US 2141973 A
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Dec. 27, 1938. w a H HNCH 2,141,973
METHOD OF AND APPARATUS FOR FACSIMILE- SIGNALING Filed March 4, 1937 4 Sheets-Sheet 1 Dec. 27, 1938. w. G. H. FINCH METHOD OF AND APPARATUS FOR FACSIMILE SIGNALING 4 Shee'ts-Sheet 2 Filed March 4, 1957 Dec. 27, 1938. i w H, FlNcH 2,141,973
METHOD OF AND APPARATUS FOR FACSIMILE SIGNALING Filed March 4, 1937 4 Sheets-Sheet 4 3nventor William $345 11?! 6 2 V (lttomeg Patented Dec; 27, 1938 UNITED STATES-PATENT. OFFICE METHOD OF AND APPARATUS FOR FACSIMILE SIGNALIN G William 'G. n. Finch, Spuyten Duyvil, N. Y. Application March 4, 1937, Serial No. 128,920
4 Claims. (01. 178-695) This invention relates to facsimile systems and more particularly relates to novel methods of and means for maintaining synchronous relation between a receiver and transmitter.
Picture transmission between remote points by electrical signals requires scanning of the picture to be transmitted in a predetermined manner and entails similar scanning at a receiver or translator inproper synchronism with the transmitter scanning. Each picture may be resolved into a plurality of elemental areas. The tona tions or shading of the elemental areas are translated by optical means into corresponding electrical signals of intensity varying with the tonations. At the receiver, a picture translating mechanism is used which converts ,the varying intensity receivedpicture signals into corresponding shading or tonations. By maintaining predetermined and accurate synchronization between the transmitter and receiver scanning mechanisms with respect to the record sheet, a composite picture is produced at the receiver to form a facsimile of the transmited picture.
Synchronizing systems for maintaining the receiver in step or synchronism with the transmitter have heretofore involved complex mechanical mechanisms depending, in most cases,
upon cyclic synchronizing signals sent transmitter. A commonly used system an electrically operated clutch at the which starts up the receiver scanner at ginning of each line of scanning at the electroby the involves receiver the beinstant a synchronizing signal is received and corresponding tothebeginning of the-transmission of a scanning line. Near the end of the scanning line, the receiver scanner is automatically at the drum and held in this condition until the stopped synchronizing signal releases it into. action for the next scanning line.
The use of a' friction clutch corresponds to the well-known start-stop synchronizing system which synchronizing system is excellent for telegr'aphy purposes, but is not as useful for facsimile systems. In my Reissue Patent No. 19,575 of May 21, 1935, the disadvantages of the frict on clutchstart-stop synchronizing systems are discussed and I disclose a start-stop synchronizing system employing a positive clutch. The positive clutch permits engagement of the mechanism at a predetermined portion cycle and does not have'the disadvantage page which is scanner of the of slipinherent in the friction'clutch. A
modification of the positive clutch synchronizing system isdisclosed in 863 of July 14, 1936, where an overmy Patent No. 2,047,-
runnin clutch is used to permit positive engagement instantaneously.
Starting and stopping of the receiver scanner mechanism to maintain synchronous movement thereof generates inertial reaction forces which 5 cause wear and tear of the mechanism, produce noise, and also sets up vibrations at the receiver which must be dampened to avoid irregularities in the facsimile reproduction. Accordingly, various attempts have been made to drive the receiver scanner by a synchronous motor which is driven by an electrical current of a frequency identical with that of the current energizing the transmitter motor. Elaborate circuits and apparatus are required by this type of synchronizing sys- 1 tem, but for accurate reproductions, it has been, to date, the closest approach to perfect synchronous action. No noise, mechanical wear or unnecessary vibrations areset up at the receiver,
and correspondingly better quality reproduction can be made. My co-pending application, Serial No. 116,302, flied Dec. 17, 1936, is an example of a direct synchronous drive for the facsimile re- 4:eiver. z
. All the prior attempts at maintaining synchronism between the transmitter and receiver scanning mechanism depended upon the established principle of maintaining each successive line of scanning in proper phase position upon the record sheet. This principle may be ex- 50 pressed by stating that the beginning of each succesive scanning line was required to start at the predetermined beginning edge of the record sheet. The term phase synchronism entails that each scanning'line should be in accurate g alignment with the scanning pattern so that all the shaded intonations marked on the record sheet would fall into their predetermined position and reproduce the transmitted'picture. This result was accomplished by either stopping. the 40 scanner at the starting point of each line and starting it in phase synchronism, in response to the synchronizing signal transmitted when the transmitterscanner reaches that predetermined position of each line, or by using a synchronous be displaced with respect to each other as long as the successive displacements do not exceed a reasonable amount.
The extension of the phase synchronizing principle which I have discovered may be visualized by considering a stack of thin books of the same size. By viewing the stack from one side, we have an analogy for the successive scanning lines of a picture. The prior concept of phase synchronism required that the stack be-aligned so that its edges form-a vertical line. In accordance with my discovery, this stack of books or scanning lines may be tilted so that the edge of the stack would beat an angle with respect to the predetermined vertical position. This tilted or angular displacement may be to the right or left of this predetermined position. Each successive scanning line, or in the analogy. book, will be displaced to the right or left of the preceding book. In a preferred condition, each successive book or scanning line is displaced in the same direction and by the same amount so that the edge defining the beginning of each scanning line or book will lie on a substantially straight line at a definite inclination or angular deviation from the predetermined'vertical line position.
