Streamline Image Analysis: a new tool for investigating defects in nematic liquid crystals

Abstract

A bidimensional investigation of the director field near defects normal to the symmetry plane in a nematic liquid crystal is here presented, based upon a new 'streamline' image processing of the data obtained by polarized light microscopy. With a visualization of vector field streamlines related to the actual director configuration, the disclination topological strength is revealed. The streamline visualization is also suitable for detecting smooth local variations of the director of field as functions of both space and time. Moreover, the orientation of the director field projection in the cell plane is determined with high sensitivity (2%) and the possible presence of the out-of-plane escape of the director field is evaluated.