Blue laser diode light for underwater optical vision guidance in AUV docking

The underwater optical vision guidance technique is important for AUV short-range docking. Most of the docking lights are blue or green LED lights. However, LED lights have large divergence angle and cannot meet long range optical guidance. In this paper, we designed a blue laser diode docking light named as Beijixing with adjustable divergence angle and carried out the experiment. The divergence angle variation model of the docking light propagating in water is established according to the optical properties of water and the beam-spread function. The experimental results show that at a distance of 18m, when the divergence angle is 0.06° with strong directivity, the images captured by Nano SeaCam appear saturated, and the spot images captured by StarfishCam are light columns, which are difficulty for spot centroid extraction. When the angle is 10°, the light spots captured by Nano-SeaCam overlap, but StarfishCam can distinguish the spots. The research is beneficial for the design of docking lights for underwater optical vision guidance in AUV docking.