Single-shot digital holographic interferometry using a high power pulsed laser for full field measurement of traveling waves
Faculty of Sciences. Physics
AIP conference proceedings / American Institute of Physics. - New York
, p. 444-450
University of Antwerp
In the past, interferometric holographic techniques have been used extensively to perform full-field, yet time-averaged analysis of vibrational patterns. When time-resolved information was needed, optical scanning single-point measurement techniques, such as heterodyne interferometric vibrometry, were available. Recently, stroboscopically illuminated digital holography has proven to yield both full-field and time-resolved information of vibrations with nanometer range amplitudes. In this technique, short laser pulses, synchronized to the vibration phase, are recorded. Good results have been achieved for high-frequency vibrations. However, due to the low energy in a single pulse, acquisition time increases for decreasing vibration frequency in order to receive enough energy on the camera, introducing problems such as artifacts due to slow movements of the object or electronic read-out noise. In this work, stroboscopic holography is combined with a high power, frequency doubled pulsed Nd:YAG laser, which produces enough energy in a single pulse to perform single-shot holographic recordings. This new setup allows imaging vibrations ranging from quasi-static deformations to high-frequency vibrations (1 - 20000 Hz), while avoiding the earlier mentioned acquisition issues. The additional challenge is to synchronize the lasers flash tube and Q-switch to the image acquisition and the vibration phase of the measured object. Results of measurements on a stretched circular latex membrane will be presented. The out-of-plane displacement of the membrane is visualized over the entire surface as a function of time, thus providing true four-dimensional information. Extracting the vibration phase map is useful, for instance to reveal travelling waves, which are invisible on time averaged images.