Study On CMOS Artificial Retina Microchip For Subretinal Electrical Stimulation

Artificial visual functions recovery has attracted the most attention in the field of artificial organs. In general, there are three types of solutions according to the different positions of electrical stimulation, named cortical prosthesis, optic nerve prosthesis and retinal prosthesis. Cortical prosthesis and optic nerve prosthesis require more complicated operations and may bring more risks comparing with retinal prosthesis owing to implant in the cortical region and optic nerve place. Retinal prosthesis has been presented for over ten years by Humayun and actually developed in two different directions: epiretinal prosthesis and subretinal prosthesis. Subretinal prosthesis put the implant in subretinal space and meets first the outer retina. It can utilize more live retinal cells of blind patients to process vision information and decrease the current threshold of electrical stimulation, accordingly, possesses the essential advantages. Various artificial visual functions recovery technologies have been researched detailedly. Especially, Second Sight Corp. and Optobionics Corp. in USA have implanted their devices in the eyes of blind patients for clinical experiments. There are enormous blind patients in China, however, the research in this field is started relatively late. Since the present subretinal prosthesis solutions need extraocular illuminating equipments to enhance visual information, this dissertation developes a subretinal CMOS artificial retina microchip at the circuit level for normal light illumination under the support of NSFC (No.30470469).Firstly, this dissertation introduces the concept, classification and characteristics of artificial visual functions recovery technology. The research progresses in this fiels are reviewed and its development tendencies are analyzed. Then, the theoretic and experimental groundworks for design a subretinal CMOS artificial retina microchip are summarized, which include the principles of action potential generated by neuronal electrical stimulation, the effectivity, safety and threshold of retinal electrical stimulation, electrode material and the electric performances of electrode-retina interface.Aimed at the disadvantages of the present subretinal prosthesis, this dissertation proposes a light-control CMOS oscillating pixel structure for subretinal electrical stimulation under normal light illumination. In the novel solution, the photocurrent of photodetectors controles the discharge process of the pixel capacitor to realizes the...