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Accepted papers to appear in an upcoming issue

OSA now posts prepublication articles as soon as they are accepted and cleared for production. See the FAQ for additional information.

A replacement of the Lorentz law for the shape of the spectral lines in the infrared region

Andrea Carati and Alberto Maiocchi

Doc ID: 259745 Received 23 Feb 2016; Accepted 26 Apr 2016; Posted 28 Apr 2016  View: PDF

Abstract: We propose a new phenomenological law for the shape of the spectral lines in the infrared, which accounts for the exponential decay of the extinction coefficient in the high frequency region, observed in many spectra. We apply this law to the measured infrared spectra of LiF, NaCl and MgF₂,finding a good agreement, over a wide range of frequencies.

A tutorial on Maxwell Garnett approximation. I. Introduction

Vadim Markel

Doc ID: 260083 Received 29 Feb 2016; Accepted 24 Apr 2016; Posted 28 Apr 2016  View: PDF

Abstract: This tutorial is devoted to the Maxwell Garnett approximation and related theories. Topics covered inthe first, introductory part of the tutorial include the Lorentz local-field correction, the Clausius-Mossottirelation and its role in the modern numerical technique known as the Discrete Dipole Approximation(DDA), the Maxwell Garnett mixing formula for isotropic and anisotropic media, multi-componentmixtures and the Bruggeman mixing formula, the concept of smooth field, and Wiener and Bergman-Milton bounds.

Closed fringe demodulation using phasedecomposition by Fourier basis functions

Pramod Rastogi and Rishikesh Kulkarni

Doc ID: 259394 Received 22 Feb 2016; Accepted 24 Apr 2016; Posted 25 Apr 2016  View: PDF

Abstract: We report a new technique for the demodulation of a closed fringe pattern by representing the phase asa weighted linear combination of a certain number of linearly independent Fourier basis functions in agiven row/column at a time. A state space model is developed with the weights of the basis functionsas the elements of the state vector. Iterative extended Kalman filter is effectively utilized for the robustestimation of the weights. A coarse estimate of the fringe density based on the fringe frequency map isused to determine the initial row/column to start with and subsequently the optimal number of basisfunctions. The performance of the proposed method is evaluated with several noisy fringe patterns.Experimental results are also reported to support the practical applicability of the proposed method.

Classical theory of thermal radiation from a solid

Wei Guo

Doc ID: 259502 Received 29 Feb 2016; Accepted 24 Apr 2016; Posted 25 Apr 2016  View: PDF

Abstract: In this work, a solid at a finite temperature is modeled as an ensemble of identical atoms, each of whichmoves around a lattice site inside an isotropic harmonic potential. The motion of one such atom is studiedfirst. It is found that the atom moves like a time-dependent current density and, thus, can emit electromagneticradiation. Since all the atoms are identical, they can radiate too. The resultant radiation fromthe atoms is the familiar thermal radiation from the solid. After its general expression is obtained, theintensity of the thermal radiation is discussed for its properties, and specifically calculated in the lowtemperaturelimit. Both atomic motion and radiation are formulated in the classical domain.

First-principles definition and measurement of planetary electromagnetic-energy budget

Michael Mishchenko, James Lock, Andrew Lacis, Larry Travis, and Brian Cairns

Doc ID: 260991 Received 10 Mar 2016; Accepted 24 Apr 2016; Posted 25 Apr 2016  View: PDF

Abstract: The imperative to quantify the Earth’s electromagnetic-energy budget with an extremely high accuracy has been widely recognized but has never been formulated in the framework of fundamental physics. In this paper we give a first-principles definition of the planetary electromagnetic-energy budget using the Poynting-vector formalism and discuss how it can, in principle, be measured. Our derivation is based on an absolute minimum of theoretical assumptions, is free of outdated concepts of phenomenological radiometry, and naturally leads to the conceptual formulation of an instrument called the double hemispherical cavity radiometer (DHCR). The practical measurement of the planetary energy budget would require flying a constellation of several dozen planet-orbiting satellites hosting identical well-calibrated DHCRs.

