(IUCr) Uniaxial crystals

Figure 8
Stereographic representation of the optical indicatrix for a uniaxial sample with the principal section PS' and two perpendicular tilt axes $[\Theta _{1}]$ and $[\Theta _{2}]$ of the microscope tilting-stage (the traces of the tilt axes are shown here as great circles). The azimuthal angle $[\phi ^{\prime}]$ corresponds to the propagation direction $[S^{\prime}]$ .