A CMOS smart pixel for active 3-D vision applications

A CMOS smart pixel aimed at three-dimensional vision applications is introduced. It is suitable for scannerless laser ranging systems which employ the indirect time-of-flight measuring technique to recover distance information. The pixel is operated with trains of light pulses generated by an external source to illuminate the scene and contains most of the processing electronics to perform signal accumulation and noise reduction operations. The smart pixel architecture includes an N-well photodiode plus a self-biasing voltage amplifier and a switched-capacitor fully differential stage. The pixel is fabricated in standard CMOS 0.6 μm technology and measures 180×160 μm² (including the photodiode) with a fill factor of 14%. Electrooptical test results confirm the smart pixel functionality in a range of distance from 3 m to 9 m, and the accuracy achieved for preliminary distance measurements is 15 cm. Both the accuracy and the extension of the range of distance are supposed to be improved by reducing setup and environmental noise contributions that limit the pixel performance.