Underwater Laser-illuminated Range-gated Imaging scaled by 22.5 cm ns−1 with serial targets

We have developed a novel target set to scale our Underwater Laser-illuminated Range-gated Imaging (ULRI) video system in a 3m-tank with turbid water (attenuation coefficient 1.0m−1). As light speed in water is 22.5cmns−1, the target set consists of a series of 3-bar targets at 22.5 cm intervals along the laser illumination direction, with the targets separated vertically. As a result, a sequence of good gated images, in steps of 1 ns delay, is presented, which is a revelation of the ‘sliced-view’ phenomenon for ns-level range-gating in such a limited water body. The Depth of Gating (DOG) and DOG-profile of the URLI system are measured for the first time, which can be used for evaluating gating-performance efficiently.