US1875940A - Picture transmission - Google Patents

Description

Sept. 6, 1932. F. SCZHROTEJR 1,875,940

PICTURE TRANSMISSION Original Filed Feb. 25, 1929 T 24 JM/Z/F/A-k 110001470? mum/me INVENTQB v FRITZ SCHROTER BY 0%. QM

ATTORNEY Patentecl Sept. 6, 1932 UNITED STATES FRITZ SCI-IRFJ TER, OF BERLIN, 'GERMANY, ASSIGNOR' TO TELEFUNKEN GESELLSCHAFT' PATENT OFFICE,

FUR DRAHTLOSETELEGRAPH'IE' M. B, 11., 0F BERLIN, GERMANY, A CORPORATION OF GERMANY PICTURE TRANSMISSION,

Original application filed February 23, 1929, Serial No. 342,059. Patent No. 1,784,850, dated December-'16, 1930, and in Germany March 3,1928. Divided and this application filed November 18, 1930: Serial No. 496,386. e

effects of the fading phenomena during, op:

eration aresubstantially eliminated, and this result has been accomplished, in the present instance, by continuallyaltering thetransmitted wave.

According to the present invention, the

transmitted wave is changed as to; its free quencyin the short time interval between the exploration and scanning of any two suc cessive lines on a picture which is to be transmitted. It is, of course, possible, and also Within the spirit and scopeof the'invention,

to make this shift in frequency evens during the transmission of anyone linevof the picture without waiting until the completion of any particular line of scanning, should conditions where the is necessary arise, However, the

invention will be described only in connec tion with the former of the two above disclosed methods, since a system ,willhread1lyj suggest itself to anyone skilled in the art to which the invention relates by which the modified form of frequency shift may be accomplished. p 7

Other objects of the invention will, ofcourse, at once become apparentfrom a reading of the following specification. and claims when considered together with the accompanying drawing, wherein Fig. 1 illustrates one form of transmitter for use with my invention, and Fig. 2 illustrates a suitable receiver to cooperate with the transmitter of Fig 1, although itis to be understoodthat certain modifications and changes may be made in the showing and arrangement forth provided such changes fall withinthe spirit and scope of the hereinafter-appended claims.v a

The means, as shown by the drawing, for.

accomplishing the objects of the invention may consist, for instance, in the use of a re volving contact which is coupled with the scanning device or associated with the picture carrying drum and whose positions, actuate the element whereby the frequency of;the transmittedwave is altered in the-time interval between the exploration of any two successive picture lines. Of course,it is pos sible to chan e the frequency in manyways,

for example, y causing the contact to change;

the connection and flow of a direct current, or, perhaps break the flow of a direct current which serves to magnetize an iron-core .choke coil" with the result that the inductance thereofis influenced or changed. The said contact mayalso be used toconnect or dis-o connect a driving mechanism for acondenser and, as has been shown n thepresent in; stance, a change-1n frequency by way of an increase or a decrease thereof may alsov beaccomplishedunder certain conditions by the short circuiting of a resistance-member.

By such automatically produced changes in frequency the picturelines scannedin sequence maybe transmitted atdiiferent frequencies andsince the fading phenomena:

manifests this but rarely on two different frequencies in the same manner ,it is possible to improve the quality and efficiencyof trans-, mission by making use of two distinctifrequencies. 1

In so far as the use of the hereinafter de-:

scribed method, and the arrangementto be adopted at the receiving end, are'concer'ned; automatic changes in the receiving apparatus must be effected broadly in accordance withchanges in the transmission ,wavelength,

For .instance,in the case of heterodyne reception the locallygeneratedzwave should suit ably be so changed that the same beat frequency will always be preserved. However, it is also possible to work without any alterations of the heterodyne frequency by adjusting the heterodyne to a frequency which is equal to the frequency of the longer wave minus half the difference between the two other then, under certain conditions, it may i benecessary to change thetuning conditions atthe receiving end 1n accordance withthe changes in the wave length at the transmiss1on end. In such cases, of course, the receiving-arrangement must be so chosen and adapted that the changes in tuning are effected in synchronism with the changes in the wave length at the transmitting end. As

has been above pointed out, however, if the changes in the transmitted wave length-are small it is possible to leave the receiving apparatus unchanged, but whether or not the receiving apparatus is changed or unchanged will depend largely upon working conditions, which are diflerent for each case.

