Fresnel Reflection Model Research Articles

Analysis of tissue-substrate adhesion by hyperspectral surface plasmon resonance microscopy.

The preparation of histology slides is a critical step in histopathology, and poor-quality histology slides with weak adhesion of tissue sections to the substrate often affect diagnostic accuracy and sometimes lead to diagnostic failure due to tissue section detachment. This issue has been ofconcern and some methods have been proposed to enhance tissue-substrate adhesion. Unfortunately, quantitative analysis of the adhesion between tissue sections and glass slides is still challenging. In this work, the adhesion of mouse brain tissue sections on gold-coated glass slides was analyzed using a laboratory-fabricated hyperspectral surface plasmon resonance microscopy (HSPRM) system that enabled single-pixel spectral SPR sensing and provided two-dimensional (2D) distribution of resonance wavelengths (RWs). The existence of the nanoscale water gap between the tissue section and the substrate was verified by fitting the RW measured in each pixel using the five-layer Fresnel reflection model. In addition, a 2D image of the tissue-substrate adhesion distance (AD) was obtained from the measured 2D distribution of RWs. The results showed that tissue-substrate AD was 20-35 nm in deionized water and 4-24 nm in saline solution. The HSPRM system used in this work has a wide wavelength range of 400-1000 nm and can perform highly sensitive and label-free detection over a large dynamic detection range with high spectral and spatial resolutions, showing significant potential applications in stain-free tissue imaging, quantitative analysis of tissue-substrate adhesion, accurate identification of tumor cells, and rapid histopathological diagnosis.

Modeling Wavelength Dependent Mid‐Infrared (5.5–25 μm) Optical Constants of Silicate Glasses: A Genetic Algorithm Approach

AbstractWavelength‐dependent mid‐infrared (400–1,800 cm−1; 5.56–25 μm) optical constants (real and imaginary indices of refraction; n and k) are determined using reflectance spectra at a spectral sampling of 4 cm−1 for several silicate glasses of varying SiO2 wt% which include (a) basaltic volcanic glass from Kīlauea, Hawaii, (b) synthetic andesite, (c) two synthetic dacites, (d) obsidian volcanic glass from Mount Lassen, California, (e) synthetic rhyodacite, and (f) rhyolitic volcanic glass from Mexico. Because glasses are optically isotropic, no specific orientation was required for spectral measurements, and polished glass samples were measured at random orientations using micro‐FTIR spectrometer. Lorentz‐Lorenz dispersion theory and Fresnel reflectance model for high symmetry materials were used to model the optical constants by optimizing oscillator parameters in modeled spectra to match laboratory spectra. A genetic algorithm (GA) approach automatically finds the natural oscillators and their parameters for each spectrum, and then uses these parameters in a non‐linear least squares optimization routine. The study compared spectral parameters such as Christiansen feature, reststrahlen bands (RBs), and the peaks centered around 860–1,100 (peak 1) and 400–480 cm−1 (peak 2) of n and k to their respective SiO2 wt% of the glasses. CF, RBs, peak 1 of n and k, and peak 2 of n shift to higher wavenumbers with increased SiO2 wt%, whereas peak 2 of k shifts to lower wavenumbers with increased SiO2 wt%. Derived optical constants of these glasses will improve quantitative abundance mapping of volcanic materials on the surfaces of silicate targets in the Solar System.

Double Approach in the Investigation of Light Scattering by a Nickel Metal Cylinder

In the present work, we have investigated the light scattering from a Nickel metal cylinder under normal incidence. A double approach using the Fresnel reflectance model and Lorenz-Mie approach shows that the Fresnel model cannot follow the changes in the scattering regime when the size parameter changes. Experiments show that, even for large cylinders, the Fresnel model overestimates the effects of reflection in the forward direction. The simulation using the Lorenz-Mie formalism shows that as the size parameter changes the scattering regime changes and for size parameter lower than one the distribution of light intensity tends to become uniform and, for size parameter equal or lower than 0.1 the distribution is uniform and independent on the scattering angle, with a strong polarization around 70%.

