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Accepted papers to appear in an upcoming issue

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A new colour appearance model for self-luminous stimuli

Stijn Hermans, Kevin Smet, and Peter Hanselaer

Doc ID: 340340 Received 23 Jul 2018; Accepted 14 Oct 2018; Posted 15 Oct 2018  View: PDF

Abstract: A model for brightness and hue perception of self-luminous stimuli surrounded bya self-luminous achromatic background has been developed based on a series of visualexperiments. In the model, only the absolute spectral radiance values of the stimulus andbackground are used as input. Normalized cone excitations are calculated using the 10° CIE2006 cone fundamentals. A von Kries chromatic adaptation transform applied in the CIE2006 cone space is adopted and luminance compression and adaptation due to the selfluminousbackground are included by using a Michaelis-Menten function. Model parametersare determined by fitting the model to the experimental visual data obtained for brightness,hue and the amount of colour versus neutral. The model is validated with additionalexperimental data. An absolute brightness scale expressed in "bright" is proposed.

Singular knot bundle in light

Danica Sugic and Mark Dennis

Doc ID: 340666 Received 26 Jul 2018; Accepted 12 Oct 2018; Posted 15 Oct 2018  View: PDF

Abstract: As the size of an optical vortex knot, imprinted in a coherent light beam, is decreased,nonparaxial effects alter the structure of the knotted optical singularity. For knot structuresapproaching the scale of wavelength, longitudinal polarization effects become non-negligibleand the electric and magnetic fields differ, leading to intertwined knotted nodal structures in thetransverse and longitudinal polarization components which we call a knot bundle of polarizationsingularities. We analyze their structure using polynomial beam approximations, and numericaldiffraction theory. The analysis reveals features of spin-orbit effects and polarization topology intightly-focused geometry, and we propose an experiment to measure this phenomenon.

Manipulate far-zone scattered field bycontrolling distribution characteristics of aparticulate medium

Tao Wang, zhanghang Zhu, ziyuan wang, and Ke Cheng

Doc ID: 346531 Received 21 Sep 2018; Accepted 12 Oct 2018; Posted 15 Oct 2018  View: PDF

Abstract: Within the validity of the first-order Born approximation and the far-fieldapproximation, the possibility for producing scattered fields with various intensitydistributions was discussed. It is shown that when light waves are scattered from randomdistributedparticles collection, the intensity distribution of the scattered field can bemanipulated by properly controlling the distribution characteristics of particles in thecollection. To illustrate this result, three special cases of particulate medium are discussed toproduce scattered spectral density with Gaussian distributions, circular flattened distributions,and ring-like distributions, respectively.

Generalization of the axicon shape: the gaxicon

Rafael Gonzalez Acuña and Julio Gutierrez-Vega

Doc ID: 344503 Received 29 Aug 2018; Accepted 11 Oct 2018; Posted 11 Oct 2018  View: PDF

Abstract: We generalize the shape of the traditional axicon by finding analytically the functionof the output surface when the input surface is not flat but an arbitrary continuous function whichpossess rotational symmetry. Several illustrative examples are presented and tested using raytracing techniques without the paraxial approximation.

Leukocyte recognition in human fecal samples using texturefeatures

Xiangzhou Wang, Lin Liu, Xiaohui Du, Jing Zhang, Juanxiu Liu, Ni Ming, Ruqian Hao, and Yong Liu

Doc ID: 328861 Received 23 Apr 2018; Accepted 10 Oct 2018; Posted 10 Oct 2018  View: PDF

Abstract: Unlike urine or blood samples with a single background, human fecal samples contain large amounts of food debris, amorphousparticles, and undigested plant cells. It is difficult to segment such impurities when mixed with leukocytes. Cell degradationresults in ambiguous nuclei, incompleteness of the cell membrane and a changeable cell morphology, which are hard torecognize. Aiming at the segmentation problem, a threshold segmentation method combining inscribed circle and circumscribedcircle is proposed to effectively remove the adhesion impurities with a segmentation accuracy reaching 97.6%. For theidentification problem, five texture features including LBP-Uniform, Gabor, HOG, GLCM, and Haar were extracted and classifiedusing four kinds of classifier (SVM, ANN, AdaBoost, and RandomForest). The experimental results show that using HOG featureswith SVM classifier can achieve a precision of 88.46% and a recall of 88.72%.

