Linear birefringence of polymer foils determined by optical means.

An interferential method is used for determining the linear birefringence of the thin polymer foils. The channeled spectra of anisotropic polyethylene terephthalate (PET) transparent films, placed between two identical crossed polarizers were recorded and the linear birefringence was estimated by using the conditions of the minima and maxima of flux density in the channeled spectrum. This method is very fast, allowing the estimation of the linear birefringence over the entire visible range from a single recording of the channeled spectrum. The obtained results are consistent with those previously reported in the literature. [ABSTRACT FROM AUTHOR]