Self-Assembled InAs Nanowires as Optical Reflectors

PubMed Central

Floris, Francesco; Fornasari, Lucia; Marini, Andrea; Roddaro, Stefano; Beltram, Fabio; Cecchini, Marco; Sorba, Lucia; Rossella, Francesco

2017-01-01

Subwavelength nanostructured surfaces are realized with self-assembled vertically-aligned InAs nanowires, and their functionalities as optical reflectors are investigated. In our system, polarization-resolved specular reflectance displays strong modulations as a function of incident photon energy and angle. An effective-medium model allows one to rationalize the experimental findings in the long wavelength regime, whereas numerical simulations fully reproduce the experimental outcomes in the entire frequency range. The impact of the refractive index of the medium surrounding the nanostructure assembly on the reflectance was estimated. In view of the present results, sensing schemes compatible with microfluidic technologies and routes to innovative nanowire-based optical elements are discussed. PMID:29160860

Monolithic integration of elliptic-symmetry diffractive optical element on silicon-based 45 degrees micro-reflector.

PubMed

Lan, Hsiao-Chin; Hsiao, Hsu-Liang; Chang, Chia-Chi; Hsu, Chih-Hung; Wang, Chih-Ming; Wu, Mount-Learn

2009-11-09

A monolithically integrated micro-optical element consisting of a diffractive optical element (DOE) and a silicon-based 45 degrees micro-reflector is experimentally demonstrated to facilitate the optical alignment of non-coplanar fiber-to-fiber coupling. The slanted 45 degrees reflector with a depth of 216 microm is fabricated on a (100) silicon wafer by anisotropic wet etching. The DOE with a diameter of 174.2 microm and a focal length of 150 microm is formed by means of dry etching. Such a compact device is suitable for the optical micro-system to deflect the incident light by 90 degrees and to focus it on the image plane simultaneously. The measured light pattern with a spot size of 15 microm has a good agreement with the simulated result of the elliptic-symmetry DOE with an off-axis design for eliminating the strongly astigmatic aberration. The coupling efficiency is enhanced over 10-folds of the case without a DOE on the 45 degrees micro-reflector. This device would facilitate the optical alignment of non-coplanar light coupling and further miniaturize the volume of microsystem.

A biological sub-micron thickness optical broadband reflector characterized using both light and microwaves

PubMed Central

Vukusic, P.; Kelly, R.; Hooper, I.

2008-01-01

Broadband optical reflectors generally function through coherent scattering from systems comprising one of three designs: overlapped; chirped; or chaotic multilayer reflectors. For each, the requirement to scatter a broad band of wavelengths is met through the presence of a variation in nanostructural periodicity running perpendicular to the systems' outer surfaces. Consequently, the requisite total thickness of the multilayer can often be in excess of 50 μm. Here, we report the discovery and the microwave-assisted characterization of a natural system that achieves excellent optical broadband reflectivity but that is less than 1 μm thick. This system, found on the wing scales of the butterfly Argyrophorus argenteus, comprises a distinctive variation in periodicity that runs parallel to the reflecting surface, rather than perpendicular to it. In this way, the requirement for an extensively thick system is removed. PMID:19042180

InGaAs Multiple Quantum Well Modulating Retro-reflector for Free Space Optical Communications

DTIC Science & Technology

2002-01-01

PIN optical modulators grown on GaAs substrates by molecular beam epitaxy ,J. Vac Sci. B 18, 1609-16 13 (2000). Peter G. Goetz, W. S. Rabinovich...reflector is then interrogated by a cw laser beam from a conventional optical communications system and returns a modulated signal beam to the...optical communication systems. By mounting an electro-optic shutter in front of the corner- cube, the retro-reflected beam can be turned on or off (or at

Scattering from a cylindrical reflector: modified theory of physical optics solution.

PubMed

Yalçin, Ugur

2007-02-01

The problem of scattering from a perfectly conducting cylindrical reflector is examined with the method of the modified theory of physical optics. In this technique the physical optics currents are modified by using a variable unit vector on the scatterer's surface. These current components are obtained for the reflector, which is fed by an offset electric line source. The scattering integral is expressed by using these currents and evaluated asymptotically with the stationary phase method. The results are compared numerically by using physical optics theory, geometrical optics diffraction theory, and the exact solution of the Helmholtz equation. It is found that the modified theory of physical optics scattering field equations agrees with the geometrical optics diffraction theory and the exact solution of the Helmholtz equation.

Reflector system for a lighting fixture

DOEpatents

Siminovitch, Michael J.; Page, Erik; Gould, Carl T.

1998-01-01

Disclosed herein is a reflector system for a lighting fixture having a illumination source surrounded by an envelope. The reflector system includes a first reflector surrounding the illumination source. The reflector system also includes a second reflector which is non-contiguous with the first reflector and which surrounds the illumination source. The illumination source creates light rays which are reflected by the first and second reflectors. The first reflector directs light rays toward the center line of the fixture. However, the reflected rays despite being so reflected do not substantially intersect the envelope. The reflected light rays from the second reflector being directed so that they diverge from the center line of the fixture avoiding intersection with the semi-transparent envelope.

Reflector system for a lighting fixture

DOEpatents

Siminovitch, Michael J.; Page, Erik; Gould, Carl T.

2001-01-01

Disclosed herein is a reflector system for a lighting fixture having a illumination source surrounded by an envelope. The reflector system includes a first reflector surrounding the illumination source. The reflector system also includes a second reflector which is non-contiguous with the first reflector and which surrounds the illumination source. The illumination source creates light rays which are reflected by the first and second reflectors. The first reflector directs light rays toward the center line of the fixture. However, the reflected rays despite being so reflected do not substantially intersect the envelope. The reflected light rays from the second reflector being directed so that they diverge from the center line of the fixture avoiding intersection with the semi-transparent envelope.

Reflector system for a lighting fixture

DOEpatents

Siminovitch, M.J.; Page, E.; Gould, C.T.

1998-09-08

Disclosed herein is a reflector system for a lighting fixture having a illumination source surrounded by an envelope. The reflector system includes a first reflector surrounding the illumination source. The reflector system also includes a second reflector which is non-contiguous with the first reflector and which surrounds the illumination source. The illumination source creates light rays which are reflected by the first and second reflectors. The first reflector directs light rays toward the center line of the fixture. However, the reflected rays despite being so reflected do not substantially intersect the envelope. The reflected light rays from the second reflector being directed so that they diverge from the center line of the fixture avoiding intersection with the semi-transparent envelope. 5 figs.

Solar central receiver heliostat reflector assembly

DOEpatents

Horton, Richard H.; Zdeb, John J.

1980-01-01

A heliostat reflector assembly for a solar central receiver system comprises a light-weight, readily assemblable frame which supports a sheet of stretchable reflective material and includes mechanism for selectively applying tension to and positioning the sheet to stretch it to optical flatness. The frame is mounted on and supported by a pipe pedestal assembly that, in turn, is installed in the ground. The frame is controllably driven in a predetermined way by a light-weight drive system so as to be angularly adjustable in both elevation and azimuth to track the sun and efficiently continuously reflect the sun's rays to a focal zone, i.e. central receiver, which forms part of a solar energy utilization system, such as a solar energy fueled electrical power generation system. The frame may include a built-in system for testing for optical flatness of the reflector. The preferable geometric configuration of the reflector is octagonal; however, it may be other shapes, such as hexagonal, pentagonal or square. Several different embodiments of means for tensioning and positioning the reflector to achieve optical flatness are disclosed. The reflector assembly is based on the stretch frame concept which provides an extremely light-weight, simple, low-cost reflector assembly that may be driven for positioning and tracking by a light-weight, inexpensive drive system.

Tunable ring laser with internal injection seeding and an optically-driven photonic crystal reflector.

PubMed

Zheng, Jie; Ge, Chun; Wagner, Clark J; Lu, Meng; Cunningham, Brian T; Hewitt, J Darby; Eden, J Gary

2012-06-18

Continuous tuning over a 1.6 THz region in the near-infrared (842.5-848.6 nm) has been achieved with a hybrid ring/external cavity laser having a single, optically-driven grating reflector and gain provided by an injection-seeded semiconductor amplifier. Driven at 532 nm and incorporating a photonic crystal with an azobenzene overlayer, the reflector has a peak reflectivity of ~80% and tunes at the rate of 0.024 nm per mW of incident green power. In a departure from conventional ring or external cavity lasers, the frequency selectivity for this system is provided by the passband of the tunable photonic crystal reflector and line narrowing in a high gain amplifier. Sub - 0.1 nm linewidths and amplifier extraction efficiencies above 97% are observed with the reflector tuned to 842.5 nm.

A new approach for shaping of dual-reflector antennas

NASA Technical Reports Server (NTRS)

Lee, Teh-Hong; Burnside, W. D.; Rudduck, Roger C.

1987-01-01

The shaping of 2-D dual-reflector antenna systems to generate a prescribed distribution with uniform phase at the aperture of the second reflector is examined. This method is based on the geometrical nature of Cassegrain and Gregorian dual-reflector antennas. The method of syntheses satisfies the principles of geometrical optics which are the foundations of dual-reflector designs. Instead of setting up differential equations or heuristically designing the subreflector, a set of algebraic equations is formulated and solved numerically to obtain the desired surfaces. The caustics of the reflected rays from the subreflector can be obtained and examined. Several examples of 2-D dual-reflector shaping are shown to validate the study. Geometrical optics and physical optics are used to calculate the scattered fields from the reflectors.

Development of optical ground verification method for μm to sub-mm reflectors

NASA Astrophysics Data System (ADS)

Stockman, Y.; Thizy, C.; Lemaire, P.; Georges, M.; Mazy, E.; Mazzoli, A.; Houbrechts, Y.; Rochus, P.; Roose, S.; Doyle, D.; Ulbrich, G.

2017-11-01

Large reflectors and antennas for the IR to mm wavelength range are being planned for many Earth observation and astronomical space missions and for commercial communication satellites as well. Scientific observatories require large telescopes with precisely shaped reflectors for collecting the electro-magnetic radiation from faint sources. The challenging tasks of on-ground testing are to achieve the required accuracy in the measurement of the reflector shapes and antenna structures and to verify their performance under simulated space conditions (vacuum, low temperatures). Due to the specific surface characteristics of reflectors operating in these spectral regions, standard optical metrology methods employed in the visible spectrum do not provide useful measurement results. The current state-of-the-art commercial metrology systems are not able to measure these types of reflectors because they have to face the measurement of shape and waviness over relatively large areas with a large deformation dynamic range and encompassing a wide range of spatial frequencies. 3-D metrology (tactile coordinate measurement) machines are generally used during the manufacturing process. Unfortunately, these instruments cannot be used in the operational environmental conditions of the reflector. The application of standard visible wavelength interferometric methods is very limited or impossible due to the large relative surface roughnesses involved. A small number of infrared interferometers have been commercially developed over the last 10 years but their applications have also been limited due to poor dynamic range and the restricted spatial resolution of their detectors. These restrictions affect also the surface error slopes that can be captured and makes their application to surfaces manufactured using CRFP honeycomb technologies rather difficult or impossible. It has therefore been considered essential, from the viewpoint of supporting future ESA exploration missions, to

Lead foil wrapping of the plastic scintillators for the gamma ray detection: optical reflector or spectrum intensifier?

NASA Astrophysics Data System (ADS)

Taheri, A.; Askari, M.; Taghan Sasanpour, M.

2017-08-01

This paper studies the effect of lead wrapping on the response of the plastic scintillators as gamma detectors. Experimental tests and Geant4 simulations showed that lead wrapping cannot increase the gamma absorption efficiency of the detector but, as a reflector, it can improve the optical properties of the detector. The reflectivity of the lead foil as an optical reflector was determined equal to 66% using an experimental-simulation combined method. Based on the obtained results, the optical collection efficiency of the detector was also increased about 4% after employing the lead reflector.

Large Deployable Reflector (LDR) system concept and technology definition study. Volume 1: Executive summary, analyses and trades, and system concepts

NASA Technical Reports Server (NTRS)

Agnew, Donald L.; Jones, Peter A.

1989-01-01

A study was conducted to define reasonable and representative large deployable reflector (LDR) system concepts for the purpose of defining a technology development program aimed at providing the requisite technological capability necessary to start LDR development by the end of 1991. This volume includes the executive summary for the total study, a report of thirteen system analysis and trades tasks (optical configuration, aperture size, reflector material, segmented mirror, optical subsystem, thermal, pointing and control, transportation to orbit, structures, contamination control, orbital parameters, orbital environment, and spacecraft functions), and descriptions of three selected LDR system concepts. Supporting information is contained in appendices.

Feasibility study of a synthesis procedure for array feeds to improve radiation performance of large distorted reflector antennas

NASA Technical Reports Server (NTRS)

Stutzman, W. L.; Takamizawa, K.; Werntz, P.; Lapean, J.; Barts, R.

1991-01-01

The following subject areas are covered: General Reflector Antenna Systems Program version 7(GRASP7); Multiple Reflector Analysis Program for Cylindrical Antennas (MRAPCA); Tri-Reflector 2D Synthesis Code (TRTDS); a geometrical optics and a physical optics synthesis techniques; beam scanning reflector, the type 2 and 6 reflectors, spherical reflector, and multiple reflector imaging systems; and radiometric array design.

Analysis and testing of a soft actuation system for segmented reflector articulation and isolation

NASA Technical Reports Server (NTRS)

Jandura, Louise; Agronin, Michael L.

1991-01-01

Segmented reflectors have been proposed for space-based applications such as optical communication and large-diameter telescopes. An actuation system for mirrors in a space-based segmented mirror array has been developed as part of the National Aeronautics and Space Administration-sponsored Precision Segmented Reflector program. The actuation system, called the Articulated Panel Module (APM), articulates a mirror panel in 3 degrees of freedom in the submicron regime, isolates the panel from structural motion, and simplifies space assembly of the mirrors to the reflector backup truss. A breadboard of the APM has been built and is described. Three-axis modeling, analysis, and testing of the breadboard is discussed.

Laser reflector with an interference coating

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

Vol'pyan, O D; Semenov, A A; Yakovlev, P P

1998-10-31

An analysis was made of the reflectivity of interference coatings intended for the use in optical pumping of solid-state lasers. Ruby and Nd{sup 3+}:YAG lasers were used as models in comparative pumping efficiency measurements, carried out employing reflectors with interference and silver coatings. Estimates of the service life of reflectors with interference coatings were obtained. The power of a thermo-optical lens was reduced by the use of such coatings in cw lasers. (laser system components)

The wavefront compensation of free space optics utilizing micro corner-cube-reflector arrays

NASA Astrophysics Data System (ADS)

You, Shengzui; Yang, Guowei; Li, Changying; Bi, Meihua; Fan, Bing

2018-01-01

The wavefront compensation effect of micro corner-cube-reflector arrays (MCCRAs) in modulating retroreflector (MRR) free-space optical (FSO) link is investigated theoretically and experimentally. Triangular aperture of MCCRAs has been optically characterized and studied in an indoor atmospheric turbulence channel. The use of the MCCRAs instead of a single corner-cube reflector (CCR) as the reflective device is found to improve dramatically the quality of the reflected beam spot. We draw a conclusion that the MCCRAs can in principle yield a powerful wavefront compensation in MRR FSO communication links.

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.

A figure control sensor for the Large Deployable Reflector (LDR)

NASA Technical Reports Server (NTRS)

Bartman, R.; Dubovitsky, S.

1988-01-01

A sensing and control system is required to maintain high optical figure quality in a segmented reflector. Upon detecting a deviation of the segmented surface from its ideal form, the system drives segment mounted actuators to realign the individual segments and thereby return the surface to its intended figure. When the reflector is in use, a set of figure sensors will determine positions of a number of points on the back surface of each of the reflector's segments, each sensor being assigned to a single point. By measuring the positional deviations of these points from previously established nominal values, the figure sensors provide the control system with the information required to maintain the reflector's optical figure. The optical lever, multiple wavelength interferometer, and electronic capacitive sensor, the most promising technologies for the development of the figure sensor, are illustrated. It is concluded that to select a particular implementation of the figure sensors, performance requirement will be refined and relevant technologies investigated further.

Autocollimation system for measuring angular deformations with reflector designed by quaternionic method

NASA Astrophysics Data System (ADS)

Hoang, Phong V.; Konyakhin, Igor A.

2017-06-01

Autocollimators are widely used for angular measurements in instrument-making and the manufacture of elements of optical systems (wedges, prisms, plane-parallel plates) to check their shape parameters (rectilinearity, parallelism and planarity) and retrieve their optical parameters (curvature radii, measure and test their flange focusing). Autocollimator efficiency is due to the high sensitivity of the autocollimation method to minor rotations of the reflecting control element or the controlled surface itself. We consider using quaternions to optimize reflector parameters during autocollimation measurements as compared to the matrix technique. Mathematical model studies have demonstrated that the orthogonal positioning of the two basic unchanged directions of the tetrahedral reflector of the autocollimator is optimal by the criterion of reducing measurement errors where the axis of actual rotation is in a bisecting position towards them. Computer results are presented of running quaternion models that yielded conditions for diminishing measurement errors provided apriori information is available on the position of rotation axis. A practical technique is considered for synthesizing the parameters of the tetrahedral reflector that employs the newly-retrieved relationships. Following the relationships found between the angles of the tetrahedral reflector and the angles of the parameters of its initial orientation, an applied technique was developed to synthesize the control element for autocollimation measurements in case apriori information is available on the axis of actual rotation during monitoring measurements of shaft or pipeline deformation.

A comparison between GO/aperture-field and physical-optics methods for offset reflectors

NASA Technical Reports Server (NTRS)

Rahmat-Samii, Y.

1984-01-01

Both geometrical optics (GO)/aperture-field and physical-optics (PO) methods are used extensively in the diffraction analysis of offset parabolic and dual reflectors. An analytical/numerical comparative study is performed to demonstrate the limitations of the GO/aperture-field method for accurately predicting the sidelobe and null positions and levels. In particular, it is shown that for offset parabolic reflectors and for feeds located at the focal point, the predicted far-field patterns (amplitude) by the GO/aperture-field method will always be symmetric even in the offset plane. This, of course, is inaccurate for the general case and it is shown that the physical-optics method can result in asymmetric patterns for cases in which the feed is located at the focal point. Representative numerical data are presented and a comparison is made with available measured data.

Dual annular rotating "windowed" nuclear reflector reactor control system

DOEpatents

Jacox, Michael G.; Drexler, Robert L.; Hunt, Robert N. M.; Lake, James A.

1994-01-01

A nuclear reactor control system is provided in a nuclear reactor having a core operating in the fast neutron energy spectrum where criticality control is achieved by neutron leakage. The control system includes dual annular, rotatable reflector rings. There are two reflector rings: an inner reflector ring and an outer reflector ring. The reflectors are concentrically assembled, surround the reactor core, and each reflector ring includes a plurality of openings. The openings in each ring are capable of being aligned or non-aligned with each other. Independent driving means for each of the annular reflector rings is provided so that reactor criticality can be initiated and controlled by rotation of either reflector ring such that the extent of alignment of the openings in each ring controls the reflection of neutrons from the core.

Electromagnetic backscattering by corner reflectors

NASA Technical Reports Server (NTRS)

Balanis, C. A.; Griesser, T.

1986-01-01

The Geometrical Theory of Diffraction (GTD), which supplements Geometric Optics (GO), and the Physical Theory of Diffraction (PTD), which supplements Physical Optics (PO), are used to predict the backscatter cross sections of dihedral corner reflectors which have right, obtuse, or acute included angles. These theories allow individual backscattering mechanisms of the dihedral corner reflectors to be identified and provide good agreement with experimental results in the azimuthal plane. The advantages and disadvantages of the geometrical and physical theories are discussed in terms of their accuracy, usefulness, and complexity. Numerous comparisons of analytical results with experimental data are presented. While physical optics alone is more accurate and more useful than geometrical optics alone, the combination of geometrical optics and geometrical diffraction seems to out perform physical optics and physical diffraction when compared with experimental data, especially for acute angle dihedral corner reflectors.

Disordered animal multilayer reflectors and the localization of light

PubMed Central

Jordan, T. M.; Partridge, J. C.; Roberts, N. W.

2014-01-01

Multilayer optical reflectors constructed from ‘stacks’ of alternating layers of high and low refractive index dielectric materials are present in many animals. For example, stacks of guanine crystals with cytoplasm gaps occur within the skin and scales of fish, and stacks of protein platelets with cytoplasm gaps occur within the iridophores of cephalopods. Common to all these animal multilayer reflectors are different degrees of random variation in the thicknesses of the individual layers in the stack, ranging from highly periodic structures to strongly disordered systems. However, previous discussions of the optical effects of such thickness disorder have been made without quantitative reference to the propagation of light within the reflector. Here, we demonstrate that Anderson localization provides a general theoretical framework to explain the common coherent interference and optical properties of these biological reflectors. Firstly, we illustrate how the localization length enables the spectral properties of the reflections from more weakly disordered ‘coloured’ and more strongly disordered ‘silvery’ reflectors to be explained by the same physical process. Secondly, we show how the polarization properties of reflection can be controlled within guanine–cytoplasm reflectors, with an interplay of birefringence and thickness disorder explaining the origin of broadband polarization-insensitive reflectivity. PMID:25339688

Performance improvements of symmetry-breaking reflector structures in nonimaging devices

DOEpatents

Winston, Roland

2004-01-13

A structure and method for providing a broken symmetry reflector structure for a solar concentrator device. The component of the optical direction vector along the symmetry axis is conserved for all rays propagated through a translationally symmetric optical device. This quantity, referred to as the translational skew invariant, is conserved in rotationally symmetric optical systems. Performance limits for translationally symmetric nonimaging optical devices are derived from the distributions of the translational skew invariant for the optical source and for the target to which flux is to be transferred. A numerically optimized non-tracking solar concentrator utilizing symmetry-breaking reflector structures can overcome the performance limits associated with translational symmetry.

Tailored reflectors for illumination.

PubMed

Jenkins, D; Winston, R

1996-04-01

We report on tailored reflector design methods that allow the placement of general illumination patterns onto a target plane. The use of a new integral design method based on the edge-ray principle of nonimaging optics gives much more compact reflector shapes by eliminating the need for a gap between the source and the reflector profile. In addition, the reflectivity of the reflector is incorporated as a design parameter. We show the performance of design for constant irradiance on a distant plane, and we show how a leading-edge-ray method may be used to achieve general illumination patterns on nearby targets.

Distributed Bragg Reflectors With Reduced Optical Absorption

DOEpatents

Klem, John F.

2005-08-16

A new class of distributed Bragg reflectors has been developed. These distributed Bragg reflectors comprise interlayers positioned between sets of high-index and low-index quarter-wave plates. The presence of these interlayers is to reduce photon absorption resulting from spatially indirect photon-assisted electronic transitions between the high-index and low-index quarter wave plates. The distributed Bragg reflectors have applications for use in vertical-cavity surface-emitting lasers for use at 1.55 .mu.m and at other wavelengths of interest.

Reflectivity Spectra for Commonly Used Reflectors

NASA Astrophysics Data System (ADS)

Janecek, Martin

2012-06-01

Monte Carlo simulations play an important role in developing and evaluating the performance of radiation detection systems. To accurately model a reflector in an optical Monte Carlo simulation, the reflector's spectral response has to be known. We have measured the reflection coefficient for many commonly used reflectors for wavelengths from 250 nm to 800 nm. The reflectors were also screened for fluorescence and angular distribution changes with wavelength. The reflectors examined in this work include several polytetrafluoroethylene (PTFE) reflectors, Spectralon, GORE diffuse reflector, titanium dioxide paint, magnesium oxide, nitrocellulose filter paper, Tyvek paper, Lumirror, Melinex, ESR films, and aluminum foil. All PTFE films exhibited decreasing reflectivity with longer wavelengths due to transmission. To achieve >;0.95 reflectivity in the 380 to 500 nm range, the PTFE films have to be at least 0.5 mm thick-nitrocellulose is a good alternative if a thin diffuse reflector is needed. Several of the reflectors have sharp declines in reflectivity below a cut-off wavelength, including TiO2 (420 nm), ESR film (395 nm), nitrocellulose (330 nm), Lumirror (325 nm), and Melinex (325 nm). PTFE-like reflectors were the only examined reflectors that had reflectivity above 0.90 for wavelengths below 300 nm. Lumirror, Melinex, and ESR film exhibited fluorescence. Lumirror and Melinex are excited by wavelengths between 320 and 420 nm and have their emission peaks located at 440 nm, while ESR film is excited by wavelengths below 400 nm and the emission peak is located at 430 nm. Lumirror and Melinex also exhibited changing angular distributions with wavelength.

Single-mode, narrow-linewidth external cavity quantum cascade laser through optical feedback from a partial-reflector.

PubMed

Cendejas, Richard A; Phillips, Mark C; Myers, Tanya L; Taubman, Matthew S

2010-12-06

An external-cavity (EC) quantum cascade (QC) laser using optical feedback from a partial-reflector is reported. With this configuration, the otherwise multi-mode emission of a Fabry-Perot QC laser was made single-mode with optical output powers exceeding 40 mW. A mode-hop free tuning range of 2.46 cm(-1) was achieved by synchronously tuning the EC length and QC laser current. The linewidth of the partial-reflector EC-QC laser was measured for integration times from 100 μs to 4 seconds, and compared to a distributed feedback QC laser. Linewidths as small as 480 kHz were recorded for the EC-QC laser.

Control of active reflector system for radio telescope

NASA Astrophysics Data System (ADS)

Zhou, Guo-hua; Li, Guo-ping; Zhang, Yong; Zhang, Zhen-chao

2016-10-01

According to the control requirements of the active reflector surface in the 110 m radio telescope at QiTai(QTT) Xinjiang, a new displacement actuator and a new displacement control system were designed and manufactured and then their characteristics were tested by a dual-frequency laser interferometer in the micro-displacement laboratory. The displacement actuator was designed by a scheme of high precision worm and roller screw structures, and the displacement control system was based on a ARM micro-processor. Finally, the S curve acceleration control methods were used to design the hardware platform and software algorithm for the active reflection surface of the control system. The test experiments were performed based on the laser metrology system on an active reflector close-loop antenna prototype for large radio telescope. Experimental results indicate that it achieves a 30 mm working stroke and 5 μm RMS motion resolution. The accuracy (standard deviation) is 3.67 mm, and the error between the determined and theoretical values is 0.04% when the rated load is 300 kg, the step is 2 mm and the stroke is 30mm. Furthermore, the active reflector integrated system was tested by the laser sensors with the accuracy of 0.25 μm RMS on 4-panel radio telescope prototype, the measurement results show that the integrated precision of the active reflector closed-loop control system is less than 5 μm RMS, and well satisfies the technical requirements of active reflector control system of the QTT radio telescope in 3 mm wavelength.

Highly accurate photogrammetric measurements of the Planck reflectors

NASA Astrophysics Data System (ADS)

Amiri Parian, Jafar; Gruen, Armin; Cozzani, Alessandro

2017-11-01

The Planck mission of the European Space Agency (ESA) is designed to image the anisotropies of the Cosmic Background Radiation Field over the whole sky. To achieve this aim, sophisticated reflectors are used as part of the Planck telescope receiving system. The system consists of secondary and primary reflectors which are sections of two different ellipsoids of revolution with mean diameters of 1 and 1.6 meters. Deformations of the reflectors which influence the optical parameters and the gain of receiving signals are investigated in vacuum and at very low temperatures. For this investigation, among the various high accuracy measurement techniques, photogrammetry was selected. With respect to the photogrammetric measurements, special considerations had to be taken into account in design steps, measurement arrangement and data processing to achieve very high accuracies. The determinability of additional parameters of the camera under the given network configuration, datum definition, reliability and precision issues as well as workspace limits and propagating errors from different sources are considered. We have designed an optimal photogrammetric network by heuristic simulation for the flight model of the primary and the secondary reflectors with relative precisions better than 1:1000'000 and 1:400'000 to achieve the requested accuracies. A least squares best fit ellipsoid method was developed to determine the optical parameters of the reflectors. In this paper we will report about the procedures, the network design and the results of real measurements.

Precision segmented reflectors for space applications

NASA Technical Reports Server (NTRS)

Lehman, David H.; Pawlik, Eugene V.; Meinel, Aden B.; Fichter, W. B.

1990-01-01

A project to develop precision segmented reflectors (PSRs) which operate at submillimeter wavelengths is described. The development of a light efficient means for the construction of large-aperture segmented reflecting space-based telescopes is the primary aim of the project. The 20-m Large Deployable Reflector (LDR) telescope is being developed for a survey mission, and it will make use of the reflector panels and materials, structures, and figure control being elaborated for the PSR. The surface accuracy of a 0.9-m PSR panel is shown to be 1.74-micron RMS, the goal of 100-micron RMS positioning accuracy has been achieved for a 4-m erectable structure. A voice-coil actuator for the figure control system architecture demonstrated 1-micron panel control accuracy in a 3-axis evaluation. The PSR technology is demonstrated to be of value for several NASA projects involving optical communications and interferometers as well as missions which make use of large-diameter segmented reflectors.

Precision segmented reflectors for space applications

NASA Astrophysics Data System (ADS)

Lehman, David H.; Pawlik, Eugene V.; Meinel, Aden B.; Fichter, W. B.

1990-08-01

A project to develop precision segmented reflectors (PSRs) which operate at submillimeter wavelengths is described. The development of a light efficient means for the construction of large-aperture segmented reflecting space-based telescopes is the primary aim of the project. The 20-m Large Deployable Reflector (LDR) telescope is being developed for a survey mission, and it will make use of the reflector panels and materials, structures, and figure control being elaborated for the PSR. The surface accuracy of a 0.9-m PSR panel is shown to be 1.74-micron RMS, the goal of 100-micron RMS positioning accuracy has been achieved for a 4-m erectable structure. A voice-coil actuator for the figure control system architecture demonstrated 1-micron panel control accuracy in a 3-axis evaluation. The PSR technology is demonstrated to be of value for several NASA projects involving optical communications and interferometers as well as missions which make use of large-diameter segmented reflectors.

Advanced reflector materials for solar concentrators

NASA Astrophysics Data System (ADS)

Jorgensen, Gary; Williams, Tom; Wendelin, Tim

1994-10-01

This paper describes the research and development at the US National Renewable Energy Laboratory (NREL) in advanced reflector materials for solar concentrators. NREL's research thrust is to develop solar reflector materials that maintain high specular reflectance for extended lifetimes under outdoor service conditions and whose cost is significantly lower than existing products. Much of this work has been in collaboration with private-sector companies that have extensive expertise in vacuum-coating and polymer-film technologies. Significant progress and other promising developments will be discussed. These are expected to lead to additional improvements needed to commercialize solar thermal concentration systems and make them economically attractive to the solar manufacturing industry. To explicitly demonstrate the optical durability of candidate reflector materials in real-world service conditions, a network of instrumented outdoor exposure sites has been activated.

Feasibility study of a synthesis procedure for array feeds to improve radiation performance of large distorted reflector antennas

NASA Technical Reports Server (NTRS)

Stutzman, W. L.; Takamizawa, K.; Werntz, P.; Lapean, J.; Barts, R.; Shen, B.; Dunn, D.

1992-01-01

The topics covered include the following: (1) performance analysis of the Gregorian tri-reflector; (2) design and performance of the type 6 reflector antenna; (3) a new spherical main reflector system design; (4) optimization of reflector configurations using physical optics; (5) radiometric array design; and (7) beam efficiency studies.

The Design and Analysis of Electrically Large Custom-Shaped Reflector Antennas

DTIC Science & Technology

2013-06-01

GEO) satellite data are imported into STK and plotted to visualize the regions of the sky that the spherical reflector must have line of sight for...Magnetic Conductor PO Physical Optics STK Systems Tool Kit TE Transverse Electric xvii Acronym Definition TLE Two Line Element TM Transverse Magnetic...study for the spherical reflector, Systems Tool Kit ( STK ) software from Analytical Graphics Inc. (AGI) is used. In completing the cross-shaped

Scanning properties of large dual-shaped offset and symmetric reflector antennas

NASA Astrophysics Data System (ADS)

Galindo-Israel, Victor; Veruttipong, Watt; Norrod, Roger D.; Imbriale, William A.

1992-04-01

Several characteristics of dual offset (DOSR) and symmetric shaped reflectors are examined. Among these is the amelioration of the added cost of manufacturing a shaped reflector antenna, particularly a doubly curved surface for the DOSR, if adjustable panels, which may be necessary for correction of gravity and wind distortions, are also used for improving gain by shaping. The scanning properties of shaped reflectors, both offset and circularly symmetric, are examined and compared to conic section scanning characteristics. Scanning of the pencil beam is obtained by lateral and axial translation of a single point-source feed. The feed is kept pointed toward the center of the subreflector. The effects of power spillover and aperture phase error as a function of beam scanning is examined for several different types of large reflector designs including DOSR, circularly symmetric large f/D and smaller f/D dual reflector antenna systems. It is graphically illustrated that the Abbe-sine condition for improving scanning of an optical system cannot, inherently, be satisfied in a dual-shaped reflector system shaped for high gain and low feed spillover.

Large Deployable Reflector Science and Technology Workshop. Volume 3: Systems and Technology Assessment

NASA Technical Reports Server (NTRS)

Leidich, C. A. (Editor); Pittman, R. B. (Editor)

1984-01-01

The results of five technology panels which convened to discuss the Large Deployable Reflector (LDR) are presented. The proposed LDR is a large, ambient-temperature, far infrared/submillimeter telescope designed for space. Panel topics included optics, materials and structures, sensing and control, science instruments, and systems and missions. The telescope requirements, the estimated technology levels, and the areas in which the generic technology work has to be augmented are enumerated.

Cryo-optical testing of large aspheric reflectors operating in the sub mm range

NASA Astrophysics Data System (ADS)

Roose, S.; Houbrechts, Y.; Mazzoli, A.; Ninane, N.; Stockman, Y.; Daddato, R.; Kirschner, V.; Venacio, L.; de Chambure, D.

2006-02-01

The cryo-optical testing of the PLANCK primary reflector (elliptical off-axis CFRP reflector of 1550 mm x 1890 mm) is one of the major issue in the payload development program. It is requested to measure the changes of the Surface Figure Error (SFE) with respect to the best ellipsoid, between 293 K and 50 K, with a 1 μm RMS accuracy. To achieve this, Infra Red interferometry has been used and a dedicated thermo mechanical set-up has been constructed. This paper summarises the test activities, the test methods and results on the PLANCK Primary Reflector - Flight Model (PRFM) achieved in FOCAL 6.5 at Centre Spatial de Liege (CSL). Here, the Wave Front Error (WFE) will be considered, the SFE can be derived from the WFE measurement. After a brief introduction, the first part deals with the general test description. The thermo-elastic deformations will be addressed: the surface deformation in the medium frequency range (spatial wavelength down to 60 mm) and core-cell dimpling.

Flat Engineered Multichannel Reflectors

NASA Astrophysics Data System (ADS)

Asadchy, V. S.; Díaz-Rubio, A.; Tcvetkova, S. N.; Kwon, D.-H.; Elsakka, A.; Albooyeh, M.; Tretyakov, S. A.

2017-07-01

Recent advances in engineered gradient metasurfaces have enabled unprecedented opportunities for light manipulation using optically thin sheets, such as anomalous refraction, reflection, or focusing of an incident beam. Here, we introduce a concept of multichannel functional metasurfaces, which are able to control incoming and outgoing waves in a number of propagation directions simultaneously. In particular, we reveal a possibility to engineer multichannel reflectors. Under the assumption of reciprocity and energy conservation, we find that there exist three basic functionalities of such reflectors: specular, anomalous, and retroreflections. Multichannel response of a general flat reflector can be described by a combination of these functionalities. To demonstrate the potential of the introduced concept, we design and experimentally test three different multichannel reflectors: three- and five-channel retroreflectors and a three-channel power splitter. Furthermore, by extending the concept to reflectors supporting higher-order Floquet harmonics, we forecast the emergence of other multichannel flat devices, such as isolating mirrors, complex splitters, and multi-functional gratings.

All-reflective optical target illumination system with high numerical aperture

DOEpatents

Sigler, Robert D.

1978-01-01

An all-reflective optical system for providing illumination of a target focal region at high numerical aperture from a pair of co-axially, confluent collimated light beams. A target cavity is defined by a pair of opposed inner ellipsoidal reflectors having respective first focal points within a target region and second focal points at a vertex opening in the opposing reflector. Outwardly of each inner reflector is the opposed combination of a spherical reflector, and an outer generally ellipsoidal reflector having an aberrated first focal point coincident with the focus of the opposing spherical reflector and a second focal point coincident with the second focal point of the opposing inner ellipsoidal reflector through a vertex opening in the spherical reflector. The confluent collimated beams are incident through vertex openings in the outer ellipsoidal reflectors onto respective opposing spherical reflectors. Each beam is reflected by the associated spherical reflector onto the opposing outer ellipsoidal reflector and focused thereby onto the opposing inner ellipsoidal reflector, and then onto the target region.

Reflectivity quenching of ESR multilayer polymer film reflector in optically bonded scintillator arrays

NASA Astrophysics Data System (ADS)

Loignon-Houle, Francis; Pepin, Catherine M.; Charlebois, Serge A.; Lecomte, Roger

2017-04-01

The 3M-ESR multilayer polymer film is a widely used reflector in scintillation detector arrays. As specified in the datasheet and confirmed experimentally by measurements in air, it is highly reflective (> 98 %) over the entire visible spectrum (400-1000 nm) for all angles of incidence. Despite these outstanding characteristics, it was previously found that light crosstalk between pixels in a bonded LYSO scintillator array with ESR reflector can be as high as ∼30-35%. This unexplained light crosstalk motivated further investigation of ESR optical performance. Analytical simulation of a multilayer structure emulating the ESR reflector showed that the film becomes highly transparent to incident light at large angles when surrounded on both sides by materials of refractive index higher than air. Monte Carlo simulations indicate that a considerable fraction (∼25-35%) of scintillation photons are incident at these leaking angles in high aspect ratio LYSO scintillation crystals. The film transparency was investigated experimentally by measuring the scintillation light transmission through the ESR film sandwiched between a scintillation crystal and a photodetector with or without layers of silicone grease. Strong light leakage, up to nearly 30%, was measured through the reflector when coated on both sides with silicone, thus elucidating the major cause of light crosstalk in bonded arrays. The reflector transparency was confirmed experimentally for angles of incidence larger than 60 ° using a custom designed setup allowing illumination of the bonded ESR film at selected grazing angles. The unsuspected ESR film transparency can be beneficial for detector arrays exploiting light sharing schemes, but it is highly detrimental for scintillator arrays designed for individual pixel readout.

Dual annular rotating [open quotes]windowed[close quotes] nuclear reflector reactor control system

DOEpatents

Jacox, M.G.; Drexler, R.L.; Hunt, R.N.M.; Lake, J.A.

1994-03-29

A nuclear reactor control system is provided in a nuclear reactor having a core operating in the fast neutron energy spectrum where criticality control is achieved by neutron leakage. The control system includes dual annular, rotatable reflector rings. There are two reflector rings: an inner reflector ring and an outer reflector ring. The reflectors are concentrically assembled, surround the reactor core, and each reflector ring includes a plurality of openings. The openings in each ring are capable of being aligned or non-aligned with each other. Independent driving means for each of the annular reflector rings is provided so that reactor criticality can be initiated and controlled by rotation of either reflector ring such that the extent of alignment of the openings in each ring controls the reflection of neutrons from the core. 4 figures.

Optical Coating Performance for Heat Reflectors of the JWST-ISIM Electronic Component

NASA Technical Reports Server (NTRS)

Rashford, Robert A.; Perrygo, Charles M.; Garrison, Matthew B.; White, Bryant K.; Threat, Felix T.; Quijada, Manuel A.; Jeans, James W.; Huber, Frank K.; Bousquet, Robert R.; Shaw, Dave

2011-01-01

A document discusses a thermal radiator design consisting of lightweight composite materials and low-emittance metal coatings for use on the James Webb Space Telescope (JWST) structure. The structure will have a Thermal Subsystem unit to provide passive cooling to the Integrated Science Instrument Module (ISIM) control electronics. The ISIM, in the JWST observatory, is the platform that provides the mounting surfaces for the instrument control electronics. Dissipating the control electronic generated-heat away from JWST is of paramount importance so that the spacecraft s own heat does not interfere with the infrared-light gathering of distant cosmic sources. The need to have lateral control in the emission direction of the IEC (ISIM Electronics Compartment) radiators led to the development of a directional baffle design that uses multiple curved mirrorlike surfaces. This concept started out from the so-called Winston non-imaging optical concentrators that use opposing parabolic reflector surfaces, where each parabola has its focus at the opposite edge of the exit aperture. For this reason they are often known as compound parabolic concentrators or CPCs. This radiator system with the circular section was chosen for the IEC reflectors because it offers two advantages over other designs. The first is that the area of the reflector strips for a given radiator area is less, which results in a lower mass baffle assembly. Secondly, the fraction of energy emitted by the radiator strips and subsequently reflected by the baffle is less. These fewer reflections reduced the amount of energy that is absorbed and eventually re-emitted, typically in a direction outside the design emission range angle. A baffle frame holds the mirrors in position above a radiator panel on the IEC. Together, these will direct the majority of the heat from the IEC above the sunshield away towards empty space.

State-of-the-art low-cost solar reflector materials

NASA Astrophysics Data System (ADS)

Kennedy, C.; Jorgensen, G.

1994-11-01

Solar thermal technologies generate power by concentrating sunlight with large mirrors. The National Renewable Energy Laboratory (NREL) is working with industrial partners to develop the optical reflector materials needed for the successful deployment of this technology. The reflector materials must be low in cost and maintain high specular reflectance for extended lifetimes in severe outdoor environments. Currently, the best candidate materials for solar mirrors are silver-coated low-iron glass and silvered polymer films. Polymer reflectors are lighter in weight, offer greater flexibility in system design, and have the potential for lower cost than glass mirrors. In parallel with collaborative activities, several innovative candidate reflector-material constructions were investigated at NREL. The low-cost material requirement necessitates manufacturing compatible with mass-production techniques. Future cooperative efforts with the web-coating industry offers the promise of exciting new alternative materials and the potential for dramatic cost savings in developing advanced solar reflector materials.

REVIEW ARTICLE: Bioluminescent signals and the role of reflectors

NASA Astrophysics Data System (ADS)

Herring, Peter J.

2000-11-01

Organisms in a well lit environment use optical signals derived from the selective reflection of ambient light. In a dim or dark environment it is very difficult (because of low photon numbers) to detect the contrast between light reflected from the organism and that from the background, and many organisms use bioluminescent signals instead. The use of such signals on land is largely restricted to sexual signalling by the luminous beetles, but in the deep ocean their use is widespread, involving both many different organisms and a range of uses which parallel those of reflective signals on land. Some bioluminescent signals rely almost entirely on an optically unmodified light source (e.g. a secretion) but others depend upon complex optical structures, particularly reflectors, in the light-emitting organs. Reflectors in the light organs of many shrimp, squid and fish are based on constructive interference systems but employ different biological materials. They and other structures modify the angular, spectral and intensity distributions of bioluminescent signals. The ready availability of highly efficient biological reflectors has been a formative influence in the evolution of bioluminescent signalling in the sea.

Zirconium hydride reactor control reflector systems: summary report

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

Horton, P.H.; Kurzeka, W.J.

1972-06-30

The beryllium reflector control system development for SNAP reactors is documented, from the initial SNAP 10A System through the current 5-kW(e) Thermoelectric System. Described are the various reflector concepts used in these systems for shadowshielded and 4 pi -shielded nuclear systems. The development of the key components, such as the actuators, bearings, and drive mechanisms for these systems, is also traced from the SNAP 10A concept through to the current system. Developmental test results are outlined, showing the performance capability improvements made throughout the life of the SNAP programs. Component development was highly successful, as proven by a number ofmore » reactor systems tests, including the launch and operation of the SNAP 10A flight. 46 references. (auth)« less

Special test equipment and fixturing for MSAT reflector assembly alignment

NASA Technical Reports Server (NTRS)

Young, Jeffrey A.; Zinn, Michael R.; Mccarten, David R.

1994-01-01

The MSAT Reflector Assembly is a state of the art subsystem for Mobile Satellite (MSAT), a geosynchronous-based commercial mobile telecommunication satellite program serving North America. The Reflector Assembly consisted of a deployable, three-hinge, folding-segment Boom, deployable 5.7 x 5.3-meter 16-rib Wrap-Rib Reflector, and a Reflector Pointing Mechanism (RPM). The MSAT spacecraft was based on a Hughes HS601 spacecraft bus carrying two Reflector Assemblies independently dedicated for L-band transmit and receive operations. Lockheed Missiles and Space Company (LMSC) designed and built the Reflector Assembly for MSAT under contract to SPAR Aerospace Ltd. Two MSAT satellites were built jointly by SPAR Aerospace Ltd. and Hughes Space and Communications Co. for this program, the first scheduled for launch in 1994. When scaled for wavelength, the assembly and alignment requirements for the Reflector Assembly were in many instances equivalent to or exceeded that of a diffraction-limited visible light optical system. Combined with logistical constraints inherent to large, compliant, lightweight structures; 'bolt-on' alignment; and remote, indirect spacecraft access; the technical challenges were formidable. This document describes the alignment methods, the special test equipment, and fixturing for Reflector Assembly assembly and alignment.

Curvature of blended rolled edge reflectors at the shadow boundary contour

NASA Technical Reports Server (NTRS)

Ellingson, S. W.

1988-01-01

A technique is advanced for computing the radius of curvature of blended rolled edge reflector surfaces at the shadow boundary, in the plane perpendicular to the shadow boundary contour. This curvature must be known in order to compute the spurious endpoint contributions in the physical optics (PO) solution for the scattering from reflectors with rolled edges. The technique is applicable to reflectors with radially-defined rim-shapes and rolled edge terminations. The radius of curvature for several basic reflector systems is computed, and it is shown that this curvature can vary greatly along the shadow boundary contour. Finally, the total PO field in the target zone of a sample compact range system is computed and corrected using the shadow boundary radius of curvature, obtained using the technique. It is shown that the fields obtained are a better approximation to the true scattered fields.

Computer prediction of dual reflector antenna radiation properties

NASA Technical Reports Server (NTRS)

Christodoulou, C.

1981-01-01

A program for calculating radiation patterns for reflector antennas with either smooth analytic surfaces or with surfaces composed of a number of panels. Techniques based on the geometrical optics (GO) approach were used in tracing rays over the following regions: from a feed antenna to the first reflector surface (subreflector); from this reflector to a larger reflector surface (main reflector); and from the main reflector to a mathematical plane (aperture plane) in front of the main reflector. The equations of GO were also used to calculate the reflected field components for each ray making use of the feed radiation pattern and the parameters defining the surfaces of the two reflectors. These resulting fields form an aperture distribution which is integrated numerically to compute the radiation pattern for a specified set of angles.

Wirelessly Controllable Inflated Electroactive Polymer (EAP) Reflectors

NASA Technical Reports Server (NTRS)

Bao, Xiaoqi; Bar-Cohen, Yoseph; Chang, Zensheu; Sherrit, Stewart; Badescu, Mircea

2005-01-01

Inflatable membrane reflectors are attractive for deployable, large aperture, lightweight optical and microwave systems in micro-gravity space environment. However, any fabrication flaw or temperature variation may results in significant aberration of the surface. Even for a perfectly fabricated inflatable membrane mirror with uniform thickness, theory shows it will form a Hencky curve surface but a desired parabolic or spherical surface. Precision control of the surfaceshape of extremely flexible membrane structures is a critical challenge for the success of this technology. Wirelessly controllable inflated reflectors made of electroactive polymers (EAP) are proposed in this paper. A finite element model was configured to predict the behavior of the inflatable EAP membranes under pre-strains, pressures and distributed electric charges on the surface. To explore the controllability of the inflatable EAP reflectors, an iteration algorism was developed to find the required electric actuation for correcting the aberration of the Hencky curve to the desired parabolic curve. The correction capability of the reflectors with available EAP materials was explored numerically and is presented in this paper.

45 Mbps cat's eye modulating retro-reflector link over 7 Km

NASA Astrophysics Data System (ADS)

Rabinovich, W. S.; Mahon, R.; Goetz, P. G.; Swingen, L.; Murphy, J.; Ferraro, M.; Burris, R.; Suite, M.; Moore, C. I.; Gilbreath, G. C.; Binari, S.

