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Accepted papers to appear in an upcoming issue

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Chromatic Induction in Space and Time

Andrew Coia and Steven Shevell

Doc ID: 312642 Received 03 Nov 2017; Accepted 15 Feb 2018; Posted 15 Feb 2018  View: PDF

Abstract: Color appearance is affected by variations in both space and time. In the spatial domain, a chromatic stimulus within a patterned surround can appear as a different hue than the same stimulus within a uniform surround. In the temporal domain, a changing chromaticity will appear to lead the color of a simultaneously pulsed identical chromaticity. Perception of motion reveals a similar phenomenon: a flashed object will appear to lag behind an identically located moving object. This flash-lag effect for motion, however, is not susceptible to illusory motion, implying an early level of neural processing. The current study tests whether the flash-lag effect for color also depends on an early neural representation prior to chromatic induction from a surrounding pattern. METHODS/STIMULI: Matching experiments were conducted with a patterned chromatic surround. Baseline measurements for chromatic induction were taken by matching the color of a flashed ring within a uniform surround to a flashed ring within a patterned surround. Baseline measurements for the flash-lag effect were also made by matching the color of a flashed ring within a uniform surround to a ring changing in chromaticity over time and also within a uniform surround. The main experiments combined chromatic induction and the flash-lag stimuli in three conditions: (1) both the changing and flashed rings were within a patterned surround; (2) the changing ring was within a patterned surround and the flashed ring within a uniform surround; and (3) the changing ring was within a uniform surround and the flashed ring within a patterned surround. RESULTS/DISCUSSION: Unlike the motion-induced flash lag, flash-lag measurements for a changing chromaticity were affected by perceptual changes caused by the surround. Thus, chromatic induction is incorporated into the neural representation mediating the flash-lag effect for color. 

Influence of permittivity on gradient force exerted on Mie spheres

Jun Chen, Kaikai Li, and Xiao Li

Doc ID: 319662 Received 12 Jan 2018; Accepted 14 Feb 2018; Posted 14 Feb 2018  View: PDF

Abstract: In optical trapping, whether a particle could be stably trapped into the focus region greatly depends on the strength of the gradient force. Individual theoretical study on gradient force exerted on a Mie particle is rare because the mathematical separation of the gradient force and the scattering force in Mie regime is difficult. Based on the recent forces separation work by J. J. Du et al. (J. J. Du, C. H. Yuen, X. Li, K. Ding, G. Q. Du, Z. F. Lin, C. T. Chan, and J. Ng, Sci. Rep. 7, 18042, 2017), we investigate the influence of permittivity (an important macroscopic physical quantity) on the gradient force exerted on a Mie particle by cooperating numerical calculation using fast Fourier transform and analytical analysis using multipole expansion. It is revealed that gradient forces exerted on small spheres are mainly determined by electric dipole moment except for certain permittivity with which the real part of polarizability of electric dipole approaches zero, and gradient forces exerted on larger spheres are complex because of the superposition of the multipole moments. The classification of permittivity corresponding to different varying tendencies of gradient forces exerted on small spheres or larger Mie particles are illustrated. Absorption of particles favors the trapping of small spheres by gradient force, while is bad for the trapping of larger particles. Moreover, the absolute values of the maximal gradient forces exerted on larger Mie particles decline greatly versus the varied imaginary part of permittivity. This work provides elaborate investigation on the different varying tendencies of gradient forces versus permittivity, which favors more accurate and free optical trapping.

Impact of Intraocular Lens Displacement on the Fixation Axis

Simon Schröder, Jens Schrecker, Loay Daas, Timo Eppig, and Achim langenbucher

Doc ID: 318206 Received 21 Dec 2017; Accepted 13 Feb 2018; Posted 14 Feb 2018  View: PDF

Abstract: To investigate the impact of intraocular lens (IOL) decentration ≤±1mm and IOL tilt ≤±10° on the fixation axis and spherical equivalent refraction (SE), 50 pseudo-phakic eyes were simulated using numerical ray-tracing. We computed the position of the object point whose image ends up at the virtual fovea for each scenario and estimated the corresponding change of fixation axis and SE. The eye turned opposite to the direction of IOL decentration or tilt to compensate for the associated prismatic effect (angle <1.2°). Decentration of the aspheric IOL resulted in a hyperopic shift (<0.57D), tilt in a myopic shift (<0.77D).

Factorization of the coherency matrix of polarization optics

Colin Sheppard, Aymeric LE GRATIET, and Alberto Diaspro

Doc ID: 320199 Received 23 Jan 2018; Accepted 09 Feb 2018; Posted 14 Feb 2018  View: PDF

Abstract: We show that the coherency matrix associated with a general depolarizing Mueller matrix can be factorized into the product of a matrix, the coherency matrix factor, and its conjugate transpose. The coherency matrix factor contains all the information in the Mueller matrix, and directly shows useful properties in an illustrative fashion. Propagation through a nondeterministic uniform medium is analized. Some examples for simple systems are shown, and an experimental Mueller matrix considered. The coherency matrix and the coherency matrix factor can be diagonalized, even if the Mueller matrix cannot.

