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A new scheme focusing on modification and control of distortion in the reflection and transmission of Goos-Hanchen (GH) shifted beams, is discussed. The absorptivity, reflectivity, and transmissivity are measured for the new atomic scheme. The GH-shifted beam is modified by control fields and incident angle. The sum of absorption, transmission, and reflection coefficients is equal to one. For positive reflection GH-shift region, there is negative transmission GH shift. The distortion in the reflected and transmitted beam is controlled with incident angle and control fields. The results discussed in this article show significant applications in micro-optics and nano-optics, acoustics, and plasma physics. Nous discutons dans cet article un nouveau schema qui se focalise sur la modification et le controle de la distorsion dans la reflexion et la transmission d'un faisceau sous decalage de Goos-Hanchen. Nous mesurons l'absorptivite, la reflectivite et la transmissivite dans ce nouveau schema atomique. Le faisceau a decalage GH est modifie par des champs de controle et l'angle d'incidence. La somme des coefficients d'absorption, de transmission et de reflexion est egale a un. Pour la region GH decalee de reflexion positive, il y a une region GH decalee de transmission negative. La distorsion dans les faisceaux reflechi et transmis est controlee par l'angle d'incidence et champs de controle. Les resultats presentes ici montrent des applications interessantes en micro-optique/nano-optique, acoustique et physique du plasma. [Traduit par la Redaction] Mots-cles: optique quantique, decalage de Goos-Hanchen, distorsion des faisceaux, champ de controle., 1. Introduction The light pulse is used for data communication in the telecom industry. Distortion reduces the information contents of a stream of pulses. Noise-free communication of data is possible [...]

The need to reduce energy consumption in buildings has led to the widespread adoption of energy efficient light sources, such as LEDs. Diffused light reflectors are usually preferred to distribute LED illumination uniformly across the room. In this study, unpigmented PMMA films were studied for their diffused reflectance properties. PMMA films were cast onto a cold plate under varied humidity conditions to promote the formation of a porous microstructure via soiid/liquid/liquid phase separation. The relationship between casting conditions, nonsolvent content, microstructure, and diffused reflectance was studied. The diffused reflectance was evaluated using a UV/Vis spectrophotometer with an integration sphere, and the microstructure was evaluated with an SEM. It was found that increasing the nonsolvent concentration either through increased absorption of ambient humidity or by directly incorporating water into the recipe creates pores that efficiently refract visible light. Reflectance in the mid 80% was obtained just by exploiting the difference in refractive index between the PMMA and the air-filled pores. High diffused reflectance has been achieved in PMMA films purely by manipulating the film's microstructure without the use of other expensive polymers or pigments., INTRODUCTION The US Energy Information Administration (EIA) estimated that in 2010, lighting comprised 19% or 700 TWh of total US electricity consumption [1]. Energy savings from improved LED lighting in [...]

Determination of the working temperature of photovoltaic (PV) modules is an essential task in research and engineering projects. It acquires more relevance in the current environment, characterized by increasing figures of installed PV power, module efficiency, solar applications, and operational configurations. However, most of the current procedures for temperature determination of PV modules are simply based on empirical correlations, carried out at conditions defined by some specific standards, with the corresponding lack of accuracy when modules work under real conditions. Thus, the present work looks into a formal procedure for temperature determination by conducting a power balance between the dynamic incoming and outgoing power fluxes. Some additional parameters are included when compared with classic expressions. In particular, the spectral reflectance of the tandem glass-semiconductor is measured to determine the reflected fraction of solar irradiance. The relationship between reflectance and equilibrium temperature is determined for a representative group of PV modules, and the influence that the working point exerts on the module temperature has also been taken into account. Finally, the influence of spectral distribution on module temperature has been quantified by simulations carried out by using a spectral model. In this way, determination of absolute temperature is achieved within a [+ or -]2[degrees]C range, regardless of module characteristics and climatic or operational conditions. In addition, temperature differences between PV modules that work under the same external conditions can be predicted within [+ or -]0.5[degrees]C. To summarize, a thermal model suitable for different PV modules and working configurations is presented. Some new parameters are introduced in the calculus process, and the influence of the most relevant ones has been quantified. In this way, the present work is aimed at making a contribution to the study of PV module temperature. [DOI: 10.1115/1.4002246] Keywords: PV module temperature, thermal modeling, spectral reflectance, thermal performance

This paper addresses the impact of bead density on paint pavement marking retroreflectivity. The writers collected retroreflectivity data and glass bead images on 40 segments of two-lane highways. Bead density is defined as the surface percentage of glass beads exposed above the paint marking material. Numerous methods for determining bead density were considered and studied. A new approach, referred to as a computer-aided counting method, was developed and a bead density analysis program was written. The program was used to analyze 108 images to obtain a bead density value for each image. A correlation study was conducted between pavement marking retroreflectivity and bead density. The findings of the study show that the normal range of glass bead density for older markings is 9-24% of the paint marking surface area. Furthermore, bead density values have a positive correlation with marking retroreflectivity readings; higher bead density leads to higher retroreflectivity. White paint markings have significantly higher retroreflectivity values than do yellow markings when the bead density values are the same. DOI: 10.1061/(ASCE)TE.1943-5436.0000142 CE Database subject headings: Pavement markings; Imaging techniques. Author keywords: Pavement marking; Retroreflectivity; Glass beads; Bead density; Image analysis.