2006-09-01

Modulating retro-reflectors (MRR) allow free space optical links with no need for pointing, tracking or a laser on one end of the link. They work by coupling a passive optical retro-reflector with an optical modulator. The most common kind of MRR uses a corner cube retro-reflector. These devices must have a modulator whose active area is as large as the area of the corner cube. This limits the ability to close longer range high speed links because the large aperture need to return sufficient light implies a large modulator capacitance. To overcome this limitation we developed the concept of a cat's eye MRR. Cat's eye MRRs place the modulator in the focal plane of a lens system designed to passively retro-reflect light. Because the light focuses onto the modulator, a small, low capacitance, modulator can be used with a large optical aperture. However, the position of the focal spot varies with the angle of incidence so an array of modulators must be placed in the focal plane, In addition, to avoid having to drive all the modulator pixels, an angle of arrival sensor must be used. We discuss several cat's eye MRR systems with near diffraction limited performance and bandwidths of 45 Mbps. We also discuss a link to a cat's eye MRR over a 7 Km range.

Caustic Singularities Of High-Gain, Dual-Shaped Reflectors

NASA Technical Reports Server (NTRS)

Galindo, Victor; Veruttipong, Thavath W.; Imbriale, William A.; Rengarajan, Sambiam

1991-01-01

Report presents study of some sources of error in analysis, by geometric theory of diffraction (GTD), of performance of high-gain, dual-shaped antenna reflector. Study probes into underlying analytic causes of singularity, with view toward devising and testing practical methods to avoid problems caused by singularity. Hybrid physical optics (PO) approach used to study near-field spillover or noise-temperature characteristics of high-gain relector antenna efficiently and accurately. Report illustrates this approach and underlying principles by presenting numerical results, for both offset and symmetrical reflector systems, computed by GTD, PO, and PO/GO methods.

Wavefront Correction for Large, Flexible Antenna Reflector

NASA Technical Reports Server (NTRS)

Imbriale, William A.; Jammejad, Vahraz; Rajagopalan, Harish; Xu, Shenheng

2010-01-01

A wavefront-correction system has been proposed as part of an outer-space radio communication system that would include a large, somewhat flexible main reflector antenna, a smaller subreflector antenna, and a small array feed at the focal plane of these two reflector antennas. Part of the wavefront-correction system would reside in the subreflector, which would be a planar patch-element reflectarray antenna in which the phase shifts of the patch antenna elements would be controlled via microelectromechanical systems (MEMS) radio -frequency (RF) switches. The system would include the following sensing-and-computing subsystems: a) An optical photogrammetric subsystem built around two cameras would estimate geometric distortions of the main reflector; b) A second subsystem would estimate wavefront distortions from amplitudes and phases of signals received by the array feed elements; and c) A third subsystem, built around small probes on the subreflector plane, would estimate wavefront distortions from differences among phases of signals received by the probes. The distortion estimates from the three subsystems would be processed to generate control signals to be fed to the MEMS RF switches to correct for the distortions, thereby enabling collimation and aiming of the received or transmitted radio beam to the required precision.

16 CFR 1512.16 - Requirements for reflectors.

Code of Federal Regulations, 2011 CFR

2011-01-01

..., preferred assembly method that shall insure that the reflector meets the optical requirements of this...(m)(2). The reflectors and/or mounts shall incorporate a distinct, preferred assembly method that... on the rim. (2) If the retroreflective material is applied to the rim in the form of a self-adhesive...

A physical optics/equivalent currents model for the RCS of trihedral corner reflectors

NASA Technical Reports Server (NTRS)

Balanis, Constantine A.; Polycarpou, Anastasis C.

1993-01-01

The scattering in the interior regions of both square and triangular trihedral corner reflectors is examined. The theoretical model presented combines geometrical and physical optics (GO and PO), used to account for reflection terms, with equivalent edge currents (EEC), used to account for first-order diffractions from the edges. First-order, second-order, and third-order reflection terms are included. Calculating the first-order reflection terms involves integrating over the entire surface of the illuminated plate. Calculating the second- and third-order reflection terms, however, is much more difficult because the illuminated area is an arbitrary polygon whose shape is dependent upon the incident angles. The method for determining the area of integration is detailed. Extensive comparisons between the high-frequency model, Finite-Difference Time-Domain (FDTD) and experimental data are used for validation of the radar cross section (RCS) of both square and triangular trihedral reflectors.

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.

Effects of deterministic surface distortions on reflector antenna performance

NASA Technical Reports Server (NTRS)

Rahmat-Samii, Y.

1985-01-01

Systematic distortions of reflector antenna surfaces can cause antenna radiation patterns to be undesirably different from those of perfectly smooth reflector surfaces. In this paper, a simulation model for systematic distortions is described which permits an efficient computation of the effects of distortions in the reflector pattern. The model uses a vector diffraction physical optics analysis for the determination of both the co-polar and cross-polar fields. An interpolation scheme is also presented for the description of reflector surfaces which are prescribed by discrete points. Representative numerical results are presented for reflectors with sinusoidally and thermally distorted surfaces. Finally, comparisons are made between the measured and calculated patterns of a slowly-varying distorted offset parabolic reflector.

EXPERIMENTAL AND ANALYTICAL STUDIES OF REFLECTRO CONTROL FOR THE ADVANCED ENGINEERING TEST REACTOR. PART A. EXPERIMENTAL STUDIES WITH THE REFLECTOR CONTROL SYSTEM MODEL. PART B. ANALYTICAL STUDIES OF REFLECTOR CONTROL

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

Bertelson, P.C.; Francis, T.L.

1959-10-21

Studies of reflector control for the Advanced Engineering Test Reactor were made. The performance of various parts of the reflector control system model such as the safety reflector and the water jet educator, boric acid injection, and demineralizer systems is discussed. The experimental methods and results obtained are discussed. Four reflector control schemes were studied. The schemes were a single-region and three-region reflector schemes two separate reflectors, and two connected reflectors. Calculations were made of shim and safety reflector worth for a variety of parameters. Safety reflector thickness was varied from 7.75 to 0 inches, with and without boron. Boricmore » acid concentration was varied from 100 to 2% of saturation in the shim reflectors. Neutron flux plots are presented (C.J.G.)« less

Large Deployable Reflector (LDR)

NASA Technical Reports Server (NTRS)

Alff, W. H.

1980-01-01

The feasibility and costs were determined for a 1 m to 30 m diameter ambient temperature, infrared to submillimeter orbiting astronomical telescope which is to be shuttle-deployed, free-flying, and have a 10 year orbital life. Baseline concepts, constraints on delivery and deployment, and the sunshield required are examined. Reflector concepts, the optical configuration, alignment and pointing, and materials are also discussed. Technology studies show that a 10 m to 30 m diameter system which is background and diffraction limited at 30 micron m is feasible within the stated time frame. A 10 m system is feasible with current mirror technology, while a 30 m system requires technology still in development.

Terrace retro-reflector array for poloidal polarimeter on ITER.

PubMed

Imazawa, R; Kawano, Y; Ono, T; Kusama, Y

2011-02-01

A new concept of a terrace retro-reflector array (TERRA) as part of the poloidal polarimeter for ITER is proposed in this paper. TERRA reflects a laser light even from a high incident angle in the direction of the incident-light path, while a conventional retro-reflector array cannot. Besides, TERRA can be installed in a smaller space than a corner-cube retro-reflector. In an optical sense, TERRA is equivalent to a Littrow grating, the blaze angle of which varies, depending on the incident angle. The reflected light generates a bright and dark fringe, and the bright fringe is required to travel along the incident-light path to achieve the objects of laser-aided diagnostics. In order to investigate the propagation properties of laser light reflected by TERRA, we have developed a new diffraction formula. Conditions for the propagation of the bright fringe in the direction of the incident light have been obtained using the Littrow grating model and have been confirmed in a simulation applying the new diffraction formula. Finally, we have designed laser transmission optics using TERRA for the ITER poloidal polarimeter and have calculated the light propagation of the system. The optical design obtains a high transmission efficiency, with 88.6% of the incident power returned. These results demonstrate the feasibility of applying TERRA to the ITER poloidal polarimeter.

Primary reflector for solar energy collection systems

NASA Technical Reports Server (NTRS)

Miller, C. G. (Inventor); Stephens, J. B.

1978-01-01

A fixed, linear, ground-based primary reflector is disclosed which has an extended curved sawtooth-contoured surface covered with a metalized polymeric reflecting material. The device reflects solar energy to a movably supported collector that is kept at the concentrated line focus of the reflector primary. The primary reflector may be constructed by a process utilizing well-known freeway paving machinery.

Wavefront control of large optical systems

NASA Technical Reports Server (NTRS)

Meinel, Aden B.; Meinel, Marjorie P.; Breckinridge, J. B.

1990-01-01

Several levels of wavefront control are necessary for the optimum performance of very large telescopes, especially segmented ones like the Large Deployable Reflector. In general, the major contributors to wavefront error are the segments of the large primary mirror. Wavefront control at the largest optical surface may not be the optimum choice because of the mass and inaccessibility of the elements of this surface that require upgrading. The concept of two-stage optics was developed to permit a poor wavefront from the large optics to be upgraded by means of a wavefront corrector at a small exit pupil of the system.

Wavelength-controlled external-cavity laser with a silicon photonic crystal resonant reflector

NASA Astrophysics Data System (ADS)

Gonzalez-Fernandez, A. A.; Liles, Alexandros A.; Persheyev, Saydulla; Debnath, Kapil; O'Faolain, Liam

2016-03-01

We report the experimental demonstration of an alternative design of external-cavity hybrid lasers consisting of a III-V Semiconductor Optical Amplifier with fiber reflector and a Photonic Crystal (PhC) based resonant reflector on SOI. The Silicon reflector comprises a polymer (SU8) bus waveguide vertically coupled to a PhC cavity and provides a wavelength-selective optical feedback to the laser cavity. This device exhibits milliwatt-level output power and sidemode suppression ratio of more than 25 dB.

A Method for Producing a Shaped Contour Radiation Pattern Using a Single Shaped Reflector and a Single Feed

NASA Technical Reports Server (NTRS)

Cherrette, A. R.; Lee, S. W.; Acosta, R. J.

1988-01-01

Eliminating the corporate feed network in shaped contour beam antennas will reduce the expense, weight, and RF loss of the antenna system. One way of producing a shaped contour beam without using a feed network is to use a single shaped reflector with a single feed element. For a prescribed contour beam and feed, an optimization method for designing the reflector shape is given. As a design example, a shaped reflector is designed to produce a continental U.S. coverage (CONUS) beam. The RF performance of the shaped reflector is then verified by physical optics.

Hybrid integrated single-wavelength laser with silicon micro-ring reflector

NASA Astrophysics Data System (ADS)

Ren, Min; Pu, Jing; Krishnamurthy, Vivek; Xu, Zhengji; Lee, Chee-Wei; Li, Dongdong; Gonzaga, Leonard; Toh, Yeow T.; Tjiptoharsono, Febi; Wang, Qian

2018-02-01

A hybrid integrated single-wavelength laser with silicon micro-ring reflector is demonstrated theoretically and experimentally. It consists of a heterogeneously integrated III-V section for optical gain, an adiabatic taper for light coupling, and a silicon micro-ring reflector for both wavelength selection and light reflection. Heterogeneous integration processes for multiple III-V chips bonded to an 8-inch Si wafer have been developed, which is promising for massive production of hybrid lasers on Si. The III-V layer is introduced on top of a 220-nm thick SOI layer through low-temperature wafer-boning technology. The optical coupling efficiency of >85% between III-V and Si waveguide has been achieved. The silicon micro-ring reflector, as the key element of the hybrid laser, is studied, with its maximized reflectivity of 85.6% demonstrated experimentally. The compact single-wavelength laser enables fully monolithic integration on silicon wafer for optical communication and optical sensing application.

Off-axis reflective optical apparatus

NASA Technical Reports Server (NTRS)

Ames, Lawrence L. (Inventor); Leary, David F. (Inventor); Mammini, Paul V. (Inventor)

2005-01-01

Embodiments of the present invention are directed to a simple apparatus and a convenient and accurate method of mounting the components to form an off-axis reflective optical apparatus such as a collimator. In one embodiment, an off-axis reflective optical apparatus comprises a mounting block having a ferrule holder support surface and an off-axis reflector support surface which is generally perpendicular to the ferrule holder support surface. An optical reflector is mounted on the off-axis reflector support surface and has a reflected beam centerline. The optical reflector has a conic reflective surface and a conic center. A ferrule holder is mounted on the ferrule holder support surface. The ferrule holder provides a ferrule for coupling to an optical fiber and orienting a fiber tip of the optical fiber along a fiber axis toward the optical reflector. The fiber axis is nonparallel to the reflected beam centerline. Prior to mounting the optical reflector to the off-axis reflector support surface and prior to mounting the ferrule holder to the ferrule holder support surface, the optical reflector is movable on the off-axis reflector surface and the ferrule holder is movable on the ferrule holder support surface to align the conic center of the optical reflector with respect to the fiber tip of the optical fiber, and the apparatus has at least one of the following features: (1) the optical reflector is movable on the off-axis reflector support surface to adjust a focus of the fiber tip with respect to the optical reflector, and (2) the ferrule holder is movable on the ferrule holder support surface to adjust the focus of the fiber tip with respect to the optical reflector.

MEMS tracking mirror system for a bidirectional free-space optical link.

PubMed

Jeon, Sungho; Toshiyoshi, Hiroshi

2017-08-20

We report on a bidirectional free-space optical system that is capable of automatic connection and tracking of an optical link between two nodes. A piezoelectric micro-electro-mechanical systems (MEMS) optical scanner is used to steer a laser beam of two wavelengths superposed to visually present a communication zone, to search for the position of the remote node by means of the retro-reflector optics, and to transmit the data between the nodes. A feedback system is developed to control the MEMS scanner to dynamically establish the optical link within a 10-ms transition time and to keep track of the moving node.

Realization of LOS (Line of Sight) stabilization based on reflector using carrier attitude compensation method

NASA Astrophysics Data System (ADS)

Mao, Yao; Tian, Jing; Ma, Jia-guang

2015-02-01

The techonology of LOS stabilization is widely applicated in moving carrier photoelectric systems such as shipborne, airborne and so on. In application situations with compact structure, such as LOS stabilization system of unmanned aerial vehicle, LOS stabilization based on reflector is adopted, and the detector is installed on the carrier to reduce the volume of stabilized platform and loading weight. However, the LOS deflection angle through reflector and the rotation angle of the reflector has a ratio relation of 2:1, simple reflector of stable inertial space can not make the optical axis stable. To eliminate the limitation of mirror stabilizing method, this article puts forward the carrier attitude compensation method, which uses the inertial sensor installed on the carrier to measure the attitude change of the carrier, and the stabilized platform rotating half of the carrier turbulence angle to realize the LOS stabilization.

Composite materials for precision space reflector panels

NASA Technical Reports Server (NTRS)

Tompkins, Stephen S.; Funk, Joan G.; Bowles, David E.; Towell, Timothy W.; Connell, John W.

1992-01-01

One of the critical technology needs of large precision reflectors for future astrophysical and optical communications satellites lies in the area of structural materials. Results from a materials research and development program at NASA Langley Research Center to provide materials for these reflector applications are discussed. Advanced materials that meet the reflector panel requirements are identified, and thermal, mechanical and durability properties of candidate materials after exposure to simulated space environments are compared. A parabolic, graphite-phenolic honeycomb composite panel having a surface accuracy of 70.8 microinches rms and an areal weight of 1.17 lbm/sq ft was fabricated with T50/ERL1962 facesheets, a PAEI thermoplastic surface film, and Al and SiO(x) coatings.

Electrophoretic deposited TiO 2 pigment-based back reflectors for thin film solar cells

DOE PAGES

Bills, Braden; Morris, Nathan; Dubey, Mukul; ...

2015-01-16

Highly reflective coatings with strong light scattering effect have many applications in optical components and optoelectronic devices. This paper reports titanium dioxide (TiO 2) pigment-based reflectors that have 2.5 times higher broadband diffuse reflection than commercially produced aluminum or silver based reflectors and result in efficiency enhancements of a single-junction amorphous Si solar cell. Electrophoretic deposition is used to produce pigment-based back reflectors with high pigment density, controllable film thickness and site-specific deposition. Electrical conductivity of the pigment-based back reflectors is improved by creating electrical vias throughout the pigment-based back reflector by making holes using an electrical discharge / dielectricmore » breakdown approach followed by a second electrophoretic deposition of conductive nanoparticles into the holes. While previous studies have demonstrated the use of pigment-based back reflectors, for example white paint, on glass superstrate configured thin film Si solar cells, this work presents a scheme for producing pigment-based reflectors on complex shape and flexible substrates. Finally, mechanical durability and scalability are demonstrated on a continuous electrophoretic deposition roll-to-roll system which has flexible metal substrate capability of 4 inch wide and 300 feet long.« less

Backscatter analysis of dihedral corner reflectors using physical optics and the physical theory of diffraction

NASA Technical Reports Server (NTRS)

Griesser, Timothy; Balanis, Constantine A.

1987-01-01

The backscatter cross-sections of dihedral corner reflectors in the azimuthal plane are presently determined by both physical optics (PO) and the physical theory of diffraction (PTD), yielding results for the vertical and horizontal polarizations. In the first analysis method used, geometrical optics is used in place of PO at initial reflections in order to maintain the planar character of the reflected wave and reduce the complexity of the analysis. In the second method, PO is used at almost every reflection in order to maximize the accuracy of the PTD solution at the expense of a rapid increase in complexity. Induced surface current densities and resulting cross section patterns are illustrated for the two methods.

The design of optical module of LED street lamp with non-axial symmetrical reflector

NASA Astrophysics Data System (ADS)

Lu, Ming-Jun; Chen, Chi-An; Chen, Yi-Yung; Whang, Allen Jong-Woei

2010-05-01

In recently, many research focus on the LED applications for environmental protection so a number of LED street lamps are presented. Although LED has many advantages for environmental protection, its special optical characteristics, such as intensity distribution, always limit the advantages in many applications. Therefore, we always need to do the secondary optical design for LED street lamp to replace the traditional optical designs that are designed for high-pressure sodium lamps and mercury lamps. According to the situation, we design an optical module of LED street lamp with LEDs and secondary optical design. First, the LEDs are placed on freeform reflector for the specific illuminated conditions. We design the optical module of street lamp with the two conditions that include the uniformity and the ratio of length to width in the illuminated area and without any light pollution. According to the simulation with the designed optical module, the uniformity in the illuminated area is about 0.6 that is better than the general condition, 0.3, and the ratio of length to width in the illuminated area is 3:1 in which the length is 30 meters and the width is 10 meters. Therefore, the design could let LED street lamp fits the two conditions, uniformity and ratio in the illuminated area.

The development of composite materials for spacecraft precision reflector panels

NASA Technical Reports Server (NTRS)

Tompkins, Stephen S.; Bowles, David E.; Funk, Joan G.; Towell, Timothy W.; Lavoie, J. A.

1990-01-01

One of the critical technology needs for large precision reflectors required for future astrophysics and optical communications is in the area of structural materials. Therefore, a major area of the Precision Segmented Reflector Program at NASA is to develop lightweight composite reflector panels with durable, space environmentally stable materials which maintain both surface figure and required surface accuracy necessary for space telescope applications. Results from the materials research and development program at NASA Langley Research Center are discussed. Advanced materials that meet the reflector panel requirements are identified. Thermal, mechanical and durability properties of candidate materials after exposure to simulated space environments are compared to the baseline material.

Nonimaging reflectors for efficient uniform illumination.

PubMed

Gordon, J M; Kashin, P; Rabl, A

1992-10-01

Nonimaging reflectors that are an extension of the design principle that was developed for compound parabolic concentrator type devices are proposed for illumination applications. The optical designs presented offer maximal lighting efficiency while they retain sharp angular control of the radiation and highly uniform flux densities on distant target planes. Our results are presented for symmetrical configurations in two dimensions (troughlike reflectors) for flat and for tubular sources. For fields of view of practical interest (half-angle in the 30-60 degrees range), these devices can achieve minimum-tomaximum intensity ratios of 0.7, while they remain compact and incur low reflective losses.

Optical cavity furnace for semiconductor wafer processing

DOEpatents

Sopori, Bhushan L.

2014-08-05

An optical cavity furnace 10 having multiple optical energy sources 12 associated with an optical cavity 18 of the furnace. The multiple optical energy sources 12 may be lamps or other devices suitable for producing an appropriate level of optical energy. The optical cavity furnace 10 may also include one or more reflectors 14 and one or more walls 16 associated with the optical energy sources 12 such that the reflectors 14 and walls 16 define the optical cavity 18. The walls 16 may have any desired configuration or shape to enhance operation of the furnace as an optical cavity 18. The optical energy sources 12 may be positioned at any location with respect to the reflectors 14 and walls defining the optical cavity. The optical cavity furnace 10 may further include a semiconductor wafer transport system 22 for transporting one or more semiconductor wafers 20 through the optical cavity.

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.

Gratings and Random Reflectors for Near-Infrared PIN Diodes

NASA Technical Reports Server (NTRS)

Gunapala, Sarath; Bandara, Sumith; Liu, John; Ting, David

2007-01-01

Crossed diffraction gratings and random reflectors have been proposed as means to increase the quantum efficiencies of InGaAs/InP positive/intrinsic/ negative (PIN) diodes designed to operate as near-infrared photodetectors. The proposal is meant especially to apply to focal-plane imaging arrays of such photodetectors to be used for near-infrared imaging. A further increase in quantum efficiency near the short-wavelength limit of the near-infrared spectrum of such a photodetector array could be effected by removing the InP substrate of the array. The use of crossed diffraction gratings and random reflectors as optical devices for increasing the quantum efficiencies of quantum-well infrared photodetectors (QWIPs) was discussed in several prior NASA Tech Briefs articles. While the optical effects of crossed gratings and random reflectors as applied to PIN photodiodes would be similar to those of crossed gratings and random reflectors as applied to QWIPs, the physical mechanisms by which these optical effects would enhance efficiency differ between the PIN-photodiode and QWIP cases: In a QWIP, the multiple-quantum-well layers are typically oriented parallel to the focal plane and therefore perpendicular or nearly perpendicular to the direction of incidence of infrared light. By virtue of the applicable quantum selection rules, light polarized parallel to the focal plane (as normally incident light is) cannot excite charge carriers and, hence, cannot be detected. A pair of crossed gratings or a random reflector scatters normally or nearly normally incident light so that a significant portion of it attains a component of polarization normal to the focal plane and, hence, can excite charge carriers. A pair of crossed gratings or a random reflector on a PIN photodiode would also scatter light into directions away from the perpendicular to the focal plane. However, in this case, the reason for redirecting light away from the perpendicular is to increase the length of the

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 7 2010-10-01 2010-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 7 2012-10-01 2012-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 7 2014-10-01 2014-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

46 CFR 169.726 - Radar reflector.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Radar reflector. 169.726 Section 169.726 Shipping COAST... Control, Miscellaneous Systems, and Equipment § 169.726 Radar reflector. Each nonmetallic vessel less than 90 feet in length must exhibit a radar reflector of suitable size and design while underway. Markings ...

Correcting Thermal Deformations in an Active Composite Reflector

NASA Technical Reports Server (NTRS)

Bradford, Samuel C.; Agnes, Gregory S.; Wilkie, William K.

2011-01-01

Large, high-precision composite reflectors for future space missions are costly to manufacture, and heavy. An active composite reflector capable of adjusting shape in situ to maintain required tolerances can be lighter and cheaper to manufacture. An active composite reflector testbed was developed that uses an array of piezoelectric composite actuators embedded in the back face sheet of a 0.8-m reflector panel. Each individually addressable actuator can be commanded from 500 to +1,500 V, and the flatness of the panel can be controlled to tolerances of 100 nm. Measuring the surface flatness at this resolution required the use of a speckle holography interferometer system in the Precision Environmental Test Enclosure (PETE) at JPL. The existing testbed combines the PETE for test environment stability, the speckle holography system for measuring out-of-plane deformations, the active panel including an array of individually addressable actuators, a FLIR thermal camera to measure thermal profiles across the reflector, and a heat source. Use of an array of flat piezoelectric actuators to correct thermal deformations is a promising new application for these actuators, as is the use of this actuator technology for surface flatness and wavefront control. An isogrid of these actuators is moving one step closer to a fully active face sheet, with the significant advantage of ease in manufacturing. No extensive rib structure or other actuation backing structure is required, as these actuators can be applied directly to an easy-to-manufacture flat surface. Any mission with a surface flatness requirement for a panel or reflector structure could adopt this actuator array concept to create lighter structures and enable improved performance on orbit. The thermal environment on orbit tends to include variations in temperature during shadowing or changes in angle. Because of this, a purely passive system is not an effective way to maintain flatness at the scale of microns over several

Computer prediction of large reflector antenna radiation properties

NASA Technical Reports Server (NTRS)

Botula, A.

1980-01-01

A FORTRAN program for calculating reflector antenna radiation patterns was rewritten and extended to include reflectors composed of a number of panels. These individual panels must be analytic surfaces. The theoretical foundation for the program is as follows: Geometrical optics techniques are used to trace rays from a feed antenna to the reflector surface and back to a mathematical plane just in front of the reflector. The resulting tangential electric field distribution, assumed to be the only source of forward radiation, is integrated numerically to calculate the radiation pattern for a desired set of angles. When the reflector is composed of more than one panel, each panel is treated as a separated antenna, the ray-tracing procedure and integration being repeated for each panel. The results of the individual aperture plane integrations are stored and summed to yield the relative electric field strength over the angles of interest. An example and several test cases are included to demonstrate the use of the program and verify the new method of computation.

Bright color optical switching device by polymer network liquid crystal with a specular reflector.

PubMed

Lee, Gae Hwang; Hwang, Kyu Young; Jang, Jae Eun; Jin, Yong Wan; Lee, Sang Yoon; Jung, Jae Eun

2011-07-04

The color optical switching device by polymer network liquid crystal (PNLC) with color filter on a specular reflector shows excellent performance; white reflectance of 22%, color gamut of 32%, and contrast ratio up to 50:1 in reflective mode measurement. The view-angle dependence of the reflectance can be adjusted by changing the PNLC thickness. The color chromaticity shown by the device is close to the limit value of color filters, and its value nearly remains with respect to the operating voltage. These optical properties of the device can be explained from the prediction based on multiple interactions between the light and the droplets of liquid crystal. The high reflectance, vivid color image, and moderate responds time allow the PNLC device to drive good color moving image. It can widely extend the applications of the reflective device.

Optical analysis of a photovoltaic V-trough system installed in western India.

PubMed

Maiti, Subarna; Sarmah, Nabin; Bapat, Pratap; Mallick, Tapas K

2012-12-20

The low concentrating photovoltaic (PV) system such as a 2× V-trough system can be a promising choice for enhancing the power output from conventional PV panels with the inclusion of thermal management. This system is more attractive when the reflectors are retrofitted to the stationary PV panels installed in a high aspect ratio in the north-south direction and are tracked 12 times a year manually according to preset angles, thus eliminating the need of diurnal expensive tracking. In the present analysis, a V-trough system facing exactly the south direction is considered, where the tilt angle of the PV panels' row is kept constant at 18.34°. The system is installed on the terrace of CSIR-Central Salt and Marine Chemicals Research Institute in Bhavnagar, Gujarat, India (21.47 N, 71.15 E). The dimension of the entire PV system is 9.64 m×0.55 m. The V-troughs made of anodized aluminum reflectors (70% specular reflectivity) had the same dimensions. An in-house developed; experimentally validated Monte Carlo ray-trace model was used to study the effect of the angular variation of the reflectors throughout a year for the present assembly. Results of the ray trace for the optimized angles showed the maximum simulated optical efficiency to be 85.9%. The spatial distribution of solar intensity over the 0.55 m dimension of the PV panel due to the V-trough reflectors was also studied for the optimized days in periods that included solstices and equinoxes. The measured solar intensity profiles with and without the V-trough system were used to calculate the actual optical efficiencies for several sunny days in the year, and results were validated with the simulated efficiencies within an average error limit of 10%.

Heat dissipation in water-cooled reflectors

NASA Technical Reports Server (NTRS)

Kozai, Toyoki

1994-01-01

The energy balance of a lamp varies with the thermal and optical characteristics of the reflector. The photosynthetic radiation efficiency of lamps, defined as input power divided by photosynthetically active radiation (PAR, 400-700 nm) emitted from the lamp ranges between 0.17 and 0.26. The rest of the energy input is wasted as longwave (3000 nm and over) and non-PAR shortwave radiation (from 700 nm to 3000 nm), convective, and conductive heat from the lamp, reflector, and ballast, and simply for increasing the cooling load. Furthermore, some portion of the PAR is uselessly absorbed by the inner walls, shelves, vessels, etc. and some portion of the PAR received by the plantlets is converted into sensible and latent heat. More than 98% of the energy input is probably converted into heat, with only less than 2% of the energy input being converted into chemical energy as carbohydrates by photosynthesis. Therefore, it is essential to reduce the generation of heat in the culture room in order to reduce the cooling load. Through use of a water-cooled reflector, the generation of convective and conductive heat and longwave radiation from the reflector can be reduced, without reduction of PAR.

High-output LED-based light engine for profile lighting fixtures with high color uniformity using freeform reflectors.

PubMed

Gadegaard, Jesper; Jensen, Thøger Kari; Jørgensen, Dennis Thykjær; Kristensen, Peter Kjær; Søndergaard, Thomas; Pedersen, Thomas Garm; Pedersen, Kjeld

2016-02-20

In the stage lighting and entertainment market, light engines (LEs) for lighting fixtures are often based on high-intensity discharge (HID) bulbs. Switching to LED-based light engines gives possibilities for fast switching, additive color mixing, a longer lifetime, and potentially, more energy-efficient systems. The lumen output of a single LED is still not sufficient to replace an HID source in high-output profile fixtures, but combining multiple LEDs can create an LE with a similar output, but with added complexity. This paper presents the results of modeling and testing such a light engine. Custom ray-tracing software was used to design a high-output red, green and blue LED-based light engine with twelve CBT-90 LEDs using a dual-reflector principle. The simulated optical system efficiency was 0.626 with a perfect (R=1) reflector coating for light delivered on a target surface through the entire optical system. A profile lighting fixture prototype was created, and provided an output of 6744 lumen and an efficiency of 0.412. The lower efficiency was mainly due to a non-optimal reflector coating, and the optimized design is expected to reach a significantly higher efficiency.

Solar receiver heliostat reflector having a linear drive and position information system

DOEpatents

Horton, Richard H.

1980-01-01

A heliostat for a solar receiver system comprises an improved drive and control system for the heliostat reflector assembly. The heliostat reflector assembly is controllably driven in a predetermined way by a light-weight drive system so as to be angularly adjustable in both elevation and azimuth to track the sun and efficiently continuously reflect the sun's rays to a focal zone, i.e., heat receiver, which forms part of a solar energy utilization system, such as a solar energy fueled electrical power generation system. The improved drive system includes linear stepping motors which comprise low weight, low cost, electronic pulse driven components. One embodiment comprises linear stepping motors controlled by a programmed, electronic microprocessor. Another embodiment comprises a tape driven system controlled by a position control magnetic tape.

Nonimaging compound parabolic concentrator-type reflectors with variable extreme direction.

PubMed

Gordon, J M; Rabl, A

1992-12-01

The properties of nonimaging compound parabolic concentrator (CPC)-type devices are examined in which the extreme direction is not constant but rather is a variable that can change along the reflector. One can then retain the maximal concentration or radiative efficiency of the CPC while the flux map on the absorber or target is modified, depending on whether the device is used for optical concentration or for lighting. Two general classes of reflector are derived, and all the nonimaging devices developed to date are shown to be special cases of the general solution. These two classes are the nonimaging analog of converging and diverging devices of imaging optics.

Pyramidal-Reflector Solar Heater

NASA Technical Reports Server (NTRS)

1982-01-01

Motor-driven reflector compensates for seasonal changes in Sun's altitude. System has flat-plate absorbers mounted on north side of attic interior. Skylight window on south-facing roof admits Sunlight into attic, lined with mirrors that reflect light to absorbers. Reflectors are inner surfaces of a pyramid lying on its side with window at its base and absorber plates in a cross-sectional plane near its apex.

Large-Scale All-Dielectric Metamaterial Perfect Reflectors

DOE PAGES

Moitra, Parikshit; Slovick, Brian A.; li, Wei; ...

2015-05-08

All-dielectric metamaterials offer a potential low-loss alternative to plasmonic metamaterials at optical frequencies. In this paper, we take advantage of the low absorption loss as well as the simple unit cell geometry to demonstrate large-scale (centimeter-sized) all-dielectric metamaterial perfect reflectors made from silicon cylinder resonators. These perfect reflectors, operating in the telecommunications band, were fabricated using self-assembly based nanosphere lithography. In spite of the disorder originating from the self-assembly process, the average reflectance of the metamaterial perfect reflectors is 99.7% at 1530 nm, surpassing the reflectance of metallic mirrors. Moreover, the spectral separation of the electric and magnetic resonances canmore » be chosen to achieve the required reflection bandwidth while maintaining a high tolerance to disorder. Finally, the scalability of this design could lead to new avenues of manipulating light for low-loss and large-area photonic applications.« less

Lithographic wavelength control of an external cavity laser with a silicon photonic crystal cavity-based resonant reflector.

PubMed

Liles, Alexandros A; Debnath, Kapil; O'Faolain, Liam

2016-03-01

We report the experimental demonstration of a new design for external cavity hybrid lasers consisting of a III-V semiconductor optical amplifier (SOA) with fiber reflector and a photonic crystal (PhC)-based resonant reflector on SOI. The silicon reflector is composed of an SU8 polymer bus waveguide vertically coupled to a PhC cavity and provides a wavelength-selective optical feedback to the laser cavity. This device exhibits milliwatt-level output power and side-mode suppression ratios of more than 25 dB.

Detection of reflector surface from near field phase measurements

NASA Technical Reports Server (NTRS)

Ida, Nathan

1991-01-01

The deviation of a reflector antenna surface from a perfect parabolic shape causes degradation of the performance of the antenna. The problem of determining the shape of the reflector surface in a reflector antenna using near field phase measurements is not a new one. A recent issue of the IEEE tansactions on Antennas and Propagation (June 1988) contained numerous descriptions of the use of these measurements: holographic reconstruction or inverse Fourier transform. Holographic reconstruction makes use of measurement of the far field of the reflector and then applies the Fourier transform relationship between the far field and the current distribution on the reflector surface. Inverse Fourier transformation uses the phase measurements to determine the far field pattern using the method of Kerns. After the far field pattern is established, an inverse Fourier transform is used to determine the phases in a plane between the reflector surface and the plane in which the near field measurements were taken. These calculations are time consuming since they involve a relatively large number of operations. A much faster method can be used to determine the position of the reflector. This method makes use of simple geometric optics to determine the path length of the ray from the feed to the reflector and from the reflector to the measurement point. For small physical objects and low frequencies, diffraction effects have a major effect on the error, and the algorithm provides incorrect results. It is believed that the effect is less noticeable for large distortions such as antenna warping, and more noticeable for small, localized distortions such as bumps and depressions such as might be caused by impact damage.

Nonimaging optics maximizing exergy for hybrid solar system

NASA Astrophysics Data System (ADS)

Winston, Roland; Jiang, Lun; Abdelhamid, Mahmoud; Widyolar, Bennett K.; Ferry, Jonathan; Cygan, David; Abbasi, Hamid; Kozlov, Alexandr; Kirk, Alexander; Elarde, Victor; Osowski, Mark

2016-09-01

The project team of University of California at Merced (UC-Merced), Gas Technology Institute (GTI) and MicroLink Devices Inc. (MicroLink) are developing a hybrid solar system using a nonimaging compound parabolic concentrator (CPC) that maximizes the exergy by delivering direct electricity and on-demand heat. The hybrid solar system technology uses secondary optics in a solar receiver to achieve high efficiency at high temperature, collects heat in particles and uses reflective liftoff cooled double junction (2J) InGaP/GaAs solar cells with backside infrared (IR) reflectors on the secondary optical element to raise exergy efficiency. The nonimaging optics provides additional concentration towards the high temperature thermal stream and enables it to operate efficiently at 650 °C while the solar cell is maintained at 40 °C to operate as efficiently as possible.

Deployable reflector structure

NASA Technical Reports Server (NTRS)

Mikulas, Martin, Jr. (Inventor); Hoberman, Charles (Inventor)

1993-01-01

A deployable reflector structure is presented. The structure has a number of movable reflector panels pivotably supported on rigid arms. Several such arms are pivotably connected to a central structure. The arm can move in starburst fashion from a packaged stage, where all arms are vertical, to a deployed stage, where all arms are horizontal. All of the movable reflector panels are maintained at a predetermined angle to an axis of the reflector structure when the arms are pivoted. The reflector panels are stacked tightly on top of each other in the packaged state of the reflector structure. Simple mechanisms are used for avoiding interference between panels on different arms in the packaged stage and for fitting the movable panels together like tiles in the deployed stage.

Multi-band reflector antenna with double-ring element frequency selective subreflector

NASA Technical Reports Server (NTRS)

Wu, Te-Kao; Lee, S. W.

1993-01-01

Frequency selective subreflectors (FSS) are often employed in the reflector antenna system of a communication satellite or a deep space exploration vehicle for multi-frequency operations. In the past, FSS's have been designed for diplexing two frequency bands. For example, the Voyager FSS was designed to diplex S and X bands and the TDRSS FSS was designed to diplex S and Ku bands. Recently, NASA's CASSINI project requires an FSS to multiplex four frequency (S/X/Ku/Ka) bands. Theoretical analysis and experimental verifications are presented for a multi-band flat pannel FSS with double-ring elements. Both the exact formulation and the thin-ring approximation are described for analyzing and designing this multi-ring patch element FSS. It is found that the thin-ring approximation fails to predict the electrically wide ring element FSS's performance. A single screen double-ring element FSS is demonstrated for the tri-band system that reflects the X-band signal while transmitting through the S- and Ku-band signals. In addition, a double screen FSS with non-similar double-ring elements is presented for the Cassini's four-band system which reflects the X- and Ka-band signals while passing the S- and Ku-band signals. To accurately predict the FSS effects on a dual reflector antenna's radiation pattern, the FSS subreflector's transmitted/reflected field variation as functions of the polarization and incident angles with respect to the local coordinates was taken into account. An FSS transmission/reflection coefficient table is computed for TE and TM polarizations at various incident angles based on the planar FSS model. Next, the hybrid Geometric Optics (GO) and Physical Optics (PO) technique is implemented with linearly interpolating the FSS table to efficiently determine the FSS effects in a dual reflector antenna.

Shape control of slack space reflectors using modulated solar pressure

PubMed Central

Borggräfe, Andreas; Heiligers, Jeannette; Ceriotti, Matteo; McInnes, Colin R.

2015-01-01

The static deflection profile of a large spin-stabilized space reflector because of solar radiation pressure acting on its surface is investigated. Such a spacecraft consists of a thin reflective circular film, which is deployed from a supporting hoop structure in an untensioned, slack manner. This paper investigates the use of a variable reflectivity distribution across the surface to control the solar pressure force and hence the deflected shape. In this first analysis, the film material is modelled as one-dimensional slack radial strings with no resistance to bending or transverse shear, which enables a semi-analytic derivation of the nominal deflection profile. An inverse method is then used to find the reflectivity distribution that generates a specific, for example, parabolic deflection shape of the strings. Applying these results to a parabolic reflector, short focal distances can be obtained when large slack lengths of the film are employed. The development of such optically controlled reflector films enables future key mission applications such as solar power collection, radio-frequency antennae and optical telescopes. PMID:26345083

Shape control of slack space reflectors using modulated solar pressure.

PubMed

Borggräfe, Andreas; Heiligers, Jeannette; Ceriotti, Matteo; McInnes, Colin R

2015-07-08

The static deflection profile of a large spin-stabilized space reflector because of solar radiation pressure acting on its surface is investigated. Such a spacecraft consists of a thin reflective circular film, which is deployed from a supporting hoop structure in an untensioned, slack manner. This paper investigates the use of a variable reflectivity distribution across the surface to control the solar pressure force and hence the deflected shape. In this first analysis, the film material is modelled as one-dimensional slack radial strings with no resistance to bending or transverse shear, which enables a semi-analytic derivation of the nominal deflection profile. An inverse method is then used to find the reflectivity distribution that generates a specific, for example, parabolic deflection shape of the strings. Applying these results to a parabolic reflector, short focal distances can be obtained when large slack lengths of the film are employed. The development of such optically controlled reflector films enables future key mission applications such as solar power collection, radio-frequency antennae and optical telescopes.

The ABCD matrix for parabolic reflectors and its application to astigmatism free four-mirror cavities

NASA Astrophysics Data System (ADS)

Dupraz, K.; Cassou, K.; Martens, A.; Zomer, F.

2015-10-01

The ABCD matrix for parabolic reflectors is derived for any incident angles. It is used in numerical studies of four-mirror cavities composed of two flat and two parabolic mirrors. Constraints related to laser beam injection efficiency, optical stability, cavity-mode, beam-waist size and high stacking power are satisfied. A dedicated alignment procedure leading to stigmatic cavity-modes is employed to overcome issues related to the optical alignment of parabolic reflectors.

Space reflector technology and its system implications

NASA Technical Reports Server (NTRS)

Billman, K. W.; Gilbreath, W. P.; Bowen, S. W.

1979-01-01

The technical feasibility of providing nearly continuous solar energy to a world-distributed set of conversion sites by means of a system of orbiting, large-area, low-areal-density reflecting structures is examined. Requisite mirror area to provide a chosen, year-averaged site intensity is shown. A modeled reflector structure, with suitable planarity and ability to meet operational torques and loads, is discussed. Typical spatial and temporal insolation profiles are presented. These determine the sizing of components and the output electric power from a baselined photovoltaic conversion system. Technical and economic challenges which, if met, would allow the system to provide a large fraction of future world energy needs at costs competitive to circa-1995 fossil and nuclear sources are discussed.

Modular reflector concept study

NASA Technical Reports Server (NTRS)

Vaughan, D. H.

1981-01-01

A study was conducted to evaluate the feasibility of space erecting a 100 meter paraboloidal radio frequency reflector by joining a number of individually deployed structural modules. Three module design concepts were considered: (1) the deployable cell module (DCM); (2) the modular paraboloidal erectable truss antenna (Mod-PETA); and (3) the modular erectable truss antenna (META). With the space shuttle (STS) as the launch system, the methodology of packaging and stowing in the orbiter, and of dispensing, deploying and joining, in orbit, were studied and the necessary support equipment identified. The structural performance of the completed reflectors was evaluated and their overall operational capability and feasibility were evaluated and compared. The potential of the three concepts to maintain stable shape in the space environment was determined. Their ability to operate at radio frequencies of 1 GHz and higher was assessed assuming the reflector surface to consist of a number of flat, hexagonal facets. A parametric study was performed to determine figure degradation as a function of reflector size, flat facet size, and f/D ratio.

High-frequency techniques for RCS prediction of plate geometries and a physical optics/equivalent currents model for the RCS of trihedral corner reflectors, parts 1 and 2

NASA Technical Reports Server (NTRS)

Balanis, Constantine A.; Polka, Lesley A.; Polycarpou, Anastasis C.

1994-01-01

Formulations for scattering from the coated plate and the coated dihedral corner reflector are included. A coated plate model based upon the Uniform Theory of Diffraction (UTD) for impedance wedges was presented in the last report. In order to resolve inaccuracies and discontinuities in the predicted patterns using the UTD-based model, an improved model that uses more accurate diffraction coefficients is presented. A Physical Optics (PO) model for the coated dihedral corner reflector is presented as an intermediary step in developing a high-frequency model for this structure. The PO model is based upon the reflection coefficients for a metal-backed lossy material. Preliminary PO results for the dihedral corner reflector suggest that, in addition to being much faster computationally, this model may be more accurate than existing moment method (MM) models. An improved Physical Optics (PO)/Equivalent Currents model for modeling the Radar Cross Section (RCS) of both square and triangular, perfectly conducting, trihedral corner reflectors is presented. The new model uses the PO approximation at each reflection for the first- and second-order reflection terms. For the third-order reflection terms, a Geometrical Optics (GO) approximation is used for the first reflection; and PO approximations are used for the remaining reflections. The previously reported model used GO for all reflections except the terminating reflection. Using PO for most of the reflections results in a computationally slower model because many integrations must be performed numerically, but the advantage is that the predicted RCS using the new model is much more accurate. Comparisons between the two PO models, Finite-Difference Time-Domain (FDTD) and experimental data are presented for validation of the new model.

Inflection point caustic problems and solutions for high-gain dual-shaped reflectors

NASA Technical Reports Server (NTRS)

Galindo-Israel, Victor; Veruttipong, Thavath; Imbriale, William; Rengarajan, Sembiam

1990-01-01

The singular nature of the uniform geometrical theory of diffraction (UTD) subreflector scattered field at the vicinity of the main reflector edge (for a high-gain antenna design) is investigated. It is shown that the singularity in the UTD edge-diffracted and slope-diffracted fields is due to the reflection distance parameter approaching infinity in the transition functions. While the geometrical optics (GO) and UTD edge-diffracted fields exhibit singularities of the same order, the edge slope-diffracted field singularity is more significant and is substantial for greater subreflector edge tapers. The diffraction analysis of such a subreflector in the vicinity of the main reflector edge has been carried out efficiently and accurately by a stationary phase evaluation of the phi-integral, whereas the theta-integral is carried out numerically. Computational results from UTD and physical optics (PO) analysis of a 34-m ground station dual-shaped reflector confirm the analytical formulations for both circularly symmetric and offset asymmetric subreflectors. It is concluded that the proposed PO(theta)GO(phi) technique can be used to study the spillover or noise temperature characteristics of a high-gain reflector antenna efficiently and accurately.

Correlating High Resolution Radar Reflectors with Visible Layering of the Polar Layered Deposits, Mars

NASA Astrophysics Data System (ADS)

Christian, S.; Holt, J. W.; Choudhary, P.; Fishbaugh, K. E.; Plaut, J. J.

2010-12-01

The Shallow Radar (SHARAD) onboard NASA’s Mars Reconnaissance Orbiter (MRO) has successfully detected many subsurface reflectors in the North Polar Layered Deposits (NPLD) of Mars. Confirming that these reflectors are caused by varying fractions of dust within the ice will be of primary importance in any attempt to model the composition of the NPLD, particularly if such a study incorporates optical data based on the assumption of a shared mechanism between layering and radar reflectance. As a first step towards examining this assumption, we have quantitatively studied the relationship between radar reflectors and adjacent visible layers exposed in an NPLD outcrop using statistical analyses and geometric comparisons. A clustering analysis of vertical separation distances between radar reflectors returned strong values at 11.8, 15.8, 20.3, 27.9, and 35.3 m, which strongly agree with published visible layer clusters [Fishbaugh et al., LPSC, 2009] and known frequency analysis results [Milkovich and Head, JGR, 2005]. Furthermore, in order to understand subsurface structures and reflector geometry we have gridded reflector surfaces in three dimensions, taking into account the influence of surface slopes to obtain accurate subsurface geometries. These geometries reveal average reflector dips of 0.4°, which are consistent with optical layer slopes on the order of 1.0°. Unexpected long wavelength topography resulting from subsurface structures visible to SHARAD complicated the attempt to compare radar reflector geometries with layer boundary elevation profiles obtained from the stratigraphic column produced using a digital elevation model (DEM) of High Resolution Imaging Science Experiment (HiRISE) stereo imagery [Fishbaugh et al., GRL, 2010]. The limitation imposed by the small extent of the DEM was resolved by increasing exposure coverage through the incorporation of images from Context Camera (CTX), also on MRO. In doing so, we were able to resolve the disparity

Angle amplifying optics using plane and ellipsoidal reflectors

DOEpatents

Glass, Alexander J.

1977-01-01

An optical system for providing a wide angle input beam into ellipsoidal laser fusion target illumination systems. The optical system comprises one or more pairs of centrally apertured plane and ellipsoidal mirrors disposed to accept the light input from a conventional lens of modest focal length and thickness, to increase the angular divergence thereof to a value equivalent to that of fast lenses, and to direct the light into the ellipsoidal target illumination system.

Comparison-based optical study on a point-line-coupling-focus system with linear Fresnel heliostats.

PubMed

Dai, Yanjun; Li, Xian; Zhou, Lingyu; Ma, Xuan; Wang, Ruzhu

2016-05-16

Concentrating the concept of a beam-down solar tower with linear Fresnel heliostat (PLCF) is one of the feasible choices and has great potential in reducing spot size and improving optical efficiency. Optical characteristics of a PLCF system with the hyperboloid reflector are introduced and investigated theoretically. Taking into account solar position and optical surface errors, a Monte Carlo ray-tracing (MCRT) analysis model for a PLCF system is developed and applied in a comparison-based study on the optical performance between the PLCF system and the conventional beam-down solar tower system with flat and spherical heliostats. The optimal square facet of linear Fresnel heliostat is also proposed for matching with the 3D-CPC receiver.

