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1

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

2

PDV Probe Alignment Technique  

SciTech Connect

This alignment technique was developed while performing heterodyne velocimetry measurements at LLNL. There are a few minor items needed, such as a white card with aperture in center, visible alignment laser, IR back reflection meter, and a microscope to view the bridge surface. The work was performed on KCP flyers that were 6 and 8 mils wide. The probes used were Oz Optics manufactured with focal distances of 42mm and 26mm. Both probes provide a spot size of approximately 80?m at 1550nm. The 42mm probes were specified to provide an internal back reflection of -35 to -40dB, and the probe back reflections were measured to be -37dB and -33dB. The 26mm probes were specified as -30dB and both measured -30.5dB. The probe is initially aligned normal to the flyer/bridge surface. This provides a very high return signal, up to -2dB, due to the bridge reflectivity. A white card with a hole in the center as an aperture can be used to check the reflected beam position relative to the probe and launch beam, and the alignment laser spot centered on the bridge, see Figure 1 and Figure 2. The IR back reflection meter is used to measure the dB return from the probe and surface, and a white card or similar object is inserted between the probe and surface to block surface reflection. It may take several iterations between the visible alignment laser and the IR back reflection meter to complete this alignment procedure. Once aligned normal to the surface, the probe should be tilted to position the visible alignment beam as shown in Figure 3, and the flyer should be translated in the X and Y axis to reposition the alignment beam onto the flyer as shown in Figure 4. This tilting of the probe minimizes the amount of light from the bridge reflection into the fiber within the probe while maintaining the alignment as near normal to the flyer surface as possible. When the back reflection is measured after the tilt adjustment, the level should be about -3dB to -6dB higher than the probes specified back reflection. This 3 to 6dB increase in back reflection from the surface relative to the probes specified back reflection is the optimal level for acquiring data from the flyer. Data obtained with the LLNL system is shown in Figure 5.

Whitworth, T L; May, C M; Strand, O T

2007-10-26

3

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

4

Characterization and bioactivity study of nanohydroxyapatite on superhydrophilic vertically aligned carbon nanotubes using optical techniques  

NASA Astrophysics Data System (ADS)

Vertically-aligned multi-walled carbon nanotubes (VACNT) is of particular interest in regenerative medicine. Templateinduced hydroxyapatite (HA) has broad prospects in applied fields of bone regenerative medicine. Thus, it becomes very attractive a combination these two excellent materials to bone tissue engineering applications. In this study the HA/VACNT nanocomposites were used as scaffolds to Human osteoblast cells culture. Superhydrophilic VACNT films were obtained by CVD method and funcionalized by oxygen plasma. The fabrication of HA/VACNT nanocomposites was performed with a direct electrodeposition of the thin HA films on the VACNT films. The bioactivity and biomineralization in vitro process of superhydrophilic HA/VACNT nanocomposites were investigated using simulated body fluid (SBF) and optical techniques. The characterization of of HA/VACNT nanocomposites was performed before and after soaking 21 days in SBF and compared to superydrophilic VACNT films. Fourier transform infrared spectroscopy, micro X-ray fluorescence spectrometer by energy-dispersive and X-ray difractogram were employed to investigate the structural and chemical properties. The morphology was investigated by FEG-SEM analysis. After 21 days was identified that others biological apatites were formed only on HA/VACNT nanocomposites. Optical techniques showing a powerful tool to characterizated and investigated the bioactivity in vitro process. These findings were very atractive to application of this new nanocomposite to bone tissue regeneration.

Ferreira Irineu, Joao Anderson; Marsi, Teresa C.; Santos, Tiago G.; Santo, Ana Maria E.; Rangel, Joao L.; Mengui, Ursula A.; Martin, Airton A.; Corat, Evaldo J.; Marciano, Fernanda R.; Lobo, Anderson O.

2012-03-01

5

Alignment of Optical Maps  

Microsoft Academic Search

We introduce a new scoring method for calculation of alignments of optical maps. Missing cuts, false cuts, and sizing errors present in optical maps are addressed by our alignment score through calculation of corresponding likelihoods. The size error model is derived through the application of Central Limit Theorem and validated by residual plots col- lected from real data. Missing cuts

Anton Valouev; Lei Li; Yu-chi Liu; David C. Schwartz; Yi Yang; Yu Zhang; Michael S. Waterman

2005-01-01

6

Alignment of Optical Maps  

Microsoft Academic Search

ABSTRACT We introduce a new scoring method for calculation of alignments of optical maps. Missing cuts, false cuts, and sizing errors present in optical maps are addressed by our alignment score through calculation of corresponding likelihoods. The size error model is derived through the application of Central Limit Theorem and validated by residual plots col- lected from real data. Missing

Anton Valouev; Lei Li; Yu-chi Liu; David C. Schwartz; Yi Yang; Yu Zhang; Michael S. Waterman

2006-01-01

7

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

8

Alignment Tolerances for ALMA Optics  

Microsoft Academic Search

A tolerance analysis of the alignment of the ALMA FE optics is presented. The following performance criteria are taken into account: a) loss of on- axis efficiency from aperture plane misalignment; b) focal plane co- alignment of the two beams of each band; c) aberrations when off-axis mirrors operate between wavefronts not centered on the foci of the ellipsoid; d)

B. Lazareff

9

Optically Aligned Drill Press  

NASA Technical Reports Server (NTRS)

Precise drill press equipped with rotary-indexing microscope. Microscope and drill exchange places when turret rotated. Microscope axis first aligned over future hole, then rotated out of way so drill axis assumes its precise position. New procedure takes less time to locate drilling positions and produces more accurate results. Apparatus adapted to such other machine tools as milling and measuring machines.

Adderholdt, Bruce M.

1994-01-01

10

Prism Window for Optical Alignment  

NASA Technical Reports Server (NTRS)

A prism window has been devised for use, with an autocollimator, in aligning optical components that are (1) required to be oriented parallel to each other and/or at a specified angle of incidence with respect to a common optical path and (2) mounted at different positions along the common optical path. The prism window can also be used to align a single optical component at a specified angle of incidence. Prism windows could be generally useful for orienting optical components in manufacture of optical instruments. "Prism window" denotes an application-specific unit comprising two beam-splitter windows that are bonded together at an angle chosen to obtain the specified angle of incidence.

Tang, Hong

2008-01-01

11

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

NASA Astrophysics Data System (ADS)

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 and shock breakout times of 1- to 5-mm targets at a location remote to the NIF target chamber. A third imaging system measures self-emission of the targets. These 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 systematically checked. Counter-propagating laser beams (orange and red) align these diagnostics to a listing of tolerances. Floating apertures, placed before and after lens groups, display misalignment by showing 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, beam splitters, 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 is achieved before each shot.

Malone, Robert M.; Celeste, John R.; Celliers, Peter M.; Frogget, Brent C.; Guyton, Robert L.; Kaufman, Morris I.; Lee, Tony L.; MacGowan, Brian J.; Ng, Edmund W.; Reinbachs, Imants P.; Robinson, Ronald B.; Tunnell, Thomas W.; Watts, Phillip W.

2007-09-01

12

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

13

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 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 meters. 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, R M; Celeste, J R; Celliers, P M; Frogget, B .; Guyton, R L; Kaufman, M I; Lee, T L; MacGowan, B J; Ng, E W; Reinbachs, I P; Robinson, R B; Tunnell, T W; Watts, P W

2007-07-31

14

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

15

Reducing beam shaper alignment complexity: diagnostic techniques for alignment and tuning  

NASA Astrophysics Data System (ADS)

Safe and efficient optical alignment is a critical requirement for industrial laser systems used in a high volume manufacturing environment. Of specific interest is the development of techniques to align beam shaping optics within a beam line; having the ability to instantly verify by a qualitative means that each element is in its proper position as the beam shaper module is being aligned. There is a need to reduce these types of alignment techniques down to a level where even a newbie to optical alignment will be able to complete the task. Couple this alignment need with the fact that most laser system manufacturers ship their products worldwide and the introduction of a new set of variables including cultural and language barriers, makes this a top priority for manufacturers. Tools and methodologies for alignment of complex optical systems need to be able to cross these barriers to ensure the highest degree of up time and reduce the cost of maintenance on the production floor. Customers worldwide, who purchase production laser equipment, understand that the majority of costs to a manufacturing facility is spent on system maintenance and is typically the largest single controllable expenditure in a production plant. This desire to reduce costs is driving the trend these days towards predictive and proactive, not reactive maintenance of laser based optical beam delivery systems [10]. With proper diagnostic tools, laser system developers can develop proactive approaches to reduce system down time, safe guard operational performance and reduce premature or catastrophic optics failures. Obviously analytical data will provide quantifiable performance standards which are more precise than qualitative standards, but each have a role in determining overall optical system performance [10]. This paper will discuss the use of film and fluorescent mirror devices as diagnostic tools for beam shaper module alignment off line or in-situ. The paper will also provide an overview methodology showing how it is possible to reduce complex alignment directions into a simplified set of instructions for layman service engineers.

Lizotte, Todd E.

2011-10-01

16

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

17

Fiber optics welder having movable aligning mirror  

DOEpatents

A system for welding fiber optic waveguides together. The ends of the two fibers to be joined together are accurately, collinearly aligned in a vertical orientation and subjected to a controlled, diffuse arc to effect welding and thermal conditioning. A front-surfaced mirror mounted at a 45.degree. angle to the optical axis of a stereomicroscope mounted for viewing the junction of the ends provides two orthogonal views of the interface during the alignment operation.

Higgins, Robert W. (Los Alamos, NM); Robichaud, Roger E. (Jemez Springs, NM)

1981-01-01

18

Optical and magneto-optical properties of aligned Ni nanowires embedded in polydimethylsiloxane  

NASA Astrophysics Data System (ADS)

We report the magnetic, optical and magneto-optical properties of aligned Nickel nanowires embedded in polydimethylsiloxane matrix. The NWs prepared by electrodeposition method in anodic alumina template and then dispersed in ethanol and placed in a heater to evaporate the ethanol and finally dispersed in PDMS matrix to reach to the composite. The used external magnetic field arranges the NWs and our aligned NWs were investigated by magnetic hysteresis loop, surface plasmon resonance and spectral magneto-optical techniques. Our results show that these aligned NWs have a sufficient squareness, a strong increase of the magneto-optical response in visible range and very good surface plasmon resonance.

Hamidi, S. M.; Sobhani, A.; Aftabi, A.; Najafi, M.

2015-01-01

19

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

20

Three wavelength optical alignment of the Nova laser  

SciTech Connect

The Nova laser, presently under construction at Lawrence Livermore National Laboratory, will be capable of delivering more than 100 kJ of focused energy to an Inertial Confinement Fusion (ICF) target. Operation at the fundamental wavelength of the laser (1.05 ..mu..m) and at the second and third harmonic will be possible. This paper will discuss the optical alignment systems and techniques being implemented to align the laser output to the target at these wavelengths prior to each target irradiation. When experiments require conversion of the laser light to wavelengths of 0.53 ..mu..m and 0.35 ..mu..m prior to target irradiation, this will be accomplished in harmonic conversion crystals located at the beam entrances to the target chamber. The harmonic alignment system will be capable of introducing colinear alignment beams of all three wavelengths into the laser chains at the final spatial filter. The alignment beam at 1.05 ..mu..m will be about three cm in diameter and intense enough to align the conversion crystals. Beams at 0.53 ..mu..m and 0.35 ..mu..m will be expanded by the spatial filter to full aperture (74 cm) and used to illuminate the target and other alignment aids at the target chamber focus. This harmonic illumination system will include viewing capability as well. A final alignment sensor will be located at the target chamber. It will view images of the chamber focal plane at all three wavelengths. In this way, each beam can be aligned at the desired wavelength to produce the focal pattern required for each target irradiation. The design of the major components in the harmonic alignment system will be described, and a typical alignment sequence for alignment to a target will be presented.

Swift, C.D.; Bliss, E.S.; Jones, W.A.; Seppala, L.G.

1983-11-16

21

Free space optical alignment system using GPS  

NASA Astrophysics Data System (ADS)

This paper presents results from an ongoing effort at the University of Oklahoma to develop a real-time active alignment system for free-space optical communication system. An initial prototype of a FSO active alignment system using Global Positioning System (GPS) sensors, two gimbals, and point-to-point spread spectrum RF communication is described. The positions of both FSO transceivers are exchanged over the radio frequency (RF) communication link. A controller uses the exchanged information to calculate azimuth and elevation bearings to achieve initial alignment between the transceivers. The gimbals are used to steer the beams. The paper also presents a binary scan algorithm developed to expedite the initial alignment process. The algorithm incorporates power measurements as feed back to the original transceiver for comparison. In minimizing convergence time, simulation results confirm that the algorithm performs better than raster scan, spiral scan, and raster spiral scan algorithms, all of which are used in laser satellite communications. The results also show that the initial design is not able to achieve real-time alignment. For real-time alignment, different augmenting technologies (for example, steering mirrors) should be considered.

Saw, Wee-Leong; Refai, Hazem H.; Sluss, James J., Jr.

2005-04-01

22

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

23

Optical alignment and testing of the Michelle spectrometer  

Microsoft Academic Search

We describe the optical alignment and image quality testing of Michelle, the all-reflective mid-IR astronomical spectrometer and imager being built at the Royal Observatory Edinburgh for the UKIRT and GEMINI telescopes. The design strategy called for optical alignment by manufacture, with the only means for adjustment being the machining of sacrificial pads under key optical components. The success of this

Eli Ettedgui-Atad; Alistair C. Glasse; T. E. Baillie; Ian R. Bryson; Garry F. Morrison

1998-01-01

24

Computer-aided alignment for the segmented mirrors of three-mirror optical system  

Microsoft Academic Search

Computer-aided alignment (CAA) is a significant technique to correct errors which are caused by the misalignment of each element in an optical system. It is especially important in such areas as space remote sensing optical systems, since manual adjustment is impossible when it operates in orbit. In this paper, a three-mirror optical system is adopted as an example to perform

Yifan Huang; Lin Li

2008-01-01

25

New technique for reducing the angle random walk at the output of fiber optic gyroscopes during alignment processes of inertial navigation systems  

NASA Astrophysics Data System (ADS)

Angle random walk (ARW) is the noise component at the output of a fiber optic gyroscope (FOG) and it affects the FOG short-term accuracy. Practical applications of FOGs inside an inertial navigation system necessitate monitoring the Earth's rotation rate component along the FOG sensitive axis to determine the initial attitude of the moving object. The ARW increases the measurement uncertainty, thus affecting the overall accuracy. We introduce a new filtering approach that significantly reduces the ARW at the FOG output to a level that can ensure an accurate measurement of the Earth rotation rate. The filtering approach employs the forward linear prediction (FLP) technique to design a tap delay line filter and a new criterion, based on controlling the step size parameter, is introduced to ensure the fastest possible convergence of the adaptive algorithm, while keeping the minimal possible mean square error. The proposed FLP filter of 300 tap weights is capable of reducing the ARW from 4.66 to 0.0694 deg/h((root)Hz)-1. Although it introduces longer delay at the FOG output, a 600-tap weight FLP filter reduces the ARW to 0.015 deg/h((root)Hz)-1. The presence of the FLP filter at the FOG output significantly improves the estimation accuracy while monitoring the Earth rotation and it can successfully replace all other conventional filtering techniques.

Noureldin, Aboelmagd; Irvine-Halliday, Dave; Tabler, Herb; Mintchev, Martin P.

2001-10-01

26

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

27

Optoelectromechanical switch array with passively aligned free-space optical components  

Microsoft Academic Search

An all-optical switch array with micro mirrors driven by electrostatic micro motors has been developed in a LIGA-technique. The system has been designed for single mode application at the telecommunication wavelength of 1.55 ?m. All fixed optical components are passively aligned inside a LIGA-structured micro optical bench. The signals are detoured inside the optical bench by means of micro mirrors,

Antonio C. M. Ruzzu; Dirk Haller; Jürgen A. Mohr; Ulrike Wallrabe

2003-01-01

28

Novel alignment techniques used in multiphoton ionization experiments for laser plasma beat wave  

NASA Astrophysics Data System (ADS)

This paper describes the techniques used to create a fully ionized plasma by the multiphoton ionization of gases at pressures of a few Torr to give an initial electron density precision of better than a few percent, necessary for beat-wave experiments. A gas containment vessel has been constructed using high vacuum techniques with a temperature control system to maintain the fill gas pressure constant. Novel alignment techniques are used that do not require an alignment target placed in the vessel. This involves the use of a rotating pencil beam to determine the focusing of the optics.

Amiranoff, F.; Benkheiri, P.; Dyson, A.; Gregory, C.; Jacquet, F.; Marques, J. R.; Matthieussent, G.; Mine, Ph.; Montes, B.; Poilleux, P.; Stenz, C.

1990-08-01

29

Precision alignment of integrated optics in surface electrode ion traps for quantum information processing  

NASA Astrophysics Data System (ADS)

The integration of optics for efficient light delivery and the collection of fluorescence from trapped ions in surface electrode ion traps is a key component to achieving scalability for quantum information processing. Diffractive optical elements (DOEs) present a promising approach as compared to bulk optics because of their small physical profile and their flexibility in tailoring the optical wavefront. The precise alignment of the optics for coupling fluorescence to and from the ions, however, poses a particular challenge. Excitation and manipulation of the ions requires a high degree of optical access, significantly restricting the area available for mounting components. The ion traps, DOEs, and other components are compact, constraining the manipulation of various elements. For efficient fluorescence collection from the ions the DOE must be have a large numerical aperture (NA), which results in greater sensitivity to misalignment. The ion traps are sensitive devices, a mechanical approach to alignment such as contacting the trap and using precision motors to back-off a set distance not only cannot achieve the desired alignment precision, but risks damage to the ion trap. We have developed a non-contact precision optical alignment technique. We use line foci produced by off-axis linear Fresnel zone plates (FZPs) projected on alignment targets etched in the top metal layer of the ion trap and demonstrate micron-level alignment accuracy.

Young, Amber L.; Hunker, Jeffrey D.; Ellis, A. Robert; Samora, Sally; Wendt, Joel R.; Stick, Daniel L.

2014-03-01

30

Backup Alignment Devices on Shuttle: Heads-Up Display or Crew Optical Alignment Sight  

NASA Technical Reports Server (NTRS)

NASA s Space Shuttle was built to withstand multiple failures while still keeping the crew and vehicle safe. Although the design of the Space Shuttle had a great deal of redundancy built into each system, there were often additional ways to keep systems in the best configuration if a failure were to occur. One such method was to use select pieces of hardware in a way for which they were not primarily intended. The primary function of the Heads-Up Display (HUD) was to provide the crew with a display of flight critical information during the entry phase. The primary function of the Crew Optical Alignment Sight (COAS) was to provide the crew an optical alignment capability for rendezvous and docking phases. An alignment device was required to keep the Inertial Measurement Units (IMUs) well aligned for a safe Entry; nominally this alignment device would be the two on-board Star Trackers. However, in the event of a Star Tracker failure, the HUD or COAS could also be used as a backup alignment device, but only if the device had been calibrated beforehand. Once the HUD or COAS was calibrated and verified then it was considered an adequate backup to the Star Trackers for entry IMU alignment. There were procedures in place and the astronauts were trained on how to accurately calibrate the HUD or COAS and how to use them as an alignment device. The calibration procedure for the HUD and COAS had been performed on many Shuttle missions. Many of the first calibrations performed were for data gathering purposes to determine which device was more accurate as a backup alignment device, HUD or COAS. Once this was determined, the following missions would frequently calibrate the HUD in order to be one step closer to having the device ready in case it was needed as a backup alignment device.

Chavez, Melissa A.

2011-01-01

31

Radio-optical alignments in a low radio luminosity sample  

E-print Network

We present an optically-based study of the alignment between the radio axes and the optical major axes of eight z~0.7 radio galaxies in a 7C sample. The radio galaxies in this sample are ~20-times less radio luminous than 3C galaxies at the same redshift, and are significantly less radio-luminous than any other well-defined samples studied to date. Using Nordic Optical Telescope images taken in good seeing conditions at rest-frame wavelengths just longward of the 4000A break, we find a statistically significant alignment effect in the 7C sample. Furthermore, in two cases where the aligned components are well separated from the host we have been able to confirm spectroscopically that they are indeed at the same redshift as the radio galaxy. However, a quantitative analysis of the alignment in this sample and in a corresponding 3C sample from HST archival data indicates that the percentage of aligned flux may be lower and of smaller spatial scale in the 7C sample. Our study suggests that alignments on the 50-kpc scale are probably closely related to the radio luminosity, whereas those on the 15 kpc scale are not. We discuss these results in the context of popular models for the alignment effect.

Mark Lacy; Susan E. Ridgway; Margrethe Wold; Per B. Lilje; Steve Rawlings

1999-03-21

32

Use of a Faro Arm for optical alignment  

NASA Astrophysics Data System (ADS)

We discuss the use of a Faro Arm - a portable coordinate measuring machine - in the re-alignment and testing of the Southern African Large Telescope's Spherical Aberration Corrector. In pushing this versatile tool to its limits, we have arrived at a better understanding of its true capabilities and developed ways to compensate for some of its weaknesses. It is possible to achieve excellent results (~5 microns) when making relative measurements and keeping the Arm's orientation relatively constant. The Faro is also extremely useful in providing live feedback while making fine adjustments. However, single measurements of the same position are considerably less reliable (~50 microns) when the Arm is operated in widely different orientations. If the latter is unavoidable, one may largely counteract this by taking continuous streams of measurements (1000 readings) for a given point while exercising the Arm as much as possible in order to average the encoder errors. Various other techniques and accessories that we have found useful, as well as some painful lessons, are described here and a few examples are given to demonstrate how we have used a Faro Arm in our challenging optical alignment project.

Crause, Lisa A.; O'Donoghue, Darragh E.; O'Connor, James E.; Strümpfer, Francois

2010-07-01

33

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

34

Functional alignments and self-tests for tilted and decentered optics  

SciTech Connect

The alignment of tilted and decentered optics is ordinarily difficult, because such optics have neither simple alignment points amenable to ordinary boresight methods, nor a simple alignment theory. Several different alignment examples which provide insight into a practical universal approach to all such systems are explored. The examples detailed are segments of the Antares Laser Fusion Project's optical train.

Bauke, W.; Cross, E.W.

1983-01-01

35

Focal Plane Alignment Utilizing Optical CMM  

NASA Technical Reports Server (NTRS)

In many applications, an optical detector has to be located relative to mechanical reference points. One solution is to specify stringent requirements on (1) mounting the optical detector relative to the chip carrier, (2) soldering the chip carrier onto the printed circuit board (PCB), and (3) installing the PCB to the mechanical structure of the subsystem. Figure 1 shows a sketch of an optical detector mounted relative to mechanical reference with high positional accuracy. The optical detector is typically a fragile wafer that cannot be physically touched by any measurement tool. An optical coordinate measuring machine (CMM) can be used to position optical detectors relative to mechanical reference points. This approach will eliminate all requirements on positional tolerances. The only requirement is that the PCB is manufactured with oversized holes. An exaggerated sketch of this situation is shown in Figure 2. The sketch shows very loose tolerances on mounting the optical detector in the chip carrier, loose tolerance on soldering the chip carrier to the PCB, and finally large tolerance on where the mounting screws are located. The PCB is held with large screws and oversized holes. The PCB is mounted loosely so it can move freely around. The optical CMM measures the mechanical reference points. Based on these measurements, the required positions of the optical detector corners can be calculated. The optical CMM is commanded to go to the position where one detector corner is supposed to be. This is indicated with the cross-hairs in Figure 2(a). This figure is representative of the image of the optical CMM monitor. Using a suitable tapping tool, the PCB is manually tapped around until the corner of the optical detector is at the crosshairs of the optical CMM. The CMM is commanded to another corner, and the process is repeated a number of times until all corners of the optical detector are within a distance of 10 to 30 microns of the required position. The situation is sketched in Figure 2(b) (the figure also shows the tapping tool and where to tap). At this point the fasteners for the PCB are torqued slightly so the PCB can still move. The PCB location is adjusted again with the tapping tool. This process is repeated 3 to 4 times until the final torque is achieved. The oversized mounting holes are then filled with a liquid bonding agent to secure the board in position (not shown in the sketch). A 10- to 30-micron mounting accuracy has been achieved utilizing this method..

Liebe, Carl Christian; Meras, Patrick L.; Clark, Gerald J.; Sedaka, Jack J.; Kaluzny, Joel V.; Hirsch, Brian; Decker, Todd A.; Scholtz, Christopher R.

2012-01-01

36

Previous R&D of vibrating wire alignment technique for HEPS  

E-print Network

The alignment tolerance of multipoles on a girder is better than 30um in the storage ring of High Energy Photon Source HEPS which will be the next project at IHEP Institute of High Energy Physics. This is difficult to meet the precision only using the traditional optical survey method. In order to achieve this goal, vibrating wire alignment technique with high precision and sensitivity is considered to be used in this project. This paper presents some previous research works about theory, scheme design and achievements.

Lei Wu; Xiaolong Wang; Chunhua Li; Huamin Qu

2014-11-18

37

Genetic Algorithm Phase Retrieval for the Systematic Image-Based Optical Alignment Test Bed  

NASA Astrophysics Data System (ADS)

A real-valued genetic algorithm with random rank-based selection is shown to successfully estimate the multiple phases of a segmented optical system modeled on the seven-mirror Systematic Image-Based Optical Alignment test bed located at NASA's Marshall Space Flight Center. Comparisons are made between this and more traditional phase-retrieval methods. No significant increase in computational speed is observed using the genetic algorithm technique.

Taylor, Jaime R.; King, B. Alex, III; Steincamp, Jim; Rakoczy, John

2006-02-01

38

Performance of Optical Flow Techniques  

Microsoft Academic Search

While different optical flow techniques continue to appear, there has been a lack of quantitative evaluation of existing methods. For a common set of real and synthetic image sequences, we report the results of a number of regularly cited optical flow techniques, including instances of differential, matching, energy-based and phase-based methods. Our comparisons are primarily empirical, and concentrate on the

John L. Barron; David J. Fleet; Steven S. Beauchemin

1994-01-01

39

Precision alignment and calibration of optical systems using computer generated holograms  

NASA Astrophysics Data System (ADS)

As techniques for manufacturing and metrology advance, optical systems are being designed with more complexity than ever before. Given these prescriptions, alignment and calibration can be a limiting factor in their final performance. Computer generated holograms (CGHs) have several unique properties that make them powerful tools for meeting these demanding tolerances. This work will present three novel methods for alignment and calibration of optical systems using computer generated holograms. Alignment methods using CGHs require that the optical wavefront created by the CGH be related to a mechanical datum to locate it space. An overview of existing methods is provided as background, then two new alignment methods are discussed in detail. In the first method, the CGH contact Ball Alignment Tool (CBAT) is used to align a ball or sphere mounted retroreflector (SMR) to a Fresnel zone plate pattern with micron level accuracy. The ball is bonded directly onto the CGH substrate and provides permanent, accurate registration between the optical wavefront and a mechanical reference to locate the CGH in space. A prototype CBAT was built and used to align and bond an SMR to a CGH. In the second method, CGH references are used to align axi-symmetric optics in four degrees of freedom with low uncertainty and real time feedback. The CGHs create simultaneous 3D optical references where the zero order reflection sets tilt and the first diffracted order sets centration. The flexibility of the CGH design can be used to accommodate a wide variety of optical systems and maximize sensitivity to misalignments. A 2-CGH prototype system was aligned multiplied times and the alignment uncertainty was quantified and compared to an error model. Finally, an enhanced calibration method is presented. It uses multiple perturbed measurements of a master sphere to improve the calibration of CGH-based Fizeau interferometers ultimately measuring aspheric test surfaces. The improvement in the calibration is a function of the interferometer error and the aspheric departure of the desired test surface. This calibration is most effective at reducing coma and trefoil from figure error or misalignments of the interferometer components. The enhanced calibration can reduce overall measurement uncertainty or allow the budgeted error contribution from another source to be increased. A single set of sphere measurements can be used to calculate calibration maps for closely related aspheres, including segmented primary mirrors for telescopes. A parametric model is developed and compared to the simulated calibration of a case study interferometer.

Coyle, Laura Elizabeth

40

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

41

Call for Papers Optical System Alignment, Tolerancing,  

E-print Network

. (United States); Daniel G. Smith, Nikon Research Corp. of America (United States); Yana Z. Williams, GE Center · San Diego, CA United States Conference Chairs: José Sasián, College of Optical Sciences, The Univ. of Arizona (United States); Richard N. Youngworth, Light Capture, Inc. (United States) Program

Jahns, Jürgen

42

XY-stage for alignment of optical elements in MOEMS  

NASA Astrophysics Data System (ADS)

The alignment of optical elements in a Micro-Opto-Electro- Mechanical System, is of prime importance in order to realize a reliable and low loss system. Fabrication errors or temperature changes deteriorate the alignment accuracy. These errors can be compensated with the aid of an active alignment system. The aim of the paper is to investigate an active system in order to align microlenses and fibers. A high lateral precision is required for single mode fiber injection, typically better than 1 micrometers . The alignment along the optical axis is less critical. Our system consists of a microlens placed between one input fiber and one output fiber. The fibers are held in V-grooves and the microlens is mounted on an XY-stage. The lens is fabricated by melting resist technology and subsequent etching in quartz. The mechanical parts are realized by wire electro-discharge machining (wire-EDM). Two piezo-electrical actuators move the flexible bearings of the stage in the X and Y direction. We will present the results obtained with this system and we will discuss its potential.

Peter, Yves-Alain; Herzig, Hans Peter; Bottinelli, Stefano

1998-09-01

43

Optical alignment of the Far-Ultraviolet Spectroscopic Explorer (FUSE)  

NASA Astrophysics Data System (ADS)

The FUSE, scheduled for a summer 1999 launch, is an astrophysics satellite designed to provide high spectral resolving power over the interval 90.5-118.7 nm. The FUSE optical path consists of four co-aligned, normal incidence, off-axis parabolic primary mirrors which illuminate separate Rowland circle spectrograph channels equipped with holographic gratings and delay line microchannel plate detectors. The spectrograph comprises the upper half of the instrument structure, and was internally aligned prior to delivery to the integration team.

Conard, Steven J.; Redman, Kevin W.; Barkhouser, Robert H.; Johnson, Joel A.

1999-10-01

44

CWDM based HDMI interconnect incorporating passively aligned POF linked optical subassembly modules  

NASA Astrophysics Data System (ADS)

A four-channel transmitter OSA (TOSA) and a receiver optical sub-assembly (ROSA) module were presented. They take advantage of a coarse WDM (CWDM) scheme, employing two types of VCSELs at 780 and 850 nm, where no wavelength filters are involved in the TOSA. The ROSA and TOSA were constructed through a fully passive alignment process using components produced by virtue of a cost effective plastic injection molding technique. In order to build a high quality optical HDMI interconnect, four channel optical links between these modules ware established via two graded-index plastic optical fibers (GI-POFs). The HDMI interconnect was thoroughly evaluated in terms of the alignment tolerance, the light beam propagation, and the data transmission capability. For the ROSA, the measured tolerance, as affected by the photodiode alignment, was ~45 ?m and over 200 ?m for the transverse and longitudinal directions, respectively. For the TOSA, the tolerance, which is mostly dependent upon the VCSEL alignment, was ~20 ?m and more than 200 ?m for the transverse and longitudinal directions, respectively. The beam profiles for the TOSA and ROSA were monitored to confirm their feasibility from the optical coupling perspective. A digital signal at 2.5 Gb/s was efficiently transmitted through the HDMI interconnect with a bit error ratio of below 10-16. A 1080p HDMI signal from a Blu-ray player was delivered through the interconnect to an LCD monitor and successfully displayed a high quality video.

Lee, Hak-Soon; Lee, Sang-Shin; Son, Yung-Sung

2011-08-01

45

CWDM based HDMI interconnect incorporating passively aligned POF linked optical subassembly modules.  

PubMed

A four-channel transmitter OSA (TOSA) and a receiver optical sub-assembly (ROSA) module were presented. They take advantage of a coarse WDM (CWDM) scheme, employing two types of VCSELs at 780 and 850 nm, where no wavelength filters are involved in the TOSA. The ROSA and TOSA were constructed through a fully passive alignment process using components produced by virtue of a cost effective plastic injection molding technique. In order to build a high quality optical HDMI interconnect, four channel optical links between these modules ware established via two graded-index plastic optical fibers (GI-POFs). The HDMI interconnect was thoroughly evaluated in terms of the alignment tolerance, the light beam propagation, and the data transmission capability. For the ROSA, the measured tolerance, as affected by the photodiode alignment, was ~45 ?m and over 200 ?m for the transverse and longitudinal directions, respectively. For the TOSA, the tolerance, which is mostly dependent upon the VCSEL alignment, was ~20 ?m and more than 200 ?m for the transverse and longitudinal directions, respectively. The beam profiles for the TOSA and ROSA were monitored to confirm their feasibility from the optical coupling perspective. A digital signal at 2.5 Gb/s was efficiently transmitted through the HDMI interconnect with a bit error ratio of below 10-16. A 1080p HDMI signal from a Blu-ray player was delivered through the interconnect to an LCD monitor and successfully displayed a high quality video. PMID:21934900

Lee, Hak-Soon; Lee, Sang-Shin; Son, Yung-Sung

2011-08-01

46

Hydrodynamic optical alignment for microflow cytometry†  

PubMed Central

A microfabricated flow cytometer has been developed that is capable of detecting nearly all of the microparticles in an aqueous suspension. Current design allows for integrated coupling between an optical fiber-based detection system and the particle stream via hydrodynamic focusing. By adjusting the relative flow-rates at the auxiliary inputs of the focusing manifold, the particle stream can be steered out-of-plane relative to the illuminating laser, and similarly the particle stream can be squeezed or expanded. The microfabricated device was constructed in polydimethylsiloxane with cross-sectional microfluidic dimensions of 125 ?m × 125 ?m. Using the present device and method, fluorescent microparticles in aqueous solution were counted at an absolute counting efficiency of 91 ± 4%. The coefficient of variation of the fluorescence pulse-heights for far-red fluorescent microparticles was 15%. The device exhibited a linear response to fluorescence intensity calibration microparticles as shown by comparison with a commercial cytometer instrument. PMID:21279198

Kennedy, Matthew J.; Stelick, Scott J.; Sayam, Lavanya G.; Yen, Andrew; Erickson, David

2013-01-01

47

Optical digital techniques  

NASA Technical Reports Server (NTRS)

Optical interface losses between transmitter-to-fiber interface, connector-to-connector interface, and fiber-to-receiver interface were studied. System effects such as pulse dispersion, risetimes of the sources and detectors, type of fibers used, output power of the sources, and detector sensitivity were considered. Data bus systems such as TEE, Star, and Hybrid were analyzed. The matter of single fiber versus bundle technologies for future avionics systems was considered. The existing data bus system on Space Shuttle was examined and an optical analog was derived for a fiber bundle system, along with the associated power margin. System tests were performed on a feasibility model of a 9-port Star data bus system including BER, star losses, connector losses, etc. The same system was subjected to EMI between the range of 200 Hz to 10 GHz at 20V/m levels. A lightning test was also performed which simulated the conditions similar to those on Space Shuttle. The data bus system was found to be EMI and lightning hard. It is concluded that an optical data bus system is feasible for shuttle orbiter type vehicles.

