Low-coherence interferometer system for the simultaneous measurement of refractive index and thickness.
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 n(p) and group index n(g) can be determined automatically in a wide thickness range of from 10 microm to a few millimeters. Two unique techniques are presented to measure n(p), n(g), and t simultaneously. One allows us to determine n(p), n(g), 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 delta n of index is approximately expressed as a function of (n(p) - 1) on the basis of measured values of n(p) and n(g) 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 microm. The measurement time is also 3 min or more.
Maruyama
Hideki
H
Research and Development Laboratory, Kyushu Matsushita Electric Company, Ltd., Fukuoka, Japan. maruyama@rdm.kme.mei.co.jp
Inoue
Shogo
S
Mitsuyama
Teruki
T
Ohmi
Masato
M
Haruna
Masamitsu
M
D002138:Calibration; D007368:Interferometry / Q000295:instrumentation*; D008962:Models, Theoretical; D012031:Refractometry