High-resolution transport-of-intensity quantitative phase microscopy with annular illumination

摘要

For quantitative phase imaging (QPI) based on transport-of-intensity equation(TIE), partially coherent illumination provides speckle-free imaging,compatibility with brightfield microscopy, and transverse resolution beyondcoherent diffraction limit. Unfortunately, in a conventional microscope withcircular illumination aperture, partial coherence tends to diminish the phasecontrast, exacerbating the inherent noise-to-resolution tradeoff in TIEimaging, resulting in strong low-frequency artifacts and compromised imagingresolution. Here, we demonstrate how these issues can be effectively addressedby replacing the conventional circular illumination aperture with an annularone. The matched annular illumination not only strongly boosts the phasecontrast for low spatial frequencies, but significantly improves the practicalimaging resolution to near the incoherent diffraction limit. By incorporatinghigh-numerical aperture (NA) illumination as well as high-NA objective, it isshown, for the first time, that TIE phase imaging can achieve a transverseresolution up to 208 nm, corresponding to an effective NA of 2.66. Time-lapseimaging of in vitro Hela cells revealing cellular morphology and subcellulardynamics during cells mitosis and apoptosis is exemplified. Given itscapability for high-resolution QPI as well as the compatibility with widelyavailable brightfield microscopy hardware, the proposed approach is expected tobe adopted by the wider biology and medicine community.