Accepted papers to appear in an upcoming issue
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COLOR VARIANCE ANDACHROMATIC SETTINGS
Michael Webster and Siddhart Srivatsav
DOI: 10.1364/JOSAA.382316 Received 06 Nov 2019; Accepted 17 Jan 2020; Posted 17 Jan 2020 View: PDF
Abstract: The average color in a scene is a potentially important cue to the illuminant and thus for colorconstancy, but it remains unknown how well and in what ways observers can estimate themean chromaticity. We examined this by measuring the variability in “achromatic” settingsfor stimuli composed of different distributions of colors with varying contrast ranges alongthe luminance, SvsLM and LvsM cardinal axes. Observers adjusted the mean chromaticity ofthe palette to set the average to gray. Variability in the settings increased as chromaticcontrast or (to a lesser extent) luminance contrast increased. Signals along the cardinal axesare relatively independent in many detection and discrimination tasks, but showed stronginterference in the white estimates. This “cross-masking” and the effects of chromaticvariance in general may occur because observers cannot explicitly perceive or represent themean of a set of qualitatively different hues (e.g. that red and green hues average to gray), andthus may infer the mean only indirectly (e.g. from the relative saturation of different hues).
A Comparison of Two Methods of Hue Scaling
Courtney Matera, Kara Emery, Vicki Volbrecht, kavita vemuri, Paul Kay, and Michael Webster
DOI: 10.1364/JOSAA.382402 Received 06 Nov 2019; Accepted 17 Jan 2020; Posted 17 Jan 2020 View: PDF
Abstract: Hue-scaling functions are designed to characterize color appearance by assessingthe relative strength of the red vs. green and blue vs. yellow opponent-sensations comprisingdifferent hues. However, these judgments can be non-intuitive and may pose difficulties formeasurement and analysis. We explored an alternative scaling method based on positioning adial to represent the relative similarity or distance of each hue from the labeled positions forthe opponent categories. The hue-scaling and hue-similarity rating methods were comparedfor 28 observers. Settings on both tasks were comparable though the similarity ratings showedless inter-observer variability and weaker categorical bias, suggesting that these categoricalbiases may reflect properties if the task rather than the percepts. Alternatively, properties thatare concordant for the two paradigms provide evidence for characteristics that do reflect colorappearance. Individual differences on both tasks suggest that color appearance depends onmultiple, narrowly-tuned color processes which are inconsistent with conventional coloropponenttheory.
Chromatic discriminations along two cardinal axes share a commonattentional resource
XIAOHUA ZHUANG and Dingcai Cao
DOI: 10.1364/JOSAA.382161 Received 04 Nov 2019; Accepted 13 Jan 2020; Posted 13 Jan 2020 View: PDF
Abstract: Attentional modulation is specific to either luminance or chromatic contrast discrimination,implying separate attentional resources for processing luminance and chromatic informationprocessing [e.g., Morrone, M.C., Denti, V., Spinelli, D. (2002). Color and luminance contrastsattract independent attention. Current Biology, 12, 1134-37]. However, there are two distinctvisual pathways process chromatic information: the parvocellular (PC-) and koniocellular (KC-)pathways. It is unclear whether there are separate attentional resources modulating the chromaticprocesses in these pathways. Here, we examined the attentional modulation effects on chromaticcontrast discrimination with chromaticities along the l or s cardinal axis on a cone chromaticityspace for preferentially stimulating either the inferred PC- or KC-pathway, respectively. A dualtaskinterference paradigm was used and chromatic contrast discrimination sensitivities underdual-task condition were compared with that under a single-task condition. The results revealedthat compared with the single-task condition, attending to a competing central task in the dualtaskcondition decreased the peripheral discrimination sensitivity in both chromatic cardinal axes,and sensitivity reduced regardless whether the dual tasks were along the same or differentchromatic cardinal axes. These findings indicate that attentional effects on chromatic processesare not specific to cardinal axis, suggesting that the PC- and KC-pathways may share a commonattention resource in modulating chromatic processing.
Tritan color vision deficiency may be associated withan OPN1SW splicing defect and haploinsufficiency
Maureen Neitz, Elise Krekling, Lene Hagen, Hilde Pedersen, Jessica Rowlan, Rachel Barborek, Jay Neitz, Adam Crain, and Rigmor Baraas
DOI: 10.1364/JOSAA.381919 Received 29 Oct 2019; Accepted 13 Jan 2020; Posted 14 Jan 2020 View: PDF
Abstract: Here we present evidence implicating disrupted RNA splicing as a potential cause of inherited tritan color vision.Initially we tested fifty-one subjects for color vision deficiencies. One made significant tritan errors, the others wereclassified as normal trichromats. The putative tritan subject was the only one of the fifty-one subjects found to beheterozygous for an OPN1SW gene mutation that disrupts RNA splicing in an in vitro assay. In order to gather furthersupport for the role of the splicing mutation in tritan color vision, the putative tritan subject’s mother and sister wereexamined. They also made tritan errors and had the same OPN1SW gene mutation.
