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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.

Single Image Super-Resolution Using Locally Adaptive Multiple Linear Regression

Joonki Paik, Soohwan Yu, Wonseok Kang, and Seungyong Ko

Doc ID: 247315 Received 07 Aug 2015; Accepted 28 Sep 2015; Posted 02 Oct 2015  View: PDF

Abstract: This paper presents a regularized super-resolution (SR) reconstruction method using locally adaptive multiple linear regression to overcome the limitation of spatial resolution of digital images. In order to make the SR problem better-posed, the proposed method incorporates the locally adaptive multiple linear regression into the regularization process as a local prior. The local regularization prior assumes that the target high-resolution (HR) pixel is generated by a linear combination of similar pixels in differently scaled patches and optimum weight parameters. In addition, we adapt a modified version of the non-local means filter as a smoothness prior to utilize the patch redundancy. Experimental results show that the proposed algorithm better restores HR images than existing state-of-the-art methods in the sense of most objective measures in the literature.

Region-based active contours with cosine fitting energy for image segmentation

Yugang Wang, Ting-Zhu Huang, and Hui Wang

Doc ID: 239683 Received 30 Apr 2015; Accepted 27 Sep 2015; Posted 28 Sep 2015  View: PDF

Abstract: In this paper, by employing the cosine function to express the so-called data fitting term in traditional active contour models, we propose an active contour model with the global cosine fitting energy for segmenting synthetical and real-world images. After that, in order to segment the image with intensity inhomogeneity, we extend the proposed global model to the local cosine fitting energy. In addition, we introduce level set regularization terms into the proposed models to avoid the expensive computational cost which is usually caused by the re-initialization of the evolving level set function. Experimental results indicate that the proposed models are accurate and effective when applied to segment different types of images. Moreover, our models are more efficient and robust for segmenting the images with strong noise and clutter than the Chan-Vese (C-V) model and the local binary fitting (LBF) model.

Intrinsic parameter determination of a paracatadioptric camera by the intersection of two sphere projections

Yue Zhao and Yalin Wang

Doc ID: 243006 Received 15 Jun 2015; Accepted 27 Sep 2015; Posted 28 Sep 2015  View: PDF

Abstract: In this paper, a linear calibration method is proposed for a paracatadioptric camera using the images of two spheres. Two spheres are selected in space, and the two groups of their projection circles on the unit viewing sphere are made to intersect at four points. The quadrilateral consisting of four points is a rectangle, so a group of orthogonal directions can be determined in space to obtain a group of orthogonal vanishing points in the paracatadioptric image plane. Because of the relationship between orthogonal vanishing points and intrinsic camera parameters, the intrinsic parameters of a paracatadioptric camera can be linearly solved by at least five views satisfying the above conditions. First, one estimates the sphere images and their antipodal sphere images. Second, by solving the intersection of the images of two spheres and the intersection of the images of their antipodal spheres, a group of orthogonal vanishing points can be obtained in the image plane. Finally, by taking the relationship between the orthogonal vanishing points and the intrinsic camera parameters as constraint conditions, the intrinsic parameters of the paracatadioptric camera can be obtained. Simulation results and real image data demonstrate the effectiveness of our new algorithms.

Non-Dyadic Fisheye Lens Correction Model for Image Enhancement

Joonki Paik, Jinho Park, Donggyun Kim, and Daehee Kim

Doc ID: 243722 Received 26 Jun 2015; Accepted 27 Sep 2015; Posted 28 Sep 2015  View: PDF

Abstract: This paper presents a non-dyadic framework to improve example-based enhancement of radially distorted images acquired by a very wide-angle lens. In order to remove both jagging and blurring artifacts in the correction process of the fisheye lens' barrel distortion, the proposed method first performs non-dyadic or multiple-step geometric correction based on the parabolic equation-based lens distortion model. At each correction step, an example-based image enhancement method removes undesired geometric correction artifacts such as jagging and blurring. Experimental results demonstrate that the proposed method outperforms existing fisheye lens image enhancement methods in the sense of both subjective and objective measures. Based on both theoretical advancement and experimental results, the proposed method can be used for various wide-view imaging applications including vehicle front- and rear-view cameras and wide-angle video surveillance systems.

