Phase measurement deflectometry based on dual-frequency nonlinear fringes

To address the challenges of edge compression, phase ambiguity, and phase jumps and discontinuities in phase unwrapping in traditional phase measurement deflectometry (PMD) for high-precision 3D measurement of large curvature mirror objects, a dual-frequency nonlinear fringe pattern and its phase extraction and compensation model are proposed. An adaptive mirror curvature distribution is achieved by designing a combination of radial fringes with a nonlinear change in density and tangential fringes with denser inward and sparser outward. High-precision phase measurement is achieved through high-frequency components, while the periodic ambiguity problem of high-frequency phase is solved by using low-frequency components. The experiment shows that the proposed method has an RMSE of 0.05558 μm for steep mirrors, which is 37.71% higher than that of the traditional method. The PV value is 0.41792 μm, which is 43.58% higher. This significantly improves the detection performance of the optical component.