本論文描述了一個應用臨界電壓飄移消除(TVC)技術及可程式化電流控制閥值電壓(PCCT)技術之超低電壓0.5伏特脈衝寬度調變互補式金氧半導體影像感測器，使影像感測晶片可達到雜訊抑制和動態範圍延展的效果。一個64×40的影像感測器應用這些技術後，其量測結果顯示出擁有82dB動態範圍、0.055%rms固定模式雜訊(FPN)和0.65 LSBrms隨機雜訊，同時僅消耗147.3 pW/frame∙pixel於78.5幀率，使其成為了一個相當具高功率效率的高動態範圍影像感測器。此影像感測器實現了像素陣列及其周邊十位元以每條欄共用的斜波式類比數位轉換器，並使得像素間距為10μm達到25.4%填充因子，使用0.18μm互補式金氧半導體製程。
此論文貢獻了許多創新之處，此帶來的功效已概述如上。首先是提出一個創新具TVC技術的三電晶體畫素比較器在其兩次操作上給予不同的電流值。將畫素重置到曝光的電位差轉換為一個不與電晶體臨界電壓相關的脈衝寬度，並消除了由電晶體臨界電壓造成的變異和於低電壓操作下影像感測器的均勻性。第二為提出一個創新可調整的單端反相器架構比較器的閥值電壓方式，稱為PCCT技術。此技術簡單地實現低供應電壓下動態範圍延展技術於脈衝寬度調變應用。第三為一個用於像素上自動控制像素比較器運行之省電技術，避免了不必要的功率消耗當比較器完成了脈衝寬度轉換。總結，這些創新完成了具高功耗效率和高動態範圍的互補式金氧半導體影像感測器，適用於生醫環境如可攜式、值入式或者甚至拋棄式的醫療產品。

This thesis describes an ultra-low voltage 0.5V PWM CMOS imager with threshold-variation-canceling (TVC) scheme and programmable current-controlled threshold (PCCT) scheme to achieve noise suppression and dynamic range extension. A prototype 64×40 pixel imager employed these schemes experimentally achieve 82dB dynamic range, 0.055%rms fixed-pattern-noise (FPN), and random noise of 0.65 LSBrms, while consuming 147.3 pW/frame∙pixel at 78.5 fps, making it one of the most power-efficient wide-dynamic-range imagers. The imager implements pixels and their associated 10b column parallel ramp ADCs, enabling a pixel pitch of 10μm with 25.4% fill factor in a 0.18μm CMOS process.
The innovations are contributed by this thesis, leading to the performance outlined above. First, a novel 3T in-pixel comparator with TVC scheme in two phase operations is biased in different current value. The difference of voltage from pixel reset and exposure transforms to a transistor threshold independent pulse width, eliminating the offset FPN from MOSFET threshold variation and improves the uniformity of imager at low voltage operation. Second, a novel adjusting method for giving the threshold of single-ended inverter-based comparator is proposed as PCCT scheme, which easily implements the dynamic-range-extension method of PWM with functional threshold of comparator with low supply voltage. Third, a power saving scheme used in pixel circuit for auto controlling the function of in-pixel comparator, avoiding the consumption of unnecessary power from completed comparator as pulse width occurred. Together, these innovations result in power-efficient wide-dynamic-range CMOS imager, which is suitable for using in biomedical environment as portable, implantable, or even disposable applications.