A new traffic sign recognition method for intelligentvehicles

ayoub ellahyani, Mohamed El Ansari, redouan lahmyed, and Alain Tremeau

Doc ID: 331747 Received 16 May 2018; Accepted 10 Oct 2018; Posted 10 Oct 2018  View: PDF

Abstract: Traffic sign recognition is one of the main componentsof intelligent transportation systems (ITS). It improvessafety by informing the driver of the current state of theroad, e.g. warnings, prohibitions, restrictions and otherinformation useful for driving. This paper presents anew road signs recognition method which is achievedin three main steps. The first step maps the input imagefrom the Cartesian coordinate system to the logpolarone. The second step computes histogram of orientedgradients (HOG), local binary pattern (LBP) andlocal self-similarity characteristics (LSS) from the imagerepresented in the log-polar coordinate system. Thethird step performs the classification on the basis ofthe random forest classifier and the features computedin the second step. The proposed method has beentested on the German Traffic Sign Recognition Benchmarkdataset and the results obtained are satisfactorywhen compared to the state of the art approaches.

Is multiplexed off-axis holography for quantitativephase imaging more spatial bandwidth-efficient thanon-axis holography?

Gili Dardikman and Natan Shaked

Doc ID: 344260 Received 27 Aug 2018; Accepted 10 Oct 2018; Posted 10 Oct 2018  View: PDF

Abstract: Digital holographic microcopy is a thriving imaging modality that attracts considerable research interest due to itsability to not only create excellent label-free contrast, but also supply valuable physical information regarding thedensity and dimensions of the sample with nanometer-scale axial sensitivity. Three basic holographic recordinggeometries currently exist, including on-axis, off-axis and slightly off-axis holography, each of them enabling avariety of architectures in terms of bandwidth use and compression capacity. Specifically, off-axis holography andslightly off-axis holography allow spatial hologram multiplexing, enabling compressing more information into thesame digital hologram. In this paper, we define an efficiency score used to analyze the various possiblearchitectures, and compare the signal-to-noise ratio and mean squared error obtained using each of them,determining the optimal holographic method.

A wide-field emmetropic human eye model based onocular wavefront measurements andgeometry-independent gradient index lens

Muhammad Akram, Rigmor Baraas, and karthikeyan baskaran

Doc ID: 335638 Received 29 Jun 2018; Accepted 09 Oct 2018; Posted 10 Oct 2018  View: PDF

Abstract: There is a need to better understand the peripheral optics of the human eye and its correction. Currenteye models have some limitations to accurately predict the wavefront errors for the emmetropic eye overa wide-field. The aim here was to develop an anatomically correct optical model of the human eye thatclosely reproduces the wavefront of an average Caucasian-only emmetropic eye across a wide visual field.Using an optical design program, a schematic eye was constructed based on ocular wavefront measurementsof the right eyes of thirty healthy young emmetropic individuals over a wide visual field (from 40nasal to 40 temporal and up to 20 inferior field). Anatomical parameters, asymmetries and dispersionproperties of the eye’s different optical components were taken into account. A geometry-independentgradient index (GRIN) model was employed to better represent the crystalline lens. The RMS wavefronterror, wavefront shapes, dominant Zernike coefficients, nasal-temporal asymmetries and dispersionproperties of the developed schematic eye closely matched the corresponding measured values across thevisual field. The developed model can help in the design of wide-field ophthalmic instruments and isuseful in the study and simulations of the peripheral optics of the human eye.

Design of axisymmetrical refractive opticalelement generating required illuminancedistribution and wavefront

Leonid Doskolovich, Dmitry Bykov, Kseniya Andreeva, and Nikolay Kazanskiy

Doc ID: 339970 Received 18 Jul 2018; Accepted 09 Oct 2018; Posted 10 Oct 2018  View: PDF

Abstract: Design of axisymmetrical refractive optical element transforming a given incidentbeam into an output beam with prescribed illuminance distribution and wavefront is considered.The wavefront of the output beam is represented by the eikonal function defined in a certainplane behind the optical element. The design of the optical element is reduced to the solutionof two explicit ordinary differential equations of the first order. These equations can be easilyintegrated using conventional numerical methods. As examples, we consider the design of twooptical elements transforming a spherical beam from a point Lambertian light source into theuniform-illuminance beams with a plane wavefront and with a complex wavefront providing thesubsequent focusing into a line segment on the optical axis.

