[OPTICAL REVIEW Vol. 17, No. 5 (2010) 481-485]
© 2010 The Japan Society of Applied Physics
Resolution Improvement in Vertical-Cavity-Surface-Emitting-Laser Diode Interferometry Based on Linear Least-Squares Estimation of Phase Gradients of Phase-Locked Fringes
Seiichi KAKUMA* and Yasuhiko KATASE
Division of Applied Physics, Graduate School of Engineering, Hokkaido University, N13W8, Kita-ku, Sapporo 060-8628, Japan
(Received April 20, 2010; Accepted July 17, 2010)
A frequency scanning interferometer using a vertical-cavity-surface-emitting-laser diode (VCSEL) capable of wide-frequency scanning has been constructed for precise distance measurements. The frequency scanning velocity of the VCSEL has been stabilized by the phase-locked loop technique, which enables us to precisely determine the phase gradient of the scanned interference fringe by linear least-squares fitting. In our test measurements, the absolute lengths from 8 to 14 mm have been measured with a resolution of nearly sub-micrometer. Compared with a conventional frequency scanning interferometer using a Fabry–Perot laser diode, the resolution of length measurement has been improved by two orders of magnitude.
Key words: frequency scanning interferometry, VCSEL, absolute length measurement