Three-dimensional imaging with single orientation is a potential and novel technique. We successfully demonstrate that three-dimensional（3D） structure can be determined by a single orientation diffraction measuremen...Three-dimensional imaging with single orientation is a potential and novel technique. We successfully demonstrate that three-dimensional（3D） structure can be determined by a single orientation diffraction measurement for a phase object of double-layer Mie-scattering silica spheres on a Si3N4 membrane. Coherent diffraction pattern at high numerical aperture was acquired with an optical laser, and the oversampled pattern was projected from a planar detector onto the Ewald sphere.The double-layered spheres are reconstructed from the spherical diffraction pattern and a 2D curvature-corrected pattern,which improve convergence speed and stability of reconstruction.展开更多
Coherent diffraction imaging(CDI)provides lens-free imaging with diffraction-limited resolution and has become an important imaging modality at synchrotron facilities worldwide.The performance of current CDI approache...Coherent diffraction imaging(CDI)provides lens-free imaging with diffraction-limited resolution and has become an important imaging modality at synchrotron facilities worldwide.The performance of current CDI approaches remains limited,particularly in their ability to handle dynamic samples or achieve consistent high-quality reconstructions.Here,we propose a novel coherent imaging approach for dynamic samples,which exploits the inter-frame continuity of the sample’s local structures as an additional constraint in phasing a sequence of diffraction patterns.Our algorithm incorporates an adaptive similarity determination procedure,eliminating the requirement for invariant regions in the sample and ensuring broad applicability to diverse sample types.We demonstrated the feasibility of this technique through experiments on various dynamic samples,achieving high-fidelity reconstructions within a few hundred iterations.With the same simple setup as conventional CDI,high image quality,and the ability to separate the sample transmission from its illumination probe,our method has the potential to significantly advance X-ray imaging and electron microscopy techniques for dynamic sample analysis.展开更多
Coherent Diffraction Imaging(CDI)is an experimental technique to image isolated structures by recording the scattered light.The sample density can be recovered from the scattered field through a Fourier Transform oper...Coherent Diffraction Imaging(CDI)is an experimental technique to image isolated structures by recording the scattered light.The sample density can be recovered from the scattered field through a Fourier Transform operation.However,the phase of the field is lost during the measurement and has to be algorithmically retrieved.Here we present SPRING,an analysis framework tailored to X-ray Free Electron Laser(XFEL)single-shot single-particle diffraction data that implements the Memetic Phase Retrieval method to mitigate the shortcomings of conventional algorithms.We benchmark the approach on data acquired in two experimental campaigns at SwissFEL and European XFEL.Results reveal unprecedented stability and resilience of the algorithm’s behavior on the input parameters,and the capability of identifying the solution in conditions hardly treatable with conventional methods.A user-friendly implementation of SPRING is released as open-source software,aiming at being a reference tool for the CDI community at XFEL and synchrotron facilities.展开更多
Single-shot multi-frame phase imaging plays an important role in detecting continuous extreme physical phenomena,particularly suitable for measuring the density of media with non-repeatable changes and uncertainties.H...Single-shot multi-frame phase imaging plays an important role in detecting continuous extreme physical phenomena,particularly suitable for measuring the density of media with non-repeatable changes and uncertainties.However,traditional single-pattern multiplexed imaging faces challenges in retrieving amplitude and phase information of multiple frames without sacrificing spatial resolution and phase accuracy。展开更多
Coherent diffraction imaging(CDI)enables diffraction-limited high-resolution imaging without using high-quality lenses.It will be desirable to combine it with multiple spectral light sources to achieve chemically reso...Coherent diffraction imaging(CDI)enables diffraction-limited high-resolution imaging without using high-quality lenses.It will be desirable to combine it with multiple spectral light sources to achieve chemically resolved imaging capability.Here,we demonstrate a single-frame multiwavelength CDI approach that can provide complex transmittance images of a sample at multiple wavelengths.The superior performance of our method in terms of rapid convergence and improved image quality over current methods has been validated through high-harmonic extreme ultraviolet experiments.The feasibility of our method for single-frame chemical imaging is also demonstrated by the simulation.This work can pave the way for implementing in situ chemical imaging with tabletop high-harmonic generation extreme ultraviolet sources.展开更多
