Pulse frequency modulation based CMOS image sensor for subretinal stimulation

We have developed a CMOS image sensor based on pulse frequency modulation for subretinal implantation. The sensor chip forms part of the proposed intraocular retinal prosthesis system where data and power transmission are provided wirelessly from an extraocular unit. Image sensing and electrical stimulus are integrated onto the same chip. Image of sufficient resolution has been demonstrated using 16/spl times/16 pixels. Biphasic current stimulus pulses at above threshold levels of the human retina (500 /spl mu/A) at varying frame rates (4 Hz to 8 kHz) have been achieved. The implant chip was fabricated using standard CMOS technology.