Abstract
We have developed an aquatic inelastic hyperspectral lidar with unrestricted focal-depth and enough sensitivity and spatio-temporal resolution to detect and resolve position and behavior of individual sub-millimeter aquatic organisms. We demonstrate ranging with monitoring of elastic echoes, water Raman signals and fluorescence from chlorophyllbearing phytoplankton and dye tagged organisms. The system is based on a blue CW diode laser and a Scheimpflug optical arrangement.
Highlights
1 BACKGROUND Underwater suspended particle monitoring has an important role in aquatic ecosystem research
Individual submillimeter organism detection is difficult to accomplish by sonar which is the most common and mature technique used in aquatic monitoring [2]
Laser optical particle counters (LOPC) and in-line digital holography are capable of detecting underwater submillimeter organisms with high precision [3, 4]
Summary
Underwater suspended particle monitoring has an important role in aquatic ecosystem research. There is considerable diversity in the layered vertical structures of salinity, illumination, and temperature as well as biomass distribution which exhibits rapid changes, e.g., the diel vertical migration of zooplankton shows changes even on a scale of one hour [1]. When it comes to monitoring these phenomena, remote sensing and real-time methods provide advantages over conventional methods, such as water sampling, which is laborious and intrusive. Light detection and ranging (lidar) techniques are readily used for atmospheric fauna and particle detection, as well as for aquatic monitoring with airborne systems. We here introduce a novel lidar technique, which provides hyperspectral monitoring and spatiotemporal resolution with a reasonable sensitivity [7]
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