CMOS影像感測器在最近頗受注目，其市場在最近三、四年來蓬勃發展，而且被預期會持續下去。其應用早已經滲透到以下這些產品，如網眼、保全攝影機、數位相機、以及攝錄像機等。若跟其競爭對手CCD來相比的話，CMOS影像感測器具有高度的電路整合能力，因此在某些需要系統整合和低功率的應用上，其佔有極大的優勢。
由於人眼對於邊緣影像較為敏感，因而行處理電路的匹配問題極度受到重視，尤其在低照度時，行間的定態雜訊會隨著訊號一起被放大，嚴重影響成像品質。因此，本研究的內容包含下列幾項：（a）針對CMOS影像感測器的讀取電路架構與不匹配原因來做考察。（b）找出電路中不匹配的主要來源，並在受限於像素間距與晶片面積的情況下，提出減緩該影響的方法。（c）以實作晶片來驗證模擬分析的結果，故晶片中除了原先的設計外，還包含刻意加入不匹配參數的電路。（d）建立一套影像量測系統來測試晶片。
本晶片使用台灣積體電路公司0.18μm 1P6M 3.3V混合訊號製程，晶片面積1.163×1.163 mm2。像素陣列採用3-T架構的主動式像素感測器，以及NW/Psub接面的光二極體。讀取電路則是一共設計了三種不同架構，而且每一種架構都包含了額外兩組加入不匹配參數的電路，以利分析。

CMOS image sensors have drawn much attention in these days. The market is booming in different product sectors for the recent 3-4 years and is expected to continue growing in the future. The market share has successfully penetrated into areas such as web cameras, security cameras, digital still cameras and video camcorders. Compared with its technical competing products, CCD (charge-coupled devices), the highly circuit integration capability of the CMOS image sensors makes it superior in certain new imaging applications which requires system compactness and lower power consumption.
Column circuit matching issue is critical for integrated CMOS image sensors due to sensitive edge detection capability of human vision. At low illumination conditions, the column-to-column fixed pattern noise is further critical due to signal amplification. Therefore, the contents of this study are itemized as: (a) The design issues of the integrated CMOS imagers, which include column readout circuit architecture and mismatch of the readout circuits, are investigated. (b) The major sources of mismatch are identified and design solutions are proposed to minimize the effect under the constraint of pixel-size pitch match and chip area consumption. (c) The test chip with different design parameters related to circuit matching are implemented and fabricated to verify the analysis results. (d) An imager characterization system is constructed to measure the test chip.
The test chip is fabricated in TSMC 0.18μm 1P6M 3.3V mixed-mode process and occupies the area of 1.163×1.163 mm2. The pixel arrays adopt three-transistor (3-T) active pixel sensor (APS) and NW/Psub photodiode. Three types of readout circuit are implemented, and each one contains two mismatch factors to be analyzed.

[1] M. Loinaz, K. Singh, A. Blanksby, D. Inglis, K. Azadet, and B. Ackland, “A 200mW 3.3V CMOS color camera IC producing 352X288 24b Video at 30 frames/s,” ISSCC Digest of Technical Papers, pp.168-169, 1998.
[2] S. Decker, R. McGrath, K. Brehmer, C. Sodini, “A 256X256 CMOS Imaging Array with Wide Dynamic Range Pixels and Column-Parallel Digital Output,” ISSCC Digest of Technical Papers, pp.176-177, 1998.
[3] D. Yang, A. El Gamal, B. Fowler, H. Tian, “A 640X512 CMOS Image Sensor with Ultra Wide Dynamic Range Floating-Point Pixel-level ADC“ ISSCC Digest of Technical Papers, pp. 308-309, 1999.
[4] H. Yamashita, C. G. Sodini, “A 128X128 CMOS Imager with 4X128 bit-serial Column-Parallel PE array”, ISSCC Digest of Technical Papers, pp. 96-97, 2001.
[5] K. Yoon, C. Kim, B. Lee, D. Lee, “Single-chip CMOS Image Sensor for Mobile Applications“, ISSCC Digest of Technical Papers, pp. 36-37, 2002.
[6] I. Takayanagi, M. Shirakawa, K. Mitani, M. Sugawara, S. Iversen, J. Moholt, J. Nakamura, E. R. Fossum,“A 1 ¼ inch 8.3M Pixel Digital Output CMOS APS for UDTV Application”, ISSCC Digest of Technical Papers, pp. 216-217, 2003.
[7] S. Kagami, T. Komuro, and M. Ishikawa, “A High-Speed Vision System with In-Pixel Programmable ADCs and PEs for Real-Time Visual Sensing,” The 8th IEEE International Workshop on Advanced Motion Control, pp.439-443, Mar. 2004.
