Etsuzo Ohdaira and Masao Ide
A phase difference type ultrasonic walking aid for the blind which uses pulse reflection can be used easily without requiring much difficult training. This new aid features three transducers on the frame of a pair of spectacles. The transducer at the center is for a transmitter, while the transducers on both sides are for receivers. The walking aid detects the distance and direction of an obstacle (target) from the travelling time of ultrasonic pulses transmitted and reflected on the obstacle and the time difference between the pulses reflected from the obstacle and received by their respective receivers. A weak point of an aid of this type is that sometimes slant, flat obstacles such as board fences could not be detected. The new model of the previous aid on which this paper reports overcame this weak point by using plural ultrasonic frequencies. The environment recognition power was improved by this walking aid.
Keywords: Ultrasonic walking aid, Ultrasonic device built into a spectacle frame, Pulses reflected method, Plural frequency of ultrasound, Detection of obliquely placed obstacles