Fourier Holo-Ptychographic Microscopy: A Hybrid Digital Holography-Fourier Ptychography Approach to Synthetic-Aperture Quantitative Phase Microscopy

In this paper, we present a novel hybrid digital holography-Fourier ptychography approach, termed Fourier holo-ptychographic microscopy (FHPM), for high-accuracy, speckle-free synthetic-aperture quantitative phase imaging (QPI). FHPM acquires low-frequency quantitative phase information, which is inherently limited by the numerical aperture (NA) of the objective lens based on off-axis digital holographic microscopy. This accurate but noisy initial object information, which fills the central aperture in the Fourier space, is subsequently refined by Fourier ptychographic microscopy (FPM) based on intensity-only measurements under tilted illuminations. Meanwhile, the signal-to-noise ratio and imaging resolution (frequency bandwidth) can be significantly improved simultaneously. FHPM achieves efficient synthetic-aperture QPI (9 image acquisitions to near incoherent diffraction limit), compensates the imaging aberrations, and overcomes the stringent matched-illumination requirement inherent to FPM. To the best of our knowledge, this is the first integration of interferometric and non-interferometric phase measurements into a single system, harnessing their complementary strengths. Experimental results on a USAF target and biological cells demonstrate that FHPM achieves accurate, speckle-free QPI while improving the half-pitch imaging resolution from 615 nm to 274 nm (effective NA of ∼0.98) using a 20×, 0.5NA objective lens, rendering it a promising tool for biomedical research.