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https://www.readbyqxmd.com/read/29348514/3d-imaging-through-scatterers-with-interferenceless-optical-system
#1
Saswata Mukherjee, A Vijayakumar, Manoj Kumar, Joseph Rosen
Imaging through a scattering medium is a challenging task. We propose and demonstrate an interferenceless incoherent opto-digital technique for 3D imaging through a scatterer with a single lens and a digital camera. The light diffracted from a point object is modulated by a scattering mask. The modulated wavefront is projected on an image sensor using a spherical lens and the impulse response is recorded. An object is placed at the same axial location as the point object and another intensity pattern is recorded with identical experimental conditions and with the same scattering mask...
January 18, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29347810/plasma-q-plate-for-generation-and-manipulation-of-intense-optical-vortices
#2
Kenan Qu, Qing Jia, Nathaniel J Fisch
An optical vortex is a light wave with a twisting wavefront around its propagation axis and null intensity in the beam center. Its unique spatial structure of field lends itself to a broad range of applications, including optical communication, quantum information, superresolution microscopy, and multidimensional manipulation of particles. However, accessible intensity of optical vortices have been limited to material ionization threshold. This limitation might be removed by using the plasma medium. Here we propose the design of suitably magnetized plasmas which, functioning as a q-plate, leads to a direct conversion from a high-intensity Gaussian beam into a twisted beam...
November 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347296/temperature-dependence-of-the-nonlinear-optical-response-of-smectic-liquid-crystals-containing-gold-nanorods
#3
R S Silva, P B de Melo, L Omena, A M Nunes, M G A da Silva, M R Meneghetti, I N de Oliveira
The present study is devoted to the investigation of the nonlinear optical properties of a smectic liquid crystal doped with gold nanorods. Using the Z-scan technique, we investigate the changes in the optical birefringence of a homeotropic sample upon laser exposure, considering the configurations of normal and oblique incidence. Our results reveal that the birefringence variations may be governed by distinct physical mechanisms, depending on the relative angle between the far-field director and the wave vector of the excitation laser beam...
December 2017: Physical Review. E
https://www.readbyqxmd.com/read/29335097/aspheric-versus-wavefront-guided-aspheric-photorefractive-keratectomy-in-eyes-with-significant-astigmatism
#4
Amir Faramarzi, Majid Moshirfar, Farid Karimian, Siamak Delfazayebaher, Bahareh Kheiri
PURPOSE: To compare the refractive and higher-order aberrations (HOAs) outcomes after photorefractive keratectomy (PRK) in patients with significant astigmatism using aspheric versus wavefront-guided aspheric profiles. SETTING: Ophthalmic Research Center and Department of Ophthalmology, Shahid Beheshti University of Medical Sciences, Negah Eye Hospital, Tehran, Iran. DESIGN: Prospective randomized case series. METHODS: One eye of each patient with a refractive astigmatism more than 2...
December 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/29335095/vector-analysis-of-astigmatic-changes-and-optical-quality-outcomes-after-wavefront-guided-laser-in%C3%A2-situ-keratomileusis-using-a-high-resolution-aberrometer
#5
Juan A Durán, Elisa Gutiérrez, Rebeca Atienza, David P Piñero
PURPOSE: To assess the ocular optical quality results as well as the astigmatic changes after wavefront-guided laser in situ keratomileusis (LASIK) in eyes with myopic astigmatism. SETTING: Instituto Clínico-Quirúrgico Oftalmológico, Bilbao, Vizcaya, Spain. DESIGN: Prospective case series. METHODS: Thirty-three eyes having wavefront-guided LASIK with the Star S4IR excimer laser combined with the iDesign system were enrolled in the study...
