General idea of the spatial 2D correlation method for different KL modes m^KL ∈ {6, 20, 35, 46}. When different modes are applied on the DM (first line), the patterns seen by the WFS show different spatial scales (second line). The grey pixels correspond to the missing slopes w^WFS (x) = 0 in the PSIM model that are hidden by the pupil. A lateral mis-registration would shift the peak in the correlation between the PSIM and the measured IM (third line).