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Strehl ratio

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https://www.readbyqxmd.com/read/28248317/perfect-x-ray-focusing-via-fitting-corrective-glasses-to-aberrated-optics
#1
Frank Seiboth, Andreas Schropp, Maria Scholz, Felix Wittwer, Christian Rödel, Martin Wünsche, Tobias Ullsperger, Stefan Nolte, Jussi Rahomäki, Karolis Parfeniukas, Stylianos Giakoumidis, Ulrich Vogt, Ulrich Wagner, Christoph Rau, Ulrike Boesenberg, Jan Garrevoet, Gerald Falkenberg, Eric C Galtier, Hae Ja Lee, Bob Nagler, Christian G Schroer
Due to their short wavelength, X-rays can in principle be focused down to a few nanometres and below. At the same time, it is this short wavelength that puts stringent requirements on X-ray optics and their metrology. Both are limited by today's technology. In this work, we present accurate at wavelength measurements of residual aberrations of a refractive X-ray lens using ptychography to manufacture a corrective phase plate. Together with the fitted phase plate the optics shows diffraction-limited performance, generating a nearly Gaussian beam profile with a Strehl ratio above 0...
March 1, 2017: Nature Communications
https://www.readbyqxmd.com/read/28211182/accommodation-and-pupil-behaviour-of-binocularly-viewing-early-presbyopes
#2
Meznah S Almutairi, Basal H Altoaimi, Arthur Bradley
PURPOSE: To study accommodation behaviour of early presbyopes with the full suite of accommodative stimuli, and to monitor changes in spherical aberration, pupil size and image quality that accompany the accommodative response. METHODS: Using a high resolution Shack-Hartmann aberrometer, we measured refractive state as a binocularly viewed 0.30 logMAR (6/12 or 20/40) letter E was moved from 2 m to 20 cm and simultaneously monitored pupil diameter and spherical aberration for 19 subjects (mean age: 42 ± 7...
March 2017: Ophthalmic & Physiological Optics: the Journal of the British College of Ophthalmic Opticians (Optometrists)
https://www.readbyqxmd.com/read/28178942/in-vitro-comparative-optical-bench-analysis-of-a-spherical-and-aspheric-optic-design-of-the-same-iol-model
#3
Tamer Tandogan, Gerd U Auffarth, Chul Y Choi, Stephanie Liebing, Christian Mayer, Ramin Khoramnia
BACKGROUND: To analyse objective optical properties of the spherical and aspheric design of the same intraocular lens (IOL) model using optical bench analysis. METHODS: This study entailed a comparative analysis of 10 spherical C-flex 570 C and 10 aspheric C-flex 970 C IOLs (Rayner Intraocular Lenses Ltd., Hove, UK) of 26 diopters [D] using an optical bench (OptiSpheric, Trioptics, Germany). In all lenses, we evaluated the modulation transfer function (MTF) at 50 lp/mm and 100 lp/mm and the Strehl Ratio using a 3-mm (photopic) and 4...
February 8, 2017: BMC Ophthalmology
https://www.readbyqxmd.com/read/28152553/the-effect-of-aberrations-on-objectively-assessed-image-quality-and-depth-of-focus
#4
Antonio J Del Águila-Carrasco, Scott A Read, Robert Montés-Micó, D Robert Iskander
The effects of aberrations on image quality and the objectively assessed depth of focus (DoF) were studied. Aberrometry data from 80 young subjects with a range of refractive errors was used for computing the visual Strehl ratio based on the optical transfer function (VSOTF), and then, through-focus simulations were performed in order to calculate the objective DoF (using two different relative thresholds of 50% and 80%; and two different pupil diameters) and the image quality (the peak VSOTF). Both lower order astigmatism and higher order aberration (HOA) terms up to the fifth radial order were considered...
