| 摘要 |
PROBLEM TO BE SOLVED: To enable measuring an optical path difference of at least one wavelength with high precision by a sinusoidal wavelength scanning interferometer. SOLUTION: A sinusoidal wavelength scanning parallel light from an SWS light source unit 10 is divided via a beam splitter 20. One light enters a mirror 22 sinusoidally vibrated by a piezoelectric element 24, and the other light enters the measurement surface of an object to be measured. A light reflected by a reflecting surface (reference surface) of the mirror 22 and a light reflected by the measurement surface of the object to be measured are combined by the beam splitter 20 and interfere with each other. On the basis of an interference signal S(t) obtained in this manner, a signal showing sinusoidal phase change is obtained, and the amplitude and the phase of the signal are obtained. By using the obtained amplitude, optical path difference of at least one wavelength is obtained. By using the obtained phase, optical path difference of at most one wavelength is obtained. By combining both results, an optical path difference of at least one wavelength is calculated with high precision.
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