Comparison of the FRISP method with a FDTD simulation of a microsphere with a diameter of 10 μm, a refractive index of n = 1.5 and a wavelength of 634 nm. The normalized intensity distribution of a simulated photonic nanojets generated by the microsphere along the propagation axis a) for the FRISP method and b) for a FDTD simulation with Ansys. c) Comparison of the intensity profiles at the focal spot position along the vertical dashed lines to determine the FWHM. d) Intensity profiles along the horizontal dashed lines through the center of the micro sphere.