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-varied illuminations. However, to date, the effective imaging numerical aperture (NA) achievable with a commercial LED board is still limited to the range of 0.3-0.7 with a 4 × /0.1NA objective due to the geometric constraint with the declined illumination intensities and attenuated signal-to-noise ratio (SNR). Thus the highest achievable half-pitch resolution is usually constrained between 500-1000 nm, which cannot meet the requirements of high-resolution biomedical imaging applications. Although it is possible to improve the resolution by using a high-NA objective lens, the FP approach is less appealing as the decrease of field-of-view (FOV) will far exceed the improvement of spatial resolution in this case. 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 4 × /0.1NA objective with the final effective imaging performance of 1.05NA at a half-pitch resolution of 244 nm with the incident wavelength of 465 nm across a wide FOV of 14.60 mm2, corresponding to a SBP of 245 megapixels. Our work provides an essential step of FP towards high-throughput imaging applications.
Highlights
High-resolution (HR) wide-field imaging is essential for biological, biomedical research and digital pathology, which require large space-bandwidth product (SBP) to provide computational and statistical analyses for thousands of cells simultaneously across a wide field-of-view (FOV) [1, 2]
We initially present a subwavelength resolution Fourier ptychography (SRFP) platform with an elaborate hemispherical digital condenser to provide high-angle programmable plane-wave illuminations of 0.95 numerical aperture (NA), which breaks the constraint of planar geometry of the LED board and the brightness of our LED elements can be adjustable to provide adequate illumination
We compare the performance of the SRFP platform with the incoherent microscopy and the traditional FP platform as shown in Fig.2, Fig.3 and Fig
Summary
High-resolution (HR) wide-field imaging is essential for biological, biomedical research and digital pathology, which require large space-bandwidth product (SBP) to provide computational and statistical analyses for thousands of cells simultaneously across a wide field-of-view (FOV) [1, 2]. Conventional microscopes are always restricted by the inherent trade-offs between the spatial resolution and FOV, limiting their SBPs and application areas. Fourier ptychography (FP) [3,4,5] is a fast-growing computational imaging technique with HR, wide FOV and quantitative phase, which shares its root with conventional ptychography [6, 7], synthetic aperture imaging [8, 9] and structured-illumination imaging [10, 11]. Due to its flexible setup, promising performance without mechanical scanning and interferometric measurements, FP has wide applications in the digital pathology [12], whole slide imaging systems [13] and combined with fluorescence imaging [14, 15]
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