Picture Tube

If one beam of light can be transmitted along a glass tube, why not transmit detailed images along the same path? The problem has steadily resisted the best efforts of optical researchers. But now the University of Rochester's Indian-born Dr. Narinder Singh Kapany, 30, has succeeded by applying a technique he refers to as "fiber optics." With his new method, said Dr. Kapany last week, he has already designed a glass "gastroscope" which can be snaked down the throat for a detailed closeup view of the human stomach.

Fiber optics derives its name from its use of hair-thin strands of optical glass as light carriers. Light entering an ordinary clear glass or plastic rod is reflected over and over again from the inner surface until it emerges again at the far end. This familiar principle causes the rod to act as a "light pipe." Dr. Kapany conceived the idea of bunching thousands of microscopic glass rods, each of which would transmit a single point of light. The bundle of points of light should form an image in much the same way the pattern of ink dots in a newspaper illustration forms a picture.

With the aid of Bausch & Lomb tech nicians, Dr. Kapany made up several glass-fiber bundles, each of them containing up to a quarter of a million individual strands a thousandth of an inch in diame ter. So long as he kept the fiber's ends in the same relative position at each end of the bundle, he found that he could pass exact images through the flexible bundles even when they were tied in knots.

The experiments suggested a number of practical applications of the fiber-optics principle. Used in medical instruments, the fiber bundles would permit doctors to examine and even photograph internal areas beyond the range of existing instruments. In the area of high-speed photography, fiber bundles might be used to cut the image into strips which would be registered side by side rather than one after another on the film, thus speeding up the camera action. The images would be reassembled by filtering them through a second fiber bundle when the film was being processed.

Fiber optics might even be applied to code work. If a quarter of a million fibers are woven at random into a bundle so that its two ends are not identical, the image which passes in one end will be hopelessly scrambled when it emerges. The only way to unscramble it is to feed it back the way it came through an identical bundle. Since it is possible to produce two identical random bundles by winding the fibers on a drum and cutting the coil in half, the receiver could be equipped with a "decoding" bundle. Linked into a television circuit, says Dr. Kapany, the bundles would provide a code unbreakable by any known cryptographic method.

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