Figure 6: Near-instantaneous surface profile reconstruction.

Detailed surface profile reconstruction of a glass bead in air (a) and polymer vesicles in buffer solution hovering next to the substrate (b) and in contact with the substrate (c); insets present the corresponding RICM images (scale bar, 10 μm), schematic representations of the system and ΔS^P/Δx versus x from a simulated non-planar fit (black exes) to experimental data (light red symbols/line, without/with smoothing). Four different procedures (listed in increasing order of accuracy) are used to reconstruct the bottom shape of these specimens: discrete planar (gray dots) and non-planar (dashed green line) methods, continuous ODE (closed/open red circles, NRL/non-NRL) approach and non-planar fit (thin black line). A sphere profile (thick orange line) is fitted to selected reconstructed heights from the ODE method and the non-planar fit is used to define the expected surface profile so that the error of the other procedures can be quantified (d). (e) A three-dimensional reconstruction of the bottom shape of a non-symmetric polymer vesicle hovering next to the substrate (~37 nm) as observed from three different points of view approximately located at M, N and O in the RICM image, with the corresponding bottom view also shown; heights in the colour bar and positions are given in microns, scale bar, 10 μm in the RICM image.