A shape from silhouette approach to imaging ocean mines

The application of shape-from-silhouette methods for 3D imaging of underwater objects is explored in this paper. While there is a significant body of literature on the shape-from-silhouette technique, the reconstruction of an underwater object from a sequence of 2D LIDAR images presents additional difficulties in both the creation and processing of silhouettes from the data, as the water optics and scattering can severely distort the silhouettes. In a recent data collection experiment, a LIDAR system was used to take images of an irregularly shaped object from several viewing angles. LIDAR returns were collected both with the object suspended in air and with the object well below the ocean surface. A number of image-processing techniques were used to enhance the underwater images to create silhouettes sufficiently clear to support image reconstruction. Several 3D images were formed by applying the shape-from-silhouette technique to the 2D LIDAR silhouettes. With the in-air data serving as a benchmark, the 3D images of the underwater object suggest the potential for this approach.