US1694301A

US1694301A - Electrical transmission of pictures

Info

Publication number: US1694301A
Application number: US142734A
Authority: US
Inventors: Ernst F W Alexanderson
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1926-10-19
Filing date: 1926-10-19
Publication date: 1928-12-04
Anticipated expiration: 1945-12-04
Also published as: FR35520E; DE510214C; GB290298A; FR40242E; GB279457A; FR642847A; NL24807C; DE477444C

Description

Dec. 4, 1928.

E. F. W. ALEXANDERSON ELECTRICAL TRANSMISSION OF PICTURES Filed Oct. 19, 1926 3 Sheets-Sheet l Inventor-z Er-nstEWALexanders on,

His Attor'rleg.

Dec. 4, 1928. 1,694,301

E. F. w. ALEXANDERSON ELECTRICAL TRANSMISSION OF PICTURES Filed Oct. 19, 1926 3 Sheets-Sheet 2 E rnst E W Alexander-son, by His Attorneg.

E. F. w. ALEXANDERSON ELECTRICAL TRANSMISSION OF PICTURES Dec. 4, 1928.

Filed Oct. 19, 1926 3 Sheets-Sheet Inventor:

ErntFM/Alexgnderson,

b His Attorneg.

Patented Dec. 4, 1928.

UNITED STATES PATENT Fries.

ERNST F. W. ALEXANDERSON, OF SCHENECTADY,- NEWYORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK.

ELECTRICAL TRANSMISSION OF PICTURES.

Application filed October 19', 1926. Serial. No 142,734.

invention relates to the electrical transmission of pictures and an object of my invention is the provision of improved methods and means for the rapid and eflicient I transmission of pictures by electrical means.

My invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

Referring to the drawings, Figs. 1 and 2 are a diagrammatic representation respectively of a transmitting apparatus and a receiving apparatus embodying my invention; Fig. 3 is a diagram similar to Fig. 2 but drawn to a larger scale; and Figs. 4, 5 and 6 are modifications thereof. a

The picture to be transmitted may be an ordinary still picture, a moving picture,- or a view, and by the term picture as used throughout this description and in the claims I in tend to include all forms of pictures, draw-,

ings, printed pages and views of either still or moving objects. In Fig. 1 I have chosen to illustrate my invention being used to transmit a scene or view 1 of two moving characters. In front of the scene is the apparatus for scanning the picture and producing electrical variations corresponding with'the variations of the picture as determined by the unit areas thereof. As shown, it comprises'a hollow cylinder 2 having a series of lenses 3 mounted thereon and rotatedby an electric motor 4, the construction of the, cylinder being shown more clearly in the receiver shown by Fig. 3. .The lenses 3 are identical in construction and are mounted in the wall of the hollow cylinder in a spiral. Within the cylinder and behind the lenses at the focal point thereof is shown-a group of four small mirrors 5 which are arranged each to reflect a light beam from a different unit area of the picture into the window of one of the four photo-electric cells 7. I

The arrangement is such that as each lens 3 passes thegroup of mirrors each photo-electric cell receives light from a narrow vertical band or strip of unit areas of the view. Thus, with the apparatus shown, each lens as it passes the mirrors sends four beams of light to the photo-electric cells corresponding to the illumination of unit areas in four parallelyertical strips or hands of the View. In one'revolution of the cylinder the entire View will have been covered. In accordance with present practice in exhibiting moving pictures the cylinder may'be operated at a speed of approximately sixteen revolutions per second'. If, howcver,a .still picture is to be transmitted and is to be received on a light sensitive film or paper instead of being thrown on the screen 12 to be observed, a slower speed may suffice. I have shown my invention applied to wireless transmission wherein each photo-electric cell 7 is connected to a device 8 which may include means for amplifying the impulses received thereby and for producing and modulating a radio car rier wave which may be broadcast from antennae 9. The wave lengths of the carrier waves produced by each device 8' will be separated by a suitable interval to facilitate tuning of the receivers used therewith. It is to be understood, however,'that my invention is not ber or screen 12, a hollow cylinder 13having a series of lenses 14 set therein in a spiral similar to the cylinder 2 of the transmitter shown in Fig. 1 and a driving motor 15. By suitable means, examples of which are well known in the art, motors 4 and 15 are caused to run in synchronism, hence the cylinders 2 and 13 rotate synchronously. Within the cylinder 13 and at the focal point of the lenses 14 are four small mirrors 16 similar to mirrors 5 of Fig. 1. At a point opposite the end of the cylinder13 are four oscillographs 18 having small mirrors 19 and in a suitable position to throw light on these mirrors I provide suitable means, shown in the drawing as comprising four light sources 20. A light beam from each of these sources is condensed by a suitable lens 21 on one of the oscillograph mirrors from whence it is reflected to an-. other lens 22 and condensed on one of the four mirrors 16. The four light beams reof each of the four spots of light thrown on the screen is controlled respectively by the tour oscillographs. For energizing these oscillographs I have shown four carrier wave receiving sets 25 each having .a receiving loop 26 and tuned to receivethe carrier wavessent out by the respective sending devices 8.