A facsimile reproduced in accordance with my discovered principle will be practically identical with the original reproduction but with the border line edges corresponding to the beginnings and ends of each scanning line .being at an inclina-- tion to the corresponding lines of the original picture. Angular deviations as much as five to have successfully transmitted photographs, half seven degrees produce negligible distortions in most applications of facsimile apparatus. I
tone pictures, black and white drawings, typewritten matter and the like with my invention, and after trimming the border edges of the picture so that they are rectangular so as to correspond to the original picture, in a manner to be hereinafter described in detail, it was difficult 'for observers to differentiate between these novelly produced reproductions and ordinary reproductions thereof. .In accordance with my present invention I' employ the extended phase synchronizing principle which I have discovered to radically simplify the method and mechanism of maintaining a facsimile transmitter, and receiver in synchronism. The receiver synchronizing mechanism is directly coupled to the driving motor and the. motor is maintained at a substantially constant speed, which speed is not necessarily identical with the transmitter motor speed, but is sufficiently close to permit picture reproduction by my novel principle. As long as the driving motor speed is substantially constant, the scanner need not be periodicallystopped to maintain phase synchronism as in prior devices, but the continuously rotating motor will cause the scanning lines. to be successively advanced or retarded from their predetermined position by equal amounts to produce the facsimile.
No precautionsv need be made to maintain the receiver driving motor in perfect speed-synchro nism with the transmitting motor nor need any attemptbe made to maintain each successive scanning line in perfect phase synchronism with the corresponding scanning at-the transmitter.
'rhefacsimilereceiverofsuchasystem isparticularly simplified and the reproductions do not have any imperfections due to spurious vibrationsas in prior'start-stop devices. No clutch is required. The receiver is set to'a speed close to: the predetermined motor speed for the system and means are provided for automatically maintaining the motor at this adjusted speed which need not be identical with the corresponding speed of the transmitter motor. I also provide means for automatically starting the receiver scanning mechanism. at the proper starting position on the record sheet so that the reproduction will be properly centered upon the sheet.
Accordingly, it is an object of my present invention to provide a novel method of and means for facsimile transmission and reception.
Another object of my present invention is to provide a novel method of and apparatus for maintaining a facsimile receiver in proper synchronism with the transmitter. I
A further object of my present invention is to provide a novel 'method of and apparatus for making a facsimile reproduction.
Still a further object of my present invention is to provide a novel method of facsimile recording.
' These and other objects of my present invention will become apparent in the following dc .9
Figure 4 is an enlarged detail of the fork prongs and slots corresponding to the view at 4-4 of Figure 2.
Figure 5 is a cross-sectional view taken along 5-5 of the fork prongs and slots at Figure 4.
Figure 6 is a diagram showing the marking strips on the .stroboscope disks, in developed form.
4 Figure 7 is a schematic diagram of a facsimile receiving unit employing the mechanical speed control unit and having means for starting the operation at a predetermined position on the picture drum. 1
Figure 8 is an end view of an electrical speedgovemor mechanism for use in place of the mechanical governor with the cover plate removed.
. Figure.9 is a cross-sectional view through the cover plate showing the contact springs and disks for the electrical governor.
Figure 10 is a partial view of a modified form of the electrical speed governor of Figure 8.
Figure 11. is a diagrammatic representation of the circuit employing the electrical speed control as incorporated in the facsimile receiver.
Figure 12 is a schematic diagram of a modified arrangement for connecting the electrical governor to control -a motor circuit whichgovernor corresponds to the illustration of Figure 10.
Figure 13 is an enlarged schematic representation of the standard scanning arrangement of a facsmile reproduction. a
Figure 14 is an enlarged schematic representation, corresponding to Figure 13, to illustrate how Figures to 19 are photographic illustrations of facsimile reproductions as produced by a facsimile receiver designed and operated in accordance with my present invention. Figure 1''! corresponds to the transmitted picture and is a reproduction made with perfect phase and speed synchronism. Figure 16 is a reproduction made at a scanning speed slower than the transmitter scanning speed; Figure 15 being the same picture 16 but with its borders trimmed parallel to the dotted lines. Figure 18 is a reproduction made at a scanning speed faster than the transmitter scanning speed; Figure 19 being the same picture 18 but with its borders trimmed parallel to the dotted lines.
Although the speed control and phase adjustment mechanism of my present invention is particularly useful for facsimile receivers in general, it may also be applied to the transmitter or combination transmitter and receiver units to keep the motor close to the predetermined constant speed for driving the scanning mechanism. The transmitter may bedriven by a synchronous motor at the predetermined speed while the receiver is driven by the motor and control devices to be hereinafter described in more detail. Figure 1 is a plan view of a facsimile unit of the rotating drum type. It is to be understood, however, that flat-bed continuous sheet systems or other facsimile scanning methods may be employed with the synchronizing system of my present invention. f
The electrical motor 20 is directly coupled to the rotatable drum 2| throughreduction gearing included at 22. The drum 2| is supported by a spindle 23 operated in the tail-stock 24 and is readily removable in a manner disclosed in my Patent No. 2,047,863 referred to above. The record sheet 25 is mounted on the drum 2| by suit able sheet mounting clamps 29. The area on the record sheet 25 surrounding the clamp portion 23 is generally termed the underlap portion, at which portion of rotation of the drum 2!, synchronizing signals. are generated and transmitted at the transmitter and in prior systems used for'periodic synchronizing at the receiver. Such synchronizing signals are transmittedat the proper time by means of a camswitch 10 actuated once per revolution of the drum. Leads 1| connect the cam switch to proper circuits for example, as shown in my Patent No. 2,047,863, already referred to. For a facsimile receiver, the cam switch 10 is used to divert the received signals to the synchronizing mechanism during the underlap period for operating the electrome chanical synchronizing mechanism for maintain ing accurate phase synchronism as described in the same patent. However, in my present invention, I employ the cam switch 10 at thereceiver, not for cyclically maintaining synchronous conditions but for initially starting oft the drum 21 so that the first line will be in proper position on the record sheet 25 in order that the.Dicture reproduced may be centrally aligned.