A hyperspectral database of fruits and vegetables

Robert Ennis, Florian Schiller, matteo toscani, and Karl Gegenfurtner

Doc ID: 312492 Received 02 Nov 2017; Accepted 09 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: We have built a hyperspectral database of 42 fruits and vegetables. Both the outside (skin) and inside of theobjects were imaged. We used a Specim VNIR HS-CL-30-V8E-OEM mirror-scanning hyperspectral camera andtook pictures at a spatial resolution of ~57px/deg by 800 pixels at a wavelength resolution of ~1.12 nanometers.A stable, broadband illuminant was used. Images and software are freely available on our webserver(http://www.allpsych.uni-giessen.de/GHIFVD; pronounced “gift”). We performed two kinds of analyses on theseimages. First, when comparing the insides and outsides of the objects, we observed that the insides were lighterthan the skins, and that the hues of the insides and skins were significantly correlated (circular correlation =0.638). Second, we compared the color distribution within each object to corresponding human colordiscrimination thresholds. We found a significant correlation (0.75) between the orientation of ellipses fit to thechromaticity distributions of our fruits and vegetables with the orientations of interpolated MacAdamdiscrimination ellipses. This indicates a close relationship between sensory processing and the characteristics ofenvironmental objects.

Assessment of the Orthogonal and Non-OrthogonalCoupled Mode Theory for parallel optical waveguidescouplers

Gaetano Bellanca, Piero Orlandi, and Paolo Bassi

Doc ID: 314305 Received 24 Nov 2017; Accepted 09 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: The Coupled Mode Theory (CMT) is a powerful approach routinely used to calculate the effects of spatialmode interactions in perturbed structures, such as optical waveguides. One of its basic hypothesesrequires that perturbations are weak. This is usually not the case for devices fabricated with modernsemiconductor based technologies. In this paper, the CMT is studied in these critical cases to assess itsvalidity. Attention will be focused on the quite common case of parallel coupled waveguides. For thesestructures, results can in fact be compared to the exact ones, obtained using super-modes. The study willshow that not all the possible expressions of the coupling coefficients are equivalent and which one canbe pragmatically used to obtain results with minimum errors with respect to exact solutions.

Rough surface reconstruction at grazing angles by an iterated marching method

Yuxuan Chen and Mark Spivack

Doc ID: 319235 Received 08 Jan 2018; Accepted 09 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: An iterated marching method is presented for reconstruction of rough perfectly reflecting 1-dimensional surfaces from scattered dataarising from a scalar wave at grazing incidence. This is based on coupled integral equations adapted from an earlier approach using the parabolic equation, relating the scattered field at a plane to the unknown surface profile. Taking the flat surface as an initial guess, these are solved here using at most three iterations. The method is applied to scattered field data generated from the full Helmholtz equations. This approach improves stability and self-consistency. The reconstructed surface profiles are foundto be in good agreement with the exact forms. The sensitivity with respect to random noise is also investigated, and the algorithm is found to exhibit a type of self-regularization.

Three dimensional localized Airy Cartesian and AiryHelical Cartesian wave packets in free space

zhengzhong Huang and Dongmei Deng

Doc ID: 314153 Received 23 Nov 2017; Accepted 06 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: We have analytically investigated the three dimensional (3D) Airy-Cartesian (AiC) and Airy-Helical-Cartesian(AiHC) wave packets by solving the (3+1) dimensional free space Schrödinger equation. The complex amplitude ofthe AiC and AiHC wave packets is described by the product of the Hermite polynomials, the Gaussian functions andthe Airy functions. We find that the AiC and AiHC wave packets will gradually spread along the propagationdistances, but attenuate along the time domain. The distributions of the radiation force depend on the distributionfactor. In addition, the chirp factor has the effect of the energy concentration of the wave packets. The different 3Dspatiotemporal profiles, the photoelasticity and vortex rings can be obtained by choosing different values of themode number, the distribution factor, the chirp factor, the initial velocity and the propagation distances.

Broad band wide angle polarization insensitive metasurface solar absorber

M. H. Heidari and Seyed Hasan Sedighy

Doc ID: 314236 Received 23 Nov 2017; Accepted 05 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: In this paper, a new ultra-thin and broadband wide angle polarization insensitive metasurface solar absorber is designed and optimized. The proposed metasurface absorber topology is optimized by using genetic algorithm (GA) to enhance the bandwidth and decrease the unit cell area. The proposed unit cell is designed with four-folded symmetric sub unit cells rotated in clockwise direction to achieve polarization independent response. The unit cell with 320×320 nm2 area and 50 nm thickness has broad band (≥90%) absorption response in the visible frequency region of the solar spectrum and infrared from 350 THz to 700 THz for normal incident angle and higher than 70% for incident angles up to 40º at both polarizations.

