyclicalspeedvarying means comprising a crank connected to the driving means at the receiver; a crank connected to the cyclically moving member atthe receiver; the centers of rotation at the cranks being out of alignment. with each other and non:-

coaxial; and. a link connecting the outer ends of said cranks; said cranks and link comprising a quadric chain arrangement; said driving crank being driven at a constant speed, and said driven crank being driven at a cyclically variable speed, the speed of the driven crank connected to the cyclically movable'member being relatively slow immediately before and after the receipt of the synchronizingsignal and being relatively high during the remainder of the cycle WILLIAM G.

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