Rollers '26 may be pressed against the drum and sheet 25 to assist in smooth mounting thereof. The electro-optical scanning mechanism 21 is mounted on tracks 28 in a manner to minimize transverse vibration or movement thereof with respect to,the ,drum 2 I. The electro-optical scanning carriage 21 contains the optical lens system 30 for focussing ,the beam of light upon the record sheet 25. For -a transmitter, the electrooptical system 21 translates varying elemental shading of the picture 25 into corresponding electrical signals which are'transmitted. In a facsimile receiver, the electro-optical system 21 produces a beam of light focussed upon picture 25 through lens system 30 varying in intensity in accordance with the received picture signals. A feed screw 31 is mechanically connected to the bottom of electro-optical carriage 21 and moves the carriage parallel to the axis of the rotatable drum 25 at a predetermined speed. The feed screw II is geared to the reduction gear box 22 by rod 32 and the gear system enclosed in housing 33. Details of the mechanical and electro-optical features of the illustrated facsimile unit are thoroughly disclosed in my Patent No. 2,047,863.
A mechanical governor 34 is shown attached to a shaft 35 extending from the drive motor 20. The mechanical governor is used to maintain the speed of rotation of the motor 20 substantially constant at the speed which the governor is adjusted to by the operator. The stroboscope disks 36 attached to the rotating system of the motor and governor have alternate black and white markings which guide the operator in the speed adjustment of the motor 20. A synchronous motor is not practicable to use for the motor 20. Motor 20 is preferably of a constant, or variable speed type which can maintain a reasonably constant speed for constant electrical andmechanical conditions. A direct current, compound or series wound motor or alternating current induction motor and the like may be used as the motor 20. Once the facsimile unit is set in operation, the speed is maintained and negligible changes in the torque demands on the motor occur. With substantially constant electrical voltage conditions, the motor will tend to, rotate approximately at a predetermined speed. However, for the purposes of my invention, it is preferable to employ some speed control device to maintain the motor speed practicably as constant as possible, thus eliminating speed changes due to temperature or voltage or other variations which might occur' during the progress of reproduction of a picture. In Figures 1 to '1 are illustrated details of the mechanical governor speed control; and in Figures 8 to 12, electrical governor speed control.
Figures 2 and 3 are detailed illustrations of a preferred mechanical governor attached to the extension shaft 35, of motor 20. The mechanical governor 34 comprises a friction disk or plate 31 loosely mounted upon the shaft extension 35. A plurality of leaf springs 38 are connectedbetween the hub 39 of the disks 31 and a ring 40 secured to the rod 35 at a distance from the disk 31. Ring 40 is secured by set screw ll to the rod 35. A weight/'42 is secured to the central portion of each flexible leaf spring 38. The rotation of motor shaft'35 will cause the springs 33 and friction disks 31v to rotate therewith. The mass of the weights 42 will move outwardly dueto the centrifugal force of rotation, to correspondingly deflect the leaf springs 38. The deflection of leaf springs 33 will causepthe loosely mounted friction disk 31 to move closer toward ring 40 toward the right in the illustration of Figure 2. This movement of the friction disk 31 toward the right will be proportional to the speed of rotation of shaft 35 and the motor 20. A pad 43 of felt or. other suitable material is set into an adjustable block 44, to coact with a surface of the friction disk 31. When the disk 31 moves sumciently to the right, it will frictionally engage ator can adjust the position of the The speed of motor "is accordingly determined by the setting of the block 44 and the felt pad 48. When the speed oi motor 20 exceeds the speed corresponding to the predetermined setting of the pad 43, the frictional disk 31 will be actuated with greater force against the pad due to the centrifugal action of the weights 2 and increase the frictional resistance to rotation to correspondingly maintain a substantially constant speed. In order to facilitate the setting of the padllgwith respect to the friction disk ll, by the thumb screw 44, a pair of stroboscope disks It is mounted to rotate with the shaft 35. These disks contain alternate black and white markings to cooperate with the tuning fork 46 held by the operator above the rotating disk 36.
An enlarged partial plan view of the tuning fork N is. shown inFigure 4 as consisting of two prongs 41 which may be set in vibration by striking on a flat surface. Attached to theend of the prongs are two plates lland 4! containing corresponding slots SI and II. The operator views the stroboscope disks 3' through/the slots and Ii. Figure 5 is a cross-sectional view taken through the forked prongs and slotted plates.
