Science.gov

Sample records for focal length optics

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

    DOEpatents

    Crandall, David Lynn

    2011-08-01

    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.

  2. Sighting optics including an optical element having a first focal length and a second focal length and methods for sighting

    DOEpatents

    Crandall, David Lynn

    2011-08-16

    Sighting optics include a front sight and a rear sight positioned in a 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.

  3. The focal length control method for optical remote sensor

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Zhao, Xiting; Jiao, Wenchun; Wei, Xuemin

    2015-10-01

    With the rapid development of the optical remote sensor technology, it puts forward higher requirements to the sensor's index. For space camera with large field of view, long focal distance, the image quality and the focal length of the various parameters of the optical system puts forward higher requirements. Therefore how to meet the control index of the sensors put forward new problems for the alignment. The present reports on focal length mainly around the focal length calculation and accurate measurement, but there is no report about how to accurately control the focal length. This article proposed a method for combinatorial optimization based on the focal length and image quality evaluation, geometrical parameter error of the iterative optimization to obtain the best mirror distance compensation combination, that establish mirror-distance compensation control curve to guide the camera alignment process. The focus control precision is less than 1%, the field of view system surface shape is better than 0.08 λ.

  4. Design of a variable-focal-length optical system

    NASA Technical Reports Server (NTRS)

    Ricks, D.; Shannon, R. R.

    1984-01-01

    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.

  5. Analysis of factors important for measurements of focal length of optical systems

    NASA Astrophysics Data System (ADS)

    Pokorný, P.; Opat, J.; Mikš, A.; Novák, J.; Novák, P.

    2015-09-01

    A focal length is a basic optical characteristic of an optical system. Thus, it is important to be able to measure this value for a given optical system very accurately in practice. At present there exist various physical principles of the focal length measurement which can achieve a different measurement accuracy. In our work we analyse several methods of measurement of the focal length with respect to factors, which are important for a measurement accuracy. The analysis is performed on examples.

  6. Thin waveplate lenses of switchable focal length--new generation in optics.

    PubMed

    Tabiryan, Nelson V; Serak, Svetlana V; Roberts, David E; Steeves, Diane M; Kimball, Brian R

    2015-10-01

    We present new lenses - waveplate lenses created in liquid crystal and liquid crystal polymer materials. Using an electrically-switchable liquid-crystal half-wave retarder we realized switching between focused and defocused beams by the waveplate lens. A combination of two such lenses allowed the collimation of a laser beam as well as the change of focal length of optical system. PMID:26480092

  7. Continuously variable focal length lens

    SciTech Connect

    Adams, Bernhard W; Chollet, Matthieu C

    2013-12-17

    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.

  8. Optical system design of solar-blind UV target simulator with long focal length

    NASA Astrophysics Data System (ADS)

    Chen, Yu; Huo, Furong; Zheng, Liqin

    2014-11-01

    Ultraviolet (UV) radiation of 200nm-300nm waveband from the sun is absorbed by atmosphere, which is often referred to the solar-blind region of the solar spectrum. Solar-blind characteristics of this waveband have important application value, especially in military fields. The application of solar-blind waveband has developed very rapidly, which is receiving more and more attention. Sometimes, to test the performance of a UV optical system, a standard solar-blind UV target simulator is needed as the UV light source. In this paper, an optical system of a solar-blind UV target simulator is designed with waveband 240nm-280nm. To simulate a far UV target, the focal length of this UV optical system needs to be long. Besides, different field of view (FOV) of the system should meet aplanatic condition. The optional materials are very few for UV optical systems, in which only CaF2 and JGS1 are commonly used. Various aberrations are difficult to be corrected. To save production cost and enhance the precision of fabrication and test, aspheric surfaces and binary elements are not adopted in the system. Moreover, doublet or triplet cannot be used in UV optical system considering possible cracking for different thermal expansion coefficients of different materials. After optimization, the system is composed of 4 lenses with focal length 500mm. MTF curves of different FOV coincide together. The maximum RMS radius of the optimized system has almost the same size as Airy disk, which proves the good image quality after system optimization. The aplanatic condition is met very well in this system. In the spot diagram, root mean square (RMS) radius changes from 3 microns to 3.6 microns, which has similar size with Airy disk and meets aplanatic condition very well. This optical system of solar-blind UV target simulator also has relatively loose tolerance data, which can prove the system is designed in an optimal state.

  9. The effect of the aero optic's additional focal length on the airborne platform laser communication

    NASA Astrophysics Data System (ADS)

    Hu, Yuan; Gao, Tianyuan; Cheng, Dewen; Tong, Shoufeng; Jiang, Huilin

    2015-05-01

    The aero optics effects caused by high speed flight may have a serious impact on the performance of space laser communication systems. In the field of space laser communication technology engineering and its practical application, this is a research problem that is highly significant. For the complex flow field that is generated by the interaction between the aircraft surface and air, the aero optics effects are usually divided into two parts, namely, laminar flow and turbulent flow. This paper discusses the principle of how the aero optics effect causes the image of the space laser communication optical system to blur and leads to a dispersed spot. The research focuses on the additional focal length (AFL) effect caused by the laminar flow field, a simulation analysis of the relationship between the flight altitude, speed, window shape and the system performance, and provides solutions to the defocus phenomenon that has been observed in airborne tests. Finally it is hoped that the paper can provide a solution that effectively compensates for the AFL effect on laser communication optical systems, and improves the communication between aircrafts.

  10. Variable focal length deformable mirror

    DOEpatents

    Headley, Daniel; Ramsey, Marc; Schwarz, Jens

    2007-06-12

    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.

  11. Crystal diffraction lens with variable focal length

    DOEpatents

    Smither, R.K.

    1991-04-02

    A method and apparatus for altering the focal length of a focusing element of one of a plurality of pre-determined focal lengths by changing heat transfer within selected portions of the element by controlled quantities is disclosed. 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. 19 figures.

  12. Focal length and focal depth of metallic superlens

    NASA Astrophysics Data System (ADS)

    Cao, Pengfei; Cheng, Lin; Li, Ying; Zhang, Xiaoping; Kong, Weijie; Gong, Li; Zhao, Xining

    2012-10-01

    We consider the problems of focal length and focal depth of subwavelength imaging via a silver slab of metallic superlens. The performance limit of the metallic superlens was associated with the losses in the metallic film. The transmittance through a metal film is quite low and decreases exponentially with the thickness of the metal film. In the visible wavelength region, the permittivity of Ag can be approximated by the Drude model, so it can be described as the plural permittivity. The real part ( ɛ' ) of permittivity of the metal slab has been preferably index matched to the host material, and the imaginary part ( ɛ'' ) is considered to prevent ideal reconstruction of the image. Because superlens are usually made of metals with significant intrinsic loss ( ɛ''>0 ), the image is blurred and it is regarded as an ultimate limitation to a near field perfect lens. The real part ( ɛ' )and the imaginary part ( ɛ'' ) of permittivity of the metal slab is the function of the incident wavelength, so we discuss the relationship of the focal length, focal depth and the incident wavelength. We also derive the expression for the resolution limit of metallic lens and demonstrate that the area of its subwavelength performance is usually limited to the near-field zone.

  13. Subharmonic focal-length intensities formed by Fresnel lenses.

    PubMed

    Davis, J A; Field, A M; Cottrell, D M

    1994-12-10

    Binary Fresnel lenses produce focused spots at subharmonics of the principal focal length of the lens. The intensities of these focal spots can be controlled by variation of the relative widths of the rings of the Fresnel lens compared with the spacings between the rings. Theory is presented and experimentalverification is provided with Fresnel lenses written onto the magneto-optic spatial light modulator. PMID:20963052

  14. Confocal microscopy and variable-focal length microlenses

    NASA Astrophysics Data System (ADS)

    Mac Raighne, Aaron M.; Yang, Lisong; Dunbar, L. Andrea; McCabe, Eithne M.; Scharf, Toralf

    2004-07-01

    Confocal microscopy has a unique optical sectioning property which allows three-dimensional images at different depths. Use of a microlens array is a potential alternative to the Nipkow disk for parallel imaging with high throughput in real-time confocal microscopy. The use of variable-focal-length microlenses can provide a way to axially scan the foci electronically avoiding the inflexible mechanical movement of the lens or the sample. Here we demonstrate a combination of a variable-focal-length microlens array and a fiber optic bundle as a way to create a high throughput aperture array that would be potentially applied as confocal imaging in vivo biological specimens. Variable focal length microlenses that we use consist of a liquid crystal film sandwiched between a pair of conductive substrates with patterned electrodes. The incident side of the microlens array was determined by examining the focus distribution in the axial direction. The variation of the focal length obtained by changing the voltage and corresponding focus intensity were measured through a conventional microscope. Meanwhile, the fiber bundle was characterized by coupling with either coherent or incoherent light source. We use the fiber bundle as both a multiple aperture and an image-carrying element and combine it with a microlens array to built up a confocal system. Axial responses are measured in two optical arrangements as a route to investigate endoscope potential.

  15. Optofluidic lens with tunable focal length and asphericity

    PubMed Central

    Mishra, Kartikeya; Murade, Chandrashekhar; Carreel, Bruno; Roghair, Ivo; Oh, Jung Min; Manukyan, Gor; van den Ende, Dirk; Mugele, Frieder

    2014-01-01

    Adaptive micro-lenses enable the design of very compact optical systems with tunable imaging properties. Conventional adaptive micro-lenses suffer from substantial spherical aberration that compromises the optical performance of the system. Here, we introduce a novel concept of liquid micro-lenses with superior imaging performance that allows for simultaneous and independent tuning of both focal length and asphericity. This is achieved by varying both hydrostatic pressures and electric fields to control the shape of the refracting interface between an electrically conductive lens fluid and a non-conductive ambient fluid. Continuous variation from spherical interfaces at zero electric field to hyperbolic ones with variable ellipticity for finite fields gives access to lenses with positive, zero, and negative spherical aberration (while the focal length can be tuned via the hydrostatic pressure). PMID:25224851

  16. Optofluidic lens with tunable focal length and asphericity

    NASA Astrophysics Data System (ADS)

    Mishra, Kartikeya; Murade, Chandrashekhar; Carreel, Bruno; Roghair, Ivo; Oh, Jung Min; Manukyan, Gor; van den Ende, Dirk; Mugele, Frieder

    2014-09-01

    Adaptive micro-lenses enable the design of very compact optical systems with tunable imaging properties. Conventional adaptive micro-lenses suffer from substantial spherical aberration that compromises the optical performance of the system. Here, we introduce a novel concept of liquid micro-lenses with superior imaging performance that allows for simultaneous and independent tuning of both focal length and asphericity. This is achieved by varying both hydrostatic pressures and electric fields to control the shape of the refracting interface between an electrically conductive lens fluid and a non-conductive ambient fluid. Continuous variation from spherical interfaces at zero electric field to hyperbolic ones with variable ellipticity for finite fields gives access to lenses with positive, zero, and negative spherical aberration (while the focal length can be tuned via the hydrostatic pressure).

  17. Optofluidic lens with tunable focal length and asphericity.

    PubMed

    Mishra, Kartikeya; Murade, Chandrashekhar; Carreel, Bruno; Roghair, Ivo; Oh, Jung Min; Manukyan, Gor; van den Ende, Dirk; Mugele, Frieder

    2014-01-01

    Adaptive micro-lenses enable the design of very compact optical systems with tunable imaging properties. Conventional adaptive micro-lenses suffer from substantial spherical aberration that compromises the optical performance of the system. Here, we introduce a novel concept of liquid micro-lenses with superior imaging performance that allows for simultaneous and independent tuning of both focal length and asphericity. This is achieved by varying both hydrostatic pressures and electric fields to control the shape of the refracting interface between an electrically conductive lens fluid and a non-conductive ambient fluid. Continuous variation from spherical interfaces at zero electric field to hyperbolic ones with variable ellipticity for finite fields gives access to lenses with positive, zero, and negative spherical aberration (while the focal length can be tuned via the hydrostatic pressure). PMID:25224851

  18. Focal lengths of Venus Monitoring Camera from limb locations

    NASA Astrophysics Data System (ADS)

    Limaye, Sanjay S.; Markiewicz, W. J.; Krauss, R.; Ignatiev, N.; Roatsch, T.; Matz, K. D.

    2015-08-01

    The Venus Monitoring Camera (VMC) carried by European Space Agency's Venus Express orbiter (Svedhem et al., 2007) consists of four optical units, each with a separate filter casting an image on a single CCD (Markiewicz et al., 2007a, 2007b). The desire to capture as much of the planet in a single frame during the spacecraft's 24 h, 0.84 eccentricity orbit led to optics with 18° field of view. Analysis of Venus images obtained by the VMC indicated that the computed limb radius and altitude of haze layers were somewhat inconsistent with prior knowledge and expectations. Possible causes include errors in the knowledge of image geometry, misalignment of the optic axis from the pointing direction, and optical distortion. These were explored and eliminated, leaving only deviations from the ground and pre-solar damage estimate of the focal length lengths as the most likely reason. We use the location of planet's limb to estimate the focal length of each camera using images of the planet when the orbiter was more than 20,000 km from planet center. The method relies on the limb radius to be constant at least over a small range of solar zenith angles. We were able to achieve better estimates for the focal lengths for all four cameras and also estimate small offsets to the boresight alignment. An outcome of this analysis is the finding that the slant unit optical depth varies more rapidly with solar zenith angle in the afternoon as compared to morning, with lowest values at local noon. A variation of this level is also observed with latitude. Both are indicative of the presence of overlying haze above the clouds, and the morning afternoon asymmetry suggests different photochemical processes in destruction and production of the haze.

  19. A potential individual cell malignancy indicator: focal length

    NASA Astrophysics Data System (ADS)

    Wang, Weina; Lear, Kevin L.

    2011-03-01

    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.

  20. Rigorous electromagnetic analysis of metallic cylindrical focusing micromirrors designed by a modified focal-length function

    NASA Astrophysics Data System (ADS)

    Mei, Guo-Ai; Ye, Jiasheng; Zhang, Yan

    2011-12-01

    Through exploiting a modified focal-length function, two-dimensional metallic cylindrical focusing micromirrors (MCFMs) with different preset focal depths are designed. Rigorous electromagnetic theory and the boundary element method are applied to analyzing the focal characteristics, including the actual focal depth, the relative focal depth, the focal spot size and the diffraction efficiency. Through setting the preset focal depth to be positive or negative, numerical results reveal that the designed MCFMs can successfully modulate the optical field distribution to achieve a long axial focal depth or increased lateral resolution, respectively. In addition, due to the inherent achromatic aberration property of the metallic reflective system, the common long-focal-depth region of the designed MCFM under multiwavelength illumination is greatly enlarged, in comparison with a dielectrically cylindrical microlens. It is expected that the designed MCFMs should have many practical applications in micro optics systems.

  1. Long Focal Length Large Mirror Fabrication System

    NASA Technical Reports Server (NTRS)

    Bennett, H. E.

    2003-01-01

    The goals of this ambitious program are (1) to develop systems to make large superpolished optical mirrors, (2) to develop low scatter polishing techniques using centrifugal elutriation, (3) to develop a means of measuring scatter at any point on the mirror, (4) to polish a Hindle sphere to measure the optical figure of a one meter diameter convex mandrel, and (5) to fabricate low scatter, large adaptive optic graphite filled, cyanate ester replica transfer mirrors using these mandrels. Deliverables are a 30 cm diameter superpolished composite AO mirror. We fabricated a 1/3rd meter superpolished zerodur flat mandrel and with the support of our major subcontractor, Composite Mirror Applications Inc (CMA) we have demonstrated a 30 cm lightweight cyanate ester mirror with an rms microroughness between 0.6 and 0.8 nm and 8 faceplate influence function of 5 cm. The influence function was chosen to be comparable to the atmospheric correlation coefficient r(sub 0) which is about 5 cm at sea level. There was no print-thru of the graphite fibers in the cyanate ester surface (the bane of many previous efforts to use cyanate ester mirrors). Our subcontractor has devised a means for developing a 30-50 nm thick layer of graphite free pure ester resin on the surface of the mirrors. This graphite fiber filled material has a thermal expansion coefficient in the 10(exp -8) centimeter per Kelvin range (the same range of expansion coefficient as Zerodur and ULE glasses) and does not take up water and swell, so it is a nearly ideal mirror material in these areas. Unfortunately for these 0.8mm thick faceplates, the number of plies is not enough to result in isometric coverage. Isolated figure irregularities can appear, making it necessary to go to thicker faceplates. The influence function will then only approximate the length of r(sub 0), at higher altitudes or longer wavelengths. The influence function goes as the cube of the thickness, so we are now making a faceplate optimized for an infrared wavelength, possibly that used for the AO system of the Keck telescope, instead of 0.63 microns. We have polished a 55 cm diameter mandrel to better than 1/20th wave optical figure in the visible using centrifugal elutriation. CMA has just told us that it needs to retool to get optimum mirror faceplate quality in this size, so implementing the 55 cm AO mirror may be delayed somewhat. We expect to complete our 1/3 rd meter AO mirror on time using novel piezoelectric actuators with a throw of one micrometer per volt, as compared to 0.005 micrometers per volt for conventional piezoelectric actuators. We will then demonstrate its AO performance interferometrically.

  2. Focal Length Affects Depicted Shape and Perception of Facial Images.

    PubMed

    Třebický, Vít; Fialová, Jitka; Kleisner, Karel; Havlíček, Jan

    2016-01-01

    Static photographs are currently the most often employed stimuli in research on social perception. The method of photograph acquisition might affect the depicted subject's facial appearance and thus also the impression of such stimuli. An important factor influencing the resulting photograph is focal length, as different focal lengths produce various levels of image distortion. Here we tested whether different focal lengths (50, 85, 105 mm) affect depicted shape and perception of female and male faces. We collected three portrait photographs of 45 (22 females, 23 males) participants under standardized conditions and camera setting varying only in the focal length. Subsequently, the three photographs from each individual were shown on screen in a randomized order using a 3-alternative forced-choice paradigm. The images were judged for attractiveness, dominance, and femininity/masculinity by 369 raters (193 females, 176 males). Facial width-to-height ratio (fWHR) was measured from each photograph and overall facial shape was analysed employing geometric morphometric methods (GMM). Our results showed that photographs taken with 50 mm focal length were rated as significantly less feminine/masculine, attractive, and dominant compared to the images taken with longer focal lengths. Further, shorter focal lengths produced faces with smaller fWHR. Subsequent GMM revealed focal length significantly affected overall facial shape of the photographed subjects. Thus methodology of photograph acquisition, focal length in this case, can significantly affect results of studies using photographic stimuli perhaps due to different levels of perspective distortion that influence shapes and proportions of morphological traits. PMID:26894832

  3. Focal Length Affects Depicted Shape and Perception of Facial Images

    PubMed Central

    Třebický, Vít; Fialová, Jitka; Kleisner, Karel; Havlíček, Jan

    2016-01-01

    Static photographs are currently the most often employed stimuli in research on social perception. The method of photograph acquisition might affect the depicted subject’s facial appearance and thus also the impression of such stimuli. An important factor influencing the resulting photograph is focal length, as different focal lengths produce various levels of image distortion. Here we tested whether different focal lengths (50, 85, 105 mm) affect depicted shape and perception of female and male faces. We collected three portrait photographs of 45 (22 females, 23 males) participants under standardized conditions and camera setting varying only in the focal length. Subsequently, the three photographs from each individual were shown on screen in a randomized order using a 3-alternative forced-choice paradigm. The images were judged for attractiveness, dominance, and femininity/masculinity by 369 raters (193 females, 176 males). Facial width-to-height ratio (fWHR) was measured from each photograph and overall facial shape was analysed employing geometric morphometric methods (GMM). Our results showed that photographs taken with 50 mm focal length were rated as significantly less feminine/masculine, attractive, and dominant compared to the images taken with longer focal lengths. Further, shorter focal lengths produced faces with smaller fWHR. Subsequent GMM revealed focal length significantly affected overall facial shape of the photographed subjects. Thus methodology of photograph acquisition, focal length in this case, can significantly affect results of studies using photographic stimuli perhaps due to different levels of perspective distortion that influence shapes and proportions of morphological traits. PMID:26894832

  4. Extending plasma channel of filamentation with a multi-focal-length beam.

    PubMed

    Hong, Zuofei; Zhang, Qingbin; Ali Rezvani, S; Lan, Pengfei; Lu, Peixiang

    2016-02-22

    We propose a novel scheme that lengthens the plasma channel in filamentation with a multi-focal-length beam. Instead of one focal length introduced by a conventional convex lens, the multi-focal-length beam modulated by a spatial light modulator (SLM) produces a filament in an extended range with limited but strictly manipulated laser energy. The results show that the scheme is capable of doubling the filament length compared to a single-lens scheme with a 2-mJ input pulse. The filament location and length can be simply tuned by altering the spatial amplitude and phase or employing higher energies. Furthermore, the extended filament length leads to the generation of a broadened continuum ranging from visible (VIS) to infrared (IR) domain. This versatile scheme offers an efficient tool for the development of a variety of applications involving ultrafast nonlinear optics. PMID:26907055

  5. Biomimetic small scale variable focal length lens unit using synthetic elastomer actuators

    NASA Astrophysics Data System (ADS)

    Kim, Baek-chul; Chung, Jinah; Lee, Y.; Nam, Jae-Do; Moon, Hyungpil; Choi, Hyouk Ryeol; Koo, J. C.

    2011-04-01

    Having a combination of a gel-like soft lens, ligaments, and the Ciliary muscles, the human eyes are effectively working for various focal lengths without a complicated group of lens. The simple and compact but effective optical system should deserve numerous attentions from various technical field especially portable information technology device industry. Noting the limited physical space of those deivces, demanding shock durability, and massive volume productivity, the present paper proposes a biomimetic optical lens unit that is organized with a circular silicone lens and an annular dielectric polymer actuator. Unlike the traditional optical lens mechanism that normally acquires a focus by changing its focal distance with moving lens or focal plane. the proposed optical system changes its lens thickness using a annulary connected polymer actuator in order to get image focuses. The proposed biomimetic lens system ensures high shock durability, compact physical dimensions, fast actuations, simple manufacturing process, and low production cost.

  6. Shaping a Subwavelength Needle with Ultra-long Focal Length by Focusing Azimuthally Polarized Light

    PubMed Central

    Qin, Fei; Huang, Kun; Wu, Jianfeng; Jiao, Jiao; Luo, Xiangang; Qiu, Chengwei; Hong, Minghui

    2015-01-01

    Flat optics, which could planarize and miniaturize the traditional optical elements, possesses the features of extremely low profile and high integration for advanced manipulation of light. Here we proposed and experimentally demonstrated a planar metalens to realize an ultra-long focal length of ~240λ with a large depth of focus (DOF) of ~12λ, under the illumination of azimuthally polarized beam with vortical phase at 633 nm. Equally important is that such a flat lens could stably keep a lateral subwavelength width of 0.42λ to 0.49λ along the needle-like focal region. It exhibits one-order improvement in the focal length compared to the traditional focal lengths of 20~30λ of flat lens, under the criterion of having subwavelength focusing spot. The ultra-long focal length ensures sufficient space for subsequent characterization behind the lens in practical industry setups, while subwavelength cross section and large DOF enable high resolution in transverse imaging and nanolithography and high tolerance in axial positioning in the meantime. Such planar metalens with those simultaneous advantages is prepared by laser pattern generator rather than focused ion beam, which makes the mass production possible. PMID:25943500

  7. Alignment techniques required by precise measurement of effective focal length

    NASA Technical Reports Server (NTRS)

    Wise, T. D.

    1980-01-01

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

  8. Exhaustive linearization for robust camera pose and focal length estimation.

    PubMed

    Penate-Sanchez, Adrian; Andrade-Cetto, Juan; Moreno-Noguer, Francesc

    2013-10-01

    We propose a novel approach for the estimation of the pose and focal length of a camera from a set of 3D-to-2D point correspondences. Our method compares favorably to competing approaches in that it is both more accurate than existing closed form solutions, as well as faster and also more accurate than iterative ones. Our approach is inspired on the EPnP algorithm, a recent O(n) solution for the calibrated case. Yet we show that considering the focal length as an additional unknown renders the linearization and relinearization techniques of the original approach no longer valid, especially with large amounts of noise. We present new methodologies to circumvent this limitation termed exhaustive linearization and exhaustive relinearization which perform a systematic exploration of the solution space in closed form. The method is evaluated on both real and synthetic data, and our results show that besides producing precise focal length estimation, the retrieved camera pose is almost as accurate as the one computed using the EPnP, which assumes a calibrated camera. PMID:23969384

  9. Focal plane array optical proximity sensor

    NASA Technical Reports Server (NTRS)

    Johnston, A. R. (Inventor)

    1984-01-01

    An optical proximity sensor for optically detecting an object within a predetermined detection volume is described. More specifically, an optical proximity sensor is disclosed having an illuminator assembly including lens and a plurality of light-emitting diodes located at first predetermined positions along the focal plane of the illuminator lens. A detector assembly including a detector lens and a plurality of photodiodes located at second predetermined positions along the focal plane of the detector lens is also provided. The two lenses are spaced apart a predetermined distance in order to define a predetermined detection volume. Additionally, a combination of optical proximity sensors, according to the invention, is disclosed wherein the sensors can be used in conjunction with a vehicle to provide a safety system for warning an operator when an object is within a volume defined by the proximity sensor combination.

  10. Optical interconnections to focal plane arrays

    SciTech Connect

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

    2000-11-01

    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.

  11. High speed multi focal plane optical system

    NASA Technical Reports Server (NTRS)

    Minott, P. O. (Inventor)

    1983-01-01

    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.

  12. Simple volume expanding fabrication method for focal length controlled micro-lens array

    NASA Astrophysics Data System (ADS)

    Kim, Junoh; Lee, Muyung; Kim, Cheol Joong; Lee, Jin Su; Won, Yong Hyub

    2015-03-01

    This study describes easy fabrication method for micro-lens array which has desired focal length in such a way that without the use of reflow technique. The process includes conventional lithographic process only which can be compatible with general semiconductor process. As constituent material, Negative photo-resist SU-8 with its developer PGMEA is used. Two main phenomena during lithography process are adjusted to expand the volume of the PR. During UV exposure, hardening proceeds from the top of the PR. Just after first exposure, using this property, very thin membrane on the top of the surface of the PR can be formed by short time exposure. In the development process, unexposed area of the PR is removed by chemical reaction with developer which causes the volume expansion if the unexposed area is covered with thin cured film. This method is to form the lens as the molecules in the volume are not easily escaped from the covered region. The thickness of the thin film depends on the exposure dose of 2mJ cm-2 μm-1 which determines the degree of expansion. The symmetrical volume expansion creates the membrane of lens shape and the focal length is directly related with second exposure dose. An extended research of affecting the change of the focal length of lens using volume expansion method by changing any other elements is discussed. This process can achieve a focal length selective for the applications of micro-optics.

  13. Focal length stabilization of a tunable lens integrated focus shifting unit

    NASA Astrophysics Data System (ADS)

    Eberle, Gregory; Boesser, Benjamin; Wegener, Konrad

    2014-03-01

    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.

  14. Optical analysis on induction of focal accommodation using cylindrical lenses

    NASA Astrophysics Data System (ADS)

    Mano, Yuichiro; Kakeya, Hideki

    2008-02-01

    In the present paper the authors analyze detailed optics of stereoscopic display combining cylindrical lenses and embedded striped patterns, which has been proposed to reduce the contradiction between binocular parallax and focal accommodation of the eyes. The proposed system lets the viewer see an image including high frequency striped patterns through a cylindrical lens. When the viewer is shown a striped pattern through a cylindrical lens, the depth on which his/her eyes focus depends on the inclination angle of stripes, for the cylindrical lens works as a lens with different focal length depending on the orientation of lines. To control the status of accommodation correctly, it is necessary to obtain the correspondence between the inclination angle of stripes and the focusing distance. To attain this goal we make a computer simulator to calculate the 3D optical paths. The validity of the computer simulator is confirmed by physical experiments with a cylindrical lens and a camera finder to measure the focal convergence of striped lines. We also confirm that this system can induce desired focal accommodation by measuring the eyes of the viewer seeing striped patterns through a cylindrical lens.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

  16. Large-aperture laser differential confocal ultra-long focal length measurement and its system.

    PubMed

    Zhao, Weiqian; Li, Zhigang; Qiu, Lirong; Ren, Huan; Shao, Rongjun

    2015-06-29

    A new laser differential confocal ultra-long focal length measurement (LDCFM) method is proposed with the capability to self-calibrate the reference lens (RL) focal length and the axial space between the test lens and RL. Using the property that the focus of laser differential confocal ultra-long focal length measurement system (LDCFS) precisely corresponds to the null point of the differential confocal axial intensity curve, the proposed LDCFM measures the RL focal length f(R)' by precisely identifying the positions of the focus and last surface of RL, measures the axial space d(0) between RL and test ultra-long focal length lens (UFL) by identifying the last surface of RL and the vertex of UFL last surface, and measures the variation l in focus position of LDCFS with and without test UFL, and then calculates the UFL focal length f(T)' by the above measured f(R)', d(0) and l. In addition, a LDCFS based on the proposed method is developed for a large aperture lens. The experimental results indicate that the relative uncertainty is less than 0.01% for the test UFL, which has an aperture of 610 mm and focal length of 31,000 mm. LDCFM provides a novel approach for the high-precision focal-length measurement of large-aperture UFL. PMID:26191747

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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.

  18. Ultralong focal length microlens array fabricated based on SU-8 photoresist.

    PubMed

    Bian, Rui; Xiong, Ying; Chen, Xiangyu; Xiong, Penghui; Hou, Shuangyue; Chen, Shan; Zhang, Xiaobo; Liu, Gang; Tian, Yangchao

    2015-06-01

    In this paper, a novel method to fabricate ultralong focal length microlens arrays has been proposed. The microlens arrays were fabricated based on surface tension when heating temperature is over a glass transition temperature of SU-8 photoresist. An ultralong focal length was achieved by the large radius of curvature of a photoresist surface. Microlenses of widths from 30 to 210 μm were successfully fabricated. The longest focal length was up to 4.4 mm from the microlens of 210 μm width. The formation mechanism was also studied and validated by simulation based on the finite element method. PMID:26192669

  19. Focal-length-tunable elastomer-based liquid-filled plano-convex mini lens.

    PubMed

    Fang, Chaolong; Dai, Bo; Zhuo, Ran; Yuan, Xupeng; Gao, Xiumin; Wen, Jing; Sheng, Bin; Zhang, Dawei

    2016-01-15

    A liquid plano-convex lens with focal length tuning is proposed, which is formed by sinking an oil droplet onto the bottom of an elastomer. A simple and low-cost fabrication method is presented. The lens aperture and initial focal length can be controlled during the fabrication. Furthermore, focal length tuning is demonstrated. The lens made of a 40mg oil droplet can achieve the tuning range from 12 to 17mm. The effective aperture of the lens is about 2.8mm. In the demonstration of an imaging system, the lens assists in focusing and a clear image can be observed. PMID:26766725

  20. Focal length measurement based on the wavefront difference method by a Fizeau interferometer.

    PubMed

    Yang, Zhongming; Gao, Zhishan; Dou, Jiantai; Wang, Xinxing

    2014-09-01

    A method for measuring the focal length of the lens by a Fizeau interferometer is proposed. Based on the Gaussian imaging equation and the longitudinal displacements of the object point and image point, a precise formula for focal length calculation is deduced. The longitudinal displacement of the object points is determined by the wavefront difference method with a subnanometer resolution. An experimental system for focal length measurements is set up to verify the principle. The sources of uncertainty in measurement are discussed. Both the positive and negative lens experimental results indicate that the measurement accuracy is less than 0.16% under normal experimental environment. PMID:25321352

  1. Focal length calibration of an electrically tunable lens by digital holography.

    PubMed

    Wang, Zhaomin; Qu, Weijuan; Yang, Fang; Asundi, Anand Krishna

    2016-02-01

    The electrically tunable lens (ETL) is a novel current-controlled adaptive optical component which can continuously tune its focus in a specific range via changing its surface curvature. To quantitatively characterize its tuning power, here we assume the ETL to be a pure phase object and present a novel calibration method to dynamically measure its wavefront by use of digital holographic microscopy (DHM). The least squares method is then used to fit the radius of curvature of the wavefront. The focal length is obtained by substituting the radius into the Zemax model of the ETL. The behavior curve between the focal length of the ETL and its driven current is drawn, and a quadratic mathematic model is set up to characterize it. To verify our model, an ETL and offset lens combination is proposed and applied to ETL-based transport of intensity equation (TIE) phase retrieval microscopy. The experimental result demonstrates the calibration works well in TIE phase retrieval in comparison with the phase measured by DHM. PMID:26836076

  2. Embedding perspective cue in holographic projection display by virtual variable-focal-length lenses

    NASA Astrophysics Data System (ADS)

    Li, Zhaohui; Zhang, Jianqi; Wang, Xiaorui; Zhao, Fuliang

    2014-10-01

    To make a view perspective cue emerging in reconstructed images, a new approach is proposed by incorporating virtual variable-focal-length lenses into computer generated Fourier hologram (CGFH). This approach is based on a combination of monocular vision principle and digital hologram display, thus it owns properties coming from the two display models simultaneously. Therefore, it can overcome the drawback of the unsatisfied visual depth perception of the reconstructed three-dimensional (3D) images in holographic projection display (HPD). Firstly, an analysis on characteristics of conventional CGFH reconstruction is made, which indicates that a finite depthof- focus and a non-adjustable lateral magnification are reasons of the depth information lack on a fixed image plane. Secondly, the principle of controlling lateral magnification in wave-front reconstructions by virtual lenses is demonstrated. And the relation model is deduced, involving the depth of object, the parameters of virtual lenses, and the lateral magnification. Next, the focal-lengths of virtual lenses are determined by considering perspective distortion of human vision. After employing virtual lenses in the CGFH, the reconstructed image on focal-plane can deliver the same depth cues as that of the monocular stereoscopic image. Finally, the depthof- focus enhancement produced by a virtual lens and the effect on the reconstruction quality from the virtual lens are described. Numerical simulation and electro-optical reconstruction experimental results prove that the proposed algorithm can improve the depth perception of the reconstructed 3D image in HPD. The proposed method provides a possibility of uniting multiple display models to enhance 3D display performance and viewer experience.

  3. Measuring the lens focal length by laser reflection-confocal technology.

    PubMed

    Yang, Jiamiao; Qiu, Lirong; Zhao, Weiqian; Shao, Rongjun; Li, Zhigang

    2013-06-01

    A laser reflection-confocal focal-length measurement (LRCFM) is proposed for the high-accuracy measurement of lens focal length. LRCFM uses the peak points of confocal response curves to precisely identify the lens focus and vertex of the lens last surface. LRCFM then accurately measures the distance between the two positions to determine the lens focal length. LRCFM uses conic fitting, which significantly enhances measurement accuracy by inhibiting the influence of environmental disturbance and system noise on the measurement results. The experimental results indicate that LRCFM has a relative expanded uncertainty of less than 0.0015%. Compared with existing measurement methods, LRCFM has high accuracy and a concise structure. Thus, LRCFM is a feasible method for high-accuracy focal-length measurements. PMID:23736337

  4. Determination of the focal length of microlens array by spherical wavefronts

    NASA Astrophysics Data System (ADS)

    Kumar, Marimuthu Senthil; Sharma, Rahul; Narayanamurthy, Chittur Subramanian; Kumar, Alur Seelin Kiran

    2014-06-01

    We propose an experimental method consisting of a standard Fizeau interferometer with transmission sphere (TS) for the determination of the focal length of microlens array (MLA) by spherical wavefronts. The TS is axially translated to produce a spherical wavefront of different curvatures with respect to the MLA. The align mode provision of the interferometer helps to monitor the tilt of the MLA with respect to the spherical wavefront. The focal length is determined from the measured distance of adjacent image spots for various spherical wavefronts at the focal plane of the MLA. Error analysis and experimental demonstration with an off-the-shelf MLA are addressed here.

  5. Focal characteristics of spheroidal geodesic lenses for integrated optical processing

    NASA Technical Reports Server (NTRS)

    Vahey, D. W.; Wood, V. E.

    1977-01-01

    Aspheric shaping of geodesic lenses in optical waveguides is suggested as a means for correcting spherical aberrations. The technique is complementary to the method of Spiller and Harper, in which geodesic lens aberrations are reduced by thickening the waveguiding layer in the lens region. The properties of a family of oblate-spheroidal lenses with no third-order spherical aberrations are described theoretically. Diffraction-limited performance over apertures up to one-half the full lens aperture is predicted for lenses with true f/numbers (focal length divided by useful aperture) in the range 2-12. By combining spheroidal-shaping and mode-index correction techniques, geodesic lenses free from both third- and fifth-order aberrations can be designed. These lenses show diffraction-limited performance over apertures of a centimeter or more when true f/numbers are in the range 1.5-9.5.

  6. Large-aperture ultra-long focal length measurement and its system by laser confocal techniques

    NASA Astrophysics Data System (ADS)

    Li, Zhigang; Qiu, Lirong; Zhao, Weiqian; Guo, Yongkui; Yuan, Quan

    2015-09-01

    A new laser confocal ultralong focal length measurement method (LCFM) is proposed with the capability to self-calibrate the reference lens (RL) focal length and the axial space between the test lens and the RL. Using the property that the focus of a laser confocal ultralong focal length measurement system (LCFS) precisely corresponds to the peak point of the confocal axial intensity curve, the proposed LCFM measures the RL focal length f\\text{R}\\prime by precisely identifying the positions of the focus and the last surface of the RL, measures the axial space d0 between the RL and the test ultra-long focal-length lens (UFL) by identifying the last surface of the RL and the vertex of the UFL last surface, measures the variation l in focus position of the LCFS with and without the test UFL, and then calculates the UFL focal length f\\text{T}\\prime using the above-measured f\\text{R}\\prime , d0, and l. Furthermore, the LCFM uses conic fitting, which obviously enhances the measurement accuracy by reducing the influences of random disturbances. In addition, an LCFS based on the proposed method is developed for large aperture lens. The experimental results indicate that the relative uncertainty is less than 0.015% for the test UFL, which has an aperture of 610?mm and a focal length of 31?000?mm. Compared with existing methods, the LCFM utilizes a concise structure and has good stability, making it especially suitable for practical engineering applications.

  7. Measurement of the effective focal shift in an optical trap

    NASA Astrophysics Data System (ADS)

    Neuman, Keir C.; Abbondanzieri, Elio A.; Block, Steven M.

    2005-06-01

    The focus of an oil-immersion microscope objective is shifted because of the refractive-index mismatch between the cover glass and the aqueous sample. We present a procedure with which to determine the focal shift by use of an inverted microscope equipped with optical tweezers. As the position of the sample chamber is scanned vertically, we measure the axial displacement of an optically trapped bead; the relative motion of the bead with respect to the surface supplies the effective focal shift. Measurements of this quantity deviate from electromagnetic calculations of the focal shift, a discrepancy attributable to the depth-dependent decrease in axial trap stiffness that arises from spherical aberration.

  8. Bioluminescence microscopy using a short focal-length imaging lens

    PubMed Central

    Ogoh, K; Akiyoshi, R; May-Maw-Thet; Sugiyama, T; Dosaka, S; Hatta-Ohashi, Y; Suzuki, H

    2014-01-01

    Bioluminescence from cells is so dim that bioluminescence microscopy is performed using an ultra low-light imaging camera. Although the image sensor of such cameras has been greatly improved over time, such improvements have not been made commercially available for microscopes until now. Here, we customized the optical system of a microscope for bioluminescence imaging. As a result, bioluminescence images of cells could be captured with a conventional objective lens and colour imaging camera. As bioluminescence microscopy requires no excitation light, it lacks the photo-toxicity associated with fluorescence imaging and permits the long-term, nonlethal observation of living cells. Thus, bioluminescence microscopy would be a powerful tool in cellular biology that complements fluorescence microscopy. PMID:24386879

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

    NASA Astrophysics Data System (ADS)

    Lin, Chih-Wei; Shaw, Dein

    2009-07-01

    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.

  10. Calibration for the errors resulted from aberration in long focal length measurement

    NASA Astrophysics Data System (ADS)

    Yao, Jiang; Luo, Jia; He, Fan; Bai, Jian; Wang, Kaiwei; Hou, Xiyun; Hou, Changlun

    2014-09-01

    In this paper, a high-accuracy calibration method for errors resulted from aberration in long focal length measurement, is presented. Generally, Gaussian Equation is used for calculation without consideration of the errors caused by aberration. However, the errors are the key factor affecting the accuracy in the measurement system of a large aperture and long focal length lens. We creatively introduce an effective way to calibrate the errors, with detailed analysis of the long focal length measurement based on divergent light and Talbot interferometry. Aberration errors are simulated by Zemax. Then, we achieve auto-correction with the help of Visual C++ software and the experimental results reveal that the relative accuracy is better than 0.01%.By comparing modified values with experimental results obtained in knife-edge testing measurement, the proposed method is proved to be highly effective and reliable.

  11. Optical system design for the aerial camera with dual band, common optical path, long focal, oblique view and focusing

    NASA Astrophysics Data System (ADS)

    He, Yulan; Xiao, Xiangguo; Li, Yuan; Shao, Xinzheng; Wang, Nanxi; Qiang, Hua; Lu, Feng

    2015-10-01

    A visible, MWIR, long focal, oblique view and focusing optical system of aerial camera is described, and in this paper we design an innovative optical system with common optical path and catadioptics configuration. The focal length of this optical system is 1.45m in the visible waveband (0.7~0.9μm,) and 0.61m in MWIR waveband (3.7~4.8μm), and the oblique view scanning range is within 20km~100km. To meet the requirements for the sharp imaging quality under the circumstances of high altitude environment and real time variable range, this aerial camera is focused by making back cutoff length longer to add a mirror, then MTF of optical system is all above 0.4 in Nyquest frequency.

  12. Focal Plane Alignment Utilizing Optical CMM

    NASA Technical Reports Server (NTRS)

    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

    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..

  13. Broadband reflective metasurface for focusing underwater ultrasonic waves with linearly tunable focal length

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoxiao; Xia, Xiangxiang; Tian, Jingxuan; Liu, Zhengyou; Wen, Weijia

    2016-04-01

    We report a metasurface for focusing reflected ultrasonic waves over a wide frequency band of 0.45-0.55 MHz. The broadband focusing effect of the reflective metasurface is studied numerically and then confirmed experimentally using near-field scanning techniques. The focusing mechanism can be attributed to the hyperboloidal reflection phase profile imposed by different depths of concentric grooves on the metasurface. In particular, the focal lengths of the reflective metasurface are extracted from simulations and experiments, and both exhibit good linear dependence on frequency over the considered frequency band. The proposed broadband reflective metasurface with tunable focal length has potential applications in the broad field of ultrasonics, such as ultrasonic tomographic imaging, high intensity focused ultrasound treatment, etc.

  14. Focal length measurement of a microlens-array by grating shearing interferometry.

    PubMed

    Zhu, Xianchang; Hu, Song; Zhao, Lixin

    2014-10-10

    Based on grating shearing interferometry, a simple technique is introduced for focal length measurements of a microlens-array (MLA). The measurement system is composed of a He-Ne laser, condenser, collimator, the MLA under testing, a Ronchi grating, and CCD sensor. The plane wavefront from the collimator is transformed to a spherical wavefront by the MLA, while the curvature center is at the focus. Interference stripes appear at the overlap between the zero-order and first-order diffractive patterns of the grating and are detected by the CCD sensor. By analyzing the period change of stripes, the focal length is determined after the defocus of the grating is calculated. To validate the feasibility, an experiment is performed. The measurement uncertainty is discussed and measurement accuracy was determined to be 2%. PMID:25322367

  15. Optical design of the Post Focal Relay of MAORY

    NASA Astrophysics Data System (ADS)

    Lombini, M.; Diolaiti, E.

    The Multi Conjugate Adaptive Optics Relay (MAORY) for the European Extremely Large Telescope shall re-image the telescope focal plane for the client instruments installed on two exit ports. By means of natural and artificial (laser) reference sources for wavefront sensing, and of deformable mirrors for wavefront correction, MAORY shall be able to compensate the wavefront disturbances affecting the scientific observations, achieving high Strehl ratio and high sky coverage. The optical interfaces to the client instruments must replicate the telescope one while the volume allocation on the Nasmyth platform is under definition at the moment of this writing. We show the latest version of the optical design that matches the current requests and its optical performance. The laser guide stars channel, separated from the science path by means of a dichroic beam-splitter, is also presented.

  16. Multiple-Path-Length Optical Absorbance Cell

    NASA Technical Reports Server (NTRS)

    2001-01-01

    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,

  17. Calibration of Hubble Space Telescope Focal-Length Variations Using the Embedding Technique

    NASA Astrophysics Data System (ADS)

    Barford, Lee; Tufillaro, Nicholas; Usikov, Daniel; Marochnik, Leonid; McCutcheon, Robert

    2001-06-01

    A modeling method that allows one to rapidly build data-driven models of nonlinear components is discussed. The models are constructed from input/output time domain data and their 'embeddings'. The notion of models built from embedded data is described in the Taken's Embedding Theorem and has been extensively explored for modeling systems in the physics literature. The authors from Agilent Laboratories are developing practical methods to extend these results to non-autonomous systems by creating tools that allow engineers to rapidly build models for driven nonlinear components. These models can be used in simulation, process control, diagnostics, and sensor calibration. Using these methods a 'black-box' data-driven model is generated to calibrate Hubble Space Telescope (HST) focal-length changes on a 5-minute time grid for the period from 1995-1999. These models are built using a program, CHAOS, developed by Agilent Laboratories. The data-driven model predicts the focus for the measured points about 36% better than the Full-Temperature Model (FTM) constructed from a detailed knowledge of the telescope structure. As demonstrated by this HST focal-length calibration, data-driven models, such as those generated with the CHAOS package, have great potential for application to a wide spectrum of HST/Next Generation Space Telescope (NGST) calibration problems. In particular, for sensor calibration applications, blackbox nonlinear models can be generated rapidly, which have similar or better performance than models built from a detailed understanding of the system structure.

  18. Simultaneous measurement of focal length and index of refraction of a microlens using a compound microscope

    NASA Astrophysics Data System (ADS)

    Chollet, Franck; Ashraf, Mohammed

    2009-10-01

    The fabrication of microlenses has spurred a lot of interest and resulted in multiple techniques of fabrication in the past decade. However the metrology of these lenses has received less attention and remains a complex and time-consuming task that does not allow frequent control during development and manufacturing. We propose a simple technique based on a standard compound microscope that would allow measuring the focal length of a plano-convex lens and at the same time obtain a measure of the index of refraction of the lens material. The method relies on observing the different images of an object placed in the illumination path of the microscope. Among these images, some are created by the light going through the lens and others by its reflection on the surface. We show that with the image distance and size it is possible to retrieve the focal length and the average index of refraction of the lens material in the case of quasi-spherical lenses. The accuracy obtained by the technique is better than a few per cent and its cost is negligible as it only uses existing equipment.

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

    NASA Astrophysics Data System (ADS)

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

    2007-07-01

    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.

  20. Tunable liquid crystal lens array by encapsulation with a photo-reactive polymer for short focal length

    NASA Astrophysics Data System (ADS)

    Kim, Se-Um; Lee, Sanghun; Na, Jun-Hee; Lee, Sin-Doo

    2014-02-01

    We demonstrated an electrically tunable liquid crystal (LC) lens array with a short focal length by self-encapsulation with a polymer layer of photo-reactive mesogens (RMs). The underlying concept relies primarily on the encapsulation of the LC with a thin curvilinear polymer layer in contact with air for the reduction of the focal length. The polymer-encapsulated (PE)-LC lens array was produced on a patterned substrate by selective wetting inscription through the phase separation of the LC and the RMs. In the field-off state, the focal length of the PE-LC lens was measured to be about 3 mm which is shorter than a conventional case by a factor of three (about 9 mm). The wettability inscription by ultraviolet light enables to build up any size of the LC lens in array over large-area without using a wet-chemical etching process for flexible optoelectronic and photonic applications.

  1. Shape distortions of infrared focal plane array and optical readout

    NASA Astrophysics Data System (ADS)

    Liu, Ming; Zhao, Yuejin; Liu, Xiaohua; Yu, Xiaomei; Wang, Xin; Li, Ting

    2008-02-01

    The optical readout principle of focal plane array (FPA) infrared image system based on bi-material cantilever and micro mirror structure is introduced briefly. And the ideal angular sensitivity of the optical readout is about 1.5e-6 radian. While there are two kinds of unexpected shape distortion of FPA, reflecting direction dispersion and reflecting surface bending. With that the distortion limits for perfect detection are calculated. Then the reflecting surface bending effect is analyzed in detail. It shows that the sensitivity may lie on not only the cliff-edge optical filtering effect, which is well known already, but also the light spot moving effect, if the reflecting surface is bended. This effect means that each micro mirror's imaging area on the image plane may not be illuminated equivalently but have a light spot within its boundary if it is bended. And the spot's position changes along with the reflect angle of the mirror. Then the experiment results are given to support this thought. Though there are still obvious shape distortions exist, we obtained IR images of objects about 500K.

  2. Optical Arc-Length Sensor For TIG Welding

    NASA Technical Reports Server (NTRS)

    Smith, Matthew A.

    1990-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Reinert, Jason

    2004-01-01

    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

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

    NASA Astrophysics Data System (ADS)

    Gandhi, Suketu R.; Bernstein, Richard B.

    1986-06-01

    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.

  5. FOCAL PLANE WAVEFRONT SENSING USING RESIDUAL ADAPTIVE OPTICS SPECKLES

    SciTech Connect

    Codona, Johanan L.; Kenworthy, Matthew

    2013-04-20

    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.

  6. CdTe Focal Plane Detector for Hard X-Ray Focusing Optics

    NASA Technical Reports Server (NTRS)

    Seller, Paul; Wilson, Matthew D.; Veale, Matthew C.; Schneider, Andreas; Gaskin, Jessica; Wilson-Hodge, Colleen; Christe, Steven; Shih, Albert Y.; Inglis, Andrew; Panessa, Marco

    2015-01-01

    The demand for higher resolution x-ray optics (a few arcseconds or better) in the areas of astrophysics and solar science has, in turn, driven the development of complementary detectors. These detectors should have fine pixels, necessary to appropriately oversample the optics at a given focal length, and an energy response also matched to that of the optics. Rutherford Appleton Laboratory have developed a 3-side buttable, 20 millimeter x 20 millimeter CdTe-based detector with 250 micrometer square pixels (80 x 80 pixels) which achieves 1 kiloelectronvolt FWHM (Full-Width Half-Maximum) @ 60 kiloelectronvolts and gives full spectroscopy between 5 kiloelectronvolts and 200 kiloelectronvolts. An added advantage of these detectors is that they have a full-frame readout rate of 10 kilohertz. Working with NASA Goddard Space Flight Center and Marshall Space Flight Center, 4 of these 1 millimeter-thick CdTe detectors are tiled into a 2 x 2 array for use at the focal plane of a balloon-borne hard-x-ray telescope, and a similar configuration could be suitable for astrophysics and solar space-based missions. This effort encompasses the fabrication and testing of flight-suitable front-end electronics and calibration of the assembled detector arrays. We explain the operation of the pixelated ASIC readout and measurements, front-end electronics development, preliminary X-ray imaging and spectral performance, and plans for full calibration of the detector assemblies. Work done in conjunction with the NASA Centers is funded through the NASA Science Mission Directorate Astrophysics Research and Analysis Program.

