Oil spill fluorosensing lidar for inclined onshore or shipboard operation

An oil spill detection fluorosensing lidar for onshore or shipboard operation is described. Some difficulties for its operation arise from the inclined path of rays. This is due to the increased reflection of the laser beam at the air-water interface, the decreased fluorescence signal, and the increased background light when compared with other instruments having a close-to-nadir measuring geometry. The analysis of these problems shows that they significantly reduce the detection distance in the presence of a flat water surface. However, waves on the water surface weaken the influence of the laser beam reflections but at the same time cause a variable fluorescence signal, which makes specific signal processing necessary for increased detection ranges. A fluorescence data processing method is proposed that efficiently eliminates the background water column fluorescence from signals such as yellow substance. This enables oil fluorescence to be distinguished from variable natural water fluorescence.