A STUDY ON THE TACTILE RECOGNITION OF FINGER USING ELECTRICAL STIMULUS

In this paper, the fundamental characteristics of tactile recognition by electrical stimulus in order to develop a vision substitution syste m were described. The electrical stimulus pulse or DC voltage was appl ied at a touch board, and a conducting band which was connected to the ground level was fastened around a root of finger. First of all, the resistance of finger by the DC voltage was measured and the equivalent circuit of a finger was estimated. It was found that the most of resi stance of this mechanism was concentrated at the contact of tip of fin ger and its value reached to MOMEGA order. And this resistance widely varied by the contact condition. The resistance of finger itself was r elatively low and the contact resistance of band connection was about 30 kOMEGA. Total stray capacitance was about 26-62 nF, which was calcu lated by our experiments. Secondly, the minimum recognition voltage to applied stimulus pulse was measured by changing frequency, duty-ratio and voltage of pulse. It was found that the most sensitive pulse was in situation of that the frequency range was within from 60 Hz to 300 Hz, the duty-ratio of 20%, and the minimum sensitive voltage was about 13 V. Lastly, this electrical stimulus pulse was applied to the touch Braille board. A touch Braille board was controlled by a computer (PC 8801). In this system, an input letter from keyboard is translated to Braille code data by a computer automatically, which express the lette r by the 6 points for the brind. And a Braille data is output at a tou ch board. By touching on the contact point of the touch board, a perso n can recognize Braille points by electrical stimulus. It was found th at the Braille recognition by electrical stimulus pulse was available as same as it could be done by raised points.