The Shanghai soft X-ray free-electron laser(SXFEL)user facility project started in 2016 and is expected to be open to users by 2022.It aims to deliver ultra-intense coherent femtosecond X-ray pulses to five endstation...The Shanghai soft X-ray free-electron laser(SXFEL)user facility project started in 2016 and is expected to be open to users by 2022.It aims to deliver ultra-intense coherent femtosecond X-ray pulses to five endstations covering a range of 100–620 eV for ultrafast X-ray science.Two undulator lines are designed and constructed,based on different lasing modes:self-amplified spontaneous emission and echo-enabled harmonic generation.The coherent scattering and imaging(CSI)endstation is the first of five endstations to be commissioned online.It focuses on high-resolution single-shot imaging and the study of ultrafast dynamic processes using coherent forward scattering techniques.Both the single-shot holograms and coherent diffraction patterns were recorded and reconstructed for nanoscale imaging,indicating the excellent coherence and high peak power of the SXFEL and the possibility of‘‘diffraction before destruction’’experiments at the CSI endstation.In this study,we report the first commissioning results of the CSI endstation.展开更多
Coherent diffractive imaging （CDI） is a lensless imaging technique and can achieve a resolution beyond the Rayleigh or Abbe limit. The ptychographical iterative engine （PIE） is a CDI phase retrieval algorithm that...Coherent diffractive imaging （CDI） is a lensless imaging technique and can achieve a resolution beyond the Rayleigh or Abbe limit. The ptychographical iterative engine （PIE） is a CDI phase retrieval algorithm that uses multiple diffraction patterns obtained through the scan of a localized illumination on the specimen, which has been demonstrated successfully at optical and X-ray wavelengths. In this paper, a general PIE algorithm （gPIE） is presented and demonstrated with an He-Ne laser light diffraction dataset. This algorithm not only permits the removal of the accurate model of the illumination function in PIE, but also provides improved convergence speed and retrieval quality.展开更多
This paper introduces a deep learning (DL)-based method for phase retrieval tailored to single-shot, multiple-frame coherent X-ray diffraction imaging (CXDI), designed specifically for visualizing local nanostructural...This paper introduces a deep learning (DL)-based method for phase retrieval tailored to single-shot, multiple-frame coherent X-ray diffraction imaging (CXDI), designed specifically for visualizing local nanostructural dynamics within a larger sample. Current phase retrieval methods often struggle with achieving high spatiotemporal resolutions, handling dynamic imaging, and managing computational costs, which limits their applicability in observing nanostructural dynamics. This study addresses these gaps by developing a novel method that leverages a feedforward architecture with a physics-informed strategy utilizing measurement settings, enabling the reconstruction of dynamic “movies" from time-evolving diffraction images of the illuminated area. The method incorporates key enhancements, such as temporal convolution blocks to capture spatiotemporal correlations and a unified TV regularization applied to the reconstructed object, resulting in improved noise reduction and spatial smoothness. An expanded evaluation framework, including multiple metrics and systematic sensitivity analysis, is employed to comprehensively assess the method’s performance and robustness. Proof-of-concept experiments, including numerical simulations and imaging experiments of a moving Ta test chart and colloidal gold particles (dispersed in aqueous polyvinyl alcohol solutions) with synchrotron hard X-rays, validate the high imaging performance of this method. Experimental results demonstrate that structures in the sample have been successfully reconstructed at short exposure times, significantly outperforming both traditional methods and current DL-based methods. The proposed method provides efficient and reliable reconstruction of dynamic images with low computational costs, making it suitable for exploring fast-evolving phenomena in synchrotron- or free-electron laser-based applications requiring high spatiotemporal resolutions.展开更多
Visualization of internal deformation fields in crystalline materials helps bridge the gap between theoretical models and practical applications.Applying Bragg coherent diffraction imaging under X-ray dynamical diffra...Visualization of internal deformation fields in crystalline materials helps bridge the gap between theoretical models and practical applications.Applying Bragg coherent diffraction imaging under X-ray dynamical diffraction conditions provides a promising approach to the longstanding challenge of investigating the deformation fields in micron-sized crystals.Here,we present an automatic differentiation-based reconstruction method that integrates dynamical scattering theory to accurately reconstruct deformation fields in large crystals.Using this forward model,our simulated and experimental results demonstrate that three-dimensional local strain information inside a large crystal can be accurately reconstructed under coherent X-ray dynamical diffraction conditions with Bragg coherent X-ray diffraction imaging.These findings open an avenue for extending the investigation of local deformation fields to microscale crystals while maintaining nanoscale resolution,leveraging the enhanced coherence and brightness of advanced X-ray sources.展开更多