-N ow referring more particularly to 'the drawingaccompanying this description, a showingof one exemplification of the'idea 1 embodying'this invention, it has been presup; posed that the carrier frequency relation to the receiver is little changed so that the special measures describedfor changing the receiver may be dispensed with in this case.'f

"As shownby the accompanying drawing,

the'picture drum 1 carries the picture to be transmitted and for the purpose of concrete illustration of one embodiment of the inventionfa reflection type of transmitter using opaque or semi-opaque pictures has been shown; This picture carrying drum 1s driven from a synchronous motor of any desired type or characteristics, which-is maintained by any 'well known scheme in synchronism with a like element at the transmitter."

For convenience of illustration this synchros nous motor has not been illustrated.

As shown by the drawing, the angle a designates the portion of the picture drum which is free from the picture elements. It is this portion of the picture drum which serves for securing the picture to the drum and bythe present invention this is the portion of the picture carrying drum whose passage timebefore the scanning element is to be utilized in order to vary the wave lengthv of thetransmitter.

'The photo cell 2, which'is preferably of the annular type for 'a reflection type transmitter,'is arranged adjacent'the picture carrying drum 1 for the purpose of scanning the picture. Light from a source 3 is projected through a small, diaphragm 4 and lens 4: to

produce a point image of the luminous source rate motor 6 has been shown for the purpose of driving this perforated light chopper disk.

Associatedv with the picture'drum 1 is a commutating arrangement I which, through an appropriate speed reduction or driving gear mechanism, is so arranged as to run at one half the speed of the picture carrying drum The commutator 7 has half of itscircumference covered byv a conducting segment 8, while the remaining part of the commutator is an insulating segment. circuit through the battery 11 can be made through the electromagnet 10 by way of the sliding contact 9 only when the commutator is so turnedthat the contact 9passes overthe conducting segment 8 butwhile contact 9.-rests on the insulating portion of the commutator there is an open circuit in this path.

The change fromthe current interruption period (as shown by the drawing) to the current flowperiod byway of the contact 9 takes place at the instant when the angle passes through the scanning zone'in front of the photo cell This'action is utilized for the purpose of influencing the transmitter as follows: when current flows from the bat tery 11 through the electromagnet 10,the contact 9,'the conducting segment 8 and back to ground, a relay or switch 12 is closed and in this manner a portion of a resistance 13 conheated in series with a direct current generator 15 is short circuitedr This results in a change in the anode potential upon a vacuum tube 16 acting across the'terminals of'resistorl4.' V i i The tube 16 is so arranged as to act as a crystal controlled generator. The tube arrangement-16 comprises an oscillatory circuit consisting of parallelly connected inductance 17 and capacity 18 and in addition 'a tickler or regeneration coil 19 anda control carried by the drum 1 to:the next in'accordance with the arrangement hereinbefore disclosed. I

*As shown the dr awing the energy from I the oscillator 16 is amplifiedby means of an amplifier 21and is then directed to a modulator 22 which is also supplied with current variations from the'photo cell 2' which are first amplified in an amplifier 24 of well known characteristics or type. The output of the modulator 22 is then directed to a transmitter 23' ofany desired type and is transmitted by means of the antenna system 24.

Instead of a change in the carrier wave at the sending end, an intermediate modulation wave, if used, could be altered, for also in this manner the alteration in the carrier frequency will be insured automatically. F or instance, the scanning disk note could be varied, if such a disk is used at the sending end of the system.

To make reference now more particularly to Fig. 2 covering the receiver form of arrangement suitable for combination with the transmitting system of Fig. 1, signals as transmitted from the transmitting antenna 24, or the wire line equivalent, are received upon the antenna and suitably amplified through the receiver amplifier 31. Connected with the output of the receiver amplifier 31 is a local oscillator, generally designated 32, adapted to produce with the incoming signal oscillations a beat frequency of suitable value, which signals are then detected and amplified in detector-amplifier system 33 g I claim and des re to secure by Letters Pat-. cut is the following:

and through the conductors 52 are directed to a glow lamp, or the equivalent, for the purpose of producing variable intensity glow to influence a suitable picture recording surface carried upon a record drum 36. Light from the glow lamp, or the equivalent, is directed through the optical system 35 so as to focus sharply upon the record drum. The record drum, as it is rotated in synchronism with the drum 1 of Fig. 1, drives through a shaft 37 a second commutating arrangement 50 to be more particularly described hereinafter.

