Proceedings Article | 30 September 2024
KEYWORDS: Optical surfaces, Fringe analysis, 3D modeling, Multiple scattering, Statistical modeling, Modeling, Polarization, Equipment, Scattering, Reflection
In optical metrology, the growing demand for accurate measurement technologies is driven by the increasing applications of three-dimensional (3D) microscopy and imaging. The advancement of these technologies relies on the modelling of the measurement process, where an initial step involves characterising the interaction between electromagnetic fields and surfaces, to determine the scattered electromagnetic field, and the subsequent propagation of the scattered light through the instrument. Virtual instruments (VIs) can play a critical role by replicating optical instruments through surface scattering models, 3D imaging theory and error-generation models. The development of VIs contributes to a better understanding of instrument characteristics, optimising configurations and evaluating uncertainties. VIs can be customised to simulate various optical setups, providing researchers with flexibility to explore optimal measurement settings. Furthermore, the integration of sophisticated computational tools and machine learning to VIs can enable real-time, in-depth and optimal analysis of optical instrument modelling. Coherence scanning interferometry (CSI) is a widely used optical technique for high-accuracy surface topography measurement. A virtual CSI (VCSI) models the CSI measurement process using physics-based models. Approximate scattering models, utilising basic scalar diffraction and linear imaging theories, facilitate CSI modelling that can offer insights into the fundamental sources of measurement error for smooth surfaces. However, with the increasing use of complex freeform manufactured structures in engineering, aerospace and biology, scrutinising complex surface features becomes more critical. As a result, rigorous scattering models, based on solutions of Maxwell’s equations, can be used as tools for addressing more complex light-matter interactions. Capable of calculating light scattered fields from any surface geometry while taking into account different light phenomena, such as polarisation, rigorous models provide high-accuracy solutions. In this study, we compare the simulated fringe pattern and reconstructed profiles obtained by virtual coherence scanning, employing both approximate and rigorous scattering models for sinusoidal and vee-groove samples.
