Further applications of holography to photoelasticity

Abstract

A holographic method for reconstructing the polarization of light emitted by a photoelastic model is presented. Isochromatic and the entire family of isoclinic fringe patterns may be obtained by examining the holographic image, a posteriori. This is accomplished by using two orthogonally polarized reference beams so arranged that the reconstructed crosstalk images do not overlap. An analysis is preseted crosstalk images do not overlap. An analysis is presented which shows that, to reconstruct polarization, the phase relationship between the two reference beams must be maintained. This requirement is more stringent than that normally required in holography. Experimental verification is presented. The use of double-exposure holography to obtain isopachic-isochromatic fringe patterns in the reconstructed image is discussed. An analytic treatment of the method is presented. Expressions relating the isopachic-isochromatic fringe pattern in the reconstructed virtual image to the principal stresses are developed. Differences between this analysis and that presented in a recent paper are discussed. Experimental results are obtained and compared to theory and to other experimental results with good agreement.