世界上有百萬以上的人，因為色素性視網膜炎以及老年性黃斑部退化疾病而導致失明。這兩種疾病導致感光細胞發生不可逆的退化，使得視覺傳輸路徑的第一站無法正常地連結。根據研究發現，患者可以藉由視網膜或視覺皮質區上的電刺激，成功地形成視覺感知。這種產生電刺激的人工裝置稱作視覺輔具，通常是長期的植入在眼睛或是大腦上，取代受損的組織，提供患者日常生活需要的視覺功能。目前使用視覺輔具來重建盲人的視覺，對於神經復健工程是相當重要的研究。
本論文的研究，著重於植入式刺激器以及量測系統的考量與設計。為了刺激盲人剩餘的神經細胞，設計六位元的類比數位轉換器，以調整輸出電流的波形，使得患者可以得到基本的景像辨別能力。此外，文中提出新型的量測電路，觀察植入之後電極組織介面的狀況，這將有利於評估刺激成效以及刺激參數的調整。

More than millions of people worldwide are suffering from blindness as a result of retinitis pigmentosa (RP) and age-related macular degradation (AMD). Both of them result in irreversible photoreceptor degeneration, disconnecting the first station of vision from normal pathway. So far, it has been demonstrated that applying electrical stimulation pulse to diseased retina (or directly stimulating the primary visual cortex) can lead to a successful elicitation in visual perception. Such a stimulation pulse can be generated by a man-made device called visual prosthesis. In general, the device is chronically implanted inside the eye or brain to serve as a substitute for the impaired tissue, such that the sufferer can perform several visual tasks in daily life. Restoring sight of vision for blind with visual prosthesis has been of considerable importance in today’s neural rehabilitation engineering.
Motivated by this, we present in this thesis the considerations and design of implantable stimulator and impedance measurement system. In order to activate the targeted residual neural cells of the blind, a 6-bit digital-to-analog converter (DAC) has been designed. It can be in charge of outputting a stimulus waveform, thereby providing the patient basic discrimination regarding the scene. In addition, a new architecture of impedance measurement system is proposed to diagnosis the status of electrode-tissue interface after implantation. It is also useful for evaluating the effect on stimulation and adjustment of stimulus parameters.

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