We propose a high-accuracy artifacts-free single-frame digital holographic phase demodulation scheme for relatively lowcarrier frequency holograms-deep learning assisted variational Hilbert quantitative phase imaging(...We propose a high-accuracy artifacts-free single-frame digital holographic phase demodulation scheme for relatively lowcarrier frequency holograms-deep learning assisted variational Hilbert quantitative phase imaging(DL-VHQPI).The method,incorporating a conventional deep neural network into a complete physical model utilizing the idea of residual compensation,reliably and robustly recovers the quantitative phase information of the test objects.It can significantly alleviate spectrum-overlapping-caused phase artifacts under the slightly off-axis digital holographic system.Compared to the conventional end-to-end networks(without a physical model),the proposed method can reduce the dataset size dramatically while maintaining the imaging quality and model generalization.The DL-VHQPI is quantitatively studied by numerical simulation.The live-cell experiment is designed to demonstrate the method's practicality in biological research.The proposed idea of the deep learning-assisted physical model might be extended to diverse computational imaging techniques.展开更多
This paper proposed a high-sensitivity phase imaging eddy current magneto-optical (PI-ECMO) system for carbon fiber reinforced polymer (CFRP) defect detection. In contrast to other eddy current-based detection systems...This paper proposed a high-sensitivity phase imaging eddy current magneto-optical (PI-ECMO) system for carbon fiber reinforced polymer (CFRP) defect detection. In contrast to other eddy current-based detection systems, the proposed system employs a fixed position excitation coil while enabling the detection point to move within the detection region. This configuration effectively mitigates the interference caused by the lift-off effect, which is commonly observed in systems with moving excitation coils. Correspondingly, the relationship between the defect characteristics (orientation and position) and the surface vertical magnetic field distribution (amplitude and phase) is studied in detail by theoretical analysis and numerical simulations. Experiments conducted on woven CFRP plates demonstrate that the designed PI-ECMO system is capable of effectively detecting both surface and internal cracks, as well as impact defects. The excitation current is significantly reduced compared with traditional eddy current magneto-optical (ECMO) systems.展开更多
A possible novel application of hard x-ray emitted during laser-plasma interaction was discussed. We established an Optical Transform Function to study the joint effect of the spectral distribution and temporal profil...A possible novel application of hard x-ray emitted during laser-plasma interaction was discussed. We established an Optical Transform Function to study the joint effect of the spectral distribution and temporal profile of the laser-produced x-ray on x-ray phase imaging. Though the laser-produced x-ray pulse duration is short and incoherent, the analysis confirms that the current x-ray phase imaging theory still holds for laser-produced x-ray phase imaging.展开更多
Quantitative phase imaging(QPI)is a label-free technique that provides optical path length information for transparent specimens,finding utility in biology,materials science,and engineering.Here,we present QPI of a th...Quantitative phase imaging(QPI)is a label-free technique that provides optical path length information for transparent specimens,finding utility in biology,materials science,and engineering.Here,we present QPI of a three-dimensional(3D)stack of phase-only objects using a wavelength-multiplexed diffractive optical processor.Utilizing multiple spatially engineered diffractive layers trained through deep learning,this diffractive processor can transform the phase distributions of multiple two-dimensional objects at various axial positions into intensity patterns,each encoded at a unique wavelength channel.These wavelength-multiplexed patterns are projected onto a single field of view at the output plane of the diffractive processor,enabling the capture of quantitative phase distributions of input objects located at different axial planes using an intensity-only image sensor.Based on numerical simulations,we show that our diffractive processor could simultaneously achieve all-optical QPI across several distinct axial planes at the input by scanning the illumination wavelength.A proof-of-concept experiment with a 3D-fabricated diffractive processor further validates our approach,showcasing successful imaging of two distinct phase objects at different axial positions by scanning the illumination wavelength in the terahertz spectrum.Diffractive network-based multiplane QPI designs can open up new avenues for compact on-chip phase imaging and sensing devices.展开更多
The low-density imaging performance of a zone plate-based nano-resolution hard x-ray computed tomography(CT)system can be significantly improved by incorporating a grating-based Lau interferometer. Due to the diffract...The low-density imaging performance of a zone plate-based nano-resolution hard x-ray computed tomography(CT)system can be significantly improved by incorporating a grating-based Lau interferometer. Due to the diffraction, however,the acquired nano-resolution phase signal may suffer splitting problem, which impedes the direct reconstruction of phase contrast CT(nPCT) images. To overcome, a new model-driven nPCT image reconstruction algorithm is developed in this study. In it, the diffraction procedure is mathematically modeled into a matrix B, from which the projections without signal splitting can be generated invertedly. Furthermore, a penalized weighted least-square model with total variation(PWLSTV) is employed to denoise these projections, from which nPCT images with high accuracy are directly reconstructed.Numerical experiments demonstrate that this new algorithm is able to work with phase projections having any splitting distances. Moreover, results also reveal that nPCT images of higher signal-to-noise-ratio(SNR) could be reconstructed from projections having larger splitting distances. In summary, a novel model-driven nPCT image reconstruction algorithm with high accuracy and robustness is verified for the Lau interferometer-based hard x-ray nano-resolution phase contrast imaging.展开更多
