US1686355A - Translating device - Google Patents

Description

MWU HEE'LWLIWUL @Lrmwnn 'nuvwn Oct.I 2, 1928, l 1,686,355

, E. c. WENTE TRANSLATING DEVICE Filed March 22', 1924 l vlil-*attentiou.2,191213. y' -4 U'NiTED STATES' PATENT OFFICE.

EDWARD C. WENTE,- OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC GOM- IPANY, INCORPORATED, OF NEW YORK, N. Y., CORPORATION OF NEW YORK.

applicati@ inea Maren e2, 1924. serial No. 7o1,o1s.

This invention relates to translating dcvices and more particularly to an electromagnetic device for converting alternating current of varying amplitudes into a light record, the tone'values of the successive elemental areas of which correspond to the` envelope of the Asuccessive instantaneous an1- plitudes of the alternating current.

. Inapplicants Patent No. 1,638,555, Aug. 9, 1927, Serial No.635`,886, filed May 1, 1923 an arrangement is disclosed for obtaining a light record, the successive tone values of which are a function of the instantaneous amplitudes of an impressed current of any desired wave form, such as that of a wave corresponding to speech. It is often found desirable to transmit current of-such a wave form as modulations of a' carrier wave of higher frquency. In .such case i-t has been customaryto obtain the light sensitive record -from the modulated carrier wave in two steps.

The carrier wave is first demodulated to product current of wave form identical with that of the modulating wave form which current is then used to operate an electromag-l netic device or light valve to produce the light record.

A11 object of this invention is to accomplish both these steps inthe light valve by means of a novel adjustment thereon Y This object maybe attained by providing in combination with Aa light source, a light valve comprising a pair of electrical conductors arranged in planes at rightangles toy a magnetic field so as to define under certain circumstances an aperture through lwhich light is transmitted. Electrical waves .of

' Avarying amplitude are supplied to the con- Vductors to'cause movement thereof relatively 'to each other. The separate conductors are arranged in adjacent planes so that each con- `of varying amplltude.

The novel features which are considered lcharacteristic of this invention are set forth with particularity in --the appended claims. The invent1on both as to its organization and method of operation 'together lwith other objects and advantages thereof will be. under# stood from the following' description having reference to the accompanying drawing consisting of the following figures.

Fig. 1 is a diagrammatic showing of an arrangement for modulating carrier waves in accordance with the'tone yalues of elemental areas of a transparency of a picture to be transmitted by electricity;

Fig. 2 is a diagrammatic showing of an arrangement for transmitting telegraph signals by means of carrier waves.

Fig. 3 is a diagrammatic showing of a light record producing arrangement for use with either Fig. 1 or Figp2. y

Fig'. 4 is a cross section ofthe optical system of- Fig. 3 on a plane at right angles to the paper. s

Referring now to Fig. 1, a modulator M is supplied with carrier'waves from a source C and with picture currentfrom a photoelecj' triccell P and picture amplifierl PA.. Modulated carrier waves from the modulated M are impressed upon the transmission line L; vThe photoelectric cell P is located within a transparent drum 5 which is driven in any .suitablemanner by shaft 6. Mounted on the drum 5 is a transparency of the picture to be transmitted. Light from a source 7- is .fo-14 v cussed by means of lens 8 upon the transparency of the picture through an aperture in ascreen 9. The' intensity of the light affecting the photoelectric cell P'is determined bythe tone value or density of the elemental area ofthe transparency of the picture ,which is, at any instant, adjacent to the aperture in the screen 9 at the focal point rof the light beam.'l The intensity of the light within the photo-electric cell P in. turn determines the amount of current iiowing 'from' the battery 10through. thephotoelectnc cell P and re'-}'--f`.-sl

sistance 11 and consequently the potential drop through the resistance 11 which potential is impressed upon the input circuit of A .Y

the picture amplifier PA. The amplified icture current is impressed upon the moduator' M-by resistance 12 simultaneously with carrier current from the. source C by trans'A former 13. Modulated carrier w ves from the modulator M are then impre sed uponl the line L by means of transformer 14.

