Simple method for thickness measurement in opaque samples with a Michelson-Sagnac interferometer

Abstract

We present in this work a method to measure thicknesses of opaque samples. The technique combines the use of low coherence interferometry with a Michelson-Sagnac configuration. This ring set-up let us to measure both faces of the sample simultaneously. So it is possible to obtain the thickness by measuring the optical path difference between a reference and both surfaces of the sample. Experimental results up to 1mm are shown in metal gauge block. A resolution better than 10 micronswas obtained.