Fresnel diffraction from the edge of a transparent plate in general case

Hamid Salvdari and Mohammad Tavassoly

Doc ID: 314348 Received 27 Nov 2017; Accepted 05 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: Fresnel diffraction from the edge of a transparent plate with arbitrary orientation of its surfaces is formulated in transmission mode. It is shown theoretically and evaluated experimentally that thickness of a plate and angles between its surfaces, near the edge, can be determined accurately. This renders to construct quantitative 3-D image of the plate edge. It is also illustrated that the recorded diffraction pattern of a plate edge can be regarded as a hologram produced by interference of two diffracted waves: one passing above the plate and the other transmitting through the plate near the edge. Thus, the hologram permits reconstructing the 3-D image of the plate’s edge and the approach can be utilized in constructing 3-D images of phase objects and in quantitative phase microscopy.

Accuracy enhanced and synthetic wavelengthadjustable optical metrology via spectrally resolveddigital holography

Daniel Claus, Giancarlo Pedrini, Dominic Buchta, and Wolfgang Osten

Doc ID: 306786 Received 08 Sep 2017; Accepted 05 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: This paper demonstrates the usefulness of spectrally resolved digital holography for dual wavelength opticalmetrology. Based on the large degree of phase information available, multiple de-correlated dual wavelengthphase maps can be generated, which when averaged result in a signal to noise ratio improvement. Compared tosingle wavelength averaging no further post-processing of the reconstructed dual wavelength phase map isrequired. Moreover, the constraint imposed on the wavelength stability as experienced in conventional dualwavelength method can be relaxed and the corresponding synthetic wavelength is adapted to the object underinvestigation. In addition, the possibility of optical sectioning based on the narrow width coherence envelope isalso demonstrated in transmission mode.

Far-field super-oscillation imaging based on the super-oscillation elements and PSF feature extraction algorithm

Qingkun Xie, Jing Wang, Yanru Jiang, Jian Liang, EnShi Qu, and Liyong Ren

Doc ID: 313146 Received 09 Nov 2017; Accepted 05 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: Suffering from the limited number aperture (NA), resolution higher than 0.5λ cannot be obtained in conventional far-field optical imaging systems. Recently, researches of optical superoscillation lens (SOL) have been demonstrated to realize sub-diffractive focusing both in theory and practice successfully. Nevertheless, these systems usually have characteristics of localized field of view and low-intensity focal spot surrounded by huge side-lobes, which profoundly restricts its application for super-resolution imaging. In this paper, we artificially segment the SOL into two simple-fabrication portions to generate the superoscillation optical field and realize off-axis far-field imaging. Meanwhile, the point spread function (PSF) feature extraction algorithm is proposed to break the limitation of low core intensity of PSF and then effectively extract sub-diffractive structure annihilated by huge side-lobes. Simulations demonstrate its feasibility and reliability in sub-diffraction information recovery, and targets with a resolution of 250 nm are well recovered in the super-oscillation area.

The new CIE 2017 colour fidelity index Rf: a better index to predict perceived colour difference?

Sophie Boissard, Coralie Cauwerts, and Pascale Avouac

Doc ID: 312297 Received 30 Oct 2017; Accepted 05 Feb 2018; Posted 08 Feb 2018  View: PDF

Abstract: The CIE General Colour Rendering Index Ra is currently widely and internationally used to assess the ability of white light sources to render colours. But over the past decades, there has been increasing evidence of its limitations. As a result of several years of scientific work, the Commission Internationale de l’Eclairage (CIE) published in April 2017 an updated calculation method. To reduce misinterpretation by users and make a clear distinction with the other aspects of colour quality, the colour rendering index was renamed colour fidelity index (CIE-Rf). Before proposing this index as a new international standard for colour fidelity prediction, there is a need for validation. This paper presents a psychovisual experiment designed to address this aim. Twelve observers evaluated colour differences of 16 colour samples under eight pairs of light sources. 3000K and 4000K LEDs and fluorescent sources with CIE-Rf values ranging from 64 to 94 were investigated. Results show that the prediction of colour differences is significantly better in CIECAM02-UCS colour space than in CIE U*V*W* or CIELAB, whatever the colour matching functions (CMFs). A high correlation was found between perceived colour differences and CIE-Rf. This psychovisual experiment did not make possible to detect significant differences with the other tested colour fidelity indices (CIE-Ra, CQS-Qf, CRI2012, CRI-CAM02UCS and IES-Rf). However, there are some signs of an improvement of the prediction by CIE-Rf in comparison to CIE-Ra. To increase, in further works, the chance to detect potential significant differences between colour fidelity indices, some modifications of the experimental protocol are suggested.

Towards omni-directional and automated imaging system for measuring oceanic whitecap coverage

Raied Al-Lashi, Merlin Webster, Steve R. Gunn, and Helen Czerski

Doc ID: 321158 Received 01 Feb 2018; Accepted 03 Feb 2018; Posted 07 Feb 2018  View: PDF

Abstract: Accurate measurements of the oceanic whitecap coverage from whitecap images are required for better understanding the air-gas transfer and aerosol production processes. However, this is a challenging task because the whitecap patches are formed immediately after the wave breaks and are spread over a wide area. The main challenges in designing a whitecap imaging instrument are the small field of view of the camera lens, processing large numbers of images, recording data over long time periods, and deployment difficulties in stormy conditions. This paper describes the design of a novel high-resolution optical instrument for imaging oceanic whitecaps and the automated algorithm processing the collected images. The instrument was successfully deployed in 2013 as part of the HiWINGS campaign in the North Atlantic Ocean. The instrument uses a fish-eye camera lens to image the whitecaps in wide angle of view (180º).

