Metalens-Assisted System for Underwater Imaging

The ability to image under water is highly desirable for a variety of applications including biological monitoring and seafloor survey, yet the image quality is usually hampered by the presence of scattering medium in water. Polarization imaging has proven to be an effective method for image enhancement; however, conventional systems require mechanically rotating polarizers which compromises the system's footprint or a set of polarization filters which limits the system's efficiency. Here, a compact polarization imaging apparatus that leverages a multifunctional planar dielectric metalens to simultaneously capture two orthogonally polarized images of an underwater scene is presented. Using a metalens to image target objects through milky water in a single shot, large enhancement of image contrast and depth estimation of target objects in real-time are demonstrated. This work shows the effectiveness of metalens for tackling challenging imaging tasks in complex environments.