Measuring photoelastic dispersion coefficients in material samples with digital holography

Sidney Leal da Silva; Felipe Maia Prado; Daniel José Toffoli; Niklaus Ursus Wetter

doi:10.1117/12.2544874

21 February 2020 Measuring photoelastic dispersion coefficients in material samples with digital holography

Sidney Leal da Silva, Felipe Maia Prado, Daniel José Toffoli, Niklaus Ursus Wetter

Proceedings Volume 11306, Practical Holography XXXIV: Displays, Materials, and Applications; 113060P (2020) https://doi.org/10.1117/12.2544874
Event: SPIE OPTO, 2020, San Francisco, California, United States

Abstract

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.

Citation Download Citation

Sidney Leal da Silva, Felipe Maia Prado, Daniel José Toffoli, and Niklaus Ursus Wetter "Measuring photoelastic dispersion coefficients in material samples with digital holography", Proc. SPIE 11306, Practical Holography XXXIV: Displays, Materials, and Applications, 113060P (21 February 2020); https://doi.org/10.1117/12.2544874

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