A small-size pulsed lidar designed for obstacles detection in natural underwater environment

In this paper, we designed a pint-sized underwater pulsed lidar system for underwater obstacles detection based on a 532nm Nd-YAG pulsed laser as a source and a Hamamatsu photomultiplier tube (PMT) as a detector. In order to acquire the location of the obstacles, an algorithm was devised to handle the echo signal. Through this algorithm, the background noise was suppressed and the accurate range information of the target was obtained. A high-capacity lithium battery was employed to support this lidar system operating as long as eight hours continuously. To ensure our lidar system working steady in the natural underwater environment, a stable waterproof housing was designed for the system which has good water-tightness at 40m depth underwater. This system is small, compact and hand-held. An experiment was conducted in laboratory which proof that the system can achieve target detection within 25m. At last, this lidar system was tested in natural underwater environment of Fuxian Lake in Yunnan Province. There are lots of organic particles and other impurity particles in Fuxian Lake and the attenuation coefficient of the lake is about 0.67m(-1). The results showed that this small-size lidar system was able to catch sight of the target within 20 meters and perform smoothly in the natural underwater environment.