  7. CdTe focal plane detector for hard x-ray focusing optics

    NASA Astrophysics Data System (ADS)

    Seller, Paul; Wilson, Matthew D.; Veale, Matthew C.; Schneider, Andreas; Gaskin, Jessica; Wilson-Hodge, Colleen; Christe, Steven; Shih, Albert Y.; Gregory, Kyle; Inglis, Andrew; Panessa, Marco

    2015-08-01

    The demand for higher resolution x-ray optics (a few arcseconds or better) in the areas of astrophysics and solar science has, in turn, driven the development of complementary detectors. These detectors should have fine pixels, necessary to appropriately oversample the optics at a given focal length, and an energy response also matched to that of the optics. Rutherford Appleton Laboratory have developed a 3-side buttable, 20 mm x 20 mm CdTe-based detector with 250 μm square pixels (80x80 pixels) which achieves 1 keV FWHM @ 60 keV and gives full spectroscopy between 5 keV and 200 keV. An added advantage of these detectors is that they have a full-frame readout rate of 10 kHz. Working with NASA Goddard Space Flight Center and Marshall Space Flight Center, 4 of these 1mm-thick CdTe detectors are tiled into a 2x2 array for use at the focal plane of a balloon-borne hard-x-ray telescope, and a similar configuration could be suitable for astrophysics and solar space-based missions. This effort encompasses the fabrication and testing of flightsuitable front-end electronics and calibration of the assembled detector arrays. We explain the operation of the pixelated ASIC readout and measurements, front-end electronics development, preliminary X-ray imaging and spectral performance, and plans for full calibration of the detector assemblies. Work done in conjunction with the NASA Centers is funded through the NASA Science Mission Directorate Astrophysics Research and Analysis Program.

  8. The optical design of relay optics for heterodyne millimeter wave focal plane arrays.

    NASA Astrophysics Data System (ADS)

    Olmi, L.

    2000-03-01

    Since the use of focal plane arrays on millimeter and sub-millimeter telescopes has become more and more important, it has also become evident that there is a need of optimized auxiliary optics that would efficiently couple the telescope to the receiver over large fields of view (i.e., ⪆5-10 beams). In this work the author systematically analyzes several relay optics configurations for heterodyne focal plane arrays, all based on the "Gaussian beam telescope" concept. Because, in examining the image performance of auxiliary optics design at millimeter wavelengths one cannot follow the usual image quality criteria, the author analyzes the designs using both the Strehl ratio and the coupling efficiency to evaluate the quality of the off-axis wavefronts and the loss in power coupling with the horn. Coupling efficiency and Strehl ratio cannot be included in the optimization procedures of commercial optical modelling packages and the author thus describes how to optimize the design using a customized algorithm. The author shows that the minimization of the appropriate error function can reduce the anamorphism of the exit pupil and reduce the loss in the horn coupling.

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

    PubMed

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

    2013-02-11

    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

  10. Precise annealing of focal plane arrays for optical detection

    SciTech Connect

    Bender, Daniel A.

    2015-09-22

    Precise annealing of identified defective regions of a Focal Plane Array ("FPA") (e.g., exclusive of non-defective regions of the FPA) facilitates removal of defects from an FPA that has been hybridized and/or packaged with readout electronics. Radiation is optionally applied under operating conditions, such as under cryogenic temperatures, such that performance of an FPA can be evaluated before, during, and after annealing without requiring thermal cycling.

  11. Optical sensitivity non-uniformity analysis and optimization of a tilt optical readout focal plane array

    NASA Astrophysics Data System (ADS)

    Fu, Jianyu; Shang, Haiping; Shi, Haitao; Li, Zhigang; Ou, Yi; Chen, Dapeng; Zhang, Qingchuan

    2016-02-01

    An optical readout focal plane array (FPA) usually has a differently tilted reflector/absorber at the initial state due to the micromachining technique. The angular deviation of the reflector/absorber has a strong impact on the optical sensitivity non-uniformity, which is a key factor which affects the imaging uniformity. In this study, a theoretical analysis has been developed, and it is found that the stress matching in SiO2-Aluminum (Al) bilayer leg could make a contribution towards reducing the optical sensitivity non-uniformity. Ion implantation of phosphorus (P) has been utilized to control the stress in SiO2 film. By controlling the implantation energy and dose, the stress and stress stability are modified. The optical readout FPA has been successfully fabricated with the stress-control technique based on P+ implantation. It is demonstrated that the gray response non-uniformity of optical readout FPA has decreased from 25.69% to 10.7%.

  12. Astrocytes phagocytose focal dystrophies from shortening myelin segments in the optic nerve of Xenopus laevis at metamorphosis

    PubMed Central

    Mills, Elizabeth A.; Davis, Chung-ha O.; Bushong, Eric A.; Boassa, Daniela; Kim, Keun-Young; Ellisman, Mark H.; Marsh-Armstrong, Nicholas

    2015-01-01

    Oligodendrocytes can adapt to increases in axon diameter through the addition of membrane wraps to myelin segments. Here, we report that myelin segments can also decrease their length in response to optic nerve (ON) shortening during Xenopus laevis metamorphic remodeling. EM-based analyses revealed that myelin segment shortening is accomplished by focal myelin-axon detachments and protrusions from otherwise intact myelin segments. Astrocyte processes remove these focal myelin dystrophies using known phagocytic machinery, including the opsonin milk fat globule-EGF factor 8 (Mfge8) and the downstream effector ras-related C3 botulinum toxin substrate 1 (Rac1). By the end of metamorphic nerve shortening, one-quarter of all myelin in the ON is enwrapped or internalized by astrocytes. As opposed to the removal of degenerating myelin by macrophages, which is usually associated with axonal pathologies, astrocytes selectively remove large amounts of myelin without damaging axons during this developmental remodeling event. PMID:26240339

  13. Experimental characterization, evaluation, and diagnosis of advanced hybrid infrared focal plane array electro-optical performance

    NASA Astrophysics Data System (ADS)

    Lomheim, Terrence S.; Schumann, Lee W.; Kohn, Stanley E.

    1998-07-01

    High performance scanning time-delay-and-integration and staring hybrid focal plane devices with very large formats, small pixel sizes, formidable frame and line rates, on-chip digital programmability, and high dynamic ranges, are being developed for a myriad of defense, civil, and commercial applications that span the spectral range from shortwave infrared (SWIR) to longwave infrared (LWIR). An essential part in the development of such new advanced hybrid infrared focal planes is empirical validation of their electro-optical (EO) performance. Many high-reliability, high-performance applications demand stringent and near flawless EO performance over a wide variety of operating conditions and environments. Verification of focal plane performance compliance over this wide range of parametric conditions requires the development and use of accurate, flexible, and statistically complete test methods and associated equipment. In this paper we review typical focal plane requirements, the ensuing measurement requirements (quantity, accuracy, repeatability, etc.), test methodologies, test equipment requirements, electronics and computer-based data acquisition requirements, statistical data analysis and display requirements, and associated issues. We also discuss special test requirements for verifying the performance of panchromatic thermal and multispectral imaging focal planes where characterization of dynamic modulation transfer function (MTF), and point-image response and optical overload is generally required. We briefly overview focal plane radiation testing. We conclude with a discussion of the technical challenges of characterizing future advanced hybrid focal plane testing where it is anticipated that analog-to- digital conversion will be included directly on focal plane devices, thus creating the scenario of 'photons-in-to-bits- out' within the focal plane itself.

  14. Measurement of Trap Length for an Optical Trap

    NASA Technical Reports Server (NTRS)

    Wrbanek, Susan Y.

    2009-01-01

    The trap length along the beam axis for an optical trap formed with an upright, oil-immersion microscope was measured. The goals for this effort were twofold. It was deemed useful to understand the depth to which an optical trap can reach for purposes of developing a tool to assist in the fabrication of miniature devices. Additionally, it was desired to know whether the measured trap length favored one or the other of two competing theories to model an optical trap. The approach was to trap a microsphere of known size and mass and raise it from its initial trap position. The microsphere was then dropped by blocking the laser beam for a pre-determined amount of time. Dropping the microsphere in a free-fall mode from various heights relative to the coverslip provides an estimate of how the trapping length changes with depth in water in a sample chamber on a microscope slide. While it was not possible to measure the trap length with sufficient precision to support any particular theory of optical trap formation, it was possible to find regions where the presence of physical boundaries influenced optical traps, and determine that the trap length, for the apparatus studied, is between 6 and 7 m. These results allow more precise control using optical micromanipulation to assemble miniature devices by providing information about the distance over which an optical trap is effective.

  15. Dynamic optical properties in graphene: Length versus velocity gauge

    SciTech Connect

    Dong, H. M.; Han, K.; Xu, W.

    2014-02-14

    The dynamic optical properties of graphene are theoretically investigated in both length gauge and velocity gauge in the presence of ultrafast optical radiation field. The two gauges present different results of dynamic photo-induced carriers and optical conductance due to distinct dependencies on electric field and non-resonant optical absorption, while the two gauges give identical results in the steady state time. It shows that the choice of gauge affects evidently the dynamic optical properties of graphene. The velocity gauge represents an outcome of a real physical experiment.

  16. Graded-index optical fiber tweezers with long manipulation length.

    PubMed

    Gong, Yuan; Huang, Wei; Liu, Qun-Feng; Wu, Yu; Rao, Yunjiang; Peng, Gang-Ding; Lang, Jinyi; Zhang, Ke

    2014-10-20

    Long manipulation length is critical for optical fiber tweezers to enhance the flexibility of non-contact trapping. In this paper a long manipulation distance of more than 40 μm is demonstrated experimentally by the graded-index fiber (GIF) tweezers, which is fabricated by chemically etching a GIF taper with a large cone angle of 58°. The long manipulation distance is obtained by introducing an air cavity between the lead-in single mode fiber and the GIF as well as by adjusting the laser power in the existence of a constant background flow. The influence of the cavity length and the GIF length on the light distribution and the focusing length of the GIF taper is investigated numerically, which is helpful for optimizing the parameters to perform stable optical trapping. This kind of optical fiber tweezers has advantages including low-cost, easy-to-fabricate and easy-to-use. PMID:25401560

  17. Focal plane optics in far-infrared and submillimeter astronomy

    NASA Technical Reports Server (NTRS)

    Hildebrand, R. H.

    1985-01-01

    The construction of airborne observatories, high mountain-top observatories, and space observatories designed especially for infrared and submillimeter astronomy has opened fields of research requiring new optical techniques. A typical far-IR photometric study involves measurement of a continuum spectrum in several passbands between approx 30 microns and 1000 microns and diffraction-limited mapping of the source. At these wavelengths, diffraction effects strongly influence the design of the field optics systems which couple the incoming flux to the radiation sensors (cold bolometers). The Airy diffraction disk for a typical telescope at submillimeter wavelengths approx 100 microns-1000 microns is many millimeters in diameter; the size of the field stop must be comparable. The dilute radiation at the stop is fed through a Winston nonimaging concentrator to a small cavity containing the bolometer. The purpose of this paper is to review the principles and techniques of infrared field optics systems, including spectral filters, concentrators, cavities, and bolometers (as optical elements), with emphasis on photometric systems for wavelengths longer than 60 microns.

  18. Focal plane optics in far-infrared and submillimeter astronomy

    NASA Technical Reports Server (NTRS)

    Hildebrand, R. H.

    1986-01-01

    The construction of airborne observatories, high mountain-top observatories, and space observatories designed especially for infrared and submillimeter astronomy has opened fields of research requiring new optical techniques. A typical far-IR photometric study involves measurement of a continuum spectrum in several passbands between approx 30 microns and 1000 microns and diffraction-limited mapping of the source. At these wavelengths, diffraction effects strongly influence the design of the field optics systems which couple the incoming flux to the radiation sensors (cold bolometers). The Airy diffraction disk for a typical telescope at submillimeter wavelengths approx 100 microns-1000 microns is many millimeters in diameter; the size of the field stop must be comparable. The dilute radiation at the stop is fed through a Winston nonimaging concentrator to a small cavity containing the bolometer. The purpose of this paper is to review the principles and techniques of infrared field optics systems, including spectral filters, concentrators, cavities, and bolometers (as optical elements), with emphasis on photometric systems for wavelengths longer than 60 microns.

  19. Smart polymers containing substituted coumarin side groups enable photo-induced tuning of focal length of intraocular lenses

    NASA Astrophysics Data System (ADS)

    Schraub, Martin; Hampp, Norbert

    2011-03-01

    Over the past 100 years medicine evolved continuously, which can clearly be seen in the rising average of life expectancy. But as the population becomes older and older the number of old age diseases increases. Cataract is such an old age disease and worldwide the number one reason for blindness. Implantation of IOL's is up-to-date the only possibility to restore vision. In this study we present novel polymers containing derivatized coumarins in the side chains as smart materials for IOL manufacturing. These materials enable tuning of the focal length of an already implanted IOL by 2 diopters via photo induced dimerization and cleavage of the coumarin side groups respectively. The advantages of these new polymers are increased dimerization rates while decreasing the energy dose needed for photochemical dimerization of the coumarin side groups.

  20. Optical path-length matrix method for estimating skin spectrum

    NASA Astrophysics Data System (ADS)

    Yamamoto, Satoshi; Fujiwara, Izumi; Yamauchi, Midori; Tsumura, Norimichi; Ogawa-Ochiai, Keiko

    2012-11-01

    In this article, we propose a new methodthe optical path-length matrix method (OPLM)as a faster alternative to the Monte Carlo for multi-layered media (MCML), which is often used to simulate the skin spectrum. Theoretically, peripheral oxygen saturation can be estimated by iterating MCML, but it is not a realistic strategy because it requires huge computation time. The optical path-length matrix is obtained as the probabilistic density histograms of the optical path length in skin using MCML, and once the matrix is obtained, skin spectral reflectance can be calculated by accumulating all combinations of elements in the matrix and by setting an absorption coefficient based on the Beer-Lambert law. The computational time of OPLM was approximately 26,000 times faster than that of MCML.

  1. Mid-wave infrared metasurface microlensed focal plane array for optical crosstalk suppression.

    PubMed

    Akın, Onur; Demir, Hilmi Volkan

    2015-10-19

    Spatial crosstalk is one of the fundamental drawbacks of diminishing pixel size in mid-wave infrared focal plane arrays (IR-FPAs). We proposed an IR-FPA using the concept of optical phase discontinuities for substantial optical crosstalk suppression. This IR-FPA consists of asymmetrically tailored V-shaped optical antennas. Full-wave simulations confirmed major improvements in narrowing the intensity distribution of incident light beam by over 30-folds and concentrating these distributions in the central pixel of IR-FPA by achieving optical crosstalks of <1%. PMID:26480363

  2. On the use of clessidra prism arrays in long-focal-length X-ray focusing.

    PubMed

    Jark, Werner; Matteucci, Marco; Menk, Ralf Hendrik

    2008-07-01

    Clessidra (hour-glass) X-ray lenses have an overall shape of an old hour glass, in which two opposing larger triangular prisms are formed of smaller identical prisms or prism-like objects. In these lenses, absorbing and otherwise optically inactive material was removed with a material-removal strategy similar to that used by Fresnel in the lighthouse lens construction. It is verified that when the single prism rows are incoherently illuminated they can be operated as independent micro-lenses with coinciding image positions for efficient X-ray beam concentration. Experimental data for the line width and the refraction efficiency in one-dimensional focusing are consistent with the expectations. Imperfections in the structures produced by state-of-the-art deep X-ray lithography directed only 35% of the incident intensity away from the image and widened it by just 10% to 125 microm. An array of micro-lenses with easily feasible prism sizes is proposed as an efficient retrofit for the refocusing optics in an existing beamline, where it would provide seven-fold flux enhancement. PMID:18552435

  3. Test Bed For Control Of Optical-Path Lengths

    NASA Technical Reports Server (NTRS)

    O'Neal, Michael C.; Eldred, Daniel D.; Liu, Dankai; Redding, David C.

    1994-01-01

    Truss structure and ancillary equipment constitute test bed for experiments in methods of controlling lengths of optical paths under conditions of structural vibration and deformation. Accommodates both passive and active methods of control. Experimental control system reduces millimeter-level disturbances in optical path length to nanometers. Developed for control, alignment, and aiming of distributed optical systems on large flexible structures. Test bed includes tower 2.5 meters high with two horizontal arms extending at right angles from its top. Rigidly mounted on massive steel block providing measure of isolation from ground vibrations. Optical motion-compensation system similar to one described previously in NASA Tech Briefs enclosed in flexure-mounted frame, called "trolley," at end of longer horizontal arm.

  4. Measurement of the Length of an Optical Trap

    NASA Technical Reports Server (NTRS)

    Wrbanek, Susan Y.

    2010-01-01

    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.

  5. Double peacock eye optical element for extended focal depth imaging with ophthalmic applications.

    PubMed

    Romero, Lenny A; Millán, María S; Jaroszewicz, Zbigniew; Kolodziejczyk, Andrzej

    2012-04-01

    The aged human eye is commonly affected by presbyopia, and therefore, it gradually loses its capability to form images of objects placed at different distances. Extended depth of focus (EDOF) imaging elements can overcome this inability, despite the introduction of a certain amount of aberration. This paper evaluates the EDOF imaging performance of the so-called peacock eye phase diffractive element, which focuses an incident plane wave into a segment of the optical axis and explores the element's potential use for ophthalmic presbyopia compensation optics. Two designs of the element are analyzed: the single peacock eye, which produces one focal segment along the axis, and the double peacock eye, which is a spatially multiplexed element that produces two focal segments with partial overlapping along the axis. The performances of the peacock eye elements are compared with those of multifocal lenses through numerical simulations as well as optical experiments in the image space. The results demonstrate that the peacock eye elements form sharper images along the focal segment than the multifocal lenses and, therefore, are more suitable for presbyopia compensation. The extreme points of the depth of field in the object space, which represent the remote and the near object points, have been experimentally obtained for both the single and the double peacock eye optical elements. The double peacock eye element has better imaging quality for relatively short and intermediate distances than the single peacock eye, whereas the latter seems better for far distance vision. PMID:22559691

  6. Ultra-low-loss tapered optical fibers with minimal lengths.

    PubMed

    Nagai, Ryutaro; Aoki, Takao

    2014-11-17

    We design and fabricate ultra-low-loss tapered optical fibers (TOFs) with minimal lengths. We first optimize variations of the torch scan length using the flame-brush method for fabricating TOFs with taper angles that satisfy the adiabaticity criteria. We accordingly fabricate TOFs with optimal shapes and compare their transmission to TOFs with a constant taper angle and TOFs with an exponential shape. The highest transmission measured for TOFs with an optimal shape is in excess of 99.7% with a total TOF length of only 23 mm, whereas TOFs with a constant taper angle of 2 mrad reach 99.6% transmission for a 63 mm TOF length. PMID:25402084

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

    PubMed

    Matjasec, Ziga; Campelj, Stanislav; Donlagic, Denis

    2013-05-20

    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

  8. Phase Length Optical Phase-Locked-Loop Sensor

    NASA Technical Reports Server (NTRS)

    Heyman, Joseph S. (Inventor)

    1988-01-01

    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.

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

    PubMed

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

    2012-05-21

    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 κ · β (where κ is the trap stiffness and 1/β 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

  10. Focal-Plane Imaging of Crossed Beams in Nonlinear Optics Experiments

    NASA Technical Reports Server (NTRS)

    Bivolaru, Daniel; Herring, G. C.

    2007-01-01

    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.

  11. In Vivo Mapping of Cortical Columnar Networks in the Monkey with Focal Electrical and Optical Stimulation

    PubMed Central

    Roe, Anna Wang; Chernov, Mykyta M.; Friedman, Robert M.; Chen, Gang

    2015-01-01

    There are currently largescale efforts to understand the brain as a connection machine. However, there has been little emphasis on understanding connection patterns between functionally specific cortical columns. Here, we review development and application of focal electrical and optical stimulation methods combined with optical imaging and fMRI mapping in the non-human primate. These new approaches, when applied systematically on a large scale, will elucidate functionally specific intra-areal and inter-areal network connection patterns. Such functionally specific network data can provide accurate views of brain network topology. PMID:26635539

  12. Talbot multi-focal holographic fluorescence endoscopy for optically sectioned imaging.

    PubMed

    Lin, Chen Yen; Lin, Wei-Tang; Chen, Hsi-Hsun; Wong, Jau-Min; Singh, Vijay Raj; Luo, Yuan

    2016-01-15

    A wide-field multi-plane endoscopic system incorporating multiplexed volume holographic gratings and Talbot illumination to simultaneously acquire optically sectioned fluorescence images of tissue structures from different depths is presented. The proposed endoscopic system is configured such that multiple Talbot-illumination planes occur inside a volumetric sample and serve as the input focal planes for the subsequent multiplexed volume holographic imaging gratings. We describe the design, implementation, and experimental data demonstrating this endoscopic system's ability to obtain optically sectioned multi-plane fluorescent images of tissue samples in wide-field fashion without scanning in lateral and axial directions. PMID:26766710

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

    NASA Technical Reports Server (NTRS)

    Thurlow, P. E.

    1981-01-01

    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.

  14. Type II superlattice infrared focal plane arrays: Optical, electrical, and mid-wave infrared imaging characterization.

    NASA Astrophysics Data System (ADS)

    Little, John; Svensson, Stefan; Goldberg, Arnie; Kennerly, Steve; Olver, Kim; Hongsmatip, Trirat; Winn, Michael; Uppal, Parvez

    2006-03-01

    We have studied the infrared optical and temperature dependent electrical properties of 320 x 256 arrays of GaSb/InAs type II superlattice infrared photodiodes. Good agreement between single-pixel and focal plane array measurements of the photon-to- electron/hole conversion efficiency was obtained, and the infrared absorption coefficient extracted from these measurements was found to be comparable to that of HgCdTe with the same bandgap as the type II superlattice. Temperature and voltage dependent dark current measurements and the voltage dependent photocurrent generated by a 300 K background scene were described well using a semi-empirical model of the photodiode. We will show high-quality images obtained from the mid-infrared focal plane array operating at 78 K.

  15. Optical fiber length measurement by external phase modulation type optical heterodyne reflectometry

    SciTech Connect

    Kimura, T.; Sawada, I.; Sasaki, N.; Noda, K. )

    1989-04-01

    A method for measuring optical fiber length is proposed and demonstrated experimentally with external phase modulation optical heterodyne reflectometry using a He-Ne laser as a light source. The system offers a simple length measuring method with satisfactory resolution. The reflected waves from fiber faults, if any, also can be detected by this method by observing two signals which occur at fault points and the fiber end.

  16. Parallel optical-path-length-shifting digital holography.

    PubMed

    Awatsuji, Yasuhiro; Koyama, Takamasa; Tahara, Tatsuki; Ito, Kenichi; Shimozato, Yuki; Kaneko, Atsushi; Nishio, Kenzo; Ura, Shogo; Kubota, Toshihiro; Matoba, Osamu

    2009-12-01

    The authors propose an optical-path-length-shifting digital holography as a technique capable of single-shot recording of three-dimensional information of objects. With a single image sensor, the proposed technique can simultaneously record all of the holograms required for the in-line digital holography that reconstruct the image of an object from two intensity measurements at different planes. The technique can be optically implemented by using an optical-path-length-shifting array device located in the common path of the reference and object waves. The array device has periodic structure of two-step optical-path difference. The configuration of the array device of the proposed technique is simpler than the phase-shifting array device required for parallel phase-shifting digital holographies. Therefore, the optical system of the proposed technique is more suitable for the realization of a single-shot in-line digital holography system that removes the conjugate image from the reconstructed image. The authors conducted both a numerical simulation and a preliminary experiment of the proposed technique. The reconstructed images were quantitatively evaluated by using root mean squared error. In comparison to single-shot digital holography using the Fresnel transform alone, with the proposed technique the root mean squared errors of the technique were reduced to less than 1/6 in amplitude and 1/3 in phase. Also the results of the simulation and experiment agreed well with the images of an object. Thus the effectiveness of the proposed technique is verified. PMID:19956287

  17. Measurement and compensation of laser-induced wavefront deformations and focal shifts in near IR optics.

    PubMed

    Stubenvoll, Martin; Schäfer, Bernd; Mann, Klaus

    2014-10-20

    We demonstrate the feasibility of passive compensation of the thermal lens effect in fused silica optics, placing suitable optical materials with negative dn/dT in the beam path of a high power near IR fiber laser. Following a brief overview of the involved mechanisms, photo-thermal absorption measurements with a Hartmann-Shack sensor are described, from which coefficients for surface/coating and bulk absorption in various materials are determined. Based on comprehensive knowledge of the 2D wavefront deformations resulting from absorption, passive compensation of thermally induced aberrations in complex optical systems is possible, as illustrated for an F-Theta objective. By means of caustic measurements during high-power operation we are able to demonstrate a 60% reduction of the focal shift in F-Theta lenses through passive compensation. PMID:25401572

  18. Optical scattering lengths in large liquid-scintillator neutrino detectors

    SciTech Connect

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

    2010-05-15

    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.

  19. Three-dimensional imaging system by using a low-voltage-driving LC lens with a tunable focal length

    NASA Astrophysics Data System (ADS)

    Kawamura, Marenori; Ishikuro, Shunsuke

    2015-09-01

    We develop a three-dimensional imaging system by using a low-voltage-driving liquid crystal (LC) lens for determining depth mapping properties of three-dimensional objects. The sequential photo images without the magnification and reduction are taken by electrically controlling a focal plane along a depth direction with no mechanical movements. The depth mapping properties can be obtained by processing an image digital filter from the different focal images.

  20. Focal Activation of Cells by Plasmon Resonance Assisted Optical Injection of Signaling Molecules

    PubMed Central

    2015-01-01

    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 (Ca2+) release from intracellular stores. Upon optical injection of IP3 or AdA at doses above the activation threshold, we observed increases in cytosolic Ca2+ concentration within the injected cell initiating the propagation of a Ca2+ wave throughout nearby cells. As confirmed by octanol-induced inhibition, the intercellular Ca2+ 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

  1. Holographic illumination in optical readout focal plane array infrared imaging system.

    PubMed

    Liu, Ming; Zhao, Yuejin; Dong, Liquan; Yu, Xiaomei; Liu, Xiaohua; Hui, Mei; You, Jianfeng; Yi, Yuliang

    2009-11-15

    An IR imaging system based on a microelectromechanical system (MEMS) microcantilever is uncooled, low-cost, and more reliable than traditional systems. However, it is difficult to avoid unwanted shape distortions in fabrication, which can degrade image quality in many ways, so we use holography to compensate for these shape distortions in an optical readout focal plane array (FPA) IR imaging system. The experiment shows that it is a feasible way to improve system performance, especially when it is too difficult to perfect the techniques of an FPA fabrication. PMID:19927206

  2. Remote focal scanning optical projection tomography with an electrically tunable lens

    PubMed Central

    Chen, Lingling; Kumar, Sunil; Kelly, Douglas; Andrews, Natalie; Dallman, Margaret J.; French, Paul M. W.; McGinty, James

    2014-01-01

    We describe a remote focal scanning technique for optical projection tomography (OPT) implemented with an electrically tunable lens (ETL) that removes the need to scan the specimen or objective lens. Using a 4× objective lens the average spatial resolution is improved by ∼46% and the light collection efficiency by a factor of ∼6.76, thereby enabling increased acquisition speed and reduced light dose. This convenient implementation is particularly appropriate for lower magnifications and larger sample diameters where axial objective scanning would encounter problems with speed and stability. PMID:25360356

  3. Design and performance of a beam line with a 1 m focal length toroidal grating monochromator at the ACO storage ring

    NASA Astrophysics Data System (ADS)

    Gudat, W.; Kisker, E.; Rothberg, G. M.; Depautex, C.

    We describe a new beam line at the ACO storage ring for solid state photoelectron spectorscopy incorporating a 1 m focal length toroidal grating monochromator for the photon energy range 6 eV to 120 eV custom-built by Jobin-Yvon Instruments S.A. Test results for the TGM with laboratory line light sources are reported as well as performance data with synchrotron radiation.

  4. Measurement of optical modulation functions in sparsely sampled mosaic focal plane arrays

    NASA Technical Reports Server (NTRS)

    Young, J. B.; Thurlow, P. E.

    1982-01-01

    It is pointed out that the measurement of optical modulation functions for detectors in focal plane arrays may be somewhat more difficult under 'full-up' systems conditions as compared to ideal laboratory conditions. An idealized optical modulation test arrangement is considered along with a full-up scanned system involving an earth mapper in polar orbit. In testing the system in full-up condition, a problem arises with respect to the acquisition of knife edge response data. In order to overcome this problem, a preferred method is developed for obtaining KER data on a single scan. A special 'phased edge' reticle is developed for use in the test set-up. Attention is given to aspects of knife edge reconstruction.

  5. A substrate-free optical readout focal plane array with a heat sink structure

    NASA Astrophysics Data System (ADS)

    Rmwen, Liu; Yanmei, Kong; Binbin, Jiao; Zhigang, Li; Haiping, Shang; Dike, Lu; Chaoqun, Gao; Dapeng, Chen; Qingchuan, Zhang

    2013-02-01

    A substrate-free optical readout focal plane array (FPA) operating in 8-12 μm with a heat sink structure (HSS) was fabricated and its performance was tested. The temperature distribution of the FPA with an HSS investigated by using a commercial FLIR IR camera shows excellent uniformity. The thermal cross-talk effect existing in traditional substrate-free FPAs was eliminated effectively. The heat sink is fabricated successfully by electroplating copper, which provides high thermal capacity and high thermal conductivity, on the frame of substrate-free FPA. The FPA was tested in the optical-readout system, the results show that the response and NETD are 13.6 grey/K (F / # = 0.8) and 588 mK, respectively.

  6. Measuring integrated cellular mechanical stress response at focal adhesions by optical tweezers

    NASA Astrophysics Data System (ADS)

    Bordeleau, François; Bessard, Judicael; Marceau, Normand; Sheng, Yunlong

    2011-09-01

    The ability of cells to sustain mechanical stress is largely modulated by the cytoskeleton. We present a new application of optical tweezers to study cell's mechanical properties. We trap a fibronectin-coated bead attached to an adherent H4II-EC3 rat hepatoma cell in order to apply the force to the cell surface membrane. The bead position corresponding to the cell's local mechanical response at focal adhesions is measured with a quadrant detector. We assessed the cell response by tracking the evolution of the equilibrium force for 40 cells selected at random and selected a temporal window to assess the cell initial force expression at focal adhesions. The mean value of the force within this time window over 40 randomly selected bead/cell bounds was 52.3 pN. Then, we assessed the responses of the cells with modulation of the cytoskeletons, namely the ubiquitous actin-microfilaments and microtubules, plus the differentiation-dependent keratin intermediate filaments. Notably, a destabilization of the first two networks led to around 50 and 30% reductions in the mean equilibrium forces, respectively, relative to untreated cells, whereas a loss of the third one yielded a 25% increase. The differences in the forces from untreated and treated cells are resolved by the optical tweezers experiment.

  7. Laser Metrology for an Optical-Path-Length Modulator

    NASA Technical Reports Server (NTRS)

    Gursel, Yekta

    2005-01-01

    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.

  8. 3D modeling of architectural objects from video data obtained with the fixed focal length lens geometry

    NASA Astrophysics Data System (ADS)

    Deliś, Paulina; Kędzierski, Michał; Fryśkowska, Anna; Wilińska, Michalina

    2013-12-01

    The article describes the process of creating 3D models of architectural objects on the basis of video images, which had been acquired by a Sony NEX-VG10E fixed focal length video camera. It was assumed, that based on video and Terrestrial Laser Scanning data it is possible to develop 3D models of architectural objects. The acquisition of video data was preceded by the calibration of video camera. The process of creating 3D models from video data involves the following steps: video frames selection for the orientation process, orientation of video frames using points with known coordinates from Terrestrial Laser Scanning (TLS), generating a TIN model using automatic matching methods. The above objects have been measured with an impulse laser scanner, Leica ScanStation 2. Created 3D models of architectural objects were compared with 3D models of the same objects for which the self-calibration bundle adjustment process was performed. In this order a PhotoModeler Software was used. In order to assess the accuracy of the developed 3D models of architectural objects, points with known coordinates from Terrestrial Laser Scanning were used. To assess the accuracy a shortest distance method was used. Analysis of the accuracy showed that 3D models generated from video images differ by about 0.06 ÷ 0.13 m compared to TLS data. Artykuł zawiera opis procesu opracowania modeli 3D obiektów architektonicznych na podstawie obrazów wideo pozyskanych kamerą wideo Sony NEX-VG10E ze stałoogniskowym obiektywem. Przyjęto założenie, że na podstawie danych wideo i danych z naziemnego skaningu laserowego (NSL) możliwe jest opracowanie modeli 3D obiektów architektonicznych. Pozyskanie danych wideo zostało poprzedzone kalibracją kamery wideo. Model matematyczny kamery był oparty na rzucie perspektywicznym. Proces opracowania modeli 3D na podstawie danych wideo składał się z następujących etapów: wybór klatek wideo do procesu orientacji, orientacja klatek wideo na podstawie współrzędnych odczytanych z chmury punktów NSL, wygenerowanie modelu 3D w strukturze TIN z wykorzystaniem metod automatycznej korelacji obrazów. Opracowane modele 3D zostały porównane z modelami 3D tych samych obiektów, dla których została przeprowadzona samokalibracja metodą wiązek. W celu oceny dokładności opracowanych modeli 3D obiektów architektonicznych wykorzystano punkty naziemnego skaningu laserowego. Do oceny dokładności wykorzystano metodę najkrótszej odległości. Analiza dokładności wykazała, że dokładność modeli 3D generowanych na podstawie danych wideo wynosi około 0.06 ÷ 0.13m względem danych NSL.

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

    NASA Technical Reports Server (NTRS)

    Fernandez, Michela Munoz

    2006-01-01

    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.

  10. Fiber optically coupled infrared focal plane array system for use in missile warning receiver applications

    NASA Astrophysics Data System (ADS)

    Daniels, Arnold; Liepmann, Till W.

    1999-07-01

    The location and installation of mid-infrared missile warning receiver sensors is limited by the mechanical constraints of the detector/dewar assembly and the associated cryogenic cooler assembly. The size, shape, and weight of these assemblies limit the installation alternatives, and prevent placing the missile warning receiver system in the optimum locations. Hence, their coverage and detection performance is limited. A micro-lens array coupled to a coherent fiber optic bundle and an infrared focal plane array were designed and experimentally implemented, to allow the mid-wave sensor and cryogenic devices to be located remotely from the receiver aperture. This eliminates the receiver aperture placement restrictions while easing the integration and maintenance of the sensor/dewar and cooler. Modulation transfer function and noise equivalent temperature difference measurements were performed to determine the performance of the imaging system.

  11. The focal plane adaptive optics test box of the Observatoire du Mont-Mégantic

    NASA Astrophysics Data System (ADS)

    Deschênes, William; Brousseau, Denis; Lavigne, Jean-Francois; Thibault, Simon; Véran, Jean-Pierre

    2014-08-01

    With the upcoming construction of Extremely Large Telescopes, several existing technologies are being pushed beyond their performance limit and it becomes essential to develop and evaluate new alternatives. The "Observatoire du Mont Mégantic" (OMM) hosts a telescope having a 1.6-meter diameter primary. The OMM telescope is known to be an excellent location to develop and test precursor instruments which are then upscaled to larger telescopes (ex. SPIOMM which led to SITELLE at the CFHT). We present a specifically designed focal plane box for the OMM which will allow to evaluate, directly on-sky, the performance of a number of next generation adaptive optics related technologies The system will able us to compare the performance of several new wavefront sensors in contrast with the current standard, the Shack-Hartman wavefront sensor.

  12. On the performance of optical filters for the XMM focal plane CCD-camera EPIC

    NASA Astrophysics Data System (ADS)

    Stephan, K.-H.; Reppin, C.; Maier, H. J.; Frischke, D.; Fuchs, D.; Müller, P.; Moeller, S.; Gürtler, P.

    1995-02-01

    Optical filters have been developed for the X-ray astronomy project XMM (X-ray Multi Mirror Mission) [1] of ESA, where specific CCDs will serve as focal plane cameras on board the observatory. These detectors are sensitive from the X-ray to the NIR (near infrared) spectral region. For observations in X-ray astronomy an optical filter must be placed in front of the CCD, suppressing visible and UV (ultraviolet) radiation of stars by more than 6 orders of magnitude while being highly transparent at photon energies above 100 eV. The flight model filter is designed to have an effective area of 73 mm diameter without making use of a supporting grid. Efforts have been made to utilize plastic foils to tailor filters meeting these specific requirements. It was found, that a typical filter could be composed, e.g., of a polypropylene foil of 20 μg/cm2 thickness serving as a carrier, coated with metallic films of Al or Al and Sn of about 20-25 μg/cm2 thickness. Other possible carriers are polycarbonate (Lexan, Macrolon) and poly-para-xylylene (Parylene N) films of similar thicknesses. The preparation and characterization of these three types of carrier foils as well as of two sample filters is described, including mechanical tests as well as optical transmission measurements in the photon energy range from 1 eV to 2 keV.

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

    PubMed

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

    2012-01-16

    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

  14. Fourier optics analysis of phase-mask-based path-length-multiplexed optical coherence tomography.

    PubMed

    Yin, Biwei; Dwelle, Jordan; Wang, Bingqing; Wang, Tianyi; Feldman, Marc D; Rylander, Henry G; Milner, Thomas E

    2015-11-01

    Optical coherence tomography (OCT) is an imaging technique that constructs a depth-resolved image by measuring the optical path-length difference between broadband light backscattered from a sample and a reference surface. For many OCT sample arm optical configurations, sample illumination and backscattered light detection share a common path. When a phase mask is placed in the sample path, features in the detected signal are observed, which suggests that an analysis of a generic common path OCT imaging system is warranted. In this study, we present a Fourier optics analysis using a Fresnel diffraction approximation of an OCT system with a path-length-multiplexing element (PME) inserted in the sample arm optics. The analysis may be generalized for most phase-mask-based OCT systems. A radial-angle-diverse PME is analyzed in detail, and the point spread function, coherent transfer function, sensitivity of backscattering angular diversity detection, and signal formation in terms of sample spatial frequency are simulated and discussed. The analysis reveals important imaging features and application limitations of OCT imaging systems with a phase mask in the sample path optics. PMID:26560931

  15. Calibration of optical tweezers with positional detection in the back focal plane

    SciTech Connect

    Tolic-Noerrelykke, Simon F.; Schaeffer, Erik; Howard, Jonathon; Pavone, Francesco S.; Juelicher, Frank; Flyvbjerg, Henrik

    2006-10-15

    We explain and demonstrate a new method of force and position calibrations for optical tweezers with back-focal-plane photodetection. The method combines power spectral measurements of thermal motion and the response to a sinusoidal motion of a translation stage. It consequently does not use the drag coefficient of the trapped object as an input. Thus, neither the viscosity, nor the size of the trapped object, nor its distance to nearby surfaces needs to be known. The method requires only a low level of instrumentation and can be applied in situ in all spatial dimensions. It is both accurate and precise: true values are returned, with small error bars. We tested this experimentally, near and far from surfaces in the lateral directions. Both position and force calibrations were accurate to within 3%. To calibrate, we moved the sample with a piezoelectric translation stage, but the laser beam could be moved instead, e.g., by acousto-optic deflectors. Near surfaces, this precision requires an improved formula for the hydrodynamical interaction between an infinite plane and a microsphere in nonconstant motion parallel to it. We give such a formula.

  16. Design and performance of the cryogenic focal plane optics assembly for the Infrared Astronomical Satellite (IRAS)

    NASA Technical Reports Server (NTRS)

    Bamberg, J. A.; Zaun, N. H.

    1985-01-01

    The Infrared Astronomical Satellite (IRAS) has successfully completed its mission of providing an unbiased all-sky survey of astronomical objects in the 8 to 120 micrometer wavelength region. The design and performance of the Focal Plane Optics Assembly (FPOA) for the IRAS instrument is described in this paper. The FPOA consists of 62 survey field stops, 62 individual small field lenses, 124 small spectral filters, and a precision multi-part aluminum housing. The FPOA is capable of repeated thermal cycling from ambient temperature to 2 Kelvin. The spectral filters, along with the detector spectral responses, provide infrared bandpasses of 8-15, 18-30, 46-78, and 85-117 micrometers. The combination of very long wavelengths, liquid helium temperatures, and small size provided a significant design challenge. Spectral filter and field lens designs for the four spectral bands are described. Also, discussed are techniques which were developed for mechanical mounting of the small lenses and spectral filters, and to assure their optical alignment.

  17. Performance of an optimized substrate-free focal plane array for optical readout uncooled infrared detector

    NASA Astrophysics Data System (ADS)

    Cheng, Teng; Zhang, Qingchuan; Chen, Dapeng; Shi, Haitao; Gao, Jie; Wu, Xiaoping

    2009-02-01

    This note presents an optimized substrate-free focal plane array (FPA), which is implemented in an optical readout uncooled infrared (IR) detector. The supporting frame of such FPA is a temperature-variable one due to the large decreases in both the heat capacity and the thermal conductance. This brings a unique thermal characteristic: the supporting frame functions as a "thermal isolation" frame which reduces the thermal conductance and therefore increases the temperature change and also functions as a "thermal diffusion" frame which certainly results in the temperature prechange in the ones not absorbing IR radiation. This characterization could significantly increase the temperature change of microcantilevers and therefore improve the performance of the substrate-free FPA. In the proposed IR detector, the fabricated 160×160 FPA has an average noise equivalent temperature difference (NETD) and a response time of 330 mK and 16 ms, respectively. The performance of the IR detector theoretically increases by about 5.5 times compared with the one using a substrate FPA. Here, the geometry of the substrate FPA is just the same as the fabricated FPA, but the supporting frame is assumed to be a temperature-constant one. If the optical readout sensitivity can be increased enough using an enhanced IR absorber, the fabricated FPA thus has the potential to achieve a NETD value of 70 mK.

  18. Optical-code-based IP longest prefix match with variable-length optical gates

    NASA Astrophysics Data System (ADS)

    Onohara, Kiyoshi; Kitayama, Ken-Ichi; Wada, Naoya

    2002-10-01

    A bottleneck arises in backbone electronic Internet Protocol (IP) routers because the lookup in a routing table is performed according to the longest prefix match. To resolve this problem, a versatile optical-code- (OC-) based longest prefix match that uses variable-length optical gates for photonic IP packet routing has been developed. The developed OC-based IP routing with the longest prefix match will reduce the number of routing entries so that the matching entry can be found more quickly. Moreover, the new routing procedure will help make photonic routers more compact and cost effective.

  19. Active control of focal length and beam deflection in a metallic nanoslit array lens with multiple sources.

    PubMed

    Cetin, A E; Güven, K; Müstecaplioğlu, O E

    2010-06-15

    We propose an all-optical method to actively control the transmission of nanoslit arrays for scanning and lensing applications. We show that by utilizing two lateral control slits, the transmitted beam can be actively steered. PMID:20548359

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

    SciTech Connect

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

    2014-03-03

    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 j{sub ph} 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 j{sub ph} ≠ 0) charge-carrier diffusion length l{sub d} {sub eff} as a function of j{sub ph} for j{sub ph} → 0 inferred from our experimental data proved to be consistent with the behavior of l{sub d} {sub eff} vs j{sub ph} 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.

  1. 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

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

    2014-01-01

    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. PMID:25013793

  2. Estimation of partial optical path length in the brain in subject-specific head models for near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Nakamura, Kotaro; Kurihara, Kazuki; Kawaguchi, Hiroshi; Obata, Takayuki; Ito, Hiroshi; Okada, Eiji

    2016-01-01

    Three-dimensional head models with the structures constructed from the MR head images of 40 volunteers were constructed to analyze light propagation in the subject-specific head models. The mean optical path length in the head and the partial optical path length in the brain at 13 fiducial points for each volunteer were estimated to evaluate the intersubject and spatial variability in the optical path lengths. Although the intersubject variability in the optical path lengths is very high, the spatial variability in the average of the mean optical path length and partial optical path length is similar to the previously reported data. The mean optical path length in the head increases, whereas the partial optical path length in the brain decreases with an increase in the depth of the brain surface. The partial optical path length is highly correlated with the depth of the brain surface in comparison to the mean optical path length in the head.

  3. Estimation of partial optical path length in the brain in subject-specific head models for near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Nakamura, Kotaro; Kurihara, Kazuki; Kawaguchi, Hiroshi; Obata, Takayuki; Ito, Hiroshi; Okada, Eiji

    2016-04-01

    Three-dimensional head models with the structures constructed from the MR head images of 40 volunteers were constructed to analyze light propagation in the subject-specific head models. The mean optical path length in the head and the partial optical path length in the brain at 13 fiducial points for each volunteer were estimated to evaluate the intersubject and spatial variability in the optical path lengths. Although the intersubject variability in the optical path lengths is very high, the spatial variability in the average of the mean optical path length and partial optical path length is similar to the previously reported data. The mean optical path length in the head increases, whereas the partial optical path length in the brain decreases with an increase in the depth of the brain surface. The partial optical path length is highly correlated with the depth of the brain surface in comparison to the mean optical path length in the head.

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

    NASA Astrophysics Data System (ADS)

    Tarbell, Theodore D.

    2006-06-01

    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 measurements of photospheric vector magnetic fields over a 160 x 320 arcsecond field of view; a Narrowband Filter Imager (NFI) with a tunable birefringent filter for magnetic, Doppler, and intensity maps over the same field of view; and a Broadband Filter Imager (BFI) for highest resolution images in six wavelengths (G band, Ca II H, continua, etc.) over two-thirds of that field of view. A polarization modulator in the telescope allows measurement of Stokes parameters at all wavelengths in the SP and NFI. The NFI wavelengths include both photospheric and chromospheric lines (Fe I, Mg b, Na D, H-alpha). All images are stabilized by a tip-tilt mirror and correlation tracker. This presentation will include pictures and description of the instrument, results from calibration and sun testing, portions of the draft science plan, and some preliminary JOP's. Solar-B is an international cooperative mission between JAXA/ISAS of Japan, NASA of the United States, and PPARC of the United Kingdom. The Solar Optical Telescope has been developed by the National Astronomical Observatory of Japan, Mitsubishi Electric Company, and JAXA/ISAS. The FPP has been developed by the Lockheed Martin Advanced Technology Center, High Altitude Observatory, and NASA.

  5. On the resolution enhancement of optical beams with extreme focal depth

    NASA Astrophysics Data System (ADS)

    Gordon, Ronald Lawrence

    1998-07-01

    A recurring problem in optical design concerns the optimization of the resolution of a beam whose focal depth is several orders of magnitude larger than its wavelength. The cornerstone of such an optimization is the specification of a figure of merit by which the resolution of a typical beam is to be evaluated. In this thesis, the figure of merit takes the form of the mean encircled energy. Aside from providing simple equations for numerical optimization, this merit function allows for a tractible analysis of the behavior of the optimal solution to these equations through asymptotic methods. Such analysis is illustrated here first for the simplest case of symmetric Gaussian beams for both the 2D and 3D cases, where asymptotic analysis is used to find an accurate global approximation for the beam that maximizes mean encircled energy fraction over a given region of interest. For an apertured beam, the equation for the optimal mean encircled energy fraction takes the form of an integral eigenvalue equation, and asymptotic methods are possible for small aperture diameters. On the other hand, when the aperture width is large, it is better to decompose the beam into Hermite- or Laguerre-Gaussian modes. Here, a novel method is derived for computing the matrix whose eigenvector-corresponding to the largest eigenvalue-contains the coefficients of the individual modes in the optimal beam. Much of the analysis presented here is derived for symmetric beams; on the other hand, it is shown that the results for the optimal unapertured beam can be extended to elliptical beams with few modifications. The results in this thesis take on many forms, ranging from approximate expressions for parameters describing the optimal beams to comparisons between the globally optimal beams and corresponding simpler beams. One valuable lesson learned, however, is that although the globally optimal mean encircled energy fraction is rarely more than 10% greater than that for the optimal Gaussian beam, it turns out that in most cases, the beam obtained by an optimization technique specified here has far superior focal depth and resolution properties than those of the optimal Gaussians.

  6. Precision optical characterization on nanometer length and femtosecond time scales

    NASA Astrophysics Data System (ADS)

    Bender, Daniel

    This dissertation details progress made in ultrafast optics and time resolved near-field microscopy. First, I will discuss experiments in ultrafast optics. Careful characterization of ultrashort laser pulses is critical for many applications. Because pulse durations are less than a fraction of a picosecond, direct electronic measurement is not possible and optical techniques must be used. I will describe a simple, real-time scheme for visualizing subtle pulse distortion that occurs on the femtosecond time scale. The procedure for generating the modified spectrum autointerferometric correlation (MOSAIC) from the second harmonic generation frequency resolved optical gating (SHG FROG) dataset is shown. The MOSAIC trace provides complimentary visual pulse assessment to SHG FROG. Spectral phase retrieval from the pulse spectrum and MOSAIC is examined. Next, I discuss the concept of laser cooling of solids, i.e. all optical refrigeration in glasses, crystals and semiconductors. Near-field scanning optical microscopy (NSOM) is used in tandem with atomic force microscopy (AFM) to characterize semiconductor heterostructures for potential use in laser cooling. A novel combination of normal force feedback AFM and collection mode NSOM provide unique coincident imagery. Subsurface defects, which adversely affect laser cooling efficiency, are identified and lower nonradiative recombination lifetime by a factor of 10 compared to defect free areas. Time correlated single photon counting (TCSPC) resolves near-field fluorescence lifetimes and simultaneously gives correlation with surface topography. Fluorescence lifetime images (FLIMs) give direct correspondence to and supply supplemental data for AFM.

  7. Modeling and design of WDM optical buffers in asynchronous and variable-length optical packet switches

    NASA Astrophysics Data System (ADS)

    Ma, Xiaohua

    2007-01-01

    This paper aims to analyze the influence of wavelength conversion on the design of optical fiber delay line (FDL) buffers in a wavelength-division multiplexing (WDM) packet switch. We focus on the network scenario that variable-length packets arrive at the optical switch asynchronously. Through a detailed analysis of the behaviors of packets in the WDM FDL buffer, an approximate analytical traffic model is established. And the theoretical model is proved to be reasonable by simulations. Based on the model, it is clear that, under the same traffic load per wavelength channel, the utilization of tunable wavelength converters (TWCs) to resolve the output contention significantly reduces the number of fiber delay lines (FDLs) in optical buffers, and to achieve a given packet loss probability under a certain number of FDLs, the required number of tunable wavelengths can be predicted. The model can also estimate the optimal value of the basic time unit of the FDLs, and examine the influence of WDM on the optimal value. Finally, the impact of wavelength conversion on the optical switch size is analyzed. To the best of our knowledge, it is the first time that modeling on this problem is presented.

