Download or read book Coherent Diffractive Imaging Using Curved Beam Illumination written by H. N. Chapman and published by . This book was released on 2005 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: The potential of coherent diffractive imaging has in recent years become well recognized. In this technique an essentially parallel beam of coherent x-rays illuminates a support region containing an unknown sample. Outside that region the wavefield is known--typically the sample is isolated so that outside the support there is no scattering. When the diffraction pattern is measured with sufficient signal to noise ratio an iterative technique can be used to solve for the transmission function of the sample. The technique offers extremely high resolution reconstructions of a sample.
Download or read book A Study on New Approaches in Coherent X ray Microscopy of Biological Specimens written by Klaus Giewekemeyer and published by Universitätsverlag Göttingen. This book was released on 2011 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of coherent x rays for microscopic imaging has seen a rapid and ongoing development within the past decade, driven by an increasing availability of highly brilliant and coherent sources worldwide. Accordingly, novel methods have been developed, which replace the microscope‘s objective lens by a numerical reconstruction scheme. The aim of the present work is to study how very recent experimental and algorithmic developments in the field can be implemented towards a highly sensitive and fully quantitative microscopy method for imaging of biological cells. To this end, different experimental approaches are studied, based on coherent far-field as well as near-field diffraction. At first, an application of the novel ptychographic imaging method to single biological cells is presented. In particular, it is demonstrated how weakly scattering biological specimens can be imaged with fully quantitative density contrast. Alongside, a sueccessful extension of the method towards soft x-ray energies is described.In the second part of the work it is shown how x-ray waveguides can be used as a point source for propagation-based microscopy of single cells in the hard x-ray regime. The specifically devised iterative reconstruction scheme allows for full quantitativity and high sensitivity and thus enables an application to single biological cells. The work contains a thorough introduction into the x-ray optical methods applied and aims at a useful and self-contained overview on aspects of signal and Fourier theory relevant for the used numerical propagation schemes.
Download or read book Coherent Diffractive Imaging with Enhanced Contrast Mechanisms written by Arjun Rana and published by . This book was released on 2021 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coherent diffractive imaging (CDI) is an imaging technique which uses reconstructionalgorithms in place of lenses to avoid aberration, which becomes vital in the x-ray regime. Over the last two decades, CDI has served as an invaluable tool to reveal the structure and chemical composition of a wide range of material and biological systems, providing insight across many disciplines. As part of the modern scientific frontier, CDI continues to evolve as an integral tool for the investigation of increasingly complex systems, while pushing the spatiotemporal limit. This work contains three studies which demonstrate extended capabilities of CDI through the utilization of fundamental light-matter interactions in tandem with advanced algorithms. First, the development of a novel broadband reconstruction algorithm called "Spectrum Probe and Image Reconstruction" (SPIRE) is presented in the context of attosecond imaging. An understanding of incoherent scattering permits the development of SPIRE which is shown to outperform other broadband reconstruction algorithms through the use of novel constraints. SPIRE is tested with a set of numerical simulations and a tabletop experiment with a white LED source. The results demonstrate the viability of CDI with broadband illumination and on ultrafast time scales. Second, x-ray magnetic circular dichroism (XMCD) is used to probe the magnetization of a geometrically confined ferromagnet on the nanoscale. A novel vector tomography algorithm titled "Vector REal Space Iterative Reconstruction Engine (Vector RESIRE)" is used to directly reconstruct the 3D magnetization vector field in addition to the sample structure, without any prior assumptions. Topological analysis of the reconstruction result reveals a network of non-trivial magnetic point defects known as hedgehogs. The 3D spatial distribution of hedgehogs serve to validate the current theory of hedgehog confinement and potential of metalattices in spintronics applications. In the appendix, polarization-dependent imaging contrast (PIC) is used to map the orientation of the crystal c-axis of calcium carbonate in a coral skeleton. Hierarchical clustering is applied to 4D scanning transmission electron microscope (STEM) data from the same sample to gain additional information about the crystal grain structure. The PIC and 4D STEM results are correlated to elucidate growth and nucleation conditions for coral.
