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. 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.

  4. Precise Measurement of Effective Focal Length

    NASA Technical Reports Server (NTRS)

    Wise, T. D.; Young, J. B.

    1983-01-01

    Computerized instrument measures effective focal lengths to 0.01 percent accuracy. Laser interferometers measure mirror angle and stage coordinate y in instrument for accurate measurment of focal properties of optical systems. Operates under computer control to measure effective focal length, focal surface shape, modulation transfer function, and astigmatism.

  5. Continuously variable focal length lens

    DOEpatents

    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.

  6. 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.

  7. 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.

  8. Microlenses with focal length controlled by chemical processes

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

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

  9. 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

  10. Laser multi-reflection confocal long focal-length measurement

    NASA Astrophysics Data System (ADS)

    Li, Zhigang; Qiu, Lirong; Zhao, Weiqian; Xiao, Yang

    2016-06-01

    We propose a new laser multi-reflection confocal focal-length measurement (MCFM) method to meet the requirements of a high-precision measurement for a long focal-length more than 2 m. It places an optical flat and a reflector behind the test lens for reflecting the measuring beam repeatedly, and then, uses the property that the peak points of confocal response curves precisely corresponds to the convergence points of a multi-reflected measuring beam to exactly identify the positions of the convergence points. Subsequently, it obtains the position variation of the reflector with a different number of reflections by a distance measuring instrument, and thereby achieving the high precise long focal-length measurement. The theoretical analyses and preliminary experimental results indicate that MCFM has a relative standard uncertainty of 0.066% for a test lens with the focal-length of 9.76 m. MCFM can provide a novel approach for the high-precision focal-length measurement.

  11. Design and fabrication of long focal length microlens arrays

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

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

  12. 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.

  13. 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

  14. 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

  15. 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).

  16. 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.

  17. 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

  18. 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

  19. 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

  20. Refractive beryllium x-ray lens with variable focal length

    NASA Astrophysics Data System (ADS)

    Cederstroem, Bjoern; Danielsson, Mats; Lundqvist, Mats

    2001-01-01

    A refractive lens for hard X-rays comprising two saw-tooth profiles is presented. This lens has the same focusing properties as a parabolic compound refractive lens. One advantage is the remarkably low fabrication cost, since curved surfaces are replaced by planar ones. In addition, the focal length of the lens can be easily varied by adjusting the angle between the two halves. Since the index of refraction depends on the X-ray energy, the lens is chromatic and acts as a band- pass filter for a broad energy spectrum. Combined with the tunability of the focal length, this allows versatile spectral shaping of the X-ray beam. Calculations and numerical examples of the focusing properties are presented. Due to its low atomic number, beryllium is an excellent choice for refractive optics and a prototype in beryllium has been fabricated using diamond turning technique. Surface metrology shows a deviation from the ideal shape of about 400 nm rms, indicating a loss of intensity of between 20% and 50%, depending on the geometry an X-ray energy.

  1. 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

  2. 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

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

    PubMed

    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

  4. Laser multi-reflection differential confocal long focal-length measurement.

    PubMed

    Li, Zhigang; Qiu, Lirong; Zhao, Weiqian; Zhao, Qi

    2016-06-20

    We propose a new laser multi-reflection differential confocal focal-length measurement (LDCFM) method to meet the requirements of high-precision measurements of long focal lengths. An optical flat and a reflector are placed behind a test lens for reflecting the measuring beam repeatedly. Then, LDCFM uses the property that the null points of differential confocal response curves precisely correspond to the convergence points of the multi-reflected measuring beam to exactly determine the positions of the convergence points accurately. Subsequently, the position variation of the reflector is measured with different reflection times by using a distance-measuring instrument, and thereby the long focal length is measured precisely. Theoretical analyses and preliminary experimental results indicate that the LDCFM method has a relative expanded standard uncertainty (k=2) of 0.04% for the test lens with a focal length of 9.76 m. The LDCFM method can provide a novel approach for high-precision focal-length measurements. PMID:27409117

  5. 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.

