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.