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Accepted papers to appear in an upcoming issue

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Optical evaluation of new design multifocalIOLs with extended depth of focus

Eva Filippaki, Laure Gobin, Jaini Mandoda, Sébastien Lamy, and Fannie Castignoles

Doc ID: 352072 Received 20 Nov 2018; Accepted 14 Mar 2019; Posted 15 Mar 2019  View: PDF

Abstract: In this study, we investigate in vitro the optical performance of new designextended depth of focus (EDOF) complementary IOLs (ACTIVE, Cristalens Industrie,France), compared with traditional bifocal ones. Evaluation of their optical quality wasachieved by measuring the Point Spread Function (PSF) at multiple distances (through focus)using an optical bench. In addition, the Modulation Transfer Function (MTF) through focuswas calculated, correlating our results with actual visual outcomes. Our results may suggestthat these new EDOF IOLs, when implanted together, could possibly better controlmultifocality, offering an increased depth of focus at all distances.

Modeling and optimization of closed-loop retinalmotion tracking in scanning light ophthalmoscopy

Xinqi Hu and Qiang Yang

Doc ID: 345703 Received 11 Sep 2018; Accepted 12 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: The model of the closed-loop retinal motion tracking in an adaptive optics scanning light ophthalmoscope (AOSLO)was built and the tracking performance was optimized by minimizing the root-mean-square (RMS) of the residualmotion. We started with an evaluation of the fidelity of the retinal motion measurement, and then analyzed thetransfer function of the system and power spectral density of retinal motion from human eyes, to achieve theoptimal control gain and sampling frequency. The performance was further enhanced by incorporating retinalmotion prediction during the period that the slow scanner was retracing. After optimization, residual imagemotion performance was improved by 33% with a nearly 50% reduction in computational cost in comparison toour previous setup, reaching a 3dB bandwidth of 15-17 Hz, which is close to the frame rate (~21 fps) of this AOSLOsystem.

Comparison of MAP method with classical methods forbandpass correction of white LED spectra

Guo Xia, Yan Ma, Xu Chen, Shiqun Jin, and Chan Huang

Doc ID: 348487 Received 17 Oct 2018; Accepted 12 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: The bandwidth of the spectrometer is an important error influencing factor during the spectral measurement. In orderto obtain accurate results, the bandpass correction is an indispensable step in spectral data processing. For dealing with suchproblem several methods have been proposed, including the Differential Operator method using local polynomialapproximation and the Richardson-Lucy method combining with the regularization. Here we employ a method based on themaximum a posterior estimation. Through a large number of experiments of white LED spectra, the efficiency of the employedmethod is verified. By comparing the error of reference spectrum, it was found that this method can effectively correct spectrathus to provide more accurate information for further analysis.

Improved linear response in a modal wavefront sensor

Bosanta Boruah and Santanu Konwar

Doc ID: 355750 Received 19 Dec 2018; Accepted 12 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: The modal wavefront sensor provides a direct and less computationally intensive way, relative to a zonalwavefront sensor, of estimating the various aberration modes present in a beam of light. Such wavefrontsensors are particularly useful when the optical system concerned is effected by a limited number ofaberration modes. Unfortunately the basic design of the modal wavefront sensor suffers from reducedlinear response and inter-modal cross talk. As a result of the reduced linear response the magnitude of anaberration mode estimated by a modal wavefront sensor may differ from the actual strength of the aberrationmode. This difference is even more if other aberration modes, in addition to the aberration modeto be detected, also referred to as the sensor mode, are present in the beam. In this paper we proposea modal wavefront sensing scheme where the sensor output has significantly enhanced linear response.The proposed scheme also provides superior inter-modal cross talk immunity, especially for a few selectedaberration modes. We first show theoretically how by incorporating a variable magnitude of thesensor mode into the beam the precise strength of the same mode can be estimated. Results from numericalsimulation and an experiment using a proof of principle setup demonstrate the improved performanceby the proposed scheme.

