Accurate 3-D Shape Measurement for Large Objects Using Speckle-Assisted Fringe Projection and Global Markers Localization

Abstract

Digital fringe projection (DFP) three-dimensional (3D) shape measurement technique has been extensively researched and applied due to its advantages of high accuracy and high efficiency. To retain the measurement accuracy for large objects, results of multiple measurements are required to be aligned based on the combination of DFP and auxiliary positioning instruments, which decreases the measurement efficiency and limits the practical application. This paper presents an accurate and efficient scheme for large-scale 3D shape measurement based on speckle-assisted fringe projection and global markers localization. Taking advantage of the triple-view geometric constraints and stereo structured-light model, arbitrary 3D surface can be reconstructed with high quality by projecting only four patterns. To align multiple local shape data of large objects without using auxiliary positioning instruments, an accurate data registration method based on global markers reconstruction and localization is presented, which firstly calculates 3D coordinates of all non-coded markers pasted on the object surface by sequential matching, incremental markers reconstruction and global optimization based on bundle adjustment followed by multiple local data registration through local-to-global ICP matching. The experimental results indicate that the proposed method can substantially decrease the accumulated measurement error and achieve commensurate accuracy with the auxiliary positioning methods.