Time Average Holography In Vibration Analysis

This paper deals with the quantitative interpretation of time-average holograms of vibrating objects. It is shown that the images obtained during reconstruction of such holograms are modulated by a system of fringes described by the square of the zero-order Bessel function of the first kind. A procedure for quantitative interpretation of these fringes is described and illustrated with examples. The experimental results, obtained directly from the time-average holograms, show good agreement with the exact solution of the differential equation of motion based on the beam theory and with the mode shapes determined by the finite element modeling of the vibrating beam.