This paper presents a simplified data acquisition and analysis technique for use in determining the main refractive indices and thickness of a uniaxial anisotropic layer cut out parallel to the optical axis, by processing the conoscopic interference figures obtained using a polarizing microscope equipped with a CCD camera. For negative uniaxial crystals, the equations used permit the calculation of the optical sign of the studied material so it is not necessary to insert a quartz wedge into the conoscopic beam. The technique can also be applied to the study of liquid crystal layers in a planar orientation.

Abstract.Anisotropy is an important property of the transparent ordered solids such as crystals, liquid crystals or polymer foils consisting in the dependence of their physical parameters on the propagation direction and light polarization state. The most common birefringent materials are the crystals (including here the liquid crystals) with asymmetric structures and the plastics under mechanical stress. For uniax materials there is a single direction governing the optical anisotropy (called as optical axis), whereas all directions perpendicular to it are optically equivalent. The uniax materials are characterized by two values of the refractive index. The ordinary value (n o ) is measured with linearly polarized radiations acting perpendicular on the principal section, while the extraordinary value (n e ) corresponds to linearly polarized radiations with their electric field intensity contained in this section [1]. Some results obtained by different methods in estimating the main refractive indices and birefringence of some uniax anisotropy layers are given and a comparative study of the accuracy of the applied methods is discussed in this paper.

No abstract

We present a new mathematical technique which can be used to determine the main refractive indices and the birefringence of an anisotropic layer by using a polarizing microscope in conoscopic illumination. The values of the birefringence for the yellow radiation of a Na lamp are determined here for a Carpathian quartz sample, but the technique can also be applied to the study of other uniaxial substances such as liquid crystals, model membranes or biological tissues. The validity of the proposed method was tested by comparing the results with those obtained with a Rayleigh interferometer and by using the technology of channeled spectra.

No abstract