Design and Evaluation of Electronic-Microsaccade with Balanced Stimulation for Artificial Vision System

Vision loss brings huge inconvenience to patients in their daily lives. Retinal prosthesis, regarded as the most hopeful treatment for blindness caused by retina degeneration, can achieve vision recovery by applying electrical stimulation if the retina nerve remains intact. However, if these nerve cells or even the eyeball are damaged, the artificial vision system is more promising. Like the human eye, implementing a microsaccade in the artificial vision system is necessary to avoid vision fading when focusing on a specific object for a long time. In this work, an electronic-microsaccade (E-Saccade) circuit is proposed and a 3 x 3 pixels prototype vision circuit is fabricated in 0.18 µm 1P6M CMOS technology. The main purpose of the circuit is to apply convolution operation with a time-varying kernel on a still image. The circuit consists of stimulus-trigger-generator (STG), switch matrix, and biphasic-current-source (BCS). In addition, a synchronization logic (SL) is proposed to prevent unbalanced stimulation which will damage electrodes and nerve cells. Experimental results show that the proposed circuit successfully shift biphasic stimulus current in 8 directions at microsaccade frequencies of up to 10 Hz. Moreover, all unbalanced stimulation is removed by the SL, making the system intrinsically safe.