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Antiferromagnetic imaging is critical for understanding and optimizing the properties of antiferromagnetic materials and devices. Despite the widespread use of high-energy electrons for atomic-scale imaging, they have low sensitivity to spin textures. Typically, the magnetic contribution to the phase of a high-energy electron wave is weaker than one percent of the electrostatic potential. Here, we demonstrate direct imaging of antiferromagnetic lattice through precise phase retrieval via electron ptychography, paving the way for magnetic lattice imaging of antiferromagnetic materials and devices. [ABSTRACT FROM AUTHOR]

• Have good tolerance to low coherence for both far- and near-field ptychography. • Require no prior knowledge of the source coherence properties. • Can be integrated into all of the existing ptychography engines. • Reduce the Krylov subspace searching scope for the numerical monochromatization. • Reduce the needed probe modes for mixed-state (Nature, 2013, 494: 68–71) method. Ptychography is now integrated as a tool in mainstream microscopy allowing quantitative and high-resolution imaging capabilities over a wide field of view. However, its ultimate performance is inevitably limited by the available coherent flux when implemented using electrons or laboratory X-ray sources. We present a universal reconstruction algorithm with high tolerance to low coherence for both far-field and near-field ptychography. The approach is practical for partial temporal and spatial coherence and requires no prior knowledge of the source properties. Our initial visible-light and electron data show that the method can dramatically improve the reconstruction quality and accelerate the convergence rate of the reconstruction. The approach also integrates well into existing ptychographic engines. It can also improve mixed-state and numerical monochromatisation methods, requiring a smaller number of coherent modes or lower dimensionality of Krylov subspace while providing more stable and faster convergence. We propose that this approach could have significant impact on ptychography of weakly scattering samples. [ABSTRACT FROM AUTHOR]

• A material pattern reconstruction technique based on terahertz waves is proposed for the first time, and experimental result similar to the ideal simulation is obtained. • A generalized model for general image reconstruction is proposed. • Combined with the deep blind degradation algorithm based on physical features and the random shuffle strategy, completed the establishment of the mapping relationship of the data set in the complex real environment. • Based on the existing technology, a scheme combining game theory and neural network is proposed to effectively improve the quality of material pattern reconstruction of terahertz ptychography. • The inclusion noise and high humidity of the weak terahertz radiation source simulate the working environment of the terahertz optical imaging system under harsh conditions. Finally, good imaging results approximate to the ideal conditions are obtained by our method. Ptychography is an imaging technique that uses the redundancy of information generated by the overlapping of adjacent light regions to calculate the relative phase of adjacent regions and reconstruct the image. In the terahertz domain, in order to make the ptychography technology better serve engineering applications, we propose a set of deep learning terahertz ptychography system that is easier to realize in engineering and plays an outstanding role. To address this issue, we propose to use a powerful deep blind degradation model which uses isotropic and anisotropic Gaussian kernels for random blurring, chooses the downsampling modes from nearest interpolation, bilinear interpolation, bicubic interpolation and down-up-sampling method, and introduces Gaussian noise, JPEG compression noise, and processed detector noise. Additionally, a random shuffle strategy is used to further expand the degradation space of the image. Using paired low/high resolution images generated by the deep blind degradation model, we trained a multi-layer residual network with residual scaling parameters and dense connection structure to achieve the neural network super-resolution of terahertz ptychography for the first time. We use two representative neural networks, SwinIR and RealESRGAN, to compare with our model. Experimental result shows that the proposed method achieved better accuracy and visual improvement than other terahertz ptychographic image super-resolution algorithms. Further quantitative calculation proved that our method has significant advantages in terahertz ptychographic image super-resolution, achieving a resolution of 33.09 dB on the peak signal-to-noise ratio (PSNR) index and 3.05 on the naturalness image quality estimator (NIQE) index. This efficient and engineered approach fills the gap in the improvement of terahertz ptychography by using neural networks. [ABSTRACT FROM AUTHOR]

• Extending the modeling of locally separated samples to the standard ePIE algorithm in the context of fly-scan ptychography. • The approach is much better than mixed-state method in large step size fly-scan ptychography. • The further integration with mixed-state method allows addressing vibration issues in high-speed fly-scan scenarios. • This algorithm offers a promising solution for high-speed fly-scan ptychography applications. Ptychography is a coherent diffractive imaging method that can achieve diffraction-limited resolution. A fly-scan mode in ptychography can mitigate time costs comparing to traditional step-scan processes. However, expanding fly-scan step size may lead to the failure of traditional phase retrieval algorithm. Here, the method we adopt differs from the multi-mode method that has become popular at X-ray synchrotrons in that it models each diffraction pattern as a sum of shifted object patches, rather than the incoherent sum of a number of modes. This methodology is extended to the standard ePIE algorithm called Multi-object ePIE (Mo-ePIE), and simulation and experimental results demonstrate its effectiveness in handling large step size fly-scan, achieving reconstructions with up to 25 maximum fly-scan pixels. Furthermore, the reintegration with multi-mode probe methods can address potential issues of system decoherence, further enhancing the quality of reconstruction. This algorithm exhibits substantial potential in accelerating ptychography experiments, offering a promising solution for high-speed applications. [ABSTRACT FROM AUTHOR]

• Improve the convergence of reconstruction against detector noise in ptychography. • Use a dynamic convex optimization strategy to achieve a preferable reconstruction quality. • Potential to enhance the accuracy and efficiency of computational imaging. Ptychography is a promising technique for phase retrieval, allowing for super-resolution imaging with a coherent beam source that shifts. The complex transmission function of illumination and object can be retrieved with the support of a ptychographic iterative kernel. When subjected to noisy datasets, conventional reconstruction algorithms can easily be trapped in local minima or even fail to convergence. The present work proposes a new approach called dynamic sigmoid-remolding ptychographic iterative engine (dsPIE) that relies on a dynamic convex optimization strategy. The dsPIE method is designed to improve the robustness in ptychography against detector noise. Computational and experimental results show that the proposed dsPIE method exhibits high robustness and finer reconstructed stability for mixed detector noises that conventional PIE algorithms typically struggle to converge. This method has important implications for the field of computational imaging in high-noise environments. [ABSTRACT FROM AUTHOR]

