High-precision 3D imaging of underwater coaxial scanning photon counting Lidar based on spatiotemporal correlation

•An underwater coaxial scanning photon counting Lidar system based on two-dimensional turntable is developed.•A spatiotemporal correlation method based on instrument response function matched filtering preprocessing is proposed.•The ranging accuracy and resolution of the system are better than 1.0 cm.•An effective method are provided for high precision and high resolution 3D imaging of underwater targets. A coaxial scanning photon counting Lidar is developed to achieve three-dimensional (3D) imaging of underwater targets. A spatiotemporal correlation-based method is proposed to achieve high-precision detection, which involves preprocessing using matched filtering with the instrument response function. A single-point repeatability measurement of a planar target and a 3D image of a resolution plate are performed using the Lidar system and the signal reconstruction algorithm. The experimental results demonstrate that the ranging accuracy is better than 1.0 cm. Compared with the maximum likelihood estimation method, the proposed method exhibits higher ranging accuracy when the target distance does not change steeply. Additionally, the 3D imaging results of the target model consisting of a car and a suitcase can clearly distinguish features such as the rearview mirror, headlight, handle, and lock. The system has potential applications in underwater target identification, ocean engineering construction, underwater archaeology, and other fields requiring high-precision 3D imaging.