A CMOS image sensor with spiking pixels for retinal stimulation

This paper presents a CMOS image sensor intended for a novel optoelectronic retinal prosthesis. Each pixel acts as an independent oscillator, whose frequency is controlled by the incident light intensity. A 9 x 9 pixel array was fabricated in AMS 0.35 mum CMOS Opto Process. Each pixel´s area amounts to 25600 mum² with the array occupying 2.89 mm². Measured results show that the sensor achieves an overall dynamic range of 143 dB (from 34 mHz to 502 KHz) when the controlling bias current value varies from 0.2 pA to 5 muA respectively. Similarly, when the incident light intensity varies from 0.35 muW/cm² to 3.5 mW/cm², the pixel´s oscillation frequency changes from 0.24 Hz to 2.2 KHz respectively. This performance suffices for the optical stimulation of photosensitized RGCs.