Snapshot macroscopic Fourier ptychography: far-field synthetic aperture imaging via illumination multiplexing and camera array acquisition

Fourier Ptychographic Microscopy (FPM) is a computational imaging technique that offers large field-of-view, high-resolution quantitative phase imaging, enabling simultaneous phase retrieval and aperture synthesis. Building on this foundation, Holloway et al. from Rice University extended FPM to the far field by incorporating aperture scanning, achieving synthetic aperture far-field imaging of reflecting objects with rough surfaces and enhancing the resolution by a factor of six.

 

However, in practical applications, far-field Fourier ptychographic imaging technology faces challenges in real-time imaging of dynamic targets and scenes. In far-field detection, the typical approach uses aperture scanning-based FP to serially acquire sub-aperture images. This process, while extending the aperture, reduces temporal resolution. Aperture scanning limits the ability of Fourier Ptychography to achieve high temporal resolution imaging of dynamic scenes and moving targets in far-field detection.

 

The research groups led by Professors Qian Chen and Chao Zuo from Nanjing University of Science and Technology, in collaboration with Professor Guoan Zheng from the University of Connecticut, have proposed an efficient and robust far-field synthetic aperture imaging technique based on camera arrays and illumination multiplexing, known as Illumination-Multiplexed Snapshot Synthetic Aperture Imaging (IMSS-SAI). By utilizing a camera array, the approach achieves real-time, high-quality dynamic far-field super-resolution imaging with a resolution enhancement up to four times the single-aperture diffraction limit. The related research, titled "Snapshot Macroscopic Fourier Ptychography: Far-field Synthetic Aperture Imaging via Illumination Multiplexing and Camera-Array Acquisition," was published in the first issue of Advanced Imaging in 2024.

 

The article proposes a far-field Fourier ptychographic imaging technique that combines a camera array with wavelength-multiplexed illumination. The illumination system employs mixed R/G/B wavelengths, while the imaging system uses a 5×5 camera array for parallel sampling, as illustrated in Figure 1. IMSS-SAI establishes a model of the offset distribution of multiplexed wavelengths in the frequency domain, causing the spectrum information of target images illuminated by different wavelengths within a single sub-aperture to overlap. By refined the state-multiplexed Fourier ptychography algorithm, IMSS-SAI decouples the incoherent images of a single aperture, obtaining sub-aperture coherent images with information redundancy.

 

Fig. 1 Overview of the IMSS-SAI framework.

 

A key feature of the IMSS-SAI technique is its ability to achieve synthetic aperture far-field detection in a single exposure, enabling real-time synthetic aperture far-field imaging of moving scenes and dynamic targets. To verify this, researchers used IMSS-SAI to achieve real-time super-resolution imaging of dynamic scene targets at 30 frames per second. The single-frame reconstruction results are shown in Figure 2, where the constructed system was used for dynamic high-resolution imaging of a rotating music box two meters away.

 

Fig. 2 Constructed music box dynamic rotating imaging results. (a) Comparison of the recorded low-resolution image (under F-number 12) with the predicted super-resolved image. (b1-b4) Raw image, Averaging result, Recovery result and Denoising result of region of interest 1, respectively. (c1-c4) Raw image, Averaging result, Recovery result and Denoising result of region of interest 2, respectively. (d1-d6) The instantaneous frames of the eagle emblem captured every 0.5 seconds (15 frames) with IMSS-SAI.

 

The IMSS-SAI technique employs a single-exposure method using a camera array combined with wavelength multiplexing image decoupling to obtain information redundancy. This approach addresses the need for long-duration serial acquisition, overcoming the low temporal resolution limitations of far-field Fourier ptychographic techniques, thereby achieving high spatiotemporal resolution far-field imaging. The article uses single-exposure technology to provide new support for high spatiotemporal resolution imaging of dynamic scenes and moving targets. Furthermore, the IMSS-SAI technique has the potential to expand the application range of optoelectronic detection systems. It shows powerful potential in traditional application areas such as Earth observation, astronomical remote sensing, and military detection, and opens up vast opportunities for the development of next-generation high-resolution intelligent far-field optoelectronic detection systems.