Tight focusing properties of circular partiallycoherent Gaussian beam

Huichuan Lin, Xiaoming Zhou, Ziyang Chen, Yan Li, and Jixiong Pu

Doc ID: 340552 Received 25 Jul 2018; Accepted 09 Oct 2018; Posted 12 Oct 2018  View: PDF

Abstract: Tight focusing properties of circular partially coherent Gaussian (CPCG) beamwith linear polarization have been studied based on vectorial Debye theory. Expressions forthe intensity distribution and degree of coherence near the focus are derived. Numericalcalculations are performed to show the intensity distribution and degree of coherence ofCPCG beam in the focal region. It is interesting to find that after focusing CPCG beamthrough a high numerical-aperture (NA) objective we can obtain a super-length optical needle(>12λ) with homogeneous intensity along the propagation axis and wavelength beam size(~λ). Moreover, the numerical calculations of coherence illustrate that, in the range of fullwidth at half maximum(FWHM) of the optical needle, for any two of the parallel electric fieldcomponents of the optical needle the coherence is close to 1, but for any two of orthometricelectric field components the value of coherence is between 0.4 and 0.9. Such the nondiffractingoptical needle may have potential applications in atom optical experiments, suchas in atom traps and atom switches.

Twisted vortex Gaussian Schell-model beams

Charlotte Stahl and Gregory Gbur

Doc ID: 345383 Received 07 Sep 2018; Accepted 05 Oct 2018; Posted 08 Oct 2018  View: PDF

Abstract: We introduce a new class of partially coherent vortex beams in which the angular momentum of the beam is provided from two different sources: the underlying vortex of the random beam and the ``twist' given to the ensemble of beams. The statistical and propagation properties of such beams are investigated, and their orbital angular momentum properties analyzed. The combination of distinct orbital angular momentum sources allows unusual behaviors that are previously unobserved.

Generalized quantification of threedimensionalresolution in optical diffractiontomography using the projection of maximalspatial bandwidths

Chansuk Park, Seungwoo Shin, and YongKeun Park

Doc ID: 334524 Received 07 Jun 2018; Accepted 04 Oct 2018; Posted 04 Oct 2018  View: PDF

Abstract: Optical diffraction tomography (ODT) is a three-dimensional (3D) quantitativephase imaging technique, which enables the reconstruction of the 3D refractive index (RI)distribution of a transparent sample. Due to its fast, non-invasive, and quantitative imagingcapability, ODT has emerged as a powerful tool for various applications. However, the spatialresolution of ODT has only been quantified along the lateral and axial directions for limitedconditions; it has not been investigated for arbitrary-oblique directions. In this paper, wesystematically quantify the 3D spatial resolution of ODT by exploiting the spatial bandwidthof the reconstructed scattering potential. The 3D spatial resolution is calculated for varioustypes of systems, including the illumination-scanning, sample-rotation, and hybrid scanningrotationmethods. In particular, using the calculated 3D spatial resolution, we provide thespatial resolution as well as the arbitrary sliced angle. Furthermore, to validate the presentmethod, the point spread function of an ODT system is experimentally obtained using thedeconvolution of a 3D RI distribution of a microsphere and is compared with the calculatedresolution.

Interferometry-based modal analysis with finite aperture effects

Davood Mardani Najafabadi, Ayman Abouraddy, and George Atia

Doc ID: 334746 Received 22 Jun 2018; Accepted 04 Oct 2018; Posted 04 Oct 2018  View: PDF

Abstract: We analyze the effects of aperture finiteness on interferograms recorded to unveil the modal content of optical beams in arbitrary basis using generalized interferometry. We develop a scheme for modal reconstructionfrom interferometric measurements that accounts for the ensuing clipping effects. Clipping-cognizant reconstruction is shown to yield significant performance gains over traditional schemes that overlook such effects that do arise in practice. Our work can inspire further research on reconstructionschemes and algorithms that account for practical hardware limitations in a variety of contexts.

All-optical DNA variant discovery utilizingextended DV-curve-based wavelengthmodulation

Ehsan Maleki, Hossein Babashah, Somayyeh Koohi, and Zahra Kavehvash

Doc ID: 336011 Received 25 Jun 2018; Accepted 03 Oct 2018; Posted 03 Oct 2018  View: PDF

Abstract: This paper presents a novel optical processing approach for exploring genomesequences built upon optical correlator for global alignment and extended DV-curve method forlocal alignment. To overcome the problem of traditional DV-curve (dual-vector-curve) methodfor presenting an accurate and simplified output, we propose Hybrid Amplitude WavelengthPolarization Optical DV-curve (HAWPOD) method, built upon DV-curve method, to analyzegenome sequences in three steps: DNA coding, alignment, and post-analysis. For this purpose,a tunable graphene-based color filter is designed for wavelength modulation of optical signals.Moreover, all-optical implementation of the HAWPOD method is developed, while its accuracy isvalidated through numerical simulations in LUMERICAL FDTD (finite-difference time-domain).The results express that the proposed method is much faster than its electrical counterparts.

