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A simple and compact electronic speckle pattern interferometry (ESPI) built with holographic optical elements (HOEs) used for the study of out-of-plane vibration is reported. Carefully fabricated reflection and transmission HOEs provide reference and object beams in the interferometer. All the alignment difficulties in conventional ESPI systems are minimized using HOEs. The time average ESPI subtraction method is used to generate correlation fringes. The background speckle noise is removed by introducing a phase shift between sequential images. The amplitude and phase maps are obtained using path difference modulation in an unbalanced ESPI.
Bavigadda, V., Jallapuram, J.,Mihaylova, E., Toal, V.:Electronic speckle pattern interferometer using holographic optical elements for vibration measurements.Optics Letters, Vol. 35, No. 19, October 1, 2010, pp.3273-3275