  6. 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

  7. All-in-quartz optics for low focal shifts

    NASA Astrophysics Data System (ADS)

    Blomqvist, Mats; Blomster, Ola; Pålsson, Magnus; Campbell, Stuart; Becker, Frank; Rath, Wolfram

    2011-02-01

    High laser power levels in combination with increasing beam quality bring optics performance into focus, particularly with regard to systems with low focal shifts along the optical axis. In industrial applications, this often influences the overall performance of the process, especially if the focal shift is comparable to or in excess of the Rayleigh length. It is commonly accepted that the focal shifts are of thermal nature where lens material, lens coating, geometry and surface contamination all contribute to the direction and extent of the focal shifts. In this paper we will present a novel design of lens packages where a patented all-in-quartz concept is explored. By mounting quartz lenses in hermetically sealed quartz tubes and applying water cooling on the perimeter of the quartz tubes we will reduce or eliminate a number of contributing factors to focal shift problems. The hermetic sealing, carried out in a clean-room environment, will minimize lens surface contamination. Differences in thermal expansion between lens and housing are eliminated as the lens and housing will be of the same material. Absorption of scattered laser light will be efficient as the energy is removed quickly by cooling water and not absorbed by fixed surroundings. Finally, indirect heating from the housing transmitted by radiation and convection to the lenses is avoided. Values of the normalized System Focal Shift Factors (SFSF) for the all-in-quartz optics will be compared to standard lens assemblies at multi-kW laser power levels.

  8. Design of a dual-effect lens on lanthanum-modified lead zirconate titanate for continuous variation of focal length

    NASA Astrophysics Data System (ADS)

    Castro, Francisco; Nabet, Bahram

    1995-05-01

    The design of a Fresnel lens with continuous focal length is proposed for use in optical processing. A convex lens is induced in lanthanum-modified lead zirconate titanate through the application of an electric-field profile supplied by the indium tin oxide electrodes that make up the zones of a Fresnel lens. The use of a numerical method based on fast Fourier transform algorithms was required to analyze accurately the induced field inside a Fresnel lens with an initial focal length of 0.4 m (at 470 nm) and 20 indium tin oxide electrodes. The effective focal location obtained by the combined mechanisms is derived. This design is expected to produce continuous variations of approximately 16% in focal length; the ability of previous designs to achieve focal length switching is maintained.

  9. Focal Length Controllable Ultrasonic Array Transducer with Adjustable Curvature

    NASA Astrophysics Data System (ADS)

    Kim, Jungsoon; Kim, Moojoon; Ha, Kanglyel

    2012-07-01

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

  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. Short focal length Kirkpatrick-Baez mirrors for a hard x-ray nanoprobe

    SciTech Connect

    Liu Wenjun; Ice, Gene E.; Tischler, Jonathan Z.; Khounsary, Ali; Liu, Chian; Assoufid, Lahsen; Macrander, Albert T.

    2005-11-15

    We describe progress in the fabrication of short-focal-length total-external-reflection Kirkpatrick-Baez x-ray mirrors with ultralow figure errors. The short focal length optics produce nanoscale beams (<100 nm) on conventional ({approx}64 m long) beamlines at third generation synchrotron sources. The total-external reflection optics are inherently achromatic and efficiently focus a white (polychromatic) or a tunable monochromatic spectrum of x rays. The ability to focus independent of wavelength allows novel new experimental capabilities. Mirrors have been fabricated both by computer assisted profiling (differential polishing) and by profile coating (coating through a mask onto ultra-smooth surfaces). A doubly focused 85x95 nm{sup 2} hard x-ray nanobeam has been obtained on the UNICAT beamline 34-ID at the Advanced Photon Source. The performance of the mirrors, techniques for characterizing the spot size, and factors limiting focusing performance are discussed.

  12. Short Focal Length Kirkpatrick-Baez Mirrors for a Hard X-Ray Nanoprobe

    SciTech Connect

    Liu, Wenjun; Ice, Gene E; Tischler, Jonathan Zachary; Khounsary, Ali; Liu, Chian; Assoufid, Lahsen; Macrander, Albert T.