Iterative Design of Multilayered Dielectric Microspheres with Tunable Transparency Windows

Nicholas Hudak, Benjamin Garrett, Brendan DeLacy, and Mark Mirotznik

Doc ID: 357363 Received 10 Jan 2019; Accepted 12 Mar 2019; Posted 12 Mar 2019  View: PDF

Abstract: Suspensions of microparticles dispersed in air or liquids are useful for designing a media with desirable optical extinction properties within the visible or infrared spectrum. We describe here a numerical iterative optimization algorithm used to design multilayered concentric dielectric spheres with prescribed optical scattering properties. Our method integrates a computationally efficient rigorous electromagnetic solver, based on Mie theory, within an optimization loop to determine specific particle configurations that best meet a desired optical response. In particular, we show that this method can be used to design all dielectric spherical particles that possess narrow tunable transparency windows while removing any angular dependency on the optical response.

Field-effect transistor based on surface plasmon polaritons

Igor Dzedolik and Sergey Skachkov

Doc ID: 356749 Received 04 Jan 2019; Accepted 11 Mar 2019; Posted 15 Mar 2019  View: PDF

Abstract: Surface plasmon polaritons (SPPs) can be excited by a spaser on the surface of metal strip waveguide embedded into dielectric medium. If a local inhomogeneity of the strip waveguide permittivity is generated by an external electric field, the propagating SPPs are partially reflected from the inhomogeneity, and they partially pass through this inhomogeneity. Such external electric field can be applied on the metal electrode located under the isolated nano-plate in the middle of the strip waveguide. In this case, a signal on the control electrode changes the permittivity of near-surface layer of the nano-plate. Thus, the control signal modulates the intensity of SPP signal transmitted on the strip waveguide. The plasmon field-effect transistor (FET) can be designed based on this principle. The “NOR” (Peirce’s arrow) plasmon logic gate, which is a functionally complete basis for logical operations in processors operating at optical frequencies, can be designed by using the plasmon FET.

Impact of time-variant turbulence behavior onprediction for adaptive optics systems

Maaike van Kooten, Niek Doelman, and Matthew Kenworthy

Doc ID: 355906 Received 21 Dec 2018; Accepted 09 Mar 2019; Posted 11 Mar 2019  View: PDF

Abstract: For high contrast imaging systems, the time delay is one of the major limiting factors for the performanceof the extreme adaptive optics (AO) sub-system and, in turn, the final contrast. The time delay is due tothe finite time needed to measure the incoming disturbance and then apply the correction. By predictingthe behavior of the atmospheric disturbance over the time delay we can in principle achieve a betterAO performance. Atmospheric turbulence parameters which determine the wavefront phase fluctuationshave time-varying behavior. We present a stochastic model for wind speed and model time-variant atmosphericturbulence effects using varying wind speed. We test a low-order, data-driven predictor, thelinear minimum mean square error predictor, for a near-infrared AO system under varying conditions.Our results show varying wind can have a significant impact on the performance of wavefront prediction,preventing it from reaching optimal performance. The impact depends on the strength of the wind fluctuationswith the greatest loss in expected performance being for high wind speeds.

Haidinger’s brushes elicited at varying degrees ofpolarization rapidly and easily assesses total macularpigmentation

Shelby Temple, Nicholas Roberts, and Gary Misson

Doc ID: 352122 Received 20 Nov 2018; Accepted 07 Mar 2019; Posted 08 Mar 2019  View: PDF

Abstract: Macular pigments (MPs), by absorbing potentially toxic short wavelength (400 – 500 nm) visible light, provideprotection against photo-chemical damage thought to be relevant in the pathogenesis of age-related maculardegeneration (AMD). A method of screening for low levels of MPs could be part of a prevention strategy forhelping people to delay the onset of AMD. We introduce a new method for assessing MP density that takesadvantage of the polarization-dependent absorption of blue light by MPs, which results in the entopticphenomenon called Haidinger's brushes (HB). Subjects were asked to identify the direction of rotation of HBwhen presented with a circular stimulus illuminated with an even intensity of polarized white light in which theelectric field vector was rotating either clockwise or anti-clockwise. By reducing the degree of polarization of thestimulus light, a threshold for perceiving HB (degree of polarization threshold) was determined and correlated(r2 = 0.66) to macular pigment optical density assessed using dual-wavelength fundus autofluoresence. Thespeed and ease of measurement of degree of polarization threshold makes it well suited for large-scalescreening of macular pigmentation.