Bibliography
[1] J.N. Burghartz, T. Engelhardt, H.-G. Graf, C. Harendt, H. Richter, C. Scherjon, K. Warkentin, “CMOS Imager Technologies for Biomedical Applications,” in Proc. IEEE ISSCC Dig. Tech. Papers, pp.142-602, Feb. 2008
[2] H.-G. Graf, C. Harendt, T. Engelhardt, C. Scherjon, K. Warkentin, H. Richter, J.N. Burghartz, “High Dynamic Range CMOS Imager Technologies for Biomedical Applications,” IEEE J. Solid-State Circuits, vol.44, no.1, pp.281-289, Jan. 2009
[3] S.U. Ay, “A 1.32pW/frame•pixel 1.2V CMOS energy-harvesting and imaging (EHI) APS imager,” in Proc. IEEE ISSCC Dig. Tech. Papers, pp.116-118, Feb. 2011
[4] S.U. Ay, “A CMOS Energy Harvesting and Imaging (EHI) Active Pixel Sensor (APS) Imager for Retinal Prosthesis,” IEEE Trans. Biomedical Circuits and Systems, vol. 5, no. 6, pp. 535-545, Dec. 2011
[5] S. Hanson, D. Sylvester, “A 0.45–0.7V sub-microwatt CMOS image sensor for ultra-low power applications,” in IEEE Symp. VLSI Circuits Dig. , pp.176-177, 2009
[6] S. Hanson, F. ZhiYoong, D. Blaauw, D. Sylvester, “A 0.5 V Sub-Microwatt CMOS Image Sensor With Pulse-Width Modulation Read-Out,” IEEE J. Solid-State Circuits, vol.45, no.4, pp.759-767, Apr. 2010
[7] D.G. Chen, D. Matolin, A. Bermak, C. Posch, “Pulse-Modulation Imaging—Review and Performance Analysis,” IEEE Trans. Biomedical Circuits and System, vol.5, no.1, pp.64-82, Feb. 2011
[8] J. Ohta, Smart CMOS Imager Sensors and Applications, CRC Press
[9] P. J. W. Noble, “Self-scanned silicon image detector arrays,” IEEE Trans. Electron Devices, vol. ED-15, no. 4, pp. 202-209, Apr. 1968
[10] A. El Gamal and H. Eltoukhy, “Cmos image sensors,” IEEE Circuits Devices Mag., vol. 21, no. 3, pp. 6–20, May/Jun. 2005
[11] P. Noble, “Self-scanned image detector arrays,” IEEE Trans. Electron Devices, vol. 15, no. 4, pp. 202–209, Apr. 1968
[12] E. Fossum, “Active pixel sensors: Are ccd’s dinosaurs?” in Proc. SPIE Charged-Coupled Devices and Solid State Optical Sensors III, vol. 1900, pp. 30–39, 1993
[13] R. Guidash, T.-H. Lee, P. Lee, D. Sackett, C. Drowley, M. Swenson, L. Arbaugh, R. Hollstein, F. Shapiro, and S. Domer, “A 0.6 μm cmos pinned photodiode color imager technology,” in Proc. Int. Electron Devices Meeting Tech. Dig., pp. 927–929, Dec. 1997
[14] J.-E. Eklund, C. Svensson, and A. Astrom, “Vlsi implementation of a focal plane image processor-a realization of the near-sensor image processing concept,” IEEE Trans. Very Large Scale Integr. (VLSI) Syst., vol. 4, no. 3, pp. 322–335, Sep. 1996
[15] B.J. Hosticka, W. Brockherde, A. Bussmann, T. Heimann, R. Jeremias, A. Kemna, C. Nitta, and O. Schrey. “CMOS imaging for automotive applications,” IEEE Trans. Electron Devices, 50(1):173–183, Jan. 2003
[16] S. Yuanyuan, Z. Weigong, G. Yong, T. Xiaohui, “Research on a method to extend dynamic range of CMOS APS,” IEEE International Workshop on Imaging Systems and Techniques 2008, pp.212-216, Sep. 2008
[17] D. Stoppa, A. Simoni, L. Gonzo, M. Gottardi, G.-F. Dalla Betta, "Novel CMOS image sensor with a 132-dB dynamic range," IEEE J. Solid-State Circuits, vol.37, no.12, pp. 1846- 1852, Dec. 2002