We have developed a high-throughput, tabletop ptychographic imaging system based on a high-order harmonic, extreme ultraviolet (EUV) light source. Driven by a 1.8 W, 180 fs, 4 kHz, 515 nm femtosecond laser, three neighboring high-order harmonics centered around 46.8 nm is obtained with a total power of 43 μW. Utilizing the light source without any monochromatization, we conducted multi-wavelength ptychography imaging with a large field of view (FOV) of 100 μm × 100 μm, and at a high rate of 0.4 Mpix/h. [ABSTRACT FROM AUTHOR]

Coherent diffraction imaging (CDI) and its scanning version, ptychography, are lensless imaging approaches used to iteratively retrieve a sample's complex scattering amplitude from its measured diffraction patterns. These imaging methods are most useful in extreme ultraviolet (EUV) and X-ray regions of the electromagnetic spectrum, where efficient imaging optics are difficult to manufacture. CDI relies on high signal-to-noise ratio diffraction data to recover the phase, but increasing the flux can cause saturation effects on the detector. A conventional solution to this problem is to place a beam stop in front of the detector. The pixel masking method is a common solution to the problem of missing frequencies due to a beam stop. This paper describes the information redundancy in the recorded data set and expands on how the reconstruction algorithm can exploit this redundancy to estimate the missing frequencies. Thereafter, we modify the size of the beam stop in experimental and simulation data to assess the impact of the missing frequencies, investigate the extent to which the lost portion of the diffraction spectrum can be recovered, and quantify the effect of the beam stop on the image quality. The experimental findings and simulations conducted for EUV imaging demonstrate that when using a beam stop, the numerical aperture of the condenser is a crucial factor in the recovery of lost frequencies. Our thorough investigation of the reconstructed images provides information on the overall quality of reconstruction and highlights the vulnerable frequencies if the beam stop size is larger than the extent of the illumination NA. The outcome of this study can be applied to other sources of frequency loss, and it will contribute to the improvement of experiments and reconstruction algorithms in CDI. • Ptychography a lensless imaging technique used in extreme ultraviolet and X-ray imaging retrieves a sample's complex amplitude. • Verify the limits of the pixel masking method to recover the missing information due to a beam stop in a EUV setup. • Quantify the quality of reconstructed image at the presence of a beam stop based on simulation and EUV experimental data to identify the vulnerable spatial frequencies. [ABSTRACT FROM AUTHOR]

Synchrotron X-ray microtomography and ptychography were used to characterize the 3D network structure, morphology and distribution of metal carbides in an as-cast IN713LC Ni superalloy. MC typed carbides were found to distribute mainly on the grain boundary between the matrix γ and γ' phase. The differences in solidification cooling rate had a minor influence on the volume fraction of the MC type carbides, but significantly affected the carbide size, distribution and network morphology. Depending on the local composition of the remaining liquid phase and geometric constraints, the carbides can form either spherical or strip or network morphologies. The research demonstrated clearly the advantage and technical potential of using the two complementary tomography techniques synergistically to characterize non-destructively complex multiple-phase structures in three dimensional space with a spatial resolution of ~30 nm. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The complex cellular structures maintain the biological activities of cells. Revealing the structure of cells at the nanoscale is of great significance for cell biology. Coherent X-ray diffraction imaging (CDI) at advanced X-ray light sources has the advantages of in-situ , high-resolution, and quantitative imaging, and has been widely used in the field of cell imaging. In this review, we introduce the basic principle of CDI, various CDI methods, and the typical achievements in cellular imaging. Combined with frozen-hydrated technique, cryogenic full-field CDI can be used to image cell native structures. Scanning CDI (also called ptychography) extends the imaging field of view and can achieve panoramic structural and functional images of the whole mammalian cells. The single-pulse imaging at X-ray free electron laser has for the first time obtained nanoscale structural images of living cells in experiment, providing unprecedented opportunities for revealing the dynamic activities of living cells at the nanoscale. • The novel coherent X-ray diffraction imaging methods for cell imaging at nanoscale were introduced in this review paper. • The latest achievements of cell nanostructure imaging with CDI was summarized in this review. • The advantage of full-field CDI is high resolution and contrast imaging at a 2D resolution of ∼15 nm and 3D of ∼40 nm. • X-ray ptychography combines the advantages of high resolution and large field of view at whole mammalian cells imaging. • XFEL single pulse imaging is a promising way to reveal the dynamic activities of living cells. [ABSTRACT FROM AUTHOR]

Highlights • An X-ray ptychography model of imaging amorphous materials. • Demonstration of the validity of the 1976 nature paper on "Seeing order in amorphous Materials". • Stereoscopic electron imaging of amorphous materials modelled. • The difficulty of three-dimensional imaging of amorphous matter illustrated. • Why electron ptycho-tomography may solve the amorphous structure problem. Abstract The nature of the atomic structure of many non-crystalline materials remains a long-standing open question. We use X-ray scattering to model electron images of amorphous materials, where the analogue 'atoms' consist of 1 μm diameter glass beads. The beads form a substantially random close-packed structure, but are partially ordered in places. X-ray ptycho-tomography reveals the exact position of the beads in 3D and so can be used to compare the modelled electron image with full knowledge of the underlying real structure. Using this, we repeat an experiment reported by Archie Howie and colleagues in 1978 that sought to test for real structure in bright-field electron images of amorphous materials; we demonstrate the validity of the technique, at least in the case of the resolution of the microscopes available at that time and the first Born approximation. We also illustrate how extremely demanding it would have been to infer 3D structure of amorphous material from pairs of stereoscopic images obtained with the same experimental kit: an approach that Archie proposed in the 1970s. We briefly discuss the possibility of using electron ptycho-tomography to solve the amorphous structure problem. [ABSTRACT FROM AUTHOR]