Fabrication and Thermo-Optical Properties of the MLS Composite Primary Reflector

NASA Technical Reports Server (NTRS)

Willis, Paul B.; Dyer, Jack; Dummer, Sam

2000-01-01

The Microwave Limb Sounder (MLS) is a limb-sounding radiometer sensing emissions in the millimeter and sub-millimeter range. MLS will contribute to an understanding of atmospheric chemistry by assessing stratospheric and tropospheric ozone depletion, climate forcings and volcanic effects. The heart of the antenna is the primary reflector, constructed from graphite/cyanate composites in a facesheet/core construction. The reflector has an aperture of one square meter, a mass of 8.7 kilos and final figure accuracy of 4.37 microns rms. The surface is also modified to ensure RF reflectivity, prevent solar concentration and provide thermal balance to the spacecraft The surface is prepared by precision beadblasting, then coated with vapor deposited aluminum (VDA) and finally a layer of silicon suboxide (SiO(x)) to control the infrared emissivity. The resulting surface has a solar absorptance of 0.43 and an absorptance/emittance ratio of 1.3. BRDF analysis shows that 93% of the incident thermal energy is reflected outside a 10 degree angle of cone. For its mass and aperture, we believe this reflector to have the highest figure accuracy yet achieved in a composite antenna construction.

Optical design of CCAT

NASA Astrophysics Data System (ADS)

Cortés-Medellín, Germán; Herter, Terry

2006-06-01

The Cornell Caltech Atacama Telescope (CCAT) is a 25m-class sub-millimeter radio telescope capable of operating from 300GHz up to 1.5 THz. The CCAT optical design is an f/8 Ritchey-Chretien (RC) system in a dual Nasmyth focus configuration and a 20 arc-min FOV (diffraction limited imaging performance better than 0.31" at the edge of the field). The large FOV is capable to accommodate up to 1200x1200 (Nyquist Sampled) Pixels at 200 microns, with better than 96% Strehl ratio. The telescope pedestal assembly is a counterbalanced elevation over azimuth design. The main reflector surface is segmented and actively controlled to attain diffraction-limited operation up to 200 microns. A flat Mirror located behind the main reflector vertex provides the optical path relay to either of the two Nasmyth platforms and to a bent-Cassegrain focus for surface calibration. We present the imaging characteristics of the CCAT over the 20arc-min FOV at 200 microns at the Nasmyth focal plane, as well as the positioning sensitivity analysis of CCAT's 3.2m-diameter sub-reflector given in terms of the telescope optical performance, antenna pointing requirements and sub-reflector chopping characteristics.

Design of a high-efficiency train headlamp with low power consumption using dual half-parabolic aluminized reflectors.

PubMed

Liang, Wei-Lun; Su, Guo-Dung J

2018-02-20

We propose a train headlamp system using dual half-circular parabolic aluminized reflectors. Each half-circular reflector contains five high-efficiency and small-package light-emitting diode (LED) chips, and the halves are 180° rotationally symmetric. For traffic safety, the headlamp satisfies the Code of Federal Regulations. To predict the pattern of illumination, an analytical derivation is developed for the optical path of a ray that is perpendicular to and emitted from the center of an LED chip. This ray represents the main ray emitted from the LED chip and is located at the maximum illuminance of the spot projected by the LED source onto a screen. We then analyze the design systematically to determine the locations of the LED chips in the reflector that minimize electricity consumption while satisfying reliability constraints associated with traffic safety. Compared to a typical train headlamp system with an incandescent or halogen lamp needing several hundred watts, the proposed system only uses 20.18 W to achieve the luminous intensity requirements.

Optical heterodyne accelerometry: passively stabilized, fully balanced velocity interferometer system for any reflector

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

Buttler, William T.; Lamoreaux, Steven K.

2010-08-10

We formalize the physics of an optical heterodyne accelerometer that allows measurement of low and high velocities from material surfaces under high strain. The proposed apparatus incorporates currently common optical velocimetry techniques used in shock physics, with interferometric techniques developed to self-stabilize and passively balance interferometers in quantum cryptography. The result is a robust telecom-fiber-based velocimetry system insensitive to modal and frequency dispersion that should work well in the presence of decoherent scattering processes, such as from ejecta clouds and shocked surfaces.

Broadband Integrated Lens for Illuminating Reflector Antenna With Constant Aperture Efficiency

NASA Astrophysics Data System (ADS)

Fernandes, Carlos A.; Lima, Eduardo B.; Costa, Jorge R.

2010-12-01

A new integrated shaped lens antenna configuration is described with frequency stable radiation pattern and phase center position across a broad 1:3 frequency band, which can be used for focal plane reflector feeding in quasi-optical radio telescope systems. The lens is compatible with the integration of ultrawideband uniplanar printed feeds at its base and equally broadband mixing devices, like the Hot Electron Bolometer (HEB), although these are not used in the present work. Measurements on a scaled mm-wave lab prototype have confirmed stable performance versus frequency, with only dB directivity variation, and better than 94% Gaussicity, thanks to the possibility to impose a predefined output radiation pattern template. Simulations were performed to test the illumination of an off-set parabolic reflector by the lens radiation pattern, which confirmed reasonably constant aperture efficiency in the order of 78% across the 100% bandwidth.

Bifocal reflector for electrohydraulic lithotripters.

PubMed

Prieto, F E; Loske, A M

1999-03-01

To describe the design and construction of a bifocal reflector that could be used in electrohydraulic extracorporeal shockwave lithotripters in order to increase their efficiency. The new reflector is obtained by joining two sectors of two rotationally symmetric ellipsoidal reflectors having different distances between their foci, which results in a bifocal composite reflector with the F1 foci in coincidence and the two F2 foci separated by a certain distance. As in conventional reflectors, shockwaves are generated by the electrical breakdown of water between two electrodes, located at the focus (F1) closest to the reflector. A prototype was constructed and tested in an experimental shockwave generator of our own make, using two different types of kidney-stone models, one to test the stone fragmentation abilities, and the other to test the stone pitting abilities. Fragmentation data for the new reflector were compared with those of a conventional ellipsoidal reflector tested on the same device. The new design appeared to be more efficient in breaking up both types of kidney-stone models than the conventional reflector. Pressure measurements were obtained with both reflectors using needle hydrophones. The physical background of shockwave reflection on both reflectors is also explained. With this new reflector, it could be possible, in principle, to reduce the treatment time of extracorporeal shockwave lithotripsy.

Nuclear reactor reflector

DOEpatents

Hopkins, Ronald J.; Land, John T.; Misvel, Michael C.

1994-01-01

A nuclear reactor reflector is disclosed that comprises a stack of reflector blocks with vertical water flow passages to cool the reflector. The interface between blocks is opposite support points for reactor fuel rods. Water flows between the reflector and the reactor barrel from passages in a bottom block. The top block contains a flange to limit this flow and the flange has a slot to receive an alignment pin that is welded to the barrel. The pin is held in the slot by two removable shims. Alignment bars extend the length of the stack in slots machined in each block when the stack is assembled.

Nuclear reactor reflector

DOEpatents

Hopkins, R.J.; Land, J.T.; Misvel, M.C.

1994-06-07

A nuclear reactor reflector is disclosed that comprises a stack of reflector blocks with vertical water flow passages to cool the reflector. The interface between blocks is opposite support points for reactor fuel rods. Water flows between the reflector and the reactor barrel from passages in a bottom block. The top block contains a flange to limit this flow and the flange has a slot to receive an alignment pin that is welded to the barrel. The pin is held in the slot by two removable shims. Alignment bars extend the length of the stack in slots machined in each block when the stack is assembled. 12 figs.

Primary reflector for solar energy collection systems and method of making same

NASA Technical Reports Server (NTRS)

Miller, C. G.; Stephens, J. B. (Inventor)

1979-01-01

Solar energy is reflected to a movably supported collector that is kept at the concentrated line focus of the reflector primary by a fixed, linear, ground-based primary reflector having an extended curved sawtooth contoured surface covered with a metalized polymeric reflecting material. The primary reflector was constructed by a process utilizing well-known freeway paving machinery.

The DART Cylindrical, Infrared, 1 Meter Membrane Reflector

NASA Technical Reports Server (NTRS)

Morgan, Rhonda M.; Agnes, Greg S.; Barber, Dan; Dooley, Jennifer; Dragovan, Mark; Hatheway, Al E.; Marcin, Marty

2004-01-01

The Dual Anamorphic Reflector Telescopes (DART) is an architecture for large aperture space telescopes that enables the use of membranes. A membrane can be readily shaped in one direction of curvature using a combination of boundary control and tensioning, yielding a cylindrical reflector. Two cylindrical reflectors (orthogonal and confocal) comprise the 'primary mirror' of the telescope system. The aperture is completely unobstructed and ideal for infrared and high contrast observations.

Membrane Shell Reflector Segment Antenna

NASA Technical Reports Server (NTRS)

Fang, Houfei; Im, Eastwood; Lin, John; Moore, James

2012-01-01

The mesh reflector is the only type of large, in-space deployable antenna that has successfully flown in space. However, state-of-the-art large deployable mesh antenna systems are RF-frequency-limited by both global shape accuracy and local surface quality. The limitations of mesh reflectors stem from two factors. First, at higher frequencies, the porosity and surface roughness of the mesh results in loss and scattering of the signal. Second, the mesh material does not have any bending stiffness and thus cannot be formed into true parabolic (or other desired) shapes. To advance the deployable reflector technology at high RF frequencies from the current state-of-the-art, significant improvements need to be made in three major aspects: a high-stability and highprecision deployable truss; a continuously curved RF reflecting surface (the function of the surface as well as its first derivative are both continuous); and the RF reflecting surface should be made of a continuous material. To meet these three requirements, the Membrane Shell Reflector Segment (MSRS) antenna was developed.

Novel back-reflector architecture with nanoparticle based buried light-scattering microstructures for improved solar cell performance

NASA Astrophysics Data System (ADS)

Desta, Derese; Ram, Sanjay K.; Rizzoli, Rita; Bellettato, Michele; Summonte, Caterina; Jeppesen, Bjarke R.; Jensen, Pia B.; Tsao, Yao-Chung; Wiggers, Hartmut; Pereira, Rui N.; Balling, Peter; Larsen, Arne Nylandsted

2016-06-01

A new back-reflector architecture for light-management in thin-film solar cells is proposed that includes a morphologically smooth top surface with light-scattering microstructures buried within. The microstructures are pyramid shaped, fabricated on a planar reflector using TiO2 nanoparticles and subsequently covered with a layer of Si nanoparticles to obtain a flattened top surface, thus enabling growth of good quality thin-film solar cells. The optical properties of this back-reflector show high broadband haze parameter and wide angular distribution of diffuse light-scattering. The n-i-p amorphous silicon thin-film solar cells grown on such a back-reflector show enhanced light absorption resulting in improved external quantum efficiency. The benefit of the light trapping in those solar cells is evidenced by the gains in short-circuit current density and efficiency up to 15.6% and 19.3% respectively, compared to the reference flat solar cells. This improvement in the current generation in the solar cells grown on the flat-topped (buried pyramid) back-reflector is observed even when the irradiation takes place at large oblique angles of incidence. Finite-difference-time-domain simulation results of optical absorption and ideal short-circuit current density values agree well with the experimental findings. The proposed approach uses a low cost and simple fabrication technique and allows effective light manipulation by utilizing the optical properties of micro-scale structures and nanoscale constituent particles.

Low-loss off-axis feeds for symmetric dual-reflector antennas

NASA Technical Reports Server (NTRS)

Veruttipong, T.; Galindo-Israel, V.; Imbriale, W.

1986-01-01

Circularly symmetric, dual reflector, high gain antenna systems often require feeds placed off the system's axis because of the need for multiple feeds to use the reflector antenna. Also, the constraint requiring the hyperboloid or shaped subreflector to remain circularly symmetric is sometimes added. In a Cassegrainian system, the subreflector and feed may be rotated off axis around the paraboloid focus and retain main reflector focusing. However, substantial spillover results in considerable noise with a high gain/low noise temperature system. In a shaped system, the tilt of the shaped subreflector and feed together results in substantial defocusing as well as spillover noise. If the subreflector is tilted approximately one-half the angle of the feed tilt in either the Cassegrainian or the dual shaped reflector antenna, it is found that spillover and noise are substantially reduced with tolerable defocusing. An extensive numerical analysis of these effects was conducted to determine the characteristics of a planned 70-meter, dual shaped reflector versus Cassegrainian antenna and to gain some understanding of the cause of the observed effects.

CO2 laser cutting of ultra thin (75 μm) glass based rigid optical solar reflector (OSR) for spacecraft application

NASA Astrophysics Data System (ADS)

Mishra, Shubham; Sridhara, N.; Mitra, Avijit; Yougandar, B.; Dash, Sarat Kumar; Agarwal, Sanjay; Dey, Arjun

2017-03-01

Present study reports for the first time laser cutting of multilayered coatings on both side of ultra thin (i.e., 75 μm) glass substrate based rigid optical solar reflector (OSR) for spacecraft thermal control application. The optimization of cutting parameters was carried out as a function of laser power, cutting speed and number of cutting passes and their effect on cutting edge quality. Systematic and in-detail microstructural characterizations were carried out by optical and scanning electron microscopy techniques to study the laser affected zone and cutting edge quality. Sheet resistance and water contact angle experiments were also conducted locally both prior and after laser cut to investigate the changes of electrical and surface properties, if any.

Large incidence angle and defocus influence cat's eye retro-reflector

NASA Astrophysics Data System (ADS)

Zhang, Lai-xian; Sun, Hua-yan; Zhao, Yan-zhong; Yang, Ji-guang; Zheng, Yong-hui

2014-11-01

Cat's eye lens make the laser beam retro-reflected exactly to the opposite direction of the incidence beam, called cat's eye effect, which makes rapid acquiring, tracking and pointing of free space optical communication possible. Study the influence of cat's eye effect to cat's eye retro-reflector at large incidence angle is useful. This paper analyzed the process of how the incidence angle and focal shit affect effective receiving area, retro-reflected beam divergence angle, central deviation of cat's eye retro-reflector at large incidence angle and cat's eye effect factor using geometrical optics method, and presented the analytic expressions. Finally, numerical simulation was done to prove the correction of the study. The result shows that the efficiency receiving area of cat's eye retro-reflector is mainly affected by incidence angle when the focal shift is positive, and it decreases rapidly when the incidence angle increases; the retro-reflected beam divergence and central deviation is mainly affected by focal shift, and within the effective receiving area, the central deviation is smaller than beam divergence in most time, which means the incidence beam can be received and retro-reflected to the other terminal in most time. The cat's eye effect factor gain is affected by both incidence angle and focal shift.

Deployment simulation of a deployable reflector for earth science application

NASA Astrophysics Data System (ADS)

Wang, Xiaokai; Fang, Houfei; Cai, Bei; Ma, Xiaofei

2015-10-01

A novel mission concept namely NEXRAD-In-Space (NIS) has been developed for monitoring hurricanes, cyclones and other severe storms from a geostationary orbit. It requires a space deployable 35-meter diameter Ka-band (35 GHz) reflector. NIS can measure hurricane precipitation intensity, dynamics and its life cycle. These information is necessary for predicting the track, intensity, rain rate and hurricane-induced floods. To meet the requirements of the radar system, a Membrane Shell Reflector Segment (MSRS) reflector technology has been developed and several technologies have been evaluated. However, the deployment analysis of this large size and high-precision reflector has not been investigated. For a pre-studies, a scaled tetrahedral truss reflector with spring driving deployment system has been made and tested, deployment dynamics analysis of this scaled reflector has been performed using ADAMS to understand its deployment dynamic behaviors. Eliminating the redundant constraints in the reflector system with a large number of moving parts is a challenging issue. A primitive joint and flexible struts were introduced to the analytical model and they can effectively eliminate over constraints of the model. By using a high-speed camera and a force transducer, a deployment experiment of a single-bay tetrahedral module has been conducted. With the tested results, an optimization process has been performed by using the parameter optimization module of ADAMS to obtain the parameters of the analytical model. These parameters were incorporated to the analytical model of the whole reflector. It is observed from the analysis results that the deployment process of the reflector with a fixed boundary experiences three stages. These stages are rapid deployment stage, slow deployment stage and impact stage. The insight of the force peak distributions of the reflector can help the optimization design of the structure.

Evaluation of Hardware and Procedures for Astronaut Assembly and Repair of Large Precision Reflectors

NASA Technical Reports Server (NTRS)

Lake, Mark S.; Heard, Walter L., Jr.; Watson, Judith J.; Collins, Timothy J.

2000-01-01

A detailed procedure is presented that enables astronauts in extravehicular activity (EVA) to efficiently assemble and repair large (i.e., greater than 10m-diameter) segmented reflectors, supported by a truss, for space-based optical or radio-frequency science instruments. The procedure, estimated timelines, and reflector hardware performance are verified in simulated 0-g (neutral buoyancy) assembly tests of a 14m-diameter, offset-focus, reflector test article. The test article includes a near-flight-quality, 315-member, doubly curved support truss and 7 mockup reflector panels (roughly 2m in diameter) representing a portion of the 37 total panels needed to fully populate the reflector. Data from the tests indicate that a flight version of the design (including all reflector panels) could be assembled in less than 5 hours - less than the 6 hours normally permitted for a single EVA. This assembly rate essentially matches pre-test predictions that were based on a vast amount of historical data on EVA assembly of structures produced by NASA Langley Research Center. Furthermore, procedures and a tool for the removal and replacement of a damaged reflector panel were evaluated, and it was shown that EVA repair of this type of reflector is feasible with the use of appropriate EVA crew aids.

Distributed gain in plasmonic reflectors and its use for terahertz generation.

PubMed

Sydoruk, O; Syms, R R A; Solymar, L

2012-08-27

Semiconductor plasmons have potential for terahertz generation. Because practical device formats may be quasi-optical, we studied theoretically distributed plasmonic reflectors that comprise multiple interfaces between cascaded two-dimensional electron channels. Employing a mode-matching technique, we show that transmission through and reflection from a single interface depend on the magnitude and direction of a dc current flowing in the channels. As a result, plasmons can be amplified at an interface, and the cumulative effect of multiple interfaces increases the total gain, leading to plasmonic reflection coefficients exceeding unity. Reversing the current direction in a distributed reflector, however, has the opposite effect of plasmonic deamplification. Consequently, we propose structurally asymmetric resonators comprising two different distributed reflectors and predict that they are capable of terahertz oscillations at low threshold currents.

Analytical approximation of a distorted reflector surface defined by a discrete set of points

NASA Technical Reports Server (NTRS)

Acosta, Roberto J.; Zaman, Afroz A.

1988-01-01

Reflector antennas on Earth orbiting spacecrafts generally cannot be described analytically. The reflector surface is subjected to a large temperature fluctuation and gradients, and is thus warped from its true geometrical shape. Aside from distortion by thermal stresses, reflector surfaces are often purposely shaped to minimize phase aberrations and scanning losses. To analyze distorted reflector antennas defined by discrete surface points, a numerical technique must be applied to compute an interpolatory surface passing through a grid of discrete points. In this paper, the distorted reflector surface points are approximated by two analytical components: an undistorted surface component and a surface error component. The undistorted surface component is a best fit paraboloid polynomial for the given set of points and the surface error component is a Fourier series expansion of the deviation of the actual surface points, from the best fit paraboloid. By applying the numerical technique to approximate the surface normals of the distorted reflector surface, the induced surface current can be obtained using physical optics technique. These surface currents are integrated to find the far field radiation pattern.

New adaptive method to optimize the secondary reflector of linear Fresnel collectors

DOE PAGES

Zhu, Guangdong

2017-01-16

Performance of linear Fresnel collectors may largely depend on the secondary-reflector profile design when small-aperture absorbers are used. Optimization of the secondary-reflector profile is an extremely challenging task because there is no established theory to ensure superior performance of derived profiles. In this work, an innovative optimization method is proposed to optimize the secondary-reflector profile of a generic linear Fresnel configuration. The method correctly and accurately captures impacts of both geometric and optical aspects of a linear Fresnel collector to secondary-reflector design. The proposed method is an adaptive approach that does not assume a secondary shape of any particular form,more » but rather, starts at a single edge point and adaptively constructs the next surface point to maximize the reflected power to be reflected to absorber(s). As a test case, the proposed optimization method is applied to an industrial linear Fresnel configuration, and the results show that the derived optimal secondary reflector is able to redirect more than 90% of the power to the absorber in a wide range of incidence angles. Here, the proposed method can be naturally extended to other types of solar collectors as well, and it will be a valuable tool for solar-collector designs with a secondary reflector.« less

New adaptive method to optimize the secondary reflector of linear Fresnel collectors

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

Zhu, Guangdong

Performance of linear Fresnel collectors may largely depend on the secondary-reflector profile design when small-aperture absorbers are used. Optimization of the secondary-reflector profile is an extremely challenging task because there is no established theory to ensure superior performance of derived profiles. In this work, an innovative optimization method is proposed to optimize the secondary-reflector profile of a generic linear Fresnel configuration. The method correctly and accurately captures impacts of both geometric and optical aspects of a linear Fresnel collector to secondary-reflector design. The proposed method is an adaptive approach that does not assume a secondary shape of any particular form,more » but rather, starts at a single edge point and adaptively constructs the next surface point to maximize the reflected power to be reflected to absorber(s). As a test case, the proposed optimization method is applied to an industrial linear Fresnel configuration, and the results show that the derived optimal secondary reflector is able to redirect more than 90% of the power to the absorber in a wide range of incidence angles. Here, the proposed method can be naturally extended to other types of solar collectors as well, and it will be a valuable tool for solar-collector designs with a secondary reflector.« less

A geological history of reflecting optics.

PubMed

Parker, Andrew Richard

2005-03-22

Optical reflectors in animals are diverse and ancient. The first image-forming eye appeared around 543 million years ago. This introduced vision as a selection pressure in the evolution of animals, and consequently the evolution of adapted optical devices. The earliest known optical reflectors--diffraction gratings--are 515 Myr old. The subsequent fossil record preserves multilayer reflectors, including liquid crystals and mirrors, 'white' and 'blue' scattering structures, antireflective surfaces and the very latest addition to optical physics--photonic crystals. The aim of this article is to reveal the diversity of reflecting optics in nature, introducing the first appearance of some reflector types as they appear in the fossil record as it stands (which includes many new records) and backdating others in geological time through evolutionary analyses. This article also reveals the commercial potential for these optical devices, in terms of lessons from their nano-level designs and the possible emulation of their engineering processes--molecular self-assembly.

Membrane Reflector Vertical Cavity Lasers at Near- and Midwave-Infrared

DTIC Science & Technology

2014-05-30

independent broadband reflectors based on cross-stacked gratings, Optics Express, (04 2011): 9050. doi: 10.1364/OE.19.009050 Tapas Kumar Saha, Mingyu Lu... Mingyu Lu, Huiqing Zhai, Deyin Zhao, Weidong Zhou. Design of a compact grating coupler with controllable linewidths via transverse resonance and

Visible light focusing flat lenses based on hybrid dielectric-metal metasurface reflector-arrays

PubMed Central

Fan, Qingbin; Huo, Pengcheng; Wang, Daopeng; Liang, Yuzhang; Yan, Feng; Xu, Ting

2017-01-01

Conventional metasurface reflector-arrays based on metallic resonant nanoantenna to control the wavefront of light for focusing always suffer from strong ohmic loss at optical frequencies. Here, we overcome this challenge by constructing a non-resonant, hybrid dielectric-metal configuration consisting of TiO2 nanofins associated with an Ag reflector substrate that provides a broadband response and high polarization conversion efficiency in the visible range. A reflective flat lens based on this configuration shows an excellent focusing performance with the spot size close to the diffraction limit. Furthermore, by employing the superimposed phase distribution design to manipulate the wavefront of the reflected light, various functionalities, such as multifocal and achromatic focusing, are demonstrated for the flat lenses. Such a reflective flat lens will find various applications in visible light imaging and sensing systems. PMID:28332611

MHD compressor---expander conversion system integrated with GCR inside a deployable reflector

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

Tuninetti, G.; Botta, E.; Criscuolo, C.

1989-04-20

This work originates from the proposal MHD Compressor-Expander Conversion System Integrated with a GCR Inside a Deployable Reflector''. The proposal concerned an innovative concept of nuclear, closed-cycle MHD converter for power generation on space-based systems in the multi-megawatt range. The basic element of this converter is the Power Conversion Unit (PCU) consisting of a gas core reactor directly coupled to an MHD expansion channel. Integrated with the PCU, a deployable reflector provides reactivity control. The working fluid could be either uranium hexafluoride or a mixture of uranium hexafluoride and helium, added to enhance the heat transfer properties. The original Statementmore » of Work, which concerned the whole conversion system, was subsequently redirected and focused on the basic mechanisms of neutronics, reactivity control, ionization and electrical conductivity in the PCU. Furthermore, the study was required to be inherently generic such that the study was required to be inherently generic such that the analysis an results can be applied to various nuclear reactor and/or MHD channel designs''.« less

Thermal Stability of a 4 Meter Primary Reflector for the Scanning Microwave Limb Sounder

NASA Technical Reports Server (NTRS)

Cofield, Richard; Kasl, Eldon P.

2010-01-01

We describe the fabrication and thermal-stability analysis and test of a composite demonstration model of the Scanning Microwave Limb Sounder (SMLS) primary reflector, having full 4m height and 1/3 the width planned for flight. SMLS is a space-borne heterodyne radiometer which will measure pressure, temperature and atmospheric constituents from thermal emission between 180 and 660 GHz. Current MLS instruments in low Earth orbit scan pencil-beam antennas (sized to resolve about one scale height) vertically over the atmospheric limb. SMLS, planned for the Global Atmospheric Composition Mission of the NRC Decadal Survey, adds azimuthal scanning for better horizontal and temporal resolution and coverage than typical orbit spacing provides. SMLS combines the wide scan range of the parabolic torus with unblocked offset Cassegrain optics. The resulting system is diffraction-limited in the vertical plane but highly astigmatic in the horizontal, having a beam aspect ratio [tilde operator]1:20. Symmetry about the nadir axis ensures that beam shape is nearly invariant over +/-65(white bullet) azimuth. The a feeds a low-noise SIS receiver whose FOV is swept over the reflector system by a small scanning mirror. Using finiteelement models of antenna reflectors and structure, we evaluate thermal deformations and the resulting optical performance for 4 orbital environments and isothermal soak. We compare deformations with photogrammetric measurements made during wide-range (ambient+[-97,+75](white bullet) C) thermal soak tests of the primary in a chamber. This range exceeds predicted orbital soak ranges by large factors, implying in-orbit thermal stability of 0.21(mu)m rms/(white bullet)C, which meets SMLS requirements.

Satellite-Tracking Millimeter-Wave Reflector Antenna System For Mobile Satellite-Tracking

NASA Technical Reports Server (NTRS)

Densmore, Arthur C. (Inventor); Jamnejad, Vahraz (Inventor); Woo, Kenneth E. (Inventor)

2001-01-01

A miniature dual-band two-way mobile satellite-tracking antenna system mounted on a movable vehicle includes a miniature parabolic reflector dish having an elliptical aperture with major and minor elliptical axes aligned horizontally and vertically, respectively, to maximize azimuthal directionality and minimize elevational directionality to an extent corresponding to expected pitch excursions of the movable ground vehicle. A feed-horn has a back end and an open front end facing the reflector dish and has vertical side walls opening out from the back end to the front end at a lesser horn angle and horizontal top and bottom walls opening out from the back end to the front end at a greater horn angle. An RF circuit couples two different signal bands between the feed-horn and the user. An antenna attitude controller maintains an antenna azimuth direction relative to the satellite by rotating it in azimuth in response to sensed yaw motions of the movable ground vehicle so as to compensate for the yaw motions to within a pointing error angle. The controller sinusoidally dithers the antenna through a small azimuth dither angle greater than the pointing error angle while sensing a signal from the satellite received at the reflector dish, and deduces the pointing angle error from dither-induced fluctuations in the received signal.

Piezocomposite Actuator Arrays for Correcting and Controlling Wavefront Error in Reflectors

NASA Technical Reports Server (NTRS)

Bradford, Samuel Case; Peterson, Lee D.; Ohara, Catherine M.; Shi, Fang; Agnes, Greg S.; Hoffman, Samuel M.; Wilkie, William Keats

2012-01-01

Three reflectors have been developed and tested to assess the performance of a distributed network of piezocomposite actuators for correcting thermal deformations and total wave-front error. The primary testbed article is an active composite reflector, composed of a spherically curved panel with a graphite face sheet and aluminum honeycomb core composite, and then augmented with a network of 90 distributed piezoelectric composite actuators. The piezoelectric actuator system may be used for correcting as-built residual shape errors, and for controlling low-order, thermally-induced quasi-static distortions of the panel. In this study, thermally-induced surface deformations of 1 to 5 microns were deliberately introduced onto the reflector, then measured using a speckle holography interferometer system. The reflector surface figure was subsequently corrected to a tolerance of 50 nm using the actuators embedded in the reflector's back face sheet. Two additional test articles were constructed: a borosilicate at window at 150 mm diameter with 18 actuators bonded to the back surface; and a direct metal laser sintered reflector with spherical curvature, 230 mm diameter, and 12 actuators bonded to the back surface. In the case of the glass reflector, absolute measurements were performed with an interferometer and the absolute surface was corrected. These test articles were evaluated to determine their absolute surface control capabilities, as well as to assess a multiphysics modeling effort developed under this program for the prediction of active reflector response. This paper will describe the design, construction, and testing of active reflector systems under thermal loads, and subsequent correction of surface shape via distributed peizeoelctric actuation.

POMESH - DIFFRACTION ANALYSIS OF REFLECTOR ANTENNAS

NASA Technical Reports Server (NTRS)

Hodges, R. E.

1994-01-01

POMESH is a computer program capable of predicting the performance of reflector antennas. Both far field pattern and gain calculations are performed using the Physical Optics (PO) approximation of the equivalent surface currents. POMESH is primarily intended for relatively small reflectors. It is useful in situations where the surface is described by irregular data that must be interpolated and for cases where the surface derivatives are not known. This method is flexible and robust and also supports near field calculations. Because of the near field computation ability, this computational engine is quite useful for subreflector computations. The program is constructed in a highly modular form so that it may be readily adapted to perform tasks other than the one that is explicitly described here. Since the computationally intensive portions of the algorithm are simple loops, the program can be easily adapted to take advantage of vector processor and parallel architectures. In POMESH the reflector is represented as a piecewise planar surface comprised of triangular regions known as facets. A uniform physical optics (PO) current is assumed to exist on each triangular facet. Then, the PO integral on a facet is approximated by the product of the PO current value at the center and the area of the triangle. In this way, the PO integral over the reflector surface is reduced to a summation of the contribution from each triangular facet. The source horn, or feed, that illuminates the subreflector is approximated by a linear combination of plane patterns. POMESH contains three polarization pattern definitions for the feed; a linear x-polarized element, linear y-polarized element, and a circular polarized element. If a more general feed pattern is required, it is a simple matter to replace the subroutine that implements the pattern definitions. POMESH obtains information necessary to specify the coordinate systems, location of other data files, and parameters of the desired

Optical Analysis of Cassegrainian Point Focus Concentrators

NASA Technical Reports Server (NTRS)

Waterbury, S. S.; Schwinkendorf, W. E.

1984-01-01

A Cassegrainian solar concentrator, using a 7-meter diameter primary reflector, was analyzed in three forms: (1) an unmodified Cassegrainian, (2) the Ritchey-Chretien configuration, and (3) the unmodified Cassegrainian with a non-imaging tertiary reflector. Optical performance was not significantly improved with the Ritchey-Chretien; however, the tertiary resulted in significant improvement in intercept factor and optical efficiency. The effects of misalignment of the secondary and tertiary reflectors on the optical performance of the collector were also analyzed.

DAZZLE project: UAV to ground communication system using a laser and a modulated retro-reflector

NASA Astrophysics Data System (ADS)

Thueux, Yoann; Avlonitis, Nicholas; Erry, Gavin

2014-10-01

The advent of the Unmanned Aerial Vehicle (UAV) has generated the need for reduced size, weight and power (SWaP) requirements for communications systems with a high data rate, enhanced security and quality of service. This paper presents the current results of the DAZZLE project run by Airbus Group Innovations. The specifications, integration steps and initial performance of a UAV to ground communication system using a laser and a modulated retro-reflector are detailed. The laser operates at the wavelength of 1550nm and at power levels that keep it eye safe. It is directed using a FLIR pan and tilt unit driven by an image processing-based system that tracks the UAV in flight at a range of a few kilometers. The modulated retro-reflector is capable of a data rate of 20Mbps over short distances, using 200mW of electrical power. The communication system was tested at the Pershore Laser Range in July 2014. Video data from a flying Octocopter was successfully transmitted over 1200m. During the next phase of the DAZZLE project, the team will attempt to produce a modulated retro-reflector capable of 1Gbps in partnership with the research institute Acreo1 based in Sweden. A high speed laser beam steering capability based on a Spatial Light Modulator will also be added to the system to improve beam pointing accuracy.

Design optimization of a smooth headlamp reflector to SAE/DOT beam-shape requirements

NASA Astrophysics Data System (ADS)

Shatz, Narkis E.; Bortz, John C.; Dassanayake, Mahendra S.

1999-10-01

The optical design of Ford Motor Company's 1992 Mercury Grand Marquis headlamp utilized a Sylvania 9007 filament source, a paraboloidal reflector and an array of cylindrical lenses (flutes). It has been of interest to Ford to determine the practicality of closely reproducing the on- road beam pattern performance of this headlamp, with an alternate optical arrangement whereby the control of the beam would be achieved solely by means of the geometry of the surface of the reflector, subject to a requirement of smooth-surface continuity; replacing the outer lens with a clear plastic cover having no beam-forming function. To this end the far-field intensity distribution produced by the 9007 bulb was measured at the low-beam setting. These measurements were then used to develop a light-source model for use in ray tracing simulations of candidate reflector geometries. An objective function was developed to compare candidate beam patterns with the desired beam pattern. Functional forms for the 3D reflector geometry were developed with free parameters to be subsequently optimized. A solution was sought meeting the detailed US SAE/DOT constraints for minimum and maximum permissible levels of illumination in the different portions of the beam pattern. Simulated road scenes were generated by Ford Motor Company to compare the illumination properties of the new design with those of the original Grand Marquis headlamp.

Precision segmented reflector, figure verification sensor

NASA Technical Reports Server (NTRS)

Manhart, Paul K.; Macenka, Steve A.

1989-01-01

The Precision Segmented Reflector (PSR) program currently under way at the Jet Propulsion Laboratory is a test bed and technology demonstration program designed to develop and study the structural and material technologies required for lightweight, precision segmented reflectors. A Figure Verification Sensor (FVS) which is designed to monitor the active control system of the segments is described, a best fit surface is defined, and an image or wavefront quality of the assembled array of reflecting panels is assessed

Effect of Facet Displacement on Radiation Field and Its Application for Panel Adjustment of Large Reflector Antenna

NASA Astrophysics Data System (ADS)

Wang, Wei; Lian, Peiyuan; Zhang, Shuxin; Xiang, Binbin; Xu, Qian

2017-05-01

Large reflector antennas are widely used in radars, satellite communication, radio astronomy, and so on. The rapid developments in these fields have created demands for development of better performance and higher surface accuracy. However, low accuracy and low efficiency are the common disadvantages for traditional panel alignment and adjustment. In order to improve the surface accuracy of large reflector antenna, a new method is presented to determinate panel adjustment values from far field pattern. Based on the method of Physical Optics (PO), the effect of panel facet displacement on radiation field value is derived. Then the linear system is constructed between panel adjustment vector and far field pattern. Using the method of Singular Value Decomposition (SVD), the adjustment value for all panel adjustors are obtained by solving the linear equations. An experiment is conducted on a 3.7 m reflector antenna with 12 segmented panels. The results of simulation and test are similar, which shows that the presented method is feasible. Moreover, the discussion about validation shows that the method can be used for many cases of reflector shape. The proposed research provides the instruction to adjust surface panels efficiently and accurately.

Extreme Precision Antenna Reflector Study Results

NASA Technical Reports Server (NTRS)

Sharp, G. R.; Gilger, L. D.; Ard, K. E.

1985-01-01

Thermal and mechanical distortion degrade the RF performance of antennas. The complexity of future communications antennas requires accurate, dimensionally stable antenna reflectors and structures built from materials other than those currently used. The advantages and disadvantages of using carbon fibers in an epoxy matrix are reviewed as well as current reflector fabrications technology and adjustment. The manufacturing sequence and coefficient of thermal expansion of carbon fiber/borosilicate glass composites is described. The construction of a parabolic reflector from this material and the assembling of both reflector and antenna are described. A 3M-aperture-diameter carbon/glass reflector that can be used as a subassembly for large reflectors is depicted. The deployment sequence for a 10.5M-aperture-diameter antenna, final reflector adjustment, and the deployment sequence for large reflectors are also illustrated.

Effect of back reflectors on photon absorption in thin-film amorphous silicon solar cells

NASA Astrophysics Data System (ADS)

Hossain, Mohammad I.; Qarony, Wayesh; Hossain, M. Khalid; Debnath, M. K.; Uddin, M. Jalal; Tsang, Yuen Hong

2017-10-01

In thin-film solar cells, the photocurrent conversion productivity can be distinctly boosted-up utilizing a proper back reflector. Herein, the impact of different smooth and textured back reflectors was explored and effectuated to study the optical phenomena with interface engineering strategies and characteristics of transparent contacts. A unique type of wet-chemically textured glass-substrate 3D etching mask used in superstrate (p-i-n) amorphous silicon-based solar cell along with legitimated back reflector permits joining the standard light-trapping methodologies, which are utilized to upgrade the energy conversion efficiency (ECE). To investigate the optical and electrical properties of solar cell structure, the optical simulations in three-dimensional measurements (3D) were performed utilizing finite-difference time-domain (FDTD) technique. This design methodology allows to determine the power losses, quantum efficiencies, and short-circuit current densities of various layers in such solar cell. The short-circuit current densities for different reflectors were varied from 11.50 to 13.27 and 13.81 to 16.36 mA/cm2 for the smooth and pyramidal textured solar cells, individually. Contrasted with the comparable flat reference cell, the short-circuit current density of textured solar cell was increased by around 24%, and most extreme outer quantum efficiencies rose from 79 to 86.5%. The photon absorption was fundamentally improved in the spectral region from 600 to 800 nm with no decrease of photocurrent shorter than 600-nm wavelength. Therefore, these optimized designs will help to build the effective plans next-generation amorphous silicon-based solar cells.

Optical scattering from rough-rolled aluminum surfaces.

PubMed

Rönnelid, M; Adsten, M; Lindström, T; Nostell, P; Wäckelgård, E

2001-05-01

Bidirectional, angular resolved scatterometry was used to evaluate the feasibility of using rolled aluminum as reflectors in solar thermal collectors and solar cells. Two types of rolled aluminum with different surface roughnesses were investigated. The results show that the smoother of the two samples [rms height, (0.20 ? 0.02) mum] can be used as a nonimaging, concentrating reflector with moderate reflection losses compared with those of optically smooth aluminum reflectors. The sample with the rougher surface [rms height, (0.6 ? 0.1) mum] is not suitable as a concentrating element but can be used as planar reflectors. The orientation of the rolling grooves is then of importance for minimizing reflection losses in the system.

Uniform sunlight concentration reflectors for photovoltaic cells.

PubMed

Rabady, Rabi Ibrahim

2014-03-20

Sunlight concentration is essential to reach high temperatures of a working fluid in solar-thermal applications and to reduce the cost of photovoltaic (PV) electricity generation systems. Commonly, sunlight concentration is realized by parabolic or cylindrical reflectors, which do not provide uniform concentration on the receiver finite surface. Uniform concentration of sunlight is favored especially for the PV conversion applications since it not only enhances the conversion efficiency of sunlight but also reduces the thermal variations along the receiving PV cell, which can be a performance and life-span limiting factor. In this paper a reflector profile that uniformly infiltrates the concentrated sunlight into the receiving unit is attempted. The new design accounts for all factors that contribute to the nonuniform concentration, like the reflector curvature, which spatially reflects the sunlight nonuniformly, and the angular dependency of both the reflector reflectivity and the sunlight transmission through the PV cell.

The Planck Telescope reflectors

NASA Astrophysics Data System (ADS)

Stute, Thomas

2004-09-01

The mechanical division of EADS-Astrium GmbH, Friedrichshafen is currently engaged with the development, manufacturing and testing of the advanced dimensionally stable composite reflectors for the ESA satellite borne telescope Planck. The objective of the ESA mission Planck is to analyse the first light that filled the universe, the cosmic microwave background radiation. Under contract of the Danish Space Research Institute and ESA EADS-Astrium GmbH is developing the all CFRP primary and secondary reflectors for the 1.5-metre telescope which is the main instrument of the Planck satellite. The operational frequency ranges from to 25 GHz to 1000 GHz. The demanding high contour accuracy and surface roughness requirements are met. The design provides the extreme dimensional stability required by the cryogenic operational environment at around 40 K. The elliptical off-axis reflectors display a classical lightweight sandwich design with CFRP core and facesheets. Isostatic mounts provide the interfaces to the telescope structure. Protected VDA provides the reflecting surface. The manufacturing is performed at the Friedrichshafen premises of EADS-Space Transportation GmbH, the former Dornier composite workshops. Advanced manufacturing technologies like true angle lay-up by CNC fibre placement and filament winding are utilized. The protected coating is applied at the CAHA facilities at the Calar Alto Observatory, Spain. The exhaustive environmental testing is performed at the facilities of IABG, Munich (mechanical testing) and for the cryo-optical tests at CSL Liege. The project is in advanced state with both Qualification Models being under environmental testing. The flight models will be delivered in 2004. The paper gives an overview over the requirements and the main structural features how these requirements are met. Special production aspects and available test results are reported.

Innovative design of parabolic reflector light guiding structure

NASA Astrophysics Data System (ADS)

Whang, Allen J.; Tso, Chun-Hsien; Chen, Yi-Yung

2008-02-01

Due to the idea of everlasting green architecture, it is of increasing importance to guild natural light into indoors. The advantages are multifold - to have better color rendering index, excellent energy savings from environments viewpoints and make humans more healthy, etc. Our search is to design an innovative structure, to convert outdoor sun light impinges on larger surfaces, into near linear light beam sources, later convert this light beam into near point sources which enters the indoor spaces then can be used as lighting sources indoors. We are not involved with the opto-electrical transformation, to the guild light into to the building, to perform the illumination, as well as the imaging function. Because non-imaging optics, well known for apply to the solar concentrators, that can use non-imaging structures to fulfill our needs, which can also be used as energy collectors in solar energy devices. Here, we have designed a pair of large and small parabolic reflector, which can be used to collect daylight and change area from large to small. Then we make a light-guide system that is been designed by us use of this parabolic reflector to guide the collection light, can pick up the performance for large surface source change to near linear source and a larger collection area.

Dynamics and Control of Tethered Antennas/Reflectors in Orbit

DTIC Science & Technology

1992-02-01

reflector system. The optimal linear quadratic Gaussian (LQG) digital con- trol of the orbiting tethered antenna/reflector system is analyzed. The...flexibility of both the antenna and the tether are included in this high order system model. With eight point actuators optimally positioned together with...able to maintain satisfactory pointing accuracy for low and moderate altitude orbits under the influence of solar pressure. For the higher altitudes a

Planar shock reflection on a wedged concave reflector

NASA Astrophysics Data System (ADS)

Yu, Fan-Ming; Sheu, Kuen-Dong

2001-04-01

The investigation of shock reflection and shock diffraction phenomena upon a wedged concave reflector produced by a planar incident shock wave has been done in the shock tube facility of Institute of Aeronautics and Astronautics, National Cheng- Kung University. The experiment proceeds upon three wedged concave reflectors models the upper and lower wedge angles arrangement of them are (50 degrees, 50 degrees) - 35 degrees, 35 degrees) and (50 degrees, 35 degrees), respectively. They were tested at Mach numbers of 1.2 - 1.65 and 2.0. On the first reflector, following the regular reflection on the 50 degree-wedged surface by the incident shock wave, a Mach shock diffraction behavior has been observed as shock moves outward from the apex of the reflector. On the apex of the reflector, it behaviors as a sector of the blast shock moving on a diverging channel. On the shadowgraph pictures it has been observed there exists a pattern of gas dynamics focus upon the second reflector. The Mach reflection from the 35 degree- wedged surface as being generated by the planar incident shock wave, on which the overlapping of the two triple points from both wedged surface offers the focusing mechanism. The shock interference, which proceeds by the Mach shock reflection and the regular shock diffraction from the reflector, generates a very complicate rolling-up of slip lines system. On the third reflector, the mixed shock interference behavior has been observed of which two diffraction shocks from concave 50 degree-wedged surface and 35 degree-wedged surface interfere with each other. The measurement of the peak pressure along a ray from the model apex parallel to incident shock direction indicates that the measured maximum pressure rising is larger near the apex of the reflector. Considering the measured maximum pressure increment due to the reflection shocks indicate that the wave strength upon large apex angle reflector is greater than it is upon small apex angle reflector

Fiber optic sensor based on reflectivity configurations to detect heart rate

NASA Astrophysics Data System (ADS)

Yunianto, M.; Marzuki, A.; Riyatun, R.; Lestari, D.

2016-11-01

Research of optical fiber-based heart rate detection sensor has been conducted using the reflection configurationon the thorax motion modified. Optical fiber used in this research was Plastic Optical Fiber (POF) with a diameter of 0.5. Optical fiber system is made with two pieces of fiber, the first fiber is to serve as a transmitter transmitting light from the source to the reflector membrane, the second fiber serves as a receiver. One of the endsfrom the two fibersis pressed and positioned perpendicular of reflector membrane which is placed on the surface of the chest. The sensor works on the principle of intensity changes captured by the receiver fiber when the reflector membrane gets the vibe from the heart. The light source used is in the form of Light Emitting Diode (LED) and Light Dependent Resistor (LDR) as a light sensor. Variations are performed on the reflector membrane diameter. The light intensity received by the detector increases along with the increasing width of the reflector membrane diameter. The results show that this sensor can detect the harmonic peak at a frequency of 1.5 Hz; 7.5 Hz; 10.5 Hz; and 22.5 Hz in a healthy human heart with an average value of Beat Per Minute (BPM) by 78 times, a prototype sensor that is made can work and function properly.

The optical design and simulation of the collimated solar simulator

NASA Astrophysics Data System (ADS)

Zhang, Jun; Ma, Tao

2018-01-01

The solar simulator is a lighting device that can simulate the solar radiation. It has been widely used in the testing of solar cells, satellite space environment simulation and ground experiment, test and calibration precision of solar sensor. The solar simulator mainly consisted of short—arc xenon lamp, ellipsoidal reflectors, a group of optical integrator, field stop, aspheric folding mirror and collimating reflector. In this paper, the solar simulator's optical system basic size are given by calculation. Then the system is optically modeled with the Lighttools software, and the simulation analysis on solar simulator using the Monte Carlo ray -tracing technique is conducted. Finally, the simulation results are given quantitatively by diagrammatic form. The rationality of the design is verified on the basis of theory.

Atmospheric turbulence effects measured along horizontal-path optical retro-reflector links.

PubMed

Mahon, Rita; Moore, Christopher I; Ferraro, Mike; Rabinovich, William S; Suite, Michele R

2012-09-01

The scintillation measured over close-to-ground retro-reflector links can be substantially enhanced due to the correlations experienced by both the direct and reflected echo beams. Experiments were carried out at China Lake, California, over a variety of ranges. The emphasis in this paper is on presenting the data from the 1.1 km retro-reflecting link that was operated for four consecutive days. The dependence of the measured irradiance flux variance on the solar fluence and on the temperature gradient above the ground is presented. The data are consistent with scintillation minima near sunrise and sunset, rising rapidly during the day and saturating at irradiance flux variances of ~10. Measured irradiance probability distributions of the retro-reflected beam are compared with standard probability density functions. The ratio of the irradiance flux variances on the retro-reflected to the direct, single-pass case is investigated with two data sets, one from a monostatic system and the other using an off-axis receiver system.

Optical coatings on polymers

NASA Astrophysics Data System (ADS)

Bauer, Thomas

2005-09-01

Optical transparent polymers are used for technical optics for more than 50 years and currently replace glass as optical material in several application fields. Optical functional coatings like mirrors, filters, beam splitters and anti-reflection coatings gain increasingly in importance. New light sources and head mounted systems need light and effective reflector designs. The paper gives an overview about vacuum coating technologies for metal and dielectric layers on polymers for technical optics. Especially for polymers controlling the complete process chain from injection moulding to storing, coating and shipping decides on the technological and commercial success.