Now making reference to the oscillator system 32, the arrangement comprises the vacuum tube 38 provided with the usual grid and plate coils 39 and 40 which are inductively associated, and across one is placed a variable capacity element 41 for the purpose of tuning the system. Current for the tube 38 is supplied from a direct current source 43 which is shunted by resistor element 42 and in series with the source 43 is a resistor 44 which may be tapped at a variable point 45.

Similarly to the manner shown in Fig. l,

" when the record drum 36 is being rotated, the

commutator 50, which is in the nature of a non-conducting ring provided with a semicircular conducting strip 51, permits or prevents current to flow through the circuit in- T cluding the battery 52,the relay winding 47,

-.frequency is relatively slight in view of the fact that the oscillator is crystal controlled, but nevertheless it is sufiicient to produce a change in theresulting beat frequency sulfifcientto permit reception of the variable frequency picture modulated carrier sent out from the transmitting arrangement of Fig. 1, so that with suitable tuning the system for the contact48, the conducting portion of the commutator the contact53and back to the battery 52. In the position shown, current cannot flow and ithei relay 46 isttherefore'open. 7

.As. the record drum36 is rotated and arranged so as to carry with it the commutator This closure of the relay 46 will erated thereby. To be sure, this change in recordingshown by Fig. 2 provides a means by which the detr mental effects of fading maybe avolded through the continuously varying character of the transmitted wave.

Having now described my invention, what 1. Inapicture receiving apparatus, a supporting drum for a recording surface, a source for producmgrecordmgs upon the recording surface carried by saidcrecord drum, means for receiving transmitted s1gnals perlodically varying in frequency by predetermined amounts,.a local oscillator for generating a frequency suitable for producing a constant beat frequency from the varyingfrequency received signals, and'means operable at predetermined time periods for varyingthe frequency of the local oscillator for inaintalning a constant beat frequency irrespective of the change'in the frequency of the received slgnals.

:means for utilizing the resulting beat fre quency energy for producing a record of the received signals, and means responsive at predetermined periods duringthe recording action for altering thefrequency of the local oscillator for, maintaining a constant beat frequency at periods of change in frequency ofthe incoming signal energy. 1 8 0 3. In a picture receiving apparatus, a re'cord drum carrying a recording surface, optical means for influencing the record surface carried upon'said record drum, means for causing said optical system to trace a pre determined path along a record'surface carried upon said drum, means for receiving varying frequency transmitted signals, a local oscillator for generating frequencies to produce with said received signal frequencies a-beat frequency of predetermined value for able for. producing a desired beat frequencies fromthe received signals, producing from the resulting beat frequencies visible indications of the received signals, and varying at predetermined time intervals the locally generated frequencyfor maintaining a constant beat frequency at periods of change in the frequency of the incoming signalling energy.

' FRITZ soH o'rE controlling said optical system, and means;

ol'aerable at predetermined periods in the re cording upon said record surface corresponding to periods of changes in the frequency of the incoming signal energy for varying the frequency of the said local oscillator for maintaining constant beat frequency irrespective of the frequency of the incoming signal energy.

4. In a pic for producing visible picture representations, means for receiving transmitted signals which vary periodically in carrier frequency by predetermined amounts, means for producing from the received carrier frequencies beat frequencies from which the visible representations are produced, and means operable atypredetermined time periods corresponding to the exact periods of change in the received carrier frequency for maintainingconstant beat frequencies in'the receiver.

5; In a si nalling system, means for receiving si nalling oscillations transmitted with a periodically varying carrier frequency, means for generating locally constantfrequ-ency energy for producing with the received signals beat frequencies of pre- 7 determined value, means for producing from 1 the resulting beat frequencies visible indicafrequenciesof predete mined value from the j received signals, and varying at predetermined time periods the locally generated frequency for maintaining constant beat frequency in the receiver irrespective of the chzl nge inthe frequency'of the received signa s.

ture receiv ng apparatus, means 7, In alrec eiving system, the method which comprises receiving signals'varying in frequency at a substantial-112 constant rate,

locally generating energy 0 a frequencysuit-

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