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[IEEE 2018 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium) - Boston, MA, USA (2018.7.8-2018.7.13)] 2018 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium) - Sub-Diffraction Holographic Imaging with Resonant Scatterers in Proximity of the Objects
摘要： To overcome the well-known 'diffraction limit' in the resolution of electromagnetic imaging systems, we propose the use of resonant near-field scatterers incorporated in the holographic imaging techniques. These scatterers convert a portion of the evanescent spectrum in the proximity of the object to propagating spectrum which is measurable by the antenna in the far-field.
关键词： microwave and millimeter wave imaging,sub-diffraction imaging,resonant scatterers
更新于2025-09-23 15:22:29
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Anisotropic nano-scale resolution in 3D Bragg coherent diffraction imaging
摘要： We demonstrate that the resolution of three-dimensional (3D) real-space images obtained from Bragg coherent x-ray diffraction measurements is direction dependent. We propose and demonstrate the effectiveness of a metric to determine the spatial resolution of images that accounts for the directional dependence. The measured direction dependent resolution of (cid:2)4–9 nm is higher than the best previously obtained 3D measurements. Finally, we quantify the relationship between the resolution of recovered real-space images and dosage and discuss its implications in the light of next generation synchrotrons.
关键词： synchrotrons,resolution,Bragg coherent x-ray diffraction imaging,dosage,direction dependent
更新于2025-09-23 15:21:21
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Coherent Tabletop EUV Ptychography of Nanopatterns
摘要： Coherent diffraction imaging (CDI) or lensless X-ray microscopy has become of great interest for high spatial resolution imaging of, e.g., nanostructures and biological specimens. There is no optics required in between an object and a detector, because the object can be fully recovered from its far-field diffraction pattern with an iterative phase retrieval algorithm. Hence, in principle, a sub-wavelength spatial resolution could be achieved in a high-numerical aperture configuration. With the advances of ultrafast laser technology, high photon flux tabletop Extreme Ultraviolet (EUV) sources based on the high-order harmonic generation (HHG) have become available to small-scale laboratories. In this study, we report on a newly established high photon flux and highly monochromatic 30 nm HHG beamline. Furthermore, we applied ptychography, a scanning CDI version, to probe a nearly periodic nanopattern with the tabletop EUV source. A wide-field view of about 15 × 15 μm was probed with a 2.5 μm?diameter illumination beam at 30 nm. From a set of hundreds of far-field diffraction patterns recorded for different adjacent positions of the object, both the object and the illumination beams were successfully reconstructed with the extended ptychographical iterative engine. By investigating the phase retrieval transfer function, a diffraction-limited resolution of reconstruction of about 32 nm is obtained.
关键词： high-order harmonic generation,ptychography,lensless X-ray microscopy,Extreme Ultraviolet,Coherent diffraction imaging
更新于2025-09-23 15:21:21
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Real-time coherent diffraction inversion using deep generative networks
摘要： Phase retrieval, or the process of recovering phase information in reciprocal space to reconstruct images from measured intensity alone, is the underlying basis to a variety of imaging applications including coherent diffraction imaging (CDI). Typical phase retrieval algorithms are iterative in nature, and hence, are time-consuming and computationally expensive, making real-time imaging a challenge. Furthermore, iterative phase retrieval algorithms struggle to converge to the correct solution especially in the presence of strong phase structures. In this work, we demonstrate the training and testing of CDI NN, a pair of deep deconvolutional networks trained to predict structure and phase in real space of a 2D object from its corresponding far-field diffraction intensities alone. Once trained, CDI NN can invert a diffraction pattern to an image within a few milliseconds of compute time on a standard desktop machine, opening the door to real-time imaging.