1979-01-01

48

Optical alignment of electrodes on electrical discharge machines  

NASA Technical Reports Server (NTRS)

Shadowgraph system projects magnified image on screen so that alignment of small electrodes mounted on electrical discharge machines can be corrected and verified. Technique may be adapted to other machine tool equipment where physical contact cannot be made during inspection and access to tool limits conventional runout checking procedures.

Boissevain, A. G.; Nelson, B. W.

1972-01-01

49

Fixturing And Alignment Of Free-Form Optics For Diamond Turning  

Microsoft Academic Search

The fabrication of free-form optics presents unique challenges not only to the diamond turning process, but also to the process by which the whorkpiece is located with respect to the machine axes. While rotationally symmetric parts only require alignment in, at most, three directions, free-form optics require alignment in up to six directions. Distinct from alignment in an optical system,

Alex Sohn

50

New technique for aberration diagnostics and alignment of an extreme ultraviolet Schwarzschild objective  

NASA Astrophysics Data System (ADS)

Schwarzschild objectives are widely used in the extreme ultraviolet (EUV)/soft X-ray spectral region both as reduction and magnification optics, e.g. for small-field projection lithography and microscopy, respectively. When using a Schwarzschild objective as a micro-exposure tool (MET) at high spatial resolution (half-pitch?0.1 ?m), in addition to the tight requirements on the design and surface figure for the single optics, also an accurate alignment between the two mirrors is needed to reach the planned spatial imaging detail. Ideally, at-wavelength alignment should be done in order to overcome limitations due to diffractive effects. While this can be easily performed on synchrotron beam lines, it becomes time expensive (and components consuming) on low-power laboratory plasma sources. In this work we propose and test a new technique to align a EUV Schwarzschild objective by means of ultraviolet light. The aligned objective allowed the attainment of lithographic patterning with edge response of 90 nm, as part of the laboratory-scale MET for EUV projection lithography realized at the ENEA Frascati Research Centre.

Bollanti, S.; Di Lazzaro, P.; Flora, F.; Mezi, L.; Murra, D.; Torre, A.

2013-08-01

51

An alignment strategy for the optics of LINC-NIRVANA  

NASA Astrophysics Data System (ADS)

LINC-NIRVANA is an instrument to combine the light from both LBT primary mirrors in an imaging Fizeau interferometer. The goals in terms of resolution and field of view are quite ambitious, which leads to a complex instrument consisting of a bunch of subsystems. The layer oriented MCAO system alone is already quite complicated and to get everything working together properly is not a small challenge. As we are reaching the completion of LINC-NIRVANA's subsystems, it becomes more and more important to define a strategy to align all these various subsystems. The specific layout of LINC-NIRVANA imposes some restrictions and difficulties on the sequence and the method of this alignment. The main problem for example is that we have to get two perfectly symmetrical focal planes to be able to properly combine them interferometrically. This is the major step on which all further alignment is based on, since all the subsystems (collimator and camera optics, wavefront sensors, cold IR optics, etc.) rely on these focal planes as a reference. I will give a small introduction on the optics of the instrument and line out the resulting difficulties as well as the strategy that we want to apply in order to overcome these.

Meschke, Daniel; Bertram, Thomas; Bizenberger, Peter

2012-09-01

52

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

53

Optically induced orientational transitions in nematics with planar alignment  

E-print Network

Theoretical study of dynamical phenomena induced by a linearly polarized plane wave incident perpendicularly on a planar aligned nematic layer with the light intensity as the control parameter is reported. We find the threshold of the Optically Induced Freedericksz Transition for the planar state as a function of the problem parameters. It occurs that the threshold is substantially lower than that expected before. Above the primary instability the director settles either to a stationary or to an oscillatory states depending on a thickness of the layer. These states become unstable at a secondary threshold through a heteroclinic bifurcation and the director settles to a new stationary distorted state.

Dmitry O. Krimer

2008-10-01

54

Remote alignment of adaptive optical systems with far-field optimization  

NASA Astrophysics Data System (ADS)

A novel scheme for remote alignment of adaptive optical systems is presented. In comparison to conventional methods where near-field measurements (in the form of near-field phase across the adaptive component or gaps between neighboring segments) are used for feedback control, Far-Field Optimization utilizes only the far-field intensity. A figure of merit based solely on the point spread function is used to iteratively configure the adaptive elements to optical alignment. In this review paper, we first describe the far-field optimization method and then discuss its application to three different adaptive optical systems - a deformable mirror, a segmented mirror and a multiple mirror telescope. The convergence, efficiency and robustness of the iterative far-field optimization are illustrated with computer simulations. Experimental validation of the novel technique for adaptive optics alignment is demonstrated with results from a laboratory test with a segmented mirror. Potential utility of far-field optimization for dynamic wavefront control (e.g. atmospheric turbulence compensation) is briefly discussed.

Mehta, Naresh C.

1991-05-01

55

Self-Alignment Techniques for Inertial Measurement Units  

Microsoft Academic Search

This paper presents the result of a study on self-alignment algorithms for inertial measurement units (IMU). The primary concern is the fine alignment of an inertial platform whose base is subject to vibration and whose sensors are subject to noise. The main contribution of the paper is a new self-alignment algorithm. The algorithm incorporates together the special property of platform

J. C. Hung; H. V. White

1975-01-01

56

Novel techniques for optical performance monitoring in optical systems  

NASA Astrophysics Data System (ADS)

The tremendous increase of data traffic in the worldwide Internet has driven the rapid development of optical networks to migrate from numerous point-to-point links towards meshed, transparent optical networks with dynamically routed light paths. This increases the need for appropriate network supervision methods. In view of this, optical performance monitoring (OPM) has emerged as an indispensable element for the quality assurance of an optical network. This thesis is devoted to the proposal of several new and accurate techniques to monitor different optical impairments so as to enhance proper network management. When the optical signal is carried on fiber links with optical amplifiers, the accumulated amplified spontaneous emission (ASE) noise will result in erroneous detection of the received signals. The first part of the thesis presents a novel, simple, and robust in-band optical signal to noise ratio (OSNR) monitoring technique using phase modulator embedded fiber loop mirror (PM-FLM). This technique measures the in-band OSNR accurately by observing the output power of a fiber loop mirror filter, where the transmittance is adjusted by an embedded phase modulator driven by a low-frequency periodic signal. The robustness against polarization mode dispersion, chromatic dispersion, bit-rate, and partially polarized noise is experimentally demonstrated. Chromatic dispersion (CD) is due to the fact that light with different frequencies travel at different speeds inside fiber. It causes pulse spreading and intersymbol interference (ISI) which would severely degrade the transmission performance. By feeding a signal into a fiber loop which consists of a high-birefringence (Hi-Bi) fiber, we experimentally show that the amount of experienced dispersion can be deduced from the RF power at a specific selected frequency which is determined by the length of the Hi-Bi fiber. Experimental results show that this technique can provide high monitoring resolution and dynamic range. Polarization mode dispersion (PMD) splits an optical pulse into two orthogonally polarized pulses traveling along the fiber at different speeds, causing crosstalk and ISI. The third part of the thesis demonstrates two different PMD monitoring schemes. The first one is based on the analysis of frequency-resolved state-of-polarization (SOP) rotation, with signal spectrum broadened by self-phase modulation (SPM) effect. Experimental results show that the use of broadened signal spectrum induced by SPM not only relaxes the filter requirement and reduces the computational complexity, but also improves the estimation accuracy, and extends the monitoring range of the pulsewidth. The second one is based on the delay-tap asynchronous waveform sampling technique. By examining the statistical distribution of the measured scatter plot, unambiguous PMD measurement range up to 50% of signal bit-period is demonstrated. The final part of the thesis focuses on the monitoring of alignment status between the pulse carver and data modulator in an optical system. We again employ the two-tap asynchronous sampling technique to perform such kind of monitoring in RZ-OOK transmission system. Experimental results show that both the misalignment direction and magnitude can be successfully determined. Besides, we propose and experimentally demonstrate the use of off-center optical filtering technique to capture the amount of spectrum broadening induced by the misalignment between the pulse-carver and the data modulator in RZ-DPSK transmission system. The same technique was also applied to monitor the synchronization between the old and the new data in synchronized phase re-modulation (SPRM) system.

Ku, Yuen Ching

57

Chlorine sensing by optical techniques  

NASA Astrophysics Data System (ADS)

Techniques of diffuse reflectance and fluorescence spectroscopy have been utilized for the development of new quantitative methods for the analysis of chlorine. The reflectance method involves the use of a dry reagent chemistry, prepared by immobilizing (sigma) -tolidine on a nylon 66 membrane, which is interrogated by means of optical fibers. Chlorine concentrations in the range 0-5 ppm can be measured with a limit of detection of 0.043 ppm. The fluorescence technique is demonstrated by the measurement of quenching of 9-vinylanthracene by chlorine. Efficient quenching of fluorescence of this dye is observed with a Stern-Volmer constant of 8667 M-7. The findings demonstrate the possibility of developing an analytical method for the determination of chlorine based on fluorescence quenching and optical fibers.

Momin, S. A.; Narayanaswamy, Ramaier

1991-09-01

58

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

59

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

60

Active alignment for interferometric techniques onboard the International Space Station  

NASA Astrophysics Data System (ADS)

Different interferometric techniques are required to cover most of the scientific needs in the field of fluid dynamics science in microgravity research. The Fluid Science Laboratory (FSL), currently under upgrade for the Columbus Orbital Facility of the International Space Station (ISS), shall provide Holographic Interferometry, Digital Holography, Electronic Speckle Pattern Interferometry (ESPI) and Shearing Interferometry among other diagnostic tools. On earth, these highly sensitive interferometers are operated in a thermal and mechanical controlled environment. In opposition to the situation on ground the multi-user facility of the FSL has severe constraints for what concerns volume, mass, modularity, operational needs and its environment. This results in a three-dimensional modular drawer structure for the design of the optical-mechanical set-up, where performance limitations must be expected compared to systems on ground. In a rather uncontrolled thermal environment onboard the ISS this leads to misalignment due to thermo-mechanical changes of the Aluminum structure during experiment runs which finally result in interferogram distortions and therefore to significant measurement errors. In this paper we report about a misalignment detection- and active compensation concept developed on the basis of a thermo-mechanical and optical analysis of the set-up. The detection system is based on a simplified Hartmann-Sensor. It is able to separate wave front tilt and curvature errors due to misalignments of the interferometers itself from the effects caused by the experiment. The closed-loop compensation system uses optical components of the set-up driven by piezoelectric actuators. Due to its active approach this concept allows for the real time accessibility of the experimental effects in the framework of "Telescience." Extensive functional tests as well as representative thermal tests show the suitability of the proposed technique to compensate interferogram distortions due to thermal-mechanical deformations. Thus, it is able to ensure interferometric measurements with sub-wavelength accuracy onboard the ISS.

Kebbel, Volker; Becker, Joachim; Jueptner, Werner

2004-08-01

61

Diffuse Infrared Background Experiment (DIRBE) optics module breadboard alignment methods and results  

NASA Technical Reports Server (NTRS)

The Diffuse Infrared Background Experiment (DIRBE) optics module will be assembled at ambient temperature but will operate at liquid helium temperature. The challenging task of ensuring that is possible to maintain alignment through cryogenic cooling and cryogenic vibration has been demonstrated in a DIRBE optics module breadboard program. This paper discusses the configuration of the DIRBE optics module breadboard, ambient temperature optical alignment methods used to assemble the breadboard, and cryogenic testing of the breadboard. The alignment of the optical assembly at ambient temperature, at 77 K, and after a 77 K vibration was within specification.

Magner, Thomas J.

1987-01-01

62

Self-aligned growth of single-walled carbon nanotubes using optical near-field effects  

NASA Astrophysics Data System (ADS)

Self-aligned growth of ultra-short single-walled carbon nanotubes (SWNTs) was realized by utilizing optical near-field effects in a laser-assisted chemical vapor deposition (LCVD) process. By introducing the optical near-field effects, bridge structures containing single suspended SWNT channels were successfully fabricated through the LCVD process at a relatively low substrate temperature. Raman spectroscopy and I-V analyses have been carried out to characterize the SWNT-bridge structures. Numerical simulations using a high-frequency structure simulator revealed that significant enhancement of local heating occurs at metallic electrode tips under laser irradiation; it is about one order of magnitude higher than that in the rest of the electrodes. This technique suggests a novel approach to in situ low-temperature fabrication of SWNT-based devices in a precisely controlled manner, based on the nanoscale heating enhancement induced by the optical near-field effects.

Xiong, W.; Zhou, Y. S.; Mahjouri-Samani, M.; Yang, W. Q.; Yi, K. J.; He, X. N.; Liou, S. H.; Lu, Y. F.

2009-01-01

63

Self-aligned growth of single-walled carbon nanotubes using optical near-field effects.  

PubMed

Self-aligned growth of ultra-short single-walled carbon nanotubes (SWNTs) was realized by utilizing optical near-field effects in a laser-assisted chemical vapor deposition (LCVD) process. By introducing the optical near-field effects, bridge structures containing single suspended SWNT channels were successfully fabricated through the LCVD process at a relatively low substrate temperature. Raman spectroscopy and I-V analyses have been carried out to characterize the SWNT-bridge structures. Numerical simulations using a high-frequency structure simulator revealed that significant enhancement of local heating occurs at metallic electrode tips under laser irradiation; it is about one order of magnitude higher than that in the rest of the electrodes. This technique suggests a novel approach to in situ low-temperature fabrication of SWNT-based devices in a precisely controlled manner, based on the nanoscale heating enhancement induced by the optical near-field effects. PMID:19417270

Xiong, W; Zhou, Y S; Mahjouri-Samani, M; Yang, W Q; Yi, K J; He, X N; Liou, S H; Lu, Y F

2009-01-14

64

Genetic Algorithm Phase Retrieval for the Systematic Image-Based Optical Alignment Testbed  

NASA Technical Reports Server (NTRS)

Phase retrieval requires calculation of the real-valued phase of the pupil fimction from the image intensity distribution and characteristics of an optical system. Genetic 'algorithms were used to solve two one-dimensional phase retrieval problem. A GA successfully estimated the coefficients of a polynomial expansion of the phase when the number of coefficients was correctly specified. A GA also successfully estimated the multiple p h e s of a segmented optical system analogous to the seven-mirror Systematic Image-Based Optical Alignment (SIBOA) testbed located at NASA s Marshall Space Flight Center. The SIBOA testbed was developed to investigate phase retrieval techniques. Tiphilt and piston motions of the mirrors accomplish phase corrections. A constant phase over each mirror can be achieved by an independent tip/tilt correction: the phase Conection term can then be factored out of the Discrete Fourier Tranform (DFT), greatly reducing computations.

Taylor, Jaime; Rakoczy, John; Steincamp, James

2003-01-01

65

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

66

Optical Device for Converting a Laser Beam into Two Co-aligned but Oppositely Directed Beams  

NASA Technical Reports Server (NTRS)

Optical systems consisting of a series of optical elements require alignment from the input end to the output end. The optical elements can be mirrors, lenses, sources, detectors, or other devices. Complex optical systems are often difficult to align from end-to-end because the alignment beam must be inserted at one end in order for the beam to traverse the entire optical path to the other end. The ends of the optical train may not be easily accessible to the alignment beam. Typically, when a series of optical elements is to be aligned, an alignment laser beam is inserted into the optical path with a pick-off mirror at one end of the series of elements. But it may be impossible to insert the beam at an end-point. It can be difficult to locate the pick-off mirror at the desired position because there is not enough space, there is no mounting surface, or the location is occupied by a source, detector, or other component. Alternatively, the laser beam might be inserted at an intermediate location (not at an end-point) and sent, first in one direction and then the other, to the opposite ends of the optical system for alignment. However, in this case, alignment must be performed in two directions and extra effort is required to co-align the two beams to make them parallel and coincident, i.e., to follow the same path as an end-to-end beam. An optical device has been developed that accepts a laser beam as input and produces two co-aligned, but counter-propagating beams. In contrast to a conventional alignment laser placed at one end of the optical path, this invention can be placed at a convenient position within the optical train and aligned to send its two beams simultaneously along precisely opposite paths that, taken together, trace out exactly the same path as the conventional alignment laser. This invention allows the user the freedom to choose locations within the optical train for placement of the alignment beam. It is also self-aligned by design and requires almost no adjustment.

Jennings, Donald

2013-01-01

67

Alignment and integration of ASSIST: a test bench for VLT adaptive optics facility  

NASA Astrophysics Data System (ADS)

ASSIST, The Adaptive Secondary Setup and Instrument STimulator, is being developed to provide a testing facility for the ESO Adaptive Optics Facility (AOF). It will allow the off-telescope testing of three elements of the VLT AOF; the Deformable Secondary Mirror (DSM) and the AO systems for MUSE and HAWK-I (GALACSI and GRAAL). The core of ASSIST consists of a 2-mirror setup (AM1-AM2) allowing the on-axis test of the DSM in interferometric mode. However, during the initial stages of ASSIST integration, DSM would not be present. This makes the task of aligning AM1-AM2 to within an accuracy of 0.05mm/1 arcmin rather challenging. A novel technique known as Shack-Hartmann method has been developed and tested in the lab for this purpose. A Shack Hartmann wavefront sensor will be used to measure the mis-alignment between AM1-AM2 by recording the coma and astigmatism in the presence of large spherical aberration introduced because of tilt/decenter of AM2 with respect to AM1. Thereafter, 20 optical components including lenses, flat mirrors and beam-splitter cubes divided into five sub-assemblies should be aligned to AM1-AM2- DSM axis which ultimately passes through the mechanical axis of large AMOS rotator.

Deep, Atul; Arsenault, Robin; Boland, Wilfried; Delabre, Bernard; Hubin, Norbert; La Penna, Paolo; Madec, Pierre-Yves; Molster, Frank; Stuik, Remko; Tordo, Sebastien; Wiegers, Emiel

2010-08-01

68

Molecular alignment and orientation with a hybrid Raman scattering technique  

NASA Astrophysics Data System (ADS)

We demonstrate a scheme for the preparation of molecular alignment and angular momentum orientation using a hybrid combination of two limits of Raman scattering. First a weak, impulsive pump pulse initializes the system via the nonresonant dynamic Stark effect. Then, having overcome the influence of the vacuum fluctuations, an amplification pulse selectively enhances the initial coherences by transient stimulated Raman scattering, generating alignment and angular momentum orientation of molecular hydrogen. The amplitude and phase of the resulting coherent dynamics are experimentally probed, indicating an amplification factor of 4.5. An analytic theory is developed to model the dynamics.

Bustard, Philip J.; Lausten, R.; Sussman, Benjamin J.

2012-11-01

69

A Fast and Scalable Kymograph Alignment Algorithm for Nanochannel-Based Optical DNA Mappings  

PubMed Central

Optical mapping by direct visualization of individual DNA molecules, stretched in nanochannels with sequence-specific fluorescent labeling, represents a promising tool for disease diagnostics and genomics. An important challenge for this technique is thermal motion of the DNA as it undergoes imaging; this blurs fluorescent patterns along the DNA and results in information loss. Correcting for this effect (a process referred to as kymograph alignment) is a common preprocessing step in nanochannel-based optical mapping workflows, and we present here a highly efficient algorithm to accomplish this via pattern recognition. We compare our method with the one previous approach, and we find that our method is orders of magnitude faster while producing data of similar quality. We demonstrate proof of principle of our approach on experimental data consisting of melt mapped bacteriophage DNA. PMID:25875920

Noble, Charleston; Nilsson, Adam N.; Freitag, Camilla; Beech, Jason P.; Tegenfeldt, Jonas O.; Ambjörnsson, Tobias

2015-01-01

70

The alignment and isostatic mount bonding technique of the aerospace Cassegrain telescope primary mirror  

NASA Astrophysics Data System (ADS)

In order to meet both optical performance and structural stiffness requirements of the aerospace Cassegrain telescope, iso-static mount is used as the interface between the primary mirror and the main plate. This article describes the alignment and iso-static mount bonding technique of the primary mirror by assistance of CMM. The design and assembly of mechanical ground support equipment (MGSE) which reduces the deformation of primary mirror by the gravity effect is also presented. The primary mirror adjusting MGSE consists of X-Y linear translation stages, rotation stage and kinematic constrain platform which provides the function of decenter, orientation, tilt and height adjustment of the posture sequentially. After CMM measurement, the radius of curvature, conic constant, decenter and tilt, etc. will be calculated. According to these results, the posture of the mirror will be adjusted to reduce the tilt by the designed MGSE within 0.02 degrees and the distance deviation from the best fitted profile of mirror to main plate shall be less than 0.01 mm. After that, EC 2216 adhesive is used to bond mirror and iso-static mount. During iso-static mount bonding process, CMM is selected to monitor the relative position deviation of the iso-static mount until the adhesive completely cured. After that, the wave front sensors and strain gauges are used to monitor the strain variation while the iso-static mount mounted in the main plate with the screws by the torque wrench. This step is to prevent deformation of the mirror caused from force of the iso-static mount during the mounting process. In the end, the interferometer is used for the optical performance test with +1G and -1G to check the alignment and bonding technique is well or not.

Lin, Wei Cheng; Chang, Shenq-Tsong; Lin, Yu-Chuan; Hsu, Ming-Ying; Chang, Yu-Ting; Chang, Sheng-Hsiung; Huang, Ting-Ming

2012-10-01

71

Holographic Weapons Sight as Crew Optical Alignment Sight  

NASA Technical Reports Server (NTRS)

Crew Optical Alignment Sights (COAS) are used by spacecraft pilots to provide a visual reference to a target spacecraft for lateral relative position during rendezvous and docking operations. NASA s Orion vehicle, which is currently under development, has not included a COAS in favor of automated sensors, but the crew office has requested such a device be added for situational awareness and contingency support. The current Space Shuttle COAS was adopted from Apollo heritage, weighs several pounds, and is no longer available for procurement which would make re-use difficult. In response, a study was conducted to examine the possibility of converting a commercially available weapons sight to a COAS for the Orion spacecraft. The device used in this study was the XPS series Holographic Weapon Sight (HWS) procured from L-3 EOTech. This device was selected because the targeting reticule can subtend several degrees, and display a graphic pattern tailored to rendezvous and docking operations. Evaluations of the COAS were performed in both the Orion low-fidelity mockup and rendezvous simulations in the Reconfigurable Operational Cockpit (ROC) by crewmembers, rendezvous engineering experts, and flight controllers at Johnson Space Center. These evaluations determined that this unit s size and mounting options can support proper operation and that the reticule visual qualities are as good as or better than the current Space Shuttle COAS. The results positively indicate that the device could be used as a functional COAS and supports a low-cost technology conversion solution.

Merancy, Nujoud; Dehmlow, Brian; Brazzel, Jack P.

2011-01-01

72

Null test fourier domain alignment technique for phase-shifting point diffraction interferometer  

DOEpatents

Alignment technique for calibrating a phase-shifting point diffraction interferometer involves three independent steps where the first two steps independently align the image points and pinholes in rotation and separation to a fixed reference coordinate system, e.g, CCD. Once the two sub-elements have been properly aligned to the reference in two parameters (separation and orientation), the third step is to align the two sub-element coordinate systems to each other in the two remaining parameters (x,y) using standard methods of locating the pinholes relative to some easy to find reference point.

Naulleau, Patrick (5239 Miles Ave., Apt. A, Oakland, CA 94618); Goldberg, Kenneth Alan (1622 Oxford St., #5t, Berkeley, CA 94709)

2000-01-01

73

Optical Alignment of the JWST ISIM to the OTE Simulator (OSIM): Current Concept and Design Studies  

NASA Technical Reports Server (NTRS)

The James Webb Space Telescope's (JWST) Integrated Science Instrument Module (ISIM) is the scientific payload of the observatory and contai ns four science instruments. During alignment and test of the integrated ISIM (i.e. ISIM + science instruments) at NASA's Goddard Space Fli ght Center (GSFC), the Optical telescope element SIMulator (OSIM) wil l be used to optically stimulate the science instruments to verify their operation and performance. In this paper we present the design of two cryogenic alignment fixtures that will be used to determine and verify the proper alignment of OSIM to ISIM during testing at GSFC. The se fixtures, the Master Alignment Target Fixture (MATF) and the ISIM Alignment Target Fixture (IATF), will provide continuous, 6 degree of freedom feedback to OSIM during initial ambient alignment as well as during cryogenic vacuum testing.

Frey, Bradley J.; Davila, Pamela S.; Marsh, James M.; Ohl, Raymond G.; Sullivan, Joseph

2007-01-01

74

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

75

A novel optical vector spectrum analysis technique  

Microsoft Academic Search

- Abstract: A novel technique for measuring frequencydependent magnitude and phase information across an optical channel is presented using tunable, integrated ring-resonator-based optical filters and a detector with a small bandwidth relative to the full channel width. 02003 Optical Society of America OCIS codes: 130.3120 (Integrated optics devices), 230.7390 (Waveguides, planar) 1. Jntmduction A novel optical vector spectral analysis (OVSA)

C. K. Madsen; M. Cappuzzo; E. Chen; L. Gomez; A. Griffin; E. J. Laskowski; Wong-Foy; C. Rolle

2004-01-01

76

Alignment control study for the solar optical telescope  

NASA Technical Reports Server (NTRS)

Analysis of the alignment and focus errors than can be tolerated, methods of sensing such errors, and mechanisms to make the necessary corrections were addressed. Alternate approaches and their relative merits were considered. The results of this study indicate that adequate alignment control can be achieved.

1976-01-01

77

Single-walled carbon nanotube transistors fabricated by advanced alignment techniques utilizing CVD growth and dielectrophoresis  

Microsoft Academic Search

Single-walled carbon nanotube field effect transistors (SWNT-FETs) are fabricated by two different alignment techniques. The first technique is based on direct synthesis of an aligned SWNTs array on quartz wafer using chemical vapor deposition. The transistor with three SWNTs and atomic layer deposited (ALD) Al2O3 gate oxide shows a contact resistance of 280K?, a maximum on-current of ?7?A, and a

S. Kim; Y. Xuan; P. D. Ye; Saeed Mohammadi; S. W. Lee

2008-01-01

78

Vertically aligned SWNTs synthesized on quartz substrate and their optical properties  

E-print Network

Vertically aligned SWNTs synthesized on quartz substrate and their optical properties ·> Yoichi sought. However, whereas the vertical growth of MWNTs by chemical vapor deposition (CVD) is well known that even flexible SWNTs can take the vertically aligned configuration by means of our alcohol CCVD process

Maruyama, Shigeo

79

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

80

Substrate patterning for liquid crystal alignment by optical interference  

SciTech Connect

Inhomogeneous liquid crystal (LC) alignment surfaces comprising a succession of microdomains favoring different LC alignment directions have been demonstrated for a number of optoelectronic applications. However, the prevalent method used to fabricate these surfaces is time consuming and produce functional areas that are too small for practical use. Here, we demonstrate a simple method based on photopatterning of an azodye layer with an interference pattern produced by intercepting two coherent UV beams. This method can produce alignment patterns within seconds with a practical size of {approx}(0.5 cm){sup 2}.

Lu Xuemin; Lee, Fuk Kay; Sheng, Ping; Kwok, H.S.; Chigrinov, V.; Tsui, Ophelia K.C. [Department of Physics, Hong Kong University of Science and Technology, Hong Kong (China); Department of Electrical and Electronic Engineering, Hong Kong University of Science and Technology, Hong Kong (China); Department of Physics, Hong Kong University of Science and Technology, Hong Kong (China)

2006-06-12

81

Optical Modeling of the Alignment and Test of the NASA James Webb Space Telescope  

NASA Technical Reports Server (NTRS)

Optical modeling challenges of the ground alignment plan and optical test and verification of the NASA James Webb Space Telescope are discussed. Issues such as back-out of the gravity sag of light-weighted mirrors, as well as the use of a sparse-aperture auto-collimating flat system are discussed. A walk-through of the interferometer based alignment procedure is summarized, and sensitivities from the sparse aperture wavefront test are included as examples.'

Howard, Joseph M.; Hayden, Bill; Keski-Kuha, Ritva; Feinberg, Lee

2007-01-01

82

Self-aligned hybrid integration of semiconductor lasers with micromachined micro-optics for optoelectronic packaging  

NASA Astrophysics Data System (ADS)

The first self-aligned hybrid integration of semiconductor edge-emitting lasers and three-dimensional micro-optics was demonstrated. New self-alignment structures and micro-optics were constructed integrally on a Si chip employing surface micromachining methods. The divergent beam from the semiconductor laser was effectively collimated using the micro-Fresnel lens. The hybrid integration of semiconductor lens and three-dimensional micro-optics including micro-lenses, mirrors and gratings allowed micro-optical systems to be fabricated on a single Si substrate.

Lin, L. Y.; Lee, S. S.; Pister, K. S. J.; Wu, M. C.

1995-05-01

83

Model-based far-field alignment algorithm for Gaussian beamlike single-mode optical devices.  

PubMed

Single-mode device-to-fiber alignment automation is usually achieved with a classical mathematical optimization approach. We present a different approach, which is based on the identification of particular intrinsic characteristics of the coupled optical power and on estimating residual axial, transverse, and angular misalignments in the far field. Such a model-based approach is based on the physical nature of the optical coupling phenomenon and can replace or be complementary to already known automated alignment methods. An alignment algorithm is described and validated experimentally using two single-mode fibers as Gaussian beam emitter and receiver. PMID:17415400

St-Amant, Yves; Gariépy, Daniel; Rancourt, Denis

2007-04-20

84

Analysis of the influence of manufacturing and alignment related errors on an optical tweezer system  

NASA Astrophysics Data System (ADS)

In this work we present the design process as well as experimental results of an optical system for trapping particles in air. For positioning applications of micro-sized objects onto a glass wafer we developed a highly efficient optical tweezer. The focus of this paper is the iterative design process where we combine classical optics design software with a ray optics based force simulation tool. Thus we can find the best compromise which matches the optical systems restrictions with stable trapping conditions. Furthermore we analyze the influence of manufacturing related tolerances and errors in the alignment process of the optical elements on the optical forces. We present the design procedure for the necessary optical elements as well as experimental results for the aligned system.

Kampmann, R.; Sinzinger, S.

2014-12-01

85

Omnium-G parabolic dish optical efficiency: a comparison of two independent measurement techniques  

SciTech Connect

Measurements made at SERI of the optical efficiency of the Omnium-G parabolic dish concentrator are described. Two independent techniques were used: the cold-water calorimeter method and the heat of fusion method. Results from both techniques agree quite well and indicate that the optical efficiency for a 10-cm receiver aperture is 25%. Optical efficiency measured in early 1979 was 37%, and in mid 1979 it had degraded to 21%. An optical alignment procedure is described that resulted in the increase in optical efficiency from 21% to the current value of 25%.

Bohn, M.; Gaul, H.

1980-10-01

86

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

87

Localized surface plasmon resonance anisotropy in template aligned silver nanoparticles: A case of biaxial metal optics  

NASA Astrophysics Data System (ADS)

Generalized ellipsometry is used to extract the dielectric functions of self-aligned silver nanoparticles on silicon ripple patterns which account for the anisotropic Localized Surface Plasmon Resonance shown by such nanostructures. The biaxial nature of dielectric functions shows its presence through the modified in-plane plasmonic behaviour as compared to the case of random nanoparticles. The nature of in-plane optical coupling and out of plane metallic behavior is further investigated by tuning the interparticle gap along the ripple direction and also varying the ripple periodicity. Thus, we propose that generalized ellipsometry may be used as an effective process monitoring technique to develop anisotropic plasmonic substrates with potential applications in photovoltaic systems as a plasmonic back reflector.

Ranjan, Mukesh; Bhatnagar, Mukul; Mukherjee, Subroto

2015-03-01

88

Surface-tension-driven multi-chip self-alignment techniques for heterogeneous 3D integration  

Microsoft Academic Search

Surface-tension-driven self-alignment (SA) is a promising technique for heterogeneous die-level stacking. Multiple dies can be manipulated in parallel at minimal cost. A defined amount of water present between the die and a carrier substrate is used to align the components. The minimization of the water-air interface is the driving force. Most studies were performed with a completely wetted chip surface

Fengda Sun; Yusuf Leblebici; Thomas Brunschwiler

2011-01-01

89

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

90

The deterministic optical alignment of the HERMES spectrograph  

NASA Astrophysics Data System (ADS)

The High Efficiency and Resolution Multi Element Spectrograph (HERMES) is a four channel, VPH-grating spectrograph fed by two 400 fiber slit assemblies whose construction and commissioning has now been completed at the Anglo Australian Telescope (AAT). The size, weight, complexity, and scheduling constraints of the system necessitated that a fully integrated, deterministic, opto-mechanical alignment system be designed into the spectrograph before it was manufactured. This paper presents the principles about which the system was assembled and aligned, including the equipment and the metrology methods employed to complete the spectrograph integration.

Gers, Luke; Staszak, Nicholas

2014-07-01

91

Optical tweezers technique and its applications  

NASA Astrophysics Data System (ADS)

Since their advent in the 1980s, optical tweezers have attracted more and more attention due to their unique non-contact and non-invasion characteristics and their wide applications in physics, biology, chemistry, medical science and nanoscience. In this paper, we introduce the basic principle, the history and typical applications of optical tweezers and review our recent experimental works on the development and application of optical tweezers technique. We will discuss in detail several technological issues, including high precision displacement and force measurement in single-trap and dual-trap optical tweezers, multi-trap optical tweezers with each trap independently and freely controlled by means of space light modulator, and incorporation of cylindrical vector optical beams to build diversified optical tweezers beyond the conventional Gaussian-beam optical tweezers. We will address the application of these optical tweezers techniques to study biophysical problems such as mechanical deformation of cell membrane and binding energy between plant microtubule and microtubule associated proteins. Finally we present application of the optical tweezers technique for trapping, transporting, and patterning of metallic nanoparticles, which can be harnessed to manipulate surface plasmon resonance properties of these nanoparticles.

Guo, HongLian; Li, ZhiYuan

2013-12-01

92

Genetic Algorithm Phase Retrieval for the Systematic Image-Based Optical Alignment Testbed  

NASA Technical Reports Server (NTRS)

A reduced surrogate, one point crossover genetic algorithm with random rank-based selection was used successfully to estimate the multiple phases of a segmented optical system modeled on the seven-mirror Systematic Image-Based Optical Alignment testbed located at NASA's Marshall Space Flight Center.

Rakoczy, John; Steincamp, James; Taylor, Jaime

2003-01-01

93

Accurate monitoring of large aligned objects with videometric techniques  

Microsoft Academic Search

This paper describes a new videometric technique designed to monitor the deformations and misalignments of large vital components in the centre of a future particle detector. It relies on a geometrical principle called “reciprocal collimation” of two CCD cameras: the combination of the video devices in pair gives rise to a network of well located reference lines that surround the

Francis Klumb; Michael John Price; Pierre Grussenmeyer

1999-01-01

94

Optical modeling activities for NASA's James Webb Space Telescope (JWST): Part V. Operational alignment updates  

NASA Astrophysics Data System (ADS)

This paper is part five of a series on the ongoing optical modeling activities for the James Webb Space Telescope (JWST). The first two papers discussed modeling JWST on-orbit performance using wavefront sensitivities to predict line of sight motion induced blur, and stability during thermal transients. The third paper 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, and the fourth introduced the software toolkits used to perform much of the optical analysis for JWST. The work here models observatory operations by simulating line-of-sight image motion and alignment drifts over a two-week period. Alignment updates are then simulated using wavefront sensing and control processes to calculate and perform the corrections. A single model environment in Matlab is used for evaluating the predicted performance of the observatory during these operations.

