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

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Dharmsaktu, K S
Arvind Kumar
Tripathi, Renu
Singh, K
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A technique has been proposed to analyze small in-plane component of vibrations by measuring the fringe shift, and analysing the correlation output of captured vibrating Young's fringes with a photorefractive correlator. Fringes are formed due to interference between the reconstructed speckled beam recorded for stationary object beam, and vibrated speckled beam transmitting through a BaTiO 3 crystal after introducing a small shift in the di!user position. The correlation peak intensity is a!ected due to mismatch of vibrations between two piezomirrors in the object beam. High correlation output gives an indication of the frequency matching of known reference and unknown vibrations, thus giving information on the frequency of vibration. Vibration 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 plane.
Speckle metrology, Young's fringes, Photorefractive correlator