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13 May 2013 Excess fraction measurement of a transparent glass thickness in wavelength tuning interferometry
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The interference fringe order of a transparent glass plate was determined using a three-surface wavelength-tuning Fizeau interferometer and an excess fraction method. We employed multiple-surface interferometry considering the potential for simultaneous measurement of the surface shape and geometric thickness. The optical thickness signal was separated from the three interference signals in the frequency space. A frequency selective phase-shifting algorithm and a discrete Fourier analysis detected the phase of the modulated interference fringes. The optical thickness obtained by wavelengthtuning Fizeau interferometry is related to the group refractive index. In contrast, the optical thickness deviation obtained by the phase-shifting technique is related to the ordinary refractive index. These two kinds of optical thicknesses were synthesized with the help of the dispersion relation of a fused-silica glass. Finally, the interference fringe order was determined using an excess fraction method that could eliminate the initial uncertainty of the refractive index.
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Yangjin Kim, Kenichi Hibino, Kanako Harada, Naohiko Sugita, and Mamoru Mitsuishi "Excess fraction measurement of a transparent glass thickness in wavelength tuning interferometry", Proc. SPIE 8788, Optical Measurement Systems for Industrial Inspection VIII, 878803 (13 May 2013);

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