Determining the refractive index profile of micro-optical elements using transflective digital holographic microscopy

This study proposes a novel method for directly measuring the spatial distribution of the refractive index of transparent or semi-transparent micro-optical elements using digital holographic microscopy, which involves transmission and reflection architectures. The proposed transflective digital holographic microscope system simultaneously records both the transmitted and the reflected waves from the micro-optical element and then numerically reconstructs the phase information and refractive index profile. No prior knowledge of the thickness and curvature of the element to be measured is required. In this study, the spatial refractive index profiles of a microlens array and a gradient index lens are demonstrated experimentally. Unlike the conventional scanning refractive ray method, the proposed method supports the rapid full-field nondestructive measurement and direct observation of the spatial index variation and structure of micro-optical elements.