When simulating light collection in scintillators, modeling the angular distribution of optical light reflectance from surfaces is very important. Since light reflectance is poorly understood, either purely specular or purely diffuse reflectance is generally assumed. In this paper we measure the optical reflectance distribution for eleven commonly used reflectors. A 440 nm, output power stabilized, un-polarized laser is shone onto a reflector at a fixed angle of incidence. The reflected light's angular distribution is measured by an array of silicon photodiodes. The photodiodes are movable to cover 2[pi] of solid angle. The light-induced current is, through a multiplexer, read out with a digital multimeter. A LabVIEW program controls the motion of the laser and the photodiode array, the multiplexer, and the data collection. The laser can be positioned at any angle with a position accuracy of 10 arc minutes. Each photodiode subtends 6.3[degrees], and the photodiode array can be positioned at any angle with up to 10 arc minute angular resolution. The dynamic range for the current measurements is [10.sup.5] : 1. The measured light reflectance distribution was measured to be specular for several ESR films as well as for aluminum foil, mostly diffuse for polytetrafluoroethylene (PTFE) tape and titanium dioxide paint, and neither specular nor diffuse for Lumirror[R], Melinex[R] and Tyvek[R]. Instead, a more complicated light distribution was measured for these three materials. Index Terms--Lambertian reflection, light collection, Monte Carlo methods.

Microspherical solar cells and modules have been fabricated. The spherical nature of these semi-transparent devices allows the microspherical cells to harvest both directly incident and diffuse components of sunlight thereby improving the solar energy conversion efficiency. Indoor and outdoor characterizations of these three dimensional semi-transparent cells and modules are carried out using a Lambertian reflector in order to assess the maximum efficiency of the devices. In the absence of the reflector the cell efficiency is 13.5% under standard illumination (100 mW [cm.sup.-2], A.M. 1.5, 25 [degrees]C). However, this is significantly enhanced in the presence of the reflector. Microspherical modules with the reflector are directly compared to similar semi-transparent modules comprised of traditional planar devices, in outdoor tests at low light intensity (2.5 25 mW [cm.sup.-2]) to further demonstrate the benefits of the design particularly at low angle of incident radiation. Keywords: Spherical solar ceils; Lambertian reflector; Efficiency

Fully quantitative analyses of DRIFTS data are required when the surface concentrations and the specific rate constants of reaction (or desorption) of adsorbates are needed to validate microkinetic models. The relationship between the surface coverage of adsorbates and various functions derived from the signal collected by DRIFTS is discussed here. The Kubelka-Munk and pseudoabsorbance (noted here as absorbance, for the sake of brevity) transformations were considered, since those are the most commonly used functions when data collected by DRIFTS are reported. Theoretical calculations and experimental evidence based on the study of CO adsorption on Pt/Si[O.sub.2] and formate species adsorbed on Pt/Ce[O.sub.2] showed that the absorbance (i.e., = log 1/R', with R' = relative reflectance) is the most appropriate, yet imperfect, function to give a linear representation of the adsorbate surface concentration in the examples treated here, for which the relative reflectance R' is typically > 60%. When the adsorbates lead to a strong signal absorption (e.g., R' < 60%), the Kubelka-Munk function is actually more appropriate. The absorbance allows a simple correction of baseline drifts, which often occur during time-resolved data collection over catalytic materials. Baseline corrections are markedly more complex in the case of the other mathematical transforms, including the function proposed by Matyshak and Krylov (Catal. Today 1995, 25, 1-87), which has been proposed as an appropriate representation of surface concentrations in DRIFTS spectroscopy.

The reduction in size and the increase in speed of opto- and magnetoelectronic devices is making the probability of nonequilibrium electron-phonon phenomena greater, leading to increased thermal resistance in these devices. The measurement of electron-phonon coupling in materials in these devices is becoming increasingly important for accurate thermal management. Here femtosecond thermoreflectance is used to measure the electron-phonon coupling factor in thin Ni films of varying thickness grown on Si and glass substrates. The thermoreflectance response is measured at 1.3 and 1.55 eV, yielding drastically different responses due to the Fermi-level transition at 1.3 eV in Ni. The influence of this transition on the thermoreflectance response results in a measurement of the electron-phonon coupling factor that is twice as high as that recorded in previous measurements that were unaffected by the Fermi-level transition. OCIS codes: 120.5700, 160.3380, 240.0310, 260.2160, 260.3060, 310.6860.