Download or read book Ultrafast Coherent Diffractive Imaging at FLASH written by H. N. Chapman and published by . This book was released on 2006 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using the FLASH facility we have demonstrated high-resolution coherent diffractive imaging with single soft-X-ray free-electron laser pulses [1]. The intense focused FEL pulse gives a high resolution low-noise coherent diffraction pattern of an object before that object turns into a plasma and explodes. Our experiments are an important milestone in the development of single-particle diffractive imaging with future X-ray free-electron lasers [2, 3]. Our apparatus provides a new and unique tool at FLASH to perform imaging of biological specimens beyond conventional radiation damage resolution limits [2, 4] and to acquire images of ultrafast processes initiated by an FEL pulse or other laser pulse. Coherent diffractive imaging is an ideal method for high-resolution ultrafast imaging with an FEL. Since no optical element is required, the method can in principle be scaled to atomic resolution with short enough wavelength. Spatial and temporal coherence are necessary to ensure that the scattered light waves from all positions across the sample are correlated when they interfere at the detector, giving rise to a coherent diffraction pattern that can be phased and inverted to give a high-resolution image of the sample. In contrast to crystals, where scattering from the many unit cells constructively interfere to give Bragg spots, the coherent diffraction pattern of a non-periodic object is continuous. Such a coherent diffraction pattern contains as much as twice the information content of the pattern of its crystallized periodic counterpart--exactly the amount of information needed to solve the phase problem and deterministically invert the pattern to yield an image of the object [5, 6]. The computer algorithm that performs this function replaces the analogue computations of a lens: summing the complex-valued amplitudes of scattered waves to form an image at a particular plane. Our experimental geometry is shown in Fig. 1. We focus a coherent X-ray pulse from the FLASH source onto the sample and record the far-field diffraction pattern of the object on an area detector (a direct-detection CCD chip) centered on the forward direction. The CCD is protected from destruction by the intense forward scattered beam by a mirror that reflects only the diffracted light onto the detector; the direct beam harmlessly passes through a hole in the mirror. The mirror is coated with a resonant X-ray multilayer coating. We fabricated the coating so that the layer period varies across the mirror in such a way that only in-band X-rays propagating from near the sample interaction point are efficiently reflected. In this way the mirror is a very effective filter that rejects noise such as broadband emission from the sample (e.g. when it turns into a plasma and explodes) and off-axis stray light from scattering and emission of beam line components. This arrangement was crucial here to record clean single-pulse diffraction patterns that could be phased and inverted.
Download or read book Hard X ray Microscopy Enhanced by Coherent Image Reconstruction written by Jakob Soltau and published by Universitätsverlag Göttingen. This book was released on 2022 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: X-ray microscopy is used to study the structure, dynamics and bulk properties of matter with high spatial resolutions. It is widely applied, from physics and chemistry to material and life sciences. In the past two decades, progress in X-ray microscopy was driven either by improvements in X-ray optics or by improvements in the image reconstruction by using algorithms as computational lenses. In this work both approaches are combined to exploit the advantages of X-ray imaging with a large numerical aperture and the advantages of coherent image reconstruction. It is shown that a combined X-ray microscope using both, advanced optics and algorithms, is neither limited by flawed optics nor by constraints imposed by reconstruction algorithms, which enables to go beyond current limits in resolution and applications. The thesis is structured in four parts. In the first part hard X-ray lenses, so called multilayer zone plates, are simulated to investigate volume diffraction effects within the multilayer structure, and to study the potential for smaller focus sizes and higher efficiencies. In the second part, the multilayer zone plates are characterized and implemented in an X-ray microscope. In the third part, a new imaging scheme is presented, which combines in-line holography and coherent diffractive imaging. This method overcomes the current resolution limit of in-line holography and can achieve super-resolution with respect to the numerical aperture of the illuminating beam. Finally, in the fourth part a multilayer zone plate is used as an objective lens with a known transfer function in a novel coherent full-field imaging experiment based on iterative phase retrieval, for high resolution and quantitative contrast.
Download or read book Phase retrieval for object and probe in the optical near field written by Anna-Lena Robisch and published by Göttingen University Press. This book was released on 2016 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lensless, holographic X-ray microscopy is a non-invasive imaging technique that provides resolution on the nanometer scale. Therefore, a divergent, coherent and especially clean wave front impinging on the sample is needed. Yet, focusing X-rays by even the most advanced X-ray mirrors causes so called figure errors of high spatial frequency content. The results are strongly deteriorated intensity profiles that are often even more pronounced than the holographic image of the sample itself. A common strategy to compensate these figure errors is to divide the hologram by the pure intensity profile of the beam (the so called flat field). However, this division is only valid in the limiting case of an illumination focused down to a point source. In reality, as a consequence of a fi nite spot size, one has to accept a loss in resolution when performing the flat field correction. An approach different from the described straightforward procedure is necessary. Here, the simultaneous reconstruction of object and probe is proposed using holograms which were not flat field corrected before phase retrieval. To this end, a method has been developed that allows simultaneously reconstructing object and probe in amplitude and phase from holographic intensity recordings. The experimental way of proceeding was mainly inspired by well-established holographic full-field X-ray imaging techniques that require holograms defocused to different degrees. Consequently, the conclusion seems reasonable that diversity in the optical near-field arises mainly from variation of the propagation distance of light. This so called longitudinal diversity is used to properly phase the transmission function of the sample of interest. The algorithmic strategy of simultaneous phase retrieval for object and probe draws on far-field ptychography where lateral translations of the sample create diverse diffraction patterns. In view of the need for longitudinal diversity realized by shifts of the sample along the optical axis, ptychography has been generalized and adapted for the optical near-field. Hence, translations of the sample in all three dimensions of space need to be exploited to collect enough information about object and probe such that both can be reconstructed simultaneously in amplitude and phase. Concepts have been put into practice by simulations as well as by experiments with coherent visible light and hard X-rays from synchrotron sources. The presented approach offers the opportunity to perform high resolution imaging, to be extended to tomography and to be adapted to super-resolution experiments.
