Experiments on sensing of the sea bottom of shallow water were carried out with an airborne lidar. To reduce glint reflections from the sea water surface in lidar returns, the axial region of the receiving lidar telescope was screened by a shadow field stop. In this case, the entire lidar return from water depth is formed only by multiply scattered radiation. Such lidar configuration improves the contrast of signals from the sea bottom. Operation of the lidar with the shadow field stop was simulated by the Monte Carlo method. It is demonstrated that the application of the shadow field stop in the airborne hydrooptical lidar is an effective method of increasing the contrast of lidar returns from the sea bottom. From nonaxial underwater lidar returns comprising only multiple scattering, the effective water extinction index was reconstructed using the logarithmic derivative method. Due to the influence of multiple scattering, this parameter depends on the field-of-view angle of the lidar receiver; however, in any case it has physically reliable values.
lidar; hydro-optics; scattering phase function