The Bloch wave formalism is employed to explain the asymmetry of the spectral response of various distributed-feedback lasers with respect to the gap by terminating the laser facets judicially. The analysis proves that the phase and amplitude of the reflection coefficient for Bloch waves are extremely helpful in determining the spectral characteristics of such distributed-feedback lasers.

Various studies are conducted to analyze carrier illumination (CI), a photoelectrothermal modulated optical reflectance (PMOR) technique that is used for one dimensional active doping profile characterization of ultrashallow junctions. The described method makes use of the power curve's first derivative at low, as well as high illumination powers, but is still not very reliable, as it has a limited extraction range.

This paper aims at demonstrating the possibility of merging data from various medium-resolution spaceborne sensors to produce a consistent time series of surface bidirectional reflectance distribution function (BRDF) and albedo products. The spectral, directional, temporal, and spatial aspects of the multisensor fusion are presented. Emphasis is then given on the spectral normalization for the fusion of Medium Resolution Imaging Spectrometer Instrument (MERIS) data with Moderate Resolution Imaging Spectroradiometer (MODIS) and VEGETATION (VGT) data. Two methods are evaluated: a simple statistical method, which relies on a linear regression using all the available spectral bands, and a more innovative method called the spectral mode method, which is based on the restitution of the surface spectral signature by a combination of universal spectral functions. Analysis with Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) hyperspectral data and satellite products reveals that the spectral mode method is more efficient. This approach is used to merge top-of-canopy bidirectional reflectances from MERIS and VGT for the restitution of BRDF and albedo over a subset of West Africa. Compared to the products obtained with MERIS alone, the fusion with VGT demonstrates an improvement of the spatial coverage and a reduction of product uncertainty by about a third. Index Terms--Albedo, bidirectional reflectance distribution function (BRDF), fusion, Medium Resolution Imaging Spectrometer (MERIS), Moderate Resolution Imaging Spectroradiometer (MODIS), spectral normalization, VEGETATION sensor.

A simple technique to suppress the reflection coefficients [S.sub.11] and [S.sub.22] of surface acoustic wave (SAW) filters is proposed. It is shown by simulation that they can be suppressed to less than -20 dB without deteriorating the transmission characteristics.

A robust statistics-based nonnegative matrix factorization (RNMF) approach is described to recover the measurement in reflectance spectroscopy and it is based on the minimization of a robust cost function and yields two equations updated alternately. The results on the spectral library of reflectance spectra are presented to show the much-improved performance of the RNMF approach.

Three-dimensional appearance models consisting of spatially varying reflectance functions defined on a known shape can be used in analysis-by-synthesis approaches to a number of visual tasks. The construction of these models requires the measurement of reflectance, and the problem of recovering spatially varying reflectance from images of known shape has drawn considerable interest. To date, existing methods rely on either: 1) low-dimensional (e.g., parametric) reflectance models, or 2) large data sets involving thousands of images (or more) per object. Appearance models based on the former have limited accuracy and generality since they require the selection of a specific reflectance model a priori, and while approaches based on the latter may be suitable for certain applications, they are generally too costly and cumbersome to be used for image analysis. We present an alternative approach that seeks to combine the benefits of existing methods by enabling the estimation of a nonparametric spatially varying reflectance function from a small number of images. We frame the problem as scattered-data interpolation in a mixed spatial and angular domain, and we present a theory demonstrating that the angular accuracy of a recovered reflectance function can be increased in exchange for a decrease in its spatial resolution. We also present a practical solution to this interpolation problem using a new representation of reflectance based on radial basis functions. This representation is evaluated experimentally by testing its ability to predict appearance under novel view and lighting conditions. Our results suggest that since reflectance typically varies slowly from point to point over much of an object's surface, we can often obtain a nonparametric reflectance function from a sparse set of images. In fact, in some cases, we can obtain reasonable results in the limiting case of only a single input image. Index Terms--Reflectance, BRDF, image synthesis, image-based rendering, radial basis functions.

We have developed a simple technique to decorrelate remote sensing color band data from depth in optically shallow water. The method linearizes color band data with respect to depth by subtracting an optically deepwater value from the entire waveband under consideration and taking the natural logarithm of the result. Next, this linearized waveband is rotated about the model 2 regression line computed against a bathymetry band. The rotated color band is decorrelated from water depth. We demonstrate the technique for a small area of Kailua Bay, Oahu, HI, using Quickbird multispectral and Scanning Hydrographic Operational Airborne Lidar Survey LIDAR data. Results indicate that color band data are effectively decorrelated from depth, while bottom reflector variability is maintained, thus providing the basis for further analysis of the depth-invariant wavebands. The primary benefit of our technique is that wavebands are rotated independently, preserving relative spectral information. Index Terms--Bathymetry, coastal remote sensing, Kailua Bay, LIDAR, Quickbird, radiative transfer, reflectance.

