Measurement of absolute optical thickness of mask glass by wavelength-tuning Fourier analysis

Optical thickness is a fundamental characteristic of an optical component. A measurement method combining discrete Fourier-transform (DFT) analysis and a phase-shifting technique gives an appropriate value for the absolute optical thickness of a transparent plate. However, there is a systematic erro...

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Bibliographic Details
Published in:Optics letters 2015-07, Vol.40 (13), p.3169-3172
Main Authors: Kim, Yangjin, Hbino, Kenichi, Sugita, Naohiko, Mitsuishi, Mamoru
Format: Article
Language:English
Subjects:
Blanks
Fourier analysis
Glass
Masks
Measurement methods
Optical components
Optical thickness
Systematic errors
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Summary:Optical thickness is a fundamental characteristic of an optical component. A measurement method combining discrete Fourier-transform (DFT) analysis and a phase-shifting technique gives an appropriate value for the absolute optical thickness of a transparent plate. However, there is a systematic error caused by the nonlinearity of the phase-shifting technique. In this research the absolute optical-thickness distribution of mask blank glass was measured using DFT and wavelength-tuning Fizeau interferometry without using sensitive phase-shifting techniques. The error occurring during the DFT analysis was compensated for by using the unwrapping correlation. The experimental results indicated that the absolute optical thickness of mask glass was measured with an accuracy of 5 nm.
ISSN:0146-9592
1539-4794
DOI:10.1364/OL.40.003169