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

Area of Science:

• Optics and Photonics
• Image Reconstruction
• Diffraction-Limited Imaging

Background:

• High spatial resolution is crucial for many imaging applications.
• Designing high-resolution lenses for large fields of view is challenging.
• Random diffusers can create wavelength-limited speckle patterns easily.

Purpose of the Study:

• To develop a novel imaging modality for high-resolution imaging.
• To address limitations of traditional high-resolution lens design.
• To enable high-resolution imaging in both microscopic and macroscopic settings.

Main Methods:

• Introduced near-field Fourier ptychography, utilizing a speckle pattern projected onto the object.
• Employed a low-resolution lens and translated the object or speckle pattern.
• Used ptychographic phase retrieval to reconstruct the object, speckle, and transfer function simultaneously.

Main Results:

• Achieved a numerical aperture (NA) of 0.85 from a 0.12 NA lens in microscopy.
• Obtained a ~7-fold resolution gain in macroscale photography.
• Demonstrated that speckle pattern feature size, not collection optics, dictates resolution.

Conclusions:

• Near-field Fourier ptychography offers a versatile solution for high-resolution imaging.
• The technique is applicable to light, X-ray, and electron imaging systems.
• Enables quantitative absorption and phase contrast imaging with enhanced resolution.