Fourier optics analysis of phase mask based pathlength-multiplexed OCT

Biwei Yin, Jordan Dwelle, Bingqing Wang, Tianyi Wang, Marc Feldman, H. Rylander, and Thomas Milner

Doc ID: 247808 Received 12 Aug 2015; Accepted 26 Sep 2015; Posted 28 Sep 2015  View: PDF

Abstract: Optical coherence tomography (OCT) is an imaging technique that constructs depth-resolved image by measuring optical pathlength difference between broadband light backscattered from a sample and a reference surface. For many OCT sample arm optical configurations, sample illumination and backscattered light detection share a common path. When a phase mask is placed in the sample path, features in the detected signal are observed and suggests that an analysis of a generic common path OCT imaging system is warranted. In this study, we present a Fourier optics analysis using a Fresnel diffraction approximation of an OCT system with a pathlength multiplexing element (PME) inserted in sample arm optics. The analysis may be generalized for most phase mask based OCT systems. A radial-angle-diverse PME is analyzed in detail, point spread function (PSF), coherent transfer function, sensitivity of scattering angle diversity detection and signal formation in terms of sample spatial frequency is simulated and discussed. The analysis reveals important imaging features and application limitations of OCT imaging systems with a phase mask in the sample path optics.

Determining the Size and Refractive Index of Microspheres using the Mode Assignments from Mie Resonances

Thomas Preston and Jonathan Reid

Doc ID: 245515 Received 07 Jul 2015; Accepted 25 Sep 2015; Posted 28 Sep 2015  View: PDF

Abstract: A new method for determining the radius and refractive index of microspheres using Mie resonances is presented. Previous methods have relied on searching a multidimensional space in order to find the radius and refractive index that minimize the difference between observed and calculated Mie resonances. For anything but simple refractive index functions this process can be very time consuming. Here, we demonstrate that once the mode assignment for the observed Mie resonances is known, no search is necessary and the radius and refractive index of best-fit can be found immediately. This superior and faster way to characterize microspheres using Mie resonances should supplant previous fitting algorithms. The derivation and implementation of the equations that give the parameters of best-fit are shown and discussed. Testing is performed on systems of physical interest and the effect of noise on measured peak positions is investigated.

A plane wave analysis of coherent holographic image reconstruction by phase transfer

Jeffrey Field, David Winters, and Randy Bartels

Doc ID: 246908 Received 28 Jul 2015; Accepted 24 Sep 2015; Posted 24 Sep 2015  View: PDF

Abstract: Fluorescent imaging plays a critical role in a myriad of scientific endeavors, particularly in the biological sciences. Three-dimensional imaging of fluorescent intensity often requires serial data acquisition, that is voxel-by-voxel collection of fluorescent light emitted throughout the specimen with a non-imaging single-element detector. While non-imaging fluorescence detection offers some measure of scattering robustness, the rate at which dynamic specimens can be imaged is severely limited. Other fluorescent imaging techniques utilize imaging detection to enhance collection rates. A notable example is light-sheet fluorescence microscopy, also known as selective-plane illumination microscopy (SPIM), which illuminates a large region within the specimen and collects emitted fluorescent light at an angle either perpendicular or oblique to the illumination light sheet. Unfortunately, scattering of the emitted fluorescent light can cause blurring of the collected images in highly turbid biological media. We recently introduced an imaging technique called coherent holographic image reconstruction by phase transfer (CHIRPT) that combines light-sheet-like illumination with non-imaging fluorescent light detection. By combining the speed of light-sheet illumination with the scattering robustness of non-imaging detection, CHIRPT is poised to have a dramatic impact on biological imaging, particularly for in vivo preparations. Here we present the mathematical formalism for CHIRPT imaging under spatially coherent illumination and present experimental data that verifies the theoretical model.

