keyword
MENU ▼
Read by QxMD icon Read
search

WaveFront

keyword
https://www.readbyqxmd.com/read/28437961/novel-asymmetric-cryptosystem-based-on-distorted-wavefront-beam-illumination-and-double-random-phase-encoding
#1
Honghao Yu, Jun Chang, Xin Liu, Chuhan Wu, Yifan He, Yongjian Zhang
Herein, we propose a new security enhancing method that employs wavefront aberrations as optical keys to improve the resistance capabilities of conventional double-random phase encoding (DRPE) optical cryptosystems. This study has two main innovations. First, we exploit a special beam-expander afocal-reflecting to produce different types of aberrations, and the wavefront distortion can be altered by changing the shape of the afocal-reflecting system using a deformable mirror. Then, we reconstruct the wavefront aberrations via the surface fitting of Zernike polynomials and use the reconstructed aberrations as novel asymmetric vector keys...
April 17, 2017: Optics Express
https://www.readbyqxmd.com/read/28437936/ultra-thin-and-high-efficiency-graphene-metasurface-for-tunable-terahertz-wave-manipulation
#2
Zhen Liu, Benfeng Bai
We propose a type of ultra-thin metasurfaces composed of rectangular graphene patches supporting orthogonal plasmonic resonances, which can work in transmission or reflection modes for dynamic terahertz wavefront manipulation with high polarization conversion ratio. By controlling the response of each patch via electrical biasing, the phase of the output wave can be tuned in a wide range over 180° while keeping its amplitude high and relatively stable. We demonstrate several functional devices based on such metasurfaces: a linear polarization converter with nearly 100% polarization conversion ratio, a switchable anomalous wave deflection device, and a dual-polarity focusing mirror with the focal spot tunable in both the transversal and longitudinal directions...
April 17, 2017: Optics Express
https://www.readbyqxmd.com/read/28437914/a-sagnac-fourier-spectrometer
#3
Matthias Lenzner, Jean-Claude Diels
A spectrometer based on a Sagnac interferometer, where one of the mirrors is replaced by a transmission grating, is introduced. Since the action of a transmission grating is reversible, both directions experience the same diffraction at a given wavelength. At the output, the crossed wavefronts are imaged onto a camera, where their Fizeau fringe pattern is recorded. Each spectral element produces a unique spatial frequency, hence the Fourier transform of the recorded interferogram contains the spectrum. Since the grating is tuned to place zero spatial frequency at a selected wavelength, the adjoining spectrum is heterodyned with respect to this wavelength...
April 17, 2017: Optics Express
https://www.readbyqxmd.com/read/28435215/a-comparison-of-mesopic-visual-acuity-and-objective-visual-quality-following-cataract-surgery-with-hydrophobic-acrylic-intraocular-lenses
#4
George Hh Beiko, Miso Gostimir, Lila Haj-Ahmad
PURPOSE: To evaluate mesopic visual acuity and visual quality as measured by objective scatter index (OSI) in pseudophakic eyes with long-term follow-up after implantation of hydrophobic acrylic lenses made from two different lens materials. SETTING: This study was carried out in a private clinic. DESIGN: This study was an observational cohort study. METHODS: This pilot study included 181 eyes of 136 patients who had undergone cataract surgery with implantation of monofocal hydrophobic acrylic intraocular lenses (IOLs), either Alcon AcrySof (82 eyes) or Abbott Medical Optics' Tecnis (99 eyes)...
2017: Clinical Ophthalmology
https://www.readbyqxmd.com/read/28433446/functional-magnetic-resonance-imaging-to-assess-the-neurobehavioral-impact-of-dysphotopsia-with-multifocal-intraocular-lenses
#5
Andreia M Rosa, Ângela C Miranda, Miguel Patrício, Colm McAlinden, Fátima L Silva, Joaquim N Murta, Miguel Castelo-Branco
PURPOSE: To investigate the association between dysphotopsia and neural responses in visual and higher-level cortical regions in patients who recently received multifocal intraocular lens (IOL) implants. DESIGN: Cross-sectional study. PARTICIPANTS: Thirty patients 3 to 4 weeks after bilateral cataract surgery with diffractive IOL implantation and 15 age- and gender-matched control subjects. METHODS: Functional magnetic resonance imaging (fMRI) was performed when participants viewed low-contrast grating stimuli...