The precision segmented reflectors: Moderate mission figure control subsystem

NASA Technical Reports Server (NTRS)

Sevaston, G.; Redding, D.; Lau, K.; Breckenridge, W.; Levine, B.; Nerheim, N.; Sirlin, S.; Kadogawa, H.

1991-01-01

A system concept for a space based segmented reflector telescope figure control subsystem is described. The concept employs a two phase architecture in which figure initialization and figure maintenance are independent functions. Figure initialization is accomplished by image sharpening using natural reference targets. Figure maintenance is performed by monitoring the relative positions and alignments of the telescope components using an optical truss. Actuation is achieved using precision positioners. Computer simulation results of figure initialization by pairwise segment coalignment/cophasing and simulated annealing are presented along with figure maintenance results using a wavefront error regulation algorithm. Both functions are shown to perform at acceptable levels for the class of submillimeter telescopes that are serving as the focus of this technology development effort. Component breadboard work as well as plans for a system testbed are discussed.

System overview on electromagnetic compensation for reflector antenna surface distortion

NASA Technical Reports Server (NTRS)

Acosta, R. J.; Zaman, A. J.; Terry, J. D.

1993-01-01

The system requirements and hardware implementation for electromagnetic compensation of antenna performance degradations due to thermal effects was investigated. Future commercial space communication antenna systems will utilize the 20/30 GHz frequency spectrum and support very narrow multiple beams (0.3 deg) over wide angle field of view (15-20 beamwidth). On the ground, portable and inexpensive very small aperture terminals (VSAT) for transmitting and receiving video, facsimile and data will be employed. These types of communication system puts a very stringent requirement on spacecraft antenna beam pointing stability (less than .01 deg), high gain (greater than 50 dB) and very lowside lobes (less than -25 dB). Thermal analysis performed on the advanced communication technology satellite (ACTS) has shown that the reflector surfaces, the mechanical supporting structures and metallic surfaces on the spacecraft body will distort due thermal effects from a varying solar flux. The antenna performance characteristics (e.g., pointing stability, gain, side lobe, etc.) will degrade due to thermal distortion in the reflector surface and supporting structures. Specifically, antenna RF radiation analysis has shown that pointing error is the most sensitive antenna performance parameter to thermal distortions. Other antenna parameters like peak gain, cross polarization level (beam isolation), and side lobe level will also degrade with thermal distortions. In order to restore pointing stability and in general antenna performance several compensation methods were proposed. In general these compensation methods can be classified as being either of mechanical or electromagnetic type. This paper will address only the later one. In this approach an adaptive phased array antenna feed is used to compensate for the antenna performance degradation. Extensive work has been devoted to demonstrate the feasibility of adaptive feed compensation on space communication antenna systems. This

A satellite-tracking millimeter-wave reflector antenna system for mobile satellite-tracking

NASA Technical Reports Server (NTRS)

Densmore, Arthur C. (Inventor); Jamnejad, Vahraz (Inventor); Woo, Kenneth E. (Inventor)

1995-01-01

A miniature dual-band two-way mobile satellite tracking antenna system mounted on a movable ground vehicle includes a miniature parabolic reflector dish having an elliptical aperture with major and minor elliptical axes aligned horizontally and vertically, respectively, to maximize azimuthal directionality and minimize elevational directionality to an extent corresponding to expected pitch excursions of the movable ground vehicle. A feed-horn has a back end and an open front end facing the reflector dish and has vertical side walls opening out from the back end to the front end at a lesser horn angle and horizontal top and bottom walls opening out from the back end to the front end at a greater horn angle. An RF circuit couples two different signal bands between the feed-horn and the user. An antenna attitude controller maintains an antenna azimuth direction relative to the satellite by rotating it in azimuth in response to sensed yaw motions of the movable ground vehicle so as to compensate for the yaw motions to within a pointing error angle. The controller sinusoidally dithers the antenna through a small azimuth dither angle greater than the pointing error angle while sensing a signal from the satellite received at the reflector dish, and deduces the pointing angle error from dither-induced fluctuations in the received signal.

Study of retro reflector array for the polarimeter-interferometer system on EAST Tokamak

NASA Astrophysics Data System (ADS)

Lan, T.; Wang, S. X.; Liu, H. Q.; Liu, J.; Jie, Y. X.; Zou, Z. Y.; Li, W. M.; Gao, X.; Qin, H.

2015-12-01

In this paper, we experimentally verify the feasibility of replacing individual retro reflectors (RRs) with retro reflector array (RRA) in EAST POlarimeter/INTerferometer (POINT) system, by considering mode transformation and power wastage. Being exposed to plasma environment directly, RRs have risks of deformation, erosion and deposition. RRA is preferable because it can be installed within a smaller space and provide a gap of several centimeters for the shutter design. This protective structure can reduce the cost of device maintenance and bring down system errors. According to Helmholtz-Kirchhoff integral theorem, the optimized incident diameter for the RRA, constituted by seven hexagonal RR cells, is 40 mm in POINT system. The corresponding bench tests are carried out by measuring the propagation properties of reflected beams by plane RRA for perpendicular incidence and reflected beams by terrace RRA for oblique incidence. The experimental results illustrate that RRA can be satisfactorily applied in POINT system at the optimized incident diameter. In view of the energy wastage caused by plasma film coating, it is found that RRA has more advantages for diagnostics using shorter wavelengths, such as the case in ITER.

Subreflector extension for improved efficiencies in Cassegrain antennas - GTD/PO analysis. [Geometrical Theory of Diffraction/Physical Optics

NASA Technical Reports Server (NTRS)

Rahmat-Samii, Yahya

1986-01-01

Both offset and symmetric Cassegrain reflector antennas are used in satellite and ground communication systems. It is known that the subreflector diffraction can degrade the performance of these reflectors. A geometrical theory of diffraction/physical optics analysis technique is used to investigate the effects of the extended subreflector, beyond its optical rim, on the reflector efficiency and far-field patterns. Representative numerical results are shown for an offset Cassegrain reflector antenna with different feed illumination tapers and subreflector extensions. It is observed that for subreflector extensions as small as one wavelength, noticeable improvements in the overall efficiencies can be expected. Useful design data are generated for the efficiency curves and far-field patterns.

Global search and rescue - A new concept. [orbital digital radar system with passive reflectors

NASA Technical Reports Server (NTRS)

Sivertson, W. E., Jr.

1976-01-01

A new terrestrial search and rescue concept is defined embodying the use of simple passive radiofreqeuncy reflectors in conjunction with a low earth-orbiting, all-weather, synthetic aperture radar to detect, identify, and position locate earth-bound users in distress. Users include ships, aircraft, small boats, explorers, hikers, etc. Airborne radar tests were conducted to evaluate the basic concept. Both X-band and L-band, dual polarization radars were operated simultaneously. Simple, relatively small, corner-reflector targets were successfully imaged and digital data processing approaches were investigated. Study of the basic concept and evaluation of results obtained from aircraft flight tests indicate an all-weather, day or night, global search and rescue system is feasible.

Corrosion protection for silver reflectors

DOEpatents

Arendt, Paul N.; Scott, Marion L.

1991-12-31

A method of protecting silver reflectors from damage caused by contact with gaseous substances which are often present in the atmosphere and a silver reflector which is so protected. The inventive method comprises at least partially coating a reflector with a metal oxide such as aluminum oxide to a thickness of 15 .ANG. or less.

Beam-Steerable Flat-Panel Reflector Antenna

NASA Technical Reports Server (NTRS)

Lee, Choon Sae; Lee, Chanam; Miranda, Felix A.

2005-01-01

Many space applications require a high-gain antenna that can be easily deployable in space. Currently, the most common high-gain antenna for space-born applications is an umbrella-type reflector antenna that can be folded while being lifted to the Earth orbit. There have been a number of issues to be resolved for this type of antenna. The reflecting surface of a fine wire mesh has to be light in weight and flexible while opening up once in orbit. Also the mesh must be a good conductor at the operating frequency. In this paper, we propose a different type of high-gain antenna for easy space deployment. The proposed antenna is similar to reflector antennas except the curved main reflector is replaced by a flat reconfigurable surface for easy packing and deployment in space. Moreover it is possible to steer the beam without moving the entire antenna system.

Deployable reflector configurations

NASA Astrophysics Data System (ADS)

Meinel, A. B.; Meinel, M. P.; Woolf, N. J.

Both the theoretical reasons for considering a non-circular format for the Large Deployable Reflector, and a potentially realizable concept for such a device, are discussed. The optimum systems for diffraction limited telescopes with incoherent detection have either a single filled aperture, or two such apertures as an interferometer to synthesize a larger aperture. For a single aperture of limited area, a reflector in the form of a slot can be used to give increased angular resolution. It is shown how a 20 x 8 meter telescope can be configured to fit the Space Shuttle bay, and deployed with relatively simple operations. The relationship between the sunshield design and the inclination of the orbit is discussed. The possible use of the LDR as a basic module to permit the construction of supergiant space telescopes and interferometers both for IR/submm studies and for the entire ultraviolet through mm wave spectral region is discussed.

Optical multilayers with an amorphous fluoropolymer

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

Chow, R.; Loomis, G.E.; Lindsey, E.F.

1994-07-01

Multilayered coatings were made by physical vapor deposition (PVD) of a perfluorinated amorphous polymer, Teflon AF2400, together with other optical materials. A high reflector at 1064 run was made with ZnS and AF2400. An all-organic 1064-nm reflector was made from AF2400 and polyethylene. Oxide (HfO{sub 2}, SiO{sub 2}) compatibility was also tested. Each multilayer system adhered to itself. The multilayers were influenced by coating stress and unintentional temperature rises during PVD deposition.

Large Deployable Reflector Science and Technology Workshop. Volume 3: Systems and Technology Assessment. Introduction

NASA Technical Reports Server (NTRS)

1984-01-01

The Large Deployable Reflector (LDR), a proposed 20 m diameter telescope designed for infrared and submillimeter astronomical measurements from space, is discussed in terms of scientific purposes, capabilities, current status, and history of development. The LDR systems goals and functional/telescope requirements are enumerated.

Lamp system with conditioned water coolant and diffuse reflector of polytetrafluorethylene(PTFE)

DOEpatents

Zapata, Luis E.; Hackel, Lloyd

1999-01-01

A lamp system with a very soft high-intensity output is provided over a large area by water cooling a long-arc lamp inside a diffuse reflector of polytetrafluorethylene (PTFE) and titanium dioxide (TiO.sub.2) white pigment. The water is kept clean and pure by a one micron particulate filter and an activated charcoal/ultraviolet irradiation system that circulates and de-ionizes and biologically sterilizes the coolant water at all times, even when the long-arc lamp is off.

Technical-economic feasibility of orbiting sunlight reflectors

NASA Astrophysics Data System (ADS)

Alferov, Z.; Minin, V.

1986-02-01

The use of deflectors in orbit as a means of providing artificial illumination is examined. Considerations of technical and economic feasibility are addressed. Three main areas of application are distinguished: reflecting sunlight onto the surface of the Earth; concentration of the flow of solar energy on an orbiting receiver; and retransmission of optical radiation. The advantages of the artificial Earth illumination application of the orbiting reflector scheme in terms of energy savings in lighting cities, and additional daylight time for critical periods of farming operations are discussed.

Spatially continuous distributed fiber optic sensing using optical carrier based microwave interferometry.

PubMed

Huang, Jie; Lan, Xinwei; Luo, Ming; Xiao, Hai

2014-07-28

This paper reports a spatially continuous distributed fiber optic sensing technique using optical carrier based microwave interferometry (OCMI), in which many optical interferometers with the same or different optical path differences are interrogated in the microwave domain and their locations can be unambiguously determined. The concept is demonstrated using cascaded weak optical reflectors along a single optical fiber, where any two arbitrary reflectors are paired to define a low-finesse Fabry-Perot interferometer. While spatially continuous (i.e., no dark zone), fully distributed strain measurement was used as an example to demonstrate the capability, the proposed concept may also be implemented on other types of waveguide or free-space interferometers and used for distributed measurement of various physical, chemical and biological quantities.

A geological history of reflecting optics

PubMed Central

Parker, Andrew Richard

2005-01-01

Optical reflectors in animals are diverse and ancient. The first image-forming eye appeared around 543 million years ago. This introduced vision as a selection pressure in the evolution of animals, and consequently the evolution of adapted optical devices. The earliest known optical reflectors—diffraction gratings—are 515 Myr old. The subsequent fossil record preserves multilayer reflectors, including liquid crystals and mirrors, ‘white’ and ‘blue’ scattering structures, antireflective surfaces and the very latest addition to optical physics—photonic crystals. The aim of this article is to reveal the diversity of reflecting optics in nature, introducing the first appearance of some reflector types as they appear in the fossil record as it stands (which includes many new records) and backdating others in geological time through evolutionary analyses. This article also reveals the commercial potential for these optical devices, in terms of lessons from their nano-level designs and the possible emulation of their engineering processes—molecular self-assembly. PMID:16849159

Tracking reflector assembly for a skylight

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

Dominquez, R.L.

1984-02-07

A tracking reflector assembly for a skylight includes a ring-shaped base member rotatably supported above the skylight by a plurality of rollers which engage a channel formed within an annular wall of the ring. A reflector is pivotally coupled to the ring for reflecting light into the skylight to supplement light which strikes the skylight directly. A vertical drive motor operates in response to a pair of photosensors for raising and lowering the reflector to follow changes in the angular elevation of the sun. The ring-shaped base member includes a toothed lower surface engaged by a gear coupled to amore » horizontal drive motor for rotating the ring-shaped base member in response to a third photosensor for following east-to-west movement of the sun. Each of the aforementioned photosensors is normally shaded and actuates the associated drive motor only when being struck by direct sunlight. A vertical limit switch limits the amount by which the reflector may be pivotally raised to avoid reflecting midday summer sunlight into the skylight. Another switch is responsive to closure of the reflector over the base member for preventing the vertical drive motor from attempting to further pivot the reflector downwardly. A fourth photosensor senses darkness resulting from sunset or heavy overcast conditions for pivoting the reflector downwardly and returning the base member and reflector to an easterly direction. A limit switch senses the return of the base member to the full east position for terminating actuation of the horizontal drive motor. A user operated switch selectively enables the tracking reflector assembly to operate automatically or causes the reflector to be lowered and the base member to be returned to the full east position until the user again enables the automatic control circuitry.« less

Back surface reflectors for solar cells

NASA Technical Reports Server (NTRS)

Chai, A. T.

1980-01-01

Sample solar cells were fabricated to study the effects of various back surface reflectors on the device performance. They are typical 50 micrometers thick, space quality, silicon solar cells except for variations of the back contact configuration. The back surfaces of the sample cells are polished to a mirror like finish, and have either conventional full contacts or grid finger contacts. Measurements and evaluation of various metallic back surface reflectors, as well as cells with total internal reflection, are presented. Results indicate that back surface reflectors formed using a grid finger back contact are more effective reflectors than cells with full back metallization and that Au, Ag, or Cu are better back surface reflector metals than Al.

Solar thermal collectors using planar reflector

NASA Technical Reports Server (NTRS)

Espy, P. N.

1978-01-01

Specular reflectors have been used successfully with flat-plate collectors to achieve exceptionally high operating temperatures and high delivered energy per unit collector area. Optimal orientation of collectors and reflectors can result in even higher performance with an improved relationship between energy demand and supply. This paper reports on a study providing first order optimization of collector-reflector arrays in which single- and multiple-faceted reflectors in fixed or singly adjustable configurations provide delivered energy maxima in either summer or winter.

Modulating Retro-Reflectors: Technology, Link Budgets and Applications

NASA Technical Reports Server (NTRS)

Salas, Alberto Guillen; Stupl, Jan; Mason, James

2012-01-01

Satellite communications systems today -- usually radio frequency (RF) -- tend to have low data rates and use a lot of on-board power. For CubeSats, communications often dominate the power budget. We investigate the use of modulating retro-reflectors (MRRs), previously demonstrated on the ground, for high data-rate communication downlinks from small satellites. A laser ground station would illuminate a retro-reflector on-board the satellite while an element in the retro-reflector modulates the intensity of the reflected signal, thereby encoding a data stream on the returning beam. A detector on the ground receives the data, keeping the complex systems and the vast majority of power consumption on the ground. Reducing the power consumption while increasing data rates would relax constraints on power budgets for small satellites, leaving more power available for payloads. In the future, this could enable the use of constellations of nano-satellites for a variety of missions, possibly leading to a paradigm shift in small satellite applications.

A method to design blended rolled edges for compact range reflectors

NASA Technical Reports Server (NTRS)

Gupta, Inder J.; Burnside, Walter D.

1989-01-01

A method to design blended rolled edges for arbitrary rim shape compact range reflectors is presented. The reflectors may be center-fed or offset-fed. The method leads to rolled edges with minimal surface discontinuities. It is shown that the reflectors designed using the prescribed method can be defined analytically using simple expressions. A procedure to obtain optimum rolled edges parameter is also presented. The procedure leads to blended rolled edges that minimize the diffracted fields emanating from the junction between the paraboloid and the rolled edge surface while satisfying certain constraints regarding the reflector size and the minimum operating frequency of the system.

A method to design blended rolled edges for compact range reflectors

NASA Technical Reports Server (NTRS)

Gupta, Inder J.; Ericksen, Kurt P.; Burnside, Walter D.

1990-01-01

A method to design blended rolled edges for arbitrary rim shape compact range reflectors is presented. The reflectors may be center-fed or offset-fed. The method leads to rolled edges with minimal surface discontinuities. It is shown that the reflectors designed using the prescribed method can be defined analytically using simple expressions. A procedure to obtain optimum rolled edges parameters is also presented. The procedure leads to blended rolled edges that minimize the diffracted fields emanating from the junction between the paraboloid and the rolled edge surface while satisfying certain constraints regarding the reflector size and the minimum operating frequency of the system.

High-Precision Shape Control of In-Space Deployable Large Membrane/Thin-Shell Reflectors

NASA Technical Reports Server (NTRS)

Watkins, Ronald; Goebel, Dan; Hofer, Richard

2010-01-01

This innovation has been developed to improve the resolutions of future spacebased active and passive microwave antennas for earth-science remote sensing missions by maintaining surface figure precisions of large membrane/thin-shell reflectors during orbiting. The intention is for these sensing instruments to be deployable at orbit altitudes one or two orders of magnitude higher than Low Earth Orbit (LEO), but still being able to acquire measurements at spatial resolution and sensitivity similar to those of LEO. Because active and passive microwave remote sensors are able to penetrate through clouds to acquire vertical profile measurements of geophysical parameters, it is desirable to elevate them to the higher orbits to obtain orbital geometries that offer large spatial coverage and more frequent observations. This capability is essential for monitoring and for detailed understanding of the life cycles of natural hazards, such as hurricanes, tropical storms, flash floods, and tsunamis. Major components of this high-precision antenna-surface-control system include a membrane/thin shell reflector, a metrology sensor, a controller, actuators, and corresponding power amplifier and signal conditioning electronics (see figure). Actuators are attached to the back of the reflector to produce contraction/ expansion forces to adjust the shape of the thin-material reflector. The wavefront-sensing metrology system continuously measures the surface figure of the reflector, converts the surface figure to digital data and feeds the data to the controller. The controller determines the control parameters and generates commands to the actuator system. The flexible, piezoelectric polymer actuators are thus activated, providing the control forces needed to correct any distortions that exist in the reflector surface. Piezoelectric polymer actuators are very thin and flexible. They can be implemented on the back of the membrane/thin-shell reflector without introducing significant

Don't Forget the Reflector.

ERIC Educational Resources Information Center

Morton, N.

1991-01-01

Various modes of reflection are classified and practical examples of devices, such as cat's eyes, are discussed. Typical light rays are traced through several systems, providing exercises with varying degrees of difficulty. Corner-cube retroreflectors, glass spheres, reflecting luminaries, light concentrators, parabolic reflectors, and off-set and…

Corner reflector SAR interferometry as an element of a landslide early warning system

NASA Astrophysics Data System (ADS)

Singer, J.; Riedmann, M.; Lang, O.; Anderssohn, J.; Thuro, K.; Wunderlich, Th.; Heunecke, O.; Minet, Ch.

2012-04-01

The development of efficient and cost-effective landslide monitoring techniques is the central aim of the alpEWAS research project (www.alpewas.de). Within the scope of the project a terrestrial geosensor network on a landslide site in the Bavarian Alps has been set up, consisting of low cost GNSS with subcentimeter precision, time domain reflectometry (TDR) and video tacheometry (VTPS). To increase the spatial sampling, 16 low-cost Radar Corner Reflectors (CRs) were installed on the site in 2011. The CRs are to reflect radar signals back to the TerraSAR-X radar satellite, allowing for precise displacement measurements. The subject of this study is the application of the CR SAR Interferometry (CRInSAR) technique, and the integration of the derived motion field into an early warning system for landslide monitoring based on terrestrial measurements. An accurate validation data set is realized independently of the monitoring network using millimeter precision GNSS and tacheometer measurements. The 12 CRs from Astrium Geo-Information Services employed over the test site were specifically designed for TerraSAR-X satellite passes. They are made of concrete with integrated metal plates weighing about 80 to 100 kg. They are of triangular trihedral shape with minimal dimensions to obtain a Radar Cross Section 100 times stronger than that of the surrounding area. The concrete guarantees stability against harsh weather conditions, and robustness with respect to vandalism or theft. In addition, the Technical University of Munich (TUM) and the German Aerospace Center (DLR) installed another four CRs made entirely out of aluminum, with the TUM reflectors being of similar minimum size than the Astrium reflectors. Three CRs were placed on assumed stable ground outside the slope area and shall act as reference reflectors. Since the installation date of most CRs (25/08/2011), TerraSAR-X HighResolution SpotLight data have been repeatedly acquired from ascending orbit over the test

K- and Ka-band mobile-vehicular satellite-tracking reflector antenna system for the NASA ACTS mobile terminal

NASA Technical Reports Server (NTRS)

Densmore, Art; Jamnejad, Vahraz; Wu, T. K.; Woo, Ken

1993-01-01

This paper describes the development of the K- and Ka-band mobile-vehicular satellite-tracking reflector antenna system for NASA's ACTS Mobile Terminal (AMT) project. ACTS is NASA's Advanced Communications Technology Satellites. The AMT project will make the first experimental use of ACTS soon after the satellite is operational, to demonstrate mobile communications via the satellite from a van on the road. The AMT antenna system consists of a mechanically steered small reflector antenna, using a shared aperture for both frequency bands and fitting under a radome of 23 cm diameter and 10 cm height, and a microprocessor controlled antenna controller that tracks the satellite as the vehicle moves about. The RF and mechanical characteristics of the antenna and the antenna tracking control system are discussed. Measurements of the antenna performance are presented.

Photogrammetry research for FAST eleven-meter reflector panel surface shape measurement

NASA Astrophysics Data System (ADS)

Zhou, Rongwei; Zhu, Lichun; Li, Weimin; Hu, Jingwen; Zhai, Xuebing

2010-10-01

In order to design and manufacture the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) active reflector measuring equipment, measurement on each reflector panel surface shape was presented, static measurement of the whole neutral spherical network of nodes was performed, real-time dynamic measurement at the cable network dynamic deformation was undertaken. In the implementation process of the FAST, reflector panel surface shape detection was completed before eleven-meter reflector panel installation. Binocular vision system was constructed based on the method of binocular stereo vision in machine vision, eleven-meter reflector panel surface shape was measured with photogrammetry method. Cameras were calibrated with the feature points. Under the linearity camera model, the lighting spot array was used as calibration standard pattern, and the intrinsic and extrinsic parameters were acquired. The images were collected for digital image processing and analyzing with two cameras, feature points were extracted with the detection algorithm of characteristic points, and those characteristic points were matched based on epipolar constraint method. Three-dimensional reconstruction coordinates of feature points were analyzed and reflective panel surface shape structure was established by curve and surface fitting method. The error of reflector panel surface shape was calculated to realize automatic measurement on reflector panel surface shape. The results show that unit reflector panel surface inspection accuracy was 2.30mm, within the standard deviation error of 5.00mm. Compared with the requirement of reflector panel machining precision, photogrammetry has fine precision and operation feasibility on eleven-meter reflector panel surface shape measurement for FAST.

In-line optical fiber metallic mirror reflector for monolithic common path optical coherence tomography probes.

PubMed

Singh, Kanwarpal; Reddy, Rohith; Sharma, Gargi; Verma, Yogesh; Gardecki, Joseph A; Tearney, Guillermo

2018-03-01

Endoscopic optical coherence tomography probes suffer from various artifacts due to dispersion imbalance and polarization mismatch between reference and sample arm light. Such artifacts can be minimized using a common path approach. In this work, we demonstrate a miniaturized common path probe for optical coherence tomography using an inline fiber mirror. A common path optical fiber probe suitable for performing high-resolution endoscopic optical coherence tomography imaging was developed. To achieve common path functionality, an inline fiber mirror was fabricated using a thin gold layer. A commercially available swept source engine was used to test the designed probe in a cadaver human coronary artery ex vivo. We achieved a sensitivity of 104 dB for this probe using a swept source optical coherence tomography system. To test the probe, images of a cadaver human coronary artery were obtained, demonstrating the quality that is comparable to those obtained by OCT systems with separate reference arms. Additionally, we demonstrate recovery of ranging depth by use of a Michelson interferometer in the detection path. We developed a miniaturized monolithic inline fiber mirror-based common path probe for optical coherence tomography. Owing to its simplicity, our design will be helpful in endoscopic applications that require high-resolution probes in a compact form factor while reducing system complexity. Lasers Surg. Med. 50:230-235, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

An advanced optical system for laser ablation propulsion in space

NASA Astrophysics Data System (ADS)

Bergstue, Grant; Fork, Richard; Reardon, Patrick

2014-03-01

We propose a novel space-based ablation driven propulsion engine concept utilizing transmitted energy in the form of a series of ultra-short optical pulses. Key differences are generating the pulses at the transmitting spacecraft and the safe delivery of that energy to the receiving spacecraft for propulsion. By expanding the beam diameter during transmission in space, the energy can propagate at relatively low intensity and then be refocused and redistributed to create an array of ablation sites at the receiver. The ablation array strategy allows greater control over flight dynamics and eases thermal management. Research efforts for this transmission and reception of ultra-short optical pulses include: (1) optical system design; (2) electrical system requirements; (3) thermal management; (4) structured energy transmission safety. Research has also been focused on developing an optical switch concept for the multiplexing of the ultra-short pulses. This optical switch strategy implements multiple reflectors polished into a rotating momentum wheel device to combine the pulses from different laser sources. The optical system design must minimize the thermal load on any one optical element. Initial specifications and modeling for the optical system are being produced using geometrical ray-tracing software to give a better understanding of the optical requirements. In regards to safety, we have advanced the retro-reflective beam locking strategy to include look-ahead capabilities for long propagation distances. Additional applications and missions utilizing multiplexed pulse transmission are also presented. Because the research is in early development, it provides an opportunity for new and valuable advances in the area of transmitted energy for propulsion as well as encourages joint international efforts. Researchers from different countries can cooperate in order to find constructive and safe uses of ordered pulse transmission for propulsion in future space

The effect of various systems of fastening of the auxiliary reflector on the parameters of an ADE type antenna

NASA Astrophysics Data System (ADS)

Buzuev, Iu. B.; Erukhimovich, Iu. A.; Litinskii, O. A.; Timofeeva, A. A.

1980-09-01

An experimental study is presented of the influence of various systems of fastening of the auxiliary reflector on the parameters of an ADE type antenna operating at a frequency of 11 GHz. Two fastening systems are recommended: (1) a toroidal shell made of glass-reinforced polyurethane foam (gamma = 0.1-0.2 g/cu cm) with special designed inner and outer air/dielectric interfaces; and (2) the complete or partial filling of the space between the walls of the horn and the surface of the auxiliary reflector by polyurethane foam (gamma = 0.03 g/cu cm), the outer surface being glass-fiber-reinforced.

Progress in the development of advanced solar reflectors

NASA Astrophysics Data System (ADS)

Kennedy, C.; Jorgensen, G.

1994-01-01

Solar thermal technologies require large mirrors to provide concentrated sunlight for renewable power generation. Such materials must be inexpensive and maintain high specular reflectance for extended lifetimes in severe outdoor environments. Polymer reflectors are lighter than glass mirrors, offer greater system design flexibility, and have the potential for lower cost. During the past year, collaborative cost-shared research and development between the National Renewable Energy Laboratory (NREL) and industrial partners has identified candidate materials that perform better than the state-of-the-art commercial silvered-polymer reflectors in terms of corrosion degradation and resistance to delamination failure. Additional cooperative efforts will produce new alternative materials with reduced costs due to high speed production line capability. NREL welcomes continued and expanded interest and web coating industry involvement in developing advanced solar reflector materials.

Thermal Stability of a 4 Meter Primary Reflector for the Scanning Microwave Limb Sounder

NASA Technical Reports Server (NTRS)

Cofield, Richard E.; Kasl, Eldon P.

2011-01-01

The Scanning Microwave Limb Sounder (SMLS) is a space-borne heterodyne radiometer which will measure pressure, temperature and atmospheric constituents from thermal emission in [180,680] GHz. SMLS, planned for the NRC Decadal Survey's Global Atmospheric Composition Mission, uses a novel toric Cassegrain antenna to perform both elevation and azimuth scanning. This provides better horizontal and temporal resolution and coverage than were possible with elevation-only scanning in the two previous MLS satellite instruments. SMLS is diffraction-limited in the vertical plane but highly astigmatic in the horizontal (beam aspect ratio approx. 1:20). Nadir symmetry ensures that beam shape is nearly invariant over plus or minus 65 deg azimuth. A low-noise receiver FOV is swept over the reflector system by a small azimuth-scanning mirror. We describe the fabrication and thermal-stability test of a composite demonstration primary reflector, having full 4m height and 1/3 the width planned for flight. Using finite-element models of reflectors and structure, we evaluate thermal deformations and optical performance for 4 orbital environments and isothermal soak. We compare deformations with photogrammetric measurements made during soak tests in a chamber. The test temperature range exceeds predicted orbital ranges by large factors, implying in-orbit thermal stability of 0.21 micron rms (root mean square)/C, which meets SMLS requirements.

Portable, solid state, fiber optic coupled Doppler interferometer system for detonation and shock diagnostics

NASA Technical Reports Server (NTRS)

Fleming, K. J.; Crump, O. B.

1994-01-01

VISAR (Velocity Interferometer System for Any Reflector) is a specialized Doppler interferometer system that is gaining world-wide acceptance as the standard for shock phenomena analysis. The VISAR's large power and cooling requirements, and the sensitive and complex nature of the interferometer cavity have restricted the traditional system to the laboratory. This paper describes the new portable VISAR, its peripheral sensors, and the role it played in optically measuring ground shock of and underground nuclear detonation. The Solid State VISAR uses a prototype diode pumped Nd:YAG laser and solid state detectors that provide a suitcase-size system with low power requirements. A special window and sensors were developed for fiber optic coupling (1 kilometer long) to the VISAR. The system has proven itself as a reliable, easy to use instrument that is capable of field test use and rapid data reduction using only a notebook personal computer (PC).

Bioinspired Omnidirectional Self-Stable Reflectors with Multiscale Hierarchical Structures.

PubMed

Han, Zhiwu; Mu, Zhengzhi; Li, Bo; Feng, Xiaoming; Wang, Ze; Zhang, Junqiu; Niu, Shichao; Ren, Luquan

2017-08-30

Structured surfaces, demonstrating various wondrous physicochemical performances, are ubiquitous phenomena in nature. Butterfly wings with impressive structural colors are an interesting example for multiscale hierarchical structures (MHSs). However, most natural structural colors are relatively unstable and highly sensitive to incident angles, which limit their potential practical applications to a certain extent. Here, we reported a bioinspired color reflector with omnidirectional reflective self-stable (ORS) properties, which is inspired by the wing scales of Papilio palinurus butterfly. Through experimental exploration and theoretical analysis, it was found that the vivid colors of such butterfly wings are structure-based and possess novel ORS properties, which attributes to the multiple optical actions between light and the complex structures coupling the inverse opal-like structures (IOSs) and stacked lamellar ridges (SLRs). On the basis of this, we designed and successfully fabricated the SiO 2 -based bioinspired color reflectors (BCRs) through a facile and effective biotemplate method. It was confirmed that the MHSs in biotemplate are inherited by the obtained SiO 2 -based BCRs. More importantly, the SiO 2 -based BCRs also demonstrated the similar ORS properties in a wide wavelength range. We forcefully anticipate that the reported MHS-based ORS performance discovered in butterfly wing scales here could offer new thoughts for scientists to solve unstable reflection issues in particular optical field. The involved biotemplate fabrication method offers a facile and effective strategy for fabricating functional nanomaterials or bioinspired nanodevices with 3D complex nanostructures, such as structured optical devices, displays, and optoelectronic equipment.

Reflector Technology Development and System Design for Concentrating Solar Power Technologies

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

Adam Schaut

2011-12-30

Alcoa began this program in March of 2008 with the goal of developing and validating an advanced CSP trough design to lower the levelized cost of energy (LCOE) as compared to existing glass based, space-frame trough technology. In addition to showing a pathway to a significant LCOE reduction, Alcoa also desired to create US jobs to support the emerging CSP industry. Alcoa's objective during Phase I: Concept Feasibility was to provide the DOE with a design approach that demonstrates significant overall system cost savings without sacrificing performance. Phase I consisted of two major tasks; reflector surface development and system conceptmore » development. Two specific reflective surface technologies were investigated, silver metallized lamination, and thin film deposition both applied on an aluminum substrate. Alcoa prepared samples; performed test validation internally; and provided samples to the NREL for full-spectrum reflectivity measurements. The final objective was to report reflectivity at t = 0 and the latest durability results as of the completion of Phase 1. The target criteria for reflectance and durability were as follows: (1) initial (t = 0), hemispherical reflectance >93%, (2) initial spectral reflectance >90% for 25-mrad reading and >87% for 7-mrad reading, and (3) predicted 20 year durability of less than 5% optical performance drop. While the results of the reflective development activities were promising, Alcoa was unable to down-select on a reflective technology that met the target criteria. Given the progress and potential of both silver film and thin film technologies, Alcoa continued reflector surface development activities in Phase II. The Phase I concept development activities began with acquiring baseline CSP system information from both CSP Services and the DOE. This information was used as the basis to develop conceptual designs through ideation sessions. The concepts were evaluated based on estimated cost and high-level structural

The X-ray Reflectors in the Nucleus of the Seyfert Galaxy NGC 1068

NASA Technical Reports Server (NTRS)

Colbert, Edward J. M.; Weaver, Kimberly A.; Krolik, Julian H.; Mulchaey, John S.; Mushotzky, Richard F.; White, Nicholas E. (Technical Monitor)

2002-01-01

Based on observations of the Seyfert nucleus in NGC 1068 with ASCA, RXTE and BeppoSAX, we report the discovery of a flare (increase in flux by a factor of approximately 1.6) in the 6.7 keV Fe K line component between observations obtained four months apart, with no significant change in the other (6.21, 6.4, and 6.97 keV) Fe Kalpha line components. During this time, the continuum flux decreased by approximately 20%. The RXTE spectrum requires an Fe K absorption edge near 8.6 keV (Fe XXIII- XXV). The spectral data indicate that the 2-10 keV continuum emission is dominated (approximately 2/3 of the luminosity) by reflection from a previously unidentified region of warm, ionized gas located approximately or less than 0.2 pc from the AGN. The remaining approximately 1/3 of the observed X-ray emission is reflected from optically thick, neutral gas. The coronal gas in the inner Narrow-Line Region (NLR) and/or the cold gas at the inner surface of the obscuring 'torus' are possible cold reflectors. The inferred properties of the warm reflector are: size (diameter) approximately or less than 0.2 pc, gas density n approximately or greater than 10(exp 5.5)/cu cm, ionization parameter xi is approximately 10(exp 3.5) erg cm s(exp -1), and covering fraction 0.003 (L(sub 0)/ 10(exp 43.5) erg s(exp -1)(exp -1) less than (omega/4pi) less than 0.024 (L(sub 0)/ 10(exp 43.5) erg s(exp -1) (exp -1) where L(sub 0) is the intrinsic 2-10 keV X-ray luminosity of the AGN. We suggest that the warm reflector gas is the source of the (variable) 6.7 keV Fe line emission, and the 6.97 keV Fe line emission. The 6.7 keV line flare is assumed to be due to an increase in the emissivity of the warm reflector gas from a decrease (by 20-30%) in L(sub 0). The properties of the warm reflector are most consistent with an intrinsically X-ray weak AGN with L(sub 0) approximately equals 10(exp 43.0) erg s(exp -1). The optical and UV emission that scatters from the warm reflector into our line of sight is

Convergence studies of deterministic methods for LWR explicit reflector methodology

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

Canepa, S.; Hursin, M.; Ferroukhi, H.

2013-07-01

The standard approach in modem 3-D core simulators, employed either for steady-state or transient simulations, is to use Albedo coefficients or explicit reflectors at the core axial and radial boundaries. In the latter approach, few-group homogenized nuclear data are a priori produced with lattice transport codes using 2-D reflector models. Recently, the explicit reflector methodology of the deterministic CASMO-4/SIMULATE-3 code system was identified to potentially constitute one of the main sources of errors for core analyses of the Swiss operating LWRs, which are all belonging to GII design. Considering that some of the new GIII designs will rely on verymore » different reflector concepts, a review and assessment of the reflector methodology for various LWR designs appeared as relevant. Therefore, the purpose of this paper is to first recall the concepts of the explicit reflector modelling approach as employed by CASMO/SIMULATE. Then, for selected reflector configurations representative of both GII and GUI designs, a benchmarking of the few-group nuclear data produced with the deterministic lattice code CASMO-4 and its successor CASMO-5, is conducted. On this basis, a convergence study with regards to geometrical requirements when using deterministic methods with 2-D homogenous models is conducted and the effect on the downstream 3-D core analysis accuracy is evaluated for a typical GII deflector design in order to assess the results against available plant measurements. (authors)« less

Evaluation of deer warning reflectors in Virginia.

DOT National Transportation Integrated Search

2003-01-01

A deer warning reflector consists of a red, double-sided reflector mounted on posts, similar to those used for roadside delineators along roadways. As vehicles approach and move through the road section, it is purported that the reflector reflects th...

REFLECTOR FOR NEUTRONIC REACTORS

DOEpatents

Fraas, A.P.

1963-08-01

A reflector for nuclear reactors that comprises an assembly of closely packed graphite rods disposed with their major axes substantially perpendicular to the interface between the reactor core and the reflector is described. Each graphite rod is round in transverse cross section at (at least) its interface end and is provided, at that end, with a coaxial, inwardly tapering hole. (AEC)

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.

SweepSAR: Beam-forming on Receive Using a Reflector-Phased Array Feed Combination for Spaceborne SAR

NASA Technical Reports Server (NTRS)

Freeman, A.; Krieger, G.; Rosen, P.; Younis, M.; Johnson, W. T. K.; Huber, S.; Jordan, R.; Moreira, A.

2012-01-01

In this paper, an alternative approach is described that is suited for longer wavelength SARs in particular, employing a large, deployable reflector antenna and a much simpler phased array feed. To illuminate a wide swath, a substantial fraction of the phased array feed is excited on transmit to sub-illuminate the reflector. Shorter transmit pulses are required than for conventional SAR. On receive, a much smaller portion of the phased array feed is used to collect the return echo, so that a greater portion of the reflector antenna area is used. The locus of the portion of the phased array used on receive is adjusted using an analog beam steering network, to 'sweep' the receive beam(s) across the illuminated swath, tracking the return echo. This is similar in some respects to the whiskbroom approach to optical sensors, hence the name: SweepSAR.SweepSAR has advantages over conventional SAR in that it requires less transmit power, and if the receive beam is narrow enough, it is relatively immune to range ambiguities. Compared to direct radiating arrays with digital beam- forming, it is much simpler to implement, uses currently available technologies, is better suited for longer wavelength systems, and does not require extremely high data rates or onboard processing.

Photogrammetrically Measured Distortions of Composite Structure Microwave Reflectors at -90K

NASA Technical Reports Server (NTRS)

Mule, Peter; Hill, Michael D.; Sampler, Henry P.

2000-01-01

The Microwave Anisotropy Probe (MAP) Observatory, scheduled for a late 2000 launch, is designed to measure temperature fluctuations (anisotropy) and produce a high sensitivity and high spatial resolution (better than 0.3 deg. at 90 GHz.) map of the Cosmic Microwave Background (CMB) radiation over the entire sky between 22 and 90 GHz. MAP utilizes back-to-back composite Gregorian telescopes supported on a composite truss structure to focus the microwave signals into 10 differential microwave receivers. Proper position and shape of the telescope reflectors at the operating temperature of -90 K is a critical element to ensure mission success. We describe the methods and analysis used to validate the in-flight position and shape predictions for the reflectors based on photogrammetric metrology data taken under vacuum with the reflectors at -90 K. Contour maps showing reflector distortion were generated. The resulting reflector distortion data are shown to be crucial to the analytical assessment of the MAP instrument's microwave system in-flight performance.

Integrated reflector antenna design and analysis

NASA Technical Reports Server (NTRS)

Zimmerman, M. L.; Lee, S. W.; Ni, S.; Christensen, M.; Wang, Y. M.

1993-01-01

Reflector antenna design is a mature field and most aspects were studied. However, of that most previous work is distinguished by the fact that it is narrow in scope, analyzing only a particular problem under certain conditions. Methods of analysis of this type are not useful for working on real-life problems since they can not handle the many and various types of perturbations of basic antenna design. The idea of an integrated design and analysis is proposed. By broadening the scope of the analysis, it becomes possible to deal with the intricacies attendant with modem reflector antenna design problems. The concept of integrated reflector antenna design is put forward. A number of electromagnetic problems related to reflector antenna design are investigated. Some of these show how tools for reflector antenna design are created. In particular, a method for estimating spillover loss for open-ended waveguide feeds is examined. The problem of calculating and optimizing beam efficiency (an important figure of merit in radiometry applications) is also solved. Other chapters deal with applications of this general analysis. The wide angle scan abilities of reflector antennas is examined and a design is proposed for the ATDRSS triband reflector antenna. The development of a general phased-array pattern computation program is discussed and how the concept of integrated design can be extended to other types of antennas is shown. The conclusions are contained in the final chapter.

Large aluminium convex mirror for the cryo-optical test of the Planck primary reflector

NASA Astrophysics Data System (ADS)

Gloesener, P.; Flébus, C.; Cola, M.; Roose, S.; Stockman, Y.; de Chambure, D.

2017-11-01

In the frame of the PLANCK mission telescope development, it is requested to measure the reflector changes of the surface figure error (SFE) with respect to the best ellipsoid, between 293 K and 50 K, with 1 μm RMS accuracy. To achieve this, Infra Red interferometry has been selected and a dedicated thermo mechanical set-up has been constructed. In order to realise the test set-up for this reflector, a large aluminium convex mirror with radius of 19500 mm has been manufactured. The mirror has to operate in a cryogenic environment lower than 30 K, and has a contribution to the RMS WFE with less than 1 μm between room temperature and cryogenic temperature. This paper summarises the design, manufacturing and characterisation of this mirror, showing it has fulfilled its requirements.

Surface accuracy analysis and mathematical modeling of deployable large aperture elastic antenna reflectors

NASA Astrophysics Data System (ADS)

Coleman, Michael J.

One class of deployable large aperture antenna consists of thin light-weight parabolic reflectors. A reflector of this type is a deployable structure that consists of an inflatable elastic membrane that is supported about its perimeter by a set of elastic tendons and is subjected to a constant hydrostatic pressure. A design may not hold the parabolic shape to within a desired tolerance due to an elastic deformation of the surface, particularly near the rim. We can compute the equilibrium configuration of the reflector system using an optimization-based solution procedure that calculates the total system energy and determines a configuration of minimum energy. Analysis of the equilibrium configuration reveals the behavior of the reflector shape under various loading conditions. The pressure, film strain energy, tendon strain energy, and gravitational energy are all considered in this analysis. The surface accuracy of the antenna reflector is measured by an RMS calculation while the reflector phase error component of the efficiency is determined by computing the power density at boresight. Our error computation methods are tailored for the faceted surface of our model and they are more accurate for this particular problem than the commonly applied Ruze Equation. Previous analytical work on parabolic antennas focused on axisymmetric geometries and loads. Symmetric equilibria are not assumed in our analysis. In addition, this dissertation contains two principle original findings: (1) the typical supporting tendon system tends to flatten a parabolic reflector near its edge. We find that surface accuracy can be significantly improved by fixing the edge of the inflated reflector to a rigid structure; (2) for large membranes assembled from flat sheets of thin material, we demonstrate that the surface accuracy of the resulting inflated membrane reflector can be improved by altering the cutting pattern of the flat components. Our findings demonstrate that the proper choice

16 CFR 1512.16 - Requirements for reflectors.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 1512.16 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FEDERAL HAZARDOUS SUBSTANCES ACT... vehicle headlamps. The use of reflector combinations off the center plane of the bicycle (defined in...) Front reflector. The reflector or mount shall not contact the ground plane when the bicycle is resting...

CAD/CAM for development and fabrication of cosecant reflector antennas

NASA Astrophysics Data System (ADS)

Petri, U.

The application of CAD/CAM techniques to lower the cost of redesigning and manufacturing specialized cosecant reflector antennas for use in the mm-wave range is described and demonstrated. Consideration is given to the theoretical computation of reflector surfaces; the representation of a reflector surface in a CAD system; the numerically controlled milling of an Al, wood, or plastic model antenna; and the construction of the antenna (by spraying the 300-micron Sn-alloy conducting layer onto the coated model surface and then applying a 1-mm-thick epoxy-matrix GFRP layer, a 20-30-mm layer of flexible polyurethane foam, and a final GFRP layer). Diagrams and photographs are provided.

ICI optical data storage tape

NASA Technical Reports Server (NTRS)

Mclean, Robert A.; Duffy, Joseph F.

1992-01-01

Optical data storage tape is now a commercial reality. The world's first successful development of a digital optical tape system is complete. This is based on the Creo 1003 optical tape recorder with ICI 1012 write-once optical tape media. Flexible optical media offers many benefits in terms of manufacture; for a given capital investment, continuous, web-coating techniques produce more square meters of media than batch coating. The coated layers consist of a backcoat on the non-active side; on the active side there is a subbing layer, then reflector, dye/polymer, and transparent protective overcoat. All these layers have been tailored for ease of manufacture and specific functional characteristics.

Orbit Determination with Angle-only Data from the First Korean Optical Satellite Tracking System, OWL-Net

NASA Astrophysics Data System (ADS)

Choi, J.; Jo, J.

2016-09-01

The optical satellite tracking data obtained by the first Korean optical satellite tracking system, Optical Wide-field patrol - Network (OWL-Net), had been examined for precision orbit determination. During the test observation at Israel site, we have successfully observed a satellite with Laser Retro Reflector (LRR) to calibrate the angle-only metric data. The OWL observation system is using a chopper equipment to get dense observation data in one-shot over 100 points for the low Earth orbit objects. After several corrections, orbit determination process was done with validated metric data. The TLE with the same epoch of the end of the first arc was used for the initial orbital parameter. Orbit Determination Tool Kit (ODTK) was used for an analysis of a performance of orbit estimation using the angle-only measurements. We have been developing batch style orbit estimator.

Improved wavelength coded optical time domain reflectometry based on the optical switch.

PubMed

Zhu, Ninghua; Tong, Youwan; Chen, Wei; Wang, Sunlong; Sun, Wenhui; Liu, Jianguo

2014-06-16

This paper presents an improved wavelength coded time-domain reflectometry based on the 2 × 1 optical switch. In this scheme, in order to improve the signal-noise-ratio (SNR) of the beat signal, the improved system used an optical switch to obtain wavelength-stable, low-noise and narrow optical pulses for probe and reference. Experiments were set up to demonstrate a spatial resolution of 2.5m within a range of 70km and obtain the beat signal with line width narrower than 15 MHz within a range of 50 km in fiber break detection. A system for wavelength-division-multiplexing passive optical network (WDM-PON) monitoring was also constructed to detect the fiber break of different channels by tuning the current applied on the gating section of the distributed Bragg reflector (DBR) laser.

The Position and Attitude of Sub-reflector Modeling for TM65 m Radio Telescope

NASA Astrophysics Data System (ADS)

Sun, Z. X.; Chen, L.; Wang, J. Q.

