Birefringence Measurement by Polarised Light Microscopy
topic
Birefringence measurement of polyester: mount fibre in immersion oil on compensator stage polarised light microscope; rotate analyser to extinction (Bräce–Köhler compensator) or use tilting compensator (Berek type) to measure optical path difference Γ (nm). Δn = Γ/d (d=fibre diameter in nm). Accuracy: ±0.0005 Δn. Non-destructive, single fibre measurement. Alternative: optical fibre refractometry, prism coupling for oriented films.
Role
Birefringence measurement by polarised light microscopy is a key practical skill in fibre physics and textile science, directly quantifying molecular orientation. Understanding its optical basis (anisotropic refractive index) and procedure is essential for fibre structure research.