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Optical analysis of a photovoltaic V-trough system installed in western India

APPLIED OPTICS 2012年第36期51卷 8606-8614页

作者： Maiti, Subarna Sarmah, Nabin Bapat, Pratap Mallick, Tapas K. CSIR Cent Salt & Marine Chem Res Inst SPEU Solar Energy Grp Bhavnagar 364002 Gujarat India Heriot Watt Univ Sch Engn & Phys Sci IMPEE Edinburgh EH14 4AS Midlothian Scotland

The low concentrating photovoltaic (PV) system such as a 2x V-trough system can be a promising choice for enhancing the power output from conventional PV panels with the inclusion of thermal management. This system is more attractive when the reflectors are retrofitted to the stationary PV panels installed in a high aspect ratio in the north-south direction and are tracked 12 times a year manually according to preset angles, thus eliminating the need of diurnal expensive tracking. In the present analysis, a V-trough system facing exactly the south direction is considered, where the tilt angle of the PV panels' row is kept constant at 18.34 degrees. The system is installed on the terrace of CSIR-Central Salt and Marine Chemicals Research Institute in Bhavnagar, Gujarat, India (21.47 N, 71.15 E). The dimension of the entire PV system is 9.64 m x 0.55 m. The V-troughs made of anodized aluminum reflectors (70% specular reflectivity) had the same dimensions. An in-house developed;experimentally validated Monte Carlo ray-trace model was used to study the effect of the angular variation of the reflectors throughout a year for the present assembly. Results of the ray trace for the optimized angles showed the maximum simulated optical efficiency to be 85.9%. The spatial distribution of solar intensity over the 0.55 m dimension of the PV panel due to the V-trough reflectors was also studied for the optimized days in periods that included solstices and equinoxes. The measured solar intensity profiles with and without the V-trough system were used to calculate the actual optical efficiencies for several sunny days in the year, and results were validated with the simulated efficiencies within an average error limit of 10%. (C) 2012 Optical Society of America

关键词： computation methods Metrological instrumentation Ray tracing Reflectors Solar radiation Thermal management

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Depth extraction of 3D objects using axially distributed image sensing

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OPTICS EXPRESS 2012年第21期20卷 23044-23052页

作者： Hong, Suk-Pyo Shin, Donghak Lee, Byung-Gook Kim, Eun-Soo Kwangwoon Univ Display Res Center 3DRC 3D HoloDigilog Human Media Res Ctr HoloDigilog Seoul 139701 South Korea Dongseo Univ Inst Ambient Intelligence Pusan 617716 South Korea

Axially distributed image sensing (ADS) technique is capable of capturing 3D objects and reconstructing high-resolution slice plane images for 3D objects. In this paper, we propose a computational method for depth extraction of 3D objects using ADS. In the proposed method, the high-resolution elemental images are recorded by simply moving the camera along the optical axis and the recorded elemental images are used to generate a set of 3D slice images using the computational reconstruction algorithm based on ray back-projection. To extract depth of 3D object, we propose the simple block comparison algorithm between the first elemental image and a set of 3D slice images. This provides a simple computation process and robustness for depth extraction. To demonstrate our method, we carry out the preliminary experiments of three scenarios for 3D objects and the results are presented. To our best knowledge, this is the first report to extract the depth information using an ADS method. (C)2012 Optical Society of America

关键词： computation methods Integral imaging Lens arrays Machine vision Reconstruction algorithms Three dimensional imaging

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Framework for computing the spatial coherence effects of polycapillary x-ray optics

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OPTICS EXPRESS 2012年第4期20卷 3975-3982页

作者： Zysk, Adam M. Schoonover, Robert W. Xu, Qiaofeng Anastasio, Mark A. IIT Dept Biomed Engn Med Imaging Res Ctr Chicago IL 60616 USA Washington Univ Dept Biomed Engn St Louis MO 63130 USA

Despite the extensive use of polycapillary x-ray optics for focusing and collimating applications, there remains a significant need for characterization of the coherence properties of the output wavefield. In this work, we present the first quantitative computational method for calculation of the spatial coherence effects of polycapillary x-ray optical devices. This method employs the coherent mode decomposition of an extended x-ray source, geometric optical propagation of individual wavefield modes through a polycapillary device, output wavefield calculation by ray data resampling onto a uniform grid, and the calculation of spatial coherence properties by way of the spectral degree of coherence. (C) 2012 Optical Society of America

关键词： computation methods Far field diffraction Image quality Light propagation Optical devices X ray optics

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Design and analysis of multi-wavelength diffractive optics

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OPTICS EXPRESS 2012年第3期20卷 2814-2823页

