Fringe-free holographic measurements of large-amplitude vibrations.
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.
Joud
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Laboratoire Kastler-Brossel, UMR 8552 CNRS, Ecole Normale Supérieure, Université Paris 6, 24 rue Lhomond 75231 Paris Cedex 05, France.
Verpillat
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Laloë
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Atlan
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Hare
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Gross
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