Intensity Of Specular Reflection Research Articles

Analysis of Gloss Unevenness and Bidirectional Reflectance Distribution Function in Specular Reflection.

Gloss is associated significantly with material appearance, and observers often focus on gloss unevenness. Gloss unevenness is the intensity distribution of reflected light observed within a highlight area, that is, the variability. However, it cannot be analyzed easily because it exists only within the highlight area and varies in appearance across the reflection angles. In recent years, gloss has been analyzed in terms of the intensity of specular reflection and its angular spread, or the bidirectional reflectance distribution function (BRDF). In this study, we develop an apparatus to measure gloss unevenness that can alter the angle with an angular resolution of 0.02°. Additionally, we analyze the gloss unevenness and BRDF in terms of specular reflection. Using a high angular resolution, we measure and analyze high-gloss materials, such as mirrors and plastics, and glossy materials, such as photo-like inkjet paper and coated paper. Our results show that the magnitude of gloss unevenness is the largest at angles marginally off the center of the specular reflection angle. We discuss an approach for physically defining gloss unevenness based on the BRDF.

RECURRENT RELATIONS IN GRAZING NONCOPLANAR X-RAY DIFFRACTION IN MULTILAYER SURFACE CRYSTAL STRUCTURES

The specular reflection of X rays from multilayer crystal structures on the surface of a single crystal under conditions of grazing noncoplanar diffraction is considered. Recurrent relations of a new type are obtained. A high sensitivity of the angular dependence of the specular reflection intensity in the diffraction region to the thickness and number of layers, their deformation, and degree of amorphization is shown.

Heat Treatment Effect on Structural and Optical Properties of Germanium Nanowires Obtained by Electrochemical Deposition

This work is dedicated to the heat treatment effect on structural and optical properties of germanium nanowires obtained by electrochemical deposition from an aqueous solution. Raman spectroscopy shows an increase in the initial crystalline fraction in the sample annealed at 600 °C compared with that annealed at 300 °C. As‐prepared sample is amorphous and crystallized under the action of probe laser radiation. Measurements carried out at wavelengths of 488 and 633 nm give close estimates of the crystalline phase, but different threshold values. The crystallization threshold upon excitation with a laser with a wavelength of 488 nm is higher. The intensity of specular reflection at the boundary of the IR and visible ranges drops, which indicates an increase in the contribution of diffuse reflection and absorption. A detailed study of diffuse reflection in the visible range shows higher absorption at 633 nm than at 488 nm, which is consistent with the obtained estimates of the crystallization threshold values.

Влияние облучения низкоэнергетическими ионами гелия на спектральный коэффициент отражения монокристаллических молибденовых зеркал

The results of a comparative study of the effect of irradiation with helium ions on the optical properties of single-crystal molybdenum mirrors with crystallographic orientations <110> and <111> are presented. The irradiation regime corresponds to the conditions in plasma cleaning systems of the entrance mirrors from contamination in optical diagnostics of ITER while helium is using as a working gas. As a result of such irradiation, a change in specular reflection and diffuse scattering of the mirror occurs, which is practically independent of the initial structure of the surface layer of the mirror and the duration of the irradiation process. Authors explain the observed changes in the optical characteristics of the mirror by the formation of nanosized bubbles in the surface skin layer. Rayleigh scattering of incident radiation on these bubles decreases the intensity of specular reflection and increases diffuse scattering. A model of the formation and growth of nanosized bubbles and their effect on optical properties is proposed. The obtained results should be taken into account when analyzing experimental data in optical diagnostics of ITER after removing contaminants using helium, when choosing a working gas for mirror cleaning, and also for the formation of a nanoporous structure in a thin surface layer of metals.