Contributions to Accommodative Loss ofAgeing Human Lens by Shape and Stiffness:An Assessment using Finite Element Models

Kehao Wang, Masato Hoshino, Kentaro Uesugi, Naoto Yagi, and Barbara Pierscionek

Doc ID: 351176 Received 06 Nov 2018; Accepted 06 Mar 2019; Posted 07 Mar 2019  View: PDF

Abstract: Ageing changes to the various components of the accommodative system of theeye lens contribute to the loss of focusing power. The relative contributions of each ageingcomponent, however, are not well defined. This study investigates the contribution ofgeometric parameters and material properties on accommodation simulated using modelsbased on human lenses aged 16, 35 and 48 years. Each model was tested using two differentsets of material properties and a range of zonular fibre angles and compared to results from invivo measurements. The geometries and material parameters of older and younger lensmodels were interchanged to investigate the role of shape and material on accommodativecapacity. Results indicate that geometry has the greater role in accommodation.

Convex optimization-based blind deconvolution for images taken with coherent illumination

R Doelman and Michel Verhaegen

Doc ID: 354788 Received 07 Dec 2018; Accepted 04 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: A rank-constrained reformulation of the blind deconvolution problem on images taken with coherent illumination is proposed.Since the reformulation is affine in the decision variables, we propose a novel convex heuristic for the blind deconvolution problem.The proposed heuristic allows for easy incorporation of prior information on the decision variables and the use of the phase diversity concept.The convex optimization problem can be iteratively re-parameterized to obtain better estimates.The proposed methods are demonstrated on numerically illustrative examples.

Use of 4-aperture DIMM instrument for atmosphericcoherence time estimation: An analytical development

mohsen panahi, Ramin Shomali, and mahmood mollabashi

Doc ID: 355360 Received 13 Dec 2018; Accepted 02 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: We report an analytic method to estimate the Fried parameter r0, the average wind speed v and subsequentlythe atmospheric coherence time t0 via a 4- aperture differential image motion monitor (4-apertureDIMM) instrument. The theory developed here, shows that the velocity of defocus aberration is statisticallyrelated to atmospheric turbulence parameters which are measured by means of angle of arrival (AA)fluctuations. Then, by using the variance of the defocus velocity of 4-spots and the derived analytic relation,the atmospheric coherence time can be estimated. In parallel to the analytic work, some sequencesof a star image with 700 Hz acquisition frequency are considered to simulate the atmospheric defocusand its variations by the 4-aperture DIMM instrument for the first ten-kilometers near the ground in bothone-layer and three-layer atmospheric models. The estimations from the analytic method are found tobe in good agreement with the simulation data obtained for a star light propagating through differentatmospheric conditions.

Doppler Fluctuation Spectroscopy ofIntracellular Dynamics in Living Tissue

Zhe Li, Hao Sun, John Turek, Shadia Jalal, Michael Childress, and David Nolte

Doc ID: 354728 Received 06 Dec 2018; Accepted 01 Mar 2019; Posted 04 Mar 2019  View: PDF

Abstract: Intracellular dynamics in living tissue are dominated by active transport driven bybioenergetic processes far from thermal equilibrium. Intracellular constituents typicallyexecute persistent walks. In the limit of long mean-free paths, the persistent walks areballistic, exhibiting a “Doppler edge” in light scattering fluctuation spectra. At shortertransport lengths, the fluctuations are described by lifetime-broadened Doppler spectra.Dynamic light scattering from transport in the ballistic, diffusive or the cross-over regime isderived analytically, including the derivation of autocorrelation functions through a drivendamped harmonic oscillator analog for light scattering from persistent walks. The theory isvalidated through Monte Carlo simulations. Experimental evidence for the Doppler edge in3D living tissue is obtained using biodynamic imaging based on low-coherence interferometryand digital holography.

