US1716903A - Synchronizing method and arrangement therefor - Google Patents

Abstract

266,008. Telefunken Ges. f³r Drahtlose Telegraphie. Feb. 15, 1926, [Convention date]. Copying-telegraphs; synchronous movements.- Portions of the drum or other picture carrier not occupied by the picture or signals are utilized for transmission of an auxiliary frequency for use in the regulation of synchronism without stopping the transmitter or receiver. The transmitting and receiving drums 1, 2 are driven through gearing 15, 16 from motors 11, 12 under the control of La Cour wheels 13, 14 respectively. The picture on the drum 1 is explored by the movement, parallel to the axis of the drum, of a beamof light from a source 5 and lens 4 passing through the back of a light-sensitive cell 3, and reflected back on to the cell. The varying potential thus produced across a resistance 21 is amplified and transmitted to the receiving station where, after further amplification, it is applied to a Kerr cell 6 to control the intensity of the' light from a source 10 incident on the sensitive surface on 'the drum 2. The space between the edges of the picture on the drum 1 is provided with means, such as equally-spaced lines, for producing current fluctuations of predetermined frequency in the circuit of the cell 3. These fluctuations produce corresponding fluctuations in the intensity of the beam incident on the drum 2 and are utilized in conjunction with a stroboscopic disc 8, rotated in the path of the beam through gearing from the drum 2, to indicate lack of synchronism. Movement parallel to the axis of the drum 2 is imparted to the beam and to the disc 8. The La Cour wheel 14 is brought into synchronism with the wheel 13 by manual adjustment of the condenser 26 in the circuit of a valve oscillator 25 which supplies the magnet of the wheel 14 through an amplifier 27, a telephonic-microphonic relay 30, and an amplifier 28. Alternatively, the auxiliary frequency may be produced by non-optical, means such as a switching device actuated by the drum 1. The auxiliary frequency may itself, be used to control the motors 11 and 12. The Specification as open to inspection under Sect. 91 (3) (a) comprises also an automatic adjustment of the condenser 26. This subjectmatter does not appear in the Specification as accepted.

Description

Julie 11, 1929.

F. SCHROETER SYNCHRONIZING METHOD AND ARRANGEMENT THEREFOR Filed Jan. 25, 1927 o mu Mu w

INVENTOR \TZ SCHROETER BY A4 /fl /am TORNEY Patented June 11, 1929 UNITED- STATES PATENT OFFICE.

FRITZ SCHBOE'IER, BERLIN, GERMANY, ASSIGNOB TO GESELLSCHAFT FHB DRAETLOSE TELEGRAPHIE M. B. H. HALLESCHES, OF BERLIN, GERMANY, A COB- IOBATION F GERMANY.

SYNCHRQNIZING METHOD AND ARRANGEMENT THEREFOR.

Application filed January 25, 1927, Serial No. 163,335, and in Germany February 15, 1926.

The invention relates-to a method and to arrangements for the synchronization and phase adjustment of moved drives in picture transmission, high-speed telegraphy, and

similar fields of application. The invention is predicated, both at the transmitter as well as at the receiver end, on the existence of contact-makers being as constant as feasible and variable in frequency fOr instance, tuning forks, oscillating quartz crystals, or most preferably thermionic generators which drive synchronizing motors in a reactionless arrangement, by way of the mostly necessary amplifier stages, the .moved drives being coiipled with said synchronizing motors.

Such local contact-makers (rhythm producers) at both stations heretofore were used in this manner that their frequencies were adjusted and balanced outside the picture-transmission periods proper by way of the radio or line communication. This, in the case of tube generators which are kept properly constant, is the easiest way of keeping the two frequencies in agreement and to thus maintain synchronism during the entire period of transmission. However, unless agreement between the frequencies is insured by special means such as the use of air condensers which are little dependent upon the temperature,

3 while carefully keeping all potentials at a constant value, etc., it is hard, if not impossible,

to preserve synchronism during the transmission of a picture. Hence, the object of the invention, in all such cases where synchronism between both contact-makers is attended with difiiculties on account of the local generators, is to disclose means adapted to a simple control and to balancing and adjustment during the time of picture transmission; and more particularly speaking it has recourse for this purpose to What is known as the dead picture angle which results in connect-ion with the use of the drums or cyljinders for picture transmission by that the picture to be transmitted or the receiving film must be held in position by certain means, for which purpose a certain part of the surface of the cylinder is required on which the securing means are-carried. In the description and illustration of the invention as hereinafter indicated, the assumption is made that the picture transmission comprises an analyzmg lightray for the decomposition or resolution of the picture at the transmission end,

and a corresponding light ray for the picture assembly or recomposition at the receiving end. During part of the time of revolution of the picture drums, the impinging light ray is thus caused to pass over the so-called dead angle, and these times, according to this invention, are employed for checking the tube generators or other contact-makers at both ends, without special transmission means being required therefor.

The ways and means used for accomplishing this end will be best understood by reference to the accompanying drawing, wherein:

Fig. 1 shows a diagrammatic form of the transmitter; and I Fig. 2 shows a diagrammatic form of the receiver.

