  Whole slide imaging provides a wide field-of-view (FOV) across cross-sections
of biopsy or surgery samples, significantly facilitating pathological analysis
and clinical diagnosis. Such high-quality images that enable detailed
visualization of cellular and tissue structures are essential for effective
patient care and treatment planning. To obtain such high-quality images for
pathology applications, there is a need for scanners with high spatial
bandwidth products, free from aberrations, and without the requirement for
z-scanning. Here we report a whole slide imaging system based on angular
ptychographic imaging with a closed-form solution (WSI-APIC), which offers
efficient, tens-of-gigapixels, large-FOV, aberration-free imaging. WSI-APIC
utilizes oblique incoherent illumination for initial high-level segmentation,
thereby bypassing unnecessary scanning of the background regions and enhancing
image acquisition efficiency. A GPU-accelerated APIC algorithm analytically
reconstructs phase images with effective digital aberration corrections and
improved optical resolutions. Moreover, an auto-stitching technique based on
scale-invariant feature transform ensures the seamless concatenation of whole
slide phase images. In our experiment, WSI-APIC achieved an optical resolution
of 772 nm using a 10x/0.25 NA objective lens and captures 80-gigapixel
aberration-free phase images for a standard 76.2 mm x 25.4 mm microscopic
slide.
