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1

Sighting optics including an optical element having a first focal length and a second focal length  

DOEpatents

One embodiment of sighting optics according to the teachings provided herein may include a front sight and a rear sight positioned in spaced-apart relation. The rear sight includes an optical element having a first focal length and a second focal length. The first focal length is selected so that it is about equal to a distance separating the optical element and the front sight and the second focal length is selected so that it is about equal to a target distance. The optical element thus brings into simultaneous focus, for a user, images of the front sight and the target.

Crandall, David Lynn (Idaho Falls, ID)

2011-08-01

2

Design of a variable-focal-length optical system  

NASA Technical Reports Server (NTRS)

Requirements to place an entire optical system with a variable focal length ranging from 20 to 200 cm within a overall length somewhat less than 100 cm placed severe restrictions on the design of a zoom lens suitable for use on a comet explorer. The requirements of a wavelength range of 0.4 to 1.0 microns produced even greater limitations on the possibilities for a design that included a catadioptric (using mirrors and glass) front and followed by a zooming refractive portion. Capabilities available commercial zoom lenses as well as patents of optical systems are reviewed. Preliminary designs of the refractive optics zoom lens and the catadioptric system are presented and evaluated. Of the two, the latter probably has the best chance of success, so long as the shortest focal lengths are not really needed.

Ricks, D.; Shannon, R. R.

1984-01-01

3

Variable focal length microlenses  

NASA Astrophysics Data System (ADS)

Refractive surface relief microlenses (150 ?m diameter) are immersed in nematic liquid crystal in a cell. Application of a variable voltage across the cell effectively varies the refractive index of the liquid crystal and results in a change of the focal length by the lensmakers formula (E. Hecht, Optics, 2nd edn., Addison-Wesley, Reading, Massachusetts, 1987, p. 138). We describe the cell design and construction and demonstrate a range of focal lengths from +490 to +1000 ?m for 2 to 12 V applied. A diverging lens results when the voltage is lower. Theoretical models are developed to account for some of the observed aberrations.

Commander, L. G.; Day, S. E.; Selviah, D. R.

2000-04-01

4

Characterization of a long-focal-length polycapillary optic for high-energy x-rays  

Microsoft Academic Search

Polycapillary fibers and a prototype collector for high energy x rays with a 2 m focal length have been fabricated and characterized. Measurements of a prototype collector, performed in collimating mode, show that the optic has high transmission, good uniformity, and small exit divergence. The transmission as a function of energy was analyzed using an extended single fiber geometrical optic

Cari; Suparmi; Sushil D. Padiyar; Walter M. Gibson; Carolyn A. MacDonald; Cheryl D. Alexander; Marshall K. Joy; Christine H. Russell; Ze Wu Chen

2000-01-01

5

Optical design of long focal length and wide field on an aerial CCD camera  

NASA Astrophysics Data System (ADS)

Reconnaissance range and image resolution are increasingly paid more attention to with the development of airborne reconnaissance, the optical system should be in characteristics of long focal length and wide field. At the same flight altitude, the wider field can enlarge ground covering width and increase the reconnaissance range Longer focal length can improve ground sample distance (GSD). Merits and advantages of reflecting system, catadioptric system and refractive system were represented, with the help of code V software, a refractive system was designed to meet the requirements, Optical material with special dispersion was adopted to remove second order spectrum. It has a focal length of 903mm, with the field angle of 4.5°×4.5°, the size of CCD pixels is 10um×10um, spectral scope is from 0.43um to 0.74um, modulation transfer function(MTF) is all above 0.5 in whole field when spatial frequency is at 50lp/mm, distortion is less than 1%, image quality reaches the diffraction limit. The system with long focal length and wide field can satisfy the demand of the wide ground overlay area and high resolution, and can apply in high altitude photograph.

Cheng, Xiaowei; Che, Ying; Xue, Changxi

2009-05-01

6

Rotating type miniature camera phone multi-focal-length optical system  

NASA Astrophysics Data System (ADS)

We have designed a practical mass produced rotating type miniature camera phone multi-focal-length optical system. The compact and short system, with 3× magnification, 1.3 megapixel sensor elements and total length of less than 10.7 mm, is described and evaluated in detail. Using Zemax lens design software, we start the design with thin lenses first order layout, and then spherical thick lenses, to aspherical lenses. Plastic lens materials are used whenever applicable, and diffractive lens elements are also employed to optimize the design. The beam spot diagrams and modulation transfer function of our design are found appropriate for good optical qualities.

Chen, Junewen; Tseng, Yao-Chen; Chuang, Kai-Chun; Chen, Jung-Chao; Lin, Shu-Yuan

2009-03-01

7

Continuously variable focal length lens  

DOEpatents

A material preferably in crystal form having a low atomic number such as beryllium (Z=4) provides for the focusing of x-rays in a continuously variable manner. The material is provided with plural spaced curvilinear, optically matched slots and/or recesses through which an x-ray beam is directed. The focal length of the material may be decreased or increased by increasing or decreasing, respectively, the number of slots (or recesses) through which the x-ray beam is directed, while fine tuning of the focal length is accomplished by rotation of the material so as to change the path length of the x-ray beam through the aligned cylindrical slows. X-ray analysis of a fixed point in a solid material may be performed by scanning the energy of the x-ray beam while rotating the material to maintain the beam's focal point at a fixed point in the specimen undergoing analysis.

Adams, Bernhard W; Chollet, Matthieu C

2013-12-17

8

Compact optical imaging system for star tracker with long focal length and perfect thermal adaptability  

NASA Astrophysics Data System (ADS)

A star tracker optical imaging system is designed for Polaris detection. System parameters determination and its configuration chosen method are given. Based on Macsutov-Cassegrain configuration, the system is designed imagery tele-centric. It works at 0.6?m~1.1?m waveband and the view field is 0.5 degree. The tube length of the system is 80mm, which is only 8 percent of its focal length. Its MTF reaches diffraction limit and the spot diagrams are quit near a circle. About 80% of the energy is encircled in a CCD pixel. And the distortion is less than 1%. Moreover, it has a perfect thermal adaptability from -40° to 60°.

Ji, Yiqun; Shi, Rongbao; He, Hucheng; Xu, Li; Liu, Xuxia; Jin, Yangming; Shen, Weimin

2012-11-01

9

Development of a process camera lens with variable focal length  

Microsoft Academic Search

Process cameras of today are equipped exclusively with fixed focal length lenses. The development of a process lens with variable focal length is described. The design principles of its optical, mechanical, and electronic groups of components are explained. The prototype of the new lens reaches the image quality of fixed focal length lenses.

H. Grumpelt; P. Hanke; E. Rothe; M. Schuck; W. Smilga; H. Walter

1981-01-01

10

Variable focal length deformable mirror  

DOEpatents

A variable focal length deformable mirror has an inner ring and an outer ring that simply support and push axially on opposite sides of a mirror plate. The resulting variable clamping force deforms the mirror plate to provide a parabolic mirror shape. The rings are parallel planar sections of a single paraboloid and can provide an on-axis focus, if the rings are circular, or an off-axis focus, if the rings are elliptical. The focal length of the deformable mirror can be varied by changing the variable clamping force. The deformable mirror can generally be used in any application requiring the focusing or defocusing of light, including with both coherent and incoherent light sources.

Headley, Daniel (Albuquerque, NM); Ramsey, Marc (Albuquerque, NM); Schwarz, Jens (Albuquerque, NM)

2007-06-12

11

Microlenses with focal length controlled by chemical processes  

NASA Astrophysics Data System (ADS)

The influence of chemical processing on the optical properties of microlenses formed on a gelatin-sensitized layer was investigated. The gelatin is sensitized with tot'hema and eosin, irradiated with a Gaussian profile laser beam and subsequently chemically processed. Microlenses with a focal length of 400??m were obtained after alcohol processing. Additionally, focal lengths could be controlled by varying the alum concentration, and lenses with focal length up to 1.2?mm were obtained. The microlenses become stable after alum processing. Their optical properties remain unchanged.

Muric, B. D.; Panic, B. M.

2012-05-01

12

Crystal diffraction lens with variable focal length  

DOEpatents

A method and apparatus for altering the focal length of a focusing element o one of a plurality of pre-determined focal lengths by changing heat transfer within selected portions of the element by controlled quantities. Control over heat transfer is accomplished by manipulating one or more of a number of variables, including: the amount of heat or cold applied to surfaces; type of fluids pumped through channels for heating and cooling; temperatures, directions of flow and rates of flow of fluids; and placement of channels.

Smither, Robert K. (Hinsdale, IL)

1991-01-01

13

Design and fabrication of long focal length microlens arrays  

NASA Astrophysics Data System (ADS)

In this paper, we present microlens arrays (MLA) with long focal length (in millimeter range) based on thermal reflow process. The focal length of microlens is usually in the same order of lens diameter or several hundred microns. To extend focal length, we made a photoresist (SU-8) MLA covered by a Polydimethylsiloxane (PDMS) film on a glass substrate. Because the refractive index difference between PDMS and photoresist interface is lower than that of air and MLA interface, light is less bended when passing through MLA and is focused at longer distance. Microlenses of diameters from 50 ?m to 240 ?m were successfully fabricated. The longest focal length was 2.1 mm from the microlens of 240 ?m diameter. The numerical aperture (NA) was reduced 0.06, which is much lower than the smallest NA (~ 0.15) by regular thermal reflow processes. Cured PDMS has high transmittance and becomes parts of MLA without too much optical power loss. Besides, other focal lengths can be realized by modifying the refractive index different between two adjacent materials as described in this paper.

Hsieh, Hsin-Ta; Lin, Vinna; Hsieh, Jo-Lan; Su, Guo-Dung John

2011-10-01

14

Focal Length Measurements for the National Ignition Facility Large Lenses  

SciTech Connect

The focal length of the spatial filter and final focus lenses for the National Ignition Facility are measured to < {+-} 0.01% using a combination of master lenses and production-oriented techniques for relative focal length.

Parham, T G; McCarville, T J; Johnson, M A; Kiikka, C

2002-01-25

15

A potential individual cell malignancy indicator: focal length  

NASA Astrophysics Data System (ADS)

The label-free technique of optofluidic intracavity spectroscopy (OFIS) utilizes the optical transmission spectrum of a cell in a microfluidic Fabry-Pérot (F-P) cavity to distinguish cells from cancerous cell lines and baseline normal blood cells. The classification between canine hemangiosarcoma (HSA) cancer cells and monocytes in canine normal peripheral blood mononuclear cells (PBMCs) had been demonstrated with 95% sensitivity and 98% specificity. Now with a new optical model that treats the cell settled at the bottom of the cavity as a thin lens, the focal length of cells was extracted and used as an individual cell malignancy indicator.

Wang, Weina; Lear, Kevin L.

2011-02-01

16

Multilayer Laue Lenses with Focal Length of 10 mm  

NASA Astrophysics Data System (ADS)

Multilayer laue lenses are diffractive optics with a high potential for producing X-ray foci in the order of 10 nm or even below. Particularly for hard X-rays (E > 6 keV) these optics promise better resolution and higher efficiencies than currently available Fresnel zone plates. Magnetron sputter deposition has been used for the fabrication of multilayer laue lenses using the layer materials MoSi2 and Si. The lens design has been defined to get focal length in the order of 10 mm. One of the lenses with an aperture of about 20 ?m has been used as focusing optics in the nanoprobe beamline P06 at PETRA III. Ptychography has been applied to characterize the caustic of the focused beam and to determine the size of the X-ray focus. A spot size of about 39 nm could be obtained with a photon energy of 21 keV and a focal length of 9.9 mm.

Braun, S.; Kubec, A.; Menzel, M.; Niese, S.; Krüger, P.; Seiboth, F.; Patommel, J.; Schroer, C.

2013-03-01

17

Recursive Estimation of Motion, Structure, and Focal Length  

Microsoft Academic Search

We present a formulation for recursive recoveryof motion, pointwise structure, and focal length from featurecorrespondences tracked through an image sequence.In addition to adding focal length to the state vector, severalrepresentational improvements are made over earlierstructure from motion formulations, yielding a stable andaccurate estimation framework which applies uniformly toboth true perspective and orthographic projection. Resultson synthetic and real imagery illustrate the...

Ali Azarbayejani; Alex P. Pentland

1995-01-01

18

Acoustic lens with variable focal length for photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

A liquid acoustic lens with variable focal length is described for photoacoustic microscopy. This liquid lens takes advantage of the elastic and deformable lens interface to tune its focal length in a pneumatical manner. The curvature of the lens interface as well as the dependant focal length was characterized as a function of the infusion volume of the liquid. Experiments were carried out to demonstrate the zooming ability of this liquid acoustic lens. Targets embedded at different depths were photoacoustically imaged without performing mechanically axial scanning.

Song, Chaolong; Xi, Lei; Jiang, Huabei

2013-11-01

19

Focal length measurement by fiber point diffraction longitudinal interferometry  

NASA Astrophysics Data System (ADS)

A focal length measurement method by fiber point-diffraction longitudinal interferometry is proposed. By applying two different longitudinal displacements for the object point respectively and measuring the corresponding displacements of the image point, the lens focal length is derived by Newton formula. The displacements of the object point are introduced by glass plates with known refractive index and thickness. The corresponding displacements of the image point are measured interfeorometrically based on the modeling of the longitudinal interferometry of two point sources. Experiments and error analysis reveal that this method has an accuracy less than 0.15% under normal laboratory environment.

Chen, Lingfeng; Hao, Jinjian; Chen, Zhipu; Guo, Xiaofei

2014-07-01

20

Scanning microscopy using a short-focal-length Fresnel zone plate.  

PubMed

We demonstrate a form of scanning microscopy using a short-focal-length Fresnel zone plate and a low-NA relay telescope. Owing to a focal length of only 5 microm, the zone plate produces large wavefront tilt and consequently severe vignetting for off-axis illumination. By scanning an optically trapped fluorescent sphere, we measure the vignetted collection region of the zone-plate imaging system. The fluorescence collection efficiency is sharply peaked and has a lateral width of 550 nm, which agrees with numerical simulations. PMID:19823557

Schonbrun, Ethan; Ye, Winnie N; Crozier, Kenneth B

2009-07-15

21

Fabrication of microlens arrays with varied focal lengths on curved surfaces using an electrostatic deformed template  

NASA Astrophysics Data System (ADS)

A microlens array (MLA) with varied focal length was fabricated on a curved surface for the application of compound-eye imaging. Electrostatic deformed concave membrane was used as the initial molding template, and the deformation was determined by different applied voltage. By transferring the pattern to another polymeric template and deforming it by negative pressure, MLAs on a curved surface were fabricated successfully by using this molding process and polymeric template. The fabricated MLAs were optically characterized and the result demonstrated a larger field-of-view than that of flat MLAs and better imaging performance than that of MLAs with uniform focal length on curved surfaces.

Sun, Hongda; Deng, Shengfeng; Cui, Xiaobin; Lu, Miao

2014-06-01

22

Improvement in the measurement of focal length using spot patterns and spherical aberration.  

PubMed

Using an optical setup that includes a square array of 3×3 holes, we used nine meridional rays to measure the effective focal length of a lens. We observed the selected meridional rays as a spot pattern on a diffuse screen. First, we generated a regular square spot pattern (reference pattern) without a lens to test, and then we generated two spot patterns in two different axial positions when the lens being tested refracts the rays. By selecting two sets of four rays of each spot pattern, we were able to measure the difference of the longitudinal (primary) spherical aberration in two positions. With this difference we were able to improve the calculation of the effective focal length. To determine the method's precision, we first simulated the relative error in the effective focal length considering the error in the measurement of the ray heights. Then we determined the experimental relative error by means of the standard deviation of the focal lengths obtained for each spot (in the image of reference and for the images at the two different locations) for both sets of four spots. The experimental results agree very well with the simulation. The error analysis allows us to establish under what conditions it is possible to obtain relative errors of less than 1% in the effective focal length. PMID:23938404

Mejía, Yobani

2013-08-10

23

4-bit digital liquid lens for variable focal length  

Microsoft Academic Search

We present 4-bit digital liquid lens for variable focal length using the binary control of four bit actuators (b4, b3, b2, and b1 actuators). The input volume into the lens is precisely controlled in 24 levels depending on the binary control of the bit actuators such as digital actuation mode (b4b3b2b1). Compared to previous analog liquid lens, it precisely control

Dong Woo Lee; Young-Ho Cho

2009-01-01

24

A 4 bit digital liquid lens for variable focal length  

Microsoft Academic Search

We present a 4 bit digital liquid lens for variable focal length using a 4 bit actuator (b1, b2, b3 and b4 bit actuators). The 4 bit actuator, where 1, 2, 4 and 8 unit pneumatic actuators are serially connected with binary-combination, pushes a discrete fluidic volume into the lens in 24 different levels. Thus, the 4 bit digital actuation

Dong Woo Lee; Young-Ho Cho

2010-01-01

25

Focal Length Controllable Ultrasonic Array Transducer with Adjustable Curvature  

NASA Astrophysics Data System (ADS)

In the underwater imaging field, the control of the focal length of a transducer is very useful. As one of the control methods, we suggested an ultrasonic array transducer with adjustable curvature by using air pressure. The curvature of the transducer was investigated according to the air pressure level in the back space of the transducer. Concave-, planar-, and convex-type transducers were obtained with different air pressure levels. The acoustic fields of the transducer were measured for different shapes of the radiation surface.

Kim, Jungsoon; Kim, Moojoon; Ha, Kanglyel

2012-07-01

26

Optical interconnections to focal plane arrays  

SciTech Connect

The authors have successfully demonstrated an optical data interconnection from the output of a focal plane array to the downstream data acquisition electronics. The demonstrated approach included a continuous wave laser beam directed at a multiple quantum well reflectance modulator connected to the focal plane array analog output. The output waveform from the optical interconnect was observed on an oscilloscope to be a replica of the input signal. They fed the output of the optical data link to the same data acquisition system used to characterize focal plane array performance. Measurements of the signal to noise ratio at the input and output of the optical interconnection showed that the signal to noise ratio was reduced by a factor of 10 or more. Analysis of the noise and link gain showed that the primary contributors to the additional noise were laser intensity noise and photodetector receiver noise. Subsequent efforts should be able to reduce these noise sources considerably and should result in substantially improved signal to noise performance. They also observed significant photocurrent generation in the reflectance modulator that imposes a current load on the focal plane array output amplifier. This current loading is an issue with the demonstrated approach because it tends to negate the power saving feature of the reflectance modulator interconnection concept.

Rienstra, J.L.; Hinckley, M.K.

2000-11-01

27

High speed multi focal plane optical system  

NASA Technical Reports Server (NTRS)

An apparatus for eliminating beamsplitter generated optical aberrations in a pupil concentric optical system providing a plurality of spatially separated images on different focal planes or surfaces is presented. The system employs a buried surface beamsplitter having spherically curved entrance and exit faces which are concentric to a system aperture stop with the entrance face being located in the path of a converging light beam directed there from an image forming objective element which is also concentric to the aperture stop.

Minott, P. O. (inventor)

1983-01-01

28

Effects of environment factors on imaging performance of long focal length space camera  

NASA Astrophysics Data System (ADS)

In course of developing, testing, launching and working in orbit, Space camera has to undergo the shock of external loads and changing environment. The optical performance of a long focal length space camera is largely determined by external mechanical loads and ambient temperature. The performance of the camera is a result of the interaction between environment factors. The performance of the optical system should be making an accurate forecast when a modern optical instrument is designed. In this paper, the research methods are reviewed firstly. Then the related technologies are described. The analysis methods of environment temperature and structural characteristics effecting space camera imaging performance are also discussed.

Guo, Quanfeng; Jin, Guang; Dong, Jihong; Li, Wei; Li, Yanchun; Wang, Haiping; Wang, Kejun; Zhao, Weiguo

2012-10-01

29

Focal length stabilization of a tunable lens integrated focus shifting unit  

NASA Astrophysics Data System (ADS)

A focus shifting unit integrated with a tunable lens allows for rapid response times, high accuracy, small footprint and simple controllability without the need for any translational mechanics. The focus shifting unit is designed for laser material microprocessing applications where tolerances of a few micrometers are required. However, the optical fluid inside the tunable lens can be severely altered by long term thermal influences from the environment and high powered laser beams. Utilizing the working principles of a cylinder lens, a discrete proportional-integral-derivative controller with an anti-reset windup is simulated and designed for offline regulation of the focal length of the tunable lens. This allows for integration into a three-dimensional scanhead system to reliably deflect the focused laser spot at the workpiece level over long periods of time, i.e. > 8 hours. Deviation of the focal length of the tunable lens is identified by the cylinder lens through ellipticity of a probe laser beam. The focal length is subsequently corrected by altering the input current into the tunable lens by means of the control system which is based on numerical methods. The thermal behavior of the tunable lens, system identification and synthesis of the controller, design of the focus shifting optical system and validation of the controller are studied.

Eberle, Gregory; Boesser, Benjamin; Wegener, Konrad

2014-03-01

30

Analysis of difference in orientations and focal lengths of two arbitrary perspective viewing cameras  

NASA Astrophysics Data System (ADS)

For stereo imaging, it is a general practice to use two cameras of same focal lengths, with their viewing axis normal to the line joining the camera centres. This paper analyses the result of difference in orientations and focal lengths of two arbitrary prespective viewing cameras, by deriving the epipolar lines and its correspoinding equations. This enables one to find the correspondence search space in terms of focal length accuracies as well as camera orientation parameteres. Relevant numerically simulated results are also given.

Ramachandran, Aishwarya; Balasubramanian, R.; Swaminathan, K.; Das, Sukhendu

2007-01-01

31

The Modernization of a Long-Focal Length Fringe-Type Laser Velocimeter  

NASA Technical Reports Server (NTRS)

A long-focal length laser velocimeter constructed in the early 1980's was upgraded using current technology to improve usability, reliability and future serviceability. The original, free-space optics were replaced with a state-of-the-art fiber-optic subsystem which allowed most of the optics, including the laser, to be remote from the harsh tunnel environment. General purpose high-speed digitizers were incorporated in a standard modular data acquisition system, along with custom signal processing software executed on a desktop computer, served as the replacement for the signal processors. The resulting system increased optical sensitivity with real-time signal/data processing that produced measurement precisions exceeding those of the original system. Monte Carlo simulations, along with laboratory and wind tunnel investigations were used to determine system characteristics and measurement precision.

Meyers, James F.; Lee, Joseph W.; Cavone, Angelo A.; Fletcher, Mark T.

2012-01-01

32

Actual focal length of a symmetric biconvex microlens and its application in determining the transmitted beam waist position.  

PubMed

The actual focal length of a three-dimensional continuous profile symmetric biconvex microlens with normal monochromatic plane wave illumination is theoretically determined using a full-field separation of variables method in the oblate spheroidal coordinate system. The investigations are performed for microlenses of 5, 10, and 20 wavelength diameters by calculating the electromagnetic field distributions inside of and adjacent to the microlenses. The importance and potential application of the microlens actual focal length in the design of microlens optical systems are demonstrated by showing that for normal monochromatic TEM00 mode Gaussian beam illumination, the transmitted beam waist position through a single microlens, calculated using Self's beam waist position transformation formula [Appl. Opt.22, 658 (1983)] with the microlens actual focal length, closely matches the exact value given by the separation of variables method. PMID:20962947

Wang, Jian; Barton, John P

2010-10-20

33

Aberrations in saw-tooth refractive lenses in short focal length x-ray focusing  

NASA Astrophysics Data System (ADS)

Saw-tooth refractive lenses (SRL) provide a comparatively attractive option for X-ray focusing for various reasons, including their simple, continuous tunability in energy and focal length. Optimal focusing of a conventional SRL at short focal lengths is limited by the SRL's length in relation to the focal length. Three approaches to overcome this limitation are described. Analytical solutions verified with ray-tracing are presented. These are bending, variation of the saw-tooth tip angles, and variation of the period.

Antimonov, Mikhail A.; Khounsary, Ali M.; Shastri, Sarvjit D.

2013-10-01

34

Dynamic Opto-VLSI lens and lens-let generation with programmable focal length  

Microsoft Academic Search

In this paper we present and demonstrate a dynamic lens and lens array generation method with programmable focal length based on an Opto-VLSI processor. The Opto-VLSI is driven by computer generated algorithm to generate a discrete Fresnel lens phase hologram. By optimizing the phase hologram, lenses and lens arrays of different focal lengths ranging from 300mm to infinity can be

Zhenglin Wang; Kamal Alameh; Rong Zheng; Salem Adherom

2005-01-01

35

Focal length measurement of microlens array for Shack-Hartmann wavefront sensor using interferometer  

NASA Astrophysics Data System (ADS)

We have proposed a method to determine the focal length of microlens array (MLA) based on the measurement of transverse displacement of image spot in the focal plane for a change of angle of incidence of plane wavefront. An existing interferometer test setup, meant for the surface figure measurement of MLA substrate, along with a charge-coupled device (CCD) is used for this purpose. The interferometer generates as well as measures the angle of incidence of plane wavefront at the MLA, and the transverse displacement of the image spot is determined from images recorded with the CCD. We have also discussed the theory of estimation of the focal length of MLA with spherical wavefront. Error analysis is carried out for both methods and is compared. The proposed plane wavefront method is experimentally demonstrated with an off-the-shelf MLA, and the measured focal length is within 1% of catalogue value.

Kumar, M. Senthil; Narayanamurthy, C. S.; Kumar, A. S. Kiran

2013-12-01

36

Microlenses focal length measurement using Z-scan and parallel moiré deflectometry  

NASA Astrophysics Data System (ADS)

In this paper, a simple and accurate method based on Z-scan and parallel moiré deflectometry for measuring the focal length of microlenses is reported. A laser beam is focused by one lens and is re-collimated by another lens, and then strikes a parallel moiré deflectometer. In the presence of a microlens near the focal point of the first lens, the radius of curvature of the beam is changed; the parallel moiré fringes are formed only due to the beam divergence or convergence. The focal length of the microlens is obtained from the moiré fringe period graph without the need to know the position of the principal planes. This method is simple, more reliable, and completely automated. The implementation of the method is straightforward. Since a focused laser beam and Z-scan in free space are used, it can be employed for determining small focal lengths of small size microlenses without serious limitation on their size.

Rasouli, Saifollah; Rajabi, Y.; Sarabi, H.

2013-12-01

37

Simplified model of an O-ring-driven liquid-filled lens for calculating focal length  

NASA Astrophysics Data System (ADS)

The purpose of this study was to develop a mathematical model that could be used to obtain the approximate focal length of O-ring-driven liquid-filled lenses. An O-ring-driven liquid-filled lens is composed of a base plate, a glass-covered liquid reservoir, a pliable membrane, an O-ring, a spring, and three actuators. The movement of the ring changes the focal length or the focus position. In previous studies, the commercial software ANSYS was used to find the membrane deformation and ZEMAX was used to find the focal length. The procedures used in those previous studies are complicated and generally require considerable design work. The proposed mathematical method employs the principle of liquid volume conservation to simplify the calculations that approximate the focal length of the lens. The result is confirmed on ZEMAX to ensure that the method is practicable. Consequently, focal lengths of lenses with different ring thicknesses, radii, and squeezing depths to contact the membrane can be calculated immediately.

Lin, Chih-Wei; Shaw, Dein

2009-07-01

38

Focal length measurement of a varifocal liquid lens with capacitance detection  

NASA Astrophysics Data System (ADS)

This paper reports on a detailed deformation model of varifocal liquid lenses fabricated by Parylene-on-liquid-deposition (POLD), which can be applied to measure and adjust the focal length of such lenses without using extra sensors or sensing mechanisms. The lens was fabricated by encapsulating a liquid between a transparent electrode and a polymer film that was covered with a metal electrode. When voltage is applied to the two electrodes, the lens deforms due to the electrostatic force, and its focal length and the capacitance between the two electrodes change simultaneously. This characteristic enables the focal length of the lens to be adjusted and detected by measuring the capacitance change. The focal length of the fabricated varifocal liquid lens changed from 153.6 to 82.6 mm by applying 150-V. The focal length change of the liquid lens was calculated from the change in its capacitance. Finally, to confirm the efficiency of this varifocal liquid lens, we fabricated a confocal distance sensor using the lens for laser scanning and demonstrated that this system can be used to measure distances of 94-140 mm with an average error of 0.83 mm and a standard deviation of 0.77 mm.

Noda, Kentaro; Binh-Khiem, Nguyen; Takei, Yusuke; Takahata, Tomoyuki; Matsumoto, Kiyoshi; Shimoyama, Isao

2014-04-01

39

Meeting the Optical Requirements of Large Focal-Plane Arrays  

Microsoft Academic Search

Technological advances will allow the placement of many Terahertz detectors at the focal plane of a single telescope. For a telescope of a given diameter and wavelength of operation, there is a limit to the number of usable detectors imposed by diffraction and optical aberrations. These effects can be ameliorated through an optical design where the magnification of the telescope's

Antony A. Stark

2003-01-01

40

Angular spectrum calculations for arbitrary focal length with a scaled convolution.  

PubMed

Nyquist sampling theorem in an image calculation with angular spectrum method restricts a propagation distance and a focal length of a lens. In order to avoid these restrictions, we studied suitable expressions for the image computations depending on their conditions. Additionally, a lateral scale in an observation plane can be magnified freely by using a scaled convolution in each expression. PMID:21934791

Odate, Satoru; Koike, Chiaki; Toba, Hidemitsu; Koike, Tetsuya; Sugaya, Ayako; Sugisaki, Katsumi; Otaki, Katsura; Uchikawa, Kiyoshi

2011-07-18

41

Reconstruction of Linearly Parameterized Models from Single Images with a Camera of Unknown Focal Length  

Microsoft Academic Search

This paper deals with the problem of recovering thedimensions of an object and its pose from a single imageacquired with a camera of unknown focal length. Itis assumed that the object in question can bemodeledas a polyhedron where the coordinates of the verticescan be expressed as a linear function of a dimensionvector, #. The reconstruction program takes as inputa set

David Jelinek; Camillo J. Taylor

1999-01-01

42

Reconstruction of Linearly Parameterized Models from Single Images with a Camera of Unknown Focal Length  

Microsoft Academic Search

Abstract?his paper deals with the problem of recovering the dimensions of an object and its pose from a single image acquired with a camera of unknown focal length. It is assumed that the object in question can be modeled as a polyhedron where the coordinates of the vertices can be expressed as a linear function of a dimension vector, $\\\\lambda$.

David Jelinek; Camillo J. Taylor

2001-01-01

43

Information Theoretic Focal Length Selection for Real-Time Active 3-D Object Tracking  

Microsoft Academic Search

Active object tracking, for example, in surveillance tasks, becomes more and more important these days. Besides the tracking algorithms themselves methodologies have to be developed for reasonable active control of the degrees of freedom of all involved cameras. In this paper we present an information theoretic ap- proach that allows the optimal selection of the focal lengths of two cameras

Joachim Denzler; Matthias Zobel; Heinrich Niemann

2003-01-01

44

The testing of heliograph mirrors and the measurement of mirrors of long focal length  

Microsoft Academic Search

The method of testing the general surface consists in observing the reflection from the mirror of a system of squares on the test board, the magnification given by the mirror being utilised to determine the curvature. The method of examination is applicable to the rapid measurement of mirrors of long focal length, especially of those forms silvered on the back,

Wm Shackleton

1921-01-01

45

Multi-focal optical-resolution photoacoustic microscopy in vivo  

PubMed Central

Although ultrasound arrays were exploited in photoacoustic imaging to improve imaging speed, ultrasound-array-based optical-resolution photoacoustic microscopy (OR-PAM) has never been achieved previously. Here we present our development of multi-focal OR-PAM using a microlens array for optical illumination and an ultrasound array for photoacoustic detection. Our system is capable of imaging hemoglobin concentration and oxygenation in individual microvessels in vivo at high speed. Compared with a single focus, multiple foci reduce the scanning load and increase the imaging speed significantly. The current multi-focal system can acquire 1000 × 500 × 200 voxels at ~10-?m lateral resolution within 4 min.

Song, Liang; Maslov, Konstantin; Wang, Lihong V.

2011-01-01

46

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

47

Shack-Hartmann wavefront sensor with high sensitivity by using long focal length microlens array  

NASA Astrophysics Data System (ADS)

The performance of Shack-Hartmann wavefront sensor (SHWFS) is mainly described by the accuracy, spatial resolution, dynamic range, and sensitivity of the measurement. These factors are particularly affected by the design of the microlens array (MLA). In order to provide a large dynamic range of wavefront measurement, most of the conventional and commercial SHWFS implemented a short focal length lenslet array, which means that the measurement sensitivity is being sacrificed and the accuracy of the wavefront sensor will be degraded. However, it is also critical to detect very small displacement of SHWFS spot in order to reconstruct it into a fine wavefront variation. We fabricated long focal length MLA with various structure arrangement by thermal reflow process with Polydimethysiloxane (PDMS) cover on the glass substrate and implemented them on the image system. A longer focal length will provide high sensitivity in determining the average slope across each lenslet under a given wavefront, and the spatial resolution of the wavefront sensor is increased by the number of lenslets across the detector. The experimental setup consists of the fabricated 245 ?m diameter MLA which provides a 5.2 mm long focal distance and is paired with the CMOS as the detector. The observable smallest sensitivity is around wavelength/20 (?=630nm).

Lin, Vinna; Wei, Hsiang-Chun; Su, Guo-Dung J.

2011-09-01

48

Extended algorithm for the design of diffractive optical elements around the focal plane  

Microsoft Academic Search

We present a multiplane algorithm for three-dimensional uniform illumination. The large-diameter diffractive optical element simulated by this algorithm homogeneously concentrates more than 86.5% of the incident energy into a 200 mum length of columnar space around the focal plane. The intensity profile in the whole space is nearly flattop, and the beam's quality measured by the root mean square is

Rong Wu; Fang-Jie Shu; Wei Zhang; Xiao-Bo Zhang; Yong-Ping Li

2007-01-01

49

Focal length measurement of microlens-array by the clarity function of digital image  

NASA Astrophysics Data System (ADS)

In this paper, a method for the focal length measurement of Microlens-array (MLA) is introduced. The measuring setup is composed by monochromatic, condenser, collimator, MLA, microscope and CCD sensor. An experiment was performed using a MLA whose focal length is about 8 mm and a GUI based on Matlab software was developed to analyze the image gathered at the vertex and the focus by the clarity of digital image processing technology. The measuring uncertainty of this method is about 0.8% and this method introduced in this paper can finish tens of microlens array measurement at a single shot. Compared with traditional technology for MLA measuring, this method not only has a preferable precision but also super efficiency.

Zhu, Xianchang; Wu, Fan; Cao, Xuedong; Wu, Shibin; Zhang, Peng; Jing, Hongwei

2012-10-01

50

Multiple-Path-Length Optical Absorbance Cell  

NASA Technical Reports Server (NTRS)

An optical absorbance cell that offers a selection of multiple optical path lengths has been developed as part of a portable spectrometric instrument that measures absorption spectra of small samples of water and that costs less than does a conventional, non-portable laboratory spectrometer. The instrument is intended, more specifically, for use in studying colored dissolved organic matter (CDOM) in seawater, especially in coastal regions. Accurate characterization of CDOM is necessary for building bio-optical mathematical models of seawater. The multiple path lengths of the absorption cell afford a wide range of sensitivity needed for measuring the optical absorbances associated with the wide range of concentrations of CDOM observed in nature. The instrument operates in the wavelength range of 370 to 725 nm. The major subsystems of the instrument (see figure) include a color-balanced light source; the absorption cell; a peristaltic pump; a high-precision, low-noise fiber optic spectrometer; and a laptop or other personal computer. A fiber-optic cable transmits light from the source to the absorption cell. Other optical fibers transmit light from the absorption cell to the spectrometer,

2001-01-01

51

Hard X-ray microbeam lithography using a Fresnel zone plate with a long focal length.  

PubMed

Focused hard X-ray microbeams for use in X-ray nanolithography have been investigated. A 7.5?keV X-ray beam generated at an undulator was focused to about 3?µm using a Fresnel zone plate fabricated on silicon. The focused X-ray beam retains a high degree of collimation owing to the long focal length of the zone plate, which greatly facilitates hard X-ray nanoscale lithography. The focused X-ray microbeam was successfully utilized to fabricate patterns with features as small as 100?nm on a photoresist. PMID:21335899

Lee, S Y; Cho, I H; Kim, J M; Kang, H C; Noh, D Y

2011-03-01

52

Special lenslet array with long focal length range for Shack-Hartmann Wavefront Sensor  

NASA Astrophysics Data System (ADS)

Since its emergence in the early 1970s, Shack-Hartmann Wavefront Sensing technology has been investigated and explored world-widely by the researchers and engineers. However, there are few papers or reports to study the system performance and key factors to affect the performance of a Shack-Hartmann Wavefront Sensor (SHWS), in this paper, through experimental study of the system stability of a SHWS, it is found that the image sensor and detector, normally a CCD, should be placed exactly at the focal plane of the lenslet array, otherwise it will bring in significant wavefront measurement error. In order to improve the system performance, a special lenslet array with long focal range is designed, and it is functioned by a spatial light modulator for sampling wavefront in a SHWS. Diffractive lenses with long focal length range can provide pseudo-nondiffracting beams, and a long range of focusing plane. The performances and effects of the modified SHWS with such a special lenslet array generated by a programmable SLM, are investigated, and the experimental results show that the system stability and measurement repeatability are not sensitive to the sensing distance, and can keep at a good level in a long range.

Zhao, L. P.; Bai, N.; Li, X.; Fang, Z. P.; Hein, A. A.; Zhong, Z. W.

2007-06-01

53

Materials for intraocular lenses enabling photo-controlled tuning of focal length in vivo  

NASA Astrophysics Data System (ADS)

Typical postoperative complications in cataract surgery are that refractive power and curvature of the implanted intraocular lens (IOL) do not have optimum values, requiring the patient to wear viewing aids. This is mainly because biometric data relevant for calculation of the IOL's shape cannot be determined with the required precision. Hence, there is a need for methods to tune the focal length postoperatively in a non-invasive manner. We have developed polymers where we can induce a change in refractive index by linking or cleaving bonds between a su.ciently large number of side groups of the polymer main chain in a photoinduced cycloaddition or cycloreversion reaction, respectively. These photoreactions lead to a change in refractive index great enough to be interesting for the concept of in vivo tunable IOL's. The photochemical reaction can be triggered by a two-photon process (TPA) using a pulsed laser system, i.e. the energy required for bond breaking is provided by two photons in the visible range. This is important because light in the UV cannot induce undesired changes of the refractive index owing to the strong UV-absorption of the cornea. Undesired changes due to light in the visible range of the spectrum are unlikely to happen because photon density of sun light is much too low for TPA. Due to the excellent spatial resolution that can be achieved with two-photon processes one cannot only modify the refractive index of the entire lens but also selectively in well defined areas enabling to correct for aberrations such as astigmatism. Here, we present new polymers that do not only exhibit a photo induced change of refractive index great enough to induce a change of focal length of more than two diopters in a standard IOL. These new polymers have also significantly improved material properties with respect to the fabrication of the IOL and the TPA-sensitivities and the light energy required to induce the refractive index change.

Träger, Jens; Heinzer, Jasmin; Kim, Hee-Cheol; Hampp, Norbert

2007-06-01

54

Optical Arc-Length Sensor For TIG Welding  

NASA Technical Reports Server (NTRS)

Proposed subsystem of tungsten/inert-gas (TIG) welding system measures length of welding arc optically. Viewed by video camera, in one of three alternative optical configurations. Length of arc measured instead of inferred from voltage.

Smith, Matthew A.

1990-01-01

55

Modeling of a Variable Focal Length Flat Lens Using Left Handed Metamaterials  

NASA Technical Reports Server (NTRS)

Left Handed Metamaterials (LHM) were originally purposed by Victor Veselago in1968. These substances would allow a flat structure to focus electromagnetic (EM) waves because they have a negative index of refraction. A similar structure made from conventional materials, those with a positive index of refraction, would disperse the waves. But until recently, these structures have been purely theoretical because substances with both a negative permittivity and negative permeability, material properties necessary for a negative index of refraction, do not naturally exist, Recent developments have produced a structure composed of an array of thin wires and split ring resonators that shows a negative index of refraction. area smaller than a square wavelength. How small the area is can be determined by how perfectly the lens is polished and how pure the substance is that composes the lens. These lenses must also be curved for focusing to occur. The focal length is determined by the curvature of the lens and the material. On the other hand, a flat structure made from LHM would focus light because of the effect of a negative index of refraction in Snell s law. The focal length could also be varied by simply adjusting the distance of the lens from the source of radiation. This could create many devices that are adjustable to different situations in fields such as biomedical imaging and communication. the software package XFDTD which solves Maxwell s equations in the frequency domain as well as the time domain. The program used Drude models of materials to simulate the effect of negative permittivity and negative permeability. Because of this, a LHM can be simulated as a solid block of material instead of an array of wires and split ring resonators. After a flat lens is formed, I am to examine the focusing effect of the lens and determine if a higher resolution flat lens can be developed. Traditional lenses made from conventional materials cannot focus an EM wave onto an My goal was to model LHMs and create a flat lens from them. This was to be done using

Reinert, Jason

2004-01-01

56

Influence of the focal length of the laser beam focusing lens on MPI yield  

NASA Astrophysics Data System (ADS)

For a multiphoton ionization (MPI) process which follows an nth-order laser power law ( n ? 2), the ionization yield at any given value of the laser power depends upon the focal length, f, of the the focusing lens. For a spherical lens it is shown that, for any fixed laser power, the MPI intensity is proportional to f4-2 n. Thus it is possible to determine the power law index, n, from the slope, s, of a log-log plot of the ion signal versus f (at constant laser power) via the equation n = 2 - s/2. Confirmatory experiments have been carried out using a MPI time-of-flight mass spectrometer with two series of laser beam focusing lenses, with f in the range 17-50 cm. Results are presented for the MPI of triethylenediamine (DABCO) at 532 nm (a 2 + 2 REMPI process), for Hg at 553.88 nm (a 2 + 3 REMPI), Hg at 532 nm (non-resonant, n = 5), and Hg at 280.39 nm (a 2 + 1 REMPI). The f4-2 n relationship is independent of the laser beam profile (uniform, gaussian or annular). The importance for MPI of coherence of the laser radiation is demonstrated.

Gandhi, Suketu R.; Bernstein, Richard B.

1986-06-01

57

Measuring a laser focal spot on a large intensity range: effect of optical component laser damages on the focal spot  

NASA Astrophysics Data System (ADS)

LIL and LMJ are two French high power lasers dedicated to fusion and plasma experiments. Mastering the characteristics of the focal spots focused on the targets during the experiments is very important. In order to analyze the focal spots in its high power lasers, the CEA has developed an independent set-up that enables to measure energy spatial profiles over a 5 decade dynamic range by the means of several acquisitions taken at different power levels. The different data sets are then stitched to obtain a high dynamic picture of the beam. The experiment can also be used as a photometer enabling to measure the energy transmitted by an optical component. We used this set-up to study the effect of different parameters on the energy spatial profile of the focal spots. We have measured the effect of laser damages (on the optical components of the beam) on the energy scattered around the main focal spot. We also demonstrated that the level of this scattered power can be calculated from a near-field picture of the beam or even with pictures of the damaged components taken with an appropriate lighting.

Bouillet, Stéphane; Chico, Sandrine; Le Deroff, Laurent; Razé, Gérard; Courchinoux, Roger

2009-08-01

58

FOCAL PLANE WAVEFRONT SENSING USING RESIDUAL ADAPTIVE OPTICS SPECKLES  

SciTech Connect

Optical imperfections, misalignments, aberrations, and even dust can significantly limit sensitivity in high-contrast imaging systems such as coronagraphs. An upstream deformable mirror (DM) in the pupil can be used to correct or compensate for these flaws, either to enhance the Strehl ratio or suppress the residual coronagraphic halo. Measurement of the phase and amplitude of the starlight halo at the science camera is essential for determining the DM shape that compensates for any non-common-path (NCP) wavefront errors. Using DM displacement ripples to create a series of probe and anti-halo speckles in the focal plane has been proposed for space-based coronagraphs and successfully demonstrated in the lab. We present the theory and first on-sky demonstration of a technique to measure the complex halo using the rapidly changing residual atmospheric speckles at the 6.5 m MMT telescope using the Clio mid-IR camera. The AO system's wavefront sensor measurements are used to estimate the residual wavefront, allowing us to approximately compute the rapidly evolving phase and amplitude of speckle halo. When combined with relatively short, synchronized science camera images, the complex speckle estimates can be used to interferometrically analyze the images, leading to an estimate of the static diffraction halo with NCP effects included. In an operational system, this information could be collected continuously and used to iteratively correct quasi-static NCP errors or suppress imperfect coronagraphic halos.

Codona, Johanan L.; Kenworthy, Matthew, E-mail: jlcodona@gmail.com [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)

2013-04-20

59

Focal Plane Wavefront Sensing Using Residual Adaptive Optics Speckles  

NASA Astrophysics Data System (ADS)

Optical imperfections, misalignments, aberrations, and even dust can significantly limit sensitivity in high-contrast imaging systems such as coronagraphs. An upstream deformable mirror (DM) in the pupil can be used to correct or compensate for these flaws, either to enhance the Strehl ratio or suppress the residual coronagraphic halo. Measurement of the phase and amplitude of the starlight halo at the science camera is essential for determining the DM shape that compensates for any non-common-path (NCP) wavefront errors. Using DM displacement ripples to create a series of probe and anti-halo speckles in the focal plane has been proposed for space-based coronagraphs and successfully demonstrated in the lab. We present the theory and first on-sky demonstration of a technique to measure the complex halo using the rapidly changing residual atmospheric speckles at the 6.5 m MMT telescope using the Clio mid-IR camera. The AO system's wavefront sensor measurements are used to estimate the residual wavefront, allowing us to approximately compute the rapidly evolving phase and amplitude of speckle halo. When combined with relatively short, synchronized science camera images, the complex speckle estimates can be used to interferometrically analyze the images, leading to an estimate of the static diffraction halo with NCP effects included. In an operational system, this information could be collected continuously and used to iteratively correct quasi-static NCP errors or suppress imperfect coronagraphic halos.

Codona, Johanan L.; Kenworthy, Matthew

2013-04-01

60

Optimizing the Elemental Sensitivity and Focal Spot Size of a Monolithic Polycapillary Optic Using Micro-X-Ray Fluorescence  

SciTech Connect

A commercial micro-X-ray fluorescence (MXRF) instrument with an aperture X-ray guide was used to compare elemental sensitivities and focal spot sizes with those obtained by focusing the source with a monolithic polycapillary optic retrofitted into the system. The capillary provided an intensity gain of 125 at 4 keV vs. using a pinhole beam collimator; however, this gain advantage declined with increasing analyte line energy as a result of the capillary being designed shorter than its optimal length to fit into the commercial instrument. A minimum capillary focal spot FWHM of 36 {micro}m was achieved, whereas the smallest pinhole aperture available of 50 {micro}m in diameter produced a focal spot width of 69 {micro}m FWHM. Hence, better MXRF lateral resolution could be obtained with the capillary with a simultaneous improvement in elemental sensitivity.

Worley, C.; Havrilla, G.; Gao, N.; Xia, Q.-F.

1998-10-01

61

X-ray imaging inside the focal spot of polycapillary optics using the coded aperture concept.  

PubMed

We present a method for x-ray imaging of objects inside the focal spot of polycapillary optics that resolves details smaller than the focal spot dimensions. This method employs coded aperture imaging, in which the micro-structure of polycapillary optics is treated as the coding pattern. Projection of the object is decoded from a magnified x-ray image of the polycapillary structure which is specifically sharpened by the object. Field of view can be extended by scanning the object across the focal spot. PMID:23481750

D?browski, K M; Dul, D T; Korecki, P

2013-02-11

62

Polarization-dependent optical tuning of focal intensity of liquid crystal polymer microlens array  

Microsoft Academic Search

This work demonstrates the feasibility of a microlens array (MLA) with a focal intensity that can be optically tuned by controlling the polarization of incident light. The proposed MLA has a focusing unit based on birefringent liquid crystalline polymer (LCP) and a tuning unit with a photo-alignment layer for controlling the polarization state of incident laser light. The optically variable

S.-Y. Huang; T.-C. Tung; C.-L. Ting; H.-C. Jau; M.-S. Li; H.-K. Hsu; A. Y.-G. Fuh

2011-01-01

63

Focal ratio degradation and transmission in VIRUS-P optical fibers  

NASA Astrophysics Data System (ADS)

We have conducted extensive tests of both transmission and focal ratio degradation (FRD) on two integral field units currently in use on the VIRUS-P integral field spectrograph. VIRUS-P is a prototype for the VIRUS instrument proposed for the Hobby-Eberly Telescope at McDonald Observatory. All tests have been conducted at an input f-ratio of F/3.65 and with an 18% central obscuration in order to simulate optical conditions on the HET. Transmission measurements were conducted with narrow-band interference filters (FWHM: 10 nm) at 10 discrete wavelengths (337 to 600 nm), while FRD tests were made at 365 nm, 400 nm and 600 nm. The influence of wavelength, end immersion, fiber type and length on both FRD and transmission is explored. Most notably, we find no wavelength dependence on FRD down to 365 nm. All fibers tested are within the VIRUS instrument specifications for both FRD and transmission. We present the details of our differential FRD testing method and explain a simple and robust technique of aligning the test bench and optical fiber axes to within +/-0.1 degrees.