Abstract A single shot ptychographic iterative engine based on chromatic aberrations is proposed to retrieve the object with fast data acquisition and convergence. In the imaging system, the specimen is irradiated by a RGB illumination source, and the RGB light transmitted through the specimen is recorded by a color sensor. There are three different sizes of the spots on the object surface generated by the lens with chromatic aberrations and the aperture stop, which can produce partially overlapping between adjacent wavelength illumination areas that will lock the object's phase information and ensure retrieve the object successfully. In the reconstruction algorithm, an initial object guess is established by spectrum synthesis method to accelerate convergence and suppress noise. The data acquisition time is dramatically reduced by our proposed single shot method. Highlights • This method overcomes the time-consuming data acquisition and positioning error of PIE. • The initial object spectrum synthesis can accelerate convergence and suppress noise. • Single shot method makes it possible to observe images of the moving object and live cell. [ABSTRACT FROM AUTHOR]

Highlights • Existing STEM reconstructions of electric potentials assume very thin (<50 Å) samples. • A new approach suitable to reconstruct samples hundreds of Ångström thick is given. • A large probe forming aperture (>50 mrad) is needed to reduce dynamical scattering. • Probe spreading is incorporated via a multiple plane phase contrast transfer function. • Minimizing high-order lens aberrations is the main barrier to implementation. Abstract Most reconstructions of the electrostatic potential of a specimen at atomic resolution assume a thin and weakly scattering sample, restricting accurate quantification to specimens only tens of Ångströms thick. We demonstrate that using large-angle-illumination scanning transmission electron microscopy (STEM)—a probe forming aperture with convergence angle larger than about 50 mrad—allows us to better meet the weak phase object approximation and thereby accurately reconstruct the electrostatic potential in samples thicker than the order of 100 Å. [ABSTRACT FROM AUTHOR]

Highlights • Ptychography provides much stronger robustness to temporal incoherence than HRTEM. • For a given aperture size, ptychography provides double the resolution of HRTEM. • The bandpass contrast transfer function of ptychography facilitates interpretability. • Under equivalent conditions ptychographic imaging is much clearer than HRTEM imaging. Abstract Radiation damage places a fundamental limitation on the ability of microscopy to resolve many types of materials at high resolution. Here we evaluate the dose efficiency of phase contrast imaging with electron ptychography. The method is found to be far more resilient to temporal incoherence than conventional and spherical aberration optimized phase contrast imaging, resulting in significantly greater clarity at a given dose. This robustness is explained by the presence of achromatic lines in the four dimensional ptychographic dataset. [ABSTRACT FROM AUTHOR]

Abstract Near-field ptychography provides advantages over far-field ptychography that large field-of-view (FOV) can be imaged with fewer diffraction images, and with weaker requirements on the detector dynamic range and beam coherence, which has drawn attention recently. However, the propagation distance of traditional angular spectrum (AS) method is limited and the reconstruction of the smallest resolvable object detail is restricted by the sensor's pixel size. To this end, we propose an adaptive-window angular spectrum (AWAS) algorithm to solve both problems by adding the window adaptively associated with the propagation distance and avoid the extra computations via extra scaling factors. Meanwhile, it features validity for the independent sample size and the sample number on the observation plane. This algorithm is strictly deduced from the Rayleigh–Sommerfeld formula and based on the linear convolution, which can be evaluated by fast Fourier transform effectively. The burden of calculations is comparable to traditional AS method. The performance has been achieved both in two-dimensional and three-dimensional near-field ptychography with simulations and experiments. This method will make near-field ptychography more practical and can be used in X-ray or electron-microscopy and other computational imaging techniques. [ABSTRACT FROM AUTHOR]

Integrating neural networks for data compression directly in the Read-Out Integrated Circuits (ROICs), i.e. the pixelated front-end, would result in a significant reduction in off-chip data transfer, overcoming the I/O bottleneck. Our ROIC test chip (AI-In-Pixel-65) is designed in a 65 nm Low Power CMOS process for the readout of pixelated X-ray detectors. Each pixel consists of an analog front-end for signal processing and a 10b analog-to-digital converter operating at 100KSPS. We compare two non-reconfigurable techniques, Principal Component Analysis (PCA) and an AutoEncoder (AE) as lossy data compression engines implemented within the pixelated area. The PCA algorithm achieves 50 × compression, adds one clock cycle latency, and results in a 21% increase in the pixel area. The AE achieves 70 × compression, adds 30 clock cycle latency, and results in a similar area increase. [ABSTRACT FROM AUTHOR]

• An adaptive noise-blind-separation (aNBS) algorithm is proposed to deal with mixed noises in ptychography. • The aNBS algorithm needs no regularization constraints, noise prior assumptions and dynamic iteration parameters. • The aNBS algorithm exhibits no sensitivity discrepancy for mixed noises of different types. • Results indicate that the algorithm maintains robust convergence when noise intensity increases over two orders of magnitude. Noise, one of the severe challenges in phase retrieval, may bring the algorithms to fall into local minima or even disrupt the convergence, thereby adversely affecting the imaging quality and convergence efficiency in the ptychography. Here, we propose an adaptive noise-blind-separation (aNBS) algorithm to deal with mixed noises of different types without sensitivity discrepancy in ptychography. In the aNBS algorithm, apart from the coherent probe of the illumination wavelength, virtual probes of different wavelengths are introduced to capture the noise energies, and the coupling mixed noises are adaptively blind-separated into the virtual noise probes in ptychography. The proposed algorithm can blindly separate coherent diffraction signals and noises without requiring additional regularization constraints, noise prior assumptions or dynamic iteration parameters. Simulations and experiments are comparatively conducted with the momentum-accelerated ptychographical iterative engine algorithm without dealing with noises and the least-square maximum-likelihood ptychographical iterative engine algorithm using a mixed Poisson-Gaussian likelihood model. Results indicate that the aNBS-based ptychography significantly enhances the convergence robustness when the noise intensity increases by more than two orders of magnitude. Compared with existing methods, the proposed aNBS algorithm demonstrates superior robustness and generality for the phase retrieval in coherent diffraction imaging and can be widely applied to various fields, such as ptychography, holography, and tomography. [ABSTRACT FROM AUTHOR]

