A laser profilometer as a space perception system for blind people

We have exploited laser telemetry to extend the reach of the hand or of the cane while retaining a natural posture. A laser telemeter of similar dimensions as a TV remote control device is held in the hand. It is a class II device for ocular safety. The blind person perceives the direction in which the laser beam is pointing thanks to his internal conciousness of the position and of the movements of his members (proprioception). The distance to the first obstacle encountered by the laser beam is measured at a rate of about 25 measurements per second. The range of the telemeter (10 cm to 20 m) is divided into suitable intervals of distance. To each interval there corresponds a musical note sent to an earpiece. By an adequate bending of the wrist, one obtains sections of the surrounding space. The sequence of distances is immediately converted into a musical line at the rate of the scan. The natural proprioceptive perception of the movements, combined with the musical line furnishes the subject with a cerebral image of the profiles of the obstacles. The fundamental information is constituted above all by the variation of the musical notes, so we prefer to call the set-up a profilometer. The extraction of profiles in various directions allows one to acquire three-dimensional spatial information out to 20 m. About 50 blind volunteers have experimented with the system for simple exercises, including the detection of a post and of a hole in the floor and orientation by a wall to find one's way. It turned out that the proprioception and the spatial perception of subjects often had to be improved by re-education. We are taking these factors into account for optimization of the learning techniques.