Vision Probe

All sorts of gadgets have been developed to help the blind to "see" by sound or touch, but none has come into widespread use. They are generally too complicated, heavy, expensive or conspicuous. Dunn Engineering Associates, Inc. of Cambridge, Mass, is demonstrating a small, simple, inconspicuous device that may have more practical appeal. Its designer, the late Dr. Clifford Martin Witcher of M.I.T., was blind himself.

Physicist Witcher lost his sight when he was five years old, but blindness did not slow him down appreciably. He graduated from Georgia Tech, won a Ph.D. at Columbia. For sight he substituted an amazing ability to comprehend by ear. He grasped with ease the meaning of equations that he could not see; he designed complicated machinery without being able to draw or read a blueprint. Sighted students watched with wonderment while he worked with dangerous power tools.

During World War II, Dr. Witcher did distinguished work on radar. Later he turned to a scientific study of the special needs of blind people. This work took him to Haskins Laboratories, New York City, and later to M.I.T., where he concentrated on practical gadgets. The one demonstrated last week, the only one to be completed before Dr. Witcher's death last month, is called an Audible Vision Probe. It is about as big as a short, fattish fountain pen, and a thin wire leads from it to an earphone. At one end of the probe is a small lens, and inside is a photocell that is sensitive to differences of light and shade.

When a blind person wants to find, for instance, the windows of a room, he swings his probe around and listens for a faint ticking sound in his earphone. The faster the ticking the stronger the light that is reaching the photocell.

Most promising uses for the probe are in connection with a blind person's job. The probe may enable him to read meters, gauges and thermometers, locate lights on telephone switchboards and tell the color of test solutions during chemical analyses. Dunn Engineering has built 50 of the probes, which have been turned over to New York's American Foundation for the Blind for practical testing.

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