本論文提出一個多模式動態偵測影像感測器，可提供8-bit灰階影像、2-bit事件偵測和8-bit幀間差異的暫態差異感測、以及畫素陣列子區塊中動態事件累計的顯著偵測。所提出的在乒乓¬-脈衝寬度調節器(Pulse Width Modulation)設計於畫素電路中以完成相鄰兩幀的相減來實現連續圖像視覺系統上的動態偵測。
為了在畫素電路中達到相鄰兩幀訊號相減的功能，使用MIMCAP電容作為儲存位元並以電荷耦合操作讓兩個訊號能從電荷面相減，並且結合兩組相同電路成乒乓架構來交錯儲存模式和相減讀出模式，因此可達到連續相減訊號讀出以維持資料傳輸率。畫素中脈衝寬度調節器提供低電壓操作和訊號數位化讀出，脈衝寬度訊號傳至縱向共用的數位計數器讀出，使整體架構功耗降低且傳輸速率提升。在動態追蹤的幀間差異感測和顯著偵測模式下，感光操作採用全局式快門來避免動態模糊。顯著偵測模式統計畫素陣列8×8區塊中動態事件的數量，利用同時讀取八行的電流總量並由縱向共用的電容反饋跨阻抗放大器(Capacitive Trans-Impedance Amplifier)和單斜坡類比數位轉換器(Single-Slope Analog-to-Digital Converter)回報區塊中事件的總數。
為了驗證本電路，一個操作於0.8V並搭載64×64乒乓PWM畫素陣列的多模式動態偵測影像感測器原型使用0.18微米1P6M互補式金氧半導體製作，晶片總面積為2000×2100平方微米。量測結果顯示此晶片在影像擷取模式下達到每秒360幀、功耗71.2微瓦；在8-bit幀間差異模式下達到每秒510幀、74.4微瓦；以及區塊顯著偵測模式下每秒890幀、121.6微瓦。

This thesis presents a multi-mode motion detection CMOS image sensor, providing 8-bit gray level image capturing(IC), temporal difference reporting with 8-bit frame difference(FD) and 2-bit event detection(ED), and saliency detection(SD) with block-level event counting. The proposed ping-pong pulse width modulation(PWM) is implemented in pixel circuit for consecutive frames subtraction to realize motion detection for frame-based vision system
To achieve frame difference between two consecutive frames in pixel circuit, MIMCAP capacitor is implemented as memory cell and used for subtraction by charge domain switching capacity technique. By combining two identical circuits into ping-pong structure, two memory cells are operated in storage and differencing phase separately so that consecutive difference signal can be achieved, maintaining original data rate. In pixel PWM supports low voltage operation and time domain digitization readout, transferring pulse width signal to column-shared digital counter, for lower power consumption and higher data bandwidth. For motion detection FD and SD modes, global shutter is adopted to avoid motion blur. In SD mode, motion events in every 8×8 blocks of pixel array are estimated by turning on 8 rows simultaneously. Column-shared capacitive trans-impedance amplifier(CTIA) sums up 8 event currents, and Single-slope analog-to-digital converter(SS-ADC) converts output into digital code.
An 0.8V global shutter multi-mode motion detection vision sensor prototype with 64×64 ping-pong PWM pixel array has been fabricated in 0.18μm 1P6M standard CMOS technology with a chip area of 2000×2100μm2. The measurement result shows that the proposed sensor achieves 360 fps and 71.2μW in IC mode, 510 fps and 74.4μW in FD mode, 890 fps and 121.6μW in SD mode.

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