High-resolution 3D Phase Imaging using a Partitioned Detection Aperture: a Wave-Optic Analysis

Roman Barankov, Jean-Charles Baritaux, and Jerome Mertz

Doc ID: 248014 Received 19 Aug 2015; Accepted 24 Sep 2015; Posted 24 Sep 2015  View: PDF

Abstract: Quantitative phase imaging has become a topic of considerable interest in the microscopy community. We have recently described one such technique based on the use of a partitioned detection aperture, which can be operated in a single shot with an extended source [Opt. Lett. {\bf 37}, 4062 (2012)]. We follow up on this work by providing a rigorous theory of our technique using paraxial wave optics, where we derive fully three-dimensional spread functions for both phase and intensity. Using these functions we discuss methods of phase reconstruction for in- and out-of-focus samples, insensitive to weak attenuations of light. Our approach provides a strategy for detection-limited lateral resolution with an extended depth of field, and is applicable to imaging smooth and rough samples.

Rapid calculation of paraxial wave propagation for cylindrically symmetric optics

Chris Jacobsen and Kenan Li

Doc ID: 241832 Received 27 May 2015; Accepted 22 Sep 2015; Posted 23 Sep 2015  View: PDF

Abstract: When calculating the focusing properties of cylindrically symmetric focusing optics, numerical wave propagation calculations can be carried out using the Quasi-Discrete Hankel Transform (QDHT). We describe here an implementation of the QDHT where a partial transform matrix can be stored to speed up repeated wave propagations over specified distances, with reduced computational memory requirements. The accuracy of the approach is then verified by comparison with analytical results, over propagation distances with both small and large Fresnel numbers. We then demonstrate the utility of this approach for calculating the focusing properties of Fresnel zone plate optics that are commonly used for x-ray imaging applications, and point to future applications of this approach.

Photonic crystal based All optical NOT Logic Gate

brahm singh and Swati Rawal

Doc ID: 240939 Received 14 May 2015; Accepted 22 Sep 2015; Posted 28 Sep 2015  View: PDF

Abstract: In the present paper, we have utilized the concept of Photonic Crystals(PhC’s) for the implementation of optical NOT gate inverter. The designed structure has hexagonal arrangement of Silicon(Si) rods in air substrate. The logic function is based on the phenomenon of the existence of photonic bandgap and resulting guided modes in defect photonic crystal waveguides. We have plotted the transmission, Extinction ratio and tolerance analysis graphs for the structure and it has been observed that maximum Output is obtained for a telecom wavelength of 1.554μm. Dispersion curves are obtained using Plane Wave Expansion(PWE) method and the transmission is simulated using finite element method(FEM).The proposed structure is applicable for photonic integrated circuits due to its simple structure and clear operating principle.

Generation and propagation of an electromagnetic Gaussian Schell-model vortex beam

Yangjian Cai, Xianlong Liu, Fei Wang, Lin Liu, and Chengliang Zhao

Doc ID: 248224 Received 19 Aug 2015; Accepted 21 Sep 2015; Posted 24 Sep 2015  View: PDF

Abstract: We outline the propagation of an electromagnetic Gaussian Schell-model (EGSM) vortex beam through a paraxial ABCD optical system, and analyze the vortex phase-induced changes of the statistical properties, such as the average intensity, the state of polarization and the degree of polarization (DOP), of a focused EGSM beam. It is found that one can shape the beam profile of an EGSM vortex beam in the focal plane through varying its initial topological charge, DOP and coherence widths. Furthermore, we first report experimental generation of an EGSM vortex beam and measure its focusing properties in experiment. Our experimental results are consistent with the numerical results, and may be useful in material thermal processing and particle trapping.

Long Distance Bessel Beam Propagation Through Kolmogorov Turbulence

Philip Birch, C. Chatwin, Iniabasi Ituen, and Rupert Young

Doc ID: 243749 Received 29 Jun 2015; Accepted 20 Sep 2015; Posted 21 Sep 2015  View: PDF

Abstract: Free space optical communication has the potential to transmit information with both high speed and security. However, since it is unguided it suffers from losses due to atmospheric turbulence and diffraction. To overcome the diffraction limits the long distance propagation of Bessel beams is considered and compared against the Gaussian beam properties. The Bessel beams are shown to have a number of benefits over Gaussian beams when propagating through atmospheric turbulence.

