HiLo Microscopy with Caustic Illumination

HiLo microscopy is a widefield microscopy technique that provides optical sectioning by computationally combining two images, one with structured illumination and one with uniform illumination. The structured illumination can be achieved by various methods, such as speckle and periodic grids. In this work, we present a novel HiLo strategy that uses an off-the-shelf holographic diffuser and a low-coherence LED source to create random caustic patterns. This method has several advantages over existing ones, such as simplicity and cost-effectiveness. We achieve 4.5 µm optical sectioning capability and demonstrate the performance of our method by imaging a thick and highly scattering brain section. We anticipate that our caustic-based structured illumination approach will enhance the versatility of HiLo microscopy and extend to various imaging applications.