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1

Optical center alignment technique based on inner profile measurement method  

NASA Astrophysics Data System (ADS)

Center alignment is important technique to tune up the spindle of various precision machines in manufacturing industry. Conventionally such a tool as a dial indicator has been used to adjust and to position the axis by manual operations of a technical worker. However, it is not easy to precisely control its axis. In this paper, we developed the optical center alignment technique based on inner profile measurement using a ring beam device. In this case, the center position of the cylinder hole can be determined from circular profile detected by optical sectioning method using a ring beam device. In our trials, the resolution of the center position is proved less than 10 micrometers in extreme cases. This technique is available for practical applications in machine tool industry.

Wakayama, Toshitaka; Yoshizawa, Toru

2014-05-01

2

Passive alignment and soldering technique for optical components  

NASA Astrophysics Data System (ADS)

The passive-alignment-packaging technique presented in this work provides a method for mounting tolerance-insensitive optical components e.g. non-linear crystals by means of mechanical stops. The requested tolerances for the angle deviation are +/-100 ?rad and for the position tolerance +/-100 ?m. Only the angle tolerances were investigated, because they are more critical. The measurements were carried out with an autocollimator. Fused silica components were used for test series. A solder investigation was carried out. Different types of solder were tested. Due to good solderability on air and low induced stress in optical components, Sn based solders were indicated as the most suitable solders. In addition several concepts of reflow soldering configuration were realized. In the first iteration a system with only the alignment of the yaw angle was implemented. The deviation for all materials after the thermal and mechanical cycling was within the tolerances. The solderability of BBO and LBO crystals was investigated and concepts for mounting were developed.

Faidel, Heinrich; Gronloh, Bastian; Winzen, Matthias; Liermann, Erik; Esser, Dominik; Morasch, Valentin; Luttmann, Jörg; Leers, Michael; Hoffmann, Dieter

2012-03-01

3

Pupil Alignment Measuring Technique and Alignment Reference for Instruments or Optical Systems  

NASA Technical Reports Server (NTRS)

A technique was created to measure the pupil alignment of instruments in situ by measuring calibrated pupil alignment references (PARs) in instruments. The PAR can also be measured using an alignment telescope or an imaging system. PAR allows the verification of the science instrument (SI) pupil alignment at the integrated science instrument module (ISIM) level of assembly at ambient and cryogenic operating temperature. This will allow verification of the ISIM+SI alignment, and provide feedback to realign the SI if necessary.

Hagopian, John G.

2010-01-01

4

In situ focus characterization by ablation technique to enable optics alignment at an XUV FEL source  

SciTech Connect

In situ focus characterization is demonstrated by working at an extreme ultraviolet (XUV) free-electron laser source using ablation technique. Design of the instrument reported here allows reaching a few micrometres resolution along with keeping the ultrahigh vacuum conditions and ensures high-contrast visibility of ablative imprints on optically transparent samples, e.g., PMMA. This enables on-line monitoring of the beam profile changes and thus makes possible in situ alignment of the XUV focusing optics. A good agreement between focal characterizations retrieved from in situ inspection of ablative imprints contours and from well-established accurate ex situ analysis with Nomarski microscope has been observed for a typical micro-focus experiment.

Gerasimova, N.; Dziarzhytski, S.; Weigelt, H. [Deutsches Electronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg (Germany); Chalupsky, J.; Hajkova, V.; Vysin, L.; Juha, L. [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Prague (Czech Republic)

2013-06-15

5

Optics Alignment Panel  

NASA Technical Reports Server (NTRS)

The Optics Alignment Panel (OAP) was commissioned by the HST Science Working Group to determine the optimum alignment of the OTA optics. The goal was to find the position of the secondary mirror (SM) for which there is no coma or astigmatism in the camera images due to misaligned optics, either tilt or decenter. The despace position was reviewed of the SM and the optimum focus was sought. The results of these efforts are as follows: (1) the best estimate of the aligned position of the SM in the notation of HDOS is (DZ,DY,TZ,TY) = (+248 microns, +8 microns, +53 arcsec, -79 arcsec), and (2) the best focus, defined to be that despace which maximizes the fractional energy at 486 nm in a 0.1 arcsec radius of a stellar image, is 12.2 mm beyond paraxial focus. The data leading to these conclusions, and the estimated uncertainties in the final results, are presented.

Schroeder, Daniel J.

1992-01-01

6

Systematic Image Based Optical Alignment and Tensegrity  

NASA Technical Reports Server (NTRS)

This presentation will review the objectives and current status of two Small Business Innovative Research being performed by the Sirius Group, under the direction of MSFC. They all relate to the development of advanced optical systems technologies for automated segmented mirror alignment techniques and fundamental design methodologies for ultralight structures. These are important to future astronomical missions in space.

Zeiders, Glenn W.; Montgomery, Edward E, IV (Technical Monitor)

2001-01-01

7

Optical alignment techniques for line-imaging velocity interferometry and line-imaging self-emission of targets at the National Ignition Facility (NIF)  

SciTech Connect

The National Ignition Facility (NIF) requires optical diagnostics for measuring shock velocities in shock physics experiments. The nature of the NIF facility requires the alignment of complex three-dimensional optical systems of very long distances. Access to the alignment mechanisms can be limited, and any alignment system must be operator friendly. The Velocity Interferometer System for Any Reflector (VISAR) measures shock velocities, shock breakout times, and emission of 1- to 5-mm targets at a location remote to the NIF target chamber. Three optical systems using the same vacuum chamber port each have a total track of 21 m. All optical lenses are on kinematic mounts or sliding rails, enabling pointing accuracy of the optical axis to be checked. Counter-propagating laser beams (orange and red) align these diagnostics to a listing of tolerances. Movable aperture cards, placed before and after lens groups, show the spread of alignment spots created by the orange and red alignment lasers. Optical elements include 1-in. to 15-in. diameter mirrors, lenses with up to 10.5-in. diameters, beamsplitters, etalons, dove prisms, filters, and pellicles. Alignment of more than 75 optical elements must be verified before each target shot. Archived images from eight alignment cameras prove proper alignment before each shot.

Malone, Robert; Celeste, John; Celliers, Peter; Frogget, Brent; Robert Guyton,,; Kaufman, Morris; Lee, Tony; MacGowan, Brian; Ng, Edmend; Reinbachs, Imants; Robinson, Ronald; Tunnell, Thomas; Watts, Phillip

2007-08-01

8

Call for Papers Optical System Alignment, Tolerancing,  

E-print Network

. Malone, National Security Technologies, LLC (United States); Maria D. Nowak, Raymond G. Ohl IV, NASA loosening tolerances using active elements alignment in electro-optical systems alignment in metrology

Jahns, Jürgen

9

Optical analysis and alignment applications using the infrared Smartt interferometer  

SciTech Connect

The possibility of using the infrared Smartt interferometer for optical analysis and alignment of infrared laser systems has been discussed previously. In this paper, optical analysis of the Gigawatt Test Facility at Los Alamos, as well as a deformable mirror manufactured by Rocketdyne, are discussed as examples of the technique. The possibility of optically characterizing, as well as aligning, pulsed high energy laser systems like Helios and Antares is discussed in some detail.

Viswanathan, V.K.; Bolen, P.D.; Liberman, I.; Seery, B.D.

1981-01-01

10

Optical alignment techniques for line-imaging velocity interferometry and line-imaging self-emulsion of targets at the National Ignition Facility (NIF)  

SciTech Connect

The National Ignition Facility (NIF) requires optical diagnostics for measuring shock velocities in shock physics experiments. The Velocity Interferometer System for Any Reflector (VISAR) measures shock velocities, shock breakout times, and emission of 1- to 5-mm targets at a location remote to the NIF target chamber. Three optical systems using the same vacuum chamber port each have a total track of 69 feet. All optical lenses are on kinematic mounts or sliding rails, enabling pointing accuracy of the optical axis to be checked. Counter-propagating laser beams (orange and red) align these diagnostics to a listing of tolerances. The orange alignment laser is introduced at the entrance to the two-level interferometer table and passes forward through the optical systems to the recording streak cameras. The red alignment laser is introduced in front of the recording streak cameras and passes in the reverse direction through all optical elements, out of the interferometer table, eventually reaching the target chamber center. Red laser wavelength is selected to be at the 50 percent reflection point of a special beamsplitter used to separate emission light from the Doppler-shifted interferometer light. Movable aperture cards, placed before and after lens groups, show the spread of alignments spots created by the orange and red alignment lasers. Optical elements include 1- to 15-inch-diameter mirrors, lenses with up to 10.5-inch diameters, beamsplitters, etalons, dove prisms, filters, and pellicles. Alignment of more than 75 optical elements must be verified before each target shot. Archived images from eight alignment cameras prove proper alignment before each shot.

Robert M. Malone, Brent C. Frogget, Morris I. Kaufman, Thomas W. Tunnell, Robert L. Guyton, Imants P. Reinbachs, Phillip W. Watts, et al.

2007-08-31

11

Micro-Optical Bench for Alignment-Free Optical Coupling  

NASA Astrophysics Data System (ADS)

We propose an optical coupling module, the micro-optical bench, designed for the purpose of completely passive alignment of optical components. The principle is for one to position a planar microlens array, semiconductor device submounts, and optical fibers by using reference planes and V grooves made on a Si substrate. A prototype was fabricated, and we achieved an optical coupling loss of less than 3 dB; small deviations among channels as low as 1 dB were achieved without any precise alignment. For multimode fibers, a coupling loss of approximately 0.5 dB was obtained.

Aoki, Yasuhiko; Kato, Toshio; Mizuno, Rogerio Jun; Iga, Kenichi

1999-02-01

12

High precision geometrical characterization and alignment of miniaturized optics  

NASA Astrophysics Data System (ADS)

Miniaturized optical systems like endoscopy or cell phone lenses systems comprise several optical elements like lenses, doublets and plane optics. To receive a good imaging quality the distances and angles between the different optical elements have to be as accurate as possible. In the first step we will describe how the distances and angles between different elements can be monitored and finally we will describe a technique to actively align small optics (diameter approx. 1mm and smaller) with respect to each other. For the measurement electronic autocollimators combined with white-light-interferometers are used. The electronic autocollimator reveals the exact centration errors between optical elements and the low coherence interferometer reveals the distances between surfaces. The accuracy of the centration error measurement is in the range of 0.1?m and the accuracy of the distance measurement is 1?m. Both methods can be applied to assembled multi-element optics. That means geometrical positions of all single surfaces of the final optical system can be analysed without loss of information. Both measurement techniques complement one another. Once the exact x,y,z - Position of each optical surface and element is known computer controlled actuators will be used to improve the alignment of the optics. For this purpose we use piezo-electric-actuators. This method had been applied to cement e.g. doublets for endoscope optics. In this case the optical axis of one lens has been aligned with respect to the optical axis of a second reference lens. Traditional techniques usually rely on an uncertain mechanical reference.

Langehanenberg, Patrik; Heinisch, Josef; Dumitrescu, Eugen

2012-03-01

13

Optical alignment of the Global Precipitation Measurements (GPM) star trackers  

NASA Astrophysics Data System (ADS)

The optical alignment of the star trackers on the Global Precipitation Measurement (GPM) core spacecraft at NASA Goddard Space Flight Center (GSFC) was challenging due to the layout and structural design of the GPM Lower Bus Structure (LBS) in which the star trackers are mounted as well as the presence of the star tracker shades that blocked line-of-sight to the primary star tracker optical references. The initial solution was to negotiate minor changes in the original LBS design to allow for the installation of a removable item of ground support equipment (GSE) that could be installed whenever measurements of the star tracker optical references were needed. However, this GSE could only be used to measure secondary optical reference cube faces not used by the star tracker vendor to obtain the relationship information and matrix transformations necessary to determine star tracker alignment. Unfortunately, due to unexpectedly large orthogonality errors between the measured secondary adjacent cube faces and the lack of cube calibration data, we required a method that could be used to measure the same reference cube faces as originally measured by the vendor. We describe an alternative technique to theodolite autocollimation for measurement of an optical reference mirror pointing direction when normal incidence measurements are not possible. This technique was used to successfully align the GPM star trackers and has been used on a number of other NASA flight projects. We also discuss alignment theory as well as a GSFC-developed theodolite data analysis package used to analyze angular metrology data.

Hetherington, Samuel; Osgood, Dean; McMann, Joe; Roberts, Viki; Gill, James; McLean, Kyle

2013-09-01

14

Computer vision applications for coronagraphic optical alignment and image processing  

E-print Network

Modern coronagraphic systems require very precise alignment between optical components and can benefit greatly from automated image processing. We discuss three techniques commonly employed in the fields of computer vision and image analysis as applied to the Gemini Planet Imager, a new facility instrument for the Gemini South Observatory. We describe how feature extraction and clustering methods can be used to aid in automated system alignment tasks, and also present a search algorithm for finding regular features in science images used for calibration and data processing. Along with discussions of each technique, we present our specific implementation and show results of each one in operation.

Savransky, Dmitry; Poyneer, Lisa A; Macintosh, Bruce A; 10.1364/AO.52.003394

2013-01-01

15

AGORA: Assembly Guided by Optical Restriction Alignment  

PubMed Central

Background Genome assembly is difficult due to repeated sequences within the genome, which create ambiguities and cause the final assembly to be broken up into many separate sequences (contigs). Long range linking information, such as mate-pairs or mapping data, is necessary to help assembly software resolve repeats, thereby leading to a more complete reconstruction of genomes. Prior work has used optical maps for validating assemblies and scaffolding contigs, after an initial assembly has been produced. However, optical maps have not previously been used within the genome assembly process. Here, we use optical map information within the popular de Bruijn graph assembly paradigm to eliminate paths in the de Bruijn graph which are not consistent with the optical map and help determine the correct reconstruction of the genome. Results We developed a new algorithm called AGORA: Assembly Guided by Optical Restriction Alignment. AGORA is the first algorithm to use optical map information directly within the de Bruijn graph framework to help produce an accurate assembly of a genome that is consistent with the optical map information provided. Our simulations on bacterial genomes show that AGORA is effective at producing assemblies closely matching the reference sequences. Additionally, we show that noise in the optical map can have a strong impact on the final assembly quality for some complex genomes, and we also measure how various characteristics of the starting de Bruijn graph may impact the quality of the final assembly. Lastly, we show that a proper choice of restriction enzyme for the optical map may substantially improve the quality of the final assembly. Conclusions Our work shows that optical maps can be used effectively to assemble genomes within the de Bruijn graph assembly framework. Our experiments also provide insights into the characteristics of the mapping data that most affect the performance of our algorithm, indicating the potential benefit of more accurate optical mapping technologies, such as nano-coding. PMID:22856673

2012-01-01

16

Combining Ontology Alignment with Model Driven Engineering Techniques for Home  

E-print Network

Combining Ontology Alignment with Model Driven Engineering Techniques for Home Devices intro- duce an approach combining ontology alignment techniques with those of Model Driven Engineering domain to reach a dynamic service adap- tation. Keywords: SOA, Plug-n-play protocols, ontology alignment

17

Optical alignment of Centaur's inertial guidance system  

NASA Technical Reports Server (NTRS)

During Centaur launch operations the launch azimuth of the inertial platform's U-accelerometer input axis must be accurately established and maintained. This is accomplished by using an optically closed loop system with a long-range autotheodolite whose line of sight was established by a first-order survey. A collimated light beam from the autotheodolite intercepts a reflecting Porro prism mounted on the platform azimuth gimbal. Thus, any deviation of the Porro prism from its predetermined heading is optically detected by the autotheodolite. The error signal produced is used to torque the azimuth gimbal back to its required launch azimuth. The heading of the U-accelerometer input axis is therefore maintained automatically. Previously, the autotheodolite system could not distinguish between vehicle sway and rotational motion of the inertial platform unless at least three prisms were used. One prism was mounted on the inertial platform to maintain azimuth alignment, and two prisms were mounted externally on the vehicle to track sway. For example, the automatic azimuth-laying theodolite (AALT-SV-M2) on the Saturn vehilce used three prisms. The results of testing and modifying the AALT-SV-M2 autotheodolite to simultaneously monitor and maintain alignment of the inertial platform and track the sway of the vehicle from a single Porro prism.

Gordan, Andrew L.

1987-01-01

18

Optical Techniques Nanomicroscopy  

E-print Network

Optical Techniques Nanomicroscopy Drug Development Medicinal Plants Sessions Nanomicroscopy Medical Biophysics Structure and Mechanics of F nction Medicinal Plants Nano Medicine Drug Encapsulation and Deli er

Fischer, Wolfgang

19

Low cost, high performance, self-aligning miniature optical systems  

PubMed Central

The most expensive aspects in producing high quality miniature optical systems are the component costs and long assembly process. A new approach for fabricating these systems that reduces both aspects through the implementation of self-aligning LIGA (German acronym for lithographie, galvanoformung, abformung, or x-ray lithography, electroplating, and molding) optomechanics with high volume plastic injection molded and off-the-shelf glass optics is presented. This zero alignment strategy has been incorporated into a miniature high numerical aperture (NA = 1.0W) microscope objective for a fiber confocal reflectance microscope. Tight alignment tolerances of less than 10 ?m are maintained for all components that reside inside of a small 9 gauge diameter hypodermic tubing. A prototype system has been tested using the slanted edge modulation transfer function technique and demonstrated to have a Strehl ratio of 0.71. This universal technology is now being developed for smaller, needle-sized imaging systems and other portable point-of-care diagnostic instruments. PMID:19543344

Kester, Robert T.; Christenson, Todd; Kortum, Rebecca Richards; Tkaczyk, Tomasz S.

2009-01-01

20

New techniques for initial alignment of strapdown inertial navigation system  

Microsoft Academic Search

Some new techniques for initial alignment of strapdown inertial navigation system are proposed in this paper. A new solution for the precise azimuth alignment is given in detail. A new prefilter, which consists of an IIR filter and a Kalman filter using hidden Markov model, is designed to attenuate the influence of sensor noise and outer disturbance. Navigation algorithm in

Shaolin Lü; Ling Xie; Jiabin Chen

2009-01-01

21

Advanced Optical Measurement Techniques  

NASA Technical Reports Server (NTRS)

This research analyzes four areas: (1) Improved Techniques for Optical Measurement; (2) KC-135 Low Gravity Simulation Flight Preparation; (3) In-Line Holographic Microscopy; and (4) Holographic Optical Schlieren System (HOSS). The first task provides for laboratory breadboarding of advanced optical measurement techniques which appear promising for use in Material Processing System (MPS) flight experiments. A laboratory schlieren system has been constructed which simulates a similar optical system on the Fluids Experiment System (FES) which is to be flown on Spacelab 3. The second task allows improved optical systems and breadboards to be built for experiments and hardware tests on the KC-135 aircraft. A new, more stable Mach-Zehnder interferometer has been developed and components have been ordered. The third task is concerned with improvements on the optical system being used to study immiscible fluids. Experiments studying the dynamics of nucleation and the separation of immiscible fluids have been conducted. The four task involves building breadboard reconstruction systems for holograms taken in the HOSS. The HOSS is an early prototype of the Fluids Experiments System (FES) which is scheduled to fly on Spacelab 3.

Owen, R. B.; Johnston, M. H.; Witherow, W. K.

1985-01-01

22

Multichip hybrid integration on PLC platform using passive alignment technique  

Microsoft Academic Search

A multi-chip hybrid integration technique on a planar lightwave circuit (PLC) platform achieves bonding accuracy of better than 1.0 ?m and adequate bonding strength. This procedure consists of a chip-by-chip alignment step and a simultaneous solder reflowing step. In the chip-by-chip assembly step, opto-electronic chips were successively placed at their optimum positions by passive alignment while keeping the platform temperature

Y. Nakasuga; T. Hashimoto; Y. Yamada; H. Terui; M. Yanagisawa; K. Moriwaki; Y. Akahori; Y. Tohmori; K. Kato; S. Sekine; M. Horiguchi

1996-01-01

23

Computer-aided alignment of the complex optical system  

Microsoft Academic Search

Complex optical system, especially the all-reflecting off-axis spherical system is developed and used in the remote sensing camera and the UVX lithophotography. The alignment becomes more important to such system. In this paper, a computer-aided alignment method is described. The wavefront errors are obtained by using the autocollimating interferometric test at some field of views. A serial of aberrations explained

Bin Zhang; Xiaohui Zhang; Cheng Wang; Changyuan Han

2000-01-01

24

Modeling alignment shift of soldered optical fiber  

Microsoft Academic Search

Solder is often used as an adhesive to attach optical fibers to a circuit board. In this proceeding we will discuss efforts to model the motion of an optical fiber during the wetting and solidification of the adhesive solder droplet. The extent of motion is determined by several competing forces, during three “stages” of solder joint formation. First, capillary forces

A. Powell

2000-01-01

25

Automatic alignment of double optical paths in excimer laser amplifier  

NASA Astrophysics Data System (ADS)

A kind of beam automatic alignment method used for double paths amplification in the electron pumped excimer laser system is demonstrated. In this way, the beams from the amplifiers can be transferred along the designated direction and accordingly irradiate on the target with high stabilization and accuracy. However, owing to nonexistence of natural alignment references in excimer laser amplifiers, two cross-hairs structure is used to align the beams. Here, one crosshair put into the input beam is regarded as the near-field reference while the other put into output beam is regarded as the far-field reference. The two cross-hairs are transmitted onto Charge Coupled Devices (CCD) by image-relaying structures separately. The errors between intersection points of two cross-talk images and centroid coordinates of actual beam are recorded automatically and sent to closed loop feedback control mechanism. Negative feedback keeps running until preset accuracy is reached. On the basis of above-mentioned design, the alignment optical path is built and the software is compiled, whereafter the experiment of double paths automatic alignment in electron pumped excimer laser amplifier is carried through. Meanwhile, the related influencing factors and the alignment precision are analyzed. Experimental results indicate that the alignment system can achieve the aiming direction of automatic aligning beams in short time. The analysis shows that the accuracy of alignment system is 0.63?rad and the beam maximum restoration error is 13.75?m. Furthermore, the bigger distance between the two cross-hairs, the higher precision of the system is. Therefore, the automatic alignment system has been used in angular multiplexing excimer Main Oscillation Power Amplification (MOPA) system and can satisfy the requirement of beam alignment precision on the whole.

Wang, Dahui; Zhao, Xueqing; Hua, Hengqi; Zhang, Yongsheng; Hu, Yun; Yi, Aiping; Zhao, Jun

2013-05-01

26

German Encyclopedia Alignment Based on Information Retrieval Techniques  

E-print Network

German Encyclopedia Alignment Based on Information Retrieval Techniques Roman Kern1 and Michael. Collaboratively created online encyclopedias have become increasingly popular. Especially in terms of completeness they have be- gun to surpass their printed counterparts. Two German publishers of traditional encyclopedias

Hammerton, James

27

Alignment and focusing tolerance influences on optical performance  

SciTech Connect

Alignment errors among components of an optical system may substantially degrade the image quality. Focus errors also affect system performance. The potential for serious degradation of image quality is substantial and requires that the tolerances for these errors receive significant attention early in system design. The image quality and reconnaissance performance of an all-reflecting Cassegrain is compared to an all-refractive optical system under conditions of zero and anticipated real world misalignments.

Cross, E.W.

1982-01-01

28

Application of the Brewster angle illumination technique to eliminate resist-induced alignment errors  

NASA Astrophysics Data System (ADS)

Resist coating on alignment marks can be asymmetrical due to the spinning motion. Alignment errors may result from this asymmetrical coating because the alignment signal can contain asymmetry when the optics detects the mark through the resist. The amount of signal asymmetry depends on the mark topography, resist thickness, spin speed, location on the wafer and the alignment technique. We have proposed a Brewster angle illumination technique (BAIT) as an effective means to greatly reduce the resist-induced alignment error by reducing alignment signal reflections from the surface of the resist. In this paper, we present the experimental results. We built an interferometric alignment system to implement BAIT. By scanning a resist-coated mark in close proximity to an exposed reference mark, drift and other system offsets are minimized, allowing an offset detectability of 6 nm. Resist-induced alignment errors with a radial dependence on mark position and magnitudes up to 25 nm have been measured when BAIT is not used. However, when BAIT is employed the resist-induced errors at all positions on the wafer are reduced to less than 10 nm and are close to the resolution limit of the alignment setup. The validity of the data was established by changing the polarization of the light from TM to TE, thereby destroying the BAIT condition while holding all other parameters constant. A study of the dependence of resist-induced alignment error on spin speed reveals that the amount of asymmetry in the resist profile increases monotonically as the spin speed increases. This effect is due to two factors: that the resist is thinner and that the spin speed is also faster. Further study using a thinner to dilute the resist isolated these factors and showed that the resist-induced alignment errors depend more sensitively on spin speed than the resist thickness. In most of the cases, the BAIT alignment system is immune to resist coating asymmetry and the error magnitude stays below 10 nm. However, the BAIT cannot work effectively when resist thickness becomes thinner than 0.6 micrometer. This limitation of BAIT technique was attributed to the ripples in the resist profile causing local impinging angles to deviate significantly from the Brewster angle.

Chen, Xun; Ghazanfarian, Amir Aalam; McCord, Mark A.; Pease, Roger Fabian W.

1998-06-01

29

Aligning Arrays of Lenses and Single-Mode Optical Fibers  

NASA Technical Reports Server (NTRS)

A procedure now under development is intended to enable the precise alignment of sheet arrays of microscopic lenses with the end faces of a coherent bundle of as many as 1,000 single-mode optical fibers packed closely in a regular array (see Figure 1). In the original application that prompted this development, the precise assembly of lenses and optical fibers serves as a single-mode spatial filter for a visible-light nulling interferometer. The precision of alignment must be sufficient to limit any remaining wavefront error to a root-mean-square value of less than 1/10 of a wavelength of light. This wavefront-error limit translates to requirements to (1) ensure uniformity of both the lens and fiber arrays, (2) ensure that the lateral distance from the central axis of each lens and the corresponding optical fiber is no more than a fraction of a micron, (3) angularly align the lens-sheet planes and the fiber-bundle end faces to within a few arc seconds, and (4) axially align the lenses and the fiber-bundle end faces to within tens of microns of the focal distance. Figure 2 depicts the apparatus used in the alignment procedure. The beam of light from a Zygo (or equivalent) interferometer is first compressed by a ratio of 20:1 so that upon its return to the interferometer, the beam will be magnified enough to enable measurement of wavefront quality. The apparatus includes relay lenses that enable imaging of the arrays of microscopic lenses in a charge-coupled-device (CCD) camera that is part of the interferometer. One of the arrays of microscopic lenses is mounted on a 6-axis stage, in proximity to the front face of the bundle of optical fibers. The bundle is mounted on a separate stage. A mirror is attached to the back face of the bundle of optical fibers for retroreflection of light. When a microscopic lens and a fiber are aligned with each other, the affected portion of the light is reflected back by the mirror, recollimated by the microscopic lens, transmitted through the relay lenses and the beam compressor/expander, then split so that half goes to a detector and half to the interferometer. The output of the detector is used as a feedback control signal for the six-axis stage to effect alignment.

Liu, Duncan

2004-01-01

30

Inverting Image Data For Optical Testing And Alignment  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

31

Survey techniques developed to align stacked beamlines at CEBAF  

SciTech Connect

The Continuous Electron Beam Accelerator Facility (CEBAF) in Newport News, Virginia is a new accelerator designed to produce 4 GeV 200 micro-amp continuous wave beams for nuclear physics research. It consists of two superconducting linacs each accelerating electrons by 400 MeV and linked by arcs allowing five pass recirculation. These linacs form the straight sections in a racetrack shaped accelerator contained in over 1.3 km of tunnel. The beam lines will consist of 42 superconducting accelerating cryomodules (in the linacs only), over 400 dipoles, 650 quadrupoles, and 100 sextupoles, most of the which are concentrated in the two arc sections of the machine. It is here that the single beam fine from the linacs is split into five beams of offering energy and transported to the opposite linac where it is recombined into a single beam to again pass through a linac and receive additional acceleration. These recirculation arcs are designed to maintain beam quality through a lattice which is achromatic, isochronous and whose length is equal to a multiple number of RF wavelengths. The short term relative alignment tolerances coupled with the beam fine design reflect the beam quality issues while absolute positioning determines the range of adjustment needed to match the RF phase in the linac segments. The alignment techniques which use a monumented control network as a reference, are designed to position stacked magnets and their support systems to these tolerances. Specialized procedures were tailored from existing hardware and software systems to address each phase or step of the alignment process. This allowed a relatively rapid expansion of alignment services at a new laboratory where surveying support was not seriously addressed until more then one third of the enclosure had been built.

Curtis, C.J.; Oren, W.; Tremblay, K.J. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States)

1994-04-01

32

A Concept for Zero-Alignment Micro Optical Systems  

SciTech Connect

We are developing a method of constructing compact, three-dimensional photonics systems consisting of optical elements, e.g., lenses and mirrors, photo-detectors, and light sources, e.g., VCSELS or circular-grating lasers. These optical components, both active and passive, are mounted on a lithographically prepared silicon substrate. We refer to the substrate as a micro-optical table (MOT) in analogy with the macroscopic version routinely used in optics laboratories. The MOT is a zero-alignment, microscopic optical-system concept. The position of each optical element relative to other optical elements on the MOT is determined in the layout of the MOT photomask. Each optical element fits into a slot etched in the silicon MOT. The slots are etched using a high-aspect-ratio silicon etching (HARSE) process. Additional positioning features in each slot's cross-section and complementary features on each optical element permit accurate placement of that element's aperture relative to the MOT substrate. In this paper we present the results of the first fabrication and micro-assembly experiments of a silicon-wafer based MOT. Based on these experiments, estimates of position accuracy are reported. We also report on progress in fabrication of lens elements in a hybrid sol-gel material (HSGM). Diffractive optical elements have been patterned in a 13-micron thick HSGM layer on a 150-micron thick soda-lime glass substrate. The measured ms surface roughness was 20 nm. Finally, we describe modeling of MOT systems using non-sequential ray tracing (NSRT).

DESCOUR, MICHAEL R.; KOLOLUOMA,TERHO; LEVEY,RAVIV; RANTALA,JUHA T.; SHUL,RANDY J.; WARREN,MIAL E.; WILLISON,CHRISTI LEE

1999-09-16

33

Alignment of off-axis optical system with multi mirrors using derivative of Zernike polynomial coefficient  

Microsoft Academic Search

The precise alignment of multiple element large optical system is a challenging task. In order to increase the alignment process efficiency, computer aided alignment methods utilizing Zernike polynomial coefficients have been developed over the last few decades. Recently, differential wavefront sampling(DWS) algorithm revealed that derivative information about the wavefront is a very useful to separate wavefront coupling effect between optical

Yunjong Kim; Ho-Soon Yang; Sug-Whan Kim; Yun-Woo Lee

2009-01-01

34

Elevation angle alignment of quasi optical receiver mirrors of collective Thomson scattering diagnostic by sawtooth measurements  

SciTech Connect

Localized measurements of the fast ion velocity distribution function and the plasma composition measurements are of significant interest for the fusion community. Collective Thomson scattering (CTS) diagnostics allow such measurements with spatial and temporal resolution. Localized measurements require a good alignment of the optical path in the transmission line. Monitoring the alignment during the experiment greatly benefits the confidence in the CTS measurements. An in situ technique for the assessment of the elevation angle alignment of the receiver is developed. Using the CTS diagnostic on TEXTOR without a source of probing radiation in discharges with sawtooth oscillations, an elevation angle misalignment of 0.9 Degree-Sign was found with an accuracy of 0.25 Degree-Sign .

Moseev, D. [FOM DIFFER - Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Nieuwegein (Netherlands); Max-Planck-Institut fuer Plasmaphysik, Euratom Association-IPP, 85748 Garching (Germany); Meo, F.; Korsholm, S. B.; Leipold, F.; Michelsen, P. K.; Nielsen, S. K.; Salewski, M.; Stejner, M. [Association EURATOM - DTU, Department of Physics, Technical University of Denmark, Riso Campus, 4000 Roskilde (Denmark); Bindslev, H. [Faculty of Science and Technology, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Furtula, V. [Chalmers University of Technology, SE-412 96 Gothenburg (Sweden); Kantor, M. [FOM DIFFER - Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Nieuwegein (Netherlands); FZ Juelich GmbH, EURATOM, Trilateral Euregio Cluster, D-52425 Juelich (Germany); Ioffe Institute, RAS, Saint Petersburg 194021 (Russian Federation)

2012-10-15

35

Elevation angle alignment of quasi optical receiver mirrors of collective Thomson scattering diagnostic by sawtooth measurements.  

PubMed

Localized measurements of the fast ion velocity distribution function and the plasma composition measurements are of significant interest for the fusion community. Collective Thomson scattering (CTS) diagnostics allow such measurements with spatial and temporal resolution. Localized measurements require a good alignment of the optical path in the transmission line. Monitoring the alignment during the experiment greatly benefits the confidence in the CTS measurements. An in situ technique for the assessment of the elevation angle alignment of the receiver is developed. Using the CTS diagnostic on TEXTOR without a source of probing radiation in discharges with sawtooth oscillations, an elevation angle misalignment of 0.9° was found with an accuracy of 0.25°. PMID:23126995

Moseev, D; Meo, F; Korsholm, S B; Bindslev, H; Furtula, V; Kantor, M; Leipold, F; Michelsen, P K; Nielsen, S K; Salewski, M; Stejner, M

2012-10-01

36

Rigorous method for compensation selection and alignment of microlithographic optical systems  

SciTech Connect

The assembly of an optical system requires the correction of aberrations in the entire imaging field by making selected rigid-body motions of the optical elements. We present a rigorous method for determining which adjustment motions, called compensators, to use for alignment. These compensators are found by employing techniques from linear algebra that choose the most independent vectors from a set which are interdependent. The method finds the smallest number of compensators to correct for misalignments of a given magnitude. As an example the method is applied to a four-mirror scanning ring-field EUV lithography system. It is shown that out of 32 degrees of freedom in the configuration of the optical elements, only eight compensators are required on the optics. By adjusting these compensators a misaligned configuration giving a 30 {lambda} wavefront error can be assembled to {lambda}/50 in the absence of measurement noise.

Chapman, H.N.; Sweeney, D.W.

1998-03-25

37

Theoferometer for High Accuracy Optical Alignment and Metrology  

NASA Technical Reports Server (NTRS)

The accurate measurement of the orientation of optical parts and systems is a pressing problem for upcoming space missions, such as stellar interferometers, requiring the knowledge and maintenance of positions to the sub-arcsecond level. Theodolites, the devices commonly used to make these measurements, cannot provide the needed level of accuracy. This paper describes the design, construction, and testing of an interferometer system to fill the widening gap between future requirements and current capabilities. A Twyman-Green interferometer mounted on a 2 degree of freedom rotation stage is able to obtain sub-arcsecond, gravity-referenced tilt measurements of a sample alignment cube. Dubbed a 'theoferometer,' this device offers greater ease-of-use, accuracy, and repeatability than conventional methods, making it a suitable 21st-century replacement for the theodolite.

Toland, Ronald; Leviton, Doug; Koterba, Seth

2004-01-01

38

Passive alignment method of polymer PLC devices by using a hot embossing technique  

Microsoft Academic Search

A novel fabrication process using a hot embossing technique has been developed for micromechanical passive alignment of polymer planar lightwave circuit (PLC) devices. With only one step of embossing, single-mode waveguide straight channels and micropedestals for passive aligning are simultaneously defined on a polymer thin film with an accuracy of ±0.5 ?m. This process reduces the steps for fabricating alignment

Jin Tae Kim; Keun Byoung Yoon; Choon-Gi Choi

2004-01-01

39

Neural nets for aligning optical components in harsh environments: Beam smoothing spatial filter as an example  

NASA Technical Reports Server (NTRS)

The goal is to develop an approach to automating the alignment and adjustment of optical measurement, visualization, inspection, and control systems. Classical controls, expert systems, and neural networks are three approaches to automating the alignment of an optical system. Neural networks were chosen for this project and the judgements that led to this decision are presented. Neural networks were used to automate the alignment of the ubiquitous laser-beam-smoothing spatial filter. The results and future plans of the project are presented.

Decker, Arthur J.; Krasowski, Michael J.

1991-01-01

40

Ribbon plastic optical fiber linked optical transmitter and receiver modules featuring a high alignment tolerance.  

PubMed

Ribbon plastic optical fiber (POF) linked four-channel optical transmitter (Tx) and receiver (Rx) modules have been proposed and realized featuring an excellent alignment tolerance. The two modules share a common configuration involving an optical sub-assembly (OSA) with vertical cavity surface emitting lasers (VCSELs)/photodetectors (PDs), and their driver ICs, which are integrated onto a single printed circuit board (PCB) substrate. The OSA includes an alignment structure, a beam router and a fiber guide, which were produced by using plastic injection molding. We have accomplished a fully passive alignment between the VCSELs/PDs and the ribbon POF by taking advantage of the alignment structure that serves as a reference during the alignment of the constituent parts of the OSA. The electrical link, which largely determines the operation speed, has been remarkably shortened, due to a direct wire-bonding between the VCSELs/PDs and the driver circuits. The light sources and the detectors can be individually positioned, thereby overcoming the pitch limitations of the ribbon POF, which is made up of perfluorinated graded-index (GI) POF with a 62.5 ?m core diameter. The overall alignment tolerance was first assessed by observing the optical coupling efficiency in terms of VCSEL/PD misalignment. The horizontal and vertical 3-dB alignment tolerances were about 20 ?m and 150 ?m for the Tx and 50 ?m and over 200 ?m for the Rx, respectively. The VCSEL-to-POF coupling loss for the Tx and the POF-to-PD loss for the Rx were 3.25 dB and 1.35 dB at a wavelength of 850 nm, respectively. Subsequently, a high-speed signal at 3.2 Gb/s was satisfactorily delivered via the Tx and Rx modules over a temperature range of -30 to 70°C with no significant errors; the channel crosstalk was below -30 dB. Finally, the performance of the prepared modules was verified by transmitting a 1080p HDMI video supplied by a Bluelay player to an LCD TV. PMID:21369260

Lee, Hak-Soon; Park, Jun-Young; Cha, Sang-Mo; Lee, Sang-Shin; Hwang, Gyo-Sun; Son, Yung-Sung

2011-02-28

41

The technique of coital alignment and its relation to female orgasmic response and simultaneous orgasm  

Microsoft Academic Search

To enhance male-female sexual compatibility, principles of physical alignment were formulated to make clitoral contact possible in coitus. The Coital Alignment technique combines (a) the “riding high” variation of the “missionary” coital posture, with (b) genitally focused pres-sure-counterpressure stimulus applied in the coordination of sexual movement. It was hypothesized that the Alignment technique would correlate with high frequency of female

Edward W. Eichel; Joanne De Simone Eichel; Sheldon Kule

1988-01-01

42

Comparative analysis of polarimetric signatures of aligned and optically active (“homochiral”) dust particles  

NASA Astrophysics Data System (ADS)

We model light scattering by aligned particles and particles that contain homochiral organics, i.e. organics that possess optical activity (circular birefringence and circular dichroism), to check for a method to distinguish between these particles based on their linear and circular polarization. For aligned particles, we consider alignment in a magnetic field that aligns the particles with the longest particle dimension perpendicular to the magnetic field lines. We model those particles as polydisperse ensembles of prolate and oblate spheroids made of ice, silicate and cosmic organics. We model optically active particles as aggregates of submicron monomers made of chlorophyll, which has optical constants with values similar to those of silicates but possesses distinct optical activity in the visible. The results of the modeling show that alignment and optical activity produce a rather similar shape of phase angle dependences of linear and circular polarization, making it difficult to distinguish between them. However, a difference was found in the exact backscattering and forward scattering directions, where aligned particles have non-zero linear polarization and zero circular polarization whereas optically active particles have non-zero circular polarization and zero linear polarization. We also studied correlations between linear and circular polarization and found that at small phase angles both aligned and optically active particles show correlation between linear and circular polarization. However, at phase angles larger than 100°, linear and circular polarizations correlate for aligned particles and anticorrelate for optically active particles. This difference in correlations may be used to distinguish between two mechanisms of formation of circular polarization. Also, the spectral dependence of circular polarization for these two mechanisms is very different because it is defined by the refractive index for aligned particles and circular dichroism and birefringence for optically active particles. Our results can be helpful in determining the mechanism responsible for formation of circular polarization at scattering of light by dust particles in comets, star-forming regions and circumstellar disks, and by aerosols in atmospheres of exoplanets.

Kolokolova, Ludmilla; Nagdimunov, Lev

2014-10-01

43

Electronic implementation of optical burst switching techniques  

NASA Astrophysics Data System (ADS)

Extensive research effort is ongoing in energy-efficient Internet-based communications. Optical Flow Switching (OFS) and Optical Burst Switching (OBS) offer potentially efficient alternatives to IP-router-based networks for large data transactions, but significant challenges remain. OFS requires each user to install expensive core network technology, limiting application to highly specialized nodes. OBS can achieve higher scalability but burst assembly/disassembly procedures reduce power efficiency. Finally both OFS and OBS use all-optical switching technologies for which energy efficiency and flexibility remain subject to debate. Our study aims at combining the advantages of both OBS and OFS while avoiding their shortcomings. We consider using a two-way resource reservation protocol for periodic concatenations of large (e.g. 1 Mb) packets or Media Frames (MFs). These chains of MFs (MFCs) are semi-transparent with a periodicity referred to as the "transparency degree". Each MFC is assembled and stored at an end-user machine during the resource reservation procedure and is then switched and buffered electronically along its path. The periodic configuration of each MFC enables interleaving of several chains using buffering only to align the MFs in each MFC in time, largely reducing the buffer requirements with respect to OBS. This periodicity also enables a simple scheduling algorithm to schedule large transactions with minimal control plane processing, achieving link utilization approaching 99.9%. In summary, results indicate that implementing optical burst switching techniques in the electronic domain is a compelling path forward to high-throughput power-efficient networking.

Albanese, Ilijc; Darcie, Thomas E.; Ganti, Sudhakar

2013-10-01

44

Enzyme activity assays within microstructured optical fibers enabled by automated alignment  

PubMed Central

A fluorescence-based enzyme activity assay has been demonstrated within a small-core microstructured optical fiber (MOF) for the first time. To achieve this, a reflection-based automated alignment system has been developed, which uses feedback and piezoelectric actuators to maintain optical alignment. The auto-alignment system provides optical stability for the time required to perform an activity assay. The chosen assay is based on the enzyme proprotein convertase 5/6 (PC6) and has important applications in women’s health. PMID:23243579

Warren-Smith, Stephen C.; Nie, Guiying; Schartner, Erik P.; Salamonsen, Lois A.; Monro, Tanya M.

2012-01-01

45

New Adaptive Optics Technique Demonstrated  

NASA Astrophysics Data System (ADS)

First ever Multi-Conjugate Adaptive Optics at the VLT Achieves First Light On the evening of 25 March 2007, the Multi-Conjugate Adaptive Optics Demonstrator (MAD) achieved First Light at the Visitor Focus of Melipal, the third Unit Telescope of the Very Large Telescope (VLT). MAD allowed the scientists to obtain images corrected for the blurring effect of atmospheric turbulence over the full 2x2 arcminute field of view. This world premiere shows the promises of a crucial technology for Extremely Large Telescopes. ESO PR Photo 19a/07 ESO PR Photo 19a/07 The MCAO Demonstrator Telescopes on the ground suffer from the blurring effect induced by atmospheric turbulence. This turbulence causes the stars to twinkle in a way which delights the poets but frustrates the astronomers, since it blurs the fine details of the images. However, with Adaptive Optics (AO) techniques, this major drawback can be overcome so that the telescope produces images that are as sharp as theoretically possible, i.e., approaching space conditions. Adaptive Optics systems work by means of a computer-controlled deformable mirror (DM) that counteracts the image distortion induced by atmospheric turbulence. It is based on real-time optical corrections computed from image data obtained by a 'wavefront sensor' (a special camera) at very high speed, many hundreds of times each second. The concept is not new. Already in 1989, the first Adaptive Optics system ever built for Astronomy (aptly named "COME-ON") was installed on the 3.6-m telescope at the ESO La Silla Observatory, as the early fruit of a highly successful continuing collaboration between ESO and French research institutes (ONERA and Observatoire de Paris). Ten years ago, ESO initiated an Adaptive Optics program to serve the needs for its frontline VLT project. Today, the Paranal Observatory is without any doubt one of the most advanced of its kind with respect to AO with no less than 7 systems currently installed (NACO, SINFONI, CRIRES and four AO systems for the interferometric mode of the VLT). ESO PR Photo 19b/07 ESO PR Photo 19b/07 The Globular Cluster Omega Centauri (MAD/VLT) Present AO systems can only correct the effect of atmospheric turbulence in a relative small region of the sky - typically 15 arcseconds, the correction degrading very quickly when moving away from the central axis. Engineers have therefore developed new techniques to overcome this limitation, one of which is multi-conjugate adaptive optics (MCAO). At the end of 2003, ESO, together with partners in Italy and Portugal, started the development of a MCAO Demonstrator, named MAD. "The aim of MAD is to prove the feasibility and performances of new adaptive optics techniques, such as MCAO, meant to work on large fields of view and to serve as a very powerful test tool in understanding some of the critical issues that will determine the development of future instruments, for both the VLT and the Extremely Large Telescopes," said Norbert Hubin, head of the AO group at ESO. MAD is an advanced generation adaptive optics system, capable of compensating for the atmospheric turbulence disturbance on a large field of view (FoV) on the sky. It can successfully correct a 1-2 arcmin FoV, much larger than the ~15 arcsec typically provided by the existing adaptive optics facilities. MAD was fully developed and extensively characterized by ESO using a dedicated turbulence generator (MAPS, Multi Atmospheric Phase screens and Stars) able to reproduce in the laboratory the temporal evolution and the vertical structure of the turbulence observed at the Observatory. ESO PR Photo 19c/07 ESO PR Photo 19c/07 The MCAO Concept MAD was then disassembled and shipped to Paranal for re-integration at the Nasmyth Visitor focus of UT3. The integration took about 1 month, after which the system was ready for daylight testing and further characterization. "On the night of 25 March, we could successfully close the first MCAO loop on the open cluster NGC 3293," said Enrico Marchetti, the MAD Project Manager. "The system behavio

2007-03-01

46

TOW optical and infrared test and alignment calibration capability  

Microsoft Academic Search

This paper describes the design of test equipment constructed to enable the Marine Corps Logistics Base the capability to provide the required optical\\/IR boresight and electronic tests for rebuild and TOSH (TOW optical sight hardening) modification for the TOW (tube launched, optically tracked, wire guided) guided missile launcher optical\\/infrared sight. Optical modification and calibration are performed to improve system accuracy

Martin Wolk; Edward P. Armstrong; Edward L. Mann

1996-01-01

47

Single actuator alignment control for improved frequency stability of a cavity-based optical frequency reference.  

PubMed

We demonstrate a method of controlling the alignment of a laser beam to a Fabry-Perot resonator through synchronous detection of the misalignment arising from modulating the orientation of a single beam-steering mirror. The horizontal and vertical tilt of the mirror are modulated in quadrature to drive a circular motion of the beam orientation. A corresponding modulation of the intensity of the optical field circulating in the cavity is measured at either the reflected or transmitted port and demodulated synchronously to derive two error signals to indicate the vertical and horizontal misalignment. These signals are fed back to the beam-steering mirror to suppress fluctuations below 30 Hz. This method avoids the complexity of monitoring off-axis cavity modes and is particularly effective in the case where unwanted pointing fluctuations are introduced by one or two elements in the optical setup. We have applied the technique to two Fabry-Perot resonators in use as precision frequency references, delivering a result of 10 dB suppression of alignment fluctuations at 1 Hz and an improvement in frequency stability by up to a factor of 4. PMID:18709070

Dawkins, Samuel T; Luiten, André N

2008-03-20

48

Phase Retrieval Using a Genetic Algorithm on the Systematic Image-Based Optical Alignment Testbed  

NASA Technical Reports Server (NTRS)

NASA s Marshall Space Flight Center s Systematic Image-Based Optical Alignment (SIBOA) Testbed was developed to test phase retrieval algorithms and hardware techniques. Individuals working with the facility developed the idea of implementing phase retrieval by breaking the determination of the tip/tilt of each mirror apart from the piston motion (or translation) of each mirror. Presented in this report is an algorithm that determines the optimal phase correction associated only with the piston motion of the mirrors. A description of the Phase Retrieval problem is first presented. The Systematic Image-Based Optical Alignment (SIBOA) Testbeb is then described. A Discrete Fourier Transform (DFT) is necessary to transfer the incoming wavefront (or estimate of phase error) into the spatial frequency domain to compare it with the image. A method for reducing the DFT to seven scalar/matrix multiplications is presented. A genetic algorithm is then used to search for the phase error. The results of this new algorithm on a test problem are presented.

Taylor, Jaime R.

