Three Dimensional Measurement of Submerged Objects in Transparent Vessels Using a Manipulator-mounted Laser Range Finder

Abstract

An important need exists to digitally archive 3D models of objects, such as specimens of rare underwater creatures. These objects are sometimes preserved in liquid contained in transparent vessels. When measuring submerged objects, light refraction should be considered. Refraction can be considered with ray tracing, but the 3D coordinates of the vessel are necessary to use this method. In this paper, we propose a method that takes advantage of transparent vessels not being completely transparent to measure both a vessel's surface and a submerged object using a laser range finder mounted on a manipulator. The method uses a camera to detect reflections from the vessel surface and the submerged object. A captured image may have multiple reflections from various paths, so it is necessary to identify the correct reflections. The proposed method identifies the reflections from the vessel on the basis of epipolar constraints related to the position of the laser range finder and identifies the reflections from the object by ray tracing. Experimental results demonstrated the effectiveness of the proposed method.