Howard, Joseph M.; Ha, Kong Q.; Shiri, Ron; Smith, J. Scott; Mosier, Gary; Muheim, Danniella

2008-07-01

95

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.

96

Division Ix: Optical & Infrared Techniques  

NASA Astrophysics Data System (ADS)

Division IX provides a forum for astronomers engaged in the planning, development, construction, and calibration of optical and infrared telescopes and instrumentation, as well as observational procedures including data processing. A few years ago, discussions were started about changes in the structure of Division IX, with the aim of bringing it more in line with today's world of large coordinated projects and multi-national observatories. The course of this process, and further steps to be taken in the period from 2009 to 2012, were at the focus of the deliberations at the business meeting of Division IX at the IAU General Assembly in Rio de Janeiro.

Quirrenbach, Andreas; Silva, David R.; Kudritzki, Rolf-Peter; Burton, Michael G.; Cui, Xiangqun; McLean, Ian S.; Milone, Eugene F.; Murthy, Jayant; Ridgway, Stephen T.; Tautvaišiene, Gražina; Tokovinin, Andrei A.; Torres, Guillermo

2010-05-01

97

Alignment techniques required by precise measurement of effective focal length  

NASA Technical Reports Server (NTRS)

The characteristics of false color imagery produced by instrumentation on earth resource mapping satellites are examined. The spatial fidelity of the imagery is dependent upon the geometric accuracy (GA) and the band-to-band registration (BBR) with which the telescope instrument is assembled. BBR and GA require knowledge of telescope effective focal length (EFL) to one part in 10,000 in order that the next generation of earth mappers be able to carry out their missions. The basis for this level of precision is briefly considered, and a description is given of the means by which such precise EFL measurements have been carried out. Attention is given to accuracy requirements, the technique used to measure effective focal length, possible sources of error in the EFL measurement, approaches for eliminating errors, and the results of the efforts to control measurement errors in EFL determinations.

Wise, T. D.

1980-01-01

98

A new global alignment approach for underwater optical mapping  

Microsoft Academic Search

Lately, underwater vehicles have become important tools for exploration, monitoring and creation of maps of the seabed. Within mapping applications, the maps obtained from optical data are becoming essential in different study areas such as biological, geological and archaeological surveys, or in detection of benthic temporal changes. However, the underwater medium is very challenging for optical sensors and does not

Armagan Elibol; Rafael Garcia; Nuno Gracias

2011-01-01

99

Tear film measurement by optical reflectometry technique.  

PubMed

Evaluation of tear film is performed by an optical reflectometer system with alignment guided by a galvanometer scanner. The reflectometer system utilizes optical fibers to deliver illumination light to the tear film and collect the film reflectance as a function of wavelength. Film thickness is determined by best fitting the reflectance-wavelength curve. The spectral reflectance acquisition time is 15 ms, fast enough for detecting film thickness changes. Fast beam alignment of 1 s is achieved by the galvanometer scanner. The reflectometer was first used to evaluate artificial tear film on a model eye with and without a contact lens. The film thickness and thinning rate have been successfully quantified with the minimum measured thickness of about 0.3 ?m. Tear films in human eyes, with and without a contact lens, have also been evaluated. A high-contrast spectral reflectance signal from the precontact lens tear film is clearly observed, and the thinning dynamics have been easily recorded from 3.69 to 1.31 ?m with lipid layer thickness variation in the range of 41 to 67 nm. The accuracy of the measurement is better than ±0.58% of the film thickness at an estimated tear film refractive index error of ±0.001. The fiber-based reflectometer system is compact and easy to handle. PMID:24500519

Lu, Hui; Wang, Michael R; Wang, Jianhua; Shen, Meixiao

2014-02-01

100

Tear film measurement by optical reflectometry technique  

PubMed Central

Abstract. Evaluation of tear film is performed by an optical reflectometer system with alignment guided by a galvanometer scanner. The reflectometer system utilizes optical fibers to deliver illumination light to the tear film and collect the film reflectance as a function of wavelength. Film thickness is determined by best fitting the reflectance-wavelength curve. The spectral reflectance acquisition time is 15 ms, fast enough for detecting film thickness changes. Fast beam alignment of 1 s is achieved by the galvanometer scanner. The reflectometer was first used to evaluate artificial tear film on a model eye with and without a contact lens. The film thickness and thinning rate have been successfully quantified with the minimum measured thickness of about 0.3 ?m. Tear films in human eyes, with and without a contact lens, have also been evaluated. A high-contrast spectral reflectance signal from the precontact lens tear film is clearly observed, and the thinning dynamics have been easily recorded from 3.69 to 1.31 ?m with lipid layer thickness variation in the range of 41 to 67 nm. The accuracy of the measurement is better than ±0.58% of the film thickness at an estimated tear film refractive index error of ±0.001. The fiber-based reflectometer system is compact and easy to handle. PMID:24500519

Lu, Hui; Wang, Michael R.; Wang, Jianhua; Shen, Meixiao

2014-01-01

101

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

102

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

Microsoft Academic Search

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

M. S. Katow

1986-01-01

103

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

104

Enzyme-etching technique to fabricate micropatterns of aligned collagen fibrils.  

PubMed

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

2014-06-01

105

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

106

Precision assembly and alignment of large optic modules for the National Ignition Facility  

SciTech Connect

The National Ignition Facility (NIF), currently under design and construction at Lawrence Livermore National Laboratory (LLNL), will be the world`s biggest laser. The optics for the multipass, 192-beam, high-power, neodymium-glass laser will be assembled and aligned in the NIF Optics Assembly Building (OAB), adjacent to the huge Laser and Target Area Building (LTAB), where they will be installed. To accommodate the aggressive schedule for initial installation and activation, rapid assembly and alignment of large aperture optics into line replaceable units (LRUs) will occur through the use of automated handling, semi-autonomous operations, and strict protocols. The OAB will have to maintain rigorous cleanliness levels, achieve both commonality and versatility to handle the various optic types, and allow for just-in-time processing and delivery of the optics into the LTAB without undoing their strict cleanliness and precise alignment. This paper describes the Project`s design philosophy of modularity and hardware commonality and presents the many design challenges encountered. It also describes how, by using a mixture of commercially available and newly designed equipment, we have developed unique systems for assembly and alignment, inspection and verification, and LRU loading and transfer.

Hurst, P.; Grasz, E.

1998-05-12

107

Optimization of an optical configuration in a vertical alignment liquid crystal cell for wide viewing angle.  

PubMed

We propose an optical structure for a vertical alignment (VA) liquid crystal (LC) cell with a wide viewing angle. The proposed LC cell consists of an A-plate and two C-plates for optical compensation. Optical compensation and optimization to eliminate off-axis light leakage in the entire visible wavelength range are performed on a Poincaré sphere using the Stokes vector and the Muller matrix method. After optimizing the wavelength dispersion of the retardation films that are used, we prove that the proposed VA LC cell can improve the viewing angle and contrast ratio by calculating optical characteristics, particularly in diagonal directions. PMID:19107171

Ji, Seung-Hoon; Hee Lee, Seung; Lee, Gi-Dong

2009-01-01

108

Microstructural and optical properties of nanocrystalline ZnO deposited onto vertically aligned carbon nanotubes by physical vapor deposition  

SciTech Connect

Nanocrystalline ZnO films with thicknesses of 5 nm, 10 nm, 20 nm, and 50 nm were deposited via magnetron sputtering onto the surface of vertically aligned multi-walled carbon nanotubes (MWCNTs). The ZnO/CNTs heterostructures were characterized by scanning electron microscopy, high resolution transmission electron microscopy, and X-ray diffraction studies. No structural degradation of the CNTs was observed and photoluminescence (PL) measurements of the nanostructured ZnO layers show that the optical properties of these films are typical of ZnO deposited at low temperatures. The results indicate that magnetron sputtering is a viable technique for growing heterostructures and depositing functional layers onto CNTs.

Borkar, Tushar [Department of Materials Science and Engineering and Center for Advanced Research and Technology, University of North Texas, Denton 76203 (United States)] [Department of Materials Science and Engineering and Center for Advanced Research and Technology, University of North Texas, Denton 76203 (United States); Chang, Won Seok [Korea Institute of Machinery and Materials, 104 Sinseongno, Yuseong-gu, Daejeon 305-343 (Korea, Republic of)] [Korea Institute of Machinery and Materials, 104 Sinseongno, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Hwang, Jun Yeon, E-mail: Junyeon.Hwang@kist.re.kr [Department of Materials Science and Engineering and Center for Advanced Research and Technology, University of North Texas, Denton 76203 (United States); Institute of Advanced Composite Materials, Korea Institute of Science and Technology, Jeonbuk 565-902 (Korea, Republic of); Shepherd, Nigel D.; Banerjee, Rajarshi [Department of Materials Science and Engineering and Center for Advanced Research and Technology, University of North Texas, Denton 76203 (United States)] [Department of Materials Science and Engineering and Center for Advanced Research and Technology, University of North Texas, Denton 76203 (United States)

2012-10-15

109

Electro-Optics of a Transflective Liquid Crystal Display with Hybrid-Aligned Liquid Crystal Texture  

Microsoft Academic Search

The electrooptics of a newly proposed transflective liquid crystal display (LCD) with hybrid-aligned liquid crystal texture is optimized by simulation. The transflective LCD possesses an ultralow threshold voltage of 0 V and an operating voltage of 3 V. By using the dual cell-gap technology and a symmetric optical structure, the normalized voltage dependences of transmission and reflection overlap completely, and

Chiu-Lien Yang

2004-01-01

110

Constellation-X Spectroscopy X-Ray Telescope Segmented Optic Assembly and Alignment Implementation  

E-print Network

Constellation-X Spectroscopy X-Ray Telescope Segmented Optic Assembly and Alignment Implementation. ABSTRACT The Constellation-X mission will perform X-Ray science with improvements in energy resolution and effective area over its predecessor missions. The primary instrument on each of the four Constellation

111

A six sigma review of miniature optics alignment  

NASA Astrophysics Data System (ADS)

The key to high quality optics is a set of guidelines. Create an understanding of the Criteria for Quality. Focus on understanding and controlling process variation. Examine verification and validation of methods. Take a view of the horizon as well as drilling down so you know when to put down the shovel.

Tesar, John

2009-08-01

112

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

113

Optical inspection techniques for security instrumentation  

Microsoft Academic Search

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.

Rudolf L. van Renesse

1996-01-01

114

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

115

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

116

Design of a flexure-based alignment device for adjustable and stable mounting of optical components  

NASA Astrophysics Data System (ADS)

Measurement systems such as systems based on interferometric combination of beams of light, require highly accurate alignment of optical components such as mirrors to achieve fringes. Moreover, the stability of such alignment mechanisms must be even higher. Alignment devices based on flexures provide accurate alignment with excellent resolution, without play or hysteresis. TNO TPD developed mechanisms for adjustment of mirrors in two degrees of freedom, meaning two rotations, and used these mechanisms in setups to achieve picometer stability. The paper describes the design process and the development of a set of alignment mechanisms. Theoretical and practical aspects are mentioned. First the design aspects for designing stable mounts are given, and then two mechanisms are described. The mechanisms consist of a monolithic adjustment mount for a mirror that is made by wire erosion in such a way that the mirror can rotate about two axes. Adjustment screws in combination with a lever and a gear provide easy and accurate adjustment of the rotation of the mirror. The combination of flexures result in a virtual point of rotation that is positioned on the centre of the mirror surface. In this case, the optical path length of the deflected light path will not change. Two degree of freedom rotation mechanisms have a generic design, so the design can be used in multiple instruments. The measurement systems show high stability of the components.

Giesen, Peter; van der Lee, Noenke

2004-09-01

117

Study of optical destruction techniques for optical discs  

NASA Astrophysics Data System (ADS)

The topic of this dissertation is on the investigation of optical techniques for completely destroying data stored in optical discs. Complete and secure destruction of data is important when disposal of an optical disc containing sensitive and possibly classified information is concerned, since some information can be retrieved even from a fragment of a disc. After several candidate techniques and related systems are examined and fundamental system components are identified, an optical data destruction (ODD) system using a focused high power laser beam is devised, and a prototype system is designed and constructed. The ODD system uses a high power laser diode (HPLD) to expose data marks on optical discs and maintains the focused laser beam on a data layer by a focus servo using a diffractive optical element (DOE). The optical characteristics of the beam emitted from an HPLD are thoroughly investigated, and a few methods of modeling an HPLD beam in an optical system are studied. With the understanding of the HPLD beam properties, a limited-divergence raytracing (LDRT) model is developed to predict the propagation behavior of the HPLD beam in an optical system and shows good agreement with the real HPLD beam. This LDRT method is used to model the HPLD beam in the ODD system and simulate the resultant focus error signal with and without fabrication errors. The DOE focus sensor overcomes the problems in conventional focus sensors associated with the use of an intense line beam. The DOE comprising two angled gratings is designed to use only two weak 3rd order beams for focus sensing and fabricated on a chrome-coated glass substrate using a maskless lithography tool. The constructed ODD system is then used to perform destruction tests on various optical discs, which are examined using static and dynamic methods of data observation and retrieval. The observations show that data marks are optical invisible or completely covered with numerous micro-bubbles. These test results demonstrate that secure and complete destruction of data on optical discs is achieved using an ODD system. Successful destruction, however, depends greatly on exposure conditions and the type of optical media.

Choi, Taeyoung

118

A comparison between using incoherent or coherent sources to align and test an adaptive optical telescope  

NASA Astrophysics Data System (ADS)

The concept in the initial alignment of the segmented mirror adaptive optics telescope called the phased array mirror extendable large aperture telescope (Pamela) is to produce an optical transfer function (OTF) which closely approximates the diffraction limited value which would correspond to a system pupil function that is unity over the aperture and zero outside. There are differences in the theory of intensity measurements between coherent and incoherent radiation. As a result, some of the classical quantities which describe the performance of an optical system for incoherent radiation can not be defined for a coherent field. The most important quantity describing the quality of an optical system is the OTF and for a coherent source the OTF is not defined. Instead a coherent transfer function (CTF) is defined. The main conclusion of the paper is that an incoherent collimated source and not a collimated laser source is preferred to calibrate the Hartmann wavefront sensor (WFS) of an aligned adaptive optical system. A distant laser source can be used with minimum problems to correct the system for atmospheric turbulence. The collimation of the HeNe laser alignment source can be improved by using a very small pin hole in the spatial filter so only the central portion of the beam is transmitted and the beam from the filter is nearly constant in amplitude. The size of this pin hole will be limited by the sensitivity of the lateral effect diode (LEDD) elements.

Anderson, Richard

1994-10-01

119

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

120

Electro-optical effects in hybrid aligned flexoelectric nematic layers  

NASA Astrophysics Data System (ADS)

Liquid crystal cells with hybrid boundary anchoring, filled with nematic possessing flexoelectric properties, and subjected to external electric field, were studied numerically in order to find the influence of flexoelectricity on their behavior. Such layers may adopt three kinds of director structures: uniform planar, uniform homeotropic, and non-uniform which is intermediate between the former two. Stability of these structures depends on flexoelectric coefficients, anchoring strengths, thickness of the layer, dielectric anisotropy, and elastic constants. Changes of bias voltage cause transitions between them, which lead to electro-optical effects if the layers are placed between crossed polarizers. Three cases of transitions were considered: (i) transition between bright planar and dark non-uniform states, (ii) between dark planar and bright non-uniform states, and (iii) between dark homeotropic and bright non-uniform states. The director distributions in various states corresponding to various grey levels were calculated, and the electro-optic characteristics were obtained. The dynamics of the transitions between dark, bright, and intermediate states was determined taking into account the backflow effect. It was found that the transitions are faster when the nematic is devoid of flexoelectric properties.

Derfel, G.; Buczkowska, M.

2013-11-01

121

Curl-B technique applied to Swarm constellation for determining field-aligned currents  

Microsoft Academic Search

The constellation of the Swarm satellites provides for the first time the opportunity to determine field-aligned currents in the ionosphere uniquely. This is achieved by employing the Curl-B relation of Ampere's law directly to measurements of a satellite pair flying side-by-side. The new technique is applied to a set of consistent magnetic field and current data generated by a global

P. Ritter; H. Lühr

2006-01-01

122

Application of holographic optical techniques to bulk memory.  

NASA Technical Reports Server (NTRS)

Current efforts to exploit the spatial redundancy and built-in imaging of holographic optical techniques to provide high information densities without critical alignment and tight mechanical tolerances are reviewed. Read-write-erase in situ operation is possible but is presently impractical because of limitations in available recording media. As these are overcome, it should prove feasible to build holographic bulk memories with mechanically replaceable hologram plates featuring very fast (less than 2 microsec) random access to large (greater than 100 million bit) data blocks and very high throughput (greater than 500 Mbit/sec). Using volume holographic storage it may eventually be possible to realize random-access mass memories which require no mechanical motion and yet provide very high capacity.

Anderson, L. K.

1971-01-01

123

Optical fiber to waveguide coupling technique  

NASA Astrophysics Data System (ADS)

A technique for permanently coupling optical fibers edge-on to thin film waveguides was investigated and its feasibility demonstrated. It offers the fine micropositioner adjustment via a needle vacuum chuck for maximum optical coupling, offers robust mechanical support to the fibers from etched Si V-grooves, separates the support and fine adjustment cementing steps to minimize curing and thermal stresses, relaxes the requirements on fiber circularity and concentricity, is compatible with waveguide devices, and is suitable for close-spaced arrays of fibers.

Albares, D. J.; Trask, T. W.

1990-03-01

124

Time-varying gyrocompass alignment for fiber-optic-gyro inertial navigation system with large misalignment angle  

NASA Astrophysics Data System (ADS)

Conventional strapdown gyrocompass alignment methods are based on the assumption that the fiber-optic-gyro inertial navigation system has a small azimuth misalignment angle. A large azimuth misalignment angle would lead to an extension of the alignment duration. A time-varying gyrocompass alignment method to solve this problem is provided. An appropriate parameter setting is given for the gyrocompass alignment with a large misalignment angle. Also, a proper protocol for a parametric switch is derived. Simulation and trail results show that the proposed method has better alignment performance than conventional ones, as the system has large misalignment angles.

Ben, Yueyang; Li, Qian; Zhang, Yi; Huo, Liang

2014-09-01

125

Diagnostic apparatus and method for use in the alignment of one or more laser means onto a fiber optics interface  

DOEpatents

Diagnostic apparatus for use in determining the proper alignment of a plurality of laser beams onto a fiber optics interface is disclosed. The apparatus includes a lens assembly which serves two functions, first to focus a plurality of laser beams onto the fiber optics interface, and secondly to reflect and image the interface using scattered light to a monitor means. The monitor means permits indirect observation of the alignment or focusing of the laser beams onto the fiber optics interface.

Johnson, Steve A. (Tracy, CA); Shannon, Robert R. (Tucson, AZ)

1987-01-01

126

Diagnostic apparatus and method for use in the alignment of one or more laser means onto a fiber optics interface  

DOEpatents

Diagnostic apparatus for use in determining the proper alignment of a plurality of laser beams onto a fiber optics interface is disclosed. The apparatus includes a lens assembly which serves two functions, first to focus a plurality of laser beams onto the fiber optics interface, and secondly to reflect and image the interface using scattered light to a monitor means. The monitor means permits indirect observation of the alignment or focusing of the laser beams onto the fiber optics interface.

Johnson, S.A.; Shannon, R.R.

1985-01-18

127

Asymmetric dyes align inside carbon nanotubes to yield a large nonlinear optical response  

NASA Astrophysics Data System (ADS)

Asymmetric dye molecules have unusual optical and electronic properties. For instance, they show a strong second-order nonlinear optical (NLO) response that has attracted great interest for potential applications in electro-optic modulators for optical telecommunications and in wavelength conversion of lasers. However, the strong Coulombic interaction between the large dipole moments of these molecules favours a pairwise antiparallel alignment that cancels out the NLO response when incorporated into bulk materials. Here, we show that by including an elongated dipolar dye (p,p?-dimethylaminonitrostilbene, DANS, a prototypical asymmetric dye with a strong NLO response) inside single-walled carbon nanotubes (SWCNTs), an ideal head-to-tail alignment in which all electric dipoles point in the same sense is naturally created. We have applied this concept to synthesize solution-processible DANS-filled SWCNTs that show an extremely large total dipole moment and static hyperpolarizability (?0?=?9,800?×?10?30?e.s.u.), resulting from the coherent alignment of arrays of ?70 DANS molecules.

Cambré, Sofie; Campo, Jochen; Beirnaert, Charlie; Verlackt, Christof; Cool, Pegie; Wenseleers, Wim

2015-03-01

128

Asymmetric dyes align inside carbon nanotubes to yield a large nonlinear optical response.  

PubMed

Asymmetric dye molecules have unusual optical and electronic properties. For instance, they show a strong second-order nonlinear optical (NLO) response that has attracted great interest for potential applications in electro-optic modulators for optical telecommunications and in wavelength conversion of lasers. However, the strong Coulombic interaction between the large dipole moments of these molecules favours a pairwise antiparallel alignment that cancels out the NLO response when incorporated into bulk materials. Here, we show that by including an elongated dipolar dye (p,p'-dimethylaminonitrostilbene, DANS, a prototypical asymmetric dye with a strong NLO response) inside single-walled carbon nanotubes (SWCNTs), an ideal head-to-tail alignment in which all electric dipoles point in the same sense is naturally created. We have applied this concept to synthesize solution-processible DANS-filled SWCNTs that show an extremely large total dipole moment and static hyperpolarizability (?0?=?9,800?×?10(-30)?e.s.u.), resulting from the coherent alignment of arrays of ?70 DANS molecules. PMID:25643253

Cambré, Sofie; Campo, Jochen; Beirnaert, Charlie; Verlackt, Christof; Cool, Pegie; Wenseleers, Wim

2015-03-01

129

Daytime Polar Alignment of Telescope Mountings Using GPS and Internal Reference Optics  

Microsoft Academic Search

A technique is presented for performing polar alignment of astronomical telescope mountings to high precision during daylight hours. This work originated in the requirement to erect a truck mounted astronomical telescope at multiple locations during the day in order to measure the atmospheric convective turbulence Fried Parameter r0 by tracking stars at various zenith angles. The custom equatorial mounting built

R. R. Mellon; D. Scheld; R. E. Stencel

1998-01-01

130

Method for auto-alignment of digital optical phase conjugation systems based on digital propagation.  

PubMed

Optical phase conjugation (OPC) has enabled many optical applications such as aberration correction and image transmission through fiber. In recent years, implementation of digital optical phase conjugation (DOPC) has opened up the possibility of its use in biomedical optics (e.g. deep-tissue optical focusing) due to its ability to provide greater-than-unity OPC reflectivity (the power ratio of the phase conjugated beam and input beam to the OPC system) and its flexibility to accommodate additional wavefront manipulations. However, the requirement for precise (pixel-to-pixel matching) alignment of the wavefront sensor and the spatial light modulator (SLM) limits the practical usability of DOPC systems. Here, we report a method for auto-alignment of a DOPC system by which the misalignment between the sensor and the SLM is auto-corrected through digital light propagation. With this method, we were able to accomplish OPC playback with a DOPC system with gross sensor-SLM misalignment by an axial displacement of up to~1.5?cm, rotation and tip/tilt of ~5° and in-plane displacement of ~5?mm (dependent on the physical size of the sensor and the SLM). Our auto-alignment method robustly achieved a DOPC playback peak-to-background ratio (PBR) corresponding to more than ~30?% of the theoretical maximum. As an additional advantage, the auto-alignment procedure can be easily performed at will and, as such, allows us to correct for small mechanical drifts within the DOPC systems, thus overcoming a previously major DOPC system vulnerability. We believe that this reported method for implementing robust DOPC systems will broaden the practical utility of DOPC systems. PMID:24977504

Jang, Mooseok; Ruan, Haowen; Zhou, Haojiang; Judkewitz, Benjamin; Yang, Changhuei

2014-06-16

131

Imaging techniques with refractive beam shaping optics  

NASA Astrophysics Data System (ADS)

Applying of the refractive beam shapers in real research optical setups as well as in industrial installations requires very often manipulation of a final laser spot size. In many cases this task can be easily solved by using various imaging optical layouts presuming creating an image of a beam shaper output aperture. Due to the unique features of the refractive beam shapers of field mapping type, like flat wave front and low divergence of the collimated resulting beam with flattop or another intensity profile, there is a freedom in building of various imaging systems with using ordinary optical components, including off-the-shelf ones. There will be considered optical layouts providing high, up to 1/200×, de-magnifying factors, combining of refractive beam shapers like ?Shaper with scanning systems, building of relay imaging systems with extended depth of field. These optical layouts are widely used in such laser technologies like drilling holes in PCB, welding, various micromachining techniques with galvo-mirror scanning, interferometry and holography, various SLM-based applications. Examples of real implementations and experimental results will be presented as well.

Laskin, Alexander; Laskin, Vadim

2012-10-01

132

Liquid Crystal Displays and Novel Optical Thin Films Enabled by Photo-Alignment  

Microsoft Academic Search

Photo-alignment and photo-patterning of monomeric- and polymeric liquid crystals by the linear photo-polymerisation (LPP) technology enables novel molecular configurations in liquid crystal displays (LCDs) as well as a plethora of new thin-film optical elements on single plastic substrates. A molecular building block design of LPP photo-co-polymers with display-specific functional groups is depicted. Contrast and brightness of twisted nematic (TN)-LCDs are

Martin Schadt

2001-01-01

133

Optical Simulation of Axially Symmetrical Vertically Aligned Liquid Crystal Displays With Circularly Symmetric Iso-Contrast  

Microsoft Academic Search

This investigation reports the optical simulation of axially symmetric vertically aligned liquid crystal displays (ASVA LCDs). The circularly symmetric iso-light leakage and iso-transmittance contours of one subpixel result in the circularly symmetric iso-contrast contours. The contrast ratio of the area close to - and -axes at a polar angle of around 30 exceeds 10. The LCs near some azimuthal angles

Cheng-Kai Liu; Chi-Lun Ting; Ming-Shian Li; Andy Ying-Guey Fuh; Ko-Ting Cheng

2011-01-01

134

Remote alignment of adaptive optical systems with far-field optimization  

Microsoft Academic Search

A novel scheme for remote alignment of adaptive optical systems is presented. In comparison to conventional methods where near-field measurements (in the form of near-field phase across the adaptive component or gaps between neighboring segments) are used for feedback control, Far-Field Optimization utilizes only the far-field intensity. A figure of merit based solely on the point spread function is used

Naresh C. Mehta

1991-01-01

135

Optical phase conjugation: principles, techniques, and applications  

NASA Astrophysics Data System (ADS)

Over the last three decades, optical phase conjugation (OPC) has been one of the major research subjects in the field of nonlinear optics and quantum electronics. OPC defines usually a special relationship between two coherent optical beams propagating in opposite directions with reversed wave front and identical transverse amplitude distributions. The unique feature of a pair of phase-conjugate beams is that the aberration influence imposed on the forward beam passed through an inhomogeneous or disturbing medium can be automatically removed for the backward beam passed through the same disturbing medium. To date there have been three major technical approaches that can efficiently produce the backward phase-conjugate beam. The first approach is based on the degenerate (or partially degenerate) four-wave mixing processes, the second is based on various backward simulated (Brillouin, Raman, Rayleigh-wing or Kerr) scattering processes, and the third is based on one-photon or multi-photon pumped backward stimulated emission (lasing) processes. Among these three different approaches, there is a common physical mechanism that plays the same essential role in generating a backward phase-conjugate beam, which is the formation of the induced holographic grating and the subsequent wave-front restoration via a backward reading beam. In most experimental studies, certain types of resonance enhancements of induced refractive-index changes are desirable for obtaining higher grating-refraction efficiency. The momentum of OPC studies has recently become even stronger because there are more prospective potentials and achievements for applications. OPC-associated techniques can be successfully utilized in many different application areas: such as high-brightness laser oscillator/amplifier systems, cavity-less lasing devices, laser target-aiming systems, aberration correction for coherent-light transmission and reflection through disturbing media, long distance optical fiber communications with ultra-high bit-rate, optical phase locking and coupling systems, and novel optical data storage and processing systems.

He, Guang S.

2002-05-01

136

Alignment, assembly, and testing of high-energy x-ray optics  

NASA Astrophysics Data System (ADS)

We are developing grazing incidence x-ray imaging optics for a balloon-borne hard x-ray telescope (HERO). The HERO payload, scheduled for launch in May 2006, consists of 8 mirror modules with 12 mirror shells each fabricated using electroform-nickel replication off super polished cylindrical mandrels. An optical system for alignment and assembly of the shells into their modules will be described together with an assessment of the systematic errors associated with this process. Full details of the assembly procedures and results of the on-ground x-ray testing of the HERO modules will be provided.

Gubarev, Mikhail; Alexander, Cheryl; Ramsey, Brian

2005-08-01

137

Optical Alignment Retention In The AN/GVS-5 Hand Held Laser Rangefinder  

NASA Astrophysics Data System (ADS)

In the design of military optical systems there frequently exists conflicts among requirements for high performance or precision, size and weight, and the ability to withstand harsh environments. The AN/GVS-5 Hand Held Laser Rangefinder developed for the U.S. Army is a good example of such a system comprising precise alignment of three optical axes in a five pound, field deployed equipment. Final success of the program was the result of innovative design, careful material selection, and attention to detail in manufacture and process control.

Guyer, Robert C.; Stenton, Conrad

1982-05-01

138

Study cell invasion by optical techniques  

NASA Astrophysics Data System (ADS)

Cancer is a world-wide health problem associated with an increasing death rate. The mechanisms of how normal cells transform into cancer cells are not fully understood. Intensive investigations have been undertaken to identify genes whose unregulated expression are involved in this process. In this study, we have grown, on collagen gel, adherent mouse embryo fibroblasts (MEFs) knocked out for Cyl-1 (MEF Cyl1-/-) which have been transfected with the human proto-oncogene cyclin D1 (CCND1) under the control of an inducible expression system. CCND1 expression can be regulated in the fibroblasts via the presence of an inducer, isopropyl ?-D-Thiogalactopyranoside (IPTG). In the absence of IPTG, CCND1 expression is silenced. The migration ability of the resultant cells on the collagen gel has been monitored by complementary optical techniques: the conventional light microscopy; optical coherence tomography and Fourier Transform Infrared Microspcopic Spectroscopy (FTIR) using Synchrotron beam source. It is found that the cells expressing CCND1 exhibited cell invasion morphology and had different matrix compositions near the cell layer in comparison to the cells not expressing CCND1. The results from this study are consistent with published findings that expression of CCND1 has oncogenic potential and is involved in cell invasion in vitro. Application of complementary optical techniques proves to be an efficient way obtaining morphological and composition information of cell invasion.

Yang, Ying; Hoban, Paul R.; Sule-Suso, Joseph; Holley, Sarah; El Haj, Alicia J.; Bahrami, Fariba; Wang, Ruikang K.

2006-02-01

139

Novel Technique for Achieving Dual-Domain Alignment in Twisted Nematic Liquid Crystal Display and Its Application  

Microsoft Academic Search

A simple technique for achieving dual-domain alignment in a twisted nematic liquid crystal display (TN-LCD) is proposed. By incorporating the use of linearly polarized deep UV (DUV) for liquid crystal alignment, only one rubbing and one photolithographic process are added to conventional TN fabrication. We fabricated dual-domain twisted nematic (DDTN) cells using this technique with a practical pixel resolution. This

Syed H. Jamal; Jack R. Kelly; John L. West

1995-01-01

140

An Approach to Ontology Alignment Problems based on Category Matching Technique  

NASA Astrophysics Data System (ADS)

When ontology description data by different authors would become widespread in the world, we will be faced with the difficulties of the ontology alignment (OA) problem required for integration and interoperability of ontologies. The OA problem is the problem to find couples of semantically same classes / properties between two ontologies, and includes points of different naming of classes / properties, polysemous naming of classes / properties, different granularity of classes / properties, different hierarchical structures, and so on. We applied our semantic category matching (SCM) tool to the ontology alignment problems. Our approach found pairs of semantically corresponding categories from two different classification hierarchies such as Yahoo directory or library classification as UDC or NDC, based on natural language processing, similarity searching of huge vector spaces, and structural consistency analysis. We tackled problems of the EON2004 Ontology Alignment Contest. For examples, the Contest's random name problems (#201, #202) could not be solved using conventional character string resemblance techniques. However, when we applied SCM to these problems, the results showed that SCM had improved the accuracy as compared to the conventional method (F-measure: 0.021=>0.949, 0.021=>0.580), and exceeded the accuracy average in all problem areas by over 10 % as compared to conventional methods. Our team participated as a competitor in EON OA Contest and could obtain satisfactory results.

Hoshiai, Tadashi; Yamane, Yasuo; Tsuda, Hiroshi

141

Optical and structural properties of amorphous SexTe100-x aligned nanorods  

PubMed Central

In the present work, we report studies on optical and structural phenomenon in as-deposited thin films composed of aligned nanorods of amorphous SexTe100-x (x?=?3, 6, 9, and 12). In structural studies, field emission scanning electron microscopic (FESEM) images suggest that these thin films contain high yield of aligned nanorods. These nanorods show a completely amorphous nature, which is verified by X-ray diffraction patterns of these thin films. Optical studies include the measurement of spectral dependence of absorption, reflection, and transmission of these thin films, respectively. On the basis of optical absorption data, a direct optical band gap is observed. This observation of a direct optical band gap in these nanorods is interesting as chalcogenides normally show an indirect band gap, and due to this reason, these materials could not become very popular for semiconducting devices. Therefore, this is an important report and will open up new directions for the application of these materials in semiconducting devices. The value of this optical band gap is found to decrease with the increase in selenium (Se) concentration. The reflection and absorption data are employed to estimate the values of optical constants (extinction coefficient (k) and refractive index (n)). From the spectral dependence of these optical constants, it is found that the values of refractive index (n) increase, whereas the values of extinction coefficient (k) decrease with the increase in photon energy. The real and imaginary parts of dielectric constants calculated with the values of extinction coefficient (k) and refractive index (n), are found to vary with photon energy and dopant concentration. PMID:24321447

2013-01-01

142

Development, performance assessment, and verification of a calibration and alignment technique for a precision IMU  

NASA Astrophysics Data System (ADS)

The various methods which were used to develop the calibration and alignment mechanization for the MX inertial measurement unit and to assess system performance are described. These include covariance analysis, simulation, analysis of instrument and system data, post-processing of system data and an absolute azimuth verification technique. Comparison of error parameter estimates between instrument and system tests is shown to be useful for the evaluation of parameter stability and mismodeling. Open loop measurement residuals are shown to be useful for assessing performance. Where possible, results are presented which illustrate these methods.

Weinman, R. W.; Rutkoskie, J. V.

1981-08-01

143

A synchronization technique for optical PPM signals  

NASA Technical Reports Server (NTRS)

A technique for maintaining synchronization between optical PPM (pulse-position modulation) pulses and a receiver clock by means of a delay-tracking loop is described and analyzed. The tracking loop is driven by a doubly stochastic Poisson process that contains information about the location of the desired slot boundaries. The slot boundaries are subject to slowly varying random delays that are ultimately tracked by the loop. The concept of fractional rms delay error is introduced to quantify the effects of signal and background induced shot noise on the performance of the delay-tracking loop.

Vilnrotter, V. A.; Rodemich, E. R.; Tan, H. H.