Recording and erasure of photorefractive holograms in undoped BTO crystal at moderate – to – high intensities of 639.7 nm laser under action of 532 nm laser pre-illumination

Waleria Lopes, Helton Medeiros, Gean Santos, Tainnes Araujo, Jesiel Carvalho, Pedro dos Santos, and Maria de Araujo

Doc ID: 336479 Received 18 Jul 2018; Accepted 01 Oct 2018; Posted 02 Oct 2018  View: PDF

Abstract: We investigate recording and erasure of photorefractive holographic gratings in an undoped Bi12TiO20 crystal in a moderate–to–high intensities regime of the recording beams at 639.7 nm without and with the action of laser pre-illumination at 532 nm. The detected hologram without pre-illumination indicates the participation of two photorefractive electronic gratings in its recording process and the diffracted signal by itself exhibits a five-fold enhancement when the total intensity increases from 38.4 mW/cm2 to 214.5 mW/cm2. The dependence of the measured total diffraction efficiency on intensity was investigated and showed a linear behavior. At least three gratings are present in regime of pre-illumination and participate of the write and erasure holographic mechanisms. Two of them are electronic and one is hole-based with a phase difference ∆φ between them. A theoretical approach used to analyze the total diffraction efficiency based upon the photorefractivity standard model and considering the presence of the three gratings showed very good agreement with the holographic erasure experimental data and permitted us to compute ∆φ which exhibited a strong and non-usual dependence on the total intensity.

Radiative transport in quasi-homogeneous randommedia

Jeremy Hoskins, Joseph Kraisler, and John Schotland

Doc ID: 341203 Received 31 Jul 2018; Accepted 26 Sep 2018; Posted 27 Sep 2018  View: PDF

Abstract: We consider the theory of radiative transport in quasi-homogeneous random media. We derive the radiativetransport equation that governs the propagation of light in such media. This result provides conditionsunder which it is justified to apply radiative transport theory to spatially-inhomogeneous media.

Reciprocity Theorem and Accuracy Evaluation onScattering Fields by Dielectric Gratings

Hideaki Wakabayashi, Masamitsu Asai, and Jiro Yamakita

Doc ID: 340594 Received 25 Jul 2018; Accepted 21 Sep 2018; Posted 21 Sep 2018  View: PDF

Abstract: In the theory of gratings, a diffraction solution must satisfy the energy balance and the reciprocity. Thispaper the diffraction by multilayered dielectric gratings including lossy layers of which the solutions donot satisfy the energy balance. Applying the shadow theory to the matrix eigenvalues method, the symmetryof scattering factors in the theory and that of diffraction efficiencies are shown in some formulaeand then are validated numerically. In addition, the reciprocity errors for diffraction efficiencies and scatteringfactors are newly considered as an accuracy criterion. It is shown that, on numerical calculations,the reciprocity error for diffraction efficiencies have only to be checked.

X-ray tomography of extended objects: a comparison of data acquisition approaches

Ming Du, Rafael Vescovi, Kamel Fezzaa, Chris Jacobsen, and Doga Gursoy

Doc ID: 331496 Received 11 May 2018; Accepted 03 Aug 2018; Posted 06 Aug 2018  View: PDF

Abstract: The penetration power of x-rays allows one to image large objects. For example, centimeter-sized specimens can be imaged with micron-level resolution using synchrotron sources. In this case, however, the limited beam diameter and detector size preclude the acquisition of the full sample in a single take, necessitating strategies for combining data from multiple regions. Object stitching involves the combination of local tomography data from overlapping regions, while projection stitching involves the collection of projections at multiple offset positions from the rotation axis followed by data merging and reconstruction. We compare these two approaches in terms of radiation dose applied to the specimen, and reconstructed image quality. Object stitching involves an easier data alignment problem, and immediate viewing of subregions before the entire dataset has been acquired. Projection stitching is more dose-efficient, and avoids certain artifacts of local tomography; however, it also involves a more difficult data assembly and alignment procedure, in that it is more sensitive to accumulative registration error.

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