  8. Novel volumetric 3D display based on point light source optical reconstruction using multi focal lens array

    NASA Astrophysics Data System (ADS)

    Lee, Jin su; Lee, Mu young; Kim, Jun oh; Kim, Cheol joong; Won, Yong Hyub

    2015-03-01

    Generally, volumetric 3D display panel produce volume-filling three dimensional images. This paper discusses a volumetric 3D display based on periodical point light sources(PLSs) construction using a multi focal lens array(MFLA). The voxel of discrete 3D images is formed in the air via construction of point light source emitted by multi focal lens array. This system consists of a parallel beam, a spatial light modulator(SLM), a lens array, and a polarizing filter. The multi focal lens array is made with UV adhesive polymer droplet control using a dispersing machine. The MFLA consists of 20x20 circular lens array. Each lens aperture of the MFLA shows 300um on average. The polarizing filter is placed after the SLM and the MFLA to set in phase mostly mode. By the point spread function, the PLSs of the system are located by the focal length of each lens of the MFLA. It can also provide the moving parallax and relatively high resolution. However it has a limit of viewing angle and crosstalk by a property of each lens. In our experiment, we present the letter `C', `O', `DE' and ball's surface with the different depth location. It could be seen clearly that when CCD camera is moved to its position following as transverse axis of the display system. From our result, we expect that varifocal lens like EWOD and LC-lens can be applied for real time volumetric 3D display system.

  9. Automated optical testing of LWIR objective lenses using focal plane array sensors

    NASA Astrophysics Data System (ADS)

    Winters, Daniel; Erichsen, Patrik; Domagalski, Christian; Peter, Frank; Heinisch, Josef; Dumitrescu, Eugen

    2012-10-01

    The image quality of today's state-of-the-art IR objective lenses is constantly improving while at the same time the market for thermography and vision grows strongly. Because of increasing demands on the quality of IR optics and increasing production volumes, the standards for image quality testing increase and tests need to be performed in shorter time. Most high-precision MTF testing equipment for the IR spectral bands in use today relies on the scanning slit method that scans a 1D detector over a pattern in the image generated by the lens under test, followed by image analysis to extract performance parameters. The disadvantages of this approach are that it is relatively slow, it requires highly trained operators for aligning the sample and the number of parameters that can be extracted is limited. In this paper we present lessons learned from the R and D process on using focal plane array (FPA) sensors for testing of long-wave IR (LWIR, 8-12 m) optics. Factors that need to be taken into account when switching from scanning slit to FPAs are e.g.: the thermal background from the environment, the low scene contrast in the LWIR, the need for advanced image processing algorithms to pre-process camera images for analysis and camera artifacts. Finally, we discuss 2 measurement systems for LWIR lens characterization that we recently developed with different target applications: 1) A fully automated system suitable for production testing and metrology that uses uncooled microbolometer cameras to automatically measure MTF (on-axis and at several o-axis positions) and parameters like EFL, FFL, autofocus curves, image plane tilt, etc. for LWIR objectives with an EFL between 1 and 12mm. The measurement cycle time for one sample is typically between 6 and 8s. 2) A high-precision research-grade system using again an uncooled LWIR camera as detector, that is very simple to align and operate. A wide range of lens parameters (MTF, EFL, astigmatism, distortion, etc.) can be easily and accurately measured with this system.

  10. Active optical zoom system

    DOEpatents

    Wick, David V.

    2005-12-20

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

  11. To construct a stable and tunable optical trap in the focal region of a high numerical aperture lens

    NASA Astrophysics Data System (ADS)

    Kandasamy, Gokulakrishnan; Ponnan, Suresh; Sivasubramonia Pillai, T. V.; Balasundaram, Rajesh K.

    2014-05-01

    Based on the diffraction theory, the focusing properties of a radially polarized quadratic Bessel-Gaussian beam (QBG) with on-axis radial phase variance wavefront are investigated theoretically in the focal region of a high numerical aperture (NA) objective lens. The phase wavefront C and pupil beam parameter μ of QBG are the functions of the radial coordinate. The detailed numerical calculation of the focusing property of a QBG beam is presented. The numerical calculation shows that the beam parameter μ and phase parameter C have greater effect on the total electric field intensity distribution. It is observed that under the condition of different μ, evolution principle of focal pattern differs very remarkably on increasing C. Also, some different focal shapes may appear, including rhombic shape, quadrangular shape, two-spherical crust focus shape, two-peak shape, one dark hollow focus, two dark hollow focuses pattern, and triangle dark hollow focus, which find wide optical applications such as optical trapping and nanopatterning.

  12. Role of Suspended Fiber Structural Stiffness and Curvature on Single-Cell Migration, Nucleus Shape, and Focal-Adhesion-Cluster Length

    PubMed Central

    Meehan, Sean; Nain, Amrinder S.

    2014-01-01

    It has been shown that cellular migration, persistence, and associated cytoskeletal arrangement are highly dependent on substrate stiffness (modulus: N/m2 and independent of geometry), but little is known on how cells respond to subtle changes in local geometry and structural stiffness (N/m). Here, using fibers of varying diameter (400, 700, and 1200 nm) and length (1 and 2 mm) deposited over hollow substrates, we demonstrate that single mouse C2C12 cells attached to single suspended fibers form spindle morphologies that are sensitive to fiber mechanical properties. Over a wide range of increasing structural stiffness (2 to 100+ mN/m), cells exhibited decreases in migration speed and average nucleus shape index of ∼57% (from 58 to 25 μm/h) and ∼26% (from 0.78 to 0.58), respectively, whereas the average paxillin focal-adhesion-cluster (FAC, formed at poles) length increased by ∼38% (from 8 to 11 μm). Furthermore, the increase in structural stiffness directly correlates with cellular persistence, with 60% of cells moving in the direction of increasing structural stiffness. At similar average structural stiffness (25 ± 5 mN/m), cells put out longer FAC lengths on smaller diameters, suggesting a conservation of FAC area, and also exhibited higher nucleus shape index and migration speeds on larger-diameter fibers. Interestingly, cells were observed to deform fibers locally or globally through forces applied through the FAC sites and cells undergoing mitosis were found to be attached to the FAC sites by single filamentous tethers. These varied reactions have implications in developmental and disease biology models as they describe a strong dependence of cellular behavior on the cell’s immediate mechanistic environment arising from alignment and geometry of fibers. PMID:25468339

  13. Adaptive optical zoom sensor.

    SciTech Connect

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

    2005-11-01

    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.

  14. Fabrication of long-focal-length plano-convex microlens array by combining the micro-milling and injection molding processes.

    PubMed

    Chen, Lei; Kirchberg, Stefan; Jiang, Bing-Yan; Xie, Lei; Jia, Yun-Long; Sun, Lei-Lei

    2014-11-01

    A uniform plano-convex spherical microlens array with a long focal length was fabricated by combining the micromilling and injection molding processes in this work. This paper presents a quantitative study of the injection molding process parameters on the uniformity of the height of the microlenses. The variation of the injection process parameters, i.e., barrel temperature, mold temperature, injection speed, and packing pressure, was found to have a significant effect on the uniformity of the height of the microlenses, especially the barrel temperature. The filling-to-packing switchover point is also critical to the uniformity of the height of the microlenses. The optimal uniformity was achieved when the polymer melts completely filled the mold cavity, or even a little excessively filled the cavity, during the filling stage. In addition, due to the filling resistance, the practical filling-to-packing switchover point can vary with the change of the filling processing conditions and lead to a non-negligible effect on the uniformity of the height of the microlenses. Furthermore, the effect of injection speed on the uniformity of the height of the microlenses was analyzed in detail. The results indicated that the effect of injection speed on the uniformity of the height of the microlenses is mainly attributed to the two functions of injection speed: transferring the filling-to-packing switchover point and affecting the distribution of residual flow stress in the polymer melt. PMID:25402902

  15. The design and validation of an optical coherence tomography-based classification system for focal vitreomacular traction.

    PubMed

    Steel, D H W; Downey, L; Greiner, K; Heimann, H; Jackson, T L; Koshy, Z; Laidlaw, D A H; Wickham, L; Yang, Y

    2016-02-01

    PurposeTo develop and validate a classification system for focal vitreomacular traction (VMT) with and without macular hole based on spectral domain optical coherence tomography (SD-OCT), intended to aid in decision-making and prognostication.MethodsA panel of retinal specialists convened to develop this system. A literature review followed by discussion on a wide range of cases formed the basis for the proposed classification. Key features on OCT were identified and analysed for their utility in clinical practice. A final classification was devised based on two sequential, independent validation exercises to improve interobserver variability.ResultsThis classification tool pertains to idiopathic focal VMT assessed by a horizontal line scan using SD-OCT. The system uses width (W), interface features (I), foveal shape (S), retinal pigment epithelial changes (P), elevation of vitreous attachment (E), and inner and outer retinal changes (R) to give the acronym WISPERR. Each category is scored hierarchically. Results from the second independent validation exercise indicated a high level of agreement between graders: intraclass correlation ranged from 0.84 to 0.99 for continuous variables and Fleiss' kappa values ranged from 0.76 to 0.95 for categorical variables.ConclusionsWe present an OCT-based classification system for focal VMT that allows anatomical detail to be scrutinised and scored qualitatively and quantitatively using a simple, pragmatic algorithm, which may be of value in clinical practice as well as in future research studies. PMID:26768921

  16. Propagation equation of Hermite-Gauss beams through a complex optical system with apertures and its application to focal shift.

    PubMed

    Peng, Sun; Jin, Guo; Tingfeng, Wang

    2013-07-01

    Based on the generalized Huygens-Fresnel diffraction integral (Collins' formula), the propagation equation of Hermite-Gauss beams through a complex optical system with a limiting aperture is derived. The elements of the optical system may be all those characterized by an ABCD ray-transfer matrix, as well as any kind of apertures represented by complex transmittance functions. To obtain the analytical expression, we expand the aperture transmittance function into a finite sum of complex Gaussian functions. Thus the limiting aperture is expressed as a superposition of a series of Gaussian-shaped limiting apertures. The advantage of this treatment is that we can treat almost all kinds of apertures in theory. As application, we define the width of the beam and the focal plane using an encircled-energy criterion and calculate the intensity distribution of Hermite-Gauss beams at the actual focus of an aperture lens. PMID:24323153

  17. Relations between ac-dc components and optical path length in photoplethysmography

    NASA Astrophysics Data System (ADS)

    Lee, Chungkeun; Sik Shin, Hang; Lee, Myoungho

    2011-07-01

    Photoplethysmography is used in various areas such as vital sign measurement, vascular characteristics analysis, and autonomic nervous system assessment. Photoplethysmographic signals are composed of ac and dc, but it is difficult to find research about the interaction of photoplethysmographic components. This study suggested a model equation combining two Lambert-Beer equations at the onset and peak points of photoplethysmography to evaluate ac characteristics, and verified the model equation through simulation and experiment. In the suggested equation, ac was dependent on dc and optical path length. In the simulation, dc was inversely proportionate to ac sensitivity (slope), and ac and optical path length were proportionate. When dc increased from 10% to 90%, stabilized ac decreased from 1 to 0.89 +/- 0.21, and when optical path length increased from 10% to 90%, stabilized ac increased from 1 to 1.53 +/- 0.40.

  18. DNA as a Metrology Standard for Length and Force Measurements with Optical Tweezers

    PubMed Central

    Rickgauer, John Peter; Fuller, Derek N.; Smith, Douglas E.

    2006-01-01

    Optical tweezers have broad applications in studies of structures and processes in molecular and cellular biophysics. Use of optical tweezers for quantitative molecular-scale measurement requires careful calibration in physical units. Here we show that DNA molecules may be used as metrology standards for force and length measurements. Analysis of DNA molecules of two specific lengths allows simultaneous determination of all essential measurement parameters. We validate this biological-calibration method experimentally and with simulated data, and show that precisions in determining length scale factor (∼0.2%), length offset (∼0.03%), force scale factor (∼2%), and compliance of the traps (∼3%) are limited only by current measurement variation, much of which arises from polydispersity of the microspheres (∼2%). We find this procedure to be simpler and more convenient than previous methods, and suggest that it provides an easily replicated standard that can insure uniformity of measurements made in different laboratories. PMID:16963512

  19. Beamlet focal plane diagnostic

    SciTech Connect

    Caird, J.A.; Nielsen, N.D.; Patton, H.G.; Seppala, L.G.; Thompson, C.E.; Wegner, P.J.

    1996-12-01

    This paper describes the major optical and mechanical design features of the Beamlet Focal Plane Diagnostic system as well as measurements of the system performance, and typical data obtained to date. We also discuss the NIF requirements on the focal spot that we are interested in measuring, and some of our plans for future work using this system.

  20. Cavity length resonances in a nanosecond singly resonant optical parametric oscillator.

    PubMed

    Henriksson, Markus; Sjöqvist, Lars; Pasiskevicius, Valdas; Laurell, Fredrik

    2010-05-10

    Resonant output energy enhancement in a singly resonant nondegenerate type-I optical parametric oscillator with a volume Bragg grating output coupler is demonstrated. The resonances occur when the pump laser and parametric oscillator cavity length ratio is an integer or a fraction of small integers. Although the length resonances are similar to those observed in doubly resonant optical parametric oscillators, the physical mechanism is distinctly different. The resonances in the singly resonant oscillator are caused by correlation of the instantaneous power between the quasi-periodic multimode pump laser beam and the OPO signal. PMID:20588926

  1. PLR analysis of optical packet switch with different packet length distribution

    NASA Astrophysics Data System (ADS)

    Liu, Huanlin; Chen, Qianbin; Pan, Yingjun

    2006-09-01

    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.

  2. Temporal characterization of FEL micropulses as function of cavity length detuning using frequency-resolved optical gating

    SciTech Connect

    Richman, B.A.; DeLong, K.W.; Trebino, R.

    1995-12-31

    Results of frequency resolved optical gating (FROG) measurements on the Stanford mid-IR FEL system show the effect of FEL cavity length detuning on the micropulse temporal structure. The FROG technique enables the acquisition of complete and uniquely invertible amplitude and phase temporal dependence of optical pulses. Unambiguous phase and amplitude profiles are recovered from the data. The optical pulses are nearly transform limited, and the pulse length increases with cavity length detuning.

  3. Design and tolerance of a free-form optical system for an optical see-through multi-focal-plane display.

    PubMed

    Hu, Xinda; Hua, Hong

    2015-11-20

    By elegantly combining recent advancements of free-form optical technology and multi-focal-plane (MFP) display technology, we developed a high-performance true 3D augmented reality (AR) display that is capable of rendering a large volume of 3D scenes with accurate focus cues; this display overcomes the accommodation-convergence discrepancy problem in conventional AR display. In this paper, we concentrate on various aspects of engineering challenges in the design and integration of a free-form optical see-through eyepiece with MFP technology for our AR display prototype. We present the design and optimization strategy in coupling free-form optics with a rotational-symmetric lens system to achieve high image quality. A comprehensive tolerance analysis of this complicated optical system is also presented, including an effective tolerance method for random surface figure errors on aspheric and free-form surfaces. Finally, the image quality of the virtual display is evaluated, which shows the as-built performance matches very well with the optical design results and tolerance analysis. PMID:26836568

  4. A balanced, phase sensitive back-focal plane interferometry technique to determine dynamics of a trapped bead in optical tweezers

    NASA Astrophysics Data System (ADS)

    Roy, Basudev; Pal, Sambit Bikas; Haldar, Arijit; Gupta, Ratnesh Kumar; Ghosh, Nirmalya; Banerjee, Ayan

    2012-04-01

    Back-focal plane interferometry is typically used to determine displacements of a trapped bead which lead to trapping force measurements in optical tweezers. In most cases, intensity shifts of the back-scattered interference pattern due to displacements of the bead are measured by a position sensitive detector placed in the microscope back-focal plane. However, in intensity-based measurements, the axial displacement resolution is typically worse than the lateral resolution since for axial displacements, the inherent resolution of the position detector cannot be used. In this paper, we demonstrate that measurement of the phase of the back-scattered light yields high axial displacement resolution, and can also be used for lateral displacement measurement. In our experiments, we separate out the back-scattered light from the trapped bead and reflected light from the top surface of the sample chamber by a confocal arrangement consisting of a spatial filter used in combination with two apertures. We proceed to beat the two separated components in a Mach-Zehnder interferometer where we employ balanced detection to improve our fringe contrast, and thus the sensitivity of the phase measurement. For lateral displacement sensing, we match experimental results to within 10% with a theoretical simulation determining the shift of the overall phase contour of the back-scattered light due to a given lateral displacement by using plane wave decomposition in conjunction with Mie scattering theory. Our technique is also able to track the Brownian motion of trapped beads from the phase jitter so that, similar to intensity-based measurements, we can use it to determine the spring constant of the trap, and thus the trapping force. The sensitivity of our technique is limited by path drifts of the external interferometer which we have currently stabilized by locking it to a frequency stabilized diode laser to obtain displacement measurement resolution ~200 pm.

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    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.

  6. Determination of the minority carrier diffusion length of SnS using electro-optical measurements

    NASA Astrophysics Data System (ADS)

    Ramakrishna Reddy, K. T.; Nwofe, P. A.; Miles, R. W.

    2013-05-01

    The minority carrier diffusion length of the "absorber layer" in a solar cell is generally accepted to be one of the most important parameters that govern the performance of a solar cell device. In this work, thin films of SnS have been thermally evaporated onto cadmium sulphide/indium tin oxide/glass substrates, to fabricate heterojunction solar cell devices. The minority carrier diffusion length was determined for the first time for SnS layers using spectral response measurements in conjunction with optical absorption coefficient versus wavelength measurements. The minority carrier diffusion length was determined to be in the range 0.18-0.23 µm for the SnS/CdS devices investigated in this work.

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

    SciTech Connect

    Suetterlin, Daniel; Erni, Daniel; Schlott, Volker; Sigg, Hans; Jaeckel, Heinz; Murk, Axel

    2010-10-15

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    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.

  9. Utilization of coincidence criteria in absolute length measurements by optical interferometry in vacuum and air

    NASA Astrophysics Data System (ADS)

    Schödel, R.

    2015-08-01

    Traceability of length measurements to the international system of units (SI) can be realized by using optical interferometry making use of well-known frequencies of monochromatic light sources mentioned in the Mise en Pratique for the realization of the metre. At some national metrology institutes, such as Physikalisch-Technische Bundesanstalt (PTB) in Germany, the absolute length of prismatic bodies (e.g. gauge blocks) is realized by so-called gauge-block interference comparators. At PTB, a number of such imaging phase-stepping interference comparators exist, including specialized vacuum interference comparators, each equipped with three highly stabilized laser light sources. The length of a material measure is expressed as a multiple of each wavelength. The large number of integer interference orders can be extracted by the method of exact fractions in which the coincidence of the lengths resulting from the different wavelengths is utilized as a criterion. The unambiguous extraction of the integer interference orders is an essential prerequisite for correct length measurements. This paper critically discusses coincidence criteria and their validity for three modes of absolute length measurements: 1) measurements under vacuum in which the wavelengths can be identified with the vacuum wavelengths, 2) measurements under air in which the air refractive index is obtained from environmental parameters using an empirical equation, and 3) measurements under air in which the air refractive index is obtained interferometrically by utilizing a vacuum cell placed along the measurement pathway. For case 3), which corresponds to PTB’s Kösters-Comparator for long gauge blocks, the unambiguous determination of integer interference orders related to the air refractive index could be improved by about a factor of ten when an ‘overall dispersion value,’ suggested in this paper, is used as coincidence criterion.

  10. Phase-shifting algorithm inside an optical cavity for absolute length measurement.

    PubMed

    Hibino, Kenichi

    2016-02-10

    Phase-shifting interferometry inside an optical cavity is useful for measuring the length of a cubic object and the diameter of a metal sphere. A new error-compensating phase-shifting algorithm is proposed, with which a spatially uniform phase error caused by nonlinear phase modulation can be eliminated. It is shown that the conventional algorithm design for harmonic analysis cannot compensate for this dc error unless the sampling weight definition is extended to a complex number. Specifically, a 3% quadratic nonlinearity in the phase modulation is found to yield a systematic error of 1.5 nm in the object length in many conventional algorithms. A new 13-frame algorithm is described that applies a modified discrete Fourier window and can reduce the dc error to less than 0.5 nm. PMID:26906383

  11. Electro-optical measurements of picosecond bunch length of a 45 MeV electron beam

    SciTech Connect

    Tsang, T.; Castillo, V.; Larsen, R.; Lazarus, D. M.; Nikas, D.; Ozben, C.; Semertzidis, Y. K.; Srinivasan-Rao, T.; Kowalski, L.

    2001-05-01

    We have measured the temporal duration of 45 MeV picosecond electron beam bunches using a noninvasive electro-optical (EO) technique. The amplitude of the EO modulation was found to increase linearly with electron beam charge and decrease inversely with distance from the electron beam. The rise time of the temporal signal was limited by our detection system to {approx}70 ps. The EO signal due to ionization caused by the electrons traversing the EO crystal was also observed. It has a distinctively long decay time constant and signal polarity opposite to that due to the field induced by the electron beam. The electro-optical technique may be ideal for the measurement of bunch length of femtosecond, relativistic, high energy, charged, particle beams.

  12. Transit time of optical pulses propagating through a finite length medium.

    PubMed

    Bloemer, Mark; Myneni, Krishna; Centini, Marco; Scalora, Michael; D'Aguanno, Giuseppe

    2002-05-01

    We present experimental and theoretical results on the transit time of optical pulses propagating through bulk media of finite length, specifically GaAs and silica. The transit time of the peak of the pulse varies with the central wavelength due to the étalon effects caused by the reflectivity at the air/medium boundaries. For transform limited optical pulses, the transit time as a function of wavelength follows the transmittance spectrum, that is, the longest transit time occurs at the transmittance maxima where the cavity dwell time is the longest and the shortest transit time occurs at the transmittance minima. The results are dramatically different for chirped pulses obtained by modulating the injection current of a diode laser. The range in the transit times for chirped pulses is a factor of four times larger compared with transform limited pulses. In addition, the transit time for chirped pulses propagating through the GaAs sample is negative at certain wavelengths. Also, the transmitted pulse is not distorted. Although modulating the injection current of a diode laser is the most common method for generating optical pulses, to our knowledge this is the first reported observation of the transit time of these chirped optical pulses propagating through a simple étalon structure. PMID:12059739

  13. Optic Disc - Fovea Distance, Axial Length and Parapapillary Zones. The Beijing Eye Study 2011

    PubMed Central

    Jonas, Rahul Arvo; Wang, Ya Xing; Yang, Hua; Li, Jian Jun; Xu, Liang; Panda-Jonas, Songhomitra; Jonas, Jost Bruno

    2015-01-01

    Purpose To measure the distance between the optic disc center and the fovea (DFD) and to assess its associations. Methods The population-based cross-sectional Beijing Eye Study 2011 included 3468 individuals aged 50+ years. The DFD was measured on fundus photographs. Results Readable fundus photographs were available for 2836 (81.8%) individuals. Mean DFD was 4.76 ± 0.34mm (median: 4.74 mm; range: 3.76–6.53mm). In multivariate analysis, longer DFD was associated with longer axial length (P<0.001; standardized correlation coefficient beta: 0.62), higher prevalence of axially high myopia (P<0.001; beta:0.06), shallower anterior chamber depth (P<0.001; beta:-0.18), thinner lens thickness (P = 0.004; beta: -0.06), smaller optic disc-fovea angle (P = 0.02; beta: -0.04), larger parapapillary alpha zone (P = 0.008; beta: 0.05), larger parapapillary beta/gamma zone (P<0.001; beta: 0.11), larger optic disc area (P<0.001; beta: 0.08), lower degree of cortical cataract (P = 0.002; beta: -0.08), and lower prevalence of age-related macular degeneration (P = 0.001; beta: -0.06). Bruch´s membrane opening-fovea distance (DFD minus disc radius minus parapapillary beta/gamma zone width) in non-glaucomatous eyes was not significantly (P = 0.60) related with axial length in emmetropic or axially myopic eyes (axial length ≥23.5 mm), while it increased significantly (P<0.001; r: 0.32) with longer axial length in eyes with an axial length of <23.5mm. Ratio of mean DFD to disc diameter was 2.65 ± 0.30. If the ratio of disc-fovea distance to disc diameter was considered constant and if the individual disc diameter was calculated as the individual disc-fovea distance divided by the constant factor of 2.65, the resulting calculated disc diameter differed from the directly measured disc diameter by 0.16 ±0.13 mm (median: 0.13 mm, range: 0.00–0.89 mm) or 8.9 ± 7.3% (median: 7.4%; range: 0.00–70%) of the measured disc diameter. Conclusions DFD (mean: 4.76mm) increases with longer axial length, larger parapapillary alpha zone and parapapillary beta/gamma zone, and larger disc area. The axial elongation associated increase in DFD was due to an enlargement of parapapillary beta/gamma zone while the Bruch’s membrane opening-fovea distance did not enlarge with longer axial length. This finding may be of interest for the process of emmetropization and myopization. Due to its variability, the disc-fovea distance has only limited clinical value as a relative size unit for structures at the posterior pole. PMID:26390438

  14. Revealing Optical Properties of Reduced-Dimensionality Materials at Relevant Length Scales.

    PubMed

    Ogletree, D Frank; Schuck, P James; Weber-Bargioni, Alexander F; Borys, Nicholas J; Aloni, Shaul; Bao, Wei; Barja, Sara; Lee, Jiye; Melli, Mauro; Munechika, Keiko; Whitelam, Stephan; Wickenburg, Sebastian

    2015-10-14

    Reduced-dimensionality materials for photonic and optoelectronic applications including energy conversion, solid-state lighting, sensing, and information technology are undergoing rapid development. The search for novel materials based on reduced-dimensionality is driven by new physics. Understanding and optimizing material properties requires characterization at the relevant length scale, which is often below the diffraction limit. Three important material systems are chosen for review here, all of which are under investigation at the Molecular Foundry, to illustrate the current state of the art in nanoscale optical characterization: 2D semiconducting transition metal dichalcogenides; 1D semiconducting nanowires; and energy-transfer in assemblies of 0D semiconducting nanocrystals. For each system, the key optical properties, the principal experimental techniques, and important recent results are discussed. Applications and new developments in near-field optical microscopy and spectroscopy, scanning probe microscopy, and cathodoluminescence in the electron microscope are given detailed attention. Work done at the Molecular Foundry is placed in context within the fields under review. A discussion of emerging opportunities and directions for the future closes the review. PMID:26332202

  15. 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)

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

    2013-04-01

    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.

  16. Effective optical path length for tandem diffuse cubic cavities as gas absorption cell

    NASA Astrophysics Data System (ADS)

    Yu, J.; Gao, Q.; Zhang, Y. G.; Zhang, Z. G.; Wu, S. H.

    2014-12-01

    Tandem diffuse cubic cavities designed by connecting two single diffuse cubic-shaped cavities, A and B, with an aperture (port fraction fap) in the middle of the connecting baffle was developed as a gas absorption cell. 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 (TDLAS). Experimental results manifested an enhancement of EOPL for the tandem diffuse cubic cavities as the decrease of fap and can be expressed as the sum of EOPL of two single cubic cavities at fap < 0.01, which coincided well with theoretical analysis. The simulating EOPL was smaller than experimental results at fap > 0.01, which indicated that back scattering light from cavity B to cavity A cannot be ignored at this condition.

  17. Beam splitter and method for generating equal optical path length beams

    DOEpatents

    Qian, Shinan; Takacs, Peter

    2003-08-26

    The present invention is a beam splitter for splitting an incident beam into first and second beams so that the first and second beams have a fixed separation and are parallel upon exiting. The beam splitter includes a first prism, a second prism, and a film located between the prisms. The first prism is defined by a first thickness and a first perimeter which has a first major base. The second prism is defined by a second thickness and a second perimeter which has a second major base. The film is located between the first major base and the second major base for splitting the incident beam into the first and second beams. The first and second perimeters are right angle trapezoidal shaped. The beam splitter is configured for generating equal optical path length beams.

  18. Precise measurement of single-mode fiber lengths using a gain-switched distributed feedback laser with delayed optical feedback.

    PubMed

    Wada, Kenji; Matsukura, Satoru; Tanaka, Amaka; Matsuyama, Tetsuya; Horinaka, Hiromichi

    2015-09-01

    A simple method to measure single-mode optical fiber lengths is proposed and demonstrated using a gain-switched 1.55-μm distributed feedback laser without a fast photodetector or an optical interferometer. From the variation in the amplified spontaneous emission noise intensity with respect to the modulation frequency of the gain switching, the optical length of a 1-km single-mode fiber immersed in water is found to be 1471.043915 m ± 33 μm, corresponding to a relative standard deviation of 2.2 × 10(-8). This optical length is an average value over a measurement time of one minute under ordinary laboratory conditions. PMID:26368406

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

    PubMed

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

    2014-05-20

    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 μm) 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

  20. 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)

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

    2009-01-01

    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.

  1. Focal construct geometry for high intensity energy dispersive x-ray diffraction based on x-ray capillary optics

    NASA Astrophysics Data System (ADS)

    Li, Fangzuo; Liu, Zhiguo; Sun, Tianxi; Jiang, Bowen; Zhu, Yu

    2016-03-01

    We presented a focal construct geometry (FCG) method for high intensity energy dispersive X-ray diffraction by utilizing a home-made ellipsoidal single-bounce capillary (ESBC) and a polycapillary parallel X-ray lens (PPXRL). The ESBC was employed to focus the X-rays from a conventional laboratory source into a small focal spot and to produce an annular X-ray beam in the far-field. Additionally, diffracted polychromatic X-rays were confocally collected by the PPXRL attached to a stationary energy-resolved detector. Our FCG method based on ESBC and PPXRL had achieved relatively high intensity diffraction peaks and effectively narrowed the diffraction peak width which was helpful in improving the potential d-spacing resolution for material phase analysis.

  2. Focal construct geometry for high intensity energy dispersive x-ray diffraction based on x-ray capillary optics.

    PubMed

    Li, Fangzuo; Liu, Zhiguo; Sun, Tianxi; Jiang, Bowen; Zhu, Yu

    2016-03-14

    We presented a focal construct geometry (FCG) method for high intensity energy dispersive X-ray diffraction by utilizing a home-made ellipsoidal single-bounce capillary (ESBC) and a polycapillary parallel X-ray lens (PPXRL). The ESBC was employed to focus the X-rays from a conventional laboratory source into a small focal spot and to produce an annular X-ray beam in the far-field. Additionally, diffracted polychromatic X-rays were confocally collected by the PPXRL attached to a stationary energy-resolved detector. Our FCG method based on ESBC and PPXRL had achieved relatively high intensity diffraction peaks and effectively narrowed the diffraction peak width which was helpful in improving the potential d-spacing resolution for material phase analysis. PMID:26979685

  3. Phase-noise-compensated optical frequency domain reflectometry with measurement range beyond laser coherence length realized using concatenative reference method.

    PubMed

    Fan, Xinyu; Koshikiya, Yusuke; Ito, Fumihiko

    2007-11-15

    A novel type of optical frequency domain reflectometry with a measurement range much longer than the laser coherence length is proposed and experimentally demonstrated. To reduce the influence of laser phase noise, the measurement signal is compensated by using reference signals generated from a single auxiliary interferometer supported by a newly proposed compensation process. The compensation is accomplished numerically with a computer for each section of the delay fiber length in an auxiliary interferometer after only one data acquisition. By using the proposed technique, it is confirmed experimentally that the laser phase noise is well compensated even beyond the coherence length. PMID:18026262

  4. Optical detection of individual ultra-short carbon nanotubes enables their length characterization down to 10 nm

    PubMed Central

    Gao, Zhenghong; Oudjedi, Laura; Faes, Romain; Moroté, Fabien; Jaillet, Christèle; Poulin, Philippe; Lounis, Brahim; Cognet, Laurent

    2015-01-01

    Ultrashort single-walled carbon nanotubes, i.e. with length below ~30 nm, display length-dependent physical, chemical and biological properties that are attractive for the development of novel nanodevices and nanomaterials. Whether fundamental or applicative, such developments require that ultrashort nanotube lengths can be routinely and reliably characterized with high statistical data for high-quality sample production. However, no methods currently fulfill these requirements. Here, we demonstrate that photothermal microscopy achieves fast and reliable optical single nanotube analysis down to ~10 nm lengths. Compared to atomic force microscopy, this method provides ultrashort nanotubes length distribution with high statistics, and neither requires specific sample preparation nor tip-dependent image analysis. PMID:26603487

  5. Optical detection of individual ultra-short carbon nanotubes enables their length characterization down to 10?nm

    NASA Astrophysics Data System (ADS)

    Gao, Zhenghong; Oudjedi, Laura; Faes, Romain; Morot, Fabien; Jaillet, Christle; Poulin, Philippe; Lounis, Brahim; Cognet, Laurent

    2015-11-01

    Ultrashort single-walled carbon nanotubes, i.e. with length below ~30?nm, display length-dependent physical, chemical and biological properties that are attractive for the development of novel nanodevices and nanomaterials. Whether fundamental or applicative, such developments require that ultrashort nanotube lengths can be routinely and reliably characterized with high statistical data for high-quality sample production. However, no methods currently fulfill these requirements. Here, we demonstrate that photothermal microscopy achieves fast and reliable optical single nanotube analysis down to ~10?nm lengths. Compared to atomic force microscopy, this method provides ultrashort nanotubes length distribution with high statistics, and neither requires specific sample preparation nor tip-dependent image analysis.

  6. Effect of focal size on the laser ignition of compressed natural gas-air mixture

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

  7. Pillar cuvettes: capillary-filled, microliter quartz cuvettes with microscale path lengths for optical spectroscopy.

    PubMed

    Holzner, Gregor; Kriel, Frederik Hermanus; Priest, Craig

    2015-05-01

    The goal of most analytical techniques is to reduce the lower limit of detection; however, it is sometimes necessary to do the opposite. High sample concentrations or samples with high molar absorptivity (e.g., dyes and metal complexes) often require multiple dilution steps or laborious sample preparation prior to spectroscopic analysis. Here, we demonstrate dilution-free, one-step UV-vis spectroscopic analysis of high concentrations of platinum(IV) hexachloride in a micropillar array, that is, "pillar cuvette". The cuvette is spontaneously filled by wicking of the liquid sample into the micropillar array. The pillar height (thus, the film thickness) defines the optical path length, which was reduced to between 10 and 20 μm in this study (3 orders of magnitude smaller than in a typical cuvette). Only one small droplet (∼2 μL) of sample is required, and the dispensed volume need not be precise or even known to the analyst for accurate spectroscopy measurements. For opaque pillars, we show that absorbance is linearly related to platinum concentration (the Beer-Lambert Law). For fully transparent or semitransparent pillars, the measured absorbance was successfully corrected for the fractional surface coverage of the pillars and the transmittance of the pillars and reference. Thus, both opaque and transparent pillars can be applied to absorbance spectroscopy of high absorptivity, microliter samples. It is also shown here that the pillar array has a useful secondary function as an integrated (in-cuvette) filter for particulates. For pillar cuvette measurements of platinum solutions spiked with 6 μm diameter polystyrene spheres, filtered and unfiltered samples gave identical spectra. PMID:25844800

  8. The optics of the growing lungfish eye: lens shape, focal ratio and pupillary movements in Neoceratodus forsteri (Krefft, 1870).

    PubMed

    Bailes, Helena J; Trezise, Ann E O; Collin, Shaun P

    2007-01-01

    Lungfish (order Dipnoi) evolved during the Devonian period and are believed to be the closest living relatives to the land vertebrates. Here we describe the previously unknown morphology of the lungfish eye in order to examine ocular adaptations present in early sarcopterygian fish. Unlike many teleosts, the Australian lungfish Neoceratodus forsteri possesses a mobile pupil with a slow pupillary response similar to amphibians. The structure of the eye changes from juvenile to adult, with both eye and lens becoming more elliptical in shape with growth. This change in structure results in a decrease in focal ratio (the distance from lens center to the retina divided by the lens radius) and increased retinal illumination in adult fish. Despite a degree of lenticular correction for spherical aberration, there is considerable variation across the lens. A re-calculation of spatial resolving power using measured focal ratios from cryosectioning reveals a low ability to discriminate fine detail. The dipnoan eye shares more features with amphibian eyes than with most teleost eyes, which may echo the visual needs of this living fossil. PMID:17822577

  9. Focal properties of geodesic waveguide lenses

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    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.

  10. Measuring optical fiber length by use of a short-pulse optical fiber ring laser in a self-injection seeding scheme.

    PubMed

    Wang, Yi-Ping; Wang, Dong Ning; Jin, Wei

    2006-09-01

    A method for measuring the length of an optical fiber by use of an optical fiber ring laser pulse source is proposed and demonstrated. The key element of the optical fiber ring laser is a gain-switched Fabry-Perot laser diode operated in a self-injection seeding scheme. This method is especially suitable for measuring a medium or long fiber, and a resolution of 0.1 m is experimentally achieved. The measurement is implemented by accurately determining the pulse frequency that can maximize the output power of the fiber ring laser. The measurement results depend only on the refractive index of the fiber corresponding to this single wavelength, instead of the group index of the fiber, which represents a great advantage over both optical time-domain reflectometry and optical low-coherence reflectometry methods. PMID:16912784

  11. Development of transrectal diffuse optical tomography combined with 3D-transrectal ultrasound imaging to monitor the photocoagulation front during interstitial photothermal therapy of primary focal prostate cancer

    NASA Astrophysics Data System (ADS)

    He, Jie; Weersink, Robert; Veilleux, Israel; Mayo, Kenwrick; Zhang, Anqi; Piao, Daqing; Alam, Adeel; Trachtenberg, John; Wilson, Brian C.

    2013-03-01

    Interstitial near-infrared laser thermal therapy (LITT) is currently undergoing clinical trials as an alternative to watchful waiting or radical surgery in patients with low-risk focal prostate cancer. Currently, we use magnetic resonance image (MRI)-based thermography to monitor treatment delivery and determine indirectly the completeness of the target tissue destruction while avoiding damage to adjacent normal tissues, particularly the rectal wall. However, incomplete tumor destruction has occurred in a significant fraction of patients due to premature termination of treatment, since the photocoagulation zone is not directly observed. Hence, we are developing transrectal diffuse optical tomography (TRDOT), in combination with transrectal 3D ultrasound (3D-TRUS), to address his limitation. This is based on the large changes in optical scattering expected upon tissue coagulation. Here, we present forward simulations of a growing coagulated lesion with optical scattering contrast, using an established finite element analysis software platform (NIRFAST). The simulations were validated in tissue-simulating phantoms, with measurements acquired by a state-of-the-art continuous wave (CW) TRDOT system and a recently assembled bench-top CW-DOT system, with specific source-detector configurations. Two image reconstruction schemes were investigated and evaluated, specifically for the accurate delineation of the posterior boundary of the coagulation zone as the critical parameter for treatment guidance in this clinical application.

  12. 3D optical two-mirror scanner with focus-tunable lens.

    PubMed

    Pokorny, Petr; Miks, Antonin

    2015-08-01

    The paper presents formulas for a ray tracing in the optical system of two-mirror optical scanner with a focus-tunable lens. Furthermore, equations for the calculation of focal length which ensure focusing of a beam in the desired point in a detection plane are derived. The uncertainty description of such focal length follows as well. The chosen vector approach is general; therefore, the application of formulas in various configurations of the optical systems is possible. In the example situation, the authors derived formulas for mirrors' rotations and the focal length depending on the position of the point in the detection plane. PMID:26368115

  13. Distinct Length Scales in the VO{sub 2} Metal–Insulator Transition Revealed by Bi-chromatic Optical Probing

    SciTech Connect

    Wang, Lei; Novikova, Irina B.; Klopf, John M.; Madaras, Scott E.; Williams, Gwyn P.; Madaras, Eric; Lu, Liwei; Wolf, Stuart A.; Lukaszew, Rosa A.

    2014-01-01

    Upon a heating-induced metal–instulator transition (MIT) in VO{sub 2}, microscopic metallic VO{sub 2} puddles nucleate and coarsen within the insulating matrix. This coexistence of the two phases across the transition spans distinct length scales as their relative domain sizes change. Far-field optical probing is applied to follow the dynamic evolution of the highly correlated metallic domains as the MIT progresses.

  14. Electro-optic KTN Devices

    NASA Astrophysics Data System (ADS)

    Yagi, Shogo; Fujiura, Kazuo

    We have grown KTN crystals with optical quality, and developed high-speed beam deflectors and variable focal length lenses based on KTN's large electro-optic effect. Furthermore, by using the KTN beam deflectors, we have developed a swept light source for OCT operable at 200 kHz.

  15. Small pixel oversampled IR focal plane arrays

    NASA Astrophysics Data System (ADS)

    Caulfield, John; Curzan, Jon; Lewis, Jay; Dhar, Nibir

    2015-06-01

    We report on a new high definition high charge capacity 2.1 Mpixel MWIR Infrared Focal Plane Array. This high definition (HD) FPA utilizes a small 5 um pitch pixel size which is below the Nyquist limit imposed by the optical systems Point Spread Function (PSF). These smaller sub diffraction limited pixels allow spatial oversampling of the image. We show that oversampling IRFPAs enables improved fidelity in imaging including resolution improvements, advanced pixel correlation processing to reduce false alarm rates, improved detection ranges, and an improved ability to track closely spaced objects. Small pixel HD arrays are viewed as the key component enabling lower size, power and weight of the IR Sensor System. Small pixels enables a reduction in the size of the systems components from the smaller detector and ROIC array, the reduced optics focal length and overall lens size, resulting in an overall compactness in the sensor package, cooling and associated electronics. The highly sensitive MWIR small pixel HD FPA has the capability to detect dimmer signals at longer ranges than previously demonstrated.

  16. Optical elements with extended depth of focus and arbitrary distribution of intensity along the focal segment obtained by angular modulation of the optical power

    NASA Astrophysics Data System (ADS)

    Kakarenko, K.; Ducin, I.; Jaroszewicz, Z.; Kołodziejczyk, A.; Petelczyc, K.; Stompor, A.; Sypek, M.

    2015-04-01

    Light Sword Lens (LSL), i.e., an optical element with extended depth of focus (EDOF) characterized by angular modulation of the optical power in its conventional form is characterized by a linear relationship between the optical power and the angular coordinate of the corresponding angular lens sector. This dependence may be manipulated in function of the required design needs. In the present communicate this additional degree of freedom of design is used for elimination of the LSL shape discontinuity.

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

    SciTech Connect

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

    1982-11-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

  19. Optical modeling of plasma-deposited ZnO films: Electron scattering at different length scales

    SciTech Connect

    Knoops, Harm C. M. Loo, Bas W. H. van de; Smit, Sjoerd; Ponomarev, Mikhail V.; Weber, Jan-Willem; Sharma, Kashish; Kessels, Wilhelmus M. M.; Creatore, Mariadriana

    2015-03-15

    In this work, an optical modeling study on electron scattering mechanisms in plasma-deposited ZnO layers is presented. Because various applications of ZnO films pose a limit on the electron carrier density due to its effect on the film transmittance, higher electron mobility values are generally preferred instead. Hence, insights into the electron scattering contributions affecting the carrier mobility are required. In optical models, the Drude oscillator is adopted to represent the free-electron contribution and the obtained optical mobility can be then correlated with the macroscopic material properties. However, the influence of scattering phenomena on the optical mobility depends on the considered range of photon energy. For example, the grain-boundary scattering is generally not probed by means of optical measurements and the ionized-impurity scattering contribution decreases toward higher photon energies. To understand this frequency dependence and quantify contributions from different scattering phenomena to the mobility, several case studies were analyzed in this work by means of spectroscopic ellipsometry and Fourier transform infrared (IR) spectroscopy. The obtained electrical parameters were compared to the results inferred by Hall measurements. For intrinsic ZnO (i-ZnO), the in-grain mobility was obtained by fitting reflection data with a normal Drude model in the IR range. For Al-doped ZnO (Al:ZnO), besides a normal Drude fit in the IR range, an Extended Drude fit in the UV-vis range could be used to obtain the in-grain mobility. Scattering mechanisms for a thickness series of Al:ZnO films were discerned using the more intuitive parameter “scattering frequency” instead of the parameter “mobility”. The interaction distance concept was introduced to give a physical interpretation to the frequency dependence of the scattering frequency. This physical interpretation furthermore allows the prediction of which Drude models can be used in a specific frequency range.

  20. Length control of an optical resonator using second-order transverse modes.

    PubMed

    Miller, John; Evans, Matthew

    2014-04-15

    We present the analysis of an unorthodox technique for locking a laser to a resonant optical cavity. Error signals are derived from the interference between the fundamental cavity mode and higher-order spatial modes of order two excited by mode mismatch. This scheme is simple, inexpensive, and, in contrast to similar techniques, first-order insensitive to beam jitter. After mitigating sources of technical noise, performance is fundamentally limited by quantum shot noise. PMID:24979027

  1. Direct demonstration of distortionless picosecond-pulse propagation in kilometer-length optical fibers.

    PubMed

    Bloom, D M; Mollenauer, L F; Lin, C; Taylor, D W; Delgaudio, A M

    1979-09-01

    We describe the use of a mode-locked color-center laser to demonstrate nearly distortionless propagation of ~5-psec-wide, Fourier-transform-limited pulses, at or near the zero-dispersion wavelength, in two fused-silica, singlemode fibers of 0.76- and 2.5-km length, respectively. We also report the detection of sharply defined cross correlations between pulses directly from the laser and those had been delayed many microseconds by passage through a fiber. PMID:19687882

  2. Unilateral Isolated Proximal Femoral Focal Deficiency

    PubMed Central

    Doğer, Emek; Köpük, Şule Y.; Çakıroğlu, Yiğit; Çakır, Özgür; Yücesoy, Gülseren

    2013-01-01

    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. PMID:23984135

  3. Predictions of Transient Flame Lift-Off Length With Comparison to Single-Cylinder Optical Engine Experiments

    SciTech Connect

    Senecal, P. K.; Pomraning, E.; Anders, J. W.; Weber, M. R.; Gehrke, C. R.; Polonowski, C. J.; Mueller, C. J.

    2014-05-28

    A state-of-the-art, grid-convergent simulation methodology was applied to three-dimensional calculations of a single-cylinder optical engine. A mesh resolution study on a sector-based version of the engine geometry further verified the RANS-based cell size recommendations previously presented by Senecal et al. (“Grid Convergent Spray Models for Internal Combustion Engine CFD Simulations,” ASME Paper No. ICEF2012-92043). Convergence of cylinder pressure, flame lift-off length, and emissions was achieved for an adaptive mesh refinement cell size of 0.35 mm. Furthermore, full geometry simulations, using mesh settings derived from the grid convergence study, resulted in excellent agreement with measurements of cylinder pressure, heat release rate, and NOx emissions. On the other hand, the full geometry simulations indicated that the flame lift-off length is not converged at 0.35 mm for jets not aligned with the computational mesh. Further simulations suggested that the flame lift-off lengths for both the nonaligned and aligned jets appear to be converged at 0.175 mm. With this increased mesh resolution, both the trends and magnitudes in flame lift-off length were well predicted with the current simulation methodology. Good agreement between the overall predicted flame behavior and the available chemiluminescence measurements was also achieved. Our present study indicates that cell size requirements for accurate prediction of full geometry flame lift-off lengths may be stricter than those for global combustion behavior. This may be important when accurate soot predictions are required.

  4. Predictions of Transient Flame Lift-Off Length With Comparison to Single-Cylinder Optical Engine Experiments

    DOE PAGESBeta

    Senecal, P. K.; Pomraning, E.; Anders, J. W.; Weber, M. R.; Gehrke, C. R.; Polonowski, C. J.; Mueller, C. J.

    2014-05-28

    A state-of-the-art, grid-convergent simulation methodology was applied to three-dimensional calculations of a single-cylinder optical engine. A mesh resolution study on a sector-based version of the engine geometry further verified the RANS-based cell size recommendations previously presented by Senecal et al. (“Grid Convergent Spray Models for Internal Combustion Engine CFD Simulations,” ASME Paper No. ICEF2012-92043). Convergence of cylinder pressure, flame lift-off length, and emissions was achieved for an adaptive mesh refinement cell size of 0.35 mm. Furthermore, full geometry simulations, using mesh settings derived from the grid convergence study, resulted in excellent agreement with measurements of cylinder pressure, heat release rate,more » and NOx emissions. On the other hand, the full geometry simulations indicated that the flame lift-off length is not converged at 0.35 mm for jets not aligned with the computational mesh. Further simulations suggested that the flame lift-off lengths for both the nonaligned and aligned jets appear to be converged at 0.175 mm. With this increased mesh resolution, both the trends and magnitudes in flame lift-off length were well predicted with the current simulation methodology. Good agreement between the overall predicted flame behavior and the available chemiluminescence measurements was also achieved. Our present study indicates that cell size requirements for accurate prediction of full geometry flame lift-off lengths may be stricter than those for global combustion behavior. This may be important when accurate soot predictions are required.« less

  5. High-Speed Mechanical Actuator for Precision Optical Path Length Control

    NASA Astrophysics Data System (ADS)

    Machida, Kosuke; Moriwaki, Shigenori; Mio, Norikatsu

    2009-01-01

    We have developed a high-speed mechanical actuator that can be used for optical systems requiring wide-band feedback control. To attain the wide-band control, we have fabricated a moving-magnet-type electromagnetic actuator with a simple structure. Using this actuator, we achieved a control system for a Michelson interferometer with a servo bandwidth defined by the unity gain frequency of the control loop as large as 30 kHz. We have also measured the amount of wobble motion of the actuator and its long-term stability. Here, we report the characteristics of the actuator.

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

    SciTech Connect

    Krejcik, P.; /SLAC

    2006-10-04

    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.

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

    SciTech Connect

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

    2009-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Grosjean, T.; Gauthier, I.

    2013-05-01

    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 (0.36λ) can be produced over distances reaching 50λ and with longitudinal intensities about 3.5×104 times above the transverse intensities. Same confinement abilities over distances larger than 335 λ 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 λ whose longitudinal intensities are about 200-fold larger than the transverse ones.

  9. Optical microcavities enhance the exciton coherence length and eliminate vibronic coupling in J-aggregates

    SciTech Connect

    Spano, F. C.

    2015-05-14

    The properties of polaritons in J-aggregate microcavities are explored using a Hamiltonian which treats exciton-vibrational coupling and exciton-photon coupling on equal footing. When the cavity mode is resonant with the lowest-energy (0-0) transition in the J-aggregate, two polaritons are formed, the lowest-energy polariton (LP) and its higher-energy partner (P{sub 1}), separated by the Rabi splitting. Strong coupling between the material and cavity modes leads to a decoupling of the exciton and vibrational degrees of freedom and an overall reduction of disorder within the LP. Such effects lead to an expanded material coherence length in the LP which leads to enhanced radiative decay rates. Additional spectral signatures include an amplification of the 0-0 peak coincident with a reduction in the 0-1 peak in the photoluminescence spectrum. It is also shown that the same cavity photon responsible for the LP/P{sub 1} splitting causes comparable splittings in the higher vibronic bands due to additional resonances between vibrationally excited states in the electronic ground state manifold and higher energy vibronic excitons.

