Microsphere-assisted interferometry with high numerical apertures for 3D topography measurements.

Abstract

Improving the lateral resolution is a key focus of the research on optical measuring systems to expand the fields of application for optical metrology. By means of microspheres put on an object in a microscope, and therefore used as a near-field support, it has already been shown that a superresolution of structures below Abbe's diffraction limit is possible. The following investigations give more detailed theoretical and experimental insight into the physical mechanisms responsible for the transition of near-field information to the far field. In particular, the effects of microspheres as near-field support on the behavior of phase-evaluating interference microscopes close to the optical resolution limit are studied experimentally as well as with numerical simulations. Special attention is drawn to measured data taken with a Linnik microscope of high numerical aperture. Finally, the measurement results of grating structures with a period below Abbe's diffraction limit are presented.