2003-01-01

49

Wavelength-addressed intra-board optical interconnection by plug-in alignment with a micro hole array  

NASA Astrophysics Data System (ADS)

Intra-board interconnection between optical waveguide channels is suitable for assembling high-speed optoelectronic printed wiring boards (OE-PWB). Here, we propose a novel optical interconnection method combining techniques for both wavelength-based optical waveguide addressing and plug-in optical waveguide alignment with a micro-hole array (MHA). This array was fabricated by the mask transfer method. For waveguide addressing, we used a micro passive wavelength selector (MPWS) module, which is a type of Littrow mount monochromator consisting of an optical diffraction grating, a focusing lens, and the MHA. From the experimental results, we found that the wavelength addressing operation of the MPWS module was effective for intra-board optical interconnection.

Nakama, Kenichi; Tokiwa, Yuu; Mikami, Osamu

2010-09-01

50

Synthesis, optical properties and alignment of poly(9,9-dioctylfuorene) nanofibers.  

PubMed

Poly(9,9-dioctlylfluorene) (PFO) nanofibers were fabricated by solution template wetting of anodic alumina membranes. Nanofibers with controlled thickness of 23 nm and length between 0.8 and 10 ?m, were obtained, regulated by the dimensions of the used template. Nanofibers displayed spectroscopic characteristics associated with the formation of significant percentages of planar and elongated ? phase within the amorphous PFO glassy-phase. Optical polarized microscopy displayed high birefringence resulting from the high degree of internal order induced by ? phase generation within the fibers. The structural intra-chain reorganization associated with formation of ? phase was promoted by the strong geometrical confinement imposed on the material by the porous template during polymer wetting and solvent evaporation. Flow and shear force alignment techniques were used to control the orientation of fabricated PFO nanofibers, yielding to formation of large oriented nanofiber arrays on transparent substrates. PMID:25299850

Iacopino, Daniela; Redmond, Gareth

2014-10-31

51

Synthesis, optical properties and alignment of poly(9,9-dioctylfuorene) nanofibers  

NASA Astrophysics Data System (ADS)

Poly(9,9-dioctlylfluorene) (PFO) nanofibers were fabricated by solution template wetting of anodic alumina membranes. Nanofibers with controlled thickness of 23 nm and length between 0.8 and 10 ?m, were obtained, regulated by the dimensions of the used template. Nanofibers displayed spectroscopic characteristics associated with the formation of significant percentages of planar and elongated ? phase within the amorphous PFO glassy-phase. Optical polarized microscopy displayed high birefringence resulting from the high degree of internal order induced by ? phase generation within the fibers. The structural intra-chain reorganization associated with formation of ? phase was promoted by the strong geometrical confinement imposed on the material by the porous template during polymer wetting and solvent evaporation. Flow and shear force alignment techniques were used to control the orientation of fabricated PFO nanofibers, yielding to formation of large oriented nanofiber arrays on transparent substrates.

Iacopino, Daniela; Redmond, Gareth

2014-10-01

52

Current progress of optical alignment procedure of CLASP's Lyman-alpha polarimetry instrument  

NASA Astrophysics Data System (ADS)

The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a sounding-rocket instrument currently under development at the National Astronomical Observatory of Japan (NAOJ) as a part of an international collaboration. CLASP's optics are composed of a Cassegrain telescope and a spectro-polarimeter which are designed to achieve an unprecedentedly accurate polarization measurement of the Ly-? line at 121.6nm emitted from the solar upper-chromosphere and transition region. CLASP's first flight is scheduled for August 2015. Reaching such accuracy requires a careful alignment of the optical elements to optimize the image quality at 121.6 nm. However Ly-? is absorbed by air and therefore the optics alignment has to be done under vacuum condition which makes any experiment difficult. To bypass this issue, we proposed to align the telescope and the spectrograph separately in visible light. Hence we present our alignment procedure for both telescope and spectro-polarimeter. We will explain details about the telescope preliminary alignment before mirrors coating, which was done in April 2014, present the telescope combined optical performance and compare them to CLASP tolerance. Then we will present details about an experiment designed to confirm our alignment procedure for the CLASP spectro-polarimeter. We will discuss the resulting image quality achieved during this experiment and the lessons learned.

Giono, G.; Ishikawa, R.; Katsukawa, Y.; Bando, T.; Kano, R.; Suematsu, Y.; Narukage, N.; Sakao, Taro; Kobayashi, K.; Auchère, F.

2014-07-01

53

Study on computer-aided alignment method of a three-mirror off-axis aspherical optical system  

Microsoft Academic Search

The precise alignment of multiple element off-axis optical system is a challenging task. In order to increase the alignment process efficiency, computer-aided alignment methods utilizing Zernike polynomial coefficients have been developed. In this paper, the misalignment state of three-mirror off-axis optical system is simulated in CODEV and computer-aided alignment software. The corresponding relationship between the misalignment and Zernike polynomial coefficients

Xi-Ting Zhao; Wen-Chun Jiao; Zhi-Bo Liao; Yun Wang; Jia-Yi Chen

2010-01-01

54

Ultra-high-precision alignment technology for lens manufacturing used for high-end optics  

NASA Astrophysics Data System (ADS)

This article describes the progress in the area of modern centration technology by using digital image processing. This work is motivated by the continuously increasing demand for high-end optics. During the last years the surface lens quality has been continuously improved. Today the image quality is more determined by the manufacturing tolerances for the mechanical interface which is responsible for decenter and tilt of the lenses respectively the subgroups. Some of the aberrations are directly linked to the decenter of the lenses, Coma for example. Hence it is necessary to realize the subgroups with tolerances below lpm. To determine the decenter of a lens an auto collimation telescope is used to image the reflex of the lens surfaces onto a detector, commonly a half covert photodiode. Rotating the lens generates a sinusoidal signal, which is evaluated by a lock-in amplifier to drive two actuators to adjust the alignment chuck. Typical internal reflections caused by stray light for example disturb the current procedure in such a way that it is impossible to get a stable alignment process. Digital image processing allows us to fix these problems with image recognition. We will demonstrate how a modified auto collimation telescope in combination with the developed software algorithms made the manufacturing process more accurate, faster and useable for a broad spectrum of lenses. It has been proofed by some thousand diverse lenses that with these new technique subgroups can be centered within 0.25?m.

Schiffner, Sebastian; Sure, Thomas

2013-09-01

55

Optical manipulation of self-aligned graphene flakes in liquid crystals.  

PubMed

Graphene recently emerged as a new two-dimensional material platform with unique optical, thermal and electronic properties. Single- or few-atom-thick graphene flakes can potentially be utilized to form structured bulk composites that further enrich these properties and enable a broad range of new applications. Here we describe optical manipulation of self-aligned colloidal graphene flakes in thermotropic liquid crystals of nematic and cholesteric types. Three-dimensional rotational and translational manipulation of graphene flakes by means of holographic optical tweezers allows for non-contact spatial patterning of graphene, control of liquid crystal defects, and low-power optical realignment of the liquid crystal director using these flakes. Potential applications include optically- and electrically-controlled reconfigurable liquid crystalline dispersions of spontaneously aligning colloidal graphene flakes and new electro-optic devices with graphene-based interconnected transparent electrodes at surfaces and in the bulk of liquid crystals. PMID:23389026

Twombly, Christopher W; Evans, Julian S; Smalyukh, Ivan I

2013-01-14

56

A novel method for fabrication of a PLC platform for hybrid integration of an optical module by passive alignment  

Microsoft Academic Search

A novel fabrication method and structure of a planar lightwave circuit (PLC) platform for hybrid integration of an optical module by passive alignment technology is presented. Precise formation of V-grooves in the PLC platform can be easily obtained by the proposed process. The passive alignments of optical elements, including optical fiber, are achieved in one-mask. LD modules were implemented by

Soo-Jin Park; Ki-Tae Jeong; Sang-Ho Park; Hee-Kyung Sung

2002-01-01

57

Optical control of ground-state atomic orbital alignment: Cl,,2 P3/2... atoms  

E-print Network

Optical control of ground-state atomic orbital alignment: Cl,,2 P3/2... atoms from HCl,,v=2,J=1-of-flight mass spectrometry. The 35 Cl 2 P3/2 atoms are aligned by two mechanisms: 1 the time-dependent transfer is conserved during the photodissociation and thus contributes to the total 35 Cl 2 P3/2 photofragment atomic

Zare, Richard N.

58

The coital alignment technique and directed masturbation: A comparative study on female orgasm  

Microsoft Academic Search

To evaluate the effectiveness of two sexual therapy techniques, a nonclinical population of 36 married women were randomly assigned with their spouses to either a sexual enrichment workshop with instruction on the coital alignment technique (19 women) or directed masturbation (17 women). Both workshops yielded clinically significant improvements in orgasm consistency during sexual intercourse, orgasm strength, and the overall number

David Farley Hurlbert; Carol Apt

1995-01-01

59

Real-time Optical Alignment and Diagnostic System (ROADS)  

NASA Technical Reports Server (NTRS)

The ultimate and most frequent usage of ROADS will be the alignment of subassemblies (collector and collimator) prior to their installation in a chamber. The system as designed has inherent associated capabilities well applied to acceptance testing of the No. 4 mirror, prediction of in-chamber performance, generation of a catalog of test results and other data, providing data for the plotting of isointensity lines, and other applications which are discussed. The ROADS system will collect, process, display, analyze, and retain data as required for components, partial subassemblies, complete subassemblies, complete modules, and multimodular arrays.

1972-01-01

60

Spatial light modulator-controlled alignment and spinning of birefringent particles optically trapped in an array.  

PubMed

We demonstrate the use of a phase-only liquid-crystal spatial light modulator (SLM) for polarization-controlled rotation and alignment of an array of optically trapped birefringent particles. A collimated beam incident upon a two-dimensional lenslet array yields multiple foci, scaled to produce optical gradient traps with efficient three-dimensional trapping potentials. The state of polarization of each trapping beam is encoded by the SLM, which acts as a matrix of wave plates with computer-controlled phase retardations. Control of the rotation frequency and alignment direction of the particles is achieved by the transfer of tunable photon spin angular momentum. PMID:12962388

Eriksen, René L; Rodrigo, Peter J; Daria, Vincent R; Glückstad, Jesper

2003-09-01

61

Electrical dependencies of optical modulation capabilities in digitally addressed parallel aligned liquid crystal on silicon devices  

NASA Astrophysics Data System (ADS)

Parallel aligned liquid crystal on silicon (PA-LCoS) displays have found wide acceptance in applications requiring phase-only modulation. Among LCoS devices, and PA-LCoS as a specific case, digital addressing has become a very common technology. In principle, modern digital technology provides some benefits with respect to analog addressing such as reduced interpixel cross-talk, lower power consumption and supply voltage, gray level scale repeatability, high programmability, and noise robustness. However, there are also some degradating issues, such as flicker, which may be enhanced. We analyze the characteristics of the digital pulse width modulated voltage signals in relation to their effect on the optical modulation capabilities of LCoS displays. We apply calibration techniques developed in our laboratory, basically the classical linear polarimeter extended to take into account the existence of flicker. Various digital sequence formats are discussed, focusing the analysis on the variations in the magnitude of the applied voltages across the LC layer. From this analysis, we obtain how to amplify the retardance dynamic range and how to enhance linearity in the device without enhancing flicker and without diminishing the number of available quantization levels. Electrical configurations intended for phase-only and intensity modulation regimes, useful in diffractive optics, are given.

Martínez, Francisco Javier; Márquez, Andrés; Gallego, Sergi; Ortuño, Manuel; Francés, Jorge; Beléndez, Augusto; Pascual, Inmaculada

2014-06-01

62

Optical metrology and alignment of the James Webb Space Telescope Integrated Science Instrument Module  

NASA Astrophysics Data System (ADS)

The James Webb Space Telescope (JWST) is an infrared space telescope scheduled for launch in 2013. JWST has a 6.5 meter diameter deployable and segmented primary mirror, a deployable secondary mirror, and a deployable sun-shade. The optical train of JWST consists of the Optical Telescope Element (OTE), and the Integrated Science Instrument Module (ISIM), which contains four science instruments. When the four science instruments are integrated to ISIM at NASA Goddard Space Flight Center, the structure becomes the ISIM Element. The ISIM Element is assembled at ambient cleanroom conditions using theodolite, photogrammetry, and laser tracker metrology, but it operates at cryogenic temperature, and temperature-induced mechanical and alignment changes are measured using photogrammetry. The OTE simulator (OSIM) is a high-fidelity, cryogenic, telescope simulator that features a ~1.5 meter diameter powered mirror. OSIM is used to test the optical performance of the science instruments in the ISIM Element, including focus, pupil shear, and wavefront error. OSIM is aligned to the flight coordinate system in six degrees of freedom via OSIM-internal cryogenic mechanisms and feedback from alignment sensors. We highlight optical metrology methods, introduce the ISIM and the Science Instruments, describe the ambient alignment and test plan, the cryogenic test plan, and verification of optical performance of the ISIM Element in cryo-vacuum environment.

Connelly, Joseph A.; Bos, Brent J.; Davila, Pamela S.; Eichhorn, William L.; Frey, Bradley J.; Hagopian, John G.; Hylan, Jason E.; Marsh, James M.; McGuffey, Douglas B.; McMann, Joseph; Nowak, Maria D.; Ohl, Raymond G., IV; Redman, Kevin W.; Sabatke, Derek; Sampler, Henry P.; Stock, Joseph; Sullivan, Joseph; Wenzel, Gregory W.; Wright, Geraldine A.; Young, Philip

2008-08-01

63

Stitching Techniques Advance Optics Manufacturing  

NASA Technical Reports Server (NTRS)

Because NASA depends on the fabrication and testing of large, high-quality aspheric (nonspherical) optics for applications like the James Webb Space Telescope, it sought an improved method for measuring large aspheres. Through Small Business Innovation Research (SBIR) awards from Goddard Space Flight Center, QED Technologies, of Rochester, New York, upgraded and enhanced its stitching technology for aspheres. QED developed the SSI-A, which earned the company an R&D 100 award, and also developed a breakthrough machine tool called the aspheric stitching interferometer. The equipment is applied to advanced optics in telescopes, microscopes, cameras, medical scopes, binoculars, and photolithography."

2010-01-01

64

Integration, alignment, and verification of optical system assembly for FORMOSAT-5  

NASA Astrophysics Data System (ADS)

FORMOSAT-5 consists of a spacecraft bus and an electro-optical payload. The payload is an f/8 Cassegrain type telescope with 3.6-m effective focal length. The spacecraft has a ground sampling distance of 2-m for panchromatic and 4-m for multispectral bands, with a 24-km swath width. FORMOSAT-5 is the first space program that National Space Organization (NSPO) takes full responsibility for the complete satellite and payload system engineering. The optical system assembly (OSA) has been successfully aligned and is now undergoing final performance verification tests at system level. To help create this unique instrument, NSPO has developed the computer aided alignment method assisted with the mechanical ground support equipment to carry out the assembly, alignment, and verification of the complex systems. This method offers an integrated capability for interferometric alignment and characterization of the large instrument. A detail OSA integration and verification steps, including primary mirror, secondary mirror, corrector lens and baffles alignment are presented. This paper describes the overall capability of this method and uses decomposed Zernike polynomials from the alignment and characterization of the OSA to verify the reduction of the wavefront errors and misalignments. It further demonstrates the successful completion of the instrument and satisfaction with the main system requirements.

Chen, Ching-Wei; Huang, Po-Hsuan; Chen, Chia-Ray; Chan, Chia-Yen; Lien, Chun-Chieh; Huang, Po-Han; Hsu, Ming-Ying; Chang, Shenq-Tsong; Huang, Ting-Ming

2014-09-01

65

Aligning and testing non-null optical system with deflectometry  

NASA Astrophysics Data System (ADS)

We present our analysis methodology for a 20.3 cm prototype optical tracker to determine why instabilities occur below 50 Hz and suggest improvements. The Navy Precision Optical Interferometer makes use of six small optical telescope stations spaced along a Y-array to synthesize an equivalent single larger telescope. Piezoelectric-driven optical trackers steer 12.5 cm output beams from each station to an optics laboratory up to 700 m distant. A percentage of this starlight is split off and used in a closed-loop feedback to update the pointing of the telescope and steering of the tracker. Steering stabilizes atmospheric induced beam trajectory deviations, required for fringe generation. Because of closedloop feedback, we require all fundamental frequencies to be at least 3 times the desired operational frequency, or 150 Hz. These trackers are modified commercial aluminum gimbal mounts with flex-pivot axles and very small damping ratio. Steering is tip/tilt mirror rotation by push-only actuators and a return spring. It is critical contact be maintained between actuator, mirror mount and return spring. From our dynamic analysis, the 122 N return spring is 2.9 times that required, and has a natural frequency equal to 238 Hz. The range of steering, 140 microradian, is double that required and the 0.077 microradian precision is 2.6 times that required. The natural frequency of the tracker is 66 Hz and the tuned closed-loop operational frequency is only 22 Hz. We conclude the low fundamental frequency of the mount limits its performance below 50 Hz and stiffening the structure is required.

Zhao, Weirui; Huang, Run; Su, Peng; Burge, James H.

2014-09-01

66

Real-time optical associative retrieval technique  

NASA Technical Reports Server (NTRS)

A real-time optical associative retrieval technique is presented. The associative retrieval model enables a large amount of data to be stored and recalled by partial information optically in real time. The real-time capability is achieved by using an electronically addressed spatial light modulator based on the pocket-size liquid crystal display television. The potential application of the technique to the perceptive vision requirements in telerobotics for achieving NASA's goals of automation in space is described.

Liu, H.-K.; Kung, S. Y.; Davis, J. A.

1986-01-01

67

Magneto-optical spectroscopy of highly aligned carbon nanotubes: Identifying the role of threading magnetic flux  

E-print Network

of 1D magnetoexcitonic bands14,15 based on the Aharonov- Bohm effect.16,21­23 PL measurements were bands with Aharonov-Bohm-phase-dependent energies, masses, and oscillator strengths, successfullyMagneto-optical spectroscopy of highly aligned carbon nanotubes: Identifying the role of threading

Kono, Junichiro

68

Optical Alignment And Testing Of The Diffuse Ir Background Experiment IR Cryogenic Telescope  

NASA Astrophysics Data System (ADS)

Optical alignment methods have been developed for thermal, vibration and assembly testing of the Diffuse Infrared Background Experiment ( DIRBE ) telescope. Much of the data was aquired Using videotape of CCTV images. Vibration and performance testing of the 32 hz tuning-fork chopper was carried out using strobe videography.

Wood, H. John

1988-04-01

69

Optical multiple object tracking techniques  

NASA Technical Reports Server (NTRS)

Two multichannel multiple-object tracking techniques are reviewed. In the diffraction grating technique, the input scene is picked up by a TV camera and imaged onto a liquid-crystal light valve (LCLV), and the output side of the light valve is illuminated with a suitably polarized and collimated coherent laser beam to yield a reflected beam with polarization modulated according to the intensity of the incoherent input. This reflected beam passes through a beam splitter cube and an analyzer, resulting in an intensity modulated coherent image. An array of spectrum islands containing the information of the input appears after crossing a contact screen/lens combination. In the multiple-focus hololens technique, the scene of moving objects is sent into the LCTVSLM through a camera; a collimated laser beam is incident upon the LCTV screen; a low-pass filter is inserted between the LCTVSLM and the hololens for the removal of the high order diffractions due to the grid structure of the LCTV. The feasibility of the LCTVSLM and multiple-focus hololens technique is demonstrated.

Liu, Hua-Kuang; Chao, Tien-Hsin

1989-01-01

70

Enzyme-etching technique to fabricate micropatterns of aligned collagen fibrils  

PubMed Central

A technique to tailor-make pre-coated, pre-aligned bovine collagen fibrils, derived from neonatal cardiomyocytes, on the surface of a glass slide into a designated pattern is reported. The unwanted collagen-coated area was erased by a collagenase solution and the tailored area was retained by attaching a microfabricated polydimethylsiloxane stamp directly to the collagen-coated surface. Using this technique, collagen patterns with designated orientations and with clear pattern boundaries and defined shapes were fabricated. PMID:24562408

Liu, Honghai; Chen, Ruikai; Yang, Huaxiao; Qin, Wan; Borg, Thomas K.; Dean, Delphine; Xu, Meifeng; Gao, Bruce Z.

2014-01-01

71

Alignment and Integration Techniques for Mirror Segment Pairs on the Constellation X Telescope  

NASA Technical Reports Server (NTRS)

We present the concepts behind current alignment and integration techniques for testing a Constellation-X primary-secondary mirror segment pair in an x-ray beam line test. We examine the effects of a passive mount on thin glass x-ray mirror segments, and the issues of mount shape and environment on alignment. We also investigate how bonding and transfer to a permanent housing affects the quality of the final image, comparing predicted results to a full x-ray test on a primary secondary pair.

Hadjimichael, Theo; Lehan, John; Olsen, Larry; Owens, Scott; Saha, Timo; Wallace, Tom; Zhang, Will

2007-01-01

72

Ultralong quantum optical data storage using an optical locking technique  

NASA Astrophysics Data System (ADS)

Several types of quantum memory protocols have been presented over the last ten years, including photon echoes, off-resonant Raman scattering, ultraslow light-based quantum mapping processes and resonant Raman optical echoes. These quantum optical memory protocols are limited by a storage time on a scale as short as milliseconds, determined by the spin phase decay time of the storage medium. For applications of long-distance quantum communications, a quantum repeater composed of quantum entanglement swapping and quantum memory must be used. Achieving longer storage times in quantum memory therefore brings a definite advantage to applications of quantum repeaters for long-distance quantum communications. Here, we propose a quantum optical data storage protocol to extend the storage time by several orders of magnitude beyond the conventional limitation of the order of milliseconds. The present ultralong quantum optical storage technique is achieved by introducing an optical locking method to the resonant Raman optical echo protocol.

Ham, Byoung S.

2009-09-01

73

Introduction to high-resolution accelerator alignment using x-ray optics.  

SciTech Connect

A novel alignment technique utilizing the x-ray beam of a dedicated alignment undulator in conjunction with pinholes and position-sensitive detectors for positioning accelerator components in an x-ray free-electron laser will be presented. In this concept two retractable pinholes at each end of the main undulator line define a stable and reproducible x-ray beam axis (XBA). Targets are precisely positioned on the XBA using a pinhole camera technique. Position-sensitive detectors responding to both x-ray and electron beams enable the direct transfer of the position setting from the XBA to the electron beam. This system has the potential to deliver superior alignment accuracy in the micron range for target pinholes in the transverse directions over long distances. It defines the beam axis for the electron-beam-based alignment with high reproducibility. This concept complements the electron-beam-based alignment and the existing survey methods advancing the alignment accuracy of long accelerators to an unprecedented level. Further improvements of the transverse accuracy using x-ray zone plates and a concurrent measurement scheme during accelerator operation, providing real-time feedback for transverse position corrections, will be discussed.

Yang, B. X.; Friedsam, H.

2006-01-01

74

Alignment and integration of thin, lightweight x-ray optics into modules  

NASA Astrophysics Data System (ADS)

Future X-ray telescopes with high angular resolution and high throughput optics will help enable new high energy observations. X-ray optics in development at NASA Goddard Space Flight Center by the Next Generation X-ray Optics (NGXO) group utilizes a Flight Mirror Assembly (FMA) comprised of dozens of mirror modules populated with mirror segments aligned to a common focus. Mirror segments are currently aligned and permanently fixed into a module one at a time with emphasis on preventing degradation of the overall module performance. To meet cost and schedule requirements, parallelization and automation of the module integration process must be implemented. Identification of critical mirror segment alignment factors in addition to the progress towards a robust and automated module integration process is presented. There is a fundamental need for a reliable mirror segment alignment and bonding process that will be performed on hundreds or thousands of mirror segments. Results from module X-ray performance verification tests are presented to confirm module performance meets requirements.

Biskach, Michael P.; Chan, Kai-Wing; Mazzarella, James R.; McClelland, Ryan S.; Saha, Timo T.; Schofield, Mark J.; Zhang, William W.

2014-07-01

75

Techniques for Solution- Assisted Optical Contacting  

NASA Technical Reports Server (NTRS)

A document discusses a solution-assisted contacting technique for optical contacting. An optic of surface flatness Lambda/20 was successfully contacted with one of moderate surface quality, or Lambda/4. Optics used were both ultra-low expansion (ULE) glass (Lambda/4 and Lambda/20) and fused silica (Lambda/20). A stainless steel template of the intended interferometer layout was designed and constructed with three contact points per optic. The contact points were all on a common side of the template. The entire contacting jig was tilted at about 30 . Thus, when the isopropanol was applied, each optic slid due to gravity, resting on the contact points. All of the contacting was performed in a relatively dusty laboratory. A number of successful contacts were achieved where up to two or three visible pieces of dust could be seen. These were clearly visible due to refraction patterns between the optic and bench. On a number of optics, the final step of dropping isopropyl between the surfaces was repeated until a successful contact was achieved. The new procedures realized in this work represent a simplification for optical contacting in the laboratory. They will both save time and money spent during the contacting process, and research and development phases. The techniques outlined are suitable for laboratory experiments, research, and initial development stages.

DeVine, Glenn; Ware, Brent; Wuchenich, Danielle M.; Spero, Robert E.; Klipstein, William M.; McKenzie, Kirk

2012-01-01

76

Applying Harmonic Optical Microscopy for Spatial Alignment of Atrial Collagen Fibers  

PubMed Central

Background Atrial fibrosis creates a vulnerable tissue for atrial fibrillation (AF), but the spatial disarray of collagen fibers underlying atrial fibrosis is not fully elucidated. Objective This study hypothesizes that harmonics optical microscopy can illuminate the spatial mal-alignment of collagen fibers in AF via a layer-by-layer approach. Patients and Methods Atrial tissues taken from patients who underwent open-heart surgery were examined by harmonics optical microscopy. Using the two-dimensional Fourier transformation method, a spectral-energy description of image texture was constituted and its entropy was used to quantify the mal-alignment of collagen fibers. The amount of collagen fiber was derived from its area ratio to total atrial tissue in each image. Serum C-terminal pro-collagen pro-peptide (CICP), pro-matrix metalloproteinase-1 (pro-MMP-1), and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) were also evaluated. Results 46 patients were evaluated, including 20 with normal sinus rhythm and 26 with AF. The entropy of spectral-energy distribution of collagen alignment was significantly higher in AF than that in sinus rhythm (3.97±0.33 vs. 2.80±0.18, p<0.005). This difference was more significant in the permanent AF group. The amount of collagen was also significantly higher in AF patients (0.39±0.13 vs. 0.18±0.06, p<0.005) but serum markers of cardiac fibrosis were not significantly different between the two groups. Conclusions Harmonics optical microscopy can quantify the spatial mal-alignment of collagen fibers in AF. The entropy of spectral-energy distribution of collagen alignment is a potential tool for research in atrial remodeling. PMID:21085489

Tsai, Ming-Rung; Chang, Yi-Chung; Hsu, Rong-Bin; Yu, Hsu-Yu; Sun, Chi-Kuang; Ho, Yi-Lwun

2010-01-01

77

Advanced optical storage techniques for computers.  

PubMed

The growing demand for data storage in computing systems has stimulated the investigation of optical memory techniques because they offer a potential improvement in packing density of about two orders of magnitude over the apparent limits of conventional magnetic storage techniques. Physical properties and optical memory characteristics of magnetooptic thin-films of manganese bismuth have been investigated with regard to both bit-oriented and holographic memories. All the required technology for design of a bit-oriented memory appears to be available, but several key components required for a holographic memory still remain to be developed. PMID:20119301

Aagard, R L; Lee, T C; Chen, D

1972-10-01

78

Mounting and Alignment of Full-Shell Replicated X-Ray Optics  

NASA Technical Reports Server (NTRS)

We are developing grazing-incidence x-ray optics for astronomy. The optics are full-cylinder mirror shells fabricated using electroformed-nickel replication off super-polished mandrels. For space-based applications where weight is at a premium, very-thin-walled, light-weight mirrors are required. Such shells have been fabricated at MSFC with greater than 15 arcsec resolution. The challenge, however, is to preserve this resolution during mounting and assembly. We present here a status report on a mounting and alignment system currently under development at Marshall Space Flight Center to meet this challenge.

Gubarev, Mikhail; Arnold, William; Kester, Thomas; Ramsey, Brian; Smithers, Martin

2007-01-01

79

Dental diagnostics using optical coherence techniques  

SciTech Connect

Optical radiation can be used for diagnostic purposes in oral medicine. However, due to the turbid, amorphous, and inhomogeneous nature of dental tissue conventional techniques used to transilluminate materials are not well suited to dental tissues. Optical coherence techniques either in the time- of frequency-domain offer the capabilities of discriminating scattered from unscattered light, thus allowing for imaging through turbid tissue. Currently, using optical time-domain reflectometry we are able to discriminate specular from diffuse reflections occurring at tissue boundaries. We have determined the specular reflectivity of enamel and dentin to be approximately 6.6 x 10{sup -5} and 1.3 x 10{sup -6}, respectively. Implications to periodontal imaging will be discussed.

Nathel, H. [Lawrence Livermore National Lab., CA (United States); Colston, B. [Univ. of California, San Francisco, CA (United States); Armitage, G. [Univ. of California, Davis, CA (United States)] [and others

1994-11-15

80

Optical pupil relay design for SILEX - Optimising wavefront error and transmit/receive beams co-alignment  

NASA Astrophysics Data System (ADS)

This paper describes some of the key parameters that have been considered for the European Satellite Interorbital Link EXperiment (SILEX) optical relay lens design. Particular attention has been given to the specific requirement of transmit/receive beams co-alignment. The method of evaluating co-alignment errors is described and the effect of manufacturing tolerances and environmental long term stability on the co-alignment error investigated.

Jonas, Reginald P.

1992-06-01

81

Optical Measurement Technique for Space Column Characterization  

NASA Technical Reports Server (NTRS)

A simple optical technique for the structural characterization of lightweight space columns is presented. The technique is useful for determining the coefficient of thermal expansion during cool down as well as the induced strain during tension and compression testing. The technique is based upon object-to-image plane scaling and does not require any photogrammetric calibrations or computations. Examples of the measurement of the coefficient of thermal expansion are presented for several lightweight space columns. Examples of strain measured during tension and compression testing are presented along with comparisons to results obtained with Linear Variable Differential Transformer (LVDT) position transducers.

Barrows, Danny A.; Watson, Judith J.; Burner, Alpheus W.; Phelps, James E.

2004-01-01

82

Nonlinear optical studies of liquid crystal alignment on a rubbed polyvinyl alcohol surface Xing Wei, Seok-Cheol Hong, Xiaowei Zhuang,* Tomohisa Goto,  

E-print Network

Nonlinear optical studies of liquid crystal alignment on a rubbed polyvinyl alcohol surface Xing at the surface appear to be well aligned by rubbing, and the adsorbed liquid crystal molecules are aligned of the polymer chains and the liquid crystal molecules, indicating that the surface-induced bulk alignment

Zhuang, Xiaowei

83

The KMOS Integral Field System: fabrication, alignment, and test of 1000+ optical surfaces  

NASA Astrophysics Data System (ADS)

The Centre for Advanced Instrumentation (CfAI) of Durham University (UK) has recently successfully completed the development of 24 Integral Field Units (IFUs) for the K-band Multi-Object Spectrometer (KMOS). KMOS is a second generation instrument for ESO’s Very Large Telescope (VLT) which is due for delivery during the summer of 2012. The KMOS IFU is based on the Advanced Image Slicer Concept developed by the CfAI and previously successfully implemented on the Gemini Near-InfraRed Spectrograph and JWST NIRSpec. Each IFU contains 14 channels which have to be accurately aligned. In addition, all 24 IFUs have to be co-aligned requiring the accurate alignment of an unprecedented grand total of 1152 optical surfaces. In this paper we describe how this has been achieved through the use of complex monolithic multi-faceted metal mirror arrays, which were fabricated in-house by means of freeform diamond machining. We will summarise the results from the metrology performed on each of the optical components and describe how these were integrated and aligned into the system. We will also summarise the results from the system level acceptance tests, which demonstrate the excellent performance of the IFUs. Each of the 24 IFUs is essentially diffraction limited across the entire field (Strehl ratios ~ 0.8) with throughput predictions (based on measurements of the surface roughness) rising from 86% at a wavelength of 1 micron to 93% at 2.5 micron. We believe that this level of performance has not previously been achieved in any image slicing IFU and showcases the potential of the current state-of-the-art technology.

Dubbeldam, Cornelis M.; Clark, Paul; Content, Robert; Kirby, Andrew K.; Parkin, Ken; Robertson, David J.; Rolt, Stephen; Ryder, David A.; Sharples, Ray M.

2012-09-01

84

Simple fabrication of a double-layer multi-channel optical waveguide using passive alignment.  

PubMed

This study proposes a simple and cost-effective method of fabricating a double-layer polymeric optical waveguide, using two hot-embossing processes with a single stamp and template for passive alignment between the top and bottom layers. The two hot-embossing processes were conducted sequentially on the top layer and the bottom layer of the polymer layer. The second hot-embossing process was conducted after fabricating the buffer layer on the surface of the polymeric channel structure to control deformation and destruction of the previously fabricated polymeric channel structure. Passive alignment of the channel structure for the top layer and the bottom layer was automatically performed by simple insertion of the stamp and polymer layer using a metal template with the same dimensions (width x length) as the stamp. Regarding the polymer layer, the buffer layer on the side with the channel structure was coated, whereas the layer contacting the stamp did not have a buffer layer. For the purposes of this study, a 2 x 50 channel polymeric multimode optical waveguide was fabricated using a stamp with 50 straight ribs, without any coupling between the layers. The fabricated optical waveguide was controlled within positional tolerances of less than ± 5 ?m between layers; propagation loss of below 0.2 dB/cm at 850 nm; and channel uniformity of below 0.5 dB. PMID:21263659

Ryu, Jin Hwa; Lee, Tea Ho; Cho, In-Kui; Kim, Chang-Seok; Jeong, Myung Yung

2011-01-17

85

TiO2 nanowire dispersions in viscous polymer matrix: electrophoretic alignment and optical properties  

NASA Astrophysics Data System (ADS)

The changes in optical properties during TiO2 nanowire orientation in polydimethylsiloxane (PDMS) matrix under the influence of an electric field are strongly influenced by nanowire (NW) diameter. It was demonstrated for the first time that either positive or negative change in transmittance can be induced by NW alignment parallel to the electric field depending on the NW diameter. These effects can be explained by the interplay between scattering and reflectance. Experimental findings reported could be important for smart window applications for the regulation of visible or even infrared transparency, thus reducing the energy consumption by air conditioning systems in buildings and automobiles in the future.

Šutka, Andris; Saal, Kristjan; Kisand, Vambola; Lõhmus, Rünno; Joost, Urmas; Timusk, Martin

2014-10-01

86

TiO2 nanowire dispersions in viscous polymer matrix: electrophoretic alignment and optical properties.  

PubMed

The changes in optical properties during TiO2 nanowire orientation in polydimethylsiloxane (PDMS) matrix under the influence of an electric field are strongly influenced by nanowire (NW) diameter. It was demonstrated for the first time that either positive or negative change in transmittance can be induced by NW alignment parallel to the electric field depending on the NW diameter. These effects can be explained by the interplay between scattering and reflectance. Experimental findings reported could be important for smart window applications for the regulation of visible or even infrared transparency, thus reducing the energy consumption by air conditioning systems in buildings and automobiles in the future. PMID:25249192

Sutka, Andris; Saal, Kristjan; Kisand, Vambola; Lõhmus, Rünno; Joost, Urmas; Timusk, Martin

2014-10-17

87

Self-assembled coronene nanofibers: optical waveguide effect and magnetic alignment  

NASA Astrophysics Data System (ADS)

To fabricate organic nanofibers that function as active optical waveguides with semiconductor properties, a facile procedure was developed to grow single crystalline nanofibers via ?-? stacking of the polycyclic aromatic molecule, coronene, through solution evaporation on a substrate. The fabricated nanofibers with millimeter-scale lengths have well-defined shapes, smooth surfaces, and low-defect structures. The nanofibers are demonstrated to function as efficient active waveguides that propagate their fluorescence (FL) along the fiber axis over their entire length. We further demonstrate that the nanofibers can be highly aligned on the substrate when solution evaporation is conducted in a magnetic field of 12 T. The mechanism of the magnetic alignment can be elucidated by considering the anisotropy of the diamagnetic susceptibility of a single coronene molecule and the crystal structure of a nanofiber. Owing to the high degree of alignment, the nanofibers rarely cross each other, allowing for measurement of the waveguiding properties of single isolated nanofibers. The nanofibers propagate their FL of ? > 500 nm with a low propagation loss of 0-3 dB per 100 ?m, indicating that the nanofibers function as sub-wavelength scale, low-loss waveguides. Thus, they are promising building blocks for miniaturized optoelectronic circuits.

Takazawa, Ken; Inoue, Jun-Ichi; Mitsuishi, Kazutaka

2014-03-01

88

Self-assembled coronene nanofibers: optical waveguide effect and magnetic alignment.  

PubMed

To fabricate organic nanofibers that function as active optical waveguides with semiconductor properties, a facile procedure was developed to grow single crystalline nanofibers via ?-? stacking of the polycyclic aromatic molecule, coronene, through solution evaporation on a substrate. The fabricated nanofibers with millimeter-scale lengths have well-defined shapes, smooth surfaces, and low-defect structures. The nanofibers are demonstrated to function as efficient active waveguides that propagate their fluorescence (FL) along the fiber axis over their entire length. We further demonstrate that the nanofibers can be highly aligned on the substrate when solution evaporation is conducted in a magnetic field of 12 T. The mechanism of the magnetic alignment can be elucidated by considering the anisotropy of the diamagnetic susceptibility of a single coronene molecule and the crystal structure of a nanofiber. Owing to the high degree of alignment, the nanofibers rarely cross each other, allowing for measurement of the waveguiding properties of single isolated nanofibers. The nanofibers propagate their FL of ? > 500 nm with a low propagation loss of 0-3 dB per 100 ?m, indicating that the nanofibers function as sub-wavelength scale, low-loss waveguides. Thus, they are promising building blocks for miniaturized optoelectronic circuits. PMID:24608753

Takazawa, Ken; Inoue, Jun-ichi; Mitsuishi, Kazutaka

2014-04-21

89

Optical replication techniques for image slicers  

E-print Network

The Smart Focal Planes (SmartFP) activity is a European Joint Research Activity funded to develop novel optical technologies for future large telescope instrumentation. In this paper, we will discuss the image slicer developments being carried out as part of this initiative. Image slicing technique s have many applications in the plans for instrumentation on Extremely Large Telescopes and will be central to the delivery of the science case. A study of a virtual "multi-object multi-ifu spectrograph and imager" (MOMSI) for a hypothetical OWL-class telescope reveals the need for focal plane splitting, deployable imagers and very small beam steering elements like deployable IFUs. The image slicer workpackage, lead from Durham University in collaboration with LFM Bremen, TNO Delft, UKATC Edinburgh, CRAL Lyon, LAM Marseille, Padua University and REFLEX Prague, is evaluating technologies for manufacturing micro optics in large numbers to enable multi-object integral field spectroscopy.

J. Schmoll; D. J. Robertson; C. M. Dubbeldam; J. Yao; F. Bortoletto; L. Pina; R. Hudec; E. Prieto; C. Norrie; S. Ramsay-Howat; W. Preuss

2005-09-22

90

Optical replication techniques for image slicers  

E-print Network

The Smart Focal Planes (SmartFP) activity is a European Joint Research Activity funded to develop novel optical technologies for future large telescope instrumentation. In this paper, we will discuss the image slicer developments being carried out as part of this initiative. Image slicing technique s have many applications in the plans for instrumentation on Extremely Large Telescopes and will be central to the delivery of the science case. A study of a virtual "multi-object multi-ifu spectrograph and imager" (MOMSI) for a hypothetical OWL-class telescope reveals the need for focal plane splitting, deployable imagers and very small beam steering elements like deployable IFUs. The image slicer workpackage, lead from Durham University in collaboration with LFM Bremen, TNO Delft, UKATC Edinburgh, CRAL Lyon, LAM Marseille, Padua University and REFLEX Prague, is evaluating technologies for manufacturing micro optics in large numbers to enable multi-object integral field spectroscopy.

Schmoll, J; Dubbeldam, C M; Bortoletto, F; Pina, L; Hudec, R; Prieto, E; Norrie, C; Ramsay-Howat, S

2005-01-01

91

New short-time alignment technique for 70-meter antenna surface panels  

NASA Technical Reports Server (NTRS)

With severely limited field modification time for upgrading the 64-m antenna to 70-m diameter, a new shorter time method for aligning the surface panels of the main reflector was needed. For each target on the surface panel, both distance (or range) and elevation angle measurements are made. A new technique for setting the surface panels at zenith look has been devised. This article describes the software required to convert the computed target distortions obtained from the JPL-IDEAS structural analysis computer program (defining the gravity load change from a 45-deg elevation angle to zenith look) into the theodolite reading at zenith look. The technique results in a perfectly shaped reflector at the 45-deg rigging elevation, with acceptable surface error tolerance.

Katow, M. S.

1986-01-01

92

Neural-network-directed alignment of optical systems using the laser-beam spatial filter as an example  

NASA Technical Reports Server (NTRS)

This report describes an effort at NASA Lewis Research Center to use artificial neural networks to automate the alignment and control of optical measurement systems. Specifically, it addresses the use of commercially available neural network software and hardware to direct alignments of the common laser-beam-smoothing spatial filter. The report presents a general approach for designing alignment records and combining these into training sets to teach optical alignment functions to neural networks and discusses the use of these training sets to train several types of neural networks. Neural network configurations used include the adaptive resonance network, the back-propagation-trained network, and the counter-propagation network. This work shows that neural networks can be used to produce robust sequencers. These sequencers can learn by example to execute the step-by-step procedures of optical alignment and also can learn adaptively to correct for environmentally induced misalignment. The long-range objective is to use neural networks to automate the alignment and operation of optical measurement systems in remote, harsh, or dangerous aerospace environments. This work also shows that when neural networks are trained by a human operator, training sets should be recorded, training should be executed, and testing should be done in a manner that does not depend on intellectual judgments of the human operator.

Decker, Arthur J.; Krasowski, Michael J.; Weiland, Kenneth E.

1993-01-01

93

Modulated alignment dual-axis (MAD) confocal microscopy for deep optical sectioning in tissues  

NASA Astrophysics Data System (ADS)

A strategy is presented to enable optical-sectioning microscopy with improved contrast and imaging depth using low-power (0.5 mW) diode laser illumination. While the DAC architecture's intersecting illumination and collection beams significantly improves the spatial-filtering and opticalsectioning performance of confocal microscopy, we propose that modulating the spatial alignment of the dual-axis beams at a frequency f, such the focal volume signal of the microscope is modulated at 2f, further provides nearly an order-of-magnitude improvement in optical-sectioning contrast. Lock-in detection is used to remove the unmodulated background light, thereby enhancing our ability to image deeply within highly scattering tissues.

Leigh, Steven Y.; Chen, Ye; Liu, Jonathan T. C.

2014-05-01

94

Optical multichannel analyzer techniques for high resolution optical spectroscopy  

SciTech Connect

The development of optical multichannel analyzer techniques for UV/VIS spectroscopy is presented. The research focuses on the development of spectroscopic techniques for measuring high resolution spectral lineshape functions from the exciton phosphorescence in H/sub 2/-1,2,4,5-tetrachlorobenzene. It is found that the temperature dependent frequency shifts and widths confirm a theoretical model based on an exchange theory. The exchange of low energy phonon modes which couple with excited state exciton transitions is shown to display the proper temperature dependent behavior. In addition to the techniques for using the optical multichannel analyzer (OMA) to perform low light level target integration, the use of the OMA for capturing spectral information in transient pulsed laser applications is discussed. An OMP data acquisition system developed for real-time signal processng is described. Both hardware and software interfacing considerations for control and data acquisition by a microcomputer are described. The OMA detector is described in terms of the principles behind its photoelectron detection capabilities and its design is compared with other optoelectronic devices.

Chao, J.L.

1980-06-01

95

Optical stimulation of the prostate nerves: A potential diagnostic technique  

NASA Astrophysics Data System (ADS)

There is wide variability in sexual potency rates (9--86%) after nerve-sparing prostate cancer surgery due to limited knowledge of the location of the cavernous nerves (CN's) on the prostate surface, which are responsible for erectile function. Thus, preservation of the CN's is critical in preserving a man's ability to have spontaneous erections following surgery. Nerve-mapping devices, utilizing conventional Electrical Nerve Stimulation (ENS) techniques, have been used as intra-operative diagnostic tools to assist in preservation of the CN. However, these technologies have proven inconsistent and unreliable in identifying the CN's due to the need for physical contact, the lack of spatial selectivity, and the presence of electrical artifacts in measurements. Optical Nerve Stimulation (ONS), using pulsed infrared laser radiation, is studied as an alternative to ENS. The objective of this study is sevenfold: (1) to develop a laparoscopic laser probe for ONS of the CN's in a rat model, in vivo; (2) to demonstrate faster ONS using continuous-wave infrared laser radiation; (3) to describe and characterize the mechanism of successful ONS using alternative laser wavelengths; (4) to test a compact, inexpensive all-single-mode fiber configuration for optical stimulation of the rat CN studies; (5) to implement fiber optic beam shaping methods for comparison of Gaussian and flat-top spatial beam profiles during ONS; (6) to demonstrate successful ONS of CN's through a thin layer of fascia placed over the nerve and prostate gland; and (7) to verify the experimentally determined therapeutic window for safe and reliable ONS without thermal damage to the CN's by comparison with a computational model for thermal damage. A 5.5-Watt Thulium fiber laser operated at 1870 nm and two pigtailed, single mode, near-IR diode lasers (150-mW, 1455-nm laser and 500-mW, 1550-nm laser) were used for non-contact stimulation of the rat CN's. Successful laser stimulation, as measured by an intracavernous pressure (ICP) response in the penis, was achieved with the laser operating in CW mode. CW optical nerve stimulation provides a significantly faster ICP response time using a lower laser power laser than conventional pulsed stimulation. An all-single-mode fiber design was successfully tested in a rat model. The CN reached a threshold temperature of ˜ 42 °C, with response times as short as 3 s, and ICP responses in the rat penis of up to 50 mmHg compared to a baseline of 5--10 mmHg. Chemical etching of the distal single-mode-fiber tip produced a concave shape and transformed the Gaussian to a flat-top spatial beam profile, resulting in simplified alignment of the laser beam with the nerve. This novel, all-single-mode-fiber laser nerve stimulation system introduces several advantages including: (1) a less expensive and more compact ONS configuration; (2) elimination of alignment and cleaning bulk optical components; and (3) improved spatial beam profile for simplified alignment. For the fascia layers over the CN's (240--600 microm), the 1550 nm laser with an optical penetration depth of ˜ 930 microm in water was substituted for the 1455 nm laser. Successful ONS was achieved, for the first time, in fascia layers up to 450 microm thick which is critical for future clinical translation of this method for intra-operative identification and preservation of CN's during prostate cancer surgery. In order to define the upper limit of the therapeutic window for ONS of CN in a rat model, in vivo, identification of the thermal damage threshold for the CN after laser irradiation was investigated by direct comparison of the visible thermal damage data with a theoretical thermal damage calculation utilizing a standard Arrhenius integral model.

Tozburun, Serhat

96

Core Alignment of Butt Coupling Between Single-Mode and Multimode Optical Fibers by Monitoring Brillouin Scattering Signal  

Microsoft Academic Search

We propose a new method to optimize the core alignment of the butt coupling between a single-mode optical fiber (SMF) and a graded-index multimode optical fiber (GI-MMF) by monitoring the spectrum of Brillouin scattered light. This method is stable, free from costly or elaborate equipments, applicable to the coupling of optical fibers with different core diameters or materials, and available

Yosuke Mizuno; Kentaro Nakamura

2011-01-01

97

Passive Optically Encoded Transponder (POET) An Acquisition And Alignment Target For Autonomous Robotics  

NASA Astrophysics Data System (ADS)

Relative position information concerning an object that is to be acquired, attached to, or manipulated in some way by a robotic system is usually supplied by a known database or through vision information of some kind. Vision systems normally require some degree of intelligence to produce complete position information and therefore are relatively sophisticated, slow, or both. Simple "targets" require some amount of pattern recognition in autonomous operations and do not usually lend themselves to precision applications. This paper describes work on a discrete optical element prototype target which when interrogated by a video camera system, will provide noncontact relative position information about all 6 degrees-of-freedom (DOF). This information is available within the active field of view (FOV) of the transponder and could be processed by microprocessor-based, software algorithms with simple pattern recognition capabilities. The interrogation system (camera) is composed of a standard charge injection device (CID) array video camera, a controllable macrozoom lens, a liquid crystal shutter (LCS), and a point-source multispectral illuminator. This allows the transponder to be used where a standard video camera vision system is needed, or already implemented, and results in a relatively fast system (approximately 10 Hz). A passive optically encoded transponder (POET) implemented in a "stick-on" holographic optical element (HOE) is proposed as a next generation target, to supply relative position information in all 6 DOF for acquisition and precision alignment. In applications requiring maximum bandwidth and resolution, the fact that no "pattern recognition" is required in the proposed system results in the ability to interrogate the transponder in real time with a dedicated nonvision, interrogation system, resulting in a multiorder of magnitude increase in speed. The transponder (target) is configured to provide optimum information for the intended use. Being configurable, it can provide an acquisition signal and alignment information within a wide, operational field of view. The fact that this transponder is a simple, straightforward optical design opens the possibility to implement it in a lightweight, small, economical, "stick-on" holographic alignment target to be used in many industrial and space robotic applications where a classical, standard device is needed.

