Application of the digital holography in the calculation of displacements

Digital Holography is applied to make micro-displacements determination of a steel bar and an aluminum sheet. The displacement of aluminum sheet is made under immersion conditions in water and air. An experimental installation is presented for digital holograms registration with plane reference beam, using a CCD camera as detector. The "HOLODIG" computing system was developed for digital reconstruction of the image using the direct method, the intensity and phase image and interferograms were obtained. Taking into account the phase interferogram and making the unwrapping, the phase was determinated for every point of the study surphace. As examples of method application, the displacement of a square section steel bar, tested in air, and an aluminum sheet, tested in air and submerged in water, were determined. Experimental values of t he displacement obtained agree with the applied ones. In the case of aluminum plate submerged in water, the magnitude of the measured displacement is proportional to water refraction index.