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Appl Opt. 2002 Oct 1;41(28):5866-71.

Differential wavelength-scanning heterodyne interferometer for measuring large step height.

Author information

  • 1The authors are with the Institute of Optical Sciences, National Central University, Jungli City, Taoyuan, Taiwan. SHLU@itri.org.tw

Abstract

An interferometer based on the differential heterodyne configuration and wavelength-scanning interferometry for measuring large step heights is presented. The proposed interferometer is less sensitive to environmental disturbances than other interferometers and can accurately measure interference phases. A tunable diode laser is utilized to illuminate the interferometer and thus solve the phase ambiguity problem. Counting the interference fringes as the wavelength is scanned through a known change in wavelength directly determines the step height. Three gauge blocks of different lengths, 5, 10, and 50 mm, are individually wrung on a steel plate to simulate large step heights. Comparing the results measured by the proposed interferometer with those by the gauge block interferometer reveals that the accuracy is approximately 100 nm.

PMID:
12371543
[PubMed]
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