Image-based Perceptual Editing: Leather “Authenticity” as a Case Study

Traditionally, the appearance of an object in an image is edited to elicit a preferred perception. However, the editing method might be arbitrary and might not consider the human perception mechanism. In this study, the authors explored image-based leather “authenticity” editing using an estimation model that considers a perception mechanism derived in their previous work. They created leather rendered images by emphasizing or suppressing image properties corresponding to the “authenticity.” Subsequently, they performed two subjective experiments, one using fully edited images and another using partially edited images whose specular reflection intensity was constant. Participants observed the leather rendered images and evaluated the differences in the perception of “authenticity.” The authors found that the “authenticity” perception could be changed by manipulating the intensity of specular reflection and the texture (grain and surface irregularity) in the images. The results of this study could be used to tune the properties of images to make them more appealing.

An effective method to calculate RHEED rocking curves from nanoheteroepitaxial systems

An effective method to calculate RHEED rocking curves from nanoheteroepitaxial systems

The Kinetics of Growth of a Nanosized Germanium Film Deposited on the Si(001) Surface by Magnetron Sputtering

Abstract—The kinetics of growth of a nanosized germanium film deposited by magnetron sputtering on the Si(001) surface is studied using a developed experimental X-ray reflectometry technique distinguished by the joint recording of specularly reflected and diffusely scattered radiation. By using this technique, it is possible to perform in situ both the analysis of the morphology of the growing film and the control of its thickness with an accuracy to 1 nm. Dependences of the intensity of specular reflection, diffuse scattering, rate of growth, and mean square roughness and density of the film on the deposition time are obtained. According to the results of the measurement of specularly reflected radiation, the film roughness increases with time according to a power law. However, at a thickness of the film of 4 nm, a clearly defined maximum of diffuse scattering is observed, the angular position of which corresponds to the critical angle of total external reflection of germanium of 0.31°. This pattern of distribution of scattered radiation is explained by the manifestation of the Yoneda effect that consists in the anomalous X-ray scattering, the maximum of which corresponds to the critical angle θC of total external reflection from the film. It is established experimentally that, at the initial stage of growth, the film is formed by the Volmer–Weber mechanism. It is found using in situ X-ray reflectometry that the formation of a continuous layer of a germanium film occurs at its thickness of 7 nm; the subsequent growth of the film proceeds according to the power law σf ~ tβ, where β = 0.23.

Specular reflection intensity modulated by grazing-incidence diffraction in a wide angular range

Grazing-incidence X-ray diffraction (GID) is a well known technique for the characterization of crystal surfaces. A theoretical study has been performed of the sensitivity of GID to the structure of a crystal surface and distorted nanometre-thin surface layers. To simulate GID from crystals that have a complex subsurface structure, a matrix formalism of the dynamical diffraction theory has been applied. It has been found that the azimuthal rocking curves of a crystal that has a distorted subsurface, measured over a wide angular range, show asymmetric thickness oscillations with two distinguishable sets of frequencies: one corresponding to the diffraction in the single-crystal subsurface layer and the second corresponding to the diffraction in the single-crystal substrate. Therefore, azimuthal rocking curves allow characterization of the subsurface structure of a single crystal. Furthermore, thickness oscillations induced by evanescent diffraction modulate the specular reflection intensity, showing high-intensity modulations. This will potentially allow implementation of subsurface crystal characterization using, for instance, a laboratory-scale X-ray diffractometer.

Efficacy of toothpastes in the prevention of erosive tooth wear in permanent and deciduous teeth

