Fig. 3.

(a) Mean spectra for a fixed lc_h of 150 nm and σ_h from 10–50 nm. (b) Mean spectra for a fixed σ_h of 35 nm and lc_h from 60–240 nm. (c) Mean spectra are calculated by averaging over pixels in the red circle and further averaging over 10 samples. (d) Averaged Fourier transforms of I_h(x′, y′, k) (surface) and I_n(x′, y′, k) (RI fluctuations). The frequencies of spectra are translated into the depths from surface.