[18] S.Kavadias, B. Dierickx, D. Scheffer, A. Alaerts, D. Uwaerts, and J. Bogaerts. “A logarithmic response CMOS image sensor with on-chip calibration,” IEEE J. Solid-State Circuits, 35(8):1146–1152, Aug. 2000
[19] M. Loose, K. Meier, and J. Schemmel, “A self-calibrating single-chip CMOS camera with logarithmic response,” IEEE J. Solid-State Circuits, 36(4):586– 596, Apr. 2001
[20] L.W. Lai, C.H. Lai, and Y.C. King, “A Novel Logarithmic Response CMOS Image Sensor with High Output Voltage Swing and In-Pixel Fixed-Pattern Noise Reduction,” IEEE Sensors Journal, 4(1):122–126, Feb. 2004
[21] B. Choubey, S. Aoyoma, S. Otim, D. Joseph, and S. Collins, “An Electronic- Calibration Scheme for Logarithmic CMOS Pixels,” IEEE Sensors Journal, 6(4):950–956, Aug. 2006
[22] G.G. Storm, J.E.D Hurwitz, D. Renshaw, K.M. Findlater, R.K. Henderson, M.D. Purcell, “Combined linear-logarithmic CMOS image sensor,” in Proc. IEEE ISSCC Dig. Tech. Papers, pp. 116- 517, Feb. 2004
[23] G. Storm, R. Henderson, J.E.D Hurwitz, D. Renshaw, K. Findlater, M. Purcell, “Extended Dynamic Range From a Combined Linear-Logarithmic CMOS Image Sensor,” IEEE J. Solid-State Circuits, vol.41, no.9, pp.2095-2106, Sep. 2006
[24] M. Vatteroni, P. Valdastri, A. Sartori, A. Menciassi, P. Dario, “Linear–Logarithmic CMOS Pixel With Tunable Dynamic Range,” IEEE Trans. Electron Devices, vol.58, no.4, pp.1108-1115, Apr. 2011
[25] S. Decker, D. McGrath, K. Brehmer, and C. Sodini, “A 256 × 256 CMOS imaging array with wide dynamic range pixels and column-parallel digital output,” IEEE J. Solid-State Circuits, vol. 33, no. 12, pp. 2081-2091, Dec. 1998
[26] R. Oi and K. Aizawa, “Wide dynamic range imaging by sensitivity adjustable CMOS image sensor,” in Proc. International Conference on Image Processing (ICIP'03), vol. 2, Barcelona, Spain, pp. 583-586, Sep. 2003
[27] N. Akahane, S. Sugawa, S. Adachi, K. Mori, T. Ishiuchi, and K. Mizobuchi, “A sensitivity and linearity improvement of a 100-dB dynamic range CMOS image sensor using a lateral overflow integration capacitor,” IEEE J. Solid-State Circuits, vol. 41, no. 4, pp. 851-858, Apr. 2006
[28] S. Decker, D. McGrath, K. Brehmer, and C.G.Sodini, “A 256 × 256 CMOS imaging array with wide dynamic range pixels and column-parallel digital output,” IEEE J. Solid-State Circuits, 33(12):2081–2091, Dec. 1998
[29] Y. Muramatsu, S. Kurosawa, M. Furumiya, H. Ohkubo, and Y. Nakashiba, “A Signal-Processing CMOS Image Sensor using Simple Analog Operation,” in Proc. IEEE ISSCC Dig. Tech. Papers, pp. 98–99, Feb. 2001
[30] S.T. Smith, P. Zalud, J. Kalinowski, N.J. McCaffrey, P.A. Levine, and M.L. Lin. “BLINC: a 640 × 480 CMOS active pixel video camera with adaptive digital processing, extended optical dynamic range, and miniature form factor,” in Proc. SPIE, volume 4306, pp. 41–49, Jan. 2001
[31] D. Yang, A. Gamal, B. Fowler, and H. Tian, “A 640 × 512 CMOS image sensor with ultrawide dynamic range floating-point pixel-level ADC,” IEEE J. Solid-State Circuits, vol. 34, no. 12, pp. 1821-1834, Dec. 1999