关键词： phase retrieval,deep learning,coherent diffraction imaging,real-time imaging,neural networks
更新于2025-09-10 09:29:36
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Multi-Modality Imaging (Applications and Computational Techniques) || Use of Photon Scattering Interactions in Diagnosis and Treatment of Disease
摘要： This chapter looks at photon scattering applications in medicine. In the energy range of interest there are two types of scattering events, incoherent (Compton) and coherent (Rayleigh) scattering, and this chapter looks at how these events can be usefully used in the diagnosis and treatment of disease. In the first part we present an overview of Compton cameras for gamma imaging in the context of proton beam therapy, where they can be used for proton range verification. Proton beam therapy is currently in need of range verification for quality assurance and to improve treatment efficacy and safety. We will first briefly introduce potential methods for in vivo proton range verification, of which prompt gamma imaging is a promising example. We describe the process of gamma emission during proton irradiation, as well as the challenges of its detection and interpretation. The use of Compton camera for prompt gamma imaging has advantages over other gamma detectors since it does not require mechanical collimators and has a typical field of view of 180?. The Compton camera’s principle of operation and design criteria for prompt gamma imaging are described, as well as image reconstruction techniques such as back-projection and stochastic origin ensemble. The second part of the chapter presents tissue diffraction, based upon coherent scattering as a diagnostic tool. X-ray diffraction (XRD) is a technique which can be used to calculate the atomic or molecular structure of a material by measuring X-ray scattering profiles. While XRD has been a longstanding tool in analytical and materials science, this section reviews the relatively new application of XRD to the differentiation of healthy and cancerous tissue and how the results compare to conventional histopathology. As well as outlining the typical signatures expected of different tissue types, the hardware and data processing requirements will be discussed, particularly in the context of the trade-offs that would need to be considered in the design and development of a clinically deployable system.
关键词： Compton scattering,X-ray diffraction,Imaging,Tissue analysis,Coherent scattering
更新于2025-09-10 09:29:36
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Development and evaluation of realistic optical cell models for rapid and label-free cell assay by diffraction imaging
摘要： Methods for rapid and label-free cell assay are highly desired in life science. Single-shot diffraction imaging presents strong potentials to achieve this goal as evidenced by past experimental results using methods such as polarization diffraction imaging flow cytometry. We present here a platform of methods toward solving these problems and results of optical cell model (OCM) evaluations by calculations and analysis of cross-polarized diffraction image (p-DI) pairs. Four types of realistic OCMs have been developed with two prostate cell structures and adjustable refractive index parameters to investigate the effects of cell morphology and index distribution on calculated p-DI pairs. Image patterns have been characterized by a gray-level co-occurrence matrix (GLCM) algorithm and 4 GLCM parameters and linear depolarization ratio δL have been selected to compare calculated against measured data of prostate cells. Our results show that the irregular shapes of and heterogeneity in refractive index (RI) distributions for organelles play significant roles in the spatial distribution of scattered light by cells in comparison to the average RI values and their differences among the organelles. Discrepancies in GLCM and δL parameters between calculated and measured p-DI data provide useful insight for understanding light scattering by single cells and improving OCM.
关键词： cell models,light scattering,diffraction imaging,cell analysis
更新于2025-09-10 09:29:36
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Bragg coherent diffraction imaging of iron diffusion into gold nanocrystals
摘要： Understanding how diffusion takes place within nanocrystals is of great importance for their stability and for controlling their synthesis. In this study, we used the strain sensitivity of Bragg coherent diffraction imaging (BCDI) to study the diffusion of iron into individual gold nanocrystals in situ at elevated temperatures. The BCDI experiments were performed at the I-07 beamline at Diamond Light Source, UK. The diffraction pattern of individual gold nanocrystals was measured around the (11-1) Bragg peak of gold before and after iron deposition as a function of temperature and time. Phase retrieval algorithms were used to obtain real space reconstructions of the nanocrystals from their measured diffraction patterns. Alloying of iron with gold at sample temperatures of 300 °C–500 °C and dealloying of iron from gold at 600 °C were observed. The volume of the alloyed region in the nanocrystals was found to increase with the dose of iron. However, no significant time dependence was observed for the structure following each iron deposition, suggesting that the samples reached equilibrium relatively quickly. The resulting phase distribution within the gold nanocrystals after the iron depositions suggests a contraction due to diffusion of iron. Our results show that BCDI is a useful technique for studying diffusion in three dimensions and alloying behaviour in individual crystalline grains.
