We have developed a low-coherence interferometer system used for the simultaneous measurement of refractive index n and thickness t of transparent plates. Both the phase index np and group index ng can be determined automatically in a wide thickness range of from 10 μm to a few millimeters. Two unique techniques are presented to measure np, ng, and t simultaneously. One allows us to determine np, ng, and t accurately by using a special sample holder, in which the measurement accuracy is 0.3% for the thickness t above 0.1 mm. In the other technique the chromatic dispersion δn of index is approximately expressed as a function of (np − 1) on the basis of measured values of np and ng for a variety of materials, and then the simultaneous measurement is performed with a normal sample holder. In addition, a measurement accuracy of less than 1% is achieved even when the sample is as thin as 20 μm. The measurement time is also 3 min or more.
© 2002 Optical Society of America
[Optical Society of America ]
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.4820) Instrumentation, measurement, and metrology : Optical systems
(120.5710) Instrumentation, measurement, and metrology : Refraction
Hideki Maruyama, Shogo Inoue, Teruki Mitsuyama, Masato Ohmi, and Masamitsu Haruna, "Low-Coherence Interferometer System for the Simultaneous Measurement of Refractive Index and Thickness," Appl. Opt. 41, 1315-1322 (2002)