Coherent diffractive imaging(CDI),with its lensless geometry and theoretically perfect transfer function,is considered as one of the most promising paradigms to achieve the Abbe resolution limit.However,recent advance...Coherent diffractive imaging(CDI),with its lensless geometry and theoretically perfect transfer function,is considered as one of the most promising paradigms to achieve the Abbe resolution limit.However,recent advances on pushing the resolution limit in high-numerical-aperture(NA)CDIs has thus far been challenging.Here,we report a nearly 0.9NA CDI with an optimized imaging factor(k=0.501),pushing the Abbe resolution diffraction limit for the first time in ultra-high-NA scenarios.Leveraging this the ultra-high NA and the Abbe-limit k-factor,we demonstrate a record-high imaging resolution of 0.57λfor CDIs.Our approach builds upon a novel computational framework termed‘rigorous Fraunhofer diffraction’that eliminates the Ewald sphere effect in CDIs,particularly for high NAs.Our framework transforms the general challenge of high-NA,resolution-limited CDIs from relying on approximate and complicated geometric corrections to a solvable problem through rigorous model-based computation.展开更多
While ptychography is an algorithm based on coherent illumination,satisfactory reconstructions can still be generated in most experiments,even though the radiation sources that are used are not ideally coherent.The un...While ptychography is an algorithm based on coherent illumination,satisfactory reconstructions can still be generated in most experiments,even though the radiation sources that are used are not ideally coherent.The underlying physics of this phenomenon is that the diffraction patterns of partially coherent illumination can be treated as those of purely coherent illumination by altering the intensities of the diffracted beams relative to their real values.On the other hand,due to the inconsistency in the altering interference among all the diffraction beams,noise/distortion is always involved in the reconstructed images.Furthermore,for a weak object,the noise/distortion in the reconstruction can be mostly reduced by using a highly curved beam for illumination in the data recording and forcing the dark field diffraction to be zero in the reconstruction.展开更多
We propose and experimentally demonstrate a noniterative diffractive imaging method for reconstructing the complex-valued transmission function of an object illuminated by spatially partially coherent light from the f...We propose and experimentally demonstrate a noniterative diffractive imaging method for reconstructing the complex-valued transmission function of an object illuminated by spatially partially coherent light from the far-field diffraction pattern.Our method is based on a pinhole array mask,which is specially designed such that the correlation function in the mask plane can be obtained directly by inverse Fourier transforming the diffraction pattern.Compared to the traditional iterative diffractive imaging methods using spatially partially coherent illumination,our method is noniterative and robust to the degradation of the spatial coherence of the illumination.In addition to diffractive imaging,the proposed method can also be applied to spatial coherence property characterization,e.g.,free-space optical communication and optical coherence singularity measurement.展开更多
Lensless imaging is an approach to microscopy in which a high-resolution image of an object is reconstructed from one or more measured diffraction patterns,providing a solution in situations where the use of imaging o...Lensless imaging is an approach to microscopy in which a high-resolution image of an object is reconstructed from one or more measured diffraction patterns,providing a solution in situations where the use of imaging optics is not possible.However,current lensless imaging methods are typically limited by the need for a light source with a narrow,stable and accurately known spectrum.We have developed a general approach to lensless imaging without spectral bandwidth limitations or sample requirements.We use two time-delayed coherent light pulses and show that scanning the pulse-to-pulse time delay allows the reconstruction of diffraction-limited images for all the spectral components in the pulse.In addition,we introduce an iterative phase retrieval algorithm that uses these spectrally resolved Fresnel diffraction patterns to obtain high-resolution images of complex extended objects.We demonstrate this two-pulse imaging method with octave-spanning visible light sources,in both transmission and reflection geometries,and with broadband extreme-ultraviolet radiation from a high-harmonic generation source.Our approach enables effective use of low-flux ultra-broadband sources,such as table-top high-harmonic generation systems,for high-resolution imaging.展开更多