The fork it is chosen with a natural frequency of vibration equal to a multiple or sub-multiple of the predetermined speed of rotation for the motor 20. Where greater accuracy is desired a design of fork is used which is less aflected by temperature and weather variations. However, even though a small percentage of vibrational variation is to be expected from an exposed fork of, this type, such variations are not at all material in view of the principle of phase synchronism which I have discovered and hereinabove described. Where a speed of 2100 revolutions per minute is used for the motor 10 corresponding to 35 revolutions per second, a tuning fork having 87.5 vibrations 'per second for example, may be used. The alternate black and white markings on disk It are arranged to permit the vibration frequency of the tuning fork to open and shut from view through the shutters ll and 40, the markingsas viewed beneath them so that when the predetermined speed is reached, the markings will appear to be stationary. To permit flexibility in the choice of forkfrequency and the predened speed of motor II, I use two sets of str copic markings for the disk 38; one set having five alternate black and white equal length markings. Figure 6 is a development of the markings on the periphery on'the disk as. The strip '2 contains five sets of black and white marks; and the strip 53, six sets. When the speed of rotation of-the motor 20 approaches substantially the predetermined speed, namely 2100 revolutions per minute, in the illustrated example, the disk containing the markings 52 of five sets of black anQ-white markings will appear as stationary when viewed beneath the shutters ll-Ii of the fork l8 vibrating at 87.5. vibrations per se ond.
The speed of the motor 20 is now suitable for reproduction of a picture with my facsimile system. It is not necessary to test for accurate synchronous speed with respect to the transmitter motor since the method herein described of adiusting and maintaining the speed of motor 2| constant and the new principle of phase synchronism does not require accurate synchronism. The only pre-requisite is to have a substantially constant rotative drive at a speed near the synchronous speed. The permissible degree of variation in speed is dependent upon the degree of distortion permissible at the reproduction as well as the design parameters of the facsimile receiving unit and will be discussed in detail hereinafter.
' In order that the facsimile reproduction be assembled properly on. the record sheet, it is necessary to have some means for starting the scanhing operation so that the edge of the reproduced picture will be close to the underlap portion of the drum or otherwise close to the edge of the record sheet upon which the reproduction is made. In Figure 7 there is' diagrammatically illustrated a system for automatically accom pushing this result. The motor 20 drives the picture drum 2| through the intermediate worm and worm gear arrangement 22'. A practical speed for the drum II is revolutions per minute; The mechanical governor I4 is shown attached to the extension shaft ll of the motor '20 as already described. The electrical motor 20 isconnected' to a power supply byvleads l4 and connection plug ll. A starting resistance It is connected in series with one of the motor leads 54. A short circuiting switch 51 is connected across resistance 58.
The facsimile signals are introduced to the receiver unit It at the input terminals II. The signals are amplified and rectified if necessary and are further introduced to the push-pull output amplifier stage 00-. The output amplifier 0-H ispreferably a class B amplifier where zero signal input produces zero plate current. Output transformer 82 connects the output stage II-Bl to the translating device '3. Although I schematically illustrate a neon lamp 8! for translating the facsimile signals into corresponding varying intensity light'beam N focussed upon J the record sheet 25 by lens system I, it is to be understood that any other translating device may be employed. Thus, for example, a galvanometer light shutter or an electromechanical stylus may be used.
In order to attain the initial phase synchronism of the drum driven at constant speed by motor ill, I make use of acyclic synchronizing signal which is transmitted in a well known manner before the beginning of each scanningline, as described hereinabove. This synchronizing signal is preferably transmitted once per revolution of the transmitting drum during the underlap portion thereof. A cam It is connected to the drum 2| by shaft 01 to rotate therewith.
A projection I is made on cam CI to open the cam switch ll during the underlap portion of the drum 2|. Cam or synchronizing switch 10 is connected across the synchronizing magnet I! translating mechanism 61 and the synchronizing magnet will not be in electrical circuit, connection at this time. However, at the underlap portion corresponding to the position of clamps 29, the synchronizing switch I6 will be opened by the cam nib 66 and permit the synchronizing signals to be impressed upon the synchronizing magnet I2. The synchronizing signal is of a predetermined magnitude and actuates the magnet I2 to attract its armature 13 to the upper position. Armature I3 contains a'switch contact 14 which coacts with a fixed contact I5. Contacts 14 and I6 are electrically connected across the resistance 56. The synchronizing armature I3 is of the self-locking type, well known, for example, in the 'annunicator. art. A leaf spring I6 is drawn to schematically indicate such a self-locking armature arrangement whereby when the armature I2 is attracted from its open position shown 29 in dotted lines at 13', it will move against the spring I6, pass the tip of the spring I6 and be locked in the closed position illustrated, closing contacts I4 and 15- to short circuit the resistor 56. I do not intend to be restricted to any speciflc form of locking relay-armature arrangement corresponding to 12-13.
The procedure for operating the system in Figure 7 includes the step of adjusting the mechanical governor-3 4 close to the predetermined position by means of the thumb screw 44 and assisted by the stroboscopic action of fork 46 and disks 36. This step is performed with resistance 56 short circuited either by means of the switch 51 or the armature I3 manually. placed in selflocked position. The governor 34 willautomatically maintain the motor 26 at the adjusted speed. The switch 51 andarmature 13 are then thrown open to place the resistance 56 in circuit with the motor leads 54. The value of resistance 56 is designed to materially reduce the speed of the motor 26. I have satisfactorily used a value of 5 ohms for the resistance 56 in series with a driving motor using one ampere.
when the resistance 56 is placed with the motor, the speed of the motor is slowed down and the mechanical governor 34 becomes inoperative at the lowered speed so as not to aflect the phasing adjustment operation. During the slowing down period which starts at the insertion of resistance 56, the angular position of drum 2| will progressively change until the underlap portion 26 will attain the corresponding phasing action is thus performed automatically since the speeding up is practically instantaneous and the drum starts substantially in phase relation with the transmitter drum so that the re-- corded picture will be centrally aligned on the record sheet 25 as will now be evident. The shelf- -locking lever I3 maintains the resistance 56 short circuited so that the mechanical governor 34 alone controls the speed of the motor and keeps it, at the predetermined adjusted speed, and substantially constant.
