Light Reflection Technique Research Articles

Phase-shifting determination and pattern recognition using a modified Sagnac interferometer with multiple reflections.

This work has implemented a diverse modification of the Sagnac interferometer to accommodate various measurement requirements, including phase shifting, pattern recognition, and a morphological analysis. These modifications were introduced to validate the adaptability and versatility of the system. To enable phase shifting using the multiple light reflection technique, a half-wave plate (HWP) was utilized with rotations at 0, π/8, π/4, and 3π/8radians, generating four interference patterns. It is possible to observe a distinct circular fringe width as the polarized light experiences diffraction at the interferometer's output as it travels through a circular aperture with various diameters ranging from 0.4 to 1mm. Further modifications were made to the setup by inserting a pure glass and a fluoride-doped tin oxide (FTO) transparent substrate into the common path. This modification aimed to detect and analyze a horizontal fringe pattern. Subsequently, the FTO substrate was replaced with a bee leg to facilitate morphology recognition. A deep learning-based image processing technique was employed to analyze the bee leg morphology. The experimental results showed that the proposed scheme succeeded in achieving the phase shift, measuring hole diameters with errors smaller than 1.6%, separating distinct transparent crystals, and acquiring the morphological view of a bee's leg. The method also has successfully achieved an accurate surface area and background segmentation with an accuracy over 87%. Overall, the outcomes demonstrated the potential of proposed interferometers for various applications, and the advantages of the optical sensors were highlighted, particularly in microscopic applications.

Clay-shielded estuarine gastropods are better protected against environmental acidification than unshielded individuals

The effects of progressive global acidification on the shells of marine organisms is a topic of much current interest. Most studies on molluscan shell resistance to dissolution consider the carbonate mineral component, with less known about the protective role of the outer organic periostracum. Outer-shell resistance would seem especially important to gastropods living in carbonate-undersaturated and calcium-deficient estuarine waters that threaten shell dissolution and constrain CaCO3 production. We tested this prediction using gastropods from an acidified estuarine population (Neripteron violaceum) that form a clay shield outside the periostracum. Specifically, we aimed to show that the carbonate shell component lacks integrity, that the formation of the clay shield is directed by the organism, and that the clay shield functions to protect against shell dissolution. We found no evidence for any specific carbonate dissolution resistance strategy in the thin, predominantly aragonitic shells of these gastropods. Shield formation was directed by an ornamented periostracum which strongly bonded illite elements (e.g., Fe, Al and S), that become available through suspension in the water column. In unshielded individuals, CaCO3 erosion was initiated randomly across the shell (not age-related) and progressed rapidly when the periostracum was breached. A light reflectance technique showed qualitatively that shield consolidation is negatively-related to shell erosion. These findings support a conceptual framework for gastropod outer-shell responses to acidification that considers both environmental and evolutionary constraints on shell construction. We describe a novel strategy for shell protection against dissolution, highlighting the diversity of mechanisms available to gastropods facing extreme coastal acidification.

Characterizing optical phase-change materials with spectroscopic ellipsometry and polarimetry

This paper discusses the fundamentals, applications, potential and limitations of polarized light reflection techniques for the characterization of phase-change materials (PCMs). These techniques include spectroscopic ellipsometry, time-resolved ellipsometry and imaging ellipsometry as well as polarimetry. We explore the capabilities of spectroscopic ellipsometry in the determination of the extinction coefficient of PCMs and the capabilities of imaging ellipsometry to characterize PCMs. We show that ellipsometry is capable of more than the determination of thickness and optical properties, and it can be exploited to gain information about crystallization/amorphization kinetics and mapping anisotropies.