2016-01-01

In the course of astronomical observations, with changes in angle of pitch, the large radio telescope will have different degrees of deformation in the sub-reflector support, back frame, main reflector etc, which will lead to the dramatic decline of antenna efficiency in both high and low elevation. A sub-reflector system of the Tian Ma 65 m radio telescope has been installed in order to compensate for the gravitational deformations of the sub-reflector support and the main reflector. The position and attitude of the sub-reflector are variable in order to improve the pointing performance and the efficiency at different elevations. In this paper, it is studied that the changes of position and attitude of the sub-reflector have influence on the efficiency of antenna in the X band and Ku band. A model has been constructed to determine the position and attitude of the sub-reflector with elevation, as well as the point compensation model, by observing the radio source. In addition, antenna efficiency was tested with sub-reflector position adjusted and fixed. The results show that the model of sub-reflector can effectively improve the efficiency of the 65 m radio telescope. In X band, the aperture efficiency of the radio telescope reaches more than 60% over the entire elevation range.

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.

Fabrication of Spherical Reflectors in Outer Space

NASA Technical Reports Server (NTRS)

Wang, Yu; Dooley, Jennifer; Dragovan, Mark; Serivens, Wally

2005-01-01

A process is proposed for fabrication of lightweight spherical reflectors in outer space for telescopes, radio antennas, and light collectors that would be operated there. The process would obviate the relatively massive substrates and frames needed to support such reflectors in normal Earth gravitation. According to the proposal, fabrication of a reflector would begin with blowing of a bubble to the specified reflector radius. Taking advantage of the outer-space vacuum as a suitable environment for evaporative deposition of metal, a metal-evaporation source would be turned on and moved around the bubble to deposit a reflective metal film over the specified reflector area to a thickness of several microns. Then the source would be moved and aimed to deposit more metal around the edge of the reflector area, increasing the thickness there to approximately equal to 100 micron to form a frame. Then the bubble would be deflated and peeled off the metal, leaving a thin-film spherical mirror having an integral frame. The mirror would then be mounted for use. The feasibility of this technology has been proved by fabricating a prototype at JPL. As shown in the figure, a 2-in. (.5-cm) diameter hemispherical prototype reflector was made from a polymer bubble coated with silver, forming a very smooth surface.

Compensation for Phase Anisotropy of a Metal Reflector

NASA Technical Reports Server (NTRS)

Hong, John

2007-01-01

A method of compensation for the polarization- dependent phase anisotropy of a metal reflector has been proposed. The essence of the method is to coat the reflector with multiple thin alternating layers of two dielectrics that have different indices of refraction, so as to introduce an opposing polarization-dependent phase anisotropy. The anisotropy in question is a phenomenon that occurs in reflection of light at other than normal incidence: For a given plane wave having components polarized parallel (p) and perpendicular (s) to the plane of incidence, the phase of s-polarized reflected light differs from the phase p-polarized light by an amount that depends on the angle of incidence and the complex index of refraction of the metal. The magnitude of the phase difference is zero at zero angle of incidence (normal incidence) and increases with the angle of incidence. This anisotropy is analogous to a phase anisotropy that occurs in propagation of light through a uniaxial dielectric crystal. In such a case, another uniaxial crystal that has the same orientation but opposite birefringence can be used to cancel the phase anisotropy. Although it would be difficult to prepare a birefringent material in a form suitable for application to the curved surface of a typical metal reflector in an optical instrument, it should be possible to effect the desired cancellation of phase anisotropy by exploiting the form birefringence of multiple thin dielectric layers. (The term "form birefringence" can be defined loosely as birefringence arising, in part, from a regular array of alternating subwavelength regions having different indices of refraction.)

Fiber optic sensor employing successively destroyed coupled points or reflectors for detecting shock wave speed and damage location

DOEpatents

Weiss, Jonathan D.

1995-01-01

A shock velocity and damage location sensor providing a means of measuring shock speed and damage location. The sensor consists of a long series of time-of-arrival "points" constructed with fiber optics. The fiber optic sensor apparatus measures shock velocity as the fiber sensor is progressively crushed as a shock wave proceeds in a direction along the fiber. The light received by a receiving means changes as time-of-arrival points are destroyed as the sensor is disturbed by the shock. The sensor may comprise a transmitting fiber bent into a series of loops and fused to a receiving fiber at various places, time-of-arrival points, along the receiving fibers length. At the "points" of contact, where a portion of the light leaves the transmitting fiber and enters the receiving fiber, the loops would be required to allow the light to travel backwards through the receiving fiber toward a receiving means. The sensor may also comprise a single optical fiber wherein the time-of-arrival points are comprised of reflection planes distributed along the fibers length. In this configuration, as the shock front proceeds along the fiber it destroys one reflector after another. The output received by a receiving means from this sensor may be a series of downward steps produced as the shock wave destroys one time-of-arrival point after another, or a nonsequential pattern of steps in the event time-of-arrival points are destroyed at any point along the sensor.

Influence of surface error on electromagnetic performance of reflectors based on Zernike polynomials

NASA Astrophysics Data System (ADS)

Li, Tuanjie; Shi, Jiachen; Tang, Yaqiong

2018-04-01

This paper investigates the influence of surface error distribution on the electromagnetic performance of antennas. The normalized Zernike polynomials are used to describe a smooth and continuous deformation surface. Based on the geometrical optics and piecewise linear fitting method, the electrical performance of reflector described by the Zernike polynomials is derived to reveal the relationship between surface error distribution and electromagnetic performance. Then the relation database between surface figure and electric performance is built for ideal and deformed surfaces to realize rapidly calculation of far-field electric performances. The simulation analysis of the influence of Zernike polynomials on the electrical properties for the axis-symmetrical reflector with the axial mode helical antenna as feed is further conducted to verify the correctness of the proposed method. Finally, the influence rules of surface error distribution on electromagnetic performance are summarized. The simulation results show that some terms of Zernike polynomials may decrease the amplitude of main lobe of antenna pattern, and some may reduce the pointing accuracy. This work extracts a new concept for reflector's shape adjustment in manufacturing process.

Widely tunable mid-infrared quantum cascade lasers using sampled grating reflectors.

PubMed

Mansuripur, Tobias S; Menzel, Stefan; Blanchard, Romain; Diehl, Laurent; Pflügl, Christian; Huang, Yong; Ryou, Jae-Hyun; Dupuis, Russell D; Loncar, Marko; Capasso, Federico

2012-10-08

We demonstrate a three-section, electrically pulsed quantum cascade laser which consists of a Fabry-Pérot section placed between two sampled grating distributed Bragg reflectors. The device is current-tuned between ten single modes spanning a range of 0.46 μm (63 cm(-1)), from 8.32 to 8.78 μm. The peak optical output power exceeds 280 mW for nine of the modes.

Analysis and design of the ultraviolet warning optical system based on interference imaging

NASA Astrophysics Data System (ADS)

Wang, Wen-cong; Hu, Hui-jun; Jin, Dong-dong; Chu, Xin-bo; Shi, Yu-feng; Song, Juan; Liu, Jin-sheng; Xiao, Ting; Shao, Si-pei

2017-10-01

Ultraviolet warning technology is one of the important methods for missile warning. It provides a very effective way to detect the target for missile approaching alarm. With the development of modern technology, especially the development of information technology at high speed, the ultraviolet early warning system plays an increasingly important role. Compared to infrared warning, the ultraviolet warning has high efficiency and low false alarm rate. In the modern warfare, how to detect the threats earlier, prevent and reduce the attack of precision-guided missile has become a new challenge of missile warning technology. Because the ultraviolet warning technology has high environmental adaptability, the low false alarm rate, small volume and other advantages, in the military field applications it has been developed rapidly. For the ultraviolet warning system, the optimal working waveband is 250 nm 280 nm (Solar Blind UV) due to the strong absorption of ozone layer. According to current application demands for solar blind ultraviolet detection and warning, this paper proposes ultraviolet warning optical system based on interference imaging, which covers solar blind ultraviolet (250nm-280nm) and dual field. This structure includes a primary optical system, an ultraviolet reflector array, an ultraviolet imaging system and an ultraviolet interference imaging system. It makes use of an ultraviolet beam-splitter to achieve the separation of two optical systems. According to the detector and the corresponding application needs of two visual field of the optical system, the calculation and optical system design were completed. After the design, the MTF of the two optical system is more than 0.8@39lp/mm.A single pixel energy concentration is greater than 80%.

Silicon single mode waveguide modulator based upon switchable Bragg reflector

NASA Astrophysics Data System (ADS)

Azogui, Jonathan; Ramon, Yonathan; Businaro, Luca; Ciasca, Gabriele; Gerardino, Annamaria; Zalevsky, Zeev

2018-02-01

In this paper we present the development of an electro optical "Bragg" modulator for telecommunication, in both design and fabrication. The device consists from a regular single mode silicon waveguide (WG) in which an effective Bragg reflector is "turned on" within the WG by means of external bias, due to the plasma dispersion effect, in which the (complexed) refractive index is affected by carrier concentration within the Silicon. Three different strategies are presented for both design and fabrication.

Photogrammetrically Measured Distortions of Composite Structure Microwave Reflectors at Approximately 90 K

NASA Technical Reports Server (NTRS)

Mule, Peter; Hill, Michael D.; Sampler, Henry P.

2000-01-01

The Microwave Anisotropy Probe (MAP) Observatory, scheduled for a fall 2000 launch, is designed to measure temperature fluctuations (anisotropy) and produce a high sensitivity and high spatial resolution (better than 0.3 deg.) map of the cosmic microwave background (CMB) radiation over the entire sky between 22 and 90 GHz. MAP utilizes back-to-back composite Gregorian telescopes supported on a composite truss structure to focus the microwave signals into 10 differential microwave receivers. Proper position and shape of the telescope reflectors at the operating temperature of approximately 90 K is a critical element to ensuring mission success. We describe the methods and analysis used to validate the in-flight position and shape predictions for the reflectors based on photogrammetric (PG) metrology data taken under vacuum with the reflectors at approximately 90 K. Contour maps showing reflector distortion analytical extrapolations were generated. The resulting reflector distortion data are shown to be crucial to the analytical assessment of the MAP instrument's microwave system in-flight performance.

Illumination from space with orbiting solar-reflector spacecraft

NASA Technical Reports Server (NTRS)

Canady, J. E., Jr.; Allen, J. L., Jr.

1982-01-01

The feasibility of using orbiting mirrors to reflect sunlight to Earth for several illumination applications is studied. A constellation of sixteen 1 km solar reflector spacecraft in geosynchronous orbit can illuminate a region 333 km in diameter to 8 lux, which is brighter than most existing expressway lighting systems. This constellation can serve one region all night long or can provide illumination during mornings and evenings to five regions across the United States. Preliminary cost estimates indicate such an endeavor is economically feasible. The studies also explain how two solar reflectors can illuminate the in-orbit nighttime operations of Space Shuttle. An unfurlable, 1 km diameter solar reflector spacecraft design concept was derived. This spacecraft can be packaged in the Space, Shuttle, transported to low Earth orbit, unfurled, and solar sailed to operational orbits up to geosynchronous. The necessary technical studies and improvements in technology are described, and potential environmental concerns are discussed.

Experimental study of an adaptive CFRC reflector for high order wave-front error correction

NASA Astrophysics Data System (ADS)

Lan, Lan; Fang, Houfei; Wu, Ke; Jiang, Shuidong; Zhou, Yang

2018-03-01

The recent radio frequency communication system developments are generating the need for creating space antennas with lightweight and high precision. The carbon fiber reinforced composite (CFRC) materials have been used to manufacture the high precision reflector. The wave-front errors caused by fabrication and on-orbit distortion are inevitable. The adaptive CFRC reflector has received much attention to do the wave-front error correction. Due to uneven stress distribution that is introduced by actuation force and fabrication, the high order wave-front errors such as print-through error is found on the reflector surface. However, the adaptive CFRC reflector with PZT actuators basically has no control authority over the high order wave-front errors. A new design architecture assembled secondary ribs at the weak triangular surfaces is presented in this paper. The virtual experimental study of the new adaptive CFRC reflector has conducted. The controllability of the original adaptive CFRC reflector and the new adaptive CFRC reflector with secondary ribs are investigated. The virtual experimental investigation shows that the new adaptive CFRC reflector is feasible and efficient to diminish the high order wave-front error.

Pressure-release versus rigid reflector for extracorporeal shockwave lithotripsy.

PubMed

Loske, Achim M; Prieto, Fernando E

2002-06-01

To evaluate the advantages and disadvantages of using a pressure-release reflector instead of a rigid reflector to concentrate shockwaves for extracorporeal shockwave lithotripsy (SWL). As in all electrohydraulic lithotripters, shockwaves were generated by electrical breakdown of water between two electrodes, located at the focus (F1) closest to a paraellipsoidal reflector. A pressure-release reflector, made out of polyurethane foam, was constructed and tested on a research lithotripter using kidney stone models. Fragmentation data and pressure measurements were compared with those of a conventional rigid reflector tested on the same device. The weight of stone model fragments remaining after shockwave exposure was less with the pressure-release reflector after screening through a 3.0 x 3.0-mm mesh. The residual fragment weight was less with the rigid reflector using 1.0 x 1.0- and 0.6 x 0.6-mm meshes. Pressure-release reflectors may maintain acceptable stone fragmentation while offering improved patient safety and should be considered for SWL.

Reflector surface distortion analysis techniques (thermal distortion analysis of antennas in space)

NASA Technical Reports Server (NTRS)

Sharp, R.; Liao, M.; Giriunas, J.; Heighway, J.; Lagin, A.; Steinbach, R.

1989-01-01

A group of large computer programs are used to predict the farfield antenna pattern of reflector antennas in the thermal environment of space. Thermal Radiation Analysis Systems (TRASYS) is a thermal radiation analyzer that interfaces with Systems Improved Numerical Differencing Analyzer (SINDA), a finite difference thermal analysis program. The programs linked together for this analysis can now be used to predict antenna performance in the constantly changing space environment. They can be used for very complex spacecraft and antenna geometries. Performance degradation caused by methods of antenna reflector construction and materials selection are also taken into consideration. However, the principal advantage of using this program linkage is to account for distortions caused by the thermal environment of space and the hygroscopic effects of the dry-out of graphite/epoxy materials after the antenna is placed into orbit. The results of this type of analysis could ultimately be used to predict antenna reflector shape versus orbital position. A phased array antenna distortion compensation system could then use this data to make RF phase front corrections. That is, the phase front could be adjusted to account for the distortions in the antenna feed and reflector geometry for a particular orbital position.

A Simple Tool for the Design and Analysis of Multiple-Reflector Antennas in a Multi-Disciplinary Environment

NASA Technical Reports Server (NTRS)

Katz, Daniel S.; Cwik, Tom; Fu, Chuigang; Imbriale, William A.; Jamnejad, Vahraz; Springer, Paul L.; Borgioli, Andrea

2000-01-01

The process of designing and analyzing a multiple-reflector system has traditionally been time-intensive, requiring large amounts of both computational and human time. At many frequencies, a discrete approximation of the radiation integral may be used to model the system. The code which implements this physical optics (PO) algorithm was developed at the Jet Propulsion Laboratory. It analyzes systems of antennas in pairs, and for each pair, the analysis can be computationally time-consuming. Additionally, the antennas must be described using a local coordinate system for each antenna, which makes it difficult to integrate the design into a multi-disciplinary framework in which there is traditionally one global coordinate system, even before considering deforming the antenna as prescribed by external structural and/or thermal factors. Finally, setting up the code to correctly analyze all the antenna pairs in the system can take a fair amount of time, and introduces possible human error. The use of parallel computing to reduce the computational time required for the analysis of a given pair of antennas has been previously discussed. This paper focuses on the other problems mentioned above. It will present a methodology and examples of use of an automated tool that performs the analysis of a complete multiple-reflector system in an integrated multi-disciplinary environment (including CAD modeling, and structural and thermal analysis) at the click of a button. This tool, named MOD Tool (Millimeter-wave Optics Design Tool), has been designed and implemented as a distributed tool, with a client that runs almost identically on Unix, Mac, and Windows platforms, and a server that runs primarily on a Unix workstation and can interact with parallel supercomputers with simple instruction from the user interacting with the client.

New main reflector, subreflector and dual chamber concepts for compact range applications

NASA Technical Reports Server (NTRS)

Pistorius, C. W. I.; Burnside, W. D.

1987-01-01

A compact range is a facility used for the measurement of antenna radiation and target scattering problems. Most presently available parabolic reflectors do not produce ideal uniform plane waves in the target zone. Design improvements are suggested to reduce the amplitude taper, ripple and cross polarization errors. The ripple caused by diffractions from the reflector edges can be reduced by adding blended rolled edges and shaping the edge contour. Since the reflected edge continues smoothly from the parabola onto the rolled surface, rather than being abruptly terminated, the discontinuity in the reflected field is reduced which results in weaker diffracted fields. This is done by blending the rolled edges from the parabola into an ellipse. An algorithm which enables one to design optimum blended rolled edges was developed that is based on an analysis of the continuity of the surface radius of curvature and its derivatives across the junction. Futhermore, a concave edge contour results in a divergent diffracted ray pattern and hence less stray energy in the target zone. Design equations for three-dimensional reflectors are given. Various examples were analyzed using a new physical optics method which eliminates the effects of the false scattering centers on the incident shadow boundaries. A Gregorian subreflector system, in which both the subreflector and feed axes are tilted, results in a substantial reduction in the amplitude taper and cross polarization errors. A dual chamber configuration is proposed to eliminate the effects of diffraction from the subreflector and spillover from the feed. A computationally efficient technique, based on ray tracing and aperture integration, was developed to analyze the scattering from a lossy dielectric slab with a wedge termination.

Research on the Calculation Method of Optical Path Difference of the Shanghai Tian Ma Telescope

NASA Astrophysics Data System (ADS)

Dong, J.; Fu, L.; Jiang, Y. B.; Liu, Q. H.; Gou, W.; Yan, F.

2016-03-01

Based on the Shanghai Tian Ma Telescope (TM), an optical path difference calculation method of the shaped Cassegrain antenna is presented in the paper. Firstly, the mathematical model of the TM optics is established based on the antenna reciprocity theorem. Secondly, the TM sub-reflector and main reflector are fitted by the Non-Uniform Rational B-Splines (NURBS). Finally, the method of optical path difference calculation is implemented, and the expanding application of the Ruze optical path difference formulas in the TM is researched. The method can be used to calculate the optical path difference distributions across the aperture field of the TM due to misalignment like the axial and lateral displacements of the feed and sub-reflector, or the tilt of the sub-reflector. When the misalignment quantity is small, the expanding Ruze optical path difference formulas can be used to calculate the optical path difference quickly. The paper supports the real-time measurement and adjustment of the TM structure. The research has universality, and can provide reference for the optical path difference calculation of other radio telescopes with shaped surfaces.

The effect of reflector geometry on the acoustic field and bubble dynamics produced by an electrohydraulic shock wave lithotripter.

PubMed

Zhou, Yufeng; Zhong, Pei

2006-06-01

A theoretical model for the propagation of shock wave from an axisymmetric reflector was developed by modifying the initial conditions for the conventional solution of a nonlinear parabolic wave equation (i.e., the Khokhlov-Zabolotskaya-Kuznestsov equation). The ellipsoidal reflector of an HM-3 lithotripter is modeled equivalently as a self-focusing spherically distributed pressure source. The pressure wave form generated by the spark discharge of the HM-3 electrode was measured by a fiber optic probe hydrophone and used as source conditions in the numerical calculation. The simulated pressure wave forms, accounting for the effects of diffraction, nonlinearity, and thermoviscous absorption in wave propagation and focusing, were compared with the measured results and a reasonably good agreement was found. Furthermore, the primary characteristics in the pressure wave forms produced by different reflector geometries, such as that produced by a reflector insert, can also be predicted by this model. It is interesting to note that when the interpulse delay time calculated by linear geometric model is less than about 1.5 micros, two pulses from the reflector insert and the uncovered bottom of the original HM-3 reflector will merge together. Coupling the simulated pressure wave form with the Gilmore model was carried out to evaluate the effect of reflector geometry on resultant bubble dynamics in a lithotripter field. Altogether, the equivalent reflector model was found to provide a useful tool for the prediction of pressure wave form generated in a lithotripter field. This model may be used to guide the design optimization of reflector geometries for improving the performance and safety of clinical lithotripters.

The effect of reflector geometry on the acoustic field and bubble dynamics produced by an electrohydraulic shock wave lithotripter

PubMed Central

Zhou, Yufeng; Zhong, Pei

2007-01-01

A theoretical model for the propagation of shock wave from an axisymmetric reflector was developed by modifying the initial conditions for the conventional solution of a nonlinear parabolic wave equation (i.e., the Khokhlov–Zabolotskaya–Kuznestsov equation). The ellipsoidal reflector of an HM-3 lithotripter is modeled equivalently as a self-focusing spherically distributed pressure source. The pressure wave form generated by the spark discharge of the HM-3 electrode was measured by a fiber optic probe hydrophone and used as source conditions in the numerical calculation. The simulated pressure wave forms, accounting for the effects of diffraction, nonlinearity, and thermoviscous absorption in wave propagation and focusing, were compared with the measured results and a reasonably good agreement was found. Furthermore, the primary characteristics in the pressure wave forms produced by different reflector geometries, such as that produced by a reflector insert, can also be predicted by this model. It is interesting to note that when the interpulse delay time calculated by linear geometric model is less than about 1.5 μs, two pulses from the reflector insert and the uncovered bottom of the original HM-3 reflector will merge together. Coupling the simulated pressure wave form with the Gilmore model was carried out to evaluate the effect of reflector geometry on resultant bubble dynamics in a lithotripter field. Altogether, the equivalent reflector model was found to provide a useful tool for the prediction of pressure wave form generated in a lithotripter field. This model may be used to guide the design optimization of reflector geometries for improving the performance and safety of clinical lithotripters. PMID:16838506

Active feed array compensation for reflector antenna surface distortions. Ph.D. Thesis - Akron Univ., Ohio

NASA Technical Reports Server (NTRS)

Acosta, Roberto J.

1988-01-01

The feasibility of electromagnetic compensation for reflector antenna surface distortions is investigated. The performance characteristics of large satellite communication reflector antenna systems degrade as the reflector surface distorts, mainly due to thermal effects from solar radiation. The technique developed can be used to maintain the antenna boresight directivity and sidelobe level independent of thermal effects on the reflector surface. With the advent of monolithic microwave integrated circuits (MMIC), a greater flexibility in array fed reflector antenna systems can be achieved. MMIC arrays provide independent control of amplitude and phase for each of the many radiating elements in the feed array. By assuming a known surface distortion profile, a simulation study is carried out to examine the antenna performance as a function of feed array size and number of elements. Results indicate that the compensation technique can effectively control boresight directivity and sidelobe level under peak surface distortion in the order of tenth of a wavelength.

Demonstrating Fermat's Principle in Optics

ERIC Educational Resources Information Center

Paleiov, Orr; Pupko, Ofir; Lipson, S. G.

2011-01-01

We demonstrate Fermat's principle in optics by a simple experiment using reflection from an arbitrarily shaped one-dimensional reflector. We investigated a range of possible light paths from a lamp to a fixed slit by reflection in a curved reflector and showed by direct measurement that the paths along which light is concentrated have either…

Projections of limiting states for load-bearing structures of reflectors made of polymer composites

NASA Astrophysics Data System (ADS)

Doronin, S. V.

2017-12-01

This paper deals with limiting states typical for reflector antennas for terrestrial satellite communication systems. Reflectors made of polymer composites are studied. These limiting states are projected by results of the numerical analysis of the stress and strain states. The analysis is executed for reflectors under conditions of static and dynamic loading. It takes into account both overshoot of the state variables of allowed level and the processes of long-term structural material degradation.

The effects of stainless steel radial reflector on core reactivity for small modular reactor

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

Kang, Jung Kil, E-mail: jkkang@email.kings.ac.kr; Hah, Chang Joo, E-mail: changhah@kings.ac.kr; Cho, Sung Ju, E-mail: sungju@knfc.co.kr

Commercial PWR core is surrounded by a radial reflector, which consists of a baffle and water. Radial reflector is designed to reflect neutron back into the core region to improve the neutron efficiency of the reactor and to protect the reactor vessels from the embrittling effects caused by irradiation during power operation. Reflector also helps to flatten the neutron flux and power distributions in the reactor core. The conceptual nuclear design for boron-free small modular reactor (SMR) under development in Korea requires to have the cycle length of 4∼5 years, rated power of 180 MWth and enrichment less than 5more » w/o. The aim of this paper is to analyze the effects of stainless steel radial reflector on the performance of the SMR using UO{sub 2} fuels. Three types of reflectors such as water, water/stainless steel 304 mixture and stainless steel 304 are selected to investigate the effect on core reactivity. Additionally, the thickness of stainless steel and double layer reflector type are also investigated. CASMO-4/SIMULATE-3 code system is used for this analysis. The results of analysis show that single layer stainless steel reflector is the most efficient reflector.« less

33 CFR 118.120 - Radar reflectors and racons.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Radar reflectors and racons. 118... BRIDGES BRIDGE LIGHTING AND OTHER SIGNALS § 118.120 Radar reflectors and racons. The District Commander may require or authorize the installation of radar reflectors and racons on bridge structures, stakes...

33 CFR 118.120 - Radar reflectors and racons.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Radar reflectors and racons. 118... BRIDGES BRIDGE LIGHTING AND OTHER SIGNALS § 118.120 Radar reflectors and racons. The District Commander may require or authorize the installation of radar reflectors and racons on bridge structures, stakes...

33 CFR 118.120 - Radar reflectors and racons.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Radar reflectors and racons. 118... BRIDGES BRIDGE LIGHTING AND OTHER SIGNALS § 118.120 Radar reflectors and racons. The District Commander may require or authorize the installation of radar reflectors and racons on bridge structures, stakes...

33 CFR 118.120 - Radar reflectors and racons.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Radar reflectors and racons. 118... BRIDGES BRIDGE LIGHTING AND OTHER SIGNALS § 118.120 Radar reflectors and racons. The District Commander may require or authorize the installation of radar reflectors and racons on bridge structures, stakes...

33 CFR 118.120 - Radar reflectors and racons.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Radar reflectors and racons. 118... BRIDGES BRIDGE LIGHTING AND OTHER SIGNALS § 118.120 Radar reflectors and racons. The District Commander may require or authorize the installation of radar reflectors and racons on bridge structures, stakes...

Fiber optic sensor employing successively destroyed coupled points or reflectors for detecting shock wave speed and damage location

DOEpatents

Weiss, J.D.

1995-08-29

A shock velocity and damage location sensor providing a means of measuring shock speed and damage location is disclosed. The sensor consists of a long series of time-of-arrival ``points`` constructed with fiber optics. The fiber optic sensor apparatus measures shock velocity as the fiber sensor is progressively crushed as a shock wave proceeds in a direction along the fiber. The light received by a receiving means changes as time-of-arrival points are destroyed as the sensor is disturbed by the shock. The sensor may comprise a transmitting fiber bent into a series of loops and fused to a receiving fiber at various places, time-of-arrival points, along the receiving fibers length. At the ``points`` of contact, where a portion of the light leaves the transmitting fiber and enters the receiving fiber, the loops would be required to allow the light to travel backwards through the receiving fiber toward a receiving means. The sensor may also comprise a single optical fiber wherein the time-of-arrival points are comprised of reflection planes distributed along the fibers length. In this configuration, as the shock front proceeds along the fiber it destroys one reflector after another. The output received by a receiving means from this sensor may be a series of downward steps produced as the shock wave destroys one time-of-arrival point after another, or a nonsequential pattern of steps in the event time-of-arrival points are destroyed at any point along the sensor. 6 figs.

Efficiency enhancement and angle-dependent color change in see-through organic photovoltaics using distributed Bragg reflectors

NASA Astrophysics Data System (ADS)

Dong, Wan Jae; Lo, Nhat-Truong; Jung, Gwan Ho; Ham, Juyoung; Lee, Jong-Lam

2016-03-01

A distributed Bragg reflector (DBR) is conducted as a bottom reflector in see-through organic photovoltaics (OPVs) with an active layer of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester (P3HT:PCBM). The DBR consists of alternative layers of the high- and low-refractive index materials of Ta2O5 (n = 2.16) and SiO2 (n = 1.46). The DBR selectively reflects the light within a specific wavelength region (490 nm-630 nm) where the absorbance of P3HT:PCBM is maximum. The see-through OPVs fabricated on DBR exhibit efficiency enhancement by 31% compared to the device without DBR. Additionally, the angle-dependent transmittance of DBR is analysed using optical simulation and verified by experimental results. As the incident angle of light increases, peak of reflectance shifts to shorter wavelength and the bandwidth gets narrower. This unique angle-dependent optical properties of DBR allows the facile color change of see-through OPVs.

Beyond Wires and Seeds: Reflector-guided Breast Lesion Localization and Excision.

PubMed

Mango, Victoria L; Wynn, Ralph T; Feldman, Sheldon; Friedlander, Lauren; Desperito, Elise; Patel, Sejal N; Gomberawalla, Ameer; Ha, Richard

2017-08-01

Purpose To evaluate outcomes of Savi Scout (Cianna Medical, Aliso Viejo, Calif) reflector-guided localization and excision of breast lesions by analyzing reflector placement, localization, and removal, along with target excision and rates of repeat excision (referred to as re-excision). Materials and Methods A single-institution retrospective review of 100 women who underwent breast lesion localization and excision by using the Savi Scout surgical guidance system from June 2015 to May 2016 was performed. By using image guidance 0-8 days before surgery, 123 nonradioactive, infrared-activated, electromagnetic wave reflectors were percutaneously inserted adjacent to or within 111 breast targets. Twenty patients had two or three reflectors placed for bracketing or for localizing multiple lesions, and when ipsilateral, they were placed as close as 2.6 cm apart. Target and reflector were localized intraoperatively by one of two breast surgeons who used a handpiece that emitted infrared light and electromagnetic waves. Radiographs of the specimen and pathologic analysis helped verify target and reflector removal. Target to reflector distance was measured on the mammogram and radiograph of the specimen, and reflector depth was measured on the mammogram. Pathologic analysis was reviewed. Re-excision rates and complications were recorded. By using statistics software, descriptive statistics were generated with 95% confidence intervals (CIs) calculated. Results By using sonographic (40 of 123; 32.5%; 95% CI: 24.9%, 41.2%) or mammographic (83 of 123; 67.5%; 95% CI: 58.8% 75.1%) guidance, 123 (100%; 95% CI: 96.4%, 100%) reflectors were placed. Mean mammographic target to reflector distance was 0.3 cm. All 123 (100%; 95% CI: 96.4%, 100%) targets and reflectors were excised. Pathologic analysis yielded 54 of 110 malignancies (49.1%; 95% CI: 39.9%, 58.3%; average, 1.0 cm; range, 0.1-5 cm), 32 high-risk lesions (29.1%; 95% CI: 21.4%, 38.2%), and 24 benign lesions (21.8%; 95% CI

Adaptive Nulling in Hybrid Reflector Antennas

DTIC Science & Technology

1992-09-01

correction of reflector distortion and vernier beamsteering, MEEE Trans. Antennas Propagat, 36:1351-1358. 4 Cherrette , A.R., et al (1989) Compensation of...Propagat, 36:1351-1358. 4. Cherrette , A.R., et al (1989) Compensation of reflector antenna surface distortion using an array feed,IEEE Trans. Antennas

Self-referencing remote optical probe

DOEpatents

O'Rourke, Patrick E.; Prather, William S.; Livingston, Ronald R.

1991-01-01

A probe for remote spectrometric measurements of fluid samples having a hollow probe body with a sliding reflective plug therein and a lens at one end, ports for admitting and expelling the fluid sample and a means for moving the reflector so that reference measurement can be made with the reflector in a first position near the lens and a sample measurement can be made with the reflector away from the lens and the fluid sample between the reflector and the lens. Comparison of the two measurements will yield the composition of the fluid sample. The probe is preferably used for remote measurements and light is carried to and from the probe via fiber optic cables.

Artificially controlled backscattering in single mode fibers based on femtosecond laser fabricated reflectors

NASA Astrophysics Data System (ADS)

Wang, Xiaoliang; Chen, Daru; Li, Haitao; Wu, Qiong

2018-04-01

A novel method to artificially control the backscattering of the single-mode fiber (SMF) is proposed and investigated for the first time. This method can help to fabricate a high backscattering fiber (HBSF), such as by fabricating reflectors in every one meter interval of an SMF based on the exposure of the femtosecond laser beam. The artificially controlled backscattering (ACBS) can be much higher than the natural Rayleigh backscattering (RB) of the SMF. The RB power and ACBS power in the unit length fiber are derived according to the theory of the RBS. The total relative power and the relative back power reflected in the unit length of the HBSF have been simulated and presented. The simulated results show that the HBSF has the characteristics of both low optical attenuation and high backscattering. The relative back power reflected in the unit length of the HBSF is 25dB larger than the RB power of the SMF when the refractive index modulation quantity of the reflectors is 0.009. Some preliminary experiments also indicate that the method fabricating reflectors to increase the backscattering power of the SMF is practical and promising.

RF/optical shared aperture for high availability wideband communication RF/FSO links

DOEpatents

Ruggiero, Anthony J; Pao, Hsueh-yuan; Sargis, Paul

2014-04-29

An RF/Optical shared aperture is capable of transmitting and receiving optical signals and RF signals simultaneously. This technology enables compact wide bandwidth communications systems with 100% availability in clear air turbulence, rain and fog. The functions of an optical telescope and an RF reflector antenna are combined into a single compact package by installing an RF feed at either of the focal points of a modified Gregorian telescope.

RF/optical shared aperture for high availability wideband communication RF/FSO links

DOEpatents

Ruggiero, Anthony J; Pao, Hsueh-yuan; Sargis, Paul

2015-03-24

An RF/Optical shared aperture is capable of transmitting and receiving optical signals and RF signals simultaneously. This technology enables compact wide bandwidth communications systems with 100% availability in clear air turbulence, rain and fog. The functions of an optical telescope and an RF reflector antenna are combined into a single compact package by installing an RF feed at either of the focal points of a modified Gregorian telescope.

External insulation systems for cryogenic storage systems. Volume 1: Optical properties of Kapton and report of process variable study

NASA Technical Reports Server (NTRS)

Frank, A. M.

1974-01-01

Investigations are conducted into the optical properties of the glass and Kapton substrate materials, and three variables were chosen: deposition rate, sputter gas pressure, and film contamination time. Substrate tests have shown that fabrication of an dielectric broadband reflector would require an extremely complex and expensive filter design.

Approaching conversion limit with all-dielectric solar cell reflectors.

PubMed

Fu, Sze Ming; Lai, Yi-Chun; Tseng, Chi Wei; Yan, Sheng Lun; Zhong, Yan Kai; Shen, Chang-Hong; Shieh, Jia-Min; Li, Yu-Ren; Cheng, Huang-Chung; Chi, Gou-chung; Yu, Peichen; Lin, Albert

2015-02-09

Metallic back reflectors has been used for thin-film and wafer-based solar cells for very long time. Nonetheless, the metallic mirrors might not be the best choices for photovoltaics. In this work, we show that solar cells with all-dielectric reflectors can surpass the best-configured metal-backed devices. Theoretical and experimental results all show that superior large-angle light scattering capability can be achieved by the diffuse medium reflectors, and the solar cell J-V enhancement is higher for solar cells using all-dielectric reflectors. Specifically, the measured diffused scattering efficiency (D.S.E.) of a diffuse medium reflector is >0.8 for the light trapping spectral range (600nm-1000nm), and the measured reflectance of a diffuse medium can be as high as silver if the geometry of embedded titanium oxide(TiO(2)) nanoparticles is optimized. Moreover, the diffuse medium reflectors have the additional advantage of room-temperature processing, low cost, and very high throughput. We believe that using all-dielectric solar cell reflectors is a way to approach the thermodynamic conversion limit by completely excluding metallic dissipation.

Shape adjustment optimization and experiment of cable-membrane reflectors

NASA Astrophysics Data System (ADS)

Du, Jingli; Gu, Yongzhen; Bao, Hong; Wang, Congsi; Chen, Xiaofeng

2018-05-01

Cable-membrane structures are widely employed for large space reflectors due to their lightweight, compact and easy package. In these structures, membranes are attached to cable net, serving as reflectors themselves or as supporting structures for other reflective surface. The cable length and membrane shape have to be carefully designed and fabricated to guarantee the desired reflector surface shape. However, due to inevitable error in cable length and membrane shape during the manufacture and assembly of cable-membrane reflectors, some cables have to be designed to be capable of length adjustment. By carefully adjusting the length of these cables, the degeneration in reflector shape precision due to this inevitable error can be effectively reduced. In the paper a shape adjustment algorithm for cable-membrane reflectors is proposed. Meanwhile, model updating is employed during shape adjustment to decrease the discrepancy of the numerical model with respect to the actual reflector. This discrepancy has to be considered because during attaching membranes to cable net, the accuracy of the membrane shape is hard to guarantee. Numerical examples and experimental results demonstrate the proposed method.

An Optical Actuation System and Curvature Sensor for a MR-compatible Active Needle

PubMed Central

Ryu, Seok Chang; Quek, Zhan Fan; Renaud, Pierre; Black, Richard J.; Daniel, Bruce L.; Cutkosky, Mark R.

2015-01-01

A side optical actuation method is presented for a slender MR-compatible active needle. The needle includes an active region with a shape memory alloy (SMA) wire actuator, where the wire generates a contraction force when optically heated by a laser delivered though optical fibers, producing needle tip bending. A prototype, with multiple side heating spots, demonstrates twice as fast an initial response compared to fiber tip heating when 0.8 W of optical power is applied. A single-ended optical sensor with a gold reflector is also presented to measure the curvature as a function of optical transmission loss. Preliminary tests with the sensor prototype demonstrate approximately linear response and a repeatable signal, independent of the bending history. PMID:26509099

UV dichroic coatings on metallic reflectors

NASA Astrophysics Data System (ADS)

Raghunath, C.; Babu, N. J.; chandran, K. M.

2008-05-01

The work presented here explains the design and deposition process of dichroic coating on metallic reflectors developed for UV curing systems. Special designs are adopted to achieve the spectral band and optimized to suit to the requirements. A mirror, which reflects the UV radiation (220 - 400 nm) and absorbs visible and infrared radiation (400 - 2000nm), is described in detail.

Photovoltaic generator with a spherical imaging lens for use with a paraboloidal solar reflector

DOEpatents

Angel, Roger P

2013-01-08

The invention is a generator for photovoltaic conversion of concentrated sunlight into electricity. A generator according to the invention incorporates a plurality of photovoltaic cells and is intended for operation near the focus of a large paraboloidal reflector pointed at the sun. Within the generator, the entering concentrated light is relayed by secondary optics to the cells arranged in a compact, concave array. The light is delivered to the cells at high concentration, consistent with high photovoltaic conversion efficiency and low cell cost per unit power output. Light enters the generator, preferably first through a sealing window, and passes through a field lens, preferably in the form of a full sphere or ball lens centered on the paraboloid focus. This lens forms a concentric, concave and wide-angle image of the primary reflector, where the intensity of the concentrated light is stabilized against changes in the position of concentrated light entering the generator. Receiving the stabilized light are flat photovoltaic cells made in different shapes and sizes and configured in a concave array corresponding to the concave image of a given primary reflector. Photovoltaic cells in a generator are also sized and interconnected so as to provide a single electrical output that remains high and stable, despite aberrations in the light delivered to the generator caused by, for example, mispointing or bending of the primary reflector. In some embodiments, the cells are set back from the image formed by the ball lens, and part of the light is reflected onto each cell small secondary reflectors in the form of mirrors set around its perimeter.

Reflector for efficient coupling of a laser beam to air or other fluids

DOEpatents

Kare, Jordin T.

1992-01-01

A reflector array is disclosed herein that provides a controlled region or regions of plasma breakdowns from a laser beam produced at a remotely-based laser source. The plasma may be applied to produce thrust to propel a spacecraft, or to diagnose a laser beam, or to produce shockwaves. The spacecraft propulsion system comprises a reflector array attached to the vehicle. The reflector array comprises a plurality of reflectors spaced apart on a reflective surface, with each reflector acting as an independent focusing mirror. The reflectors are spaced closely together to form a continuous or partially-continuous surface. The reflector array may be formed from a sheet of reflective material, such as copper or aluminum. In operation, a beam of electromagnetic energy, such as a laser beam, is directed at the reflectors which focus the reflected electromagnetic energy at a plurality of regions off the surface. The energy concentrated in the focal region causes a breakdown of the air or other fluid in the focal region, creating a plasma. Electromagnetic energy is absorbed in the plasma and it grows in volume, compressing and heating the adjacent fluid thereby providing thrust. Laser pulses may be applied repetitively. After each such thrust pulse, fresh air can be introduced next to the surface either laterally, or through a perforated surface. If air or some other gas or vapor is supplied, for example from a tank carried on board a vehicle, this invention may also be used to provide thrust in a vacuum environment.

Reflector for efficient coupling of a laser beam to air or other fluids

DOEpatents

Kare, J.T.

1992-10-06

A reflector array is disclosed herein that provides a controlled region or regions of plasma breakdowns from a laser beam produced at a remotely-based laser source. The plasma may be applied to produce thrust to propel a spacecraft, or to diagnose a laser beam, or to produce shock waves. The spacecraft propulsion system comprises a reflector array attached to the vehicle. The reflector array comprises a plurality of reflectors spaced apart on a reflective surface, with each reflector acting as an independent focusing mirror. The reflectors are spaced closely together to form a continuous or partially-continuous surface. The reflector array may be formed from a sheet of reflective material, such as copper or aluminum. In operation, a beam of electromagnetic energy, such as a laser beam, is directed at the reflectors which focus the reflected electromagnetic energy at a plurality of regions off the surface. The energy concentrated in the focal region causes a breakdown of the air or other fluid in the focal region, creating a plasma. Electromagnetic energy is absorbed in the plasma and it grows in volume, compressing and heating the adjacent fluid thereby providing thrust. Laser pulses may be applied repetitively. After each such thrust pulse, fresh air can be introduced next to the surface either laterally, or through a perforated surface. If air or some other gas or vapor is supplied, for example from a tank carried on board a vehicle, this invention may also be used to provide thrust in a vacuum environment. 10 figs.

Self-referencing remote optical probe

DOEpatents

O'Rourke, P.E.; Prather, W.S.; Livingston, R.R.

1991-08-13

A probe is described for remote spectrometric measurements of fluid samples having a hollow probe body with a sliding reflective plug therein and a lens at one end, ports for admitting and expelling the fluid sample and a means for moving the reflector so that reference measurement can be made with the reflector in a first position near the lens and a sample measurement can be made with the reflector away from the lens and the fluid sample between the reflector and the lens. Comparison of the two measurements will yield the composition of the fluid sample. The probe is preferably used for remote measurements and light is carried to and from the probe via fiber optic cables. 3 figures.

Gravity deformation measurements of 70m reflector surfaces

NASA Technical Reports Server (NTRS)

Brenner, Michael; Imbriale, William A.; Britcliffe, Michael K.

2001-01-01

Two of NASA's Deep Space Network (DSN) 70-meter reflectors are measured using a Leica TDM-5000 theodolite. The main reflector surface was measured at five elevation angles so that a gravity deformation model could be derived that described the main reflector distortions over the entire range of elevation angles. The report describes the measurement equipment and accuracy and the results derived from the data.

A Wideband Corner-Reflector Antenna for 240 to 400 MHz.

DTIC Science & Technology

1983-09-19

8217 .; ,:,:. .-.:.,.;.. - -... - .- . -.. .-- v...- ..... .-. .-.- 1,.:..- FIGURES 1. Corner Reflector with Open-Sleeve Dipole Feed ............ ...... 7 2...Open-Sleeve Dipole Feed for Corner Reflector, 240-400 MHz........ 8 3. Closeup Photo of Open-Sleeve Dpole ..................... ...... 8 4. VSWR of...4-ft Corner Reflector, Open-Sleeve Dipole Feed .......... 9 5. Gain of Corner Reflector............ .............. . ....... 9 6. Measured E- and H

Optical Metrology for the Segmented Optics on the Constellation-X Spectroscopy X-Ray Telescope

NASA Technical Reports Server (NTRS)

Content, David; Colella, David; Fleetwood, Charles; Hadjimichael, Theo; Lehan, John; McMann, Joseph; Reid, Paul; Saha, Timo; Wright, Geraldine; Zhang, William

2004-01-01

We present the metrology requirements and metrology implementation necessary to prove out the reflector technology for the Constellation X(C-X) spectroscopy X-ray telescope (SXT). This segmented, 1.6m diameter highly nested Wolter-1 telescope presents many metrology and alignment challenges. In particular, these mirrors have a stringent imaging error budget as compared to their intrinsic stiffness; This is required for Constellation-X to have sufficient effective area with the weight requirement. This has implications for the metrology that can be used. A variety of contract and noncontact optical profiling and interferometric methods are combined to test the formed glass substrates before replication and the replicated reflector segments.The reflectors are tested both stand-alone and in-situ in an alignment tower.Some of these methods have not been used on prior X-ray telescopes and some are feasible only because of the segmented approach used on the SXT. Methods discussed include high precision coordinate measurement machines using very low force or optical probe axial interferometric profiling azimuthal circularity profiling and use of advanced null optics such as conical computer generated hologram (CGHs).

REFLECTOR CONTROL OF A BOILING-WATER REACTOR

DOEpatents

Treshow, M.

1962-05-22

A line connecting the reactor with a spent steam condenser contains a valve set to open when the pressure in the reactor exceeds a predetermined value and an orifice on the upstream side of the valve. Another line connects the reflector with this line between the orifice and the valve. An excess steam pressure causes the valve to open and the flow of steam through the line draws water out of the reflector. Provision is also made for adding water to the reflector when the steam pressure drops. (AEC)

Deployable reflector configurations. [for space telescope

NASA Technical Reports Server (NTRS)

Meinel, A. B.; Meinel, M. P.; Woolf, N. J.

1983-01-01

Both the theoretical reasons for considering a non-circular format for the Large Deployable Reflector, and a potentially realizable concept for such a device, are discussed. The optimum systems for diffraction limited telescopes with incoherent detection have either a single filled aperture, or two such apertures as an interferometer to synthesize a larger aperture. For a single aperture of limited area, a reflector in the form of a slot can be used to give increased angular resolution. It is shown how a 20 x 8 meter telescope can be configured to fit the Space Shuttle bay, and deployed with relatively simple operations. The relationship between the sunshield design and the inclination of the orbit is discussed. The possible use of the LDR as a basic module to permit the construction of supergiant space telescopes and interferometers both for IR/submm studies and for the entire ultraviolet through mm wave spectral region is discussed.

Movable-molybdenum-reflector reactivity experiments for control studies of compact space power reactor concepts

NASA Technical Reports Server (NTRS)

Fox, T. A.

1973-01-01

An experimental reflector reactivity study was made with a compact cylindrical reactor using a uranyl fluoride - water fuel solution. The reactor was axially unreflected and radially reflected with segments of molybdenum. The reflector segments were displaced incrementally in both the axial and radial dimensions, and the shutdown of each configuration was measured by using the pulsed-neutron source technique. The reactivity effects for axial and radial displacement of reflector segments are tabulated separately and compared. The experiments provide data for control-system studies of compact-space-power-reactor concepts.

Feedback dew-point sensor utilizing optimally cut plastic optical fibres

NASA Astrophysics Data System (ADS)

Hadjiloucas, S.; Irvine, J.; Keating, D. A.

2000-01-01

A plastic optical fibre reflectance sensor that makes full use of the critical angle of the fibres is implemented to monitor dew formation on a Peltier-cooled reflector surface. The optical configuration permits isolation of optoelectronic components from the sensing head and better light coupling between the reflector and the detecting fibre, giving a better signal of the onset of dew formation on the reflector. Continuous monitoring of the rate of change in reflectance as well as the absolute reflectance signals, the use of a novel polymethyl-methacrylate-coated hydrophobic film reflector on the Peltier element and the application of feedback around the point of dew formation, further reduces the possibility of contamination of the sensor head. Under closed-loop operation, the sensor is capable of cycling around the point of dew formation at a frequency of 2.5 Hz.

Acoustic levitation with self-adaptive flexible reflectors.

PubMed

Hong, Z Y; Xie, W J; Wei, B

2011-07-01

Two kinds of flexible reflectors are proposed and examined in this paper to improve the stability of single-axis acoustic levitator, especially in the case of levitating high-density and high-temperature samples. One kind is those with a deformable reflecting surface, and the other kind is those with an elastic support, both of which are self-adaptive to the change of acoustic radiation pressure. High-density materials such as iridium (density 22.6 gcm(-3)) are stably levitated at room temperature with a soft reflector made of colloid as well as a rigid reflector supported by a spring. In addition, the containerless melting and solidification of binary In-Bi eutectic alloy (melting point 345.8 K) and ternary Ag-Cu-Ge eutectic alloy (melting point 812 K) are successfully achieved by applying the elastically supported reflector with the assistance of a laser beam.