1986-01-01

144

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

145

Using naturally occurring polysaccharides to align molecules with nonlinear optical activity  

NASA Technical Reports Server (NTRS)

The Biophysics and Advanced Materials Branch of the Microgravity Science and Applications Division at Marshall Space Flight Center has been investigating polymers with the potential for nonlinear optical (NLO) applications for a number of years. Some of the potential applications for NLO materials include optical communications, computing, and switching. To this point the branch's research has involved polydiacetylenes, phthalocyanins, and other synthetic polymers which have inherent NLO properties. The aim of the present research is to investigate the possibility of using naturally occurring polymers such as polysaccharides or proteins to trap and align small organic molecules with useful NLO properties. Ordering molecules with NLO properties enhances 3rd order nonlinear effects and is required for 2nd order nonlinear effects. Potential advantages of such a system are the flexibility to use different small molecules with varying chemical and optical properties, the stability and cost of the polymers, and the ability to form thin, optically transparent films. Since the quality of any polymer films depends on optimizing ordering and minimizing defects, this work is particularly well suited for microgravity experiments. Polysaccharide and protein polymers form microscopic crystallites which must align to form ordered arrays. The ordered association of crystallites is disrupted by gravity effects and NASA research on protein crystal growth has demonstrated that low gravity conditions can improve crystal quality.

Prasthofer, Thomas

1996-01-01

146

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

NASA Astrophysics Data System (ADS)

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.

1986-08-01

147

Optical test bench for high precision metrology and alignment of zoom sub-assembly components  

NASA Astrophysics Data System (ADS)

Thales Angénieux (TAGX) designs and manufactures zoom lens assemblies for cinema applications. These objectives are made of mobile lens assemblies. These need to be precisely characterized to detect alignment, polishing or glass index homogeneity errors, which amplitude may range to a few hundreds of nanometers. However these assemblies are highly aberrated with mainly spherical aberration (>30 ?m PV). PHASICS and TAGX developed a solution based on the use of a PHASICS SID4HR wave front sensor. This is based on quadri-wave lateral shearing interferometry, a technology known for its high dynamic range. A 100-mm diameter He:Ne source illuminates the lens assembly entrance pupil. The transmitted wave front is then directly measured by the SID4- HR. The measured wave front (WFmeas) is then compared to a simulation from the lens sub-assembly optical design (WFdesign). We obtain a residual wave front error (WFmanufactured), which reveals lens imperfections due to its manufacturing. WFmeas=WFdesign+(WFEradius+WFEglass+WFEpolish)=WF design + WFmanufactured The optical test bench was designed so that this residual wave front is measured with a precision below 100 nm PV. The measurement of fast F-Number lenses (F/2) with aberrations up to 30 ?m, with a precision of 100 nm PV was demonstrated. This bench detects mismatches in sub-assemblies before the final integration step in the zoom. Pre-alignment is also performed in order to overpass the mechanical tolerances. This facilitates the completed zoom alignment. In final, productivity gains are expected due to alignment and mounting time savings.

Leprêtre, F.; Levillain, E.; Wattellier, B.; Delage, P.; Brahmi, D.; Gascon, A.

2013-09-01

148

Self-Calibration Technique for 3-point Intrinsic Alignment Correlations in Weak Lensing Surveys  

E-print Network

The intrinsic alignment (IA) of galaxies has been shown to be a significant barrier to precision cosmic shear measurements. (Zhang, 2010, ApJ, 720, 1090) proposed a self-calibration technique for the power spectrum to calculate the induced gravitational shear-galaxy intrinsic ellipticity correlation (GI) in weak lensing surveys with photo-z measurements which is expected to reduce the IA contamination by at least a factor of 10 for currently proposed surveys. We confirm this using an independent analysis and propose an expansion to the self-calibration technique for the bispectrum in order to calculate the dominant IA gravitational shear-gravitational shear-intrinsic ellipticity correlation (GGI) contamination. We first establish an estimator to extract the galaxy density-density-intrinsic ellipticity (ggI) correlation from the galaxy ellipticity-density-density measurement for a photo-z galaxy sample. We then develop a relation between the GGI and ggI bispectra, which allows for the estimation and removal of the GGI correlation from the cosmic shear signal. We explore the performance of these two methods, compare to other possible sources of error, and show that the GGI self-calibration technique can potentially reduce the IA contamination by up to a factor of 5-10 for all but a few bin choices, thus reducing the contamination to the percent level. The self-calibration is less accurate for adjacent bins, but still allows for a factor of three reduction in the IA contamination. The self-calibration thus promises to be an efficient technique to isolate both the 2-point and 3-point intrinsic alignment signals from weak lensing measurements.

M. A. Troxel; Mustapha Ishak

2011-12-23

149

A rapid topographic mapping and eye alignment method using optical imaging in Macaque visual cortex  

PubMed Central

In optical imaging experiments, it is often advantageous to map the field of view and to converge the eyes without electrophysiological recording. This occurs when limited space precludes placement of an electrode or in chronic optical chambers in which one may not want to introduce an electrode each session or for determining eye position in studies of ocular disparity response in visual cortex of anesthetized animals. For these purposes, we have developed a spot imaging method that can be conducted rapidly and repeatedly throughout an experiment. Using small 0.2° – 0.5° spots, the extent of the imaged field of view is mapped by imaging cortical response to single spots, placed at different positions (0.2° steps) in either the horizontal or vertical axes. By shifting the relative positions of two spots, one presented to each eye, eye convergence can be assessed to within 0.1° resolution. Once appropriate eye alignment is determined, stimuli for further optical imaging procedures (e.g. imaging random dot stimuli for study of disparity responses) can then be confidently placed. This procedure can be quickly repeated throughout the experiment to ensure maintained eye alignment. PMID:19013530

HD, Lu; G, Chen; DY, Ts’o; AW, Roe

2009-01-01

150

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

151

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

PubMed

The changes in optical properties during TiO? 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

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

2014-10-17

152

PROBING SOFT MATTER WITH OPTICAL TECHNIQUES  

E-print Network

crystals (LCs), polymer-LC composites, cellulose fibers · Dynamic light scattering (DLS) investigations liquid crystal. #12;POLARIZATION OPTICAL MICROSCOPY VERSUS "USUAL" MICROSCOPY POLARIZATION OPTICAL at investigations of optically anisotropic materials (minerals, ceramics, polymers, liquid crystalline compounds

?umer, Slobodan

153

Pupil alignment reference (PAR) for the Mid-Infrared Instrument (MIRI) for optical alignment and verification on the Integrated Science Instrument Module (ISIM) in James Webb Space Telescope (JWST)  

Microsoft Academic Search

The Mid Infrared Instrument (MIRI), one of the four instruments on the Integrated Science Instrument Module (ISIM) of the James Webb Space Telescope (JWST), supports all of the science objectives of the observatory. MIRI optical alignment is an important step in the verification process, directly affecting mission success. The MIRI optical alignment is verified on the ground at the integrated

Cagatay Aymergen; Phillip Driggers; Raymond Ohl IV; Ray Lundquist; Pam Davila; Brent Bos; Scott Antonille; David Kubalak; Suong Le; Leonard Hanssen; Vilem Mikula; Claef Hakun; Corina Guishard; Jeffrey Guzek; Joe Connelly; Joseph McMann

2009-01-01

154

Pinned, optically aligned diagnostic dock for use on the Z facility.  

PubMed

The pinned optically aligned diagnostic dock (PODD) is a multi-configuration diagnostic platform designed to measure x-ray emission on the Z facility. The PODD houses two plasma emission acquisition (PEA) systems, which are aligned with a set of precision machined pins. The PEA systems are modular, allowing a single diagnostic housing to support several different diagnostics. The PEA configurations fielded to date include both time-resolved and time-integrated, 1D spatially resolving, elliptical crystal spectrometers, and time-integrated, 1D spatially resolving, convex crystal spectrometers. Additional proposed configurations include time-resolved, monochromatic mirrored pinhole imagers and arrays of filtered x-ray diodes, diamond photo-conducting diode detectors, and bolometers. The versatility of the PODD system will allow the diagnostic configuration of the Z facility to be changed without significantly adding to the turn-around time of the machine. Additionally, the PODD has been designed to allow instrument setup to be completed entirely off-line, leaving only a refined alignment process to be performed just prior to a shot, which is a significant improvement over the instrument the PODD replaces. Example data collected with the PODD are presented. PMID:23126888

Gomez, M R; Rochau, G A; Bailey, J E; Dunham, G S; Kernaghan, M D; Gard, P; Robertson, G K; Owen, A C; Argo, J W; Nielsen, D S; Lake, P W

2012-10-01

155

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

NASA Astrophysics Data System (ADS)

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.

1993-08-01

156

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

157

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

158

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

159

Optical switching: switch fabrics, techniques, and architectures  

Microsoft Academic Search

The switching speeds of electronics cannot keep up with the transmission capacity offered by optics. All-optical switch fabrics play a central role in the effort to migrate the switching functions to the optical layer. Optical packet switching provides an almost arbitrary fine granularity but faces significant challenges in the processing and buffering of bits at high speeds. Generalized multiprotocol label

Georgios I. Papadimitriou; Chrisoula Papazoglou; Andreas S. Pomportsis

2003-01-01

160

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

161

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

162

Automated alignment system for optical wireless communication systems using image recognition.  

PubMed

In this Letter, we describe the realization of a tracked line-of-sight optical wireless communication system for indoor data distribution. We built a laser-based transmitter with adaptive focus and ray steering by a microelectromechanical systems mirror. To execute the alignment procedure, we used a CMOS image sensor at the transmitter side and developed an algorithm for image recognition to localize the receiver's position. The receiver is based on a self-developed optoelectronic integrated chip with low requirements on the receiver optics to make the system economically attractive. With this system, we were able to set up the communication link automatically without any back channel and to perform error-free (bit error rate <10??) data transmission over a distance of 3.5 m with a data rate of 3 Gbit/s. PMID:24978803

Brandl, Paul; Weiss, Alexander; Zimmermann, Horst

2014-07-01

163

A self-aligned fabrication method of dual comb drive using multilayers SOI process for optical MEMS applications  

Microsoft Academic Search

A novel method for fabricating a self-aligned electrostatic dual comb drive using a multi-layer SOI process is developed. The present method utilizes four aligned masks, greatly simplify the existing SOI-MEMS fabrication methods in manufacturing optical MEMS devices. Here, the actuating structure consists of fixed combs and moving combs that are composed of single crystal silicon, nitride and polysilicon. One mask

W. T. Lin; J. C. Chiou; C. Tsou

2005-01-01

164

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

165

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

166

Novel techniques for optical performance monitoring in optical systems  

Microsoft Academic Search

The tremendous increase of data traffic in the worldwide Internet has driven the rapid development of optical networks to migrate from numerous point-to-point links towards meshed, transparent optical networks with dynamically routed light paths. This increases the need for appropriate network supervision methods. In view of this, optical performance monitoring (OPM) has emerged as an indispensable element for the quality

Yuen Ching Ku

2007-01-01

167

Nova laser alignment control system  

SciTech Connect

Alignment of the Nova laser requires control of hundreds of optical components in the ten beam paths. Extensive application of computer technology makes daily alignment practical. The control system is designed in a manner which provides both centralized and local manual operator controls integrated with automatic closed loop alignment. Menudriven operator consoles using high resolution color graphics displays overlaid with transport touch panels allow laser personnel to interact efficiently with the computer system. Automatic alignment is accomplished by using image analysis techniques to determine beam references points from video images acquired along the laser chain. A major goal of the design is to contribute substantially to rapid experimental turnaround and consistent alignment results. This paper describes the computer-based control structure and the software methods developed for aligning this large laser system.

Van Arsdall, P.J.; Holloway, F.W.; McGuigan, D.L.; Shelton, R.T.

1984-03-29

168

Optical beam forming techniques for phased array antennas  

NASA Technical Reports Server (NTRS)

Three optical beam forming techniques are identified as applicable to large spaceborne phased array antennas. They are 1) the fiber replacement of conventional RF phased array distribution and control components, 2) spatial beam forming, and 3) optical beam splitting techniques. Two novel optical beam forming approaches, i.e., the spatial beam forming with a 'smart pixel' spatial light modulator (SLM) and the optical beam splitting approaches are conceived with integrated quasi-optical components. Also presented are the transmit and receive array architectures with the new SLM.

Wu, Te-Kao; Chandler, Charles W.

1993-01-01

169

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

170

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

PubMed

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

2014-06-01

171

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

172

Optical properties of homeotropically aligned flexoelectric nematic layers deformed by direct current electric field  

NASA Astrophysics Data System (ADS)

Optical properties of homeotropically aligned flexoelectric nematic layers deformed by dc electric fields were analyzed by calculating the phase difference ?? between ordinary and extraordinary light rays passing through a layer placed between crossed polarizers. A phase difference arises when the bias voltage U exceeds the threshold value UT. Close to the threshold, ?? increases linearly with U. The possibility of using this effect to detect the flexoelectric properties of the nematic was explored by simulated experiments. The method considered in this paper is based on measurement of the slope of the linear section of the voltage dependence of ??, which depends on the sum of the flexoelectric coefficients and which differs from a well-known theoretical slope that ignores flexoelectric properties. The difference between the slopes reveals the flexoelectric properties of the nematic. The effectiveness of the proposed method is discussed.

Buczkowska, M.; Derfel, G.

2011-09-01

173

Optical alignment and testing of the Diffuse IR Background Experiment IR cryogenic telescope  

NASA Technical Reports Server (NTRS)

Diffuse Infrared Background Experiment (DIRBE) optical alignment and testing methods are discussed. Using strobe videography, vibration and performance testing of a 32 hz tuning-fork chopper was carried out. The Cosmic Background explorer satellite provides improved microwave and IR all-sky maps of the cosmic background radiation from a polar orbit. A liquid helium cryostat houses the DIRBE and the Far IR Absolute Spectrophotometer (FIRAS) instruments at a temperature of 2 K. Differential MicRowave Radiometers (DMRs) provide large scale maps of anisotropy of the 3 K background at wavelengths of 3.3, 5.7, and 9.6 mm. The DIRBE telescope is an IR photometric instrument with 10 wavelength bands between 1 and 300 microns, designed to measure radiation from the epoch of galaxy formation. Stringent stray light requirements mean that the DIRBE flight instrument has to be built and tested in a class 100 environment.

Wood, H. John

1989-01-01

174

Image Quality of the Evryscope: Method for On-Site Optical Alignment  

NASA Astrophysics Data System (ADS)

Previous wide field surveys have been conducted by taking many images each night to cover thousands of square degrees. The Evryscope is a new type of system designed to search for transiting exoplanets around nearby bright stars, M-dwarfs, white dwarfs, and other transients. The Evryscope is an array of 70 mm telescopes that will continuously image 10200 square degrees of the night sky at once. One of the image quality requirements is for the PSFs to be well-sampled at two pixels across and it was found that tilt caused by slight misalignment between the optics and the CCD increased the size of the FWHM towards the edges and corners of the image. Here we describe the image quality of the Evryscope cameras and the alignment procedure to achieve the required 2 pixel FWHM.

Wulfken, Philip J.; Law, Nicholas M.

2015-01-01

175

Antifouling leaching technique for optical lenses  

USGS Publications Warehouse

The effectiveness of optical lenses deployed in water less than 100 m deep is significantly reduced by biofouling caused by the settlement of macrofauna, such as barnacles, hydroids, and tunicates. However, machineable porous plastic rings can be used to dispense antifoulant into the water in front of the lens to retard macrofaunal growth without obstructing the light path. Unlike coatings which can degrade the optical performance, antifouling rings do not interfere with the instrument optics. The authors have designed plastic, reusable cup-like antifouling rings to slip over the optical lenses of a transmissometer. These rings have been used for several deployments on shallow moorings in Massachusetts Bay, MA and have increased the time before fouling degrades optical characteristics

Strahle, William J.; Perez, C. L.; Martini, Marinna A.

1994-01-01

176

Antares beam-alignment-system performance  

SciTech Connect

The beam alignment system for the 24-beam-sector Antares CO/sub 2/ fusion laser automatically aligns more than 200 optical elements. A visible-wavelength alignment technique is employed which uses a telescope/TV system to view point-light sources appropriately located down the beamline. The centroids of the light spots are determined by a video tracker, which generates error signals used by the computer control system to move appropriate mirrors in a closed-loop system. Final touch-up alignment is accomplished by projecting a CO/sub 2/ alignment laser beam through the system and sensing its position at the target location. The techniques and control algorithms employed have resulted in alignment accuracies exceeding design requirements. By employing video processing to determine the centroids of diffraction images and by averaging over multiple TV frames, we achieve alignment accuracies better than 0.1 times system diffraction limits in the presence of air turbulence.

Appert, Q.D.; Bender, S.C.

1983-01-01

177

Photo-Generation of Linearly Polymerized Liquid Crystal Aligning Layers Comprising Novel, Integrated Optically Patterned Retarders and Color Filters  

NASA Astrophysics Data System (ADS)

For the first time photo cross-linking of linearly polymerizable polymers (LPPs) is shown to induce uniaxial planar alignment in adjacent liquid crystal polymer (LCP)-layers on single substrates. Ways and novel materials allowing integration of LPP-aligning layers with optical retarders in patterned, hybrid LPP-LCP-configurations with freely adjustable optical axes are presented. The novel multifunctional, anisotropic photopolymer configurations are shown to render in-situ optical retarders and polarization interference filters for black-white and color liquid crystal displays (LCDs) feasible. The molecular mechanisms inducing the anisotropic film properties and their thermal and optical stabilities are outlined. The photo-patternable, high resolution hybrid configurations are shown to exhibit excellent thermal and light stability.

Schadt, Martin; Seiberle, Hubert; Schuster, Andreas; Kelly, Stephen

1995-06-01

178

Micro-optics and lithography simulation are key enabling technologies for shadow printing lithography in mask aligners  

NASA Astrophysics Data System (ADS)

Mask aligners are lithographic tools used to transfer a pattern of microstructures by shadow printing lithography onto a planar wafer. Contact lithography allows us to print large mask fields with sub-micron resolution, but requires frequent mask cleaning. Thus, contact lithography is used for small series of wafer production. Proximity lithography, where the mask is located at a distance of typically 30-100 ?m above the wafer, provides a resolution of approximately 3-5 ?m, limited by diffraction effects. Proximity lithography in mask aligners is a very cost-efficient method widely used in semiconductor, packaging and MEMS manufacturing industry for high-volume production. Micro-optics plays a key role in improving the performance of shadow printing lithography in mask aligners. Refractive or diffractive micro-optics allows us to efficiently collect the light from the light source and to precisely shape the illumination light (customized illumination). Optical proximity correction and phase shift mask technology allow us to influence the diffraction effects in the aerial image and to enhance resolution and critical dimension. The paper describes the status and future trends of shadow printing lithography in mask aligners and the decisive role of micro-optics as key enabling technology.

Voelkel, Reinhard; Vogler, Uwe; Bramati, Arianna; Noell, Wilfried

2015-02-01

179

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

180

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

181

Photoresponsive Carbohydrate-based Giant Surfactants: Automatic Vertical Alignment of Nematic Liquid Crystal for the Remote-Controllable Optical Device.  

PubMed

Photoresponsive carbohydrate-based giant surfactants (abbreviated as CELAnD-OH) were specifically designed and synthesized for the automatic vertical alignment (VA) layer of nematic (N) liquid crystal (LC), which can be applied for the fabrication of remote-controllable optical devices. Without the conventional polymer-based LC alignment process, a perfect VA layer was automatically constructed by directly adding the 0.1 wt % CELA1D-OH in the N-LC media. The programmed CELA1D-OH giant surfactants in the N-LC media gradually diffused onto the substrates of LC cell and self-assembled to the expanded monolayer structure, which can provide enough empty spaces for N-LC molecules to crawl into the empty zones for the construction of VA layer. On the other hand, the CELA3D-OH giant surfactants forming the condensed monolayer structure on the substrates exhibited a planar alignment (PA) rather than a VA. Upon tuning the wavelength of light, the N-LC alignments were reversibly switched between VA and PA in the remote-controllable LC optical devices. Based on the experimental results, it was realized that understanding the interactions between N-LC molecules and amphiphilic giant surfactants is critical to design the suitable materials for the automatic LC alignment. PMID:25738306

Kim, Dae-Yoon; Lee, Sang-A; Kang, Dong-Gue; Park, Minwook; Choi, Yu-Jin; Jeong, Kwang-Un

2015-03-25

182

Wavefront sensing techniques for adaptive optics systems  

NASA Astrophysics Data System (ADS)

The design and fabrication of a fiber optic pH sensor working on the basis of evanescent wave absorption is presented. A pH sensitive dye is immobilized on the uncladded portion of the optic fiber by sol-gel route. The sensitivity of the device is found to increase when multiple sol-gel coatings are used as the cladding in the sensing region. The sensor response and its dynamic range are reported for two pH indicator dyes, vis. bromocresol purple and bromocresol green.

Ray, Mina; Sarkar, Samir K.; Chakraborty, Rabindra N.; Basuray, Amitabha

2001-09-01

183

A Study of Synchronization Techniques for Optical Communication Systems  

NASA Technical Reports Server (NTRS)

The study of synchronization techniques and related topics in the design of high data rate, deep space, optical communication systems was reported. Data cover: (1) effects of timing errors in narrow pulsed digital optical systems, (2) accuracy of microwave timing systems operating in low powered optical systems, (3) development of improved tracking systems for the optical channel and determination of their tracking performance, (4) development of usable photodetector mathematical models for application to analysis and performance design in communication receivers, and (5) study application of multi-level block encoding to optical transmission of digital data.

Gagliardi, R. M.

1975-01-01

184

Optical system for Argus 355-nm 90-mm aperture target-illumination experiments  

SciTech Connect

The requirements of laser alignment, crystal tuning, target alignment, and laser beam diagnosis are provided by this optical system. Initial setup and preshot alignment techniques are discussed. Layout and operation are contrasted with the 532 nm target experiments.

Johnson, B.C.; Boyd, R.; Hermes, G.; Hildum, J.S.; Linford, G.; Martin, W.E.

1982-02-01

185

SMF PBSEDFAEDFA Optical Performance Monitoring Techniques for  

E-print Network

OSNR monitoring, OSNR monitoring using half symbol delay for SNR monitoring of RZ-DQPSK signal, optical signal to noise ratio (OSNR), chromatic dispersion (CD), polarization mode dispersion (PMD years in particular on OSNR and CD monitoring for various modulation formats. We will present research

Wai, Ping-kong Alexander

186

Optical Diffusometry Techniques and Applications in Biological ...  

E-print Network

Sep 22, 2008 ... ping the particles was confirmed by artificially inducing a flow ... assay. Typically this requires 30 min for virus binding and 15 min for optical ..... 16 Cui, Y., Wei, Q. Q., Park, H. K., and Lieber, C. M., 2001, “Nanowire Nanosen-.

2008-09-22

187

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

188

Recent flight-test results of optical airdata techniques  

NASA Technical Reports Server (NTRS)

Optical techniques for measuring airdata parameters have been 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 free stream static temperature and density are feasible for in-flight as applications. The best feature of these concepts is that the airdata measurements are obtained nonintrusively, and for the most part well into the freestream region of the flowfield about the aircraft. Current requirements for measuring airdata 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. This paper summarizes results from several flight-test programs and identifies the technology advances required to make optical airdata techniques practical.

Bogue, Rodney K.

1992-01-01

189

Basic Concepts of Optical Mapping Techniques in Cardiac Electrophysiology  

Microsoft Academic Search

Optical mapping is a tool used in cardiac electrophysiology to study the heart’s normal rhythm and arrhythmias. The optical mapping technique provides a unique opportunity to obtain membrane potential recordings with a higher temporal and spatial resolution than electrical mapping. Additionally, it allows simultaneous recording of membrane potential and calcium transients in the whole heart. This article presents the basic

Mina Attin; William T. Clusin

2009-01-01

190

Optical switching and control techniques using nonlinear optical wave mixing  

Microsoft Academic Search

It is shown experimentally that thermooptically induced beam guides and phase grating structures can be used to efficiently switch an optical beam by redirecting its energy in times of 20 and 2 nsec, respectively. Beam guiding was achieved by passing a focused TEM at infinity laser pulse through an absorbing liquid to which an absorbing dye had been added. Heating

Lauren M. Peterson

1987-01-01

191

Interference cancellation technique of optical AND gate receiver using optical thyristor.  

PubMed

We demonstrate an interference cancellation technique of optical AND gate receiver using optical thyristor for fiber-optic code division multiple access (FO-CDMA) systems. In particular, we fabricate the optical thyristor operating as optical hard-limiter and evaluate that the optical AND gate receiver using fabricated optical thyristor excludes the peaks of side-lobe and cross-correlation result in the system performance degradation. It found that the optical AND gate receiver using optical thyristor excludes the intensity of interference signal resulting in that the peaks of side-lobe and cross-correlation can be fully eliminated for any two users. Therefore, the optical AND gate receiver using optical thyristor is shown to be effective to accommodate more simultaneous users. PMID:18773033

Kang, Tae-Gu

2008-09-01

192

Antares automatic beam alignment system  

SciTech Connect

Antares is a 24-beam-line CO/sub 2/ laser system for controlled fusion research, under construction at Los Alamos Scientific Laboratory (LASL). Rapid automatic alignment of this system is required prior to each experiment shot. The alignment requirements, operational constraints, and a developed prototype system are discussed. A visible-wavelength alignment technique is employed that uses a telescope/TV system to view point light sources appropriately located down the beamline. Auto-alignment is accomplished by means of a video centroid tracker, which determines the off-axis error of the point sources. The error is nulled by computer-driven, movable mirrors in a closed-loop system. The light sources are fiber-optic terminations located at key points in the optics path, primarily at the center of large copper mirrors, and remotely illuminated to reduce heating effects.

Appert, Q.; Swann, T.; Sweatt, W.; Saxman, A.

1980-01-01

193

(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

194

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

195

Optical techniques for shock visualization and detection  

SciTech Connect

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. [National Aeronautics and Space Administration, Cleveland, OH (United States). Lewis Research Center; Johnson, D.K. [Univ. of Akron, OH (United States). Dept. of Mathematical Science

1995-12-31

196

Techniques for optically compressing light intensity ranges  

DOEpatents

A pin hole camera assembly for use in viewing an object having a relatively large light intensity range, for example a crucible containing molten uranium in an atomic vapor laser isotope separator (AVLIS) system is disclosed herein. The assembly includes means for optically compressing the light intensity range appearing at its input sufficient to make it receivable and decipherable by a standard video camera. A number of different means for compressing the intensity range are disclosed. These include the use of photogray glass, the use of a pair of interference filters, and the utilization of a new liquid crystal notch filter in combination with an interference filter. 18 figs.

Rushford, M.C.

1989-03-28

197

Techniques for optically compressing light intensity ranges  

DOEpatents

A pin hole camera assembly for use in viewing an object having a relatively large light intensity range, for example a crucible containing molten uranium in an atomic vapor laser isotope separator (AVLIS) system is disclosed herein. The assembly includes means for optically compressing the light intensity range appearing at its input sufficient to make it receivable and decipherable by a standard video camera. A number of different means for compressing the intensity range are disclosed. These include the use of photogray glass, the use of a pair of interference filters, and the utilization of a new liquid crystal notch filter in combination with an interference filter.

Rushford, Michael C. (Livermore, CA)

1989-01-01

198

The Virgo automatic alignment system  

Microsoft Academic Search

The automatic alignment system of the Virgo interferometer differs substantially from those used in similar experiments, since it uses a variant of the Anderson technique. This implies a completely different control topology with respect to other detectors, and the main feature is a strong coupling of different degrees of freedom in the optical signals. It also provides two extra output

F. Acernese; P. Amico; M. Al-Shourbagy; S. Aoudia; S. Avino; D. Babusci; G. Ballardin; R. Barillé; F. Barone; L. Barsotti; M. Barsuglia; F. Beauville; M. A. Bizouard; C. Boccara; F. Bondu; L. Bosi; C. Bradaschia; S. Braccini; A. Brillet; V. Brisson; L. Brocco; D. Buskulic; E. Calloni; E. Campagna; F. Cavalier; R. Cavalieri; G. Cella; E. Chassande-Mottin; C. Corda; A.-C. Clapson; F. Cleva; J.-P. Coulon; E. Cuoco; V. Dattilo; M. Davier; R. De Rosa; L. Di Fiore; A. Di Virgilio; B. Dujardin; A. Eleuteri; D. Enard; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; S. Frasca; F. Frasconi; A. Freise; L. Gammaitoni; A. Gennai; A. Giazotto; G. Giordano; L. Giordano; R. Gouaty; D. Grosjean; G. Guidi; S. Hebri; H. Heitmann; P. Hello; L. Holloway; S. Kreckelbergh; P. La Penna; V. Loriette; M. Loupias; G. Losurdo; J.-M. Mackowski; E. Majorana; C. N. Man; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; M. Mazzoni; L. Milano; C. Moins; J. Moreau; N. Morgado; B. Mours; A. Pai; C. Palomba; F. Paoletti; S. Pardi; A. Pasqualetti; R. Passaquieti; D. Passuello; B. Perniola; F. Piergiovanni; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; K. Qipiani; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; P. Ruggi; G. Russo; S. Solimeno; A. Spallicci; R. Stanga; R. Taddei; D. Tombolato; M. Tonelli; A. Toncelli; E. Tournefier; F. Travasso; G. Vajente; D. Verkindt; F. Vetrano; A. Viceré; J.-Y. Vinet; H. Vocca; M. Yvert; Z. Zhang

2006-01-01

199

Real-time optical image processing techniques  

NASA Technical Reports Server (NTRS)

Nonlinear real-time optical processing on spatial pulse frequency modulation has been pursued through the analysis, design, and fabrication of pulse frequency modulated halftone screens and the modification of micro-channel spatial light modulators (MSLMs). Micro-channel spatial light modulators are modified via the Fabry-Perot method to achieve the high gamma operation required for non-linear operation. Real-time nonlinear processing was performed using the halftone screen and MSLM. The experiments showed the effectiveness of the thresholding and also showed the needs of higher SBP for image processing. The Hughes LCLV has been characterized and found to yield high gamma (about 1.7) when operated in low frequency and low bias mode. Cascading of two LCLVs should also provide enough gamma for nonlinear processing. In this case, the SBP of the LCLV is sufficient but the uniformity of the LCLV needs improvement. These include image correlation, computer generation of holograms, pseudo-color image encoding for image enhancement, and associative-retrieval in neural processing. The discovery of the only known optical method for dynamic range compression of an input image in real-time by using GaAs photorefractive crystals is reported. Finally, a new architecture for non-linear multiple sensory, neural processing has been suggested.

Liu, Hua-Kuang

1988-01-01

200

Automatic inspection technique for optical surface flaws  

NASA Astrophysics Data System (ADS)

Industrial inspection of optical component surface flaws requires objective, high efficient and fast measurement methods and instruments. In this paper, a novel method, which is practical for on- line inspecting optical component surface flaws in manufacturing industry, is discribed. Laser beam goes through a lean- placed mirror with a slot in center onto the surface of the specimen. The imformation of surface flaws is obtained through analysing the frequency spectrum of reflective light which is detected by a photomultiplier, the specimen scanning control and signal processing are finished by a low - cost and handy single- board microcomputer. The theory that applies the scanning frequency spectrum method , the method for determining flaw size and measuring sensitivity as well as control model for various specimen are analysed in detail .A system has been built according to the idea discribed above. By using the system, several specimen are measured, the comparison and analysis between exprimental results and actual flaw conditions are given. The minimum detectable flaw is 3 micrometer, the measuring error is also given.

Yang, GuoGuang; Gao, Wenliang; Cheng, Shangyi

1991-01-01

201

Physical optics of the laser-schlieren shock tube technique  

Microsoft Academic Search

The physical optics of the laser-schlieren technique for the measurement of rate processes in shock waves is examined in detail. The method utilized the Kirchhoff-Hyggens 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

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

1981-01-01

202

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

203

Improved docking alignment system  

NASA Technical Reports Server (NTRS)

Improved techniques are provided for the alignment of two objects. The present invention is particularly suited for 3-D translation and 3-D rotational alignment of objects in outer space. A camera is affixed to one object, such as a remote manipulator arm of the spacecraft, while the planar reflective surface is affixed to the other object, such as a grapple fixture. A monitor displays in real-time images from the camera such that the monitor displays both the reflected image of the camera and visible marking on the planar reflective surface when the objects are in proper alignment. The monitor may thus be viewed by the operator and the arm manipulated so that the reflective surface is perpendicular to the optical axis of the camera, the roll of the reflective surface is at a selected angle with respect to the camera, and the camera is spaced a pre-selected distance from the reflective surface.

Monford, Leo G. (inventor)

1988-01-01

204

Proposal for using optical transition radiation for electron beam alignment and emittance measurement for the free emittance measurement for the free electron laser experiments at ATF  

SciTech Connect

Optical transiton radiation (OTR) produced from thin intercepting foils have been employed to image the spatial profile of the electron beam in several free electron laser experiments. It was found that the images from OTR were significantly sharper than the images produced from phosphor screens. Furthermore, OTR`s sensitivity of its angular distribution and polarization to energy and divergence of the electron beam was exploited to diagnose energy and emittance of the electron beam. OTR has been proven to be vital in electron beam alignment in FEL experiments. This report gives a summary of the basic theory of transition radiation and techniques using transition radiation for electron beam imaging and emittance measurement. The possibility was explored for employing these techniques in the HGHG FEL and the visible FEL experiments in ATF (Accelerator Test Facility).

Qiu, Xu Z.; Wang, Xijie; Ben-Zvi, I.

1994-10-01

205

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

206

Packaging of high density fiber\\/laser modules using passive alignment techniques  

Microsoft Academic Search

A method for packaging a laser-fiber module is explored in which the critical laser-fiber alignment is carried out, not with the laser activated, but by a passive method based on the registration principles of photolithography. The method relies on an index scheme in which fiducial marks are lithographically placed on the laser chip and on a fiber carrier. At 850

M. S. Cohen; M. F. Cina; E. Bassous; M. M. Opyrsko; J. L. Speidell; F. J. Canora; M. J. DeFranza

1992-01-01

207

A Novel Scheme for DVL-Aided SINS In-Motion Alignment Using UKF Techniques  

PubMed Central

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

208

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

209

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

210

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

211

Tumor margin detection using optical biopsy techniques  

NASA Astrophysics Data System (ADS)

The aim of this study is to use the Resonance Raman (RR) and fluorescence spectroscopic technique for tumor margin detection with high accuracy based on native molecular fingerprints of breast and gastrointestinal (GI) tissues. This tumor margins detection method utilizes advantages of RR spectroscopic technique in situ and in real-time to diagnose tumor changes providing powerful tools for clinical guiding intraoperative margin assessments and postoperative treatments. The tumor margin detection procedures by RR spectroscopy were taken by scanning lesion from center or around tumor region in ex-vivo to find the changes in cancerous tissues with the rim of normal tissues using the native molecular fingerprints. The specimens used to analyze tumor margins include breast and GI carcinoma and normal tissues. The sharp margin of the tumor was found by the changes of RR spectral peaks within 2 mm distance. The result was verified using fluorescence spectra with 300 nm, 320 nm and 340 nm excitation, in a typical specimen of gastric cancerous tissue within a positive margin in comparison with normal gastric tissues. This study demonstrates the potential of RR and fluorescence spectroscopy as new approaches with labeling free to determine the intraoperative margin assessment.

Zhou, Yan; Liu, Cheng-hui; Li, Jiyou; Li, Zhongwu; Zhou, Lixin; Chen, Ke; Pu, Yang; He, Yong; Zhu, Ke; Li, Qingbo; Alfano, Robert R.