Calculation of vectorial diffraction in optical systems

Jeongmin Kim, Yuan Wang, and Xiang Zhang

Doc ID: 314083 Received 22 Nov 2017; Accepted 03 Feb 2018; Posted 05 Feb 2018  View: PDF

Abstract: Vectorial diffraction theory that considers light polarization is essential to predict performance of opticalsystems that have high numerical aperture or use engineered polarization or phase. Vectorial diffractionintegrals to describe light diffraction typically require boundary fields on aperture surfaces. Estimatingsuch boundary fields can be challenging in complex systems that induce multiple depolarizations, unlessvectorial ray tracing using 3x3 Jones matrices is employed. The tracing method, however, has not been sufficientlydetailed to cover complex systems, and more importantly seems influenced by system geometry(transmission vs. reflection). Here, we provide a full tutorial on vectorial diffraction calculation in opticalsystems. We revisit vectorial diffraction integrals and present our approach of consistent vectorial raytracing irrespective of system geometry. Our method is demonstrated in simple optical systems to betterdeliver our idea, and then in a complex system where point spread function broadening by a conjugatereflector is studied.

Linear solutions to metamaterial volume hologramdesign using a variational approach

Daniel Marks and David Smith

Doc ID: 315284 Received 08 Dec 2017; Accepted 01 Feb 2018; Posted 01 Feb 2018  View: PDF

Abstract: Multiplex volume holograms are conventionally constructed by the repeated exposure of a photosensitivemedium to a sequence of external fields, each field typically being the superposition of a referencewave that reconstructs the hologram and the other being a desired signal wave. Because there are nosources of radiation internal to the hologram, the pattern of material modulation is limited to the solutionsto Helmholtz’s equation in the medium. If the three-dimensional structure of the medium couldbe engineered at each point rather than limited to the patterns produced by standing waves, more versatilestructures may result that can overcome the typical limitations to hologram dynamic range imposedby sequentially superimposing holograms. Metamaterial structures and other synthetic electromagneticmaterials offer the possibility of achieving high medium contrast engineered at the subwavelength scale.By posing the multiplex volume holography problem as a linear medium design problem, we explore thepotential improvements that such engineered synthetic media may provide over conventional multiplexvolume holograms.

Correlation between the perception of color, shadows and surface textures and the realism of a scene invirtual reality

Pedro Pardo, Isabel Suero, and Angel Luis Perez

Doc ID: 309491 Received 02 Nov 2017; Accepted 01 Feb 2018; Posted 01 Feb 2018  View: PDF

Abstract: Head mounted displays allow to go through immersive experiences in virtual reality and are expected to bepresent in more and more applications, in both recreational and professional fields. In this context, last years havewitnessed significant advances in rendering techniques following physical models of lighting and shading. The aimof this paper is to check the fidelity of the visual appearance of real objects captured through a 3D scanner,rendered in a personal computer and displayed in a virtual reality device. We have compared forward renderingversus deferred rendering in real-time computing using two different illuminations and five artworks replica. Thesurvey contains seven items for each artwork (Color, Shading, Texture, Definition, Geometry, Chromatic Aberrationand Pixelation) and an extra item related to the global realism. The results confirm recent advances in virtualreality, stating a considerable visual fidelity of the image generated as compared to the real world, with a rate closeto 4 in a 5-step perceptive scale. Results have shown a high correlation of the realism’s sensation with the fidelity ofcolor reproduction, the material texture and the definition of artworks replica. Moreover, statistically significantdifferences between two rendering modes have been stated, showing the higher value of realism sensation for thedeferred rendering mode.

A Mathematical Approach to Best Luminance Maps

Ali Alsam and Hans Jakobs Rivertz

Doc ID: 308686 Received 24 Oct 2017; Accepted 31 Jan 2018; Posted 01 Feb 2018  View: PDF

Abstract: An algorithm to calculate the best global mapping from colour to greyscale is presented. We assert that the best mapping minimises the difference between the multi-channel local tensor and to the tensor resultant mono-chromatic image.To minimise the objective function, we represent the grayscale image as a weighted sum of the RGB channels, three channels and their second order polynomial and three channels and their root polynomial. The optimisation searches for the best weights to combine the linear, polynomial and root polynomial functions.Our result show that the optimal weights can half the root mean saqure difference between the colour gradients and those achieved by the conventional lumiance transformation. Further improvement are achieved by adding the squared and root squared channels to the solution. The improvements are also visually evident.

