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Myung-Geun Han, Joseph A Garlow, Matthew S J Marshall, Amanda L Tiano, Stanislaus S Wong, Sang-Wook Cheong, Frederick J Walker, Charles H Ahn, Yimei Zhu
The ability to map out electrostatic potentials in materials is critical for the development and the design of nanoscale electronic and spintronic devices in modern industry. Electron holography has been an important tool for revealing electric and magnetic field distributions in microelectronics and magnetic-based memory devices, however, its utility is hindered by several practical constraints, such as charging artifacts and limitations in sensitivity and in field of view. In this article, we report electron-beam-induced-current (EBIC) and secondary-electron voltage-contrast (SE-VC) with an aberration-corrected electron probe in a transmission electron microscope (TEM), as complementary techniques to electron holography, to measure electric fields and surface potentials, respectively...
February 6, 2017: Ultramicroscopy
Hsuan T Chang, J-W Shui, K-P Lin
In this paper, a joint multiple-image encryption and multiplexing system, which utilizes both the nonnegative matrix factorization (NMF) scheme and digital holography, is proposed. A number of images are transformed into noise-like digital holograms, which are then decomposed into a defined number of basis images and a corresponding weighting matrix using the NMF scheme. The determined basis images are similar to the digital holograms and appear as noise-like patterns, which are then stored as encrypted data and serve as the lock in an encryption system...
February 1, 2017: Applied Optics
Wenqiang Wan, Wen Qiao, Wenbin Huang, Ming Zhu, Yan Ye, Xiangyu Chen, Linsen Chen
Limited by the refreshable data volume of commercial spatial light modulator (SLM), electronic holography can hardly provide satisfactory 3D live video. Here we propose a holography based multiview 3D display by separating the phase information of a lightfield from the amplitude information. In this paper, the phase information was recorded by a 5.5-inch 4-view phase plate with a full coverage of pixelated nano-grating arrays. Because only amplitude information need to be updated, the refreshing data volume in a 3D video display was significantly reduced...
January 23, 2017: Optics Express
Matthias P L Sentis, Fabrice R A Onofri, Fabrice Lamadie
A new and computationally efficient approach is proposed for determining the refractive index of spherical and transparent particles, in addition to their size and 3D position, using digital in-line holography. The method is based on the localization of the maximum intensity position of the photonic jet with respect to the particle center retrieved from the back propagation of recorded holograms. Rigorous electromagnetic calculations and experimental results demonstrate that for liquid-liquid systems and droplets with a radius > 30µm, a refractive index measurement with a resolution inferior to 4 × 10<sup>-3</sup> is achievable, revealing a significant potential for the use of this method to investigate multiphase flows...
January 23, 2017: Optics Express
Jing Liu, Guoxian Zhang, Kai Zhao, Xiaoyu Jiang
A compressive holography algorithm is proposed for the objects composed of point sources in this work. The proposed algorithm is based on Gabor holography, an amazingly simple and effective encoder for compressed sensing. In the proposed algorithm, the three-dimensional sampling space is uniformly divided into a number of grids since the virtual object may appear anywhere in the sampling space. All the grids are mapped into an indication vector, which is sparse in nature considering that the number of grids occupied by the virtual object is far less than that of the whole sampling space...
January 20, 2017: Applied Optics
Zhaomin Wang, Jiannan Jiao, Weijuan Qu, Fang Yang, Hongru Li, Ailing Tian, Anand Asundi
A linear programming phase unwrapping method in dual-wavelength digital holography is proposed and verified experimentally. The proposed method uses the square of height difference as a convergence standard and theoretically gives the boundary condition in a searching process. A simulation was performed by unwrapping step structures at different levels of Gaussian noise. As a result, our method is capable of recovering the discontinuities accurately. It is robust and straightforward. In the experiment, a microelectromechanical systems sample and a cylindrical lens were measured separately...
January 20, 2017: Applied Optics
Lulu Wang
This paper presents the application of the electromagnetic induction holography (EMIH) approach to imaging the electromagnetic activity of the brain, with a particular focus on stroke detection. An integral equation formulation is presented to describe the scattered magnetic field from the distribution of optically small dielectric and magnetic objects of arbitrary shapes adsorbed onto a planar electromagnetic substrate. A numerical computer model was developed in a MATLAB environment to validate the theory...