February 1, 2017: Journal of Vision
https://www.readbyqxmd.com/read/28150357/prevalence-and-correlates-of-somatoform-disorders-in-the-elderly-results-of-a-european-study
#5
Maria Christina Dehoust, Holger Schulz, Martin Härter, Jana Volkert, Susanne Sehner, Anna Drabik, Karl Wegscheider, Alessandra Canuto, Kerstin Weber, Mike Crawford, Alan Quirk, Luigi Grassi, Chiara DaRonch, Manuel Munoz, Berta Ausin, Anna Santos-Olmo, Arieh Shalev, Ora Rotenstein, Yael Hershkowitz, Jens Strehle, Hans-Ulrich Wittchen, Sylke Andreas
Somatoform disorders have rarely been addressed in epidemiological and health care services studies of the elderly. The few existing studies vary considerably in their methodologies limiting comparability of findings. Data come from the MentDis_ICF65+ study, in which a total of 3142 community-dwelling respondents aged 65-84 years from six different countries were assessed by the Composite International Diagnostic Interview adapted to the needs of the elderly (CIDI65+). The 12-month prevalence rate for any somatoform disorders was found to be 3...
February 1, 2017: International Journal of Methods in Psychiatric Research
https://www.readbyqxmd.com/read/28105741/potential-use-of-cubic-phase-masks-for-extending-the-range-of-clear-vision-in-presbyopes-initial-calculation-and-simulation-studies
#6
Justo Arines, Citlalli Almaguer, Eva Acosta
PURPOSE: In this paper we analyse the potential use of a non-symmetrical optical element, a cubic phase mask, for extending the range of clear vision of presbyopic eyes. Additionally, we will discuss the appropriateness of the visual Strehl ratio to analyse this sort of presbyopic solution based on non-symmetrical phase masks contrasted with through-focus retinal images. METHODS: In order to evaluate the performance of the cubic phase mask we employed computational Fourier Optics to compute the different visual Strehl criteria as well as simulate the retinal images...
January 20, 2017: Ophthalmic & Physiological Optics: the Journal of the British College of Ophthalmic Opticians (Optometrists)
https://www.readbyqxmd.com/read/27958424/spectral-phase-effects-and-control-requirements-of-coherent-beam-combining-for-ultrashort-ultrahigh-intensity-laser-systems
#7
Yong Cui, Yan-Qi Gao, Ze-Xi Zhao, Zhong-Yang Xu, Ning An, Da-Wei Li, Jian-Wei Yu, Tao Wang, Guang Xu, Wei-Xin Ma, Ya-Ping Dai
Based on the premise that further improvements to the size and damage threshold of large-aperture optical components are severely limited, coherent beam combining (CBC) is a promising way to scale up the available peak power of pulses for ultrashort ultrahigh intensity laser systems. Spectral phase effects are important issues and have a significant impact on the performance of CBC. In this work, we analyze systematically factors such as spectral dispersions and longitudinal chromatism, and get the general spectral phase control requirements of CBC for ultrashort ultrahigh intensity laser systems...
December 10, 2016: Applied Optics
https://www.readbyqxmd.com/read/27958406/single-acquisition-wide-field-superresolution-for-telescopes
#8
Steve Wereley, Yuxing Zhang, Jian-Wei Khor, Craig Snoeyink
A simple optical setup is introduced here that is capable of improving the diffraction-limited angular resolution of a telescope at minimal cost to image quality. The system consists of, at minimum, an axicon and a convex lens located in the optical path of the telescope, which can increase the angular resolution by up to 38%. Analytical results for this resolution gain along with the Strehl ratio of this system are presented along with experimental results, which show a 30% improvement in single-acquisition image resolution with a Strehl ratio of 0...
December 10, 2016: Applied Optics
https://www.readbyqxmd.com/read/27895981/perceived-image-quality-with-simulated-segmented-bifocal-corrections
#9
Carlos Dorronsoro, Aiswaryah Radhakrishnan, Pablo de Gracia, Lucie Sawides, Susana Marcos
Bifocal contact or intraocular lenses use the principle of simultaneous vision to correct for presbyopia. A modified two-channel simultaneous vision simulator provided with an amplitude transmission spatial light modulator was used to optically simulate 14 segmented bifocal patterns (+ 3 diopters addition) with different far/near pupillary distributions of equal energy. Five subjects with paralyzed accommodation evaluated image quality and subjective preference through the segmented bifocal corrections. There are strong and systematic perceptual differences across the patterns, subjects and observation distances: 48% of the conditions evaluated were significantly preferred or rejected...