Quasinormal mode solvers for resonators with dispersivematerials

Philippe Lalanne, Wei Yan, Alexandre Gras, Christophe Sauvan, Jean-Paul Hugonin, Mondher Besbes, Guillaume Demesy, minh duy truong, Boris Gralak, Frederic Zolla, Andre Nicolet, Felix binkowski, Lin Zschiedrich, Sven Burger, j Zimmerling, Rob Remis, H. Urbach, Haitao Liu, and Thomas Weiss

Doc ID: 353138 Received 28 Nov 2018; Accepted 27 Feb 2019; Posted 06 Mar 2019  View: PDF

Abstract: Optical resonators are widely used in modern photonics. Their spectral response and temporal dynamics arefundamentally driven by their natural resonances, the so-called quasinormal modes (QNMs), with complexfrequencies. For optical resonators made of dispersive materials, the QNM computation requires solving a nonlineareigenvalue problem. This rises a difficulty that is only scarcely documented in the literature. We review our recentefforts for implementing efficient and accurate QNM-solvers for computing and normalizing the QNMs of micro- andnano-resonators made of highly-dispersive materials. We benchmark several methods for three geometries, atwo-dimensional plasmonic crystal, a two-dimensional metal grating, and a three-dimensional nanopatch antenna ona metal substrate, in the perspective to elaborate standards for the computation of resonance modes.

Reflection behavior of two-dimensional superquadraticsubwavelength gratings for siliconbasedphotovoltaics

Ke Chen, Rui Wu, Hongmei Zheng, Guojun Zhang, Yuanyuan Wang, Haishuo Wang, and Shunhua Chen

Doc ID: 352736 Received 26 Nov 2018; Accepted 27 Feb 2019; Posted 27 Feb 2019  View: PDF

Abstract: We theoretically introduce a concept of two-dimensional super-quadraticsubwavelength gratings (2D SQSWGs) to further investigate how geometrical shapeinfluences the reflection behavior for biomimetic moth-eye structures, and the outline shapecan be controlled by changing the degree of the grating's profile function. Numerical studieson the reflection behavior of the 2D SQSWGs and nanorod gratings reveal that the parabolashapedgrating (degree n = 2) with a nearly linear graded index profile has superiorantireflection performance, and its average weighted reflectivity (Rave) is as low as 0.99%under AM1.5 solar illumination. Moreover, research results indicate that the 2D nanoconegratings (n = 1) have the best angle-independent optical property. The research findings canbe used to guide the design of photovoltaic cells based on biomimetic moth-eye structures,and the concept of 2D SQSWGs can be potentially applied to other photovoltaic and opticaldevices.

Tear film stability assessment by cornealreflex image degradation

Mikel Aldaba, Alejandro Mira-Agudelo, John Barrera Ramírez, CARLOS GARCIA, and Jaume Pujol

Doc ID: 348098 Received 07 Nov 2018; Accepted 26 Feb 2019; Posted 28 Feb 2019  View: PDF

Abstract: Tear film stability assessment is one of the main tests in dry eye diagnosis.However, up to date, no test methodology has been adopted as the gold standard due toseveral reasons, such as the methods being invasive, subjective, or unfeasible for the clinicalenvironment. In this article, a method that overcomes the above-mentioned limitations for tearfilm stability measurements is presented, and is based on the degradation of corneal refleximages caused by breaks up. The experimental setup, which is based on recording the cornealreflex image or the first Purkinje image, is described, as well as the method used to determinetear film stability by means of the associated break up time using the corneal reflex imagedegradation. Images obtained through simulations of the experimental setup are also shown.Moreover, break up time measurements performed using both the conventional fluoresceinmethod and the proposed method in nine healthy adults are presented. Both the experimentaland simulation images show corneal reflex image degradation due to the appearance of breaksup in the tear film, highlighting the potential of the method to assess tear film stability. Inconclusion, we have shown that the corneal reflex image degrades when the tear film breaksup and, thus, the proposed method can be used to assess tear film stability.