February 1, 2017: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Yunseok Seo, Geunho Song, Philip Kim, Subir Sachdev, Sang-Jin Sin
Recent experiments have uncovered evidence of the strongly coupled nature of graphene: the Wiedemann-Franz law is violated by up to a factor of 20 near the charge neutral point. We describe this strongly coupled plasma by a holographic model in which there are two distinct conserved U(1) currents. We find that our analytic results for the transport coefficients for the two current model have a significantly improved match to the density dependence of the experimental data than the models with only one current...
January 20, 2017: Physical Review Letters
Federico Forneris, Andrea Mattevi
No abstract text is available yet for this article.
February 2, 2017: Proceedings of the National Academy of Sciences of the United States of America
Efren Fernandez-Grande, Angeliki Xenaki, Peter Gerstoft
This study examines a near-field acoustic holography method consisting of a sparse formulation of the equivalent source method, based on the compressive sensing (CS) framework. The method, denoted Compressive-Equivalent Source Method (C-ESM), encourages spatially sparse solutions (based on the superposition of few waves) that are accurate when the acoustic sources are spatially localized. The importance of obtaining a non-redundant representation, i.e., a sensing matrix with low column coherence, and the inherent ill-conditioning of near-field reconstruction problems is addressed...
January 2017: Journal of the Acoustical Society of America
Chuan-Xing Bi, Yuan Liu, Liang Xu, Yong-Bin Zhang
The accuracy, resolution, and economic cost of near-field acoustic holography (NAH) are highly dependent on the number of spatial sampling points. Generally, higher accuracy and resolution require more spatial sampling points, which may increase the workload of measurement or the hardware cost. Compressive sensing (CS) is able to solve the underdetermined problems by utilizing the sparsity of signals, and thus it can be applied to NAH to reduce the number of spatial sampling points but at the same time provide a high-resolution reconstruction image...
January 2017: Journal of the Acoustical Society of America
Dani Kogan, Siddharth Sivankutty, Viktor Tsvirkun, Géraud Bouwmans, Esben Ravn Andresen, Hervé Rigneault, Dan Oron
Multicore fiber bundles are widely used in endoscopy due to their miniature size and their direct imaging capabilities. They have recently been used, in combination with spatial light modulators, in various realizations of endoscopy with little or no optics at the distal end. These schemes require characterization of the relative phase offsets between the different cores, typically done using off-axis holography, thus requiring both an interferometric setup and, typically, access to the distal tip. Here we explore the possibility of employing phase retrieval to extract the necessary phase information...
February 1, 2017: Optics Letters
Shuming Jiao, Wenbin Zou
Parallel phase-shifting digital holography can record high-quality holograms efficiently from fast-moving objects in a dynamic scene. However, a phase-shifting array device with a cell size identical to image sensors is required, which imposes difficulty in practice. This Letter proposes a novel scheme to employ a low-resolution phase-shifting array device to achieve high-resolution parallel phase-shifting digital holography, based on image inpainting performed on incomplete holograms. The experimental results validate the effectiveness of the proposed scheme...
February 1, 2017: Optics Letters
Xiangyu Quan, Osamu Matoba, Yasuhiro Awatsuji
A new optical configuration of incoherent digital holography is presented to improve the quality of reconstructed images when the random polarization state of incoherent light is used. The proposed system improves the signal-to-noise ratio of the holograms by suppressing the unmodulated terms of a spatial light modulator. To generate the self-interference of a quasi-incoherent point-like source, we use a dual-focusing lens with diffraction gratings. The preliminary experimental results confirm the validity of the proposed method by reconstructing two point-like sources generated by a LED light source...
February 1, 2017: Optics Letters
Armin Feist, Nora Bach, Nara Rubiano da Silva, Thomas Danz, Marcel Möller, Katharina E Priebe, Till Domröse, J Gregor Gatzmann, Stefan Rost, Jakob Schauss, Stefanie Strauch, Reiner Bormann, Murat Sivis, Sascha Schäfer, Claus Ropers
We present the development of the first ultrafast transmission electron microscope (UTEM) driven by localized photoemission from a field emitter cathode. We describe the implementation of the instrument, the photoemitter concept and the quantitative electron beam parameters achieved. Establishing a new source for ultrafast TEM, the Göttingen UTEM employs nano-localized linear photoemission from a Schottky emitter, which enables operation with freely tunable temporal structure, from continuous wave to femtosecond pulsed mode...