Murphy, Jeremy D.; MacQueen, Phillip J.; Hill, Gary J.; Grupp, Frank; Kelz, Andreas; Palunas, Povilas; Roth, Martin; Fry, Alexander

2008-07-01

64

Phase-Length Optical Phase-Locked-Loop Sensor (PLOPS)  

NASA Technical Reports Server (NTRS)

PLOPS system designed to provide high-resolution measurement of change in optical length from optical-system source to any optical reflector, including diffuse reflector. Serves as adjustable optical ruler, providing high resolution in measurements of small and large changes in distance to target. Use is broad and includes most measurement situations requiring information on length, vibration, and their derivatives. Applications include building dynamics, remote sensing of vibrations in such systems as turbine-based machinery, monitoring of structural dynamics, noncontacting sensing of surface contours, measurement of large strains as in earthquake monitoring, measurement of atmospheric dynamics and turbulence, high-resolution sensing of humidity, detection of surface acoustic waves by optical microscopy, and related areas.

Heyman, Joseph S.; Rogawski, Robert S.

1988-01-01

65

A general solution to the P4P problem for camera with unknown focal length  

Microsoft Academic Search

This paper presents a general solution to the determina- tion of the pose of a perspective camera with unknown fo- cal length from images of four 3D reference points. Our problem is a generalization of the P3P and P4P problems previously developed for fully calibrated cameras. Given four 2D-to-3D correspondences, we estimate camera posi- tion, orientation and recover the camera

Martin Bujnak; Zuzana Kukelova; Tomás Pajdla

2008-01-01

66

Advances in on-focal-plane A/D with low-power optical readout  

NASA Astrophysics Data System (ADS)

Development of per pixel analog to digital conversion technology for staring focal plane arrays has resulted in improvements in well capacity, power consumption, linearity and signal to noise performance compared to present analog readout approaches. This new digital approach has also allowed the application of alternative on focal readout approaches. These include passive optical devices for readout as well as current mode switching wired output. Test results and design considerations of a recently completed 128 X 128 staring array are presented. The design was based on MOSAD, Multiplexed OverSample A/D, which places a filtering A/D modulator at each pixel. This readout has been linked on focal plane to passive reflective optical modulators providing high data rate digital outputs as an alternative to wired interconnect. A comparative study of current mode wired switching verses optical mode readout was completed. These results will also be presented. Both the optical readout and focal plane array designs were developed with funding from the U.S. Army Night Vision and Electronic Sensors Directorate.

Mandl, William J.

1998-07-01

67

Optimizing optics for IRST with small fill-factor focal plane arrays  

NASA Astrophysics Data System (ADS)

The relationships between optical point spread function, focal plane array geometries and IRST performance in terms of Pd and FAR were investigated in the past. However, specific design algorithms for extreme cases, such as that of small fill-factor arrays, were not presented to date. In this report we present a new optical design algorithm which optimizes Pd and FAR performance in a specific IRST application. Performance predictions are compared to actual hardware tests.

Tidhar, Gil; Shfaram, Harel

2006-06-01

68

Polarization-dependent optical tuning of focal intensity of liquid crystal polymer microlens array  

NASA Astrophysics Data System (ADS)

This work demonstrates the feasibility of a microlens array (MLA) with a focal intensity that can be optically tuned by controlling the polarization of incident light. The proposed MLA has a focusing unit based on birefringent liquid crystalline polymer (LCP) and a tuning unit with a photo-alignment layer for controlling the polarization state of incident laser light. The optically variable refractive indices of LCP allow a positive or negative MLA to be realized by controlling the polarization of the incident light.

Huang, S.-Y.; Tung, T.-C.; Ting, C.-L.; Jau, H.-C.; Li, M.-S.; Hsu, H.-K.; Fuh, A. Y.-G.

2011-07-01

69

Polarization-dependent optical tuning of focal intensity of liquid crystal polymer microlens array  

Microsoft Academic Search

This work demonstrates the feasibility of a microlens array (MLA) with a focal intensity that can be optically tuned by controlling\\u000a the polarization of incident light. The proposed MLA has a focusing unit based on birefringent liquid crystalline polymer\\u000a (LCP) and a tuning unit with a photo-alignment layer for controlling the polarization state of incident laser light. The optically\\u000a variable

S.-Y. Huang; T.-C. Tung; C.-L. Ting; H.-C. Jau; M.-S. Li; H.-K. Hsu; A. Y.-G. Fuh

2011-01-01

70

The compound microscope: optical tube length or parfocalization?  

NASA Astrophysics Data System (ADS)

In various well-known textbooks for undergraduate students of physics, the compound microscope is described as having a standardized 'optical tube length'. On the other hand, in order to fulfil the parfocalization condition required by the human visual system to understand the relation between what is viewed with and without the microscope, the distance between the object and its image through the objective must remain constant as objectives are interchanged. In this paper, we show that these two requirements are not compatible in microscopes containing a revolver with various objectives and that the 'optical tube length' (which differs from the mechanical tube length) cannot be standardized. Moreover, we consider the Deutsche Industrie Norm (DIN) and the Japanese Industry Standards (JIS) norms employed in the microscope industry for standardization of the object-to-intermediate image distance, the parfocal distance and the mechanical tube length.

Simon, J. M.; Comastri, S. A.

2005-11-01

71

FOCAL: X-ray optics for accurate spectroscopy  

Microsoft Academic Search

A crystal spectrometer has been constructed in the Focusing Compensated Asymmetric Laue geometry covering the energy range between 30 and 120 keV. We summarize the crystal optics and show the usefulness of the instrument for spectroscopy of stationary and fast moving X-ray sources. Results are reported from several tests employing a 169Yb gamma-ray source and the Lyman radiation of one-electron

H. F. Beyer; Th. Stöhlker; D. Banas; D. Liesen; D. Protic; K. Beckert; P. Beller; J. Bojowald; F. Bosch; E. Förster; B. Franzke; A. Gumberidze; S. Hagmann; J. Hoszowska; P. Indelicato; O. Klepper; H.-J. Kluge; St. König; Chr. Kozhuharov; X. Ma; B. Manil; I. Mohos; A. Orsic-Muthig; F. Nolden; U. Popp; A. Simionovici; D. Sierpowski; U. Spillmann; Z. Stachura; M. Steck; S. Tachenov; M. Trassinelli; A. Warczak; O. Wehrhan; E. Ziegler

2004-01-01

72

Measurement of the Length of an Optical Trap  

NASA Technical Reports Server (NTRS)

NASA Glenn has been involved in developing optical trapping and optical micromanipulation techniques in order to develop a tool that can be used to probe, characterize, and assemble nano and microscale materials to create microscale sensors for harsh flight environments. In order to be able to assemble a sensor or probe candidate sensor material, it is useful to know how far an optical trap can reach; that is, the distance beyond/below the stable trapping point through which an object will be drawn into the optical trap. Typically, to measure the distance over which an optical trap would influence matter in a horizontal (perpendicular to beam propagation) direction, it was common to hold an object in one optical trap, place a second optical trap a known distance away, turn off the first optical trap, and note if the object was moved into the second trap when it was turned on. The disadvantage of this technique is that it only gives information of trap influence distance in horizontal (x y) directions. No information about the distance of the influence of the trap is gained in the direction of propagation of the beam (the z direction). A method was developed to use a time-of-flight technique to determine the length along the propagation direction of an optical trap beam over which an object may be drawn into the optical trap. Test objects (polystyrene microspheres) were held in an optical trap in a water-filled sample chamber and raised to a pre-determined position near the top of the sample chamber. Next, the test objects were released by blocking the optical trap beam. The test objects were allowed to fall through the water for predetermined periods of time, at the end of which the trapping beam was unblocked. It was noted whether or not the test object returned to the optical trap or continued to fall. This determination of the length of an optical trap's influence by this manner assumes that the test object falls through the water in the sample chamber at terminal velocity for the duration of its fall, so that the distance of trap influence can be computed simply by: d = VTt, where d is the trap length (or distance of trap reach), VT is the terminal velocity of the test object, and t is the time interval over which the object is allowed to fall.

Wrbanek, Susan Y.

2010-01-01

73

All-optical, thermo-optical path length modulation based on the vanadium-doped fibers.  

PubMed

This paper presents an all-fiber, fully-optically controlled, optical-path length modulator based on highly absorbing optical fiber. The modulator utilizes a high-power 980 nm pump diode and a short section of vanadium-co-doped single mode fiber that is heated through absorption and a non-radiative relaxation process. The achievable path length modulation range primarily depends on the pump's power and the convective heat-transfer coefficient of the surrounding gas, while the time response primarily depends on the heated fiber's diameter. An absolute optical length change in excess of 500 µm and a time-constant as short as 11 ms, were demonstrated experimentally. The all-fiber design allows for an electrically-passive and remote operation of the modulator. The presented modulator could find use within various fiber-optics systems that require optical (remote) path length control or modulation. PMID:23736401

Matjasec, Ziga; Campelj, Stanislav; Donlagic, Denis

2013-05-20

74

A focal plane processor for continuous-time 1-D optical correlation applications  

Microsoft Academic Search

This paper describes a 1-D Focal Plane Processor incorporating 200 pixels for Continuous-Time Optical Correlation Applications. Each pixel incorporates a 2 mm times 10.9 mum photodiode whose current is scaled, at the pixel level, by 5 independent 3-bit programmable-gain current amplifiers. Correlation patterns, defined as 5 sets of 200 3-bits numbers, are communicated to the chip via a standard I2C

G. Linan-Cembrano; L. Carranza; B. Alexandre; E. Roca; A. Rodriguez-Vazquez

2009-01-01

75

Optimized back-focal-plane interferometry directly measures forces of optically trapped particles.  

PubMed

Back-focal-plane interferometry is used to measure displacements of optically trapped samples with very high spatial and temporal resolution. However, the technique is closely related to a method that measures the rate of change in light momentum. It has long been known that displacements of the interference pattern at the back focal plane may be used to track the optical force directly, provided that a considerable fraction of the light is effectively monitored. Nonetheless, the practical application of this idea has been limited to counter-propagating, low-aperture beams where the accurate momentum measurements are possible. Here, we experimentally show that the connection can be extended to single-beam optical traps. In particular, we show that, in a gradient trap, the calibration product ? · ? (where ? is the trap stiffness and 1/? is the position sensitivity) corresponds to the factor that converts detector signals into momentum changes; this factor is uniquely determined by three construction features of the detection instrument and does not depend, therefore, on the specific conditions of the experiment. Then, we find that force measurements obtained from back-focal-plane displacements are in practice not restricted to a linear relationship with position and hence they can be extended outside that regime. Finally, and more importantly, we show that these properties are still recognizable even when the system is not fully optimized for light collection. These results should enable a more general use of back-focal-plane interferometry whenever the ultimate goal is the measurement of the forces exerted by an optical trap. PMID:22714216

Farré, Arnau; Marsà, Ferran; Montes-Usategui, Mario

2012-05-21

76

On spatial resolution of quasi-optical focal plane antenna array imagers  

NASA Astrophysics Data System (ADS)

The spatial resolution of millimeter wave (MMW), submillimeter wave (SMMW) and infrared (IR) quasi-optical imagers based on the usage of focal plane antenna arrays (FPAA) is limited by several common factors. Analytical expressions for the point spread functions (PSF) of FPAA imagers are derived for both coherent and spatially incoherent imaging. The possibility of developing advanced super-resolution imaging algorithms using PSFs determined to a high accuracy is discussed.

Volkov, Leonid V.; Voronko, Alexander I.; Volkova, Natalie L.

2004-08-01

77

The Focal Plane Package of the Solar Optical telescope on Solar B  

Microsoft Academic Search

The Solar-B satellite will be launched into a full-sun low-earth orbit in the fall of 2006 from Japan's Uchinoura Space center. It includes the 50-cm diameter Solar Optical Telescope with its Focal Plane Package (FPP), for near-UV and visible observations of the photosphere and chromosphere at very high (diffraction limited) angular resolution. The FPP has a Spectro-Polarimeter (SP) for precision

Theodore D. Tarbell

2006-01-01

78

The Focal Plane Package for the Solar Optical Telescope on Solar-B  

Microsoft Academic Search

Solar-B is a space science mission of the Japanese Aerospace Exploration Agency (JAXA) and a NASA Solar Terrestrial Probes mission. It includes the 50-cm aperture Solar Optical Telescope (SOT), with its Focal Plane Package (FPP) designed for high resolution photospheric and chromospheric imaging and spectro-polarimetry. There are also two coronal instruments, the X-Ray Telescope and Extreme-ultraviolet Imaging Spectrometer. Solar-B will

T. D. Tarbell

2005-01-01

79

Focal-Plane Imaging of Crossed Beams in Nonlinear Optics Experiments  

NASA Technical Reports Server (NTRS)

An application of focal-plane imaging that can be used as a real time diagnostic of beam crossing in various optical techniques is reported. We discuss two specific versions and demonstrate the capability of maximizing system performance with an example in a combined dual-pump coherent anti-Stokes Raman scattering interferometric Rayleigh scattering experiment (CARS-IRS). We find that this imaging diagnostic significantly reduces beam alignment time and loss of CARS-IRS signals due to inadvertent misalignments.

Bivolaru, Daniel; Herring, G. C.

2007-01-01

80

Phase Length Optical Phase-Locked-Loop Sensor  

NASA Technical Reports Server (NTRS)

The invention is a device that provides a high resolution measurement of the change in optical phase length from the device optical system source to an optical reflector. The invention consists of a optical phase locked loop that uses a laser beam as a carrier of an intensity modulated energy source. The novelty of the invention appears to lie in the overall combination of elements which provide high resolution without loss of wide dynamic range. The invention does not depend on coherent reflection from a target, and thus can measure targets that do not have special preparation or corner reflectors. The use of carrier modulation achieves high resolution without the problems of high speed pulse duration systems. Thus the invention has the advantages of simplicity, low cost, and small size without sacrificing resolution.

Heyman, Joseph S. (inventor)

1988-01-01

81

Submillisecond measurements of system optical modulation functions in mosaic focal plane arrays  

NASA Technical Reports Server (NTRS)

Measurements of system optical modulation functions (MTF, SWR) may be distorted by time-dependent environmental effects (thermal, vibration, flexure) and by electronics drift. Fast data collection may therefore be advantageous by minimizing drift time. The problem of fast data collection is accentuated when modulation data must be taken on a large number of detectors in a focal plane array. A method has been developed for the generation and storage of knife edge data from focal plane arrays, where data collection time per detector is in the submillisecond range. Once knife edge collects are completed, MTF response is found using conventional convolution techniques. SWR is obtained directly from knife edge response using a computerized simulation algorithm which bypasses use of MTF harmonics. Requirements for detector electronics speed, damping, and dynamic range are considered.

Thurlow, P. E.

1981-01-01

82

Polymers for refractive index change in intraocular lenses: a novel approach for photoinduced tuning of focal length  

NASA Astrophysics Data System (ADS)

Before an intraocular lens (IOL) is implanted during cataract surgery, biometric data of the patient's eye have to be determined to calculate the thickness and shape of the IOL. In particular the postoperative anterior chamber depth is an important parameter to predict the correct shape of the IOL. This value, however, cannot be measured without significant uncertainities. We present a solution to this problem, describe novel polymers suitable for IOLs which refractive indices can be changed non-invasively in a photo-induced process. The focal length can be modified by about 2 D, which is sufficient to achive ideal acuteness of vision for almost all patients with implanted IOLs. The change in refractive index is accomplished by linking or cleaving bonds between a sufficiently large number of side groups of the polymer main chain in a photoinduced cyloaddition or cycloreversion, respectively. The photochemical reaction can also be triggered by a two-photon process (TPA) using a pulsed laser system, i.e. the energy required for bond breaking is provided by two photons in the visible range. Light in the UV as well as the visible range of the spectrum cannot induce undesired changes of the refractive index owing to the strong UV-absorption of the cornea and photon densities much too low for TPA, respectively. Due to the excellent spatial resolution that can be achieved with two-photon processes not only modification of the refractive index of the entire lens but also selectively in well defined areas is possible enabling the correction for aberrations such as astigmatism.

Träger, Jens; Kim, Hee-Cheol; Hampp, Norbert

2006-03-01

83

Water absorption length measurement with the ANTARES optical beacon system  

NASA Astrophysics Data System (ADS)

ANTARES is a neutrino telescope located in the Mediterranean Sea with the aim of detecting high energy neutrinos of extra-terrestrial origin. It consists of a three dimensional array on 12 detection lines of photomultiplier tubes (PMTs) able to detect the Cherenkov light induced by muons produced in the interaction of neutrinos with the surrounding water and seabed. To reach the best angular resolution, good time and positioning calibrations are required. The propagation of Cherenkov photons strongly depends on the optical properties of the sea water, which has an impact on the reconstruction efficiency. The determination of the optical parameters, as the absorption and scattering lengths, is crucial to calculate properly the effective area and the angular resolution of the detector. The ANTARES optical beacon system consists of pulsed and fast, well controlled light sources distributed throughout the detector to carry out in situ the relative time calibration of the detector components. In this contribution we show some results on the sea water optical properties and their stability measured with the optical beacon system.

Yepes-Ramirez, Harold; ANTARES Collaboration

2011-01-01

84

Interferometric Dispersion Measurements on Short Lengths of Monomode Optical Fibre.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. Second and third order dispersion measurements were made on short lengths (~1m) of three types of low birefringence monomode optical fibre using the technique of 'white light' interferometry based upon a Mach Zehnder interferometer. The interferometer output was analysed with a scanning monochromator over the wavelength range 770-910 nm for various optical path length differences. Novel optical and electronic signal processing techniques were developed to improve the stability of the interferometer and hence improve the signal to noise ratio of the measurements. Rigorous analysis of the experimental data using a non linear least squares fitting algorithm combined with statistical tests designed to detect inadequencies in the theoretical functions have resulted in a temporal resolution of 7 times 10 ^{-5}ps/nm in a metre length of fibre. This is equivalent to a second order dispersion resolution of 0.07 ps/nm/km. The third order dispersion resolution was 0.02 ps/nm^2/km. Comparison of the experimental results with the theoretical chromatic dispersion derived from material dispersion, waveguide dispersion and the effect of material dispersion on waveguide dispersion gave excellent agreement. A technique has been developed to measure first order dispersion based on a modified frequency modulated continuous wave (FMCW) radar technique. Novel electronic signal processing was incorporated into the 'white light' interferometric system in order to obtain these measurements. The results were found to be in agreement with those predicted from the physical properties of the test fibres.

Merritt, Paul A.

85

Focal activation of cells by plasmon resonance assisted optical injection of signaling molecules.  

PubMed

Experimental methods for single cell intracellular delivery are essential for probing cell signaling dynamics within complex cellular networks, such as those making up the tumor microenvironment. Here, we show a quantitative and general method of interrogation of signaling pathways. We applied highly focused near-infrared laser light to optically inject gold-coated liposomes encapsulating bioactive molecules into single cells for focal activation of cell signaling. For this demonstration, we encapsulated either inositol trisphosphate (IP3), an endogenous cell signaling second messenger, or adenophostin A (AdA), a potent analogue of IP, within 100 nm gold-coated liposomes, and injected these gold-coated liposomes and their contents into the cytosol of single ovarian carcinoma cells to initiate calcium (Ca(2+)) release from intracellular stores. Upon optical injection of IP3 or AdA at doses above the activation threshold, we observed increases in cytosolic Ca(2+) concentration within the injected cell initiating the propagation of a Ca(2+) wave throughout nearby cells. As confirmed by octanol-induced inhibition, the intercellular Ca(2+) wave traveled via gap junctions. Optical injection of gold-coated liposomes represents a quantitative method of focal activation of signaling cascades of broad interest in biomedical research. PMID:24877558

Orsinger, Gabriel V; Williams, Joshua D; Romanowski, Marek

2014-06-24

86

Optical scattering lengths in large liquid-scintillator neutrino detectors.  

PubMed

For liquid-scintillator neutrino detectors of kiloton scale, the transparency of the organic solvent is of central importance. The present paper reports on laboratory measurements of the optical scattering lengths of the organic solvents phenylxylylethane, linear alkylbenzene (LAB), and dodecane, which are under discussion for next-generation experiments such as SNO+ (Sudbury Neutrino Observatory), HanoHano, or LENA (Low Energy Neutrino Astronomy). Results comprise the wavelength range of 415-440 nm. The contributions from Rayleigh and Mie scattering as well as from absorption/re-emission processes are discussed. Based on the present results, LAB seems to be the preferred solvent for a large-volume detector. PMID:20515130

Wurm, M; von Feilitzsch, F; Göger-Neff, M; Hofmann, M; Lachenmaier, T; Lewke, T; Marrodán Undagoitia, T; Meindl, Q; Möllenberg, R; Oberauer, L; Potzel, W; Tippmann, M; Todor, S; Traunsteiner, C; Winter, J

2010-05-01

87

Optical scattering lengths in large liquid-scintillator neutrino detectors  

NASA Astrophysics Data System (ADS)

For liquid-scintillator neutrino detectors of kiloton scale, the transparency of the organic solvent is of central importance. The present paper reports on laboratory measurements of the optical scattering lengths of the organic solvents phenylxylylethane, linear alkylbenzene (LAB), and dodecane, which are under discussion for next-generation experiments such as SNO+ (Sudbury Neutrino Observatory), HanoHano, or LENA (Low Energy Neutrino Astronomy). Results comprise the wavelength range of 415-440 nm. The contributions from Rayleigh and Mie scattering as well as from absorption/re-emission processes are discussed. Based on the present results, LAB seems to be the preferred solvent for a large-volume detector.

Wurm, M.; von Feilitzsch, F.; Göger-Neff, M.; Hofmann, M.; Lachenmaier, T.; Lewke, T.; Undagoitia, T. Marrodán; Meindl, Q.; Möllenberg, R.; Oberauer, L.; Potzel, W.; Tippmann, M.; Todor, S.; Traunsteiner, C.; Winter, J.

2010-05-01

88

Constructing atom optical elements from periodic potentials of finite length  

NASA Astrophysics Data System (ADS)

The manipulation of the dispersion properties of a Bose-Einstein condensate (BEC) with moving optical lattices has enabled considerable control of atomic matter waves and, more recently, the generation of bright matter wave solitons [1]. Here, we computationally propagate BEC's through periodic optical potentials of finite spatial/temporal lengths. It is seen that to vary the effective mass requires potentials that are relatively strong compared to the transverse waveguide confinement. The role of both the linear and non-linear wave mechanics in practical issues such as loading the atoms into the potentials are explored. We also report on work in progress examining matter waves propagation through a chip-based magnetic lattice [2]. [1] Eiermann, B et.al Phys. Rev. Lett. 92 230401 (2004) [2] G"unther, A et.al Phys. Rev. Lett. 95 170405 (2005)

Bromley, Michael W. J.; Salazar, Oscar O.; Esry, Brett D.

2006-05-01

89

Difference length scheduling for asynchronous optical packet switching  

NASA Astrophysics Data System (ADS)

The average queue delay of optical packet increases when the packets block in the virtual output queue header in the asynchronous optical packet switching. We analyze the character of variable length Internet packet and propose the preemptive short packets priority (PSPP) algorithm for reducing the total packet waiting time in the queue. In the PSPP algorithm, the short packet can preempt the transmission time of the long packet and can be served first. The analysis and the simulation shows the PSPP algorithm can make the average waiting time of the short packet decrease to zero almost and can decrease the total packet average waiting time largely when the traffic load is middle and low. The PSPP can guarantee the low average waiting delay for the real time TCP traffic implementation.

Liu, Huanlin; Chen, Qianbin; Pan, Yingjun

2006-10-01

90

Free space optical communication performance analysis with focal plane based wavefront measurement  

NASA Astrophysics Data System (ADS)

In order to decrease the Bit Error Rate (BER) and increase coupling efficiency of free space optical (FSO) communication system, we compute and compensate the wavefront aberrations of the laser signal with the wavefront measurement method based on the focal plane proposed in this paper. The aberrations of laser signal are calculated based on the two images which are respectively generated from focal plane (PF) channel and the defocused plane (DF) channel. Assuming the On–Off Keying (OOK) modulation is used under the condition of weak turbulence, the fundamental of wavefront measurement method based on focal plane is introduced. By numerical simulation, we analyze the variation trend of coupling efficiency and BER, using the method we proposed to measure and compensate the wavefront aberrations for the FSO communication system. The experiment results show that the wavefront measurement error can reach nearly 0.004 wavelengths, the average coupling efficiency increases from 10.32% to 63.82%, and the average BER of FSO communication system decreases from 10?5 to 10?13.

Liu, Wei; Shi, Wenxiao; Wang, Bin; Yao, Kainan; Lv, Yaowen; Wang, Jihong

2013-11-01

91

Fiber-optic liquid level sensor based on coupling optical path length variation.  

PubMed

The concept for a new and simple fiber-optic liquid level sensor is presented and experimental results are shown to demonstrate the principle. The sensing principle is based on light intensity modulation when rising and falling mode of liquid level causes coupling optical path distance variation between two optical fibers. Near continuous mode of liquid level variation could be monitored with resolution as low as 1 mm can be measured in the length scale of 25 cm. PMID:22667647

Nath, Pabitra; Singh, Hidam Kumarjit; Tiwari, Dhananjay; Basumatry, Tenisen

2012-05-01

92

Clinical and optic coherence tomography findings of focal choroidal excavation in Chinese patients  

PubMed Central

Background To describe the clinical and optical coherence tomography (OCT) features of focal choroidal excavation in Chinese patients. Methods Retrospectively, thirty-seven eyes (in 31 patients) that demonstrated focal choroidal excavation on spectral-domain OCT were collected. Their clinical characteristics and other features were also collected and analyzed. Results In total, 42 focal choroidal excavations were identified in 31 patients, including 25 unilateral and 6 bilateral (37 eyes). The abnormal changes in these eyes with choroidal excavation were more prominent at the outer part of the neuro-retina, the retinal pigment epithelium (RPE) and the choroid. The average transverse diameter and depth of the excavations were 670.8 ?m and 106.9 ?m, respectively. In addition to the conforming and nonconforming types, the excavations could also be classified into 2 types according to their shape: type 1 – small with a sharp, cut-down contour; and type 2 – slightly larger with a gradual edge. The transverse diameter/depth ratio of the two types were significantly different (type1: 4.57?±?1.65, type 2: 10.0?±?5.2; p?=?0.000). Four central serous chorioretinopathy (CSCR) cases were confirmed by fluorescein angiography; in these cases, the retinal detachment was larger than the area of excavation, and the inner segment/outer segment (IS/OS) and external limiting membrane (ELM) were above those of the normal part. Concomitant CNV was also found in another 2 cases. Conclusions Focal choroidal excavation was not uncommon in Chinese patients. The choroid and the RPE at the excavation were impaired or vulnerable to other damage. Additionally, OCT might be useful in the differentiation between nonconforming excavations and ones with CSCR.

2014-01-01

93

CLASSICAL AREAS OF PHENOMENOLOGY: Theoretical analysis and experimental research on thermal focal length of a YVO4\\/Nd:YVO4 composite crystal  

Microsoft Academic Search

This paper investigates the temperature field distribution and thermal focal length within a laser diode array (LDA) end-pumped YVO4\\/Nd:YVO4 rectangular composite crystal. A general expression of the temperature field distribution within the Nd:YVO4 rectangular crystal was obtained by analysing the characteristics of the Nd:YVO4 crystal and solving the Poisson equation with boundary conditions. The temperature field distributions in the Nd:YVO4

Cheng Zhou

2009-01-01

94

Laser Metrology for an Optical-Path-Length Modulator  

NASA Technical Reports Server (NTRS)

Laser gauges have been developed to satisfy requirements specific to monitoring the amplitude of the motion of an optical-path-length modulator that is part of an astronomical interferometer. The modulator includes a corner-cube retroreflector driven by an electromagnetic actuator. During operation of the astronomical interferometer, the electromagnet is excited to produce linear reciprocating motion of the corner-cube retroreflector at an amplitude of 2 to 4 mm at a frequency of 250, 750, or 1,250 Hz. Attached to the corner-cube retroreflector is a small pick-off mirror. To suppress vibrations, a counterweight having a mass equal to that of the corner-cube retroreflector and pick-off mirror is mounted on another electromagnetic actuator that is excited in opposite phase. Each gauge is required to measure the amplitude of the motion of the pick-off mirror, assuming that the motions of the pick-off mirror and the corner-cube retroreflector are identical, so as to measure the amplitude of motion of the corner- cube retroreflector to within an error of the order of picometers at each excitation frequency. Each gauge is a polarization-insensitive heterodyne interferometer that includes matched collimators, beam separators, and photodiodes (see figure). The light needed for operation of the gauge comprises two pairs of laser beams, the beams in each pair being separated by a beat frequency of 80 kHz. The laser beams are generated by an apparatus, denoted the heterodyne plate, that includes stabilized helium-neon lasers, acousto-optical modulators, and associated optical and electronic subsystems. The laser beams are coupled from the heterodyne plate to the collimators via optical fibers.

Gursel, Yekta

2005-01-01

95

Coherent Optical Focal Plane Array Receiver for PPM Signals: Investigation and Applications  

NASA Technical Reports Server (NTRS)

The performance of a coherent optical focal plane array receiver for PPM signals under atmospheric turbulence is investigated and applications of this system are addressed. The experimental demonstration of this project has already been explained in previous publications [1]. This article shows a more exhaustive analysis of the expressions needed to obtain the Bit Error Rate (BER) for the real system under study in the laboratory. Selected experimental results of this system are described and compared with theoretical BER expressions, and array combining gains are presented. Receiver sensitivity in terms of photons per bit (PPB) is examined; BER results are shown as a function of signal to noise ratios, (SNR), as well as a function of photons per symbol, and photons per bit.

Fernandez, Michela Munoz

2006-01-01

96

A superconducting focal plane array for ultraviolet, optical, and near-infrared astrophysics.  

PubMed

Microwave Kinetic Inductance Detectors, or MKIDs, have proven to be a powerful cryogenic detector technology due to their sensitivity and the ease with which they can be multiplexed into large arrays. A MKID is an energy sensor based on a photon-variable superconducting inductance in a lithographed microresonator, and is capable of functioning as a photon detector across the electromagnetic spectrum as well as a particle detector. Here we describe the first successful effort to create a photon-counting, energy-resolving ultraviolet, optical, and near infrared MKID focal plane array. These new Optical Lumped Element (OLE) MKID arrays have significant advantages over semiconductor detectors like charge coupled devices (CCDs). They can count individual photons with essentially no false counts and determine the energy and arrival time of every photon with good quantum efficiency. Their physical pixel size and maximum count rate is well matched with large telescopes. These capabilities enable powerful new astrophysical instruments usable from the ground and space. MKIDs could eventually supplant semiconductor detectors for most astronomical instrumentation, and will be useful for other disciplines such as quantum optics and biological imaging. PMID:22274494

Mazin, Benjamin A; Bumble, Bruce; Meeker, Seth R; O'Brien, Kieran; McHugh, Sean; Langman, Eric

2012-01-16

97

In vivo optical reflectance imaging of spreading depression waves in rat brain with and without focal cerebral ischemia  

Microsoft Academic Search

Spreading depression SD waves occur in focal cerebral ischemia of the brain. Optical reflectance imaging at 550±10-nm wavelength using a charge-coupled device CCD camera, called op- tical intrinsic signal imaging OISI in the neuroscience community, provides high resolution imaging of SD waves based on changes in blood perfusion. We present optical images of SD waves in normal rat brain induced

Shangbin Chen; Zhe Feng; Pengcheng Li; Steven L. Jacques; Shaoqun Zeng; Qingming Luo

2006-01-01

98

4-level run-length limited optical storage on photo-chromic materials  

Microsoft Academic Search

4-Level Run-Length Limited (4L-RLL) optical storage based on photo-chromic materials is firstly investigated in this paper to our knowledge. Unlike binary recording, information in Multi-Level Run-Length Limited (ML-RLL) modulation system is carried in both the amplitude and length of the marks. ML-RLL optical storage can increase the recording density and data transfer rate with no changes to the optical\\/mechanical unit.

Heng Hu; Longfa Pan; Hua Hu; Duanyi Xu

2005-01-01

99

Optical testing by absolute length measurement with wavelength tuning interferometer  

NASA Astrophysics Data System (ADS)

The surface shape and the absolute optical thickness of a fused-silica glass parallel plate were measured by wavelength tuning interferometry. An excess fractions method combined with the Fourier based frequency analysis removed a systematic error. The interference orders of the optical thickness fringes were finally estimated, which resulted in an accuracy of a few nanometers for the optical thickness measurement.

Hibino, Kenichi; Kim, Yangjin; Ito, Makoto

2013-05-01

100

Correlation of Choroidal Thickness and Volume Measurements with Axial Length and Age Using Swept Source Optical Coherence Tomography and Optical Low-Coherence Reflectometry  

PubMed Central

Purpose. To report choroidal thickness and volume in healthy eyes using swept source optical coherence tomography (SS-OCT). Methods. A prospective observational study of 122 patients examined with swept source OCT (DRI-OCT, Topcon, Japan). In each eye, we performed 256 horizontal scans, 12?mm in length and centered on the fovea. We calculated choroidal thickness manually with a built-in caliper and automatically using DRI-OCT mapping software. Choroidal volume was also automatically calculated. We measured axial length with optical low-coherence reflectometry (Lenstar LS 900, Haag-Streit, Switzerland). Results. The choroid has focally increased thickness under the fovea. Choroid was thinnest in the outer nasal quadrant. In stepwise regression analysis, age was estimated as the most significant factor correlating with decreased choroidal thickness (F = 23.146, P < 0.001) followed by axial length (F = 4.902, P = 0.03). Refractive error was not statistically significant (F = 1.16, P = 0.28). Conclusions. SS-OCT is the first commercially available system that can automatically create choroidal thickness and volume maps. Choroidal thickness is increased at the fovea and is thinnest nasally. Age and axial length are critical for the estimation of choroidal thickness and volume. Choroidal measurements derived from SS-OCT images have potential value for objectively documenting disease-related choroidal thickness abnormalities and monitoring progressive changes over time.

Michalewski, Janusz; Nawrocka, Zofia; Bednarski, Maciej; Nawrocki, Jerzy

2014-01-01

101

Determination of charge-carrier diffusion length in the photosensing layer of HgCdTe n-on-p photovoltaic infrared focal plane array detectors  

NASA Astrophysics Data System (ADS)

In the present paper, we propose a method for evaluating the bulk diffusion length of minority charge carriers in the photosensing layer of photovoltaic focal plane array (FPA) photodetectors. The method is based on scanning a strip-shaped illumination spot with one of the detector diodes at a low level of photocurrents jph being registered; such scanning provides data for subsequent analysis of measured spot-scan profiles within a simple diffusion model. The asymptotic behavior of the effective (at jph ? 0) charge-carrier diffusion length ld eff as a function of jph for jph ? 0 inferred from our experimental data proved to be consistent with the behavior of ld eff vs jph as predicted by the model, while the obtained values of the bulk diffusion length of minority carriers (electrons) in the p-HgCdTe film of investigated HgCdTe n-on-p FPA photodetectors were found to be in a good agreement with the previously reported carrier diffusion-length values for HgCdTe.

Vishnyakov, A. V.; Stuchinsky, V. A.; Brunev, D. V.; Zverev, A. V.; Dvoretsky, S. A.

2014-03-01

102

Adaptive optical zoom sensor.  

SciTech Connect

In order to optically vary the magnification of an imaging system, continuous mechanical zoom lenses require multiple optical elements and use fine mechanical motion to precisely adjust the separations between individual or groups of lenses. By incorporating active elements into the optical design, we have designed and demonstrated imaging systems that are capable of variable optical magnification with no macroscopic moving parts. Changing the effective focal length and magnification of an imaging system can be accomplished by adeptly positioning two or more active optics in the optical design and appropriately adjusting the optical power of those elements. In this application, the active optics (e.g. liquid crystal spatial light modulators or deformable mirrors) serve as variable focal-length lenses. Unfortunately, the range over which currently available devices can operate (i.e. their dynamic range) is relatively small. Therefore, the key to this concept is to create large changes in the effective focal length of the system with very small changes in the focal lengths of individual elements by leveraging the optical power of conventional optical elements surrounding the active optics. By appropriately designing the optical system, these variable focal-length lenses can provide the flexibility necessary to change the overall system focal length, and therefore magnification, that is normally accomplished with mechanical motion in conventional zoom lenses.

Sweatt, William C.; Bagwell, Brett E.; Wick, David Victor

2005-11-01

103

Active optical zoom system  

NASA Astrophysics Data System (ADS)

In order to optically vary the magnification of an imaging system, continuous mechanical zoom lenses require multiple optical elements and use fine mechanical motion to precisely adjust the separations between individual or groups of lenses. By incorporating active elements into the optical design, we have designed and demonstrated imaging systems that are capable of variable optical magnification with no macroscopic moving parts. Changing the effective focal length and magnification of an imaging system can be accomplished by adeptly positioning two or more active optics in the optical design and appropriately adjusting the optical power of those elements. In this application, the active optics (e.g. liquid crystal spatial light modulators or deformable mirrors) serve as variable focal-length lenses. Unfortunately, the range over which currently available devices can operate (i.e. their dynamic range) is relatively small. Therefore, the key to this concept is to create large changes in the effective focal length of the system with very small changes in the focal lengths of individual elements by leveraging the optical power of conventional optical elements surrounding the active optics. By appropriately designing the optical system, these variable focal-length lenses can provide the flexibility necessary to change the overall system focal length, and therefore magnification, that is normally accomplished with mechanical motion in conventional zoom lenses.

Wick, David V.; Martinez, Ty; Payne, Don M.; Sweatt, William C.; Restaino, Sergio R.

2005-05-01

104

Fiber optic gyroscope vibration error due to fiber tail length asymmetry based on elastic-optic effect  

NASA Astrophysics Data System (ADS)

In the assembly of fiber optic gyroscope (FOG), the summation of the fiber tail length of waveguide and fiber ring in two directions cannot be exactly equal (i.e., fiber tail length of FOG in two directions is asymmetry). We analyze and calculate the vibration error of FOG due to this fiber tail length asymmetry based on elastic-optic effect. Inertial navigation simulation is performed to show attitude and positioning errors caused by this vibration error, which clearly shows the importance of reducing fiber-tail length asymmetry in high-accuracy applications.

Zhang, Yonggang; Gao, Zhongxing

2012-12-01

105

Dependence of semiconductor laser intermodulation distortions on fiber length and its reduction by optical injection locking  

Microsoft Academic Search

We experimentally investigate the dependence of semiconductor laser intermodulation distortions (IMDs) on fiber transmission length. IMDs in fiber optic link are degraded over transmission through dispersive fiber. We show that IMDs can be reduced and made less dependent on fiber transmission length by using injection-locked DFB and Fabry-Perot (FP) semiconductor lasers

H.-K. Sung; Y.-K. Seo; W.-Y. Choi

2000-01-01

106

A systematic study of focal ratio and effects of optical misalignment for LST  

NASA Technical Reports Server (NTRS)

Possible large space telescope geometries are studied to determine performance and the effects of misalignments. The results are displayed parametrically as a function of relative back focal distance (RBFD). As RBFD increases, a larger high resolution field is obtained, and misalignment effects become less severe.

Wyman, C. L.

1974-01-01

107

Generation of a sub-wavelength focal spot with a long transversally polarized optical needle using a double-ring-shaped azimuthally polarized beam  

NASA Astrophysics Data System (ADS)

Based on the vector diffraction theory, we study the tight focusing performance of a double-ring-shaped azimuthally polarized beam through a high numerical aperture objective using a spiral phase plate or a seven-belt complex filter modulated spiral phase hologram (SCF-SPH). The effect of truncation parameters on the tight focusing is demonstrated. The dependence of various polarizations on the intensity, focal shift and side lobe are also investigated. It is shown that the focal shift can be removed successfully and the side lobe can be reduced effectively by introducing a SCF-SPH into the imaging system. Also, a sub-wavelength focal spot along with a long transversally polarized optical needle is achieved. The polarization evolution of the wavefront near the focal plane is analyzed by calculating the Stokes polarization parameters. It is revealed that the annihilation of the polarization singularity at the beam center makes a bright focal spot possible.

Nie, Zhongquan; Li, Zhongguo; Shi, Guang; Zhang, Xueru; Wang, Yuxiao; Song, Yinglin

2014-08-01

108

High-efficiency high-power diode laser beam shaping and focusing with constant optical-path length equalization  

NASA Astrophysics Data System (ADS)

In this work we report on a novel optical design for beam shaping and focalization of high-power diode laser bars. The goals of our study are: the increase the optical throughput of the beam shaping device with respect to standard solutions and either to enhance the irradiance on a target or to inject the laser beam into a smaller fibre than with respect to beam shaping system based on plane surfaces. The high power diode laser bars pose serious difficulties in their optical handling due to their strong difference between the two transverse axes, which induce a strong astigmatic and asymmetric output radiation. As is well known, the beam quality is very different in the two axes called slow axis and fast axis, and in particular the slow axis is composed by the superposition of several multimodal sources. The beam quality in this axis is very low (its etendue may exceed 2000 mm mrad). On the other hand, the fast axis has a very high beam quality, near diffraction limited, although with very high divergence (30°-50°). The common solution for the application of the laser radiation is a fast axis aspheric micro lens in front of the emitters, in order to achieve its collimation. Typical values of the fast axis collimated beam are 0.7mm and less than 6mrad. However, the so obtained collimated beam is poorly focusable with a standard lens, and a few methods were proposed to overcome the problem. The more relevant solutions include: the stepped mirror technique, the plane parallel mirrors pair, micro prisms array and confocal micro lens array. Each of these techniques is based on the equalization of the beam parameter product by the subdivision of the beam in the slow axis and its reshaping. For all these techniques the efficiency spans from 50% to 70%. The best focalization results allow the coupling in a fibre of 400?m diameter, with NA-0.22. The aim of this work is the design and the realization of a new device, that is considered as target the following aspects: 1) the maximum optical efficiency in the beam shaping process, 2) the optimal equalization of the beam parameter product for the two axes, 3) the use of few optical elements and 4) a very compact size. These goals are addressed by a scheme that splits the collimated beam from the laser diode into different portions while the length of the optical paths of each sub element is kept constant, and by the subsequent use of short focal length aspheric lenses for the focalization of the transformed beam. Each sub-beam is deflected by a couple of plane parallel mirrors, whose normal is directed to equalize the BPP without any mutual shadowing. An optimal solution can be easily envisaged for a laser source of common size of 0.7 x 10 mm. The condition on equal optical path length has the noticeable property of placing the virtual position of the individual portions into which the original beam is split at the same distance with respect to target. Thanks to this, their subsequent focusing is unaffected by the axial displacement of the common solution by the stepped mirrors. In fact, to correct this effect, this latter technique requires the use of a prism pair, involving complexity, size enlargement and higher costs. In this work both an extensive ray tracing and optical analysis is presented as well as the experimental characterization of an experimental model. Moreover, we also report on the technique for the realization of th tilted-face plane mirrors of which is composed our beam shaping device. The scheme of beam shaping here reported can be extended to higher power beam by means of the technique of the beam combination by polarization coupling or that of the optical beam compression. Examples of theses developments are discussed in the paper, and experimental results presented. The most direct applications of the class of optical devices here reported are the high power diode laser direct application in material processing or manufacturing, the coupling into multimode optical fiber of the diode laser radiation as well as the fiber laser end pumping.

Bonora, Stefano; Villoresi, Paolo

2006-04-01

109

Effective optical path length investigation for cubic diffuse cavity as gas absorption cell  

NASA Astrophysics Data System (ADS)

A simple cubic-shaped cavity with a high-diffuse-reflectivity inner coating as a novel gas detection cell was developed. The effective optical path length (EOPL) was evaluated by comparing the oxygen absorption signal in the cavity and in air based on tunable diode laser absorption spectroscopy. The law for a spherical cavity was applied and modified to a cubic cavity as a function of reflectivity ?, port fraction f, and the side length. Single-pass average path length of the cubic cavity was 0.723(7) times the side length. EOPL can be modified conveniently by adjusting the parameters of the cavity.

Yu, Jia; Zheng, Fu; Gao, Qiang; Li, Yinjie; Zhang, Yungang; Zhang, Zhiguo; Wu, Shaohua

2014-07-01

110

Comparison of length measurements provided by a femtosecond optical frequency comb.  

PubMed

This paper presents a comparison of length measurements between the wavelength and the adjacent pulse repetition interval length (APRIL) provided by a femtosecond optical frequency comb. A theoretical estimation of the frequency stability for stabilizing the wavelength and APRIL, the frequency parameters that affect the stability of the APRIL in air, and the ambiguity in the length measurement by the APRIL are investigated. We find that the APRIL can be used as a low-cost measurement for the absolute length over a range of hundreds of meters in laboratory conditions. PMID:24664052

Wei, Dong; Aketagawa, Masato

2014-03-24

111

Optical length change measurement via RF frequency shift analysis of incoherent light source based optoelectronic oscillator.  

PubMed

Radio-frequency (RF) frequency shift of incoherent light source based optoelectronic oscillator (OEO) is employed to measure the optical length change. In the proposed OEO using an incoherent light source, the optical length under test is inserted in the optoelectronic hybrid loop. The frequency shift of RF oscillation modes at the output of the OEO reflects the optical length change, with the change being measured via frequency shift analysis. Two OEO configurations are theoretically designed and experimentally performed, while an amplified spontaneous emission (ASE) source serves as the incoherent light source. A linear relationship between the frequency shift and the optical length change has been confirmed for measurement, and a reconfigurable measurement sensitivity is available by selecting different oscillation modes. Moreover, the use of ASE greatly reduces the complexity and the cost for stabilization control on light source, while the derived results are consistent with that obtained in a laser source based OEO both in the measured optical length changes and the phase noise performance. A sensitivity of -28 KHz/cm, -480 KHz/cm or higher, and a resolution of nano-meter scale are obtained, which can be used to monitor the displacement, the changes in refractive index, temperature. PMID:24921811

Zou, Xihua; Li, Ming; Pan, Wei; Luo, Bin; Yan, Lianshan; Shao, Liyang

2014-05-01

112

System for variable stripe length optical gain measurements in structures containing silicon nanocrystals  

NASA Astrophysics Data System (ADS)

The variable stripe length (VSL) is a convenient method for the measurement of optical gain. However, several inherent experimental constraints such as pump beam non-uniformity, diffraction from the movable cache and sample edges, and gain saturation challenge its proper implementation. A modified VSL configuration, which addresses these constraints, has been developed and implemented for gain measurements in SiO2 structures containing silicon nanocrystals. A microprocessor based acquisition of several control parameters provides reliable and reproducible optical gain measurements.

Koshel, D.; Barba, D.; Martin, F.; Ross, G. G.

2009-06-01

113

PLR analysis of optical packet switch with different packet length distribution  

NASA Astrophysics Data System (ADS)

The paper studies the performance of an all-optical packet switch (OPS) for different packet length. The packet loss ratio, considered the OPS without FDL and with FDL buffer, with different length distribution are analyzed under the Poisson arrival process and a burst super exponential arrival process respectively. The experiment and analysis show that the performance of different length packet is influence by the packet arrival process and the buffer size. When the OPS without buffer, the PLR under bursty traffic yields the higher packet loss ratio (PLR). PLR with Poisson arrival packet is not influenced by the packet length distribution, while with the super exponential traffic, the packet length distribution influences the PLR, and the fixed length packet yields higher PLR compared to the variable length exponential packet and the experiential Internet traffic. When the OPS with buffer, PLR with Poisson arrival packet yields lower than with super exponential packet under the same load, and the experiential length super exponential packet leads to highest PLR, while the fixed length Poisson process packet brings on lowest PLR.

Liu, Huanlin; Chen, Qianbin; Pan, Yingjun

2006-10-01

114

Focal point images of phase-shifted laser beam using femtosecond optical polarigraphy  

NASA Astrophysics Data System (ADS)

Intensity distribution of high intensity femtosecond laser pulse has been measured using time-resolved optical polarigraphy. Ultrashort laser pulses from Ti:sapphire laser propagating in CS2 are studied and compared the difference between gaussian and phaseshifted beams.

Nagamura, Aritsune; Shibata, Hiroki; Toyoda, Koichi

2002-02-01

115

Temperature effects on the optical path length of infrared liquid transmission cells.  

PubMed

Infrared (IR) spectroscopy is widely used for studies of temperature-dependent properties of liquids and solutions, such as thermal denaturation of proteins and other molecules of biological interest. The variation of the spectroscopic signals with temperature can be affected by the changes in the optical path length due to the thermal expansion of the components of the sample cell. In this report we investigate the temperature dependence of the optical path length for a liquid IR sample cell of a design typical for aqueous solution experiments. The path lengths were measured from the interference fringes, both in dry cells and with cells partially filled with water. We found that the optical path length variations are significant, on the order of several percent within the temperature range used (0-87 °C). Several commercially available spacers (Teflon, mylar, and lead) and gaskets (Teflon, lead, silicone rubber, Viton, and neoprene) were tested to find materials with either the smallest or most reproducible effect. Teflon, due to its phase transition (known as the "knee point") near room temperature, leads to abrupt changes in path length when used as either spacer or gasket component. On the other hand, Teflon is preferred for its inertness, while several of the other tested materials, most notably lead, are not practically usable due to adhesion to the cell windows upon heating and contact with the aqueous sample. The combination that yielded the most reproducible results, with minimal complications due to adhesion, was Teflon spacer with neoprene gaskets. The implications of the optical path length changes for the temperature-dependent IR experiments and their possible corrections are discussed. PMID:22054091

Amunson, Krista E; Anderson, Benjamin A; Kubelka, Jan

2011-11-01

116

Optimal length of an electro-optical Q-switch with optical activity crystal La 3Ga 5SiO 14  

Microsoft Academic Search

With the polarization plane gyration and the electro-optic effect existing simultaneously in an optical activity crystal, the theory on interaction of optical activity and electro-optic effect on the arbitrary linearly polarized light propagating through the crystal along the optical axis is studied. The electro-optical Q-switch is designed successfully. With the conclusion of the theory, the optimal length of optical activity

Shaojun Zhang; Zhaobing Tian; Qingpu Wang; Xin Yin; Shichen Li

2007-01-01

117

Influence of temperature on divergence angle of a focal telescope used in laser optical communication.  

