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。

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.

ABSTRACT 2
CONTENTS 3
LIST OF FIGURES 5
LIST OF TABLES 8
CHAPTER 1 INTRODUCTION 9
1.1 MOTIVATION 9
1.2 THESIS CONTRIBUTION 10
1.3 THESIS ORGANIZATION 11
CHAPTER 2 BACKGROUND INFORMATION 13
2.1 SOLID-STATE IMAGING SENSING 14
2.1.1 CMOS Active Pixel Sensor 14
2.1.2 Standard Process APS 15
2.1.3 4T-APS 17
2.2 OVERVIEW OF RANGE MEASUREMENT TECHNIQUE 19
2.2.1 Passive Triangulation 19
2.2.2 Active Triangulation 20
2.2.3 Time-of-Flight Imaging 21
2.2.4 Discussion 24
2.3 THE CONSIDERATIONS OF TOF IMAGER 26
2.3.1 Optical Power of Light Source 26
2.3.2 Noise Limitation of Range Accuracy 27
2.3.3 Background Light Saturation Issue 30
2.4 SUMMARY 31
CHAPTER 3 TOF IMAGER WITH BGL SUBTRACTION AND SENSITIVITY IMPROVEMENT USING PHASE-SHIFT TECHNIQUE. 33
3.1 BGL SUPPRESSION TECHNIQUE IN INDIRECT TOF 33
3.1.1 Minimum-Charge Transfer (MCT) 34
3.1.2 Charge-Domain Subtraction 34
3.1.3 Voltage-Domain Subtraction 36
3.1.4 Column-level BGL Suppression 37
3.1.5 Summary 38
3.2 PROPOSED BGL SUPPRESSION AND SENSITIVITY ENHANCEMENT SCHEME 40
3.2.1 Proposed Current-Domain Subtraction 40
3.2.2 “Phase-Shift-Readout” Technique 42
3.3 SUMMARY 44
CHAPTER 4 PROTOTYPE DESIGN OF POLARITY-SWITCHING AND PHASE-SHIFT-READOUT TOF DEPTH IMAGE SENSOR 45
4.1 SYSTEM ARCHITECTURE OF TOF IMAGER 46
4.2 TOF PIXEL CIRCUIT 47
4.2.1 Integration Amplifier of ToF Pixel 48
4.2.2 Operation of ToF Pixel Circuit 50
4.2.3 Operation of Phase Shift Read out 52
4.2.4 Simulation of Depth Measurement 54
4.3 SINGLE-SLOPE ADC 56
4.3.1 Comparator 57
4.3.2 Counter and Output Latch 59
4.3.3 Ramp Generator 60
4.3.4 Read out simulation 57
4.3.5 Column and Row Select Circuit 61
4.4 TX BUFFER AND DELAY CONTROL 62
4.5 CHIP OPERATION 64
4.6 SUMMARY 65
CHAPTER 5 MEASUREMENT RESULTS 66
5.1 MEASUREMENT ENVIRONMENT SETUP 66
5.2 IMAGER DIE 69
5.3 PSR TECHNIQUE MEASUREMENT 70
5.4 BGL SUPPRESSION MEASUREMENT 72
5.5 DEPTH MEASUREMENT 72
5.6 SUMMARY 74
CHAPTER 6 CONCLUSIONS 75
6.1 SUMMARY 75
6.2 FUTURE WORK 75
BIBLIOGRAPHY 77

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