| Around the world, many research teams are striving to give blind people their vision back through the use of electrical microstimulation. However, the design and conception of such visual implant is not without its share of difficulties. Indeed, significant improvements are required over the characteristics and performance of implants currently used but geared towards different, applications. In the current context where results from physiological experiments allowing us to determine the optimal strategies and parameters to be employed are still pending, and considering the variety of suggested approaches, a product with a broad range of flexibility in its performance is highly desirable.; To this day, scientific literature presents as with a variety of approaches and circuits that give adequate results for many of these critical aspects. However, we know of no systems that constitute a comprehensive solution providing all required characteristics. Moreover, designs geared towards implantable devices generally overlook details about their external components, and vice-versa, while an optimal solution can only be achieved by considering all of its interdependent components.; The objective of this work is to outline a complete system geared towards a significant and complete solution, where none of its components is either left to chance or conveniently overlooked. Stemming from our efforts are various original elements and a concrete and evolutive basis exhibiting the following characteristics: (1) a modular architecture, which we believe is the only approach combining a reasonable footprint, the possibility of a wide visual field, and high energy efficiency; (2) a high degree of flexibility from both the available stimulation modes as well as from the supported modulation strategies; (3) low power consumption, made possible specifically by all adaptive control of the transmitted power for optimal efficiency without sacrificing safety; (4) increased safety features through (a) usage of a predictive approach to regulate the power transmitted and (b) the addition of various methods that increase diagnostics capabilities as related to the state of the system post-implementation; (5) an architecture allowing for easy modifications and improvements to the system.; A working prototype of the system, including two application specific integrated circuits implemented in a CMOS 0.18 mum process controlled and powered via an inductive link, is capable of delivering up to 500 000 stimulation pulses per second. The wireless communication link attains a data rate in excess of 1.5 Mbps with a bit error rate lower than 10-6. The power consumption of the stimulation module is lower than 900 muW and it is expected that an implant including 1 000 electrodes based on the proposed design could work with less than 50 mW in total.; This contribution constitutes, to the best of our knowledge, the first, system combining an integrated stimulator and its external controller, able to work in real-time, whose measured performances satisfy the main specifications drawn from physiological experiments related to this field of research. The most important elements of the proposed system, the ones defining its capabilities and performance, as well as the considerations that led to the choices made for its implementation, are detailed in this thesis.; It should be noted that even though the solutions found in this document are geared towards a visual implant, many of them are also applicable and are of benefit to other implantable systems.; Finally, it is worth mentioning that the elements presented here go significantly further than simple proofs-of-concepts. Indeed, we present a concrete implementation of a prototype for a visual implant built upon practically every element detailed here. Also, a system intended for validation of the stimulation module through in-vivo freely moving animal behavioral experiments is presented. Considerations relative to this... |
