Topographic Reconstruction Through a Wavy Interface Using a Structure Light Technique

Three dimensional (3D) surface imaging has been an active area of research for decades and has reached a stage of maturity, thanks to digital cameras and ever-increasing computational power. Its utilization in science and technology is rapidly growing due to its potentials in civil engineering, mapping, structural monitoring and inspection, archaeology, and cultural heritage documentation, to name a few. In this research we will focus on development of a 3D surface imaging technique for applications in a special environment in civil engineering, i.e. underwater. Some of the most important methods of 3D surface imaging are based on the use of structured light. These techniques simplify the problem of 3D reconstruction with the help of controlled illumination and can yield excellent results in practice. They basically consist of acquiring 2D image(s) of the scene while illuminating the scene with spatially varying intensity pattern(s). The nonplanar geometric shape of the surface distorts the projected structured-light pattern as seen from the camera. The principle of structured-light 3D surface imaging techniques is to extract the 3D surface shape based on the information from the distortion of the projected structured light pattern. In this dissertation, a new structured-light method for underwater 3D surface imaging has been developed which can simultaneously estimate both the geometric shape of the water surface and the geometric shape of underwater objects. The method utilizes a projector outside of water and an underwater camera. It requires only a single image and thus can be applied to dynamic as well as static scenes. The proposed method is specifically applicable to 3D reconstruction for structural monitoring in hazardous areas that are inaccessible to direct inspection. Experimental results show the utility of this method in non-invasive underwater 3D reconstruction applications. The performance of the new method is studied through a sensitivity analysis for different parameters of the suggested method.