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 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
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 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
Laser wakefield accelerators(LWFAs)offer acceleration gradients up to 1000 times higher than those of conventional radio-frequency accelerators,offering a pathway to significantly more compact and cost-effective accel...Laser wakefield accelerators(LWFAs)offer acceleration gradients up to 1000 times higher than those of conventional radio-frequency accelerators,offering a pathway to significantly more compact and cost-effective accelerator systems.This breakthrough opens up new possibilities for laboratory-scale light sources.All-optical inverse Compton scattering(AOCS)sources driven by LWFAs produce high-brightness,quasimonochromatic X rays with micrometer-scale source sizes,delivering the spatial coherence and resolution required for X-ray phase-contrast imaging(XPCI).These features position AOCS X-ray sources as promising tools for applications in biology,medicine,physics,and materials science.However,previous AOCS-based imaging studies have primarily focused on X-ray absorption imaging.In this work,we report successful experimental demonstrations of edge-enhanced in-line XPCI using energy-tunable,quasi-monochromatic AOCS X rays.With a spatial resolution of~20μm,our results clearly show the potential of high-resolution,AOCS-based XPCI applications.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
Phase retrieval is a fundamental yet challenging problem in computational imaging due to the intrinsic loss of phase information in optical measurements,leading the inverse problem highly ill-posed.Existing iterative ...Phase retrieval is a fundamental yet challenging problem in computational imaging due to the intrinsic loss of phase information in optical measurements,leading the inverse problem highly ill-posed.Existing iterative projection and model-based methods often suffer from speckle-like artifacts and limited reconstruction fidelity.Recent advances in deep learning have enabled rapid phase inference,but network-based approaches face challenges in dataset construction,generalization,and interpretability.Here,we introduce a gradient-inspired neural optimization framework that embeds a closed-form gradient from the physical forward model into the neural learning process.This hybrid design retains the interpretability and determinism of physics-based modeling while leveraging the expressive power of neural representations,enabling robust and accurate phase recovery.We demonstrate the efficacy of this approach through proof-of-principle experiments on multiplane phase retrieval and Fourier ptychographic microscopy,achieving a favorable balance between reconstruction quality and computational efficiency compared with conventional optimization and untrained network methods.Our framework establishes a unified paradigm that combines physical modeling and neural optimization,and it can be generalized to other computational imaging applications.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
Phase retrieval problems occur in a wide range of optical systems characterized by different forward path complexities.The Gerchberg–Saxton algorithm deep unrolling technique is a state-of-the-art phase retrieval met...Phase retrieval problems occur in a wide range of optical systems characterized by different forward path complexities.The Gerchberg–Saxton algorithm deep unrolling technique is a state-of-the-art phase retrieval method.Its inference speed is determined by the complexity of the forward path.We propose FourierGSNet,an efficient Gerchberg–Saxton algorithm deep unrolling method,to achieve faster phase retrieval for applications with high forward path complexities.FourierGSNet does not directly unroll Gerchberg–Saxton iterations with the forward path of the system.Instead,it extracts physics knowledge from unrolled iterations using the Fourier transform as a simplified forward path and injects the knowledge into a cascaded neural network for phase retrieval for the actual system.We evaluated FourierGSNet on three applications with three degrees of complexities:(i)coherent diffractive imaging with Fourier transform as a simple forward path,(ii)near-field X-ray imaging with Fresnel diffraction as a medium-complexity forward path,and(iii)laser beam shaping with the entire simulated optical train as a complex forward path.We compare FourierGSNet with direct unrolling,two fitting methods,and state-of-the-art data-driven methods.Experiments show that FourierGSNet is significantly faster in inference than direct unrolling on highcomplexity applications while achieving equal or higher accuracy than compared methods.展开更多
