Physically-Based Models for the Reflection, Transmission and Subsurface Scattering of Light by Smooth and Rough Surfaces, with Applications to Realistic Image Synthesis

NASA Astrophysics Data System (ADS)

He, Xiao Dong

This thesis studies light scattering processes off rough surfaces. Analytic models for reflection, transmission and subsurface scattering of light are developed. The results are applicable to realistic image generation in computer graphics. The investigation focuses on the basic issue of how light is scattered locally by general surfaces which are neither diffuse nor specular; Physical optics is employed to account for diffraction and interference which play a crucial role in the scattering of light for most surfaces. The thesis presents: (1) A new reflectance model; (2) A new transmittance model; (3) A new subsurface scattering model. All of these models are physically-based, depend on only physical parameters, apply to a wide range of materials and surface finishes and more importantly, provide a smooth transition from diffuse-like to specular reflection as the wavelength and incidence angle are increased or the surface roughness is decreased. The reflectance and transmittance models are based on the Kirchhoff Theory and the subsurface scattering model is based on Energy Transport Theory. They are valid only for surfaces with shallow slopes. The thesis shows that predicted reflectance distributions given by the reflectance model compare favorably with experiment. The thesis also investigates and implements fast ways of computing the reflectance and transmittance models. Furthermore, the thesis demonstrates that a high level of realistic image generation can be achieved due to the physically -correct treatment of the scattering processes by the reflectance model.

Light Reflector

NASA Astrophysics Data System (ADS)

1988-01-01

Ultra Sales, Inc.'s fluorescent lighting fixture gets a boost in reflectivity through installation of Lightdriver, a thin tough thermoplastic film plated with aluminum, capable of reflecting 95 percent of visible light striking it. Lightdriver increases brightness without adding bulbs, and allows energy savings by removing some bulbs because the mirrorlike surface cuts light loss generally occasioned by conventional low reflectivity white painted surface above the bulbs in many fluorescent fixtures. Forty-five percent reduction in lighting electricity is attainable.

Optical inverse-square displacement sensor

DOEpatents

Howe, Robert D.; Kychakoff, George

1989-01-01

This invention comprises an optical displacement sensor that uses the inverse-square attenuation of light reflected from a diffused surface to calculate the distance from the sensor to the reflecting surface. Light emerging from an optical fiber or the like is directed onto the surface whose distance is to be measured. The intensity I of reflected light is angle dependent, but within a sufficiently small solid angle it falls off as the inverse square of the distance from the surface. At least a pair of optical detectors are mounted to detect the reflected light within the small solid angle, their ends being at different distances R and R+.DELTA.R from the surface. The distance R can then be found in terms of the ratio of the intensity measurements and the separation length as ##EQU1##

Optical device for measuring a surface characteristic of an object by multi-color interferometry

NASA Technical Reports Server (NTRS)

Meyer, William V. (Inventor); Smart, Anthony E. (Inventor)

2001-01-01

An interferometer having a light beam source that produces a plurality of separate and distinct wavelengths of light. Optic fibers are used to transport the wavelengths of light toward an object surface and to allow light reflected from the object to pass through a polarizer to improve the polarization ratio of the reflected light to determine a characteristic of the object surface.

The differential equation of an arbitrary reflecting surface

NASA Astrophysics Data System (ADS)

Melka, Richard F.; Berrettini, Vincent D.; Yousif, Hashim A.

2018-05-01

A differential equation describing the reflection of a light ray incident upon an arbitrary reflecting surface is obtained using the law of reflection. The derived equation is written in terms of a parameter and the value of this parameter determines the nature of the reflecting surface. Under various parametric constraints, the solution of the differential equation leads to the various conic surfaces but is not generally solvable. In addition, the dynamics of the light reflections from the conic surfaces are executed in the Mathematica software. Our derivation is the converse of the traditional approach and our analysis assumes a relation between the object distance and the image distance. This leads to the differential equation of the reflecting surface.

Fiber optic temperature sensor

NASA Technical Reports Server (NTRS)

Sawatari, Takeo (Inventor); Gaubis, Philip A. (Inventor)

2000-01-01

A fiber optic temperature sensor uses a light source which transmits light through an optical fiber to a sensor head at the opposite end of the optical fiber from the light source. The sensor head has a housing coupled to the end of the optical fiber. A metallic reflective surface is coupled to the housing adjacent the end of the optical fiber to form a gap having a predetermined length between the reflective surface and the optical fiber. A detection system is also coupled to the optical fiber which determines the temperature at the sensor head from an interference pattern of light which is reflected from the reflective surface.

Fiber optic temperature sensor

NASA Technical Reports Server (NTRS)

Sawatari, Takeo (Inventor); Gaubis, Philip A. (Inventor); Mattes, Brenton L. (Inventor); Charnetski, Clark J. (Inventor)

1999-01-01

A fiber optic temperature sensor uses a light source which transmits light through an optical fiber to a sensor head at the opposite end of the optical fiber from the light source. The sensor head has a housing coupled to the end of the optical fiber. A metallic reflective surface is coupled to the housing adjacent the end of the optical fiber to form a gap having a predetermined length between the reflective surface and the optical fiber. A detection system is also coupled to the optical fiber which determines the temperature at the sensor head from an interference pattern of light which is reflected from the reflective surface.

Camouflage Visualization

DTIC Science & Technology

1992-04-07

reflected light seen by the viewer does not depend on the viewer’s position. Such surfaces are dull or matte and the luminance of the diffuse reflected light...vegetation and reflect only the skylight . Generally, the reflectance of the ambient light is approximately represented as a global value, constant over all the...allowing the ambient contribution provided by skylight to vary with the orientation of the surface relative to zenith. This approximation takes into

Reflective diffraction grating

DOEpatents

Lamartine, Bruce C.

2003-06-24

Reflective diffraction grating. A focused ion beam (FIB) micromilling apparatus is used to store color images in a durable medium by milling away portions of the surface of the medium to produce a reflective diffraction grating with blazed pits. The images are retrieved by exposing the surface of the grating to polychromatic light from a particular incident bearing and observing the light reflected by the surface from specified reception bearing.

Removal of Surface-Reflected Light for the Measurement of Remote-Sensing Reflectance from an Above-Surface Platform

DTIC Science & Technology

2010-12-01

remote - sensing reflectance) can be highly inaccurate if a spectrally constant value is applied (although errors can be reduced by carefully filtering measured raw data). To remove surface-reflected light in field measurements of remote sensing reflectance, a spectral optimization approach was applied, with results compared with those from remote sensing models and from direct measurements. The agreement from different determinations suggests that reasonable results for remote sensing reflectance of clear

Removal of Surface-Reflected Light for the Measurement of Remote-Sensing Reflectance from an Above-Surface Platform

DTIC Science & Technology

2010-12-06

remote - sensing reflectance) can be highly inaccurate if a spectrally constant value is applied (although errors can be reduced by carefully filtering measured raw data). To remove surface-reflected light in field measurements of remote sensing reflectance, a spectral optimization approach was applied, with results compared with those from remote sensing models and from direct measurements. The agreement from different determinations suggests that reasonable results for remote sensing reflectance of clear

A theory of photometric stereo for a class of diffuse non-Lambertian surfaces

NASA Technical Reports Server (NTRS)

Tagare, Hemant D.; Defigueiredo, Rui J. P.

1991-01-01

A theory of photometric stereo is proposed for a large class of non-Lambertian reflectance maps. The authors review the different reflectance maps proposed in the literature for modeling reflection from real-world surfaces. From this, they obtain a mathematical class of reflectance maps to which the maps belong. They show that three lights can be sufficient for a unique inversion of the photometric stereo equation for the entire class of reflectance maps. They also obtain a constraint on the positions of light sources for obtaining this solution. They investigate the sufficiency of three light sources to estimate the surface normal and the illuminant strength. The issue of completeness of reconstruction is addressed. They shown that if k lights are sufficient for a unique inversion, 2k lights are necessary for a complete inversion.

Optical inverse-square displacement sensor

DOEpatents

Howe, R.D.; Kychakoff, G.

1989-09-12

This invention comprises an optical displacement sensor that uses the inverse-square attenuation of light reflected from a diffused surface to calculate the distance from the sensor to the reflecting surface. Light emerging from an optical fiber or the like is directed onto the surface whose distance is to be measured. The intensity I of reflected light is angle dependent, but within a sufficiently small solid angle it falls off as the inverse square of the distance from the surface. At least a pair of optical detectors are mounted to detect the reflected light within the small solid angle, their ends being at different distances R and R + [Delta]R from the surface. The distance R can then be found in terms of the ratio of the intensity measurements and the separation length as given in an equation. 10 figs.

Solar module having reflector between cells

DOEpatents

Kardauskas, Michael J.

1999-01-01

A photovoltaic module comprising an array of electrically interconnected photovoltaic cells disposed in a planar and mutually spaced relationship between a light-transparent front cover member in sheet form and a back sheet structure is provided with a novel light-reflecting means disposed between adjacent cells for reflecting light falling in the areas between cells back toward said transparent cover member for further internal reflection onto the solar cells. The light-reflecting comprises a flexible plastic film that has been embossed so as to have a plurality of small V-shaped grooves in its front surface, and a thin light-reflecting coating on said front surface, the portions of said coating along the sides of said grooves forming light-reflecting facets, said grooves being formed so that said facets will reflect light impinging thereon back into said transparent cover sheet with an angle of incidence greater than the critical angle, whereby substantially all of the reflected light will be internally reflected from said cover sheet back to said solar modules, thereby increasing the current output of the module.

Simulation of oceanic whitecaps and their reflectance characteristics in the short wavelength infrared.

PubMed

Schwenger, Frédéric; Repasi, Endre

2017-02-20

The knowledge of the spatial energy (or power) distribution of light beams reflected at the dynamic sea surface is of great practical interest in maritime environments. For the estimation of the light energy reflected into a specific spatial direction a lot of parameters need to be taken into account. Both whitecap coverage and its optical properties have a large impact upon the calculated value. In published literature, for applications considering vertical light propagation paths, such as bathymetric lidar, the reflectance of sea surface and whitecaps are approximated by constant values. For near-horizontal light propagation paths the optical properties of the sea surface and the whitecaps must be considered in greater detail. The calculated light energy reflected into a specific direction varies statistically and depends largely on the dynamics of the wavy sea surface and the dynamics of whitecaps. A 3D simulation of the dynamic sea surface populated with whitecaps is presented. The simulation considers the evolution of whitecaps depending on wind speed and fetch. The radiance calculation of the maritime scene (open sea/clear sky) populated with whitecaps is done in the short wavelength infrared spectral band. Wave hiding and shadowing, especially occurring at low viewing angles, are considered. The specular reflection of a light beam at the sea surface in the absence of whitecaps is modeled by an analytical statistical bidirectional reflectance distribution function (BRDF) of the sea surface. For whitecaps, a specific BRDF is used by taking into account their shadowing function. To ensure the credibility of the simulation, the whitecap coverage is determined from simulated image sequences for different wind speeds and compared to whitecap coverage functions from literature. The impact of whitecaps on the radiation balance for bistatic configuration of light source and receiver is calculated for a different incident (zenith/azimuth angles) of the light beam and is presented for two different wind speeds.

Method and apparatus for reading lased bar codes on shiny-finished fuel rod cladding tubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goldenfield, M.P.; Lambert, D.V.

1990-10-02

This patent describes, in a nuclear fuel rod identification system, a method of reading a bar code etched directly on a surface of a nuclear fuel rod. It comprises: defining a pair of light diffuser surfaces adjacent one another but in oppositely inclined relation to a beam of light emitted from a light reader; positioning a fuel rod, having a cylindrical surface portion with a bar code etched directly thereon, relative to the light diffuser surfaces such that the surfaces are disposed adjacent to and in oppositely inclined relation along opposite sides of the fuel rod surface portion and themore » fuel rod surface portion is aligned with the beam of light emitted from the light reader; directing the beam of light on the bar code on fuel rod cylindrical surface portion such that the light is reflected therefrom onto one of the light diffuser surfaces; and receiving and reading the reflected light from the bar code via the one of the light diffuser surfaces to the light reader.« less

Diode-pumped laser with improved pumping system

DOEpatents

Chang, Jim J.

2004-03-09

A laser wherein pump radiation from laser diodes is delivered to a pump chamber and into the lasing medium by quasi-three-dimensional compound parabolic concentrator light channels. The light channels have reflective side walls with a curved surface and reflective end walls with a curved surface. A flow tube between the lasing medium and the light channel has a roughened surface.

Interactions of light with rough dielectric surfaces - Spectral reflectance and polarimetric properties

NASA Technical Reports Server (NTRS)

Yon, S. A.; Pieters, C. M.

1988-01-01

The nature of the interactions of visible and NIR radiation with the surfaces of rock and mineral samples was investigated by measuring the reflectance and the polarization properties of scattered and reflected light for slab samples of obsidian and fine-grained basalt, prepared to controlled surface roughness. It is shown that the degree to which radiation can penetrate a surface and then scatter back out, an essential criterion for mineralogic determinations based on reflectance spectra, depends not only upon the composition of the material, but also on its physical condition such as sample grain size and surface roughness. Comparison of the experimentally measured reflectance and polarization from smooth and rough slab materials with the predicted models indicates that single Fresnel reflections are responsible for the largest part of the reflected intensity resulting from interactions with the surfaces of dielectric materials; multiple Fresnel reflections are much less important for such surfaces.

Defect mapping system

DOEpatents

Sopori, Bhushan L.

1995-01-01

Apparatus for detecting and mapping defects in the surfaces of polycrystalline materials in a manner that distinguishes dislocation pits from grain boundaries includes a laser for illuminating a wide spot on the surface of the material, a light integrating sphere with apertures for capturing light scattered by etched dislocation pits in an intermediate range away from specular reflection while allowing light scattered by etched grain boundaries in a near range from specular reflection to pass through, and optical detection devices for detecting and measuring intensities of the respective intermediate scattered light and near specular scattered light. A center blocking aperture or filter can be used to screen out specular reflected light, which would be reflected by nondefect portions of the polycrystalline material surface. An X-Y translation stage for mounting the polycrystalline material and signal processing and computer equipment accommodate rastor mapping, recording, and displaying of respective dislocation and grain boundary defect densities. A special etch procedure is included, which prepares the polycrystalline material surface to produce distinguishable intermediate and near specular light scattering in patterns that have statistical relevance to the dislocation and grain boundary defect densities.

Defect mapping system

DOEpatents

Sopori, B.L.

1995-04-11

Apparatus for detecting and mapping defects in the surfaces of polycrystalline materials in a manner that distinguishes dislocation pits from grain boundaries includes a laser for illuminating a wide spot on the surface of the material, a light integrating sphere with apertures for capturing light scattered by etched dislocation pits in an intermediate range away from specular reflection while allowing light scattered by etched grain boundaries in a near range from specular reflection to pass through, and optical detection devices for detecting and measuring intensities of the respective intermediate scattered light and near specular scattered light. A center blocking aperture or filter can be used to screen out specular reflected light, which would be reflected by nondefect portions of the polycrystalline material surface. An X-Y translation stage for mounting the polycrystalline material and signal processing and computer equipment accommodate rastor mapping, recording, and displaying of respective dislocation and grain boundary defect densities. A special etch procedure is included, which prepares the polycrystalline material surface to produce distinguishable intermediate and near specular light scattering in patterns that have statistical relevance to the dislocation and grain boundary defect densities. 20 figures.

Thin-film thickness measurement method based on the reflection interference spectrum

NASA Astrophysics Data System (ADS)

Jiang, Li Na; Feng, Gao; Shu, Zhang

2012-09-01

A method is introduced to measure the thin-film thickness, refractive index and other optical constants. When a beam of white light shines on the surface of the sample film, the reflected lights of the upper and the lower surface of the thin-film will interfere with each other and reflectivity of the film will fluctuate with light wavelength. The reflection interference spectrum is analyzed with software according to the database, while the thickness and refractive index of the thin-film is measured.

Reflection Matrix Method for Controlling Light After Reflection From a Diffuse Scattering Surface

DTIC Science & Technology

2016-12-22

reflective inverse diffusion, which was a proof-of-concept experiment that used phase modulation to shape the wavefront of a laser causing it to refocus...after reflection from a rough surface. By refocusing the light, reflective inverse diffusion has the potential to eliminate the complex radiometric model...photography. However, the initial reflective inverse diffusion experiments provided no mathematical background and were conducted under the premise that the

Analysis for Mar Vel Black and acetylene soot low reflectivity surfaces for star tracker sunshade applications

NASA Technical Reports Server (NTRS)

Yung, E.

1974-01-01

Mar Vel Black is a revolutionary new extremely low reflectivity anodized coating developed by Martin Marietta of Denver. It is of great interest in optics in general, and in star trackers specifically because it can reduce extraneous light reflections. A sample of Mar Vel Black was evaluated. Mar Vel Black looks much like a super black surface with many small peaks and very steep sides so that any light incident upon the surface will tend to reflect many times before exiting that surface. Even a high reflectivity surface would thus appear to have a very low reflectivity under such conditions. Conversely, acetylene soot does not have the magnified surface appearance of a super black surface. Its performance is, however, predictable from the surface structure, considering the known configuration of virtually pure carbon.

Disparity, motion, and color information improve gloss constancy performance.

PubMed

Wendt, Gunnar; Faul, Franz; Ekroll, Vebjørn; Mausfeld, Rainer

2010-09-01

S. Nishida and M. Shinya (1998) found that observers have only a limited ability to recover surface-reflectance properties under changes in surface shape. Our aim in the present study was to investigate how the degree of surface-reflectance constancy depends on the availability of information that may help to infer the reflectance and shape properties of surfaces. To this end, we manipulated the availability of (i) motion-induced information (static vs. dynamic presentation), (ii) disparity information (with the levels "monocular," "surface disparity," and "surface + highlight disparity"), and (iii) color information (grayscale stimuli vs. hue differences between diffuse and specular reflections). The task of the subjects was to match the perceived lightness and glossiness between two surfaces with different spatial frequency and amplitude by manipulating the diffuse component and the exponent of the Phong lighting model in one of the surfaces. Our results indicate that all three types of information improve the constancy of glossiness matches--both in isolation and in combination. The lightness matching data only revealed an influence of motion and color information. Our results indicate, somewhat counterintuitively, that motion information has a detrimental effect on lightness constancy.

Measuring Light Reflectance of BGO Crystal Surfaces

NASA Astrophysics Data System (ADS)

Janecek, Martin; Moses, William W.

2008-10-01

A scintillating crystal's surface reflectance has to be well understood in order to accurately predict and optimize the crystal's light collection through Monte Carlo simulations. In this paper, we measure the inner surface reflectance properties for BGO. The measurements include BGO crystals with a mechanically polished surface, rough-cut surface, and chemically etched surface, and with various reflectors attached, both air-coupled and with coupling compound. The measurements are performed with a laser aimed at the center of a hemispherical shaped BGO crystal. The hemispherical shape eliminates any non-perpendicular angles for light entering and exiting the crystal. The reflected light is collected with an array of photodiodes. The laser can be set at an arbitrary angle, and the photodiode array is rotated to fully cover 2pi of solid angle. The current produced in the photodiodes is readout with a digital multimeter connected through a multiplexer. The two rows of photodiodes achieve 5-degree by 4-degree resolution, and the current measurement has a dynamic range of 105:1. The acquired data was not described by the commonly assumed linear combination of specular and diffuse (Lambertian) distributions, except for a very few surfaces. Surface roughness proved to be the most important parameter when choosing crystal setup. The reflector choice was of less importance and of almost no consequence for rough-cut surfaces. Pure specular reflection distribution for all incidence angles was measured for polished surfaces with VM2000 film, while the most Lambertian distribution for any surface finish was measured for titanium dioxide paint. The distributions acquired in this paper will be used to create more accurate Monte Carlo models for light reflection distribution within BGO crystals.

Structured light optical microscopy for three-dimensional reconstruction of technical surfaces

NASA Astrophysics Data System (ADS)

Kettel, Johannes; Reinecke, Holger; Müller, Claas

2016-04-01

In microsystems technology quality control of micro structured surfaces with different surface properties is playing an ever more important role. The process of quality control incorporates three-dimensional (3D) reconstruction of specularand diffusive reflecting technical surfaces. Due to the demand on high measurement accuracy and data acquisition rates, structured light optical microscopy has become a valuable solution to solve this problem providing high vertical and lateral resolution. However, 3D reconstruction of specular reflecting technical surfaces still remains a challenge to optical measurement principles. In this paper we present a measurement principle based on structured light optical microscopy which enables 3D reconstruction of specular- and diffusive reflecting technical surfaces. It is realized using two light paths of a stereo microscope equipped with different magnification levels. The right optical path of the stereo microscope is used to project structured light onto the object surface. The left optical path is used to capture the structured illuminated object surface with a camera. Structured light patterns are generated by a Digital Light Processing (DLP) device in combination with a high power Light Emitting Diode (LED). Structured light patterns are realized as a matrix of discrete light spots to illuminate defined areas on the object surface. The introduced measurement principle is based on multiple and parallel processed point measurements. Analysis of the measured Point Spread Function (PSF) by pattern recognition and model fitting algorithms enables the precise calculation of 3D coordinates. Using exemplary technical surfaces we demonstrate the successful application of our measurement principle.

Measurement of refractive indices of tunicates' tunics: light reflection of the transparent integuments in an ascidian Rhopalaea sp. and a salp Thetys vagina.

PubMed

Kakiuchida, Hiroshi; Sakai, Daisuke; Nishikawa, Jun; Hirose, Euichi

2017-01-01

Tunic is a cellulosic, integumentary matrix found in tunicates (Subphylum Tunicata or Urochordata). The tunics of some ascidian species and pelagic tunicates, such as salps, are nearly transparent, which is useful in predator avoidance. Transparent materials can be detected visually using light reflected from their surfaces, with the different refractive indices between two media, i.e., tunic and seawater, being the measure of reflectance. A larger difference in refractive indices thus provides a larger measure of reflectance. We measured the refractive indices of the transparent tunic of Thetys vagina (salp: Thaliacea) and Rhopalae a sp. (ascidian: Ascidiacea) using an Abbe refractometer and an ellipsometer to estimate the light reflection at the tunic surface and evaluate the anti-reflection effect of the nipple array structure on the tunic surface of T. vagina . At D-line light (λ = 589 nm), the refractive indices of the tunics were 0.002-0.004 greater than seawater in the measurements by Abbe refractometer, and 0.02-0.03 greater than seawater in the measurements by ellipsometer. The refractive indices of tunics were slightly higher than that of seawater. According to the simulation of light reflection based on rigorous coupled wave analysis (RCWA), light at a large angle of incidence will be completely reflected from a surface when its refractive indices are smaller than seawater. Therefore, the refractive index of integument is important for enabling transparent organisms to remain invisible in the water column. In order to minimize reflectance, the refractive index should be similar to, but never smaller than, that of the surrounding seawater. The simulation also indicated that the presence or absence of a nipple array does not cause significant difference in reflectance on the surface. The nipple array on the tunic of the diurnal salp may have another function, such as bubble repellence, other than anti-reflection.

Specimen illumination apparatus with optical cavity for dark field illumination

DOEpatents

Pinkel, Daniel; Sudar, Damir; Albertson, Donna

1999-01-01

An illumination apparatus with a specimen slide holder, an illumination source, an optical cavity producing multiple reflection of illumination light to a specimen comprising a first and a second reflective surface arranged to achieve multiple reflections of light to a specimen is provided. The apparatus can further include additional reflective surfaces to achieve the optical cavity, a slide for mounting the specimen, a coverslip which is a reflective component of the optical cavity, one or more prisms for directing light within the optical cavity, antifading solutions for improving the viewing properties of the specimen, an array of materials for analysis, fluorescent components, curved reflective surfaces as components of the optical cavity, specimen detection apparatus, optical detection equipment, computers for analysis of optical images, a plane polarizer, fiberoptics, light transmission apertures, microscopic components, lenses for viewing the specimen, and upper and lower mirrors above and below the specimen slide as components of the optical cavity. Methods of using the apparatus are also provided.

Spectropolarimetric Imaging Observations

NASA Astrophysics Data System (ADS)

Bradley, Christine Lavella

The capability to map anthropogenic aerosol quantities and properties over land can provide significant insights for climate and environmental studies on global and regional scales. One of the primary challenges in aerosol information monitoring is separating two signals measured by downward-viewing airborne or spaceborne instruments: the light scattered from the aerosols and light reflected from the Earth's surface. In order to study the aerosols independently, the surface signal needs to be subtracted out from the measurements. Some observational modalities, such as multispectral and multiangle, do not provide enough information to uniquely define the Earth's directional reflectance properties for this task due to the high magnitude and inhomogeneity of albedo for land surface types. Polarization, however, can provide additional information to define surface reflection. To improve upon current measurement capabilities of aerosols over urban areas, Jet Propulsion Laboratory developed the Multiangle SpectroPolarimetric Imager (MSPI) that can accurately measure the Degree of Linear Polarization to 0.5%. In particular, data acquired by the ground-based prototype, GroundMSPI, is used for directional reflectance studies of outdoor surfaces in this dissertation. This work expands upon an existing model, the microfacet model, to characterize the polarized bidirectional reflectance distribution function (pBRDF) of surfaces and validate an assumption, the Spectral Invariance Hypothesis, on the surface pBRDF that is used in aerosol retrieval algorithms. The microfacet model is commonly used to represent the pBRDF of Earth's surface types, such as ocean and land. It represents a roughened surface comprised of randomly oriented facets that specularly reflect incoming light into the upward hemisphere. The analytic form of the pBRDF for this model assumes only a single reflection of light from the microfaceted surface. If the incoming illumination is unpolarized, as it is with natural light from the Sun, the reflected light is linearly polarized perpendicular to the plane that contains the illumination and view directions, the scattering plane. However, previous work has shown that manmade objects, such as asphalt and brick, show a polarization signature that differs from the single reflection microfacet model. Using the polarization ray-tracing (PRT) program POLARIS-M, a numerical calculation for the pBRDF is made for a roughened surface to account for multiple reflections that light can experience between microfacets. Results from this numerical PRT method shows rays that experience two or more reflections with the microfacet surface can be polarized at an orientation that differs from the analytical single reflection microfacet model. This PRT method is compared against GroundMSPI data of manmade surfaces. An assumption made regarding the pBRDF for this microfacet model is verified with GroundMSPI data of urban areas. This is known as the Spectral Invariance Hypothesis and asserts that the magnitude and shape of the polarized bidirectional reflectance factor (pBRF) is the same for all wavelengths. This simplifies the microfacet model by assuming some surface parameters such as the index of refraction are spectrally neutral. GroundMSPI acquires the pBRF for five prominent region types, asphalt, brick, cement, dirt, and grass, for day-long measurements on clear sky conditions. Over the course of each day, changing solar position in the sky provides a large range of scattering angles for this study. The pBRF is measured for the three polarimetric wavelengths of GroundMSPI, 470, 660, and 865nm, and the best fit slope of the spectral correlation is reported. This investigation shows agreement to the Spectral Invariance Hypothesis within 10% for all region types excluding grass. Grass measurements show a large mean deviation of 31.1%. This motivated an angle of linear polarization (AoLP) analysis of cotton crops to isolate single reflection cases, or specular reflections, from multiple scattering cases of light in vegetation. Results from this AoLP method show that specular reflections off the top surface of leaves follow the Spectral Invariance Hypothesis.

Nonimaging optical illumination system

DOEpatents

Winston, R.; Ries, H.

1996-12-17

A nonimaging illumination optical device for producing a selected far field illuminance over an angular range. The optical device includes a light source, a light reflecting surface, and a family of light edge rays defined along a reference line with the reflecting surface defined in terms of the reference line as a parametric function R(t) where t is a scalar parameter position and R(t)=k(t)+Du(t) where k(t) is a parameterization of the reference line, and D is a distance from a point on the reference line to the reflection surface along the desired edge ray through the point. 35 figs.

Nonimaging optical illumination system

DOEpatents

Winston, R.; Ries, H.

1998-10-06

A nonimaging illumination optical device for producing a selected far field illuminance over an angular range. The optical device includes a light source a light reflecting surface, and a family of light edge rays defined along a reference line with the reflecting surface defined in terms of the reference lines a parametric function R(t) where t is a scalar parameter position and R(t)=k(t)+Du(t) where k(t) is a parameterization of the reference line, and D is a distance from a point on the reference line to the reflection surface along the desired edge ray through the point. 35 figs.

Determining biological tissue optical properties via integrating sphere spatial measurements

DOEpatents

Baba, Justin S [Knoxville, TN; Letzen, Brian S [Coral Springs, FL

2011-01-11

An optical sample is mounted on a spatial-acquisition apparatus that is placed in or on an enclosure. An incident beam is irradiated on a surface of the sample and the specular reflection is allowed to escape from the enclosure through an opening. The spatial-acquisition apparatus is provided with a light-occluding slider that moves in front of the sample to block portions of diffuse scattering from the sample. As the light-occluding slider moves across the front of the sample, diffuse light scattered into the area of the backside of the light-occluding slider is absorbed by back side surface of the light-occluding slider. By measuring a baseline diffuse reflectance without a light-occluding slider and subtracting measured diffuse reflectance with a light-occluding slider therefrom, diffuse reflectance for the area blocked by the light-occluding slider can be calculated.

Focusing corner cube

DOEpatents

Monjes, J.A.

1985-09-12

This invention retortreflects and focuses a beam of light. The invention comprises a modified corner cube reflector wherein one reflective surface is planar, a second reflective surface is spherical, and the third reflective surface may be planar or convex cylindrical.

Light reflected from colored mulches affects aroma and phenol content of sweet basil (Ocimum basilicum L.) leaves.

PubMed

Loughrin, J H; Kasperbauer, M J

2001-03-01

Basil (Ocimum basilicum L.) is an herb the leaves of which are used to add a distinct aroma and flavor to food. It was hypothesized that the size and chemical composition of sun-grown basil leaves could be influenced by the color of light reflected from the soil surface and by the action of the reflected light through the natural growth regulatory system within the growing plants. Leaf morphology, aroma compounds, and soluble phenolics were compared in basil that had been grown over six colors of polyethylene row covers. Altering the ratios of blue, red, and far-red light reflected to growing plants influenced both leaf morphology and chemistry. Leaves developing over red surfaces had greater area, moisture percentage (succulence), and fresh weight than those developing over black surfaces. Basil grown over yellow and green surfaces produced significantly higher concentrations of aroma compounds than did basil grown over white and blue covers. Leaves grown over yellow and green mulches also contained significantly higher concentrations of phenolics than those grown over the other colors. Clearly, the wavelengths (color) of light reflected to growing basil plants affected leaf size, aroma, and concentrations of soluble phenolics, some of which are antioxidants.

An interferometer having fused optical fibers, and apparatus and method using the interferometer

NASA Technical Reports Server (NTRS)

Hellbaum, Richard F. (Inventor); Claus, Richard O. (Inventor); Murphy, Kent A. (Inventor); Gunther, Michael F. (Inventor)

1992-01-01

An interferometer includes a first optical fiber coupled to a second optical fiber by fusing. At a fused portion, the first and second optical fibers are cut to expose respective cores. The cut or fused end of the first and second optical fibers is arranged to oppose a diaphragm or surface against which a physical phenomenon such as pressure or stress, is applied. In a first embodiment, a source light which is generally single-mode monochromatic, coherent light, is input to the first optical fiber and by evanescence, effectively crosses to the second optical fiber at the fused portion. Source light from the second optical fiber is reflected by the diaphragm or surface, and received at the second optical fiber to generate an output light which has an intensity which depends upon interference of reference light based on the source light, and the reflected light reflected from the diaphragm or surface. The intensity of the output light represents a positional relationship or displacement between the interferometer and the diaphragm or surface.

Measurement of the configuration of a concave surface by the interference of reflected light

NASA Technical Reports Server (NTRS)

Kumazawa, T.; Sakamoto, T.; Shida, S.

1985-01-01

A method whereby a concave surface is irradiated with coherent light and the resulting interference fringes yield information on the concave surface is described. This method can be applied to a surface which satisfies the following conditions: (1) the concave face has a mirror surface; (2) the profile of the face is expressed by a mathematical function with a point of inflection. In this interferometry, multilight waves reflected from the concave surface interfere and make fringes wherever the reflected light propagates. Interference fringe orders. Photographs of the fringe patterns for a uniformly loaded thin silicon plate clamped at the edge are shown experimentally. The experimental and the theoretical values of the maximum optical path difference show good agreement. This simple method can be applied to obtain accurate information on concave surfaces.

Removal of surface-reflected light for the measurement of remote-sensing reflectance from an above-surface platform.

PubMed

Lee, Zhongping; Ahn, Yu-Hwan; Mobley, Curtis; Arnone, Robert

2010-12-06

Using hyperspectral measurements made in the field, we show that the effective sea-surface reflectance ρ (defined as the ratio of the surface-reflected radiance at the specular direction corresponding to the downwelling sky radiance from one direction) varies not only for different measurement scans, but also can differ by a factor of 8 between 400 nm and 800 nm for the same scan. This means that the derived water-leaving radiance (or remote-sensing reflectance) can be highly inaccurate if a spectrally constant ρ value is applied (although errors can be reduced by carefully filtering measured raw data). To remove surface-reflected light in field measurements of remote sensing reflectance, a spectral optimization approach was applied, with results compared with those from remote-sensing models and from direct measurements. The agreement from different determinations suggests that reasonable results for remote sensing reflectance of clear blue water to turbid brown water are obtainable from above-surface measurements, even under conditions of high waves.

System for characterizing semiconductor materials and photovoltaic device

DOEpatents

Sopori, B.L.

1996-12-03

Apparatus for detecting and mapping defects in the surfaces of polycrystalline material in a manner that distinguishes dislocation pits from grain boundaries includes a first laser of a first wavelength for illuminating a wide spot on the surface of the material, a second laser of a second relatively shorter wavelength for illuminating a relatively narrower spot on the surface of the material, a light integrating sphere with apertures for capturing light scattered by etched dislocation pits in an intermediate range away from specular reflection while allowing light scattered by etched grain boundaries in a near range from specular reflection to pass through, and optical detection devices for detecting and measuring intensities of the respective intermediate scattered light and near specular scattered light. A center blocking aperture or filter can be used to screen out specular reflected light, which would be reflected by nondefect portions of the polycrystalline material surface. An X-Y translation stage for mounting the polycrystalline material and signal processing and computer equipment accommodate raster mapping, recording, and displaying of respective dislocation and grain boundary defect densities. A special etch procedure is included, which prepares the polycrystalline material surface to produce distinguishable intermediate and near specular light scattering in patterns that have statistical relevance to the dislocation and grain boundary defect densities. A reflectance measurement of the piece of material is obtained by adding together the signals from the optical detection devices. In the case where the piece of material includes a photovoltaic device, the current induced in the device by the illuminating light can be measured with a current sensing amplifier after the light integrating sphere is moved away from the device. 22 figs.

System for characterizing semiconductor materials and photovoltaic device

DOEpatents

Sopori, Bhushan L.

1996-01-01

Apparatus for detecting and mapping defects in the surfaces of polycrystalline material in a manner that distinguishes dislocation pits from grain boundaries includes a first laser of a first wavelength for illuminating a wide spot on the surface of the material, a second laser of a second relatively shorter wavelength for illuminating a relatively narrower spot on the surface of the material, a light integrating sphere with apertures for capturing light scattered by etched dislocation pits in an intermediate range away from specular reflection while allowing light scattered by etched grain boundaries in a near range from specular reflection to pass through, and optical detection devices for detecting and measuring intensities of the respective intermediate scattered light and near specular scattered light. A center blocking aperture or filter can be used to screen out specular reflected light, which would be reflected by nondefect portions of the polycrystalline material surface. An X-Y translation stage for mounting the polycrystalline material and signal processing and computer equipment accommodate raster mapping, recording, and displaying of respective dislocation and grain boundary defect densities. A special etch procedure is included, which prepares the polycrystalline material surface to produce distinguishable intermediate and near specular light scattering in patterns that have statistical relevance to the dislocation and grain boundary defect densities. A reflectance measurement of the piece of material is obtained by adding together the signals from the optical detection devices. In the case where the piece of material includes a photovoltaic device, the current induced in the device by the illuminating light can be measured with a current sensing amplifier after the light integrating sphere is moved away from the device.

Simulation of laser beam reflection at the sea surface

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric; Repasi, Endre

2011-05-01

A 3D simulation of the reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation is suitable for both the calculation of images of SWIR (short wave infrared) imaging sensor and for determination of total detected power of reflected laser light for a bistatic configuration of laser source and receiver at different atmospheric conditions. Our computer simulation comprises the 3D simulation of a maritime scene (open sea/clear sky) and the simulation of laser light reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. The propagation model for water waves is applied for sea surface animation. To predict the view of a camera in the spectral band SWIR the sea surface radiance must be calculated. This is done by considering the emitted sea surface radiance and the reflected sky radiance, calculated by MODTRAN. Additionally, the radiances of laser light specularly reflected at the wind-roughened sea surface are modeled in the SWIR band considering an analytical statistical sea surface BRDF (bidirectional reflectance distribution function). This BRDF model considers the statistical slope statistics of waves and accounts for slope-shadowing of waves that especially occurs at flat incident angles of the laser beam and near horizontal detection angles of reflected irradiance at rough seas. Simulation results are presented showing the variation of the detected laser power dependent on the geometric configuration of laser, sensor and wind characteristics.

Enhanced chiral response from the Fabry-Perot cavity coupled meta-surfaces

NASA Astrophysics Data System (ADS)

Yang, Ze-Jian; Hu, De-Jiao; Gao, Fu-Hua; Hou, Yi-Dong

2016-08-01

The circular dichroism (CD) signal of a two-dimensional (2D) chiral meta-surface is usually weak, where the difference between the transmitted (or reflected) right and left circular polarization is barely small. We present a general method to enhance the reflective CD spectrum, by adding a layer of reflective film behind the meta-surface. The light passes through the chiral meta-surface and propagates towards the reflector, where it is reflected back and further interacts with the chiral meta-surface. The light is reflected back and forth between these two layers, forming a Fabry-Perot type resonance, which interacts with the localized surface plasmonic resonance (LSPR) mode and greatly enhances the CD signal of the light wave leaving the meta-surface. We numerically calculate the CD enhancing effect of an L-shaped chiral meta-surface on a gold film in the visible range. Compared with the single layer meta-surface, the L-shaped chiral meta-surface has a CD maximum that is dramatically increased to 1. The analysis of reflection efficiency reveals that our design can be used to realize a reflective circular polarizer. Corresponding mode analysis shows that the huge CD originates from the hybrid mode comprised of FP mode and LSPR. Our results provide a general approach to enhancing the CD signal of a chiral meta-surface and can be used in areas like biosensing, circular polarizer, integrated photonics, etc. Project supported by the National Natural Science Foundation of China (Grant No. 61377054).

Lensing duct

DOEpatents

Beach, R.J.; Benett, W.J.

1994-04-26

A lensing duct to condense (intensify) light using a combination of front surface lensing and reflective waveguiding is described. The duct tapers down from a wide input side to a narrow output side, with the input side being lens-shaped and coated with an antireflective coating for more efficient transmission into the duct. The four side surfaces are uncoated, preventing light from escaping by total internal reflection as it travels along the duct (reflective waveguiding). The duct has various applications for intensifying light, such as in the coupling of diode array pump light to solid state lasing materials, and can be fabricated from inexpensive glass and plastic. 3 figures.

The polarization patterns of skylight reflected off wave water surface.

PubMed

Zhou, Guanhua; Xu, Wujian; Niu, Chunyue; Zhao, Huijie

2013-12-30

In this paper we propose a model to understand the polarization patterns of skylight when reflected off the surface of waves. The semi-empirical Rayleigh model is used to analyze the polarization of scattered skylight; the Harrison and Coombes model is used to analyze light radiance distribution; and the Cox-Munk model and Mueller matrix are used to analyze reflections from wave surface. First, we calculate the polarization patterns and intensity distribution of light reflected off wave surface. Then we investigate their relationship with incident radiation, solar zenith angle, wind speed and wind direction. Our results show that the polarization patterns of reflected skylight from waves and flat water are different, while skylight reflected on both kinds of water is generally highly polarized at the Brewster angle and the polarization direction is approximately parallel to the water's surface. The backward-reflecting Brewster zone has a relatively low reflectance and a high DOP in all observing directions. This can be used to optimally diminish the reflected skylight and avoid sunglint in ocean optics measurements.

Broadband angle-independent antireflection coatings on nanostructured light trapping solar cells

NASA Astrophysics Data System (ADS)

Vázquez-Guardado, Abraham; Boroumand, Javaneh; Franklin, Daniel; Chanda, Debashis

2018-03-01

Backscattering from nanostructured surfaces greatly diminishes the efficacy of light trapping solar cells. While the analytical design of broadband, angle-independent antireflection coatings on nanostructured surfaces proved inefficient, numerical optimization proves a viable alternative. Here, we numerically design and experimentally verify the performance of single and bilayer antireflection coatings on a 2D hexagonal diffractive light trapping pattern on crystalline silicon substrates. Three well-known antireflection coatings, aluminum oxide, silicon nitride, and silicon oxide, which also double as high-quality surface passivation materials, are studied in the 400-1000 nm band. By varying thickness and conformity, the optimal parameters that minimize the broadband total reflectance (specular and scattering) from the nanostructured surface are obtained. The design results in a single-layer antireflection coating with normal-angle wavelength-integrated reflectance below 4% and a bilayer antireflection coating demonstrating reflection down to 1.5%. We show experimentally an angle-averaged reflectance of ˜5.2 % up to 60° incident angle from the optimized bilayer antireflection-coated nanostructured surface, paving the path toward practical implementation of the light trapping solar cells.

Nonimaging optical illumination system

DOEpatents

Winston, Roland; Ries, Harald

2000-01-01

A nonimaging illumination optical device for producing a selected far field illuminance over an angular range. The optical device includes a light source 102, a light reflecting surface 108, and a family of light edge rays defined along a reference line 104 with the reflecting surface 108 defined in terms of the reference line 104 as a parametric function R(t) where t is a scalar parameter position and R(t)=k(t)+Du(t) where k(t) is a parameterization of the reference line 104, and D is a distance from a point on the reference line 104 to the reflection surface 108 along the desired edge ray through the point.

Nonimaging optical illumination system

DOEpatents

Winston, Roland; Ries, Harald

1998-01-01

A nonimaging illumination optical device for producing a selected far field illuminance over an angular range. The optical device includes a light source 102, a light reflecting surface 108, and a family of light edge rays defined along a reference line 104 with the reflecting surface 108 defined in terms of the reference line 104 as a parametric function R(t) where t is a scalar parameter position and R(t)=k(t)+Du(t) where k(t) is a parameterization of the reference line 104, and D is a distance from a point on the reference line 104 to the reflection surface 108 along the desired edge ray through the point.

Nonimaging optical illumination system

DOEpatents

Winston, Roland; Ries, Harald

1996-01-01

A nonimaging illumination optical device for producing a selected far field illuminance over an angular range. The optical device includes a light source 102, a light reflecting surface 108, and a family of light edge rays defined along a reference line 104 with the reflecting surface 108 defined in terms of the reference line 104 as a parametric function R(t) where t is a scalar parameter position and R(t)=k(t)+Du(t) where k(t) is a parameterization of the reference line 104, and D is a distance from a point on the reference line 104 to the reflection surface 108 along the desired edge ray through the point.

How Can Polarization States of Reflected Light from Snow Surfaces Inform Us on Surface Normals and Ultimately Snow Grain Size Measurements?

NASA Astrophysics Data System (ADS)

Schneider, A. M.; Flanner, M.; Yang, P.; Yi, B.; Huang, X.; Feldman, D.

2016-12-01

The Snow Grain Size and Pollution (SGSP) algorithm is a method applied to Moderate Resolution Imaging Spectroradiometer data to estimate snow grain size from space-borne measurements. Previous studies validate and quantify potential sources of error in this method, but because it assumes flat snow surfaces, however, large scale variations in surface normals can cause biases in its estimates due to its dependence on solar and observation zenith angles. To address these variations, we apply the Monte Carlo method for photon transport using data containing the single scattering properties of different ice crystals to calculate polarization states of reflected monochromatic light at 1500nm from modeled snow surfaces. We evaluate the dependence of these polarization states on solar and observation geometry at 1500nm because multiple scattering is generally a mechanism for depolarization and the ice crystals are relatively absorptive at this wavelength. Using 1500nm thus results in a higher number of reflected photons undergoing fewer scattering events, increasing the likelihood of reflected light having higher degrees of polarization. In evaluating the validity of the model, we find agreement with previous studies pertaining to near-infrared spectral directional hemispherical reflectance (i.e. black-sky albedo) and similarities in measured bidirectional reflectance factors, but few studies exist modeling polarization states of reflected light from snow surfaces. Here, we present novel results pertaining to calculated polarization states and compare dependences on solar and observation geometry for different idealized snow surfaces. If these dependencies are consistent across different ice particle shapes and sizes, then these findings could inform the SGSP algorithm by providing useful relationships between measurable physical quantities and solar and observation geometry to better understand variations in snow surface normals from remote sensing observations.

Borehole optical lateral displacement sensor

DOEpatents

Lewis, R.E.

1998-10-20

There is provided by this invention an optical displacement sensor that utilizes a reflective target connected to a surface to be monitored to reflect light from a light source such that the reflected light is received by a photoelectric transducer. The electric signal from the photoelectric transducer is then imputed into electronic circuitry to generate an electronic image of the target. The target`s image is monitored to determine the quantity and direction of any lateral displacement in the target`s image which represents lateral displacement in the surface being monitored. 4 figs.

Goniometric measurements of light scattered in the principal plane from leaves

NASA Technical Reports Server (NTRS)

Brakke, Thomas W.

1992-01-01

A laboratory goniometer was designed and built by NASA for acquiring bidirectional scattering data in the principal plane from leaves. Goniometric measurements were taken on individual tree leaves of yellow poplar, red maple, and red oak. Reflectance measurements were taken every 5* and transmittance measurements every 10 in the principal plane. The results indicate that light reflected from leaves usually has a significant specular component. Reflectances measured for 60 incident angle were the most specular. The most isotropic scattering occurred with transmitted light and with 0 incident light reflected from the abaxial surface. The most significant difference observed between the species was due to the heavy wax layer found on the abaxial surface of red oak, which caused the abaxial reflectance to be more specular than it was in the other two species.

Simulation of a polarized laser beam reflected at the sea surface: modeling and validation

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric

2015-05-01

A 3-D simulation of the polarization-dependent reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation considers polarized or unpolarized laser sources and calculates the polarization states upon reflection at the sea surface. It is suitable for the radiance calculation of the scene in different spectral wavebands (e.g. near-infrared, SWIR, etc.) not including the camera degradations. The simulation also considers a bistatic configuration of laser source and receiver as well as different atmospheric conditions. In the SWIR, the detected total power of reflected laser light is compared with data collected in a field trial. Our computer simulation combines the 3-D simulation of a maritime scene (open sea/clear sky) with the simulation of polarized or unpolarized laser light reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. To predict the input of a camera equipped with a linear polarizer, the polarized sea surface radiance must be calculated for the specific waveband. The s- and p-polarization states are calculated for the emitted sea surface radiance and the specularly reflected sky radiance to determine the total polarized sea surface radiance of each component. The states of polarization and the radiance of laser light specularly reflected at the wind-roughened sea surface are calculated by considering the s- and p- components of the electric field of laser light with respect to the specular plane of incidence. This is done by using the formalism of their coherence matrices according to E. Wolf [1]. Additionally, an analytical statistical sea surface BRDF (bidirectional reflectance distribution function) is considered for the reflection of laser light radiances. Validation of the simulation results is required to ensure model credibility and applicability to maritime laser applications. For validation purposes, field measurement data (images and meteorological data) was analyzed. An infrared laser, with or without a mounted polarizer, produced laser beam reflection at the water surface and images were recorded by a camera equipped with a polarizer with horizontal or vertical alignment. The validation is done by numerical comparison of measured total laser power extracted from recorded images with the corresponding simulation results. The results of the comparison are presented for different incident (zenith/azimuth) angles of the laser beam and different alignment for the laser polarizers (vertical/horizontal/without) and the camera (vertical/horizontal).

Bidirectional Reflectance Function Measurement of Molecular Contaminant Scattering in the Vacuum Ultraviolet

NASA Technical Reports Server (NTRS)

Herren, Kenneth A.; Gregory, Don A.

2006-01-01

Bi-directional reflectance distribution function (BRDF) measurements of optical surfaces both before and after molecular contamination were done using UV, VUV and visible light. Molecular contamination of optical surfaces from outgassed material has been shown in many cases to proceed from acclimation centers, and to produce many roughly hemispherical "islands" of contamination on the surface. Vacuum Ultraviolet (VW) wavelengths are used here to measure angularly scattered light from optical surfaces.

Luminance-based specular gloss characterization.

PubMed

Leloup, Frédéric B; Pointer, Michael R; Dutré, Philip; Hanselaer, Peter

2011-06-01

Gloss is a feature of visual appearance that arises from the directionally selective reflection of light incident on a surface. Especially when a distinct reflected image is perceptible, the luminance distribution of the illumination scene above the sample can strongly influence the gloss perception. For this reason, industrial glossmeters do not provide a satisfactory gloss estimation of high-gloss surfaces. In this study, the influence of the conditions of illumination on specular gloss perception was examined through a magnitude estimation experiment in which 10 observers took part. A light booth with two light sources was utilized: the mirror image of only one source being visible in reflection by the observer. The luminance of both the reflected image and the adjacent sample surface could be independently varied by separate adjustment of the intensity of the two light sources. A psychophysical scaling function was derived, relating the visual gloss estimations to the measured luminance of both the reflected image and the off-specular sample background. The generalization error of the model was estimated through a validation experiment performed by 10 other observers. In result, a metric including both surface and illumination properties is provided. Based on this metric, improved gloss evaluation methods and instruments could be developed.

A dual-reflective electrothermal MEMS micromirror for full circumferential scanning endoscopic imaging

NASA Astrophysics Data System (ADS)

Wu, Lei; Xie, Huikai

2008-02-01

This paper reports the design, fabrication and measurements of a dual-reflective, single-crystal silicon based micromirror that can perform full circumferential scanning (FCS) for endoscopic optical coherence tomography (EOCT). In the proposed FCS-EOCT probe, two optical fibers are used to deliver light beams to either surface of the micromirror, which can rotate +/-45° (or 90°) and thus a 180° optical scanning is obtained from each mirror surface, resulting in full circumferential scans. A novel surface- and bulk-combined micromachining process based on SOI wafers is developed for fabricating the dual reflective micromirror. The single-crystal-silicon device layer of SOI wafers is used for mirror flatness, and Al is coated on both sides for high reflectivity. With one light beam delivered to each mirror surface, full 360° scans have been observed. Other measured data include the resonant frequency: 328Hz, radius of curvatures: - 124 mm (front surface) and 127 mm (back surface), and the reflectances: 81.3% (front surface) and 79.0% (back surface).

Numerical reproduction and explanation of road surface mirages under grazing-angle scattering.

PubMed

Lu, Jia; Zhou, Huaichun

2017-07-01

The mirror-like reflection image of the road surface under grazing-angle scattering can be easily observed in daily life. It was suggested that road surface mirages may occur due to a light-enhancing effect of the rough surface under grazing-angle scattering. The main purpose of this work is to explain the light-enhancing mechanism of rough surfaces under grazing-angle scattering. The off-specular reflection from a random rough magnesium oxide ceramic surface is analyzed by using the geometric optics approximation method. Then, the geometric optics approximation method is employed to develop a theoretical model to predict the observation effect of the grazing-angle scattering phenomenon of the road surface. The rough surface is assumed to consist of small-scale rough surface facets. The road surface mirage is reproduced from a large number of small-scale rough surface facets within the eye's resolution limit at grazing scattering angles, as the average bidirectional reflectance distribution function value at the bright location is about twice that of the surface in front of the mirage. It is suggested that the light-enhancing effect of the rough surface under grazing-angle scattering is not proper to be termed as "off-specular reflection," since it has nothing to do with the "specular" direction with respect to the incident direction.

Optical Polarization of Light from a Sorghum Canopy Measured Under Both a Clear and an Overcast Sky

NASA Technical Reports Server (NTRS)

Vanderbilt, Vern; Daughtry, Craig; Biehl, Larry; Dahlgren, Robert

2014-01-01

Introduction: We tested the hypothesis that the optical polarization of the light reflected by a sorghum canopy is due to a Fresnel-type redirection, by sorghum leaf surfaces, of light from an unpolarized light source, the sun or overcast sky, toward the measuring sensor. If it can be shown that the source of the polarization of the light scattered by the sorghum canopy is a first surface, Fresnel-type reflection, then removing this surface reflected light from measurements of canopy reflectance presumably would allow better insight into the biochemical processes such as photosynthesis and metabolism that occur in the interiors of sorghum canopy leaves. Methods: We constructed a tower 5.9m tall in the center of a homogenous sorghum field. We equipped two Barnes MMR radiometers with polarization analyzers on the number 1, 3 and 7 Landsat TM wavelength bands. Positioning the radiometers atop the tower, we collected radiance data in 44 view directions on two days, one day with an overcast sky and the other, clear and sunlit. From the radiance data we calculated the linear polarization of the reflected light for each radiometer wavelength channel and view direction. Results and Discussion: Our experimental results support our hypothesis, showing that the amplitude of the linearly polarized portion of the light reflected by the sorghum canopy varied dramatically with view azimuth direction under a point source, the sun, but the amplitude varied little with view azimuth direction under the hemispherical source, the overcast sky. Under the clear sky, the angle of polarization depended upon the angle of incidence of the sunlight on the leaf, while under the overcast sky the angle of polarization depended upon the zenith view angle. These results support a polarized radiation transport model of the canopy that is based upon a first surface, Fresnel reflection from leaves in the sorghum canopy.

Infrared deflectometry for the inspection of diffusely specular surfaces

NASA Astrophysics Data System (ADS)

Höfer, Sebastian; Burke, Jan; Heizmann, Michael

2016-12-01

Deflectometry is a full-field gradient technique that lends itself very well to testing specular surfaces. It uses the geometry of specular reflection to determine the gradient of the surface under inspection. In consequence, a necessary precondition to apply deflectometry is the presence of at least partially specular reflection. Surfaces with larger roughness have increasingly diffuse reflection characteristics, making them inaccessible to usual deflectometry. However, many industrially relevant surfaces exist that change their reflection characteristic during production and processing. An example is metal sheets that are used as car body parts. Whereas the molded but otherwise raw metal sheets show a mostly diffuse reflection without sufficient specular reflection, the final car body panels have a high specular reflectance due to the lacquering. In consequence, it would be advantageous to apply the same inspection approach both for the raw material and for the final product. To solve this challenge, specular reflection from rough surfaces can be achieved using light with a larger wavelength, as the specular reflectivity of a surface depends on the ratio of the surface roughness and the wavelength of the light applied. Wavelengths in the thermal infrared range create enough specular reflection to apply deflectometry on many visually rough metal surfaces. This contribution presents the principles of thermal deflectometry, its special challenges, and illustrates its use with examples from the inspection of industrially produced surfaces.

Dependence on Solar Phase Angle and Grain Size of the Spectral Reflectance of the Railroad Valley Playa for GOSAT/GOSAT-2 Vicarious Calibration

NASA Astrophysics Data System (ADS)

Arai, T.; Matsunaga, T.

2017-12-01

GOSAT and the next generation GOSAT-2 satellites estimate the concentration of greenhouse gasses, and distribution of aerosol and cloud to observe solar light reflection and radiation from surface and atmosphere of the Earth. Precise information of the surface and the bidirectional reflectance distribution function (BRDF) are required for the estimation because the surface reflectance of solar light varies with the observation geometry and the surface condition. The purpose of this study is to search an appropriate BRDF model of the GOSAT calibration site (Railroad Valley playa). In 2017, JAXA, NIES, and NASA/OCO-2 teams collaboratively performed 9th vicarious experiments by the simultaneous observation with GOSAT, OCO-2, and ground-based equipment (Kuze et al., 2014) at the Railroad Valley from June 25 to 30. We performed the BRDF measurement to observe solar light reflection by varying with observed angles using a spectroradiometer (FieldSpec4, ASD Inc.) mounted on a one-axis goniometer. The surface sand was shifted to several sizes of grain (75, 125, 250, 500, and 1000 μm), which was measured for the limited area of 5mm diameter with a collimating lens (74-UV, OceanOptics). The BRDF parameters for the observed reflectance were determined by the least squares fitting with the free parameters of a single scattering albedo and an asymmetric factor (Hapke, 2012) for the ultraviolet to near infrared wavelength bands of GOSAT. The resulting value of the single scattering albedo increased with decreasing the grain size of the sands. The observed reflectance of the fine grain sands (below 250 μm) is not varied with observed phase angles (solar incident light - surface sand - detector) as a Lambertian reflectance, but the spectra of coarse grain sands (above 500 μm) are varied with the observation angles. Therefore, a priori information of the target surface such as grain size is required for the determination of the precise reflectance of the target.

Photon Doppler velocimetry measurements of transverse surface velocities

NASA Astrophysics Data System (ADS)

Johnson, C. R.; LaJeunesse, J. W.; Sable, P. A.; Dawson, A.; Hatzenbihler, A.; Borg, J. P.

2018-06-01

The goal of this work was to develop a technique for making transverse surface velocity measures utilizing Photon Doppler Velocimetry (PDV). Such a task is achieved by transmitting light and collecting Doppler-shifted light at an angle relative to the normal axis, where measured velocities are representative of a component of the transverse velocity. Because surface characteristics have an intrinsic effect on light scatter, different surface preparations were explored to direct reflectivity, including diffusion by means of sandpapering, or increasing retroreflectivity by coating with microspheres, milling v-cuts, and electrochemically etching grooves. Testing of these surface preparations was performed using an experiment featuring a 30 mm diameter aluminum disk rotating at 6000 or 6600 RPM. A single PDV collimator was positioned along the rotational axis of the disk at various angles, resolving the apparent transverse velocity. To characterize surface preparations, light return and velocities were recorded as a function of probe angle ranging from 0° to 51° from the surface normal for each preparation. Polished and electrochemically etched surfaces did not provide enough reflected light to resolve a beat frequency; however, sandpapered surfaces, retroreflective microspheres, and milled v-cuts provided adequate reflected light for incidence angles up to 51°. Applications of the surface preparations were then studied in gas gun experiments. Retroreflective microspheres were studied in a planar impact experiment, and milled v-cuts were studied in an oblique impact experiment. A normal and transverse profile of particle velocity was resolved in the oblique impact experiment.

Hyperspectral interferometry: Sizing microscale surface features in the pine bark beetle.

PubMed

Beach, James M; Uertz, James L; Eckhardt, Lori G

2015-10-01

A new method of interferometry employing a Fabry-Perot etalon model was used to locate and size microscale features on the surface of the pine bark beetle. Oscillations in the reflected light spectrum, caused by self-interference of light reflecting from surfaces of foreleg setae and spores on the elytrum, were recorded using white light hyperspectral microscopy. By making the assumption that pairs of reflecting surfaces produce an etalon effect, the distance between surfaces could be determined from the oscillation frequency. Low frequencies of less than 0.08 nm(-1) were observed in the spectrum below 700 nm while higher frequencies generally occupied wavelengths from 600 to 850 nm. In many cases, two frequencies appeared separately or in combination across the spectrum. The etalon model gave a mean spore size of 3.04 ± 1.27 μm and a seta diameter of 5.44 ± 2.88 μm. The tapering near the setae tip was detected as a lowering of frequency. Spatial fringes were observed together with spectral oscillations from surfaces on the exoskeleton at higher magnification. These signals were consistent with embedded multi-layer reflecting surfaces. Possible applications for hyperspectral interferometry include medical imaging, detection of spore loads in insects and other fungal carriers, wafer surface and subsurface inspection, nanoscale materials, biological surface analysis, and spectroscopy calibration. This is, to our knowledge, the first report of oscillations directly observed by microscopy in the reflected light spectra from Coleoptera, and the first demonstration of broadband hyperspectral interferometry using microscopy that does not employ an internal interferometer. © 2015 Wiley Periodicals, Inc.

Device for collecting and analyzing matrix-isolated samples

DOEpatents

Reedy, Gerald T.

1979-01-01

A gas-sample collection device is disclosed for matrix isolation of individual gas bands from a gas chromatographic separation and for presenting these distinct samples for spectrometric examination. The device includes a vacuum chamber containing a rotatably supported, specular carrousel having a number of external, reflecting surfaces around its axis of rotation for holding samples. A gas inlet is provided for depositing sample and matrix material on the individual reflecting surfaces maintained at a sufficiently low temperature to cause solidification. Two optical windows or lenses are installed in the vacuum chamber walls for transmitting a beam of electromagnetic radiation, for instance infrared light, through a selected sample. Positioned within the chamber are two concave mirrors, the first aligned to receive the light beam from one of the lenses and focus it to the sample on one of the reflecting surfaces of the carrousel. The second mirror is aligned to receive reflected light from that carrousel surface and to focus it outwardly through the second lens. The light beam transmitted from the sample is received by a spectrometer for determining absorption spectra.

Simulating polarized light scattering in terrestrial snow based on bicontinuous random medium and Monte Carlo ray tracing

NASA Astrophysics Data System (ADS)

Xiong, Chuan; Shi, Jiancheng

2014-01-01

To date, the light scattering models of snow consider very little about the real snow microstructures. The ideal spherical or other single shaped particle assumptions in previous snow light scattering models can cause error in light scattering modeling of snow and further cause errors in remote sensing inversion algorithms. This paper tries to build up a snow polarized reflectance model based on bicontinuous medium, with which the real snow microstructure is considered. The accurate specific surface area of bicontinuous medium can be analytically derived. The polarized Monte Carlo ray tracing technique is applied to the computer generated bicontinuous medium. With proper algorithms, the snow surface albedo, bidirectional reflectance distribution function (BRDF) and polarized BRDF can be simulated. The validation of model predicted spectral albedo and bidirectional reflectance factor (BRF) using experiment data shows good results. The relationship between snow surface albedo and snow specific surface area (SSA) were predicted, and this relationship can be used for future improvement of snow specific surface area (SSA) inversion algorithms. The model predicted polarized reflectance is validated and proved accurate, which can be further applied in polarized remote sensing.

Light reflection models for computer graphics.

PubMed

Greenberg, D P

1989-04-14

During the past 20 years, computer graphic techniques for simulating the reflection of light have progressed so that today images of photorealistic quality can be produced. Early algorithms considered direct lighting only, but global illumination phenomena with indirect lighting, surface interreflections, and shadows can now be modeled with ray tracing, radiosity, and Monte Carlo simulations. This article describes the historical development of computer graphic algorithms for light reflection and pictorially illustrates what will be commonly available in the near future.