Download or read book Lensless Imaging with High harmonic Sources written by and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coherent diffractive imaging (CDI) is a family of computational imaging techniques that uses iterative reconstruction algorithms to decipher the information encoded in one or more interference patterns to reconstruct an image of an object located in another propagation plane. The lensless nature of these techniques makes them well-suited for imaging with coherent extreme ultraviolet (EUV) or x-ray illumination as refractive optics are limited at these wavelengths. In particular, this work investigates the use of CDI techniques in combination with high-harmonic generation. High-harmonic generation~(HHG) sources can generate EUV illumination beams with a high degree of spatial coherence in a compact tabletop setup. In this work we use Fourier-Transform spectroscopy~(FTS) to separate sets of nearly monochromatic diffraction patterns from a broadband HHG diffraction pattern. These monochromatic diffraction patterns can used to reconstruct spectrally resolved images through reconstruction methods that are similar to those applied in conventional CDI. In Chapter 4 we describe how we use a common path interferometer and a noncollinear chirped pulse amplifier system to generate phase locked 25 fs pulse pairs with a central wavelength of approximately 800 nm and a combined pulse energy of 10 mJ. These infrared driving laser pulses are focused at slightly separated locations in a noble gas jet to upconvert them into a pair of almost identical high-harmonic pulses. In FTS-based imaging experiments, we illuminate a sample with the HHG pulse pairs and record the far-field diffraction pattern as a function of pulse-to-pulse time delay. The spatial separation of our two harmonic beams results in spatial interference between two laterally sheared copies of the diffraction pattern. As a consequence of the geometry, the spectrally separated diffraction patterns obtained in these measurements are similar, but not identical to the standard CDI case. In this work, we demonstrated an algorithm, called diffractive shear interferometry (DSI), to reconstruct images from such diffraction patterns. Using this algorithm, the information present in these diffraction patterns is used to reconstruct complex images of the sample. The reverse problem is either constrained by combining an diffraction pattern with a finite object support prior in Chapter 5 or with other diffraction patterns with a different relative orientation between the shear and the object. One of the advantages of coherent diffractive imaging techniques is that it they reconstruct the full complex electric field at the sample. In reflection mode, such phase difference can be easily attributed to height differences of the reflecting surface. However, most research in diffractive imaging has focused on transmission mode imaging. At the EUV wavelengths generated by HHG sources normal incidence reflection coefficients are vanishingly small. However towards grazing incidence the reflection coefficients approach one. Such a geometry does come at a cost of added experimental and computational complexity. While far-field diffraction between colinear planes can be described by a straight forward Fourier transform of the electric field, for the propagation between non-collinear planes, an additional non-linear coordinate transformation is required. This coordinate transformation depends on the tilt angle of the fields and becomes very sensitive to the exact tilt-angle towards grazing incidence. While CDI itself requires accurate knowledge of the wave propagation, a technique known as ptychography offers more flexibility, as it is often possible to solve for more variables than just the object field. In Chapter 7 we use that property to demonstrate an auto-calibration algorithm that can iteratively calibrate the tilt-angle during a ptychographic reconstruction. Using this approach we were able to refine the tilt angle close to the correct value even when the initial estimates were off by more than 5 degrees, greatly improving flexibility in reflection-mode lensless imaging.