Nickel coarsening is considered a significant cause of solid oxide cell (SOC) performance degradation. Therefore, understanding the morphological changes in the nickel-yttria stabilized zirconia (Ni-YSZ) fuel electrode is crucial for the wide spread usage of SOC technology. This paper reports a study of the initial 3D microstructure evolution of a SOC analyzed in the pristine state and after 3 and 8 h of annealing at 850 °C, in dry hydrogen. The analysis of the evolution of the same location of the electrode shows a substantial change of the nickel and pore network during the first 3 h of treatment, while only negligible changes are observed after 8 h. The nickel coarsening results in loss of connectivity in the nickel network, reduced nickel specific surface area and decreased total triple phase boundary density. For the condition of this experiment, nickel coarsening is shown to be predominantly curvature driven, and changes in the electrode microstructure parameters are discussed in terms of local microstructural evolution. [ABSTRACT FROM AUTHOR]

A comparative study of a model adhesive interface formed between laser-pretreated Ti15-3-3-3 and the thermoplastic polymer PEEK has been carried out in order to characterize the interfaces’ structural details and the infiltration of the surface nano-oxide by the polymer at multiple scales. Destructive approaches such as scanning and transmission electron microscopy of microsections prepared by focused ion beam, and non-destructive imaging approaches including laser scanning and scanning electron microscopy of pretreated surfaces as well as synchrotron computed tomography techniques (micro- and ptychographic tomographies) were employed for resolving the large, μm-sized melt-structures and the fine nano-oxide substructure within the buried interface. Scanning electron microscopy showed that the fine, open-porous nano-oxide homogeneously covers the larger macrostructure features which in turn cover the joint surface. The open-porous nano-oxide forming the interface itself appears to be fully infiltrated and wetted by the polymer. No voids or even channels were detected down to the respective resolution limits of scanning and transmission electron microscopy. [ABSTRACT FROM AUTHOR]

The ability to record large field-of-view images without a loss in spatial resolution is of crucial importance for imaging science. For most imaging techniques however, an increase in field-of-view comes at the cost of decreased resolution. Here we present a novel extension to ptychographic coherent diffractive imaging that permits simultaneous full-field imaging of multiple locations by illuminating the sample with spatially separated, interfering probes. This technique allows for large field-of-view imaging in amplitude and phase while maintaining diffraction-limited resolution, without an increase in collected data i.e. diffraction patterns acquired. [ABSTRACT FROM AUTHOR]

In ptychography, the precise axial distance between the sample and the detector is of vital importance to retrieve the tested object with high quality, but the axial distance error cannot be entirely eliminated in the practical experiments. An autofocusing strategy based on dichotomy is proposed to rapidly correct the axial distance error. In this strategy, the total variation function that is valid for both amplitude- and phase-modulating specimens is applied to determine whether the current distance is smaller or larger than the true distance. Further, the dichotomy is used to exponentially shrink the step-size of the correction by iterative computations, which means that for the early iterations large modified step-size is used and for later iterations only small step-size is considered. Therefore, the dichotomy is beneficial to quickly confirm the accurate axial distance with few computations. Simulations and experiments are conducted to demonstrate that our proposed strategy, based on the extended ptychographic iterative engine (ePIE), is capable of calibrating the sample–detector distance with high accuracy and efficiency. [ABSTRACT FROM AUTHOR]

Over 50 years of development, synchrotron based X-ray microscopy has become a routine and powerful tool for the analysis of nanoscale structure and chemistry in many areas of science. Scanning X-ray microscopy is particularly well suited to the study of chemical and magnetic states of matter and has become available at most synchrotron light sources using a variety of optical schemes, detectors and sample environments. The Advanced Light Source at Lawrence Berkeley National Laboratory has an extensive program of soft X-ray scanning microscopy which supports a broad range of scientific research using a suite of advanced tools for high spatio-temporal resolution and control of active materials. Instruments operating within an energy range between 200–2500 eV with spatial resolution down to 7 nm and sub 20 picosecond time resolution are available. These capabilities can be routinely used in combination with a variety of sample stimuli, including gas or fluid flow, temperature control from 100 to 1200 K, DC bias and pulsed or continuous microwave excitation. We present here a complete survey of our instruments, their most advanced capabilities and a perspective on how they complement each other to solve complex problems in energy, materials and environmental science. • The Advanced Light Source at Berkeley Lab operates four soft X-ray microscopes. • The instruments operate within an energy range between 200–2500 eV. • Spatial resolution down to 7 nm and sub 20 ps time resolution are possible. • Sample environment includes gas or fluid flow, temperatures from 100 to 1200 K. • External stimuli include DC bias and pulsed or continuous microwave excitation. [ABSTRACT FROM AUTHOR]