A unified account of gloss and lightness perception in terms of gamut relativity.

PubMed

Vladusich, Tony

2013-08-01

A recently introduced computational theory of visual surface representation, termed gamut relativity, overturns the classical assumption that brightness, lightness, and transparency constitute perceptual dimensions corresponding to the physical dimensions of luminance, diffuse reflectance, and transmittance, respectively. Here I extend the theory to show how surface gloss and lightness can be understood in a unified manner in terms of the vector computation of "layered representations" of surface and illumination properties, rather than as perceptual dimensions corresponding to diffuse and specular reflectance, respectively. The theory simulates the effects of image histogram skewness on surface gloss/lightness and lightness constancy as a function of specular highlight intensity. More generally, gamut relativity clarifies, unifies, and generalizes a wide body of previous theoretical and experimental work aimed at understanding how the visual system parses the retinal image into layered representations of surface and illumination properties.

Effect of surface topographic features on the optical properties of skin: a phantom study

NASA Astrophysics Data System (ADS)

Liu, Guangli; Chen, Jianfeng; Zhao, Zuhua; Zhao, Gang; Dong, Erbao; Chu, Jiaru; Xu, Ronald X.

2016-10-01

Tissue-simulating phantoms are used to validate and calibrate optical imaging systems and to understand light transport in biological tissue. Light propagation in a strongly turbid medium such as skin tissue experiences multiple scattering and diffuse reflection from the surface. Surface roughness introduces phase shifts and optical path length differences for light which is scattered within the skin tissue and reflected from the surface. In this paper, we study the effect of mismatched surface roughness on optical measurement and subsequent determination of optical properties of skin tissue. A series of phantoms with controlled surface features and optical properties corresponding to normal human skin are fabricated. The fabrication of polydimethylsiloxane (PDMS) phantoms with known surface roughness follows a standard soft lithography process. Surface roughness of skin-simulating phantoms are measured with Bruker stylus profiler. The diffuse reflectance of the phantom is validated by a UV/VIS spectrophotometer. The results show that surface texture and roughness have considerable influence on the optical characteristics of skin. This study suggests that surface roughness should be considered as an important contributing factor for the determination of tissue optical properties.

Variable area light reflecting assembly

DOEpatents

Howard, T.C.

1986-12-23

Device is described for tracking daylight and projecting it into a building. The device tracks the sun and automatically adjusts both the orientation and area of the reflecting surface. The device may be mounted in either a wall or roof of a building. Additionally, multiple devices may be employed in a light shaft in a building, providing daylight to several different floors. The preferred embodiment employs a thin reflective film as the reflecting device. One edge of the reflective film is fixed, and the opposite end is attached to a spring-loaded take-up roller. As the sun moves across the sky, the take-up roller automatically adjusts the angle and surface area of the film. Additionally, louvers may be mounted at the light entrance to the device to reflect incoming daylight in an angle perpendicular to the device to provide maximum reflective capability when daylight enters the device at non-perpendicular angles. 9 figs.

Variable area light reflecting assembly

DOEpatents

Howard, Thomas C.

1986-01-01

Device for tracking daylight and projecting it into a building. The device tracks the sun and automatically adjusts both the orientation and area of the reflecting surface. The device may be mounted in either a wall or roof of a building. Additionally, multiple devices may be employed in a light shaft in a building, providing daylight to several different floors. The preferred embodiment employs a thin reflective film as the reflecting device. One edge of the reflective film is fixed, and the opposite end is attached to a spring-loaded take-up roller. As the sun moves across the sky, the take-up roller automatically adjusts the angle and surface area of the film. Additionally, louvers may be mounted at the light entrance to the device to reflect incoming daylight in an angle perpendicular to the device to provide maximum reflective capability when daylight enters the device at non-perpendicular angles.

Is There Ecological Information in Optical Polarization Data?

NASA Technical Reports Server (NTRS)

Vanderbilt, Vern; Daughtry, Craig; Dahlgren, Robert

2015-01-01

Optical linear polarization? In remote sensing it's due to specular reflection. The first surface that incident light encounters - a smooth water surface or the waxy first surface of a leaf's cuticle, if it's even somewhat smooth (i.e. shiny) - will specularly reflect and linearly polarize the incident light. We provide three examples of the types of ecological information contained in remotely sensed optical linear polarization measurements. Remove the surface reflection to better see the interior. The linearly polarized light reflected by leaf surfaces contains no information about cellular pigments, metabolites, or water contained in the leaf interiors of a plant canopy, because it never enters the leaf interior to interact with them. Thus, for purposes of remotely sensing the leaf interiors of a plant canopy, the linearly polarized light should be subtracted from the total reflected light, because including it would add noise to the measurement. In particular 'minus specular' vegetation indices should allow improved monitoring of a plant canopy's physiological processes. Estimate plant development stage and yield. Wheat and sorghum grain heads, following emergence, rapidly extend upward and very quickly tower over nearby leaves, partially blocking our view of the sunlight reflected by those leaf surfaces. The resulting decrease in the amount of surface reflected and polarized sunlight, if monitored over time, potentially allows per-field estimates of the dates of the heading and flowering development stages to be interleaved with weather data in models, which is key to better estimating per-field grain yield. Similar polarization changes may occur in other grasses, such as oats, barley, corn and rice, each a crop so widely grown that it potentially affects climate at the regional scale. Wetlands Mapping. The sunlight specularly reflected by surface waters is blindingly bright, spectrally flat and polarized - all of which telegraphs that the ground area is inundated. Inundated soils exchange methane with the atmosphere; non-inundated soils, carbon dioxide. Aquatic plants growing through the water surface pipe the soil-produced methane via the stomata to the atmosphere, enhancing exchanges rates by factors of 10-20 compared to ebullition (bubbling) or diffusion through the water column to the atmosphere. Thus, mapping wetland areas into three community types - inundated areas with emergent vegetation, open water and uplands - provides potentially key information to water, carbon and energy budgets at landscape to global scales.

Polarization of Light by Leaves and Plant Canopies

NASA Technical Reports Server (NTRS)

Vanderbilt, V. C.

2006-01-01

This talk will focus first on the information contained in the surface-scattered light from leaves, plant canopies and surface waters. This light is in general polarized and depends upon surface roughness. Thus, for example, - The surface reflection from shiny green leaves measured in the specular direction shows no chlorophyll absorption bands, no 'red edge.' - Conversely, the degree of linear polarization of such light displays marked variation with wavelength having local maxima in the chlorophyll absorption bands and an inverted red edge. - Plant canopies with shiny leaves distributed in angle like the area on a sphere, specularly reflect sunlight in the subsolar or specular direction- but also in every other view direction. - Canopies of green plants may appear white not green when viewed obliquely toward the sun. - In a light to moderate wind, the often blindingly bright glitter of sunlight off smooth water surfaces provides a strong, angularly narrow signature reflection characteristic of inundated vegetated areas that are big sources of atmospheric methane, a climatically important greenhouse gas. (Conversely, a blindingly bright glitter-type reflection is uncharacteristic of upland or wind ruffled open water areas that are poor sources of atmospheric methane.) Because some of these results may be 'head scratchers,' it's always important to properly calibrate ones instruments. Indeed, as the second portion of the talk will show, the characteristics of the light measuring instrument, particularly its entrance aperture, may affect the results and should be taken into account during across-instrument data comparisons.

Exciting surface plasmon polaritons in the Kretschmann configuration by a light beam

NASA Astrophysics Data System (ADS)

Vinogradov, A. P.; Dorofeenko, A. V.; Pukhov, A. A.; Lisyansky, A. A.

2018-06-01

We consider exciting surface plasmon polaritons in the Kretschmann configuration. Contrary to common belief, we show that a plane-wave incident at an angle greater than the angle of total internal reflection does not excite surface plasmon polaritons. These excitations do arise, however, if the incident light forms a narrow beam composed of an infinite number of plane waves. The surface plasmon polariton is formed at the geometrical edge of the beam as a result of interference of reflected plane waves.

A Feasibility Study on Generation of Acoustic Waves Utilizing Evanescent Light

NASA Astrophysics Data System (ADS)

Matsuya, I.; Matozaki, K.; Kosugi, A.; Ihara, I.

2014-06-01

A new approach of generating acoustic waves utilizing evanescent light is presented. The evanescent light is a non-propagating electromagnetic wave that exhibits exponential decay with distance from the surface at which the total internal reflection of light is formed. In this research, the evanescent light during total internal reflection at prism surface is utilized for generating acoustic waves in aluminium and the feasibility for ultrasonic measurements is discussed. Pulsed Nd:YAG laser with 0.36 J/cm2 power density is used and the incident angle during the total internal reflection is arranged to be 69.0° for generating the evanescent light. It has been demonstrated that the amplitude of the acoustic waves by means of evanescent light is about 1/14 as large as the one generated by the conventional pulsed laser. This reveals the possibility of using a laser ultrasonic technique with near-field optics.

Preschoolers' use of reflective properties: identification of reflections on partially transparent surfaces.

PubMed

Costanzo, E S; Wittgenstein, K M; Benson, K

2001-12-01

This exploratory study extended past studies of children's ability to reference the mirror as a tool in locating the source of reflected images to preschoolers' ability to use the affordances of a transparency. Thirty-six children (3.5 to 5 years old) were shown nonreflected lights and lights reflected on a partially transparent, glassy surface. Children did not spontaneously locate the source of the reflected image. However, they were able to verbally discriminate reflected from nonreflected images following training. These findings indicate that, although preschoolers may not spontaneously use transparencies as a perceptual tool, the ability to distinguish visual differences of reflected from nonreflected images on transparencies is likely within preschool children's developmental capacity.

Paraboloid Structured Silicon Surface for Enhanced Light Absorption: Experimental and Simulative Investigations

NASA Astrophysics Data System (ADS)

Khan, Firoz; Baek, Seong-Ho; Kaur, Jasmeet; Fareed, Imran; Mobin, Abdul; Kim, Jae Hyun

2015-09-01

In this paper, we present an optical model that simulates the light trapping and scattering effects of a paraboloid texture surface first time. This model was experimentally verified by measuring the reflectance values of the periodically textured silicon (Si) surface with the shape of a paraboloid under different conditions. A paraboloid texture surface was obtained by electrochemical etching Si in the solution of hydrofluoric acid, dimethylsulfoxide (DMSO), and deionized (DI) water. The paraboloid texture surface has the advantage of giving a lower reflectance value than the hemispherical, random pyramidal, and regular pyramidal texture surfaces. In the case of parabola, the light can be concentrated in the direction of the Si surface compared to the hemispherical, random pyramidal, and regular pyramidal textured surfaces. Furthermore, in a paraboloid textured surface, there can be a maximum value of 4 or even more by anisotropic etching duration compared to the hemispherical or pyramidal textured surfaces which have a maximum h/ D (depth and diameter of the texture) value of 0.5. The reflectance values were found to be strongly dependent on the h/ D ratio of the texture surface. The measured reflectance values were well matched with the simulated ones. The minimum reflectance value of ~4 % was obtained at a wavelength of 600 nm for an h/ D ratio of 3.75. The simulation results showed that the reflectance value for the h/ D ratio can be reduced to ~0.5 % by reducing the separations among the textures. This periodic paraboloidal structure can be applied to the surface texturing technique by substituting with a conventional pyramid textured surface or moth-eye antireflection coating.

Electro-Optic Modulator.

DTIC Science & Technology

An electro - optic modulator is used to modulate coherent light beams by the application of an electric potential. It combines a Fabry-Perot etalon and...a diffraction grating in a single unit. An etalon is constructed with an electro - optic material between reflecting surfaces. A voltage applied...between alternate, spaced-apart electrodes of a metal grid attached to one reflecting surface induces a diffraction grating in the electro optic material. Light entering the etalon is diffracted, reflected and efficiently coupled out.

Colour Model for Outdoor Machine Vision for Tropical Regions and its Comparison with the CIE Model

NASA Astrophysics Data System (ADS)

Sahragard, Nasrolah; Ramli, Abdul Rahman B.; Hamiruce Marhaban, Mohammad; Mansor, Shattri B.

2011-02-01

Accurate modeling of daylight and surface reflectance are very useful for most outdoor machine vision applications specifically those which are based on color recognition. Existing daylight CIE model has drawbacks that limit its ability to predict the color of incident light. These limitations include lack of considering ambient light, effects of light reflected off the ground, and context specific information. Previously developed color model is only tested for a few geographical places in North America and its accountability is under question for other places in the world. Besides, existing surface reflectance models are not easily applied to outdoor images. A reflectance model with combined diffuse and specular reflection in normalized HSV color space could be used to predict color. In this paper, a new daylight color model showing the color of daylight for a broad range of sky conditions is developed which will suit weather conditions of tropical places such as Malaysia. A comparison of this daylight color model and daylight CIE model will be discussed. The colors of matte and specular surfaces have been estimated by use of the developed color model and surface reflection function in this paper. The results are shown to be highly reliable.

Light interaction in sapphire/MgF2/Al triple-layer omnidirectional reflectors in AlGaN-based near ultraviolet light-emitting diodes

PubMed Central

Lee, Keon Hwa; Moon, Yong-Tae; Song, June-O; Kwak, Joon Seop

2015-01-01

This study examined systematically the mechanism of light interaction in the sapphire/MgF2/Al triple-layer omnidirectional reflectors (ODR) and its effects on the light output power in near ultraviolet light emitting diodes (NUV-LEDs) with the ODR. The light output power of NUV-LEDs with the triple-layer ODR structure increased with decreasing surface roughness of the sapphire backside in the ODR. Theoretical modeling of the roughened surface suggests that the dependence of the reflectance of the triple-layer ODR structure on the surface roughness can be attributed mainly to light absorption by the Al nano-structures and the trapping of scattered light in the MgF2 layer. Furthermore, the ray tracing simulation based upon the theoretical modeling showed good agreement with the measured reflectance of the ODR structure in diffuse mode. PMID:26010378

Light interaction in sapphire/MgF2/Al triple-layer omnidirectional reflectors in AlGaN-based near ultraviolet light-emitting diodes.

PubMed

Lee, Keon Hwa; Moon, Yong-Tae; Song, June-O; Kwak, Joon Seop

2015-05-26

This study examined systematically the mechanism of light interaction in the sapphire/MgF2/Al triple-layer omnidirectional reflectors (ODR) and its effects on the light output power in near ultraviolet light emitting diodes (NUV-LEDs) with the ODR. The light output power of NUV-LEDs with the triple-layer ODR structure increased with decreasing surface roughness of the sapphire backside in the ODR. Theoretical modeling of the roughened surface suggests that the dependence of the reflectance of the triple-layer ODR structure on the surface roughness can be attributed mainly to light absorption by the Al nano-structures and the trapping of scattered light in the MgF2 layer. Furthermore, the ray tracing simulation based upon the theoretical modeling showed good agreement with the measured reflectance of the ODR structure in diffuse mode.

WhitebalPR: automatic white balance by polarized reflections

NASA Astrophysics Data System (ADS)

Fischer, Gregor; Kolbe, Karin; Sajjaa, Matthias

2008-02-01

This new color constancy method is based on the polarization degree of that light which is reflected at the surface of an object. The subtraction of at least two images taken under different polarization directions detects the polarization degree of the neutrally reflected portions and eliminates the remitted non-polarized colored portions. Two experiments have been designed to clarify the performance of the procedure, one to multicolored objects and another to objects of different surface characteristics. The results show that the mechanism of eliminating the remitted, non-polarized colored portions of light works very fine. Independent from its color, different color pigments seem to be suitable for measuring the color of the illumination. The intensity and also the polarization degree of the reflected light depend on the surface properties significantly. The results exhibit a high accuracy of measuring the color of the illumination for glossy and matt surfaces. Only strongly scattering surfaces account for a weak signal level of the difference image and a reduced accuracy. An embodiment is proposed to integrate the new method into digital cameras.

High reflectivity mirrors and method for making same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heikman, Sten; Jacob-Mitos, Matthew; Li, Ting

2016-06-07

A composite high reflectivity mirror (CHRM) with at least one relatively smooth interior surface interface. The CHRM includes a composite portion, for example dielectric and metal layers, on a base element. At least one of the internal surfaces is polished to achieve a smooth interface. The polish can be performed on the surface of the base element, on various layers of the composite portion, or both. The resulting smooth interface(s) reflect more of the incident light in an intended direction. The CHRMs may be integrated into light emitting diode (LED) devices to increase optical output efficiency

Scattering-Type Surface-Plasmon-Resonance Biosensors

NASA Technical Reports Server (NTRS)

Wang, Yu; Pain, Bedabrata; Cunningham, Thomas; Seshadri, Suresh

2005-01-01

Biosensors of a proposed type would exploit scattering of light by surface plasmon resonance (SPR). Related prior biosensors exploit absorption of light by SPR. Relative to the prior SPR biosensors, the proposed SPR biosensors would offer greater sensitivity in some cases, enough sensitivity to detect bioparticles having dimensions as small as nanometers. A surface plasmon wave can be described as a light-induced collective oscillation in electron density at the interface between a metal and a dielectric. At SPR, most incident photons are either absorbed or scattered at the metal/dielectric interface and, consequently, reflected light is greatly attenuated. The resonance wavelength and angle of incidence depend upon the permittivities of the metal and dielectric. An SPR sensor of the type most widely used heretofore includes a gold film coated with a ligand a substance that binds analyte molecules. The gold film is thin enough to support evanescent-wave coupling through its thickness. The change in the effective index of refraction at the surface, and thus the change in the SPR response, increases with the number of bound analyte molecules. The device is illuminated at a fixed wavelength, and the intensity of light reflected from the gold surface opposite the ligand-coated surface is measured as a function of the angle of incidence. From these measurements, the angle of minimum reflection intensity is determined

Tunable natural nano-arrays: controlling surface properties and light reflectance

NASA Astrophysics Data System (ADS)

Watson, Jolanta A.; Myhra, Sverre; Watson, Gregory S.

2006-01-01

The general principles of optical design based on the theories of reflection, refraction and diffraction have been rigorously developed and optimized over the last three centuries. Of increasing importance has been the ability to predict and devise new optical technologies designed for specific functions. A key design feature of many of today's optical materials is the control of reflection and light transmittance through the medium. A sudden transition or impedance mismatch from one optical medium to another can result in unwanted reflections from the surface plane. Modification of a surface by creation of a gradual change in refractive index over a significant portion of a wavelength range will result in a reduction in reflection. An alternative surface modification to the multi layered stack coating (gradient index coating) is to produce a surface with structures having a period and height shorter than the light wavelength. These structures act like a pseudo-gradient index coating and can be described by the effective medium theory. Bernhard and Miller some forty years ago were the first to observe such structures found on the surface of insects. These were found in the form of hexagonally close packed nanometre sized protrusions on the corneal surface of certain moths. In this study we report on similar structures which we have found on certain species of cicada wings demonstrating that the reflective/transmission properties of these natural nano-structures can be tuned by controlled removal of the structure height using Atomic Force Microscopy (AFM).

Mask-to-wafer alignment system

DOEpatents

Sweatt, William C.; Tichenor, Daniel A.; Haney, Steven J.

2003-11-04

A modified beam splitter that has a hole pattern that is symmetric in one axis and anti-symmetric in the other can be employed in a mask-to-wafer alignment device. The device is particularly suited for rough alignment using visible light. The modified beam splitter transmits and reflects light from a source of electromagnetic radiation and it includes a substrate that has a first surface facing the source of electromagnetic radiation and second surface that is reflective of said electromagnetic radiation. The substrate defines a hole pattern about a central line of the substrate. In operation, an input beam from a camera is directed toward the modified beam splitter and the light from the camera that passes through the holes illuminates the reticle on the wafer. The light beam from the camera also projects an image of a corresponding reticle pattern that is formed on the mask surface of the that is positioned downstream from the camera. Alignment can be accomplished by detecting the radiation that is reflected from the second surface of the modified beam splitter since the reflected radiation contains both the image of the pattern from the mask and a corresponding pattern on the wafer.

All-reflective optical target illumination system with high numerical aperture

DOEpatents

Thomas, Carlton E.; Sigler, Robert D.; Hoeger, John G.

1979-01-01

An all-reflective optical system for providing illumination of a target focal region at high numerical aperture from a pair of confluent collimated light beams. The collimated beams are each incident upon an associated concave eccentric pupil paraboloidal reflective surface, and thereby each focused through an opening in an associated outer ellipsoidal reflective surface onto a plane reflector. Each beam is reflected by its associated plane reflector onto the opposing concave surface of the outer ellipsoids to be focused through an opening in the plane surface onto an opposing inner concave ellipsoidal reflective surface, and thence onto the target region.

Nonspecular reflection of light at an inhomogeneous interface between two media and in a nanostructured layer with a quasi-zero refractive index

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gadomsky, O. N., E-mail: gadomsky@mail.ru; Gadomskaya, I. V.

2015-02-15

We have derived formulas for the amplitudes of light reflection and refraction at an inhomogeneous interface between two media and in a nanostructured layer with a quasi-zero refractive index. These formulas are applied to explain the experimental spectra of nonspecular light reflection using a nanostructured (PMMA + Ag) layer with silver nanoparticles on a silicon surface as an example. We show that a surface wave is formed in the nanostructured layer at various angles of light incidence and the layer with a quasi-zero refractive index is an antireflection coating that provides uniform 5% silicon antireflection in the wavelength range frommore » 450 to 1000 nm.« less

Imaging Spectrometer Designs Utilizing Immersed Gratings With Accessible Entrance Slit

DOEpatents

Chrisp, Michael P.; Lerner, Scott A.

2006-03-21

A compact imaging spectrometer comprises an entrance slit, a catadioptric lens with a mirrored surface, a grating, and a detector array. The entrance slit directs light to the mirrored surface of the catadioptric lens; the mirrored surface reflects the light back through the lens to the grating. The grating receives the light from the catadioptric lens and diffracts the light to the lens away from the mirrored surface. The lens transmits the light and focuses it onto the detector array.

Representations and uses of light distribution functions

NASA Astrophysics Data System (ADS)

Lalonde, Paul Albert

1998-11-01

At their lowest level, all rendering algorithms depend on models of local illumination to define the interplay of light with the surfaces being rendered. These models depend both on the representations of light scattering at a surface due to reflection and to an equal extent on the representation of light sources and light fields. Both emission and reflection have in common that they describe how light leaves a surface as a function of direction. Reflection also depends on an incident light direction. Emission can depend on the position on the light source We call the functions representing emission and reflection light distribution functions (LDF's). There are some difficulties to using measured light distribution functions. The data sets are very large-the size of the data grows with the fourth power of the sampling resolution. For example, a bidirectional reflectance distribution function (BRDF) sampled at five degrees angular resolution, which is arguably insufficient to capture highlights and other high frequency effects in the reflection, can easily require one and a half million samples. Once acquired this data requires some form of interpolation to use them. Any compression method used must be efficient, both in space and in the time required to evaluate the function at a point or over a range of points. This dissertation examines a wavelet representation of light distribution functions that addresses these issues. A data structure is presented that allows efficient reconstruction of LDFs for a given set of parameters, making the wavelet representation feasible for rendering tasks. Texture mapping methods that take advantage of our LDF representations are examined, as well as techniques for filtering LDFs, and methods for using wavelet compressed bidirection reflectance distribution functions (BRDFs) and light sources with Monte Carlo path tracing algorithms. The wavelet representation effectively compresses BRDF and emission data while inducing only a small error in the reconstructed signal. The representation can be used to evaluate efficiently some integrals that appear in shading computation which allows fast, accurate computation of local shading. The representation can be used to represent light fields and is used to reconstruct views of environments interactively from a precomputed set of views. The representation of the BRDF also allows the efficient generation of reflected directions for Monte Carlo array tracing applications. The method can be integrated into many different global illumination algorithms, including ray tracers and wavelet radiosity systems.

Optical instrument employing reticle having preselected visual response pattern formed thereon

NASA Technical Reports Server (NTRS)

Haines, R. F. (Inventor)

1977-01-01

An optical instrument for use in locating indicator lights or the like on a work surface is described. It comprises a tubular housing, a lens mounted within the housing and including an inner surface coated with a dichroic material that is capable of reflecting a portion of the light incident thereon, a plate mounted within the housing opposite the lens and having a central aperture, a transparent substrate disposed within the housing intermediate the lens and the plate, the substrate including a first surface disposed in a facing relationship to the dichroic material, and a reticle formed on the first surface and comprised of a material capable of reflecting light.

Light-operated proximity detector with linear output

DOEpatents

Simpson, M.L.; McNeilly, D.R.

1984-01-01

A light-operated proximity detector is described in which reflected light intensity from a surface whose proximity to the detector is to be gauged is translated directly into a signal proportional to the distance of the detector from the surface. A phototransistor is used to sense the reflected light and is connected in a detector circuit which maintains the phtotransistor in a saturated state. A negative feedback arrangement using an operational amplifier connected between the collector and emitter of the transistor provides an output at the output of the amplifier which is linearly proportional to the proximity of the surface to the detector containing the transistor. This direct proportional conversion is true even though the light intensity is varying with the proximity in proportion to the square of the inverse of the distance. The detector may be used for measuring the distance remotely from any target surface.

Light-operated proximity detector with linear output

DOEpatents

Simpson, Marc L.; McNeilly, David R.

1985-01-01

A light-operated proximity detector is described in which reflected light intensity from a surface whose proximity to the detector is to be gauged is translated directly into a signal proportional to the distance of the detector from the surface. A phototransistor is used to sense the reflected light and is connected in a detector circuit which maintains the phototransistor in a saturated state. A negative feedback arrangement using an operational amplifier connected between the collector and emitter of the transistor provides an output at the output of the amplifier which is linearly proportional to the proximity of the surface to the detector containing the transistor. This direct proportional conversion is true even though the light intensity is varying with the proximity in proportion to the square of the inverse of the distance. The detector may be used for measuring the distance remotely from any target surface.

Electroluminescent device having improved light output

DOEpatents

Tyan,; Yuan-Sheng, [Webster, NY; Preuss, Donald R [Rochester, NY; Farruggia, Giuseppe [Webster, NY; Kesel, Raymond A [Avon, NY; Cushman, Thomas R [Rochester, NY

2011-03-22

An OLED device including a transparent substrate having a first surface and a second surface, a transparent electrode layer disposed over the first surface of the substrate, a short reduction layer disposed over the transparent electrode layer, an organic light-emitting element disposed over the short reduction layer and including at least one light-emitting layer and a charge injection layer disposed over the light emitting layer, a reflective electrode layer disposed over the charge injection layer and a light extraction enhancement structure disposed over the first or second surface of the substrate; wherein the short reduction layer is a transparent film having a through-thickness resistivity of 10.sup.-9 to 10.sup.2 ohm-cm.sup.2; wherein the reflective electrode layer includes Ag or Ag alloy containing more than 80% of Ag; and the total device size is larger than 10 times the substrate thickness.

Moth eye-inspired anti-reflective surfaces for improved IR optical systems & visible LEDs fabricated with colloidal lithography and etching.

PubMed

Chan, Lesley W; Morse, Daniel E; Gordon, Michael J

2018-05-08

Near- and sub-wavelength photonic structures are used by numerous organisms (e.g. insects, cephalopods, fish, birds) to create vivid and often dynamically-tunable colors, as well as create, manipulate, or capture light for vision, communication, crypsis, photosynthesis, and defense. This review introduces the physics of moth eye (ME)-like, biomimetic nanostructures and discusses their application to reduce optical losses and improve efficiency of various optoelectronic devices, including photodetectors, photovoltaics, imagers, and light emitting diodes. Light-matter interactions at structured and heterogeneous surfaces over different length scales are discussed, as are the various methods used to create ME-inspired surfaces. Special interest is placed on a simple, scalable, and tunable method, namely colloidal lithography with plasma dry etching, to fabricate ME-inspired nanostructures in a vast suite of materials. Anti-reflective surfaces and coatings for IR devices and enhancing light extraction from visible light emitting diodes are highlighted.

Optical system for determining physical characteristics of a solar cell

DOEpatents

Sopori, Bhushan L.

2001-01-01

The invention provides an improved optical system for determining the physical characteristics of a solar cell. The system comprises a lamp means for projecting light in a wide solid-angle onto the surface of the cell; a chamber for receiving the light through an entrance port, the chamber having an interior light absorbing spherical surface, an exit port for receiving a beam of light reflected substantially normal to the cell, a cell support, and an lower aperture for releasing light into a light absorbing baffle; a means for dispersing the reflection into monochromatic components; a means for detecting an intensity of the components; and a means for reporting the determination.

To compute lightness, illumination is not estimated, it is held constant.

PubMed

Gilchrist, Alan L

2018-05-03

The light reaching the eye from a surface does not indicate the black-gray-white shade of a surface (called lightness) because the effects of illumination level are confounded with the reflectance of the surface. Rotating a gray paper relative to a light source alters its luminance (intensity of light reaching the eye) but the lightness of the paper remains relatively constant. Recent publications have argued, as had Helmholtz (1866/1924), that the visual system unconsciously estimates the direction and intensity of the light source. We report experiments in which this theory was pitted against an alternative theory according to which illumination level and surface reflectance are disentangled by comparing only those surfaces that are equally illuminated, in other words, by holding illumination level constant. A 3-dimensional scene was created within which the rotation of a target surface would be expected to become darker gray according to the lighting estimation theory, but lighter gray according to the equi-illumination comparison theory, with results clearly favoring the latter. In a further experiment cues held to indicate light source direction (cast shadows, attached shadows, and glossy highlights) were completely eliminated and yet this had no effect on the results. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Reduction of short wavelength reflectance of multi-wall carbon nanotubes through ultraviolet laser irradiation

NASA Astrophysics Data System (ADS)

Stephens, Michelle S.; Simonds, Brian J.; Yung, Christopher S.; Conklin, Davis; Livigni, David J.; Oliva, Alberto Remesal; Lehman, John H.

2018-05-01

Multi-wall carbon nanotube coatings are used as broadband, low-reflectance absorbers for bolometric applications and for stray light control. They are also used as high emittance blackbody radiators. Irradiation of single wall carbon nanotubes with ultraviolet (UV) laser light has been shown to remove amorphous carbon debris, but there have been few investigations of the interaction of UV light with the more complex physics of multi-wall carbon nanotubes. We present measurements of reflectance and surface morphology before and after exposure of multi-wall carbon nanotube coatings to 248 nm UV laser light. We show that UV exposure reduces the reflectivity at wavelengths below 600 nm and present modeling of the thermal cycling the UV exposure causes at the surface of the carbon nanotubes. This effect can be used to flatten the spectral shape of the reflectivity curve of carbon nanotube absorber coatings used for broadband applications. Finally, we find that the effect of UV exposure depends on the nanotube growth process.

Interference of conically scattered light in surface plasmon resonance.

PubMed

Webster, Aaron; Vollmer, Frank

2013-02-01

Surface plasmon polaritons on thin metal films are a well studied phenomena when excited using prism coupled geometries such as the Kretschmann attenuated total reflection configuration. Here we describe a novel interference pattern in the conically scattered light emanating from such a configuration when illuminated by a focused beam. We observe conditions indicating only self-interference of scattered surface plasmon polaritions without any contributions from specular reflection. The spatial evolution of this field is described in the context of Fourier optics and has applications in highly sensitive surface plasmon based biosensing.

Polarization Signals of Common Spacecraft Materials

NASA Technical Reports Server (NTRS)

Gravseth, Ian; Culp, Robert D.; King, Nicole

1996-01-01

This is the final report documenting the results of the polarization testing of near-planar objects with various reflectance properties. The purpose of this investigation was to determine the portion of the reflected signal which is polarized for materials commonly used in space applications. Tests were conducted on several samples, with surface characteristics ranging from highly reflective to relatively dark. The measurements were obtained by suspending the test object in a beam of collimated light. The amount of light falling on the sample was controlled by a circular aperture placed in the light field. The polarized reflectance at various phase angles was then measured. A nonlinear least squares fitting program was used for analysis. For the specular test objects, the reflected signals were measured in one degree increments near the specular point. Otherwise, measurements were taken every five degrees in phase angle. Generally, the more diffuse surfaces had lower polarized reflectances than their more specular counterparts. The reflected signals for the more diffuse surfaces were spread over a larger phase angle range, while the signals from the more specular samples were reflected almost entirely within five degrees of angular deviation from the specular point. The method used to test all the surfaces is presented. The results of this study will be used to support the NASA Orbital Debris Optical Signature Tests. These tests are intended to help better understand the reflectance properties of materials often used in space applications. This data will then be used to improve the capabilities for identification and tracking of space debris.

Optic probe for semiconductor characterization

DOEpatents

Sopori, Bhushan L [Denver, CO; Hambarian, Artak [Yerevan, AM

2008-09-02

Described herein is an optical probe (120) for use in characterizing surface defects in wafers, such as semiconductor wafers. The optical probe (120) detects laser light reflected from the surface (124) of the wafer (106) within various ranges of angles. Characteristics of defects in the surface (124) of the wafer (106) are determined based on the amount of reflected laser light detected in each of the ranges of angles. Additionally, a wafer characterization system (100) is described that includes the described optical probe (120).

Anti-reflective device having an anti-reflective surface formed of silicon spikes with nano-tips

NASA Technical Reports Server (NTRS)

Bae, Youngsam (Inventor); Manohara, Harish (Inventor); Mobasser, Sohrab (Inventor); Lee, Choonsup (Inventor)

2011-01-01

Described is a device having an anti-reflection surface. The device comprises a silicon substrate with a plurality of silicon spikes formed on the substrate. A first metallic layer is formed on the silicon spikes to form the anti-reflection surface. The device further includes an aperture that extends through the substrate. A second metallic layer is formed on the substrate. The second metallic layer includes a hole that is aligned with the aperture. A spacer is attached with the silicon substrate to provide a gap between an attached sensor apparatus. Therefore, operating as a Micro-sun sensor, light entering the hole passes through the aperture to be sensed by the sensor apparatus. Additionally, light reflected by the sensor apparatus toward the first side of the silicon substrate is absorbed by the first metallic layer and silicon spikes and is thereby prevented from being reflected back toward the sensor apparatus.

Anti- reflective device having an anti-reflection surface formed of silicon spikes with nano-tips

NASA Technical Reports Server (NTRS)

Bae, Youngsman (Inventor); Mooasser, Sohrab (Inventor); Manohara, Harish (Inventor); Lee, Choonsup (Inventor); Bae, Kungsam (Inventor)

2009-01-01

Described is a device having an anti-reflection surface. The device comprises a silicon substrate with a plurality of silicon spikes formed on the substrate. A first metallic layer is formed on the silicon spikes to form the anti-reflection surface. The device further includes an aperture that extends through the substrate. A second metallic layer is formed on the substrate. The second metallic layer includes a hole that is aligned with the aperture. A spacer is attached with the silicon substrate to provide a gap between an attached sensor apparatus. Therefore, operating as a Micro-sun sensor, light entering the hole passes through the aperture to be sensed by the sensor apparatus. Additionally, light reflected by the sensor apparatus toward the first side of the silicon substrate is absorbed by the first metallic layer and silicon spikes and is thereby prevented from being reflected back toward the sensor apparatus.

Tuning selective reflection of light by surface anchoring in cholesteric cells with oblique helicoidal structures

NASA Astrophysics Data System (ADS)

Iadlovska, Olena S.; Maxwell, Graham R.; Babakhanova, Greta; Mehl, Georg H.; Welch, Christopher; Shiyanovskii, Sergij V.; Lavrentovich, Oleg D.

2018-04-01

Selective reflection of light by oblique helicoidal cholesteric (ChOH) can be tuned in a very broad spectral range by an applied electric field. In this work, we demonstrate that the peak wavelength of the selective reflection can be controlled by surface alignment of the director in sandwich cells. The peak wavelength is blue-shifted when the surface alignment is perpendicular to the bounding plates and red-shifted when it is planar. The effect is explained by the electric field redistribution within the cell caused by spatially varying heliconical ChOH structure. The observed phenomenon can be used in sensing applications.

Innovative roadway light source and dye combinations to improve visibility and reduce environmental impacts.

DOT National Transportation Integrated Search

2013-04-01

Sky glow light pollution is caused largely by reflected light off of roadway and other surfaces. The : authors investigated the feasibility of a system consisting of a specialized LED streetlight and a dyebased : roadway surface coating that would re...

Filter Enhances Fluorescent-Penetrant-Inspecting Borescope

NASA Technical Reports Server (NTRS)

Molina, Orlando G.

1990-01-01

Slip-on eyepiece for commercial ultraviolet-light borescope reduces both amount of short-wave ultraviolet light that reaches viewer's eye and apparent intensity of unwanted reflections of white light from surfaces undergoing inspection. Fits on stock eyepiece of borescope, which illuminates surface inspected with intense ultraviolet light. Surface, which is treated with fluorescent dye, emits bright-green visible light wherever dye penetrates - in cracks and voids. Eyepiece contains deep-yellow Wratten 15 (G) filter, which attenuates unwanted light strongly but passes yellow-green fluorescence so defects seen clearly.

Local surface curvature analysis based on reflection estimation

NASA Astrophysics Data System (ADS)

Lu, Qinglin; Laligant, Olivier; Fauvet, Eric; Zakharova, Anastasia

2015-07-01

In this paper, we propose a novel reflection based method to estimate the local orientation of a specular surface. For a calibrated scene with a fixed light band, the band is reflected by the surface to the image plane of a camera. Then the local geometry between the surface and reflected band is estimated. Firstly, in order to find the relationship relying the object position, the object surface orientation and the band reflection, we study the fundamental theory of the geometry between a specular mirror surface and a band source. Then we extend our approach to the spherical surface with arbitrary curvature. Experiments are conducted with mirror surface and spherical surface. Results show that our method is able to obtain the local surface orientation merely by measuring the displacement and the form of the reflection.

Increased efficiency with surface texturing in ITO/InP solar cells

NASA Technical Reports Server (NTRS)

Jenkins, Phillip; Landis, Geoffrey A.; Fatemi, Navid; Li, Xiaonan; Scheiman, David; Bailey, Sheila

1992-01-01

Optimization of an InP solar cell with a V-grooved surface is discussed. Total internal reflection in the coverglass reduces surface reflection and can recover light reflected from the front metallization. Results from the first ITO/InP solar cells on low-angle V-grooved substrates are presented, showing a 5.8 percent increase in current.

Earth's Reflection: Albedo

ERIC Educational Resources Information Center

Gillette, Brandon; Hamilton, Cheri

2011-01-01

When viewing objects of different colors, you might notice that some appear brighter than others. This is because light is reflected differently from various surfaces, depending on their physical properties. The word "albedo" is used to describe how reflective a surface is. The Earth-atmosphere has a combined albedo of about 30%, a number that is…

Specular Reflection from Rough Surfaces Revisited

ERIC Educational Resources Information Center

Yasuda, Kensei; Kim, Alvin; Cho, Hayley; Timofejev, Timofej; Walecki, Wojciech J.; Klep, James; Edelson, Amy S.; Walecki, Abigail S.; Walecki, Eve S.; Walecki, Peter S.

2016-01-01

In his beautiful paper, Hasan Fakhruddin reported observations of mirror-like reflections in the rough surface of a ground glass plate. Similar effects have been recently employed for metrology of the roughness of optical diffusers used in modern light emitting device illumination systems. We report the observations of specular reflection in…

Polarization and Color Filtering Applied to Enhance Photogrammetric Measurements of Reflective Surfaces

NASA Technical Reports Server (NTRS)

Wells, Jeffrey M.; Jones, Thomas W.; Danehy, Paul M.

2005-01-01

Techniques for enhancing photogrammetric measurement of reflective surfaces by reducing noise were developed utilizing principles of light polarization. Signal selectivity with polarized light was also compared to signal selectivity using chromatic filters. Combining principles of linear cross polarization and color selectivity enhanced signal-to-noise ratios by as much as 800 fold. More typical improvements with combining polarization and color selectivity were about 100 fold. We review polarization-based techniques and present experimental results comparing the performance of traditional retroreflective targeting materials, cornercube targets returning depolarized light, and color selectivity.

Structure for monolithic optical circuits

NASA Technical Reports Server (NTRS)

Evanchuk, Vincent L. (Inventor)

1984-01-01

A method for making monolithic optical circuits, with related optical devices as required or desired, on a supporting surface (10) consists of coating the supporting surface with reflecting metal or cladding resin, spreading a layer of liquid radiation sensitive plastic (12) on the surface, exposing the liquid plastic with a mask (14) to cure it in a desired pattern of light conductors (16, 18, 20), washing away the unexposed liquid plastic, and coating the conductors thus formed with reflective metal or cladding resin. The index of refraction for the cladding (22) is selected to be lower than for the conductors so that light in the conductors will be reflected by the interface with the cladding. For multiple level conductors, as where one conductor must cross over another, the process may be repeated to fabricate a bridge with columns (24, 26) of conductors to the next level, and conductor (28) between the columns. For more efficient transfer of energy over the bridge, faces at 45.degree. may be formed to reflect light up and across the bridge.

A real-time photo-realistic rendering algorithm of ocean color based on bio-optical model

NASA Astrophysics Data System (ADS)

Ma, Chunyong; Xu, Shu; Wang, Hongsong; Tian, Fenglin; Chen, Ge

2016-12-01

A real-time photo-realistic rendering algorithm of ocean color is introduced in the paper, which considers the impact of ocean bio-optical model. The ocean bio-optical model mainly involves the phytoplankton, colored dissolved organic material (CDOM), inorganic suspended particle, etc., which have different contributions to absorption and scattering of light. We decompose the emergent light of the ocean surface into the reflected light from the sun and the sky, and the subsurface scattering light. We establish an ocean surface transmission model based on ocean bidirectional reflectance distribution function (BRDF) and the Fresnel law, and this model's outputs would be the incident light parameters of subsurface scattering. Using ocean subsurface scattering algorithm combined with bio-optical model, we compute the scattering light emergent radiation in different directions. Then, we blend the reflection of sunlight and sky light to implement the real-time ocean color rendering in graphics processing unit (GPU). Finally, we use two kinds of radiance reflectance calculated by Hydrolight radiative transfer model and our algorithm to validate the physical reality of our method, and the results show that our algorithm can achieve real-time highly realistic ocean color scenes.

Laser-scanned fluorescence of nonlased/normal, lased/normal, nonlased/carious, and lased/carious enamel

NASA Astrophysics Data System (ADS)

Zakariasen, Kenneth L.; Barron, Joseph R.; Paton, Barry E.

1992-06-01

Research has shown that low levels of CO2 laser irradiation raise enamel resistance to sub-surface demineralization. Additionally, laser scanned fluorescence analysis of enamel, as well a laser and white light reflection studies, have potential for both clinical diagnosis and comparative research investigations of the caries process. This study was designed to compare laser fluorescence and laser/white light reflection of (1) non-lased/normal with lased/normal enamel and (2) non-lased/normal with non-lased/carious and lased/carious enamel. Specimens were buccal surfaces of extracted third molars, coated with acid resistant varnish except for either two or three 2.25 mm2 windows (two window specimens: non-lased/normal, lased/normal--three window specimens: non-lased/normal, non-lased carious, lased/carious). Teeth exhibiting carious windows were immersed in a demineralizing solution for twelve days. Non-carious windows were covered with wax during immersion. Following immersion, the wax was removed, and fluorescence and laser/white light reflection analyses were performed on all windows utilizing a custom scanning laser fluorescence spectrometer which focuses light from a 25 mWatt He-Cd laser at 442 nm through an objective lens onto a cross-section >= 3 (mu) in diameter. For laser/white light reflection analyses, reflected light intensities were measured. A HeNe laser was used for laser light reflection studies. Following analyses, the teeth are sectioned bucco-lingually into 80 micrometers sections, examined under polarized light microscopy, and the lesions photographed. This permits comparison between fluorescence/reflected light values and the visualized decalcification areas for each section, and thus comparisons between various enamel treatments and normal enamel. The enamel specimens are currently being analyzed.

Bidirectional reflectance distribution function of Spectralon white reflectance standard illuminated by incoherent unpolarized and plane-polarized light.

PubMed

Bhandari, Anak; Hamre, Børge; Frette, Øvynd; Zhao, Lu; Stamnes, Jakob J; Kildemo, Morten

2011-06-01

A Lambert surface would appear equally bright from all observation directions regardless of the illumination direction. However, the reflection from a randomly scattering object generally has directional variation, which can be described in terms of the bidirectional reflectance distribution function (BRDF). We measured the BRDF of a Spectralon white reflectance standard for incoherent illumination at 405 and 680 nm with unpolarized and plane-polarized light from different directions of incidence. Our measurements show deviations of the BRDF for the Spectralon white reflectance standard from that of a Lambertian reflector that depend both on the angle of incidence and the polarization states of the incident light and detected light. The non-Lambertian reflection characteristics were found to increase more toward the direction of specular reflection as the angle of incidence gets larger.

Polarization selecting optical element using a porro prism incorporating a thin film polarizer in a single element

DOEpatents

Hendrix, James Lee

2001-05-08

A Porro prism and a light polarizer are combined in a single optical element termed a Hendrix Prism. The design provides retro-reflection of incoming light of a predetermined polarization in a direction anti-parallel to the direction of light incidence, while reflecting undesired light, i.e., that having a polarization orthogonal to the predetermined polarization, from the surface of the light polarizer. The undesired light is reflected in a direction that does not interfere with the intended operation of the device in which the Hendrix Prism is installed yet provides feedback to the system in which it is used.

Sheet-like chiro-optical material designs based C(Y) surfaces

NASA Astrophysics Data System (ADS)

Saba, M.; Robisch, A.-L.; Thiel, M.; Hess, O.; Schroeder-Turk, Gerd E.

2017-04-01

A spatial structure for which mirror reflection cannot be represented by rotations and translations is chiral. For photonic crystals and metamaterials, chirality implies the possibility of circular dichroism, that is, that the propagation of left-circularly polarized light may differ from that of right-circularly polarized light. Here we draw attention to chiral sheet- or surface-like geometries based on chiral triply-periodic minimal surfaces. Specifically we analyse two photonic crystal designs based on the C(Y) minimal surface, by band structure analysis and by scattering matrix calculations of the reflection coefficient, for high-dielectric contrasts.

High dynamic range fringe acquisition: A novel 3-D scanning technique for high-reflective surfaces

NASA Astrophysics Data System (ADS)

Jiang, Hongzhi; Zhao, Huijie; Li, Xudong

2012-10-01

This paper presents a novel 3-D scanning technique for high-reflective surfaces based on phase-shifting fringe projection method. High dynamic range fringe acquisition (HDRFA) technique is developed to process the fringe images reflected from the shiny surfaces, and generates a synthetic fringe image by fusing the raw fringe patterns, acquired with different camera exposure time and the illumination fringe intensity from the projector. Fringe image fusion algorithm is introduced to avoid saturation and under-illumination phenomenon by choosing the pixels in the raw fringes with the highest fringe modulation intensity. A method of auto-selection of HDRFA parameters is developed and largely increases the measurement automation. The synthetic fringes have higher signal-to-noise ratio (SNR) under ambient light by optimizing HDRFA parameters. Experimental results show that the proposed technique can successfully measure objects with high-reflective surfaces and is insensitive to ambient light.

Pyrolytic carbon coated black silicon

NASA Astrophysics Data System (ADS)

Shah, Ali; Stenberg, Petri; Karvonen, Lasse; Ali, Rizwan; Honkanen, Seppo; Lipsanen, Harri; Peyghambarian, N.; Kuittinen, Markku; Svirko, Yuri; Kaplas, Tommi

2016-05-01

Carbon is the most well-known black material in the history of man. Throughout the centuries, carbon has been used as a black material for paintings, camouflage, and optics. Although, the techniques to make other black surfaces have evolved and become more sophisticated with time, carbon still remains one of the best black materials. Another well-known black surface is black silicon, reflecting less than 0.5% of incident light in visible spectral range but becomes a highly reflecting surface in wavelengths above 1000 nm. On the other hand, carbon absorbs at those and longer wavelengths. Thus, it is possible to combine black silicon with carbon to create an artificial material with very low reflectivity over a wide spectral range. Here we report our results on coating conformally black silicon substrate with amorphous pyrolytic carbon. We present a superior black surface with reflectance of light less than 0.5% in the spectral range of 350 nm to 2000 nm.

Optical fiber head for providing lateral viewing

DOEpatents

Everett, Matthew J.; Colston, Billy W.; James, Dale L.; Brown, Steve; Da Silva, Luiz

2002-01-01

The head of an optical fiber comprising the sensing probe of an optical heterodyne sensing device includes a planar surface that intersects the perpendicular to axial centerline of the fiber at a polishing angle .theta.. The planar surface is coated with a reflective material so that light traveling axially through the fiber is reflected transverse to the fiber's axial centerline, and is emitted laterally through the side of the fiber. Alternatively, the planar surface can be left uncoated. The polishing angle .theta. must be no greater than 39.degree. or must be at least 51.degree.. The emitted light is reflected from adjacent biological tissue, collected by the head, and then processed to provide real-time images of the tissue. The method for forming the planar surface includes shearing the end of the optical fiber and applying the reflective material before removing the buffer that circumscribes the cladding and the core.

Sub-pixel accuracy thickness calculation of poultry fillets from scattered laser profiles

NASA Astrophysics Data System (ADS)

Jing, Hansong; Chen, Xin; Tao, Yang; Zhu, Bin; Jin, Fenghua

2005-11-01

A laser range imaging system based on the triangulation method was designed and implemented for online high-resolution thickness calculation of poultry fillets. A laser pattern was projected onto the surface of the chicken fillet for calculation of the thickness of the meat. Because chicken fillets are relatively loosely-structured material, a laser light easily penetrates the meat, and scattering occurs both at and under the surface. When laser light is scattered under the surface it is reflected back and further blurs the laser line sharpness. To accurately calculate the thickness of the object, the light transportation has to be considered. In the system, the Bidirectional Reflectance Distribution Function (BSSRDF) was used to model the light transportation and the light pattern reflected into the cameras. BSSRDF gives the reflectance of a target as a function of illumination geometry and viewing geometry. Based on this function, an empirical method has been developed and it has been proven that this method can be used to accurately calculate the thickness of the object from a scattered laser profile. The laser range system is designed as a sub-system that complements the X-ray bone inspection system for non-invasive detection of hazardous materials in boneless poultry meat with irregular thickness.

Diffuse-Illumination Systems for Growing Plants

NASA Technical Reports Server (NTRS)

May, George; Ryan, Robert

2010-01-01

Agriculture in both terrestrial and space-controlled environments relies heavily on artificial illumination for efficient photosynthesis. Plant-growth illumination systems require high photon flux in the spectral range corresponding with plant photosynthetic active radiation (PAR) (400 700 nm), high spatial uniformity to promote uniform growth, and high energy efficiency to minimize electricity usage. The proposed plant-growth system takes advantage of the highly diffuse reflective surfaces on the interior of a sphere, hemisphere, or other nearly enclosed structure that is coated with highly reflective materials. This type of surface and structure uniformly mixes discrete light sources to produce highly uniform illumination. Multiple reflections from within the domelike structures are exploited to obtain diffuse illumination, which promotes the efficient reuse of photons that have not yet been absorbed by plants. The highly reflective surfaces encourage only the plant tissue (placed inside the sphere or enclosure) to absorb the light. Discrete light sources, such as light emitting diodes (LEDs), are typically used because of their high efficiency, wavelength selection, and electronically dimmable properties. The light sources are arranged to minimize shadowing and to improve uniformity. Different wavelengths of LEDs (typically blue, green, and red) are used for photosynthesis. Wavelengths outside the PAR range can be added for plant diagnostics or for growth regulation

Hollow lensing duct

DOEpatents

Beach, Raymond J.; Honea, Eric C.; Bibeau, Camille; Mitchell, Scott; Lang, John; Maderas, Dennis; Speth, Joel; Payne, Stephen A.

2000-01-01

A hollow lensing duct to condense (intensify) light using a combination of focusing using a spherical or cylindrical lens followed by reflective waveguiding. The hollow duct tapers down from a wide input side to a narrow output side, with the input side consisting of a lens that may be coated with an antireflective coating for more efficient transmission into the duct. The inside surfaces of the hollow lens duct are appropriately coated to be reflective, preventing light from escaping by reflection as it travels along the duct (reflective waveguiding). The hollow duct has various applications for intensifying light, such as in the coupling of diode array pump light to solid state lasing materials.

Neutron imaging with lithium indium diselenide: Surface properties, spatial resolution, and computed tomography

NASA Astrophysics Data System (ADS)

Lukosi, Eric D.; Herrera, Elan H.; Hamm, Daniel S.; Burger, Arnold; Stowe, Ashley C.

2017-11-01

An array of lithium indium diselenide (LISe) scintillators were investigated for application in neutron imaging. The sensors, varying in thickness and surface roughness, were tested using both reflective and anti-reflective mounting to an aluminum window. The spatial resolution of each LISe scintillator was calculated using the knife-edge test and a modulation transfer function analysis. It was found that the anti-reflective backing case yielded higher spatial resolutions by up to a factor of two over the reflective backing case despite a reduction in measured light yield by an average of 1.97. In most cases, the use of an anti-reflective backing resulted in a higher spatial resolution than the 50 μm-thick ZnS(Cu):6 LiF comparison scintillation screen. The effect of surface roughness was not directly correlated to measured light yield or observed spatial resolution, but weighting the reflective backing case by the random surface roughness revealed that a linear relationship exists between the fractional change (RB/ARB) of the two. Finally, the LISe scintillator array was used in neutron computed tomography to investigate the features of halyomorpha halys with the reflective and anti-reflective backing.

Broadband omnidirectional antireflection coating based on subwavelength surface Mie resonators

PubMed Central

Spinelli, P.; Verschuuren, M.A.; Polman, A.

2012-01-01

Reflection is a natural phenomenon that occurs when light passes the interface between materials with different refractive index. In many applications, such as solar cells or photodetectors, reflection is an unwanted loss process. Many ways to reduce reflection from a substrate have been investigated so far, including dielectric interference coatings, surface texturing, adiabatic index matching and scattering from plasmonic nanoparticles. Here we present an entirely new concept that suppresses the reflection of light from a silicon surface over a broad spectral range. A two-dimensional periodic array of subwavelength silicon nanocylinders designed to possess strongly substrate-coupled Mie resonances yields almost zero total reflectance over the entire spectral range from the ultraviolet to the near-infrared. This new antireflection concept relies on the strong forward scattering that occurs when a scattering structure is placed in close proximity to a high-index substrate with a high optical density of states. PMID:22353722

Degrees of polarization of reflected light eliciting polarotaxis in dragonflies (Odonata), mayflies (Ephemeroptera) and tabanid flies (Tabanidae).

PubMed

Kriska, György; Bernáth, Balázs; Farkas, Róbert; Horváth, Gábor

2009-12-01

With few exceptions insects whose larvae develop in freshwater possess positive polarotaxis, i.e., are attracted to sources of horizontally polarized light, because they detect water by means of the horizontal polarization of light reflected from the water surface. These insects can be deceived by artificial surfaces (e.g. oil lakes, asphalt roads, black plastic sheets, dark-coloured cars, black gravestones, dark glass surfaces, solar panels) reflecting highly and horizontally polarized light. Apart from the surface characteristics, the extent of such a 'polarized light pollution' depends on the illumination conditions, direction of view, and the threshold p* of polarization sensitivity of a given aquatic insect species. p* means the minimum degree of linear polarization p of reflected light that can elicit positive polarotaxis from a given insect species. Earlier there were no quantitative data on p* in aquatic insects. The aim of this work is to provide such data. Using imaging polarimetry in the red, green and blue parts of the spectrum, in multiple-choice field experiments we measured the threshold p* of ventral polarization sensitivity in mayflies, dragonflies and tabanid flies, the positive polarotaxis of which has been shown earlier. In the blue (450nm) spectral range, for example, we obtained the following thresholds: dragonflies: Enallagma cyathigerum (0%

Optical properties of micromachined polysilicon reflective surfaces with etching holes

NASA Astrophysics Data System (ADS)

Zou, Jun; Byrne, Colin; Liu, Chang; Brady, David J.

1998-08-01

MUMPS (Multi-User MEMS Process) is receiving increasingly wide use in micro optics. We have investigated the optical properties of the polysilicon reflective surface in a typical MUMPS chip within the visible light spectrum. The effect of etching holes on the reflected laser beam is studied. The reflectivity and diffraction patterns at five different wavelengths have been measured. The optical properties of the polysilicon reflective surface are greatly affected by the surface roughness, the etching holes, as well as the material. The etching holes contribute to diffraction and reduction of reflectivity. This study provides a basis for optimal design of micromachined free-space optical systems.

Design of a solar concentrator considering arbitrary surfaces

NASA Astrophysics Data System (ADS)

Jiménez-Rodríguez, Martín.; Avendaño-Alejo, Maximino; Verduzco-Grajeda, Lidia Elizabeth; Martínez-Enríquez, Arturo I.; García-Díaz, Reyes; Díaz-Uribe, Rufino

2017-10-01

We study the propagation of light in order to efficiently redirect the reflected light on photocatalytic samples placed inside a commercial solar simulator, and we have designed a small-scale prototype of Cycloidal Collectors (CCs), resembling a compound parabolic collector. The prototype consists of either cycloidal trough or cycloidal collector having symmetry of rotation, which has been designed considering an exact ray tracing assuming a bundle of rays propagating parallel to the optical axis and impinging on a curate cycloidal surface, obtaining its caustic surface produced by reflection.

Surface-plasmon mediated total absorption of light into silicon.

PubMed

Yoon, Jae Woong; Park, Woo Jae; Lee, Kyu Jin; Song, Seok Ho; Magnusson, Robert

2011-10-10

We report surface-plasmon mediated total absorption of light into a silicon substrate. For an Au grating on Si, we experimentally show that a surface-plasmon polariton (SPP) excited on the air/Au interface leads to total absorption with a rate nearly 10 times larger than the ohmic damping rate of collectively oscillating free electrons in the Au film. Rigorous numerical simulations show that the SPP resonantly enhances forward diffraction of light to multiple orders of lossy waves in the Si substrate with reflection and ohmic absorption in the Au film being negligible. The measured reflection and phase spectra reveal a quantitative relation between the peak absorbance and the associated reflection phase change, implying a resonant interference contribution to this effect. An analytic model of a dissipative quasi-bound resonator provides a general formula for the resonant absorbance-phase relation in excellent agreement with the experimental results.

Engineering design of sub-micron topographies for simultaneously adherent and reflective metal-polymer interfaces

NASA Technical Reports Server (NTRS)

Brown, Christopher A.

1993-01-01

The approach of the project is to base the design of multi-function, reflective topographies on the theory that topographically dependent phenomena react with surfaces and interfaces at certain scales. The first phase of the project emphasizes the development of methods for understanding the sizes of topographic features which influence reflectivity. Subsequent phases, if necessary, will address the scales of interaction for adhesion and manufacturing processes. A simulation of the interaction of electromagnetic radiation, or light, with a reflective surface is performed using specialized software. Reflectivity of the surface as a function of scale is evaluated and the results from the simulation are compared with reflectivity measurements made on multi-function, reflective surfaces.

System and technique for retrieving depth information about a surface by projecting a composite image of modulated light patterns

NASA Technical Reports Server (NTRS)

Hassebrook, Laurence G. (Inventor); Lau, Daniel L. (Inventor); Guan, Chun (Inventor)

2010-01-01

A technique, associated system and program code, for retrieving depth information about at least one surface of an object, such as an anatomical feature. Core features include: projecting a composite image comprising a plurality of modulated structured light patterns, at the anatomical feature; capturing an image reflected from the surface; and recovering pattern information from the reflected image, for each of the modulated structured light patterns. Pattern information is preferably recovered for each modulated structured light pattern used to create the composite, by performing a demodulation of the reflected image. Reconstruction of the surface can be accomplished by using depth information from the recovered patterns to produce a depth map/mapping thereof. Each signal waveform used for the modulation of a respective structured light pattern, is distinct from each of the other signal waveforms used for the modulation of other structured light patterns of a composite image; these signal waveforms may be selected from suitable types in any combination of distinct signal waveforms, provided the waveforms used are uncorrelated with respect to each other. The depth map/mapping to be utilized in a host of applications, for example: displaying a 3-D view of the object; virtual reality user-interaction interface with a computerized device; face--or other animal feature or inanimate object--recognition and comparison techniques for security or identification purposes; and 3-D video teleconferencing/telecollaboration.

System and technique for retrieving depth information about a surface by projecting a composite image of modulated light patterns

NASA Technical Reports Server (NTRS)

Guan, Chun (Inventor); Hassebrook, Laurence G. (Inventor); Lau, Daniel L. (Inventor)

2008-01-01

A technique, associated system and program code, for retrieving depth information about at least one surface of an object. Core features include: projecting a composite image comprising a plurality of modulated structured light patterns, at the object; capturing an image reflected from the surface; and recovering pattern information from the reflected image, for each of the modulated structured light patterns. Pattern information is preferably recovered for each modulated structured light pattern used to create the composite, by performing a demodulation of the reflected image. Reconstruction of the surface can be accomplished by using depth information from the recovered patterns to produce a depth map/mapping thereof. Each signal waveform used for the modulation of a respective structured light pattern, is distinct from each of the other signal waveforms used for the modulation of other structured light patterns of a composite image; these signal waveforms may be selected from suitable types in any combination of distinct signal waveforms, provided the waveforms used are uncorrelated with respect to each other. The depth map/mapping to be utilized in a host of applications, for example: displaying a 3-D view of the object; virtual reality user-interaction interface with a computerized device; face--or other animal feature or inanimate object--recognition and comparison techniques for security or identification purposes; and 3-D video teleconferencing/telecollaboration.

Light Reflection from Water Surfaces Perturbed by Falling Rain Droplets

ERIC Educational Resources Information Center

Molesini, Giuseppe; Vannoni, Maurizio

2009-01-01

An account of peculiar light patterns produced by reflection in a pool under falling rain droplets was recently reported by Molesini and Vannoni (2008 Eur. J. Phys. 29 403-11). The mathematical approach, however, only covered the case of a symmetrical location of a light source and the observer's eyes with respect to the vertical of the falling…

The effects of surface structure mutations in Arabidopsis thaliana on the polarization of reflections from virus-infected leaves.

