Fig. 5. Equivalence of IMPACT and F-SHARP.

a Schematic working principles; IMPACT modulates half of the spatial light modulator (SLM) pixels, each with a unique frequency while light from the other, static half acts as reference wave. A 1D discrete Fourier transform (DFT) of the square root of the recorded two-photon signal separates the modulated pixels' correction phases ϕ_n of the spectrum ${\widehat{B}}_{\omega }$ from the contributions of ${\widehat{B}}_{\omega }^{*}$ and the mixing terms ${\widehat{A}}_{\omega }$. F-SHARP relies on external scanning and phase stepping mechanisms to deliver an estimate of the scattered field ${\widehat{E}}_{m,n}$ in the focal region. The correction phases ϕ_m,n of the first iteration are obtained by a 2D DFT.