The optical design of near-infrared phase contrast imaging(NI-PCI)diagnosis on HL-2A is introduced in this paper.This scheme benefits from the great progress of near-infrared laser technology and is a broadening of tr...The optical design of near-infrared phase contrast imaging(NI-PCI)diagnosis on HL-2A is introduced in this paper.This scheme benefits from the great progress of near-infrared laser technology and is a broadening of traditional phase contrast technology.This diagnostic can work as a keen tool to measure plasma wavenumber spectra by inferring string-integrated plasma density fluctuations.Design of both the front optical path which is the path before the laser transmitting into the tokamak plasma and the rear optics which is the path after the laser passing through the plasma is detailed.The 1550 nm laser is chosen as the probe beam and highprecision optical components are designed to fit the laser beam,in which a phase plate with a 194-nm-deep silver groove is the key.Compared with the conventional 10.6μm laser-based PCI system on HL-2A,NI-PCI significantly overcomes the unwanted phase scintillation effect and promotes the measurement capability of high-wavenumber turbulence with an increased maximal measurable wavenumber from 15 cm^(-1)to 32.6 cm^(-1).展开更多
Quantitative phase imaging(QPI)has emerged as a valuable tool for biomedical research thanks to its unique capabilities for quantifying optical thickness variation of living cells and tissues.Among many QPI methods,Fo...Quantitative phase imaging(QPI)has emerged as a valuable tool for biomedical research thanks to its unique capabilities for quantifying optical thickness variation of living cells and tissues.Among many QPI methods,Fourier ptychographic microscopy(FPM)allows long-term label-free observation and quantitative analysis of large cell populations without compromising spatial and temporal resolution.However,high spatio-temporal resolution imaging over a long-time scale(from hours to days)remains a critical challenge:optically inhomogeneous structure of biological specimens as well as mechanical perturbations and thermal fluctuations of the microscope body all result in time-varying aberration and focus drifts,significantly degrading the imaging performance for long-term study.Moreover,the aberrations are sample-and environmentdependent,and cannot be compensated by a fixed optical design,thus necessitating rapid dynamic correction in the imaging process.Here,we report an adaptive optical QPI method based on annular illumination FPM.In this method,the annular matched illumination configuration(i.e.,the illumination numerical aperture(NA)strictly equals to the objective NA),which is the key for recovering low-frequency phase information,is further utilized for the accurate imaging aberration characterization.By using only 6 low-resolution images captured with 6 different illumination angles matching the NA of a 10x,0.4 NA objective,we recover high-resolution quantitative phase images(synthetic NA of 0.8)and characterize the aberrations in real time,restoring the optimum resolution of the system adaptively.Applying our method to live-cell imaging,we achieve diffraction-limited performance(full-pitch resolution of 655 nm at a wavelength of 525 nm)across a wide field of view(1.77mm2)over an extended period of time.展开更多
Quantitative phase imaging(QPI)is a label-free computational imaging technique used in various fields,including biology and medical research.Modern QPI systems typically rely on digital processing using iterative algo...Quantitative phase imaging(QPI)is a label-free computational imaging technique used in various fields,including biology and medical research.Modern QPI systems typically rely on digital processing using iterative algorithms for phase retrieval and image reconstruction.Here,we report a diffractive optical network trained to convert the phase information of input objects positioned behind random diffusers into intensity variations at the output plane,all-optically performing phase recovery and quantitative imaging of phase objects completely hidden by unknown,random phase diffusers.This QPI diffractive network is composed of successive diffractive layers,axially spanning in total~70λ,where is the illumination wavelength;unlike existing digital image reconstruction and phase retrieval methods,it forms an all-optical processor that does not require external power beyond the illumination beam to complete its QPI reconstruction at the speed of light propagation.This all-optical diffractive processor can provide a low-power,high frame rate and compact alternative for quantitative imaging of phase objects through random,unknown diffusers and can operate at different parts of the electromagnetic spectrum for various applications in biomedical imaging and sensing.The presented QPI diffractive designs can be integrated onto the active area of standard CCD/CMOS-based image sensors to convert an existing optical microscope into a diffractive QPI microscope,performing phase recovery and image reconstruction on a chip through light diffraction within passive structured layers.展开更多
Holography provides access to the optical phase.The emerging compressive phase retrieval approach can achieve in-line holographic imaging beyond the information-theoretic limit or even from a single shot by exploring ...Holography provides access to the optical phase.The emerging compressive phase retrieval approach can achieve in-line holographic imaging beyond the information-theoretic limit or even from a single shot by exploring the signal priors.However,iterative projection methods based on physical knowledge of the wavefield suffer from poor imaging quality,whereas the regularization techniques sacrifice robustness for fidelity.In this work,we present a unified compressive phase retrieval framework for in-line holography that encapsulates the unique advantages of both physical constraints and sparsity priors.In particular,a constrained complex total variation(CCTV)regularizer is introduced that explores the well-known absorption and support constraints together with sparsity in the gradient domain,enabling practical high-quality in-line holographic imaging from a single intensity image.We developed efficient solvers based on the proximal gradient method for the non-smooth regularized inverse problem and the corresponding denoising subproblem.Theoretical analyses further guarantee the convergence of the algorithms with prespecified parameters,obviating the need for manual parameter tuning.As both simulated and optical experiments demonstrate,the proposed CCTV model can characterize complex natural scenes while utilizing physically tractable constraints for quality enhancement.This new compressive phase retrieval approach can be extended,with minor adjustments,to various imaging configurations,sparsifying operators,and physical knowledge.It may cast new light on both theoretical and empirical studies.展开更多
