Quantitative détermination of large vibrational amplitudes of a mechanical structure

The method of projected fringes is applied in developing two techniques for determining the equal amplitude lines of the vibration of a mechanical structure. The first technique consists in visualizing the contour lines of vibration on the surface by means of an optical filtering method applied to just one system of deformed fringes. The second technique determines these same contour lines from the variations in the visibility of an interference phenomenon resulting from the superposition of two systems of fringes having symmetric deformations.