2014-03-01

212

Alignment procedures for micro-optics Matthias Mohaupt, Erik Beckert, Ramona Eberhardt, Andreas Tnnermann  

E-print Network

. Depending on the pixel size and the design of the micro lens array, the assembly requirements in x - and y the CCD pixel lines with an accuracy of 5 µrad to 50 µrad. The alignment accuracy of hal-01055691,version1. The alignment of the collimating lens is the most important assembly task during the manufacturing of laser

Boyer, Edmond

213

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

214

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

of the polymer chains and the liquid crystal molecules, indicating that the surface-induced bulk alignment of a liquid crystal film by rubbed polymer surfaces is via an orientational epitaxylike mechanism. PACS numberNonlinear optical studies of liquid crystal alignment on a rubbed polyvinyl alcohol surface Xing

Zhuang, Xiaowei

215

Optical beam forming techniques for phased array antennas  

NASA Technical Reports Server (NTRS)

Conventional phased array antennas using waveguide or coax for signal distribution are impractical for large scale implementation on satellites or spacecraft because they exhibit prohibitively large system size, heavy weight, high attenuation loss, limited bandwidth, sensitivity to electromagnetic interference (EMI) temperature drifts and phase instability. However, optical beam forming systems are smaller, lighter, and more flexible. Three optical beam forming techniques are identified as applicable to large spaceborne phased array antennas. They are (1) the optical fiber replacement of conventional RF phased array distribution and control components, (2) spatial beam forming, and (3) optical beam splitting with integrated quasi-optical components. The optical fiber replacement and the spatial beam forming approaches were pursued by many organizations. Two new optical beam forming architectures are presented. Both architectures involve monolithic integration of the antenna radiating elements with quasi-optical grid detector arrays. The advantages of the grid detector array in the optical process are the higher power handling capability and the dynamic range. One architecture involves a modified version of the original spatial beam forming approach. The basic difference is the spatial light modulator (SLM) device for controlling the aperture field distribution. The original liquid crystal light valve SLM is replaced by an optical shuffling SLM, which was demonstrated for the 'smart pixel' technology. The advantages are the capability of generating the agile beams of a phased array antenna and to provide simultaneous transmit and receive functions. The second architecture considered is the optical beam splitting approach. This architecture involves an alternative amplitude control for each antenna element with an optical beam power divider comprised of mirrors and beam splitters. It also implements the quasi-optical grid phase shifter for phase control and grid amplifier for RF power. The advantages are no SLM is required for this approach, and the complete antenna system is capable of full monolithic integration.

Wu, Te-Kao; Chandler, C.

1993-01-01

216

In-flight alignment\\/calibration techniques for unaided tactical guidance  

Microsoft Academic Search

An evaluation is conducted of various alignment\\/calibration procedures which permit the use of low-cost sensors in unaided navigation satisfying tactical mission requirements. The missile navigation system and its interface with the reference launch aircraft navigation system are illustrated in a figure. Strapdown gyros and accelerometers are included in the missile's inertial sensor subsystem. To provide the optimum cost-effective utilization of

J. W. Kraemer; N. J. Roessler; D. M. Brandin

1978-01-01

217

Study on application of optical clearing technique in skin diseases  

NASA Astrophysics Data System (ADS)

So far, the study of the optical clearing is almost always about healthy tissue. However, the ultimate goal is to detect diseases for clinical application. Optical clearing on diseased skins is explored. The effect is evaluated by applying a combined liquid paraffin and glycerol mixed solution on several kinds of diseased skins in vitro. Scanning experiments from optical coherence tomography show that it has different effects among fibroma, pigmented nevus, and seborrheic keratosis. Based on the results, we conclude that different skin diseases have different compositions and structures, and their optical parameters and biological characteristics should be different, which implies that the optical clearing technique may have selectivity and may not be suitable for all kinds of skin diseases.

Shan, Hao; Liang, Yanmei; Wang, Jingyi; Li, Yan

2012-11-01

218

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

219

Physical optics of the laser-schlieren shock tube technique  

SciTech Connect

The physical optics of the laser-schlieren technique for the measurement of rate processes in shock waves is examined in detail. The method utilized the Kirchhoff-Hyggens 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.

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

1981-01-15

220

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

221

Alignment telescope for Antares  

SciTech Connect

The Antares Automatic Alignment System employs a specially designed telescope for alignment of its laser beamlines. There are two telescopes in the system, and since each telescope is a primary alignment reference, stringent boresight accuracy and stability over the focus range were required. Optical and mechanical designs, which meet this requirement as well as that of image quality over a wide wavelength band, are described. Special test techniques for initial assembly and alignment of the telescope are also presented. The telescope, which has a 180-mm aperture FK51-KZF2 type glass doublet objective, requires a boresight accuracy of 2.8 ..mu..rad at two focal lengths, and object distances between 11 meters and infinity. Travel of a smaller secondary doublet provides focus from 11 m to infinity with approximately 7.8 m effective focal length. By flipping in a third doublet, the effective focal length is reduced to 2.5 m. Telescope alignment was accomplished by using a rotary air bearing to establish an axis in front of the system and placing the focus of a Laser Unequal Path Interferometer (LUPI) at the image plane.

Appert, Q.D.; Swann, T.A.; Ward, J.H.; Hardesty, C.; Wright, L.

1983-01-01

222

Nanoscale optical and electrical characterization of horizontally aligned single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

During the recent years, a significant amount of research has been performed on single-walled carbon nanotubes (SWCNTs) as a channel material in thin-film transistors (Pham et al. IEEE Trans Nanotechnol 11:44-50, 2012). This has prompted the application of advanced characterization techniques based on combined atomic force microscopy (AFM) and Raman spectroscopy studies (Mureau et al. Electrophoresis 29:2266-2271, 2008). In this context, we use confocal Raman microscopy and current sensing atomic force microscopy (CS-AFM) to study phonons and the electronic transport in semiconducting SWCNTs, which were aligned between palladium electrodes using dielectrophoresis (Kuzyk Electrophoresis 32:2307-2313, 2011). Raman imaging was performed in the region around the electrodes on the suspended CNTs using several laser excitation wavelengths. Analysis of the G+/G- splitting in the Raman spectra (Sgobba and Guldi Chem Soc Rev 38:165-184, 2009) shows CNT diameters of 2.5 ± 0.3 nm. Neither surface modification nor increase in defect density or stress at the CNT-electrode contact could be detected, but rather a shift in G+ and G- peak positions in regions with high CNT density between the electrodes. Simultaneous topographical and electrical characterization of the CNT transistor by CS-AFM confirms the presence of CNT bundles having a stable electrical contact with the transistor electrodes. For a similar load force, reproducible current-voltage ( I/ V) curves for the same CNT regions verify the stability of the electrical contact between the nanotube and the electrodes as well as the nanotube and the AFM tip over different experimental sessions using different AFM tips. Strong variations observed in the I/ V response at different regions of the CNT transistor are discussed.

Rodriguez, Raul D.; Toader, Marius; Hermann, Sascha; Sheremet, Evgeniya; Müller, Susanne; Gordan, Ovidiu D.; Yu, Haibo; Schulz, Stefan E.; Hietschold, Michael; Zahn, Dietrich RT

2012-12-01

223

Nanoscale optical and electrical characterization of horizontally aligned single-walled carbon nanotubes  

PubMed Central

During the recent years, a significant amount of research has been performed on single-walled carbon nanotubes (SWCNTs) as a channel material in thin-film transistors (Pham et al. IEEE Trans Nanotechnol 11:44–50, 2012). This has prompted the application of advanced characterization techniques based on combined atomic force microscopy (AFM) and Raman spectroscopy studies (Mureau et al. Electrophoresis 29:2266–2271, 2008). In this context, we use confocal Raman microscopy and current sensing atomic force microscopy (CS-AFM) to study phonons and the electronic transport in semiconducting SWCNTs, which were aligned between palladium electrodes using dielectrophoresis (Kuzyk Electrophoresis 32:2307–2313, 2011). Raman imaging was performed in the region around the electrodes on the suspended CNTs using several laser excitation wavelengths. Analysis of the G+/G? splitting in the Raman spectra (Sgobba and Guldi Chem Soc Rev 38:165–184, 2009) shows CNT diameters of 2.5?±?0.3 nm. Neither surface modification nor increase in defect density or stress at the CNT-electrode contact could be detected, but rather a shift in G+ and G? peak positions in regions with high CNT density between the electrodes. Simultaneous topographical and electrical characterization of the CNT transistor by CS-AFM confirms the presence of CNT bundles having a stable electrical contact with the transistor electrodes. For a similar load force, reproducible current–voltage (I/V) curves for the same CNT regions verify the stability of the electrical contact between the nanotube and the electrodes as well as the nanotube and the AFM tip over different experimental sessions using different AFM tips. Strong variations observed in the I/V response at different regions of the CNT transistor are discussed. PMID:23259903

2012-01-01

224

Optical strain measuring techniques for high temperature tensile testing  

NASA Technical Reports Server (NTRS)

A number of optical techniques used for the analysis of in-plane displacements or strains are reviewed. The application would be for the high temperature, approximately 1430 C (2600 F), tensile testing of ceramic composites in an oxidizing atmosphere. General descriptions of the various techniques and specifics such as gauge lengths and sensitivities are noted. Also, possible problems with the use of each method in the given application are discussed.

Gyekenyesi, John Z.; Hemann, John H.

1987-01-01

225

Simple technique to measure toric intraocular lens alignment and stability using a smartphone.  

PubMed

Toric intraocular lenses (IOLs) are commonly implanted to correct corneal astigmatism at the time of cataract surgery. Their use requires preoperative calculation of the axis of implantation and postoperative measurement to determine whether the IOL has been implanted with the proper orientation. Moreover, toric IOL alignment stability over time is important for the patient and for the longitudinal evaluation of toric IOLs. We present a simple, inexpensive, and precise method to measure the toric IOL axis using a camera-enabled cellular phone (iPhone 5S) and computer software (ImageJ). PMID:25316617

Teichman, Joshua C; Baig, Kashif; Ahmed, Iqbal Ike K

2014-12-01

226

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

227

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

228

Ultraviolet imprinting and aligned ink-jet printing for multilayer patterning of electro-optic polymer modulators.  

PubMed

The present work demonstrates an electro-optic polymer-based Mach-Zehnder (MZ) modulator fabricated utilizing advanced ultraviolet (UV) imprinting and aligned ink-jet printing technologies for patterning and layer deposition. The bottom electrode layer is designed and directly ink-jet printed on the substrate to form the patterned layer. The waveguide structure is formed into a bottom cladding polymer using a transparent flexible mold-based UV imprinting method. All other layers can be ink-jet printed. The top electrode is aligned and printed over the MZ arm. The modulator demonstrates a V-pi of 8 V at 3 kHz. This technology shows great potential in minimizing the fabrication complexity and roll-to-roll compatibility for manufacturing low cost, lightweight, and conformal modulators at high throughput. PMID:23938881

Lin, Xiaohui; Ling, Tao; Subbaraman, Harish; Zhang, Xingyu; Byun, Kwangsub; Guo, L Jay; Chen, Ray T

2013-05-15

229

Performance and characterization of a MEMS-based device for alignment and manipulation of x-ray nanofocusing optics  

NASA Astrophysics Data System (ADS)

X-ray microscopy is a powerful, non-invasive tool used for nanometer-scale resolution imaging, and it is widely applied in various areas of science and technology. To push the spatial resolution of x-ray microscopy studies in the hard x-ray regime below 10 nm, Multilayer Laue Lenses (MLL) can be used as nanofocusing elements. To ensure distortion-free x-ray imaging, high-stability microscopy systems are required. MEMS-based manipulators are a promising route to achieve high stability when used for alignment and manipulation of nanofocusing optics. In this work, we present a tip-tilt MEMS-based device suitable for MLL alignment. We fully characterize the device and demonstrate better-than 10 millidegree angular positioning resolution when utilizing capacitive displacement sensors, and better-than 0.8 millidegree resolution when using laser interferometry.

Xu, Weihe; Lauer, Kenneth; Yan, Hui; Milanovic, Veljko; Lu, Ming; Nazaretski, Evgeny

2015-03-01

230

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

231

Study of microfluidic measurement techniques using novel optical imaging diagnostics  

E-print Network

Head of Department, Dennis L. O?Neal December 2005 Major Subject: Mechanical Engineering iii ABSTRACT Study of Microfluidic Measurement Techniques Using Novel Optical Imaging Diagnostics. (December 2005) Jaesung Park, B... diameter?..???????.............................................. 35 3.4 A structure of micro test section.??......................................................... 36 3.5 Tested microchannel with true image size, l/D, as function of the distance...

Park, Jaesung

2007-04-25

232

External (transient) latchup phenomenon investigated by optical mapping (TIM) technique  

Microsoft Academic Search

Substrate current distribution as trigger for external latchup (LU) and transient latchup (TLU) is detected successfully by means of optical transient interferometric mapping (TIM) technique. The substrate current flow is studied on transient base and for various guard-ring configurations. TIM uncovers proximity effects causing substrate current crowding which are important for the definition of LU protection concepts.

K. Domanski; M. Heer; K. Esmark; D. Pogany; W. Stadler; E. Gornik

2007-01-01

233

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

234

Surface alignment, anchoring transitions, optical properties, and topological defects in the thermotropic nematic phase of organo-siloxane tetrapodes.  

PubMed

We perform optical, surface anchoring, and textural studies of an organo-siloxane "tetrapode" material in the broad temperature range of the nematic phase. The optical, structural, and topological features are compatible with the uniaxial nematic order rather than with the biaxial nematic order, in the entire nematic temperature range -25 °C < T < 46 °C studied. For homeotropic alignment, the material experiences surface anchoring transition, but the director can be realigned into an optically uniaxial texture by applying a sufficiently strong electric field. The topological features of textures in cylindrical capillaries, in spherical droplets and around colloidal inclusions are consistent with the uniaxial character of the long-range nematic order. In particular, we observe isolated surface point defects - boojums and bulk point defects - hedgehogs that can exist only in the uniaxial nematic liquid crystal. PMID:24651889

Kim, Young-Ki; Senyuk, Bohdan; Shin, Sung-Tae; Kohlmeier, Alexandra; Mehl, Georg H; Lavrentovich, Oleg D

2014-01-21

235

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

236

Self-Aligned Surface Tunnel Transistors Fabricated by a Regrowth Technique  

NASA Astrophysics Data System (ADS)

A self-aligned process for fabricating surface tunnel transistors (STTs)has been developed in an attempt to improve both miniaturization andintegration of STTs. In this process, the keys to obtaining a flat regrownlayer and fine tunnel junctions are to keep from contaminating the surfaceduring the lithography process before regrowth and to control the side-wallprofile of the gate region in which tunnel junctions are formed. The carboncontamination can be reduced significantly by using a double hard maskconsisting of Si3N4 and SiO2, and oxygen contamination can be removed byatomic hydrogen irradiation. The side-wall profile, that is etched surfacemorphology and side-wall angle, can be optimized by adjusting the compositionof the H3PO4:H2O2:H2O etching solution. During regrowth, a flat surfacemorphology and fine tunnel junctions were obtained at the low temperature of400°C. Self-aligned InGaAs-based STTs with gate-controlled negativedifferential resistance (NDR) characteristics showing a peak-to-valley (P/V)ratio of 2.5 were obtained.

Chun, Yong; Uemura, Tetsuya; Baba, Toshio

1999-10-01

237

Optical coherence tomography as film thickness measurement technique  

NASA Astrophysics Data System (ADS)

Optical coherence tomography (OCT) is a powerful optical method, noninvasive and noncontact diagnostic method. Although it is usually used for medical examinations, particularly in ocular exploration; it can also be used in optical metrology as measure technique. In this work, we use OCT to measure thicknesses of films. In OCT, depth profiles are constructed by measuring the time delay of back reflected light by interferometry measurements. Frequency in k-space is proportional to optical path difference. Then the reflectivity profile is obtained by a Fourier transformation, and the difference between two successive peaks of the resulting spectrum gives the film thickness. Several films, food-type, of different thicknesses were investigated and the results were very accurate.

Manallah, Aissa; Bouafia, Mohamed; Meguellati, Said

2015-01-01

238

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

239

Benchmarking process integration and layout decomposition of directed self-assembly and self-aligned multiple patterning techniques  

NASA Astrophysics Data System (ADS)

In this paper, we present a benchmarking study of directed self-assembly (DSA) and self-aligned multiple patterning (SAMP) techniques for potential applications in manufacturing 10-nm (half-pitch) IC devices. Using the self-aligned quadruple patterning (SAQP) process as an example, we compare their process characteristics and complexity/costs, identify the integration challenges, and propose various patterning solutions for both BEOL and FEOL applications. Major differences in DSA and SAQP mask strategy, layout decomposition algorithm, and pattern-generation modeling are discussed, and critical requirements of overlay accuracy and CD control for implementing a DSA process in NAND wordline patterning are indentified. DSA technique is found to be a complementary solution for certain niche applications and we suggest that our industry should allocate more R and D resources to solve the 2-D SAMP layout decomposition challenges for logic BEOL patterning. We also propose an "out-of-the-box" idea of combining DSA and SADP process to significantly improve the 2-D design flexibility and develop a layout decomposition algorithm for this hybrid process

Chen, Yijian; Zhou, Jun; You, Jun; Liu, Hongyi

2014-03-01

240

Path radiance technique for retrieving aerosol optical thickness over land  

NASA Astrophysics Data System (ADS)

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 ?m) during the first Landsat Intensive Observation Period. The retrieved mean aerosol optical thickness for TM band 1 at 0.49 ?m and band 3 at 0.66 ?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.

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

1999-01-01

241

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

242

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

243

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

244

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

245

A new signal processing technique for fiber optic interferometric sensors  

NASA Astrophysics Data System (ADS)

A new signal processing technique for fiber optic interferometric sensors is presented. This technique provides a way to monitor interferometric sensors such that high accuracy is maintained even using relatively inexpensive Fabry-Perot (FP) lasers, as a basis for implementing low-cost, high performance fiber optic sensor systems. Application of this technique in temperature measurement has been demonstrated with a fiber optic Fabry-Perot Interferometer (FFPI) as a sensing head. Good performance of temperature sensor is obtained using a low-quality multimode FP laser, and even better performance is observed with a distributed feedback (DFB) laser diode. The accuracies are measured to be 4.58% for a FP laser and 2.32% for a DFB laser, respectively. However, the unambiguous measurement range is limited to 7°C using a laser diode as a light source emitting at a wavelength of 1.3-?m. Dual wavelength technique is employed to overcome this limitation. The unambiguous dynamic range is extended to 43°C using one 1.3-?m laser diode and one 1.55- ?m laser diode. Further improvement in dynamic range using lasers with a smaller wavelength separation is possible.

Fang, Jianxun

246

Application of techniques for fault localization on optical cable  

NASA Astrophysics Data System (ADS)

For fiber-optic links (FOL), the sufficient time of repairing (removing & reinstalling) fiber-optic cables (FOC) and the natural ageing of optical fibers (OF) have been stipulating and propelling the problems of safe communication. The latters used to and are nowadays resolved by mean of either reserving line, cables, fibers, digital streams or improving quality of FOC grooming. In the latter case, the implementation of a prognostic control of FOC plays sufficient role in fault prediction on maintenance stage of FOL. The prognostic control is performed by mean of Remote Test Fiber Systems (RFTS) on the basis of both direct controlling OF parameters and indirect methods of FOC monitoring, including, being applied at Volgograd City Telephone Network, RLTP Method (Rate Loss Time Prediction) designed for copper/ steel media. Thus for example a prediction method on the basis of protective sheath monitoring results of FOC. This method is very effective when applied for buried long-haul FOC and in widespread use in Russia. One of the problems ofthe method performance is how to maintenance satisfactory sheath condition ofFOC. In general, the main trouble is how to localize faults on the protective sheath. There are however some classical techniques which are similar to the applied techniques in fault localization in copper media, but when applied for FOL, the techniques have specifics. The purpose of the paper is to analyze specifics ofthe classical technique implementation for fault localization ofprotective sheath of FOC.

Voronkov, Andrey A.; Morochkovsky, Vladimir V.

2007-03-01

247

Application of classical techniques for fault localization on optical cable  

NASA Astrophysics Data System (ADS)

For fiber-optic links (FOL), the sufficient time of repairing (removing & reinstalling) fiber-optic cables (FOC) and the natural aging of optical fibers (OF) have been stipulating and propelling the problems of safe communication. The latters used to and are nowadays resolved by mean of either reserving line, cables, fibers, digital streams or improving quality of FOC grooming. In the latter case, the implementation of a prognostic control of FOC plays sufficient role in fault prediction on maintenance stage of FOL. The prognostic control is performed by mean of Remote Test Fiber Systems (RFTS) on the basis of both direct controlling OF parameters and indirect methods of FOC monitoring, including, being applied at Vol-gograd City Telephone Network, RLTP Method (Rate Loss Time Prediction) designed for copper/steel media. Thus for example a prediction method on the basis of protective sheath monitoring results of FOC. This method is very effective when applied for buried long-haul FOC and in widespread use in Russia. One of the problems of the method performance is how to maintenance satisfactory sheath condition of FOC. In general, the main trouble is how to localize faults on the protective sheath. There are however some classical techniques which are similar to the applied techniques in fault localization in copper media, but when applied for FOL, the techniques have specifics. The purpose of the paper is to analyze specifics of the classical technique implementation for fault localization of protective sheath of FOC.

Platonov, Alexander N.

2001-10-01

248

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

249

Radio-Optical Alignment and Recent Star Formation Associated with Ionized Filaments in the Halo of NGC 5128 (Centaurus A)  

NASA Astrophysics Data System (ADS)

We used a direct CCD camera at the Magellan I telescope at Las Campanas Observatory and the Focal Reducer/Low Dispersion Spectrograph (FORS1) at the Antu Very Large Telescope (VLT) ESO Paranal Observatory to image fields centered on the inner and outer optical filaments in the halo of NGC 5128. In the V versus U-V color-magnitude diagrams we have identified young blue supergiants associated with these line-emitting filaments located between the inner radio lobe and the northern middle lobe. Around the outer filament, stars as young as 10 Myr were detected. They are principally aligned with the direction of the radio jet, but a vertical north-south alignment along the edge of the H I cloud is also present. Young stars in the inner filament field are found inside the bright knots of photoionized gas and are strongly aligned in the direction of the center of the galaxy at the same position angle as the inner radio jet. Fitting the Padova isochrones on UV color-magnitude diagrams, we find that blue stars around the inner filaments have ages similar to the ones around the outer filaments ~10-15 Myr and the same abundance of Z=0.004. The presence of young blue supergiants clearly shows that the bright blue knots in the northeastern halo of NGC 5128 are associations of young stars with photoionized gas. The temperature of the brightest stars is T~12,000-16,000 K, insufficient to account alone for the high excitation lines observed in the surrounding ionized gas. Thus, the optical emission jet is principally seen due to its alignment with the radio structure of the active galactic nucleus (AGN). The highly collimated star formation is present only in the northeastern halo of the galaxy, suggesting interaction of the jet with the gas clouds deposited during the last accretion event as the preferred triggering mechanism. From these observations, we infer a lower limit for the age of the NGC 5128 jet at 107 yr. The triggering of the star formation in the dense clouds in the halo of the galaxy by the jet supports the alignment effect observed in high-redshift radio galaxies. It also suggests that radio galaxies should have higher than normal star formation rates. Based on observations collected at the European Southern Observatory, Paranal, Chile, within the Observing Program 63.N-0229, and on observations collected by Magellan I telescope at Las Campanas Observatory, Chile.

Rejkuba, M.; Minniti, D.; Courbin, F.; Silva, D. R.

2002-01-01

250

Measurement of losses in optical components using filtered optical feedback cavity ring down technique  

NASA Astrophysics Data System (ADS)

A filtered optical feedback cavity ring down (FOF-CRD) technique employing a continuous wave Fabry-Perot diode laser is employed to measure the total optical losses, i.e., absorption and scattering in optical components with arbitrary thickness. The FOF from the ring down cavity (RDC) is re-injected into the oscillator cavity of the diode laser, and the coupling efficiency of the laser into the RDC is significantly enhanced due to the FOF effect. An optical component having parallel optical surfaces is inserted exactly normal to the light beam in the RDC. The optical losses of the component are obtained from the change in the ring-down time of the RDC containing the component with respect to that of the empty RDC. The measurement results for different samples are in good agreement with conventional laser calorimetry data. The experimental results have demonstrated that the FOF-CRD technique is simple, inexpensive and fast for measuring optical losses of optical components used in high-power laser system.

Qu, Zhechao; Li, Bincheng; Han, Yanling

2011-11-01

251

Measurement of losses in optical components using filtered optical feedback cavity ring down technique  

NASA Astrophysics Data System (ADS)

A filtered optical feedback cavity ring down (FOF-CRD) technique employing a continuous wave Fabry-Perot diode laser is employed to measure the total optical losses, i.e., absorption and scattering in optical components with arbitrary thickness. The FOF from the ring down cavity (RDC) is re-injected into the oscillator cavity of the diode laser, and the coupling efficiency of the laser into the RDC is significantly enhanced due to the FOF effect. An optical component having parallel optical surfaces is inserted exactly normal to the light beam in the RDC. The optical losses of the component are obtained from the change in the ring-down time of the RDC containing the component with respect to that of the empty RDC. The measurement results for different samples are in good agreement with conventional laser calorimetry data. The experimental results have demonstrated that the FOF-CRD technique is simple, inexpensive and fast for measuring optical losses of optical components used in high-power laser system.

Qu, Zhechao; Li, Bincheng; Han, Yanling

2012-01-01

252

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

253

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

254

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

255

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

256

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

257

Evaluation of a computerized measurement technique for joint alignment before and during periacetabular osteotomy  

PubMed Central

Periacetabular osteotomy (PAO) is intended to treat a painful dysplastic hip. Manual radiological angle measurements are used to diagnose dysplasia and to define regions of insufficient femoral head coverage for planning PAO. No method has yet been described that recalculates radiological angles as the acetabular bone fragment is reoriented. In this study, we propose a technique for computationally measuring the radiological angles from a joint contact surface model segmented from CT-scan data. Using oblique image slices, we selected the lateral and medial edge of the acetabulum lunate to form a closed, continuous, 3D curve. The joint surface is generated by interpolating the curve and the radiological angles are measured directly using the 3D surface. This technique was evaluated using CT data for both normal and dysplastic hips. Manual measurements made by three independent observers showed minor discrepancies between the manual observations and the computerized technique. Inter-observer error (mean difference±standard deviation) was 0.04±3.53° Observer 1; ?0.46±3.13° for Observer 2; and 0.42±2.73° for Observer 3. The measurement error for the proposed computer method was ?1.30±3.30°. The computerized technique demonstrates sufficient accuracy compared to manual techniques, making it suitable for planning and intraoperative evaluation of radiological metrics for periacetabular osteotomy. PMID:17786597

ARMIGER, ROBERT S.; ARMAND, MEHRAN; LEPISTO, JYRI; MINHAS, DAVNEET; TALLROTH, KAJ; MEARS, SIMON C.; WAITES, MATTHEW D.; TAYLOR, RUSSELL H.

2009-01-01

258

Defect-mediated modulation of optical properties in vertically aligned ZnO nanowires via substrate-assisted Ga incorporation  

NASA Astrophysics Data System (ADS)

We report the defect-mediated modulation of optical properties in vertically aligned ZnO nanowires via a substrate-assisted Ga incorporation method. We find that Ga atoms were incorporated into a ZnO lattice via the diffusion of liquid Ga droplets from a GaAs substrate in which as-grown ZnO nanowires were placed face down on the GaAs substrate and annealed at 650 °C. Based on structural and compositional characterization, it was confirmed that the substrate-assisted incorporation of Ga can induce a high defect density in vertically aligned ZnO nanowires grown on a Si substrate. In addition, distinct differences in optical properties between as-grown and Ga-incorporated ZnO nanowires were found and discussed in terms of defect-mediated modifications of energy band states, which were associated with the generation and recombination of photoexcited carriers. Furthermore, it was clearly observed that for Ga-incorporated ZnO nanowires, the photocurrent rise and decay processes were slower and the photocurrents under UV illumination were significantly higher compared with as-grown nanowires.

Park, Jong Bae; Tea Chun, Young; Boo Lee, Young; Inn Sohn, Jung; Hong, Woong-Ki

2015-04-01

259

Thermal-vacuum testing and in-situ optical alignment measurements of the HALOE telescope/sun sensor assembly  

NASA Technical Reports Server (NTRS)

Design features, test data and projected performance levels of the telescope/sun sensor assembly for the Halogen Occultation Experiment (HALOE) on board the Upper Atmosphere Research Satellite are described. HALOE will gather data on stratospheric chemical species with an IR telescope pointed through the atmosphere at the sun during occultation periods. The pointing accuracy will need to be 1 arcmin elevation and 1.6 arcmin azimuthal. Adjustments of the gimbaled instrument are guided by a sun sensor and its associated electronics. The components were subjected to thermal-vacuum, optical boresight stability tests and the data generated were compared with a finite element model of the telescope and sun sensor. The tests consisted of exposure to various thermal gradients while the telescope and sun sensor alignments were tracked by optical deflectometry. The thermal behavior was compared with predictions made with a finite difference model. Alignments were within tolerable ranges and the thermal behavior model was concluded valid for predicting the thermal behavior of orbiting instruments.

Foss, R. A.; Smith, D. M.; Faison, R. W.; Spiers, R. B.

1985-01-01

260

Defect-mediated modulation of optical properties in vertically aligned ZnO nanowires via substrate-assisted Ga incorporation.  

PubMed

We report the defect-mediated modulation of optical properties in vertically aligned ZnO nanowires via a substrate-assisted Ga incorporation method. We find that Ga atoms were incorporated into a ZnO lattice via the diffusion of liquid Ga droplets from a GaAs substrate in which as-grown ZnO nanowires were placed face down on the GaAs substrate and annealed at 650 °C. Based on structural and compositional characterization, it was confirmed that the substrate-assisted incorporation of Ga can induce a high defect density in vertically aligned ZnO nanowires grown on a Si substrate. In addition, distinct differences in optical properties between as-grown and Ga-incorporated ZnO nanowires were found and discussed in terms of defect-mediated modifications of energy band states, which were associated with the generation and recombination of photoexcited carriers. Furthermore, it was clearly observed that for Ga-incorporated ZnO nanowires, the photocurrent rise and decay processes were slower and the photocurrents under UV illumination were significantly higher compared with as-grown nanowires. PMID:25771907

Park, Jong Bae; Chun, Young Tea; Lee, Young Boo; Sohn, Jung Inn; Hong, Woong-Ki

2015-04-01

261

Low-Cost Hybrid WDM Module Integrated on Planar Lightwave Circuit (PLC) with a Coated WDM Filter Using Passive Alignment Technique  

Microsoft Academic Search

We have developed a low cost 1.25 Gbps WDM bidirectional module using two integrated optical subassemblies which are composed of a planar lightwave circuit (PLC) platform and a silicon optical bench (SiOB) platform. The low cost module is achieved by employing a flip-chip bonding method with passive alignment using a Fabry-Perot laser diode (FP-LD) with a monitoring waveguide-photodiode (PD) on

Jung Woon Lim; Sung Hwan Hwang; Seon Hoon Kim; Boo-Gyoun Kim; Byung Sup Rho

2007-01-01

262

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

263

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

264

Liquid sound speeds at pressure from the optical analyzer technique  

SciTech Connect

The optical analyzer technique has proved to be a useful means of obtaining wave velocities at high pressures. Stepped wedges of the investigated material emit shock, and later, rarefaction waves into a transparent analyzer covering the material. The time interval between shock and rarefaction plotted versus wedge thickness gives a linear plot whose intercept fixes the target/driver thickness ratio for exact wave overtake, and thus gives a relation between the shock velocity and overtaking wave velocity at pressure. The slope of this line is intimately related to the wave velocity at pressure of the analyzer in front of the wedge. This aspect of the technique has not yet been exploited. We present the appropriate analysis, some data on bromoform (one of the analyzers used), and discuss some possible applications of this technique.

Fritz, J.N.; Morris, C.E.; Hixson, R.S.; McQueen, R.G.

1993-08-01

265

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

266

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

267

Advances in polymer optical devices and waveguide fabrication techniques  

NASA Astrophysics Data System (ADS)

We report progress in the development of polymer waveguides and devices for photonic applications in three areas: non-photolithographic techniques for polymer waveguide fabrication, bistability in laterally-coupled polymer microring resonators, and ultrafast photoconductive switches fabricated from semiconducting polymers. The non-photolithographic techniques for waveguide fabrication under development include laser milling with an excimer laser and programmable automatic dispensing of multimode polymer waveguides using an Essemtech automatic dispenser. Asymmetric diffraction gratings fabricated using phase masks and the interference of two excimer laser beams have exhibited concentration of optical power into the 1st diffraction order. Polymer micro-ring resonators laterally coupled to a bus line were fabricated by lithography from benzocyclobutene with radii as small as 10 ?m and free spectral ranges on the order of 20 nm. These devices exhibit bistability in the frequency domain which can arise from thermal or nonlinear optical changes in refractive index and that may have application for all-optical switching. Metal-polymer-metal switches fabricated with interdigitated electrodes in an inverted structure exhibited fast transient photoconductive pulsewidths under 20 ps in response to femtosecond pump laser pulses, but the measurement was bandwidth limited by the oscilloscope. Here we report pump-probe measurements that indicate carrier lifetimes on the order of 2 ps.

Herman, Warren N.; Chen, Wei-Yen; Kim, Younggu; Hutchinson, Glenn; Cao, Wei Lou; Leng, Yongzhang; Yun, Victor; Liang, Hongye; Peng, Yi-Hsing; Du, Min; Lucas, Lisa; Ho, Ping-Tong; Goldhar, Julius; Lee, Chi H.

2004-10-01

268

Development of Optical Diagnostic Techniques for Microgravity Materials Processing  

NASA Technical Reports Server (NTRS)

Materials processing including crystal growth, either under a gravity environment on ground or a microgravity environment in space, involves complicated phenomena of fluid motions in gas or liquid phases as well as interaction of various species. To obtain important physical insight, it is very necessary to provide gross-field optical diagnostics for monitoring various physical properties. Materials processing inhibits easy access by ordinary instruments and thus characterizing gross-field physical properties is very challenging. Typical properties of importance can be fluid velocity, temperature, and species concentration for fluids, and surface topology and defects for solids. Observing surface grow rate during crystal growth is also important. Material microstructures, i.e., integrity of crystal structures, is strongly influenced by the existence of thermally-induced flow as well as local nucleation of particles during solidification, which may act in many detrimental ways. In both ground-based and microgravity experiments, the nature of product property changes resulting from three-dimensional fluid or particle motions need be characterized. Gross-field diagnostics is thus required to identify their effects on product defects and process deficiencies. The quantitative visualization techniques can also be used for validation of numerical modeling. For optical nonintrusive gross-field diagnostic techniques, two approaches were developed as summer projects. One optical approach allows us to provide information of species concentration and temperature for monitoring in real time. The other approach, that is, the concept which is formulated for detection of surface topography measurement can provide unprecedented spatial resolution during crystal growth.

