Incoherent optical sectioning based super-resolution in structured illumination microscopy

Structured illumination microscopy (SIM) enables super-resolution imaging with low phototoxicity, rendering it a powerful tool for visualizing subcellular architectures in cell imaging. However, the imaging of intracellular ultrastructures in depth is substantially compromised by out-of-focus background fluorescence. To address this limitation, we developed incoherent optical sectioning structured illumination microscopy (IOS-SIM), a super-resolution approach that enhances optical sectioning via axially confined fringe modulation under incoherent illumination. The proposed algorithm framework incorporates an initial image preprocessing step for background suppression, followed by conventional SIM reconstruction. Accordingly, we investigated the structured illumination model under an incoherent light source, particularly the axial modulation characteristics of the fringes. To validate the efficacy and superiority of IOS-SIM, we conducted a comprehensive multi-metric comparison against the prevailing super-resolution SIM. Experimental results demonstrate that IOS-SIM achieves exceptional background suppression and a markedly improved signal-to-background ratio (SBR). The performance of this method across diverse biological imaging scenarios substantiates its value in biomedical research.