Application of the Quanta Image Sensor Concept toLinear Polarization Imaging – A Theoretical Study

Leo Anzagira and Eric Fossum

Doc ID: 257929 Received 22 Jan 2016; Accepted 20 Apr 2016; Posted 21 Apr 2016  View: PDF

Abstract: Research efforts in linear polarization imaging have largely targeted the development of novel polarizing filterswith improved performance, and the monolithic integration of image sensors and polarization filter arrays.However, as pixel sizes in CMOS image sensors continue to decrease, the same limitations which impact color andmonochrome CMOS image sensors will undoubtedly affect polarization imagers. Issues of low signal capacity anddynamic range in small pixels will severely limit the useful polarization information that can be obtained. In thispaper, we propose to leverage the benefits of the relatively new Quanta Image Sensor (QIS) concept to mitigate theanticipated limitations of linear polarization imaging as pixel sizes decrease. We address by theoretical calculationand simulation, implementation issues such as alignment of polarization filters over extremely small pixels used inthe QIS concept and polarization image formation from single bit output of such pixels. We also present designinnovations aimed at exploiting the benefits of this new imaging concept for simultaneous color and linearpolarization imaging.

General analytical expressions for impact ofpolarization aberration on lithographic imaging underlinearly polarized illumination

shen lina, Xiangzhao Wang, Si Li, Guanyong Yan, Boer Zhu, and Heng Zhang

Doc ID: 250779 Received 24 Sep 2015; Accepted 20 Apr 2016; Posted 22 Apr 2016  View: PDF

Abstract: With the shrink of critical dimension (CD), the impact of polarization aberration on lithographic imaging becomesincreasingly non-ignorable. In this paper, the linear relationships between image placement error and odd Pauli-Zernike polarization aberrations, as well as that between best focus shift and even Pauli-Zernike polarizationaberrations are established by analyzing the imaging of alternating phase-shifting mask. The relationalexpressions of polarization aberration sensitivities (PAS) and polarization angle of illumination are obtained basedon these linear relationships. Then the expressions for the zero-value points and extremum points of PAS arederived, and the impact of polarization angle of illumination on PAS is analyzed. The derived analytical expressionsmatch simulation results well, which can be used to analyze the detrimental impact of polarization aberration onlithographic imaging and provide theoretical basis for exploring polarization aberration measurement and controltechniques.

Spectral imaging using consumer level devices and kernel-based regression

Ville Heikkinen, Clara Cámara, Tapani Hirvonen, and Niko Penttinen

Doc ID: 258590 Received 08 Feb 2016; Accepted 18 Apr 2016; Posted 18 Apr 2016  View: PDF

Abstract: Hyperspectral reflectance factor image estimations were performed in 400--700 nm wavelength range using portable consumer level laptop display as an adjustable light source for trichromatic camera. Targets in interest were ColorChecker Classic samples, Munsell Matte samples, geometrically challenging tempera icon paintings from turn of the 20$^{th}$ century and human hands. Measurements and simulations were performed using Nikon D80 RGB camera and Dell Vostro 2520 laptop screen as light source. Estimations were performed without spectral characteristics of the devices and with emphasizing simplicity for training sets and estimation model optimization. Spectral and color error images are shown for the estimations using line scanned hyperspectral images as the ground-truth. Estimations were performed using kernel-based regression models via first degree inhomogeneous polynomial kernel and a Matérn kernel, where in latter case the median heuristic approach for model optimization and link function for bounded estimation were evaluated. Results suggest modest requirements for training set and show that all estimation models have markedly improved accuracy with respect to the DE00 color error (up to 99\% for paintings and hands) and the Pearson distance (up to 98\% for paintings and 99\% for hands) from weak training set (Digital ColorChecker SG) case when small representative training data were used in the estimation.

Aperture averaging in multiple-input single-output free space optical systems using partially coherent radial array beams

Yahya Baykal, Muhsin Gökçe, and Murat Uysal

Doc ID: 258742 Received 03 Feb 2016; Accepted 17 Apr 2016; Posted 18 Apr 2016  View: PDF

Abstract: Multiple-input single-output (MISO) techniques are employed in free space optical (FSO) links to mitigate thedegrading effects of atmospheric turbulence. In this paper, for the MISO FSO system, partially coherent radial arrayand a finite sized receiver aperture are used at the transmitter and the receiver, respectively. Using the extendedHuygens Fresnel principle, we formulate the average power and the power correlation at the finite sized slowdetector in weak atmospheric turbulence. System performance indicators such as the power scintillation index andthe aperture averaging factor are found. Effects of the source size, ring radius, receiver aperture radius, linkdistance, structure constant and the degree of source coherence are analyzed on the performance of the MISO FSOsystem. In the limiting cases, the numerical results are found to be the same when compared to the existingcoherent and partially coherent Gaussian beam scintillation indices.