Cha, Soyoung Stephen

1999-01-01

269

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

270

Shiva automatic pinhole alignment  

SciTech Connect

This paper describes a computer controlled closed loop alignment subsystem for Shiva, which represents the first use of video sensors for large laser alignment at LLNL. The techniques used on this now operational subsystem are serving as the basis for all closed loop alignment on Nova, the 200 terawatt successor to Shiva.

Suski, G.J.

1980-09-05

271

Optical and digital microscopic imaging techniques and applications in pathology  

PubMed Central

The conventional optical microscope has been the primary tool in assisting pathological examinations. The modern digital pathology combines the power of microscopy, electronic detection, and computerized analysis. It enables cellular-, molecular-, and genetic-imaging at high efficiency and accuracy to facilitate clinical screening and diagnosis. This paper first reviews the fundamental concepts of microscopic imaging and introduces the technical features and associated clinical applications of optical microscopes, electron microscopes, scanning tunnel microscopes, and fluorescence microscopes. The interface of microscopy with digital image acquisition methods is discussed. The recent developments and future perspectives of contemporary microscopic imaging techniques such as three-dimensional and in vivo imaging are analyzed for their clinical potentials. PMID:21483100

Chen, Xiaodong; Zheng, Bin; Liu, Hong

2012-01-01

272

Simple technique for integrating compact silicon devices within optical fibers.  

PubMed

In this work, we present a simple fabrication process enabling the integration of a subwavelength amorphous silicon layer inside optical fibers by means of the arc discharge technique. To assess our method, we have fabricated a compact in-line Fabry-Perot interferometer consisting of a thin (<1???m) a-Si:H layer completely embedded within a standard single-mode optical fiber. The device exhibits low loss (1.3 dB) and high interference fringe visibility (~80%) both in reflection and transmission, due to the high refractive index contrast between silica and a-Si:H. A high linear temperature sensitivity up to 106??pm/°C is demonstrated in the range 120°C-400°C. The proposed interferometer is attractive for point monitoring applications as well as for ultrahigh-temperature sensing in harsh environments. PMID:24562226

Micco, A; Ricciardi, A; Quero, G; Crescitelli, A; Bock, W J; Cusano, A

2014-02-15

273

Optical signal processing techniques and applications of optical phase modulation in high-speed communication systems  

NASA Astrophysics Data System (ADS)

In recent years, optical phase modulation has attracted much research attention in the field of fiber optic communications. Compared with the traditional optical intensity-modulated signal, one of the main merits of the optical phase-modulated signal is the better transmission performance. For optical phase modulation, in spite of the comprehensive study of its transmission performance, only a little research has been carried out in terms of its functions, applications and signal processing for future optical networks. These issues are systematically investigated in this thesis. The research findings suggest that optical phase modulation and its signal processing can greatly facilitate flexible network functions and high bandwidth which can be enjoyed by end users. In the thesis, the most important physical-layer technology, signal processing and multiplexing, are investigated with optical phase-modulated signals. Novel and advantageous signal processing and multiplexing approaches are proposed and studied. Experimental investigations are also reported and discussed in the thesis. Optical time-division multiplexing and demultiplexing. With the ever-increasing demand on communication bandwidth, optical time division multiplexing (OTDM) is an effective approach to upgrade the capacity of each wavelength channel in current optical systems. OTDM multiplexing can be simply realized, however, the demultiplexing requires relatively complicated signal processing and stringent timing control, and thus hinders its practicability. To tackle this problem, in this thesis a new OTDM scheme with hybrid DPSK and OOK signals is proposed. Experimental investigation shows this scheme can greatly enhance the demultiplexing timing misalignment and improve the demultiplexing performance, and thus make OTDM more practical and cost effective. All-optical signal processing. In current and future optical communication systems and networks, the data rate per wavelength has been approaching the speed limitation of electronics. Thus, all-optical signal processing techniques are highly desirable to support the necessary optical switching functionalities in future ultrahigh-speed optical packet-switching networks. To cope with the wide use of optical phase-modulated signals, in the thesis, an all-optical logic for DPSK or PSK input signals is developed, for the first time. Based on four-wave mixing in semiconductor optical amplifier, the structure of the logic gate is simple, compact, and capable of supporting ultrafast operation. In addition to the general logic processing, a simple label recognition scheme, as a specific signal processing function, is proposed for phase-modulated label signals. The proposed scheme can recognize any incoming label pattern according to the local pattern, and is potentially capable of handling variable-length label patterns. Optical access network with multicast overlay and centralized light sources. In the arena of optical access networks, wavelength division multiplexing passive optical network (WDM-PON) is a promising technology to deliver high-speed data traffic. However, most of proposed WDM-PONs only support conventional point-to-point service, and cannot meet the requirement of increasing demand on broadcast and multicast service. In this thesis, a simple network upgrade is proposed based on the traditional PON architecture to support both point-to-point and multicast service. In addition, the two service signals are modulated on the same lightwave carrier. The upstream signal is also remodulated on the same carrier at the optical network unit, which can significantly relax the requirement on wavelength management at the network unit.

Deng, Ning

274

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

275

Numerical simulation to align a segment mirror  

Microsoft Academic Search

A technique of great help in the optical test is the subaperture method, this method is proposed to align the segments of a primary mirror of telescope, using the ideal form of the primary mirror, which is defined using the sagita z(x, y). When the surface under test is segmented each segment has a sagita zi(xi, yi) that is rotated

J. Fausto M. Escobar-Romero; Fermin-Solomon S. Granados-Agustin; Alejandro Cornejo-Rodriguez

2004-01-01

276

Chip-to-chip optical interconnections between stacked self-aligned SOI photonic chips.  

PubMed

Photonic silicon devices are key enabling technologies for next generation High Performance Computers. In this paper, we report the possibility to stack and optically interconnect SOI based photonic chips for future System-In-Package photonic architecture. Combining vertical grating couplers and state-of-the-art flip-chip technology, we demonstrated low loss penalties and wide spectral range optical interconnections between stacked photonic chips. PMID:22453462

Bernabé, Stéphane; Kopp, Christophe; Volpert, Marion; Harduin, Julie; Fédéli, Jean-Marc; Ribot, Hervé

2012-03-26

277

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

278

Broadband, Polarization-Sensitive Photodetector Based on Optically-Thick Films of Macroscopically Long, Dense, and Aligned Carbon Nanotubes  

PubMed Central

Increasing performance demands on photodetectors and solar cells require the development of entirely new materials and technological approaches. We report on the fabrication and optoelectronic characterization of a photodetector based on optically-thick films of dense, aligned, and macroscopically long single-wall carbon nanotubes. The photodetector exhibits broadband response from the visible to the mid-infrared under global illumination, with a response time less than 32??s. Scanning photocurrent microscopy indicates that the signal originates at the contact edges, with an amplitude and width that can be tailored by choosing different contact metals. A theoretical model demonstrates the photothermoelectric origin of the photoresponse due to gradients in the nanotube Seebeck coefficient near the contacts. The experimental and theoretical results open a new path for the realization of optoelectronic devices based on three-dimensionally organized nanotubes. PMID:23443054

Nanot, Sébastien; Cummings, Aron W.; Pint, Cary L.; Ikeuchi, Akira; Akiho, Takafumi; Sueoka, Kazuhisa; Hauge, Robert H.; Léonard, François; Kono, Junichiro

2013-01-01

279

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. PMID:25426317

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

2014-01-01

280

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

281

Feasibility and optical performance of one axis three positions sun-tracking polar-axis aligned CPCs for photovoltaic applications  

SciTech Connect

A new design concept, called one axis three positions sun-tracking polar-axis aligned CPCs (3P-CPCs, in short), was proposed and theoretically studied in this work for photovoltaic applications. The proposed trough-like CPC is oriented in the polar-axis direction, and the aperture is daily adjusted eastward, southward, and westward in the morning, noon and afternoon, respectively, by rotating the CPC trough, to ensure efficient collection of beam radiation nearly all day. To investigate the optical performance of such CPCs, an analytical mathematical procedure is developed to estimate daily and annual solar gain captured by such CPCs based on extraterrestrial radiation and monthly horizontal radiation. Results show that the acceptance half-angle of 3P-CPCs is a unique parameter to determine their optical performance according to extraterrestrial radiation, and the annual solar gain stays constant if the acceptance half-angle, {theta}{sub a}, is less than one third of {omega}{sub 0,min}, the sunset hour angle in the winter solstice, otherwise decreases with the increase of {theta}{sub a}. For 3P-CPCs used in China, the annual solar gain, depending on the climatic conditions in site, decreased with the acceptance half-angle, but such decrease was slow for the case of {theta}{sub a}{<=}{omega}{sub 0,min}/3, indicating that the acceptance half-angle should be less than one third of {omega}{sub 0,min} for maximizing annual energy collection. Compared to fixed east-west aligned CPCs (EW-CPCs) with a yearly optimal acceptance half-angle, the fixed south-facing polar-axis aligned CPCs (1P-CPCs) with the same acceptance half-angle as the EW-CPCs annually collected about 65-74% of that EW-CPCs did, whereas 3P-CPCs annually collected 1.26-1.45 times of that EW-CPCs collected, indicating that 3P-CPCs were more efficient for concentrating solar radiation onto their coupling solar cells. (author)

Tang, Runsheng; Yu, Yamei [Education Ministry Key Laboratory of Advanced Technology and Preparation for Renewable Energy Materials, Yunnan Normal University, Kunming 650092 (China)

2010-09-15

282

Three-dimensional imaging technique using optical diffraction  

NASA Astrophysics Data System (ADS)

This paper presents a novel fast and simple technique to measure three-dimensional (3D) objects. An integrated 3D camera is built, which features a motorized off-axis rotating aperture. A regular spot pattern projection adds texture onto smooth 3D objects. When rotating, the off-axis aperture translates depth information into blurred image diameter. The displacement of each spot between two arbitrary aperture positions reveals depth. A pseudo- correlation algorithm based on optical diffraction is proposed to measure spot displacement fast and accurately. When subtracting two consecutive images of a roughly Gaussian-shaped displaced spot, the normalized subtraction intensity peak height is directly proportional to the spot displacement. The peak height to displacement calibration curve is specifically defined by optical parameters of the imaging system. Proper combination of off-axis aperture location and magnification ratio determines the size of the measurement range. Experiment observations show that the calibration curve is highly smooth and sensitive to the spot displacement at sub-pixel level. Real-time processing is possible with only order of image size arithmetic operations. The proposed technique holds potential for various industrial machine vision applications.

Tan, Sheng; Hart, Douglas P.

2002-02-01

283

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

284

Optimal analysis for segmented mirror capture and alignment in space optics system  

Microsoft Academic Search

A great deal segmented mirror errors consisting of piston and tip-tilt exist when space large aperture segmented optics system deploys. These errors will result in the departure of segmented mirrors images from the view. For that, proper scanning function should be adopted to control actuators rotating the segmented mirror, so that the images of segmented mirror can be put into

Xiaofang Zhang; Xin Yu; Xia Wang; Lei Zhao

2008-01-01

285

Optical Alignment and Test of the James Webb Space Telescope Integrated Science Instrument Module  

Microsoft Academic Search

The James Webb Space Telescope (JWST) is a 6.6 m diameter, segmented, deployable telescope for cryogenic IR space astronomy (~40 K). 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 SI's and Guider are mounted to a composite metering structure with

J. G. Hagopian; R. Ohl; B. Bos; P. Davila; W. Eichhorn; J. Hylan; M. Hill; M. Nowak; B. Pasquale; H. Sampler; M. Wilson; B. Gallagher; J. Hardaway; J. Sullivan; P. Young; T. Keepers; R. Quigley

2007-01-01

286

Measuring the In-Process Figure, Final Prescription, and System Alignment of Large Optics and Segmented Mirrors Using Lidar Metrology  

NASA Technical Reports Server (NTRS)

The fabrication of large optics is traditionally a slow process, and fabrication capability is often limited by measurement capability. W hile techniques exist to measure mirror figure with nanometer precis ion, measurements of large-mirror prescription are typically limited to submillimeter accuracy. Using a lidar instrument enables one to measure the optical surface rough figure and prescription in virtuall y all phases of fabrication without moving the mirror from its polis hing setup. This technology improves the uncertainty of mirror presc ription measurement to the micron-regime.

Ohl, Raymond; Slotwinski, Anthony; Eegholm, Bente; Saif, Babak

2011-01-01

287

Docking alignment system  

NASA Technical Reports Server (NTRS)

Improved techniques are provided for alignment of two objects. The present invention is particularly suited for three-dimensional translation and three-dimensional rotational alignment of objects in outer space. A camera 18 is fixedly mounted to one object, such as a remote manipulator arm 10 of the spacecraft, while the planar reflective surface 30 is fixed to the other object, such as a grapple fixture 20. A monitor 50 displays in real-time images from the camera, such that the monitor displays both the reflected image of the camera and visible markings on the planar reflective surface when the objects are in proper alignment. The monitor may thus be viewed by the operator and the arm 10 manipulated so that the reflective surface is perpendicular to the optical axis of the camera, the roll of the reflective surface is at a selected angle with respect to the camera, and the camera is spaced a pre-selected distance from the reflective surface.

Monford, Leo G. (Inventor)

1990-01-01

288

Radio & Optical Interferometry: Basic Observing Techniques and Data Analysis  

E-print Network

Astronomers usually need the highest angular resolution possible, but the blurring effect of diffraction imposes a fundamental limit on the image quality from any single telescope. Interferometry allows light collected at widely-separated telescopes to be combined in order to synthesize an aperture much larger than an individual telescope thereby improving angular resolution by orders of magnitude. Radio and millimeter wave astronomers depend on interferometry to achieve image quality on par with conventional visible and infrared telescopes. Interferometers at visible and infrared wavelengths extend angular resolution below the milli-arcsecond level to open up unique research areas in imaging stellar surfaces and circumstellar environments. In this chapter the basic principles of interferometry are reviewed with an emphasis on the common features for radio and optical observing. While many techniques are common to interferometers of all wavelengths, crucial differences are identified that will help new practi...

Monnier, John D

2012-01-01

289

Manufacturing microcomponents for optical information technology using the LIGA technique  

NASA Astrophysics Data System (ADS)

Recently, splices and connectors for fibers ribbons, optical cross connects and especially planar waveguide devices have been fabricated via LIGA in combination with precision engineering techniques. LIGA combines high precision and mass production capability, necessary for products designed for applications in the telecom and datacom market. In this presentation the fabrication of three-level molding and embossing tools is presented, which have been used for the manufacturing of waveguide prestructures consisting of waveguide channels and bier-to-waveguide coupling grooves. The precision of the tools is better than 1 micrometers in all directions, which allows for simple passive pigtailing. A first product, a precision of the tool is better than 1 micrometers in all directions, which allows for simple passive pigtailing. A first product, sixfold array of 4 X 4 multimode star couplers has been realized. The molding behavior of PMMA and COC material has been tested and compared. Production and assembly was tested by fabricating a series of 300 star couplers. The average insertion los has been found better than 9dB, the uniformity better than 3dB, both measured at 830nm. THe device is designed for application in optical backplanes for high-speed computers.

Bauer, Hans-Dieter; Ehrfeld, Wolfgang; Hossfeld, Jens; Paatzsch, Thomas

1999-09-01

290

Optimum Character Encryption And Extraction For Optical Correlation Techniques  

NASA Astrophysics Data System (ADS)

An important subset of pattern recognition applications permit the representation of data by characters which have been optimized for the type of data and the type of search to be performed. An example of this is the search for biologically important patterns within the sequences of nucleotide subunits of deoxyribonucleic acid (DNA). In this case the four distinct subunits of DNA must be represented and "wildcard" or metacharacters are needed to permit flexible searches for sequence patterns. Due to the rapidly increasing availability of DNA sequence information, more rapid and interactive analytical techniques are needed to make full use of this data. This study seeks to design optimal characters for use in an optical correlator recognition device. Characters which are compact, easily distinguishable and compatible with current coherent light modulators have been designed. Preliminary work on these representations has been guided by computer modeling of the optical recognition process. Promising characters have been tested experimentally in a VanderLugt system. The use of laser printers and photo-typesetters to prepare original test images will be discussed.

Hawk, James F.; Martin, James C.; Gregory, Don A.; Christens-Barry, William A.

1990-02-01

291

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

292

Alignment of direct detection device micrographs using a robust Optical Flow approach.  

PubMed

The introduction of direct detection devices in cryo-EM has shown that specimens present beam-induced motion (BIM). Consequently, in this work, we develop a BIM correction method at the image level, resulting in an integrated image in which the in-plane BIM blurring is compensated prior to particle picking. The methodology is based on a robust Optical Flow (OF) approach that can efficiently correct for local movements in a rapid manner. The OF works particularly well if the BIM pattern presents a substantial degree of local movements, which occurs in our data sets for Falcon II data. However, for those cases in which the BIM pattern corresponds to global movements, we have found it advantageous to first run a global motion correction approach and to subsequently apply OF. Additionally, spatial analysis of the Optical Flow allows for quantitative analysis of the BIM pattern. The software that incorporates the new approach is available in XMIPP (http://xmipp.cnb.csic.es). PMID:25681631

Abrishami, Vahid; Vargas, Javier; Li, Xueming; Cheng, Yifan; Marabini, Roberto; Sorzano, Carlos Óscar Sánchez; Carazo, José María

2015-03-01

293

Absorber Alignment Measurement Tool for Solar Parabolic Trough Collectors: Preprint  

SciTech Connect

As we pursue efforts to lower the capital and installation costs of parabolic trough solar collectors, it is essential to maintain high optical performance. While there are many optical tools available to measure the reflector slope errors of parabolic trough solar collectors, there are few tools to measure the absorber alignment. A new method is presented here to measure the absorber alignment in two dimensions to within 0.5 cm. The absorber alignment is measured using a digital camera and four photogrammetric targets. Physical contact with the receiver absorber or glass is not necessary. The alignment of the absorber is measured along its full length so that sagging of the absorber can be quantified with this technique. The resulting absorber alignment measurement provides critical information required to accurately determine the intercept factor of a collector.

Stynes, J. K.; Ihas, B.

2012-04-01

294

Design of Optical Systems with Extended Depth of Field: An Educational Approach to Wavefront Coding Techniques  

ERIC Educational Resources Information Center

A practical activity designed to introduce wavefront coding techniques as a method to extend the depth of field in optical systems is presented. The activity is suitable for advanced undergraduate students since it combines different topics in optical engineering such as optical system design, aberration theory, Fourier optics, and digital image…

Ferran, C.; Bosch, S.; Carnicer, A.

2012-01-01

295

Optical techniques to understand biofunctional adaptation in human dentine  

NASA Astrophysics Data System (ADS)

Human tooth structure in the oral environment is subjected to mechanical forces and thermal fluctuations. Dentine, the major component of the tooth structure, is a bio-composite, mainly composed of a highly mineralized phase and a collagenous phase. When subjected to changes in load and/or temperature, dentine will experience stresses and strains distribution within their structure. Though such effects are found to cause deleterious effects on artificial dental restorations, biological structures such as dentine seem to posses an inherent ability to adapt to functional thermo-mechanical loads. Optical techniques enable visualization and quantification of deformation, strain and stress on dental structures and provide a better understanding on their thermo-mechanical response. In this study 2-dimensional and 3-dimensional digital photoelasticity, digital moiré interferometry and Electronic Speckle Pattern Interferometry (ESPI) are all shown to be quite promising in this application. This paper will highlight these techniques and the corresponding applications. These experiments will aid in designing and development of better dental restorations and implants in clinical practice.

Kishen, Anil; Asundi, Anand K.

2004-08-01

296

A conceptual design for the Thirty Meter Telescope alignment and phasing system  

NASA Astrophysics Data System (ADS)

The primary, secondary and tertiary mirrors of the Thirty Meter Telescope (TMT), taken together, have approximately 12,000 degrees of freedom in optical alignment. The Alignment and Phasing System (APS) will use starlight and a variety of Shack-Hartmann based measurement techniques to position the segment pistons, tips, and tilts, segment figures, secondary rigid body motion, secondary figure and the tertiary figure to correctly align the TMT. We present a conceptual design of the APS including the requirements, alignment modes, predicted performance, software architecture, and an optical design.

Troy, Mitchell; Chanan, Gary; Michaels, Scott; Bartos, Randy; Bothwell, Graham; Give'on, Amir; Hein, Randy; Radin, Max; Roberts, Jenny; Rodgers, J. Michael; Scherr, Lawrence M.; Seo, Byoung-Joon; Zimmerman, David

2008-07-01

297

CLASP (Capture and Locking alignment Spring Positioner): A micromachined fiber auto-positioning device  

SciTech Connect

This work provides a method of mechanical alignment of an array of single mode fibers to an array of optical devices. The technique uses a micromachined metal spring, which captures a vertical, pre- positioned fiber, moves it into accurate alignment, and holds it for attachment. The spring is fabricated from electroplated mickel, using photodefined polyimide as a plating mask. The nickel is plated about 80 {mu}m thick, so that a large fiber depth is captured. In one application, the nickel springs can be aligned to optics on the back side of the substrate. This entire concept is referred to as CLASP (Capture and Locking Alignment Spring Positioner). These springs can be used for general alignment and capture of any fiber to any optical input or output device. Passive alignment of fiber arrays to {plus}/{minus} 2{mu}m accuracy has been demonstrated, with a clear path to improved accuracy.

Kravitz, S.H.; word, J.C.; Bauer, T.M.; Seigal, P.K.; Armendariz, M.G.

1996-03-01

298

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

299

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

300

A conceptual design for the Thirty Meter Telescope alignment and phasing system  

Microsoft Academic Search

The primary, secondary and tertiary mirrors of the Thirty Meter Telescope (TMT), taken together, have approximately 12,000 degrees of freedom in optical alignment. The Alignment and Phasing System (APS) will use starlight and a variety of Shack-Hartmann based measurement techniques to position the segment pistons, tips, and tilts, segment figures, secondary rigid body motion, secondary figure and the tertiary figure

Mitchell Troy; Gary Chanan; Scott Michaels; Randy Bartos; Graham Bothwell; Amir Give'on; Randy Hein; Max Radin; Jenny Roberts; J. Michael Rodgers; Lawrence M. Scherr; Byoung-Joon Seo; David Zimmerman

2008-01-01

301

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

302

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

303

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

304

Evaluation of spectrally efficient indoor optical wireless transmission techniques   

E-print Network

. Secondly, a novel optical wireless transmitter concept is developed. This concept uses discrete power level stepping to generate intensity modulated optical signals, such as orthogonal frequency division multiplexing (OFDM) waveforms. The transmitter...

Fath, Thilo Christian Martin

2014-06-30

305

Online technique for detecting state of onboard fiber optic gyroscope  

NASA Astrophysics Data System (ADS)

Although angle random walk (ARW) of fiber optic gyroscope (FOG) has been well modeled and identified before being integrated into the high-accuracy attitude control system of satellite, aging and unexpected failures can affect the performance of FOG after launch, resulting in the variation of ARW coefficient. Therefore, the ARW coefficient can be regarded as an indicator of "state of health" for FOG diagnosis in some sense. The Allan variance method can be used to estimate ARW coefficient of FOG, however, it requires a large amount of data to be stored. Moreover, the procedure of drawing slope lines for estimation is painful. To overcome the barriers, a weighted state-space model that directly models the ARW to obtain a nonlinear state-space model was established for FOG. Then, a neural extended-Kalman filter algorithm was implemented to estimate and track the variation of ARW in real time. The results of experiment show that the proposed approach is valid to detect the state of FOG. Moreover, the proposed technique effectively avoids the storage of data.

Miao, Zhiyong; Xu, Dingjie; He, Kunpeng; Pang, Shuwan; Tian, Chunmiao

2015-02-01

306

Digital detection techniques for dynamic optical tomographic imaging  

NASA Astrophysics Data System (ADS)

In this paper we present a novel application of digital detection and data-acquisition techniques to a prototype dynamic optical tomography system. The core component is a digital signal processor (DSP) that is responsible for collecting and processing the digitized data set. Utilizing the processing power of the DSP, real-time data rates for this 16-source, 32-detector system, can be achieved at rates as high as 140Hz per tomographic frame. Many of the synchronously-timed processes are controlled by a complex programmable logic device (CPLD) that is used in conjunction with the DSP to orchestrate data flow. The operation of the instrument is managed through a comprehensive graphical user interface, which was designed using the LabVIEW software package. Performance analysis demonstrates very low system noise (~.60pW RMS noise equivalent power) and excellent signal precision (<0.1%) for most practical cases. First experiments on tissue phantoms show that dynamic behavior can be accurately captured using this system.

Lasker, Joseph M.; Masciotti, James; Schoenecker, Mathew; Schmitz, Christoph; Hielscher, Andreas H.

2007-02-01

307

Online technique for detecting state of onboard fiber optic gyroscope.  

PubMed

Although angle random walk (ARW) of fiber optic gyroscope (FOG) has been well modeled and identified before being integrated into the high-accuracy attitude control system of satellite, aging and unexpected failures can affect the performance of FOG after launch, resulting in the variation of ARW coefficient. Therefore, the ARW coefficient can be regarded as an indicator of "state of health" for FOG diagnosis in some sense. The Allan variance method can be used to estimate ARW coefficient of FOG, however, it requires a large amount of data to be stored. Moreover, the procedure of drawing slope lines for estimation is painful. To overcome the barriers, a weighted state-space model that directly models the ARW to obtain a nonlinear state-space model was established for FOG. Then, a neural extended-Kalman filter algorithm was implemented to estimate and track the variation of ARW in real time. The results of experiment show that the proposed approach is valid to detect the state of FOG. Moreover, the proposed technique effectively avoids the storage of data. PMID:25725877

Miao, Zhiyong; Xu, Dingjie; He, Kunpeng; Pang, Shuwan; Tian, Chunmiao

2015-02-01

308

Measurement of laser frequency response through heterodyne technique using optical modulation  

E-print Network

An optical modulation technique for measuring the parasitic-free frequency response of high frequency semiconductor lasers is demonstrated. In this technique, we heterodyne light from two continuously tunable external cavity travelling wave ring...

Ahmed, Syed Faisal

1994-01-01

309

Alignment and Integration of Lightweight Mirror Segments  

NASA Technical Reports Server (NTRS)

The optics for the International X-Ray Observatory (IXO) require alignment and integration of about fourteen thousand thin mirror segments to achieve the mission goal of 3.0 square meters of effective area at 1.25 keV with an angular resolution of five arc-seconds. These mirror segments are 0.4 mm thick, and 200 to 400 mm in size, which makes it difficult not to impart distortion at the sub-arc-second level. This paper outlines the precise alignment, permanent bonding, and verification testing techniques developed at NASA's Goddard Space Flight Center (GSFC). Improvements in alignment include new hardware and automation software. Improvements in bonding include two module new simulators to bond mirrors into, a glass housing for proving single pair bonding, and a Kovar module for bonding multiple pairs of mirrors. Three separate bonding trials were x-ray tested producing results meeting the requirement of sub ten arc-second alignment. This paper will highlight these recent advances in alignment, testing, and bonding techniques and the exciting developments in thin x-ray optic technology development.

Evans, Tyler; Biskach, Michael; Mazzarella, Jim; McClelland, Ryan; Saha, Timo; Zhang, Will; Chan, Kai-Wing

2011-01-01

310

Alignment and integration of lightweight mirror segments  

NASA Astrophysics Data System (ADS)

The optics for the International X-Ray Observatory (IXO) require alignment and integration of about fourteen thousand thin mirror segments to achieve the mission goal of 3.0 square meters of effective area at 1.25 keV with an angular resolution of five arc-seconds. These mirror segments are 0.4 mm thick, and 200 to 400 mm in size, which makes it difficult not to impart distortion at the sub-arc-second level. This paper outlines the precise alignment, permanent bonding, and verification testing techniques developed at NASA's Goddard Space Flight Center (GSFC). Improvements in alignment include new hardware and automation software. Improvements in bonding include two module new simulators to bond mirrors into, a glass housing for proving single pair bonding, and a Kovar module for bonding multiple pairs of mirrors. Three separate bonding trials were x-ray tested producing results meeting the requirement of sub ten arc-second alignment . This paper will highlight these recent advances in alignment, testing, and bonding techniques and the exciting developments in thin x-ray optic technology development.

Evans, Tyler; Biskach, Michael; Mazzarella, Jim; McClelland, Ryan; Saha, Timo; Zhang, William; Chan, Kai-Wing

2011-09-01

311

Utilizing vertically aligned CdSe/CdS nanorods within a luminescent solar concentrator  

NASA Astrophysics Data System (ADS)

Optical characterisation methodologies are employed to validate a nanorod self-alignment technique for use in luminescent solar concentrators (LSCs). The nanorods utilised in this work were CdSe/CdS core/shell nanorods, and the self-alignment technique relied on the evaporation of a highly concentrated nanorod/xylene solution onto a glass substrate. Position and angular dependent light absorptivity measurements revealed evidence of vertical nanorod alignment over a limited region at the centre of the LSC sample. Vertical nanorod alignment is beneficial for absorbing diffuse/scattered sunlight and provides for a high light trapping efficiency in the LSC.

Fisher, Martyn; Farrell, Daniel; Zanella, Marco; Lupi, Antonio; Stavrinou, Paul N.; Chatten, Amanda J.

2015-01-01

312

Phase Modulation Characteristics Analysis of Optically-Addressed Parallel-Aligned Nematic Liquid Crystal Phase-Only Spatial Light Modulator Combined with a Liquid Crystal Display  

Microsoft Academic Search

An optically addressed parallel-aligned nematic-liquid-crystal spatial light modulator (PAL-SLM) has been studied as a dynamic phase-only light modulation device. The phase modulation characteristics of the PAL-SLM using a liquid crystal display (LCD) as an addressing mask were investigated by analyzing diffraction efficiencies resulting from binary gratings projected from the LCD. A more than 2? phase-only modulation depth was achieved. The

Fanghong Li; Naohisa Mukohzaka; Narihiro Yoshida; Yasunori Igasaki; Haruyoshi Toyoda; Takashi Inoue; Yuji Kobayashi; Tsutomu Hara

1998-01-01

313

Polarization spectroscopy to determine alignment depolarization P3=2 atoms using a pump-probe laser technique  

E-print Network

Polarization spectroscopy to determine alignment depolarization of the 133 Cs 6p2 P3=2 atoms using, 620 E. Spring Street, Oxford, OH 45056, USA a r t i c l e i n f o Article history: Received 5 August.50.+d Keywords: Spectroscopy Atom­atom collisions Polarization a b s t r a c t We have experimentally

Bayram, S. Burçin

314

Achieving Alignment.  

ERIC Educational Resources Information Center

Describes how school districts can implement alignment between student learning standards and assessments used to measure that learning. Focuses on alignment between standards and assessment in No Child Left Behind Act, the types of alignment studies requested by states and districts, and using the results of alignment studies to inform practice.…

Ananda, Sri

2003-01-01

315

Optical and surface morphological properties of polarizing films fabricated from a chromonic dye by the photoalignment technique.  

PubMed

The inherent chromonic lyotropic liquid crystalline properties of a dye have been manipulated to fabricate multi-axial micropolarizing thin films by means of the photoalignment technique. The dye aqueous solution is deposited on a photopatterned polymer film to result in the macroscopic alignment of the dye molecules, followed by drying at ambient temperature. The solid polarizing dye layers thus produced exhibit very a high contrast ratio and degree of polarization in the region of visible light. Addition of a small amount of surfactant to the dye solution is a prerequisite for the generation of a nematic chromonic phase and for the formation of homogeneous thin dye layers on the polymer film. The correlation between the optical and surface morphological properties of the dye layers is discussed. PMID:15745005

Ruslim, Christian; Hashimoto, Masanori; Matsunaga, Daisaku; Tamaki, Takashi; Ichimura, Kunihiro

2004-01-01

316

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-dither algorithm for adaptive optics robustly and in continuous-time. Similar architectures have been The inherent decades, significant work has been done in the field of adaptive optics in order to alleviate or at least

Cauwenberghs, Gert

317

New techniques for optical absorption measurement of implanted nanoparticles in float glass  

Microsoft Academic Search

New techniques are reported for optical absorption and waveguide loss measurement of copper, gold and silver implanted float glass. Implantations were carried out on the tin face of the float glass since this face is an optical waveguide. Specially made triangle shape masks were used during implantation to study the optical loss–implant length relation. Absorption coefficients were extracted as 2.4

I Okur; P. D Townsend; P. J Chandler

1999-01-01

318

IMD Compensation for CDMA through FEC Coding and Nonlinearity Recovery Technique for Optical Fiber Feeder System  

Microsoft Academic Search

Optical feeding between base stations (BS) and radio network control (RNC), proposed in this paper, is an efficient technique for third generation wideband CDMA mobile communication systems. The proposed technique provides the compensation to the intermodulation distortion (IMD) instituted by both the power amplifier (an electrical component) and the laser diode (an optical component). This IMD can impose strong limitations

Raziq P. Yaqub

1999-01-01

319

A technique for the optical analysis of deformed telescope mirrors  

NASA Technical Reports Server (NTRS)

The NASTRAN-ACCOS V programs' interface merges structural and optical analysis capabilities in order to characterize the performance of the NASA Goddard Space Flight Center's Solar Optical Telescope primary mirror, which has a large diameter/thickness ratio. The first step in the optical analysis is to use NASTRAN's FEM to model the primary mirror, simulating any distortions due to gravitation, thermal gradients, and coefficient of thermal expansion nonuniformities. NASTRAN outputs are then converted into an ACCOS V-acceptable form; ACCOS V generates the deformed optical surface on the basis of these inputs, and imaging qualities can be determined.

Bolton, John F.