  10. OPO (optical parametric oscillators) performance with a long-pulse-length, single-frequency Nd:YAG laser pump

    SciTech Connect

    Byer, R.L.; Kozlovsky, W.J.; Gustafson, E.K.; Eckardt, R.C.

    1988-01-01

    With the advent of new nonlinear materials and single-frequency pump sources, there is renewed interest in Optical Parametric Oscillators (OPO's). The authors used a single-mode diode-laser-pumped monolithic Nd:YAG nonplanar ring laser that is both amplified and frequency-doubled, to pump a monolithic MgO:LiNbO3 pulsed singly resonant OPO. Optical parametric oscillators offer wide tunability by using a solid-state nonlinear crystal as the gain medium. Since the parametric gain does not come from atomic or molecular transition, the operating wavelength range is limited only by crystal dispersion, the optical transmission ranges for the pump, signal, and idler. Repeatable, reliable, and damage-free operation of OPO's has been difficult to obtain because the nonlinear nature of the gain has required the use of high-peak-power lasers as the pump sources. The short-pulse-length, high-peak-power lasers that were available for early OPO development had fluctuating spatial and temporal mode properties that were responsible for many problems in OPO operation.

  11. Application of maximum likelihood estimator in nano-scale optical path length measurement using spectral-domain optical coherence phase microscopy

    PubMed Central

    Motaghian Nezam, S. M. R.; Joo, C; Tearney, G. J.; de Boer, J. F.

    2009-01-01

    Spectral-domain optical coherence phase microscopy (SD-OCPM) measures minute phase changes in transparent biological specimens using a common path interferometer and a spectrometer based optical coherence tomography system. The Fourier transform of the acquired interference spectrum in spectral-domain optical coherence tomography (SD-OCT) is complex and the phase is affected by contributions from inherent random noise. To reduce this phase noise, knowledge of the probability density function (PDF) of data becomes essential. In the present work, the intensity and phase PDFs of the complex interference signal are theoretically derived and the optical path length (OPL) PDF is experimentally validated. The full knowledge of the PDFs is exploited for optimal estimation (Maximum Likelihood estimation) of the intensity, phase, and signal-to-noise ratio (SNR) in SD-OCPM. Maximum likelihood (ML) estimates of the intensity, SNR, and OPL images are presented for two different scan modes using Bovine Pulmonary Artery Endothelial (BPAE) cells. To investigate the phase accuracy of SD-OCPM, we experimentally calculate and compare the cumulative distribution functions (CDFs) of the OPL standard deviation and the square root of the Cramér-Rao lower bound (1/2SNR) over 100 BPAE images for two different scan modes. The correction to the OPL measurement by applying ML estimation to SD-OCPM for BPAE cells is demonstrated. PMID:18957999

  12. Design of vari-focal panoramic annular lenses based on Alvarez surfaces

    NASA Astrophysics Data System (ADS)

    Luo, Yujie; Bai, Jian; Yao, Yuan

    2014-11-01

    We propose a novel design of panoramic annular lenses (PAL) for the imaging of 360° surroundings with a large field of view (FOV) ranging from 30°~105°, which can partly realize the zooming function. Its wavelength band is between 486 and 656 nanometers. The conventional vari-focal PAL is based on the axial shift of some optical components, which will make the blind zone larger and out of the sensing area, while our design is based on the lateral shift, which can make some imaging area zoom in, keep the area of blind zone stay the same, and minimize the whole scale of this system. In order to change the focal length of conventional PAL system, we introduce several pairs of free-form surfaces (Alvarez surfaces) which can be regarded as several plano-spherical lenses and change the focal power of the whole optical system. As we set two different configurations (long focal length and wide angle), all of the optical parameters are designed and optimized with the help of the software (Zemax).

  13. Proposal and experimental verification of Bragg wavelength distribution measurement within a long-length FBG by synthesis of optical coherence function.

    PubMed

    Hotate, Kazuo; Kajiwara, Koji

    2008-05-26

    In this paper, a sensor system for measuring continuous Bragg wavelength distribution in a long-length fiber Bragg grating is newly proposed, using synthesis of optical coherence function (SOCF), which is one of the spatial resolving techniques used for reflectometry. Experimental results are also reported. In the process of synthesizing optical coherence function, it is found that an apodization scheme is necessary to obtain the reflection spectrum of local section in a long-length FBG around the coherence peak. As a verification of this method, the detection of local Bragg wavelength shift due to temperature change within a short section in a long-length FBG is demonstrated experimentally. PMID:18545498

  14. White-light interferometers with polarizing optics for length measurements with an applicable zero-point detection

    NASA Astrophysics Data System (ADS)

    Ullmann, V.; Emam, S.; Manske, E.

    2015-08-01

    For absolute length and form measurements at a large working distance (>150 mm) two special interferometers, a tandem interferometer and a Michelson interferometer with achromatic polarizing optics are constructed. In our experiments, both consist of a combination of one low-coherence interferometer and one laser interferometer. For the low-coherence interferometer part, a simple white-light source with less than 100 µW optical power output is chosen. It bases upon a low-cost fiber-coupled near-infrared LED with a large spectral width (FWHM > 68 nm at 825 nm). The use of achromatic polarizing optics such as broadband polarizing beamsplitters and achromatic quarter-wave plates in the low-coherence interferometer parts increases the contrast level of the white-light signal fringe pattern to nearly 100%. Furthermore, the fringe pattern in a polarized interferometer has no subsignatures and is unique. Hence, different algorithms are tested for signal processing and automated zero-point detection of the white-light signature. The software for an automated measurement is tested in a standard room without thermal control and without damped oscillation. Therefore, in experiments with the tandem interferometer, it was possible to measure the zero-point position of a white-light signature with a peak-to-peak difference of 154 nm under uncontrolled environmental conditions without thermal stabilization. The white-light Michelson interferometer with polarizing achromatic optics allows zero-point detections with a standard deviation (mean value) of less than 15 nm. The drift is proved through measurement results.

  15. Direct high-precision measurement of the effective optical path length of multi-pass cell with optical frequency domain reflectometer.

    PubMed

    Du, Z H; Gao, H; Cao, X H

    2016-01-11

    Multi-pass cells (MPCs) are commonly used in trace-gas detection and weak spectrum measurement. It is essential to accomplish a high-precision measurement of MPCs' effective optical path length (EOPL). A direct high-precision measuring method of MPCs' EOPL with optical frequency domain reflectometer (OFDR) was reported and demonstrated in this paper. Several important parameters of a MPC, such as EOPL and base length, were derived with high-precision by identifying the complicated signal of OFDR. The MPC's EOPL was also verified with the prevailing absorbance method. The results showed that the MPC's EOPL measured by each of these two methods is highly consistent. However, the relative uncertainty with the OFDR dramatically decreased 2 orders of magnitude (about 0.0085%) than that with the absorbance method. It demonstrated that the OFDR method with fewer measurement links is more conducive to a direct measurement. The performances of beam spread and stray light in the White-cell were also evaluated with the method. PMID:26832272

  16. 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)

    1976-01-01

    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.

  17. Optical design and multi-length-scale scanning spectro-microscopy possibilities at the Nanoscopium beamline of Synchrotron Soleil.

    PubMed

    Somogyi, Andrea; Medjoubi, Kadda; Baranton, Gil; Le Roux, Vincent; Ribbens, Marc; Polack, François; Philippot, Pascal; Samama, Jean Pierre

    2015-07-01

    The Nanoscopium 155 m-long beamline of Synchrotron Soleil is dedicated to scanning hard X-ray nanoprobe techniques. Nanoscopium aims to reach ≤100 nm resolution in the 5-20 keV energy range for routine user experiments. The beamline design tackles the tight stability requirements of such a scanning nanoprobe by creating an overfilled secondary source, implementing all horizontally reflecting main beamline optics, applying high mechanical stability equipment and constructing a dedicated high-stability building envelope. Multi-technique scanning imaging and tomography including X-ray fluorescence spectrometry and spectro-microscopy, absorption, differential phase and dark-field contrasts are implemented at the beamline in order to provide simultaneous information on the elemental distribution, speciation and sample morphology. This paper describes the optical concept and the first measured performance of the Nanoscopium beamline followed by the hierarchical length-scale multi-technique imaging experiments performed with dwell times down to 3 ms per pixel. PMID:26134820

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

    SciTech Connect

    Williams, Kiel; /SLAC

    2012-09-07

    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.

  19. Kinoforms long focal objectives for astronomy

    NASA Astrophysics Data System (ADS)

    Gan, Michael A.

    1990-08-01

    A new class of long focal apochromatic optical systems is described which permits the formation of images in different spectral ranges. The systems are composed of kinoform elements combined with conventional optical elements. The correction of monochromatic and chromatic aberrations is discussed theoretically with respect to their occurrence in long-focal, large-f-number astronomical lenses. Kinoform elements are compared to traditional optical elements, and the synthesis of long focal apochromats is shown to be possible with kinoform elements and typical optics. A discussion of diffraction efficiency and spectral selectivity in kinoform elements shows that acceptable characteristics for these optics can be achieved over a wide spectral range. Kinoform element objectives can be applied to high-resolution refractors, stellar sensors, large-telescope guiders, and collimators. The apochromatic lenses based on kinoform elements weigh 30-40 percent less than traditional lenses and offer high correction of chromatic aberrations, low thermal sensitivity, and a minor augmentation of stray light.

  20. A CMOS image sensor method of focal spot size measurement.

    PubMed

    Tuchyna, T; Paix, D

    2004-06-01

    A phosphor opto-coupled monochrome CMOS image sensor with a slit diaphragm was used to investigate focal spot characteristics. Images were captured during x-ray exposure with a triggered frame grabber and subsequently enhanced. Dimensions of the focal spot width (1.39mm) and length (1.92mm) were determined from the focal spot intensity profiles and their corresponding Full Width at Half Maxima (FWHM) in two orthogonal orientations. The CMOS image sensor measurements demonstrated differences in the measured width and length dimensions when compared to film measurements. The obtained nominal focal spot values however showed that image-sensor determined focal spot dimensions agreed with the direct film and film-screen methods when based on the AS/NZS defined nominal focal spot values. The CMOS image sensor tested appears to lack the measurement accuracy required for the measurement of small focal spot sizes due in part to its limited camera sensitivity. PMID:15462588

  1. Influence of the Conjugation Length on the Optical Spectra of Single Ladder-Type (p-Phenylene) Dimers and Polymers.

    PubMed

    Baderschneider, Sebastian; Scherf, Uli; Köhler, Jürgen; Hildner, Richard

    2016-01-21

    We employ low-temperature single-molecule photoluminescence spectroscopy on a π-conjugated ladder-type (p-phenylene) dimer and the corresponding polymer methyl-substituted ladder-type poly(p-phenylene), MeLPPP, to study the impact of the conjugation length (π-electron delocalization) on their optical properties on a molecular scale. Our data show that the linear electron-phonon coupling to intramolecular vibrational modes is very sensitive to the conjugation length, a well-known behavior of organic (macro-) molecules. In particular, the photoluminescence spectra of single dimers feature a rather strong low-energy (150 cm(-1)) skeletal mode of the backbone, which does not appear in the spectra of individual chromophores on single MeLPPP chains. We attribute this finding to a strongly reduced electron-phonon coupling strength and/or vibrational energy of this mode for MeLPPP with its more delocalized π-electron system as compared to the dimer. In contrast, the line widths of the purely electronic zero-phonon lines (ZPL) in single-molecule spectra do not show differences between the dimer and MeLPPP; for both systems the ZPLs are apparently broadened by fast unresolved spectral diffusion. Finally, we demonstrate that the low-temperature ensemble photoluminescence spectrum of the dimer cannot be reproduced by the distribution of spectral positions of the ZPLs. The dimer's bulk spectrum is rather apparently broadened by electron-phonon coupling to the low-energy skeletal mode, whereas for MeLPPP the inhomogeneous bulk line shape resembles the distribution of spectral positions of the ZPLs of single chromophores. PMID:26696134

  2. Association of retinal thickness and optic disc-to-fovea angle to axial length of young healthy eyes

    PubMed Central

    Yamashita, Takehiro; Sakamoto, Taiji; Terasaki, Hiroto; Tanaka, Minoru; Kii, Yuya; Uchino, Eisuke; Hisatomi, Toshio; Nakao, Kumiko

    2015-01-01

    Aim To determine the relationship between the axial length (AL) and the retinal thickness in the posterior pole and to the optic disc-to-fovea (ODF) angle of healthy eyes. Procedures A prospective, observational cross-sectional study (registration number, UMIN000006040) of 64 healthy right eyes (mean age 26.0±4.5 years) was performed. The thickness of the 64 areas within the central 24° area were measured in the Spectralis spectral domain–optical coherent tomographic images obtained by posterior pole scans. Each area was 3°×3°. The ODF angle was measured in each fundus photograph. The relationships between the AL and the retinal thickness of each of the 64 areas and the ODF angle were investigated by linear regression analyses. Results The mean AL was 25.0±1.3 mm and the mean ODF angle was 17.2°±1.0°. The average retinal thickness of the four areas around the fovea was constant and not significantly correlated with the AL. However, the retinal thicknesses of 54 of the other 60 areas were significantly and negatively correlated with the AL (R=−0.25 to −0.56, P<0.05). The ODF angle was also constant and not significantly correlated with the AL (R=−0.17, P=0.19). Conclusion The lack of significant correlations between the AL and the retinal thicknesses of the central 6° or the ODF angle suggests that there might be some feedback system to keep the central retinal thickness and ODF angle constant regardless of an elongation of the AL. PMID:26664037

  3. Life Science-Related Physics Laboratory on Geometrical Optics

    ERIC Educational Resources Information Center

    Edwards, T. H.; And Others

    1975-01-01

    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)

  4. Compact Color Schlieren Optical System

    NASA Technical Reports Server (NTRS)

    Buchele, Donald R.; Griffin, Devon W.

    1996-01-01

    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.

  5. New method of estimating wavelength-dependent optical path length ratios for oxy- and deoxyhemoglobin measurement using near-infrared spectroscopy.

    PubMed

    Umeyama, Shinji; Yamada, Toru

    2009-01-01

    In near-infrared spectroscopy (NIRS), concentration changes in oxy- and deoxyhemoglobin are calculated using an attenuation change of the measurement light and by solving a linear equation based on the modified Lambert-Beer law. While solving this equation, we need to know the wavelength-dependent mean optical path lengths of the measurement lights. However, it is very difficult to know these values by a continuous-wave-type (CW-type) system. We propose a new method of estimating wavelength-dependent optical path length ratios of the measurement lights based on the data obtained by a triple wavelength CW-type NIRS instrument. The proposed method does not give a path length itself, but it gives a path length ratio. Thus, it is possible to obtain the accurate hemoglobin concentration changes without cross talk, although the method cannot contribute to the quantification of the absolute magnitude of hemoglobin changes. The method is based on the principle that two possible estimations of hemoglobin concentration changes calculated using a triple-wavelength measurement system should be identical. The method was applied to the experimental data of human subjects' foreheads. The estimated path length ratios were very similar to literature values obtained by using picosecond laser pulses and a streak camera detector [M. Essenpreis et al., Appl. Opt. 32(4), 418-425 (1993)]. PMID:19895139

  6. Focal vibration in neurorehabilitation.

    PubMed

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

    2014-04-01

    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

  7. Partial (focal) seizure

    MedlinePlus

    ... Jacksonian seizure; Seizure - partial (focal); Temporal lobe seizure; Epilepsy - partial seizures ... Abou-Khalil BW, Gallagher MJ, Macdonald RL. Epilepsies. In: Daroff RB, ... 6th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 67. ...

  8. Analysis of adaptive laser scanning optical system with focus-tunable components

    NASA Astrophysics Data System (ADS)

    Pokorný, P.; Mikš, A.; Novák, J.; Novák, P.

    2015-05-01

    This work presents a primary analysis of an adaptive laser scanner based on two-mirror beam-steering device and focustunable components (lenses with tunable focal length). It is proposed an optical scheme of an adaptive laser scanner, which can focus the laser beam in a continuous way to a required spatial position using the lens with tunable focal length. This work focuses on a detailed analysis of the active optical or opto-mechanical components (e.g. focus-tunable lenses) mounted in the optical systems of laser scanners. The algebraic formulas are derived for ray tracing through different configurations of the scanning optical system and one can calculate angles of scanner mirrors and required focal length of the tunable-focus component provided that the position of the focused beam in 3D space is given with a required tolerance. Computer simulations of the proposed system are performed using MATLAB.

  9. 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)

    Wieland, Christopher F.

    2008-10-01

    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.

  10. Thin waveplate lenses: new generation in optics

    NASA Astrophysics Data System (ADS)

    Tabiryan, Nelson V.; Serak, Svetlana V.; Roberts, David E.; Steeves, Diane M.; Kimball, Brian R.

    2015-10-01

    We present new lenses - waveplate lenses created in liquid crystal materials. Waveplate lenses allowed focusing and defocusing laser beam depending on the sign of the circularity of laser beam polarization. Using an electrically-switchable liquid-crystal half-wave retarder we realized switching between focused and defocused beams by the waveplate lens. A combination of two such lenses allowed the collimation of a laser beam as well as the change of focal length of optical system. Lenses of varied size and focal length are presented.

  11. NICMOS flight focal plane assembly

    NASA Astrophysics Data System (ADS)

    Shin, Lloyd; Winters, Gregory S.

    1993-11-01

    This paper discusses the mechanical design and assembly of the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) focal plane assembly (FPA). The FPA consists of a mercury-cadmium-telluride (MCT) detector array hybridized to a silicon multiplexer (MUX), a sapphire carrier, an alumina ceramic multi-layer board (CMLB) including electrical components, a base plate, and flex cables. The FPA is designed for the following conditions; (1) shock and vibration during launch, (2) Coefficient of Thermal Expansion (CTE) of dissimilar materials at cryogenic temperature, (3) outgassing limitations to meet NASA's specifications, and (4) optical assembly tolerances. Also, the FPA is designed to be easily integrated into its dewar with provisions for mechanical as well as optical alignment. The FPA is assembled by building up two subassemblies in a parallel path, and then integrating the two subassemblies with the flex cables for the final assembly. These procedures are described in this paper, including alignment tolerances required and measured.

  12. Modeling the Size Distribution of Focal Adhesions

    PubMed Central

    Gov, Nir S.

    2006-01-01

    We calculate the size distribution of two-dimensional aggregates, for different simple dynamical growth models. The resulting size distributions of these domains, at steady state, are shown to depend strongly on the mode of domain growth. We then compare to the measured size-distribution of focal-adhesion domains. Using our calculation and the measured exponential distribution of focal-adhesion domain lengths can be used to test the validity of recent models proposed to describe the dynamics of these complexes in adhering cells. PMID:16861281

  13. The design of a stepper motor control-based high-precision varifocal imaging optical system

    NASA Astrophysics Data System (ADS)

    Xiang, Bai

    2012-11-01

    This study, while introducing the theories and makeup of conventional cam varifocal system, indicates the two faults stemming from their inherent mechanism and potentiometer-based focal-length measurement: 1) inability to stop optic axis vibration and 2) considerable error in real-time output of focal-length value. As a result, a stepper motor, instead of cam mechanism, was employed to control mirrors of variofocus and mirrors of compensation in moving accurately along straight-ling rails so that continuous focal-length variation and surface image positioning were accomplished; a linear encoder was substituted for potentiometer in realizing real-time output of focal-length value and also in closed-loop control of stepper motor. Compared with the cam mechanism, this system provides 90% less vibration and 80% more positioning precision, thereby basically solving the problems of the cam system and enabling the high-precision angular measurement.

  14. Optical design of glancing incidence extreme ultraviolet telescopes.

    PubMed

    Mangus, J D

    1970-05-01

    Glancing incidence telescope designs employing surfaces of revolution and of the same geometry as the Wolter type 2 telescope (a concave paraboloid followed by a confocal convex hyperboloid) are investigated for primarily solar physics applications in the spectral region greater than 100 A. The optical properties of the telescopes are evaluated in terms of minimum spot size and flattened focal surface as a function of optical acceptance (throughput) and folding ratio (physical length of the telescope/effective focal length). One meter focal length systems with full fields of 0.8 deg, throughputs of 15 x 10(-4) sr and 30 x 10(-4) sr, and maximum grazing angles of 13 deg are shown to exhibit optimum imaging properties for a folding ratio on the order of 0.85. PMID:20076325

  15. Decision-aided maximum likelihood phase estimation with optimum block length in hybrid QPSK/16QAM coherent optical WDM systems

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Wang, Yulong

    2016-01-01

    We propose a general model to entirely describe XPM effects induced by 16QAM channels in hybrid QPSK/16QAM wavelength division multiplexed (WDM) systems. A power spectral density (PSD) formula is presented to predict the statistical properties of XPM effects at the end of dispersion management (DM) fiber links. We derive the analytical expression of phase error variance for optimizing block length of QPSK channel coherent receiver with decision-aided (DA) maximum-likelihood (ML) phase estimation (PE). With our theoretical analysis, the optimum block length can be employed to improve the performance of coherent receiver. Bit error rate (BER) performance in QPSK channel is evaluated and compared through both theoretical derivation and Monte Carlo simulation. The results show that by using the DA-ML with optimum block length, bit signal-to-noise ratio (SNR) improvement over DA-ML with fixed block length of 10, 20 and 40 at BER of 10-3 is 0.18 dB, 0.46 dB and 0.65 dB, respectively, when in-line residual dispersion is 0 ps/nm.

  16. Biomimetic optical system using polymer lenses with tunable focus

    NASA Astrophysics Data System (ADS)

    Liang, Dan; Xiang, Ke; Du, Jia-Wei; Yang, Jun-Nan; Wang, Xuan-Yin

    2014-10-01

    A biomimetic system using polymer lenses for the optical design and application is developed. The system mainly consisted of a bionic cornea lens, voice coil motor, compression ring, bionic crystalline lens, substrate, and CCD sensor. By controlling the current of the voice coil motor, we could change the motion of the compression ring to alter the curvature radius of the bionic crystalline lens, thus adjusting the focal length of the whole system. The integrated constructure of the optical system was presented, as well as the detailed description of the lens composition, material, and fabrication process. Images under different displacement loads were captured, the relationship among the curvature radius, observed back focal length, and predicted effective focal length was analyzed, and the spot diagram of the optical system was simulated using ZEMAX software. The focal length of the optical system ranged from 17.3 to 24.5 mm under a tiny displacement load from 0 to 0.14 mm. Besides, the images captured at different rotating angles presented almost identical patterns and the same image quality, which showed good robustness to the gravity. The biomimetic optical system is of interest to develop an integrated, low-cost, and stable imaging system.

  17. Focal brainstem gliomas

    PubMed Central

    Sabbagh, Abdulrahman J.; Alaqeel, Ahmed M.

    2015-01-01

    Improved neuronavigation guidance as well as intraoperative imaging and neurophysiologic monitoring technologies have enhanced the ability of neurosurgeons to resect focal brainstem gliomas. In contrast, diffuse brainstem gliomas are considered to be inoperable lesions. This article is a continuation of an article that discussed brainstem glioma diagnostics, imaging, and classification. Here, we address open surgical treatment of and approaches to focal, dorsally exophytic, and cervicomedullary brainstem gliomas. Intraoperative neuronavigation, intraoperative neurophysiologic monitoring, as well as intraoperative imaging are discussed as adjunctive measures to help render these procedures safer, more acute, and closer to achieving surgical goals. PMID:25864061

  18. Towards Dualband Megapixel QWIP Focal Plane Arrays

    NASA Technical Reports Server (NTRS)

    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

    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.

  19. MTI Focal Plane Assembly Design and Performance

    SciTech Connect

    Ballard, M.; Rienstra, J.L.

    1999-06-17

    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.

  20. The design and application of large area intensive lens array focal spots measurement system

    NASA Astrophysics Data System (ADS)

    Chen, Bingzhen; Yao, Shun; Yang, Guanghui; Dai, Mingchong; Wang, Zhiyong

    2014-12-01

    Concentrating Photovoltaic (CPV) modules are getting thinner and using smaller cells now days. Correspondingly, large area intensive lens arrays with smaller unit dimension and shorter focal length are wanted. However, the size and power center of lens array focal spots usually differ from the design value and are hard to measure, especially under large area situation. It is because the machining error and deformation of material of the lens array are hard to simulate in the optical design process. Thus the alignment error between solar cells and focal spots in the module assembly process will be hard to control. Under this kind of situation, the efficiency of CPV module with thinner body and smaller cells is much lower than expected. In this paper, a design of large area lens array focal spots automatic measurement system is presented, as well as its prototype application results. In this system, a four-channel parallel light path and its corresponding image capture and process modules are designed. These modules can simulate focal spots under sunlight and have the spots image captured and processed using charge coupled devices and certain gray level algorithm. Thus the important information of focal spots such as spot size and location will be exported. Motion control module based on grating scale signal and interval measurement method are also employed in this system in order to get test results with high speed and high precision on large area lens array no less than 1m×0.8m. The repeatability of the system prototype measurement is +/-10μm with a velocity of 90 spot/min. Compared to the original module assembled using coordinates from optical design, modules assembled using data exported from the prototype is 18% higher in output power, reaching a conversion efficiency of over 31%. This system and its design can be used in the focal spot measurement of planoconvex lens array and Fresnel lens array, as well as other kinds of large area lens array application with small focal spots.

  1. Solid-state curved focal plane arrays

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2005-03-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Ford, Virginia; Parks, Rick; Coleman, Michelle

    2004-01-01

    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.

  4. Focal Plane Metrology for the LSST Camera

    SciTech Connect

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

    2007-01-10

    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 {micro}m P-V) over the entire field of view (640 mm diameter) at the operating temperature (T {approx} -100 C) and over the operational elevation angle range. We briefly describe the hierarchical 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.

  5. Focal plane metrology for the LSST camera

    NASA Astrophysics Data System (ADS)

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

    2006-06-01

    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 μm 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.

  6. Dense Pattern Optical Multipass Cell

    NASA Technical Reports Server (NTRS)

    Silver, Joel A. (Inventor)

    2009-01-01

    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.

  7. Dense pattern optical multipass cell

    DOEpatents

    Silver, Joel A [Santa Fe, NM

    2009-01-13

    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.

  8. Electro-Optical Characteristics of P+n In0.53Ga0.47As Hetero-Junction Photodiodes in Large Format Dense Focal Plane Arrays

    NASA Astrophysics Data System (ADS)

    DeWames, R.; Littleton, R.; Witte, K.; Wichman, A.; Bellotti, E.; Pellegrino, J.

    2015-08-01

    This paper is concerned with focal plane array (FPA) data and use of analytical and three-dimensional numerical simulation methods to determine the physical effects and processes limiting performance. For shallow homojunction P+n designs the temperature dependence of dark current for T < 300 K depends on the intrinsic carrier concentration of the In0.53Ga0.47As material, implying that the dominant dark currents are generation and recombination (G-R) currents originating in the depletion regions of the double layer planar heterostructure (DLPH) photodiode. In the analytical model differences from bulk G-R behavior are modeled with a G-R like perimeter-dependent shunt current conjectured to originate at the InP/InGaAs interface. In this description the fitting property is the effective conductivity, σ eff( T), in mho cm-1. Variation in the data suggests σ eff (300 K) values of 1.2 × 10-11-4.6 × 10-11 mho cm-1). Substrate removal extends the quantum efficiency (QE) spectral band into the visible region. However, dead-layer effects limit the QE to 10% at a wavelength of 0.5 μm. For starlight-no moon illumination conditions, the signal-to-noise ratio is estimated to be 50 at an operating temperature of 300 K. A major result of the 3D numerical simulation of the device is the prediction of a perimeter G-R current not associated with the properties of the metallurgical interface. Another is the prediction that for a junction positioned in the larger band gap InP cap layer the QE is bias-dependent and that a relatively large reverse bias ≥0.9 V is needed for the QE to saturate to the shallow homojunction value. At this higher bias the dark current is larger than the shallow homojunction value. The 3D numerical model and the analytical model agree in predicting and explaining the measured radiatively limited diffusion current originating at the n-side of the junction. The calculations of the area-dependent G-R current for the condition studied are also in agreement. Unique advantages of the 3D numerical simulation are the ability to mimic real device structures, achieve deeper understanding of the real physical effects associated with the various methods of junction formation, and predict how device designs will function.

  9. Ultrasound of Focal Neuropathies.

    PubMed

    Hobson-Webb, Lisa D; Padua, Luca

    2016-04-01

    Focal neuropathies represent the most common indication for referral to electrodiagnostic laboratories. The etiologies range from chronic compression, as might be seen in carpal tunnel syndrome, to acute traumatic nerve injuries that require rapid intervention. The gold standard for diagnosis, electrodiagnostic testing, cannot provide the complementary anatomical information necessary to guide accurate diagnosis and treatment. An expanding body of literature supports the use of neuromuscular ultrasound as a standard component for evaluating focal neuropathies. In the current review, the role of ultrasound in both common and unusual compression neuropathies is reviewed, along with the use of ultrasound in traumatic nerve injury. The evidence demonstrates that nerve ultrasound has an essential, complementary role with electrodiagnostic testing. PMID:27035249

  10. OPO performance with a long pulse length, single frequency Nd:YAG laser pump. [Optical Parametric Oscillators

    NASA Technical Reports Server (NTRS)

    Kozlovsky, W. J.; Gustafson, E. K.; Eckardt, R. C.; Byer, R. L.

    1988-01-01

    With the advent of new nonlinear materials and single-frequency pump sources, there is renewed interest in optical parametric oscillators (OPOs). A single-mode diode-laser-pumped monolithic Nd:YAG nonplanar ring laser that is both amplified and frequency doubled is used to pump a monolithic MgO:LiNbO3 pulsed singly resonant OPO. The OPO signal output was temperature tuned from 834 to 958 nm, producing an idler tuning from 1.47 to 1.2 microns. Efforts toward a CW all-solid-state doubly resonant OPO are also described.

  11. Aberration-free short focal length x-ray lenses.

    PubMed

    Alianelli, Lucia; del Rio, Manuel Sánchez; Fox, Oliver J L; Korwin-Mikke, Katarzyna

    2015-12-01

    We treat the problem of defining the ideal x-ray refractive lens design for point focusing of low emittance x-ray beams at third- and fourth-generation synchrotron sources. The task is accomplished by using Fermat's principle to define a lens shape that is completely free from geometrical aberrations. Current microfabrication resolution limits are identified, and a design that tolerates the inherent fabrication imperfections is proposed. The refractive lens design delivers nanometer-sized focused x-ray beams and is compatible with current microfabrication techniques. PMID:26625057

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

    NASA Technical Reports Server (NTRS)

    Sewell, James S.; Bozada, Christopher A.

    1994-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

  14. Focal cortical dysplasia - review.

    PubMed

    Kabat, Joanna; Król, Przemysław

    2012-04-01

    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. PMID:22844307

  15. Wide-Range Thermometry at Micro/Nano Length Scales with In2O3 Octahedrons as Optical Probes.

    PubMed

    Senapati, Subrata; Nanda, Karuna Kar

    2015-10-28

    We report the temperature-dependent photoluminescence and Raman spectra of In2O3 octahedrons synthesized by an evaporation-condensation process. The luminescence obtained here is due to the defect-related deep level emission, which shows highly temperature-dependent behavior in 83-573 K range. Both the position as well as the intensity varies with temperature. Similarly, Raman spectroscopy in 83-303 K range shows temperature-dependent variation in peak intensity but no change in the peak position. Interestingly, the variation of intensity for different peaks is consistent with Placzek theory which invokes the possibility of temperature sensing. We demonstrate the reversibility of peak intensity with temperature for consecutive cycles and excellent stability of the octahedrons toward cryogenic temperature sensing. Overall, both the temperature-dependent photoluminescence and Raman spectra can be explored to determine temperature in the cryogenic range at micro/nano length scales. As an example, we evaluate the temperature-dependent Raman spectra of WO3 that undergoes a phase transition around 210 K and temperature-dependent luminescence of Rhodamine 6G (Rh6G) where intensity varies with temperature. PMID:26447886

  16. Introduction into service of mature pushbroom electro-optic sensors

    NASA Astrophysics Data System (ADS)

    Brownie, Ralph S.

    2000-11-01

    Pushbroom Electro-Optic sensors have been developed and brought into full production, entering service in year 2000 on RAF Jaguar and Belgian Air Force F-16. The use of fiber- optic gyroscopes, closely coupled to the focal plane electronics, permits correction of all motion effects and provides practical high quality, stereo imagery at high V/H ratios. This paper describes technical features and samples of imagery from a scalable range of sensors incorporating focal lengths from 38mm to 900mm and operating throughout the full flight envelope of modern fighter aircraft.

  17. Focal adhesions in osteoneogenesis

    PubMed Central

    Biggs, M.J.P; Dalby, M.J

    2010-01-01

    As materials technology and the field of tissue engineering advances, the role of cellular adhesive mechanisms, in particular the interactions with implantable devices, becomes more relevant in both research and clinical practice. A key tenet of medical device technology is to use the exquisite ability of biological systems to respond to the material surface or chemical stimuli in order to help develop next-generation biomaterials. The focus of this review is on recent studies and developments concerning focal adhesion formation in osteoneogenesis, with an emphasis on the influence of synthetic constructs on integrin mediated cellular adhesion and function. PMID:21287830

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

    PubMed

    Mikš, Antonín; Novák, Pavel

    2012-10-20

    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

  19. [The focal renal lesions].

    PubMed

    Tuma, Jan

    2013-06-01

    The focal renal lesions are altogether common. Most frequently are found Columna Bertini hypertrophies (so called pseudotumors) and simple renal cysts. The role of sonography in the practice is to distinguish pseudotumors from real renal tumors, and simple renal cysts from complex cysts. The differentiation of complex renal cysts is possible with the help of the CEUS (= contrast enhanced ultrasound) and other imaging modalities such as CT or MRI. In these cases, the CEUS imaging agent has clear advantages over CT and MRI, because it is composed of gas bubbles, which are only slightly smaller than red blood cells and remains exclusively intravascularly while the CT and MRI contrast agents diffuse into the interstitial space without any real perfusion. The real tumors can be differentiated from certain focal non-tumorous changes based on the ultrasound and clinic. The further differentiation of individual kidney tumors and metastases using ultrasound, MRI, CT and CEUS is only partly possible. In all uncertain or unclear cases, therefore, an open or ultrasound-guided biopsy is useful. PMID:23735765

  20. Determination of critical diameters for intrinsic carrier diffusion-length of GaN nanorods with cryo-scanning near-field optical microscopy

    PubMed Central

    Chen, Y. T.; Karlsson, K. F.; Birch, J.; Holtz, P. O.

    2016-01-01

    Direct measurements of carrier diffusion in GaN nanorods with a designed InGaN/GaN layer-in-a-wire structure by scanning near-field optical microscopy (SNOM) were performed at liquid-helium temperatures of 10 K. Without an applied voltage, intrinsic diffusion lengths of photo-excited carriers were measured as the diameters of the nanorods differ from 50 to 800 nm. The critical diameter of nanorods for carrier diffusion is concluded as 170 nm with a statistical approach. Photoluminescence spectra were acquired for different positions of the SNOM tip on the nanorod, corresponding to the origins of the well-defined luminescence peaks, each being related to recombination-centers. The phenomenon originated from surface oxide by direct comparison of two nanorods with similar diameters in a single map has been observed and investigated. PMID:26876009

  1. Creation of identical multiple focal spots with prescribed axial distribution.

    PubMed

    Yu, Yanzhong; Zhan, Qiwen

    2015-01-01

    We present a scheme for the construction of coaxially equidistant multiple focal spots with identical intensity profiles for each individual focus and a predetermined number and spacing. To achieve this, the radiation field from an antenna is reversed and then gathered by high numerical aperture objective lenses. Radiation patterns from three types of line sources, i.e., the electric current, magnetic current and electromagnetic current distributions, with cosine-squared taper are respectively employed to generate predominately longitudinally polarized bright spots, azimuthally polarized doughnuts, and focal spots with a perfect spherically symmetric intensity distribution. The required illuminations at the pupil plane of a 4Pi focusing configuration for the creation of these identical multiple focal spots can be easily derived by solving the inverse problem of the antenna radiation field. These unique focal field distributions may find potential applications in laser direct writing and optical microscopy, as well as multiple-particle trapping, alignment, and acceleration along the optical axis. PMID:26424051

  2. Creation of identical multiple focal spots with prescribed axial distribution

    PubMed Central

    Yu, Yanzhong; Zhan, Qiwen

    2015-01-01

    We present a scheme for the construction of coaxially equidistant multiple focal spots with identical intensity profiles for each individual focus and a predetermined number and spacing. To achieve this, the radiation field from an antenna is reversed and then gathered by high numerical aperture objective lenses. Radiation patterns from three types of line sources, i.e., the electric current, magnetic current and electromagnetic current distributions, with cosine-squared taper are respectively employed to generate predominately longitudinally polarized bright spots, azimuthally polarized doughnuts, and focal spots with a perfect spherically symmetric intensity distribution. The required illuminations at the pupil plane of a 4Pi focusing configuration for the creation of these identical multiple focal spots can be easily derived by solving the inverse problem of the antenna radiation field. These unique focal field distributions may find potential applications in laser direct writing and optical microscopy, as well as multiple-particle trapping, alignment, and acceleration along the optical axis. PMID:26424051

  3. Creation of identical multiple focal spots with prescribed axial distribution

    NASA Astrophysics Data System (ADS)

    Yu, Yanzhong; Zhan, Qiwen

    2015-10-01

    We present a scheme for the construction of coaxially equidistant multiple focal spots with identical intensity profiles for each individual focus and a predetermined number and spacing. To achieve this, the radiation field from an antenna is reversed and then gathered by high numerical aperture objective lenses. Radiation patterns from three types of line sources, i.e., the electric current, magnetic current and electromagnetic current distributions, with cosine-squared taper are respectively employed to generate predominately longitudinally polarized bright spots, azimuthally polarized doughnuts, and focal spots with a perfect spherically symmetric intensity distribution. The required illuminations at the pupil plane of a 4Pi focusing configuration for the creation of these identical multiple focal spots can be easily derived by solving the inverse problem of the antenna radiation field. These unique focal field distributions may find potential applications in laser direct writing and optical microscopy, as well as multiple-particle trapping, alignment, and acceleration along the optical axis.

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

    NASA Astrophysics Data System (ADS)

    Javad Eslamibidgoli, Mohammad; Lagowski, Jolanta B.

    2012-02-01

    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.

  5. How Bond Length Alternation and Thermal Disorder Affect the Optical Excitation Energies of π-Conjugated Chains: A Combined Density Functional Theory and Molecular Dynamics Study.

    PubMed

    Bois, Juliana; Körzdörfer, Thomas

    2016-04-12

    We dissect the sources of error leading to inaccuracies in the description of the geometry and optical excitation energies of π-conjugated polymers. While the ground-state bond length alternation is shown to be badly reproduced by standard functionals, the recently adapted functionals PBEh* and ωPBE* as well as the double hybrid functional XYGJ-OS manage to replicate results obtained at the CCSD(T) level. By analysis of the bond length alternation in the excited state, a sensitive dependence of the exciton localization on the long-range behavior of the functional and the amount of Hartree-Fock exchange present is shown. Introducing thermal disorder through molecular dynamics simulations allows the consideration of a range of thermally accessible configurations of each oligomer, including trans to cis rotations, which break the conjugation of the backbone. Thermal disorder has a considerable effect when combined with functionals that overestimate the delocalization of the excitation, such as B3LYP. For functionals with a larger amount of exact exchange such as our PBEh* and ωPBE*, however, the effect is small, as excitations are often localized enough to fit between twists in the chain. PMID:26960057

  6. Angle amplifying optics using plane and ellipsoidal reflectors

    DOEpatents

    Glass, Alexander J.

    1977-01-01

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

  7. Focal dermal hypoplasia: updates.

    PubMed

    Wang, L; Jin, X; Zhao, X; Liu, D; Hu, T; Li, W; Jiang, L; Dan, H; Zeng, X; Chen, Q

    2014-01-01

    Focal dermal hypoplasia (FDH), or Goltz-Gorlin syndrome, is a rare syndrome and may result in multisystem disorders. Several reviews of FDH have been published. However, the last comprehensive review of this disorder appeared more than 20 years ago. To date, a number of new clinical manifestations have been reported and considerable knowledge has accumulated regarding etiology and pathogenetic mechanisms. The purpose of this review is to gather these more recent data and to provide organized and reliable information. So we reviewed 159 cases of FDH that had been reported from 1990 to 2012, summarized the new discoveries, and suggested a potential standard for the diagnosis of FDH. We also reported on a Chinese girl with FDH, who was clinically and histologically in accord with FDH, as an example. PMID:23463902

  8. Pediatric focal epilepsy syndromes.

    PubMed

    Sánchez Fernández, Iván; Loddenkemper, Tobias

    2012-10-01

    Benign epilepsy with centrotemporal spikes, early-onset childhood occipital epilepsy (Panayiotopoulos syndrome [PS]) and late-onset childhood occipital epilepsy (Gastaut type [LOCE-G]) are the principal pediatric focal epilepsy syndromes. They share major common characteristics: the appearance and resolution of electroclinical features are age related, there is a strong genetic predisposition, the clinical course is often mild with infrequent and easy to control seizures, interictal epileptiform activity is disproportionately abundant when compared with the clinical correlate, and tends to potentiate and generalize during sleep. In this review, we outline the relevant pathophysiology underlying this electroclinical spectrum. Then, the initial description of individual syndromes is followed by a summary of overlapping features and intermediate presentations that question the boundaries between these entities and provide the basis for the concept of a childhood seizure susceptibility syndrome. Additionally, we outline the main features of the related epileptic encephalopathies. An outlook on potential future lines of research completes this review. PMID:23027100

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

    NASA Astrophysics Data System (ADS)

    Khoei, Ramin

    2009-11-01

    In this work, the design study of a switchable dual field of view thermal optical system for 3-5 μm 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 μm pixel pitch is imaging the rays gathered by thermal optics. To avoid vignetting which is caused by the presence of the detector cold shield, a relay lens is used to image the entrance pupil of optics on the cold shield.

  10. Focal region fields of distorted reflectors

    NASA Technical Reports Server (NTRS)

    Buris, N. E.; Kauffman, J. F.

    1988-01-01

    The problem of the focal region fields scattered by an arbitrary surface reflector under uniform plane wave illumination is solved. The physical optics (PO) approximation is used to calculate the current induced on the reflector. The surface of the reflector is described by a number of triangular domain-wise 5th degree bivariate polynomials. A 2-dimensional Gaussian quadrature is employed to numerically evaluate the integral expressions of the scattered fields. No Freshnel or Fraunhofer zone approximations are made. The relation of the focal fields problem to surface compensation techniques and other applications are mentioned. Several examples of distorted parabolic reflectors are presented. The computer code developed is included, together with instructions on its usage.

  11. Intelligent Optical Systems Using Adaptive Optics

    NASA Technical Reports Server (NTRS)

    Clark, Natalie

    2012-01-01

    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.

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

    PubMed

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

    2013-02-20

    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

  13. Optically recorded tunable microlenses based on dye-doped liquid crystal cells

    NASA Astrophysics Data System (ADS)

    Lucchetti, Liana; Tasseva, Jordanka

    2012-04-01

    We report on optically recorded microlenses in conventional liquid crystal cells doped with the azo-dye methyl-red. The focal length can be tuned electrically and changed in a wide range with just a small variation of the applied dc voltage. No patterned electrodes, built-in polymeric lens, or patterned molecular reorientation are required.

  14. Fabrication of D-type fiber optic sensors with a long interaction length and studying effects of critical parameters on sensor response

    NASA Astrophysics Data System (ADS)

    Guleryuz, Burcu; Durucan, Caner; Aslan, Mustafa M.

    2014-05-01

    Today evanescent wave based fiber optic (F/O) platforms are in favor of the use for monitoring molecular interactions since they are practical, economic and easy to operate which make them ideal turnkey systems for clinical, pharmaceutical, environmental and security applications. The side polishing is one of techniques for reshaping the geometry of the waveguide to make the F/O sensor more sensitive to surrounding refractive index (RI) in evanescent field. In this study D-type F/O sensors with a 25 mm-long interaction lengths are fabricated. In addition to that, effects of the critical parameters such as the polishing depth, the wavelength, and the temperature on the sensor response are determined for the RI in the range of 1.33 - 1.47. The developing key of these F/O sensors is reaching high strength and penetration depth of evanescent wave in varying RI of the surrounding bio-layer. Development steps of D-type F/O sensors are; fabrication of supporting elements - silicon V channels, F/O cable preparation, adhesion, lapping and polishing, fusing the FC connectors, construction of the optical system, and RI measurements. Details of these steps are explained and the general characteristics of the D-type F/O sensor are presented. Results indicate that the sensor's responses in three different RI ranges can be improved by the polishing depth. A maximum sensitivity of around 2x105 for the D-type F/O sensors is demonstrated in the RI range of 1.44-1.46.

  15. Focal plane scanner with reciprocating spatial window

    NASA Technical Reports Server (NTRS)

    Mao, Chengye (Inventor)

    2000-01-01

    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.

  16. Optical sensitivity analysis of deformed mirrors for microcantilever array IR imaging.

    PubMed

    Shi, Haitao; Zhang, Qingchuan; Qian, Jian; Mao, Liang; Cheng, Teng; Gao, Jie; Wu, Xiaoping; Chen, Dapeng; Jiao, Binbin

    2009-03-16

    Optical sensitivity is a major issue to improve the sensor responsivity and the spatial resolution of uncooled optomechanical focal plane arrays (FPA). The optical sensitivity is closely related to the mirror length and the undesired mirror deformation induced from the imbalanced residual stresses in different layers. In this paper, the influences of mirror length and deformation on the optical sensitivity are discussed by Fourier Optics. Theoretical analysis and experiments demonstrate that the optical sensitivity is seriously degraded by undesired mirror deformation, and that there exists an optimal mirror length which makes the optical sensitivity achieve its maximum under a certain mirror deformation. Based on the results, an optimized mirror configuration is presented to increase the optical sensitivity of substrate-free bi-material microcantilever array (SFBMA). PMID:19293864

  17. Focal adhesion kinase

    PubMed Central

    Stone, Rebecca L; Baggerly, Keith A; Armaiz-Pena, Guillermo N; Kang, Yu; Sanguino, Angela M; Thanapprapasr, Duangmani; Dalton, Heather J; Bottsford-Miller, Justin; Zand, Behrouz; Akbani, Rehan; Diao, Lixia; Nick, Alpa M; DeGeest, Koen; Lopez-Berestein, Gabriel; Coleman, Robert L; Lutgendorf, Susan; Sood, Anil K

    2014-01-01

    This investigation describes the clinical significance of phosphorylated focal adhesion kinase (FAK) at the major activating tyrosine site (Y397) in epithelial ovarian cancer (EOC) cells and tumor-associated endothelial cells. FAK gene amplification as a mechanism for FAK overexpression and the effects of FAK tyrosine kinase inhibitor VS-6062 on tumor growth, metastasis, and angiogenesis were examined. FAK and phospho-FAKY397 were quantified in tumor (FAK-T; pFAK-T) and tumor-associated endothelial (FAK-endo; pFAK-endo) cell compartments of EOCs using immunostaining and qRT-PCR. Associations between expression levels and clinical variables were evaluated. Data from The Cancer Genome Atlas were used to correlate FAK gene copy number and expression levels in EOC specimens. The in vitro and in vivo effects of VS-6062 were assayed in preclinical models. FAK-T and pFAK-T overexpression was significantly associated with advanced stage disease and increased microvessel density (MVD). High MVD was observed in tumors with elevated endothelial cell FAK (59%) and pFAK (44%). Survival was adversely affected by FAK-T overexpression (3.03 vs 2.06 y, P = 0.004), pFAK-T (2.83 vs 1.78 y, P < 0.001), and pFAK-endo (2.33 vs 2.17 y, P = 0.005). FAK gene copy number was increased in 34% of tumors and correlated with expression levels (P < 0.001). VS-6062 significantly blocked EOC and endothelial cell migration as well as endothelial cell tube formation in vitro. VS-6062 reduced mean tumor weight by 56% (P = 0.005), tumor MVD by 40% (P = 0.0001), and extraovarian metastasis (P < 0.01) in orthotopic EOC mouse models. FAK may be a unique therapeutic target in EOC given the dual anti-angiogenic and anti-metastatic potential of FAK inhibitors. PMID:24755674

  18. Robust focusing optics for high-power laser welding

    NASA Astrophysics Data System (ADS)

    McAllister, Blake

    2014-02-01

    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.

  19. Statistical Earthquake Focal Mechanism Forecasts

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  20. Efficient subwavelength focusing of light with a long focal depth

    NASA Astrophysics Data System (ADS)

    Huang, He; Li, Qing; Fu, Jian; Wu, James; Lin, Feng; Wu, Xingkun

    2015-10-01

    We demonstrate an efficient method for far-field subwavelength focusing by a novel two-component axicon structure. Annular beams generated by a fiber axicon are focused using a micro-cone reflector, creating a quasi-Bessel beam with a high convergence angle of up to 40°. A center focal spot diameter of 0.41λ was achieved at a power efficiency of over 40%, with a focal depth of 9λ and a working distance as long as 35 μm. We further demonstrate that experimental knife-edge measurements mapping the beam focal intensity agree with numerical simulations of the structure. This method shows demonstrable promise in overcoming the optical focusing limit of single-element axicons and great potential for use in high tolerance, high-resolution applications in optical systems.

  1. Intrinsic parameterization of a computational optical system for long-distance displacement structural monitoring

    NASA Astrophysics Data System (ADS)

    Martins, Luís F. Lages; Rebordão, José Manuel N. V.; Ribeiro, Álvaro Silva

    2015-01-01

    We aim at the intrinsic parameterization of a computational optical system applied in long-distance displacement measurement of large-scale structures. In this structural-monitoring scenario, the observation distance established between the digital camera and reference targets, which is composed of the computational optical system, can range from 100 up to 1000 m, requiring the use of long-focal length lenses in order to obtain a suitable sensitivity for the three-dimensional displacement measurement of the observed structure which can be of reduced magnitude. Intrinsic parameterization of long-focal length cameras is an emergent issue since conventional approaches applied for reduced focal length cameras are not suitable mainly due to ill-conditioned matrices in least squares estimation procedures. We describe the intrinsic parameterization of a long-focal length camera (600 mm) by the diffractive optical element method and present the obtained estimates and measurement uncertainties, discussing their contribution for the system's validation by calibration field test and displacement measurement campaigns in a long-span suspension bridge.

  2. Optical system design of visible camera for space debris

    NASA Astrophysics Data System (ADS)

    Wang, Hu; Luo, Jianjun

    2013-08-01

    In order to detect the space debris, a visible camera for space debris was proposed.The visible camera was mainly consisted of primary mirror , secondary mirror.In order to balance aberration, six correcting lens were used in the optical system. To reduce the visible camera system size, two mirrors were joined,which could fold the system and shorten the overall length.The focal length was 12000 mm ,field of view was 1. 0 and the f-number was 10.0.The imaging quafity of the optical system in visible camera approached to diffraction limit.

  3. The Characteristics of Broad and Narrow Focal Zone Lithotripters

    NASA Astrophysics Data System (ADS)

    Pishchalnikov, Yuri A.; McAteer, James A.; VonDerHaar, R. Jason; Pishchalnikova, Irina V.; Williams, James C.

