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We present a new technique for quantitative phase and amplitude microscopy from a single color image with coded illumination. Our system consists of a commercial brightfield microscope with one hardware modification-an inexpensive 3D printed condenser insert. The method, color-multiplexed Differential Phase Contrast (cDPC), is a single-shot variant of Differential Phase Contrast (DPC), which recovers the phase of a sample from images with asymmetric illumination. We employ partially coherent illumination to achieve resolution corresponding to 2× the objective NA. Quantitative phase can then be used to synthesize DIC and phase contrast images or extract shape and density. We demonstrate amplitude and phase recovery at camera-limited frame rates (50 fps) for various in vitro cell samples and c. elegans in a micro-fluidic channel.

Phase contrast microscopy has played a central role in the development of modern biology, geology, and nanotechnology. It can visualize the structure of translucent objects that remains hidden in regular optical microscopes. The optical layout of a phase contrast microscope is based on a 4  f image processing setup and has essentially remained unchanged since its invention by Zernike in the early 1930s. Here, we propose a conceptually new approach to phase contrast imaging that harnesses the non-local optical response of a guided-mode-resonator metasurface. We highlight its benefits and demonstrate the imaging of various phase objects, including biological cells, polymeric nanostructures, and transparent metasurfaces. Our results showcase that the addition of this non-local metasurface to a conventional microscope enables quantitative phase contrast imaging with a 0.02π phase accuracy. At a high level, this work adds to the growing body of research aimed at the use of metasurfaces for analog optical computing. The authors present an approach to phase imaging by using the non-local optical response of a guided-moderesonator metasurface. They demonstrate that this metasurface can be added to a conventional microscope to enable quantitative phase contrast imaging.

X-ray phase contrast imaging has overcome the limitations of X-ray absorption imaging in many fields. Particular effort has been directed towards developing phase retrieval methods: These reveal quantitative information about a sample, which is a requirement for performing X-ray phase tomography, allows material identification and better distinction between tissue types, etc. Phase retrieval seems impossible with conventional X-ray sources due to their low spatial coherence. In the only previous example where conventional sources have been used, collimators were employed to produce spatially coherent secondary sources. We present a truly incoherent phase retrieval method, which removes the spatial coherence constraints and employs a conventional source without aperturing, collimation, or filtering. This is possible because our technique, based on the pixel edge illumination principle, is neither interferometric nor crystal based. Beams created by an X-ray mask to image the sample are smeared due to the incoherence of the source, yet we show that their displacements can still be measured accurately, obtaining strong phase contrast. Quantitative information is extracted from only two images rather than a sequence as required by several coherent methods. Our technique makes quantitative phase imaging and phase tomography possible in applications where exposure time and radiation dose are critical. The technique employs masks which are currently commercially available with linear dimensions in the tens of centimeters thus allowing for a large field of view. The technique works at high photon energy and thus promises to deliver much safer quantitative phase imaging and phase tomography in the future.

Cryo-electron microscopy is an essential tool for high-resolution structural studies of biological systems. This method relies on the use of phase contrast imaging at high defocus to improve information transfer at low spatial frequencies at the expense of higher spatial frequencies. Here we demonstrate that electron ptychography can recover the phase of the specimen with continuous information transfer across a wide range of the spatial frequency spectrum, with improved transfer at lower spatial frequencies, and as such is more efficient for phase recovery than conventional phase contrast imaging. We further show that the method can be used to study frozen-hydrated specimens of rotavirus double-layered particles and HIV-1 virus-like particles under low-dose conditions (5.7 e/Å 2 ) and heterogeneous objects in an Adenovirus-infected cell over large fields of view (1.14 × 1.14 μm), thus making it suitable for studies of many biologically important structures. Cryo-electron microscopy is widely employed in structural biology and uses phase contrast imaging. Here, the authors employ electron ptychography, a quantitative phase retrieval method for high-contrast, low-dose phase imaging of cryo-state rotavirus and immature HIV-1 virus-like particles, and show that electron ptychography is more efficient for phase recovery than conventional phase contrast imaging.

Light with a helical phase has had an impact on optical imaging, pushing the limits of resolution or sensitivity. Here, special emphasis will be given to classical light microscopy of phase samples and to Fourier filtering techniques with a helical phase profile, such as the spiral phase contrast technique in its many variants and areas of application. This article is part of the themed issue ‘Optical orbital angular momentum’.

