| Nowadays, side-looking sonar is the only equipment able to carry out long-range underwater imaging. The use of optics is limited to short-range identification by means of conventional video-cameras. However, active optical systems (lidars) manufacturing, using a blue-green laser, will enable optics to hold its place in the field of long-range underwater imaging. After a short comparison between acoustics and optics in underwater detection and a description of the proper features of underwater optical propagation, we present the different conceivable imaging principles and propose a method to determine their performances. The experimentations described concern a lidar imager mock-up using one of the imaging principles proposed. The pictures obtained deal... |