    2008-09-01

    The focal width of a lithotripter is a measure of the diameter of its focal zone, the region where acoustic pressures are at least half the maximum positive pressure generated at a given power level. Different lithotripters have different focal widths. The Dornier HM3, for example, has a focal width of ˜10-12 mm and for many years this was the widest focal zone among clinical machines. Electromagnetic lithotripters tend to have narrower focal zones, in the range of ˜4-6 mm. Recent studies suggesting that focal width plays an important role in stone breakage prompted this assessment of two electromagnetic lithotripters. Acoustical mapping using a fiber optic probe hydrophone (FOPH-500) and breakage of U-30 gypsum model stones were used to compare a conventional lithotripter (Dornier DoLi-50) and a broad focal zone device (XiXin XX-ES). FOPH mapping characterized the focal width of the DoLi to be about 5mm and that of the XX-ES to be much wider (˜18 mm). For stone breakage experiments the DoLi was fired at power level 3 (mid-range) and the XX-ES was operated at the recommended clinical setting of 9.3 kV. Both lithotripters were fired at 60 SW/min. U-30 model stones held in a 2mm mesh basket were positioned at the clinical target point on the acoustic axis and at 5mm steps laterally, and the number of SW's to complete fragmentation was counted. Breakage on-axis was similar for the two machines (DoLi 676±105 SW's versus XX-ES 644±123 SW's, p>0.6), but at 15mm the DoLi required nearly twice the number of SW's as the XX-ES (DoLi 3006±780 SW's versus 1726±972 SW's, p<0.006). This demonstrates that a broad focal zone lithotripter is more effective in breaking stones off axis and supports the idea that focal width is an important feature, likely to be relevant in the clinical setting where respiratory motion may limit the effectiveness of narrow focal zone machines.

  4. "METHOD": A tool for mechanical, electrical, thermal, and optical characterization of single lens module design

    NASA Astrophysics Data System (ADS)

    Besson, Pierre; Dominguez, Cesar; Voarino, Philippe; Garcia-Linares, Pablo; Weick, Clement; Lemiti, Mustapha; Baudrit, Mathieu

    2015-09-01

    The optical characterization and electrical performance evaluation are essential in the design and optimization of a concentrator photovoltaic system. The geometry, materials, and size of concentrator optics are diverse and different environmental conditions impact their performance. CEA has developed a new concentrator photovoltaic system characterization bench, METHOD, which enables multi-physics optimization studies. The lens and cell temperatures are controlled independently with the METHOD to study their isolated effects on the electrical and optical performance of the system. These influences can be studied in terms of their effect on optical efficiency, focal distance, spectral sensitivity, electrical efficiency, or cell current matching. Furthermore, the irradiance map of a concentrator optic can be mapped to study its variations versus the focal length or the lens temperature. The present work shows this application to analyze the performance of a Fresnel lens linking temperature to optical and electrical performance.

  5. Optical design of the multi-spectral camera (MSC) for high-resolution Earth observation

    NASA Astrophysics Data System (ADS)

    Jang, Hong-Sul; Jung, Dae-Jun; Lee, Seunghoon

    2005-12-01

    The Multi-Spectral Camera (MCS) is the electro-optical imaging isntrument for high-resolution observation of the Earth with push broom scanning in the space. The MSC uses compact and light weighted optical design to tkae image with high MTF (modulation transfer function) performance. The Ritchey-Chretien with focal correct lens is selected to implement enough performance in the wide swath width. The focal plane has one panchromatic (PAN) and four multi-spectral (MS) CCD (charge coupled device) for the imaging of visible and near-infrared wavelength. The PAN and MS have their own focus correct lens to correct field aberration and also to make proper effective focal length. Here we present the optical design and analysis of the MSC.

  6. Curved focal plane detector array for wide field cameras.

    PubMed

    Dumas, Delphine; Fendler, Manuel; Baier, Nicolas; Primot, Jérôme; le Coarer, Etienne

    2012-08-01

    Miniaturization is the main goal for system design in future cameras. This paper offers a novel method to scale down the optical system and to improve the image quality. As with the human retina, the detector array is spherically bent to fit the curved image surface; so the field curvature aberration is directly suppressed, leading to a better resolution and a simplified optical design. By thinning the substrate, the device is monolithically curved without modifying the fabrication process of the active pixels. Optical characterizations have been performed on planar and curved focal plane based cameras to illustrate the optical advantages of detector array curvature. PMID:22859030

  7. Focal plane electronics for the GAIA focal plane demonstrator

    NASA Astrophysics Data System (ADS)

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

    2006-09-01

    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.

  8. Study of focal shift effect in planar GaN high contrast grating lenses.

    PubMed

    He, Shumin; Wang, Zhenhai; Liu, Qifa; Wang, Wei

    2015-11-16

    In this paper, systematical study on the focal shift phenomenon in planar lenses based on GaN high contrast gratings was performed using finite element method (FEM). Influence of parameters including device size, designed focal length, total phase difference on the focusing performance is presented. It shows that the focal shift is mainly determined by the Fresnel number of the lens, which is nearly equal to the total phase difference divided by π. The influence of the lens size and designed focal length can be attributed to the change of Fresnel number. Theoretical analysis based on diffraction theory is employed to predict the focal shift, which is in accordance with the numerical simulation. PMID:26698420

  9. Micro-optics metrology using advanced interferometry

    NASA Astrophysics Data System (ADS)

    Reichelt, Stephan; Bieber, Alexander; Aatz, Bernd; Zappe, Hans

    2005-06-01

    Interferometric testing of micro-optical components involves some challenges due to problems such as Fresnel diffraction artefacts, the non-common path interferometer configuration, coherent noise as well disturbing interferences, and uncertainties in distance measurements. Recently we have developed a versatile Mach-Zehnder / Twyman-Green hybride interferometer for micro-optics testing. The system combines the advantages of both interferometer types and allows full characterization of lens and surface figure errors as well as radius of curvature and focal length measurements. The interferometer system is explained and measurement results of micro-lenses are presented. Furthermore, this paper is concerned with the metrology challenges of interferometric testing on microscopic scales.

  10. Focal properties of a plane grating in a convergent beam.

    PubMed

    Hall, J T

    1966-06-01

    Focusing from a plane grating can be accomplished by using convergent radiation incident on the grating in such a manner that any incident angle alpha(n), the resulting diffraction angle beta(n), will be on the same side of the grating normal. The theory for the focal properties is developed by applying Fermat's principle of least time to selected terms resulting from a finite series expansion of the system's distance function. Derivations are given for finding the focal curve equation, astigmatism, and coma, of the most usable configuration of the optical components. Discussions of the aberrations disclose methods for eliminating the astigmatism and reducing the coma. PMID:20049009

  11. Imaging of focal calvarial lesions.

    PubMed

    Mitra, I; Duraiswamy, M; Benning, J; Joy, H M

    2016-04-01

    Focal calvarial lesions may present as a visible, palpable, or symptomatic lump; however, with increasing use of cross-sectional imaging they are often encountered as an incidental finding. Knowledge of the possible disease entities along with a structured approach to imaging is required to suggest an appropriate diagnosis and assist in management planning. Abnormalities range from common neoplastic lesions to rarer congenital conditions, benign pathologies, and calvarial defects that can mimic lesions. The aim of this article is to demonstrate the salient imaging features that may help to limit the differential diagnosis of a focal calvarial lesion. PMID:26873626

  12. Optical system for an astrometric survey from space

    NASA Astrophysics Data System (ADS)

    Phillips, James D.; Reasenberg, Robert D.

    1998-08-01

    We present an optical design for a spaceborne instrument, of about half m aperture, to perform a combined astrometic and photometric survey via a scan similar to that of Hipparcos. A CCD detector array with time delayed integration will permit an astrometic mission accuracy better than 50 microarcseconds for stars brighter than 10th magnitude. 1 1/2 orders better than Hipparcos. The passband is nominally 0.4 to 0.9 microns. For the instrument to have both high measurements rate and high accuracy, the optical system just satisfy several requirements. It should have aberration well under diffraction, for high precision in centroiding and as a means of keeping unmolded shifts of the image centroids small. The system should have a wide field of view so that there is a large overlap of successive scans, have a large field of view for scientific throughput, and have low image distortion so that the stellar images moved at constant rate along columns of detector pixels. The design presented meets these requirements using aspheric surfaces that are manufacturable. We have demonstrated that the instrument will determine the temperature of an observed star without requiring a dispersive element or color filters. The design is thus free of transmissive elements, and protected from the systematic errors that they might have induced, e.g., due to thermal variation variation and to chromatic effects. This study was inspired by our previous consideration of scientific throughput. Our study of data reduction from a scanning astrometic survey mission demonstrated that there is a substantial gain in mission accuracy if the spacecraft precesses without discontinuities such as those that result from gas jet firings. Our study of methods of processing the spacecraft showed that smooth rotation would be possible using solar radiation pressure, but only if the spacecraft rotation rate were increased. Maintaining the integration time for each object would require an optical design of shorter focal length. Meanwhile, our study of mission accuracy as a function of focal length showed that another increase of accuracy would result from shorter focal length, via the greater number of lower-accuracy measurements. Therefore we performed this optical study to find a design with shorter focal length, having a proportionate increase in infield of view. We conceived and investigated a family of short focal length, wide-field designs, and developed a methodology to facilitate selection from among them. The new baseline design achieves diffraction-limited images over a 2.2 degree FOV with a 1.1 degree square central blockage, and has a 7.5 m focal length.

  13. Diffraction optical elements with nematic liquid crystals and their applications

    NASA Astrophysics Data System (ADS)

    Stashkevitch, Ihar V.

    1998-02-01

    In this paper consideration is being given to the principle underlying the operation of switchable diffraction elements based on the relief grating of isotropic materials and nematic liquid crystals contacting it. Electrical control of the phase grating diffraction efficiency has been experimentally realized. The problems of LC orientation on the relief substrate have been considered. Consideration has also been given to the optical diffraction lens with switchable focal lengths and to two-layer systems operating with radiation of any polarization. It has been demonstrated that LC having large value of optical anisotropy are most suitable for this application. The requirements to liquid crystals to be used in optical elements are covered.

  14. Combining Single-Molecule Optical Trapping and Small-Angle X-Ray Scattering Measurements to Compute the Persistence Length of a Protein ER/K [alpha]-Helix

    SciTech Connect

    Sivaramakrishnan, S.; Sung, J.; Ali, M.; Doniach, S.; Flyvbjerg, H.; Spudich, J.A.

    2010-01-12

    A relatively unknown protein structure motif forms stable isolated single {alpha}-helices, termed ER/K {alpha}-helices, in a wide variety of proteins and has been shown to be essential for the function of some molecular motors. The flexibility of the ER/K {alpha}-helix determines whether it behaves as a force transducer, rigid spacer, or flexible linker in proteins. In this study, we quantify this flexibility in terms of persistence length, namely the length scale over which it is rigid. We use single-molecule optical trapping and small-angle x-ray scattering, combined with Monte Carlo simulations to demonstrate that the Kelch ER/K {alpha}-helix behaves as a wormlike chain with a persistence length of 15 nm or 28 turns of {alpha}-helix. The ER/K {alpha}-helix length in proteins varies from 3 to 60 nm, with a median length of 5 nm. Knowledge of its persistence length enables us to define its function as a rigid spacer in a translation initiation factor, as a force transducer in the mechanoenzyme myosin VI, and as a flexible spacer in the Kelch-motif-containing protein.

  15. Diffractive optics in adverse environments

    NASA Technical Reports Server (NTRS)

    Behrmann, Gregory P.

    1993-01-01

    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.

  16. ORFEUS focal plane instrumentation: The Berkeley spectrometer

    NASA Technical Reports Server (NTRS)

    Hurwitz, Mark; Bowyer, Stuart

    1988-01-01

    A spectrograph for the ORFEUS mission that incorporates four varied line-space, spherically figured diffraction gratings was designed. The ORFEUS, a 1-m normal incidence telescope is equipped with 2 focal plane spectrographs. The Berkeley spectrograph was developed with an optimizing raytracing computer code. Each grating accepts the light from 20 percent of the aperture of the telescope primary mirror and has a unique set of characteristics to cover a sub-bandpass within the 390 to 1200 A spectral range. Two photon-counting detectors incorporating a time delay readout system are used to record the spectra from all four gratings simultaneously. The nominal design achieves a spectral resolution (FWHM) in excess of 5500 at all wavelengths within the bandpass. The resolution is limited primarily by the detector spatial resolution. The 1 sigma astigmatism of this design varies between 13 and 150 micrometer on the same focal surface. An independent, direct imaging system tracks the drift of the target within the spectrometer aperture and allows measurement of the misalignment between the telescope optical axis and that of the external star tracker. The resolution and astigmatism achievable with this design are superior to those of a standard Rowland spectrograph designed with the same constraints.

  17. Focal glomerulosclerosis treated with heparin.

    PubMed Central

    Lines, D R; Coleman, M; Gallus, A

    1989-01-01

    A boy with focal glomerulosclerosis as a result of nephrotic syndrome became unresponsive to corticosteroids and cyclophosphamide. He was given prolonged subcutaneous heparin with reduction in proteinuria, return of corticosteroid sensitivity, and no further deterioration (possibly improvement) in histological appearance. He remained completely well after five years. PMID:2774618

  18. An Optical Wavefront Sensor Based on a Double Layer Microlens Array

    PubMed Central

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

    2011-01-01

    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. PMID:22346643

  19. Broad-band optical test bench (OPTISHOP) to measure MTF and transmittance of visible and IR optical components

    NASA Astrophysics Data System (ADS)

    Cabib, Dario; Rahav, Amir; Barak, Tamir

    2007-04-01

    CI Systems has developed a new cost effective and modular Optical Test Bench to measure Modulation Transfer Function (MTF) and transmittance of optical components in the Visible/Near Infrared (0.4-1.7 microns) and infrared (3 to 14 microns) spectral ranges (the OPTISHOP system). The optical design concept of the system allows the user to switch from MTF (on- and off-axis) to transmittance measurements, without need of optical alignment by the user. In addition, broad band sources are used for illumination, so that these optical properties can be measured in the whole relevant wavelength range of the components to be tested (usually visible and/or near infrared separately from the infrared range). Other lens measurements such as effective focal length can be made. Back focal length, distortion and field curvature are being developed. The system is based on the standard and proven CTS (Collimator Test System) product line of CI, which is made of reflective optics for wide wavelength coverage, and it is ruggedly built for use in the laboratory, production line or maintenance depot. An advantage of the CTS configuration is that the source-collimator assembly is enclosed in a robust mechanical envelope, which prevents accidental misalignements and breakage, optical misalignments due to environment temperature drifts, soiling of the optics, and easier system transportation. The system is described here, including calibration and validation techniques.

  20. Statistical earthquake focal mechanism forecasts

    NASA Astrophysics Data System (ADS)

    Kagan, Yan Y.; Jackson, David D.

    2014-04-01

    Forecasts of the focal mechanisms of future shallow (depth 0-70 km) earthquakes are important for seismic hazard estimates and Coulomb stress, and other models of earthquake occurrence. Here we report on a high-resolution global forecast of earthquake rate density as a function of location, magnitude and focal mechanism. In previous publications we reported forecasts of 0.5° spatial resolution, covering the latitude range from -75° to +75°, based on the Global Central Moment Tensor earthquake catalogue. In the new forecasts we have improved the spatial resolution to 0.1° and the latitude range from pole to pole. Our focal mechanism estimates require distance-weighted combinations of observed focal mechanisms within 1000 km of each gridpoint. Simultaneously, we calculate an average rotation angle between the forecasted mechanism and all the surrounding mechanisms, using the method of Kagan & Jackson proposed in 1994. This average angle reveals the level of tectonic complexity of a region and indicates the accuracy of the prediction. The procedure becomes problematical where longitude lines are not approximately parallel, and where shallow earthquakes are so sparse that an adequate sample spans very large distances. North or south of 75°, the azimuths of points 1000 km away may vary by about 35°. We solved this problem by calculating focal mechanisms on a plane tangent to the Earth's surface at each forecast point, correcting for the rotation of the longitude lines at the locations of earthquakes included in the averaging. The corrections are negligible between -30° and +30° latitude, but outside that band uncorrected rotations can be significantly off. Improved forecasts at 0.5° and 0.1° resolution are posted at http://eq.ess.ucla.edu/kagan/glob_gcmt_index.html.

  1. All-optical atom surface traps implemented with one-dimensional planar diffractive microstructures.

    PubMed

    Alloschery, O; Mathevet, R; Weiner, J; Lezec, H J

    2006-12-25

    We characterize the loading, containment and optical properties of all-optical atom traps implemented by diffractive focusing with one-dimensional (1D) microstructures milled on gold films. These on-chip Fresnel lenses with focal lengths of the order of a few hundred microns produce optical-gradient-dipole traps. Cold atoms are loaded from a mirror magneto-optical trap (MMOT) centered a few hundred microns above the gold mirror surface. Details of loading optimization are reported and perspectives for future development of these structures are discussed. PMID:19532148

  2. Progress on developing wavefront sensorless adaptive optics optical coherence tomography for in vivo retinal imaging in mice

    NASA Astrophysics Data System (ADS)

    Zam, Azhar; Zhang, Pengfei; Jian, Yifan; Sarunic, Marinko V.; Bonora, Stefano; Pugh, Edward N.; Zawadzki, Robert J.

    2015-03-01

    We present a new design for a wavefront sensorless adaptive optics (WS-AO) Fourier domain optical coherence tomography (FD-OCT) system for small animal retinal imaging in vivo. Without the optical complications necessary for inclusion of a wavefront sensor in the optical system, this version of WS-AO FD-OCT system has a simplified optical design, including elimination of long focal length scanning optics and optical conjugation of vertical and horizontal scanners. This modification provides a modular large Field of View for retinal screening (25 degree visual angle), while also allowing a "zoom" capability for allocating all the scanning resources to a smaller region of interest, allowing high resolution aberration-corrected imaging. In the present system we used a 0 Dpt contact lens to stabilize the mouse eye position and to allow long duration imaging. Defocus (axial focus position) in our system is controlled by the collimation of the OCT sample arm entrance beam.

  3. Electrically controllable ionic polymeric gels as adaptive optical lenses

    NASA Astrophysics Data System (ADS)

    Salehpoor, Karim; Shahinpoor, Mohsen; Mojarrad, Mehran

    1996-02-01

    Reversible change in optical properties of ionic polymeric gels, 2-acrylamido-2-methylpropane sulfonic acid (PAMPS) and polyacrylic acid plus sodium acrylate cross-linked with bisacrylamide (PAAM), under the effect of an electric field is reported. The shape of a cylindrical piece of the gel, with flat top and bottom surfaces, changed when affected by an electric field. The top surface became curved and the sense of the curvature (whether concave or convex) depended on the polarity of the applied electric field. The curvature of the surface changed from concave to convex and vice versa by changing the polarity of the electric field. By the use of an optical apparatus, focusing capability of the curved surface was verified and the focal length of the deformed gel was measured. The effect of the intensity of the applied electric field on the surface curvature and thus, on the focal length of the gel are tested. Different mechanisms are discussed; either of them or their combination may explain the surface deformation and curvature. Practical difficulties in the test procedure and the future potential of the electrically adaptive and active optical lenses are also discussed. These adaptive lenses may be considered as smart adaptive lenses for contact lens or other optical applications requiring focal point undulation.

  4. Focal hyperhidrosis: diagnosis and management

    PubMed Central

    Haider, Aamir; Solish, Nowell

    2005-01-01

    HYPERHIDROSIS, A CONDITION CHARACTERIZED by excessive sweating, can be generalized or focal. Generalized hyperhidrosis involves the entire body and is usually part of an underlying condition, most often an infectious, endocrine or neurologic disorder. Focal hyperhidrosis is idiopathic, occurring in otherwise healthy people. It affects 1 or more body areas, most often the palms, armpits, soles or face. Almost 3% of the general population, largely people aged between 25 and 64 years, experience hyperhidrosis. The condition carries a substantial psychological and social burden, since it interferes with daily activities. However, patients rarely seek a physician's help because many are unaware that they have a treatable medical disorder. Early detection and management of hyperhidrosis can significantly improve a patient's quality of life. There are various topical, systemic, surgical and nonsurgical treatments available with efficacy rates greater than 90%–95%. PMID:15632408

  5. Episodic focal lingual dystonic spasms.

    PubMed

    Edwards, Mark; Schott, Geoffrey; Bhatia, Kailash

    2003-07-01

    We present the clinical history of a woman with idiopathic episodic focal lingual dystonic spasms. Although dystonic spasms of the tongue have been reported as a primary persistent phenomenon and as a feature of secondary dystonias, primary episodic lingual dystonias are rare, tend to be unilateral, and in contrast to most other paroxysmal movement disorders, do not appear responsive to anti-epileptic drugs. PMID:12815668

  6. Persistent Focal Behavior and Physical Activity Performance

    ERIC Educational Resources Information Center

    Erfle, Stephen E.

    2014-01-01

    This article examines the proclivity and performance attributes of focal students across time and activities using data from 9,345 students. Three systematic focal behavior partitions are examined: Across activities, across time, and across activities and time. A student's performance is focal if it ends in 0 or 5 for push-ups and 0 for…

  7. Persistent Focal Behavior and Physical Activity Performance

    ERIC Educational Resources Information Center

    Erfle, Stephen E.

    2014-01-01

    This article examines the proclivity and performance attributes of focal students across time and activities using data from 9,345 students. Three systematic focal behavior partitions are examined: Across activities, across time, and across activities and time. A student's performance is focal if it ends in 0 or 5 for push-ups and 0 for

  8. Focal Plane Phase Masks for PIAA: Design and Manufacturing

    NASA Astrophysics Data System (ADS)

    Newman, K.; Conway, J.; Belikov, R.; Guyon, O.

    2016-05-01

    The Phase Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC) is a coronagraph architecture for the direct detection of extrasolar planets, which can achieve close to the theoretical performance limit of any direct detection system. The primary components of a PIAACMC system are the Phase Induced Amplitude Apodization (PIAA) optics and the complex phase-shifting focal plane mask. PIAA optics have been produced and demonstrated with high coronagraph performance. In this paper, we describe the design process for the phase-shifting focal plane mask, and strategies for smoothing the mask profile. We describe the mask manufacturing process and show manufacturing results. Errors in the fabricated mask profile degrade the system performance, but we can recover performance by refining the manufacturing process and implementing wavefront control.

  9. Focal cortical dysplasia – review

    PubMed Central

    Kabat, Joanna; Król, Przemysław

    2012-01-01

    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. PMID:22844307

  10. Optical design of athermalization stepping-zoom dual FOV MWIR system

    NASA Astrophysics Data System (ADS)

    Du, Ping; Zhao, Cui-ling; Geng, Yaguang; Ma, Tao

    2015-03-01

    According to the athermalization theory a optical passive athermalization stepping-zoom dual FOV MWIR system in 3μm~5μm designed in this paper, Through the rational combination of infrared optical materials and aspheric surface realized the design of optical passive athermalization. The optical system only use five lens and the optical materials is commonly such as germanium, silicon and Znse. The focal length is 90mm/150mm, the total length is 139mm. The MTF of the two fields are ≥0.5@16lp/mm at -45°C~+60°C, which shows its optical performance approximates to the diffraction limit.

  11. The Camera for LSST and its Focal Plane Array

    NASA Astrophysics Data System (ADS)

    Rasmussen, Andrew; Gilmore, K.; Kahn, S. M.; Geary, J.; Marshall, S.; Nordby, M.; O'Connor, P.; Olivier, S.; Oliver, J.; Radeka, V.; Schalk, T.; Schindler, R.; Tyson, J.; Van Berg, R.; LSST Camera Team

    2010-01-01

    Optically fed by LSST's fast and wide-field optics, the camera has a 9.6 square degree FOV in a 3.2 Gigapixel focal plane array. The focal plane is tiled by 189 4Kx4K CCD science sensors with 10μm (0.2 arcsec) pixels and also houses four diagnostic ("corner raft") packages that provide guide- and wavefront-sensors at opposing sides of the field. The focal plane array is highly modular and features a parallelized readout scheme, allowing the entire array to be read in 2 seconds. Dedicated front- and back-end electronics boards housed within the cryostat vacuum vessel operate sensors in raft groups (3x3 sensors; 144 data channels) while mechanically identical "rafts” are precision-mounted on a rigid silicon carbide grid structure. Three large, refractive lens elements act as the optical system's corrector (the third, L3, provides the vacuum barrier for the cryostat), and one of six possible band-pass filters is positioned in the beam at any given time. Mechanisms within the camera include a mechanical shutter and a carousel filter changer assembly. The camera control system manages all aspects of camera operation including image capture, thermal monitoring and control, vacuum control, filter changes, and communication with the observatory control system. The data acquisition system records and pre-processes raw images, provides up to 3 days of storage capacity, and provides very high throughput data transfer to downstream data management.

  12. Multispectral Focal Plane Assembly for Satellite Remote Sensing

    SciTech Connect

    Rienstra, J.; Ballard, M.

    1997-12-31

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

    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.

  14. An expert system for preliminary optical design.

    NASA Astrophysics Data System (ADS)

    Moss, G. H.

    1989-04-01

    An expert system has been developed which will undertake the preliminary design of optical systems. During the preliminary design the optical designer considers the specification of an optical system and derives parameters such as lens type, focal length, etc. These parameters are then converted into power group layouts with curvatures, thicknesses, etc ready for optimisation by lens design software. The preliminary design will have been arrived at by utilising previous design knowledge and 'rules of thumb' acquired through experience. It is this stage of the design process which has been implemented by an expert system, and will hopefully prove a valuable aid to the optical designer during the important creative stage of the design process.

  15. 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)

    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

    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.

  16. Holographic Optical Elements as Scanning Lidar Telescopes

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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.

  17. SNAP Satellite Focal Plane Development

    SciTech Connect

    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

    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.

  18. Focal plane detectors possible detector technologies for OWL/AIRWATCH

    SciTech Connect

    Flyckt, Esso

    1998-06-15

    New satellite-born projects OWL and AIRWATCH will need single-photon focal-plane detectors of a million pixels in a design which is optimized to the focusing optics and electronics at acceptable cost. We discuss different phototube possibilities and their pros and cons with crude cost estimates. We conclude that a multichannel-photomultiplier solution is safe. A better compromise may be to adapt a 6 or 9 inch X-ray image intensifier tube or develop a 12 inch image intensifier for detecting individual photons, and adapt the optics to have many mirror modules. The possibility of developing super-large-area phototubes is also discussed.

  19. Focal plane detectors possible detector technologies for OWL/AIRWATCH

    NASA Astrophysics Data System (ADS)

    Flyckt, Esso

    1998-06-01

    New satellite-born projects OWL and AIRWATCH will need single-photon focal-plane detectors of a million pixels in a design which is optimized to the focusing optics and electronics at acceptable cost. We discuss different phototube possibilities and their pros and cons with crude cost estimates. We conclude that a multichannel-photomultiplier solution is safe. A better compromise may be to adapt a 6 or 9 inch X-ray image intensifier tube or develop a 12 inch image intensifier for detecting individual photons, and adapt the optics to have many mirror modules. The possibility of developing super-large-area phototubes is also discussed.

  20. Optical system

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  1. Modeling anamorphic optical surfaces in the MOEMS-based zoom lens

    NASA Astrophysics Data System (ADS)

    Cheng, Xuemin; Hao, Qun

    2010-11-01

    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.

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

    SciTech Connect

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

    1995-08-11

    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.

  3. Multi-focal multiphoton lithography.

    PubMed

    Ritschdorff, Eric T; Nielson, Rex; Shear, Jason B

    2012-03-01

    Multiphoton lithography (MPL) provides unparalleled capabilities for creating high-resolution, three-dimensional (3D) materials from a broad spectrum of building blocks and with few limitations on geometry, qualities that have been key to the design of chemically, mechanically, and biologically functional microforms. Unfortunately, the reliance of MPL on laser scanning limits the speed at which fabrication can be performed, making it impractical in many instances to produce large-scale, high-resolution objects such as complex micromachines, 3D microfluidics, etc. Previously, others have demonstrated the possibility of using multiple laser foci to simultaneously perform MPL at numerous sites in parallel, but use of a stage-scanning system to specify fabrication coordinates resulted in the production of identical features at each focal position. As a more general solution to the bottleneck problem, we demonstrate here the feasibility for performing multi-focal MPL using a dynamic mask to differentially modulate foci, an approach that enables each fabrication site to create independent (uncorrelated) features within a larger, integrated microform. In this proof-of-concept study, two simultaneously scanned foci produced the expected two-fold decrease in fabrication time, and this approach could be readily extended to many scanning foci by using a more powerful laser. Finally, we show that use of multiple foci in MPL can be exploited to assign heterogeneous properties (such as differential swelling) to micromaterials at distinct positions within a fabrication zone. PMID:22282105

  4. Characterizing the Kepler Focal Plane

    NASA Astrophysics Data System (ADS)

    Caldwell, Douglas A.; Koch, D. G.; Van Cleve, J.; Rabbette, M.; Jenkins, J. M.; Borucki, W. J.

    2007-12-01

    The Kepler Mission is designed to determine the frequency of Earth-size planets in the habitable zone of solar like stars using a wide field photometer to monitor more than 100,000 stars for periodic transits. Launch is scheduled for February 2009. The Kepler focal plane covers 110 square degrees of sky with 42 back-illuminated CCDs each with two readout amplifiers, for a total of 84 data channels. The photometer is currently going through integration and testing at Ball Aerospace & Technologies Corporation. The tests are designed to ensure that the photometer will meet its required specifications and to characterize its performance where possible. We will report the results of a month long test to characterize the focal plane by measuring read noise, bias level, dark current, gain, linearity, pixel response, full-well and saturation levels, along with the thermal dependence of these characteristics. In addition, we will report on a high-precision photometry test conducted with a flight grade CCD module and readout electronics to ensure that flight system is capable of detecting Earth-Sun equivalent transits of 84 parts per million. Funding for this mission is provided by NASA's Discovery Program Office, SMD.

  5. Optical implementation of multifocal programmable lens with single and multiple axes

    NASA Astrophysics Data System (ADS)

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

    2011-01-01

    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.

  6. A transparent thin-film sensor for multi-focal image reconstruction and depth estimation.

    PubMed

    Koppelhuber, Alexander; Birklbauer, Clemens; Izadi, Shahram; Bimber, Oliver

    2014-04-21

    We present a fully transparent and flexible light-sensing film that, based on a single thin-film luminescent concentrator layer, supports simultaneous multi-focal image reconstruction and depth estimation without additional optics. Together with the sampling of two-dimensional light fields propagated inside the film layer under various focal conditions, it allows entire focal image stacks to be computed after only one recording that can be used for depth estimation. The transparency and flexibility of our sensor unlock the potential of lensless multilayer imaging and depth sensing with arbitrary sensor shapes--enabling novel human-computer interfaces. PMID:24787782

  7. Fast focal zooming scheme for direct drive fusion implemented by inserting KD2PO4 crystal

    NASA Astrophysics Data System (ADS)

    Zhong, Zheqiang; Hu, Xiaochuan; Zhang, Bin

    2016-06-01

    The highly required uniformity of target in direct-drive fusion is difficult to achieve and maintain during the entire laser fusion implosion. To mitigate the increasing nonuniformity, the fast focal zooming scheme implemented by inserting an electro-optic (EO) crystal in the front end of beamline has been proposed. Functioning as a phase plate, the specifically designed EO crystal may add the induced spherical wavefront to the laser beam and alter its focusing characteristics. However, in order to zoom out the focal spot by half, the required voltage for KD2PO4 (DKDP) with single pair of electrodes is relatively high. In order to decrease the voltage while maintaining the zooming performance, the DKDP cylinder with multi pairs of electrodes has been presented. The continuous phase plate (CPP) is designed according to both the injected beam and the output field. However, the conventional CPP is designed based on the assumption of an injected beam without wavefront distortion, which would zoom in the focal spot variation in the focal zooming scheme. In order to zoom out the focal spot, a redesigned CPP has been proposed by adding a spherical wavefront to the phase variation of the conventional CPP and further optimizing. On the basis, the focusing characteristics of laser beam during the fast focal zooming process have been analyzed. Results indicate that the focal spot size decreases with the increasing voltage on DKDP crystal, meanwhile the uniformity maintains high during the focal zooming process.

  8. Silicon pore optics development for ATHENA

    NASA Astrophysics Data System (ADS)

    Collon, Maximilien J.; Vacanti, Giuseppe; Günther, Ramses; Yanson, Alex; Barrière, Nicolas; Landgraf, Boris; Vervest, Mark; Chatbi, Abdelhakim; Beijersbergen, Marco W.; Bavdaz, Marcos; Wille, Eric; Haneveld, Jeroen; Koelewijn, Arenda; Leenstra, Anne; Wijnperle, Maurice; van Baren, Coen; Müller, Peter; Krumrey, Michael; Burwitz, Vadim; Pareschi, Giovanni; Conconi, Paolo; Christensen, Finn E.

    2015-09-01

    The ATHENA mission, a European large (L) class X-ray observatory to be launched in 2028, will essentially consist of an X-ray lens and two focal plane instruments. The lens, based on a Wolter-I type double reflection grazing incidence angle design, will be very large (~ 3 m in diameter) to meet the science requirements of large effective area (1-2 m2 at a few keV) at a focal length of 12 m. To meet the high angular resolution (5 arc seconds) requirement the X-ray lens will also need to be very accurate. Silicon Pore Optics (SPO) technology has been invented to enable building such a lens and thus enabling the ATHENA mission. We will report in this paper on the latest status of the development, including details of X-ray test campaigns.

  9. Rapid, Accurate, and Non-Invasive Measurement of Zebrafish Axial Length and Other Eye Dimensions Using SD-OCT Allows Longitudinal Analysis of Myopia and Emmetropization

    PubMed Central

    Collery, Ross F.; Veth, Kerry N.; Dubis, Adam M.; Carroll, Joseph; Link, Brian A.

    2014-01-01

    Refractive errors in vision can be caused by aberrant axial length of the eye, irregular corneal shape, or lens abnormalities. Causes of eye length overgrowth include multiple genetic loci, and visual parameters. We evaluate zebrafish as a potential animal model for studies of the genetic, cellular, and signaling basis of emmetropization and myopia. Axial length and other eye dimensions of zebrafish were measured using spectral domain-optical coherence tomography (SD-OCT). We used ocular lens and body metrics to normalize and compare eye size and relative refractive error (difference between observed retinal radial length and controls) in wild-type and lrp2 zebrafish. Zebrafish were dark-reared to assess effects of visual deprivation on eye size. Two relative measurements, ocular axial length to body length and axial length to lens diameter, were found to accurately normalize comparisons of eye sizes between different sized fish (R2 = 0.9548, R2 = 0.9921). Ray-traced focal lengths of wild-type zebrafish lenses were equal to their retinal radii, while lrp2 eyes had longer retinal radii than focal lengths. Both genetic mutation (lrp2) and environmental manipulation (dark-rearing) caused elongated eye axes. lrp2 mutants had relative refractive errors of −0.327 compared to wild-types, and dark-reared wild-type fish had relative refractive errors of −0.132 compared to light-reared siblings. Therefore, zebrafish eye anatomy (axial length, lens radius, retinal radius) can be rapidly and accurately measured by SD-OCT, facilitating longitudinal studies of regulated eye growth and emmetropization. Specifically, genes homologous to human myopia candidates may be modified, inactivated or overexpressed in zebrafish, and myopia-sensitizing conditions used to probe gene-environment interactions. Our studies provide foundation for such investigations into genetic contributions that control eye size and impact refractive errors. PMID:25334040

  10. 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)

    Ladany, I.; Hammer, J. M.

    1980-01-01

    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.

  11. Acousto-optic infrared spectral imager for Pluto fast flyby

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  12. Focal axis resolver for offset reflector antennas

    NASA Technical Reports Server (NTRS)

    Schmidt, R. F. (Inventor)

    1983-01-01

    Method and apparatus for determining the focal axis of an asymmetrical antenna such as an offset paraboloid reflector whose physical rim is not coincident with the boundary of the electrical aperture but whose focal point is known is provided. A transmitting feed horn array consisting of at least two feed horn elements is positioned asymmetrically on either side of an estimated focal axis which is generally inclined with respect to the boresight axis of the antenna. The feed horn array is aligned with the estimated focal axis so that the phase centers (CP sub 1, CP sub 2) of the two feed horn elements are located on a common line running through the focal point (F) orthogonally with respect to the estimated focal axis.

  13. Achromatic Focal Plane Mask for Exoplanet Imaging Coronagraphy

    NASA Technical Reports Server (NTRS)

    Newman, Kevin Edward; Belikov, Ruslan; Guyon, Olivier; Balasubramanian, Kunjithapatham; Wilson, Dan

    2013-01-01

    Recent advances in coronagraph technologies for exoplanet imaging have achieved contrasts close to 1e10 at 4 lambda/D and 1e-9 at 2 lambda/D in monochromatic light. A remaining technological challenge is to achieve high contrast in broadband light; a challenge that is largely limited by chromaticity of the focal plane mask. The size of a star image scales linearly with wavelength. Focal plane masks are typically the same size at all wavelengths, and must be sized for the longest wavelength in the observational band to avoid starlight leakage. However, this oversized mask blocks useful discovery space from the shorter wavelengths. We present here the design, development, and testing of an achromatic focal plane mask based on the concept of optical filtering by a diffractive optical element (DOE). The mask consists of an array of DOE cells, the combination of which functions as a wavelength filter with any desired amplitude and phase transmission. The effective size of the mask scales nearly linearly with wavelength, and allows significant improvement in the inner working angle of the coronagraph at shorter wavelengths. The design is applicable to almost any coronagraph configuration, and enables operation in a wider band of wavelengths than would otherwise be possible. We include initial results from a laboratory demonstration of the mask with the Phase Induced Amplitude Apodization coronagraph.

  14. Focal axis resolver for offset reflector antennas

    NASA Technical Reports Server (NTRS)

    Schmidt, R. F.

    1980-01-01

    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.

  15. Optical passive athermalization for infrared zoom system

    NASA Astrophysics Data System (ADS)

    Li, Shenghui; Yang, Changcheng; Zheng, Jia; Lan, Ning; Xiong, Tao; Li, Yong

    2007-12-01

    In an infrared zoom system, it is difficult to obtain the best thermal compensation for all effective focal length (EFL) simultaneously by moving a single lens group. According to the principle of optical passive athermalization, the equations of focal length, achromatization and athermalization of both long and short EFL are established respectively. By analyzing the thermal aberration value relations between long EFL and short EFL, the thermal aberration values of the switching groups for short EFL athermalization are calculated. Firstly, the athermalization of long EFL is designed. Then through reasonable optical materials matching of the switching groups, the short EFL achieves athermalization as well. In this paper, a re-imaging switching zoom system is designed. It has a relative aperture of f/4.0, 100% cold shield efficiency, the EFL of 180mm/30mm at 3.7-4.8μm. The long EFL includes four refractive elements and one hybrid refractive/diffractive element. The switching groups of short EFL have two types, one is composed of four refractive elements, and the other is composed of two refractive elements and one hybrid refractive/diffractive element. Both of the short EFL achieve athermalization. With the aluminum materials of system structures, the zoom system achieves optical passive athermalization. It has the diffraction limited image quality and stable image plane from -30°C to 70°C.

  16. Uncooled infrared focal plane array imaging in China

    NASA Astrophysics Data System (ADS)

    Lei, Shuyu

    2015-06-01

    This article reviews the development of uncooled infrared focal plane array (UIFPA) imaging in China in the past decade. Sensors based on optical or electrical read-out mechanism were developed but the latter dominates the market. In resistive bolometers, VOx and amorphous silicon are still the two major thermal-sensing materials. The specifications of the IRFPA made by different manufactures were collected and compared. Currently more than five Chinese companies and institutions design and fabricate uncooled infrared focal plane array. Some devices have sensitivity as high as 30 mK; the largest array for commercial products is 640×512 and the smallest pixel size is 17 μm. Emphasis is given on the pixel MEMS design, ROIC design, fabrication, and packaging of the IRFPA manufactured by GWIC, especially on design for high sensitivities, low noise, better uniformity and linearity, better stabilization for whole working temperature range, full-digital design, etc.

  17. Optical Design of Telescopes and other Reflective Systems using SLIDERS

    NASA Technical Reports Server (NTRS)

    Howard, Joseph M.

    2007-01-01

    Optical design tools are presented to provide automatic generation of reflective optical systems for design studies and educational use. The tools are graphical in nature and use an interactive slider interface with freely available optical design software, OSLO EDU. Operation of the sliders provides input to adjust first-order and other system parameters (e.g. focal length), while appropriate system construction parameters are automatically updated to correct aberrations. Graphical output is also presented in real-time (e.g. a lens drawing) to provide the opportunity for a truly visual approach to optical design. Available systems include two- three- and four-mirror telescopes, relays, and afocal systems, either rotationally symmetric or having just a plane of symmetry. Demonstrations are presented, including a brief discussion of interfacing optical design software to MATLAB, and general research opportunities at NASA.

  18. Athermal design for infrared refractive, diffractive, reflective hybrid optical system

    NASA Astrophysics Data System (ADS)

    Cheng, Ximin; Xie, Weimin; Bai, Yu; Jia, Xin; Xing, Tingwen

    2014-09-01

    Thermal properties and dispersive capacity of diffractive optical elements were expounded in this paper, and the conclusion that optothermal expansion coefficient of diffractive optical element is independent of refractive index of the material was derived. The design method to athermalize the hybrid infrared optical system was studied, a new hybrid system with diffractive surface was structured on the foundation of refractive/reflective optical system using optical design software ZEMAX, and the surface was simulated by MATLAB. The image quality was improved obviously compared with the one without diffractive surface. The system worked at 3.7~4.8μm band with its' effective focal length of 70mm, field of view of 2° and possessed better athermal performance in the temperature range -40°~+60°. The image quality achieved diffractive limit, besides, a compact structure, small volume and light weight were other advantages of the hybrid system.

  19. Optical design of optical transfer function instrument

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

    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.

  20. Terahertz detectors and focal plane arrays

    NASA Astrophysics Data System (ADS)

    Rogalski, A.; Sizov, F.

    2011-09-01

    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.

  1. Pixel scaling in infrared focal plane arrays.

    PubMed

    Catrysse, Peter B; Skauli, Torbjorn

    2013-03-01

    We discuss effects that arise in pixels of IR focal plane arrays (FPAs) when pixel size scales down to approach the wavelength of the incident radiation. To study these effects, we perform first-principles electromagnetic simulations of pixel structures based on a mercury-cadmium-telluride photoconductor for use in FPAs. Specifically, we calculate the pixel quantum efficiency and crosstalk as pixel size scales from 16 μm, which is in the range of current detectors, down to 0.75 μm, corresponding to subwavelength detectors. Our numerical results indicate the possibility of wavelength-size (~4 μm) and even subwavelength-size (~1 μm) pixels for IR FPAs. In addition, we explore opportunities that emerge for controlling light with subwavelength structures inside FPA pixels. As an illustration, we find that the low-pass filtering effect of a metal film aperture can exemplify the impact and the possible role that wavelength-scale optics plays in very small pixels. PMID:23458820

  2. Adaptive beam shaping by controlled thermal lensing in optical elements.

    PubMed

    Arain, Muzammil A; Quetschke, Volker; Gleason, Joseph; Williams, Luke F; Rakhmanov, Malik; Lee, Jinho; Cruz, Rachel J; Mueller, Guido; Tanner, D B; Reitze, David H

    2007-04-20

    We describe an adaptive optical system for use as a tunable focusing element. The system provides adaptive beam shaping via controlled thermal lensing in the optical elements. The system is agile, remotely controllable, touch free, and vacuum compatible; it offers a wide dynamic range, aberration-free focal length tuning, and can provide both positive and negative lensing effects. Focusing is obtained through dynamic heating of an optical element by an external pump beam. The system is especially suitable for use in interferometric gravitational wave interferometers employing high laser power, allowing for in situ control of the laser modal properties and compensation for thermal lensing of the primary laser. Using CO(2) laser heating of fused-silica substrates, we demonstrate a focal length variable from infinity to 4.0 m, with a slope of 0.082 diopter/W of absorbed heat. For on-axis operation, no higher-order modes are introduced by the adaptive optical element. Theoretical modeling of the induced optical path change and predicted thermal lens agrees well with measurement. PMID:17415383

  3. The Control of Conjugation Lengths and Steric Hindrance to Modulate Aggregation-Induced Emission with High Electroluminescence Properties and Interesting Optical Properties.

    PubMed

    Xue, Miao-Miao; Xie, Yue-Min; Cui, Lin-Song; Liu, Xiang-Yang; Yuan, Xiao-Dong; Li, Yong-Xi; Jiang, Zuo-Quan; Liao, Liang-Sheng

    2016-01-01

    A series of novel AIE-active (aggregation-induced emission) molecules, named SAF-2-TriPE, SAF-3-TriPE, and SAF-4-TriPE, were designed and synthesized through facile reaction procedures. We found that incorporation of the spiro-acridine-fluorene (SAF) group, which is famous for its excellent hole-transporting ability and rigid structure, at different substitution positions on the phenyl ring affected the conjugation lengths of these compounds. Consequently, we have obtained molecules with different emission colors and properties without sacrificing good EL (electroluminescence) characteristics. Accordingly, a device that was based on compound SAF-2-TriPE displayed superior EL characteristics: it emitted green light with ηc, max =10.5 cd A(-1) and ηext, max =4.22 %, whereas a device that was based on compound SAF-3-TriPE emitted blue-green light with ηc, max =3.9 cd A(-1) and ηext, max = 1.71 %. These compounds also displayed different AIE performances: when the fraction of water in the THF solutions of these compounds was increased, we observed a significant improvement in the ΦF of compounds SAF-2-TriPE and SAF-3-TriPE; in contrast, compound SAF-4-TriPE showed an abnormal phenomenon, in that it emitted a strong fluorescence in both pure THF solution and in the aggregated state without a significant change in ΦF . Overall, this systematic study confirmed a relationship between the regioisomerism of the luminophore structure and its AIE activity and the resulting electroluminescent performance in non-doped devices. PMID:26586115

  4. Photometric oculometry. I. An analysis of the optical principles in slit-lamp fluorophotometry.

    PubMed

    Krogsaa, B; Fledelius, H; Larsen, J; Lund-Andersen, H

    1984-04-01

    The optical principles of slit-lamp fluorophotometry are analysed by aid of a mathematical model of the optical system. The analysis forms the theoretical basis for a slit-lamp technique called photometric oculometry, which makes possible an estimation of intraocular axial distances and axial length. The technique is based on a calculation--by aid of a mathematical model of the eye--of the ratio between intraocular movement of the slit-lamp focal plane and corresponding movement of the slit-lamp. Intraocular axial distances can be calculated by aid of this ratio and a direct measurement of the slit-lamp movement when the focal plane is moved in the optical axis from retina to cornea. These items are prerequisites for a quantitative determination of the blood-retinal barrier permeability to fluorescein during vitreous fluorophotometry. PMID:6720293

  5. Treatment of focal dystonias with botulinum neurotoxin

    PubMed Central

    Benecke, Reiner; Blitzer, Andrew; Comella, Cynthia L.

    2016-01-01

    This is a review on the use of injections of botulinum toxin for the treatment of focal dystonias. Disorders covered include cranial dystonia, cervical dystonia, spasmodic dysphonia, and focal hand dystonia. Considered are clinical aspects, alternative treatment strategies and principles of use of botulinum toxin injections. PMID:19103214

  6. Optics for mobile phone imaging

    NASA Astrophysics Data System (ADS)

    Vigier-Blanc, Emmanuelle E.

    2004-02-01

    Micro cameras for mobile phones require specific opto electronic designs using high-resolution micro technologies for compromising optical, electronical and mechanical requirements. The purpose of this conference is to present the optical critical parameters for imaging optics embedded into mobile phones. We will overview the optics critical parameters involved into micro optical cameras, as seen from user point of view, and their interdependence and relative influence onto optical performances of the product, as: -Focal length, field of view and array size. -Lens speed and depth of field: what is hidden behind lens speed, how to compromise small aperture, production tolerances, sensitivity, good resolution in corners and great depth of field -Relative illumination, this smooth fall off of intensity toward edge of array -Resolution; how to measure it, the interaction of pixel size, small dimensions -Sensitivity, insuring same sensitivity as human being under both twilight and midday sunny conditions. -Mischievous effects, as flare, glare, ghost effects and how to avoid them -How to match sensor spectrum and photopic eye curve: IR filter, and color balancing. We will compromise above parameters and see how to match with market needs and productivity insurance.

  7. Characterization and simulation of optical sensors.

    PubMed

    Grapinet, M; De Souza, Ph; Smal, J-C; Blosseville, J-M

    2013-11-01

    Numerical simulation is gradually becoming an advantage in active safety. This is why the development of realistic numerical models enabling to substitute real truth by simulated truth is primordial. In order to provide an accurate and cost effective solution to simulate real optical sensor behavior, the software Pro-SiVIC™ has been developed. Simulations with the software Pro-SiVIC™ can replace real tests with optical sensors and hence allow substantial cost and time savings during the development of solutions for driver assistance systems. An optical platform has been developed by IFSTTAR (French Institute of Science and Technology for Transport, Development and Networks) to characterize and validate any existing camera, in order to measure their characteristics as distortion, vignetting, focal length, etc. By comparing real and simulated sensors with this platform, this paper demonstrates that Pro-SiVIC™ accurately reproduces real sensors' behavior. PMID:23735581

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

    NASA Astrophysics Data System (ADS)

    Hinnrichs, Michele

    2011-06-01

    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.

  9. Measuring Crack Length in Coarse Grain Ceramics

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.; Ghosn, Louis J.

    2010-01-01

    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.

  10. Focal liver lesions found incidentally

    PubMed Central

    Algarni, Abdullah A; Alshuhri, Abdullah H; Alonazi, Majed M; Mourad, Moustafa Mabrouk; Bramhall, Simon R

    2016-01-01

    Incidentally found focal liver lesions are a common finding and a reason for referral to hepatobiliary service. They are often discovered in patients with history of liver cirrhosis, colorectal cancer, incidentally during work up for abdominal pain or in a trauma setting. Specific points should considered during history taking such as risk factors of liver cirrhosis; hepatitis, alcohol consumption, substance exposure or use of oral contraceptive pills and metabolic syndromes. Full blood count, liver function test and tumor markers can act as a guide to minimize the differential diagnosis and to categorize the degree of liver disease. Imaging should start with B-mode ultrasound. If available, contrast enhanced ultrasound is a feasible, safe, cost effective option and increases the ability to reach a diagnosis. Contrast enhanced computed tomography should be considered next. It is more accurate in diagnosis and better to study anatomy for possible operation. Contrast enhanced magnetic resonance is the gold standard with the highest sensitivity. If doubt still remains, the options are biopsy or surgical excision. PMID:27028805

  11. Early vision and focal attention

    NASA Astrophysics Data System (ADS)

    Julesz, Bela

    1991-07-01

    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.