Ptychography is a lensless imaging technique that is aberration-free and capable of imaging both the amplitude and the phase of radiation reflected or transmitted from an object using iterative algorithms. Working with extreme ultraviolet (EUV) light, ptychography can provide better resolution than conventional optical microscopy and deeper penetration than scanning electron microscope. As a compact lab-scale EUV light sources, high harmonic generation meets the high coherence requirement of ptychography and gives more flexibilities in both budget and experimental time compared to synchrotrons. The ability to measure phase makes reflection-mode ptychography a good choice for characterising both the surface topography and the internal structural changes in EUV multilayer mirrors. This paper describes the use of reflection-mode ptychography with a lab-scale high harmonic generation based EUV light source to perform quantitative measurement of the amplitude and phase reflection from EUV multilayer mirrors with engineered substrate defects. Using EUV light at 29.6 nm from a tabletop high harmonic generation light source, a lateral resolution down to ∼ 88 nm and a phase resolution of 0. 08 rad (equivalent to topographic height variation of 0.27 nm) are achieved. The effect of surface distortion and roughness on EUV reflectivity is compared to topographic properties of the mirror defects measured using both atomic force microscopy and scanning transmission electron microscopy. Modelling of reflection properties from multilayer mirrors is used to predict the potential of a combination of on-resonance, actinic ptychographic imaging at 13.5 nm and atomic force microscopy for characterising the changes in multilayered structures. [ABSTRACT FROM AUTHOR]

We review the main developments and first commissioning experiments at the CARNAÚBA X-ray nanoprobe beamline, recently installed at the brand-new Sirius 4th-generation synchrotron radiation source at the Brazilian Synchrotron Light Laboratory (LNLS). The paper briefly discusses the X-ray nanoprobe instrument, emphasizing the first deployed experimental station TARUMÃ, and showcases preliminary results in a broad range of areas that benefit from diverse sample environments. Research domains like photovoltaics, photonics, electrocatalysis, geoscience, and agriculture are investigated from the viewpoint of chemistry, atomic structure, morphology, and redox dynamics phenomena covered by the beamline techniques. Finally, future capabilities are presented based on a new instrument under development. • The CARNAUBA X-ray nanoprobe beamline has been commissioned and it is open to the scientific community. • The first deployed station, named TARUMÃ, has been commissioned and reached design parameters. • The beamline has delivered preliminary science outcomes. [ABSTRACT FROM AUTHOR]

Sparsely and randomly distributed internal defects in the optical component can cause an inferior signal quality and serious measurement errors. A modified three-dimensional extend ptychographic iterative engine (modified-3PIE), which splits a sample into axial sections with known positions, is proposed to evaluate and reconstruct internal defects. The axial positions of internal defects are calculated to reduce the number of axial sections. There are only several axial sections with defects that are located at the calculated positions, and other sections are free-propagation parts. The complex amplitude transmittances of internal defects at different axial section positions are simultaneously retrieved. Simulation and experiments are conducted to verify the performance of the proposed method. Our proposed method does not require a reference beam and imaging system, and it can be applied to reconstruct a large area of the sample. [ABSTRACT FROM AUTHOR]

Crucial for the advancement of electrochemical materials science is understanding the lateral variations in the elemental and chemical state of constituents induced by electrochemical reactions at nanoscales. This requires in situ studies to provide observables that contribute to both modeling beyond the phenomenological level and transducing exactly the functionally relevant quantities A range of X-ray coherent diffraction imaging (CDI) approaches has recently been proposed for imaging beyond the diffraction limit with potentially dramatic improvements of time resolution with chemical sensitivity. In this paper we report a selection of ptychography results obtained in situ after successive steps of electrochemically driven growth, complemented with absorption and phase spectroscopy at high lateral resolution. We demonstrate the onset of morphological instability feature formation and correlate the chemical state of Mn with local growth rate controlled by the current density distribution resulting from morphological evolution. [ABSTRACT FROM AUTHOR]

Recent development in fast pixelated detector technology has allowed a two dimensional diffraction pattern to be recorded at every probe position of a two dimensional raster scan in a scanning transmission electron microscope (STEM), forming an information-rich four dimensional (4D) dataset. Electron ptychography has been shown to enable efficient coherent phase imaging of weakly scattering objects from a 4D dataset recorded using a focused electron probe, which is optimised for simultaneous incoherent Z-contrast imaging and spectroscopy in STEM. Therefore coherent phase contrast and incoherent Z-contrast imaging modes can be efficiently combined to provide a good sensitivity of both light and heavy elements at atomic resolution. In this work, we explore the application of electron ptychography for atomic resolution imaging of strongly scattering crystalline specimens, and present experiments on imaging crystalline specimens including samples containing defects, under dynamical channelling conditions using an aberration corrected microscope. A ptychographic reconstruction method called Wigner distribution deconvolution (WDD) was implemented. Experimental results and simulation results suggest that ptychography provides a readily interpretable phase image and great sensitivity for imaging light elements at atomic resolution in relatively thin crystalline materials. [ABSTRACT FROM AUTHOR]

For solid oxide fuel and electrolysis cells, precise tracking of 3D microstructural change in the electrodes during operation is considered critical to understand the complex relationship between electrode microstructure and performance. Here, for the first time, we report a significant step towards this aim by visualizing a complete redox cycle in a solid oxide cell (SOC) electrode. The experiment demonstrates synchrotron-based ptychography as a method of imaging SOC electrodes, providing an unprecedented combination of 3D image quality and spatial resolution among non-destructive imaging techniques. Spatially registered 3D reconstructions of the same location in the electrode clearly show the evolution of the microstructure from the pristine state to the oxidized state and to the reduced state. A complete mechanical destruction of the zirconia backbone is observed via grain boundary fracture, the nickel and pore networks undergo major reorganization and the formation of internal voids is observed in the nickel-oxide particles after the oxidation. These observations are discussed in terms of reaction kinetics, electrode mechanical stress and the consequences of redox cycling on electrode performance. [ABSTRACT FROM AUTHOR]

Label-free imaging uses inherent contrast mechanisms within cells to create image contrast without introducing dyes/labels, which may confound results. Quantitative phase imaging is label-free and offers higher content and contrast compared to traditional techniques. High-contrast images facilitate generation of individual cell metrics via more robust segmentation and tracking, enabling formation of a label-free dynamic phenotype describing cell-to-cell heterogeneity and temporal changes. Compared to population-level averages, individual cell-level dynamic phenotypes have greater power to differentiate between cellular responses to treatments, which has clinical relevance e.g. in the treatment of cancer. Furthermore, as the data is obtained label-free, the same cells can be used for further assays or expansion, of potential benefit for the fields of regenerative and personalised medicine. [ABSTRACT FROM AUTHOR]