    2005-01-01

    We describe progress in the fabrication of short-focal-length total-external-reflection Kirkpatrick-Baez x-ray mirrors with ultralow figure errors. The short focal length optics produce nanoscale beams (<100 nm) on conventional ({approx} 64 m long) beamlines at third generation synchrotron sources. The total-external reflection optics are inherently achromatic and efficiently focus a white (polychromatic) or a tunable monochromatic spectrum of x rays. The ability to focus independent of wavelength allows novel new experimental capabilities. Mirrors have been fabricated both by computer assisted profiling (differential polishing) and by profile coating (coating through a mask onto ultra-smooth surfaces). A doubly focused 85 x 95 nm{sup 2} hard x-ray nanobeam has been obtained on the UNICAT beamline 34-ID at the Advanced Photon Source. The performance of the mirrors, techniques for characterizing the spot size, and factors limiting focusing performance are discussed.

  13. 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.

  14. Variant of the anastigmatic telescope with three mirrors for back focal length.

    PubMed

    Herrera, J; Vázquez, S; Luna, E; Salas, L; Nuñez, J; Sohn, E; Ruiz, E

    2011-05-01

    In this paper, an optical design is presented for an anastigmatic telescope with back focal length corrected with exact ray tracing to eliminate spherical, coma, and astigmatism aberrations. The telescope is formed of three conical mirrors, two of them polished on the same substratum. The optical design is divided into three stages: we began the design obtaining the Gaussian parameters in a first-order solution; posteriorly, were obtained analytically the three mirrors' asphericity in a third-order design. The final design stage consists of the implementation of the Fermat's principle, the Abbe sine condition, and the Coddington equations for the exact correction for the three aforementioned aberrations. PMID:21532673

  15. Infrared fiber optic focal plane dispersers

    NASA Technical Reports Server (NTRS)

    Goebel, J. H.

    1981-01-01

    Far infrared transmissive fiber optics as a component in the design of integrated far infrared focal plane array utilization is discussed. A tightly packed bundle of fibers is placed at the focal plane, where an array of infrared detectors would normally reside, and then fanned out in two or three dimensions to individual detectors. Subsequently, the detectors are multiplexed by cryogenic electronics for relay of the data. A second possible application is frequency up-conversion (v sub 1 + v sub 2 = v sub 3), which takes advantage of the nonlinear optical index of refraction of certain infrared transmissive materials in fiber form. Again, a fiber bundle is utilized as above, but now a laser of frequency v sub 1 is mixed with the incoming radiation of frequency v sub 1 within the nonlinear fiber material. The sum, v sub 2 is then detected by near infrared or visible detectors which are more sensitive than those available at v sub 2. Due to the geometrical size limitations of detectors such as photomultipliers, the focal plane dispersal technique is advantageous for imaging up-conversion.

  16. UV-curable liquid-core fiber lenses with controllable focal length.

    PubMed

    Bai, Gongxun; Tsang, Yuen H; Jim, Kwok Lung; Zhang, Xuming

    2013-03-11

    Lensed fiber optics is of great importance to many applications such as optical sensing, optical coupling, laser trapping etc. In this paper we have demonstrated a unique method to fabricate liquid-core lensed fibers by filling UV curable adhesive into hollow fibers, and to control the focal length and spot size by pumping liquid into or out of the fiber end. In experiment, tuning of focal length from 2.414 to 0.810 mm has been obtained, and solidification of the adhesive core has also been carried out successfully. Further simulation suggests that the focused spot size can be reduced to <10 micron by adjusting the refractive index and fiber geometry. Such technique has the potential to manufacture custom-made solid lensed fibers and liquid-core solid-tip lensed fibers in volume at low cost. The same technique may be used for input and output coupling of optofluidic waveguides with external optical components like optical fibers and lasers. PMID:23482122

  17. Array of lenses with individually tunable focal-length based on transparent ion-implanted EAPs

    NASA Astrophysics Data System (ADS)