作者： Kim, Ganghun Dominguez-Caballero, Jose A. Menon, Rajesh Univ Utah Dept Elect & Comp Engn Salt Lake City UT 84112 USA MIT Dept Mech Engn Cambridge MA 02139 USA

We present an extension of the direct-binary-search algorithm for designing high-efficiency multi-wavelength diffractive optics that reconstruct in the Fresnel domain. A fast computation method for solving the optimization problem is proposed. Examples of three-wavelength diffractive optics with over 90% diffraction efficiency are presented. These diffractive optical elements reconstruct three distinct image patterns when probed using the design wavelengths. Detailed parametric and sensitivity studies are conducted, which provide insight into the diffractive optic's performance when subject to different design conditions as well as common systematic and fabrication errors. (C) 2012 Optical Society of America

关键词： Beam shaping computation methods Diffraction efficiency Diffractive lenses Diffractive optical elements Diffractive optics

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Contour coding based rotating adaptive model for human detection and tracking in thermal catadioptric omnidirectional vision

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APPLIED OPTICS 2012年第27期51卷 6641-6652页

作者： Tang, Yazhe Li, Youfu City Univ Hong Kong Dept Mech & Biomed Engn Hong Kong Hong Kong Peoples R China

In this paper, we introduce a novel surveillance system based on thermal catadioptric omnidirectional (TCO) vision. The conventional contour-based methods are difficult to be applied to the TCO sensor for detection or tracking purposes due to the distortion of TCO vision. To solve this problem, we propose a contour coding based rotating adaptive model (RAM) that can extract the contour feature from the TCO vision directly as it takes advantage of the relative angle based on the characteristics of TCO vision to change the sequence of sampling automatically. A series of experiments and quantitative analyses verify that the performance of the proposed RAM-based contour coding feature for human detection and tracking are satisfactory in TCO vision. (C) 2012 Optical Society of America

关键词： computation methods Imaging systems Infrared imaging Neural networks Optical flow Thermal imaging

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First principles study of the ternary complex model of EL2 defect in GaAs saturable absorber

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OPTICS EXPRESS 2012年第6期20卷 6258-6266页

作者： Li, Dechun Yang, Ming Cai, Yongqing Zhao, Shengzhi Feng, Yuanping Shandong Univ Sch Informat Sci & Engn Jinan 250100 Peoples R China Natl Univ Singapore Fac Sci Dept Phys Singapore 117542 Singapore

First principles calculations are performed for the perfect GaAs crystal, the double Ga vacancies (V-Ga)(2), and the ternary complex defect (AsGaVAsVGa), using the state-of-the-art computational method with the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional to correct the band gap and account for a proper description of the interaction between defects states and bulk states. Three shallow acceptor defect levels are found due to the creation of (V-Ga)(2) with nearest-neighbor As dangling bonds. However, for GaAs with the ternary complex defects (AsGaVAsVGa), the As antisite As-Ga and the V-As's nearest-neighbor Ga dangling bonds provoke several donor defect states. The lowest donor defect state locates at 0.85 eV below the bottom of conduction band, which is very close to the experimental observation of the EL2 defect level. In addition, structual evolution from (V-Ga)(2) defect to the ternary defect complex (AsGaVAsVGa) is simulated by ab initio molecular dynamic (MD) calculation at different temperatures. The MD results demonstrate that the ternary complex defect (AsGaVAsVGa) can be converted from the double Ga vacancies (V-Ga)(2) at room temperature, and it can exist stably at higher temperature. The present work is helpful to unravel the microstructure and the forming mechanism of the EL2 defect, to find out methods to improve the performance of the GaAs saturable absorber by changing the growth conditions of GaAs crystal. (C) 2012 Optical Society of America

关键词： computation methods Photon counting Q switched lasers Remote sensing Saturable absorbers Wavelength conversion

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Quantification of lamellar orientation in corneal collagen using second harmonic generation images

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OPTICS LETTERS 2012年第16期37卷 3312-3314页

作者： Mega, Yair Robitaille, Mike Zareian, Ramin McLean, James Ruberti, Jeffrey DiMarzio, Charles Northeastern Univ Dept Elect & Comp Engn Boston MA 02115 USA Northeastern Univ Dept Mech & Ind Engn Boston MA 02115 USA

