Fig. 1.

Computational optimization of true birefringence vector by normal and one tilted illumination. (a) System schematic. The insert shows the in-plane $(\Theta )$ and through-plane ($\text{α}$) orientations of fiber tracts. (b) The angle definitions in the normal illumination incidences (left) and the orientation images obtained from this incidence (${\text{θ}}_1$, right). (c) The angle definitions in the tilted illumination incidences (left) and the corresponding orientation images (${\text{θ}}_2$, right). (d) The computational retrieved inclination angle image ($\alpha$, right). The angles of orientation in (b)-(d) are indicated by the color wheel. The brightness of the images is modulated by corresponding apparent birefringence $\Delta n_1^{\prime }$, $\Delta {n^{\prime }}_2$ and the true birefringence, $\Delta n$. The intensity of the true birefringence image is indicated by the scale bar in (d). Sclar bars: 1 mm.