Underwater vision enhancement in turbid water by range-gated imaging system

Summary form only given. The importance of visual formation in the operation of robots cannot be undervalued always, since about 80% of human sensed information is due to vision. Although developments of underwater robotics vehicles (URV) have been rapid in recent years, the underwater vision is still regarded as a major tough undertaking, particularly in turbid water condition. Sonar imaging offers a large range for detection but often falls short in achieving the required resolution for identification. The normal optical image method such as underwater camera offers inherently high resolution capability, but the absorption and scattering characteristics of the marine medium severely limits the range performance, e.g. the visible range in the Singapore coastline area is only 2-3 meters. Currently, an experimental range-gated imaging system has been finished and precisely demonstrated ns (10E-9 sec) level gated images in a short turbid water tank (<3m). Our system uses very short (5 ns), high energy (160mj/p), 532 nm laser pulse as an active illuminating, and a fast gated intensified CCD camera for capturing image. The camera gated width i.e. optical gated duration (OGD) and illumination laser pulse width should match as good as possible, and the delay between them should correspond to the light round trip time to a target.