[32] K. Mabuchi, N. Nakamura, E. Funatsu, T. Abe, T. Umeda, T. Hoshino, R. Suzuki, and H. Sumi, “CMOS image sensor using a floating diffusion driving buried photodiode,” in Proc. IEEE ISSCC Dig. Tech. Papers, pp. 112–516, Feb. 2004
[33] M. Sasaki, M. Mase, S. Kawahito, and Y. Tadokoro, “A wide dynamic range CMOS image sensor with multiple short-time exposures,” in Proc. IEEE Sensors, volume 2, pp. 967–972, Oct. 2004
[34] M. Mase, S. Kawahito, M. Sasaki, Y. Wakamori, and M. Furuta. “A Wide Dynamic Range CMOS Image Sensor with Multiple Exposure-Time Signal Outputs and 12-bit Column-Parallel Cyclic AD Converters,” IEEE J. Solid- State Circuits, 40(12):2787–2795, Dec. 2005
[35] P. Acosta-Serafini, I. Masaki, and C. Sodini, “A 1/3" VGA linear wide dynamic range CMOS image sensor implementing a predictive multiple sampling algorithm with overlapping integration intervals,” IEEE J. Solid-State Circuits, vol. 39, no. 9, pp. 1487-1496, Sep. 2004
[36] X. Liu and A. El Gamal, “Photocurrent Estimation for a Self-Reset CMOS Image Sensor,” in Proc. SPIE, volume 4669, pp. 304–312, San Jose, CA, 2002
[37] K.P. Frohmader, “A novel MOS compatible light intensity-to-frequency converter suited for monolithic integration,” IEEE J. Solid-State Circuits, 17(3):588–591, Jun. 1982
[38] R. M¨uller, “I2/L timing circuit for the 1 ms-10 s range,” IEEE J. Solid-State Circuits, 12(2):139–143, Apr. 1977
[39] V. Brajovic and T. Kanade, “A sorting image sensor: An example of massively parallel intensity-to-time processing for low-latency computational sensors,” in Proc. IEEE Int’l Conf. Robotics & Automation, pp. 1638–1643, Minneapolis, MN, Apr. 1996
[40] M.L. Simpson, G.S. Sayler, G. Patterson, D.E. Nivens, E.K. Bolton, J.M. Rochelle, and J.C. Arnott, “An integrated CMOS microluminometer for lowlevel luminescence sensing in the bioluminescent bioreporter integrated circuit,” Sensors & Actuators B, 72:134–140, 2001
[41] E.K. Bolton, G.S. Sayler, D.E. Nivens, J.M. Rochelle, S. Ripp, and M.L. Simpson, “Integratged CMOS photodetectors and signal processing for very low level chemical sensing with the bioluminescent bioreporter integrated circuits,” Sensors & Actuators B, 85:179–185, 2002
[42] J. Ohta, N. Yoshida, K. Kagawa, and M. Nunoshita, “Proposal of Application of Pulsed Vision Chip for Retinal Prosthesis,” Jpn. J. Appl. Phys., 41(4B):2322–2325, Apr. 2002
[43] K. Kagawa, K. Isakari, T. Furumiya, A. Uehara, T. Tokuda, J. Ohta, and M. Nunoshita, “Pixel design of a pulsed CMOS image sensor for retinal prosthesis with digital photosensitivity control,” Electron. Lett., 39(5):419– 421, May 2003
[44] A. Uehara, K. Kagawa, T. Tokuda, J. Ohta, and M. Nunoshita, “Backilluminated pulse-frequency-modulated photosensor using a silicon-onsapphire technology developed for use as an epi-retinal prosthesis device,” Electron. Lett., 39(15):1102–1104, Jul. 2003
[45] D. C. Ng, T. Furumiya, K. Yasuoka, A. Uehara, K. Kagawa, T. Tokuda, M. Nunoshita, and J. Ohta, “Pulse Frequency Modulation-based CMOS Image Sensor for Subretinal Stimulation,” IEEE Trans. Circuits & Systems II, 53(6):487–491, Jun. 2006