The Influence of Imaging Resolution on Color Fidelity in Digital Archiving

Pengchang Zhang, Ari Ide, and Toque Jay Arre

Doc ID: 231978 Received 08 Jan 2015; Accepted 19 Sep 2015; Posted 21 Sep 2015  View: PDF

Abstract: Color fidelity is one of paramount importance in digital archiving. In this paper, the relationship between color fidelity and imaging resolution was explored by calculating the color difference of an IT8 color chart using CIELAB color difference formula from scanning and simulation images. Microscopic spatial sampling was used in selecting the image pixels for the calculation to highlight the loss of color information. A ratio, called relative imaging definition (RID), was defined to express the correlation between image resolution and color fidelity. The results show that in order for color difference to remain unrecognizable, the imaging resolution should be at least 10 times higher than the physical dimension of the smallest feature in the object being studied.

Smart Light Random Memory Sprays Retinex: A Fast Retinex Implementation for High-Quality Brightness Adjustment and Color Correction

Nikola Banić and Sven Lončarić

Doc ID: 241021 Received 02 Jun 2015; Accepted 19 Sep 2015; Posted 21 Sep 2015  View: PDF

Abstract: Removing the influence of the illumination on image colors and adjusting the brightness across the scene are important image enhancement problems. This is achieved by applying adequate color constancy and brightness adjustment methods. One of the earliest models to deal with both of these problems was the Retinex theory. Some of the Retinex implementations tend to give high-quality results by performing local operations, but they are computationally relatively slow. One of the recent Retinex implementations is Light Random Sprays Retinex (LRSR). In this paper, a new method is proposed for brightness adjustment and color correction that overcomes the main disadvantages of LRSR. There are three main contributions of this paper: first, a concept of memory sprays is proposed to reduce the number of LRSR’s per-pixel operations to a constant regardless of the parameter values thus enabling a fast Retinex-based local image enhancement; second, an effective remapping of image intensities is proposed that results in significantly higher quality; and third, the problem of LRSR’s halo effect is significantly reduced by using an alternative illumination processing method. The proposed method enables a fast Retinex-based image enhancement by processing Retinex paths in constant number of steps regardless of the path size. Due to the halo effect removal and remapping of the resulting intensities the method outperforms many of the well-known image enhancement methods in terms of resulting image quality. The results are presented and discussed. It is shown that the proposed method outperforms most of the tested methods in terms of image brightness adjustment, color correction, and computational speed.

Uniform Refraction In Negative Refractive Index Materials

Cristian Gutierrez and Eric Stachura

Doc ID: 246300 Received 21 Jul 2015; Accepted 18 Sep 2015; Posted 21 Sep 2015  View: PDF

Abstract: We study the problem of constructing an optical surface separating two homogeneous, isotropic media, one of which has a negative refractive index. In doing so, we develop a vector form of Snell’s law, which is used to study surfaces possessing a certain uniform refraction property, both in the near and far field cases. In the near field problem, unlike the case when both materials have positive refractive index, we show that the resulting surfaces can be neither convex nor concave.

A single additive mechanism predicts Lateral Interactions effects- computational model

Hava Matichin, Hedva Spitzer, and Shmuel Einav

Doc ID: 221826 Received 18 Sep 2014; Accepted 17 Sep 2015; Posted 21 Sep 2015  View: PDF

Abstract: The mechanism underlying the lateral interactions (LI) phenomenon is still an enigma. Over the years, several groups have tried to explain the phenomenon and suggested models to predict its psychophysical results. Most of these models comprise both inhibitory and facilitatory mechanisms for describing the LI phenomenon. Their studies' assumption that a significant inhibition mechanism exists is based on the classical interpretation of the threshold elevation perceived in psychophysical experiments. In this work, we suggest a different interpretation of the threshold elevation obtained experimentally. Our model proposes and demonstrates how a facilitatory additive mechanism can solely predict both the facilitation and "inhibition" aspects of the phenomenon, without the need for an additional inhibitory mechanism, at least for the two flankers' configurations. Though the model is simple it succeeds to predict the LI effect under a large variety of stimuli configurations and parameters. The model is in agreement with both classical and recent psychophysical and neurophysiological results. We suggest that the LI mechanism plays a role in creating an educated guess to form a continuation of gratings and textures based on the surrounding visual stimuli.

