Wedge angle measurement of transparent objects by adopting transmitted differential interference contrast technique

Abstract

Effects of the wedge prism angle on the accuracy of angle measurement using the transmitted phase shifting differential interference contrast (DIC) technique were studied in this paper. The optical model was constructed and serious of simulations were conducted to fulfill this study. Various prism angles were tested in the simulations. As expected, results indicated that the reconstructed wedge angle measured by the DIC system was incorrect because the light propagation became irregular. Regardless of the profile reconstruction result, the original optical path differences of light were highly correlated to the prism angle. Therefore, modification is needed to calculate the wedge angle accurately when the DIC approach is adopted. It is also found that the magnification of the objective lens (correspond to the numerical aperture and the working distance) have significant effects on the measurement. These results suggest that modification is needed to calculate the wedge angle accurately when the DIC approach is adopted. This study might provide some valuable information for adopting the DIC technique when it comes to complex geometry measurement in the future.