PubMed

Maxwell, D J; Partridge, J C; Roberts, N W; Boonham, N; Foster, G D

2017-01-01

The way in which light is polarized when reflected from leaves can be affected by infection with plant viruses. This has the potential to influence viral transmission by insect vectors due to altered visual attractiveness of infected plants. The optical and topological properties of cuticular waxes and trichomes are important determinants of how light is polarized upon reflection. Changes in expression of genes involved in the formation of surface structures have also been reported following viral infection. This paper investigates the role of altered surface structures in virus-induced changes to polarization reflection from leaves. The percentage polarization of reflections from Arabidopsis thaliana cer5, cer6 and cer8 wax synthesis mutants, and the gl1 leaf hair mutant, was compared to those from wild-type (WT) leaves. The cer5 mutant leaves were less polarizing than WT on the adaxial and abaxial surfaces; gl1 leaves were more polarizing than WT on the adaxial surfaces. The cer6 and cer8 mutations did not significantly affect polarization reflection. The impacts of Turnip vein clearing virus (TVCV) infection on the polarization of reflected light were significantly affected by cer5 mutation, with the reflections from cer5 mutants being higher than those from WT leaves, suggesting that changes in CER5 expression following infection could influence the polarization of the reflections. There was, however, no significant effect of the gl1 mutation on polarization following TVCV infection. The cer5 and gl1 mutations did not affect the changes in polarization following Cucumber mosaic virus (CMV) infection. The accumulation of TVCV and CMV did not differ significantly between mutant and WT leaves, suggesting that altered expression of surface structure genes does not significantly affect viral titres, raising the possibility that if such regulatory changes have any adaptive value it may possibly be through impacts on viral transmission.

Rayleigh and Wood anomalies in the diffraction of light from a perfectly conducting reflection grating

NASA Astrophysics Data System (ADS)

Maradudin, A. A.; Simonsen, I.; Polanco, J.; Fitzgerald, R. M.

2016-02-01

By means of a modal method we have calculated the angular dependence of the reflectivity and the efficiencies of several other diffracted orders of a perfectly conducting lamellar reflection grating illuminated by p-polarized light. These dependencies display the signatures of Rayleigh and Wood anomalies, usually associated with diffraction from a metallic grating. The Wood anomalies here are caused by the excitation of the surface electromagnetic waves supported by a periodically corrugated perfectly conducting surface, whose dispersion curves in both the nonradiative and radiative regions of the frequency-wavenumber plane are calculated.

Fabrication of spherical mitigation pit on KH2PO4 crystal by micro-milling and modeling of its induced light intensification.

PubMed

Cheng, Jian; Chen, Mingjun; Liao, Wei; Wang, Haijun; Xiao, Yong; Li, Mingquan

2013-07-15

Micro-machining is the most promising method for KH(2)PO(4) crystal to mitigate the surface damage growth in high power laser system. In this work, spherical mitigation pit is fabricated by micro-milling with an efficient machining procedure. The light intensification caused by rear surface features before and after mitigation is numerically modeled based on the finite-difference time-domain method. The results indicate that the occurrence of total internal reflections should be responsible for the largest light intensification inside the crystal. For spherical pits after mitigation, the light intensification can be greatly alleviated by preventing the occurrence of total internal reflections. The light intensification caused by spherical mitigation pit is strongly dependent on the width-depth ratio and it is suggested that the width-depth ratio of spherical mitigation pit must be devised to be larger than 5.0 to achieve the minimal light intensification for the mitigation of surface damage growth. Laser damage tests for KH(2)PO(4) crystal validate that the laser damage resistance of initially damaged surface can be retrieved to near the level of ideal surface by replacing initial damage site with predesigned mitigation pit.

Modular wide spectrum lighting system for diagnosis, conservation, and restoration

NASA Astrophysics Data System (ADS)

Miccoli, Matteo; Melis, Marcello

2013-05-01

In the framework of imaging, lighting systems have always played a key role due to the primary importance of both the uniformity of the illumination and the richness of the emitted spectra. Multispectral imaging, i.e. imaging systems working inside and outside the visible wavelength range, are even more demanding and require to pay further attention to a number of parameters characterizing the lighting system. A critical issue for lighting systems, even in the visible light, is the shape of the emitted spectra and (only in the visible range) the Color Rendering Index. The color we perceive from a surface is our eyes' interpretation of the linear spectral combination of the illuminant spectrum and the surface spectral reflectance. If there is a lack of energy in a portion of the visible spectrum, that portion will turn into black to our eyes (and to whatever instrument) regardless the actual reflectance of the surface. In other words a lack in the exciting energy hides part of the spectral reflectance of the observed subject. Furthermore, the wider is the investigated spectrum, the fewer are the sources of light able to cover such a range. In this paper we show how we solved both the problems of the not uniformity of the light beam, independently on the incident angle, and of the selection of a light source with energy rich and continuous enough emitted spectrum.

Unexpected Attraction of Polarotactic Water-Leaving Insects to Matt Black Car Surfaces: Mattness of Paintwork Cannot Eliminate the Polarized Light Pollution of Black Cars

PubMed Central

Blaho, Miklos; Herczeg, Tamas; Kriska, Gyorgy; Egri, Adam; Szaz, Denes; Farkas, Alexandra; Tarjanyi, Nikolett; Czinke, Laszlo; Barta, Andras; Horvath, Gabor

2014-01-01

The horizontally polarizing surface parts of shiny black cars (the reflection-polarization characteristics of which are similar to those of water surfaces) attract water-leaving polarotactic insects. Thus, shiny black cars are typical sources of polarized light pollution endangering water-leaving insects. A new fashion fad is to make car-bodies matt black or grey. Since rough (matt) surfaces depolarize the reflected light, one of the ways of reducing polarized light pollution is to make matt the concerned surface. Consequently, matt black/grey cars may not induce polarized light pollution, which would be an advantageous feature for environmental protection. To test this idea, we performed field experiments with horizontal shiny and matt black car-body surfaces laid on the ground. Using imaging polarimetry, in multiple-choice field experiments we investigated the attractiveness of these test surfaces to various water-leaving polarotactic insects and obtained the following results: (i) The attractiveness of black car-bodies to polarotactic insects depends in complex manner on the surface roughness (shiny, matt) and species (mayflies, dolichopodids, tabanids). (ii) Non-expectedly, the matt dark grey car finish is much more attractive to mayflies (being endangered and protected in many countries) than matt black finish. (iii) The polarized light pollution of shiny black cars usually cannot be reduced with the use of matt painting. On the basis of these, our two novel findings are that (a) matt car-paints are highly polarization reflecting, and (b) these matt paints are not suitable to repel polarotactic insects. Hence, the recent technology used to make matt the car-bodies cannot eliminate or even can enhance the attractiveness of black/grey cars to water-leaving insects. Thus, changing shiny black car painting to matt one is a disadvantageous fashion fad concerning the reduction of polarized light pollution of black vehicles. PMID:25076137

Unexpected attraction of polarotactic water-leaving insects to matt black car surfaces: mattness of paintwork cannot eliminate the polarized light pollution of black cars.

PubMed

Blaho, Miklos; Herczeg, Tamas; Kriska, Gyorgy; Egri, Adam; Szaz, Denes; Farkas, Alexandra; Tarjanyi, Nikolett; Czinke, Laszlo; Barta, Andras; Horvath, Gabor

2014-01-01

The horizontally polarizing surface parts of shiny black cars (the reflection-polarization characteristics of which are similar to those of water surfaces) attract water-leaving polarotactic insects. Thus, shiny black cars are typical sources of polarized light pollution endangering water-leaving insects. A new fashion fad is to make car-bodies matt black or grey. Since rough (matt) surfaces depolarize the reflected light, one of the ways of reducing polarized light pollution is to make matt the concerned surface. Consequently, matt black/grey cars may not induce polarized light pollution, which would be an advantageous feature for environmental protection. To test this idea, we performed field experiments with horizontal shiny and matt black car-body surfaces laid on the ground. Using imaging polarimetry, in multiple-choice field experiments we investigated the attractiveness of these test surfaces to various water-leaving polarotactic insects and obtained the following results: (i) The attractiveness of black car-bodies to polarotactic insects depends in complex manner on the surface roughness (shiny, matt) and species (mayflies, dolichopodids, tabanids). (ii) Non-expectedly, the matt dark grey car finish is much more attractive to mayflies (being endangered and protected in many countries) than matt black finish. (iii) The polarized light pollution of shiny black cars usually cannot be reduced with the use of matt painting. On the basis of these, our two novel findings are that (a) matt car-paints are highly polarization reflecting, and (b) these matt paints are not suitable to repel polarotactic insects. Hence, the recent technology used to make matt the car-bodies cannot eliminate or even can enhance the attractiveness of black/grey cars to water-leaving insects. Thus, changing shiny black car painting to matt one is a disadvantageous fashion fad concerning the reduction of polarized light pollution of black vehicles.

Motion of glossy objects does not promote separation of lighting and surface colour

PubMed Central

2017-01-01

The surface properties of an object, such as texture, glossiness or colour, provide important cues to its identity. However, the actual visual stimulus received by the eye is determined by both the properties of the object and the illumination. We tested whether operational colour constancy for glossy objects (the ability to distinguish changes in spectral reflectance of the object, from changes in the spectrum of the illumination) was affected by rotational motion of either the object or the light source. The different chromatic and geometric properties of the specular and diffuse reflections provide the basis for this discrimination, and we systematically varied specularity to control the available information. Observers viewed animations of isolated objects undergoing either lighting or surface-based spectral transformations accompanied by motion. By varying the axis of rotation, and surface patterning or geometry, we manipulated: (i) motion-related information about the scene, (ii) relative motion between the surface patterning and the specular reflection of the lighting, and (iii) image disruption caused by this motion. Despite large individual differences in performance with static stimuli, motion manipulations neither improved nor degraded performance. As motion significantly disrupts frame-by-frame low-level image statistics, we infer that operational constancy depends on a high-level scene interpretation, which is maintained in all conditions. PMID:29291113

Space Object Classification and Characterization Via Multiple Model Adaptive Estimation

DTIC Science & Technology

2014-07-14

BRDF ) which models light distribution scattered from the surface due to the incident light. The BRDF at any point on the surface is a function of two...uu B vu B nu obs I u sun I u I hu (b) Reflection Geometry Fig. 2: Reflection Geometry and Space Object Shape Model of the BRDF is ρdiff(i...Space Object Classification and Characterization Via Multiple Model Adaptive Estimation Richard Linares Director’s Postdoctoral Fellow Space Science

Fiber optic inclination detector system having a weighted sphere with reference points

DOEpatents

Cwalinski, Jeffrey P.

1995-01-01

A fiber optic inclination detector system for determining the angular displacement of an object from a reference surface includes a simple mechanical transducer which requires a minimum number of parts and no electrical components. The system employs a single light beam which is split into two light beams and provided to the transducer. Each light beam is amplitude modulated upon reflecting off the transducer to detect inclination. The power values associated with each of the reflected light beams are converted by a pair of photodetectors into voltage signals, and a microprocessor manipulates the voltage signals to provide a measure of the angular displacement between the object and the reference surface.

System and process for detecting and monitoring surface defects

NASA Technical Reports Server (NTRS)

Mueller, Mark K. (Inventor)

1994-01-01

A system and process for detecting and monitoring defects in large surfaces such as the field joints of the container segments of a space shuttle booster motor. Beams of semi-collimated light from three non-parallel fiber optic light panels are directed at a region of the surface at non-normal angles of expected incidence. A video camera gathers some portion of the light that is reflected at an angle other than the angle of expected reflectance, and generates signals which are analyzed to discern defects in the surface. The analysis may be performed by visual inspection of an image on a video monitor, or by inspection of filtered or otherwise processed images. In one alternative embodiment, successive predetermined regions of the surface are aligned with the light source before illumination, thereby permitting efficient detection of defects in a large surface. Such alignment is performed by using a line scan gauge to sense the light which passes through an aperture in the surface. In another embodiment a digital map of the surface is created, thereby permitting the maintenance of records detailing changes in the location or size of defects as the container segment is refurbished and re-used. The defect detection apparatus may also be advantageously mounted on a fixture which engages the edge of a container segment.

Real-time defect detection on highly reflective curved surfaces

NASA Astrophysics Data System (ADS)

Rosati, G.; Boschetti, G.; Biondi, A.; Rossi, A.

2009-03-01

This paper presents an automated defect detection system for coated plastic components for the automotive industry. This research activity came up as an evolution of a previous study which employed a non-flat mirror to illuminate and inspect high reflective curved surfaces. According to this method, the rays emitted from a light source are conveyed on the surface under investigation by means of a suitably curved mirror. After the reflection on the surface, the light rays are collected by a CCD camera, in which the coating defects appear as shadows of various shapes and dimensions. In this paper we present an evolution of the above-mentioned method, introducing a simplified mirror set-up in order to reduce the costs and the complexity of the defect detection system. In fact, a set of plane mirrors is employed instead of the curved one. Moreover, the inspection of multiple bend radius parts is investigated. A prototype of the machine vision system has been developed in order to test this simplified method. This device is made up of a light projector, a set of plane mirrors for light rays reflection, a conveyor belt for handling components, a CCD camera and a desktop PC which performs image acquisition and processing. Like in the previous system, the defects are identified as shadows inside a high brightness image. At the end of the paper, first experimental results are presented.

Optical-diffraction method for determining crystal orientation

DOEpatents

Sopori, B.L.

1982-05-07

Disclosed is an optical diffraction technique for characterizing the three-dimensional orientation of a crystal sample. An arbitrary surface of the crystal sample is texture etched so as to generate a pseudo-periodic diffraction grating on the surface. A laser light beam is then directed onto the etched surface, and the reflected light forms a farfield diffraction pattern in reflection. Parameters of the diffraction pattern, such as the geometry and angular dispersion of the diffracted beam are then related to grating shape of the etched surface which is in turn related to crystal orientation. This technique may be used for examining polycrystalline silicon for use in solar cells.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kidane, Getnet S; Desilva, Upul P.; He, Chengli

A gas turbine includes first and second parts having outer surfaces located adjacent to each other to create an interface where wear occurs. A wear probe is provided for monitoring wear of the outer surface of the first part, and includes an optical guide having first and second ends, wherein the first end is configured to be located flush with the outer surface of the first part. A fiber bundle includes first and second ends, the first end being located proximate to the second end of the optical guide. The fiber bundle includes a transmit fiber bundle comprising a firstmore » plurality of optical fibers coupled to a light source, and a receive fiber bundle coupled to a light detector and configured to detect reflected light. A processor is configured to determine a length of the optical guide based on the detected reflected light.« less

An automatic detection software for differential reflection spectroscopy

NASA Astrophysics Data System (ADS)

Yuksel, Seniha Esen; Dubroca, Thierry; Hummel, Rolf E.; Gader, Paul D.

2012-06-01

Recent terrorist attacks have sprung a need for a large scale explosive detector. Our group has developed differential reflection spectroscopy which can detect explosive residue on surfaces such as parcel, cargo and luggage. In short, broad band ultra-violet and visible light is shone onto a material (such as a parcel) moving on a conveyor belt. Upon reflection off the surface, the light intensity is recorded with a spectrograph (spectrometer in combination with a CCD camera). This reflected light intensity is then subtracted and normalized with the next data point collected, resulting in differential reflection spectra in the 200-500 nm range. Explosives show spectral finger-prints at specific wavelengths, for example, the spectrum of 2,4,6, trinitrotoluene (TNT) shows an absorption edge at 420 nm. Additionally, we have developed an automated software which detects the characteristic features of explosives. One of the biggest challenges for the algorithm is to reach a practical limit of detection. In this study, we introduce our automatic detection software which is a combination of principal component analysis and support vector machines. Finally we present the sensitivity and selectivity response of our algorithm as a function of the amount of explosive detected on a given surface.

Surface optical vortices

NASA Astrophysics Data System (ADS)

Lembessis, V. E.; Babiker, M.; Andrews, D. L.

2009-01-01

It is shown how the total internal reflection of orbital-angular-momentum-endowed light can lead to the generation of evanescent light possessing rotational properties in which the intensity distribution is firmly localized in the vicinity of the surface. The characteristics of these surface optical vortices depend on the form of the incident light and on the dielectric mismatch of the two media. The interference of surface optical vortices is shown to give rise to interesting phenomena, including pattern rotation akin to a surface optical Ferris wheel. Applications are envisaged to be in atom lithography, optical surface tweezers, and spanners.

Bidirectional reflectance distribution function based surface modeling of non-Lambertian using intensity data of light detection and ranging.

PubMed

Li, Xiaolu; Liang, Yu; Xu, Lijun

2014-09-01

To provide a credible model for light detection and ranging (LiDAR) target classification, the focus of this study is on the relationship between intensity data of LiDAR and the bidirectional reflectance distribution function (BRDF). An integration method based on the built-in-lab coaxial laser detection system was advanced. A kind of intermediary BRDF model advanced by Schlick was introduced into the integration method, considering diffuse and specular backscattering characteristics of the surface. A group of measurement campaigns were carried out to investigate the influence of the incident angle and detection range on the measured intensity data. Two extracted parameters r and S(λ) are influenced by different surface features, which illustrate the surface features of the distribution and magnitude of reflected energy, respectively. The combination of two parameters can be used to describe the surface characteristics for target classification in a more plausible way.

Coherent diffraction surface imaging in reflection geometry.

PubMed

Marathe, Shashidhara; Kim, S S; Kim, S N; Kim, Chan; Kang, H C; Nickles, P V; Noh, D Y

2010-03-29

We present a reflection based coherent diffraction imaging method which can be used to reconstruct a non periodic surface image from a diffraction amplitude measured in reflection geometry. Using a He-Ne laser, we demonstrated that a surface image can be reconstructed solely from the reflected intensity from a surface without relying on any prior knowledge of the sample object or the object support. The reconstructed phase image of the exit wave is particularly interesting since it can be used to obtain quantitative information of the surface depth profile or the phase change during the reflection process. We believe that this work will broaden the application areas of coherent diffraction imaging techniques using light sources with limited penetration depth.

Structured light stereo catadioptric scanner based on a spherical mirror

NASA Astrophysics Data System (ADS)

Barone, S.; Neri, P.; Paoli, A.; Razionale, A. V.

2018-08-01

The present paper describes the development and characterization of a structured light stereo catadioptric scanner for the omnidirectional reconstruction of internal surfaces. The proposed approach integrates two digital cameras, a multimedia projector and a spherical mirror, which is used to project the structured light patterns generated by the light emitter and, at the same time, to reflect into the cameras the modulated fringe patterns diffused from the target surface. The adopted optical setup defines a non-central catadioptric system, thus relaxing any geometrical constraint in the relative placement between optical devices. An analytical solution for the reflection on a spherical surface is proposed with the aim at modelling forward and backward projection tasks for a non-central catadioptric setup. The feasibility of the proposed active catadioptric scanner has been verified by reconstructing various target surfaces. Results demonstrated a great influence of the target surface distance from the mirror's centre on the measurement accuracy. The adopted optical configuration allows the definition of a metrological 3D scanner for surfaces disposed within 120 mm from the mirror centre.

Method of making and structure for monolithic optical circuits

NASA Technical Reports Server (NTRS)

Evanchuk, Vincent L. (Inventor)

1983-01-01

A method for making monolithic optical circuits, with related optical devices as required or desired, on a supporting surface (10) consists of coating the supporting surface with reflecting metal or cladding resin, spreading a layer of liquid radiation senstivie plastic (12) on the surface, exposing the liquid plastic with a mask (14) to cure it in a desired pattern of light conductors (16, 18, 20), washing away the unexposed liquid plastic, and coating the conductors thus formed with reflective metal or cladding resin. The index of refraction for the cladding (22) is selected to be lower than for the conductors so that light in the conductors will be reflected by the interface with the cladding. For multiple level conductors, as where one conductor must cross over another, the process may be repeated to fabricate a bridge with columns (24, 26) of conductors to the next level, and conductor (28) between the columns. For more efficient transfer of energy over the bridge, faces at 45.degree. may be formed to reflect light up and across the bridge.

Angle-resolved reflection spectroscopy of high-quality PMMA opal crystal

NASA Astrophysics Data System (ADS)

Nemtsev, Ivan V.; Tambasov, Igor A.; Ivanenko, Alexander A.; Zyryanov, Victor Ya.

2018-02-01

PMMA opal crystal was prepared by a simple hybrid method, which includes sedimentation, meniscus formation and evaporation. We investigated three surfaces of this crystal by angle-resolved reflective light spectroscopy and SEM study. The angle-resolved reflective measurements were carried out in the 400-1100 nm range. We have determined the high-quality ordered surface of the crystal region. Narrow particle size distribution of the surface has been revealed. The average particle diameter obtained with SEM was nearly 361 nm. The most interesting result was that reflectivity of the surface turned out up to 98% at normal light incidence. Using a fit of dependences of the maximum reflectivity wavelength from an angle based on the Bragg-Snell law, the wavelength of maximum 0° reflectivity, the particle diameter and the fill factor have been determined. For the best surface maximum reflectivity wavelength of a 0° angle was estimated to be 869 nm. The particle diameter and fill factor were calculated as 372 nm and 0.8715, respectively. The diameter obtained by fitting is in excellent agreement with the particle diameter obtained with SEM. The reflectivity maximum is assumed to increase significantly when increasing the fill factor. We believe that using our simple approach to manufacture PMMA opal crystals will significantly increase the fabrication of high-quality photonic crystal templates and thin films.

Ellipsometry of single-layer antireflection coatings on transparent substrates

NASA Astrophysics Data System (ADS)

Azzam, R. M. A.

2017-11-01

The complex reflection coefficients of p- and s-polarized light and ellipsometric parameters of a transparent substrate of refractive index n2, which is coated by a transparent thin film whose refractive index n1 =√{n2 } satisfies the anti-reflection condition at normal incidence, are considered as functions of film thickness d and angle of incidence ϕ. A unique coated surface, with n1 =√{n2 } and film thickness d equal to half of the film-thickness period Dϕ at angle ϕ and wavelength λ, reflects light of the same wavelength without change of polarization for all incident polarization states. (The reflection Jones matrix of such coated surface is the 2 × 2 identity matrix pre-multiplied by a scalar, hence tanΨ = 1,Δ = 0.) To monitor the deposition of an antireflection coating, the normalized Stokes parameters of obliquely reflected light (e.g. at ϕ =70∘) are measured until predetermined target values of those parameters are detected. This provides a more accurate means of film thickness control than is possible using a micro-balance technique or an intensity reflectance method.

Nanoscale silver-assisted wet etching of crystalline silicon for anti-reflection surface textures.

PubMed

Li, Rui; Wang, Shuling; Chuwongin, Santhad; Zhou, Weidong

2013-01-01

We report here an electro-less metal-assisted chemical etching (MacEtch) process as light management surface-texturing technique for single crystalline Si photovoltaics. Random Silver nanostructures were formed on top of the Si surface based on the thin film evaporation and annealing process. Significant reflection reduction was obtained from the fabricated Si sample, with approximately 2% reflection over a wide spectra range (300 to 1050 nm). The work demonstrates the potential of MacEtch process for anti-reflection surface texture fabrication of large area, high efficiency, and low cost thin film solar cell.

Polarization Of Light In The Natural Environment

NASA Astrophysics Data System (ADS)

Coulson, Kinsell L.

1990-01-01

This paper provides a characterization of the fields of light polarization with which the optical designer or user of optical devices in the natural environment must be concerned. After a brief historical outline of the principal developments in polarization theory and observations during the last two centuries, the main emphasis is on the two primary processes responsible for the polarization of light in nature--scattering of light by particles of the atmosphere and reflection from soils, vegetation, snow, and water at the earth's surface. Finally, a seven minute film on polarization effects which can be seen in everyday surroundings will be shown. Scattering by atmospheric particles is responsible for high values of polarization in various atmospheric conditions and at certain scattering geometries. Such scattering particles include molecules of the atmospheric gases, aerosols of dust, haze, and air pollution, water droplets of fog and clouds, and the ice crystals of cirrus. It is seen that development of the theory of scattering by such particles has outstripped the measurements necessary for validation of the theory, a fact which points up the importance of symposia such as the present one. The reverse is true, however, for the polarizing properties of natural surfaces. Only in the case of still water is the theory of reflection adequate to characterize in a quantitative fashion the polarizing effects produced by the reflection of light from such natural surfaces. Polarization of light by reflection from vegetation is of prime importance in a remote sensing context, but much further work is needed to characterize vegetative reflectance for the purpose. The short film on polarization effects provides a good visualization technique and training aid for students interested in the field.

Pyrolytic carbon coated black silicon

PubMed Central

Shah, Ali; Stenberg, Petri; Karvonen, Lasse; Ali, Rizwan; Honkanen, Seppo; Lipsanen, Harri; Peyghambarian, N.; Kuittinen, Markku; Svirko, Yuri; Kaplas, Tommi

2016-01-01

Carbon is the most well-known black material in the history of man. Throughout the centuries, carbon has been used as a black material for paintings, camouflage, and optics. Although, the techniques to make other black surfaces have evolved and become more sophisticated with time, carbon still remains one of the best black materials. Another well-known black surface is black silicon, reflecting less than 0.5% of incident light in visible spectral range but becomes a highly reflecting surface in wavelengths above 1000 nm. On the other hand, carbon absorbs at those and longer wavelengths. Thus, it is possible to combine black silicon with carbon to create an artificial material with very low reflectivity over a wide spectral range. Here we report our results on coating conformally black silicon substrate with amorphous pyrolytic carbon. We present a superior black surface with reflectance of light less than 0.5% in the spectral range of 350 nm to 2000 nm. PMID:27174890

Increased effective reflection and transmission at the GaN-sapphire interface of LEDs grown on patterned sapphire substrates

NASA Astrophysics Data System (ADS)

Dongxue, Wu; Ping, Ma; Boting, Liu; Shuo, Zhang; Junxi, Wang; Jinmin, Li

2016-10-01

The effect of patterned sapphire substrate (PSS) on the top-surface (P-GaN-surface) and the bottom-surface (sapphire-surface) of the light output power (LOP) of GaN-based LEDs was investigated, in order to study the changes in reflection and transmission of the GaN-sapphire interface. Experimental research and computer simulations were combined to reveal a great enhancement in LOP from either the top or bottom surface of GaN-based LEDs, which are prepared on patterned sapphire substrates (PSS-LEDs). Furthermore, the results were compared to those of the conventional LEDs prepared on the planar sapphire substrates (CSS-LEDs). A detailed theoretical analysis was also presented to further support the explanation for the increase in both the effective reflection and transmission of PSS-GaN interface layers and to explain the causes of increased LOP values. Moreover, the bottom-surface of the PSS-LED chip shows slightly increased light output performance when compared to that of the top-surface. Therefore, the light extraction efficiency (LEE) can be further enhanced by integrating the method of PSS and flip-chip structure design. Project supported by the National High Technology Program of China (No. Y48A040000) and the National High Technology Program of China (No. Y48A040000).

The continuum slope of Mars - Bidirectional reflectance investigations and applications to Olympus Mons

NASA Astrophysics Data System (ADS)

Fischer, E. M.; Pieters, C. M.

1993-04-01

Two primary causes of near-IR continuum slope variations have been observed in an investigation of the bidirectional reflectance characteristics of ferric coatings on the continuum slope of Mars. First, the presence of a thin ferric coating on a dark substrate produces a negative continuum slope due to the wavelength-dependent transparency of the ferric coating. Second, wavelength-dependent directional reflectance occurs when the surface particles are tightly packed, particle sizes are on the order of or smaller than the wavelength of light, or the surface is otherwise smooth on the order of the wavelength of light. Based on these results, the annuli on the flanks of Olympus Mons which are defined by reflectance and continuum slope are consistent with spatial variations in surface texture and possibly with spatial variations in the thickness of a ferric dust coating or rind.

Determining the Thickness and Refractive Index of a Mirror

ERIC Educational Resources Information Center

Uysal, Ahmet

2010-01-01

When a laser beam reflects from a back surface glass mirror and falls on a screen, a pattern of discrete bright spots is created by partial reflection and refraction of the light at the air-glass interface and reflection at the mirror surface (Fig. 1). This paper explains how this phenomenon can be used to determine the refractive index and the…

Simulation of laser beam reflection at the sea surface modeling and validation

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric; Repasi, Endre

2013-06-01

A 3D simulation of the reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation is suitable for the pre-calculation of images for cameras operating in different spectral wavebands (visible, short wave infrared) for a bistatic configuration of laser source and receiver for different atmospheric conditions. In the visible waveband the calculated detected total power of reflected laser light from a 660nm laser source is compared with data collected in a field trial. Our computer simulation comprises the 3D simulation of a maritime scene (open sea/clear sky) and the simulation of laser beam reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. To predict the view of a camera the sea surface radiance must be calculated for the specific waveband. Additionally, the radiances of laser light specularly reflected at the wind-roughened sea surface are modeled considering an analytical statistical sea surface BRDF (bidirectional reflectance distribution function). Validation of simulation results is prerequisite before applying the computer simulation to maritime laser applications. For validation purposes data (images and meteorological data) were selected from field measurements, using a 660nm cw-laser diode to produce laser beam reflection at the water surface and recording images by a TV camera. The validation is done by numerical comparison of measured total laser power extracted from recorded images with the corresponding simulation results. The results of the comparison are presented for different incident (zenith/azimuth) angles of the laser beam.

Fatigue zones in metals identified by polarized light photography

NASA Technical Reports Server (NTRS)

Walsh, F. D.

1967-01-01

Polarized light technique clearly defines the fatigue zones in metal for measuring and photographing. White light is passed through a vertical polarizing filter and then is reflected onto the surface of the fracture specimen.

Output-increasing, protective cover for a solar cell

DOEpatents

Hammerbacher, Milfred D.

1995-11-21

A flexible cover (14) for a flexible solar cell (12) protects the cell from the ambient and increases the cell's efficiency. The cell(12)includes silicon spheres (16) held in a flexible aluminum sheet matrix (20,22). The cover (14) is a flexible, protective layer (60) of light-transparent material having a relatively flat upper, free surface (64) and an irregular opposed surface (66). The irregular surface (66) includes first portions (68) which conform to the polar regions (31R) of the spheres (16) and second convex (72) or concave (90) portions (72 or 90) which define spaces (78) in conjunction with the reflective surface (20T) of one aluminum sheet (20). Without the cover (14) light (50) falling on the surface (20T) between the spheres (16) is wasted, that is, it does not fall on a sphere (16). The surfaces of the second portions are non-parallel to the direction of the otherwise wasted light (50), which fact, together with a selected relationship between the refractive indices of the cover and the spaces, result in sufficient diffraction of the otherwise wasted light (50) so that about 25% of it is reflected from the surface (20T) onto a sphere (16).

Shear sensitive monomer-polymer laminate structure and method of using same

NASA Technical Reports Server (NTRS)

Singh, Jag J. (Inventor); Eftekhari, Abe (Inventor); Parmar, Devendra S. (Inventor)

1993-01-01

Monomer cholesteric liquid crystals have helical structures which result in a phenomenon known as selective reflection, wherein incident white light is reflected in such a way that its wavelength is governed by the instantaneous pitch of the helix structure. The pitch is dependent on temperature and external stress fields. It is possible to use such monomers in flow visualization and temperature measurement. However, the required thin layers of these monomers are quickly washed away by a flow, making their application time dependent for a given flow rate. The laminate structure according to the present invention comprises a liquid crystal polymer substrate attached to a test surface of an article. A light absorbing coating is applied to the substrate and is thin enough to permit bonding steric interaction between the liquid crystal polymer substrate and an overlying liquid crystal monomer thin film. Light is directed through and reflected by the liquid crystal monomer thin film and unreflected light is absorbed by the underlying coating. The wavelength of the reflected light is indicative of the shear stress experienced by the test surface. Novel aspects of the invention include its firm bonding of a liquid crystal monomer to a model and its use of a coating to reduce interference from light unreflected by the monomer helical structure.

Review of the CIE system of colorimetry and its use in dentistry.

PubMed

Westland, Stephen

2003-01-01

When we observe the light reflected from surfaces in a scene or look directly at light emitted by light sources, we experience the sensation of color. Color is just one attribute of a complex and not fully understood set of properties that define the appearance of our surroundings. To measure or specify the color of an object, we need to take into account the nature of the light under which the object is viewed, the spectral reflectance properties of the surface, and the properties of the human color vision system. In this article the CIE system of colorimetry is briefly reviewed and its limitations are described. The consequences of these limitations for color measurement in dentistry are discussed.

Transparent selective illumination means suitable for use in optically activated electrical switches and optically activated electrical switches constructed using same

DOEpatents

Wilcox, R.B.

1991-09-10

A planar transparent light conducting means and an improved optically activated electrical switch made using the novel light conducting means are disclosed. The light conducting means further comprise light scattering means on one or more opposite planar surfaces thereof to transmit light from the light conducting means into adjacent media and reflective means on other surfaces of the light conducting means not containing the light scattering means. The optically activated electrical switch comprises at least two stacked photoconductive wafers, each having electrodes formed on both surfaces thereof, and separated by the planar transparent light conducting means. The light scattering means on the light conducting means face surfaces of the wafers not covered by the electrodes to transmit light from the light conducting means into the photoconductive wafers to uniformly illuminate and activate the switch. 11 figures.

Transparent selective illumination means suitable for use in optically activated electrical switches and optically activated electrical switches constructed using same

DOEpatents

Wilcox, Russell B.

1991-01-01

A planar transparent light conducting means and an improved optically activated electrical switch made using the novel light conducting means are disclosed. The light conducting means further comprise light scattering means on one or more opposite planar surfaces thereof to transmit light from the light conducting means into adjacent media and reflective means on other surfaces of the light conducting means not containing the light scattering means. The optically activated electrical switch comprises at least two stacked photoconductive wafers, each having electrodes formed on both surfaces thereof, and separated by the planar transparent light conducting means. The light scattering means on the light conducting means face surfaces of the wafers not covered by the electrodes to transmit light from the light conducting means into the photoconductive wafers to uniformly illuminate and activate the switch.

Understanding Europa's Surface Texture from Remote Sensing Photopolarimetry

NASA Astrophysics Data System (ADS)

Nelson, R. M.; Boryta, M. D.; Hapke, B. W.; Shkuratov, Y.; Vandervoort, K.; Vides, C. L.

2016-12-01

We use a Goniometric Photopolarimeter (GPP) to make angular scattering reflectance and polarization measurements of the light reflected from particulate materials that simulate a planetary regolith. We compare these laboratory results to astronomical remote sensing observations in an effort to understand the chemical and textural state of object's surface. The GPP employs the Helmholtz Reciprocity Principle (1,2) -the incident light is linearly polarized - the intensity of the reflected component is measured. The light encounters fewer optical surfaces, improving signal to noise. These lab data are physically equivalent to the astronomical data. Our reflectance and polarization phase curves of highly reflective, fine grained, media simulate the regolith of Jupiter's satellite Europa. Our laboratory data exhibit polarization phase curves that are remarkably similar to reports by experienced astronomers (4). Our previous reflectance phase curve data of the same materials also agree with the reflectance phase curves reported by same astronomical observers (5). We find these materials exhibit an increase in circular polarization ratio with decreasing phase angle (3). This suggests coherent backscattering (CB) of photons in the regolith (3). Shkuratov et al. report that the polarization properties of these particulate media are also consistent with the CB enhancement process (5). Our results replicate the astronomical data and indicate that Europa's regolith is fine-grained, highly porous with void space exceeding 90%. Future spacecraft missions to the Jovian system will enhance science return by incorporating angular scattering measurements of the reflectance and polarizatin of the surface. Minnaert, M. (1941).Asrophys. J., 93, 403-410. Hapke, B. W. (2012). ISBN 978-0-521-88349-8 Nelson, R. M. et al. (1998). Icarus, 131, 223-230. Rosenbush, V. et al. (2015). ISBN 978-1-107-04390-9, pp 340-359. Shkuratov, Yu. et al. (2002) Icarus 159, 396-416.

Bidirectional reflectance distribution function effects in ladar-based reflection tomography.

PubMed

Jin, Xuemin; Levine, Robert Y

2009-07-20

Light reflection from a surface is described by the bidirectional reflectance distribution function (BRDF). In this paper, BRDF effects in reflection tomography are studied using modeled range-resolved reflection from well-characterized geometrical surfaces. It is demonstrated that BRDF effects can cause a darkening at the interior boundary of the reconstructed surface analogous to the well-known beam hardening artifact in x-ray transmission computed tomography (CT). This artifact arises from reduced reflection at glancing incidence angles to the surface. It is shown that a purely Lambertian surface without shadowed components is perfectly reconstructed from range-resolved measurements. This result is relevant to newly fabricated carbon nanotube materials. Shadowing is shown to cause crossed streak artifacts similar to limited-angle effects in CT reconstruction. In tomographic reconstruction, these effects can overwhelm highly diffuse components in proximity to specularly reflecting elements. Diffuse components can be recovered by specialized processing, such as reducing glints via thresholded measurements.

Measurement of the curvature of a surface using parallel light beams

DOEpatents

Chason, Eric H.; Floro, Jerrold A.; Seager, Carleton H.; Sinclair, Michael B.

1999-01-01

Apparatus for measuring curvature of a surface wherein a beam of collimated light is passed through means for producing a plurality of parallel light beams each separated by a common distance which then reflect off the surface to fall upon a detector that measures the separation of the reflected beams of light. This means can be an etalon and the combination of a diffractive element and a converging lens. The curvature of the surface along the line onto which the multiple beams fall can be calculated from this information. A two-dimensional map of the curvature can be obtained by adding a second etalon (or a second combination of a diffractive element and a converging lens) which is rotated 90.degree. about the optical axis relative to the first etalon and inclined at the same angle. The second etalon creates an individual set of parallel light beams from each of the individual beams created by the first etalon with the sets of parallel light beams from the second etalon rotated 90.degree. relative to the line onto which the single set of parallel beams from the first etalon would have fallen.

Measurement of the curvature of a surface using parallel light beams

DOEpatents

Chason, E.H.; Floro, J.A.; Seager, C.H.; Sinclair, M.B.

1999-06-15

Apparatus is disclosed for measuring curvature of a surface wherein a beam of collimated light is passed through a means for producing a plurality of parallel light beams each separated by a common distance which then reflect off the surface to fall upon a detector that measures the separation of the reflected beams of light. This means can be an etalon and the combination of a diffractive element and a converging lens. The curvature of the surface along the line onto which the multiple beams fall can be calculated from this information. A two-dimensional map of the curvature can be obtained by adding a second etalon (or a second combination of a diffractive element and a converging lens) which is rotated 90[degree] about the optical axis relative to the first etalon and inclined at the same angle. The second etalon creates an individual set of parallel light beams from each of the individual beams created by the first etalon with the sets of parallel light beams from the second etalon rotated 90[degree] relative to the line onto which the single set of parallel beams from the first etalon would have fallen. 5 figs.

Optimizations for optical velocity measurements in narrow gaps

NASA Astrophysics Data System (ADS)

Schlüßler, Raimund; Blechschmidt, Christian; Czarske, Jürgen; Fischer, Andreas

2013-09-01

Measuring the flow velocity in small gaps or near a surface with a nonintrusive optical measurement technique is a challenging measurement task, as disturbing light reflections from the surface appear. However, these measurements are important, e.g., in order to understand and to design the leakage flow in the tip gap between the rotor blade end face and the housing of a turbomachine. Hence, methods to reduce the interfering light power and to correct measurement errors caused by it need to be developed and verified. Different alternatives of minimizing the interfering light power for optical flow measurements in small gaps are presented. By optimizing the beam shape of the applied illumination beam using a numerical diffraction simulation, the interfering light power is reduced by up to a factor of 100. In combination with a decrease of the reflection coefficient of the rotor blade surface, an additional reduction of the interfering light power below the used scattered light power is possible. Furthermore, a correction algorithm to decrease the measurement uncertainty of disturbed measurements is derived. These improvements enable optical three-dimensional three-component flow velocity measurements in submillimeter gaps or near a surface.

Large-aperture ground glass surface profile measurement using coherence scanning interferometry.

PubMed

Bae, Eundeok; Kim, Yunseok; Park, Sanguk; Kim, Seung-Woo

2017-01-23

We present a coherence scanning interferometer configured to deal with rough glass surfaces exhibiting very low reflectance due to severe sub-surface light scattering. A compound light source is prepared by combining a superluminescent light-emitting diode with an ytterbium-doped fiber amplifier. The light source is attuned to offer a short temporal coherence length of 15 μm but with high spatial coherence to secure an adequate correlogram contrast by delivering strongly unbalanced optical power to the low reflectance target. In addition, the infrared spectral range of the light source is shifted close to the visible side at a 1,038 nm center wavelength, so a digital camera of multi-mega pixels available for industrial machine vision can be used to improve the correlogram contrast further with better lateral image resolutions. Experimental results obtained from a ground Zerodur mirror of 200 mm aperture size and 0.9 μm rms roughness are discussed to validate the proposed interferometer system.

A finger-free wrist-worn pulse oximeter for the monitoring of chronic obstructive pulmonary disease

NASA Astrophysics Data System (ADS)

Chu, Chang-Sheng; Chuang, Shuang-Chao; Lee, Yeh Wen; Fan, Chih-Hsun; Chung, Lung Pin; Li, Yu-Tang; Chen, Jyh-Chern

2016-03-01

Herein, a finger-free wrist-worn pulse oximeter is presented. This device allows patients to measure blood oxygen level and pulse rate without hindering their normal finger movement. This wrist-worn pulse oximeter is built with a reflectance oximetry sensor, which consists of light emitting diodes and photodiode light detectors located side by side. This reflectance oximetry sensor is covered with an optical element with micro structured surface. This micro structured optical element is designed to modulate photon propagation beneath the skin tissue so that the photoplethysmogram signals of reflected lights or backscattered lights detected by the photodetector are therefore enhanced.

Spatially modulated interferometer and beam shearing device therefor

NASA Technical Reports Server (NTRS)

Reininger, Francis M. (Inventor)

2004-01-01

A spatially modulated interferometer incorporates a beam shearing system having a plurality of reflective surfaces defining separate light paths of equal optical path length for two separate output beams. The reflective surfaces are arranged such that when the two beams emerge from the beam shearing system they contain more than 50 percent of the photon flux within the selected spectral pass band. In one embodiment, the reflective surfaces are located on a number of prism elements combined to form a beam shearing prism structure. The interferometer utilizing the beam sharing system of the invention includes fore-optics for collecting light and focusing it into a beam to be sheared, and a detector located at an exit pupil of the device. In a preferred embodiment, the interferometer has no moving parts.

Monte Carlo simulation of light reflection from cosmetic powders on the skin

NASA Astrophysics Data System (ADS)

Okamoto, Takashi; Motoda, Masafumi; Igarashi, Takanori; Nakao, Keisuke

2011-07-01

The reflection and scattering properties of light incident on skin covered with powder particles have been investigated. A three-layer skin structure with a spot is modeled, and the propagation of light in the skin and the scattering of light by particles on the skin surface are simulated by means of a Monte Carlo method. Under the condition in which only single scattering of light occurs in the powder layer, the reflection spectra of light from the skin change dramatically with the size of powder particles. The color difference between normal skin and spots is found to diminish more when powder particles smaller than the wavelength of light are used. It is shown that particle polydispersity suppresses substantially the extreme spectral change caused by monodisperse particles with a size comparable to the light wavelength.

Achromatic illumination system for small targets

DOEpatents

Sigler, Robert D.

1979-01-01

A pair of light beams is directed to provide illumination that is substantially uniform from all directions on a small target by a system comprising a pair of corrector windows, a pair of planar reflecting surfaces, a pair of paraboloidal mirrors and a reflecting mirror cavity. The components are arranged so that each of the beams passes through a corrector and is reflected from the planar surface to the paraboloidal mirror, from which it is focused through a hole in the planar surface to the interior of the cavity. The surface of the interior portion of the cavity is shaped to reflect the focused beam three times before the focused reflected beam strikes the target.

Reflection type skin friction meter

NASA Technical Reports Server (NTRS)

Bandyopadhyay, Promode R. (Inventor); Weinstein, Leonard M. (Inventor)

1993-01-01

A housing block is provided having an upper surface conforming to the test surface of a model or aircraft. An oil film is supplied upstream of a transparent wedge window located in this upper surface by an oil pump system located external to the housing block. A light source located within the housing block supplies a light beam which passes through this transparent window and is reflected back through the transparent window by the upper surface of the oil film to a photo-sensitive position sensor located within the housing. This position sensor allows the slope history of the oil film caused by and aerodynamic flow to be determined. The skin friction is determined from this slope history. Internally located mirrors augment and sensitize the reflected beam as necessary before reaching the position sensor. In addition, a filter may be provided before this sensor to filter the beam.

Solids-based concentrated solar power receiver

DOEpatents

None

2018-04-10

A concentrated solar power (CSP) system includes channels arranged to convey a flowing solids medium descending under gravity. The channels form a light-absorbing surface configured to absorb solar flux from a heliostat field. The channels may be independently supported, for example by suspension, and gaps between the channels are sized to accommodate thermal expansion. The light absorbing surface may be sloped so that the inside surfaces of the channels proximate to the light absorbing surface define downward-slanting channel floors, and the flowing solids medium flows along these floors. Baffles may be disposed inside the channels and oriented across the direction of descent of the flowing solids medium. The channels may include wedge-shaped walls forming the light-absorbing surface and defining multiple-reflection light paths for solar flux from the heliostat field incident on the light-absorbing surface.

Cylindrical microlens with an internally reflecting surface and a method of fabrication

DOEpatents

Beach, Raymond J.; Freitas, Barry L.

2004-03-23

A fast (high numerical aperture) cylindrical microlens, which includes an internally reflective surface, that functions to deviate the direction of the light that enters the lens from its original propagation direction is employed in optically conditioning laser diodes, laser diode arrays and laser diode bars.

A Cylindrical Microlens With An Internally Reflective Surface And A Method Of Fabrication

DOEpatents

Beach, Raymond J.; Freitas, Barry L.

2005-09-27

A fast (high numerical aperture) cylindrical microlens, which includes an internally reflective surface, that functions to deviate the direction of the light that enters the lens from its original propagation direction is employed in optically conditioning laser diodes, laser diode arrays and laser diode bars.

Effect of core quantum-dot size on power-conversion-efficiency for silicon solar-cells implementing energy-down-shift using CdSe/ZnS core/shell quantum dots.

PubMed

Baek, Seung-Wook; Shim, Jae-Hyoung; Seung, Hyun-Min; Lee, Gon-Sub; Hong, Jin-Pyo; Lee, Kwang-Sup; Park, Jea-Gun

2014-11-07

Silicon solar cells mainly absorb visible light, although the sun emits ultraviolet (UV), visible, and infrared light. Because the surface reflectance of a textured surface with SiNX film on a silicon solar cell in the UV wavelength region (250-450 nm) is higher than ∼27%, silicon solar-cells cannot effectively convert UV light into photo-voltaic power. We implemented the concept of energy-down-shift using CdSe/ZnS core/shell quantum-dots (QDs) on p-type silicon solar-cells to absorb more UV light. CdSe/ZnS core/shell QDs demonstrated clear evidence of energy-down-shift, which absorbed UV light and emitted green-light photoluminescence signals at a wavelength of 542 nm. The implementation of 0.2 wt% (8.8 nm QDs layer) green-light emitting CdSe/ZnS core/shell QDs reduced the surface reflectance of the textured surface with SiNX film on a silicon solar-cell from 27% to 15% and enhanced the external quantum efficiency (EQE) of silicon solar-cells to around 30% in the UV wavelength region, thereby enhancing the power conversion efficiency (PCE) for p-type silicon solar-cells by 5.5%.

The effect of geometric and electric constraints on the performance of polymer-stabilized cholesteric liquid crystals with a double-handed circularly polarized light reflection band

NASA Astrophysics Data System (ADS)

Relaix, Sabrina; Mitov, Michel

2008-08-01

Polymer-stabilized cholesteric liquid crystals (PSCLCs) with a double-handed circularly polarized reflection band are fabricated. The geometric and electric constraints appear to be relevant parameters in obtaining a single-layer CLC structure with a clear-cut double-handed circularly polarized reflection band since light scattering phenomena can alter the reflection properties when the PSCLC is cooled from the elaboration temperature to the operating one. A compromise needs to be found between the LC molecule populations, which are bound to the polymer network due to strong surface effects or not. Besides, a monodomain texture is preserved if the PSCLC is subjected to an electric field at the same time as the thermal process intrinsic to the elaboration process. As a consequence, the light scattering is reduced and both kinds of circularly polarized reflected light beams are put in evidence. Related potential applications are smart reflective windows for the solar light management or reflective polarizer-free displays with higher brightness.

Unpolarized emissivity with shadow and multiple reflections from random rough surfaces with the geometric optics approximation: application to Gaussian sea surfaces in the infrared band.

PubMed

Bourlier, Christophe

2006-08-20

The emissivity from a stationary random rough surface is derived by taking into account the multiple reflections and the shadowing effect. The model is applied to the ocean surface. The geometric optics approximation is assumed to be valid, which means that the rough surface is modeled as a collection of facets reflecting locally the light in the specular direction. In particular, the emissivity with zero, single, and double reflections are analytically calculated, and each contribution is studied numerically by considering a 1D sea surface observed in the near infrared band. The model is also compared with results computed from a Monte Carlo ray-tracing method.

Method and apparatus for simultaneous spectroelectrochemical analysis

DOEpatents

Chatterjee, Sayandev; Bryan, Samuel A; Schroll, Cynthia A; Heineman, William R

2013-11-19

An apparatus and method of simultaneous spectroelectrochemical analysis is disclosed. A transparent surface is provided. An analyte solution on the transparent surface is contacted with a working electrode and at least one other electrode. Light from a light source is focused on either a surface of the working electrode or the analyte solution. The light reflected from either the surface of the working electrode or the analyte solution is detected. The potential of the working electrode is adjusted, and spectroscopic changes of the analyte solution that occur with changes in thermodynamic potentials are monitored.

Photoinduced surface plasmon switching at VO2/Au interface.

PubMed

Kumar, Nardeep; Rúa, Armando; Aldama, Jennifer; Echeverría, Karla; Fernández, Félix E; Lysenko, Sergiy

2018-05-28

Angle-resolved reflection, light scattering and ultrafast pump-probe spectroscopy combined with a surface plasmon-polariton (SPP) resonance technique in attenuated total reflection geometry was used to investigate the light-induced plasmonic switching in a photorefractive VO 2 /Au hybrid structure. Measurements of SPP scattering and reflection shows that the optically-induced formation of metallic state in a vanadium dioxide layer deposited on a gold film significantly alters the electromagnetic field enhancement and SPP propagation length at the VO 2 /Au interface. The ultrafast optical manipulation of SPP resonance is shown on a picosecond timescale. Obtained results demonstrate high potential of photorefractive vanadium oxides as efficient plasmonic modulating materials for ultrafast optoelectronic devices.

Coupling mediated by photorefractive phase grating between visible radiation and surface plasmon polaritons in iron-doped LiNbO3 crystal slabs coated with indium-tin oxide

NASA Astrophysics Data System (ADS)

Wang, Hao; Zhao, Hua; Xu, Chao; Li, Liang; Hu, Guangwei; Zhang, Jingwen

2014-10-01

Photorefractive (PR) phase gratings were used in coupling energy between visible light and surface plasmon polaritons in indium-tin oxide (ITO)-coated iron-doped lithium niobate (Fe:LN) crystal slabs via electrostatic modification at the ITO/LN interface based on a strong photovoltaic effect. The energy coupling is considered to be responsible for several interesting observations: (1) dynamic reflectivity change from 3.25 to 37.0% of the very first reflection at the entrance slab interface, (2) total light reflectivity as high as 89%, and (3) two-dimensional diffraction patterns without external feedback needed.

Vision Screening

MedlinePlus

... testing when performed at a doctor's office. Corneal light reflex testing This simple test can be performed ... focuses on a penlight, the position of the light reflection from the front surface (cornea) of the ...

Transfer the multiscale texture of crystalline Si onto thin-film micromorph cell by UV nanoimprint for light trapping

NASA Astrophysics Data System (ADS)

Liu, Daiming; Wang, Qingkang; Wang, Qing

2018-05-01

Surface texturing is of great significance in light trapping for solar cells. Herein, the multiscale texture, consisting of microscale pyramids and nanoscale porous arrangement, was fabricated on crystalline Si by KOH etching and Ag-assisted HF etching processes and subsequently replicated onto glass with high fidelity by UV nanoimprint method. Light trapping of the multiscale texture was studied by spectral (reflectance, haze ratio) characterizations. Results reveal the multiscale texture provides the broadband reflection reducing, the highlighted light scattering and the additional self-cleaning behaviors. Compared with bare cell, the multiscale textured micromorph cell achieves a 4% relative increase in power conversion efficiency. This surface texturing route paves a promising way for developing low-cost, large-scale and high-efficiency solar applications.

Plasma surface reflectance spectroscopy for non-invasive and continuous monitoring of extracellular component of blood

NASA Astrophysics Data System (ADS)

Sakota, Daisuke; Takatani, Setsuo

2012-04-01

To achieve the quantitative optical non-invasive diagnosis of blood during extracorporeal circulation therapies, the instrumental technique to extract extracellular spectra from whole blood was developed. In the circuit, the continuous blood flow was generated by a centrifugal blood pump. The oxygen saturation was maintained 100% by an oxygenator. The developed glass optical flow cell was attached to the outlet tubing of the oxygenator. The halogen lamp including the light from 400 to 900 nm wavelength was used for the light source. The light was guided into an optical fiber. The light emitted by the fiber was collimated and emitted to the flow cell flat surface at the incident angle of 45 degrees. The light just reflected on the boundary between inner surface of the flow cell and plasma at 45 degrees was detected by the detection fiber. The detected light was analyzed by a spectral photometer. The obtained spectrum from 400 to 600nm wavelength was not changed with respect to the hematocrit. In contrast, the signal in the spectral range was changed when the plasma free hemoglobin increased. By using two spectral range, 505+/-5 nm and 542.5+/-2.5 nm, the differential spectrum was correlated with the free hemoglobin at R2=0.99. On the other hand, as for the hematocrit, the differential spectrum was not correlated at R2=0.01. Finally, the plasma free hemoglobin was quantified with the accuracy of 22+/-19mg/dL. The result shows that the developed plasma surface reflectance spectroscopy (PSRS) can extract the plasma spectrum from flowing whole blood.

Study on the fabrication of back surface reflectors in nano-crystalline silicon thin-film solar cells by using random texturing aluminum anodization

NASA Astrophysics Data System (ADS)

Shin, Kang Sik; Jang, Eunseok; Cho, Jun-Sik; Yoo, Jinsu; Park, Joo Hyung; Byungsung, O.

2015-09-01

In recent decades, researchers have improved the efficiency of amorphous silicon solar cells in many ways. One of the easiest and most practical methods to improve solar-cell efficiency is adopting a back surface reflector (BSR) as the bottom layer or as the substrate. The BSR reflects the incident light back to the absorber layer in a solar cell, thus elongating the light path and causing the so-called "light trapping effect". The elongation of the light path in certain wavelength ranges can be enhanced with the proper scale of BSR surface structure or morphology. An aluminum substrate with a surface modified by aluminum anodizing is used to improve the optical properties for applications in amorphous silicon solar cells as a BSR in this research due to the high reflectivity and the low material cost. The solar cells with a BSR were formed and analyzed by using the following procedures: First, the surface of the aluminum substrate was degreased by using acetone, ethanol and distilled water, and it was chemically polished in a dilute alkali solution. After the cleaning process, the aluminum surface's morphology was modified by using a controlled anodization in a dilute acid solution to form oxide on the surface. The oxidized film was etched off by using an alkali solution to leave an aluminum surface with randomly-ordered dimple-patterns of approximately one micrometer in size. The anodizing conditions and the anodized aluminum surfaces after the oxide layer had been removed were systematically investigated according to the applied voltage. Finally, amorphous silicon solar cells were deposited on a modified aluminum plate by using dc magnetron sputtering. The surfaces of the anodized aluminum were observed by using field-emission scanning electron microscopy. The total and the diffuse reflectances of the surface-modified aluminum sheets were measured by using UV spectroscopy. We observed that the diffuse reflectances increased with increasing anodizing voltage. The properties of the solar cells on anodized aluminum substrates were analyzed by using a solar simulator.

Comparison of the bidirectional reflectance distribution function of various surfaces

NASA Technical Reports Server (NTRS)

Fernandez, Rene; Seasholtz, Richard G.; Oberle, Lawrence G.; Kadambi, Jaikrishnan R.

1988-01-01

Described is the development and use of a system to measure the Bidirectional Reflectance Distribution Function (BRDF) of various surfaces. The BRDF measurements are used in the analysis and design of optical measurement systems, such as laser anemometers. An argon ion laser (514 nm) is the light source. Preliminary results are presented for eight samples: two glossy black paints, two flat black paints, black glass, sand blasted aluminum, unworked aluminum, and a white paint. A BaSO4 white reflectance standard was used as the reference sample throughout the tests. The reflectance characteristics of these surfaces are compared.

Patterns and properties of polarized light in air and water

PubMed Central

Cronin, Thomas W.; Marshall, Justin

2011-01-01

Natural sources of light are at best weakly polarized, but polarization of light is common in natural scenes in the atmosphere, on the surface of the Earth, and underwater. We review the current state of knowledge concerning how polarization and polarization patterns are formed in nature, emphasizing linearly polarized light. Scattering of sunlight or moonlight in the sky often forms a strongly polarized, stable and predictable pattern used by many animals for orientation and navigation throughout the day, at twilight, and on moonlit nights. By contrast, polarization of light in water, while visible in most directions of view, is generally much weaker. In air, the surfaces of natural objects often reflect partially polarized light, but such reflections are rarer underwater, and multiple-path scattering degrades such polarization within metres. Because polarization in both air and water is produced by scattering, visibility through such media can be enhanced using straightforward polarization-based methods of image recovery, and some living visual systems may use similar methods to improve vision in haze or underwater. Although circularly polarized light is rare in nature, it is produced by the surfaces of some animals, where it may be used in specialized systems of communication. PMID:21282165

Optimized 2D array of thin silicon pillars for efficient antireflective coatings in the visible spectrum

PubMed Central

Proust, Julien; Fehrembach, Anne-Laure; Bedu, Frédéric; Ozerov, Igor; Bonod, Nicolas

2016-01-01

Light reflection occuring at the surface of silicon wafers is drastically diminished by etching square pillars of height 110 nm and width 140 nm separated by a 100 nm gap distance in a square lattice. The design of the nanostructure is optimized to widen the spectral tolerance of the antireflective coatings over the visible spectrum for both fundamental polarizations. Angle and polarized resolved optical measurements report a light reflection remaining under 5% when averaged in the visible spectrum for both polarizations in a wide angular range. Light reflection remains almost insensitive to the light polarization even in oblique incidence. PMID:27109643

The light wave flow effect in a plane-parallel layer with a quasi-zero refractive index under the action of bounded light beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gadomsky, O. N., E-mail: gadomsky@mail.ru; Shchukarev, I. A., E-mail: blacxpress@gmail.com

2016-08-15

It is shown that external optical radiation in the 450–1200 nm range can be efficiently transformed under the action of bounded light beams to a surface wave that propagates along the external and internal boundaries of a plane-parallel layer with a quasi-zero refractive index. Reflection regimes with complex and real angles of refraction in the layer are considered. The layer with a quasi-zero refractive index in this boundary problem is located on a highly reflective metal substrate; it is shown that the uniform low reflection of light is achieved in the wavelength range under study.

Hybrid catadioptric system for advanced optical cavity velocimetry

DOEpatents

Frayer, Daniel K.

2018-02-06

A probe including reflector is disclosed to measure the velocity distribution of a moving surface along many lines of sight. Laser light, directed to the surface by the probe and then reflected back from the surface, is Doppler shifted by the moving surface, collected into probe, and then directed to detection equipment through optic fibers. The received light is mixed with reference laser light and using photonic Doppler velocimetry, a continuous time record of the surface movement is obtained. An array of single-mode optical fibers provides an optic signal to one or more lens groups and a reflector, such as a parabolic reflector having a mirrored interior surface.

Snake velvet black: Hierarchical micro- and nanostructure enhances dark colouration in Bitis rhinoceros

NASA Astrophysics Data System (ADS)

Spinner, Marlene; Kovalev, Alexander; Gorb, Stanislav N.; Westhoff, Guido

2013-05-01

The West African Gaboon viper (Bitis rhinoceros) is a master of camouflage due to its colouration pattern. Its skin is geometrically patterned and features black spots that purport an exceptional spatial depth due to their velvety surface texture. Our study shades light on micromorphology, optical characteristics and principles behind such a velvet black appearance. We revealed a unique hierarchical pattern of leaf-like microstructures striated with nanoridges on the snake scales that coincides with the distribution of black colouration. Velvet black sites demonstrate four times lower reflectance and higher absorbance than other scales in the UV - near IR spectral range. The combination of surface structures impeding reflectance and absorbing dark pigments, deposited in the skin material, provides reflecting less than 11% of the light reflected by a polytetrafluoroethylene diffuse reflectance standard in any direction. A view-angle independent black structural colour in snakes is reported here for the first time.

Snake velvet black: hierarchical micro- and nanostructure enhances dark colouration in Bitis rhinoceros.

PubMed

Spinner, Marlene; Kovalev, Alexander; Gorb, Stanislav N; Westhoff, Guido

2013-01-01

The West African Gaboon viper (Bitis rhinoceros) is a master of camouflage due to its colouration pattern. Its skin is geometrically patterned and features black spots that purport an exceptional spatial depth due to their velvety surface texture. Our study shades light on micromorphology, optical characteristics and principles behind such a velvet black appearance. We revealed a unique hierarchical pattern of leaf-like microstructures striated with nanoridges on the snake scales that coincides with the distribution of black colouration. Velvet black sites demonstrate four times lower reflectance and higher absorbance than other scales in the UV-near IR spectral range. The combination of surface structures impeding reflectance and absorbing dark pigments, deposited in the skin material, provides reflecting less than 11% of the light reflected by a polytetrafluoroethylene diffuse reflectance standard in any direction. A view-angle independent black structural colour in snakes is reported here for the first time.

"Colgate-Plus"--An Imperfect Light Pipe.

ERIC Educational Resources Information Center

Ouseph, P. J.

1993-01-01

Describes the effects when a clear toothbrush is used as total internally reflecting light pipe when attached to a laser. Several explanations are given describing the nonuniformity of the transmitted light resulting from surface and internal irregularities found in the toothbrush. (MVL)

Effects of hydrogen peroxide on the light reflectance and morphology of bovine enamel.

