Invited Paper IPF-TuM1
Imaging in the Underwater Environment: Current Status and Future Trends

Tuesday, October 21, 2008, 8:00 am, Room 312

Natural waters are largely opaque to electromagnetic energy except for a narrow wavelength range between 400 and 700 nm - the visible light spectrum. If the water body, the ocean for example, contained only pure water, it would be possible to view objects through several hundred meters of path length. Unfortunately, natural waters are never pure, but contain large concentrations of suspended and dissolved matter that act to scatter and absorb light energy. The combined attenuation effects of scatter and absorption greatly reduce imaging range. The useful imaging range of conventional camera and flood light combinations is limited to between 1 and 2 optical attenuation lengths, translating to a few tens of meters in clear ocean water, but < 5 m in most coastal and estuarine environments. The development, over the last two decades, of laser-based systems employing synchronous scan and range-gated approaches have increased imaging range to 4 - 5 attenuation lengths and recent improvements in pulsed laser beam form and efficiency and signal processing techniques can potentially increase imaging range another 2 attenuation lengths. However, future improvements in underwater imaging will likely not be driven by better light sources and detectors or sensor architecture, but by how such systems are deployed. Advances in autonomous underwater platforms are allowing imaging researchers to think beyond traditional co-located source and detector approaches to scenarios where the imaging components are distributed within underwater sensing networks. Such approaches could potentially overcome limitations due to imaging range by using knowledge of local environmental variability and may provide opportunities to image across much greater ranges.