    Niklaus, Muhamed; Rosset, Samuel; Shea, Herbert

    2010-04-01

    We report on the fabrication and characterization of 2x2 arrays of mm-diameter PDMS lenses whose focal length can be electrically tuned. Dielectric elastomer actuators generally rely on carbon powder or carbon grease electrodes, which are not transparent, precluding the polymer actuator from also being a lens. However compliant electrodes fabricated by low-energy ion implantation are over 50% transparent in the visible, enabling the polymer lens to simultaneously be an actuator. We have developed a chip-scale process to microfabricate lens arrays, consisting of a molded socket bonded to a Pyrex chip supporting 4 membrane actuators. The actuators are interconnected via an incompressible fluid. The Pyrex chip has four through-holes, 1 to 3 mm in diameter, on which a 30 μm thick Polydimethysiloxane (PDMS) layer is bonded. The PDMS layer is implanted on both sides with 5 keV gold ions to define the transparent electrodes for EAP actuation. Applying a voltage to one of the lens/actuators leads to an area expansion and hence to a change in radius of curvature, varying the focal length. We report tuning the focal length from 4 mm to 8 mm at 1.7 kV, and present changes in optical transmission and membrane stiffness following gamma and proton irradiation.

  18. Measurement of focal length using phase shifted moiré deflectometry

    NASA Astrophysics Data System (ADS)

    Trivedi, Satyaprakash; Dhanotia, Jitendra; Prakash, Shashi

    2013-06-01

    In present communication, a simple technique for determining the focal length using moiré deflectometry has been proposed. Necessary mathematical premise expressing the focal length of lens in terms of defocusing distance and the slope of wavefront phase has been deduced. Using a four-step phase shifting technique the testing procedure for determining the focal length has been demonstrated. Uncertainty in measurement has been estimated. Good co-relation between the measured value and the standard value has been obtained.

  19. 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.

  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. Short-focal-length compound refractive lenses for x-rays

    SciTech Connect

    Dudchik, Y.I.; Kolchevsky, N.N.; Komarov, F.F.; Piestrup, M.A.; Cremer, J.T.; Gary, C.K.; Pantell, R.H.

    2005-08-15

    We have fabricated and tested short focal-length compound refractive lenses (CRLs) composed of micro-bubbles embedded in epoxy. The bubbles were formed in epoxy inside glass capillaries. The interface between the bubbles formed 90 to 196 spherical bi-concave microlenses reducing the overall focal length inversely by the number of lenses. When compared with CRLs manufactured using other methods, the micro-bubble lenses have shorter focal lengths, better imaging, and focusing qualities with higher transmissions and gains for moderate energy x-rays (e.g. 7-12 keV). We used beamline 2-3 at the Stanford Synchrotron Radiation Laboratory (SSRL) to measure focal lengths between 100-150 mm and absorption apertures between 90 to 120 {micro}m. Transmission profiles were measured giving, for example, a peak transmission of 27% for a 130-mm focal length CRL at 8 keV. The focal-spot sizes were also measured yielding, for example, an elliptical spot of 5 x 14-{micro}m{sup 2} resulting from an approximate 80-fold demagnification of the 0.44 x 1.7 mm{sup 2} source. The measured gains in intensity over that of unfocused beam were between 9 and 26. Theoretical gain calculations that include spherical aberrations show that these values are reasonable. The micro-bubble technique opens a new opportunity for designing lenses in the 8-9 keV range with focal lengths less than 30-40 mm.

  3. 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.

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

    PubMed

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

    2014-03-01

    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

  6. A 3D fiber probe based on orthogonal micro focal-length collimation and fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Cui, Jiwen; Li, Junying; Feng, Kunpeng; Tan, Jiubin; Zhang, Jian

    2016-07-01

    A 3D fiber probe is proposed for the precision measurement of micro parts with high aspect ratios. The probing system consists of two measuring systems: two mutually orthogonal micro focal-length collimation optical paths for the radial tactile probing measurement, and a matched fiber Bragg grating (FBG) pair interrogation system for the axial tactile probing measurement. The fiber probe consists of a fiber stylus and a probe tip, the fiber stylus works as a micro focal-length cylindrical lens, and the FBG inscribed in the fiber stylus works as a measuring FBG. The radial displacement of the probe tip is transformed into the centroid position shift of the two mutually orthogonal micro focal-length collimation optical paths; the axial displacement of the probe tip is transformed into the power ratio change of the matched FBG pair interrogation system. Experimental results indicate that the probe has a radial sensitivity of 71 pixel μm‑1 in both X and Y directions, and an axial sensitivity of 4.9% μm‑1 in Z direction; the probe can reach a radial resolution of 5 nm, and an axial resolution of 8 nm. The probe has a capability of decoupling the 3D tactility and it can be applied in the measurement of micro parts.

