Fig. 4.

Inversion results. In all graphs, reference data are shown in black, ${\mathrm{SHEF}}_9$ results for a $90\mu \mathrm{m}$ top layer are shown in blue and ${\mathrm{SHEF}}_9$ results for a $300\mu \mathrm{m}$ top layer are shown in red. (a–f) The stage 1 results, in which initial guesses for top and bottom layer scattering spectra are recovered. (a–c) The reference scattering spectra for their respective base layers, and homogeneous ${\mathrm{SHEF}}_9$ results for data taken with the $f_{x1}$ spatial frequency band. (d–f) The reference scattering spectra for the top layer alone and the homogeneous SHEF results using data from the $f_{x2}$ spatial frequency band. (g–i) The top layer absorption spectra fits from stage 2, using results from stage 1 for top and bottom layer scattering. (j–l) The stage 3 results in which recovery of the bottom layer reduced scattering coefficient spectrum is refined. (m–o) The stage 4 results that provide the final result for the top layer absorption spectrum.