Near-field Fourier ptychography: super-resolution phase retrieval via speckle illumination

Abstract

Achieving high spatial resolution is the goal of many imaging systems. Designing a high-resolution lens with diffraction-limited performance over a large field of view remains a difficult task in imaging system design. On the other hand, creating a complex speckle pattern with wavelength-limited spatial features is effortless and can be implemented via a simple random diffuser. With this observation and inspired by the concept of near-field ptychography, we report a new imaging modality, termed near-field Fourier ptychography, for tackling high-resolution imaging challenges in both microscopic and macroscopic imaging settings. The meaning of 'near-field' is referred to placing the object at a short defocus distance with a large Fresnel number. In our implementations, we project a speckle pattern with fine spatial features on the object instead of directly resolving the spatial features via a high-resolution lens. We then translate the object (or speckle) to different positions and acquire the corresponding images using a low-resolution lens. A ptychographic phase retrieval process is used to recover the complex object, the unknown speckle pattern, and the coherent transfer function at the same time. In a microscopic imaging setup, we use a 0.12 numerical aperture (NA) lens to achieve a NA of 0.85 in the reconstruction process. In a macroscale photographic imaging setup, we achieve ~7-fold resolution gain using a photographic lens. The final achievable resolution is not determined by the collection optics. Instead, it is determined by the feature size of the speckle pattern. The reported imaging modality can be employed in light, coherent X-ray, and transmission electron imaging systems to increase resolution and provide quantitative absorption and phase contrast of the object.

15 pages, 14 figures

References in corpus (4)

• Wide-field, high-resolution Fourier ptychographic microscopy
• Phase recovery and holographic image reconstruction using deep learning in neural networks
• Exploiting speckle correlations to improve the resolution of wide-field fluorescence microscopy
• Structured illumination microscopy with unknown patterns and a statistical prior

Cited by in corpus (5)

• Wide-field, high-resolution lensless on-chip microscopy via near-field blind ptychographic modulation
• Full-field Fourier ptychography (FFP): spatially varying pupil modeling and its application for rapid field-dependent aberration metrology
• Field-portable quantitative lensless microscopy based on translated speckle illumination and sub-sampled ptychographic phase retrieval
• Ptychographic modulation engine (PME): a low-cost DIY microscope add-on for coherent super-resolution imaging
• Translation position extracting in incoherent Fourier ptychography