Variable wavelength microinterferometry of textile fibres

摘要

SUMMARYA specific microinterferometric method, referred to as variable wavelength interferometry (VAWI), and its object‐adapted version (AVAWI) are proposed for measuring the spectral dispersion of birefringence and/or spectral dispersion of the refractive indicesnandn⊥ of textile fibres. The method uses monochromatic light with variable wavelength (Λ). The only parameters that are directly measured are the inter‐fringe spacings(b)and the fibre thickness (or diameter), while other quantities are observed, read from the calibration graphb(Λ), and derived from quite simple formulae. A double‐refracting interference microscope fitted with a tungsten‐halogen lamp (12 V/100 W) and a wedge interference filter are used. No liquid immersion is required, and the fibre under study can simply be surrounded by an air medium. Results of measurements made on PPT and PA‐6 fibres are given