26 June 2017 Phase and group refractive indices of air calculation by fitting of phase difference measured using a combination of laser and low-coherence interferometry
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Abstract
The air refractive index is an important parameter in interferometric length measurements, since it substantially affects the measurement accuracy. We present a refractive index of air measurement method based on monitoring the phase difference between the ambient air and vacuum inside a permanently evacuated double-spaced cell. The cell is placed in one arm of the Michelson interferometer equipped with two light sources—red LED and HeNe laser, while the low-coherence and laser interference signals are measured separately. Both phase and group refractive indices of air can be calculated from the measured signals. The method was experimentally verified by comparing the obtained refractive index values with two different techniques.
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Tomáš Pikálek, Martin Šarbort, Ondřej Číp, Minh Tuan Pham, Adam Lešundák, Lenka Pravdová, Zdeněk Buchta, "Phase and group refractive indices of air calculation by fitting of phase difference measured using a combination of laser and low-coherence interferometry", Proc. SPIE 10329, Optical Measurement Systems for Industrial Inspection X, 103293I (26 June 2017); doi: 10.1117/12.2269952; https://doi.org/10.1117/12.2269952
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