December 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/29328187/kilohertz-binary-phase-modulator-for-pulsed-laser-sources-using-a-digital-micromirror-device
#6
Maximilian Hoffmann, Ioannis N Papadopoulos, Benjamin Judkewitz
The controlled modulation of an optical wavefront is required for aberration correction, digital phase conjugation, or patterned photostimulation. For most of these applications, it is desirable to control the wavefront modulation at the highest rates possible. The digital micromirror device (DMD) presents a cost-effective solution to achieve high-speed modulation and often exceeds the speed of the more conventional liquid crystal spatial light modulator but is inherently an amplitude modulator. Furthermore, spatial dispersion caused by DMD diffraction complicates its use with pulsed laser sources, such as those used in nonlinear microscopy...
January 1, 2018: Optics Letters
https://www.readbyqxmd.com/read/29328141/improved-particle-position-accuracy-from-off-axis-holograms-using-a-chebyshev-model
#7
Johan Öhman, Mikael Sjödahl
Side scattered light from micrometer-sized particles is recorded using an off-axis digital holographic setup. From holograms, a volume is reconstructed with information about both intensity and phase. Finding particle positions is non-trivial, since poor axial resolution elongates particles in the reconstruction. To overcome this problem, the reconstructed wavefront around a particle is used to find the axial position. The method is based on the change in the sign of the curvature around the true particle position plane...
January 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29328107/modulation-transfer-function-of-liquid-crystal-microlenses-and-microprisms-using-double-dielectric-layer
#8
Oleksandr Sova, Victor Reshetnyak, Tigran Galstian
We investigate electrically tunable liquid crystal (LC) microlenses and microprisms based on double dielectric optically hidden (DDOH) layers. Comparative theoretical study of the spatial resolution limits in the creation of a spatially modulated electric field by the DDOH layer is conducted. Both the depth of the resulting optical phase modulation and its deviation from the desired wavefront are obtained for sine and sawtooth geometries of the DDOH layer's structure. A comparison is provided with the standard LC reorientation approach using patterned electrodes...
January 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29328104/statistical-properties-of-single-mode-fiber-coupling-of-satellite-to-ground-laser-links-partially-corrected-by-adaptive-optics
#9
Lucien Canuet, Nicolas Védrenne, Jean-Marc Conan, Cyril Petit, Geraldine Artaud, Angelique Rissons, Jerome Lacan
In the framework of satellite-to-ground laser downlinks, an analytical model describing the variations of the instantaneous coupled flux into a single-mode fiber after correction of the incoming wavefront by partial adaptive optics (AO) is presented. Expressions for the probability density function and the cumulative distribution function as well as for the average fading duration and fading duration distribution of the corrected coupled flux are given. These results are of prime interest for the computation of metrics related to coded transmissions over correlated channels, and they are confronted by end-to-end wave-optics simulations in the case of a geosynchronous satellite (GEO)-to-ground and a low earth orbit satellite (LEO)-to-ground scenario...
January 1, 2018: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
https://www.readbyqxmd.com/read/29328092/talbot-carpet-at-the-transverse-plane-produced-in-the-diffraction-of-plane-wave-from-amplitude-radial-gratings
#10
Saifollah Rasouli, Ali Mohammad Khazaei, Davud Hebri
We experimentally demonstrate and theoretically predict a new and unprecedented optical carpet that includes all the geometric shadow and far-field and near-field diffraction patterns at the transverse plane in the diffraction from a radial grating illuminated by a plane wavefront. The main feature of using radial grating is the continuous change of the spatial period along the radial direction. Therefore, the geometric shadow, and the near-field and far-field diffraction regimes are mixed at various propagation distances, and the traditional definitions for the different diffraction regimes would not apply here...
January 1, 2018: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
https://www.readbyqxmd.com/read/29328086/geometric-optics-of-a-refringent-sphere-illuminated-by-a-point-source-caustics-wavefronts-and-zero-phase-fronts-for-every-rainbow-k-order
#11
Paul-Étienne Ouellette
This study relates to a refringent sphere illuminated by a point source placed at a distance h from its center; for h→∞ the light beam becomes parallel. A selection of variables, principally angular with the center of the sphere as a common point, allows a global, straightforward, and geometrically transparent way to the rays, caustics, and wavefronts, internal as well as external, for every k order, k being the number of internal reflections. One obtains compact formulas for generating the rays and the wavefronts...
