Large-field structured illumination microscopy based on 2D grating and a spatial light modulator.

Structured illumination microscopy (SIM) has been widely used in biological research due to its merits of fast imaging speed, minimal invasiveness, super-resolution, and optical sectioning imaging capability. However, the conventional SIM that uses a spatial light modulator (SLM) for fringe projection often has a limited imaging field of view. Herein, we report a large-field SIM technique that combines a 2D grating for fringe pattern projection and an SLM for selecting fringe orientation and performing phase shifting digitally. The proposed SIM technique breaks the bottleneck of fringe number limited by the digital projection devices, while maintaining the advantage of high-speed (digital) phase shifting of conventional SIM. The method avoids the pixilation and dispersion effects of the SLMs. Finally, a 1.8-fold resolution enhancement in a large field of 690 × 517 µm under a 20×/NA0.75 objective is experimentally demonstrated. The proposed technique can be widely applied to biology, chemistry, and industry.