Simultaneous interferometric measurement of the absolute thickness and surface shape of a transparent plate using wavelength tuning Fourier analysis and phase shifting

作者：Kim Yangjin^*; Hibino Kenichi; Kizaki Toru; Sugita Naohiko; Mitsuishi Mamoru

来源：Precision Engineering-Journal of the International Societies for Precision Engineering and Nanotechnology, 2017, 48: 347-351.

DOI：10.1016/j.precisioneng.2017.01.011

• Absolute optical thickness
• Surface shape
• Interferometry
• Wavelength tuning
• Discrete Fourier analysis

The absolute optical thickness and surface shape of optical devices are considered as the fundamental characteristics when designing optical equipment. The thickness and surface shape should be measured simultaneously to reduce cost. In this research, the absolute optical thickness and surface shape of a 6-mm-thick fused silica transparent plate of diameter 100 mm was measured simultaneously by a three surface Fizeau interferometer. A measurement method combining the wavelength tuning Fourier and phase shifting technique was proposed. The absolute optical thickness that corresponds to the group refractive index was determined by wavelength tuning Fourier analysis. At the beginning and end of the wavelength tuning, the fractional phases of the interference fringes were measured by the phase shifting technique and optical thickness deviations with respect to the ordinary refractive index and surface shape were determined. These two kinds of optical thicknesses were synthesized using the Sellmeier equation for the refractive index of fused silica glass, and the least square fitting method was used to determine the final absolute optical thickness distribution. The experimental results indicate that the all the measurement uncertainties for the absolute optical thickness and surface shape were approximately 3 nm and 35 nm, respectively.

• 出版日期2017-4