With the development of the XFEL （X-ray free electron laser）, high quality diffraction patterns from nanocrystals have been achieved. The nanocrystals with different sizes and random orientations are injected to the...With the development of the XFEL （X-ray free electron laser）, high quality diffraction patterns from nanocrystals have been achieved. The nanocrystals with different sizes and random orientations are injected to the XFEL beams and the diffraction patterns can be obtained by the so-called ＂diffraction-and-destruction＂ mode. The recovery of orientations is one of the most critical steps in reconstructing the 3D structure of nanocrystals. There is already an approach to solve the orientation problem by using the automated indexing software in crystallography. However, this method cannot distinguish the twin orientations in the cases of the symmetries of Bravais lattices higher than the point groups. Here we propose a new method to solve this problem. The shape transforms of nanocrystals can be determined from all of the intensities around the diffraction spots, and then Fourier transformation of a single crystal cell is obtained. The actual orientations of the patterns can be solved by comparing the values of the Fourier transformations of the crystal cell on the intersections of all patterns. This so-called ＂multiple-common-line＂ method can distinguish the twin orientations in the XFEL diffraction patterns successfully.展开更多
基金Project supported by the Major State Basic Research Development Program of China(Grant No.2014CB910401)the National Natural Science Foundation of China(Grant Nos.31430031,21390414,and U1332118)
文摘Three-dimensional imaging with single orientation is a potential and novel technique. We successfully demonstrate that three-dimensional（3D） structure can be determined by a single orientation diffraction measurement for a phase object of double-layer Mie-scattering silica spheres on a Si3N4 membrane. Coherent diffraction pattern at high numerical aperture was acquired with an optical laser, and the oversampled pattern was projected from a planar detector onto the Ewald sphere.The double-layered spheres are reconstructed from the spherical diffraction pattern and a 2D curvature-corrected pattern,which improve convergence speed and stability of reconstruction.
基金supported by the National Natural Science Foundation of China(Grant no.12074167)the Shenzhen Science and Technology Innovation Program(Grant no.JCYJ20241202125334045).
文摘Coherent diffraction imaging(CDI)provides lens-free imaging with diffraction-limited resolution and has become an important imaging modality at synchrotron facilities worldwide.The performance of current CDI approaches remains limited,particularly in their ability to handle dynamic samples or achieve consistent high-quality reconstructions.Here,we propose a novel coherent imaging approach for dynamic samples,which exploits the inter-frame continuity of the sample’s local structures as an additional constraint in phasing a sequence of diffraction patterns.Our algorithm incorporates an adaptive similarity determination procedure,eliminating the requirement for invariant regions in the sample and ensuring broad applicability to diverse sample types.We demonstrated the feasibility of this technique through experiments on various dynamic samples,achieving high-fidelity reconstructions within a few hundred iterations.With the same simple setup as conventional CDI,high image quality,and the ability to separate the sample transmission from its illumination probe,our method has the potential to significantly advance X-ray imaging and electron microscopy techniques for dynamic sample analysis.
基金the Swiss National Science Foundation (via grant no. 200021E_193642, grant no. 200021-232306, and the NCCR MUST)ETH Zurich (via collaborative grant 23-2ETH-050) for financial support+7 种基金MP, OV, and MB further acknowledge the Research Council of Finland for financial support (including projects 326291, 330118, and 341288)TF acknowledges funding by the Deutsche Forschungsgemeinschaft within CRC 1477 “Light-Matter Interactions at Interfaces” (project number 441234705)PHWS acknowledges support from the Swedish Research Council through project 2018-00740FRNCM acknowledges the Swedish Research Council (2018-00234 and 2019-06092) and the Carl Tryggers Stiftelse för Vetenskaplig Forskning (CTS 19-227)JAS acknowledges the Swedish Research Council (2023-06350)the Göran Gustafsson Foundation (2044)the Carl Tryggers Stiftelse för Vetenskaplig Forskning (CTS 21-1427)The Maloja instrument received funding from the Swiss National Science Foundation through R’Equip Grant No. 206021_182988. We thank the IT Services Group (ISG) of the Department of Physics at ETH Zurich for the excellent support and management of the computing hardware on which the spring software has been developed and tested.