1986-01-01

320

Digital vs. optical techniques in synthetic aperture radar data processing  

Microsoft Academic Search

The basic aspects of synthetic aperture radar image formation are reviewed. The required processing consists of a two-dimensional matched filtering operation which can be implemented either optically or digitally. An examination of the standard tilted-plane optical processing approach reveals that the required procedure can be performed in a conceptually simple, yet elegant, manner. The less mature digital technology can also

D. A. Ausherman

1977-01-01

321

An optical surveillance technique based on cavity mode analysis of SL-RSOA for GPON  

Microsoft Academic Search

An optical in-service surveillance technique based on cavity mode analysis of self-injection locked reflective semiconductor optical amplifier (SL-RSOA) for gigabit-capable passive optical network (GPON) is proposed. At each optical network unit (ONU), an upstream transmitter utilizing SL-RSOA can generate both upstream data signal and surveillance signal due to presence of external cavity. We can able to detect both upstream data

Madhan Thollabandi; Hakjeon Bang; Kyung-Woo Shim; Swook Hann; Chang-Soo Park

2009-01-01

322

Journal of Molecular Structure 349 (1995) 265-268 Alignment-orientation transition at optical excitation of molecules in  

E-print Network

which depends quadratically on the intensity of the irradiating light; second, it is a quantum effect that the external magnetic field which causes ordinary Zeeman effect, when EM 0: M can not cause the alignment

Auzinsh, Marcis

323

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

324

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

325

Two Techniques for Optical Imaging Through Turbid Media  

E-print Network

absorption involves the selective energy absorption of photons by atoms with the proper energy transitions ingested by a patient. Ultrasound uses high-frequency sound waves to construct #12;Imaging: Non-optical EM

Petta, Jason

326

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

327

IOO Assignment Integrated Optical Microsystems Group (IOMS) Optical Loss Spectra with Prism Coupling Technique  

E-print Network

IOO Assignment ­ Integrated Optical Microsystems Group (IOMS) Optical Loss Spectra with Prism of integrated optics are best characterized optically by making use of the prism coupling method. It can provide measurements using another prism coupling setup and employing lasers at various wavelengths, instead

Al Hanbali, Ahmad

328

Synthesis, transfer printing, electrical and optical properties, and applications of materials composed of self-assembled, aligned single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Super growth of single-walled carbon nanotubes (SWNTs) has emerged as a unique method for synthesizing self-assembled, pristine, aligned SWNT materials composed of ultra-long (millimeter-long) nanotubes. This thesis focuses on novel routes of synthesizing such self-assembled SWNTs and the challenges that arise in integrating this material into next-generation applications. First of all, this work provides unique insight into growth termination of aligned SWNTs, emphasizing the mechanism that inhibits the growth of infinitely long nanotubes. Exhaustive real-time growth studies, combined with ex-situ and in-situ TEM characterization emphasizes that Ostwald ripening and subsurface diffusion of catalyst particles play a key role in growth termination. As a result, rational steps to solving this problem can enhance growth, and may ultimately lead to the meter or kilometer-long SWNTs that are necessary for a number of applications. In addition, other novel synthesis routes are discussed, such as the ability to form macroscopic fibrils of SWNTs, called "flying carpets" from 40 nm thick substrates, and the ability to achieve supergrowth of SWNTs that are controllably doped with nitrogen. In the latter case, molecular heterojunctions of doped and undoped sections in a single strand of ultralong SWNTs are demonstrated Secondly, as supergrowth is conducted on alumina coated SiO2 substrates, any applications will require that one can transfer the SWNTs to host surfaces with minimal processing. This work demonstrates a unique contact transfer route by which both patterned arrays of SWNTs, or homogenous SWNT carpets, can be transferred to any host surface. In the first case, the SWNTs are grown vertically aligned, and transferred in patterns of horizontally aligned SWNT. This transfer process relies on simple water-vapor etching of amorphous carbons at the catalyst following growth, and strong van der Waals adhesion of the high surface-area SWNT to host surfaces (gecko effect). Next, as the SWNTs produced in supergrowth are notably large in diameter (2-5 nm), this work provides the first characterization of these SWNTs using combined microscopy and infrared polarized absorption studies. Perfectly aligned SWNTs are transferred to infrared optical windows and mounted in a rotatable vacuum cell in which polarization dependent characterization is carried out. By modeling features observed in absorption to expected optical excitonic transition energies, diameter distributions are rapidly extracted. In addition, other concepts of optical characterization in ultra-long aligned SWNTs are explored. For example, the concept of using polarized near-IR characterization for such SWNT samples is inadequate to characterize the bulk alignment due to the mismatch of the excitation wavelength and the SWNT length. Therefore, comparing anisotropy in polarized near-IR Raman or absorption gives substantially different results than anisotropic electrical transport measurements. In addition to optical characterization, this work uniquely finds that the electrical transport properties of SWNTs is ultimately limited by SWNT-SWNT junctions. This is evident in temperature-dependent DC and AC conductivity measurements that emphasize localization-induced transport characteristics. A number of non-classical electrical transport features are observed that can simply be related to the sensitivity of electrical transport to SWNT-SWNT junctions. This means that despite the incredible electrical properties of individual SWNTs, it is necessary to focus on the growth and processing of ultra-long SWNTs in order to realistically make nanotube-based materials comparable in transport characteristics to conventional materials. Finally, this work concludes by demonstrating progress on the fabrication of new SWNT-based applications. First of all, a new type of solid-state supercapacitor material is fabricated where vertically aligned SWNT are coated with metal-oxide dielectric and counterelectrode layers to form efficient supercapacitors. This design benefits from the

Pint, Cary L.

329

Image Correlation Method for DNA Sequence Alignment  

PubMed Central

The complexity of searches and the volume of genomic data make sequence alignment one of bioinformatics most active research areas. New alignment approaches have incorporated digital signal processing techniques. Among these, correlation methods are highly sensitive. This paper proposes a novel sequence alignment method based on 2-dimensional images, where each nucleic acid base is represented as a fixed gray intensity pixel. Query and known database sequences are coded to their pixel representation and sequence alignment is handled as object recognition in a scene problem. Query and database become object and scene, respectively. An image correlation process is carried out in order to search for the best match between them. Given that this procedure can be implemented in an optical correlator, the correlation could eventually be accomplished at light speed. This paper shows an initial research stage where results were “digitally” obtained by simulating an optical correlation of DNA sequences represented as images. A total of 303 queries (variable lengths from 50 to 4500 base pairs) and 100 scenes represented by 100 x 100 images each (in total, one million base pair database) were considered for the image correlation analysis. The results showed that correlations reached very high sensitivity (99.01%), specificity (98.99%) and outperformed BLAST when mutation numbers increased. However, digital correlation processes were hundred times slower than BLAST. We are currently starting an initiative to evaluate the correlation speed process of a real experimental optical correlator. By doing this, we expect to fully exploit optical correlation light properties. As the optical correlator works jointly with the computer, digital algorithms should also be optimized. The results presented in this paper are encouraging and support the study of image correlation methods on sequence alignment. PMID:22761742

Curilem Saldías, Millaray; Villarroel Sassarini, Felipe; Muñoz Poblete, Carlos; Vargas Vásquez, Asticio; Maureira Butler, Iván

2012-01-01

330

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

331

Optical See-Through Head Mounted Display Direct Linear Transformation Calibration Robustness in the Presence of User Alignment Noise  

NASA Technical Reports Server (NTRS)

Augmented Reality (AR) is a technique by which computer generated signals synthesize impressions that are made to coexist with the surrounding real world as perceived by the user. Human smell, taste, touch and hearing can all be augmented, but most commonly AR refers to the human vision being overlaid with information otherwise not readily available to the user. A correct calibration is important on an application level, ensuring that e.g. data labels are presented at correct locations, but also on a system level to enable display techniques such as stereoscopy to function properly [SOURCE]. Thus, vital to AR, calibration methodology is an important research area. While great achievements already have been made, there are some properties in current calibration methods for augmenting vision which do not translate from its traditional use in automated cameras calibration to its use with a human operator. This paper uses a Monte Carlo simulation of a standard direct linear transformation camera calibration to investigate how user introduced head orientation noise affects the parameter estimation during a calibration procedure of an optical see-through head mounted display.

Axholt, Magnus; Skoglund, Martin; Peterson, Stephen D.; Cooper, Matthew D.; Schoen, Thomas B.; Gustafsson, Fredrik; Ynnerman, Anders; Ellis, Stephen R.

2010-01-01

332

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

333

Characterization of optical components using contact and non-contact interferometry techniques: advanced metrology for optical components  

NASA Astrophysics Data System (ADS)

Advanced metrology plays an important role in the research, production and quality control of optical components. With surface finish, form error and other parameter specifications becoming more stringent, precision measurements are increasingly demanded by optics manufacturers and users. The modern metrologist now has both contact and noncontact measurement solutions available and a combination of these techniques now provides a more detailed understanding of optical components. Phase Grating Interferometry (PGI) with sub-nanometre vertical resolution and sub-micron lateral resolution can provide detailed characterization of a wide range of components including shallow and steep-sided optics. PGI is ideal for precision form measurement of a comprehensive range of lenses, moulds and other spherical or aspheric products. Because of the complex nature of these components, especially precision aspheric and asphero-diffractive optics, control of the form is vital to ensure they perform correctly. Recent hardware and software developments now make it possible to gain a better understanding and control of the form and function of this optics. Another change is the use of high speed 3D non-contact measurement of optics which is becoming more popular. Often scanning interferometric techniques such as coherence correlation interferometry (CCI) can be used to study components not suited to 2D contact analysis, including fragile surfaces and structured surfaces. Scanning interferometry can also be used to measure film thickness and uniformity of any coating present. In this paper the use of both PGI and CCI to measure optical lenses and coatings is discussed.

Yu, Yang; Conroy, Mike; Smith, Richard

2012-10-01

334

Weather watch studies by means of an optical technique  

NASA Technical Reports Server (NTRS)

A series of articles is presented on a passive, optical, cross beam system. The passive, optical, cross beam system was evaluated as a remote sensor of atmospheric conditions. The system employed the light scattered from natural aerosols to sense atmospheric mean and turbulent motion. A space-time correlation of the output of two optical sensors was used to evaluate the mean convective wind speed. In approximately 20% of the tests, signal-to-noise levels were sufficient to allow estimation of convective wind speeds. The feasibility of employing intersecting beams to evaluate the atmospheric turbulent motion was also investigated. The intersecting beams produced maximums in the space-time correlation curves for other than zero delay. The non-zero time delay maximums indicate the cross beam system was detecting aerosol layers in the atmosphere, rather than information from the common intersecting volume.

Turner, R. E. (editor)

1974-01-01

335

Ultrafast optical technique for the characterization of altered materials  

DOEpatents

Disclosed herein is a method and a system for non-destructively examining a semiconductor sample having at least one localized region underlying a surface through into which a selected chemical species has been implanted or diffused. A first step induces at least one transient time-varying change in optical constants of the sample at a location at or near to a surface of the sample. A second step measures a response of the sample to an optical probe beam, either pulsed or continuous wave, at least during a time that the optical constants are varying. A third step associates the measured response with at least one of chemical species concentration, chemical species type, implant energy, a presence or absence of an introduced chemical species region at the location, and a presence or absence of implant-related damage. The method and apparatus in accordance with this invention can be employed in conjunction with a measurement of one or more of the following effects arising from a time-dependent change in the optical constants of the sample due to the application of at least one pump pulse: (a) a change in reflected intensity; (b) a change in transmitted intensity; (c) a change in a polarization state of the reflected and/or transmitted light; (d) a change in the optical phase of the reflected and/or transmitted light; (e) a change in direction of the reflected and/or transmitted light; and (f) a change in optical path length between the sample`s surface and a detector. 22 figs.

Maris, H.J.

1998-01-06

336

Ultrafast optical technique for the characterization of altered materials  

DOEpatents

Disclosed herein is a method and a system for non-destructively examining a semiconductor sample (30) having at least one localized region underlying a surface (30a) through into which a selected chemical species has been implanted or diffused. A first step induces at least one transient time-varying change in optical constants of the sample at a location at or near to a surface of the sample. A second step measures a response of the sample to an optical probe beam, either pulsed or continuous wave, at least during a time that the optical constants are varying. A third step associates the measured response with at least one of chemical species concentration, chemical species type, implant energy, a presence or absence of an introduced chemical species region at the location, and a presence or absence of implant-related damage. The method and apparatus in accordance with this invention can be employed in conjunction with a measurement of one or more of the following effects arising from a time-dependent change in the optical constants of the sample due to the application of at least one pump pulse: (a) a change in reflected intensity; (b) a change in transmitted intensity; (c) a change in a polarization state of the reflected and/or transmitted light; (d) a change in the optical phase of the reflected and/or transmitted light; (e) a change in direction of the reflected and/or transmitted light; and (f) a change in optical path length between the sample's surface and a detector.

Maris, Humphrey J. (Barrington, RI)

1998-01-01

337

Amplitude independent instantaneous frequency measurement using all optical technique.  

PubMed

A novel all-optical system which independently measures both the amplitude and frequency of an RF signal is proposed and demonstrated. A photonic Hilbert transformer provides two orthogonal measurements of an RF signal. These are compared using four wave mixing in a highly nonlinear fiber, producing two independent outputs enabling determination of both signal frequency and amplitude. This all optical approach requires only simple, low cost DC electronics at the receiver. The system is demonstrated up to 20 GHz but can be scaled to 40 GHz and beyond. PMID:24514511

Bui, Lam Anh; Mitchell, Arnan

2013-12-01

338

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

339

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

340

Light dosimetry technique for endoscopic PDT using microlens optical fiber  

NASA Astrophysics Data System (ADS)

A simple procedure is presented for determining the irradiance of light striking tissues during light delivery using a microlens optical fiber via an endoscope. The particular example is photodynamic therapy (PDT) of laryngeal cancer. A microlens optical fiber is an optical fiber with a small lens assembly at its terminus which magnifies the image of the end of the fiber yielding a uniform irradiance in a plane distant from the fiber. Prior to the therapy, the relation between fiber-target distance, h [cm], and the diameter of the uniform beam, d(h) [cm], was established and the area of the beam was calculated: A(h) equals (pi) d(h)2/4. The laser power P [W] required to achieve a desired irradiance E [W/cm2] was P(h) equals EA(h), and this relation was prepared as a simple graph for routine use in the clinic. During the therapy, the doctor advances the optical fiber through the working channel of the endoscope to touch the target tissue site while observing through the optical channel, and marks the fiber on the outside of the endoscope. The doctor then retracts the fiber until an aiming beam transmitted through the fiber fully illuminates the desired target area, and again marks the fiber on the outside of the endoscope. The difference in the two marks on the fiber outside the endoscope yields h, the height of the fiber above the target tissue. The laser operator then uses the P(h) equals EA(h) graph to select the proper laser power to achieve the desired E. Although trivially simple, this dosimetry procedure was critical to the proper implementation of PDT for laryngeal cancer.

Jacques, Steven L.

1999-06-01

341

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

342

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

343

Serially grafted polymer optical waveguides fabricated by light-induced self-written waveguide technique.  

PubMed

Serially grafted polymer optical waveguides were fabricated by the light-induced self-written (LISW) waveguide technique for the first time to our knowledge. To realize functional waveguide cores by the LISW technique, transparent materials at the writing wavelength were selected. By inserting thin transparent partitions, a serial-graft structure consisting of passive and active waveguides without any misalignment was realized automatically. This technique is advantageous for its extremely easy process over conventional fabrication techniques. PMID:18246159

Sugihara, Okihiro; Yasuda, Shuhei; Cai, Bin; Komatsu, Kyoji; Kaino, Toshikuni

2008-02-01

344

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

345

A technique for computation of star magnitudes relative to an optical sensor  

NASA Technical Reports Server (NTRS)

The theory and techniques used to compute star magnitudes relative to any optical detector (such as the Mariner Mars 1971 Canopus star tracker) are described. Results are given relative to various star detectors.

Rhoads, J. W.

1972-01-01

346

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

347

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

348

Planar waveguide based optical performance monitoring techniques and their applications in all-optical networks  

NASA Astrophysics Data System (ADS)

Over the past few years, DWDM has been widely adopted across the telecommunications industry to expand capacity in telecommunication infrastructure. The success of DWDM in increasing raw capacity on point-to-point fiber routes and the rapid growth of data communications accelerates the pace to all-optical networking. The goal of all- optical networking is to create a transparent optical layer that can easily manage the transport of signal entirely in the optical domain, reducing the need for processing and interpretation of signals, while increasing the reliability and restorability of high- bandwidth networks. However, the premise of transparent or all-optical networks requires the availability of tools to measure and control the smallest granular component of such networks-the wavelength channel, not only in the transportation system, but also in core switching segments. This dissertation studied the optical performance measuring tools for WDM networks, and categorized the optical performance monitoring into two layers: optical-physical-layer performance monitoring and optical-path-layer performance monitoring. With potential mass-production capability for future wide range application, planar waveguide technology is selected as the focus of this dissertation. In the optical-physical-layer, arrayed waveguide grating (AWG) based multi-channel wavelength, power and OSNR monitoring circuit were proposed. Modeling and design were performed to provide optimized performance. Multi- channel wavelength monitoring circuit was demonstrated with precise wavelength monitoring capability. Optical-path-layer performance layer monitoring becomes necessary while optical cross-connect (OXC) is implemented. Focusing on one type of OXC, this dissertation studied the possibility to build a low cost, robust and transparent monitoring scheme using similar planar waveguide technology which been used in optical- physical-layer monitoring. Furthermore, the applications of optical performance monitoring in all-optical networks were discussed, including system turn-up, dynamic gain spectrum flattening and power equalizing after OXC.

Zhong, Shan

349

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

350

Code division multiple-access techniques in optical fiber networks. I. Fundamental principles  

Microsoft Academic Search

An examination is made of fiber-optic code-division multiple-access (FO-CDMA), a technique in which low information data rates are mapped into very-high-rate address codes (signature sequences) for the purpose of achieving random, asynchronous communications free of network control, among many users. The need for a special class of signature sequences to achieve the multiple-access capability using fiber-optic signal processing techniques is

J. A. Salehi

1989-01-01

351

Investigation of ferroelectric properties of bismuth ferrite films by the second optical harmonic generation technique  

Microsoft Academic Search

The specific features of the ferroelectric polarization switching in bismuth ferrite thin films doped with neodymium ions are investigated by the optical second harmonic generation technique. The structure and nonlinear optical properties of the samples prepared are studied in the course of ferroelectric polarization switching in planar geometry over wide ranges of film thicknesses and electric field frequencies.

N. É. Sherstyuk; N. A. Il'in; S. V. Semin; E. D. Mishina; V. M. Mukhortov

2009-01-01

352

Infrared optical element mounting techniques for wide temperature ranges  

SciTech Connect

We describe the optimization of a mounting system for the infrared (IR) optics of a spaceborne interferometer working in the temperature range between -120 deg. C and +150 deg. C. The concept is based on an aluminum alloy frame with designed mechanical compliance, which allows for compensation of the different coefficient of thermal expansion between the optics and the holder; at the same time, the system provides for the high stiffness required to reach natural frequencies above 200 Hz, which are mandatory in most space missions. Thermal adapters with properly chosen thermomechanical characteristics are interposed between the metallic structure and the lens, so as to reduce the interface stresses on the mechanically weak IR material, due to both the thermoelastic and acceleration loads. With the proposed mount, the competitive requirements of stiffness and stress-free mounting can be matched in wide temperature ranges. The case study of the interferometer of a miniaturized Fourier transform IR spectrometer is presented.

Saggin, Bortolino; Tarabini, Marco; Scaccabarozzi, Diego

2010-01-20

353

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

354

Optical Properties of Astronomical Silicates with Infrared Techniques  

NASA Astrophysics Data System (ADS)

Infrared observations are uniquely able to observe the astrophysical processes deep within dusty regions and to provide key information on the characteristics of the dust itself. This information is critical for learning the role of dust in gas physics, for exploring how dust processing occurs, and for understanding the formation and destruction mechanisms of dust grains. Though relevant astronomical and ground-based observations already exist, the properties of dust at these long wavelengths are poorly known, and since observed spectral features of dust are used to infer characteristics of the surrounding neighborhood, these large uncertainties lead to ambiguity in interpretation. The OPASI-T program addresses the need for high fidelity optical characterization data in the far and mid infrared, aiming at the creation of a unique library of the optical properties of metal-enriched silicate condensates. Such database will cover a wide wavelength range connecting numerical data with laboratory and astronomical spectra in the mid infrared, while providing new data in the unexplored far-infrared and millimeter regime. Both new and established experiments are used to measure the transmission and reflection properties of amorphous silicates across the infrared, which are then analyzed by way of numerical methods in order to determine the variations of their optical constants and complex dielectric function as a function of wavelength. I will present room-temperature measurements of SiO in a KBr matrix from 5 to 25 ?m and its optical properties as derived from a least-squares nonlinear fit applied to a mixed approach coupling the Maxwell-Garnett theory, the Lorentz dispersive model for mixtures, and the averaged equation for transmission. This material is based upon work supported by NASA through the ROSES/APRA program. This research was supported by an appointment (Cataldo) at the Goddard Space Flight Center administered by Universities Space Research Association through a contract with NASA.

Cataldo, Giuseppe; Rinehart, S. A.; Benford, D.; Dwek, E.; Kinzer, R. E.; Nuth, J.; Silverberg, R.; Wollack, E.

2011-05-01

355

Diamond-turned optics aid alignment and assembly of a dual-field infrared imaging missile tracker  

NASA Astrophysics Data System (ADS)

Diamond-turning as a manufacturing method for infrared optics opens new possibilities for solving packaging problems. Optical surfaces and mechanical mounting features may be related to one another to reduce design complexity, tolerance accumulation, and cost.

Guyer, Robert C.; Evans, Clinton E.; Ross, Brien D.

1998-12-01

356

Flipped-exponential Nyquist pulse technique to optimize the PAPR in optical direct detection OFDM system  

NASA Astrophysics Data System (ADS)

In this paper, a novel technique based on flipped-exponential (FE) Nyquist pulse method is proposed for peak-to-average power ratio (PAPR) reduction in optical direct detection orthogonal frequency-division multiplexing (DD-OFDM) system. The method is based on a proper selection of the FE Nyquist pulses for shaping the different subcarriers of the OFDM. We experimentally demonstrated an optical DD-OFDM transmission system with this novel technique to achieve significant improvement in PAPR reduction in the optical OFDM system. The received sensitivity of the OFDM signal after suffered from strong nonlinear effects in standard single-mode fiber (SMF) has been experimentally investigated.

Xiao, Jiangnan; Yu, Jianjun; Cao, Zizheng; Li, Fan; Chen, Lin

2013-01-01

357

Dynamic vacuum measurement by an optical interferometric technique  

NASA Astrophysics Data System (ADS)

A homodyne Michelson interferometer was developed to realize a dynamic vacuum standard. The interferometer measures variation in optical path due to refractive index changes related to the pressure of the gas. The measurement arm of the interferometer is formed by two quasi-parallel mirrors which act as a multiplication set-up to allow an increment of the optical path and consequently of the sensitivity. The interference signal is detected by a high speed camera: starting from the recorded interference pattern, two quadrature regions are identified and analyzed by custom software to obtain the quadrature phase signals. The dynamic vacuum system is mainly composed of a large low-pressure chamber VA (about 800?L) connected by a valve and a replaceable orifice to a high pressure chamber VB of about 2?L, hosting the interferometer. The fast pressure drop from 100?kPa to 100?Pa is obtained by a gas expansion from VB to VA. The velocity of the expansion process can be easily varied by substituting the orifice connecting the two chambers. The response of the system was first tested with a slow process of about 40?s at different gains of the measurement arm of the interferometer. Subsequently, a fast process (< 3?s) was considered and the result of the optical device was compared to the measurements performed by two capacitance diaphragm gauges (133?kPa and 1.33?kPa full scale). The gauges are equipped with special electronics to give each nominal reading every 0.7?ms. The two measurements performed by the dynamic vacuum standard and capacitance diaphragm gauges showed an agreement better than 12%.

Mari, Domenico; Bergoglio, Mercede; Pisani, Marco; Zucco, Massimo

2014-12-01

358

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

1998-01-01

359

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

360

Antenna pointing compensation based on precision optical measurement techniques  

NASA Technical Reports Server (NTRS)

The pointing control loops of the Deep Space Network 70 meter antennas extend only to the Intermediate Reference Structure (IRS). Thus, distortion of the structure forward of the IRS due to unpredictable environmental loads can result in uncompensated boresight shifts which degrade blind pointing accuracy. A system is described which can provide real time bias commands to the pointing control system to compensate for environmental effects on blind pointing performance. The bias commands are computed in real time based on optical ranging measurements of the structure from the IRS to a number of selected points on the primary and secondary reflectors.

Schumacher, L. L.; Vivian, H. C.

1988-01-01

361

Study on metal nanoparticles induced third-order optical nonlinearity in phenylhydrazone derivatives with DFWM technique  

SciTech Connect

The third-order nonlinear optical properties of newly synthesized phenylhydrazone derivatives and the influence of noble metal nanoparticles (Ag and Au) on their nonlinear optical responses were investigated by employing Degenerate Four wave Mixing (DFWM) technique with a 7 nanosecond, 10Hz Nd: YAG laser pulses at 532nm. Metal nanoparticles were prepared by laser ablation and the particle formation was confirmed using UV-Visible spectroscopy, Transmission Electron Microscopy (TEM). The nonlinear optical susceptibility were measured and found to be of the order 10{sup ?13}esu. The results are encouraging and conclude that the materials are promising candidate for future optical device applications.

Sudheesh, P.; Chandrasekharan, K. [Laser and Nonlinear Optics Laboratory, Department of Physics, National Institute of Technology Calicut (India); Rao, D. Mallikharjuna [Nano Display Laboratory, School of Nanoscience and Technology, National Institute of Technology Calicut (India)

2014-01-28

362

Reduction of semiconductor optical amplifier switching times by preimpulse step-injected current technique  

Microsoft Academic Search

A practical way to implement a technique for the reduction of the semiconductor optical amplifier electrooptic switching time is presented. The technique, called PISIC (preimpulse step-injected current), was tested and achieved a reduction of the SOA switching times from almost 2 ns (simple-step current response) to little more than 200 ps (step with prepulse response). Forecasts obtained through simulations, using

Cristiano M. Gallep; Evandro Conforti

2002-01-01

363

Optical 3D Measurement Techniques in Archaeology: Recent Developments and Applications  

Microsoft Academic Search

This paper is intended to give an overview on current surveying techniques that use remotely sensed data, and their applications in archaeology. The focus is on optical 3D measurement techniques based on image and range sensors. Data and methods are briefly reviewed, whereas data processing and related problems are only touched in passing. For the purpose of this review we

Karsten Lambers; Fabio Remondino

2007-01-01

364

Research on modern testing technique of optical system magnifying ratio based on CCD imaging theory  

Microsoft Academic Search

The paper discusses a new kind of modern testing method used in magnification of telescopic optical system, which applied the technique of photoelectric imaging creation automatically based on DLP theory and the technique of collecting image based on CCD imaging theory. This method simplifies customary measuring process, realizes objective and automatic measuring, and avoids subjective error which artificial factor leads

Lixia Shi; Chang Zeng

2005-01-01

365

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

366

Frequency-Shifted Interferometry — A Versatile Fiber-Optic Sensing Technique  

PubMed Central

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

367

Analysis of nonlinear optical materials properties by simple powder technique  

NASA Astrophysics Data System (ADS)

The article describes a simple technique for comparative analysis of the second harmonic generation properties of new samples and etalon materials by their powders. The effectiveness of the method was tested and and measuring of nonlinear coefficient and damage threshold of the well known materials: KDP, LiIO3, m-nitroaniline was demonstrated. The parameters of the new promising nonlinear material DNPAP were measured.

Morozov, O. A.; Naumov, A. K.; Lovchev, A. V.; Garipov, M. R.

2015-03-01

368

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

369

Pupil alignment considerations for large deployable space telescopes  

NASA Astrophysics Data System (ADS)

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, David A.

2011-10-01

370

A simple optical spectral calibration technique for pulsed THz sources.  

PubMed

We have quantified the sensitivity of a simple method to measure the frequency spectrum of pulsed terahertz (THz) radiation. The THz pulses are upconverted to the optical regime by sideband generation in a zinc telluride (ZnTe) crystal using a continuous wave (cw) narrow-bandwidth near-infrared laser. A single-shot spectral measurement of sideband pulses with a high resolution spectrometer directly provides the spectral information of the THz pulses without the need of adjustable elements in the detection setup. This method has been applied at the free electron laser FELIX, where, for a wavelength of 150 ?m (2 THz), pulse trains of 5 ?s duration with an integrated energy of 800 nJ, as well as single pulses with an energy as low as 13 nJ could be characterized on a single-shot basis. PMID:21165003

Wijnen, Frans J P; Berden, Giel; Jongma, Rienk T

2010-12-01

371

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

372

A technique for extracting and analyzing the polarization aberration of hyper-numerical aperture image optics  

NASA Astrophysics Data System (ADS)

For hyper-numerical aperture (NA) lithographic optics, one of the design goals is to minimize polarization aberration (PA). However PA represented by Jones pupil can not be acquired by design software CODE V™ directly. And most researchers generate PA by computer randomly in study of various presentation of PA. Optical designers and instrument developers should analyze the realistic PA in optical design procedure, which is most important for controlling the PA before the optics is fabricated. This work presents a technique for extracting and analyzing the realistic PA caused by large incident angle of light, film coatings and intrinsic birefringence of lens materials in hyper-NA optics. The PA and its decomposition is obtained and analyzed for optics with different coatings using the technology in this paper. The results show that the subset aberrations of PAs can compensate each other via different coatings on the PO. The results also reveal that coating design should balance the transmission and its aberration (apodization).

Li, Yanqiu; Guo, Xuejia; Liu, Xiaolin; Liu, Lihui

2013-12-01

373

Carbon nanotube alignment using meniscus action  

Microsoft Academic Search

Effective, large-scale alignment of single-walled carbon nanotubes (SWNTs) is necessary for making them a useful nanoelectronic technology. While techniques have been developed to align SWNTs during growth or through dielectrophoresis, no technique to date can align SWNTs on a large-scale while controlling SWNT density and taking advantage of chirally pure SWNTs. We present a novel alignment technique using mechanical action

Joshua D. Wood; Joseph W. Lyding

2009-01-01

374

Novel x-ray optics for medical diagnostic techniques  

NASA Astrophysics Data System (ADS)

A new hard X - ray hologram with using crystal Fresnel zone plates (ZP) has been described. An image of Fourier hologram for hard X- ray is presented. X-ray phase contrast methods for medical diagnostics techniques are presented. We have developed an X-ray microscope, based on micro focus source which is capable of high resolution phasecontrast imaging and holograms. We propose a new imaging technique with the x-ray energy 8 keV. The method is expected to have wide applications in imaging of low absorbing samples such as biological and medical tissue. We used FIB to reproduction three dimension structures of damaged spinal cord of rat before and after combined treatment with NT3 and NR2D. PUBLISHER'S NOTE 12/16/09: This SPIE Proceedings paper has been updated with an erratum correcting several issues throughout the paper. The corrected paper was published in place of the earlier version on 9/1/2009. If you purchased the original version of the paper and no longer have access, please contact SPIE Digital Library Customer Service at CustomerService@SPIEDigitalLibrary.org for assistance.

Kuyumchyan, A.; Arvanian, V.; Kuyumchyan, D.; Aristov, V.; Shulakov, E.

2009-08-01

375

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

376

Gas flow effects on precision solder self-alignment  

Microsoft Academic Search

Self-aligning soldering technology is being developed for low cost, passive, precision optical alignments. To avoid contamination problems, the solder reflow process must use reacting or inert gas instead of chemical flux materials. Since the accuracy of these optical alignments should reach the range of a few micrometers (?m), the gas flow may affect the aligning process. Therefore, the effects of

Bingzhi Su; M. Gershovich; Y. C. Lee

1997-01-01

377

Gas flow effects on precision solder self-alignment  

Microsoft Academic Search

Self-aligning soldering technology is being developed for low cost, passive, precision optical alignments. To avoid contamination problems, a solder reflow process must use reacting or inert gas instead of chemical flux materials. Since the accuracy of these optical alignments should reach the range of a few ?m, the gas flow may affect the aligning process. Therefore, the effects of the

Bingzhi Su; M. Gershovich; Y. C. Lee

1997-01-01

378

MOSAIC - A space-multiplexing technique for optical processing of large images  

NASA Technical Reports Server (NTRS)

A technique for Fourier processing of images larger than the space-bandwidth products of conventional or smart spatial light modulators and two-dimensional detector arrays is described. The technique involves a spatial combination of subimages displayed on individual spatial light modulators to form a phase-coherent image, which is subsequently processed with Fourier optical techniques. Because of the technique's similarity with the mosaic technique used in art, the processor used is termed an optical MOSAIC processor. The phase accuracy requirements of this system were studied by computer simulation. It was found that phase errors of less than lambda/8 did not degrade the performance of the system and that the system was relatively insensitive to amplitude nonuniformities. Several schemes for implementing the subimage combination are described. Initial experimental results demonstrating the validity of the mosaic concept are also presented.

Athale, Ravindra A.; Astor, Michael E.; Yu, Jeffrey

1993-01-01

379

Molecular alignment enhancement phenomenon of polymer formed from a liquid crystal monomer in a liquid crystal solvent  

NASA Astrophysics Data System (ADS)

We report an abnormal alignment enhancement phenomenon of polymer molecules. The alignment order of a rigid-skeleton polymer made from a liquid crystalline monomer in a low-molecular-weight liquid crystal solvent was drastically enhanced with increasing temperature, even though the alignment order of the solution of the liquid crystal and monomer decreased. From polymer molecular alignment observations using polarizing Raman scattering microscopy, it was found that the polymer alignment order was three times greater than that of the original aligned monomer and polymer. This super alignment technique of polymer using a molecular-scaled self-assembly mechanism is applicable to the formation of electrically and/or optically functional nanopolymer wires.

Fujikake, Hideo; Murashige, Takeshi; Sato, Hiroto; Kawakita, Masahiro; Kikuchi, Hiroshi

2003-03-01

380

Ultrafast Optical Techniques for High-Speed Devices and Mm-Wave Circuit Testing  

Microsoft Academic Search

The recent development of ultrafast short pulse lasers, especially the Ti-sapphire laser, has engendered dramatic advances in pulsewidth and average power of femtosecond laser oscillators and amplifiers. In addition the femtosecond short pulse lasers have led to many applications, such as electro-optic sampling, photoconductive sampling, and time-resolved spectroscopy. In effort to apply the ultrafast optical techniques to high speed electronics,

Joungho Kim

1993-01-01

381

Code division multiple-access techniques in optical fiber networks. II. Systems performance analysis  

Microsoft Academic Search

For pt.I see ibid., vol.37, no.8, p.824-33 (1989). In Part I a technique based on optical orthogonal codes was presented to establish a fiber-optic code-division multiple-access (FO-CDMA) communications system. The results are used to derive the bit error rate of the proposed FO-CDMA system as a function of data rate, code length, code weight, number of users, and receiver threshold.

J. A. Salehi; C. A. Brackett

1989-01-01

382

Investigation of ferroelectric properties of bismuth ferrite films by the second optical harmonic generation technique  

Microsoft Academic Search

The specific features of the ferroelectric polarization switching in bismuth ferrite thin films doped with neodymium ions\\u000a are investigated by the optical second harmonic generation technique. The structure and nonlinear optical properties of the\\u000a samples prepared are studied in the course of ferroelectric polarization switching in planar geometry over wide ranges of\\u000a film thicknesses and electric field frequencies.

N. É. Sherstyuk; N. A. Il’in; S. V. Semin; E. D. Mishina; V. M. Mukhortov

2009-01-01

383

Alignment maps of tissues: I. Microscopic elliptical polarimetry.  

PubMed Central

An automated method for generating a fiber alignment map in tissues, tissue-equivalents, and other fibrillar materials exhibiting linear and circular optical properties and scattering is presented. This method consists of interrogating the sample with elliptically polarized light from a rotated quarter-wave plate and an effective circular analyzer, and implementing nonlinear regression techniques to estimate parameters defining the optical properties of the optic train and the sample. Thus, an account is made for imperfect and misaligned optic elements. The optic train was modeled using the Mueller matrix representation and the combined sample properties by an exponential matrix. Because a sample's Mueller matrix does not uniquely determine the linear, circular, or scattering properties, the circular properties and effective scattering are estimated for a matched isotropic sample to determine and correct for the linear birefringence of an aligned sample. The method's utility is demonstrated by generating an alignment map of an arterial media-equivalent, a relevant test case because of its circumferential alignment and thus showing the method's sample orientation independence. PMID:11606305

Tower, T T; Tranquillo, R T

2001-01-01

384

An optical surveillance technique based on cavity mode analysis of SL-RSOA for GPON  

NASA Astrophysics Data System (ADS)

An optical in-service surveillance technique based on cavity mode analysis of self-injection locked reflective semiconductor optical amplifier (SL-RSOA) for gigabit-capable passive optical network (GPON) is proposed. At each optical network unit (ONU), an upstream transmitter utilizing SL-RSOA can generate both upstream data signal and surveillance signal due to presence of external cavity. We can able to detect both upstream data and surveillance signals from all ONUs simultaneously at the optical line terminal (OLT) by assigning a distinct cavity mode frequency to each upstream transmitter. We also estimate the power penalty induced by the surveillance signals on the upstream data channel during simultaneous detection mechanism. Further, we propose an alternative method to detect the surveillance signals by allocating a separate monitoring time slot in upstream GPON transmission convergence (GTC) frame so as to reduce the influence of surveillance signals on the upstream data channel.

