Abstract

DIB, L. F. G.; HENRIQUE, M. C.; SAITA, M. T.  and  BARBOSA, E. A.. Vibration measurement by projection of phase-modulated and amplitude-modulated structured light. J. appl. res. technol [online]. 2023, vol.21, n.1, pp.1-11.  Epub May 23, 2023. ISSN 2448-6736.  https://doi.org/10.22201/icat.24486736e.2023.21.1.1076.

Most of the whole-field optical methods for vibration measurement have low sensitivity when the points of the studied surface vibrate with the same amplitude. Those techniques also usually require complex and/or expensive solutions which are difficult to implement in engineering processes when the vibration amplitudes are relatively high. In order to overcome those limitations we propose a method for out-of-plane vibration measurement which uses structured light projection. The vibrating surface is obliquely illuminated by straight and parallel interference fringes produced by a Twyman-Green interferometer with a 532-nm laser as light source. In order to enable fringe visualization two techniques were employed, namely, the phase modulation of the fringe pattern by using a vibrating mirror in the interferometer, and a stroboscopic illumination by using a Fabry-Perot etalon amplitude modulator. We demonstrated the technique by measuring the vibration amplitudes of small objects in the millimeter and submillimeter range.

Keywords : fringe projection; interferometry; vibration measurement; phase modulation; stroboscopy.

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