Imaging velocities of a vibrating object by stroboscopic sideband holography

TL;DR

This paper introduces a method combining sideband holography with stroboscopic illumination to image instantaneous velocities of vibrating objects, capable of handling high-frequency vibrations up to several MHz.

Contribution

It presents a novel approach that synchronizes stroboscopic illumination with sideband holography to measure instantaneous velocities of vibrating objects.

Findings

Successfully imaged velocities of a 2 kHz vibrating clarinet reed.

Detected harmonic ranks up to ±100.

Produced a velocity movie demonstrating the method.

Abstract

We propose here to combine sideband holography with stroboscopic illumination synchronized with the vibration of an object. By sweeping the optical frequency of the reference beam such a way the holographic detection is tuned on the successive sideband harmonic ranks, we are able to image the instantaneous velocities of the object. Since the stroboscopic illumination is made with an electronic device, the method is compatible with fast (up to several MHz) vibration motions. The method is demonstrated with a vibrating clarinet reed excited sinusoidally at 2 kHz, and a stroboscopic illumination with cyclic ratio 0.15. Harmonic rank up to n = $\pm$100 are detected, and a movie of the instantaneous velocities is reported.