PubMed

Kwon, Y H; Huo, M S; Kim, K H; Kim, S K; Kim, Y J

2002-05-01

The purpose of this study was to examine the effects of a bleaching agent (30% hydrogen peroxide) on the surface of bovine enamel using a scanning electron microscope and a UV-VIS-NIR spectrophotometer. Five non-carious bovine incisors were bleached for 0, 1, 2 and 3 days using 30% hydrogen peroxide. The light reflectance spectrum was measured using a spectrophotometer with diffuse reflectance mode. Colour values and colour differences in the teeth were evaluated from the reflectance measurements with the CIE L*a*b* colour coordinate system. Surface alterations in the bleached and unbleached teeth were studied using a scanning electron microscope. The change of reflectance in the teeth was related to the change of colour. Most reflectance change occurred within a 1-day bleaching, and this result was confirmed by a CIE L*a*b* colour coordinate system. The colour differences in the bleached teeth were significant enough to be perceived by the observer's eye. The comparison of bleached to unbleached bovine enamel revealed that the bleached surface showed non-uniform slight morphological alterations, and it developed varying degrees of surface porosity. This study indicates that the bleached bovine teeth showed apparent colour differences as well as slight morphological alterations after bleaching.

A study of the polarization of light scattered by vegetation. M.S. Thesis

NASA Technical Reports Server (NTRS)

Woessner, P. N.

1985-01-01

This study was undertaken in order to better understand the factors that govern the polarization of light scattered from vegetation and soils. The intensity and polarization of light scattered by clover and grass in vivo and soil were measured at a number of different angles of incidence and reflectance. Both individual leaves and natural patches of leaves were measured. The light transmitted through the leaves was found to be negatively polarized. The light scattered from the upper leaf surface was found to be positively polarized in a manner which could be accounted for qualitatively but not quantitatively by the Fresnel reflection coefficients modified by a shadowing function of the form cos sup2 (g/2), where g is the phase angle. Findings indicate that the polarization of light scattered by vegetation is a more complex process than previously thought, and that besides the surface-scattered component of light, the volume-scattered and multiply-scattered components also contribute significantly to the polarization.

Testing Limits on Matte Surface Color Perception in Three-Dimensional Scenes with Complex Light Fields

PubMed Central

Doerschner, K.; Boyaci, H.; Maloney, L. T.

2007-01-01

We investigated limits on the human visual system’s ability to discount directional variation in complex lights field when estimating Lambertian surface color. Directional variation in the light field was represented in the frequency domain using spherical harmonics. The bidirectional reflectance distribution function of a Lambertian surface acts as a low-pass filter on directional variation in the light field. Consequently, the visual system needs to discount only the low-pass component of the incident light corresponding to the first nine terms of a spherical harmonics expansion (Basri & Jacobs, 2001; Ramamoorthi & Hanrahan, 2001) to accurately estimate surface color. We test experimentally whether the visual system discounts directional variation in the light field up to this physical limit. Our results are consistent with the claim that the visual system can compensate for all of the complexity in the light field that affects the appearance of Lambertian surfaces. PMID:18053846

A parallel bubble column system for the cultivation of phototrophic microorganisms.

PubMed

Havel, Jan; Franco-Lara, Ezequiel; Weuster-Botz, Dirk

2008-07-01

An incubator with up to 16 parallel bubble columns was equipped with artificial light sources assuring a light supply with a homogenous light spectrum directly above the bioreactors. Cylindrical light reflecting tubes were positioned around every single bubble column to avoid light scattering effects and to redirect the light from the top onto the cylindrical outer glass surface of each bubble column. The light reflecting tubes were equipped with light intensity filters to control the total light intensity for every single photo-bioreactor. Parallel cultivations of the unicellular obligate phototrophic cyanobacterium, Synechococcus PCC7942, were studied under different constant light intensities ranging from 20 to 102 microE m(-2)s(-1) at a constant humidified air flow rate supplemented with CO(2).

Effects of surface contamination on the infrared emissivity and visible-light scattering of highly reflective surfaces at cryogenic temperatures

NASA Technical Reports Server (NTRS)

Viehmann, W.; Eubanks, A. G.

1972-01-01

A technique is described for the simultaneous in situ measurement of film thickness, refractive index, total normal emissivity, visible-light scattering, and reflectance of contaminant films on a highly reflective liquid-nitrogen cooled, stainless steel substrate. Emissivities and scattering data are obtained for films of water, carbon dioxide, silicone oil, and a number of aromatic and aliphatic hydrocarbons as a function of film thickness between zero and 20 microns. Of the contaminants investigated, water has by far the greatest effect on emissivity, followed by silicone oil, aliphatic hydrocarbons, aromatic hydrocarbons, and carbon dioxide. The emissivity increases more rapidly with film thickness between zero and 2.5 microns than at thicknesses greater than 2.5 microns. Scattering of visible light changes very little below 2 microns thickness but increases rapidly with thickness beyond 2 to 3 microns. The effect of contaminant films on passive radiation coolers is discussed.

Potential Sources of Polarized Light from a Plant Canopy

NASA Technical Reports Server (NTRS)

Vanderbilt, Vern; Daughtry, Craig; Dahlgren, Robert

2016-01-01

Field measurements have demonstrated that sunlight polarized during a first surface reflection by shiny leaves dominates the optical polarization of the light reflected by shiny-leafed plant canopies having approximately spherical leaf angle probability density functions ("Leaf Angle Distributions" - LAD). Yet for other canopies - specifically those without shiny leaves and/or spherical LADs - potential sources of optically polarized light may not always be obvious. Here we identify possible sources of polarized light within those other canopies and speculate on the ecologically important information polarization measurements of those sources might contain.

Optimization of morphological parameters for mitigation pits on rear KDP surface: experiments and numerical modeling.

PubMed

Yang, Hao; Cheng, Jian; Chen, Mingjun; Wang, Jian; Liu, Zhichao; An, Chenhui; Zheng, Yi; Hu, Kehui; Liu, Qi

2017-07-24

In high power laser systems, precision micro-machining is an effective method to mitigate the laser-induced surface damage growth on potassium dihydrogen phosphate (KDP) crystal. Repaired surfaces with smooth spherical and Gaussian contours can alleviate the light field modulation caused by damage site. To obtain the optimal repairing structure parameters, finite element method (FEM) models for simulating the light intensification caused by the mitigation pits on rear KDP surface were established. The light intensity modulation of these repairing profiles was compared by changing the structure parameters. The results indicate the modulation is mainly caused by the mutual interference between the reflected and incident lights on the rear surface. Owing to the total reflection, the light intensity enhancement factors (LIEFs) of the spherical and Gaussian mitigation pits sharply increase when the width-depth ratios are near 5.28 and 3.88, respectively. To achieve the optimal mitigation effect, the width-depth ratios greater than 5.3 and 4.3 should be applied to the spherical and Gaussian repaired contours. Particularly, for the cases of width-depth ratios greater than 5.3, the spherical repaired contour is preferred to achieve lower light intensification. The laser damage test shows that when the width-depth ratios are larger than 5.3, the spherical repaired contour presents higher laser damage resistance than that of Gaussian repaired contour, which agrees well with the simulation results.

Coatings Boost Solar-Cell Outputs

NASA Technical Reports Server (NTRS)

Rohatgi, Ajeet; Campbell, Robert B.; O'Keefe, T. W.; Rai-Choudbury, Posenjit; Hoffman, Richard A.

1988-01-01

Efficiencies increased by more-complete utilization of incident light. Electrical outputs of thin solar photovoltaic cells made of dendritic-web silicon increased by combination of front-surface, antireflective coatings and back-surface, reflective coatings. Improvements achieved recently through theoretical and experimental studies of ways to optimize coatings for particular wavelengths of incident light, cell thicknesses, and cell materials.

Optical performance of segmented aperture windows for solar tower receivers

NASA Astrophysics Data System (ADS)

Buck, Reiner

2017-06-01

Segmented quartz windows are a concept to build larger windows for receivers that require a closed aperture. Reflection losses are a significant loss factor for such solar receivers. Without any additional measures, the reflection loss can reach about 12%. One important measure to improve transmission is the application of anti-reflective coatings, which is beneficial in any case. Another option is modifying the window geometry, especially the edge surfaces of the glass segments. A certain fraction of the reflection losses are caused by a light-guide effect in the glass body, for rays entering through the front surface. Changing the cut surfaces in a way reducing the light-guide effect can significantly improve transmission of a segmented window. Several possible configurations are evaluated and discussed. The results of ray-tracing simulations verify the improvement. The final selection of the window configuration depends on the optical properties and on mechanical strength, manufacturing and cost considerations. This has to be evaluated for any specific receiver design.

Method for determining shear direction using liquid crystal coatings

NASA Technical Reports Server (NTRS)

Reda, Daniel C.

1995-01-01

A method is provided for determining shear direction wherein a beam of white light is directed onto the surface of a liquid crystal coating to cause the white light to be dispersed (reflected) from the surface in a spectrum having bands of different colors in a fixed spatial 2 (angular) sequence. The system is calibrated by locating an observer, e.g., a video and movie camera, such that a particular color band (preferably at or near the center of the reflected spectrum) is observed to thereby provide a reference color band. Because the application of shear causes either clockwise or counterclockwise rotation of the reflected spectrum dependent on the direction of the shear, a determination is then made of the reflected color band observed by the observer when the surface of the liquid crystal is subjected to shear to thereby determine the direction of the shear based on the directional (rotation) relation of the observed color band with respect to the reference color band in the spatial sequence of color bands.

New light-shielding technique for shortening the baffle length of a star sensor

NASA Astrophysics Data System (ADS)

Kawano, Hiroyuki; Sato, Yukio; Mitani, Kenji; Kanai, Hiroshi; Hama, Kazumori

2002-10-01

We have developed a star sensor with a short baffle of 140 mm. Our baffle provides a Sun rejection angle of 35 degrees with stray light attenuation less than the intensity level of a visual magnitude of Mv = +5 for a wide field of view lens of 13x13 degrees. The application of a new light shielding technique taking advantage of total internal reflection phenomena enables us to reduce the baffle length to about three fourths that of the conventional two-stage baffle. We have introduced two ideas to make the baffle length shorter. The one is the application of a nearly half sphere convex lens as the first focusing lens. The bottom surface reflects the scattering rays with high incident angles of over 50 degrees by using the total internal reflection phenomena. The other is the painting of the surface of the baffle with not frosted but gloss black paint. The gloss black paint enables most of the specular reflection rays to go back to outer space without scattering. We confirm the baffle performance mentioned above by scattering ray tracing simulation and a light attenuation experiment in a darkroom on the ground.

Comparisons of luminaires: Efficacies and system design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albright, L.D.; Both, A.J.

1994-12-31

After reviewing basic information, three design examples have been presented to demonstrate a process of supplemental lighting design. The sequences of each example suggest careful thought and analysis are required to obtain supplemental lighting designs that provide both high levels of PAR and suitable uniformity. The end results should suggest how an analysis can evolve to achieve desired results, and the types of tools and adjustments required. It appears possible to design research greenhouses and plant growth chambers to achieve a {+-}10% PAR uniformity using HIPS luminaires. Further, HPS luminaires (and, by extension, NEHD, etc.) are required to achieve highmore » PAR levels and have the decided advantage of providing the possibility of aiming, which reduces the region of the {open_quotes}edge effect{close_quotes}. Further, for designing plant lighting systems, a modification of the standard IES luminaire data file structure is potentially useful. Luminaire installation is an important factor to obtain PAR uniformity. Spacing and mounting height are critically important. Additionally, the mounting angle of each luminaire must be carefully adjusted to conform with design assumptions. This is true for both plant growth chambers and greenhouses. Surface reflectances are particularly important when designing for small lighted regions such as plant growth chambers and research greenhouses. It is not obvious, just from looking at a surface, what its reflectance is. It is suggested that an effort be mounted to develop valid surface reflectance data to be used by designers. The importance of the surfaces (particularly the walls) in achieving PAR uniformity suggests the importance of periodic cleaning/maintenance to retain initial reflectance values.« less

The Effect of Incident Light Polarization on Vegetation Bidirectional Reflectance Factor

NASA Technical Reports Server (NTRS)

Georgiev, Georgi T.; Thome, Kurt; Ranson, Kurtis J.; King, Michael D.; Butler, James J.

2010-01-01

The Laboratory-based Bidirectional Reflectance Factor (BRF) polarization study of vegetation is presented in this paper. The BRF was measured using a short-arc Xenon lamp/monochromator assembly producing an incoherent, tunable light source with a well-defined spectral bandpass at visible and near-infrared wavelengths of interest at 470 nm and 870 nm and coherent light source at 1.656 microns. All vegetation samples were measured using P and S linearly polarized incident light over a range of incident and scatter angles. By comparing these results, we quantitatively examine how the BRF of the samples depends on the polarization of the incident light. The differences are significant, depend strongly on the incident and scatter angles, and can be as high as 120% at 67 deg incident and 470nm. The global nature of Earth's processes requires consistent long-term calibration of all instruments involved in data retrieval. The BRF defines the reflection characteristics of Earth surface. It provides the reflectance of a target in a specific direction as a function of illumination and viewing geometry. The BRF is a function of wavelength and reflects the structural and optical properties of the surface. Various space and airborne radiometric and imaging remote sensing instruments are used in the remote sensing characterization of vegetation canopies and soils, oceans, or especially large pollution sources. The satellite data is validated through comparison with airborne, ground-based and laboratory-based data in an effort to fully understand the vegetation canopy reflectance, The Sun's light is assumed to be unpolarized at the top of the atmosphere; however it becomes polarized to some degree due to atmospheric effects by the time it reaches the vegetation canopy. Although there are numerous atmospheric correction models, laboratory data is needed for model verification and improvement.

Fabrication of multi-functional silicon surface by direct laser writing

NASA Astrophysics Data System (ADS)

Verma, Ashwani Kumar; Soni, R. K.

2018-05-01

We present a simple, quick and one-step methodology based on nano-second laser direct writing for the fabrication of micro-nanostructures on silicon surface. The fabricated surfaces suppress the optical reflection by multiple reflection due to light trapping effect to a much lower value than polished silicon surface. These textured surfaces offer high enhancement ability after gold nanoparticle deposition and then explored for Surface Enhanced Raman Scattering (SERS) for specific molecular detection. The effect of laser scanning line interval on optical reflection and SERS signal enhancement ability was also investigated. Our results indicate that low optical reflection substrates exhibit uniform SERS enhancement with enhancement factor of the order of 106. Furthermore, this methodology provide an alternative approach for cost-effective large area fabrication with good control over feature size.

Ultraviolet (UV)-reflective paint with ultraviolet germicidal irradiation (UVGI) improves decontamination of nosocomial bacteria on hospital room surfaces.

PubMed

Jelden, Katelyn C; Gibbs, Shawn G; Smith, Philip W; Hewlett, Angela L; Iwen, Peter C; Schmid, Kendra K; Lowe, John J

2017-06-01

An ultraviolet germicidal irradiation (UVGI) generator (the TORCH, ClorDiSys Solutions, Inc.) was used to compare the disinfection of surface coupons (plastic from a bedrail, stainless steel, and chrome-plated light switch cover) in a hospital room with walls coated with ultraviolet (UV)-reflective paint (Lumacept) or standard paint. Each surface coupon was inoculated with methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant Enterococcus faecalis (VRE), placed at 6 different sites within a hospital room coated with UV-reflective paint or standard paint, and treated by 10 min UVC exposure (UVC dose of 0-688 mJ/cm 2 between sites with standard paint and 0-553 mJ/cm 2 with UV-reflective paint) in 8 total trials. Aggregated MRSA concentrations on plastic bedrail surface coupons were reduced on average by 3.0 log 10 (1.8 log 10 Geometric Standard Deviation [GSD]) with standard paint and 4.3 log 10 (1.3 log 10 GSD) with UV-reflective paint (p = 0.0005) with no significant reduction differences between paints on stainless steel and chrome. Average VRE concentrations were reduced by ≥4.9 log 10 (<1.2 log 10 GSD) on all surface types with UV-reflective paint and ≤4.1 log 10 (<1.7 log 10 GSD) with standard paint (p < 0.05). At 5 aggregated sites directly exposed to UVC light, MRSA concentrations on average were reduced by 5.2 log 10 (1.4 log 10 GSD) with standard paint and 5.1 log 10 (1.2 log 10 GSD) with UV-reflective paint (p = 0.017) and VRE by 4.4 log 10 (1.4 log 10 GSD) with standard paint and 5.3 log 10 (1.1 log 10 GSD) with UV-reflective paint (p < 0.0001). At one indirectly exposed site on the opposite side of the hospital bed from the UVGI generator, MRSA concentrations on average were reduced by 1.3 log 10 (1.7 log 10 GSD) with standard paint and 4.7 log 10 (1.3 log 10 GSD) with UV-reflective paint (p < 0.0001) and VRE by 1.2 log 10 (1.5 log 10 GSD) with standard paint and 4.6 log 10 (1.1 log 10 GSD) with UV-reflective paint (p < 0.0001). Coating hospital room walls with UV-reflective paint enhanced UVGI disinfection of nosocomial bacteria on various surfaces compared to standard paint, particularly at a surface placement site indirectly exposed to UVC light.

Suomi satellite brings to light a unique frontier of nighttime environmental sensing capabilities

PubMed Central

Miller, Steven D.; Mills, Stephen P.; Elvidge, Christopher D.; Lindsey, Daniel T.; Lee, Thomas F.; Hawkins, Jeffrey D.

2012-01-01

Most environmental satellite radiometers use solar reflectance information when it is available during the day but must resort at night to emission signals from infrared bands, which offer poor sensitivity to low-level clouds and surface features. A few sensors can take advantage of moonlight, but the inconsistent availability of the lunar source limits measurement utility. Here we show that the Day/Night Band (DNB) low-light visible sensor on the recently launched Suomi National Polar-orbiting Partnership (NPP) satellite has the unique ability to image cloud and surface features by way of reflected airglow, starlight, and zodiacal light illumination. Examples collected during new moon reveal not only meteorological and surface features, but also the direct emission of airglow structures in the mesosphere, including expansive regions of diffuse glow and wave patterns forced by tropospheric convection. The ability to leverage diffuse illumination sources for nocturnal environmental sensing applications extends the advantages of visible-light information to moonless nights. PMID:22984179

Pressure-sensitive optrode

DOEpatents

Hirschfeld, T.B.

1985-04-09

An apparatus and method are disclosed for sensing changes in pressure and for generating optical signals related to changes in pressure. Light from a fiber optic is directed to a movable surface which is coated with a light-responsive material, and which moves relative to the end of the fiber optic in response to changes in pressure. The same fiber optic collects a portion of the reflected or emitted light from the movable surface. Changes in pressure are determined by measuring changes in the amount of light collected. 5 figs.

Nonlinear photomagnetism of metals: Theory of nonlinear photoinduced dc current

NASA Astrophysics Data System (ADS)

Afonin, V. V.; Gurevich, V. L.; Laiho, R.

1995-07-01

Photoinduced magnetic flux has recently been observed in normal metals exposed to light. This effect is partly due to the fact that the light reflected from a metal surface transfers to the conduction electrons some of its quasimomentum. This creates a dc surface current which, for an appropriate geometry, brings about the photomagnetic effect. There is another contribution to the current that is due to anisotropy of the probabilities of electron transitions induced by the light, in combination with diffuse reflection of the electrons at the surface. We present here a theory of the dependence of the photoinduced current on the intensity of light Q. We assume that the light intensity is either constant or the time scale of its variation is much larger than the inverse Rabi frequency corresponding to the interband electron transition. At comparatively low intensities the current is proportional to Q. At higher intensities it varies as Q1/2. The physical origin of such behavior is analyzed. Various factors that allow a lowering of the critical intensity for the onset of the nonlinear behavior are discussed.

Initial Studies of the Bidirectional Reflectance Distribution Function of Multi-Walled Carbon Nanotube Structures for Stray Light Control Applications

NASA Technical Reports Server (NTRS)

Butler, J. J.; Tveekrem, J. L.; Quijada, M. A.; Getty, S. A.; Hagopian, J. G.; Georglev, G. T.

2010-01-01

The presentation examines the application of low reflectance surfaces in optical instruments, multi-walled carbon nanotubes (MWCNTs), research objects, MWCNT samples, measurement of 8 deg. directional/hemispherical reflectance, measurement of bidirectional reflectance distribution function (BRDF), and what is current the "blackest ever black".

Method and apparatus for detecting the presence and thickness of carbon and oxide layers on EUV reflective surfaces

DOEpatents

Malinowski, Michael E.

2005-01-25

The characteristics of radiation that is reflected from carbon deposits and oxidation formations on highly reflective surfaces such as Mo/Si mirrors can be quantified and employed to detect and measure the presence of such impurities on optics. Specifically, it has been shown that carbon deposits on a Mo/Si multilayer mirror decreases the intensity of reflected HeNe laser (632.8 nm) light. In contrast, oxide layers formed on the mirror should cause an increase in HeNe power reflection. Both static measurements and real-time monitoring of carbon and oxide surface impurities on optical elements in lithography tools should be achievable.

Cylindrically distributing optical fiber tip for uniform laser illumination of hollow organs

NASA Astrophysics Data System (ADS)

Buonaccorsi, Giovanni A.; Burke, T.; MacRobert, Alexander J.; Hill, P. D.; Essenpreis, Matthias; Mills, Timothy N.

1993-05-01

To predict the outcome of laser therapy it is important to possess, among other things, an accurate knowledge of the intensity and distribution of the laser light incident on the tissue. For irradiation of the internal surfaces of hollow organs, modified fiber tips can be used to shape the light distribution to best suit the treatment geometry. There exist bulb-tipped optical fibers emitting a uniform isotropic distribution of light suitable for the treatment of organs which approximate a spherical geometry--the bladder, for example. For the treatment of organs approximating a cylindrical geometry--e.g. the oesophagus--an optical fiber tip which emits a uniform cylindrical distribution of light is required. We report on the design, development and testing of such a device, the CLD fiber tip. The device was made from a solid polymethylmethacrylate (PMMA) rod, 27 mm in length and 4 mm in diameter. One end was shaped and 'silvered' to form a mirror which reflected the light emitted from the delivery fiber positioned at the other end of the rod. The shape of the mirror was such that the light fell with uniform intensity on the circumferential surface of the rod. This surface was coated with BaSO4 reflectance paint to couple the light out of the rod and onto the surface of the tissue.

Ultraviolet reflecting photonic microstructures in the King Penguin beak.

PubMed

Dresp, Birgitta; Jouventin, Pierre; Langley, Keith

2005-09-22

King and emperor penguins (Aptenodytes patagonicus and Aptenodytes forsteri) are the only species of marine birds so far known to reflect ultraviolet (UV) light from their beaks. Unlike humans, most birds perceive UV light and several species communicate using the near UV spectrum. Indeed, UV reflectance in addition to the colour of songbird feathers has been recognized as an important signal when choosing a mate. The king penguin is endowed with several highly coloured ornaments, notably its beak horn and breast and auricular plumage, but only its beak reflects UV, a property considered to influence its sexual attraction. Because no avian UV-reflecting pigments have yet been identified, the origin of such reflections is probably structural. In an attempt to identify the structures that give rise to UV reflectance, we combined reflectance spectrophotometry and morphological analysis by both light and electron microscopy, after experimental removal of surface layers of the beak horn. Here, we characterize for the first time a multilayer reflector photonic microstructure that produces the UV reflections in the king penguin beak.

Passive Optical Detection of a Vibrating Surface

DTIC Science & Technology

2014-01-01

modulation from any given surface? Clearly a detailed mathematical model of light scattering (i.e., BRDF ) is needed, so that we may take the partial...reflectance distribution function ( BRDF ): “The BRDF is a derivative, a distri- bution function, relating the irradiance incident from one given...direction to its contribution to the reflected radiance in another direction.” In other words, the BRDF is a multidimensional surface: the relevant variables

Contamination study

NASA Astrophysics Data System (ADS)

Johnson, R. Barry; Herren, Kenneth A.

1990-09-01

The time dependence of the angular reflectance from molecularly contaminated optical surfaces in the Vacuum Ultraviolet (VUV) is measured. The light scattering measurements are accomplished in situ on optical surfaces in real time during deposition of molecular contaminants. The measurements are taken using non-coherent VUV sources with the predominant wavelengths being the Krypton resonance lines at 1236 and 1600 A. Detection of the scattered light is accomplished using a set of three solar blind VUV photomultipliers. An in-plane VUV BRDF (Bidirectional Reflectance Distribution Functions) experiment is described and details of the ongoing program to characterize optical materials exposed to the space environment is reported.

Anti-reflective coating for visible light using a silver nanodisc metasurface with a refractive index of less than 1.0

NASA Astrophysics Data System (ADS)

Yasuda, Hideki; Matsuno, Ryo; Koito, Naoki; Hosoda, Hidemasa; Tani, Takeharu; Naya, Masayuki

2017-12-01

Suppression of visible-light reflection from material surfaces is an important technology for many applications such as flat-panel displays, camera lenses, and solar panels. In this study, we developed an anti-reflective coating design based on a silver nanodisc metasurface. The effective refractive index of a 10-nm-thick monolayer of silver nanodiscs was less than 1.0, which enabled strong suppression of reflection from the underlying substrate. The nanodisc structure was easy to fabricate using a conventional roll-to-roll wet-coating method. The anti-reflective structure was fabricated over a large area.

Relation between textured surface and diffuse reflectance of Cu films

NASA Astrophysics Data System (ADS)

Shukla, Gaurav; Angappane, S.

2018-04-01

Cu nanostructures namely chevron, slanted and vertical posts deposited on Si substrate by glancing angle deposition (GLAD) technique using DC magnetron sputtering are studied to understand the optical reflectance properties of various textures. The X-ray diffraction analysis confirmed the crystalline nature of the different structures of deposited Cu films. The FESEM images confirmed the formation of chevron, slanted and vertical posts. From the optical reflectance spectra, we found that the reflectance is more for chevron than vertical and slanted posts which have almost the same reflectance over the entire wavelength. The films with chevron texture would find various applications, like, light detector, light trapping, sensors etc.

Optical Reflectance Measurements for Commonly Used Reflectors

NASA Astrophysics Data System (ADS)

Janecek, Martin; Moses, William W.

2008-08-01

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 2pi 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 6.3deg, 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 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 Lumirrorreg, Melinexreg and Tyvekreg. Instead, a more complicated light distribution was measured for these three materials.

Silver nanocube aggregation gradient materials in search for total internal reflection with high phase sensitivity

NASA Astrophysics Data System (ADS)

König, Tobias A. F.; Ledin, Petr A.; Russell, Michael; Geldmeier, Jeffrey A.; Mahmoud, Mahmoud. A.; El-Sayed, Mostafa A.; Tsukruk, Vladimir V.

2015-03-01

We fabricated monolayer coatings of a silver nanocube aggregation to create a step-wise optical strip by applying different surface pressures during slow Langmuir-Blodgett deposition. The varying amount of randomly distributed nanocube aggregates with different surface coverages in gradient manner due to changes in surface pressure allows for continuous control of the polarization sensitive absorption of the incoming light over a broad optical spectrum. Optical characterization under total internal reflection conditions combined with electromagnetic simulations reveal that the broadband light absorption depends on the relative orientation of the nanoparticles to the polarization of the incoming light. By using computer simulations, we found that the electric field vector of the s-polarized light interacts with the different types of silver nanocube aggregations to excite different plasmonic resonances. The s-polarization shows dramatic changes of the plasmonic resonances at different angles of incidence (shift of 64 nm per 10° angle of incidence). With a low surface nanocube coverage (from 5% to 20%), we observed a polarization-selective high absorption of 80% (with an average 75%) of the incoming light over a broad optical range in the visible region from 400 nm to 700 nm. This large-area gradient material with location-dependent optical properties can be of particular interest for broadband light absorption, phase-sensitive sensors, and imaging.We fabricated monolayer coatings of a silver nanocube aggregation to create a step-wise optical strip by applying different surface pressures during slow Langmuir-Blodgett deposition. The varying amount of randomly distributed nanocube aggregates with different surface coverages in gradient manner due to changes in surface pressure allows for continuous control of the polarization sensitive absorption of the incoming light over a broad optical spectrum. Optical characterization under total internal reflection conditions combined with electromagnetic simulations reveal that the broadband light absorption depends on the relative orientation of the nanoparticles to the polarization of the incoming light. By using computer simulations, we found that the electric field vector of the s-polarized light interacts with the different types of silver nanocube aggregations to excite different plasmonic resonances. The s-polarization shows dramatic changes of the plasmonic resonances at different angles of incidence (shift of 64 nm per 10° angle of incidence). With a low surface nanocube coverage (from 5% to 20%), we observed a polarization-selective high absorption of 80% (with an average 75%) of the incoming light over a broad optical range in the visible region from 400 nm to 700 nm. This large-area gradient material with location-dependent optical properties can be of particular interest for broadband light absorption, phase-sensitive sensors, and imaging. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06430e

White-Light, Dispersed-Fringe Interferometric Keratometer

NASA Technical Reports Server (NTRS)

Hochberg, Eric B.; Baroth, Edmund C.

1992-01-01

Proposed keratometer based on scheme involving spectral dispersal of white-light interference fringes. Instrument operates in "snapshot" mode: no scanning necessary, not necessary to immobilize patient's eye. Insensitive to vibration, involves no phase shifting, and has variable sensitivity. Intended primarily for use in medical assessments of human corneas, also used to measure shapes of animal corneas, lenses, and other aspherical or spherical reflective or partly reflective surfaces.

Fourier Transform-Plasmon Waveguide Spectroscopy: A Nondestructive Multifrequency Method for Simultaneously Determining Polymer Thickness and Apparent Index of Refraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bobbitt, Jonathan M; Weibel, Stephen C; Elshobaki, Moneim

2014-12-16

Fourier transform (FT)-plasmon waveguide resonance (PWR) spectroscopy measures light reflectivity at a waveguide interface as the incident frequency and angle are scanned. Under conditions of total internal reflection, the reflected light intensity is attenuated when the incident frequency and angle satisfy conditions for exciting surface plasmon modes in the metal as well as guided modes within the waveguide. Expanding upon the concept of two-frequency surface plasmon resonance developed by Peterlinz and Georgiadis [ Opt. Commun. 1996, 130, 260], the apparent index of refraction and the thickness of a waveguide can be measured precisely and simultaneously by FT-PWR with an averagemore » percent relative error of 0.4%. Measuring reflectivity for a range of frequencies extends the analysis to a wide variety of sample compositions and thicknesses since frequencies with the maximum attenuation can be selected to optimize the analysis. Additionally, the ability to measure reflectivity curves with both p- and s-polarized light provides anisotropic indices of refraction. FT-PWR is demonstrated using polystyrene waveguides of varying thickness, and the validity of FT-PWR measurements are verified by comparing the results to data from profilometry and atomic force microscopy (AFM).« less

Fourier transform-plasmon waveguide spectroscopy: a nondestructive multifrequency method for simultaneously determining polymer thickness and apparent index of refraction.

PubMed

Bobbitt, Jonathan M; Weibel, Stephen C; Elshobaki, Moneim; Chaudhary, Sumit; Smith, Emily A

2014-12-16

Fourier transform (FT)-plasmon waveguide resonance (PWR) spectroscopy measures light reflectivity at a waveguide interface as the incident frequency and angle are scanned. Under conditions of total internal reflection, the reflected light intensity is attenuated when the incident frequency and angle satisfy conditions for exciting surface plasmon modes in the metal as well as guided modes within the waveguide. Expanding upon the concept of two-frequency surface plasmon resonance developed by Peterlinz and Georgiadis [Opt. Commun. 1996, 130, 260], the apparent index of refraction and the thickness of a waveguide can be measured precisely and simultaneously by FT-PWR with an average percent relative error of 0.4%. Measuring reflectivity for a range of frequencies extends the analysis to a wide variety of sample compositions and thicknesses since frequencies with the maximum attenuation can be selected to optimize the analysis. Additionally, the ability to measure reflectivity curves with both p- and s-polarized light provides anisotropic indices of refraction. FT-PWR is demonstrated using polystyrene waveguides of varying thickness, and the validity of FT-PWR measurements are verified by comparing the results to data from profilometry and atomic force microscopy (AFM).

A Tracking Sun Photometer Without Moving Parts

NASA Technical Reports Server (NTRS)

Strawa, Anthony W.

2012-01-01

This innovation is small, lightweight, and consumes very little electricity as it measures the solar energy attenuated by gases and aerosol particles in the atmosphere. A Sun photometer is commonly used on the Earth's surface, as well as on aircraft, to determine the solar energy attenuated by aerosol particles in the atmosphere and their distribution of sizes. This information is used to determine the spatial and temporal distribution of gases and aerosols in the atmosphere, as well as their distribution sizes. The design for this Sun photometer uses a combination of unique optics and a charge coupled device (CCD) array to eliminate moving parts and make the instrument more reliable. It could be selfcalibrating throughout the year. Data products would be down-welling flux, the direct-diffuse flux ratio, column abundance of gas phase constituents, aerosol optical depth at multiple-wavelengths, phase functions, cloud statistics, and an estimate of the representative size of atmospheric particles. These measurements can be used to obtain an estimate of aerosol size distribution, refractive index, and particle shape. Incident light is received at a light-reflecting (inner) surface, which is a truncated paraboloid. Light arriving from a hemispheric field of view (solid angle 2 steradians) enters the reflecting optic at an entrance aperture at, or adjacent to, the focus of the paraboloid, and is captured by the optic. Most of this light is reflected from an inner surface. The light proceeds substantially parallel to the paraboloid axis, and is detected by an array detector located near an exit aperture. Each of the entrance and exit apertures is formed by the intersection of the paraboloid with a plane substantially perpendicular to the paraboloid axis. Incident (non-reflected) light from a source of limited extent (the Sun) illuminates a limited area on the detector array. Both direct and diffuse illumination may be reflected, or not reflected, before being received on the detector array. As the Sun traverses a path in the sky over some time interval, the track of the Sun can be traced on the detector array. A suitably modified Sun photometer might be used to study the dynamics of an environment on another planet or satellite with an atmosphere.

The contribution of the diffuse light component to the topographic effect on remotely sensed data

NASA Technical Reports Server (NTRS)

Justice, C.; Holben, B.

1980-01-01

The topographic effect is measured by the difference between the global radiance from inclined surfaces as a function of their orientation relative to the sensor position and light source. The short wave radiant energy incident on a surface is composed of direct sunlight, scattered skylight, and light reflected from surrounding terrain. The latter two components are commonly known as the diffuse component. The contribution of the diffuse light component to the topographic effect was examined and the significance of this diffuse component with respect to two direct radiance models was assessed. Diffuse and global spectral radiances were measured for a series of slopes and aspects of a uniform and surface in the red and photographic infrared parts of the spectrum, using a nadir pointing two channel handheld radiometer. The diffuse light was found to produce a topographic effect which varied from the topographic effect for direct light. The topographic effect caused by diffuse light was found to increase slightly with solar elevation and wavelength for the channels examined. The correlations between data derived from two simple direct radiance simulation models and the field data were not significantly affected when the diffuse component was removed from the radiances. Radiances from a 60 percent reflective surface, assuming no atmospheric path radiance, the diffuse light topographic effect contributed a maximum range of 3 pixel values in simulated LANDSAT data from all aspects with slopes up to 30 degrees.

Laser velocimeter for near-surface measurements

NASA Technical Reports Server (NTRS)

Johnson, Dennis A. (Inventor)

1992-01-01

The present invention relates to a laser Doppler velocimeter for near-wall measurements which includes at least one beam-turning device. The beam-turning device receives laser light, reflects and redirects the light at various angles in order to obtain measurements for all three velocity components at grazing incident angles. The beam-turning device includes a mirror or prism at one end which reflects the received light in a particular direction. A collector lens receives the particle scattered light from which the relevant velocity components are determined. The beam-turning device can also be a miniature fiber optic head which outputs laser light and can be turned in any direction.

Effects of leaf age within growth stages of pepper and sorghum plants on leaf thickness, water, chlorophyll, and light reflectance. [in spectral vegetation discrimination

NASA Technical Reports Server (NTRS)

Gausman, H. W.; Cardenas, R.; Berumen, A.

1974-01-01

Pepper and sorghum plants (characterized by porous and compact leaf mesophylls, respectively) were used to study the influence of leaf age on light reflectance. Measurements were limited to the upper five nodal positions within each growth stage, since upper leaves make up most of the reflectance surfaces remotely sensed. The increase in leaf thickness and water content with increasing leaf age was taken into consideration, since each of these factors affects the reflectance as well as the selection of spectral wavelength intervals for optimum discrimination of vegetation.

Directional reflectance and milli-scale feather morphology of the African Emerald Cuckoo, Chrysococcyx cupreus.

PubMed

Harvey, Todd Alan; Bostwick, Kimberly S; Marschner, Steve

2013-09-06

Diverse plumages have evolved among birds through complex morphological modifications. We investigate how the interplay of light with surface and subsurface feather morphology determines the direction of light propagation, an understudied aspect of avian visual signalling. We hypothesize that milli-scale modifications of feathers produce anisotropic reflectance, the direction of which may be predicted by the orientation of the milli-scale structure. The subject of this study is the African Emerald Cuckoo, Chrysococcyx cupreus, noted for its shimmering green iridescent appearance. Using a spherical gantry, we measured the change in the directional reflectance across the feather surface and over a hemisphere of incident lighting directions. Using a microCT scanner, we also studied the morphology of the structural branches of the barb. We tracked the changes in the directional reflectance to the orientation of the structural branches as observed in the CT data. We conclude that (i) the far-field signal of the feather consists of multiple specular components, each associated with a different structural branch and (ii) the direction of each specular component is correlated to the orientation of the corresponding structure.

Directional reflectance and milli-scale feather morphology of the African Emerald Cuckoo, Chrysococcyx cupreus

PubMed Central

Harvey, Todd Alan; Bostwick, Kimberly S.; Marschner, Steve

2013-01-01

Diverse plumages have evolved among birds through complex morphological modifications. We investigate how the interplay of light with surface and subsurface feather morphology determines the direction of light propagation, an understudied aspect of avian visual signalling. We hypothesize that milli-scale modifications of feathers produce anisotropic reflectance, the direction of which may be predicted by the orientation of the milli-scale structure. The subject of this study is the African Emerald Cuckoo, Chrysococcyx cupreus, noted for its shimmering green iridescent appearance. Using a spherical gantry, we measured the change in the directional reflectance across the feather surface and over a hemisphere of incident lighting directions. Using a microCT scanner, we also studied the morphology of the structural branches of the barb. We tracked the changes in the directional reflectance to the orientation of the structural branches as observed in the CT data. We conclude that (i) the far-field signal of the feather consists of multiple specular components, each associated with a different structural branch and (ii) the direction of each specular component is correlated to the orientation of the corresponding structure. PMID:23825113

Design and evaluation of an imaging spectrophotometer incorporating a uniform light source.

PubMed

Noble, S D; Brown, R B; Crowe, T G

2012-03-01

Accounting for light that is diffusely scattered from a surface is one of the practical challenges in reflectance measurement. Integrating spheres are commonly used for this purpose in point measurements of reflectance and transmittance. This solution is not directly applicable to a spectral imaging application for which diffuse reflectance measurements are desired. In this paper, an imaging spectrophotometer design is presented that employs a uniform light source to provide diffuse illumination. This creates the inverse measurement geometry to the directional illumination/diffuse reflectance mode typically used for point measurements. The final system had a spectral range between 400 and 1000 nm with a 5.2 nm resolution, a field of view of approximately 0.5 m by 0.5 m, and millimeter spatial resolution. Testing results indicate illumination uniformity typically exceeding 95% and reflectance precision better than 1.7%.

Method and apparatus for measuring surface density of explosive and inert dust in stratified layers

DOEpatents

Sapko, Michael J.; Perlee, Henry E.

1988-01-01

A method for determining the surface density of coal dust on top of rock dust or rock dust on top of coal dust is disclosed which comprises directing a light source at either a coal or rock dust layer overlaying a substratum of the other, detecting the amount of light reflected from the deposit, generating a signal from the reflected light which is converted into a normalized output (V), and calculating the surface density from the normalized output. The surface density S.sub.c of coal dust on top of rock dust is calculated according to the equation: S.sub.c =1/-a.sub.c ln(V) wherein a.sub.c is a constant for the coal dust particles, and the surface density S.sub.r of rock dust on top of coal dust is determined by the equation: ##EQU1## wherein a.sub.r is a constant based on the properties of the rock dust particles. An apparatus is also disclosed for carrying out the method of the present invention.

Surface Temperature Measurement Using Hematite Coating

NASA Technical Reports Server (NTRS)

Bencic, Timothy J. (Inventor)

2015-01-01

Systems and methods that are capable of measuring temperature via spectrophotometry principles are discussed herein. These systems and methods are based on the temperature dependence of the reflection spectrum of hematite. Light reflected from these sensors can be measured to determine a temperature, based on changes in the reflection spectrum discussed herein.

Non-Lambertian effects on remote sensing of surface reflectance and vegetation index

NASA Technical Reports Server (NTRS)

Lee, T. Y.; Kaufman, Y. J.

1986-01-01

This paper discusses the effects of non-Lambertian reflection from a homogeneous surface on remote sensing of the surface reflectance and vegetation index from a satellite. Remote measurement of the surface characteristics is perturbed by atmospheric scattering of sun light. This scattering tends to smooth the angular dependence of non-Lambertian surface reflectances, an effect that is not present in the case of Lambertian surfaces. This effect is calculated to test the validity of a Lambertian assumption used in remote sensing. For the three types of vegetations considered in this study, the assumption of Lambertian surface can be used satisfactorily in the derivation of surface reflectance from remotely measured radiance for a view angle outside the backscattering region. Within the backscattering region, however, the use of the assumption can result in a considerable error in the derived surface reflectance. Accuracy also deteriorates with increasing solar zenith angle. The angular distribution of the surface reflectance derived from remote measurements is smoother than that at the surface. The effect of surface non-Lambertianity on remote sensing of vegetation index is very weak. Since the effect is similiar in the visible and near infrared part of the solar spectrum for the vegetations treated in this study, it is canceled in deriving the vegetation index. The effect of the diffuse skylight on surface reflectance measurements at ground level is also discussed.

Design of an optical lens combined with a total internal reflection (TIR) freeform surface for a LED front fog lamp

NASA Astrophysics Data System (ADS)

Wang, Hong; Li, Xiufeng; Ge, Peng

2017-02-01

We propose a design method of an optical lens combined with a total internal reflection (TIR) freeform surface for a LED front fog lamp. The TIR freeform surface controls the edge rays of the LED source. It totally reflects the edge rays and makes them emit from the top surface of the lens. And the middle rays of the LED source go through the refractive surface and reach the measured plane. We simulate the model by Monte Carlo method. Simulation results show that the front fog lamp system can satisfy the requirement of ECE R19 Rev7. The light control efficiency can reach up to 76%.

The determination of surface albedo from meteorological satellites

NASA Technical Reports Server (NTRS)

Johnson, W. T.

1977-01-01

A surface albedo was determined from visible data collected by the NOAA-4 polar orbiting meteorological satellite. To filter out the major cause of atmospheric reflectivity, namely clouds, techniques were developed and applied to the data resulting in a map of global surface albedo. Neglecting spurious surface albedos for regions with persistent cloud cover, sun glint effects, insufficient reflected light and, at this time, some unresolved influences, the surface albedos retrieved from satellite data closely matched those of a global surface albedo map produced from surface and aircraft measurements and from characteristic albedos for land type and land use.

In-vacuum scattered light reduction with black cupric oxide surfaces for sensitive fluorescence detection.

PubMed

Norrgard, E B; Sitaraman, N; Barry, J F; McCarron, D J; Steinecker, M H; DeMille, D

2016-05-01

We demonstrate a simple and easy method for producing low-reflectivity surfaces that are ultra-high vacuum compatible, may be baked to high temperatures, and are easily applied even on complex surface geometries. Black cupric oxide (CuO) surfaces are chemically grown in minutes on any copper surface, allowing for low-cost, rapid prototyping, and production. The reflective properties are measured to be comparable to commercially available products for creating optically black surfaces. We describe a vacuum apparatus which uses multiple blackened copper surfaces for sensitive, low-background detection of molecules using laser-induced fluorescence.

Measurement of the absolute reflectance of polytetrafluoroethylene (PTFE) immersed in liquid xenon

NASA Astrophysics Data System (ADS)

Neves, F.; Lindote, A.; Morozov, A.; Solovov, V.; Silva, C.; Bras, P.; Rodrigues, J. P.; Lopes, M. I.

2017-01-01

The performance of a detector using liquid xenon (LXe) as a scintillator is strongly dependent on the collection efficiency for xenon scintillation light, which in turn is critically dependent on the reflectance of the surfaces that surround the active volume. To improve the light collection in such detectors the active volume is usually surrounded by polytetrafluoroethylene (PTFE) reflector panels, used due to its very high reflectance—even at the short wavelength of scintillation light of LXe (peaked at 178 nm). In this work, which contributed to the overall R&D effort towards the LUX-ZEPLIN (LZ) experiment, we present experimental results for the absolute reflectance measurements of three different PTFE samples (including the material used in the LUX detector) immersed in LXe for its scintillation light. The obtained results show that very high bi-hemispherical reflectance values (>= 97%) can be achieved, enabling very low energy thresholds in liquid xenon scintillator-based detectors.

Research notes : reflecting on road signs.

DOT National Transportation Integrated Search

2001-03-01

Signs need to be visible and readable at night as well as during the day. For nighttime visibility, signs are illuminated through retroreflection. flection occurs when light rays (e.g. from vehicle headlights) strike the surface and are reflect...

SO2 frost - UV-visible reflectivity and Io surface coverage

NASA Technical Reports Server (NTRS)

Nash, D. B.; Fanale, F. P.; Nelson, R. M.

1980-01-01

The reflectance spectrum in the range 0.24-0.85 microns of SO2 frost is measured in light of the discovery of SO2 gas in the atmosphere of Io and the possible discovery of the frost on its surface. Frost deposits up to 1.5 mm thick were grown in vacuum at 130 K and bi-directional reflectance spectra were obtained. Typical SO2 frost is found to exhibit very low reflectivity (2-5%) at 0.30 microns, rising steeply at 0.32 microns to attain a maximum reflectivity (75-80%) at 4.0 microns and uniformly high reflectivity throughout the visible and near infrared. Comparison with the full disk spectrum of Io reveals that no more than 20% of the surface can be covered with optically thick SO2 frost. Combinations of surface materials including SO2 frost which can produce the observed spectrum are indicated.

Infrared reflectometry of skin: Analysis of backscattered light from different skin layers

NASA Astrophysics Data System (ADS)

Pleitez, Miguel A.; Hertzberg, Otto; Bauer, Alexander; Lieblein, Tobias; Glasmacher, Mathias; Tholl, Hans; Mäntele, Werner

2017-09-01

We have recently reported infrared spectroscopy of human skin in vivo using quantum cascade laser excitation and photoacoustic or photothermal detection for non-invasive glucose measurement . Here, we analyze the IR light diffusely reflected from skin layers for spectral contributions of glucose. Excitation of human skin by an external cavity tunable quantum cascade laser in the spectral region from 1000 to 1245 cm- 1, where glucose exhibits a fingerprint absorption, yields reflectance spectra with some contributions from glucose molecules. A simple three-layer model of skin was used to calculate the scattering intensities from the surface and from shallow and deeper layers using the Boltzmann radiation transfer equation. Backscattering of light at wavelengths around 10 μm from the living skin occurs mostly from the Stratum corneum top layers and the shallow layers of the living epidermis. The analysis of the polarization of the backscattered light confirms this calculation. Polarization is essentially unchanged; only a very small fraction (< 3%) is depolarized at 90° with respect to the laser polarization set at 0°. Based on these findings, we propose that the predominant part of the backscattered light is due to specular reflectance and to scattering from layers close to the surface. Diffusely reflected light from deeper layers undergoing one or more scattering processes would appear with significantly altered polarization. We thus conclude that a non-invasive glucose measurement based on backscattering of IR light from skin would have the drawback that only shallow layers containing some glucose at concentrations only weakly related to blood glucose are monitored.

Seasonal Surface Changes in Namibia and Central Angola

NASA Technical Reports Server (NTRS)

2003-01-01

Brightness variations in the terrain along a portion of southwestern Africa are displayed in these views from the Multi-angle Imaging SpectroRadiometer (MISR). The panels portray an area that includes Namibia's Skeleton Coast and Etosha National Park as well as Angola's Cuando Cubango. The top panels were acquired on March 6, 2001, during the region's wet season, and the bottom panels were acquired on September 1, 2002, during the dry season. Corresponding changes in the abundance of vegetation are apparent. The images on the left are natural color (red, green, blue) images from MISR's vertical-viewing (nadir) camera. The images on the right represent one of MISR's derived surface products.

The radiance (light intensity) in each pixel of the so-called 'top-of-atmosphere' images on the left includes light that is reflected by the Earth's surface in addition to light that is transmitted and reflected by the atmosphere. The amount of radiation reflected by the surface into all upward directions, as opposed to any single direction, is important when studying Earth's energy budget. A quantity called the surface 'directional hemispherical reflectance' (DHR), sometimes called the 'black-sky albedo', captures this information, and is depicted in the images on the right. MISR's multi-angle views lead to more accurate estimates of the amount of radiation reflected into all directions than can be obtained as a result of looking at a single (e.g., vertically downward) view angle. Furthermore, to generate this surface product accurately, it is necessary to compensate for the effects of the intervening atmosphere, and MISR provides the ability to characterize and account for scattering of light by airborne particulates (aerosols).

The DHR is called a hemispherical reflectance because it measures the amount of radiation reflected into all upward directions, and which therefore traverses an imaginary hemisphere situated above each surface point. The 'directional' part of the name describes the illumination geometry, and indicates that in the absence of an intervening atmosphere, light from the Sun illuminates the surface from a single direction (that is, there is no diffuse skylight, hence the 'black-sky' terminology). The DHR is retrieved over land surfaces in each of MISR's four wavelength bands, and the images on the right are red, green, blue spectral composites. Regions where DHR could not be derived, either due to an inability to retrieve the necessary atmospheric characteristics or due to the presence of clouds, are shown in dark gray.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. These data products were generated from a portion of the imagery acquired during Terra orbits 6466 and 14388. The panels cover an area of about 380 kilometers x 760 kilometers, and utilize data from blocks 102 to 107 within World Reference System-2 path 181.

MISR was built and is managed by NASA's Jet Propulsion Laboratory,Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center,Greenbelt, MD. JPL is a division of the California Institute of Technology.

Deriving Polarization Properties of Desert-Reflected Solar Spectra with PARASOL Data

NASA Technical Reports Server (NTRS)

Sun, Wenbo; Baize, Rosemary R.; Lukashin, Constantine

2015-01-01

Reflected solar radiation from desert is strongly polarized by sand particles. To date, there is no reliable desert surface reflection model to calculate desert reflection matrix. In this study, the PARASOL data are used to retrieve physical properties of desert. These physical properties are then used in the ADRTM to calculate polarization of desert-reflected light for the whole solar spectra.

New kind of polarotaxis governed by degree of polarization: attraction of tabanid flies to differently polarizing host animals and water surfaces.

PubMed

Egri, Ádám; Blahó, Miklós; Sándor, András; Kriska, György; Gyurkovszky, Mónika; Farkas, Róbert; Horváth, Gábor

2012-05-01

Aquatic insects find their habitat from a remote distance by means of horizontal polarization of light reflected from the water surface. This kind of positive polarotaxis is governed by the horizontal direction of polarization (E-vector). Tabanid flies also detect water by this kind of polarotaxis. The host choice of blood-sucking female tabanids is partly governed by the linear polarization of light reflected from the host's coat. Since the coat-reflected light is not always horizontally polarized, host finding by female tabanids may be different from the established horizontal E-vector polarotaxis. To reveal the optical cue of the former polarotaxis, we performed choice experiments in the field with tabanid flies using aerial and ground-based visual targets with different degrees and directions of polarization. We observed a new kind of polarotaxis being governed by the degree of polarization rather than the E-vector direction of reflected light. We show here that female and male tabanids use polarotaxis governed by the horizontal E-vector to find water, while polarotaxis based on the degree of polarization serves host finding by female tabanids. As a practical by-product of our studies, we explain the enigmatic attractiveness of shiny black spheres used in canopy traps to catch tabanids.

New kind of polarotaxis governed by degree of polarization: attraction of tabanid flies to differently polarizing host animals and water surfaces

NASA Astrophysics Data System (ADS)

Egri, Ádám; Blahó, Miklós; Sándor, András; Kriska, György; Gyurkovszky, Mónika; Farkas, Róbert; Horváth, Gábor

2012-05-01

Aquatic insects find their habitat from a remote distance by means of horizontal polarization of light reflected from the water surface. This kind of positive polarotaxis is governed by the horizontal direction of polarization (E-vector). Tabanid flies also detect water by this kind of polarotaxis. The host choice of blood-sucking female tabanids is partly governed by the linear polarization of light reflected from the host's coat. Since the coat-reflected light is not always horizontally polarized, host finding by female tabanids may be different from the established horizontal E-vector polarotaxis. To reveal the optical cue of the former polarotaxis, we performed choice experiments in the field with tabanid flies using aerial and ground-based visual targets with different degrees and directions of polarization. We observed a new kind of polarotaxis being governed by the degree of polarization rather than the E-vector direction of reflected light. We show here that female and male tabanids use polarotaxis governed by the horizontal E-vector to find water, while polarotaxis based on the degree of polarization serves host finding by female tabanids. As a practical by-product of our studies, we explain the enigmatic attractiveness of shiny black spheres used in canopy traps to catch tabanids.

Gap plasmon-based metasurfaces: fundamentals and applications (Conference Presentation)

NASA Astrophysics Data System (ADS)

Pors, Anders

2016-04-01

Plasmonic metasurfaces, which can be considered as the two-dimensional analog of metal-based metamaterials, have recently attracted considerable attention due to the possibility to fully control the reflected or transmitted light, while featuring relatively low losses even at optical wavelengths and being suitable for planar fabrication techniques. Among all the different design approaches, one particular configuration, consisting of a subwavelength thin dielectric spacer sandwiched between an optically thick metal film and an array of metal nanobricks (also known as nanopatches), has gained awareness from researchers working in practical any frequency regime as its realization only requires on step of lithography, yet with the possibility to fully control the amplitude and phase of the reflected light. At optical wavelengths, the full control of the reflected light is closely associated with gap surface plasmon (GSP) resonances and, hence, the configuration is also known as GSP-based metasurface. In this work, we highlight the connection between the properties of GSP modes and the optical response of GSP-based metasurfaces, particularly discussing the possibility to independently control either the reflection phases for two orthogonal polarizations or both the amplitude and phase of the reflected light for one polarization by proper choice of geometrical and material parameters [1]. Having obtained thorough insight into the optical response of GSP-based metasurfaces, we design and realize at optical and near-infrared wavelengths a broad range of inhomogeneous metasurfaces targeting different applications. For example, we exemplify the control of reflection amplitude by performing plasmonic color printing on a subwavelength scale [2], while full control of reflection phases for orthogonal polarizations are illustrated by the realization of unidirectional polarization-controlled surface plasmon polariton couplers [3] and compact polarimeters [4]. Finally, the simultaneous control of the amplitude and phase of reflected light allow us to perform calculus operations, such as differentiation and integration, on the incident light [5], which signifies the possibility to do optical signal processing using GSP-based metasurfaces. References: 1. A. Pors and S. I. Bozhevolnyi, "Gap plasmon-based phase-amplitude metasurfaces: material constraints", Opt. Mater. Express 5, 2448-2458 (2015). 2. A. S. Roberts, A. Pors, O. Albrektsen, and S. I. Bozhevolnyi, "Subwavelength plasmonic color printing for ambient use", Nano Lett. 14, 783-787 (2014). 3. A. Pors, M. G. Nielsen, T. Bernardin, J.-C. Weeber, and S. I. Bozhevolnyi, "Efficient unidirectional polarization-controlled excitation of surface plasmon polaritons", Light: Sci. Applications 3, e197 (2014). 4. A. Pors, M. G. Nielsen, and S. I. Bozhevolnyi, "Plasmonic metagratings for simultaneous determination of Stokes parameters", Optica 2, 716-723 (2015). 5. A. Pors, M. G. Nielsen, and S. I. Bozhevolnyi, "Analog computing using reflective plasmonic metasurfaces", Nano Lett. 15, 791-797 (2015).

[Modeling and Simulation of Spectral Polarimetric BRDF].

PubMed

Ling, Jin-jiang; Li, Gang; Zhang, Ren-bin; Tang, Qian; Ye, Qiu

2016-01-01

Under the conditions of the polarized light, The reflective surface of the object is affected by many factors, refractive index, surface roughness, and so the angle of incidence. For the rough surface in the different wavelengths of light exhibit different reflection characteristics of polarization, a spectral polarimetric BRDF based on Kirchhof theory is proposee. The spectral model of complex refraction index is combined with refraction index and extinction coefficient spectral model which were got by using the known complex refraction index at different value. Then get the spectral model of surface roughness derived from the classical surface roughness measuring method combined with the Fresnel reflection function. Take the spectral model of refraction index and roughness into the BRDF model, then the spectral polarimetirc BRDF model is proposed. Compare the simulation results of the refractive index varies with wavelength, roughness is constant, the refraction index and roughness both vary with wavelength and origin model with other papers, it shows that, the spectral polarimetric BRDF model can show the polarization characteristics of the surface accurately, and can provide a reliable basis for the application of polarization remote sensing, and other aspects of the classification of substances.

Laboratory insights into the detection of surface biosignatures by remote-sensing techniques

NASA Astrophysics Data System (ADS)

Poch, O.; Pommerol, A.; Jost, B.; Roditi, I.; Frey, J.; Thomas, N.

2014-03-01

With the progress of direct imaging techniques, it will be possible in the short or long-term future to retrieve more efficiently the information on the physical properties of the light reflected by rocky exoplanets (Traub et al., 2010). The search for visible-infrared absorption bands of peculiar gases (O2, CH4 etc.) in this light could give clues for the presence of life (Kaltenegger and Selsis, 2007). Even more uplifting would be the direct detection of life itself, on the surface of an exoplanet. Considering this latter possibility, what is the potential of optical remote-sensing methods to detect surface biosignatures? Reflected light from the surface of the Earth exhibits a strong surface biosignature in the form of an abrupt change of reflectance between the visible and infrared range of the spectrum (Seager et al., 2005). This spectral feature called "vegetation red-edge" is possibly the consequence of biological evolution selecting the right chemical structures enabling the plants to absorb the visible energy, while preventing them from overheating by reflecting more efficiently the infrared. Such red-edge is also found in primitive photosynthetic bacteria, cyanobacteria, that colonized the surface of the Earth ocean and continents billions of years before multicellular plants (Knacke, 2003). If life ever arose on an Earth-like exoplanet, one could hypothesize that some form of its surface-life evolves into similar photo-active organisms, also exhibiting a red-edge. In this paper, we will present our plan and preliminary results of a laboratory study aiming at precising the potentiality of remote sensing techniques in detecting such surface biosignatures. Using equipment that has been developed in our team for surface photometry studies (Pommerol 2011, Jost 2013, Pommerol 2013), we will investigate the reflectance spectra and bidirectional reflectance function of soils containing bacteria such as cyanobacteria, in various environmental conditions. We will also present our plan to incorporate polarization measurements, and particularly circular polarization, because it can be a marker of homochirality, which is supposed to be a universal property of life. Finally, the analyses of both biotic and abiotic materials will help to assess if (or in which peculiar conditions) remote sensing techniques can discriminate between false positive and strong biomarkers. Ultimately, these laboratory data can serve as reference data to guide and interpret future observations, paving the way for the detection of life on distant exoplanets.

The effect of surface anisotropy on the accuracy of total ozone estimates from satellite observations

NASA Technical Reports Server (NTRS)

Fraser, R. S.; Ahmad, Z.

1978-01-01

The total amount of ozone in a vertical column of the earth's atmosphere is being derived from satellite measurements of the intensity of ultraviolet sunlight scattered by the earth-atmosphere system. The algorithm for deriving the ozone amount utilizes the assumption that the earth's surface reflects the incident light isotropically according to Lambert's law. Natural surface reflection deviates more or less from this law. Two extreme examples of anisotropic reflection from dark ocean and from bright snow are analyzed by means of models for their effects on the derived values of ozone.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akhmedzhanov, I M; Kibalov, D S; Smirnov, V K

We report a detailed numerical simulation of the reflection of visible light from a sub-wavelength grating with a rectangular profile on the silicon surface. Simulation is carried out by the effective refractive index method and rigorous coupled-wave analysis. The dependences of the reflectance on the grating depth, fill factor and angle of incidence for TE and TM polarisations are obtained and analysed. Good agreement between the results obtained by the two methods for grating periods of ∼100 nm is found. The possibility of reducing the polarised light reflectance to about 1% by adjusting the depth and the grating fill factormore » is demonstrated. The characteristics of the Brewster effect manifestation (pseudo-Brewster angle) in the system under study are considered. The possibility of the pseudo-Brewster angle existence and its absence for both polarisations of the incident light is shown as a function of the parameters of a rectangular nanostructure on the surface. (laser applications and other topics in quantum electronics)« less

Reflectance, illumination, and appearance in color constancy

PubMed Central

McCann, John J.; Parraman, Carinna; Rizzi, Alessandro

2013-01-01

We studied color constancy using a pair of identical 3-D Color Mondrian displays. We viewed one 3-D Mondrian in nearly uniform illumination, and the other in directional, nonuniform illumination. We used the three dimensional structures to modulate the light falling on the painted surfaces. The 3-D structures in the displays were a matching set of wooden blocks. Across Mondrian displays, each corresponding facet had the same paint on its surface. We used only 6 chromatic, and 5 achromatic paints applied to 104 block facets. The 3-D blocks add shadows and multiple reflections not found in flat Mondrians. Both 3-D Mondrians were viewed simultaneously, side-by-side. We used two techniques to measure correlation of appearance with surface reflectance. First, observers made magnitude estimates of changes in the appearances of identical reflectances. Second, an author painted a watercolor of the 3-D Mondrians. The watercolor's reflectances quantified the changes in appearances. While constancy generalizations about illumination and reflectance hold for flat Mondrians, they do not for 3-D Mondrians. A constant paint does not exhibit perfect color constancy, but rather shows significant shifts in lightness, hue and chroma in response to the structure in the nonuniform illumination. Color appearance depends on the spatial information in both the illumination and the reflectances of objects. The spatial information of the quanta catch from the array of retinal receptors generates sensations that have variable correlation with surface reflectance. Models of appearance in humans need to calculate the departures from perfect constancy measured here. This article provides a dataset of measurements of color appearances for computational models of sensation. PMID:24478738

Computer modeling of bidirectional spectra: the role of geometry of illumination/observation

NASA Astrophysics Data System (ADS)

Grynko, Ye.; Shkuratov, Yu.; Mall, U.

