Subwavelength resolution Fourier ptychography with hemispherical digital condensers

TL;DR

This paper introduces a subwavelength resolution Fourier ptychography system using a hemispherical digital condenser, achieving high NA and resolution over a wide field of view, advancing high-resolution biomedical imaging.

Contribution

The work presents a novel SRFP platform with a hemispherical digital condenser that significantly improves resolution and NA without sacrificing FOV, surpassing limitations of traditional planar illumination setups.

Findings

Achieved 244 nm half-pitch resolution at 465 nm wavelength.

Realized an effective imaging NA of 1.05 with a wide FOV of 14.60 mm².

Provided a SBP of 245 megapixels for high-resolution imaging.

Abstract

Fourier ptychography (FP) is a promising computational imaging technique that overcomes the physical space-bandwidth product (SBP) limit of a conventional microscope by applying angular diversity illuminations. However, to date, the effective imaging numerical aperture (NA) achievable with a commercial LED board is still limited to the range of 0.3 to 0.7 with a 4X0.1 NA objective due to the constraint of planar geometry with weak illumination brightness and attenuated signal-to-noise ratio (SNR). Thus the highest achievable half-pitch resolution is usually constrained between 500 to 1000 nm, which cannot fulfill some needs of high-resolution biomedical imaging applications. Although it is possible to improve the resolution by using a higher magnification objective with larger NA instead of enlarging the illumination NA, the SBP is suppressed to some extent, making the FP technique less appealing, since the reduction of field-of-view (FOV) is much larger than the improvement of resolution in this FP platform. Herein, in this paper, we initially present a subwavelength resolution Fourier ptychography (SRFP) platform with a hemispherical digital condenser to provide high-angle programmable plane-wave illuminations of 0.95NA, attaining a 4X0.1 NA objective with the final effective imaging performance of 1.05NA at a half-pitch resolution of 244 nm with a wavelength of 465 nm across a wide FOV of 14.60 mm2, corresponding to an SBP of 245 megapixels. Our work provides an essential step of FP towards high-NA imaging applications without scarfing the FOV, making it more practical and appealing.