Model-based 3D reconstruction method with a concave mirror for deflectometry

Phase measuring deflectometry (PMD) has been widely studied and applied in specular surface measurement, but measurement accuracy is affected due to the limited depth of field (DOF) of the camera lens. Meanwhile, there are many discontinuous specular surfaces in various fields such as aviation and advanced manufacturing, which cannot be measured by the traditional PMDs. This paper proposes a model-based PMD by using concave mirror- assisted imaging (CM-MPMD), which extends the effective DOF range for measurement. The model is established using reverse ray tracing to achieve measurement of discontinuous specular surfaces. The accuracy and reliability are verified by measuring discontinuous free mirror, plane mirror with marked points and quantitative steps.