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Proceedings Paper

Sinusoidal wavelength-scanning interferometers using a superluminescent diode
Author(s): Osami Sasaki; Norihiko Murata; Kazuhiro Akiyama; Takamasa Suzuki
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Paper Abstract

Two different sinusoidal wavelength-scanning (SWS) interferometers with a SWS light source using a superluminescent laser diode are proposed for step-profile measurement and real-time distance measurement, respectively. An optical path difference (OPD) longer than a wavelength is measured from detection of sinusoidal phase- modulation amplitude Zb of the interference signal that is proportional to the OPD and the scanning width 2b. In step-profile measurement, if measurement error in the OPD obtained from Zb is smaller than a half wavelength, this measured value of the OPD is combined with a fractional value of the OPD obtained from the conventional phase of the interference signal. This combination enables us to measure the OPD longer than a wavelength with a high accuracy of a few nm. In real-time distance measurement, the amplitude Zb is kept at a specified constant value for changes of OPD by controlling the scanning width 2b of the wavelength with a feedback system. The amplitude Zb is detected by processing the interference signal with electric circuits in real-time. The value of b is easily controlled in the SWS light source, and an OPD longer than a wavelength is measured from the value of b with an accuracy of about a wavelength.

Paper Details

Date Published: 17 August 1999
PDF: 9 pages
Proc. SPIE 3745, Interferometry '99: Applications, (17 August 1999); doi: 10.1117/12.357778
Show Author Affiliations
Osami Sasaki, Niigata Univ. (Japan)
Norihiko Murata, Niigata Univ. (Japan)
Kazuhiro Akiyama, Niigata Univ. (Japan)
Takamasa Suzuki, Niigata Univ. (Japan)

Published in SPIE Proceedings Vol. 3745:
Interferometry '99: Applications
Werner P. O. Jueptner; Krzysztof Patorski, Editor(s)

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