  12. Focal liver lesions found incidentally.

    PubMed

    Algarni, Abdullah A; Alshuhri, Abdullah H; Alonazi, Majed M; Mourad, Moustafa Mabrouk; Bramhall, Simon R

    2016-03-28

    Incidentally found focal liver lesions are a common finding and a reason for referral to hepatobiliary service. They are often discovered in patients with history of liver cirrhosis, colorectal cancer, incidentally during work up for abdominal pain or in a trauma setting. Specific points should considered during history taking such as risk factors of liver cirrhosis; hepatitis, alcohol consumption, substance exposure or use of oral contraceptive pills and metabolic syndromes. Full blood count, liver function test and tumor markers can act as a guide to minimize the differential diagnosis and to categorize the degree of liver disease. Imaging should start with B-mode ultrasound. If available, contrast enhanced ultrasound is a feasible, safe, cost effective option and increases the ability to reach a diagnosis. Contrast enhanced computed tomography should be considered next. It is more accurate in diagnosis and better to study anatomy for possible operation. Contrast enhanced magnetic resonance is the gold standard with the highest sensitivity. If doubt still remains, the options are biopsy or surgical excision. PMID:27028805

  13. Focal brain inflammation and autism.

    PubMed

    Theoharides, Theoharis C; Asadi, Shahrzad; Patel, Arti B

    2013-01-01

    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. PMID:23570274

  14. Large format focal plane array integration with precision alignment, metrology and accuracy capabilities

    NASA Astrophysics Data System (ADS)

    Neumann, Jay; Parlato, Russell; Tracy, Gregory; Randolph, Max

    2015-09-01

    Focal plane alignment for large format arrays and faster optical systems require enhanced precision methodology and stability over temperature. The increase in focal plane array size continues to drive the alignment capability. Depending on the optical system, the focal plane flatness of less than 25μm (.001") is required over transition temperatures from ambient to cooled operating temperatures. The focal plane flatness requirement must also be maintained in airborne or launch vibration environments. This paper addresses the challenge of the detector integration into the focal plane module and housing assemblies, the methodology to reduce error terms during integration and the evaluation of thermal effects. The driving factors influencing the alignment accuracy include: datum transfers, material effects over temperature, alignment stability over test, adjustment precision and traceability to NIST standard. The FPA module design and alignment methodology reduces the error terms by minimizing the measurement transfers to the housing. In the design, the proper material selection requires matched coefficient of expansion materials minimizes both the physical shift over temperature as well as lowering the stress induced into the detector. When required, the co-registration of focal planes and filters can achieve submicron relative positioning by applying precision equipment, interferometry and piezoelectric positioning stages. All measurements and characterizations maintain traceability to NIST standards. The metrology characterizes the equipment's accuracy, repeatability and precision of the measurements.

  15. Compact dual field of view SWIR/MWIR optical system

    NASA Astrophysics Data System (ADS)

    Vizgaitis, Jay N.; Witte, Kyle; Littleton, Roy; Perconti, Philip

    2011-06-01

    This paper discusses the design and development of a dual field of view, all-refractive infrared optical system that images the mid-wave infrared (MWIR) light in one field of view and the short wave infrared (SWIR) light in the narrower second field of view onto the same detector. The narrow field of view images the SWIR radiation at a slow f/number of 10.0, while the wide field of view images the MWIR radiation at f/1.9. The field of view is changed via a single lens that changes its axial position within the lens, resulting in an axial zoom and an overall magnification change of 6X. The change in focal length and f/number at the same time enables an increased focal length without having to increase the aperture size by the ratio of the focal length change. The large field of view change is achieved by both the motion of the lens, and the use of the spectral properties of the materials that change with wavelength. The change in spectral bands is accomplished via the use of a spectral filter wheel.

  16. Focal Choroidal Excavation in Best Vitelliform Macular Dystrophy: Case Report.

    PubMed

    Esfahani, Mohammad Riazi; Esfahani, Hamid Riazi; Mahmoudi, Alireza; Johari, Mohammad Karim; Hemati, Karim

    2015-05-01

    Focal choroidal excavation (FCE) was first reported as a choroidal posteriorly excavated zone without any scleral change. Choroidal excavation also divided into conforming and nonconforming type. Numerous reports demonstrated association between FCE and other disease such as choroidal neovascularization and central serous choroidoretinopathy. Here, we report a rare case of FCE in a patient with Best disease. The patient was diagnosed by spectoral domain optical coherence tomography (SD-OCT). To the best of our knowledge, our patient is the second report of choroidal excavation in Best vitelliform macular dystrophy. PMID:26155505

  17. Automatic location of microscopic focal planes for computerized stereology

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    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 μm on the training data as well as the test data.

  18. HyperSuprime: imaging optics

    NASA Astrophysics Data System (ADS)

    Komiyama, Yutaka; Miyazaki, Satoshi; Doi, Yoshiyuki; Nakaya, Hidehiko; Furusawa, Hisanori; Takeshi, Kunio; Nariai, Kyoji

    2006-06-01

    We summarize the optical design of the wide-field corrector for HyperSuprime which is being considered as a next generation prime focus camera for Subaru Telescope. Two optical designs are investigated under several design constraints such as image quality, field curvature, focal length, etc. The corrector with 2 degree field of view attains good image quality at the wavelength between 600 nm and 1100 nm although the first lens is large (1.2 m in diameter) and three aspherical surfaces are required. The image quality for shorter wavelength than 600 nm is fair. The incident light blocked at the edge of the field is only 20% and the transmission is more than 80% if the multi-layer coating applied for the current Subaru prime focus corrector is available. The corrector with 1.5 degree field of view is designed as a smaller version of 2 degree corrector. The properties and performance of 1.5 degree corrector resemble those of 2 degree corrector, but 1.5 degree corrector has a merit that the focal plane is flat. The availability of large fused-silica blank up to about 200 kg is promising.

  19. Far-field radially polarized focal spot from plasmonic spiral structure combined with central aperture antenna

    PubMed Central

    Mao, Lei; Ren, Yuan; Lu, Yonghua; Lei, Xinrui; Jiang, Kang; Li, Kuanguo; Wang, Yong; Cui, Chenjing; Wen, Xiaolei; Wang, Pei

    2016-01-01

    Manipulation of a vector micro-beam with an optical antenna has significant potentials for nano-optical technology applications including bio-optics, optical fabrication, and quantum information processing. We have designed and demonstrated a central aperture antenna within an Archimedean spiral that extracts the bonding plasmonic field from a surface to produce a new vector focal spot in far-field. The properties of this vector focal field are revealed by confocal microscopy and theoretical simulations. The pattern, polarization and phase of the focal field are determined by the incident light and by the chirality of the Archimedean spiral. For incident light with right-handed circular polarization, the left-handed spiral (one-order chirality) outputs a micro-radially polarized focal field. Our results reveal the relationship between the near-field and far-field distributions of the plasmonic spiral structure, and the structure has the potential to lead to advances in diverse applications such as plasmonic lenses, near-field angular momentum detection, and optical tweezers. PMID:27009383

  20. Far-field radially polarized focal spot from plasmonic spiral structure combined with central aperture antenna

    NASA Astrophysics Data System (ADS)

    Mao, Lei; Ren, Yuan; Lu, Yonghua; Lei, Xinrui; Jiang, Kang; Li, Kuanguo; Wang, Yong; Cui, Chenjing; Wen, Xiaolei; Wang, Pei

    2016-03-01

    Manipulation of a vector micro-beam with an optical antenna has significant potentials for nano-optical technology applications including bio-optics, optical fabrication, and quantum information processing. We have designed and demonstrated a central aperture antenna within an Archimedean spiral that extracts the bonding plasmonic field from a surface to produce a new vector focal spot in far-field. The properties of this vector focal field are revealed by confocal microscopy and theoretical simulations. The pattern, polarization and phase of the focal field are determined by the incident light and by the chirality of the Archimedean spiral. For incident light with right-handed circular polarization, the left-handed spiral (one-order chirality) outputs a micro-radially polarized focal field. Our results reveal the relationship between the near-field and far-field distributions of the plasmonic spiral structure, and the structure has the potential to lead to advances in diverse applications such as plasmonic lenses, near-field angular momentum detection, and optical tweezers.

  1. Far-field radially polarized focal spot from plasmonic spiral structure combined with central aperture antenna.

    PubMed

    Mao, Lei; Ren, Yuan; Lu, Yonghua; Lei, Xinrui; Jiang, Kang; Li, Kuanguo; Wang, Yong; Cui, Chenjing; Wen, Xiaolei; Wang, Pei

    2016-01-01

    Manipulation of a vector micro-beam with an optical antenna has significant potentials for nano-optical technology applications including bio-optics, optical fabrication, and quantum information processing. We have designed and demonstrated a central aperture antenna within an Archimedean spiral that extracts the bonding plasmonic field from a surface to produce a new vector focal spot in far-field. The properties of this vector focal field are revealed by confocal microscopy and theoretical simulations. The pattern, polarization and phase of the focal field are determined by the incident light and by the chirality of the Archimedean spiral. For incident light with right-handed circular polarization, the left-handed spiral (one-order chirality) outputs a micro-radially polarized focal field. Our results reveal the relationship between the near-field and far-field distributions of the plasmonic spiral structure, and the structure has the potential to lead to advances in diverse applications such as plasmonic lenses, near-field angular momentum detection, and optical tweezers. PMID:27009383

  2. The Nuclear Spectroscopic Telescope Array (NuSTAR): optics overview and current status

    NASA Astrophysics Data System (ADS)

    Hailey, Charles J.; An, Hongjun; Blaedel, Kenneth L.; Brejnholt, Nicolai F.; Christensen, Finn E.; Craig, William W.; Decker, Todd A.; Doll, Melanie; Gum, Jeff; Koglin, Jason E.; Jensen, Carsten P.; Hale, Layton; Mori, Kaya; Pivovaroff, Michael J.; Sharpe, Marton; Stern, Marcela; Tajiri, Gordon; Zhang, William W.

    2010-07-01

    The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission scheduled for launch in February 2012. NuSTAR will deploy two imaging CdZnTe spectrometers in the 6-79 keV energy band. The two NuSTAR optics utilize multilayer-coated, thermally-slumped glass integrated into a titanium-glass-epoxy-graphite composite structure, along with an extendable mast, to obtain 10.15 meter focal length. Using this approach, the NuSTAR optics will obtain subarcminute imaging with large effective area over its entire energy band. NuSTAR's conic-approximation Wolter-I optics are the first true hard X-ray focusing optics to be deployed on a satellite experiment. We report on the design of the NuSTAR optics, present the status of the two flight optics under construction, and report preliminary measurements that can be used to predict performance.

  3. Optical design of temperature self-adaptive dual-field infrared system

    NASA Astrophysics Data System (ADS)

    LI, Ming; Hong, Li-juan; Jin, Min; Zhang, Teng-peng

    2015-10-01

    Based on the theory of athermalization, an optical system of temperature self-adaptive dual field of view was designed in this paper, appling in 3μm~5μm medium wave infrared camera system. This system achieved the design of optical passive athermalization by reasonable selection in terms of infrared optical materials and aspheric surface. Only five lenses were applied in this optical system, meanwhile, optical materials like germanium, silicon and ZnSe were all ordinary and cost-effective. The focal distance was 50mm/100mm, with total length of 125mm and pixel size of 17μm. The MTF of the two field of view were both greater than 0.5 at 30lp/mm in -45°C~+60°C, with its optical performance approximating the diffraction limit.

  4. Electroactive and Optically Adaptive Bionanocomposite for Reconfigurable Microlens.

    PubMed

    Sadasivuni, Kishor Kumar; Ponnamma, Deepalekshmi; Ko, Hyun-U; Zhai, Lindong; Kim, Hyun-Chan; Kim, Jaehwan

    2016-05-26

    This paper introduces an electroactive bionanocomposite based on poly(diethylene glycol adipate) (PDEGA) and cellulose nanocrystals (CNCs). The bionanocomposites were made using CNCs extracted from cotton and by optimizing its concentration in terms of the optical transmittance and viscosity. The characteristic properties of the materials were analyzed using contact angle measurements and Fourier transformation infrared spectra. Using the PDEGA/CNC bionanocomposite at a very low concentration of CNCs, a configurable lens having a robust, self-contained tunable optical structure was developed. The shape and curvature of the soft PDEGA/CNC device were controlled by applying voltage, and the focal length was measured. The simple structure, high optical transparency, biodegradability, thermal stability, high durability, and low power consumption make the new material particularly useful in fabricating a reconfigurable lens for future electronic and optical devices. PMID:27163166

  5. Arc Length Gone Global

    ERIC Educational Resources Information Center

    Boudreaux, Gregory M.; Wells, M. Scott

    2007-01-01

    Everyone with a thorough knowledge of single variable calculus knows that integration can be used to find the length of a curve on a given interval, called its arc length. Fortunately, if one endeavors to pose and solve more interesting problems than simply computing lengths of various curves, there are techniques available that do not require an…

  6. Focal renal masses: magnetic resonance imaging

    SciTech Connect

    Choyke, P.L.; Kressel, H.Y.; Pollack, H.M.; Arger, P.M.; Axel, L.; Mamourian, A.C.

    1984-08-01

    Thirty patients with focal renal masses were evaluated on a .12-Tesla resistive magnetic resonance unit using partial saturation and spin echo pulse sequence. Fifteen patients had cystic lesions, nine patients had renal cell carcinoma, two had metastatic lesions, one had an angiomyolipoma, and three had focal bacterial infection. Renal cell carcinomas demonstrated areas of increased signal using a partial saturation sequence. Magnetic resonance imaging accurately detected perinephric extension and vascular invasion in all patients. Metastatic disease to the kidney was uniformly low in signal, in contrast to primary renal cell carcinoma; an angiomyolipoma demonstrated very high signal intensity. Two masses resulting from acute focal bacterial nephritis were uniformly low in signal. Magnetic resonance imaging appears to be an accurate way of detecting, identifying, and staging focal renal masses.

  7. Surgery for drug-resistant focal epilepsy

    PubMed Central

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

    2014-01-01

    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. PMID:24791080

  8. Optical zoom camera module using two poly-dimethylsiloxane deformable mirrors.

    PubMed

    Huang, Yu-Hung; Wei, Hsiang-Chun; Hsu, Wei-Yao; Cheng, Yuan-Chieh; Su, Guo-Dung John

    2014-10-10

    Miniaturization is an essential trend in the design of portable devices. Motor-driven lens technology is a traditional way to achieve autofocus and optical zoom functions. This approach usually requires considerable space and consumes significant power. Reflective optics is a methodology that not only can fold the optical path, but it has the advantage of low chromatic aberration. In this paper, we use a deformable mirror as a reflecting element in an optical zoom system. For its low Young's modulus and residual stress, we choose polydimethylsiloxane as a deformable membrane that can provide a large stroke. The optical zoom module consists of a pair of micromachined deformable mirrors. The thickness of this module is 10 mm, which enables 2× optical zoom. The smallest effective focal length is 4.7 mm at a full field angle of 52°, and the f-number is 4.4. The largest effective focal length of the module is 9.4 mm, and the f-number is 6.4. PMID:25322427

  9. Treatment planning for prostate focal laser ablation in the face of needle placement uncertainty

    SciTech Connect

    Cepek, Jeremy Fenster, Aaron; Lindner, Uri; Trachtenberg, John; Davidson, Sean R. H.; Haider, Masoom A.; Ghai, Sangeet

    2014-01-15

    Purpose: To study the effect of needle placement uncertainty on the expected probability of achieving complete focal target destruction in focal laser ablation (FLA) of prostate cancer. Methods: Using a simplified model of prostate cancer focal target, and focal laser ablation region shapes, Monte Carlo simulations of needle placement error were performed to estimate the probability of completely ablating a region of target tissue. Results: Graphs of the probability of complete focal target ablation are presented over clinically relevant ranges of focal target sizes and shapes, ablation region sizes, and levels of needle placement uncertainty. In addition, a table is provided for estimating the maximum target size that is treatable. The results predict that targets whose length is at least 5 mm smaller than the diameter of each ablation region can be confidently ablated using, at most, four laser fibers if the standard deviation in each component of needle placement error is less than 3 mm. However, targets larger than this (i.e., near to or exceeding the diameter of each ablation region) require more careful planning. This process is facilitated by using the table provided. Conclusions: The probability of completely ablating a focal target using FLA is sensitive to the level of needle placement uncertainty, especially as the target length approaches and becomes greater than the diameter of ablated tissue that each individual laser fiber can achieve. The results of this work can be used to help determine individual patient eligibility for prostate FLA, to guide the planning of prostate FLA, and to quantify the clinical benefit of using advanced systems for accurate needle delivery for this treatment modality.

  10. Design, fabrication and evaluation of chalcogenide glass Luneburg lenses for LiNbO3 integrated optical devices

    NASA Technical Reports Server (NTRS)

    Wood, V. E.; Busch, J. R.; Verber, C. M.

    1982-01-01

    Optical waveguide Luneburg lenses of arsenic trisulfide glass are described. The lenses are formed by thermal evaporation of As2S3 through suitably placed masks onto the surface of LiNbO3:Ti indiffused waveguides. The lenses are designed for input apertures up to 1 cm and for speeds of f/5 or better. They are designed to focus the TM sub 0 guided mode of a beam of wavelength, external to the guide, of 633 nm. The refractive index of the As2S3 films and the changes induced in the refractive index by exposure to short wavelength light were measured. Some correlation between film thickness and optical properties was noted. The short wavelength photosensitivity was used to shorten the lens focal length from the as deposited value. Lenses of rectangular shape, as viewed from above the guide, as well as conventional circular Luneburg lenses, were made. Measurements made on the lenses include thickness profile, general optical quality, focal length, quality of focal spot, and effect of ultraviolet irradiation on optical properties.

  11. Spatial calibration of an optical see-through head-mounted display.

    PubMed

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

    2008-08-15

    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. PMID:18599125

  12. A holographic projection system with an electrically tuning and continuously adjustable optical zoom.

    PubMed

    Lin, Hung-Chun; Collings, Neil; Chen, Ming-Syuan; Lin, Yi-Hsin

    2012-12-01

    A holographic projection system with optical zoom is demonstrated. By using a combination of a LC lens and an encoded Fresnel lens on the LCoS panel, we can control zoom in a holographic projector. The magnification can be electrically adjusted by tuning the focal length of the combination of the two lenses. The zoom ratio of the holographic projection system can reach 3.7:1 with continuous zoom function. The optical zoom function can decrease the complexity of the holographic projection system. PMID:23262672

  13. Tailoring the Optical Dipole Force for Molecules by Field-Induced Alignment

    NASA Astrophysics Data System (ADS)

    Purcell, S. M.; Barker, P. F.

    2009-10-01

    We report on the ability to tailor the optical dipole force for molecules by tuning their effective polarizability with strong field alignment using polarized fields. We have measured a difference of 20% in the dipole force on cold CS2 molecules when changing from linear to near-circular polarization using peak field intensities of 5.7×1011Wcm-2. A variation in the focal length with laser polarization of a molecular-optical lens formed by a single focused laser beam was also measured. This provides a new way of modifying this force for many molecules.

  14. Spatial calibration of an optical see-through head mounted display

    PubMed Central

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

    2010-01-01

    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. PMID:18599125

  15. Curved-Focal-Plane Arrays Using Deformed-Membrane Photodetectors

    NASA Technical Reports Server (NTRS)

    Nikzad, Shouleh; Jones, Todd

    2004-01-01

    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.

  16. Extended Depth-of-Field Projector by Fast Focal Sweep Projection.

    PubMed

    Iwai, Daisuke; Mihara, Shoichiro; Sato, Kosuke

    2015-04-01

    A simple and cost-efficient method for extending a projector's depth-of-field (DOF) is proposed. By leveraging liquid lens technology, we can periodically modulate the focal length of a projector at a frequency that is higher than the critical flicker fusion (CFF) frequency. Fast periodic focal length modulation results in forward and backward sweeping of focusing distance. Fast focal sweep projection makes the point spread function (PSF) of each projected pixel integrated over a sweep period (IPSF; integrated PSF) nearly invariant to the distance from the projector to the projection surface as long as it is positioned within sweep range. This modulation is not perceivable by human observers. Once we compensate projection images for the IPSF, the projected results can be focused at any point within the range. Consequently, the proposed method requires only a single offline PSF measurement; thus, it is an open-loop process. We have proved the approximate invariance of the projector's IPSF both numerically and experimentally. Through experiments using a prototype system, we have confirmed that the image quality of the proposed method is superior to that of normal projection with fixed focal length. In addition, we demonstrate that a structured light pattern projection technique using the proposed method can measure the shape of an object with large depth variances more accurately than normal projection techniques. PMID:26357096

  17. Integrated fiber optic probe for dynamic light scattering

    NASA Technical Reports Server (NTRS)

    Dhadwal, Harbans S.; Khan, Romel R.; Suh, Kwang

    1993-01-01

    An integrated fiber optic probe, comprising a monomode optical fiber fusion spliced to a short length of a graded-index multimode fiber, is fabricated for use as a coherent receiver in dynamic light scattering. The multimode fiber is cleaved to provide a gradient-index fiber lens with a focal length of 125 microns and an f-number close to unity. An integrated fiber receiver is used to measure the intensity-intensity autocorrelation data from a 0.05 percent by weight concentration of an aqueous suspension of polystyrene latex spheres. Analysis of 100 independent data sets indicates that the particle size can be recovered with an accuracy of +/- 1 percent.

  18. The design and evaluation of grazing incidence relay optics

    NASA Technical Reports Server (NTRS)

    Davis, John M.; Chase, R. C.; Silk, J. K.; Krieger, A. S.

    1989-01-01

    X-ray astronomy, both solar and celestial, has many needs for high spatial resolution observations which have to be performed with electronic detectors. If the resolution is not to be detector limited, plate scales in excess of 25 microns arc/sec, corresponding to focal lengths greater than 5 m, are required. In situations where the physical size is restricted, the problem can be solved by the use of grazing incidence relay optics. A system was developed which employs externally polished hyperboloid-hyperboloid surfaces to be used in conjunction with a Wolter-Schwarzschild primary. The secondary is located in front of the primary focus and provides a magnification of 4, while the system has a plate scale of 28 microns arc/sec and a length of 1.9 m. The design, tolerance specification, fabrication and performance at visible and X-ray wavelengths of this optical system are described.

  19. Hand-held optical fuel pin scanner

    DOEpatents

    Kirchner, T.L.; Powers, H.G.

    1980-12-07

    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.

  20. Hand-held optical fuel pin scanner

    DOEpatents

    Kirchner, Tommy L.; Powers, Hurshal G.

    1987-01-01

    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.

  1. Projection optics for a laser velocimeter

    NASA Technical Reports Server (NTRS)

    Rhodes, D. B.

    1979-01-01

    Projection optics for laser velocimeter (LV) scans constant focal volume over entire focus-position range. Optics thus simplify LV measurements over large flow fields (such as those encountered in wind tunnels) by eliminating calibrations required when focal volume varies with position.

  2. NMDA receptor binding in focal epilepsies

    PubMed Central

    McGinnity, C J; Koepp, M J; Hammers, A; Riaño Barros, D A; Pressler, R M; Luthra, S; Jones, P A; Trigg, W; Micallef, C; Symms, M R; Brooks, D J; Duncan, J S

    2015-01-01

    Objective To demonstrate altered N-methyl-d-aspartate (NMDA) receptor availability in patients with focal epilepsies using positron emission tomography (PET) and [18F]GE-179, a ligand that selectively binds to the open NMDA receptor ion channel, which is thought to be overactive in epilepsy. Methods Eleven patients (median age 33 years, 6 males) with known frequent interictal epileptiform discharges had an [18F]GE-179 PET scan, in a cross-sectional study. MRI showed a focal lesion but discordant EEG changes in two, was non-localising with multifocal EEG abnormalities in two, and was normal in the remaining seven patients who all had multifocal EEG changes. Individual patient [18F]GE-179 volume-of-distribution (VT) images were compared between individual patients and a group of 10 healthy controls (47 years, 7 males) using Statistical Parametric Mapping. Results Individual analyses revealed a single cluster of focal VT increase in four patients; one with a single and one with multifocal MRI lesions, and two with normal MRIs. Post hoc analysis revealed that, relative to controls, patients not taking antidepressants had globally increased [18F]GE-179 VT (+28%; p<0.002), and the three patients taking an antidepressant drug had globally reduced [18F]GE-179 VT (−29%; p<0.002). There were no focal abnormalities common to the epilepsy group. Conclusions In patients with focal epilepsies, we detected primarily global increases of [18F]GE-179 VT consistent with increased NMDA channel activation, but reduced availability in those taking antidepressant drugs, consistent with a possible mode of action of this class of drugs. [18F]GE-179 PET showed focal accentuations of NMDA binding in 4 out of 11 patients, with difficult to localise and treat focal epilepsy. PMID:25991402

  3. Focal Mechanism determination of local M

    NASA Astrophysics Data System (ADS)

    Vales, Dina; Custrio, Susana; Carrilho, Fernando

    2015-04-01

    We determine the focal mechanisms of local small (ML<3.9) earthquakes that occurred between 2013 and 2014 in mainland Portugal. These low magnitude events were recorded by several stations that provide first-motion polarity solutions. However, only few stations are located near the epicenter and record a waveform with a signal-to-noise ratio (SNR) high enough to allow full waveform modelling. To overcome this limitation, we used a new approach called cyclic scanning of the polarity solutions (CSPS) (Fojtkov and Zahradnik, 2014), which performs a joint inversion of full waveform and first motion polarities to retrieve the focal mechanism. This methodology has the advantage of yielding reliable focal mechanism solutions, even when high SNR waveforms are available from only a few near field stations (or in the limiting case, only with one single station). To apply the CSPS method one needs to: i) run the the FOCal MEChanism (FOCMEC) code (Snoke, 2003) to obtain a suite of the DC solutions corresponding to the first motion polarities, and then ii) perform the waveform modelling in order to decrease the uncertainty. The ISOLated Asperities (ISOLA) software (Sokos and Zahradnk, 2008, 2013) is used in this second step. We applied this method to weak events recorded by a network of 30 broadband seismic stations that transmit data in real-time to Instituto Portugus do Mar e da Atmosfera (IPMA), the institution responsible for seismic monitoring in Portugal. We interpret the obtained fault plane solutions in light of active faults and regional tectonics, and in comparison with focal mechanisms previously inferred for events in the region. The focal mechanisms obtained for small earthquakes allow us to significantly expand the database of available focal mechanisms in mainland Portugal, contributing to the understanding of active deformation in the region.

  4. Leg Length Inequality

    PubMed Central

    Sharpe, Colin R.

    1983-01-01

    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. PMID:21283327

  5. Leg length inequality.

    PubMed

    Sharpe, C R

    1983-02-01

    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. PMID:21283327

  6. MTF measurement of infrared optical systems

    NASA Astrophysics Data System (ADS)

    Lengwenus, Andre; Erichsen, Patrik

    2009-09-01

    Advances in electro-optic and infrared systems have led to new ways in modeling complex objectives for IR imaging devices. One important indicator for the performance of an imaging system is the modulation transfer function (MTF). In this contribution we disclose the main aspects of IR-MTF measurement and focus on the ImageMaster® Universal IR product line from Trioptics GmbH Germany. These devices cover the whole spectral range from SWIR to LWIR and can be configured to measure optical systems with focal lengths between 1 mm and 2000 mm. The instrument is fully automatized to a very high degree, so it is suitable for laboratory use as well as instruments designed for the high volume production environment.

  7. THE IMAGING PROPERTIES OF THE GAS PIXEL DETECTOR AS A FOCAL PLANE POLARIMETER

    SciTech Connect

    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.; and others

    2014-06-01

    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.

  8. Dependence of the absorption of pulsed CO{sub 2}-laser radiation by silane on wavenumber, fluence, pulse duration, temperature, optical path length, and pressure of absorbing and nonabsorbing gases

    SciTech Connect

    Blazejowski, J.; Gruzdiewa, L.; Rulewski, J.; Lampe, F.W.

    1995-05-15

    The absorption of three lines [{ital P}(20), 944.2 cm{sup {minus}1}; {ital P}(14), 949.2 cm{sup {minus}1}; and {ital R}(24), 978.5 cm{sup {minus}1}] of the pulsed CO{sub 2} laser (00{sup 0}1--10{sup 0}0 transition) by SiH{sub 4} was measured at various pulse energy, pulse duration, temperature, optical path length, and pressure of the compound and nonabsorbing foreign gases. In addition, low intensity infrared absorption spectrum of silane was compared with high intensity absorption characteristics for all lines of the pulsed CO{sub 2} laser. The experimental dependencies show deviations from the phenomenological Beer--Lambert law which can be considered as arising from the high intensity of an incident radiation and collisions of absorbing molecules with surroundings. These effects were included into the expression, being an extended form of the Beer--Lambert law, which reasonably approximates all experimental data. The results, except for extending knowledge on the interaction of a high power laser radiation with matter, can help understanding and planning processes leading to preparation of silicon-containing technologically important materials.

  9. The Focal Surface of the Euso Telescope

    NASA Astrophysics Data System (ADS)

    Kawasaki, Yoshiya; Bertaina, M.; Ebisuzaki, T.; Kajino, F.; Miyazaki, Y.; Nagano, M.; Sakaki, N.; Sato, M.; Shimizu, H. M.; Takizawa, Y.; Ameri, M.; Catalano, O.; Cuneo, S.; Fontanelli, F.; Gracco, V.; Musico, P.; Pallavicini, M.; Petrolini, A.; Pratolongo, F.; Sannino, M.; Bleurvacq, N.; Cadoux, F.; Chapron, C.; Gorodetzky, P.; Nedelec, P.; Patzak, T.; Plagnol, E.; Takahashi, Y.

    The Extreme Universe Space Observatory (EUSO) is a space mission to study extremely high-energy cosmic rays. The EUSO instrument is a wide-angle refractive telescope in near-ultraviolet wavelength region to observe time-resolved atmospheric fluorescence images of the extensive air showers from the International Space Station. The Focal surface is an aspherical curved surface, and its area amounts to about 4.5 m2. The focal surface detector is designed as a mosaic of multianode photomultipliers (MAPMT) for the single photoelectron counting capability. The strongest requirement for the focal surface detector is the maximization of the photon detection efficiency together with the uniformity over the focal surface. We have developed a new type of MAPMT. It is modified from the ordinary one and has a grid between the photocathode and the first dynode to electrostatically demagnify the photoelectron image on the dynode. We are also developing the HV supply system for a great number of MAPMTs. EUSO experiments the day-time and night-time every 90 minutes. The heat flow must be considered to stabilize the PMT characteristics, in parallel with the heat dissipation of the electronics attached on the focal surface supporting structure.

  10. Design and performance estimate of a focal reducer for the 2.3 m Thai National Telescope.

    PubMed

    Buisset, Christophe; Deboos, Alexis; Lépine, Thierry; Poshyachinda, Saran; Soonthornthum, Boonrucksar

    2016-01-25

    We have designed a new kind of focal reducer for the 2.3 m Thai National Telescope (TNT) to image the TNT specified FOV Δθ = 14.6' with an angular resolution α ≈1.2 arcsec. This, at a minimum cost by using common glasses, spherical surfaces and by requiring comfortable mechanical tolerance. This focal reducer comprises 1 lens placed at the level of the fork entrance and 1 lens placed in front of the detector. In this paper, we present the focal reducer paraxial model, we describe the optical design and we present the performance. PMID:26832523

  11. Optical design of the x-ray telescope for XEUS

    NASA Astrophysics Data System (ADS)

    Willingale, R.; Kunieda, H.; Okajima, T.; Naitoh, M.

    2005-08-01

    XEUS is a single focus X-ray telescope which will provide a collecting area of 10-20 m2 at 1 keV with angular resolution 2-5 arc seconds. Such a large area can be achieved with low mass using pore optics manufactured from silicon. The aperture utilisation of the pore optics is ~ 0:5 and with an aperture diameter of 7 m and gold reflecting surfaces the effective area can be 14 m2 at 1 keV and 1.5 m2 at 8 keV, providing it is possible to launch the required mass. Diffraction imposes a limit on the angular resolution that can be obtained with pore optics. If the focal length is 30 m then the angular resolution limit would be ~ 1 arc second but the pore size must be 0.2 mm. If the pore size is limited by manufacturing to 0.6 mm then the goal of 2 arc seconds half energy width will require a focal length ≥ 40 m. The hard X-ray response can be extended using multilayer coatings on the innermost shells giving ~ 1270 cm2 effective area at 40 keV for an increase in Si mass of ~ 96 kg.

  12. Submillisecond Optical Knife-Edge Testing

    NASA Technical Reports Server (NTRS)

    Thurlow, P.

    1983-01-01

    Fast computer-controlled sampling of optical knife-edge response (KER) signal increases accuracy of optical system aberration measurement. Submicrosecond-response detectors in optical focal plane convert optical signals to electrical signals converted to digital data, sampled and feed into computer for storage and subsequent analysis. Optical data are virtually free of effects of index-of-refraction gradients.

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

    PubMed

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

    2014-05-01

    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. PMID:24817618

  14. Neandertal clavicle length

    PubMed Central

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

    2014-01-01

    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

  15. Optical fuel pin scanner

    DOEpatents

    Kirchner, Tommy L.; Powers, Hurshal G.

    1983-01-01

    An optical scanner for indicia arranged in a focal plane at a cylindrical outside surface by use of an optical system including a rotatable dove prism. The dove prism transmits a rotating image of an encircled cylindrical surface area to a stationary photodiode array.

  16. Measuring microfocus focal spots using digital radiography

    SciTech Connect

    Fry, David A

    2009-01-01

    Measurement of microfocus spot size can be important for several reasons: (1) Quality assurance during manufacture of microfocus tubes; (2) Tracking performance and stability of microfocus tubes; (3) Determining magnification (especially important for digital radiography where the native spatial resolution of the digital system is not adequate for the application); (4) Knowledge of unsharpness from the focal spot alone. The European Standard EN 12543-5 is based on a simple geometrical method of calculating focal spot size from unsharpness of high magnification film radiographs. When determining microfocus focal spot dimensions using unsharpness measurements both signal-to-noise (SNR) and magnification can be important. There is a maximum accuracy that is a function of SNR and therefore an optimal magnification. Greater than optimal magnification can be used but it will not increase accuracy.

  17. Design of 10x uncooled thermal infrared zoom optical system

    NASA Astrophysics Data System (ADS)

    Mu, Da; Du, Yu-nan; Mi, Shi-long; Guo, Yan-chi

    2013-09-01

    For 320x240 pixel2 uncooled focal plane array detector, an infrared continuous zoom optical system of 10x zoom ratio for long-wavelength is designed in this paper. This system can be applied in joint transform correlator and other infrared tracing systems. The spectral band of the system is 8μm~12μm, the focal length is 20mm ~200mm , and the F number of the system is 2. The relative aperture is invariant during the zoom process, and the variable magnification curve and compensation curve are smooth as well. The system only consists of 7 lenses and one aspherical surface. The results have shown that when the maximum spatial frequency is 17lp/mm, the MTF(Modulation Transfer Function) curves in the whole range of focal length are all above 0.5 which are closed to diffraction limited curve. The stability of image plane is well, and the imaging quality is perfect, which show that the system meets the requirement of technical specification.

  18. Large-format InGaAs focal plane arrays for SWIR imaging

    NASA Astrophysics Data System (ADS)

    Hood, Andrew D.; MacDougal, Michael H.; Manzo, Juan; Follman, David; Geske, Jonathan C.

    2012-06-01

    FLIR Electro Optical Components will present our latest developments in large InGaAs focal plane arrays, which are used for low light level imaging in the short wavelength infrared (SWIR) regime. FLIR will present imaging from their latest small pitch (15 μm) focal plane arrays in VGA and High Definition (HD) formats. FLIR will present characterization of the FPA including dark current measurements as well as the use of correlated double sampling to reduce read noise. FLIR will show imagery as well as FPA-level characterization data.

  19. Design of an infrared four-mirror optical system with large relative aperture

    NASA Astrophysics Data System (ADS)

    Cong, Bin; Wu, Zheng

    2015-04-01

    Reflective optics is used widely in optical systems for their achromatization, large aperture and lightweight compared with refractive systems. An infrared four-mirror optical system with large relative aperture working in the 7.7~10.3 micron long wavelength infrared band is designed by using four reflective mirrors. The design principle, design results are described in this paper. The system has a circinal wide field of view with 1.5°×1.5°. The MTF of the system is diffraction-limited and the distortion is less than 1.0%. The ratio of focal length to total length is about 1/1.04,so the structure of the system is compact. The image quality is evaluated for each field, which shows that the design makes a good system with high image quality.

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

    NASA Technical Reports Server (NTRS)

    Vilnrotter, Victor A.; Hoppe, Daniel J.

    2011-01-01

    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).

  1. Rasmussen's encephalitis presenting as focal cortical dysplasia

    PubMed Central

    O'Rourke, D.J.; Bergin, A.; Rotenberg, A.; Peters, J.; Gorman, M.; Poduri, A.; Cryan, J.; Lidov, H.; Madsen, J.; Harini, C.

    2014-01-01

    Rasmussen's encephalitis is a rare syndrome characterized by intractable seizures, often associated with epilepsia partialis continua and symptoms of progressive hemispheric dysfunction. Seizures are usually the hallmark of presentation, but antiepileptic drug treatment fails in most patients and is ineffective against epilepsia partialis continua, which often requires surgical intervention. Co-occurrence of focal cortical dysplasia has only rarely been described and may have implications regarding pathophysiology and management. We describe a rare case of dual pathology of Rasmussen's encephalitis presenting as a focal cortical dysplasia (FCD) and discuss the literature on this topic. PMID:25667877

  2. Rasmussen's encephalitis presenting as focal cortical dysplasia.

    PubMed

    O'Rourke, D J; Bergin, A; Rotenberg, A; Peters, J; Gorman, M; Poduri, A; Cryan, J; Lidov, H; Madsen, J; Harini, C

    2014-01-01

    Rasmussen's encephalitis is a rare syndrome characterized by intractable seizures, often associated with epilepsia partialis continua and symptoms of progressive hemispheric dysfunction. Seizures are usually the hallmark of presentation, but antiepileptic drug treatment fails in most patients and is ineffective against epilepsia partialis continua, which often requires surgical intervention. Co-occurrence of focal cortical dysplasia has only rarely been described and may have implications regarding pathophysiology and management. We describe a rare case of dual pathology of Rasmussen's encephalitis presenting as a focal cortical dysplasia (FCD) and discuss the literature on this topic. PMID:25667877

  3. Ambroxol-induced focal epileptic seizure.

    PubMed

    Lapenta, Leonardo; Morano, Alessandra; Fattouch, Jinane; Casciato, Sara; Fanella, Martina; Giallonardo, Anna Teresa; Di Bonaventura, Carlo

    2014-01-01

    It is well known that in epileptic patients some compounds and different drugs used for the treatment of comorbidities can facilitate or provoke seizures, this evidence regarding a wide spectrum of pharmacological categories. The potential facilitating factors usually include direct toxic effects or pharmacological interactions of either active ingredients or excipients. We report the case of a patient with drug-resistant epilepsy who experienced focal epileptic seizures, easily and constantly reproducible, after each administration of a cough syrup. This is, to our knowledge, the first electroencephalogram-documented case of focal epileptic seizures induced by cough syrup containing ambroxol as active ingredient. PMID:24824664

  4. Arrhythmogenic Substrate of the Pulmonary Veins Assessed by High-Resolution Optical Mapping

    PubMed Central

    Arora, Rishi; Verheule, Sander; Scott, Luis; Navarrete, Antonio; Katari, Vikram; Wilson, Emily; Vaz, Dev; Olgin, Jeffrey E.

    2007-01-01

    Background It has recently been recognized that atrial fibrillation can originate from focal sources in the pulmonary veins (PVs). However, the mechanisms of focal atrial fibrillation have not been well characterized. We assessed the electrophysiological characteristics of the PVs using high-resolution optical mapping. Methods and Results Coronary-perfused, isolated whole-atrial preparations from 33 normal dogs were studied. Programmed electrical stimulation was performed, and a 4-cm2 area of the PV underwent optical mapping of transmembrane voltage to obtain 256 simultaneous action potentials. Marked conduction slowing was seen at the proximal PV, compared with the rest of the vein, on both the epicardial (31.3±4.47 versus 90.2±20.7 cm/s, P=0.001) and endocardial (45.8±6.90 versus 67.6±10.4 cm/s, P=0.012) aspects. Pronounced repolarization heterogeneity was also noted, with action potential duration at 80% repolarization being longest at the PV endocardium. Nonsustained reentrant beats were induced with single extrastimuli, and the complete reentrant loop was visualized (cycle length, 155±30.3 ms); reentrant activity could be sustained with isoproterenol. Sustained focal discharge (cycle length, 330 to 1100 ms) was seen from the endocardial surface in the presence of isoproterenol; each focus was localized near the venous ostium. Conclusions The normal PV seems to have the necessary substrate to support reentry as well as focal activity. Although reentry occurred more distally in the vein, focal activity seemed to occur more proximally. PMID:12665495

  5. Kalman Filter for Calibrating a Telescope Focal Plane

    NASA Technical Reports Server (NTRS)

    Kang, Bryan; Bayard, David

    2006-01-01

    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.

  6. Design considerations for long focal length reconnaissance systems from an applications point of view

    NASA Astrophysics Data System (ADS)

    Koper, H. F.; Murray, T. J.

    1980-01-01

    This paper reviews recent changes in tactical doctrine within the Navy as related to reconnaissance data collection in the lethal anti-air environment which is anticipated throughout the 1980's and 1990's. The Long Range Oblique Photographic (LOROP) camera, never before utilized in the Navy inventory, is now considered a valid means for improving survivability and providing the degree of information necessary to support the battle group. An analysis of the 'nice to have' features of the LOROP camera and their relation to Navy requirements are presented for both the tactical, hot war scenario and the peacetime, open-ocean surveillance scenario.

  7. A do-it-yourself optical bench

    NASA Astrophysics Data System (ADS)

    Dvořák, Leoš

    2011-10-01

    When teaching geometrical optics, especially the parts concerning lenses, there are many experiments that can be done just by holding the lenses in your (or your pupils') hands. But if you want to measure something, for example focal lengths, or combine two lenses to demonstrate the principle of a telescope, then something that can fix the lenses is needed. Of course, we can do such demonstrations and measurements using a commercially available optical bench. But a classical optical bench is usually a large and heavy construction that is not easy to transport. Often only one (or even none) may be available per classroom. In many school experiments something less robust, simpler, and less expensive would perhaps suit the needs better. Here we describe a simple and flexible optical bench that may be constructed by students themselves. Apart from the price of the lenses, the construction is also very cheap. So, if you have some spare lenses available, you can build a small optical bench for 10 or less. Each group of students can then use their own optical bench to do experiments.

  8. Optics for nano-satellite X-ray monitor

    NASA Astrophysics Data System (ADS)

    Tichý, Vladimír.; Burrows, David N.; Prieskorn, Zachary; Hudec, René

    The Schmidt lobster eye design for a grazing incidence X-ray optics provides wide field of view of the order of many degrees, for this reason it can be a convenient approach for the construction of space X-ray monitors. It is possible to assemble Schmidt lobster eye telescopes with dimensions and focal lengths acceptable for nano class satellites. In this paper, draft of nano-class space mission providing monitoring of specific sky area is presented. Preliminary optical design study for such mission is performed. Two of possible opticle designs are presented. For those designs, field of view, effective input area and other basic optical parameters are calculated. Examples of observed images are presented.

  9. Smart optical writing head design for laser-based manufacturing

    NASA Astrophysics Data System (ADS)

    Amin, M. Junaid; Riza, Nabeel A.

    2014-03-01

    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.

  10. Optical design study and prototyping of a dual-field zoom lens imaging in the 1-5 micron infrared waveband

    NASA Astrophysics Data System (ADS)

    Reshidko, Dmitry; Reshidko, Pavel; Carmeli, Ran

    2015-09-01

    Optical systems can provide simultaneous imaging in several spectral bands and thus be much more useful. A new and current generation of focal plane arrays is allowing detection in more than one spectral region. The design of a refractive imaging lens for such detectors requires correcting chromatic aberrations over the wider range of wavelengths. However, the fewer available refracting materials, the material properties that change between the spectral bands, and the system transmission requirements make the design of such lenses particularly challenging. We present a dual-field zoom lens designed for a cooled detector sensing across short-wave infrared (SWIR) and midwave infrared (MWIR) spectral bands (continuous imaging for 1-5 μm). This zoom lens has a 75 mm focal length in the wide mode and a 250mm focal length in the narrow mode, and operates at f/4.7 in both discrete zoom positions. The lens is actively compensated to work in thermal environments from -20°C to +60°C. We discuss the optical design methodology, review the selection of materials and coatings for the optical elements, and analyze the transmission of the lens and optical performance. A prototype system has been manufactured and assembled. We validate our design with experimental data.

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

    PubMed Central

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

    2011-01-01

    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. η2p = .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. PMID:21443344

  12. Focal choroidal excavation in patients with central serous chorioretinopathy

    PubMed Central

    Luk, F O J; Fok, A C T; Lee, A; Liu, A T W; Lai, T Y Y

    2015-01-01

    Purpose To evaluate the prevalence and clinical features of focal choroidal excavation (FCE) in patients presenting with central serous chorioretinopathy (CSC). Methods This is a retrospective consecutive case series of consecutive patients with CSC who were referred for spectral domain optical coherence tomography (SD-OCT) between January 2010 and December 2011. Medical records were reviewed and clinical features including presence of FCE in SD-OCT, fluorescence angiography (FA), and indocyanine green angiography (ICGA) were studied. Results Among the 116 CSC patients assessed, FCE was found in 11 eyes of 7 (6.0%) patients. FCE was associated with subretinal fluid in six eyes of six patients and serous pigment epithelial detachment in three eyes of two patients. The mean central subfield retinal thickness of CSC eyes with FCE was 283.7 μm, compared with 377.5 μm for CSC eyes without FCE (Mann–Whitney U-test, P=0.020). Five FCE eyes of five patients had focal leakage on FA. Choroidal hyperpermeability on ICGA was found in seven CSC eyes with FCE, with four eyes showing hypofluorescent spot corresponding to the FCE. After a mean follow-up of 16 months, visual acuity of all 11 eyes with FCE remained stable or improved at the last follow-up. Conclusion FCE is not an uncommon feature in patients with CSC and might be associated with choroidal hemodynamic disturbances. PMID:25853402

  13. Technological developments of the OGRE focal plane array

    NASA Astrophysics Data System (ADS)

    Tutt, James H.; McEntaffer, Randall L.; DeRoo, Casey; Schultz, Ted; Rogers, Thomas; Murray, Neil; Holland, Andrew; Weatherill, Daniel; Holland, Karen; Colebrook, David; Farn, David

    2015-09-01

    The Off-plane Grating Rocket Experiment (OGRE) is a high resolution soft X-ray spectrometer sub-orbital rocket payload designed as a technology development platform for three low Technology Readiness Level (TRL) components. The incident photons will be focused using a light-weight, high resolution, single-crystal silicon optic. They are then dispersed conically according to wavelength by an array of off-plane gratings before being detected in a focal plane camera comprised of four Electron Multiplying Charge-Coupled Devices (EM-CCDs). While CCDs have been extensively used in space applications; EM-CCDs are seldom used in this environment and even more rarely for X-ray photon counting applications, making them a potential technology risk for larger scale X-ray observatories. This paper will discuss the reasons behind choosing EM-CCDs for the focal plane detector and the developments that have been recently made in the prototype camera electronics and thermal control system.

  14. High operating temperature interband cascade focal plane arrays

    SciTech Connect

    Tian, Z.-B.; Godoy, S. E.; Kim, H. S.; Schuler-Sandy, T.; Montoya, J. A.; Krishna, S.

    2014-08-04

    In this paper, we report the initial demonstration of mid-infrared interband cascade (IC) photodetector focal plane arrays with multiple-stage/junction design. The merits of IC photodetectors include low noise and efficient photocarrier extraction, even for zero-bias operation. By adopting enhanced electron barrier design and a total absorber thickness of 0.7 μm, the 5-stage IC detectors show very low dark current (1.10 × 10{sup −7} A/cm{sup 2} at −5 mV and 150 K). Even with un-optimized fabrication and standard commercial (mis-matched) read-out circuit technology, infrared images are obtained by the 320 × 256 IC focal plane array up to 180 K with f/2.3 optics. The minimum noise equivalent temperature difference of 28 mK is obtained at 120 K. These initial results indicate great potential of IC photodetectors, particularly for high operating temperature applications.

  15. Coefficients of Effective Length.

    ERIC Educational Resources Information Center

    Edwards, Roger H.

    1981-01-01

    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)

  16. Myofilament length dependent activation

    SciTech Connect

    de Tombe, Pieter P.; Mateja, Ryan D.; Tachampa, Kittipong; Mou, Younss Ait; Farman, Gerrie P.; Irving, Thomas C.

    2010-05-25

    The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. The main cellular mechanism that underlies this phenomenon is an increase in the responsiveness of cardiac myofilaments to activating Ca{sup 2+} ions at a longer sarcomere length, commonly referred to as myofilament length-dependent activation. This review focuses on what molecular mechanisms may underlie myofilament length dependency. Specifically, the roles of inter-filament spacing, thick and thin filament based regulation, as well as sarcomeric regulatory proteins are discussed. Although the 'Frank-Starling law of the heart' constitutes a fundamental cardiac property that has been appreciated for well over a century, it is still not known in muscle how the contractile apparatus transduces the information concerning sarcomere length to modulate ventricular pressure development.

  17. Length Paradox in Relativity

    ERIC Educational Resources Information Center

    Martins, Roberto de A.

    1978-01-01

    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)

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

    PubMed

    Feng, Zexin; Huang, Lei; Gong, Mali

    2014-04-21

    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

  19. Stabilization of a Laser Welding Process Against Focal Shift Effects using Beam Manipulation

    NASA Astrophysics Data System (ADS)

    Thiel, C.; Weber, R.; Johannsen, J.; Graf, T.

    Two measures to enhance welding process stability with respect to a varying focal position are presented and discussed with regards to possible effects of laser power efficiency increase. Spatial beam movement was caused by a deflecting mirror and proved to create a welding process with a higher constancy in welding depth when changing focal position. A larger cross sectional area of the weld seam was measured showing increased laser absorption when compared to a static beam. Sinusoidal laser power modulation was tested for varying focus positions and proves to induce a deeper weld seam at moderately increased cross sectional areas. The power modulated welding process is dominated by the influence of melt dynamics which can be guided by choosing suitable modulation parameters. Both systems can be used to stabilize the welding process against loss of joint area or loss of connection which may occur due to focal shift in high brightness laser beam optics.

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

    NASA Astrophysics Data System (ADS)

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

    2004-10-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    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.