Comparative analysis of imaging configurations and objectives for Fourier microscopy

Rashid Zia, Jonathan Kurvits, and Mingming Jiang

Doc ID: 245829 Received 15 Jul 2015; Accepted 15 Sep 2015; Posted 16 Sep 2015  View: PDF

Abstract: Fourier microscopy is becoming an increasingly important tool for the analysis of optical nanostructures and quantum emitters. However, achieving quantitative Fourier space measurements requires a thorough understanding of the impact of aberrations introduced by optical microscopes, which have been optimized for conventional real-space imaging. Here, we present a detailed framework for analyzing the performance of microscope objectives for several common Fourier imaging configurations. To this end, we model objectives from Nikon, Olympus, and Zeiss using parameters that were inferred from patent literature and confirmed, where possible, by physical disassembly. We then examine the aberrations most relevant to Fourier microscopy, including the alignment tolerances of apodization factors for different objective classes, the effect of magnification on the modulation transfer function, and vignetting-induced reductions of the effective numerical aperture for wide-field measurements. Based on this analysis, we identify an optimal objective class and imaging configuration for Fourier microscopy. In addition, as a resource for future studies, the Zemax files for the objectives and setups used in this analysis have been made publicly available.

Freeform lens for rectangular illumination with target plane rotating a certain angle

Liu Dianhong, Xiaohui Zhang, and Chen Chen

Doc ID: 246758 Received 27 Jul 2015; Accepted 15 Sep 2015; Posted 16 Sep 2015  View: PDF

Abstract: We have proposed a method for rectangular illumination in (μ ,ν ) coordinate system with high collection efficiency and favorable uniformity. In our proposed approach, with target plane rotating a certain angle around z axis, one of the diagonal on rectangular target plane moves to the coordinate axis, then we partitions the light source and target plane into grids, intersection points of grids are one-to-one corresponding from source to target plane. This improved method will avoid one-to-many correspondence topological relationship in traditional ( μ,ν ) mapping method, uniformity of illuminance pattern will be promoted. Based on the method, lens is designed for rectangular target plane illumination, uniformity over 0.83 and the efficiency about 0.92 are obtained with a 1 mm× 1 mm LED Lambertian source.

Measurement of Transmission and Reflection of Light from a Thick Anisotropic Crystal Modeled by a Sum of Incoherent Partial Waves

Bart Kahr, Shane Nichols, Oriol Arteaga, and Alexander Martin

Doc ID: 242537 Received 08 Jun 2015; Accepted 15 Sep 2015; Posted 18 Sep 2015  View: PDF

Abstract: Formulae for modeling ellipsometric measurements of bianisotropic crystals assume perfectly coherent plane wave illumination. As such, the finite coherence of typical spectroscopic ellipsometers renders such formulae invalid for crystals thicker than a few microns. Reflection measurements of thick crystalline slabs show depolarization. Researchers have proposed strategies for the full accounting for multiply reflected incoherent waves in anisotropic, arbitrarily oriented crystals (K. Postava, T. Yamaguchi, and R. Kantor, Appl. Opt. 41, 2521-2531 (2002).), but to the best of our knowledge these methods have not been tested by explicit measurements. It is shown that by a summation of multiply reflected incoherent waves, transmission and reflection measurements of thick quartz slabs can be interpreted in terms of the constitutive material parameters.