PubMed

Divergence angle of antenna is an important parameter in laser optical communication. It determines the power of the receiver terminal. In this paper, the influence of temperature on the divergence angle is discussed. Theoretical analysis and experiment results demonstrate that the relationship between the variance of temperature and of divergence angle is linear. PMID:22714349

Zheng, Guoxian; Zhou, Feng; Liu, Jianfeng; Li, Tuotuo; An, Ning; Zhang, Binglong

2012-06-01

118

Modeling the temporal evolution of an aero-optical aberration with the minimum description length principle.  

PubMed

A method of building a dynamical model for temporal evolution of an aero-optical aberration is presented. Based on the proper orthogonal decomposition (POD) of the optical aberration, the minimum description length (MDL) principle is used to select a dynamical model for the POD coefficients. The MDL principle can balance the model error against model size so as to prevent the model from overfitting. This strategy is validated with the numerical simulation of the aero-optical aberration caused by the supersonic mixing layer, and the model obtained can accurately predict the time evolution of the POD coefficients in short time. The potential application of our method in extending the bandwidth of the adaptive optics system is also discussed. PMID:24875993

Gao, Qiong; Jiang, Zongfu; Yi, Shihe

2014-06-01

119

Numerical Simulation of Refractive-Microlensed HgCdTe Infrared Focal Plane Arrays Operating in Optical Systems  

NASA Astrophysics Data System (ADS)

The optoelectronic performance of the mid-wavelength HgCdTe infrared focal plane array (IRFPA) with refractive microlenses integrated on its CdZnTe substrate has been numerically simulated. A reduced light-distribution model based on scalar Kirchhoff diffraction theory was adopted to reveal the true behavior of IRFPAs operating in an optical system under imaging conditions. The pixel crosstalk obtained and the energy-gathering characteristics demonstrated that the microlenses can delay the rise in crosstalk when the image point shifts toward pixel boundaries, and can restrict the major optical absorption process in any case within a narrow region around the pixel center. The dependence of the microlenses' effects on the system's properties was also analyzed; this showed that intermediate relative aperture and small microlens radius are required for optimized device performance. Simulation results also indicated that for detectors farther from the center of the field of view, the efficacy of microlenses in crosstalk suppression and energy gathering is still maintained, except for a negligible difference in the lateral magnification from an ordinary array without microlenses.

Li, Yang; Ye, Zhen-Hua; Hu, Wei-Da; Lei, Wen; Gao, Yan-Lin; He, Kai; Hua, Hua; Zhang, Peng; Chen, Yi-Yu; Lin, Chun; Hu, Xiao-Ning; Ding, Rui-Jun; He, Li

2014-05-01

120

Analysis and Evaluation of Technical Data on the Photochromic and Non-Linear Optical Properties of Materials. Appendix. Eye/Sensor Protection by an Optical Fuse Mirror at a Focal Plane: Feasibility Assessment.  

National Technical Information Service (NTIS)

A possible approach to protecting eyes and electrooptical sensors is to use a device having a focal plane with an optical switch or optical fuse at or near the focus. The fuse could be manually reset to a fresh undamaged section following its failure. A v...

R. F. Cozzens

1989-01-01

121

Pit Depth and Width Modulation Multilevel Run-Length Limited Read-Only Optical Storage  

NASA Astrophysics Data System (ADS)

When the techniques of integrating the variation of the pit depth and width simultaneously are adopted to conventional DVD, the high-density multilevel run-length limited read-only optical storage method is achieved. The dynamic range of readout signal is greatly enlarged in comparison with keeping one parameter varied, and the recording levels number can be obviously increased. The discs can be manufactured using standard photoresist mastering and replication techniques with great compatibility to conventional binary read-only discs. Experimental results show that eight-level read-only optical disc can be realized and the capacity can be increased to 20 GB.

Song, Jie; Pei, Jing; Xu, Duan-Yi; Xiong, Jian-Ping; Chen, Ken; Pan, Long-Fa

2006-06-01

122

Optical biopsy of breast tissue using differential path-length spectroscopy  

NASA Astrophysics Data System (ADS)

Differential path-length spectroscopy (DPS) was used to determine the local optical properties of breast tissue in vivo. DPS measurements were made on healthy and malignant breast tissue using a fibre-optic needle probe, and were correlated to the histological outcome of core-needle biopsies taken from the same location as the measurements. DPS yields information on the local tissue blood content, the local blood oxygenation, the average micro-vessel diameter, the ?-carotene concentration and the scatter slope. Our data show that malignant breast tissue is characterized by a significant decrease in tissue oxygenation and a higher blood content compared to normal breast tissue.

van Veen, Robert L. P.; Amelink, Arjen; Menke-Pluymers, Marian; van der Pol, Carmen; Sterenborg, Henricus J. C. M.

2005-06-01

123

Graphene-based electro-optical control of the beat length of dielectric couplers  

NASA Astrophysics Data System (ADS)

We describe the properties of dielectric couplers wherein tunability is achieved by inserting graphene layers in the region which separates the waveguides. We show that, in spite of the atomic thickness of graphene, the strong dependence of its optical parameters on the bias voltage allows coupling between the waveguides, and then the beat length of the coupler, to be dramatically changed. We also demonstrate that simple analytical models based on classic waveguide theory can be efficiently applied for the analysis of complex graphene-based electro-optical structures.

Locatelli, Andrea; Capobianco, Antonio-Daniele; Nalesso, Gianfranco; Boscolo, Stefano; Midrio, Michele; De Angelis, Costantino

2014-05-01

124

Focal volume optics and experimental artifacts in confocal fluorescence correlation spectroscopy.  

PubMed Central

Fluorescence correlation spectroscopy (FCS) can provide a wealth of information about biological and chemical systems on a broad range of time scales (<1 micros to >1 s). Numerical modeling of the FCS observation volume combined with measurements has revealed, however, that the standard assumption of a three-dimensional Gaussian FCS observation volume is not a valid approximation under many common measurement conditions. As a result, the FCS autocorrelation will contain significant, systematic artifacts that are most severe with confocal optics when using a large detector aperture and aperture-limited illumination. These optical artifacts manifest themselves in the fluorescence correlation as an apparent additional exponential component or diffusing species with significant (>30%) amplitude that can imply extraneous kinetics, shift the measured diffusion time by as much as approximately 80%, and cause the axial ratio to diverge. Artifacts can be minimized or virtually eliminated by using a small confocal detector aperture, underfilled objective back-aperture, or two-photon excitation. However, using a detector aperture that is smaller or larger than the optimal value (approximately 4.5 optical units) greatly reduces both the count rate per molecule and the signal-to-noise ratio. Thus, there is a tradeoff between optimizing signal-to-noise and reducing experimental artifacts in one-photon FCS.

Hess, Samuel T; Webb, Watt W

2002-01-01

125

Extended Nijboer-Zernike representation of the vector field in the focal region of an aberrated high-aperture optical system.  

PubMed

Taking the classical Ignatowsky/Richards and Wolf formulas as our starting point, we present expressions for the electric field components in the focal region in the case of a high-numerical-aperture optical system. The transmission function, the aberrations, and the spatially varying state of polarization of the wave exiting the optical system are represented in terms of a Zernike polynomial expansion over the exit pupil of the system; a set of generally complex coefficients is needed for a full description of the field in the exit pupil. The field components in the focal region are obtained by means of the evaluation of a set of basic integrals that all allow an analytic treatment; the expressions for the field components show an explicit dependence on the complex coefficients that characterize the optical system. The electric energy density and the power flow in the aberrated three-dimensional distribution in the focal region are obtained with the expressions for the electric and magnetic field components. Some examples of aberrated focal distributions are presented, and some basic characteristics are discussed. PMID:14686507

Braat, Joseph J M; Dirksen, Peter; Janssen, Augustus J E M; van de Nes, Arthur S

2003-12-01

126

Run-Length-Limited (4, 13) Code for High Density Optical Storage Systems  

Microsoft Academic Search

In this paper, we propose a new (4, 13) run-length-limited (RLL) code for high-density optical storage systems. The code rate of this code is 1\\/3, and the resulting density ratio is 1.67, which is larger than that of EFMPlus code used for digital versatile disc (DVD) systems. The bit error rate (BER) performance of the code is analyzed considering noise

Xin Yang; Mali Gong; Lei Huang; Haitao Zhang

2004-01-01

127

Single-shot electron bunch length measurements using a spatial electro-optical autocorrelation interferometer  

SciTech Connect

A spatial, electro-optical autocorrelation (EOA) interferometer using the vertically polarized lobes of coherent transition radiation (CTR) has been developed as a single-shot electron bunch length monitor at an optical beam port downstream the 100 MeV preinjector LINAC of the Swiss Light Source. This EOA monitor combines the advantages of step-scan interferometers (high temporal resolution) [D. Mihalcea et al., Phys. Rev. ST Accel. Beams 9, 082801 (2006) and T. Takahashi and K. Takami, Infrared Phys. Technol. 51, 363 (2008)] and terahertz-gating technologies [U. Schmidhammer et al., Appl. Phys. B: Lasers Opt. 94, 95 (2009) and B. Steffen et al., Phys. Rev. ST Accel. Beams 12, 032802 (2009)] (fast response), providing the possibility to tune the accelerator with an online bunch length diagnostics. While a proof of principle of the spatial interferometer was achieved by step-scan measurements with far-infrared detectors, the single-shot capability of the monitor has been demonstrated by electro-optical correlation of the spatial CTR interference pattern with fairly long (500 ps) neodymium-doped yttrium aluminum garnet (Nd:YAG) laser pulses in a ZnTe crystal. In single-shot operation, variations of the bunch length between 1.5 and 4 ps due to different phase settings of the LINAC bunching cavities have been measured with subpicosecond time resolution.

Suetterlin, Daniel [PUBLICA Swiss Federal Pension Fund, CH-3000 Berne (Switzerland); Paul Scherrer Institute, CH-5232 Villigen (Switzerland); Erni, Daniel [General and Theoretical Electrical Engineering (ATE), Faculty of Engineering, University of Duisburg-Essen, D-47048 Duisburg (Germany); Schlott, Volker [Department of Large Research Facilities, Paul Scherrer Institute, CH- 5232 Villigen (Switzerland); Sigg, Hans [Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, CH- 5232 Villigen (Switzerland); Jaeckel, Heinz [Department of Information Technology and Electrical Engineering, Electronics Laboratory, ETHZ, CH-8092 Zurich (Switzerland); Murk, Axel [Department of Microwave Physics, Institute of Applied Physics, University of Berne, CH-3012 Berne (Switzerland)

2010-10-15

128

Single-shot electron bunch length measurements using a spatial electro-optical autocorrelation interferometer.  

PubMed

A spatial, electro-optical autocorrelation (EOA) interferometer using the vertically polarized lobes of coherent transition radiation (CTR) has been developed as a single-shot electron bunch length monitor at an optical beam port downstream the 100 MeV preinjector LINAC of the Swiss Light Source. This EOA monitor combines the advantages of step-scan interferometers (high temporal resolution) [D. Mihalcea et al., Phys. Rev. ST Accel. Beams 9, 082801 (2006) and T. Takahashi and K. Takami, Infrared Phys. Technol. 51, 363 (2008)] and terahertz-gating technologies [U. Schmidhammer et al., Appl. Phys. B: Lasers Opt. 94, 95 (2009) and B. Steffen et al., Phys. Rev. ST Accel. Beams 12, 032802 (2009)] (fast response), providing the possibility to tune the accelerator with an online bunch length diagnostics. While a proof of principle of the spatial interferometer was achieved by step-scan measurements with far-infrared detectors, the single-shot capability of the monitor has been demonstrated by electro-optical correlation of the spatial CTR interference pattern with fairly long (500 ps) neodymium-doped yttrium aluminum garnet (Nd:YAG) laser pulses in a ZnTe crystal. In single-shot operation, variations of the bunch length between 1.5 and 4 ps due to different phase settings of the LINAC bunching cavities have been measured with subpicosecond time resolution. PMID:21034105

Sütterlin, Daniel; Erni, Daniel; Schlott, Volker; Sigg, Hans; Jäckel, Heinz; Murk, Axel

2010-10-01

129

The Facility for Optical Calibration At Low Light Levels~(FOCAL}3)  

NASA Astrophysics Data System (ADS)

We present information on a newly constructed optical calibration facility developed specifically for testing and calibration of low-light devices, including auroral imagers, photomultiplier tubes, star sensors and other instruments. A combination cleanroom/darkroom is utilized to isolate instruments from airborn particulate and from stray light. One of the key components of the calibration facilty is a custom integrating sphere that provides a uniform light source for imager calibration with an intensity range comparable to weak to strong auroral emissions. Capabilities also include a monochromator to characterize spectral responses of optical systems with up to 0.1 nm resolution, a collimator that provides the capability for viewing low-light test patterns focused at infinity, and other supporting hardware. The selection of test slides currently available for use in the collimator are well-suited for characterizing parameters such as point spread function, modulation transfer function, spatial resolution, distortions, etc. Current applications using this facility include the ePOP satellite (auroral imagers), ROPA rocket (auroral imagers), and the Star Sensor for the IBEX mission (PMT star sensor). In this presentation, results are shown from calibration tasks associated with these instruments.

Sadler, B. R.; Lessard, M. R.; Cogger, L. L.

2006-12-01

130

New Efficient Run-Length Limited Code for Multilevel Read-Only Optical Disc  

NASA Astrophysics Data System (ADS)

Multilevel recording with run-length limited (RLL) modulation is a novel way to significantly increase the recording density without changing the optical or mechanical units of current optical disc systems. In this paper, a new efficient 4-ary RLL(2,13) code with special constraint is designed for four-level RLL modulation on read-only digital versatile disc (DVD-ROM). This code can result in alternate multilevel pits and lands on the disc, and reduce the difficulty of multilevel disc replication. Further more, simulation results show the symbol error rate (SER) performance can be improved about 3 dB when the proposed code is used for optical recording channel with partial-response maximum-likelihood (PRML) detection.

Hu, Hua; Pan, Longfa; Xiong, Jianping; Ni, Yi

2007-06-01

131

Changes in diffusion path length with old age in diffuse optical tomography  

NASA Astrophysics Data System (ADS)

Diffuse, optical near infrared imaging is increasingly being used in various neurocognitive contexts where changes in optical signals are interpreted through activation maps. Statistical population comparison of different age or clinical groups rely on the relative homogeneous distribution of measurements across subjects in order to infer changes in brain function. In the context of an increasing use of diffuse optical imaging with older adult populations, changes in tissue properties and anatomy with age adds additional confounds. Few studies investigated these changes with age. Duncan et al. measured the so-called diffusion path length factor (DPF) in a large population but did not explore beyond the age of 51 after which physiological and anatomical changes are expected to occur [Pediatr. Res. 39(5), 889-894 (1996)]. With increasing interest in studying the geriatric population with optical imaging, we studied changes in tissue properties in young and old subjects using both magnetic resonance imaging (MRI)-guided Monte-Carlo simulations and time-domain diffuse optical imaging. Our results, measured in the frontal cortex, show changes in DPF that are smaller than previously measured by Duncan et al. in a younger population. The origin of these changes are studied using simulations and experimental measures.

Bonnéry, Clément; Leclerc, Paul-Olivier; Desjardins, Michèle; Hoge, Rick; Bherer, Louis; Pouliot, Philippe; Lesage, Frédéric

2012-05-01

132

Gold nanorod length controls dispersion, local ordering, and optical absorption in polymer nanocomposite films.  

PubMed

The dispersion, local orientation and optical absorption of polystyrene (PS, degree of polymerization P) nanocomposites containing PS-grafted gold nanorods (Au NRs, PS degree of polymerization N), with aspect ratios (? = length/diameter) ranging from 2.5 to 6.3, are studied using quantitative scanning electron microscopy (SEM) and optical spectroscopy. The experimentally observed nanorod assemblies and optical absorptions are compared with predictions from self-consistent field theory (SCFT) and finite difference time domain (FDTD) calculations, respectively. A pair correlation function for Au NRs is calculated from SEM images, and contains no correlation peaks for P/N = 0.9, indicating nanorods are dispersed within the nanocomposite. Large correlation peaks are observed for P/N = 7.6, representative of interparticle separation distances within nanorod aggregates, which do not vary with ?. On the basis of SCFT calculations, aggregation is attributed to significant depletion-attraction forces in the composite for P/N > 1. When Au NRs disperse, the longitudinal surface plasmon resonance (LSPR) peak red shifts from the visible into the near-IR as ? increases. No shift in the dispersed LSPR position is observed for v = 2.5 and 3.3 upon aggregation because the ratio of the interparticle distance to the nanorod length is too large for surface plasmon coupling. However, for v = 6.3, significant coupling between surface plasmons leads to a blue shift of the LSPR by approximately 140 nm, in agreement with FDTD calculations. PMID:24643463

Wang, Dongliang; Hore, Michael J A; Ye, Xingchen; Zheng, Chen; Murray, Christopher B; Composto, Russell J

2014-05-21

133

Exciton coherence length fluctuations in chromophore aggregates probed by multidimensional optical spectroscopy  

PubMed Central

The coherent third order optical response of molecular aggregates with fluctuating frequencies, couplings, and transition dipole moments is studied. We derived stochastic nonlinear exciton equations (SNEEs) by combining the quasiparticle picture of excitons with the path integral over stochastic bath paths described by the stochastic Liouville equations. Coherent two-dimensional (2D) spectra are calculated for a tetramer model system whose transition dipole orientations undergo two-state stochastic jumps on an arbitrary timescale. Correspondence between domains of ordered dipoles, which determine the exciton coherence length and the absorption peaks, is established. Signatures of domain coherence length fluctuations are observed in the cross peak dynamics of the 2D spectra in specific pulse polarization configurations.

Sanda, Frantisek; Perlik, Vaclav; Mukamel, Shaul

2010-01-01

134

Run-Length-Limited (4, 13) Code for High Density Optical Storage Systems  

NASA Astrophysics Data System (ADS)

In this paper, we propose a new (4, 13) run-length-limited (RLL) code for high-density optical storage systems. The code rate of this code is 1/3, and the resulting density ratio is 1.67, which is larger than that of EFMPlus code used for digital versatile disc (DVD) systems. The bit error rate (BER) performance of the code is analyzed considering noise and channel jitter. The (4, 13) RLL code has very low complexity of hardware since the mapping rule is simple. The encoding and decoding circuits of the code are implemented using a complex programmable logic device (CPLD) chip.

Yang, Xin; Gong, Mali; Huang, Lei; Zhang, Haitao

2004-07-01

135

Optical path length calculation of the auxiliary telescopes of the Very Large Telescope project  

NASA Astrophysics Data System (ADS)

The Optical Path Length (OPL) requirement for the Auxiliary Telescopes (AT's) is the variation of the OPL from the star to the output of M11 during short time windows corresponding to the exposure time of the interferometric instrument. The OPL variations considered in this design are those generated during the telescope tracking by the vibrations of all the mirrors. These vibrations include all telescope dependent effects and in particular: dynamic wind load on the AT, all internal vibration sources: bearings, cable wraps, normal micro seismic activities. The article presents the philosophy followed by AMOS for the optimisation of the design of the telescope to fulfill the OPL requirements.

Delrez, Christophe; Schumacher, Jean-Marc; Flebus, Carlo; Gloesener, Pierre; Koehler, Bertrand

136

Phase Sensitivity of an Infinite Length Optical Fiber Subjected to a Forcing Function at a Definite Frequency and Wavenumber.  

National Technical Information Service (NTIS)

The model developed in this report provides an exact solution to the equations of motion for an infinite length, axisymmetric, isotropic, forced cylindrical rod. The resulting mechanical stresses are inserted into the governing equations of optical phase ...

A. J. Hull

1995-01-01

137

Development of a magneto-optical imaging equipment for long length 2G-HTS tapes  

NASA Astrophysics Data System (ADS)

We developed a characterization method suitable for high- Tc superconducting long tapes in prospect of practical use. In order to find low Jc regions with higher spatial resolution and to feedback to fabrication process of the next generation superconducting tapes of 123 system, we chose magneto-optical imaging (MOI) technique as one possibility. Previously, the maximum length that our MOI equipment can deal with was limited to 5 cm by cryostat size. Therefore, we needed to develop new MOI equipment corresponding to high- Tc tapes of several hundred-meter lengths. It is the most important requirement of the new MOI equipment that the maximum length up to 500 m in reel to reel can be measured. The other characteristic specifications of this apparatus are variable temperature (20-100 K), 16 mm square area observation at a time, and application of magnetic fields up to 100 mT. By using this MOI equipment, we observed several kinds of 2G-HTS tapes produced by techniques such as IBAD(CeO2)/TFA-MOD(YBCO), IBAD(CeO 2)/PLD(YBCO) on hastelloy tapes and confirmed the performance of the equipment.

Machi, Takato; Chikumoto, Noriko; Nakao, Koichi; Aoki, Yuji; Kitoh, Yutaka; Fuji, Hiroshi; Izumi, Teruo; Ibi, Akira; Yamada, Yutaka

2006-10-01

138

Novel method for laser focal point positioning on the cover slip for TPP-based microfabrication and detection of the cured structure under optical microscope  

NASA Astrophysics Data System (ADS)

Detection of a single cured structure in two-photon photopolymerization (TPP) based microstructure fabrication requires the laser focal spot to be exactly positioned on the cover slip. This is due to the fact that if the laser focal position is not exactly on the cover slip, the structure may not stick to the cover slip and flow away with the liquid during the washing and developing stages. In this paper, we report a scheme of laser spot positioning for the implementation of TPP process and the detection of a single cured microstructure under an optical microscope. For this, a novel yet very simple approach is devised and an uncomplicated procedure is developed. Experimental results are also included to prove the worthiness of the devised method.

Najam, Muhammad Tallal Bin; Arif, Khalid Mahmood; Lee, Yong-Gu

2013-04-01

139

Surfactant-triggered disassembly of electrostatic complexes probed at optical and quartz crystal microbalance length scales.  

PubMed

A critical advantage of electrostatic assemblies over covalent and crystalline bound materials is that associated structures can be disassembled into their original constituents. Nanoscale devices designed for the controlled release of functional molecules already exploit this property. To bring some insight into the mechanisms of disassembly and release, we study the disruption of molecular electrostatics-based interactions via competitive binding with ionic surfactants. To this aim, free-standing micrometer-size wires were synthesized using oppositely charged poly(diallyldimethylammonium chloride) and poly(acrylic acid) coated iron oxide nanoparticles. The disassembly is induced by the addition of sodium dodecyl sulfates that complex preferentially the positive polymers. The process is investigated at two different length scales: the length scale of the particles (10 nm) through the quartz crystal microbalance technique and that of the wires (>1 ?m) via optical microscopy. Upon surfactant addition, the disassembly is initiated at the surface of the wires by the release of nanoparticles and by the swelling of the structure. In a second step, erosion involving larger pieces takes over and culminates in the complete dissolution of the wires, confirming the hypothesis of a surface-type swelling and erosion process. PMID:24773519

Schonbeck, N; Kvale, K; Demarcy, T; Giermanska, J; Chapel, J-P; Berret, J-F

2014-05-20

140

Optical design of a long range dual field of view thermal imaging camera in 3-5mum waveband  

Microsoft Academic Search

In this work, the design study of a switchable dual field of view thermal optical system for 3-5 mum is presented. A mechanical holder switches in and out lenses to the whole optical system to change the focal length from 60. A cooled 320×256 focal plane array with 30 mum pixel pitch is imaging the rays gathered by thermal optics.

Ramin Khoei

2009-01-01

141

Effect of focal size on the laser ignition of compressed natural gas–air mixture  

NASA Astrophysics Data System (ADS)

Laser ignition of compressed natural gas–air mixtures was investigated in a constant volume combustion chamber (CVCC) as well as in a single cylinder engine. Laser ignition has several potential advantages over conventional spark ignition system. Laser ignition relies on the fact that optical breakdown (plasma generation) in gases occurs at high intensities of ?1011 W/cm2. Such high intensities can be achieved by focusing a pulsed laser beam to small focal sizes. The focal spot size depends on several parameters such as laser wavelength, beam diameter at the converging lens, beam quality and focal length. In this investigation, the focal length of the converging lens and the beam quality were varied and the corresponding effects on minimum ignition energy as well as pressure rise were recorded. The flame kernel was visualized and correlated with the rate of pressure rise inside the combustion chamber. This investigation will be helpful in the optimization of laser and optics parameters in laser ignition. It was found that beam quality factor and focal length of focusing lens have a strong impact on the minimum ignition energy required for combustion. Combustion duration depends on the energy density at the focal spot and size of the flame kernel.

Srivastava, Dhananjay Kumar; Wintner, Ernst; Agarwal, Avinash Kumar

2014-07-01

142

A Method for Determining the Nominal Occular Hazard Zone for Gaussian Beam Laser Rangers with a Firmware Controlled Variable Focal Length  

NASA Technical Reports Server (NTRS)

LIDAR systems that maintain a constant beam spot size on a retroreflector in order to increase the accuracy of bearing and ranging data must use a software controlled variable position lens. These systems periodically update the estimated range and set the position of the focusing lens accordingly. In order to precisely calculate the r NOHD for such a system, the software method for setting the variable position lens and gaussian laser propagation can be used to calculate the irradiance at any point given the range estimation. NASA s Space Shuttle LIDAR, called the Trajectory Control Sensor (TCS), uses this configuration. Analytical tools were developed using Excel and VBA to determine the radiant energy to the International Space Station (ISS) crewmembers eyes while viewing the shuttle on approach and departure. Various viewing scenarios are considered including the use of through-the-lens imaging optics and the window transmissivity at the TCS wavelength. The methodology incorporates the TCS system control logic, gaussian laser propagation, potential failure mode end states, and guidance from American National Standard for the Safe Use of Lasers (ANSI Z136.1-2007). This approach can be adapted for laser safety analyses of similar LIDAR systems.

Picco, C. E.; Shavers, M. R.; Victor, J. M.; Duron, J. L.; Bowers, W. h.; Gillis, D. B.; VanBaalen, M.

2009-01-01

143

Determination of carrier diffusion length in MOCVD-grown GaN epilayers on sapphire by optical techniques  

Microsoft Academic Search

Two optical techniques for the determination of a bipolar diffusion length LD of optically excited carriers in GaN epitaxial layers, namely a time-resolved picosecond four-wave mixing (FWM) on free carrier grating and time-integrated photoluminescence (PL) are presented and examined. The PL technique is based on time-integrated photoluminescence (PL) spectra measurements from the front and back sides of the sample under

E. V. Lutsenko; A. L. Gurskii; V. N. Pavlovskii; G. P. Yablonskii; T. Malinauskas; K. Jaraši?nas; B. Schineller; M. Heuken

2006-01-01

144

Precision timing and Rf signal dissemination for XFEL by delivering optical frequency comb through length-stabilized fiber  

Microsoft Academic Search

We have developed the precision timing and rf signal dissemination system for the X-ray free electron laser (XFEL), under construction in Japan. The optical frequency comb was transmitted through a 1-km length-stabilized optical fiber for disseminating both rf and timing signals. The phase fluctuations of the rf signals at 5.712 GHz was suppressed down to 0.0042 radian that is used

Mitsuru Musha; Toshio Ryuo; Ken'ichi Nakagawa; Ken-ichi Ueda

2011-01-01

145

Optical time-of-flight chemical detection: spatially resolved analyte mapping with extended-length continuous chemically modified optical fibers.  

PubMed

We theoretically evaluate and experimentally verify a novel strategy for spatially resolved analyte mapping over extended remote areas. The approach combines a method for the fabrication of continuous extended-length sensors with optical time-of-flight chemical detection (OTOF-CD). The use of OTOF-CD makes it possible to locate the zones in the fiber where attenuation or fluorescence takes place, to determine the magnitude of these variations, and to relate the magnitude of the variations to the local concentration or concentrations of a single analyte or several analytes. Simulation experiments suggest that OTOF-CD should provide spatial resolution close to its theoretical limit by deconvolution of the returned wave form with all time-dependent experimental variables (laser pulse width, reagent fluorescence lifetime, etc.). The signal-processing technique should be useful for a wide variety of sensors based on absorption, refractive index, or statically and dynamically quenched fluorescence. Experimental results with a model system (a 48-m-long oxygen sensor) compare favorably with those predicted by numerical simulations. Possible experimental difficulties in the realization of these novel sensors are discussed as are ways to overcome them. PMID:9569756

Potyrailo, R A; Hieftje, G M

1998-04-15

146

Effects of material parameter on interaction length to occur optical phase conjugation via stimulated Brillouin scattering in semiconductors  

NASA Astrophysics Data System (ADS)

In the present formulation using hydrodynamic model and coupled mode scheme of plasmas the interaction length necessary to achieve optical phase conjugation is obtained from steady-state Brillouin gain coefficient for a semiconductor crystal. The analytical investigation of steady-state gain of stimulated Brillouin scattering (SBS) is made by assuming that the SBS is resulted from the nonlinear interaction of an intense electromagnetic wave with acoustic perturbation internally generated due to acousto-optic property of the semiconductor crystal. Numerical estimates confirm that when cyclotron frequency is tuned with pump frequency, interaction length is found to be nearly 10 m smaller than that obtained in absence of magnetic filed. Pump intensity and free carrier concentration both helpful in reducing the required interaction length.

Nimje, Nilesh; Yadav, Nishchhal; Ghosh, S.

2012-01-01

147

Ostrich ocular optics.  

PubMed

The optical structure of the eyes of ostriches (Struthio camelus; Struthionidae; Struthioniformes) was determined by the construction of a schematic eye model for paraxial optics. The eye is large (axial length = 38 mm) and of globose shape with an anterior focal length (posterior nodal distance) of 21.8 mm. The optical design of the eye is such that the lens and cornea contribute equally to its total optical power. Interspecific comparison shows that optically the ostrich eye is a larger scaled version of the eyes of common starlings (Sturnus vulgaris) and an owl (Strix aluco). PMID:11805377

Martin, G R; Ashash, U; Katzir, G

2001-01-01

148

Focal properties of geodesic waveguide lenses  

NASA Technical Reports Server (NTRS)

The focal properties of uncorrected geodesic lenses in ion-exchanged glass waveguides are reported. A 13.8-mm-focal-length lens resolved beams with an angular separation of 27.6 mrad, while a 28-mm-focal-length lens resolved beams with an angular separation of only 3.3 mrad. Intensity profiles of the focal region of the former lens revealed a 40-micron spot size when the input aperture was 5 mm, and a spot size of 7.7 microns when the aperture was reduced to 1 mm. This value is close to the diffraction-limited spot size of 5.7 microns.

Verber, C. M.; Vahey, D. W.; Wood, V. E.

1976-01-01

149

Active optical zoom for laser communication  

NASA Astrophysics Data System (ADS)

Changing the field-of-view of a laser communication system in real-time without mechanical motion could significantly improve signal strength and reduce drop out rates. By incorporating active elements into the optical design, we have designed and demonstrated imaging systems that are capable of variable effective focal lengths with no macroscopic moving parts (i.e. active optical zoom). This technique, in which the active optics serve as variable focal-length lenses, could easily be applied to laser communication systems to improve capability. The key to this concept is to create relatively large changes in the field-of-view of the system with very small changes in the focal lengths of individual elements by leveraging the optical power of conventional optical elements surrounding the active optics. By appropriately designing the optical system, these variable focal-length lenses can provide the flexibility necessary to change the overall system focal length, and therefore field-of-view, that is normally accomplished with mechanical motion in conventional zoom systems.

Martinez, Ty; Wick, David V.; Payne, Don M.; Restaino, Sergio R.

2005-05-01

150

Cavity length as a key to security in a chaotic optical communication scheme  

Microsoft Academic Search

Three diode lasers are used as message, transmitter and receive lasers. The message laser is amplitude modulated by a simple message and its output is optically coupled to the transmitter laser ensuring optical modulation of message. The transmitter laser is rendered chaotic by application of appropriate optical feedback. The receiver laser is used to decode the message. Effective signal masking

John Paul; Siva Sivaprakasam; Paul S. Spencer; Keith A. Shore

2002-01-01

151

Compact color schlieren optical system  

NASA Technical Reports Server (NTRS)

A compact optical system for use with rainbow schlieren deflectometry is described. Both halves of the optical system consist of well-corrected telescopes whose refractive elements are all from manufacturer's stock catalogs, with the reflective primary being a spherical surface. As a result, the system is relatively easy to construct and meets the requirement of long focal length for quantitative rainbow schlieren measurements.

Buchele, Donald R.; Griffin, Devon W.

1993-01-01

152

Chemometric determination of the length distribution of single walled carbon nanotubes through optical spectroscopy.  

PubMed

Current synthesis methods for producing single walled carbon nanotubes (SWCNTs) do not ensure uniformity of the structure and properties, in particular the length, which is an important quality indicator of SWCNTs. As a result, sorting SWCNTs by length is an important post-synthesis processing step. For this purpose, convenient analysis methods are needed to characterize the length distribution rapidly and accurately. In this study, density gradient ultracentrifugation was applied to prepare length-sorted SWCNT suspensions containing individualized surfactant-wrapped SWCNTs. The length of sorted SWCNTs was first determined by atomic force microscope (AFM), and their absorbance was measured in ultraviolet-visible near-infrared (UV-vis-NIR) spectroscopy. Chemometric methods are used to calibrate the spectra against the AFM-measured length distribution. The calibration model enables convenient analysis of the length distribution of SWCNTs through UV-vis-NIR spectroscopy. Various chemometric techniques are investigated, including pre-processing methods and non-linear calibration models. Extended inverted signal correction, extended multiplicative signal correction and Gaussian process regression are found to provide good prediction of the length distribution of SWCNTs with satisfactory agreement with the AFM measurements. In summary, spectroscopy in conjunction with advanced chemometric techniques is a powerful analytical tool for carbon nanotube research. PMID:22093341

Si, Rongmei; Wang, Ke; Chen, Tao; Chen, Yuan

2011-12-01

153

Design of a Simple Detection Cell with Extended Optical Path Length for Capillary Electrophoresis: Application to Multiresidue Pesticide Analysis  

Microsoft Academic Search

Absorbance detection in capillary electrophoresis (CE), offers an excellent mass sensitivity, but poor concentration detection limits owing to very small injection volumes (normally 1 to 10 nL). This aspect can be a limiting factor in the applicability of CE\\/UV to detect species at trace levels, particularly pesticide residues. In the present work, the optical path length of an “on?column” detection cell

Mário S. Galhiane; Sandra R. Rissato; Bernhard M. Apon

2005-01-01

154

Effect of conjugation path length on quadratic nonlinear optical properties of monomer and aggregates of zwitterionic merocyanine dyes.  

PubMed

We present a quantum-chemical analysis of the conjugation path length effect on first hyperpolarizabilities of a series of zwitterionic merocyanine dyes whose synthesis has been reported earlier (J. Am. Chem. Soc.2002, 124, 9431, J. Am. Chem. Soc. 1997, 119, 3144). The effect of the conjugation path lengths is evaluated to demonstrate the engineering guidelines for enhancing molecular optical nonlinearity. The first hyperpolarizabilities are calculated for extended conjugated monomer and H and J type aggregates of merocyanine dyes, to provide insight into the intermolecular interactions and the relationship between structural and collective nonlinear optical properties. The molecular geometries for monomers are obtained via B3LYP/6-31G(d,p) level optimization including the SCRF/PCM approach, and the dynamic nonlinear optical (NLO) properties for monomer and aggregates are calculated with the ZINDO/CV method, including solvent effects. It is found that the chain length dependence of the first nonlinearity peaks at n = 6 and then it starts changing slowly for monomer and aggregates of zwitterionic merocyanine dyes. It is concluded that an excellent NLO response in solution might vanish when the active chromophore forms higher H aggregates. The importance of our results on the design of electrooptic materials has been discussed. PMID:16836460

Ray, Paresh C; Bonifassi, P; Leszczynski, J

2006-07-20

155

Tuning the focal point of a plasmonic lens by nematic liquid crystal  

NASA Astrophysics Data System (ADS)

A theoretical and numerical investigation of tunable plasmonic nano-optic lens on the basis of liquid crystal are proposed as a new method of active modulating the output beam. The focal length can be controlled easily by exposing plasmonic nano-optic lens to constant external electric field. The physical principle of this phenomenon is evaluated from the phase of Fabry-Perot (F-P) resonance in slits and electro-optical effect of liquid crystal. Our numerical simulations reveal that large tuning range of the focal length up to 725 nm can be achieved. The results in this article provide a potential way to realize tunable plasmonic lens, which can be applied as an efficient element in ultrahigh nano-scale integrated photonic circuits for miniaturization and tuning purposes.

Bahramipanah, M.; Abrishamian, M. S.; Mirtaheri, S. A.

2012-12-01

156

CO[sub 2] laser beam propagation with ZnSe optics  

SciTech Connect

Beam propagation characteristics of ZnSe optics used in kiloWatt power CO[sub 2] laser aided material processing applications are determined using the Prometec Laser Beam Analyzer. The laser used was a Rofin Sinar RS6000 CO[sub 2] laser with mode aperturing. Beam power varied from 500W to 6300W and beam modes used were TEM[sub 00], TEM[sub 01], TEM[sub 10] and TEM[sub 20]. Both transmissive and reflective optics were examined. The ZnSe lenses tested included meniscus, diffractive and cylindrical lenses of 5in focal length and a 10in focal length integrading lens. Reflective optics included an integrator and a 5in focal length parabolic mirror for welding. Parameters obtained included beam propagation profiles, intensity profiles, depth of focus, spot size and back focal length. A subset of the data obtained is presented here. Details of the work will appear in a full length paper.

Leong, K.H.; Liu, Yi; Holdridge, D.J.

1992-01-01

157

CO{sub 2} laser beam propagation with ZnSe optics  

SciTech Connect

Beam propagation characteristics of ZnSe optics used in kiloWatt power CO{sub 2} laser aided material processing applications are determined using the Prometec Laser Beam Analyzer. The laser used was a Rofin Sinar RS6000 CO{sub 2} laser with mode aperturing. Beam power varied from 500W to 6300W and beam modes used were TEM{sub 00}, TEM{sub 01}, TEM{sub 10} and TEM{sub 20}. Both transmissive and reflective optics were examined. The ZnSe lenses tested included meniscus, diffractive and cylindrical lenses of 5in focal length and a 10in focal length integrading lens. Reflective optics included an integrator and a 5in focal length parabolic mirror for welding. Parameters obtained included beam propagation profiles, intensity profiles, depth of focus, spot size and back focal length. A subset of the data obtained is presented here. Details of the work will appear in a full length paper.

Leong, K.H.; Liu, Yi; Holdridge, D.J.

1992-11-01

158

Measurement of Optical Path Length for Cerebral Near-Infrared Spectroscopy in Newborn Infants  

Microsoft Academic Search

The time taken for an extremely short pulse of near-infrared laser light to traverse the heads of 6 preterm infants was measured after death. The values obtained were used to calculate a differential path length factor (DPF), defined as the mean distance travelled by the photons divided by the distance between the points where light entered and left the head.

J. S. Wyatt; M. Cope; D. T. Delpy; P. van der Zee; S. R. Arridge; A. D. Edwards; E. O. R. Reynolds

1990-01-01

159

Optical Properties of Single-Walled Carbon Nanotubes Separated in a Density Gradient; Length, Bundling, and Aromatic Stacking Effects.  

PubMed

Single-walled carbon nanotubes (SWNTs) are promising materials for in vitro and in vivo biological applications due to their high surface area and inherent near infrared photoluminescence and Raman scattering properties. Here, we use density gradient centrifugation to separate SWNTs by length and degree of bundling. Following separation, we observe a peak in photoluminescence quantum yield (PL QY) and Raman scattering intensity where SWNT length is maximized and bundling is minimized. Individualized SWNTs are found to exhibit high PL QY and high resonance-enhanced Raman scattering intensity. Fractions containing long, individual SWNTs exhibit the highest PL QY and Raman scattering intensities, compared to fractions containing single, short SWNTs or SWNT bundles. Intensity gains of approximately ~1.7 and 4-fold, respectively, are obtained compared with the starting material. Spectroscopic analysis reveals that SWNT fractions at higher displacement contain increasing proportions of SWNT bundles, which causes reduced optical transition energies and broadening of absorption features in the UV-Vis-NIR spectra, and reduced PL QY and Raman scattering intensity. Finally, we adsorb small aromatic species on "bright," individualized SWNT sidewalls and compare the resulting absorption, PL and Raman scattering effects to that of SWNT bundles. We observe similar effects in both cases, suggesting aromatic stacking affects the optical properties of SWNTs in an analogous way to SWNT bundles, likely due to electronic structure perturbations, charge transfer, and dielectric screening effects, resulting in reduction of the excitonic optical transition energies and exciton lifetimes. PMID:21258607

Tabakman, Scott M; Welsher, Kevin; Hong, Guosong; Dai, Hongjie

2010-10-28

160

Optical absorption coefficient and minority carrier diffusion length measurements in low-cost silicon solar cell material  

SciTech Connect

The optical absorption coefficient of silicon solar cell material grown by three low-cost growth methods was measured in the wavelength interval 0.8< or =lambda< or =1.0 ..mu..m, the wavelength region of interest in surface photovoltage measurements of the minority carrier diffusion length. The square root of the absorption coefficient was found to vary linearly with photon energy over the wavelengths studied, and the measured data agree with a linear empirical fit to within 0.5% RMS. The absorption coefficients obtained are slightly lower than those reported by Runyan, with the greatest disagreement at long wavelengths. Minority carrier diffusion lengths computed using the present absorption coefficients are approximately 16% greater than those calculated using Runyan's data. Excellent sample-to-sample agreement within and between lots indicates that for two of the growth methods studied, material quality as judged by optical properties has not been sacrificed by the use of low-cost growth methods. Samples grown by the third growth method studied showed measurably poorer optical quality.

Swimm, R.T.; Dumas, K.A.

1982-11-01

161

Focal Reducer for CQUEAN (Camera for QUasars in EArly uNiverse)  

NASA Astrophysics Data System (ADS)

A focal reducer is developed for CQUEAN (Camera for QUasars in EArly uNiverse), which is a CCD imaging system on the 2.1 m Otto Struve telescope at the McDonald observatory. It allows CQUEAN to secure a wider field of view by reducing the effective focal length by a factor of three. The optical point spread function without seeing effects is designed to be within one pixel (0.283 arcsec) over the field of view of 4.82 arcmin × 4.82 arcmin in optimum wavelength ranges of 0.8-1.1 ?m. In this paper, we describe and discuss the characteristics of optical design, the lens and barrel fabrications and the alignment processes.The observation results show that the image quality of the focal reducer confirms the expectations from the design.

Lim, Juhee; Chang, Seunghyuk; Pak, Soojong; Kim, Youngju; Park, Won-Kee; Im, Myungshin

2013-08-01

162

Novel procedure for the simultaneous determination of the Debye length and electro-optic coefficient for an optically active photorefractive Bi 12SiO 20 crystal  

NASA Astrophysics Data System (ADS)

We present a novel procedure based on an improved physical model and a versatile numerical fitting technique, to simultaneously determinate the Debye screening length and electro-optic coefficient using a thick sample of an optically active photorefractive crystal Bi 12SiO 20 (BSO). For the computation, experimental data of gain vs. grating spacing were obtained by a two-beam coupling arrangement. Unlike former calculation models, in our work, the general expression for the diffraction efficiency in the presence of self-diffraction is considered, and the influence of the optical activity in the coupling parameters is had into account for the calculation of the gain values. The fitting of the experimental data to the predicted theoretical behavior by our model is achieved by finding the closest theoretical curve to a set of data sampled from a spline-smoothed curve of the experimental data. Both, the Debye screening length ls and the electro-optic coefficient r41 are used as fitting parameters by searching in a rather wide range for each one of the parameters, so that, the estimation of their values is obtained in a more reliable and direct way from the same experiment. The calculations are performed in diffusion regimen and the procedure leads to ls = 0.22 ?m and r41 = 4.5 × 10 - 12 m/V. Because the optical activity can alter the maximum gain and self-diffraction effects influence the energy exchange, the procedure reveals to be physically appropriated for the simultaneous determination of these physical parameters when thick photorefractive crystals with high optical activity are considered.

Gómez, Jorge A.; Gómez, Héctor Lorduy; Salazar, Ángel

2011-01-01

163

Imaging and full-length biometry of the eye during accommodation using spectral domain OCT with an optical switch  

PubMed Central

Abstract: An optical switch was implemented in the reference arm of an extended depth SD-OCT system to sequentially acquire OCT images at different depths into the eye ranging from the cornea to the retina. A custom-made accommodation module was coupled with the delivery of the OCT system to provide controlled step stimuli of accommodation and disaccommodation that preserve ocular alignment. The changes in the lens shape were imaged and ocular distances were dynamically measured during accommodation and disaccommodation. The system is capable of dynamic in vivo imaging of the entire anterior segment and eye-length measurement during accommodation in real-time.

Ruggeri, Marco; Uhlhorn, Stephen R.; De Freitas, Carolina; Ho, Arthur; Manns, Fabrice; Parel, Jean-Marie

2012-01-01

164

Unilateral Isolated Proximal Femoral Focal Deficiency  

PubMed Central

Objective. To discuss a patient with a prenatal diagnosis of unilateral isolated femoral focal deficiency. Case. Antenatal diagnosis of unilateral isolated femoral focal deficiency was made at 20 weeks of gestation. The length of left femur was shorter than the right, and fetal femur length was below the fifth percentile. Proximal femoral focal deficiency was diagnosed. After delivery, the diagnosis was confirmed with skeletal radiographs and magnetic resonance imaging. In prenatal ultrasonographic examination, the early recognition and exclusion of skeletal dysplasias is important; moreover, treatment plans should be initiated, and valuable information should be provided to the family.

Doger, Emek; Kopuk, Sule Y.; Cak?roglu, Yigit; Cak?r, Ozgur; Yucesoy, Gulseren

2013-01-01

165

Eavesdropping in chaotic optical communication using the feedback length of an external-cavity laser as a key.  

PubMed

An external-cavity laser (ECL) operating in a chaotic state is usually used in a chaotic optical secure communication system and its feedback length (FL) is often regarded as an additional key. Our analyses show that an eavesdropper's (Eve) laser can synchronize with a transmitter (Alice) without any knowledge of the FL by simply increasing the injection strength. A sequence of a 1 Gbit/s nonreturn-to-zero message encoded by the FL as the key is successfully eavesdropped. The reason for the synchronization deviation between Alice's and Eve's lasers is given. Our results indicate that the FL as a key cannot enhance the security of chaotic optical communication using long-ECLs. PMID:19543362

Zhao, Qingchun; Wang, Yuncai; Wang, Anbang

2009-06-20

166

Length and Elongation Sensor.  

National Technical Information Service (NTIS)

A length and elongation sensor includes an elastomeric optical wave guide and a time domain reflectometer. The elastomeric optical wave guide consists of a urethane outer cladding and an optical gel core. A transparent window is hermetically sealed to the...

L. E. Sansone

1996-01-01

167

Measurement of the magneto-optical correlation length in turbid media  

NASA Astrophysics Data System (ADS)

In multiple light scattering media, magnetic field induced circular birefringence (Faraday effect) influences interference effects such as speckle pattern or coherent backscattering. It was predicted that in the diffusive regime the relevant correlation length with respect to the Faraday rotation l*F differs, in general, from the transport mean free path l*. We have experimentally verified the prediction that the ratio l*F/l* equals 2 for Rayleigh scattering and decreases to 1 with increasing scatterer size. We also discuss the influence of the structure factor on l*F.

Lenke, Ralf; Eisenmann, Christoph; Reinke, Daniel; Maret, Georg

2002-11-01

168

X-ray Pulse Length Characterization using the Surface Magneto Optic Kerr Effect  

SciTech Connect

It will be challenging to measure the temporal profile of the hard X-ray SASE beam independently from the electron beam in the LCLS and other 4th generation light sources. A fast interaction mechanism is needed that can be probed by an ultrafast laser pulse in a pump-probe experiment. It is proposed to exploit the rotation in polarization of light reflected from a thin magnetized film, known as the surface magneto optic Kerr effect (SMOKE), to witness the absorption of the x-ray pulse in the thin film. The change in spin orbit coupling induced by the x-ray pulse occurs on the subfemtosecond time scale and changes the polarization of the probe beam. The limitation to the technique lies with the bandwidth of the probe laser pulse and how short the optical pulse can be made. The SMOKE mechanism will be described and the choices of materials for use with 1.5 {angstrom} x-rays. A schematic description of the pump-probe geometry for x-ray diagnosis is also described.