White, G. K.

1987-02-01

98

Space optical navigation techniques: an overview  

NASA Astrophysics Data System (ADS)

Optical or vision-based navigation is an enabling technology for satellite autonomous navigation associated to different navigation approaches such as cruising, fly-by, terrain relative navigation, landing, rendezvous and docking between spacecrafts, rigidity of multi-satellite constellations. Since 2001, in many different ESA projects, the author and his team (at INETI and currently at FCUL) have been associated to most of the developments of the optical components of autonomous navigation, in cooperation with space primes or GNC subsystems suppliers. A unique experience related to seemingly simple photonic concepts associated to computational vision, photonic noises, camera tradeoffs and system concepts has emerged, and deserves a synthesis especially because some of these concepts are being implemented in the ESA Proba 3 mission and ESA is currently updating the technology in view of forthcoming planetary missions to Jupiter, Jupiter moons and asteroids. It is important to note that the US have already flown several missions relying on autonomous navigation and that NASA experience is at least one decade old. System approaches, sources of difficulty, some tradeoffs in both (and between) hardware and software, critical interface issues between the imaging and GNC (Guidance, Navigation and Control) subsystems, image processing techniques, utilization of apriori or to be estimated information, uncertainties, simulation of the imaging chain and non-cooperative environments will be addressed synthetically for both passive (optical) and active (lidar) systems.

Rebordão, J. M.

2013-11-01

99

Design, alignment and applications of optical systems for parallel processing with ultra-short laser pulses  

NASA Astrophysics Data System (ADS)

During the last years, the average power of commercial ultra-short pulsed laser sources increased significantly. The efficient utilization of the high average laser power in the field of material processing requires an effective distribution of the laser power onto the work piece. One approach to increase the efficiency is the application of beam splitting devices to enable parallel processing. But the shaping and steering of multiple beams requires particular optical systems which are not state of the art today. Limitations for large spot arrays are evaluated and considered for the design concept of appropriate optical systems. For the purpose of micro structuring with high demands on the spatial accuracy, an optical system based on a diffractive 14×14 beam splitter (DOE) is designed and set up. All partial beams are coupled into a scanner device by using a relay lens system. Furthermore, this relay lens system offers a practicable solution to remove higher diffraction orders of the DOE. Due to the scanner a highly dynamic, simultaneous deflection of all partial laser beams can be achieved. For the alignment and the experimental evaluation of the complex optical system appropriate measurement devices are necessary. The simultaneous determination of several spot positions is realized by a camera system and adapted evaluation software. First experiments of large-area processing metal foils show promising results.

Büsing, L.; Eifel, S.; Loosen, Peter

2014-05-01

100

Alignment of Vertical Shaft Hydro Units. Facilities Instructions, Standards, and Techniques. Volume 2-1.  

National Technical Information Service (NTIS)

This bulletin provides an introduction to the concepts and procedures used to align, plumb, and evenly load bearings on vertical shaft hydrounits with most thrust and guide bearing configurations. The objectives of unit alignment are discussed and general...

H. Watson, D. Temple, W. Duncan

1989-01-01

101

Alignment of palatally impacted canine with open window technique and modified K-9 spring.  

PubMed

The patient was an 18-year-old female who had an Angle Class I malocclusion with a left palatally impacted maxillary canine. The orthodontic treatment of a palatally impacted canine is aimed at bringing the tooth into its correct position in the dental arch without causing any periodontal damage. To achieve this goal, a variety of surgical and orthodontic techniques have been proposed in relation to the position of the impacted tooth and there are various treatment methods used for traction. The duration of the traction was 3 months and alignment duration was 12 months the total treatment time was 15 months. In the following case, we presented that maxillary palatally impacted canine was brought into the arch with open window method for canine exposure and modified K-9 spring for traction, that is simple spring for orthodontic traction of the palatally impacted canines. PMID:24963263

Shastri, Dipti; Nagar, Amit; Tandon, Pradeep

2014-04-01

102

Alignment of palatally impacted canine with open window technique and modified K-9 spring  

PubMed Central

The patient was an 18-year-old female who had an Angle Class I malocclusion with a left palatally impacted maxillary canine. The orthodontic treatment of a palatally impacted canine is aimed at bringing the tooth into its correct position in the dental arch without causing any periodontal damage. To achieve this goal, a variety of surgical and orthodontic techniques have been proposed in relation to the position of the impacted tooth and there are various treatment methods used for traction. The duration of the traction was 3 months and alignment duration was 12 months the total treatment time was 15 months. In the following case, we presented that maxillary palatally impacted canine was brought into the arch with open window method for canine exposure and modified K-9 spring for traction, that is simple spring for orthodontic traction of the palatally impacted canines. PMID:24963263

Shastri, Dipti; Nagar, Amit; Tandon, Pradeep

2014-01-01

103

Application of adaptive Kalman filter technique in initial alignment of strapdown inertial navigation system  

Microsoft Academic Search

In order to improve the alignment precision and convergence speed of strap-down inertial navigation system, an initial alignment method based on Sage-Husa adaptive filter is presented. We also derived the exactitude alignment error model and adaptive Kalman filter equation in the azimuth of small misalignment angle. As usual, known the noise statistical characteristics, Kalman filter is suitable; but in the

Huang Chunmei; Su Wanxin; Liu Peiwei; Ma Minglong

2010-01-01

104

Modulated-alignment dual-axis (MAD) confocal microscopy for deep optical sectioning in tissues  

PubMed Central

A strategy is presented to enable optical-sectioning microscopy with improved contrast and imaging depth using low-power (0.5 - 1 mW) diode laser illumination. This technology combines the inherent strengths of focal-modulation microscopy and dual-axis confocal (DAC) microscopy for rejecting out-of-focus and multiply scattered background light in tissues. The DAC architecture is unique in that it utilizes an intersecting pair of illumination and collection beams to improve the spatial-filtering and optical-sectioning performance of confocal microscopy while focal modulation selectively ‘labels’ in-focus signals via amplitude modulation. Simulations indicate that modulating the spatial alignment of dual-axis beams at a frequency f generates signals from the focal volume of the microscope that are modulated at 2f with minimal modulation of background signals, thus providing nearly an order-of-magnitude improvement in optical-sectioning contrast compared to DAC microscopy alone. Experiments show that 2f lock-in detection enhances contrast and imaging depth within scattering phantoms and fresh tissues. PMID:24940534

Leigh, Steven Y.; Chen, Ye; Liu, Jonathan T.C.

2014-01-01

105

Large-Stroke Self-Aligned Vertical Comb Drive Actuators for Adaptive Optics Applications  

SciTech Connect

A high-stroke micro-actuator array was designed, modeled, fabricated and tested. Each pixel in the 4x4 array consists of a self-aligned vertical comb drive actuator. This micro-actuator array was designed to become the foundation of a micro-mirror array that will be used as a deformable mirror for adaptive optics applications. Analytical models combined with CoventorWare{reg_sign} simulations were used to design actuators that would move up to 10{micro}m in piston motion with 100V applied. Devices were fabricated according to this design and testing of these devices demonstrated an actuator displacement of 1.4{micro}m with 200V applied. Further investigation revealed that fabrication process inaccuracy led to significantly stiffer mechanical springs in the fabricated devices. The increased stiffness of the springs was shown to account for the reduced displacement of the actuators relative to the design.

Carr, E J; Olivier, S S; Solgaard, O

2005-10-27

106

New metrology techniques improve the production of silicon diffractive optics  

NASA Astrophysics Data System (ADS)

Silicon immersion gratings and grisms offer significant advantages in compactness and performance over frontsurface gratings and over grisms made from lower-index materials. At the same time, the high refractive index of Si (3.4) leads to very stringent constraints on the allowable groove position errors, typically rms < 20 nm over 100 mm and repetitive error of <5 nm amplitude. For both types of devices, we produce grooves in silicon using photolithography, plasma etching, and wet etching. To date, producers have used contact photolithography to pattern UV sensitive photoresist as the initial processing step, then transferred this pattern to a layer of silicon nitride that, in turn, serves as a hard mask during the wet etching of grooves into silicon. For each step of the groove production, we have used new and sensitive techniques to determine the contribution of that step to the phase non-uniformity. Armed with an understanding of the errors and their origins, we could then implement process controls for each step. The plasma uniformity was improved for the silicon nitride mask etch process and the phase contribution of the plasma etch step was measured. We then used grayscale lithography, a technique in which the photoresist is deliberately underexposed, to measure large-scale nonuniformities in the UV exposure system to an accuracy of 3-5%, allowing us to make corrections to the optical alignment. Additionally, we used a new multiple-exposure technique combined with laser interferometry to measure the relationship between UV exposure dose and line edge shift. From these data we predict the contribution of the etching and photolithographic steps to phase error of the grating surface. These measurements indicate that the errors introduced during the exposure step dominate the contributions of all the other processing steps. This paper presents the techniques used to quantify individual process contributions to phase errors and steps that were taken to improve overall phase uniformity.

Brooks, Cynthia B.; Gully-Santiago, Michael; Grigas, Michelle; Jaffe, Daniel T.

2014-07-01

107

Optical Modeling Activities for NASA's James Webb Space Telescope (JWST). 3; Wavefront Aberrations due to Alignment and Figure Compensation  

NASA Technical Reports Server (NTRS)

This is part three of a series describing the ongoing optical modeling activities for James Webb Space Telescope (JWST). The first two discussed modeling JWST on-orbit performance using wavefront sensitivities to predict line of sight motion induced blur, and stability during thermal transients. The work here investigates the aberrations resulting from alignment and figure compensation of the controllable degrees of freedom (primary and secondary mirrors), which may be encountered during ground alignment and on-orbit commissioning of the observatory. The optical design of the telescope is a three-mirror anastigmat, with an active fold mirror at the exit pupil for fine guiding. The primary mirror is over 6.5 meters in diameter, and is composed of 18 hexagonal segments that can individually positioned on hexapods, as well as compensated for radius of curvature. This effectively gives both alignment and figure control of the primary mirror. The secondary mirror can be moved in rigid body only, giving alignment control of the telescope. The tertiary mirror is fixed, however, as well as the location of the science instrumentation. Simulations are performed of various combinations of active alignment corrections of component figure errors, and of primary mirror figure corrections of alignment errors. Single field point and moderate field knowledge is assumed in the corrections. Aberrations over the field are reported for the varying cases, and examples presented.

Howard, Joseph

2007-01-01

108

Optical inspection techniques for security instrumentation  

NASA Astrophysics Data System (ADS)

This paper reviews four optical inspection systems, in which development TNO Institute of Applied Physics was involved: (1) intaglio scanning and recognition, (2) banknote quality inspection, (3) visualization and reading of a finger pattern, and (4) 3DAS authentication. (1) Intaglio is reserved for high security printing. It renders a tactile relief that can be recognized by a laser scanning technique. This technique is applied by various national banks to detect counterfeit banknotes returning from circulation. A new system is proposed that will detect intaglio on arbitrary wrinkled banknotes. (2) A banknote fitness inspection system (BFIS) that inspects banknotes in specularly reflected light is described. As modern banknotes are provided increasingly with reflective security foils, a new system is proposed that inspects banknotes in specular and diffuse reflection, as well as in transmission. (3) An alternative visualization method for visualization of finger patterns is described, employing a reflective elastomer. A CD scanning system reads the finger patterns. (4) A nonwoven structure has two advantageous properties for card authentication: a random structure which renders each few square millimeters of the pattern uniqueness (identification) and a 3D structure which makes it virtually impossible to be counterfeited (authentication). Both properties are inspected by an extremely simple lenseless reader.

van Renesse, Rudolf L.

1996-03-01

109

The characterization of particle clouds using optical imaging techniques  

E-print Network

Optical imaging techniques can be used to provide a better understanding of the physical properties of particle clouds. The purpose of this thesis is to design, perform and evaluate a set of experiments using optical imaging ...

Bruce, Elizabeth J. (Elizabeth Jane), 1972-

1998-01-01

110

RESEARCH ARTICLE Optical plume velocimetry: a new flow measurement technique  

E-print Network

RESEARCH ARTICLE Optical plume velocimetry: a new flow measurement technique for use in seafloor collected in these environments. We develop a non- invasive method, called optical plume velocimetry (OPV

Wilcock, William

111

Spectroelectrochemistry: The Combination of Optical and Electrochemical Techniques.  

ERIC Educational Resources Information Center

Two different techniques, electrochemistry and spectroscopy, can be combined for studying the redox chemistry of inorganic, organic, and biological molecules. Several commonly used spectroelectrochemical methods and their applications are described. Includes discussions of optically transparent electrodes, optical absorption/fluorescence…

Heineman, William R.

1983-01-01

112

Patella re-alignment in children with a modified Grammont technique  

PubMed Central

Background and purpose In skeletally immature patients, surgical options due to recurrent patella dislocation are limited, because bony procedures bear the risk of growth disturbances. In this retrospective study, we report the long-term functional and radiographic outcome in skeletally immature patients using the modified Grammont surgical technique. Patients Between 1999 and 2004, 65 skeletally immature knees (49 children) were treated with a modified Grammont procedure: an open lateral release and a shift of the patella tendon insertion below the growth plate on the tuberositas tibia, allowing the tendon to medialize. At mean 8 (5.6–11) years after surgery, 58 knees in 43 patients were evaluated by clinical examination, from functional scores (Lysholm, Tegner), and from radiographs of the knees. Results Mean Lysholm score was 82 postoperatively. Tegner score decreased from 6.2 to 5. Eight knees had a single dislocation within 3 months of surgery. 3 knees had repeated late dislocations, all with a high grade of trochlea dysplasia. 6 knees showed mild signs of osteoarthritis. No growth disturbances were observed. Interpretation The modified Grammont technique in skeletally immature patients allows restoration of the distal patella tendon alignment by dynamic positioning. Long-term results showed that there were no growth disturbances and that there was good functional outcome. However, patients with a high grade of trochlea dysplasia tended to re-dislocate. PMID:23039166

2012-01-01

113

Towards an Accurate Alignment of the VLBI Frame and the Future Gaia Optical Frame: Global VLBI Imaging Observations of a Sample of Candidate Sources for this Alignment  

NASA Astrophysics Data System (ADS)

The space astrometry mission Gaia will construct a dense optical QSO-based celestial reference frame. For consistency between optical and radio positions, it will be important to align the Gaia and VLBI frames with the highest accuracy. However, the number of quasars that are bright at optical wavelengths (for the best position accuracy with Gaia), that have a compact core (to be detectable on VLBI scales), and that do not exhibit complex structures (to ensure a good astrometric quality) was found to be limited. It was then realized that the densification of the list of such objects was necessary. Therefore, we initiated a multi-step VLBI observational project, dedicated to finding additional suitable radio sources for aligning the two frames. The sample consists of ~450 optically- bright weak extragalactic radio sources, which have been selected by cross-correlating optical and radio catalogs. The initial observations, aimed at checking whether these sources are detectable with VLBI, and conducted with the European VLBI Network (EVN) in 2007, showed an excellent ~90% detection rate. The second step, dedicated to identifying the most point-like sources of the sample, by imaging their VLBI structures, was initiated in 2008. Approximately 25% of the detected targets were observed with the Global VLBI array (EVN+VLBA; Very Long Baseline Array) during a pilot imaging experiment, revealing that approximately 50% of them are point-like sources on VLBI scales. The rest of the sources were observed during three additional imaging experiments in March 2010, November 2010, and March 2011. In this paper, we present the results of these imaging campaigns and report plans for the final stage of the project, which will be dedicated to accurately measuring the VLBI position of the most point-like sources.

Bourda, G.; Collioud, A.; Charlot, P.; Porcas, R.; Garrington, S.

2012-12-01

114

An optical leveling technique for parallel near-field photolithography system  

NASA Astrophysics Data System (ADS)

An optical leveling technique is reported for a compact parallel (multi-cantilever) scanning near-field photolithography (SNP) prototype. This instrument operates in liquid and was designed to overcome the challenge of low sample throughput of previous serial scanning SNPs. A combination of zone plate lens array, probe array, and standard atomic force microscope feedback technique are employed to deliver parallel probe operation in the current SNP. Compared to the commonly used two-end or multi-end "force feedback" alignment techniques, the optical levelling technique applied provides a simple solution to maintaining all levers in an array within the near-field region. As a proof-of-principle experiment, the operation of the prototype was demonstrated by producing nano-scale patterns in parallel using scanning near-field photolithography.

Liu, Zhuming; Chen, Xinyong; Zhang, Yuan; Weaver, John; Roberts, Clive J.

2012-10-01

115

A technique for controlling the alignment of silver nanowires with an electric field  

NASA Astrophysics Data System (ADS)

Highly aligned silver nanowire arrays are synthesized under direct current electric field (DCEF) treatment by a solid state ionics method without any template at normal temperature and pressure. The degree of alignment of the synthesized nanowires increases with increase of the DCEF strength. The mechanism of the effect of the DCEF on the nanowire alignment is discussed briefly. Moreover, the alignment of the individual nanowires in a bundle is further proved by observing the polarization dependence in the experiment of the polarized reflection measurements.

Cao, Yang; Liu, Wei; Sun, Jialin; Han, Yaping; Zhang, Jianhong; Liu, Sheng; Sun, Hongsan; Guo, Jihua

2006-05-01

116

Updates to the optical alignment and test plan for the James Webb Space Telescope integrated science instrument module  

NASA Astrophysics Data System (ADS)

NASA's James Webb Space Telescope (JWST) is a 6.6m diameter, segmented, deployable telescope for cryogenic IR space astronomy (~40K). The JWST Observatory architecture includes the Optical Telescope Element (OTE) and the Integrated Science Instrument Module (ISIM) element that contains four science instruments (SI) including a Guider. The SIs and Guider are mounted to a composite metering structure with outer dimensions of ~2.2x2.2x1.7m. The SI and Guider units are integrated to the ISIM structure and optically tested at NASA Goddard Space Flight Center as an instrument suite using a telescope simulator (Optical telescope element SIMulator; OSIM). OSIM is a high-fidelity, cryogenic JWST telescope simulator that features a ~1.5m diameter powered mirror. The SIs are aligned to the structure's coordinate system under ambient, clean room conditions using optomechanical metrology. OSIM is aligned to the ISIM mechanical coordinate system at the cryogenic operating temperature via internal mechanisms and feedback from alignment sensors in six degrees of freedom. SI performance, including focus, pupil shear, pupil roll, boresight, wavefront error, and image quality, is evaluated at the operating temperature using OSIM. This work updates the assembly and ambient and cryogenic optical alignment, test and verification plan for ISIM.

Ohl, R.

2009-08-01

117

Intraocular lens alignment from an en face optical coherence tomography image Purkinje-like method  

NASA Astrophysics Data System (ADS)

Measurement of intraocular lens (IOL) alignment implanted in patients in cataract surgery is important to understand their optical performance. We present a method to estimate tilt and decentration of IOLs based on optical coherence tomography (OCT) images. En face OCT images show Purkinje-like images that correspond to the specular reflections from the corneal and IOL surfaces. Unlike in standard Purkinje-imaging, the tomographic nature of OCT allows unequivocal association of the reflection with the corresponding surface. The locations of the Purkinje-like images are linear combinations of IOL tilt, IOL decentration, and eye rotation. The weighting coefficients depend on the individual anterior segment geometry, obtained from the same OCT datasets. The methodology was demonstrated on an artificial model eye with set amounts of lens tilt and decentration and five pseudophakic eyes. Measured tilt and decentration in the artificial eye differed by 3.7% and 0.9%, respectively, from nominal values. In patients, average IOL tilt and decentration from Purkinje were 3.30±4.68 deg and 0.16±0.16 mm, respectively, and differed on average by 0.5 deg and 0.09 mm, respectively, from direct measurements on distortion-corrected OCT images. Purkinje-based methodology from anterior segment en face OCT imaging provided, therefore, reliable measurements of IOL tilt and decentration.

Sun, Mengchan; de Castro, Alberto; Ortiz, Sergio; Perez-Merino, Pablo; Birkenfeld, Judith; Marcos, Susana

2014-06-01

118

Merging and alignment of Dirac points in a shaken honeycomb optical lattice  

NASA Astrophysics Data System (ADS)

Inspired by the recent creation of a honeycomb optical lattice and the realization of a Mott-insulating state in a square lattice by shaking, we study here the shaken honeycomb optical lattice. For a periodic shaking of the lattice, Floquet theory may be applied to derive a time-independent Hamiltonian. In this effective description, the hopping parameters are renormalized by a Bessel function, which depends on the shaking direction, amplitude, and frequency. Consequently, the hopping parameters can vanish and even change sign, in an anisotropic manner, thus yielding different band structures. Here, we study the merging and the alignment of Dirac points and dimensional crossovers from the two-dimensional system to one-dimensional chains and zero-dimensional dimers. We also consider next-nearest-neighbor hopping, which breaks the particle-hole symmetry and leads to a metallic phase when it becomes dominant over the nearest-neighbor hopping. Furthermore, we include weak repulsive on-site interactions and find the density profiles for different values of the hopping parameters and interactions, both in a homogeneous system and in the presence of a trapping potential. Our results may be experimentally observed by use of momentum-resolved Raman spectroscopy.

Koghee, Selma; Lim, Lih-King; Goerbig, M. O.; Smith, C. Morais

2012-02-01

119

Transparent silicon strip sensors for the optical alignment of particle detector systems.  

National Technical Information Service (NTIS)

Modern large-area precision tracking detectors require increasing accuracy for the alignment of their components. A novel multi-point laser alignment system has been developed for such applications. The position of detector components with respect to refe...

W. Blum, H. Kroha, P. Widmann

1995-01-01

120

Optical techniques for determining dynamic material properties  

SciTech Connect

Miniature plates are laser-launched with a 10-Joule Nd:YAG for one-dimensional (1-D) impacts on to target materials much like gas gun experiments and explosive plane wave plate launch. By making the experiments small, flyer plates (3 mm diameter x 50 micron thick) and targets (10 mm diameter x 200 micron thick), 1-D impact experiments can be performed in a standard laser-optical laboratory with minimum confinement and collateral damage. The laser-launched plates do not require the traditional sabot on gas guns nor the explosives needed for explosive planewave lenses, and as a result are much more amenable to a wide variety of materials and applications. Because of the small size very high pressure gradients can be generated with relative ease. The high pressure gradients result in very high strains and strain rates that are not easily generated by other experimental methods. The small size and short shock duration (1 - 20 ns) are ideal for dynamically measuring bond strengths of micron-thick coatings. Experimental techniques, equipment, and dynamic material results are reported.

Paisley, D.L.; Stahl, D.B.

1996-12-31

121

Transformer insulation monitoring by optical sensing techniques  

NASA Astrophysics Data System (ADS)

High voltage transformers use paper to insulate the electrical windings present in the core which is then subsequently immersed in oil. In service, the temperature of the windings will increase to typically 80 degrees C. If the transformer is loaded to beyond its design ratings, the temperature can exceed 100 degrees C causing the cellulose chains in the paper to cleave at an accelerated rate, resulting in the degradation of mechanical strength and performance of the insulation. If unchecked, this can lead to catastrophic failure of the transformed and accompanying disruption to electricity supply and large economic losses to the operating utility. Furfuraldehyde (FFA) is a chemical by-product which is released into the oil by the thermal degradation of the paper winding. The concentration of FFA within the oil has been directly related to the condition of the paper insulation. We have developed absorbance and fluorescence optical techniques incorporating a novel FFA- sensitive material which we have invested at our laboratories. This material has been incorporated into a prototype portable optoelectronic instrument for the measurement of FFA at the site of the transformer. Results of experiments will be presented, and the implication of these results for condition monitoring of HV transformer will be discussed.

Uttamchandani, Deepak G.; Blue, Robert; Farish, O.

1998-08-01

122

MEMS Integrated Submount Alignment for Optoelectronics  

NASA Astrophysics Data System (ADS)

One of the most expensive and time-consuming production processes for single-mode fiber-optic components is the alignment of the photonic chip or waveguide to the fiber. The alignment equipment is capital intensive and usually requires trained technicians to achieve desired results. Current technology requires active alignment since tolerances are only ~0.2 ? m or less for a typical laser diode. This is accomplished using piezoelectric actuated stages and active optical feedback. Joining technologies such as soldering, epoxy bonding, or laser welding may contribute significant postbond shift, and final coupling efficiencies are often less than 80%. This paper presents a method of adaptive optical alignment to freeze in place directly on an optical submount using a microelectromechanical system (MEMS) shape memory alloy (SMA) actuation technology. Postbond shift is eliminated since the phase change is the alignment actuation. This technology is not limited to optical alignment but can be applied to a variety of MEMS actuations, including nano-actuation and nano-alignment for biomedical applications. Experimental proof-of-concept results are discussed, and a simple analytical model is proposed to predict the stress strain behavior of the optical submount. Optical coupling efficiencies and alignment times are compared with traditional processes. The feasibility of this technique in high-volume production is discussed.

Shakespeare, W. Jeffrey; Pearson, Raymond A.; Grenestedt, Joachim L.; Hutapea, Parsaoran; Gupta, Vikas

2005-02-01

123

Optical addressing technique for a CMOS RAM  

NASA Technical Reports Server (NTRS)

Progress on optically addressing a CMOS RAM for a feasibility demonstration of free space optical interconnection is reported in this paper. The optical RAM chip has been fabricated and functional testing is in progress. Initial results seem promising. New design and SPICE simulation of optical gate cell (OGC) circuits have been carried out to correct the slow fall time of the 'weak pull down' OGC, which has been characterized experimentally. Methods of reducing the response times of the photodiodes and the associated circuits are discussed. Even with the current photodiode, it appears that an OGC can be designed with a performance that is compatible with a CMOS circuit such as the RAM.

Wu, W. H.; Bergman, L. A.; Allen, R. A.; Johnston, A. R.

1988-01-01

124

Coherent microscopy by laser optical feedback imaging (LOFI) technique  

Microsoft Academic Search

The application of the non-conventional imaging technique LOFI (laser optical feedback imaging) to coherent microscopy is presented. This simple and efficient technique using frequency-shifted optical feedback needs the sample to be scanned in order to obtain an image. The effects on magnitude and phase signals such as vignetting and field curvature occasioned by the scanning with galvanometric mirrors are discussed.

O. Hugon; F. Joud; E. Lacot; O. Jacquin; H. Guillet de Chatellus

2011-01-01

125

Blood flow tracking using optical correlation techniques  

Microsoft Academic Search

It has been previously shown that tracking small particle motion can be accomplished by tracking the speckle pattern it produces. The joint transform correlator and the Sandia National Laboratories (SNL) acoustooptic correlator that were used to track speckle motion are described. Results demonstrate that optical correlation is capable of tracking speckle with an accuracy comparable to digital methods. Optical correlation

N. Clark; M. K. Giles; S. H. Harrison; C. P. Hofer

1992-01-01

126

Ultralong quantum optical data storage using an optical locking technique  

Microsoft Academic Search

Several types of quantum memory protocols have been presented over the last ten years, including photon echoes, off-resonant Raman scattering, ultraslow light-based quantum mapping processes and resonant Raman optical echoes. These quantum optical memory protocols are limited by a storage time on a scale as short as milliseconds, determined by the spin phase decay time of the storage medium. For

Byoung S. Ham

2009-01-01

127

Novel spectroscopic technique for in situ monitoring of collagen fibril alignment in gels.  

PubMed

Development of collagen fibril alignment in contracting fibroblast-populated and externally tensioned acellular collagen gels was studied using elastic scattering spectroscopy. Spectra of the backscattered light (320-860 nm) were acquired with a 2.75-mm source-detector separation probe placed perpendicular to the gel surface and rotated to achieve different angles to the collagen fibril alignment. Backscatter was isotropic for noncontracted/unloaded gels (disorganized matrix). As gels were contracted/externally loaded (collagen alignment developed), anisotropy of backscatter increased: more backscatter was detected perpendicular than parallel to the direction of the fibril alignment. An "anisotropy factor" (AF) was calculated to characterize this effect as the ratio of backscatter intensities at orthogonal positions. Before contraction (or zero strain) the AF was close to unity at all wavelengths. In contrast, at 72 h, backscatter anisotropy varied from AF(400 nm) = 2.14 +/- 0.29 to AF(700 nm) = 3.04 +/- 0.48. It also increased over threefold up to a strain of 20%. The AF strongly correlated with the contraction time/strain. Different directions of the backscatter were detected in gel zones with known differences in the matrix alignment. Thus, backscatter anisotropy allows in situ nondestructive determination of collagen fibril alignment and quantitative monitoring of its development. PMID:15240498

Kostyuk, Oksana; Brown, Robert A

2004-07-01

128

Parallel optical interconnect between surface-mounted devices on FR4 printed wiring board using embedded waveguides and passive optical alignments  

NASA Astrophysics Data System (ADS)

Technologies to design and fabricate high-bit-rate chip-to-chip optical interconnects on printed wiring boards (PWB) are studied. The aim is to interconnect surface-mounted component packages or modules using board-embedded optical waveguides. In order to demonstrate the developed technologies, a parallel optical interconnect was integrated on a standard FR4-based PWB. It consists of 4-channel BGA-mounted transmitter and receiver modules as well as of four polymer multimode waveguides fabricated on top of the PWB using lithographic patterning. The transmitters and receivers built on low-temperature co-fired ceramic (LTCC) substrates include flip-chip mounted VCSEL or photodiode array and 4x10 Gb/s driver or receiver IC. Two microlens arrays and a surface-mounted micro-mirror enable optical coupling between the optoelectronic device and the waveguide array. The optical alignment is based on the marks and structures fabricated in both the LTCC and optical waveguide processes. The structures were optimized and studied by the use of optical tolerance analyses based on ray tracing. The characterized optical alignment tolerances are in the limits of the accuracy of the surface-mount technology.

Karppinen, Mikko; Alajoki, Teemu; Tanskanen, Antti; Kataja, Kari; Mäkinen, Jukka-Tapani; Karioja, Pentti; Immonen, Marika; Kivilahti, Jorma

2006-04-01

129

Optical receiver techniques for integrated photonic links  

E-print Network

Integrated photonics has emerged as an I/O technology set to disrupt the communication fabric of many-core computer systems. The optical technology uses wavelength-division-multiplexing and a high degree of integration in ...

Georgas, Michael S. (Michael Stephen)

2014-01-01

130

Laser-fiber coupling by means of a silicon micro-optical bench and a self-aligned soldering process  

NASA Astrophysics Data System (ADS)

The alignment of laser diodes to monomode fibers has to meet extremely close tolerances for a low coupling loss. Typically < 0.5 micrometers in lateral and vertical direction and less than two degrees in angle deviation are allowed for a coupling loss below 2 dB. Presently such close tolerances can only be met by gluing or soldering both components on separate base plates and combining them via piezoactivated alignment monitoring the output of the circuit and then gluing them using UV-hardening epoxies. Such a procedure is not very economical and not useful for mass applications. This paper presents the principle and realization of a silicon micro-optical bench for laser-fiber-coupling, which avoids the above mentioned disadvantages. The micro-optical bench is realized using well controlled plasma etching processes to transfer the guiding patterns for the laser and the fiber into the silicon substrate, keeping geometry tolerances below +/- 0.5 micrometers in lateral and vertical direction. Mounting the laser diode by means of a self-aligned soldering process, an additional contribution to the precise alignment of the laser is further improved.

Schmidt, Jan P.; Cordes, A.; Mueller, Joerg; Burkhardt, Hans

1995-02-01

131

Optical fiber sensor technique for strain measurement  

DOEpatents

Laser light from a common source is split and conveyed through two similar optical fibers and emitted at their respective ends to form an interference pattern, one of the optical fibers having a portion thereof subjected to a strain. Changes in the strain cause changes in the optical path length of the strain fiber, and generate corresponding changes in the interference pattern. The interference pattern is received and transduced into signals representative of fringe shifts corresponding to changes in the strain experienced by the strained one of the optical fibers. These signals are then processed to evaluate strain as a function of time, typical examples of the application of the apparatus including electrodeposition of a metallic film on a conductive surface provided on the outside of the optical fiber being strained, so that strains generated in the optical fiber during the course of the electrodeposition are measurable as a function of time. In one aspect of the invention, signals relating to the fringe shift are stored for subsequent processing and analysis, whereas in another aspect of the invention the signals are processed for real-time display of the strain changes under study.

Butler, Michael A. (Albuquerque, NM); Ginley, David S. (Albuquerque, NM)

1989-01-01

132

The optical manifestation of dispersive field-aligned bursts in auroral breakup arcs  

NASA Astrophysics Data System (ADS)

High-resolution optical observations of a substorm expansion show dynamic auroral rays with surges of luminosity traveling up the magnetic field lines. Observed in ground-based imagers, this phenomenon has been termed auroral flames, whereas the rocket signatures of the corresponding energy dispersions are more commonly known as field-aligned bursts. In this paper, observations of auroral flames obtained at 50 frames/s with a scientific-grade Complementary Metal Oxide Semiconductor (CMOS) sensor (30° × 30° field of view, 30 m resolution at 120 km) are used to provide insight into the nature of the precipitating electrons similar to high-resolution particle detectors. Thanks to the large field of view and high spatial resolution of this system, it is possible to obtain a first-order estimate of the temporal evolution in altitude of the volume emission rate from a single sensor. The measured volume emission rates are compared with the sum of modeled eigenprofiles obtained for a finite set of electron beams with varying energy provided by the TRANSCAR auroral flux tube model. The energy dispersion signatures within each auroral ray can be analyzed in detail during a fraction of a second. The evolution of energy and flux of the precipitation shows precipitation spanning over a large range of energies, with the characteristic energy dropping from 2.1 keV to 0.87 keV over 0.2 s. Oscillations at 2.4 Hz in the magnetic zenith correspond to the period of the auroral flames, and the acceleration is believed to be due to Alfvenic wave interaction with electrons above the ionosphere.

Dahlgren, H.; Semeter, J. L.; Marshall, R. A.; Zettergren, M.

2013-07-01

133

Recent flight-test results of optical airdata techniques  

NASA Technical Reports Server (NTRS)

Optical techniques for measuring airdata parameters were demonstrated with promising results on high performance fighter aircraft. These systems can measure the airspeed vector, and some are not as dependent on special in-flight calibration processes as current systems. Optical concepts for measuring freestream static temperature and density are feasible for in-flight applications. The best feature of these concepts is that the air data measurements are obtained nonintrusively, and for the most part well into the freestream region of the flow field about the aircraft. Current requirements for measuring air data at high angle of attack, and future need to measure the same information at hypersonic flight conditions place strains on existing techniques. Optical technology advances show outstanding potential for application in future programs and promise to make common use of optical concepts a reality. Results from several flight-test programs are summarized, and the technology advances required to make optical airdata techniques practical are identified.

Bogue, Rodney K.

1993-01-01

134

A novel scheme for DVL-aided SINS in-motion alignment using UKF techniques.  

PubMed

In-motion alignment of Strapdown Inertial Navigation Systems (SINS) without any geodetic-frame observations is one of the toughest challenges for Autonomous Underwater Vehicles (AUV). This paper presents a novel scheme for Doppler Velocity Log (DVL) aided SINS alignment using Unscented Kalman Filter (UKF) which allows large initial misalignments. With the proposed mechanism, a nonlinear SINS error model is presented and the measurement model is derived under the assumption that large misalignments may exist. Since a priori knowledge of the measurement noise covariance is of great importance to robustness of the UKF, the covariance-matching methods widely used in the Adaptive KF (AKF) are extended for use in Adaptive UKF (AUKF). Experimental results show that the proposed DVL-aided alignment model is effective with any initial heading errors. The performances of the adaptive filtering methods are evaluated with regards to their parameter estimation stability. Furthermore, it is clearly shown that the measurement noise covariance can be estimated reliably by the adaptive UKF methods and hence improve the performance of the alignment. PMID:23322105

Li, Wanli; Wang, Jinling; Lu, Liangqing; Wu, Wenqi

2013-01-01

135

Optical modulation techniques for underwater detection, ranging and imaging  

Microsoft Academic Search

The focus of this paper is to describe research being conducted at NAVAIR in Patuxent River, MD to improve optical detection, ranging and imaging in the underwater environment through the use of optical modulation techniques. The modulation provides a way to discriminate against unwanted scattered light that would otherwise reduce detection sensitivity. Another benefit of modulating the transmitted light is

Linda Mullen; Brandon Cochenour; Alan Laux; Derek Alley

2011-01-01

136

Field results of antifouling techniques for optical instruments  

Microsoft Academic Search

The focus of today's oceanographic research is shifting to shallow water environments. This region of study complicates measurement techniques by forcing the protection of the instruments from bio-fouling. The most common methods of protecting optical surfaces use compounds such as tin and copper. These paints are designed to work most effectively against large fouling organisms. Yet optical degradation also occurs

W. J. Strahle; F. S. Hotchkiss; M. A. Martini

1998-01-01

137

Erbium transfer to optical fiber preforms by vapor phase technique  

Microsoft Academic Search

Erbium-doped optical fibers have been manufactured with a vapor phase technique. A `hot line' has been designed and realized which allows us to fabricate low and high alumina contents fibers, to make laser sources and optical amplifiers working in the third telecommunication window.

Guiseppe Cocito; Livio Cognolato; Angelantonio Gnazzo; C. Bruschi; D. Cout

1994-01-01

138

Optical techniques for determining dynamic material properties  

Microsoft Academic Search

Miniature plates are laser-launched with a 10-Joule Nd:YAG for 1D impacts on to target materials much like gas gun experiments and explosive plane wave plate launch. By making the experiments small, flyer plates (3 mm diameter X 50 micron thick) and targets (10 mm diameter X 200 micron thick), 1D impact experiments can be performed in a standard laser-optical laboratory

Dennis L. Paisley; David B. Stahl

1997-01-01

139

Optical techniques for determining dynamic material properties  

Microsoft Academic Search

Miniature plates are laser-launched with a 10-Joule Nd:YAG for one-dimensional (1-D) impacts on to target materials much like gas gun experiments and explosive plane wave plate launch. By making the experiments small, flyer plates (3 mm diameter x 50 micron thick) and targets (10 mm diameter x 200 micron thick), 1-D impact experiments can be performed in a standard laser-optical

D. L. Paisley; D. B. Stahl

1996-01-01

140

(Optical characterization techniques applied to ceramic oxides)  

SciTech Connect

The traveler collaborated with M.J.M. Leask, J.M. Baker, B. Bleaney, and others at the Clarendon Laboratory, Oxford University, Oxford, UK, to Study Tetragonal rare-earth phosphates and vanadates by optical and magnetic spectroscopy. This work is related to similar studies that have been performed at ORNL by the Synthesis and Properties of Novel Materials Group in the Solid State Division.

Abraham, M.M.

1990-10-15

141

Versatile multilevel soft lithography method with micrometer alignment using all-flexible rubber stamps and moiré fringe technique.  

PubMed

Soft lithography has gathered wide interest for the fabrication of unconventional micrometer and nanometer-sized structures and devices. Nevertheless, accurate alignment is essential to achieve multilevel soft lithography. Because of the soft nature of the stamp materials, such as soft polydimethylsiloxane, they are susceptible to mechanical distortions, which lower the registration accuracy. To reduce the distortions we backed the stamp with a polymer foil and minimized the overall forces applied to the stamp. We furthermore employed an alignment method using additive type moiré fringe technique that is easy to implement and does not require extensive processing steps. The alignment results show less than 1 ?m misalignment when the stamp is brought again onto a previously structured rigid template. When performing two consecutive lithography steps by transfer printing of thin gold films, we were able to obtain average registration accuracy of 1.3 ?m over an area of 400 mm(2). This method is versatile and can be used for several soft lithography techniques. Better results can be obtained with smaller moiré gratings and the use of harder materials. PMID:22316418

Fakhr, Omar; Karrai, Khaled; Lugli, Paolo

2012-02-28

142

Optical ranging techniques in turbid waters  

NASA Astrophysics Data System (ADS)

In this paper simulation and experimental results are presented for two hybrid lidar-radar modulation techniques for underwater laser ranging. Both approaches use a combination of multi-frequency and single frequency modulation with the goal of simultaneously providing good range accuracy, unambiguous range, and backscatter suppression. The first approach uses a combination of dual and single frequency modulation. The performance is explored as a function of increasing average frequency while keeping the difference frequency of the dual tones constant. The second approach uses a combination of a stepped multi-tone modulation called frequency domain reflectometry (FDR) and single frequency modulation. The FDR technique is shown to allow simultaneous detection of the range of both the volumetric center of the backscattered "clutter" signal and the desired object. Experimental and simulated results are in good agreement for both techniques and performance out to ten attenuations lengths is reported.

Illig, David W.; Jemison, William D.; Lee, Robert W.; Laux, Alan; Mullen, Linda J.

2014-05-01

143

Optical techniques for shock visualization and detection  

NASA Technical Reports Server (NTRS)

While the classical methods of shadowgraph and schlieren do yield a shadow in the neighborhood of a shock, they often suffer from low power densities and the need for relatively long distances. Scanning methods may help in solving these problems. The paper describes various scanning techniques, presents experimental data obtained by mechanical scanning, and identifies conditions at which the data were taken.

Adamovsky, G.; Johnson, D. K.

1995-01-01

144

High speed optical interrogator calibration technique  

Microsoft Academic Search

We present a novel technique for the calibration of a high speed FBG interrogation system which incorporates an Arrayed Waveguide Grating (AWG). It uses temperature tuning to wavelength sweep the AWG to generate calibration data and to determine the optimum temperature of AWG for the actual test. For ideal operation the FBG wavelengths under zero stimulus would lie midway between

David S. George; Stephen Hill; Robert I. Howden; Graham W. Smith

2009-01-01

145

Field results of antifouling techniques for optical instruments  

USGS Publications Warehouse

An anti-fouling technique is developed for the protection of optical instruments from biofouling which leaches a bromide compound into a sample chamber and pumps new water into the chamber prior to measurement. The primary advantage of using bromide is that it is less toxic than the metal-based antifoulants. The drawback of the bromide technique is also discussed.

Strahle, W.J.; Hotchkiss, F.S.; Martini, M.A.

1998-01-01

146

Phase retrieval techniques for adaptive optics  

SciTech Connect

We have developed and tested a method for minimizing static aberrations in adaptive optics systems. In order to correct the static phase aberrations, we need to measure the aberrations through the entire system. We have employed various phase retrieval algorithms to detect these aberrations. We have performed simulations of our experimental setup demonstrating that phase retrieval can improve the static aberrations to below the 20 nm rms level, with the limiting factor being local turbulence in the A0 system. Experimentally thus far, we have improved the static aberrations down to the 50 nm level, with the limiting factor being the ability to adjust the deformable mirror. This should be improved with better control algorithms now being implemented.

Carrano, C. J., LLNL

1998-03-01

147

Light deviation based optical techniques applied to solid propellant combustion  

NASA Astrophysics Data System (ADS)

The Investigation in Combustion of Energetic Materials (InCoME) program is aimed at validating the numerical simulation of composite propellant combustion using nonintrusive optical techniques. The Focusing Schlieren Technique (FST) was selected; it allows catching light deviation from a thin vertical planar section centered above the propellant combustion surface. The optical system is described in the paper. Significant results are presented showing the capabilities of this technique when applied to solid propellant combustion in terms of studying flame structure, flame propagation, and particle tracking.

Cauty, F.; Eradès, C.; Desse, J.-M.

2011-10-01

148

Alignment validation  

SciTech Connect

The four experiments, ALICE, ATLAS, CMS and LHCb are currently under constructionat CERN. They will study the products of proton-proton collisions at the Large Hadron Collider. All experiments are equipped with sophisticated tracking systems, unprecedented in size and complexity. Full exploitation of both the inner detector andthe muon system requires an accurate alignment of all detector elements. Alignmentinformation is deduced from dedicated hardware alignment systems and the reconstruction of charged particles. However, the system is degenerate which means the data is insufficient to constrain all alignment degrees of freedom, so the techniques are prone to converging on wrong geometries. This deficiency necessitates validation and monitoring of the alignment. An exhaustive discussion of means to validate is subject to this document, including examples and plans from all four LHC experiments, as well as other high energy experiments.

ALICE; ATLAS; CMS; LHCb; Golling, Tobias

2008-09-06

149

Relation between anchorings of liquid crystals and conformation changes in aligning agents by the Langmuir-Blodgett film technique investigation  

NASA Astrophysics Data System (ADS)

The anchoring direction of liquid crystals on a solid substrate surface depends upon many parameters characterizing the liquid-crystal-substrate interface, a variation of which may change this anchoring direction leading to the so-called anchoring transition. Here, based on the Langmuir-Blodgett film technique, we present two model systems to study the relation between anchoring directions and the conformation changes in aligning agents. A double-armed crown ether liquid crystal and a side chain polymer liquid crystal at an air-water interface both show phase transitions, accompanied by conformation changes. However, when the monolayers in different phases were transferred onto solid substrates to orient liquid crystals, we found that for the crown ether material the conformation change can alter the anchoring of liquid crystals between homeotropic and homogeneous alignments, while for the polymer liquid crystal, despite the conformation changes, the liquid crystals can only be aligned homeotropically. The involved mechanisms were briefly discussed in terms of the Landau-type phenomenological theory.

Zhu, Yang-Ming; Lu, Zu-Hong; Wei, Yu

1995-01-01

150

Controlling the optical dipole force for molecules with field-induced alignment  

SciTech Connect

We measure the role of field-induced alignment on the dipole force for molecules using a single focused nonresonant laser beam. We show that through the alignment process we can modify the effective polarizability by field polarization and thus control the center-of-mass motion of the molecule. We observe a maximum change of 20% in the dipole force on CS{sub 2} molecules when changing from linearly to circularly polarized light. Additionally, the effect of the dipole force on different vibrational states is also studied.

Purcell, S. M.; Barker, P. F. [Department of Physics and Astronomy, University College London, London, WC1E 6BT (United Kingdom)

2010-09-15

151

Switchable optical polarizer based on electrochromism in stretch-aligned polyaniline  

NASA Astrophysics Data System (ADS)

We report on the polarizing electrochromic (EC) effect of a conjugated polymer. This has been achieved in a planar flexible electrochemical device cell comprised of a patterned stretch-aligned thin film of polyaniline and an electrolyte, all made on a polyethylene foil substrate. The resulting device exhibits polarized absorption characteristics, of a dichroic ratio of 4, that can be controlled by the voltage applied. Also, thin flexible EC polarizers have been realized by combining two stretch-aligned polyaniline films with orthogonal stretching direction. In the resulting EC polarizer the orientation of the polarized absorption can be switched between two orthogonal directions, depending on the voltage applied.

Andersson, Peter; Berggren, Magnus; Kugler, Thomas

2003-08-01

152

Pathfinder first light: alignment, calibration, and commissioning of the LINC-NIRVANA ground-layer adaptive optics subsystem  

NASA Astrophysics Data System (ADS)

We present descriptions of the alignment and calibration tests of the Pathfinder, which achieved first light during our 2013 commissioning campaign at the LBT. The full LINC-NIRVANA instrument is a Fizeau interferometric imager with fringe tracking and 2-layer natural guide star multi-conjugate adaptive optics (MCAO) systems on each eye of the LBT. The MCAO correction for each side is achieved using a ground layer wavefront sensor that drives the LBT adaptive secondary mirror and a mid-high layer wavefront sensor that drives a Xinetics 349 actuator DM conjugated to an altitude of 7.1 km. When the LINC-NIRVANA MCAO system is commissioned, it will be one of only two such systems on an 8-meter telescope and the only such system in the northern hemisphere. In order to mitigate risk, we take a modular approach to commissioning by decoupling and testing the LINC-NIRVANA subsystems individually. The Pathfinder is the ground-layer wavefront sensor for the DX eye of the LBT. It uses 12 pyramid wavefront sensors to optically co-add light from natural guide stars in order to make four pupil images that sense ground layer turbulence. Pathfinder is now the first LINC-NIRVANA subsystem to be fully integrated with the telescope and commissioned on sky. Our 2013 commissioning campaign consisted of 7 runs at the LBT with the tasks of assembly, integration and communication with the LBT telescope control system, alignment to the telescope optical axis, off-sky closed loop AO calibration, and finally closed loop on-sky AO. We present the programmatics of this campaign, along with the novel designs of our alignment scheme and our off-sky calibration test, which lead to the Pathfinder's first on-sky closed loop images.

