Dimensional characterization of opaque samples with a ring interferometer

In the present work, we introduce an optical method to characterize opaque samples. The technique combines low coherence interferometry with a ring configuration. This set-up, let us to obtain the thickness of the sample and the topography of both faces simultaneously by measuring the optical path difference with a reference arm. Experimental results in metal gauge blocks up to 1 mm are shown. A resolution better than 5 μm was obtained.