The View in the Dark

The director of the Vincennes zoo usually went home just before dark. The residents of his beaver cage rarely came out in the daylight. It seemed as if the man and the broad-tailed mammals might never meet. Then a crew of Dutch technicians crept close to the edge of the beaver pond on a black, moonless night. They sighted in with a short, cylindrical gadget, and the director finally saw his beavers--scuttling across the face of a TV picture tube that had been set up in his office.

It would surely have been easier to give the director a flashlight and urge him to stay on the job after sundown; the mechanical eye that sees so well in the dark is far too expensive a gadget to be used for casual beaver watching. But the demonstration was impressive proof that the device invented by Dutch Physicist Albert Bouwers is astonishingly sensitive. Its practical applications seem limited only by the imagination of its users.

Painful Brilliance. Manufactured by the Old Delft optical company in Holland, Dr. Bouwers' night eye was originally designed to brighten the dim pictures on doctors' fluoroscopes, to give a good look at a patient's internal organs without the need for powerful and dangerous doses of X rays. But soon after the first tests, the military showed an understandable and urgent interest. For the night eye needs no artificial light source, like the snooperscopes of World War II, which merely detected the reflections of infrared light shot out by the scopes themselves. The Dutch device is built around a lens-and-mirror telescope that concentrates whatever natural light is available--however dim, however undetectable by the naked eye.

Illumination soft as starshine can be focused on one end of a six-inch glass tube, where it knocks electrons loose from a photosensitive layer of cesium and antimony. The free electrons are whisked to the opposite end of the tube by powerful electrostatic charges and they hit the far wall with considerable energy. The collisions build a picture on a phosphorescent screen, a picture that is 1,000 times brighter than the original. Picked up by a TV camera and projected on a TV picture tube, the scene can be brightened still more.

Secure Sentries. Objects that are only dimly visible to the eye glow with an almost painful brilliance on the electronic screen. On nights when even the stars are blacked out, the night eye can pick up meaningful glimmers. A sentry scanning his assigned sector could use the Bouwers telescope with perfect security; his snooperscope-equipped buddy would see over a much shorter range and would always be faced with the danger of discovery by an enemy fitted out with infrared detectors.

Working with the Aerojet-General Corp. of the U.S., Old Delft is aiming at an expanding military market. Plans for the night eyes are still secret, but they would be a welcome addition to Marine landing craft, the rugged little boats that would be so much more versatile if they could be equipped to see their way toward an unfamiliar enemy beach in the dark.

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