Hue Opponency: Chromatic Valence Functions, Individual Differences, Cortical Winner-Take-All Opponent Modeling and the Relationship between Spikes and Sensitivity

Vincent Billock

Doc ID: 312620 Received 02 Nov 2017; Accepted 31 Jan 2018; Posted 01 Feb 2018  View: PDF

Abstract: Neural spike rate data is more restricted in range than related psychophysical data. For example, several studiessuggest a compressive (roughly cube root) nonlinear relationship between wavelength opponent spike rates in primatemidbrain and color appearance in humans, two rather widely separated domains. This presents an opportunity topartially bridge a chasm between these two domains and an opportunity to probe the putative nonlinearity with otherpsychophysical data. Here neural wavelength-opponent data are used to create cortical competition models for hueopponency. This effort led to creation of useful models of spiking neuron Winner-Take-All (WTA) competition and MAXselection. When fed with actual primate data the spiking WTA models generate reasonable wavelength-opponent spikerate behaviors. An average psychophysical observer for red-green and blue-yellow opponency is curated from eightapplicable studies in the refereed and dissertation literatures, with cancellation data roughly every 10 nm in 18 subjectsfor yellow-blue opponency and 15 subjects for red-green opponency. A direct mapping between spiking neurons withbroadband wavelength sensitivity and human psychophysical luminance yields a power law exponent of 0.27, similar tothe cube root nonlinearity. Similarly, direct mapping between the WTA model opponent spike rates and psychophysicalopponent data suggests power law relationships with exponents between 0.24 and 0.41.

Optical sectioning enhancement using higher-order moment signals in random speckle-structured illumination microscopy

Andrew Vigoren and James Zavislan

Doc ID: 313979 Received 23 Nov 2017; Accepted 31 Jan 2018; Posted 01 Feb 2018  View: PDF

Abstract: The optical sectioning capability of structured illumination using random speckle patterns is shown by simulations to improve when cumulants beyond the traditional second order are used as the image- forming signals. The improvement scales with the cumulant order, asymptotically approaching confocal performance. As actual experiments operate with finite-size sample estimators instead of true cumulants, purely statistical (non-optical) effects can result in non-ideal behavior. We analyze the finite ensemble effects along with the experimental effects of detector dynamic range through Monte Carlo simulations. Despite these real-world factors, we show when the third-order-derived signal can demonstrate improved sectioning at good signal-to-noise levels set by finite-sample effects.

Discrimination of spectral reflectance underenvironmental illumination

Takuma Morimoto and Hannah Smithson

Doc ID: 312508 Received 02 Nov 2017; Accepted 30 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: Color constancy is the ability to recover a stable perceptual estimate of surface reflectance, regardless of the lightingenvironment. However, we know little about how observers make judgments of the surface color of glossy objects,particularly in complex lighting environments that introduce complex spatial patterns of chromatic variation across theobject’s surface. To address this question, we measured thresholds for reflectance discrimination using computerrenderedstimuli under environmental illumination. In Experiment 1, we found that the effects of glossiness and shapeon discrimination thresholds were small. Importantly, discrimination ellipses extended along the direction in which thechromaticities in the environmental illumination spread. In Experiment 2, we also found that observers’ abilities tojudge surface colors were worse in lighting environments with an atypical chromatic distribution.

Are hue and saturation carried in different neural channels?

Sarah Regan, Robert Lee, Donald MacLeod, and Hannah Smithson

Doc ID: 312522 Received 02 Nov 2017; Accepted 30 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: Chromatic discrimination data show that a smaller physical stimulus change is required to detect a change in hue than to detect a change in saturation (D. B. Judd, Palette 30, 1968; M. V Danilova and J. D. Mollon, Proc. R. Soc. London. Ser. B 283, 2016) and, on this basis, it has been suggested that hue and saturation are carried in different neural channels (R. G. Kuehni, Color Space and Its Divisions, 331, 2003). We used an adaptation paradigm to test explicitly for separate mechanisms, measuring hue and saturation detection thresholds before and after adaptation to hue and saturation stimuli. Within-condition adaptation did not elevate detection thresholds significantly more than between-condition adaptation. We therefore did not find psychophysical evidence for a neural channel that that extracts hue thresholds more effectively than the neural channel or channels that determine saturation thresholds.

Propagation characteristics of controllable dark-hollowbeams in the quadratic-index medium

Gholamreza Honarasa

Doc ID: 312710 Received 03 Nov 2017; Accepted 29 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: In this paper, the propagation of the Controllable dark-hollow beam (CDHB) passing through the quadratic-index medium is studied. An analytical expression for the propagation of the CDHBs in the quadratic-index medium is presented based on the ABCD matrix method and the effect of the beam parameters on the evolution of a CDHB is investigated. It is found that the intensity distribution of the CDHBs evolves periodically during propagation in the quadratic-index medium. The results indicate that the distance in which the dark hollow center of the CDHB is disappeared can be increased by the beam parameters.

