Recently introduced speckle-correlations based techniques enable noninvasive imaging of objects hidden behind scattering layers. In these techniques the hidden object Fourier amplitude is retrieved from the scattered light autocorrelation, and the lost Fourier phase is recovered via iterative phase-retrieval algorithms, which suffer from convergence to wrong local-minima solutions and cannot solve ambiguities in object-orientation. Here, inspired by notions used in astronomy, we experimentally demonstrate that in addition to Fourier amplitude, the object phase information is naturally and inherently encoded in scattered light bispectrum (the Fourier transform of triple-correlation), and can also be extracted from a single high-resolution speckle pattern, based on which we present a single-shot imaging scheme to deterministically and unambiguously retrieve diffraction-limited images of objects hidden behind scattering layers.

Recently introduced angular-memory-effect based techniques enable non-invasive imaging of objects hidden behind thin scattering layers. However, both the specklecorrelation and the bispectrum analysis are based on the statistical average of large amounts of speckle grains, which determines that they can hardly access the important information of the point-spread-function (PSF) of a highly scattering imaging system. Here, inspired by notions used in astronomy, we present a phase-diversity speckle imaging scheme, based on recording a sequence of intensity speckle patterns at various imaging planes, and experimentally demonstrate that in addition to being able to retrieve diffraction-limited image of hidden objects, phase-diversity can also simultaneously estimate the pupil function and the PSF of a highly scattering imaging system without any guide-star nor reference.

Recent advancements in whole slide imaging (WSI) have moved pathology closer to digital practice. Existing systems require precise mechanical control and the cost is prohibitive for most individual pathologists. Here we report a low-cost and high-throughput WSI system termed OpenWSI. The reported system is built using off-the-shelf components including a programmable LED array, a photographic lens, and a low-cost computer numerical control (CNC) router. Different from conventional WSI platforms, our system performs real-time single-frame autofocusing using color-multiplexed illumination. For axial positioning control, we perform coarse adjustment using the CNC router and precise adjustment using the ultrasonic motor ring in the photographic lens. By using a 20X objective lens, we show that the OpenWSI system has a resolution of ~0.7 µm. It can acquire whole slide images of a 225-mm 2 region in ~2 mins, with throughput comparable to existing high-end platforms. The reported system offers a turnkey solution to transform the highend WSI platforms into one that can be made broadly available and utilizable without loss of capacity. OCIS codes: (170.0180) Microscopy; (170.4730) Optical pathology; (120.4570) Optical design of instrumentsDigital pathology via whole slide imaging (WSI) promises better and faster diagnosis and prognosis of cancers and other diseases [1]. A major milestone was accomplished in 2017 when the Philips' WSI system was approved for the primary diagnostic use in the US [2]. In a conventional WSI system, the tissue slide is mechanically scanned to different x-y positions and the digital images are acquired using a high numerical aperture (NA) objective lens. The small depth of field of the objective, however, poses a challenge for proper focusing during the scanning process [3,4]. Many existing systems create a focus map prior to the scanning process. For each point on the map, the system needs to scan the sample to different axial positions and acquire a z-stack. The best focus position can then be inferred based on the image with the highest Brenner gradient or other figure of merits [5][6][7]. In this z-stack approach, surveying the focus points for every tile would require a prohibitive amount of time. Most systems select a subset of tiles for focus point surveying to save time. Different from the z-stack approach, we have recently demonstrated a focus map surveying method based on singleframe autofocusing [8,9]. In this approach, we illuminate the sample from two different incident angles. If the object is placed at an out-offocus position, the captured image would contain two copies of the object separated by a certain distance. The defocus distance can then be recovered based on the two-copy separation.In this letter, we report the development of a low-cost, highthroughput DIY WSI system termed OpenWSI. The reported system is built using off-the-shelf components including a programmable LED array, a photographic lens, and a low-cost computer numerical control (CNC) router. Different from con...

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