In recent years, X-ray ptychography has been established as a valuable tool for high-resolution imaging. Nevertheless, the spatial resolution and sensitivity in coherent diffraction imaging are limited by the signal that is detected over noise and over background scattering. Especially, coherent imaging of weakly scattering specimens suffers from incoherent background that is generated by the interaction of the central beam with matter along its propagation path in particular close to and inside of the detector. Common countermeasures entail evacuated flight tubes or detector-side beamstops, which improve the experimental setup in terms of background reduction or better coverage of high dynamic range in the diffraction patterns. Here, we discuss an alternative approach: we combine two ptychographic scans with and without beamstop and reconstruct them simultaneously taking advantage of the complementary information contained in the two scans. We experimentally demonstrate the potential of this scheme for hard X-ray ptychography by imaging a weakly scattering object composed of catalytic nanoparticles and provide the analysis of the signal-to-background ratio in the diffraction patterns. [ABSTRACT FROM AUTHOR]

The structural and compositional properties of tin halide perovskites (CH(NH 2) 2 SnI 3 , FASnI 3) with and without an ionic liquid of 1-Ethyl-3-methylimidazolium bis(trifluormethylsulfonyl) imide (EMITFSI) were investigated using the scanning transmission soft X-ray microscopy (STXM) and spectro-ptychography techniques at the Sn M 5,4 -edge, I M 5,4 -edge, O K-edge, C K-edge, and N K-edge. The study offers a comprehensive interpretation of the spectral characteristics of main components (C, N, Sn, and I) in Sn-based perovskites through STXM-based techniques and further reveals differences between the perovskite samples with and without adding EMITFSI ionic liquid. The chemical imaging of Sn and I shows that the perovskite sample without ionic liquid has Sn-rich regions in iodine cavities, while the ionic liquid-treated sample exhibits a more homogeneous perovskite phase. Furthermore, the C and N K-edge XANES resonance features support the interaction between the non-volatile ionic liquid and FA+, thus playing a protective role in the formation and stabilization of perovskite phase. • The state-of-the-art bulk sensitive STXM at high-resolution. • Ptychography mode and conventional absorption mode has been successfully applied to characterize key molecular properties and the heterogeneity of perovskite films. • We find surprisingly that the Sn-based perovskite sample presents a perovskite phase with a more homogeneous chemical environment and structure after the addition of EMITFSI. • The non-volatile organic cations in EMITFSI form a protective layer around the organic components of the perovskite, contributing positively to its formation and stability. [ABSTRACT FROM AUTHOR]

• Position-guided vibration separation is proposed for improving ptychographic imaging. • The approach exploits the position data recorded by interferometer during exposures. • The approach can greatly suppress sample random vibration effects on ptychography. • The approach is much better than mixed-state method in suppressing random vibration. • The approach can decrease stability requirements on ptychography instruments. As a variant of the coherent X-ray diffraction imaging (CDI) method, ptychography provides an ultrahigh resolution of sub-10 nm for extended samples through iterative phasing of diffraction patterns; this advantage makes ptychography have great application potential in nanoscience, materials, biology and magnetics. However, irregular vibrations of motion stages in ptychography experiment system can induce incoherent blurring of diffraction patterns, thereby resulting in degradation of recovered image quality. Herein, we propose a new ptychography approach, termed position-guided vibration separation, to improve ptychography reconstruction in the presence of sample random vibration relative to the illumination by utilizing the instantaneous position data recorded by a laser interferometer (LIM) during exposures of the pixel detector. This approach provides a solution to the sample-stage random vibration problem by mapping the object mixed states onto the LIM-measured vibrational positions. Both the simulation and experimental results demonstrate the effectiveness of this approach in suppressing the random vibration effects on ptychography. Therefore, this new approach can significantly decrease the mechanical stability requirements on ptychography experiment instruments. [ABSTRACT FROM AUTHOR]

• Adaptive iterative guided filtering is proposed for ptychographical imaging. • The noise of recovered image is seppressed. • The resolution is hold and the image sharpness is enhanced. Ptychography is a lens-free imaging method which can outstrip the resolution limitations of optical apparatuses, even so the algorithm automatically totes background noise during the imaging process. In order to rehabilitate a more exquisite image, an adaptive iterative guided filtering method is designed. The guided filter is incorporated into the computation process of ptychography. The self-adaptive functionality is achieved by controlling the constraint factors of iteration times. The high edge-preserving performance of guided filtering could rub out background noise without messing up resolution. Furthermore, compared with other spatial filtering algorithms, it is validated that the proposed algorithm has the best refactoring and the highest computing efficiency. [ABSTRACT FROM AUTHOR]

The ability to image light elements in both crystalline and noncrystalline materials at near atomic resolution with an enhanced contrast is highly advantageous to understand the structure and properties of a wide range of beam sensitive materials including biological specimens and molecular hetero-structures. This requires the imaging system to have an efficient phase contrast transfer at both low and high spatial frequencies. In this work we introduce a new phase contrast imaging method in a scanning transmission electron microscope (STEM) using a pre-specimen phase plate in the probe forming aperture, combined with a fast pixelated detector to record diffraction patterns at every probe position, and phase reconstruction using ptychography. The phase plate significantly enhances the contrast transfer of low spatial frequency information, and ptychography maximizes the extraction of the phase information at all spatial frequencies. In addition, the STEM probe with the presence of the phase plate retains its atomic resolution, allowing simultaneous incoherent Z-contrast imaging to be obtained along with the ptychographic phase image. An experimental image of Au nanoparticles on a carbon support shows high contrast for both materials. Multislice image simulations of a DNA molecule shows the capability of imaging soft matter at low dose conditions, which implies potential applications of low dose imaging of a wide range of beam sensitive materials. [ABSTRACT FROM AUTHOR]

