Coherent Imaging to Study Traveling Waves

Orateur : Pascal PICART (LAUM CNRS Université du Maine, Le Mans)

In the domains of acoustics, vibro-acoustics, vibrations of structures or flow-induced vibrations, Laser Doppler Vibrometer is used for dynamics measurements. To get simultaneously a collection of data points at the surface of the inspected vibrating object, multipoint vibrometer was developed. Full-field evaluation can be obtained with coherent imaging based on digital holographic interferometry. Such an approach is well suited because of the high density of measuring points and the reduced measurement time. The use of time-averaging and quasi-time-averaging in digital Fresnel holography was proposed and discussed in the past. However, the stationary regime is a particular case for investigating the structure vibration behavior (propagation of traveling waves), and the characterization of structures under operational or real functioning conditions requires analysis in the time domain. Then, providing a real-time follow-up of the vibration amplitude, whatever the excitation condition, is a challenge for full-field optical metrology. This seminar aims at describing recent advances in high-speed holographic imaging ; especially we will focus on the use of such an approach to investigate traveling acoustic waves in mechanical structures. Limits are related to few parameters that will be highlighted so as to establish a wish list for the near future.

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