Another arrangement for impressing carrierwaves modulated in accordance with signals upon the line 'L is shown in Fig. 2. rier waves from thesource C are impressed Carupon -the input circuit of amplifier A by means of'transformer 13. Amplified carrier waves in the output circuit of amplifier A are then impressed upon the line L by means of transformer 14. The input circuit of amplifier A may be short circuited by means of key to interrupt the transmission of carrier waves to the line L. Consequently, by manipulating key 15 in accordance with a message code, impulses of carrier waves may be impressed upon the line L corresponding to said code.

Areceiving arrangement is shown in Fig. 3. Modulated carrier waves from the line VL are amplified in the amplifier CA Y and impressed by means of transformer 16 on the conductors 17 18 of light valve V. The general features of light valve V are identical with the light valve described in applicants Patent No. 1,638,555, supra. rlhe arrangement of the conducting wires is specifically different as will be explained herein- Referring to Fig. 4, it is' seen that the conductors 17, 18 according to the preferred arrangement of the present invention are mounted in adjacent planes so that they may move independentlyv of one another. Under no-current. conditions they 'are so adjusted that the light passage from the light source 20 to the recording blank 21 is just closed by the conductors 17, 18. By nocurrent condition is meant broadly the condition when the amplitude of the carrier wave is zero. It is not necessarily the condition when no current is flowing in the movable conductors of the light valve.4 Light.

. from the source 20 is directed by means of lens 22 upon the conductors 17, 18. The source 20 is lso arranged with respect to the lens 22 and conductors 17, 18 that the conductors are intensely and uniformly illuminated over a surface at least as wide, in a direction transverse to the conductors, as the maximum opening of the valve, that is, the maximum separation of the conductors 17, 18 and sufficiently wide in the direction of the conductors 17 18 to expose the width of the trace on therecord blank 21 in the direction of rotation. The width of the trace is determined by the width of the aperture in the `screen 24. An image of the aperture formed by a small section of the conductors 17 18 is projected upon the light sensitiverecord blank 21. The magnetic field within which the conductors 17, 18 are mounted is set up 'by a coil 25.

Referring' again to Fig. 3, the record blank 21 is mounted on a drum 26 which is driven in suitable manner by a'shaft 27. d With the conductors 17 18 mounted, as shown in Fig. 4 so that n'o light is: transmitted when no current is traversing conductors 17 18, the valve will operate as al demodulator when actuated by modulated carrier transmission of light for one-half of each v cycle and remain closed during the other half.

If the adjustment is made as just explained so that the light is cut off-with the strips in normal position, the light transmitted during each alternate half cycle is directly proportional to the amplitude of motion of the conductors. If the motion of the conductors follows the current amplitude the transmitted light impulses follow the envelope of the impressed modulated carrier wave. As a result of the movement of thelight sensitive record blank 21, in a direction at right angles to the conductors 17 18, that is, in ,the direction of their movement, the record is in the form of a trace of varyingbrightness corresponding to the envelope of the carrier wave.

In order to have, the motion of the conductors follow the instantaneous value of the current as accurately as vpossible it is important that the damping of the conductors e sufficiently large. The frequency of the modulations that may be recorded by the deviceis largely determined by this quantity.

d To make this point clear an example is given for the transmission of a 4x5 inch picture with a carrier wave of 1200 cycles-per second withthe equipmentof Figs. 3 and 4.

The valve will transmit 1200 light impulses per second to therecording blank 21,

whichmay be a photographic lm. If the film is run suiciently. fast it will after development show 1200 dots in the space the image traversed in 1 second. If the plcture.

is to have one hundred dots per linear incha value which obtains in a good grade of news paper half tonethe drum runs at -a linear speed 'of 12 inches per second.` If the drum A .is 2 inches in diameter, the revolutions per second should be 12 divided by 2H. For the 4x 5 inch picture 400 revolutions would be required so that the time required for transmitting this picture would bel 4oo 2n=210 seconds' @13% minutes.

portional to the envelope of the carrier wave l Y i at each instant unless thedamping of the vibrating system has been suitably chosen. The response to changes in current 'amplitude will be most' exact if the system isjmade aperiodie; condition, however, means lower sensitivity anda dampingso large is in general not necessary or advisable."V thefamplitude drops to one vtenth of its A.initial valuev in'going from one dot to thenext .when the current is suddenl 'inten-u ted, satisfactory results will be lo tained.;

condition would require a. d

fined as the reciprocal of the time required initial value when the impressed vforce is removed). This value of damping may be obtained by shunting the valve with a suitable resistance. v