December 11, 2016: Ultramicroscopy
Ying Li, Haifeng Du, Jie Zhang, Zhengwang Liu, Mingliang Tian, Renchao Che
The physical properties of nanometer scale semiconductors are known to be sensitively influenced by their aspect ratios, but the intrinsic mechanisms still remain unclear. Shape-controlled anisotropic PbSe nanorods were obtained by means of the addition of MnCl2, and the aspect ratio of the nanorods can be continuously tuned from 1 to 10 by simply modulating the amount of chloride ions. It was demonstrated that an optimized concentration of Cl(-) anions is about 0.04mmol, which controls the competition between thermodynamics and kinetics mechanisms...
January 13, 2017: Journal of Colloid and Interface Science
Fatma Ozturk Kirbay, Caner Geyik, Emine Guler, Ozan Yesiltepe, Zinar Pinar Gumus, Dilek Odaci Demirkol, Hakan Coskunol, Suna Timur
Atypical antipsychotic drugs induce hepatic toxicity. Thus, it is of importance to eliminate the side effects of these drugs. Herein we describe the preparation of nanoemulsions with a dietary supplement; wheat germ oil (WGO), to ameliorate the liver damage induced by clozapine and olanzapine. THLE-2 cell line was used as a model to investigate the effects of these nanoemulsions on cell viability as well as antioxidative efficiency after antipsychotic insult. In this context, a conventional cell culture method; MTT was used along with a novel cellular imaging technique called digital holography (DH) to evaluate cell viability...
January 20, 2017: Colloids and Surfaces. B, Biointerfaces
Zi-An Li, Fengshan Zheng, Amir Hossein Tavabi, Jan Caron, Chiming Jin, Haifeng Du, András Kovács, Mingliang Tian, Michael Farle, Rafal E Dunin-Borkowski
We use in situ Lorentz microscopy and off-axis electron holography to investigate the formation and characteristics of skyrmion lattice defects and their relationship to the underlying crystallographic structure of a B20 FeGe thin film. We obtain experimental measurements of spin configurations at grain boundaries, which reveal inversions of crystallographic and magnetic chirality across adjacent grains, resulting in the formation of interface spin stripes at the grain boundaries. In the absence of material defects, we observe that skyrmions lattices possess dislocations and domain boundaries, in analogy to atomic crystals...
February 2, 2017: Nano Letters
Seung-Yeol Lee, Yong-Hae Kim, Seong-M Cho, Gi Heon Kim, Tae-Youb Kim, Hojun Ryu, Han Na Kim, Han Byeol Kang, Chi-Young Hwang, Chi-Sun Hwang
The development of digital holography is anticipated for the viewing of 3D images by reconstructing both the amplitude and phase information of the object. Compared to analog holograms written by a laser interference, digital hologram technology has the potential to realize a moving 3D image using a spatial light modulator. However, to ensure a high-resolution 3D image with a large viewing angle, the hologram panel requires a near-wavelength scale pixel pitch with a sufficient large numbers of pixels. In this manuscript, we demonstrate a digital hologram panel based on a chalcogenide phase-change material (PCM) which has a pixel pitch of 1 μm and a panel size of 1...
January 24, 2017: Scientific Reports
Hiroaki Suzuki, Zentaro Akase, Kodai Niitsu, Toshiaki Tanigaki, Daisuke Shindo
Charging of a SiO2 particle induced by electron illumination was investigated by changing the illuminated area of the particle and its support film through control of the position of the mask plate inserted in a transmission electron microscope illumination system. The electric fields around the charged SiO2 particle were analyzed using electron holography. The amount of charge was evaluated quantitatively by comparing the reconstructed phase images with the simulated phase images. When the support film was not covered against the incident electron beam, secondary electrons emitted from the conductive support film were attracted to the charged particle, resulting in particle discharge...
January 17, 2017: Microscopy
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