Sub-pixel scale structured illumination for lateral resolution enhancement of non-diffraction-limited flow imaging

In fluid flow imaging, intensity gradients are a good measure of spatial variations in scalar properties, which play an important role in controlling transport processes. However, current flow imaging techniques exhibit system-limited spatial resolutions, thus inhibiting the ability to accurately detect intensity gradients. To address this challenge, we present a method and system, inspired by Structured Illumination Microscopy (SIM), which can be implemented in dynamic flow imaging to enhance pixel resolution and, thereby, the estimation of scalar gradients. We utilize sub-pixel-scale patterned light matching the system pixel scale and multi-frame imaging that creates quasi-static images over four frames, with scalability for high-speed imaging. These multi-frame images are then processed using a bespoke recombination algorithm that produces a new image with twice the pixel resolution compared to the original images. The sub-pixel spatial-resolution enhancement capabilities are shown with static images and dynamic fluid flow, for which enhancement in the flow gradient is demonstrated.