Krejcik, P.; /SLAC

2006-10-04

169

Presbyopia and the optical changes in the human crystalline lens with age  

Microsoft Academic Search

Lenses from 27 human eyes ranging in age from 10 to 87 years were used to determine how accommodation and age affect the optical properties of the lens. A scanning laser technique was used to measure focal length and spherical aberration of the lenses, while the lenses were subjected to stretching forces applied through the ciliary body\\/zonular complex. The focal

Adrian Glasser; Melanie C. W. Campbell

1998-01-01

170

Bunch Length Monitoring at the A0 Photoinjector Using a Quasi-Optical Schottky Detector  

SciTech Connect

Noninvasive bunch duration monitoring has a crucial importance for modern accelerators intended for short wavelength FEL's, colliders and in some beam dynamics experiments. Monitoring of the bunch compression in the Emittance Exchange Experiment at the A0 Photoinjector was done using a parametric presentation of the bunch duration via Coherent Synchrotron Radiation (CSR) emitted in a dipole magnet and measured with a wideband quasi-optical Schottky Barrier Detector (SBD). The monitoring resulted in a mapping of the quadrupole parameters allowing a determination of the region of highest compression of the bunch in the sub-picosecond range. The obtained data were compared with those measured using the streak camera. A description of the technique and the results of simulations and measurements are presented and discussed in this report.

Kazakevich, G.; Davidsaver, M.; Edwards, H.; Fliller, R.; Koeth, T.; Lumpkin, A.; Nagaitsev, S.; Ruan, J.; Thurman-Keup, R.; /Fermilab; Jeong, Y.U.; /KAERI, Taejon; Kubarev, V.; /Novosibirsk, IYF

2009-05-01

171

Longitudinally polarized electric and magnetic optical nano-needles of ultra high lengths  

NASA Astrophysics Data System (ADS)

We demonstrate a method to generate longitudinally polarized electric and magnetic light spots over ultra-long distances. The method proposed here relies on the generation of radially and azimuthally polarized Bessel beams at the limit between propagating and evanescent regimes, by projecting radially and azimuthally polarized doughnut beams onto an axicon-based system of numerical aperture (NA) equal to 1. Tight electric and magnetic light spots (0.36?) can be produced over distances reaching 50? and with longitudinal intensities about 3.5×104 times above the transverse intensities. Same confinement abilities over distances larger than 335 ? is also predicted with longitudinal intensities 883 fold above the transverse ones. Experimental characterization of these tiny optical needles with polarization-resolved heterodyne SNOM reveals electric and magnetic light spots smaller than 0.4 ? whose longitudinal intensities are about 200-fold larger than the transverse ones.

Grosjean, T.; Gauthier, I.

2013-05-01

172

Space telescope optical telescope assembly/scientific instruments. Phase B: Preliminary design and program definition study. Volume 2A. focal plane camera  

NASA Technical Reports Server (NTRS)

Trade studies were conducted to ensure the overall feasibility of the focal plane camera in a radial module. The primary variable in the trade studies was the location of the pickoff mirror, on axis versus off-axis. Two alternatives were: (1) the standard (electromagnetic focus) SECO submodule, and (2) the MOD 15 permanent magnet focus SECO submodule. The technical areas of concern were the packaging affected parameters of thermal dissipation, focal plane obscuration, and image quality.

1976-01-01

173

Defocus compensation system of long focal aerial camera based on auto-collimation  

NASA Astrophysics Data System (ADS)

Nowadays, novel aerial reconnaissance camera emphasizes on the shooting performance in high altitude or in long distance of oblique photography. In order to obtain the larger scale pictures which are easier for image interpretation, we need the camera has long focal length. But long focal length camera is easier to be influenced by environmental condition and lead to great change of lens' back focus which can result in the lens' resolution decreased greatly. So, we should do precise defocusing compensation to long focal aerial camera system. In order to realize defocusing compensation, a defocusing compensation system based on autocollimation is designed. Firstly, the reason which can lead to long focal camera's defocusing was discussed, then the factors such as changes of atmospheric pressure and temperature and oblique photographic distance were pointed out, and mathematical equation which could compute camera's defocusing amount was presented. Secondly, after camera's defocusing was analyzed, electro-optical autocollimation of higher automation and intelligent was adopted in the system. Before shooting , focal surface was located by electro-optical autocollimation focal detection mechanism, the data of airplane's height was imported through electronic control system. Defocusing amount was corrected by computing defocusing amount and the signal was send to focusing control motor. And an efficient improved mountain climb-searching algorithm was adopted for focal surface locating in the correction process. When confirming the direction of curve, the improved algorithm considered both twice focusing results and four points. If four points continue raised, the curve would be confirmed as rising direction. On the other hand, if four points continue decreased, the curve would be confirmed as decrease direction. In this way, we could avoid the local peak value appeared in two focusing steps. The defocusing compensation system consists of optical component and precise control system and precise driver component. Based on FPGA hardware system, hardware function is realized by VHDL. It has been using on some kinds of long focal CCD cameras and film cameras. It not only has good dimensional stability and structural stability in harsh environment, but also has ability of focal surface precision detection and accurate focusing.

Zhang, Yu-Ye; Zhao, Yu-Liang; Xu, Zhao-Lin

2010-05-01

174

Optical Design of a Broadband Infrared Spectrometer for Bunch Length Measurement at the Linac Coherent Light Source  

SciTech Connect

The electron pulses generated by the Linac Coherent Light Source at the SLAC National Accelerator Laboratory occur on the order of tens of femtoseconds and cannot be directly measured by conventional means. The length of the pulses can instead be reconstructed by measuring the spectrum of optical transition radiation emitted by the electrons as they move toward a conducting foil. Because the emitted radiation occurs in the mid-infrared from 0.6 to 30 microns a novel optical layout is required. Using a helium-neon laser with wavelength 633 nm, a series of gold-coated off-axis parabolic mirrors were positioned to direct a beam through a zinc selenide prism and to a focus at a CCD camera for imaging. Constructing this layout revealed a number of novel techniques for reducing the aberrations introduced into the system by the off-axis parabolic mirrors. The beam had a recorded radius of less than a millimeter at its final focus on the CCD imager. This preliminary setup serves as a model for the spectrometer that will ultimately measure the LCLS electron pulse duration.

Williams, Kiel; /SLAC

2012-09-07

175

Fabrication of ZnO nanorods and assessment of changes in optical and gas sensing properties by increasing their lengths  

NASA Astrophysics Data System (ADS)

We report a low-temperature process to synthesize highly oriented arrays of ZnO nanorods, based on the epitaxial growth of the ZnO seed layer at a low temperature of 70 °C. The ZnO seed layer was deposited by sol-gel process under mild conditions on the glass substrates. The morphologies and crystal structures of the film and nanorods were characterized by x-ray diffraction and scanning electron microscopy, respectively. ZnO nanorods were grown on ZnO seed layers by hydrothermal method. The effect of growth period on the morphology and optical characteristics (e.g. optical transmission and band-gap energy), hydrophilicity and gas sensing properties of the grown ZnO seed layer (film) and nanorods were investigated. The long nanorods on the seed layer were observed. The increase in the length of the nanorods resulted in a significant reduction in the optical band-gap energy of the nanorods, which was attributed to the formation of further defects in the nanorods during their fast growth. The surface of the ZnO nanorods grown for 6 h was relatively hydrophilic (with a water contact angle of 18°). The fabricated sensors were used to gauge different concentrations of ethanol vapor in the air at different temperatures and evaluated the surface resistance of the sensors as a function of operating temperature and ethanol concentrations. The results showed that the sensitivity of the nanorods changed from 1.3 to 6 (at 300 °C) by increasing the growth period.

Mehrabian, Masood; Mirabbaszadeh, Kavoos; Afarideh, Hossein

2013-12-01

176

Direct optical switching of bistable cholesteric textures in chiral azobenzene-doped liquid crystals.  

PubMed

The direct optical switching of bistable cholesteric textures (i.e., planar and focal conic textures) in chiral azobenzene-doped liquid crystals (LCs) is demonstrated. Chiral azobenzene is a chiral dopant with optically tuned helical twisting power that results from the photo-isomerization between trans- and cis- isomers via exposure to UV or visible light. The pitch length of the material can be optically and repeatedly elongated and shortened. With regard to free energy, LCs tend to be stable at planar (focal conic) textures when pitch length is elongated (shortened) by exposure to UV (visible) light. Thus, direct optical switchable LC displays are investigated. PMID:24104076

Fuh, Andy Ying-Guey; Wu, Zong-Han; Cheng, Ko-Ting; Liu, Cheng-Kai; Chen, Yuan-Di

2013-09-23

177

Life Science-Related Physics Laboratory on Geometrical Optics  

ERIC Educational Resources Information Center

Describes a laboratory experiment on geometrical optics designed for life science majors in a noncalculus introductory physics course. The thin lens equation is used by the students to calculate the focal length of the lens necessary to correct a myopic condition in an optical bench simulation of a human eye. (Author/MLH)

Edwards, T. H.; And Others

1975-01-01

178

Fractional-length sync-pumped degenerate optical parametric oscillator for 500-MHz 3-?m mid-infrared frequency comb generation.  

PubMed

We demonstrate a mid-IR frequency comb centered at 3120 nm with 650-nm (20-THz) bandwidth at a comb-teeth spacing of 500 MHz. The generated comb is based on a compact ring-type synchronously pumped optical parametric oscillator (SPOPO) operating at degeneracy and pumped by a mode-locked Er-doped 1560 nm fiber laser at a repetition rate of 100 MHz. We achieve high-repetition rate by using a fractional-length cavity with a roundtrip length of 60 cm, which is one-fifth of the length dictated by conventional synchronous pumping. PMID:24562236

Ingold, Kirk A; Marandi, Alireza; Rudy, Charles W; Vodopyanov, Konstantin L; Byer, Robert L

2014-02-15

179

Smart X-ray optics  

NASA Astrophysics Data System (ADS)

This paper describes reflective adaptive/active optics for applications including studies of biological radiation damage. The optics work on the polycapillary principle, but use arrays of channels in thin silicon. For optimum performance the x-rays should reflect once off a channel wall in each of two successive arrays. This reduces aberrations since then the Abbe sine condition is approximately satisfied. Adaptivity is achieved by flexing the arrays via piezo actuation, providing further aberration reduction and controllable focal length.

Michette, A. G.; Pfauntsch, S. J.; Sahraei, S.; Shand, M.; Morrison, G. R.; Hart, D.; Vojnovic, B.; Stevenson, T.; Parkes, W.; Dunare, C.; Willingale, R.; Feldman, C.; Button, T.; Zhang, D.; Rodriguez-Sanmartin, D.; Wang, H.

2009-09-01

180

Compact Color Schlieren Optical System  

NASA Technical Reports Server (NTRS)

Compact, rugged optical system developed for use in rainbow schlieren deflectometry. Features unobscured telescope with focal-length/aperture-width ratio of 30. Made of carefully selected but relatively inexpensive parts. All of lenses stock items. By-product of design is optical system with loose tolerances on interlens spacing. One of resulting advantages, insensitivity to errors in fabrication of optomechanical mounts. Another advantage is ability to compensate for some of unit-to-unit variations inherent in stock lenses.

Buchele, Donald R.; Griffin, Devon W.

1996-01-01

181

Focal dermal hypoplasia without focal dermal hypoplasia.  

PubMed

Focal dermal hypoplasia (FDH; Goltz-Gorlin syndrome) is an X-linked dominant disorder affecting mainly tissues of ectodermal and mesodermal origin. The phenotype is characterized by hypoplastic linear skin lesions, eye malformations, hair and teeth anomalies, and multiple limbs malformations. The disorder is caused by PORCN mutations. Here we describe a mother and daughter with FDH in whom a c.938T>G in PORCN was detected. Neither of the two had FDH, but otherwise the phenotype was classical. Focal skin hypoplasia is a hallmark of FDH but the present family indicates that FDH should also be considered in absence of this skin manifestation. PMID:24357603

Contreras-Capetillo, Silvina N; Lombardi, Maria Paola; Pinto-Escalante, Doris; Hennekam, Raoul C

2014-03-01

182

Effect of conjugation length on nonlinear optical parameters of anthraquinone dyes investigated using He–Ne laser operating in CW mode  

NASA Astrophysics Data System (ADS)

We report the studies on third-order optical nonlinearity and optical limiting of anthraquinone dyes. Z-scan technique was employed to evaluate the nonlinear parameters such as nonlinear absorption coefficient ?eff and nonlinear index of refraction n2. Continuous wave He–Ne laser was used as the source of excitation. The estimated values of ?eff, n2 and ?(3) are of the order of 10?3 cm/W, 10?5 esu and 10?7 esu respectively. The presence of donor and acceptor groups in the structure results in increase in conjugation length. This resulted in the enhancement of nonlinear optical parameters values of the dye. Multiple diffraction rings were observed when the samples were exposed to laser beam due to thermal lensing. Dyes exhibited good optical limiting behavior under the experimental conditions. The results indicate that the dyes investigated here are materialise as candidates for photonics device applications such as optical power limiters.

Pramodini, S.; Poornesh, P.

2014-10-01

183

Novel multifusion optical imaging sensing principles  

Microsoft Academic Search

The goal of this study is to present novel, multifusion, optical imaging sensing principles, based on laser polarimetric imaging of targets surrounded by scattered media, using the Mueller matrices based formalism. Specifically, the novelty of the imaging system consists in the fusion of dual-energy imaging principles, with polarimetric imaging principles at varying focal lengths and exposures. The experimental results indicate

G. C. Giakos

2004-01-01

184

Focal edge association to glaucoma diagnosis.  

PubMed

Glaucoma is an optic nerve disease resulting in the loss of vision. There are two common types of glaucoma: open angle glaucoma and angle closure glaucoma. Glaucoma type classification is important in glaucoma diagnosis. Clinically, ophthalmologists examine the iridocorneal angle between iris and cornea to determine the glaucoma type as well as the degree of closure. However, manual grading of the iridocorneal angle images is subjective and often time consuming. In this paper, we propose focal edge for automated iridocorneal angle grading. The iris surface is located to determine focal region and focal edges. The association between focal edges and angle grades is built through machine learning. A modified grading system with three grades is adopted. The experimental results show that the proposed method can correctly classify 87.3% open angle and 88.4% closed angle. Moreover, it can correctly classify 75.0% grade 1 and 77.4% grade 0 for angle closure cases. PMID:22255334

Cheng, Jun; Liu, Jiang; Wong, Damon Wing Kee; Tan, Ngan Meng; Lee, Beng Hai; Cheung, Carol; Baskaran, Mani; Wong, Tien Yin; Aung, Tin

2011-01-01

185

Gas spectroscopy and optical path-length assessment in scattering media using a frequency-modulated continuous-wave diode laser  

NASA Astrophysics Data System (ADS)

Simultaneous assessment of the spectroscopic absorption signal of gas enclosed in a scattering medium and the corresponding optical path length of the probing light is demonstrated using a single setup. Sensitive gas absorption measurements are performed by a tunable diode laser using wavelength-modulation spectroscopy, while the path length is evaluated by the frequency-modulated cw technique commonly used in the field of telecommunication. Proof-of-principle measurements are demonstrated with water vapor as the absorbing gas and using polystyrene foam as an inhomogeneously scattering medium. The combination of these techniques opens up new possibilities for straightforward evaluation of gas presence and exchange in scattering media.

Mei, Liang; Jayaweera, Hiran; Lundin, Patrik; Svanberg, Sune; Somesfalean, Gabriel

2011-08-01

186

Gas spectroscopy and optical path-length assessment in scattering media using a frequency-modulated continuous-wave diode laser.  

PubMed

Simultaneous assessment of the spectroscopic absorption signal of gas enclosed in a scattering medium and the corresponding optical path length of the probing light is demonstrated using a single setup. Sensitive gas absorption measurements are performed by a tunable diode laser using wavelength-modulation spectroscopy, while the path length is evaluated by the frequency-modulated cw technique commonly used in the field of telecommunication. Proof-of-principle measurements are demonstrated with water vapor as the absorbing gas and using polystyrene foam as an inhomogeneously scattering medium. The combination of these techniques opens up new possibilities for straightforward evaluation of gas presence and exchange in scattering media. PMID:21847151

Mei, Liang; Jayaweera, Hiran; Lundin, Patrik; Svanberg, Sune; Somesfalean, Gabriel

2011-08-15

187

An optical vernier technique for in situ measurement of the length of long Fabry-Pérot cavities  

Microsoft Academic Search

We propose a method for in situ measurement of the length of kilometre-sized Fabry-Pérot cavities in laser gravitational wave detectors. The method is based on the vernier, which occurs naturally when the laser beam incident on the cavity has a sideband. By changing the length of the cavity over several wavelengths we obtain a set of carrier resonances alternating with

M. Rakhmanov; M. Evans; H. Yamamoto

1999-01-01

188

Focal vibration in neurorehabilitation.  

PubMed

During the last decade, many studies have been carried out to understand the effects of focal vibratory stimuli at various levels of the central nervous system and to study pathophysiological mechanisms of neurological disorders as well as the therapeutic effects of focal vibration in neurorehabilitation. This review aimed to describe the effects of focal vibratory stimuli in neurorehabilitation including the neurological diseases or disorders like stroke, spinal cord injury, multiple sclerosis, Parkinson's' disease and dystonia. In conclusion, focal vibration stimulation is well tolerated, effective and easy to use, and it could be used to reduce spasticity, to promote motor activity and motor learning within a functional activity, even in gait training, independent from etiology of neurological pathology. Further studies are needed in the future well-designed trials with bigger sample size to determine the most effective frequency, amplitude and duration of vibration application in the neurorehabilitation. PMID:24842220

Murillo, N; Valls-Sole, J; Vidal, J; Opisso, E; Medina, J; Kumru, H

2014-04-01

189

A surface micromachined optical scanner array using photoresist lenses fabricated by a thermal reflow process  

Microsoft Academic Search

This paper presents the design, fabrication, and operation of a newly developed micromechanical optical scanner array using a translating microlens. We have used photoresist reflow technique to form a microlens on a surface micromachined XY-stage of the scratch-drive actuation mechanism. The lens scanner is placed at the focal length from an incident optical fiber to collimate the transmitting light. The

Hiroshi Toshiyoshi; Guo-Dung John Su; Jason LaCosse; Ming C. Wu

2003-01-01

190

CONTROL OF LASER RADIATION PARAMETERS: Diffraction efficiency of layer transmission optics  

NASA Astrophysics Data System (ADS)

The efficiency of diffraction optics, in the form of transmission gratings and zone plates, in the soft x-ray range is considered. Analytic expressions are obtained for the diffraction efficiency. These expressions contain all the parameters of transmission gratings and zone plates: the optical constants of the materials, thickness, focal length, magnification, aperture angles, etc.

Vinogradov, Aleksandr V.; Postnov, A. A.

1995-12-01

191

Focal plane metrology for the LSST camera  

Microsoft Academic Search

Meeting the science goals for the Large Synoptic Survey Telescope (LSST) translates into a demanding set of imaging performance requirements for the optical system over a wide (3.5°) field of view. In turn, meeting those imaging requirements necessitates maintaining precise control of the focal plane surface (10 mum P-V) over the entire field of view (640 mm diameter) at the

Andrew P. Rasmussen; Layton Hale; Peter Kim; Eric Lee; Martin Perl; Rafe Schindler; Peter Takacs; Timothy Thurston

2006-01-01

192

Simplified model for optical rectification of broadband terahertz pulses in lossy waveguides including a new generalized expression for the coherence length.  

PubMed

We present a simplified coupled mode theory (CMT), suited for high losses, to describe ultra-broadband THz generation through optical rectification (OR) of fs infrared pulses in waveguides. We derive a new expression that incorporates loss effects into the coherence length for OR. The simplified approach reproduces the results of a computationally rigorous integral CMT that must be used for broadband THz generation. With the new model we perform a parametric study to establish the optimal conditions for OR in symmetric, five-layer, metal/cladding/core structures with electro optic polymer cores. We find conversion efficiencies as high as 35 × 10?? W?¹ and bandwidths up to 20 THz when pumping at 1900 nm. We find that low-loss-cladding layers enhance the efficiency for phase-matched structures, increase the interaction length, and improve the stability of the efficiency with respect to variations in waveguide parameters. PMID:24104348

Vallejo, Felipe A; Hayden, L Michael

2013-10-01

193

Lateral compliance and elastic stability of a dual-coated optical fiber of finite length, with application to nano-rods embedded into low-modulus elastic media  

Microsoft Academic Search

We address the lateral compliance and elastic stability of a dual-coated fiber of finite length (such as, e.g., an optical fiber interconnect) and apply the obtained solution to a nano-rod (nano-wire, nano-fiber, carbon nano-tube) embedded into a low-modulus elastic medium. The latter situation is encountered in nano-composites, as well as in some advanced heat-spreaders employing nano-rod-arrays. Both the photonic (dual-coated

E. Suhir

2009-01-01

194

AFM-based measurement of the mechanical properties of thin polymer films and determination of the optical path length of nearly index-matched cavities  

NASA Astrophysics Data System (ADS)

Two technologies, immersion and imprint lithography, represent important stepping stones for the development of the next generation of lithography tools. However, although the two approaches offer important advantages, both pose many significant technological challenges that must be overcome before they can be successfully implemented. For imprint lithography, special care must be taken when choosing an etch barrier because studies have indicated that some physical material properties may be size dependent. Additionally, regarding immersion lithography, proper image focus requires that the optical path length between the lens and substrate be maintained during the entire writing process. The work described in this document was undertaken to address the two challenges described above. A new mathematical model was developed and used in conjunction with AFM nano-indentation techniques to measure the elastic modulus of adhesive, thin polymer films as a function of the film thickness. It was found that the elastic modulus of the polymer tested did not change appreciably from the value determined using bulk measurement techniques in the thickness range probed. Additionally, a method for monitoring and controlling the optical path length within the gap of a nearly index-matching cavity based on coherent broadband interference was developed. In this method, the spectrum reflected for a cavity illuminated with a modelocked Ti:Sapphire laser was collected and analyzed using Fourier techniques. It was found that this method could determine the optical path length of the cavity, quickly and accurately enough to control a servo-based feedback system to correct deviations in the optical path length in real time when coupled with special computation techniques that minimized unnecessary operations.

Wieland, Christopher F.

195

Optical vernier technique for in-situ measurement of the length of long Fabry-Perot cavities  

Microsoft Academic Search

We propose a method for in-situ measurement of the length of kilometer size\\u000aFabry-Perot cavities in laser gravitational wave detectors. The method is based\\u000aon the vernier, which occurs naturally when the laser incident on the cavity\\u000ahas a sideband. By changing the length of the cavity over several wavelengths\\u000awe obtain a set of carrier resonances alternating with sideband

M. Rakhmanov; M. Evans; H. Yamamoto

1998-01-01

196

About focal tolerances of the segments of Deutsches Grossteleskop  

NASA Astrophysics Data System (ADS)

In order to address the variance in the focal lengths of the segments for the Deutsches Grossteleskop (DGT), a method is delineated to calculate permissible focal tolerances. Sets of arbitrarily distributed delta-f (differences in focal lengths), where for each the average is zero and the standard deviation is normalized to 1 mm, are used to calculate the permissible tolerance. The DGT's correlation function provides the criteria for the analysis, and the results demonstrate that the two types of segmentation considered should have a delta-f of 0.072 for the four-quadrant configuration and of 0.360 for the 13-piece configuration.

Kuehne, Christoph

1990-08-01

197

Passive Thermal Compensation of the Optical Bench of the Galaxy Evolution Explorer  

NASA Technical Reports Server (NTRS)

The Galaxy Evolution Explorer is an orbiting space telescope that will collect information on star formation by observing galaxies and stars in ultraviolet wavelengths. The optical bench supporting detectors and related optical components used an interesting and unusual passive thermal compensation technique to accommodate thermally-induced focal length changes in the optical system. The proposed paper will describe the optical bench thermal compensation design including concept, analysis, assembly and testing results.

Ford, Virginia; Parks, Rick; Coleman, Michelle

2004-01-01

198

Imprinting aberrations in the Stokes parameters of a focal spot  

NASA Astrophysics Data System (ADS)

We explore polarization distribution in point spread functions and Stokes parameter signatures of pupil aberrations. With the aid of stress-engineered optical elements, we explore how pupil aberrations map onto Stokes parameters in the focal plane.

Beckley, Amber M.; Brown, Thomas G.

2010-07-01

199

Extra focal convective suppressing solar collector. Final technical progress report.  

National Technical Information Service (NTIS)

This progress report describes work done on the Extra Focal Convective Suppressing Solar Collector. The topics of the report include sensor refinement for the tracking electronics, tracking controller refinement, system optics evaluation, absorber system ...

1996-01-01

200

Towards dualband megapixel QWIP focal plane arrays  

NASA Astrophysics Data System (ADS)

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024 × 1024 pixel quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NE?T) of 17 mK at a 95 K operating temperature with f/2.5 optics at 300 K background and the LWIR detector array has demonstrated a NE?T of 13 mK at a 70 K operating temperature with the same optical and background conditions as the MWIR detector array after the subtraction of system noise. Both MWIR and LWIR focal planes have shown background limited performance (BLIP) at 90 K and 70 K operating temperatures respectively, with similar optical and background conditions. In addition, we have demonstrated MWIR and LWIR pixel co-registered simultaneously readable dualband QWIP focal plane arrays. In this paper, we will discuss the performance in terms of quantum efficiency, NE?T, uniformity, operability, and modulation transfer functions of the 1024 × 1024 pixel arrays and the progress of dualband QWIP focal plane array development work.

Gunapala, S. D.; Bandara, S. V.; Liu, J. K.; Mumolo, J. M.; Hill, C. J.; Rafol, S. B.; Salazar, D.; Woolaway, J.; LeVan, P. D.; Tidrow, M. Z.

2007-04-01

201

Toward dualband megapixel QWIP focal plane arrays  

NASA Astrophysics Data System (ADS)

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024x1024 pixel InGaAs/GaAs/AlGaAs based quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NE?T) of 17 mK at a 95K operating temperature with f/2.5 optics at 300K background and the LWIR detector array has demonstrated a NE?T of 13 mK at a 70K operating temperature with the same optical and background conditions as the MWIR detector array after the subtraction of system noise. Both MWIR and LWIR focal planes have shown background limited performance (BLIP) at 90K and 70K operating temperatures respectively, with similar optical and background conditions. It is well known that III-V compound semiconductor materials such as GaAs, InP, etc. are easy to grow and process into devices. In addition, III-V compound semiconductors are available in large diameter wafers, up to 8-inches. Thus, III-V compound semiconductor based infrared focal plane technologies such as QWIP, InSb, and strain layer superlattices (SLS) are potential candidates for the development of large format focal planes such as 4096x4096 pixels and larger. In this paper, we will discuss the possibility of extending the infrared detector array size up to 16 megapixels.

Gunapala, S. D.; Bandara, S. V.; Liu, J. K.; Mumolo, J. M.; Hill, C. J.; Kurth, E.; Woolaway, J.; LeVan, P. D.; Tidrow, M. Z.

2007-05-01

202

Towards Dualband Megapixel QWIP Focal Plane Arrays  

NASA Technical Reports Server (NTRS)

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024 x 1024 pixel quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NEDT) of 17 mK at a 95 K operating temperature with f/2.5 optics at 300 K background and the LWIR detector array has demonstrated a NEDT of 13 mK at a 70 K operating temperature with the same optical and background conditions as the MWIR detector array after the subtraction of system noise. Both MWIR and LWIR focal planes have shown background limited performance (BLIP) at 90 K and 70 K operating temperatures respectively, with similar optical and background conditions. In addition, we have demonstrated MWIR and LWIR pixel co-registered simultaneously readable dualband QWIP focal plane arrays. In this paper, we will discuss the performance in terms of quantum efficiency, NEDT, uniformity, operability, and modulation transfer functions of the 1024 x 1024 pixel arrays and the progress of dualband QWIP focal plane array development work.

Gunapala, S. D.; Bandara, S. V.; Liu, J. K.; Mumolo, J. M.; Hill, C. J.; Rafol, S. B.; Salazar, D.; Woolaway, J.; LeVan, P. D.; Tidrow, M. Z.

2006-01-01

203

MTI focal plane assembly design and performance  

NASA Astrophysics Data System (ADS)

The focal plane assembly for the Multispectral Thermal Imager (MTI) consists of sensor chip assemblies, optical filters, and a vacuum enclosure. Sensor chip assemblies, composed of linear detector arrays and readout integrated circuits, provide spatial resolution in the cross-track direction for the pushbroom imager. Optical filters define 15 spectral bands in a range from 0.45 micrometer to 10.7 micrometer. All the detector arrays are mounted on a single focal plane and are designed to operate at 75 K. Three pairs of sensor chip assemblies (SCAs) are required to provide cross-track coverage in all 15 spectral bands. Each pair of SCAs includes detector arrays made from silicon, indium antimonide, and mercury cadmium telluride. Readout integrated circuits multiplex the signals from the detectors to 18 separate video channels. Optical filter assemblies defining the spectral bands are mounted over the linear detector arrays. Each filter assembly consists of several filter strips bonded together side-by- side. The MTI focal plane assembly has been integrated with the rest of the payload and has undergone detailed testing and calibration. This paper includes representative test data for the various spectral bands and the overall performance of the focal plane assembly.

Rienstra, Jeffrey L.; Ballard, Mary

1999-10-01

204

MTI Focal Plane Assembly Design and Performance  

SciTech Connect

The focal plane assembly for the Multispectral Thermal Imager (MTI) consists of sensor chip assemblies, optical filters, and a vacuum enclosure. Sensor chip assemblies, composed of linear detector arrays and readout integrated circuits, provide spatial resolution in the cross-track direction for the pushbroom imager. Optical filters define 15 spectral bands in a range from 0.45 {micro}m to 10.7 {micro}m. All the detector arrays are mounted on a single focal plane and are designed to operate at 75 K. Three pairs of sensor chip assemblies (SCAs) are required to provide cross-track coverage in all 15 spectral bands. Each pair of SCAs includes detector arrays made from silicon, iridium antimonide, and mercury cadmium telluride. Read out integrated circuits multiplex the signals from the detectors to 18 separate video channels. Optical filter assemblies defining the spectral bands are mounted over the linear detector arrays. Each filter assembly consists of several filter strips bonded together side-by-side. The MTI focal plane assembly has been integrated with the rest of the payload and has undergone detailed testing and calibration. This paper includes representative test data for the various spectral bands and the overall performance of the focal plane assembly.

Ballard, M.; Rienstra, J.L.

1999-06-17

205

Solid-state curved focal plane arrays  

NASA Technical Reports Server (NTRS)

The present invention relates to curved focal plane arrays. More specifically, the present invention relates to a system and method for making solid-state curved focal plane arrays from standard and high-purity devices that may be matched to a given optical system. There are two ways to make a curved focal plane arrays starting with the fully fabricated device. One way, is to thin the device and conform it to a curvature. A second way, is to back-illuminate a thick device without making a thinned membrane. The thick device is a special class of devices; for example devices fabricated with high purity silicon. One surface of the device (the non VLSI fabricated surface, also referred to as the back surface) can be polished to form a curved surface.

Nikzad, Shouleh (Inventor); Hoenk, Michael (Inventor); Jones, Todd (Inventor)

2010-01-01

206

Measuring Length  

NSDL National Science Digital Library

This article focuses on young students encountering the measurement of length. The article cites examples of key concepts in recognizing length as an attribute and in proper and improper ways to measure length. Conservation and additivity of length, standard and non-standard units, iteration, and the zero point are among the topics presented.

2009-08-01

207

A monolithic polycapillary focusing optic for polychromatic neutron diffraction applications  

Microsoft Academic Search

We have conducted measurements at five different thermal neutron wavelengths to determine the transmission characteristics of a tapered monolithic focusing lens with a focal length of 100 mm, suitable for time-of-flight diffraction. Both the width of the focused beam and the intensity gain of the optic increase as a function of wavelength. We have performed similar measurements on a polychromatic

D. F. R. Mildner; H. H. Chen-Mayer; W. M. Gibson; T. Gnäupel-Herold; M. E. Miller; H. J. Prask; A. J. Schultz; R. Vitt; R. Youngman

2002-01-01

208

Dense pattern optical multipass cell  

DOEpatents

A multiple pass optical cell and method comprising providing a pair of opposed cylindrical mirrors having curved axes with substantially equal focal lengths, positioning an entrance hole for introducing light into the cell and an exit hole for extracting light from the cell, wherein the entrance hole and exit hole are coextensive or non-coextensive, introducing light into the cell through the entrance hole, and extracting light from the cell through the exit hole.

Silver, Joel A [Santa Fe, NM

2009-01-13

209

Dense Pattern Optical Multipass Cell  

NASA Technical Reports Server (NTRS)

A multiple pass optical cell and method comprising providing a pair of opposed cylindrical mirrors having curved axes with substantially equal focal lengths, positioning an entrance hole for introducing light into the cell and an exit hole for extracting light from the cell, wherein the entrance hole and exit hole are coextensive or non-coextensive, introducing light into the cell through the entrance hole, and extracting light from the cell through the exit hole.

Silver, Joel A. (Inventor)

2009-01-01

210

Focal plane metrology for the LSST camera  

NASA Astrophysics Data System (ADS)

Meeting the science goals for the Large Synoptic Survey Telescope (LSST) translates into a demanding set of imaging performance requirements for the optical system over a wide (3.5°) field of view. In turn, meeting those imaging requirements necessitates maintaining precise control of the focal plane surface (10 ?m P-V) over the entire field of view (640 mm diameter) at the operating temperature (T ~ -100°C) and over the operational elevation angle range. We briefly describe the heirarchical design approach for the LSST Camera focal plane and the baseline design for assembling the flat focal plane at room temperature. Preliminary results of gravity load and thermal distortion calculations are provided, and early metrological verification of candidate materials under cold thermal conditions are presented. A detailed, generalized method for stitching together sparse metrology data originating from differential, non-contact metrological data acquisition spanning multiple (non-continuous) sensor surfaces making up the focal plane, is described and demonstrated. Finally, we describe some in situ alignment verification alternatives, some of which may be integrated into the camera's focal plane.

Rasmussen, Andrew P.; Hale, Layton; Kim, Peter; Lee, Eric; Perl, Martin; Schindler, Rafe; Takacs, Peter; Thurston, Timothy

2006-06-01

211

Focal Cardiac Myocytolysis.  

National Technical Information Service (NTIS)

During the course of a clinical pathologic study of cardiac lesions observed in 375 autopsies at ABCC, focal cardiac myocytolysis (FCM) was found in 21 hearts. There was no evidence that FCM was related to prior exposure at the time of the bomb. Myocardia...

A. Steer T. Kawashima T. Nakashima D. S. Dock K. K. Lee

1975-01-01

212

Analysis of sensitivity and optical path-length in non-invasive measurement of glucose with near infrared spectroscopy  

NASA Astrophysics Data System (ADS)

Non-invasive glucose monitoring with optical methods has obtained increasing interest, in that the methods have shown great benefit for diabetes. Nevertheless, low sensitivity and signal to noise ratio (ratio of effective photons) are two major difficulties in non-invasively NIR spectral monitoring of blood glucose concentration. Designing the optical probe properly is one of the effective ways to improve measuring sensitivity and ratio of effective photons. In this paper, definition about ratio of effective photons in measurement of glucose is introduced. And then effect of glucose on optical properties of human skin is analyzed, based on this, two kind of sensitivities for diffuse reflectance, namely sensitivity to absorption and that to scattering, is derived. To investigate the ratio of effective photons and sensitivities, Monte Carlo simulations have been performed on a three-layered media with optical parameters similar to those of human skin. The results have shown that (1) high ratio of effective photons, even as high as 60%, can be obtained by choosing proper the separation between source and detector; (2) sensitivity of diffuse reflectance to absorption and scattering has different dependence on source-detector separation, which enables one can have different options by making use of different effect from glucose level changing. In the end, some suggestions have been put forward to improve precision of measurement of blood glucose.

Luo, Yunhan; Liu, Rong; Chen, Wenliang; Cui, Houxin; Xu, Kexin

2005-03-01

213

Fast steering mirror implementation for reduction of focal-spot wander in a long-distance free-space optical communication link  

Microsoft Academic Search

One of the causes of power loss in a free-space optical communication link is beam motion or received spot wander. The power spectrum of the spot motion indicates that most of the frequency content is less than ~500 Hz. A fast steering mirror (FSM) controlled by a position-sensing detector (PSD) has the potential to correct for a significant portion of

Michele R. Suite; Harris R. Burris; Christopher I. Moore; Michael J. Vilcheck; Rita Mahon; Carmen Jackson; Mena F. Stell; Mark A. Davis; William S. Rabinovich; William J. Scharpf; Anne E. Reed; G. C. Gilbreath

2004-01-01

214

MWIR and LWIR Megapixel QWIP Focal Plane Arrays  

NASA Technical Reports Server (NTRS)

A mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024x1024 pixel quantum well infrared photodetector (QWIP) focal plane array has been demonstrated with excellent imagery. MWIR focal plane has given noise equivalent differential temperature (NETD) of 19 mK at 95K operating temperature with f/2.5 optics at 300K background and LWIR focal plane has given NEDT of 13 mK at 70K operating temperature with same optical and background conditions as MWIR array. Both of these focal plane arrays have shown background limited performance (BLIP) at 90K and 70K operating temperatures with the same optics and background conditions. In this paper, we will discuss their performance in quantum efficiency, NETD, uniformity, and operability.

Gunapala, Sarath D.; Bandara, S. V.; Liu, J. K.; Rafol, S. B.; Thang, J.; Mumolo, Jason; Tidrow, M.; LeVan, P. D.; Hill, C.

2004-01-01

215

Formation of multiple focal spots using a high NA lens with a complex spiral phase mask  

NASA Astrophysics Data System (ADS)

The formation of a transversally polarized beam by transmitting a tightly focused double-ring-shaped azimuthally polarized beam through a complex spiral phase mask and high numerical aperture lens is presented based on vector diffraction theory. The generation of transversally polarized focal spot segment splitting and multiple focal spots is illustrated numerically. Moreover, we found that a properly designed complex spiral phase mask can move the focal spots along the optical axis in the z direction. Therefore, one can achieve a focal segment of two, three or multiple completely transversely polarized focal spots, which finds applications in optical trapping and in material processing technologies.

Lalithambigai, K.; Anbarasan, P. M.; Rajesh, K. B.

2014-07-01

216

Active optical system for any field angle zoom  

NASA Astrophysics Data System (ADS)

We have theoretically proposed a new type of active optical zoom system. It can change the magnification of an imaging system at any field angle, namely, it can change the effective focal length at a limited region of interest and simultaneously maintain high resolution. It is comprised of two static aspheric mirrors and two deformable mirrors; furthermore, by changing the curvature of mirrors the focal length can be adjusted from -399 to -558.6 mm. The system reduces the bandwidth of data transmission and may find potential applications in high speed photography.

Hu, Shaolei; Zhao, Xin; Dong, Weihui; Xie, Yongjun

2011-11-01

217

A combined electron beam/optical lithography process step for the fabrication of sub-half-micron-gate-length MMIC chips  

NASA Technical Reports Server (NTRS)

Advanced radar and communication systems rely heavily on state-of-the-art microelectronics. Systems such as the phased-array radar require many transmit/receive (T/R) modules which are made up of many millimeter wave - microwave integrated circuits (MMIC's). The heart of a MMIC chip is the Gallium Arsenide (GaAs) field-effect transistor (FET). The transistor gate length is the critical feature that determines the operating frequency of the radar system. A smaller gate length will typically result in a higher frequency. In order to make a phased array radar system economically feasible, manufacturers must be capable of producing very large quantities of small-gate-length MMIC chips at a relatively low cost per chip. This requires the processing of a large number of wafers with a large number of chips per wafer, minimum processing time, and a very high chip yield. One of the bottlenecks in the fabrication of MIMIC chips is the transistor gate definition. The definition of sub-half-micron gates for GaAs-based field-effect transistors is generally performed by direct-write electron beam lithography (EBL). Because of the throughput limitations of EBL, the gate-layer fabrication is conventionally divided into two lithographic processes where EBL is used to generate the gate fingers and optical lithography is used to generate the large-area gate pads and interconnects. As a result, two complete sequences of resist application, exposure, development, metallization and lift-off are required for the entire gate structure. We have baselined a hybrid process, referred to as EBOL (electron beam/optical lithography), in which a single application of a multi-level resist is used for both exposures. The entire gate structure, (gate fingers, interconnects and pads), is then formed with a single metallization and lift-off process. The EBOL process thus retains the advantages of the high-resolution E-beam lithography and the high throughput of optical lithography while essentially eliminating an entire lithography/metallization/lift-off process sequence. This technique has been proven to be reliable for both trapezoidal and mushroom gates and has been successfully applied to metal-semiconductor and high-electron-mobility field-effect transistor (MESFET and HEMT) wafers containing devices with gate lengths down to 0.10 micron and 75 x 75 micron gate pads. The yields and throughput of these wafers have been very high with no loss in device performance. We will discuss the entire EBOL process technology including the multilayer resist structure, exposure conditions, process sensitivities, metal edge definition, device results, comparison to the standard gate-layer process, and its suitability for manufacturing.

Sewell, James S.; Bozada, Christopher A.

1994-01-01

218

Focal plane imaging systems for millimeter wavelengths  

Microsoft Academic Search

The authors discuss critical aspects of imaging system design and describe several different imaging systems employing focal plane array receivers operating in the 3-mm-2-mm wavelength range. Recent progress in millimeter-wavelength optics, antennas, receivers and other components permits greatly enhanced system performance in a wide range of applications. A radiometric camera for all-weather autonomous aircraft landing capability and a high sensitivity

P. F. Goldsmith; C.-T. Hsieh; G. R. Huguenin; J. Kapitzky; E. L. Moore

1993-01-01

219

Focal Plane Metrology for the LSST Camera  

Microsoft Academic Search

Meeting the science goals for the Large Synoptic Survey Telescope (LSST) translates into a demanding set of imaging performance requirements for the optical system over a wide (3.5{sup o}) field of view. In turn, meeting those imaging requirements necessitates maintaining precise control of the focal plane surface (10 μm P-V) over the entire field of view (640 mm diameter) at

Andrew P. A Rasmussen; Layton Hale; Peter Kim; Eric Lee; Martin Perl; Rafe Schindler; Peter Takacs; Timothy Thurston

2007-01-01

220

Theoretical and experimental analysis of basic parameters of two-element optical systems.  

PubMed

Our work presents detailed theoretical analysis of two-element optical systems of telephoto lenses and objectives of anallactic telescopes with internal focusing. The first element of such systems has positive optical power and the second element has negative optical power. This type of optical system is widespread in practice mainly in the field of photographic lenses and in surveying instruments (theodolites, leveling instruments, etc.) where the anallactic telescope with internal focusing is being used. In our work we propose methods to determine the basic parameters of such objectives, i.e., the focal lengths of both the elements of the objective lens and their mutual axial separation. Furthermore, the detailed analysis of aberration properties of such optical systems is performed and methods for measuring the focal lengths of individual elements and their mutual distance without the need for disassembling the investigated optical system are presented. PMID:23089783

Mikš, Antonín; Novák, Pavel

2012-10-20

221

Optical fiber imaging laser radar  

Microsoft Academic Search

We have developed the Optical Fiber Imaging Laser Radar based on the focal plane array detection using the small number of detectors less than the number of the focal plane array resolution. For this focal array detection, first, we made the optical fiber dissector which has one vertical cross section of the 35 x 35 optical fibers square array at

Akira Akiyama; Takahiro Watanabe; Minoru Doshida; Kazuhisa Kanda; Yukiteru Kakimoto; Hiroyuki Yasuo; Masahiro Kuwabara; Hideo Kumagai; Hiromitsu Ishii

2003-01-01

222

Ultra-low-loss optical fiber enabling purely passive 10 Gb/s PON systems with 100 km length.  

PubMed

We demonstrate time division multiplexing (TDM) and wavelength division multiplexing/TDM (WDM/TDM) long reach 10 Gb/s passive optical network (PON) architectures of 100 km reach with no infield amplification or dispersion compensation. The purely passive nature of the 100 km systems is enabled by the use of ultra-low-loss optical fiber with average attenuation of 0.17 dB/km and downstream transmission with a 10 Gb/s signal modulated with the duobinary format. The high tolerance of duobinary to dispersion, stimulated Brillouin scattering (SBS), and self-phase modulation (SPM) are all key factors to achieving good system performance at this distance, as is the significantly reduced loss from the ultra-low-loss fiber. We show that this combination of fiber and downstream signal format allow split ratios up to 1:128 for both system architectures. The achievable split ratio is reduced for standard single-mode fiber and/or use of an NRZ modulated downstream signal. Standard strength forward error correction (FEC) is used for the WDM/TDM system but is not required for the TDM system. PMID:19219143

Downie, John D; Ruffin, A Boh; Hurley, Jason

2009-02-16

223

Coaxial feed array for a short focal-length reflector  

Microsoft Academic Search

The design of array feeds for deep dishes is complicated by the need to closely pack the elements to minimize scan gain loss and coma sidelobes. An example is the design of a 4-element multibeam feed for the Lovell radio telescope at Jodrell Bank, UK, which is prime-focus fed reflector with a diameter (D) of 76.2 m and f\\/D=0.3, where

T. S. Bird

1997-01-01

224

Focal cortical dysplasia - review  

PubMed Central

Summary Focal cortical dysplasia is a malformation of cortical development, which is the most common cause of medically refractory epilepsy in the pediatric population and the second/third most common etiology of medically intractable seizures in adults. Both genetic and acquired factors are involved in the pathogenesis of cortical dysplasia. Numerous classifications of the complex structural abnormalities of focal cortical dysplasia have been proposed – from Taylor et al. in 1971 to the last modification of Palmini classification made by Blumcke in 2011. In general, three types of cortical dysplasia are recognized. Type I focal cortical dysplasia with mild symptomatic expression and late onset, is more often seen in adults, with changes present in the temporal lobe. Clinical symptoms are more severe in type II of cortical dysplasia usually seen in children. In this type, more extensive changes occur outside the temporal lobe with predilection for the frontal lobes. New type III is one of the above dysplasias with associated another principal lesion as hippocampal sclerosis, tumor, vascular malformation or acquired pathology during early life. Brain MRI imaging shows abnormalities in the majority of type II dysplasias and in only some of type I cortical dysplasias. The most common findings on MRI imaging include: focal cortical thickening or thinning, areas of focal brain atrophy, blurring of the gray-white junction, increased signal on T2- and FLAIR-weighted images in the gray and subcortical white matter often tapering toward the ventricle. On the basis of the MRI findings, it is possible to differentiate between type I and type II cortical dysplasia. A complete resection of the epileptogenic zone is required for seizure-free life. MRI imaging is very helpful to identify those patients who are likely to benefit from surgical treatment in a group of patients with drug-resistant epilepsy. However, in type I cortical dysplasia, MR imaging is often normal, and also in both types the lesion seen on MRI may be smaller than the seizure-generating region seen in the EEG. The abnormalities may also involve vital for life brain parts, where curative surgery will not be an option. Therefore, other diagnostic imaging techniques such as FDG PET, MEG, DTI and intra-cranial EEG are widely used to establish the diagnosis and to decide on management. With advances in both genetics and neuroimaging, we may develop a better understanding of patients with drug-resistant epilepsy, which will help us to provide more successful pharmacological and/or surgical treatment in the future.

Kabat, Joanna; Krol, Przemyslaw

2012-01-01

225

Design and optimization of programmable lens array for adaptive optics  

Microsoft Academic Search

The ability of a liquid-crystal spatial light modulator (LC-SLM) to generate lens and lens arrays of variable focal lengths and selectable fields of view (FOV) makes them excellent candidates for many adaptive optics applications including free-space optical telecommunications, astronomy and retinal imaging. In this paper, we report a range of dynamic lens and lens array designs and optimization using a

Zhenglin Wang; Seow Hwang Eng; Kamal Alameh

2007-01-01

226

Automated inspection station for optical inspection of multifocal intraocular lenses  

NASA Astrophysics Data System (ADS)

An automated inspection station is a specifically designed for quality assurance inspection of multifocal intraocular lenses in the manufacturing environment. The station provides automatic measurements for all required optical parameters of the AMO ARRAYTM multifocal IOL, which includes labeling parameters such as effective focal length, aqueous diopter power (distance power), add power (near power), and depth-of-focus (DOF) around the distance power, and optical quality parameters such as resolution efficiency, image contrast modulation (MTF), through focus response (TFR), and astigmatism.

Sun, Rong; Bolton, Paul W.; Portney, Valdemar

1994-02-01

227

Length Scales and Structural Dynamics in Nematogen Pseudonematic Domains Measured with 2D IR Vibrational Echoes and Optical Kerr Effect Experiments.  