Color weak compensation using local affine isometry based on discrimination threshold matching

Jin Chao, Reiner Lenz, Rika Mochizuki, and TAKANORI KOJIMA

Doc ID: 242797 Received 10 Jun 2015; Accepted 13 Sep 2015; Posted 16 Sep 2015  View: PDF

Abstract: We develop algorithms for color-weak compensation and color-weak simulation based on Riemannian geometry models of color spaces. The objective function introduced measures the match of color discrimination thresholds of average normal observers and a color-weak observer. The developed matching process makes use of local affine maps between color spaces of color normal and color-weak observers. The method can be used to generate displays of images that provide color normal and color weak observers with similar color-difference experience. It can also be used to simulate the perception of a color-weak observer for color normal observers. We also introduce a new database of measurements of color discrimination threshold data for color normal and color-weak observers obtained at different lightness levels in CIELUV space. The compensation methods include compensations of chromaticity using local affine maps between chromaticity planes of color normal and color-weak observers, and 1D compensation on lightness. We describe how to determine correspondences between the origins of local coordinates in color spaces of color normal and color-weak observers using a neighborhood expansion method. After matching the origins of the two coordinate systems a local affine map is estimated by solving a nonlinear equation, or singular-value-decomposition(SVD). We apply the methods to natural images and evaluate their performance using the semantic differential (SD) method.

Analyzing the propagation behavior of scintillation index and bit error rate of partially coherent flat-topped laser beam in oceanic turbulence


Doc ID: 241795 Received 27 May 2015; Accepted 12 Sep 2015; Posted 14 Sep 2015  View: PDF

Abstract: In the present paper, on the basis of the extended Huygens–Fresnel principle, semi-analytical expression for describing on-axis scintillation index of a Partially Coherent Flat-Topped (PCFT) laser beam in weak to moderate oceanic turbulence is derived and consequently by using the Log-Normal intensity probability density function, the Bit Error Rate (BER) is evaluated. The effects of source factors (such as wavelength, order of flatness, beam width) and turbulent ocean parameters (such as Kolmogorov microscale, relative strengths of temperature and salinity fluctuations, rate of dissipation of the mean squared temperature, and rate of dissipation of the turbulent kinetic energy per unit mass of fluid) on propagation behavior of scintillation index and hence on BER are studied by detail. Results indicate that in comparison with Gaussian beam, a PCFT laser beam with the higher order of flatness is found to have lower scintillations. Also, scintillation index and BER is most affected when salinity fluctuations in the ocean dominate temperature fluctuations.

A Spatial Frequency Based Metric for Image Super- Resolution

Matthew Woods and Aggelos Katsaggelos

Doc ID: 241846 Received 27 May 2015; Accepted 11 Sep 2015; Posted 14 Sep 2015  View: PDF

Abstract: The image processing technique known as super-resolution (SR) has the potential to allow engineers to specify lower resolution and, therefore, less expensive cameras for a given task by enhancing the base camera’s resolution. This is especially true in the remote detection and classification of objects in the environment such as aircraft or human faces. Performing each of these tasks requires a minimum image “sharpness” which is quantified by a maximum resolvable spatial frequency which is, in turn, a function of the camera optics, pixel sampling density, and signal-to-noise ratio (SNR). Much of the existing SR literature focuses on SR performance metrics for candidate algorithms such as perceived image quality or peak SNR. These metrics can be misleading because they also credit de-blurring and/or de-noising in addition to true SR. In this paper, we propose a new, task-based metric where the performance of an SR algorithm is, instead, directly tied to the probability of successfully detecting critical spatial frequencies within the scene.

(TUTORIAL) Computational Optical Imaging and Photography: Plenoptic Camera, Light Field Capture, Image Refocus, and Superresolution

Edmund Lam

Doc ID: 245927 Received 14 Jul 2015; Accepted 10 Sep 2015; Posted 10 Sep 2015  View: PDF

Abstract: Photography is a cornerstone of imaging. Ever since cameras became consumer products more than a century ago, we have witnessed great technological progress in both the optics and the recording medium, with digital sensors replacing photographic films in most instances. The latest revolution is computational photography, which seeks to make image reconstruction computation an integral part of the image formation process; in this way, there can be new capabilities or better performance in the overall imaging system. A leading effort in this area is called the plenoptic camera, which aims at capturing the light field of an object; proper reconstruction algorithms can then adjust the focus after the image capture. In this tutorial paper, we first illustrate the concept of plenoptic function and light field from the perspective of geometric optics. This is followed by a discussion on early attempts and recent advances in the construction of the plenoptic camera. We will then describe the imaging model and computational algorithms that can reconstruct images at different focus points, using mathematical tools from both ray optics and Fourier optics. Last but not least, we will consider the tradeoff in spatial resolution, and highlight some research work to increase the spatial resolution of the resulting images.

