Abstract

We report an imaging scheme, termed aperture-scanning Fourier ptychography, for 3D refocusing and super-resolution macroscopic imaging. The reported scheme scans an aperture at the Fourier plane of an optical system and acquires the corresponding intensity images of the object. The acquired images are then synthesized in the frequency domain to recover a high-resolution complex sample wavefront; no phase information is needed in the recovery process. We demonstrate two applications of the reported scheme. In the first example, we use an aperture-scanning Fourier ptychography platform to recover the complex hologram of extended objects. The recovered hologram is then digitally propagated into different planes along the optical axis to examine the 3D structure of the object. We also demonstrate a reconstruction resolution better than the detector pixel limit (i.e., pixel super-resolution). In the second example, we develop a camera-scanning Fourier ptychography platform for super-resolution macroscopic imaging. By simply scanning the camera over different positions, we bypass the diffraction limit of the photographic lens and recover a super-resolution image of an object placed at the far field. This platform's maximum achievable resolution is ultimately determined by the camera's traveling range, not the aperture size of the lens. The FP scheme reported in this work may find applications in 3D object tracking, synthetic aperture imaging, remote sensing, and optical/electron/X-ray microscopy.

Highlights

  • Fourier ptychography (FP) is a phase retrieval technique that uses the concept of angular diversity to recover high-resolution complex sample images [1,2,3]

  • Similar to other phase retrieval techniques [4,5,6,7,8,9,10,11,12,13,14], the recovery process of FP consists of alternating enforcement of the known sample information in the spatial domain, and a fixed constraint in the Fourier domain

  • The recovery process of FP shares its roots with ptychography [15,16,17,18,19,20,21,22,23,24,25,26,27], a lensless imaging approach that applies translational diversity to recover its complex image

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Summary

Introduction

Fourier ptychography (FP) is a phase retrieval technique that uses the concept of angular diversity to recover high-resolution complex sample images [1,2,3]. To fully sample the field transferred by this lens to its image plane, we need at least 0.5 billion effective pixels on the image sensor, which is orders of magnitude higher than the pixel count of existing CCD/CMOS image sensors Combination of multiple acquired low-resolution images subsequently can yield a wide-field, high-resolution image with a final pixel count matching the full information capacity of the optical system Another advantage of the reported scheme is its ability to record the exiting complex wavefront, i.e., the hologram, of the sample. Much like a through-focus image stack from a conventional microscope setup, this data still contains useful information regarding the sample’s three dimensional structure

Macroscopic imaging beyond the diffraction limit via camera-scanning FP
Conclusion

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