Acoustic levitation with self-adaptive flexible reflectors

NASA Astrophysics Data System (ADS)

Hong, Z. Y.; Xie, W. J.; Wei, B.

2011-07-01

Two kinds of flexible reflectors are proposed and examined in this paper to improve the stability of single-axis acoustic levitator, especially in the case of levitating high-density and high-temperature samples. One kind is those with a deformable reflecting surface, and the other kind is those with an elastic support, both of which are self-adaptive to the change of acoustic radiation pressure. High-density materials such as iridium (density 22.6 gcm-3) are stably levitated at room temperature with a soft reflector made of colloid as well as a rigid reflector supported by a spring. In addition, the containerless melting and solidification of binary In-Bi eutectic alloy (melting point 345.8 K) and ternary Ag-Cu-Ge eutectic alloy (melting point 812 K) are successfully achieved by applying the elastically supported reflector with the assistance of a laser beam.

Continuous planar phospholipid bilayer supported on porous silicon thin film reflector.

PubMed

Cunin, Frédérique; Milhiet, Pierre-Emmanuel; Anglin, Emily; Sailor, Michael J; Espenel, Cédric; Le Grimellec, Christian; Brunel, Daniel; Devoisselle, Jean-Marie

2007-10-01

Reconstituting artificial membranes for in vitro studies of cell barrier mechanisms and properties is of major interest in biology. Here, artificial membranes supported on porous silicon photonic crystal reflectors are prepared and investigated. The materials are of interest for label-free probing of supported membrane events such as protein binding, molecular recognition, and transport. The porous silicon substrates are prepared as multilayered films consisting of a periodically varying porosity, with pore dimensions of a few nanometers in size. Planar phospholipid bilayers are deposited on the topmost surface of the oxidized hydrophilic mesoporous silicon films. Atomic force microscopy provides evidence of continuous bilayer deposition at the surface, and optical measurements indicate that the lipids do not significantly infiltrate the porous region. The presence of the supported bilayer does not obstruct the optical spectrum from the porous silicon layer, suggesting that the composite structures can act as effective optical biosensors.

Wideband QAMC reflector's antenna for low profile applications

NASA Astrophysics Data System (ADS)

Grelier, M.; Jousset, M.; Mallégol, S.; Lepage, A. C.; Begaud, X.; LeMener, J. M.

2011-06-01

A wideband reflector's antenna based on quasi-artificial magnetic conductor is proposed. To validate the design, an Archimedean spiral has been backed to this new reflector. In comparison to classical solution using absorbent material, the prototype presents a very low thickness of λ/15 at the lowest operating frequency and an improved gain over a 2.4:1 bandwidth. The whole methodology to design this reflector can be applied to other wideband antennas.

Structural and thermal testing of lightweight reflector panels

NASA Technical Reports Server (NTRS)

Mcgregor, J.; Helms, R.; Hill, T.

1992-01-01

The paper describes the test facility developed for testing large lightweight reflective panels with very accurate and stable surfaces, such as the mirror panels of composite construction developed for the NASA's Precision Segmented Reflector (PSR). Special attention is given to the panel construction and the special problems posed by the characteristics of these panels; the design of the Optical/Thermal Vacuum test facility for structural and thermal testing, developed at the U.S. AFPL; and the testing procedure. The results of the PSR panel test program to date are presented. The test data showed that the analytical approaches used for the panel design and for the prediction of the on-orbit panel behavior were adequate.

Deployable reflector design for Ku-band operation

NASA Technical Reports Server (NTRS)

Tankersley, B. C.

1974-01-01

A project was conducted to extend the deployable antenna technology state-of-the art through the design, analysis, construction, and testing of a lightweight, high surface tolerance, 12.5 foot diameter reflector for Ku-band operation. The applicability of the reflector design to the Tracking and Data Relay Satellite (TDRS) program was one requirement to be met. A documentary of the total program is presented. The performance requirements used to guide and constrain the design are discussed. The radio frequency, structural/dynamic, and thermal performance results are reported. Appendices are used to provide test data and detailed fabrication drawings of the reflector.

Large area soft x-ray collimator to facilitate x-ray optics testing

NASA Technical Reports Server (NTRS)

Espy, Samuel L.

1994-01-01

The first objective of this program is to design a nested conical foil x-ray optic which will collimate x-rays diverging from a point source. The collimator could then be employed in a small, inexpensive x-ray test stand which would be used to test various x-ray optics and detector systems. The second objective is to demonstrate the fabrication of the x-ray reflectors for this optic using lacquer-smoothing and zero-stress electroforming techniques.

Properties of solar generators with reflectors and radiators

NASA Astrophysics Data System (ADS)

Ebeling, W. D.; Rex, D.; Bierfischer, U.

1980-06-01

Radiation cooled concentrator systems using silicon and GaAs cells were studied. The principle of radiation cooling by the reflector surfaces is discussed for cylindrical parabolic reflectors (SARA), truncated hexagonal pyramids, and a small trough configuration. Beam paths, collection properties for imperfect orientation, and thermal optimization parameters were analyzed. The three concentrating systems with radiation cooling offer advantages over the plane panel and over the large trough. With silicon solar cells they exhibit considerably lower solar cell consumption per Kw and also lower mass per kW. With GaAs cells the SARA system reduces the number of solar cells needed per kW to less than 10%. Also in all other cases SARA offers the best values for alpha and F sub sol, as long as narrow angular tolerances of the panel orientation can be met. Analysis of the energy collecting properties for imperfect orientation shows the superiority of the hexagonal concentrator. This device can produce power for even large angles between the sun and the panel normal.

Lamp bulb with integral reflector

DOEpatents

Levin, Izrail; Shanks, Bruce; Sumner, Thomas L.

2001-01-01

An improved electrodeless discharge lamp bulb includes an integral ceramic reflector as a portion of the bulb envelope. The bulb envelope further includes two pieces, a reflector portion or segment is cast quartz ceramic and a light transmissive portion is a clear fused silica. In one embodiment, the cast quartz ceramic segment includes heat sink fins or stubs providing an increased outside surface area to dissipate internal heat. In another embodiment, the quartz ceramic segment includes an outside surface fused to eliminate gas permeation by polishing.

Long-range, full-duplex, modulated-reflector cell phone for voice/data transmission

DOEpatents

Neagley, Daniel L.; Briles, Scott D.; Coates, Don M.; Freund, Samuel M.

2002-01-01

A long-range communications apparatus utilizing modulated-reflector technology is described. The apparatus includes an energy-transmitting base station and remote units that do not emit radiation in order to communicate with the base station since modulated-reflector technology is used whereby information is attached to an RF carrier wave originating from the base station which is reflected by the remote unit back to the base station. Since the remote unit does not emit radiation, only a low-power power source is required for its operation. Information from the base station is transmitted to the remote unit using a transmitter and receiver, respectively. The range of such a communications system is determined by the properties of a modulated-reflector half-duplex link.

The Effect of Boundary Support and Reflector Dimensions on Inflatable Parabolic Antenna Performance

NASA Technical Reports Server (NTRS)

Coleman, Michael J.; Baginski, Frank; Romanofsky, Robert R.

2011-01-01

For parabolic antennas with sufficient surface accuracy, more power can be radiated with a larger aperture size. This paper explores the performance of antennas of various size and reflector depth. The particular focus is on a large inflatable elastic antenna reflector that is supported about its perimeter by a set of elastic tendons and is subjected to a constant hydrostatic pressure. The surface accuracy of the antenna is measured by an RMS calculation, while the reflector phase error component of the efficiency is determined by computing the power density at boresight. In the analysis, the calculation of antenna efficiency is not based on the Ruze Equation. Hence, no assumption regarding the distribution of the reflector surface distortions is presumed. The reflector surface is modeled as an isotropic elastic membrane using a linear stress-strain constitutive relation. Three types of antenna reflector construction are considered: one molded to an ideal parabolic form and two different flat panel design patterns. The flat panel surfaces are constructed by seaming together panels in a manner that the desired parabolic shape is approximately attained after pressurization. Numerical solutions of the model problem are calculated under a variety of conditions in order to estimate the accuracy and efficiency of these antenna systems. In the case of the flat panel constructions, several different cutting patterns are analyzed in order to determine an optimal cutting strategy.

Inverting Image Data For Optical Testing And Alignment

NASA Technical Reports Server (NTRS)

Shao, Michael; Redding, David; Yu, Jeffrey W.; Dumont, Philip J.

1993-01-01

Data from images produced by slightly incorrectly figured concave primary mirror in telescope processed into estimate of spherical aberration of mirror, by use of algorithm finding nonlinear least-squares best fit between actual images and synthetic images produced by multiparameter mathematical model of telescope optical system. Estimated spherical aberration, in turn, converted into estimate of deviation of reflector surface from nominal precise shape. Algorithm devised as part of effort to determine error in surface figure of primary mirror of Hubble space telescope, so corrective lens designed. Modified versions of algorithm also used to find optical errors in other components of telescope or of other optical systems, for purposes of testing, alignment, and/or correction.

Geometrical optics design of a compact range Gregorian subreflector system by the principle of the central ray

NASA Technical Reports Server (NTRS)

Clerici, Giancarlo; Burnside, Walter D.

1989-01-01

In recent years, the compact range has become very popular for measuring Radar Cross Section (RCS) and antenna patterns. The compact range, in fact, offers several advantages due to reduced size, a controlled environment, and privacy. On the other hand, it has some problems of its own, which must be solved properly in order to achieve high quality measurement results. For example, diffraction from the edges of the main reflector corrupts the plane wave in the target zone and creates spurious scattering centers in RCS measurements. While diffraction can be minimized by using rolled edges, the field of an offset single reflector compact range is corrupted by three other errors: the taper of the reflected field, the cross polarization introduced by the tilt of the feed and the aperture blockage introduced by the feed itself. These three errors can be eliminated by the use of a subreflector system. A properly designed subreflector system offers very little aperture blockage, no cross-polarization introduced and a minimization of the taper of the reflected field. A Gregorian configuration has been adopted in order to enclose the feed and the ellipsoidal subreflector in a lower chamber, which is isolated by absorbers from the upper chamber, where the main parabolic reflector and the target zone are enclosed. The coupling between the two rooms is performed through a coupling aperture. The first cut design for such a subreflector system is performed through Geometrical Optics ray tracing techniques (GO), and is greatly simplified by the use of the concept of the central ray introduced by Dragone. The purpose of the GO design is to establish the basic dimensions of the main reflector and subreflector, the size of the primary and secondary illuminating surfaces, the tilt angles of the subreflector and feed, and estimate the feed beamwidth. At the same time, the shape of the coupling aperture is initially determined.

Apparatus For Linewidth Reduction in Distributed Feedback or Distributed Bragg Reflector Semiconductor Lasers Using Vertical Emission

NASA Technical Reports Server (NTRS)

Cook, Anthony L. (Inventor); Hendricks, Herbert D. (Inventor)

2000-01-01

The linewidth of a distributed feedback semiconductor laser or a distributed Bragg reflector laser having one or more second order gratings is reduced by using an external cavity to couple the vertical emission back into the laser. This method and device prevent disturbance of the main laser beam, provide unobstructed access to laser emission for the formation of the external cavity, and do not require a very narrow heat sink. Any distributed Bragg reflector semiconductor laser or distributed feedback semiconductor laser that can produce a vertical emission through the epitaxial material and through a window in the top metallization can be used. The external cavity can be formed with an optical fiber or with a lens and a mirror or grating.

A generalized method for determining radiation patterns of aperture antennas and its application to reflector antennas. M.S. Thesis

NASA Technical Reports Server (NTRS)

Paknys, J. R.

1982-01-01

The reflector antenna may be thought of as an aperture antenna. The classical solution for the radiation pattern of such an antenna is found by the aperture integration (AI) method. Success with this method depends on how accurately the aperture currents are known beforehand. In the past, geometrical optics (GO) has been employed to find the aperture currents. This approximation is suitable for calculating the main beam and possibly the first few sidelobes. A better approximation is to use aperture currents calculated from the geometrical theory of diffraction (GTD). Integration of the GTD currents over and extended aperture yields more accurate results for the radiation pattern. This approach is useful when conventional AI and GTD solutions have no common region of validity. This problem arises in reflector antennas. Two dimensional models of parabolic reflectors are studied; however, the techniques discussed can be applied to any aperture antenna.

Reconfigurable antenna using plasma reflector

NASA Astrophysics Data System (ADS)

Jusoh, Mohd Taufik; Ahmad, Khairol Amali; Din, Muhammad Faiz Md; Hashim, Fakroul Ridzuan

2018-02-01

This paper presents the feasibility study and design of plasma implementation in industrial, scientific and medical (ISM) communication band. A reflector antenna with rounded shaped is proposed to collimate beam in particular direction radiated by a quarter wave antenna operating at 2.4GHz. The simulations result has shown that by using plasma as the reflector elements, the gain, directivity and radiation patterns are identical with metal elements with only small different in the broadside direction. The versatility of the antenna is achievable by introducing electrical reconfigurable option to change the beam pattern.

Durability of reflector materials in the space environment

NASA Technical Reports Server (NTRS)

Whitaker, Ann F.; Finckenor, Miria M.; Edwards, David; Kamenetzky, Rachel R.; Linton, Roger C.

1995-01-01

Various reflector configurations were flown as part of the Long Duration Exposure Facility (LDEF) A0171 experiment. These reflectors consisted of nickel substrates with aluminum, enhanced aluminum (multiple layers of aluminum and silver), silver, and silver alloy coatings with glassy ceramic overcoatings. These samples have been evaluated for changes in reflectance due to 5.8 years in the space environment. The reflector materials have also been evaluated using angstrometer, Rutherford backscattering (RBS), and electron spectroscopy for chemical analysis (ESCA) techniques.

EMC design for actuators in the FAST reflector

NASA Astrophysics Data System (ADS)

Zhang, Hai-Yan; Wu, Ming-Chang; Yue, You-Ling; Gan, Heng-Qian; Hu, Hao; Huang, Shi-Jie

2018-04-01

An active reflector is one of the three main innovations incorporated in the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The deformation of such a huge spherically shaped reflector into different transient parabolic shapes is achieved by using 2225 hydraulic actuators which change the position of the 2225 nodes through the connected down tied cables. For each different tracking process of the telescope, more than 1/3 of these 2225 actuators must be in operation to tune the parabolic aperture accurately and meet the surface error restriction. This means that some of these actuators are inevitably located within the main beam of the receiver, and Electromagnetic Interference (EMI) from the actuators must be mitigated to ensure the scientific output of the telescope. Based on the threshold level of interference detrimental to radio astronomy described in ITU-R Recommendation RA.769 and EMI measurements, the shielding efficiency (SE) requirement for each actuator is set to be 80 dB in the frequency range from 70 MHz to 3 GHz. Therefore, Electromagnetic Compatibility (EMC) was taken into account in the actuator design by measures such as power line filters, optical fibers, shielding enclosures and other structural measures. In 2015, all the actuators had been installed at the FAST site. Till now, no apparent EMI from the actuators has been detected by the receiver, which demonstrates the effectiveness of these EMC measures.

Study of Membrane Reflector Technology

NASA Technical Reports Server (NTRS)

Knapp, K.; Hedgepeth, J.

1979-01-01

Very large reflective surfaces are required by future spacecraft for such purposes as solar energy collection, antenna surfaces, thermal control, attitude and orbit control with solar pressure, and solar sailing. The performance benefits in large membrane reflector systems, which may be derived from an advancement of this film and related structures technology, are identified and qualified. The results of the study are reported and summarized. Detailed technical discussions of various aspects of the study are included in several separate technical notes which are referenced.

Concepts and analysis for precision segmented reflector and feed support structures

NASA Technical Reports Server (NTRS)

Miller, Richard K.; Thomson, Mark W.; Hedgepeth, John M.

1990-01-01

Several issues surrounding the design of a large (20-meter diameter) Precision Segmented Reflector are investigated. The concerns include development of a reflector support truss geometry that will permit deployment into the required doubly-curved shape without significant member strains. For deployable and erectable reflector support trusses, the reduction of structural redundancy was analyzed to achieve reduced weight and complexity for the designs. The stiffness and accuracy of such reduced member trusses, however, were found to be affected to a degree that is unexpected. The Precision Segmented Reflector designs were developed with performance requirements that represent the Reflector application. A novel deployable sunshade concept was developed, and a detailed parametric study of various feed support structural concepts was performed. The results of the detailed study reveal what may be the most desirable feed support structure geometry for Precision Segmented Reflector/Large Deployable Reflector applications.

49 CFR 393.26 - Requirements for reflectors.

Code of Federal Regulations, 2010 CFR

2010-10-01

... case of motor vehicles so constructed that requirement for a 381 mm (15-inch) minimum height above the... used in lieu of reflex reflectors if the material as used on the vehicle, meets the performance... motor vehicle. (3) Such surfaces shall be at least 3 inches from any required lamp or reflector unless...

Systematic analysis of diffuse rear reflectors for enhanced light trapping in silicon solar cells

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

Pfeffer, Florian; Eisenlohr, Johannes; Basch, Angelika

Simple diffuse rear reflectors can enhance the light path length of weakly absorbed near infrared light in silicon solar cells and set a benchmark for more complex and expensive light trapping structures like dielectric gratings or plasmonic particles. We analyzed such simple diffuse rear reflectors systematically by optical and electrical measurements. We applied white paint, TiO 2 nanoparticles, white backsheets and a silver mirror to bifacial silicon solar cells and measured the enhancement of the external quantum efficiency for three different solar cell geometries: planar front and rear side, textured front and planar rear side, and textured front and rearmore » side. We showed that an air-gap between the solar cell and the reflector decreases the absorption enhancement significantly, thus white paint and TiO 2 nanoparticles directly applied to the rear cell surface lead to the highest short circuit current density enhancements. Here, the short circuit current density gains for a 200 um thick planar solar cell reached up to 1.8 mA/cm 2, compared to a non-reflecting black rear side and up to 0.8 mA/cm 2 compared to a high-quality silver mirror rear side. For solar cells with textured front side the short circuit current density gains are in the range between 0.5 and 1.0 mA/cm 2 compared to a non-reflecting black rear side and do not significantly depend on the angular characteristic of the rear side reflector but mainly on its absolute reflectance.« less

Systematic analysis of diffuse rear reflectors for enhanced light trapping in silicon solar cells

DOE PAGES

Pfeffer, Florian; Eisenlohr, Johannes; Basch, Angelika; ...

2016-04-08

Simple diffuse rear reflectors can enhance the light path length of weakly absorbed near infrared light in silicon solar cells and set a benchmark for more complex and expensive light trapping structures like dielectric gratings or plasmonic particles. We analyzed such simple diffuse rear reflectors systematically by optical and electrical measurements. We applied white paint, TiO 2 nanoparticles, white backsheets and a silver mirror to bifacial silicon solar cells and measured the enhancement of the external quantum efficiency for three different solar cell geometries: planar front and rear side, textured front and planar rear side, and textured front and rearmore » side. We showed that an air-gap between the solar cell and the reflector decreases the absorption enhancement significantly, thus white paint and TiO 2 nanoparticles directly applied to the rear cell surface lead to the highest short circuit current density enhancements. Here, the short circuit current density gains for a 200 um thick planar solar cell reached up to 1.8 mA/cm 2, compared to a non-reflecting black rear side and up to 0.8 mA/cm 2 compared to a high-quality silver mirror rear side. For solar cells with textured front side the short circuit current density gains are in the range between 0.5 and 1.0 mA/cm 2 compared to a non-reflecting black rear side and do not significantly depend on the angular characteristic of the rear side reflector but mainly on its absolute reflectance.« less

Impact of one-dimensional photonic crystal back reflector in thin-film c-Si solar cells on efficiency

NASA Astrophysics Data System (ADS)

Jalali, Tahmineh

2018-05-01

In this work, the effect of one-dimensional photonic crystal on optical absorption, which is implemented at the back side of thin-film crystalline silicon (c-Si) solar cells, is extensively discussed. The proposed structure acts as a Bragg reflector which reflects back light to the active layer as well as nanograting which couples the incident light to enhance optical absorption. To understand the optical mechanisms responsible for the enhancement of optical absorption, quantum efficiency and current density for all structures are calculated and the effect of influential parameters, such as grating period is investigated. The results confirm that our proposed structure have a great deal for substantial efficiency enhancement in a broad range from 400 to 1100 nm.

Polarization independent polymer waveguide tunable receivers incorporating a micro-optic circulator

NASA Astrophysics Data System (ADS)

Wu, Xiaoping; Park, Tae-Hyun; Park, Su-Hyun; Seo, Jun-Kyu; Oh, Min-Cheol

2018-06-01

In order to simplify the receiver configuration in a wavelength division multiplexed optical fiber network, compact wavelength tunable filters have long been expected to be used as channel selectors. Bragg reflector inherently has the most suitable reflection spectrum for filtering a single wavelength from the densely multiplexed wavelength signal. Polymer has high thermo-optic coefficient and good thermal insulation property compared to the other optical waveguide materials such as silicon and silica materials. This can be used to broadly tune the reflection spectrum of Bragg reflector using a simple micro-heater. In this work, a micro-optic circulator component and a polymeric Bragg reflector device are assembled to produce a small form factor tunable receiver. Compared to the integrated-optical versions, the micro-optics are based on well-developed manufacturing processes and can achieve competitive production yields. The device exhibits high reflectivity with a flat top passband, and a polarization dependence of 0.06 nm achieved by virtue of the low birefringence of LFR polymer, which make a significant contribution to the implementation of polarization independent tunable receiver. The wavelength tuning range of 40 nm is demonstrated by using a bottom located heater with a groove for heat isolation.

Concentrating Solar Power Projects - Linear Fresnel Reflector Projects |

Science.gov Websites

Kimberlina solar thermal power plant, a linear Fresnel reflector system located near Bakersfield, California Solar Thermal Project eLLO Solar Thermal Project (Llo) IRESEN 1 MWe CSP-ORC pilot project Kimberlina Solar Thermal Power Plant (Kimberlina) Liddell Power Station Puerto Errado 1 Thermosolar Power Plant

Optimal integration of daylighting and electric lighting systems using non-imaging optics

NASA Astrophysics Data System (ADS)

Scartezzini, J.-L.; Linhart, F.; Kaegi-Kolisnychenko, E.

2007-09-01

Electric lighting is responsible for a significant fraction of electricity consumption within non-residential buildings. Making daylight more available in office and commercial buildings can lead as a consequence to important electricity savings, as well as to the improvement of occupants' visual performance and wellbeing. Over the last decades, daylighting technologies have been developed for that purpose, some of them having proven to be highly efficient such as anidolic daylighting systems. Based on non-imaging optics these optical devices were designed to achieve an efficient collection and redistribution of daylight within deep office rooms. However in order to benefit from the substantial daylight provision obtained through these systems and convert it into effective electricity savings, novel electric lighting strategies are required. An optimal integration of high efficacy light sources and efficient luminaries based on non-imaging optics with anidolic daylighting systems can lead to such novel strategies. Starting from the experience gained through the development of an Anidolic Integrated Ceiling (AIC), this paper presents an optimal integrated daylighting and electric lighting system. Computer simulations based on ray-tracing techniques were used to achieve the integration of 36W fluorescent tubes and non-imaging reflectors with an advanced daylighting system. Lighting power densities lower than 4 W/m2 can be achieved in this way within the corresponding office room. On-site monitoring of an integrated daylighting and electric lighting system carried out on a solar experimental building confirmed the energy and visual performance of such a system: it showed that low lighting power densities can be achieved by combining an anidolic daylighting system with very efficient electric light sources and luminaries.

Broadband and polarization reflectors in the lookdown, Selene vomer

PubMed Central

Zhao, Shulei; Brady, Parrish Clawson; Gao, Meng; Etheredge, Robert Ian; Kattawar, George W.; Cummings, Molly E.

2015-01-01

Predator evasion in the open ocean is difficult because there are no objects to hide behind. The silvery surface of fish plays an important role in open water camouflage. Various models have been proposed to account for the broadband reflectance by the fish skin that involve one-dimensional variations in the arrangement of guanine crystal reflectors, yet the three-dimensional organization of these guanine platelets have not been well characterized. Here, we report the three-dimensional organization and the optical properties of integumentary guanine platelets in a silvery marine fish, the lookdown (Selene vomer). Our structural analysis and computational modelling show that stacks of guanine platelets with random yaw angles in the fish skin produce broadband reflectance via colour mixing. Optical axes of the guanine platelets and the collagen layer are aligned closely and provide bulk birefringence properties that influence the polarization reflectance by the skin. These data demonstrate how the lookdown preserves or alters polarization states at different incident polarization angles. These optical properties resulted from the organization of these guanine platelets and the collagen layer may have implications for open ocean camouflage in varying light fields. PMID:25673301

Preliminary design approach for large high precision segmented reflectors

NASA Technical Reports Server (NTRS)

Mikulas, Martin M., Jr.; Collins, Timothy J.; Hedgepeth, John M.

1990-01-01

A simplified preliminary design capability for erectable precision segmented reflectors is presented. This design capability permits a rapid assessment of a wide range of reflector parameters as well as new structural concepts and materials. The preliminary design approach was applied to a range of precision reflectors from 10 meters to 100 meters in diameter while considering standard design drivers. The design drivers considered were: weight, fundamental frequency, launch packaging volume, part count, and on-orbit assembly time. For the range of parameters considered, on-orbit assembly time was identified as the major design driver. A family of modular panels is introduced which can significantly reduce the number of reflector parts and the on-orbit assembly time.

Internal high-reflectivity omni-directional reflectors

NASA Astrophysics Data System (ADS)

Xi, J.-Q.; Ojha, Manas; Plawsky, J. L.; Gill, W. N.; Kim, Jong Kyu; Schubert, E. F.

2005-07-01

An internal high-reflectivity omni-directional reflector (ODR) for the visible spectrum is realized by the combination of total internal reflection using a low-refractive-index (low-n) material and reflection from a one-dimensional photonic crystal (1D PC). The low-n layer limits the range of angles in the 1D PC to values below the Brewster angle, thereby enabling high reflectivity and omni-directionality. This ODR is demonstrated using GaP as ambient, nanoporous SiO2 with a very low refractive index (n=1.10), and a four-pair TiO2/SiO2 multilayer stack. The results indicate a two orders of magnitude lower angle-integrated transverse-electric-transverse-magnetic polarization averaged mirror loss of the ODR compared with conventional distributed Bragg reflectors and metal reflectors. This indicates the high potential of the internal ODRs for optoelectronic semiconductor devices, e.g., light-emitting diodes.

Impact of HFIR LEU Conversion on Beryllium Reflector Degradation Factors

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

Ilas, Dan

2013-10-01

An assessment of the impact of low enriched uranium (LEU) conversion on the factors that may cause the degradation of the beryllium reflector is performed for the High Flux Isotope Reactor (HFIR). The computational methods, models, and tools, comparisons with previous work, along with the results obtained are documented and discussed in this report. The report documents the results for the gas and neutronic poison production, and the heating in the beryllium reflector for both the highly enriched uranium (HEU) and LEU HFIR configurations, and discusses the impact that the conversion to LEU may have on these quantities. A time-averagingmore » procedure was developed to calculate the isotopic (gas and poisons) production in reflector. The sensitivity of this approach to different approximations is gauged and documented. The results show that the gas is produced in the beryllium reflector at a total rate of 0.304 g/cycle for the HEU configuration; this rate increases by ~12% for the LEU case. The total tritium production rate in reflector is 0.098 g/cycle for the HEU core and approximately 11% higher for the LEU core. A significant increase (up to ~25%) in the neutronic poisons production in the reflector during the operation cycles is observed for the LEU core, compared to the HEU case, for regions close to the core s horizontal midplane. The poisoning level of the reflector may increase by more than two orders of magnitude during long periods of downtime. The heating rate in the reflector is estimated to be approximately 20% lower for the LEU core than for the HEU core. The decrease is due to a significantly lower contribution of the heating produced by the gamma radiation for the LEU core. Both the isotopic (gas and neutronic poisons) production and the heating rates are spatially non-uniform throughout the beryllium reflector volume. The maximum values typically occur in the removable reflector and close to the midplane.« less

Gaussian-Beam/Physical-Optics Design Of Beam Waveguide

NASA Technical Reports Server (NTRS)

Veruttipong, Watt; Chen, Jacqueline C.; Bathker, Dan A.

1993-01-01

In iterative method of designing wideband beam-waveguide feed for paraboloidal-reflector antenna, Gaussian-beam approximation alternated with more nearly exact physical-optics analysis of diffraction. Includes curved and straight reflectors guiding radiation from feed horn to subreflector. For iterative design calculations, curved mirrors mathematically modeled as thin lenses. Each distance Li is combined length of two straight-line segments intersecting at one of flat mirrors. Method useful for designing beam-waveguide reflectors or mirrors required to have diameters approximately less than 30 wavelengths at one or more intended operating frequencies.

High performance organic distributed Bragg reflector lasers fabricated by dot matrix holography.

PubMed

Wan, Wenqiang; Huang, Wenbin; Pu, Donglin; Qiao, Wen; Ye, Yan; Wei, Guojun; Fang, Zongbao; Zhou, Xiaohong; Chen, Linsen

2015-12-14

We report distributed Bragg reflector (DBR) polymer lasers fabricated using dot matrix holography. Pairs of distributed Bragg reflector mirrors with variable mirror separations are fabricated and a novel energy transfer blend consisting of a blue-emitting conjugated polymer and a red-emitting one is spin-coated onto the patterned substrate to complete the device. Under optical pumping, the device emits sing-mode lasing around 622 nm with a bandwidth of 0.41 nm. The working threshold is as low as 13.5 μJ/cm² (~1.68 kW/cm²) and the measured slope efficiency reaches 5.2%. The distributed feedback (DFB) cavity and the DBR cavity resonate at the same lasing wavelength while the DFB laser shows a much higher threshold. We further show that flexible DBR lasers can be conveniently fabricated through the UV-imprinting technique by using the patterned silica substrate as the mold. Dot matrix holography represents a versatile approach to control the number, the size, the location and the orientation of DBR mirrors, thus providing great flexibility in designing DBR lasers.

New core-reflector boundary conditions for transient nodal reactor calculations

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

Lee, E.K.; Kim, C.H.; Joo, H.K.

1995-09-01

New core-reflector boundary conditions designed for the exclusion of the reflector region in transient nodal reactor calculations are formulated. Spatially flat frequency approximations for the temporal neutron behavior and two types of transverse leakage approximations in the reflector region are introduced to solve the transverse-integrated time-dependent one-dimensional diffusion equation and then to obtain relationships between net current and flux at the core-reflector interfaces. To examine the effectiveness of new core-reflector boundary conditions in transient nodal reactor computations, nodal expansion method (NEM) computations with and without explicit representation of the reflector are performed for Laboratorium fuer Reaktorregelung und Anlagen (LRA) boilingmore » water reactor (BWR) and Nuclear Energy Agency Committee on Reactor Physics (NEACRP) pressurized water reactor (PWR) rod ejection kinetics benchmark problems. Good agreement between two NEM computations is demonstrated in all the important transient parameters of two benchmark problems. A significant amount of CPU time saving is also demonstrated with the boundary condition model with transverse leakage (BCMTL) approximations in the reflector region. In the three-dimensional LRA BWR, the BCMTL and the explicit reflector model computations differ by {approximately}4% in transient peak power density while the BCMTL results in >40% of CPU time saving by excluding both the axial and the radial reflector regions from explicit computational nodes. In the NEACRP PWR problem, which includes six different transient cases, the largest difference is 24.4% in the transient maximum power in the one-node-per-assembly B1 transient results. This difference in the transient maximum power of the B1 case is shown to reduce to 11.7% in the four-node-per-assembly computations. As for the computing time, BCMTL is shown to reduce the CPU time >20% in all six transient cases of the NEACRP PWR.« less

Demonstration of a Single-Crystal Reflector-Filter for Enhancing Slow Neutron Beams

DOE PAGES

Muhrer, Guenter; Schönfeldt, Troels; Iverson, Erik B.; ...

2016-06-14

The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystalmore » reflector-filter and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains the long-wavelength benefit of the polycrystalline reflector-filter, without suffering the same loss of important intermediate wavelength neutrons. Ultimately, this finding extends the applicability of the reflector-filter concept to intermediate wavelengths, and furthermore indicates that the reflector-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering.« less

Unpolarized resonance grating reflectors with 44% fractional bandwidth.

PubMed

Niraula, Manoj; Magnusson, Robert

2016-06-01

There is immense scientific interest in the properties of resonant thin films embroidered with periodic nanoscale features. This device class possesses considerable innovation potential. Accordingly, we report unpolarized broadband reflectors enabled by a serial arrangement of a pair of polarized subwavelength gratings. Optimized with numerical methods, our elemental gratings consist of a partially etched crystalline-silicon film on a quartz substrate. The resulting reflectors exhibit extremely wide spectral reflection bands in one polarization. By arranging two such reflectors sequentially with orthogonal periodicities, there results an unpolarized spectral band that exceeds those of the individual polarized bands. In the experiments reported herein, we achieve zero-order reflectance exceeding 97% under unpolarized light incidence over a 500 nm wide wavelength band. This wideband represents a ∼44% fractional band in the near infrared. Moreover, the resonant unpolarized broadband accommodates an ultra-high reflection band spanning ∼85  nm and exceeding 99.9% in efficiency. The elemental polarization-sensitive reflectors based on one-dimensional (1D) resonant gratings have a simple design and robust performance, and are straightforward to fabricate. Hence, this technology is a promising alternative to traditional multilayer thin-film reflectors, especially at longer wavelengths of light where multilayer deposition may be infeasible or impractical.

The Corner Reflector.

ERIC Educational Resources Information Center

Harris, Whitney S., Jr.

1983-01-01

The nature of the corner reflector array left on the moon by the July 1969 Apollo astronauts is described. The array was used to reflect earth-originating laser beams back to earth, and yielded a more accurate determination (to within six inches) of distance from the earth to the moon. (MP)

Bandwidth Study of the Microwave Reflectors with Rectangular Corrugations

NASA Astrophysics Data System (ADS)

Zhang, Liang; He, Wenlong; Donaldson, Craig R.; Cross, Adrian W.

2016-09-01

The mode-selective microwave reflector with periodic rectangular corrugations in the inner surface of a circular metallic waveguide is studied in this paper. The relations between the bandwidth and reflection coefficient for different numbers of corrugation sections were studied through a global optimization method. Two types of reflectors were investigated. One does not consider the phase response and the other does. Both types of broadband reflectors operating at W-band were machined and measured to verify the numerical simulations.

Whole-angle spherical retroreflector using concentric layers of homogeneous optical media.

PubMed

Oakley, John P

2007-03-01

Spherical retroreflectors have a much greater acceptance angle than conventional retroreflectors such as corner cubes. However, the optical performance of known spherical reflectors is limited by spherical aberration. It is shown that third-order spherical aberration may be corrected by using two or more layers of homogeneous optical media of different refractive indices. The performance of the retroreflector is characterized by the scattering (or radar) cross section, which is calculated by using optical design software. A practical spherical reflector is described that offers a significant increase in optical performance over existing devices. No gradient index components are required, and the device is constructed by using conventional optical materials and fabrication techniques. The experimental results confirm that the device operates correctly at the design wavelength of 690 nm.

Method of manufacturing large dish reflectors for a solar concentrator apparatus

DOEpatents

Angel, Roger P [Tucson, AZ; Olbert, Blain H [Tucson, AZ

2011-12-27

A method of manufacturing monolithic glass reflectors for concentrating sunlight in a solar energy system is disclosed. The method of manufacturing allows large monolithic glass reflectors to be made from float glass in order to realize significant cost savings on the total system cost for a solar energy system. The method of manufacture includes steps of heating a sheet of float glass positioned over a concave mold until the sheet of glass sags and stretches to conform to the shape of the mold. The edges of the dish-shaped glass are rolled for structural stiffening around the periphery. The dish-shaped glass is then silvered to create a dish-shaped mirror that reflects solar radiation to a focus. The surface of the mold that contacts the float glass preferably has a grooved surface profile comprising a plurality of cusps and concave valleys. This grooved profile minimizes the contact area and marring of the specular glass surface, reduces parasitic heat transfer into the mold and increases mold lifetime. The disclosed method of manufacture is capable of high production rates sufficiently fast to accommodate the output of a conventional float glass production line so that monolithic glass reflectors can be produced as quickly as a float glass production can make sheets of float glass to be used in the process.

Optical alignment of high resolution Fourier transform spectrometers

NASA Technical Reports Server (NTRS)

Breckinridge, J. B.; Ocallaghan, F. G.; Cassie, A. G.

1980-01-01

Remote sensing, high resolution FTS instruments often contain three primary optical subsystems: Fore-Optics, Interferometer Optics, and Post, or Detector Optics. We discuss the alignment of a double-pass FTS containing a cat's-eye retro-reflector. Also, the alignment of fore-optics containing confocal paraboloids with a reflecting field stop which relays a field image onto a camera is discussed.

Large Deployable Reflector (LDR) feasibility study update

NASA Technical Reports Server (NTRS)

Alff, W. H.; Banderman, L. W.

1983-01-01

In 1982 a workshop was held to refine the science rationale for large deployable reflectors (LDR) and develop technology requirements that support the science rationale. At the end of the workshop, a set of LDR consensus systems requirements was established. The subject study was undertaken to update the initial LDR study using the new systems requirements. The study included mirror materials selection and configuration, thermal analysis, structural concept definition and analysis, dynamic control analysis and recommendations for further study. The primary emphasis was on the dynamic controls requirements and the sophistication of the controls system needed to meet LDR performance goals.

Method and Apparatus for Linewidth Reduction in Distributed Feedback or Distributed Bragg Reflector Semiconductor Lasers using Vertical Emission

NASA Technical Reports Server (NTRS)

Cook, Anthony L. (Inventor); Hendricks, Herbert D. (Inventor)

1998-01-01

The linewidth of a distributed feedback semiconductor laser or a distributed Bragg reflector laser having one or more second order gratings is reduced by using an external cavity to couple the vertical emission back into the laser. This method and device prevent disturbance of the main laser beam. provide unobstructed access to laser emission for the formation of the external cavity. and do not require a very narrow heat sink. Any distributed Bragg reflector semiconductor laser or distributed feedback semiconductor laser that can produce a vertical emission through the epitaxial material and through a window in the top metallization can be used. The external cavity can be formed with an optical fiber or with a lens and a mirror of grating.

Distributed feedback laser diode integrated with distributed Bragg reflector for continuous-wave terahertz generation.

PubMed

Kim, Namje; Han, Sang-Pil; Ryu, Han-Cheol; Ko, Hyunsung; Park, Jeong-Woo; Lee, Donghun; Jeon, Min Yong; Park, Kyung Hyun

2012-07-30

A widely tunable dual mode laser diode with a single cavity structure is demonstrated. This novel device consists of a distributed feedback (DFB) laser diode and distributed Bragg reflector (DBR). Micro-heaters are integrated on the top of each section for continuous and independent wavelength tuning of each mode. By using a single gain medium in the DFB section, an effective common optical cavity and common modes are realized. The laser diode shows a wide tunability of the optical beat frequency, from 0.48 THz to over 2.36 THz. Continuous wave THz radiation is also successfully generated with low-temperature grown InGaAs photomixers from 0.48 GHz to 1.5 THz.

A technology program for the development of the large deployable reflector for space based astronomy

NASA Technical Reports Server (NTRS)

Kiya, M. K.; Gilbreath, W. P.; Swanson, P. N.

1982-01-01

Technologies for the development of the Large Deployable Reflector (LDR), a NASA project for the 1990's, for infrared and submillimeter astronomy are presented. The proposed LDR is a 10-30 diameter spaceborne observatory operating in the spectral region from 30 microns to one millimeter, where ground observations are nearly impossible. Scientific rationales for such a system include the study of ancient signals from galaxies at the edge of the universe, the study of star formation, and the observation of fluctuations in the cosmic background radiation. System requirements include the ability to observe faint objects at large distances and to map molecular clouds and H II regions. From these requirements, mass, photon noise, and tolerance budgets are developed. A strawman concept is established, and some alternate concepts are considered, but research is still necessary in the areas of segment, optical control, and instrument technologies.

Design and analysis of reflector for uniform light-emitting diode illuminance.

PubMed

Tsai, Chung-Yu

2013-05-01

A light-emitting diode (LED) projection system is proposed, composed of an LED chip and a variable-focus-parabolic (VFP) reflector, in which the focal length varies as a function of the vertical displacement of the incidence point relative to the horizontal centerline of the LED chip. The light-ray paths within the projection system are analyzed using an exact analytical model and a skew-ray tracing approach. The profile of the proposed VFP reflector and the position of the LED chip are then optimized in such a way as to enhance the uniformity of the illuminance distribution on the target region of the image plane. The validity of the optimized design is demonstrated by means of ZEMAX simulations. It is shown that the optimized VFP projector system yields a significant improvement in illuminance uniformity compared to conventional spherical and parabolic projectors and therefore minimizes the glare effect.

Astigmatism in reflector antennas.

NASA Technical Reports Server (NTRS)

Cogdell, J. R.; Davis, J. H.

1973-01-01

Astigmatic phase error in large parabolic reflector antennas is discussed. A procedure for focusing an antenna and diagnosing the presence and degree of astigmatism is described. Theoretical analysis is conducted to determine the nature of this error in such antennas.

A Nonlinear Dynamic Model and Free Vibration Analysis of Deployable Mesh Reflectors

NASA Technical Reports Server (NTRS)

Shi, H.; Yang, B.; Thomson, M.; Fang, H.

2011-01-01

This paper presents a dynamic model of deployable mesh reflectors, in which geometric and material nonlinearities of such a space structure are fully described. Then, by linearization around an equilibrium configuration of the reflector structure, a linearized model is obtained. With this linearized model, the natural frequencies and mode shapes of a reflector can be computed. The nonlinear dynamic model of deployable mesh reflectors is verified by using commercial finite element software in numerical simulation. As shall be seen, the proposed nonlinear model is useful for shape (surface) control of deployable mesh reflectors under thermal loads.

A comparison of reflector antenna designs for wide-angle scanning

NASA Technical Reports Server (NTRS)

Zimmerman, M.; Lee, S. W.; Houshmand, B.; Rahmatsamii, Y.; Acosta, R. J.

1989-01-01

Conventional reflector antennas are typically designed for up to + or - 20 beamwidths scan. An attempt was made to stretch this scan range to some + or - 300 beamwidths. Six single and dual reflector antennas were compared. It is found that a symmetrical parabolic reflector with f/D = 2 and a single circular waveguide feed has the minimum scan loss (only 0.6 dB at Theta sub 0 = 8 deg, or a 114 beamwidths scan). The scan is achieved by tilting the parabolic reflector by an angle equal to the half-scan angle. The f/D may be shortened if a cluster 7 to 19 elements instead of one element is used for the feed. The cluster excitation is adjusted for each new beam scan direction to compensate for the imperfect field distribution over the reflector aperture. The antenna can be folded into a Cassegrain configuration except that, due to spillover and blockage considerations, the amount of folding achievable is small.

Test progress on the electrostatic membrane reflector

NASA Technical Reports Server (NTRS)

Mihora, D. J.

1981-01-01

An extemely lightweight type of precision reflector antenna, being developed for potential deployment from the space shuttle, uses electrostatic forces to tension a thin membrane and form it into a concave reflector surface. The typical shuttle-deployed antenna would have a diameter of 100 meters and an RMS surface smoothness of 10 to 1 mm for operation at 1 to 10 GHz. NASA Langley Research Center built and is currently testing a subscale (16 foot diameter) model of the membrane reflector portion of such an antenna. Preliminary test results and principal factors affecting surface quality are addressed. Factors included are the effect of the perimeter boundary, splicing of the membrane, the long-scale smoothness of commercial membranes, and the spatial controllability of the membrane using voltage adjustments to alter the electrostatic pressure. Only readily available commercial membranes are considered.

Broadband and polarization reflectors in the lookdown, Selene vomer.

PubMed

Zhao, Shulei; Brady, Parrish Clawson; Gao, Meng; Etheredge, Robert Ian; Kattawar, George W; Cummings, Molly E

2015-03-06

Predator evasion in the open ocean is difficult because there are no objects to hide behind. The silvery surface of fish plays an important role in open water camouflage. Various models have been proposed to account for the broadband reflectance by the fish skin that involve one-dimensional variations in the arrangement of guanine crystal reflectors, yet the three-dimensional organization of these guanine platelets have not been well characterized. Here, we report the three-dimensional organization and the optical properties of integumentary guanine platelets in a silvery marine fish, the lookdown (Selene vomer). Our structural analysis and computational modelling show that stacks of guanine platelets with random yaw angles in the fish skin produce broadband reflectance via colour mixing. Optical axes of the guanine platelets and the collagen layer are aligned closely and provide bulk birefringence properties that influence the polarization reflectance by the skin. These data demonstrate how the lookdown preserves or alters polarization states at different incident polarization angles. These optical properties resulted from the organization of these guanine platelets and the collagen layer may have implications for open ocean camouflage in varying light fields. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Vacuum-deposited polymer/silver reflector material

NASA Astrophysics Data System (ADS)

Affinito, John D.; Martin, Peter M.; Gross, Mark E.; Bennett, Wendy D.

1994-09-01

Weatherable, low cost, front surface, solar reflectors on flexible substrates would be highly desirable for lamination to solar concentrator panels. The method to be described in this paper may permit such reflector material to be fabricated for less the 50$CNT per square foot. Vacuum deposited Polymer/Silver/Polymer reflectors and Fabry-Perot interference filters were fabricated in a vacuum web coating operation on polyester substrates. Reflectivities were measured in the wavelength range from .4 micrometers to .8 micrometers . It is hoped that a low cost substrate can be used with the substrate laminated to the concentrator and the weatherable acrylic polymer coating facing the sun. This technique should be capable of deposition line speeds approaching 1500 linear feet/minute2. Central to this technique is a new vacuum deposition process for the high rate deposition of polymer films. This polymer process involves the flash evaporation of an acrylic monomer onto a moving substrate. The monomer is subsequently cured by an electron beam or ultraviolet light. This high speed polymer film deposition process has been named the PML process- for Polymer Multi- Layer.

Simulation requirements for the Large Deployable Reflector (LDR)

NASA Technical Reports Server (NTRS)

Soosaar, K.

1984-01-01

Simulation tools for the large deployable reflector (LDR) are discussed. These tools are often the transfer function variety equations. However, transfer functions are inadequate to represent time-varying systems for multiple control systems with overlapping bandwidths characterized by multi-input, multi-output features. Frequency domain approaches are the useful design tools, but a full-up simulation is needed. Because of the need for a dedicated computer for high frequency multi degree of freedom components encountered, non-real time smulation is preferred. Large numerical analysis software programs are useful only to receive inputs and provide output to the next block, and should be kept out of the direct loop of simulation. The following blocks make up the simulation. The thermal model block is a classical heat transfer program. It is a non-steady state program. The quasistatic block deals with problems associated with rigid body control of reflector segments. The steady state block assembles data into equations of motion and dynamics. A differential raytrace is obtained to establish a change in wave aberrations. The observation scene is described. The focal plane module converts the photon intensity impinging on it into electron streams or into permanent film records.

46 CFR 28.235 - Anchors and radar reflectors.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 1 2011-10-01 2011-10-01 false Anchors and radar reflectors. 28.235 Section 28.235....235 Anchors and radar reflectors. (a) Each vessel must be fitted with an anchor(s) and chain(s), cable... rigged with gear that provides a radar signature from a distance of 6 miles, each nonmetallic hull vessel...

46 CFR 28.235 - Anchors and radar reflectors.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 1 2010-10-01 2010-10-01 false Anchors and radar reflectors. 28.235 Section 28.235....235 Anchors and radar reflectors. (a) Each vessel must be fitted with an anchor(s) and chain(s), cable... rigged with gear that provides a radar signature from a distance of 6 miles, each nonmetallic hull vessel...

46 CFR 28.235 - Anchors and radar reflectors.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 1 2012-10-01 2012-10-01 false Anchors and radar reflectors. 28.235 Section 28.235....235 Anchors and radar reflectors. (a) Each vessel must be fitted with an anchor(s) and chain(s), cable... rigged with gear that provides a radar signature from a distance of 6 miles, each nonmetallic hull vessel...