Large color gamut displays with diffraction gratings

Francesco Aieta, Peter Morovic, Ján Morovic, Marco Fiorentino, Charles Santori, and David Fattal

Doc ID: 257856 Received 26 Jan 2016; Accepted 14 Apr 2016; Posted 20 Apr 2016  View: PDF

Abstract: The ability to display a broad variety of colors has great benefits not only in the context of entertainment but also as a means to streamline design, prototyping and manufacturing processes. Displays that use RGB filters or backlights cannot span all colors that occur in nature. To improve the accuracy of color reproduction there have been attempts to include additional color primaries in displays. Existing solutions, however, impact cost, scalability, or spatial resolution and are predominantly applicable to projections system. We propose an approach based on combining diffraction gratings extractors and the HANS imaging pipeline initially developed for printing. This combination offers an unprecedented potential to attain very large color gamuts with the same backlights commercially used today.

The propagation properties of the first order and the second order Airy Gaussian vortex beams through gradient-index medium

Ruihuang Zhao, Weihao Yu, Fu Deng, Jiayao Huang, and Dongmei Deng

Doc ID: 259811 Received 24 Feb 2016; Accepted 13 Apr 2016; Posted 13 Apr 2016  View: PDF

Abstract: The propagation of the Airy Gaussian Vortex(AiGV) beams through the gradient-index medium is investigated analytically and numerically with the transfer matrix method. Deriving the analytic expression of the AiGV beams based on the Huygens diffraction integral formula, we get propagate path, intensity and phase distributions, and the Poynting vector of the first order and the second order AiGV beams which propagate through the paraxial $ABCD$ system. The ballistic trajectory is no longer conventional parabolic but trigonometric shapes in the gradient-index medium. Especially, the AiGV beams represent the singular behavior at propagation path and the light intensity distribution. The phase distribution, and the Poynting vector exhibit reverse when the AiGV beams through the singularity. As the order increased, the main lobe of the AiGV beams is overlapped by the vortex core gradually. And the side lobe is weakening when the AiGV beams propagate nearly to the singularity. Additionally, the figure of the Poynting vector of the AiGV beams is proved that the direction of energy flow corresponding to the intensity distribution. The vortex of the second order AiGV beams is larger, and the propagation velocity is faster than that of the first order.

Focused fields of given power with maximum longitudinal electric field component inside a substrate

Quincy van den Berg, H. Urbach, and Silvania Pereira

Doc ID: 259101 Received 12 Feb 2016; Accepted 11 Apr 2016; Posted 14 Apr 2016  View: PDF

Abstract: Closed formulas are presented for the electromagnetic field of given power in the lens pupil which maximizes the longitudinal electric field at arbitrary depth when focusing through an interface. Absorbing media are considered.

Colorimetric Analysis of Outdoor Illumination acrossVarieties of Atmospheric Conditions

Shahram Peyvandi, Javier Hernandez-Andres, Francisco José Olmo Reyes, Juan Luis Nieves, and Javier Romero

Doc ID: 259168 Received 08 Feb 2016; Accepted 10 Apr 2016; Posted 11 Apr 2016  View: PDF

Abstract: The solar illumination at ground level is subject to a good deal of change in spectral and colorimetric properties.With an aim of understanding the influence of atmospheric components and phases of daylighton colorimetric specifications of downward radiation, more than 5,600,000 spectral irradiance functions ofdaylight, sunlight and skylight were simulated by the radiative transfer code, SBDART [1], under the atmosphericconditions of clear sky without aerosol particles, clear sky with aerosol particles, and overcastsky. The interquartile range of the correlated color temperatures (CCT) for daylight indicated values from5,712 to 7,757K among the three atmospheric conditions. A minimum CCT of 3,600K was found fordaylight when aerosol particles are present in the atmosphere. Our analysis indicated that hemisphericdaylight with CCT less than 3,600K may be observed in rare conditions in which the level of aerosol ishigh in the atmosphere. In an atmosphere with aerosol particles, we also found that the chromaticity ofdaylight may shift along the green-purple direction of the Planckian locus, with a magnitude dependingon the spectral extinction by aerosol particles and the amount of water vapor in the atmosphere. Thedata analysis showed that an extremely high value of CCT, in an atmosphere without aerosol particles,for daylight and skylight at low sun, is mainly due to the effect of Chappuis absorption band of ozoneat 600 nm. In this paper, we compare our data with well-known observations from previous researchincluding the ones used by the CIE to define natural daylight illuminants.