Referring to the drawing 1 is the transmission drum, 2 the receiving drum, 3 the photo-electric cell mounted at the transmission equipment and adapted to explore the picture by reflected light. The light issuing from a lamp 5 is rendered convergent by means of a lens 4, and impinges upon the pic ture surface in the shape of a conical light pencil which is passed through the central tube piece of a conveniently formed cell 3, being reflected at the picture surface in the shape of a diffuse ray bundle (indicated by broken lines), and thus produces, by virtue of the variations in its intensity corresponding to the changes and distributions of light and dark on the explored picture, proportioned current variations which are transmitted to the sender. At the receiving end is a light-control cell 6 which is here supposed to be a Kerr cell of the kinddisclosed by Karolus. This cell is diagrammatically indicated as a simple light-permeable condenser through which the ray cone issuing from lamp 1O and passed through lens 9 is sent. Between the plates of Kerr cell 6 (type Karolus) the brightness of the light is controlled in well-known manner. The lens 7 throws a picture of the illuminated slit of 6 upon the cylinder 2. However, before this happens, the' rays pass through a disk 8which revolves at the same rate of speed as the cylinder 2 in the path of the light rays; Arrangements are so .made that the edge of the said disk 8'is permeable to the light with the exception of a portion which corresponds to the dead angle of the cylinder. The value of this feature will be better understood from what fol-,

I a stationary figure or outline, in a way wellknown from stroboscopic work." But when lows further below. a

11 and 12 are driving motors for the picture-bearing I drums. They have here been supposed to consist of shunt-wound direct current motors, and they are driven at. as constant a potential as possible. If desired, spa v cial 'speed controlling 'means may be'pr'o'vided:

for rough adjustment of the correct speed. For the object of synchronization by the local contact-makers, similar to the La Cour -wheel scheme,v there are used the toothed sirens or additional excitation by the local frequency wheelsl3 and 14, respectively, provided with the corresponding exciting electromagnets 18 and 19, respectively, which are fed by means of a direct current auxiliary excitation and an or contact-maker; It is supposed that during the rotation of the cylinders 1 and 2, the latter are not subject tov axial shifting, but that the optical resolving. and reassembly devices for the picture move along the drum axes, in other words, at the sendingend the elements 35 and at the receiving end the corresponding elements 6 to 10. The current variations produced by the photo-electric cell 3 cause corresponding variations of the control potential of the amplifier'tube 22 in the resistance 21 and a batteryv 20 connected in series with said cell 3, said potential variations being brought to actin well-known manner upon the transmitter. In the receiver equipment, in case of wireless transmission, the currents comin in at the receiver 23 are intensifiedby ampli ers 24., the resultant potentials being supplied to the Kerr cell 6 to be controlled thereby in accordancewith the variations of the incoming currents.

Tooth-wheel 17 corresponds to the toothwheels 16 andv 15, respectively, so that with a convenient mechanical coupling, disk 8 rotates at the same rate of speed as the drums 1 and 2. In the dead picture angle of the transmitting cylinder, over the entire lengthof the cylinder, there is rovided a sort of line screen or figure wit periodic brightness In the illustration here shown, this lng upon a light background. When the dead picture angle of cylinder 1, that is, the part not occupied by the picture to be transinitted, passes under the analyzing or explor mg luminous spot, the said line screen (which may consist of a few heavy lines) causesperiodic variations in current in the photo-electriccell 3, which are radiated by the sender for. brief periods as a sound. If, then, on the disk 8, a line screen correspond ing to the other at the same speed of rotation and the desired frequency, is provided, if this, line screen is located in the ,proper place, it will-be subject to illuminatiiin-from the Kerr cell 6 at a frequency produced by the transmission screen so that, in the pres- -ly from each other,

he that the stroboscopic figure upon the disk ence of perfect synchronism, it seems to form 8 will seemingly revolve in one direction or inthe other. This travel of the figure can. be best observed with the eye,.and the rotary condenser'26 of the contact-making tube generator at the receiverend is conveniently adjusted untilthe figure seems a standstill upon 8.

The local generator at the receiving end con. sists of a regeneratively coupled thermionic generator 25 with a 'variable condenser 26 of the rotar type, an additional loosely coupled amp ifier stage 27 which, through a nonagain to come to reacting coupling 29, 30, serves to control a third and, if desired, a fourth amplifier stage 28. Reaction is prevented by that 29 consists of atelephone, and 30 of a microphone, respectively. Of course, instead of this arrangement, reaction can beprevented also by that the amplification is combined withfrequency multiplication by that in each stage, "for instance, the double frequency is obtained at the plate end, which is thereupon further amplified. At the transmitting end, of course, a corresponding generator is provided (not shown in the figure). The local manerators are kept in rhythm as far as feasi le,and, according to the invention, balanced,'if.necessary, by the variation of the For this object it is, of cours'e,.neccssary that thedead picture angle should be of convenient size; the securing means of-the film is suitably doubled so that there result for each revolution of the cylinder two such angles displaced by 180 degrees with reference to each other. It is natural that the stroboscopic phenomenon can be utilized by the aid they are contact-maker in the receiving equipmentf of disk 8 only if the drums turn a. sufficiently great number of times each second so that the .mit only the tone frequency produced by the "auxiliary screen in the dead angle. By providing a slip coupling of well-known kind, the

