Seiichi KAKUMA^* and Yasuhiko KATASE

Division of Applied Physics, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan

(Received June 5, 2012; Accepted August 17, 2012)

In laser frequency scanning interferometry for measurements of absolute lengths, a small drift in the measured length during the frequency scan yields an enlarged offset error in the measured result. Although such an error is unavoidable for an on-site interferometric system, methods for solving this problem have not been developed. We propose a frequency scanning interferometric system immune to the dynamic length change employing a pair of vertical-cavity surface-emitting laser diodes whose frequencies are equally scanned in opposite directions. The offset error is canceled by averaging the two phase shifts of the interferograms obtained from the light sources.

Key words: VCSEL, frequency scanning interferometry, length drift, absolute length

^*E-mail address: kakuma@eng.hokudai.ac.jp