Design of an Underwater Micro-Scanning Single-Photon Laser Imaging System Based on SPAD Array

There is an urgent need for new concept underwater observation and detection equipment in marine exploration, becoming a key development direction for marine resource detection, marine scientific research, underwater rescue, and underwater defense. With the advancement of new SPAD array technology, its application in terrestrial/underwater Lidar has gained attention. This paper addresses the issues of insufficient photoelectric imaging sensitivity and high noise under strong underwater scattering conditions by investigating an underwater micro-scanning laser single-photon imaging system based on a 32×32 avalanche photodiode (SPAD) array. The system uses a SPAD array with time-correlated single-photon counting (TCSPC) functionality combined with a high-power, high-repetition-rate blue-green laser and micro-scanning imaging methods to detect weak photon echo signals underwater. It employs 2×2 low-resolution micro-scanning imaging to achieve 64×64 micro-scanning high-resolution single-photon imaging and recognition for both terrestrial and underwater targets. Additionally, the design of the optical system, optomechanical structure, and underwater pressure-sealed tank is carried out. An underwater micro-scanning single-photon laser imaging experimental system based on the SPAD array is developed. Through imaging experiments on land and underwater, the feasibility and effectiveness of the system's technical approach are demonstrated, providing effective technical and methodological support for further detection systems in actual marine environments.