Simple setup for optical characterization of microlenses

Scientific articles focusing on fabrication of micro-components often evaluate their optical performances by techniques such as scanning electron microscopy or surface topography only. However, deriving the optical characteristics from the shape of the optical element requires using propagation algorithms. In this paper, we present a simple and intuitive method, based on the measurement of the intensity point spread function generated by the micro-component. The setup is less expensive than common systems and does not require heavy equipments, since it requires only a microscope objective, a CMOS camera and a displacement stage. This direct characterization method consists in scanning axially and recording sequentially the focal volume. Our system, in transmissive configuration, consists in the investigation of the focus generated by the microlens, allowing measuring the axial and lateral resolutions, estimating the Strehl ratio and calculating the numerical aperture of the microlens. The optical system can also be used in reflective configuration in order to characterize micro-reflective components such as molds. The fixed imaging configuration allows rapid estimation of quality and repeatability of fabricated micro-optical elements.