Mapping surface flaws on float glass through Fourier ptychographic quantitative phase imaging

Abstract

Glass is increasingly used as a load-carrying construction material both in buildings and vehicles, and growing emphasis is consequently given to its safety properties. How the mechanical properties of glass relate to the inevitable presence of surface defects, and how these defects can be efficiently measured, are important scientific questions. We demonstrate that Fourier ptychographic microscopy can be used to detect, count, and topographically measure glass surface defects through the reconstructed quantitative phase images. We characterized several key parameters, including the length, width, orientation, eccentricity, and depth of the identified flaws and cross-validated our results with atomic force microscopy topography maps. The sign of the phase shift makes it feasible to discriminate surface flaws from impurities residing on the glass surface. The method is quantitative, scalable, and allows extended areas to be screened. The proposed technique has the potential to improve the understanding of surface flaws in glass and thereby contribute to better mechanical models for predicting glass failure and fracture under quasi-static and dynamic loading.