低コヒーレンス複合干渉計による水晶振動子の厚さ測定

概要

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A low coherence interferometry is a method for non-invasive optical ranging measurement of microstructures. A simultaneous measurement method of geometricai thickness and refractive index of quartz crystal with the low coherence interferometry has been proposed. However, it is hard to align a sample arm in the Michelson interferometer, because a beam of measurement arm must be incident on both sample and measurement mirror. Moreover, only the geometrical thickness and refractive index at the edge of sample can be measured. In this study, a novel configuration of low coherence interferometer is proposed in order to solve these problems. This system utilizes double Michelson interferometers. The interferometer consists of two reference mirrors which are used for scanning an optical path length and for determining a reference point. Both distributions of geometrical thickness and refractive index with this method can be measured. An experimental verification of our method is demonstrated by the use of microscope glass cover-slip and quartz crystal as samples. It was found that the measurement values of samples were in good agreement with the thickness measured by a dial gauge and the refractive index cited from the literature.
1999-10-05