X-ray speckle tracking based methods can provide results with best reported angular accuracy up to 2 nrad. However,duo to the multi-frame requirement for phase retrieval and the possible instability of the x-ray beam,...X-ray speckle tracking based methods can provide results with best reported angular accuracy up to 2 nrad. However,duo to the multi-frame requirement for phase retrieval and the possible instability of the x-ray beam, mechanical and background vibration, the actual accuracy will inevitably be degraded by these time-dependent fluctuations. Therefore,not only spatial position, but also temporal features of the speckle patterns need to be considered in order to maintain the superiority of the speckle-based methods. In this paper, we propose a parallel acquisition method with advantages of real time and high accuracy, which has potential applicability to dynamic samples imaging as well as on-line beam monitoring.Through simulations, we demonstrate that the proposed method can reduce the phase error caused by the fluctuations to1% at most compared with current speckle tracking methods. Meanwhile, it can keep the accuracy deterioration within0.03 nrad, making the high theoretical accuracy a reality. Also, we find that waveforms of the incident beam have a little impact on the phase retrieved and will not influence the actual accuracy, which relaxes the requirements for speckle-based experiments.展开更多
The principle of ptychography is applied in known plain text attack on the double random phase encoding （DRPE） system. We find that with several pairs of plain texts and cipher texts, the model of attack on DRPE can...The principle of ptychography is applied in known plain text attack on the double random phase encoding （DRPE） system. We find that with several pairs of plain texts and cipher texts, the model of attack on DRPE can be converted to the model of ptyehographical imaging. Owing to the inherent merits of the ptyehographical imaging, the DRPE system can be breached totally in a fast and nearly perfect way, which is unavailable for currently existing attack methods. Further, since the decryption keys can be seen as an object to be imaged from the perspective of imaging, the ptychographical technique may be a kind of new direction to further analysis of the security of other encryption systems based on double random keys.展开更多
We propose and implement a wide-field vibrational phase contrast detection to obtain imaging of imaginary components of third-order nonlinear susceptibility in a coherent anti-Stokes Raman scattering （CARS） microsco...We propose and implement a wide-field vibrational phase contrast detection to obtain imaging of imaginary components of third-order nonlinear susceptibility in a coherent anti-Stokes Raman scattering （CARS） microscope with full suppression of the non-resonant background. This technique is based on the unique ability of recovering the phase of the generated CARS signal based on holographic recording. By capturing the phase distributions of the generated CARS field from the sample and from the environment under resonant illumination, we demonstrate the retrieval of imaginary components in the CARS microscope and achieve background free coherent Raman imaging.展开更多
X-ray grating interferometer has attracted widely attention in the past years due to its capability in achieving x-ray phase contrast imaging with low brilliance source. However, the widely used phase stepping informa...X-ray grating interferometer has attracted widely attention in the past years due to its capability in achieving x-ray phase contrast imaging with low brilliance source. However, the widely used phase stepping information extraction method reduces system stability and prolongs data acquisition time by several times compared with conventional x-ray absorption- based imaging. The mechanical stepping can be avoided by using a staggered grating, but at the cost of low vertical spatial resolution. In this paper, employing a modified staggered grating and the angular signal radiography, we proposed a single-shot grating-based x-ray differential phase contrast imaging with decent vertical spatial resolution. The theoretical framework was deduced and proved by numerical experiments. Absorption, phase, and scattering computed tomography can be performed without phase stepping. Therefore, we believe this fast and highly stable imaging method with decent resolution would be widely applied in x-ray grating-based phase contrast imaging.展开更多
A fast and simple method to extract phase-contrast images from interferograms is proposed, and its effectiveness is demonstrated through simulation and experiment. For x-ray differential phase contrast imaging, a stro...A fast and simple method to extract phase-contrast images from interferograms is proposed, and its effectiveness is demonstrated through simulation and experiment. For x-ray differential phase contrast imaging, a strong attenuation signal acts as an overwhelming background intensity that obscures the weak phase signal so that no obvious phase-gradient information is detectable in the raw image. By subtracting one interferogram from another, chosen at particular intervals,the phase signal can be isolated and magnified.展开更多
Non-interferometric X-ray quantitative phase imaging(XQPI),much simpler than the interferometric scheme,has provided high-resolution and reliable phase-contrast images.We report on implementing the volumetric XQPI ima...Non-interferometric X-ray quantitative phase imaging(XQPI),much simpler than the interferometric scheme,has provided high-resolution and reliable phase-contrast images.We report on implementing the volumetric XQPI images using concurrent-bidirectional scanning of the orthogonal plane on the optical axis of the Foucault differential filter;we then extracted data in conjunction with the transport-intensity equation.The volumetric image of the laminate microstructure of the gills of a fish was successfully reconstructed to demonstrate our XQPI method.The method can perform 3D rendering without any rotational motion for laterally extended objects by manipulating incoherent X-rays using the pinhole array.展开更多
