(IUCr) Birefringence imaging

Figure 3
Stereographic representation of the optical indicatrix for a biaxial sample representing the two permitted vibration directions corresponding to the direction of propagation S' and determined using the Biot-Fresnel construction. The dashed lines marked $[\Theta _{1}]$ and $[\Theta _{2}]$ are traces of the two perpendicular tilt axes of the tilting stage. The orientation angle $[\phi ^{\prime}]$ corresponds to the direction of propagation S' and represents the angle between the tilt axis $[\Theta _{1}]$ and one of the axes of the relevant section of the optical indicatrix.