1 Snapshot parallel refractive index tomography

Phase Imaging enables label-free visualization of transparent biological samples, offering critical insight into cellular structure and transient dynamics with minimal phototoxicity. However, existing three-dimensional (3D) phase imaging techniques typically require sequential scanning or interferometric setups, limiting temporal resolution and increasing system complexity. To overcome these challenges, we propose Snapshot Parallel Refractive Index Tomography (SPRIT), a snapshot, 3D refractive index (RI) imaging technique. SPRIT employs a diffractive optical element to capture multifocal intensity images. The volumetric RI distribution is reconstructed by deconvolving the intensity measurement with the 3D transfer functions of the system. By incorporating partially coherent illumination, SPRIT achieves higher spatial resolution than coherent imaging systems, with the degree of enhancement governed by the illumination and detection numerical aperture. We demonstrate volumetric imaging of live Chilomonas at 50 Hz with SPRIT, showcasing its ability to resolve fine subcellular structures in real-time. With its snapshot, high-resolution capabilities, SPRIT offers a powerful tool for label-free 3D imaging in cellular biology and medical diagnostics.