3D imaging techniques such as computed tomography,ultrasonography,and magnetic resonance imaging usually combine many scans computationally.Here,we report a 3D imaging approach using an optical-laser diffraction micro...3D imaging techniques such as computed tomography,ultrasonography,and magnetic resonance imaging usually combine many scans computationally.Here,we report a 3D imaging approach using an optical-laser diffraction microscope with two different wavelength lasers in the same orientation.A double-layered sample constructed of silica spheres is used for coherent diffraction imaging;with two lasers at 543 and 432 nm.The diffraction patterns obtained using a planar detector at a high numerical a pert are arc projected onto the Ewald spheres.3D images of the double-layered sample are successfully reconstructed from the two-color spherical diffraction patterns.展开更多
Large-scale computational imaging can provide remarkable space-bandwidth product that is beyond the limit of optical systems.In coherent imaging(CI),the joint reconstruction of amplitude and phase further expands the ...Large-scale computational imaging can provide remarkable space-bandwidth product that is beyond the limit of optical systems.In coherent imaging(CI),the joint reconstruction of amplitude and phase further expands the information throughput and sheds light on label-free observation of biological samples at micro-or even nano-levels.The existing large-scale CI techniques usually require scanning/modulation multiple times to guarantee measurement diversity and long exposure time to achieve a high signal-to-noise ratio.Such cumbersome procedures restrict clinical applications for rapid and lowphototoxicity cell imaging.In this work,a complex-domain-enhancing neural network for large-scale CI termed CI-CDNet is proposed for various large-scale CI modalities with satisfactory reconstruction quality and efficiency.CI-CDNet is able to exploit the latent coupling information between amplitude and phase(such as their same features),realizing multidimensional representations of the complex wavefront.The cross-field characterization framework empowers strong generalization and robustness for various coherent modalities,allowing high-quality and efficient imaging under extremely low exposure time and few data volume.We apply CI-CDNet in various large-scale CI modalities including Kramers–Kronigrelations holography,Fourier ptychographic microscopy,and lensless coded ptychography.A series of simulations and experiments validate that CI-CDNet can reduce exposure time and data volume by more than 1 order of magnitude.We further demonstrate that the high-quality reconstruction of CI-CDNet benefits the subsequent high-level semantic analysis.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
Phase imaging coupled to micro-tomography acquisition has emerged as a powerful tool to investigate specimens in a non-destructive manner. While the intensity data can be acquired and recorded, the phase information o...Phase imaging coupled to micro-tomography acquisition has emerged as a powerful tool to investigate specimens in a non-destructive manner. While the intensity data can be acquired and recorded, the phase information of the signal has to be “retrieved” from the data modulus only. Phase retrieval is an ill-posed non-linear problem and regularization techniques including a priori knowledge are necessary to obtain stable solutions. Several linear phase recovery methods have been proposed and it is expected that some limitations resulting from the linearization of the direct problem will be overcome by taking into account the non-linearity of the phase problem. To achieve this goal, we propose and evaluate a non-linear algorithm for in-line phase micro-tomography based on an iterative Landweber method with an analytic calculation of the Fréchet derivative of the phase-intensity relationship and of its adjoint. The algorithm was applied in the projection space using as initialization the linear mixed solution. The efficacy of the regularization scheme was evaluated on simulated objects with a slowly and a strongly varying phase. Experimental data were also acquired at ESRF using a propagation-based X-ray imaging technique for the given pixel size 0.68 μm. Two regularization scheme were considered: first the initialization was obtained without any prior on the ratio of the real and imaginary parts of the complex refractive index and secondly a constant a priori value was assumed on ?. The tomographic central slices of the refractive index decrement were compared and numerical evaluation was performed. The non-linear method globally decreases the reconstruction errors compared to the linear algorithm and is achieving better reconstruction results if no prior is introduced in the initialization solution. For in-line phase micro-tomography, this non-linear approach is a new and interesting method in biomedical studies where the exact value of the a priori ratio is not known.展开更多
同步辐射光源凭借其高亮度、高相干性等独特优势,在科研领域中取得了广泛的应用,在一众成像方法中,其与叠层成像技术的结合备受关注。叠层成像技术通过逐点交叠扫描的方式,采集样品的衍射图样,并利用冗余信息迭代重建样品的复振幅分布...同步辐射光源凭借其高亮度、高相干性等独特优势,在科研领域中取得了广泛的应用,在一众成像方法中,其与叠层成像技术的结合备受关注。叠层成像技术通过逐点交叠扫描的方式,采集样品的衍射图样,并利用冗余信息迭代重建样品的复振幅分布。随着光学成像元件的不断发展和应用场景的拓展,目前已在扫描记录过程和重建算法领域发展出了多种快速叠层成像方法。该文概述了高能同步辐射光源(High Energy Photon Source,HEPS)的进展及叠层成像的基本原理,并从飞行扫描技术、多光束扫描技术和深度学习重建算法3个方面具体介绍了同步辐射中快速叠层成像技术的最新研究进展。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
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supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0530000)the Discipline Construction Foundation of“Double World-class Project”.
