Phase and fringe order determination in wavelength scanning interferometry

Giuseppe Moschetti, Alistair Barrie Forbes, Richard K. Leach, Xiang Jiang, Daniel O'Connor

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)


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.
Original languageEnglish
Pages (from-to)8997-9012
Number of pages16
JournalOptics Express
Issue number8
Early online date15 Apr 2016
Publication statusPublished - 18 Apr 2016


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