Monocular Photogrammetric System for 3D Reconstruction of Welds in Turbid Water

Abstract

This article presents a methodology for the 3D reconstruction of welds under water. A monocular measuring system, equipped with a hemispherical (dome) port, and its methodology are introduced. Furthermore, a simple but effective approach for the alignment of a dome port and the entrance pupil of a lens is presented. The alignment is mechanically supported by the presented lens alignment shell. Turbidity experiments in the laboratory quantify the accuracy of the 3D reconstruction of an underwater welded hollow weld in comparison with a high-quality reference measurement. The analyses show that the system is capable to reconstruct the surface of the weld in high quality using least-squares image matching. The quality level ranges from 0.06 mm in clear water to 0.11 mm in turbid water featuring a visibility of ~ 140 mm.