Kopon, Derek; Conrad, Al; Arcidiacono, Carmelo; Herbst, Tom; Viotto, Valentina; Farinato, Jacopo; Bergomi, Maria; Ragazzoni, Roberto; Marafatto, Luca; Baumeister, Harald; Bertram, Thomas; Berwein, Jürgen; Briegel, Florian; Hofferbert, Ralph; Kittmann, Frank; Kürster, Martin; Mohr, Lars; Radhakrishnan, Kalyan

2014-08-01

153

Liquidus temperature and optical properties measurement by containerless techniques  

NASA Technical Reports Server (NTRS)

Reactive alloy liquidus temperatures measured by conventional, contained techniques are often in error due to reactions with containers and gaseous impurities. This paper describes a new liquidus temperature measurement technique that avoids these problems by employing containerless processing. This technique relies on precise and accurate noncontact temperature measurements (NCTM), which are made possible by spectral emissivity values. The spectral emissivities, epsilon(sub lambda), are measured along with the optical properties (real, n, and imaginary, k, components of the index of refraction) using polarimetric techniques on electromagnetically levitated specimens. Results from work done at Vanderbilt University and Intersonics on the Ti-Al system are presented to demonstrate the above techniques.

Anderson, Collin D.

1993-01-01

154

Neutron optics requirements for neutron imaging techniques  

NASA Astrophysics Data System (ADS)

The utilization of X-rays for material research is common in many respects since their discovery at the end of the 19th century. New sources as electron synchrotrons or free-electron lasers push the methodology and the application ranges further. A similar approach started 50 years later with neutrons when sources with reasonable high intensity became available. Today, there are many similarities and complementarities visible between X-ray and neutron studies and the involved techniques. Therefore, it is worth to compare and to adapt from the advanced X-ray techniques and to translate it into the neutron world. Despite of the lack of neutron intensities compared to the most brilliant X-ray beams, the specific properties of neutrons (contrast, spin, magnetic moment, penetration power) are utilized and they will further play an important role in non-invasive studies on the micro- and macro scale. This paper wants to encourage to "look over the fence" into activities of the X-ray community as currently running in the COST action MP-1203.

Lehmann, E.; Morgano, M.; Peetermans, S.

2014-07-01

155

Compact and passive-alignment 4-channel x 2.5-Gbps optical interconnect modules based on silicon optical benches with 45 degrees micro-reflectors.  

PubMed

Compact and passive-alignment 4-channel x 2.5-Gbps optical interconnect modules are developed based on the silicon optical benches (SiOBs) of 5 x 5 mm2. A silicon-based 45 degrees micro-reflector and V-groove arrays are fabricated on the SiOB using anisotropic wet etching. Moreover, high-frequency transmission lines of 4 channel x 2.5 Gbps, and bonding pads with Au/Sn eutectic solder are also deposited on the SiOB. The vertical-cavity surface-emitting laser (VCSEL) array and photo-detector (PD) array are flip-chip assembled on the intended positions. The multi-mode fiber (MMF) ribbons are passively aligned and mounted onto the V-groove arrays. Without the assistance of additional optics, the coupling efficiencies of VCSEL-to-MMF in the transmitting part and MMF-to-PD in the receiving part can be as high as -5.65 and -1.98 dB, respectively, under an optical path of 180 microm. The 1-dB coupling tolerance of greater than +/- 20 microm is achieved for both transmitting and receiving parts. Eye patterns of both parts are demonstrated using 15-bit PRBS at 2.5 Gbps. PMID:20052136

Hsiao, Hsu-Liang; Lan, Hsiao-Chin; Chang, Chia-Chi; Lee, Chia-Yu; Chen, Siou-Ping; Hsu, Chih-Hung; Chang, Shuo-Fu; Lin, Yo-Shen; Kuo, Feng-Ming; Shi, Jin-Wei; Wu, Mount-Learn

2009-12-21

156

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)

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.

Wilkerson, Gary W.; Huegele, Vinson

1998-01-01

157

Optical techniques for time and frequency transfer  

NASA Technical Reports Server (NTRS)

Light has been used as a means for time synchronization for a long time. The flight time was supposed to be negligible. The first scientific determination of the velocity of the light was done by measuring a round trip flight time on a given distance. The well known flying clock experiment leading to Einstein's General Relativity is another example. The advent of lasers, particularly short pulse and modulated ones, as well as the improvements of the timing equipments have led to new concepts for time and frequency transfer. We describe some experiments using different techniques and configurations which have been proposed and tested in this field since the beginning of the space age. Added to that, we set out advantages, drawbacks, and performances achieved in the different cases.

Baumont, Francoise; Gaignebet, Jean

1994-01-01

158

Optical sensing techniques for temperature measurement.  

PubMed

Temperature is an important parameter that needs accurate measurement. Theoretical descriptions of the fluorescence ratio method, fluorescence lifetime sensing, and interferometric methods for temperature measurement are given. Fluorescence lifetime sensing calibration plots have been developed for temperature measurement from 20°C to 600°C using Er(3+)-doped glass, and from 20°C to 90°C using Sm(3+)-doped CaF(2). Lifetime sensing results of Pr(3+)-doped YAG and Ho(3+)-doped fluoride crystals for temperature measurement are also summarized. Mach-Zehnder interferometer measurements revealed that the passage of a 300 mW laser beam of 915 nm changed the temperature of the Yb(3+)-doped YAG crystal by 7.1°C. The interferometer technique is useful for measuring absolute temperature changes in laser cooling studies. PMID:23385939

Reddy, B Rami; Kamma, Indumathi; Kommidi, Praveena

2013-02-01

159

Elucidation of the growth process of vertically aligned SWNT films via in situ optical absorbance measurements  

E-print Network

measurements Erik Einarsson, Yoichi Murakami, and Shigeo Maruyama Department of Mechanical Engineering-section of the vertically aligned SWNT film. [1] S. Maruyama, E. Einarsson, Y. Murakami, and T. Edamura, Chem. Phys. Lett. 403 (2005) 320. [2] E. Einarsson, Y. Murakami, T. Edamura, S. Maruyama, to be submitted. [3] S

Maruyama, Shigeo

160

Preliminary studies on a magneto-optical procedure for aligning RHIC magnets  

SciTech Connect

Colloid dispersions of magnetite were used at SLAC and KEK to locate multipole magnet centers. We study the possible adaption of this method, to align RHIC magnets. A procedure for locating magnetic centers with respect to external fiducial markers, using electronic coordinate determination and digital TV image processing is described.

Goldman, M.A.; Sikora, R.E.; Shea, T.J.

1993-06-01

161

Neurovascular coupling: in vivo optical techniques for functional brain imaging  

PubMed Central

Optical imaging techniques reflect different biochemical processes in the brain, which is closely related with neural activity. Scientists and clinicians employ a variety of optical imaging technologies to visualize and study the relationship between neurons, glial cells and blood vessels. In this paper, we present an overview of the current optical approaches used for the in vivo imaging of neurovascular coupling events in small animal models. These techniques include 2-photon microscopy, laser speckle contrast imaging (LSCI), voltage-sensitive dye imaging (VSDi), functional photoacoustic microscopy (fPAM), functional near-infrared spectroscopy imaging (fNIRS) and multimodal imaging techniques. The basic principles of each technique are described in detail, followed by examples of current applications from cutting-edge studies of cerebral neurovascular coupling functions and metabolic. Moreover, we provide a glimpse of the possible ways in which these techniques might be translated to human studies for clinical investigations of pathophysiology and disease. In vivo optical imaging techniques continue to expand and evolve, allowing us to discover fundamental basis of neurovascular coupling roles in cerebral physiology and pathophysiology. PMID:23631798

2013-01-01

162

Noncontact optical fiber coating removal technique with hot air stream  

Microsoft Academic Search

We will discuss a novel noncontact removal technique of optical fiber coating in continuous and uninterrupted manner with hot air stream. We observed the mean breaking tensile strengths of the optical fibers coated with the UV-cured protective polymer and stripped using noncontact removal method were 5.6 and 5.1 GPa, respectively. A high-speed camera with 10 000 frames\\/s frame rates was

Hyunsoo Park; Seihyoung Lee; Un-Chul Paek; Youngjoo Chung

2005-01-01

163

Alignment of optical system components using an ADM beam through a null assembly  

NASA Technical Reports Server (NTRS)

A system for testing an optical surface includes a rangefinder configured to emit a light beam and a null assembly located between the rangefinder and the optical surface. The null assembly is configured to receive and to reflect the emitted light beam toward the optical surface. The light beam reflected from the null assembly is further reflected back from the optical surface toward the null assembly as a return light beam. The rangefinder is configured to measure a distance to the optical surface using the return light beam.

Hayden, Joseph E. (Inventor); Olczak, Eugene G. (Inventor)

2010-01-01

164

Optical Alignment and Diffraction Analysis for AIRES: An Airborne Infrared Echelle Spectrometer  

NASA Technical Reports Server (NTRS)

The optical design is presented for a long-slit grating spectrometer known as AIRES (Airborne InfraRed Echelle Spectrometer). The instrument employs two gratings in series: a small order sorter and a large steeply blazed echelle. The optical path includes four pupil and four field stops, including two narrow slits. A detailed diffraction analysis is performed using GLAD by Applied Optics Research to evaluate critical trade-offs between optical throughput, spectral resolution, and system weight and volume. The effects of slit width, slit length, oversizing the second slit relative to the first, on- vs off-axis throughput, and clipping at the pupil stops and other optical elements are discussed.

Haas, Michael R.; Fonda, Mark (Technical Monitor)

2002-01-01

165

Techniques For Characterization Of High-Loss Optical Fibers  

NASA Astrophysics Data System (ADS)

Optical fibers developed for sensor applications often exhibit high optical losses. While these losses may be entirely acceptable for the design application, efforts to improve fiber performance still require loss quantification and the identification of optical loss mechanisms. Existing fiber loss characterization techniques (e.g., optical time domain reflectometry) are generally only appropriate for low loss (communication grade) fibers and may give little or no information on loss mechanisms. At the Pacific Northwest Laboratory, techniques have been developed for the characterization of high-loss (tens of dB per meter) optical fibers which allow discrimination between scattering and absorptive losses. Two techniques are presented. In the "differential scattering" method, differential fiber scattering losses are acquired over the length of the fiber to obtain a scattering loss coefficient. This information combined with a conventional total fiber loss measurement (e.g., using the "cut-back" method) allows inference of the absorptive part of the fiber loss. In the second method, "scanning aperture" characteriza-tion, the fiber is scanned by a moving aperture to yield curves of differential and integral scatter intensity versus length. This curve not only provides corroboration of the previously acquired differential scattering data, but also points out high-loss regions in the optical fiber. Both methods will be fully described. Experimental data on representative fibers will be presented.

Griffin, Jeffrey W.; Craig, Richard A.; Stahl, Kurt A.

1990-01-01

166

A comparative review of optical surface contamination assessment techniques  

NASA Technical Reports Server (NTRS)

This paper will review the relative sensitivities and practicalities of the common surface analytical methods that are used to detect and identify unwelcome adsorbants on optical surfaces. The compared methods include visual inspection, simple reflectometry and transmissiometry, ellipsometry, infrared absorption and attenuated total reflectance spectroscopy (ATR), Auger electron spectroscopy (AES), scanning electron microscopy (SEM), secondary ion mass spectrometry (SIMS), and mass accretion determined by quartz crystal microbalance (QCM). The discussion is biased toward those methods that apply optical thin film analytical techniques to spacecraft optical contamination problems. Examples are cited from both ground based and in-orbit experiments.

Heaney, James B.

1987-01-01

167

Noncontact Optical Fiber Coating Removal Technique With Hot Air Stream  

NASA Astrophysics Data System (ADS)

We will discuss a novel noncontact removal technique of optical fiber coating in continuous and uninterrupted manner with hot air stream. We observed the mean breaking tensile strengths of the optical fibers coated with the UV-cured protective polymer and stripped using noncontact removal method were 5.6 and 5.1 GPa, respectively. A high-speed camera with 10 000 frames/s frame rates was used to observe the sequential steps of the explosion and vaporization of optical fiber coating materials.

Park, Hyunsoo; Lee, Seihyoung; Paek, Un-Chul; Chung, Youngjoo

2005-02-01

168

Optical analysis of AlGaInP laser diodes with real refractive index guided self-aligned structure  

NASA Astrophysics Data System (ADS)

Optical modes of AlGaInP laser diodes with real refractive index guided self-aligned (RISA) structure were analyzed theoretically on the basis of two-dimension semivectorial finite-difference methods (SV-FDMs) and the computed simulation results were presented. The eigenvalue and eigenfunction of this two-dimension waveguide were obtained and the dependence of the confinement factor and beam divergence angles in the direction of parallel and perpendicular to the pn junction on the structure parameters such as the number of quantum wells, the Al composition of the cladding layers, the ridge width, the waveguide thickness and the residual thickness of the upper P-cladding layer were investigated. The results can provide optimized structure parameters and help us design and fabricate high performance AlGaInP laser diodes with a low beam aspect ratio required for optical storage applications.

Xu, Yun; Zhu, Xiaopeng; Ye, Xiaojun; Kang, Xiangning; Cao, Qing; Guo, Liang; Chen, Lianghui

2004-05-01

169

Physical optics of the laser-schlieren shock tube technique.  

PubMed

The physical optics of the laser-schlieren technique for the measurement of rate processes in shock waves is examined in detail. The method utilizes the Kirchhoff-Huygens integral with the usual thin lens, paraxial, and Fresnel approximations, all of which are appropriate for the typical laser schlieren experiment. The resolution and sensitivity of the technique are defined for all detector separations, and a reliable method for locating the time origin in the schlieren signal is provided. Diffraction is found to have a significant effect on the shock front generated signal, and geometrical optics treatments of this signal are shown to be inadequate. PMID:20309094

Kiefer, J H; Al-Alami, M Z; Hajduk, J C

1981-01-15

170

Optical phase imaging using a synthetic aperture phase retrieval technique.  

PubMed

Optical phase imaging enables visualization of transparent samples, numerical refocusing, and other computational processing. Typically phase is measured quantitatively using interferometric techniques such as digital holography. Researchers have demonstrated image enhancement by synthetic aperture imaging based on digital holography. In this work we introduce a novel imaging technique that implements synthetic aperture imaging using phase retrieval, a non-interferometric technique. Unlike digital holography, phase retrieval obviates the need for a reference arm and provides a more compact, less expensive, and more stable experimental setup. We call this technique synthetic aperture phase retrieval. PMID:24787826

Lee, Dennis J; Weiner, Andrew M

2014-04-21

171

An Optical Characterization Technique for Parabolic Trough Solar Collectors Using Images of the Absorber Reflection  

NASA Astrophysics Data System (ADS)

As the concentrating solar power industry competes to develop a less-expensive parabolic trough collector, assurance is needed that new parabolic trough collectors maintain accurate optical alignment. Previous optical characterization techniques are either too slow, ill-suited for field testing, or do not allow the collector to be tested in realistic orientations. The Observer method presented here enables the rapid optical characterization of parabolic trough collectors in any orientation in the field. The Observer method directly measures the combined optical angular errors in the reflector surface shape and the absorber position, which can be separated into its two components: reflector surface slope and absorber misalignment. The data acquisition requires the placement of photogrammetry targets on and around the collector. Multiple photographs of the absorber and its reflection are taken with a digital camera from different angles with respect to the collector. The images are processed to determine the camera location of each image using photogrammetry bundle analysis. The absorber and its reflection are found in the photographs using image-processing techniques. A Monte Carlo uncertainty model was developed to determine the uncertainty in the Observer measurements. The uncertainty was estimated for a wide array of measurement test scenarios to demonstrate the user's control over the measurement uncertainty. To validate the Observer method, the absorber alignment technique was compared to traditional photogrammetry; the absorber position measured with the two methods compared with a root-mean-square difference of 1.5 mm in the transverse direction and 0.86 mm along the optical axis. The reflector surface slope error measurement was compared to both VSHOT and SOFAST, two well-established optical characterization tools, by measuring a single reflector panel in the laboratory. The VSHOT and SOFAST measurements agreed with the Observer with a root-mean-square difference of 1.6 mrad and 2.1 mrad, respectively. In the field, the Observer method's capability to test collectors in any orientation was demonstrated by mounting the camera on a radio-controlled helicopter and measuring a collector oriented at 90° above the horizon. The absorber measurement capability was demonstrated in the field for a collector facing both horizontally and vertically.

Owkes, Jeanmarie Kathleen

172

Low-temperature growth of aligned ZnO nanorods: effect of annealing gases on the structural and optical properties.  

PubMed

Aligned ZnO nanorods were grown on ZnO/Si substrate via simple aqueous solution process at low-temperature of - 65 degrees C by using zinc nitrate and hexamethylenetetramine (HMTA). The detailed morphological and structural properties measured by FESEM, XRD, EDS and TEM confirmed that the as-grown nanorods are vertically aligned, well-crystalline possessing wurtzite hexagonal phase and grown along the [0001] direction. The room-temperature photoluminescence spectrum of the grown nanorods exhibited a strong and broad green emission and small ultraviolet emission. The as-prepared ZnO nanorods were post-annealed in nitrogen (N2) and oxygen (O2) environments and further characterized in terms of their morphological, structural and optical properties. After annealing the nanorods exhibit well-crystallinity and wurtzite hexagonal phase. Moreover, by annealing the PL spectra show the enhancement in the UV emission and suppression in the green emission. The presented results demonstrate that simply by post-annealing process, the optical properties of ZnO nanostructures can be controlled. PMID:24738429

Umar, Ahmad; Hahn, Yoon-Bong; Al-Hajry, A; Abaker, M

2014-06-01

173

Optical Frequency Upconversion Technique for Transmission of Wireless MIMO-Type Signals over Optical Fiber  

PubMed Central

The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20?km standard single mode fiber (SMF). The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C) modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4?GHz or 5?GHz carrier frequency, 1?Gb/s data rate, and 16-quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength. PMID:24772009

Shaddad, R. Q.; Mohammad, A. B.; Al-Gailani, S. A.; Al-Hetar, A. M.

2014-01-01

174

Optical frequency upconversion technique for transmission of wireless MIMO-type signals over optical fiber.  

PubMed

The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF). The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C) modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength. PMID:24772009

Shaddad, R Q; Mohammad, A B; Al-Gailani, S A; Al-Hetar, A M

2014-01-01

175

Enhanced optical output power of blue light-emitting diodes with quasi-aligned gold nanoparticles  

PubMed Central

The output power of the light from GaN-based light-emitting diodes (LEDs) was enhanced by fabricating gold (Au) nanoparticles on the surface of p-GaN. Quasi-aligned Au nanoparticle arrays were prepared by depositing Au thin film on an aligned suspended carbon nanotube thin film surface and then putting the Au-CNT system on the surface of p-GaN and thermally annealing the sample. The size and position of the Au nanoparticles were confined by the carbon nanotube framework, and no other additional residual Au was distributed on the surface of the p-GaN substrate. The output power of the light from the LEDs with Au nanoparticles was enhanced by 55.3% for an injected current of 100 mA with the electrical property unchanged compared with the conventional planar LEDs. The enhancement may originate from the surface plasmon effect and scattering effect of the Au nanoparticles. PMID:24393473

2014-01-01

176

Color schlieren optics - A review of techniques and applications  

NASA Astrophysics Data System (ADS)

The history, underlying principles, and current status of color schlieren techniques are surveyed. The advantages of this optical tool for certain applications are discussed in terms of one- and two-dimensional visualizations, qualitative and quantitative analyses, and system sensitivity, range, and resolution. It is emphasized that schlieren techniques are more firmly rooted in the history of optics than is commonly recognized. A figure is included which illustrates and classifies most of the available color schlieren techniques in terms of source and cutoff masks added to the Toepler schlieren arrangement. Most of the applications cited here take advantage of color coding and color contrast in visualizing complex refractive fields and yielding both qualitative and quantitative results. The purpose is to present a unified framework to help other investigators decide whether color schlieren is useful for particular application and, if so, which technique to use.

Settles, G. S.

177

Implementation of Accelerated Beam-Specific Matched-Filter-Based Optical Alignment  

SciTech Connect

Accurate automated alignment of laser beams in the National Ignition Facility (NIF) is essential for achieving extreme temperature and pressure required for inertial confinement fusion. The alignment achieved by the integrated control systems relies on algorithms processing video images to determine the position of the laser beam images in real-time. Alignment images that exhibit wide variations in beam quality require a matched-filter algorithm for position detection. One challenge in designing a matched-filter based algorithm is to construct a filter template that is resilient to variations in imaging conditions while guaranteeing accurate position determination. A second challenge is to process the image as fast as possible. This paper describes the development of a new analytical template that captures key recurring features present in the beam image to accurately estimate the beam position under good image quality conditions. Depending on the features present in a particular beam, the analytical template allows us to create a highly tailored template containing only those selected features. The second objective is achieved by exploiting the parallelism inherent in the algorithm to accelerate processing using parallel hardware that provides significant performance improvement over conventional processors. In particular, a Xilinx Virtex II Pro FPGA hardware implementation processing 32 templates provided a speed increase of about 253 times over an optimized software implementation running on a 2.0 GHz AMD Opteron core.

Awwal, A S; Rice, K L; Taha, T M

2009-01-29

178

Optical supervised filtering technique based on Hopfield neural network  

NASA Astrophysics Data System (ADS)

Hopfield neural network is commonly preferred for optimization problems. In image segmentation, conventional Hopfield neural networks (HNN) are formulated as a cost-function-minimization problem to perform gray level thresholding on the image histogram or the pixels' gray levels arranged in a one-dimensional array [R. Sammouda, N. Niki, H. Nishitani, Pattern Rec. 30 (1997) 921-927; K.S. Cheng, J.S. Lin, C.W. Mao, IEEE Trans. Med. Imag. 15 (1996) 560-567; C. Chang, P. Chung, Image and Vision comp. 19 (2001) 669-678]. In this paper, a new high speed supervised filtering technique is proposed for image feature extraction and enhancement problems by modifying the conventional HNN. The essential improvement in this technique is to use 2D convolution operation instead of weight-matrix multiplication. Thereby, neural network based a new filtering technique has been obtained that is required just 3 × 3 sized filter mask matrix instead of large size weight coefficient matrix. Optical implementation of the proposed filtering technique is executed easily using the joint transform correlator. The requirement of non-negative data for optical implementation is provided by bias technique to convert the bipolar data to non-negative data. Simulation results of the proposed optical supervised filtering technique are reported for various feature extraction problems such as edge detection, corner detection, horizontal and vertical line extraction, and fingerprint enhancement.

Bal, Abdullah

2004-11-01

179

Study of optical techniques for the Ames unitary wind tunnels. Part 1: Schlieren  

NASA Technical Reports Server (NTRS)

Alignment procedures and conceptual designs for the rapid alignment of the Ames Unitary Wind Tunnel schlieren systems were devised. The schlieren systems can be aligned by translating the light source, the mirrors, and the knife edge equal distances. One design for rapid alignment consists of a manual pin locking scheme. The other is a motorized electronic position scheme. A study of two optical concepts which can be used with the schlieren system was made. These are the 'point diffraction interferometers' and the 'focus schlieren'. Effects of vibrations were studied.

Lee, George

1992-01-01

180

The formation of vertically aligned biaxial tungsten nanorods using a novel shadowing growth technique.  

PubMed

Biaxially textured tungsten nanorods (A15 crystal structure) have been grown by oblique angle DC magnetron sputtering using a novel rotation mode called 'two-step rotation'. In this mode, the substrate is given a fast rotation through 180 degrees at 90 rpm and this is followed by a rest period of 30 s. These nanorods are vertically aligned and have a [100] texture normal to the substrate along with preferential in-plane texture as shown by x-ray pole figure analysis. In contrast, the tungsten nanorods obtained without substrate rotation are slanted at an angle of approximately 45 degrees and have a [100] texture tilted 16 degrees with respect to the substrate normal. The flux is incident from two diametrically opposite points on the sample at an oblique angle, averaging out the growth into vertical columns that retain the in-plane texture. Scanning electron microscopy shows that the tungsten nanorods have a mixture of {211} and {421} crystal habits; these planes are both minimum surface energy planes for a cubic A15 crystal structure. PMID:19847032

Krishnan, R; Parker, T; Lee, S; Lu, T-M

2009-11-18

181

Optical metrology and alignment of the James Webb Space Telescope Integrated Science Instrument Module  

Microsoft Academic Search

The James Webb Space Telescope (JWST) is an infrared space telescope scheduled for launch in 2013. JWST has a 6.5 meter diameter deployable and segmented primary mirror, a deployable secondary mirror, and a deployable sun-shade. The optical train of JWST consists of the Optical Telescope Element (OTE), and the Integrated Science Instrument Module (ISIM), which contains four science instruments. When

Joseph A. Connelly; Brent J. Bos; Pamela S. Davila; William L. Eichhorn; Bradley J. Frey; John G. Hagopian; Jason E. Hylan; James M. Marsh; Douglas B. McGuffey; Joseph McMann; Maria D. Nowak; Raymond G. Ohl IV; Kevin W. Redman; Derek Sabatke; Henry P. Sampler; Joseph Stock; Joseph Sullivan; Gregory W. Wenzel; Geraldine A. Wright; Philip Young

2008-01-01

182

Optical imaging techniques for point-of-care diagnostics.  

PubMed

Improving access to effective and affordable healthcare has long been a global endeavor. In this quest, the development of cost-effective and easy-to-use medical testing equipment that enables rapid and accurate diagnosis is essential to reduce the time and costs associated with healthcare services. To this end, point-of-care (POC) diagnostics plays a crucial role in healthcare delivery in both developed and developing countries by bringing medical testing to patients, or to sites near patients. As the diagnosis of a wide range of diseases, including various types of cancers and many endemics, relies on optical techniques, numerous compact and cost-effective optical imaging platforms have been developed in recent years for use at the POC. Here, we review the state-of-the-art optical imaging techniques that can have a significant impact on global health by facilitating effective and affordable POC diagnostics. PMID:23044793

Zhu, Hongying; Isikman, Serhan O; Mudanyali, Onur; Greenbaum, Alon; Ozcan, Aydogan

2013-01-01

183

Optical Imaging Techniques for Point-of-care Diagnostics  

PubMed Central

Improving the access to effective and affordable healthcare has long been a global endeavor. In this quest, the development of cost-effective and easy-to-use medical testing equipment that enable rapid and accurate diagnosis is essential to reduce the time and costs associated with healthcare services. To this end, point-of-care (POC) diagnostics plays a crucial role in healthcare delivery in both the developed and developing countries by bringing medical testing to patients, or to sites near patients. As the diagnosis of a wide range of diseases, including various types of cancers and many endemics relies on optical techniques, numerous compact and cost-effective optical imaging platforms have been developed in recent years for use at the POC. Here, we review the state-of-the-art optical imaging techniques that can have significant impact on global health by facilitating effective and affordable POC diagnostics. PMID:23044793

Zhu, Hongying; Isikman, Serhan O.; Mudanyali, Onur; Greenbaum, Alon; Ozcan, Aydogan

2012-01-01

184

Evaluation of optical reflectance techniques for imaging of alveolar structure  

NASA Astrophysics Data System (ADS)

Three-dimensional (3-D) visualization of the fine structures within the lung parenchyma could advance our understanding of alveolar physiology and pathophysiology. Current knowledge has been primarily based on histology, but it is a destructive two-dimensional (2-D) technique that is limited by tissue processing artifacts. Micro-CT provides high-resolution three-dimensional (3-D) imaging within a limited sample size, but is not applicable to intact lungs from larger animals or humans. Optical reflectance techniques offer the promise to visualize alveolar regions of the large animal or human lung with sub-cellular resolution in three dimensions. Here, we present the capabilities of three optical reflectance techniques, namely optical frequency domain imaging, spectrally encoded confocal microscopy, and full field optical coherence microscopy, to visualize both gross architecture as well as cellular detail in fixed, phosphate buffered saline-immersed rat lung tissue. Images from all techniques were correlated to each other and then to corresponding histology. Spatial and temporal resolution, imaging depth, and suitability for in vivo probe development were compared to highlight the merits and limitations of each technology for studying respiratory physiology at the alveolar level.

Unglert, Carolin I.; Namati, Eman; Warger, William C.; Liu, Linbo; Yoo, Hongki; Kang, DongKyun; Bouma, Brett E.; Tearney, Guillermo J.

2012-07-01

185

Can optical remote sensing techniques detect air contaminants?  

Microsoft Academic Search

The American Petroleum Institute (API) is sponsoring a program to evaluate if and how optical remote sensing techniques can be used to detect air contaminant emissions at a processing facility. This study is also gathering database information to assess whether dispersion modeling accurately depicts air plume migrations within a petrochemical site. In early 1995, an initial field study was conducted

R. J. Paine; J. O. Zwicker; H. J. Feldman

1998-01-01

186

Application of optical correlation techniques to particle imaging velocimetry  

Microsoft Academic Search

Pulsed laser sheet velocimetry yields nonintrusive measurements of velocity vectors across an extended 2-dimensional region of the flow field. The application of optical correlation techniques to the analysis of multiple exposure laser light sheet photographs can reduce and\\/or simplify the data reduction time and hardware. Here, Matched Spatial Filters (MSF) are used in a pattern recognition system. Usually MSFs are

Mark P. Wernet; Robert V. Edwards

1988-01-01

187

Application of optical correlation techniques to particle imaging  

Microsoft Academic Search

Pulsed laser sheet velocimetry yields noninstrusive measurements of velocity vectors across an extended 2-dimensional region of the flow field. The application of optical correlation techniques to the analysis of multiple exposure laser light sheet photographs can reduce and\\/or simplify the data reduction time and hardware. Here, Matched Spatial Filters (MSF) are used in a pattern recognition system. Usuallay MSFs are

Mark P. Wernet; Robert V. Edwards

1988-01-01

188

Path Radiance Technique for Retrieving Aerosol Optical Thickness over Land  

NASA Technical Reports Server (NTRS)

The key issue in retrieving aerosol optical thickness over land from short-wave satellite radiances is to identify and separate the signal due to scattering by a largely transparent aerosol layer from the noise due to reflection by the background surface, where the signal is relatively uniform compared to the highly inhomogeneous surface contribution. Sensitivity studies in aerosol optical thickness retrievals reveal that the apparent reflectance at the top of the atmosphere is very susceptible to the surface reflectance, especially when aerosol optical thickness is small. Uncertainties associated with surface reflectance estimation can greatly amplify the error of the aerosol optical thickness retrieval. To reduce these uncertainties, we have developed a "path radiance" method to retrieve aerosol optical thickness over land by extending the traditional technique that uses the "dark object" approach to extract the aerosol signal. This method uses the signature of the correlation of visible and mid-IR reflectance at the surface, and couples the correlation with the atmospheric effect. We have applied this method to a Landsat TM (Thematic Mapper) image acquired over the Oklahoma Southern Great Plains (SGP) site of DoE's ARM (Department of Energy's Atmospheric Radiation Measurement) program on September 27, 1997, a very clear day (aerosol optical thickness of 0.07 at 0.5 pm) during the first Landsat IOP (Intensive Observation Period). The retrieved mean aerosol optical thickness for TM band 1 at 0.49 pm and band 3 at 0.66 pm agree very well with the ground-based sun-photometer measurements at the ARM site. The ability to retrieve small aerosol optical thickness makes this path radiance technique promising. More importantly, the path radiance is relatively insensitive to surface inhomogeneity. The retrieved mean path radiances in reflectance units have very small standard deviations for both TM blue and red bands. This small variability of path radiance further supports the current aerosol retrieval method.

Tsay, S.-C.; Wen, G.; Cahalan, R. F.; Oreopoulos, L.

1999-01-01

189

Path Radiance Technique for Retrieving Aerosol Optical Thickness Over Land  

NASA Technical Reports Server (NTRS)

The key issue in retrieving aerosol optical thickness over land from shortwave satellite radiances is to identify and separate the signal due to scattering by a largely transparent aerosol layer from the noise due to reflection by the background surface, where the signal is relatively uniform compared to the highly inhomogeneous surface contribution. Sensitivity studies in aerosol optical thickness retrievals reveal that the apparent reflectance at the top of the atmosphere is very susceptible to the surface reflectance, especially when aerosol optical thickness is small. Uncertainties associated with surface reflectance estimation can greatly amplify the error of the aerosol optical thickness retrieval. To reduce these uncertainties, we have developed a "path radiance" method to retrieve aerosol optical thickness over land by extending the traditional technique that uses the "dark object" approach to extract the aerosol signal. This method uses the signature of the correlation of visible and mid-IR reflectance at the surface, and couples the correlation with the atmospheric effect. We have applied this method to a Landsat TM (Thematic Mapper) image acquired over the Oklahoma Southern Great Plains (SGP) site of DoE's ARM (Department of Energy's Atmospheric Radiation Measurement) program on September 27,1997, a very clear day (aerosol optical thickness of 0.07 at 0.5 microns) during the first Landsat Intensive Observation Period (IOP). The retrieved mean aerosol optical thickness for TM band 1 at 0.49 micron and band 3 at 0.66 micron agree very well with the ground-based sun-photometer measurements at the ARM site. The ability to retrieve small aerosol optical thickness makes this path radiance technique promising. More importantly, the path radiance is relatively insensitive to surface inhomogeneity. The retrieved mean path radiances in reflectance units have very small standard deviations for both TM blue and red bands. This small variability of path radiance further supports the current aerosol retrieval method.

Tsay, S.-C.; Wen, G.; Cahalan, R. F.; Oreopoulos, L.

1999-01-01

190

Path radiance technique for retrieving aerosol optical thickness over land  

SciTech Connect

The key issue in retrieving aerosol optical thickness over land from shortwave satellite radiances is to identify and separate the signal due to scattering by a largely transparent aerosol layer from the noise due to reflection by the background surface, where the signal is relatively uniform compared to the highly inhomogeneous surface contribution. Sensitivity studies in aerosol optical thickness retrievals reveal that the apparent reflectance at the top of the atmosphere is very susceptible to the surface reflectance, especially when aerosol optical thickness is small. Uncertainties associated with surface reflectance estimation can greatly amplify the error of the aerosol optical thickness retrieval. To reduce these uncertainties, we have developed a ''path radiance'' method to retrieve aerosol optical thickness over land by extending the traditional technique that uses the ''dark object'' approach to extract the aerosol signal. This method uses the signature of the correlation of visible and middle-IR reflectance at the surface and couples the correlation with the atmospheric effect. We have applied this method to a Landsat TM (Thematic Mapper) image acquired over the Oklahoma southern Great Plains site of the Department of Energy Atmospheric Radiation Measurement (ARM) program on September 27, 1997, a very clear day (aerosol optical thickness of 0.07 at 0.5 {mu}m) during the first Landsat Intensive Observation Period. The retrieved mean aerosol optical thickness for TM band 1 at 0.49 {mu}m and band 3 at 0.66 {mu}m agree very well with the ground-based Sun photometer measurements at the ARM site. The ability to retrieve small aerosol optical thickness makes this path radiance technique promising. More importantly, the path radiance is relatively insensitive to surface inhomogeneity. The retrieved mean path radiances in reflectance units have very small standard deviations for both TM blue and red bands. This small variability of path radiance further supports the current aerosol retrieval method. (c) 1999 American Geophysical Union.

Wen, Guoyong [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States)] [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States); Tsay, Si-Chee [NASA Goddard Space Flight Center, Greenbelt, Maryland (United States)] [NASA Goddard Space Flight Center, Greenbelt, Maryland (United States); Cahalan, Robert F. [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States) [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States); NASA Goddard Space Flight Center, Greenbelt, Maryland (United States); Oreopoulos, Lazaros [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States)] [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States)

1999-12-27

191

Optical manipulation of airborne particles: techniques and applications.  

PubMed

In the following paper, we discuss new methods to trap and manipulate airborne liquid aerosol droplets. We discuss the single gradient force trapping of water aerosols in the 2-14 micron diameter range using both 532 nm and 1064 nm light, as well as the holographic optical trapping of arrays of aerosols. Using this holographic technique, we are able to show controlled aerosol coagulation. We also discuss two techniques based on the radiation pressure trapping of aerosols, namely the dual beam fibre trap and the controlled guiding of aerosols using Bessel beams. We conclude with a discussion of new topics for study based upon these techniques and some possible applications. PMID:18214112

McGloin, David; Burnham, Daniel R; Summers, Michael D; Rudd, Daniel; Dewar, Neil; Anand, Suman

2008-01-01

192

Vertically aligned rolled-up SiO2 optical microcavities in add-drop configuration  

NASA Astrophysics Data System (ADS)

A significant step towards integrated vertically rolled-up microcavities is demonstrated by interfacing an as-fabricated SiO2 microtube optical ring resonator with tapered fibers. In this transmission configuration, resonant filtering of optical signals at telecommunication wavelengths is shown in subwavelength thick walled microcavities. Moreover, we present a four-port add-drop filter based on a lifted doubly interfaced vertically rolled-up microcavity. Our work opens opportunities for vertical resonant light transfer in 3D multi-level optical data processing as well as for massively parallel optofluidic analysis of biomaterials in lab-on-a-chip systems.

Böttner, Stefan; Li, Shilong; Jorgensen, Matthew R.; Schmidt, Oliver G.

2013-06-01

193

Optical measurement techniques for high Reynolds number train investigations  

NASA Astrophysics Data System (ADS)

This article reports on experimental aerodynamic investigations on a generic high-speed train configuration performed within two different wind tunnels. Both wind tunnels are specialized facilities for high Reynolds number investigations and offer low turbulence levels. The wind tunnels are the cryogenic wind tunnel located in Cologne (KKK) and in the high-pressure wind tunnel located in Göttingen (HDG). Both facilities are part of the German Dutch wind tunnel association (DNW). The adaptation and application of three optical measurement techniques for such high Reynolds number investigations is described in the article. The optical methods are: Particle Image Velocimetry for the measurement of velocity fields, Background Oriented Schlieren technique for density gradient measurements, and a white light Digital Speckle Photography technique for model deformation monitoring.

Loose, S.; Richard, H.; Bosbach, J.; Thimm, M.; Becker, W.; Raffel, M.

2006-04-01

194

Electro-optic techniques in electron beam diagnostics  

SciTech Connect

Electron accelerators such as laser wakefield accelerators, linear accelerators driving free electron lasers, or femto-sliced synchrotrons, are capable of producing femtosecond-long electron bunches. Single-shot characterization of the temporal charge profile is crucial for operation, optimization, and application of such accelerators. A variety of electro-optic sampling (EOS) techniques exists for the temporal analysis. In EOS, the field profile from the electron bunch (or the field profile from its coherent radiation) will be transferred onto a laser pulse co-propagating through an electro-optic crystal. This paper will address the most common EOS schemes and will list their advantages and limitations. Strong points that all techniques share are the ultra-short time resolution (tens of femtoseconds) and the single-shot capabilities. Besides introducing the theory behind EOS, data from various research groups is presented for each technique.

van Tilborg, Jeroen; Toth, Csaba; Matlis, Nicholas; Plateau, Guillaume; Leemans, Wim

2011-06-17

195

Nonlinear Magneto-optical Rotation via Alignment-to-Orientation Conversion  

SciTech Connect

Nonlinear magneto-optical rotation (NMOR) is investigated at highlight powers where the rotation is significantly modified by AC Stark shifts. These shifts are shown to change the overall sign of rotation for closed F-->F+1 transitions as light power is increased. The effect is demonstrated by measurements in rubidium and density matrix calculations. The results are important for applications of nonlinear optical rotation such as sensitive magnetometry.

Budker, D.; Kimball, D.F.; Rochester, S.M.; Yashchuk, V.V.

2000-03-10

196

Innovative, Inexpensive Etching Technique Developed for Polymer Electro- Optical Structures  

NASA Technical Reports Server (NTRS)

Electro-optic, polymer-based integrated optic devices for high-speed communication and computing applications offer potentially significant advantages over conventional inorganic electro-optic crystals. One key area of integrated optical technology--primary processing and fabrication--may particularly benefit from the use of polymer materials. However, as efforts concentrate on the miniaturization of electro-integrated circuit pattern geometries, the ability to etch fine features and smoothly sloped sidewalls is essential to make polymers useful for electro-integrated circuit applications. There are many existing processes available to etch polymer materials, but they all yield nearly vertical sidewalls. Vertical sidewalls are too difficult to reliably cover with a metal layer, and incomplete metalization degrades microwave performance, particularly at high frequency. However, obtaining a very sloped sidewall greatly improves the deposition of metal on the sidewall, leading to low-loss characteristics, which are essential to integrating these devices in highspeed electro-optic modulators. The NASA Lewis Research Center has developed in-house an inexpensive etching technique that uses a photolithography method followed by a simple, wet chemical etching process to etch through polymer layers. In addition to being simpler and inexpensive, this process can be used to fabricate smoothly sloped sidewalls by using a commercial none rodible mask: Spin-On-Glass. A commercial transparent material, Spin-On-Glass, uses processes and equipment similar to that for photoresist techniques.

Nguyen, Hung D.

1999-01-01

197

A patient alignment solution for lung SBRT setups based on a deformable registration technique  

SciTech Connect

Purpose: In this work, the authors propose a novel registration strategy for translation-only correction scenarios of lung stereotactic body radiation therapy setups, which can achieve optimal dose coverage for tumors as well as preserve the consistency of registrations with minimal human interference. Methods: The proposed solution (centroid-to-centroidor CTC solution) uses the average four-dimensional CT (A4DCT) as the reference CT. The cone-beam CT (CBCT) is deformed to acquire a new centroid for the internal target volume (ITV) on the CBCT. The registration is then accomplished by simply aligning the centroids of the ITVs between the A4DCT and the CBCT. Sixty-seven cases using 64 patients (each case is associated with separate isocenters) have been investigated with the CTC method and compared with the conventional gray-value (G) mode and bone (B) mode registration methods. Dosimetric effects among the tree methods were demonstrated by 18 selected cases. The uncertainty of the CTC method has also been studied. Results: The registration results demonstrate the superiority of the CTC method over the other two methods. The differences in the D99 and D95 ITV dose coverage between the CTC method and the original plan is small (within 5%) for all of the selected cases except for one for which the tumor presented significant growth during the period between the CT scan and the treatment. Meanwhile, the dose coverage differences between the original plan and the registration results using either the B or G method are significant, as tumor positions varied dramatically, relative to the rib cage, from their positions on the original CT. The largest differences between the D99 and D95 dose coverage of the ITV using the B or G method versus the original plan are as high as 50%. The D20 differences between any of the methods versus the original plan are all less than 2%. Conclusions: The CTC method can generate optimal dose coverage to tumors with much better consistency compared with either the G or B method, and it is especially useful when the tumor position varies greatly from its position on the original CT, relative to the rib cage.

Lu Bo; Mittauer, Kathryn; Li, Jonathan; Samant, Sanjiv; Dagan, Roi; Okunieff, Paul; Kahler, Darren; Liu, Chihray [Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, Florida 32610 (United States)

2012-12-15

198

Path Radiance Techniques for Retrieving Aerosol Optical Thickness over Land  

NASA Technical Reports Server (NTRS)

The key issue in retrieving aerosol optical thickness over land from shortwave satellite radiances is to identify and separate the signal due to scattering by a largely transparent aerosol layer from the noise due to reflection by the background surface, where the signal is relatively uniform compared to the highly inhomogeneous surface contribution. Sensitivity studies in aerosol optical thickness retrievals reveal that the apparent reflectance at the top of the atmosphere is very susceptible to the surface reflectance, especially when aerosol optical thickness is small. Uncertainties associated with surface reflectance estimation can greatly amplify the error of the aerosol optical thickness retrieval. To reduce these uncertainties, we have developed a "path radiance" method to retrieve aerosol optical thickness over land by extending the traditional technique that uses the "dark object" approach to extract the aerosol signal. This method uses the signature of the correlation of visible and mid-IR reflectance at the surface, and couples the correlation with the atmospheric effect. We have applied this method to a TM (Landsat Thematic Mapper) image acquired over the Oklahoma Southern Great Plains (SGP) site of DoE's ARM (Atmospheric Radiation Measurement) program on September 27, 1997, a very clear day during the first Landsat IOP (Intensive Observation Period). The retrieved mean aerosol optical thickness for TM band 1 at 0.49 micrometers and band 3 at 0.66 micrometers agree very well with the ground-based sun-photometer measurements at the ARM site. The ability to retrieve small aerosol optical thickness (such as 0.07 at 0.5 micrometers as in the example considered here) makes this path radiance technique promising. More importantly, the path radiance is relatively insensitive to surface inhomogeneity. The retrieved mean path radiances in reflectance units have very small standard deviations for both TM blue and red bands. This small variability of path radiance further supports the current aerosol retrieval method.

Wen, Guoyong; Tsay, Si-Chee; Cahalan, Robert F.; Oreopoulos, Lazaros

1999-01-01

199

Fabrication techniques for colymer/Si optical waveguide  

NASA Astrophysics Data System (ADS)

In this paper fabrication techniques were investigated for polymer/Si optical waveguide. The aluminum film was used as photolithographic mask instead of photoresist to improve waveguide profile. The influence of aluminum metal cladding produced by sputtering process on the optical character of the device was discussed. The absorption loss was calculated and measured by using effective index method and cut-back method, respectively. Optimized etching parameters were given in reactive ion etching using oxygen, such as radio frequency power and gas flow rate. Measured near-field mode pattern indicated fabrication waveguide achieved single-mode transmission at wavelength 1.55 ?m.

Zhao, Y.; Zhang, D. M.; Wang, F.; Cui, Z. C.; Yi, M. B.; Ma, C. S.; Guo, W. B.; Liu, S. Y.

2004-11-01

200

Anti-drift and auto-alignment mechanism for an astigmatic atomic force microscope system based on a digital versatile disk optical head  

NASA Astrophysics Data System (ADS)

In this work, an anti-drift and auto-alignment mechanism is applied to an astigmatic detection system (ADS)-based atomic force microscope (AFM) for drift compensation and cantilever alignment. The optical path of the ADS adopts a commercial digital versatile disc (DVD) optical head using the astigmatic focus error signal. The ADS-based astigmatic AFM is lightweight, compact size, low priced, and easy to use. Furthermore, the optical head is capable of measuring sub-atomic displacements of high-frequency AFM probes with a sub-micron laser spot (˜570 nm, FWHM) and a high-working bandwidth (80 MHz). Nevertheless, conventional DVD optical heads suffer from signal drift problems. In a previous setup, signal drifts of even thousands of nanometers had been measured. With the anti-drift and auto-alignment mechanism, the signal drift is compensated by actuating a voice coil motor of the DVD optical head. A nearly zero signal drift was achieved. Additional benefits of this mechanism are automatic cantilever alignment and simplified design.

Hwu, E.-T.; Illers, H.; Wang, W.-M.; Hwang, I.-S.; Jusko, L.; Danzebrink, H.-U.

2012-01-01

201

Anti-drift and auto-alignment mechanism for an astigmatic atomic force microscope system based on a digital versatile disk optical head.  

PubMed

In this work, an anti-drift and auto-alignment mechanism is applied to an astigmatic detection system (ADS)-based atomic force microscope (AFM) for drift compensation and cantilever alignment. The optical path of the ADS adopts a commercial digital versatile disc (DVD) optical head using the astigmatic focus error signal. The ADS-based astigmatic AFM is lightweight, compact size, low priced, and easy to use. Furthermore, the optical head is capable of measuring sub-atomic displacements of high-frequency AFM probes with a sub-micron laser spot (~570 nm, FWHM) and a high-working bandwidth (80 MHz). Nevertheless, conventional DVD optical heads suffer from signal drift problems. In a previous setup, signal drifts of even thousands of nanometers had been measured. With the anti-drift and auto-alignment mechanism, the signal drift is compensated by actuating a voice coil motor of the DVD optical head. A nearly zero signal drift was achieved. Additional benefits of this mechanism are automatic cantilever alignment and simplified design. PMID:22299958

Hwu, E-T; Illers, H; Wang, W-M; Hwang, I-S; Jusko, L; Danzebrink, H-U

2012-01-01

202

Effects of machining parameters and optical alignment in off-centered conic mirrors  

SciTech Connect

Expressions are derived in simple, closed form (in terms of the aperture coordinates) for the optical signatures resulting from misalignment and from several controllable machining parameters in the manufacture of diamond-turned mirrors of the type comprising conic sections of revolution. Limited in validity to the lowest order in terms of the magnitudes of both angular misalignment and machining parameters, these wavefront error expressions are generally valid for optics of arbitrarily wide aperture. Through control of these signatures, dynamically induced part distortions can, in some cases, be eliminated.

Yoder, R.C.

1985-12-16

203

Hermetic fiber optic-to-metal connection technique  

DOEpatents

A glass-to-glass hermetic sealing technique is disclosed which can be used to splice lengths of glass fibers together. A solid glass preform is inserted into the cavity of a metal component which is then heated to melt the glass. An end of an optical fiber is then advanced into the molten glass and the entire structure cooled to solidify the glass in sealing engagement with the optical fiber end and the metal cavity. The surface of the re-solidified glass may be machined for mating engagement with another component to make a spliced fiber optic connection. The resultant structure has a helium leak rate of less than 1.times.10.sup.-8 cm.sup.3 /sec.

Kramer, Daniel P. (Centerville, OH)

1992-09-01

204

Hermetic fiber optic-to-metal connection technique  

SciTech Connect

A glass-to-glass hermetic sealing technique is disclosed which can be used to splice lengths of glass fibers together. A solid glass preform is inserted into the cavity of a metal component which is then heated to melt the glass. An end of an optical fiber is then advanced into the molten glass and the entire structure cooled to solidify the glass in sealing engagement with the optical fiber end and the metal cavity. The surface of the re-solidified glass may be machined for mating engagement with another component to make a spliced fiber optic connection. The resultant structure has a helium leak rate of less than 1[times]10[sup [minus]8]cm[sup 3]/sec. 5 figs.