A method [atmospheric correction via simulated annealing (ACSA)] is proposed that enhances the atmospheric correction of hyperspectral images over dark surfaces. It is based on the minimization of a smoothness criterion to avoid the assumption of linear variations of the reflectance within gas absorption bands. We first show that this commonly used approach generally fails over dark surfaces when the signal to noise ratio strongly declines. In this case, important residual features highly correlated with the shape of gas absorption bands are observed in the estimated surface reflectance. We add a geometrical constraint to deal with this correlation. A simulated annealing approach is used to solve this constrained optimization problem. The parameters involved in the implementation of the algorithm (initial temperature, number of iterations, cooling schedule, and correlation threshold) are automatically determined by using a standard simulated annealing theory, reflectance databases, and sensor characteristics. Applied to a HyMap image with available ground truths, we verify that ACSA adequately recovers ground reflectance over clear land surfaces, and that the added spectral shape constraint does not introduce any spurious feature in the spectrum. The analysis of an AVIRIS image of Central Switzerland clearly shows the ability of the method to perform enhanced water vapor estimations over dark surfaces. Over a lake (reflectance equal to 0.02, low signal to noise ratio equal to about 6), ACSA retrieves unbiased water vapor amounts (2.86 cm [+ or -] 0.36 cm) in agreement with in situ measurements (2.97 cm [+ or -] 0.30 cm). This corresponds to a reduction of the standard deviation by a factor 3 in comparison with standard unconstrained procedures (1.95 cm [+ or -] 1.08 cm). Similar results are obtained using a Hyperion image of DoE ARM SGP test site containing a very dark area of the land surface. Index Terms--Atmospheric correction, dark surfaces, hyperspectral remote sensing, simulated annealing.

The classical Chandrasekhar's formula relating the surface reflectance to the top of the atmosphere radiance rigorously applies to a Lambertian surface. For a homogeneous non-Lambertian surface in a plane-parallel atmosphere, an extension of this formula was proposed in the 1980s and has been recently implemented in the second simulation of the satellite signal in the solar spectrum (6S) algorithm. To analyze this extension, the rigorous formula of the top of the atmosphere signal is derived in a plane-parallel atmosphere bounded by a homogeneous non-Lambertian surface. Then the 6S algorithm extension is compared with the exact formula and approximations and their validity are pointed out. The methods used for the derivation of the exact formula are classical. They are based on the separation of direct and diffuse components of the radiation fields, on the introduction of the Green's function of the problem, and on integrations of boundary values of the radiation fields with the Green's function. OCIS codes: 010.1300, 010.1310, 010.1320, 280.1310, 290.4210.

Radiative properties of thin films are derived based on the concept of optical coherence theory. Instead of the previous approach of deriving the property formulas based on the degree of coherence, a direct integration approach to obtain the averaged properties over a finite spectral resolution is developed. The analytical results are in excellent agreement with the measured spectra. The formulas are compact in form and easy to use to invert optical properties or film thicknesses with measured reflectance or transmittance. Rigorous criteria for incoherent and coherent limits can be easily reduced from the general formulas and the resulting equations corresponding to those of geometric and wave optics, respectively. These criteria are very useful in determining under what situations simpler wave optics and geometric optics formulas can be applied. OCIS codes: 030.1640, 230.4170, 260.3160, 310.0310.

For planar-integrated free-space optical (PIFSO) systems high-reflectance thin-film coatings are crucial. Evaporated metal films are preferred for their relative technological simplicity. We propose a three-layer Al-Ag-Al coating composition that combines the high reflectance of Ag with the chemical passivity of Al and its good adherence to glass. Two special measures are taken to prevent delamination: one is an anchoring of the edges of the coating in narrow ditches that are etched into the substrate and the other is the use of an adhesive Al underlayer; to reduce absorption this underlayer is implemented only in sparsely distributed discrete areas. The optical properties of such composite coatings are investigated theoretically. The fabrication complexity is only slightly increased compared to PIFSO systems with one-layer Al reflectors. In experimental tests we verified a reflectance of approximately 98% and an adherence comparable to that of simple Al coatings. OCIS codes: 310.0310, 310.6860, 050.1970, 350.3950.

Nitride-based flip-chip (FC) light-emitting diodes (LEDs) emitting at 465 nm with Ni transparent ohmic contact layers and Ag reflective mirrors were fabricated. Reliability tests of the LED lamps were also performed by injecting 30-mA dc current into the devices at room temperature.

