Evaluation of surface acoustic waves on the human skin using quasi-time-averaged digital Fresnel holograms

Leclercq, Mathieu; Karray, Mayssa; Isnard, Vincent; Gautier, François; Picart, Pascal

doi:10.1364/ao.52.00a136

Cited by 19 publications

(11 citation statements)

References 60 publications

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“…Thanks to the development of high resolution CCD cameras and the increasing power of computers, digital holographic/ interferometric measurements are nowadays under development and have already been used to analyze various processes of vibration kinematics [22,23] or fluid mechanics [24], but only a few works have been made to characterize the density fluctuations associated to an acoustic process. There exists pioneering works performed fifteen years ago by Wetzel and Herman [25][26][27], in which analog holography has been used to measure temperature fluctuations at the end of a couple of parallel plates submitted to a high amplitude acoustic field.…”

Section: Introductionmentioning

confidence: 99%

Measurement of density fluctuations using digital holographic interferometry in a standing wave thermoacoustic oscillator

Pénelet

Leclercq

Wassereau

et al. 2016

Experimental Thermal and Fluid Science

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a b s t r a c tThis paper describes an optical set-up for measuring density fluctuations associated to acoustic oscillations in a thermoacoustic prime-mover. A time-resolved, full-field holographic interferometry technique is used, which enables to measure the optical phase difference between a reference beam and a probe beam passing through the acoustic resonator. The paper first presents the experimental set-up and the processing of holograms from which the instantaneous variations of the gas density along the line of sight of the probe beam are obtained. Then, the measurement technique is applied to the analysis of density fluctuations in the neighborhood of the heated side of a stack in a standing wave thermoacoustic prime mover during the transient regime of wave amplitude growth. The experimental results reveal that there exists very significant entrance effects, which lead to the generation of higher harmonics as well as mean (time-averaged) mass rarefaction in the vicinity of the stack termination. Finally, a short discussion is provided, based on a simplified modeling of higher harmonics generation in temperature associated to the oscillations of an inviscid gas through the stack, but the model fails in explaining the magnitude of the phenomena observed.

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Section: Introductionmentioning

confidence: 99%

Measurement of density fluctuations using digital holographic interferometry in a standing wave thermoacoustic oscillator

Pénelet

Leclercq

Wassereau

et al. 2016

Experimental Thermal and Fluid Science

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“…The object reconstructed from the digital hologram is then amplitude-modulated by a Bessel function [25]. In experiments for which 0 ≪ α < 1, the cyclic ratio is too high to be classified as "impulse" and too short to be considered as "time-average" and this intermediary regime is called "quasi-time-averaging" [28]. It follows that considering the cyclic ratio α precisely defines the recording regime.…”

Section: A Time Evolutionmentioning

confidence: 99%

“…Vibration analysis with optical holographic interferometry began with the works of Powell and Stetson [24,25] who first established the principle of time-averaging. The use of time-averaging and quasitime-averaging in digital Fresnel holography was then discussed [26][27][28]. In time-averaging related type recordings, the phase of the vibration signal is lost.…”

Section: Introductionmentioning

confidence: 99%

Multi-point vibrometer based on high-speed digital in-line holography

et al. 2015

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This paper describes a digital holographic setup based on in-line holography and a high-speed recording to get a multipoint vibrometer. The use of a high-speed sensor leads to specificities that enable the in-line configuration to be used. The case of transient vibrations is investigated through a full simulation of the holographic process. The simulation shows that the first instants are critical since distortion may occur, resulting in errors in the phase measurement. Experimental results are provided by exciting an aluminum beam with a transient signal. A comparison with the velocity measured by a pointwise vibrometer is provided. Frequency response functions are extracted and the experimental results confirm the ability of the method to provide full-field contactless measurements at the high-speed time scale evolution of the vibration.

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“…Retrieving the vibration amplitude and phase (necessary for some applications, see Ref [5].) has been demonstrated by recording the quasi-time-averaged holograms to visualize and analyze acoustic waves propagating at the surface of the human skin [6]. Linear regression method has been used for processing vibration patterns yielding the vibration amplitude as an argument of true Bessel function, not its absolute value, thus offering the noise level reduction [7].…”

Section: Introductionmentioning

confidence: 99%

Effective procedure for determination of unknown vibration frequency and phase using time-averaged digital holography

et al. 2017

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In time-averaged digital holography (TADH), one records a hologram of a periodically oscillating object by using the exposure time typically much longer than the oscillating period. Problems arise when the total available exposure time is restricted or when the oscillation period is unknown. In this work we investigate effects of short exposure time to the quality of the recorded hologram and show that, to record high fidelity information in a shortest possible time, close estimates of the oscillating period and the phase are required. To that end we propose an advanced procedure based on short hologram exposures that allows obtaining such estimates. The procedure is efficient both in the number of recordings and their total exposure time.

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Evaluation of surface acoustic waves on the human skin using quasi-time-averaged digital Fresnel holograms

Cited by 19 publications

References 60 publications

Measurement of density fluctuations using digital holographic interferometry in a standing wave thermoacoustic oscillator

Measurement of density fluctuations using digital holographic interferometry in a standing wave thermoacoustic oscillator

Multi-point vibrometer based on high-speed digital in-line holography

Effective procedure for determination of unknown vibration frequency and phase using time-averaged digital holography

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