April 19, 2017: Ophthalmology
https://www.readbyqxmd.com/read/28432217/rar%C3%AE-2-is-required-for-vertebrate-somitogenesis
#6
Amanda Janesick, Weiyi Tang, Tuyen T L Nguyen, Bruce Blumberg
During vertebrate somitogenesis, retinoic acid is known to establish the position of the determination wavefront, controlling where new somites are permitted to form along the anteroposterior body axis. Less is understood about how RAR regulates somite patterning, rostral-caudal boundary setting, specialization of myotome subdivisions, or the specific RAR subtype that is required for somite patterning. Characterizing the function of RARβ has been challenging due to the absence of embryonic phenotypes in murine loss-of-function studies...
April 21, 2017: Development
https://www.readbyqxmd.com/read/28430247/precise-calibration-of-pupil-images-in-pyramid-wavefront-sensor
#7
Yong Liu, Quanquan Mu, Zhaoliang Cao, Lifa Hu, Chengliang Yang, Li Xuan
The pyramid wavefront sensor (PWFS) is a novel wavefront sensor with several inspiring advantages compared with Shack-Hartmann wavefront sensors. The PWFS uses four pupil images to calculate the local tilt of the incoming wavefront. Pupil images are conjugated with a telescope pupil so that each pixel in the pupil image is diffraction-limited by the telescope pupil diameter, thus the sensing error of the PWFS is much lower than that of the Shack-Hartmann sensor and is related to the extraction and alignment accuracy of pupil images...
April 20, 2017: Applied Optics
https://www.readbyqxmd.com/read/28430239/research-on-intelligent-algorithms-for-amplitude-optimization-of-wavefront-shaping
#8
Qi Feng, Bin Zhang, Zhipeng Liu, Chengyou Lin, Yingchun Ding
This paper demonstrates further research on intelligent algorithms of binary amplitude optimization for wavefront shaping by numerical simulations. A better fitness function of the genetic algorithm (GA) has been presented after a comparative analysis of enhancement. With this new discriminant, we have achieved a relative enhancement of 0.225, which is higher than the theoretical value (0.159). In addition, we have also proposed a kind of modified particle swarm optimization algorithm (PSO), which has a higher enhancement than the unmodified PSO and a faster convergence speed than the GA...
April 20, 2017: Applied Optics
https://www.readbyqxmd.com/read/28416817/controlling-propagation-and-coupling-of-waveguide-modes-using-phase-gradient-metasurfaces
#9
Zhaoyi Li, Myoung-Hwan Kim, Cheng Wang, Zhaohong Han, Sajan Shrestha, Adam Christopher Overvig, Ming Lu, Aaron Stein, Anuradha Murthy Agarwal, Marko Lončar, Nanfang Yu
Research on two-dimensional designer optical structures, or metasurfaces, has mainly focused on controlling the wavefronts of light propagating in free space. Here, we show that gradient metasurface structures consisting of phased arrays of plasmonic or dielectric nanoantennas can be used to control guided waves via strong optical scattering at subwavelength intervals. Based on this design principle, we experimentally demonstrate waveguide mode converters, polarization rotators and waveguide devices supporting asymmetric optical power transmission...
April 17, 2017: Nature Nanotechnology
https://www.readbyqxmd.com/read/28410097/progressive-minimal-path-method-for-segmentation-of-2d-and-3d-line-structures
#10
Wei Liao, Stefan Worz, Chang-Ki Kang, Zang-Hee Cho, Karl Rohr
We propose a novel minimal path method for the segmentation of 2D and 3D line structures. Minimal path methods perform propagation of a wavefront emanating from a start point at a speed derived from image features, followed by path extraction using backtracing. Usually, the computation of the speed and the propagation of the wave are two separate steps, and point features are used to compute a static speed. We introduce a new continuous minimal path method which steers the wave propagation progressively using dynamic speed based on path features...