  2. Luneburg lens with extended flat focal surface for electronic scan applications.

    PubMed

    Li, Ying; Zhu, Qi

    2016-04-01

    Luneburg lens with flat focal surface has been developed to work together with planar antenna feeds for beam steering applications. According to our analysis of the conventional flattened Luneburg lens, it cannot accommodate enough feeding elements which can cover its whole scan range with half power beamwidths (HPBWs). In this paper, a novel Luneburg lens with extended flat focal surface is proposed based on the theory of Quasi-Conformal Transformation Optics (QCTO), with its beam steering features reserved. To demonstrate this design, a three-dimensional (3D) prototype of this novel extend-flattened Luneburg lens working at Ku band is fabricated based on 3D printing techniques, whose flat focal surface is attached to a 9-element microstrip antenna array to achieve different scan angles. Our measured results show that, with different antenna elements being fed, the HPBWs can cover the whole scan range. PMID:27137012

  3. Precision Laser Annealing of Focal Plane Arrays

    SciTech Connect

    Bender, Daniel A.; DeRose, Christopher; Starbuck, Andrew Lea; Verley, Jason C.; Jenkins, Mark W.

    2015-09-01

    We present results from laser annealing experiments in Si using a passively Q-switched Nd:YAG microlaser. Exposure with laser at fluence values above the damage threshold of commercially available photodiodes results in electrical damage (as measured by an increase in photodiode dark current). We show that increasing the laser fluence to values in excess of the damage threshold can result in annealing of a damage site and a reduction in detector dark current by as much as 100x in some cases. A still further increase in fluence results in irreparable damage. Thus we demonstrate the presence of a laser annealing window over which performance of damaged detectors can be at least partially reconstituted. Moreover dark current reduction is observed over the entire operating range of the diode indicating that device performance has been improved for all values of reverse bias voltage. Additionally, we will present results of laser annealing in Si waveguides. By exposing a small (<10 um) length of a Si waveguide to an annealing laser pulse, the longitudinal phase of light acquired in propagating through the waveguide can be modified with high precision, <15 milliradian per laser pulse. Phase tuning by 180 degrees is exhibited with multiple exposures to one arm of a Mach-Zehnder interferometer at fluence values below the morphological damage threshold of an etched Si waveguide. No reduction in optical transmission at 1550 nm was found after 220 annealing laser shots. Modeling results for laser annealing in Si are also presented.

  4. Focal xanthogranulomatous pyelonephritis simulating malignancy in children.

    PubMed

    López-Medina, A; Ereño, M J; Fernández-Cantón, G; Zuazo, A

    1995-01-01

    Xantogranulomatous pyelonephritis is a severe chronic form of renal parenquimal infection that usually results in diffuse renal destruction. An unusual case of xanthogranulomatous pyelonephritis in a child is reported which presented as a focal mass without calculus in a functioning kidney and was diagnosed as a renal tumor. PMID:7620425

  5. Idiopathic focal foveolar hyperplasia in infants.

    PubMed

    Holland, A J; Freeman, J K; Le Quesne, G W; Khong, T Y

    1997-09-01

    Idiopathic focal foveolar hyperplasia (FFH) is a rare cause of gastric outlet obstruction in infants. We present two cases, including the first reported association with infantile hypertrophic pyloric stenosis. The diagnostic ultrasound appearance of FFH is described. Optimal treatment is surgical excision of the involved mucosa with pyloroplasty or pyloromyotomy. PMID:9238115

  6. Dual band QWIP focal plane array

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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.

  7. Salivary gland myoepithelioma with focal capsular invasion.

    PubMed

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

    2009-07-01

    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

  8. Large Format Multicolor QWIP Focal Plane Arrays

    NASA Technical Reports Server (NTRS)

    Soibel, A.; Gunapala, S. D.; Bandara, S. V.; Liu, J. K.; Mumolo, J. M.; Ting, D. Z.; Hill, C. J.; Nguyen, J.

    2009-01-01

    Mid-wave infrared (MWIR) and long-wave infrared (LWIR) multicolor focal plane array (FPA) cameras are essential for many DoD and NASA applications including Earth and planetary remote sensing. In this paper we summarize our recent development of large format multicolor QWIP FPA that cover MWIR and LWIR bands.

  9. Complex source description of focal regions.

    PubMed

    Monzon, Cesar; Forester, Donald W; Moore, Peter

    2006-04-01

    Closed-form solutions of the two-dimensional homogeneous wave equation are presented that provide focal-region descriptions corresponding to a converging bundle of rays. The solutions do have evanescent wave content and can be described as a source-sink pair or particle-antiparticle pair, collocated in complex space, with the complex location being critical in the determination of beam shape and focal region size. The wave solutions are not plagued by singularities, have a finite energy, and have a limitation on how small the focal size can get, with a penalty for limiting small spot sizes in the form of impractically high associated reactive energy. The electric-field-defined spot-size limiting value is 0.35lambda x 0.35lambda, which is about 38% of the Poynting-vector-defined minimum spot size (0.8lambda x 0.4lambda) and corresponds to a condition related to the maximum possible beam angle. A multiple set of solutions is introduced, and the elementary solutions are used to produce new solutions via superposition, resulting in fields with chiral character or with increased depth of focus. We do not claim generality, as the size of focal regions exhibited by the closed-form solutions has a lower bound and hence is not able to account for Pendry's "ideal lens" scenario. PMID:16604758

  10. Sensory-motor integration in focal dystonia.

    PubMed

    Avanzino, Laura; Tinazzi, Michele; Ionta, Silvio; Fiorio, Mirta

    2015-12-01

    Traditional definitions of focal dystonia point to its motor component, mainly affecting planning and execution of voluntary movements. However, focal dystonia is tightly linked also to sensory dysfunction. Accurate motor control requires an optimal processing of afferent inputs from different sensory systems, in particular visual and somatosensory (e.g., touch and proprioception). Several experimental studies indicate that sensory-motor integration - the process through which sensory information is used to plan, execute, and monitor movements - is impaired in focal dystonia. The neural degenerations associated with these alterations affect not only the basal ganglia-thalamic-frontal cortex loop, but also the parietal cortex and cerebellum. The present review outlines the experimental studies describing impaired sensory-motor integration in focal dystonia, establishes their relationship with changes in specific neural mechanisms, and provides new insight towards the implementation of novel intervention protocols. Based on the reviewed state-of-the-art evidence, the theoretical framework summarized in the present article will not only result in a better understanding of the pathophysiology of dystonia, but it will also lead to the development of new rehabilitation strategies. PMID:26164472

  11. Ataxia and focal dystonia in Kallmann syndrome.

    PubMed

    Hernando-Quintana, Natalia; Playán-Usón, Jesús; Crespo-Burillo, José Antonio; Marín-Cárdenas, Miguel Ángel; Gazulla, José

    2016-02-01

    A case of Kallmann syndrome (KS) associated with rare neurological manifestations is presented. Cerebellar ataxia probably caused by a small posterior fossa and a focal dystonia affecting the left lower limb expand the spectrum of neurological manifestations occurring in KS. Further studies are needed to better understand these manifestations. PMID:26862419

  12. Editorial: Redefining Length

    SciTech Connect

    Sprouse, Gene D.

    2011-07-15

    Technological changes have moved publishing to electronic-first publication where the print version has been relegated to simply another display mode. Distribution in HTML and EPUB formats, for example, changes the reading environment and reduces the need for strict pagination. Therefore, in an effort to streamline the calculation of length, the APS journals will no longer use the printed page as the determining factor for length. Instead the journals will now use word counts (or word equivalents for tables, figures, and equations) to establish length; for details please see http://publish.aps.org/authors/length-guide. The title, byline, abstract, acknowledgment, and references will not be included in these counts allowing authors the freedom to appropriately credit coworkers, funding sources, and the previous literature, bringing all relevant references to the attention of readers. This new method for determining length will be easier for authors to calculate in advance, and lead to fewer length-associated revisions in proof, yet still retain the quality of concise communication that is a virtue of short papers.

  13. Overexpression of adenosine kinase in cortical astrocytes generates focal neocortical epilepsy in mice: Laboratory investigation

    PubMed Central

    Shen, Hai-Ying; Sun, Hai; Hanthorn, Marissa M.; Zhi, Zhongwei; Lan, Jing-Quan; Poulsen, David J.; Wang, Ruikang K.; Boison, Detlev

    2013-01-01

    Object New experimental models and diagnostic methods are needed to better understand the pathophysiology of focal neocortical epilepsies in a search for improved epilepsy treatment options. We hypothesized that a focal disruption of adenosine homeostasis in the neocortex might be sufficient to trigger electrographic seizures. We further hypothesized that a focal disruption of adenosine homeostasis might affect microcirculation and thus offer a diagnostic opportunity for the detection of a seizure focus located in the neocortex. Methods Focal disruption of adenosine homeostasis was achieved by injecting an adeno-associated virus (AAV) engineered to overexpress adenosine kinase (ADK), the major metabolic clearance enzyme for the brain’s endogenous anticonvulsant adenosine, into the neocortex of mice. Eight weeks following virus injection, the affected brain area was imaged via optical microangiography (OMAG) to detect changes in microcirculation. After completion of imaging, cortical electroencephalography (EEG) recordings were obtained from the imaged brain area. Results Viral expression of the Adk cDNA in astrocytes generated a focal area (~ 2 mm in diameter) of ADK overexpression within the neocortex. OMAG scanning revealed a reduction in vessel density within the affected brain area of approximately 23% and 29% compared to control animals and the contralateral hemisphere, respectively. EEG recordings revealed electrographic seizures within the focal area of ADK overexpression at a rate of 1.3 ± 0.2 seizures per hour. Conclusions Our findings suggest that focal adenosine deficiency is sufficient to generate a neocortical focus of hyperexcitability, which is also characterized by reduced vessel density. We conclude that our model constitutes a useful tool to study neocortical epilepsies and that OMAG constitutes a non-invasive diagnostic tool for the imaging of seizure foci with disrupted adenosine homeostasis. PMID:24266544

  14. Calculation of the illuminance distribution in the focal spot of a focusing system taking into account aberrations in this system and divergence of a focused laser beam

    SciTech Connect

    Gitin, Andrey V

    2007-03-31

    The dependence of the focal-spot size of a 'deep' parabolic mirror reflector on the laser-beam divergence is analysed by the method of elementary reflections. The dependence of the focal-beam diameter of an ideal focusing optical system on the laser-beam parameters is described. The expression is obtained for calculating the illumination distribution in the focal spot of a 'deep' mirror reflector which takes into account both aberrations and light-gathering power of the reflector and the divergence of a focused laser beam. (optical systems)

  15. Vision and Wide-Field Imagers with Curved Focal Planes

    NASA Astrophysics Data System (ADS)

    Arianpour, Ashkan

    This dissertation provides details regarding the implementation of curved-focal surface fiber coupled imaging for medical and wide-field applications. An optomechanical fluid-filled eye model with visual acuity better than 20/20 vision was design and characterized. A wearable telescopic contact lens was worn on the optomechanical eye model and the performance characterized. Measurements of the contact lens surfaces were modeled to quantify the impact of contact lens fabrication on end-result resolution. Separately, the limitations of the field of view in fiber coupled monocentric imaging are analyzed. This dissertation describes a novel technique to address this based on conformal micro-optics. The design, simulation, and fabrication of an embossed surface relief micro-prism that increases the field of view are demonstrated.

  16. Benefits of small pixel focal plane array technology

    NASA Astrophysics Data System (ADS)

    Caulfield, John; Curzan, Jon; Lewis, Jay

    2015-08-01

    We report on the demonstration of a high definition high charge capacity 2.1 Mpixel mid-wave infrared (MWIR) Focal Plane Array (FPA). This high definition (HD) FPA utilizes a 2040 x 1156 format and a 5 μm pixel pitch. This small pixel size enables sampling at spatial frequencies greater than the classical Nyquist limit imposed by the optical systems Point Spread Function (PSF). We show that oversampling IRFPAs (Infrared FPA) enable improved fidelity in imaging including resolution improvements, advanced pixel correlation processing to reduce false alarm rates, improved detection ranges, and an improved ability to track closely spaced objects. The small pixel IRFPA achieves good performance in the MWIR band and is expected to detect dimmer signals at longer ranges than previously demonstrated.

  17. Simple Experimental Methods for Determining the Apparent Focal Shift in a Microscope System

    PubMed Central

    Bratton, Benjamin P.; Shaevitz, Joshua W.

    2015-01-01

    Three-dimensional optical microscopy is often complicated by a refractive index mismatch between the sample and objective lens. This mismatch causes focal shift, a difference between sample motion and focal-plane motion, that hinders the accuracy of 3D reconstructions. We present two methods for measuring focal shift using fluorescent beads of different sizes and ring-stained fluorescent beads. These simple methods are applicable to most situations, including total internal reflection objectives and samples very close to the interface. For distances 0–1.5 μm into an aqueous environment, our 1.49-NA objective has a relative focal shift of 0.57 ± 0.02, significantly smaller than the simple n2/n1 approximation of 0.88. We also expand on a previous sub-critical angle theory by means of a simple polynomial extrapolation. We test the validity of this extrapolation by measuring the apparent focal shift in samples where the refractive index is between 1.33 and 1.45 and with objectives with numerical apertures between 1.25 and 1.49. PMID:26270960

  18. The finite element modeling and thermal analysis of the special focal plane of LAMOST

    NASA Astrophysics Data System (ADS)

    Zuo, Heng; Yang, Dehua; Li, Guoping

    2010-07-01

    The Large Area Multi-Object Spectroscopic Telescope (LAMOST) is a meridian reflecting Schmidt telescope with a 40m optical axis between the reflecting Schmidt plate and the spherical primary mirror. In the middle is located the spherical focal plane, through which there are corresponding 4000+ unit mounting holes for the fibers, and on its back, there attached a support truss adapted from Serrurier concept. The mechanical stabilization of the focal plane system naturally has magnificent impact on the observation efficiency of the LAMOST. A comprehensive Finite Element Model of the focal plane system has been built to evaluate thermally induced degradation of its mechanical accuracy using the nodal modification technique within ANSYS, and diverse temperature load cases have been considered on the Finite Element model and related thermal analyses have been carried out to investigate thermal deformation of the focal plane. Subsequently the calculated deflection of the working surface has been extracted and reconstructed with least square fitting in MATLAB. The results show that temperature change around the telescope has little effect on the performance of the focal plane within temperature variation requirements of the LAMOST. The methods of modeling and analyzing used in this research are informative for future large telescope projects.

  19. Beam delivery by adaptive optics for material processing applications using high-power CO2 lasers

    NASA Astrophysics Data System (ADS)

    Haferkamp, Heinz; Seebaum, Dirk

    1994-09-01

    The use of high power CO2 lasers for various applications in material and production technologies has increasingly grown, and new applications are on their way to being used in industry. Due to varying beam path lengths, proper beam delivery is essential to obtain constant working conditions when using machines with moving beam guidance. The focussing characteristics of divergent laser beams change with the distance between laser source and processing head. To keep the energy distribution on the workpiece surface on the same level while working with flying optics, the use of deformable mirror systems has proven to be a suitable solution. In this case, a newly-developed system is brought into the beam guidance system to keep the focal spot diameter constant. As far as applications are concerned, where the distance of the focal spot to the surface of the workpiece is of major interest for the performance of the process, these optical devices are also used to tune the focal length. For example collision danger or dynamic limitations of the handling system may mean that the focal spot has to follow the surface outline without keeping the distance between processing head and material surface constant. Besides cutting and shaping by material removal applications, welding is a kind of application where a focus shift without moving the processing head may be advantageous, especially for 3D processes. Therefore, another deformable mirror is installed near to the focusing optics. Investigations have been carried out on the location of the deformable mirror close to the laser source (RS 3000 RF), and inside the processing head.

  20. Design of the Focal Plane for the Pleiades HR Instrument

    NASA Astrophysics Data System (ADS)

    Plaisant, Gérard; Le Goff, Roland; Deswarte, David

    This paper presents the design of the focal plane of the future French observation satellite PLEIADES. The purpose of this focal plane is to analyse images in panchromatic (Pa) as far as multi- spectral (Xs) bands in push-broom mode. The size of the observed image is close to 400 mm and it shall be analysed in 30.000 samples in Pa and 7.500 in Xs, resulting in an on- ground resolution lower than 1 meter in Pa. Compared to the previous French SPOT instrument series, the optical architecture is largely simplified : the Xs images are separated in the field of view and detected by four parallel CCD lines integrated in the same package. The spectral selection is made by means of strip filters placed very close in front of the Xs detector. Pa and Xs images are shifted in the field of view. Folding mirrors are used to cope with both constraints : the CCD package size and the required limitation of the distance Pa-Xs. The detection in Pa is made thanks to a Time Delay Integration (TDI) CCD in order to improve the radiometric performances. Five TDI CCD providing each 6000 pixels are optically butted to form a continuous line. The thermo-mechanical concept makes use of the characteristics of the SiC structure. It allows to evacuate the CCDs and their close electronics power towards a radiator while maintaining stable the detection lines geometry. The development is presently in phase B ; the phase C/D will start in 2002.

  1. Post-focal filamentation of an externally focused femtosecond laser pulse in air

    NASA Astrophysics Data System (ADS)

    Geints, Yu E.; Zemlyanov, A. A.

    2013-03-01

    Self-focusing and filamentation of externally focused ultrashort laser radiation in air are discussed. The influence of initial beam focusing on the filamentation length is numerically studied, and the conditions under which a light filament can resurrect after the linear focus are determined. We have found that the probability of this post-focal filamentation increases with an increase of laser power regardless of the type of filamentation (single/multiple).

  2. Hyperspectral modeling of an infrared focal plane array

    NASA Astrophysics Data System (ADS)

    Mouzali, Salima; Lefebvre, Sidonie; Rommeluère, Sylvain; Ferrec, Yann; Primot, Jérôme

    2014-10-01

    Infrared Focal Plane Arrays (FPA) are increasingly used to measure multi- or hyperspectral images. Therefore, it is crucial to control and modelize their spectral response. The purpose of this paper is to propose a modeling approach, adjustable by experimental data, and applicable to the main cooled detector technologies. A physical model is presented, taking into account various optogeometrical properties of the detector, such as disparities of the pixels cut-off wavelengths. It describes the optical absorption phenomenon inside the pixel, by considering it as a stack of optical bulk layers. Then, an analytical model is proposed, based on the interference phenomenon occurring into the structure. This model considers only the three major waves interfering. It represents a good approximation of the physical model and a complementary understanding of the optical process inside the structure. This approach is applied to classical cooled FPAs as well as to specific instruments such as Microspoc (MICRO SPectrometer On Chip), a concept of miniaturized infrared Fourier transform spectrometer, integrated on a classical Mercury-Cadmium-Telluride FPA, and cooled by a cryostat.

  3. Development of microchannel plate x-ray optics

    NASA Technical Reports Server (NTRS)

    Kaaret, Philip

    1995-01-01

    The goal of this research program was to develop a novel technique for focusing x-rays based on the optical system of a lobster's eye. A lobster eye employs many closely packed reflecting surfaces arranged within a spherical or cylindrical shell. These optics have two unique properties: they have unlimited fields of view and can be manufactured via replication of identical structures. Because the angular resolution is given by the ratio of the size of the individual optical elements to the focal length, optical elements with size on the order of one hundred microns are required to achieve good angular resolution with a compact telescope. We employed anisotropic etching of single crystal silicon wafers for the fabrication of micron-scale optical elements. This technique, commonly referred to as silicon micromachining, is based on silicon fabrication techniques developed by the microelectronics industry. We have succeeded in producing silicon lenses with a geometry suitable for a 1-d focusing x-ray optics. These lenses have an aspect ratio (40:1) suitable for x-ray reflection and have very good optical surface alignment. We have developed a number of process refinements which improved the quality of the lens geometry and the repeatability of the etch process. In addition to the silicon fabrication, an x-ray beam line was constructed at Columbia for testing the optics. Most recently, we have done several experiments to find the fundamental limits that the anisotropic etch process placed on the etched surface roughness.

  4. Development of microchannel plate x-ray optics

    NASA Astrophysics Data System (ADS)

    Kaaret, Philip

    1995-02-01

    The goal of this research program was to develop a novel technique for focusing x-rays based on the optical system of a lobster's eye. A lobster eye employs many closely packed reflecting surfaces arranged within a spherical or cylindrical shell. These optics have two unique properties: they have unlimited fields of view and can be manufactured via replication of identical structures. Because the angular resolution is given by the ratio of the size of the individual optical elements to the focal length, optical elements with size on the order of one hundred microns are required to achieve good angular resolution with a compact telescope. We employed anisotropic etching of single crystal silicon wafers for the fabrication of micron-scale optical elements. This technique, commonly referred to as silicon micromachining, is based on silicon fabrication techniques developed by the microelectronics industry. We have succeeded in producing silicon lenses with a geometry suitable for a 1-d focusing x-ray optics. These lenses have an aspect ratio (40:1) suitable for x-ray reflection and have very good optical surface alignment. We have developed a number of process refinements which improved the quality of the lens geometry and the repeatability of the etch process. In addition to the silicon fabrication, an x-ray beam line was constructed at Columbia for testing the optics. Most recently, we have done several experiments to find the fundamental limits that the anisotropic etch process placed on the etched surface roughness.

  5. Relativistic Length Agony Continued

    NASA Astrophysics Data System (ADS)

    Redzic, D. V.

    2014-06-01

    We made an attempt to remedy recent confusing treatments of some basic relativistic concepts and results. Following the argument presented in an earlier paper (Redzic 2008b), we discussed the misconceptions that are recurrent points in the literature devoted to teaching relativity such as: there is no change in the object in Special Relativity, illusory character of relativistic length contraction, stresses and strains induced by Lorentz contraction, and related issues. We gave several examples of the traps of everyday language that lurk in Special Relativity. To remove a possible conceptual and terminological muddle, we made a distinction between the relativistic length reduction and relativistic FitzGerald-Lorentz contraction, corresponding to a passive and an active aspect of length contraction, respectively; we pointed out that both aspects have fundamental dynamical contents. As an illustration of our considerations, we discussed briefly the Dewan-Beran-Bell spaceship paradox and the 'pole in a barn' paradox.

  6. Development and Testing of an Innovative Two-Arm Focal-Plane Thermal Strap (TAFTS)

    NASA Technical Reports Server (NTRS)

    Urquiza, E.; Vasquez, C.; Rodriguez, J.; Van Gorp, B.

    2011-01-01

    Maintaining temperature stability in optical focal planes comes with the intrinsic challenge of creating a pathway that is both extremely flexible mechanically and highly conductive thermally. The task is further complicated because science-caliber optical focal planes are extremely delicate, yet their mechanical resiliency is rarely tested and documented. The mechanical engineer tasked with the thermo-mechanical design must then create a highly conductive thermal link that minimizes the tensile and shear stresses transmitted to the focal plane without design parameters on an acceptable stiffness. This paper will describe the development and testing of the thermal link developed for the Portable Remote Imaging Spectrometer (PRISM) instrument. It will provide experimentally determined mechanical stiffness plots in the three axes of interest. Analytical and experimental thermal conductance results for the two-arm focal-plane thermal strap (TAFTS), from cryogenic to room temperatures, are also presented. The paper also briefly describes some elements of the fabrication process followed in developing a novel design solution, which provides high conductance and symmetrical mechanical loading, while providing enhanced flexibility in all three degrees of freedom.

  7. Determination of accuracy of measurements by NREL`s Scanning Hartmann Optical Test instrument

    SciTech Connect

    Jorgensen, G.; Wendelin, T.; Carasso, M.

    1991-04-01

    NREL`s Scanning Hartmann Optical Test (SHOT) instrument is routinely used to characterize the surface of candidate dish concentration elements for solar thermal applications. An approach was devised to quantify the accuracy of these measurements. Excellent reproducibility was exhibited and high confidence established. The SHOT instrument was designed to allow the surface figure of large optical test articles to be accurately specified. Such test articles are nominally parabolic with an f/D ratio (in which f=focal length and D=aperture diameter) in the range of 0.5--1.0. Recent modifications of SHOT have extended the characterization range out to about f/D=3.0. A series of experiments was designed to investigate and quantify the uncertainties associated with optical characterization performed by SHOT. This approach involved making a series of measurements with an arbitrary test article positioned at a number of locations transverse to the optical axis of SHOT. 3 refs.

  8. Determination of accuracy of measurements by NREL's Scanning Hartmann Optical Test instrument

    SciTech Connect

    Jorgensen, G.; Wendelin, T.; Carasso, M.

    1991-04-01

    NREL's Scanning Hartmann Optical Test (SHOT) instrument is routinely used to characterize the surface of candidate dish concentration elements for solar thermal applications. An approach was devised to quantify the accuracy of these measurements. Excellent reproducibility was exhibited and high confidence established. The SHOT instrument was designed to allow the surface figure of large optical test articles to be accurately specified. Such test articles are nominally parabolic with an f/D ratio (in which f=focal length and D=aperture diameter) in the range of 0.5--1.0. Recent modifications of SHOT have extended the characterization range out to about f/D=3.0. A series of experiments was designed to investigate and quantify the uncertainties associated with optical characterization performed by SHOT. This approach involved making a series of measurements with an arbitrary test article positioned at a number of locations transverse to the optical axis of SHOT. 3 refs.

  9. Formation of optical microlens by laser polymerization method

    NASA Astrophysics Data System (ADS)

    Suzuki, Kaoru

    2001-11-01

    Optical lens of micrometer order diameter for coupling between optical fiber and laser diode were formed by argon ion laser polymerization method at visible light cured resin. Test resin materials consisted of triethylene glycol dimethacrylate for main resin, camphorquinon for photo initiator of visible light area, hydroquinon for inhibitor, and N,N-dimethylmethacrylate for reducing agent. In order to obtain the micro lens of short focal length and small spherical aberration, the use of this technique makes it possible to simultaneously form the polymerized aria on glass plate at the argon ion laser beam irradiation zone. The polmerized aria made a high quality micro lens without using molding pattern. We have verified our claims with visual inspection, ray trajectory calculations for measurement of side long spherical aberration (transverse aberration), Fourier transform infrared spectroscopy for degree of conversion analysis of polymerized resin area, and Duc de Chaulnes method for measurement of lens shape. The lens has a diameter of 300micrometers or more, a focal length of 500micrometers or more with an NA of 0.5, and transverse aberration plot of about 100% of the within the limits of +/- 25micrometers . This method can be applied for producing circular, non-circular, linear, and array micro lenses by scanning or patterning of argon ion laser beam.

  10. Visual Scanning Hartmann Optical Tester (VSHOT) Uncertainty Analysis (Milestone Report)

    SciTech Connect

    Gray, A.; Lewandowski, A.; Wendelin, T.

    2010-10-01

    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.

  11. Dynamic reactive astrocytes after focal ischemia

    PubMed Central

    Ding, Shinghua

    2014-01-01

    Astrocytes are specialized and most numerous glial cell type in the central nervous system and play important roles in physiology. Astrocytes are also critically involved in many neural disorders including focal ischemic stroke, a leading cause of brain injury and human death. One of the prominent pathological features of focal ischemic stroke is reactive astrogliosis and glial scar formation associated with morphological changes and proliferation. This review paper discusses the recent advances in spatial and temporal dynamics of morphology and proliferation of reactive astrocytes after ischemic stroke based on results from experimental animal studies. As reactive astrocytes exhibit stem cell-like properties, knowledge of dynamics of reactive astrocytes and glial scar formation will provide important insights for astrocyte-based cell therapy in stroke. PMID:25657720

  12. Gastric hyperplastic polyp with focal cancer

    PubMed Central

    Markowski, Adam Roman; Guzinska-Ustymowicz, Katarzyna

    2016-01-01

    This paper reports a rare case of early adenocarcinoma within the gastric hyperplastic polyp, that was completely resected during an endoscopic procedure, and discusses current recommendations in such cases. Endoscopic resection of polyps with focal dysplasia or cancer is commonly indicated, as long as the procedure can be performed safely. After complete excision of a polyp with atypical focal lesion, endoscopic surveillance is suggested. The frequency of surveillance endoscopy should depend on the precise histopathological diagnosis and possibility of confirming the completeness of the endoscopic resection. If the completeness of the procedure is confirmed both macro- and microscopically, gastric resection does not have to be performed. A follow-up esophago-gastroduodenoscopy should be performed at 1 year and then at 3 years. PMID:25361760

  13. Gastric hyperplastic polyp with focal cancer.

    PubMed

    Markowski, Adam Roman; Guzinska-Ustymowicz, Katarzyna

    2016-05-01

    This paper reports a rare case of early adenocarcinoma within the gastric hyperplastic polyp, that was completely resected during an endoscopic procedure, and discusses current recommendations in such cases. Endoscopic resection of polyps with focal dysplasia or cancer is commonly indicated, as long as the procedure can be performed safely. After complete excision of a polyp with atypical focal lesion, endoscopic surveillance is suggested. The frequency of surveillance endoscopy should depend on the precise histopathological diagnosis and possibility of confirming the completeness of the endoscopic resection. If the completeness of the procedure is confirmed both macro- and microscopically, gastric resection does not have to be performed. A follow-up esophago-gastroduodenoscopy should be performed at 1 year and then at 3 years. PMID:25361760

  14. Myxoid adrenal adenoma with focal pseudoglandular pattern.

    PubMed

    De Padua, Michelle; Rajagopal, V

    2008-05-01

    Adrenal cortical tumors with myxoid change are rare tumors. To our knowledge, only 22 cases have been described so far in literature, which include 13 carcinomas and 9 adenomas. A pseudoglandular pattern has been described in 9 of these tumors. We report a case of a myxoid adenoma of the left adrenal gland in a 67-year-old woman, with a focal pseudoglandular pattern involving about 20% of the studied tumor. Rest of the tumor was composed of anastomosing cords of tumor cells. Abundant myxoid stroma was present, which stained positively with alcian blue and was weakly focally positive with periodic acid Schiff. Immunophenotype was consistent with an adrenal tumor, i.e., positive for vimentin, inhibin, and melan A. Cytokeratin AE1/AE3 and chromogranin were negative. MIB-1 index was < 0.1%. PMID:18579979

  15. Focal colors are universal after all

    PubMed Central

    Regier, Terry; Kay, Paul; Cook, Richard S.

    2005-01-01

    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. PMID:15923257

  16. Focal motor seizures complicating carotid endarterectomy.

    PubMed

    Youkey, J R; Clagett, G P; Jaffin, J H; Parisi, J E; Rich, N M

    1984-09-01

    We studied four patients with focal motor seizures complicating carotid endarterectomy and compared them with 14 other cases reported previously. Seventeen of the 18 patients had high-grade carotid stenoses. A severe unilateral headache usually preceded seizure activity, which was followed by prolonged Todd's paralysis. Eight patients had histories of ipsilateral stroke. There was no association with perioperative hypertension. Two patients who were receiving heparin sodium had intracerebral hemorrhages that caused one of the two postoperative deaths. The patency of all endarterectomized carotid arteries was recorded by arteriography or noninvasive studies. These data suggest that patients who have severe unilateral headaches following ipsilateral carotid endarterectomy for high-grade stenoses are at risk for focal motor seizures. The roles of antithrombotic agents and anti-seizure medication in this setting are unclear. PMID:6433857

  17. Talin determines the nanoscale architecture of focal adhesions

    PubMed Central

    Liu, Jaron; Wang, Yilin; Goh, Wah Ing; Goh, Honzhen; Baird, Michelle A.; Ruehland, Svenja; Teo, Shijia; Bate, Neil; Critchley, David R.; Davidson, Michael W.; Kanchanawong, Pakorn

    2015-01-01

    Insight into how molecular machines perform their biological functions depends on knowledge of the spatial organization of the components, their connectivity, geometry, and organizational hierarchy. However, these parameters are difficult to determine in multicomponent assemblies such as integrin-based focal adhesions (FAs). We have previously applied 3D superresolution fluorescence microscopy to probe the spatial organization of major FA components, observing a nanoscale stratification of proteins between integrins and the actin cytoskeleton. Here we combine superresolution imaging techniques with a protein engineering approach to investigate how such nanoscale architecture arises. We demonstrate that talin plays a key structural role in regulating the nanoscale architecture of FAs, akin to a molecular ruler. Talin diagonally spans the FA core, with its N terminus at the membrane and C terminus demarcating the FA/stress fiber interface. In contrast, vinculin is found to be dispensable for specification of FA nanoscale architecture. Recombinant analogs of talin with modified lengths recapitulated its polarized orientation but altered the FA/stress fiber interface in a linear manner, consistent with its modular structure, and implicating the integrin–talin–actin complex as the primary mechanical linkage in FAs. Talin was found to be ∼97 nm in length and oriented at ∼15° relative to the plasma membrane. Our results identify talin as the primary determinant of FA nanoscale organization and suggest how multiple cellular forces may be integrated at adhesion sites. PMID:26283369

  18. Extended depth of focus adaptive optics spectral domain optical coherence tomography

    PubMed Central

    Sasaki, Kazuhiro; Kurokawa, Kazuhiro; Makita, Shuichi; Yasuno, Yoshiaki

    2012-01-01

    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. PMID:23082278

  19. Physical Activity Performance of Focal Middle School Students

    ERIC Educational Resources Information Center

    Erfle, Stephen E.; Gelbaugh, Corey M.

    2013-01-01

    Histograms of push-ups and curl-ups from a sample of more than 9,000 students show periodic spikes at five and 10 unit intervals. This article argues that these spikes are related to focal points, a game theoretic concept popularized by Nobel Laureate Thomas Schelling. Being focal on one test makes one more likely to be focal on the other. Focal

  20. Application study of the optical biopsy system for small experimental animals

    NASA Astrophysics Data System (ADS)

    Sato, Hidetoshi; Suzuki, Toshiaki; Morita, Shin-ichi; Maruyama, Atsushi; Shimosegawa, Toru; Matsuura, Yuji; Kanai, Gen'ichi; Ura, Nobuo; Masutani, Koji; Ozaki, Yukihiro

    2008-02-01

    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.

  1. The Kepler photometer focal plane array

    NASA Astrophysics Data System (ADS)

    Argabright, V. S.; VanCleve, J. E.; Bachtell, E. E.; Hegge, M. J.; McArthur, S. P.; Dumont, F. C.; Rudeen, A. C.; Pullen, J. L.; Teusch, D. A.; Tennant, D. S.; Atcheson, P. D.

    2008-07-01

    The Kepler instrument is designed to detect Earth size planets in the "habitable zone" orbiting 9focal plane array resulting in ~13° diameter FOV, so that greater than 100,000 suitable stars in the FOV are continuously monitored over a three and a half year mission. Detection of planetary transits is made possible through 20 ppm differential photometry using pixel data from a focal plane array specifically developed for Kepler. The Kepler focal plane array is suspended above the primary mirror and consists of twenty one 2K x 2K Science CCD modules mounted on a curved Invar substrate with four output taps per module. Four fine guidance sensor (FGS) CCD modules are mounted to the corners of the Invar substrate to gather additional pointing information for the Attitude Control System in order to attain the required <2.5 milli-pixel pointing accuracy. A space staring radiator and a closed loop thermal control system maintains the CCD module temperatures at -85°C with <10mK thermal stability. Low noise electronics reads out both the Science and FGS CCD modules at a 3 MHz pixel rate. In order to achieve a 4-sigma detection of an Earth-sized planet orbiting a 12th magnitude Sun-like star, the overall noise budget allocates 150 e- to the read noise of each Science CCD module output. This paper discusses key elements of the Kepler focal plane array design, development, characterization and performance results.

  2. Likelihood analysis of earthquake focal mechanism distributions

    NASA Astrophysics Data System (ADS)

    Kagan, Yan Y.; Jackson, David D.

    2015-06-01

    In our paper published earlier we discussed forecasts of earthquake focal mechanism and ways to test the forecast efficiency. Several verification methods were proposed, but they were based on ad hoc, empirical assumptions, thus their performance is questionable. We apply a conventional likelihood method to measure the skill of earthquake focal mechanism orientation forecasts. The advantage of such an approach is that earthquake rate prediction can be adequately combined with focal mechanism forecast, if both are based on the likelihood scores, resulting in a general forecast optimization. We measure the difference between two double-couple sources as the minimum rotation angle that transforms one into the other. We measure the uncertainty of a focal mechanism forecast (the variability), and the difference between observed and forecasted orientations (the prediction error), in terms of these minimum rotation angles. To calculate the likelihood score we need to compare actual forecasts or occurrences of predicted events with the null hypothesis that the mechanism's 3-D orientation is random (or equally probable). For 3-D rotation the random rotation angle distribution is not uniform. To better understand the resulting complexities, we calculate the information (likelihood) score for two theoretical rotational distributions (Cauchy and von Mises-Fisher), which are used to approximate earthquake source orientation pattern. We then calculate the likelihood score for earthquake source forecasts and for their validation by future seismicity data. Several issues need to be explored when analyzing observational results: their dependence on forecast and data resolution, internal dependence of scores on forecasted angle and random variability of likelihood scores. Here, we propose a simple tentative solution but extensive theoretical and statistical analysis is needed.

  3. [Maintaining telomere length].

    PubMed

    Wysoczańska, Barbara

    2013-01-01

    Telomeres protect the ends of chromosomes maintaining genome stability. The activity of telomerase enzyme, or alternatively the process of recombination, regulates the length of telomeres. In the absence of these mechanisms, excessive shortening of telomeres reach its critical level. Excessively shortened telomeres do not protect chromosome ends, the cell division cycle is stopped while the inactivity of replication process generates cellular senescence and cell death. On the other hand, critically shortened telomeres may promote chromosomal instability. These changes can lead to the development of carcinogenesis. In this process enzymatic activity of telomerase is reactivated. To maintain the protection of the chromosome ends, telomeres bind the stabilizing protein complex (shelterin). The presence of these protective proteins prevents undesirable DNA damage and initiates the repair system pathways. Molecular technologies enable the evaluation of telomere lengths, the analysis of telomerase expression and activity, and detection of mutations, polymorphic and epigenetic changes in telomere--shelterin--telomerase complex related genes. The purpose of research is to describe new mechanisms that affect the biology of telomere lengths, and to determine the impact on bone marrow failures, development of haematological malignancies, neurodegenerative diseases and others disorders associated with chromosomal instability. The model of modern therapies based on telomere biology explains the significance of the maintenance of telomere lengths in the process of cellular senescence and carcinogenesis. PMID:24379272

  4. Mappability and read length

    PubMed Central

    Li, Wentian; Freudenberg, Jan

    2014-01-01

    Power-law distributions are the main functional form for the distribution of repeat size and repeat copy number in the human genome. When the genome is broken into fragments for sequencing, the limited size of fragments and reads may prevent an unique alignment of repeat sequences to the reference sequence. Repeats in the human genome can be as long as 104 bases, or 105 − 106 bases when allowing for mismatches between repeat units. Sequence reads from these regions are therefore unmappable when the read length is in the range of 103 bases. With a read length of 1000 bases, slightly more than 1% of the assembled genome, and slightly less than 1% of the 1 kb reads, are unmappable, excluding the unassembled portion of the human genome (8% in GRCh37/hg19). The slow decay (long tail) of the power-law function implies a diminishing return in converting unmappable regions/reads to become mappable with the increase of the read length, with the understanding that increasing read length will always move toward the direction of 100% mappability. PMID:25426137

  5. Measuring the Flatness of Focal Plane for Very Large Mosaic CCD Camera

    SciTech Connect

    Hao, Jiangang; Estrada, Juan; Cease, Herman; Diehl, H.Thomas; Flaugher, Brenna L.; Kubik, Donna; Kuk, Keivin; Kuropatkine, Nickolai; Lin, Huan; Montes, Jorge; Scarpine, Vic

    2010-06-08

    Large mosaic multiCCD camera is the key instrument for modern digital sky survey. DECam is an extremely red sensitive 520 Megapixel camera designed for the incoming Dark Energy Survey (DES). It is consist of sixty two 4k x 2k and twelve 2k x 2k 250-micron thick fully-depleted CCDs, with a focal plane of 44 cm in diameter and a field of view of 2.2 square degree. It will be attached to the Blanco 4-meter telescope at CTIO. The DES will cover 5000 square-degrees of the southern galactic cap in 5 color bands (g, r, i, z, Y) in 5 years starting from 2011. To achieve the science goal of constraining the Dark Energy evolution, stringent requirements are laid down for the design of DECam. Among them, the flatness of the focal plane needs to be controlled within a 60-micron envelope in order to achieve the specified PSF variation limit. It is very challenging to measure the flatness of the focal plane to such precision when it is placed in a high vacuum dewar at 173 K. We developed two image based techniques to measure the flatness of the focal plane. By imaging a regular grid of dots on the focal plane, the CCD offset along the optical axis is converted to the variation the grid spacings at different positions on the focal plane. After extracting the patterns and comparing the change in spacings, we can measure the flatness to high precision. In method 1, the regular dots are kept in high sub micron precision and cover the whole focal plane. In method 2, no high precision for the grid is required. Instead, we use a precise XY stage moves the pattern across the whole focal plane and comparing the variations of the spacing when it is imaged by different CCDs. Simulation and real measurements show that the two methods work very well for our purpose, and are in good agreement with the direct optical measurements.

  6. [Focal therapy for prostate cancer: German version].

    PubMed

    Kasivisvanathan, V; Shah, T T; Donaldson, I; Kanthabalan, A; Moore, C M; Emberton, M; Ahmed, H U

    2015-02-01

    Focal therapy is a treatment strategy for men with localized prostate cancer that may serve as an alternative option to radical therapy. A number of minimally invasive ablative technologies are available to deliver treatment, and the energies most commonly used include high-intensity focused ultrasound and cryotherapy. The benefit of a tissue-preserving approach is the limitation of damage to key structures such as the neurovascular bundles, external urinary sphincter, rectal mucosa and bladder neck. This in turn minimizes side effects typically associated with radical therapies whilst also aiming to maintain oncological control. Over 30 single-centre studies of focal therapy have been published to date reporting excellent continence rates, good potency rates and acceptable short-term oncological outcomes. However, there are a number of controversial aspects associated with focal therapy including the index lesion hypothesis, patient selection criteria, assessment of treatment effect and the lack of medium- and long-term oncological outcomes. In the process of the adoption of new technology, there is a limited window of opportunity to provide this evidence in well-designed prospective trials. Men should be allowed to benefit from the potential advantages of this novel treatment whilst under close surveillance. An English version of this article is available under dx.doi.org/10.1007/s00120-014-3734-7. PMID:25690574

  7. Impaired brain GABA in focal dystonia.

    PubMed

    Levy, Lucien M; Hallett, Mark

    2002-01-01

    Patients with task-specific dystonia (writer's cramp) have impaired cortical inhibition likely arising from striatal dysfunction. However, the levels of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) in the brains of these patients are not known. In this study, we evaluated 7 patients with right-sided focal, task-specific dystonia and 17 normal control subjects. A novel method using two-dimensional J-resolved magnetic resonance spectroscopy revealed that brain GABA levels are decreased in specific brain regions of the focal dystonia patients compared to normal controls. A significant decrease in GABA level was observed in the sensorimotor cortex and lentiform nuclei contralateral to the affected hand, while there was only a small nonsignificant decrease in the ipsilateral sensorimotor cortex and lentiform nuclei. GABA changes in the posterior occipital region of patients were not significant. The impaired cortical GABA level correlates with prior physiologic studies showing reduced intracortical inhibition. Reduced GABA in the striatum is consistent with striatal dysfunction since GABA is a principal neurotransmitter in that region. The reduction of brain GABA in dystonia patients may explain the clinical symptomatology of focal dystonia. Magnetic resonance spectroscopy may be a useful noninvasive tool in the evaluation of regional brain GABA changes and in monitoring the effects of various therapies. PMID:11782988

  8. Mechanism of Focal Adhesion Kinase Mechanosensing

    PubMed Central

    Sturm, Sebastian; Bullerjahn, Jakob Tmas; Bronowska, Agnieszka; Grter, Frauke

    2015-01-01

    Mechanosensing at focal adhesions regulates vital cellular processes. Here, we present results from molecular dynamics (MD) and mechano-biochemical network simulations that suggest a direct role of Focal Adhesion Kinase (FAK) as a mechano-sensor. Tensile forces, propagating from the membrane through the PIP2 binding site of the FERM domain and from the cytoskeleton-anchored FAT domain, activate FAK by unlocking its central phosphorylation site (Tyr576/577) from the autoinhibitory FERM domain. Varying loading rates, pulling directions, and membrane PIP2 concentrations corroborate the specific opening of the FERM-kinase domain interface, due to its remarkably lower mechanical stability compared to the individual alpha-helical domains and the PIP2-FERM link. Analyzing downstream signaling networks provides further evidence for an intrinsic mechano-signaling role of FAK in broadcasting force signals through Ras to the nucleus. This distinguishes FAK from hitherto identified focal adhesion mechano-responsive molecules, allowing a new interpretation of cell stretching experiments. PMID:26544178

  9. Mechanism of Focal Adhesion Kinase Mechanosensing.

    PubMed

    Zhou, Jing; Aponte-Santamaría, Camilo; Sturm, Sebastian; Bullerjahn, Jakob Tómas; Bronowska, Agnieszka; Gräter, Frauke

    2015-11-01

    Mechanosensing at focal adhesions regulates vital cellular processes. Here, we present results from molecular dynamics (MD) and mechano-biochemical network simulations that suggest a direct role of Focal Adhesion Kinase (FAK) as a mechano-sensor. Tensile forces, propagating from the membrane through the PIP2 binding site of the FERM domain and from the cytoskeleton-anchored FAT domain, activate FAK by unlocking its central phosphorylation site (Tyr576/577) from the autoinhibitory FERM domain. Varying loading rates, pulling directions, and membrane PIP2 concentrations corroborate the specific opening of the FERM-kinase domain interface, due to its remarkably lower mechanical stability compared to the individual alpha-helical domains and the PIP2-FERM link. Analyzing downstream signaling networks provides further evidence for an intrinsic mechano-signaling role of FAK in broadcasting force signals through Ras to the nucleus. This distinguishes FAK from hitherto identified focal adhesion mechano-responsive molecules, allowing a new interpretation of cell stretching experiments. PMID:26544178

  10. Substrate, focal adhesions, and actin filaments: a mechanical unit with a weak spot for mechanosensitive proteins

    NASA Astrophysics Data System (ADS)

    Kirchenbchler, David; Born, Simone; Kirchgener, Norbert; Houben, Sebastian; Hoffmann, Bernd; Merkel, Rudolf

    2010-05-01

    Mechanosensing is a vital prerequisite for dynamic remodeling of focal adhesions and cytoskeletal structures upon substrate deformation. For example, tissue formation, directed cell orientation or cell differentiation are regulated by such mechanosensing processes. Focal adhesions and the actin cytoskeleton are believed to be involved in these processes, but where mechanosensing molecules are located and how elastic substrate, focal adhesions and the cytoskeleton couple with each other upon substrate deformation still remains obscure. To approach these questions we have developed a sensitive method to apply defined spatially decaying deformation fields to cells cultivated on ultrasoft elastic substrates and to accurately quantify the resulting displacements of the actin cytoskeleton, focal adhesions, as well as the substrate. Displacement fields were recorded in live cell microscopy by tracking either signals from fluorescent proteins or marker particles in the substrate. As model cell type we used myofibroblasts. These cells are characterized by highly stable adhesion and force generating structures but are still able to detect mechanical signals with high sensitivity. We found a rigid connection between substrate and focal adhesions. Furthermore, stress fibers were found to be barely extendable almost over their whole lengths. Plastic deformation took place only at the very ends of actin filaments close to focal adhesions. As a result, this area became elongated without extension of existing actin filaments by polymerization. Both ends of the stress fibers were mechanically coupled with detectable plastic deformations on either site. Interestingly, traction force dependent substrate deformation fields remained mostly unaffected even when stress fiber elongations were released. These data argue for a location of mechanosensing proteins at the ends of actin stress fibers and describe, except for these domains, the whole system to be relatively rigid for tensile strain with a mechanical coupling between the front and rear end of a cell.

  11. Focus in Grade 1: Teaching with Curriculum Focal Points

    ERIC Educational Resources Information Center

    Fuson, Karen; Clements, Douglas; Beckmann, Sybilla

    2010-01-01

    "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…

  12. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Electrophysical and optical properties of spherical and cylindrical liquid-crystal optically addressed lenses

    NASA Astrophysics Data System (ADS)

    Guralnik, I. R.; Samagin, S. A.

    2004-07-01

    New experimental results on direct measurements of the phase response of spherical liquid-crystal (LC) optically addressed lenses (OALs) are presented. A simple and easy-to-use formula for the focal length of an adaptive modal LC lens is obtained for the first time. The complex conductance is measured with an accuracy that is sufficient to find the aperture region contribution and the calculated conductance is in good qualitative agreement with the experiment. The possibility of using OALs for self-correction of defocusing and as adaptive laser-beam deflectors is proposed and demonstrated experimentally.

  13. Coronagraphic phase diversity: a simple focal plane sensor for high-contrast imaging.

    PubMed

    Sauvage, J-F; Mugnier, L; Paul, B; Villecroze, R

    2012-12-01

    Exoplanet direct imaging is a challenging goal of today's astronomical instrumentation. Several high-contrast imaging instruments dedicated to this task are currently being integrated; they are ultimately limited by the presence of quasi-static speckles in the imaging focal plane. These speckles originate in residual quasi-static optical aberrations, which must be measured and compensated for, typically at a nanometric level. We present a novel focal plane wavefront sensor (WFS) designed for this particular application. It is an extension of the phase diversity technique to coronagraphic imaging. This sensor requires no dedicated hardware and uses only two scientific images differing from a known aberration, which can be conveniently introduced by the adaptive optics subsystem. The aberrations are therefore calibrated all the way down to the scientific camera, without any differential aberrations between the sensor and the scientific camera. We show the potential of this WFS by means of simulations, and we perform a preliminary experimental validation. PMID:23202053

  14. Optimized focal and pupil plane masks for vortex coronagraphs on telescopes with obstructed apertures

    NASA Astrophysics Data System (ADS)

    Ruane, Garreth J.; Absil, Olivier; Huby, Elsa; Mawet, Dimitri; Delacroix, Christian; Carlomagno, Brunella; Piron, Pierre; Swartzlander, Grover A.

    2015-09-01

    We present methods for optimizing pupil and focal plane optical elements that improve the performance of vortex coronagraphs on telescopes with obstructed or segmented apertures. Phase-only and complex masks are designed for the entrance pupil, focal plane, and the plane of the Lyot stop. Optimal masks are obtained using both analytical and numerical methods. The latter makes use of an iterative error reduction algorithm to calculate "correcting" optics that mitigate unwanted diffraction from aperture obstructions. We analyze the achieved performance in terms of starlight suppression, contrast, off-axis image quality, and chromatic dependence. Manufacturing considerations and sensitivity to aberrations are also discussed. This work provides a path to joint optimization of multiple coronagraph planes to maximize sensitivity to exoplanets and other faint companions.

  15. Curved Focal-Plane Arrays Using Back-Illuminated High-Purity Photodetectors

    NASA Technical Reports Server (NTRS)

    Nikzad, Shouleh; Hoenk, Michael E.

