Digital Demodulation Using I/Q Signals and Optical Phase Control Applied to a Vibrometer

Angel Manuel Galvez-Limaco, Jose Henrique Galeti, Emilio Carlos Nelli Silva, Ricardo Tokio Higuti, Michael J. Connelly, Claudio Kitano

Research output: Contribution to journalArticlepeer-review

Abstract

An efficient and cost effective optical phase detection vibrometer based on a modified closed loop homodyne Michelson interferometer is presented. Real-time phase demodulation is carried out, using an embedded platform that performs data acquisition, signal processing, PI (proportional-integral) control and the generation of signals that drive the electrooptic Pockels cell phase shifter and the piezoelectric actuator under test. Two phase quadrature signals are generated from a single interferometric output, using the interleaving action, in alternation, of a digitally generated modulating signal, and then the well-known differential-cross-multiplication technique is applied to perform the computation of the phase shift of interest. The quadrature condition is reached using the PI loop based on an error signal obtained from a Lissajous figure derived from out-of-phase signals. The vibrometer is capable of measuring nanometric displacements, and is simple, inexpensive, accurate, immune to fading and self-consistent. The new method was used to determine the displacement frequency response curves of two prototypes of multi-actuated flextensional piezoelectric actuators. Measurements were made between 500 Hz and 15 kHz, and the results agreed with those obtained by the standard SCM-Signal Coincidence Method.

Original languageEnglish
Article number9102231
Pages (from-to)11313-11325
Number of pages13
JournalIEEE Sensors Journal
Volume20
Issue number19
DOIs
Publication statusPublished - 1 Oct 2020

Keywords

  • metrology
  • Optical interferometry
  • piezoelectric transducers
  • signal processing

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