Utilization of CD and DVD Pick-Up Heads for Scratch Inspection of Magnetic Disk in Dynamic State Using Microcontroller

A non-destructive technique to inspect a scratch on all magnetic disks in the beginning process of hard disk drive (HDD) manufacturing by using CD and DVD pick-up heads as the detector is proposed. It requires a 100% disk inspection of micrometer-sized scratches in a quick measurement with low cost inventing. Most of the previous studies were in static state but this is the first time to be done in dynamic study using the microcontroller in order to promptly serve for industrial utilization. The size, position, and shape characteristic of scratches are examined using light reflection technique. The results show that, when the laser beam is targeted on a magnetic disk in a position, either scratch or non-scratch, the reflected light intensity differs. The DVD pick-up head can detect the width and the surface characteristic of the scratches, which is similar to the results from scanning electron microscope (SEM) for all scratches sizes less than 100 µm. It is also found that using a DVD pick-up head provides a better resolution of shape characteristic and roughness of scratches surface than a CD pick-up head. Hence, the scratch size of 10s µm scale on the magnetic disk can be accurately characterized by this proposed technique, which can be further utilized for magnetic disk inspection in the hard disk drive manufacturing process.

Source apportionment revisited for long-term measurements of fine aerosol trace elements at two locations in southern Norway

Abstract Five-year-long (1991–1996) aerosol trace element data sets for the fine (PM2) size fraction from the sites of Birkenes and Skreadalen in southern Norway were reanalysed by US EPA positive matrix factorization PMF5 in order to assess the sources and their contribution to the PM2 aerosol. The data sets contained the concentrations of the particulate mass (PM), black carbon (BC) and 21 elements in over 700 samples for each of the two sites. The PM was obtained from weighing with a microbalance and BC was determined with a light reflectance technique. The data for the elements were obtained by a combination of particle-induced X-ray emission and instrumental neutron activation analysis. Eight source factors were retained for each site, i.e., (i) secondary sulfate, which accounted for around 40% of the average measured PM2 mass, (ii) wood burning, with BC, K, Zn and As, which accounted for about 17%, (iii) an iodine factor (with also Br and Se), which is probably related to a marine biogenic source and was responsible for about 6.5%, (iv) aged sea salt with Na, Mg, Cl and Ca, but heavily depleted in Cl; (v) a crustal factor containing Al, Si, Ca, Ti and Fe; (vi) a heavy oil burning factor with V and Ni in a ratio of 3–4; (vii) a general pollution factor (with Cu, Zn, As, Se, Sb and Pb), and (viii) an almost pure manganese factor, which is attributed to Mn and FeMn industries in southern Norway. The results were substantially different from those of an earlier PMF analysis, in which use was made of PMF2.

Noninvasive light-reflection technique for measuring optical properties of human teeth

Noninvasive light-reflection technique for measuring optical properties of human teeth

Effect of silica nanoparticles to prevent calcium carbonate scaling using an in situ turbidimetre

Scale minerals in the oil and gas industries are a major concern to reservoir and operations engineering. The main types of oilfield scales found are carbonate and sulfate scales. Calcium carbonate (CaCO3) is a major component of fouling in heat transfer surfaces across different sectors of industry, resulting in additional capital, maintenance and operating costs. Various techniques, including the use of chemical inhibitors, have been used to prevent the formation of scale. In the last decade, there have been considerable advances in the development of chemicals, effective in small concentrations for the control of scale deposits.The purpose of this study was to investigate the possibilities of utilizing nanoparticles as sacrificial surface for enhancement and control of the nucleation and crystallization of CaCO3, as a method for fouling mitigation. Here, the turbidity profile of the solution, using a light reflection technique, is used to monitor the process. The outcomes of this study will improve revenues by preventing the unscheduled shutdown of facilities and avoidance of using an excess of scale inhibitors. Silica nanoparticles of different size and surface functional groups were added to the solution. The results showed a reduction in the induction period, consequently indicating improved control over crystallization. Modified silica nanotemplates exhibited the highest reduction in induction time at room temperature. This resulted in preventing scale formation on the wall of the crystallizer. This conclusion is very significant, and further studies are proposed, which will attempt to understand the mechanisms of reactions between the nanoparticles and scaling ions.