In-line x-ray phase contrast imaging has attracted much attention due to two major advantages： its effectiveness in imaging weakly absorbing materials, and the simplicity of its facilities. In this paper a comprehens...In-line x-ray phase contrast imaging has attracted much attention due to two major advantages： its effectiveness in imaging weakly absorbing materials, and the simplicity of its facilities. In this paper a comprehensive theory based on Wigner distribution developed by Wu and Liu [Med. Phys. 31 2378-2384 （2004）] is reviewed. The influence of x-ray source and detector on the image is discussed. Experiments using a microfocus x-ray source and a CCD detector are conducted, which show the role of two key factors on imaging： the tube voltage and tube current. High tube current and moderate tube voltage are suggested for imaging.展开更多
A general theoretical framework is presented to explain the formation of the phase signal in an x-ray microscope integrated with a grating interferometer,which simultaneously enables the high spatial resolution imagin...A general theoretical framework is presented to explain the formation of the phase signal in an x-ray microscope integrated with a grating interferometer,which simultaneously enables the high spatial resolution imaging and the improved image contrast.By using this theory,several key parameters of phase contrast imaging can be predicted,for instance,the fringe visibility and period,and the conversion condition from the differential phase imaging(DPI)to the phase difference imaging(PDI).Additionally,numerical simulations are performed with certain x-ray optical components and imaging geometry.Comparison with the available experimental measurement[Appl.Phys.Lett.113063105(2018)]demonstrates the accuracy of this developed quantitative analysis method of x-ray phase-sensitive microscope imaging.展开更多
Compared with the conventional X-ray absorption imaging, the X-ray phase-contrast imaging shows higher contrast on samples with low attenuation coefficient like blood vessels and soft tissues. Among the modalities of ...Compared with the conventional X-ray absorption imaging, the X-ray phase-contrast imaging shows higher contrast on samples with low attenuation coefficient like blood vessels and soft tissues. Among the modalities of phase-contrast imaging, the grating-based phase contrast imaging has been widely accepted owing to the advantage of wide range of sample selections and exemption of coherent source. However, the downside is the substantially larger amount of data generated from the phase-stepping method which slows down the reconstruction process. Graphic processing unit(GPU) has the advantage of allowing parallel computing which is very useful for large quantity data processing. In this paper, a compute unified device architecture(CUDA) C program based on GPU is introduced to accelerate the phase retrieval and filtered back projection(FBP) algorithm for grating-based tomography. Depending on the size of the data, the CUDA C program shows different amount of speed-up over the standard C program on the same Visual Studio 2010 platform. Meanwhile, the speed-up ratio increases as the size of data increases.展开更多
In theory, we find that the actual function of the analyzer grating in the Talbot–Lau interferometer is segmenting the self-images of the phase grating and choosing integral areas, which make sure that each period of...In theory, we find that the actual function of the analyzer grating in the Talbot–Lau interferometer is segmenting the self-images of the phase grating and choosing integral areas, which make sure that each period of self-images in one detector pixel contributes the same signal to the detector. Furthermore, in the case of the lack of an analyzer grating, the shifting curves are still existent in theory as long as the number of fringes is non-integral in a detector pixel, which is a sufficient condition for creating shifting curve. The sufficient condition is available for not only the Talbot–Lau interferometer and the inverse geometry of Talbot–Lau interferometer, but also the x-ray phase contrast imaging system based on geometrical optics. In practical applications, we propose a method to improve the performances of the existing systems by employing the sufficient condition. This method can shorten the system length, is applicable to large period gratings, and can use the detectors with large pixels and large field of view. In addition, the experimental arrangement can be simplified due to the lack of an analyzer grating. In order to improve detection sensitivity and resolution, we also give an optimal fringe period.We believe that the theory and method proposed here is a step forward for x-ray phase contrast imaging.展开更多
A phase contrast imaging（PCI） diagnostic has recently been developed on HL-2 A tokamak. It can diagnose plasma density fluctuations with maximum wave number of 15 cm^（-1） and wave number resolution of 2 cm^（-1）....A phase contrast imaging（PCI） diagnostic has recently been developed on HL-2 A tokamak. It can diagnose plasma density fluctuations with maximum wave number of 15 cm^（-1） and wave number resolution of 2 cm^（-1）. The time resolution reaches 2 μs. A 10.6 μm CO_2 laser is expanded to a beam with a diameter of 30 mm and injected into the plasma as an incident beam,injecting into plasma. The emerging scattered and unscattered beams are contrasted by a phase plate. The ideas of optical path design are presented in this paper, together with the parameters of the main optical components. The whole optical path of PCI is not only carefully designed, but also constructed on HL-2 A. First calibration results show the ability of this system to catch plasma turbulence in a wide frequency domain.展开更多
基金We are grateful for financial supports from the National Natural Science Foundation of China(61905115,62105151,62175109,U21B2033,62227818)Leading Technology of Jiangsu Basic Research Plan(BK20192003)+5 种基金Youth Foundation of Jiangsu Province(BK20190445,BK20210338)Biomedical Competition Foundation of Jiangsu Province(BE2022847)Key National Industrial Technology Cooperation Foundation of Jiangsu Province(BZ2022039)Fundamental Research Funds for the Central Universities(30920032101)Open Research Fund of Jiangsu Key Laboratory of Spectral Imaging&Intelligent Sense(JSGP202105,JSGP202201)National Science Center,Poland(2020/37/B/ST7/03629).The authors thank F.Sun for her contribution to this paper in terms of language expression and grammatical correction.