Thollabandi, Madhan; Bang, Hakjeon; Shim, Kyung-Woo; Hann, Swook; Park, Chang-Soo

2009-10-01

385

A multiplexing technique for fibre Bragg grating sensors with the same reflection wavelength by the synthesis of optical coherence function  

Microsoft Academic Search

We propose a technique for multiplexing fibre Bragg grating (FBG) sensors with the same Bragg wavelength. We have already developed a technique for the synthesis of an optical coherence function, in which we can select one signal among various reflections along an optical path in an interferometer. By applying the technique, the reflection spectrum of each FBG in arrayed FBGs

Kazuo Hotate; Momoyo Enyama; Shinji Yamashita; Yusuke Nasu

2004-01-01

386

Probing excited states of NO involved in multistate interactions using the optical-optical double resonance-multiphoton ionization technique  

SciTech Connect

Many new transitions from the (3ssigma) A/sup 2/..sigma../sup +/ state to higher Rydberg and valence states in /sup 14/N/sup 16/O have been observed by the technique of optical-optical double resonance-multiphoton ionization. Upper states include members from the np, nd, nf Rydberg states (n = 3 to 6) and several vibrational levels of the B/sup 2/PI and L/sup 2/PI valence states. The spectral simplification aspect of the double resonance technique allows for the observation of these spectra without appreciable band overlap. Analysis of our data leads to the identification of several previously unobserved mixed Rydberg-valence vibrational levels. Discussions of the Rydberg-valence interactions in the 68,600-71,200-cm/sup -1/ energy region of /sup 14/N/sup 16/O are presented in light of these results. 31 references, 12 figures, 15 tables.

Cheung, W.Y.; Chupka, W.A.; Colson, S.D.; Gauyacq, D.; Avouris, P.; Wynne, J.J.

1986-03-13

387

FIRAS optical alignment and performance during vibration qualification and cryogenic cycling. [Far InfraRed Absolute Spectrometer  

NASA Technical Reports Server (NTRS)

NASA's Cosmic Background Explorer (COBE) is designed to investigate the Cosmic Background Radiation (CBR), that permeates the universe as a consequence of the Big Bang. This 3 degree Kelvin radiation is a fossil that contains much information about the early universe. The Far Infrared Absolute Spectrophotometer (FIRAS), will investigate the spectral isotropy of this ancient remnant and look for clues as to the subsequent evolution of the universe. The instrument is a cryogenically cooled, modified Michelson interferometer which operates in the 1 cm to 100 micron wavelength range. FIRAS is designed to provide absolute spectral information, therefore, all possible perturbations to the instrument response must be investigated to minimize distortions of the data. This paper discusses the methodology and resultant variations in the instrument performance noted during room temperature, and liquid nitrogen, (LN2) temperature vibration qualification. Reference alignment shifts in critical components such as the instrument wire-grid beamsplitter are correlated to changes in the instrument spectral response.

Hagopian, John G.

1989-01-01

388

Combined laser calorimetry and photothermal technique for absorption measurement of optical coatings  

SciTech Connect

To the best of our knowledge, a combined sensitive technique employing both laser calorimetry and a surface thermal lens scheme for measuring absorption values of optical coatings is presented for the first time. Laser calorimetric and pulsed surface thermal lens signals are simultaneously obtained with a highly reflecting UV coating sample irradiated at 193 nm. The advantages and potential applications of the combined technique and the experimental factors limiting the measurement sensitivity are discussed.

Li Bincheng; Blaschke, Holger; Ristau, Detlev

2006-08-10

389

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

390

Investigation of the microstructure of coatings for high power lasers by non-optical techniques  

SciTech Connect

The microstructure of optical coatings strongly influence their resistance to high fluence laser, scatter properties, as well as, their mechanical and environmental stability. The relative merits of non-optical techniques, such as: scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and focused ion beam, are discussed as they apply to optical multilayer coatings. The combination of these techniques provides a unique method to analyze defects in coatings. The long term objective of this work is to: understand the initiation and growth mechanisms of defects in optical coatings, investigate failure mechanisms of laser coatings, and suggest methods for reducing the number of defects during the deposition process. To date, our defect analysis using non-optical techniques has focused on hafnia/silica multilayers for high power lasers. In summary, the information we have compiled about the defect seeds: indicates that seed size has an influence upon the mechanical stability of the whole defect, indicates that seed shape and chemical composition reveal potential seed sources in the coating system, and demonstrates that defects can be initiated either as a single event or continuously during the deposition process. Also, it is shown that different vendors have characteristic defects and seeds.

Tench, R.J.; Kozlowski, M.R.; Chow, R.

1994-06-01

391

Ultrabroadband phased-array radio frequency (RF) receivers based on optical techniques  

NASA Astrophysics Data System (ADS)

Military operations require the ability to locate and identify electronic emissions in the battlefield environment. However, recent developments in radio detection and ranging (RADAR) and communications technology are making it harder to effectively identify such emissions. Phased array systems aid in discriminating emitters in the scene by virtue of their relatively high-gain beam steering and nulling capabilities. For the purpose of locating emitters, we present an approach realize a broadband receiver based on optical processing techniques applied to the response of detectors in conformal antenna arrays. This approach utilizes photonic techniques that enable us to capture, route, and process the incoming signals. Optical modulators convert the incoming signals up to and exceeding 110 GHz with appreciable conversion efficiency and route these signals via fiber optics to a central processing location. This central processor consists of a closed loop phase control system which compensates for phase fluctuations induced on the fibers due to thermal or acoustic vibrations as well as an optical heterodyne approach for signal conversion down to baseband. Our optical heterodyne approach uses injection-locked paired optical sources to perform heterodyne downconversion/frequency identification of the detected emission. Preliminary geolocation and frequency identification testing of electronic emissions has been performed demonstrating the capabilities of our RF receiver.

Overmiller, Brock M.; Schuetz, Christopher A.; Schneider, Garrett; Murakowski, Janusz; Prather, Dennis W.

2014-03-01

392

OPTICAL ABSORPTION SPECTRA OF AG-MICROCLUSTERS FORMED BY MATRIX TECHNIQUES  

E-print Network

. Introduction. -- The matrix isolation of atomic species which normally exist as large aggregates is a method in the field of matrix isolation the main problem has not yet been solved satisfactorily : aggregation occursOPTICAL ABSORPTION SPECTRA OF AG-MICROCLUSTERS FORMED BY MATRIX TECHNIQUES W. S C H U L Z E , H. U

Paris-Sud XI, Université de

393

Spray and combustion characterization for internal combustion engines using optical measuring techniques – A review  

Microsoft Academic Search

The number of studies on spray and combustion characteristics in IC (internal combustion) engines using optical techniques has rapidly increased in the past few years due to an increase in the number of alternative fuels and stricter emission standard regulations. This study investigates better ways of controlling the combustion process, thus ensuring optimum performance and minimum emission levels produced during

S. N. Soid; Z. A. Zainal

2011-01-01

394

New optical security device based on one-hundred-year-old photographic technique  

Microsoft Academic Search

A new optical security application of an old color photographic technique (Lippmann photography, invented in 1891) is presented. Today, this type of photography can be applied as a unique security device on security documents, such as, e.g., identification cards, passports, credit cards, and other documents where a high degree of security is needed. A Lippmann photograph is very similar to

Hans I. Bjelkhagen

1999-01-01

395

VisualAudio: an Optical Technique to Save the Sound of Phonographic Records  

Microsoft Academic Search

The optical retrieval and storage technique called VisualAudio provides a way to extract sound information from a phonographic record without any mechanical contact. The process is straightforward: we take a picture of each side of the disk using a dedicated analog camera, we store the film as our working copy, and when needed, we scan the film and process the

Sylvain Stotzer; Ottar Johnsen; Frédéric Bapst; Cédric Milan; Christoph Sudan; S. Cavaglieri; Pio Pellizzari; Nazionale Svizzera

396

Survey Paper Optical techniques for 3D surface reconstruction in computer-assisted  

E-print Network

Survey Paper Optical techniques for 3D surface reconstruction in computer-assisted laparoscopic in laparoscopic surgery and discusses the technical challenges and future per- spectives towards clinical. As direct viewing of the surgical target is not possible, an endoscopic camera (laparoscope) gener- ates

Bartoli, Adrien

397

ADVANCES IN OPTICALLY PUMPED He4 MAGNETOMETERS : RESONANCE AND NONRESONANCE TECHNIQUES  

E-print Network

to the observed magnetic field are presented in this paper. The orientation dependence of the amplitude and frequency of the magnetic resonance signal observed by optical techniques has been measured. These results are theoretically interpreted by taking into account the contribution of the indi- vidual magnetic resonances

Boyer, Edmond

398

Measurement of volume resistivity\\/conductivity of metallic alloy in inhibited seawater by optical interferometry techniques  

Microsoft Academic Search

Optical interferometry techniques were used for the first time to measure the volume resistivity\\/conductivity of carbon steel samples in seawater with different concentrations of a corrosion inhibitor. In this investigation, the real-time holographic interferometry was carried out to measure the thickness of anodic dissolved layer or the total thickness, Utotal, of formed oxide layer of carbon steel samples during the

K. Habib

2011-01-01

399

Technique to improve carrier-to-interference ratio of optical single sideband with carrier modulated signals  

NASA Astrophysics Data System (ADS)

We propose and demonstrate a simple technique to improve the carrier-to-interference ratio (CIR) of optical single sideband with carrier modulated signals for fiber-radio applications. The proposed scheme is demonstrated via experiment and simulation with a two-tone test showing that an improvement in CIR of 9 dB can be achieved.

Lim, Christina; Lee, Ka-Lun; Nirmalathas, Ampalavanapillai; Novak, Dalma; Waterhouse, Rod

2006-11-01

400

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

401

Nondestructive defect delineation in SiC wafers based on an optical stress technique  

Microsoft Academic Search

The potential of using the optical stress technique to delineate the various defects in silicon carbide (SiC) wafers has been fully demonstrated. The observed defects include micropipes, dislocations, stress striations, grain boundary or dislocation walls, and regions of polytype nonuniformity. Revealed dislocation density is in the range 104-105 cm-2.

Xianyun Ma; Mathew Parker; Tangali S. Sudarshan

2002-01-01

402

Iterative deconvolution technique for measurements of diffraction-limited images on optical microscopes  

PubMed Central

Diffraction limit is usually a thorny problem in an optical inspection system. In this investigation, a model-based deconvolution technique was developed to recover diffraction-limited images, where images with sizes smaller than the diffraction limit could be recognized. Experiments were carried out with a traditional microscope at 200× magnification coupled with a halogen light source for a series of line width samples. The point spread function of the imaging optics was first obtained from an estimated model and then combined with a nonlinear deconvolution algorithm to calculate the full width at half maximum and reconstruct the line widths. Experimental results indicate that a measurement error below one pixel size of the measurement system is achievable. Accordingly, the target of nanoscale line width inspection based on a low cost and real-time image processing technique can be fulfilled, which greatly increases the ability of nanoscaling on optical microscopes.

Lu, Wenlong; Chang, Ming; Chen, Po-Cheng; Luo, Wun-Mao

2014-01-01

403

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

404

Surface alignment, anchoring transitions, optical properties, and topological defects in the nematic phase of thermotropic bent-core liquid crystal A131  

NASA Astrophysics Data System (ADS)

We study optical, structural, and surface anchoring properties of thermotropic nematic bent-core material A131. The focus is on the features associated with orientational order as the material has been reported to exhibit not only the usual uniaxial nematic but also the biaxial nematic phase. We demonstrate that A131 experiences a surface anchoring transition from a perpendicular to tilted alignment when the temperature decreases. The features of the tilted state are consistent with surface-induced birefringence associated with smectic layering near the surface and a molecular tilt that changes along the normal to the substrates. The surface-induced birefringence is reduced to zero by a modest electric field that establishes a uniform uniaxial nematic state. Both refractive and absorptive optical properties of A131 are consistent with the uniaxial order. We found no evidence of the “polycrystalline” biaxial behavior in the cells placed in crossed electric and magnetic fields. We observe stable topological point defects (boojums and hedgehogs) and nonsingular “escaped” disclinations pertinent only to the uniaxial order. Finally, freely suspended films of A131 show uniaxial nematic and smectic textures; a decrease in the film thickness expands the temperature range of stability of smectic textures, supporting the idea of surface-induced smectic layering. Our conclusion is that A131 features only a uniaxial nematic phase and that the apparent biaxiality is caused by subtle surface effects rather than by the bulk biaxial phase.

Senyuk, B.; Wonderly, H.; Mathews, M.; Li, Q.; Shiyanovskii, S. V.; Lavrentovich, O. D.

2010-10-01

405

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

406

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

407

A precise technique for measurement of optical-fiber hole concentricity in the ferrule of an optical connector  

SciTech Connect

A precise optical method was developed for measuring the concentricity of a longitudinal hole in a cylinder relative to the outer cylindrical surface. The work was done to provide improved accuracy over existing methods for measuring the concentricity ofan optical fiber relative to the outer ferrule diameter in an optical connector. Fiber concentricity is very important for reliable coupling of high optical power densities from one connectorized fiber cable to another. The technique involves the use of a laser interferometer to measure the passage of the ferrule into and out of a light beam whose attenuated energy is measured simultaneously to high precision. Combined measurements of the passage of a precisely fit pin or fiber in the ferrule hole through the light beam allow the concentricity of the fiber hole to be measured relative to the outer ferrule diameter. Repeatability measurements were made under different experimental arrangements, with both a collimated light beam and a slightly convergent light beam. Depending on the particular arrangement, the standard deviation for concentricity measurement in a given plane of the ferrule ranged from 2.37 microinches to 4.19 microinches.

Klingsporn, P.E.

1996-12-01

408

Metal Grating Patterning on Fiber Facets by UV-Based Nano Imprint and Transfer Lithography Using Optical Alignment  

Microsoft Academic Search

UV-based nano imprint and transfer lithography (NITL) is proposed as a flexible, low cost and versatile approach for defining sub-micron metal patterns on optical fiber facets in a single-processing step. NITL relies on a specially prepared mold carrying the pattern that is to be transferred to the facet. The fiber's light-guiding properties allow control of the position of the metal

Stijn Scheerlinck; Peter Dubruel; Peter Bienstman; Etienne Schacht; Dries Van Thourhout; Roel Baets

2009-01-01

409

Micromanipulation robot for automatic fiber alignment  

Microsoft Academic Search

Optical fiber alignment devices are highly necessary in optical communications. In this paper, we developed a micromanipulation robot for automatically performing optical fiber alignment task. The system consists of a precision parallel robot with 6 D.O.Fs, a nano positioning stage with 5 D.O.Fs, two microscopes, two CCD cameras, an optical power meter and a fusion device. Directed by the micro-vision

Liguo Chen; Weibin Rong; Lining Sun; Hui Xie

2005-01-01

410

Long-range Brillouin optical time-domain analysis sensor employing pulse coding techniques  

NASA Astrophysics Data System (ADS)

In this paper we describe and implement a long-range Brillouin optical time-domain analysis (BOTDA) sensor, for both temperature and strain measurements, using optical pulse coding techniques. A theoretical analysis of Simplex coding applied to BOTDA systems is presented and experimentally demonstrated for both Brillouin loss and Brillouin gain configurations. With the proposed technique, ~7.1 dB and ~10.3 dB of signal-to-noise ratio improvements are demonstrated in BOTDA measurements using 127-bit and 511-bit Simplex codes, respectively. This feature allows us to extend the dynamic range of the measurements, overcoming the limitations to the maximum usable optical power imposed by pump depletion and modulation instability; thus, the sensing range can be extended by several tens of kilometers while keeping meter-scale spatial resolution. Experimental results show the capabilities of optical pulse coding techniques to achieve 1 m spatial resolution over 50 km of standard single-mode fiber enabling temperature and strain resolutions equal to 2.2 °C and 44 µ?, respectively.

Soto, Marcelo A.; Bolognini, Gabriele; Di Pasquale, Fabrizio; Thévenaz, Luc

2010-09-01

411

Application of nondestructive optical techniques in the detection of surface and subsurface defects in sapphire  

NASA Astrophysics Data System (ADS)

Advancements in optical manufacturing and testing technologies for sapphire material are required to support the increasing use of large aperture sapphire panels as windscreens for various electro-optical system applications. It is well known that the grinding and polishing operations employed to create optical surfaces leads to the introduction of surface stress and sub-surface damage which can affect critical opto-mechanical performance characteristics such as strength and durability. Traditional methods for measuring these defects are destructive and, therefore, unsuitable as in-process, high volume inspection tools. A number of non-destructive optical techniques were investigated at Exotic Electro-Optics under funding by the Office of Naval Research and the Air Force Research Laboratory including Raman spectroscopy, laser polarimetry and the Twyman effect to characterize process-induced defects in sapphire panels. Preliminary experimental results using these techniques have shown that surface stress and sub-surface damage may be non-destructively measured. Raman spectroscopy has shown promise in quantifying surface stress, laser polarimetry is of questionable utility and the Twyman effect may be used qualitatively to monitor relative stress and sub-surface damage. This information will ultimately provide a better understanding of the overall manufacturing process leading to optimized process time and cost.

Akwani, Ikerionwu A.; Hibbard, Douglas L.; Jacoby, Keith T.

2007-04-01

412

Using Complementary Acoustic and Optical Techniques for Quantitative Monitoring of Biomolecular Adsorption at Interfaces  

PubMed Central

The great wealth of different surface sensitive techniques used in biosensing, most of which claim to measure adsorbed mass, can at first glance look unnecessary. However, with each technique relying on a different transducer principle there is something to be gained from a comparison. In this tutorial review, different optical and acoustic evanescent techniques are used to illustrate how an understanding of the transducer principle of each technique can be exploited for further interpretation of hydrated and extended polymer and biological films. Some of the most commonly used surface sensitive biosensor techniques (quartz crystal microbalance, optical waveguide spectroscopy and surface plasmon resonance) are briefly described and five case studies are presented to illustrate how different biosensing techniques can and often should be combined. The case studies deal with representative examples of adsorption of protein films, polymer brushes and lipid membranes, and describe e.g., how to deal with strongly vs. weakly hydrated films, large conformational changes and ordered layers of biomolecules. The presented systems and methods are compared to other representative examples from the increasing literature on the subject. PMID:25586027

Konradi, Rupert; Textor, Marcus; Reimhult, Erik

2012-01-01

413

Optical signal to noise ratio monitoring using single channel sampling technique.  

PubMed

In this paper, we propose a novel method to depict 2-dimension (2-D) phase portrait by using single-channel-sampling (SCS) technique, which can be used for optical performance monitoring. Single low speed sampling scheme reduces cost and complexity of monitoring system setup significantly. In the experimental demonstration, optical signal to noise ratio (OSNR) is monitored from 10 dB to 30 dB by statistical analysis on pattern evolution of the generated 2-D phase portrait in both NRZ and RZ systems. The chromatic dispersion (CD) influence on OSNR monitoring performance is also investigated. PMID:24664036

Yu, Yi; Zhang, Banghong; Yu, Changyuan

2014-03-24

414

Radio frequency phototube and optical clock: High resolution, high rate and highly stable single photon timing technique  

SciTech Connect

A new timing technique for single photons based on the radio frequency phototube and optical clock or femtosecond optical frequency comb generator is proposed. The technique has a 20 ps resolution for single photons, is capable of operating with MHz frequencies and achieving 10 fs instability level.

Amur Margaryan

2011-10-01

415

Thirteen new BL Lacertae objects discovered by an efficient x ray/radio/optical technique  

NASA Technical Reports Server (NTRS)

The discovery of 13 serendipitous BL Lac objects in the Einstein IPC Slew Survey by means of x ray/radio vs. x ray/optical color-color diagrams and confirmation by optical spectroscopy are reported. These 13 BL Lacs were discovered using a technique which exploits the characteristic broad band spectra of BL Lacs. New VLA detections provide accurate fluxes (f(6 cm) is approximately 0.5 mJy) and 2 in. positions, facilitating the determination of an optical counterpart. All 13 new BL Lacs show essentially featureless optical spectra. Nine of these lie within the range of colors of known x ray selected BL Lacs. Of the remaining four, one is apparently x ray louder (by a factor of 1.5) or optically quieter (by 0.8 mags); and three are optically louder (by 1-1.3 mags) than x ray selected BL Lacs. Approximately 50 new BL Lacs in total are expected from VLA work and upcoming Australia Telescope observations, yielding a complete Slew Survey sample of approximately 90 BL Lacs.

Schachter, Jonathan F.; Stocke, John T.; Perlman, Eric; Elvis, Martin S.; Luu, Jane; Huchra, John P.; Humphreys, Roberta; Remillard, Ron; Wallin, John

1992-01-01

416

Alignment fixture  

DOEpatents

A part alignment fixture is provided which may be used for precise variable lateral and tilt alignment relative to the fixture base of various shaped parts. The fixture may be used as a part holder for machining or inspection of parts or alignment of parts during assembly and the like. The fixture includes a precisely machined diameter disc-shaped hub adapted to receive the part to be aligned. The hub is nested in a guide plate which is adapted to carry two oppositely disposed pairs of positioning wedges so that the wedges may be reciprocatively positioned by means of respective micrometer screws. The sloping faces of the wedges contact the hub at respective quadrants of the hub periphery. The lateral position of the hub relative to the guide plate is adjusted by positioning the wedges with the associated micrometer screws. The tilt of the part is adjusted relative to a base plate, to which the guide plate is pivotally connected by means of a holding plate. Two pairs of oppositely disposed wedges are mounted for reciprocative lateral positioning by means of separate micrometer screws between flanges of the guide plate and the base plate. Once the wedges are positioned to achieve the proper tilt of the part or hub on which the part is mounted relative to the base plate, the fixture may be bolted to a machining, inspection, or assembly device.

Bell, Grover C. (Norris, TN); Gibson, O. Theodore (Lenoir City, TN)

1980-01-01

417

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

418

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

419

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

420

Bandwidth-efficient phase modulation techniques for stimulated Brillouin scattering suppression in fiber optic parametric amplifiers.  

PubMed

Two novel bandwidth efficient pump-dithering Stimulated Brillouin Scattering (SBS) suppression techniques are introduced. The techniques employ a frequency-hopped chirp and an RF noise source to impart phase modulation on the pumps of a two pump Fiber Optical Parametric Amplifier (FOPA). The effectiveness of the introduced techniques is confirmed by measurements of the SBS threshold increase and the associated improvements relative to the current state of the art. Additionally, the effect on the idler signal integrity is presented as measured following amplification from a two pump FOPA employing both techniques. The measured 0.8 dB penalty with pumps dithered by an RF noise source, after accruing 160 ps/nm of dispersion with 38 dB conversion gain in a two-pump FOPA is the lowest reported to date. PMID:20721202

Coles, J B; Kuo, B P-P; Alic, N; Moro, S; Bres, C-S; Chavez Boggio, J M; Andrekson, P A; Karlsson, M; Radic, S

2010-08-16

421

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

422

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

423

Alignment and Alignment Modulation of Single Wall Carbon Nanotubes Using Lyotropic Chromonic Liquid Crystals  

Microsoft Academic Search

We report alignment and local alignment modulation of single wall carbon nanotubes (SWNTs) dispersed in a nematic solvent of lyotropic chromonic liquid crystals (LCLCs). Polarized optical absorption suggests that when SWNTs are coated with surfactant molecules, e.g., sodium dodecyl benzene sulfonate (NaDDBS), the SWNTs align along the nematic director of the LCLCs, possibly due to elastic interaction between the anisotropic

M. F. Islam; I. I. Smalyukh; O. D. Lavrentovich; A. G. Yodh

2006-01-01

424

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

425

In-Band OSNR Monitoring Technique Based on Link-by-Link Estimation for Dynamic Transparent Optical Networks  

Microsoft Academic Search

A cost-effective optical performance monitoring system, based on link-by-link optical signal-to-noise ratio (OSNR) estimation, is proposed for a dynamic transparent optical network. The proposed technique estimates the OSNR by monitoring the channel powers at the input and output of each optical link and the total input power to the inline EDFAs. In-band OSNR monitoring was successfully demonstrated at 42.7 Gb\\/s

Jun Haeng Lee; Noboru Yoshikane; Takehiro Tsuritani; Tomohiro Otani

2008-01-01

426

Optical encryption by combining image scrambling techniques in fractional Fourier domains  

NASA Astrophysics Data System (ADS)

In this paper, we propose a novel scheme for optical information hiding (encryption) of two-dimensional images by combining image scrambling techniques in fractional Fourier domains. The image is initially randomly shifted using the jigsaw transform algorithm, and then a pixel scrambling technique based on the Arnold transform (ART) is applied. The scrambled image is then encrypted in a randomly chosen fractional Fourier domain. These processes can then be iteratively repeated. The parameters of the architecture, including the jigsaw permutation indices, Arnold frequencies, and fractional Fourier orders, form a very large key space enhancing the security level of the proposed encryption system. Optical implementations are discussed as numerical implementation algorithms. Numerical simulation results are presented to demonstrate the system's flexibility and robustness.

Liu, Shi; Sheridan, John T.

2013-01-01

427

Multimodal imaging of vascular network and blood microcirculation by optical diagnostic techniques  

SciTech Connect

We present a multimodal optical diagnostic approach for simultaneous non-invasive in vivo imaging of blood and lymphatic microvessels, utilising a combined use of fluorescence intravital microscopy and a method of dynamic light scattering. This approach makes it possible to renounce the use of fluorescent markers for visualisation of blood vessels and, therefore, significantly (tenfold) reduce the toxicity of the technique and minimise side effects caused by the use of contrast fluorescent markers. We demonstrate that along with the ability to obtain images of lymph and blood microvessels with a high spatial resolution, current multimodal approach allows one to observe in real time permeability of blood vessels. This technique appears to be promising in physiology studies of blood vessels, and especially in the study of peripheral cardiovascular system in vivo. (optical technologies in biophysics and medicine)

Kuznetsov, Yu L; Kalchenko, V V; Meglinski, I V

2011-04-30

428

Measurement of Young's modulus of cementitious materials using an electro-optic holographic technique  

NASA Astrophysics Data System (ADS)

The electro-optic holographic technique has already been used to determine Young's dynamic modulus in homogeneous materials based on the resonance frequency of the analysed samples. This paper shows a modification of the determination method of this frequency that speeds up this process thus obtaining Young's modulus. Based on the visualisation of real time fringes drawn by exciting the rods at the 1000-10,000 Hz range, the proposed method allows us to determine their resonance frequencies. This procedure has been used in the analysis of non-homogeneous materials such as mortar and concrete. The results obtained by this method show good correlation with those determined by the conventional compression method established by Una Norma Española (UNE) regulations, but with a smaller variability as far as measurements are concerned. The variation coefficient is less than 1% with the optical method as opposed to 3% with the compression technique.

González-Peña, Rolando; Martí-López, Luis; Cibrián-Ortiz de Anda, Rosa M.; Molina-Jiménez, Teresa; Piqueres-Ayela, Carlos

2001-12-01

429

The use of optical techniques in the interpretation of heat transfer measurements  

NASA Astrophysics Data System (ADS)

Optical techniques were used to study the flow structure, and to gain a better understanding of the convective heat transfer inside rotating cavities. Flow visualization was used to determine the amount of coolant necessary to seal an air cooled rotor stator system, to delineate regimes of vortex breakdown in rotating cavities with axial throughflow, and to identify the flow regimes in a rotating cavity with a radial outflow of coolant. The LDA measurements of the radial and tangential components of velocity inside the rotating cavity were used to correlate the flow visualization results. For the radial outflow case, these velocity measurements are in good agreement with theoretical predictions. Measured Nusselt numbers reveal the presence of heat transfer regimes corresponding to those identified by the optical techniques.

Owen, J. M.; Pincombe, J. R.

1980-09-01

430

Optical Fourier techniques for medical image processing and phase contrast imaging  

PubMed Central

This paper briefly reviews the basics of optical Fourier techniques (OFT) and applications for medical image processing as well as phase contrast imaging of live biological specimens. Enhancement of microcalcifications in a mammogram for early diagnosis of breast cancer is the main focus. Various spatial filtering techniques such as conventional 4f filtering using a spatial mask, photoinduced polarization rotation in photosensitive materials, Fourier holography, and nonlinear transmission characteristics of optical materials are discussed for processing mammograms. We also reviewed how the intensity dependent refractive index can be exploited as a phase filter for phase contrast imaging with a coherent source. This novel approach represents a significant advance in phase contrast microscopy. PMID:18458764

Yelleswarapu, Chandra S.; Kothapalli, Sri-Rajasekhar; Rao, D.V.G.L.N.

2008-01-01

431

An optical authentication system based on encryption technique and multimodal biometrics  

NASA Astrophysics Data System (ADS)

A major concern nowadays for a biometric credential management system is its potential vulnerability to protect its information sources. To prevent a genuine user's templates from both internal and external threats, a novel and simple method combined optical encryption with multimodal biometric authentication technique is proposed. In this method, the standard biometric templates are generated real-timely by the verification keys owned by legal user so that they are unnecessary to be stored in a database. Compared with the traditional recognition algorithms, storage space and matching time are greatly saved. In addition, the verification keys are difficult to be forged due to the utilization of optical encryption technique. Although the verification keys are lost or stolen, they are useless for others in absence of the legal owner's biometric. A series of numerical simulations are performed to demonstrate the feasibility and performance of this method.

Yuan, Sheng; Zhang, Tong; Zhou, Xin; Liu, Xuemei; Liu, Mingtang

2013-12-01

432

A novel noninvasive all optical technique to monitor physiology of an exercising muscle  

NASA Astrophysics Data System (ADS)

An all optical technique based on near-infrared spectroscopy and mid-infrared imaging (MIRI) is applied as a noninvasive, in vivo tool to monitor the vascular status of skeletal muscle and the physiological changes that occur during exercise. A near-infrared spectroscopy (NIRS) technique, namely, steady state diffuse optical spectroscopy (SSDOS) along with MIRI is applied for monitoring the changes in the values of tissue oxygenation and thermometry of an exercising muscle. The NIRS measurements are performed at five discrete wavelengths in a spectral window of 650-850 nm and MIRI is performed in a spectral window of 8-12 µm. The understanding of tissue oxygenation status and the behavior of the physiological parameters derived from thermometry may provide a useful insight into muscle physiology, therapeutic response and treatment.

Saxena, Vishal; Marcu, Laura; Karunasiri, Gamani

2008-11-01

433

Optical spatial heterodyne interferometric Fourier transform technique (OSHIFT) and a resulting interferometer  

NASA Astrophysics Data System (ADS)

This article reports on the novel patent pending Optical Spatial Heterodyne Interferometric Fourier Transform Technique (the OSHIFT technique), the resulting interferometer also referred to as OSHIFT, and its preliminary results. OSHIFT was borne out of the following requirements: wavefront sensitivity on the order of 1/100 waves, high-frequency wavefront spatial sampling, snapshot 100Hz operation, and the ability to deal with discontinuous wavefronts. The first two capabilities lend themselves to the use of traditional interferometric techniques; however, the last two prove difficult for standard techniques, e.g., phase shifting interferometry tends to take a time sequence of images and most interferometers require estimation of a center fringe across wavefront discontinuities. OSHIFT overcomes these challenges by employing a spatial heterodyning concept in the Fourier (image) plane of the optic-under-test. This concept, the mathematical theory, an autocorrelation view of operation, and the design with results of OSHIFT will be discussed. Also discussed will be future concepts such as a sensor that could interrogate an entire imaging system as well as a methodology to create innovative imaging systems that encode wavefront information onto the image. Certain techniques and systems described in this paper are the subject of a patent application currently pending in the United States Patent Office.

Georges, James A., III

2007-09-01

434

DSP-based optical modulation technique for long-haul transmission  

NASA Astrophysics Data System (ADS)

Fiber nonlinearity and equalization-enhanced phase noise (EEPN) generate rapid perturbations and critically limit the system capacity and range of long-haul optical transmission. It is possible to cancel the rapid perturbations by introducing a particular correlation between multiple signals at the transmitter and analyzing the received signals using digital signal processing. In this paper, we review our proposed techniques to cancel rapid perturbations of polarization multiplexed signals due to fiber nonlinearity and EEPN. Numerical simulation of quaternary phase-shift keying based signals shows 1.2 dB and 0.5 dB improvement respectively from the proposed cancellation techniques for fiber nonlinearity and EEPN.

Yoshida, T.; Sugihara, T.; Uto, K.

2015-01-01

435

Influence of aluminum on doping of ytterbium in optical fiber synthesized by vapor phase technique  

NASA Astrophysics Data System (ADS)

The process conditions of vapor phase doping technique for fabricating rare earth (RE) doped optical fiber have been systematically investigated to achieve better control over RE incorporation. Experimental results showed that the amount of RE incorporation can be precisely controlled by adjusting Al ion concentration in the inlet gas mixture. The extent of RE incorporation can also be predicted for any composition of inlet gas mixture if all other process parameters remain constant. The investigation helps to obtain the optimum conditions necessary to produce fibers of given specification and thus achieve greater reproducibility. For the first time co-operative phenomenon has been established through gas phase technique.

Saha, Maitreyee; Pal, Atasi; Pal, Mrinmay; Sen, Ranjan

2015-01-01

436

Non-degenerated photoluminescence excitation correlation spectroscopy using an optical sampling technique  

SciTech Connect

We have developed a highly time-resolved photoluminescence spectroscopy based on the excitation correlation method. Successive irradiation of a pair of ultrashort light pulses with different wavelength combinations taken from two sub-picosecond lasers has exposed both temporal and energetic correlation in photoluminescence intensity associated with a nonlinear response of a sample. An optical sampling technique has been introduced successfully in order to avoid consideration of the synchronization control of ultrashort light pulses. We have demonstrated the abilities of this technique by applying to the nonlinear photoluminescence dynamics of organic dye molecules in solution.

Hasegawa, Takayuki; Masumoto, Naofumi; Harada, Tomonori; Makino, Takayuki; Takagi, Yoshihiro [Graduate School of Material Science, University of Hyogo, Koto, Kamigori, Ako-gun, Hyogo 678-1297 (Japan)

2012-10-15

437

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

438

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

E-print Network

) Denis Phares (Member) Dennis L. O?Neal (Head of Department) May 2004 Major Subject: Mechanical Engineering iii ABSTRACT Study of Formation and Convective Transport of Aerosols Using Optical Diagnostic Technique. (May 2004) Tae... dp Particle Diameter dpipe Pipe Diameter g Acceleration of Gravity h Plank Constant I Intensity I(b) Intensity of Background I(o) Intensity of Object is Scattering Parameter JC Critical Current Density K Evaporation Constant L...

Kim, Tae-Kyun

2004-09-30

439

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

440

Investigation of pacemaker shift in the rabbit sinoatrial node using the optical mapping technique  

Microsoft Academic Search

Changes of the activation sequence in the rabbit sinoatrial node under the influence of low temperature and I\\u000a f selective blocker ivabradine have been studied using the optical mapping technique. Both factors caused a shift of the pacemaker\\u000a within the sinoatrial node region. These results are compared with the data obtained recently in the investigation of pacemaker\\u000a shift under the

D. V. Abramochkin; V. S. Kuzmin; G. S. Sukhova; L. V. Rosenshtraukh

2010-01-01