基于图像信息熵的ptychography轴向距离误差校正

在轴向距离参与运算的ptychography算法中,轴向距离误差会使重建图像变模糊并降低图像的分辨率.本文基于菲涅耳衍射理论建立了轴向距离误差模型,根据不同轴向距离误差对重构图像清晰度的影响,提出用图像信息熵确定图像最清晰时的轴向距离,并重建出清晰的ptychography图像.比较了图像能量变化、Tamura系数和图像信息熵这三种图像清晰度评价函数在轴向距离误差校正过程中的分布情况,发现它们均具有单峰性,且峰值确定的轴向距离相同.图像信息熵相比其他两种图像清晰度评价函数具有更高的灵敏性.仿真以及实验均证明了基于图像信息熵的ptychography轴向误差校正的可行性.

部分相干条件下的弱散射样品ptychography iterative engine成像

分析了照明相干性对ptychography iterative engine(PIE)成像技术的影响机理,指出利用零级衍射光范围内的衍射斑进行图像重建,可以避免由于部分相干性所引入的矛盾因素,并大幅度提高再现像质量,但再现像的对比度会明显降低.而采用散射斑强度的高次方进行图像重建时,相位的倍增作用可使相干性不足所引起的对比度降低大部分得以弥补,从而大大降低PIE技术对光源相干性的依赖并拓展其可应用范围.

Soft X-ray ptychography method at SSRF

Ptychography is a diffraction-based X-ray microscopy technique in which an extended sample is scanned by a coherent beam with overlapped illuminated areas and complex transmission function of the sample is obtained by applying iterative phase retrieval algorithms to the diffraction patterns recorded at each scanned position.It permits quantitatively imaging of non-crystalline specimens at a resolution limited only by the X-ray wavelength and the maximal scattering angle detected.In this paper,the development of soft X-ray ptychography method at the BL08U1 A beamline of Shanghai Synchrotron Radiation Facility is presented.The experimental setup,experimental parameters selection criteria,and post-experimental data analyzing procedures are presented in detail with a prospect of high-resolution image reconstruction in real time.The performance of this newly implemented method is demonstrated through the measurements of a resolution test pattern and two real samples:Pt-Co alloy nanoparticles and a breast cancer cell.The results indicate that strong scattering specimens can be reconstructed to sub-20 nm resolution,while a sub-25 nm resolution for biological specimens can be achieved.

Optical Transfer Function Reconstruction in Incoherent Fourier Ptychography

An optical transfer function （OTF） reconstruction model is first embedded into incoherent Fourier ptychography （IFP）. The leading result is a proposed algorithm that can recover both the super-resolution image and the OTF of an imaging system with unknown aberrations simultaneously. This model overcomes the difficult problem of OTF estimation that the previous IFP faces. The effectiveness of this algorithm is demonstrated by numerical simulations, and the superior reconstruction is presented. We believe that the reported algorithm can extend the original IFP for more complex conditions and may provide a solution by using structured light for characterization of optical systems＇ aberrations.

基于Ptychography的极紫外光刻投影物镜波像差检测技术

Ptychography是一种基于扫描式相干衍射成像的相位恢复技术,实验装置简单,抗干扰能力强。将Ptychography技术用于投影物镜波像差的检测,并分析了检测不同数值孔径投影物镜波像差所采用的光场传播公式、离散化条件及实验架构。数值仿真与实验结果表明,Ptychography技术用于波像差检测时检测标记的通光率需要在45%~80%范围内;增加标记图案的复杂性并在计算过程中增加配准环节可提高收敛速度与检测精度;波像差检测精度在10^(-3)λ以内。将Ptychography技术应用于极紫外光刻投影物镜波像差检测是可行的。

Synthetic aperture ptychography:coded sensor translation for joint spatial-Fourier bandwidth expansion

Conventional ptychography translates an object through a localized probe beam to widen the field of view in real space.Fourier ptychography translates the object spectrum through a pupil aperture to expand the Fourier bandwidth in reciprocal space.Here we report an imaging modality,termed synthetic aperture ptychography(SAP),to get the best of both techniques.In SAP,we illuminate a stationary object using an extended plane wave and translate a coded image sensor at the far field for data acquisition.The coded layer attached on the sensor modulates the object exit waves and serves as an effective ptychographic probe for phase retrieval.The sensor translation process in SAP synthesizes a large complex-valued wavefront at the intermediate aperture plane.By propagating this wavefront back to the object plane,we can widen the field of view in real space and expand the Fourier bandwidth in reciprocal space simultaneously.We validate the SAP approach with transmission targets and reflection silicon microchips.A 20-mm aperture was synthesized using a 5-mm sensor,achieving a fourfold gain in resolution and 16-fold gain in field of view for object recovery.In addition,the thin sample requirement in ptychography is no longer required in SAP.One can digitally propagate the recovered exit wave to any axial position for post-acquisition refocusing.The SAP scheme offers a solution for far-field sub-diffraction imaging without using lenses.It can be adopted in coherent diffraction imaging setups with radiation sources from visible light,extreme ultraviolet,and X-ray,to electron.

A general phase retrieval algorithm based on a ptychographical iterative engine for coherent diffractive imaging

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.

X-ray ptychographic tomography reveals buried 3D structural defects in metal halide perovskites

Metal halide perovskites(MHPs)are an emerging class of semiconductors that have demonstrated their promise at various energy frontiers.Especially,perovskite-based solar cells(PSCs)are considered as a disruptive photovoltaic technology with their power conversion efficiency rapidly climbing to certified 25.7%[1].