文摘Laser wakefield accelerators(LWFAs)offer acceleration gradients up to 1000 times higher than those of conventional radio-frequency accelerators,offering a pathway to significantly more compact and cost-effective accelerator systems.This breakthrough opens up new possibilities for laboratory-scale light sources.All-optical inverse Compton scattering(AOCS)sources driven by LWFAs produce high-brightness,quasimonochromatic X rays with micrometer-scale source sizes,delivering the spatial coherence and resolution required for X-ray phase-contrast imaging(XPCI).These features position AOCS X-ray sources as promising tools for applications in biology,medicine,physics,and materials science.However,previous AOCS-based imaging studies have primarily focused on X-ray absorption imaging.In this work,we report successful experimental demonstrations of edge-enhanced in-line XPCI using energy-tunable,quasi-monochromatic AOCS X rays.With a spatial resolution of~20μm,our results clearly show the potential of high-resolution,AOCS-based XPCI applications.
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supported by the National Natural Science Foundation of China(Grant No.62275178)。
文摘Phase retrieval is a fundamental yet challenging problem in computational imaging due to the intrinsic loss of phase information in optical measurements,leading the inverse problem highly ill-posed.Existing iterative projection and model-based methods often suffer from speckle-like artifacts and limited reconstruction fidelity.Recent advances in deep learning have enabled rapid phase inference,but network-based approaches face challenges in dataset construction,generalization,and interpretability.Here,we introduce a gradient-inspired neural optimization framework that embeds a closed-form gradient from the physical forward model into the neural learning process.This hybrid design retains the interpretability and determinism of physics-based modeling while leveraging the expressive power of neural representations,enabling robust and accurate phase recovery.We demonstrate the efficacy of this approach through proof-of-principle experiments on multiplane phase retrieval and Fourier ptychographic microscopy,achieving a favorable balance between reconstruction quality and computational efficiency compared with conventional optimization and untrained network methods.Our framework establishes a unified paradigm that combines physical modeling and neural optimization,and it can be generalized to other computational imaging applications.
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 EU In Sha Pe Project funded by the European Union(Grant No.101058523)the AIMS5.0 Project funded by the EU Chips Joint Undertaking(Chips JU)the Dutch National Funding Agency(RVO)(Grant No.101112089)。
文摘Phase retrieval problems occur in a wide range of optical systems characterized by different forward path complexities.The Gerchberg–Saxton algorithm deep unrolling technique is a state-of-the-art phase retrieval method.Its inference speed is determined by the complexity of the forward path.We propose FourierGSNet,an efficient Gerchberg–Saxton algorithm deep unrolling method,to achieve faster phase retrieval for applications with high forward path complexities.FourierGSNet does not directly unroll Gerchberg–Saxton iterations with the forward path of the system.Instead,it extracts physics knowledge from unrolled iterations using the Fourier transform as a simplified forward path and injects the knowledge into a cascaded neural network for phase retrieval for the actual system.We evaluated FourierGSNet on three applications with three degrees of complexities:(i)coherent diffractive imaging with Fourier transform as a simple forward path,(ii)near-field X-ray imaging with Fresnel diffraction as a medium-complexity forward path,and(iii)laser beam shaping with the entire simulated optical train as a complex forward path.We compare FourierGSNet with direct unrolling,two fitting methods,and state-of-the-art data-driven methods.Experiments show that FourierGSNet is significantly faster in inference than direct unrolling on highcomplexity applications while achieving equal or higher accuracy than compared methods.
