Fig. 6.

Diagram showing the trajectory of a photon scattered twice (bottom) inside a spheroid, compared with the phase reference trajectory (up). ${\mathit{u}}_{\mathit{i}}$, ${\mathit{u}}_{\mathbf{1}}$ and ${\mathit{u}}_{\mathit{s}}$ are the directions of the photon incoming, scattered once and outcoming respectively. Scaterring events are located at position ${\mathit{r}}_{\mathbf{1}}$ and ${\mathit{r}}_{\mathbf{2}}$ with $\delta ={\mathit{r}}_{\mathbf{2}}-{\mathit{r}}_{\mathbf{1}}$.