PubMed

Nematogen liquids in the isotropic phase are macroscopically homogeneous but on multinanometer length scales have pseudonematic domains with correlation lengths that grow as the isotropic to nematic phase transition temperature (TNI) is approached from above. Orientational relaxation of nematogens in the isotropic phase manifests as two fast power laws and a slow exponential decay when measured by optical heterodyne detected optical Kerr effect (OHD-OKE) experiments. The long time exponential relaxation is associated with complete randomization of pseudonematic domains. We examine the effect of local orientational correlation on spectral diffusion (structural evolution) experienced by a vibrational probe molecule within the pseudonematic domains of 4-cyano-4'-pentylbiphenyl (5CB) using two-dimensional infrared (2D IR) vibrational echo spectroscopy. The addition of low concentration 4-pentyl-4'-thiocyanobiphenyl (5SCB) as a long-lived vibrational probe to 5CB is shown to lower TNI of the sample slightly, but the fast power law dynamics and exponential decays observed by OHD-OKE spectroscopy are unchanged. We compare the complete orientational relaxation and spectral diffusion for samples of 5SCB in 5CB to 5SCB in 4-pentylbiphenyl (5B) at four temperatures above TNI. 5B has a molecular structure similar to 5CB but is not a nematogen. At all but the lowest temperature, the spectral diffusion in 5CB and 5B is described well as a triexponential decay with very similar time constants. The results demonstrate that the presence of local orientational order at temperatures well above TNI does not affect the spectral diffusion (structural evolution) within pseudonematic domains when the correlation lengths are short. However, when the temperature of the sample is held very close to TNI, the spectral diffusion in 5CB slows dramatically while that in 5B does not. It is only as the correlation length becomes very long that its presence impacts the spectral diffusion (structural fluctuations) sensed by the vibrational probes located in pseudonematic domains. The orientational relaxation is modeled with schematic mode coupling theory (MCT). Fitting with MCT provides density and orientational correlation functions. The density correlation decays are similar for 5B and 5CB, but the orientational correlation decays are much slower for 5CB. Additionally, the time dependence of the spectral diffusion in 5CB is strikingly similar to that of the density correlation function decay, while the orientational correlation function decay is far too slow to contribute to the spectral diffusion. Therefore, density fluctuations are likely the source of spectral diffusion at temperatures at least 5 K above TNI. PMID:24521155

Sokolowsky, Kathleen P; Bailey, Heather E; Fayer, Michael D

2014-07-17

228

Variable-focal lens using electroactive polymer actuator  

NASA Astrophysics Data System (ADS)

The paper describes a simple and cost-effective design and fabrication process of a liquid-filled variable-focal lens. The lens was made of soft polymer material, its shape and curvature can be controlled by hydraulic pressure. An electroactive polymer is used as an actuator. A carbon-polymer composite (CPC) was used. The device is composed of elastic membrane upon a circular lens chamber, a reservoir of liquid, and a channel between them. It was made of three layers of polydimethylsiloxane (PDMS), bonded using the partial curing technique. The channels and reservoir were filled with incompressible liquid after curing process. A CPC actuator was mechanically attached to reservoir to compress or decompress the liquid. Squeezing the liquid between the reservoir and the lens chamber will push the membrane inward or outward resulting in the change of the shape of the lens and alteration of its focal length. Depending on the pressure the lens can be plano-convex or plano-concave or even switch between the two configurations. With only a few minor modifications it is possible to fabricate bi-convex and bi-concave lenses. The lens with a 1 mm diameter and the focal length from infinity to 17 mm is reported. The 5x15mm CPC actuator with the working voltage of only up to +/-2.5 V was capable to alter the focal length within the full range of the focal length in 10 seconds.

Vunder, V.; Punning, A.; Aabloo, A.

2011-03-01

229

Pharmacotherapy of focal epilepsy.  

PubMed

Introduction: Epilepsy is the most common neurological condition worldwide with significant psychosocial and physical morbidity. Its management requires expertise and good pharmacological knowledge of the available options. Areas covered: This review covers the management of focal epilepsy addressing the common questions arising through the patients' journey, including timing of starting initial treatment, monotherapy options, add-on treatment for refractory cases and withdrawal of medication during remission. Expert opinion: Initiating anti-epileptic drug (AED) treatment requires assessment of patient preferences and of evidence of benefit and harm. Evidence of benefit will come primarily from randomised controlled trials, although in epilepsy, most trials are undertaken to inform regulatory decision and have important limitations for informing clinical decisions. Evidence about harm may come not only from randomised trials but also from other sources. Most patients will start treatment following a second focal seizure. Carbamazepine and lamotrigine are good initial monotherapy options. Newer AEDs have proof of efficacy as monotherapy but evidence is insufficient to recommend them as first-line treatments. For refractory cases, there are an increasing number of AEDs available, but evidence of efficacy is primarily from placebo-controlled trials, and there is no robust evidence to inform a choice among treatments. PMID:24856909

Iyer, Anand; Marson, Anthony

2014-08-01

230

Intelligent Optical Systems Using Adaptive Optics  

NASA Technical Reports Server (NTRS)

Until recently, the phrase adaptive optics generally conjured images of large deformable mirrors being integrated into telescopes to compensate for atmospheric turbulence. However, the development of smaller, cheaper devices has sparked interest for other aerospace and commercial applications. Variable focal length lenses, liquid crystal spatial light modulators, tunable filters, phase compensators, polarization compensation, and deformable mirrors are becoming increasingly useful for other imaging applications including guidance navigation and control (GNC), coronagraphs, foveated imaging, situational awareness, autonomous rendezvous and docking, non-mechanical zoom, phase diversity, and enhanced multi-spectral imaging. The active components presented here allow flexibility in the optical design, increasing performance. In addition, the intelligent optical systems presented offer advantages in size and weight and radiation tolerance.

Clark, Natalie

2012-01-01

231

The Effect of Side-Chain Length on the Solid-State Structure and Optical Properties of F8BT: A DFT Study  

NASA Astrophysics Data System (ADS)

Using the long-range corrected hybrid density functional theory (DFT/B97D) approach, we have performed bulk solid state calculations to investigate the influence of side-chain length on the molecular packing and optical properties of poly (9,9-di-n-octylfluorene-alt-benzothiadiazole) or F8BT. Two different packing structures, the lamellar and nearly hexagonal, were obtained corresponding to longer and shorter side-chains respectively. This behavior can be attributed to the micro-phase separations between the flexible side-chains and the rigid backbones and is in agreement with previous investigations for other hairy-rod polymers. In addition, as a result of the efficient inter-chain interactions for the lamellar structure, the dihedral angle between the F8 and BT units is reduced providing a more planar configuration for the backbone which leads to the decreased band gap (by 0.2-0.3 eV) in comparison to the hexagonal phase and the gas phase with no side-chain. Time-dependent DFT (TDDFT/B3LYP) was also used to study the excited states of the monomer of F8BT optimized in solid-state structures with different side-chain lengths. It is found that the absorption spectrum is red shifted for the polymers with lamellar structure relative to the polymers in hexagonal and gas phases.

Javad Eslamibidgoli, Mohammad; Lagowski, Jolanta B.

2012-02-01

232

Geometric Optics  

NSDL National Science Digital Library

This interactive simulation adapted from the University of Colorado's Physics Education Technology project illustrates how lenses refract light to form images. Manipulate the object, screen, lens, and focal length and observe how the image adjusts.

Foundation, Wgbh E.

2007-08-09

233

All-reflective optical bifocal zooming system without moving elements based on deformable mirror for space camera application.  

PubMed

The space camera with variable focal length is capable of capturing images with variable resolution and variable field of view. This is useful for space-borne reconnaissance because the camera can switch between coarse and fine reconnaissance flexibly. However, the traditional optical zooming relies on moving elements which might influence the momentum balance of the satellite platform. Therefore, we present a prototype design using the piezo deformable mirror (PDM) to realize an all-reflective optical bifocal zooming system. By changing the curvature radius of the PDM, the focal length can be switched between 48 and 192 mm without moving elements involved. With the focal length experiencing 4× magnification, the system performance is still approaching diffraction-limited performance, and the maximum stroke of the PDM is also within its physical limits. Experiments demonstrate that the principle is correct and the design is successful. PMID:23434990

Zhao, Hui; Fan, Xuewu; Zou, Gangyi; Pang, Zhihai; Wang, Wei; Ren, Guorui; Du, Yunfei; Su, Yu

2013-02-20

234

Math Focal Points: Grade 5  

NSDL National Science Digital Library

For teachers of grade 5, NCTM offers online resources, many interactive, that support teaching of the specific areas defined by NCTM as Focal Points. Focal points are clusters of related knowledge, skills, and concepts, and for Grade 5 they are Division of Whole Numbers, Fractions and Decimals and 3-D Shapes. Commentary and links to Focal Points for grades K-8 are provided. Links to background information and further training opportunities are provided.

Herrera, Terese A.

2011-09-19

235

Studying charged particle optics: an undergraduate course  

Microsoft Academic Search

This paper describes some computer-based activities to bring the study of charged particle optics to undergraduate students, to be performed as a part of a one-semester accelerator-based experimental course. The computational simulations were carried out using the commercially available SIMION program. The performance parameters, such as the focal length and P-Q curves are obtained. The three-electrode einzel lens is exemplified

V. Ovalle; D. R. Otomar; J. M. Pereira; N. Ferreira; R. R. Pinho; A. C. F. Santos

2008-01-01

236

Studying charged particle optics: an undergraduate course  

Microsoft Academic Search

This paper describes some computer-based activities to bring the study of charged particle optics to undergraduate students, to be performed as a part of a one-semester accelerator-based experimental course. The computational simulations were carried out using the commercially available SIMION program. The performance parameters, such as the focal length and P-Q curves are obtained. The three-electrode einzel lens is exemplified

237

Focal and segmental glomerulosclerosis.  

PubMed

An increasing cause of end-stage renal disease is the pathological lesion focal and segmental glomerulosclerosis (FSGS). FSGS is characterized by proteinuria and frequently nephrotic syndrome with ensuing renal failure. The etiology remains unknown in the majority of individuals. The idiopathic form of FSGS is most common; however, secondary forms of FSGS do exist. There is a form of FSGS that is fulminant that frequently recurs after renal transplantation with an estimated frequency of approximately 30%, suggesting that the pathogenesis is not solely a result of intrinsic kidney disease. Recently, hereditary forms of the disease were recognized as well as those associated with other congenital syndromes. Known genetic causes of the hereditary form of this disease have been suggested to account for upwards of 18% of cases. This review will address recent discoveries of the genetic mechanisms of hereditary FSGS and the current interpretations of their interactions at the slit diaphragm. PMID:16952054

Daskalakis, N; Winn, M P

2006-11-01

238

Electro-optically actuated liquid-lens zoom  

NASA Astrophysics Data System (ADS)

Progressive miniaturization and mass market orientation denote a challenge to the design of dynamic optical systems such as zoom-lenses. Two working principles can be identified: mechanical actuation and application of active optical components. Mechanical actuation changes the focal length of a zoom-lens system by varying the axial positions of optical elements. These systems are limited in speed and often require complex coupled movements. However, well established optical design approaches can be applied. In contrast, active optical components change their optical properties by varying their physical structure by means of applying external electric signals. An example are liquidlenses which vary their curvatures to change the refractive power. Zoom-lenses benefit from active optical components in two ways: first, no moveable structures are required and second, fast response characteristics can be realized. The precommercial development of zoom-lenses demands simplified and cost-effective system designs. However the number of efficient optical designs for electro-optically actuated zoom-lenses is limited. In this paper, the systematic development of an electro-optically actuated zoom-lens will be discussed. The application of aberration polynomials enables a better comprehension of the primary monochromatic aberrations at the lens elements during a change in magnification. This enables an enhanced synthesis of the system behavior and leads to a simplified zoom-lens design with no moving elements. The change of focal length is achieved only by varying curvatures of targeted integrated electro-optically actuated lenses.

Pütsch, O.; Loosen, P.

2012-05-01

239

Effect of annular obstruction and numerical aperture in the focal region of high NA objective lens  

NASA Astrophysics Data System (ADS)

In this article, based on the vector diffraction theory, the effect of annular apodization and numerical aperture in the focal region of tightly focused azimuthally polarized Bessel Gaussian beam by high NA lens is investigated numerically. The results show that our proposed system generates a longitudinally polarized beam in sub wavelength focal spot having large uniform focal depth of incident beam with annular aperture for lower NA. Such kind of subwavelength focal segment may find wide applications in optical traps, biological applications, atmospheric sciences and optical manipulation technology.

Suresh, P.; Rajesh, K. B.; Sivasubramonia Pillai, T. V.; Jaroszewicz, Z.

2014-05-01

240

High performance optical materials cyclo olefin polymer ZEONEX  

NASA Astrophysics Data System (ADS)

ZEON CORPORATION developed innovative optical plastic Cyclo Olefin Polymer (COP), ZEONEX (R) with own technology in 1990 then started commercial production of ZEONEX(R) for optical applications with its very unique properties such as high light transmission, low birefringence, low water absorption, and high glass-transition temperature etc. ZEONEX(R) exhibits outstanding optical performance even under high humidity and temperature conditions. In order to meet increasing requirements of optical market, ZEON CORPORATION newly developed ZEONEX(R)F52R which has high glass-transition temperature 156 deg. C and shows the feature of very low focal length change after high-temperature and high-humidity test.

Obuchi, Kazuyuki; Komatsu, Masaaki; Minami, Koji

2007-09-01

241

Megapixel Multi-band QWIP Focal Plane Arrays  

NASA Technical Reports Server (NTRS)

A mid-wavelength 1024x1024 pixel quantum well infrared photodetector (QW) focal plane array has been demonstrated with excellent imagery. Noise equivalent differential temperature (NETD) of 19 mK was achieved at 95K operating temperature with f/2.5 optics at 300K background. This focal plane array has shown background limited performance (BLIP) at 90K operating temperature with the same optics and background conditions. In this paper, we will discuss its performance in quantum efficiency, NETD, uniformity, and operability.

Gunapala, S. D.; Bandara, S. V.; Liu, J. K.; Rafo, S. B.; Hill, C.; Mumolo, J.; Thang, J.; Tidrow, M.; LeVan, P. D.

2004-01-01

242

Optical fiber imaging laser radar  

Microsoft Academic Search

We develop an optical fiber imaging laser radar based on the focal plane array detection method using a small number of detectors less than the number of the focal plane array resolution. For the development of this kind of the focal array detection method, we produce the optical fiber dissector, the movable aperture, and the small-number parallel multichannel pulse counter

Akira Akiyama; Yukiteru Kakimoto; Kazuhisa Kanda; Masahiro Kuwabara; Hiroyuki Yasuo; Eiichiro Mutoh; Hideo Kumagai; Takahiro Watanabe; Minoru Doshida; Hiromitsu Ishii

2005-01-01

243

Robust focusing optics for high-power laser welding  

NASA Astrophysics Data System (ADS)

As available power levels from both fiber and disc lasers rapidly increase, so does the need for more robust beam delivery solutions. Traditional transmissive optics for 1 micron lasers have proven to be problematic in the presence of higher power densities and are more susceptible to focal shift. A new, fully-reflective, optical solution has been developed using mirrors rather than lenses and windows to achieve the required stable focal spot, while still protecting the delicate fiber end. This patent-approved beam focusing solution, referred to as high power reflective focusing optic (HPRFO), involves specialty mirrors and a flowing gas orifice that prevents ingress of contaminants into the optically sensitive region of the assembly. These mirrors also provide a unique solution for increasing the distance between the sensitive optics and the contamination-filled region at the work, without sacrificing spot size. Longer focal lengths and lower power densities on large mass, water-cooled, copper mirrors deliver the robustness needed at increasingly high power levels. The HPRFO exhibits excellent beam quality and minimal focal shift at a fraction of commercially available optics, and has demonstrated consistent reliability on applications requiring 15 kW with prolonged beam-on times.

McAllister, Blake

2014-02-01

244

Finger Length  

NSDL National Science Digital Library

Although life experience plays a huge role in shaping who we are, the foundations of our personality begin in the womb. This Science Update describes a recent study that looks to finger length for signs of a man's pre-natal exposure to testosterone.

Science Update;

2005-03-28

245

Multiple quantum well staring focal plane array  

NASA Astrophysics Data System (ADS)

Multiple quantum well (MQW) devices have evolved from single detectors to fully operational medium resolution (128 x 128 array) IR systems, such as long wave IR (LWIR) cameras capable of optical imaging. The required operating temperature has increased from 40 K to nearly 77 K, and dark current has been reduced from very high values to values that are manageable with processing electronics. This paper provides fabrication, modeling, test, and optimized multiplexing results to demonstrate the advantages of MQW IR staring focal plane array technology.

Gooden, C. E.; Leblanc, R. A.; Stokes, B.; Beck, W. A.; Faska, T.

1992-02-01

246

Smart focal plane technologies for ELT instruments  

NASA Astrophysics Data System (ADS)

Smart Focal Planes are devices that enable the efficient sampling of a telescope's focal plane to feed spectroscopic and imaging instruments. Examples are integral field units (fiber and image slicers), cryogenic beam manipulators, and MOEMS (micro-opto-electromechanical systems) such as miniature slit shutters. These technologies are critical in making best use of the current 8m class telescopes for key science goals such as spectroscopic surveys of high redshift galaxies, and will be even more important for Extremely Large Telescope (ELT) instruments. In fact, the density of pixels in an ELT focal plane with several milliarcsecond resolution will mean that sub-sampling of the field will be needed even for imaging. We have proposed a joint European project to develop these technologies, building on expertise from partners in the UK, France, the Netherlands, Spain, Germany and others, and led by the UK. We describe the current status of these technologies, showing how they will contribute to the feasibility and performance of proposed instruments for ELTs, and concentrating on capabilities within Europe. We then outline the proposed future developments, highlighting the technical challenges, such as the difficulties of manufacturing and verifying complex image slicers with thousands of optical surfaces, and building highly reliable cryogenic mechanisms such as pick-off arms, beam steering mirrors and reconfigurble slit mechanisms.

Cunningham, Colin R.; Ramsay-Howat, Suzanne K.; Garzon, Francisco; Parry, Ian R.; Prieto, Eric; Robertson, David J.; Zamkotsian, Frederic

2004-07-01

247

Focal plane scanner with reciprocating spatial window  

NASA Technical Reports Server (NTRS)

A focal plane scanner having a front objective lens, a spatial window for selectively passing a portion of the image therethrough, and a CCD array for receiving the passed portion of the image. All embodiments have a common feature whereby the spatial window and CCD array are mounted for simultaneous relative reciprocating movement with respect to the front objective lens, and the spatial window is mounted within the focal plane of the front objective. In a first embodiment, the spatial window is a slit and the CCD array is one-dimensional, and successive rows of the image in the focal plane of the front objective lens are passed to the CCD array by an image relay lens interposed between the slit and the CCD array. In a second embodiment, the spatial window is a slit, the CCD array is two-dimensional, and a prism-grating-prism optical spectrometer is interposed between the slit and the CCD array so as to cause the scanned row to be split into a plurality of spectral separations onto the CCD array. In a third embodiment, the CCD array is two-dimensional and the spatial window is a rectangular linear variable filter (LVF) window, so as to cause the scanned rows impinging on the LVF to be bandpass filtered into spectral components onto the CCD array through an image relay lens interposed between the LVF and the CCD array.

Mao, Chengye (Inventor)

2000-01-01

248

The field distribution in the focal plane of a paraboloidal reflector  

Microsoft Academic Search

The electromagnetic field in the focal plane of a finite axially-symmetrical paraboloidal reflector illuminated by a plane wave of arbitrary polarization incident nearly normally at the vertex, has been investigated. This paper describes the investigation, explains the method, and summarizes some of its results. The reflector is assumed to be of a focal length which is large compared with the

W. Watson

1964-01-01

249

Diffraction optics for terahertz waves  

NASA Astrophysics Data System (ADS)

Conventional lenses are important components for many terahertz applications, but ordinary lenses are very difficult to fabricate for short-focal lengths. Multi-level phase-corrected zoned lens antennas have been investigated with particular application at terahertz wavelengths. These zoned lenses (or diffractive optics) give better performance than ordinary lenses, and because of their planar construction are easier and cheaper to fabricate. The depths of cut needed for a grooved zone plate are quite small, even when materials with low dielectric constants are used. Zoned lenses have been built and tested at various frequencies from 100 GHz to 1.5 THz, with phase correction levels of half-wave, quarter-wave, or eighth-wavelength. The inherent losses in transparent materials increase monotonically over this frequency range. Typical low-loss materials include polystyrene, polyethylene, Teflon, polycarbonate, polystyrene foam, foamed polyethylene, low density polytetrafluoroethylene (PTFE), TPX, quartz, sapphire, and silicon. Low dielectric-constant materials are normally preferred to reduce reflection and attenuation losses. Techniques for cutting or milling the materials to small dimensions are important, because at 1.0 THz an eighth-wavelength correction for silicon is only 15 ?m. Another characteristic of zoned diffraction optics is their frequency behavior. Previous investigations have considered their bandwidth dependence and quasi-periodic extended frequency response for a specified focal length. As frequency changes, the focal point moves along the axis of the zoned lens. An analysis is given to explain this effect.

Wiltse, James C.

2004-09-01

250

Biometric, optical and physical changes in the isolated human crystalline lens with age in relation to presbyopia  

Microsoft Academic Search

The biometric, optical and physical properties of 19 pairs of isolated human eye-bank lenses ranging in age from 5 to 96 years were compared. Lens focal length and spherical aberration were measured using a scanning laser apparatus, lens thickness and the lens surface curvatures were measured by digitizing the lens profiles and equivalent refractive indices were calculated for each lens

Adrian Glasser; Melanie C. W. Campbell

1999-01-01

251

Design of microlens illuminated aperture array fabricated by aligned ultraviolet imprinting process for optical read only memory card system  

Microsoft Academic Search

A microlens illuminated aperture array (MLIAA) was designed for the multiprobe optical read only memory card system. As a method to integrate the microlens array (MLA) with the aperture array containing 1000×1000 apertures, an aligned ultraviolet imprinting process was used to satisfy the system objectives of reduced focal length and reduced spot size. An analysis using diffraction theory was performed

Hongmin Kim; Jeeseung Lee; Jiseok Lim; Seok-Min Kim; Shinill Kang; Young-Joo Kim; Christopher Busch

2006-01-01

252

Finger Length  

NSDL National Science Digital Library

This Science Update explores male agression patterns and their correlation to pre-natal testosterone exposure. Although life experience plays a huge role in shaping who we are, the foundations of our personality begin in the womb. One recent study looks to finger length for signs of a man's pre-natal exposure to testosterone.n women, the index and ring finger are roughly equal in length. But in most men, the ring finger is longer. That's a result of fetal exposure to testosterone. Psychologists Alison Bailey and Pete Hurd, of the University of Alberta in Canada, studied these finger ratios in male college students. And they found that men with more dramatic differences tended to be more aggressive. Additional links to resources are given for further inquiry.

American Association for the Advancement of Science (;)

2005-03-28

253

Accelerating diffractive optics design with GPU-based parallel technique  

NASA Astrophysics Data System (ADS)

In this paper GPU based data parallel technique is used to reduce calculating time in diffractive optics elements (DOE) design. By using compute unified device architecture (CUDA) framework, comparison of acceleration radio of some major methods using in DOE design, including Gerchberg Saxton algorithm for global optimization in conjunction with Rayleigh-Sommerfeld diffractive integrating transformation, genetic algorithm with a finite-difference time-domain method and simulated annealing algorithm, is made with demonstrational DOE-lens design, whose focal spot size is 0.5 ?m, incident light wavelength is 650 nm, focal length is 3mm, DOE aperture size is 2mm.

Liu, Kan; Li, Hui; Zhang, Xinyu; Li, Dehua; Wei, Mingyue; Li, Bin; Xie, Changsheng; Zhang, Tianxu

2010-08-01

254

Multispectral linear array focal plane  

NASA Technical Reports Server (NTRS)

A description is provided of a sensor chip array for a unified multispectral focal plane for the Multispectral Linear Array (MLA) instrument. The involved concept of sensing multispectral earth resources imagery through the use of spectral filters deposited directly on a single row of silicon charge-coupled device (CCD) chips has been considered for a number of years. A simplified focal plane was designed after a number of experiments. Technology considerations regarding the design of the multispectral focal plane are discussed. Experimental data are presented which show that the arising problems have been or can be solved.

Hall, J. A.; Blaha, F. C.; Mckee, R. C.

1982-01-01

255

Analytic method to optimize aperture design in focal modulation microscopy.  

PubMed

Focal modulation microscopy (FMM) has been demonstrated more effective than confocal microscopy for imaging of thick biological tissues. To improve its penetration depth further, we propose a simple analytical method to enlarge the modulation depth, the unique property of FMM directly linked to its signal-to-noise ratio. The modulation depth increases as the excitation intensity of the binary phase aperture status is pushed further away from the focal region of the detection optics, thereby creating a dark region in the focal volume, which we call maximally flat crater (MFC). By direct algebraic manipulation, MFCs are achieved for both scalar and vector diffraction optics. Numerical results show that the modulation depth from MFC is very close to the maximum values, with a small difference less than 3% for the same number of subapertures. Applications of bifocus produced by MFC apertures are also discussed. PMID:24690867

Duan, Yubo; Sheppard, Colin J R; Rehman, Shakil; Chen, Nanguang

2014-03-15

256

Statistical Earthquake Focal Mechanism Forecasts  

NASA Astrophysics Data System (ADS)

The new whole Earth focal mechanism forecast, based on the GCMT catalog, has been created. In the present forecast, the sum of normalized seismic moment tensors within 1000 km radius is calculated and the P- and T-axes for the focal mechanism are evaluated on the basis of the sum. Simultaneously we calculate an average rotation angle between the forecasted mechanism and all the surrounding mechanisms. This average angle shows tectonic complexity of a region and indicates the accuracy of the prediction. The method was originally proposed by Kagan and Jackson (1994, JGR). Recent interest by CSEP and GEM has motivated some improvements, particularly to extend the previous forecast to polar and near-polar regions. The major problem in extending the forecast is the focal mechanism calculation on a spherical surface. In the previous forecast as our average focal mechanism was computed, it was assumed that longitude lines are approximately parallel within 1000 km radius. This is largely accurate in the equatorial and near-equatorial areas. However, when one approaches the 75 degree latitude, the longitude lines are no longer parallel: the bearing (azimuthal) difference at points separated by 1000 km reach about 35 degrees. In most situations a forecast point where we calculate an average focal mechanism is surrounded by earthquakes, so a bias should not be strong due to the difference effect cancellation. But if we move into polar regions, the bearing difference could approach 180 degrees. In a modified program focal mechanisms have been projected on a plane tangent to a sphere at a forecast point. New longitude axes which are parallel in the tangent plane are corrected for the bearing difference. A comparison with the old 75S-75N forecast shows that in equatorial regions the forecasted focal mechanisms are almost the same, and the difference in the forecasted focal mechanisms rotation angle is close to zero. However, though the forecasted focal mechanisms are similar, closer to the 75 latitude degree, the difference in the rotation angle is large (around a factor 1.5 in some places). The Gamma-index was calculated for the average focal mechanism moment. A non-zero Index indicates that earthquake focal mechanisms around the forecast point have different orientations. Thus deformation complexity displays itself in the average rotation angle and in the Index. However, sometimes the rotation angle is close to zero, whereas the Index is large, testifying to a large CLVD presence. Both new 0.5x0.5 and 0.1x0.1 degree forecasts are posted at http://eq.ess.ucla.edu/~kagan/glob_gcmt_index.html.

Kagan, Y. Y.; Jackson, D. D.

2013-12-01

257

Focal spot calibration in a digital breast tomosynthesis system  

NASA Astrophysics Data System (ADS)

Digital breast tomosynthesis (DBT) technology is a promising modality for the early detection of breast cancer and could provide clear diagnostic images in which the effect of tissue overlap is alleviated. Accurate calibration of the system geometry is essential for successful image reconstruction in DBT systems. The geometrical calibration of the focal spot in the X-ray tube at the detector plane is one of the most critical parameters of a DBT system. In this paper, a new method using a multi-hole collimator and an iterative calibration algorithm is reported in order to estimate the position of the focal spot at the detector plane. The iterative algorithm is based on the area-distance relationship in the collimator image. The linearity of this relationship has been verified both empirically and theoretically. A focal spot estimate has been achieved regardless of the location of the focal spot in the image. A total of 15 projection images acquired with the DBT system have been successfully reconstructed with geometric information about the focal spot position provided by our new method, and the focal spot estimate method proposed in this paper could be a useful solution for locating optical sources that cannot be viewed or accessed.

Choi, Jaegu; Hwang, Sun-Jo; Choi, Young-Wook

2012-05-01

258

Focal plane electronics for the GAIA focal plane demonstrator  

NASA Astrophysics Data System (ADS)

The GAIA mission of the European Space Agency (ESA) comprises two Astro telescopes with a very large common focal plane. The focal plane assembly consist of about 180 CCDs and accompanying video chains. The CCDs are operating in a TDI mode with complex windowing- and binning modes. Low noise, large dynamic range, linearity are mandatory for success of the Mission. Therefore, ESA has initiated a technology demonstrator, which should demonstrate the technical feasibility. Astrium-SAS in Toulouse and DLR-IPF in Berlin have successfully performed the study, in which DLR has developed the CCD- video electronics and the Interconnection Modules for the Focal Plane Demonstrator. The requirements, the conceptional design and the results are presented in this paper.

Michaelis, Harald; Behnke, Thomas; Lichopoj, Alexander; Solbrig, Michael

2006-10-01

259

Focal shift of focused truncated Lorentz-Gauss beam.  

PubMed

Based on the Collins diffraction integral formula and the complex Gaussian expansion of the aperture function, an analytical expression for a Lorentz-Gauss beam focused by an optical system with a thin lens and a circular aperture has been derived. The focal shift of the focused truncated Lorentz-Gauss beam is investigated with numerical examples, and the dependence of the focal shift on the different parameters of the focused truncated Lorentz-Gauss beam is discussed in detail. This research is useful to the applications of highly divergent laser beams. PMID:18830337

Zhou, Guoquan

2008-10-01

260

Multicolor megapixel QWIP focal plane arrays for remote sensing instruments  

NASA Astrophysics Data System (ADS)

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024x1024 pixel quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NE?T) of 17 mK at a 95K operating temperature with f/2.5 optics at 300K background and the LWIR detector array has demonstrated a NE?T of 13 mK at a 70K operating temperature with the same optical and background conditions as the MWIR detector array after the subtraction of system noise. Both MWIR and LWIR focal planes have shown background limited performance (BLIP) at 90K and 70K operating temperatures respectively, with similar optical and background conditions. In addition, we have demonstrated MWIR and LWIR pixel co-registered simultaneously readable dualband QWIP focal plane arrays. In this paper, we will discuss the performance in terms of quantum efficiency, NE?T, uniformity, operability, and modulation transfer functions of the 1024x1024 pixel arrays and the progress of dualband QWIP focal plane array development work.

Gunapala, S. D.; Bandara, S. V.; Liu, J. K.; Hill, C. J.; Rafol, S. B.; Mumolo, J. M.; Trinh, J. T.; Tidrow, M. Z.; LeVan, P. D.

2006-09-01

261

Diffractive optics in adverse environments  

NASA Technical Reports Server (NTRS)

An investigation at the Army Research Laboratory is in progress to characterize DOE performance in mil-spec environments. One of the most significant environmental influences is temperature. An analysis of a diffractive lens is presented in which optical performance is described as a function of temperature. In particular, we review the thermal dependence of focal length and diffraction efficiency. It is shown that the change in these parameters is independent of lens shape and relates only to material properties. Thermalized hybrid refractive/diffractive designs are discussed.

Behrmann, Gregory P.

1993-01-01

262

An Optical Wavefront Sensor Based on a Double Layer Microlens Array  

PubMed Central

In order to determine light aberrations, Shack-Hartmann optical wavefront sensors make use of microlens arrays (MLA) to divide the incident light into small parts and focus them onto image planes. In this paper, we present the design and fabrication of long focal length MLA with various shapes and arrangements based on a double layer structure for optical wavefront sensing applications. A longer focal length MLA could provide high sensitivity in determining the average slope across each microlens under a given wavefront, and spatial resolution of a wavefront sensor is increased by numbers of microlenses across a detector. In order to extend focal length, we used polydimethysiloxane (PDMS) above MLA on a glass substrate. Because of small refractive index difference between PDMS and MLA interface (UV-resin), the incident light is less refracted and focused in further distance. Other specific focal lengths could also be realized by modifying the refractive index difference without changing the MLA size. Thus, the wavefront sensor could be improved with better sensitivity and higher spatial resolution.

Lin, Vinna; Wei, Hsiang-Chun; Hsieh, Hsin-Ta; Su, Guo-Dung John

2011-01-01

263

Calculation of the scheme of recording a volume axial holographic optical element in the infrared region of the spectrum  

NASA Astrophysics Data System (ADS)

Main parameters of the scheme of recording a volume axial holographic optical element (HOE) in the infrared region of the spectrum are calculated. The recording scheme is based on a modified scheme of the cyclic Hariharan-Sen interferometer. For the HOE 400 mm in diameter with a focal length of 800 mm, the calculated parameters of the recording scheme are presented that demonstrate that the diameter of the optical element is much less than the HOE diameter.

Batomunkuev, Yu. Ts.; Meshcheryakov, N. A.

2010-12-01

264

SIRTF focal plane technologies  

NASA Technical Reports Server (NTRS)

The Space Infrared Telescope Facility (SIRTF) will have three science instruments, the Infrared Array Camera (IRAC) which will obtain multispectral images between 1.8 micron and 26 microns, the Infrared Spectrometer (IRS) which is a set of two dispersive spectrometers covering the wavelength range between 2.5 and 200 microns, and the Multiband Imaging Photometer for SIRTF (MIPS) which is a general-purpose photometric instrument which operates between 30 and 1,200 microns. Taken together, the full wavelength range of these instruments extends from 1.8 micron to 1,200 microns, equivalent to nearly a factor of 700 in photon energy and diffraction limited image size. In addition to supporting this unprecedented spectral and optical coupling requirement, the SIRTF detectors must operate at lower temperatures than previously demonstrated and be optimized for new levels of performance in order to achieve the goals of the science mission. Thus, development of the detector arrays for the SIRTF instruments is one of the most challenging aspects of the instrument development activities.

Capps, Richard W.; Bothwell, Mary

1991-01-01

265

Exploring focal and aberration properties of electrostatic lenses through computer simulation  

Microsoft Academic Search

The interactive nature of computer simulation allows students to develop a deeper understanding of the laws of charged particle optics. Here, the use of commercially available optical design programs is described as a tool to aid in solving charged particle optics problems. We describe simple and practical demonstrations of basic electrostatic lens properties, such as the determination of focal points,

Omer Sise; David J. Manura; Mevlut Dogan

2008-01-01

266

Math Focal Points: Grade 7  

NSDL National Science Digital Library

In this wiki page, Math Focal Points: Grade 7, the third of the Middle School Portal series, it offers resources that support the teaching of the three areas of emphasis highlighted for seventh-grade learners. The three focal points and the related sections of resources are apply proportionality, including scale factor, percentage, and unit rate problems. Wiki pages in the section titled ratio and proportion deal with real-world situations, such as finding percentages and building scale models, as well as online scenarios that help students visualize the mathematical concepts involved.

2008-05-01

267

Focal epithelial hyperplasia: Case report.  

PubMed

The purpose of the present article is to present a 15 year-old patient with focal epithelial hyperplasia and to review the references on the subject-related etiological, pathological, diagnostic and treatment aspects. Focal epithelial hyperplasia is a rare human papilloma virus (HPV) related to oral lesion with very low frequency within our population. Surgical treatment with a biopsy was performed, acanthosis and parakeratosis are consistent histopathological features, since the patient had no history of sexual contact and HIV infection, the virus was probably acquired from environmental sources. PMID:22071419

Puriene, Alina; Rimkevicius, Arunas; Gaigalas, Mindaugas

2011-01-01

268

Microlens array based LCD projection display with software-only focal distance control  

NASA Astrophysics Data System (ADS)

State of the art LED pico-projectors using single-channeled optical layouts are always constricted by a trade-off between achievable flux and minimum system size. Furthermore, their limited depth of focus require additional mechanically moving components for focusing if variable projection distances are essential for their specific application. We present a novel microlens-array based LCD projector breaking these constraints of conventional LED illuminated systems, thus enabling a super compact, robust and bright module while offering new features for electronic focal distance control without additional mechanical components. While the short focal length of each contributing channel maintains a certain system slimness, the superposition of all individual projections on a screen done by image-preprocessing leads to dramatic flux enhancement without blurring effects. Starting with a description of the working principle of array projection we focus on key properties regarding depth of focus for examining novel image-preprocessing algorithms that enable for only software-controlled focal distance. Further improved program code enables sharp images even onto freeform screen geometries. The realized prototype utilizes a transmissive LCD microdisplay along with a monolithic array of 45 microlenses actively aligned to the top of the display coverglass. While the display is illuminated by a collimated white LED; each channel is assigned to one primary color by applying a color filter array buried below the microlenses to obtain a full color image on the screen. The displayed image content is controlled via PC by a novel software tool, whose correct operation is verified by experimental results.

Sieler, Marcel; Schreiber, Peter; Bräuer, Andreas

2013-03-01

269

An in-plane optofluidic microchip for focal point control.  

PubMed

A polydimethylsiloxane (PDMS) optofluidic microfluidic chip comprising a tunable optofluidic in-plane biconvex microlens and a tunable optofluidic in-plane microprism is proposed for controlling the focal length and deviation angle of a light beam. In the proposed device, the microlens comprises an expansion chamber containing a high refractive index stream sandwiched between two low refractive index streams. Meanwhile, the microprism comprises a triangular chamber filled with two liquids, one with a higher refractive index than that of PDMS and the other a lower refractive index than that of PDMS. It is shown that the radius of curvature (and therefore the focal length) of the microlens can be adjusted by controlling the flow rate ratio of the core and cladding streams. In addition, it is shown that the deviation angle of the light ray exiting the microprism depends on the refractive indices of the two working fluids, the apex angle of the prism chamber, and the flow rate ratio of the two working fluids. In general, the results show that the biconvex microlens enables the focal length to be adjusted in the range of 2.9-7.6 mm when using benzothiazole and ethylene glycol-ethanol as the core and cladding fluids, respectively. Moreover, a deviation angle range of -6.2° to 22.3° can be achieved when using a microprism chamber with an apex angle of 90° and benzothiazole and DI water as the working fluids. The integrated optofluidic chip therefore can manipulate the focal length and deviation angle of a light beam by adjusting the relative flow rates of fluids. PMID:23918038

Chao, Kuo-Sheng; Lin, Meng-Shiang; Yang, Ruey-Jen

2013-10-01

270

Optical design of a broadband scanning adaptive optics ophthalmoscope for the mouse eye  

NASA Astrophysics Data System (ADS)

The short focal length of the mouse eye gives rise to an optically thick retina (50 D). If in addition, multiple wavelengths are to be used simultaneously to image an arbitrary combination of retinal layers, the ? 10 D of longitudinal chromatic aberration means a total of 60 D of vergence must be covered. This dictates that marginal rays will cover a wide range of angles with respect to the optical axis at the pupil of a mouse (or murine) adaptive optics ophthalmoscope, in order to section through the entire retina with any wavelength simultaneously. In this work, we discuss the compromises associated with the design of a mouse adaptive optics ophthalmoscope using off-the-shelf spherical reflective and refractive optics.

Sulai, Yusufu N.; Dubra, Alfredo

2014-03-01

271

Design and Fabrication of Continuous-Profile Diffractive Micro-Optical Elements as a Beam Splitter  

NASA Astrophysics Data System (ADS)

An optimization algorithm that combines a rigorous electromagnetic computation model with an effective iterative method is utilized to design diffractive micro-optical elements that exhibit fast convergence and better design quality. The design example is a two-dimensional 1-to-2 beam splitter that can symmetrically generate two focal lines separated by 80 µm at the observation plane with a small angle separation of +/-16°. Experimental results are presented for an element with continuous profiles fabricated into a monocrystalline silicon substrate that has a width of 160 µm and a focal length of 140 µm at a free-space wavelength of 10.6 µm.

Feng, Di; Yan, Yingbai; Jin, Guofan; Fan, Shoushan

2004-10-01

272

A simple method for quality evaluation of micro-optical components based on 3D IPSF measurement.  

PubMed

This paper presents a simple method based on the measurement of the 3D intensity point spread function for the quality evaluation of high numerical aperture micro-optical components. The different slices of the focal volume are imaged thanks to a microscope objective and a standard camera. Depending on the optical architecture, it allows characterizing both transmissive and reflective components, for which either the imaging part or the component itself are moved along the optical axis, respectively. This method can be used to measure focal length, Strehl ratio, resolution and overall wavefront RMS and to estimate optical aberrations. The measurement setup and its implementation are detailed and its advantages are demonstrated with micro-ball lenses and micro-mirrors. This intuitive method is adapted for optimization of micro-optical components fabrication processes, especially because heavy equipments and/or data analysis are not required. PMID:24921515

Baranski, Maciej; Perrin, Stephane; Passilly, Nicolas; Froehly, Luc; Albero, Jorge; Bargiel, Sylwester; Gorecki, Christophe

2014-06-01

273

Staring Focal Plane Array System Modeling.  

National Technical Information Service (NTIS)

This report analyzes the problems of modeling staring focal plane array systems. Two problem areas are highlighted; the difficulty in modeling the operator interface and the inadequate characterization of focal plane array noise sources. The effects of al...

J. G. Murphy

1989-01-01

274

Ultrafast diffractive optical micro-trap arrays for neutral atom quantum computing  

NASA Astrophysics Data System (ADS)

We design and fabricate arrays of diffractive optical elements (DOEs) to realize neutral atom micro-traps for quantum computing. We initialize a single atom at each site of an array of optical tweezer traps for a customized spatial configuration. Each optical trapping volume is tailored to ensure only one or zero trapped atoms. Specifically designed DOEs can define an arbitrary optical trap array for initialization and improve collection efficiency in readout by introducing high-numerical aperture, low-profile optical elements into the vacuum environment. We will discuss design and fabrication details of ultra-fast collection DOEs integrated monolithically and coaxially with tailored DOEs that establish an optical array of micro-traps through far-field propagation. DOEs, as mode converters, modify the lateral field at the front focal plane of an optical assembly and transform it to the desired field pattern at the back focal plane of the optical assembly. We manipulate the light employing coherent or incoherent addition with judicious placement of phase and amplitude at the lens plane. This is realized through a series of patterning, etching, and depositing material on the lens substrate. The trap diameter, when this far-field propagation approach is employed, goes as 2.44?F/#, where the F/# is the focal length divided by the diameter of the lens aperture. The 8-level collection lens elements in this presentation are, to our knowledge, the fastest diffractive elements realized; ranging from F/1 down to F/0.025.

Kemme, S. A.; Brady, G. R.; Ellis, A. R.; Wendt, J. R.; Peters, D. W.; Biedermann, G. W.; Carter, T. R.; Samora, S.; Isaacs, J. A.; Ivanov, V. V.; Saffman, M.

2012-02-01

275

Accurate cell counts in live mouse embryos using optical quadrature and differential interference contrast microscopy  

NASA Astrophysics Data System (ADS)

Present imaging techniques used in in vitro fertilization (IVF) clinics are unable to produce accurate cell counts in developing embryos past the eight-cell stage. We have developed a method that has produced accurate cell counts in live mouse embryos ranging from 13-25 cells by combining Differential Interference Contrast (DIC) and Optical Quadrature Microscopy. Optical Quadrature Microscopy is an interferometric imaging modality that measures the amplitude and phase of the signal beam that travels through the embryo. The phase is transformed into an image of optical path length difference, which is used to determine the maximum optical path length deviation of a single cell. DIC microscopy gives distinct cell boundaries for cells within the focal plane when other cells do not lie in the path to the objective. Fitting an ellipse to the boundary of a single cell in the DIC image and combining it with the maximum optical path length deviation of a single cell creates an ellipsoidal model cell of optical path length deviation. Subtracting the model cell from the Optical Quadrature image will either show the optical path length deviation of the culture medium or reveal another cell underneath. Once all the boundaries are used in the DIC image, the subtracted Optical Quadrature image is analyzed to determine the cell boundaries of the remaining cells. The final cell count is produced when no more cells can be subtracted. We have produced exact cell counts on 5 samples, which have been validated by Epi-Fluorescence images of Hoechst stained nuclei.

Warger, William C., II; Newmark, Judith A.; Zhao, Bing; Warner, Carol M.; DiMarzio, Charles A.

2006-03-01

276

MRI of Focal Liver Lesions  

PubMed Central

Magnetic resonance imaging, MRI has more advantages than ultrasound, computed tomography, CT, positron emission tomography, PET, or any other imaging modality in diagnosing focal hepatic masses. With a combination of basic T1 and T2 weighted sequences, diffusion weighted imaging, DWI, and hepatobiliary gadolinium contrast agents, that is gadobenate dimeglumine (Gd-BOPTA) and gadoxetic acid (Gd-EOB), most liver lesions can be adequately diagnosed. Benign lesions, as cyst, hemangioma, focal nodular hyperplasia, FNH or adenoma, can be distinguished from malignant lesions. In a non-cirrhotic liver, the most common malignant lesions are metastases which may be hypovascular or hypervascular. In the cirrhotic liver hepatocellular carcinoma, HCC, is of considerable importance. Besides, intrahepatic cholangiocarcinoma and other less common malignancies has to be assessed. In this review, the techniques and typical MRI features are presented as well as the new algorithm issued by American Association for the Study of the Liver Diseases (AASLD).

Albiin, Nils

2012-01-01

277

Infrared focal plane array modeling  

NASA Astrophysics Data System (ADS)

A model for staring focal plane arrays is described. The model characterizes two types of detectors, the platinum silicide (PtSi) Schottky-barrier diode and the mercury-cadmiun-tellurium (MCT) detector. The MCT devices provide high performance in both the 3-5-micron and 8-12-micron regions, while the Schottky devices, functioning only in the 3-5-micron band, provide high density and economy.

Leblanc, Richard; Contini, Casey

1990-10-01

278

Fabrication of micro-optical devices at the end of a multimode optical fiber with negative tone lift-off EBL  

NASA Astrophysics Data System (ADS)

A fabrication method based on negative tone lift off EBL is developed for constructing nano-structures at end faces of multimode optical fibers. With this new approach, precise and robust nano-structures with high spatial resolutions can be fabricated with minimum damage to the optical fiber face during the fabrication process. Based on this approach, high numerical aperture micro Fresnel zone plates (MZP) with focal lengths ˜3 µm were fabricated on the face of an optical fiber. The focusing characteristics of the fabricated MZP showed good consistency with the numerical simulations at the specified wavelength (˜405 nm).

Sundaram, Vijay M.; Wen, Sy-Bor

2012-12-01

279

[Focal liver lesion, incidental finding].  

PubMed

The differential diagnosis of incidentally found Focal Liver Lesions (FLL) is complex. Screening procedures so far are only defined for patients with liver cirrhosis. Characterization of a FLL begins as soon as it is detected. Taking patients history and thorough clinical examination are essential. An imaging procedure that is used to detect liver masses should also allow the examiner to determine whether the lesion is benign or malignant. Conventional B-mode US and colour Doppler imaging are effective at detecting and characterizing typical liver cysts and calcifications. Laboratory data, computed tomography, magnetic resonance imaging and imaging guided liver biopsy are complementary methods.Contrast Enhanced Ultrasound (CEUS) is a well established diagnostic imaging technique for a variety of indications and applications. One of the most important applications is in the liver where it is frequently a first-line technique for the detection and diagnosis (characterization) of focal liver lesions (FLL). In this setting the accurate differentiation of benign from malignant lesions is critical to ensure the patient undergoes the appropriate therapeutic option. This has been documented in recently published guidelines, in particular in terms of the enhancement patterns of the most common FLL hemangioma, focal nodular hyperplasia hepatocellular adenoma and their differentiation from malignant lesions. In this article the role of CEUS in the characterization of incidentally found FLL is described. PMID:23033169

Dietrich, C F; Jenssen, C

2012-10-01

280

Holographic Optical Elements as Scanning Lidar Telescopes  

NASA Technical Reports Server (NTRS)

We have developed and investigated the use of holographic optical elements (HOEs) and holographic transmission gratings for scanning lidar telescopes. For example, rotating a flat HOE in its own plane with the focal spot on the rotation axis makes a very simple and compact conical scanning telescope. We developed and tested transmission and reflection HOEs for use at the first three harmonic wavelengths of Nd:YAG lasers. The diffraction efficiency, diffraction angle, focal length, focal spot size and optical losses were measured for several HOEs and holographic gratings, and found to be suitable for use as lidar receiver telescopes, and in many cases could also serve as the final collimating and beam steering optic for the laser transmitter. Two lidar systems based on this technology have been designed, built, and successfully tested in atmospheric science applications. This technology will enable future spaceborne lidar missions by significantly lowering the size, weight, power requirement and cost of a large aperture, narrow field of view scanning telescope.

Schwemmer, Geary K.; Rallison, Richard D.; Wilkerson, Thomas D.; Guerra, David V.

2005-01-01

281

Modeling anamorphic optical surfaces in the MOEMS-based zoom lens  

NASA Astrophysics Data System (ADS)

MOEMS (Micro-opto-electromechanical systems) based zoom lens is a kind of optical system combining the off-axis reflective DM (deformable mirrors) and the on-axis refractive elements. It usually has two deformable mirrors. The magnification of one DM would be variable while its surface profile is changed by controlling the actuators, which results in a focal shift in the image space of the zoom lens. To compensate the variation of the focal plane position, the surface profile of another DM is varied. Therefore the focal length of the whole optical system would be varied and have a stabilized image position. In this paper, modeling anamorphic optical surfaces in the MOEMS-based zoom lens is described. The anamorphic profile of the DM is designed to satisfy the following requirements. First, the aberration coefficients of the DMs and the refractive surfaces are composed in the vector space to achieve the coefficients of the system. And the initial configuration of the refractive elements is determined to fulfill the system requirements and specifications at the wide angle and long focal length positions. Then the anamorphic profile of the DM is designed to compensate the off axis aberrations by creating two zeros of low order astigmatism, achieved a reasonable result.

