Far‐Field Synthetic Aperture Imaging via Fourier Ptychography with Quasi‐Plane Wave Illumination

Fourier ptychography (FP) technique is a promising super‐resolution tool in noninterferometric synthetic aperture research thanks to its unique capabilities for circumventing the physical limitation of space bandwidth product. However, FP imaging in the long‐range scenario suffers from field‐of‐view (FOV) attenuation due to spherical‐wave imaging characteristics, and the speckle noise of most targets further restricts the FP's application in far‐field detection. Herein, a remote FP (R‐FP) technique is proposed to address the issues by combining the idea of quasi‐plane wave illumination and the total variation‐guided filtering (TVGF) method. Compared with conventional macroscopic Fourier ptychographic imaging, R‐FP overcomes the contradiction between FOV and detection range and mitigates the effect of speckle noise by utilizing the TVGF method, as demonstrated by high‐resolution imaging of various targets (including United States Air Force (USAF) resolution chart, spade poker, and fingerprint). In particular, the long‐range FP capability of the proposed approach is demonstrated by the synthetic aperture imaging of a King poker card at 12 m away. To the best of the authors’ knowledge, R‐FP achieves the farthest detection range of macroscopic Fourier ptychographic imaging up to date, demonstrating its potential for application in far‐field detection.