Fringe-free holographic measurements of large-amplitude vibrations

Abstract

In the measurement of the amplitude of vibration of objects, holographic imaging techniques usually involve fringe counting; because of the limited resolution of the 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 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 rad have been measured.

Improved holographic method for vibration amplitude measurement from nano to microscale

“…On the other hand, in case the density of dark fringes is too low (small amplitudes) [6,8,10] or too high (great amplitudes) [14] one has to modify the TADH to FS-TADH by application of frequency shift to reference wave. In FS-TADH the frequency of the reference wave is shifted by an integer multiple nω of the object vibration frequency …”

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

“…Such methods are quite useful for modal analysis and the determination of structural intensity [49,50], to measure 3D vibrations [40], surface acoustic wave [51], the high amplitude autooscillations of a clarinet reed [52], or 3D displacement on a cat's post-mortem tympanic membrane [53]. Hybrid techniques combining heterodyne holography with time-averaging or frequency shifting were also proposed recently [54][55][56].…”

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

“…Such methods are quite useful for modal analysis and the determination of structural intensity [45,46], to measure 3D vibrations [47], surface acoustic wave [48], the high amplitude autooscillations of a clarinet reed [49] or 3D displacement on a cat's post-mortem tympanic membrane [50]. Hybrid techniques combining heterodyne holography with time-averaging or frequency shifting were also proposed recently [51][52][53]. Lastly, the use of high speed recordings was reported [54][55][56][57][58][59][60].…”