Phase and fringe order determination in wavelength scanning interferometry

Moschetti, Guiseppe; Forbes, Alistair; Leach, Richard K.; Jiang, Xiang; O'Connor, Daniel

Abstract

A method to obtain unambiguous surface height measurements using wavelength scanning interferometry with an improved repeatability, comparable to that obtainable using phase shifting interferometry, is reported. Rather than determining the conventional fringe frequency-derived z height directly, the method uses the frequency to resolve the fringe order ambiguity, and combine this information with the more accurate and repeatable fringe phase derived z height. A theoretical model to evaluate the method’s performance in the presence of additive noise is derived and shown to be in good agreement with experiments. The measurement repeatability is improved by a factor of ten over that achieved when using frequency information alone, reaching the sub-nanometre range. Moreover, the z-axis non-linearity (bleed-through or ripple error) is reduced by a factor of ten. These order of magnitude improvements in measurement performance are demonstrated through a number of practical measurement examples.

• Journal Article Type: Article
• Acceptance Date: Apr 16, 2016
• Online Publication Date: Apr 16, 2016
• Publication Date: Apr 16, 2016
• Deposit Date: Apr 18, 2016
• Publicly Available Date: Apr 18, 2016
• Journal: Optics Express
• Electronic ISSN: 1094-4087
• Publisher: Optical Society of America
• Peer Reviewed: Peer Reviewed
• Volume: 24
• Issue: 8
• Pages: 8997-9012
• DOI: https://doi.org/10.1364/OE.24.008997
• Public URL: https://nottingham-repository.worktribe.com/output/784913
• Publisher URL: https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-8-8997
• Additional Information: © 2016 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.