Ten-year study of fine aerosol at Sde Boker, Israel, using PIXE: Time trends, seasonal variation, correlations, and source areas for anthropogenic elements

From January 1995 through December 2004 aerosol samples were collected at Sde Boker, Israel, with a Gent stacked filter unit sampler. The collections were done according to a 2–2–3day schedule, which resulted in about 150 samples per year. The samples were analysed for the particulate mass (PM) by weighing, for black carbon (BC) by a light reflectance technique, and for up to 46 elements by a combination of PIXE and instrumental neutron activation analysis. Here, we report on the fine (PM2) size fraction data for the PM, BC, and the following nine anthropogenic elements S, V, Ni, Cu, Zn, As, Se, Sb, and Pb, and discuss their time trends, seasonal variation, correlations, and source areas. The largest changes in the annual medians over the 10-year period were found for S, Ni, Se, Sb, and Pb, i.e., of −34%, −25%, −47%, +26%, and −40%, respectively. The seasonal variation was largest for S, with 1.6times higher concentrations in summer than in the other three seasons. Vanadium and Ni were very highly correlated with each other (r=0.95), pointing to a dominant common source, which is undoubtedly oil burning. Trajectory statistics, using 10-day back trajectories with arrival at 300m above ground, were applied to assess the source areas. Sulphur originated mostly from south-eastern Europe (i.e., Turkey, Bulgaria, Romania, Ukraine, and southern Russia) and As from the south-eastern part of European Russia, whilst the source picture for Zn was rather unclear. The other six anthropogenic elements and BC seemed to originate mainly from regional sources.

A direct optical method for the study of grain boundary melting

The structure and evolution of grain boundaries underlies the nature of polycrystalline materials. Here we describe an experimental apparatus and light reflection technique for measuring disorder at grain boundaries in optically clear material, in thermodynamic equilibrium. The approach is demonstrated on ice bicrystals. Crystallographic orientation is measured for each ice sample. The type and concentration of impurity in the liquid can be controlled and the temperature can be continuously recorded and controlled over a range near the melting point. The general methodology is appropriate for a wide variety of materials.

Spectroscopic ellipsometry and polarimetry for materials and systems analysis at the nanometer scale: state-of-the-art, potential, and perspectives

This paper discusses the fundamentals, applications, potential, limitations, and future perspectives of polarized light reflection techniques for the characterization of materials and related systems and devices at the nanoscale. These techniques include spectroscopic ellipsometry, polarimetry, and reflectance anisotropy. We give an overview of the various ellipsometry strategies for the measurement and analysis of nanometric films, metal nanoparticles and nanowires, semiconductor nanocrystals, and submicron periodic structures. We show that ellipsometry is capable of more than the determination of thickness and optical properties, and it can be exploited to gain information about process control, geometry factors, anisotropy, defects, and quantum confinement effects of nanostructures.

Comparison of light transmission and reflection techniques to determine concentrations in flow tank experiments

Transmissive and reflective intensity measurements for visual concentration determinations in 2D flow tank experiments were compared and evaluated for their applicability in the study of flow and transport phenomena. A density-dependent heterogeneous flow experiment was conducted and transmission and reflection images of the dyed saltwater plume were analyzed. A single light source and dark curtains forced the light to pass through the porous media only, thus facilitating the transmission measurements. The reflection images delivered a more homogeneous spatial illumination than the transmission images. Major perturbations of the transmission images were lens flare effects and light dispersion within the bead–water–Plexiglas system which smear the front of the plume. Based on the conducted evaluation of transmissive and reflective intensity measurements, the reflection data delivered more reliable intensity values to derive solute concentrations in intermediate scale flow tank experiments.

Determining mechanical properties of rabbit skin with light reflection technique verified with latex

An experimental technique to evaluate the elastic limit for rabbit skin is developed and described. The experimental technique is designed to measure small changes in the normalized reflectivity as a function of applied stretch, with a laser wavelength of 632.8 nm and power of 1 mW. When the samples of rabbit skin are stretched, the reflectivity increases until a critical point (elastic limit) is reached. After this point, the curve drops off very quickly. The elastic limit for the male dorsal samples is less than that for the female samples, with an average strain of 14.4 and 34.6% in males and females, respectively. Moreover, our results show that the average slope of the regression lines is greater for the male dorsal samples than the dorsal female samples. This indicates that the male dorsal skin is rougher than that of the female.

