PHOTOGRAPHIC TRANSMISSIONS

Evening Star, Issue 20317, 28 October 1929, Page 10

PHOTOGRAPHIC TRANSMISSIONS

PRODUCED ON BEAM OF LIGHT At the recent National Electric Light Association Convention at Atlantic City, U.S.A., the Wcstinghouso Compuny gave an exhibition of sending photographs through space on a beam of light. .. , The light beam served as the only connection , between. a facsimile transinittcr and receiver, which by an electrolytic process reproduced transmitted images ’This device, the latest invention of Dr Vladimir prominent Wcstinghouso research scientist, is typical of the advances being made in Weslinghouse research development. The transmission of tho facsimile is a verv interesting performance. . An ordinary photograph or typewritten letter is placed on tho cylinder, which slowly rotates, and at the same time progresses longitudinally. Light from an ordinary appearing lamp focussed on tho picture explores every point or it. Tho reflected light,is then gathered by a parabolic reflector, which the reflection to a photo-electric tube, or “electric eye.” This tube issues an electrical impulse corresponding to the imago on tho photograph. •\s demonstrated by. Dr Zworykin, tho impulses from the photo-electrm tube arc amplified, then passed through a gas-glow tube, which produces the carrier light beam. This carrier beam, trained on another photo-electric tube located in a parabolic reflector across the room, transforms the variation of tho intensity of the beam into electric impulses, which in turn operate the receiving equipment. With the new typo of transnuttcr the transmitted image is reproduced without any further development, as is required when tho picture is recorded on photographic paper. The new device reproduces tho picture by sending tho actual current through a specially compounded paper which has been passed through a water bath in order to make it more conductive. The action.of the electricity on the chemicals in the paper, through electrolysis, changes the colour of the paper and recreates tho original image. Tho reproduction, sin by Grin, can bo reproduced continuously on a long roll of paper. A knife edge, curved m spiral from one side to the other, is on tho surface of the cylinder. On top of the paper there is a straight knife edge which, with tho spiral edge, forms the two electrical contacts of the receiver. As the cylinder with the spiral rotates it produces a sliding contact along the straight edge. This contact moves from one side to tho other, and makes one lino of the reproduced image with each complete revolution. The paper slowly advances through tho receiver, the motion being exactly tho same as the motion of the transmitting cylinder, therefore the two motions exactly reproduce the scanning of tho photograph by tho transmitter, and thus recreate tho image on the paper as tho varying current produces more or less chemical change in the paper. Although Dr Zworykin’s invention is at present still in the experimental stage it is expected that it will be developed further to make it of value commercially.