In order to obtain a continuous trace of varying brightness the drum would need to run at a much lower linear speed, so that successive impulses of light would expose overlapping surfaces. In a modified arrangement the drum is rotated in a direction at right angles to the movement of the conductors 17, 18. The speed of rotation could be the sameas that given hereinbefore as an eX- ample. The record' with this arrangement would be in the form of dots having uniformsv dimensions in the direction of the trace'and lengths at right angles to the trace `corresponding to the envelope of the modulated carrier wave. By slowin down the; speed of rotation of the recording drum the recfor a displacement to drop to ord could' be obt-ained in the form of a continuous line of varying width corresponding to the envelope' of the modulated carrier wave. i In the preferred embodiment ofthe lnvenl tion the natural frequency of the valve strips is made the same as the frequency of the carrier waves. This is desirable not only because it increases the sensitivity of the valve butalso because it reducesthe effect of disturbing currents of different frequency which may -find access to the valve under .actual operating conditions.

For the transmission of pictures by electricity the arrangementof Fig. 1 is combined with that of Fi 3 by connecting the lines L together. The ldrums 5 and 26 are driven in synchronism by any suitable arrangement such, for example, as that shown in the vcoending a plication of M. B. Long, Serial go. 681,34 v,filed December 1.8, 1923. They not only rotate in nchronisn but are also moved axially relatively to the shafts. As

-the drum 5 rotates, carrier current-modulated in accordance with the varying tone values of the successive elemental areas of the picture is transmittd over line L and impressed in amplified form upon the conductors of light valve V. The movement of these conductors relatively to each other allows 'l'fjr-:originating in the arrangement o more or less light from the source 20, depend-f ing upon the amplitude values of the envelope of the modulated' wavesy to affect lthe, elemental areas of the light sensitive record blank 21 on'the drum 26. It is thus evident that the reproduction of the picture from the modulated carrier waves is effected in` a sin# gle step by means of the light valve V and d itsassociated optical apparatus.

For the reception oftelegraphv Fig. 2 by means of the arrangement of Fig. 3,- no syn-- chronizing apparatus is required. The impulses of carrier current corresponding to4 the message code are transmitted over the line L and cause an intelligible light record,

on record blank 21. providing that drum '2 6 is rota-ted at a uniform speed. l

A n important feature of this invention is the transformer -coupling between the am pliier CA and the light valve V. -In 'any practical recording or reproducing system amplification is essential and thenecessary amplification is best accomplished by the use of electron discharge devices; In systems of this kind heretofore known, this required the direct connect-ion ofthe light valve to the electron discharge device, as exem lilied in. the copending application of M.

pedance of only a few ohms, while the dis- Long. i supra. Since-the light valve V has an im.

charge device has an impedance ofseveral thousandohms', such direct connectio'ris necessarily ineflicient and necessitates fai large f amount of amplication. By this invention alternating currents are supplieddirectly to the light valve and an efficient coupling trans former 16 is used between th'e'electron discharge yamplifier C A and the li ht valve V. The `transformer 16 .is a ste own trans-f former and--matches-the hig out ut im pedance oftheamplilier CA. to the ow impedance of the valve V. Two embodiment-sof the invention have been specifically described. The scope of the the amount of light passing throu h said pasge in accordance with only hal of the enope ofthe amplitudes of said modulated waves.

2, In alight recording system, a light valve comprlsin amovable conductor located in a magnetic eld, alightpassag normally closed lby said conductor and opened only during one directionof movement thereof, means'to supply electric current of varying amplitude and irection to said conductor to cause movement e thereof, and means` to obtain a record of thef;20 i i amount of light allowed to pass throughsaid- Passa e.:

.closed by said rconductor and only opened during one direction of movement of said conuctor, a source oflight for said passage, and'.

n an optical arrangement,ajlight'valve `compr1s1nga movable conductor located av magnetic lield, a light passage normally 5- means to supply electric currentgjoi'f varying clarity to sald conductor to causemovement t ereof whereby llight is allowed pass through-said passagewhen current of one,

- polarity only is passing through said conductor. Y I Y 4. In an electro-optical system, a directed beam of light, an aperture on which said `beam is focussed, an electrically controlled movable screen comprising a conductor located in -avmagnetic field normally closing said aperture, a source of modulated carrier l0.