November 1, 2016: Biomedical Optics Express
https://www.readbyqxmd.com/read/27828088/virtual-pyramid-wavefront-sensor-for-phase-unwrapping
#10
Vyas Akondi, Brian Vohnsen, Susana Marcos
Noise affects wavefront reconstruction from wrapped phase data. A novel method of phase unwrapping is proposed with the help of a virtual pyramid wavefront sensor. The method was tested on noisy wrapped phase images obtained experimentally with a digital phase-shifting point diffraction interferometer. The virtuality of the pyramid wavefront sensor allows easy tuning of the pyramid apex angle and modulation amplitude. It is shown that an optimal modulation amplitude obtained by monitoring the Strehl ratio helps in achieving better accuracy...
October 10, 2016: Applied Optics
https://www.readbyqxmd.com/read/27791380/polarization-insensitive-metalenses-at-visible-wavelengths
#11
M Khorasaninejad, A Y Zhu, C Roques-Carmes, W T Chen, J Oh, I Mishra, R C Devlin, F Capasso
In this Letter, we demonstrate highly efficient, polarization-insensitive planar lenses (metalenses) at red, green, and blue wavelengths (λ = 660, 532, and 405 nm). Metalenses with numerical apertures (NA) of 0.85 and 0.6 and corresponding efficiencies as high as 60% and 90% are achieved. These metalenses are less than 600 nm-thick and can focus incident light down to diffraction-limited spots as small as ∼0.64λ and provide high-resolution imaging. In addition, the focal spots are very symmetric with high Strehl ratios...
November 9, 2016: Nano Letters
https://www.readbyqxmd.com/read/27776082/effect-of-decentration-on-the-optical-quality-of-two-intraocular-lenses
#12
Carolina Ortiz, José J Esteve-Taboada, Lurdes Belda-Salmerón, Daniel Monsálvez-Romín, Alberto Domínguez-Vicent
PURPOSE: To analyze the effect of decentration on the optical quality of two diffractive-refractive intraocular lenses, a bifocal and a trifocal, when displaced laterally (horizontal direction) from the center. METHODS: The AT LISA 809M IOL (+3.75 D add) with two main foci and the AT LISA tri 839MP intraocular lens with three main foci (Carl Zeiss Meditec AG, Jena, Germany) were analyzed. The optical quality of the intraocular lenses was measured with the PMTF (power and modulation transfer function [MTF] measurement for refractive and diffractive intraocular lenses) optical bench (Lambda-X, Nivelles, Belgium)...
December 2016: Optometry and Vision Science: Official Publication of the American Academy of Optometry
https://www.readbyqxmd.com/read/27759711/can-down-gaze-during-near-work-cause-peripheral-deprivation-in-asian-eyes
#13
Renfeng Xu, Huachun Wang, Feng Jiang, Chunyan Xue, Zhenping Huang, Arthur Bradley
PURPOSE: We hypothesize that the typically narrower palpebral apertures of East Asian eyes in combination with the narrowing of this aperture during down-gaze combine to reduce light levels and image contrast in the inferior retina during near work, thus creating peripheral deprivation in these eyes that could generate deprivation myopia in children culturally encouraged to perform near work. METHODS: We photographed the right eyes of 53 Chinese children during down-gaze (from 10 to 40 degrees) from the fixation point and the primary gaze position...
December 2016: Optometry and Vision Science: Official Publication of the American Academy of Optometry
https://www.readbyqxmd.com/read/27749846/experimental-demonstration-of-a-light-beam-with-superior-aberration-resilience
#14
Md Gaffar, Ranjan Kalita, Bosanta R Boruah
In this Letter, we present the experimental results of a focused light beam that exhibits superior resilience to various common monochromatic aberrations. The light beam, obtained by applying a helical phase mask on an azimuthally polarized beam, has an Airy pattern that is like a circularly symmetric focal spot. Our results show that the beam in the presence of aberrations has better performance in terms of the Strehl ratio and the effect on the radius of the encircled energy relative to a normal linearly polarized or circularly polarized beam...
October 1, 2016: Optics Letters
https://www.readbyqxmd.com/read/27607647/influence-of-non-kolmogorov-atmospheric-turbulence-on-the-beam-quality-of-vortex-beams
#15
Jinhong Li, Weiwei Wang, Meiling Duan, Jinlin Wei
Based on the extended Huygens-Fresnel principle and the definition of second-order moments of the Wigner distribution function (WDF), the analytical expressions for the propagation factors (M<sup>2</sup>-factors) and Strehl ratio S<sub>R</sub> of the Gaussian Schell-model (GSM) vortex beams and GSM non-vortex beams propagation through non-Kolmogorov atmospheric turbulence are derived, and used to study the influence of non-Kolmogorov atmospheric turbulence on beam quality of the GSM vortex beams...