Low‐Z and monolithic material components with arbitrary thickness profiles are extensively utilized in heat conduction, biocompatible implants, microfluidics and integrated optics, where precise thickness measurement is crucial for quality control and performance analysis. X‐ray micro‐computed tomography (micro‐CT) is widely employed for thickness metrology of such samples due to its nondestructive nature, high resolution and 3D imaging capabilities. However, the time‐consuming projection acquisition and image reconstruction processes hinder it from efficient or dynamic thickness measurements. Additionally, micro‐CT struggles with laminar samples. To overcome these limitations, we introduce X‐ray phase contrast imaging for the thickness metrology of low‐Z materials with arbitrary profiles by accurately retrieving the phase shift of X‐rays passing through the sample from a single projection. Calibration using a standard nylon fiber demonstrates that within a 1.33 mm field of view (FOV) the method achieves a mean absolute error of 0.68 µm for cylindrical fibers with diameters of 407.14 µm. We further demonstrate the method's capability for efficient measurement and damage assessment using a worn fiber with complex geometry. Additionally, we applied this method to the thickness measurement and error analysis of a microlens array with varying sub‐lens parameters. The 3D profiles of all sub‐lenses were obtained from a single projection, facilitating error analysis of height, symmetry and eccentricity. The results highlight the method's advantages, including being in situ, non‐contact and high precision, and having a large FOV, flexible adjustability and penetrative measurement capabilities. Our open device design suggests potential applications for dynamic thickness measurements and real‐time monitoring of samples within in situ loading devices. A thickness metrology method based on X‐ray phase contrast imaging is proposed. By precisely retrieving the phase shift of X‐rays passing through the sample, high‐precision arbitrary thickness profile measurement can be achieved with a single X‐ray projection. A measurement case of a microlens array is presented to demonstrate the effectiveness of this method.

X-ray propagation-based phase contrast imaging, a well established imaging technology in synchrotron radiation facilities, enables high-resolution 3D structural reconstruction. Nevertheless, the phase retrieval process required to restore quantitative phase information from holograms remains a significant challenge. Existing software solutions face problems such as performance bottlenecks and limitations in hardware support. Here, we describe a high-performance software named HiHolo based on the CUDA-MPI architecture for the holographic regime, and propose three improved iterative phase retrieval algorithms, providing an efficient framework for achieving high-quality holographic reconstruction. Experimental results demonstrate that HiHolo achieves 24%–37% performance improvement compared with current mainstream software and exhibits near-linear scalability in multi-GPU systems. The alternating projections with probe algorithm effectively reduces artifacts in traditional empty beam correction by simultaneously optimizing both object and probe wavefields; the extrapolation iteration method enhances the spatial resolution of limited field of view through the computational technique; furthermore, the parallel iterative reprojection optimizes the efficiency of 3D reconstruction, achieving a speedup of about 6–14 times compared with the serial version.

Here, high‐throughput tomography (HiTT), a fast and versatile phase‐contrast imaging platform for life‐science samples on the EMBL beamline P14 at DESY in Hamburg, Germany, is presented. A high‐photon‐flux undulator beamline is used to perform tomographic phase‐contrast acquisition in about two minutes which is linked to an automated data processing pipeline that delivers a 3D reconstructed data set less than a minute and a half after the completion of the X‐ray scan. Combining this workflow with a sophisticated robotic sample changer enables the streamlined collection and reconstruction of X‐ray imaging data from potentially hundreds of samples during a beam‐time shift. HiTT permits optimal data collection for many different samples and makes possible the imaging of large sample cohorts thus allowing population studies to be attempted. The successful application of HiTT on various soft tissue samples in both liquid (hydrated and also dehydrated) and paraffin‐embedded preparations is demonstrated. Furthermore, the feasibility of HiTT to be used as a targeting tool for volume electron microscopy, as well as using HiTT to study plant morphology, is demonstrated. It is also shown how the high‐throughput nature of the work has allowed large numbers of `identical' samples to be imaged to enable statistically relevant sample volumes to be studied. High‐throughput tomography, a propagation‐based phase‐contrast X‐ray imaging technique that can visualize 1 mm3 biological samples of various types at high resolution, is presented. 3D reconstructions of the imaged volumes are calculated automatically once data collection is complete. The entire process from pressing start on data collection to viewing the final data takes less than three minutes. This speed, in combination with the use of an automated sample changer to exchange the samples, truly enables high‐throughput X‐ray imaging for the first time.

This work introduces a novel setup for computed tomography of heavy and bulky specimens at the SYRMEP beamline of the Italian synchrotron Elettra. All the key features of the setup are described and the first application to off‐center computed tomography scanning of a human chest phantom (approximately 45 kg) as well as the first results for vertical helical acquisitions are discussed. This work introduces a novel setup to scan heavy and bulky specimen at the SYRMEP beamline, which will be the basis for future phase contrast lung computed tomography imaging in patients.

This review provides a brief overview, albeit from a somewhat personal perspective, of the evolution and key features of various hard X-ray phase-contrast imaging (PCI) methods of current interest in connection with translation to a wide range of imaging applications. Although such methods have already found wide-ranging applications using synchrotron sources, application to dynamic studies in a laboratory/clinical context, for example for in vivo imaging, has been slow due to the current limitations in the brilliance of compact laboratory sources and the availability of suitable high-performance X-ray detectors. On the theoretical side, promising new PCI methods are evolving which can record both components of the phase gradient in a single exposure and which can accept a relatively large spectral bandpass. In order to help to identify the most promising paths forward, we make some suggestions as to how the various PCI methods might be compared for performance with a particular view to identifying those which are the most efficient, given the fact that source performance is currently a key limiting factor on the improved performance and applicability of PCI systems, especially in the context of dynamic sample studies. The rapid ongoing development of both suitable improved sources and detectors gives strong encouragement to the view that hard X-ray PCI methods are poised for improved performance and an even wider range of applications in the near future.