Kramer, D.P.

1992-09-01

205

Fast electro-optical mode in photo-aligned reflective deformed helix ferroelectric liquid crystal cells.  

PubMed

The electro-optical behavior of deformed helix ferroelectric liquid crystal in reflective mode is described in this paper. The electrically controlled reflectance has been measured at subkilohertz driving voltage frequency for different polarizations of the incident light and compared quite successfully with the simulation results. PMID:22739902

Guo, Qi; Brodzeli, Zourab; Pozhidaev, Eugene P; Fan, Fan; Chigrinov, Vladimir G; Kwok, Hoi Sing; Silvestri, Leonardo; Ladouceur, Francois

2012-06-15

206

Optical modulation techniques for underwater detection, ranging and imaging  

NASA Astrophysics Data System (ADS)

The focus of this paper is to describe research being conducted at NAVAIR in Patuxent River, MD to improve optical detection, ranging and imaging in the underwater environment through the use of optical modulation techniques. The modulation provides a way to discriminate against unwanted scattered light that would otherwise reduce detection sensitivity. Another benefit of modulating the transmitted light is that coherent detection of the modulation envelope results in the ability to accurately measure the range to the underwater object. Ways to use the hardware and methods developed for the detection, ranging, and imaging scenario to satisfy other mission requirements are also being investigated. The requirements for the modulation scheme, modulation frequency, and laser characteristics (pulsed, continuous, optical power level) depend on the targeted application. The implementation of this optical modulation technique in a variety of underwater sensors has become possible due to recent advances in laser and receiver technology. A review of the work being done in this area of research will be presented, and results from laboratory experiments will be discussed.

Mullen, Linda; Cochenour, Brandon; Laux, Alan; Alley, Derek

2011-06-01

207

Optical Fiber Technique for In-Reactor Mechanical Properties Measurement  

SciTech Connect

In-reactor measurement of material properties is required for a better understanding of radiation effects on materials. We present an optical fiber based technique for measuring changes in elastic properties which involves exciting and measuring flexural vibrations in a thin cantilever beam. By exciting the beam and measuring the natural frequency, changes in the modulus of elasticity can be monitored. The technique is demonstrated by monitoring the elastic property changes of a beam fabricated from copper, as the copper undergoes recrystallization at elevated temperature.

Robert S. Schley; Zilong Hua; David H. Hurley; Heng Ban

2012-07-01

208

Optical fiber technique for in-reactor mechanical properties measurement  

NASA Astrophysics Data System (ADS)

In-reactor measurement of material properties is required for a better understanding of radiation effects on materials. We present an optical fiber based technique for measuring changes in elastic properties which involves exciting and measuring flexural vibrations in a thin cantilever beam. By exciting the beam and measuring the resonant frequency, changes in the modulus of elasticity can be monitored. The technique is demonstrated by monitoring the elastic property changes of a beam fabricated from copper, as the copper undergoes recrystallization at elevated temperature.

Schley, R. S.; Hurley, D. H.; Hua, Z. A.

2013-01-01

209

Optical fiber modulation techniques for single mode fiber sensors  

Microsoft Academic Search

\\u000a In order to be able to implement the signal processing techniques discussed in Chapter 5 a means is required of measuring\\u000a changes in one or more of the parameters describing the optical beam: amplitude, phase, direction and frequency of the light\\u000a wave. Temporal modulation of one, or more, of these parameters enables information to be encoded onto or extracted from

R. P. Tatam

210

Fiber distributed Brillouin sensing with optical correlation domain techniques  

NASA Astrophysics Data System (ADS)

Fiber distributed Brillouin sensing is discussed, focusing mainly on optical correlation domain techniques. By synthesizing a delta-function like optical coherence function between pump and probe lightwave traveling along an optical fiber in opposite directions, which is realized by modulating laser source frequency by an appropriate waveform, stimulated Brillouin scattering can be selectively excited at one specific position along the fiber. The selected position can easily be swept by changing the modulation frequency, so the distributed measurement can be achieved. In the system, Brillouin Optical Correlation Domain Analysis (BOCDA), the position to be measured can be selected randomly along the fiber, which is a special feature of the system. Spatial resolution of 1.6 mm and measurement speed of 1000 samples/s have already been demonstrated. With a similar way, distribution of spontaneous Brillouin scattering can also be measured along the fiber. Spatial resolution of 10 mm and measurement speed of 50 samples/s have already been demonstrated in the system, Brillouin Optical Correlation Domain Reflectometry (BOCDR). Brillouin dynamic grating (BDG), which is acoustic-wave generated refractive-index grating caused in the stimulated Brillouin scattering process, was found to cause a Bragg reflection for the orthogonally polarized lightwave in an polarization maintaining fiber. By measuring both the BDG and the Brillouin scattering, discriminative distributed measurement of strain and temperature has been realized by the BOCDA scheme with a 10 mm spatial resolution.

Hotate, Kazuo

2013-12-01

211

Optical Microscopy Techniques to Inspect for Metallic Whiskers  

NASA Technical Reports Server (NTRS)

Metal surface finishes of tin, zinc and cadmium are often applied to electronic components, mechanical hardware and other structures. These finishes sometimes unpredictably may form metal whiskers over periods that can take from hours to months or even many years. The metal whiskers are crystalline structures commonly having uniform cross sectional area along their entire length. Typical whisker dimensions are nominally on the order of only a few microns (um) across while their lengths can extend from a few microns to several millimeters. Metal whiskers pose a reliability hazard to electronic systems primarily as an electrical shorting hazard. The extremely narrow dimensions of metal whiskers can make observation with optical techniques very challenging. The videos herein were compiled to demonstrate the complexities associated with optical microscope inspection of electronic and mechanical components and assemblies for the presence or absence of metal whiskers. The importance of magnification, light source and angle of illumination play critical roles in being able to detect metal whiskers when present. Furthermore, it is demonstrated how improper techniques can easily obscure detection. It is hoped that these videos will improve the probability of detecting metal whiskers with optical inspection techniques.

Brusse, Jay A.

2006-01-01

212

Understanding and measuring the effects of soft nanopatterning techniques on internal alignment of polymer chains in Poly(3-hexylthiophene) nanolines  

NASA Astrophysics Data System (ADS)

We investigate the effects of three h-PDMS stamp-based nanopatterning techniques on the extent of internal alignment of poly(3-hexylthiophene) molecules and crystallite size within the fabricated nanolines. Atomic force phase imaging, x-ray diffraction and thin-film field-effect transistor measurements help provide insight into the kinds of driving forces that promote crystallization of P3HT, which is highly desirable for possible application in various optoelectronic devices. Specifically, we verify that the effects of differing rates of solvent evaporation have a clear but limited role in promoting growth of large crystallites in both unpatterned films and nanolines, which in turn results in an isotropic distribution of chains in the edge-on or face on phase regardless of the patterning technique used or the size of the h-PDMS stamp's lines. Further studies with substrates treated with silanized monolayers are necessary in order to ascertain the possibility of induced crystallite orientation due to nano-confinement by the stamps.

Lau, Thomas

213

JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS, VOL. 118, 45724582, doi:10.1002/jgra.50415, 2013 The optical manifestation of dispersive field-aligned bursts  

E-print Network

The optical manifestation of dispersive field-aligned bursts in auroral breakup arcs H. Dahlgren,1 J. L dynamic auroral rays with surges of luminosity traveling up the magnetic field lines. Observed in ground-based imagers, this phenomenon has been termed auroral flames, whereas the rocket signatures

214

Application of optical correlation techniques to particle imaging velocimetry  

NASA Technical Reports Server (NTRS)

Pulsed laser sheet velocimetry yields nonintrusive measurements of velocity vectors across an extended 2-dimensional region of the flow field. The application of optical correlation techniques to the analysis of multiple exposure laser light sheet photographs can reduce and/or simplify the data reduction time and hardware. Here, Matched Spatial Filters (MSF) are used in a pattern recognition system. Usually MSFs are used to identify the assembly line parts. In this application, the MSFs are used to identify the iso-velocity vector contours in the flow. The patterns to be recognized are the recorded particle images in a pulsed laser light sheet photograph. Measurement of the direction of the partical image displacements between exposures yields the velocity vector. The particle image exposure sequence is designed such that the velocity vector direction is determined unambiguously. A global analysis technique is used in comparison to the more common particle tracking algorithms and Young's fringe analysis technique.

Wernet, Mark P.; Edwards, Robert V.

1988-01-01

215

New optical tomographic & topographic techniques for biomedical applications  

NASA Astrophysics Data System (ADS)

The mammalian middle ear contains the eardrum and the three auditory ossicles, and forms an impedance match between sound in air and pressure waves in the fluid of the inner ear. Without this intermediate system, with its unsurpassed efficiency and dynamic range, we would be practically deaf. Physics-based modeling of this extremely complex mechanical system is necessary to help our basic understanding of the functioning of hearing. Highly realistic models will make it possible to predict the outcome of surgical interventions and to optimize design of ossicle prostheses and active middle ear implants. To obtain such models and with realistic output, basic input data is still missing. In this dissertation I developed and used two new optical techniques to obtain two essential sets of data: accurate three-dimensional morphology of the middle ear structures, and elasticity parameters of the eardrum. The first technique is a new method for optical tomography of macroscopic biomedical objects, which makes it possible to measure the three-dimensional geometry of the middle ear ossicles and soft tissues which are connecting and suspending them. I made a new and high-resolution version of this orthogonal-plane fluorescence optical sectioning method, to obtain micrometer resolution in macroscopic specimens. The result is thus a complete 3-D model of the middle (and inner) ear of gerbil in unprecedented quality. On top of high-resolution morphological models of the middle ear structures, I applied the technique in other fields of research as well. The second device works according to a new optical profilometry technique which allows to measure shape and deformations of the eardrum and other membranes or objects. The approach is called projection moire profilometry, and creates moire interference fringes which contain the height information. I developed a setup which uses liquid crystal panels for grid projection and optical demodulation. Hence no moving parts are present and the setup is entirely digitally controlled. This measurement method is developed to determine the elasticity parameters of the eardrum in-situ. Other surface shapes however can also be measured.

Buytaert, Jan

216

Geometrical measurements of fibre-optic starter tubes using a novel optical technique  

NASA Astrophysics Data System (ADS)

A novel optical technique is described for making geometrical measurements on silica starter tubes. The measurement takes place in an air medium and uses a collimated source and spatial filtering to image the set of transmitted rays onto a CCTV system. An analysis relates this line structure observed to the geometry of the starter tube.

Meggitt, B. T.

1989-10-01

217

Technology of alignment mark in electron beam lithography  

NASA Astrophysics Data System (ADS)

Electron beam direct wring lithography has been an indispensable approach by which all sorts of novel nano-scale devices include many kinds optical devices can be fabricated. Alignment accuracy is a key factor especially to those devices which need multi-level lithography. In addition to electron beam lithography system itself the quality of alignment mark directly influences alignment accuracy. This paper introduces fundamental of alignment mark detection and discusses some techniques of alignment mark fabrication along with considerations for obtaining highly accurate alignment taking JBX5000LS and JBX6300FS e-beam lithography systems for example. The fundamental of alignment mark detection is expounded first. Many kinds of factors which can impact on the quality of alignment mark are analyzed including mark materials, depth of mark groove and influence of multi-channel process. It has been proved from experiments that material used as metal mark with higher average atomic number is better beneficial for getting high alignment accuracy. Depth of mark groove is required to 1.5?5 ?m on our experience. The more process steps alignment mark must pass through, the more probability of being damaged there will be. So the compatibility of alignment mark fabrication with the whole device process and the protection of alignment mark are both need to be considered in advance.

Zhao, Min; Xu, Tang; Chen, Baoqin; Niu, Jiebin

2014-08-01

218

Optical multiple access techniques for on-board routing  

NASA Technical Reports Server (NTRS)

The purpose of this research contract was to design and analyze an optical multiple access system, based on Code Division Multiple Access (CDMA) techniques, for on board routing applications on a future communication satellite. The optical multiple access system was to effect the functions of a circuit switch under the control of an autonomous network controller and to serve eight (8) concurrent users at a point to point (port to port) data rate of 180 Mb/s. (At the start of this program, the bit error rate requirement (BER) was undefined, so it was treated as a design variable during the contract effort.) CDMA was selected over other multiple access techniques because it lends itself to bursty, asynchronous, concurrent communication and potentially can be implemented with off the shelf, reliable optical transceivers compatible with long term unattended operations. Temporal, temporal/spatial hybrids and single pulse per row (SPR, sometimes termed 'sonar matrices') matrix types of CDMA designs were considered. The design, analysis, and trade offs required by the statement of work selected a temporal/spatial CDMA scheme which has SPR properties as the preferred solution. This selected design can be implemented for feasibility demonstration with off the shelf components (which are identified in the bill of materials of the contract Final Report). The photonic network architecture of the selected design is based on M(8,4,4) matrix codes. The network requires eight multimode laser transmitters with laser pulses of 0.93 ns operating at 180 Mb/s and 9-13 dBm peak power, and 8 PIN diode receivers with sensitivity of -27 dBm for the 0.93 ns pulses. The wavelength is not critical, but 830 nm technology readily meets the requirements. The passive optical components of the photonic network are all multimode and off the shelf. Bit error rate (BER) computations, based on both electronic noise and intercode crosstalk, predict a raw BER of (10 exp -3) when all eight users are communicating concurrently. If better BER performance is required, then error correction codes (ECC) using near term electronic technology can be used. For example, the M(8,4,4) optical code together with Reed-Solomon (54,38,8) encoding provides a BER of better than (10 exp -11). The optical transceiver must then operate at 256 Mb/s with pulses of 0.65 ns because the 'bits' are now channel symbols.

Mendez, Antonio J.; Park, Eugene; Gagliardi, Robert M.

1992-01-01

219

Optical correlation techniques for the investigation of colloidal systems  

E-print Network

This review aims to provide a simple introduction to the application of optical correlation methods in colloidal science. In particular, I plan to show that full appraisal of the intimate relation between light scattering and microscopy allows designing novel powerful investigation techniques that combine their powers. An extended version of this paper will appear in "ColloidalFoundations of Nanoscience", edited by D. Berti and G. Palazzo, Elsevier (ISBN 978-0-444-59541-6). I am very grateful to the publisher for having granted me the permission to post this preprint on arXiv.

Piazza, Roberto

2013-01-01

220

Measurement of wavefront and Wigner distribution function for optics alignment and full beam characterization of FELs  

NASA Astrophysics Data System (ADS)

Free-electron lasers deliver EUV and soft x-ray pulses with the highest brilliance available and high spatial coherence. Users of such facilities have high demands on the coherence properties of the beam, for instance when working with coherent di ractive imaging (CDI). Experimentally, we are recovering the phase distribition with an EUV Hartmann wavefront sensor. This allows for online adjustment of focusing optics such as ellipsoidal or Kirkpatrick-Baez mirrors minimizing the aberrations in the focused beam. To gain highly resolved spatial coherence information, we have performed a caustic scan at beamline BL2 of the free-electron laser FLASH using the ellipsoidal focusing mirror and a movable EUV sensitized CCD detector. This measurement allows for retrieving the Wigner distribution function, being the two-dimensional Fourier transform of the mutual intensity of the beam. Computing the reconstruction on a four-dimensional grid, this yields the entire Wigner distribution which describes the beam propagation completely. Hence, we are able to provide comprehensive information about spatial coherence properties of the FLASH beam including the global degree of coherence. Additionally, we derive the beam propagation parameters such as Rayleigh length, waist diameter and M2.

Mey, Tobias; Schäfer, Bernd; Mann, Klaus; Keitel, Barbara; Kreis, Svea; Kuhlmann, Marion; Plönjes, Elke; Tiedtke, Kai

2013-05-01

221

Self-amplified optical pattern-recognition technique  

NASA Technical Reports Server (NTRS)

A self-amplified optical pattern-recognition technique that utilizes a photorefractive crystal as a real-time volume holographic filter with recording accomplished by means of laser beams of proper polarization and geometric configuration is described. After the holographic filter is recorded, it can be addressed with extremely weak object beams and an even weaker reference beam to obtain a pattern-recognition signal. Because of beam-coupling energy transfer from the input object beam to the diffracted beam, the recognition signal is greatly amplified. Experimental results of this technique using BaTiO3 crystal show that 5 orders of magnitude of amplification of a recognition signal can be obtained.

Liu, Hua-Kuang

1992-01-01

222

Development of optical systems. [holographic technique for monitoring crystal growth  

NASA Technical Reports Server (NTRS)

Several key aspects of multi-color holography and laser speckle technique to study holographic reconstructions are considered in the report. Holographic fringe contrast in two-color holography in the presence of a fluid cell in the object beam is discussed in detail. A specific example of triglycine sulfate crystal growth is also considered. A breadboard design using fiber optics and diode lasers for three-color holography for fluid experiments is presented. A possible role of multi-color holography in various new applications is summarized. Finally, the use of a a laser speckle technique is demonstrated for the study of holographic reconstructions. The demonstration is performed using a Spacelab 3 hologram.

Vikram, Chandra S.

1995-01-01

223

Detecting nanoparticles in tissue using an optical iterative technique  

PubMed Central

Determining the physical penetration depth of nanoparticles (NPs) into tissues is a challenge that many researchers have been facing in recent years. This paper presents a new noninvasive method for detecting NPs in tissue using an optical iterative technique based on the Gerchberg-Saxton (G-S) algorithm. At the end of this algorithm the reduced scattering coefficient (µs'), of a given substance, can be estimated from the standard deviation (STD) of the retrieved phase of the remitted light. Presented in this paper are the results of a tissue simulation which indicate a linear ratio between the STD and the scattering components. A linear ratio was also observed in the tissue-like phantoms and in ex vivo experiments with and without NPs (Gold nanorods and nano Methylene Blue). The proposed technique is the first step towards determining the physical penetration depth of NPs.

Yariv, Inbar; Rahamim, Gilad; Shliselberg, Elad; Duadi, Hamootal; Lipovsky, Anat; Lubart, Rachel; Fixler, Dror

2014-01-01

224

Pathfinder first light: alignment, calibration, and commissioning of the LINC-NIRVANA ground-layer adaptive optics subsystem  

E-print Network

We present descriptions of the alignment and calibration tests of the Pathfinder, which achieved first light during our 2013 commissioning campaign at the LBT. The full LINC-NIRVANA instrument is a Fizeau interferometric imager with fringe tracking and 2-layer natural guide star multi-conjugate adaptive optics (MCAO) systems on each eye of the LBT. The MCAO correction for each side is achieved using a ground layer wavefront sensor that drives the LBT adaptive secondary mirror and a mid-high layer wavefront sensor that drives a Xinetics 349 actuator DM conjugated to an altitude of 7.1 km. When the LINC-NIRVANA MCAO system is commissioned, it will be one of only two such systems on an 8-meter telescope and the only such system in the northern hemisphere. In order to mitigate risk, we take a modular approach to commissioning by decoupling and testing the LINC-NIRVANA subsystems individually. The Pathfinder is the ground-layer wavefront sensor for the DX eye of the LBT. It uses 12 pyramid wavefront sensors to opt...

Kopon, Derek; Arcidiacono, Carmelo; Herbst, Tom; Viotto, Valentina; Farinato, Jacopo; Bergomi, Maria; Ragazzoni, Roberto; Marafatto, Luca; Baumeister, Harald; Bertram, Thomas; Berwein, Jürgen; Briegel, Florian; Hofferbert, Ralph; Kittmann, Frank; Kürster, Martin; Mohr, Lars; Radhakrishnan, Kalyan

2014-01-01

225

Application of optical spectroscopic techniques for disease diagnosis  

NASA Astrophysics Data System (ADS)

Optical spectroscopy, a truly non-invasive tool for remote diagnostics, is capable of providing valuable information on the structure and function of molecules. However, most spectroscopic techniques suffer from drawbacks, which limit their application. As a part of my dissertation work, I have developed theoretical and experimental methods to address the above mentioned issues. I have successfully applied these methods for monitoring the physical, chemical and biochemical parameters of biomolecules involved in some specific life threatening diseases like lead poisoning and age-related macular degeneration (AMD). I presented optical studies of melanosomes, which are one of the vital organelles in the human eye, also known to be responsible for a disease called age-related macular degeneration (AMD), a condition of advanced degeneration which causes progressive blindness. I used Raman spectroscopy, to first chemically identify the composition of melanosome, and then monitor the changes in its functional and chemical behavior due to long term exposure to visible light. The above study, apart from explaining the role of melanosomes in AMD, also sets the threshold power for lasers used in surgeries and other clinical applications. In the second part of my dissertation, a battery of spectroscopic techniques was successfully applied to explore the different binding sites of lead ions with the most abundant carrier protein molecule in our circulatory system, human serum albumin. I applied optical spectroscopic tools for ultrasensitive detection of heavy metal ions in solution which can also be used for lead detection at a very early stage of lead poisoning. Apart from this, I used Raman microspectroscopy to study the chemical alteration occurring inside a prostate cancer cell as a result of a treatment with a low concentrated aqueous extract of a prospective drug, Nerium Oleander. The experimental methods used in this study has tremendous potential for clinical application and will gain widespread acceptance within next few years from bench to bedside as an inexpensive and non-invasive tool compared to the other technologies.

Saha, Anushree

226

An infrared technique for the alignment control of highly viscous mesophases: the formation of homeotropic and planar domains for hexagonal columnar mesophase of triphenylene mesogens  

NASA Astrophysics Data System (ADS)

A new phenomenon was found for the alignment change of hexagonal columnar (Colh) mesophase of a typical discotic liquid crystal of triphenylene derivatives, which is caused by a polarizing infrared laser irradiation with a wavelength to excite the vibrational mode of the selected chemical bond in the mesogen. A series of experiments has revealed that the polarization direction of incident laser is correlated to the molecular alignment generated by the irradiation, where the molecules are reoriented in a way that the molecules no longer absorb the incidence. The resultant new domain has a certain level of uniformity for the alignment from an optical point of view and remains for several hours to minutes depending on the temperature against the isotoropization. The manual scanning of the beam successfully gives uniform domains with a shape and one can generate a character "H", for example, with lath-like shaped uniform domains in the mesophase film. It was found that such new domains could be freezed into the polymer film by photopolymerization when the mesogens have polymerizable groups in the molecular flamework. This strongly indicate that the combination of the infrared control of the molecular alignment of Colh mesophase and the following photopolymerization could realize highly functional polymer films where the structured domains with a variety of shapes and alignments are assembled in the film. Recently, it was also demonstrated that a homeotropic domain could be generated using a circularly polarized incidence at 6.18 ?m which corresponds to the wavelength to excite the aromatic C-C stretching band, being coincident with the relation of the alignment to the polarization direction of incidence.

Shimizu, Y.; Monobe, H.; Hori, H.; Awazu, K.

2005-08-01

227

Real-Time Optical Hough Transform and Morphological Inspection Techniques.  

NASA Astrophysics Data System (ADS)

A real-time optical Hough transform inspection processor is described and applied to the industrial case study of the inspection of cigarette packages. The inspections are performed in real-time using a color Epson liquid crystal television as the input spatial light modulator. A new selective, real-time edge-enhancement technique is used to enhance edges only at the selected orientations which will Hough transform to peaks (this maximizes the signal to noise ratio in the Hough transform output). Several slices of the Hough transform are generated in parallel with a new computer generated hologram utilizing 1D modulated error diffusion. We benchmark our Hough transform processor with the inspection of 100 sample cigarette packages. Correct classification of all the packages (with defects that we intended to inspect for) was attained. We also discuss the confidence with which we can apply our laboratory sample set results to the industrial installation of our inspection processor. Extensions of the Hough transform are also described which generalize the Hough space to recognize shapes other than straight lines (e.g. circles, ellipses). We propose a new high speed acousto-optic architecture to implement these generalized Hough transforms. We also describe how the exact position of input lines can be extracted from Hough transform peak data. Typically, only the contour on which an input line resides is extracted from Hough data. Digital simulations illustrating both generalized Hough transformations and determination of input line position from Hough data are presented. Basic morphological transformations and their real-time optical implementation are discussed. We describe how morphological transformations are useful in inspection and show digital simulations and optical results of an inspection application (string detection in chopped tobacco) where morphological transformations are used.

Richards, Jeffrey Scott

228

Precision alignment device  

DOEpatents

Apparatus for providing automatic alignment of beam devices having an associated structure for directing, collimating, focusing, reflecting, or otherwise modifying the main beam. A reference laser is attached to the structure enclosing the main beam producing apparatus and produces a reference beam substantially parallel to the main beam. Detector modules containing optical switching devices and optical detectors are positioned in the path of the reference beam and are effective to produce an electrical output indicative of the alignment of the main beam. This electrical output drives servomotor operated adjustment screws to adjust the position of elements of the structure associated with the main beam to maintain alignment of the main beam.

Jones, Nelson E. (Huntington Beach, CA)

1990-01-01

229

Precision alignment device  

DOEpatents

Apparatus for providing automatic alignment of beam devices having an associated structure for directing, collimating, focusing, reflecting, or otherwise modifying the main beam. A reference laser is attached to the structure enclosing the main beam producing apparatus and produces a reference beam substantially parallel to the main beam. Detector modules containing optical switching devices and optical detectors are positioned in the path of the reference beam and are effective to produce an electrical output indicative of the alignment of the main beam. This electrical output drives servomotor operated adjustment screws to adjust the position of elements of the structure associated with the main beam to maintain alignment of the main beam. 5 figs.

Jones, N.E.

1988-03-10

230

Optical detection techniques and light delivery with UV LEDs and optical fibres  

Microsoft Academic Search

Following the recent introduction of AlGaN\\/GaN based ultraviolet Light Emitting Diodes (UV-LEDs) in the 250 nm to 350 nm wavelength region, a wide range of research activities have begun. For example, using the high levels of power of available UV-light, chemical reactions can be stimulated. However, when optical detection techniques are considered, light intensity and wavelength accuracy are more important

M. Belz; F. A. Klein; H. S. Eckhardt; K.-F. Klein; D. Dinges; K. T. V. Grattan

2007-01-01

231

Hybrid technique for enhanced optical ranging in turbid water environments  

NASA Astrophysics Data System (ADS)

A hybrid approach is described that enhances the performance of an underwater optical ranging system. This approach uses high-frequency modulation and a spatial delay line filter to suppress unwanted backscatter. A dual frequency approach is also implemented to reduce the effects of forward scatter and remove the ambiguity associated with using the phase of the single, high-frequency modulation envelope to measure range. Controlled laboratory experiments were conducted to evaluate the effectiveness of the hybrid technique to reject multiple scattered light and improve range precision. The experimental results were compared with data generated from a theoretical model developed to predict the performance of the technique as a function of system and environmental variables. Model and experimental results are shown that reveal the ability of the approach to provide accurate ranging to an underwater object in a variety of water environments. Model predictions also indicate that advancements in transmitter and receiver technology will extend the range and improve the accuracy of the technique beyond what has been achieved thus far.

Lee, Robert W.; Laux, Alan; Mullen, Linda J.

2014-05-01

232

Beam alignment with the axis of a rotation stage for laser fabrication of microcircular structures  

NASA Astrophysics Data System (ADS)

An optical technique to align laser beam with the axis of a rotating stage is proposed for laser fabrication of circular microstructures. The laser beam is first aligned parallel to the rotation axis and subsequently adjusted to coincide with the axis. An optical arrangement consisting of two quadrant photodiodes for the x- and y-directions and a specially designed beam splitter is utilized for the alignment. Mathematical modeling of the alignment system is carried out to estimate alignment errors caused by misalignment of mirror surfaces in the beam path. It is shown that parallelness of the laser beam to the rotation axis is a key factor to reduce alignment errors. The proposed method was applied to a microstereolithography system and proved that the laser beam can be aligned within a distance of about 25 ?m from the rotation axis.

Jeong, Sung-Jin; Lee, Sun-Kyu; Jeong, Sung-Ho

2004-07-01

233

Coherent microscopy by laser optical feedback imaging (LOFI) technique O. Hugon, F. Joud1  

E-print Network

1 Coherent microscopy by laser optical feedback imaging (LOFI) technique O. Hugon, F. Joud1 , E.hugon@ujf-grenoble.fr Abstract The application of the non conventional imaging technique LOFI (Laser Optical Feedback Imaging (Laser Optical Feedback Imaging) was developed [13] and has been used for miscellaneous applications [14

Boyer, Edmond

234

Can optical remote sensing techniques detect air contaminants?  

SciTech Connect

The American Petroleum Institute (API) is sponsoring a program to evaluate if and how optical remote sensing techniques can be used to detect air contaminant emissions at a processing facility. This study is also gathering database information to assess whether dispersion modeling accurately depicts air plume migrations within a petrochemical site. In early 1995, an initial field study was conducted at an open field site (Duke Forest, North Carolina). To duplicate actual air contaminant transport, tracer gas was released from simulated point, area and volume sources. Tracer gas bag samples and optical remote sensing (ORS) measurements located up to 200 m from the source captured samples and gathered data. Using results from the first test, API moved forward with a second field study, Project OPTEX (Operational Petrochemical Tracer Experiment). This field study investigated and tried to duplicate actual air contaminant migrations occurring within an operating facility. In Project OPTEX, researchers used open-path Fourier transform infrared (OP-FTIR) spectroscopy to infer air contaminant emissions in an actual industrial environment. Information gathered from this study would then be used to model and verify air plume migrations from plant sources and to beyond the fenceline.

Paine, R.J. [ENSR Corp., Acton, MA (United States); Zwicker, J.O. [Remote Sensing-Air, St. Louis, MO (United States); Feldman, H.J. [American Petroleum Inst., Washington, DC (United States)

1998-01-01

235

Tumor Functional and Molecular Imaging Utilizing Ultrasound and Ultrasound-Mediated Optical Techniques  

PubMed Central

Tumor functional and molecular imaging has significantly contributed to cancer preclinical research and clinical applications. Among typical imaging modalities, ultrasonic and optical techniques are two commonly used methods; both share several common features such as cost efficiency, absence of ionizing radiation, relatively inexpensive contrast agents, and comparable maximum-imaging depth. Ultrasonic and optical techniques are also complementary in imaging resolution, molecular sensitivity, and imaging space (vascular and extravascular). The marriage between ultrasonic and optical techniques takes advantages of both techniques. This review introduces tumor functional and molecular imaging using microbubble-based ultrasound and ultrasound-mediated optical imaging techniques. PMID:23219728

Yuan, Baohong; Rychak, Joshua

2014-01-01

236

Magnetically determined particle alignment factors of sintered rare-earth cobalt permanent magnets  

Microsoft Academic Search

Values for the particle alignment factor have been obtained, during the past few years, by several workers.1, 2, 3, 4 The various techniques which have been used include magnetic, x-ray, and optical experiments. However, particle alignment factors are not now routinely obtained during the processing of permanent magnets. There is a requirement for ’’real time’’ feedback for production purposes, and

C. W. Searle; V. Davis; R. D. Hutchens

1982-01-01

237

Response Surface Methods for Spatially-Resolved Optical Measurement Techniques  

NASA Technical Reports Server (NTRS)

Response surface methods (or methodology), RSM, have been applied to improve data quality for two vastly different spatial ly-re solved optical measurement techniques. In the first application, modern design of experiments (MDOE) methods, including RSM, are employed to map the temperature field in a direct-connect supersonic combustion test facility at NASA Langley Research Center. The laser-based measurement technique known as coherent anti-Stokes Raman spectroscopy (CARS) is used to measure temperature at various locations in the combustor. RSM is then used to develop temperature maps of the flow. Even though the temperature fluctuations at a single point in the flowfield have a standard deviation on the order of 300 K, RSM provides analytic fits to the data having 95% confidence interval half width uncertainties in the fit as low as +/-30 K. Methods of optimizing future CARS experiments are explored. The second application of RSM is to quantify the shape of a 5-meter diameter, ultra-light, inflatable space antenna at NASA Langley Research Center.

Danehy, P. M.; Dorrington, A. A.; Cutler, A. D.; DeLoach, R.

2003-01-01

238

Bit-by-bit optical code scrambling technique for secure optical communication.  

PubMed

We propose and demonstrate a novel bit-by-bit code scrambling technique based on time domain spectral phase encoding/decoding (SPE/SPD) scheme using only a single phase modulator to simultaneously generate and decode the code hopping sequence and DPSK data for secure optical communication application. In the experiment, 2.5-Gb/s DPSK data has been generated, decoded and securely transmitted over 34 km by scrambling five 8-chip, 20-Gchip/s Gold codes with prime-hop patterns. The proposed scheme can rapidly reconfigure the optical code hopping sequence bit-by-bit with the DPSK data, and thus it is very robust to conventional data rate energy detection and DPSK demodulation attack, exhibiting the potential to provide unconditional transmission security and realize even one-time pad. PMID:21369173

Wang, Xu; Gao, Zhensen; Wang, Xuhua; Kataoka, Nobuyuki; Wada, Naoya

2011-02-14

239

Novel failure analysis techniques using photon probing with a scanning optical microscope  

Microsoft Academic Search

Three new failure analysis techniques for integrated circuits (ICs) have been developed using localized photon probing with a scanning optical microscope (SOM). The first two are light-induced voltage alteration (LIVA) imaging techniques that (1) localize open-circuited and damaged junctions and (2) image transistor logic states. The third technique uses the SOM to control logic states optically from the IC backside.

Edward I. Cole Jr; Jerry M. Soden; James L. Rife; Daniel L. Barton; Christopher L. Henderson

1994-01-01

240

Development of random hole optical fiber and crucible technique optical fibers  

NASA Astrophysics Data System (ADS)

This dissertation reports the development of two new categories of optical fibers. These are the Random Hole Optical Fiber (RHOF) and the Crucible Technique Hybrid Fiber (CTF). The RHOF is a new class of microstructure fiber which possesses air holes which vary in diameter and location along the length of the fiber. Unlike all prior microstructure fibers, these RHOF do not have continuous air holes which extend throughout the fiber. The CTF is a method for incorporating glasses with vastly differing thermal properties into a single optical fiber. Each of these two classes of fiber brings a new set of optical characteristics into being. The RHOF exhibit many of the same guidance properties as the previously researched microstructure fibers, such as reduced mode counts in a large area core. CTF fibers show great promise for integrating core materials with extremely high levels of nonlinearity or gain. The initial goal of this work was to combine the two techniques to form a fiber with exceedingly high efficiency of nonlinear interactions. Numerous methods have been endeavored in the attempt to achieve the fabrication of the RHOF. Some of the methods include the use of sol-gel glass, microbubbles, various silica powders, and silica powders with the incorporation of gas producing agents. Through careful balancing of the competing forces of surface tension and internal pressure it has been possible to produce an optical fiber which guides light successfully. The optical loss of these fibers depends strongly on the geometrical arrangement of the air holes. Fibers with a higher number of smaller holes possess a markedly lower attenuation. RHOF also possess, to at least some degree the reduced mode number which has been extensively reported in the past for ordered hole fibers. Remarkably, the RHOF are also inherently pressure sensitive. When force is applied to an RHOF either isotropically, or on an axis perpendicular to the length of the fiber, a wavelength dependent loss is observed. This loss does not come with a corresponding response to temperature, rendering the RHOF highly anomalous in the area of fiber optic sensing techniques. Furthermore an ordered hole fiber was also tested to determine that this was not merely a hitherto undisclosed property of all microstructure fibers. Crucible technique fibers have also been fabricated by constructing an extremely thick walled silica tube, which is sealed at the bottom. A piece of the glass that is desired for the core (such as Lead Indium Phosphate) is inserted into the hole which is in the center of the tube. The preform is then drawn on an fiber draw tower, resulting in a fiber with a core consisting of a material which has a coefficient of thermal expansion (CTE) or a melting temperature (Tm) which is not commonly compatible with those of silica.

Kominsky, Daniel

241

The effect of initial alignment on the optical properties of Fe3O4 nanoparticles doped in nematic liquid crystals  

NASA Astrophysics Data System (ADS)

Recently the nonlinear effects of the different materials doped liquid crystals are more interesting. In all previous works, nonlinearity of samples with the homeotropic alignment is investigated because of the larger component of the refractive index in this direction. Here, there are spherical Fe3O4 nanoparticles that have both parallel and perpendicular components. We were looking for the effect of initial alignment on the nonlinearity of pure and doped nematic liquid crystals (NLCs). The experimental results emphasize, even the same compositional percentage of nanoparticles prepared by two different alignment configurations are showing different results when dispersed in the same NLCs. Comparing nonlinear studies, the magnitude of nonlinear refraction index, n2 and nonlinear absorption coefficient, ? increase 102 and 101 times, respectively, in homeotropic alignment samples and the sign of these parameters is changed rather than homogeneous ones.

Dehghani, Z.; Iranizad, E. Saievar

2014-02-01

242

In situ growth of aligned CdS nanowire arrays on Cd foil and their optical and electron field emission properties  

SciTech Connect

Aligned CdS nanowire arrays have been fabricated directly on a Cd foil via a simple solvothermal method. The metal Cd foil serves as both the Cd source and substrate during fabrication of the aligned CdS nanowire arrays. The morphology, structure, and composition of the samples are characterized by x-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive x-ray spectroscopy, and selected-area electron diffraction, and the results reveal the formation of aligned single-crystalline CdS nanowires with uniform diameters of 20-40 nm. The photoluminescence and Raman spectra disclose the optical properties of the products and the possible growth mechanism is suggested. The electron field emission properties are also investigated and analyzed. The screening effect is observed to play a vital role in the electron field emission properties due to the coalescent ends of the nanowires. The simple synthesis methodology in conjunction with the good field emission and optical properties makes the materials both scientifically and technologically interesting.

Qian, G. X.; Hung, T. F.; Chu, Paul K. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Huo, K. F. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Hubei Province Key Laboratory of Refractories and Ceramics Ministry, Province Jointly-Constructed Cultivation Base for State Key Laboratory, College of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Fu, J. J. [Hubei Province Key Laboratory of Refractories and Ceramics Ministry, Province Jointly-Constructed Cultivation Base for State Key Laboratory, College of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China)

2008-07-01

243

Fabrication of nanowire channels with unidirectional alignment and controlled length by a simple, gas-blowing-assisted, selective-transfer-printing technique.  

PubMed

A printing-based lithographic technique for the patterning of V(2)O(5) nanowire channels with unidirectional orientation and controlled length is introduced. The simple, directional blowing of a patterned polymer stamp with N(2) gas, inked with randomly distributed V(2)O(5) nanowires, induces alignment of the nanowires perpendicular to the long axis of the line patterns. Subsequent stamping on the amine-terminated surface results in the selective transfer of the aligned nanowires with a controlled length corresponding to the width of the relief region of the polymer stamp. By employing such a gas-blowing-assisted, selective-transfer-printing technique, two kinds of device structures consisting of nanowire channels and two metal electrodes with top contact, whereby the nanowires were aligned either parallel (parallel device) or perpendicular (serial device) to the current flow in the conduction channel, are fabricated. The electrical properties demonstrate a noticeable difference between the two devices, with a large hysteresis in the parallel device but none in the serial device. Systematic analysis of the hysteresis and the electrical stability account for the observed hysteresis in terms of the proton diffusion in the water layer of the V(2)O(5) nanowires, induced by the application of an external bias voltage higher than a certain threshold voltage. PMID:19197970

Kim, Yong-Kwan; Kang, Pil Soo; Kim, Dae-Il; Shin, Gunchul; Kim, Gyu Tae; Ha, Jeong Sook

2009-03-01

244

Response Surface Methods For Spatially-Resolved Optical Measurement Techniques  

NASA Technical Reports Server (NTRS)

Response surface methods (or methodology), RSM, have been applied to improve data quality for two vastly different spatially-resolved optical measurement techniques. In the first application, modern design of experiments (MDOE) methods, including RSM, are employed to map the temperature field in a direct-connect supersonic combustion test facility at NASA Langley Research Center. The laser-based measurement technique known as coherent anti-Stokes Raman spectroscopy (CARS) is used to measure temperature at various locations in the combustor. RSM is then used to develop temperature maps of the flow. Even though the temperature fluctuations at a single point in the flowfield have a standard deviation on the order of 300 K, RSM provides analytic fits to the data having 95% confidence interval half width uncertainties in the fit as low as +/- 30 K. Methods of optimizing future CARS experiments are explored. The second application of RSM is to quantify the shape of a 5-meter diameter, ultra-lightweight, inflatable space antenna at NASA Langley Research Center. Photogrammetry is used to simultaneously measure the shape of the antenna at approximately 500 discrete spatial locations. RSM allows an analytic model to be developed that describes the shape of the majority of the antenna with an uncertainty of 0.4 mm, with 95% confidence. This model would allow a quantitative comparison between the actual shape of the antenna and the original design shape. Accurately determining this shape also allows confident interpolation between the measured points. Such a model could, for example, be used for ray tracing of radio-frequency waves up to 95 GHz. to predict the performance of the antenna.

Danehy, P. M.; Dorrington, A. A.; Cutler, A. D.; DeLoach, R.

2003-01-01

245

Remote sensing of stress using electro-optics imaging technique  

NASA Astrophysics Data System (ADS)

Emotional or physical stresses induce a surge of adrenaline in the blood stream under the command of the sympathetic nerve system, which, cannot be suppressed by training. The onset of this alleviated level of adrenaline triggers a number of physiological chain reactions in the body, such as dilation of pupil and an increased feed of blood to muscles etc. This paper reports for the first time how Electro-Optics (EO) technologies such as hyperspectral [1,2] and thermal imaging[3] methods can be used for the detection of stress remotely. Preliminary result using hyperspectral imaging technique has shown a positive identification of stress through an elevation of haemoglobin oxygenation saturation level in the facial region, and the effect is seen more prominently for the physical stressor than the emotional one. However, all results presented so far in this work have been interpreted together with the base line information as the reference point, and that really has limited the overall usefulness of the developing technology. The present result has highlighted this drawback and it prompts for the need of a quantitative assessment of the oxygenation saturation and to correlate it directly with the stress level as the top priority of the next stage of research.

Chen, Tong; Yuen, Peter; Hong, Kan; Tsitiridis, Aristeidis; Kam, Firmin; Jackman, James; James, David; Richardson, Mark; Oxford, William; Piper, Jonathan; Thomas, Francis; Lightman, Stafford

2009-09-01

246

A Robust Continuous-Time Multi-Dithering Technique for Laser Communications using Adaptive Optics  

E-print Network

A Robust Continuous-Time Multi-Dithering Technique for Laser Communications using Adaptive Optics communication links with adaptive past, such as multi-dithering [4] and sequential perturbations [8], optics-dither algorithm for adaptive optics robustly and in continuous-time. Similar architectures have been The inherent

Cauwenberghs, Gert

247

A 660 GHz Local Oscillator Subsystem: Design, Testing and Alignment  

NASA Astrophysics Data System (ADS)

A 660 GHz local oscillator (LO) sub-system for the Submillimeter Array is designed, tested and aligned in the laboratory by optical and radio alignment. The LO unit employs a cascade tuneless frequency doubler-tripler based on the planar GaAs Schottky diode technology. It is found that a phase shifter inserted between the first and second multiplier stages can improve the frequency response of the unit, reduce the ripples due to the impedance mismatch between the 2 stages. A new technique for the optical and radio alignment of the beam emerging from the unit is also introduced. A near-field scanner which measures the complex beam pattern facilitates the final alignment and helps to verify proper focusing of the LO output beam.

Chang, Su-Wei; Tong, Cheuk-Yu Edward; Hedden, Abigail; Hwang, Yuh-Jing; Blundell, Raymond

2009-10-01

248

Metrology optical power budgeting in SIM using statistical analysis techniques  

Microsoft Academic Search

The Space Interferometry Mission (SIM) is a space-based stellar interferometry instrument, consisting of up to three interferometers, which will be capable of micro-arc second resolution. Alignment knowledge of the three interferometer baselines requires a three-dimensional, 14-leg truss with each leg being monitored by an external metrology gauge. In addition, each of the three interferometers requires an internal metrology gauge to

Gary M. Kuan

2008-01-01

249

Repeatable alignment--Part II: Consistent photographic alignment accuracy.  

PubMed

Predictable aesthetic results necessitate the implementation of various dental principles for tooth display, alignment, and relative proportion. In order to ensure accurate communication, clinicians must clearly document visual information regarding violations of these tooth arrangement principles via dental photography. Accuracy in the alignment of photographs is crucial for subsequent treatment planning and evaluation. This article discusses several alignment complications that may be encountered while capturing diagnostic dental photographs. A technique for repeatable alignment accuracy is proposed. PMID:14509098

Snow, Stephen R

2003-08-01

250

Study of optical techniques for the Ames unitary wind tunnel, part 7  

NASA Technical Reports Server (NTRS)

A summary of optical techniques for the Ames Unitary Plan wind tunnels are discussed. Six optical techniques were studied: Schlieren, light sheet and laser vapor screen, angle of attack, model deformation, infrared imagery, and digital image processing. The study includes surveys and reviews of wind tunnel optical techniques, some conceptual designs, and recommendations for use of optical methods in the Ames Unitary Plan wind tunnels. Particular emphasis was placed on searching for systems developed for wind tunnel use and on commercial systems which could be readily adapted for wind tunnels. This final report is to summarize the major results and recommendations.

Lee, George

1993-01-01

251

Differential Deposition Technique for Figure Corrections in Grazing Incidence X-ray Optics  

NASA Technical Reports Server (NTRS)

A differential deposition technique is being developed to correct the low- and mid-spatial-frequency deviations in the axial figure profile of Wolter type grazing incidence X-ray optics. These deviations arise due to various factors in the fabrication process and they degrade the performance of the optics by limiting the achievable angular resolution. In the differential deposition technique, material of varying thickness is selectively deposited along the length of the optic to minimize these deviations, thereby improving the overall figure. High resolution focusing optics being developed at MSFC for small animal radionuclide imaging are being coated to test the differential deposition technique. The required spatial resolution for these optics is 100 m. This base resolution is achievable with the regular electroform-nickel-replication fabrication technique used at MSFC. However, by improving the figure quality of the optics through differential deposition, we aim at significantly improving the resolution beyond this value.

Kilaru, Kiranmayee; Ramsey, Brian D.; Gubarev, Mikhail

2009-01-01

252

Comparison of two optical techniques for label-free detection of biomolecular microarrays on solids  

E-print Network

. Optical techniques have played an instrumental role at almost every stage of advancement in life sciencesComparison of two optical techniques for label-free detection of biomolecular microarrays on solids on solid supports, we are in an exciting era of life sciences when molecular-level and cellular level

Zhu, Xiangdong

253

Laser pointing stability measured by an oblique-incidence optical transmittance difference technique  

E-print Network

Laser pointing stability measured by an oblique-incidence optical transmittance difference an oblique-incidence optical transmittance technique for determining the pointing stability of a laser. In this technique, we follow the angular drift of a monochromatic laser beam by measuring the relative changes

Zhu, Xiangdong

254

Towards an accurate alignment of the VLBI frame and the future Gaia frame - VLBI observations of optically-bright weak extragalactic radio sources: Status and future prospects  

NASA Astrophysics Data System (ADS)

The space astrometry mission Gaia will construct a dense optical QSO-based celestial reference frame. For consistency between optical and radio positions, it will be important to align the Gaia and VLBI frames with the highest accuracy. However, the number of quasars that are bright in optical wavelength (for the best position with Gaia), that have a compact core (to be detectable on VLBI scales), and that do not exhibit complex structures (to ensure a good astrometric quality), is currently rather limited (Bourda et al. 2008). It was hence realized that the densification of the list of such objects was necessary. Accordingly, we initiated a multi-step VLBI observational project, dedicated to finding additional suitable radio sources for aligning the two frames. The sample consists of ~450 optically-bright radio sources, which have been selected by cross-correlating optical and radio catalogs. The initial observations, aimed at checking whether these sources are detectable with VLBI, and conducted with the European VLBI Network in 2007, showed an excellent ~90% detection rate (Bourda et al. 2010). The second step, dedicated to extract the most point-like sources of the sample, by imaging their VLBI structures, was initiated in 2008. About 25% of the detected targets were observed with the Global VLBI array during a pilot imaging experiment, revealing ~50% of them as point-like sources on VLBI scales (Bourda et al. 2011). The rest of the sources were observed in March and November 2010 with the final imaging experiment planned in February 2011. In this paper, we present the results of these two imaging campaigns from 2010. And finally, the third step of this project, dedicated to measuring accurately the VLBI position of the most point-like sources of the sample, will be engaged in 2011.

Bourda, G.; Collioud, A.; Charlot, P.; Porcas, R.; Garrington, S.