Iterative Color Constancy with Temporal Filtering for Image Sequence with no Relative Motion Between Camera and Scene

JOSEMAR SIMÃO, Raquel Vassallo, and Hans-Jörg Schneebeli

Doc ID: 243602 Received 26 Jun 2015; Accepted 09 Sep 2015; Posted 10 Sep 2015  View: PDF

Abstract: Color constancy is the ability to perceive the color of a surface as invariant even under changing illumination. In outdoor applications, such as mobile robot navigation or surveillance, the lack of this ability harms the segmentation, tracking and object recognition tasks. The main approaches for color constancy are generally targeted to static images and intend to estimate the scene lluminant color from the images. We present an iterative color constancy method with temporal filtering applied to image sequences in which reference colors are estimated from previous corrected images. Furthermore, two strategies to sample colors from the images are tested. The proposed method has been tested using image sequences with no relative movement between the scene and the camera. It also has been compared with known color constancy algorithms such as Gray-World, Max-RGB and Gray-Edge. In most cases, the iterative color constancy method achieved better results than the other approaches.

Stitching interferometry of high numerical aperture cylindrical optics without using fringe-nulling routine

Junzheng Peng, Qingquan Wang, Xiang Peng, and yu yingjie

Doc ID: 244149 Received 02 Jul 2015; Accepted 08 Sep 2015; Posted 09 Sep 2015  View: PDF

Abstract: Stitching interferometry is a common method for measuring the figure error of high numerical aperture optics. However, subaperture measurement usually requires a fringe-nulling routine, making the stitching procedure complexity and time-consuming. The challenge when measuring a surface without fringenulling routine is, that the rays do no longer hit the surface perpendicularly. This violation of the nulltest condition can lead to high fringe density and introduce high-order misalignment aberrations into the measurement result. This paper demonstrates that the high-order misalignment aberrations can be characterized by the low-order misalignment aberrations, then an efficient method is proposed to separate the high-order misalignment aberrations from subaperture data. With the proposed method, the fringe-nulling routine is not required. Instead, the subaperture data is measured under nonzero fringe pattern. Then all possible misalignment aberrations are removed with the proposed method. Finally, the full aperture map is acquired by connecting all subaperture data together. Experimental results showing the feasibility of the proposed procedure is presented.

Unified beam splitter of fused silica grating under second Bragg incidence

Changhe Zhou, Zhumei Sun, Hongchao Cao, and Jun Wu

Doc ID: 242329 Received 05 Jun 2015; Accepted 04 Sep 2015; Posted 08 Sep 2015  View: PDF

Abstract: The unified design for 1×2 beam splitter of dielectric rectangular transmission gratings under second Bragg incidence is theoretically investigated for TE and TM polarized light respectively. The empirical equations of the relative grating parameters (ratio of the absolute one to incidence wavelength) for this design are also obtained with simplified modal method. The influences of polarization of incident light and relative grating parameters on the performance of the beam splitter are thoroughly studied based on simplified modal method and rigorous coupled-wave analysis. Two specific gratings are demonstrated with even split and high diffraction efficiency (>94% for TE polarization and >97% for TM counterpart). The unified profiles of the 1×2 beam splitter are independent from incidence wavelength since the refractive index of fused silica is roughly a constant over a wide range of wavelength, which should be promising for future applications.