In order that the operator may definitely know that the recording has started in phase synchrowill be described in detail hereinafter.
in circuit ing magnet I2 and is impressed with the synchronizing signals simultaneously with the synchro- 10 nizing magnet I2. When solenoid 6| is energized itattracts armature 82 to close the circuit of the signal lamp I1 and cause lamp 'II tolight.
Accordingly, when the phase synchronizing operation is successfully performed and the switch 63 l in the lamp circuit II is closed, the lamp .II will flicker, being lit once per revolution of the drum,
- namely, one hundred times per minute in this case.
Once phase synchronism is established, the receiver drum is continuously rotated at the predeterminew speed to which the motor 26 was originally adjusted and which speed is very close to the corresponding transmitter speed. Naturally if diiferent reduction gearing ratios at 22' are used for the transmitter and receiver, the speeds of corresponding motors will be difierent. My present invention is concerned with operating the motor 26 at a rate close to the. predetermined speed for the receiver which speed is known to the operator. After the initial phase synchronism is established the.recordi ng of the picture by the translating mechanism, 63 and upon the record sheet 25 is started with no further attention being required. The drum will rotate close to its predetermined rate'and'whether it is some- I what faster or slower than the actual speed of the transmitter drum is not important in view of my discovery. Examples of results made under diflerent speed conditions are illustrated and After the picture reception has commenced, it is not necessary to employ the flickering light l1 and therefore I provide a switch 83 to open the circuit of the lamp II. I also prefer to employ a switch 64 to short circuit the solenoids I2 and 6! from the anode return lead I3 of the output stage 66--6I. The switch 84 is closed after the initial phase synchronism is established. The switches 5.1, 83 and 64 are preferably all connected to a common shaft or lever for simultaneous operation. ,The arrange-' ment is such that for phasing position, switches 51 and 84 are opened and switch 83 is closed; and in running position, switches 51 and 64 are closed and switch 83 is opened.
Summarizing the operating procedure for operating the system of my present invention employing a mechanical governor speed control:
1. Insert the record sheet'25 in position on the scanning mechanisnfi namely the drum 2|.
2. Close switch 51, or close contacts "-15 by manual positioning of lever I3 into the selfi and the system is ready for reproduction on therecord sheet.
6. Throw the switches 51, a4 and a: ma "opg erating position," namely closing switch l1 and N and opening switch OI. I
I have also. successfully employed electrical governors in place ofthe mechanical governor Hand wheel 9| is rotatably supported in a bracket 02 and is used to adjust the tensiai in the spring l8. Posts 86 and Oil are integral with respective conducting plates 83 and 94 for electrical connection to contact springs 95 and N. The contact springs 85 and 98 are respectively connected to contact rings or disks 91 and 9| insulatingly supported in the and cover plate I! for the electrical governor mechanism.
When the electrical governor I is rotated over a predetermined speed, the contacts 85 are opened due to-the centrifugal action on the spring biased arm 81. An external motor control circuit is connected to the contact disks 9! and II for control by the speed sensitive contacts OI which open when a predetermined speed is exceeded.
Figure 10 illustrates a modification of the gov- .ernor I" which modification reverses the conbracket III.
lfigure .11 is a diagrammatic illustration of the use of the electrical governor with a motor. This illustration employs the governor iiiiiillustrated in Figures 8 and 9 wherein the contacts open during lover speed from the predetermined setting. The stroboscopic markings are placed on the periphery I01 of the housing for the governor Ill. Contact'a'rms I08 and I0! connect the electrical governor I00 across the resistance Ill placed in series with the motor power leads 54. when the contacts of the governor I GI are closed, the resistance H0 is shortcircuited and the circuit of the motor is connected directly to the power supply. When the motor exceeds the predetermined speed as set by the hand wheel 9i, the contacts 85 within governor I" will open the short-circuit across resistance ilil to decrease the current supply to the motor 20. The speed of the motor 20 will be momentarily decreased when the contacts 85 will close to short circuit the resistance- H0. Contacts 85 are sensitive to minute speed variations and control the insertion of the resistance ill in series with the motor to maintain the average'speed of the motor at the predetermined value. The inertia of the motor armature smooths out any fluctuations which the insertion of resistance ill might cause, and produce a substantially uniform torque and speed at the scanner driven by motor 2|.