Second harmonic generation (SHG) is a well-established optical modality widely used in biomedical optics to image collagen based tissues. The coherent signal of the forward direction SHG produces a high resolution image that can resolve individual fibers (groups of fibrils). In highly ordered collagen lamellae, such as in the corneal stroma, it is important to determine the orientation of the fibers as they contribute significantly to the biomechanics of the tissue. However, due to the crimped structure of the fibers, it is challenging to robustly determine their orientation using an independent computational method, compared to the straight fibers problem. Previous work in the field used the polarization of the fundamental or other techniques involving a more manual selection of the orientation, in order to differentiate between various directions in corneal structures. Yet those lack accuracy and independency. We present a robust independent technique to determine the orientation of the fibers in the corneal structure. The experimental results presented here, taken from different lamellae, demonstrate strongly the correct orientation. (C) 2012 Optical Society of America

关键词： computation methods Fourier transforms Image processing Nonlinear spatial filtering Polarization Second harmonic generation

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Simple and effective method for the analytic description of important optical beams when truncated by finite apertures

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APPLIED OPTICS 2012年第16期51卷 3370-3379页

作者： Zamboni-Rached, Michel Recami, Erasmo Balma, Massimo Univ Estadual Campinas DMO FEEC Sao Paulo Brazil Ist Nazl Fis Nucl Sez Milano I-20133 Milan Italy Univ Statale Bergamo Fac Ingn Bergamo Italy Univ Estadual Campinas DMO FEEC Sao Paulo Brazil SELEX Galileo San Maurizio Caselle Tor Italy

In this paper we present a simple and effective method, based on appropriate superpositions of Bessel-Gauss beams, which in the Fresnel regime is able to describe in analytic form the three-dimensional evolution of important waves as Bessel beams, plane waves, Gaussian beams, and Bessel-Gauss beams when truncated by finite apertures. One of the by-products of our mathematical method is that one can get in a few seconds, or minutes, high-precision results, which normally require quite lengthy numerical simulations. The method works in electromagnetism (optics, microwaves) as well as in acoustics. (C) 2012 Optical Society of America

关键词： computation methods Fresnel diffraction Gaussian beams Light beams Mathematical methods Numerical simulation

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De-entangling colorfulness and fidelity for a complete statistical description of color quality

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OPTICS LETTERS 2012年第23期37卷 4997-4999页

作者： Quintero, Jesus M. Hunt, Charles E. Carreras, Josep IREC Catalonia Inst Energy Res Barcelona 08930 Spain Univ Nacl Colombia Dept Elect & Elect Engn Bogota 111321 Colombia Univ Calif Davis Calif Lighting Technol Ctr Davis CA 95618 USA

In this Letter, the main attributes known to affect color quality are treated statistically over a set of 118 spectra representing the current mainstream lighting technology. The color rendering index (CRI) is used to assess color fidelity while colorfulness is used to complement CRI-R-a, supported by the growing evidence that assessment of light spectra cannot overlook color preference inputs. Colorfulness is evaluated by our optimal color (O-c) index, through a code that computes the (MacAdam) theoretical maximum volumetric gamut of objects under a given illuminant for all the spectra in our database. Pearson correlation coefficients for CRI-R-a, the (Y. Ohno's) color quality scale (CQS) and O-c show a high correlation (0.950) between CRI-R-a and CQS-Q(a), while O-c shows the lowest correlation (0.577) with CRI-R-a, meaning that O-c represents the best complement to CRI-R-a and Qa for an in-depth study of color quality. (C) 2012 Optical Society of America

关键词： Color difference Color rendering Color spaces computation methods Light sources Spectral properties

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Irradiance tailoring for extended sources using a point-source freeform design algorithms

Irradiance tailoring for extended sources using a point-sour...

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Conference on Optical Systems Design

作者： Wester, Rolf Bruneton, Adrien Baeuerle, Axel Stollenwerk, Jochen Loosen, Peter Fraunhofer Inst Laser Technol ILT D-52074 Aachen Germany

ISBN: (纸本)9780819493019

The advent and rapid development of efficient high power LED sources with their unique emission characteristics enables the development of illumination systems that meet very strict requirements concerning light distribution and efficiency. Most of the algorithms used to design the necessary optical freeform surfaces rely on the point source assumption. As long as the distance between LED and those surfaces is sufficiently large, this is a good approximation. One further important design goal is to make the optical components as small as possible, which makes the point source assumption less accurate. The existing design algorithms thus have to be accompanied by methods to treat the finite-sized LED sources. We examine the limits that are set by the finite size of the light sources and present algorithms to optimize optical freeform surfaces up to these limits. Point source results are iteratively improved to get the desired illumination pattern employing finite sized LEDs. At each iteration step the illumination pattern used in the point source computations is adapted so that the real illumination pattern of an LED approximates the originally desired pattern.

关键词： Nonimaging optics computation methods Illumination design Nonspherical lens design LED illumination

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