Schematic representation of the calculation of the wavefront for a dielectric microsphere. a) Slicing the simulation volume with a micro sphere with refractive index n₁ in an environment with n₀ into M separate layers with a thickness Δz. Scheme of the calculation of the wave front U_m for a layer with 2 different refractive indices (n₀ and n₁). In (i) the regions with different refractive indices n_i are identified. The wavefront U_m−1 serves in (ii) as input wavefront and will be propagated over the distance Δz. The propagation is determined separately for each refractive index (n₀ and n₁) resulting in the wavefronts U_m, n₀ and U_m, n₁. Finally, these wavefronts will be combined in (iii) to U_m.