文摘We propose a high-accuracy artifacts-free single-frame digital holographic phase demodulation scheme for relatively lowcarrier frequency holograms-deep learning assisted variational Hilbert quantitative phase imaging(DL-VHQPI).The method,incorporating a conventional deep neural network into a complete physical model utilizing the idea of residual compensation,reliably and robustly recovers the quantitative phase information of the test objects.It can significantly alleviate spectrum-overlapping-caused phase artifacts under the slightly off-axis digital holographic system.Compared to the conventional end-to-end networks(without a physical model),the proposed method can reduce the dataset size dramatically while maintaining the imaging quality and model generalization.The DL-VHQPI is quantitatively studied by numerical simulation.The live-cell experiment is designed to demonstrate the method's practicality in biological research.The proposed idea of the deep learning-assisted physical model might be extended to diverse computational imaging techniques.
基金the National Natural Science Foundation of China under Grants No.U2030205,No.62003075,No.61903065,and No.62003074Sichuan Science and Technology Planning Project under Grant No.2022JDJQ0040.
文摘This paper proposed a high-sensitivity phase imaging eddy current magneto-optical (PI-ECMO) system for carbon fiber reinforced polymer (CFRP) defect detection. In contrast to other eddy current-based detection systems, the proposed system employs a fixed position excitation coil while enabling the detection point to move within the detection region. This configuration effectively mitigates the interference caused by the lift-off effect, which is commonly observed in systems with moving excitation coils. Correspondingly, the relationship between the defect characteristics (orientation and position) and the surface vertical magnetic field distribution (amplitude and phase) is studied in detail by theoretical analysis and numerical simulations. Experiments conducted on woven CFRP plates demonstrate that the designed PI-ECMO system is capable of effectively detecting both surface and internal cracks, as well as impact defects. The excitation current is significantly reduced compared with traditional eddy current magneto-optical (ECMO) systems.
基金This work is supported in part by the National Natural Science Foundation of China under Grant No. 69978023.
文摘A possible novel application of hard x-ray emitted during laser-plasma interaction was discussed. We established an Optical Transform Function to study the joint effect of the spectral distribution and temporal profile of the laser-produced x-ray on x-ray phase imaging. Though the laser-produced x-ray pulse duration is short and incoherent, the analysis confirms that the current x-ray phase imaging theory still holds for laser-produced x-ray phase imaging.
基金supported by the U.S.Department of Energy,Office of Basic Energy Sciences,Division of Materials Sciences and Engineering(Grant No.DE-SC0023088).
文摘Quantitative phase imaging(QPI)is a label-free technique that provides optical path length information for transparent specimens,finding utility in biology,materials science,and engineering.Here,we present QPI of a three-dimensional(3D)stack of phase-only objects using a wavelength-multiplexed diffractive optical processor.Utilizing multiple spatially engineered diffractive layers trained through deep learning,this diffractive processor can transform the phase distributions of multiple two-dimensional objects at various axial positions into intensity patterns,each encoded at a unique wavelength channel.These wavelength-multiplexed patterns are projected onto a single field of view at the output plane of the diffractive processor,enabling the capture of quantitative phase distributions of input objects located at different axial planes using an intensity-only image sensor.Based on numerical simulations,we show that our diffractive processor could simultaneously achieve all-optical QPI across several distinct axial planes at the input by scanning the illumination wavelength.A proof-of-concept experiment with a 3D-fabricated diffractive processor further validates our approach,showcasing successful imaging of two distinct phase objects at different axial positions by scanning the illumination wavelength in the terahertz spectrum.Diffractive network-based multiplane QPI designs can open up new avenues for compact on-chip phase imaging and sensing devices.
基金Project supported by the National Natural Science Foundation of China(Grant No.12027812)the Guangdong Basic and Applied Basic Research Foundation of Guangdong Province,China(Grant No.2021A1515111031)。
文摘The low-density imaging performance of a zone plate-based nano-resolution hard x-ray computed tomography(CT)system can be significantly improved by incorporating a grating-based Lau interferometer. Due to the diffraction, however,the acquired nano-resolution phase signal may suffer splitting problem, which impedes the direct reconstruction of phase contrast CT(nPCT) images. To overcome, a new model-driven nPCT image reconstruction algorithm is developed in this study. In it, the diffraction procedure is mathematically modeled into a matrix B, from which the projections without signal splitting can be generated invertedly. Furthermore, a penalized weighted least-square model with total variation(PWLSTV) is employed to denoise these projections, from which nPCT images with high accuracy are directly reconstructed.Numerical experiments demonstrate that this new algorithm is able to work with phase projections having any splitting distances. Moreover, results also reveal that nPCT images of higher signal-to-noise-ratio(SNR) could be reconstructed from projections having larger splitting distances. In summary, a novel model-driven nPCT image reconstruction algorithm with high accuracy and robustness is verified for the Lau interferometer-based hard x-ray nano-resolution phase contrast imaging.