Contrast-dependent red-green hue shift

Steven Buck, Fred Rieke, and Tanner DeLawyer

Doc ID: 312957 Received 07 Nov 2017; Accepted 29 Jan 2018; Posted 29 Jan 2018  View: PDF

Abstract: On bright surrounds, red-green-balanced yellow targets become greenish brown with decreased target luminance,and red-green-balanced brown targets become reddish yellow with increased target luminance. These effectsimply luminance- and/or contrast-dependent weighting of M- and L-cone signals in post-receptoral pathways.We show psychophysically that luminance contrast between surround and target is the primary determinant of themagnitude of RG hue shift, requiring surround luminance at least twice the target luminance and increasing withfurther increases of surround/target contrast. There is a much smaller effect of absolute stimulus luminance, withdimmer stimuli showing slightly larger hue shifts.To evaluate a possible retinal origin of the changes in cone-signal weightings underlying the hue shift, we recordedspike responses from both ON- and OFF-center midget ganglion cells in peripheral primate retina. We found noevidence that the relative strength of L- and M-cone post-receptoral responses changed systematically with changeof surround irradiance. Nor was there any systematic difference between ON- and OFF-subtypes. This suggests thatthe change in cone signal weighting occurs later in the visual system.

Quantization noise as a determinant for color thresholds in machine vision

Irina Palchikova, Evgenii Smirnov, and Evgeny Palchikov

Doc ID: 312516 Received 02 Nov 2017; Accepted 28 Jan 2018; Posted 29 Jan 2018  View: PDF

Abstract: Color discrimination simulation is applied to study a uniformity of the color space of machine vision devices whoseoperation is based on a three-component color model and which involve analog-to-digital conversion of signalswith a resolution of 8 bits per channel. Algorithms for finding the intervals of the dominant wavelength and colorsaturation of a specimen are developed. The spectral dependence of intervals of color parameters calculated usingthe digital images is found. It is shown that machine vision possesses the color discrimination thresholds, whichcan be drawn in the CIE1931 xy chromaticity diagram in the form of equal-contrast ellipses similar to the MacAdamellipses. At resolution of 6 bits the sizes of a reference MacAdam’s ellipse it is a little less, and at resolution of 7 bits– it is a little more, than of the machine vision ellipses sizes. A hypothesis is proposed, which implies that theprocess of an encoding of the visual neural signals may include procedures similar to an analog-to-digitalconversion.

Individual variations in colour-concept space replicate across languages

David Bimler and Mari Uusküla

Doc ID: 312544 Received 03 Nov 2017; Accepted 28 Jan 2018; Posted 01 Feb 2018  View: PDF

Abstract: The cross-cultural nature of color categories and concepts is central to the Berlin-Kay tradition of color-languageuniversalism. In an extension, we examine the cognitive organization of color concepts – the pattern of associationsamong them – where cross-cultural regularities may also exist. We focus here on individual variations in that pattern.Listing data provide a convenient probe of ‘associational space’, and are amenable to factor analysis, using a correlationalindex of between-list similarity. The rotated factors are ‘Points-of-View’: alternative prototypal ways of organizing theconcepts, and extremes of a spectrum of listing-sequence variation. Points-of-view proved to be comparable for threelanguages (Hungarian, Italian, Estonian) when visualized with multidimensional scaling. This allowed a similarinterpretation of the spectrum of variation in each language, as individual differences in the weight of a conceptualdistinction between chromatic and ‘achromatic’ terms, supporting the case for cross-language convergence.

The Verriest Lecture: Color vision in an uncertainworld

David Foster

Doc ID: 315012 Received 11 Dec 2017; Accepted 25 Jan 2018; Posted 26 Jan 2018  View: PDF

Abstract: The natural world is optically unconstrained. Surface properties may vary from one point to another and reflectedlight may vary from one instant to the next. The aim of this work is to quantify some of the resulting physicalfailures of color vision performance. In computational simulations with images of vegetated and nonvegetatedoutdoor scenes, it is shown that color provides an unreliable guide to surface identity. It is also shown that changesin illuminant may cause colors to no longer match and the relations between individual colors to vary. Thesefailures are generally well described by a measure of the randomness of the colors in scenes, the Shannon entropy.Although uncertainty is intrinsic to the environment, its consequences for color vision can be predicted.

Wavefront measurement using computational adaptiveoptics

Fredrick South, Yuan-Zhi Liu, Andrew Bower, Yang XU, P. Scott Carney, and Stephen Boppart

Doc ID: 308342 Received 03 Oct 2017; Accepted 25 Jan 2018; Posted 25 Jan 2018  View: PDF

Abstract: In many optical imaging applications, it is necessary to correct for aberrations to obtain high quality images.Optical coherence tomography (OCT) provides access to the amplitude and phase of the backscatteredoptical field for three-dimensional (3D) imaging samples. Computational adaptive optics (CAO)modifies the phase of the OCT data in the spatial frequency domain to correct optical aberrations withoutusing a deformable mirror, as is commonly done in hardware-based adaptive optics. This providesimprovement of image quality throughout the 3D volume, enabling imaging across greater depth rangesand in highly aberrated samples. However, the CAO aberration correction has a complicated relation tothe imaging pupil, and is not a direct measurement of the pupil aberrations. Here we present new methodsfor recovering the wavefront aberrations directly from the OCT data without the use of hardwareadaptive optics. This enables both computational measurement and correction of optical aberrations.

