Optical Coherence Tomography for the Study of Polymer and Polymer Matrix Composites

ABSTRACT Based on low‐coherence interferometry, a hybrid optical coherence tomography (OCT) system has been built. It coupled time‐domain OCT (TD‐OCT) and Fourier‐domain OCT (FD‐OCT) into one system. TD‐OCT can take the advantage of a large axial scan range while FD‐OCT has superior performance in fast imaging as no axial scan is needed. The two imaging modalities shared a broad bandwidth light source with a centre wavelength of 1550 nm, which is less scattering and can give better penetration depth in the polymer‐based material than the shorter wavelength used for biomedical applications. 2D translation stages were incorporated in the system to make cross‐sectional and volume imaging available. It can provide larger scan range as well as less image distortion compared with galvo scanners. Finally, we reported on successfully characterized specimens such as polymer coatings and glass‐fibre composites. The cross‐sectional and volumetric images obtained clearly show the microstructure of the materials. The thickness as well as the defects, e.g. microcrack and delamination can be determined.