Deconvolution methods for structured illuminationmicroscopy

Nadezda Chakrova, Bernd Rieger, and Sjoerd Stallinga

Doc ID: 259859 Received 23 Feb 2016; Accepted 08 Apr 2016; Posted 08 Apr 2016  View: PDF

Abstract: We compare two recently developed multiple-frame deconvolution approaches for reconstruction of structuredillumination microscopy (SIM) data: the pattern-illuminated Fourier Ptychography algorithm (piFP)and the joint Richardson-Lucy deconvolution (jRL). The quality of the images reconstructed by thesemethods is compared in terms of the achieved resolution improvement, noise enhancement and inherentartefacts. Furthermore, we study the issue of object-dependent resolution improvement by consideringthe modulation transfer functions derived from different types of objects. The performance of the consideredmethods is tested in experiments and benchmarked with that of a commercial SIM microscope. Wefind that the piFP method resolves equally well periodic and isolated structures, whereas the jRL methodprovides significantly higher resolution for isolated objects compared to the periodic ones. Images reconstructedby the piFP and jRL algorithms are comparable to the images reconstructed using the generalizedWiener filter applied in most commercial SIM microscopes. An advantage of the discussed algorithms isthat they allow reconstruction of SIM images acquired under different types of illumination, such asmulti-spot or random illumination.

An always-on low power optical system for skin-based touchless machine control

Michela Lecca, Massimo Gottardi, Elisabetta Farella, and Bojan Milosevic

Doc ID: 257002 Received 07 Jan 2016; Accepted 02 Apr 2016; Posted 11 Apr 2016  View: PDF

Abstract: Embedded vision systems are smart energy efficient devices that capture and process a visual signal in order to extract high level information about the surrounding observed world. Thanks to these capabilities, embedded vision systems attract more and more interest from research and industry. In this work, we present a novel low power optical embedded system tailored to detect the human skin under various illuminant conditions. We employ the presented sensor as a smart switch to activate one or more appliances connected to it. The system is composed by an always on low power RGB color sensor, a proximity sensor and an energy efficient microcontroller (MCU). The architecture of the color sensor allows a hardware pre-processing of the RGB signal, which is converted into the $rg$ space directly on chip reducing the power consumption. The $rg$ signal is delivered to the MCU, where it is classified as skin or non-skin. Each time the signal is classified as skin, the proximity sensor is activated to check the distance of the detected object. If it appears to be in the desired proximity range, the system detects the interaction and switches on/off the connected appliances. The experimental validation of the proposed system on a prototype shows that processing both distance and color remarkably improves the performance of the two separated components. This makes the system a promising tool for energy efficient, touchless control of machines.

Omni-directional transformation-optics cloak made from lenses and glenses

Johannes Courtial, Tomas Tyc, Stephen Oxburgh, Euan Cowie, Gregory Chaplain, Gavin Macauley, and Chris White

Doc ID: 258587 Received 10 Feb 2016; Accepted 01 Apr 2016; Posted 04 Apr 2016  View: PDF

Abstract: We present a design for an omni-directional transformation-optics (TO) cloak comprising thin lenses and glenses (generalised thin lenses) [Chaplain et al., submitted (2016)]. It should be possible to realise such devices in pixellated form. Our design is a piecewise non-affine generalisation of piecewise affine pixellated-transformation-optics devices [Oxburgh et al., Proc. SPIE 9193, 91931E (2014) and J. Opt. (in press, 2016)]. It is intended to be a step in the direction of TO devices made entirely from lenses, which should be readily realisable on large length scales and for a broad range of wavelengths.

Polarization oscillations of near-field thermal emission

John Schotland, Manabu Machida, and Evgenii Narimanov

Doc ID: 260780 Received 10 Mar 2016; Accepted 01 Apr 2016; Posted 15 Apr 2016  View: PDF

Abstract: We consider the polarization of thermal emission in the near-field of various materials including dielectrics and metallic systems with resonant surface modes. We find that at thermal equilibrium, the degree of polarization exhibits spatial oscillations with a period of approximately half the optical wavelength, independent of material composition. This result contrasts with that of Setala, Kaivola and Friberg [Phys. Rev. Lett. {\bf 88}, 1 902 (2002)], who find monotonic decay of the degree of polarization for systems in local thermal equilib

Improving the axial and lateral resolution of three-dimensional fluorescence microscopy using random speckle illuminations

Anne Sentenac, awoke negash, simon labouesse, Nicolas Sandeau, Marc Allain, Hugues Giovannini, Jerôme Idier, Rainer Heintzmann, Patrick Chaumet, and Kamal Belkebir

Doc ID: 259490 Received 23 Feb 2016; Accepted 30 Mar 2016; Posted 08 Apr 2016  View: PDF

Abstract: We consider a fluorescence microscope in which several three-dimensional images of a sample are recorded for different speckle illuminations. We show, on synthetic data, that by summing the positive deconvolution of each speckle image, one obtains a sample reconstruction with an axial and transverse resolutions that compare favourably to that of an ideal confocal microscope.