基金supported by the Major State Basic Research Development Program of China(No.2014CB910401)the National Natural Science Foundation of China(Nos.31430031,21390414,and U1332118)
文摘3D imaging techniques such as computed tomography,ultrasonography,and magnetic resonance imaging usually combine many scans computationally.Here,we report a 3D imaging approach using an optical-laser diffraction microscope with two different wavelength lasers in the same orientation.A double-layered sample constructed of silica spheres is used for coherent diffraction imaging;with two lasers at 543 and 432 nm.The diffraction patterns obtained using a planar detector at a high numerical a pert are arc projected onto the Ewald spheres.3D images of the double-layered sample are successfully reconstructed from the two-color spherical diffraction patterns.
基金supported by the National Natural Science Foundation of China(Grant Nos.61827901,61991451,62131003)the BIT Research and Innovation Promoting Project(Grant No.2022YCXZ006).
文摘Large-scale computational imaging can provide remarkable space-bandwidth product that is beyond the limit of optical systems.In coherent imaging(CI),the joint reconstruction of amplitude and phase further expands the information throughput and sheds light on label-free observation of biological samples at micro-or even nano-levels.The existing large-scale CI techniques usually require scanning/modulation multiple times to guarantee measurement diversity and long exposure time to achieve a high signal-to-noise ratio.Such cumbersome procedures restrict clinical applications for rapid and lowphototoxicity cell imaging.In this work,a complex-domain-enhancing neural network for large-scale CI termed CI-CDNet is proposed for various large-scale CI modalities with satisfactory reconstruction quality and efficiency.CI-CDNet is able to exploit the latent coupling information between amplitude and phase(such as their same features),realizing multidimensional representations of the complex wavefront.The cross-field characterization framework empowers strong generalization and robustness for various coherent modalities,allowing high-quality and efficient imaging under extremely low exposure time and few data volume.We apply CI-CDNet in various large-scale CI modalities including Kramers–Kronigrelations holography,Fourier ptychographic microscopy,and lensless coded ptychography.A series of simulations and experiments validate that CI-CDNet can reduce exposure time and data volume by more than 1 order of magnitude.We further demonstrate that the high-quality reconstruction of CI-CDNet benefits the subsequent high-level semantic analysis.
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.
文摘Phase imaging coupled to micro-tomography acquisition has emerged as a powerful tool to investigate specimens in a non-destructive manner. While the intensity data can be acquired and recorded, the phase information of the signal has to be “retrieved” from the data modulus only. Phase retrieval is an ill-posed non-linear problem and regularization techniques including a priori knowledge are necessary to obtain stable solutions. Several linear phase recovery methods have been proposed and it is expected that some limitations resulting from the linearization of the direct problem will be overcome by taking into account the non-linearity of the phase problem. To achieve this goal, we propose and evaluate a non-linear algorithm for in-line phase micro-tomography based on an iterative Landweber method with an analytic calculation of the Fréchet derivative of the phase-intensity relationship and of its adjoint. The algorithm was applied in the projection space using as initialization the linear mixed solution. The efficacy of the regularization scheme was evaluated on simulated objects with a slowly and a strongly varying phase. Experimental data were also acquired at ESRF using a propagation-based X-ray imaging technique for the given pixel size 0.68 μm. Two regularization scheme were considered: first the initialization was obtained without any prior on the ratio of the real and imaginary parts of the complex refractive index and secondly a constant a priori value was assumed on ?. The tomographic central slices of the refractive index decrement were compared and numerical evaluation was performed. The non-linear method globally decreases the reconstruction errors compared to the linear algorithm and is achieving better reconstruction results if no prior is introduced in the initialization solution. For in-line phase micro-tomography, this non-linear approach is a new and interesting method in biomedical studies where the exact value of the a priori ratio is not known.
文摘同步辐射光源凭借其高亮度、高相干性等独特优势,在科研领域中取得了广泛的应用,在一众成像方法中,其与叠层成像技术的结合备受关注。叠层成像技术通过逐点交叠扫描的方式,采集样品的衍射图样,并利用冗余信息迭代重建样品的复振幅分布。随着光学成像元件的不断发展和应用场景的拓展,目前已在扫描记录过程和重建算法领域发展出了多种快速叠层成像方法。该文概述了高能同步辐射光源(High Energy Photon Source,HEPS)的进展及叠层成像的基本原理,并从飞行扫描技术、多光束扫描技术和深度学习重建算法3个方面具体介绍了同步辐射中快速叠层成像技术的最新研究进展。
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.
