Enhanced denoising for weak signal preservation in structured illumination microscopy

Structured illumination microscopy (SIM) is a powerful super-resolution technology in biological science because of its fast imaging speed, low phototoxicity, and full-field imaging. Despite this, SIM is hampered by out-of-focus background noise, which can obscure weak fluorescence signals and render them unrecognisable. Previous denoising algorithms tended to eliminate the noise along with the weak signals, causing a decrease in image quality. To address this issue, we propose OPIE-SIM, a denoising algorithm based on out-of-focus plane information extraction that salvages the weak signal from the out-of-focus background noise. The OPIE-SIM algorithm enhances weak fluorescence signals by combining out-of-focus layer information with focal plane data and correcting the differences in point spread functions (PSF). This approach eliminates out-of-focus background noise and preserves the integrity of weak fluorescence structures while significantly reducing image acquisition time compared to traditional over-focusing imaging techniques. Through extensive simulations and experiments, we verified the feasibility of our approach. Compared with other denoising algorithms, our method generates images with a higher signal-to-noise ratio while maintaining the integrity of weak fluorescence structures.