基金supported by the National Key Research and Development Program of China(Nos.2019YFE03090100 and 2022YFE03100002)National Natural Science Foundation of China(No.12075241)。
文摘The optical design of near-infrared phase contrast imaging(NI-PCI)diagnosis on HL-2A is introduced in this paper.This scheme benefits from the great progress of near-infrared laser technology and is a broadening of traditional phase contrast technology.This diagnostic can work as a keen tool to measure plasma wavenumber spectra by inferring string-integrated plasma density fluctuations.Design of both the front optical path which is the path before the laser transmitting into the tokamak plasma and the rear optics which is the path after the laser passing through the plasma is detailed.The 1550 nm laser is chosen as the probe beam and highprecision optical components are designed to fit the laser beam,in which a phase plate with a 194-nm-deep silver groove is the key.Compared with the conventional 10.6μm laser-based PCI system on HL-2A,NI-PCI significantly overcomes the unwanted phase scintillation effect and promotes the measurement capability of high-wavenumber turbulence with an increased maximal measurable wavenumber from 15 cm^(-1)to 32.6 cm^(-1).
基金supported by the National Natural Science Foundation of China(61905115,62105151,62175109,U21B2033,62105156)Leading Technology of Jiangsu Basic Research Plan(BK20192003),Youth Foundation of Jiangsu Province(BK20190445,BK20210338)+1 种基金Fundamental Research Funds for the Central Universities(30920032101)Open Research Fund of Jiangsu Key Laboratory of Spectral Imaging&Intelligent Sense(JSGP202105,JSGP202201).
文摘Quantitative phase imaging(QPI)has emerged as a valuable tool for biomedical research thanks to its unique capabilities for quantifying optical thickness variation of living cells and tissues.Among many QPI methods,Fourier ptychographic microscopy(FPM)allows long-term label-free observation and quantitative analysis of large cell populations without compromising spatial and temporal resolution.However,high spatio-temporal resolution imaging over a long-time scale(from hours to days)remains a critical challenge:optically inhomogeneous structure of biological specimens as well as mechanical perturbations and thermal fluctuations of the microscope body all result in time-varying aberration and focus drifts,significantly degrading the imaging performance for long-term study.Moreover,the aberrations are sample-and environmentdependent,and cannot be compensated by a fixed optical design,thus necessitating rapid dynamic correction in the imaging process.Here,we report an adaptive optical QPI method based on annular illumination FPM.In this method,the annular matched illumination configuration(i.e.,the illumination numerical aperture(NA)strictly equals to the objective NA),which is the key for recovering low-frequency phase information,is further utilized for the accurate imaging aberration characterization.By using only 6 low-resolution images captured with 6 different illumination angles matching the NA of a 10x,0.4 NA objective,we recover high-resolution quantitative phase images(synthetic NA of 0.8)and characterize the aberrations in real time,restoring the optimum resolution of the system adaptively.Applying our method to live-cell imaging,we achieve diffraction-limited performance(full-pitch resolution of 655 nm at a wavelength of 525 nm)across a wide field of view(1.77mm2)over an extended period of time.
文摘Quantitative phase imaging(QPI)is a label-free computational imaging technique used in various fields,including biology and medical research.Modern QPI systems typically rely on digital processing using iterative algorithms for phase retrieval and image reconstruction.Here,we report a diffractive optical network trained to convert the phase information of input objects positioned behind random diffusers into intensity variations at the output plane,all-optically performing phase recovery and quantitative imaging of phase objects completely hidden by unknown,random phase diffusers.This QPI diffractive network is composed of successive diffractive layers,axially spanning in total~70λ,where is the illumination wavelength;unlike existing digital image reconstruction and phase retrieval methods,it forms an all-optical processor that does not require external power beyond the illumination beam to complete its QPI reconstruction at the speed of light propagation.This all-optical diffractive processor can provide a low-power,high frame rate and compact alternative for quantitative imaging of phase objects through random,unknown diffusers and can operate at different parts of the electromagnetic spectrum for various applications in biomedical imaging and sensing.The presented QPI diffractive designs can be integrated onto the active area of standard CCD/CMOS-based image sensors to convert an existing optical microscope into a diffractive QPI microscope,performing phase recovery and image reconstruction on a chip through light diffraction within passive structured layers.
基金the National Natural Science Foundation of China(Grant No.61827825)for financial support.