In this article we combine the well-known Ptychographical Iterative Engine (PIE) with the Hybrid Input-Output (HIO) algorithm. The important insight is that the HIO feedback function should be kept strictly separate from the reconstructed object, which is done by introducing a separate feedback function per probe position. We have also combined HIO with floating PIE (fPIE) and extended PIE (ePIE). Simulations indicate that the combined algorithm performs significantly better in many situations. Although we have limited our research to a combination with HIO, the same insight can be used to combine ptychographical algorithms with any phase retrieval algorithm that uses a feedback function. [ABSTRACT FROM AUTHOR]

Recently, we proposed a model of securing a ptychography-based monochromatic image encryption system via the classical Photon-counting imaging (PCI) technique. In this study, we examine a single-channel multispectral sparse-based photon-counting ptychography imaging (SMPI)-based cryptosystem. A ptychography-based cryptosystem creates a complex object wave field, which can be reconstructed by a series of diffraction intensity patterns through an aperture movement. The PCI sensor records only a few complex Bayer patterned samples that have been utilized in the decryption process. Sparse sensing and nonlinear properties of the classical PCI system, together with the scanning probes, enlarge the key space, and such a combination therefore enhances the system’s security. We demonstrate that the sparse samples have adequate information for image decryption, as well as information authentication by means of optical correlation. [ABSTRACT FROM AUTHOR]

Three-dimensional analysis of microporous and fine-grained particles in natural stone is important for understanding their internal fluid flow processes and to allow their internal dynamics to be modeled. These processes are of great interest in oil, gas and groundwater studies, as well as for the weathering of natural building materials. For features above 1 μm methods such as X-ray micro-computed tomography (μ-CT) can provide non-destructive, quantitative analysis. Non-destructive 3D imaging at resolutions below 300–400 nm, however, has remained a challenge until recent developments at synchrotron beam lines. In this paper we visualize the microstructure of clay mineral samples extracted from two different sandstones at 3D spatial resolutions down to 45 nm, using ptychographic X-ray computed tomography (PXCT). Furthermore, the relative humidity of the environment during these experiments was controlled in order to assess its influence on the analyzed samples. Based on these high-quality images, we were able to acquire non-destructively quantitative 3D information on mineral content and distribution, porosity and connectivity of clay mineral clusters inside sandstone. [ABSTRACT FROM AUTHOR]

Instrumentation and current capabilities of soft X-ray (50–2000 eV) spectromicroscopy are outlined with examples from recently published and some new work. Four common techniques are treated—transmission X-ray microscopy (TXM), scanning transmission X-ray microscopy (STXM), X-ray photoemission electron microscopy (XPEEM) and scanning photoemission microscopy (SPEM). I also present a fifth, emerging technique, that of soft X-ray spectro-ptychography which has significantly improved spatial resolution and provides new contrast mechanisms. Perspectives for near future (5–10 years) evolution of soft X-ray spectromicroscopy are outlined based on current trends and instrumentation under development. [ABSTRACT FROM AUTHOR]

In Part I of this series of two papers, we demonstrated the formation of a high efficiency phase-contrast image at atomic resolution using a pixelated detector in the scanning transmission electron microscope (STEM) with ptychography. In this paper we explore the technique more quantitatively using theory and simulations. Compared to other STEM phase contrast modes including annular bright field (ABF) and differential phase contrast (DPC), we show that the ptychographic phase reconstruction method using pixelated detectors offers the highest contrast transfer efficiency and superior low dose performance. Applying the ptychographic reconstruction method to DPC segmented detectors also improves the detector contrast transfer and results in less noisy images than DPC images formed using difference signals. We also find that using a minimum array of 16×16 pixels is sufficient to provide the highest signal-to-noise ratio (SNR) for imaging beam sensitive weak phase objects. Finally, the convergence angle can be adjusted to enhance the contrast transfer based on the spatial frequencies of the specimen under study. [ABSTRACT FROM AUTHOR]

We reconsider the closed form solution of the ptychographic phase problem called the Wigner Distribution Deconvolution Method (WDDM), which has remained discarded for twenty years. Ptychographic reconstruction is nowadays always undertaken by iterative algorithms. WDDM gives rise to a 4 dimensional data cube of all the relative phases between points in the diffraction plane. Here we demonstrate a novel method to use all this information, instead of just the small subset used in the original ‘stepping out’ procedure developed in the 1990s, thus greatly suppressing noise. We further develop a method for designing an improved probe (illumination function) to further decrease noise effects during the deconvolution division. Combining these two with an iterative procedure for the deconvolution, which avoids the usual difficulty of a divide by a small number, we show in model calculations that WDDM competes well with the modern conventional iterative methods like ePIE (the extended Ptychographical Iterative Engine). [ABSTRACT FROM AUTHOR]

Abstract: Phase-diverse X-ray coherent diffractive imaging (CDI) provides a route to high sensitivity and spatial resolution with moderate radiation dose. It also provides a robust solution to the well-known phase-problem, making on-line image reconstruction feasible. Here we apply phase-diverse CDI to a cellular sample, obtaining images of an erythrocyte infected by the sexual stage of the malaria parasite, Plasmodium falciparum, with a radiation dose significantly lower than the lowest dose previously reported for cellular imaging using CDI. The high sensitivity and resolution allow key biological features to be identified within intact cells, providing complementary information to optical and electron microscopy. This high throughput method could be used for fast tomographic imaging, or to generate multiple replicates in two-dimensions of hydrated biological systems without freezing or fixing. This work demonstrates that phase-diverse CDI is a valuable complementary imaging method for the biological sciences and ready for immediate application. [Copyright &y& Elsevier]

