Dynamic holographic interferometry by photorefractive crystals for quantitative deformation measurements

Aholographic interferometer that uses two-wave mixing in a photorefractive (Bi₁₂SiO₂₀) crystal under an applied ac field is described. The interferometer uses a repetitive sequence of separate record and readout times to obtain quasi real-time holographic interferograms of vibrating objects. It is shown that a good signal-to-noise ratio of the interferometer is obtained by turning off the object illumination and the applied ac field during readout of the hologram. The good signal-to-noise ratio of the resulting holographic interferograms enables phase measurement, which allows for quantitative deformation analysis.