Reflectance spectroscopy is widely used in the remote sensing of the Moon. Ground based and space spectrophotometric observations provide information about physical properties and chemical composition of lunar regolith. The main spectral features such as spectral slope and parameters of the absorption bands are different for different minerals and depend on the surface roughness, particle size, degrees of maturity and cristallinity, etc. In order to interpret reflectance measurements a model describing the light interaction with a regolith-like surface is needed. However, the problem of light scattering in dense particulate media consisting of irregular particles larger than the wavelength of light (which is the case for lunar regolith) has not yet been solved and only approximate models exist. Spectrophotometric properties of such surfaces can be analyzed in the geometric optics approach with one-dimensional (1-D) light scattering models (e.g., [1]). Although the 1-D models are successfully applied to interprete planetary regolith spectra they do not give an answer how spectral features depend on the geometrical illumination/observation condition of the surface. Laboratory measurements prove that the changing lighting conditions play a significant role in the formation of the above mentioned spectral features [2, 3]. In the presented work we use computer modeling to simulate light reflection from a regolith-like surface. Our computer experiment includes two stages: The simulation of the medium and ray tracing [4, 5]. Particles with random irregular shape are randomly distributed in a cyclically closed model volume which forms a semi-infinite medium (surface). Their surface is described by flat facets.The applied technique uses a Monte Carlo ray tracing method with parallel rays falling under a given angle relative to the average surface normal. The interaction of a ray with a particle surface facet is determined by Fresnel formulas and Snell's law. The model delivers the absolute surface reflectance as function of wavelength for a given geometrical illumination/observation condition In this paper we study the dependence of the reflectance spectra on the phase angle. The angle of incidence is constant and equals to 70°. The phase angle changes from 0° to 160°. For the substance which the particles are made of we chose average value 1 for the complex refractive index corresponding to lunar mare and highlands. Our calculations reveal a strong dependence of the spectral slopes on the phase angle. This confirms the previous general conclusion given in [2] that the larger the phase angle is the redder is the spectrum. A decomposition of the reflected flux into different scattering components shows that this is caused by the indicatrix of single scattering. Multiple scattering has almost no influence on spectral slope. The shape of the absorption bands also varies with phase angle but this dependence is not regular. The 1 µm feature is more pronounced at small and moderate phase angles and becomes wide and less visible at very large phase angles. References. [1] Yu. Shkuratov et al., Icarus, 137, 235-246 (1999). [2] C. M. Pieters et al., LPSC XXII, Abstract #1069 (1991). [3] A. Cord et al., Icarus, 165, 414-427 (2003). [4] Ye. Grynko and Yu. Shkuratov, J. Quant. Spectrosc. Rad. Trans. 78, 319- 340 (2003). [5] Yu. Shkuratov and Ye. Grynko, Icarus, 173, 16-28 (2006). 2

Reflective insulating blinds for windows and the like

DOEpatents

Barnes, P.R.; Shapira, H.B.

1979-12-07

Energy-conserving window blinds are provided. The blinds are fabricated from coupled and adjustable slats, each slat having an insulation layer and a reflective surface to face outwardly when the blinds are closed. A range of desired light and air transmission may be selected with the reflective surfaces of the slats adapted to direct sunlight upward toward the ceiling when the blinds are open. When the blinds are closed, the insulation of the slats reduces the heat loss or gain produced by the windows. If desired, the reflective surfaces of the slats may be concave. The edges of the slats are designed to seal against adjacent slats when the blinds are closed to ensure minimum air flow between slats.

Reflective insulating blinds for windows and the like

DOEpatents

Barnes, Paul R.; Shapira, Hanna B.

1981-01-01

Energy-conserving window blinds are provided. The blinds are fabricated from coupled and adjustable slats, each slat having an insulation layer and a reflective surface to face outwardly when the blinds are closed. A range of desired light and air transmission may be selected with the reflective surfaces of the slats adapted to direct sunlight upward toward the ceiling when the blinds are open. When the blinds are closed, the insulation of the slats reduces the heat loss or gain produced by the windows. If desired, the reflective surfaces of the slats may be concave. The edges of the slats are designed to seal against adjacent slats when the blinds are closed to ensure minimum air flow between slats.

Surface composition of Mercury from reflectance spectrophotometry

NASA Technical Reports Server (NTRS)

Vilas, Faith

1988-01-01

The controversies surrounding the existing spectra of Mercury are discussed together with the various implications for interpretations of Mercury's surface composition. Special attention is given to the basic procedure used for reducing reflectance spectrophotometry data, the factors that must be accounted for in the reduction of these data, and the methodology for defining the portion of the surface contributing the greatest amount of light to an individual spectrum. The application of these methodologies to Mercury's spectra is presented.

Metal-dielectric frequency-selective surface for high performance solar window coatings

NASA Astrophysics Data System (ADS)

Toor, Fatima; Guneratne, Ananda C.; Temchenko, Marina

2016-03-01

We demonstrate a solar control window film consisting of metallic nanoantennas designed to reflect infrared (IR) light while allowing visible light to pass through. The film consists of a capacitive frequency-selective surface (CFSS) which acts as a band-stop filter, reflecting only light at target wavelengths. The designed CFSS when installed on windows will lower air conditioning costs by reflecting undesired wavelengths of light and thus reduce the amount of heat that enters a building. State-of-the-art commercial solar control films consist of a multilayer stack which is costly ( 13/m2 to 40/m2) to manufacture and absorbs IR radiation, causing delamination or glass breakage when attached to windows. Our solar control film consists of a nanostructured metallic layer on a polyethylene terephthalate (PET) substrate that reflects IR radiation instead of absorbing it, solving the delamination problem. The CFSS is also easy to manufacture with roll-to-roll nanoimprint lithography at a cost of <$12/m2. We design the CFSS using the COMSOL Wave Optics module to solve for electromagnetic wave propagation in optical media via the finite element method. The simulation domain is reduced to a single unit cell with periodic boundary conditions to account for the symmetries of the planar, periodic CFSS. The design is optimized using parametric sweeps around the various geometric components of the metallic nanoantenna. Our design achieves peak reflection of 80% at 1000 nm and has a broadband IR response that will allow for optimum solar control without significantly affecting the transmission of visible light.

Noninvasive assessment of articular cartilage surface damage using reflected polarized light microscopy

NASA Astrophysics Data System (ADS)

Huynh, Ruby N.; Nehmetallah, George; Raub, Christopher B.

2017-06-01

Articular surface damage occurs to cartilage during normal aging, osteoarthritis, and in trauma. A noninvasive assessment of cartilage microstructural alterations is useful for studies involving cartilage explants. This study evaluates polarized reflectance microscopy as a tool to assess surface damage to cartilage explants caused by mechanical scraping and enzymatic degradation. Adult bovine articular cartilage explants were scraped, incubated in collagenase, or underwent scrape and collagenase treatments. In an additional experiment, cartilage explants were subject to scrapes at graduated levels of severity. Polarized reflectance parameters were compared with India ink surface staining, features of histological sections, changes in explant wet weight and thickness, and chondrocyte viability. The polarized reflectance signal was sensitive to surface scrape damage and revealed individual scrape features consistent with India ink marks. Following surface treatments, the reflectance contrast parameter was elevated and correlated with image area fraction of India ink. After extensive scraping, polarized reflectance contrast and chondrocyte viability were lower than that from untreated explants. As part of this work, a mathematical model was developed and confirmed the trend in the reflectance signal due to changes in surface scattering and subsurface birefringence. These results demonstrate the effectiveness of polarized reflectance microscopy to sensitively assess surface microstructural alterations in articular cartilage explants.

Improved broadband and quasi-omnidirectional anti-reflection properties with biomimetic silicon nanostructures.

PubMed

Huang, Yi-Fan; Chattopadhyay, Surojit; Jen, Yi-Jun; Peng, Cheng-Yu; Liu, Tze-An; Hsu, Yu-Kuei; Pan, Ci-Ling; Lo, Hung-Chun; Hsu, Chih-Hsun; Chang, Yuan-Huei; Lee, Chih-Shan; Chen, Kuei-Hsien; Chen, Li-Chyong

2007-12-01

Nature routinely produces nanostructured surfaces with useful properties, such as the self-cleaning lotus leaf, the colour of the butterfly wing, the photoreceptor in brittlestar and the anti-reflection observed in the moth eye. Scientists and engineers have been able to mimic some of these natural structures in the laboratory and in real-world applications. Here, we report a simple aperiodic array of silicon nanotips on a 6-inch wafer with a sub-wavelength structure that can suppress the reflection of light at a range of wavelengths from the ultraviolet, through the visible part of the spectrum, to the terahertz region. Reflection is suppressed for a wide range of angles of incidence and for both s- and p-polarized light. The antireflection properties of the silicon result from changes in the refractive index caused by variations in the height of the silicon nanotips, and can be simulated with models that have been used to explain the low reflection from moth eyes. The improved anti-reflection properties of the surfaces could have applications in renewable energy and electro-optical devices for the military.

The polarization of light in coastal and open oceans: Reflection and transmission by the air-sea interface and application for the retrieval of water optical properties

NASA Astrophysics Data System (ADS)

Foster, Robert

For decades, traditional remote sensing retrieval methods that rely solely on the spectral intensity of the water-leaving light have provided indicators of aquatic ecosystem health. With the increasing demand for new water quality indicators and improved accuracy of existing ones, the limits of traditional remote sensing approaches are becoming apparent. Use of the additional information intrinsic to the polarization state of light is therefore receiving more attention. One of the major challenges inherent in any above-surface determination of the water-leaving radiance, scalar or vector, is the removal of extraneous light which has not interacted with the water body and is therefore not useful for remote sensing of the water itself. Due in-part to the lack of a proven alternative, existing polarimeter installations have thus far assumed that such light was reflected by a flat sea surface, which can lead to large inaccuracies in the water-leaving polarization signal. This dissertation rigorously determines the full Mueller matrices for both surface-reflected skylight and upwardly transmitted light by a wind-driven ocean surface. A Monte Carlo code models the surface in 3D and performs polarized ray-tracing, while a vector radiative transfer (VRT) simulation generates polarized light distributions from which the initial Stokes vector for each ray is inferred. Matrices are computed for the observable range of surface wind speeds, viewing and solar geometries, and atmospheric aerosol loads. Radiometer field-of-view effects are also assessed. Validation of the results is achieved using comprehensive VRT simulations of the atmosphere-ocean system based on several oceanographic research cruises and specially designed polarimeters developed by the City College of New York: one submerged beneath the surface and one mounted on a research vessel. When available, additional comparisons are made at 9 km altitude with the NASA Research Scanning Polarimeter (RSP). Excellent agreement is achieved between all instrumentation, demonstrating the accuracy of the modeling approach and validating the computed Mueller matrices. Further, the results are used to demonstrate the feasibility for polarimetric retrieval of the total attenuation coefficient for Case II waters, a feat which is not possible using scalar remote sensing methods.

Single-Molecule Light-Sheet Imaging of Suspended T Cells.

PubMed

Ponjavic, Aleks; McColl, James; Carr, Alexander R; Santos, Ana Mafalda; Kulenkampff, Klara; Lippert, Anna; Davis, Simon J; Klenerman, David; Lee, Steven F

2018-05-08

Adaptive immune responses are initiated by triggering of the T cell receptor. Single-molecule imaging based on total internal reflection fluorescence microscopy at coverslip/basal cell interfaces is commonly used to study this process. These experiments have suggested, unexpectedly, that the diffusional behavior and organization of signaling proteins and receptors may be constrained before activation. However, it is unclear to what extent the molecular behavior and cell state is affected by the imaging conditions, i.e., by the presence of a supporting surface. In this study, we implemented single-molecule light-sheet microscopy, which enables single receptors to be directly visualized at any plane in a cell to study protein dynamics and organization in live, resting T cells. The light sheet enabled the acquisition of high-quality single-molecule fluorescence images that were comparable to those of total internal reflection fluorescence microscopy. By comparing the apical and basal surfaces of surface-contacting T cells using single-molecule light-sheet microscopy, we found that most coated-glass surfaces and supported lipid bilayers profoundly affected the diffusion of membrane proteins (T cell receptor and CD45) and that all the surfaces induced calcium influx to various degrees. Our results suggest that, when studying resting T cells, surfaces are best avoided, which we achieve here by suspending cells in agarose. Copyright © 2018. Published by Elsevier Inc.

[Study of hyperspectral polarized reflectance of vegetation canopy at nadir viewing direction].

PubMed

Lŭ, Yun-Feng

2013-04-01

In the present study, corn canopy is the objective. Firstly the polarization of corn canopy was analyzed based on polarization reflection mechanism; then, the polarization of canopy was measured in different growth period at nadir before heading. The result proved the theoretical derivation that the light reflected from corn canopy is polarized, and found that in the total reflection the polarization light accounts for up to 10%. This shows that polarization measurement provides auxiliary information for remote sensing, but also illustrates that the use of the polarization information retrieval of atmospheric parameters should be considered when the surface polarization affects on it.

Large-scale cauliflower-shaped hierarchical copper nanostructures for efficient photothermal conversion

NASA Astrophysics Data System (ADS)

Fan, Peixun; Wu, Hui; Zhong, Minlin; Zhang, Hongjun; Bai, Benfeng; Jin, Guofan

2016-07-01

Efficient solar energy harvesting and photothermal conversion have essential importance for many practical applications. Here, we present a laser-induced cauliflower-shaped hierarchical surface nanostructure on a copper surface, which exhibits extremely high omnidirectional absorption efficiency over a broad electromagnetic spectral range from the UV to the near-infrared region. The measured average hemispherical absorptance is as high as 98% within the wavelength range of 200-800 nm, and the angle dependent specular reflectance stays below 0.1% within the 0-60° incident angle. Such a structured copper surface can exhibit an apparent heating up effect under the sunlight illumination. In the experiment of evaporating water, the structured surface yields an overall photothermal conversion efficiency over 60% under an illuminating solar power density of ~1 kW m-2. The presented technology provides a cost-effective, reliable, and simple way for realizing broadband omnidirectional light absorptive metal surfaces for efficient solar energy harvesting and utilization, which is highly demanded in various light harvesting, anti-reflection, and photothermal conversion applications. Since the structure is directly formed by femtosecond laser writing, it is quite suitable for mass production and can be easily extended to a large surface area.Efficient solar energy harvesting and photothermal conversion have essential importance for many practical applications. Here, we present a laser-induced cauliflower-shaped hierarchical surface nanostructure on a copper surface, which exhibits extremely high omnidirectional absorption efficiency over a broad electromagnetic spectral range from the UV to the near-infrared region. The measured average hemispherical absorptance is as high as 98% within the wavelength range of 200-800 nm, and the angle dependent specular reflectance stays below 0.1% within the 0-60° incident angle. Such a structured copper surface can exhibit an apparent heating up effect under the sunlight illumination. In the experiment of evaporating water, the structured surface yields an overall photothermal conversion efficiency over 60% under an illuminating solar power density of ~1 kW m-2. The presented technology provides a cost-effective, reliable, and simple way for realizing broadband omnidirectional light absorptive metal surfaces for efficient solar energy harvesting and utilization, which is highly demanded in various light harvesting, anti-reflection, and photothermal conversion applications. Since the structure is directly formed by femtosecond laser writing, it is quite suitable for mass production and can be easily extended to a large surface area. Electronic supplementary information (ESI) available: XRD patterns of the fs laser structured Cu surface as produced and after the photothermal conversion test, directly measured temperature values on Cu surfaces, temperature rise on Cu surfaces at varied solar irradiation angles, comparison of the white light and IR images of the structured Cu surface with the polished Cu surface, temperature rise on the peripheral zones of the blue coating surface. See DOI: 10.1039/c6nr03662g

Angular and Seasonal Variation of Spectral Surface Reflectance Ratios: Implications for the Remote Sensing of Aerosol over Land

NASA Technical Reports Server (NTRS)

Remer, L. A.; Wald, A. E.; Kaufman, Y. J.

1999-01-01

We obtain valuable information on the angular and seasonal variability of surface reflectance using a hand-held spectrometer from a light aircraft. The data is used to test a procedure that allows us to estimate visible surface reflectance from the longer wavelength 2.1 micrometer channel (mid-IR). Estimating or avoiding surface reflectance in the visible is a vital first step in most algorithms that retrieve aerosol optical thickness over land targets. The data indicate that specular reflection found when viewing targets from the forward direction can severely corrupt the relationships between the visible and 2.1 micrometer reflectance that were derived from nadir data. There is a month by month variation in the ratios between the visible and the mid-IR, weakly correlated to the Normalized Difference Vegetation Index (NDVI). If specular reflection is not avoided, the errors resulting from estimating surface reflectance from the mid-IR exceed the acceptable limit of DELTA-rho approximately 0.01 in roughly 40% of the cases, using the current algorithm. This is reduced to 25% of the cases if specular reflection is avoided. An alternative method that uses path radiance rather than explicitly estimating visible surface reflectance results in similar errors. The two methods have different strengths and weaknesses that require further study.

Polarized reflectance and transmittance properties of windblown sea surfaces.

PubMed

Mobley, Curtis D

2015-05-20

Generation of random sea surfaces using wave variance spectra and Fourier transforms is formulated in a way that guarantees conservation of wave energy and fully resolves wave height and slope variances. Monte Carlo polarized ray tracing, which accounts for multiple scattering between light rays and wave facets, is used to compute effective Mueller matrices for reflection and transmission of air- or water-incident polarized radiance. Irradiance reflectances computed using a Rayleigh sky radiance distribution, sea surfaces generated with Cox-Munk statistics, and unpolarized ray tracing differ by 10%-18% compared with values computed using elevation- and slope-resolving surfaces and polarized ray tracing. Radiance reflectance factors, as used to estimate water-leaving radiance from measured upwelling and sky radiances, are shown to depend on sky polarization, and improved values are given.

Multiple scattering in the remote sensing of natural surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Wen-Hao; Weeks, R.; Gillespie, A.R.

1996-07-01

Radiosity models predict the amount of light scattered many times (multiple scattering) among scene elements in addition to light interacting with a surface only once (direct reflectance). Such models are little used in remote sensing studies because they require accurate digital terrain models and, typically, large amounts of computer time. We have developed a practical radiosity model that runs relatively quickly within suitable accuracy limits, and have used it to explore problems caused by multiple-scattering in image calibration, terrain correction, and surface roughness estimation for optical images. We applied the radiosity model to real topographic surfaces sampled at two verymore » different spatial scales: 30 m (rugged mountains) and 1 cm (cobbles and gravel on an alluvial fan). The magnitude of the multiple-scattering (MS) effect varies with solar illumination geometry, surface reflectivity, sky illumination and surface roughness. At the coarse scale, for typical illumination geometries, as much as 20% of the image can be significantly affected (>5%) by MS, which can account for as much as {approximately}10% of the radiance from sunlit slopes, and much more for shadowed slopes, otherwise illuminated only by skylight. At the fine scale, radiance from as much as 30-40% of the scene can have a significant MS component, and the MS contribution is locally as high as {approximately}70%, although integrating to the meter scale reduces this limit to {approximately}10%. Because the amount of MS increases with reflectivity as well as roughness, MS effects will distort the shape of reflectance spectra as well as changing their overall amplitude. The change is proportional to surface roughness. Our results have significant implications for determining reflectivity and surface roughness in remote sensing.« less

High efficiency incandescent lighting

DOEpatents

Bermel, Peter; Ilic, Ognjen; Chan, Walker R.; Musabeyoglu, Ahmet; Cukierman, Aviv Ruben; Harradon, Michael Robert; Celanovic, Ivan; Soljacic, Marin

2014-09-02

Incandescent lighting structure. The structure includes a thermal emitter that can, but does not have to, include a first photonic crystal on its surface to tailor thermal emission coupled to, in a high-view-factor geometry, a second photonic filter selected to reflect infrared radiation back to the emitter while passing visible light. This structure is highly efficient as compared to standard incandescent light bulbs.

Two-dimensional PSF prediction of multiple-reflection optical systems with rough surfaces

NASA Astrophysics Data System (ADS)

Tayabaly, Kashmira; Spiga, Daniele; Sironi, Giorgia; Pareschi, Giovani; Lavagna, Michele

2016-09-01

The focusing accuracy in reflective optical systems, usually expressed in terms of the Point Spread Function (PSF) is chiefly determined by two factors: the deviation of the mirror shape from the nominal design and the surface finishing. While the effects of the former are usually well described by the geometrical optics, the latter is diffractive/interferential in nature and determined by a distribution of defects that cover several decades in the lateral scale (from a few millimeters to a few microns). Clearly, reducing the level of scattered light is crucial to improve the focusing of the collected radiation, particularly for astronomical telescopes that aim to detect faint light signals from our Universe. Telescopes are typically arranged in multiple reflections configuration and the behavior of the multiply-scattered radiation becomes difficult to predict and control. Also it is difficult to disentangle the effect of surface scattering from the PSF degradation caused by the shape deformation of the optical elements. This paper presents a simple and unifying method for evaluating the contribution of optical surfaces defects to the two-dimensional PSF of a multi-reflections system, regardless of the classification of a spectral range as "geometry" or "roughness". This method, entirely based on Huygens-Fresnel principle in the far-field approximation, was already applied in grazing-incidence X-ray mirrors and experimentally validated for a single reflection system, accounting for the real surface topography of the optics. In this work we show the extension of this formalism to a double reflection system and introducing real microroughness data. The formalism is applied to a MAGIC-I panel mirror that was fully characterized, allowing us to predict the PSF and the validation with real measurements of the double reflection ASTRI telescope, a prototype of CTA-SST telescope.

Replication of Leaf Surface Structures for Light Harvesting

PubMed Central

Huang, Zhongjia; Yang, Sai; Zhang, Hui; Zhang, Meng; Cao, Wei

2015-01-01

As one of the most important hosts of natural light harvesting, foliage normally has complicated surface structures to capture solar radiances. Bio-mimicking leaf surface structures can provide novel designs of covers in photovoltaic systems. In this article, we reported on replicating leaf surface structures on poly-(methyl methacrylate) polymers to prompt harvesting efficiencies. Prepared via a double transfer process, the polymers were found to have high optical transparencies and transmission hazes, with both values exceeding 80% in some species. Benefiting from optical properties and wrinkled surfaces, the biomimetic polymers brought up to 17% gains to photovoltaic efficiencies. Through Monte-Carlo simulations of light transport, ultrahigh haze values and low reflections were attributed to lightwave guidance schemes lead by the nano- and micro-morphologies which are inherited from master leaves. Thus, leaf surface bio-mimicking can be considered as a strategic direction to design covers of light harvesting systems. PMID:26381702

New formulation of the laws of reflection of light

NASA Astrophysics Data System (ADS)

Pérez, Ángel Luis; Martínez, Guadalupe; Suero, María. Isabel

2013-11-01

A new formulation of the laws of reflection of light based on the particle model is presented, and it is shown the equivalence between the new and the classic formulations. The proposed formulation has a significant educational value, as it allows drawing analogies between the phenomena of light reflection and elastic collisions, which are very well known by students. The proposed formulation is: "If at one point on a surface whose orientation in space is defined by a unit vector k, strikes an incident ray corresponding to a plane wave (propagating through a homogeneous and isotropic medium) whose direction of propagation coincides with that from a unit vector ui [expressed in terms of its components with respect to an orthonormal coordinate system, with one of its axis coinciding with the direction of k (ui = uix i + uiy j + uiz k)], it will be reflected so that the unit vector whose direction coincides with that from the reflected ray, ur, will only differ from the unit vector whose direction coincides with that from the incident ray, in the change of the sign of the component in the direction of k (ur = uix i + uiy j - uiz k)". Stated in everyday language, is equivalent of saying that the reflection of light occurs as if the photons underwent perfectly elastic collisions with the surface in question. As an example, this formulation is applied for the resolution of the classic reflection problem of the three plane mirrors forming a trirectangular trihedron.

Water Detection Based on Sky Reflections

NASA Technical Reports Server (NTRS)

Rankin, Arturo L.; Matthies, Larry H.

2010-01-01

This software has been designed to detect water bodies that are out in the open on cross-country terrain at mid- to far-range (approximately 20 100 meters), using imagery acquired from a stereo pair of color cameras mounted on a terrestrial, unmanned ground vehicle (UGV). Non-traversable water bodies, such as large puddles, ponds, and lakes, are indirectly detected by detecting reflections of the sky below the horizon in color imagery. The appearance of water bodies in color imagery largely depends on the ratio of light reflected off the water surface to the light coming out of the water body. When a water body is far away, the angle of incidence is large, and the light reflected off the water surface dominates. We have exploited this behavior to detect water bodies out in the open at mid- to far-range. When a water body is detected at far range, a UGV s path planner can begin to look for alternate routes to the goal position sooner, rather than later. As a result, detecting water hazards at far range generally reduces the time required to reach a goal position during autonomous navigation. This software implements a new water detector based on sky reflections that geometrically locates the exact pixel in the sky that is reflecting on a candidate water pixel on the ground, and predicts if the ground pixel is water based on color similarity and local terrain features

Free-form surface design method for a collimator TIR lens.

PubMed

Tsai, Chung-Yu

2016-04-01

A free-form (FF) surface design method is proposed for a general axial-symmetrical collimator system consisting of a light source and a total internal reflection lens with two coupled FF boundary surfaces. The profiles of the boundary surfaces are designed using a FF surface construction method such that each incident ray is directed (refracted and reflected) in such a way as to form a specified image pattern on the target plane. The light ray paths within the system are analyzed using an exact analytical model and a skew-ray tracing approach. In addition, the validity of the proposed FF design method is demonstrated by means of ZEMAX simulations. It is shown that the illumination distribution formed on the target plane is in good agreement with that specified by the user. The proposed surface construction method is mathematically straightforward and easily implemented in computer code. As such, it provides a useful tool for the design and analysis of general axial-symmetrical optical systems.

High contrast near-infrared polarized reflectance images of demineralization on tooth buccal and occlusal surfaces at lambda = 1310-nm.

PubMed

Wu, J; Fried, D

2009-03-01

Sound enamel manifests peak transparency in the near-IR (NIR) at 1310-nm, therefore the near-IR is ideally suited for high contrast imaging of dental caries. The purpose of this study was to acquire images of early demineralized enamel on the buccal and occlusal surfaces of extracted human teeth using NIR reflectance imaging and compare the contrast of those images with the contrast of images taken using other methods. Fifteen human molars were used in this in vitro study. Teeth were painted with a clear acid-resistant varnish, leaving two 2 mm x 2 mm windows on the buccal and occlusal surfaces of each tooth for demineralization. Artificial lesions were produced in the exposed windows after a 2-day exposure to a demineralizing solution at pH 4.5. Lesions were imaged using NIR transillumination, NIR and visible light reflectance, and fluorescence imaging methods. Crossed polarizers were used where appropriate to improve contrast. Polarization sensitive optical coherence tomography (PS-OCT) was also used to non-destructively assess the depth and severity of demineralization in each sample window. NIR reflectance imaging had the highest image contrast for both the buccal and occlusal groups and it was significantly higher contrast than visible light reflectance (P < 0.05). The results of the study suggest that NIR reflectance imaging is a promising new method for acquiring high contrast images of early demineralization on tooth surfaces. Copyright 2009 Wiley-Liss, Inc.

General method to evaluate substrate surface modification techniques for light extraction enhancement of organic light emitting diodes

NASA Astrophysics Data System (ADS)

Krummacher, B. C.; Mathai, M. K.; Choong, V.; Choulis, S. A.; So, F.; Winnacker, A.

2006-09-01

The external light output of organic light emitting diodes (OLEDs) can be increased by modifying the light emitting surface. The apparent light extraction enhancement is given by the ratio between the efficiency of the unmodified device and the efficiency of the modified device. This apparent light extraction enhancement is dependent on the OLED architecture itself and is not the correct value to judge the effectiveness of a technique to enhance light outcoupling due to substrate surface modification. We propose a general method to evaluate substrate surface modification techniques for light extraction enhancement of OLEDs independent from the device architecture. This method is experimentally demonstrated using green electrophosphorescent OLEDs with different device architectures. The substrate surface of these OLEDs was modified by applying a prismatic film to increase light outcoupling from the device stack. It was demonstrated that the conventionally measured apparent light extraction enhancement by means of the prismatic film does not reflect the actual performance of the light outcoupling technique. Rather, by comparing the light extracted out of the prismatic film to that generated in the OLED layers and coupled into the substrate (before the substrate/air interface), a more accurate evaluation of light outcoupling enhancement can be achieved. Furthermore we show that substrate surface modification can change the output spectrum of a broad band emitting OLED.

Prediction of Viking lander camera image quality

NASA Technical Reports Server (NTRS)

Huck, F. O.; Burcher, E. E.; Jobson, D. J.; Wall, S. D.

1976-01-01

Formulations are presented that permit prediction of image quality as a function of camera performance, surface radiance properties, and lighting and viewing geometry. Predictions made for a wide range of surface radiance properties reveal that image quality depends strongly on proper camera dynamic range command and on favorable lighting and viewing geometry. Proper camera dynamic range commands depend mostly on the surface albedo that will be encountered. Favorable lighting and viewing geometries depend mostly on lander orientation with respect to the diurnal sun path over the landing site, and tend to be independent of surface albedo and illumination scattering function. Side lighting with low sun elevation angles (10 to 30 deg) is generally favorable for imaging spatial details and slopes, whereas high sun elevation angles are favorable for measuring spectral reflectances.

Ultrasensitive biochemical sensing device and method of sensing analytes

DOEpatents

Pinchuk, Anatoliy

2017-06-06

Systems and methods biochemically sense a concentration of a ligand using a sensor having a substrate having a metallic nanoparticle array formed onto a surface of the substrate. A light source is incident on the surface. A matrix is deposited over the nanoparticle array and contains a protein adapted to binding the ligand. A detector detects s-polarized and p-polarized light from the reflective surface. Spacing of nanoparticles in the array and wavelength of light are selected such that plasmon resonance occurs with an isotropic point such that -s and -p polarizations of the incident light result in substantially identical surface Plasmon resonance, wherein binding of the ligand to the protein shifts the resonance such that differences between the -S and -P polarizations give in a signal indicative of presence of the ligand.

Control of crankshaft finish by scattering technique

NASA Astrophysics Data System (ADS)

Fontani, Daniela; Francini, Franco; Longobardi, Giuseppe; Sansoni, Paola

2001-06-01

The paper describes a new sensor dedicated to measure and check the surface quality of mechanical products. The results were obtained comparing the light scattered from two different ranges of angles by means of 16 photodiodes. The device is designed for obtaining valid data from curved surfaces as that of a crankshaft. Experimental measurements show that the ratio between scattered and reflected light intensity increases with the surface roughness. This device was developed for the off-tolerance detection of mechanical pieces in industrial production. Results of surface quality on crankshaft supplied by Renault were carried out.

Implementation of cost-effective diffuse light source mechanism to reduce specular reflection and halo effects for resistor-image processing

NASA Astrophysics Data System (ADS)

Chen, Yung-Sheng; Wang, Jeng-Yau

2015-09-01

Light source plays a significant role to acquire a qualified image from objects for facilitating the image processing and pattern recognition. For objects possessing specular surface, the phenomena of reflection and halo appearing in the acquired image will increase the difficulty of information processing. Such a situation may be improved by the assistance of valuable diffuse light source. Consider reading resistor via computer vision, due to the resistor's specular reflective surface it will face with a severe non-uniform luminous intensity on image yielding a higher error rate in recognition without a well-controlled light source. A measurement system including mainly a digital microscope embedded in a replaceable diffuse cover, a ring-type LED embedded onto a small pad carrying a resistor for evaluation, and Arduino microcontrollers connected with PC, is presented in this paper. Several replaceable cost-effective diffuse covers made by paper bowl, cup and box inside pasted with white paper are presented for reducing specular reflection and halo effects and compared with a commercial diffuse some. The ring-type LED can be flexibly configured to be a full or partial lighting based on the application. For each self-made diffuse cover, a set of resistors with 4 or 5 color bands are captured via digital microscope for experiments. The signal-to-noise ratio from the segmented resistor-image is used for performance evaluation. The detected principal axis of resistor body is used for the partial LED configuration to further improve the lighting condition. Experimental results confirm that the proposed mechanism can not only evaluate the cost-effective diffuse light source but also be extended as an automatic recognition system for resistor reading.

Vector Sky Glint Corrections for Above Surface Retrieval of the Subsurface Polarized Light Field

NASA Astrophysics Data System (ADS)

Gilerson, A.; Foster, R.; McGilloway, A.; Ibrahim, A.; El-habashi, A.; Carrizo, C.; Ahmed, S.

2016-02-01

Knowledge of the underwater light field is fundamental to determining the health of the world's oceans and coastal regions. For decades, traditional remote sensing retrieval methods that rely solely on the spectral intensity of the water-leaving light have provided indicators of marine ecosystem health. As the demand for retrieval accuracy rises, use of the polarized nature of light as an additional remote sensing tool is becoming necessary. In order to observe the underwater polarized light field from above the surface (for ship, shore, or satellite applications), a method of correcting the above water signal for the effects of polarized surface-reflected skylight is needed. For three weeks in July-August 2014, the NASA Ship Aircraft Bio-Optical Research (SABOR) cruise continuously observed the polarized radiance of the ocean and the sky using a HyperSAS-POL system. The system autonomously tracks the Sun position and the heading of the research vessel in order to maintain a fixed relative solar azimuth angle (i.e. ±90°) and therefore avoid the specular reflection of the sunlight. Additionally, in-situ inherent optical properties (IOPs) were continuously acquired using a set of instrument packages modified for underway measurement, hyperspectral radiometric measurements were taken manually at all stations, and an underwater polarimeter was deployed when conditions permitted. All measurements, above and below the sea surface, were combined and compared in an effort to first develop a glint (sky + Sun) correction scheme for the upwelling polarized signal from a wind-driven ocean surface and compare with one assuming that the ocean surface is flat. Accurate retrieval of the subsurface vector light field is demonstrated through comparisons with polarized radiative transfer codes and direct measurements made by the underwater polarimeter.

[The research of UV-responsive sensitivity enhancement of fluorescent coating films by MgF2 layer].

PubMed

Lu, Zhong-Rong; Ni, Zheng-Ji; Tao, Chun-Xian; Hong, Rui-Jin; Zhang, Da-Wei; Huang, Yuan-Shen

2014-03-01

A low cost and less complicated expansion approach of wavelength responses with a Lumogen phosphor coating was adopted, as they increased the quantum efficiency of CCD and CMOS detectors in ultra-violet by absorbing UV light and then re emitting visible light. In this paper, the sensitivity enhancement of fluorescence coatings was studied by adding an anti-reflection film or barrier film to reduce the loss of the scattering and reflection on the incident interface. The Lumogen and MgF2/Lumogen film were deposited on quartz glasses by physical vacuum deposition. The surface morphology, transmittance spectrum, reflectance spectrum and fluorescence emission spectrum were obtained by atomic force microscope (AFM), spectrophotometer and fluorescence spectrometer, respectively. The results indicated that MgF2 film had obvious positive effect on reducing scattering and reflection loss in 500-700 nm, and enhancing the absorption of Lumogen coating in ultraviolet spectrum. Meanwhile, the fluorescent emission intensity had a substantial increase by smoothing the film surface and thus reducing the light scattering. At the same time, the MgF2 layer could protect Lumogen coating from damaging and contamination, which give a prolong lifetime of the UV-responsive CCD sensors with fluorescent coatings.

Wavelength independent interferometer

NASA Technical Reports Server (NTRS)

Hochberg, Eric B. (Inventor); Page, Norman A. (Inventor)

1991-01-01

A polychromatic interferometer utilizing a plurality of parabolic reflective surfaces to properly preserve the fidelity of light wavefronts irrespective of their wavelengths as they pass through the instrument is disclosed. A preferred embodiment of the invention utilizes an optical train which comprises three off-axis parabolas arranged in conjunction with a beam-splitter and a reference mirror to form a Twyman-Green interferometer. An illumination subsystem is provided and comprises a pair of lasers at different preselected wavelengths in the visible spectrum. The output light of the two lasers is coaxially combined by means of a plurality of reflectors and a grating beam combiner to form a single light source at the focal point of the first parabolic reflection surface which acts as a beam collimator for the rest of the optical train. By using visible light having two distinct wavelengths, the present invention provides a long equivalent wavelength interferogram which operates at visible light wherein the effective wavelength is equal to the product of the wavelengths of the two laser sources divided by their difference in wavelength. As a result, the invention provides the advantages of what amounts to long wavelength interferometry but without incurring the disadvantage of the negligible reflection coefficient of the human eye to long wavelength frequencies which would otherwise defeat any attempt to form an interferogram at that low frequency using only one light source.

Spectrally enhanced imaging of occlusal surfaces and artificial shallow enamel erosions with a scanning fiber endoscope

PubMed Central

Nelson, Leonard Y.; Seibel, Eric J.

2012-01-01

Abstract. An ultrathin scanning fiber endoscope, originally developed for cancer diagnosis, was used to image dental occlusal surfaces as well as shallow artificially induced enamel erosions from human extracted teeth (n=40). Enhanced image resolution of occlusal surfaces was obtained using a short-wavelength 405-nm illumination laser. In addition, artificial erosions of varying depths were also imaged with 405-, 404-, 532-, and 635-nm illumination lasers. Laser-induced autofluorescence images of the teeth using 405-nm illumination were also obtained. Contrast between sound and eroded enamel was quantitatively computed for each imaging modality. For shallow erosions, the image contrast with respect to sound enamel was greatest for the 405-nm reflected image. It was also determined that the increased contrast was in large part due to volume scattering with a smaller component from surface scattering. Furthermore, images obtained with a shallow penetration depth illumination laser (405 nm) provided the greatest detail of surface enamel topography since the reflected light does not contain contributions from light reflected from greater depths within the enamel tissue. Multilayered Monte Carlo simulations were also performed to confirm the experimental results. PMID:22894502

Spectrally enhanced imaging of occlusal surfaces and artificial shallow enamel erosions with a scanning fiber endoscope

NASA Astrophysics Data System (ADS)

Zhang, Liang; Nelson, Leonard Y.; Seibel, Eric J.

2012-07-01

An ultrathin scanning fiber endoscope, originally developed for cancer diagnosis, was used to image dental occlusal surfaces as well as shallow artificially induced enamel erosions from human extracted teeth (n=40). Enhanced image resolution of occlusal surfaces was obtained using a short-wavelength 405-nm illumination laser. In addition, artificial erosions of varying depths were also imaged with 405-, 404-, 532-, and 635-nm illumination lasers. Laser-induced autofluorescence images of the teeth using 405-nm illumination were also obtained. Contrast between sound and eroded enamel was quantitatively computed for each imaging modality. For shallow erosions, the image contrast with respect to sound enamel was greatest for the 405-nm reflected image. It was also determined that the increased contrast was in large part due to volume scattering with a smaller component from surface scattering. Furthermore, images obtained with a shallow penetration depth illumination laser (405 nm) provided the greatest detail of surface enamel topography since the reflected light does not contain contributions from light reflected from greater depths within the enamel tissue. Multilayered Monte Carlo simulations were also performed to confirm the experimental results.

Additive manufacturing of reflective optics: evaluating finishing methods

NASA Astrophysics Data System (ADS)

Leuteritz, G.; Lachmayer, R.

2018-02-01

Individually shaped light distributions become more and more important in lighting technologies and thus the importance of additively manufactured reflectors increases significantly. The vast field of applications ranges from automotive lighting to medical imaging and bolsters the statement. However, the surfaces of additively manufactured reflectors suffer from insufficient optical properties even when manufactured using optimized process parameters for the Selective Laser Melting (SLM) process. Therefore post-process treatments of reflectors are necessary in order to further enhance their optical quality. This work concentrates on the effectiveness of post-process procedures for reflective optics. Based on already optimized aluminum reflectors, which are manufactured with a SLM machine, the parts are differently machined after the SLM process. Selected finishing methods like laser polishing, sputtering or sand blasting are applied and their effects quantified and compared. The post-process procedures are investigated on their impact on surface roughness and reflectance as well as geometrical precision. For each finishing method a demonstrator will be created and compared to a fully milled sample and among themselves. Ultimately, guidelines are developed in order to figure out the optimal treatment of additively manufactured reflectors regarding their optical and geometrical properties. Simulations of the light distributions will be validated with the developed demonstrators.

Capturing latent fingerprints from metallic painted surfaces using UV-VIS spectroscope

NASA Astrophysics Data System (ADS)

Makrushin, Andrey; Scheidat, Tobias; Vielhauer, Claus

2015-03-01

In digital crime scene forensics, contactless non-destructive detection and acquisition of latent fingerprints by means of optical devices such as a high-resolution digital camera, confocal microscope, or chromatic white-light sensor is the initial step prior to destructive chemical development. The applicability of an optical sensor to digitalize latent fingerprints primarily depends on reflection properties of a substrate. Metallic painted surfaces, for instance, pose a problem for conventional sensors which make use of visible light. Since metallic paint is a semi-transparent layer on top of the surface, visible light penetrates it and is reflected off of the metallic flakes randomly disposed in the paint. Fingerprint residues do not impede light beams making ridges invisible. Latent fingerprints can be revealed, however, using ultraviolet light which does not penetrate the paint. We apply a UV-VIS spectroscope that is capable of capturing images within the range from 163 to 844 nm using 2048 discrete levels. We empirically show that latent fingerprints left behind on metallic painted surfaces become clearly visible within the range from 205 to 385 nm. Our proposed streakiness score feature determining the proportion of a ridge-valley pattern in an image is applied for automatic assessment of a fingerprint's visibility and distinguishing between fingerprint and empty regions. The experiments are carried out with 100 fingerprint and 100 non-fingerprint samples.

Low-temperature relative reflectivity measurements of reflective and scintillating foils used in rare event searches

NASA Astrophysics Data System (ADS)

Langenkämper, A.; Ulrich, A.; Defay, X.; Feilitzsch, F. v.; Lanfranchi, J.-C.; Mondragón, E.; Münster, A.; Oppenheimer, C.; Potzel, W.; Roth, S.; Schönert, S.; Steiger, H.; Trinh Thi, H. H.; Wawoczny, S.; Willers, M.; Zöller, A.

2018-03-01

In this work we investigate the reflectivity of highly reflective multilayer polymer foils used in the CRESST experiment. The CRESST experiment searches directly for dark matter via operating scintillating CaWO4 crystals as targets for elastic dark matter-nucleon scattering. In order to suppress background events, the experiment employs the so-called phonon-light technique which is based on the simultaneous measurement of the heat signal in the main CaWO4 target crystal and of the emitted scintillation light with a separate cryogenic light detector. Both detectors are surrounded by a highly reflective and scintillating multilayer polymer foil to increase the light collection efficiency and to veto surface backgrounds. While this study is motivated by the CRESST experiment, the results are also relevant for other rare event searches using scintillating cryogenic bolometers in the field of the search of dark matter and neutrinoless double beta decay (0 νββ). In this work a dedicated experiment has been set up to determine the relative reflectivity at 300 K and 20 K of three multilayer foils ("VM2000", "VM2002", "Vikuiti") produced by the company 3M. The intensity of a light beam reflected off the foil is measured with a CCD camera. The ratio of the intensities at 300 K and 20 K corresponds to the relative reflectivity change. The measurements performed in this work show no variation of the reflectivity with temperature at a level of ∼1%.

Light emitting device having peripheral emissive region

DOEpatents

Forrest, Stephen R

2013-05-28

Light emitting devices are provided that include one or more OLEDs disposed only on a peripheral region of the substrate. An OLED may be disposed only on a peripheral region of a substantially transparent substrate and configured to emit light into the substrate. Another surface of the substrate may be roughened or include other features to outcouple light from the substrate. The edges of the substrate may be beveled and/or reflective. The area of the OLED(s) may be relatively small compared to the substrate surface area through which light is emitted from the device. One or more OLEDs also or alternatively may be disposed on an edge of the substrate about perpendicular to the surface of the substrate through which light is emitted, such that they emit light into the substrate. A mode expanding region may be included between each such OLED and the substrate.

An Ingenious Super Light Trapping Surface Templated from Butterfly Wing Scales

NASA Astrophysics Data System (ADS)

Han, Zhiwu; Li, Bo; Mu, Zhengzhi; Yang, Meng; Niu, Shichao; Zhang, Junqiu; Ren, Luquan

2015-08-01

Based on the super light trapping property of butterfly Trogonoptera brookiana wings, the SiO2 replica of this bionic functional surface was successfully synthesized using a simple and highly effective synthesis method combining a sol-gel process and subsequent selective etching. Firstly, the reflectivity of butterfly wing scales was carefully examined. It was found that the whole reflectance spectroscopy of the butterfly wings showed a lower level (less than 10 %) in the visible spectrum. Thus, it was confirmed that the butterfly wings possessed a super light trapping effect. Afterwards, the morphologies and detailed architectures of the butterfly wing scales were carefully investigated using the ultra-depth three-dimensional (3D) microscope and field emission scanning electronic microscopy (FESEM). It was composed by the parallel ridges and quasi-honeycomb-like structure between them. Based on the biological properties and function above, an exact SiO2 negative replica was fabricated through a synthesis method combining a sol-gel process and subsequent selective etching. At last, the comparative analysis of morphology feature size and the reflectance spectroscopy between the SiO2 negative replica and the flat plate was conducted. It could be concluded that the SiO2 negative replica inherited not only the original super light trapping architectures, but also the super light trapping characteristics of bio-template. This work may open up an avenue for the design and fabrication of super light trapping materials and encourage people to look for more super light trapping architectures in nature.

Analyses of Impact of Needle Surface Properties on Estimation of Needle Absorption Spectrum: Case Study with Coniferous Needle and Shoot Samples

PubMed Central

Yang, Bin; Knyazikhin, Yuri; Lin, Yi; Yan, Kai; Chen, Chi; Park, Taejin; Choi, Sungho; Mõttus, Matti; Rautiainen, Miina; Myneni, Ranga B.; Yan, Lei

2017-01-01

Leaf scattering spectrum is the key optical variable that conveys information about leaf absorbing constituents from remote sensing. It cannot be directly measured from space because the radiation scattered from leaves is affected by the 3D canopy structure. In addition, some radiation is specularly reflected at the surface of leaves. This portion of reflected radiation is partly polarized, does not interact with pigments inside the leaf and therefore contains no information about its interior. Very little empirical data are available on the spectral and angular scattering properties of leaf surfaces. Whereas canopy-structure effects are well understood, the impact of the leaf surface reflectance on estimation of leaf absorption spectra remains uncertain. This paper presents empirical and theoretical analyses of angular, spectral, and polarimetric measurements of light reflected by needles and shoots of Pinus koraiensis and Picea koraiensis species. Our results suggest that ignoring the leaf surface reflected radiation can result in an inaccurate estimation of the leaf absorption spectrum. Polarization measurements may be useful to account for leaf surface effects because radiation reflected from the leaf surface is partly polarized, whereas that from the leaf interior is not. PMID:28868160

Recend advances of using VIIRS DNB for surface PM2.5 and fire monitoring

NASA Astrophysics Data System (ADS)

Wang, J.; Polivka, T. N.; Hyer, E. J.; Xu, X.; Ichoku, I.

2017-12-01

The launch of the Suomi National Polar-orbiting Partner- ship (S-NPP) satellite on 28 October 2011 has opened up unprecedented capabilities with the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument. With a heritage extending back over 40 years to the Defense Meteorological Satel- lite Program (DMSP) Sensor Aerospace Vehicle Electronics Package (SAP), first launched in 1970, Advanced Very High Resolution Radiometer (AVHRR, first launched 1978), and Moderate Resolution Imaging Spectroradiometer (MODIS, first launched in 1999), VIIRS boasts improved spatial resolution and a higher signal-to-noise ratio than these legacy sensors. In particular, at the spatial resolution of 750 m, the VIIRS' day-and-night band (DNB) can monitor the visible light reflected by the Earth and atmsophere in all conditions, from strong reflection of sun light by cloud to weak reflection of moon light by desert at night. While several studies have looked into the potential use of DNB for mapping city lights and for retrieving aerosol optical depth at night, there are still lots of learn about DNB. Here, we will present our recent work of using DNB together with other VIIRS data to improve detection of smaller and cooler fires, to characterize the smoldering vs. flamming phase of fires , and to derive surface PM2.5 at night. Quantiitve understanding of visible light trasnfer from surface to the top of atmospehre will be presented, along with the study to undertand the radiation of fires from visible to infrared spectrum. Varous case studies will be shown in which 30% more fire pixels were detected as comapred to tradiational infrared-mehod only. Cross validation of DNB-based regression model shows that the estimated surface PM2.5 concentration has nearly no bias and a linear correlation coefficient (R) of 0.67 with respect to the corresponding hourly observed surface PM2.5 concentration.

Reducing the maladaptive attractiveness of solar panels to polarotactic insects.

PubMed

Horváth, Gábor; Blahó, Miklós; Egri, Adám; Kriska, György; Seres, István; Robertson, Bruce

2010-12-01

Human-made objects (e.g., buildings with glass surfaces) can reflect horizontally polarized light so strongly that they appear to aquatic insects to be bodies of water. Insects that lay eggs in water are especially attracted to such structures because these insects use horizontal polarization of light off bodies of water to find egg-laying sites. Thus, these sources of polarized light can become ecological traps associated with reproductive failure and mortality in organisms that are attracted to them and by extension with rapid population declines or collapse. Solar panels are a new source of polarized light pollution. Using imaging polarimetry, we measured the reflection-polarization characteristics of different solar panels and in multiple-choice experiments in the field we tested their attractiveness to mayflies, caddis flies, dolichopodids, and tabanids. At the Brewster angle, solar panels polarized reflected light almost completely (degree of polarization d ≈ 100%) and substantially exceeded typical polarization values for water (d ≈ 30-70%). Mayflies (Ephemeroptera), stoneflies (Trichoptera), dolichopodid dipterans, and tabanid flies (Tabanidae) were the most attracted to solar panels and exhibited oviposition behavior above solar panels more often than above surfaces with lower degrees of polarization (including water), but in general they avoided solar cells with nonpolarizing white borders and white grates. The highly and horizontally polarizing surfaces that had nonpolarizing, white cell borders were 10- to 26-fold less attractive to insects than the same panels without white partitions. Although solar panels can act as ecological traps, fragmenting their solar-active area does lessen their attractiveness to polarotactic insects. The design of solar panels and collectors and their placement relative to aquatic habitats will likely affect populations of aquatic insects that use polarized light as a behavioral cue. © 2010 Society for Conservation Biology.

Interrelating meteorite and asteroid spectra at UV-Vis-NIR wavelengths using novel multiple-scattering methods

NASA Astrophysics Data System (ADS)

Martikainen, Julia; Penttilä, Antti; Gritsevich, Maria; Muinonen, Karri

2017-10-01

Asteroids have remained mostly the same for the past 4.5 billion years, and provide us information on the origin, evolution and current state of the Solar System. Asteroids and meteorites can be linked by matching their respective reflectance spectra. This is difficult, because spectral features depend strongly on the surface properties, and meteorite surfaces are free of regolith dust present in asteroids. Furthermore, asteroid surfaces experience space weathering which affects their spectral features.We present a novel simulation framework for assessing the spectral properties of meteorites and asteroids and matching their reflectance spectra. The simulations are carried out by utilizing a light-scattering code that takes inhomogeneous waves into account and simulates light scattering by Gaussian-random-sphere particles large compared to the wavelength of the incident light. The code uses incoherent input and computes phase matrices by utilizing incoherent scattering matrices. Reflectance spectra are modeled by combining olivine, pyroxene, and iron, the most common materials that dominate the spectral features of asteroids and meteorites. Space weathering is taken into account by adding nanoiron into the modeled asteroid spectrum. The complex refractive indices needed for the simulations are obtained from existing databases, or derived using an optimization that utilizes our ray-optics code and the measured spectrum of the material.We demonstrate our approach by applying it to the reflectance spectrum of (4) Vesta and the reflectance spectrum of the Johnstown meteorite measured with the University of Helsinki integrating-sphere UV-Vis-NIR spectrometer.Acknowledgments. The research is funded by the ERC Advanced Grant No. 320773 (SAEMPL).

Comparison of the bidirectional reflectance distribution function of various surfaces

NASA Astrophysics Data System (ADS)

Fernandez, Rene; Seasholtz, Richard G.; Oberle, Lawrence G.; Kadambi, Jaikrishnan R.

1989-04-01

This paper describes the development and use of a system to measure the bidirectional reflectance distribution function (BRDF) of various surfaces. The BRDF measurements are to be used in the analysis and design of optical measurement systems such as laser anemometers. An Ar-ion laser (514 nm) was the light source. Preliminary results are presented for eight samples: two glossy black paints, two flat black paints, black glass, sand-blasted Al, unworked Al, and a white paint. A BaSO4 white reflectance standard was used as the reference sample throughout the tests.

In situ measurements of scattering from contaminated optics in the Vacuum Ultraviolet

NASA Astrophysics Data System (ADS)

Herren, Kenneth A.; Linton, Roger C.; Whitaker, Ann F.

1990-07-01

NASA's In Situ Contamination Effects Facility has been used to measure the time dependence of the angular reflectance from molecularly contaminated optical surfaces in the vacuum ultraviolet. The light scattering measurements are accomplished in situ on optical surfaces in real time during deposition of molecular contaminants. The measurements are taken using noncoherent VUV sources with the predominant wavelengths being the krypton resonance lines at 1236 and 1600 angstroms. Detection of the scattered light is accomplished using a set of three solar blind VUV photomultipliers. An in-plane VUV BRDF (bidirectional reflectance distribution function) experiment is described and details of the on-going program to characterize optical materials exposed to the space environment is reported.

Intensity compensation for on-line detection of defects on fruit

NASA Astrophysics Data System (ADS)

Wen, Zhiqing; Tao, Yang

1997-10-01

A machine-vision sorting system was developed that utilizes the difference in light reflectance of fruit surfaces to distinguish the defective and good apples. To accommodate to the spherical reflectance characteristics of fruit with curved surface like apple, a spherical transform algorithm was developed that converts the original image to a non-radiant image without losing defective segments on the fruit. To prevent high-quality dark-colored fruit form being classified into the defective class and increase the defect detection rate for light-colored fruit, an intensity compensation method using maximum propagation was used. Experimental results demonstrated the effectiveness of the method based on maximum propagation and spherical transform for on-line detection of defects on apples.

In situ measurements of scattering from contaminated optics in the Vacuum Ultraviolet

NASA Technical Reports Server (NTRS)

Herren, Kenneth A.; Linton, Roger C.; Whitaker, Ann F.

1990-01-01

NASA's In Situ Contamination Effects Facility has been used to measure the time dependence of the angular reflectance from molecularly contaminated optical surfaces in the vacuum ultraviolet. The light scattering measurements are accomplished in situ on optical surfaces in real time during deposition of molecular contaminants. The measurements are taken using noncoherent VUV sources with the predominant wavelengths being the krypton resonance lines at 1236 and 1600 angstroms. Detection of the scattered light is accomplished using a set of three solar blind VUV photomultipliers. An in-plane VUV BRDF (bidirectional reflectance distribution function) experiment is described and details of the on-going program to characterize optical materials exposed to the space environment is reported.

Probing Ultrafast Electron Dynamics at Surfaces Using Soft X-Ray Transient Reflectivity Spectroscopy

NASA Astrophysics Data System (ADS)

Baker, L. Robert; Husek, Jakub; Biswas, Somnath; Cirri, Anthony

The ability to probe electron dynamics with surface sensitivity on the ultrafast time scale is critical for understanding processes such as charge separation, injection, and surface trapping that mediate efficiency in catalytic and energy conversion materials. Toward this goal, we have developed a high harmonic generation (HHG) light source for femtosecond soft x-ray reflectivity. Using this light source we investigated the ultrafast carrier dynamics at the surface of single crystalline α-Fe2O3, polycrystalline α-Fe2O3, and the mixed metal oxide, CuFeO2. We have recently demonstrated that CuFeO2 in particular is a selective catalyst for photo-electrochemical CO2 reduction to acetate; however, the role of electronic structure and charge carrier dynamics in mediating catalytic selectivity has not been well understood. Soft x-ray reflectivity measurements probe the M2,3, edges of the 3d transition metals, which provide oxidation and spin state resolution with element specificity. In addition to chemical state specificity, these measurements are also surface sensitive, and by independently simulating the contributions of the real and imaginary components of the complex refractive index, we can differentiate between surface and sub-surface contributions to the excited state spectrum. Accordingly, this work demonstrates the ability to probe ultrafast carrier dynamics in catalytic materials with element and chemical state specificity and with surface sensitivity.

See around the corner using active imaging

NASA Astrophysics Data System (ADS)

Steinvall, Ove; Elmqvist, Magnus; Larsson, Håkan

2011-11-01

This paper investigates the prospects of "seeing around the corner" using active imaging. A monostatic active imaging system offers interesting capabilities in the presence of glossy reflecting objects. Examples of such surfaces are windows in buildings and cars, calm water, signs and vehicle surfaces. During daylight it might well be possible to use mirrorlike reflection by the naked eye or a CCD camera for non-line of sight imaging. However the advantage with active imaging is that one controls the illumination. This will not only allow for low light and night utilization but also for use in cases where the sun or other interfering lights limit the non-line of sight imaging possibility. The range resolution obtained by time gating will reduce disturbing direct reflections and allow simultaneous view in several directions using range discrimination. Measurements and theoretical considerations in this report support the idea of using laser to "see around the corner". Examples of images and reflectivity measurements will be presented together with examples of potential system applications.

Efficient anomalous reflection through near-field interactions in metasurfaces

NASA Astrophysics Data System (ADS)

Chalabi, H.; Ra'di, Y.; Sounas, D. L.; Alù, A.

2017-08-01

Gradient metasurfaces have been extensively used in the past few years for advanced wave manipulation over a thin surface. These metasurfaces have been mostly designed based on the generalized laws of reflection and refraction. However, it was recently revealed that metasurfaces based on this approach tend to suffer from inefficiencies and complex design requirements. We have recently proposed a different approach to the problem of efficient beam steering using a surface, based on bianisotropic particles in a periodic array. Here, we show highly efficient reflective metasurfaces formed by pairs of isotropic dielectric rods, which can offer asymmetrical scattering of normally incident beams with unitary efficiency. Our theory shows that moderately broadband anomalous reflection can be achieved with suitably designed periodic arrays of isotropic nanoparticles. We also demonstrate practical designs using TiO2 cylindrical nanorods to deflect normally incident light toward a desired direction. The proposed structures may pave the way to a broader range of light management opportunities, with applications in energy harvesting, signaling, and communications.

Variable path length spectrophotometric probe

DOEpatents

O'Rourke, Patrick E.; McCarty, Jerry E.; Haggard, Ricky A.

1992-01-01

A compact, variable pathlength, fiber optic probe for spectrophotometric measurements of fluids in situ. The probe comprises a probe body with a shaft having a polished end penetrating one side of the probe, a pair of optic fibers, parallel and coterminous, entering the probe opposite the reflecting shaft, and a collimating lens to direct light from one of the fibers to the reflecting surface of the shaft and to direct the reflected light to the second optic fiber. The probe body has an inlet and an outlet port to allow the liquid to enter the probe body and pass between the lens and the reflecting surface of the shaft. A linear stepper motor is connected to the shaft to cause the shaft to advance toward or away from the lens in increments so that absorption measurements can be made at each of the incremental steps. The shaft is sealed to the probe body by a bellows seal to allow freedom of movement of the shaft and yet avoid leakage from the interior of the probe.

Dynamic data driven bidirectional reflectance distribution function measurement system

NASA Astrophysics Data System (ADS)

Nauyoks, Stephen E.; Freda, Sam; Marciniak, Michael A.

2014-09-01

The bidirectional reflectance distribution function (BRDF) is a fitted distribution function that defines the scatter of light off of a surface. The BRDF is dependent on the directions of both the incident and scattered light. Because of the vastness of the measurement space of all possible incident and reflected directions, the calculation of BRDF is usually performed using a minimal amount of measured data. This may lead to poor fits and uncertainty in certain regions of incidence or reflection. A dynamic data driven application system (DDDAS) is a concept that uses an algorithm on collected data to influence the collection space of future data acquisition. The authors propose a DDD-BRDF algorithm that fits BRDF data as it is being acquired and uses on-the-fly fittings of various BRDF models to adjust the potential measurement space. In doing so, it is hoped to find the best model to fit a surface and the best global fit of the BRDF with a minimum amount of collection space.

Shape from Shading in Pigeons

ERIC Educational Resources Information Center

Cook, Robert G.; Qadri, Muhammad A. J.; Kieres, Art; Commons-Miller, Nicholas

2012-01-01

Light is the origin of vision. The pattern of shading reflected from object surfaces is one of several optical features that provide fundamental information about shape and surface orientation. To understand how surface and object shading is processed by birds, six pigeons were tested with differentially illuminated convex and concave curved…

Measuring spatially varying, multispectral, ultraviolet bidirectional reflectance distribution function with an imaging spectrometer

NASA Astrophysics Data System (ADS)

Li, Hongsong; Lyu, Hang; Liao, Ningfang; Wu, Wenmin

2016-12-01

The bidirectional reflectance distribution function (BRDF) data in the ultraviolet (UV) band are valuable for many applications including cultural heritage, material analysis, surface characterization, and trace detection. We present a BRDF measurement instrument working in the near- and middle-UV spectral range. The instrument includes a collimated UV light source, a rotation stage, a UV imaging spectrometer, and a control computer. The data captured by the proposed instrument describe spatial, spectral, and angular variations of the light scattering from a sample surface. Such a multidimensional dataset of an example sample is captured by the proposed instrument and analyzed by a k-mean clustering algorithm to separate surface regions with same material but different surface roughnesses. The clustering results show that the angular dimension of the dataset can be exploited for surface roughness characterization. The two clustered BRDFs are fitted to a theoretical BRDF model. The fitting results show good agreement between the measurement data and the theoretical model.

Parallel detection of violations of color constancy

PubMed Central

Foster, David H.; Nascimento, Sérgio M. C.; Amano, Kinjiro; Arend, Larry; Linnell, Karina J.; Nieves, Juan Luis; Plet, Sabrina; Foster, Jeffrey S.

2001-01-01

The perceived colors of reflecting surfaces generally remain stable despite changes in the spectrum of the illuminating light. This color constancy can be measured operationally by asking observers to distinguish illuminant changes on a scene from changes in the reflecting properties of the surfaces comprising it. It is shown here that during fast illuminant changes, simultaneous changes in spectral reflectance of one or more surfaces in an array of other surfaces can be readily detected almost independent of the numbers of surfaces, suggesting a preattentive, spatially parallel process. This process, which is perfect over a spatial window delimited by the anatomical fovea, may form an early input to a multistage analysis of surface color, providing the visual system with information about a rapidly changing world in advance of the generation of a more elaborate and stable perceptual representation. PMID:11438751

Geometrical considerations in analyzing isotropic or anisotropic surface reflections.

