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A CMOS time of flight (TOF) depth image sensor with in-pixel background cancellation and sensitivity improvement using phase shifting readout technique
Conference paper

A CMOS time of flight (TOF) depth image sensor with in-pixel background cancellation and sensitivity improvement using phase shifting readout technique

Ting Liao, Nien-An Lee and Chih-Cheng Hsieh
2017 IEEE Asian Solid-State Circuits Conference, A-SSCC 2017 - Proceedings, Vol.2017-January, pp.133-136
12/2017
DOI: https://doi.org/10.1109/ASSCC.2017.8240234

Abstract

3-D camera Background cancellation CMOS image sensor Depth imaging Fixed-pattern noise suppression Time-of-flight imaging Electrical and Electronic Engineering Instrumentation
This paper presents a CMOS time-of-flight (TOF) image sensor with in-pixel background light cancellation for outdoor depth imaging application. The using 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 a 64×64 array has been fabricated in TSMC standard 0.18pm CMOS process and verified. The pixel pitch is 20pmx20pm 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.

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