, prising a movable conductor located in a magnetic iield actuated by varying current in said conductor corresponding to modulated carrier waves from said modulating means, a source of light for said light valve, and a light sensitive record blank exposed to light from said source under the control of said light valve for reproducing the picture.

6. In a system for the transmission of pictures by electricity, a source of carrier waves, a source of picture current comprising a photoelectric cell and a movable element for effecting changes in said cell in accordance with the tone values of the elemental areas of the picture, a modulatingdevice whereby carrier waves from-said source of carrier waves are modulated-by plcture currents from sald picture current source, an electromagnetic .light valve comprising a movable conductor located in a magnetic field actuated by vary-4 ing currentl in said conductorcorresponding "les llight valve having two movable mem 'to modulated carrier waves from said modulator, a source of light and a. second movable element for eliecting the reproduction. of the picture b means of light from said source .cont-rolle bysaid light valve.

'7.`In an electro-optical system, a light -valve having movable conducting members,

definin a variable-aperture, means to trans'- mit lig t through said aperture, a light sensitive recording blank exposed to said transmitted vlight, a source of alternating current modulated in accordance with a record to'be reproduced, an electron discharge amplifier for amplifying current from sald source and amplifier to the conducting members of said 8. In an electro-optical recording i iining a variable aperture, a source of light, a lens for forming an image of said source of light in the plane of Isaid aperture, a lens for forming an imgge of said aperture upon ya light m a ers desensitive record blank, and means to vary said aperture in accordance with impulses of one polarity only of an alternating current wave. 9. In an electro-optical system, a light valv having an aperture therein, a source for directing a beam of light upon said aperture, a movable conductor normally closing said ap.-

erture, and means for generating and transmitting through said ,movable conductor an-.

alternating current, said conductor vibrating 1n response to sa1d current 1n such a manner that the aperture is openedonly while said current is fiowmg in a given direction.

10. In an optical system, a light valve having an aperture therein, a source for directing a beam of light upon .said aperture, a movable conductor normaliy closing said aperture, a source of alternating current, means to modulate said current in accordance with the characteristics of a picture, and means for applying the modulated current to said conductor, said conductor responding to said current in such a manner that the aperture is opened onlywhile current is flowing in a certain direction.

11. In an optical system, a light valve having an aperture therein for the passage of light, a screen normally closing said aperture and comprising two separate elements arranged to vibrate toward and away from each other,I a source of alternating current, and

means responsive to said currentfor causing said elements to vibrate such that when the current is of one polarity said elements are separated to open the aperture and when the current is of the opposite polarity' the elements are brought together to maintain the aperture closed.

12. An electro-optical system comprising a passage through which light is transmitted, a source of.modulated carrier waves, and

vibrating means comprising' two members` movable in separated but parallel planes to vary the amount of light passing through said passage in accordance .with the envelopev f the amplitudes of said modulated waves.

13.' In an optical system, a light passage,

a source forsupplying light to said passage,

a movable screen controlling the Aamount of light passing through said passage from said source, means for observing the amount of light allowed to pass through said passage, means to 'supply alternating electric current to move said screen to varv the amount of light passing 4through said passage and to cut oli-substantially all light during a portion of each cycle of the alternating current, and means to cause relative movement betweenA the vobserving means and the light passage at such a .rate that discrete portions of the observing means are acted upon by the light passing throughsaid passage during succes- ,y

sive cycles of, the alternating. current.

141v The A,method of transmitting a picture,

which consists in sending.; currentV corresponding to the degree of shade of su v 'cessive picture elements, applying these cur- I rent impulses to operate a light valve, and, moving a sensitive ilm at a definite rate with respect to the rate ofoperation of said light valve to produce on said ilm discrete halftone dots lin area corresponding to the magnitude of the respective current impulses.

Lasagne 15.y In combination, means to generate curthat its' openings will record discrete halftone dots to make the received picture.

In witness whereof, lll hereunto' subscribe my name this 14th day of March, A. D., 1924i EDWARD C. NTE,

fjdingtoehedegr i -v vfe elements of a pictm ey means torapplyfsaid currents to operate a'

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