文摘Holography provides access to the optical phase.The emerging compressive phase retrieval approach can achieve in-line holographic imaging beyond the information-theoretic limit or even from a single shot by exploring the signal priors.However,iterative projection methods based on physical knowledge of the wavefield suffer from poor imaging quality,whereas the regularization techniques sacrifice robustness for fidelity.In this work,we present a unified compressive phase retrieval framework for in-line holography that encapsulates the unique advantages of both physical constraints and sparsity priors.In particular,a constrained complex total variation(CCTV)regularizer is introduced that explores the well-known absorption and support constraints together with sparsity in the gradient domain,enabling practical high-quality in-line holographic imaging from a single intensity image.We developed efficient solvers based on the proximal gradient method for the non-smooth regularized inverse problem and the corresponding denoising subproblem.Theoretical analyses further guarantee the convergence of the algorithms with prespecified parameters,obviating the need for manual parameter tuning.As both simulated and optical experiments demonstrate,the proposed CCTV model can characterize complex natural scenes while utilizing physically tractable constraints for quality enhancement.This new compressive phase retrieval approach can be extended,with minor adjustments,to various imaging configurations,sparsifying operators,and physical knowledge.It may cast new light on both theoretical and empirical studies.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11675253 and 11505278)。
文摘X-ray speckle tracking based methods can provide results with best reported angular accuracy up to 2 nrad. However,duo to the multi-frame requirement for phase retrieval and the possible instability of the x-ray beam, mechanical and background vibration, the actual accuracy will inevitably be degraded by these time-dependent fluctuations. Therefore,not only spatial position, but also temporal features of the speckle patterns need to be considered in order to maintain the superiority of the speckle-based methods. In this paper, we propose a parallel acquisition method with advantages of real time and high accuracy, which has potential applicability to dynamic samples imaging as well as on-line beam monitoring.Through simulations, we demonstrate that the proposed method can reduce the phase error caused by the fluctuations to1% at most compared with current speckle tracking methods. Meanwhile, it can keep the accuracy deterioration within0.03 nrad, making the high theoretical accuracy a reality. Also, we find that waveforms of the incident beam have a little impact on the phase retrieved and will not influence the actual accuracy, which relaxes the requirements for speckle-based experiments.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61575197 and 61307018the K.C.Wong Education Foundation,the President Fund of University of Chinese Academy of Sciencesthe Fusion Funds of Research and Education of Chinese Academy of Sciences
文摘The principle of ptychography is applied in known plain text attack on the double random phase encoding （DRPE） system. We find that with several pairs of plain texts and cipher texts, the model of attack on DRPE can be converted to the model of ptyehographical imaging. Owing to the inherent merits of the ptyehographical imaging, the DRPE system can be breached totally in a fast and nearly perfect way, which is unavailable for currently existing attack methods. Further, since the decryption keys can be seen as an object to be imaged from the perspective of imaging, the ptychographical technique may be a kind of new direction to further analysis of the security of other encryption systems based on double random keys.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11174019,61322509 and 11121091the National Basic Research Program of China under Grant No 2013CB921904
文摘We propose and implement a wide-field vibrational phase contrast detection to obtain imaging of imaginary components of third-order nonlinear susceptibility in a coherent anti-Stokes Raman scattering （CARS） microscope with full suppression of the non-resonant background. This technique is based on the unique ability of recovering the phase of the generated CARS signal based on holographic recording. By capturing the phase distributions of the generated CARS field from the sample and from the environment under resonant illumination, we demonstrate the retrieval of imaginary components in the CARS microscope and achieve background free coherent Raman imaging.
基金supported by the National Natural Science Foundation of China(Grant Nos.11275204,11475175,and 11405175)the China Postdoctoral Science Foundation(Grant No.2017M612097)the Fundamental Research Funds for the Central Universities(Grant No.WK2310000065)
文摘X-ray grating interferometer has attracted widely attention in the past years due to its capability in achieving x-ray phase contrast imaging with low brilliance source. However, the widely used phase stepping information extraction method reduces system stability and prolongs data acquisition time by several times compared with conventional x-ray absorption- based imaging. The mechanical stepping can be avoided by using a staggered grating, but at the cost of low vertical spatial resolution. In this paper, employing a modified staggered grating and the angular signal radiography, we proposed a single-shot grating-based x-ray differential phase contrast imaging with decent vertical spatial resolution. The theoretical framework was deduced and proved by numerical experiments. Absorption, phase, and scattering computed tomography can be performed without phase stepping. Therefore, we believe this fast and highly stable imaging method with decent resolution would be widely applied in x-ray grating-based phase contrast imaging.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61101175,61571305,and 61227802)
文摘A fast and simple method to extract phase-contrast images from interferograms is proposed, and its effectiveness is demonstrated through simulation and experiment. For x-ray differential phase contrast imaging, a strong attenuation signal acts as an overwhelming background intensity that obscures the weak phase signal so that no obvious phase-gradient information is detectable in the raw image. By subtracting one interferogram from another, chosen at particular intervals,the phase signal can be isolated and magnified.
基金supported by the National Research Foundation of Korea(NRF)funded by the Korean government(MEST)(No.2021R1C1C200514).