Download or read book X Ray Lasers 2014 written by Jorge Rocca and published by Springer. This book was released on 2015-09-19 with total page 415 pages. Available in PDF, EPUB and Kindle. Book excerpt: These proceedings comprise invited and contributed papers presented at the 14th International Conference on X-Ray Lasers (ICXRL 2014). This conference is part of a continuing series dedicated to recent developments and applications of x-ray lasers and other coherent x-ray sources with attention to supporting technologies and instrumentation. New results in the generation of intense, coherent x-rays and progress toward practical devices and their applications in numerous fields are reported. Areas of research in plasma-based x-ray lasers, 4th generation accelerator-based sources and higher harmonic generation, and other x-ray generation schemes are covered. The scope of ICXRL 2014 included, but was not limited to: Laser-pumped X-ray lasers Discharge excitation and other X-ray laser pumping methods Injection/seeding of X-ray amplifiers New lasing transitions and novel X-ray laser schemes High Harmonic sources-Free-electron laser generation in the XUV and X-ray range Novel schemes for coherent XUV and X-ray generation XUV and X-ray optics and metrology-Driving laser technology Theory and modeling of X-ray gain medium and beam characteristics Applications of high brightness and ultrashort X-ray sources
Download or read book Coherent Diffractive Imaging Using Table top Sources written by Michal Odstrčil and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Coherent X ray diffractive imaging on the single cell level of microbial samples written by Robin Niklas Wilke and published by Göttingen University Press. This book was released on 2015 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since its first experimental demonstration in 1999, Coherent X-Ray Diffractive Imaging has become one of the most promising high resolution X-Ray imaging techniques using coherent radiation produced by brilliant synchrotron storage rings. The ability to directly invert diffraction data with the help of advanced algorithms has paved the way for microscopic investigations and wave-field analyses on the spatial scale of nanometres without the need for inefficient imaging lenses. X-Ray phase contrast which is a measure of the electron density is an important contrast mode of soft biological specimens. For the case of many dominant elements of soft biological matter, the electron density can be converted into an effective mass density offering a unique quantitative information channel which may shed light on important questions such as DNA compaction in the bacterial nucleoid through ‚weighing with light‘. In this work X-Ray phase contrast maps have been obtained from different biological samples by exploring different methods. In particular, the techniques Ptychography and Waveguide-Holographic-Imaging have been used to obtain twodimensional and three-dimensional mass density maps on the single-cell-level of freeze-dried cells of the bacteria Deinococcus radiodurans, Bacillus subtilis and Bacillus thuringiensis allowing, for instance, to estimate the dry weight of the bacterial genome in a near native state. On top of this, reciprocal space information from coherent small angle X-Ray scattering (cellular Nano-Diffraction) of the fine structure of the bacterial cells has been recorded in a synergistic manner and has been analysed down to a resolution of about 2.3/nm exceeding current limits of direct imaging approaches. Furthermore, the dynamic range of present detector technology being one of the major limiting factors of ptychographic phasing of farfield diffraction data has been significantly increased. Overcoming this problem for the case of the very intense X-Ray beam produced by Kirkpatrick-Baez mirrors has been explored by using semi-transparent central stops.
Download or read book Springer Handbook of Microscopy written by Peter W. Hawkes and published by Springer Nature. This book was released on 2019-11-02 with total page 1561 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book features reviews by leading experts on the methods and applications of modern forms of microscopy. The recent awards of Nobel Prizes awarded for super-resolution optical microscopy and cryo-electron microscopy have demonstrated the rich scientific opportunities for research in novel microscopies. Earlier Nobel Prizes for electron microscopy (the instrument itself and applications to biology), scanning probe microscopy and holography are a reminder of the central role of microscopy in modern science, from the study of nanostructures in materials science, physics and chemistry to structural biology. Separate chapters are devoted to confocal, fluorescent and related novel optical microscopies, coherent diffractive imaging, scanning probe microscopy, transmission electron microscopy in all its modes from aberration corrected and analytical to in-situ and time-resolved, low energy electron microscopy, photoelectron microscopy, cryo-electron microscopy in biology, and also ion microscopy. In addition to serving as an essential reference for researchers and teachers in the fields such as materials science, condensed matter physics, solid-state chemistry, structural biology and the molecular sciences generally, the Springer Handbook of Microscopy is a unified, coherent and pedagogically attractive text for advanced students who need an authoritative yet accessible guide to the science and practice of microscopy.
Download or read book Nanoscale Photonic Imaging written by Tim Salditt and published by Springer Nature. This book was released on 2020-06-09 with total page 634 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book, edited and authored by a team of world-leading researchers, provides a broad overview of advanced photonic methods for nanoscale visualization, as well as describing a range of fascinating in-depth studies. Introductory chapters cover the most relevant physics and basic methods that young researchers need to master in order to work effectively in the field of nanoscale photonic imaging, from physical first principles, to instrumentation, to mathematical foundations of imaging and data analysis. Subsequent chapters demonstrate how these cutting edge methods are applied to a variety of systems, including complex fluids and biomolecular systems, for visualizing their structure and dynamics, in space and on timescales extending over many orders of magnitude down to the femtosecond range. Progress in nanoscale photonic imaging in Göttingen has been the sum total of more than a decade of work by a wide range of scientists and mathematicians across disciplines, working together in a vibrant collaboration of a kind rarely matched. This volume presents the highlights of their research achievements and serves as a record of the unique and remarkable constellation of contributors, as well as looking ahead at the future prospects in this field. It will serve not only as a useful reference for experienced researchers but also as a valuable point of entry for newcomers.
