| Millions of people suffering from diseases such as RP (Retinitis Pigmentosa) and AMD (Age-related Macular Degeneration) are legally blind due to the loss of photoreceptor function. Fortunately, a large percentage of the neural cells connected to the photoreceptors remain viable, and electrical stimulation of these cells has been shown to result in visual perception. With advance in microfabrication, integrated circuits, wireless technologies, and biomedicine, much attention in the field of artificial organs has been attracted by artificial visual functions recovery based on electrical stimulation of the neural cells. Under the supports of NSFC (No.30470469), this dissertation aims to develope a CMOS retinal prosthesis microchip with high perfermance at the circuit level for natural light illumination.Ultilizing the existed research achievements and related documents, this dissertation introduces the concept, classification and characteristics of artificial visual functions recovery technology. The theoretic and experimental foundations for designing a CMOS retinal prosthesis microchip are constructed after such key techeniques in the fields are analyzed as the generation principles of action potential by neuronal electrical stimulation and signal transmission process based on the multilayer structure of retina. The research progress in artifical retina is reviewed and advantage and disadvange of some mainstream schemes at the circuit level for visual recovery are also summarized. Then, a CMOS retinal prosthesis microchip with the satisfying fuction and structure is proposed in this dissertation.An OPFM (Optoelectronic Pulse Frequency Modulation) circuit for nature light illumilation is proposed. Each pixel is an independent oscillator whose frequency is proportional to the intensity of incident light while its pulsewidth holds constant. The factors effecting performance of the pixel are analyzed and some pivotal indexes of the pixel are optimized. The simulation results showed this proposed OPFM circuit possessed high dynamic range of more than 70dB and power consumtion of less than 1.46μA per pixel.A wireless inductive link is employed to power the implanted devices. The key technology in this field is summerized. And a monilithic radio frequency energy recovery circuit is presented, which consists of a full-wave rectifier, a voltage reference and a unity gain buffer. It exhibits an excellent supply independency and it can output a stable DC voltage for OPFM array in a wide range of input supply voltage.The layout of the retinal prosthesis microchip on 0.5μm 2P3M standard CMOS process is designed. The designed prototype contains an 8×8 pixels array, five independent pixels for test and a radio frequency energy recovery circuit. The pixel size is 50μm×50μm approximately.The fabricated retina prosthesis microchip is tested under tungsten lamp illumination at standard color temperature and natural light illumination, respectively. The tests involve three parts: the performance test of OPFM circuit powered by DC voltage, the performance test of the radio frequency energy recovery circuit and the performance test of OPFM circuit powered by the radio frequency energy recovery circuit. The tested rerults showed the fabricated chip possessed desired fuctions. And the results also demonstrate the potential of the integration for retinal implants.This dissertation aims at presenting a high performance CMOS microchip for visual fuction recovery at the circuitry level. Consequent researches need to be done, including electrode package, surgical implantation, physiology tests of the device, and so on, which requires interdiscipline collabrations of researcher in the fields of eye surgery medicine, neurobiology, material science and micro machine process. The author hope the dissertation can provide some help for further research in this field.
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