To evaluate the erosive preventive effect of toothpastes in permanent (PT) and deciduous teeth (dt). Enamel samples were divided into five groups (n= 20): G1: placebo toothpaste; G2: NaF toothpaste; G3: AmF-NaF-SnCl2 anti-erosion toothpaste; G4: SnF2-toothpaste; and G5: NaF anti-erosion toothpaste for children. The samples were exposed to five erosion-abrasion cycles (artificial saliva incubation; 3min in 1% citric acid; 2min in slurry, toothbrush abrasion, 50 strokes, 200g). Surface microhardness (SMH), surface specular reflection intensity (SRI), and cumulative surface loss (CSL) were measured. Comparisons among toothpastes were evaluated using Kruskal-Wallis tests and comparisons between PT and dt were evaluated using Wilcoxon's rank sum test. G1 exhibited significantly lower SMH values in PT than the other toothpastes (p< 0.05), with no significant differences among the others groups. In dt, G1 and G4 exhibited significantly different values than the other groups (p< 0.05). G4 exhibited lower values of SRI in both types of teeth. Deciduous teeth presented significantly higher SRI than PT (p< 0.05), except for G3. Deciduous teeth generally presented higher CSL than PT, except for G3. Deciduous teeth were more prone to mineral loss than permanent teeth. G5 exhibited better efficacy for both teeth, while G3 exhibited a better preventive effect only for deciduous teeth. Erosive tooth wear prevalence in children is growing and deciduous teeth are more susceptible than permanent teeth. Considering this, it is important to know the preventive effect of different toothpastes in an initial erosion-abrasion model.

Analysis of the oscillation intensity of RHEED specular reflection during the MBE growth of CaF2/Si/CaF2 structures

The results of analysis of the oscillation intensity of RHEED specular reflection during the MBE growth of CaF2/Si(111) structures in a wide temperature range from 100 to 600°С are presented. It is shown that the preliminary formation of a 2D Si buffer layer provides the two-dimensional growth of CaF2 layers. Possible reasons which for the disruption of 2D growth at high substrate temperatures are discussed.

Optical pen-size reflectometer for monitoring of early dental erosion in native and polished enamels

Application of the specular reflection intensity was previously reported for the quantification of early dental erosion. Further development of the technique and assembly of the miniaturized pen-size instrument are described. The optical system was adjusted to fit into a handy device which could potentially access different positions in the oral cavity. The assembled instrument could successfully detect early erosion progression in both polished (n=70) and native (n=20) human enamels. Different severities of enamel erosion were induced by varying incubation time of polished enamel in 1% citric acid (pH=3.60, 0.5 to 10 min), while the native incisors were treated in the commercial orange juice (Tropicana Pure Premium®, pH=3.85, 10 to 60 min). The instrument provided a good differentiation between various severities of the erosion in vitro. The size of the measurement spot affected the erosion monitoring in native enamel (human incisors). The erosion measurement in the 0.7-mm (diameter) cervical spots showed systematically lower reflection intensities compared with the analysis of central and incisal small spots. The application of larger spot areas (2.3 mm) for the erosion monitoring revealed no effect (p>0.05) of the spot position on the reflection signal. High variation of the teeth susceptibility toward in vitro erosion was detected in native enamel.

Statistical Properties of Horizontally Oriented Plates in Optically Thick Clouds From Satellite Observations

Specular reflection from horizontally oriented plates (HOPs) has significant effects on lidar backscatter. The intensity of specular reflection from HOPs is high in warm mixed-phase clouds and low in cold ice clouds. The theoretical simulations of lidar backscatter and depolarization ratio are consistent with spaceborne measurements for optically thick mixed-phase and ice clouds if an equivalent percentage of HOPs of 0.08%-0.3% is assumed. Based on the joint probability density function of the attenuated backscatter and depolarization ratio observed by the Cloud-Aerosol Lidar with Orthogonal Polarization aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations platform, it is estimated that HOPs exist in approximately 60% of optically thick (τ > 3) ice and mixed-phase cloud layers. The cloud-layer temperature is the primary factor affecting the distribution of HOPs. Specifically, HOPs exist in approximately 88% of optically thick ice and mixed-phase cloud layers warmer than -30°C, in approximately 84% of ice and mixed-phase cloud layers between -30°C and -45°C, and in approximately 29% of cold ice cloud layers below -45°C.

