Fast and information-efficient microdeflectometry with travelling cross-fringes

Microdeflectometry (µPMD) measures the slope of microscopic smooth objects. From the slope, the shape can be reconstructed [1]. The achievable height precision is in the nm-regime, independent of the NA and field size of used objective [1]. However, the disadvantages of µPMD are the poor global accuracy and the small depth of focus (DOF). To overcome these limitations, we combined µPMD with Structured-Illumination Microscopy (SIM) to achieve both a globally accurate and a locally precise height map [2]. To extend the DOF of µPMD, we exploit SIM: with SIM, we measure the surface topography and, in the best focus of each surface point, the slope is measured by µPMD. For a fast measurement, we introduce a novel scanning strategy using travelling cross-fringes to avoid a stop-and-go-scan. We can demonstrate that the information efficiency of microdeflectometry can be improved with a factor of 2 by this scanning strategy. [1] G. Häusler et al. Opt. Lett. 33, 4, pp, 396-398 (2008) [2] Z. Yang et al. DGaO Proc. P20 (2013)