文摘Non-interferometric X-ray quantitative phase imaging(XQPI),much simpler than the interferometric scheme,has provided high-resolution and reliable phase-contrast images.We report on implementing the volumetric XQPI images using concurrent-bidirectional scanning of the orthogonal plane on the optical axis of the Foucault differential filter;we then extracted data in conjunction with the transport-intensity equation.The volumetric image of the laminate microstructure of the gills of a fish was successfully reconstructed to demonstrate our XQPI method.The method can perform 3D rendering without any rotational motion for laterally extended objects by manipulating incoherent X-rays using the pinhole array.
基金Project supported by the National Natural Science Foundation of China （Grant No 10475044）.
文摘In-line x-ray phase contrast imaging has attracted much attention due to two major advantages： its effectiveness in imaging weakly absorbing materials, and the simplicity of its facilities. In this paper a comprehensive theory based on Wigner distribution developed by Wu and Liu [Med. Phys. 31 2378-2384 （2004）] is reviewed. The influence of x-ray source and detector on the image is discussed. Experiments using a microfocus x-ray source and a CCD detector are conducted, which show the role of two key factors on imaging： the tube voltage and tube current. High tube current and moderate tube voltage are suggested for imaging.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12027812 and 11804356)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2021362).
文摘A general theoretical framework is presented to explain the formation of the phase signal in an x-ray microscope integrated with a grating interferometer,which simultaneously enables the high spatial resolution imaging and the improved image contrast.By using this theory,several key parameters of phase contrast imaging can be predicted,for instance,the fringe visibility and period,and the conversion condition from the differential phase imaging(DPI)to the phase difference imaging(PDI).Additionally,numerical simulations are performed with certain x-ray optical components and imaging geometry.Comparison with the available experimental measurement[Appl.Phys.Lett.113063105(2018)]demonstrates the accuracy of this developed quantitative analysis method of x-ray phase-sensitive microscope imaging.
基金the National Basic Research Program(973) of China(No.2010CB834300)the Biomedical Engineering Cross-Research Fund of Shanghai Jiao Tong University(Nos.YG2011MS49 and YG2013MS65)
文摘Compared with the conventional X-ray absorption imaging, the X-ray phase-contrast imaging shows higher contrast on samples with low attenuation coefficient like blood vessels and soft tissues. Among the modalities of phase-contrast imaging, the grating-based phase contrast imaging has been widely accepted owing to the advantage of wide range of sample selections and exemption of coherent source. However, the downside is the substantially larger amount of data generated from the phase-stepping method which slows down the reconstruction process. Graphic processing unit(GPU) has the advantage of allowing parallel computing which is very useful for large quantity data processing. In this paper, a compute unified device architecture(CUDA) C program based on GPU is introduced to accelerate the phase retrieval and filtered back projection(FBP) algorithm for grating-based tomography. Depending on the size of the data, the CUDA C program shows different amount of speed-up over the standard C program on the same Visual Studio 2010 platform. Meanwhile, the speed-up ratio increases as the size of data increases.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11074172 and 11674232)the National Key Basic Research Program,China(Grant No.2012CB825804)the National Special Foundation for Major Science Instrument,China(Grant No.61227802)
文摘In theory, we find that the actual function of the analyzer grating in the Talbot–Lau interferometer is segmenting the self-images of the phase grating and choosing integral areas, which make sure that each period of self-images in one detector pixel contributes the same signal to the detector. Furthermore, in the case of the lack of an analyzer grating, the shifting curves are still existent in theory as long as the number of fringes is non-integral in a detector pixel, which is a sufficient condition for creating shifting curve. The sufficient condition is available for not only the Talbot–Lau interferometer and the inverse geometry of Talbot–Lau interferometer, but also the x-ray phase contrast imaging system based on geometrical optics. In practical applications, we propose a method to improve the performances of the existing systems by employing the sufficient condition. This method can shorten the system length, is applicable to large period gratings, and can use the detectors with large pixels and large field of view. In addition, the experimental arrangement can be simplified due to the lack of an analyzer grating. In order to improve detection sensitivity and resolution, we also give an optimal fringe period.We believe that the theory and method proposed here is a step forward for x-ray phase contrast imaging.
基金supported by the National Magnetic Confinement Fusion Energy Research Project(Grant Nos.2015GB120002,2013GB107000,2012GB101001)National Natural Science Foundation of China(Grant Nos.11375053,11535013)the Natural Science Foundation of Anhui Province(Grant No.1608085MA08)
文摘A phase contrast imaging（PCI） diagnostic has recently been developed on HL-2 A tokamak. It can diagnose plasma density fluctuations with maximum wave number of 15 cm^（-1） and wave number resolution of 2 cm^（-1）. The time resolution reaches 2 μs. A 10.6 μm CO_2 laser is expanded to a beam with a diameter of 30 mm and injected into the plasma as an incident beam,injecting into plasma. The emerging scattered and unscattered beams are contrasted by a phase plate. The ideas of optical path design are presented in this paper, together with the parameters of the main optical components. The whole optical path of PCI is not only carefully designed, but also constructed on HL-2 A. First calibration results show the ability of this system to catch plasma turbulence in a wide frequency domain.