Cheng, Xuemin; Hao, Qun

2010-11-01

282

Multispectral Focal Plane Assembly for Satellite Remote Sensing  

SciTech Connect

Sandia National Laboratories and several subsystem contractors are developing technologies applicable to multispectral remote sensing from space. A proof of concept multispectral sensor system is under development. The objective of building this sensor is to demonstrate and evaluate multispectral imaging technologies for various applications. The three major subsystems making up the sensor are the focal plane assembly (FPA), the cryocooler, and the telescope. This paper covers the focal plane assembly, which is the basis of the sensor system. The focal plane assembly includes sensor chip assemblies, optical filters, and a vacuum enclosure with cold shielding. Linear detector arrays provide spatial resolution in the cross-track direction for a pushbroom imager configuration. The optical filters define 15 spectral bands in a range from 0.45 microns to 10.7 microns. All the detector arrays are mounted on a single focal plane and are designed to operate at 75 K. No beam splitters are used. The four spectral bands covering the visible to near infrared have roughly 2400 pixels each, and the remaining 11 spectral bands have roughly 600 pixels each. The average total rate of multispectral data from the FPA is approximately 15.4 megapixels per second. At the time this paper is being written, the multispectral focal plane assembly is in the fabrication phase. A thermal/mechanical mockup has been built and tested for the vibration environment and to determine the thermal load. Some of the sensor chip assemblies and filters have been built and tested. Several notable features of the design are covered in the paper as well as preliminary test data.

Rienstra, J. [Sandia National Labs., Albuquerque, NM (United States); Ballard, M. [Santa Barbara Research Center, Goleta, CA (United States)

1997-12-31

283

1024x1024 Pixel MWIR and LWIR QWIP Focal Plane Arrays and 320x256 MWIR:LWIR Pixel Colocated Simultaneous Dualband QWIP Focal Plane Arrays  

NASA Technical Reports Server (NTRS)

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024x1024 pixel quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NE(Delta)T) of 17 mK at a 95K operating temperature with f/2.5 optics at 300K background and the LWIR detector array has demonstrated a NE(Delta)T of 13 mK at a 70K operating temperature with the same optical and background conditions as the MWIR detector array after the subtraction of system noise. Both MWIR and LWIR focal planes have shown background limited performance (BLIP) at 90K and 70K operating-temperatures respectively, with similar optical and background conditions. In addition, we are in the process of developing MWIR and LWIR pixel collocated simultaneously readable dualband QWIP focal plane arrays.

Gunapala, Sarath D.; Bandara, Sumith V.; Liu, John K.; Hill, Cory J.; Rafol, S. B.; Mumolo, Jason M.; Trinh, Joseph T.; Tidrow, M. Z.; Le Van, P. D.

2005-01-01

284

Optical implementation of multifocal programmable lens with single and multiple axes  

NASA Astrophysics Data System (ADS)

In this work we analyse the generation of a diffractive optical element (DOE) consisting of a multifocal Fresnel lens by means of an LCoS (liquid cristal on silicon) spatial light modulator (SLM). The multifocal lens is composed of a set of lenses of different focal length that share a common optical axis (coaxial combination) or have different axes in parallel (multi-axis combination). For both configurations, we present several ways to combine the phase distributions for three lenses with different focal lengths (f1, f2, f3), into a single-phase distribution addressed to the SLM. Numerical simulations were carried out along with the experimental analysis to corroborate the results.

Romero, Lenny A.; Millán, María S.; Pérez-Cabré, Elisabet

2011-01-01

285

1.06-micron laser damage of thin film optical coatings - A round-robin experiment involving various pulse lengths and beam diameters  

Microsoft Academic Search

In the round-robin experiment reported here, commercially available optical coatings, both antireflective and high reflective, were evaluated with respect to their laser-induced damage threshold. The results obtained are discussed with particular emphasis on the experimental approaches used at the various laboratories and their compatibility. It is noted that despite the very different conditions of the experiments, it is still possible

K. H. Guenther; E. Casparis; T. W. Humpherys; J. R. Bettis; J. Balmer; J. Ebert; E. Kiesel; M. Eichner; A. H. Guenther; R. Kuehnel; D. Milam; W. Ryseck; S. C. Seitel; A. F. Stewart; H. Weber; G. R. Wirtenson; R. M. Wood

1984-01-01

286

Focusing and imaging of a virtual all-optical tunable terahertz Fresnel zone plate.  

PubMed

A virtual all-optical tunable terahertz Fresnel zone plate is achieved utilizing the localized distribution of the transient electron plasma on a silicon wafer. Its focusing and imaging performance are experimentally demonstrated. Experimental results show that the effect of the virtual zone plate is the same as an actual one. Adjusting the spatial pattern of the electron plasma, the central wavelength and the focal length of the virtual zone plate can be all-optically dynamically steered. The research is a significant step to the development of tunable optical imaging elements. PMID:24322118

Wang, Xinke; Xie, Zhenwei; Sun, Wenfeng; Feng, Shengfei; Cui, Ye; Ye, Jiasheng; Zhang, Yan

2013-11-15

287

Design, build, and test of the NIRCam focal plane array housing  

NASA Astrophysics Data System (ADS)

The Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) has an optical prescription which terminates at two focal plane arrays for each module. The instrument will operate at 35K after experiencing launch loads at ~293K and the focal plane array housings must accommodate all associated thermal and mechanical stresses, while keeping the FPAs aligned. The main purpose of the FPAH is to provide a stray light, contamination, and radiation shield to the Focal Planes. The design includes a fold mirror used to direct incoming light up to the detectors and mechanical support for the Application Specific Integrated Circuits (ASIC). A six degree of freedom shim is used to align the Focal Plane Assembly at the operating temperature of 35 Kelvin. This paper will provide an overview of the FPAH design including an update to the Fold Mirror design described in previous papers. Analysis and test results of the ambient temperature optical and vibration testing will be presented.

Little, Danielle; Jacoby, Michael; Casco, Edwin

2011-09-01

288

NIF optics phase gradient specification.  

National Technical Information Service (NTIS)

A root-mean-square (rms) phase gradient specification seems to allow a good connection between the NIF optics quality and focal spot requirements. Measurements on Beamlet optics individually, and as a chain, indicate they meet the assumptions necessary to...

J. Auerbach J. Hunt K. Manes L. Lawson W. Williams

1997-01-01

289

A cognitive approach to monitor and control focal shifts in laser beam welding applications  

Microsoft Academic Search

Even though widely used, laser beam welding faces a strong demand for improved monitoring and control capabilities. In this work the occurring focal shift which leads to faulty welding results will be explained. An approach is taken to monitor this effect caused by the heading of the optics. By means of a camera sharing the same optical components as the

Thibault Bautze; Klaus Diepold; Tobias Kaiser

2009-01-01

290

Acousto-optic infrared spectral imager for Pluto fast flyby  

NASA Technical Reports Server (NTRS)

Acousto-optic tunable filters (AOTF's) enable the design of compact, two-dimensional imaging spectrometers with high spectral and spatial resolution and with no moving parts. Tellurium dioxide AOTF's operate from about 400 nm to nearly 5 microns, and a single device will tune continuously over one octave by changing the RF acoustic frequency applied to the device. An infrared (1.2-2.5 micron) Acousto-Optic Imaging Spectrometer (AImS) was designed that closely conforms to the surface composition mapping objectives of the Pluto Fast Flyby. It features a 75-cm focal length telescope, infrared AOTF, and 256 x 256 NICMOS-3 focal plane array for acquiring narrowband images with a spectral resolving power (lambda/delta(lambda)) exceeding 250. We summarize the instrument design features and its expected performance at the Pluto-Charon encounter.

Glenar, D. A.; Hillman, J. J.

1993-01-01

291

Monocular accommodation condition in 3D display types through geometrical optics  

Microsoft Academic Search

Eye fatigue or strain phenomenon in 3D display environment is a significant problem for 3D display commercialization. The 3D display systems like eyeglasses type stereoscopic or auto-stereoscopic multiview, Super Multi-View (SMV), and Multi-Focus (MF) displays are considered for detail calculation about satisfaction level of monocular accommodation by geometrical optics calculation means. A lens with fixed focal length is used for

Sung-Kyu Kim; Dong-Wook Kim; Min-Chul Park; Jung-Young Son

2007-01-01

292

TwoAxis MEMS Lens Alignment System for Free-Space Optical Interconnect  

Microsoft Academic Search

We present a two-axis microelectromechanical sys- tems (MEMS) lens aligner with a 260 ?m × 220 ?m transla- tion range that positions a 6.35 mm lens with focal length f = 12.1 mm for alignment compensation of free-space optical inter- connects (FSOIs) between computer servers separated by 50 mm spacing. Efficient ultrasonic linear piezoelectric motors (PMs) pro- vide actuation with

Brian E. Yoxall; Robert Walmsley; Huei-Pei Kuo; Shih-Yuan Wang; Mike Tan; David A. Horsley

2011-01-01

293

Focal-plane irradiance tailoring using the concept of Woofer-Tweeter deformable mirrors.  

PubMed

Deformable mirror (DM) is a common-used active freeform optical element. We introduce the concept of Woofer-Tweeter DM system for controlling focal-plane irradiance profiles. We firstly determine a freeform reflective surface for transforming a given incident laser beam into the desired focal-plane irradiance distribution by numerically solving a standard Monge-Ampère equation. Then, we use a low-bandwidth Woofer DM to approximate the required freeform reflective surface and a high-bandwidth Tweeter DM to compensate the residual error. Simulation results show that, compared with single DMs, the Woofer-Tweeter DM system brings the best focal-plane irradiance performances. PMID:24787776

Feng, Zexin; Huang, Lei; Gong, Mali

2014-04-21

294

SNAP Satellite Focal Plane Development  

SciTech Connect

The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square degree field in the visible and near-infrared wavelength regime. The requirements for the instrument suite and the present configuration of the focal plane concept are presented. A two year R&D phase, largely supported by the Department of Energy, is just beginning. We describe the development activities that are taking place to advance our preparedness for mission proposal in the areas of detectors and electronics.

Bebek, C.; Akerlof, C.; Aldering, G.; Amanullah, R.; Astier, P.; Baltay, C.; Barrelet, E.; Basa, S.; Bercovitz, J.; Bergstrom, L.; Berstein, G.P.; Bester, M.; Bohlin, R.; Bonissent, A.; Bower, C.; Campbell, M.; Carithers, W.; Commins, E.; Day, C.; Deustua, S.; DiGennaro, R.; Ealet, A.; Ellis, R.; Emmett, W.; Eriksson, M.; Fouchez,D.; Fruchter, A.; Genat, J-F.; Goldhaber, G.; Goobar, A.; Groom, D.; Heetderks, H.; Holland, S.; Huterer, D.; Johnson, W.; Kadel, R.; Karcher,A.; Kim, A.; Kolbe, W.; Lafever, R.; Lamoureaux, J.; Lampton, M.; Lefevre, O.; Levi, M.; Levin, D.; Linder, E.; Loken, S.; Malina, R.; Mazure, A.; McKay, T.; McKee, S.; Miquel, R.; Morgan, N.; Mortsell, E.; Mostek, N.; Mufson, S.; Musser, J.; Roe, N.; Nugent, P.; Oluseyi, H.; Pain, R.; Palaio, N.; Pankow, D.; Perlmutter, S.; Prieto, E.; Rabinowitz,D.; Refregier, A.; Rhodes, J.; Schubnell, M.; Sholl, M.; Smadja, G.; Smith, R.; Smoot, G.; Snyder, J.; Spadafora, A.; Szymkowiak, A.; Tarle,G.; Taylor, K.; Tilquin, A.; Tomasch, A.; Vincent, D.; von der Lippe, H.; Walder, J-P.; Wang, G.

2003-07-07

295

Episodic depersonalization in focal epilepsy.  

PubMed

In this report a patient with episodic depersonalization is described. As the depersonalization episodes had been attributed to partial seizures, this patient was treated with antiepileptic medication. However, clinical evaluation with long-term video/EEG revealed no evidence of seizure activity during the depersonalization episodes. On the other hand, further evaluation revealed findings that are frequently associated with focal epilepsy. In addition to episodic depersonalization, this patient had secondary generalized seizures. The relationship between episodic depersonalization, temporal lobe pathology, and epilepsy is discussed against the background of this case. PMID:16046278

Dietl, Thomas; Bien, Christian; Urbach, Horst; Elger, Christian; Kurthen, Martin

2005-09-01

296

Development of a cable reel development system using a rotary joint for kilometer lengths of two-fiber multi-mode fiber optic cable  

SciTech Connect

Brookhaven National Laboratory (BNL) recently developed a two-component system for use during remote inspections. The system consists of a mobile unit with television cameras and other equipment and a stationary base station. A variety of signals must be continually transmitted between the two system components as the mobile unit is moved from the location to another. Two channels of broadband (10MHz) NTSC video are transmitted from the mobile unit to the base station, and a bi-directional ``talk set`` provides audio communication between personnel at each location. In addition, several channels of RS-232 are required to support present and future instruments used at the mobile unit and controlled by personnel at the base station. Brookhaven developed a mobile unit which communicated with a base station over a 2-fiber multimode fiber optic cable. One of the design requirements was maintaining constant communication with the base station during the time the mobile unit was moved about. To provide uninterrupted communications, deployment of the 1-km long fiber optic cable was initially performed with a ``spinning reel`` mechanism. The spinning reel mechanism proved to be mechanically unsuitable, and so the cable deployment mechanism was redesigned to spool the cable off the reel. The requirement for uninterrupted communications required a two-channel fiber optic rotary joint in the design. Incorporation of the rotary joint into the design is described, and appropriate reference material is included.

Curtiss, J.A.; Jahelka, J.R.

1995-08-11

297

Scale Length of Disk Galaxies  

NASA Astrophysics Data System (ADS)

As a part of a Euro-VO research initiative, we have undertaken a programme aimed at studying the scale length of 54909 Sa-Sd spiral galaxies from the SDSS DR6 catalogue. We have retrieved u, g, r, i, z-band images for all galaxies in order to derive the light profiles. We also calculate asymmetry parameters to select non-disturbed disks for which we will derive exponential disk scale lengths. As images in different bands probe different optical depths and stellar populations, it is likely that a derived scale length value should depend on waveband, and our goal is to use the scale length variations with band pass, inclination, galaxy type, redshift, and surface brightness, in order to better understand the nature of spiral galaxies.

Fathi, K.; Allen, M.; Gonzalez-Solares, E.; Hatziminaoglou, E.; Peletier, R.

2009-07-01

298

Paxillin Binding Is Not the Sole Determinant of Focal Adhesion Localization or Dominant-Negative Activity of Focal Adhesion Kinase\\/Focal Adhesion Kinase related Nonkinase  

Microsoft Academic Search

The carboxy-terminal 150 residues of the focal adhesion kinase (FAK) comprise the focal adhesion- targeting sequence, which is responsible for its subcellular localization. The mechanism of focal adhesion targeting has not been fully elucidated. We describe a mutational analysis of the focal adhesion-targeting sequence of FAK to further examine the mechanism of focal adhesion targeting and explore additional functions encoded

Marion A. Cooley; Jill M. Broome; Christoph Ohngemach; Lewis H. Romer; Michael D. Schaller

299

The formation of optical membrane reflector surfaces using uniform pressure loading  

SciTech Connect

Potentially high quality optical reflector surfaces are attainable with the use of pressure formed membranes. Such reflector surfaces offer the prospect of very low weight and low cost. The formation of such surfaces, using initially flat circular membranes with uniform pressure loading, is studied in this paper. Finite axisymmetric deformations, along with both linear and nonlinear material response is considered. A wide range of focal-length-to-diameter ratios (above 0.6) are addressed and the structural/optical response mechanisms that lead to optical distortions relative to ideal parabolic reflector shapes are also considered. Results show that elastic material response can often lead to a significantly larger deviation from the ideal shape than will inelastic material response. This results primarily from the ability to limit stress nonuniformities when inelastic material response is operative. Furthermore, when under pressure loading the membrane focal length decreases monotonically with increasing radius for both linear and nonlinear material response. Further, the predicted focal length variation is increasingly nonlinear near the membrane support.

Murphy, L.M.; Tuan, C.

1987-08-01

300

The formation of optical membrane reflector surfaces using uniform pressure loading  

NASA Astrophysics Data System (ADS)

Potentially high quality optical reflector surfaces are attainable with the use of pressure formed membranes. Such reflector surfaces offer the prospect of very low weight and low cost. The formation of such surfaces, using initially flat circular membranes with uniform pressure loading, is studied. Finite axisymmetric deformations, along with both linear and nonlinear material response is considered. A wide range of focal-length-to-diameter ratios (above 0.6) are addressed and the structural/optical response mechanisms that lead to optical distortions relative to ideal parabolic reflector shapes are also considered. Results show that elastic material response can often lead to a significantly larger deviation from the ideal shape than will inelastic material response. This results primarily from the ability to limit stress nonuniformities when inelastic material response is operative. Furthermore, when under pressure loading the membrane focal length decreases monotonically with increasing radius for both linear and nonlinear material response. Further, the predicted focal length variation is increasingly nonlinear near the membrane support.

Murphy, L. M.; Tuan, C.

1987-08-01

301

Optical design of optical transfer function instrument  

NASA Astrophysics Data System (ADS)

The optical design of Optical transfer function (OTF) instrument, which is based on the image Fourier analysis method, is presented. To perform infinite conjugate testing of an optical system, the designed system is mainly composed of the object generator, lens under test, and image analyzer. The object generator offers an object at infinite distance with known spectral and spatial content. It includes the illumination system and the collimating system. The illumination system is analyzed and optimized with CODEV and LightTools software. Performance evaluation indicates that its illumination uniformity in the required area is above 95% .The collimation system based on an off-axis parabolic mirror is of the focal length of 2000mm and the entrance pupil diameter 200mm. Through optimization, the image quality of the collimator is excellent and its on-axis modulation transfer function (MTF) approaches diffraction limit. Collimated beam of the target is imaged by the lens under test. The image is magnified and acquired by image analyzer, which is made up of four parts: an infinite conjugate microscope objective, a tube lens, an eyepiece and a CCD camera. Image Results show that this designed scheme meets the requirements of this OTF instrument.

Zhang, Liangjun; Chen, Xinhua; Chen, Yuheng; Ji, Yiqun; Xiang, Chunchang; Shen, Weimin

2009-11-01

302

Single-mode laser studies: Design and performance of a fixed-wave length source and coupling of lasers to thin-film optical waveguides  

NASA Technical Reports Server (NTRS)

A module developed for the generation of a stable single wavelength to be used for a fiber optic multiplexing scheme is described. The laser is driven with RZ pulses, and the temperature is stabilized thermoelectrically. The unit is capable of maintaining a fixed wavelength within about 6 A as the pulse duty cycle is changed between 0 and 100 percent. This is considered the most severe case, and much tighter tolerances are obtainable for constant input power coding schemes. Using a constricted double heterostructure laser, a wavelength shift of 0.083 A mA is obtained due to laser self-heating by a dc driving current. The thermoelectric unit is capable of maintaining a constant laser heat-sink temperature within 0.02 C. In addition, miniature lenses and couplers are described which allow efficient coupling of single wavelength modes of junction lasers to thin film optical waveguides. The design of the miniature cylinder lenses and the prism coupling techniques allow 2 mW of single wavelength mode junction laser light to b coupled into thin film waveguides using compact assemblies. Selective grating couplers are also studied.

Ladany, I.; Hammer, J. M.

1980-01-01

303

Staurosporine induces endothelial cell apoptosis via focal adhesion kinase dephosphorylation and focal adhesion disassembly independent of focal adhesion kinase proteolysis.  

PubMed Central

The survival of endothelial cells is dependent on interactions between the matrix and integrins mediated through focal adhesions. Focal adhesion kinase (FAK) is thought to play a key role in maintaining focal adhesion function and cell survival, whereas caspase-mediated FAK proteolysis is implicated in focal adhesion disassembly during apoptosis. We examined the relationship between changes in FAK phosphorylation and proteolysis during apoptosis of primary porcine aortic endothelial cells (PAEC) induced by staurosporine, a widely used apoptogenic agent in diverse cell types. Staurosporine-induced PAEC apoptosis was detected after 1 h and was preceded by disruption and loss of FAK localization to focal adhesions within a few minutes, whereas staurosporine-induced cleavage of FAK occurred only after 8-24 h. Staurosporine induced a very rapid dephosphorylation of FAK at Tyr(861) and Tyr(397) and caused dissociation of phosphorylated FAK from focal adhesions as early as 30 s. The effect of staurosporine was very potent with striking inhibition of Tyr(861) and Tyr(397) phosphorylation and focal adhesion disruption occurring in the range 10-100 nM. Selective inhibition of a known target of staurosporine, protein kinase C, using GF109203X, and of phosphoinositide 3'-kinase using wortmannin, did not reduce FAK tyrosine phosphorylation at Tyr(861) and Tyr(397), or cause disruption of focal adhesions. Cycloheximide, the protein synthesis inhibitor, induced PAEC apoptosis more slowly than staurosporine, but did not induce FAK dephosphorylation or rapid focal adhesion disruption, and instead caused a slower loss of focal adhesions and a marked increase in FAK proteolysis. These studies show that FAK dephosphorylation and focal adhesion disassembly are very early events mediating the onset of staurosporine-induced endothelial cell apoptosis and are dissociated from FAK proteolysis. Cycloheximide induces apoptosis through a pathway involving FAK proteolysis without dephosphorylation.

Kabir, Jahangir; Lobo, Melvin; Zachary, Ian

2002-01-01

304

Focal axis resolver for offset reflector antennas  

NASA Technical Reports Server (NTRS)

Described are electrical means for determining the focal axis of an offset reflector antenna whose physical rim is not coincident with the boundary of the electrical aperture. Even and odd sensing functions are employed in the focal region, leading to both amplitude and phase criteria for resolving a focal axis generally inclined with respect to the system axis. The analytical aspects of the problem are discussed, and an example related to a 4-meter Large-Antenna Multiple-Frequency Microwave Radiometer (LAMMR) is included. The technique is useful for focal axis determination in mathematical simulations and in the physical world.

Schmidt, R. F.

1980-01-01

305

Simultaneous multispectral framing infrared camera using an embedded diffractive optical lenslet array  

NASA Astrophysics Data System (ADS)

Recent advances in micro-optical element fabrication using gray scale technology have opened up the opportunity to create simultaneous multi-spectral imaging with fine structure diffractive lenses. This paper will discuss an approach that uses diffractive optical lenses configured in an array (lenslet array) and placed in close proximity to the focal plane array which enables a small compact simultaneous multispectral imaging camera [1]. The lenslet array is designed so that all lenslets have a common focal length with each lenslet tuned for a different wavelength. The number of simultaneous spectral images is determined by the number of individually configured lenslets in the array. The number of spectral images can be increased by a factor of 2 when using it with a dual-band focal plane array (MWIR/LWIR) by exploiting multiple diffraction orders. In addition, modulation of the focal length of the lenslet array with piezoelectric actuation will enable spectral bin fill-in allowing additional spectral coverage while giving up simultaneity. Different lenslet array spectral imaging concept designs are presented in this paper along with a unique concept for prefiltering the radiation focused on the detector. This approach to spectral imaging has applications in the detection of chemical agents in both aerosolized form and as a liquid on a surface. It also can be applied to the detection of weaponized biological agent and IED detection in various forms from manufacturing to deployment and post detection during forensic analysis.

Hinnrichs, Michele

2011-05-01

306

Optimal focal-plane restoration  

NASA Technical Reports Server (NTRS)

Image restoration can be implemented efficiently by calculating the convolution of the digital image and a small kernel during image acquisition. Processing the image in the focal-plane in this way requires less computation than traditional Fourier-transform-based techniques such as the Wiener filter and constrained least-squares filter. Here, the values of the convolution kernel that yield the restoration with minimum expected mean-square error are determined using a frequency analysis of the end-to-end imaging system. This development accounts for constraints on the size and shape of the spatial kernel and all the components of the imaging system. Simulation results indicate the technique is effective and efficient.

Reichenbach, Stephen E.; Park, Stephen K.

1989-01-01

307

Stiripentol for focal refractory epilepsy.  

PubMed

Background: Nearly 30%of people with epilepsy do not have their seizures controlled with current treatments. Stiripentol is a new antiepileptic drug(AED) developed in France and recently approved by the European Medicines Agency (EMA) for the treatment of Dravet syndrome as an adjunctive therapy with valproate and clobazam, with a promising effect.Objectives: To evaluate the efficacy and tolerability of stiripentol as add-on treatment for patients with focal refractory epilepsy taking any AEDs.Search methods: We searched the Cochrane Epilepsy Group Specialized Register (19 August 2013), Cochrane Central Register of Controlled Trials(CENTRAL Issue 7, The Cochrane Library July 2013), MEDLINE (Ovid) (1946 to 19 August 2013) and EMBASE (31 May 2012).(The last search in EMBASE was made on 31th May 2012. Since then we no longer have access to that database.) We also contacted Biocodex (the manufacturer of stiripentol) and epilepsy experts to identify published, unpublished and ongoing trials.Selection criteria: Randomised controlled add-on trials of stiripentol in patients with focal refractory epilepsy.Data collection and analysis: Review authors independently selected trials for inclusion and extracted data. The outcomes investigated included 50% or greater reduction in seizure frequency, seizure freedom, adverse effects, treatment withdrawal and changes in quality of life.Main results: Using our selection criteria, one study was included (32 children with focal epilepsy). This study adopted a 'responder enriched' design.There was no clear evidence of a reduction in seizure reduction 50% seizure reduction) (RR 1.51, 95% CI 0.81 to 2.82) or in seizure freedom (RR 1.18, 95% CI 0.31 to 4.43) with add on stiripentol compared with placebo. Add-on stiripentol led to a greater risk of adverse effects considered as a whole (RR 2.65, 95% CI 1.08 to 6.47) compared with placebo. When considered as specific adverse events, the confidence intervals are very wide and include the possibility of substantial increases and small reductions in the risk of neurological (RR 2.65, 95% CI 0.88 to 8.01) or gastrointestinal adverse effects (RR 11.56, 95% CI 0.71 to 189.36). There was no clear reduction in the risk of study withdrawal (RR 0.66, 95% CI 0.30 to 1.47), which was high in both groups (35.0% in add-on placebo and 53.3% in stiripentol group). The external validity of the study was limited because only responders to stiripentol (that is patients experiencing at least a 50% decrease in seizure frequency compared with baseline) were included in the randomised add on placebo-controlled double-blind phase. Furthermore, a carry-over and a withdrawal effect probably affected the outcome related to seizure frequency. Although restricted by the very limited information derived by the only one included study, adverse effects considered as a whole seemed to occur significantly more often with add-on stiripentol compared with add-on placebo.Authors' conclusions: No conclusions can be drawn to support the use of stiripentol as add-on treatment for focal refractory epilepsy. Further large, randomised,well-conducted trials are needed. PMID:24488598

Brigo, Francesco; Storti, Monica

2014-01-01

308

Influence of the length and grafting density of PNIPAM chains on the colloidal and optical properties of quantum dot/PNIPAM assemblies  

NASA Astrophysics Data System (ADS)

Structural and optical characterization of water soluble, thermo-responsive quantum dot/poly(N-isopropyl acrylamide) (QD/PNIPAM) hybrid particles using fluorescence correlation spectroscopy (FCS) and time-correlated single photon counting (TCSPC) measurements performed at temperatures below and above the lower critical solution temperature (LCST) of PNIPAM is reported. By increasing the temperature above the LCST, the signature of the PNIPAM chain collapse covering the QDs is revealed by FCS measurements. Despite the significant structural change, the TCSPC measurements show that the fluorescence lifetimes remain of the same order of magnitude at T > LCST. Such QD/PNIPAM hybrid particles with water solubility and robust thermo-responsive behavior at physiologically relevant temperatures are potentially useful for (bio)molecular sensing and separation applications.

Tagit, Oya; Tomczak, Nikodem; Jafarpour, Aliakbar; Ja?czewski, Dominik; Han, Ming Yong; Vancso, G. Julius; Herek, Jennifer L.

2011-07-01

309

SOI diode uncooled infrared focal plane arrays  

NASA Astrophysics Data System (ADS)

An uncooled infrared focal plane array (IR FPA) is a MEMS device that integrates an array of tiny thermal infrared detector pixels. An SOI diode uncooled IR FPA is a type that uses freestanding single-crystal diodes as temperature sensors and has various advantages over the other MEMS-based uncooled IR FPAs. Since the first demonstration of an SOI diode uncooled IR FPA in 1999, the pixel structure has been improved by developing sophisticated MEMS processes. The most advanced pixel has a three-level structure that has an independent metal reflector for interference infrared absorption between the temperature sensor (bottom level) and the infrared-absorbing thin metal film (top level). This structure makes it possible to design pixels with lower thermal conductance by allocating more area for thermal isolation without reducing infrared absorption. The new MEMS process for the three-level structure includes a XeF II dry bulk silicon etching process and a double organic sacrificial layer surface micromachining process. Employing advanced MEMS technology, we have developed a 640 x 480-element SOI diode uncooled IR FPA with 25-?m square pixels. The noise equivalent temperature difference of the FPA is 40 mK with f/1.0 optics. This result clearly demonstrates the great potential of the SOI diode uncooled IR FPA for high-end applications. In this paper, we explain the advances and state-of-the-art technology of the SOI diode uncooled IR FPA.

Kimata, Masafumi; Ueno, Masashi; Takeda, Munehisa; Seto, Toshiki

2006-03-01

310

Terahertz detectors and focal plane arrays  

NASA Astrophysics Data System (ADS)

Terahertz (THz) technology is one of emerging technologies that will change our life. A lot of attractive applications in security, medicine, biology, astronomy, and non-destructive materials testing have been demonstrated already. However, the realization of THz emitters and receivers is a challenge because the frequencies are too high for conventional electronics and the photon energies are too small for classical optics. As a result, THz radiation is resistant to the techniques commonly employed in these well established neighbouring bands. In the paper, issues associated with the development and exploitation of THz radiation detectors and focal plane arrays are discussed. Historical impressive progress in THz detector sensitivity in a period of more than half century is analyzed. More attention is put on the basic physical phenomena and the recent progress in both direct and heterodyne detectors. After short description of general classification of THz detectors, more details concern Schottky barrier diodes, pair braking detectors, hot electron mixers and field-effect transistor detectors, where links between THz devices and modern technologies such as micromachining are underlined. Also, the operational conditions of THz detectors and their upper performance limits are reviewed. Finally, recent advances in novel nanoelectronic materials and technologies are described. It is expected that applications of nanoscale materials and devices will open the door for further performance improvement in THz detectors.

Rogalski, A.; Sizov, F.

2011-09-01

311

Focal Mechanisms of Acoustic Emission Events During Fault Propagation and Frictional Sliding  

NASA Astrophysics Data System (ADS)

Cylindrical samples of Aue granite with 50 mm diameter and 100 mm length were loaded to failure in triaxial compression tests. A localized shear fracture initiated at the sharp edge of a steel plate covering 2/3 of the top sample surface. Fault nucleation, propagation and post-failure frictional sliding were studied by monitoring the acoustic emission (AE) activity related to microcracking. Ten piezoceramic transducers were attached to the samples and used to locate events and determine focal mechanisms. The velocity of fault propagation and sliding was controlled by the AE rate. Crack microstructures of deformed samples were investigated using optical microscopy. Fault nucleation involves 10-30% of the total AE events observed up to stress drop. A localized process zone of AE surrounds the tip of the propagating fault. Spatial correlation of the AE is low during fault nucleation, but increases during failure propagation up to stress drop. In the sliding stage, spatial correlation remains relatively constant corresponding to D-values of 1.8-2.0. Initial P-axes orientation distribution of focal mechanisms from shear events is broad with two maxima during fault nucleation, but it narrows during fault propagation. For given time intervals, AE P-axes show a preferred orientation near the tip of the process zone, but are more irregular at the trailing edge. During experiments B-values range between 1.2-1.8, but are similar for different fault segments. After stress drop a single P-axis orientation dominates along the fault. The P-axis distribution corresponds to a preferred orientation of secondary shears at a small angle to the macroscopic fault. The shears develop during propagation at the fault tip and remain similar in orientation during sliding.

Stanchits, S.; Zang, A.; Dresen, G.

2001-12-01

312

Filopodial Initiation and a Novel Filament-organizing Center, the Focal Ring  

PubMed Central

This study examines filopodial initiation and implicates a putative actin filament organizer, the focal ring. Filopodia were optically recorded as they emerged from veils, the active lamellar extensions of growth cones. Motile histories revealed three events that consistently preceded filopodial emergence: an influx of cytoplasm into adjacent filopodia, a focal increase in phase density at veil margins, and protrusion of nubs that transform into filopodia. The cytoplasmic influx probably supplies materials needed for initiation. In correlated time lapse-immunocytochemistry, these focal phase densities corresponded to adhesions. These adhesions persisted at filopodial bases, regardless of subsequent movements. In correlated time lapse-electron microscopy, these adhesion sites contained a focal ring (an oblate, donut-shaped structure ?120 nm in diameter) with radiating actin filaments. Filament geometry may explain filopodial emergence at 30 degree angles relative to adjacent filopodia. A model is proposed in which focal rings play a vital role in initiating and stabilizing filopodia: 1) they anchor actin filaments at adhesions, thereby facilitating tension development and filopodial emergence; 2) “axial” filaments connect focal rings to nub tips, thereby organizing filament bundling and ensuring the bundle intersects an adhesion; and 3) “lateral” filaments interconnect focal rings and filament bundles, thereby helping stabilize lamellar margins and filopodia.

Steketee, Michael; Balazovich, Kenneth; Tosney, Kathryn W.

2001-01-01

313

Focal spot estimation for concave diffraction gratings  

Microsoft Academic Search

Two simple formulae are proposed, which estimate the width and the height of the focal images generated by a concave holographic grating under point source illumination. The results are compared with focal spot diagrams evaluated for some flat field spectrograph gratings and monochromator gratings. Good correlation is observed between analytical estimations and ray tracing.

L. Tsonev; E. Popov

1992-01-01

314

Focal osseous lesions in congenital lues  

Microsoft Academic Search

Five babies, aged between one to three months presented with clinical and serological evidence of syphilis. In addition to the usual periosteal and metaphyseal bone lesions of lues, areas of focal lucencies and sequestra were present. The association of sequestra in focal diaphyseal erosions may represent a non-dystrophic manifestation of the disease. The lesions were attributed to the syphilitic process.

A. Solomon; E. Rosen

1978-01-01

315

Focal plane location in digital holography  

Microsoft Academic Search

The correlation coefficient method is introduced to locate the focal plane in digital particle holography. It uses the fact that the correlation coefficient is maximum at the focal plane. The factors influencing this method are discussed with a numerical simulation of holograms. For real holograms, the Wiener filter was first proposed to process both recorded holograms and reconstructed images. The

Yan Yang; Bo-seon Kang; Yeon-jun Choo

2007-01-01

316

Measuring Crack Length in Coarse Grain Ceramics  

NASA Technical Reports Server (NTRS)

Due to a coarse grain structure, crack lengths in precracked spinel specimens could not be measured optically, so the crack lengths and fracture toughness were estimated by strain gage measurements. An expression was developed via finite element analysis to correlate the measured strain with crack length in four-point flexure. The fracture toughness estimated by the strain gaged samples and another standardized method were in agreement.

Salem, Jonathan A.; Ghosn, Louis J.

2010-01-01

317

Optical imaging with spectrum aberration correction using a filtering macrolens.  

PubMed

A filtering macrolens was developed to simultaneously achieve macro-optical imaging and correct spectrum aberration. The macrolens was a doublet lens comprising a filtering lens and a close-up lens. The shape of the filtering lens was designed to eliminate the optical path differences between the light rays in the absorbing medium. The close-up lens was designed to decrease the effective focal length of an ordinary camera lens to provide high magnification capability and collimate the diverging beams through the filtering lens. Experimental results demonstrated that the spectrum uniformity of the macro-optical images was markedly improved by the filtering macrolens. This innovation may be used in finite conjugate optical systems. PMID:23872748

Lin, Yu-Hsuan; Lai, Jyun-Yi; Tsai, Hsin-Yi; Chang, Han-Chao; Huang, Hung Ji; Chen, Yung-Fu; Huang, Kuo-Cheng

2013-07-20

318

Compressive optical MONTAGE photography  

NASA Astrophysics Data System (ADS)

The Compressive Optical MONTAGE Photography Initiative (COMP-I) is an initiative under DARPA's MONTAGE program. The goals of COMP-I are to produce 1 mm thick visible imaging systems and 5 mm thick IR systems without compromising pixel-limited resolution. Innovations of COMP-I include focal-plane coding, block-wise focal plane codes, birefringent, holographic and 3D optical elements for focal plane remapping and embedded algorithms for image formation. In addition to meeting MONTAGE specifications for sensor thickness, focal plane coding enables a reduction in the transverse aperture size, physical layer compression of multispectral and hyperspectral data cubes, joint optical and electronic optimization for 3D sensing, tracking, feature-specific imaging and conformal array deployment.

Brady, David J.; Feldman, Michael; Pitsianis, Nikos; Guo, J. P.; Portnoy, Andrew; Fiddy, Michael

2005-08-01

319

Progress in Long Scale Length Laser-Plasma Interactions  

Microsoft Academic Search

The first experiments on the National Ignition Facility (NIF) have employed the first four beams to measure propagation and laser backscattering losses in large ignition-size plasmas. Gas-filled targets between 2 mm and 7 mm length have been heated from one side by overlapping the focal spots of the four beams from one quad operated at 351 nm (3) with a

S H Glenzer; P Arnold; G Bardsley; R L Berger; G Bonanno; T Borger; D E Bower; M Bowers; R Bryant; S Buckman; S C Burkhart; K Campbell; M P Chrisp; B I Cohen; G Constantin; F Cooper; J Cox; E Dewald; L Divol; S Dixit; J Duncan; D Eder; J Edwards; G Erbert; B Felker; J Fornes; G Frieders; D H Froula; S D Gardner; C Gates; M Gonzalez; S Grace; G Gregori; A Greenwood; R Griffith; T Hall; B A Hammel; C Haynam; G Heestand; M Henesian; G Hermes; D Hinkel; J Holder; F Holdner; G Holtmeier; W Hsing; S Huber; T James; S Johnson; O S Jones; D Kalantar; J H Kamperschroer; R Kauffman; T Kelleher; J Knight; R K Kirkwood; W L Kruer; W Labiak; O L Landen; A B Langdon; S Langer; D Latray; A Lee; F D Lee; D Lund; B MacGowan; S Marshall; J McBride; T McCarville; L McGrew; A J Mackinnon; S Mahavandi; K Manes; C Marshall; E Mertens; N Meezan; G Miller; S Montelongo; J D Moody; E Moses; D Munro; J Murray; J Neumann; M Newton; E Ng; C Niemann; A Nikitin; P Opsahl; E Padilla; T Parham; G Parrish; C Petty; M Polk; C Powell; I Reinbachs; V Rekow; R Rinnert; B Riordan; M Rhodes

2003-01-01

320

Multiplicative and subtractive focal volume engineering in coherent Raman microscopy  

PubMed Central

Rigorous calculations are performed to study the effective reduction of the nonlinear excitation volumes when using phase-only masks to condition the pump and Stokes driving fields. Focal volume reduction was achieved using both a multiplicative operation of the excitation fields as well as a subtractive operation. Using a tunable optical bottle beam for the Stokes field, an effective reduction of the width of the excitation volume by a factor of 1.5 can be achieved in the focal plane. Further reduction of the focal volume introduces a rapid growth of sidelobes, which renders such volumes unsuitable for imaging applications. In addition, phase sensitive detection was found to provide information from selective sub-divisions of the engineered coherent anti-Stokes Raman scattering excitation volume. In the case of isolated nanoparticles, an apparent resolution improvement by a factor of 3 is demonstrated, and it is shown that the size of sub-diffraction-limited particles can be accurately determined using phase sensitive detection.

Raghunathan, Varun; Potma, Eric Olaf

2012-01-01

321

Optimizing focal plane electric field estimation for detecting exoplanets  

NASA Astrophysics Data System (ADS)

Detecting extrasolar planets with angular separations and contrast levels similar to Earth requires a large space-based observatory and advanced starlight suppression techniques. This paper focuses on techniques employing an internal coronagraph, which is highly sensitive to optical errors and must rely on focal plane wavefront control techniques to achieve the necessary contrast levels. To maximize the available science time for a coronagraphic mission we demonstrate an estimation scheme using a discrete time Kalman filter. The state estimate feedback inherent to the filter allows us to minimize the number of exposures required to estimate the electric field. We also show progress including a bias estimate into the Kalman filter to eliminate incoherent light from the estimate. Since the exoplanets themselves are incoherent to the star, this has the added benefit of using the control history to gain certainty in the location of exoplanet candidates as the signal-to-noise between the planets and speckles improves. Having established a purely focal plane based wavefront estimation technique, we discuss a sensor fusion concept where alternate wavefront sensors feedforward a time update to the focal plane estimate to improve robustness to time varying speckle. The overall goal of this work is to reduce the time required for wavefront control on a target, thereby improving the observatory's planet detection performance by increasing the number of targets reachable during the lifespan of the mission.

Groff, T.; Kasdin, N. J.; Riggs, A. J. E.

322

Automatic location of microscopic focal planes for computerized stereology  

NASA Astrophysics Data System (ADS)

When applying design-based stereology to biological tissue, there are two primary applications for an auto-focusing function in the software of computerized stereology system. The system must first locate the in-focus optical planes at the upper and lower surfaces of stained tissue sections, thus identifying the top and bottom as well as the thickness of the tissue. Second, the system must find the start and end along the Z-axis of stained objects within a Z-stack of images through tissue sections. In contrast to traditional autofocus algorithms that seek a global maximum or peak on the focus curve, the goal of this study was to find the two "knees" of the focus curve that represent the "just out-of-focus" focal planes. The upper surface of the tissue section is defined as the image just before focus is detected moving down the Z-stack. Continuing down, the lower surface is defined as the first image of the last set of adjacent images where focus is no longer detected. The performance of seven focus algorithms in locating the top and bottom focal planes of tissue sections was analyzed by comparing each algorithm on 34 Z-stacks including a total of 828 images. The Thresholded Absolute Gradient algorithm outperformed all others, correctly identifying the top or bottom focal plane within an average of 1 ?m on the training data as well as the test data.

Elozory, Daniel T.; Bonam, Om Pavithra; Kramer, Kurt; Goldgof, Dmitry B.; Hall, Lawrence O.; Mangual, Osvaldo; Mouton, Peter R.

2011-03-01

323

Focal brain inflammation and autism  

PubMed Central

Increasing evidence indicates that brain inflammation is involved in the pathogenesis of neuropsychiatric diseases. Autism spectrum disorders (ASD) are characterized by social and learning disabilities that affect as many as 1/80 children in the USA. There is still no definitive pathogenesis or reliable biomarkers for ASD, thus significantly curtailing the development of effective therapies. Many children with ASD regress at about age 3 years, often after a specific event such as reaction to vaccination, infection, stress or trauma implying some epigenetic triggers, and may constitute a distinct phenotype. ASD children respond disproportionally to stress and are also affected by food and skin allergies. Corticotropin-releasing hormone (CRH) is secreted under stress and together with neurotensin (NT) stimulates mast cells and microglia resulting in focal brain inflammation and neurotoxicity. NT is significantly increased in serum of ASD children along with mitochondrial DNA (mtDNA). NT stimulates mast cell secretion of mtDNA that is misconstrued as an innate pathogen triggering an auto-inflammatory response. The phosphatase and tensin homolog (PTEN) gene mutation, associated with the higher risk of ASD, which leads to hyper-active mammalian target of rapamycin (mTOR) signalling that is crucial for cellular homeostasis. CRH, NT and environmental triggers could hyperstimulate the already activated mTOR, as well as stimulate mast cell and microglia activation and proliferation. The natural flavonoid luteolin inhibits mTOR, mast cells and microglia and could have a significant benefit in ASD.

2013-01-01

324

Early vision and focal attention  

NASA Astrophysics Data System (ADS)

At the thirty-year anniversary of the introduction of the technique of computer-generated random-dot stereograms and random-dot cinematograms into psychology, the impact of the technique on brain research and on the study of artificial intelligence is reviewed. The main finding-that stereoscopic depth perception (stereopsis), motion perception, and preattentive texture discrimination are basically bottom-up processes, which occur without the help of the top-down processes of cognition and semantic memory-greatly simplifies the study of these processes of early vision and permits the linking of human perception with monkey neurophysiology. Particularly interesting are the unexpected findings that stereopsis (assumed to be local) is a global process, while texture discrimination (assumed to be a global process, governed by statistics) is local, based on some conspicuous local features (textons). It is shown that the top-down process of "shape (depth) from shading" does not affect stereopsis, and some of the models of machine vision are evaluated. The asymmetry effect of human texture discrimination is discussed, together with recent nonlinear spatial filter models and a novel extension of the texton theory that can cope with the asymmetry problem. This didactic review attempts to introduce the physicist to the field of psychobiology and its problems-including metascientific problems of brain research, problems of scientific creativity, the state of artificial intelligence research (including connectionist neural networks) aimed at modeling brain activity, and the fundamental role of focal attention in mental events.

Julesz, Bela

1991-07-01

325

Challenging subjects behind using a liquid crystal display as an optical lens  

NASA Astrophysics Data System (ADS)

Adjustable lenses are widely used in compound optical systems, including cameras and microscopes. Different techniques are used to build lenses with adjustable focusing. One of the recent techniques uses a liquid crystal spatial light modulator (LC-SLM) to generate the adjustable lens phase function. LC-SLMs provide a robust capability to design fast adjustable optical components without any movable mechanical parts. This paper presents a general method to design a compound lens with an adjustable focal length using a LC-SLM for a laser lithography application. The article describes the challenging matters behind using phase modulators in an imaging system. The maximum and minimum accessible focal lengths have been calculated for different LC-SLMs, taking into account the modulator resolution, bit depth and aperture size. A new type of random aberration caused by bit depth limitation is introduced and its dependency on the focal lengths is discussed. The proposed theoretical model to determine the lens parameters is compared with numerical and experimental data. The experimental results agree well with the theory. The focusing capabilities of a Holoeye LC-SLM will be demonstrated.

Gatabi, Javad R.; Geerts, Wilhelmus; Tamir, Dan

2012-10-01

326

Generation of a focused hollow beam by an 2?-phase plate and its application in atom or molecule optics  

NASA Astrophysics Data System (ADS)

We propose a new scheme to generate a focusing hollow beam (FHB) by use of an azimuthally distributed 2?-phase plate and a convergent thin lens. From the Fresnel diffraction theory, we calculate the intensity distributions of the FHB in free propagation space and study the relationship between the waist w0 of the incident Gaussian beam (or the focal length f of the lens) and the dark spot size (or the beam radius) at the focal point and the relationship between the maximum radial intensity of the FHB and the dark spot size (or the beam radius) at the focal point, respectively. Our study shows that the FHB can be used to cool and trap neutral atoms by intensity-gradient-induced Sisyphus cooling due to an extremely high intensity gradient of the FHB itself near the focal point, or to guide and focus a cold molecular beam. We also calculate the optical potential of the blue-detuned FHB for 85Rb atoms and find that in the focal plane, the smaller the dark spot size of the FHB is, the higher the optical potential is, and the greater the corresponding optimal detuning ? is; these qualities are beneficial to an atomic lens not only because it is profitable to obtain an atomic lens with a higher resolution, but also because it is helpful to reduce the spontaneous photon-scattering effect of atoms in the FHB.

Xia, Yong; Yin, Jianping

2005-03-01

327

Biostatistical evaluation of focal hepatic preneoplasia.  

PubMed

Qualitative analyses of focal hepatic preneoplasia are relatively easy and fast but hypothesis tests based on these analyses often lack statistical power. Evaluating focal hepatic preneoplasia quantitatively, on the other hand, requires more effort but is rewarded by an increased ability to detect differences between treatment groups and by the possibility to investigate the mechanism of a treatment under study. Due to the stereological problems inherent in the data a statistical analysis that concentrates on the evaluation of area fraction will provide clear results whereas the analysis of focal transection density and size distribution can produce misleading results. In addition, the area fraction is a valid variable even in the presence of confluent foci. The number and size distribution of focal transections in liver sections cannot be directly translated to the number and sizes of foci in the liver. As no general statements about the relationship between focal transection density and foci density as well as between focal transection size and foci size distribution can be made, there is need for a parametric mechanistic model to link the number and size distribution of focal transections to those of the underlying foci. The stereological problem therefore can be avoided by introducing a model for foci appearance and change of volume that then can be used to conclude whether the treatment induces foci and whether it changes their volume. PMID:12597456

Kopp-Schneider, Annette

2003-01-01

328

[Nuclear medicine diagnosis of focal liver lesions].  