The arrangement is such that as the first lens 14 of the spiral passes the group of mirrors 16 four spots of light are directed on the screen which as the cylinder rotates trace four vertical bands of light across one end of the screen. The next lens being slightly offset in an axial direction causes another four spots to trace another four vertical bandsnext adjacent the first four and so on for each lens of the series, the light spots from the last lens tracing bands across the opposite end of the screen. The cylinder 13 rotates in synchronism with the cylinder 3 at the sending station and as each oscillogr aph varies the amount of'light directed on one of the four mirrors 16 in response to the light received by the correspondingly arranged photo-electric cell 7 at the sending station an image of the scene 1 is projected on screen 12. By employing a plurality of small mirrors 16 together with a corresponding number of lightcontrollingmeans whereby a plurality of light spots simultaneously sweep across the screen a much more eflicient illumination of the screen is obtained. This plurality feature enables me 'to employ a fewer, number of rotating lenses and lenses of a correspondingly larger diameter than would be the case were a single mirror used and a single spot proj ected by each lens. As a result, the'illumination of the screen increases not merely in direct proportion to the number of small mirrors 16 but at a more rapid rate being approximately in proportion to the square of the number of mirrors.

In the modified form of receiver shown in Fig. 4 the light spots are reflected on the screen from a series of rotating mirrors inv stead of being projected thereon by lenses.

The disk 30 connected to be driven by the motor 31 in synchronism with the cylinder .at the sending station has mounted on its .pe-

riphery a series of mirrors 32. Starting for example with mirror 33 at one end of the series each succeeding mirror is inclined slightly more than the preceding mirror until the lastmirro'r 34 of the series is reached. Between the mirror disk 30 and the screen 12 is the lens 35 and between the lens andthe screen are the four small mirrors 36 correlenses for similar reasons.

.in the preceding modifications.

meet or, if :desired, may

sponding to the four mirrors 16 of Figs. 2 and 3. As in those figures also four oscillographs 18 having mirrors 19 control the amount of light received from the four sources 20 through condensing lenses 21 and 22. I have shown the mirror disk 30 rotatable on a vertical axis andthe four small mirrors arranged vertically, hence the four light spots traverse the screen horizontally instead of vertically as in the preceding form, the four beams be ing simultaneously reflected by each successive mirror as it comes into position.

In the modified form shown in Fig. 5, I have shown a motor-driven mirror disk like that in Fig. 4 but in this case the four small mirrors 36 are located at one-side of the line lens 38 and are simultaneously reflected byeach successive mirror 32 as it'comes into position. As before, controlled respectively by the four oscillographs 18. The same advantage in illumination efliciency may also be obtained w1th the rotating mirrors as 'with the rotating In the sending apparatus a rotating disk having reflecting mirrors such as shown in Fig. 4 or in Fig. 5, may

be usedifdesired instead of the rotating cyl" inder of lenses shown in Fig. 1.

' In the modification illustrated in Fig, 6, I have shown diagrammatically a receivlng arrangement whereby the light beams are controlled b a bein cause to traverse the image receiving mem er b a mirror arrangement like that shown in ig'. 5. Light from a single source, \such for example as an arelight 40, after passing through the condensing lens 41, passes on through the first Nicol prism 42, the cell 43, the second Nicol prism 44turned at right angles'to the 45. From the lens 45 the rays converge and are reflected by i the disk 30 to the image receiving member or screen 12. I have shown the cell 43 diagran1- matically as comprising containing asuitable liquid such as nitrobenzol in which are immersed seven pairs of spaced electrodes 48. 'The plates forming the electrodes are arranged so that light rays may pass through the space separating the plates of each pair and thus be subject to the electrostatic stress therein. The pairs of electrodes are so arranged relative to each other that the seven.beams when directed.