Download or read book Handbook of Optics Third Edition 5 Volume Set written by Optical Society of America and published by McGraw Hill Professional. This book was released on 2010-05-18 with total page 6122 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most comprehensive and up-to-date optics resource available Prepared under the auspices of the Optical Society of America, the five carefully architected and cross-referenced volumes of the Handbook of Optics, Third Edition, contain everything a student, scientist, or engineer requires to actively work in the field. From the design of complex optical systems to world-class research and development methods, this definitive publication provides unparalleled access to the fundamentals of the discipline and its greatest minds. Individual chapters are written by the world's most renowned experts who explain, illustrate, and solve the entire field of optics. Each volume contains a complete chapter listing for the entire Handbook, extensive chapter glossaries, and a wealth of references. This pioneering work offers unprecedented coverage of optics data, techniques, and applications. Volume I covers geometrical and physical optics, polarized light, components, and instruments. Volume II covers design, fabrications, testing, sources, detectors, radiometry, and photometry. Volume III, all in full color, covers vision and vision optics. Volume IV covers optical properties of materials, nonlinear optics, and quantum optics. Volume V covers atmospheric optics, modulators, fiber optics, and x-ray and neutron optics. Visit www.HandbookofOpticsOnline.com to search all five volumes and download a comprehensive index.
Download or read book Coherent Diffractive Imaging Using Randomly Coded Masks written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We experimentally demonstrate an extension to coherent diffractive imaging that encodes additional information through the use of a series of randomly coded masks, removing the need for typical object-domain constraints while guaranteeing a unique solution to the phase retrieval problem. Phase retrieval is performed using a numerical convex relaxation routine known as "PhaseCut," an iterative algorithm known for its stability and for its ability to find the global solution, which can be found efficiently and which is robust to noise. As a result, the experiment is performed using a laser diode at 532.2 nm, enabling rapid prototyping for future X-ray synchrotron and even free electron laser experiments.
Download or read book Handbook of Optics Third Edition Volume V Atmospheric Optics Modulators Fiber Optics X Ray and Neutron Optics written by Michael Bass and published by McGraw Hill Professional. This book was released on 2009-11-13 with total page 1293 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most comprehensive and up-to-date optics resource available Prepared under the auspices of the Optical Society of America, the five carefully architected and cross-referenced volumes of the Handbook of Optics, Third Edition, contain everything a student, scientist, or engineer requires to actively work in the field. From the design of complex optical systems to world-class research and development methods, this definitive publication provides unparalleled access to the fundamentals of the discipline and its greatest minds. Individual chapters are written by the world's most renowned experts who explain, illustrate, and solve the entire field of optics. Each volume contains a complete chapter listing for the entire Handbook, extensive chapter glossaries, and a wealth of references. This pioneering work offers unprecedented coverage of optics data, techniques, and applications. Volume V covers atmospheric optics, modulators, fiber optics, and x-ray and neutron optics.
Download or read book Radar Sonar and Holography written by Winston E. Kock and published by Academic Press. This book was released on 2013-10-22 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radar, Sonar, and Holography: An Introduction provides an introduction to the technology of radar and sonar. Because the new science of holography is affecting both these fields quite strongly, the book includes an explanation of the fundamental principles underlying this new art (including the subjects of wave coherence, interference, and diffraction) and of the hologram process itself. Finally, numerous examples are discussed which show how holography is providing new horizons to radar and sonar systems. The book thus also provides a simple approach to the new technology of holography. The discussions clarify the basic difference that exist between photography and holography, on the one hand, and between standard sonar and radar, on the other; and the hologram versions of these two technologies. The book should be useful as a supplementary reading assignment to early college students in science and engineering, and also to senior high students having a bent for science and engineering.
Download or read book Coherent X Ray Optics written by David Paganin and published by Oxford University Press on Demand. This book was released on 2006-01-12 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: X-ray optics is undergoing a renaissance, which may be paralleled to that experienced by visible-light optics following the invention of the laser. The associated surge of activity in "coherent" x-ray optics has been documented in this monograph, the first of its type in the field.