A novel anisotropic-medium perfectly matched layer (PML) implementation is presented for boundary truncation in the three-dimensional vector finite-element time-domain (FETD) method. This approach utilizes a complex set of vector test and basis functions in the PML region, that recover the usual basis functions in the non-PML region. Numerical examples show that the proposed PML-FETD approach has small reflection errors and no observed late-time instabilities for simulations involving up to [10.sup.6] time steps. Index Terms--Basis functions, finite-element methods, numerical stability, perfectly matched layer, reflection coefficient.

The code SHARM-3D, developed for fast and accurate simulations of the monochromatic radiance at the top of the atmosphere over spatially variable surfaces with Lambertian or anisotropic reflectance, is described. The atmosphere is assumed to be laterally uniform across the image and to consist of two layers with aerosols contained in the bottom layer. The SHARM-3D code performs simultaneous calculations for all specified incidence-view geometries and multiple wavelengths in one run. The numerical efficiency of the current version of code is close to its potential limit and is achieved by means of two innovations. The first is the development of a comprehensive precomputed lookup table of the three-dimensional atmospheric optical transfer function for various atmospheric conditions. The second is the use of a linear kernel model of the land surface bidirectional reflectance factor (BRF) in our algorithm that has led to a fully parameterized solution in terms of the surface BRF parameters. The code is also able to model inland lakes and rivers. The water pixels are described with the Nakajima--Tanaka BRF model of wind-roughened water surface with a Lambertian offset, which is designed to model approximately the reflectance of suspended matter and of a shallow lake or river bottom. OCIS codes: 280.1310, 010.1300.

An inversion procedure for the recovery of absorption coefficients of a two-layered semi-infinite diffusive medium by use of time-resolved reflectance measured at two different source-detector distances is proposed. The inversion procedure is based on the property of the photon diffusion equation; i.e., the solution of the diffusion equation for the time-resolved reflectance measured at a longer source--detector distance coincides with that measured at a shorter one by a proper temporal, spatial, and intensity transformation. This inversion procedure, used together with the results of one set of Monte Carlo simulations, is validated as working well when the values of the scattering coefficients of the two layers and the thickness of the first layer are within a range of interest in tissue optics. of America OCIS codes: 170.3660, 170.5280, 170.4580, 170.7050.

The radiation from a rectangular waveguide with a perfectly conducting infinite flange is rigorously studied by using the method of the Kobayashi potential (KP). The fields in the waveguide and half-space are expanded in terms of the waveguide modes and the Weber-Schafheitlin discontinuous integrals, respectively. Continuity of the tangential aperture fields yields matrix equations for the expansion coefficients and the matrix elements consist of double infinite integrals and double infinite series of Bessel functions, which are calculated efficiently by applying the asymptotic approximation of the Bessel function. Numerical results are presented for various physical quantities, such as the aperture admittance, reflection coefficient of the incident wave, and magnitudes of higher-order mode waves, as well as the far-radiation pattern and aperture fields. To verify the validity of our method, the results are compared with other methods and excellent agreement is obtained. Index Terms--Kobayashi potential (KP), radiation, rectangular waveguide.

Reflectance of soil crusts has been studied under artificial light but not under solar illumination. Our objectives were to (i) compare reflectance from crusted and noncrusted soil surfaces under solar illumination, and (ii) explore the relationship between crust permeability and spectral signature. Two California soils were studied, Capay (fine, smectitic, thermic Typic Haploxererts) and Reiff (coarse-loamy, mixed, superactive, nonacid, thermic Mollic Xerofluvents), with samples for the latter taken from plots under organic ([Reiff.sub.OM]) and conventional ([Reiff.sub.CM]) management. A laboratory rainfall simulator was used to form crusts which were sampled at different stages of development and permeability. A portable spectroradiometer was used to collect spectral data in direct sunlight for wet and dry crusted samples. Baseline spectra (albedo) of the dry samples were, in most cases, higher than spectra from the corresponding moist samples. Crusted samples exhibited higher baseline spectra compared with the noncrusted samples. The absorption feature at [approximately equal to] 1400 nm (related to lattice OH of montmorillonite) suggested accumulation of clay in the crust of the [Reiff.sub.CM], and clay depletion from the crusts of the Capay and [Reiff.sub.OM]. An inverse linear relationship existed between reflectance at many wavelengths and crust permeability at different stages of crust development. The reflectance at 1700 nm provided highly significant correlations with infiltration rate (IR) for all three soils, and reflectance at 2130 nm also had a highly significant correlation for the Capay. Our data suggest that spectral measurements of soil surfaces under solar illumination can differentiate between crusted and noncrusted surfaces and assist in evaluating the degree of crust development.

An overview of different techniques to characterize liquids in containers and the necessity of introducing a new technique based on the Schoch effect caused by Lamb wave stimulation in the skin of a container is given. It is shown that the Schoch effect can be used to distinguish between different liquids in containers.

