Optical system design for GM-APD lidar based on multi-angle micro-nano polarization array

To address the problems of low imaging contrast and poor signal-to-noise ratio in LiDAR systems based on Geiger-mode avalanche photodiode (GM-APD) arrays, a new LiDAR imaging method using a multi-angle micro–nano polarization array is proposed. The system uses a secondary imaging optical path to project the multi-angle micro–nano polarization array on the first image plane onto the APD detector target surface at a 1:1 ratio. This design achieves high-precision micro–nano channel registration. It allows real-time acquisition of four polarization images (0°, 45°, 90°, and 135°) and a three-dimensional distance image with a single optical path and a single detector. The system is designed for a 128 × 128 resolution APD array detector with a pixel size of 50 µm. At an operating wavelength of 1064 nm, the root-mean-square spot radius across the full field of view is smaller than the Airy disk radius. The distortion is only 0.01%. With a high-repetition-rate and high-power pulsed laser, the system can capture intensity, polarization, and distance images of the target at the same time. Pixel-level fusion between polarization and distance images is achieved, solving the problem of multi-dimensional image fusion and registration. Calibration and experiment results show that the measurement error of the four polarization angles is less than 2.45%. The contrast of the polarization image increases by 92.3% compared with traditional LiDAR intensity images. This method greatly improves the ability to sense multi-dimensional information from long-range dynamic targets.