A new optical detection method to assess the erosion inhibition by in vitro salivary pellicle layer

ObjectivesApplication of the recently developed optical method based on the monitoring of the specular reflection intensity to study the protective potential of the salivary pellicle layer against early enamel erosion. MethodsThe erosion progression was compared between two treatment groups: enamel samples coated by the 15h-in vitro-formed salivary pellicle layer (group P, n=90) and the non-coated enamel surfaces (control group C, n=90). Different severity of the erosive impact was modelled by the enamel incubation in 1% citric acid (pH=3.6) for 2, 4, 8, 10 or 15min. Erosion quantification was performed by the optical method as well as by the microhardness and calcium release analyses. ResultsOptical assessment of the erosion progression showed erosion inhibition by the in vitro salivary pellicle in short term acidic treatments (≤4min) which was also confirmed by microhardness measurements proving significantly less (p<0.05) enamel softening in the group P at 2 and 4min of erosion compared to the group C. SEM images demonstrated less etched enamel interfaces in the group P at short erosion durations as well. ConclusionsMonitoring of the specular reflection intensity can be successfully applied to quantify early erosion progression in comparative studies. In vitro salivary pellicle (2h) provides erosion inhibition but only in short term acidic exposures. Clinical significanceThe proposed optical technique is a promising tool for the fast and non-invasive erosion quantification in clinical studies.

Effects of enamel abrasion, salivary pellicle, and measurement angle on the optical assessment of dental erosion

The present study assessed the effects of abrasion, salivary proteins, and measurement angle on the quantification of early dental erosion by the analysis of reflection intensities from enamel. Enamel from 184 caries-free human molars was used for in vitro erosion in citric acid (pH 3.6). Abrasion of the eroded enamel resulted in a 6% to 14% increase in the specular reflection intensity compared to only eroded enamel, and the reflection increase depended on the erosion degree. Nevertheless, monitoring of early erosion by reflection analysis was possible even in the abraded eroded teeth. The presence of the salivary pellicle induced up to 22% higher reflection intensities due to the smoothing of the eroded enamel by the adhered proteins. However, this measurement artifact could be significantly minimized (p<0.05) by removing the pellicle layer with 3% NaOCl solution. Change of the measurement angles from 45 to 60 deg did not improve the sensitivity of the analysis at late erosion stages. The applicability of the method for monitoring the remineralization of eroded enamel remained unclear in a demineralization/remineralization cycling model of early dental erosion in vitro.

Influence of Steps on the Tilting and Adsorption Dynamics of Ordered Pentacene Films on Vicinal Ag(111) Surfaces

Here we present a structural study of pentacene (Pn) thin films on vicinal Ag(111) surfaces by He atom diffraction measurements and density functional theory (DFT) calculations supplemented with van der Waals (vdW) interactions. Our He atom diffraction results suggest initial adsorption at the step edges evidenced by initial slow specular reflection intensity decay rate as a function of Pn deposition time. In parallel with the experimental findings, our DFT+vdW calculations predict the step edges as the most stable adsorption site on the surface. An isolated molecule adsorbs as tilted on the step edge with a binding energy of 1.4 eV. In addition, a complete monolayer (ML) with pentacenes flat on the terraces and tilted only at the step edges is found to be more stable than one with all lying flat or tilted molecules, which in turn influences multilayers. Hence our results suggest that step edges can trap Pn molecules and act as nucleation sites for the growth of ordered thin films with a crystal structure similar to that of bulk Pn.

Surface roughness measurement of flat and curved machined metal parts using a near infrared super-continuum laser

We describe a system for performing high-accuracy, noncontact rms roughness measurements of flat and curved machined parts in the industrially relevant range of ∼0.05 to 0.35 μm. The system uses a near infrared (NIR) super-continuum laser to measure the intensity of specular reflection versus wavelength, at relatively long (∼1 m) stand-off distances and has the potential to be used in high speed, in-line manufacturing applications. The surface roughness value is extracted from the slope of the normalized specular intensity using the Beckmann-Kirchhoff (BK) model. According to the BK model, the normalized specular intensity in the NIR mostly depends on the surface roughness parameter alone and is independent of the absolute reflectance due to the normalization process. We discuss the benefits of performing the reflectance measurements in the NIR versus the commonly used visible spectrum. These include measurements at lower angles of incidence and the lack of need for a reference of the same metal composition. The roughness measurements performed by this system are in very good agreement with comparative data from a stylus profilometer and a white light interferometer. A potential industrial application is also demonstrated where the system is used to detect polishing defects in automotive engine crankshaft journals.

