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Quantitative phase imaging (QPI) has become an important imaging modality providing rapid, label-free measurements of a biological structure’s morphology and permittivity. In particular, reflection QPI systems are advantageous for their improved sensitivity to high-resolution axial structures and their ability to image thin and thick tissues alike. Existing reflection modalities often utilize interferometric setups requiring specialized system designs that limit their application in widespread biological research. We developed reflection intensity diffraction phase microscopy (rIDPM) to provide an easily accessible reflection QPI system for biological imaging applications. This new modality recovers a biological structure’s phase from intensity-only measurements using a standard reflection microscope modified with a translatable light source. We derived inverse scattering models for rIDPM addressing the common imaging condition of biological cells on a glass sample slide. Our models utilize the first Born approximation with a semi-infinite, partially reflective boundary condition accounting for reflections from the glass slide interface. The resulting volumetric model is linear and easily implementable providing fast, computationally efficient recovery of the object’s complex permittivity. Under these imaging conditions, we show forward-scattered fields primarily contribute to the final intensity image for objects taller than half the illumination wavelength. We show this rIDPM modality provides improved contrast of subcellular features from unstained HeLa cell samples compared to existing QPI transmission systems. We also demonstrate our model’s flexibility in recovering high-frequency features with improved contrast from designed annular illumination patterns.
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