Relative contributions of melanopsin to brightnessdiscrimination when hue and luminance also vary
Tanner DeLawyer, Sei-ichi Tsujimura, and Keizo Shinomori
DOI: 10.1364/JOSAA.382349 Received 06 Nov 2019; Accepted 13 Jan 2020; Posted 14 Jan 2020 View: PDF
Abstract: A large number of studies have shown an effect of melanopsin-dependent retinal ganglion cells (mRGCs) onhumans performing brightness discrimination tasks. These studies often utilized targets that only differ in theirmelanopsin activation levels, and not in their luminance or hue, which are both factors that have largecontributions to brightness discrimination. The purpose of the present study was to evaluate the relativecontribution of melanopsin activation to brightness discrimination when luminance and hue are also varying inaddition to melanopsin activation. Using an apparatus consisting of three separate high luminance projectors, wewere able to manipulate melanopsin isolating stimulation, and L, M, and S-cone stimulation separately, thusallowing us to vary stimuli in their melanopsin activation, luminance, and hue category independently. Weconstructed three sets of target stimuli with three different levels of melanopsin activation (100%, 131%, and167% relative melanopsin excitation) and five levels of luminance. We then had subjects do a 2-alternative forcedchoice task where they compared the previously described target stimuli set to a set of four comparison stimulithat varied in their hue category, but had identical luminances. We found that in our stimuli set the overallcontribution of melanopsin activity to brightness discrimination was small (an average of 6% increase inlikelihood to call a high melanopsin activity stimulus brighter compared to a low melanopsin activity stimulus)when luminance and hue also varied. However, a significant interaction showed that when the comparison wasbetween stimuli differing only in melanopsin stimulation (with luminance and hue unchanged) the contribution ofmelanopsin to brightness judgements was about three times larger (an average of 18% increase in likelihood tocall a high melanopsin activity stimulus brighter compared to a low melanopsin activity stimulus). This suggeststhat although luminance and hue have large effects on brightness discrimination such that the melanopsincontribution can become hard to detect, when there are minimal cone-dependent signals available melanopsin canhave a large contribution to brightness discrimination.
Caustics of the vortex beams generated byvortex lenses and vortex axicons
Sergey Kharitonov, Svetlana Khonina, Sergey Volotovsky, and Nikolay Kazanskiy
DOI: 10.1364/JOSAA.382361 Received 06 Nov 2019; Accepted 13 Jan 2020; Posted 14 Jan 2020 View: PDF
Abstract: In this work, the propagation of vortex beams is treated using a catastrophe theoryapproach. Analytic expressions are deduced to describe caustic surfaces produced by vortexlenses and vortex axicons. The obtained analytics allow us to explain the formation of theshadow region along the optical axis for vortex beams using geometric optics (previously, thezero axial intensity was explained just by diffraction effects). Thus, the presence of a vortexeikonal leads to a fundamental change in the type of axial caustic. Another importantdistinction of the caustics produced by vortex beams from those produced by non-vortexradial beams has been shown to consist in wavelength-dependence. The results of numericalsimulation show that the propagation operator defined using a geometrical opticsapproximation agrees well with the numerical simulation results obtained using a nonparaxialdiffraction operator based on the conical wave expansion.
A flexible calibration method for visualmeasurement using an improved target withvanishing constraints
Xiaoyun Chen, Jiarui Lin, Yang Linghui, Yanbiao Sun, and jigui zhu
DOI: 10.1364/JOSAA.385897 Received 12 Dec 2019; Accepted 12 Jan 2020; Posted 16 Jan 2020 View: PDF
Abstract: In this paper, an improved calibration method based on vanishing constraints isproposed for calculating the extrinsic parameters of cameras. First, we come up with aimproved target based on the conventional target with two groups of orthogonal parallel lines.The novel target is composed of two groups of parallel lines with a certain angle range from86o to 90o, which can reduce the difficulty of the target production and the manufacturingcost. Furthermore, in the optimization process, we design a new function with a more robustpenalty factor instead of using the experienced values to get the extrinsic parameters for thebinocular vision sensors. Finally, on account of using the improved target and the noveloptimiazation function, the proposed method is more flexible and robust compared withZhang’s method.
Observer Metamerism in Commercial Displays
Hao Xie, Susan Farnand, and Michael Murdoch
DOI: 10.1364/JOSAA.382228 Received 04 Nov 2019; Accepted 12 Jan 2020; Posted 13 Jan 2020 View: PDF
Abstract: Two uniform patches presented on two displays under identical viewing conditions can appear as same color to one observer, but mismatched colors to another observer. This phenomenon, called observer metamerism (OM), occurs due to individual differences in color matching functions. To avoid its potentially adverse impacts in display calibration and characterization, it is desirable to have a predictive model of OM. In this work, we report the computational results of how to use existing metrics to quantify the potential OM between commercial display pairs, and a proposed OM metric which is verified through a psychophysical experiment.
