Error Analysis of the plate beamsplitter in near optical coaxial phase measurement deflectometry

Phase-measuring deflectometry (PMD) is a key measurement technology for specular surfaces form measurement. Compared with the phase measuring deflectometry techniques based on the conventional configuration, the near optical coaxial phase measuring deflectometry (NCPMD) can achieve compact configuration, light weight and insignificant measurement error caused by structure shadows by utilizing a plate beamsplitter. However, the introduction of the plate beamsplitter will make some influence of the measurement accuracy of the NCPMD system. In the one hand, the introduction of the plate beamsplitter can reduce the measurement accuracy of the NCPMD system due to the refractive of the ray between the two surfaces of the beamsplitter. In the other hand, due to the processing and manufacturing problems of the beamsplitter, there are inevitably certain unevenness errors on the upper and lower surfaces. In this paper, a virtual simulation system of NCPMD is established, and an error model of the NCPMD system by considering both the refraction influence and reflection influence of the plate beamsplitter is presented to analyse the shape reconstruction error caused by the plate beamsplitter.