Proximity projection grating structured light illumination microscopy.

Structured illumination has been employed in fluorescence microscopy to extend its lateral resolution. It has been demonstrated that a factor of 2 improvement can be achieved. In this paper, we introduce a novel optical arrangement that can further improve the resolution. It makes use of a fine grating held in close proximity to the sample. The fringe pattern thus projected onto the sample contains grating vectors substantially higher than those that are possible with the conventional structured illumination setup. We will present experimental results to demonstrate the principle of the technique, and will show that, theoretically, it can achieve an imaging NA approaching 4.