Computational Performance of GTD-RT Applied for Evaluation of Electromagnetic Scattering on Rough Surfaces

In this paper, a new robust computational method that applies the geometrical theory of diffraction (GTD) in conjunction with the ray tracing (RT) technique is developed to evaluate the electromagnetic scattering pattern due to a plane wave represented as beam of parallel rays incident on a rough surface of quite arbitrary statistical parameters. The development of the proposed technique is explained in detail taking into consideration the generation of the geometrical model of the rough surface. The Fresnel reflection model is applied under the assumption of arbitrary electrical and optical properties of the rough surface material. Also the polarization of the plane wave primarily incident on the rough surface is taken into consideration. The algorithm developed in the present work accounts for multiple bounces of an incident ray and, hence, it can be considered arbitrary higher-order GTD-RT technique. The accuracy of the obtained results is verified through the comparison with the experimental measurements of the scattering pattern of a light beam incident on rough sheets with specific statistical properties. The numerical results of the present work are concerned with investigating the dependence of the scattering pattern on the surface roughness, refractive index, angle of incidence, and the resolution of the geometric model of the rough surface. Also, it is shown that, for limited resolution of the rough surface model, the accuracy of the calculated scattered field depends on the angle of incidence of the primary beam and the surface roughness.

MFPL: Multi-Frequency Phase Difference Combination Based Device-Free Localization

With the popularity of indoor wireless network, device-free indoor localization has attracted more and more attention. Unlike device-based localization where the target is required to carry an active transmitter, their frequent signal scanning consumes a large amount of energy, which is inconvenient for devices with limited energy. In this work, we propose the MFPL, device-free localization (DFL) system based on WiFi distance measurement. First, we combine multi-subcarrier characteristic of Channel State Information (CSI) with classical Fresnel reflection model to get the linear relationship between the change of the length of reflection path and the subcarrier phase difference. Then we calculate the Fresnel phase difference between subcarrier pairs with different spacing from CSI amplitude time series. Finally, we get the change of the length of the reflection path caused by target moving to achieve distance measurement and localization. Using a combination of subcarriers with different spacing to achieve distance measurement effectively broadens the maximum unambiguous distance of the system. To solve the complex non-linear problem of the intersection of two elliptic equations, we introduce Newton's method to transform the non-linear problem into a linear one. The effectiveness of our approach is verified using commodity WiFi infrastructures. The experimental results show our method achieves a median error of 0.87 m in actual indoor environment.

Four-Component Model-Based Decomposition of Polarimetric SAR Data for Special Ground Objects

A four-component model-based decomposition for polarimetric synthetic aperture radar (SAR) images is proposed to deal with the ground objects with orientation angles around 45°. In the previous decompositions, these special targets are mixed with the vegetated areas. With the deficiency of the previous decompositions analyzed, the ambiguity between two scattering mechanisms is clarified. A rotated Fresnel dihedral reflection model is introduced in the proposed algorithm, to model the scattering characteristics of these special targets. The nonnegative eigenvalue decomposition is applied to the remainder coherency matrix to prevent negative powers of the decomposed scattering mechanisms. Another advantage of the proposed decomposition is that it makes use of all the information provided by the coherency matrix, which remains unachieved in the previous model-based decompositions. Experimental Synthetic Aperture Radar (E-SAR) L-band polarimetric SAR data acquired over Oberpfaffenhofen, Germany, are analyzed in this letter. Experimental results indicate that the special ground objects have acquired correct scattering mechanisms, which verifies the effectiveness of the proposed method.

Numerical simulation of molten pool dynamics in high power disk laser welding

A single-phase problem is solved rather than a multiphase problem for numerical simplicity: and the solution is based on the assumption that the region of gas or plasma can be treated as a void because solid or liquid steel has a greater density level than gas or plasma. The volume-of-fluid method, which can calculate the free surface shape of the keyhole, is used in conjunction with a ray-tracing algorithm to estimate the multiple reflections. Fresnel's reflection model is simplified by the Hagen–Rubens relation for handling a laser beam interaction with materials. Factors considered in the simulations include buoyancy force, Marangoni force and recoil pressure; furthermore, pore generation is simulated by means of an adiabatic bubble model, which can also lead to the phenomenon of a keyhole collapse. Models of the shear stress on the keyhole surface and of the heat transfer to the molten pool via a plasma plume are introduced in simulations of the weld pool dynamics. Analysis of the temperature profile characteristics of the weld bead and molten pool flow in the molten pool is based on the results of the numerical simulations. The simulation results are used to estimate the weld fusion zone shape; and the results of the simulated fusion zone formation are compared with the results of the experimental fusion zone formation and found to be in good agreement. The effects of laser beam profile (Gaussian vs. measured), vapor shear stress, vapor heat source and sulfur content on the molten pool behavior and fusion zone shape are analyzed.

