Fringe free holographic measurements of large amplitude vibrations

TL;DR

This paper introduces a fringe-free holographic method for measuring large amplitude vibrations by using frequency sideband imaging, enabling local, robust, and high-amplitude measurements without fringe counting.

Contribution

The authors present a novel holographic technique that eliminates the need for fringe counting in large amplitude vibration measurements, improving robustness and local measurement capability.

Findings

Successfully measured phase modulations up to 1000 radians.

Demonstrated robustness against perturbations.

Achieved local measurement without reference points.

Abstract

In the measurement of the amplitude of vibration of objects, holographic imaging techniques usually involve fringe counting; due to the limited resolution of images, measurements of large amplitudes are not accessible. We demonstrate a technique that suppresses the necessity of fringe counting: frequency sideband imaging, where the order of the sideband is considered as a marker of the amplitude. The measurement is completely local: no comparison with another reference point on the object is necessary. It involves a sharp variation of a signal, which makes it robust against perturbations. The method is demonstrated in an experiment made with a vibrating clarinet reed; phase modulations as large as 1000 radians have been measured.