Measurement of vibration with Young's fringe modulated speckle patterns ina photorefractive correlator

A technique has been proposed to analyze small in-plane component of vibrat ions by measuring the fringe shift, and analysing the correlation output of captured vibrating Young's fringes with a photorefractive correlator. Frin ges are formed due to interference between the reconstructed speckled beam recorded for stationary object beam, and vibrated speckled beam transmittin g through a BaTiO3 crystal after introducing a small shift in the diffuser position. The correlation peak intensity is affected due to mismatch of vib rations between two piezo-mirrors in the object beam. High correlation outp ut gives an indication of the frequency matching of known reference and unk nown vibrations, thus giving information on the frequency of vibration. Vib ration amplitudes of the order of a wavelength of light have been measured by counting the number of fringes passing past a line in the observation pl ane. (C) 2001 Elsevier Science Ltd. All rights reserved.