Effect of eccentricity and light level on the timing oflight adaptation mechanisms

Pablo Barrionuevo, Beatriz Matesanz, Alejandro Gloriani, Isabel Arranz de la Fuente, Luis Issolio, Santiago Mar, and Juan Aparicio

Doc ID: 312458 Received 03 Nov 2017; Accepted 24 Jan 2018; Posted 26 Jan 2018  View: PDF

Abstract: We explored the complexity of the light adaptation process, assessing adaptation recovery (Ar) at differenteccentricities and light levels.Luminance thresholds were obtained with transient background fields at mesopic and photopic light levels fortemporal retinal eccentricities (0°-15°) with test/background stimulus size of 0.5°/1° using a staircase procedurein a two-channel Maxwellian view optical system. Ar was obtained in comparison with steady data (Gloriani et al,Vision Res., 2016).Light level affects proportionally Ar only at fovea. Photopic extrafoveal thresholds were one log unit higher fortransient conditions. Adaptation was equally fast at low light levels for different retinal locations with variationsmainly affected by noise. These results evidence different timing in the mechanisms of adaptation involved.

Effects of eccentricity on color contrast

John Vanston and Michael Crognale

Doc ID: 309418 Received 20 Oct 2017; Accepted 24 Jan 2018; Posted 24 Jan 2018  View: PDF

Abstract: Using near-threshold stimuli, human color sensitivity has been shown to decrease across the visual field, likely due in part to physiological differences between the fovea and periphery. It remains unclear to what extent this holds true for suprathreshold stimuli. The current study used suprathreshold contrast matching to examine how perceived contrast varies with eccentricity along the cardinal axes in a cone opponent space. Our data show that, despite increasing stimulus size in the periphery, the LM axis stimuli were still perceived as reduced in contrast, whereas the S axis sensitivity was observed to increase with eccentricity.

A Multi-focus Image Fusion Algorithm based onLaplacian Pyramids

Jianguo Sun, QILONG HAN, Liang Kou, liguo zhang, kejia zhang, and Zilong Jin

Doc ID: 296792 Received 25 May 2017; Accepted 24 Jan 2018; Posted 25 Jan 2018  View: PDF

Abstract: In this paper, we propose a method named Region Mosaicking on Laplacian Pyramids (RMLP) to fusemulti-focus images that is captured by microscope. First, we apply the Sum-Modified-Laplacian to measurethe focus of multi-focus images. Then the density-based region growing algorithm is utilized tosegment the focused region mask of each image. Finally, the mask is decomposed into a mask pyramidto supervise region mosaicking on a Laplacian pyramid. The region level pyramid keeps more originalinformation than the pixel level. The experiment results show that RMLP has the best performance inquantitative comparison with other methods. In addition, RMLP is insensitive to noise and can reducesthe color distortion of the fused images on two datasets.

Comparison of different theories for focusing through a plane interface: Reply

Taco Visser

Doc ID: 318373 Received 22 Dec 2017; Accepted 23 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: The correction pointed out by Kim et al. to our paper“Comparison of different theories for focusing througha plane interface,” [JOSA A 14, pp. 1482–1490 (1997)]is welcome. A few additional remarks are included inthis reply.

Quantitative study of color category boundaries

Nicole Fider and Natalia Komarova

Doc ID: 312514 Received 06 Nov 2017; Accepted 22 Jan 2018; Posted 23 Jan 2018  View: PDF

Abstract: We use World Color Survey (WCS) data to design quantitative methods to study color categorization, with the focus on the ``geometric" properties of categories, in particular, on studying their shape, and creating a consistent methodology to identify category boundaries. We introduce the notion of ``No Man's Land" (NML) and ``Some Man's Land" (SML) to distinguish color chips that belong to no color category and belong to some color category. We introduce a ``tile strength" (TS) function that characterizes color boundaries. While categories may come in a variety of shapes, and their boundaries are non-uniform and can vary in thickness, there are universal patterns that emerge. For example, the boundary-to-category-mass ratio is a decreasing function of category strength (i.e., stronger categories have relatively thinner boundaries), and boundary mass obeys a ``square root"-like law as a function of category mass (i.e., roughly speaking, color categories behave like 2D circles). We further identify a relationship between color boundaries and Shannon's entropy, which can be calculated by using the field data of the World Color Survey. We find that depending on the informational content of a given chip, it can belong to three distinct types: (I) strongly belonging to a color category; (II) belonging to a boundary between two or more categories; (III) not belonging to a category or a boundary. The last two cases can be interpreted in terms of evolution and temporal dynamics of color categories.

