A Synchronized Stroboscopic Holography Setup for Traveling Wave Analysis on Biomechanical Structures

Introduction

Digital holography is a powerful and versatile full-field measuring technique that is able to measure nanometer scale displacements of surfaces. Despite some disadvantages, the technique has become increasingly useful with the rise of commercially available high-resolution, high-bit-depth cameras. Middle ear biomechanics is one example of a research field that can benefit from digital holography [1,2]. In the past, the motion of the eardrum or tympanic membrane (TM) has been measured using a wide variety of techniques, ranging from time-averaged classic holography [3] and single point laser vibrometry [4] to X-ray stereoscopy [5]. More recently, stroboscopic digital holography was introduced in this domain, since it allows measuring the full-field time-resolved motion of the TM in a wide frequency range with a nanometer resolution [1,2]. Therefore it allows us to study traveling waves on the TM. In this work, we present a new setup for digital stroboscopic holography, including a high-energy pulsed Nd:YAG laser and synchronization electronics which makes it possible to record holograms at well-defined time instants in the vibration period at high and low vibration frequencies. As a proof-of-concept, results on a circular piece of stretched rubber are shown, as well as results on rabbit and human TM’s, together with a discussion of the challenges that arise with these samples.