An oceanographic Lidar with variable field-of-view for measuring optical properties of water

Backscattering signal from water column obtained by oceanographic Lidar is a decaying exponential function of the Lidar attenuation coefficient (K_idar). Thus K_idar can be used to derive optical properties of water. But, according to the traditional oceanographic Lidar theory, K_lidar measured under single field of view (FOV) cannot be used to effectively estimate parameters of optical properties due to the deficiency of Lidar equation. However, recent studies show that multiple-scattering analysis under different FOVs is a promising way to compensate this deficiency. Therefore, an approach using an oceanographic Lidar with variable FOV has become a potential way to measure optical properties of water. In this paper, three major parts are presented. Firstly, a shipboard oceanographic Lidar system with variable FOV designed for detecting the optical property parameters of water is introduced. Secondly, on the basis of oceanographic Lidar model developed by Walker and McLean, a practical algorithm is derived to estimate the optical property parameters of water, including a (absorption coefficient), b (scattering coefficient) and K_d (diffuse attenuation coefficient). In addition, the Lidar system has be used to carry out several experiments for measuring these optical property parameters of water. Experimental analysis verifies the feasibility of measuring multiple optical properties of seawater by the Lidar with variable FOV.