PubMed

Simonot, Lionel; Obein, Gael

2007-05-10

The bidirectional reflectance distribution function (BRDF) represents the evolution of the reflectance with the directions of incidence and observation. Today BRDF measurements are increasingly applied and have become important to the study of the appearance of surfaces. The representation and the analysis of BRDF data are discussed, and the distortions caused by the traditional representation of the BRDF in a Fourier plane are pointed out and illustrated for two theoretical cases: an isotropic surface and a brushed surface. These considerations will help characterize either the specular peak width of an isotropic rough surface or the main directions of the light scattered by an anisotropic rough surface without misinterpretations. Finally, what is believed to be a new space is suggested for the representation of the BRDF, which avoids the geometrical deformations and in numerous cases is more convenient for BRDF analysis.

Enhancement of white light OLED efficiency by combining both internal and external light extraction structures

NASA Astrophysics Data System (ADS)

Kao, I.-Ling; Ku, Chun-Neng; Chen, Yi-Ping; Lin, Ding-Zheng

2012-09-01

We proposed an internal nanostructure with a high reflective index planarization layer to solve the optical loss due to the reflective index mismatch between ITO and glass substrate. In our experiments, we found the electrical property of OLED device was significantly influenced by the internal nanostructures without planarization layer. Moreover, the internal extraction structure (IES) is not necessarily beneficial for light extraction. Therefore, we proposed a new substrate combine both internal and external extraction structure (EES) to extract trapping light. We successfully developed a high refractive index (N 1.7) planarization material with flat surface (RMS roughness < 2 nm), and improved about 70% device efficiency compared to traditional glass substrate.

A theoretical study on the optical properties of black silicon

NASA Astrophysics Data System (ADS)

Ma, Shijun; Liu, Shuang; Xu, Qinwei; Xu, Junwen; Lu, Rongguo; Liu, Yong; Zhong, Zhiyong

2018-03-01

There is a wide application prospect in black silicon, especially in solar cells and photoelectric detectors. For further optimization of black silicon, it is important to study its optical properties. Especially, the influence of the surface nanostructures on these properties and the light propagation within the nanostructures are relevant. In this paper, two kinds of black silicon models are studied via the finite differences time domain method. The simulated reflectance spectra matches well with the measured curve. Also, the light intensity distribution within the nanostructures shows that near 80% of the incident light are redirected and subjected to internal reflection, which provides powerful support for the good light trapping properties of black silicon.

Prototyping hexagonal light concentrators using high-reflectance specular films for the Large-Sized Telescopes of the Cherenkov Telescope Array

NASA Astrophysics Data System (ADS)

Okumura, A.; Dang, T. V.; Ono, S.; Tanaka, S.; Hayashida, M.; Hinton, J.; Katagiri, H.; Noda, K.; Teshima, M.; Yamamoto, T.; Yoshida, T.

2017-12-01

We have developed a prototype hexagonal light concentrator for the Large-Sized Telescopes of the Cherenkov Telescope Array. To maximize the photodetection efficiency of the focal-plane camera pixels for atmospheric Cherenkov photons and to lower the energy threshold, a specular film with a very high reflectance of 92-99% has been developed to cover the inner surfaces of the light concentrators. The prototype has a relative anode sensitivity (which can be roughly regarded as collection efficiency) of about 95 to 105% at the most important angles of incidence. The design, simulation, production procedure, and performance measurements of the light-concentrator prototype are reported.

Modelling the circular polarisation of Earth-like exoplanets: constraints on detecting homochirality

NASA Astrophysics Data System (ADS)

Hogenboom, Michael; Stam, Daphne; Rossi, Loic; Snik, Frans

2016-04-01

The circular polarisation of light is a property of electromagnetic radiation from which extensive information can be extracted. It is oft-neglected due to its small signal relative to linear polarisation and the need for advanced instrumentation in measuring it. Additionally, numerical modelling is complex as the full Stokes vector must always be computed. Circular polarisation is commonly induced through the multiple scattering of light by aerosols te{hansen} and multiple reflections of light by rough surfaces te{circplanets}. Most interestingly, distinctive spectral circular polarimetric behaviour is exhibited by light reflected by organisms due to the homochiral molecular structure of all known organisms te{chiralbailey}. Especially fascinating is the unique circular polarimetric behaviour of light reflected by photosynthesising organisms at the absorption wavelength of the chlorophyll pigment te{circpolchar}. This presents the previously unexplored possibility of circular polarimetry as a method for identifying and characterising the presence of organisms, a method which could be applied in the hunt for extraterrestrial life. To date, few telescopes exist that measure circular polarisation and none that have been deployed in space. Observations of the circular polarisation reflected by other planets in the solar system have been made with ground-based telescopes, with significant results te{circplanets}. However, none of these observations have been made at the phase angles at which exoplanets will be observed. Also, none have been made of the Earth, which is the logical starting point for the study of biologically induced circular polarisation signals. This introduces the need for numerical modelling to determine the extent to which circular polarisation is present in light reflected by exoplanets or the Earth. In this study, we model the multiple scattering and reflection of light using the doubling-adding method te{dehaan}. We will present circular polarisation signals for both spatially resolved and spatially unresolved planets, using various atmospheric and surface properties and across a range of phase angles. As a test, the calculated degree of circular polarisation resulting from the multiple scattering of light in an atmosphere with varying properties was compared with results presented by Kawata te{circatmos} and was found to be in agreement. Initial modelling of the atmospheric scattering of light by a planetary disk has shown a presence of degree of circular polarisation in the order of 10-4. This represents a static case with one cloudy hemisphere, one cloudless hemisphere and a Lambertian surface. Results containing varied patchy cloud patterns shall also be presented in a bid to reflect the random nature of planetary cloud cover. We will also present the calculated degree of circular polarisation of planets with various cloud coverage and a circularly polarising surface in order to discover the influence of organisms on the numerical results. {1} {hansen} J. E. {Hansen} and L. D. {Travis}. {Light scattering in planetary atmospheres}. {Space Science Reviews}, 16:527-610, October 1974. {circplanets} J. C. {Kemp} and R. D. {Wolstencroft}. {Circular Polarization: Jupiter and Other Planets}. {Nature}, 232:165-168, July 1971. {chiralbailey} J. {Bailey}. {Circular Polarization and the Origin of Biomolecular Homochirality}. In G. {Lemarchand} and K. {Meech}, editors, {Bioastronomy 99}, volume 213 of {Astronomical Society of the Pacific Conference Series}, 2000. {circpolchar} L. {Nagdimunov}, L. {Kolokolova}, and D. {Mackowski}. {Characterization and remote sensing of biological particles using circular polarization}. {Journal of Quantitative Spectroscopy and Radiative Transfer}, 131:59-65, December 2013. dehaan} J. F. {de Haan}, P. B. {Bosma}, and J. W. {Hovenier}. {The adding method for multiple scattering calculations of polarized light}. {Astronomy and Astrophysics}, 183:371-391, September 1987. {circatmos} Y. {Kawata}. {Circular polarization of sunlight reflected by planetary atmospheres}. {Icarus}, 33:217-232, January 1978.

Surface Relief of Mapping

NASA Astrophysics Data System (ADS)

Costa, Manuel F.; Almeida, Jose B.

1989-02-01

We will describe in this communication a noncont act method of measuring surface profile, it does not require any surface preparation, and it can be used with a very large range of surfaces from highly reflecting to non reflecting ones and as complex as textile surfaces. This method is reasonably immune to dispersion and diffraction, which usually make very difficult the application of non contact profilometry methods to a wide range of materials and situations, namely on quality control systems in industrial production lines. The method is based on the horizontal shift of the bright spot on a horizontal surface when this is illuminated with an oblique beam and moved vertically. in order to make the profilometry the sample is swept by an oblique light beam and the bright spot position is compared with a reference position. The bright spot must be as small as possible, particularly in very irregular surfaces; so the light beam diameter must be as small as possible and the incidence angle must not be too small. The sensivity of a system based on this method will be given, mostly, by the reception optical system.

Design and simulation of a lighting system for a shadowless space

NASA Astrophysics Data System (ADS)

Wang, Ye; Fang, Li

2017-10-01

This paper described implementing the shadowless space by two kinds of methods. The first method will implement the shadowless space utilizing the semblable principles used in the integrating sphere. The rays from a built in light source will eventually evolve into a uniform lighting through diffuse reflections for numerous times, consider that the spherical cavity structure and the inner surface with high reflectivity. There is possibility to create a shadowless space through diffuse reflections. At a 27.4m2 area, illuminance uniformity achieved 88.2% in this model. The other method is analogous with the method used in medical shadowless lamps. Lights will fall on the object in different angles and each light will generate a shadow. By changing the position distribution of multiple lights, increasing the number of light sources, the possibility of obtaining shadowless area will gradually increase. Based on these two approaches, two simple models are proposed showing the optical system designed for the shadowless space. By taking simulation software TracePro as design platform, this paper simulated the two systems.

The correlation and quantification of airborne spectroradiometer data to turbidity measurements at Lake Powell, Utah

NASA Technical Reports Server (NTRS)

Merry, C. J.

1979-01-01

A water sampling program was accomplished at Lake Powell, Utah, during June 1975 for correlation to multispectral data obtained with a 500-channel airborne spectroradiometer. Field measurements were taken of percentage of light transmittance, surface temperature, pH and Secchi disk depth. Percentage of light transmittance was also measured in the laboratory for the water samples. Analyses of electron micrographs and suspended sediment concentration data for four water samples located at Hite Bridge, Mile 168, Mile 150 and Bullfrog Bay indicated differences in the composition and concentration of the particulate matter. Airborne spectroradiometer multispectral data were analyzed for the four sampling locations. The results showed that: (1) as the percentage of light transmittance of the water samples decreased, the reflected radiance increased; and (2) as the suspended sediment concentration (mg/l) increased, the reflected radiance increased in the 1-80 mg/l range. In conclusion, valuable qualitative information was obtained on surface turbidity for the Lake Powell water spectra. Also, the reflected radiance measured at a wavelength of 0.58 micron was directly correlated to the suspended sediment concentration.

Fundamental characteristics of a dual-colour fibre optic SPR sensor

NASA Astrophysics Data System (ADS)

Suzuki, Hitoshi; Sugimoto, Mitsunori; Matsui, Yoshikazu; Kondoh, Jun

2006-06-01

In this paper, we present the fundamental characteristics of a novel dual-colour optical fibre surface plasmon resonance (SPR) sensor for a portable low-cost sensing system. The principle of the proposed SPR sensor is based on the differential reflectance method. Light from two light-emitting diodes (LEDs), which are flashing alternately with different wavelengths, is fed to a sensor via two optical couplers. The reflected light is detected by a photodiode. Changes of reflectance at two wavelengths are proportional to the refractive index change of the medium of interest. Taking the difference in reflectance at two wavelengths improves the sensitivity almost twofold. Measuring ethanol solutions with different refractive indices reveals that the sensor has a linear response to the refractive index change from 1.333 to 1.3616. By measuring the stability in the time response we estimate that the limit of detection (LOD) of the refractive index is 5.2 × 10-4.

Sequential, progressive, equal-power, reflective beam-splitter arrays

NASA Astrophysics Data System (ADS)

Manhart, Paul K.

2017-11-01

The equations to calculate equal-power reflectivity of a sequential series of beam splitters is presented. Non-sequential optical design examples are offered for uniform illumination using diode lasers. Objects created using Boolean operators and Swept Surfaces can create objects capable of reflecting light into predefined elevation and azimuth angles. Analysis of the illumination patterns for the array are also presented.

Quick and Easy Measurements of the Inherent Optical Property of Water by Laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Izadi, Dina; Hajiesmaeilbaigi, Fereshteh

2009-04-19

To generate realistic images of natural waters, one must consider in some detail the interaction of light with the water body. The reflectance and attenuation coefficient of the second harmonic of Nd:YAG laser light through distilled water and a sample of water from the Oman Sea were measured in a solid-state laser laboratory to estimate inherent optical properties of natural waters. These measurements determined the bottom conditions and the impurities of the water. The water's reflectivity varied depending on the angle of incidence, height of the laser from water surface, wavelength of laser light, radiant intensities, and depth of water.more » In these experiments laser light propagated through the water nonlinearly, and different reflectance showed different bottom slopes. The differences among various water samples were obtained taking into account the exponential equation in attenuation coefficient versus depth graphs.« less

Curcumin as a positive resist dye optimized for g- and h-line exposure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Renschler, C.L.; Stiefeld, R.E.; Rodriguez, J.L.

1987-06-01

It has now been firmly established, both theoretically and experimentally, that the addition of a non-bleachable absorber (or dye) to photoresist can reduce notching and other linewidth control variations associated with the patterning of reflective surfaces. Such variations are due to two separate, but closely related, effects. The first of these effects is reflection of light off scattering centers on the substrate at angles other than surface-normal.

Intrinsic Fabry-Perot optical fiber sensors and their multiplexing

DOEpatents

Wang, Anbo

2007-12-11

An intrinsic Fabry-Perot optical sensor includes a thin film sandwiched between two fiber ends. When light is launched into the fiber, two reflections are generated at the two fiber/thin film interfaces due to a difference in refractive indices between the fibers and the film, giving rise to the sensor output. In another embodiment, a portion of the cladding of a fiber is removed, creating two parallel surfaces. Part of the evanescent fields of light propagating in the fiber is reflected at each of the surfaces, giving rise to the sensor output. In a third embodiment, the refractive index of a small portion of a fiber is changed through exposure to a laser beam or other radiation. Interference between reflections at the ends of the small portion give rise to the sensor output. Multiple sensors along a single fiber are multiplexed using an optical time domain reflectometry method.

Laboratory Experiments for Exploring the Surface Plasmon Resonance

ERIC Educational Resources Information Center

Pluchery, Olivier; Vayron, Romain; Van, Kha-Man

2011-01-01

The surface plasmon wave is a surface wave confined at the interface between a dielectric and a metal. The excitation of the surface plasmon resonance (SPR) on a gold thin film is discussed within the Kretschmann configuration, where the coupling with the excitation light is achieved by means of a prism in total reflection. The electromagnetic…

Enhancing swimming pool safety by the use of range-imaging cameras

NASA Astrophysics Data System (ADS)

Geerardyn, D.; Boulanger, S.; Kuijk, M.

2015-05-01

Drowning is the cause of death of 372.000 people, each year worldwide, according to the report of November 2014 of the World Health Organization.1 Currently, most swimming pools only use lifeguards to detect drowning people. In some modern swimming pools, camera-based detection systems are nowadays being integrated. However, these systems have to be mounted underwater, mostly as a replacement of the underwater lighting. In contrast, we are interested in range imaging cameras mounted on the ceiling of the swimming pool, allowing to distinguish swimmers at the surface from drowning people underwater, while keeping the large field-of-view and minimizing occlusions. However, we have to take into account that the water surface of a swimming pool is not a flat, but mostly rippled surface, and that the water is transparent for visible light, but less transparent for infrared or ultraviolet light. We investigated the use of different types of 3D cameras to detect objects underwater at different depths and with different amplitudes of surface perturbations. Specifically, we performed measurements with a commercial Time-of-Flight camera, a commercial structured-light depth camera and our own Time-of-Flight system. Our own system uses pulsed Time-of-Flight and emits light of 785 nm. The measured distances between the camera and the object are influenced through the perturbations on the water surface. Due to the timing of our Time-of-Flight camera, our system is theoretically able to minimize the influence of the reflections of a partially-reflecting surface. The combination of a post image-acquisition filter compensating for the perturbations and the use of a light source with shorter wavelengths to enlarge the depth range can improve the current commercial cameras. As a result, we can conclude that low-cost range imagers can increase swimming pool safety, by inserting a post-processing filter and the use of another light source.

Optical Thin Film Modeling: Using FTG's FilmStar Software

NASA Technical Reports Server (NTRS)

Freese, Scott

2009-01-01

Every material has basic optical properties that define its interaction with light: The index of refraction (n) and extinction coefficient (k) vary for the material as a function of the wavelength of the incident light. Also significant are the phase velocity and polarization of the incident light These inherent properties allow for the accurate modeling of light s behavior upon contact with a surface: Reflectance, Transmittance, Absorptance.

Phase autowaves in the near-electrode layer in the electrochemical cell with a magnetic fluid

NASA Astrophysics Data System (ADS)

Chekanov, V. V.; Kandaurova, N. V.; Chekanov, V. S.

2017-06-01

A change in color of the thin pellicle when light is reflected from the surface of the magnetic fluid at the interface with the transparent electrode in the electric field was observed. The formation of variable thickness near-electrode layer leads to a change in the spectrum of the reflected light depending on the applied voltage. Autowaves, that were observed in the layer are a unique object for the study of self-organization process.

A Simple low-cost device enables four epi-illumination techniques on standard light microscopes.

PubMed

Ishmukhametov, Robert R; Russell, Aidan N; Wheeler, Richard J; Nord, Ashley L; Berry, Richard M

2016-02-08

Back-scattering darkfield (BSDF), epi-fluorescence (EF), interference reflection contrast (IRC), and darkfield surface reflection (DFSR) are advanced but expensive light microscopy techniques with limited availability. Here we show a simple optical design that combines these four techniques in a simple low-cost miniature epi-illuminator, which inserts into the differential interference-contrast (DIC) slider bay of a commercial microscope, without further additions required. We demonstrate with this device: 1) BSDF-based detection of Malarial parasites inside unstained human erythrocytes; 2) EF imaging with and without dichroic components, including detection of DAPI-stained Leishmania parasite without using excitation or emission filters; 3) RIC of black lipid membranes and other thin films, and 4) DFSR of patterned opaque and transparent surfaces. We believe that our design can expand the functionality of commercial bright field microscopes, provide easy field detection of parasites and be of interest to many users of light microscopy.

A Simple low-cost device enables four epi-illumination techniques on standard light microscopes

NASA Astrophysics Data System (ADS)

Ishmukhametov, Robert R.; Russell, Aidan N.; Wheeler, Richard J.; Nord, Ashley L.; Berry, Richard M.

2016-02-01

Back-scattering darkfield (BSDF), epi-fluorescence (EF), interference reflection contrast (IRC), and darkfield surface reflection (DFSR) are advanced but expensive light microscopy techniques with limited availability. Here we show a simple optical design that combines these four techniques in a simple low-cost miniature epi-illuminator, which inserts into the differential interference-contrast (DIC) slider bay of a commercial microscope, without further additions required. We demonstrate with this device: 1) BSDF-based detection of Malarial parasites inside unstained human erythrocytes; 2) EF imaging with and without dichroic components, including detection of DAPI-stained Leishmania parasite without using excitation or emission filters; 3) RIC of black lipid membranes and other thin films, and 4) DFSR of patterned opaque and transparent surfaces. We believe that our design can expand the functionality of commercial bright field microscopes, provide easy field detection of parasites and be of interest to many users of light microscopy.

Extensive goniometric spectral measurements at desert sites for military engineering

NASA Astrophysics Data System (ADS)

Berry, T. E.; Morgan, J. C.; Furey, J. S.; DeMoss, T. A.; Kelley, J. R.; McKenna, J. R.

2012-10-01

Remote-sensing technology designed to exploit disturbed earth signatures has become extremely useful in the detection of disturbed soil in military areas of operation. Soil reflectance can be exploited for this purpose and is dependent on atmospheric conditions. An understanding of the in situ soil background is vital to any type of change detection. Researchers from the Engineering Research and Development Center (ERDC) conducted OCONUS soil spectral measurements at ten sites in Afghanistan from July to November, 2011. Sampling sites were chosen on the basis of geomorphic setting, surface-soil characteristics, and field-expedient conditions. Goniometric spectral measurements at these sites have provided high quality bi-directional reflectance data, and their analyses are presented in the context of threat recognition and discrimination. These data can also provide the basis for BDRF model validation. Most spectral data were acquired under ambient solar lighting, but other data were collected at night and under artificial illumination conditions. Bidirectional measurements of soil reflectance in the VIS/NIR and SWIR were taken using the University of Lethbridge Goniometer System (ULGS) at dawn, mid-day, dusk and after sunset with a light. Soil surface roughness and reflectance varied, depending on the presence of desert varnish and desert pavement at some sites. Sun angle and dust and smoke in the atmosphere impacted soil reflectance and noise in the SWIR part of the light spectrum, in particular. The presence of minerals such as calcium carbonate, gypsum, and oxidized iron in the subsurface directly impacted reflectance measurements in disturbed soil.

Enhanced-Adhesion Multi-Walled Carbon Nanotubes on Titanium Substrates for Stray Light Control

NASA Technical Reports Server (NTRS)

Hagopian, John; Getty, Stephanie; Quijada, Manuel

2012-01-01

Carbon nanotubes previously grown on silicon have extremely low reflectance, making them a good candidate for stray light suppression. Silicon, however, is not a good structural material for stray light components such as tubes, stops, and baffles. Titanium is a good structural material and can tolerate the 700 C nanotube growth process. The ability to grow carbon nanotubes on a titanium substrate that are ten times blacker than the current NASA state-of-the-art paints in the visible to near infrared spectra has been achieved. This innovation will allow significant improvement of stray light performance in scientific instruments or any other optical system. This innovation is a refinement of the utilization of multiwalled carbon nano tubes for stray light suppression in spaceflight instruments. The innovation is a process to make the surface darker and improve the adhesion to the substrate, improving robustness for spaceflight use. Bright objects such as clouds or ice scatter light off of instrument structures and components and make it difficult to see dim objects in Earth observations. A darker material to suppress this stray light has multiple benefits to these observations, including enabling scientific observations not currently possible, increasing observational efficiencies in high-contrast scenes, and simplifying instruments and lowering their cost by utilizing fewer stray light components and achieving equivalent performance. The prior art was to use commercially available black paint, which resulted in approximately 4% of the light being reflected (hemispherical reflectance or total integrated scatter, or TIS). Use of multiwalled carbon nanotubes on titanium components such as baffles, entrance aperture, tubes, and stops, can decrease this scattered light by a factor of ten per bounce over the 200-nm to 2,500-nm wavelength range. This can improve system stray light performance by orders of magnitude. The purpose of the innovation is to provide an enhanced stray light control capability by making a blacker surface treatment for typical stray light control components. Since baffles, stops, and tubes used in scientific observations often undergo loads such as vibration, it was critical to develop this surface treatment on structural materials. The innovation is to optimize the carbon nanotube growth for titanium, which is a strong, lightweight structural material suitable for spaceflight use. The titanium substrate carbon nanotubes are more robust than those grown on silicon and allow for easier utilization. They are darker than current surface treatments over larger angles and larger wavelength range. The primary advantage of titanium substrate is that it is a good structural material, and not as brittle as silicon.

Relative Water Content, Bidirectional Reflectance and Bidirectional Transmittance of the Interior of Detached Leaves During Dry Down.

NASA Technical Reports Server (NTRS)

Vanderbilt, Vern; Daughtry, Craig; Dahlgren, Robert

2015-01-01

Remotely sensing the water status of plants and the water content of canopies remain long-term goals of remote sensing research [1]. Estimates of canopy water content commonly involve measurements in the 900nm to 2000nm portion of the optical spectrum [1]. We have used optical polarization techniques to remove leaf surface reflection and to demonstrate that the visible light reflected by the interior of green healthy corn leaves measured in situ inversely depends upon the leaf relative water content (RWC) [2]. In the research reported here, we again used optical polarization techniques in order to remove the leaf surface reflection from our measurements. This allowed us to monitor the interiors of detached corn leaf samples during leaf dry down measuring for each sample the RWC, bidirectional spectral reflectance and bidirectional spectral transmittance over the wavelength range 450nm to 2,500nm. Our new results like our earlier results show light scattered by the leaf interior measured in the visible wavelength region generally increased as leaf RWC decreased. However, the spectral character and the much improved signal noise of our new results shows the RWC-linked visible light scattering changes are due to leaf structural changes. Our new results show that scattering changes that occur with changing leaf RWC are not attributable to molecular configuration changes in cellular pigments.

Optical system

NASA Technical Reports Server (NTRS)

Breckinridge, J. B.; Page, N. A.; Shack, R. V.; Shannon, R. R. (Inventor)

1985-01-01

Disclosed is an otpical system used in a spacecraft to observe a remote surface and provide a spatial and spectral image of this surface. The optical system includes aspheric and spherical mirrors aligned to focus at a first focal plane an image of the surface, and a mirror at this first focal plane which reflects light back on to the spherical mirror. This spherical mirror collimates the light and directs it through a prism which disperses it. The dispersed light is then focused on an array of light responsive elements disposed at a second focal plane. The prism is designed such that it disperses light into components of different wavelengths, with the components of shorter wavelengths being dispersed more than the components of longer wavelengths to present at the second focal plane a distribution pattern in which preselected groupings of the components are dispersed over essentially equal spacing intervals.

A geometrical optics polarimetric bidirectional reflectance distribution function for dielectric and metallic surfaces.

PubMed

Hyde, M W; Schmidt, J D; Havrilla, M J

2009-11-23

A polarimetric bidirectional reflectance distribution function (pBRDF), based on geometrical optics, is presented. The pBRDF incorporates a visibility (shadowing/masking) function and a Lambertian (diffuse) component which distinguishes it from other geometrical optics pBRDFs in literature. It is shown that these additions keep the pBRDF bounded (and thus a more realistic physical model) as the angle of incidence or observation approaches grazing and better able to model the behavior of light scattered from rough, reflective surfaces. In this paper, the theoretical development of the pBRDF is shown and discussed. Simulation results of a rough, perfect reflecting surface obtained using an exact, electromagnetic solution and experimental Mueller matrix results of two, rough metallic samples are presented to validate the pBRDF.

Measurement and application of bidirectional reflectance distribution function

NASA Astrophysics Data System (ADS)

Liao, Fei; Li, Lin; Lu, Chengwen

2016-10-01

When a beam of light with certain intensity and distribution reaches the surface of a material, the distribution of the diffused light is related to the incident angle, the receiving angle, the wavelength of the light and the types of the material. Bidirectional Reflectance Distribution Function (BRDF) is a method to describe this distribution. For an optical system, the optical and mechanical materials' BRDF are unique, and if we want to calculate stray light of the system we should know the correct BRDF data of the whole materials. There are fundamental significances in the area of space remote sensor where BRDF is needed in the precise radiation calibration. It is also important in the military field where BRDF can be used in the object identification and target tracking, etc. In this paper, 11 kinds of aerospace materials' BRDF are measured and more than 310,000 groups of BRDF data are achieved , and also a BRDF database is established in China for the first time. With the BRDF data of the database, we can create the detector model, build the stray light radiation surface model in the stray light analysis software. In this way, the stray radiation on the detector can be calculated correctly.

Light radiation pressure upon an optically orthotropic surface

NASA Astrophysics Data System (ADS)

Nerovny, Nikolay A.; Lapina, Irina E.; Grigorjev, Anton S.

2017-11-01

In this paper, we discuss the problem of determination of light radiation pressure force upon an anisotropic surface. The optical parameters of such a surface are considered to have major and minor axes, so the model is called an orthotropic model. We derive the equations for force components from emission, absorption, and reflection, utilizing a modified Maxwell's specular-diffuse model. The proposed model can be used to model a flat solar sail with wrinkles. By performing Bayesian analysis for example of a wrinkled surface, we show that there are cases in which an orthotropic model of the optical parameters of a surface may be more accurate than an isotropic model.

Optic probe for multiple angle image capture and optional stereo imaging

DOEpatents

Malone, Robert M.; Kaufman, Morris I.

2016-11-29

A probe including a multiple lens array is disclosed to measure velocity distribution of a moving surface along many lines of sight. Laser light, directed to the moving surface is reflected back from the surface and is Doppler shifted, collected into the array, and then directed to detection equipment through optic fibers. The received light is mixed with reference laser light and using photonic Doppler velocimetry, a continuous time record of the surface movement is obtained. An array of single-mode optical fibers provides an optic signal to the multiple lens array. Numerous fibers in a fiber array project numerous rays to establish many measurement points at numerous different locations. One or more lens groups may be replaced with imaging lenses so a stereo image of the moving surface can be recorded. Imaging a portion of the surface during initial travel can determine whether the surface is breaking up.

Photonic Doppler velocimetry lens array probe incorporating stereo imaging

DOEpatents

Malone, Robert M.; Kaufman, Morris I.

2015-09-01

A probe including a multiple lens array is disclosed to measure velocity distribution of a moving surface along many lines of sight. Laser light, directed to the moving surface is reflected back from the surface and is Doppler shifted, collected into the array, and then directed to detection equipment through optic fibers. The received light is mixed with reference laser light and using photonic Doppler velocimetry, a continuous time record of the surface movement is obtained. An array of single-mode optical fibers provides an optic signal to the multiple lens array. Numerous fibers in a fiber array project numerous rays to establish many measurement points at numerous different locations. One or more lens groups may be replaced with imaging lenses so a stereo image of the moving surface can be recorded. Imaging a portion of the surface during initial travel can determine whether the surface is breaking up.

Analysis of the reflection of a micro drop fiber sensor

NASA Astrophysics Data System (ADS)

Sun, Weimin; Liu, Qiang; Zhao, Lei; Li, Yingjuan; Yuan, Libo

2005-01-01

Micro drop fiber sensors are effective tools for measuring characters of liquids. These types of sensors are wildly used in biotechnology, beverage and food markets. For a fiber micro drop sensor, the signal of the output light is wavy with two peaks, normally. Carefully analyzing the wavy process can identify the liquid components. Understanding the reason of forming this wavy signal is important to design a suitable sensing head and to choose a suitable signal-processing method. The dripping process of a type of liquids is relative to the characters of the liquid and the shape of the sensing head. The quasi-Gauss model of the light field from the input-fiber end is used to analyse the distribution of the light field in the liquid drop. In addition, considering the characters of the liquid to be measured, the dripping process of the optical signal from the output-fiber end can be expected. The reflection surface of the micro drop varies as serials of spheres with different radiuses and global centers. The intensity of the reflection light changes with the shape of the surface. The varying process of the intensity relates to the tense, refractive index, transmission et al. To support the analyse above, an experimental system is established. In the system, LED is chosen as the light source and the PIN transform the light signal to the electrical signal, which is collected by a data acquisition card. An on-line testing system is made to check the theory discussed above.

Analysis of optical transmission by 400-500 nm visible light into aesthetic dental biomaterials.

PubMed

Watts, D C; Cash, A J

1994-04-01

The penetration of visible light into dental biomaterials is an essential factor in photoinitiation of setting reactions and in the optical aspects of dental aesthetics. Light of visible blue wavelengths, 400-500 nm, has been applied at normal angles to 0.2-5.0 mm sections of human dentine and representative ceramic, polymerceramic composites and hybrid glass-polyalkenoate materials. The integrated optical transmission has been determined for each material section. The data have been converted to absorbance values and analysed to check for mathematical conformity to the Beer-Lambert Law. It is found that conformity (typically, P < 0.01) to the linear Beer-Lambert Law is only attained by making a substantial correction for the intensity of light reflected from the surface of aesthetic biomaterials. This is otherwise expressed by distinguishing between true and apparent absorbance. From linear regression of apparent absorbance with section thickness, the intercept depends upon the logarithm of the surface-reflection ratio. This factor ranges from 30% to 90% in the materials investigated. It follows that there is a high degree of inefficiency in the transmission of visible light into and through aesthetic biomaterials for the purposes of photoactivation using existing technology. Means by which this limitation and inefficiency may be reduced are discussed. While the reflectivity of aesthetic biomaterials has been perceived by dental practitioners, the magnitude of this effect and its implications in connection with light-cured materials have not been analysed and emphasized hitherto.

Biosignatures as revealed by spectropolarimetry of Earthshine.

PubMed

Sterzik, Michael F; Bagnulo, Stefano; Palle, Enric

2012-02-29

Low-resolution intensity spectra of Earth's atmosphere obtained from space reveal strong signatures of life ('biosignatures'), such as molecular oxygen and methane with abundances far from chemical equilibrium, as well as the presence of a 'red edge' (a sharp increase of albedo for wavelengths longer than 700 nm) caused by surface vegetation. Light passing through the atmosphere is strongly linearly polarized by scattering (from air molecules, aerosols and cloud particles) and by reflection (from oceans and land). Spectropolarimetric observations of local patches of Earth's sky light from the ground contain signatures of oxygen, ozone and water, and are used to characterize the properties of clouds and aerosols. When applied to exoplanets, ground-based spectropolarimetry can better constrain properties of atmospheres and surfaces than can standard intensity spectroscopy. Here we report disk-integrated linear polarization spectra of Earthshine, which is sunlight that has been first reflected by Earth and then reflected back to Earth by the Moon. The observations allow us to determine the fractional contribution of clouds and ocean surface, and are sensitive to visible areas of vegetation as small as 10 per cent. They represent a benchmark for the diagnostics of the atmospheric composition, mean cloud height and surfaces of exoplanets.

A LEGO Mindstorms Brewster angle microscope

NASA Astrophysics Data System (ADS)

Fernsler, Jonathan; Nguyen, Vincent; Wallum, Alison; Benz, Nicholas; Hamlin, Matthew; Pilgram, Jessica; Vanderpoel, Hunter; Lau, Ryan

2017-09-01

A Brewster Angle Microscope (BAM) built from a LEGO Mindstorms kit, additional LEGO bricks, and several standard optics components, is described. The BAM was built as part of an undergraduate senior project and was designed, calibrated, and used to image phospholipid, cholesterol, soap, and oil films on the surface of water. A BAM uses p-polarized laser light reflected off a surface at the Brewster angle, which ideally yields zero reflectivity. When a film of different refractive index is added to the surface a small amount of light is reflected, which can be imaged in a microscope camera. Films of only one molecule (approximately 1 nm) thick, a monolayer, can be observed easily in the BAM. The BAM was used in a junior-level Physical Chemistry class to observe phase transitions of a monolayer and the collapse of a monolayer deposited on the water surface in a Langmuir trough. Using a photometric calculation, students observed a change in thickness of a monolayer during a phase transition of 7 Å, which was accurate to within 1 Å of the value determined by more advanced methods. As supplementary material, we provide a detailed manual on how to build the BAM, software to control the BAM and camera, and image processing software.

Offset truss hex solar concentrator

NASA Technical Reports Server (NTRS)

White, John E. (Inventor); Sturgis, James D. (Inventor); Erikson, Raymond J. (Inventor); Waligroski, Gregg A. (Inventor); Scott, Michael A. (Inventor)

1991-01-01

A solar energy concentrator system comprises an offset reflector structure made up of a plurality of solar energy reflector panel sections interconnected with one another to form a piecewise approximation of a portion of a (parabolic) surface of revolution rotated about a prescribed focal axis. Each panel section is comprised of a plurality of reflector facets whose reflective surfaces effectively focus reflected light to preselected surface portions of the interior sidewall of a cylindrically shaped solar energy receiver. The longitudinal axis of the receiver is tilted at an acute angle with respect to the optical axis such that the distribution of focussed solar energy over the interior surface of the solar engine is optimized for dynamic solar energy conversion. Each reflector panel section comprises a flat, hexagonally shaped truss support framework and a plurality of beam members interconnecting diametrically opposed corners of the hexagonal framework recessed within which a plurality of (spherically) contoured reflector facets is disposed. The depth of the framework and the beam members is greater than the thickness of a reflector facet such that a reflector facet may be tilted (for controlling the effective focus of its reflected light through the receiver aperture) without protruding from the panel section.

Are those bugs reflective? Non-destructive biofilm imaging with white light interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larimer, Curtis J.; Brann, Michelle R.; Suter, Jonathan D.

White light interferometry (WLI) is not typically used to image bacterial biofilms that are immersed in water because there is insufficient refractive index contrast to induce reflection from the biofilm’s interface. The soft structure and water-like bulk properties of hydrated biofilms make them difficult to characterize in situ by any means, especially in a non-destructive manner. Here we describe a new method for measuring and monitoring the thickness and topology of live biofilms using a WLI microscope. A microfluidic system was used to create a reflective interface on the surface of biofilms. Live biofilm samples were monitored non-destructively over time.more » The method enables surface metrology measurements (roughness, surface area) and a novel approach to measuring thickness of the thin hydrated biofilms. Increase in surface roughness preceded observable increase in biofilm thickness, indicating that this measure may be used to predict future development of biofilms. We have also developed a flow cell that enables WLI biofilm imaging in a dynamic environment. We have used this flow cell to observe changes in biofilm structure in response to changes in environmental conditions - flow velocity, availability of nutrients, and presence of biocides.« less

Reflectance modeling of electrochemically P-type porosified silicon by Drude-Lorentz model

NASA Astrophysics Data System (ADS)

Kadi, M.; Media, E. M.; Gueddaoui, H.; Outemzabet, R.

2014-09-01

Porous silicon remains a promising material for optoelectronic application; in this field monitoring of the refractive index profile of the porous layer is required. We present in this work a procedure based on Drude-Lorentz model for calculating the optical parameters such as the high- and low-frequency dielectric constants, the plasma frequency by fitting the reflectance spectra. The experimental data of different porous silicon layer created above the bulk silicon material by electrochemical etching are extracted from reflectance measurements. The reflectance spectra are recorded in the spectral range 350-2500 nm. First, our computational procedure has been validated by its application on mono-crystalline silicon for the determination of its optical parameters. A good agreement between our results and those found in other works has been achieved in the visible-NIR range. In the second step, the model was applied to porous silicon (PS) layers. Useful optical parameters like the refractive index and the extinction coefficient, respectively, n (λ) and κ(λ), the band gap Eg, of different fabricated porous silicon layer are determined from simulated reflectance spectra. The correlation between the optical properties and the conditions of the electrochemical treatment was observed and analyzed. The main conclusion is that the reflected light from the porous silicon surface, although non-homogeneous and thus possessing the light scattering, is essentially smaller than the reflected light from the bulk crystalline silicon. These results show that the porous surface layer can act as an antireflection coating for silicon and could be used, in particular, in solar cells.

Process for sensing defects on a smooth cylindrical interior surface in tubing

DOEpatents

Dutton, G. Wayne

1987-11-17

The cylindrical interior surface of small diameter metal tubing is optically inspected to determine surface roughness by passing a slightly divergent light beam to illuminate the entire interior surface of the tubing. Impingement of the input light beam components on any rough spots on the interior surface generates forward and backward scattered radiation components. The forward scattered components can be measured by blocking direct and specular radiation components exiting the tubing while allowing the forward scattered radiation to travel past the blocking location. Collecting optics are employed to converge the forward scattered radiation onto a photodetector generating a signal indicative of surface roughness. In the back scattered mode, back scattered radiation exiting the tubing through the entrance opening is reflected 90.degree. by a beam splitter towards collecting optics and a photodetector. Alternatively, back scattered radiation can be transmitted through a fiber optic bundle towards the collecting optics. The input light beam can be supplied through a white light fiber optic bundle mounted coaxial with the first bundle.

Process for sensing defects on a smooth cylindrical interior surface in tubing

DOEpatents

Dutton, G.W.

1987-11-17

The cylindrical interior surface of small diameter metal tubing is optically inspected to determine surface roughness by passing a slightly divergent light beam to illuminate the entire interior surface of the tubing. Impingement of the input light beam components on any rough spots on the interior surface generates forward and backward scattered radiation components. The forward scattered components can be measured by blocking direct and specular radiation components exiting the tubing while allowing the forward scattered radiation to travel past the blocking location. Collecting optics are employed to converge the forward scattered radiation onto a photodetector generating a signal indicative of surface roughness. In the back scattered mode, back scattered radiation exiting the tubing through the entrance opening is reflected 90[degree] by a beam splitter towards collecting optics and a photodetector. Alternatively, back scattered radiation can be transmitted through a fiber optic bundle towards the collecting optics. The input light beam can be supplied through a white light fiber optic bundle mounted coaxial with the first bundle. 6 figs.

Process and apparatus for sensing defects on a smooth cylindrical surface in tubing

DOEpatents

Dutton, G.W.

1985-08-05

The cylindrical interior surface of small diameter metal tubing is optically inspected to determine surface roughness by passing a slightly divergent light beam to illuminate the entire interior surface of the tubing. Impingement of the input light beam components on any rough spots on the interior surface generates forward and backward scattered radiation components. The forward scattered components can be measured by blocking direct and specular radiation components exiting the tubing while allowing the forward scattered radiation to travel past the blocking location. Collecting optics are employed to converge the forward scattered radiation onto a photodetector generating a signal indicative of surface roughness. In the back scattered mode, back scattered radiation exiting the tubing through the entrance opening is reflected 90/sup 0/ by a beam splitter towards collecting optics and a photodetector. Alternatively, back scattered radiation can be transmitted through a fiber optic bundle towards the collecting optics. The input light beam can be supplied through a white light fiber optic bundle mounted coaxial with the first bundle.

Catadioptric lenses in Visible Light Communications

NASA Astrophysics Data System (ADS)

Garcia-Marquez, J.; Valencia, J. C.; Perez, H.; Topsu, S.

2015-04-01

Since few years ago, visible light communications (VLC) have experience an accelerated interest from a research point of view. The beginning of this decade has seen many improvements in VLC at an electronic level. High rates of transmission at low bit error ratios (BER) have been reported. A few numbers of start-ups have initiated activities to offer a variety of applications ranging from indoor geo-localization to internet, but in spite of these advancements, some other problems arise. Long-range transmissions mean a high BER which reduce the number of applications. In this sense, new redesigned optical collectors or in some cases, optical reflectors must be considered to ensure a low BER at higher distance transmissions. Here we also expose a preliminary design of a catadioptric and monolithical lens for a LI-FI receiver with two rotationally symmetrical main piecewise surfaces za and zb. These surfaces are represented in a system of cylindrical coordinates with an anterior surface za with a central and refractive sector surrounded by a peripheral reflective sector and a back piecewise surface zb with a central refractive sector and a reflective sector, both characterized as ideal for capturing light within large acceptance angles.

A superior architecture of brightness enhancement for display backlighting

NASA Astrophysics Data System (ADS)

Dross, Oliver; Parkyn, William A.; Chaves, Julio; Falicoff, Waqidi; Miñano, Juan Carlos; Benitez, Pablo; Alvarez, Roberto

2006-08-01

Brightness enhancement of backlighting for displays is typically achieved via crossed micro prismatic films that are introduced between a backlight unit and a transmissive (LCD) display. Prismatic films let pass light only into a restricted angular range, while, in conjunction with other reflective elements below the backlight, all other light is recycled within the backlight unit, thereby increasing the backlight luminance. This design offers no free parameters to influence the resulting light distribution and suffers from insufficient stray light control. A novel strategy of light recycling is introduced, using a microlens array in conjunction with a hole array in a reflective surface, that can provide higher luminance, superior stray light control, and can be designed to meet almost any desired emission pattern. Similar strategies can be applied to mix light from different colored LEDs being mounted upside down to shine into a backlight unit.

Polarimetric infrared imaging simulation of a synthetic sea surface with Mie scattering.

PubMed

He, Si; Wang, Xia; Xia, Runqiu; Jin, Weiqi; Liang, Jian'an

2018-03-01

A novel method to simulate the polarimetric infrared imaging of a synthetic sea surface with atmospheric Mie scattering effects is presented. The infrared emission, multiple reflections, and infrared polarization of the sea surface and the Mie scattering of aerosols are all included for the first time. At first, a new approach to retrieving the radiative characteristics of a wind-roughened sea surface is introduced. A two-scale method of sea surface realization and the inverse ray tracing of light transfer calculation are combined and executed simultaneously, decreasing the consumption of time and memory dramatically. Then the scattering process that the infrared light emits from the sea surface and propagates in the aerosol particles is simulated with a polarized light Monte Carlo model. Transformations of the polarization state of the light are calculated with the Mie theory. Finally, the polarimetric infrared images of the sea surface of different environmental conditions and detection parameters are generated based on the scattered light detected by the infrared imaging polarimeter. The results of simulation examples show that our polarimetric infrared imaging simulation can be applied to predict the infrared polarization characteristics of the sea surface, model the oceanic scene, and guide the detection in the oceanic environment.

Errors induced by the neglect of polarization in radiance calculations for Rayleigh-scattering atmospheres

NASA Technical Reports Server (NTRS)

Mishchenko, M. I.; Lacis, A. A.; Travis, L. D.

1994-01-01

Although neglecting polarization and replacing the rigorous vector radiative transfer equation by its approximate scalar counterpart has no physical background, it is a widely used simplification when the incident light is unpolarized and only the intensity of the reflected light is to be computed. We employ accurate vector and scalar multiple-scattering calculations to perform a systematic study of the errors induced by the neglect of polarization in radiance calculations for a homogeneous, plane-parallel Rayleigh-scattering atmosphere (with and without depolarization) above a Lambertian surface. Specifically, we calculate percent errors in the reflected intensity for various directions of light incidence and reflection, optical thicknesses of the atmosphere, single-scattering albedos, depolarization factors, and surface albedos. The numerical data displayed can be used to decide whether or not the scalar approximation may be employed depending on the parameters of the problem. We show that the errors decrease with increasing depolarization factor and/or increasing surface albedo. For conservative or nearly conservative scattering and small surface albedos, the errors are maximum at optical thicknesses of about 1. The calculated errors may be too large for some practical applications, and, therefore, rigorous vector calculations should be employed whenever possible. However, if approximate scalar calculations are used, we recommend to avoid geometries involving phase angles equal or close to 0 deg and 90 deg, where the errors are especially significant. We propose a theoretical explanation of the large vector/scalar differences in the case of Rayleigh scattering. According to this explanation, the differences are caused by the particular structure of the Rayleigh scattering matrix and come from lower-order (except first-order) light scattering paths involving right scattering angles and right-angle rotations of the scattering plane.

A Precise Visual Method for Narrow Butt Detection in Specular Reflection Workpiece Welding

PubMed Central

Zeng, Jinle; Chang, Baohua; Du, Dong; Hong, Yuxiang; Chang, Shuhe; Zou, Yirong

2016-01-01

During the complex path workpiece welding, it is important to keep the welding torch aligned with the groove center using a visual seam detection method, so that the deviation between the torch and the groove can be corrected automatically. However, when detecting the narrow butt of a specular reflection workpiece, the existing methods may fail because of the extremely small groove width and the poor imaging quality. This paper proposes a novel detection method to solve these issues. We design a uniform surface light source to get high signal-to-noise ratio images against the specular reflection effect, and a double-line laser light source is used to obtain the workpiece surface equation relative to the torch. Two light sources are switched on alternately and the camera is synchronized to capture images when each light is on; then the position and pose between the torch and the groove can be obtained nearly at the same time. Experimental results show that our method can detect the groove effectively and efficiently during the welding process. The image resolution is 12.5 μm and the processing time is less than 10 ms per frame. This indicates our method can be applied to real-time narrow butt detection during high-speed welding process. PMID:27649173

A Precise Visual Method for Narrow Butt Detection in Specular Reflection Workpiece Welding.

PubMed

Zeng, Jinle; Chang, Baohua; Du, Dong; Hong, Yuxiang; Chang, Shuhe; Zou, Yirong

2016-09-13

During the complex path workpiece welding, it is important to keep the welding torch aligned with the groove center using a visual seam detection method, so that the deviation between the torch and the groove can be corrected automatically. However, when detecting the narrow butt of a specular reflection workpiece, the existing methods may fail because of the extremely small groove width and the poor imaging quality. This paper proposes a novel detection method to solve these issues. We design a uniform surface light source to get high signal-to-noise ratio images against the specular reflection effect, and a double-line laser light source is used to obtain the workpiece surface equation relative to the torch. Two light sources are switched on alternately and the camera is synchronized to capture images when each light is on; then the position and pose between the torch and the groove can be obtained nearly at the same time. Experimental results show that our method can detect the groove effectively and efficiently during the welding process. The image resolution is 12.5 μm and the processing time is less than 10 ms per frame. This indicates our method can be applied to real-time narrow butt detection during high-speed welding process.

Mutual transformation of light waves by reflection holograms in photorefractive crystals of the 4-bar 3m symmetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naunyka, V. N.; Shepelevich, V. V., E-mail: vasshep@inbox.ru

2011-05-15

The mutual transformation of light waves in the case of their simultaneous diffraction from a bulk reflection phase hologram, which was formed in a cubic photorefractive crystal of the 4-bar 3m symmetry class, has been studied. The indicator surfaces of the polarization-optimized values of the relative intensity of the object wave, which make it possible to determine the amplification of this wave for any crystal cut, are constructed. The linear polarization azimuths at which the energy exchange between the light waves reaches a maximum are found numerically for crystals of different cuts.

Hazard calculations of diffuse reflected laser radiation for the SELENE program

NASA Technical Reports Server (NTRS)

Miner, Gilda A.; Babb, Phillip D.

1993-01-01

The hazards from diffuse laser light reflections off water clouds, ice clouds, and fog and from possible specular reflections off ice clouds were assessed with the American National Standards (ANSI Z136.1-1986) for the free-electron-laser parameters under consideration for the Segmented Efficient Laser Emission for Non-Nuclear Electricity (SELENE) Program. Diffuse laser reflection hazards exist for water cloud surfaces less than 722 m in altitude and ice cloud surfaces less than 850 m in altitude. Specular reflections from ice crystals in cirrus clouds are not probable; however, any specular reflection is a hazard to ground observers. The hazard to the laser operators and any ground observers during heavy fog conditions is of such significant magnitude that the laser should not be operated in fog.

Surface profilometry using the incoherent self-imaging technique in reflection mode

NASA Astrophysics Data System (ADS)

Hassani, Khosrow; Nahal, Arashmid; Tirandazi, Negin

2018-01-01

In this paper, we introduce a highly sensitive and cost-effective surface profilometry technique based on the Lau self-imaging phenomenon in reflection mode, combined with the Moiré technique. Standard incoherent grating imaging with two Ronchi rulings is deployed to produce localized Fresnel pseudoimages, except that the light wavefront gets modulated after reflecting off the surface under test and before the final image forms. A third grating is superimposed on the pseudoimage to take advantage of the magnification property of the Moiré fringes and enhance the surface-induced modulations. A five-step phase-shifting technique is used to extract the 2D surface profile of the sample from the recorded Moiré patterns. To demonstrate our technique, we measure the profile of a 250 nm step-like metallic sample. The results show a few nanometer uncertainties, very good reproducibility, and agreement with other known optical and mechanical surface profilometry methods.

Particle Shape Characterization of Lunar Regolith using Reflected Light Microscopy

NASA Astrophysics Data System (ADS)

McCarty, C. B.; Garcia, G. C.; Rickman, D.

2014-12-01

Automated identification of particles in lunar thin sections is necessary for practical measurement of particle shape, void characterization, and quantitative characterization of sediment fabric. This may be done using image analysis, but several aspects of the lunar regolith make such automations difficult. For example, many of the particles are shattered; others are aggregates of smaller particles. Sieve sizes of the particles span 5 orders of magnitude. The physical thickness of a thin section, at a nominal 30 microns, is large compared to the size of many of the particles. Image acquisition modes, such as SEM and reflected light, while superior to transmitted light, still have significant ambiguity as to the volume being sampled. It is also desirable to have a technique that is inexpensive, not resource intensive, and analytically robust. To this end, we have developed an image acquisition and processing protocol that identifies and delineates resolvable particles on the front surface of a lunar thin section using a petrographic microscope in reflected light. For a polished thin section, a grid is defined covering the entire thin section. The grid defines discrete images taken with 20% overlap, minimizing the number of particles that intersect image boundaries. In reflected light mode, two images are acquired at each grid location, with a closed aperture diaphragm. One image, A, is focused precisely on the front surface of the thin section. The second image, B, is made after the stage is brought toward the objective lens just slightly. A bright fringe line, analogous to a Becke line, appears inside all transparent particles at the front surface of the section in the second image. The added light in the bright line corresponds to a deficit around the particles. Particle identification is done using ImageJ and uses multiple steps. A hybrid 5x5 median filter is used to make images Af and Bf. This primarily removes very small particles just below the front surface of the section. Bf - (Bf/Af) is then computed. The division strongly enhances the fringe and the deficit, while minimizing the correlated information in A and B. The subtraction emphasizes the particle-epoxy boundaries. The resulting image is converted to binary, and then holes are filled. Cracks are removed using a median-based operator.

From Intensity Profile to Surface Normal: Photometric Stereo for Unknown Light Sources and Isotropic Reflectances.

PubMed

Lu, Feng; Matsushita, Yasuyuki; Sato, Imari; Okabe, Takahiro; Sato, Yoichi

2015-10-01

We propose an uncalibrated photometric stereo method that works with general and unknown isotropic reflectances. Our method uses a pixel intensity profile, which is a sequence of radiance intensities recorded at a pixel under unknown varying directional illumination. We show that for general isotropic materials and uniformly distributed light directions, the geodesic distance between intensity profiles is linearly related to the angular difference of their corresponding surface normals, and that the intensity distribution of the intensity profile reveals reflectance properties. Based on these observations, we develop two methods for surface normal estimation; one for a general setting that uses only the recorded intensity profiles, the other for the case where a BRDF database is available while the exact BRDF of the target scene is still unknown. Quantitative and qualitative evaluations are conducted using both synthetic and real-world scenes, which show the state-of-the-art accuracy of smaller than 10 degree without using reference data and 5 degree with reference data for all 100 materials in MERL database.

Magnetically tunable control of light reflection in an unusual optical protein of squid

NASA Astrophysics Data System (ADS)

Iwasaka, M.; Tagawa, K.; Kikuchi, Y.

2017-05-01

In this study, we focused on the magnetically tunable changes in the reflectivity of the protein reflectin, which is generated by squid and used to control their body surface color for camouflage in seawater. A cellular organelle called an iridosome was separated from the skin of the dorsal part of a squid (cuttlefish; Sepia esculenta), and the light reflection dynamics of iridosomes containing reflectin were measured with and without exposure to a magnetic field of 500 mT. The magnetic field induced both steady and transient increases of reflection by the iridosomes, suggesting that a reversible conformational change occurred inside the iridosomes when the magnetic field was switched on and off. The intensity of light scattering perpendicular to the direction of the magnetic field increased when the magnetic field was applied. This kind of behavior (Type I) occurred in the majority (60%) of the measured samples. Another kind of reflection change (Type II) was a transient increase in light reflection. It is speculated that the wave-shaped structure of the lipid membrane connected to reflectin proteins changed to enhance the light reflection of reflectin by altering the diamagnetic orientation of the lipid layer in the bent part of the membrane under the applied magnetic field. Overall, our results suggest that the mesoscale lipid layers changed their alignment diamagnetically and the length between iridescent layers was modified by the magnetic field, even though no obvious change in alignment occurred at the microscale.

Angular Scattering Reflectance and Polarization Measurements of Candidate Regolith Materials Measured in the Laboratory

NASA Astrophysics Data System (ADS)

Nelson, Robert M.; Boryta, Mark D.; Hapke, Bruce W.; Shkuratov, Yuriy; Vandervoort, Kurt; Vides, Christina L.

2016-10-01

The reflectance and polarization of light reflected from a solar system object indicates the chemical and textural state of the regolith. Remote sensing data are compared to laboratory angular scattering measurements and surface properties are determined.We use a Goniometric Photopolarimeter (GPP) to make angular reflectance and polarization measurements of particulate materials that simulate planetary regoliths. The GPP employs the Helmholtz Reciprocity Principle ( 2, 1) - the incident light is linearly polarized - the intensity of the reflected component is measured. The light encounters fewer optical surfaces improving signal to noise. The lab data are physically equivalent to the astronomical data.Our reflectance and polarization phase curves of highly reflective, fine grained, media simulate the regolith of Jupiter's satellite Europa. Our lab data exhibit polarization phase curves that are very similar to reports by experienced astronomers (4). Our previous reflectance phase curve data of the same materials agree with the same astronomical observers (5). We find these materials exhibit an increase in circular polarization ratio with decreasing phase angle (3). This suggests coherent backscattering (CB) of photons in the regolith (3). Shkuratov et al.(3) report that the polarization properties of these particulate media are also consistent with the CB enhancement process (5). Our results replicate the astronomical data indicating Europa's regolith is fine-grained, high porous with void space exceeding 90%.1. Hapke, B. W. (2012). ISBN 978-0-521-88349-82. Minnaert, M. (1941).Asrophys. J., 93, 403-410.3. Nelson, R. M. et al. (1998). Icarus, 131, 223-230.4. Rosenbush, V. et al. (2015). ISBN 978-1-107-04390-9, pp 340-359.5. Shkuratov, Yu. et al. (2002) Icarus 159, 396-416.

Specular Reflection from Rough Surfaces Revisited

NASA Astrophysics Data System (ADS)

Yasuda, Kensei; Kim, Alvin; Cho, Hayley; Timofejev, Timofej; Walecki, Wojciech J.; Klep, James; Edelson, Amy S.; Walecki, Abigail S.; Walecki, Eve S.; Walecki, Peter S.

2016-10-01

In his beautiful paper, Hasan Fakhruddin reported observations of mirror-like reflections in the rough surface of a ground glass plate. Similar effects have been recently employed for metrology of the roughness of optical diffusers used in modern light emitting device illumination systems. We report the observations of specular reflection in nontransparent rough surfaces at oblique angles, where roughness was treated as a variable. We present a simple trigonometry-based model explaining the observed phenomenon, which we experimentally validated using aluminum surfaces that have controlled roughness. The reported demonstration requires no special equipment, other than cellphone cameras, dielectric or metal plate, and sandpaper, and serves as an introduction to wave optics. This activity can be used to get further insight into everyday applications of wave optics for students already familiar with wave optics fundamentals.

Radiant exchange in partially specular architectural environments

NASA Astrophysics Data System (ADS)

Beamer, C. Walter; Muehleisen, Ralph T.

2003-10-01

The radiant exchange method, also known as radiosity, was originally developed for thermal radiative heat transfer applications. Later it was used to model architectural lighting systems, and more recently it has been extended to model acoustic systems. While there are subtle differences in these applications, the basic method is based on solving a system of energy balance equations, and it is best applied to spaces with mainly diffuse reflecting surfaces. The obvious drawback to this method is that it is based around the assumption that all surfaces in the system are diffuse reflectors. Because almost all architectural systems have at least some partially specular reflecting surfaces in the system it is important to extend the radiant exchange method to deal with this type of surface reflection. [Work supported by NSF.

Optical differential reflectance spectroscopy for photochromic molecules on solid surfaces

NASA Astrophysics Data System (ADS)

Nickel, Fabian; Bernien, Matthias; Lipowski, Uwe; Kuch, Wolfgang

2018-03-01

Optical reflectance of thin adsorbates on solid surfaces is able to reveal fundamental changes of molecular properties compared to bulk systems. The detection of very small changes in the optical reflectance required several technical improvements in the past decades. We present an experimental setup that is capable of high-quality measurements of submonolayers and ultrathin layers of photochromic molecules on surfaces as well as quantifying their isomerization kinetics. By using photomultipliers as detectors, an enhancement of the signal-to-noise ratio by a factor of three with a total reduction of light exposure on the sample by at least four orders of magnitude is achieved. The potential of the experimental setup is demonstrated by a characterization of the photoswitching and thermal switching of a spirooxazine derivate on a bismuth surface.

Annealed CVD molybdenum thin film surface

DOEpatents

Carver, Gary E.; Seraphin, Bernhard O.

1984-01-01

Molybdenum thin films deposited by pyrolytic decomposition of Mo(CO).sub.6 attain, after anneal in a reducing atmosphere at temperatures greater than 700.degree. C., infrared reflectance values greater than reflectance of supersmooth bulk molybdenum. Black molybdenum films deposited under oxidizing conditions and annealed, when covered with an anti-reflecting coating, approach the ideal solar collector characteristic of visible light absorber and infrared energy reflector.

Influence of aerosols, clouds, and sunglint on polarization spectra of Earthshine

NASA Astrophysics Data System (ADS)

Emde, Claudia; Buras-Schnell, Robert; Sterzik, Michael; Bagnulo, Stefano

2017-08-01

Context. Ground-based observations of the Earthshine, I.e., the light scattered by Earth to the Moon, and then reflected back to Earth, simulate space observations of our planet and represent a powerful benchmark for the studies of Earth-like planets. Earthshine spectra are strongly linearly polarized, owing to scattering by molecules and small particles in the atmosphere of the Earth and surface reflection, and may allow us to measure global atmospheric and surface properties of planet Earth. Aims: We aim to interpret already published spectropolarimetric observations of the Earthshine by comparing them with new radiative transfer model simulations including a fully realistic three-dimensional (3D) surface-atmosphere model for planet Earth. Methods: We used the highly advanced Monte Carlo radiative transfer model MYSTIC to simulate polarized radiative transfer in the atmosphere of the Earth without approximations regarding the geometry, taking into account the polarization from surface reflection and multiple scattering by molecules, aerosol particles, cloud droplets, and ice crystals. Results: We have shown that Earth spectropolarimetry is highly sensitive to all these input parameters, and we have presented simulations of a fully realistic Earth atmosphere-surface model including 3D cloud fields and two-dimensional (2D) surface property maps. Our modeling results show that scattering in high ice water clouds and reflection from the ocean surface are crucial to explain the continuum polarization at longer wavelengths as has been reported in Earthshine observations taken at the Very Large Telescope in 2011 (3.8% and 6.6% at 800 nm, depending on which part of Earth was visible from the Moon at the time of the observations). We found that the relatively high degree of polarization of 6.6% can be attributed to light reflected by the ocean surface in the sunglint region. High ice-water clouds reduce the amount of absorption in the O2A band and thus explain the weak O2A band feature in the observations.

Geometry of illumination, luminance contrast, and gloss perception.

PubMed

Leloup, Frédéric B; Pointer, Michael R; Dutré, Philip; Hanselaer, Peter

2010-09-01

The influence of both the geometry of illumination and luminance contrast on gloss perception has been examined using the method of paired comparison. Six achromatic glass samples having different lightness were illuminated by two light sources. Only one of these light sources was visible in reflection by the observer. By separate adjustment of the intensity of both light sources, the luminance of both the reflected image and the adjacent off-specular surroundings could be individually varied. It was found that visual gloss appraisal did not correlate with instrumentally measured specular gloss; however, psychometric contrast seemed to be a much better correlate. It has become clear that not only the sample surface characteristics determine gloss perception: the illumination geometry could be an even more important factor.

