Read by QxMD icon Read

Strehl ratio

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
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
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
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
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
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
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
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
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
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
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
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
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
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
Raimundo Jiménez, Almudena Valero, Joaquín Fernández, Rosario G Anera, José R Jiménez
PURPOSE: To evaluate the time course of the optical quality and visual performance with a microincision monofocal intraocular lens (Incise). SETTING: Hospital Torrecárdenas, Almería, Spain. DESIGN: Prospective study. METHODS: The visual and refractive outcomes were evaluated in eyes with the microincision IOL preoperatively and 1, 3, and 6 months postoperatively. The modulation transfer function (MTF) cutoff frequency, Strehl ratio, and objective scatter index (OSI) were used to measure optical quality...
July 2016: Journal of Cataract and Refractive Surgery
Joan A Martínez-Roda, Meritxell Vilaseca, Juan C Ondategui, Montserrat Aguirre, Jaume Pujol
BACKGROUND: We assessed the effects of aging on visual function and optical quality in a healthy adult population and provide reference values for different age ranges. METHODS: We conducted a prospective study with 198 healthy volunteers from 31 to 70 years of age. The visual acuity (VA) and contrast sensitivity (CS) at 3, 6, 12 and 18 cycles per degree (cpd) frequencies were assessed, together with values of optical quality and intraocular scattering obtained with a double-pass system (Optical Quality Analysis System - OQAS), specifically the modulation transfer function cutoff frequency (MTFcutoff ), the Strehl ratio, the OQAS values (OV) at contrasts of 100, 20 and nine per cent and the objective scatter index (OSI)...
July 24, 2016: Clinical & Experimental Optometry: Journal of the Australian Optometrical Association
Kartikeya Mishra, Frieder Mugele
In this work, we use the numerical simulation platform Zemax to investigate the optical properties of electrically tunable aspherical liquid lenses, as we recently reported in an experimental study [<author order="1"> <name> <first>K.</first> <last>Mishra</last> </name> </author> <author order="2"> <name> <first>C.</first> <last>Murade</last> </name> </author> <author order="3"> <name> <first>B...
June 27, 2016: Optics Express
Nina Leonhard, René Berlich, Stefano Minardi, Alexander Barth, Steffen Mauch, Jacopo Mocci, Matthias Goy, Michael Appelfelder, Erik Beckert, Claudia Reinlein
We explore adaptive optics (AO) pre-compensation for optical communication between Earth and geostationary (GEO) satellites in a laboratory experiment. Thus, we built a rapid control prototyping breadboard with an adjustable point-ahead angle where downlink and uplink can operate both at 1064 nm and 1550 nm wavelength. With our real-time system, beam wander resulting from artificial turbulence was reduced such that the beam hits the satellite at least 66% of the time as compared to merely 3% without correction...
June 13, 2016: Optics Express
Guangming Guo, Hong Liu, Bin Zhang
The aero-optical effects of an optical seeker with a supersonic jet for hypersonic vehicles in near space were investigated by three suites of cases, in which the altitude, angle of attack, and Mach number were varied in a large range. The direct simulation Monte Carlo based on the Boltzmann equation was used for flow computations and the ray-tracing method was used to simulate beam transmission through the nonuniform flow field over the optical window. Both imaging displacement and phase deviation were proposed as evaluation parameters, and along with Strehl ratio they were used to quantitatively evaluate aero-optical effects...
June 10, 2016: Applied Optics
C Strehl, F Buttgereit
Glucocorticoids have been successfully used for a long time to treat a wide range of chronic inflammatory diseases. Despite the well-accepted efficacy, possible adverse effects still provoke discussions among patients and physicians. In particular, the long-term use of glucocorticoids at higher dosages may cause unwanted adverse effects; therefore, the question arises if conditions for a safe long-term treatment regimen with these drugs can be defined. Studies specifically and comprehensively addressing this question are missing; therefore, a multidisciplinary task force comprised of medical experts and patients was formed to analyze and discuss the existing literature in order to identify conditions where long-term glucocorticoid treatment has an acceptably low level of harm...
September 2016: Der Internist
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"