Simulation of UV power absorbed by follicular stem cells duringsun exposure and possible implications for melanomadevelopment

Xiyong Huang, Mike Protheroe, Ahmed Al-Jumaily, Andrew Chalmers, sharad Paul, and Xiang Fu

Doc ID: 354590 Received 05 Dec 2018; Accepted 22 Feb 2019; Posted 25 Feb 2019  View: PDF

Abstract: The incidence of melanoma in children is extremely rare. However, there is convincingevidence supporting a higher risk of developing melanoma in individuals who haveexperienced excessive sun exposure during their childhood. A possible explanation for thisphenomenon is that prior to puberty, the melanocyte stem cells in the bulge region of hairfollicles are much shallower in the dermis, resulting in their increased vulnerability to sunexposure. To validate this hypothesis, a Monte Carlo simulation of light transport is applied toquantify the dose of UV power absorbed in the stem-cell layers at different depths in bothchild and adult skins. The simulated results suggest that the stem cells in vellus hair follicleswould absorb over 250 times higher UV power than those in the terminal hair follicles. Due tothe thinner epidermis in child skin, the stem cells in vellus hair follicles absorb about 1.9 and3.2 times greater ultraviolet A and ultraviolet B respectively than those in adult skin. Thesefindings provide a possible explanation to why children are particularly vulnerable to sunexposure.

Perfect matching of concave diffraction grating withcontinuously circular Bragg mirrors on SOI platform

Yuzheng Mao, Jingping Zhu, Ke Li, Bingzheng Du, and Xun Hou

Doc ID: 353081 Received 29 Nov 2018; Accepted 21 Feb 2019; Posted 22 Feb 2019  View: PDF

Abstract: A concave diffraction grating (CDG) based on circularBragg mirrors was constructed on the 220 nm silicon-oninsulator(SOI) platform. This continuous and smoothdielectric mirror is employed to eliminate the extra scatteringloss occurred at the connecting with neighbouringgrating teeth. A perfect matching between theBragg condition and the grating condition was derivedto determine the geometrical parameters of the gratingprofile. FDTD simulation shows that the reflection ofthe designed Bragg mirror can be up to 99.7% over abroad bandwidth of 330 nm. And the grating with circularBragg mirrors exhibits low insertion loss in a relativelyhigh order of M=5 with some unwanted diffractionorders suppressed, thus creating a large dispersionwhile keeping compact structure.

Measurement of the diffusion of light within paper

Geoffrey Rogers, Olympe Corblet, Thierry Fournel, and Mathieu Hébert

Doc ID: 356884 Received 07 Jan 2019; Accepted 18 Feb 2019; Posted 19 Feb 2019  View: PDF

Abstract: The diffusion of light within paper has an affect on the colors in a halftone image, and must be takeninto consideration in modeling halftone color. The diffusion can be accounted for by using the pointspread function, or equivalently the modulation transfer function (MTF) of the paper. A novel methodof measurement of paper MTF, called the bar-target series expansion method, is proposed here. Theexperimental results of the method confirm that the shape of the MTF is an exponential function, whichcorresponds to a Lorentzian line spread function as predicted by the multiple-path model of reflection.

Hyperspectral imaging in color vision research:Tutorial

David Foster and Kinjiro Amano

Doc ID: 347289 Received 01 Oct 2018; Accepted 11 Jan 2019; Posted 15 Jan 2019  View: PDF

Abstract: This tutorial offers an introduction to terrestrial and close-range hyperspectral imaging and some of its uses inhuman color vision research. The main types of hyperspectral cameras are described together with proceduresfor image acquisition, postprocessing, and calibration for either radiance or reflectance data. Imagetransformations are defined for colorimetric representations, color rendering, and cone receptor andpostreceptor coding. Several example applications are also presented. These include calculating the colorproperties of scenes, such as gamut volume and metamerism, and analyzing the utility of color in observertasks, such as identifying surfaces under illuminant changes. The effects of noise and uncertainty areconsidered both in image acquisition and in color vision applications.

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