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 mm, corresponding to a SBP of 245 megapixels. Our work provides an essential step of FP towards high-throughput imaging applications.

Ultraviolet photoacoustic microscopy (UV-PAM) has recently been demonstrated as a potential imaging tool for surgical margin analysis (SMA). UV-PAM does not require staining or micrometer-thick slicing, which is inevitable in conventional histological imaging. To promote UV-PAM as a practical intraoperative diagnostic tool, the imaging speed should be improved while preserving the high-resolution imaging capability and simplistic system design. In this Letter, we developed a galvanometer mirror-based UV-PAM (GM-UV-PAM) system for high-speed histology-like imaging. By using a UV laser with a high repetition rate (55 kHz) and a one-dimensional galvanometer mirror, our GM-UV-PAM system can generate subcellular images in less than 15 min for a typical brain biopsy ( 5 m m × 5 m m ), with a lateral resolution of ∼ 1.0 µ m . The images of mouse brain slices obtained by our GM-UV-PAM system show that it can provide histological information for SMA.

Histopathology based on formalin-fixed and paraffin-embedded tissues has long been the gold standard for surgical margin assessment (SMA). However, routine pathological practice is lengthy and laborious, failing to guide surgeons intraoperatively. In this report, we propose a practical and low-cost histological imaging method with wide-field optical-sectioning microscopy (i.e., High-and-Low-frequency (HiLo) microscopy). HiLo can achieve rapid and non-destructive imaging of freshly-excised tissues at an extremely high acquisition speed of 5 cm2/min with a spatial resolution of 1.3 µm (lateral) and 5.8 µm (axial), showing great potential as an SMA tool that can provide immediate feedback to surgeons and pathologists for intraoperative decision-making. We demonstrate that HiLo enables rapid extraction of diagnostic features for different subtypes of human lung adenocarcinoma and hepatocellular carcinoma, producing surface images of rough specimens with large field-of-views and cellular features that are comparable to the clinical standard. Our results show promising clinical translations of HiLo microscopy to improve the current standard of care.