A simple numerical approach for the analysis of nonuniform nonlinear distributed feedback (NLDFB) structures. The method was previously proposed for calculating the input-intensity dependence of the reflectivity and transmissivity of a nonlinear dielectric slab for both transverse-electric (TE) and transverse-magnetic (TM) obliquely incident plane elctromagnetic waves.

Operating a meteorological radar is generally a challenging task when in presence of a significant beam blockage as in complex orography. Apart from enhanced ground clutter, mountainous obstructions of the radar beam can significantly reduce the radar visibility and, thus, its monitoring capabilities. Self-consistent adaptive techniques to reconstruct vertical profiles of reflectivity (VPR) and near-surface rain-rate fields from high-elevation reflectivity bins are here proposed, compared, and tested for ranges up to 60 km. The methodology is based on statistical estimators trained by a large reflectivity volumetric datasets, classified into stratiform and convective rain regimes and resampled onto a uniform Cartesian grid by means of a modified Cressman technique. For what concerns reflectivity vertical profiles, two methods, respectively named statistical nonlinear reconstruction (NSR) and neural network reconstruction (NNR), are considered. The NSR method is based on the principal component analysis, applied to the radar dataset, in order to extract significant reflectivity-profile variance. A retrieval technique, based on a nonlinear multiple regression scheme, is then used to infer near-surface reflectivity from available high-altitude echoes at a given range. The NNR is based on a three-layer artificial neural network trained by means a feedforward backpropagation algorithm. For what concerns the near-surface rain retrieval, besides a power-law reflectivity-rain-rate (ZR) approach, a three-layer neural network technique is also set up in order to estimate surface rain rate from reconstructed VPR. The proposed reconstruction techniques are here illustrated by using volumetric data acquired by the C-band Doppler single-polarization radar, operated in L'Aquila, Italy. A case study, related to a rainfall event that occurred during fall 2000, is discussed. Using a test area within 60 km from the radar site and simulating the presence of beam obstructions, a comparison of NSR and NNR with conventional area average reconstruction techniques shows that the percentage improvement of both NSR and NNR approaches is significant, both for the error bias (by 30% to more than 50%, depending on altitude) and variance (by 10% to more than 20%). A sensitivity test indicates that the VPR reconstruction procedure is fairly robust to missing data, especially in terms of error bias. The comparison of estimated radar rainfall with rain gauge data measurement is also illustrated. The mean field bias closer to its optimal value and an error variance much smaller is obtained when neural network techniques are applied than with conventional ZR methods for both techniques of reconstruction. With respect to the latter, the obtained improvement is more than 40% in terms of root mean square error and is comparable when estimating near-surface rain rate using either NSR or NNR methods to reconstruct the reflectivity vertical profiles. Limitations, potential, and future developments of the proposed adaptive reconstruction techniques are finally discussed. Index Terms--Ground-based C-band radar, inversion techniques, radar meteorology, rain field reconstruction, rain-rate retrieval, vertical profile of reflectivity.

There are several factors that influence visual comfort in an interior. One of them is the luminance distribution of surfaces. In this study, the luminance distribution has been treated in [...]

A model that relates the coefficients of absorption (a) and backscattering ([b.sub.b]) to diffuse attenuation ([K.sub.d]), radiance reflectance ([R.sub.L]), and the mean cosine for downward irradiance ([[micro].sub.d]) is presented. Radiance transfer simulations are used to verify the physical validity of the model for a wide range of water column conditions. Analysis of these radiance transfer simulations suggests that absorption and backscattering can be estimated with average errors of 1% and 3%, respectively, if the value of [[micro].sub.d] is known with depth. If the input data set is restricted to variables that can be derived from measurements of upward radiance ([L.sub.u]) and downward irradiance ([E.sub.d]), it is necessary to use approximate values of [[micro].sub.d]. Examination of three different approximation schemes for [[micro].sub.d] shows that the average error for estimating a and [b.sub.b] increases to ~13%. We tested the model by using measurements of [L.sub.u] and [E.sub.d] collected from case II waters off the west coast of Scotland. The resulting estimates of a and [b.sub.b] were compared with independent in situ measurements of these parameters. Average errors for the data set were of the order of 10% for both absorption and backscattering. OCIS codes: 010.4450, 290.1350, 300.1030.

A spectral-projected gradient method and an extension of the Kubelka--Munk theory are applied to obtain the relevant parameters of the theory from measured diffuse reflectance spectra of pigmented samples illuminated with visible diffuse radiation. The initial estimate of the spectral dependence of the parameters, required by a recursive spectral-projected gradient method, was obtained by use of direct measurements and up-to-date theoretical estimates. We then tested the consistency of the Kubelka--Munk theory by repeating the procedure with samples of different thicknesses. OCIS codes: 290.3200, 290.4020, 290.4210, 290.5820, 290.7050.