The method of initially starting the drum in phase synchronism in a manner described in connection with Figure 7 is in this case performed by the synchronizing magnet 1-2 and the associated electrical circuit connections with a minor difference in the connections across the 'motor resistance H0. Contacts iii and 2, controlled by armature 13, are connected across the resistance IIII. When the armature II is in open position as illustrated, the contacts iilll2 short circuit the resistance llll thru a resistance ill and permit the motor. 20 to run over speed during this time. Since the contacts I! of governor Hill are 'opened by the over speed condition, the motor will continue to run at overspeed when contactsi i I-l ii are closed by lever 13. This procedure is followed to bring the drum in connection with Figure 7' except that in thiscasethe motor is-made to over-speed instead of run at a slower speed. 1
The principle behind my preferred phase syn chronizing operations resides in causing the motor and therefore the drum to run. for a short interval, faster or slower than the adjusted pre-' determined continuous speed in order to change the relative angular position of the drum and rapidly bring the varying drum position (with respect to the corresponding transmitter drum) to a proper and initial phase synchronous condition with the transmitter drum. When the receiver drum II or any corresponding or equivalent scanner mechanism which may be used reaches the predetermined initial phase position.
- the cam 66 will open the-synchronizing switch Ill and remove the short-circuit across magnet The transmitter synchronizing signal will cause a current to iiow through the magnet I! at this instant when the drum is in the proper phase synchronous condition. When magnet 12 is energized it attracts the armature I3 into a self-locking-position to correspondingly return the speed control of the motor to the mechanical or electrical speed governor.
Accordingly, the expedient of momentarily running the motor over-speed or under-speed after the initial setting of the governor control is to rapidly change the phase position of the,
drum until it reaches the initial phase synchronous position, and then automatically return the control of the motor sp e to the governor.
Th'e governors will maintain the speed of the I motor substantially constant for relatively long periods of time, such as ten hours or even several days. Thus, once the setting of the governor is made with the stroboscopic components, it need not be readjusted at least for the run of a picture which is tenor fifteen minutes, or for the at the beginning of each picture or facsimile receiving operation.
Figure 12 schematically illustrates a modified form for employing the electrical speed control. A compound wound direct current motor 20' is used having an armature H3 and a field Ill. A control resistance 5 is connected in series with the field I I4. The electrical governor IIII is connected across the resistance II5. This governor corresponds to the one illustrated in Figure 10 where over-speed closes the contacts and normal or under-speed maintains the contacts I02 and I04 open. When the motor 20 tends .to overspeed, the contacts I02-Ill4 short circuit the series resistor II5 thru a resistance It! and increase the current flowing through the field coil II 4 to correspondingly momentarily reduce the speed 01' the motor. When the speed is normal or tends to become slightly less than the predetermined setting, the contacts I 02-104 will open due to the tension of spring 88 to return the resistance H5 into the field circuit. The shunt wound direct current motor will accordingly be maintained at substantially constant speed by this arrangement.
The contacts IiI--II2 operated by armature 18 are connected in parallel thru resistance Ill across the governor IN and the resistance II 5. The lever 13 is positioned to close the contacts III--I I2 to short-circuit the resistance H5 thru' the resistance II? when the initial phase synchronizing operation is to be performed. The motor in this example will run slower than the predetermined speed until the drum is positioned in the proper phase and relay 12 is automatically energized by the synchronizing signal to attract armature I3 into the self-locking position above spring 16 and return the speed control of the motor 20' to the governor MI. I
I prefer to employ a switch I I6 connected in series with the circuit including contacts III and I I2 as illustrated in Figures 11 and 12. Thus once the initial phase synchronizing operation is performed, the switch I I6 may be opened to remove,
in a positive manner, the effector contacts Hi and H2 on the electrical governor. The opera- 1 tion of switch MS may be performed in conjunction with the simultaneous actuation of the switches 83 and 86 in a manner already described.
My present invention depends upon the discovery of the operation of a facsimile receiver without regard to the positioning of each successive scanning line at the predetermined phase relation corresponding to that at the transmitter. Figure 13 is an enlarged diagrammatic view 01' the scanning of a letter H by prior facsimile systems. The scanning operation is composed by a plurality of successive scanning lines I20 illustrated by parallel dotted lines. The starting edge I2I of each scanning line I 2i! is aligned parallel to the left edge I22 of the record sheet I23. Each of the edges I 2I are started at exactly the same distance from the sheet edge I22 and the letter H is composed by the synchronous alignment of the individual contributing segments I24 0! the scanning operation. The vertical sidesof the letter H are parallel to the predetermined scanning edge I 2|. The reproduction of the letter H as shown in Figure 13 requires accurate synchronous speed and accurate phasing oi! the successive scanning lines I20 with respect to the record sheet I23.
In accordance with my present invention, I maintain-the scanning speed close to, but not do maintain the scanning speed substantially constant so that whether it is slower or faster than the exact speed of the transmitter, it will remain so for the duration of the scanning operation. Figure 14 is a diagrammatic illustration of the letter K of Figure 13 reproduced in accordance with my present invention when the speed of the scanner is somewhat faster than synchronous speed corresponding to the speed of the transmitter scanner. The successive scanninglines I20 are progressively displaced to the right starting from the top. The starting point of the top scanning line I20, namely the edge I26, is shown at the correct phase position corresponding to line I2'I'. The edge I25 was placed at this synchronous phase position by means of the initial phasing operations and circuits including the synchronizing magnet 12 hereinabove dethe vertical sides of the letter H become parallel to the line 525' which defines the displaced edges of the scanning line I20. The orizontal member E26 oi the letter H remains parallel to its original condition. Lines having intermediate angles between the vertical and the horizontal are distorted by intermediate degrees, angle A representing the maximum distortion corresponding to the vertical lines of the picture.
