Open AccessSurface measuring coherence scanning interferometry beyond the specular reflection limit
Author(s) -
Melanie Thomas,
Rong Su,
Peter J. de Groot,
John N. Coupland,
Richard Leach
Publication year - 2021
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.435715
Subject(s) - optics , specular reflection , interferometry , coherence (philosophical gambling strategy) , interference (communication) , reflection (computer programming) , astronomical interferometer , grating , tilt (camera) , diffraction , physics , retroreflector , laser , computer science , mechanical engineering , computer network , channel (broadcasting) , quantum mechanics , programming language , engineering
The capability of optical surface topography measurement methods for measurement of steep and tilted surfaces is investigated through modelling of a coherence scanning interferometer. Of particular interest is the effect on the interference signal and measured topography when tilting the object at angles larger than the numerical aperture slope limit (i.e. the specular reflection limit) of the instrument. Here we use theoretical modelling to predict the results across a range of tilt angles for a blazed diffraction grating. The theoretically predicted interference patterns and surface height measurements are then verified directly with experimental measurements. Results illustrate the capabilities, limitations and modelling methods for interferometers to measure beyond the specular reflection limit.