Steadying Images by Bending Light

In Viet Nam, an Army photographer shoots sharp reconnaissance pictures despite the vibration of his small observation plane. From a shaky and make shift platform in Washington, a TV camera crew gives viewers a clear close-up portrait of Richard Nixon making his inaugural address. In North Miami, a policeman with a television camera takes shots showing distinct facial features of individuals creating a civil disturbance hundreds of feet below his quivering helicopter. In these and dozens of other applications, a remarkable new optical system is providing clear and steady images under circumstances that ordinarily cause blurred photo graphs or jiggling, distorted views.

In earlier attempts to overcome the problems caused by vibration or rapid motion, the armed forces and movie and TV companies set up their cameras and other optical devices on gyroscopically stabilized platforms that tilted to compensate for any disturbing motion. But the platforms weighed hundreds of pounds and were both expensive and difficult to install. So engineers at the Dynasciences Corp. in Blue Bell, Pa., decided to take a radically new approach. Instead of steadying the viewing instrument, they decided, it might be more practical to stabilize the image by bending light beams from the target so that they would always hit the camera film or the retina of the viewer's eye at the same point. Using this concept, the Pennsylvania company developed a portable system that weighs only a few pounds. Mounted like a collar around the lens of a camera or other optical instrument, it steadies the image more effectively than stabilization platforms.

Tiny Gyroscopes. The key part of the "Dynalens" system is an adjustable prism that is placed in front of the lens. It consists of two circular glass disks, one at each end of a short cylinder formed by a flexible bellows. The inside of the cylinder is filled with a clear liquid, usually alcohol. By tilting one or both of the glass plates, the cylinder can be made wedge-shaped, like a prism. Light beams entering the glass plate at one end of the prism are thus bent and emerge from the other plate at a different angle.

When an optical instrument is shaken or moved, two tiny gyroscopes in the Dynalens collar sense the motion and send signals that control miniature electric motors connected to the glass plates at each end of the prism. The motors, which respond almost instantaneously to movements of the optical instrument, tilt the plates to change the shape of the prism, thus bending the incoming light beams just enough to compensate for the motion. The result is a clear and remarkably steady image.

Telescopic Shots. The advantages of the Dynalens system have not been lost on Hollywood studios, which are already using it for filming aerial telescopic shots. TV networks are also equipping their mobile units with the device. And the armed forces are not only using the system for photography and surveillance but are also experimenting with Dynalens-equipped gun sights that remain fixed on their target and keep gun barrels pointed in the right direction, despite any movement of the platform itself.

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