Advanced optical simulation of scintillation detectors in GATE V8.0: first implementation of a reflectance model based on measured data

NASA Astrophysics Data System (ADS)

Stockhoff, Mariele; Jan, Sebastien; Dubois, Albertine; Cherry, Simon R.; Roncali, Emilie

2017-06-01

Typical PET detectors are composed of a scintillator coupled to a photodetector that detects scintillation photons produced when high energy gamma photons interact with the crystal. A critical performance factor is the collection efficiency of these scintillation photons, which can be optimized through simulation. Accurate modelling of photon interactions with crystal surfaces is essential in optical simulations, but the existing UNIFIED model in GATE is often inaccurate, especially for rough surfaces. Previously a new approach for modelling surface reflections based on measured surfaces was validated using custom Monte Carlo code. In this work, the LUT Davis model is implemented and validated in GATE and GEANT4, and is made accessible for all users in the nuclear imaging research community. Look-up-tables (LUTs) from various crystal surfaces are calculated based on measured surfaces obtained by atomic force microscopy. The LUTs include photon reflection probabilities and directions depending on incidence angle. We provide LUTs for rough and polished surfaces with different reflectors and coupling media. Validation parameters include light output measured at different depths of interaction in the crystal and photon track lengths, as both parameters are strongly dependent on reflector characteristics and distinguish between models. Results from the GATE/GEANT4 beta version are compared to those from our custom code and experimental data, as well as the UNIFIED model. GATE simulations with the LUT Davis model show average variations in light output of  <2% from the custom code and excellent agreement for track lengths with R 2  >  0.99. Experimental data agree within 9% for relative light output. The new model also simplifies surface definition, as no complex input parameters are needed. The LUT Davis model makes optical simulations for nuclear imaging detectors much more precise, especially for studies with rough crystal surfaces. It will be available in GATE V8.0.

Character of the opposition effect and negative polarization

NASA Technical Reports Server (NTRS)

Pieters, Carle M.; Shkuratov, Yu. G.; Stankevich, D. G.

1991-01-01

Photometric and polarimetric properties at small phase angles were measured for silicates with controlled surface properties in order to distinguish properties that are associated with surface reflection from those that are associated with multiple scattering from internal grain boundaries. These data provide insight into the causes and conditions of photometric properties observed at small phase angles for dark bodies of the solar system. Obsidian was chosen to represent a silicate dielectric with no internal scattering boundaries. Because obsidian is free of internal scatterers, light reflected from both the rough and smooth obsidian samples is almost entirely single and multiple Fresnel reflections form surface facets with no body component. Surface structure alone cannot produce an opposition effect. Comparison of the obsidian and basalt results indicates that for an opposition effect to occur, surface texture must be both rough and contain internal scattering interfaces. Although the negative polarization observed for the obsidian samples indicates single and multiple reflections are part of negative polarization, the longer inversion angle of the multigrain inversion samples implies that internal reflections must also contribute a significant negative polarization component.

Plasma nanotexturing of silicon surfaces for photovoltaics applications: influence of initial surface finish on the evolution of topographical and optical properties

PubMed Central

FISCHER, GUILLAUME; DRAHI, ETIENNE; FOLDYNA, MARTIN; GERMER, THOMAS A.; JOHNSON, ERIK V.

2018-01-01

Using a plasma to generate a surface texture with feature sizes on the order of tens to hundreds of nanometers (“nanotexturing”) is a promising technique being considered to improve efficiency in thin, high-efficiency crystalline silicon solar cells. This study investigates the evolution of the optical properties of silicon samples with various initial surface finishes (from mirror polish to various states of micron-scale roughness) during a plasma nanotexturing process. It is shown that during said process, the appearance and growth of nanocone-like structures are essentially independent of the initial surface finish, as quantified by the auto-correlation function of the surface morphology. During the first stage of the process (2 min to 15 min etching), the reflectance and light-trapping abilities of the nanotextured surfaces are strongly influenced by the initial surface roughness; however, the differences tend to diminish as the nanostructures become larger. For the longest etching times (15 min or more), the effective reflectance is less than 5 % and a strong anisotropic scattering behavior is also observed for all samples, leading to very elevated levels of light-trapping. PMID:29220984

Appearance benefits of skin moisturization.

PubMed

Jiang, Z-X; DeLaCruz, J

2011-02-01

Skin hydration is essential for skin health. Moisturized skin is generally regarded as healthy and healthy looking. It is thus speculated that there may be appearance benefits of skin moisturization. This means that there are corresponding changes in the optical properties when skin is moisturized. The appearance of the skin is the result of light reflection, scattering and absorption at various skin layers of the stratum corneum, epidermis, dermis and beyond. The appearance benefits of skin moisturization are likely primarily due to the changes in the optical properties of the stratum corneum. We hypothesize that the major optical effect of skin moisturization is the decrease of light scattering at the skin surface, i.e., the stratum corneum. This decrease of surface scattering corresponds to an increase of light penetration into the deeper layers of the skin. An experiment was conducted to measure the corresponding change in skin spectral reflectance, the skin scattering coefficient and skin translucency with a change in skin hydration. In the experiment, skin hydration was decreased with the topical application of acetone and alcohol and increased with the topical application of known moisturizers and occlusives such as PJ. It was found that both the skin spectral reflectance and the skin scattering coefficient increased when the skin was dehydrated and decreased when the skin was hydrated. Skin translucency increased as the skin became moisturized. The results agree with the hypothesis that there is less light scattering at the skin surface and more light penetration into the deeper skin layers when the skin is moisturized. As a result, the skin appears darker, more pinkish and more translucent. © 2010 John Wiley & Sons A/S.

Monolithic spectrometer

DOEpatents

Rajic, Slobodan; Egert, Charles M.; Kahl, William K.; Snyder, Jr., William B.; Evans, III, Boyd M.; Marlar, Troy A.; Cunningham, Joseph P.

1998-01-01

A monolithic spectrometer is disclosed for use in spectroscopy. The spectrometer is a single body of translucent material with positioned surfaces for the transmission, reflection and spectral analysis of light rays.

Study on light scattering characterization for polishing surface of optical elements

NASA Astrophysics Data System (ADS)

Zhang, Yingge; Tian, Ailing; Wang, Chunhui; Wang, Dasen; Liu, Weiguo

2017-02-01

Based on the principle of bidirectional reflectance distribution function (BRDF), the relationship between the surface roughness and the spatial scattering distribution of the optical elements were studied. First, a series of optical components with different surface roughness was obtained by the traditional polishing processing, and measured by Talysurf CCI 3000. Secondly, the influences of different factors on the scattering characteristics were simulated and analyzed, such as different surface roughness, incident wavelength and incident angle. Finally, the experimental device was built, and the spatial distribution of scattered light was measured with the different conditions, and then the data curve variation was analyzed. It was shown that the experimental method was reliable by comparing the simulation and experimental results. Base on this to know, many studies on light scattering characteristics for optical element polishing surface can try later.

3D-printed external light trap for solar cells.

PubMed

van Dijk, Lourens; Paetzold, Ulrich W; Blab, Gerhard A; Schropp, Ruud E I; di Vece, Marcel

2016-05-01

We present a universally applicable 3D-printed external light trap for enhanced absorption in solar cells. The macroscopic external light trap is placed at the sun-facing surface of the solar cell and retro-reflects the light that would otherwise escape. The light trap consists of a reflective parabolic concentrator placed on top of a reflective cage. Upon placement of the light trap, an improvement of 15% of both the photocurrent and the power conversion efficiency in a thin-film nanocrystalline silicon (nc-Si:H) solar cell is measured. The trapped light traverses the solar cell several times within the reflective cage thereby increasing the total absorption in the cell. Consequently, the trap reduces optical losses and enhances the absorption over the entire spectrum. The components of the light trap are 3D printed and made of smoothened, silver-coated thermoplastic. In contrast to conventional light trapping methods, external light trapping leaves the material quality and the electrical properties of the solar cell unaffected. To explain the theoretical operation of the external light trap, we introduce a model that predicts the absorption enhancement in the solar cell by the external light trap. The corresponding calculated path length enhancement shows good agreement with the empirically derived value from the opto-electrical data of the solar cell. Moreover, we analyze the influence of the angle of incidence on the parasitic absorptance to obtain full understanding of the trap performance. © 2015 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons, Ltd.

Method of Making Lightweight, Single Crystal Mirror

NASA Technical Reports Server (NTRS)

Bly, Vincent T. (Inventor)

2015-01-01

A method of making a mirror from a single crystal blank may include fine grinding top and bottom surfaces of the blank to be parallel. The blank may then be heat treated to near its melting temperature. An optical surface may be created on an optical side of the blank. A protector may be bonded to the optical surface. With the protector in place, the blank may be light weighted by grinding a non-optical surface of the blank using computer controlled grinding. The light weighting may include creating a structure having a substantially minimum mass necessary to maintain distortion of the mirror within a preset limit. A damaged layer of the non-optical surface caused by light weighting may be removed with an isotropic etch and/or repaired by heat treatment. If an oxide layer is present, the entire blank may then be etched using, for example, hydrofluoric acid. A reflecting coating may be deposited on the optical surface.

Multipoint photonic doppler velocimetry using optical lens elements

DOEpatents

Frogget, Brent Copely; Romero, Vincent Todd

2014-04-29

A probe including a fisheye lens is disclosed to measure the velocity distribution of a moving surface along many lines of sight. Laser light, directed to the surface and then reflected back from the surface, is Doppler shifted by the moving surface, collected into fisheye lens, and then directed to detection equipment through optic fibers. The received light is mixed with reference laser light and using photonic Doppler velocimetry, a continuous time record of the surface movement is obtained. An array of single-mode optical fibers provides an optic signal to an index-matching lens and eventually to a fisheye lens. The fiber array flat polished and coupled to the index-matching lens using index-matching gel. Numerous fibers in a fiber array project numerous rays through the fisheye lens which in turn project many measurement points at numerous different locations to establish surface coverage over a hemispherical shape with very little crosstalk.

Reshaping Light-Emitting Diodes To Increase External Efficiency

NASA Technical Reports Server (NTRS)

Rogowski, Robert; Egalon, Claudio

1995-01-01

Light-emitting diodes (LEDs) reshaped, according to proposal, increasing amount of light emitted by decreasing fraction of light trapped via total internal reflection. Results in greater luminous output power for same electrical input power; greater external efficiency. Furthermore, light emitted by reshaped LEDs more nearly collimated (less diffuse). Concept potentially advantageous for conventional red-emitting LEDs. More advantageous for new "blue" LEDs, because luminous outputs and efficiencies of these devices very low. Another advantage, proposed conical shapes achieved relatively easily by chemical etching of semiconductor surfaces.

POlarized Light Angle Reflectance Instrument I Polarized Incidence (POLAR:I)

NASA Technical Reports Server (NTRS)

Sarto, Anthony W.; Woldemar, Christopher M.; Vanderbilt, V. C.

1989-01-01

The light scattering properties of leaves are used as input data for models which mathematically describe the transport of photons within plant canopies. Polarization measurements may aid in the investigation of these properties. This paper describes an instrument for rapidly determining the bidirectional light scattering properties of leaves illuminated by linearly polarized light. Results for one species, magnolia, show large differences in the bidirectional light scattering properties depending whether or not the electric vector E is parallel to the foliage surface.

Color Constancy of Red-Green Dichromats and Anomalous Trichromats

PubMed Central

Foster, David H.; Amano, Kinjiro; Nascimento, Sérgio M. C.

2010-01-01

Purpose. Color-vision deficiency is associated with abnormalities in color matching and color discrimination, but its impact on the ability of people to judge the constancy of surface colors under different lights (color constancy) is less clear. This work had two aims: first, to quantify the degree of color constancy in subjects with congenital red-green color deficiency; second, to test whether the degree of color constancy in anomalous trichromats can be predicted from their Rayleigh anomaloscope matches. Methods. Color constancy of red-green color-deficient subjects was tested in a task requiring the discrimination of illuminant changes from surface-reflectance changes. Mondrian-like colored patterns, generated on the screen of a computer monitor, were used as stimuli to avoid the spatial cues provided by natural objects and scenes. Spectral reflectances were taken from the Munsell Book of Color and from natural scenes. Illuminants were taken from the daylight locus. Results. Protanopes and deuteranopes performed more poorly than normal trichromats with Munsell spectral reflectances but were less impaired with natural spectral reflectances. Protanomalous and deuteranomalous trichromats performed as well as, or almost as well as, normal trichromats, independent of the type of reflectance. Individual differences were not correlated with Rayleigh anomaloscope matches. Conclusions. Despite the evidence of clinical color-vision tests, red-green color-deficient persons are less disadvantaged than might be expected in their judgments of surface colors under different lights. PMID:19892868

A novel screen design for anti-ambient light front projection display with angle-selective absorber

NASA Astrophysics Data System (ADS)

Liao, Tianju; Chen, Weigang; He, Kebo; Zhang, Zhaoyu

2016-03-01

Ambient light is destructive to the reflective type projection system's contrast ratio which has great influence on the image quality. In contrast to the conventional front projection, short-throw projection has its advantage to reject the ambient light. Fresnel lens-shaped reflection layer is adapted to direct light from a large angle due to the low lens throw ratio to the viewing area. The structure separates the path of the ambient light and projection light, creating the chance to solve the problem that ambient light is mixed with projection light. However, with solely the lens-shaped reflection layer is not good enough to improve the contrast ratio due to the scattering layer, which contributes a necessarily wide viewing angle, could interfere with both light paths before hitting the layer. So we propose a new design that sets the draft angle surface with absorption layer and adds an angle-selective absorber to separate these two kinds of light. The absorber is designed to fit the direction of the projection light, leading to a small absorption cross section for the projection light and respectfully big absorption cross section for the ambient light. We have calculated the design with Tracepro, a ray tracing program and find a nearly 8 times contrast ratio improvement against the current design in theory. This design can hopefully provide efficient display in bright lit situation with better viewer satisfaction.

Exploring the effect of diffuse reflection on indoor localization systems based on RSSI-VLC.

PubMed

Mohammed, Nazmi A; Elkarim, Mohammed Abd

2015-08-10

This work explores and evaluates the effect of diffuse light reflection on the accuracy of indoor localization systems based on visible light communication (VLC) in a high reflectivity environment using a received signal strength indication (RSSI) technique. The effect of the essential receiver (Rx) and transmitter (Tx) parameters on the localization error with different transmitted LED power and wall reflectivity factors is investigated at the worst Rx coordinates for a directed/overall link. Since this work assumes harsh operating conditions (i.e., a multipath model, high reflectivity surfaces, worst Rx position), an error of ≥ 1.46 m is found. To achieve a localization error in the range of 30 cm under these conditions with moderate LED power (i.e., P = 0.45 W), low reflectivity walls (i.e., ρ = 0.1) should be used, which would enable a localization error of approximately 7 mm at the room's center.

Method and Apparatus for Measuring Near-Angle Scattering of Mirror Coatings

NASA Technical Reports Server (NTRS)

Chipman, Russell A. (Inventor); Daugherty, Brian J. (Inventor); McClain, Stephen C. (Inventor); Macenka, Steven A. (Inventor)

2013-01-01

Disclosed herein is a method of determining the near angle scattering of a sample reflective surface comprising the steps of: a) splitting a beam of light having a coherence length of greater than or equal to about 2 meters into a sample beam and a reference beam; b) frequency shifting both the sample beam and the reference beam to produce a fixed beat frequency between the sample beam and the reference beam; c) directing the sample beam through a focusing lens and onto the sample reflective surface, d) reflecting the sample beam from the sample reflective surface through a detection restriction disposed on a movable stage; e) recombining the sample beam with the reference beam to form a recombined beam, followed by f) directing the recombined beam to a detector and performing heterodyne analysis on the recombined beam to measure the near-angle scattering of the sample reflective surface, wherein the position of the detection restriction relative to the sample beam is varied to occlude at least a portion of the sample beam to measure the near-angle scattering of the sample reflective surface. An apparatus according to the above method is also disclosed.

Capturing the Surface Texture and Shape of Pollen: A Comparison of Microscopy Techniques

PubMed Central

Sivaguru, Mayandi; Mander, Luke; Fried, Glenn; Punyasena, Surangi W.

2012-01-01

Research on the comparative morphology of pollen grains depends crucially on the application of appropriate microscopy techniques. Information on the performance of microscopy techniques can be used to inform that choice. We compared the ability of several microscopy techniques to provide information on the shape and surface texture of three pollen types with differing morphologies. These techniques are: widefield, apotome, confocal and two-photon microscopy (reflected light techniques), and brightfield and differential interference contrast microscopy (DIC) (transmitted light techniques). We also provide a first view of pollen using super-resolution microscopy. The three pollen types used to contrast the performance of each technique are: Croton hirtus (Euphorbiaceae), Mabea occidentalis (Euphorbiaceae) and Agropyron repens (Poaceae). No single microscopy technique provided an adequate picture of both the shape and surface texture of any of the three pollen types investigated here. The wavelength of incident light, photon-collection ability of the optical technique, signal-to-noise ratio, and the thickness and light absorption characteristics of the exine profoundly affect the recovery of morphological information by a given optical microscopy technique. Reflected light techniques, particularly confocal and two-photon microscopy, best capture pollen shape but provide limited information on very fine surface texture. In contrast, transmitted light techniques, particularly differential interference contrast microscopy, can resolve very fine surface texture but provide limited information on shape. Texture comprising sculptural elements that are spaced near the diffraction limit of light (∼250 nm; NDL) presents an acute challenge to optical microscopy. Super-resolution structured illumination microscopy provides data on the NDL texture of A. repens that is more comparable to textural data from scanning electron microscopy than any other optical microscopy technique investigated here. Maximizing the recovery of morphological information from pollen grains should lead to more robust classifications, and an increase in the taxonomic precision with which ancient vegetation can be reconstructed. PMID:22720050

Novel aplanatic designs for LED concentration

NASA Astrophysics Data System (ADS)

Ricketts, Melissa; Winston, Roland; Jiang, Lun

2014-09-01

Aplanats make great concentrators because of their near perfect imaging. Aplanatic conditions can be satisfied using two surface curves (generally mirrored surfaces) in two dimensions (see Figure 1) which are constructed by successive approximation to create a highly efficient concentrator for both concentration and illumination. For concentration purposes, having a two mirror system would be impossible because the front mirror would block incoming light (see figure 2) so the idea is to replace the front mirror with a "one-way" mirror. Light from a lower index can be transmitted, so if the aplanat surface is a higher index light is allowed to enter, and be trapped. In the Jellyfish design, TIR takes place except for light striking the surface within the range of critical angles. To combat that, a small area of reflective coating is applied to the central top part of the Jellyfish, where TIR fails (In the middle) to keep the light there from directly escaping (see figure 3). The design works in both forwards and reverse. Light entering can be focused to a collecter, or the collecter can be replaced with a light source to concentrate light out. In this case, LEDs are used for their highly efficienct properties.

Design, simulation and experimental analysis of an anti-stray-light illumination system of fundus camera

NASA Astrophysics Data System (ADS)

Ma, Chen; Cheng, Dewen; Xu, Chen; Wang, Yongtian

2014-11-01

Fundus camera is a complex optical system for retinal photography, involving illumination and imaging of the retina. Stray light is one of the most significant problems of fundus camera because the retina is so minimally reflective that back reflections from the cornea and any other optical surface are likely to be significantly greater than the light reflected from the retina. To provide maximum illumination to the retina while eliminating back reflections, a novel design of illumination system used in portable fundus camera is proposed. Internal illumination, in which eyepiece is shared by both the illumination system and the imaging system but the condenser and the objective are separated by a beam splitter, is adopted for its high efficiency. To eliminate the strong stray light caused by corneal center and make full use of light energy, the annular stop in conventional illumination systems is replaced by a fiber-coupled, ring-shaped light source that forms an annular beam. Parameters including size and divergence angle of the light source are specially designed. To weaken the stray light, a polarized light source is used, and an analyzer plate is placed after beam splitter in the imaging system. Simulation results show that the illumination uniformity at the fundus exceeds 90%, and the stray light is within 1%. Finally, a proof-of-concept prototype is developed and retinal photos of an ophthalmophantom are captured. The experimental results show that ghost images and stray light have been greatly reduced to a level that professional diagnostic will not be interfered with.

Laboratory and airborne techniques for measuring fluoresence of natural surfaces

NASA Technical Reports Server (NTRS)

Stoertz, G. E.; Hemphill, W. R.

1972-01-01

Techniques are described for obtaining fluorescence spectra from samples of natural surfaces that can be used to predict spectral regions in which these surfaces would emit solar-stimulated or laser-stimulated fluorescence detectable by remote sensor. Scattered or reflected stray light caused large errors in spectrofluorometer analysis or natural sample surfaces. Most spurious light components can be eliminated by recording successive fluorescence spectra for each sample, using identical instrument settings, first with an appropriate glass or gelatin filter on the excitation side of the sample, and subsequently with the same filter on the emission side of the sample. This technique appears more accurate than any alternative technique for testing the fluorescence of natural surfaces.

Ultrafast optical technique for the characterization of altered materials

DOEpatents

Maris, H.J.

1998-01-06

Disclosed herein is a method and a system for non-destructively examining a semiconductor sample having at least one localized region underlying a surface through into which a selected chemical species has been implanted or diffused. A first step induces at least one transient time-varying change in optical constants of the sample at a location at or near to a surface of the sample. A second step measures a response of the sample to an optical probe beam, either pulsed or continuous wave, at least during a time that the optical constants are varying. A third step associates the measured response with at least one of chemical species concentration, chemical species type, implant energy, a presence or absence of an introduced chemical species region at the location, and a presence or absence of implant-related damage. The method and apparatus in accordance with this invention can be employed in conjunction with a measurement of one or more of the following effects arising from a time-dependent change in the optical constants of the sample due to the application of at least one pump pulse: (a) a change in reflected intensity; (b) a change in transmitted intensity; (c) a change in a polarization state of the reflected and/or transmitted light; (d) a change in the optical phase of the reflected and/or transmitted light; (e) a change in direction of the reflected and/or transmitted light; and (f) a change in optical path length between the sample`s surface and a detector. 22 figs.

Ultrafast optical technique for the characterization of altered materials

DOEpatents

Maris, Humphrey J.

1998-01-01

Disclosed herein is a method and a system for non-destructively examining a semiconductor sample (30) having at least one localized region underlying a surface (30a) through into which a selected chemical species has been implanted or diffused. A first step induces at least one transient time-varying change in optical constants of the sample at a location at or near to a surface of the sample. A second step measures a response of the sample to an optical probe beam, either pulsed or continuous wave, at least during a time that the optical constants are varying. A third step associates the measured response with at least one of chemical species concentration, chemical species type, implant energy, a presence or absence of an introduced chemical species region at the location, and a presence or absence of implant-related damage. The method and apparatus in accordance with this invention can be employed in conjunction with a measurement of one or more of the following effects arising from a time-dependent change in the optical constants of the sample due to the application of at least one pump pulse: (a) a change in reflected intensity; (b) a change in transmitted intensity; (c) a change in a polarization state of the reflected and/or transmitted light; (d) a change in the optical phase of the reflected and/or transmitted light; (e) a change in direction of the reflected and/or transmitted light; and (f) a change in optical path length between the sample's surface and a detector.

Monolithic spectrometer

DOEpatents

Rajic, S.; Egert, C.M.; Kahl, W.K.; Snyder, W.B. Jr.; Evans, B.M. III; Marlar, T.A.; Cunningham, J.P.

1998-05-19

A monolithic spectrometer is disclosed for use in spectroscopy. The spectrometer is a single body of translucent material with positioned surfaces for the transmission, reflection and spectral analysis of light rays. 6 figs.

Melanoma

MedlinePlus

... surfaces that reflect light more, such as water, sand, concrete, and white-painted areas. Be extra careful ... A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among ...

Two-Dimensional Laser-Speckle Surface-Strain Gauge

NASA Technical Reports Server (NTRS)

Barranger, John P.; Lant, Christian

1992-01-01

Extension of Yamaguchi's laser-speckle surface-strain-gauge method yields data on two-dimensional surface strains in times as short as fractions of second. Laser beams probe rough spot on surface of specimen before and after processing. Changes in speckle pattern of laser light reflected from spot indicative of changes in surface strains during processing. Used to monitor strains and changes in strains induced by hot-forming and subsequent cooling of steel.

Improvement of the recombination and infrared light losses by rear surface chemical polishing in silicon heterojunction solar cells

NASA Astrophysics Data System (ADS)

Yang, Xueliang; Zhang, Yi; Li, Feng; Sun, Yun

2017-06-01

Rear surface chemical polishing (RSCP) was investigated for the improvement of the internal reflection and surface passivation of heterojunction solar cells with intrinsic thin layers (HIT). The HIT solar cells without or with RSCP treatment were prepared by plasma-enhanced chemical vapor deposition and physical vapor deposition techniques. Scanning electron microscopy results showed that rounding of the spires and V-groove bottom of the pyramid as well as smoothing of incline surface of the pyramid were achieved. These effects would decrease the loss of infrared light transmittance and interface recombination at the rear surface of the cells. To experimentally corroborate these two points, two special geometries, ITO/c-Si/hydrogenated amorphous silicon (a-Si:H)/ITO and a-Si:H/c-Si/a-Si:H, were introduced as a test of the reflectance/transmittance spectra and the minority carrier lifetime. Weakened transmittance and enhanced lifetime were observed for the sample with RSCP, which are responsible for the improvement of J sc and V oc, respectively. Therefore, RSCP is a promising candidate for improving the performance of HIT solar cells.

Nonlinear reflection and refraction of ultrashort light pulses at the surfaces of resonant media and phase memory effects

NASA Astrophysics Data System (ADS)

Vlasov, R. A.; Gadomskii, O. H.; Gadomskaia, I. V.; Samartsev, V. V.

1986-06-01

The method of integrodifferential equations related to the optical Bloch equations is used to study the nonlinear reflection (or refraction) of a scanning laser beam at the surface of a resonant medium excited by traveling and standing surface electromagnetic waves at resonant frequency. The effect of the phase memory of surface atoms on the pulsed action of fields with space-time resolution is taken into account. The reversal of the scanning beam from the excited surface with phase conjugation of the wave front is considered. In addition, the spectrum of the nonlinear surface polaritons is analyzed as a function of the area of the exciting pulse and the penetration depth of polaritons in the resonant optical medium.

The Critical Angle Can Override the Brewster Angle

ERIC Educational Resources Information Center

Froehle, Peter H.

2009-01-01

As a culminating activity in their study of optics, my students investigate polarized light and the Brewster angle. In this exercise they encounter a situation in which it is impossible to measure the Brewster angle for light reflecting from a particular surface. This paper describes the activity and explains the students' observations.

Colour Mixing Based on Daylight

ERIC Educational Resources Information Center

Meyn, Jan-Peter

2008-01-01

Colour science is based on the sensation of monochromatic light. In contrast to that, surface colours are caused by reflection of wide sections of the daylight spectrum. Non-spectral colours like magenta and purple appear homologous to colours with spectral hue, if the approach of mixing monochromatic light is abandoned. It is shown that a large…

Remote measurement of surface roughness, surface reflectance, and body reflectance with LiDAR.

PubMed

Li, Xiaolu; Liang, Yu

2015-10-20

Light detection and ranging (LiDAR) intensity data are attracting increasing attention because of the great potential for use of such data in a variety of remote sensing applications. To fully investigate the data potential for target classification and identification, we carried out a series of experiments with typical urban building materials and employed our reconstructed built-in-lab LiDAR system. Received intensity data were analyzed on the basis of the derived bidirectional reflectance distribution function (BRDF) model and the established integration method. With an improved fitting algorithm, parameters involved in the BRDF model can be obtained to depict the surface characteristics. One of these parameters related to surface roughness was converted to a most used roughness parameter, the arithmetical mean deviation of the roughness profile (R_a), which can be used to validate the feasibility of the BRDF model in surface characterizations and performance evaluations.

Design of a backlighting structure for very large-area luminaries

NASA Astrophysics Data System (ADS)

Carraro, L.; Mäyrä, A.; Simonetta, M.; Benetti, G.; Tramonte, A.; Benedetti, M.; Randone, E. M.; Ylisaukko-Oja, A.; Keränen, K.; Facchinetti, T.; Giuliani, G.

2017-02-01

A novel approach for RGB semiconductor LED-based backlighting system is developed to satisfy the requirements of the Project LUMENTILE funded by the European Commission, whose scope is to develop a luminous electronic tile that is foreseen to be manufactured in millions of square meters each year. This unconventionally large-area surface of uniform, high-brightness illumination requires a specific optical design to keep a low production cost, while maintaining high optical extraction efficiency and a reduced thickness of the structure, as imposed by architectural design constraints. The proposed solution is based on a light-guiding layer to be illuminated by LEDs in edge configuration, or in a planar arrangement. The light guiding slab is finished with a reflective top interface and a diffusive or reflective bottom interface/layer. Patterning is used for both the top interface (punctual removal of reflection and generation of a light scattering centers) and for the bottom layer (using dark/bright printed pattern). Computer-based optimization algorithms based on ray-tracing are used to find optimal solutions in terms of uniformity of illumination of the top surface and overall light extraction efficiency. Through a closed-loop optimization process, that assesses the illumination uniformity of the top surface, the algorithm generates the desired optimized top and bottom patterns, depending on the number of LED sources used, their geometry, and the thickness of the guiding layer. Specific low-cost technologies to realize the patterning are discussed, with the goal of keeping the production cost of these very large-area luminaries below the value of 100$/sqm.

A far-ultraviolet contamination-irradiation facility for in situ reflectance measurements

NASA Astrophysics Data System (ADS)

Meier, Steven R.; Tveekrem, June L.; Keski-Kuha, Ritva A. M.

1998-10-01

In this article, a contamination-irradiation facility designed to measure contamination effects on far-ultraviolet optical surfaces is described. An innovative feature of the facility is the capability of depositing a contaminant, photopolymerizing the contaminant with far-ultraviolet light, and measuring the reflectance of the contaminated sample, all in situ. In addition to describing the facility, we present far-ultraviolet reflectance measurements for a contaminated mirror.

Thermal lens elimination by gradient-reduced zone coupling of optical beams

DOEpatents

Page, Ralph H.; Beach, Raymond J.

2000-01-01

A thermal gradient-reduced-zone laser includes a laser medium and an optically transparent plate with an index of refraction that is less than the index of refraction of the laser medium. The pump face of the laser medium is bonded to a surface of the optically transparent member. Pump light is directed through the transparent plate to optically pump the solid state laser medium. Heat conduction is mainly through the surface of the laser medium where the heat is introduced by the pump light. Heat flows in a direction opposite to that of the pump light because the side of the laser medium that is opposite to that of the pump face is not in thermal contact with a conductor and thus there is no heat flux (and hence, no temperature gradient), thus producing a thermal gradient-reduced zone. A laser cavity is formed around the laser medium such that laser light oscillating within the laser cavity reflects by total-internal-reflection from the interface between the pump face and the optically transparent plate and enters and exits through a thermal gradient-reduced zone.

Outer Space Research Helps Color Habitability in Earth Interiors

NASA Technical Reports Server (NTRS)

Haines, Richard F.

1977-01-01

Color is one of the most important elements in making an environment habitable. Both color and light level combine to create comfortable and efficient work areas and satisfying leisure time environments. Indeed, without light, color cannot even be experienced. It is vitally important for the designer to understand the subject of habitability and to know how to make a positive impact upon the habitability of spaces through the application of proven principles of color-design developed by the scientific community. Consider some of these possibilities and pitfalls: A color chosen in broad daylight will not appear the same under dim lighting conditions. If a designer were creating a dimly lit cocktail lounge, for example, there is little sense in using dark colors, which also tend to be more expensive. When the eyes have dark-adapted for even five minutes, any color reflecting 20 percent or less will appear black, and the color experience will be lost. Therefore, surface reflectances should be kept at least above 20 to 25 percent to maintain color where illumination is at low levels. In effect, for lower reflectance surfaces, higher levels of illumination are required to produce the most accurate color discriminability.

Surface plasmon holographic microscopy for near-field refractive index detection and thin film mapping

NASA Astrophysics Data System (ADS)

Zhao, Jianlin; Zhang, Jiwei; Dai, Siqing; Di, Jianglei; Xi, Teli

2018-02-01

Surface plasmon microscopy (SPM) is widely applied for label-free detection of changes of refractive index and concentration, as well as mapping thin films in near field. Traditionally, the SPM systems are based on the detection of light intensity or phase changes. Here, we present two kinds of surface plasmon holographic microscopy (SPHM) systems for amplitude- and phase-contrast imaging simultaneously. Through recording off-axis holograms and numerical reconstruction, the complex amplitude distributions of surface plasmon resonance (SPR) images can be obtained. According to the Fresnel's formula, in a prism/ gold/ dielectric structure, the reflection phase shift is uniquely decided by refractive index of the dielectric. By measuring the phase shift difference of the reflected light exploiting prism-coupling SPHM system based on common-path interference configuration, monitoring tiny refractive index variation and imaging biological tissue are performed. Furthermore, to characterize the thin film thickness in near field, we employ a four-layer SPR model in which the third film layer is within the evanescent field. The complex reflection coefficient, including the reflectivity and reflection phase shift, is uniquely decided by the film thickness. By measuring the complex amplitude distributions of the SPR images exploiting objective-coupling SPHM system based on common-path interference configuration, the thickness distributions of thin films are mapped with sub-nanometer resolution theoretically. Owing to its high temporal stability, the recommended SPHMs show great potentials for monitoring tiny refractive index variations, imaging biological tissues and mapping thin films in near field with dynamic, nondestructive and full-field measurement capabilities in chemistry, biomedicine field, etc.

A novel technique for the production of cool colored concrete tile and asphalt shingle roofing products

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levinson, Ronnen; Akbari, Hashem; Berdahl, Paul

The widespread use of solar-reflective roofing materials can save energy, mitigate urban heat islands and slow global warming by cooling the roughly 20% of the urban surface that is roofed. In this study we created prototype solar-reflective nonwhite concrete tile and asphalt shingle roofing materials using a two-layer spray coating process intended to maximize both solar reflectance and factory-line throughput. Each layer is a thin, quick-drying, pigmented latex paint based on either acrylic or a poly(vinylidene fluoride)/acrylic blend. The first layer is a titanium dioxide rutile white basecoat that increases the solar reflectance of a gray-cement concrete tile from 0.18more » to 0.79, and that of a shingle surfaced with bare granules from 0.06 to 0.62. The second layer is a 'cool' color topcoat with weak near-infrared (NIR) absorption and/or strong NIR backscattering. Each layer dries within seconds, potentially allowing a factory line to pass first under the white spray, then under the color spray. We combined a white basecoat with monocolor topcoats in various shades of red, brown, green and blue to prepare 24 cool color prototype tiles and 24 cool color prototypes shingles. The solar reflectances of the tiles ranged from 0.26 (dark brown; CIELAB lightness value L* = 29) to 0.57 (light green; L* = 76); those of the shingles ranged from 0.18 (dark brown; L* = 26) to 0.34 (light green; L* = 68). Over half of the tiles had a solar reflectance of at least 0.40, and over half of the shingles had a solar reflectance of at least 0.25.« less

Hexagonal arrays of round-head silicon nanopillars for surface anti-reflection applications

NASA Astrophysics Data System (ADS)

Yan, Wensheng; Dottermusch, Stephan; Reitz, Christian; Richards, Bryce S.

2016-10-01

We designed and fabricated an anti-reflection surface of hexagonal arrays of round-head silicon nanopillars. The measurements show a significant reduction in reflectivity across a broad spectral range. However, we then grew a conformal titanium dioxide coating via atomic layer deposition to achieve an extremely low weighted average reflection of 2.1% over the 460-1040 nm wavelength range. To understand the underlying reasons for the reduced reflectance, the simulations were conducted and showed that it is due to strong forward scattering of incident light into the silicon substrate. The calculated normalized scattering cross section demonstrates a broadband distribution feature, and the peak has a red-shift to longer wavelengths. Finally, we report two-dimensional weighted average reflectance as a function of both wavelength and angle of incidence and present the resulting analysis contour map.

Ultrafast dark-field surface inspection with hybrid-dispersion laser scanning

NASA Astrophysics Data System (ADS)

Yazaki, Akio; Kim, Chanju; Chan, Jacky; Mahjoubfar, Ata; Goda, Keisuke; Watanabe, Masahiro; Jalali, Bahram

2014-06-01

High-speed surface inspection plays an important role in industrial manufacturing, safety monitoring, and quality control. It is desirable to go beyond the speed limitation of current technologies for reducing manufacturing costs and opening a new window onto a class of applications that require high-throughput sensing. Here, we report a high-speed dark-field surface inspector for detection of micrometer-sized surface defects that can travel at a record high speed as high as a few kilometers per second. This method is based on a modified time-stretch microscope that illuminates temporally and spatially dispersed laser pulses on the surface of a fast-moving object and detects scattered light from defects on the surface with a sensitive photodetector in a dark-field configuration. The inspector's ability to perform ultrafast dark-field surface inspection enables real-time identification of difficult-to-detect features on weakly reflecting surfaces and hence renders the method much more practical than in the previously demonstrated bright-field configuration. Consequently, our inspector provides nearly 1000 times higher scanning speed than conventional inspectors. To show our method's broad utility, we demonstrate real-time inspection of the surface of various objects (a non-reflective black film, transparent flexible film, and reflective hard disk) for detection of 10 μm or smaller defects on a moving target at 20 m/s within a scan width of 25 mm at a scan rate of 90.9 MHz. Our method holds promise for improving the cost and performance of organic light-emitting diode displays for next-generation smart phones, lithium-ion batteries for green electronics, and high-efficiency solar cells.

Leaf Surface Effects on Retrieving Chlorophyll Content from Hyperspectral Remote Sensing

NASA Astrophysics Data System (ADS)

Qiu, Feng; Chen, JingMing; Ju, Weimin; Wang, Jun; Zhang, Qian

2017-04-01

Light reflected directly from the leaf surface without entering the surface layer is not influenced by leaf internal biochemical content. Leaf surface reflectance varies from leaf to leaf due to differences in the surface roughness features and is relatively more important in strong absorption spectral regions. Therefore it introduces dispersion of data points in the relationship between biochemical concentration and reflectance (especially in the visible region). Separation of surface from total leaf reflection is important to improve the link between leaf pigments content and remote sensing data. This study aims to estimate leaf surface reflectance from hyperspectral remote sensing data and retrieve chlorophyll content by inverting a modified PROSPECT model. Considering leaf surface reflectance is almost the same in the visible and near infrared spectral regions, a surface layer with a reflectance independent of wavelength but varying from leaf to leaf was added to the PROSPECT model. The specific absorption coefficients of pigments were recalibrated. Then the modified model was inverted on independent datasets to check the performance of the model in predicting the chlorophyll content. Results show that differences in estimated surface layer reflectance of various species are noticeable. Surface reflectance of leaves with epicuticular waxes and trichomes is usually higher than other samples. Reconstruction of leaf reflectance and transmittance in the 400-1000 nm wavelength region using the modified PROSPECT model is excellent with low root mean square error (RMSE) and bias. Improvements for samples with high surface reflectance (e.g. maize) are significant, especially for high pigment leaves. Moreover, chlorophyll retrieved from inversion of the modified model is consequently improved (RMSE from 5.9-13.3 ug/cm2 with mean value 8.1 ug/cm2, while mean correlation coefficient is 0.90) compared to results of PROSPECT-5 (RMSE from 9.6-20.2 ug/cm2 with mean value 13.1 ug/cm2, while mean correlation coefficient is 0.81). Underestimation of high chlorophyll content, which is due to underestimation of reflectance in the visible region of PROSPECT, is partially corrected or alleviated. Improvements are particularly noticeable for leaves with high surface reflectance or high chlorophyll content, which both lead to large proportions of surface reflectance to the total leaf reflectance.

Assessment of tissue viability by polarization spectroscopy

NASA Astrophysics Data System (ADS)

Nilsson, G.; Anderson, C.; Henricson, J.; Leahy, M.; O'Doherty, J.; Sjöberg, F.

2008-09-01

A new and versatile method for tissue viability imaging based on polarization spectroscopy of blood in superficial tissue structures such as the skin is presented in this paper. Linearly polarized light in the visible wavelength region is partly reflected directly by the skin surface and partly diffusely backscattered from the dermal tissue matrix. Most of the directly reflected light preserves its polarization state while the light returning from the deeper tissue layers is depolarized. By the use of a polarization filter positioned in front of a sensitive CCD-array, the light directly reflected from the tissue surface is blocked, while the depolarized light returning from the deeper tissue layers reaches the detector array. By separating the colour planes of the detected image, spectroscopic information about the amount of red blood cells (RBCs) in the microvascular network of the tissue under investigation can be derived. A theory that utilizes the differences in light absorption of RBCs and bloodless tissue in the red and green wavelength region forms the basis of an algorithm for displaying a colour coded map of the RBC distribution in a tissue. Using a fluid model, a linear relationship (cc. = 0.99) between RBC concentration and the output signal was demonstrated within the physiological range 0-4%. In-vivo evaluation using transepidermal application of acetylcholine by the way of iontophoresis displayed the heterogeneity pattern of the vasodilatation produced by the vasoactive agent. Applications of this novel technology are likely to be found in drug and skin care product development as well as in the assessment of skin irritation and tissue repair processes and even ultimately in a clinic case situation.

Biomimetic artificial Si compound eye surface structures with broadband and wide-angle antireflection properties for Si-based optoelectronic applications

NASA Astrophysics Data System (ADS)

Leem, Jung Woo; Song, Young Min; Yu, Jae Su

2013-10-01

We report the biomimetic artificial silicon (Si) compound eye structures for broadband and wide-angle antireflection by integrating nanostructures (NSs) into periodically patterned microstructures (p-MSs) via thermal dewetting of gold and subsequent dry etching. The truncated cone microstructures with a two-dimensional hexagonal symmetry pattern were fabricated by photolithography and dry etching processes. The desirable shape and density of the nanostructures were obtained by controlled dewetting. The incorporation of p-MSs into the NS/Si surface further reduced the surface total reflectance over a wide wavelength range of 300-1030 nm at near normal incidence, indicating the average reflectance (Ravg) and solar weighted reflectance (RSWR) values of ~2.5% and 2%, respectively, compared to the only NSs on the flat Si surface (i.e., Ravg ~ 4.9% and RSWR ~ 4.5%). Additionally, the resulting structure improved the angle-dependent antireflection property due to its relatively omnidirectional shape, which exhibited the Ravg < 4.3% and RSWR < 3.7% in the wavelength region of 300-1100 nm even at a high incident light angle of 70° in the specular reflectance.We report the biomimetic artificial silicon (Si) compound eye structures for broadband and wide-angle antireflection by integrating nanostructures (NSs) into periodically patterned microstructures (p-MSs) via thermal dewetting of gold and subsequent dry etching. The truncated cone microstructures with a two-dimensional hexagonal symmetry pattern were fabricated by photolithography and dry etching processes. The desirable shape and density of the nanostructures were obtained by controlled dewetting. The incorporation of p-MSs into the NS/Si surface further reduced the surface total reflectance over a wide wavelength range of 300-1030 nm at near normal incidence, indicating the average reflectance (Ravg) and solar weighted reflectance (RSWR) values of ~2.5% and 2%, respectively, compared to the only NSs on the flat Si surface (i.e., Ravg ~ 4.9% and RSWR ~ 4.5%). Additionally, the resulting structure improved the angle-dependent antireflection property due to its relatively omnidirectional shape, which exhibited the Ravg < 4.3% and RSWR < 3.7% in the wavelength region of 300-1100 nm even at a high incident light angle of 70° in the specular reflectance. Electronic supplementary information (ESI) available: See DOI: 10.1039/c3nr02806b

Portable spotter for fluorescent contaminants on surfaces

DOEpatents

Schuresko, Daniel D.

1980-01-01

A portable fluorescence-based spotter for polynuclear aromatic hydrocarbon contamination on personnel and work area surfaces under ambient lighting conditions is provided. This instrument employs beam modulation and phase sensitive detection for discriminating between fluorescence from organic materials from reflected background light and inorganic fluorescent material. The device uses excitation and emission filters to provide differentiation between classes of aromatic organic compounds. Certain inorganic fluorescent materials, including heavy metal compounds, may also be distinguished from the organic compounds, despite both having similar optical properties.

Measurement of Electron Beam Emittance Using Optical Transition Radiation and Development of a Diffuse Screen Electron Beam Monitor

DTIC Science & Technology

1990-12-01

Zerodur ,irror, 2" relfects light. 1OZ20BD.1; 20th wave zerodur mirror , 1" reflects light. LS-35; 3’ x 5’ optical breadboard; for mounting components...profile measurements using the diffuse screen were compared with measurements using a front surface mirror and a fluorescent screen. The 20 DISTRIBUTION...Beam current and profile measurements using the diffuse screen were compared with measurements using a front surface mirror and a fluorescent screen

Mechanically flexible organic electroluminescent device with directional light emission

DOEpatents

Duggal, Anil Raj; Shiang, Joseph John; Schaepkens, Marc

2005-05-10

A mechanically flexible and environmentally stable organic electroluminescent ("EL") device with directional light emission comprises an organic EL member disposed on a flexible substrate, a surface of which is coated with a multilayer barrier coating which includes at least one sublayer of a substantially transparent organic polymer and at least one sublayer of a substantially transparent inorganic material. The device includes a reflective metal layer disposed on the organic EL member opposite to the substrate. The reflective metal layer provides an increased external quantum efficiency of the device. The reflective metal layer and the multilayer barrier coating form a seal around the organic EL member to reduce the degradation of the device due to environmental elements.

Soil, water, and vegetation conditions in South Texas

NASA Technical Reports Server (NTRS)

Wiegand, C. L.; Gausman, H. W.; Leamer, R. W.; Richardson, A. J.; Everitt, J. H.; Gerbermann, A. H. (Principal Investigator)

1976-01-01

The author has identified the following significant results. Reflectance measurements with a field spectroradiometer on nine dates (between December 9 and April 8) during the growing season of two wheat varieties, Milam and Penjamo, showed that the reflectance curves had the characteristic shape of vegetated surfaces by 4 weeks after the emergence. Green light (0.55 micron) reflectance was maximal and between water absorption bands (1.65 and 2.2 microns) reflectance was minimal when green vegetation development was greatest. Computer classification was accomplished for 81,000 hectare coastal rangeland area for October 13 and December 10, 1975, overpass dates. A hard freeze occurred between these two dates and many of the deciduous woody species defoliated so that more light penetrated to the herbaceous understory in December than in October.

Surface-plasmon enhanced photoemission of a silver nano-patterned photocathode

NASA Astrophysics Data System (ADS)

Zhang, Z.; Li, R.; To, H.; Andonian, G.; Pirez, E.; Meade, D.; Maxson, J.; Musumeci, P.

2017-09-01

Nano-patterned photocathodes (NPC) take advantage of plasmonic effects to resonantly increase absorption of light and localize electromagnetic field intensity on metal surfaces leading to surface-plasmon enhanced photoemission. In this paper, we report the status of NPC research at UCLA including in particular the optimization of the dimensions of a nanohole array on a silver wafer to enhance plasmonic response at 800 nm light, the development of a spectrally-resolved reflectivity measurement setup for quick nanopattern validation, and of a novel cathode plug to enable high power tests of NPCs on single crystal substrates in a high gradient radiofrequency gun.

The effects of titanium dioxide coatings on light-derived heating and transdermal heat transfer in bovine skin

NASA Astrophysics Data System (ADS)

Bartle, S. J.; Thomson, D. U.; Gehring, R.; van der Merwe, D.

2017-11-01

The effects of titanium dioxide coatings of bovine hides on light absorption and transdermal transfer of light-derived heat were investigated. Four hair-on rug hides from Holstein cattle were purchased. Twelve samples about 20 cm on a side were cut from each hide; nine from the black-colored areas, and three from the white areas. Samples were randomized and assigned to four coating treatments: (1) white hide with no coating (White), (2) black hide with no coating (Black), (3) black hide with 50% coating (Mid), and (4) black hide with 100% coating (High). Coatings were applied to the black hide samples using a hand sprayer. Lux measurements were taken using a modified lux meter at three light intensities generated with a broad spectrum, cold halogen light source. Reflectance over a wavelength range of 380 to 900 nm was measured using a spectroradiometer. The transdermal transfer of heat derived from absorbed light was measured by applying a broad spectrum, cold halogen light source to the stratum corneum (coated) side of the sample and recording the temperature of the dermis-side using a thermal camera for 10 min at 30-s intervals. At the high light level, the White, Black, Mid, and High coating treatments had different ( P < 0.001) lux values of 64,945, 1741, 15,978, and 40,730 lx, respectively. In the visible wavelength range (400 to 750 nm), Black hides reflected 10 to 15% of the light energy, hides with the Mid coating treatment reflected 35 to 40%, and hides with the High coating treatment reflected 70 to 80% of the light energy. The natural White hide samples reflected 60 to 80% of the light energy. The average maximum temperatures at the dermis-side of the hides due to transferred heat were 34.5, 70.1, 55.0, and 31.7, for the White, Black, Mid, and High treatments, respectively. Reflective coatings containing titanium dioxide on cattle hides were effective in reducing light energy absorption and reduced light-derived heat transfer from the skin surface to deeper skin layers.

Actinic keratosis

MedlinePlus

... near surfaces that reflect light, such as water, sand, concrete, and areas painted white. Sunlight is more ... A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among ...

Use of double-layer ITO films in reflective contacts for blue and near-UV LEDs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Markov, L. K., E-mail: l.markov@mail.ioffe.ru; Smirnova, I. P.; Pavluchenko, A. S.

2014-12-15

The structural and optical properties of multilayer ITO/SiO{sub 2}/Ag composites are studied. In these composites, the ITO (indium-tin oxide) layer is produced by two different methods: electron-beam evaporation and a combined method including electron-beam evaporation and subsequent magnetron sputtering. It is shown that the reflectance of the composite based on the ITO film produced by electron-beam evaporation is substantially lower. This can be attributed to the strong absorption of light at both boundaries of the SiO{sub 2} layer, which results from the complex surface profile of ITO films deposited by electron-beam evaporation. Samples with a film deposited by the combinedmore » method have a reflectance of about 90% at normal light incidence, which, combined with their higher electrical conductivity, makes these samples advantageous for use as reflective contacts to the p-type region of AlInGaN light-emitting diodes of the flip-chip design.« less

Effect of Surface Reflectivity Variations On Uv-visible Limb Scattering Measurements of The Atmosphere

NASA Astrophysics Data System (ADS)

Oikarinen, L.

Solar UV and visible radiation scattered at the limb of the Earth's atmosphere is used for measuring density profiles of atmosperic trace gases. For example, the OSIRIS instrument on Odin and SCIAMACHY on Envisat use this technique. A limb-viewing instrument does not see Earth's surface or tropospheric clouds directly. However, in- direct light reflected from the surface or low altitude clouds can make up tens of per cents of the signal. Furthermore, the surface area that contributes to limb intensity ex- tends over 1000 km along the instrument line-of-sight and 200 km across it. Over this area surface reflectivity can vary from almost 0% to 100%. Inaccurate modelling of reflected intensity is a potential source of error in the trace gas retrieval. Generally, radiative transfer models used for analysing limb measure- ments have to assume that the surface has a constant albedo. We have used a three- dimensional Monte Carlo radiative transfer model to study the effects of surface vari- ation to limb radiance. Based on the simulations, we have developed an approximate method for averaging surface albedo for limb scattering measurements with the help of a simple single scattering radiative transfer model.

Note: Sensitive fluorescence detection through minimizing the scattering light by anti-reflective nanostructured materials

NASA Astrophysics Data System (ADS)

Xu, Supeng; Yin, Yanning; Gu, Ruoxi; Xia, Meng; Xu, Liang; Chen, Li; Xia, Yong; Yin, Jianping

2018-04-01

We demonstrate a new approach with fabrication of anti-reflective coating to substantially reduce the scattering light in an ultra-high vacuum during laser induced fluorescence (LIF) detection. To do so, the surface of the vacuum chamber in the detection region was blackened and coated with the special solar heat absorbing nanomaterials. We demonstrate that more than 97.5% of the stray light in the chamber spanning from near infrared to ultraviolet can be absorbed which effectively improves the signal to noise (S/N) ratio. With this technique, the LIF signal from the cold magnesium monofluoride molecules has been observed with an S/N ratio of ˜4 times better than without that.

Enhancement of photovoltaic cell performance using periodic triangular gratings

NASA Astrophysics Data System (ADS)

Bordatchev, Evgueni; Tauhiduzzaman, Mohammed; Dey, Rajat

2014-01-01

The solar energy industry strives to produce more efficient and yet cost effective solar panels each consisting of an array of photovoltaic (PV) cells. The goal of this study was to enhance the performance of PV cells through increasing the cells' optical efficiency defined as a percentage of surface incident light that reaches the PV material. This was achieved through the reduction of waveguide decoupling loss and Fresnel reflection losses by integrating specific nonimaging micro-optical structures on the top surface of existing PV cells. Due to this integration, optical efficiency and performance were increased through the enhancement of light trapping, light guiding, and in-coupling functionalities. Periodic triangular gratings (PTGs) were designed, nonsequentially modeled, optimized, and fabricated in polydimethylsiloxane as proposed micro-optical structures. Then the performance of PV cells with and without integrated PTGs was evaluated and compared. Initial optical simulation results show that an original PV cell (without PTG) exhibits an average optical efficiency of 32.7% over a range of incident light angles between 15 and 90 deg. Integration of the PTG allows the capture of incoming sunlight by total internal reflection (TIR), whence it is reflected back onto the PV cell for multiple consecutive chances for absorption and PV conversion. Geometry of the PTG was optimized with respect to an angle of light incidence of {15, 30, 45, 60, 75, 90} deg. Optical efficiency of the geometrically optimized PTGs was then analyzed under the same set of incident light angles and a maximum optical efficiency of 54.1% was observed for a PV cell with integrated PTG optimized at 90 deg. This is a 53.3% relative improvement in optical performance when compared to an original PV cell. Functional PTG prototypes were then fabricated with optical surface quality (below 10 nm Ra) and integrated with PV cells demonstrating an increase in maximum power by 1.08 mW/cm (7.6% improvement in PV performance) and in short circuit current by 2.39 mA/cm (6.4% improvement).

Patents -- Ivar Giaever (1976)

Science.gov Websites

biological particles, particularly proteins. Such devices comprise a non-transparent surface of metal (solid metal or a non-transparent coating of metal on some different substrate) covered with a thin transparent unaided eye, when the non-transparent surface metal reflects light relatively poorly and is at least

Improving the uniformity of luminous system in radial imaging capsule endoscope system

NASA Astrophysics Data System (ADS)

Ou-Yang, Mang; Jeng, Wei-De

2013-02-01

This study concerns the illumination system in a radial imaging capsule endoscope (RICE). Uniformly illuminating the object is difficult because the intensity of the light from the light emitting diodes (LEDs) varies with angular displacement. When light is emitted from the surface of the LED, it first encounters the cone mirror, from which it is reflected, before directly passing through the lenses and complementary metal oxide semiconductor (CMOS) sensor. The light that is strongly reflected from the transparent view window (TVW) propagates again to the cone mirror, to be reflected and to pass through the lenses and CMOS sensor. The above two phenomena cause overblooming on the image plane. Overblooming causes nonuniform illumination on the image plane and consequently reduced image quality. In this work, optical design software was utilized to construct a photometric model for the optimal design of the LED illumination system. Based on the original RICE model, this paper proposes an optimal design to improve the uniformity of the illumination. The illumination uniformity in the RICE is increased from its original value of 0.128 to 0.69, greatly improving light uniformity.

Magneto-Optic Kerr Effect in a Magnetized Electron Gun

NASA Astrophysics Data System (ADS)

Hardy, Benjamin; Grames, Joseph; CenterInjectors; Sources Team

2016-09-01

Magnetized electron sources have the potential to improve ion beam cooling efficiency. At the Gun Test Stand at Jefferson Lab, a solenoid magnet will be installed adjacent to the photogun to magnetize the electron beam. Due to the photocathode operating in a vacuum chamber, measuring and monitoring the magnetic field at the beam source location with conventional probes is impractical. The Magneto-Optical Kerr Effect (MOKE) describes the change on polarized light by reflection from a magnetized surface. The reflection from the surface may alter the polarization direction, ellipticity, or intensity, and depends linearly upon the surface magnetization of the sample. By replacing the photocathode with a magnetized sample and reflecting polarized light from the sample surface, the magnetic field at the beam source is inferred. A controlled MOKE system has been assembled to test the magnetic field. Calibration of the solenoid magnet is performed by comparing the MOKE signal with magnetic field measurements. The apparatus will provide a description of the field at electron beam source. The report summarizes the method and results of controlled tests and calibration of the MOKE sample with the solenoid magnet field measurements. This work is supported by the National Science Foundation, Research Experience for Undergraduates Award 1359026 and the Department of Energy, Laboratory Directed Research and Development Contract DE-AC05-06OR23177.

Determination of point of incidence for the case of reflection or refraction at spherical surface knowing two points lying on the ray.

PubMed

Mikš, Antonín; Novák, Pavel

2017-09-01

The paper is focused on the problem of determination of the point of incidence of a light ray for the case of reflection or refraction at the spherical optical surface, assuming that two fixed points in space that the sought light ray should go through are given. The requirement is that one of these points lies on the incident ray and the other point on the reflected/refracted ray. Although at first glance it seems to be a simple problem, it will be shown that it has no simple analytical solution. The basic idea of the solution is given, and it is shown that the problem leads to a nonlinear equation in one variable. The roots of the resulting nonlinear equation can be found by numerical methods of mathematical optimization. The proposed methods were implemented in MATLAB, and the proper function of these algorithms was verified on several examples.

Solid state laser

NASA Technical Reports Server (NTRS)

Rines, Glen A. (Inventor); Moulton, Peter F. (Inventor); Harrison, James (Inventor)

1993-01-01

A wavelength-tunable, injection-seeded, dispersion-compensated, dispersively-pumped solid state laser includes a lasing medium; a highly reflective mirror; an output coupler; at least one isosceles Brewster prism oriented to the minimum deviation angle between the medium and the mirror for directing light of different wavelengths along different paths; means for varying the angle of the highly reflective mirror relative to the light from at least one Brewster angle for selecting a predetermined laser operating wavelength; a dispersion compensation apparatus associated with the lasing medium; a laser injection seeding port disposed between the dispersion compensation apparatus and one of the mirror and coupler and including a reflective surface at an acute non-Brewster angle to the laser beam for introducing a seed input; a dispersion compensation apparatus associated with the laser medium including opposite chirality optical elements; the lasing medium including a pump surface disposed at an acute angle to the laser beam to define a discrete path for the pumping laser beam separate from the pumped laser beam.

Emissive and reflective properties of curved displays in relation to image quality

NASA Astrophysics Data System (ADS)

Boher, Pierre; Leroux, Thierry; Bignon, Thibault; Collomb-Patton, Véronique; Blanc, Pierre; Sandré-Chardonnal, Etienne

2016-03-01

Different aspects of the characterization of curved displays are presented. The limit of validity of viewing angle measurements without angular distortion on such displays using goniometer or Fourier optics viewing angle instrument is given. If the condition cannot be fulfilled the measurement can be corrected using a general angular distortion formula as demonstrated experimentally using a Samsung Galaxy S6 edge phone display. The reflective properties of the display are characterized by measuring the spectral BRDF using a multispectral Fourier optics viewing angle system. The surface of a curved OLED TV has been measured. The BDRF patterns show a mirror like behavior with and additional strong diffraction along the pixels lines and columns that affect the quality of the display when observed with parasitic lighting. These diffraction effects are very common on OLED surfaces. We finally introduce a commercial ray tracing software that can use directly the measured emissive and reflective properties of the display to make realistic simulation under any lighting environment.

Applications of fourier transform infrared spectroscopy to surface analysis problems 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, G.L.; Milosevic, M.

Applications of infrared spectroscopy to surface analysis are described in terms of the combined use of a number of techniques to solve specific surface analysis problems involving both qualitative and quantitative analysis of surface species. Emphasis is placed on the characterization of both the substrate and the surface species and the application of this to the monitoring of surface processes and the inspection of manufactured items. Lithium Hydride has been studied using remote analysis by diffuse reflectance in glove boxes containing very pure argon or controlled moisture levels with robot-operated gravimetric monitoring. These experiments are supported by internal reflectance andmore » diffuse reflectance measurements in spectrometer sample compartments to characterize the reactants. Beryllium oxide has been studied using an evacuable diffuse reflectance cell to determine the effects of vacuum baking reexposure to moisture on the surface hydroxyl species. Diffuse reflectance and emission measurements have been used to monitor the curing and reaction of environmental gases with composite materials such as graphite-expoxy structures. A direct comparison of diffuse reflectance and emission spectra was done using a barrel ellipsoid diffuse reflectance/emission detector and Spectropus optical transfer system. Grazing-incidence external-reflectance with p-polarized light was used to study the oxidation in room air of polished uranium coupons. The absorption band at 570 cm{sup {minus}1} was used to monitor the extent of oxidation with a resolution of approximately one monolayer of UO{sub 2} and to distinguish the parabolic, linear, and breakaway corrosion domains. External reflectance is compared with diffuse reflectance as a method for stain analysis and for measuring the effects of H{sub 2}O in UO{sub 2} corrosion films.« less

Applications of fourier transform infrared spectroscopy to surface analysis problems 2. Revision 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, G.L.; Milosevic, M.

Applications of infrared spectroscopy to surface analysis are described in terms of the combined use of a number of techniques to solve specific surface analysis problems involving both qualitative and quantitative analysis of surface species. Emphasis is placed on the characterization of both the substrate and the surface species and the application of this to the monitoring of surface processes and the inspection of manufactured items. Lithium Hydride has been studied using remote analysis by diffuse reflectance in glove boxes containing very pure argon or controlled moisture levels with robot-operated gravimetric monitoring. These experiments are supported by internal reflectance andmore » diffuse reflectance measurements in spectrometer sample compartments to characterize the reactants. Beryllium oxide has been studied using an evacuable diffuse reflectance cell to determine the effects of vacuum baking reexposure to moisture on the surface hydroxyl species. Diffuse reflectance and emission measurements have been used to monitor the curing and reaction of environmental gases with composite materials such as graphite-expoxy structures. A direct comparison of diffuse reflectance and emission spectra was done using a barrel ellipsoid diffuse reflectance/emission detector and Spectropus optical transfer system. Grazing-incidence external-reflectance with p-polarized light was used to study the oxidation in room air of polished uranium coupons. The absorption band at 570 cm{sup {minus}1} was used to monitor the extent of oxidation with a resolution of approximately one monolayer of UO{sub 2} and to distinguish the parabolic, linear, and breakaway corrosion domains. External reflectance is compared with diffuse reflectance as a method for stain analysis and for measuring the effects of H{sub 2}O in UO{sub 2} corrosion films.« less

Polarized Optical Scattering Measurements of Metallic Nanoparticles on a Thin Film Silicon Wafer

NASA Astrophysics Data System (ADS)

Liu, Cheng-Yang; Liu, Tze-An; Fu, Wei-En

2009-09-01

Light scattering has shown its powerful diagnostic capability to characterize optical quality surfaces. In this study, the theory of bidirectional reflectance distribution function (BRDF) was used to analyze the metallic nanoparticles' sizes on wafer surfaces. The BRDF of a surface is defined as the angular distribution of radiance scattered by the surface normalized by the irradiance incident on the surface. A goniometric optical scatter instrument has been developed to perform the BRDF measurements on polarized light scattering on wafer surfaces for the diameter and distribution measurements of metallic nanoparticles. The designed optical scatter instrument is capable of distinguishing various types of optical scattering characteristics, which are corresponding to the diameters of the metallic nanoparticles, near surfaces by using the Mueller matrix calculation. The metallic nanoparticle diameter of measurement is 60 nm on 2 inch thin film wafers. These measurement results demonstrate that the polarization of light scattered by metallic particles can be used to determine the size of metallic nanoparticles on silicon wafers.