46 CFR 28.235 - Anchors and radar reflectors.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 1 2014-10-01 2014-10-01 false Anchors and radar reflectors. 28.235 Section 28.235....235 Anchors and radar reflectors. (a) Each vessel must be fitted with an anchor(s) and chain(s), cable... rigged with gear that provides a radar signature from a distance of 6 miles, each nonmetallic hull vessel...

46 CFR 28.235 - Anchors and radar reflectors.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 1 2013-10-01 2013-10-01 false Anchors and radar reflectors. 28.235 Section 28.235....235 Anchors and radar reflectors. (a) Each vessel must be fitted with an anchor(s) and chain(s), cable... rigged with gear that provides a radar signature from a distance of 6 miles, each nonmetallic hull vessel...

Deployable reflector antenna performance optimization using automated surface correction and array-feed compensation

NASA Technical Reports Server (NTRS)

Schroeder, Lyle C.; Bailey, M. C.; Mitchell, John L.

1992-01-01

Methods for increasing the electromagnetic (EM) performance of reflectors with rough surfaces were tested and evaluated. First, one quadrant of the 15-meter hoop-column antenna was retrofitted with computer-driven and controlled motors to allow automated adjustment of the reflector surface. The surface errors, measured with metric photogrammetry, were used in a previously verified computer code to calculate control motor adjustments. With this system, a rough antenna surface (rms of approximately 0.180 inch) was corrected in two iterations to approximately the structural surface smoothness limit of 0.060 inch rms. The antenna pattern and gain improved significantly as a result of these surface adjustments. The EM performance was evaluated with a computer program for distorted reflector antennas which had been previously verified with experimental data. Next, the effects of the surface distortions were compensated for in computer simulations by superimposing excitation from an array feed to maximize antenna performance relative to an undistorted reflector. Results showed that a 61-element array could produce EM performance improvements equal to surface adjustments. When both mechanical surface adjustment and feed compensation techniques were applied, the equivalent operating frequency increased from approximately 6 to 18 GHz.

Materials and process optimization for dual-shell satellite antenna reflectors

NASA Astrophysics Data System (ADS)

Balaski, Darcy R.; van Oyen, Hans J.; Nissan, Sorin J.

A comprehensive, design-optimization test program was conducted for satellite antenna reflectors composed of two offset paraboloidal Kevlar-reinforced sandwich shells separated by a circular sandwich structure. In addition to standard mechanical properties testing, coefficient of thermal expansion and hygroscopic tests were conducted to predict reflector surface accuracy in the thermal cycling environment of orbital space. Attention was given to the relative placement of components during assembly, in view of reflector surface measurements.

A new instrument for measuring optical transmission in the atmosphere

NASA Astrophysics Data System (ADS)

Kaurila, Timo A.

2007-04-01

It is an important task to measure optical transmission of the atmosphere when testing the performance of electro-optical systems such as thermal imagers. Only by knowing atmospheric transmission precisely enough, we will be able to eliminate effects of the atmosphere on test results. For this reason a new instrument that measures optical transmission in the atmosphere has been constructed. The transmissometer consists of a transmitter/receiver unit, a reflector and control software. The instrument measures atmospheric transmission at wavelength of 1 μm and 8-12 μm by comparing the intensity of the beam propagating through the atmosphere and the reference beam inside the transmitter/receiver unit. Calibration is carried out by the aid of a visibility meter and a special calibration algorithm. An important criterion for the design was to create an instrument which could be used flexibly in field measurements. The transmissometer was tested comprehensively in the field in March and June 2006. It can measure extinction coefficients up to 3 - 12 km -1 depending on the span between the transmitter/receiver unit and reflector with accuracy of 10 - 20 %. According to the test measurements the transmissometer also fulfills the other requirement specifications.

Lightweight diaphragm mirror module system for solar collectors

DOEpatents

Butler, Barry L.

1985-01-01

A mirror module system is provided for accurately focusing solar radiation on a point or a line as defined by an array of solar collectors. Each mirror module includes a flexible membrane stretched over a frame in a manner similar to that of a drum or a trampoline and further includes a silvered glass or plastic mirror for forming an optical reflecting surface. The configuration of the optical reflecting surface is variably adjustable to provide for the accurate focusing of the solar energy on a given collector array, e.g., a point or a linear array arrangement. The flexible mirror-membrane combination is lightweight to facilitate installation and reduce system cost yet structurally strong enough to provide for the precise focusing of the incident solar radiation in a semi-rigid reflector system in which unwanted reflector displacement is minimized.

Lightweight diaphragm mirror module system for solar collectors

DOEpatents

Butler, B.L.

1984-01-01

A mirror module system is provided for accurately focusing solar radiation on a point or a line as defined by an array of solar collectors. Each mirror module includes a flexible membrane stretched over a frame in a manner similar to that of a drum or a trampoline and further includes a silvered glass or plastic mirror for forming an optical reflecting surface. The configuration of the optical reflecting surface is variably adjustable to provide for the accurate focusing of the solar energy on a given collector array, e.g., a point or a linear array arrangement. The flexible mirror-membrane combination is lightweight to facilitate installation and reduce system cost yet structurally strong enough to provide for the precise focusing of the incident solar radiation in a semi-rigid reflector system in which unwanted reflector displacement is minimized.

Hohlraum glint and laser pre-pulse detector for NIF experiments using velocity interferometer system for any reflector.

PubMed

Moody, J D; Clancy, T J; Frieders, G; Celliers, P M; Ralph, J; Turnbull, D P

2014-11-01

Laser pre-pulse and early-time laser reflection from the hohlraum wall onto the capsule (termed "glint") can cause capsule imprint and unwanted early-time shocks on indirect drive implosion experiments. In a minor modification to the existing velocity interferometer system for any reflector diagnostic on NIF a fast-response vacuum photodiode was added to detect this light. The measurements show evidence of laser pre-pulse and possible light reflection off the hohlraum wall and onto the capsule.

Emissivity measurements in thin metallized membrane reflectors used for microwave radiometer sensors

NASA Technical Reports Server (NTRS)

Schroeder, Lyle C.; Cravey, Robin L.; Scherner, Michael J.; Hearn, Chase P.; Blume, Hans-Juergen C.

1995-01-01

This paper is concerned with electromagnetic losses in metallized films used for inflatable reflectors. An inflatable membrane is made of tough elastic material such as Kapton, and it is not electromagnetically reflective by design. A film of conducting metal is added to the membrane to enhance its reflective properties. Since the impetus for use of inflatables for spacecraft is the light weight and compact packaging, it is important that the metal film be as thin as possible. However, if the material is not conductive or thick enough, the radiation due to the emissivity of the reflector could be a significant part of the radiation gathered by the radiometer. The emissivity would be of little consequence to a radar or solar collector; but for a radiometer whose signal is composed of thermal radiation, this contribution could be severe. Bulk properties of the metal film cannot be used to predict its loss. For this reason, a program of analysis and measurement was undertaken to determine the emissivities of a number of candidate metallized film reflectors. This paper describes the three types of measurements which were performed on the metallized thin films: (1) a network analyzer system with an L-band waveguide; (2) an S-band radiometer; and (3) a network analyzer system with a C-band antenna free-space transmission system.

Long-Life Self-Renewing Solar Reflector Stack

DOEpatents

Butler, Barry Lynn

1997-07-08

A long-life solar reflector includes a solar collector substrate and a base layer bonded to a solar collector substrate. The first layer includes a first reflective layer and a first acrylic or transparent polymer layer covering the first reflective layer to prevent exposure of the first reflective layer. The reflector also includes at least one upper layer removably bonded to the first acrylic or transparent polymer layer of the base layer. The upper layer includes a second reflective layer and a second acrylic or transparent polymer layer covering the second reflective layer to prevent exposure of the second reflective layer. The upper layer may be removed from the base reflective layer to expose the base layer, thereby lengthening the useful life of the solar reflector. A method of manufacturing a solar reflector includes the steps of bonding a base layer to a solar collector substrate, wherein the base reflective layer includes a first reflective layer and a first transparent polymer or acrylic layer covering the first reflective layer; and removably bonding a first upper layer to the first transparent polymer or acrylic layer of the base layer. The first upper layer includes a second reflective layer and a second transparent polymer or acrylic layer covering the second reflective layer to prevent exposure of the second reflective layer.

Weighted SAW reflector gratings for orthogonal frequency coded SAW tags and sensors

NASA Technical Reports Server (NTRS)

Puccio, Derek (Inventor); Malocha, Donald (Inventor)

2011-01-01

Weighted surface acoustic wave reflector gratings for coding identification tags and sensors to enable unique sensor operation and identification for a multi-sensor environment. In an embodiment, the weighted reflectors are variable while in another embodiment the reflector gratings are apodized. The weighting technique allows the designer to decrease reflectively and allows for more chips to be implemented in a device and, consequently, more coding diversity. As a result, more tags and sensors can be implemented using a given bandwidth when compared with uniform reflectors. Use of weighted reflector gratings with OFC makes various phase shifting schemes possible, such as in-phase and quadrature implementations of coded waveforms resulting in reduced device size and increased coding.

Array feed synthesis for correction of reflector distortion and Vernier beamsteering

NASA Technical Reports Server (NTRS)

Blank, Stephen J.; Imbriale, William A.

1988-01-01

An algorithmic procedure for the synthesis of planar array feeds for paraboloidal reflectors is described which simultaneously provides electronic correction of systematic reflector surface distortions as well as a Vernier electronic beamsteering capability. Simple rules of thumb for the optimum chioce of planar array feed configuration (i.e., the number and type of elements) are derived from a parametric study made using the synthesis procedure. A number of f/D ratios and distortion models were examined that are typical of large paraboloidal reflectors. Numerical results are presented showing that, for the range of distortion models considered, good on-axis gain restoration can be achieved with as few as seven elements. For beamsteering to +/- 1 beamwidth (BW), 19 elements are required. For arrays with either 7 or 19 elements, the results indicate that the use of high-aperture-efficiency elements (e.g., disk-on-rod and short backfire) in the array yields higher system gain than can be obtained with elements having lower aperture efficiency (e.g., open-ended waveguides). With 37 elements, excellent gain and beamsteering performance to +/- 1.5 BW are obtained independent of the assumed effective aperture of the array element. An approximate expression is derived for the focal-plane field distribution of the distorted reflector. Contour plots of the focal-plane fields are also presented for various distortion and beam scan angle cases. The results obtained show the effectiveness of the array feed approach.

Array feed synthesis for correction of reflector distortion and Vernier Beamsteering

NASA Technical Reports Server (NTRS)

Blank, S. J.; Imbriale, W. A.

1986-01-01

An algorithmic procedure for the synthesis of planar array feeds for paraboloidal reflectors is described which simultaneously provides electronic correction of systematic reflector surface distortions as well as a Vernier electronic beamsteering capability. Simple rules of thumb for the optimum choice of planar array feed configuration (i.e., number and type of elements) are derived from a parametric study made using the synthesis procedure. A number of f/D ratios and distortion models were examined that are typical of large paraboloidal reflectors. Numerical results are presented showing that, for the range of distortion models considered, good on-axis gain restoration can be achieved with as few as seven elements. For beamsteering to +/- 1 beamwidth (BW), 19 elements are required. For arrays with either 7 or 19 elements, the results indicate that the use of high-aperture-efficiency elements (e.g., disk-on-rod and short backfire) in the array yields higher system gain than can be obtained with elements having lower aperture efficiency (e.g., open-ended waveguides). With 37 elements, excellent gain and beamsteering performance to +/- 1.5 BW are obtained independent of the assumed effective aperture of the array element. An approximate expression is derived for the focal-plane field distribution of the distorted reflector. Contour plots of the focal-plane fields are also presented for various distortion and beam scan angle cases. The results obtained show the effectiveness of the array feed approach.

The Optical Design of a System using a Fresnel Lens that Gathers Light for a Solar Concentrator and that Feeds into Solar Alignment Optics

NASA Technical Reports Server (NTRS)

Wilkerson, Gary W.; Huegele, Vinson

1998-01-01

The Marshall Space Flight Center (MSFC) has been developing a space deployable, lightweight membrane concentrator to focus solar energy into a solar furnace while remaining aligned to the sun. For an inner surface, this furnace has a cylindrical heat exchanger cavity coaligned to the optical axis; the furnace warms gas to propel the spacecraft. The membrane concentrator is a 1727 mm (68.00 in.) diameter, F/1.7 Fresnel lens. This large membrane is made from polyimide and is 0.076 mm (0.0030 in.) thick; it has the Fresnel grooves cast into it. The solar concentrator system has a super fast paraboloid reflector near the lens focus and immediately adjacent to the cylindrical exchanger cavity. The paraboloid collects the wide bandwidth and some of the solar energy scattered by the Fresnel lens. Finally, the paraboloid feeds the light into the cylinder. The Fresnel lens also possesses a narrow annular zone that focuses a reference beam toward four detectors that keep the optical system aligned to the sun; thus, occurs a refracting lens that focuses two places! The result can be summarized as a composite Fresnel lens for solar concentration and alignment.

Fine tuning of transmission features in nanoporous anodic alumina distributed Bragg reflectors

NASA Astrophysics Data System (ADS)

Lim, Siew Yee; Law, Cheryl Suwen; Santos, Abel

2018-01-01

This study introduces an innovative apodisation strategy to tune the filtering features of distributed Bragg reflectors based on nanoporous anodic alumina (NAA-DBRs). The effective medium of NAA-DBRs, which is modulated in a stepwise fashion by a pulse-like anodisation approach, is apodised following a logarithmic negative function to engineer the transmission features of NAA-DBRs. We investigate the effect of various apodisation parameters such as apodisation amplitude difference, anodisation period, current density offset and pore widening time, to tune and optimise the optical properties of NAA-DBRs in terms of central wavelength position, full width at half maximum and quality of photonic stop band. The transmission features of NAA-DBRs are shown to be fully controllable with precision across the spectral regions by means of the apodisation parameters. Our study demonstrates that an apodisation strategy can significantly narrow the width and enhance the quality of the characteristic photonic stop band of NAA-DBRs. This rationally designed anodisation approach based on the combination of apodisation and stepwise pulse anodisation enables the development of optical filters with tuneable filtering features to be integrated into optical technologies acting as essential photonic elements in devices such as optical sensors and biosensors.

Enhanced light absorption of silicon solar cells with dielectric nanostructured back reflector

NASA Astrophysics Data System (ADS)

Ren, Rui; Zhong, Zheng

2018-06-01

This paper investigates the light absorption property of nanostructured dielectric reflectors in silicon thin film solar cells using numerical simulation. Flat thin film solar cell with ZnO nanostructured back reflector can produce comparable photocurrent to the control model with Ag nanostructured back reflector. Furthermore, when it is integrated with nano-pillar surface decoration, a photocurrent density of 29.5 mA/cm2 can be achieved, demonstrating a photocurrent enhancement of 5% as compared to the model with Ag nanostructured back reflector.

Structural-electromagnetic bidirectional coupling analysis of space large film reflector antennas

NASA Astrophysics Data System (ADS)

Zhang, Xinghua; Zhang, Shuxin; Cheng, ZhengAi; Duan, Baoyan; Yang, Chen; Li, Meng; Hou, Xinbin; Li, Xun

2017-10-01

As used for energy transmission, a space large film reflector antenna (SLFRA) is characterized by large size and enduring high power density. The structural flexibility and the microwave radiation pressure (MRP) will lead to the phenomenon of structural-electromagnetic bidirectional coupling (SEBC). In this paper, the SEBC model of SLFRA is presented, then the deformation induced by the MRP and the corresponding far field pattern deterioration are simulated. Results show that, the direction of the MRP is identical to the normal of the reflector surface, and the magnitude is proportional to the power density and the square of cosine incident angle. For a typical cosine function distributed electric field, the MRP is a square of cosine distributed across the diameter. The maximum deflections of SLFRA linearly increase with the increasing microwave power densities and the square of the reflector diameters, and vary inversely with the film thicknesses. When the reflector diameter becomes 100 m large and the microwave power density exceeds 102 W/cm2, the gain loss of the 6.3 μm-thick reflector goes beyond 0.75 dB. When the MRP-induced deflection degrades the reflector performance, the SEBC should be taken into account.

Dual-shaped offset reflector antenna designs from solutions of the geometrical optics first-order partial differential equations

NASA Technical Reports Server (NTRS)

Galindo-Israel, V.; Imbriale, W.; Shogen, K.; Mittra, R.

1990-01-01

In obtaining solutions to the first-order nonlinear partial differential equations (PDEs) for synthesizing offset dual-shaped reflectors, it is found that previously observed computational problems can be avoided if the integration of the PDEs is started from an inner projected perimeter and integrated outward rather than starting from an outer projected perimeter and integrating inward. This procedure, however, introduces a new parameter, the main reflector inner perimeter radius p(o), when given a subreflector inner angle 0(o). Furthermore, a desired outer projected perimeter (e.g., a circle) is no longer guaranteed. Stability of the integration is maintained if some of the initial parameters are determined first from an approximate solution to the PDEs. A one-, two-, or three-parameter optimization algorithm can then be used to obtain a best set of parameters yielding a close fit to the desired projected outer rim. Good low cross-polarization mapping functions are also obtained. These methods are illustrated by synthesis of a high-gain offset-shaped Cassegrainian antenna and a low-noise offset-shaped Gregorian antenna.

A new fabrication method for precision antenna reflectors for space flight and ground test

NASA Technical Reports Server (NTRS)

Sharp, G. Richard; Wanhainen, Joyce S.; Ketelsen, Dean A.

1991-01-01

Communications satellites are using increasingly higher frequencies that require increasingly precise antenna reflectors for use in space. Traditional industry fabrication methods for space antenna reflectors employ successive modeling techniques using high- and low-temperature molds for reflector face sheets and then a final fit-up of the completed honeycomb sandwich panel antenna reflector to a master pattern. However, as new missions are planned at much higher frequencies, greater accuracies will be necessary than are achievable using these present methods. A new approach for the fabrication of ground-test solid-surface antenna reflectors is to build a rigid support structure with an easy-to-machine surface. This surface is subsequently machined to the desired reflector contour and coated with a radio-frequency-reflective surface. This method was used to fabricate a 2.7-m-diameter ground-test antenna reflector to an accuracy of better than 0.013 mm (0.0005 in.) rms. A similar reflector for use on spacecraft would be constructed in a similar manner but with space-qualified materials. The design, analysis, and fabrication of the 2.7-m-diameter precision antenna reflector for antenna ground tests and the extension of this technology to precision, space-based antenna reflectors are described.

Active optical zoom system

DOEpatents

Wick, David V.

2005-12-20

An active optical zoom system changes the magnification (or effective focal length) of an optical imaging system by utilizing two or more active optics in a conventional optical system. The system can create relatively large changes in system magnification with very small changes in the focal lengths of individual active elements by leveraging the optical power of the conventional optical elements (e.g., passive lenses and mirrors) surrounding the active optics. The active optics serve primarily as variable focal-length lenses or mirrors, although adding other aberrations enables increased utility. The active optics can either be LC SLMs, used in a transmissive optical zoom system, or DMs, used in a reflective optical zoom system. By appropriately designing the optical system, the variable focal-length lenses or mirrors can provide the flexibility necessary to change the overall system focal length (i.e., effective focal length), and therefore magnification, that is normally accomplished with mechanical motion in conventional zoom lenses. The active optics can provide additional flexibility by allowing magnification to occur anywhere within the FOV of the system, not just on-axis as in a conventional system.

Fabrication of high reflectivity nanoporous distributed Bragg reflectors by controlled electrochemical etching of GaN

NASA Astrophysics Data System (ADS)

Lee, Seung-Min; Kang, Jin-Ho; Lee, June Key; Ryu, Sang-Wan

2016-09-01

The nanoporous medium is a valuable feature of optical devices because of its variable optical refractive index with porosity. One important application is in a GaN-based vertical cavity surface emitting laser having a distributed Bragg reflector (DBR) composed of alternating nanoporous and bulk GaNs. However, optimization of the fabrication process for high reflectivity DBRs having wellcontrolled high reflection bands has not been studied yet. We used electrochemical etching to study the fabrication process of a nanoporous GaN DBR and analyzed the relationship between the morphology and optical reflectivity. Several electrolytes were examined for the formation of the optimized nanoporous structure. A highly reflective DBRs having reflectivity of ~100% were obtained over a wide wavelength range of 450-750 nm. Porosification of semiconductors into nanoporous layers could provide a high reflectivity DBR due to controlled index-contrast, which would be advantages for the construction of a high-Q optical cavity.

Reflector and Protections in a Sodium-cooled Fast Reactor: Modelling and Optimization

NASA Astrophysics Data System (ADS)

Blanchet, David; Fontaine, Bruno

2017-09-01

The ASTRID project (Advanced Sodium Technological Reactor for Industrial Demonstration) is a Generation IV nuclear reactor concept under development in France [1]. In this frame, studies are underway to optimize radial reflectors and protections. Considering radial protections made in natural boron carbide, this study is conducted to assess the neutronic performances of the MgO as the reference choice for reflector material, in comparison with other possible materials including a more conventional stainless steel. The analysis is based upon a simplified 1-D and 2-D deterministic modelling of the reactor, providing simplified interfaces between core, reflector and protections. Such models allow examining detailed reaction rate distributions; they also provide physical insights into local spectral effects occurring at the Core-Reflector and at the Reflector-Protection interfaces.

Transparent conducting oxide contacts and textured metal back reflectors for thin film silicon solar cells

NASA Astrophysics Data System (ADS)

Franken, R. H.-J.

2006-09-01

With the growing population and the increasing environmental problems of the 'common' fossil and nuclear energy production, the need for clean and sustainable energy sources is evident. Solar energy conversion, such as in photovoltaic (PV) systems, can play a major role in the urgently needed energy transition in electricity production. At the present time PV module production is dominated by the crystalline wafer technology. Thin film silicon technology is an alternative solar energy technology that operates at lower efficiencies, however, it has several significant advantages, such as the possibility of deposition on cheap (flexible) substrates and the much smaller silicon material consumption. Because of the small thickness of the solar cells, light trapping schemes are needed in order to obtain enough light absorption and current generation. This thesis describes the research on thin film silicon solar cells with the focus on the optimization of the transparent conducting oxide (TCO) layers and textured metal Ag substrate layers for the use as enhanced light scattering back reflectors in n-i-p type of solar cells. First we analyzed ZnO:Al (TCO) layers deposited in an radio frequent (rf) magnetron deposition system equipped with a 7 inch target. We have focused on the improvement of the electrical properties without sacrificing the optical properties by increasing the mobility and decreasing the grain boundary density. Furthermore, we described some of the effects on light trapping of ZnO:Al enhanced back reflectors. The described effects are able to explain the observed experimental data. Furthermore, we present a relation between the surface morphology of the Ag back contact and the current enhancement in microcrystalline (muc-Si:H) solar cells. We show the importance of the lateral feature sizes of the Ag surface on the light scattering and introduce a method to characterize the quality of the back reflector by combining the vertical and lateral feature sizes

Contour mode resonators with acoustic reflectors

DOEpatents

Olsson, Roy H [Albuquerque, NM; Fleming, James G [Albuquerque, NM; Tuck, Melanie R [Albuquerque, NM

2008-06-10

A microelectromechanical (MEM) resonator is disclosed which has a linear or ring-shaped acoustic resonator suspended above a substrate by an acoustic reflector. The acoustic resonator can be formed with a piezoelectric material (e.g. aluminum nitride, zinc oxide or PZT), or using an electrostatically-actuated material. The acoustic reflector (also termed an acoustic mirror) uses alternating sections of a relatively low acoustic impedance Z.sub.L material and a relatively high acoustic impedance Z.sub.H material to isolate the acoustic resonator from the substrate. The MEM resonator, which can be formed on a silicon substrate with conventional CMOS circuitry, has applications for forming oscillators, rf filters, and acoustic sensors.

Development of electro-optic systems for self cleaning concentrated solar reflectors

NASA Astrophysics Data System (ADS)

Stark, Jeremy W.

loss as a function of dust deposition, (2) development of a dust deposition analyzer capable of measuring size distribution of deposited dust and provides mass concentration of dust on the surface of the mirror, and (3) optimization of electrode geometry of EDS film for minimizing optical reflection losses caused by the lamination of the film on the mirror surface while maintaining high reflection efficiency with high dust removal efficiency. The non-contact specular reflectometer and the dust deposition analyzer allowed experimental investigation of reflection losses as functions of surface mass concentration of dust on mirrors for validation of the optical model presented in this study.

Shaping of parabolic cylindrical membrane reflectors for the DART precision test bed

NASA Technical Reports Server (NTRS)

White, C.; Salama, M.; Dragovan, M.; Schroeder, J.; Barber, D.; Dooley, J.

2003-01-01

The DART is a new telescope architecture consisting of two cylindrical parabolic reflectors. The system is ideally suited to using tensioned membranes for the reflective surfaces, owing to the zero Gaussian curvature of a cylindrical parabola.

Temporal laser pulse manipulation using multiple optical ring-cavities

NASA Technical Reports Server (NTRS)

Nguyen, Quang-Viet (Inventor); Kojima, Jun (Inventor)

2010-01-01

An optical pulse stretcher and a mathematical algorithm for the detailed calculation of its design and performance is disclosed. The optical pulse stretcher has a plurality of optical cavities, having multiple optical reflectors such that an optical path length in each of the optical cavities is different. The optical pulse stretcher also has a plurality of beam splitters, each of which intercepts a portion of an input optical beam and diverts the portion into one of the plurality of optical cavities. The input optical beam is stretched and a power of an output beam is reduced after passing through the optical pulse stretcher and the placement of the plurality of optical cavities and beam splitters is optimized through a model that takes into account optical beam divergence and alignment in the pluralities of the optical cavities. The optical pulse stretcher system can also function as a high-repetition-rate (MHz) laser pulse generator, making it suitable for use as a stroboscopic light source for high speed ballistic projectile imaging studies, or it can be used for high speed flow diagnostics using a laser light sheet with digital particle imaging velocimetry. The optical pulse stretcher system can also be implemented using fiber optic components to realize a rugged and compact optical system that is alignment free and easy to use.

Positive focal shift of gallium nitride high contrast grating focusing reflectors

NASA Astrophysics Data System (ADS)

He, Shumin; Wang, Zhenhai; Liu, Qifa

2016-09-01

We design a type of metasurfaces capable of serving as a visible-light focusing reflector based on gallium nitride (GaN) high contrast gratings (HCGs). The wavefront of the reflected light is precisely manipulated by spatial variation of the grating periods along the subwavelength ridge array to achieve light focusing. Different from conventional negative focal shift effect, a positive focal shift is observed in such focusing reflectors. Detailed investigations of the influence of device size on the focusing performance, especially the focal length, are preformed via a finite element method . The results show that all performance parameters are greatly affected by the reflector size. A more concentrated focal point, or a better focusing capability, can be achieved by larger size. With increasing reflector size, the achieved focal length decreases and gradually approaches to the design, thus the corresponding positive focal shift decreases. Our results are helpful for understanding the visible-light control of the planar HCG-based focusing reflectors.

Structural design of the Large Deployable Reflector (LDR)

NASA Technical Reports Server (NTRS)

Satter, Celeste M.; Lou, Michael C.

1991-01-01

An integrated Large Deployable Reflector (LDR) analysis model was developed to enable studies of system responses to the mechanical and thermal disturbances anticipated during on-orbit operations. Functional requirements of the major subsystems of the LDR are investigated, design trades are conducted, and design options are proposed. System mass and inertia properties are computed in order to estimate environmental disturbances, and in the sizing of control system hardware. Scaled system characteristics are derived for use in evaluating launch capabilities and achievable orbits. It is concluded that a completely passive 20-m primary appears feasible for the LDR from the standpoint of both mechanical vibration and thermal distortions.

Structural design of the Large Deployable Reflector (LDR)

NASA Astrophysics Data System (ADS)

Satter, Celeste M.; Lou, Michael C.

1991-09-01

An integrated Large Deployable Reflector (LDR) analysis model was developed to enable studies of system responses to the mechanical and thermal disturbances anticipated during on-orbit operations. Functional requirements of the major subsystems of the LDR are investigated, design trades are conducted, and design options are proposed. System mass and inertia properties are computed in order to estimate environmental disturbances, and in the sizing of control system hardware. Scaled system characteristics are derived for use in evaluating launch capabilities and achievable orbits. It is concluded that a completely passive 20-m primary appears feasible for the LDR from the standpoint of both mechanical vibration and thermal distortions.

Hybrid RF / Optical Communication Terminal with Spherical Primary Optics for Optical Reception

NASA Technical Reports Server (NTRS)

Charles, Jeffrey R.; Hoppe, Daniel H.; Sehic, Asim

2011-01-01

Future deep space communications are likely to employ not only the existing RF uplink and downlink, but also a high capacity optical downlink. The Jet Propulsion Laboratory (JPL) is currently investigating the benefits of a ground based hybrid RF and deep space optical terminal based on limited modification of existing 34 meter antenna designs. The ideal design would include as large an optical aperture as technically practical and cost effective, cause minimal impact to RF performance, and remain cost effective even when compared to a separate optical terminal of comparable size. Numerous trades and architectures have been considered, including shared RF and optical apertures having aspheric optics and means to separate RF and optical signals, plus, partitioned apertures in which various zones of the primary are dedicated to optical reception. A design based on the latter is emphasized in this paper, employing spherical primary optics and a new version of a "clamshell" corrector that is optimized to fit within the limited space between the antenna sub-reflector and the existing apex structure that supports the subreflector. The mechanical design of the hybrid accommodates multiple spherical primary mirror panels in the central 11 meters of the antenna, and integrates the clamshell corrector and optical receiver modules with antenna hardware using existing attach points to the maximum extent practical. When an optical collection area is implemented on a new antenna, it is possible to design the antenna structure to accommodate the additional weight of optical mirrors providing an equivalent aperture of several meters diameter. The focus of our near term effort is to use optics with the 34 meter DSS-13 antenna at Goldstone to demonstrate spatial optical acquisition and tracking capability using an optical system that is temporarily integrated into the antenna.

Strategy for reflector pattern calculation - Let the computer do the work

NASA Technical Reports Server (NTRS)

Lam, P. T.; Lee, S.-W.; Hung, C. C.; Acosta, R.

1986-01-01

Using high frequency approximations, the secondary pattern of a reflector antenna can be calculated by numerically evaluating a radiation integral I(u,v). In recent years, tremendous effort has been expended to reducing I(u,v) to Fourier integrals. These reduction schemes are invariably reflector geometry dependent. Hence, different analyses/computer software development must be carried out for different reflector shapes/boundaries. It is pointed out, that, as the computer power improves, these reduction schemes are no longer necessary. Comparable accuracy and computation time can be achieved by evaluating I(u,v) by a brute force FFT described in this note. Furthermore, there is virtually no restriction on the reflector geometry by using the brute force FFT.

Strategy for reflector pattern calculation: Let the computer do the work

NASA Technical Reports Server (NTRS)

Lam, P. T.; Lee, S. W.; Hung, C. C.; Acousta, R.

1985-01-01

Using high frequency approximations, the secondary pattern of a reflector antenna can be calculated by numerically evaluating a radiation integral I(u,v). In recent years, tremendous effort has been expended to reducing I(u,v) to Fourier integrals. These reduction schemes are invariably reflector geometry dependent. Hence, different analyses/computer software development must be carried out for different reflector shapes/boundaries. it is pointed out, that, as the computer power improves, these reduction schemes are no longer necessary. Comparable accuracy and computation time can be achieved by evaluating I(u,v) by a brute force FFT described in this note. Furthermore, there is virtually no restriction on the reflector geometry by using the brute force FFT.

The coating design of phase-shifting reflector array with high reflectance and specified reflection phase shifts for static Michelson interferometer

NASA Astrophysics Data System (ADS)

Zhang, Xuanni; Zhang, Hui; Wang, Yijun

2016-02-01

The optical Doppler Michelson imaging interferometer is widely used for wind measurements. Four interferograms obtained simultaneously are needed to immune to environmental disturbances. Thus, a static and divided mirror Michelson interferometer is proposed. Its highlight is the phase-shifting reflector array, which divides one mirror into four quadrants coated by different multilayer films with high reflectance, specified phase steps π/2 and little polarization effects. By combining analytical and empirical method, four coatings are designed with software TFCalc. The simulated results showed good agreement with the desired optical properties. Due to the limitation of the optical material and function of the software TFCalc, there are some design errors within tolerance.

RF verification tasks underway at the Harris Corporation for multiple aperture reflector system

NASA Technical Reports Server (NTRS)

Gutwein, T. A.

1982-01-01

Mesh effects on gain and patterns and adjacent aperture coupling effects for "pie" and circular apertures are discussed. Wire effects for Harris model with Langley scale model results included for assessing D/lamda effects, and wire effects with adjacent aperture coupling were determined. Reflector surface distortion effects (pillows and manufacturing roughness) were studied.

Feasibility study of a synthesis procedure for array feeds to improve radiation performance of large distorted reflector antennas

NASA Technical Reports Server (NTRS)

Stutzman, W. L.; Takamizawa, K.; Werntz, P.; Lapean, J.; Barts, R.; Shen, B.

1992-01-01

Virginia Tech has several articles which support the NASA Langley effort in the area of large aperture radiometric antenna systems. This semi-annual report reports on the following activities: a feasibility study of a synthesis procedure for array feeds to improve radiation performance of large distorted reflector antennas and the design of array feeds for large reflector antennas.

The main beam efficiency of corner cube reflectors

NASA Astrophysics Data System (ADS)

Vowinkel, B.

1986-01-01

A computer model for the calculation of the beam pattern and the main beam efficiency of corner cube reflectors used in submillimeter heterodyne systems is described. The model includes possible mismatches at the termination of the wire antenna, the attenuation of the wave along the wire due to emission and the contribution of the wire bend to the antenna pattern. Measurements with a scale model at 15 GHz show good agreement between experiment and theory.

Incidental Reflector Comparison of Containerized Dry Fire Extinguishing Agents

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

Chapman, Bryan Scott; Wysong, Andrew Russell

This document addresses the incidental reflector reactivity worth of containerized fire extinguishing agents authorized for use in PF-4 at Los Alamos National Laboratory (LANL). The intent of the document is to analyze dry fire extinguishing agent that remains in a container and is not actively being used in a fire emergency. The incidental reflector reactivity worth is determined by comparison to various thicknesses of close fitting water reflection which is commonly used to bound incidental reflectors in criticality safety evaluations. The conclusion is that even in unlimited quantities, when containerized the authorized dry fire extinguishing agents are bound by 0.4more » inches of close fitting water.« less

Concept Design of a Multi-Band Shared Aperture Reflectarray/Reflector Antenna

NASA Technical Reports Server (NTRS)

Spence, Thomas; Cooley, Michael E.; Stenger, Peter; Park, Richard; Li, Lihua; Racette, Paul; Heymsfield, Gerald; Mclinden, Matthew

2016-01-01

A scalable dual-band (Ka/W) shared-aperture antenna system design has been developed as a proposed solution to meet the needs of the planned NASA Earth Science Aerosol, Clouds, and Ecosystem (ACE) mission. The design is comprised of a compact Cassegrain reflector/reflectarray with a fixed pointing W-band feed and a cross track scanned Ka-band Active Electronically Scanned Array (AESA). Critical Sub-scale prototype testing and flight tests have validated some of the key aspects of this innovative antenna design, including the low loss reflector/reflectarray surface. More recently the science community has expressed interest in a mission that offers the ability to measure precipitation in addition to clouds and aerosols. In this paper we present summaries of multiple designs that explore options for realizing a tri-frequency (Ku/Ka/W), shared-aperture antenna system to meet these science objectives. Design considerations include meeting performance requirements while emphasizing payload size, weight, prime power, and cost. The extensive trades and lessons learned from our previous dual-band ACE system development were utilized as the foundation for this work.

Concept Design of a Multi-Band Shared Aperture Reflectarray/Reflector Antenna

NASA Technical Reports Server (NTRS)

Spence, Thomas; Cooley, Michael; Stenger, Peter; Park, Richard; Li, Lihua; Racette, Paul; Heymsfield, Gerald; Mclinden, Matthew

2016-01-01

A scalable dual-band (KaW) shared-aperture antenna system design has been developed as a proposed solution to meet the needs of the planned NASA Earth Science Aerosol, Clouds, and Ecosystem (ACE) mission. The design is comprised of a compact Cassegrain reflector/reflectarray with a fixed pointing W-band feed and a cross track scanned Ka-band Active Electronically Scanned Array (AESA). Critical Sub-scale prototype testing and flight tests have validated some of the key aspects of this innovative antenna design, including the low loss reflector/reflectarray surface.More recently the science community has expressed interest in a mission that offers the ability to measure precipitation in addition to clouds and aerosols. In this paper we present summaries of multiple designs that explore options for realizing a tri-frequency (KuKaW), shared-aperture antenna system to meet these science objectives. Design considerations include meeting performance requirements while emphasizing payload size, weight, prime power, and cost. The extensive trades and lessons learned from our previous dual-band ACE system development were utilized as the foundation for this work.

Design, Development and Testing of the GMI Reflector Deployment Assembly

NASA Technical Reports Server (NTRS)

Guy, Larry; Foster, Mike; McEachen, Mike; Pellicciotti, Joseph; Kubitschek, Michael

2011-01-01

The GMI Reflector Deployment Assembly (RDA) is an articulating structure that accurately positions and supports the main reflector of the Global Microwave Imager (GMI) throughout the 3 year mission life. The GMI instrument will fly on the core Global Precipitation Measurement (GPM) spacecraft and will be used to make calibrated radiometric measurements at multiple microwave frequencies and polarizations. The GPM mission is an international effort managed by the National Aeronautics and Space Administration (NASA) to improve climate, weather, and hydrometeorological predictions through more accurate and frequent precipitation measurements1. Ball Aerospace and Technologies Corporation (BATC) was selected by NASA Goddard to design, build, and test the GMI instrument. The RDA was designed and manufactured by ATK Aerospace Systems Group to meet a number of challenging packaging and performance requirements. ATK developed a flight-like engineering development unit (EDU) and two flight mechanisms that have been delivered to BATC. This paper will focus on driving GMI instrument system requirements, the RDA design, development, and test activities performed to demonstrate that requirements have been met.

Simulation of parabolic reflectors for ultraviolet phototherapy

NASA Astrophysics Data System (ADS)

Grimes, David Robert

2016-08-01

Ultraviolet (UVR) phototherapy is widely used to treat an array of skin conditions, including psoriasis, eczema and vitiligo. For such interventions, a quantified dose is vital if the treatment is to be both biologically effective and to avoid the detrimental effects of over-dosing. As dose is absorbed at surface level, the orientation of patient site with respect to the UVR lamps modulates effective dose. Previous investigations have modelled this behaviour, and examined the impact of shaped anodized aluminium reflectors typically placed around lamps in phototherapy cabins. These mirrors are effective but tend to yield complex patterns of reflection around the cabin which can result in substantial dose inhomogeneity. There has been some speculation over whether using the reflective property of parabolic mirrors might improve dose delivery or homogeneity through the treatment cabin. In this work, the effects of parabolic mirrors are simulated and compared with standard shaped mirrors. Simulation results strongly suggest that parabolic reflectors reduce total irradiance relative to standard shaped reflectors, and have a negligible impact on dose homogeneity.

Brownian thermal noise in functional optical surfaces

NASA Astrophysics Data System (ADS)

Kroker, S.; Dickmann, J.; Rojas Hurtado, C. B.; Heinert, D.; Nawrodt, R.; Levin, Y.; Vyatchanin, S. P.

2017-07-01

We present a formalism to compute Brownian thermal noise in functional optical surfaces such as grating reflectors, photonic crystal slabs, or complex metamaterials. Such computations are based on a specific readout variable, typically a surface integral of a dielectric interface displacement weighed by a form factor. This paper shows how to relate this form factor to Maxwell's stress tensor computed on all interfaces of the moving surface. As an example, we examine Brownian thermal noise in monolithic T-shaped grating reflectors. The previous computations by Heinert et al. [Phys. Rev. D 88, 042001 (2013), 10.1103/PhysRevD.88.042001] utilizing a simplified readout form factor produced estimates of thermal noise that are tens of percent higher than those of the exact analysis in the present paper. The relation between the form factor and Maxwell's stress tensor implies a close correlation between the optical properties of functional optical surfaces and thermal noise.

Porous silicon based micro-opto-electro-mechanical-systems (MOEMS) components for free space optical interconnects

NASA Astrophysics Data System (ADS)

Song, Da

2008-02-01

One of the major challenges confronting the current integrated circuits (IC) industry is the metal "interconnect bottleneck". To overcome this obstacle, free space optical interconnects (FSOIs) can be used to address the demand for high speed data transmission, multi-functionality and multi-dimensional integration for the next generation IC. One of the crucial elements in FSOIs system is to develop a high performance and flexible optical network to transform the incoming optical signal into a distributed set of optical signals whose direction, alignment and power can be independently controlled. Among all the optical materials for the realization of FSOI components, porous silicon (PSi) is one of the most promising candidates because of its unique optical properties, flexible fabrication methods and integration with conventional IC material sets. PSi-based Distributed Bragg Reflector (DBR) and Fabry-Perot (F-P) structures with unique optical properties are realized by electrochemical etching of silicon. By incorporating PSi optical structures with Micro-Opto-Electro-Mechanical-Systems (MOEMS), several components required for FSOI have been developed. The first type of component is the out-of-plane freestanding optical switch. Implementing a PSi DBR structure as an optically active region, the device can realize channel selection by changing the tilting angle of the micromirror supported by the thermal bimorph actuator. All the fabricated optical switches have reached kHz working frequency and life time of millions of cycles. The second type of component is the in-plane tunable optical filter. By introducing PSi F-P structure into the in-plane PSi film, a thermally tunable optical filter with a sensitivity of 7.9nm/V has been realized for add/drop optical signal selection. Also, for the first time, a new type of PSi based reconfigurable diffractive optical element (DOE) has been developed. By using patterned photoresist as a protective mask for electrochemical

Phase-demodulation error of a fiber-optic Fabry-Perot sensor with complex reflection coefficients.

PubMed

Kilpatrick, J M; MacPherson, W N; Barton, J S; Jones, J D

2000-03-20

The influence of reflector losses attracts little discussion in standard treatments of the Fabry-Perot interferometer yet may be an important factor contributing to errors in phase-stepped demodulation of fiber optic Fabry-Perot (FFP) sensors. We describe a general transfer function for FFP sensors with complex reflection coefficients and estimate systematic phase errors that arise when the asymmetry of the reflected fringe system is neglected, as is common in the literature. The measured asymmetric response of higher-finesse metal-dielectric FFP constructions corroborates a model that predicts systematic phase errors of 0.06 rad in three-step demodulation of a low-finesse FFP sensor (R = 0.05) with internal reflector losses of 25%.

Surface measuring technique. [using a laser to scan the surface of a reflector

NASA Technical Reports Server (NTRS)

Spiers, R. B., Jr.

1980-01-01

Measurement of the surface contour of a large electrostatically formed concave reflector using a modified Foucault or knife edge test is described. The curve of the actual electrostatically formed reflector surface is compared to a curve representing a reference sphere. Measurements of surface slope and deviation are calculated every 15 cm along the reflector's horizontal and vertical diameters. Characterization of surface roughness on a small scale compared to the laser spot size at the reflector are obtained from the increased laser spot size at a distant projection screen.

Numerical form-finding method for large mesh reflectors with elastic rim trusses

NASA Astrophysics Data System (ADS)

Yang, Dongwu; Zhang, Yiqun; Li, Peng; Du, Jingli

2018-06-01

Traditional methods for designing a mesh reflector usually treat the rim truss as rigid. Due to large aperture, light weight and high accuracy requirements on spaceborne reflectors, the rim truss deformation is indeed not negligible. In order to design a cable net with asymmetric boundaries for the front and rear nets, a cable-net form-finding method is firstly introduced. Then, the form-finding method is embedded into an iterative approach for designing a mesh reflector considering the elasticity of the supporting rim truss. By iterations on form-findings of the cable-net based on the updated boundary conditions due to the rim truss deformation, a mesh reflector with a fairly uniform tension distribution in its equilibrium state could be finally designed. Applications on offset mesh reflectors with both circular and elliptical rim trusses are illustrated. The numerical results show the effectiveness of the proposed approach and that a circular rim truss is more stable than an elliptical rim truss.

The Abacus/Reflector and Integrated Symmetrical Concentrator: Concepts for Space Solar Power Collection and Transmission

NASA Technical Reports Server (NTRS)

Carrington, Connie; Fikes, John; Gerry, Mark; Perkinson, Don

2000-01-01

New energy sources are vital for the development of emerging nations, and the growth of industry in developed economies. Also vital is the need for these energy sources to be clean and renewable. For the past several years, NASA has been taking a new look at collecting solar energy in space and transmitting it to Earth, to planetary surfaces, and to orbiting spacecraft. Several innovative concepts are being studied for the space segment component of solar power beaming. One is the Abacus/Reflector, a large sun-oriented array structure fixed to the transmitter, and a rotating RF reflector that tracks a receiving rectenna on Earth. This concept eliminates the need for power-conducting slip rings in rotating joints between the solar collectors and the transmitter. Another concept is the Integrated Symmetrical Concentrator (ISC), composed of two very large segmented reflectors which rotate to collect and reflect the incident sunlight onto two centrally-located photovoltaic arrays. Adjacent to the PV arrays is the RF transmitter, which as a unit track the receiving rectenna, again eliminating power-conducting joints, and in addition reducing the cable lengths between the arrays and transmitter. The metering structure to maintain the position of the reflectors is a long mast, oriented perpendicular to the equatorial orbit plane. This paper presents a status of ongoing systems studies and configurations for the Abacus/Reflector and the ISC concepts, and a top-level study of packaging for launch and assembly.

Low Sidelobe Scanning Beams for Parabolic Reflectors,

DTIC Science & Technology

Parabolic antennas, *Sidelobes, *Electronic scanners, Parabolas, Far field, Antenna feeds , Reflectors, Low level, Amplitude, Distortion, Configurations, Secondary, Compensation, Feeding , Symposia, Taper

Preliminary design considerations for 10 to 40 meter-diameter precision truss reflectors

NASA Technical Reports Server (NTRS)

Mikulas, Martin M., Jr.; Collins, Timothy J.; Hedgepeth, John M.

1990-01-01

A simplified preliminary design capability for erectable precision segmented reflectors is presented. This design capability permits a rapid assessment of a wide range of reflector parameters as well as new structural concepts and materials. The preliminary design approach was applied to a range of precision reflectors from 10 meters to 100 meters in diameter while considering standard design drivers. The design drivers considered were: weight, fundamental frequency, launch packaging volume, part count, and on-orbit assembly time. For the range of parameters considered, on-orbit assembly time was identified as the major design driver. A family of modular panels is introduced which can significantly reduce the number of reflector parts and the on-orbit assembly time.

Extrinsic fiber optic displacement sensors and displacement sensing systems

DOEpatents

Murphy, K.A.; Gunther, M.F.; Vengsarkar, A.M.; Claus, R.O.

1994-04-05

An extrinsic Fizeau fiber optic sensor comprises a single-mode fiber, used as an input/output fiber, and a multimode fiber, used purely as a reflector, to form an air gap within a silica tube that acts as a Fizeau cavity. The Fresnel reflection from the glass/air interface at the front of the air gap (reference reflection) and the reflection from the air/glass interface at the far end of the air gap (sensing reflection) interfere in the input/output fiber. The two fibers are allowed to move in the silica tube, and changes in the air gap length cause changes in the phase difference between the reference reflection and the sensing reflection. This phase difference is observed as changes in intensity of the light monitored at the output arm of a fused biconical tapered coupler. The extrinsic Fizeau fiber optic sensor behaves identically whether it is surface mounted or embedded, which is unique to the extrinsic sensor in contrast to intrinsic Fabry-Perot sensors. The sensor may be modified to provide a quadrature phase shift extrinsic Fizeau fiber optic sensor for the detection of both the amplitude and the relative polarity of dynamically varying strain. The quadrature light signals may be generated by either mechanical or optical means. A plurality of the extrinsic sensors may connected in cascade and multiplexed to allow monitoring by a single analyzer. 14 figures.

Extrinsic fiber optic displacement sensors and displacement sensing systems

DOEpatents

Murphy, Kent A.; Gunther, Michael F.; Vengsarkar, Ashish M.; Claus, Richard O.