[46] J. Ohta, T. Tokuda, K. Kagawa, T. Furumiya, A. Uehara, Y. Terasawa,M. Ozawa, T. Fujikado, and Y. Tano, “Silicon LSI-Based Smart Stimulators for Retinal Prosthesis,” IEEE Eng. Medicine & Biology Magazine, 25(5):47–59, Oct. 2006
[47] C.L. Lee, C.C. Hsieh, “A 0.8V 64×64 CMOS imager with integrated sense-and-stimulus pixel for artificial retina applications,” Solid State Circuits Conference (A-SSCC), 2011 IEEE Asian, vol., no., pp.193-196, 14-16 Nov. 2011
[48] C.L. Lee, C.C. Hsieh, “A 0.6V CMOS Image Sensor with in-pixel biphasic current driver for biomedical application,” Circuits and Systems (ISCAS), 2011 IEEE International Symposium on , vol., no., pp.1455-1458, 15-18 May 2011
[49] M. Nagata, J. Funakoshi, and A. Iwata, “A PWM Signal Processing Core Circuit Based on a Switched Current Integration Technique,” IEEE J. Solid- State Circuits, 1998
[50] M. Nagata, M. Homma, N. Takeda, T. Morie, and A. Iwata, “A smart CMOS imager with pixel level PWM signal processing,” in Dig. Tech. Papers Symp. VLSI Circuits, pp. 141–144, Jun. 1999
[51] M. Shouho, K. Hashiguchi, K. Kagawa, and J. Ohta, “A Low-Voltage Pulse- Width-Modulation Image Sensor,” in IEEE Workshop on Charge-Coupled Devices & Advanced Image Sensors, pp. 226–229, Karuizawa, Japan, Jun. 2005
[52] S. Shishido, I. Nagahata, T. Sasaki, K. Kagawa, M. Nunoshita, and J. Ohta, “Demonstration of a low-voltage three-transistor-per-pixel CMOS imager based on a pulse-width-modulation readout scheme employed with a onetransistor in-pixel comparator,” in Proc. SPIE, San Jose, CA, 2007. Electronic Imaging
[53] C. Kwang-Bo, A.I. Krymski, E.R. Fossum, “A 1.5-V 550-μW 176×144 autonomous CMOS active pixel image sensor,” IEEE Trans. Electron Devices, vol.50, no.1, pp. 96- 105, Jan. 2003
[54] Z. Ignjatovic, M.F. Bocko, “A 0.88nW/pixel, 99.6 dB Linear-Dynamic-Range Fully-Digital Image Sensor Employing a Pixel-Level Sigma-Delta ADC,” in IEEE Symp. VLSI Circuits Dig., pp.23-24, 2006
[55] K. Kagawau, S. Shishido, M. Nunoshita, Ohta Jun, “A 3.6pW/frame-pixel 1.35V PWM CMOS Imager with Dynamic Pixel Readout and no Static Bias Current,” in Proc. IEEE ISSCC Dig. Tech. Papers, pp.54-55, Feb. 2008
[56] M.T. Chung, C.C. Hsieh, “A 0.5V, 4.95μW, 11.8fps PWM CMOS Imager with 82dB Dynamic Range and 0.055% Fixed-Pattern-Noise,” in Proc. IEEE ISSCC Dig. Tech. Papers, pp.114-115, Feb. 2012
[57] K. Cho, D. Lee, J. Lee, G. Han, “A 0.75V CMOS image sensor using time-based readout circuit,” in IEEE Symp. VLSI Circuits Dig., pp.178-179, Jun. 2009
[58] K. Cho, D. Lee, J. Lee, G. Han, “Sub-1-V CMOS Image Sensor Using Time-Based Readout Circuit,” IEEE Trans. Electron Devices, vol.57, no.1, pp.222-227, Jan. 2010
[59] M. G. O’Halloran, A Wide-Dynamic-Range Time-Based CMOS Imager, Massachusetts Institute of Technology, Feb. 2008
[60] L.W. Huang, A 1.8V Readout Integrated Circuit with Adaptive Transimpedance Control Amplifier for IR Focal Plane Arrays, National Tsing Hua University, Oct. 2011