[8] I. L. Fujimori, C.-C. Wang, and C. G. Sodini, “A 256X256 CMOS Differential Passive Pixel Imager with FPN Reduction Techniques,” IEEE Journal of Solid-State Circuits, vol.35, no. 12, pp. 2031-2037, Dec. 2000.
[9] Eric Fossum, “CMOS Image Sensors: Electronic Camera-On-A-Chip”, IEEE Trans. On Electron Devices, vol.44, no.10, pp.1698-1699,Oct. 1997.
[10] K. Salama abd A. El Gamal, “Analysis of Active Pixel Sensor Readout Circuit,” IEEE Trans. on Circuit and Systems –I: Fundamental Theory and Applications, vol. 50, no.7, Jul. 2003.
[11] G. Meynants, B. Dierickx, D. Uwaerts, J. Bogaerts, “Fixed Pattern Noise Suppression by a Differeitial Readout Chian for a Radiation Tolerant Image Sensor,” Proceeding of 2001 IEEE CCD and Advanced Image Sensor Workshop.
[12] M. F. Snoeij, A. J. P. Theuwissen and J. H. Huijsing, “Read-Out Circuit for Fixed-Pattern Noise Reduction in a CMOS Active Pixel Sensor”, Proceedings of SeSens 2002, pp.676-679.
[13] S.-G. Wuu, D.-N. Yaung, C.-H. Tseng, H.-C. Chien, C.-S. Wang, Y.-K. Fang, C.-C. Wang, C. G. Sodini, Y.-K. Hsiao, C.-K. Chang and B.-J. Chang, “High Performance 0.25um CMOS Color Imager Technology with Non-Silicided Source/Drain Pixel,” Digest of International Electron Device Meeting, pp.705-708, 2000.
[14] A. J. Blanksby, M. J. Loinaz, “Performance Analysis of a Color CMOS Photogate Image Sensor,” IEEE Trans. on Electron Devices, vol. 47, no. 1, pp.55-64, Jan. 2000.
[15] A. EI. Gamal, “Image Sensors and Digital Cameras,” course handout, Standford University, 2001.
[16] C.-C. Wang, “A Study of CMOS Technologies for Image Sensor Applications,” PhD thesis, Massachusetts Institute of Technology, Aug. 2001.
[17] B. Pain, G. Yang, M. Ortiz, C. Wrigley, B. Hancock, and T. Cunningham, “Analysis and Enhancement of Low-Light-Level Performance of Photodiode-Type CMOS Active Pixel Imagers Operated with Sub-Threshold Reset,” presented at 1999 IEEE Workshop on Charge-Coupled Devices and Advanced Image Sensors, Jun. 1999.
[18] C. C. Enz and G. C. Temes, “Circuit Techniques for Reducing the Effects of Op-Amp Imperfections: Auto-Zeroing, Correlated Double Sampling and Chopper Stabilization,” Proceedings of IEEE, vol. 84, no. 11, pp.1584–1614, Nov. 1996.
[19] H. Tian, X. Liu, S. Lim, S. Kleinfelder, A. El Gamal, “Active Pixel Sensors Fabricated in a Standard 0.18um CMOS Technology,” Proceedings of SPIE, vol. 4306, pp. 441-449, Jan. 2001.
[20] J.-S. Ho, M.-C. Chiang, H.-M. Cheng, T.-P. Lin, and M.-Jer. Kao, “A New Design for A 1280x1024 Digital CMOS Image Sensor with Enhanced Sensitivity, Dynamic Range and FPN,” International Symposium on VLSI Technology, Systems, and Applications, pp.235-238, 1999.
[21] S. J. Decker, “A Wide Dynamic Range CMOS Imager with Parallel On-Chip Analog-to-Digital Conversion,” PhD thesis, Massachusetts Institute of Technology, Sep. 1997.
[22] S.K. Mendis, S.E. Kemeny, R.C. Gee, B. Pain, C.O. Staller, Q. Kim, E.R. Fossum, “CMOS Active Pixel Image Sensors for Highly Integrated Imaging Systems,” IEEE Journal of Solid-State Circuits, vol. 32, no. 2, Feb. 1997, pp.187-197
[23] Y. Degerli, F. Lavernhe, P. Magnan, J. Farre, “Non-Stationary Noise Responses of Some Fully Differential On-Chip Readout Circuits Suitable for CMOS Image Sensors,” IEEE Trans. on Circuit and Systems–II: Analog and Digital Signal Processing, vol. 46, no. 12, pp. 1461-1474, Dec. 1999.
[24] M. Burns, G. W. Roberts, An Introduction to Mixed-Signal IC Test and Measurement, Oxford University Press, USA, 2001.