High order modes in Cavity Resonator Integrated Guided-mode Resonance Filters (CRIGFs)

Romain Laberdesque, Olivier Gauthier-Lafaye, Henri CAMON, Antoine Monmayrant, marlene petit, Olivier Demichel, and Benoît Cluzel

Doc ID: 243827 Received 29 Jun 2015; Accepted 04 Sep 2015; Posted 08 Sep 2015  View: PDF

Abstract: Cavity Resonator Integrated Guided-mode Resonance Filters (CRIGFs), are a new generation of Guided-Mode Resonance Filters (GMRFs), offering narrow-band reflection with small aperture and high angular acceptance. We report experimental characterisation and theoretical modelling of unexpected high-order reflected modes in such devices. Using couple-mode modelling and moiré analysis we provide physical insight on key mechanisms ruling CRIGFs properties. This model could serve as a simple and efficient framework to design new reflectors with tailored spatial and spectral modal reflectivities.

Fast Reconstruction of Fluorophore Concentration Variation Based on Derivation of Diffusion Equation

Xuanxuan Zhang, Fei Liu, Simin Zuo, Jing Bai, Jianwen Luo, and Jiulou Zhang

Doc ID: 243294 Received 24 Jun 2015; Accepted 04 Sep 2015; Posted 16 Sep 2015  View: PDF

Abstract: The information of fluorophore concentration variation (FCV) has the potential for drug development and tumor studies, but the reconstruction of FCV is time-consuming in dynamic fluorescence molecular tomography (DFMT). In this paper, a time-efficient reconstruction method for FCV is presented. The system equation of this method is derived from the derivation of the diffusion equation, and its size does not change with the number of frames. The computational time can be significantly reduced by using this method because the images of different frames are reconstructed separately. Simulations and phantom experiments are performed to validate the performance of the proposed method. The results show that compared with the previous method, the proposed method can obtain better results and consumes less computational time with the same number of iterations. In addition, the time consumption in a single iteration of the proposed method increases much more slowly with the number of frames.

The propagation properties of the right-hand circularly polarized Airy-Gaussian beams through right-handed materials and left-handed materials slabs

Dongmei Deng, Zijie Liang, Bo Chen, Xiangbo Yang, Fu Deng, Weihao Yu, Jiayao Huang, and Ruihuang Zhao

Doc ID: 243422 Received 30 Jun 2015; Accepted 04 Sep 2015; Posted 23 Sep 2015  View: PDF

Abstract: The propagation of the right-hand circularly polarized Airy Gaussian beams (RHCPAiGBs) through slabs of the right-handed materials (RHMs) and the left-handed materials (LHMs) is investigated with the method of transfer matrix analytically and numerically. An approximate analytical expression for the RHCPAiGBs passing through a paraxial ABCD optical system is derived on the basis of the Huygens diffraction integral formula. The intensity and the phase distributions of the RHCPAiGBs through RHMs and LHM are demonstrated. The influence of the parameter χ0 on the propagation of the RHCPAiGBs through the RHMs and LHMs slabs is investigated. The RHCPAiGBs possess the transverse-momentum currents which show the physics underlying this intriguing accelerating effect is the combined contributions of the transverse spin and the transverse orbital currents. Additionally, we go a step further to explore the radiation force including the gradient force and scattering force of the RHCPAiGBs. Keywords: right-hand circularly polarized Airy-Gaussian Beam; left-handed materials; radiation force.

(CV) Independence and interaction of luminance and chromatic contributions to spatial hyperacuity performance

Bonnie Cooper and Barry Lee

Doc ID: 198653 Received 30 Sep 2013; Accepted 02 Feb 2014; Posted 03 Feb 2014  View: PDF

Abstract: Here we test interactions of luminance and chromatic input to spatial hyperacuity mechanisms. First, we tested alignment with matching or mismatching (contrast polarity or modality) grating pairs that were adjusted to detection threshold. Thresholds with mismatched pairs were significantly elevated. Second, we determined alignment acuity as a function of luminance or chromatic contrast alone or in the presence of contrast pedestals. For in-phase pedestal conditions, performance followed the envelope of the more sensitive mechanism. However, polarity reversals revealed an asymmetric effect for luminance and chromatic conditions. This suggests that luminance can overrule chromatic mechanisms in hyperacuity; we interpret these findings in the context of spatial mechanisms.

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