Terahertz Fourier Ptychographic Imaging

TL;DR

This paper demonstrates a novel terahertz Fourier ptychographic imaging method that significantly improves spatial resolution by combining multi-angle illumination with iterative phase retrieval, enabling high-resolution imaging without major hardware changes.

Contribution

The paper introduces a proof-of-concept THz Fourier ptychographic imaging technique that enhances resolution using controlled illumination and computational reconstruction, expanding capabilities in THz imaging.

Findings

Achieved resolution enhancement in THz imaging.

Developed a robust iterative phase-retrieval algorithm.

Enabled high-resolution imaging with minimal hardware modifications.

Abstract

High-resolution imaging in the terahertz (THz) spectral range remains fundamentally constrained by the limited numerical apertures of currently existing state-of-the-art imagers, which restricts its applicability across many fields, such as imaging in complex media or nondestructive testing. To address this challenge, we introduce a proof-of-concept implementation of THz Fourier Ptychographic imaging to enhance spatial resolution without requiring extensive hardware modifications. Our method employs a motorized kinematic mirror to generate a sequence of controlled, multi-angle plane-wave illuminations, with each resulting oblique-illumination intensity image encoding a limited portion of the spatial-frequency content of the target imaging sample. These measurements are combined in the Fourier domain using an aberration-corrected iterative phase-retrieval algorithm integrated with an efficient illumination calibration scheme, which enables the reconstruction of resolution-enhanced amplitude and phase images through the synthetic expansion of the effective numerical aperture. Our work establishes a robust framework for high-resolution THz imaging and paves the way for a wide array of applications in materials characterization, spectroscopy, and non-destructive evaluation.