January 1, 2018: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
https://www.readbyqxmd.com/read/29322749/time-reversed-ultrasonically-encoded-optical-focusing-through-highly-scattering-ex-vivo-human-cataractous-lenses
#12
Yan Liu, Yuecheng Shen, Haowen Ruan, Frank L Brodie, Terence T W Wong, Changhuei Yang, Lihong V Wang
Normal development of the visual system in infants relies on clear images being projected onto the retina, which can be disrupted by lens opacity caused by congenital cataract. This disruption, if uncorrected in early life, results in amblyopia (permanently decreased vision even after removal of the cataract). Doctors are able to prevent amblyopia by removing the cataract during the first several weeks of life, but this surgery risks a host of complications, which can be equally visually disabling. Here, we investigated the feasibility of focusing light noninvasively through highly scattering cataractous lenses to stimulate the retina, thereby preventing amblyopia...
January 2018: Journal of Biomedical Optics
https://www.readbyqxmd.com/read/29315439/autorefraction-versus-manifest-refraction-in-patients-with-keratoconus
#13
Nienke Soeters, Marc B Muijzer, Jurrian Molenaar, Daniel A Godefrooij, Robert P L Wisse
PURPOSE: To compare visual performance using autorefraction and manifest refraction assessments in patients with keratoconus and investigate whether autorefraction measurements lead to suboptimal visual performance. METHODS: Corrected distance visual acuity (CDVA) was measured in 90 eyes of 61 patients with keratoconus with both autorefraction and manifest refraction, in a random order. Maximum keratometry (Kmax), cone location, and wavefront aberration were determined with Scheimpflug tomography...
January 1, 2018: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/29298373/an-organic-vortex-laser
#14
Daan Stellinga, Monika E Pietrzyk, James M E Glackin, Yue Wang, Ashu K Bansal, Graham A Turnbull, Kishan Dholakia, Ifor D W Samuel, Thomas F Krauss
Optical vortex beams are at the heart of a number of novel research directions, both as carriers of information and for the investigation of optical activity and chiral molecules. Optical vortex beams are beams of light with a helical wavefront and associated orbital angular momentum. They are typically generated using bulk optics methods or by a passive element such as a forked grating or a metasurface to imprint the required phase distribution onto an incident beam. Since many applications benefit from further miniaturisation, a more integrated yet scalable method is highly desirable...
January 3, 2018: ACS Nano
https://www.readbyqxmd.com/read/29289065/the-effect-of-applied-stress-on-the-phase-and-group-velocity-of-guided-waves-in-anisotropic-plates
#15
Brennan Dubuc, Arvin Ebrahimkhanlou, Salvatore Salamone
This paper presents an analytical formulation for the phase and group velocity of acoustoelastic guided waves in anisotropic plates. Uniform in-plane applied stress is considered, with both arbitrary propagation and stress directions. An expression for the energy velocity in a stressed anisotropic plate is derived, from which the group velocity is computed. Since the wavefront and group velocity directions generally differ, the deviation angle between the two is also studied. A method is proposed for verifying the consistency of the formulation, based on the correspondence between a direct and an indirect formulation...
December 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/29284455/visual-rehabilitation-in-moderate-keratoconus-combined-corneal-wavefront-guided-transepithelial-photorefractive-keratectomy-and-high-fluence-accelerated-corneal-collagen-cross-linking-after-intracorneal-ring-segment-implantation
#16
Hun Lee, David Sung Yong Kang, Byoung Jin Ha, Jin Young Choi, Eung Kweon Kim, Kyoung Yul Seo, Tae-Im Kim
BACKGROUND: To investigate the effects of combined corneal wavefront-guided transepithelial photorefractive keratectomy (tPRK) and accelerated corneal collagen cross-linking (CXL) after intracorneal ring segment (ICRS) implantation in patients with moderate keratoconus. METHODS: Medical records of 23 eyes of 23 patients undergoing combined tPRK and CXL after ICRS implantation were retrospectively analyzed. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent (MRSE), corneal indices based on Scheimpflug tomography, higher-order aberrations (HOAs), and corneal biomechanical properties were evaluated before and after ICRS implantation, and at 1, 3, and 6 months after combined tPRK and CXL...