Simultaneous detection of surface coverage and structure of krypton films on gold by helium atom diffraction and quartz crystal microbalance techniques

We describe a quartz crystal microbalance setup that can be operated at low temperatures in ultra high vacuum with gold electrode surfaces acting as substrate surface for helium diffraction measurements. By simultaneous measurement of helium specular reflection intensity from the electrode surface and resonance frequency shift of the crystal during film adsorption, helium diffraction data can be correlated to film thickness. In addition, effects of interfacial viscosity on the helium diffraction pattern could be observed. To this end, first, flat gold films on AT cut quartz crystals were prepared which yield high enough helium specular reflection intensity. Then the crystals were mounted in the helium diffractometer sample holder and driven by means of a frequency modulation driving setup. Different crystal geometries were tested to obtain the best quality factor and preliminary measurements were performed on Kr films on gold surfaces. While the crystal structure and coverage of krypton films as a function of substrate temperature could successfully be determined, no depinning effects could be observed.

Application of the specular and diffuse reflection analysis for in vitro diagnostics of dental erosion: correlation with enamel softening, roughness, and calcium release.

We present assembly and application of an optical reflectometer for the analysis of dental erosion. The erosive procedure involved acid-induced softening and initial substance loss phases, which are considered to be difficult for visual diagnosis in a clinic. Change of the specular reflection signal showed the highest sensitivity for the detection of the early softening phase of erosion among tested methods. The exponential decrease of the specular reflection intensity with erosive duration was compared to the increase of enamel roughness. Surface roughness was measured by optical analysis, and the observed tendency was correlated with scanning electron microscopy images of eroded enamel. A high correlation between specular reflection intensity and measurement of enamel softening (r(2) ≥ -0.86) as well as calcium release (r(2) ≥ -0.86) was found during erosion progression. Measurement of diffuse reflection revealed higher tooth-to-tooth deviation in contrast to the analysis of specular reflection intensity and lower correlation with other applied methods (r(2) = 0.42-0.48). The proposed optical method allows simple and fast surface analysis and could be used for further optimization and construction of the first noncontact and cost-effective diagnostic tool for early erosion assessment in vivo.

Detecting quasi-periodic {11n} (n = 7–11) faces in samples with Ge/Si quantum dots by grazing X-ray reflectometry

High-resolution grazing X-ray reflectometry is used to obtain experimental and theoretical data on the intensity of specular and diffuse reflection from self-organized structures grown by molecular beam epitaxy with single-layer (non-overgrown) and multilayer (overgrown) Ge/Si quantum dots (QDs). Using the positions of diffuse scattering peaks in the direct space, the slopes of quasi-periodic faces have been determined to within ±0.1° by a method employed previously for the investigation of In(Ga)As/GaAs quantum dots. Finding the quasi-periodic {11n} (n = 7−11) faces (typical of the growth of ordered QDs) in the samples with disordered Ge/Si quantum dots is evidence of the generality of mechanisms of QD formation in different systems.

X-ray specular reflection under conditions of extremely asymmetric noncoplanar diffraction from a bicrystal

The angular dependence of the intensities of X-ray specular reflection has been rigorously analyzed under conditions of noncoplanar grazing Bragg diffraction in a crystal coated with a crystalline film (bicrystal). It is shown that the anomalous angular dependence of the specular-reflection intensity is extremely sensitive to the thickness (from fractions of a nanometer up to several nanometers), deformation, and the amorphization degree of the crystalline films. The optimum conditions for recording intensities are attained at grazing angles equal to 1.5–4.0 of the critical angle of the total external reflection.