Abstract
We developed an underwater three-dimensional (3-D) imaging sensor using a 532-nm laser. The sensor system combines a dome lens with coaxial optics to realize a wide-scanning angle of 120 deg (horizontal)×30 deg (vertical) while having a compact size of 25-cm diameter and 60-cm length. A detector sensitivity time control circuit and a time-to-digital converter are used to detect a small signal and suppress the unwanted backscattered signals due to marine snow. 3-D imaging of the seafloor with 20-m width and 60-m length was demonstrated in the sea around Ishigaki Island, Japan.
Highlights
Detailed three-dimensional (3-D) imaging of the surface of the seafloor is essential for underwater exploration.[1,2] Currently, the most widely used technology for exploration is sound navigation and ranging (SONAR), because acoustic waves can propagate through a long distance in water
The corner of the pool could be detected when the sensitivity time control (STC) is on, whereas it could not be detected when it is off. These results show that the STC circuit improves the underwater performance
We developed an underwater 3-D imaging sensor using a 532-nm laser
Summary
Detailed three-dimensional (3-D) imaging of the surface of the seafloor is essential for underwater exploration.[1,2] Currently, the most widely used technology for exploration is sound navigation and ranging (SONAR), because acoustic waves can propagate through a long distance in water. 3-D imaging on the surface of the seafloor has been proposed using laser-based structured light[3,4,5,6] and time-of-flight (TOF)[7,8,9,10] techniques. In these sensors, unwanted multipass signals are greatly reduced since the laser beam exhibits high directivity. Obtaining high measurement precision at a long These factors, i.e., compactness, reduction of signals from marine snows, and relatively long-range imaging, are essential for seafloor exploration with autonomous underwater vehicles (AUVs) and remotely operated vehicles (ROVs). We demonstrate a scanning laser sensor for underwater 3-D imaging with a wide-scanning angle of 120 deg × 30 deg and compact size of 25-cm diameter and 60-cm length
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