PubMed

Confirmation and exclusion of benign focal liver lesions are the main object of liver studies in nuclear medicine. Hepatobiliary sequence scintigraphy (focal nodular hyperplasia, adenoma), blood pool scintigraphy (hemangioma) and, in some cases, colloid scintigraphy are the methods most frequently employed. Receptor scintigraphy with octreopeptides, immunoscintigraphy with monoclonal antibodies, PET and gamma camera scintigraphy with 18FDG, are used to solve special diagnostic problems, particularly in oncology. A stepwise diagnostic approach needs to be used for a successful classification of focal liver lesions and an extensive knowledge of indications for additional supplementary diagnostic procedures is required. PMID:8371998

Trampert, L; Benz, P; Ruth, T; Oberhausen, E

1993-08-01

329

Design of dual-band shared-aperture Co-zoom optical system  

NASA Astrophysics Data System (ADS)

An optical system that features visible plus mid-infrared light, shared aperture, synchronous and continuous zoom is designed with a 10× zoom ratio. Analysis is performed to differentiate visible plus mid-infrared light focal length and zoom ratio during zooming, and the change law of this difference. Upon combination with two-group and three-group zoom theories and upon derivation of the conditions for compensating zoom ratio difference, a method has been obtained to directly compensate this difference. The focal length and the zoom ratio for visible/mid-infrared light at any zoom location are similar with this method, thereby conducting synchronous observation, tracking, and measurement on the target. Design results have shown that the system is small, has a fast response, has an excellent in overall image quality, and is athermal for temperatures between ?40 °C and 60 °C.

Ming, Gao; Yang, Chen; Jun, Liu; Hong, Lv

2014-05-01

330

Numerical analysis of gradient index lens-based optical coherence tomography imaging probes  

PubMed Central

We report the numerical analysis of gradient index (GRIN) lens-based optical coherence tomography imaging probes to derive optimal design parameters. Long and short working distance probes with a small focal spot are considered. In each model, the working distance and beam waist are characterized and compared for different values of length and refractive index of the probe components. We also explore the influence of the outer tubing and refractive index of the sample media. Numerical results show that the adjustment of the maximum beam diameter and focusing angle at the end of the GRIN lens surface is very important for determining the optical performance parameters of the probe.

Jung, Woonggyu; Benalcazar, Wladimir; Ahmad, Adeel; Sharma, Utkarsh; Tu, Haohua; Boppart, Stephen A.

2010-01-01

331

The precision analysis of continuous zoom lens in airborne electro-optical pod  

NASA Astrophysics Data System (ADS)

In the research of electro-optical pod, this paper propose a mission requirements that continuous zoom lens system is using for measuring angle in the process. This paper analyzes the influence of angle measurement accuracy from focal length and optical axis errors in the process of continuous zoom, and given the mathematical model of the influence of angle measurement accuracy. The simulation analysis indicated that Angle measuring accuracy is affected by the process of continuous zoom. The simulation analysis results have certain instructive significance to engineering practice.

Yang, Xiao-xu; Li, Da-wei; Han, Jun-feng; Dong, Qiang; Huang, Wei; Wei, Yu

2014-02-01

332

Spatial calibration of an optical see-through head mounted display  

PubMed Central

We present here a method for calibrating an optical see-through Head Mounted Display (HMD) using techniques usually applied to camera calibration (photogrammetry). Using a camera placed inside the HMD to take pictures simultaneously of a tracked object and features in the HMD display, we could exploit established camera calibration techniques to recover both the intrinsic and extrinsic properties of the HMD (width, height, focal length, optic centre and principal ray of the display). Our method gives low re-projection errors and, unlike existing methods, involves no time-consuming and error-prone human measurements, nor any prior estimates about the HMD geometry.

Gilson, Stuart J.; Fitzgibbon, Andrew W.; Glennerster, Andrew

2010-01-01

333

Hand-held optical fuel pin scanner  

DOEpatents

An optical scanner for indicia arranged in a focal plane perpendicular to an optical system including a rotatable dove prism. The dove prism transmits a rotating image to a stationary photodiode array.

Kirchner, Tommy L. (Richland, WA); Powers, Hurshal G. (Richland, WA)

1987-01-01

334

Biometric, optical and physical changes in the isolated human crystalline lens with age in relation to presbyopia.  

PubMed

The biometric, optical and physical properties of 19 pairs of isolated human eye-bank lenses ranging in age from 5 to 96 years were compared. Lens focal length and spherical aberration were measured using a scanning laser apparatus, lens thickness and the lens surface curvatures were measured by digitizing the lens profiles and equivalent refractive indices were calculated for each lens using this data. The second lens from each donor was used to measure resistance to physical deformation by providing a compressive force to the lens. The lens capsule was then removed from each lens and each measurement was repeated to ascertain what role the capsule plays in determining these optical and physical characteristics. Age dependent changes in lens focal length, lens surface curvatures and lens resistance to physical deformation are described. Isolated lens focal length was found to be significantly linearly correlated with both the anterior and posterior surface curvatures. No age dependent change in equivalent refractive index of the isolated lens was found. Although decapsulating human lenses causes similar changes in focal length to that which we have shown to occur when human lenses are mechanically stretched into an unaccommodated state, the effects are due to nonsystematic changes in lens curvatures. These studies reinforce the conclusion that lens hardening must be considered as an important factor in the development of presbyopia, that age changes in the human lens are not limited to the loss of accommodation that characterizes presbyopia but that the lens optical and physical properties change substantially with age in a complex manner. PMID:10343784

Glasser, A; Campbell, M C

1999-06-01

335

Diamond diffraction optics for CO{sub 2} lasers  

SciTech Connect

A laser ablation method for the formation of a phase microrelief on diamond optical diffraction components, intended for the far-IR range, was proposed and implemented. A one-dimensional diffraction component was made for CO{sub 2} laser radiation ({lambda} = 10.6 {mu}m): it was a cylindrical lens of 4 mmx4 mm aperture and with a focal length 25 mm. Microstructuring of the surface was performed by selective ablation etching of diamond with KrF excimer laser radiation ({lambda} = 248 nm). The distribution of the field intensity in the focal region of the lens, its depth of focus, and the diffraction efficiency were determined. A high degree of correlation was found between the experimental characteristics of the lens and the results of computer modelling. (letters to the editor)

Kononenko, Vitalii V; Konov, Vitalii I; Pimenov, S M; Prokhorov, A M [Natural Science Center, A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Pavel'ev, V S; Soifer, V A [Institute for Image Processing Systems, Russian Academy of Sciences (Russian Federation)

1999-01-31

336

DIVA optical telescope  

NASA Astrophysics Data System (ADS)

The German Instrument for Multi-channel Photometry and Astrometry (DIVA), dedicated to the German (DLR) small extraterrestrial satellite program, is intended as a kind of technology precursor mission to GAIA. DIVA is scheduled for launch in 2004 and shall perform a sky survey to measure within 2 years life time the positions, parallaxes, magnitudes, etc. of about 35 million stars. The main instrument, covering the spectral range of 400-1000nm, observes 2 fields of view (0.6° x 0.77°) by a single Focal Plane Assembly (FPA). The focal length is 11200mm. The DIVA Optomechanics is based on a high precision Three Mirror Anastigmat (TMA) concept with 8 mirrors, 5 of them flat. An extremely high short term stability (torsion tolerance) of 0.3 mas over 10h only has to be realized only by passive means to achieve the astrometrical performance requirements. The paper describes the phase B2 design activities wrt. the optomechanical and thermal design of the main instrument. Special emphasis is given to an exhausting, but very pragmatic thermomechanical and optical performance trade off between a cost effective athermal design concept, applying mirrors and an optical bench made from a specially treated isotropic aluminum alloy, and a thermally stable hybrid material concept based on a Carbon Fiber Reinforced Plastics (CFRP) sandwich structure and Zerodur mirrors. The selection of the final baseline design solution shall be reported. According to the very high long and short scale surface properties of the candidate aluminum mirrors a sophisticated manufacturing procedure was established based on conventional and ion beam polishing techniques. The representative breadboard mirror test results will be given.

Graue, Roland; Kampf, Dirk; Röser, Siegfried; Bastian, Ulrich; Seifert, Walter

2003-02-01

337

Health Education Focal Points 1984, No. 2.  

National Technical Information Service (NTIS)

The publication contains responses to a previous article and describes 7 award-winning programs that received awards for excellence. In response to Carlyon's 'School Health Education: The Need for Synergism' (Focal Points, Sept 1983), the official reactio...

1984-01-01

338

Integrated Focal Plane Array Programs by DARPA.  

National Technical Information Service (NTIS)

The technology of four differing approaches to the development of integrated, staring focal plane arrays operating in the infrared regime for application on a small tactical missile are reviewed. Monolithic and hybrid architectures are included with both ...

D. Patz R. McDaniel

1980-01-01

339

Mid Infrared Multichannel Focal Plane Breadboard.  

National Technical Information Service (NTIS)

Linear arrays of nonstaggered IR detectors and technologies for assembling a couple of linear arrays into a focal plane by mechanical butting were developed. The realization of very small dark space between pixels and the possibility to realize a butting ...

1987-01-01

340

Test of the Hipparcos Payload in the Liege Vacuum Facility Focal (Abstract Only),  

National Technical Information Service (NTIS)

The Liege thermal vacuum optical bench (FOCAL) was used to control the mechanical stability of the structure of the European Space Agency's HIPPARCOS astrometry payload. The payload is designed to measure angles of .001 arcsec between stars during 2.5 yea...

C. Jamar A. Cucchiard J. Jamar D. Macau-hercot J. P. Camus

1986-01-01

341

Development of uncooled focal plane detector arrays for smart IR sensors  

Microsoft Academic Search

This paper reports on the development of silicon microbolometer uncooled IR focal plane detector arrays at the Defence Science and Technology Organization (DSTO), in collaboration with the National Defence Research Establishment (FOA). The detector arrays were designed by Electro-optic Sensor Design, which also provided specialist scientific advice on array fabrication. Detector arrays are prepared by monolithic processing at DSTO, using

Kevin C. Liddiard; Olaf Reinhold; Ulf Ringh; Christer Jansson

1997-01-01

342

High-aperture focusing systems: control of light concentration in focal region by pupil filtering  

Microsoft Academic Search

The influence of various pupil filters on the field distribution in the neighbourhood of focus within the context of the vector diffraction theory is reviewed. The principal issue is with the focal depth via the calculations of integral parameters: encircled electric energy and encircled longitudinal electromagnetic energy flow along the optical axis. It is shown that in the case of

Peep Adamson

2004-01-01

343

Surgery for drug-resistant focal epilepsy  

PubMed Central

During the colloquium on drug-resistant epilepsy (DRE) at National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore on August 16-18, 2013, a number of presentations were made on the surgically remediable lesional epilepsy syndromes, presurgical evaluation, surgical techniques, neuropathology of drug resistance focal epilepsy and surgical outcome. This pictorial essay with the illustrative case examples provides an overview of the various surgical techniques for the management of drug-resistant focal epilepsy.

Rao, Malla Bhaskara; Arivazhagan, Arimappamagan; Sinha, Sanjib; Bharath, Rose Dawn; Mahadevan, Anita; Bhat, Maya; Satishchandra, Parthasarthy

2014-01-01

344

Modeling a variable-focus liquid-filled optical lens  

NASA Astrophysics Data System (ADS)

Research has been conducted on a variable-focus liquid-filled optical lens built from a polymer elastic-film window and a rigid plastic window with a transparent refractive liquid between these windows. The pressure inside the lens deforms the elastic film, which takes the form of a paraboloid. The absolute value of the tension in the film was calculated, allowing theoretical evaluation of the focal length of the lens and its aberrations. The developed mathematical model of the liquid-filled flexible lens agrees well with experimental results.

Rawicz, Andrew H.; Mikhailenko, Iouri

1996-04-01

345

The Optical Layout Of The HEGRA Cherenkov Telescopes  

NASA Astrophysics Data System (ADS)

The raytracing technique was used to derive a suitable design for the HEGRA system of Cherenkov telescopes, which is at present commissioned at La Palma. The reflectors with a diameter of ~ 3.9 m consist of 30 spherical mirrors with focal lengths in the range of 4.88 - 4.94 m. It is shown that 93% of the photons from the Cherenkov light emitted by an extended air shower are contained in the camera pixels, 0.25 deg in diameter, for the full field of view of theta = +/- 2.5 deg. The optical performance of the HEGRA design is compared to other layouts.

Akhperjanian, A.; Kankanian, R.; Sahakian, V.; Heusler, A.; Wiedner, C.-A.; Wirth, H.

346

A monolithic polycapillary focusing optic for polychromatic neutron diffraction applications  

NASA Astrophysics Data System (ADS)

We have conducted measurements at five different thermal neutron wavelengths to determine the transmission characteristics of a tapered monolithic focusing lens with a focal length of 100 mm, suitable for time-of-flight diffraction. Both the width of the focused beam and the intensity gain of the optic increase as a function of wavelength. We have performed similar measurements on a polychromatic beam on a pulsed neutron source, where the results are subject to background from short wavelength neutrons. The use of a beryllium filter shows the increased effective gain for the longer wavelengths at the expense of an increased focused beam width by a factor of 2.

Mildner, D. F. R.; Chen-Mayer, H. H.; Gibson, W. M.; Gnäupel-Herold, T.; Miller, M. E.; Prask, H. J.; Schultz, A. J.; Vitt, R.; Youngman, R.

2002-05-01

347

Curved-Focal-Plane Arrays Using Deformed-Membrane Photodetectors  

NASA Technical Reports Server (NTRS)

A versatile and simple approach to the design and fabrication of curved-focal-plane arrays of silicon-based photodetectors is being developed. This approach is an alternative to the one described in "Curved Focal-Plane Arrays Using Back- Illuminated High-Purity Photodetectors" (NPO-30566), NASA Tech Briefs, Vol. 27, No. 10 (October 2003), page 10a. As in the cited prior article, the basic idea is to improve the performance of an imaging instrument and simplify the optics needed to obtain a given level of performance by making an image sensor (in this case, an array of photodetectors) conform to a curved focal surface, instead of designing the optics to project an image onto a flat focal surface. There is biological precedent for curved-focal-surface designs: retinas - the image sensors in eyes - conform to the naturally curved focal surfaces of eye lenses. The present approach is applicable to both front-side- and back-side-illuminated, membrane photodetector arrays and is being demonstrated on charge-coupled devices (CCDs). The very-large scale integrated (VLSI) circuitry of such a CCD or other array is fabricated on the front side of a silicon substrate, then the CCD substrate is attached temporarily to a second substrate for mechanical support, then material is removed from the back to obtain the CCD membrane, which typically has a thickness between 10 and 20 m. In the case of a CCD designed to operate in back-surface illumination, delta doping can be performed after thinning to enhance the sensitivity. This approach is independent of the design and method of fabrication of the front-side VLSI circuitry and does not involve any processing of a curved silicon substrate. In this approach, a third substrate would be prepared by polishing one of its surfaces to a required focal-surface curvature. A CCD membrane fabricated as described above would be pressed against, deformed into conformity with, and bonded to, the curved surface. The technique used to press and bond the CCD membrane would depend on the nature of the supporting material (see figure). For example, if the third substrate were made of quartz frit, the substrate would be prepared by suffusing it with epoxy. Then one would take advantage of the porosity of the frit by applying a partial vacuum to the opposite surface of the frit, causing atmospheric pressure to push the CCD membrane against the curved surface. The curing of the epoxy would bond the CCD membrane to the curved surface. Alternatively, if the third substrate were made of a nonporous material, the curved substrate surface would be prepared by coating it with a wax or an uncured epoxy. The CCD membrane would be pressed against the coated, curved surface by use of a suitably pressurized balloon. The CCD membrane would then become bonded to the curved surface by curing of the epoxy or freezing of the wax.

Nikzad, Shouleh; Jones, Todd

2004-01-01

348

Measuring Thermodynamic Length  

NASA Astrophysics Data System (ADS)

Thermodynamic length is a metric distance between equilibrium thermodynamic states. Among other interesting properties, this metric asymptotically bounds the dissipation induced by a finite time transformation of a thermodynamic system. It is also connected to the Jensen-Shannon divergence, Fisher information, and Rao’s entropy differential metric. Therefore, thermodynamic length is of central interest in understanding matter out of equilibrium. In this Letter, we will consider how to define thermodynamic length for a small system described by equilibrium statistical mechanics and how to measure thermodynamic length within a computer simulation. Surprisingly, Bennett’s classic acceptance ratio method for measuring free energy differences also measures thermodynamic length.

Crooks, Gavin E.

2007-09-01

349

Measuring Thermodynamic Length  

SciTech Connect

Thermodynamic length is a metric distance between equilibrium thermodynamic states. Among other interesting properties, this metric asymptotically bounds the dissipation induced by a finite time transformation of a thermodynamic system. It is also connected to the Jensen-Shannon divergence, Fisher information, and Rao's entropy differential metric. Therefore, thermodynamic length is of central interestin understanding matter out of equilibrium. In this Letter, we will consider how to denethermodynamic length for a small system described by equilibrium statistical mechanics and how to measure thermodynamic length within a computer simulation. Surprisingly, Bennett's classic acceptance ratio method for measuring free energy differences also measures thermodynamic length.

Crooks, Gavin E

2007-09-07

350

Improvement of the GO\\/PO method for the study of focal array fed lens antennas  

Microsoft Academic Search

Focal array fed lens antennas are very attractive for multi-beam and beam shaping applications at millimetre waves. They typically consist of an integrated lens antenna illuminated by phased sub-arrays. Due to their moderate or even large size, their radiation characteristics are generally computed using high-frequency techniques like the geometrical optics\\/physical optics (GO\\/PO) method. We introduce here a refined version of

Ngoc Tinh Nguyen; Ronan Sauleau

2009-01-01

351

Assessing the effect of laser beam width on quantitative evaluation of optical properties of intraocular lens implants  

NASA Astrophysics Data System (ADS)

The design and manufacture of intraocular lenses (IOLs) depend upon the identification and quantitative preclinical evaluation of key optical properties and environmental parameters. The confocal laser method (CLM) is a new technique for measuring IOL optical properties, such as dioptric power, optical quality, refractive index, and geometrical parameters. In comparison to competing systems, the CLM utilizes a fiber-optic confocal laser design that significantly improves the resolution, accuracy, and repeatability of optical measurements. Here, we investigate the impact of changing the beam diameter on the CLM platform for the evaluation of IOL dioptric powers. Due to the Gaussian intensity profile of the CLM laser beam, the changes in focal length and dioptric power associated with changes in beam diameter are well within the tolerances specified in the ISO IOL standard. These results demonstrate some of the advanced potentials of the CLM toward more effectively and quantitatively evaluating IOL optical properties.

Walker, Bennett N.; James, Robert H.; Chakravarty, Aurin; Calogero, Don; Ilev, Ilko K.

2014-05-01

352

The Imaging Properties of the Gas Pixel Detector as a Focal Plane Polarimeter  

NASA Astrophysics Data System (ADS)

X-rays are particularly suited to probing the physics of extreme objects. However, despite the enormous improvements of X-ray astronomy in imaging, spectroscopy, and timing, polarimetry remains largely unexplored. We propose the photoelectric polarimeter Gas Pixel Detector (GPD) as a candidate instrument to fill the gap created by more than 30 yr without measurements. The GPD, in the focus of a telescope, will increase the sensitivity of orders of magnitude. Moreover, since it can measure the energy, the position, the arrival time, and the polarization angle of every single photon, it allows us to perform polarimetry of subsets of data singled out from the spectrum, the light curve, or an image of the source. The GPD has an intrinsic, very fine imaging capability, and in this work we report on the calibration campaign carried out in 2012 at the PANTER X-ray testing facility of the Max-Planck-Institut für extraterrestrische Physik of Garching (Germany) in which, for the first time, we coupled it with a JET-X optics module with a focal length of 3.5 m and an angular resolution of 18 arcsec at 4.5 keV. This configuration was proposed in 2012 aboard the X-ray Imaging Polarimetry Explorer (XIPE) in response to the ESA call for a small mission. We derived the imaging and polarimetric performance for extended sources like pulsar wind nebulae and supernova remnants as case studies for the XIPE configuration and also discuss possible improvements by coupling the detector with advanced optics that have a finer angular resolution and larger effective areas to study extended objects with more detail.

Fabiani, S.; Costa, E.; Del Monte, E.; Muleri, F.; Soffitta, P.; Rubini, A.; Bellazzini, R.; Brez, A.; de Ruvo, L.; Minuti, M.; Pinchera, M.; Sgró, C.; Spandre, G.; Spiga, D.; Tagliaferri, G.; Pareschi, G.; Basso, S.; Citterio, O.; Burwitz, V.; Burkert, W.; Menz, B.; Hartner, G.

2014-06-01

353

Possible optical functions of the central core in lenses of trilobite eyes: spherically corrected monofocality or bifocality.  

PubMed

The function of the central core in lenses of certain schizochroal-eyed trilobites is unknown. To understand the possible optical function(s) of this central core, we performed computational ray-tracing on the lens in the schizochroal compound eyes of a Silurian Dalmanites trilobite. We computed the intensity of light focused by the lens versus the distance from the lower lens surface along the optical axis as functions of the refractive indices n(lu) and n(cc) of the lower lens unit and the central core. We determined those values of n(lu) and n(cc) that ensure that the studied central-cored trilobite lens is monofocal, bifocal, or trifocal. The sharpness (as the measure of the correction for spherical aberration) of these focal points was quantitatively studied. We show here that one of the possible optical functions of the central core could be the correction for spherical aberration, independently of the number (1, 2, or 3) of focal points. Another possible optical function of the core could be to ensure bifocality of the lens. In this case the peripheral lens region could have a given focal length and the central lens region could possess a longer or shorter focal length, if the refractive index n(cc) of the core is smaller or larger than the refractive index n(lu) of the upper lens unit. Finally, trifocality of the lenses can be considered only as a theoretical option, but by no means an optically optimally functioning possibility. PMID:23201954

Egri, Ádám; Horváth, Gábor

2012-09-01

354

LSST Camera Optics Design  

Microsoft Academic Search

The Large Synoptic Survey Telescope (LSST) uses a novel, three-mirror, telescope design feeding a camera system that includes a set of broad-band filters and three refractive corrector lenses to produce a flat field at the focal plane with a wide field of view. Optical design of the camera lenses and filters is integrated in with the optical design of telescope

V J Riot; S Olivier; B Bauman; S Pratuch; L Seppala; D Gilmore; J Ku; M Nordby; M Foss; P Antilogus; N Morgado

2012-01-01

355

Transparent Meta-Analysis: Does Aging Spare Prospective Memory with Focal vs. Non-Focal Cues?  

PubMed Central

Background Prospective memory (ProM) is the ability to become aware of a previously-formed plan at the right time and place. For over twenty years, researchers have been debating whether prospective memory declines with aging or whether it is spared by aging and, most recently, whether aging spares prospective memory with focal vs. non-focal cues. Two recent meta-analyses examining these claims did not include all relevant studies and ignored prevalent ceiling effects, age confounds, and did not distinguish between prospective memory subdomains (e.g., ProM proper, vigilance, habitual ProM) (see Uttl, 2008, PLoS ONE). The present meta-analysis focuses on the following questions: Does prospective memory decline with aging? Does prospective memory with focal vs. non-focal cues decline with aging? Does the size of age-related declines with focal vs. non-focal cues vary across ProM subdomains? And are age-related declines in ProM smaller than age-related declines in retrospective memory? Methods and Findings A meta-analysis of event-cued ProM using data visualization and modeling, robust count methods, and conventional meta-analysis techniques revealed that first, the size of age-related declines in ProM with both focal and non-focal cues are large. Second, age-related declines in ProM with focal cues are larger in ProM proper and smaller in vigilance. Third, age-related declines in ProM proper with focal cues are as large as age-related declines in recall measures of retrospective memory. Conclusions The results are consistent with Craik's (1983) proposal that age-related declines on ProM tasks are generally large, support the distinction between ProM proper vs. vigilance, and directly contradict widespread claims that ProM, with or without focal cues, is spared by aging.

Uttl, Bob

2011-01-01

356

Polished Panel Optical Receiver for Simultaneous RF/Optical Telemetry with Large DSN Antennas  

NASA Technical Reports Server (NTRS)

The polished panel optical receiver concept described here makes use of aluminum panels on the main reflector of the Deep Space Network's (DSN's) 34-meter antennas at optical wavelengths by polishing and coating their surface to efficiently reflect near-infrared wavelengths in the 1,064 1,550-nanometer range. Achievable surface smoothness is not a limiting factor for aluminum panels, and initial field experiments indicate that the surface quality of microwave aluminum panels is sufficient to concentrate the light into small, but not diffraction-limited, spots at their primary focus. Preliminary analysis of data from high-quality microwave panels has shown that the light can be concentrated into 200 400 microradian cones, resulting in spot diameters of 2-4 mm at the 10-meter primary focus F(0) shown in the figure, or 2-4 cm spots at F(1) after magnification by the subreflector, which results in an effective focal length of about 100 meters. Three distinct implementation options are possible, with theoretically identical tracking and communications performance: Option 1: The communications assembly could be placed directly behind the subreflector at F(0), but this placement would require replacing the existing all-aluminum subreflector with a new design that transmits optical wavelengths but reflects RF, thus transmitting the optical signal to the primary focus of the parabolic polished aluminum panels at F(0), as shown in the figure. Option 2: Alternately, the optical communications assembly could be located near the first available focal-spot F(1) following reflection by the subreflector (which would have to be polished), next to the input to the beam waveguide on the main reflector as shown in the figure. Option 3: Finally, the optical communications assembly could be placed inside the pedestal room, and separated from the RF signal after the ellipsoid and before the signal reached the microwave receiver via an RF/optical dichroic near F(3).

Vilnrotter, Victor A.; Hoppe, Daniel J.

2011-01-01

357

Optical designs with wide field-of-view adaptive optics for IMAKA of CFHT  

NASA Astrophysics Data System (ADS)

As a ground-layer adaptive optics (GLAO) system can correct the wavefront errors caused by turbulence close to the Canada-France-Hawaii telescope (CFHT), an intensive study is in progress to determine the feasibility and the pertinence of equipping the CFHT of such a GLAO system. More specifically, the study concerns the implementation of GLAO capabilities using a deformable mirror inserted into the optical path of an optical relay. The studied system called IMAKA would be used both for the dynamic correction of the wavefront errors caused by air turbulence and the increases of the telescope effective field of view. The objective pursued by IMAKA is to achieve a PSF with Full Width at Half Maximum of less than 0.15" over a 1-degree field of view for extended wavebands within the spectral waveband of 470 nm - 900 nm. This paper presents the main results of a study conducted by INO about the optical design challenges of the IMAKA system. INO has proposed 4 different approaches for the realization of the system and made preliminary optical designs for each of them. The science camera and deformable mirror in the proposed designs are located below the Cassegrain environment for three of the proposed configurations and between the primary mirror and the top ring for the fourth design. In all the proposed configurations, the effective focal length of the telescope with the added correction relay is about 20.63 m for a working focal ratio of about 5.74. The design configurations included in this paper have achieved nearly diffraction limited performances with a deformable mirror having a diameter inferior to 0.5 m and flat or mild curvature nominal shape. Based on our preliminary optical design and performance analysis with the 4 optical design approaches, it seems possible to achieve most of the IMAKA requirements.

Wang, Min; Doucet, Michel; Gauvin, Jonny; Châteauneuf, François; Salmon, Derrick

2010-07-01

358

Circumference and Arc Length  

NSDL National Science Digital Library

This unit will introduce you to circumference of a circle, and how to find the measurement of the edge of a piece of pizza! (Arc length!) Ok. Let's make sure you remember circumference of a circle, you know, the distance around a circle? Click on the following link and take notes! Circle Circumference Now we can use that to find the arc length, or the length of the crust part of the edge of a pizza! Take notes: Arcs in Circles Now, let's ...

Neubert, Mrs.

2011-03-24

359

Oral focal fibrous hyperplasia and squamous cell papilloma treated with an erbium laser. Case presentation.  

PubMed

Mouth and oropharynx cancer constitute 5% of all malignancies; 95% of them are head and neck squamous cell carcinomas. Carcinogenesis is a multifactor process. Mutagenesis is also determined by the human papilloma virus which has recently been found to be etiologically associated with 20 to 25% of head and neck squamous cell carcinomas, mostly in the oropharinx. Focal fibrous hyperplasia of the connective tissue comes up as an answer to a chronic irritation in which a big amount of collagen can be found. As there exist certain clinical resemblance between squamous cell papilloma, fibrous focal hyperplasia and other mesenchimal tumors it is recommended to proceed, always, with removal and study. Two cases, one of an oral papilloma and another of a focal fibrous hyperplasia in pediatric patients, treated with an Er,Cr:YSGG laser wave length (mu) of 2780 nm are presented. PMID:24654496

Boj, J; Hernandez, M; Espasa, E; Espanya, A

2014-01-01

360

Leg Length Inequality  

PubMed Central

Leg length inequality, a common abnormality, can cause musculoskeletal pain, scoliosis, and osteoarthritis of the hip. Seven percent of the asymptomatic population has a leg length inequality greater than 12 mm; the incidence is considerably higher (13%-22%) in individuals complaining of low back pain. Correction can usually be accomplished by shoe modification, and can result in dramatic relief of pain. Leg length inequality of more than half an inch is considered clinically significant. Leg length measurement should be routine in all patients complaining of low back pain, hip pain, and atypical flank and lower quadrant pain. Correction might prove very cost-effective.

Sharpe, Colin R.

1983-01-01

361

Smart optical writing head design for laser-based manufacturing  

NASA Astrophysics Data System (ADS)

Proposed is a smart optical writing head design suitable for high precision industrial laser based machining and manufacturing applications. The design uses an Electronically Controlled Variable Focus Lens (ECVFL) which enables the highest achievable spatial resolution of writing head spot sizes for axial target distances reaching 8 meters. A proof-of-concept experiment is conducted using a visible wavelength laser with a collimated beam that is coupled to beam conditioning optics which includes an electromagnetically actuated deformable membrane liquid ECVFL cascaded with a bias convex lens of fixed focal length. Electronic tuning and control of the ECVFL keeps the laser writing head far-field spot beam radii under 1 mm that is demonstrated over a target range of 20 cm to 800 cm. Applications for the proposed writing head design, which can accommodate both continuous wave and pulsed wave sources, include laser machining, high precision industrial molding of components, as well as materials processing requiring material sensitive optical power density control.

Amin, M. Junaid; Riza, Nabeel A.

2014-03-01

362

Electronic optics device with variable illumination and aperture limitation, and application thereof to an electron beam lithographic system  

US Patent & Trademark Office Database

An electronic optics device with variable illumination and aperture limitation is provided including, between a particle source and an object an image of which it is desired to project in an image plane, a set of three lenses with electronically controllable focal lengths, the first one being situated as close as possible to the source and associated, in its main plane or in the vicinity of this plane, with an aperture limitation diaphragm, the object being placed in the main plane of the third lens or in the vicinity thereof, the focal length of these three lenses being controlled so as to give to the section of the electronic beam in the object plane a value determining the desired illumination and to the image of the diaphragm a diameter and a position determining the desired aperture of the beam.

1990-04-17

363

New multiband IR imaging optics  

NASA Astrophysics Data System (ADS)

We report new multispectral materials that transmit from 0.9 to < 12 µm in wavelength. These materials fill up the glass map for multispectral optics and vary in refractive index from 2.38 to 3.17. They show a large spread in dispersion (Abbe number) and offer some unique solutions for multispectral optics designs. One of the glasses developed is a very good candidate to replace Ge, as it has a combination of excellent properties, including high Abbe number in the LWIR, high index of 3.2, 60% lower dn/dT, and better thermal stability at working temperatures. Our results also provide a wider selection of optical materials to enable simpler achromat designs. For example, we have developed other glasses that have relatively high Abbe number in both the MWIR and LWIR regions, while our MILTRAN ceramic has low Abbe number in both regions. This makes for a very good combination of glasses and MILTRAN ceramic (analogous to crown and flint glasses in the visible) for MWIR + LWIR dual band imaging. We have designed preliminary optics for one such imager with f/2.5, 51 mm focal length and 22 degrees FOV using a spaced doublet of NRL's glass and MILTRAN ceramic. NRL's approach reduces the number of elements, weight, complexity and cost compared with the approach using traditional optics. Another important advantage of using NRL glasses in optics design is their negative or very low positive dn/dT, that makes it easier to athermalize the optical system.

Bayya, Shyam; Sanghera, Jasbinder; Kim, Woohong; Gibson, Daniel; Fleet, Erin; Shaw, Brandon; Hunt, Michael; Aggarwal, Ishwar

2013-06-01

364

The Statistics of Calcium-Mediated Focal Excitations on a One-Dimensional Cable  

PubMed Central

It is well known that various cardiac arrhythmias are initiated by an ill-timed excitation that originates from a focal region of the heart. However, up to now, it is not known what governs the timing, location, and morphology of these focal excitations. Recent studies have shown that these excitations can be caused by abnormalities in the calcium (Ca) cycling system. However, the cause-and-effect relationships linking subcellular Ca dynamics and focal activity in cardiac tissue is not completely understood. In this article, we present a minimal model of Ca-mediated focal excitations in cardiac tissue. This model accounts for the stochastic nature of spontaneous Ca release on a one-dimensional cable of cardiac cells. Using this model, we show that the timing of focal excitations is equivalent to a first passage time problem in a spatially extended system. In particular, we find that for a short cable the mean first passage time increases exponentially with the number of cells in tissue, and is critically dependent on the ratio of inward to outward currents near the threshold for an action potential. For long cables excitations occurs due to ectopic foci that occur on a length scale determined by the minimum length of tissue that can induce an action potential. Furthermore, we find that for long cables the mean first passage time decreases as a power law in the number cells. These results provide precise criteria for the occurrence of focal excitations in cardiac tissue, and will serve as a guide to determine the propensity of Ca-mediated triggered arrhythmias in the heart.

Chen, Wei; Asfaw, Mesfin; Shiferaw, Yohannes

2012-01-01

365

Experimental and computer simulation investigation of the time-integrating planar acousto-optical correlator in regime of a delay time increase  

Microsoft Academic Search

Three types of time-integrating acousto optical correlator with delay time increasing have been designed developed and investigated. They based upon: 1) registration photoreceiver array is placed in lens focal plane; 2) diffracted optical bemas are separated by optical elements placed in a focal region; 3) photoreceiver array is placed in a plane situated between focal and image planes. The main

Arne S. Jensen; Karl-Ludwig Paap; Bernhard Klaassen; Evgueni N. Epikhin; Michael Y. Kvasha; Nikolai V. Masalsky; Alexander G. Sobolev; Vladimir A. Volkov

1996-01-01

366

Neandertal clavicle length.  

PubMed

The Late Pleistocene archaic humans from western Eurasia (the Neandertals) have been described for a century as exhibiting absolutely and relatively long clavicles. This aspect of their body proportions has been used to distinguish them from modern humans, invoked to account for other aspects of their anatomy and genetics, used in assessments of their phylogenetic polarities, and used as evidence for Late Pleistocene population relationships. However, it has been unclear whether the usual scaling of Neandertal clavicular lengths to their associated humeral lengths reflects long clavicles, short humeri, or both. Neandertal clavicle lengths, along with those of early modern humans and latitudinally diverse recent humans, were compared with both humeral lengths and estimated body masses (based on femoral head diameters). The Neandertal do have long clavicles relative their humeri, even though they fall within the ranges of variation of early and recent humans. However, when scaled to body masses, their humeral lengths are relatively short, and their clavicular lengths are indistinguishable from those of Late Pleistocene and recent modern humans. The few sufficiently complete Early Pleistocene Homo clavicles seem to have relative lengths also well within recent human variation. Therefore, appropriately scaled clavicular length seems to have varied little through the genus Homo, and it should not be used to account for other aspects of Neandertal biology or their phylogenetic status. PMID:24616525

Trinkaus, Erik; Holliday, Trenton W; Auerbach, Benjamin M

2014-03-25

367

Simulation run length planning  

Microsoft Academic Search

To design a stochastic simulation experiment, it is helpful to have an estimate of the simulation run lengths required to achieve desired statistical precision. Preliminary estimates of required run lengths can be obtained by approximating the stochastic model of interest by a more elementary Markov model that can be analyzed analytically. When steady-state quantities are to be estimated by sample

Ward Whitt

1989-01-01

368

Kalman Filter for Calibrating a Telescope Focal Plane  

NASA Technical Reports Server (NTRS)

The instrument-pointing frame (IPF) Kalman filter, and an algorithm that implements this filter, have been devised for calibrating the focal plane of a telescope. As used here, calibration signifies, more specifically, a combination of measurements and calculations directed toward ensuring accuracy in aiming the telescope and determining the locations of objects imaged in various arrays of photodetectors in instruments located on the focal plane. The IPF Kalman filter was originally intended for application to a spaceborne infrared astronomical telescope, but can also be applied to other spaceborne and ground-based telescopes. In the traditional approach to calibration of a telescope, (1) one team of experts concentrates on estimating parameters (e.g., pointing alignments and gyroscope drifts) that are classified as being of primarily an engineering nature, (2) another team of experts concentrates on estimating calibration parameters (e.g., plate scales and optical distortions) that are classified as being primarily of a scientific nature, and (3) the two teams repeatedly exchange data in an iterative process in which each team refines its estimates with the help of the data provided by the other team. This iterative process is inefficient and uneconomical because it is time-consuming and entails the maintenance of two survey teams and the development of computer programs specific to the requirements of each team. Moreover, theoretical analysis reveals that the engineering/ science iterative approach is not optimal in that it does not yield the best estimates of focal-plane parameters and, depending on the application, may not even enable convergence toward a set of estimates.

Kang, Bryan; Bayard, David

2006-01-01

369

Thrombospondin modulates focal adhesions in endothelial cells  

PubMed Central

We examined the effects of thrombospondin (TSP) in the substrate adhesion of bovine aortic endothelial cells. The protein was tested both as a substrate for cell adhesion and as a modulator of the later stages of the cell adhesive process. TSP substrates supported the attachment of some BAE cells, but not cell spreading or the formation of focal adhesion plaques. In contrast, cells seeded on fibrinogen or fibronectin substrates were able to complete the adhesive process, as indicated by the formation of focal adhesion plaques. Incubation of cells in suspension with soluble TSP before or at the time of seeding onto fibronectin substrates resulted in an inhibition of focal adhesion formation. Furthermore, the addition of TSP to fully adherent cells in situ or prespread on fibronectin substrates caused a reduction in the number of cells, which were positive for focal adhesions, although there was no significant effect on cell spreading. In a dose-dependent manner, TSP reduced the number of cells with adhesion plaques to approximately 60% of control levels. The distribution of remaining adhesion plaques in TSP-treated cells was also altered: plaques were primarily limited to the periphery of cells and were not present in the central cell body, as in control cells treated with BSA. The observed effects were specific for TSP and were not observed with platelet factor 4, beta-thromboglobulin, or fibronectin. The TSP-mediated loss of adhesion plaques was neutralized by the addition of heparin, fucoidan, other heparin-binding proteins, and by a monoclonal antibody to the heparin binding domain of TSP, but not by antibodies to the core or carboxy-terminal regions of TSP. The interaction of the heparin- binding domain of TSP with cell-associated heparan sulfate appears to be an important mechanistic component for this activity of TSP. These data indicate that TSP may have a role in destabilizing cell adhesion through prevention of focal adhesion formation and by loss of preformed focal adhesions.

1989-01-01

370

Improved image quality for asymmetric double-focal cone-beam SPECT  

SciTech Connect

To optimize both spatial resolution and detection efficiency in brain SPECT imaging using a rectangular camera, an asymmetric double-focal cone-beam collimator is proposed with the focal points located near the base plane of the patient's head. To fit the entire head into the field-of-view of the collimator with dimensions of 50cmx40cm and at a radius-of-rotation of 15 cm, the focal lengths of the collimator are 55 and 70 cm, respectively, in the transverse and axial directions. With this geometry, the artifacts in the reconstructed image produced by the Feldkamp algorithm are more severe compared to those in a symmetric cone-beam geometry, due to the larger vertex angle between the top of the head and the base plane. To improve the reconstructed image quality, a fully three-dimensional (3D) reconstruction algorithm developed previously for single-focal cone-beam SPECT was extended to the asymmetric double-focal cone-beam geometry. The algorithm involves nonstationary 2D filtering and a reprojection technique for estimation of the missing data caused by a single-orbit cone-beam geometry. The results from simulation studies with the 3D Defrise slab phantom demonstrated that the fully 3D algorithm provided a much improved image quality in terms of reduced slice-to-slice cross talks and shape elongation compared to that produced by the conventional Feldkamp algorithm.

Cao, Z.J.; Tsui, B.M.W. (Univ. of North Carolina, Chapel Hill, NC (United States))

1993-08-01

371

Staring focal plane array system modeling  

NASA Astrophysics Data System (ADS)

The problems are analyzed of modeling staring focal plane array systems. Two problem areas are highlighted; the difficulty in modeling the operator interface and the inadequate characterization of focal plane array noise sources. The effects of aliasing, response nonuniformity, and the 2-D nature of the spatial and temporal noise require more sophisticated handling than found in present models. Three staring array models were used to predict the Minimum Resolvable Temperature Difference (MRTD) for three Platinum Silicide staring array cameras. The predictions were then compared, analyzed, and suggestions for model improvement were made.

Murphy, John G.

1989-12-01

372

Optical properties of a nuclear reactor pumped gas laser.  

National Technical Information Service (NTIS)

Ray paths and focal lengths are derived to fourth order for a nuclear-reactor wall-pumped gas laser. Ray paths in the laser gain cell are shown to be nearly random for a long gain region. Focal lengths calculated from the ray paths exiting the laser are s...

A. Corvo

1991-01-01

373

Optical properties of a nuclear reactor pumped gas laser  

Microsoft Academic Search

Ray paths and focal lengths are derived to fourth order for a nuclear-reactor wall-pumped gas laser. Ray paths in the laser gain cell are shown to be nearly random for a long gain region. Focal lengths calculated from the ray paths exiting the laser are shown to oscillate between + or - infinity during pumping. The use of stimulated Brillouin

A. Corvo

1991-01-01

374

Photodynamic Therapy Rescue for Subretinal Fluid Exacerbation After Focal Laser Treatment in Idiopathic Central Serous Chorioretinopathy  

PubMed Central

Purpose To report a case of subretinal leakage after focal laser treatment for idiopathic central serous chorioretinopathy (ICSC). This rare complication was successfully treated with photodynamic therapy (PDT). Methods Interventional case report. Results A 36-year-old male presented with ICSC in his right eye. After a period of observation without resolution, he was treated with focal laser. That treatment resulted in a massive exacerbation of his subretinal fluid. PDT was successfully used to treat the severe exacerbation with rapid resolution of the subretinal fluid, improvement in visual acuity, decreased leakage on fluorescein angiography, and reduction of subretinal fluid on ophthalmoscopic exam and by optical coherence tomography. Conclusions Ophthalmologists should consider the use of PDT in cases where focal laser causes an exacerbation of subretinal fluid in ICSC.

Leng, Theodore; Sanislo, Steven R; Jack, Robert L

2011-01-01

375

An integrated optimal estimation approach to Spitzer Space Telescope focal plane survey  

NASA Astrophysics Data System (ADS)

This paper discusses an accurate and efficient method for focal plane survey that was used for the Spitzer Space Telescope. The approach is based on using a high-order 37-state Instrument Pointing Frame (IPF) Kalman filter that combines both engineering parameters and science parameters into a single filter formulation. In this approach, engineering parameters such as pointing alignments, thermomechanical drift and gyro drifts are estimated along with science parameters such as plate scales and optical distortions. This integrated approach has many advantages compared to estimating the engineering and science parameters separately. The resulting focal plane survey approach is applicable to a diverse range of science instruments such as imaging cameras, spectroscopy slits, and scanning-type arrays alike. The paper will summarize results from applying the IPF Kalman filter to calibrating the Spitzer Space Telescope focal plane, containing the MIPS, IRAC, and the IRS science instrument arrays.

Bayard, David S.; Kang, Bryan H.; Brugarolas, Paul B.; Boussalis, Dhemetrios

2004-10-01

376

An Integrated Optimal Estimation Approach to Spitzer Space Telescope Focal Plane Survey  

NASA Technical Reports Server (NTRS)

This paper discusses an accurate and efficient method for focal plane survey that was used for the Spitzer Space Telescope. The approach is based on using a high-order 37-state Instrument Pointing Frame (IPF) Kalman filter that combines both engineering parameters and science parameters into a single filter formulation. In this approach, engineering parameters such as pointing alignments, thermomechanical drift and gyro drifts are estimated along with science parameters such as plate scales and optical distortions. This integrated approach has many advantages compared to estimating the engineering and science parameters separately. The resulting focal plane survey approach is applicable to a diverse range of science instruments such as imaging cameras, spectroscopy slits, and scanning-type arrays alike. The paper will summarize results from applying the IPF Kalman Filter to calibrating the Spitzer Space Telescope focal plane, containing the MIPS, IRAC, and the IRS science Instrument arrays.

Bayard, David S.; Kang, Bryan H.; Brugarolas, Paul B.; Boussalis, D.

2004-01-01

377

Experimental validation of the linearized focal-plane technique (LIFT)  

NASA Astrophysics Data System (ADS)

Laser-assisted adaptive optics (AO) systems should increase dramatically the system sky coverage. Unfortunately, the laser guide star (LGS) wavefront sensing (WFS) principle is insensitive to tip/tilt, and focus measurement is corrupted by the evolution of the sodium concentration in altitude. Additionally, volumic structures of the LGS may induce quasi-static WFS errors. Hence, low-order modes have to be measured separately using faint natural guide stars (NGSs), and a so-called "truth sensor" has to be used to calibrate higher order LGS induced WFS errors. In that framework, we have proposed a new focal-plane WFS concept called the linearized focal-plane technique (LIFT), which allows us to efficiently deal with low-order mode measurement under low flux conditions. It can also be used on long exposure as a truth sensor without any hardware modification. We show here an experimental validation of LIFT in both low-order and truth sensor configurations. We compare the experimental linearity and noise propagation of LIFT to classical sensors, such as the quad-cell wavefront sensor (WFS), pyramid WFS, and Shack-Hartmann WFS.

Meimon, Serge; Plantet, Cédric; Fusco, Thierry; Conan, Jean-Marc

2011-09-01

378

Axial super resolution topography of focal adhesion by confocal microscopy.  

PubMed

The protein organization within focal adhesions has been studied by state-of-the-art super resolution methods because of its thin structure, well below diffraction limit. However, to achieve high axial resolution, most of the current approaches rely on either sophisticated optics or diligent sample preparation, limiting their application. In this report we present a phasor-based method that can be applied to fluorescent samples to determine the precise axial position of proteins using a conventional confocal microscope. We demonstrate that with about 4,000 photon counts collected along a z-scan, axial localization precision close to 10 nm is achievable. We show that, with within 10 nm, the axial location of paxillin, FAK, and talin is similar at focal adhesion sites, while F-actin shows a sharp increase in height towards the cell center. We further demonstrated the live imaging capability of this method. With the advantage of simple data acquisition and no special instrument requirement, this approach could have wide dissemination and application potentials. PMID:23897846

Chiu, Chi-Li; Gratton, Enrico

2013-10-01

379

Focal and Non-focal Prospective Memory Performance in Very Mild Dementia: A Signature Decline  

PubMed Central

Objective In a recent study, performance on a certain kind of prospective memory task (PM), labeled focal PM, was sensitive to the very early stages of Alzheimer’s disease (AD; Duchek, Balota, & Cortese, 2006). The present study sought to replicate and extend these findings by investigating both focal and non-focal PM, as well as possible influences of alleles of the apolipoprotein E (APOE) gene. Method Thirty-five healthy older adults and 33 adults in the very earliest stages of AD, as determined by the clinical dementia rating scale, completed both focal and non-focal PM tasks. Performance on these tasks has been linked to qualitatively different cognitive processes (Scullin, McDaniel, Shelton, & Lee, 2010), thereby providing leverage to illuminate the specific processes underlying PM failures in very early AD. Approximately half of the adults in each group were APOE e4 carriers and half were non-carriers. We also obtained participants’ scores on a battery of standard psychometric tests. Results There was a significant interaction between the type of PM task and dementia status, p < .05. ?2p = .12, demonstrating that the AD-related decline was more robust for focal than for non-focal PM. Further, focal PM performance significantly discriminated between the very earliest stages of AD and normal aging, explaining variance unique to that explained by typical psychometric indices. APOE status, however, was not associated with PM performance. Conclusions The pronounced deficit observed in the focal PM task suggests that spontaneous retrieval processes may be compromised in very early AD.

McDaniel, Mark A.; Shelton, Jill Talley; Breneiser, Jennifer E.; Moynan, Sarah; Balota, David A.

2011-01-01

380

Scanning microscopy using a short-focal-length Fresnel zone plate  

Microsoft Academic Search

Both confocal and near-field microscopes use small apertures to restrict light collection to confined re- gions in the object plane. The spatial resolution of these techniques is limited by the aperture size and the collection efficiency, which affects the signal-to- noise ratio. While both near-field (1) and confocal mi- croscopies (2) have proven to be powerful imaging techniques, each scanning

Ethan Schonbrun; Winnie N. Ye; Kenneth B. Crozier

2009-01-01

381

The MMT f/5 optical baffles  

NASA Astrophysics Data System (ADS)

The 6.5m MMT telescope currently has three focal configurations. The f/5 optical configuration has a system of optical baffles to prevent stray light from entering the focal plane. The system consists of a cone baffle supported on the secondary (M2) structure and set of concentric rings suspended between the secondary and the primary (M1). This paper reviews the optical configurations, mechanical design, alignment, installation, and measured performance of the system.

Callahan, S.; Caldwell, N.; Williams, G. G.; Chute, C.; Pickering, T. E.

