Determining the optical properties of highly oriented fibres using a multiple-beam technique

Abstract

Mathematical formulae are modified for the shape of multiple-beam Fizeau fringes in transmission to determine the mean refractive indices and birefringence of highly oriented fibres. These modified mathematical formulae are applied with the multiple-beam interference method to determine the optical anisotropy of polypropylene fibre with a draw ratio of 3.5. The refractive indices and birefringence results are compared with those obtained using the conventional method and are found to be in good agreement. The new method is also applied for (poly(ethylene 2,6-naphthalene-dicarboxylate), 1000 denier/248 filaments, PEN-Q50M4 (PEN) and poly(ethylene terephthalate) 1000 denier/250 filaments, PET-BHT, highly oriented yarn, Teijin, Japan (PET)) highly oriented fibres. Illustrations are given through microinterferograms.