| Popis: |
Polarized Digital Holography (PHD) is a fast and efficient tool for analyzing mechanical effects in materials. Especially when the task requires non-invasive techniques that do not damage the material in study, the use of PHD has great perspectives. The most common methods of digital reconstruction use the convolution theory to discretize the Huygens- Fresnel integral. When external stresses are applied to photoelastic materials, the relationship between these stresses and phase differences observed by polarization holography is an intrinsic characteristic of the material called the photoelastic dispersion coefficient. In photoelasticity, this coefficient depends on the wavelength. By using PHD the authors show in the present paper that the photoelastic dispersion coefficient also depends on the wavelength in Holography. A Mach- Zehnder interferometer, modified with the inclusion of linear polarizers, was built to verify this effect in a sample of photoelastic material. In this set-up, two coherent light sources with different wavelengths were used. For the analysis, a digital method was created that correlated the mean stresses differences on the photoelastic material sample and the mean phases differences at each distinct wavelength. |
