A low-power indirect time-of-flight CMOS image sensor with fixed depth noise compensation and dual-mode imaging for depth dynamic range enhancement

C Piao, Y Ahn, D Kim, J Park, J Kang… - … on Circuits and …, 2022 - ieeexplore.ieee.org
C Piao, Y Ahn, D Kim, J Park, J Kang, SJ Kim, JH Chun, J Choi
IEEE Transactions on Circuits and Systems I: Regular Papers, 2022ieeexplore.ieee.org
We present a low-power indirect time-of-flight (iTOF) image sensor with fixed depth noise
compensation and dual-mode imaging for depth dynamic range (DDR) enhancement. To
reduce the power consumption from high-frequency pixel modulation, a TX driver with a
single-sided clock chain is employed in the sensor. The inherent phase delay of the clock
chain and the delay of the row bus are measured using row-parallel and column-parallel
time-to-digital converters (TDCs) to compensate for the column and row fixed depth noise …
We present a low-power indirect time-of-flight (iTOF) image sensor with fixed depth noise compensation and dual-mode imaging for depth dynamic range (DDR) enhancement. To reduce the power consumption from high-frequency pixel modulation, a TX driver with a single-sided clock chain is employed in the sensor. The inherent phase delay of the clock chain and the delay of the row bus are measured using row-parallel and column-parallel time-to-digital converters (TDCs) to compensate for the column and row fixed depth noise (FDN). To achieve a wide depth dynamic range (WDDR), the reconfigurable pixels and column circuits support dual-mode: short-range (SR) and long-range (LR) modes. A WDDR image is generated in a single frame through the mixed reconfiguration of the pixel array and interpolation. In addition, the temporal noise is suppressed without a significant time budget through a fast multiple sampling (FMS) scheme with 10b successive approximation register (SAR) analog-to-digital (ADCs). A prototype iTOF image sensor was fabricated using a 110 nm frontside illumination (FSI) CMOS image sensor (CIS) process and fully characterized. The sensor achieved a DDR of 4 m (0.7 to 4.7 m) with less than 1.7% nonlinearity and 0.9% depth noise. The FDN was suppressed to less than 2.1 cm at a low power consumption below 70 mW through the proposed compensation scheme using row and column TDCs. The temporal noise was only 0.48 mV owing to the FMS.
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