Optical reflectance anisotropy of the growth of Fe monolayers on W(110)

We report measurements of the optical anisotropy of Fe layers grown on the W(110) surfaceusing reflection anisotropy spectroscopy (RAS). As the first monolayer of Fe is depositedonto W(110), the resonance-like RAS profile of the clean surface is reduced in intensity. Wefind evidence for the surface state on W(110) surviving as an interface state following Fedeposition. We observe an anisotropic optical response from Fe layers grown on top of thefirst two monolayers, where a broad peak at 3 eV dominates the RAS response. Theresults are simulated in terms of a layered Fresnel reflection model incorporatingeither a strained Fe overlayer or an Fe overlayer whose dielectric properties areapproximated by a simple Lorentzian oscillator. Both approaches are found toproduce simulated RA spectra that are in good agreement with experiment. Theformer approach provides evidence that RAS can detect anisotropy in strainedoverlayers and that 7 ML films have bulk-like electronic and optical properties.

Spectral properties of plasmonic resonator antennas

A theoretical study of the optical properties of metallic nano-strip antennas is presented. Such strips exhibit retardation-based resonances resulting from the constructive interference of counter propagating short-range surface plasmon-polaritons (SR-SPPs) that reflect from the antenna terminations. A Fabry-P erot model was formulated that successfully predicts both the peak position and spectral shape of their optical resonances. This model requires knowledge of the SR-SPP reflection amplitude and phase pickup upon reflection from the structure terminations. These quantities were first estimated using an intuitive Fresnel reflection model and then calculated exactly using full-field simulations based on the finite-difference frequency-domain (FDFD) method. With only three dimensionless scaling parameters, the Fabry-P erot model provides simple design rules for engineering resonant properties of such plasmonic resonator antennas.

Theoretical analysis of keyhole dynamics in polarized laser drilling

A numerical analysis of three-dimensional keyhole dynamics is accomplished for the laser drilling of 2 mm thickness carbon steel. The molten and re-solidified free surface is tracked by the volume of fluid method. One of the important features, referred to as the multiple reflections of a laser beam in a keyhole, is implemented in real-time during the computation. Fresnel reflection theory is adopted to describe the energy absorption mechanism. In particular, the effect of polarization of the laser is investigated through the Fresnel reflection model. Analyses are carried out for both circularly and linearly polarized beams. The simulation results show that the keyhole under a circularly polarized laser is symmetric along the beam axis, while for the case of a linearly polarized beam the keyhole is asymmetric and is stretched along the direction of polarization.

영상 소자를 사용하지 않는 새로운 표면 플라즈몬 공명 센서

A novel surface plasmon resonance sensor, which can measure 2-dimensional array of immobilized ligands without using imaging devices such as CCD, has been proposed. Regular surface plasmon resonance can be directly used due to the insertion of additional layers with different thickness, on which each ligands are immobilized. Surface plasmon resonance signals are separated depending on the thickness of additional layers. The possibility of multi-sensing capability of the proposed surface plasmon resonance sensor has been verified by the modeling that is based on Fresnel reflection model.

Fresnel modeling of hematite crystal surfaces and application to martian hematite spherules

The gray crystalline hematite at Meridiani Planum first discovered by the Mars Global Surveyor Thermal Emission Spectrometer (MGS-TES) instrument occurs as spherules that have been interpreted as concretions. Analysis of the TES and mini-TES spectra shows that no 390 cm −1 feature is present in the characteristic martian hematite spectrum. Here, we incorporate the mid-IR optical constants of hematite into a simple Fresnel reflectance model to understand the effect of emission angle and crystal morphology on the presence or absence of the 390 cm −1 feature in an IR hematite spectrum. Based on the results we offer two models for the internal structure of the martian hematite spherules.

SK 지수를 이용한 표면 플라즈몬 공명 바이오 센서의 측정방법의 분류

SK (SPR Kinds) index, which can categorize the complicated measurement methods of surface plasmon resonance by simple method, has been proposed and verified. SK index is composed of three digits, where each digit presents the type of immobilized ligand, the type of illumination and the kinds of varying parameter, sequentially. The measurement method of (33#) series among SK indices shows the possibility of the multi-sensing capability, by which the response of 2-dimensional array of immobilized ligands can be detected simultaneously. The proposed possibility of multi-sensing capability has been verified by the modeling that is based on Fresnel reflection model.

Experimental Studies of Amorphous and Polycrystalline Ice Films Using FT-RAIRS

A systematic investigation of amorphous and crystalline vapor deposited ice layers with thickness ranging from less than 100 nm to more than 5 μm has been performed using Fourier transform (FT) reflection−absorption infrared spectroscopy (RAIRS). Al and Au surfaces were used for the vapor deposition and very similar results were obtained on both. The spectra were recorded both with polarized and nonpolarized radiation and simulated with a simple Fresnel reflection model and empirical optical indices from the literature. Optical effects peculiar to this technique like surface suppression or enhancement of vibrational modes, saturation of intense absorptions, and IR interferences, are found to distort the spectra to a greater or lesser extent over the whole thickness range investigated. The diverse spectral band shapes and intensities are globally well reproduced with the mentioned Fresnel model. Some noteworthy discrepancies are, however, observed in the most intense peaks of the polarized spectra, which are affected by larger distortions. Whenever possible, the present measurements have been compared with published spectra recorded under similar conditions and a good accordance has been found. This comparison and the spectral simulations can reconcile seeming discrepancies in the previous literature data.