    2003-01-01

    Curved-focal-plane arrays of back-illuminated silicon-based photodetectors are being developed. 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 (e.g., a photographic film or an array of photodetectors) conform to a curved focal surface, instead of following the customary practice of designing the optics to project an image onto a flat focal surface. Eyes are natural examples of optical systems that have curved focal surfaces on which image sensors (retinas) are located. One prior approach to implementation of this concept involves the use of curved-input-surface microchannel plates as arrays of photodetectors. In comparison with microchannel plates, these curved-focal-plane arrays would weigh less, operate at much lower voltages, and consume less power. It should also be possible to fabricate the proposed devices at lower cost. It would be possible to fabricate an array of photodetectors and readout circuitry in the form of a very-large-scale integrated (VLSI) circuit on a curved focal surface, but it would be difficult and expensive to do so. In a simple and inexpensive alternate approach, a device (see figure) would have (1) a curved back surface, onto which light would be focused; and (2) a flat front surface, on which VLSI circuitry would be fabricated by techniques that are well established for flat surfaces. The device would be made from ultrapure silicon, in which it is possible to form high-resistivity, thick photodetectors that are fully depleted through their thicknesses. (As used here, "thick means having a thickness between a fraction of a millimeter and a few millimeters.) The back surface would be polished to the curvature of the focal surface of the intended application. To enable the collection of charge carriers excited by photons near the back surface or in the bulk of the device, it would be necessary to form a transparent or semitransparent back-surface electrode, possibly by delta doping. [Delta doping is so named because its density-vs.-depth characteristic is reminiscent of the Dirac function (impulse function): the dopant is concentrated in a very thin layer - nominally, a single atomic layer.

  16. Microstructured optical arrays for smart x-ray optics

    NASA Astrophysics Data System (ADS)

    Dunare, Camelia; Parkes, William; Stevenson, Tom; Michette, Alan; Pfauntsch, Slawka; Sahraei, Shahin; Shand, Matthew; Zhang, Dou; Rodriguez Sanmartin, Daniel; Button, Tim; Feldman, Charlotte; Willingale, Richard; Doel, Peter; Wang, Hongchang; James, Ady

    2009-05-01

    The Smart X-ray Optics (SXO) programme is developing advanced active-adaptive optics for X-rays. There are two main themes: large optics for applications in astronomy and small scale optics for micro-probing of biological cells and tissue samples using Ti or Cr Kα radiation (4.5keV and 5.4keV, respectively) in studies related to radiation induced cancers. For the latter objective, microstructured optical arrays (MOAs) have been proposed. These consist of an array of channels deep etched in silicon. They use grazing incidence reflection to focus the X-rays through consecutive aligned arrays of channels, ideally reflecting once off a channel wall in each array. Bending the arrays allows variable focal length. The adaptivity is achieved by flexing the arrays using PZT (Lead Zirconate Titanate)-based piezo actuators. The array bending has been modelled using finite element analysis (FEA) and the results showed that for reasonable efficiency, the wall roughness of the channels should not exceed 2nm. This paper describes two techniques of fabrication the MOAs: dry etching and wet etching. The first method requires a special equipment called "inductively coupled plasma" (ICP) using Bosch processes that are designed to produce features with a high aspect ratio with vertical walls. The second method involves using an alkaline solution for etching <110> silicon wafers. This type of wafer was selected because of the large wet etch ratio between the (111) and (100) planes that leads to smooth vertical walls. For our application tetra-methyl-ammonium hydroxide (TMAH) was used as it is fully compatible with CMOS integrated circuit processes.

  17. Vowel length in Farsi

    NASA Astrophysics Data System (ADS)

    Shademan, Shabnam

    2001-05-01

    This study tests whether Farsi vowels are contrastive with respective to length. Farsi has a six-vowel system with three lax vowels and three tense vowels. Both traditional grammarians and modern linguists believe that Farsi tense vowels are longer than lax vowels, and that there are no vowel pairs that contrast only in length. However, it has been suggested that Farsi exhibits compensatory lengthening, which is triggered by the deletion of glottal consonants in coda position in informal speech (Darzi, 1991). As a result, minimal pairs such as [tar] and [tarh] should contrast only with respect to vowel length. A corpus of 90 words of the form CVC, CVCG, CVGC, and CVCC (where V=a vowel and G=a glottal consonant) was recorded, and durations of vowels in different contexts were measured and compared. Preliminary results show that lax vowel durations fall into three groups with CVCC longer than CVCG/CVGC, and the latter longer than CVC. It remains to be seen whether CVCG/CVGC words show compensatory lengthening when the glottal consonant is deleted.

  18. Active reflective components for adaptive optical zoom systems

    NASA Astrophysics Data System (ADS)

    Jungwirth, Matthew Edward Lewis

    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.

  19. Advances in hybrid optics physical sensors for extreme environments

    NASA Astrophysics Data System (ADS)

    Riza, Nabeel A.

    2010-04-01

    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.

  20. Focal plane actuation to achieve ultra-high resolution on suborbital balloon payloads

    NASA Astrophysics Data System (ADS)

    Scowen, Paul A.; Miller, Alex; Challa, Priya; Veach, Todd; Groppi, Chris; Mauskopf, Phil

    2014-07-01

    Over the past few years there has been remarkable success flying imaging telescope systems suspended from suborbital balloon payload systems. These imaging systems have covered optical, ultraviolet, sub-­-millimeter and infrared passbands (i.e. BLAST, STO, SBI, Fireball and others). In recognition of these advances NASA is now considering ambitious programs to promote planetary imaging from high altitude at a fraction of the cost of similar fully orbital systems. The challenge with imaging from a balloon payload is delivering the full diffraction-­-limited resolution of the system from a moving payload. Good progress has been made with damping mechanisms and oscillation control to remove most macroscopic movement in the departures of the imaging focal plane from a static configuration, however a jitter component remains that is difficult to remove using external corrections. This paper reports on work to demonstrate in the laboratory the utility and performance of actuating a detector focal plane (of whatever type) to remove the final jitter terms using an agile hexapod design. The input to this demonstration is the jitter signal generated by the pointing system of a previously flown balloon mission (the Stratospheric Terahertz Observatory, STO). Our group has a mature jitter compensation system that thermally isolates the control head from the focal plane itself. This allows the hexapod to remain at ambient temperature in a vacuum environment with the focal plane cooled to cryogenic temperatures. Our lab design mounts the focal plane on the hexapod in a custom cryostat and delivers an active optical stimulus together with the corresponding jitter signal, using the actuation of the hexapod to correct for the departures from a static, stable configuration. We believe this demonstration will make the case for inclusion of this technological solution in future balloon-­-borne imaging systems requiring ultra-­-high resolution.

  1. Corrugated Quantum Well Infrared Photodetector Focal Plane Array Test Results

    NASA Technical Reports Server (NTRS)

    Goldberg, A.; Choi, K. K.; Das, N. C.; La, A.; Jhabvala, M.

    1999-01-01

    The corrugated quantum-well infrared photodetector (C-QWIP) uses total internal reflection to couple normal incident light into the optically active quantum wells. The coupling efficiency has been shown to be relatively independent of the pixel size and wavelength thus making the C-QWIP a candidate for detectors over the entire infrared spectrum. The broadband coupling efficiency of the C-QWIP makes it an ideal candidate for multiwavelength detectors. We fabricated and tested C-QWIP focal plane arrays (FPAs) with cutoff wavelengths of 11.2 and 16.2 micrometers. Each FPA has 256 x 256 pixels that are bump-bonded to a direct injection readout circuit. Both FPAs provided infrared imagery with good aesthetic attributes. For the 11.2-micrometers FPA, background-limited performance (BLIP) was observed at 60 K with f/3 optics. For the 16.2-micrometers FPA, BLIP was observed at 38 K. Besides the reduction of dark current in C-QWIP structures, the measured internal quantum efficiency (eta) remains to be high. The values for responsivity and quantum efficiency obtained from the FPA results agree well with those measured for single devices.

  2. Imaging Polarimetry With Polarization-Sensitive Focal Planes

    NASA Astrophysics Data System (ADS)

    Vorobiev, Dmitry; Ninkov, Z.

    2014-01-01

    We present a compact, lightweight, snapshot imaging polarimeter designed for operation in the near-infrared (NIR) and mid-infrared (MIR). Flux, polarization and spectral energy distribution are the fundamental measurements through which we infer properties of the sources of radiation such as intensity, temperature, chemical composition, emission mechanisms and structure. In recent decades, many scientific fields that utilize radiometry and spectroscopy have benefited from revolutionary improvements in instrumentation, for example, charge-coupled devices, hybridized infrared arrays, multi-object spectrometers and adaptive optics. Advances in polarimetric instrumentation have been more modest. Recently, the fabrication of microgrid polarizer arrays (MGPAs), facilitated the development of polarization-sensitive focal planes. These devices have inherent capability to measure the degree and angle of polarization across a scene (i.e., imaging polarimetry) instantaneously, without the need for multiple exposures and moving optics or multiple detectors. MGPA-based devices are compact, lightweight, and mechanically robust and perfectly suited for deployment on space-based and airborne platforms. We describe the design, operation and expected performance of MGPA-based imaging polarimeters and identify the applications for which these polarimeters are best suited.

  3. Focal plane wavefront sensor sensitivity for ELT planet finder

    NASA Astrophysics Data System (ADS)

    Baudoz, P.; Mas, M.; Galicher, R.; Rousset, G.

    2010-07-01

    In the framework of Extremely Large Telescope (ELT), several instruments are considered for the characterization of extrasolar planets. Since the performance of such an instrument is limited by wavefront errors, the use of extreme Adaptive Optic (AO) systems is mandatory. Studies for future planet finder instruments such as SPHERE/VLT or GPI/GEMINI show that one limitation of the performance for a planet finder is the differential aberrations that are not measured by the wavefront sensor, which is physically separated from the common optics by a beam splitter. These defects create a field of residual speckles in the focal plane that need to be calibrated to separate the planet signal from the speckle noise [1]. We propose here to simultaneously estimate these aberrations and also detect the planet directly from the final science image. To do so, we propose to couple the foreseen extreme high speed AO of an ELT planet Finder with a low speed Self-Coherent Camera (SCC [2-5]). The SCC which is based on the principle of light coherence can both estimate the wavefront errors and reduce speckle noise by calibration. After recalling the principle of the SCC, we present simulation results of the SCC performance in the context of EPICS.

  4. Flatland optics. II. Basic experiments.

    PubMed

    Lohmann, A W; Wang, D; Pe'er, A; Friesem, A A

    2001-05-01

    In "Flatland optics: fundamentals" [J. Opt. Soc. Am. A 17, 1755 (2000)] we described the basic principles of two-dimensional (2D) optics and showed that a wavelength lambda in three-dimensional (3D) space (x,y,z) may appear in Flatland (x,z) as a wave with another wavelength, lambda = lambda/cosalpha. The tilt angle alpha can be modified by a 3D (Spaceland) individual who then is able to influence the 2D optics in a way that must appear to be magical to 2D Flatland individuals-in the spirit of E. A. Abbott's science fiction story [Flatland, a Romance of Many Dimensions, 6th ed. (Dover, New York, 1952)] of 1884. We now want to establish the reality or objectivity of the 2D wavelength lambda by some basic experiments similar to those that demonstrated roughly 200 years ago the wave nature of light. Specifically, we describe how to measure the 2D wavelength lambda by mean of five different arrangements that involve Young's biprism configuration, Talbot's self-imaging effect, measuring the focal length of a Fresnel zone plate, and letting light be diffracted by a double slit and by a grating. We also performed experiments with most of these arrangements. The results reveal that the theoretical wavelength, as predicted by our Flatland optics theory, does indeed coincide with the wavelength lambda as measured by Flatland experiments. Finally, we present an alternative way to understand Flatland optics in the spatial frequency domains of Flatland and Spaceland. PMID:11336208

  5. Achromatic negative index lens with diffractive optics

    NASA Astrophysics Data System (ADS)

    Piao, Mingxu; Cui, Qingfeng; Zhang, Bo

    2015-02-01

    In this paper, achromatization of a negative index lens is achieved by introducing the diffractive optical elements (DOEs) into the negative index lens. The diffraction efficiency of the negative index material (NIM) DOEs is deduced based on the special propagating laws and imaging properties of negative index lenses, and the expression for microstructure height is given. As an example, an achromatic refractive-diffractive negative index lens with 150 mm focal length and 15 mm entrance pupil diameter is discussed from wavelength 0.848 μm through wavelength 0.912 μm to wavelength 1.114 μm. According to the deduced expression for the NIM DOEs, the diffraction efficiency is calculated, and the diffraction efficiency curve is fitted by interpolation.

  6. Adaptation of the schupmann medial telescope to a large scale astronomical optical system.

    PubMed

    Villa, J J

    1972-08-01

    The classical Schupmann medial telescope is free of the secondary-spectrum residual associated with large refractors. The difficulties in obtaining large glass disks of the necessary optical quality and the problem associated with their mounting preclude the use of this unconventional lens in large scale astronomical systems. However, to circumvent these limitations, the Schupmann lens was modified by replacing the refractive objective with a spherical mirror producing a new catadioptric lens configuration adaptable to large-scale astronomy. The design parameters and performance data are given for an f/5.4, 5.5-m focal length design covering a 2 degrees full field. PMID:20119238

  7. Adaptation in the optical properties of the crystalline lens in the eyes of the Lessepsian migrant Siganus rivulatus.

    PubMed

    Gagnon, Yakir L; Shashar, Nadav; Kröger, Ronald H H

    2011-08-15

    Vision is an important source of information for many animals. The crystalline lens plays a central role in the visual pathway and hence the ecology of fishes. In this study, we tested whether the different light regimes in the Mediterranean and Red Seas have an effect on the optical properties of the lenses in the rivulated rabbitfish, Siganus rivulatus. This species has migrated through the Suez Canal from the Red Sea and established a vital population in the Mediterranean Sea. Longitudinal spherical aberration curves and focal lengths of the fish lenses were measured by laser scans and compared between the two populations. In addition, rivulated rabbitfish from the Mediterranean Sea were exposed to colored light (yellow, green and blue) and unfiltered light for periods of 1 or 13 days to test for short-term adjustments. Lens focal length was significantly longer (3%) in the Rea Sea population. The shorter focal length of the Mediterranean population can be explained as an adaptation to the dimmer light environment, as this difference makes the Mediterranean eyes 5% more sensitive than the eyes of the Red Sea population. The difference may be due to genetic differences or, more likely, adaptive developmental plasticity. Short-term regulatory mechanisms do not seem to be involved. PMID:21795569

  8. A kinetic model for RNA-interference of focal adhesions

    PubMed Central

    2013-01-01

    Background Focal adhesions are integrin-based cell-matrix contacts that transduce and integrate mechanical and biochemical cues from the environment. They develop from smaller and more numerous focal complexes under the influence of mechanical force and are key elements for many physiological and disease-related processes, including wound healing and metastasis. More than 150 different proteins localize to focal adhesions and have been systematically classified in the adhesome project (http://www.adhesome.org). First RNAi-screens have been performed for focal adhesions and the effect of knockdown of many of these components on the number, size, shape and location of focal adhesions has been reported. Results We have developed a kinetic model for RNA interference of focal adhesions which represents some of its main elements: a spatially layered structure, signaling through the small GTPases Rac and Rho, and maturation from focal complexes to focal adhesions under force. The response to force is described by two complementary scenarios corresponding to slip and catch bond behavior, respectively. Using estimated and literature values for the model parameters, three time scales of the dynamics of RNAi-influenced focal adhesions are identified: a sub-minute time scale for the assembly of focal complexes, a sub-hour time scale for the maturation to focal adhesions, and a time scale of days that controls the siRNA-mediated knockdown. Our model shows bistability between states dominated by focal complexes and focal adhesions, respectively. Catch bonding strongly extends the range of stability of the state dominated by focal adhesions. A sensitivity analysis predicts that knockdown of focal adhesion components is more efficient for focal adhesions with slip bonds or if the system is in a state dominated by focal complexes. Knockdown of Rho leads to an increase of focal complexes. Conclusions The suggested model provides a kinetic description of the effect of RNA-interference of focal adhesions. Its predictions are in good agreement with known experimental results and can now guide the design of RNAi-experiments. In the future, it can be extended to include more components of the adhesome. It also could be extended by spatial aspects, for example by the differential activation of the Rac- and Rho-pathways in different parts of the cell. PMID:23311633

  9. Efficacy of lacosamide by focal seizure subtype.

    PubMed

    Sperling, Michael R; Rosenow, Felix; Faught, Edward; Hebert, David; Doty, Pamela; Isojärvi, Jouko

    2014-10-01

    The purpose of this post hoc exploratory analysis was to determine the effects of the antiepileptic drug, lacosamide, on focal (partial-onset) seizure subtypes. Patient data from the three lacosamide pivotal trials were grouped and pooled by focal seizure subtype at Baseline: simple partial seizures (SPS), complex partial seizures (CPS), and secondarily generalized partial seizures (SGPS). Both efficacy outcomes (median percent change from Baseline to Maintenance Phase in seizure frequency per 28 days and the proportion of patients experiencing at least a 50% reduction in seizures) were evaluated by lacosamide dose (200, 400, or 600 mg/day) compared to placebo for each seizure subtype. An additional analysis was performed to determine whether a shift from more severe focal seizure subtypes to less severe occurred upon treatment with lacosamide. In patients with CPS or SGPS at Baseline, lacosamide 400 mg/day (maximum recommended daily dose) and 600 mg/day reduced the frequency of CPS and SGPS compared to placebo. Likewise, a proportion of patients with CPS and SGPS at Baseline experienced at least a 50% reduction in the frequency of CPS and SGPS (≥50% responder rate) in the lacosamide 400 and 600 mg/day groups compared with placebo. For both outcomes, numerically greatest responses were observed in the lacosamide 600 mg/day group among patients with SGPS at Baseline. In patients with SPS at Baseline, no difference between placebo and lacosamide was observed for either efficacy outcome. An additional exploratory analysis suggests that in patients with SPS at Baseline, CPS and SGPS may have been shifted to less severe SPS upon treatment with lacosamide. The results of these exploratory analyses revealed reductions in CPS and SGPS frequency with adjunctive lacosamide. Reduction in CPS and SGPS may confound assessment of SPS since the CPS or SGPS may possibly change to SPS by effective treatment. PMID:25082395

  10. A Future Generation High Angular Resolution X-ray Telescope Based Upon Physical Optics

    NASA Astrophysics Data System (ADS)

    Gorenstein, Paul

    2013-04-01

    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.

  11. Characterization of DECam focal plane detectors

    SciTech Connect

    Diehl, H.Thomas; Angstadt, Robert; Campa, Julia; Cease, Herman; Derylo, Greg; Emes, John H.; Estrada, Juan; Kibik, Donna; Flaugher, Brenna L.; Holland, Steve E.; Jonas, Michelle; /Fermilab /Madrid, CIEMAT /LBL, Berkeley /Argonne /Pennsylvania U.

    2008-06-01

    DECam is a 520 Mpix, 3 square-deg FOV imager being built for the Blanco 4m Telescope at CTIO. This facility instrument will be used for the 'Dark Energy Survey' of the southern galactic cap. DECam has chosen 250 ?m thick CCDs, developed at LBNL, with good QE in the near IR for the focal plane. In this work we present the characterization of these detectors done by the DES team, and compare it to the DECam technical requirements. The results demonstrate that the detectors satisfy the needs for instrument.

  12. Focal hepatic infarction with bile lake formation

    SciTech Connect

    Peterson, I.M.; Neumann, C.H.

    1984-06-01

    Venous thrombosis associated with oral contraceptives is a well recognized phenomenon. Arterial thrombosis, while less common, is also a known risk, as evidenced by the increased incidence of cerebral vascular accidents and myocardial ischemia or infarction. The liver is relatively protected from the usual consequences of arterial thrombosis because of its dual blood supply. The authors present an unusual case of a young woman with a history of oral contraceptive and cigarette use who developed hepatic artery thrombosis and had focal liver lesions on computed tomography (CT) due to hepatic infarction and bile lake formation despite an intact portal venous system.

  13. Laser skin perforator with focal point detection

    NASA Astrophysics Data System (ADS)

    Ponce, L.; Arronte, M.; Cabrera, J. L.; Flores, T.

    2006-02-01

    The development of laser skin perforator device for obtaining blood samples is presented. The use of photoelectric proximity photoelectric sensor permits to determine the focal point eliminating any contact and them avoiding the risk of contamination. Perforation of about 0.2 mm - 0.5 mm in diameter can be obtained in order to take the sample of blood. The method permits to make the blood analysis not only avoiding the contamination risk but also diminishing the pain sensation in comparison with metal lancet.

  14. 9-fold Fresnel-Köhler concentrator with Fresnel lens of variable focal point.

    PubMed

    Mendes-Lopes, João; Benítez, Pablo; Zamora, Pablo; Miñano, Juan C

    2014-06-30

    Non-uniform irradiance patterns over Multi-Junction Cells gives rise to power losses, especially when considering spectral irradiance distributions over different junctions. Thermal effects on Silicone-on-Glass lenses affect spectral irradiance distributions. A new Photovoltaic Concentrator (CPV), formed by nine optical channels, each one with a Köhler configuration, has been designed to overcome these effects at high concentrations for a large acceptance angle. A Fresnel Lens with a Variable Focal Point is proposed to prevent optical crosstalk in multichannel systems. When integrated into the concentrator, improves the acceptance angle. These designs are designed to fulfill the expected requirements of four junction CPV systems. PMID:24978078

  15. Lengths on rotating platforms

    NASA Astrophysics Data System (ADS)

    Tartaglia, A.

    1999-02-01

    The paper treats the issue of the length of a rotating circumference as seen from on board the moving disk and from an inertial reference frame. It is shown that, properly defining a measuring process, the result is in both cases 2πR thus dissolving the Ehrenfest paradox. The same holds good when considering that, for the rotating observer, the perceived radius coincides with the curvature radius of a space-time helix and a complete round trip corresponds to an angle which differs from the one seen by the inertial observer. The apparent contradiction with the Lorentz contraction is discussed.

  16. Development of a real time MTF test bench for visible optical systems

    NASA Astrophysics Data System (ADS)

    Chen, Xinhua; Chen, Yuheng; Fan, Jiming; Xiang, Chunchang; Shen, Weimin

    2010-11-01

    A real-time MTF test bench for visible optical systems is presented in this paper. This test bench can perform quick on-axis and off-axis MTF measurement of optical systems whose aperture are less than 200mm in visible wavelength. A high quality off-axis parabolic collimator is used as object generator of this test bench. The image analyzer is a microscopy with CCD camera installed on a multi-axis motion stage. The software of this MTF test bench provides a good interface for the operators to set measurement parameters and control this bench. Validation of this test bench, performed with a 50mm plano-convex audit lens, shows that MTF measurement error of this bench is within 0.04. Besides MTF measurement, this bench can also perform effective focal length (EFL) and back focal length (BFL) without any hardware modification. Transmittance of optical system can also be performed on this bench with an integrating sphere.

  17. Microbolometer Terahertz Focal Plane Array and Camera with Improved Sensitivity in the Sub-Terahertz Region

    NASA Astrophysics Data System (ADS)

    Oda, Naoki; Kurashina, Seiji; Miyoshi, Masaru; Doi, Kohei; Ishi, Tsutomu; Sudou, Takayuki; Morimoto, Takao; Goto, Hideki; Sasaki, Tokuhito

    2015-10-01

    A pixel in an uncooled microbolometer terahertz (THz) focal plane array (FPA) has a suspended structure above read-out integrated circuit (ROIC) substrate. An optical cavity structure is formed between a thin metallic layer deposited on the suspended structure and a thick metallic layer deposited on the ROIC surface. The geometrical optical cavity length for our previous pixel structure, 3-4 μm, is extended three times, so that responsivity can be increased in the sub-THz region. This modification is carried out by depositing a thick SiN layer on the thick metallic layer. The modified pixel structure is applied to 640 × 480 and 320 × 240 THz-FPAs with 23.5 μm pixel pitch. Minimum detectable powers per pixel (MDP) are evaluated for these FPAs at 4.3, 2.5, 0.6, and 0.5 THz, and the MDP values are found to be improved by a factor of ten at 0.6 and 0.5 THz. The MDP values of the THz-FPAs developed in this work are compared with those of other THz detectors, such as uncooled antenna-coupled CMOS (complimentary metal-oxide semiconductor) THz-FPAs and cooled bolometer arrays. It is found that our THz-FPAs are more sensitive in the sub-THz region than the CMOS THz-FPAs, while they are much less sensitive than the cooled bolometer arrays. These THz-FPAs are incorporated into a 640 × 480 THz camera and 320 × 240 THz camera, and imaging equipment is developed. The equipment consists of a linearly polarized sub-THz source, a collimator lens, a beam homogenizer, two wire grids, a quarter-wave plate, and two THz cameras, and sub-THz images are demonstrated. It should be mentioned for the equipment that imaging of transmission and reflection is realized by moving only the quarter-wave plate, and the reflection image is taken along a direction normal to a sample surface so that the reflection image is hardly deformed.

  18. Measurement of modulation transfer function of focal plane arrays and imaging systems

    NASA Astrophysics Data System (ADS)

    Boreman, Glenn D.

    1994-05-01

    A method for measuring the modulation transfer function (MTF) of focal-plane arrays (FPA's) has been developed which uses the statistical properties of laser speckle. The entire area of the focal plane is characterized, and no optics are required for target projection. The random nature of the test pattern avoids phasing effects between the target and the detector-array structure, which greatly relaxes alignment tolerances as compared to other methods. The technique is applicable to arrays that have intentional nonlinearity of response, as well as to those arrays that are inherently linear. The test can be performed on any focal-plane configuration, either one dimensional (1D) or two dimensional (2D). The data processing is usually performed by an off-line computer. However, the test is also useful for real-time diagnostics, to facilitate adjustment of focal-plane operating parameters. In the real-time case, the necessary signal processing can be performed on a digital oscilloscope.

  19. Length of stain dosimeter

    NASA Technical Reports Server (NTRS)

    Lueck, Dale E. (Inventor)

    1994-01-01

    Payload customers for the Space Shuttle have recently expressed concerns about the possibility of their payloads at an adjacent pad being contaminated by plume effluents from a shuttle at an active pad as they await launch on an inactive pad. As part of a study to satisfy such concerns a ring of inexpensive dosimeters was deployed around the active pad at the inter-pad distance. However, following a launch, dosimeters cannot be read for several hours after the exposure. As a consequence factors such as different substrates, solvent systems, and possible volatilization of HCl from the badges were studied. This observation led to the length of stain (LOS) dosimeters of this invention. Commercial passive LOS dosimeters are sensitive only to the extent of being capable of sensing 2 ppm to 20 ppm if the exposure is 8 hours. To map and quantitate the HCl generated by Shuttle launches, and in the atmosphere within a radius of 1.5 miles from the active pad, a sensitivity of 2 ppm HCl in the atmospheric gases on an exposure of 5 minutes is required. A passive length of stain dosimeter has been developed having a sensitivity rendering it capable of detecting a gas in a concentration as low as 2 ppm on an exposure of five minutes.

  20. Focal Ca2+ Transient Detection in Smooth Muscle

    PubMed Central

    Young, John S.; Amos, Robert J.; Brain, Keith L.

    2009-01-01

    Ca2+ imaging of smooth muscle provides insight into cellular mechanisms that may not result in changes of membrane potential, such as the release of Ca2+ from internal stores, and allows multiple cells to be monitored simultaneously to assess, for example, coupling in syncytial tissue. Subcellular Ca2+ transients are common in smooth muscle, yet are difficult to measure accurately because of the problems caused by their stochastic occurrence, over an often wide field of view, in an organ that it prone to contract. To overcome this problem, we've developed a series of imaging protocols and analysis routines to acquire and then analyse, in an automated fashion, the frequency, location and amplitude of such events. While this approach may be applied in other contexts, our own work involves the detection of local purinergic Ca2+ transients for locating transmitter release with submicron resolution. ATP is released as a cotransmitter from autonomic nerves, where it binds to P2X1 receptors on the smooth muscle of the detrusor and vas deferens. Ca2+ enters the smooth muscle, resulting in purinergic neuroeffector Ca2+ transients (NCTs). The focal Ca2+ transients allow the optical monitoring of neurotransmitter release in a manner that has many advantages over electrophysiology. Apart from the greatly improved spatial resolution, optical recording has the additional advantage of allowing the recording of transmitter release from many distinguishable sites simultaneously. Furthermore, the optical plane of focus is easier to maintain or correct during long recording series than is the repositioning of an intracellular sharp microelectrode. In summary, a method for imaging of Ca2+ fluorescence is outlined which details the preparation of tissue, and the acquisition and analysis of data. We outline the use of several scripts for the analysis of such Ca2+ transients. PMID:19564842

  1. Ultrasound elastographic techniques in focal liver lesions

    PubMed Central

    Conti, Clara Benedetta; Cavalcoli, Federica; Fraquelli, Mirella; Conte, Dario; Massironi, Sara

    2016-01-01

    Elastographic techniques are new ultrasound-based imaging techniques developed to estimate tissue deformability/stiffness. Several ultrasound elastographic approaches have been developed, such as static elastography, transient elastography and acoustic radiation force imaging methods, which include point shear wave and shear wave imaging elastography. The application of these methods in clinical practice aims at estimating the mechanical tissues properties. One of the main settings for the application of these tools has been liver stiffness assessment in chronic liver disease, which has been studied mainly using transient elastography. Another field of application for these techniques is the assessment of focal lesions, detected by ultrasound in organs such as pancreas, prostate, breast, thyroid, lymph nodes. Considering the frequency and importance of the detection of focal liver lesions through routine ultrasound, some studies have also aimed to assess the role that elestography can play in studying the stiffness of different types of liver lesions, in order to predict their nature and thus offer valuable non-invasive methods for the diagnosis of liver masses. PMID:26973405

  2. The Piriform Cortex and Human Focal Epilepsy

    PubMed Central

    Vaughan, David N.; Jackson, Graeme D.

    2014-01-01

    It is surprising that the piriform cortex, when compared to the hippocampus, has been given relatively little significance in human epilepsy. Like the hippocampus, it has a phylogenetically preserved three-layered cortex that is vulnerable to excitotoxic injury, has broad connections to both limbic and cortical areas, and is highly epileptogenic – being critical to the kindling process. The well-known phenomenon of early olfactory auras in temporal lobe epilepsy highlights its clinical relevance in human beings. Perhaps because it is anatomically indistinct and difficult to approach surgically, as it clasps the middle cerebral artery, it has, until now, been understandably neglected. In this review, we emphasize how its unique anatomical and functional properties, as primary olfactory cortex, predispose it to involvement in focal epilepsy. From recent convergent findings in human neuroimaging, clinical epileptology, and experimental animal models, we make the case that the piriform cortex is likely to play a facilitating and amplifying role in human focal epileptogenesis, and may influence progression to epileptic intractability. PMID:25538678

  3. Can biologic treatment induce cutaneous focal mucinosis?

    PubMed Central

    Włodarczyk, Marcin; Sobolewska, Aleksandra; Sieniawska, Joanna; Rogowski-Tylman, Michał; Sysa-Jedrzejowska, Anna; Olejniczak-Staruch, Irmina; Narbutt, Joanna

    2014-01-01

    Skin mucinosis is a rare skin disease which clinically manifests as firm papules and waxy nodules. We report a case of a 66-year-old female psoriatic patient who developed skin mucinosis during biological therapy. Because of a previous lack of response to the local and conventional systemic treatment of psoriasis, the patient received biological therapy (infliximab from June 2008 to May 2009 – initial clinical improvement and loss of treatment effectiveness in the 36th week of the therapy; adalimumab from June 2009 to January 2010 – lack effectiveness; ustekinumab from March 2012 to the present). Throughout 2 months we observed a manifestation of the skin mucinosis as well-demarcated, yellow and brown, papulo-nodular lesions of 5–10 mm in diameter, localized on the back. Histopathological examination with alcian blue staining demonstrated mucin deposits in the dermis. On the basis of clinical and histopathological findings, the diagnosis of cutaneous focal mucinosis was established. We present the case because of the extremely rare occurrence of the disease. Scarce literature and data suggest that there is an association between focal mucinosis and thyroid dysfunction, as well as possible adverse effects of biological therapy with TNF-α antagonists. PMID:25610359

  4. Focal embolic cerebral ischemia in the rat

    PubMed Central

    Zhang, Li; Zhang, Rui Lan; Jiang, Quan; Ding, Guangliang; Chopp, Michael; Zhang, Zheng Gang

    2015-01-01

    Animal models of focal cerebral ischemia are well accepted for investigating the pathogenesis and potential treatment strategies for human stroke. Occlusion of the middle cerebral artery (MCA) with an endovascular filament is a widely used model to induce focal cerebral ischemia. However, this model is not amenable to thrombolytic therapies. As thrombolysis with recombinant tissue plasminogen activator (rtPA) is a standard of care within 4.5 hours of human stroke onset, suitable animal models that mimic cellular and molecular mechanisms of thrombosis and thrombolysis of stroke are required. By occluding the MCA with a fibrin-rich allogeneic clot, we have developed an embolic model of MCA occlusion in the rat, which recapitulates the key components of thrombotic development and of thrombolytic therapy of rtPA observed from human ischemic stroke. The surgical procedures of our model can be typically completed within approximately 30 min and are highly adaptable to other strains of rats as well as mice for both genders. Thus, this model provides a powerful tool for translational stroke research. PMID:25741989

  5. Drug discovery in focal and segmental glomerulosclerosis.

    PubMed

    Pullen, Nick; Fornoni, Alessia

    2016-06-01

    Despite the high medical burden experienced by patients with focal segmental glomerulosclerosis, the etiology of the condition remains largely unknown. Focal segmental glomerulosclerosis is highly heterogeneous in clinical and morphologic manifestations. While this presents challenges for the development of new treatments, research investments over the last 2 decades have yielded a surfeit of potential avenues for therapeutic intervention. The development of many of those ideas and concepts into new therapies, however, has been very disappointing. Here, we describe some of the factors that have potentially contributed to the poor translational performance from this research investment, including the confidence we ascribe to a target, the conduct of experimental studies, and the availability of selective reagents to test hypotheses. We will discuss the significance of genetic and systems traits as well as other methods for reducing bias. We will analyze the limitations of a successful drug development. We will use specific examples hoping that these will guide a consensus for investment and drive greater translational quality. We hope that this substrate will serve to exemplify the tremendous opportunity for intervention as well as facilitate greater collaborative effort between industry, academia, and private foundations in promoting appropriate validation of these targets. Only then will we have achieved our goal for curative therapies for this devastating disease. PMID:27165834

  6. Ultrasound elastographic techniques in focal liver lesions.

    PubMed

    Conti, Clara Benedetta; Cavalcoli, Federica; Fraquelli, Mirella; Conte, Dario; Massironi, Sara

    2016-03-01

    Elastographic techniques are new ultrasound-based imaging techniques developed to estimate tissue deformability/stiffness. Several ultrasound elastographic approaches have been developed, such as static elastography, transient elastography and acoustic radiation force imaging methods, which include point shear wave and shear wave imaging elastography. The application of these methods in clinical practice aims at estimating the mechanical tissues properties. One of the main settings for the application of these tools has been liver stiffness assessment in chronic liver disease, which has been studied mainly using transient elastography. Another field of application for these techniques is the assessment of focal lesions, detected by ultrasound in organs such as pancreas, prostate, breast, thyroid, lymph nodes. Considering the frequency and importance of the detection of focal liver lesions through routine ultrasound, some studies have also aimed to assess the role that elestography can play in studying the stiffness of different types of liver lesions, in order to predict their nature and thus offer valuable non-invasive methods for the diagnosis of liver masses. PMID:26973405

  7. Design of off-axis four-mirror optical system without obscuration based on free-form surface

    NASA Astrophysics Data System (ADS)

    Huang, Chenxu; Liu, Xin

    2015-11-01

    With the development of modern military technology, the requirements of airborne electro-optical search and tracking system are increasing on target detection and recognition. However, traditional off-axis three-mirror system couldn't meet the requirements for reducing weight and compacting size in some circumstances. Based on Seidel aberration theory, by restricting the aberration functions, the optical system could achieve initial construction parameters. During the designing process, decenters and tilts of mirrors were adjusted continuously to eliminate the obscurations. To balance off-axis aberration and increase angle of view, the free-form mirror was introduced into the optical system. Then an unobstructed optical system with effective focal length of 100 mm, FOV of 16°×16°, and relative aperture as F/7 is designed. The results show that the system structure is compact, with imaging qualities approaching diffraction limit.

  8. GREAT optics

    NASA Astrophysics Data System (ADS)

    Wagner-Gentner, Armin; Graf, Urs U.; Philipp, Martin; Rabanus, David; Stutzki, Jürgen

    2004-10-01

    The German REceiver for Astronomy at Terahertz frequencies (GREAT) is a first generation PI instrument for the SOFIA telescope, developed by a collaboration between the MPIfR, KOSMA, DLR, and the MPAe. The first three institutes each contribute one heterodyne receiver channel to operate at 1.9, 2.7 and 4.7 THz, respectively. A later addition of a e.g. 1.4 THz channel is planned. The GREAT instrument is developed to carry two cryostats at once. That means that any two of the three frequencies can be observed simultaneously. Therefore, we need to be able to quickly exchange the optics benches, the local oscillator (LO) subsystems, and the cryostats containing the mixer devices. This demands a high modularity and flexibility of our receiver concept. Our aim is to avoid the need for realignment when swapping receiver channels. After an overview of the common GREAT optics, a detailed description of several parts (optics benches, calibration units, diplexer, focal plane imager) is given. Special emphasis is given to the LO optics of the KOSMA 1.9 THz channel, because its backward wave oscillator has an astigmatic output beam profile, which has to be corrected for. We developed astigmatic off-axis mirrors to compensate this astigmatism. The mirrors are manufactured in-house on a 5 axis CNC milling machine. We use this milling machine to obtain optical components with highest surface accuracy (about 5 microns) appropriate for these wavelengths. Based on the CNC machining capabilities we present our concept of integrated optics, which means to manufacture optical subsystems monolithically. The optics benches are located on three point mounts, which in conjunction with the integrated optics concept ensure the required adjustment free optics setup.

  9. LSST Camera Optics Design

    SciTech Connect

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

    2012-05-24

    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 mirrors to optimize performance. We discuss the rationale for the LSST camera optics design, describe the methodology for fabricating, coating, mounting and testing the lenses and filters, and present the results of detailed analyses demonstrating that the camera optics will meet their performance goals.

  10. LSST camera optics design

    NASA Astrophysics Data System (ADS)

    Olivier, Scot S.; Riot, Vincent J.; Gilmore, David K.; Bauman, Brian; Pratuch, Steve; Seppala, Lynn; Ku, John; Nordby, Martin; Foss, Mike; Antilogus, Pierre; Morgado, Nazario; Sassolas, Benoit; Flaminio, Raffaele; Michel, Christophe

    2012-09-01

    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 mirrors to optimize performance. We discuss the rationale for the LSST camera optics design, describe the methodology for fabricating, coating, mounting and testing the lenses and filters, and present the results of detailed analyses demonstrating that the camera optics will meet their performance goals.

  11. Odd Length Contraction

    NASA Astrophysics Data System (ADS)

    Smarandache, Florentin

    2013-09-01

    Let's denote by VE the speed of the Earth and byVR the speed of the rocket. Both travel in the same direction on parallel trajectories. We consider the Earth as a moving (at a constant speed VE -VR) spacecraft of almost spherical form, whose radius is r and thus the diameter 2r, and the rocket as standing still. The non-proper length of Earth's diameter, as measured by the astronaut is: L = 2 r√{ 1 -|/VE -VR|2 c2 } < 2 r . Therefore Earth's diameter shrinks in the direction of motion, thus Earth becomes an ellipsoid - which is untrue. Planet Earth may increase or decrease its diameter (volume), but this would be for other natural reasons, not because of a...flying rocket! Also, let's assume that the astronaut is laying down in the direction of motion. Therefore, he would also shrink, or he would die!

  12. CT appearance of focal fatty infiltration of the liver

    SciTech Connect

    Halvorsen, R.A.; Korobkin, M.; Ram, P.C.; Thompson, W.M.

    1982-08-01

    Focal fatty infiltration of the liver is an entity that may be confused with liver metastasis on computed tomography (CT). The imaging results and medical records of 16 patients with CT appearance suggestive of focal fatty liver were reviewed, three of whom had the simultaneous presence of metastitic liver disease. Focal fatty liver often has a distinctive appearance with CT, usually with a nonspherical shape, absence of mass effect, and density close to water. Liver metastases are usually round or oval, and unless cystic or necrotic, they have CT attenuation values closer to normal liver parenchyma than water. A radionuclide liver scan almost always resolves any confusion about the differential diagnosis of focal fatty liver: a well defined focus of photon deficiency is due to neoplasm rather than focal fatty infiltration. Sonography sometimes helps to confirm the CT impression, but may be misleading if the diagnosis of focal or diffuse fatty infiltration is not suspected before the examination.

  13. Real-time monitoring of thermal lensing of a multikilowatt fiber laser optical system

    NASA Astrophysics Data System (ADS)

    Scaggs, Michael; Haas, Gil

    2012-02-01

    A laser beam waist analyzer system has been developed that permits the real time focal spot measurement of a high power fiber laser in excess of ten of kilowatts and the ability to monitor thermal lensing of a laser and its optical system. The analyzer can provide a laser's spatial profile, circularity, centroid, astigmatism and M-squared values inclusive of the optics used in the process application. The system is very compact, measures in real time with no moving parts by incorporating an all passive optical design to obtain spot diameter, M-squared, Rayleigh length, beam waist position at power levels in excess of 20 kW in less than one second from laser off to laser on.

  14. Deriving an estimate for the Fried parameter in mobile optical transmission scenarios.

    PubMed

    Giggenbach, Dirk

    2011-01-10

    Measuring the Fried parameter r(0) (atmospheric optical coherence length) in optical link scenarios is crucial to estimate a receiver's telescope performance or to dimension atmospheric mitigation techniques, such as in adaptive optics. The task of measuring r(0) is aggravated in mobile scenarios, when the receiver itself is prone to mechanical vibrations (e.g., when mounted on a moving platform) or when the receiver telescope has to track a fast-moving signal source, such as, in our case, a laser transmitter on board a satellite or aircraft. We have derived a method for estimating r(0) that avoids the influence of angle-of-arrival errors by only using short-term tilt-removed focal intensity speckle patterns. PMID:21221148

  15. Studying ATHENA optics with divergent and collimated x-ray beams

    NASA Astrophysics Data System (ADS)

    Menz, Benedikt; Bräuninger, Heinrich; Burwitz, Vadim; Hartner, Gisela; Predehl, Peter

    2014-07-01

    An open question in the measurement of X-ray optics for satellite experiments is what the PSF (point spread function) looks like in orbit and what the focal length for a source at infinite distance is. In order to measure segmented optics as proposed for ATHENA a collimated X-ray beam with a size of several square centimeters is necessary. We showed that by using a zone plate such a collimated beam can be achieved. We discuss here the requirements such a zone plate collimator has to comply in order to characterize with this collimator an ATHENA type optic. Additional we can present results obtained with a first version of such a collimator and can show so the proof of principle.

  16. Optical system design and performance of the Lockheed Sensor Test Facility /LSTF/

    NASA Astrophysics Data System (ADS)

    Fuller, J. B. C., Jr.; Grammer, J. R.

    1981-01-01

    The advancing state-of-the-art for long-wavelength infrared (LWIR) sensors has created a need for increasingly sophisticated low-background sensor test facilities. A new low-temperature, low-background, optical target collimator system has been designed and built to meet these new sensor requirements. The design incorporates a Ritchey-Chretien off-axis optical system with an effective focal length of 500 in. and an aperture of 25 in. This optical system provides excellent high-resolution, diffraction-limited performance for wavelengths of 0.76 micrometer and longer, both on-axis and off-axis. It has a useful field of view in excess of plus or minus 0.5 deg. Two scan mirrors in the collimated beam provide a beam steering capability of 6 deg.

  17. Deep Moonquake Focal Mechanisms: Recovery and Implications

    NASA Technical Reports Server (NTRS)

    Knapmeyer, Martin; Weber, Renee C.

    2011-01-01

    A defining characteristic of deep moonquakes is their tendency to occur with tidal periodicity, prompting previous studies to infer that they are related to the buildup and release of tidal stress within the Moon. In studies of tidal forcing, a key constraint is the focal mechanism: the fault parameters describing the type of failure moonquakes represent. The quality of the lunar seismic data and the limited source/receiver geometries of the Apollo seismic network prohibit the determination of deep moonquake fault parameters using first-motion polarities, as is typically done in terrestrial seismology. Without being able to resolve tidal stress onto a known failure plane, we can examine only gross qualities of the tidal stress tensor with respect to moonquake occurrence, so we cannot fully address the role of tidal stress in moonquake generation. We will examine the extent to which shear (S) and compression (P) wave amplitude ratios can constrain moonquake fault geometry by determining whether, for a given cluster, there exists a focal mechanism that can produce a radiation pattern consistent with the amplitudes measured by the Apollo instruments. Amplitudes are read in the ray coordinate frame, directly from seismograms for which the P and S arrivals are clearly identifiable on all long-period channels of the four Apollo stations. We apply an empirical station correction to account for site effects and the differences between P- and S-wave attenuation. Instead of focusing on the best fitting solution only, we formulate the inverse problem using a falsification criterion: all source orientations that do not reproduce the observed SV/P ratios within an error margin derived from the uncertainty of amplitude readings are rejected. All others are accepted as possible solutions. The inversion is carried out using an exhaustive grid search on a regular grid with predefined step size, encompassing all possible combinations of strike, dip and slip. To assess the sensitivity of the inversion for the uncertainty of the lunar interior structure, we carry out repeated inversions with different velocity structures. Our data set consist of a total of 106 events from 25 deep moonquake clusters. The largest contribution of 37 events originates from the most active cluster, A001, while other clusters are represented by 1 to 9 events. Since the definition of a cluster implies that all events share the same source orientation, a comparison of the inversion results of all events from one cluster will reduce ambiguities of the inversion. Once we obtain a suite of fault parameters for a given source, we can attempt to further constrain the focal mechanism with refined analyses of tidal stresses and predictions based on synthetic seismograms.

  18. Deep moonquake focal mechanisms: recovery and implications

    NASA Astrophysics Data System (ADS)

    Knapmeyer, M.; Weber, R. C.

    2011-12-01

    A defining characteristic of deep moonquakes is their tendency to occur with tidal periodicity, prompting previous studies to infer that they are related to the buildup and release of tidal stress within the Moon. In studies of tidal forcing, a key constraint is the focal mechanism: the fault parameters describing the type of failure moonquakes represent. The quality of the lunar seismic data and the limited source/receiver geometries of the Apollo seismic network prohibit the determination of deep moonquake fault parameters using first-motion polarities, as is typically done in terrestrial seismology. Without being able to resolve tidal stress onto a known failure plane, we can examine only gross qualities of the tidal stress tensor with respect to moonquake occurrence, so we cannot fully address the role of tidal stress in moonquake generation. We will examine the extent to which shear (S) and compression (P) wave amplitude ratios can constrain moonquake fault geometry by determining whether, for a given cluster, there exists a focal mechanism that can produce a radiation pattern consistent with the amplitudes measured by the Apollo instruments. Amplitudes are read in the ray coordinate frame, directly from seismograms for which the P and S arrivals are clearly identifiable on all long-period channels of the four Apollo stations. We apply an empirical station correction to account for site effects and the differences between P- and S-wave attenuation. Instead of focusing on the best fitting solution only, we formulate the inverse problem using a falsification criterion: all source orientations that do not reproduce the observed SV/P ratios within an error margin derived from the uncertainty of amplitude readings are rejected. All others are accepted as possible solutions. The inversion is carried out using an exhaustive grid search on a regular grid with predefined step size, encompassing all possible combinations of strike, dip and slip. To assess the sensitivity of the inversion for the uncertainty of the lunar interior structure, we carry out repeated inversions with different velocity structures. Our data set consist of a total of 106 events from 25 deep moonquake clusters. The largest contribution of 37 events originates from the most active cluster, A001, while other clusters are represented by 1 to 9 events. Since the definition of a cluster implies that all events share the same source orientation, a comparison of the inversion results of all events from one cluster will reduce ambiguities of the inversion. Once we obtain a suite of fault parameters for a given source, we can attempt to further constrain the focal mechanism with refined analyses of tidal stresses and predictions based on synthetic seismograms.

  19. Brain Network Organization in Focal Epilepsy: A Systematic Review and Meta-Analysis.

    PubMed

    van Diessen, Eric; Zweiphenning, Willemiek J E M; Jansen, Floor E; Stam, Cornelis J; Braun, Kees P J; Otte, Willem M

    2014-01-01

    Normal brain functioning is presumed to depend upon interacting regions within large-scale neuronal networks. Increasing evidence exists that interictal network alterations in focal epilepsy are associated with cognitive and behavioral deficits. Nevertheless, the reported network alterations are inconclusive and prone to low statistical power due to small sample sizes as well as modest effect sizes. We therefore systematically reviewed the existing literature and conducted a meta-analysis to characterize the changes in whole-brain interictal focal epilepsy networks at sufficient power levels. We focused on the two most commonly used metrics in whole-brain networks: average path length and average clustering coefficient. Twelve studies were included that reported whole-brain network average path length and average clustering coefficient characteristics in patients and controls. The overall group difference, quantified as the standardized mean average path length difference between epilepsy and control groups, corresponded to a significantly increased average path length of 0.29 (95% confidence interval (CI): 0.12 to 0.45, p = 0.0007) in the epilepsy group. This suggests a less integrated interictal whole-brain network. Similarly, a significantly increased standardized mean average clustering coefficient of 0.35 (CI: 0.05 to 0.65, p = 0.02) was found in the epilepsy group in comparison with controls, pointing towards a more segregated interictal network. Sub-analyses revealed similar results for functional and structural networks in terms of effect size and directionality for both metrics. In addition, we found individual network studies to be prone to low power due to the relatively small group differences in average path length and average clustering coefficient in combination with small sample sizes. The pooled network characteristics support the hypothesis that focal epilepsy has widespread detrimental effects, that is, reduced integration and increased segregation, on whole brain interictal network organization, which may relate to the co-morbid cognitive and behavioral impairments often reported in patients with focal epilepsy. PMID:25493432

  20. Novel focal point multipass cell for absorption spectroscopy on small sized atmospheric pressure plasmas

    NASA Astrophysics Data System (ADS)

    Winter, Jörn; Hänel, Mattis; Reuter, Stephan

    2016-04-01

    A novel focal point multipass cell (FPMPC) was developed, in which all laser beams propagate through a common focal point. It is exclusively constructed from standard optical elements. Main functional elements are two 90∘ off-axis parabolic mirrors and two retroreflectors. Up to 17 laser passes are demonstrated with a near-infrared laser beam. The number of laser passes is precisely adjustable by changing the retroreflector distance. At the focal point beams are constricted to fit through an aperture of 0.8 mm. This is shown for 11 beam passes. Moreover, the fast temporal response of the cell permits investigation of transient processes with frequencies up to 10 MHz. In order to demonstrate the applicability of the FPMPC for atmospheric pressure plasma jets, laser absorption spectroscopy on the lowest excited argon state (1s5) was performed on a 1 MHz argon atmospheric pressure plasma jet. From the obtained optical depth profiles, the signal-to-noise ratio was deduced. It is shown that an elevation of the laser pass number results in an proportional increase of the signal-to-noise ratio making the FPMPC an appropriate tool for absorption spectroscopy on plasmas of small dimensions.