文摘Coherent Diffraction Imaging(CDI)is an experimental technique to image isolated structures by recording the scattered light.The sample density can be recovered from the scattered field through a Fourier Transform operation.However,the phase of the field is lost during the measurement and has to be algorithmically retrieved.Here we present SPRING,an analysis framework tailored to X-ray Free Electron Laser(XFEL)single-shot single-particle diffraction data that implements the Memetic Phase Retrieval method to mitigate the shortcomings of conventional algorithms.We benchmark the approach on data acquired in two experimental campaigns at SwissFEL and European XFEL.Results reveal unprecedented stability and resilience of the algorithm’s behavior on the input parameters,and the capability of identifying the solution in conditions hardly treatable with conventional methods.A user-friendly implementation of SPRING is released as open-source software,aiming at being a reference tool for the CDI community at XFEL and synchrotron facilities.
基金China Postdoctoral Science Foundation(2023M743252,2024T170846)Key Research and Development Program of Zhejiang Province(2024SSYS0014)National Natural Science Foundation of China(62205304).
文摘Single-shot multi-frame phase imaging plays an important role in detecting continuous extreme physical phenomena,particularly suitable for measuring the density of media with non-repeatable changes and uncertainties.However,traditional single-pattern multiplexed imaging faces challenges in retrieving amplitude and phase information of multiple frames without sacrificing spatial resolution and phase accuracy。
基金supported by the National Natural Science Foundation of China(No.12074167)the Shenzhen ScienceandTechnologyInnovationProgram(No.JCYJ20241202125334045)。
文摘Coherent diffraction imaging(CDI)enables diffraction-limited high-resolution imaging without using high-quality lenses.It will be desirable to combine it with multiple spectral light sources to achieve chemically resolved imaging capability.Here,we demonstrate a single-frame multiwavelength CDI approach that can provide complex transmittance images of a sample at multiple wavelengths.The superior performance of our method in terms of rapid convergence and improved image quality over current methods has been validated through high-harmonic extreme ultraviolet experiments.The feasibility of our method for single-frame chemical imaging is also demonstrated by the simulation.This work can pave the way for implementing in situ chemical imaging with tabletop high-harmonic generation extreme ultraviolet sources.
基金the Shanghai Soft X-ray Free-Electron Laser Facility beamline projectionfunded by the Major State Basic Research Development Program of China(No.2017YFA0504802)+1 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB 37040303)National Natural Science Foundation of China(No.21727817).
文摘The Shanghai soft X-ray free-electron laser(SXFEL)user facility project started in 2016 and is expected to be open to users by 2022.It aims to deliver ultra-intense coherent femtosecond X-ray pulses to five endstations covering a range of 100–620 eV for ultrafast X-ray science.Two undulator lines are designed and constructed,based on different lasing modes:self-amplified spontaneous emission and echo-enabled harmonic generation.The coherent scattering and imaging(CSI)endstation is the first of five endstations to be commissioned online.It focuses on high-resolution single-shot imaging and the study of ultrafast dynamic processes using coherent forward scattering techniques.Both the single-shot holograms and coherent diffraction patterns were recorded and reconstructed for nanoscale imaging,indicating the excellent coherence and high peak power of the SXFEL and the possibility of‘‘diffraction before destruction’’experiments at the CSI endstation.In this study,we report the first commissioning results of the CSI endstation.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11179009 and 50875013)the Beijing Municipal Natural Science Foundation, China (Grant No. 4102036)the Beijing NOVA Program, China (Grant No. 2009A09)
文摘Coherent diffractive imaging （CDI） is a lensless imaging technique and can achieve a resolution beyond the Rayleigh or Abbe limit. The ptychographical iterative engine （PIE） is a CDI phase retrieval algorithm that uses multiple diffraction patterns obtained through the scan of a localized illumination on the specimen, which has been demonstrated successfully at optical and X-ray wavelengths. In this paper, a general PIE algorithm （gPIE） is presented and demonstrated with an He-Ne laser light diffraction dataset. This algorithm not only permits the removal of the accurate model of the illumination function in PIE, but also provides improved convergence speed and retrieval quality.
