SEEING I THE DARK

Nelson Evening Mail, Volume LXIX, 1 February 1936, Page 3

SEEING I THE DARK

WONDERFUL INVENTION NEW “ELECTRON TELESCOPE” WATCHING MOVING SCENES NEW YORK, 4th January. Science has now given man an eye to see iu the 'lark, in the form of a foot-long vacuum tube, on which the invisible’ infra-red and ultra-violet rays that fill the air form a visible, living, moving, continuous image. Ihc new tube was shown for the, first time at a ~G n eral meeting of the Anierican Association for the Advancement of Science by its discoverers and inventors, Dr. V K. Zworykin and Dr, George Morton, of the Radio Corporation of America Laboratories. To realise one of man s oldest and apparently most impossible d reams, they have taken beams of electrons and focussed them, just as the lenses_of the human eye focus light. .Like light, electrons cai-rv optical images. Then inasmuch as the eye cannot see every focussed electrons, the two scientists have made a mechanical retina, which secs the electron images exactly as the retina of the. eye sees images iu light-. This mechanical retina is a round sheet of o-lass, nine inches in diameter. Over it is spread a fluorescent chemical, which converts the electron images into visible images in ordinary light-. USED IN USUAL MANNER. The tube, including its artificial retina, is enclosed in a telescope about the size of a large camera. The telescope is pointed at objects in the usual manner. The observer, looking into its receiving end, sees the artificial retina and thereon the scene brought in on the invisible rays. The scene is greenishblack and white, without other colours. But it is as sharp and distinct as visible light. This first telescope is only a cnidc demonstrating machine, merely intended to show science that another '"insoluble” problem lias been solved. Nevertheless, many practical applications appear to be‘immediately realisable. An aeroplane fitted with such a telescope could guide itself into a secret- landing-field by an infra-red or black light beacon, so dark as to be invisible to persons near it on the field. An infra-red searchlight, which the- inventors say can be made, could, in association with the telescope, be used for sending invisible military signals at night. Biologists, who were the most interested spectators at the demonstration, foresee immediate use of the new eye.r Heretofore, they have been limited to photography for seeing in the ultra-violet and the infra-red. Now, they declare, they can soon have microscones for both kinds of ray. The -ultraviolet reveals objects smaller than, can be seen in light of any kind. The infrared rays make it possible to see some distance into living tissues, particularly the human body. With an infrared microscope a physician could look directly at the blood running through veins and arteries about an inch below the skin.

DIFFERENCE FROM- PHOTOGRAPHS

All these possibilities have been demonstrated in the last few years by photographic plates, which are sensitive to both kinds of invisible ray. But the photographs had to be developed, and they showed only “stills, and not invisible life in action. The new electron telescope, however, does not use merely the same rays which photographic plates record. It takes these ’ invisible says, - converts them into electrons, and then) re-converts'the electrons, into a visible image. To do this, the incoming invisible rays fall on a convex glass or quartz lens about an inch arid a-lialf in diameter. This lens seals.the receiving end of the new vacuum.. tube, and is coated on its inner side with .caesium, a metal sensitive to light. The caesium gives oft’ electrons in proportion to the light rays striking its surface. .. The electrons stream out at the speed' of light, inside the vacuum tube. They stream, helter-skileter, in all directions. The problem solved was how to Focus these electrons as light is focussed. It was solved by the use' of electro-static fields. The inner walls of the tube, as the end where the electrons come off the lens, are negatively charged with electricity. At the oppo-