2011-07-01

255

Feedback controlled single wavelength interrogation technique for miniature all-silica EFPI fibre optic pressure sensors  

Microsoft Academic Search

This paper proposes a novel technique to stabilise the output wavelength of a tuneable laser source to operate always in the linear range of a miniature all-silica Extrinsic Fabry-Perot Interferometric (EFPI) fibre optic pressure sensor. The technique is based on a fibre optic hybrid sensor, which consists of a miniature all-silica EFPI fibre optic pressure sensor with an incorporated in-Fibre

K. Bremer; E. Lewis; G. Leen; B. Moss; S. Lochmann; I. Mueller

2010-01-01

256

Correlation-based continuous-wave techniques for fiber optic distributed sensing with a high spatial resolution  

Microsoft Academic Search

We have proposed and developed a technique to synthesize optical coherence function into arbitrary shapes. By using the technique, Synthesis of Optical Coherence Function, distributed sensing schemes can be provided without any mechanical moving parts nor calculation. Applying the technique, we have proposed and studied a scheme to diagnose fiber optic subscribe networks. Fiber optic distributed stress sensing systems have

Kazuo Hotate

2002-01-01

257

Stabilized Ultrafast Pulse Generation and Optical Frequency Combs Techniques  

E-print Network

& Photonics Center for Research & Education in Optics & Lasers (CREOL) University of Central Florida #12;2 Outline · Introduction to Diode Lasers, Modelocking, & Motivation · How to Make Short Pulses from Laser-Field Spectrum Modelocked Spectrum Modulator #12;8 Motivation · What are optical frequency combs? ­ Coherent, cw

Van Stryland, Eric

258

Simplified technique for polarization-sensitive optical coherence tomography  

Microsoft Academic Search

We have developed a fiber-based polarization-sensitive optical coherence tomography (PS-OCT) system using non- polarization-maintaining fiber and a single detector, in which the polarization-sensitive components are implemented entirely in bulk optics in the sample arm.

Jonathan E. Roth; Jennifer A. Kozak; Siavash Yazdanfar; Andrew M. Rollins; Joseph A. Izatt

2001-01-01

259

Novel header processing technique and wavelength routing performance of an optical packet switch with a multibit optical digital-to-analog conversion-type header processor  

Microsoft Academic Search

Processing technique for a multibit optical digital-to-analog converter by processing every two-bits is proposed. Wavelength routing performance of an optical packet switch with four-bit optical header processor was realized.

H. Uenohara; T. Seki; K. Kobayashi

2004-01-01

260

Aligning and maintaining the optics for the James Webb Space Telescope (JWST) on-orbit: the wavefront sensing and control concept of operations  

NASA Astrophysics Data System (ADS)

From its orbit around the Earth-Sun second Lagrange point some million miles from Earth, the James Webb Space Telescope (JWST) will be uniquely suited to study early galaxy and star formation with its suite of infrared instruments. To maintain exceptional image quality using its 6.6 meter segmented primary mirror, wavefront sensing and control (WFS&C) is vital to ensure the optical alignment of the telescope throughout the mission. WFS&C design architecture includes using the Near-Infrared Camera (NIRCam) to provide imagery for ground-resident image processing algorithms which determine the optimal alignment of the telescope. There are two distinct mission phases for WFS&C, both of which use algorithms and NIRCam imagery to determine the required segment updates. For the first phase, WFS&C commissioning, the telescope is taken from its initial deployed state with each of the 18 primary mirror segments acting like independent telescopes, to its final phased state with each segment acting in concert as a part of a single mirror. The second phase, Wavefront Monitoring and Maintenance, continues for the rest of the mission. Here the wavefront quality is evaluated, and when needed, the mirror positions are updated to bring it back to an optimal configuration. This paper discusses the concept of operations for the commissioning and on-going maintenance of the telescope alignment using WFS&C.

Contos, Adam R.; Acton, D. Scott; Atcheson, Paul D.; Barto, Allison A.; Lightsey, Paul A.; Shields, Duncan M.

2006-06-01

261

Detection and alignment of 3D domain swapping proteins using angle-distance image-based secondary structural matching techniques.  

PubMed

This work presents a novel detection method for three-dimensional domain swapping (DS), a mechanism for forming protein quaternary structures that can be visualized as if monomers had "opened" their "closed" structures and exchanged the opened portion to form intertwined oligomers. Since the first report of DS in the mid 1990s, an increasing number of identified cases has led to the postulation that DS might occur in a protein with an unconstrained terminus under appropriate conditions. DS may play important roles in the molecular evolution and functional regulation of proteins and the formation of depositions in Alzheimer's and prion diseases. Moreover, it is promising for designing auto-assembling biomaterials. Despite the increasing interest in DS, related bioinformatics methods are rarely available. Owing to a dramatic conformational difference between the monomeric/closed and oligomeric/open forms, conventional structural comparison methods are inadequate for detecting DS. Hence, there is also a lack of comprehensive datasets for studying DS. Based on angle-distance (A-D) image transformations of secondary structural elements (SSEs), specific patterns within A-D images can be recognized and classified for structural similarities. In this work, a matching algorithm to extract corresponding SSE pairs from A-D images and a novel DS score have been designed and demonstrated to be applicable to the detection of DS relationships. The Matthews correlation coefficient (MCC) and sensitivity of the proposed DS-detecting method were higher than 0.81 even when the sequence identities of the proteins examined were lower than 10%. On average, the alignment percentage and root-mean-square distance (RMSD) computed by the proposed method were 90% and 1.8Å for a set of 1,211 DS-related pairs of proteins. The performances of structural alignments remain high and stable for DS-related homologs with less than 10% sequence identities. In addition, the quality of its hinge loop determination is comparable to that of manual inspection. This method has been implemented as a web-based tool, which requires two protein structures as the input and then the type and/or existence of DS relationships between the input structures are determined according to the A-D image-based structural alignments and the DS score. The proposed method is expected to trigger large-scale studies of this interesting structural phenomenon and facilitate related applications. PMID:20976204

Chu, Chia-Han; Lo, Wei-Cheng; Wang, Hsin-Wei; Hsu, Yen-Chu; Hwang, Jenn-Kang; Lyu, Ping-Chiang; Pai, Tun-Wen; Tang, Chuan Yi

2010-01-01

262

Extending bandwidth of optical emitters using active matching technique  

NASA Astrophysics Data System (ADS)

An optical transmitter particularly suited for high frequency applications is disclosed. The optical transmitter successfully operates in harsh environments such as those found in avionic applications. The optical transmitter employs an LED as a light source which cooperates with an active bandpass amplifier to provide a relatively wide bandwidth from about 250 MHz to about at least 1.35 GHz. The bandpass amplifier is selected to have a slope characteristic which is complementary to a roll-off characteristic of the LED and compensates for the high frequency loss of the LED. The slope characteristic of the bandpass amplifier predominates at the high frequencies of the response of the optical transmitter, whereas the frequency response of the LED dominates at the lower frequencies of the response.

Gershman, Vladimir; Daryoush, Afshin S.; Rosen, Warren A.

1993-05-01

263

Advanced materials and techniques for fibre-optic sensing  

NASA Astrophysics Data System (ADS)

Fibre-optic monitoring systems came of age in about 1999 upon the emergence of the world's first significant commercialising company - a spin-out from the UK's collaborative MAST project. By using embedded fibre-optic technology, the MAST project successfully measured transient strain within high-performance composite yacht masts. Since then, applications have extended from smart composites into civil engineering, energy, military, aerospace, medicine and other sectors. Fibre-optic sensors come in various forms, and may be subject to embedment, retrofitting, and remote interrogation. The unique challenges presented by each implementation require careful scrutiny before widespread adoption can take place. Accordingly, various aspects of design and reliability are discussed spanning a range of representative technologies that include resonant microsilicon structures, MEMS, Bragg gratings, advanced forms of spectroscopy, and modern trends in nanotechnology. Keywords: Fibre-optic sensors, fibre Bragg gratings, MEMS, MOEMS, nanotechnology, plasmon.

Henderson, Philip J.

2014-06-01

264

Feedback Stabilized Interrogation Technique for EFPI\\/FBG Hybrid Fiber-Optic Pressure and Temperature Sensors  

Microsoft Academic Search

This paper discusses a Single Wavelength Interroga- tion (SWI) technique used to measure fast changing pressure re- lated signals and over a large operational temperature range. The novel technique is based on a fiber-optic pressure and temperature hybrid sensor, and a feedback stabilization technique for a tunable laser source. The fiber-optic hybrid sensor consists of a miniature diaphragm based all-silica

Kort Bremer; Elfed Lewis; Gabriel Leen; Brian Moss; Steffen Lochmann; Ingo A. R. Mueller

2012-01-01

265

Real-time high-resolution measurement of collagen alignment in dynamically loaded soft tissue  

NASA Astrophysics Data System (ADS)

A technique for creating maps of the direction and strength of fiber alignment in collagenous soft tissues is presented. The method uses a division of focal plane polarimeter to measure circularly polarized light transmitted through the tissue. The architecture of the sensor allows measurement of the retardance and fiber alignment at the full frame rate of the sensor without any moving optics. The technique compares favorably to the standard method of using a rotating polarizer. How the new technique enables real-time capture of the full angular spread of fiber alignment and retardance under various cyclic loading conditions is illustrated.

York, Timothy; Kahan, Lindsey; Lake, Spencer P.; Gruev, Viktor

2014-06-01

266

An alternative technique for optically stimulated luminescence (OSL) experiment  

Microsoft Academic Search

An alternative technique is developed for observation of OSL by linearly increasing the intensity of the excitation source during readout. The technique allows the observation of OSL signals in the form of peaks unlike the decaying curves. The parameters of the new OSL peak can be used to obtain the intensity and the lifetime of the decay. With the technique

Enver Bulur

1996-01-01

267

Design, alignment, and deployment of the Hobby Eberly Telescope prime focus instrument package  

NASA Astrophysics Data System (ADS)

The Hobby-Eberly Telescope (HET) is undergoing an upgrade to increase the field of view to 22 arc-minutes with the dark energy survey HETDEX the initial science goal [1]. Here we report on the design, alignment, and deployment of a suite of instruments located at prime focus of the upgraded HET. This paper reviews the integration of motion control electronics and software and alignment of those electromechanical systems. Use of laser trackers, alignment telescopes, and other optical alignment techniques are covered. Deployment onto the upgraded telescope is discussed.

Vattiat, Brian; Hill, Gary J.; Lee, Hanshin; Moreira, Walter; Drory, Niv; Ramsey, Jason; Elliot, Linda; Landriau, Martin; Perry, Dave M.; Savage, Richard; Kriel, Herman; Häuser, Marco; Mangold, Florian

2014-07-01

268

Alignment reference device  

DOEpatents

An alignment reference device provides a collimated laser beam that minimizes angular deviations therein. A laser beam source outputs the beam into a single mode optical fiber. The output end of the optical fiber acts as a source of radiant energy and is positioned at the focal point of a lens system where the focal point is positioned within the lens. The output beam reflects off a mirror back to the lens that produces a collimated beam.

Patton, Gail Y. (Sunnyvale, CA); Torgerson, Darrel D. (Palo Alto, CA)

1987-01-01

269

Performance enhancement of multiple-gate ZnO metal-oxide-semiconductor field-effect transistors fabricated using self-aligned and laser interference photolithography techniques  

PubMed Central

The simple self-aligned photolithography technique and laser interference photolithography technique were proposed and utilized to fabricate multiple-gate ZnO metal-oxide-semiconductor field-effect transistors (MOSFETs). Since the multiple-gate structure could improve the electrical field distribution along the ZnO channel, the performance of the ZnO MOSFETs could be enhanced. The performance of the multiple-gate ZnO MOSFETs was better than that of the conventional single-gate ZnO MOSFETs. The higher the drain-source saturation current (12.41 mA/mm), the higher the transconductance (5.35 mS/mm) and the lower the anomalous off-current (5.7 ?A/mm) for the multiple-gate ZnO MOSFETs were obtained. PMID:24948884

2014-01-01

270

Performance enhancement of multiple-gate ZnO metal-oxide-semiconductor field-effect transistors fabricated using self-aligned and laser interference photolithography techniques.  

PubMed

The simple self-aligned photolithography technique and laser interference photolithography technique were proposed and utilized to fabricate multiple-gate ZnO metal-oxide-semiconductor field-effect transistors (MOSFETs). Since the multiple-gate structure could improve the electrical field distribution along the ZnO channel, the performance of the ZnO MOSFETs could be enhanced. The performance of the multiple-gate ZnO MOSFETs was better than that of the conventional single-gate ZnO MOSFETs. The higher the drain-source saturation current (12.41 mA/mm), the higher the transconductance (5.35 mS/mm) and the lower the anomalous off-current (5.7 ?A/mm) for the multiple-gate ZnO MOSFETs were obtained. PMID:24948884

Lee, Hsin-Ying; Huang, Hung-Lin; Tseng, Chun-Yen

2014-01-01

271

Evaluation of Mechanical Modal Characteristics Using Optical Techniques  

NASA Technical Reports Server (NTRS)

In this paper the sensitivity of embedded fiber optic sensors to changes in modal characteristics of plates is discussed. In order to determine the feasibility of embedded fiber Bragg gratings for the detection of modal shapes and modal frequencies, a comparison of holographically imaged modes and the detected dynamic strain from embedded fiber optic Bragg gratings is made. Time averaged optical holography is used for the detection of mechanical defects, or damage, in various aerospace components. The damage is detected by measuring an alteration in structural dynamics, which is visually apparent when using time-averaged holography. These shifts in the mode shapes, both in frequency of the resonance and spatial location of vibration nodes, are caused by changes in parameters that affect the structure's mechanical impedance, such as stiffness, mass and damping, resulting from cracks or holes. It is anticipated that embedded fiber optic sensor arrays may also be able to detect component damage by sensing these changes in modal characteristics. This work is designed to give an initial indication to the feasibility of damage detection through the monitoring of modal frequencies and mode shapes with fiber optic sensors.

Lekki, John; Adamovsky, Grigory; Flanagan, Patrick; Weiland, Ken

2002-01-01

272

Analyses of optical packet switching techniques based on nonlinear materials with respect to various label formats  

NASA Astrophysics Data System (ADS)

All-optical networks introduce the indisputable solution for future networking especially due to discarding slow and power-demanding electronic processing. Ultrafast data communications ultimately head towards all-optical packet data transfer and optical IP routing. In this paper, nonlinear switching techniques are evaluated with respects to particular types of nonlinear fibers with regards to their specific parameters. Optical packet labeling is discussed, considering label allocation between ITU-grid defined data wavelengths. Possible aspects of a highly-nonlinear fiber, untapered and tapered chalcogenide fibers integration into the optical switch were investigated both theoretically and experimentally.

Komanec, M.; Zvanovec, S.

2012-02-01

273

GMPLS-based dynamic OVPN technique in automatically switched optical network (ASON)  

NASA Astrophysics Data System (ADS)

Optical Virtual Private Network (OVPN) is an increasingly important application of Automatic Switched Optical Network (ASON). To meet the demands of today's different types of network services, dynamic OVPN technique is studied and two new functions are brought forward, which are dynamic connection management, and fast protection/restoration. We realize dynamic OVPN technique in the first ASON testbed in China, based on GMPLS signaling mechanism. The dynamic OVPN technique makes the optical network able to provide customers with reliable and flexible services by more functional and intelligent methods.

Zhu, Jia; Xu, Zhengchun; Li, Yanhe; Ren, Jian; Jiao, Yueguang; Zheng, Xiaoping; Zhang, Hanyi

2004-04-01

274

New phase-shift keying technique based on optical delay switching for microwave optical link  

Microsoft Academic Search

A new phase-shift keying configuration for a microwave optical link is presented. It is based on optical delay switching and consists of a light pulse source, a delay line, and a 2×1 light switch. A 2-Gb\\/s modulation at a carrier frequency of up to 40 GHz is made possible by using these fast optical devices

Seiji Fukushima; Yoshiyuki Doi; Tetsuichiro Ohno; Yutaka Matsuoka; Hiroaki Takeuchi

1999-01-01

275

High speed and low side lobe optical phased array steering by phase correction technique  

NASA Astrophysics Data System (ADS)

Laser beam scanners are important optical elements with a large variety of applications in the measurement techniques, optical communications, laser imaging ladar, etc. Agile beam steering of optical radiation using phased arrays offers significant advantages, such as weight, stability and power requirements over conventional beam steering systems. There are several kinds of optical phased array technology to be developed, such as Lithium tantalite phase shifters, lithium niobate electro-optic prism deflectors, and liquid crystal and ferroelectric liquid crystal phase modulations. However, one of the major drawbacks of these approaches is low light efficiencies because of the side lobes in far-field pattern of the steering beam. In this paper, a new low side lobe optical beam steering technique using phase correction technique is proposed. A stable and fast single-lobed far-field pattern in steering beam can be obtained from the optical phased array with a phase plate by optima design. It can result in a substantially increased light efficiency and beam quality. The quantitative calculation results of typical optical phased array are demonstrated. The low side lobe optical beam steering technology of optical phased array will benefit many practical applications such as laser ladar, laser communications and high resolution displays.

Jin, Yadong; Yan, Aimin; Hu, Zhijuan; Zhao, Zhenyu; Shi, Wangzhou

2013-09-01

276

Observing techniques for astronomical laser guide star adaptive optics  

SciTech Connect

We discuss astronomical observing requirements and their implementation using sodium-layer laser guide star adaptive optics. Specific issues requiring implementation include the ability to place the astronomical object at different locations within the field of view; reliable subtraction of Rayleigh-scattered light; efficient focusing; and stable point-spread-function characterization.

Max, C.E.; Macintosh, B.; Olivier, S.S.; Gavel, D.T.; Friedman, H.W.

1998-05-01

277

Optical techniques for the study of living tissue  

Microsoft Academic Search

The potential of light in diagnosis and therapy has been long recognised. With the advent of scientific progress in our understanding of light propagation and interaction with tissue and parallel major technological advances in how optical energy can be generated, detected and processed, this potential is being realised. Linking with this trend, this thesis is devoted to the investigation and

E. Margallo Balbás

2010-01-01

278

Multiplexed reflective-matched optical fiber grating interrogation technique  

Microsoft Academic Search

The multiplexed-reflective matched fiber grating interrogation technique was presented in this paper. The interrogation technique was based on the use of two (or more) wavelength-matched fiber Bragg gratings (FBGs) to receive the reflected signal from the sensing FBG. The two (or more) matched gratings were arranged parallelly and used as filters to convert wavelength into intensity encoded information for interrogation.

Yage Zhan; Shaolin Xue; Qinyu Yang

2007-01-01

279

Displacement measurements in structural elements by optical techniques  

Microsoft Academic Search

Speckle metrology and holographic interferometry (HI) have been used in several civil engineering applications. We present the results obtained by applying speckle photography (SP) to the study of two quadratic shearwalls with different boundary conditions, and the potential of the technique in the study of this kind of structures is described. The analysis of Young's fringes obtained with this technique

Rolando González-Peña; Rosa Mar??a Cibrián-Ortiz de Anda; Angel J Pino-Velazquez; José Soler-de la Cruz; Yhoama González-Jorge

2000-01-01

280

Global range alignment for ISAR  

Microsoft Academic Search

A new technique is developed for range alignment in inverse synthetic aperture radar (ISAR) imaging. The shifts made to the echoes are modeled as a polynomial, and the coefficients of this polynomial are chosen to optimize a global quality measure of range alignment. This technique is robust against noise and target scintillation, and avoids error accumulation. In addition, the shift

Junfeng Wang; D. Kasilingam

2003-01-01

281

Optical nonlinear properties of PbS nanoparticles studied by the Z-scan technique  

Microsoft Academic Search

The optical nonlinear properties of PbS nanoparticles in polyvinyl alcohol (PVA) sol were studied by the Z-scan technique with 50 ps pulses at 530 and 1060 nm, respectively. The sample under these two excitations shows quite contrasting nonlinear optical responses. The saturation absorption at 520 nm is observed while at 1060 nm the two-photon absorption. The optical limiting of PbS

Baolong Yu; Guosheng Yin; Congshan Zhu; Fuxi Gan

1998-01-01

282

A technique for detecting and locating polarisation nonuniformities in an anisotropic optical fibre  

SciTech Connect

One of the most important requirements for optical fibres as waveguiding media is uniformity. Polarisation-maintaining anisotropic fibres contain a special type of nonuniformity, which leads to polarisation cross-talk: optical power is transferred from one polarisation mode to the orthogonal mode. In this paper, we report a technique for detecting and locating such nonuniformities in a PANDA anisotropic single-mode fibre using polarised reflectometry. (fiber optics)

Burdin, V V; Konstantinov, Yurii A; Pervadchuk, Vladimir P; Smirnov, A S [Perm National Research Polytechnic University (PNRPU) (Russian Federation)

2013-06-30

283

Non-contact Technique of Optical Fiber Coating Removal with Hot Air Stream  

Microsoft Academic Search

SUMMARY We will discuss a novel non-contact removal technique of optical fiber coating in continuous and uninterrupted manner with hot air stream. We observed little degradation of the tensile strength of the optical fiber after removing the pro- tective polymer coating and the mean breaking tensile strength of the stripped optical fiber using non-contact removal method was 5.1GPa.

Hyun-Soo PARK; Seihyoung LEE; Un-Chul PAEK; Youngjoo CHUNG

284

Air pollution monitoring with two optical remote sensing techniques in Mexico City  

Microsoft Academic Search

An open-path Fourier Transform Infrared (FTIR) and a Differential Optical Absorption Spectrometer (DOAS) were installed and simultaneously operated along a 426 m optical path in downtown Mexico City. O3 and SO2 were measured by both optical remote sensing techniques and the results from the comparison are presented. The instruments presented comparable sensitivities for O3 and an excellent agreement (R2 >

Michel Grutter; Edgar Flores-Jardines

2004-01-01

285

Pupil Alignment Considerations for Large, Deployable Space Telescopes  

NASA Technical Reports Server (NTRS)

For many optical systems the properties and alignment of the internal apertures and pupils are not critical or controlled with high precision during optical system design, fabrication or assembly. In wide angle imaging systems, for instance, the entrance pupil position and orientation is typically unconstrained and varies over the system s field of view in order to optimize image quality. Aperture tolerances usually do not receive the same amount of scrutiny as optical surface aberrations or throughput characteristics because performance degradation is typically graceful with misalignment, generally only causing a slight reduction in system sensitivity due to vignetting. But for a large deployable space-based observatory like the James Webb Space Telescope (JWST), we have found that pupil alignment is a key parameter. For in addition to vignetting, JWST pupil errors cause uncertainty in the wavefront sensing process that is used to construct the observatory on-orbit. Furthermore they also open stray light paths that degrade the science return from some of the telescope s instrument channels. In response to these consequences, we have developed several pupil measurement techniques for the cryogenic vacuum test where JWST science instrument pupil alignment is verified. These approaches use pupil alignment references within the JWST science instruments; pupil imaging lenses in three science instrument channels; and unique pupil characterization features in the optical test equipment. This will allow us to verify and crosscheck the lateral pupil alignment of the JWST science instruments to approximately 1-2% of their pupil diameters.

Bos, Brent J.; Ohl, Raymond G.; Kubalak, Daivd A.

2011-01-01

286

Study of formation and convective transport of aerosols using optical diagnostic technique  

E-print Network

The characteristics of liquid and solid aerosols have been intensively investigated by means of optical diagnostic techniques. Part I describes the characteristics of liquid aerosol formation formed by heat transfer fluids (HTFs) from bulk liquids...

Kim, Tae-Kyun

2004-09-30

287

Digital signal processing techniques for optical coherence tomography : OCT and OCT image enhancement  

E-print Network

Digital signal processing (DSP) techniques were developed to improve the flexibility, functionality, and image quality of ultrahigh resolution optical coherence tomography (OCT) systems. To reduce the dependence of OCT ...

Adler, Desmond Christopher, 1978-

2004-01-01

288

Development of X-ray lithography and nanofabrication techniques for III-V optical devices  

E-print Network

This dissertation covers the development of fabrication techniques for Bragg-grating-based integrated optical devices in III-V materials. Work on this rich family of devices has largely been limited to numerical analysis ...

Lim, Michael H. (Michael Hong)

2002-01-01

289

Nonlinear optical properties of liquid crystals probed by Z-scan technique  

Microsoft Academic Search

We present a review of experimental data on the nonlinear optical properties of thermotropic and lyotropic liquid crystals probed by the Z-scan technique. Depending on the time scale, different processes originate a nonlinear optical response. Particularly, at nanosecond range, the physical processes associated with the nonlinear response in thermotropics are not completely understood. In lyotropics, the nonlinear response at ms

F. L. S. Cuppo; A. M. Figueiredo Neto

2003-01-01

290

Thermal and Optical Properties of Yb - and Nd -Doped Phosphate Glasses Determined by Thermal Lens Technique  

Microsoft Academic Search

In this work, we study the thermal and optical prop- erties of ion-doped phosphates glasses using the thermal lens (TL) technique. Three samples were characterized: Nd -doped Q-98; Nd -doped Q-100; and Yb -doped QX. We report multiwave- length TL measurements for a more accuracy determination of the fluorescence quantum efficiency and temperature coefficient of the optical path length change

Djalmir N. Messias; Carlos Jacinto; Maria Jose; V. Bell; Tomaz Catunda

2007-01-01

291

Combined Optical Tweezers/Ion Beam Technique to Tune Colloidal Masks for  

E-print Network

of colloidal spheres is used as a mask for a lithographic step such as illumination, deposition, or etchingCombined Optical Tweezers/Ion Beam Technique to Tune Colloidal Masks for Nanolithography Dirk L. J through a mask of colloidal particles. The use of optical tweezers combined with critical point drying

Polman, Albert

292

Vernier-effect optical interrogation technique for fiber Bragg grating sensors  

Microsoft Academic Search

This work demonstrates a new technique for real-time optical sensor interrogation by exploiting a novel Vernier effect between the multiple (comb) wavelength responses of a multiplexed fiber Bragg grating array and the fixed discrete wavelengths of an all-solid-state tunable laser. Sets of output photodetector voltages serve as high-resolution optical \\

Gregory B. Tait

2007-01-01

293

Fabrication of functional microstructured optical fibers through a selective-filling technique  

E-print Network

Fabrication of functional microstructured optical fibers through a selective-filling technique develop a method for the fabrication of functional microstructured optical fibers (MOFs) by selectively of a triangular lattice photonic crystal fiber with dye-doped curable polymer, and experimentally observe the two

Huang, Yanyi

294

Stress investigation in optical fiber ribbon cable by means of polarization sensitive techniques  

Microsoft Academic Search

We present experimental results on stress behavior in high-density optical ribbon cables, performed by means of two techniques: polarization mode dispersion and polarization optical time-domain reflectometry. Correlation between them and theoretical estimates demonstrate that in such cables part of the birefringence is deterministic

Andrea Galtarossa; Giovanni Gianello; Carlo Giacomo Someda; Marco Schiano

1994-01-01

295

Improving optical measurement accuracy using multi-technique nested uncertainties  

NASA Astrophysics Data System (ADS)

This paper compares and contrasts different combinations of scatterfield and scatterometry optical configurations as well as introduces a new approach to embedding atomic force microscopy (AFM) or other reference metrology results directly in the uncertainty analysis and library-fitting process to reduce parametric uncertainties. We present both simulation results and experimental data demonstrating this new method, which is based on the application of a Bayesian analysis to library-based regression fitting of optical critical dimension (OCD) data. We develop the statistical methods to implement this approach of nested uncertainty analysis and give several examples, which demonstrate reduced uncertainties in the final combined measurements. The approach is also demonstrated through a combined reference metrology application using several independent measurement methods.

Silver, R. M.; Zhang, N. F.; Barnes, B. M.; Zhou, H.; Heckert, A.; Dixson, R.; Germer, T. A.; Bunday, B.

2009-03-01

296

Polarisation control through an optical feedback technique and its application in precise measurements  

PubMed Central

We present an anisotropic optical feedback technique for controlling light polarisation. The technique is based on the principle that the effective gain of a light mode is modulated by the magnitude of the anisotropic feedback. A new physical model that integrates Lamb's semi-classical theory and a model of the equivalent cavity of a Fabry-Perot interferometer is developed to reveal the physical nature of this technique. We use this technique to measure the phase retardation, optical axis, angle, thickness and refractive index with a high precision of ?/1380, 0.01°, 0.002°, 59?nm and 0.0006, respectively. PMID:23771164

Chen, Wenxue; Zhang, Shulian; Long, Xingwu

2013-01-01

297

Measurement of flame temperature distribution using optical tomographic and two-color pyrometric techniques  

Microsoft Academic Search

This paper presents the technique which combines optical tomographic and two-color parametric techniques for the three-dimensional (3-D) reconstruction of temperature distribution of a burner flame. Flame images are acquired using eight optical fiber bundles and two RGB CCD (charge-coupled device) cameras from eight different directions on one side of the burner. The new tomographic algorithm which combines the LFBP (Logical

Gang Lu; Yong Yan

2012-01-01

298

Acousto-Optically Controlled Beamsteering Techniques for Mmic-Based Phased Array Antennas.  

NASA Astrophysics Data System (ADS)

Future phased array antenna systems for radar and communications will utilize MMIC phase shifters and optical distribution techniques within a subarrayed antenna architecture. While significant progress has been made in the areas of photonic signal distribution in the last decade, relatively little effort has been directed towards compatibility with MMIC technology. This thesis presents both a theoretical and experimental investigation of two acousto-optically controlled array beamsteering techniques which are compatible with MMIC technology and subarrayed antenna architectures. The first technique explores the application of parallel optical signal processing within an acousto-optic cell to generate and distribute MMIC phase shifter control commands for array beamsteering control. This technique is analyzed from both a subsystem and system point of view and theory is developed which quantifies beamsteering performance with respect to noise, dynamic range requirements in both the microwave and optical domains, channel capacity, and the non-linearity of the acousto-optic cell driver. An experimental demonstration of the beamsteering control system was performed to validate the theory. The experiment was performed at L-band using a three bit MMIC phase shifter operating at 1300 MHz. Radiation patterns computed from experimental data show the correct steered responses. The second techniques explores the application of acousto-optic deflection in conjunction with high speed intensity modulation to generate programmable microwave time delays for true time delay beamsteering. Theory is developed which shows that there is no interaction between the optical sidebands generated in the intensity modulation process and the Doppler shift generated in the acousto -optic cell. The number of achievable delays as a function the acousto-optic cell parameters and the desired isolation between delays is also quantified. Experimental results are presented which validate the theory, showing 10 and 20 ns delays using external intensity modulation of a 1310 nm diode pumped solid state laser at 650 MHz.

Jemison, William D.

299

Self-aligned laser-fiber coupling using tin/gold (20/80) solder on micro-optical silicon benches  

NASA Astrophysics Data System (ADS)

The efficiency of laserdiode-monomode fiber coupling is one of the essential assignments for interactive optical telecommunications. In this paper, we present our investigations and results of the development of such couplers, especially of a soldering process for hybridly joining a laser on a silicon microoptical bench by self adjustment. To achieve the necessary adjustment tolerances of better than 0.5 micrometers , the influence of the solder height for the self-alignment process is simulated with respect to the lowest allowable solder thickness, which still generates the necessary alignment forces. Because of the excellent properties at their coupling facet U-grooves were fabricated to mount the fiber by deep and high precision anisotropic reactive ion etching of silicon using SF6/CBrF3 gas- mixtures. The solder was deposited in buried structures by electroplating gold and tin at the eutectic ratio to allow optimum adjustment in vertical and lateral dimensions. Furthermore, the results of a fluxless soldering process in a UV-light activated forming gas atmosphere is presented and compared to the simulations. The measurement of the coupling efficiency to fibers will also be illustrated. The design of the microoptical bench allows to extend the system by incorporating e.g. a faraday rotator or other optoelectronic integrated circuits, like transceivers.

Dahms, Ulf-Peter; Muellerwiebus, Viki; Heider, Hans J.; Mahnke, Matthias; Bludszuweit, Mark; Mueller, Joerg

2000-04-01

300

Optical Trapping Techniques Applied to the Study of Cell Membranes  

NASA Astrophysics Data System (ADS)

Optical tweezers allow for manipulating micron-sized objects using pN level optical forces. In this work, we use an optical trapping setup to aid in three separate experiments, all related to the physics of the cellular membrane. In the first experiment, in conjunction with Brian Henslee, we use optical tweezers to allow for precise positioning and control of cells in suspension to evaluate the cell size dependence of electroporation. Theory predicts that all cells porate at a transmembrane potential VTMof roughly 1 V. The Schwann equation predicts that the transmembrane potential depends linearly on the cell radius r, thus predicting that cells should porate at threshold electric fields that go as 1/r. The threshold field required to induce poration is determined by applying a low voltage pulse to the cell and then applying additional pulses of greater and greater magnitude, checking for poration at each step using propidium iodide dye. We find that, contrary to expectations, cells do not porate at a constant value of the transmembrane potential but at a constant value of the electric field which we find to be 692 V/cm for K562 cells. Delivering precise dosages of nanoparticles into cells is of importance for assessing toxicity of nanoparticles or for genetic research. In the second experiment, we conduct nano-electroporation—a novel method of applying precise doses of transfection agents to cells—by using optical tweezers in conjunction with a confocal microscope to manipulate cells into contact with 100 nm wide nanochannels. This work was done in collaboration with Pouyan Boukany of Dr. Lee's group. The small cross sectional area of these nano channels means that the electric field within them is extremely large, 60 MV/m, which allows them to electrophoretically drive transfection agents into the cell. We find that nano electroporation results in excellent dose control (to within 10% in our experiments) compared to bulk electroporation. We also find that, unlike bulk electroporation, nano-electroporation directly injects nanoparticles, such as quantum dots, to the cell interior, bypassing the cell membrane without the need for endocytosis. The aging of RBC's can render them rigid, an issue for the survivability of transfusion patients. This rigidity can be assessed by examining the fluctuations in the cell membrane. In the third experiment, we use back focal plane detection—an interferometric detection scheme using an optical tweezers setup—to measure the membrane fluctuations of RBC's and K562 cells. Membrane fluctuations have long been observed in RBC's and a well developed theory exists linking them to the cells internal viscosity ?, the membrane bending modulus k and the surface tension of the membrane ?. We use back focal plane detection to measure the effect of ascorbic acid treatment on RBC aging and find no improvement in cell flexibility. K562 cells differ from RBC's in that they possess an actin cortex which the membrane attaches to. We demonstrate that K562 cells exhibit as much as an order of magnitude more variation in their fluctuations than RBC's do.

Morss, Andrew J.

301

Fiber optic diagnostic techniques for the electrical discharge machining process  

E-print Network

on both sides of the electrodes . . 27 12 Setup to observe total optical power emitted by the plasma spark along with the current measurements from the machine 34 13 Total setup for measuring the spectrum of light emitted by a tungsten lamp . 14... Detailed view of how the monochrometer is being used in the system. . 37 FIG U RE Page IS Total setup for measuring the spectrum of light emitted by a tungsten lamp with a light chopper set at a low duty cycle. . . . . . . . 38 16 Total setup for measu...

Pillans, Brandon William

2012-06-07

302

Multimode fiber-optic hydrophone based on a schlieren technique.  

PubMed

A multimode fiber-optic hydrophone is described which is based upon a schlieren acoustooptic intensity modulation mechanism. Computer modeling of critical device parameters was experimentally verified and used to indicate ultimate attainable device performance. The device was shown to be able to detect the Knudsen noise level for frequencies up to 1 kHz, to have a dynamic range of 125 dB, to have an omnidirectional receiving response, and to be able to detect displacements as small as 3.4 x 10(-3) A. The device is not susceptible to phase noise, is relatively insensitive to static pressure head variations and is electrically passive. PMID:20309136

Spillman, W B

1981-02-01

303

Ion beam induced defects in solids studied by optical techniques  

NASA Astrophysics Data System (ADS)

Optical methods can provide important insights into the mechanisms and consequences of ion beam interactions with solids. This is illustrated by four distinctly different systems. X- and Y-cut LiNbO 3 crystals implanted with 8 MeV Au 3+ ions with a fluence of 1 × 10 17 ions/cm 2 result in gold nanoparticle formation during high temperature annealing. Optical extinction curves simulated by the Mie theory provide the average nanoparticle sizes. TEM studies are in reasonable agreement and confirm a near-spherical nanoparticle shape but with surface facets. Large temperature differences in the nanoparticle creation in the X- and Y-cut crystals are explained by recrystallisation of the initially amorphised regions so as to recreate the prior crystal structure and to result in anisotropic diffusion of the implanted gold. Defect formation in alkali halides using ion beam irradiation has provided new information. Radiation-hard CsI crystals bombarded with 1 MeV protons at 300 K successfully produce F-type centres and V-centres having the I3- structure as identified by optical absorption and Raman studies. The results are discussed in relation to the formation of interstitial iodine aggregates of various types in alkali iodides. Depth profiling of I3- and I5- aggregates created in RbI bombarded with 13.6 MeV/A argon ions at 300 K is discussed. The recrystallisation of an amorphous silicon layer created in crystalline silicon bombarded with 100 keV carbon ions with a fluence of 5 × 10 17 ions/cm 2 during subsequent high temperature annealing is studied by Raman and Brillouin light scattering. Irradiation of tin-doped indium oxide (ITO) films with 1 MeV protons with fluences from 1 × 10 15 to 250 × 10 15 ions/cm -2 induces visible darkening over a broad spectral region that shows three stages of development. This is attributed to the formation of defect clusters by a model of defect growth and also high fluence optical absorption studies. X-ray diffraction studies show evidence of a strained lattice after the proton bombardment and recovery after long period storage. The effects are attributed to the annealing of the defects produced.

Comins, J. D.; Amolo, G. O.; Derry, T. E.; Connell, S. H.; Erasmus, R. M.; Witcomb, M. J.

2009-08-01

304

PAPR reduction techniques for asymmetrically clipped optical OFDM communication system  

NASA Astrophysics Data System (ADS)

In the ultraviolet communication system, ACO-OFDM technology can effectively suppress inter-symbol interference on the system performance, and further improve the transmission rate of the system. However, ACO-OFDM has a high peak to average power ratio (PAPR), and high PAPR not only reduces the power efficiency of the optical modulator, but also bring damage to the human eye or skin. In order to solve the above problem, according to ACO-OFDM signal characteristics, two clipping and filtering algorithms are used, and its performance is simulated, the simulations show that the two algorithms are able to inhibit well the PAPR of ACO-OFDM system.

Wang, Yong; Zhang, Zhaojun; Sun, Lu

2014-07-01

305

Development of Off-Plane Reflection Grating Alignment Fixtures  

NASA Astrophysics Data System (ADS)

Currently, grating spectrometers are used onboard the Chandra X-ray Observatory and XMM-Newton in orbit around the Earth. However, future goals of greater spectral resolving power and greater effective areas necessitate a new generation of high-quality spectrometers. Off-plane reflection gratings can be used to provide high throughput and spectral resolution in the 0.3-2.0 keV band, allowing for unprecedented diagnostics of energetic astrophysical processes. A grating spectrometer consists of multiple aligned gratings intersecting the converging beam of a Wolter-I telescope. Each grating will be aligned such that the diffracted spectra overlap at the focal plane. Misalignments will degrade both spectral resolution and effective area. With analytical alignment tolerances calculated, laboratory techniques to achieve these tolerances for flight-like optics must be developed. We present the results from our first and second generation alignment fixtures, as well as wavefront stitching methods.

Donovan, Benjamin D; Allured, Ryan; McEntaffer, Randall L.

2014-06-01

306

0714 - 2914 (M4-1) - Another Seyfert galaxy with aligned radio continuum and optical emission-line morphologies  

NASA Technical Reports Server (NTRS)

Direct imaging and long-slit spectroscopic mapping of the emission-line gas in the Seyfert 2 galaxy 0714 - 2914 (M4-1, MCG - 5-18-2) are reported. The nuclear regions contain an extended (1 kpc size), high-excitation nebulosity that is well aligned with the jet-like nonthermal radio source. The profiles of Forbidden O III 5007A are asymmetric, with extended red wings to the north and west of the nucleus and extended blue wings to the south and east. This switch in the sense of asymmetry is accounted for in terms of a combination of normal rotational motions in the galaxy disk and high-velocity outflow or infall associated with the Seyfert activity.

Wilson, A. S.; Baldwin, J. A.

1989-01-01

307

A calibration technique for a fiber optic gyro strapdown inertial navigation system  

NASA Astrophysics Data System (ADS)

The error model of Fiber Optic Gyro System is simpler than Mechnical gyro, Fiber Optic Gyro offer the advantage of an extremely broad bandwidth and additionally the presence of Random Walk in the output. In this paper, A Calibration Technique was developed to calibrate a fiber optic gyro strapdown inertial navigator using a low cost two-gimbal test-table. Accelerometer scale factor and bias and accelerometer and gyro misalignments are calibrated using measurements of the acceleration in the navigation frame after each rotation. A sequence of ten rotations has been chosen to stream-line the procedure. The validity of the model is tested in real fiber optic gyro system.

Zhu, Kuibao; Gao, Shuang; Zhang, Chunxi

2006-11-01

308

Analysis of cracks and damages in optical elements by a swept-source optical coherence tomography technique  

NASA Astrophysics Data System (ADS)

Optical coherence tomography (OCT) is a non- invasive technique where a near-infrared laser beam penetrates a sample and through the analysis of its scattered light information about the internal structure of the sample is calculated. Although OCT is mainly used in medicine its application to areas of enginery has been increased recently. Important features of recent OCT systems allow us to determine accurately volumetric structure not only slices. In this works we report such volumetric analysis applied to the study of scratches and damages in optical elements in order to quantify not only the scratch sizes but also its depths. This study is compared with an Schlieren technique. Experimental results are presented. The finding reveals clearly the faults locations which may be an attractive results for the optical work shop and the application of norms.

Muñoz Moreno, Gilberto; Alcalá Ochoa, Noé

2011-08-01

309

Frequency-shifted interferometry--a versatile fiber-optic sensing technique.  

PubMed

Fiber-optic sensing is a field that is developing at a fast pace. Novel fiber-optic sensor designs and sensing principles constantly open doors for new opportunities. In this paper, we review a fiber-optic sensing technique developed in our research group called frequency-shifted interferometry (FSI). This technique uses a continuous-wave light source, an optical frequency shifter, and a slow detector. We discuss the operation principles of several FSI implementations and show their applications in fiber length and dispersion measurement, locating weak reflections along a fiber link, fiber-optic sensor multiplexing, and high-sensitivity cavity ring-down measurement. Detailed analysis of FSI system parameters is also presented. PMID:24955943

Ye, Fei; Zhang, Yiwei; Qi, Bing; Qian, Li

2014-01-01

310

Alignment mechanism of liquid crystal in a stretched porous polymer film  

NASA Astrophysics Data System (ADS)

This article discusses the mechanism of nematic liquid crystal alignment in stretched porous polymer films. The polymer films were formed by extreme stretching of an isotropic porous polyolefin, such that the draw ratio was 12:1. A 6-?m-thick porous film with a high porosity coefficient of 92% revealed fine string-shaped areas that exhibited optical anisotropy due to their possessing a high degree of molecular alignment. The porous film was filled with nematic liquid crystal and then the composite film was sandwiched between transparent electrodes coated onto glass substrates, without the use of conventional alignment layers. From polarizing microscopy observations it was found that the string-like polymer areas induce liquid crystal molecular alignment. The liquid crystal cells can exhibit an electrically controlled birefringence effect. This alignment technique enables us to realize three-dimensional control of liquid crystal alignment.

Fujikake, Hideo; Kuboki, Masashi; Murashige, Takeshi; Sato, Hiroto; Kikuchi, Hiroshi; Kurita, Taiichiro

2003-09-01

311

Joint optical-electrical technique for noninvasive glucose monitoring  

Microsoft Academic Search

In Diabetes mellitus, self monitoring of blood glucose is crucial for effective treatment since it can help identify and prevent unwanted periods of hypo- and hyperglycemia; this monitoring procedure usually involves finger-stick testing which is painful to the patient and carries the risk of infection. Non-invasive techniques, including impedance and near infrared spectroscopy, have been developed to predict glucose concentration;

Edgar Guevara; Francisco Javier Gonzalez

2010-01-01

312

ADVANCES AND NEW TECHNIQUES IN LENGTH MEASUREMENTS BY OPTICAL INTERFEROMETRY  

Microsoft Academic Search

Studies of a long gauge block Kösters interferometer, performed at INMETRO, and the results of the CIPM Key Comparison CCL-2 show that the uncertainty in realization of the SI length unit achieved with this type of instrument in the range of 500 mm is ~1 part in 108. Basic advances in philosophy and techniques of high-precision temperature measurements, realized in

Alexandre Titov; Igor Malinovsky

313

Two Techniques for Optical Imaging Through Turbid Media  

E-print Network

;00 ][][ ][ ][ = velv c n -= i1][][~ ][ 2 ][ The index of refraction n of a material depends. If an incident photon does not have enough energy to be absorbed, it may induce an oscillation in the electron Techniques Radio astronomy Microwave imaging, radar Terahertz imaging Infrared, thermal Ultraviolet astronomy

Petta, Jason

314

RESEARCH ARTICLE An optical flow MTV based technique for measuring microfluidic  

E-print Network

RESEARCH ARTICLE An optical flow MTV based technique for measuring microfluidic flow for accurately measuring flow fields in microfluidic flows from molecular tagging velocimetry (MTV). Limited properties. In the same mixer, a comparative study of our MTV technique to lPIV was performed. Also

Garbe, Christoph S.

315

Performance improvement techniques for optical wireless link in presence of atmospheric turbulence  

NASA Astrophysics Data System (ADS)

Atmospheric turbulence can cause significant performance degradation in free space optical (FSO) communication system. Major effects on the beam such as beam wander and beam scintillation degrades the performance at the receiver. We investigate the impact of diversity technique and aperture averaging technique on the performance of FSO system. Performance evaluation is made in terms of average bit error rate and scintillation index.

Mehta, Nikhilesh; Joseph, Thomas; Gopal, Pooja; Chowdhury, K. B.; Jain, V. K.; Kar, Subrat

2013-03-01

316

Spatial resolution of confocal XRF technique using capillary optics  

PubMed Central

XRF (X-ray fluorescence) is a powerful technique for elemental analysis with a high sensitivity. The resolution is presently limited by the size of the primary excitation X-ray beam. A test-bed for confocal-type XRF has been developed to estimate the ultimate lateral resolution which could be reached in chemical mapping using this technique. A polycapillary lens is used to tightly focus the primary X-ray beam of a low power rhodium X-ray source, while the fluorescence signal is collected by a SDD detector through a cylindrical monocapillary. This system was used to characterize the geometry of the fluorescent zone. Capillary radii ranging from 50 ?m down to 5 ?m were used to investigate the fluorescence signal maximum level This study allows to estimate the ultimate resolution which could be reached in-lab or on a synchrotron beamline. A new tool combining local XRF and scanning probe microscopy is finally proposed. PMID:23758858

2013-01-01

317

Calibration of optical detectors using discrete Fourier transform techniques  

NASA Technical Reports Server (NTRS)

A method for determining the detector electrooptical transfer function (DEOTF) at different discrete frequencies simultaneously is presented. It involves simulation of the detector with a waveform of unknown frequency composition, such as a square wave or impulse function. The DEOTF is calculated as the ratio of the discrete Fourier transform of the detector output to the transform of the input waveform. This technique was successfully applied to Golay cell and bolometer detectors and can be used for other linear detector systems.

Hagopian, John G.; Eichhorn, William

1990-01-01

318

A simple microbeam profiling technique for x-ray optics  

Microsoft Academic Search

Enhancement of the quality of images or maps obtained using micro x-ray fluorescence spectrometry requires knowledge of the flux distribution profile of the primary x-ray beam. A simple procedure based on a wire scan was developed for the determination of an x-ray microbeam profile. This technique is simple and can be used for a given excitation\\/detection geometry without any change

M. Lankosz; J. Sieber

2000-01-01

319

Island nucleation, optical and ferromagnetic properties of vertically aligned secondary growth ZnO : Cu nanorod arrays  

NASA Astrophysics Data System (ADS)

The paper reports an island nucleation and secondary growth of aligned ZnO : Cu nanorod arrays via thermal vapor phase transport. Results analysis indicates that the secondary segment is epitaxially grown on the ZnO : Cu nanorods with the radius strongly dependent on temperature and the concentration of zinc vapor. The modified characteristic radius (Rc) model is used to explain the nucleation and secondary growth process. Temperature-dependent photoluminescence spectra indicate that the band gap emission of the secondary growth nanorods is greatly restrained. A controversial 3.31 eV emission (A line) and two different donor-acceptor pair (DAP) recombinations at 3.24 eV and 2.48 eV are observed at 13 K. The A line shows a different behavior from the two DAP emissions during the heat-up process. Intrinsic room temperature ferromagnetism (RTFM) is observed in the secondary growth ZnO : Cu nanorods and it can be explained by oxygen vacancy and copper defects related to bound magnetic polar (BMP) or double exchange mechanism.The paper reports an island nucleation and secondary growth of aligned ZnO : Cu nanorod arrays via thermal vapor phase transport. Results analysis indicates that the secondary segment is epitaxially grown on the ZnO : Cu nanorods with the radius strongly dependent on temperature and the concentration of zinc vapor. The modified characteristic radius (Rc) model is used to explain the nucleation and secondary growth process. Temperature-dependent photoluminescence spectra indicate that the band gap emission of the secondary growth nanorods is greatly restrained. A controversial 3.31 eV emission (A line) and two different donor-acceptor pair (DAP) recombinations at 3.24 eV and 2.48 eV are observed at 13 K. The A line shows a different behavior from the two DAP emissions during the heat-up process. Intrinsic room temperature ferromagnetism (RTFM) is observed in the secondary growth ZnO : Cu nanorods and it can be explained by oxygen vacancy and copper defects related to bound magnetic polar (BMP) or double exchange mechanism. Electronic supplementary information (ESI) available: Experimental details and other supporting results. See DOI: 10.1039/c2nr11768a

Huang, Jun; Zhu, Liping; Hu, Liang; Liu, Shijiang; Zhang, Jie; Zhang, Honghai; Yang, Xiaopeng; Sun, Luwei; Li, Dehui; Ye, Zhizhen

2012-02-01

320

An optical technique to measure ion engine grid distortion due to differential thermal expansion  

NASA Technical Reports Server (NTRS)

This paper describes an optical technique developed for measuring small differential grid displacements due to thermal expansion of an ion thruster accelerator system. The technique is based on confocal scanning optical microscope type II. For the measurements of small displacements where there are distances on the order of a meter or more between the lens plane and the sample, some of the optical components are moved while the sample is kept fixed. The feasibility of applying this technique to measure the thermally induced ion thruster grid displacements was demonstrated in a bench-top simulation. It is noted that this technique can also provide information on grid movement resulting from thermal transients such as the start-up.