Highlights: [•] Nanofabrication of tungsten zone plates for hard X-rays. [•] Combining zone plate optic and platinum central stop to simplify experimental arrangements. [•] Zone plate characterization in terms of ptychography at 8keV is presented. [•] Diffraction-limited focus spot size of 53nm diameter. [ABSTRACT FROM AUTHOR]

Abstract: We show for the first time that ptychography (a form of lensless diffractive imaging) can recover the spectral response of an object through simultaneous reconstruction of multiple images that represent the object's response to a particular mode present in the illumination. We solve the phase problem for each mode independently, even though the intensity arriving at every detector pixel is an incoherent superposition of several uncorrelated diffracted waves. Until recently, the addition of incoherent modes has been seen as a nuisance in diffractive imaging: here we show that not only can the difficulties they pose be removed, but that they can also be used to discover much more information about the object. If the illumination function is also mode-specific, we show that we can also solve simultaneously for a multiplicity of such illumination modes. The work opens exciting possibilities for information multiplexing in ptychography over all visible, X-ray and electron wavelengths. [Copyright &y& Elsevier]

Abstract: X-ray ptychography is a rapidly developing phase retrieval technique that combines the experimental advantages of coherent diffractive imaging with the possibility to image extended specimens. Data collection requires imaging at several scan points with high positional accuracy, which implies susceptibility to mechanical drift. This is a well-known problem in ptychographic scans, which can reduce reconstruction quality and limit the achievable resolution. Using a simple model for positional drift, we show that a set of corrected positions can be found systematically, leading to strong improvements in the reconstruction of a Siemens star dataset severely affected by drift. [Copyright &y& Elsevier]

Abstract: Ptychography offers the possibility of improving the resolution of atomic-scale (electron and X-ray) transmission microscopy without any of the demands of high quality lenses: its resolution is in theory only limited by the effective synthetic numerical aperture determined by the angular size of the detector. However, it has been realised experimentally that a major weakness of the approach is that the obtainable resolution is only as good as the accuracy to which the illuminating beam can be moved relative to the specimen. This can be catastrophic in the electron case because of thermal drift and hysteresis in the probe scan coils. We present here a computationally efficient extension of the ‘ePIE’ ptychographic reconstruction algorithm for correcting these errors retrospectively. We demonstrate its effectiveness using simulations and results from visible light and electron beam experiments that show it can correct positioning errors tens of times larger than the pixel size in the resulting image. [Copyright &y& Elsevier]

Abstract: A series of technical advances are helping to revolutionise the possibilities for X-ray and neutron imaging in colloidal science. These include the development of new imaging modalities with high coherence X-rays such as diffractive imaging, ptychography, and femtosecond holography; and Talbot phase contrast tomography with conventional laboratory based low coherence X-ray sources e.g. standard rotating anodes. A crucial insight is that the available phase contrast with synthetic organic and biological colloids can be two orders of magnitude stronger than the absorption contrast with X-rays, providing large improvements in the signal to noise ratio in the resultant images. Furthermore new developments with the sources of X-rays and neutrons are helping to increase the possibilities for this research as the available coherence, flux and collimation are improved e.g. third generation high brilliance synchrotrons, free electron lasers, high flux pulsed neutron sources and table-top X-ray lasers are being developed. Highlights of the application of these techniques and sources to colloids include: the measurement of the internal strains inside individual crystalline colloidal nanoparticles, the imaging of nanoparticles embedded in opaque solid composite materials, images of defects in the growth of colloidal crystals, and the morphology of nanofoams, intact human chromosomes, protein nanocrystals, viruses, bacteria, and blood cells. The resolution of the reconstructed images can be achieved at the 10–50nm length scale, without the need for the invasive sample preparation techniques required for transmission electron microscopy e.g. microtoming of specimens is not required. Furthermore fluorescent staining is also not required, as with super-resolution microscopies at visible optical wavelengths (e.g. STED, PALM and STORM), and thick opaque samples can be investigated, although some fragile organic and biological materials require freezing to reduce beam damage with X-rays. Neutron imaging has also benefited from the development of analogous Talbot phase contrast techniques to those possible with low coherence X-rays and a number of useful applications in non-invasive imaging at the 100μm length scale have been demonstrated e.g. the internal structure of live plants, the inner workings of fuel cells and the three-dimensional domain structure of magnetic materials. [Copyright &y& Elsevier]

Abstract: This paper demonstrates the application of the high sensitivity, low radiation dose imaging method recently presented as phase diverse coherent diffraction imaging, to the study of biological and other weakly scattering samples. The method is applied, using X-ray illumination, to quantitative imaging of the granular precursors of underwater adhesive produced by the marine sandcastle worm, Phragmatopoma californica. We are able to observe the internal structure of the adhesive precursors in a number of states. [Copyright &y& Elsevier]

Abstract: The extended-ptychographical iterative engine (e-PIE) is a recently developed powerful phase retrieval algorithm which can be used to measure the phase transfer function of a specimen and overcome conventional lens resolution limits. The major improvement over PIE is the ability to reconstruct simultaneously both the object and illumination functions, robustness to noise and speed of convergence. The technique has proven to be successful at optical and X-ray wavelengths and we describe here experimental results in transmission electron microscopy supported by corresponding simulations. These simulations show the possibilities – even with strong phase objects – and limitations of ptychography; in particular issues arising from poorly-defined probe positions. [Copyright &y& Elsevier]

Abstract: A technique for quantitatively characterizing the complex-valued focal wavefield of arbitrary optics is described and applied to reconstructing the coherent focused beam produced by a reflective/diffractive hard X-ray mirror. This phase-retrieval method, based on ptychography, represents an important advance in X-ray optics characterization because the information obtained and potential resolution far exceeds that accessible to methods of directly probing the focus. Ptychography will therefore be well-suited for characterizing and aligning future nanofocusing X-ray optics. [Copyright &y& Elsevier]