OPTICAL CHARACTERIZATION OF THE DIRECTOR FIELD IN A DISTORTED NEMATICLAYER

We develop new optical methods using transmitted polarized light for t he characterization of the out of plane component n(z) of the director field in a weakly distorted planar nematic layer. In extraordinary li ght, we relate the angles of aperture of the caustic surface to the lo cal amplitudes of the n(z) distortion. In ordinary light, a new type o f contrast due to the anisotropic light scattering is shown to give th e map of n(z)(2). We apply our methods to the study of the director di stortions occuring in the thermal convection.