Dispersive white-light spectral interferometry including the effect of thin-film for distance measurement

• Published in: Optik (Stuttgart) 2007-01, Vol.118 (7), p.319-324
• Main Authors: Hlubina, P., Ciprian, D., Luňáček, J.
• Format: Article
• Language: English
• Subjects: Distance; Exact sciences and technology; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Interferometers; Measurements common to several branches of physics and astronomy; Metrology, measurements and laboratory procedures; Nonlinear phase function; Optical instruments, equipment and techniques; Physics; Spatial dimensions (e.g.: position, lengths, volume, angles, displacements, including nanometer-scale displacements); Spectral interferometry; Thin-film structure; White light
• ISSN: 0030-4026; 1618-1336
• DOI: 10.1016/j.ijleo.2006.04.002

A spectral-domain white-light interferometric technique is used for measuring distances in a Michelson interferometer with a mirror represented by a thin-film structure (TFS) on a substrate. A fibre-optic spectrometer is employed for recording spectral interferograms that include wide wavelength range effects of dispersion in a cube beam splitter and multiple reflection within the TFS. Knowing the effective thickness of the beam splitter, its dispersion and parameters of the TFS and substrate, the positions of the second interferometer mirror are determined precisely by a least-squares fitting of the theoretical spectral interferograms to the recorded ones. We apply the technique to the beam splitter made of BK7 optical glass and to a uniform SiO 2 thin film on a silicon wafer. We compare the results of the processing that include and do not include the effect of the TFS.