Projection moire based full-field high-resolution 3D morphology measurement method for specular surfaces

The specular surfaces require high precision and high reliability in the manufacturing and application, which demands advanced morphology measurement techniques. The characteristics of the specular surfaces bring great difficulties to the accurate measurement of the morphology. In this paper, a three-dimensional morphology measurement method is proposed for specular surfaces based on the projection moire<acute accent> approach. A specular projection moire<acute accent> model is developed so the relationship between the surface and the moire<acute accent> phase is established. Both of the height and slope of the surface are considered in the model to reach the ability of high measurement precision. A solution method is proposed so the surface profile can be obtained from the moire<acute accent> phase. To solve the height-slope ambiguity during the measurement, a continuum hypothesis coupled with an optimization approach is introduced, which can solve the height and slope of the surface individually from the moire<acute accent> phase only by an arbitrary movement of the light source. A series of experiments are conducted to validate the performance of the proposed method. Results demonstrate that the method outperforms traditional monoscopic phase measuring deflectometry (PMD) in terms of resolution and precision under identical experimental configurations, and can operate effectively under extreme conditions where traditional PMD fails. The precision of the proposed method is also quantitatively evaluated in the experiments.