基金supported by the JSPS KAKENHI Grants 20K05301,JP19H05815,20K05068,and JP23H05403the JST-CREST Program(Innovative Measurement and Analysis),Japan.
文摘This paper introduces a deep learning (DL)-based method for phase retrieval tailored to single-shot, multiple-frame coherent X-ray diffraction imaging (CXDI), designed specifically for visualizing local nanostructural dynamics within a larger sample. Current phase retrieval methods often struggle with achieving high spatiotemporal resolutions, handling dynamic imaging, and managing computational costs, which limits their applicability in observing nanostructural dynamics. This study addresses these gaps by developing a novel method that leverages a feedforward architecture with a physics-informed strategy utilizing measurement settings, enabling the reconstruction of dynamic “movies" from time-evolving diffraction images of the illuminated area. The method incorporates key enhancements, such as temporal convolution blocks to capture spatiotemporal correlations and a unified TV regularization applied to the reconstructed object, resulting in improved noise reduction and spatial smoothness. An expanded evaluation framework, including multiple metrics and systematic sensitivity analysis, is employed to comprehensively assess the method’s performance and robustness. Proof-of-concept experiments, including numerical simulations and imaging experiments of a moving Ta test chart and colloidal gold particles (dispersed in aqueous polyvinyl alcohol solutions) with synchrotron hard X-rays, validate the high imaging performance of this method. Experimental results demonstrate that structures in the sample have been successfully reconstructed at short exposure times, significantly outperforming both traditional methods and current DL-based methods. The proposed method provides efficient and reliable reconstruction of dynamic images with low computational costs, making it suitable for exploring fast-evolving phenomena in synchrotron- or free-electron laser-based applications requiring high spatiotemporal resolutions.
基金Shanghai Advanced Research Institute was funded by the '100 Talents Project' of the Chinese Academy of SciencesWork at Brookhaven National Laboratory was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-SC0012704+1 种基金Measurements were conducted at the Advanced Photon Source (APS) beamline 34-ID-C, which was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357The beamline 34-ID-C was built with U.S. National Science Foundation grant DMR-9724294.
文摘Visualization of internal deformation fields in crystalline materials helps bridge the gap between theoretical models and practical applications.Applying Bragg coherent diffraction imaging under X-ray dynamical diffraction conditions provides a promising approach to the longstanding challenge of investigating the deformation fields in micron-sized crystals.Here,we present an automatic differentiation-based reconstruction method that integrates dynamical scattering theory to accurately reconstruct deformation fields in large crystals.Using this forward model,our simulated and experimental results demonstrate that three-dimensional local strain information inside a large crystal can be accurately reconstructed under coherent X-ray dynamical diffraction conditions with Bragg coherent X-ray diffraction imaging.These findings open an avenue for extending the investigation of local deformation fields to microscale crystals while maintaining nanoscale resolution,leveraging the enhanced coherence and brightness of advanced X-ray sources.
基金supported by National Natural Science Foundation of China(52130504,52450258)Key Research and Development Program of Hubei Province(2021BAA013)+2 种基金Innovation Project of Optics Valley Laboratory(OVL2023PY003)Guangdong Basic and Applied Basic Research Foundation(2023A1515030149)Major Science and Technology Innovation Project of HUST(2024ZDKJCX09).
文摘Coherent diffractive imaging(CDI),with its lensless geometry and theoretically perfect transfer function,is considered as one of the most promising paradigms to achieve the Abbe resolution limit.However,recent advances on pushing the resolution limit in high-numerical-aperture(NA)CDIs has thus far been challenging.Here,we report a nearly 0.9NA CDI with an optimized imaging factor(k=0.501),pushing the Abbe resolution diffraction limit for the first time in ultra-high-NA scenarios.Leveraging this the ultra-high NA and the Abbe-limit k-factor,we demonstrate a record-high imaging resolution of 0.57λfor CDIs.Our approach builds upon a novel computational framework termed‘rigorous Fraunhofer diffraction’that eliminates the Ewald sphere effect in CDIs,particularly for high NAs.Our framework transforms the general challenge of high-NA,resolution-limited CDIs from relying on approximate and complicated geometric corrections to a solvable problem through rigorous model-based computation.