Ring-shaped twisted Gaussian Schell-model array beams
Simin Zheng, caifu yuan, Xiaoling Ji, and Tao Wang
DOI: 10.1364/JOSAA.382599 Received 08 Nov 2019; Accepted 12 Jan 2020; Posted 13 Jan 2020 View: PDF
Abstract: A new partially coherent source which can generate a beam field with ring-shaped twisted array profile is presented and the distribution characteristics of spectral density and degree of coherence of the field are discussed. It is shown that both the spectral density and degree of coherence will rotate along the propagating direction, but in opposite rotating directions. And when the beam propagate to a certain distance, they will not rotate anymore. Furthermore, we find that the distribution properties of the ring-shaped array of the spectral density, including the number of the rings, the number of the lobes of each ring, and the distance of all adjacent lobes, can be properly controlled by adjusting structural parameters of the source.
Quantifying the Loss of Information fromBinning List-Mode Data
Eric Clarkson and MEREDITH KUPINSKI
DOI: 10.1364/JOSAA.375317 Received 13 Aug 2019; Accepted 12 Jan 2020; Posted 13 Jan 2020 View: PDF
Abstract: List-mode data is increasingly being used in SPECT and PET imaging, among otherimaging modalities. However, there are still many imaging designs that effectively bin list-modedata before image reconstruction or other estimation tasks are performed. Intuitively, the binningoperation should result in a loss of information. In this work we show that this is true for Fisherinformation and provide a computational method for quantifying the information loss. In theend we find that the information loss depends on three factors. The first factor is related to thesmoothness of the mean data function for the list-mode data. The second factor is the actualobject being imaged. Finally, the third factor is the binning scheme in relation to the other twofactors.
Color discrimination assessment in patients with hypothyroidism using the Farnsworth-Munsell 100 hue test
Kalina Racheva, Tsvetalin Totev, Emil Natchev, Nadejda Bocheva, and Margarita Vidinova
DOI: 10.1364/JOSAA.382390 Received 04 Nov 2019; Accepted 10 Jan 2020; Posted 10 Jan 2020 View: PDF
Abstract: There is evidence in the literature that hypofunction of the thyroid gland (hypothyroidism) affects color vision inrodents by influencing the production of the visual pigment opsin. The effect of hypothyroidism on color vision inhumans has not been examined in any great detail. In this cross-sectional study we evaluated color discriminationusing the Farnsworth-Munsell 100 hue test (FM-100) in 25 individuals with pre-treatment hypothyroidism (meanage 38±9.2 Yrs), and a control euthyroid group, n=26 (mean age 39.6±8.4 Yrs). There was no statistically significantdifference in the total error score (TES) between the groups, but the hypothyroid group had a significantly greaterpartial error scores (PES) along the blue-yellow (B-Y) axis compared to the red-green (R-G) axis. No statisticallysignificant differences in B-Y and R-G PES were observed in the control group. This study shows thathypothyroidism affects color vision in humans, causing significant impairment in the B-Y color subsystem.
Characterization of the electromagnetic GaussianSchell-model beam using first-order interference
Sethuraj K. R. and Bhaskar Kanseri
DOI: 10.1364/JOSAA.384061 Received 21 Nov 2019; Accepted 09 Jan 2020; Posted 10 Jan 2020 View: PDF
Abstract: We propose a method for the characterization of electromagnetic Gaussian Schell-model (EMGSM) beams.This method utilizes the first-order interference consisting of polarization state projections along with thetwo-point (generalized) Stokes parameters. The second-order field correlations employed in this methodenable us to determine both the magnitude and the argument of the complex degree of electromagneticcoherence. We experimentally demonstrate this method by characterizing an EMGSM beam, which issynthesized using a laser beam passing through a rotating ground glass diffuser. This beam characterizationmethod is expected to be potentially useful for probing the partially coherent and partially polarizedbeams having tremendous applications in broad areas of optical communication and beam propagation.
TomoGAN: Low-Dose Synchrotron X-Ray Tomographywith Generative Adversarial Networks
Zhengchun Liu, Tekin Bicer, Rajkumar Kettimuthu, Doga Gursoy, Francesco De Carlo, and Ian Foster
DOI: 10.1364/JOSAA.375595 Received 16 Aug 2019; Accepted 08 Jan 2020; Posted 09 Jan 2020 View: PDF
Abstract: Synchrotron-based x-ray tomography is a noninvasive imaging technique that allows for reconstructingthe internal structure of materials at high spatial resolutions from tens of micrometers to a few nanometers.In order to resolve sample features at smaller length scales, however, a higher radiation dose isrequired. Therefore, the limitation on the achievable resolution is set primarily by noise at these lengthscales. We present TomoGAN, a denoising technique based on generative adversarial networks, for improvingthe quality of reconstructed images for low-dose imaging conditions. We evaluate our approachin two photon-budget-limited experimental conditions: (1) sufficient number of low-dose projections(based on Nyquist sampling), and (2) insufficient or limited number of high-dose projections. In bothcases the angular sampling is assumed to be isotropic, and the photon budget throughout the experimentis fixed based on the maximum allowable radiation dose on the sample. Evaluation with both simulatedand experimental datasets shows that our approach can significantly reduce noise in reconstructed images,improving the structural similarity score of simulation and experimental data from 0.18 to 0.9 and from0.18 to 0.41, respectively. Furthermore, the quality of the reconstructed images with filtered back projectionfollowed by our denoising approach exceeds that of reconstructions with the simultaneous iterativereconstruction technique, showing the computational superiority of our approach.
