Submerged single-photon LiDAR imaging sensor used for real time 3D scene reconstruction in scattering underwater environments

We demonstrate a fully submerged underwater LiDAR transceiver system based on single photon detection technologies. The LiDAR imaging system used a silicon single-photon avalanche diode (SPAD) detector array fabricated in complementary metal-oxide semiconductor (CMOS) technology to measure photon time-of-flight using picosecond resolution time correlated single photon counting. The SPAD detector array was directly interfaced to a Graphics Processing Unit (GPU) for real time image reconstruction capability. Experiments were performed with the transceiver system and target objects immersed in a water tank at a depth of 1.8 meters, with the targets placed at a stand off distance of approximately 3 meters. The transceiver used a picosecond pulsed laser source with a central wavelength of 532 nm, operating at a repetition rate of 20 MHz and average optical power of up to 52 mW, dependent on scattering conditions. Three dimensional imaging was demonstrated by implementing a joint surface detection and distance estimation algorithm for real time processing and visualization, which achieved images of stationary targets with up to 7.5 attenuation lengths between the transceiver and the target. The average processing time per frame was approximately 33 ms, allowing real-time three-dimensional video demonstrations of moving targets at ten frames per second at up to 5.5 attenuation lengths between transceiver and target.本研究展示了一套基于单光子探测技术的全浸没式水下激光雷达（LiDAR）收发系统。该激光雷达成像系统采用基于互补金属氧化物半导体（CMOS）工艺制备的硅基单光子雪崩二极管（SPAD）探测器阵列，通过皮秒级分辨率的时间相关单光子计数技术测量光子飞行时间。该SPAD探测器阵列直接与图形处理器（GPU）相连，以实现实时图像重建功能。实验中将收发系统与目标物体浸没于水深1.8米的水槽中，目标的靶距约为3米。该收发系统采用皮秒脉冲激光源，中心波长为532纳米，重复频率为20兆赫，平均光功率最高可达52毫瓦，具体数值取决于水体散射条件。通过联合表面检测与距离估计算法实现实时处理与可视化，本系统完成了三维成像演示：在收发端与目标之间的衰减长度可达7.5的场景下，可获取静止目标的三维图像。单帧平均处理时长约为33毫秒，可在收发端与目标间衰减长度最高达5.5的场景下，以每秒10帧的速率完成运动目标的实时三维视频演示。