Kavli Affiliate: Changhuei Yang
| First 5 Authors: Pengming Song, Ruihai Wang, Lars Loetgering, Jia Liu, Peter Vouras
| Summary:
Synthetic aperture radar (SAR) utilizes an aircraft-carried antenna to emit
electromagnetic pulses and detect the returning echoes. As the aircraft travels
across a designated area, it synthesizes a large virtual aperture to improve
image resolution. Inspired by SAR, we introduce synthetic aperture
ptycho-endoscopy (SAPE) for micro-endoscopic imaging beyond the diffraction
limit. SAPE operates by hand-holding a lensless fiber bundle tip to record
coherent diffraction patterns from specimens. The fiber cores at the distal tip
modulate the diffracted wavefield within a confined area, emulating the role of
the ‘airborne antenna’ in SAR. The handheld operation introduces positional
shifts to the tip, analogous to the aircraft’s movement. These shifts
facilitate the acquisition of a ptychogram and synthesize a large virtual
aperture extending beyond the bundle’s physical limit. We mitigate the
influences of hand motion and fiber bending through a low-rank spatiotemporal
decomposition of the bundle’s modulation profile. Our tests on various samples
demonstrate the ability to resolve a 548-nm linewidth and achieve a depth of
field exceeding 2 cm. Notably, the aperture synthesizing process surpasses the
diffraction limit set by the bundle’s maximum collection angle. Requiring no
interferometric measurements, SAPE heralds new opportunities for
super-resolution endoscopic imaging beyond traditional optical constraints.
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