Fig. 1: Diagrams of a wide-field iSCAT and simulated iPSFs.

a Schematic diagram of a wide-field iSCAT imaging system. The amplitude and phase variations of the scattered field, as predicted by the Richards-Wolf model, are presented as functions of particle displacement in both two-dimensional (2D) (upper) and one-dimensional (1D) (lower) representations. The 1D plot is derived from the center point of the scattered field as an example. Notably, all points within the scattered field follow a quadratic amplitude change and a linear phase change with respect to the particle displacement, consistent with the theoretical predictions of the Richards-Wolf integral model. Scale bar: 2 \({\rm{\mu }}{\rm{m}}\). b A low NA example (NA = 0.5) of the meridional profile of the iPSFs as a function of the nanoparticle’s axial position \({{\rm{z}}}_{{\rm{p}}}\), showing periodic intensity variations with the peak intensity gradually decreasing as |\({{\rm{z}}}_{{\rm{p}}}\)| increases.