Taking the Night from Charlie

The faint moonlight barely penetrated the foliage as 15 U.S. infantrymen groped through black Vietnamese jungle near Lai Khe. But the night hid few secrets from 2nd Lieut. Robert Hibbs, 25, of Cedar Falls, Iowa. Although his own patrol was all but invisible in the dark, he had no trouble spotting the Viet Cong company approaching on his flank. Before he could withdraw, he picked up another group of V.C. moving in on him. Caught between two larger enemy forces, Hibbs ordered his men to fire a few rounds at the second Communist unit. Its gunners returned the fire, though they obviously could not see their targets, and the first V.C. company, convinced that it was under attack, also opened up--right at its buddies.

That jungle firefight took place more than two years ago, but it is still remembered as one of the first successful combat tests of the "starlight scope"--one of the prying electronic gadgets developed by the Defense Department "to take the night away from Charlie." Lieut. Hibbs was well briefed on the scope's importance; though mortally wounded, he smashed it against a tree rather than let it fall into the hands of the enemy. He won a posthumous Medal of Honor for his performance on that night patrol. Since then, thousands of starlight scopes have been shipped to Viet Nam; jungle-wise infantrymen are so impressed by their versatility that they use almost any G.I. dodge to pick up extra scopes for their outfits.

Last week the Army finally revealed some of the technical wizardry that makes the scopes work. Unlike the World War II infantry sniperscope that illuminated its target with an infra-red beam, the starlight scope needs no light of its own. Thus it is undetectable by enemy sensors. It uses only natural light, no matter how dim--moonlight, starlight, even the faint luminescence of decaying jungle foliage. Capable of amplifying light up to 40,000 times, it literally treats the darkest night as day.

Heart of the starlight scope is its image-intensifier tube, a sturdy combination of the home TV screen and miniaturized space-age electronics. Focused sharply by the scope's front lens, the slightest flickers of light are directed against a chemical film, causing it to discharge electrons. Boosted along by a 15,000-volt electrostatic field, those electrons smack into a phosphorcoated screen whose light then jars loose still another flock of electrons. The process is repeated three times, and the high-voltage electron acceleration, or energy buildup, produces a progressively brighter image. Besides the light, the only other power source is a tiny built-in battery for the electric field.

Despite the starlight scope's relative simplicity, the Army's Night Vision Laboratory at Fort Belvoir, Va., had to spend countless hours and $20 million on the design before it was ready for production. One particularly nagging problem was the difficulty of transmitting the image from one stage to the next without excessive distortion or loss of light. Army researchers, under Electrical Engineer Robert S. Wiseman, known as "Mr. Night Vision" to his colleagues, overcame that hurdle by using fiber optics. These unusual lenses are made up of bundles of extremely thin glass fibers, each of which transmits light by bouncing it from wall to wall down the length of the fiber. With their glass-fiber lenses, the Fort Belvoir team not only kept the light in a straight line but prevented wasteful leakage out of the system.

To keep starlight scopes from potential enemies and dedicated Peeping Toms, the Pentagon has so far restricted private sales. But eventually the scopes may be adapted for civilian purposes. Astronomers have already used similar devices to increase the power of their telescopes. With the technology now largely declassified, demand may build up among police, underwater explorers and airline pilots--anyone, in fact, who has a legitimate reason for wanting to see in the dark.

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