Sources of optically active aerosol particles over the Amazon forest

Abstract Size-fractionated ambient aerosol samples were collected at a pasture site and a primary rainforest site in the Brazilian Amazon Basin during two field campaigns (April–May and September–October 1999), as part of the European contribution to the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA-EUSTACH). The samples were analyzed for up to 19 trace elements by particle-induced X-ray emission analysis (PIXE), for equivalent black carbon (BC e ) by a light reflectance technique and for mass concentration by gravimetric analysis. Additionally, we made continuous measurements of absorption and light scattering by aerosol particles. The vertical chemical composition gradients at the forest site have been discussed in a companion article (Journal of Geophysical Research-Atmospheres 108 (D18), 4591 (doi:4510.1029/2003JD003465)). In this article, we present the results of a source identification and quantitative apportionment study of the wet and dry season aerosols, including an apportionment of the measured scattering and absorption properties of the total aerosol in terms of the identified aerosol sources. Source apportionments (obtained from absolute principal component analysis) revealed that the wet and dry season aerosols contained the same three main components, but in different (absolute and relative) amounts: the wet season aerosol consisted mainly of a natural biogenic component, whereas pyrogenic aerosols dominated the dry season aerosol mass. The third component identified was soil dust, which was often internally mixed with the biomass-burning aerosol. All three components contributed significantly to light extinction during both seasons. At the pasture site, up to 47% of the light absorption was attributed to biogenic particles during the wet season, and up to 35% at the tower site during the wet-to-dry transition period. The results from the present study suggest that, in addition to pyrogenic particles, biogenic and soil dust aerosols must be taken into account when modeling the physical and optical properties of aerosols in forested regions such the Amazon Basin.

New Pockels field sensor with ferroelectric liquid-crystal phase modulator

A new optical field sensor for measuring the electric field close to an electrical discharge has been developed. The new system that uses both P- and S-polarized light-division and azimuth angle modulation methods has been devised and investigated. By using a ferroelectric liquid-crystal phase modulator instead of an azimuth angle modulator, it has been possible to eliminate noise from the optical field measurement system, specifically, the birefringence effects in a long optical fiber cable. The optical cable is used for connecting a Pockels field sensor located close to the discharge with the main system located at the ground. Furthermore, it has been possible to compensate for the sensitivity difference between two optical detectors for converting P- and S-polarized light waves to an electrical signal. From this, it is found that by using a light reflection technique, the measurable minimum field strength is reduced from 100 kV/m to 1.0 kV/m in the discharge region. If the smallest phase change in the system is set to be less than 10−3 [rad], the measurable minimum field strength is reduced to 0.1 kV/m. The possible use of the probe is also considered for checking for damage caused by cosmic rays to the insulating skin of a spacecraft.

Characteristic features of the pseudogap and superconducting states of YBa2Cu3O7−x

The relaxation dynamics of the lattice and low-energy quasiparticles in a YBa2Cu3O7−x superconductor are studied by the light reflection technique with femtosecond temporal resolution in a wide temperature range. It is shown that, for T>T c, there exist two temperature regions with qualitatively and quantitatively different excitation dynamics, and the transition between these regions is of a hysteretic nature. It is also found that the character of changes observed in the charge carrier relaxation dynamics in the superconducting state testifies to the presence of an anisotropic gap with nodes at the Fermi surface.