Comparison of two microwave radiobrightness models and validation with field measurements

This paper compares microwave brightness temperature (T/sub B/) estimated by two radiobrightness models: a multilayer coherent radiative transfer (CRT) model and a single-layer Fresnel reflectance model. Two dielectric mixing schemes were used along with the models to calculate permittivity (real part of the dielectric constant). Model T/sub B/ and permittivity estimates were compared and validated against Huntsville, AL 1998 field experiment measurements. Model differences can be attributed to the mixing scheme, the radiobrightness model, or the vertical profile representation. Two sets of simulations were performed to quantify the sources of variation, one using observed son temperature and moisture profiles as input, and another using uniform profiles. Using uniform profiles, systematic differences in permittivity estimated by the mixing schemes resulted in T/sub B/ differences as large as 15 K. However, for uniform profiles, differences in T/sub B/ estimated by the radiobrightness models for a given permittivity value were less than 2 K. For cases using observed profiles, near-surface drying of the profiles resulted in T/sub B/ values from the CRT model 6-10 K higher than estimates from the Fresnel model, which determines T/sub B/ based on 0-5 cm mean moisture and temperature. Therefore, the major sources of T/sub B/ variations were the dielectric mixing scheme and the shape of the near-surface moisture profile. No radiobrightness/mixing scheme combination exhibited superiority across all plots and times.

Vacuum arc deposition of multilayer X-ray mirrors

A vacuum arc deposition technique for the production of multilayer structures is described. In the preliminary work described here, we used carbon as the low Z element and a heavy metal such as W or Pt as the high Z species to obtain periodic multilayers which can be used for X-ray reflectors. The plasma necessary for the deposition was produced by two vacuum arc plasma sources, each coupled to magnetic filters to prevent macroparticle transport to and contamination of the films. The multilayer structures were investigated by Auger spectroscopy and Rutherford backscattering spectrometry, and several multilayer samples were tested by measuring the specular reflectance and off-specular scattering, and by comparing these data with calculations using a Fresnel reflectance model. Analysis of X-ray results indicate that smooth, well defined layers are formed with reasonably small interface widths. With improvements in layer thickness reproducibility, it appears that vacuum arc deposition could produce useful multilayer X-ray interference mirrors.

Polarization-based material classification from specular reflection

A computationally simple yet powerful method for distinguishing metal and dielectric material surfaces from the polarization characteristics of specularly reflected light is introduced. The method is completely passive, requiring only the sensing of transmitted radiance of reflected light through a polarizing filter positioned in multiple orientations in front of a camera sensor. Precise positioning of lighting is not required. An advantage of using a polarization-based method for material classification is its immunity to color variations, which so commonly exist on uniform material samples. A simple polarization-reflectance model, called the Fresnel reflectance model, is developed. The fundamental assumptions are that the diffuse component of reflection is completely unpolarized and that the polarization state of the specular component of reflection is dictated by the Fresnel reflection coefficients. The material classification method presented results axiomatically from the Fresnel reflectance model, by estimating the polarization Fresnel ratio. No assumptions are required about the functional form of the diffuse and specular components of reflection. The method is demonstrated on some common objects consisting of metal and dielectric parts. >

Light scattering from an exploded lithium wire plasma

A thin lithium wire was extruded and exploded in vacuum and the resulting plasma was studied during the first 2 μsec of the discharge. Included in the study were scattering of a Q-switched ruby laser beam, high-speed streak photographs showing the laser-plasma interaction, and time-resolved emission spectra. The low pressure in the discharge chamber of 5×10−5 Torr prevented current shunting and also resulted in a ``clean'' lithium emission spectrum. The electron density calculated from mass conservation and temperature varied from 1017 to 1019 cm−3 as the plasma column oscillated in diameter. These densities matched those obtained from a Fresnel reflection model very well. Broadening or shifting of the scattered light was less than 1 Å and the intensities yielded electron densities from 2×1019 to 1022 cm−3 when interpreted as cooperative electron scattering. The emission spectra from 3500 to 6900 Å showed three Li I, seven Li II, one Li III, and one unidentified line. The spectroscopic temperature obtained from various line ratios averaged about 4 eV, whereas the temperature found from a simple ``snowplow'' model analysis varied from 4 to 25 eV. The electron density measured by Stark broadening of emission lines compared well with the average density obtained through mass conservation.