具備背景光消除及使用相位位移技巧使感光度提升的互補式金氧半導體深度影像感測器

深度影像在多元的影像應用裡扮演重要的角色。許多逐漸增長的需求量來自於消費性電子的應用，像是:遊戲介面控制、機器人視覺、手勢偵測和安全系統。基於以上的應用，發展能夠在戶外背景光下操作，能夠及時擷取深度資訊並且具有高準確度的深度影像感測器成為非常重要的一個議題。因此在本論文裡，我們提出一個可以操作在戶外強光下具有抗背景光能力且具有良好感光度的深度影像感測器。本論文描述使用了可以應用於戶外的時差測距(TOF)並且具有背景光消除的互補式金氧半導體深度影像感測器。我們使用P+/N-well接面的感光二極體(photodiode)，因此可以進行極性轉換的積分還有相位位移讀出(PSR)，所以環境造成的背景光可以在前端被消除。因為使用了相位位移讀出的技巧，像素(pixel)的感光度(sensitivity)可以被大幅的提升。我們所使用的相位位移讀出能達到直欄像素陣列上的固定圖像雜訊(FPN)消除，並且在正常的操作下不需額外畫面的擷取。一個使用了TSMC 0.18μm 標準 1P6M製程所實現的64×64的影像感測器已經被實現且仔細的驗證。影像感測器的像素間距為20μm，填充因子為33%。在線性度為1.1%下的深度量測範圍為0.75到7.5公尺。量測到在最遠距7.5公尺下的相對準度為4.2%。背景光壓抑能力達至180k lux而不會飽和。

關鍵字

深度影像；互補式金氧半導體影像感測器；時差測距法深度影像；背景光消除；固定圖像壓抑

並列摘要

Range image is one of the popular application in smart image sensor. The increase need for three-dimensional image has been created by consumer electronics applications such as gaming control, robotic vison, gesture recognition and security systems. For above applications, the design of depth camera capable of capturing three-dimensional information in real time with high accuracy under outdoor light illumination becomes very critical. In this thesis, a depth image sensor is proposed to improve the performance of background suppression at strong ambient light environments. The sensitivity is enhanced and hence improves the performance of depth information accuracy. This paper presents a CMOS time-of-flight (TOF) image sensor with in-pixel background light cancellation for outdoor depth imaging application. The usage of P+/N-well diode with proposed polarity switching integration and phase-shift readout (PSR) technique achieves the in-pixel background cancellation capability and sensitivity improvement. Moreover, the PSR also suppresses the column fixed-pattern-noise (FPN) without need of extra frame capturing. A prototype TOF sensing chip with 64×64 pixel array has been fabricated in TSMC standard 0.18μm CMOS process and verified. The pixel pitch is 20μm with a fill-factor of 33%. The achieved depth measurement range is 0.75 to 7.5 meters with a linearity error below 1.1%. The measured relative precision is 4.2% at a 7.5-meter target distance; and the background light suppression capability is up to 180k lux without saturation.

並列關鍵字

Depth imaging ； CMOS image sensor ； Time-of-flight imaging ； Background cancellation ； Fixed-pattern noise suppression

參考文獻

[1] V. Ganapathi, C. Plagemann, D. Koller, and S. Thrun, “Real time motion capture using a single time-of-flight camera,” in Proc. 2010 IEEE Comput. Soc. Conf. Computer Vision and Pattern Recognition, 2010,pp. 755–762.

[2] M. V. d. Bergh and L. V. Gool, “CombiningRGB and ToF cameras for real-time 3D hand gesture interaction,” in Proc. 2011 IEEE Workshop on Applications of Computer Vision (WACV), 2011, pp. 66–72.

[3] C.Niclass, M. Soga, H.Matsubara, S. Kato, andM. Kagami, “A 100-m range 10-frame/s 340 96-Pixel time-of-flight depth sensor in 0.18- μm CMOS,” IEEE J. Solid-State Circuits, vol. 48, no. 2, pp. 559–572, Feb.2013.

[6] B. Büttgen and P. Seitz, “Robust optical time-of-flight range imagingbased on smart pixel structures,” IEEE Trans. Circuits Syst. I, Reg.Papers, vol. 55, no. 6, pp. 1512–1525, Jul. 2008.

[7] Dipl.-Ing. Robert Lange, “3D Time-of-Flight Distance Measurement with Custom Solid-State Image Sensors in CMOS/CCD-Technology ”

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具備背景光消除及使用相位位移技巧使感光度提升的互補式金氧半導體深度影像感測器

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