关键词： gold iron,nanocrystals,diffusion,Bragg coherent diffraction imaging
更新于2025-09-09 09:28:46
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Radiation damage free ghost diffraction with atomic resolution
摘要： The x-ray free electron lasers can enable diffractive structural determination of protein nanocrystals and single molecules that are too small and radiation-sensitive for conventional x-ray diffraction. However the electronic form factor may be modified during the ultrashort x-ray pulse due to photoionization and electron cascade caused by the intense x-ray pulse. For general x-ray imaging techniques, the minimization of the effects of radiation damage is of major concern to ensure reliable reconstruction of molecular structure. Here we show that radiation damage free diffraction can be achieved with atomic spatial resolution by using x-ray parametric down-conversion and ghost diffraction with entangled photons of x-ray and optical frequencies. We show that the formation of the diffraction patterns satisfies a condition analogous to the Bragg equation, with a resolution that can be as fine as the crystal lattice length scale of several ?ngstrom. Since the samples are illuminated by low energy optical photons, they can be free of radiation damage.
关键词： atomic resolution,x-ray quantum optics,diffraction imaging
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE International Conference on Mechatronics and Automation (ICMA) - Changchun (2018.8.5-2018.8.8)] 2018 IEEE International Conference on Mechatronics and Automation (ICMA) - Status and Trends of the Large Aperture Space Optical Remote Sensor
摘要： Aiming at catching up with the leading countries, this paper gives the right development direction of large aperture optical remote sensor in China. Firstly, we introduced the current situation of large aperture remote sensors using traditional and new imaging systems. Then we summarized the monolithic and deployable remote sensors with full range spectra and high spectrum resolution are the future main development trends. Furthermore, we discussed the key technologies include large aperture lightweight monolithic reflective mirror, active support, precise deployment, co-phasing in orbit, fabrication of large aperture membrane diffractive optics element (DOE) and high performance imaging processing technology of interferometric imaging system. Finally, we conclude China should give more attention to the large aperture monolithic and deployable optical remote sensors, and tackle the key technology in 1.5m~3m aperture monolithic remote sensors at first step and 4m aperture monolithic and the deployable remote sensors next.
关键词： large aperture space optical remote sensor,interference imaging,optical synthetic aperture diffraction imaging,imaging,space deployable segmented imaging
更新于2025-09-04 15:30:14
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Rapid classification of micron-sized particles of sphere, cylinders and ellipsoids by diffraction image parameters combined with scattered light intensity
摘要： Spatial distributions of light scattered by single particles correlate closely with their morphologies in terms of refractive index (RI) distribution. Diffraction imaging of scattered light under coherent excitation presents a unique approach to acquire and extract feature parameters for particle classification. A validated method has been applied in this study to accurately simulate diffraction imaging of light scattered by homogeneous particles and obtain calculated diffraction image (DI) data. The feature parameters of DI data have been extracted by the gray-level co-occurrence matrix (GLCM) algorithm. We have developed an unsupervised machine learning algorithm based on Gaussian mixture model (GMM) to classify 1965 particles made of single and double spheres, cylinders and ellipsoids with varied RI values in parameter space. It has been shown that selected GLCM parameters combined with integrated forward scatter intensity can provide effective markers for accurate and morphology based classification. For 1791 particles of the same RI, the mean accuracy values of classifying particles into 3 particle types range from 82.6% to 97.2%. These results demonstrate the strong potential of diffraction imaging method for rapid analysis and classification of nonspherical and homogeneous particles by the GMM classifiers that is very challenging in comparison to distinguishing biological cell types.
关键词： Image analysis,Nonspherical particle analysis,Diffraction imaging,Single light scattering
更新于2025-09-04 15:30:14