Measurements of the contrast value of time-averaged speckle-modulated images of cartilage tissue are used to study tissue thermal modification in the case of laser-light treatment. This modification is related to thermally induced internal stress relaxation in the matrix of the treated tissue. The specific feature of the evolution of time-averaged speckle contrast with a change in the current temperature of modified collagen tissue is the typical looplike form of the contrast-temperature dependencies associated with irreversible changes in tissue structure and correlated with changes in the tissue diffuse transmittance and the tissue internal stress mentioned by other researchers. OCIS codes: 030.6140, 170.6930.

The most recent theoretical studies have shown that three-dimensional (3-D) radiation effects play an important role in the optical remote sensing of atmospheric aerosol and land surface reflectance. These effects may contribute notably to the error budget of retrievals in a broad range of sensor resolutions, introducing systematic biases in the land surface albedo data sets that emerge from the existing global observation systems. At the same time, 3-D effects are either inadequately addressed or completely ignored in data processing algorithms. Thus there is a need for further development of the radiative transfer theory that can rigorously treat both 3-D and surface anisotropy effects and yet be flexible enough to permit the development of fast forward and inversion algorithms. We describe a new theoretical solution to the 3-D radiative transfer problem with an arbitrary nonhomogeneous non-Lambertian surface. This solution is based on an exact semianalytical solution derived in operator form by the Green's function method. The numerical implementation is based on several parameterizations that accelerate the solution dramatically while keeping its accuracy within several percent under most general conditions.

To numerically calculate bistatic scattering from a fractal rough surface with high permittivity, a comprehensive approach of the forward-backward method (FBM) with spectral accelerate algorithm (SAA) combined with the physics-based two-grid (PBTG) method is developed. Bistatic scattering from and transmitting through one-dimensional (1-D) fractal rough surface with high permittivity, under TE and TM tapered wave incidence, are numerically simulated. Angular reflectivity and transmittivity demonstrate the energy conservation and the functional dependences upon the surface parameters. Index Terms--Bistatic scattering, fractal rough surface, high permittivity, physics-based two-grid (PBTG) forward-backward method (FBM)/ spectral accelerate algorithm (SAA), transmitting.

In this work, we investigate the effects of numerical dispersion in the finite-difference time-domain (FDTD) algorithm for layered, anisotropic media. We first derive numerical dispersion relations for diagonally anisotropic media (corresponding to an FDTD reference frame coinciding with the principal axes of a biaxial media). In addition, we incorporate the discretization effects on the reflection and transmission coefficients in layered media. We then apply this analysis to minimize the numerical dispersion error of Huygens' plane-wave sources in layered, uniaxial media. For usual discretization sizes, a typical reduction of the scattered field error on the order of 30 dB is demonstrated. Index Terms--Buried object detection, finite-difference time-domain (FDTD), numerical analysis.

In this paper we present the results of an analysis of the physically measured surface reflectance spectra of 360 matte Munsell chromatic color chips plus 10 flat achromatic vectors corresponding to Munsell value levels 10 (white) to 1 (near black) for a total sample size of 370. Each of the 370 spectra was multiplied by the spectral radiant power distribution of D65 light so that the final results represent the spectra of reflected light from Munsell color chips under D65 illumination. We simultaneously model the structure of the color chips and the spectra in a common three-dimensional Euclidean space, oriented to yield the most interpretable structure with respect of the Munsell color structure. In this orientation, axis 1 roughly corresponds to the mean power of the spectral reflectance (approximate Munsell value), axis 2 goes from Munsell red to blue-green, and axis 3 goes from Munsell green-yellow to purple. Basis factors for the spectra are also plotted against wavelength and Munsell hue. These plots have implications for theories of opponent processes. By plotting the chips and spectra in the same space we obtain virtually exact correspondences between the various Munsell hues and spectral values in nanometers for comparison to those obtained by previous researchers. Mathematical derivations are provided to validate the common Euclidean model.

Nonlinear estimation method of spectral reflectance from camera responses is proposed. The proposed method minimizes the mean square error of spectral reflectance when the reflectance can be regarded as a random sequence of Gaussian mixture distribution. In computer simulations, 168 samples of spectral reflectance from a color chart are estimated from their image signals obtained by three- and six-band cameras. It is confirmed that the proposed method improves the accuracy in comparison with the conventional Wiener estimation method. OCIS codes: 100.2000, 100.3190, 300.6550, 330.1690.