picture drum 2 in the receiving equipment of disk 8 caused to rotate by positive means at the same rate of speed and the same phase as drum 2 is allowed to slip withreference to the driving axis until the stroboscopic figure of 8 appears in the path of the rays of the Kerr cell 6 and occupies the proper position. When this condition is fulfilled, the rotation of the two drums is co-phasal. The slip clutch between drives 2 and 8, on the one hand, and the driving motor on the other hand, is here not shown for the sake of simplicity.

Having described my invention, I claim:

1. A synchronizing system for use with picture transmitting and receiving systems including, a picture transmitting and a picture receiving drum, mechanisms of substantially constant periods of rotation for driving each of said drums, a picture surface for transmission embodying substantially the entire surface of said transmitting drum and a zone having a definite auxiliary pattern embodying the remaining surface of said transmitting drum, means for reflecting light from the surface of said transmitting drum and influencing a carrier frequency, means provided by said zone of auxiliary pattern for influencing the said carrier in a constant manner, means located at said receiving drum for recording the picture area and at definite periods during the recording of said picture area reproducing said auxiliary pattern occupying said zone of said picture drum, stroboseopic means for determining phase variations in the period of rotation of said receiver and transmitter drums during the period of recording said pattern on said zone of the transmitter, and means for correcting the speed of said receiver drive mechanism for bringing the said drive into constant phase relationship with respect to said transmitter 4 drive.

2. The method of synchronizing picture transmitting and receiving systems which includes, transmitting and receiving a picture area at interrupted time intervals, transmitting and receiving during the interruption in said time intervals definite intensities of light and shade, rotating a transmitter and a receiver for said transmission and reproduction at a substantially constant rate of speed, stroboscopically determining phase variations between the speed of said transmitter and receiver during the interval of transmission of said constant light intensities, and correcting the speed of one of said instrumentalities in accordance with said stroboscopic observations.

3. The method of synchronizing picture transmitting and receiving drums which includes, rotating said transmitting and receiving drums at a substantially constant rate of speed, transmitting and receivin a picture surface during the greater part of each rotational movement of said transmitter and receiver, transmitting and receiving during a lesser part of each rotational movement of said transmitter and receiver a constant intensity of light and shade, stroboscopically determining phase variations in the'speed of said transmitter and receiver during the lesser periods in each rotational movement while transmitting said constant light intensities, and regulating the speed of one of said transmitting and receiving drums in accordance with said stroboscopic observations for bringing the two systems into synchronism.

4. In a picture transmitting and receiving system, a picture carrying drum at the transmitting and the receiving station, means for rotating the said drums at substantially synchronous speeds, a picture surface for transmission covering substantially the entire surface of said transmitting drum, a screen of predetermined light intensity coverin the remaining part of said transmitting rum, means for transmitting light intensities from both said picture surface of said screen surface during each revolution of said picture drum, a disk provided with a screen of similar characteristics to said screen at said transmitter, means for rotating said disk at a speed corresponding to said receiving drum, means provided said screen on said disk and the signal impulses from said transmitter screen for obtaining a stroboscopic effect by the rotation of said disk and said receiver drum and obtaining a visual indication of variations in phase of the rotation of said transmitter and receiver drum, and means for correcting the phase of said rotating receiving drum to correspond with that of said transmitter drum.

5. A system for synchronizing rotating picture transmitting and receiving drums which includes, means for transmitting and receiving a picture during substantially the entire rotation of said drums and interrupting the transmission during the short period for each rotation thereof, means for transmitting a fixed and predetermined light intensity during the interrupted period of picture transmission for each rotation of said drums, means for rotating each of said drums at a substantially constant rate of speed, a disk member mounted at said receiver and having over a portion of its periphery corresponding to the area ofifixed and predetermined light intensity of said transmitter drum, a screen corresponding in said light intensity to said predetermined light intensity, means for driving said disk at a speed corresponding to that of said receiver drum, means for r fleeting light intensities upon the shade portion of said disk during said periods of transmission, means provided by said screen area on said disk and said light intensities reaching the same for stroboscopically indicating phase variations between the rotation of the said transmitter and receiver drums, and means for correcting the phase relationship of said receiver drum during the said interrupted period in the picture transmission.

6. An arrangement for synchronous operation of the transmitting and receiving elements in a picture transmittingand receiving system which includes, means for transmitting-and receiving a picture area at interrupted time intervals, means for transmitting 10 and receiving impulses corresponding to definite light intensitiesduring the interrupdiflerences in speed between the movement of the transmitting and receiving elements, and means for correcting the phase difierences at sald recelvlng system for coordinating the phase relationship of the transmitter 20 and 'receiver.

FRITZ SCHROETER.

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