Streamline image analysis: a new tool for investigating defects in nematicliquid crystals

A bidimensional investigation of the director field near defects normal to the symmetry plane in a nematic liquid crystal is here presented, based upo n a new 'streamline' image processing of the data obtained by polarized lig ht 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 smoo th local variations of the director of field as functions of both space and time. Moreover, the orientation of the director field projection in the ce ll plane is determined with high sensitivity (similar to 2%) and the possib le presence of the out-of-plane escape of the director field is evaluated.