Figure 3.

Modelled QPV displacement measurement error agrees with experimental measurements. (a) Comparison of background corrected QPI image of RPE fixed cell at 120 X (top left) and polystyrene beads at 20X (bottom left) to synthetically generated uniform and non-uniform circle data, with added Perlin noise (top middle and right) and without added Perlin noise (bottom middle and right) (b) Power spectrum of the QPI data (green and magenta) and synthetic data with noise (black) in (a) shows the similarity of QPI data to the non-uniform circle synthetic data. (c) Power spectral density versus effective particle size of RPE fixed cells (n = 3). Power spectral density corresponding to both 5 µm and 40 µm structures is indicated. Sub-panel shows structure inside 40 µm RPE fixed cell illustrating the range of features captured by QPI. Scale bars show 5 µm (blue) and 40 µm (red). Colormap shows dry mass density in pg/µm². (d) Theoretical displacement estimation error (percentage difference between expected and measured displacements) at four effective particle sizes for all tested displacements and window sizes. (e) Averaging the size dependent model results as in (d), weighted by the actual distribution of particle sizes (c) gives a predicted error which is in agreement with the (f) measured error from the matched RPE cell using experimental data. Colormaps in (e) and (f) are the same.