Label-free Super-resolution Microscopy for Long-term Monitoring the Dynamic Interactions of Cellular Organelles

The ideal method for imaging living cells is one that allows for long-term,label-free observation in real-time with super-resolution capabilities.Such a method would overcome the drawbacks of phototoxicity and photobleaching associated with fluorescence labeling microscopy.Fourier ptychography is a promising label-free imaging technique that surpasses the diffraction limit of conventional microscopy while avoiding issues related to fluorescent labeling.However,previous Fourier ptychography microscopy (FPM) systems lacked high spatiotemporal resolution,preventing real-time observation of subcellular organelle structures in living cells.To address this limitation,we have developed a high-speed super-resolution microscope based hemispherical digital illumination (HDI) device.This system utilizes 61 light-emitting diodes (LEDs) to provide high-angle illumination with a numerical aperture (NA) of 0.98.By employing a 40×/0.6 NA objective lens,we have achieved lateral resolutions of around 150 nm,enabling us to capture images at a speed of over 1 Hz with the field of view measuring 118×118 μm2.HDI-FPM allows for the monitoring of various cellular processes,such as vesicular transportation,mitochondrial fusion and division,as well as cell-cell fusion over a duration of 4 h.The development of HDI-FPM represents a significant advancement in label-free imaging of living cells.It offers a comprehensive understanding of the mechanisms underlying cellular activities.

反铁磁成像的叠层相位恢复方法

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

Far-field super-resolution imaging by nonlinearly excited evanescent waves

Abbe’s resolution limit,one of the best-known physical limitations,poses a great challenge for any wave system in imaging,wave transport,and dynamics.Originally formulated in linear optics,the Abbe limit can be broken using nonlinear optical interactions.We extend the Abbe theory into a nonlinear regime and experimentally demonstrate a far-field,label-free,and scan-free super-resolution imaging technique based on nonlinear four-wave mixing to retrieve near-field scattered evanescent waves,achieving a sub-wavelength resolution ofλ∕5.6.This method paves the way for numerous new applications in biomedical imaging,semiconductor metrology,and photolithography.

X-ray focusing with efficient high-NA multilayer Laue lenses

Multilayer Laue lenses are volume diffraction elements for the efficient focusing of X-rays.With a new manufacturing technique that we introduced,it is possible to fabricate lenses of sufficiently high numerical aperture(NA)to achieve focal spot sizes below 10 nm.The alternating layers of the materials that form the lens must span a broad range of thicknesses on the nanometer scale to achieve the necessary range of X-ray deflection angles required to achieve a high NA.This poses a challenge to both the accuracy of the deposition process and the control of the materials properties,which often vary with layer thickness.We introduced a new pair of materials—tungsten carbide and silicon carbide—to prepare layered structures with smooth and sharp interfaces and with no material phase transitions that hampered the manufacture of previous lenses.Using a pair of multilayer Laue lenses(MLLs)fabricated from this system,we achieved a two-dimensional focus of 8.4×6.8 nm2 at a photon energy of 16.3 keV with high diffraction efficiency and demonstrated scanning-based imaging of samples with a resolution well below 10 nm.The high NA also allowed projection holographic imaging with strong phase contrast over a large range of magnifications.An error analysis indicates the possibility of achieving 1 nm focusing.

Shedding light on electrodeposition dynamics tracked in situ via soft X-ray coherent diffraction imaging

The in situ physicochemical analysis of nanostructured functional materials is crucial for advances in their design and production. X-ray coherent diffraction imaging （CDI） methods have recently demonstrated impressive potential for characterizing such materials with a high spatial resolution and elemental sensitivity; however, moving from the current ex situ static regime to the in situ dynamic one remains a challenge. By combining soft X-ray ptychography and single-shot keyhole CDI, we performed the first in situ spatiotemporal study on an electrodeposition process in a sealed wet environment, employed for the fabrication of oxygen-reduction catalysts, which are key components for alkaline fuel cells and metal-air batteries. The results provide the first experimental demonstration of theoretically predicted Turing-Hopf electrochemical pattern formation resulting from morphochemical coupling, adding a new dimension for the in-depth in situ characterization of electrodeposition processes in space and time.

Tumor heterogeneity and therapy resistance-implications for future treatments of prostate cancer

Aim:To develop new therapies for prostate cancer,disease heterogeneity must be addressed.This includes patient variation,multi-focal disease,cellular heterogeneity,genomic changes and epigenetic modification.This requires more representative models to be used in more innovative ways.Methods:This study used a panel of cell lines and primary prostate epithelial cell cultures derived from patient tissue.Several assays were used;alamar blue,colony forming assays,γH2AX and Ki67 immunofluorescence and comet assays.Ptychographic quantitative phase imaging(QPI),a label-free imaging technique,combined with Cell Analysis Toolbox software,was implemented to carry out real-time analysis of cells and to retrieve morphological,kinetic and population data.Results:A combination of radiation and Vorinostat may be more effective than radiation alone.Primary prostate cancer stem-like cells are more resistant to etoposide than more differentiated cells.Analysis of QPI images showed that cell lines and primary cells differ in their size,motility and proliferation rate.A QPI signature was developed in order to identify two subpopulations of cells within a heterogeneous primary culture.Conclusion:Use of primary prostate epithelial cultures allows assessment of therapies whilst taking into account cellular heterogeneity.Analysis of rare cell populations and embracing novel techniques may ultimately lead to identifying and overcoming treatment resistance.