Electronics: Man-Made Frog's Eye

Crouched motionless on a mossy stone, a frog seems to be thinking about nothing, and in a sense this is true: the frog's brain is too small and primitive for real thought. But its bright, bulging eyes have a keen, built-in intelligence of their own. They select among stimuli and report to the feeble brain only those visual items that are important to a frog's wellbeing. When a cloud drifts slowly over the sun, a frog's eyes do not bother the brain with the meaningless event. But when a bird swoops down, suddenly darkening the sky, special cells in the eyes cry alarm, and the frog plops hastily into the water. Other eye cells report the presence of the small moving objects that usually turn out to be insects—but only when the insects are close enough for the frog to have a chance of catching them. If they are too far off or are flying rapidly away, a built-in computing mechanism rejects the targets as impossible.

So sensitive and selective is the frog's-eye computer that human scientists have long tried to construct a duplicate. At a bionics* symposium sponsored by the Air Force at Wright-Patterson Air Force Base last week, Radio Corp. of America demonstrated a reasonable facsimile. RCA's artificial eye is a heavy box, 40 in. by 40 in., its end studded with 1,600 small light detectors that simulate the light-sensitive cells of a frog's retina. Behind the detectors are layers of electronic components that serve as frog nerve cells. They are interconnected in such a way that they report to the "brain," a smaller light-studded panel, only those objects that a frog would see. If a disk held in front of the large "eye" panel is moving in the proper direction at the proper speed, it appears in lights on the brain panel.

No frog could catch insects with RCA's crude and ponderous eye, but the Air Force has high hopes of developing it into a practical instrument that can view a scene and make instant, frog-quick decisions. Unblinkingly focused on a radar scope, it might report only those aircraft or missiles that are potentially hostile. In an even more refined version, it could ride in a missile and steer its warhead toward targets that it had been trained to seek.