Internal Stray Light Suppression for Single-Band Bathymetric LiDAR Optical System

The echo signals received by the optical system in light detection and ranging (LiDAR) are interfered with by diffusely reflected sunlight from the water surface and the backscattered laser from underwater. This fact makes it difficult for the photomultiplier tube (PMT) to accurately identify whether the echoes are from either the water surface or the water bottom. For this reason, this article proposed a method for internal stray light suppression optical systems in a single-band bathymetric LiDAR. A stray light suppression structure (SLSS), which is composed of an inner hood with built-in baffle vanes and a spectroscope hood with built-in grooved vanes, is proposed. The SLSS designed by the tangent method makes the stray light reflected many times and the stray light low-level propagation path is eliminated. The SLSS is verified by the experiments in optical platforms, outdoor ponds, reservoirs, and Beihai Bay of the Pacific Ocean. The results show that the proposed optical system with SLSS can eliminate the stray light at an average order of $10<^>{-10}$ , and can suppress 99.1% of stray light relative to that without the SLSS. The result implies that a significant improvement in the identification of echoes from the water surface and from the water bottom under various water environments, such as rivers, reservoirs, and oceans are obtained.