Dual-side view optical coherence tomography for thickness measurement on opaque materials.

Optical coherence tomography (OCT), as an optical interferometric imaging technique, has found wide applications in various fields. In principle, OCT is well suited for imaging layered structures, and thus, one of the typical applications is thickness measurement. However, due to the limited imaging depth resulting from light attenuation, thickness measurement by OCT is limited to non-opaque materials. In this study, we developed a novel (to the best of our knowledge) dual-side view OCT (DSV-OCT) system for thickness measurement on opaque materials. The dual-side view was achieved on a conventional swept source OCT platform by creating two symmetrical sampling arms. This allows us to image both sides of the material simultaneously and produce the surface contours of the two sides in a single C scan. Finally, the thickness of the opaque material can be calculated from the two surface contours above. We demonstrated that our DSV-OCT technique can measure the thickness of opaque material with an accuracy of about 3 µm.