' Figure 17 is a reproduction of the head of a kitten which I have chosen to illustrate the practical use of the principle and apparatus of my present invention. This illustration contains fine lines and much detail and requires proper phase coordination between successive scanning lines for a good quality facsimile reproduction.
The photograph corresponding to Figure 17 was,
inserted in a transmitter and received by apparatus of my present invention. Reception with perfect synchronous speed and line by line startstop phase synchronization methods would produce a result identical with the shape and form of Figure 17, as is evident. However, by employing the constant speed method of my present invention, namely setting'the receiver motor at a speed close to the transmitter speed and having electrical or mechanical speed governor controls such as those described maintain the receiver scanner at a constant speed, suitable quality reproductions of the transmitted image will be produced.
In practical operation, the receiver scanner which is adjusted close to the predetermined speed by stroboscopic means or the like will not be at exact synchronous speed but either a small percentage slower or faster than the synchronous speed. The slower or faster scanning speeds will produce a corresponding slight staggering of the successive scanning lines from the' predetermined position, in a manner such as described in connection with Figures 13 and '14. The angular distortion A will be proportional to the difference between the scanning speed and the synchronous speed therefor. In my experiments with my present invention, I have found necessarily at, synchronous speed. However, I that distortions corresponding to angle A of a 75 magnitude up to the order of 5' will hardly be recognizable as an optical distortion of a photograph even if matched or compared with the original. For many applications such as recognlzable facsimile transmission and even most applications of news gathering services where received facsimiles are used as newspaper pictures, such distortions of the order of 5 and even as high as 8 produce pictures which'are entirely suitable for this work and only by careful comparison with the original could distortions of some portions of the picture be recognized.
Figure 16 is a reproduction of the head of the kitten of Figure 17 as received by a facsimile receiver described in my present invention, operated at a constant speed which was somewhat slower than the synchronous speed to produce an angular distortion A of 6 /2". A 6 distortion is unusual and was purposely made to illustrate an extreme practical case. Most tuning forks and motors and current supplies can be commercially maintained soas to produce angular distortions A within one, two or three degrees. Such small angular distortions which are the usual amount in operating my system produce negligible difference between the reproduction and the original. The illustrated distortions are purposely presented to show the extreme effects which need not be encountered in most practical cases.
The dotted lines 11-?) and o-d were drawn upon the original picture corresponding to illustration 17 parallel to the border lines of this picture. The scanning operation of the receiver which produced Figure 16 was from the left to right in the direction a to b. The system ran slower than synchronous speed and the line 0-1:, defining the relative phase displacements of the successive scanning lines was produced at an angle of 6M4 to the top border of the sheet. The reproductions of Figures 15 to 19 were made with 100 lines per inch of scanning. The face of the kitten of Figure 16, if carefully compared with the standard picture 17, may be found to have some recognizable distortions; for example, the original picture of the right eye is practically circular whereas the right eye in Figure 16 is ellipsoidal. It may also be noticed that the tip of the right ear is relatively closer to the top edge of the sheet than 'in the original Figure 17, due to the progressive shifting of the scanning lines in the direction a-b toward the top edge.
The reproduction of Figure 16 having the relatively large. angle A of 6 /2 is suitable for most applications where remote photographic representation by facsimile is required. However, a better approximation to the original photograph can. be made by trimming the reproduction of Figure 16 along lines parallel to the lines 0-D and c-d which is parallel to the distortion. Figure 15 is the identical facsimile reproduction of Figure 16 having an angle A of 6 /2 but having the top and bottom border edges trimmed along the corresponding dotted lines a-b and cd. The vertical sides of Figure 15 were trimmed perpendicular to these edges to produce the frame of Figure 15 for direct comparison with the original Figure 17. It will be noted that the tip of the right ear in Figure 15 is returned to its original relative position as seen in Figure 17; even though the right eye has been made ellipsoidal this distortion becomes less noticeable when compared to the original as seen in Figure 15.
'Although I have shown Figure 15 being trimmed parallel to the actual distortion lines 0-D and c d, it is obvious that intermediate degrees of trimming may be used, which trimmings may be dictated by the actual photograph in hand.
However, I wish to emphasize that in most practical reproductions there is hardly a need for 5 trimming-operations. Such angular trimming may be expedient where larger angles have been incurred. Since most transmitted pictures have their original border lines corresponding to the frame of the original orientation of the picture,
and since these border lines appear upon the facsimile reproduction corresponding for example to the line a-b of Figure 16, a direct guide is thus afforded to the operator of the amount of distortion his picture has. This line which becomes part of the facsimile reproduction may be 7 used as a border line for trimming the picture received.
Figure 18 illustrates the reception of thephotograph of Figure 17 by the same receiver which produced Figure 16 but operated at a scanning speed somewhat faster than the original or synchronous speed. The dotted line a'b' and c'd correspond to the lines 0-11 and c-d of Figure 16 which lines define the original border edges of the transmitted-picture. The distorlong as the scanning speed remains substantially constant. The recognizable features of the kitten or any photograph reproduced by such distortions, is made possible by the extended principle of necessary phase synchronization which my present invention is based upon. Since each successive line is progressively staggered by a like amount, the distorted reproduction is a usable photograph.