Trava-Airoldi, V. J.; Garner, C. E.; Pivirotto, T. J.; Brophy, J. R.

1990-01-01

321

Core-suction technique for the fabrication of optical fiber preforms.  

PubMed

A novel technique, named "core suction," for fabricating optical fiber preforms has been devised. The technique involves drawing the molten nonconventional core glass material into the cladding tube to form the preform. The developed technique is simple, inexpensive, and shows great potential for fabricating preforms of highly nonlinear nonconventional glasses as the core material. Preforms were made with Schott SF6 and a lead-tellurium-germanate glass in silica cladding tubes, and these preforms were then pulled into fibers. PMID:16496879

Goel, Nitin K; Stolen, Roger H; Morgan, Steven; Kim, Jong-Kook; Kominsky, Dan; Pickrell, Gary

2006-02-15

322

Gracilis tendon transfer associated with distal alignment for patella alta with recurrent dislocations: an original surgical technique.  

PubMed

Many surgical techniques for the medial patellofemoral ligament have recently been suggested, all of which included problems identifying the femoral anchorage point and determining the proper extent of knee flexion for the transplant. P. Burdin proposed a different and original approach consisting in performing a gracilis muscle transfer to the medial edge of the patella, thus obtaining progressive tension of the transfer during knee flexion by means of the myotatic reflex. We report the results herein. We retrospectively assessed 17 knees treated for patellofemoral instability using this technique. Two cases presented subjective patellofemoral instability and 15 presented objective patellofemoral instability. The patients' mean age was 17.4 years (range, 8-47 years) during the first episode of dislocation. Two cases of instability were secondary to advanced neuromuscular disease. Two knees had already undergone two stabilization attempts. Fifteen knees presented trochlear dysplasia (four stage A, eight stage B, and three stage C). The mean age at surgery was 28.2 years (range, 16-47 years). In 15 cases, the gracilis transfer was associated with lowering the anterior tibial tuberosity (mean, 10mm). No patellar fracture occurred. A persistent sensory deficit of the anterior branch of the internal saphenous nerve was observed in 15 cases. One knee remained painful and retained subjective instability; total knee arthroplasty was performed 3 years after the intervention. The mean follow-up at revision was 5.5 years (range, 1.5-16.5 years). No recurrence of dislocation was reported. Eight cases retained subjective instability. The SF-36 and IKDC scores were good or excellent in 12 cases and the KOOS was good or excellent in 13 cases. Radiologically, patellar tilt persisted in six cases out of 14, translation persisted in two cases out of 14, and secondary patella baja was observed in one. Medial patellofemoral osteoarthritis was observed in five cases: one case IWANO stage I and four cases IWANO stage II. These satisfactory results seem stable over time and were acquired using a simple procedure with reduced morbidity, making it possible to avoid significant displacement of the anterior tibial tuberosity and stabilize the extensor apparatus. It can also be hoped that the onset of secondary patellofemoral osteoarthritis, undoubtedly inevitable, has been delayed. PMID:21530441

Marteau, E; Burdin, P; Brilhault, J-M

2011-06-01

323

Single Mode Fiber Optic Splicing Techniques And Statistical Analysis  

NASA Astrophysics Data System (ADS)

Two methods employed during fusion splicing as well as two methods for calculating the average splice loss per fiber-span are presented. The two splicing methods described are the telemetry and optical time domain ref lectometer (OTDR) methods. The cut-back and OTDR measuring methods for calculating the average splice loss per fiber-span are also described. A statistical model relating the various measuring uncertainties with the sample size uncertainties is used to predict the population parameters from the sample statistics. Laboratory results are also included to analyze the important parameters needed for splice optimization. The accuracy of splice loss measurements obtained using OTDRs is studied in the laboratory and is used to analyze field data. Our results show that there is no significant difference in the quality of the telemetry splicing method as compared to the OTDR splicing method. In addition, the average splice loss per fiber-span calculated from cut-back measurements was found to yield a distribution that is only 80% as accurate as the one derived from the OTDR measurements.

Paz, Eduardo; Mysore, Sudhesh; Martin, David

1985-11-01

324

Curriculum Alignment.  

ERIC Educational Resources Information Center

Curriculum alignment (CA) refers to the congruence of all the elements of a school's curriculum: curriculum goals; instructional program--what is taught and the materials used; and tests used to judge outcomes. CA can be a very powerful can be a very powerful factor in improving schools. Although further research is needed on CA, there is…

Crowell, Ronald; Tissot, Paula

325

Self-alignment of microparts using liquid surface tension—behavior of micropart and alignment characteristics  

Microsoft Academic Search

The purpose of this research is to establish a self-alignment technique for microparts assembly using liquid surface tension. The factors that influence alignment performance are examined and ways of performance improvement are discussed experimentally and theoretically. First, the relationship between the alignment accuracy and the behavior of the micropart and the water droplet is examined in the alignments with six

Kaiji Sato; Kentaro Ito; Seiichi Hata; Akira Shimokohbe

2003-01-01

326

Hybrid SCM SAC-OCDMA System Employing New Optical Spectral Amplitude Direct Decoding Detection Technique  

NASA Astrophysics Data System (ADS)

In this research, a hybrid subcarrier multiplexed spectral-amplitude-coding optical code-division-multiple-access (SCM SAC-OCDMA) system is proposed for the purpose of combining the advantages of both techniques. SAC-OCDMA is employed because of its ability to eliminate the Multiple Access Interference (MAI) when code sequences with fixed in-phase cross correlation are used. In order to enhance the channel data rate of the OCDMA systems, the SCM technique is used. As a result, the hybrid system is robust against interference and is much more spectrally efficient. The system utilizes double weight (DW) code that has a weight W equal to two, code length N equal to six and cross correlation ? equal to 1. A simple and new detection technique called optical spectral amplitude direct decoding is proposed. Based on the theory and experimental simulation results obtained, the new proposed detection technique provides a better performance than the conventional balanced detection technique.

Sahbudin, R. K. Z.; Abdullah, M. K.; Samad, M. D. A.; Mahdi, M. A.; Ismail, M.

327

Research on the key techniques of fiber optic gyroscopes in space applications  

NASA Astrophysics Data System (ADS)

The advantages and the characteristics of the fiber optic gyroscopes (FOGs) for the space application, compared with the traditional mechanical gyroscope and the laser gyroscope, have been mentioned. There are differences of the FOG designing between application in space and other conditions especially the radiation-resistant, low power cost and less weight of the FOG. The key techniques of the fiber optic gyros technology have been proposed and some test results have been discussed.

Xiao, Wen; Liu, Dewen; Zhang, Yuyan

2005-11-01

328

Replication of continuous-relief diffractive optical elements by conventional compact disc injection-molding techniques  

Microsoft Academic Search

Continuous-relief diffractive optical elements have been replicated by use of conventional compact disc injection-molding techniques. Two continuous-relief microstructures, a blazed grating and a fan-out element, were chosen to evaluate the replication process. Original elements were fabricated by direct-write electron-beam lithography. Optical measurements and atomic force microscopy were used for investigating the replication fidelity.

Fredrik Nikolajeff; Stellan Jacobsson; Sverker Hård; Åke Billman; Lars Lundbladh; Curt Lindell

1997-01-01

329

Diode pumping of a solid state laser using evanescent field fiber optic coupling: a proposed technique.  

PubMed

The use of optical fibers to evanescently couple pump energy from laser diodes to a solid state laser rod is proposed. This technique involves placing a series of optical fibers side-by-side around the barrel portion of a laser rod, parallel to the laser resonator mode. A large index difference between the core region of the optical fibers and the solid state material facilitates evanescent coupling of pump light into the laser rod. Efficient operation will be possible due to a high overlap between the laser resonating mode and the pumped volume. PMID:20700158

Howerton, P H; Cordray, D M

1991-05-20

330

Optical Limiting in TeO2-ZnO Glass from Z-Scan Technique  

NASA Astrophysics Data System (ADS)

TeO2-ZnO glasses were prepared by conventional melting procedure, and their optical properties were determined. In the present work, we measured the optical non-linearity of the glass. The measurement was carried out using a single beam z-scan technique given by Sheike Bahe et al. We could observe that the material exhibits reverse saturable absorption, and the effective nonlinear absorption coefficients are numerically evaluated. This study is important in identifying the nonlinear material as a Reverse Saturable Absorption (RSA) based optical limiter.

Thomas, Rose Leena; Vasuja; Hari, Misha; Nithyaja, B.; Mathew, S.; Rejeena, I.; Thomas, Sheenu; Nampoori, V. P. N.; Radhakrishnan, P.

331

Alignment of the MINOS FD  

SciTech Connect

The results and procedure of the alignment of the MINOS Far Detector are presented. The far detector has independent alignments of SM1 and SM2. The misalignments have an estimated uncertainty of {approx}850 {micro}m for SM1 and {approx}750 {micro}m for SM2. The alignment has as inputs the average rotations of U and V as determined by optical survey and strip positions within modules measured from the module mapper. The output of this is a module-module correction for transverse mis-alignments. These results were verified by examining an independent set of data. These alignment constants on average contribute much less then 1% to the total uncertainty in the transverse strip position.

Becker, B.; /Minnesota U.; Boehnlein, D.; /Fermilab

2004-11-01

332

A novel technique of optical interference to generate equispaced fringe pattern of concentric ring  

NASA Astrophysics Data System (ADS)

With the upcoming of the next-generation large-capacity CDs and DVDs using a blue-violet laser, the track's pitch will continue to decrease. The conventional methods for pregrooves will have a technique challenge to meet tiny-pitch specs at low cost. In order to get an equispaced fringe pattern with concentric-ring structure by using optical interference lithography, a novel optical-interference method is proposed with the use of a plane wave plus a conical wave along the same optical-axis (Z) propagation. Based on the optical interference analysis with the two waves, plane and conical waves, the resulting intensity varies consinusoidally with the phase difference, as modulated by the optical path difference between the plane and conical waves. The constructive and destructive interference will occur in the interference light field, only depending on if in phase or out of phase for the two waves. The concentric-ring structure of equispaced fringe pattern can be produced, and the fringe period depends on the wavelength of the light beams and conical constant of the conical wavefront as well. The novel optical interference system has been modeled and simulated with a kind of Mach-Zender interferometer arrangement by commercial optical code. The optical simulation results are proved to have a good agreement with that as given by the theoretical analysis.

Wang, Min; Thibault, Simon

2005-08-01

333

Dynamic interferometer alignment and its utility in UV Fourier transform spectrometer systems  

NASA Technical Reports Server (NTRS)

Dynamic alignment has been demonstrated as a practical approach to alignment maintenance for systems in the infrared region of the spectrum. On the basis of work done by OPTRA, this technique was introduced in commercial Fourier transform spectrometer systems in 1982 and in various forms is now available from a number of manufacturers. This paper reports on work by OPTRA to extend the basic technique to systems operating in the ultraviolet. In addition, this paper reports the preliminary results of the development of an alignment system using a laser diode in place of a gas laser normally found in dynamic alignment systems. A unique optical system and spatial heterodyne technique allows for achievement of a metrology system with characteristics that fully satisfy the requirements of an ultraviolet spectrometer system.

Dorval, Rick K.; Engel, James R.; Wyntjes, Geert J.

1993-01-01

334

FALCON Remote Laser Alignment System  

SciTech Connect

The FALCON Remote Laser Alignment System is used in a high radiation environment to adjust an optical assembly. The purpose of this report is to provide a description of the hardware used and to present the system configuration. Use of the system has increased the reliability and reproducibility of data as well as significantly reducing personnel radiation exposure. Based upon measured radiation dose, radiation exposure was reduced by at least a factor of two after implementing the remote alignment system.

Hamilton, T.W.; Hebner, G.A.

1993-02-01

335

FALCON Remote Laser Alignment System  

SciTech Connect

The FALCON Remote Laser Alignment System is used in a high radiation environment to adjust an optical assembly. The purpose of this report is to provide a description of the hardware used and to present the system configuration. Use of the system has increased the reliability and reproducibility of data as well as significantly reducing personnel radiation exposure. Based upon measured radiation dose, radiation exposure was reduced by at least a factor of two after implementing the remote alignment system.

Hamilton, T.W.; Hebner, G.A.

1993-01-01

336

Fusion bonding and alignment fixture  

DOEpatents

An improved vacuum fusion bonding structure and process for aligned bonding of large area glass plates, patterned with microchannels and access holes and slots, for elevated glass fusion temperatures. Vacuum pumpout of all the components is through the bottom platform which yields an untouched, defect free top surface which greatly improves optical access through this smooth surface. Also, a completely non-adherent interlayer, such as graphite, with alignment and location features is located between the main steel platform and the glass plate pair, which makes large improvements in quality, yield, and ease of use, and enables aligned bonding of very large glass structures.

Ackler, Harold D. (Sunnyvale, CA); Swierkowski, Stefan P. (Livermore, CA); Tarte, Lisa A. (Livermore, CA); Hicks, Randall K. (Stockton, CA)

2000-01-01

337

MUSE alignment onto VLT  

NASA Astrophysics Data System (ADS)

MUSE (Multi Unit Spectroscopic Explorer) is a second generation Very Large Telescope (VLT) integral field spectrograph developed for the European Southern Observatory (ESO). It combines a 1' x 1' field of view sampled at 0.2 arcsec for its Wide Field Mode (WFM) and a 7.5"x7.5" field of view for its Narrow Field Mode (NFM). Both modes will operate with the improved spatial resolution provided by GALACSI (Ground Atmospheric Layer Adaptive Optics for Spectroscopic Imaging), that will use the VLT deformable secondary mirror and 4 Laser Guide Stars (LGS) foreseen in 2015. MUSE operates in the visible wavelength range (0.465-0.93 ?m). A consortium of seven institutes is currently commissioning MUSE in the Very Large Telescope for the Preliminary Acceptance in Chile, scheduled for September, 2014. MUSE is composed of several subsystems which are under the responsibility of each institute. The Fore Optics derotates and anamorphoses the image at the focal plane. A Splitting and Relay Optics feed the 24 identical Integral Field Units (IFU), that are mounted within a large monolithic structure. Each IFU incorporates an image slicer, a fully refractive spectrograph with VPH-grating and a detector system connected to a global vacuum and cryogenic system. During 2012 and 2013, all MUSE subsystems were integrated, aligned and tested to the P.I. institute at Lyon. After successful PAE in September 2013, MUSE instrument was shipped to the Very Large Telescope in Chile where that was aligned and tested in ESO integration hall at Paranal. After, MUSE was directly transported, fully aligned and without any optomechanical dismounting, onto VLT telescope where the first light was overcame the 7th of February, 2014. This paper describes the alignment procedure of the whole MUSE instrument with respect to the Very Large Telescope (VLT). It describes how 6 tons could be move with accuracy better than 0.025mm and less than 0.25 arcmin in order to reach alignment requirements. The success of the MUSE alignment is demonstrated by the excellent results obtained onto MUSE image quality and throughput directly onto the sky.

Laurent, Florence; Renault, Edgard; Boudon, Didier; Caillier, Patrick; Daguisé, Eric; Dupuy, Christophe; Jarno, Aurélien; Lizon, Jean-Louis; Migniau, Jean-Emmanuel; Nicklas, Harald; Piqueras, Laure

2014-07-01

338

Magnetically determined particle alignment factors of sintered rare-earth cobalt permanent magnets  

NASA Astrophysics Data System (ADS)

Values for the particle alignment factor have been obtained, during the past few years, by several workers.1, 2, 3, 4 The various techniques which have been used include magnetic, x-ray, and optical experiments. However, particle alignment factors are not now routinely obtained during the processing of permanent magnets. There is a requirement for ''real time'' feedback for production purposes, and there is also a requirement for a magnetic probe of structure for a basic understanding of these sintered permanent magnets. For these reasons we have decided to consider various magnetic determinations of the particle alignment for SmCo5 permanent magnets.

Searle, C. W.; Davis, V.; Hutchens, R. D.

1982-03-01

339

Structural, Compositional, and Optical Characterizations of Vertically Aligned AlAs/GaAs/GaP Heterostructure Nanowires Epitaxially Grown on Si Substrate  

NASA Astrophysics Data System (ADS)

We structurally, compositionally, and optically characterize vertically aligned AlAs/GaAs/GaP heterostructured nanowires (NWs) grown on a Si substrate used for the integration of an optically active material into Si-based technology and its band-gap engineering. The NWs were grown using Au colloidal nanoparticles as catalysts via the vapor-liquid-solid mode. By alternately changing the source material between Ga and Al, we grew GaAs/AlAs/GaAs/AlAs/GaAs NWs with a well-controlled periodic structure and composition on a GaP segment, which was epitaxially grown on a Si substrate. No dislocations induced by the lattice mismatch were found in the GaAs segment of the NWs grown on the GaP segment despite a lattice mismatch of as large as 4%. This is because the NWs have a particular columnar structure with nanoscale diameters and can therefore relax laterally and accommodate a high strain. Stacking faults exist in zinc-blende-structured GaP and GaAs segments, while the AlAs segment has a pure wurtzite crystal structure without any stacking faults. It is found that the stacking fault in III-V NWs is significantly dependent on the stacking fault energy and ionicity. With increasing ionicity, stacking faults can be more easily introduced, and these NWs tend to have a wurtzite crystal structure. In addition, owing to the high surface nonradiative recombination rate resulting from the surface states on the GaAs NW surface, the excitonic emission of photoluminescence from the bare GaAs NW segment has a decay time of as short as 30 ps. With the growth of an AlGaAs capping layer and GaAs outer shell layer, the decay time of the excitonic emission increased 46-fold, indicating an excellent passivation effect on the GaAs segment surface.

Zhang, Guoqiang; Tateno, Kouta; Gotoh, Hideki; Sogawa, Tetsuomi; Nakano, Hidetoshi

2010-01-01

340

High Field Magneto-Optical Spectroscopy of Highly Aligned Individual and Ensemble Single-Walled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

The tubular nature of single-walled carbon nanotube (SWCNT) crystals allows them to exhibit non-intuitive quantum phenomena when threaded by a magnetic flux, which breaks the time reversal symmetry and adds an Aharonov-Bohm phase to the circumferential boundary conditions on the electronic wave function. We demonstrate that such a symmetry-breaking magnetic field can dramatically "brighten" an optically-inactive, or dark, exciton state at low temperature. This phenomenon, magnetic brightening, can be understood as a consequence of interplay between the strong intervalley Coulomb mixing and field-induced lifting of valley degeneracy. Most recently, we made the direct observation of the dark excitonic state in individual SWCNTs using low-temperature micro-photoluminescence (PL) and and verified the importance of a parallel, tube-threading magentic field with ensemble spectroscopy. For micro-PL, a magnetic field up to 5 T, applied along the nanotube axis, brightened the dark state, leading to the emergence of a new emission peak. The peak rapidly grew in intensity with increasing field at the expense of the originally-dominant bright exciton peak and finally became dominant at fields > 3 T. The directly measured dark-bright splitting values were 1-4 meV for tube diameters 1.0-1.3 nm. For ensemble PL, we used fields up to 55 T in two collection geometries to demonstrate the importance of the tube-threading component. These experiments have provided one of the most critical tests for recently-proposed theories of 1-D excitons taking into account the strong 1-D Coulomb interactions and unique band structure on an equal footing.

Shaver, J.; Srivastava, A.; Kono, J.; Crooker, S. A.; Htoon, H.; Klimov, V. I.; Fagan, J. A.; Hobbie, E. K.; Ubrig, N.; Portugall, O.; Perebeinos, V.; Avouris, Ph.

341

An efficient rate-adaptive transmission technique using shortened pulses for atmospheric optical communications.  

PubMed

In free space optical (FSO) communication, atmospheric turbulence causes fluctuation in both intensity and phase of the received light signal what may seriously impair the link performance. Additionally, turbulent inhomogeneities may produce optical pulse spreading. In this paper, a simple rate adaptive transmission technique based on the use of variable silence periods and on-off keying (OOK) formats with memory is presented. This technique was previously proposed in indoor unguided optical links by the authors with very good performance. Such transmission scheme is now extensively analyzed in terms of burst error rate, and shown in this paper as an excellent alternative compared with the classical scheme based on repetition coding and pulse-position modulation (PPM), presenting a greater robustness to adverse conditions of turbulence. PMID:20721122

Jurado-Navas, Antonio; Garrido-Balsells, José María; Castillo-Vázquez, Miguel; Puerta-Notario, Antonio

2010-08-01

342

Application of intracellular optical techniques to the study of stomatopod crustacean vision  

Microsoft Academic Search

1.The noninvasive techniques of intracellular optical physiology were used to measure reflectance changes in the deep pseudopupils of various regions of the apposition compound eyes of 3 species of stomatopod crustaceans.2.Upon exposure to light, prominent changes in reflectance were observed in all eye regions of all species studied. Generally, the response was an increasing reflectance following stimulus onset; however, in

Thomas W. Cronin

1989-01-01

343

Electric field measurements by combining nonlinear frequency conversion technique with electro-optic effect  

Microsoft Academic Search

A novel electric field measurement method by combining a nonlinear frequency conversion technique, such as second-harmonic generation, with electro-optic effect is proposed and its feasibility for electric field measurements due to dc and impulse voltages is investigated.

K. Kuriaki; N. J. Vasa; S. Yokoyama; M. Maeda; H. Takeshita

2003-01-01

344

Novel failure analysis techniques using photon probing with a scanning optical microscope  

SciTech Connect

Three new failure analysis techniques for integrated circuits (ICs) have been developed using localized photon probing with a scanning optical microscope (SOM). The first two are light-induced voltage alteration (LIVA) imaging techniques that (1) localize open-circuited and damaged junctions and (2) image transistor logic states. The third technique uses the SOM to control logic states optically from the IC backside. LIVA images are produced by monitoring the voltage fluctuations of a constant current power supply as a laser beam is scanned over the IC. High selectivity for localizing defects has been demonstrated using the LIVA approach. Logic state mapping results, similar to previous work using biased optical beam induced current (OBIC) and laser probing approaches have also been produced using LIVA. Application of the two LIVA based techniques to backside failure analysis has been demonstrated using an infrared laser source. Optical logic state control is based upon earlier work examining transistor response to photon injection. The physics of each method and their applications for failure analysis are described.

Cole, E.I. Jr.; Soden, J.M.; Rife, J.L.; Barton, D.L.; Henderson, C.L.

1993-12-31

345

What can we learn about cell signalling by combining optical imaging and patch clamp techniques?  

Microsoft Academic Search

Optical imaging is a powerful technique with which to investigate the activity, distribution and movement of biomolecules. The increased resolution of images obtained with confocal microscopy now allows us to visualize the signalling events in individual intracellular organelles. Local photobleaching and uncaging of caged compounds enable investigators to control the activity of many biologically important molecules in small localized regions

Myoung Kyu Park; Alexei V. Tepikin; Ole H. Petersen

2002-01-01

346

Wavefront correction of optical beam for large space mirrors using robust control techniques$  

E-print Network

Wavefront correction of optical beam for large space mirrors using robust control techniques$ Jae, the size of the telescope aperture needs to be increased without losing accuracy in the mirror surface by atmospheric turbu- lence. For space telescopes, the major source of image aberration is likely caused from

347

Specificity of noninvasive blood glucose sensing using optical coherence tomography technique: a pilot study  

Microsoft Academic Search

Noninvasive monitoring of blood glucose concentration in diabetic patients would significantly reduce complications and mortality associated with this disease. In this paper, we experimentally and theoretically studied specificity of noninvasive blood glucose monitoring with the optical coherence tomography (OCT) technique. OCT images and signals were obtained from skin of Yucatan micropigs and New Zealand rabbits. Obtained results demonstrate that: (1)

Kirill V. Larin; Massoud Motamedi; Taras V. Ashitkov; Rinat O. Esenaliev

2003-01-01

348

Optically stimulated luminescence from quartz measured using the linear modulation technique  

Microsoft Academic Search

The optically stimulated luminescence (OSL) from heated natural quartz has been investigated using the linear modulation technique (LMT), in which the excitation light intensity is increased linearly during stimulation. In contrast to conventional stimulation, which usually produces a monotonically decreasing signal, linearly increasing the stimulation power gives peaks in the signal as a function of time. In cases where the

E Bulur; L Bøtter-Jensen; A. S Murray

2000-01-01

349

Matter Wave Optical Techniques for Probing Many-body Scott Nicholas Sanders  

E-print Network

Matter Wave Optical Techniques for Probing Many-body Targets by Scott Nicholas Sanders A by . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thomas Greytak Chairman, Department Committee on Graduate Theses #12;#12;to my family #12;#12;Matter Wave of Philosophy in Physics Abstract This thesis reports on our investigation of the uses of matter waves to probe

Heller, Eric

350

A Survivable WDM-PON Architecture Using Optical Carrier Suppression Technique  

NASA Astrophysics Data System (ADS)

In this paper, we propose and demonstrate a novel survivable WDM-PON architecture using Optical Carrier Suppression (OCS) technique. It can provide protection against the feeder fiber failure. The simulation results for the scheme at 2.5 Gbit/s downstream signals and 2.5 Gbit/s upstream signals are presented to verify the feasibility of system.

Song, Yingxiong; Gan, Chaoqin; Gong, Yan; Chen, Benyang

2013-12-01

351

Improvement of the optical imaging technique for intact rat brain using a plano-concave lens.  

PubMed

Use of a plano-concave lens improved the quality of optical signals from the rat cerebral cortex by improving the focus. When detecting neural activity from a curved surface of an in vivo brain by optical techniques, it is not possible to adjust the focus equally over the entire detecting area in the two-dimensional plane, since the active window of the optical detector is usually flat, while the intact brain surface is spherical. It has been known that the size of the optical signal is reduced as the distance of the real image to the active window of the detector increases; therefore, the level of the signal-to-noise ratio obtained from the unfocused area often becomes insufficient for quantitative physiological analyses. By placing a plano-concave lens on the cerebral cortex, we succeeded in obtaining a two-dimensional image that has no unfocused area over an entire image recorded by the detector. PMID:25249031

Kawai, Minako; Hama, Noriyuki; Ito, Shin-Ichi; Hirota, Akihiko

2014-11-01

352

Optical performance monitoring technique using software-based synchronous amplitude histograms.  

PubMed

We propose and demonstrate a simple technique to monitor both the optical signal-to-noise ratio (OSNR) and chromatic dispersion (CD) by using the software-based synchronous amplitude histogram (SAH) analysis. We exploit the software-based synchronization technique to construct SAHs from the asynchronously sampled intensities of the signal. The use of SAHs facilitates the accurate extraction of the monitoring parameters at the center of the symbol. Thus, unlike in the case of using the technique based on the asynchronous amplitude histogram (AAH), this technique is not affected by the transient characteristics of the modulated signals. The performance of the proposed monitoring technique is evaluated experimentally by using 10-Gbaud quadrature phase-shift keying (QPSK) and quadrature amplitude modulation (QAM) signals over wide ranges of OSNR and CD. We also evaluate the robustness of the proposed technique to the signal's transient characteristics. PMID:25321978

Choi, H G; Chang, J H; Kim, Hoon; Chung, Y C

2014-10-01

353

Hardware Implementation of Multiple Fan Beam Projection Technique in Optical Fibre Process Tomography  

PubMed Central

The main objective of this project is to implement the multiple fan beam projection technique using optical fibre sensors with the aim to achieve a high data acquisition rate. Multiple fan beam projection technique here is defined as allowing more than one emitter to transmit light at the same time using the switch-mode fan beam method. For the thirty-two pairs of sensors used, the 2-projection technique and 4-projection technique are being investigated. Sixteen sets of projections will complete one frame of light emission for the 2-projection technique while eight sets of projection will complete one frame of light emission for the 4-projection technique. In order to facilitate data acquisition process, PIC microcontroller and the sample and hold circuit are being used. This paper summarizes the hardware configuration and design for this project.

Rahim, Ruzairi Abdul; Fazalul Rahiman, Mohd Hafiz; Leong, Lai Chen; Chan, Kok San; Pang, Jon Fea

2008-01-01

354

Precoding techniques for PAPR reduction in asymmetrically clipped OFDM based optical wireless system  

NASA Astrophysics Data System (ADS)

In this paper, we have analyzed different precoding based Peak-to-Average-Power (PAPR) reduction techniques for asymmetrically-clipped Orthogonal Frequency Division Multiplexing (OFDM) optical wireless communication systems. Intensity Modulated Direct Detection (IM/DD) technique is among the popular techniques for optical wireless communication systems. OFDM cannot be directly applied to IM systems because of the bipolar nature of the output signal. Therefore some variants of OFDM systems have been proposed for (IM/DD) optical wireless systems. Among them are DC-biased-OFDM, Asymmetrically-Clipped Optical OFDM (ACO-OFDM) [2] and Pulse Amplitude Modulated Discrete Multitone (PAM-DMT) [3]. Both ACO-OFDM and PAM-DMT require low average power and thus are very attractive for optical wireless systems. OFDM systems suffer from high PAPR problem that can limit its performance due to non-linear characteristics of LED. Therefore PAPR reduction techniques have to be employed. This paper analyzes precoding based PAPR reduction methods for ACO-OFDM and PAM-DMT. We have used Discrete Fourier Transform (DFT) coding, Zadoff-Chu Transform (ZCT) [8] and Discrete Cosine Transform (DCT) for ACOOFDM and only DCT for PAM-DMT since the modulating symbols are real. We have compared the performance of these precoding techniques using different QAM modulation schemes. Simulation results have shown that both DFT and ZCT offer more PAPR reduction than DCT in ACO-OFDM. For PAM-DMT, DCT precoding yields significant PAPR reduction compared to conventional PAM-DMT signal. These precoding schemes also offer the advantage of zero signaling overhead.

Ranjha, Bilal; Kavehrad, Mohsen

2013-01-01

355

Multiposition alignment of strapdown inertial navigation system  

Microsoft Academic Search

The authors demonstrate that the stationary alignment of strapdown inertial navigation system (SDINS) can be improved by employing the multiposition\\/technique. Using an observability analysis, it is shown that an optimal two-position alignment not only satisfies complete observability conditions but also minimizes alignment errors. This is done by analytic rank testing of the stripped observability matrix and numerical calculation of the

J. G. Lee; C. G. Park; H. W. Park

1993-01-01

356

Effects of phase noise in an optical six-port measurement technique.  

PubMed

We study the effects of laser phase noise on a phase diversity coherent optical frequency domain (C-OFD) technique that has been recently proposed to measure passive devices used in dense wavelength division multiplexing (DWDM) systems. Theoretical expressions are provided to calculate the laser phase-noise to intensity-noise conversion in this technique under simplified circumstances. Obtained simulation results for a realistic measurement set-up show the validity of the approximate expressions. It is concluded that this effect is one of the limiting source of error for this measurement technique. PMID:19495140

Molina-Fernández, I; de-Oliva-Rubio, J

2005-04-01

357

Techniques for generation of control and guidance signals derived from optical fields, part 2  

NASA Technical Reports Server (NTRS)

The development is reported of a high resolution technique for the detection and identification of landmarks from spacecraft optical fields. By making use of nonlinear regression analysis, a method is presented whereby a sequence of synthetic images produced by a digital computer can be automatically adjusted to provide a least squares approximation to a real image. The convergence of the method is demonstrated by means of a computer simulation for both elliptical and rectangular patterns. Statistical simulation studies with elliptical and rectangular patterns show that the computational techniques developed are able to at least match human pattern recognition capabilities, even in the presence of large amounts of noise. Unlike most pattern recognition techniques, this ability is unaffected by arbitrary pattern rotation, translation, and scale change. Further development of the basic approach may eventually allow a spacecraft or robot vehicle to be provided with an ability to very accurately determine its spatial relationship to arbitrary known objects within its optical field of view.

Hemami, H.; Mcghee, R. B.; Gardner, S. R.

1971-01-01

358

Molecular imaging with optics: primer and case for near-infrared fluorescence techniques in personalized medicine  

PubMed Central

We compare and contrast the development of optical molecular imaging techniques with nuclear medicine with a didactic emphasis for initiating readers into the field of molecular imaging. The nuclear imaging techniques of gamma scintigraphy, single-photon emission computed tomography, and positron emission tomography are first briefly reviewed. The molecular optical imaging techniques of bioluminescence and fluorescence using gene reporter/probes and gene reporters are described prior to introducing the governing factors of autofluorescence and excitation light leakage. The use of dual-labeled, near-infrared excitable and radio-labeled agents are described with comparative measurements between planar fluorescence and nuclear molecular imaging. The concept of time-independent and -dependent measurements is described with emphasis on integrating time-dependent measurements made in the frequency domain for 3-D tomography. Finally, we comment on the challenges and progress for translating near-infrared (NIR) molecular imaging agents for personalized medicine. PMID:19021311

Sevick-Muraca, Eva M.; Rasmussen, John C.

2010-01-01

359

IUS prerelease alignment  

NASA Technical Reports Server (NTRS)

Space shuttle orbiter/IUS alignment transfer was evaluated. Although the orbiter alignment accuracy was originally believed to be the major contributor to the overall alignment transfer error, it was shown that orbiter alignment accuracy is not a factor affecting IUS alignment accuracy, if certain procedures are followed. Results are reported of alignment transfer accuracy analysis.

Evans, F. A.

1978-01-01

360

New plasma technique for the deposition of silica layers for integrated optics applications  

NASA Astrophysics Data System (ADS)

An inductively coupled plasma torch has been used for the synthesis of high-purity, low OH concentration, fused silica layers, for integrated optics applications. This technique is very versatile and the same apparatus can be used to deposit silica layers doped with different elements but this work is particularly devoted to the germanium-doped silica layers. The torch, designed and built in-house, operates at atmospheric pressure and is posed by a 13.56 MHz, 5.4 kW, RF generator. The gaseous reactants are injected in the plasma tail flame by a silica nozzle. Planar silica targets are suitably moved over the torch exit in order to obtain the desired deposition. The samples made by means of this chemical vapor deposition process have been chemically and physically analyzed using various techniques: optical microscopy, scanning electron microscopy, atomic force microscopy, x-ray diffractometer, UV, visible and IR spectroscopy, to test their morphological, geometrical, chemical and optical characteristics. By this plasma- assisted technique it has been possible to achieve the deposition of pure and germanium doped silica layers with good optical and morphological characteristics. Preliminary direct UV photoinduction experiments are very promising: a high refractive index change has been measured.

Panciatichi, Cristina; Natascia De Leo, Maria C.

2000-03-01

361

Optical diagnostic techniques for use in lesions of the head and neck: review of the latest developments.  

PubMed

Optical biopsy systems are a potential adjunct to the histopathological assessment of tissue specimens; they are not invasive and can give an immediate result. We review the most common optical biopsy techniques used to detect lesions of the head and neck: elastic scattering spectroscopy, microendoscopy, narrow band imaging, fluorescence, and optical coherence tomography, and discuss their clinical use. PMID:25015019

Green, Ben; Cobb, Alistair R M; Brennan, Peter A; Hopper, Colin

2014-10-01

362

A fiber-optic diagnostic technique for mechanical detection of the laser-metal interaction underwater  

NASA Astrophysics Data System (ADS)

A new fiber-optic force sensor based on optical beam deflection for the investigation of the mechanical effects during laser-metal interaction underwater is developed. This sensor is applied to detect the laser-induced plasma ablation force and liquid-jet impact during the cavitation bubble collapse near a solid boundary when a Q-switched laser is focused on a metal in water. The experimental results indicate the liquid-jet effect outweighs the well-known laser-induced plasma ablation force. This technique has the advantages of high-frequency response, simple structure, and nondestructive examination.

Xu, R. Q.; Chen, X.; Shen, Z. H.; Lu, J.; Ni, X. W.

2004-03-01

363

USE OF DIFFERENT MORPHOLOGICAL TECHNIQUES TO ANALYZE THE CELLULAR COMPOSITION OF THE ADULT ZEBRAFISH OPTIC TECTUM  

PubMed Central

Cellular composition of the adult zebrafish (Danio rerio) optic tectal cortex was examined in this study. Morphological techniques such as 1µm thick serial plastic sections stained with osmium tetroxide and toluidine blue, modified rapid Golgi silver impregnation, GFAP immunohistochemistry, confocal microscopy, as well as scanning and transmission electron microscopy were used. Neuronal and glial components are described and the layers of the cortex are revisited. Specific neuronal arrangements as well as unique glial/ependymal cells are described. A three dimensional rendering of the astrocytic fiber arrangement in the marginal zone is presented and a composite drawing summarizes the cellular composition of the optic tectum. PMID:21823204

Corbo, Christopher P.; Othman, Nidaa A.; Gutkin, Michael C.; Alonso, Alejandra del C.; Fulop, Zoltan L.

2011-01-01

364

Production and applications of vertically aligned single-walled carbon nanotubes *Erik Einarsson  

E-print Network

-8656, Japan Synthesis of vertically aligned single-walled carbon nanotube (VA-SWNT) thin films by alcohol catalytic chemical vapor deposition has been clarified using an in situ optical absorbance measurement technique, which makes it possible to control the final film thickness. These VA-SWNT films can be detached

Maruyama, Shigeo

365

Optical microscopy as a comparative analytical technique for single-particle dissolution studies.  

PubMed

Novel, simple and cost effective methods are needed to replace advanced chemical analytical techniques, in small-scale dissolution studies. Optical microscopy of individual particles could provide such a method. The aim of the present work was to investigate and verify the applicability of optical microscopy as an analytical technique for drug dissolution studies. The evaluation was performed by comparing image and chemical analysis data of individual dissolving particles. It was shown that the data obtained by image analysis and UV-spectrophotometry produced practically identical dissolution curves, with average similarity and difference factors above 82 and below 4, respectively. The relative standard deviation for image analysis data, of the studied particle size range, varied between 1.9% and 3.8%. Consequently, it is proposed that image analysis can be used, on its own, as a viable analytical technique in single-particle dissolution studies. The possibility for significant reductions in sample preparation, operational cost, time and substance consumption gives optical detection a clear advantage over chemical analytical methods. Thus, image analysis could be an ideal and universal analytical technique for rapid small-scale dissolution studies. PMID:24751345

Svanbäck, Sami; Ehlers, Henrik; Yliruusi, Jouko

2014-07-20

366

Air pollution monitoring with two optical remote sensing techniques in Mexico City  

NASA Astrophysics Data System (ADS)

An open-path Fourier Transform Infrared (FTIR) and a Differential Optical Absorption Spectrometer (DOAS) were installed and simultaneously operated along a 426 m optical path in downtown Mexico City. O3 and SO2 were measured by both optical remote sensing techniques and the results from the comparison are presented. The instruments presented comparable sensitivities for O3 and an excellent agreement (R2 > 0.99) in their correlation. Although the sensitivity of the infrared technique for SO2 was limited to concentrations > 20 ppb or so, the agreement of the FTIR response with the more sensitive DOAS technique during the high levels of this pollutant was favorable (R2 = 0.94) and accurate to within experimental error. These episodes (>100 ppb) were found to occur several times per month. Benzene and toluene were measured by the DOAS technique and their concentrations are reported for a 3-month period during 11/2 - 12/5, 2003. The mean and highest concentration registered for benzene was 5.1 and 18.7 ppb, respectively, with an average of daily maxima at 11.5 ppb. Toluene's highest concentration during this period reached 97.3 ppb, with a mean and daily maximum average of 13.4 and 41.7 ppb, respectively. A benzene/toluene ratio of 2.6 was determined for the entire period of study and a decrease of ~20% in the daily ambient concentration of these aromatic hydrocarbons was observed on Sundays relative to weekdays.

Grutter, Michel; Flores-Jardines, Edgar

2004-11-01

367

In-line particle sizing for real-time process control by fibre-optical spatial filtering technique (SFT)  

Microsoft Academic Search

Sizing of particles in industrial processes is of great technical interest and therefore different physical-based techniques have been developed. The objective of this study was to review the characteristics of modern sizing instruments based on a modified fibre-optical spatial filtering technique (SFT). Fibre-optical spatial filtering velocimetry was modified by fibre-optical spot scanning in order to determine simultaneously the size and

Petrak Dieter; Dietrich Stefan; Eckardt Günter; Köhler Michael

2011-01-01

368

A Wafer-Bonded, Floating Element Shear-Stress Sensor Using a Geometric Moire Optical Transduction Technique  

NASA Technical Reports Server (NTRS)

This paper presents a geometric Moir optical-based floating-element shear stress sensor for wind tunnel turbulence measurements. The sensor was fabricated using an aligned wafer-bond/thin-back process producing optical gratings on the backside of a floating element and on the top surface of the support wafer. Measured results indicate a static sensitivity of 0.26 microns/Pa, a resonant frequency of 1.7 kHz, and a noise floor of 6.2 mPa/(square root)Hz.

Horowitz, Stephen; Chen, Tai-An; Chandrasekaran, Venkataraman; Tedjojuwono, Ken; Cattafesta, Louis; Nishida, Toshikazu; Sheplak, Mark

2004-01-01

369

A Simple Technique Based on a Single Optical Trap for the Determination of Bacterial Swimming Pattern  

PubMed Central

Bacterial motility is associated to a wide range of biological processes and it plays a key role in the virulence of many pathogens. Here we describe a method to distinguish the dynamic properties of bacteria by analyzing the statistical functions derived from the trajectories of a bacterium trapped by a single optical beam. The approach is based on the model of the rotation of a solid optically trapped sphere. The technique is easily implemented in a biological laboratory, since with only a small number of optical and electronic components a simple biological microscope can be converted into the required analyzer. To illustrate the functionality of this method, we probed several serovar Typhimurium mutants that differed from the wild-type with respect to their swimming patterns. In a further application, the motility dynamics of the Typhimurium mutant were characterized. PMID:23637869

Martínez, Ignacio A.; Campoy, Susana; Tort, Meritxell; Llagostera, Montserrat; Petrov, Dmitri

2013-01-01

370

An Absolute Displacement Sensor Using Moire Fringe Techniques With Multimode Optical Fibres  

NASA Astrophysics Data System (ADS)

The feasibility of the use of optical fibres to supply light to, and relay information from, an absolute moire fringe displacement sensor has been demonstrated and a prototype built. Fringe interpolation techniques are employed which reduce the susceptibility of the sensor to adventitious intensity fluctuations. The system is designed to operate over a displacement range of 100 ?m and can resolve displacements down to 12 nm: nonlinearity is ±0.8 ?m, while hysteresis and repeatability are better than 0.3 ?m. The system is largely immune to intensity variations on the input light channel, however differential attenuation between any of the four return light channels more seriously affects the measurement. In order to try and avoid this problem an optical arrangement has been investigated in which intensity information corresponding to four quadrature points on the moire-fringe profile is carried in a single return optical fibre using wavelength separation.

Jones, Barry E.; Philp, Graeme S.

1985-08-01

371

Preventing Technique of Metal Deposition on Optical Devices in Space Diode Laser Welding for Space Applications  

NASA Astrophysics Data System (ADS)

In future space developments, the welding in space may be required for the repairs of the ISS and the constructions of lunar base and space structures. The authors have studied the space Gas Hollow Tungsten Arc (GHTA) welding process since 1993. This paper describes the results for space applying the space Diode Laser (DL) welding process which the authors proposed in 2002. It is necessary to prevent the metal deposition on optical devices in order to utilize the space DL welding process in space. The authors studied the preventing technique of metal deposition which covered optical devices with the nozzle and blew the shielding gas out from nozzle outlet. The metal deposition can be reduced by supplying the nozzle with inert gas and blowing the gas out from nozzle outlet. The shielding gas argon perfectly prevents the metal deposition on optical devices when argon pressurizes the nozzle to over 19.9 Pa and spouts out from the nozzle outlet.

Suita, Yoshikazu; Tanaka, Kenji; Ohtani, Masato; Shobako, Shinichiro; Terajima, Noboru; Hiraoka, Nobuaki

372

A simple technique based on a single optical trap for the determination of bacterial swimming pattern.  

PubMed

Bacterial motility is associated to a wide range of biological processes and it plays a key role in the virulence of many pathogens. Here we describe a method to distinguish the dynamic properties of bacteria by analyzing the statistical functions derived from the trajectories of a bacterium trapped by a single optical beam. The approach is based on the model of the rotation of a solid optically trapped sphere. The technique is easily implemented in a biological laboratory, since with only a small number of optical and electronic components a simple biological microscope can be converted into the required analyzer. To illustrate the functionality of this method, we probed several Salmonella enterica serovar Typhimurium mutants that differed from the wild-type with respect to their swimming patterns. In a further application, the motility dynamics of the S. Typhimurium cheV mutant were characterized. PMID:23637869

Martínez, Ignacio A; Campoy, Susana; Tort, Meritxell; Llagostera, Montserrat; Petrov, Dmitri

2013-01-01

373

Using optical remote sensing techniques to track the development of ozone-induced stress.  

PubMed

In this paper, a literature review about optical remote sensing (RS) of O(3) stress is presented. Studies on O(3)-induced effects on vegetation reflectance have been conducted since late '70s based on the analysis of optical RS data. Literature review reveals that traditional RS techniques were able to detect changes in leaf and canopy reflectance related to O(3)-induced stress when visible symptoms already occurred. Only recently, advanced RS techniques using hyperspectral sensors, demonstrated the feasibility of detecting the stress in its early phase by monitoring excess energy dissipation pathways such as chlorophyll fluorescence and non-photochemical quenching (NPQ). Steady-state fluorescence (Fs), measured by exploiting the Fraunhofer line depth principle and NPQ related xanthophyll-cycle, estimated through the photochemical reflectance index (PRI) responded to O(3) fumigation before visible symptoms occurred. This opens up new possibilities for the early detection of vegetation O(3) stress by means of hyperspectral RS. PMID:18976842

Meroni, Michele; Panigada, Cinzia; Rossini, Micol; Picchi, Valentina; Cogliati, Sergio; Colombo, Roberto

2009-05-01

374

Muscle tissue saturation in humans studied with two non-invasive optical techniques: a comparative study  

NASA Astrophysics Data System (ADS)

Muscle tissue saturation (StO2) has been measured with two non-invasive optical techniques and the results were compared. One of the techniques is widely used in the hospitals - the CW-NIRS technique. The other is the photon timeof- flight spectrometer (pTOFS) developed in the Group of Biophotonics, Lund University, Sweden. The wavelengths used in both the techniques are 730 nm and 810 nm. A campaign was arranged to perform measurements on 21 (17 were taken for comparison) healthy adult volunteers (8 women and 13 men). Oxygen saturations were measured at the right lower arm of each volunteer. To observe the effects of different provocations on the oxygen saturation a blood pressure cuff was attached in the upper right arm. For CW-NIRS, the tissue saturation values were in the range from 70-90%, while for pTOFS the values were in the range from 55-60%.

Shaharin, Alfi; Krite Svanberg, Emilie; Ellerström, Ida; Subash, Arman Ahamed; Khoptyar, Dmitry; Andersson-Engels, Stefan; Åkeson, Jonas

2013-11-01

375

Machine learning techniques for astrophysical modelling and photometric redshift estimation of quasars in optical sky surveys  

E-print Network

Machine learning techniques are utilised in several areas of astrophysical research today. This dissertation addresses the application of ML techniques to two classes of problems in astrophysics, namely, the analysis of individual astronomical phenomena over time and the automated, simultaneous analysis of thousands of objects in large optical sky surveys. Specifically investigated are (1) techniques to approximate the precise orbits of the satellites of Jupiter and Saturn given Earth-based observations as well as (2) techniques to quickly estimate the distances of quasars observed in the Sloan Digital Sky Survey. Learning methods considered include genetic algorithms, particle swarm optimisation, artificial neural networks, and radial basis function networks. The first part of this dissertation demonstrates that GAs and PSOs can both be efficiently used to model functions that are highly non-linear in several dimensions. It is subsequently demonstrated in the second part that ANNs and RBFNs can be used as ef...