2008-07-01

382

Intense FDG activity in focal hepatic steatosis.  

PubMed

A 38-year-old woman underwent PET/CT to evaluate possible hepatic malignancy. The images revealed intense FDG activity in several hypodense regions in the liver, most prominent in the lateral segment of the left lobe. The pathological examination showed that the patient had focal hepatic steatosis. PMID:24873789

Le, Yali; Chen, Yue; Huang, Zhanwen; Cai, Liang; Zhang, Li

2014-07-01

383

Quantum Dot Based Infrared Focal Plane Arrays  

Microsoft Academic Search

In the past decade, there has been active research on infrared detectors based on intersubband transitions in self-assembled quantum dots (QDs). In the past two years, at least four research groups have independently demonstrated focal plane arrays based on this technology. In this paper, the progress from the first raster scanned image obtained with a QD detector to the demonstration

Sanjay Krishna; Sarath D. Gunapala; Sumith V. Bandara; Cory Hill; David Z. Ting

2007-01-01

384

Thermoelectrically Cooled Focal Plane Array Module.  

National Technical Information Service (NTIS)

This is the first semi-annual report of a project to develop a thermoelectrically cooled staring focal plane module. The approach is that of a backside-illuminated hybrid mosaic array coupled to a silicon CCD/MUX. The detector approach is based on a trans...

W. E. Tennant D. H. Seib

1979-01-01

385

Dual band QWIP focal plane array  

NASA Technical Reports Server (NTRS)

A quantum well infrared photodetector (QWIP) that provides two-color image sensing. Two different quantum wells are configured to absorb two different wavelengths. The QWIPs are arrayed in a focal plane array (FPA). The two-color QWIPs are selected for readout by selective electrical contact with the two different QWIPs or by the use of two different wavelength sensitive gratings.

Gunapala, Sarath D. (Inventor); Choi, Kwong Kit (Inventor); Bandara, Sumith V. (Inventor)

2005-01-01

386

[Subtle focal diffusion abnormality in the hippocampus].  

PubMed

A 53-year-old female patient presented with sudden onset confusion and disorientation. Further neurological examination was unremarkable and the patient showed a complete recovery after several hours. A magnetic resonance imaging (MRI) examination performed 2 days later revealed a tiny focal lesion in the lateral hippocampus in the diffusion weighted images consistent with transient global amnesia. PMID:22710991

Macht, S; Hellen, F; Wenzel, D; Turowski, B

2012-07-01

387

Microarray Analysis of Focal Segmental Glomerulosclerosis  

Microsoft Academic Search

Background: Focal segmental glomerulosclerosis (FSGS) is a leading cause of chronic renal failure in children. Recent studies have begun to define the molecular pathogenesis of this heterogeneous condition. Here we use oligonucleotide microarrays to obtain a global gene expression profile of kidney biopsy specimens from patients with FSGS in order to better understand the pathogenesis of this disease. Methods: We

Kristopher Schwab; David P. Witte; Bruce J. Aronow; Prasad Devarajan; S. Steven Potter; Larry T. Patterson

2004-01-01

388

Salivary gland myoepithelioma with focal capsular invasion.  

PubMed

Salivary gland tumors that display myoepithelial differentiation exclusively or predominantly are relatively uncommon, and the assessment of malignancy in a myoepithelial tumor can be difficult. We report a case of parotid gland myoepithelioma composed predominantly of spindle cells with focal capsular invasion. The patient was a 65-year-old woman who presented with a painless mass in the right preauricular region. Histologically, the tumor had a solid and multinodular growth pattern and was predominantly made up of spindle cells with a minor component of epithelioid cells with moderate cellular atypia. Focal regions of tumor cells infiltrated the capsule with tongue-like processes, but tumor infiltration into the adjacent parotid tissue was absent. The tumor cells showed strong cytoplasmic immunoexpression of vimentin, pankeratin, S-100 protein, and smooth-muscle actin. Immunostains with glial fibrillary acidic protein, melanoma marker, epithelial membrane antigen, and carcinoembryonic antigen were negative. Expression of p53 was observed focally in the nuclei of the tumor cells. A final diagnosis of salivary gland myoepithelioma with focal capsular invasion was made, and the case was regarded as a myoepithelial tumor of uncertain malignant potential. In this report, we discuss the histologic criteria required to diagnose malignancy in salivary gland myoepithelial tumors. PMID:19623529

Gun, Banu Dogan; Ozdamar, Sukru Oguz; Bahadir, Burak; Uzun, Lokman

2009-07-01

389

Length Paradox in Relativity  

ERIC Educational Resources Information Center

Describes a thought experiment using a general analysis approach with Lorentz transformations to show that the apparent self-contradictions of special relativity concerning the length-paradox are really non-existant. (GA)

Martins, Roberto de A.

1978-01-01

390

Coefficients of Effective Length.  

ERIC Educational Resources Information Center

Under certain conditions, a validity Coefficient of Effective Length (CEL) can produce highly misleading results. A modified coefficent is suggested for use when empirical studies indicate that underlying assumptions have been violated. (Author/BW)

Edwards, Roger H.

1981-01-01

391

Eigenfunction expansion of the electric fields in the focal region of a high numerical aperture focusing system.  

PubMed

The Debye-Wolf electromagnetic diffraction integral is now routinely used to describe focusing by high numerical (NA) lenses. We obtain an eigenfunction expansion of the electric vector field in the focal region in terms of Bessel and generalized prolate spheroidal functions. Our representation has many optimal and desirable properties which offer considerable simplification to the evaluation and analysis of the Debye- Wolf integral. It is potentially also useful in implementing two-dimensional apodization techniques to synthesize electromagnetic field distributions in the focal region of a high NA lenses. Our work is applicable to many areas, such as optical microscopy, optical data storage and lithography. PMID:18542431

Sherif, Sherif S; Foreman, Matthew R; Török, Peter

2008-03-01

392

Translation of spectral radiance levels, band choices, and signal-to-noise requirements to focal plane specifications and design constraints  

NASA Astrophysics Data System (ADS)

Panchromatic, multispectral, and hyperspectral image sensors spanning the visible to longwave IR (LWIR) regions of the electromagnetic spectrum are finding increased application in advanced DOD, civil, scientific, and commercial space- based programs. Research and development advancing the state-of-the-art in visible to LWIR focal plane technology requires a careful understanding of system level requirements and a methodology for the translation of these requirements to focal pane specifications. At the focal plane level, signal-to-noise based performance is generally defined in terms of wavelength dependent noise equivalent irradiance and dynamic range specifications under conditions dictated by the system application. In this paper we illustrate a process that starts with system level performance requirements and results in focal plane performance requirements. The input spectral radiances were determined with the MODTRAN atmospheric code coupled with simple sensor and focal pane signal and noise models. The process is illustrated with two different space-based sensor examples, resulting in very different focal plane designs, configurations, and physical operating conditions. Finally, these characteristics were translated to focal pane electro- optical, thermal and electronic design parameters such as: spectral quantum efficiency, integration capacitance values and areas, and likely pixel unit-cell circuit selections.

Lomheim, Terrence S.; Hernandez-Baquero, Erich D.

2002-02-01

393

Theory and design of a MEMS-enabled diffraction limited adaptive optical zoom system  

NASA Astrophysics Data System (ADS)

Micro-electro-mechanical systems (MEMS) deformable mirrors are known for their ability to correct optical aberrations, particularly when the wavefront is expanded via Zernike polynomials. This capability is combined with adaptive optical zoom to enable diffraction limited performance over broad spectral and zoom ranges. Adaptive optical zoom (AOZ) alters system magnification via variable focal length elements instead of axial translation found in traditional zoom designs. AOZ systems are simulated using an efficient approach to optical design, in which existing theories for telescope objective design and third-order aberration determination are modified to accommodate the additional degrees of freedom found with AOZ. An AOZ system with a 2.7× zoom ratio and 100mm entrance pupil diameter is presented to demonstrate the validity and capability of the theory.

Jungwirth, Matthew E. L.; Wick, David V.; Dereniak, Eustace L.

2012-05-01

394

A new staring 94-GHz focal plane array  

NASA Astrophysics Data System (ADS)

A new staring 94 GHz focal plane array (4x8 pixels) multi-chip module (MCM) using a quasi-optically pumped MMIC gate mixer is presented. The new MCM with integrated microstrip antennas, matching and bias networks are manufactured using a modified MCM-D process based on 3x15 ?m BCB. The active gate mixer MMIC was manufactured by OMMIC (D01PH process) and uses a 2x25 ?m gate width. The 30 cm dielectric lens antenna has a F/D number of approximately unity. To minimize the spillover loss, the beamwidth of the feed antennas (microstrip antennas) was matched to the opening angle of the lens by using 2x2 subarrays for each pixel. Preliminary measurement results show a feed antenna gain of approximately 10 dBi and a conversion loss close to zero at 94 GHz, and an optimal pumping power of -2 dBm at 92.4 GHz.

Svedin, Jan; Huss, Lars-Gunnar

2004-12-01

395

Optically coupled focal plane arrays using lenslets and multiplexers  

DOEpatents

A detector array including a substrate having an array of diffractive lenses formed on the top side of the substrate and an array of sensor elements formed on the backside of the substrate. The sensor elements within the sensor array are oriented on the backside so that each sensor is aligned to receive light from a corresponding diffractive lens of the lens array. The detector array may also include a second substrate having an array of diffractive elements formed on one of its surfaces, the second substrate being disposed above and in proximity to the top side of the other substrate so that the elements on the second substrate are substantially aligned with corresponding sensor elements and diffractive lenses on the other substrate.

Veldkamp, Wilfrid B. (Lexington, MA)

1991-01-01

396

Focusing of synchrotron radiation with polycapillary optics  

Microsoft Academic Search

Polycapillary optics are arrays of thousands of hollow capillary tubes. Focal spots are produced from the overlap of outputs from multiple channels at distances of 10–100 mm from the output of the optic. Synchrotron focusing was performed with two polycapillary X-ray optics. The spot size for the monolithic optic was 80 ?m, which yielded a measured gain in photon flux

F. A. Hofmann; C. A. Freinberg-Trufas; S. M. Owens; S. D. Padiyar; C. A. MacDonald

1997-01-01

397

Focal laser ablation for localized prostate cancer.  

PubMed

Throughout history, medicine has witnessed paradigm shifts that significantly change patient treatment. In surgical oncology, the introduction of lumpectomy revolutionized breast cancer treatment while partial nephrectomy has altered the management of kidney cancer. In both cases, organ preservation is combined with efficacious management of the cancer via a less invasive approach. Within urology, prostate cancer (PCa) may be the next to benefit from such a treatment paradigm. Current management of PCa involves either whole organ treatment, with the inherent side effects, while selected patients are eligible for active surveillance. Focal therapy offers a middle ground for low-risk patients with PCa, again using the principles of a minimally invasive treatment of the cancer, in this case using an energy source with few side effects, combined with maximal organ preservation. Because focal therapy for PCa is still in evolution, there is no consensus on the ideal energy source that should be used to ablate the PCa, imaging to monitor the tissue destruction in real time, how many treatments may be offered, and the ideal follow-up regimen. Long-term follow-up of patients is needed before it is recommended as a first-line treatment. Nevertheless, evidence is accumulating that radically treating PCa holds survival benefit for patients; however, the number of men needed to treat is considerable, with significant side effects; thus, more centers are investigating focal therapy as an option. This review focuses on the use of the laser as the energy source for focal ablation, while bringing historically relevant information regarding laser energy and highlighting the perceived advantageous of focal laser ablation. PMID:20477544

Lindner, Uri; Lawrentschuk, Nathan; Trachtenberg, John

2010-05-01

398

Application study of the optical biopsy system for small experimental animals  

NASA Astrophysics Data System (ADS)

An optical biopsy system for small experimental animals has been developed. The system includes endoscope probe, portable probe and two kinds of miniaturized Raman probes. The micro Raman probe (MRP) is made of optical fibers and the ball lens hollow optical fiber Raman probe (BHRP) is made of hollow fiber. The former has large focal depth and suitable to measure average spectra of subsurface tissue. The latter has rather small focal depth and it is possible to control focal length by selecting ball lens attached at the probe head. It is suitable to survey materials at the fixed depth in the tissue. The system is applied to study various small animal cancer models, such as esophagus and stomach rat models and subcutaneous mouse models of pancreatic cancers. In the studies of subcutaneous tumor model mouse, it is suggested that protein conformational changes occur in the tumor tissue within few minutes after euthanasia of the mouse. No more change is observed for the following ten minutes. Any alterations in the molecular level are not observed in normal skin, muscle tissues. Since the change completes in such a short time, it is suggested that this phenomenon caused by termination of blood circulation.

Sato, Hidetoshi; Suzuki, Toshiaki; Morita, Shin-ichi; Maruyama, Atsushi; Shimosegawa, Toru; Matsuura, Yuji; Kanai, Gen'ichi; Ura, Nobuo; Masutani, Koji; Ozaki, Yukihiro

2008-03-01

399

Extended depth of focus adaptive optics spectral domain optical coherence tomography  

PubMed Central

We present an adaptive optics spectral domain optical coherence tomography (AO-SDOCT) with a long focal range by active phase modulation of the pupil. A long focal range is achieved by introducing AO-controlled third-order spherical aberration (SA). The property of SA and its effects on focal range are investigated in detail using the Huygens-Fresnel principle, beam profile measurement and OCT imaging of a phantom. The results indicate that the focal range is extended by applying SA, and the direction of extension can be controlled by the sign of applied SA. Finally, we demonstrated in vivo human retinal imaging by altering the applied SA.

Sasaki, Kazuhiro; Kurokawa, Kazuhiro; Makita, Shuichi; Yasuno, Yoshiaki

2012-01-01

400

Variable focal lens controlled by an external voltage: An application of electrowetting  

Microsoft Academic Search

:   We use electrocapillarity in order to change the contact angle of a transparent drop, thus realizing a lens of variable focal\\u000a length (B. Berge, J. Peseux, Patent deposited in Grenoble France, October 8th 1997, num?ro d'enregistrement national 97 12781).\\u000a The key point is the application of gradients of wettability, which control the shape of the drop edge, in our

B. Berge; J. Peseux

2000-01-01

401

Progress in long scale length laser plasma interactions  

Microsoft Academic Search

The first experiments on the National Ignition Facility (NIF) have employed the first four beams to measure propagation and laser backscattering losses in large ignition-size plasmas. Gas-filled targets between 2 and 7 mm length have been heated from one side by overlapping the focal spots of the four beams from one quad operated at 351 nm (3omega) with a total

S. H. Glenzer; P. Arnold; G. Bardsley; R. L. Berger; G. Bonanno; T. Borger; D. E. Bower; M. Bowers; R. Bryant; S. Buckman; S. C. Burkhart; K. Campbell; M. P. Chrisp; B. I. Cohen; C. Constantin; F. Cooper; J. Cox; E. Dewald; L. Divol; S. Dixit; J. Duncan; D. Eder; J. Edwards; G. Erbert; B. Felker; J. Fornes; G. Frieders; D. H. Froula; S. D. Gardner; C. Gates; M. Gonzalez; S. Grace; G. Gregori; A. Greenwood; R. Griffith; T. Hall; B. A. Hammel; C. Haynam; G. Heestand; M. Henesian; G. Hermes; D. Hinkel; J. Holder; F. Holdner; G. Holtmeier; W. Hsing; S. Huber; T. James; S. Johnson; O. S. Jones; D. Kalantar; J. H. Kamperschroer; R. Kauffman; T. Kelleher; J. Knight; R. K. Kirkwood; W. L. Kruer; W. Labiak; O. L. Landen; A. B. Langdon; S. Langer; D. Latray; A. Lee; F. D. Lee; D. Lund; B. MacGowan; S. Marshall; J. McBride; T. McCarville; L. McGrew; A. J. Mackinnon; S. Mahavandi; K. Manes; C. Marshall; J. Menapace; E. Mertens; N. Meezan; G. Miller; S. Montelongo; J. D. Moody; E. Moses; D. Munro; J. Neumann; M. Newton; E. Ng; C. Niemann; A. Nikitin; P. Opsahl; E. Padilla; T. Parham; G. Parrish; C. Petty; M. Polk; C. Powell; I. Reinbachs; V. Rekow; R. Rinnert; B. Riordan; M. Rhodes; V. Roberts; H. Robey; G. Ross; S. Sailors; R. Saunders; M. Schmitt; M. B. Schneider; S. Shiromizu; M. Spaeth; A. Stephens; B. Still; L. J. Suter; G. Tietbohl; M. Tobin; J. Tuck; B. M. Van Wonterghem; R. Vidal; D. Voloshin; R. Wallace; P. Wegner; P. Whitman; E. A. Williams; K. Williams; K. Winward; K. Work; B. Young; P. E. Young; P. Zapata; R. E. Bahr; W. Seka; J. Fernandez; D. Montgomery; H. Rose

2004-01-01

402

Visual Scanning Hartmann Optical Tester (VSHOT) Uncertainty Analysis (Milestone Report)  

SciTech Connect

In 1997, an uncertainty analysis was conducted of the Video Scanning Hartmann Optical Tester (VSHOT). In 2010, we have completed a new analysis, based primarily on the geometric optics of the system, and it shows sensitivities to various design and operational parameters. We discuss sources of error with measuring devices, instrument calibrations, and operator measurements for a parabolic trough mirror panel test. These help to guide the operator in proper setup, and help end-users to understand the data they are provided. We include both the systematic (bias) and random (precision) errors for VSHOT testing and their contributions to the uncertainty. The contributing factors we considered in this study are: target tilt; target face to laser output distance; instrument vertical offset; laser output angle; distance between the tool and the test piece; camera calibration; and laser scanner. These contributing factors were applied to the calculated slope error, focal length, and test article tilt that are generated by the VSHOT data processing. Results show the estimated 2-sigma uncertainty in slope error for a parabolic trough line scan test to be +/-0.2 milliradians; uncertainty in the focal length is +/- 0.1 mm, and the uncertainty in test article tilt is +/- 0.04 milliradians.

Gray, A.; Lewandowski, A.; Wendelin, T.

2010-10-01

403

Pleiades HR in Flight Geometrical Calibration : Location and Mapping of the Focal Plane  

NASA Astrophysics Data System (ADS)

The Pleiades system, ORFEO system optical component (Optical and Radar Federated Earth Observation) consists of a constellation of two satellites for very High Resolution panchromatic and multispectral optical observation of the Earth. Its mission is to cover all European civilian needs (mapping, tracking floods and fires) and defence in the category of metric resolution: 0.7m Nadir. The first Pleiades satellite was launched at the end of last year. One of the key objectives of the Pleiades HR (PHR) project is to achieve a location accuracy that will allow the use of images in GIS (Geographical Information System) without geometrical model improvement by refining on ground control points. The image location without refined model was specified with the precision of the most commonly used tool ie the civil GPS. So the location accuracy has been specified at less than 12m for 90% of the images on a nominal satellite configuration. Very special care has been taken all along the PHR project realization to achieve this very good location accuracy. The final touch is given during the in-orbit commissioning phase which lasts until June 2012. The geometric quality implies to tune the parameters involved in the geolocation model (geometric calibration): besides attitude and orbit restitution tuning (not considered here), it consists in estimating the biases between the instrument orientation and the AOCS reference frame, and also the sight line of each detector in the focal plane. This is called static geometrical model. The analysis of dynamic perturbations outside of the model are the second most important image quality objective of in-flight commissioning, not described in this paper. Finally "image quality assessment" consists in evaluating the image quality obtained in the final products. For geolocation model, it is quantified by the absolute geolocation and the pointing accuracies, and it is a main contributor in length alteration and planimetric and altimetric accuracies. In this paper we will present both the different practices we have adopted (their advantages, limitations and complementarities) and the means we are using for the operational assessment of the location quality of PHR images. We will focus on the innovative methods and mention the improvements in progress. To conclude, we will present the very first accuracy results assessed after PHR1A launch on L1 and Sensor products.

de Lussy, F.; Greslou, D.; Dechoz, C.; Amberg, V.; Delvit, J. M.; Lebegue, L.; Blanchet, G.; Fourest, S.

2012-07-01

404

Proposed High-Level Regional Focal Points for Lunar Geography  

NASA Astrophysics Data System (ADS)

A list of 11 focal points, based on interesting features and approximately uniformly distributed around the moon is proposed. The objective of establishing these focal points is to organize photos and other images with minimal distortion and maximal mnemonic value.

Byrne, C. J.

2003-03-01

405

On internodal length.  

PubMed Central

A study has been made of changes in internodal lengths in rat tibial nerves and human sural nerves with age. Myelinated fibre counts on these nerves showed that maximum numbers were reached at an early stage of development. The slope of regression lines relating internodal length to fibre diameter was relatively flat at this stage, but became steeper with increasing age. Maximum internodal length in rat tibial nerve was closely related to growth of the limb bones. Whilst this study confirms that the largest fibres are subjected to hind limb growth for the greatest period, and therefore have the longest internodes, it does not support the generally accepted view that short internodes are the consequence of the later myelination of small fibres, and hence shorter period of extension due to growth. Images Figs. 2-3

Jacobs, J M

1988-01-01

406

Microtubule-Actin Cross-talk at Focal Adhesions  

NSDL National Science Digital Library

Focal adhesions are dynamic structures in which traction forces are exerted against the substratum during cell migration and are sites for the organization of signaling complexes. Palazzo and Gundersen discuss how focal adhesions may also be the site of cross-talk between the actin-based and microtubule-based cytoskeletons. Microtubules appear to deliver factors that can regulate the formation and dissolution of focal adhesions, whereas focal adhesions contribute to microtubule localization and stability.

Alexander F. Palazzo (Columbia University;Department of Anatomy and Cell Biology REV); Gregg G. Gundersen (Columbia University;Department of Anatomy and Cell Biology REV)

2002-07-02

407

The focal spot shape and point spread function of liquid crystal microlens with different pattern electrodes  

NASA Astrophysics Data System (ADS)

In this paper, we present a new LC lens with different pattern electrodes including triangle electrode, square electrode, pentagon electrode, hexagon and octagon electrodes. We demonstrate the focusing process of LC lens, when the electrodes are driven by the voltage signal, all the LC lens with different pattern electrodes have good focusing characters along the optical axis. In addition, a LC lens with different sub-electrode pattern is also introduced, the sub-electrodes are designed to circular pattern and each sub-electrode can be driven separately. If the sub-electrodes are driven by the same voltage signal, the LC lens can focus along the axis, while they are controlled separately, it can make the focus swing off the axis over the focal plane. We show the Interference patterns of LC lens with various pattern electrodes. The different focal spot shapes and the optical properties of LC microlens are also demonstrated experimentally.

Kang, Shengwu; Zhang, Xinyu; Sang, Hongshi; Xie, Changsheng

2013-08-01

408

Implementation of a micro-optical pickup using a focusing waveguide grating coupler  

NASA Astrophysics Data System (ADS)

A micro-optical pickup has been implemented by using a focusing waveguide grating coupler. The grating coupler was designed and fabricated on a single mode BPSG (boron phosphor silica glass) waveguide layer. The coupling area was 1×1mm2 containing more than 1,500 grating lines, where the maximum and minimum grating pitch were 296nm and 811nm, respectively. The focal length and the numerical aperture of the present grating coupler were 530 ?m and 0.68 with 632.8nm He-Ne red laser. The full width half maximum diameter of the focal spot was measured to be 450 nm and 510 nm in x and y direction.

Paek, Mun Cheol; Sohn, Yeung J.; Suh, Dongwoo; Ryu, Hojun; Park, Yongwoo

2003-09-01

409

Advances in hybrid optics physical sensors for extreme environments  

NASA Astrophysics Data System (ADS)

Highlighted are novel innovations in hybrid optical design physical sensors for extreme environments. Various hybrid design compositions are proposed that are suited for a particular sensor application. Examples includes combining freespace (wireless) and fiber-optics (wired) for gas turbine sensing and combining single crystal and sintered Silicon Carbide (SiC) materials for robust extreme environment Coefficent of Thermal Expansion (CTE) matched frontend probe design. Sensor signal processing also includes the hybrid theme where for example Black-Body radiation thermometry (pyrometry) is combined with laser interferometry to provide extreme temperature measurements. The hybrid theme also operates on the optical device level where a digital optical device such as a Digital Micromirror Device (DMD) is combined with an analog optical device such as an Electronically Controlled Variable Focal Length Lens (ECVFL) to deliver a smart and compressive Three Dimensional (3-D) imaging sensor for remote scene and object shape capture including both ambient light (passive) mode and active laser targeting and receive processing. Within a device level, the hybrid theme also operates via combined analog and digital control such as within a wavelength-coded variable optical delay line. These powerful hybrid design optical sensors have numerous applications in engineering and science applications from the military to the commercial/industrial sectors.

Riza, Nabeel A.

2010-04-01

410

Active reflective components for adaptive optical zoom systems  

NASA Astrophysics Data System (ADS)

This dissertation presents the theoretical and experimental exploration of active reflective components specifically for large-aperture adaptive optical zoom systems. An active reflective component can change its focal length by physically deforming its reflecting surface. Adaptive optical zoom (AOZ) utilizes active components in order to change magnification and achieve optical zoom, as opposed to traditional zooming systems that move elements along the optical axis. AOZ systems are theoretically examined using a novel optical design theory that enables a full-scale tradespace analysis, where optical design begins from a broad perspective and optimizes to a particular system. The theory applies existing strategies for telescope design and aberration simulation to AOZ, culminating in the design of a Cassegrain objective with a 3.3X zoom ratio and a 375mm entrance aperture. AOZ systems are experimentally examined with the development of a large-aperture active mirror constructed of a composite material called carbon fiber reinforced polymer (CFRP). The active CFRP mirror uses a novel actuation method to change radius of curvature, where actuators press against two annular rings placed on the mirror's back. This method enables the radius of curvature to increase from 2000mm to 2010mm. Closed-loop control maintains good optical performance of 1.05 waves peak-to-valley (with respect to a HeNe laser) when the active CFRP mirror is used in conjunction with a commercial deformable mirror.

Jungwirth, Matthew Edward Lewis

411

Architectures for focal plane image processing.  

NASA Astrophysics Data System (ADS)

Architectures for focal plane image processing are discussed. On-chip image preprocessing for solid-state imagers using analog CCD circuits is described for low, medium, and high density detector arrays. A spatially parallel architecture for low density, high throughput applications is described. For sparse illumination or event detection, a content-addressable architecture is proposed. A new pipelined vector pixel processor architecture for medium density infrared staring focal plane arrays is described. Neighborhood reconstruction during serial readout of high density TV-quality imagers for a pixel processor is considered using delay and analog frame memory techniques. The potential of on-chip read/write analog frame memory for image transformation and frame-to-frame processing is discussed.

Fossum, E. R.

1989-08-01

412

Intramembranous microspherical structures in focal segmental glomerulosclerosis.  

PubMed

A 45-year-old male had proteinuria for 3 years. For persistent proteinuria over 2 g/day, he underwent renal biopsy. Light microscopy revealed focal segmental glomerulosclerosis together with diffuse capillary wall thickening. Periodic acid methenamine silver (PAM) staining showed a prominent bubbly appearance without spike formation could be found in almost all capillary walls. Electron microscopy revealed many microspheres measuring 50-70 nm in diameter distributed in diffuse and global fashion together with the thickened glomerular basement membrane. A few cytoplasmic processes of the podocytes showed infolding to the GBM. The patient exhibited no symptoms and no physical and serological findings suggesting autoimmune disease, such as systemic lupus erythematosus or Sjögren's syndrome. Therefore, the present case is important, because the peculiar microstructure in the GBM was noted in focal segmental glomerulosclerosis, which has never been reported in the literature. PMID:19002748

Inoue, Yoshimoto; Kanda, Yoko; Kinoshita, Chiharu; Kanda, Chiaki; Joh, Kensuke

2008-12-01

413

Focal therapy for clinically localized prostate cancer.  

PubMed

The stage migration for newly diagnosed prostate cancer, improvements in prostate imaging, and devices capable of inducing subtotal prostate ablation have allowed for the formal study and evaluation of focal therapy for low-risk prostate cancer. Significant limitations remain: 1) the need for more accurate pre-treatment determination of cancer location, extent, and size, 2) determining appropriate methods of post-treatment surveillance and definitions of clinical progression, 3) the uncertainty whether repeat treatment, by focal or whole-gland therapy, is effective and safe. Clinical trials are ongoing to provide data on the feasibility and reliability of these new therapies, the capability of eradicating cancers, rates of secondary treatment, and impact on urinary and sexual function. PMID:22052762

Marchetti, Pablo; Eggener, Scott

2011-10-01

414

Epilepsies associated with focal cortical dysplasias (FCDs).  

PubMed

Focal cortical dysplasias (FCDs) are increasingly recognized as one of the most common causes of pharmaco-resistant epilepsies. FCDs were recently divided into various clinico-pathological subtypes due to distinct imaging, electrophysiological, and outcome characteristics. In this review, we will overview the international consensus classification of FCDs in light of more recently reported clinical, electrical, imaging and functional observations, and will also address areas of ongoing debate. In addition, we will summarize our current knowledge on pathobiology and epileptogenicity of FCDs as well as its underlying molecular and cellular mechanisms. The clinical (electroencephalographic, imaging, and functional) characteristics of major FCD subtypes and their implications on the presurgical evaluation and surgical management will be discussed in light of studies describing these characteristics and postoperative seizure outcomes in patients with medically intractable focal epilepsy due to histopathologically confirmed FCDs. PMID:24916270

Najm, Imad M; Tassi, Laura; Sarnat, Harvey B; Holthausen, Hans; Russo, Giorgio Lo

2014-07-01

415

Focal colors are universal after all  

PubMed Central

It is widely held that named color categories in the world's languages are organized around universal focal colors and that these focal colors tend to be chosen as the best examples of color terms across languages. However, this notion has been supported primarily by data from languages of industrialized societies. In contrast, recent research on a language from a nonindustrialized society has called this idea into question. We examine color-naming data from languages of 110 nonindustrialized societies and show that (i) best-example choices for color terms in these languages cluster near the prototypes for English white, black, red, green, yellow, and blue, and (ii) best-example choices cluster more tightly across languages than do the centers of category extensions, suggesting that universal best examples (foci) may be the source of universal tendencies in color naming.

Regier, Terry; Kay, Paul; Cook, Richard S.

2005-01-01

416

Epileptic seizures triggered directly by focal transcranial magnetic stimulation  

Microsoft Academic Search

Focal, secondarily generalizing epileptic seizures were released by magnetic stimulation in a patient with focal epilepsy. The stimulation induced seizures had a similar clinical appearance to the patient's spontaneous seizures. They were released exclusively by an angulated “figure-of-8” coil which stimulates the brain more focally as compared to the commonly used flat round coil. The epileptic focus could be located

J. Classen; O. W. Witte; G. Schlaug; R. J. Seitz; H. Holthausen; R. Benecke

1995-01-01

417

Focus in Grade 1: Teaching with Curriculum Focal Points  

ERIC Educational Resources Information Center

"Focus in Grade 1: Teaching with Curriculum Focal Points" describes and illustrates learning paths for the mathematical concepts and skills of each grade 1 Focal Point as presented in Curriculum Focal Points for Prekindergarten through Grade 8 Mathematics. It includes representational supports for teaching and learning that can facilitate…

Fuson, Karen; Clements, Douglas; Beckmann, Sybilla

2010-01-01

418

Focus in Grade 2: Teaching with Curriculum Focal Points  

ERIC Educational Resources Information Center

"Focus in Grade 2: Teaching with Curriculum Focal Points" describes and illustrates learning paths for the mathematical concepts and skills of each grade 2 Focal Point as presented in 'Curriculum Focal Points for Prekindergarten through Grade 8 Mathematics". It includes representational supports for teaching and learning that can facilitate…

National Council of Teachers of Mathematics, 2011

2011-01-01

419

Polarized and Focalized Linear and Classical Proofs  

Microsoft Academic Search

We give the precise correspondence between polarized linear logic andpolarized classical logic. The properties of focalization and reversion oflinear proofs [AP91, Gir91a, DJS97] are at the heart of our analysis: weshow that the tq-protocol of normalization (dened in [DJS97]) for theclassical systems LKpol and LK;pol perfectly ts normalization of polarizedproof-nets. In section 6, some more semantical considerations allow torecover LC

Iml-cnrs Marseille; Lorenzo Tortora De Falco; Myriam Quatrini; Olivier Laurent

2000-01-01

420

Florid periosteal reaction and focal fibrocartilaginous dysplasia  

Microsoft Academic Search

Focal fibrocartilaginous dysplasia (FFCD) is a rare condition causing tibia vara in childhood. It is characterized by progressive\\u000a tibia vara in young children with a characteristic radiographic lesion. This paper is thought to be the first to describe\\u000a FFCD exhibiting florid periosteal reaction at the time of presentation with a subtle faint osteolytic lesion in the diametaphysis\\u000a of the proximal

Takanobu Nakase; Natsuo Yasui; Nobuhito Araki; Shigeyuki Kuratsu; Makoto Tanaka; Hideki Yoshikawa; Takahiro Ochi

1998-01-01

421

High-precision method for determining the position of laser beam focal plane  

NASA Astrophysics Data System (ADS)

The method of wavefront doubled-frequency spherical modulation for determining the laser beam waist position has been simulated and experimentally studied. The error in determining the focal plane position is less than 10-5 D. The amplitude of the control doubled-frequency electric signal is experimentally found to correspond to 12% of the total radiation power. Reported at the 'Laser Optics' Conference (St. Petersburg, Russia, June 2012).

Malashko, Ya I.; Kleimenov, A. N.; Potemkin, I. B.; Khabibulin, V. M.

2013-12-01

422

Characterization of a CZT focal plane small prototype for hard X-ray telescope  

Microsoft Academic Search

The promise of good energy and spatial resolution coupled with high efficiency and room temperature operation has fuelled a large international effort to develop cadmium zinc telluride (CZT) for hard X-ray applications. We are involved on the development of a hard X-ray telescope based on multilayer optics and focal plane detector operative in the 10-80 keV energy range. This telescope

S. Del Sordo; L. Abbene; M. Zora; G. Agnetta; B. Biondo; A. Mangano; F. Russo; E. Caroli; N. Auricchio; A. Donati; F. Schiavone; J. B. Stephen; G. Ventura; G. Bertuccio; S. Caccia; M. Sampietro

2005-01-01

423

Three-Mirror Anastigmat Telescope with an Unvignetted Flat Focal Plane  

Microsoft Academic Search

A new optical design concept of telescopes to provide an aberration-free, wide field, unvignetted flat focal plane is described. The system employs three aspheric mirrors to remove aberrations, and provides a semi-circular field of view with minimum vignetting. The third mirror reimages the intermediate image made by the first two-mirror system with a magnification factor on the order of unity.

Kyoji Nariai; Masanori Iye

2005-01-01

424

Cerebral microvessel responses to focal ischemia.  

PubMed

Cerebral microvessels have a unique ultrastructure form, which allows for the close relationship of the endothelium and blood elements to the neurons they serve, via intervening astrocytes. To focal ischemia, the cerebral microvasculature rapidly displays multiple dynamic responses. Immediate events include breakdown of the primary endothelial cell permeability barrier, with transudation of plasma, expression of endothelial cell-leukocyte adhesion receptors, loss of endothelial cell and astrocyte integrin receptors, loss of their matrix ligands, expression of members of several matrix-degrading protease families, and the appearance of receptors associated with angiogenesis and neovascularization. These events occur pari passu with neuron injury. Alterations in the microvessel matrix after the onset of ischemia also suggest links to changes in nonvascular cell viability. Microvascular obstruction within the ischemic territory occurs after occlusion and reperfusion of the feeding arteries ("focal no-reflow" phenomenon). This can result from extrinsic compression and intravascular events, including leukocyte(-platelet) adhesion, platelet-fibrin interactions, and activation of coagulation. All of these events occur in microvessels heterogeneously distributed within the ischemic core. The panorama of acute microvessel responses to focal cerebral ischemia provide opportunities to understand interrelationships between neurons and their microvascular supply and changes that underlie a number of central nervous system neurodegenerative disorders. PMID:12902832

del Zoppo, Gregory J; Mabuchi, Takuma

2003-08-01

425

Focal Adhesion Kinase Stabilizes the Cytoskeleton  

PubMed Central

Focal adhesion kinase (FAK) is a central focal adhesion protein that promotes focal adhesion turnover, but the role of FAK for cell mechanical stability is unknown. We measured the mechanical properties of wild-type (FAKwt), FAK-deficient (FAK?/?), FAK-silenced (siFAK), and siControl mouse embryonic fibroblasts by magnetic tweezer, atomic force microscopy, traction microscopy, and nanoscale particle tracking microrheology. FAK-deficient cells showed lower cell stiffness, reduced adhesion strength, and increased cytoskeletal dynamics compared to wild-type cells. These observations imply a reduced stability of the cytoskeleton in FAK-deficient cells. We attribute the reduced cytoskeletal stability to rho-kinase activation in FAK-deficient cells that suppresses the formation of ordered stress fiber bundles, enhances cortical actin distribution, and reduces cell spreading. In agreement with this interpretation is that cell stiffness and cytoskeletal stability in FAK?/? cells is partially restored to wild-type level after rho-kinase inhibition with Y27632.

Fabry, Ben; Klemm, Anna H.; Kienle, Sandra; Schaffer, Tilman E.; Goldmann, Wolfgang H.

2011-01-01

426

The Focal Surface of EUSO Telescope  

NASA Technical Reports Server (NTRS)

The Extreme Universe Space Observatory (EUSO) is a science mission under conceptual design for the detection of extremely high energy cosmic rays and neutrinos by the observation of time-resolved images of atmospheric fluorescence photons generated along the extensive air shower, in the near ultraviolet wavelength region. A refractive telescope with double-sided double Fresnel lens will be employed to achieve a large field of view of 60 degrees. The energy and arrival direction of the primary particles will be determined by observing the time evolution of the airshower. The focal surface of the EUSO telescope will be segmented to a few hundred thousand pixels to resolve the entire field of view with the angular resolution of the order of 0.1 degree. The time evolution will be observed with the time resolution of 0.8 microsecond. A large scale array of multianode photomultiplier (MAPMT) is being studied as the EUSO focal surface. The MAPMT array is capable of detecting near ultraviolet photons at single photoelectron level. In this contribution, we will report the present status of the focal surface design including the optimization of anode segmentation and the minimization of the dead area and discuss overall experimental performance in detecting extensive airshowers.

Shimizu, H. M.; Kawasaki, Y.; Takizawa, Y.; Sakaki, N.; Teshima, M.; Ebisuzaki, T.; Takahashi, Y.; Adams, J.; Catalano, O.; Scarisi, L.; Six, N. Frank (Technical Monitor)

2002-01-01

427

Therapeutic targets in focal and segmental glomerulosclerosis  

PubMed Central

Purpose of review Focal and segmental glomerulosclerosis occurs due to a defect in the glomerular filtration barrier. This review highlights contributions from the past year that have enhanced our understanding of the pathophysiology of focal and segmental glomerulosclerosis with emphasis on discoveries which may lead to the identification of therapeutic targets. Recent findings Slit diaphragm proteins have become increasingly important in signal transduction and in mediating downstream events. Actin polymerization occurs after the podocin–nephrin–Neph-1 complex is phosphorylated by Src kinase and Fyn. Recent studies of angiotensin receptor antagonists, corticosteroids and erythropoietin unravel new mechanisms that ameliorate proteinuria by targeting the cell cycle within the podocyte. The discovery that an N-acetylmannosamine kinase (MNK) mutant mouse has glomerulopathy is suggestive that human sialylation pathways may represent therapeutic targets. Proteinuria before podocyte effacement demonstrated in laminin-?2 null mice highlights the importance of the glomerular basement membrane. Interferon-? reduced proteinuria in three models of kidney injury, showing greatest effect on glomerular endothelial cells in vitro. Summary Basic research has illuminated mechanisms by which classic therapies have antiproteinuric effects directly on the podocyte. As knowledge expands with improved molecular techniques, understanding signaling pathways in health and proteinuric states should lead to potential therapeutic targets in focal and segmental glomerulosclerosis.

Lavin, Peter J.; Gbadegesin, Rasheed; Damodaran, Tirupapuliyur V.; Winn, Michelle P.

2009-01-01

428

Lengths of Ladybugs  

NSDL National Science Digital Library

In this math lesson, learners explore the concept of using units to measure length. Learners first read "Ladybug on the Move" by Richard Fowler and measure the distance the ladybug travels on each page using yarn. Next, learners make their own "Go Ladybug Go!" books and use lima beans and a ladybug ruler to make and record measurements.

Lessonplans, Utah

2012-09-18

429

Extended Fuel Cycle Length.  

National Technical Information Service (NTIS)

Extended fuel cycle length and burnup are currently offered by Framatome and Fragema in order to satisfy the needs of the utilities in terms of fuel cycle cost and of overall systems cost optimization. We intend to point out the consequences of an increas...

M. Bruyere A. Vallee C. Collette

1986-01-01

430

A Future Generation High Angular Resolution X-ray Telescope Based Upon Physical Optics  

NASA Astrophysics Data System (ADS)

Although the highest priority objective for the next major X-ray mission is high resolution spectroscopy we will ultimately want the next generation high angular resolution X-ray observatory. This author believes that the 0.5 arc second angular resolution of the Chandra X-Ray Observatory is likely to be close to the best that can be obtained with grazing incidence optics, especially with larger effective area. Telescopes based upon physical optics, diffraction and refraction that transmit rather than reflect X-rays can have an angular resolution of a mili arc second or better. Combining the diffractive and refractive components into one unit can neutralize the chromatic aberration of each individually over a ~15% bandwidth at 6 keV. The aperture could be divided into several diffractive-refractive pairs to broaden the bandwidth. Furthermore these telescopes would be very low cost, very light weight, and more tolerant of figure errors and surface roughness than grazing incidence telescopes. However, focal lengths are of the order of 1000 km, which requires a new mission architecture consisting of long distance formation-flying between two spacecraft, one hosting the optics, the other, the detector. One of the spacecraft requires propulsion, provided by, for example, ion engines to maintain the optics-detector alignment by counteracting gravity gradient forces, and for changing targets. Although their effective area can be large and their angular resolution very high diffractive-refractive telescopes are not necessarily more sensitive than Chandra because their large focal plane scale (1 mili arc second ~ 1 mm) subjects them to a higher level of cosmic ray background and their opacity results in a lower energy limit of 2 keV. The intrinsic field of view is wide but the large focal length scale and practical limits on the size of the detector array results in a small field of view.

Gorenstein, Paul

2013-04-01

431

Microbinary element for optical wavelet transform  

NASA Astrophysics Data System (ADS)

In order to simplify an opto-electronic hybrid system for texture segmentation based on the multi-channel filtering framework in the human visual theory, a micro-binary optical element (BOE) is designed and fabricated. The BOE has the functions of splitting, filtering and imaging simultaneously. The focal length of the BOE is 150mm and the diameter is 4mm. It contains sixteen Gabor wavelet filters with scales decreased by 2 orders and with our orientations separated every 45 degree, which can be used to perform a nearly complete decomposition with wavelet transform. The relief surface structure with minimum feature scale of 1.5micrometers is fabricated by using the photolithography and ion etching technique. In this paper, the functions of the BOE and the simulation of the filtering are described in detail, the experimental results and improvement of the element are given.

Huang, Gaogui; Feng, Wenyi; Yan, Yingbai; Jin, Guofan

1997-09-01

432

Spectral-domain optical coherence tomography with a Fresnel spectrometer.  

PubMed

We propose a novel spectral-domain optical coherence tomography (SD-OCT) equipped with a Fresnel spectrometer, which utilizes a Fresnel zone plate (FZP) as both dispersion and focusing optics and thus spreads the spectral interferogram evenly in wavenumber domain because of the proportional relation between the focal length of the FZP and the wavenumber. With no need of the conversion calculation from wavelength to wavenumber in conventional SD-OCT, this new design is favorable for fast imaging with high resolution. As only a FZP and CCD are used, the Fresnel spectrometer is simple and compact. It is experimentally shown that its performance is as good as that of numerical interpolation in conventional SD-OCT. Imaging of bio-tissue by Fresnel SD-OCT is also demonstrated. PMID:22513668

Zhang, Ning; Chen, Tianyuan; Wang, Chengming; Zhang, Jian; Huo, Tiancheng; Zheng, Jinggao; Xue, Ping

2012-04-15

433

Multiple optical calibration system-based effective multiviews video processing  

NASA Astrophysics Data System (ADS)

A new multiple optical calibration system (MOCS)-based effective multiview video processing (MVP) is proposed. The proposed MOCS can be classified as intracamera processing and intercamera processing (IP). In IP, unequal brightness intensity is rectified by using a brightness difference map, and geometric distortion of the optical lens is corrected. In IP, several important factors, such as unequal camera sensor location, tilt degree of lens mount, and focal length, among multiple cameras are calibrated. Furthermore, an effective disparity matching algorithm, called an as adaptive-based disparity matching algorithm (A-DMA), is proposed for MVP. The proposed A-DMA enhances the performance of MVP in terms of accuracy of disparity estimation and computational overhead.

Bae, Kyung-Hoon; Park, Sanghoon; Cha, Si-Ho

2009-03-01

434

Optical system design for infrared imaging system of Korea Superconducting Tokamak Advanced Research (KSTAR) device  

NASA Astrophysics Data System (ADS)

The first infrared imaging system, for monitoring the temperature of the inner wall and localized hot spot such as the ICRH antenna was installed on the midplane of the D-port in the Korea Superconducting Tokamak Advanced Research (KSTAR). The cassette system of KSTAR makes a periscope inevitable for infrared imaging system. The periscope is composed of a 3 functional optical lens set (input beam shaper, beam deliverer, output beam shaper). CaF2 was chosen for the material of the lens elements. As an infrared image camera, FLIR/ThermoVision SC6000HS is used. The infrared camera has 640 × 512 pixel resolution and a camera lens set with 25.4 mm of focus length and 50 mm of input pupil. The periscope was designed to have 2.7 m of overall length, 19.07 mm of focal length and 3.81 of f-number.

Oh, S.; Seo, D.; KSTAR Team

2012-02-01

435

Grazing incidence relay optics  

NASA Technical Reports Server (NTRS)

The necessity to work in the focal plane of the primary mirrors has been one of the factors limiting the utility of grazing incidence telescopes in X-ray astronomy. In connection with the reported investigation, computer ray tracing programs have been used to study the performance of several grazing incidence relay optics (GIRO) systems used together with a large nested solar X-ray telescope. It was found that GIRO magnifiers are useful to map appropriate sized regions of the sun onto available CCD detectors. GIRO collimators can be used together with an X-ray spectrometer to study the X-ray spectrum from very small regions on the sun. Attention is given to the stationary mode, the tracking mode, and the size of GIRO elements. It is found that for a given GIRO size and magnification a use of the diverging system has the advantage of reducing the overall length of the main telescope-GIRO combination. However, the resolution provided by the diverging GIRO may not be as good as that obtained with the corresponding converging GIRO.

Chase, R. C.; Davis, J. M.; Krieger, A. S.; Underwood, J. H.

1982-01-01

436

Reconstruction of objects above and below the objective focal plane with dimensional fidelity by FINCH fluorescence microscopy.  

PubMed

Fresnel Incoherent Correlation Holography (FINCH) can faithfully reproduce objects above and below the optical plane of focus. However, as in optical imaging, the transverse magnification and optimal reconstruction depth changes based on the longitudinal distance of objects from the focal plane of the input lens with the exception that objects above and below the focal plane are in focus with FINCH and out of focus by standard optical imaging. We have analyzed these effects both theoretically and experimentally for two configurations of a FINCH fluorescence microscopy system. This information has been used to reconstruct a test planar object placed above or below the optical plane of focus with high dimensional and image fidelity. Because FINCH is inherently a super-resolving system, this advance makes it possible to create super-resolved 3D images from FINCH holograms. PMID:23037035

Siegel, Nisan; Rosen, Joseph; Brooker, Gary

2012-08-27

437

Focal damage to macaque photoreceptors produces persistent visual loss.  

PubMed

Insertion of light-gated channels into inner retina neurons restores neural light responses, light evoked potentials, visual optomotor responses and visually-guided maze behavior in mice blinded by retinal degeneration. This method of vision restoration bypasses damaged outer retina, providing stimulation directly to retinal ganglion cells in inner retina. The approach is similar to that of electronic visual protheses, but may offer some advantages, such as avoidance of complex surgery and direct targeting of many thousands of neurons. However, the promise of this technique for restoring human vision remains uncertain because rodent animal models, in which it has been largely developed, are not ideal for evaluating visual perception. On the other hand, psychophysical vision studies in macaque can be used to evaluate different approaches to vision restoration in humans. Furthermore, it has not been possible to test vision restoration in macaques, the optimal model for human-like vision, because there has been no macaque model of outer retina degeneration. In this study, we describe development of a macaque model of photoreceptor degeneration that can in future studies be used to test restoration of perception by visual prostheses. Our results show that perceptual deficits caused by focal light damage are restricted to locations at which photoreceptors are damaged, that optical coherence tomography (OCT) can be used to track such lesions, and that adaptive optics retinal imaging, which we recently used for in vivo recording of ganglion cell function, can be used in future studies to examine these lesions. PMID:24316158

Strazzeri, Jennifer M; Hunter, Jennifer J; Masella, Benjamin D; Yin, Lu; Fischer, William S; DiLoreto, David A; Libby, Richard T; Williams, David R; Merigan, William H