3D Measurement of Transparent Vessel and Submerged Object Using Laser Range Finder

Specimens of precious underwater creatures are preserved in transparent vessels with liquid. It is important to measure three-dimensional shape of submerged objects. When measuring submerged objects by image measurement, refraction of light should be considered. This problem can be solved by ray tracing, but the 3D coordinates of the vessel are necessary. In this paper, we propose a method of measuring both a vessel and an object by using a laser range finder (LRF) mounted on a manipulator. Because a transparent vessel is not completely transparent, a reflection from the vessel surface can be detected in addition to a reflection from the object. However, the captured image may have many reflections from various paths, then it is necessary to detect correct reflections. The proposed method solves this problem by examining a behavior of each reflection relating to the epipolar constraint when the posture of the LRF is changed. Experimental results show the effectiveness of the proposed method.