基金supported by the Funds from the Engineering and Physical Sciences Research Council(Grant No.EP/E034055/1)the One Hundred Talent Project of the Chinese Academy of Sciences and the Financial Support(Grant No.GFZX0205010502.12)
文摘While ptychography is an algorithm based on coherent illumination,satisfactory reconstructions can still be generated in most experiments,even though the radiation sources that are used are not ideally coherent.The underlying physics of this phenomenon is that the diffraction patterns of partially coherent illumination can be treated as those of purely coherent illumination by altering the intensities of the diffracted beams relative to their real values.On the other hand,due to the inconsistency in the altering interference among all the diffraction beams,noise/distortion is always involved in the reconstructed images.Furthermore,for a weak object,the noise/distortion in the reconstruction can be mostly reduced by using a highly curved beam for illumination in the data recording and forcing the dark field diffraction to be zero in the reconstruction.
基金This work was supported by the National Natural Science Foundation of China(Nos.11774250 , 91750201)the National Natural Science Fund for Distinguished Young Scholars(No.11525418)the sponsorship of Jiangsu Overseas Research and Training Program for Prominent Young and Middle-aged University Teachers and Presidents.This work is also part of the research program“Novel design shapes for complex optical systems,”with Project No.12797,which is(partly)financed by the Netherlands Organization for Scientific Research(NWO).
文摘We propose and experimentally demonstrate a noniterative diffractive imaging method for reconstructing the complex-valued transmission function of an object illuminated by spatially partially coherent light from the far-field diffraction pattern.Our method is based on a pinhole array mask,which is specially designed such that the correlation function in the mask plane can be obtained directly by inverse Fourier transforming the diffraction pattern.Compared to the traditional iterative diffractive imaging methods using spatially partially coherent illumination,our method is noniterative and robust to the degradation of the spatial coherence of the illumination.In addition to diffractive imaging,the proposed method can also be applied to spatial coherence property characterization,e.g.,free-space optical communication and optical coherence singularity measurement.
基金This work is financed in part by an NWO-groot investment grant of the Netherlands Organisation for Scientific Research(NWO)and Laserlab Europe(JRA Bioptichal)SW acknowledges support from NWO Veni grant 680-47-402.
文摘Lensless imaging is an approach to microscopy in which a high-resolution image of an object is reconstructed from one or more measured diffraction patterns,providing a solution in situations where the use of imaging optics is not possible.However,current lensless imaging methods are typically limited by the need for a light source with a narrow,stable and accurately known spectrum.We have developed a general approach to lensless imaging without spectral bandwidth limitations or sample requirements.We use two time-delayed coherent light pulses and show that scanning the pulse-to-pulse time delay allows the reconstruction of diffraction-limited images for all the spectral components in the pulse.In addition,we introduce an iterative phase retrieval algorithm that uses these spectrally resolved Fresnel diffraction patterns to obtain high-resolution images of complex extended objects.We demonstrate this two-pulse imaging method with octave-spanning visible light sources,in both transmission and reflection geometries,and with broadband extreme-ultraviolet radiation from a high-harmonic generation source.Our approach enables effective use of low-flux ultra-broadband sources,such as table-top high-harmonic generation systems,for high-resolution imaging.
基金Supported by National Natural Science Foundation of China (10979005)National Basic Research Program of China(2009CB918600)
文摘With the development of the XFEL （X-ray free electron laser）, high quality diffraction patterns from nanocrystals have been achieved. The nanocrystals with different sizes and random orientations are injected to the XFEL beams and the diffraction patterns can be obtained by the so-called ＂diffraction-and-destruction＂ mode. The recovery of orientations is one of the most critical steps in reconstructing the 3D structure of nanocrystals. There is already an approach to solve the orientation problem by using the automated indexing software in crystallography. However, this method cannot distinguish the twin orientations in the cases of the symmetries of Bravais lattices higher than the point groups. Here we propose a new method to solve this problem. The shape transforms of nanocrystals can be determined from all of the intensities around the diffraction spots, and then Fourier transformation of a single crystal cell is obtained. The actual orientations of the patterns can be solved by comparing the values of the Fourier transformations of the crystal cell on the intersections of all patterns. This so-called ＂multiple-common-line＂ method can distinguish the twin orientations in the XFEL diffraction patterns successfully.