Improved photon-pair generation from transitionmetaldichalcogenide monolayers embedded in onedimensionalphotonic crystals

Tiecheng Wang

Doc ID: 312477 Received 03 Nov 2017; Accepted 18 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: We have theoretically investigated photon-pair generation from transition-metal dichalcogenide (TMDC)monolayers embedded in photonic crystals (PCs) by a rigorous quantum model of spontaneous parametric downconversion. The mean number of output photon-pairs and the signal-field energy spectrum have been elaborated.Two different structures are studied, one is a monolayer 􀜅􀜁􀫛 embedded in the defective PC and the other is a stackof 􀜅􀜁􀫛 layers in the dielectric multilayer structure. It is clearly shown that an obvious improvement of thegeneration rate of the correlated photon-pairs from the monolayer 􀜅􀜁􀫛 can be realized in these two structures andthe enhancement can reach as much as 14 orders of magnitude. Such an effective improvement utilizes theimproved field localization at the defect state or the band-edge state, the propagation of photons in the PCs andcoherent superposition, the similar phenomena can occur for other TMDC monolayers. These phenomena are verybeneficial for the design of optical devices.

Nondiffracting light beams carrying fractional orbital angular momentum

Zhenshan Yang, Xia Zhang, Chenglin Bai, and minghong wang

Doc ID: 308796 Received 13 Oct 2017; Accepted 17 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: We investigate a new class of nondiffracting optical beamscarrying fractional orbital angular momentum (FOAM Bessel beams), which canbe constructed by modifying the phase step of the spiral phase plate in asetup originally for the generation of traditional Bessel beams. The FOAMBessel beams have entirely stable vortex structures, and form an infinitenumber of orthogonal and complete subsets for monochromatic scalar light in free space. With the advantages of structural stability andorthogonality-completeness, the FOAM Bessel beams are expected to be usefulfor study and application in various fields of modern optics.

Contrast-dependent red-green balance shifts depend on S-Cone Activity

Tanner DeLawyer, Melissa Tayon, Chia-li Yu, and Steven Buck

Doc ID: 313243 Received 10 Nov 2017; Accepted 17 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: Previous research from our lab has established that red-green balanced yellow targets become greenish brown assurround luminance increases, while red-green balanced brown targets become reddish yellow as surroundluminance decreases. To help assess the generality and underlying processes of this contrast-dependent red-greenhue shift, we investigated red-green hue shifts for target stimuli that appeared achromatic or blue, as well asyellow/brown. Results confirmed that the red-green hue shift was largest for yellow/brown targets and wasprogressively reduced for achromatic and blue targets, as target excitation of S cones increased. The magnitude ofthe hue shift could be predicted by the S/(L+M) excitation of the target when bright white surrounds are used. Thehue shift also requires that the target and surround are presented to the same eye, consistent with processing inmonocular pathways. Increased S-cone excitation by the surround was associated with red-green hue shifts for alltargets equally. Thus, S-cone signals from bright white surrounds might play a role in the contrast-dependent redgreenhue shift, but the source of the variation of the magnitude of the hue shift with variations in target S-coneexcitation when presented on those surrounds is unknown.

Remote Controls illusion: Strange interactionsacross space cannot be explained by simple contrastfilters

Laysa Hedjar, Venice Cowardin, and Arthur G. Shapiro

Doc ID: 312626 Received 09 Nov 2017; Accepted 14 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: The visual system has separable visual encoding for luminance and for contrast modulation (Shapiro,2008); the two dimensions can be represented with a luminance contrast vs. luminance plane. Here we usea contrast asynchrony paradigm to explore contextual effects on luminance contrast modulation: twoidentical rectangular bars (0.5x2.5 deg) have luminance levels that modulate at 2 Hz; when one bar isplaced on a bright field and the other bar on a dark field, observers perceive the bars modulating inantiphase with each other and yet becoming light and dark at the same time. The antiphase perceptioncorresponds to the change in contrast between the bars and their surrounds (a change along the contrastaxis of the plane); the in-phase perception corresponds to the luminance modulation (a change along theluminance axis of the plane). We examine spatial interaction by adding bright rectangular (0.5x2.5 deg)flankers on both sides of the dark-field bar and dark flankers on both sides of the bright-field bar.Remarkably, flankers produce an in-phase appearance when separated from the bars by between 2' and 4'of visual angle, and produce antiphase appearance when they directly adjoin the bars or are separated bymore than 8'. To estimate the dimensions of the spatial interaction, we parametrically adjust the size of thegap between bars and flankers and the length of the flankers. We attempt to account for the results withmodels based on rectified difference of Gaussian (DoG) filters and with rectified oriented difference ofGaussian (ODoG) filters. The models can account for the results when the flankers are the same height asbars, but are unable to account for the effects of increasing the flanker length. The models thereforesuggest that the spatial interaction across distances requires more complex interactions of contrast filters.

Comment on "Comparison of different theories forfocusing through a plane interface"

Jeongmin Kim, Yuan Wang, and Xiang Zhang

Doc ID: 304901 Received 15 Aug 2017; Accepted 06 Nov 2017; Posted 30 Jan 2018  View: PDF

Abstract: In light focusing through a dielectric interface, Wiserma et al. [J. Opt. Soc. Am. A 14, 1482-1490 (1997)] claims that the Debye-Wolf diffraction theory and the m-theory predict axial focal fields with "little difference". We found a possible mistake of using an inaccurate apodization factor in the m-theory integral.Here we correct the apodization factor, which then leads to better agreement on axial intensity distributions between the two theories than reported.

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