Design of channeled partial Mueller matrix polarimeters

Andrey Alenin and J. Scott Tyo

Doc ID: 257481 Received 14 Jan 2016; Accepted 30 Mar 2016; Posted 12 Apr 2016  View: PDF

Abstract: In this development we introduce a novel class of systems, channeled partial Mueller matrix polarimeters (c-pMMPs). Their analysis benefits greatly by drawing from the concepts of generalized construction of channeled polarimeters as described by the modulation matrix. The modulation matrix resembles that of the Data Reduction Method (DRM) of a conventional polarimeter, but instead of using Mueller vectors as the bases, attention is focused on the Fourier properties of the measurement conditions. By leveraging the understanding of the measurement's structure, its decomposition can be manipulated to reveal noise resilience and information about the polarimeter's ability to measure the aspect of polarization that are important for any given task. We demonstrate the theory with a numerical optimization that designs c-pMMPs for the task of monitoring the damage state of a material as presented earlier by Hoover and Tyo [Appl. Opt. 46, 8364 (2007)]. We select several example systems that produce fewer-than-full-system number of channels, yet retain the ability to discriminate objects of interest. Their respective trade-offs are discussed.

Propagation of polarized waves in inhomogeneous media

Mikhail Charnotskii

Doc ID: 255813 Received 15 Dec 2015; Accepted 11 Mar 2016; Posted 14 Mar 2016  View: PDF

Abstract: A parabolic equation for electromagnetic wave propagation in a random medium is extended to include the depolarization effects in the narrow-angle, forward-scattering setting. Closed-form parabolic equations for propagation of the coherence tensor are derived under a Markov approximation model. For a general partially coherent and partially polarized beam wave, this equation can be reduced to a system of ordinary differential equations allowing a simple numeric solution. An analytical solution exists for statistically homogeneous waves. Estimates based on the perturbation solution support the common knowledge that the depolarization at the optical frequencies is negligible for atmospheric turbulence propagation. These results indicate that the recently published theory (O. Korotkova, Opt. Lett., 40, 3077-3080, 2015) is not valid for atmospheric turbulence.

Hue preserving and saturation improved colorhistogram equalization algorithm

KI SUN SONG, Hee Kang, and Moon Gi Kang

Doc ID: 241948 Received 28 May 2015; Accepted 01 Mar 2016; Posted 15 Apr 2016  View: PDF

Abstract: In this paper, an algorithm is proposed to improve both contrast and saturation without color degradation.The local histogram equalization (HE) method offers better performance than the global HE method,whereas the local HE method sometimes produces undesirable results due to the block-based processing.The proposed contrast enhancement (CE) algorithm reflects the characteristics of the global HE method inthe local HE method to avoid the artifacts while both global and local contrasts are enhanced. There aretwo ways to apply the proposed CE algorithm to color images. One is luminance processing methods andthe other one is each channel processing methods. However, these ways incur excessive or reduced saturationand color degradation problems. The proposed algorithm solves these problems by using channeladaptive equalization and similarity of ratios between the channels. Experimental results show that theproposed algorithm enhances both contrast and saturation while preserving the hue and producing betterperformance than existing methods in terms of objective evaluation metrics.

Enhanced manifold regularization for semi-supervisedclassification

Haitao Gan, Zhizeng Luo, Yingle Fan, and Nong Sang

Doc ID: 246705 Received 24 Jul 2015; Accepted 07 Feb 2016; Posted 11 Feb 2016  View: PDF

Abstract: Manifold regularization (MR) has become one of the most widely used approaches in the semi-supervisedlearning field. It has shown the superiority by exploiting the local manifold structure of both labeledand unlabeled data. The manifold structure is modeled by constructing a Laplacian graph and thenincorporated in learning through a smoothness regularization term. Hence the labels of labeled andunlabeled data vary smoothly along the geodesics on the manifold. However, MR has ignored the discriminativeability of the labeled and unlabeled data. To address the problem, we propose an enhancedMR framework for semi-supervised classification in which the local discriminative information of thelabeled and unlabeled data is explicitly exploited. To make full use of labeled data, we firstly employ asemi-supervised clustering method to discover the underlying data space structure of the whole dataset.Then we construct a local discrimination graph to model the discriminative information of labeled andunlabeled data according to the discovered intrinsic structure. Therefore, the data points which may befrom different clusters though similar on the manifold are enforced far away from each other. Finally, thediscrimination graph is incorporated into the MR framework. In particular, we utilize semi-supervisedfuzzy c-means (SSFCM) and Laplacian regularized Kernel Minimum Squared Error (LapKMSE) for semisupervisedclustering and classification, respectively. Experimental results on several benchmark datasetsand face recognition demonstrate the effectiveness of our proposed method.

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