April 6, 2017: IEEE Transactions on Pattern Analysis and Machine Intelligence
https://www.readbyqxmd.com/read/28409812/laser-induced-birefringence-measurements-by-quantitative-polarized-phase-microscopy
#11
Thomas Doualle, Alexandre Ollé, Philippe Cormont, Serge Monneret, Laurent Gallais
A technique that provides quantitative and spatially resolved retardance measurement is studied for application to laser-induced modification in transparent materials. The method is based on the measurement of optical path differences between two wavefronts carrying different polarizations, measured by a wavefront sensor placed in the image plane of a microscope. We have applied the technique to the investigation of stress distribution induced by CO<sub>2</sub> laser processing of fused silica samples...
April 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28409786/determining-topological-charge-of-an-optical-beam-using-a-wedged-optical-flat
#12
Behzad Khajavi, Enrique J Galvez
The topological charge of a beam carrying an optical vortex is an important parameter that specifies the amount of orbital angular momentum carried by the beam and the azimuthal order of the beam mode. We present an experimental method to determine the sign and magnitude of the topological charge using a wedged optical flat as a lateral shearing interferometer. When the curvature of the wavefront is adjusted to be planar, the fringe pattern generated by the shearing interferometer consists of two conjoined forks that unambiguously identify the topological charge of the beam...
April 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28407166/evaluation-of-the-true-wavefront-aberrations-in-eyes-implanted-with-a-rotationally-asymmetric-multifocal-intraocular-lens
#13
Vyas Akondi, Pablo Pérez-Merino, Eduardo Martinez-Enriquez, Carlos Dorronsoro, Nicolás Alejandre, Ignacio Jiménez-Alfaro, Susana Marcos
PURPOSE: Standard evaluation of aberrations from wavefront slope measurements in patients implanted with a rotationally asymmetric multifocal intraocular lens (IOL), the Lentis Mplus (Oculentis GmbH, Berlin, Germany), results in large magnitude primary vertical coma, which is attributed to the intrinsic IOL design. The new proposed method analyzes aberrometry data, allowing disentangling the IOL power pupillary distribution from the true higher order aberrations of the eye. METHODS: The new method of wavefront reconstruction uses retinal spots obtained at both the near and far foci...
April 1, 2017: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/28396856/bidomain-predictions-of-virtual-electrode-induced-make-and-break-excitations-around-blood-vessels
#14
Adam J Connolly, Edward Vigmond, Martin J Bishop
INTRODUCTION AND BACKGROUND: Virtual electrodes formed by field stimulation during defibrillation of cardiac tissue play an important role in eliciting activations. It has been suggested that the coronary vasculature is an important source of virtual electrodes, especially during low-energy defibrillation. This work aims to further the understanding of how virtual electrodes from the coronary vasculature influence defibrillation outcomes. METHODS: Using the bidomain model, we investigated how field stimulation elicited activations from virtual electrodes around idealized intramural blood vessels...
2017: Frontiers in Bioengineering and Biotechnology
https://www.readbyqxmd.com/read/28396804/impact-of-treatment-decentration-on-higher-order-aberrations-after-smile
#15
Ying Yu, Wenwen Zhang, Xinliang Cheng, Jianru Cai, Hui Chen
Purpose. To evaluate decentration following femtosecond laser small incision lenticule extraction (SMILE) and sub-Bowman keratomileusis (SBK) and its impact on higher-order aberrations (HOAs). Methods. Prospective, nonrandom, and comparison study. There were 96 eyes of 52 patients who received SMILE and 96 eyes of 49 patients who received SBK in this study. Decentration was calculated 6 months after surgery with Pentacam. HOAs and visual acuity after the surgery were examined for patients in both groups before and 6 months after surgery...