Symplectic-ray-tracing based on Hamiltonianoptics in gradient-index media
DOI: 10.1364/JOSAA.378829 Received 26 Sep 2019; Accepted 08 Jan 2020; Posted 09 Jan 2020 View: PDF
Abstract: A method based on the Hamiltonian optics for ray-tracing through gradient-index(GRIN) media is proposed here. The ray equation that describes light ray paths can be writtenin the form of the Hamiltonian equations. Although the Hamiltonian equations can benumerically calculated using a finite-difference explicit method, deviations from the exactequations are generally inevitable at subsequent time-steps. An optical Hamiltonian can beconstructed of two independent terms, namely, one term dependent on position and the otherterm dependent on momentum. The symplectic integrator is applicable to such separableoptical Hamiltonian system, and makes the optical Hamiltonian equations form-invariant ateach time-step of numerical calculations. Accuracies of light ray paths calculated using thefirst order symplectic-ray-tracing in GRIN lenses approximate those calculated on the basis ofthe fourth order Runge-Kutta algorithm, which shows promising potential of the symplecticray-tracing method.
New focal-plane 3D imaging method based on temporalghost imaging: A proof of concept simulation
Bo Zunwang, Wenlin Gong, and Shensheng Han
DOI: 10.1364/JOSAA.381086 Received 23 Oct 2019; Accepted 08 Jan 2020; Posted 09 Jan 2020 View: PDF
Abstract: A new focal-plane three-dimensional (3D) imaging method based on temporal ghost imaging is proposedand demonstrated. By exploiting the advantages of temporal ghost imaging, this method enables theutilization of slow integrating cameras and facilitates 3D surface imaging within the framework of sequentialflood-illumination and focal-plane detection. The depth information is achieved by a temporalcorrelation between received and reference signals with multiple-shot, and the reflectivity informationis achieved by flash imaging with a single-shot. The feasibility and performance of this focal-plane 3Dimaging method have been verified through theoretical analysis and numerical experiments.
Predicting color matches from luminancematches
Kassandra Lee, Alex Richardson, Eric Walowit, Michael Crognale, and Michael Webster
DOI: 10.1364/JOSAA.381256 Received 06 Nov 2019; Accepted 06 Jan 2020; Posted 07 Jan 2020 View: PDF
Abstract: Spectral sensitivity varies among individuals with normal color vision, and thus for manyapplications it is important to measure and correct for the observer’s sensitivity. Fullcorrection would require measuring both color matches and luminance matches, and are rarelyimplemented. However, luminance matches (equiluminance settings) are routinely measuredand simple to conduct. We modeled how well an observer’s color matches could beapproximated by measuring only luminance sensitivity, since both depend on a common setof factors. We show that lens and macular pigment density and L/M cone ratios alterequiluminance settings in different ways and can therefore be estimated from the settings. Inturn, the density variations can account for a large proportion of the normal variation in colormatching. Thus, luminance matches may provide a simple method to at least partially predictan observer’s color matches without requiring more complex tasks or equipment.
Effect of tilt on circular zone plate performance
Sajid Ali and Chris Jacobsen
DOI: 10.1364/JOSAA.380925 Received 21 Oct 2019; Accepted 03 Jan 2020; Posted 06 Jan 2020 View: PDF
Abstract: Fresnel zone plates are frequently used as focusing and imaging optics in x-raymicroscopy, as they provide the ease of use of normal incidence optics. We consider here theeffects of tilt misalignment on their optical performance, both in the thin optics limit and in thecase of zone plates that are sufficiently thick that volume diffraction effects come into play. Usingmultislice propagation, we show that simple analytical models describe the tilt sensitivity ofthin zone plates and the thickness at which volume diffraction must be considered, and examinenumerically the performance of example zone plates for soft x-ray focusing at 0.5 keV, and hardx-ray focusing at 10 keV.
