Abstract
This paper proposes a 256 $\\times$ 256 time-of-flight (TOF) image sensor based on the center-tap (CT) demodulation pixel structure. The image sensor can capture both the two-dimensional (2D) high speed image and the three-dimensional (3D) depth image. The CT pixel consists of two split pinned photodiode (PPD) regions and two pairs of transfer transistors. The transfer transistors adopt a non-uniform doped channel (NUDC) structure, which can increase the electron transfer speed along the transfer channel and eliminate the image lag for high speed imaging. The pixel size is 10 $\\upmu$m $\\times$ 10 $\\upmu$m, and we design the implementation process of the pixel to increase the electron transfer speed. The sensor is fabricated in a 0.18 $\\upmu$m 1P5M CMOS image sensor process. Test results show that it can capture the 430-fps intensity image and the 90-fps depth image in two different imaging modes. The rectified non-linearity within the 1.0--7.5 m depth measurement range achieves less than 3 cm, and the measurement accuracy achieves 4.0 cm at 2.5 m, corresponding to the relative error of 1.6\\%.
Published Version
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