3D Shape and Displacement Measurement of Diffuse Objects by DIC-Assisted Digital Holography

Background: The state-of-the-art holographic displacement measurements can only measure one dimensional displacement with one digital holography (DH) setup. To measure 3D displacements of curved diffuse objects, both 3D shape and displacement measurements are needed which requires additional optical systems and results in complex systems. Objective: In this work, we propose a digital image correlation (DIC)-assisted DH method for 3D shape measurement and 3D displacement measurement of curved diffuse objects with one DH setup. Methods: The proposed approach is based on the combination of two popular optical techniques, DH and DIC. Specfically, 3D shape is measured by tilting the illumination angle of the object wave of DH. Then the in-plane displacement component is measured with the assistance of 2D-DIC from the intensity images of DH which are laser speckle patterns in essence. At last, the out-of-plane displacement component is determined by the displacement along sensitivity vector which is measured from the phase images of DH and a displacement compensation quantity due to 3D shape and the measured in-plane displacements. Results: Hence, with the assistance of 3D shape and 2D-DIC method, 3D displacements of curved diffuse objects are measured. The metrological performance of the proposed scheme is verified by real experiments. Conclusions: The results demonstrate that the proposed DIC-assisted DH method for 3D shape measurement and 3D displacement measurement of curved diffuse objects with high accuracy.