In-vitro monitoring of photoinduced necrosis in HeLacells using digital holographic microscopy andmachine learning
Andrei Belashov, Anna Zhikhoreva, Tatiana Belyaeva, Elena Kornilova, Anna Salova, Irina Semenova, and Oleg Vasyutinskii
DOI: 10.1364/JOSAA.382135 Received 31 Oct 2019; Accepted 03 Jan 2020; Posted 06 Jan 2020 View: PDF
Abstract: Digital holographic microscopy supplemented with thedeveloped cell segmentation and machine learning andclassification algorithms is implemented for quantitativedescription of the dynamics of cellular necrosis inducedby photodynamic treatment in vitro. It is demonstratedthat the developed algorithms operating witha set of optical, morphological and physiological parametersof cells, obtained from their phase images,can be used for automatic distinction between live andnecrotic cells. The developed classifier provides highaccuracy of about 95.5 % and allows for calculation ofsurvival rates in the course of cells death.
Optical coherence tomography modelling incorporating scattering, absorption and multiple reflections
Anna Guan, Steven Hinckley, and Steven Richardson
DOI: 10.1364/JOSAA.377121 Received 14 Oct 2019; Accepted 02 Jan 2020; Posted 03 Jan 2020 View: PDF
Abstract: A direct scattering Optical Coherence Tomography forward model was developed to simulate A-scans for both idealized and real light sources on an arbitrary given sample structure. Previous models neglected absorption, scattering and multiple reflections at interfacial layers, and so two extended models were developed to investigate the impact of these processes. The first model uses the Beer-Lambert Law to incorporate both absorption and scattering optical processes, and the second model uses a recursive form to model multiple reflections. These models were tested on a structure representative of a multi-layered skin sample. The results show that the absorption and scattering processes have significant impact on the height of the peaks in the simulated A-scans. Conversely, the incorporation of multiple reflections has very little impact on the height of these peaks. Neither of the above processes have any impact on the locations of the A-scan peaks, which are associated with the sample interfaces between layers.
Mapping the dipoles orientation distribution within a super-resolution scale via fluorescence polarization modulation
Xiao Wang, YaXin Zhang, WenXia Zhou, DongDong Xu, and JianHua Yin
DOI: 10.1364/JOSAA.380805 Received 17 Oct 2019; Accepted 02 Jan 2020; Posted 03 Jan 2020 View: PDF
Abstract: Conventional fluorescence polarization microscopy (FPM) has been largely used to monitor the orientation and the structural information of targeted biomolecules with fluorescence dipoles but suffers from the optical diffraction limit. Here, we put forward a novel method to simultaneously acquire the super-resolution image and the effective orientation distribution information of dipole-clusters at corresponding super-resolution. In this paper, the orientation distribution of dipole-clusters is statistically modeled by its mean orientation and orientation deviation, and which are respectively represented by the middle direction and the opening angle of a sector shape. According to this model and microscopy imaging theory, the joint reconstruction algorithm is deduced mathematically in detail based on the conjugate gradient least squares (CGLS) method. By applying this method to different samples, the reconstructed results prove more than twice the resolution of wide-field images and the orientation distribution information at corresponding spatial resolution. Furthermore, the high accuracy of this method in reconstructing super-resolution orientation distribution information is verified by Monte Carlo simulations.
Moiré patterns in non-parallel surfaces such as prism
Vladimir Saveljev, Jung-Young Son, Yongsuk Kim, Jong-Gun Park, and Gwanghee Heo
DOI: 10.1364/JOSAA.381169 Received 22 Oct 2019; Accepted 02 Jan 2020; Posted 03 Jan 2020 View: PDF
Abstract: The moiré effect in the 3D objects with planar facets is considered. The projected period of the inclined periodic grating was found based on the rule of the incidence angles. The formula for the period of the moiré patterns in the generalized cylindrical surfaces was obtained, particularly in the objects with arbitrary oriented (parallel and non-parallel) facets, namely, in the parallelepiped and the prism. The similarity between the projected period and the moiré period is demonstrated. The direction to the longest moiré pattern in the wedge is found theoretically and observed in experiments. The experiments confirm the theory.
Generalized Talbot self-healing and noise mitigation of faulty periodic images
Luis Romero Cortes, Hughes Guillet de Chatellus, Antonin Deville, Mohamed Seghilani, Ines Hamam, and Jose Azana
DOI: 10.1364/JOSAA.375703 Received 23 Aug 2019; Accepted 27 Dec 2019; Posted 03 Jan 2020 View: PDF
Abstract: Obtaining high-quality images from physical systems, objects and processes is fundamental for a myriad of areas of science and technology. However, in many situations, the measured images contain defects and/or are accompanied by noise, degrading the quality of the measurement. Recently, a variant of the well-known Talbot self-imaging effect has been shown to redistribute the energy of a spatially-periodic collection of images, obtaining output images with increased energy with respect to the input ones. In this work we experimentally demonstrate that such energy redistribution method has the unique capabilities of increasing the coherent energy level of a periodic set of images over that of the incoherent noise, even allowing to recover images completely buried under noise. We further demonstrate that the process can mitigate potential faults of the periodic image structure, including blocked images, spatial jitter and coherent noise, offering important enhancements (e.g., in regards to the quality of the recovered individual images) in the self-healing capabilities of Talbot self-imaging.
