Application of phase-shifted, laser feedback interferometry to the measurement of fluid physics phenomena

Ben Ovryn, Jim Andrews

Research output: Contribution to conferencePaper

Abstract

We have combined the principles of phase-shifting interferometry (PSI) and laser-feedback interferometry (LFI) to produce a new instrument that can measure both optical path length (OPL) changes and discern sample reflectivity variations. In LFI, coherent feedback of the incident light either reflected directly from a surface or reflected after transmission through a region of interest will modulate the output intensity of the laser. By combining PSI and LFI, we have produced a robust instrument, based upon a HeNe laser, with high dynamic range that can be used to measure either static (dc) or oscillatory changes along the optical path. As with other forms of interferometry, large changes in OPL require phase unwrapping. Conversely, small phase changes are limited by the fraction of a fringe that can be measured. We introduce the phase shifts with an electro-optic modulator (EOM) and use either the Carre or Hariharan algorithms to determine the phase and visibility. We have determined the accuracy and precision of our technique by measuring both the bending of a cantilevered piezoelectric bimorph and linear ramps to the EOM. Using PSI, subnanometer displacements can be measured. We have combined our interferometer with a commercial microscope and scanning piezoelectric stage and have measured the variation in OPL and visibility for drops of PDMS (silicone oil) on coated single crystal silicon. Our measurement of the contact angle agrees with the value stated in the literature.

Original languageEnglish (US)
StatePublished - Jan 1 1997
EventProceedings of the 1997 ASME Fluids Engineering Division Summer Meeting, FEDSM'97. Part 16 (of 24) - Vancouver, Can
Duration: Jun 22 1997Jun 26 1997

Other

OtherProceedings of the 1997 ASME Fluids Engineering Division Summer Meeting, FEDSM'97. Part 16 (of 24)
CityVancouver, Can
Period6/22/976/26/97

ASJC Scopus subject areas

  • Engineering(all)

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    Ovryn, B., & Andrews, J. (1997). Application of phase-shifted, laser feedback interferometry to the measurement of fluid physics phenomena. Paper presented at Proceedings of the 1997 ASME Fluids Engineering Division Summer Meeting, FEDSM'97. Part 16 (of 24), Vancouver, Can, .