upon the screen 12- form seven spots of light and, as the disk 30 rotates, trace seven bands of light acrossthe screen instead of four as The several bands may just slightly overlap. One electrode of each pair 48 has a separate connection 49 extending the four light beams are form of Kerr cell, the beams the respective mirrors 32 of the glass vessel 47 s without the cell while the remaining electrodes are connected together forconvenience by a single connection 50. The seven pairs of electrodes are thus adapted to be independently controlled for example from a corresponding number of receivers 25 or from a radio carrier current of seven channels of the Hammond type. The two prisms 42 and a l are arranged to produce planes of polarization at right angles to each other so that when there is no field between the electrodes the light beams are shut OK but when a field is applied to any of the pairs of electrodes the plane of polarization is thereby twisted so that light is let through at that point. Seven independentlf varying beams of light thus simultaneously traverse the screen with the passage of each mirror.

The advantages of the multiple beam system illustrated by rotatable lenses and rotating mirrors applies equally toother well known methods of analyzing the picture such as vibrating mirrors. A reduction of the rate of vibration to one-fourth, as shown, makes it possible to-use a large mirror and thus gain in total illumination by increase of the brilliancy of each light spot in addition tothe direct gain by using four beams instead of one. It is to be understood that the terms light? and illumination as used in the description and claims are not restricted to those rays which constitute the visible portion of the spectrum but apply equally Well to the invisible portions of the spectrum for under certain conditions it may be more desirable to make extensive use of the invisible rays in the transmitting apparatus and this also may be done in the receiving apparatus, particularly 1f it is constructed to reproduce the picture photographically instead ofvisually. 1

What I claim. as new and desire to secure by Letters Patent of the United States, is:

l. The method of transmitting pictures which comprises simultaneously scanning a' group of adjacent bands of unit areas, successively Scanning adjacent groups of saidbands,

and producing electric currents correspond ing with the tones of the picture indicated by the light emitted by said unit areas.

2. The method of transmitting pictures which comprises simultaneously scanning a group of bands of adjacent unit areas, successively scanning different groups of said bands, and producing electrical variations corresponding with the variations of the picture as indicated by the light emitted from said unit areas.

3. In picture transmission, the method of receiving a transmitted picture on an image receiving member which comprises scanning the member simultaneously. with a group of adjacent light beams, independently varying the intensity of the beams, and successively scanning adjacent areas of said member with said group of light beams.

5. The method of transmitting-a picture to an image receivingmember at a distant point,

which comprises simultaneously scanning a group of adjacent bands of unit areas, successively scanning different groups of saidv bands, producing electrical variations corresponding to variations in the color of said unit areas, scanning the receiving member by a plurality of light beams, and varying the several light beams in accordance 'With the respective electrical variations.

6. Apparatus for the transmission of pictures comprising means for successively scanning adjacent groups of bands of unit areas of the picture to be transmitted, and means for producing electrical variations corresponding to the variations of the picture as successively determined simultaneously by the unit areas of said groups.

7-. Apparatus for the transmission'of pictures comprising means forsuccessively scanning adjacent groups of bands of unit areasof the picture to be transmitted, and a plurality of photo-electric devices arranged to receive light simultaneously'from the different single unit areas of one of said groups.

8. Apparatus forthe transmission of pictures comprising means for successively scanning adjacent groups of bands of unit areas of the picture to be transmitted, a plural ty of photo-electric devices arranged to receive light respectively from said unit areas and electrical transmitting means respectively responsive to said devices.

9. Apparatus for the transmission of pictures comprising an image receiving member, means for simultaneously moving a group of adjacent light beams over a part of said member, means for causing said group of light beams to'be moved successively over difierent parts of said member, and means for controlling the intensity of the respective light beams. I 10. Apparatus for the transmission of pictures comprising an image receiving member,

a plurality of electrical receiving means,

means for projecting a plurality of adjacent beams of light on said-member, means for controlling the intensity of said beams respectively by said receiving means,'and means for causing said beams simultaneously to sweep across a part of sand image receiving member and for causing sard beams to be successively swept across different parts of said member.

11. Apparatus for the transmisslon of pletures comprising an image receiving member, a receiver comprising a plurality of means for independently receiving electrical I variations, means for 5 of adjacent light beams,vmeans for c0ntrolling the intensity of said beams respectively n by said receiving means, and a rotatable memproducing a plurality her having a plurality of light directing units, each successive unit being arranged to project simultaneously said light beams on a diflerent part of said member.

In Witness whereof, I have hereunto set my hand this 18th day of October 1926.

ERNST F. W. ALEXANDERSON.