On a novel lightness phenomenon
DOI: 10.1364/JOSAA.382476 Received 06 Nov 2019; Accepted 27 Dec 2019; Posted 03 Jan 2020 View: PDF
Abstract: Purpose of this work is to demonstrate a new lightness phenomenon useful to extend the notion of “belongingness”, crucial to explain a class of illusions including simultaneous lightness contrast, Koffka-Benussi ring, Benary cross and White effect. These phenomena manifest some kind of dissimilarity, difference or change responsible for the perceived contrast. The dissimilarity is related to the “belongingness” of the crucial gray elements to i) a unique or separated/divided object as in Koffka-Benussi ring, or ii) to the figure or to the background as in Benary and White effects. If we plausibly assume that differences and changes are biologically important to be detected and if necessary highlighted, then any visible difference might induce contrast effect. This is the main hypothesis demonstrated by the novel lightness phenomenon based on checks grouped vertically, split in two upper and lower halves, and segregated from the homogeneous gray background. The checks are alternated and vertically-horizontally reversed in the upper and lower half of the pattern. In spite of the constant visual organization and of the identical local contrast within each check, the inner area of the elements of the upper group appears darker than the one of the lower group. The visible dissimilarity, although not related to the notion of belongingness, is sufficient to elicit a clear lightness difference.
Fast and Broadband Computation of Green's Function in Cavity Resonator of Irregular Shape Using Imaginary Wave Number Extraction Technique
Mohammadreza Sanamzadeh and Leung Tsang
DOI: 10.1364/JOSAA.378022 Received 18 Sep 2019; Accepted 27 Dec 2019; Posted 03 Jan 2020 View: PDF
Abstract: A semi-analytical approach for rapid calculation of the Green's function inside the cavity of irregular shape over a broad range of frequency is presented. The method is based on the extraction of the Green's function at an imaginary wave number from itself to obtain a rapidly convergent hybrid spatial-spectral expansion of the Green's function. The method is applied to a V-grooved cavity and the results are compared with the integral equation method.
Pupil response is modulated by attention shiftin optokinetic nystagmus
DOI: 10.1364/JOSAA.379598 Received 03 Oct 2019; Accepted 26 Dec 2019; Posted 03 Jan 2020 View: PDF
Abstract: Pupil size is modulated not only by the luminance at the eye position but also bythat at the attended location. This study aims to examine whether pupil changes alsocorrespond to the luminance at the spatial location to which the attention is shifted inoptokinetic nystagmus. The test stimulus consisted of randomly positioned dots that moved tothe left or to the right on a display screen that was bright on one side of the centerline anddark on the other. The results show that pupil size changes in accordance with the luminanceat the location to which participants’ attention shifts as a result of optokinetic nystagmus (i.e.,eye movements in the direction opposite to that of the motion stimulus). This study suggeststhat pupil size is modulated by the luminance at the location to which attention shifts throughunidirectional field motion.
New class of Gaussian beam solutions in longitudinally varying medium with transverse quadratic-index profile
Joel Yeo and hao Li
DOI: 10.1364/JOSAA.382205 Received 31 Oct 2019; Accepted 26 Dec 2019; Posted 03 Jan 2020 View: PDF
Abstract: Research in laser-plasma interaction, high harmonics generation and filamentation involve Gaussian beams propagating through inhomogeneous mediums, where the refractive index varies spatially in both transverse and longitudinal directions. However, most analytical Gaussian beam solutions to the paraxial wave equation for inhomogeneous mediums are limited to mediums with refractive index only varying quadratically in the transverse direction. In this paper, we present a new class of Gaussian beam solutions for a longitudinally varying medium with a transverse quadratic-index profile. We also highlight a few examples from this class of solutions which include interesting features such as: a one-parameter generalization of the free space Gaussian beam, beam self-focusing, and beam collimation.
The Cambridge Colour Test: Reproducibility innormal trichromats
Thiago Fernandes, Natanael Santos, and Galina Paramei
DOI: 10.1364/JOSAA.380306 Received 11 Oct 2019; Accepted 23 Dec 2019; Posted 03 Jan 2020 View: PDF
Abstract: This study evaluated reproducibility of the Trivector subtest of the Cambridge Colour Test. Data for normaltrichromats were obtained in Brazil (N=111) at T0, six (T1), and 12 months later (T2), and the United Kingdom(N=79), with test directly followed by retest. Coefficients of repeatability (CORs) – Bland-Altman indices – forProtan, Deutan and Tritan vectors were similar for both datasets. Intraclass correlation coefficients (ICCs) –measures of reliability – were low or moderate for these relatively homogeneous datasets; for a heterogeneousdataset, comprising color-normal and abnormal observers, ICCs were 0.80–0.98, indicating high discriminativeaccuracy of the Trivector subtest.