1994-01-01

An extrinsic Fizeau fiber optic sensor comprises a single-mode fiber, used as an input/output fiber, and a multimode fiber, used purely as a reflector, to form an air gap within a silica tube that acts as a Fizeau cavity. The Fresnel reflection from the glass/air interface at the front of the air gap (reference reflection) and the reflection from the air/glass interface at the far end of the air gap (sensing reflection) interfere in the input/output fiber. The two fibers are allowed to move in the silica tube, and changes in the air gap length cause changes in the phase difference between the reference reflection and the sensing reflection. This phase difference is observed as changes in intensity of the light monitored at the output arm of a fused biconical tapered coupler. The extrinsic Fizeau fiber optic sensor behaves identically whether it is surface mounted or embedded, which is unique to the extrinsic sensor in contrast to intrinsic Fabry-Perot sensors. The sensor may be modified to provide a quadrature phase shift extrinsic Fizeau fiber optic sensor for the detection of both the amplitude and the relative polarity of dynamically varying strain. The quadrature light signals may be generated by either mechanical or optical means. A plurality of the extrinsic sensors may connected in cascade and multiplexed to allow monitoring by a single analyzer.

78 FR 14357 - Certain Compact Fluorescent Reflector Lamps, Products Containing Same and Components Thereof...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-05

... Reflector Lamps, Products Containing Same and Components Thereof; Institution of Investigation AGENCY: U.S... fluorescent reflector lamps, products containing same and components thereof by reason of infringement of... compact fluorescent reflector lamps, products containing same and components thereof by reason of...

Design method of LED rear fog lamp based on freeform micro-surface reflectors

NASA Astrophysics Data System (ADS)

Yu, Jindong; Wu, Heng

2017-11-01

We propose a practical method for the design of a light-emitting diode (LED) rear fog lamp based on freeform micro-surface reflectors. The lamp consists of nine LEDs and each of them has a freeform micro-surface reflector correspondingly. The micro-surface reflector design includes three steps. An initial freeform reflector is first built based on the light energy maps. The micro-surface reflector is then constructed on the bias of the initial one. Finally, a two-step method is designed to optimize the micro-surface reflector. With the proposed method, a module is designed and LCW DURIS E5 LED source whose emitting surface is 5.7 mm × 3.0 mm is adopted for simulation. A prototype is also assembled and fabricated to verify the real performance. Both the simulation and experimental results demonstrate that the luminous intensity distribution can well fulfill the requirements of ECE No.38 regulation. Furthermore, more than 79% energy can be saved when compared with the rear fog lamps using conventional sources.

Precision pointing compensation for DSN antennas with optical distance measuring sensors

NASA Technical Reports Server (NTRS)

Scheid, R. E.

1989-01-01

The pointing control loops of Deep Space Network (DSN) antennas do not account for unmodeled deflections of the primary and secondary reflectors. As a result, structural distortions due to unpredictable environmental loads can result in uncompensated boresight shifts which degrade pointing accuracy. The design proposed here can provide real-time bias commands to the pointing control system to compensate for environmental effects on pointing performance. The bias commands can be computed in real time from optically measured deflections at a number of points on the primary and secondary reflectors. Computer simulations with a reduced-order finite-element model of a DSN antenna validate the concept and lead to a proposed design by which a ten-to-one reduction in pointing uncertainty can be achieved under nominal uncertainty conditions.

All-nitride AlxGa1−xN:Mn/GaN distributed Bragg reflectors for the near-infrared

PubMed Central

Capuzzo, Giulia; Kysylychyn, Dmytro; Adhikari, Rajdeep; Li, Tian; Faina, Bogdan; Tarazaga Martín-Luengo, Aitana; Bonanni, Alberta

2017-01-01

Since the technological breakthrough prompted by the inception of light emitting diodes based on III-nitrides, these material systems have emerged as strategic semiconductors not only for the lighting of the future, but also for the new generation of high-power electronic and spintronic devices. While III-nitride optoelectronics in the visible and ultraviolet spectral range is widely established, all-nitride efficient devices in the near-infrared (NIR) are still wanted. Here, through a comprehensive protocol of design, modeling, epitaxial growth and in-depth characterization, we develop AlxGa1−xN:Mn/GaN NIR distributed Bragg reflectors and we show their efficiency in combination with GaN:(Mn,Mg) layers containing Mn-Mgk complexes optically active in the near-infrared range of wavelengths. PMID:28198432

Combined hostile fire and optics detection

NASA Astrophysics Data System (ADS)

Brännlund, Carl; Tidström, Jonas; Henriksson, Markus; Sjöqvist, Lars

2013-10-01

Snipers and other optically guided weapon systems are serious threats in military operations. We have studied a SWIR (Short Wave Infrared) camera-based system with capability to detect and locate snipers both before and after shot over a large field-of-view. The high frame rate SWIR-camera allows resolution of the temporal profile of muzzle flashes which is the infrared signature associated with the ejection of the bullet from the rifle. The capability to detect and discriminate sniper muzzle flashes with this system has been verified by FOI in earlier studies. In this work we have extended the system by adding a laser channel for optics detection. A laser diode with slit-shaped beam profile is scanned over the camera field-of-view to detect retro reflection from optical sights. The optics detection system has been tested at various distances up to 1.15 km showing the feasibility to detect rifle scopes in full daylight. The high speed camera gives the possibility to discriminate false alarms by analyzing the temporal data. The intensity variation, caused by atmospheric turbulence, enables discrimination of small sights from larger reflectors due to aperture averaging, although the targets only cover a single pixel. It is shown that optics detection can be integrated in combination with muzzle flash detection by adding a scanning rectangular laser slit. The overall optics detection capability by continuous surveillance of a relatively large field-of-view looks promising. This type of multifunctional system may become an important tool to detect snipers before and after shot.

Three-dimensional cavity nanoantennas with resonant-enhanced surface plasmons as dynamic color-tuning reflectors.

PubMed

Fan, J R; Wu, W G; Chen, Z J; Zhu, J; Li, J

2017-03-09

As plasmonic antennas for surface-plasmon-assisted control of optical fields at specific frequencies, metallic nanostructures have recently emerged as crucial optical components for fascinating plasmonic color engineering. Particularly, plasmonic resonant nanocavities can concentrate lightwave energy to strongly enhance light-matter interactions, making them ideal candidates as optical elements for fine-tuning color displays. Inspired by the color mixing effect found on butterfly wings, a new type of plasmonic, multiresonant, narrow-band (the minimum is about 45 nm), high-reflectance (the maximum is about 95%), and dynamic color-tuning reflector is developed. This is achieved from periodic patterns of plasmonic resonant nanocavities in free-standing capped-pillar nanostructure arrays. Such cavity-coupling structures exhibit multiple narrow-band selective and continuously tunable reflections via plasmon standing-wave resonances. Consequently, they can produce a variety of dark-field vibrant reflective colors with good quality, strong color signal and fine tonal variation at the optical diffraction limit. This proposed multicolor scheme provides an elegant strategy for realizing personalized and customized applications in ultracompact photonic data storage and steganography, colorimetric sensing, 3D holograms and other plasmon-assisted photonic devices.

Detail of 25' highband reflector screen pole showing the horizontal ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail of 25' high-band reflector screen pole showing the horizontal wood beams and vertical wires hung from ceramic insulators, note the dipole antenna element and 94' low-band reflector screen poles in background, view facing north - U.S. Naval Base, Pearl Harbor, Naval Radio Station, AF/FRD-10 Circularly Disposed Antenna Array, Wahiawa, Honolulu County, HI

Detail of 25' highband reflector screen poles with monopole antenna ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail of 25' high-band reflector screen poles with monopole antenna elements behind, note the metal sleeve bases of the reflector screen poles and the guy wire anchors from the dipole antenna elements (left foreground), view facing north northwest - U.S. Naval Base, Pearl Harbor, Naval Radio Station, AF/FRD-10 Circularly Disposed Antenna Array, Wahiawa, Honolulu County, HI

Optical/thermal analysis methodology for a space-qualifiable RTP furnace

NASA Technical Reports Server (NTRS)

Bugby, D.; Dardarian, S.; Cole, E.

1993-01-01

A methodology to predict the coupled optical/thermal performance of a reflective cavity heating system was developed and a laboratory test to verify the method was carried out. The procedure was utilized to design a rapid thermal processing (RTP) furnace for the Robot-Operated Material Processing in Space (ROMPS) Program which is a planned STS HH-G canister experiment involving robotics and material processing in microgravity. The laboratory test employed a tungsten-halogen reflector/lamp to heat thin, p-type silicon wafers. Measurements instrumentation consisted of 5-mil Pt/Pt-Rh thermocouples and an optical pyrometer. The predicted results, utilizing an optical ray-tracing program and a lumped-capacitance thermal analyzer, showed good agreement with the measured data for temperatures exceeding 1300 C.

Efficient high-power frequency doubling of distributed Bragg reflector tapered laser radiation in a periodically poled MgO-doped lithium niobate planar waveguide.

PubMed

Jedrzejczyk, Daniel; Güther, Reiner; Paschke, Katrin; Jeong, Woo-Jin; Lee, Han-Young; Erbert, Götz

2011-02-01

We report on efficient single-pass, high-power second-harmonic generation in a periodically poled MgO-doped LiNbO3 planar waveguide using a distributed Bragg reflector tapered diode laser as a pump source. A coupling efficiency into the planar waveguide of 73% was realized, and 1.07 W of visible laser light at 532 nm was generated. Corresponding optical and electro-optical conversion efficiencies of 26% and 8.4%, respectively, were achieved. Good agreement between the experimental data and the theoretical predictions was observed.

A new type of lamp and reflector for I.R. simulation

NASA Technical Reports Server (NTRS)

Saenger, G.

1986-01-01

The lamps and reflectors used for infrared radiation simulation tests at ESTEC did not allow researchers to predict the intensity needed for test conditions with the desired accuracy. This was due to poor reproducibility of the polar diagrams, the unknown contribution of the radiation in the long wavelength range in vacuum, imperfections in the quartz bulbs, and misalignment of the lamp in the reflector. When using a 1000 W coiled spiral quartz lamp with a diffuse reflector, these shortcomings are overcome. Due to the good reproducibility, an overall accuracy within plus or minus 2 percent should be obtained.

Highly Enriched Uranium Metal Cylinders Surrounded by Various Reflector Materials

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

Bernard Jones; J. Blair Briggs; Leland Monteirth

A series of experiments was performed at Los Alamos Scientific Laboratory in 1958 to determine critical masses of cylinders of Oralloy (Oy) reflected by a number of materials. The experiments were all performed on the Comet Universal Critical Assembly Machine, and consisted of discs of highly enriched uranium (93.3 wt.% 235U) reflected by half-inch and one-inch-thick cylindrical shells of various reflector materials. The experiments were performed by members of Group N-2, particularly K. W. Gallup, G. E. Hansen, H. C. Paxton, and R. H. White. This experiment was intended to ascertain critical masses for criticality safety purposes, as well asmore » to compare neutron transport cross sections to those obtained from danger coefficient measurements with the Topsy Oralloy-Tuballoy reflected and Godiva unreflected critical assemblies. The reflector materials examined in this series of experiments are as follows: magnesium, titanium, aluminum, graphite, mild steel, nickel, copper, cobalt, molybdenum, natural uranium, tungsten, beryllium, aluminum oxide, molybdenum carbide, and polythene (polyethylene). Also included are two special configurations of composite beryllium and iron reflectors. Analyses were performed in which uncertainty associated with six different parameters was evaluated; namely, extrapolation to the uranium critical mass, uranium density, 235U enrichment, reflector density, reflector thickness, and reflector impurities. In addition to the idealizations made by the experimenters (removal of the platen and diaphragm), two simplifications were also made to the benchmark models that resulted in a small bias and additional uncertainty. First of all, since impurities in core and reflector materials are only estimated, they are not included in the benchmark models. Secondly, the room, support structure, and other possible surrounding equipment were not included in the model. Bias values that result from these two simplifications were determined and

Reconfigurable Yagi-Uda antenna based on a silicon reflector with a solid-state plasma.

PubMed

Kim, Da-Jin; Park, Jang-Soon; Kim, Cheol Ho; Hur, Jae; Kim, Choong-Ki; Cho, Young-Kyun; Ko, Jun-Bong; Park, Bonghyuk; Kim, Dongho; Choi, Yang-Kyu

2017-12-08

This paper describes the fabrication and characterization of a reconfigurable Yagi-Uda antenna based on a silicon reflector with a solid-state plasma. The silicon reflector, composed of serially connected p-i-n diodes, forms a highly dense solid-state plasma by injecting electrons and holes into the intrinsic region. When this plasma silicon reflector is turned on, the front-realized gain of the antenna increases by more than 2 dBi beyond 5.3 GHz. To achieve the large gain increment, the structure of the antenna is carefully designed with the aid of semiconductor device simulation and antenna simulation. By using an aluminum nitride (AlN) substrate with high thermal conductivity, self-heating effects from the high forward current in the p-i-n diode are efficiently suppressed. By comparing the antenna simulation data and the measurement data, we estimated the conductivity of the plasma silicon reflector in the on-state to be between 10 4 and 10 5  S/m. With these figures, silicon material with its technology is an attractive tunable material for a reconfigurable antenna, which has attracted substantial interest from many areas, such as internet of things (IoT) applications, wireless network security, cognitive radio, and mobile and satellite communications as well as from multiple-input-multiple-output (MIMO) systems.

The novel support structure design of high stability for space borne primary reflector

NASA Astrophysics Data System (ADS)

Yu, Fei; Ding, Lin; Tan, Ting; Pei, Jing-yang.; Zhao, Xue-min; Bai, Shao-jun

2018-01-01

The novel support structure design of high stability for space borne primary mirror is presented. The structure is supported by a ball head support rod, for statically determinate support of reflector. The ball head assembly includes the supporting rod, nesting, bushing and other important parts. The liner bushing of the resistant material is used to fit for ball head approximated with the reflector material, and then the bad impact of thermal mismatch could be minimized to minimum. In order to ensure that the structure of the support will not be damaged, the glue spots for limitation is added around the reflector, for position stability of reflector. Through analysis and calculation, it can be seen that the novel support structure would not transfer the external stresses to the reflector, and the external stresses usually result from thermal mismatch and assembly misalignment. The novel method is useful for solving the problem of the bad influence form thermal stress and assembly force. In this paper, the supporting structure is introduced and analyzed in detail. The simulation results show that the ball head support reflector works more stably.

Design of reflector contours to satisfy photometric criteria using physically realizable light sources

NASA Astrophysics Data System (ADS)

Spencer, Domina E.

2001-11-01

Traditionally reflector design has been confined to the use of surfaces defined in terms of conic sections, assuming that all light sources can be considered to be point sources. In the middle of the twentieth century, it was recognized that major improvements could be made if the shape of the reflector was designed to produce a desired distribution of light form an actual light source. Cylindrical reflectors were created which illuminated airport runways using fluorescent lamps in such a way that pilots could make visual landings safely even in fog. These reflector contours were called macrofocal parabolic cylinders. Other new reflector contours introduced were macrofocal elliptic cylinders which confined the light to long rectangles. Surfaces of revolution the fourth degree were also developed which made possible uniform floodlighting of a circular region. These were called horned and peaked quartics. The optimum solution of the automotive head lighting problem has not yet been found. The paper concludes with a discussion of the possibility of developing reflectors which are neither cylindrical nor rotational but will produce the optimum field of view for the automobile driver both in clear weather and in fog.

Chaos and Beyond in a Water Filled Ultrasonic Resonance System

NASA Technical Reports Server (NTRS)

Lazlo, Adler; Yost, W.; Cantrell, John H.

2013-01-01

Finite amplitude ultrasonic wave resonances in a one-dimensional liquid-filled cavity, formed by a narrow band transducer and a plane reflector, are reported. The resonances are observed to include not only the expected harmonic and subharmonic signals (1,2) but chaotic signals as well. The generation mechanism requires attaining a threshold value of the driving amplitude that the liquid-filled cavity system becomes sufficiently nonlinear in response. The nonlinear features of the system were recently investigated via the construction of an ultrasonic interferometer having optical precision. The transducers were compressional, undamped quartz and lithium niobate crystals having the frequency range 1-10 MHz, driven by a high power amplifier. Both an optical diffraction system to characterize the diffraction pattern of laser light normally incident to the cavity and a receiving transducer attached to an aligned reflector with lapped flat and parallel surfaces were used to assess the generated resonance response in the cavity. At least 5 regions of excitation are identified.

10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 3 2012-01-01 2012-01-01 false Bare or covered (no reflector) medium base compact....35 Bare or covered (no reflector) medium base compact fluorescent lamps. (a) Sampling plan for... reflector) medium base compact fluorescent lamps; and (2) For each basic model of bare or covered (no...

10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 3 2014-01-01 2014-01-01 false Bare or covered (no reflector) medium base compact....35 Bare or covered (no reflector) medium base compact fluorescent lamps. (a) Sampling plan for... reflector) medium base compact fluorescent lamps; and (2) For each basic model of bare or covered (no...

10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 3 2013-01-01 2013-01-01 false Bare or covered (no reflector) medium base compact....35 Bare or covered (no reflector) medium base compact fluorescent lamps. (a) Sampling plan for... reflector) medium base compact fluorescent lamps; and (2) For each basic model of bare or covered (no...

Surface triads with optical properties

NASA Astrophysics Data System (ADS)

Panchuk, K. L.; Lyubchinov, E. V.; Krysova, I. V.

2018-01-01

A geometric model of formation of surfaces comprising an interconnected triple of emitter, reflector and receiver is presented in the paper. The model is based on cyclographic mapping of a spatial curve to the plane. In such map any given point (x, y, z) of the curve corresponds to a cycle with center (x, y) and radius equal to z applicate. The entire curve corresponds to a directed envelope of cycles consisting, in the general case, of two branches. It is shown that the triad of curves consisting of two branches of the envelope and the orthogonal projection of the original curve within the plane (xy) corresponds to a triad of developable surfaces. The triad of curves in the plane (xy) and the original curve together form a triad of ruled surfaces. Both triads have an optical property. Any ray of light emerging from the point of the emitter surface along the normal to it and falling on the surface of the reflector afterwards is directed along the normal vector to the surface of the receiver. The direct and inverse problems of formation of the triad of surfaces are solved. In the first case, a one-parameter set of triads of surfaces is defined from a given spatial curve. In the second case, a single triad of surfaces is defined from a pair of curves "emitter-receiver" defined on the plane (xy). Numerical examples of solutions of the direct and inverse problems are considered and the corresponding visualizations are given. The results of the work can be used in the design of reflector antennas in radar systems and systems for converting solar energy into electric and thermal energy.

Solar cell comprising a plasmonic back reflector and method therefor

DOEpatents

Ding, I-Kang; Zhu, Jia; Cui, Yi; McGehee, Michael David

2014-11-25

A method for forming a solar cell having a plasmonic back reflector is disclosed. The method includes the formation of a nanoimprinted surface on which a metal electrode is conformally disposed. The surface structure of the nanoimprinted surface gives rise to a two-dimensional pattern of nanometer-scale features in the metal electrode enabling these features to collectively form the plasmonic back reflector.

Optical systems engineering - A tutorial

NASA Technical Reports Server (NTRS)

Wyman, C. L.

1979-01-01

The paper examines the use of the systems engineering approach in the design of optical systems, noting that the use of such an approach which involves an integrated interdisciplinary approach to the development of systems is most appropriate for optics. It is shown that the high precision character of optics leads to complex and subtle effects on optical system performance, resulting from structural, thermal dynamical, control system, and manufacturing and assembly considerations. Attention is given to communication problems that often occur among users and optical engineers due to the unique factors of optical systems. It is concluded that it is essential that the optics community provide leadership to resolve communication problems and fully formalize the field of optical systems engineering.

Reflectors with directional-mixed reflection properties for application in luminaries with high-power LED diodes

NASA Astrophysics Data System (ADS)

Zaremba, Krzysztof

2008-06-01

Application of directional-mixed reflectors results in a luminance decrease of the apparent image of light emitting diodes (LEDs), which is advantageous as far as glare reduction is concerned. On the other hand, reflectors have a negative impact on luminous intensity curves of the luminaries. This work analyzes an impact of surfaces with directional-mixed reflection properties in a mirror reflector designed for a luminary equipped with high-power LEDs. We present an algorithm used to determine the shape of the reflector of the surface with small scattering, where the axis twist angle for a parabolic reflector varies in a predefined range and follows a power function.

49 CFR Appendix B to Part 224 - Reflectorization Implementation Compliance Report

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 4 2012-10-01 2012-10-01 false Reflectorization Implementation Compliance Report B Appendix B to Part 224 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION REFLECTORIZATION OF RAIL FREIGHT ROLLING STOCK Pt. 224, App. B Appendix B to Part 224...

Based on optical fiber Michelson interferometer for acoustic emission detection experimental research

NASA Astrophysics Data System (ADS)

Liang, Yijun; Qu, Dandan; Deng, Hu

2013-08-01

A type of Michelson interferometer with two optical fiber loop reflectors acoustic emission sensor is proposed in the article to detect the vibrations produced by ultrasonic waves propagating in a solid body. Two optical fiber loop reflectors are equivalent to the sensing arm and the reference arm instead of traditional Michelson interferometer end reflecter Theoretical analyses indicate that the sensitivity of the system has been remarkably increased because of the decrease of the losses of light energy. The best operating point of optical fiber sensor is fixed by theoretical derivation and simulation of computer, and the signal frequency which is detected by the sensor is the frequency of input signal. PZT (Piezoelectric Ceramic) is powered by signal generator as known ultrasonic source, The Polarization controller is used to make the reflected light interference，The fiber length is changed by adjusting the DC voltage on the PZT with the fiber loop to make the sensor system response that ΔΦ is closed to π/2. the signal basis frequency detected by the sensor is the frequency of the input signal. Then impacts the surface of the marble slab with home-made mechanical acoustic emission source. And detect it. and then the frequency characteristic of acoustic emission signal is obtained by Fourier technique. The experimental results indicate that the system can identify the frequency characteristic of acoustic emission signal, and it can be also used to detect the surface feeble vibration which is generated by ultrasonic waves propagating in material structure.

Analysis and test of a 16-foot radial rib reflector developmental model

NASA Technical Reports Server (NTRS)

Birchenough, Shawn A.

1989-01-01

Analytical and experimental modal tests were performed to determine the vibrational characteristics of a 16-foot diameter radial rib reflector model. Single rib analyses and experimental tests provided preliminary information relating to the reflector. A finite element model predicted mode shapes and frequencies of the reflector. The analyses correlated well with the experimental tests, verifying the modeling method used. The results indicate that five related, characteristic mode shapes form a group. The frequencies of the modes are determined by the relative phase of the radial ribs.

Multilayer optical dielectric coating

DOEpatents

Emmett, John L.

1990-01-01

A highly damage resistant, multilayer, optical reflective coating includes alternating layers of doped and undoped dielectric material. The doping levels are low enough that there are no distinct interfaces between the doped and undoped layers so that the coating has properties nearly identical to the undoped material. The coating is fabricated at high temperature with plasma-assisted chemical vapor deposition techniques to eliminate defects, reduce energy-absorption sites, and maintain proper chemical stoichiometry. A number of differently-doped layer pairs, each layer having a thickness equal to one-quarter of a predetermined wavelength in the material are combined to form a narrowband reflective coating for a predetermined wavelength. Broadband reflectors are made by using a number of narrowband reflectors, each covering a portion of the broadband.

Fabrication and characterization of TiO2/SiO2 based Bragg reflectors for light trapping applications

NASA Astrophysics Data System (ADS)

Dubey, R. S.; Ganesan, V.

Distributed Bragg reflectors (DBRs) have received an intensive attention due to their increasing demand in optoelectronic and photonic devices. Such reflectors are capable to prohibit the light propagation within the specified wavelength range of interest. In this paper, we present the fabrication of TiO2/SiO2 stacks based Bragg reflectors by using a simple and in-expensive sol-gel spin coating technique. The prepared single-layer thin films of TiO2 and SiO2 onto glass substrates were characterized for their optical constants. By tuning the process parameters, one-seven DBR stacks of TiO2/SiO2 were prepared. The corresponding shift of the Bragg reflection peak was observed with the increased number of DBR stacks and as much as about 90% reflectance is observed from the 7DBR stacks. The experimentally measured reflectance was compared with the simulated one, which showed good in agreement. FESEM measurement has confirmed the formation of bright and dark strips of TiO2 and SiO2 films with their thicknesses 80 and 115 nm respectively. The simulation study was explored to a design of thin film silicon solar cell using 7DBR stacks. An enhancement in light absorption in the visible wavelength range is observed which coincides with the experimental result of the reflectance. The use of DBR at the bottom of the solar cell could felicitate the better light harvesting with the occurrence of Fabry-Perot resonances in the absorbing layer.

Reflective Optics Design for an LED High Beam Headlamp of Motorbikes

PubMed Central

Ge, Peng; Wang, Xiang; Li, Yang; Wang, Hong

2015-01-01

We propose a reflective optics design for an LED motorbike high beam lamp. We set the measuring screen as an elliptical zone and divide it into many small lattices and divide the spatial angle of the LED source into many parts and make relationships between them. According to the conservation law of energy and the Snell's law, the reflector is generated by freeform optics design method. Then the optical system is simulated by Monte Carlo method using ASAP software. Light pattern of simulation could meet the standard. The high beam headlamp is finally fabricated and assembled into a physical object. Experiment results can fully comply with United Nations Economic Commission for Europe (ECE) vehicle regulations R113 revision 2 (Class C). PMID:25961073

Reflective optics design for an LED high beam headlamp of motorbikes.

PubMed

Ge, Peng; Wang, Xiang; Li, Yang; Wang, Hong

2015-01-01

We propose a reflective optics design for an LED motorbike high beam lamp. We set the measuring screen as an elliptical zone and divide it into many small lattices and divide the spatial angle of the LED source into many parts and make relationships between them. According to the conservation law of energy and the Snell's law, the reflector is generated by freeform optics design method. Then the optical system is simulated by Monte Carlo method using ASAP software. Light pattern of simulation could meet the standard. The high beam headlamp is finally fabricated and assembled into a physical object. Experiment results can fully comply with United Nations Economic Commission for Europe (ECE) vehicle regulations R113 revision 2 (Class C).

From the generalized reflection law to the realization of perfect anomalous reflectors

PubMed Central

Díaz-Rubio, Ana; Asadchy, Viktar S.; Elsakka, Amr; Tretyakov, Sergei A.

2017-01-01

The use of the generalized Snell’s law opens wide possibilities for the manipulation of transmitted and reflected wavefronts. However, known structures designed to shape reflection wavefronts suffer from significant parasitic reflections in undesired directions. We explore the limitations of the existing solutions for the design of passive planar reflectors and demonstrate that strongly nonlocal response is required for perfect performance. A new paradigm for the design of perfect reflectors based on energy surface channeling is introduced. We realize and experimentally verify a perfect design of an anomalously reflective surface using an array of rectangular metal patches backed by a metallic plate. This conceptually new mechanism for wavefront manipulation allows the design of thin perfect reflectors, offering a versatile design method applicable to other scenarios, such as focusing reflectors, surface wave manipulations, or metasurface holograms, extendable to other frequencies. PMID:28819642

Uncertainty-enabled design of electromagnetic reflectors with integrated shape control

NASA Astrophysics Data System (ADS)

Haque, Samiul; Kindrat, Laszlo P.; Zhang, Li; Mikheev, Vikenty; Kim, Daewa; Liu, Sijing; Chung, Jooyeon; Kuian, Mykhailo; Massad, Jordan E.; Smith, Ralph C.

2018-03-01

We implemented a computationally efficient model for a corner-supported, thin, rectangular, orthotropic polyvinylidene fluoride (PVDF) laminate membrane, actuated by a two-dimensional array of segmented electrodes. The laminate can be used as shape-controlled electromagnetic reflector and the model estimates the reflector's shape given an array of control voltages. In this paper, we describe a model to determine the shape of the laminate for a given distribution of control voltages. Then, we investigate the surface shape error and its sensitivity to the model parameters. Subsequently, we analyze the simulated deflection of the actuated bimorph using a Zernike polynomial decomposition. Finally, we provide a probabilistic description of reflector performance using statistical methods to quantify uncertainty. We make design recommendations for nominal parameter values and their tolerances based on optimization under uncertainty using multiple methods.

Development of a Multi-Band Shared Aperture Reflectarray/Reflector Antenna Design for NASA

NASA Technical Reports Server (NTRS)

Spence, Thomas; Cooley, Michael; Stenger, Peter; Park, Richard; Li, Lihua; Racette, Paul; Heymsfield, Gerald; Mclinden, Matthew

2016-01-01

A dual-band (Ka/W) shared-aperture antenna system design has been developed as a proposed solution to meet the needs of NASA's planned Aerosol, Clouds, and Ecosystem (ACE) mission. The design is comprised of a compact Cassegrain reflector/reflect array with a fixed W-band feed and a cross track scanned Ka-band Active Electronically Scanned Array (AESA). Critical Sub-scale prototype testing and flight tests have validated some of the key aspects of this innovative antenna design, including the low loss reflector/reflect array surface. More recently the science community has expressed interest in a mission that offers the ability to measure precipitation (Ku- band with scanning) in addition to clouds and aerosols. In this paper we present findings from a design study that explores options for realizing a tri-frequency (Ku/Ka/W), shared-aperture antenna system to meet these science objectives. Design considerations included meeting performance requirements while striving to minimize payload size, weight, prime power, and cost. The extensive trades and lessons learned from the ACE system development were utilized as the foundation for this work.

A fixed tilt solar collector employing reversible vee-trough reflectors and vacuum tube receivers for solar heating and cooling systems

NASA Technical Reports Server (NTRS)

Selcuk, M. K.

1977-01-01

The usefulness of vee-trough concentrators in improving the efficiency and reducing the cost of collectors assembled from evacuated tube receivers was studied in the vee-trough/vacuum tube collector (VTVTC) project. The VTVTC was analyzed rigorously and various mathematical models were developed to calculate the optical performance of the vee-trough concentrator and the thermal performance of the evacuated tube receiver. A test bed was constructed to verify the mathematical analyses and compare reflectors made out of glass, Alzak and aluminized FEP Teflon. Tests were run at temperatures ranging from 95 to 180 C. Vee-trough collector efficiencies of 35 to 40% were observed at an operating temperature of about 175 C. Test results compared well with the calculated values. Predicted daily useful heat collection and efficiency values are presented for a year's duration of operation temperatures ranging from 65 to 230 C. Estimated collector costs and resulting thermal energy costs are presented. Analytical and experimental results are discussed along with a complete economic evaluation.

The Use of Decentralized Control in the Design of a Large Segmented Space Reflector

NASA Technical Reports Server (NTRS)

Ryaciotaki-Boussalis, Helen; Mirmirani, Maj; Rad, Khosrow; Morales, Mauricio; Velazquez, Efrain; Chassiakos, Anastasios; Luzardo, Jose-Alberto

1997-01-01

The 3-dimensional model for a segmented reflector telescope is developed using finite element techniques. The structure is decomposed into six subsystems. System control design using neural networks is performed. Performance evaluation is demonstrated via simulation using PRO-MATLAB and SIMULINK.

Pointing and figure control system for a space-based far-IR segmented telescope

NASA Technical Reports Server (NTRS)

Lau, Kenneth

1993-01-01

A pointing and figure control system for two space-based far-IR telescopes, the 10-20 m Large Deployable Reflector and the 3.6 m Submillimeter Intermediate Mission, is described. The figure maintenance control system is designed to counter the optical elements translational and rotational changes induced by long-term thermal drifts that the support structure may experience. The pointing system applies optical truss to telescope pointing; a laser metrology system is used to transfer pointing informaton from an external fine guidance sensor to the telescope optical boresight, defined by the primary mirror, secondary mirror, and focal plane assembly.

Bifacial PV cell with reflector for stand-alone mast for sensor powering purposes

NASA Astrophysics Data System (ADS)

Jakobsen, Michael L.; Thorsteinsson, Sune; Poulsen, Peter B.; Riedel, N.; Rødder, Peter M.; Rødder, Kristin

2017-09-01

Reflectors to bifacial PV-cells are simulated and prototyped in this work. The aim is to optimize the reflector to specific latitudes, and particularly northern latitudes. Specifically, by using minimum semiconductor area the reflector must be able to deliver the electrical power required at the condition of minimum solar travel above the horizon, worst weather condition etc. We will test a bifacial PV-module with a retroreflector, and compare the output with simulations combined with local solar data.

Optical and optomechanical ultralightweight C/SiC components

NASA Astrophysics Data System (ADS)

Papenburg, Ulrich; Pfrang, Wilhelm; Kutter, G. S.; Mueller, Claus E.; Kunkel, Bernd P.; Deyerler, Michael; Bauereisen, Stefan

1999-11-01

Optical and optomechanical structures based on silicon carbide (SiC) ceramics are becoming increasingly important for ultra- lightweight optical systems that must work in adverse environments. At IABG and Dornier Satellite Systems (DSS) in Munich, a special form of SiC ceramics carbon fiber reinforced silicon carbide (C/SiCR) has been developed partly under ESA and NASA contracts. C/SiCR is a light-weight, high- strength engineering material that features tunable mechanical and thermal properties. It offers exceptional design freedom due to its reduced brittleness and negligible volume shrinkage during processing in comparison to traditional, powder-based ceramics. Furthermore, its rapid fabrication process produces near-net-shape components using conventional NC machining/milling equipment and, thus, provides substantial schedule, cost, and risk savings. These characteristics allow C/SiCR to overcome many of the problems associated with more traditional optical materials. To date, C/SiCR has been used to produce ultra-lightweight mirrors and reflectors, antennas, optical benches, and monolithic and integrated reference structures for a variety of space and terrestrial applications. This paper describes the material properties, optical system and structural design aspects, the forming and manufacturing process including high-temperature joining technology, precision grinding and cladding techniques, and the performance results of a number of C/SiCR optical components we have built.

Eternal triangle: the interaction of light source, electrical control gear, and optics

NASA Astrophysics Data System (ADS)

S'heeren, Griet

1998-04-01

In this particular 'affair' the participants are less than human but have individual personalities they bring to their relationship with each other. High pressure metal halide lamps such as BriteArc lamps have the highest luminance and radiance of all continuously operating practical light source. Since these lamps have short arcs and are available in power ratings from about 30W to 30kW they have found applications with various optical systems. Besides the lamps, such systems include an electrical control device and an optical system. To fulfil the user's requirements for a specific application, it is not only important to choose the right lamp, but crucial to achieve a harmonious marriage between the light source, electrical control device and the optics. To run a high pressure discharge lamp an ignitor/ballast system is essential This stabilizes the lamp parameters. The chemical components inside the lamp determine the lamp voltage and the gear determines, via the current, the lamp power. These are directly related in the luminance and color temperature of the emitted light. Therefore lamp performance and effective life are dependent on the ignitor, control gear and lamp combination. Since the lamp emits radiation in all directions, collection of the light from a lamp can be improved by using reflectors to deliver the light into a lens system. Since lamps with short arc gaps approach a point source they appear ideal for optical system applications. The shape of the reflector and the focusing of the lamp determine which part of the light is collected out of the light-arc. In the case of an LCD projector, the final light output also depends on the transmission characteristics of the LCD panels. Their nonlinearity causes the color of the emitted light to be different from the lamp color. All these parameters have to be optimized to obtain the highest performance. This leads to the conclusion that a carefully matched combination of lamp, ignitor/ballast and optics

An integral sunshade for optical reception antennas

NASA Technical Reports Server (NTRS)

Kerr, E. L.

1988-01-01

Optical reception antennas (telescopes) must be capable of receiving communications even when the deep-space laser source is located within a small angle of the Sun. Direst sunlight must not be allowed to shine on the primary reflector of an optical reception antenna, because too much light would be scattered into the signal detectors. A conventional sunshade that does not obstruct the antenna aperture would have to be about five times longer than its diameter in order to receive optical communications at a solar elongation of 12 degrees without interference. Such a long sunshade could not be accommodated within the dome of any existing large-aperture astronomical facility, and providing a new dome large enough would be prohibitively expensive. It is also desirable to reduce the amount of energy a space-based large-aperture optical reception facility would expend orienting a structure with such a sizable moment of inertia. Since a large aperture optical reception antenna will probably have a hexagonally segmented primary reflector, a sunshade consisting of hexagonal tubes can be mounted in alignment with the segmentation without producing any additional geometric obstruction. An analysis of the duration and recurrence of solar-conjunction communications outages (caused when a deep-space probe near an outer planet appears to be closer to the Sun than a given minimum solar elongation), and the design equations for the integral sunshade are appended.

Rapid prototyping of reflectors for vehicle lighting using laser activated remote phosphor

NASA Astrophysics Data System (ADS)

Lachmayer, Roland; Kloppenburg, Gerolf; Wolf, Alexander

2015-03-01

Bright white light sources are of significant importance for automotive front lighting systems. Today's upper class vehicles mainly use HID or LED as light source. As a further step in this development laser diode based systems offer high luminance, efficiency and allow the realization of new styling concepts and new dynamic lighting functions. These white laser diode systems can either be realized by mixing different spectral sources or by combining diodes with specific phosphors. Based on the approach of generating light using a laser and remote phosphor, lighting modules are manufactured. Four blue laser diodes (450 nm) are used to activate a phosphor coating and thus to achieve white light. A segmented paraboloid reflector generates the desired light distribution for an additional car headlamp. We use high speed milling and selective laser melting to build the reflector system for this lighting module. We compare the spectral reflection grade of these materials. Furthermore the generated modules are analyzed regarding their efficiency and light distribution. The use of Rapid Prototyping technologies allows an early validation of the chosen concept and is supposed to reduce cost and time in the product development process significantly. Therefor we discuss costs and times of the applied manufacturing technologies.

Geometrically Nonlinear Finite Element Analysis of a Composite Space Reflector

NASA Technical Reports Server (NTRS)

Lee, Kee-Joo; Leet, Sung W.; Clark, Greg; Broduer, Steve (Technical Monitor)

2001-01-01

Lightweight aerospace structures, such as low areal density composite space reflectors, are highly flexible and may undergo large deflection under applied loading, especially during the launch phase. Accordingly, geometrically nonlinear analysis that takes into account the effect of finite rotation may be needed to determine the deformed shape for a clearance check and the stress and strain state to ensure structural integrity. In this study, deformation of the space reflector is determined under static conditions using a geometrically nonlinear solid shell finite element model. For the solid shell element formulation, the kinematics of deformation is described by six variables that are purely vector components. Because rotational angles are not used, this approach is free of the limitations of small angle increments. This also allows easy connections between substructures and large load increments with respect to the conventional shell formulation using rotational parameters. Geometrically nonlinear analyses were carried out for three cases of static point loads applied at selected points. A chart shows results for a case when the load is applied at the center point of the reflector dish. The computed results capture the nonlinear behavior of the composite reflector as the applied load increases. Also, they are in good agreement with the data obtained by experiments.

Unique reflector arrangement within very wide field of view for multibeam antennas

NASA Astrophysics Data System (ADS)

Dragone, C.

1983-12-01

It is pointed out that Cassegrainian and Gregorian reflector arrangements are needed for multibeam ground station and satellite antennas. A Cassegrainian arrangement is considered, taking into account aberrations. Dragone (1982) has presented a requirement for the minimization of astigmatism. In the present investigation a formula is presented for describing the deformation coefficients needed to eliminate coma on the basis of a slight deformation of the reflectors. The importance of residual astigmatism due to a derived equation is examined, and attention is given to a compact reflector arrangement which is the result of three optimizations with respect to aberration minimization.

Collapsible structure for an antenna reflector

NASA Technical Reports Server (NTRS)

Trubert, M. R. (Inventor)

1973-01-01

A collapsible support for an antenna reflector for use in supporting spacecraft antennas is described. The support has a regid base and a number of struts which are pivoted at the base. The deployment of the struts and their final configuration for supporting the antenna are illustrated.

A coherent optical feedback system for optical information processing

NASA Technical Reports Server (NTRS)

Jablonowski, D. P.; Lee, S. H.

1975-01-01

A unique optical feedback system for coherent optical data processing is described. With the introduction of feedback, the well-known transfer function for feedback systems is obtained in two dimensions. Operational details of the optical feedback system are given. Experimental results of system applications in image restoration, contrast control and analog computation are presented.

Vibration of a Singly-curved Thin Shell Reflector with a Unidirectional Tension Field

NASA Technical Reports Server (NTRS)

Williams, R. Brett; Klein, Kerry J.; Agnes, Gregory S.

2006-01-01

Increased science requirements for space-based instruments over the past few decades have lead to the increased popularity of deployable space structures constructed from thin, lightweight films. Such structures offer both low mass and the ability to be stowed inside conventional launch vehicles. The analysis in this work pertains to large, singly-curved lightweight deployable reflectors commonly used in radar antennas and space telescopes. These types of systems, which can vary a great deal in size, often have frequency requirement that must be met. This work discusses two missions that utilize this type of aperture technology, and then develops a Rayleigh-Ritz model that predicts the natural frequencies and mode shapes for a (nearly) flat and singly-curved reflector with unidirectional in-plane loading. The results are compared with NASTRAN analyses.

Effectiveness of solar disinfection using batch reactors with non-imaging aluminium reflectors under real conditions: Natural well-water and solar light.

PubMed

Navntoft, C; Ubomba-Jaswa, E; McGuigan, K G; Fernández-Ibáñez, P

2008-12-11

Inactivation kinetics are reported for suspensions of Escherichia coli in well-water using compound parabolic collector (CPC) mirrors to enhance the efficiency of solar disinfection (SODIS) for batch reactors under real, solar radiation (cloudy and cloudless) conditions. On clear days, the system with CPC reflectors achieved complete inactivation (more than 5-log unit reduction in bacterial population to below the detection limit of 4CFU/mL) one hour sooner than the system fitted with no CPC. On cloudy days, only systems fitted with CPCs achieved complete inactivation. Degradation of the mirrors under field conditions was also evaluated. The reflectivity of CPC systems that had been in use outdoors for at least 3 years deteriorated in a non-homogeneous fashion. Reflectivity values for these older systems were found to vary between 27% and 72% compared to uniform values of 87% for new CPC systems. The use of CPC has been proven to be a good technological enhancement to inactivate bacteria under real conditions in clear and cloudy days. A comparison between enhancing optics and thermal effect is also discussed.

Optical analysis of a curved-slats fixed-mirror solar concentrator by a forward ray-tracing procedure.

PubMed

Pujol Nadal, Ramon; Martínez Moll, Víctor

2013-10-20

Fixed-mirror solar concentrators (FMSCs) use a static reflector and a moving receiver. They are easily installable on building roofs. However, for high-concentration factors, several flat mirrors would be needed. If curved mirrors are used instead, high-concentration levels can be achieved, and such a solar concentrator is called a curved-slats fixed-mirror solar concentrator (CSFMSC), on which little information is available. Herein, a methodology is proposed to characterize the CSFMSC using 3D ray-tracing tools. The CSFMSC shows better optical characteristics than the FMSC, as it needs fewer reflector segments for achieving the same concentration and optical efficiency.

Wide field strip-imaging optical system

NASA Technical Reports Server (NTRS)

Vaughan, Arthur H. (Inventor)

1994-01-01

A strip imaging wide angle optical system is provided. The optical system is provided with a 'virtual' material stop to avoid aberrational effects inherent in wide angle optical systems. The optical system includes a spherical mirror section for receiving light from a 180-degree strip or arc of a target image. Light received by the spherical mirror section is reflected to a frusto-conical mirror section for subsequent rereflection to a row of optical fibers. Each optical fiber transmits a portion of the received light to a detector. The optical system exploits the narrow cone of acceptance associated with optical fibers to substantially eliminate vignetting effects inherent in wide-angle systems. Further, the optical system exploits the narrow cone of acceptance of the optical fibers to substantially limit spherical aberration. The optical system is ideally suited for any application wherein a 180-degree strip image need be detected, and is particularly well adapted for use in hostile environments such as in planetary exploration.

Phased-array-fed antenna configuration study. Volume 1: Technology assessment

NASA Technical Reports Server (NTRS)

Sorbello, R. M.; Zaghloul, A. I.; Lee, B. S.; Siddiqi, S.; Geller, B. D.; Gerson, H. I.; Srinivas, D. N.

1983-01-01

The status of the technologies for phased-array-fed dual reflector systems is reviewed. The different aspects of these technologies, including optical performances, phased array systems, problems encountered in phased array design, beamforming networks, MMIC design and its incorporation into waveguide systems, reflector antenna structures, and reflector deployment mechanisms are addressed.

Optical design of a robotic TV camera probe for minimally invasive abdominal surgery

NASA Astrophysics Data System (ADS)

Todaro, Susanna; He, Weiyi; Killinger, Dennis

2011-03-01

Minimally invasive techniques are a promising new field of surgery; however, they limit the surgeon's access points and maneuverability. In order to increase the number of access points in minimally invasive abdominal surgery, a proposed implantable medical probe braces to the abdominal wall and provides illumination and video signal. The probe is cylindrical, about 25 mm long and 10 mm in diameter. A ring of LEDs on the end of the probe illuminates the tissue, and the resulting image is focused onto an HD video detector. It was necessary to apply beam-shaping reflectors to collimate the light onto a small target area, to avoid illuminating areas not picked up by the video. These reflectors were designed and simulated using the optical ray tracing software TracePro. Two LED chip geometries and three types of reflector geometries were analyzed, and the parameters for each geometry were optimized. For the straight-edged reflectors, the intensity patterns and optimization were compared to experimental results. Although parabolic reflectors produced the best collimation, cone reflectors with a 20-degree half-angle produced significant collimation at a much cheaper price. This work was supported by NSF REU program (award No DMR-1004873).

Optimization of optical systems.

PubMed

Champagne, E B

1966-11-01

The power signal-to-noise ratios for coherent and noncoherent optical detection are presented, with the expression for noncoherent detection being examined in detail. It is found that for the long range optical system to compete with its microwave counterpart it is necessary to optimize the optical system. The optical system may be optimized by using coherent detection, or noncoherent detection if the signal is the dominate noise factor. A design procedure is presented which, in principle, always allows one to obtain signal shot-noise limited operation with noncoherent detection if pulsed operation is used. The technique should make reasonable extremely long range, high data rate systems of relatively simple design.

Fiber optic multiplex optical transmission system

NASA Technical Reports Server (NTRS)

Bell, C. H. (Inventor)

1977-01-01

A multiplex optical transmission system which minimizes external interference while simultaneously receiving and transmitting video, digital data, and audio signals is described. Signals are received into subgroup mixers for blocking into respective frequency ranges. The outputs of these mixers are in turn fed to a master mixer which produces a composite electrical signal. An optical transmitter connected to the master mixer converts the composite signal into an optical signal and transmits it over a fiber optic cable to an optical receiver which receives the signal and converts it back to a composite electrical signal. A de-multiplexer is coupled to the output of the receiver for separating the composite signal back into composite video, digital data, and audio signals. A programmable optic patch board is interposed in the fiber optic cables for selectively connecting the optical signals to various receivers and transmitters.

Total internal reflection optical switch using the reverse breakdown of a pn junction in silicon.

PubMed

Kim, Jong-Hun; Park, Hyo-Hoon

2015-11-01

We demonstrate a new type of silicon total-internal-reflection optical switch with a simple pn junction functioning both as a reflector and a heater. The reflector is placed between asymmetrically y-branched multimode waveguides with an inclination angle corresponding to half of the branch angle. When the reflector is at rest, incident light is reflected in accordance to the refractive index difference due to the plasma dispersion effect of the pre-doped carriers. Switching to the transmission state is attained under a reverse breakdown of the pn junction by the thermo-optic effect which smears the refractive index difference. From this switching scheme, we confirmed the switching operation with a shallow total-internal-reflection region of 1 μm width. At a 6° branch angle, an extinction ratio of 12 dB and an insertion loss of -4.2  dB are achieved along with a thermal heating power of 151.5 mW.

Reflective optical imaging system

DOEpatents

Shafer, David R.

2000-01-01

An optical system compatible with short wavelength (extreme ultraviolet) radiation comprising four reflective elements for projecting a mask image onto a substrate. The four optical elements are characterized in order from object to image as convex, concave, convex and concave mirrors. The optical system is particularly suited for step and scan lithography methods. The invention increases the slit dimensions associated with ringfield scanning optics, improves wafer throughput and allows higher semiconductor device density.

Method of making reflecting film reflector

DOEpatents

Cottingham, James G.

1980-01-01

A reflector of the reflecting film type is disclosed and which may be used in a heliostatic system for concentrating solar energy and comprising a reflecting film bonded to an appropriate rigid substrate in such a way that specularity of a very high order is achieved. A method of bonding the reflecting film to the substrate is also disclosed and comprises the steps of initially adhering the film to a smooth, clean flat rigid surface with a non-bonding liquid between the rigid surface and film, and then bonding the substrate and film. The non-bonding liquid has a molecular adhesion greater than any stresses due to handling or curing of the bonding agent which is applied between the film and the opposing surface of the rigid substrate.