本論文利用在多個影像感測電路上設計不同感測架構，比較並探討不同感光元件與電路區塊對於感測動態範圍之影響。測試電路中的設計差異包含：感光元件使用光伏模式(Photovoltaic Mode)之光二極體或橫向光電晶體、像素讀取電路使用n-MOSFET或p-MOSFET、於像素陣列後是否加入讀取行放大器(Column Amplifier)。在本論文中會提出標準CMOS製程中影像感測電路的特殊後模擬方式，建立光伏模式影像感測器的雜訊量測技術，並根據不同量測環境下的雜訊量值分析各子電路的輸出雜訊貢獻。
目前市面上的影像感測器多以操作在逆偏壓之光二極體作為感光元件，在此操作模式下為了解析弱光像素的訊號會延長曝光時間，因此容易在強光像素發生二極體位能井的電荷飽和而產生過曝的現象。為解決上述效應，影像感測裝置通常會進行多次取樣(Multiple Sampling)並根據多張不同曝光時間下的影像進行後期處理，以得到高動態範圍的影像，但如此影像感測技術會消耗更多時間完成單張影像的拍攝。本研究將光感測元件操作在開路的光伏模式，由於該模式讀取之感測元件電壓(光電壓)為光電流與順向電流達到穩態後的電壓，故此操作模式下較不易發生位能井飽和的狀況，能有效提升電路之飽和光強度。
從量測上可以觀察到光伏模式之對數響應所帶來的飽和光強度提升，故本研究將以雜訊等效光強度(Noise Equivalent Intensity, NEI)作為感測動態範圍的主要改善指標。根據量測結果能觀察到：相較於使用光二極體與P-MOSFET讀取像素之感測電路，若額外加入讀取行放大器可減少約10%的雜訊等效光強度；若將光感測元件替換為橫向光電晶體則可再減少50%的雜訊等效光強度。未來若針對光電晶體之輸出電壓進行感測電路的進一步優化，可期待得到更低的雜訊等效光強度與更多的動態範圍提升。

This thesis studies the effect of different photodetectors and readout circuit combinations on CMOS image sensor dynamic range by testing circuits with various building blocks. The proposed selection of building blocks contains: utilizing photodiodes (PD) or lateral phototransistors (LPT) as photodetectors, n-MOSFETs or p-MOSFETs as transistors in pixel level readout circuits, and whether applying column-level gain with column amplifiers. During the research progress, CMOS image sensor post-simulation method, photovoltaic mode image sensor noise measuring techniques, and analyzing procedure of image sensor sub-circuits noise contribution will be proposed.
Most commercial CMOS image sensors utilize reverse-biased photodiodes as photodetectors; nevertheless, if one extends exposure time to analyze signal in low light pixels under such operation mode, photo-charges may fill potential wells of photodetectors in strong light pixels, thus leads to overexposure of those pixels. In order to resolve the issue, most image sensor designers utilize multiple sampling technique, which means acquiring high dynamic range images by performing post-processing with multiple raw images using different exposure time; however, the total exposure time may be extended due to the requirement of multiple raw images. This work focuses on photodetectors in photovoltaic mode, owing to the physics that under photovoltaic operation mode, photovoltage output is referred to the balance of photocurrent and forward-biased photodetector current but not related to full-well capacity, the saturation illuminance of photovoltaic mode photodetectors can be considerably enhanced.
Because the saturation illuminance of photodetectors in photovoltaic mode is too large to be observed in the measurement, this work takes noise-equivalent intensity (NEI) as parameter to represent the enhancement of dynamic range. Compared with test circuits utilizing only PD as photosensors and p-MOSFET pixel readout circuits before column sampling circuits, placing an additional column amplifier after pixel readout circuit can bring to 10% of NEI reduction, further replaces PD with LPT can lead to another 50% of NEI reduction. If all sensing circuits can be optimized with LPT light response, more NEI reduction and dynamic range enhancement can be expected. 

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