Target Recognition Using Neural Networks for Model Deformation Measurements

NASA Technical Reports Server (NTRS)

Ross, Richard W.; Hibler, David L.

1999-01-01

Optical measurements provide a non-invasive method for measuring deformation of wind tunnel models. Model deformation systems use targets mounted or painted on the surface of the model to identify known positions, and photogrammetric methods are used to calculate 3-D positions of the targets on the model from digital 2-D images. Under ideal conditions, the reflective targets are placed against a dark background and provide high-contrast images, aiding in target recognition. However, glints of light reflecting from the model surface, or reduced contrast caused by light source or model smoothness constraints, can compromise accurate target determination using current algorithmic methods. This paper describes a technique using a neural network and image processing technologies which increases the reliability of target recognition systems. Unlike algorithmic methods, the neural network can be trained to identify the characteristic patterns that distinguish targets from other objects of similar size and appearance and can adapt to changes in lighting and environmental conditions.

Polarimetry of nacre in iridescent shells

NASA Astrophysics Data System (ADS)

Metzler, R. A.; Burgess, C.; Regan, B.; Spano, S.; Galvez, E. J.

2014-09-01

We investigate the light transmitted or reflected from nacre (mother of pearl) taken from the iridescent shell of the bivalve Pinctad a fucata. These nacre surfaces have a rich structure, composed of aragonite crystals arranged as tablets or bricks, 5 μm wide and 400-500 nm thick, surrounded by 30nm thick organic mortar. The light reflected from these shell surfaces, or transmitted through thin polished layers, is rich in its polarization content, exhibiting a space dependent variation in the state of polarization with a high density of polarization singularities. Our goal is to use the polarization information to infer the structure of the biominerals and the role of the organic layer in determining the orientation of the crystals. In the experiments we send the light from a laser with a uniform state of polarization onto the shell, and analyze the light that is either transmitted or reflected, depending on the type of experiment, imaging it after its passage through polarization filters. We use the images from distinct filters to obtain the Stokes parameters, and hence the state of polarization, of each image point. We also construct the Mueller matrix for each imaged point, via 36 measurements. We do this for distinct physical and chemical treatments of the shell sample. Preliminary data shows that the organic layer may be responsible for organizing a multi-crystalline arrangement of aragonite tablets.

Role of intraocular lens parameters in visual rehabilitation of patients after extracapsular cataract extraction

NASA Astrophysics Data System (ADS)

Bakutkin, Valery V.; Galanzha, Vladimir A.

2001-01-01

The main method of cataract treatment is micro surgical removing of the opaque lens from the eye with implantation of an intra ocular lens. We performed the comparative study of using various IOL models differing in its materials, index of refraction, spectral properties, configuration, shape, size and other features. Before and after the IOL implantation we performed the following test: visual acuity measuring, refractometry, keratometry, laser interferometric retinometry, color perception assessment, digital photo- and videorecording of the eye with image processing and some others. We found a number of correlations between the IOL properties and some characteristics of the patient's vision. The decentration of the IOL optical part more than 1,5 mm conduced to the non-corneal astigmatism and the prismatic effect. A small diameter of the IOL optical part and high index of refraction promotes to the appearance of the optical aberrations. Leucosapphire IOLs revealed the high degree of light reflection and the minimal adhesive ability of the IOL surface. Leucosapphire IOL revealed the high degree of light reflection and the minimal adhesive ability of the IOL surface. PMMA IOL revealed the low reflective power and the high adhesive ability. The best color vision was revealed in patients with PMMA IOL with an additional compound absorbing not only UV light but also short-wave blue light.

Doppler-shifted self-reflected wave from a semiconductor

NASA Astrophysics Data System (ADS)

Schuelzgen, Alex; Hughes, S.; Peyghambarian, Nasser

1997-06-01

We report the first experimental observation of a self- reflected wave inside a very dense saturable absorber. An intense femtosecond pulse saturates the absorption and causes a density front moving into the semiconductor sample. Due to the motion of the boundary between saturated and unsaturated areas of the sample the light reflected at this boundary is red-shifted by the Doppler effect. The spectrally shifted reflection makes it possible to distinguish between surface reflection and self-reflection and is used to proof the concept of the dynamic nonlinear skin effect experimentally. Quite well agreement with model calculations is found.

High resolution non-contact interior profilometer

DOEpatents

Piltch, Martin S.; Patterson, R. Alan; Leeches, Gerald W.; Nierop, John Van; Teti, John J.

2001-01-01

Apparatus and method for inspecting the interior surfaces of devices such as vessels having a single entry port. Laser energy is launched into the vessel, and the light reflected from the interior surfaces is interfered with reference laser energy to produce an interference pattern. This interference pattern is analyzed to reveal information about the condition of the interior surfaces of the device inspected.

Large-scale cauliflower-shaped hierarchical copper nanostructures for efficient photothermal conversion.

PubMed

Fan, Peixun; Wu, Hui; Zhong, Minlin; Zhang, Hongjun; Bai, Benfeng; Jin, Guofan

2016-08-14

Efficient solar energy harvesting and photothermal conversion have essential importance for many practical applications. Here, we present a laser-induced cauliflower-shaped hierarchical surface nanostructure on a copper surface, which exhibits extremely high omnidirectional absorption efficiency over a broad electromagnetic spectral range from the UV to the near-infrared region. The measured average hemispherical absorptance is as high as 98% within the wavelength range of 200-800 nm, and the angle dependent specular reflectance stays below 0.1% within the 0-60° incident angle. Such a structured copper surface can exhibit an apparent heating up effect under the sunlight illumination. In the experiment of evaporating water, the structured surface yields an overall photothermal conversion efficiency over 60% under an illuminating solar power density of ∼1 kW m(-2). The presented technology provides a cost-effective, reliable, and simple way for realizing broadband omnidirectional light absorptive metal surfaces for efficient solar energy harvesting and utilization, which is highly demanded in various light harvesting, anti-reflection, and photothermal conversion applications. Since the structure is directly formed by femtosecond laser writing, it is quite suitable for mass production and can be easily extended to a large surface area.

Thermal barriers for compartments

DOEpatents

Kreutzer, Cory J.; Lustbader, Jason A.

2017-10-17

An aspect of the present disclosure is a thermal barrier that includes a core layer having a first surface, a second surface, and a first edge, and a first outer layer that includes a third surface and a second edge, where the third surface substantially contacts the first surface, the core layer is configured to minimize conductive heat transfer through the barrier, and the first outer layer is configured to maximize reflection of light away from the barrier.

Split off-specular reflection and surface scattering from woven materials

NASA Astrophysics Data System (ADS)

Pont, Sylvia C.; Koenderink, Jan J.

2003-03-01

We measured radiance distributions for black lining cloth and copper gauze using the convenient technique of wrapping the materials around a circular cylinder, irradiating it with a parallel light source and collecting the scattered radiance by a digital camera. One family of parallel threads (weave or weft) was parallel to the cylinder generator. The most salient features for such glossy plane weaves are a splitting up of the reflection peak due to the wavy variations in local slopes of the threads around the cylinders and a surface scattering lobe due to the threads that run along the cylinder. These scattering characteristics are quite different from the (off-)specular peaks and lobes that were found before for random rough specular surfaces. The split off-specular reflection is due to the regular structures in our samples of man-made materials. We derived simple approximations for these reflectance characteristics using geometrical optics.

Seasonal canopy reflectance patterns of wheat, sorghum, and soybean

NASA Technical Reports Server (NTRS)

Kanemasu, E. T.

1974-01-01

An investigation was conducted of canopy-reflectance patterns as a basis for the determination of surface conditions. Two fields each of wheat, sorghum, and soybeans were selected in a bottom land area. One field contained a dark-colored, silty clay loam and the other a light-colored, silt loam. The study suggests that the reflectance ratio of the 545- to 655-nm-wavelengths may be used as an indicator of crop growth.

Optical method for the characterization of laterally-patterned samples in integrated circuits

DOEpatents

Maris, Humphrey J.

2001-01-01

Disclosed is a method for characterizing a sample having a structure disposed on or within the sample, comprising the steps of applying a first pulse of light to a surface of the sample for creating a propagating strain pulse in the sample, applying a second pulse of light to the surface so that the second pulse of light interacts with the propagating strain pulse in the sample, sensing from a reflection of the second pulse a change in optical response of the sample, and relating a time of occurrence of the change in optical response to at least one dimension of the structure.

Optical method and system for the characterization of laterally-patterned samples in integrated circuits

DOEpatents

Maris, Humphrey J.

2008-03-04

Disclosed is a method for characterizing a sample having a structure disposed on or within the sample, comprising the steps of applying a first pulse of light to a surface of the sample for creating a propagating strain pulse in the sample, applying a second pulse of light to the surface so that the second pulse of light interacts with the propagating strain pulse in the sample, sensing from a reflection of the second pulse a change in optical response of the sample, and relating a time of occurrence of the change in optical response to at least one dimension of the structure.

Optical method for the characterization of laterally-patterned samples in integrated circuits

DOEpatents

Maris, Humphrey J.

2010-08-24

Disclosed is a method for characterizing a sample having a structure disposed on or within the sample, comprising the steps of applying a first pulse of light to a surface of the sample for creating a propagating strain pulse in the sample, applying a second pulse of light to the surface so that the second pulse of light interacts with the propagating strain pulse in the sample, sensing from a reflection of the second pulse a change in optical response of the sample, and relating a time of occurrence of the change in optical response to at least one dimension of the structure.

Optical method for the characterization of laterally patterned samples in integrated circuits

DOEpatents

Maris, Humphrey J [Barrington, RI

2009-03-17

Disclosed is a method for characterizing a sample having a structure disposed on or within the sample, comprising the steps of applying a first pulse of light to a surface of the sample for creating a propagating strain pulse in the sample, applying a second pulse of light to the surface so that the second pulse of light interacts with the propagating strain pulse in the sample, sensing from a reflection of the second pulse a change in optical response of the sample, and relating a time of occurrence of the change in optical response to at least one dimension of the structure.

Optical method and system for the characterization of laterally-patterned samples in integrated circuits

DOEpatents

Maris, Humphrey J [Barrington, RI

2011-02-22

Disclosed is a method for characterizing a sample having a structure disposed on or within the sample, comprising the steps of applying a first pulse of light to a surface of the sample for creating a propagating strain pulse in the sample, applying a second pulse of light to the surface so that the second pulse of light interacts with the propagating strain pulse in the sample, sensing from a reflection of the second pulse a change in optical response of the sample, and relating a time of occurrence of the change in optical response to at least one dimension of the structure.

Lunar and Planetary Science XXXV: Outer Solar System

NASA Technical Reports Server (NTRS)

2004-01-01

The session "Outer Solar System" included the following reports:New Data About Seasonal Variations of the North-South Asymmetry of Polarized Light of Jupiter; Appearance of Second Harmonic in the Jupiter Spectrum; Dynamics of Confined Liquid Mass, Spreading on Planet Surface; "Cassini" will Discover 116 New Satellites of Saturn!; Jupiter's Light Reflection Law;and Internal Structure Modelling of Europa.

Lamp with a truncated reflector cup

DOEpatents

Li, Ming; Allen, Steven C.; Bazydola, Sarah; Ghiu, Camil-Daniel

2013-10-15

A lamp assembly, and method for making same. The lamp assembly includes first and second truncated reflector cups. The lamp assembly also includes at least one base plate disposed between the first and second truncated reflector cups, and a light engine disposed on a top surface of the at least one base plate. The light engine is configured to emit light to be reflected by one of the first and second truncated reflector cups.

Ellipsoid-conic radiation collector and method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brunsting, A.; Hogg, W.R.

Disclosed is a radiation collector apparatus and method primarily for counting and analyzing a flow of dilute particulate material, such as blood cells, sperm cells and the like, through the use of light detection. The radiation collector apparatus comprises a reflector chamber having an ellipsoidal reflector surface with a pair of elipsoidal foci defining a first focus, f11, and second focus, f12, and a second reflector surface with a primary focus, f21, positioned at the same point as focus f12, and a secondary focus, f22. The second reflector surface has the configuration of one of the conic sections of revolution.more » In operation the radiation collector apparatus is provided with an intensifed beam of light and a stream of particulate material aligned to intersect the intensifed beam of light at focus f11. Detectable light signals, after two reflections, are received in a focused beam by a photosensitive detector.« less

Reverse color sequence in the diffraction of white light by the wing of the male butterfly Pierella luna (Nymphalidae: Satyrinae)

NASA Astrophysics Data System (ADS)

Vigneron, Jean Pol; Simonis, Priscilla; Aiello, Annette; Bay, Annick; Windsor, Donald M.; Colomer, Jean-François; Rassart, Marie

2010-08-01

The butterfly Pierella luna (Nymphalidae) shows an intriguing rainbow iridescence effect: the forewings of the male, when illuminated along the axis from the body to the wing tip, decompose a white light beam as a diffraction grating would do. Violet light, however, emerges along a grazing angle, near the wing surface, while the other colors, from blue to red, exit respectively at angles progressively closer to the direction perpendicular to the wing plane. This sequence is the reverse of the usual decomposition of light by a grating with a periodicity parallel to the wing surface. It is shown that this effect is produced by a macroscopic deformation of the entire scale, which curls in such a way that it forms a “vertical” grating, perpendicular to the wing surface, and functions in transmission instead of reflection.

Dynamical measurement of refractive index distribution using digital holographic interferometry based on total internal reflection.

PubMed

Zhang, Jiwei; Di, Jianglei; Li, Ying; Xi, Teli; Zhao, Jianlin

2015-10-19

We present a method for dynamically measuring the refractive index distribution in a large range based on the combination of digital holographic interferometry and total internal reflection. A series of holograms, carrying the index information of mixed liquids adhered on a total reflection prism surface, are recorded with CCD during the diffusion process. Phase shift differences of the reflected light are reconstructed exploiting the principle of double-exposure holographic interferometry. According to the relationship between the reflection phase shift difference and the liquid index, two dimensional index distributions can be directly figured out, assuming that the index of air near the prism surface is constant. The proposed method can also be applied to measure the index of solid media and monitor the index variation during some chemical reaction processes.

Surface characteristics modeling and performance evaluation of urban building materials using LiDAR data.

PubMed

Li, Xiaolu; Liang, Yu

2015-05-20

Analysis of light detection and ranging (LiDAR) intensity data to extract surface features is of great interest in remote sensing research. One potential application of LiDAR intensity data is target classification. A new bidirectional reflectance distribution function (BRDF) model is derived for target characterization of rough and smooth surfaces. Based on the geometry of our coaxial full-waveform LiDAR system, the integration method is improved through coordinate transformation to establish the relationship between the BRDF model and intensity data of LiDAR. A series of experiments using typical urban building materials are implemented to validate the proposed BRDF model and integration method. The fitting results show that three parameters extracted from the proposed BRDF model can distinguish the urban building materials from perspectives of roughness, specular reflectance, and diffuse reflectance. A comprehensive analysis of these parameters will help characterize surface features in a physically rigorous manner.

Use of polarization to improve signal to clutter ratio in an outdoor active imaging system

NASA Astrophysics Data System (ADS)

Fontoura, Patrick F.; Giles, Michael K.; Padilla, Denise D.

2005-08-01

This paper describes the methodology and presents the results of the design of a polarization-sensitive system used to increase the signal-to-clutter ratio in a robust outdoor structured lighting sensor that uses standard CCD camera technology. This lighting sensor is intended to be used on an autonomous vehicle, looking down to the ground and horizontal to obstacles in an 8 foot range. The kinds of surfaces to be imaged are natural and man-made, such as asphalt, concrete, dirt and grass. The main problem for an outdoor eye-safe laser imaging system is that the reflected energy from background clutter tends to be brighter than the reflected laser energy. A narrow-band optical filter does not reduce significantly the background clutter in bright sunlight, and problems also occur when the surface is highly absorptive, like asphalt. Therefore, most of applications are limited to indoor and controlled outdoor conditions. A series of measurements was made for each of the materials studied in order to find the best configuration for the polarizing system and also to find out the potential improvement in the signal-to-clutter ratio (STC). This process was divided into three parts: characterization of the reflected sunlight, characterization of the reflected laser light, and measurement of the improvement in the STC. The results show that by using polarization properties it is possible to design an optical system that is able to increase the signal-to-clutter ratio from approximately 30% to 100% in the imaging system, depending on the kind of surface and on the incidence angle of the sunlight. The technique was also analyzed for indoor use, with the background clutter being the room illumination. For this specific case, polarization did not improve the signal-to-clutter ratio.

The Photosensitivity of Rhodopsin Bleaching and Light-Induced Increases of Fundus Reflectance in Mice Measured In Vivo With Scanning Laser Ophthalmoscopy

PubMed Central

Zhang, Pengfei; Goswami, Mayank; Zawadzki, Robert J.; Pugh, Edward N.

2016-01-01

Purpose To quantify bleaching-induced changes in fundus reflectance in the mouse retina. Methods Light reflected from the fundus of albino (Balb/c) and pigmented (C57Bl/6J) mice was measured with a multichannel scanning laser ophthalmoscopy optical coherence tomography (SLO-OCT) optical system. Serial scanning of small retinal regions was used for bleaching rhodopsin and measuring reflectance changes. Results Serial scanning generated a saturating reflectance increase centered at 501 nm with a photosensitivity of 1.4 × 10−8 per molecule μm2 in both strains, 2-fold higher than expected were irradiance at the rod outer segment base equal to that at the retinal surface. The action spectrum of the reflectance increase corresponds to the absorption spectrum of mouse rhodopsin in situ. Spectra obtained before and after bleaching were fitted with a model of fundus reflectance, quantifying contributions from loss of rhodopsin absorption with bleaching, absorption by oxygenated hemoglobin (HbO2) in the choroid (Balb/c), and absorption by melanin (C57Bl/6J). Both mouse strains exhibited light-induced broadband reflectance changes explained as bleaching-induced reflectivity increases at photoreceptor inner segment/outer segment (IS/OS) junctions and OS tips. Conclusions The elevated photosensitivity of rhodopsin bleaching in vivo is explained by waveguide condensing of light in propagation from rod inner segment (RIS) to rod outer segment (ROS). The similar photosensitivity of rhodopsin in the two strains reveals that little light backscattered from the sclera can enter the ROS. The bleaching-induced increases in reflectance at the IS/OS junctions and OS tips resemble results previously reported in human cones, but are ascribed to rods due to their 30/1 predominance over cones in mice and to the relatively minor amount of cone M-opsin in the regions scanned. PMID:27403994

Dual beam optical interferometer

NASA Technical Reports Server (NTRS)

Gutierrez, Roman C. (Inventor)

2003-01-01

A dual beam interferometer device is disclosed that enables moving an optics module in a direction, which changes the path lengths of two beams of light. The two beams reflect off a surface of an object and generate different speckle patterns detected by an element, such as a camera. The camera detects a characteristic of the surface.

Towards perfect light coupling and absorption in nanomembranes with omni-directional anti-reflection and photonic crystal structures

NASA Astrophysics Data System (ADS)

Chadha, Arvinder Singh

Silicon photonics is realized as a promising platform to meet the requirements of higher bandwidth and low cost high density monolithic integration. More recent demonstrations of a variety of stretchable, foldable and transfer printed ultra-thin silicon integrated circuits have instigated the use of flexible silicon nanomembrane for practical applications. Equally impressive innovations are demonstrated in the area of flat screen displays, smart cards, eyeglasses, and wearable displays. However, the overall efficiency of a variety of optical device is limited by poor light management resulting from difficulty of light coupling, small absorption volume in thin-film nanomembrane, and glare at oblique incidence to name a few. The aim of this thesis is to present the work of micro- and nano-scale structures for out-of-plane light coupling and absorption for integrated silicon photonics and high performance solar cells and photodetectors, with maximum absorption in the functional layer and minimal front-surface reflection and minimal rear-surface transmission. Perfect absorption in a variety of semiconductor nanomembranes (NM) and atomic layers of two dimensional (2D) materials over different wavelength spectrum is realized due to the local field intensity enhancement at critical coupling to the guided resonances of a photonic crystal (PC). A judicious choice of grating parameters tailors the power diffracted in the zeorth order and higher order modes making the device work as a broadband reflector, an in-plane coupler or a combination of both reflector and an in-plane coupler. At surface normal incidence, the polarization dependence of the grating based reflector is eliminated by the use of 2D photonic crystals. The incorporation of such a reflector after the functional nanomembrane layer reduces the back-surface transmission. Effect of incident angle, polarization and incident plane misalignment dependence on the reflection of a silicon NM based reflector are investigated in detail. The front-surface Fresnel reflection is reduced with the incorporation of an omni-directional anti-reflection coating (Omni-ARC) based on nanostructures or by deposition of graded refractive index (GRIN) films. A design methodology based on the comparison of the rate of change of the refractive index profile of nanostructures of different shapes and thickness as an equivalent GRIN film suggests the minimum feature size needed to give near perfect ARC. Numerical models were built to account for the non - uniform GRIN film deposition on both rigid and flexible, flat and curved surfaces resulting from the variation in the resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) process technology. With the miniaturization of the devices, the effect of finite beam size and finite active area of the photonic components on the optical properties like transmission, reflection and scattering loss was studied as well. All the numerical studies presented in the thesis are validated by experimental results.

Single-layer-coated surfaces with linearized reflectance versus angle of incidence: application to passive and active silicon rotation sensors

NASA Astrophysics Data System (ADS)

Azzam, R. M. A.; Howlader, M. M. K.; Georgiou, T. Y.

1995-08-01

A transparent or absorbing substrate can be coated with a transparent thin film to produce a linear reflectance-versus-angle-of-incidence response over a certain range of angles. Linearization at and near normal incidence is a special case that leads to a maximally flat response for p -polarized, s -polarized, or unpolarized light. For midrange and high-range linearization with moderate and high slopes, respectively, the best results are obtained when the incident light is s polarized. Application to a Si substrate that is coated with a SiO2 film leads to novel passive and active reflection rotation sensors. Experimental results and an error analysis of this rotation sensor are presented.

How can horseflies be captured by solar panels? A new concept of tabanid traps using light polarization and electricity produced by photovoltaics.

PubMed

Blahó, Miklós; Egri, Ádám; Barta, András; Antoni, Györgyi; Kriska, György; Horváth, Gábor

2012-10-26

Horseflies (Diptera: Tabanidae) can cause severe problems for humans and livestock because of the continuous annoyance performed and the diseases vectored by the haematophagous females. Therefore, effective horsefly traps are in large demand, especially for stock-breeders. To catch horseflies, several kinds of traps have been developed, many of them attracting these insects visually with the aid of a black ball. The recently discovered positive polarotaxis (attraction to horizontally polarized light) in several horsefly species can be used to design traps that capture female and male horseflies. The aim of this work is to present the concept of such a trap based on two novel principles: (1) the visual target of the trap is a horizontal solar panel (photovoltaics) attracting polarotactic horseflies by means of the highly and horizontally polarized light reflected from the photovoltaic surface. (2) The horseflies trying to touch or land on the photovoltaic trap surface are perished by the mechanical hit of a wire rotated quickly with an electromotor supplied by the photovoltaics-produced electricity. Thus, the photovoltaics is bifunctional: its horizontally polarized reflected light signal attracts water-seeking, polarotactic horseflies, and it produces the electricity necessary to rotate the wire. We describe here the concept and design of this new horsefly trap, the effectiveness of which was demonstrated in field experiments. The advantages and disadvantages of the trap are discussed. Using imaging polarimetry, we measured the reflection-polarization characteristics of the photovoltaic trap surface demonstrating the optical reason for the polarotactic attractiveness to horseflies. Copyright © 2012 Elsevier B.V. All rights reserved.

Design and validation of a diffuse reflectance and spectroscopic microendoscope with poly(dimethylsioxane)-based phantoms

PubMed Central

Greening, Gage J.; Powless, Amy J.; Hutcheson, Joshua A.; Prieto, Sandra P.; Majid, Aneeka A.; Muldoon, Timothy J.

2015-01-01

Many cases of epithelial cancer originate in basal layers of tissue and are initially undetected by conventional microendoscopy techniques. We present a bench-top, fiber-bundle microendoscope capable of providing high resolution images of surface cell morphology. Additionally, the microendoscope has the capability to interrogate deeper into material by using diffuse reflectance and broadband diffuse reflectance spectroscopy. The purpose of this multimodal technique was to overcome the limitation of microendoscopy techniques that are limited to only visualizing morphology at the tissue or cellular level. Using a custom fiber optic probe, high resolution surface images were acquired using topical proflavine to fluorescently stain non-keratinized epithelia. A 635 nm laser coupled to a 200 μm multimode fiber delivers light to the sample and the diffuse reflectance signal was captured by a 1 mm image guide fiber. Finally, a tungsten-halogen lamp coupled to a 200 μm multimode fiber delivers broadband light to the sample to acquire spectra at source-detector separations of 374, 729, and 1051 μm. To test the instrumentation, a high resolution proflavine-induced fluorescent image of resected healthy mouse colon was acquired. Additionally, five monolayer poly(dimethylsiloxane)-based optical phantoms with varying absorption and scattering properties were created to acquire diffuse reflectance profiles and broadband spectra. PMID:25983372

Design and validation of a diffuse reflectance and spectroscopic microendoscope with poly(dimethylsiloxane)-based phantoms

NASA Astrophysics Data System (ADS)

Greening, Gage J.; Powless, Amy J.; Hutcheson, Joshua A.; Prieto, Sandra P.; Majid, Aneeka A.; Muldoon, Timothy J.

2015-03-01

Many cases of epithelial cancer originate in basal layers of tissue and are initially undetected by conventional microendoscopy techniques. We present a bench-top, fiber-bundle microendoscope capable of providing high resolution images of surface cell morphology. Additionally, the microendoscope has the capability to interrogate deeper into material by using diffuse reflectance and broadband diffuse reflectance spectroscopy. The purpose of this multimodal technique was to overcome the limitation of microendoscopy techniques that are limited to only visualizing morphology at the tissue or cellular level. Using a custom fiber optic probe, high resolution surface images were acquired using topical proflavine to fluorescently stain non-keratinized epithelia. A 635 nm laser coupled to a 200 μm multimode fiber delivers light to the sample and the diffuse reflectance signal was captured by a 1 mm image guide fiber. Finally, a tungsten-halogen lamp coupled to a 200 μm multimode fiber delivers broadband light to the sample to acquire spectra at source-detector separations of 374, 729, and 1051 μm. To test the instrumentation, a high resolution proflavine-induced fluorescent image of resected healthy mouse colon was acquired. Additionally, five monolayer poly(dimethylsiloxane)-based optical phantoms with varying absorption and scattering properties were created to acquire diffuse reflectance profiles and broadband spectra.

FIBER AND INTEGRATED OPTICS: Excitation of leaky modes in a system of coupled waveguides

NASA Astrophysics Data System (ADS)

Usievich, B. A.; Nurligareev, J. Kh; Sychugov, V. A.; Golant, K. M.

2007-06-01

A system of coupled single-mode waveguides with the number M of guided modes lower than the number N of single-mode waveguides is studied. Leaky modes in this system are investigated in detail. It is shown, in particular, that these modes can be excited by light incident on the side surface of the system when the reflection coefficient vanishes. It is found that the angular dependence of the coefficient of reflection from the side surface of the system can be used to refine the dispersion curve for leaky modes. It is shown that light incident at a grazing angle can propagate in the system in the direction considerably different from the propagation direction of a beam incident from a substrate, even in the case of a small difference in the refractive indices.

Photometric variability in earthshine observations.

PubMed

Langford, Sally V; Wyithe, J Stuart B; Turner, Edwin L

2009-04-01

The identification of an extrasolar planet as Earth-like will depend on the detection of atmospheric signatures or surface non-uniformities. In this paper we present spatially unresolved flux light curves of Earth for the purpose of studying a prototype extrasolar terrestrial planet. Our monitoring of the photometric variability of earthshine revealed changes of up to 23% per hour in the brightness of Earth's scattered light at around 600 nm, due to the removal of specular reflection from the view of the Moon. This variability is accompanied by reddening of the spectrum and results from a change in surface properties across the continental boundary between the Indian Ocean and Africa's east coast. Our results based on earthshine monitoring indicate that specular reflection should provide a useful tool in determining the presence of liquid water on extrasolar planets via photometric observations.

Vegetation's red edge: a possible spectroscopic biosignature of extraterrestrial plants.

PubMed

Seager, S; Turner, E L; Schafer, J; Ford, E B

2005-06-01

Earth's deciduous plants have a sharp order-of-magnitude increase in leaf reflectance between approximately 700 and 750 nm wavelength. This strong reflectance of Earth's vegetation suggests that surface biosignatures with sharp spectral features might be detectable in the spectrum of scattered light from a spatially unresolved extrasolar terrestrial planet. We assess the potential of Earth's step-function-like spectroscopic feature, referred to as the "red edge," as a tool for astrobiology. We review the basic characteristics and physical origin of the red edge and summarize its use in astronomy: early spectroscopic efforts to search for vegetation on Mars and recent reports of detection of the red edge in the spectrum of Earthshine (i.e., the spatially integrated scattered light spectrum of Earth). We present Earthshine observations from Apache Point Observatory (New Mexico) to emphasize that time variability is key to detecting weak surface biosignatures such as the vegetation red edge. We briefly discuss the evolutionary advantages of vegetation's red edge reflectance, and speculate that while extraterrestrial "light-harvesting organisms" have no compelling reason to display the exact same red edge feature as terrestrial vegetation, they might have similar spectroscopic features at different wavelengths than terrestrial vegetation. This implies that future terrestrial-planet-characterizing space missions should obtain data that allow time-varying, sharp spectral features at unknown wavelengths to be identified. We caution that some mineral reflectance edges are similar in slope and strength to vegetation's red edge (albeit at different wavelengths); if an extrasolar planet reflectance edge is detected care must be taken with its interpretation.

Influence of multi-wavelength laser irradiation of enamel and dentin surfaces at 0.355, 2.94, and 9.4 μm on surface morphology, permeability, and acid resistance.

PubMed

Chang, Nai-Yuan N; Jew, Jamison M; Simon, Jacob C; Chen, Kenneth H; Lee, Robert C; Fried, William A; Cho, Jinny; Darling, Cynthia L; Fried, Daniel

2017-12-01

Ultraviolet (UV) and infrared (IR) lasers can be used to specifically target protein, water, and mineral, respectively, in dental hard tissues to produce varying changes in surface morphology, permeability, reflectivity, and acid resistance. The purpose of this study was to explore the influence of laser irradiation and topical fluoride application on the surface morphology, permeability, reflectivity, and acid resistance of enamel and dentin to shed light on the mechanism of interaction and develop more effective treatments. Twelve bovine enamel surfaces and twelve bovine dentin surfaces were irradiated with various combinations of lasers operating at 0.355 (Freq.-tripled Nd:YAG (UV) laser), 2.94 (Er:YAG laser), and 9.4 μm (CO 2 laser), and surfaces were exposed to an acidulated phosphate fluoride gel and an acid challenge. Changes in the surface morphology, acid resistance, and permeability were measured using digital microscopy, polarized light microscopy, near-IR reflectance, fluorescence, polarization sensitive-optical coherence tomography (PS-OCT), and surface dehydration rate measurements. Different laser treatments dramatically influenced the surface morphology and permeability of both enamel and dentin. CO 2 laser irradiation melted tooth surfaces. Er:YAG and UV lasers, while not melting tooth surfaces, showed markedly different surface roughness. Er:YAG irradiation led to significantly rougher enamel and dentin surfaces and led to higher permeability. There were significant differences in acid resistance among the various treatment groups. Surface dehydration measurements showed significant changes in permeability after laser treatments, application of fluoride and after exposure to demineralization. CO 2 laser irradiation was most effective in inhibiting demineralization on enamel while topical fluoride was most effective for dentin surfaces. Lasers Surg. Med. 49:913-927, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Plasmonic active spectral filter in VIS-NIR region using metal-insulator-metal (MIM) structure on glass plate

NASA Astrophysics Data System (ADS)

Oshikane, Yasushi; Murai, Kensuke; Higashi, Takaya; Yamamoto, Fumihiko; Nakano, Motohiro; Inoue, Haruyuki

2012-10-01

Interaction between surface plasmons at two interfaces inside a meta-insulator-metal (MIM) structure is one of the interesting physical phenomena in nanophotonics. We have started to create a plasmonic active spectral filter based on the MIM structure for a developing white light-emitting diode (LED) visible-light communication. An optical active filter at visible region assisted by surface plasmon resonance (SPR) in MIM structure of vacuum-deposited thin films on glass substrate has been studied both experimentally and theoretically. Interface between the first thin silver layer (M1, around 50 nm-thick) and bulk glass slide is appropriate for excitation of SPR at particular wavelength and incident angle of illumination light. And spatial extension of the SPR wave may cause an effective propagating mode confined in the insulator layer (I, around 150 nm-thick) by both M1 and the second thick silver layer (M2, around 200 nm-thick). Such an energy conversion from the illuminating light to the propagating SPR modes corresponds to an evident absorption dip on spectral reflectance curve of the MIM structure, and the shape of dip may vary widely in response to material and configuration of the MIM. The spectral and angular reflectance of the prototypical MIM structure has been measured by spectrophotometer for P- and S-polarized light because the plasmonic effect inside the MIM structure depends strongly on the polarization of light. Such the characteristic reflection feature has also been studied by using both the usual transfer matrix method and 2D electromagnetic simulation based on the finite element method. In this talk, several striking and preliminary MIM prototypes will be introduced and discussed.

Surface-plasmon enhanced photoemission of a silver nano-patterned photocathode

DOE PAGES

Zhang, Z.; Li, R.; To, H.; ...

2016-11-22

Here, nano-patterned photocathodes (NPC) take advantage of plasmonic effects to resonantly increase absorption of light and localize electromagnetic field intensity on metal surfaces leading to surface-plasmon enhanced photoemission. In this paper, we report the status of NPC research at UCLA including in particular the optimization of the dimensions of a nanohole array on a silver wafer to enhance plasmonic response at 800 nm light, the development of a spectrally-resolved reflectivity measurement setup for quick nanopattern validation, and of a novel cathode plug to enable high power tests of NPCs on single crystal substrates in a high gradient radiofrequency gun.

Surface-plasmon enhanced photoemission of a silver nano-patterned photocathode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Z.; Li, R.; To, H.

Here, nano-patterned photocathodes (NPC) take advantage of plasmonic effects to resonantly increase absorption of light and localize electromagnetic field intensity on metal surfaces leading to surface-plasmon enhanced photoemission. In this paper, we report the status of NPC research at UCLA including in particular the optimization of the dimensions of a nanohole array on a silver wafer to enhance plasmonic response at 800 nm light, the development of a spectrally-resolved reflectivity measurement setup for quick nanopattern validation, and of a novel cathode plug to enable high power tests of NPCs on single crystal substrates in a high gradient radiofrequency gun.

Cross correlation anomaly detection system

NASA Technical Reports Server (NTRS)

Micka, E. Z. (Inventor)

1975-01-01

This invention provides a method for automatically inspecting the surface of an object, such as an integrated circuit chip, whereby the data obtained by the light reflected from the surface, caused by a scanning light beam, is automatically compared with data representing acceptable values for each unique surface. A signal output provided indicated of acceptance or rejection of the chip. Acceptance is based on predetermined statistical confidence intervals calculated from known good regions of the object being tested, or their representative values. The method can utilize a known good chip, a photographic mask from which the I.C. was fabricated, or a computer stored replica of each pattern being tested.

Solar White

NASA Image and Video Library

2017-11-20

Robert Youngquist, Ph.D., tests a sample disk with a "Solar White" cryogenic selective surface coating with a flash light, demonstrating the coating’s reflective properties. The innovative coating is predicted to reflect more than 99.9 percent of the simulated solar infrared radiation. This technology could enable storing super-cold, or cryogenic, liquids and support systems that shield astronauts against radiation during the Journey to Mars.

Discriminative illumination: per-pixel classification of raw materials based on optimal projections of spectral BRDF.

PubMed

Liu, Chao; Gu, Jinwei

2014-01-01

Classifying raw, unpainted materials--metal, plastic, ceramic, fabric, and so on--is an important yet challenging task for computer vision. Previous works measure subsets of surface spectral reflectance as features for classification. However, acquiring the full spectral reflectance is time consuming and error-prone. In this paper, we propose to use coded illumination to directly measure discriminative features for material classification. Optimal illumination patterns--which we call "discriminative illumination"--are learned from training samples, after projecting to which the spectral reflectance of different materials are maximally separated. This projection is automatically realized by the integration of incident light for surface reflection. While a single discriminative illumination is capable of linear, two-class classification, we show that multiple discriminative illuminations can be used for nonlinear and multiclass classification. We also show theoretically that the proposed method has higher signal-to-noise ratio than previous methods due to light multiplexing. Finally, we construct an LED-based multispectral dome and use the discriminative illumination method for classifying a variety of raw materials, including metal (aluminum, alloy, steel, stainless steel, brass, and copper), plastic, ceramic, fabric, and wood. Experimental results demonstrate its effectiveness.

Modeling on the cathodoluminescence properties of the thin film phosphors for field emission flat panel displays

NASA Astrophysics Data System (ADS)

Cho, Kyu-Gong

2000-12-01

In order to investigate the effects of the film roughness with the fundamental luminance parameters of thin film phosphors, Y2 O3:Eu films with different thickness and roughness values were deposited on various substrate materials using a pulsed laser deposition technique under a controlled experimental procedure. The best luminous efficiency was observed from the Y2O3:Eu films on quartz substrates due to the smaller refractive index and low absorption characteristics of the quartz substrates which produce a larger amount of total internal reflection in the film and low loss of light intensity during the multiple internal reflections. The trapped light inside the film can escape the film more easily due to rougher film surface. The better epitaxial growth capability of the Y2O 3:Eu films with the LaAlO3 substrates resulted in higher luminous efficiency in the small surface roughness region. Higher luminous efficiency was observed in reflection mode than in transmission mode due to the contribution of diffusely scattered light at the air-film interface. A new theoretical model based on the diffraction scattering theory of light, the steady-state diffusion condition of carriers and the Kanaya-Okayama's electron- beam-solid interaction range satisfactorily explains all the experimental results mentioned above. The model also provides solid understandings on the cathodoluminescence properties of the thin film phosphors with the effects of other single or multiple luminance parameters. The parameters encountered for the model are surface roughness, electron-beam-solid interaction, surface recombination rate of carriers, charge carrier diffusion properties, multiple scattering at the interfaces (air- film, film-substrate, and substrate-air), optical properties of the material, film thickness, and substrate type. The model supplies a general solution in both qualitative and quantitative ways to estimate the luminance properties of the thin film phosphors and it can be utilized to optimize the thin film phosphor properties for the application of field emission flat panel displays.

Spectral signatures of photosynthesis. I. Review of Earth organisms.

PubMed

Kiang, Nancy Y; Siefert, Janet; Govindjee; Blankenship, Robert E

2007-02-01

Why do plants reflect in the green and have a "red edge" in the red, and should extrasolar photosynthesis be the same? We provide (1) a brief review of how photosynthesis works, (2) an overview of the diversity of photosynthetic organisms, their light harvesting systems, and environmental ranges, (3) a synthesis of photosynthetic surface spectral signatures, and (4) evolutionary rationales for photosynthetic surface reflectance spectra with regard to utilization of photon energy and the planetary light environment. We found the "near-infrared (NIR) end" of the red edge to trend from blue-shifted to reddest for (in order) snow algae, temperate algae, lichens, mosses, aquatic plants, and finally terrestrial vascular plants. The red edge is weak or sloping in lichens. Purple bacteria exhibit possibly a sloping edge in the NIR. More studies are needed on pigment-protein complexes, membrane composition, and measurements of bacteria before firm conclusions can be drawn about the role of the NIR reflectance. Pigment absorbance features are strongly correlated with features of atmospheric spectral transmittance: P680 in Photosystem II with the peak surface incident photon flux density at approximately 685 nm, just before an oxygen band at 687.5 nm; the NIR end of the red edge with water absorbance bands and the oxygen A-band at 761 nm; and bacteriochlorophyll reaction center wavelengths with local maxima in atmospheric and water transmittance spectra. Given the surface incident photon flux density spectrum and resonance transfer in light harvesting, we propose some rules with regard to where photosynthetic pigments will peak in absorbance: (1) the wavelength of peak incident photon flux; (2) the longest available wavelength for core antenna or reaction center pigments; and (3) the shortest wavelengths within an atmospheric window for accessory pigments. That plants absorb less green light may not be an inefficient legacy of evolutionary history, but may actually satisfy the above criteria.

Dual-phase-shift spherical Fizeau interferometer for reduction of noise due to internally scattered light

NASA Astrophysics Data System (ADS)

Kumagai, Toshiki; Hibino, Kenichi; Nagaike, Yasunari

2017-03-01

Internally scattered light in a Fizeau interferometer is generated from dust, defects, imperfect coating of the optical components, and multiple reflections inside the collimator lens. It produces additional noise fringes in the observed interference image and degrades the repeatability of the phase measurement. A method to reduce the phase measurement error is proposed, in which the test surface is mechanically translated between each phase measurement in addition to an ordinary phase shift of the reference surface. It is shown that a linear combination of several measured phases at different test surface positions can reduce the phase errors caused by the scattered light. The combination can also compensate for the nonuniformity of the phase shift that occurs in spherical tests. A symmetric sampling of the phase measurements can cancel the additional primary spherical aberrations that occur when the test surface is out of the null position of the confocal configuration.

Unpredictable adsorption and visible light induced decolorization of nano rutile for the treatment of crystal violet

NASA Astrophysics Data System (ADS)

Dong, Yanling; Liu, Yang; Lu, Dingze; Zheng, Feng; Fang, Pengfei; Zhang, Haining

2017-04-01

Photocatalysts containing different ratios of anatase and rutile are prepared via heat treatment of Degussa P-25 titania. X-ray diffraction (XRD), Bruuauer-Emmett-Teller (BET), ultraviolet-visible light diffuse reflectance spectra (DRS), Raman spectra (Raman), positron annihilation lifetime spectra (PAL) and temperature-programmed desorption (TPD) are applied to investigate the phase composition of the synthesized catalysts. Using crystal violet (CV) as the target pollutant, the unexpected visible light decolorization of rutile is observed. Despite the decreased specific surface area, the as-synthesized rutile samples exhibit much higher adsorption capability of CV than P-25 does, which in turn leads to improved photoreaction efficiency. Since the rutile samples can't absorb the visible light, the degradation under visible light irradiation is attributed to self-sensitization of CV on the surface of rutile.

Probing near-normally propagating bulk acoustic waves using pseudo-reflection geometry Brillouin spectroscopy

NASA Astrophysics Data System (ADS)

Parsons, L. C.; Andrews, G. T.

2012-09-01

Pseudo-reflection geometry Brillouin spectroscopy can be used to probe acoustic wave dispersion approximately along the surface normal of a material system while avoiding the difficulties associated with specularly reflected light encountered in an ideal reflection configuration. As an example of its application, we show analytically that it can be used to determine both the refractive index and bulk acoustic mode velocities of optically-isotropic non-metallic materials and confirm the utility of the approach via a series of experiments on fused quartz, gallium phosphide, water, and porous silicon films.

Minimising back reflections from the common path objective in a fundus camera

NASA Astrophysics Data System (ADS)

Swat, A.

2016-11-01

Eliminating back reflections is critical in the design of a fundus camera with internal illuminating system. As there is very little light reflected from the retina, even excellent antireflective coatings are not sufficient suppression of ghost reflections, therefore the number of surfaces in the common optics in illuminating and imaging paths shall be minimised. Typically a single aspheric objective is used. In the paper an alternative approach, an objective with all spherical surfaces, is presented. As more surfaces are required, more sophisticated method is needed to get rid of back reflections. Typically back reflections analysis, comprise treating subsequent objective surfaces as mirrors, and reflections from the objective surfaces are traced back through the imaging path. This approach can be applied in both sequential and nonsequential ray tracing. It is good enough for system check but not very suitable for early optimisation process in the optical system design phase. There are also available standard ghost control merit function operands in the sequential ray-trace, for example in Zemax system, but these don't allow back ray-trace in an alternative optical path, illumination vs. imaging. What is proposed in the paper, is a complete method to incorporate ghost reflected energy into the raytracing system merit function for sequential mode which is more efficient in optimisation process. Although developed for the purpose of specific case of fundus camera, the method might be utilised in a wider range of applications where ghost control is critical.

Why do red and dark-coloured cars lure aquatic insects? The attraction of water insects to car paintwork explained by reflection–polarization signals

PubMed Central

Kriska, György; Csabai, Zoltán; Boda, Pál; Malik, Péter; Horváth, Gábor

2006-01-01

We reveal here the visual ecological reasons for the phenomenon that aquatic insects often land on red, black and dark-coloured cars. Monitoring the numbers of aquatic beetles and bugs attracted to shiny black, white, red and yellow horizontal plastic sheets, we found that red and black reflectors are equally highly attractive to water insects, while yellow and white reflectors are unattractive. The reflection–polarization patterns of black, white, red and yellow cars were measured in the red, green and blue parts of the spectrum. In the blue and green, the degree of linear polarization p of light reflected from red and black cars is high and the direction of polarization of light reflected from red and black car roofs, bonnets and boots is nearly horizontal. Thus, the horizontal surfaces of red and black cars are highly attractive to red-blind polarotactic water insects. The p of light reflected from the horizontal surfaces of yellow and white cars is low and its direction of polarization is usually not horizontal. Consequently, yellow and white cars are unattractive to polarotactic water insects. The visual deception of aquatic insects by cars can be explained solely by the reflection–polarizational characteristics of the car paintwork. PMID:16769639

In silico analysis of decomposed reflectances of C3 and C4 plants aiming at the effective assessment of crop needs

NASA Astrophysics Data System (ADS)

Baranoski, Gladimir V. G.; Van Leeuwen, Spencer; Chen, Tenn F.

2017-04-01

By separating the surface and subsurface components of foliar hyperspectral signatures using polarization optics, it is possible to enhance the remote discrimination of different plant species and optimize the assessment of different factors associated with their health status. These initiatives, in turn, can lead to higher crop yield and lower environmental impact. It is important to consider, however, that the main varieties of crops, represented by C3 (e.g., soy) and C4 (e.g., maize) plants, have markedly distinct morphological characteristics. Accordingly, the influence of these characteristics on their interactions with impinging light may affect the selection of optimal probe wavelengths for specific applications making use of combined hyperspectral and polarization measurements. In this paper, we compare the sensitivity of the total (including surface and subsurface components) and subsurface reflectance responses of C3 and C4 plants to different spectral and geometrical light incidence conditions. This investigation is supported by measured biophysical data and predictive light transport simulations. The results of our comparisons indicate that the total and subsurface reflectance responses of C3 and C4 plants depict well-defined patterns of sensitivity for varying illumination conditions. We believe that these patterns should be considered in the design of high-fidelity crop discrimination and monitoring procedures.

Application of porous silicon in solar cell

NASA Astrophysics Data System (ADS)

Maniya, Nalin H.; Ashokan, Jibinlal; Srivastava, Divesh N.

2018-05-01

Silicon is widely used in solar cell applications with over 95% of all solar cells produced worldwide composed of silicon. Nanostructured thin porous silicon (PSi) layer acting as anti-reflecting coating is used in photovoltaic solar cells due to its advantages including simple and low cost fabrication, highly textured surfaces enabling lowering of reflectance, controllability of thickness and porosity of layer, and high surface area. PSi layers have previously been reported to reduce the reflection of light and replaced the conventional anti-reflective coating layers on solar cells. This can essentially improve the efficiency and decrease the cost of silicon solar cells. Here, we investigate the reflectance of different PSi layers formed by varying current density and etching time. PSi layers were formed by a combination of current density including 60 and 80 mA/cm2 and time for fabrication as 2, 4, 6, and 8 seconds. The fabricated PSi layers were characterized using reflectance spectroscopy and field emission scanning electron microscopy. Thickness and pore size of PSi layer were increased with increase in etching time and current density, respectively. The reflectance of PSi layers was decreased with increase in etching time until 6 seconds and increased again after 6 seconds, which was observed across both the current density. Reduction in reflectance indicates the increase of absorption of light by silicon due to the thin PSi layer. In comparison with the reflectance of silicon wafer, PSi layer fabricated at 80 mA/cm2 for 6 seconds gave the best result with reduction in reflectance up to 57%. Thus, the application of PSi layer as an effective anti-reflecting coating for the fabrication of solar cell has been demonstrated.

Tempel Alive with Light

NASA Technical Reports Server (NTRS)

2005-01-01

This spectacular image of comet Tempel 1 was taken 67 seconds after it obliterated Deep Impact's impactor spacecraft. The image was taken by the high-resolution camera on the mission's flyby craft. Scattered light from the collision saturated the camera's detector, creating the bright splash seen here. Linear spokes of light radiate away from the impact site, while reflected sunlight illuminates most of the comet surface. The image reveals topographic features, including ridges, scalloped edges and possibly impact craters formed long ago.

Intracardiac light catheter for rapid scanning transmural absorbance spectroscopy of perfused myocardium: measurement of myoglobin oxygenation and mitochondria redox state.

PubMed

Femnou, Armel N; Kuzmiak-Glancy, Sarah; Covian, Raul; Giles, Abigail V; Kay, Matthew W; Balaban, Robert S

2017-12-01

Absorbance spectroscopy of intrinsic cardiac chromophores provides nondestructive assessment of cytosolic oxygenation and mitochondria redox state. Isolated perfused heart spectroscopy is usually conducted by collecting reflected light from the heart surface, which represents a combination of surface scattering events and light that traversed portions of the myocardium. Reflectance spectroscopy with complex surface scattering effects in the beating heart leads to difficulty in quantitating chromophore absorbance. In this study, surface scattering was minimized and transmural path length optimized by placing a light source within the left ventricular chamber while monitoring transmurally transmitted light at the epicardial surface. The custom-designed intrachamber light catheter was a flexible coaxial cable (2.42-Fr) terminated with an encapsulated side-firing LED of 1.8 × 0.8 mm, altogether similar in size to a Millar pressure catheter. The LED catheter had minimal impact on aortic flow and heart rate in Langendorff perfusion and did not impact stability of the left ventricule of the working heart. Changes in transmural absorbance spectra were deconvoluted using a library of chromophore reference spectra to quantify the relative contribution of specific chromophores to the changes in measured absorbance. This broad-band spectral deconvolution approach eliminated errors that may result from simple dual-wavelength absorbance intensity. The myoglobin oxygenation level was only 82.2 ± 3.0%, whereas cytochrome c and cytochrome a + a 3 were 13.3 ± 1.4% and 12.6 ± 2.2% reduced, respectively, in the Langendorff-perfused heart. The intracardiac illumination strategy permits transmural optical absorbance spectroscopy in perfused hearts, which provides a noninvasive real-time monitor of cytosolic oxygenation and mitochondria redox state. NEW & NOTEWORTHY Here, a novel nondestructive real-time approach for monitoring intrinsic indicators of cardiac metabolism and oxygenation is described using a catheter-based transillumination of the left ventricular free wall together with complete spectral analysis of transmitted light. This approach is a significant improvement in the quality of cardiac optical absorbance spectroscopic metabolic analyses.

Development and field testing of a Light Aircraft Oil Surveillance System (LAOSS)

NASA Technical Reports Server (NTRS)

Burns, W.; Herz, M. J.

1976-01-01

An experimental device consisting of a conventional TV camera with a low light level photo image tube and motor driven polarized filter arrangement was constructed to provide a remote means of discriminating the presence of oil on water surfaces. This polarized light filtering system permitted a series of successive, rapid changes between the vertical and horizontal components of reflected polarized skylight and caused the oil based substances to be more easily observed and identified as a flashing image against a relatively static water surface background. This instrument was flight tested, and the results, with targets of opportunity and more systematic test site data, indicate the potential usefulness of this airborne remote sensing instrument.

Study of cylindrical optical micro-structure technology used in infrared laser protection

NASA Astrophysics Data System (ADS)

Sun, Yanjun; Liu, Shunrui; Wang, Zhining; Zhao, Yixuan; Wu, Boqi; Leng, Yanbing; Wang, Li

2016-10-01

The paper aimed at the problem that strong absorption in visible wavelengths and equipment or operator injury caused by specular reflection exist in infrared laser protection technology to propose an infrared laser non-specular reflection optical micro-structure formed from optical window surface. It has the function of little effect on visible light transmission and large-angle scattering to 1064nm infrared laser in order to enable laser protection. The paper uses light track method to design double-side micro-cylindrical lens arrays with dislocation construction. Array period T and curvature radius of lens units R should meet the condition:0

Blue Marble Eastern Hemisphere

NASA Technical Reports Server (NTRS)

2002-01-01

Drawing on data from multiple satellite missions (not all collected at the same time), a team of NASA scientists and graphic artists created layers of global data for everything from the land surface, to polar sea ice, to the light reflected by the chlorophyll in the billions of microscopic plants that grow in the ocean. They wrapped these layers around a globe, set it against a black background, and simulated the hazy edge of the Earth's atmosphere (the limb) that appears in astronaut photography of the Earth. The land surface layer is based on photo-like surface reflectance observations (reflected sunlight) measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite in July 2004. The sea ice layer near the poles comes from Terra MODIS observations of daytime sea ice observed between August 28 and September 6, 2001. The ocean layer is a composite. In shallow water areas, the layer shows surface reflectances observed by Terra MODIS in July 2004. In the open ocean, the photo-like layer is overlaid with observations of the average ocean chlorophyll content for 2004. NASA's Aqua MODIS collected the chlorophyll data. The cloud layer shows a single-day snapshot of clouds observed by Terra MODIS across the planet on July 29, 2001. City lights on Earth's night side are visualized from data collected by the Defense Meteorological Satellite Program mission between 1994-1995. The topography layer is based on radar data collected by the Space Shuttle Endeavour during an 11-day mission in February of 2000. Topography over Antarctica comes from the Radarsat Antarctic Mapping Project, version 2.

Blue Marble Western Hemisphere

NASA Technical Reports Server (NTRS)

2002-01-01

Drawing on data from multiple satellite missions (not all collected at the same time), a team of NASA scientists and graphic artists created layers of global data for everything from the land surface, to polar sea ice, to the light reflected by the chlorophyll in the billions of microscopic plants that grow in the ocean. They wrapped these layers around a globe, set it against a black background, and simulated the hazy edge of the Earth's atmosphere (the limb) that appears in astronaut photography of the Earth. The land surface layer is based on photo-like surface reflectance observations (reflected sunlight) measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite in July 2004. The sea ice layer near the poles comes from Terra MODIS observations of daytime sea ice observed between August 28 and September 6, 2001. The ocean layer is a composite. In shallow water areas, the layer shows surface reflectances observed by Terra MODIS in July 2004. In the open ocean, the photo-like layer is overlaid with observations of the average ocean chlorophyll content for 2004. NASA's Aqua MODIS collected the chlorophyll data. The cloud layer shows a single-day snapshot of clouds observed by Terra MODIS across the planet on July 29, 2001. City lights on Earth's night side are visualized from data collected by the Defense Meteorological Satellite Program mission between 1994-1995. The topography layer is based on radar data collected by the Space Shuttle Endeavour during an 11-day mission in February of 2000. Topography over Antarctica comes from the Radarsat Antarctic Mapping Project, version 2.

Photometrical Observations "SBIRS GEO-2"

NASA Astrophysics Data System (ADS)

Sukhov, P. P.; Epishev, V. P.; Karpenko, G. F.; Sukhov, K. P.; Kudak, V. I.

2015-08-01

Photometrical observations GSS "SBIRS GEO 2" in B,V,R filters were carried near the equinoxes 2014-2015. Used velocity electrophotometer based on the FEU-79 in the pulse-counting mode. Received more than 25 light curves. From the known dimensions are defined; effective reflecting area - Sγλ, the spectral reflectance index - γλ, periods of light variation. Color-indices showed that in the reflected light flux from the GSS prevails "red" component. In the light curves are periodically dips and specular flash. This shows that GSS orbit is not in a static position specified triaxial orientation as in dynamic motion. Assumed following dynamics of the satellite "SBIRS GEO 2" in orbit. Helical scanning the Earth's surface visible infrared sensors satellite occurs with a period P1 = 15.66 sec. and swinging of the GSS about the direction of the motion vector of the satellite in an orbit with P2 = 62.64 sec., from the northern to the southern pole. Thus, during the period of swinging GSS going on 2 scan the visible part of the northern and southern hemispheres. In some dates observations dynamics work satellite in orbit changed.

Phototaxis and polarotaxis hand in hand: night dispersal flight of aquatic insects distracted synergistically by light intensity and reflection polarization.

PubMed

Boda, Pál; Horváth, Gábor; Kriska, György; Blahó, Miklós; Csabai, Zoltán

2014-05-01

Based on an earlier observation in the field, we hypothesized that light intensity and horizontally polarized reflected light may strongly influence the flight behaviour of night-active aquatic insects. We assumed that phototaxis and polarotaxis together have a more harmful effect on the dispersal flight of these insects than they would have separately. We tested this hypothesis in a multiple-choice field experiment using horizontal test surfaces laid on the ground. We offered simultaneously the following visual stimuli for aerial aquatic insects: (1) lamplit matte black canvas inducing phototaxis alone, (2) unlit shiny black plastic sheet eliciting polarotaxis alone, (3) lamplit shiny black plastic sheet inducing simultaneously phototaxis and polarotaxis, and (4) unlit matte black canvas as a visually unattractive control. The unlit matte black canvas trapped only a negligible number (13) of water insects. The sum (16,432) of the total numbers of water beetles and bugs captured on the lamplit matte black canvas (7,922) and the unlit shiny black plastic sheet (8,510) was much smaller than the total catch (29,682) caught on the lamplit shiny black plastic sheet. This provides experimental evidence for the synergistic interaction of phototaxis (elicited by the unpolarized direct lamplight) and polarotaxis (induced by the strongly and horizontally polarized plastic-reflected light) in the investigated aquatic insects. Thus, horizontally polarizing artificial lamplit surfaces can function as an effective ecological trap due to this synergism of optical cues, especially in the urban environment.

Phototaxis and polarotaxis hand in hand: night dispersal flight of aquatic insects distracted synergistically by light intensity and reflection polarization

NASA Astrophysics Data System (ADS)

Boda, Pál; Horváth, Gábor; Kriska, György; Blahó, Miklós; Csabai, Zoltán

2014-05-01

Based on an earlier observation in the field, we hypothesized that light intensity and horizontally polarized reflected light may strongly influence the flight behaviour of night-active aquatic insects. We assumed that phototaxis and polarotaxis together have a more harmful effect on the dispersal flight of these insects than they would have separately. We tested this hypothesis in a multiple-choice field experiment using horizontal test surfaces laid on the ground. We offered simultaneously the following visual stimuli for aerial aquatic insects: (1) lamplit matte black canvas inducing phototaxis alone, (2) unlit shiny black plastic sheet eliciting polarotaxis alone, (3) lamplit shiny black plastic sheet inducing simultaneously phototaxis and polarotaxis, and (4) unlit matte black canvas as a visually unattractive control. The unlit matte black canvas trapped only a negligible number (13) of water insects. The sum (16,432) of the total numbers of water beetles and bugs captured on the lamplit matte black canvas (7,922) and the unlit shiny black plastic sheet (8,510) was much smaller than the total catch (29,682) caught on the lamplit shiny black plastic sheet. This provides experimental evidence for the synergistic interaction of phototaxis (elicited by the unpolarized direct lamplight) and polarotaxis (induced by the strongly and horizontally polarized plastic-reflected light) in the investigated aquatic insects. Thus, horizontally polarizing artificial lamplit surfaces can function as an effective ecological trap due to this synergism of optical cues, especially in the urban environment.

Highly antireflective AlGaN/GaN ultraviolet photodetectors using ZnO nanorod arrays on inverted pyramidal surfaces

NASA Astrophysics Data System (ADS)

So, Hongyun; Lim, Jongwoo; Suria, Ateeq J.; Senesky, Debbie G.

2017-07-01

Highly antireflective heterostructured aluminum gallium nitride (AlGaN)/GaN ultraviolet (UV) photodetectors were demonstrated using a combination of inverted pyramidal surfaces and zinc oxide nanorod arrays (i.e., antireflective surface modification) to enhance the optical sensitivity. The microfabricated hierarchical surfaces significantly reduced the average surface reflectance to less than 0.3% in the UV region and less than 1% in the visible light region, allowing near-perfect absorption of incident light regardless of the angle of incidence (5-80°). As a result, the photodetectors fabricated on highly antireflective AlGaN/GaN surfaces showed higher sensitivity and responsivity over a broad range of incidence angles compared to photodetectors on planar AlGaN/GaN surfaces, supporting the use of a hierarchically modified sensing surface for omnidirectional UV monitoring with higher sensitivity.

Estimation of viscoelastic surface wave parameters using a low cost optical deflection method

NASA Astrophysics Data System (ADS)

Brum, J.; Balay, G.; Arzúa, A.; Núñez, I.; Negreira, C.

2010-01-01

In this work an optical deflection method was used to study surface vibrations created by a low frequency source placed on the sample's surface. The optical method consists in placing a laser beam perpendicularly the sample's surface (gelatine based phantom). A beam-splitter is placed between the laser and the sample to project the reflected beam into a screen. As the surface moves due to the action of the low frequency source the laser beam on the screen also moves. Recording this movement with a digital camera allow us to reconstruct de surface motion using the light reflection law. If the scattering of the surface is very strong (such the one in biological tissue) a lens is placed between the surface and the beam-splitter to collect the scattered light. As validation method the surface movement was measured using a 10 MHz ultrasonic transducer placed normal to the surface in pulse-eco mode. The optical measurements were in complete agreement with the acoustical measurements. The optical measurement has the following advantages over the acoustic: 2-dimensional motion could be recorded and it is low cost. Since the acquisition was synchronized and the source-laser beam distance is known, measuring the time of flight an estimation of the surface wave velocity is obtained in order to measure the elasticity of the sample. The authors conclude that a reliable optical, low cost method for obtaining surface wave parameters of biological tissue was developed and successfully validate.