Comprehensive characterisation of atmospheric aerosols in Budapest, Hungary: physicochemical properties of inorganic species

As part of an air pollution project in Budapest, aerosol samples were collected by stacked filter units and cascade impactors at an urban background site, two downtown sites, and within a road tunnel in field campaigns conducted in 1996, 1998 and 1999. Some criteria pollutants were also measured at one of the downtown sites. The aerosol samples were analysed by one or more of the following methods: instrumental neutron activation analysis, particle-induced X-ray emission analysis, a light reflection technique, gravimetry, thermal profiling carbon analysis and capillary electrophoresis. The quantities measured or derived include atmospheric concentrations of elements (from Na to U), of particulate matter, of black and elemental carbon, and total carbonaceous fraction, of some ionic species (e.g., nitrate and sulphate) in the fine ( <2 μm equivalent aerodynamic diameter, EAD) or in both coarse (10– 2 μm EAD) and fine size fractions, atmospheric concentrations of NO, NO 2, SO 2, CO and total suspended particulate matter, and meteorological parameters. The analytical results were used for characterisation of the concentration levels, elemental composition, time trends, enrichment of and relationships among the aerosol species in coarse and fine size fractions, for studying their fine-to-coarse concentration ratios, spatial and temporal variability, for determining detailed elemental mass size distributions, and for examining the extent of chemical mass closure.

Amplitude measurements of Faraday waves.

A light reflection technique is used to measure quantitatively the surface elevation of Faraday waves. The performed measurements cover a wide parameter range of driving frequencies and sample viscosities. In the capillary wave regime the bifurcation diagrams exhibit a frequency independent scaling proportional to the wavelength. We also provide numerical simulations of the full Navier-Stokes equations, which are in quantitative agreement up to supercritical drive amplitudes of epsilon approximately equal 20%. The validity of an existing perturbation analysis is found to be limited to epsilon<2.5%.

Coherent phonons and their properties

The optical phonons in semimetals, semiconductors, and superconductors were studied by the light reflection techniques with femtosecond time resolution and by the method of spontaneous Raman scattering. During measurements in the time domain, the phonon system is converted into a coherent state by the first ultrashort laser pulse and then probed at a variable delay by the second pulse. In this case, the phonons are shown to occur in a nonclassical state in which their fluctuational properties, different in various quadratures, are described by periodic functions of time. A comparison of the results obtained in the time and frequency domains gives evidence that the energies of thermal and coherent phonons coincide, while their dephasing and energy relaxation times are different.

Impact of phase out of leaded gasoline on the air quality in Budapest

As part of an air pollution study in Budapest, size-fractionated aerosol samples were collected by stacked filter units and cascade impactors, and some criteria pollutants and meteorological parameters were recorded in 1996, 1998 and 1999. The samplings were performed at three urban locations including an urban background site, a downtown site, and a tunnel. Elemental composition of the aerosol samples was measured by instrumental neutron activation analysis and/or particle-induced X-ray emission spectrometry; and black carbon (BC) was determined by a light reflectance technique. Since leaded gasoline was completely phased out in Hungary on 1 April 1999, the atmospheric concentrations of some typical transportation-related air pollutants (i.e. Pb, Br, BC and CO) were used for overviewing the actual impact of the phase out on the air quality and on the aerosol characteristics. For the background site, mean concentration of Pb and Br was not changed significantly. In the downtown site, the phase out resulted in a concentration decrease by a factor of 3–4 for Pb and Br. For the tunnel, concentrations of Pb and Br were decreased by a factor up to 9 and 28, respectively. Correlation between the pollutants, their crustal enrichment factors, and average elemental mass size distributions are also presented and discussed.

Noninvasive light-reflection technique for measuring soft-tissue stretch

A novel, to our knowledge, sensor for measuring the stretch in soft tissues such as skin is described. The technique, which is a modification of two-dimensional polarization imaging, uses changes in the reflectivity of polarized light as a monitor of skin stretch. Measurements show that the reflectivity increases with stretch. Measurements were made on guinea pig skin and on nonbiological materials. The changes in reflectivity result from the changes that take place in the interface roughness between skin or material layers and the consequential changes in the diffuse reflective characteristics of the skin. Conceptually, as the roughness of an interface decreases, a smoother reflecting interface is produced, resulting in a commensurate increase in specular reflection. A simple roughness model correctly predicts the main experimental results. Results can be extended easily to real-time stretch analysis of large tissue areas that would be applicable for predicting stresses in skin during and after the surgical closure of wounds.