Maskless and on-chip LED-array microscope with spatially varying angle calibration for centimeter-scale phase imaging

Conventional lens-based microscopes are constrained by a trade-off between resolution and field-of-view (FOV), which limits overall imaging throughput. Recent works have shown that on-chip imaging systems with LED-array-based illumination offer a cost-effective approach for large FOV phase imaging. However, this strategy faces two main challenges: (1) twin-image ambiguity can degrade phase reconstruction. While mask-based modulation can help, it adds system complexity due to fabrication and alignment requirements; and (2) the illumination angle from each LED varies across large FOVs and can degrade centimeter-scale phase reconstruction without calibration. Here, we present a computational framework to jointly achieve mask-free on-chip phase imaging and adaptive calibration of spatially varying illumination angles. The sensor FOV is divided into subregions, within each of which LED illumination is approximated as planar. LED illumination angles for each subregion are initialized geometrically. Phase retrieval is then performed within each subregion by constraining the reconstruction with a soft optical transparency prior while simultaneously refining angle estimates. Reconstructed phase maps are merged to produce a high-quality, large-FOV phase image. We demonstrate this approach by achieving centimeter-scale on-chip phase imaging (up to 2.7×1.7cm 2 ) with micron-scale resolution across various biological tissue sections. This approach provides a simple, low-cost, and scalable solution for large-FOV and label-free imaging.