The Verriest Lecture: Adventures in blue and yellow
DOI: 10.1364/JOSAA.383625 Received 19 Nov 2019; Accepted 20 Dec 2019; Posted 23 Dec 2019 View: PDF
Abstract: Conventional models of color vision assume that blue and yellow (along with red and green) are the fundamental building blocks of color appearance, yet how these hues are represented in the brain and whether and why they might be special are questions that remain shrouded in mystery. Many studies have explored the visual encoding of color categories, from the statistics of the environment to neural processing to perceptual experience. Blue and yellow are tied to salient features of the natural color world, and these features have likely shaped several important aspects of color vision. However, it remains less certain that these dimensions are encoded as primary or “unique” in the visual representation of color. There are also striking differences between blue and yellow percepts that may reflect high-level inferences about the world, and specifically about the colors of light and surfaces. Moreover, while the stimuli labeled as blue or yellow or other basic categories show a remarkable degree of constancy within the observer, they all vary independently of each other across observers. This pattern of variation again suggests that blue and yellow are not a primary or unitary dimension of color appearance, and instead suggest a representation in which different hues reflect qualitatively different categories rather than quantitative differences within an underlying low-dimensional “color space.”
Predicting the Farnsworth-Munsell D15 andHolmes-Wright-A Lantern outcomes withComputer-Based Color Vision Tests
Ali Almustanyir, Jeffery Hovis, and Glaholt Mackenzie G
DOI: 10.1364/JOSAA.381305 Received 25 Oct 2019; Accepted 17 Dec 2019; Posted 17 Dec 2019 View: PDF
Abstract: This study determined the AC1 agreement values between computer-based color vision testsand the Farnworth-Munsell D-15 (F-D15) and Holmes-Wright Type A lantern (HWA). Thecomputer-based tests were the United States Air Force Cone ContrastTest (OCCT), Cambridge Color Test, Innova Rabin Cone Contrast, Konan-Waggoner D15(KWC-D15), and Color Assessment and Diagnosis (CAD). Sixty-eight color-visiondefectivesparticipated. The KWC-D15 had the highest AC1 with the F-D15 (AC1=0.88).Both the CAD and OCCT had the highest values with the HWA (AC1>0.96). The KWCD15would be the best substitute for the F-D15. Either the CAD or OCCT would beappropriate substitutes for the HWA.
Spatially truncated Gaussian pulsed beam and itsapplication in modelling diffraction of ultrashort pulsesfrom hard apertures
Norman Girma Worku and Herbert Gross
DOI: 10.1364/JOSAA.382133 Received 30 Oct 2019; Accepted 14 Dec 2019; Posted 19 Dec 2019 View: PDF
Abstract: A new kind of pulsed beam, which we call a spatially truncated Gaussian pulsed beam, is defined torepresent a Gaussian pulsed beam which is diffracted from a semi-infinite hard aperture. The analyticalequations for the propagation of the spatially truncated Gaussian pulsed beam through non-rotationallysymmetric paraxial system with second order dispersion is derived starting from the generalized spatiotemporalHuygens integral. The spatially truncated Gaussian pulsed beam is then combined with theconventional Gaussian pulsed beam decomposition method to enable the modelling of diffraction of ageneral ultrashort pulse from an arbitrarily shaped hard aperture. The accuracy of the analytical propagationequation derived for propagation of the truncated Gaussian pulsed beam is evaluated by numericalcomparison with diffraction results obtained using the conventional pulse propagation method based onthe Fourier transform algorithm. The application of the modified Gaussian pulsed beam decompositionmethod is demonstrated by propagating an ultrashort pulse after circular aperture through a dispersivemedium and a focusing aspherical lens with large chromatic aberration.
Vectorial effect on the evolution of fractional ordervector vortex beams in a strongly nonlocal nonlinearmedium
CAIXIA LIU, Khian-Hooi Chew, Yan Wu, and Rui-Pin Chen
DOI: 10.1364/JOSAA.380433 Received 16 Oct 2019; Accepted 14 Dec 2019; Posted 16 Dec 2019 View: PDF
Abstract: Propagation of a vector vortex optical field (VVOF) with both fractional order of polarization topological charge mand fractional order of vortex topological charge n with spatially-variant states of polarization (SoP) in a stronglynonlocal nonlinear medium (SNNM) is studied. The optical field always evolves reciprocally with a cycle of stretchand shrink in SNNM with dark stripes form at z = tπzp (t denotes an integer number, and zp is a parameter thatdepends on the initial power of the VVOF and the material constant associated with the response function.), as aresult from the coherent superposition of the vortices with different order of topological charges and weightingcoefficients. In particular, the conversions between linear and circular polarization components occur duringpropagation, and the converted SoP distributions in different propagation distances depend closely on thetopological charges and the initial powers. The evolutions of the Stokes parameters of the fractional order VVOF(FO-VVOF) during propagation in a SNNM show that the spatial distributions of different polarization componentsare closely related to the topological charges, the initial powers and the propagation distances, implying that theFO-VVOF can be regarded as a superposition of two different fractional order vortices with orthogonal circularpolarization components. These results provide new strategies on tailoring polarization states in a structuredoptical field with fractional topological charges.
