Underwater long-range LiDAR based on wide baseline polarized light-sheet illumination

Underwater long-range, high-resolution, three-dimensional (3D) optical detection is critical for seabed exploration and infrastructure inspection. However, conventional optical methods face limitations in terms of detection range, depth of field (DOF), and compatibility with uncrewed underwater vehicles. To address these challenges, we present an innovative underwater long-range LiDAR system based on wide baseline polarized light-sheet illumination. The proposed system employs single-line light-sheet illumination to enhance the brightness of the laser line on the target, a wide baseline configuration to reduce backscattering, and polarization technology to further alleviate unwanted light interference. By utilizing the Scheimpflug imaging principle, the system achieves a large DOF (covering a range from 1.9 m to 65 m) and high-resolution 3D detection. Using the laser centerline method based on the distance gradient region energy, the challenges of scattering and absorption in complex underwater environments were addressed. Experiments conducted in a laboratory pool demonstrated the system's capability to achieve high-resolution 3D detection at 25 m with a distance resolution of 5 cm. The maximum detection distance was 7.4 times the attenuation length. This study provides a new approach for long-range underwater detection with potential applications in seabed topography surveying, underwater pipeline maintenance, and marine archaeology.