Ultra-thin metallic foil thickness measurement system using fiber optic low-coherence interferometry

Abstract

The thickness of metallic foil is measured by differential low-coherence interferometry. Two tandem Michelson Interferometers (MI), of which reflective surfaces measured are the corresponding surfaces of metallic foil, are used as basic interferometric system to obtain interference fringes on a spectrometer. Therefore, the interference fringes only depend on the path differences due to the thickness of metallic foil. The interference fringes are analyzed with a modified extremum method based on the least root mean square (RMS) deviation. The experimental results on thickness measurement are presented.