2017: Journal of Ophthalmology
https://www.readbyqxmd.com/read/28396591/3d-field-shaping-lens-using-all-dielectric-gradient-refractive-index-materials
#16
Tongyu Ding, Jianjia Yi, Haoyu Li, Hailin Zhang, Shah Nawaz Burokur
A novel three-dimensional (3D) optical lens structure for electromagnetic field shaping based on spatial light transformation method is proposed at microwave frequencies. The lens is capable of transforming cylindrical wavefronts into planar ones, and generating a directive emission. Such manipulation is simulated and analysed by solving Laplace's equation, and the deformation of the medium during the transformation is theoretically described in detail. The two-dimensional (2D) design method producing quasi-isotropic parameters is further extended to a potential 3D realization with all-dielectric gradient refractive index metamaterials...
April 10, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28393853/continuous-variable-quantum-authentication-of-physical-unclonable-keys
#17
Georgios M Nikolopoulos, Eleni Diamanti
We propose a scheme for authentication of physical keys that are materialized by optical multiple-scattering media. The authentication relies on the optical response of the key when probed by randomly selected coherent states of light, and the use of standard wavefront-shaping techniques that direct the scattered photons coherently to a specific target mode at the output. The quadratures of the electromagnetic field of the scattered light at the target mode are analysed using a homodyne detection scheme, and the acceptance or rejection of the key is decided upon the outcomes of the measurements...
April 10, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28388896/comparison-of-ocular-higher-order-aberrations-after-smile-and-wavefront-guided-femtosecond-lasik-for-myopia
#18
Xiaoqin Chen, Yan Wang, Jiamei Zhang, Shun-Nan Yang, Xiaojing Li, Lin Zhang
BACKGROUND: To compare changes in higher-order aberrations (HOAs) following small incision lenticule extraction (SMILE) and wavefront-guided femtosecond laser-assisted in situ keratomileusis (WFG FS-LASIK), and to investigate correlations between preoperative spherical equivalence (SE) and components of HOAs affecting visual quality. METHODS: Sixty-five myopic eyes from 38 patients were enrolled in the study retrospectively, either having undergone SMILE or WFG FS-LASIK...
April 7, 2017: BMC Ophthalmology
https://www.readbyqxmd.com/read/28386416/analysis-of-dispersion-and-absorption-characteristics-of-shear-waves-in-sinusoidally-corrugated-elastic-medium-with-void-pores
#19
Deepak Kr Pandit, Santimoy Kundu, Shishir Gupta
This theoretical work reports the dispersion and absorption characteristics of horizontally polarized shear wave (SH-wave) in a corrugated medium with void pores sandwiched between two dissimilar half-spaces. The dispersion and absorption equations have been derived in a closed form using the method of separation of variables. It has been established that there are two different kinds of wavefronts propagating in the proposed media. One of the wavefronts depends on the modulus of rigidity of elastic matrix of the medium and satisfies the dispersion equation of SH-waves...
February 2017: Royal Society Open Science
https://www.readbyqxmd.com/read/28381046/correction-of-spherical-aberration-in-multi-focal-multiphoton-microscopy-with-spatial-light-modulator
#20
Naoya Matsumoto, Alu Konno, Yasushi Ohbayashi, Takashi Inoue, Akiyuki Matsumoto, Kenji Uchimura, Kenji Kadomatsu, Shigetoshi Okazaki
We demonstrate that high-quality images of the deep regions of a thick sample can be obtained from its surface by multi-focal multiphoton microscopy (MMM). The MMM system incorporates a spatial light modulator to separate the excitation beam into a multi-focal excitation beam and modulate the pre-distortion wavefront to correct spherical aberration (SA) caused by a refractive index mismatch between the immersion medium and the biological sample. When fluorescent beads in transparent epoxy resin were observed using four SA-corrected focal beams, the fluorescence signal of the obtained images was ~52 times higher than that obtained without SA correction until a depth of ~1100 μm, similar to the result for single-focal multiphoton microscopy (SMM)...
March 20, 2017: Optics Express
keyword
keyword
104439
1
2
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read
×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"