Phase-resolved heterodyne holographic vibrometry with a strobe local oscillator

TL;DR

This paper demonstrates phase-resolved vibrometry using heterodyne holography with a strobe local oscillator, enabling precise measurement of out-of-plane sinusoidal vibrations by sequentially freezing vibration states.

Contribution

It introduces a novel strobe local oscillator scheme in heterodyne holography that improves phase retrieval of mechanical vibrations.

Findings

Successful demonstration of phase-resolved vibrometry

Effective freezing of vibration states for phase mapping

Enhanced accuracy in out-of-plane vibration measurement

Abstract

We report a demonstration of phase-resolved vibrometry, in which out-of-plane sinusoidal motion is assessed by heterodyne holography. In heterodyne holography, the beam in the reference channel is an optical local oscillator (LO). It is frequency-shifted with respect to the illumination beam to enable frequency conversion within the sensor bandwidth. The proposed scheme introduces a strobe LO, where the reference beam is frequency-shifted and modulated in amplitude, to alleviate the issue of phase retrieval. The strobe LO is both tuned around the first optical modulation side band at the vibration frequency, and modulated in amplitude to freeze selected mechanical vibration states sequentially. The phase map of the vibration can then be derived from the demodulation of successive vibration states.