Figure 10
Illustration of the filtered back projection from calculated far-field data.
First, the x-polarized anti-Stokes radiation of a z-structured model sample (blue line), e.g. layers of different polymers, was calculated at a reference plane in forward direction. The far-field detection plane covers the anti-Stokes emission angle from βmin 0° to βmin = 60° (NA = 0.87). In a second step the pseudo-inverse of the forward radiation problem is computed and filtered. Multiplication of the pseudo-inverse with the far-field data yields the presented least-square fit of the inverse source scattering problem. The resulting fit is smoothed compared to the true z-profile as a consequence of green function and the limited data set that act as low pass filter. (a) Back projected z-structure of an only axially structured sample with varying scatterer concentration along the z-direction. (b) xz-plane back projection of a layered sample with smooth variations in x-direction. The green arrow indicates the movement of the polarization density (stretched blue ellipse) into x-direction.
