Optical characterization of high numerical aperture microlenses for quality assessment and fabrication process optimization

Accurate characterization of high numerical aperture aspheric microlenses currently is a nonstandard procedure that remains an open challenge. Here, we present and discuss a characterization method based on interferometric and point spread function measurements performed in transmission by a high-resolution interferometric microscope. In particular, we show that a single phase measurement performed under fixed testing conditions can be processed in a simple way that yields wavefront aberration as well as surface topography for plano-convex microlenses with arbitrary asphericity. This approach simultaneously allows both fabrication process optimization and optical quality testing for microlenses with different optical functions without heavy modification of the testing setup. For illustration, we present the case of a microlens with a numerical aperture of ~0.4∼0.4.