Kumar, N Daniel

2008-01-01

376

Masking technique for coating thickness control on large and strongly curved aspherical optics.  

PubMed

We discuss a method to control the coating thickness deposited onto large and strongly curved optics by ion beam sputtering. The technique uses an original design of the mask used to screen part of the sputtered materials. A first multielement mask is calculated from the measured two-dimensional coating thickness distribution. Then, by means of an iterative process, the final mask is designed. By using such a technique, it has been possible to deposit layers of tantalum pentoxide having a high thickness gradient onto a curved substrate 500 mm in diameter. Residual errors in the coating thickness profile are below 0.7%. PMID:19571934

Sassolas, B; Flaminio, R; Franc, J; Michel, C; Montorio, J-L; Morgado, N; Pinard, L

2009-07-01

377

Optic disk feature extraction via modified deformable model technique for glaucoma analysis  

Microsoft Academic Search

A deformable-model based approach is presented in this paper for robust detection of optic disk and cup boundaries. Earlier work on disk boundary detection up to now could not effectively solve the problem of vessel occlusion. The method proposed here improves and extends the original snake, which is essentially a deforming-only technique, in two aspects: knowledge-based clustering and smoothing update.

Juan Xu; Opas Chutatape; Eric Sung; Ce Zheng; Paul Chew Tec Kuan

2007-01-01

378

Characterization of thermo-oxidative stability of polymer optical fibers using chemiluminescence technique  

Microsoft Academic Search

The thermo-oxidative stability of commercially available polymer optical fibers (POFs) and their components (cores and claddings) was investigated. All the bare POFs (core and cladding only) studied here were based on poly(methyl methacrylate) (PMMA) core. The fibers were exposed to 100°C\\/low humidity for about 4200h. Chemiluminescence (CL) technique was applied to investigate the thermo-oxidative stability and for measuring the transmission

Anilkumar Appajaiah; Volker Wachtendorf; Werner Daum

2006-01-01

379

Optical sensing quantum dot-labeled polyacrolein particles prepared by layer-by-layer deposition technique  

Microsoft Academic Search

Optical sensing polymer particles with tailored semiconductor nanocrystal (QD) loading are prepared by layer-by-layer deposition technique (LbL). Polyacrolein particles of 1.2?m diameter are used as solid support for deposition of hydrophilic CdSe\\/ZnS nanocrystal\\/polyelectrolyte multilayers formed by electrostatic interactions. The pH-dependent fluorescence of QDs and pH-dependent conformations of polyelectrolytes, which likely passivate the surface state of nanocrystals, allow a creation of

Alla N. Generalova; Vladimir A. Oleinikov; Margarita M. Zarifullina; Ekaterina V. Lankina; Svetlana V. Sizova; Michail V. Artemyev; Vitali P. Zubov

2011-01-01

380

X-Ray Photoresist Characterization Using in Situ Optical Monitoring Techniques  

Microsoft Academic Search

X-ray photoresists were studied using two in situ optical techniques (ellipsometry and imaging interferometry) during development. A conventional photoresist (polymethylmethacrylate\\/KTI Chemicals) and two chemically-amplified photoresists (XP -90104C\\/Shipley and AZ-PF\\/Hoechst) were investigated. Computer programs were used to model the effects of surface roughening, swelling, and dissolution of these resists. A 2048 channel linear CCD array dissolution rate monitor (DRM) was constructed

Monroe Brian Sullivan

1993-01-01

381

Study of optical techniques for the Ames unitary wind tunnel: Digital image processing, part 6  

NASA Technical Reports Server (NTRS)

A survey of digital image processing techniques and processing systems for aerodynamic images has been conducted. These images covered many types of flows and were generated by many types of flow diagnostics. These include laser vapor screens, infrared cameras, laser holographic interferometry, Schlieren, and luminescent paints. Some general digital image processing systems, imaging networks, optical sensors, and image computing chips were briefly reviewed. Possible digital imaging network systems for the Ames Unitary Wind Tunnel were explored.

Lee, George

1993-01-01

382

Global alignment: Finding rearrangements during alignment  

SciTech Connect

Motivation: To compare entire genomes from different species, biologists increasingly need alignment methods that are efficient enough to handle long sequences, and accurate enough to correctly align the conserved biological features between distant species. The two main classes of pairwise alignments are global alignment, where one string is transformed into the other, and local alignment, where all locations of similarity between the two strings are returned. Global alignments are less prone to demonstrating false homology as each letter of one sequence is constrained to being aligned to only one letter of the other. Local alignments, on the other hand, can cope with rearrangements between non-syntenic, orthologous sequences by identifying similar regions in sequences; this, however, comes at the expense of a higher false positive rate due to the inability of local aligners to take into account overall conservation maps.

Brudno, Michael; Malde, Sanket; Poliakov, Alexander; Do, Chuong B.; Couronne, Olivier; Dubchak, Inna; Batzoglou, Serafim

2003-01-06

383

High capacity fiber optic sensor networks using hybrid multiplexing techniques and their applications  

NASA Astrophysics Data System (ADS)

Fiber optic sensor network is the development trend of fiber senor technologies and industries. In this paper, I will discuss recent research progress on high capacity fiber sensor networks with hybrid multiplexing techniques and their applications in the fields of security monitoring, environment monitoring, Smart eHome, etc. Firstly, I will present the architecture of hybrid multiplexing sensor passive optical network (HSPON), and the key technologies for integrated access and intelligent management of massive fiber sensor units. Two typical hybrid WDM/TDM fiber sensor networks for perimeter intrusion monitor and cultural relics security are introduced. Secondly, we propose the concept of "Microstructure?Optical X Domin Refecltor (M-OXDR)" for fiber sensor network expansion. By fabricating smart micro-structures with the ability of multidimensional encoded and low insertion loss along the fiber, the fiber sensor network of simple structure and huge capacity more than one thousand could be achieved. Assisted by the WDM/TDM and WDM/FDM decoding methods respectively, we built the verification systems for long-haul and real-time temperature sensing. Finally, I will show the high capacity and flexible fiber sensor network with IPv6 protocol based hybrid fiber/wireless access. By developing the fiber optic sensor with embedded IPv6 protocol conversion module and IPv6 router, huge amounts of fiber optic sensor nodes can be uniquely addressed. Meanwhile, various sensing information could be integrated and accessed to the Next Generation Internet.

Sun, Qizhen; Li, Xiaolei; Zhang, Manliang; Liu, Qi; Liu, Hai; Liu, Deming

2013-12-01

384

Image quality in optical imaging by time-correlated single photon-counting technique  

NASA Astrophysics Data System (ADS)

Theoretical and experimental investigations on image quality are extremely important in optical imaging in order to better define the role of optical techniques in medical diagnostics. Today time-resolved laser transillumination can be considered a good candidate as an alternative and/or auxiliary technique in medical diagnostic field. The intrinsic quality of an image is related to the concepts of spatial resolution, noise and contrast. A common method to measure these parameters is by using Edge Response Function measurements with a black mask. We investigated these parameters using an experimental apparatus mainly composed by a picosecond solid-state laser and a time-correlated single photon-counting system. The investigated samples were suspensions of Intralipid 10% with distilled water in which a black mask was inserted and bidimensional scanning were performed. The experimental data were analyzed in order to get information on the above-mentioned image quality parameters. For spatial resolution a comparison with random walk predictions has been attempted. The results of this study can be particularly useful in identifying the best working conditions and in improving teh performance of image reconstruction algorithms since the clinical prototypes of optical mammogrpahers nowadays under pre-clinical investigation adopt time-correlated single photon-counting technique.

Mormile, M.; Esposito, R.; Romano, R.; Lepore, M.; Indovina, P. L.

2005-06-01

385

Experimental Sensitivity Table Method for Precision Alignment of Amon-Ra Instrument  

NASA Astrophysics Data System (ADS)

The Amon-Ra instrument is the main optical payload of the proposed EARTHSHINE satellite. It consists of a visible wavelength instrument and an IR energy channel instrument to measure a global Earth albedo. We report a new sensitivity technique for efficient alignment of the visible channel instrument. Whilst the sensitivity table method has been widely used in the alignment process, the straightforward application of the method tends to produce slow process convergence because of shop floor alignment practice uncertainties. We investigated the error sources commonly associated with alignment practices and used them when estimating the Zernike polynomial coefficients. Aided with single center field wavefront error (WFE) measurements and their corresponding Zernike polynomial coefficients, the method involves the construction and use of an experimental, instead of simulated, sensitivity table to be used for alignment state estimations. A trial alignment experiment for the Amon Ra optical system was performed and the results show that 71.28 nm in rms WFE was achieved only after two alignment iterations. This tends to demonstrate its superior performance to the conventional method.

Oh, Eunsong; Ahn, Ki-Beom; Kim, Sug-Whan

2014-09-01

386

Physics and applications of aligned carbon nanotubes  

Microsoft Academic Search

Ever since the discovery of carbon nanotubes (CNTs) by Iijima in 1991, there have been extensive research efforts on their synthesis, physics, electronics, chemistry, and applications due to the fact that CNTs were predicted to have extraordinary physical, mechanical, chemical, optical, and electronic properties. Among the various forms of CNTs, single-walled and multi-walled, random and aligned, semiconducting and metallic, aligned

Yucheng Lan; Yang Wang; Z. F. Ren

2011-01-01

387

New Active Optical Technique Developed for Measuring Low-Earth-Orbit Atomic Oxygen Erosion of Polymers  

NASA Technical Reports Server (NTRS)

Polymers such as polyimide Kapton (DuPont) and Teflon FEP (DuPont, fluorinated ethylene propylene) are commonly used spacecraft materials because of desirable properties such as flexibility, low density, and in the case of FEP, a low solar absorptance and high thermal emittance. Polymers on the exterior of spacecraft in the low-Earth-orbit (LEO) environment are exposed to energetic atomic oxygen. Atomic oxygen reaction with polymers causes erosion, which is a threat to spacecraft performance and durability. It is, therefore, important to understand the atomic oxygen erosion yield E (the volume loss per incident oxygen atom) of polymers being considered in spacecraft design. The most common technique for determining E is a passive technique based on mass-loss measurements of samples exposed to LEO atomic oxygen during a space flight experiment. There are certain disadvantages to this technique. First, because it is passive, data are not obtained until after the flight is completed. Also, obtaining the preflight and postflight mass measurements is complicated by the fact that many polymers absorb water and, therefore, the mass change due to water absorption can affect the E data. This is particularly true for experiments that receive low atomic oxygen exposures or for samples that have a very low E. An active atomic oxygen erosion technique based on optical measurements has been developed that has certain advantages over the mass-loss technique. This in situ technique can simultaneously provide the erosion yield data on orbit and the atomic oxygen exposure fluence, which is needed for erosion yield determination. In the optical technique, either sunlight or artificial light can be used to measure the erosion of semitransparent or opaque polymers as a result of atomic oxygen attack. The technique is simple and adaptable to a rather wide range of polymers, providing that they have a sufficiently high optical absorption coefficient. If one covers a photodiode with a uniformly thick sheet of semitransparent polymer such as Kapton H polyimide, then as atomic oxygen erodes the polymer, the short-circuit current from the photodiode will increase in an exponential manner with fluence. This nonlinear response with fluence results in a lack of sensitivity for measuring low atomic oxygen fluences. However, if one uses a variable-thickness polymer or carbon sample, which is configured as shown in the preceding figure, then a linear response can be achieved for opaque materials using a parabolic well for a circular geometry detector or a V-shaped well for a rectangular-geometry detector. Variable-thickness samples can be fabricated using many thin polymer layers. For semitransparent polymers such as Kapton H polyimide, there is an initial short-circuit current that is greater than zero. This current has a slightly nonlinear dependence on atomic oxygen fluence in comparison to opaque materials such as black Kapton as shown in the graph. For this graph figure, the total thickness of Kapton H was assumed to be 0.03 cm. The photodiode short-circuit current shown in the graph was generated on the basis of preliminary measurements-a total reflectance rho of 0.0424 and an optical absorption coefficient a of 146.5 cm(sup -1). In addition to obtaining on-orbit data, the advantage of this active erosion and erosion yield measurement technique is its simplicity and reliance upon well-characterized fluence witness materials as well as a nearly linear photodiode short-circuit current dependence upon atomic oxygen fluence. The optical technique is useful for measuring either atomic oxygen fluence or erosion, depending on the information desired. To measure the atomic oxygen erosion yield of a test material, one would need to have two photodiode sensors, one for the test material and one that uses a known erosion yield material (such as Kapton) to measure the atomic oxygen fluence.

Banks, Bruce A.; deGroh, Kim K.; Demko, Rikako

2003-01-01

388

Topical Meeting on Laser and Optical Remote Sensing: Instrumentation and Techniques Technical Digest Held in North Falmoth, Massachusetts on September 28-October 1, 1987. Volume 18.  

National Technical Information Service (NTIS)

Table of Partial Contents: Lidars in Space; Dial Measurements of Atmospheric Gases; Lidar Measurement and Analyses; Optical Techniques for Earth System Science; Unique Applications of Optical Remote Sensing; Optical Remote Sensing Methods and Devices; Rem...

J. W. Quinn

1988-01-01

389

Resonator fiber optic gyro using the triangle wave phase modulation technique  

NASA Astrophysics Data System (ADS)

Based on the Sagnac effect, resonator fiber optic gyro (R-FOG) has potential as a high accuracy inertial rotation sensor. An R-FOG based on the triangle wave phase modulation technique is proposed in this paper. The slope of the demodulation curve near the resonance dip is found to affect the ultimate sensitivity of the gyro. In order to maximize the slope of the demodulation signal, the parameters of the triangle wave are analyzed. By employing Fourier series and the method of field overlapping, the relationship between the demodulation signal and the resonance frequency deviation is analyzed. The optimum values for the modulation frequency and phase modulation index are obtained. And the relationship between the carrier component and the phase modulation index under analysis in this paper shows that the triangle wave phase modulation technique is more advantageous than the traditional modulation technique in reducing the noise induced by backscattering.

Ying, Diqing; Ma, Huilian; Jin, Zhonghe

2008-02-01

390

Jitter model and signal processing techniques for pulse width modulation optical recording  

NASA Technical Reports Server (NTRS)

A jitter model and signal processing techniques are discussed for data recovery in Pulse Width Modulation (PWM) optical recording. In PWM, information is stored through modulating sizes of sequential marks alternating in magnetic polarization or in material structure. Jitter, defined as the deviation from the original mark size in the time domain, will result in error detection if it is excessively large. A new approach is taken in data recovery by first using a high speed counter clock to convert time marks to amplitude marks, and signal processing techniques are used to minimize jitter according to the jitter model. The signal processing techniques include motor speed and intersymbol interference equalization, differential and additive detection, and differential and additive modulation.

Liu, Max M.-K.

1991-01-01

391

Novel electro-optical predistortion technique and its application in externally modulated CATV transmission systems  

NASA Astrophysics Data System (ADS)

Conventional linearization techniques such as electrical pre-distortion or optical feedforward methods have been applied to Mach-Zehnder interferometer (MZI) modulators for CATV transmission systems. However, both methods can only ensure that the output of the MZI modulator meet the standard CATV requirements on composite second-order and composite triple beat, but cannot guarantee a satisfactory end-to-end system linearity. In this paper, we propose and demonstrate a novel linearization technique, which can simultaneously suppress the nonlinear distortions generated in a transmission system and increase the received carrier- to-noise ratio. This technique is based on offsetting the MZI bias voltage from its inflection point. Both analytical and experimental results are presented.

Tsai, Kuen-Ting; Tai, Chien; Way, Winston I.

1998-06-01

392

Polarized light emission by deposition of aligned semiconductor nanorods  

NASA Astrophysics Data System (ADS)

The ability to control the position and orientation of nanorods in a device is interesting both from a scientific and a technological point of view. Because semiconductor nanorods exhibit anisotropic absorption, and spontaneous and stimulated emission, aligning individual NRs to a preferred axis is attractive for many applications in photonics such as solar cells, light-emitting devices, optical sensors, switches, etc. Electric-field-driven deposition from colloidal suspensions has proven to be an efficient method for the controlled positioning and alignment of anisotropic particles. In this work, we present a novel technique for the homogeneous deposition and alignment of CdSe/CdS NRs on a glass substrate patterned with transparent indium tin oxide interdigitated electrodes, with a spacing of a few micrometers. This method is based on applying a strong AC electric field over the electrodes during a dip-coating procedure and subsequent evaporation of the solvent. The reproducible and homogeneous deposition on large substrates is required for large size applications such as solar cells or OLEDs. The accumulation, alignment, and polarized fluorescence of the nanorods as a function of the electrical field during deposition are investigated. A preferential alignment with an order parameter of 0.92 has been achieved.

Mohammadimasoudi, Mohammad; Penninck, Lieven; Aubert, Tangi; Gomes, Raquel; Hens, Zeger; Strubbe, Filip; Neyts, Kristiaan

2014-08-01

393

September 1, 1995 / Vol. 20, No. 17 / OPTICS LETTERS 1821 Z-scan measurement technique for non-Gaussian  

E-print Network

September 1, 1995 / Vol. 20, No. 17 / OPTICS LETTERS 1821 Z-scan measurement technique for non demonstrate a new Z-scan measurement technique that permits the use of non-Gaussian beams and thick, as well Society of America The Z-scan measurement technique is a simple experi- mental procedure that gives

Boyd, Robert W.

394

Advanced Electro-Optic Surety Devices  

SciTech Connect

The Advanced Electro-Optic Surety Devices project was initiated in march 1991 to support design laboratory guidance on electro-optic device packaging and evaluation. Sandia National Laboratory requested AlliedSignal Inc., Kansas City Division (KCD), to prepare for future packaging efforts in electro-optic integrated circuits. Los Alamos National Laboratory requested the evaluation of electro-optic waveguide devices for nuclear surety applications. New packaging techniques involving multiple fiber optic alignment and attachment, binary lens array development, silicon V-groove etching, and flip chip bonding were requested. Hermetic sealing of the electro-optic hybrid and submicron alignment of optical components present new challenges to be resolved. A 10-channel electro-optic modulator and laser amplifier were evaluated for potential surety applications.

Watterson, C.E.

1997-05-01

395

Directed 3D cell alignment and elongation in microengineered hydrogels  

Microsoft Academic Search

Organized cellular alignment is critical to controlling tissue microarchitecture and biological function. Although a multitude of techniques have been described to control cellular alignment in 2D, recapitulating the cellular alignment of highly organized native tissues in 3D engineered tissues remains a challenge. While cellular alignment in engineered tissues can be induced through the use of external physical stimuli, there are

Hug Aubin; Jason W. Nichol; Ché B. Hutson; Hojae Bae; Alisha L. Sieminski; Donald M. Cropek; Paryam Akhyari; Ali Khademhosseini

2010-01-01

396

Comparison of Beam-Based Alignment Algorithms for the ILC  

SciTech Connect

The main linac of the International Linear Collider (ILC) requires more sophisticated alignment techniques than those provided by survey alone. Various Beam-Based Alignment (BBA) algorithms have been proposed to achieve the desired low emittance preservation. Dispersion Free Steering, Ballistic Alignment and the Kubo method are compared. Alignment algorithms are also tested in the presence of an Earth-like stray field.

Smith, J.C.; Gibbons, L.; Patterson, J.R.; Rubin, D.L.; /Cornell U., LEPP; Sagan, D.; /Cornell U., Phys. Dept.; Tenenbaum, P.; /SLAC

2006-03-15

397

High-resolution fiber optic temperature sensors using nonlinear spectral curve fitting technique  

NASA Astrophysics Data System (ADS)

A generic new data processing method is developed to accurately calculate the absolute optical path difference of a low-finesse Fabry-Perot cavity from its broadband interference fringes. The method combines Fast Fourier Transformation with nonlinear curve fitting of the entire spectrum. Modular functions of LabVIEW are employed for fast implementation of the data processing algorithm. The advantages of this technique are demonstrated through high performance fiber optic temperature sensors consisting of an infrared superluminescent diode and an infrared spectrometer. A high resolution of 0.01 °C is achieved over a large dynamic range from room temperature to 800 °C, limited only by the silica fiber used for the sensor.

Su, Z. H.; Gan, J.; Yu, Q. K.; Zhang, Q. H.; Liu, Z. H.; Bao, J. M.

2013-04-01

398

Realization of a polymer nanowire optical transducer by using the nanoimprint technique.  

PubMed

An optical transducer using an integrated optics polymer nanowire is proposed. The nanoimprint technique is used to fabricate an OrmoComp nanowire with 1.0 ?m width and 0.5 ?m height, but the resulting sidewalls are not perfectly vertical. Maximum sensitivity is achieved by enhancing the evanescent field in the cladding region. The possible mode fields and power confinement of the nanowire are studied with respect to their structural dimensions, the operating wavelength, and the cladding material by using the H-field finite element method. The attenuation coefficient is extracted and calculated over the different cladding media, specifically air, water, and glycerol solution. It is observed that the scattering caused due to the surface roughness is the dominant effect that provides a larger attenuation coefficient. PMID:25402916

Viphavakit, Charusluk; Atthi, Nithi; Boonruang, Sakoolkan; Themistos, Christos; Komodromos, Michael; Mohammed, Waleed S; Azizur Rahman, B M

2014-11-01

399

[Techniques of on-line monitoring volatile organic compounds in ambient air with optical spectroscopy].  

PubMed

Volatile organic compounds (VOCs) are harmful gaseous pollutants in the ambient air. The techniques of on-line monitoring VOCs are very significant for environment protection. Until now, there is no single technology that can meet all the needs of monitoring various VOCs. The characteristics and present situation of several optical methods, which can be applied to on-line monitoring VOCs, including non dispersive infrared (NDIR), Fourier transform infrared (FTIR) spectroscopy, differential optical absorption spectroscopy (DOAS), and laser spectroscopy were reviewed. Comparison was completed between the national standard methods and spectroscopic method for measuring VOCs. The main analysis was focused on the status and trends of tuning diode laser absorption spectroscopy (TDLAS) technology. PMID:20210131

Du, Zhen-Hui; Zhai, Ya-Qiong; Li, Jin-Yi; Hu, Bo

2009-12-01

400

Loss-compensation technique for fiber-optic sensors and its application to displacement measurements.  

PubMed

This paper describes a new type of fiber-optic sensor which has high immunity to the effects of variations in the fiber and connector losses. A beam-splitting transducer differentially modulates, as a function of the sensed parameter, the proportions of the incident light which it transmits and reflects. Using a four-fiber optical link, light is impinged onto the transducer from either direction, and, in each case, the transmitted and reflected light are measured. These four signals are processed to remove the influence of the fiber and connector losses. A loss-compensated displacement sensor, which uses a schlieren-type transduction mechanism, is demonstrated. The experimental results show that this loss-compensation technique can stabilize the sensor output to a high degree despite considerable variations in the transmissivities of the fiber-link components. PMID:20454156

Beheim, G

1987-02-01

401

Temperature compensation techniques for resonantly enhanced sensors and devices based on optical microcoil resonators  

NASA Astrophysics Data System (ADS)

It is well known that environmental effects have a major influence on the optical stability of resonantly enhanced sensors and devices based on optical microfiber, namely in the configuration of a microcoil resonator. We propose a geometric design to reduce such effects by chirping the refractive index of successive paired turns in the microcoil resonator. The resistance to external effects such as temperature drifts can be considerably improved by optimizing the coupling coefficients and chirping profile, such that the wavelength span of the resonant condition is maximized without compensating its sensitivity to the desired measurand. We also demonstrate another technique based on resonant wavelength tuning using a compact piezoelectric ceramic disk measuring 3 mm in diameter and 1 mm in thickness, attaining tunability as high as 6.5 pm/100 V.

Chen, G. Y.; Lee, T.; Zhang, X. L.; Brambilla, G.; Newson, T. P.

2012-10-01

402

Formation and evolution of planetary systems: the impact of high angular resolution optical techniques  

E-print Network

The direct images of giant extrasolar planets recently obtained around several main sequence stars represent a major step in the study of planetary systems. These high-dynamic range images are among the most striking results obtained by the current generation of high angular resolution instruments, which will be superseded by a new generation of instruments in the coming years. It is therefore an appropriate time to review the contributions of high angular resolution visible/infrared techniques to the rapidly growing field of extrasolar planetary science. During the last 20 years, the advent of the Hubble Space Telescope, of adaptive optics on 4- to 10-m class ground-based telescopes, and of long-baseline infrared stellar interferometry has opened a new viewpoint on the formation and evolution of planetary systems. By spatially resolving the optically thick circumstellar discs of gas and dust where planets are forming, these instruments have considerably improved our models of early circumstellar environments...

Absil, Olivier; 10.1007/s00159-009-0028-y

2009-01-01

403

Electro-optic techniques for temporal profile characterisation of relativistic Coulomb fields and coherent synchrotron radiation  

NASA Astrophysics Data System (ADS)

Electro-optic (EO) detection of relativistic Coulomb fields offers a method for non-destructive longitudinal profile measurements of ultrashort bunches. Techniques for single-shot EO characterisation of Coulomb fields which have been developed or demonstrated at the FELIX free electron laser (FEL) facility are discussed. In addition, recent FELIX experiments have used single-shot electro-optic detection to measure the temporal profile of the far-infrared electric field pulse of coherent synchrotron radiation (CSR), initial results of which are reported here. Such time-resolved CSR measurements have the potential for a completely non-invasive bunch longitudinal profile determination, without the ambiguity in profile that is present in CSR spectral measurements.

Jamison, S. P.; Berden, G.; MacLeod, A. M.; Jaroszynski, D. A.; Redlich, B.; van der Meer, A. F. G.; Gillespie, W. A.

2006-02-01

404

Synthesis, structural, optical, thermal and dielectric studies on new organic nonlinear optical crystal by solution growth technique.  

PubMed

Single crystals of L-phenylalanine-benzoic acid (LPBA) were successfully grown from aqueous solution by solvent evaporation technique. Purity of the crystals was increased by the method of recrystallization. The XRD analysis confirms that the crystal belongs to the monoclinic system with noncentrosymmetric space group P21. The chemical structure of compound was established by FT-NMR technique. The presence of functional groups was estimated qualitatively by Fourier transform infrared analysis (FT-IR). Ultraviolet-visible spectral analyses showed that the crystal has low UV cut-off at 254 nm combined with very good transparency of 90% in a wide range. The optical band gap was estimated to be 6.91 eV. Thermal behavior has been studied with TGA/DTA analyses. The existence of second harmonic generation (SHG) efficiency was found to be 0.56 times the value of KDP. The dielectric behavior of the sample was also studied for the first time. PMID:23416904

Prakash, M; Geetha, D; Lydia Caroline, M

2013-04-15

405

Differential optical absorption spectroscopy technique in emission monitoring: temperature and nonlinearity effects  

NASA Astrophysics Data System (ADS)

When applying the differential optical absorption spectroscopy (DOAS) technique for in-situ monitoring of flue-gas emissions, two main problems may occur in comparison to the atmospheric monitoring DOAS application. The first problem is due to the high and variable temperatures of flue gases, which significantly affects the magnitude of the differential absorption cross-sections. The second problem is caused by the limited choice of optical path- lengths, causing non-linearity effects due to large gas absorption. Measurements of the differential absorption cross-sections for NO, NO2, and SO2 have therefore been performed in a pyrex-glass cell contained in a heat-pipe, at temperatures between 20 and 400 degree(s)C, in the wavelength range of 205 to 440 nm. We also have performed measurements of the linear regions of the technique for measurements of SO2, NO2, and NO. The linear regions were shown to be 1 - 3200 mgm-2 for NO2, 0 - 2000 mgm-2 for SO2, and 0 - 120 mgm-2 for NO, in the spectral resolution range between 0.2 to 0.95 nm. The differential absorption cross-sections of NO2 and SO2 are strongly temperature dependent causing considerable errors in evaluated concentrations when using the DOAS technique. The relative errors due to temperature were of the order of 70% for SO2 and NO2 and of the order of 15% for NO at 400 degree(s)C.

Mellqvist, Johan M.; Axelsson, Hakan; Rosen, Arne

1993-03-01

406

Detection of Biomass in New York City Aerosols: Light Scattering and Optical Fluorescence Techniques  

NASA Astrophysics Data System (ADS)

Optical spectroscopy is an ideal method for detecting bacteria and spores in real time. Optical fluorescence spectroscopy examination of New York City aerosols is used to quantify the mass of bacteria spores present in air masses collected at 14 liters/minute onto silica fiber filters, and on silica fiber ribbons using an Environmental Beta Attenuation Monitor manufactured by MetOne Instruments configured for the PM2.5 fraction. Dipicolinic acid (DPA), a molecule found primarily in bacterial spores, is the most characteristic component of spores in trial experiments on over 200 collected aerosol samples. DPA is extracted from the spores using a heat bath and chelated with Terbium. The DPA:Tb is detected by measuring its characteristic fluorescence with emission bands at 490, 545 and 585 nm for 270 nm excitation. Light scattering also measures the size distribution for a number of a variety of bacteria - Bacillus subtilis (rod shaped), Staphylococcus aureus (spherical) and Pseudomonas aeruginosa (short rods) establishing that optical techniques satisfactorily distinguish populations based on their variable morphology. Size and morphology are obtained by applying a variation of the Gaussian Ray Approximation theory of anomalous diffraction theory to an analysis of the transmission spectra in the range of 0.4 to 1.0 microns. In test experiments, the refractive index of the inner spore core of Bacillus subtilis decreases from 1.51 to 1.39 while the spore radius enlarges from 0.38 to 0.6 micrometers. Optical determinations are verified by oil-immersion techniques and by scanning electron microscope measurements. Characterization of spores, germinating spore materials, and bacteria is considered vital to tracing bacteria in the environment, for the development of life-detection systems for planetary exploration, monitoring pathogens in environmental systems, and for the preparation of anti-terrorism strategies.

Niebauer, M.; Alimova, A.; Katz, A.; Xu, M.; Rudolph, E.; Steiner, J.; Alfano, R. R.

2005-12-01

407

pH biosensor with plastic fiber optic doped with carbone nanotubes used sol-gel technique  

NASA Astrophysics Data System (ADS)

We prepare optrodes of fiber optic plastic with sol-gel technique. Suitable concentration of carbone nanotubes (CNTs), phenol red, bromophenol blue and cresol red, design optrodes with fiber optic plastic. The surface charge of silica and the refractive index, which play an important roll on the fiber, modifies the conditions of light propagation into the plastic optical fiber. We use the transmittance to measure the pH of a solution or fluid in a range between 3 and 9.

Alvarado-Méndez, E.; Flores-Rangel, S. D.; Hernández-Cruz, D.; Trejo-Durán, M.; Andrade-Lucio, J. A.; Rojas-Laguna, R.; Estudillo-Ayala, J. M.; Vargas-Rodríguez, E.; Mata Chávez, R. I.; García-Hernández, M. G.

2010-10-01

408

Preparation of micron/submicron hybrid patterns via a two-stage UV-imprint technique and their dimensional effects on cell adhesion and alignment.  

PubMed

Cell adhesion, movement and proliferation on a biomaterial have been broadly explored and known to be induced by the morphology and structure of material surfaces. In order to explore the effects of hybrid structures (combination of micro- and nanofeatures on a pattern) on cell adhesion and alignment, a micro-featured mold was firstly prepared using partial UV-irradiation and the protruding top of the mold was then imprinted with nano-featured templates via successive UV irradiation. An oxygen inhibition effect was utilized in the course of UV curing and a two-step molding process, to form multiscale hybrid structures. The poly(dimethyl siloxane) (PDMS) replica of the hybrid mold was manufactured and employed to fabricate hybrid polymeric patterns for cell attachment. The underlying micro-feature was chosen to be a 25-µm-wide pattern and the nanostructures on the protrusions of the micropattern were different ruled nanogrooves, either parallel or perpendicular to the micro-featured pattern. In cell attachment measurement, 3T3 fibroblasts attached to poly(methyl methacrylate) (PMMA) samples seemed to be preferentially located on the recessed area of the hybrid patterns; however, 3T3 fibroblasts were aligned with nano-features, no matter if the nanogrooves were parallel or perpendicular to the micro-featured patterns. The nanogroove size was found to determine the effectiveness of cell alignment. PMID:23714853

Li, J-Y; Ho, Y-C; Chung, Y-C; Lin, F-C; Liao, W-L; Tsai, W-B

2013-09-01

409

Raman gain efficiency distribution measurement of optical fiber cable installed in the field using indirect OTDR technique  

Microsoft Academic Search

A novel indirect OTDR technique for measuring Raman gain efficiency distribution is applied to optical fiber cables installed in the field. Field measurements are successfully made on a 17-km long test fiber.

I. Yamashita; K. Oro; T. Yabu; M. Ohashi

2008-01-01

410

Monitoring natural regeneration using optical remote sensing techniques1 Dr Tim J Malthus and David T Shaw  

E-print Network

Monitoring natural regeneration using optical remote sensing techniques1 Dr Tim J Malthus and David University, Edinburgh, 5th - 9th of August 2002. ABSTRACT The regeneration of native Scots pine has become

411

Simultaneous measurement and modulation of multiple physiological parameters in the isolated heart using optical techniques  

PubMed Central

Whole-heart multi-parametric optical mapping has provided valuable insight into the interplay of electro-physiological parameters, and this technology will continue to thrive as dyes are improved and technical solutions for imaging become simpler and cheaper. Here, we show the advantage of using improved 2nd-generation voltage dyes, provide a simple solution to panoramic multi-parametric mapping, and illustrate the application of flash photolysis of caged compounds for studies in the whole heart. For proof of principle, we used the isolated rat whole-heart model. After characterising the blue and green isosbestic points of di-4-ANBDQBS and di-4-ANBDQPQ, respectively, two voltage and calcium mapping systems are described. With two newly custom-made multi-band optical filters, (1) di-4-ANBDQBS and fluo-4 and (2) di-4-ANBDQPQ and rhod-2 mapping are demonstrated. Furthermore, we demonstrate three-parameter mapping using di-4-ANBDQPQ, rhod-2 and NADH. Using off-the-shelf optics and the di-4-ANBDQPQ and rhod-2 combination, we demonstrate panoramic multi-parametric mapping, affording a 360° spatiotemporal record of activity. Finally, local optical perturbation of calcium dynamics in the whole heart is demonstrated using the caged compound, o-nitrophenyl ethylene glycol tetraacetic acid (NP-EGTA), with an ultraviolet light-emitting diode (LED). Calcium maps (heart loaded with di-4-ANBDQPQ and rhod-2) demonstrate successful NP-EGTA loading and local flash photolysis. All imaging systems were built using only a single camera. In conclusion, using novel 2nd-generation voltage dyes, we developed scalable techniques for multi-parametric optical mapping of the whole heart from one point of view and panoramically. In addition to these parameter imaging approaches, we show that it is possible to use caged compounds and ultraviolet LEDs to locally perturb electrophysiological parameters in the whole heart. PMID:22886365

Lee, Peter; Yan, Ping; Ewart, Paul; Kohl, Peter

2012-01-01

412

Assessment of Spacecraft Operational Status Using Electro-Optical Predictive Techniques  

NASA Astrophysics Data System (ADS)

The current class of small satellite systems presents an analyst responsible for monitoring spacecraft operational status and early detection of detrimental anomalies with a broad variety of sensing and identification issues and challenges. Simple, small, cube-shaped satellites, without protruding solar panel appendages, may require enhanced preflight characterization processes to support monitoring by passive, remote, nonimaging optical sensors. This paper will describe spacecraft optical signature modeling and simulation techniques to develop sensing and identification algorithms for observing and characterizing key spacecraft features. The simulation results are based on electro-optical signatures apparent to nonimaging sensors, along with related observable features derived from multicolor and multiviewing aspect scenarios. This model and simulation analysis capability is used to support programs to monitor spacecraft performance status and identify anomalies associated with spacecraft damage/deterioration due to space debris or micrometeorite impact, thruster exhaust deposition or material aging. The development of state-of-the-art optical signature modeling tools to perform high-fidelity satellite models (such as the Air Force Academy FalconSat-5 or AFRL TacSat-3) simulations to characterize spectral radiant intensities apparent to passive, remote, nonresolved imaging sensors are described in detail. Simulations are performed for a comprehensive scenario range of natural (solar and earth) illumination and viewing conditions. Results are generated for comparing baseline, streamlined geometry models with the actual higher fidelity models that capture vehicle small-size hardware components and modifications. Output consisting of radiant intensity history apparent to ground-based sensor locations for vehicle trajectories that capture a comprehensive range of illumination conditions from the sun and underlying earth scene are presented for extensive spectral band coverage spanning the electro-optical spectrum from visible wavelengths through extended long-wave infrared. The analysis of selected results is summarized with the perspective of developing future generation sensing and identification algorithms.

Swann, D.; Klem, B.; McCoy, B.

2010-09-01

413

One of align metrologies for Antarctic telescopes  

NASA Astrophysics Data System (ADS)

The preliminary site testing performed since the beginning of 2008 shows that Antarctic Dome A is an excellent astronomical site. The Chinese Antarctic optical telescopes CSTAR and the first Antarctic Survey Telescope AST3-1 has been in operation on Dome A, and several Antarctic telescopes are being developed and proposed. However, the harsh environment and manpower shortage make the in-situ alignment task difficult. The study will introduce the completed alignment work of AST3 and discuss an improved align metrology based on the previous treatments of the field dependent optical aberrations, as well as its application on Antarctic Bright Star Survey Telescope BSST.

Li, Zhengyang; Yuan, Xiangyan

2014-08-01

414

Machine learning techniques for astrophysical modelling and photometric redshift estimation of quasars in optical sky surveys  

E-print Network

Machine learning techniques are utilised in several areas of astrophysical research today. This dissertation addresses the application of ML techniques to two classes of problems in astrophysics, namely, the analysis of individual astronomical phenomena over time and the automated, simultaneous analysis of thousands of objects in large optical sky surveys. Specifically investigated are (1) techniques to approximate the precise orbits of the satellites of Jupiter and Saturn given Earth-based observations as well as (2) techniques to quickly estimate the distances of quasars observed in the Sloan Digital Sky Survey. Learning methods considered include genetic algorithms, particle swarm optimisation, artificial neural networks, and radial basis function networks. The first part of this dissertation demonstrates that GAs and PSO can both be efficiently used to model functions that are highly non-linear in several dimensions. It is subsequently demonstrated in the second part that ANNs and RBFNs can be used as effective predictors of spectroscopic redshift given accurate photometry, especially in combination with other learning-based approaches described in the literature. Careful application of these and other ML techniques to problems in astronomy and astrophysics will contribute to a better understanding of stellar evolution, binary star systems, cosmology, and the large-scale structure of the universe.

N. Daniel Kumar

2008-11-04

415

Field-free molecular alignment induced by elliptically polarized laser pulses: non invasive 3 dimensional characterization  

E-print Network

An investigation of field-free molecular alignment produced by elliptically polarized laser pulses is reported. Experiments are conducted in CO$_2$ at room temperature. A non invasive all-optical technique, based on the cross defocusing of a probe pulse, is used to measure the alignment along two orthogonal directions that is sufficient to provide a 3 dimensional characterization. The field-free molecular alignment produced by a laser of elliptical polarization is in good agreement in terms of amplitude and shape with theoretical predictions. It turns out to be almost equivalent to the superposition of the effects that one would obtain with two individual cross-polarized pulses. The investigation highlights notably the occurrence of field-free two-direction alignment alternation for a suitably chosen degree of ellipticity. The analogy between this specific ellipticity and the well known "magic angle" used in time resolved spectroscopy to prevent rotational contributions is discussed.

E. Hertz; D. Daems; S. Guérin; H. R. Jauslin; B. Lavorel; O. Faucher

2008-12-17

416

Automated alignment and on-sky performance of the Gemini planet imager coronagraph  

NASA Astrophysics Data System (ADS)

The Gemini Planet Imager (GPI) is a next-generation, facility instrument currently being commissioned at the Gemini South observatory. GPI combines an extreme adaptive optics system and integral field spectrograph (IFS) with an apodized-pupil Lyot coronagraph (APLC) producing an unprecedented capability for directly imaging and spectroscopically characterizing extrasolar planets. GPI's operating goal of 10-7 contrast requires very precise alignments between the various elements of the coronagraph (two pupil masks and one focal plane mask) and active control of the beam path throughout the instrument. Here, we describe the techniques used to automatically align GPI and maintain the alignment throughout the course of science observations. We discuss the particular challenges of maintaining precision alignments on a Cassegrain mounted instrument and strategies that we have developed that allow GPI to achieve high contrast even in poor seeing conditions.

Savransky, Dmitry; Thomas, Sandrine J.; Poyneer, Lisa A.; Dunn, Jennifer; Macintosh, Bruce A.; Sadakuni, Naru; Dillon, Daren; Goodsell, Stephen J.; Hartung, Markus; Hibon, Pascale; Rantakyrö, Fredrik; Cardwell, Andrew; Serio, Andrew

2014-07-01

417

Automated Alignment and On-Sky Performance of the Gemini Planet Imager Coronagraph  

E-print Network

The Gemini Planet Imager (GPI) is a next-generation, facility instrument currently being commissioned at the Gemini South observatory. GPI combines an extreme adaptive optics system and integral field spectrograph (IFS) with an apodized-pupil Lyot coronagraph (APLC) producing an unprecedented capability for directly imaging and spectroscopically characterizing extrasolar planets. GPI's operating goal of $10^{-7}$ contrast requires very precise alignments between the various elements of the coronagraph (two pupil masks and one focal plane mask) and active control of the beam path throughout the instrument. Here, we describe the techniques used to automatically align GPI and maintain the alignment throughout the course of science observations. We discuss the particular challenges of maintaining precision alignments on a Cassegrain mounted instrument and strategies that we have developed that allow GPI to achieve high contrast even in poor seeing conditions.

Savransky, Dmitry; Poyneer, Lisa A; Dunn, Jennifer; Macintosh, Bruce A; Sadakuni, Naru; Dillon, Daren; Goodsell, Stephen J; Hartung, Markus; Hibon, Pascale; Rantakyrö, Fredrik; Cardwell, Andrew; Serio, Andrew

2014-01-01

418

A Simple Technique to Facilitate Treatment of Urethral Strictures with Optical Internal Urethrotomy  

PubMed Central

Urethral stricture is a common condition that can lead to serious complications such as urinary infections and renal insufficiency secondary to urinary retention. Treatment options include catheterization, urethroplasty, endoscopic internal urethrotomy, and dilation. Optical internal urethrotomy offers faster recovery, minimal scarring, and less risk of infection, although recurrence is possible. However, technical difficulties associated with poor visualization of the stenosis or of the urethral lumen may increase procedural time and substantially increase the failure rates of internal urethrotomy. In this report we describe a technique for urethral catheterization via a suprapubic, percutaneous approach through the urinary bladder in order to facilitate endoscopic internal urethrotomy.

Stamatiou, Konstantinos; Papadatou, Aggeliki; Kornezos, Ioannis; Pavlis, Anargiros

2014-01-01

419

Structural and optical properties of zinc oxide film using RF-sputtering technique  

SciTech Connect

This paper reports the fabrication of zinc oxide (ZnO) film using RF-sputtering technique. Determination of the structural properties using High Resolution X-ray Diffraction (HRXRD) confirmed that ZnO film deposited on silicon (Si) substrate has a high quality. This result is in line with the Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) which were used to image the morphology of the film, in which a rough surface was demonstrated. Photoluminescence (PL) emission is included to study the optical properties of ZnO film that shows two PL peak in the UV region at 371 nm and in visible region at 530 nm respectively.

Hashim, A. J.; Jaafar, M. S.; Ghazai, Alaa J. [Nano-Optoelectronics Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800 Pinang (Malaysia); Physics Department, Science College, Thi-Qar University (Iraq)

2012-11-27

420

Measuring macular pigment optical density in vivo: a review of techniques  

Microsoft Academic Search

Background  Macular pigment has been the focus of much attention in recent years, as a potential modifiable risk factor for age-related\\u000a macular degeneration. This interest has been heightened by the ability to measure macular pigment optical density (MPOD) in\\u000a vivo.\\u000a \\u000a \\u000a \\u000a \\u000a Method  A systematic literature search was undertaken to identify all available papers that have used in vivo MPOD techniques. The\\u000a papers were

Olivia Howells; Frank Eperjesi; Hannah Bartlett

2011-01-01

421

Active cleaning techniques for removing contamination from optical surfaces in space  

NASA Technical Reports Server (NTRS)

Research in developing an active cleaning technique for removing contaminants from optical surfaces in space is reported. In situ contamination/cleaning experiments were conducted on gold and platimum coated mirrors, which were contaminated by exposure to UV radiation in a 1,3, butadiene environment. Argon and oxygen plasma exposure cleaned the mirrors equally well. Silicone cleaning experiments were also conducted. Exposure of the contaminated mirrors to helium, oxygen, and hydrogen plasmas restored the reflectance at the shorter wavelengths and degraded it at the longer wavelengths.

Shannon, R. L.; Gillette, R. B.

1973-01-01

422

Classification of remotely sensed data using OCR-inspired neural network techniques. [Optical Character Recognition  

NASA Technical Reports Server (NTRS)

Neural networks have been applied to classifications of remotely sensed data with some success. To improve the performance of this approach, an examination was made of how neural networks are applied to the optical character recognition (OCR) of handwritten digits and letters. A three-layer, feedforward network, along with techniques adopted from OCR, was used to classify Landsat-4 Thematic Mapper data. Good results were obtained. To overcome the difficulties that are characteristic of remote sensing applications and to attain significant improvements in classification accuracy, a special network architecture may be required.

Kiang, Richard K.

1992-01-01

423

Spontaneous self-alignment and structural changes of unpoled hemicyanine dopant in silica film  

NASA Astrophysics Data System (ADS)

Hemicyanine doped silica film was fabricated by sol-gel technique. Time evolution of structural changes in hemicyanine and their influence on the second order optical nonlinearity were investigated through UV-Vis absorption and the second harmonic generation measurements. Three factors were found to have dominant influence on the self alignment and optical nonlinearity of the film. Self alignment was believed to complete right after the evaporation of the solvent. Conversion of protonated hemicyanine to monomeric hemicyanine occurred within 4 hours after film deposition. During this period of time the SHG signal continued to rise and finally reached the maximum. The growth of optical nonlinearity was mainly due to deprotonation of hemicyanine molecules. Optical nonlinearity of the film can also be increased by reducing the amount of hemicyanine aggregates in the film. Blue shift of the absorption peaks for aggregate was found during the drying of the film, it was attributed to resulted from enhanced molecular interaction.

Xu, Lei; Liu, Liying; Yu, Jing; Wang, Wencheng; Li, Fuming; Zhang, Zhi-Ming

1997-10-01

424

Automated interferometric alignment system for paraboloidal mirrors  

DOEpatents

A method is described for a systematic method of interpreting interference fringes obtained by using a corner cube retroreflector as an alignment aid when aligning a paraboloid to a spherical wavefront. This is applicable to any general case where such alignment is required, but is specifically applicable in the case of aligning an autocollimating test using a diverging beam wavefront. In addition, the method provides information which can be systematically interpreted such that independent information about pitch, yaw and focus errors can be obtained. Thus, the system lends itself readily to automation. Finally, although the method is developed specifically for paraboloids, it can be seen to be applicable to a variety of other aspheric optics when applied in combination with a wavefront corrector that produces a wavefront which, when reflected from the correctly aligned aspheric surface will produce a collimated wavefront like that obtained from the paraboloid when it is correctly aligned to a spherical wavefront. 14 figures.

Maxey, L.C.

1993-09-28

425

Apodization of coupled resonator optical waveguide devices through a longitudinal offset technique  

NASA Astrophysics Data System (ADS)

In this paper, a novel technique to set the coupling constant between cells of a coupled resonator optical waveguide (CROW) device, in order to tailor the filter response, is presented. It is known that using the same K value for all the couplers produces filtering responses with significant side-lobes for the side-coupled integrated spaced sequence of resonators (SCISSOR) or significant ripples in the pass-band for the direct coupled microrings (CROW). It is also known that the side-lobes/ripples can be reduced, and the pass/reject bands can be made wider, by apodizing the K value of each individual coupler in the structure, starting from a nominal K value (either increasing or decreasing it). This technique consists on changing the effective length of the coupling section by applying a longitudinal offset between the resonators. On the contrary, the conventional techniques are based in the transversal change of the distance between the ring resonators, in steps that are commonly below the current fabrication resolution step (nm scale), leading to strong restrictions in the designs. The technique has been experimentally demonstrated employing a racetrack ring resonator geometry. The proposed longitudinal offset technique allows a more precise control of the coupling and presents an increased robustness against the fabrication limitations, since the needed resolution step is two orders of magnitude higher. Both techniques are compared in terms of the transmission response of CROW devices, under finite fabrication resolution steps. The offset technique presented is sufficient by itself for apodization, and optimized CROW's can be produced with a fixed distance between the rings, solely by changing the offsets.

Doménech, J. D.; Muñoz, P.; Capmany, J.

2010-05-01