Three-dimensional underwater measuring by structured light projection

Abstract

Structured light projection is a fast and flexible optical method for measuring the 3D shape of objects. The measurement is performed within a few seconds. The result is a dense cloud of points that accurately describes the shape of the surface. The information could be used e.g. to generate CAD models from an item designed by hand, or it could be used for product quality inspection. The desired information, such as distances, angles, profiles, etc. can conveniently be extracted from the measurement results. It is also possible to calculate and visualize the deviation between a measurement and a CAD model. Most of the research work made with this technique has been carried out in a terrestrial normal environment. However sometimes it is convenient to make measurements inside hazardous or wet media, such as fogy, cloudy, raining, scattering, or underwater, or even biologic and toxic media. In this paper are presented the first steps toward obtain 3D inform shape information of a structure which is immersed inside water. Two of the most important steps are the optical setup characterization and the study optical properties of the environment. Both give us mainly conditions of illumination and restrictions on the object surface texture. In order to characterize the CCD optics, experiments related to fringe visibility varying distance to target and density and absorption of the media are carrying out. The first experimental results are presented. © The Society for Experimental Mechanics, Inc. 2014.