In the distortion of Figure 18, it will be noted that the right ear is further away from the top edge of the sheet as compared to the original Figure 17. It will be recalled that the opposite angular distortion shown in Figure 16 produced a reverse effect, namely that the right ear became closer to the top border edge. Comparing the tip of the left ear in Figures 16 and 18 will show the obvious relative misplacement of this portion of the picture. Another recognizable distortion of Figure 18 is the left eye of the kitten as viewed in the photograph. The left eye in this case has become more ellipsoidal than the original left eye. A flatter ellipse for this eye is produced in Fig- .ure 18 as compared to the elliptical distortion of the right eye of Figure 16 due, first of all, to the greater over-all angular distortion and due to the fact that the original left eye is somewhat ellipsoidal in shape.
. Figure 19 is the. same photograph of Figure 18 at an 8 distortion but having its borders trimmed along the lines ab' and c' --d' to bring the distortion of the photograph closer to the original by this amount. It will be seen that the vertical dark portion of the kittens nose is at an angle to the vertical in theFigure 19 as compared to the vertical position thereof in the original Figure 17. The exaggerated distortion 'of 8 for Figure 19 makes the appearance of the kitten clearly distinguishable from the original Figure 17. However, this distortion is not serious for ,many applications of facsimile systems even for newspaper work. By trimming the exaggerated distorted picture of Figure 18 intermediate between the lines a'b', c--d' and the borders thereof, a compromise may be struck between the vertical distortions of the picture and the horizontal displacement after trimming to even aiford a more favorable comparison with the original photograph.
Accordingly, it will now be evident that my present invention provides a material simplification of facsimile receivers for quality facsimile reproductions. My present system.elim inates the necessity for start-stop phase synchronization at each line employing, clutches and the like; eliminates the requirement for use of synchronously driven motors at the identical speed of the transmitter; and employs relatively simple substantially constant speed motors controlled by relatively simple electrical or mechanical governors to maintain a reasonably constant speed.
' Although I have illustrated my present invention utilizing motor drives havinga constant speed as controlled by electrical and mechanical governors, it is to be understood that a constant motor speed independent of external governor control may be practically used. For example, 'a direct current motor, preferably of the compound wound type driven by a storage battery having a substantially constant voltage, will maintain excellent operating constant speed for the purposes of my present invention. After the motor has disk. By using. a constant voltage source, the
necessity for a speed governor is thus eliminated.
It will be evident that means other than thee strobos'cope and tuning fork arrangements may be used to apprise the operator when the motor is adjusted to substantially the predetermined speed of operation. Once the speed is adjusted close, not necessarily at the predetermined speed, the receiver isrprepared forthe initial phasing operation in a manner hereinabove described. The facsimile reproduction will bear a 50 distortion angle 'A' of magnitude depending upon 1mm! m anlcturescanning the diflerence between the operating or adjusted receiver scanning speed and the predetermined scanning speed at the transmitter, The system of my present invention produces a progressive staggering of the scanning lines when the receiver scanning speed is different than the original scanning speed, but due to the constant speed and no interruption of the scanner, the staggered lines form a regular pattern and combine to produce a reproduction, the edges of which are at a small angle from the predetermined position but, on the whole', producing a facsimile which in most cases is difllcult to distinguish from the original; Although I have described preferredmethods of and apparatus for carrying out the principle motive means for operating said mechanism at a predetermined rate, means for generating electrical signals in accdrdance with the elemental shading of a picture to betransmitted and means for generating predetermined cyclic signals in accordance with the transmitter scanning operation: a receiver comprising a scanner; a motor directly geared to-said scanner and operable at a substantially constant rate independent of said predetermined rate; means responsive to said cyclic signals for predetermining the initial phase position of the receiver scanning operation; -a speed changing means connectible in the motor circuit for changing the motor speed from'said constant rate; and means operable-by the cyclic signal responsive means for rendering said speed changing means ineffectual whereby said motor is sively in one direction; and means operative on said motor for automatically pr'edetermining the initial phase position for the directly geared receiver scanner operation. 1
3. In a facsimile reproduction system, a scanner; an electric motor directly geared to said scanner for driving said scanner: means for oper- '5 ating said motor at a substantially constant rate independently of the transmitter scanning rate comprising a speed governing device mechanically connected to said motor and electrically connected in the motor circuit, means for predetermining the initial phase position of the directly geared receiver scanning operation including a synchronizing magnet, a resistance connectible in the motor circuit for changing the motor speed,
and means operable by said magnet for disconnectlng said resistance from the motor circuit whereby the speed control of said motor is returned to said speed governing device when the scanner is initially in phase synchronism.
4. In a facsimile system provided with a trans mitter comprising a picture scanning mechanism, motive means for operating said mechanism at a predetermined rate, means for generating electricalsignals in accordance with the elemental shadingof a picture to be transmitted and means for generating predetermined cyclic signals in accordance with the transmitter scanning operation: a receiver comprising a scanner; a motor directly geared to said scanner andoperable at a subaantially constant rate independent of said predetermined rate; means. responsive to said cyclic signals for predeterminingthe initial phase 'positionof the receiver scanning opera- Jtion; a-speed changing means connectible' in the of my present invention, variations thereof be evident to those skilled in the art,'and accordingly, I do not intend to be lim'ted except as setforthinthefollowing v 1. In a facsimile system provided with a transmotor circuit for changing'the motor speed from .said constant rate; means operable by the cyclic signal responsive means for rendering said speed 'changlngmeans ineffectual whereby said motor when the scanner is placed in man phase chronis'm: and means to said syn-.
a. 3. men."