NEW. INVENTION

Evening Post, Volume CXXV, Issue 24, 29 January 1938, Page 8

NEW. INVENTION

, "SEEING" THROUGH FOG

Because certain chemicals change colour when ultra-short radio waves impinge upon them, it may.be possible to see objects, such as ships and aeroplanes hidden in dense fog.or darkness, according to a patent awarded to Clarence W. Hansell, of Rocky Point, New York, says the "New York Times." . The patent, which is assigned, to the Radio Corporation of America, is for a detecting device which picks up invisible waves either broadcast or reflected by the concealed object • and constructs them into a visible picture with the help of a colour-changing chemical. > , The invention may be of importance in navigation and in time of war, to detect enemy battleships' and; aeroplanes hidden by smoke screens, fog, or darkness. ■ , The chemical whicli can thus turn invisible images into visible pictures is copper sulphate. Normally, it is blue, but when all the water is extracted from it, it turns white. Extremely short-radio waves or infra-red rays, under proper conditions, have the property of removing the water from this chemical. A WHITE PICTURE. The new device calls for a screen covered with a thin film of the copper sulphate. The screen is mounted in a glass container, that looks like a vacuum tube. Except for the presence of enough water vapour to give the chemical its blue colour, the tube is under vacuum. In use, an accompanying radio transmitter sends out ultra-short radio waves that can penetrate fog and darkness. The waves are so short that they can be focused like a beam of light from an auto headlight. They are reflected by objects that come in their path. To make this image visible is the function of the copper sulphate screen. It acts' almost like magic. The reflected invisible- image is picked up by a lens and focused on the screen. When the rays composing the image strike the copper sulphate film, they extract the water from the part upon which they impinge. Over this area th§ copper sulphate screen turns from blue to white. , Thus the image becomes visible as a white object on a blue ground. The observer sees on the screen a picture of the hidden ship or plane. ■ By means of a magnifying lens, the image can be enlarged to any extent.