Correction of periodic displacement non-linearities by two-wavelength interferometry

Angus Bridges, Andrew Yacoot, Thomas Kissinger, David A Humphreys, Ralph P Tatam*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

9 Citations (Scopus)
42 Downloads (Pure)

Abstract

Non-linearities in interferometric displacement measurements commonly affect both homodyne and heterodyne optical interferometers. Unwanted back reflections (ghost reflections) or polarisation leakage introduce non-linearity terms at harmonics of the illuminating wavelength that cannot be fully corrected for with standard non-linearity correction techniques. A two-wavelength interferometric approach, operating at 632.8 and 785 nm, is presented here that
is capable of correcting such non-linearities. Non-linearities are separated from the difference between two displacement measurements made at differing wavelengths with a Fourier approach. Compared to a standard Heydemann ellipse fitting correction, the proposed approach reduces estimated residual non-linearities from 84 to 11 pm in the case of a linear displacement profile. In particular this approach is applicable to the correction of higher order non-linearities that are caused by multiple reflections, and that are therefore very sensitive to alignment conditions.
Original languageEnglish
Article number125202
Pages (from-to)1-12
Number of pages12
JournalMeasurement Science and Technology
Volume32
Issue number12
DOIs
Publication statusPublished - 31 Aug 2021

Bibliographical note

Publisher Copyright:
© 2021 National Physical Laboratory owned - UK Governmental Body.

Keywords

  • interferometry
  • non-linearity
  • dimensional metrology

Fingerprint

Dive into the research topics of 'Correction of periodic displacement non-linearities by two-wavelength interferometry'. Together they form a unique fingerprint.

Cite this