The normalized difference vegetation index (NDVI) has been widely applied in optical remote sensing. However, it has been demonstrated that NDVI is still partially affected by atmospheric path scattering and bidirectional (illumination and viewing geometry) effects. In this paper we present the benefit of using a bidirectional NDVI, and we discuss the problems in using the maximum NDVI composite method. Based on the assumption that a clear day has a larger NDVI value and a cloudy day has a smaller NDVI value (smaller reflectance in the near-infrared band and larger reflectance in red band due to atmospheric path scattering), the ratio of squared observed NDVI values and calculated NDVI values is used as a weight in our inversion method. The calculated NDVI values are derived from previously inverted bidirectional reflectance distribution functions (BRDFs). The inversion process will loop until all weights converge. Our research on the early Terra/MODIS data using a semiempirical kernel-driven BRDF model (the RossThick-LiTransit model) shows that this new method can improve inversion results whenever some cloudy pixels are not filtered out. As cloud detection and subpixel cloudiness are always a problem, this technique should still be very useful in improving the quality of BRDF inversion. Index Terms--Bidirectional reflectance distribution function, inversion, terra moderate resolution imaging spectroradiometer (MODIS), normalized difference vegetation index (NDVI).

A new method for the spectroscopic study of absorbing films is proposed. In contrast to the well-established methods that take advantage of the attenuation of total internal reflection (ATR) to obtain spectra, we intentionally arrange the optics to permit partial internal reflection from the sampling prism face. Attenuated partial internal reflection (APR) spectroscopy is introduced through theoretical calculations and experimental demonstrations. The calculated APR spectra in the infrared region were generated from the Fresnel and Airy equations. Experimentally, APR spectra of water films on a NaCl prism were obtained. APR is more sensitive than ATR, and can easily distinguish water films at the monolayer level (310 pm). The determination of film thickness from interference fringes in APR spectra is also illustrated. It is shown that APR can be used for film thickness measurements that can span 6 orders of magnitude. The limitations of APR are also discussed.

Models of soil reflectance under changing moisture conditions are needed to better quantify soil and vegetation properties from remote sensing. In this study, measurements of reflected shortwave radiation (400-2500 nm) were acquired in a laboratory setting for four different soils at various moisture contents. The observed changes in soil reflectance revealed a nonlinear dependence on moisture that was well described by an exponential model, and was similar for different soil types when moisture was expressed as degree of saturation. Reflectance saturated at much lower moisture contents in the visible and near-infrared (VNIR) spectral region than in the shortwave-infrared (SWIR) spectral region, suggesting that longer wavelengths are better suited for measuring volumetric moisture contents above ~20%. To explore the potential of a general reflectance model based solely on dry reflectance and moisture, we employed a Monte Carlo analysis that accounted for observed variability in the measured spectra. Modeling results indicated that the SWIR region offers significant potential for relating moisture and reflectance on an operational basis, with uncertainties less than half as large as in the VNIR. The results of this study help to quantify the strong influence of moisture on spectral reflectance and absorption features, and should aid in the development of operational algorithms as well as more physically based models in the future.

An analytical method has been developed for directly calculating the principal angle [[theta].sub.p] at which the phase difference between the reflection coefficients is equal to 90 [degrees] and at which the ratio of |[r.sub.p]| to |[r.sub.s]| is equal or close to a minimum. The equations given here can be used in many optical applications. For example, ellipsometric data measured at an incidence angle [[theta].sub.p] will have higher precision than data measured at other incidence angles. [[theta].sub.p] is the principal angle. Instead of three principal angles, there is only one principal angle, which can be found in the region of 0 [less than or equal to] [[theta].sub.p] [less than or equal to] 90 [degrees] for most metallic materials used in applications. Results show good agreement between the measured and the calculated spectra of [[DELTA].sub.p] and [[rho].sub.po]. OCIS codes: 260.2130, 260.3910.

We propose a matrix method for the description of light reflection and transmission by an anisotropic multilayer system consisting of thin and thick layers. A method based on partial-wave matrix summations is applicable in the field of reflection and transmission photometry and ellipsometry. In the case of a thin anisotropic film, the interference effects were described by use of a coherent summation of Jones matrices. Incoherent intensity summations for a thick weakly anisotropic layer were characterized by use of the coherency vector formalism. Observable quantities or Mueller matrix components were obtained from the matrix describing transformation of the coherence vectors. OCIS codes: 260.1180, 260.1440, 260.2130, 313.6860, 120.2130.

The measurement of the source reflection coefficient is fundamental for noise, as well as large-signal testing of microwave active devices. This paper describes a simple yet rigorous technique for fast and accurate determination of a source reflection coefficient when a load-source pull test set is used. The solution consists in measuring the waves at the device-under-test reference plane under two different bias conditions. We have proven that these measurements give enough information to compute the source reflection coefficient with accuracy suitable for most applications. Experimental results are presented and compared to data obtained with more conventional techniques. Index Terms--Active device characterization, error box, microwave measurements, network analyzer calibration, source impedance, source--pull, source reflection coefficient.