A Time of Flight (ToF) CMOS Depth Image Sensor with In-Pixel Background Cancellation and Sensitivity Improvement Using Phase Shifting Readout Technique

• Main Authors: Liao,Ting, 廖庭
• Other Authors: Hsieh, Chih Cheng
• Format: Others
• Language: en_US
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/r3q5ke

碩士 === 國立清華大學 === 電機工程學系 === 105 === 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.