Numerical simulation research and applications on scattering imaging of surface defects on optical components

摘要

The principle of microscopic scattering dark-field imaging is adopted in surface defects evaluation system (SDES) for large fine optics. However, since defects are of micron or submicron scale, scattering imaging cannot be described simply by geometrical imaging. In this paper, the simulation model of the electromagnetic field in defect scattering imaging is established on the basis of Finite-Difference Time-Domain (FDTD) method to study the scattering imaging properties of rectangular and triangular defects with different sizes by simulation. The criterion board with scribed lines and dots on it is used to carry out experiments scattering imaging and obtain grayscale value distributions of scattering dark-field images of scribed lines. The experiment results are in good agreement with the simulation results. Based on the above analysis, defect width extraction width is preliminary discussed. Findings in this paper could provide theoretical references for defect calibration in optical fabrication and inspection.