Linnik-interferometer with ring-shaped optical MEMS shutter array enabling dynamic annular illumination for fast and reliable measurement of sloped and curved surface microstructures

Abstract A ring-shaped optical micro-electro-mechanical-systems shutter array, referred to as ring shutter, is implemented in the illumination path of a Linnik coherence scanning interferometer. It acts as a dynamic spatial filter, which is imaged into the pupil plane of the microscope objectives. This filtering process limits the angles of light incident on the sample to a certain range, which, depending on the surface slope, can be exploited to significantly increase the signal-to-noise ratio of the resulting interference signals and, subsequently, the quality of surface reconstruction. The results of conventional interferometric measurements are shown and compared with those of our novel setup to demonstrate a significant effect on the reliability of the surface reconstruction. The data is additionally analyzed in the spatial frequency domain in order to explain the underlying signal formation process.