December 29, 2017: BMC Ophthalmology
https://www.readbyqxmd.com/read/29273234/body-surface-activation-mapping-of-electrical-dyssynchrony-in-cardiac-resynchronization-therapy-patients-potential-for-optimization
#17
Alan J Bank, Ryan M Gage, Antonia E Curtin, Kevin V Burns, Jeffrey M Gillberg, Subham Ghosh
BACKGROUND: Electrical synchronization is likely improved by cardiac resynchronization therapy (CRT), but is difficult to quantify with 12-lead ECG. We aimed to quantify changes in electrical synchrony and potential for optimization with CRT using a body-surface activation mapping (BSAM) system. METHODS: Standard deviation of activation times (SDAT) was calculated in 94 patients using BSAM at baseline CRT (CRTbl), native, and different CRT configurations. RESULTS: SDAT decreased 20% from native to CRTbl (p<0...
December 6, 2017: Journal of Electrocardiology
https://www.readbyqxmd.com/read/29251814/early-visual-outcomes-and-optical-quality-after-femtosecond-laser-small-incision-lenticule-extraction-for-myopia-and-myopic-astigmatism-correction-of-over-10-dioptres
#18
Bing Qin, Meiyan Li, Xun Chen, Walter Sekundo, Xingtao Zhou
PURPOSE: To investigate early visual and refractive outcomes, corneal stability and optical quality after femtosecond laser small-incision lenticule extraction (SMILE) for treating myopia and myopic astigmatism over -10 D. METHODS: Thirty eyes (30 patients) with myopia and myopic astigmatism of over -10 D were treated with VisuMax® femtosecond laser (version 3.0; Carl Zeiss Meditec AG, Jena, Germany). Six months postoperative safety, efficacy and predictability were evaluated...
December 18, 2017: Acta Ophthalmologica
https://www.readbyqxmd.com/read/29249832/high-speed-single-shot-optical-focusing-through-dynamic-scattering-media-with-full-phase-wavefront-shaping
#19
Ashton S Hemphill, Yuecheng Shen, Yan Liu, Lihong V Wang
In biological applications, optical focusing is limited by the diffusion of light, which prevents focusing at depths greater than ∼1 mm in soft tissue. Wavefront shaping extends the depth by compensating for phase distortions induced by scattering and thus allows for focusing light through biological tissue beyond the optical diffusion limit by using constructive interference. However, due to physiological motion, light scattering in tissue is deterministic only within a brief speckle correlation time. In in vivo tissue, this speckle correlation time is on the order of milliseconds, and so the wavefront must be optimized within this brief period...
November 27, 2017: Applied Physics Letters
https://www.readbyqxmd.com/read/29245820/numerical-analysis-of-wavefront-aberration-correction-using-multielectrode-electrowetting-based-devices
#20
Mo Zohrabi, Robert H Cormack, Connor Mccullough, Omkar D Supekar, Emily A Gibson, Victor M Bright, Juliet T Gopinath
We present numerical simulations of multielectrode electrowetting devices used in a novel optical design to correct wavefront aberration. Our optical system consists of two multielectrode devices, preceded by a single fixed lens. The multielectrode elements function as adaptive optical devices that can be used to correct aberrations inherent in many imaging setups, biological samples, and the atmosphere. We are able to accurately simulate the liquid-liquid interface shape using computational fluid dynamics...
December 11, 2017: Optics Express
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