September 5, 2016: Optics Express
https://www.readbyqxmd.com/read/27563677/outcomes-of-a-management-strategy-in-eyes-with-corneal-irregularity-and-cataract
#16
Mathew Kurian Kummelil, Rohit Shetty, Luci Kaweri, Shama Shaligram, Mukesh Paryani
Purpose. To evaluate the outcomes of a management strategy in patients with irregular corneas and cataract. Methods. Six eyes of four patients presented for cataract surgery with irregular corneas following corneal refractive surgery. Topoguided ablation regularised the cornea, followed by phacoemulsification and intraocular lens implantation. Zonal keratometric coefficient of variation (ZKCV) measured structural changes and visual quality metrics measured functional improvement. Results. The mean duration after corneal refractive surgery was 7...
2016: BioMed Research International
https://www.readbyqxmd.com/read/27560851/effect-of-target-luminance-on-optimum-pupil-diameter-for-presbyopic-eyes
#17
Renfeng Xu, Larry Thibos, Arthur Bradley
PURPOSE: To quantify the optimum pupil diameters for presbyopic eyes when environmental light levels vary from high photopic to low mesopic. METHODS: We computed the white light visual Strehl ratio from the polychromatic optical transfer function (VSOTF). The impact on image quality of retinal illuminance and the accompanying changes in photon noise were reflected in changing neural contrast sensitivity. VSOTF was calculated for focused and -2D defocused images, over a wide range of photopic and mesopic target luminances, and for pupil diameters ranging from 1 to 7 mm...
August 24, 2016: Optometry and Vision Science: Official Publication of the American Academy of Optometry
https://www.readbyqxmd.com/read/27556991/field-experiment-and-image-reconstruction-using-a-fourier-telescopy-imaging-system-over-a-600-m-long-horizontal-path
#18
Shu-Hai Yu, Lei Dong, Xin-Yue Liu, Xu-Dong Lin, Hao-Ran Megn, Xing Zhong
To confirm the effect of uplink atmospheric turbulence on Fourier telescopy (FT), we designed a system for far-field imaging, utilizing a T-type laser transmitting configuration with commercially available hardware, except for a green imaging laser. The horizontal light transmission distance for both uplink and downlink was ∼300  m. For both the transmitting and received beams, the height upon the ground was below 1 m. The imaging laser's pointing accuracy was ∼9.3  μrad. A novel image reconstruction approach was proposed, yielding significantly improved quality and Strehl ratio of reconstructed images...
August 20, 2016: Applied Optics
https://www.readbyqxmd.com/read/27534503/effects-of-small-misalignments-on-the-intensity-and-strehl-ratio-for-a-laser-beam-focused-by-an-off-axis-parabola
#19
Luca Labate, Paolo Ferrara, Lorenzo Fulgentini, Leonida A Gizzi
A general procedure is described to calculate the intensity and Strehl ratio, at a generic plane in the focal region, of a beam focused by an off-axis parabolic mirror in the presence of small misalignments. The general theoretical framework is first developed, which allows a full vector diffraction treatment in the case of general misalignments. Then, a parametric numerical study is reported, aimed at highlighting the tolerances of both the intensity and Strehl ratio for small misalignments, for different focusing and off-axis parabola parameters...
August 10, 2016: Applied Optics
https://www.readbyqxmd.com/read/27519076/strehl-ratio-as-the-fourier-transform-of-a-probability-density-of-error-differences
#20
Miguel A Alonso, G W Forbes
To give useful insight into the impact of mid-spatial frequency structure on optical performance, the Strehl ratio is shown to correspond to the Fourier transform of a simple statistical characterization of the aberration in the exit pupil. This statistical description is found simply by autocorrelating a histogram of the aberration values. In practice, the histogram itself can often be approximated by a convolution of underlying histograms associated with fabrication steps and, together with the final autocorrelation, it follows from the central limit theorem that the Strehl ratio as a function of the scale of the phase error is generally approximated well by a Gaussian...
August 15, 2016: Optics Letters
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