Science: Blind Man's Radar

The blind may soon have an electrical gadget to help them get around without bumping into obstacles. The basic idea, now being worked on by the Army Signal Corps, is a small box shooting out a narrow beam of light. By turning the beam from side to side, the blind man can feel his way. When the beam hits a lamppost, a fence or any such obstacle, its light reflects back to a lens and is focused on a photoelectric cell. A gentle buzz in an earphone warns him that the obstacle is near. The blind man can tell its direction by pointing his box. He can learn to tell how far away it is by the length of the buzz.

One problem in designing the instrument was to eliminate false signals from sunshine or artificial light. So the beam was made to pulsate like the radio waves from a radar transmitter, and the photoelectric tube was made insensitive to nonpulsating light.

At present, the "optical cane" is heavy (9 lbs.) and cannot "see" narrow obstacles such as hanging wires. The Signal Corps intends to iron out all such comparatively minor faults before offering its invention to the blind.