Field-Only Surface Integral Equations:Scattering from a Perfect Electric Conductor
Qiang Sun, Evert Klaseboer, Alex Yuffa, and Derek Chan
DOI: 10.1364/JOSAA.378665 Received 23 Sep 2019; Accepted 13 Dec 2019; Posted 13 Dec 2019 View: PDF
Abstract: A field-only boundary integral formulation of electromagnetics is derived withoutthe use of surface currents that appear in the Stratton–Chu formulation. For scattering by aperfect electrical conductor (PEC), the components of the electric field are obtained directly fromsurface integral equation solutions of three scalar Helmholtz equations for the field components.The divergence-free condition is enforced via a boundary condition on the normal component ofthe field and its normal derivative. Field values and their normal derivatives at the surface of thePEC are obtained directly from surface integral equations that do not contain divergent kernels.Consequently, high-order elements with fewer degrees of freedom can be used to representsurface features to a higher precision than the traditional planar elements. This theoreticalframework is illustrated with numerical examples that provide further physical insight into therole of the surface curvature in scattering problems.
The vector Durnin-Whitney beam
Israel Julián Macías, Citlalli Sosa Sánchez, Omar de Jesús Cabrera Rosas, Ernesto Ramos, and Gilberto Silva-Ortigoza
DOI: 10.1364/JOSAA.376545 Received 25 Sep 2019; Accepted 09 Dec 2019; Posted 10 Dec 2019 View: PDF
Abstract: We show that ¹E;Hº = ¹E0;H0ºei»k0S¹rº!t¼ is an exact solution to the Maxwellequations in free space, if and only if, fE0;H0; rSg form a mutually perpendicular, right-handedset and S¹rº is a solution of both the eikonal and Laplace equations. By using a family of solutionsof both the eikonal and Laplace equations and the superposition principle we define new solutionsof the Maxwell equations. We show that the vector Durnin beams are particular examples of thistype of construction. We introduce the vector Durnin-Whitney beams characterized by locallystable caustics, fold and cusp ridge types. These vector fields are a natural generalization of thevector Bessel beams. Furthermore, the scalar Durnin-Whitney-Gauss beams and their associatedcaustics are also obtained. We find that the caustics qualitatively describe, except the zero-ordervector Bessel beam, the corresponding maxima of the intensity patterns.
Field-Only Surface Integral Equations:Scattering from a Dielectric Body
Qiang Sun, Evert Klaseboer, Alex Yuffa, and Derek Chan
Doc ID: 378669 Received 23 Sep 2019; Accepted 01 Dec 2019; Posted 02 Dec 2019 View: PDF
Abstract: An efficient field-only nonsingular surface integral method to solve Maxwell’sequations for the components of the electric field on the surface of a dielectric scatterer isintroduced. In this method, both the vector wave equation and the divergence-free constraintare satisfied inside and outside the scatterer. The divergence-free condition is replaced by anequivalent boundary condition that relates the normal derivatives of the electric field acrossthe surface of the scatterer. Also, the continuity and jump conditions on the electric andmagnetic fields are expressed in terms of the electric field across the surface of the scatterer.Together with these boundary conditions, the scalar Helmholtz equation for the components of theelectric field inside and outside the scatterer is solved by a fully desingularized surface integralmethod. Comparing with the most popular surface integral methods based on the Stratton–Chuformulation or the PMCHWT formulation, our method is conceptually simpler and numericallystraightforward because there is no need to introduce intermediate quantities such as surfacecurrents and the use of complicated vector basis functions can be avoided altogether. Also, ourmethod is not affected by numerical issues such as the zero frequency catastrophe and does notcontain integrals with (strong) singularities. To illustrate the robustness and versatility of ourmethod, we show examples in the Rayleigh, Mie, and geometrical optics scattering regimes.Given the symmetry between the electric field and the magnetic field, our theoretical frameworkcan also be used to solve for the magnetic field.
Glens combinations that satisfy theedge-imaging condition of transformation optics
Tomas Tyc, Jakub Belin, Stephen Oxburgh, Chris White, Euan Cowie, and Johannes Courtial
Doc ID: 378040 Received 16 Sep 2019; Accepted 06 Nov 2019; Posted 14 Nov 2019 View: PDF
Abstract: We recently introduced the edge-imaging condition, a necessary condition on allgeneralised lenses (glenses) [Chaplain et al., J. Opt. Soc. Am. A 33, 962 (2016)] in a ray-opticaltransformation-optics (RTO) device that share a common edge [Courtial et al., Opt. Express26, 17872 (2018)]. The edge-imaging condition states that, in combination, such glenses mustimage every point to itself. Here we start the process of building up a library of combinations ofglenses that satisfy the edge-imaging condition, starting with all relevant combinations of up tothree glenses. As it grows, this library should become increasingly useful when constructinglens-based RTO devices.