  7. Arrays of microlenses with variable focal lengths fabricated by restructuring polymer surfaces with an ink-jet device

    NASA Astrophysics Data System (ADS)

    Pericet-Camara, Ramon; Best, Andreas; Nett, Sebastian K.; Gutmann, Jochen S.; Bonaccurso, Elmar

    2007-07-01

    We report of a method for fabricating two-dimensional, regular arrays of polymer microlenses with focal lengths variable between 0.2 and 4.5 mm. We first make concave microlenses by ink-jetting solvent on a polymer substrate with a commercial drop-on-demand device. Solvent evaporation restructures the surface by a series of combined effects, which are discussed. In the second step we obtain convex elastomeric microlenses by casting the template made in the first step. We demonstrate the good optical quality of the microlenses by characterising their surfaces with atomic force microscopy and white light interferometry, and by directly measuring their focal lengths with ad-hoc confocal laser scanning microscopy.

  8. Arrays of microlenses with variable focal lengths fabricated by restructuring polymer surfaces with an ink-jet device.

    PubMed

    Pericet-Camara, Ramon; Best, Andreas; Nett, Sebastian K; Gutmann, Jochen S; Bonaccurso, Elmar

    2007-07-23

    We report of a method for fabricating two-dimensional, regular arrays of polymer microlenses with focal lengths variable between 0.2 and 4.5 mm. We first make concave microlenses by ink-jetting solvent on a polymer substrate with a commercial drop-on-demand device. Solvent evaporation restructures the surface by a series of combined effects, which are discussed. In the second step we obtain convex elastomeric microlenses by casting the template made in the first step. We demonstrate the good optical quality of the microlenses by characterising their surfaces with atomic force microscopy and white light interferometry, and by directly measuring their focal lengths with ad-hoc confocal laser scanning microscopy. PMID:19547338

  9. Focal length and radius of curvature measurement using wavefront difference method

    NASA Astrophysics Data System (ADS)

    Yang, Zhongming; Gao, Zhishan; Wang, Shuai; Cheng, Jinlong; Yuan, Qun

    2015-10-01

    A method for measuring the focal length of the lens and the radius of curvature of the spherical surface using wavefront difference method is proposed. Based on Fizeau interferometer, an experimental system for focal length measurements is set up to verify the principle. Based on the point diffraction interferometer, an experimental system for radius of curvature measurements is proposed to verify the proposed method. With the focal length testing system, both the positive and negative lens experimental results indicate that the measurement accuracy is less than 0.16%under normal experimental environment. With the radius of curvature testing system, the radius of curvature of spherical mirrors and the surface figure can be measured in a higher precision simultaneously. The experimental results indicate that the measurement accuracy is in the order of 10-4 .

  10. Technique for the focal-length measurement of positive lenses using Fizeau interferometry

    SciTech Connect

    Pavan Kumar, Yeddanapudi; Chatterjee, Sanjib

    2009-02-01

    We present what we believe is a new technique for the focal-length measurement of positive lenses using Fizeau interferometery. The technique utilizes the Gaussian lens equation. The image distance is measured interferometrically in terms of the radius of curvature of the image-forming wavefront emerging from the lens. The radii of curvature of the image-forming wavefronts corresponding to two different axial object positions of known separation are measured. The focal length of the lens is determined by solving the equations obtained using the Gaussian lens equation for the two object positions. Results obtained for a corrected doublet lens of a nominal focal length of 200.0 mm with a measurement uncertainty of {+-}2.5% is presented.

  11. 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.

  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

  13. A calibration technology for multi-camera system with various focal lengths

    NASA Astrophysics Data System (ADS)

    Yang, Ruihua; Zhang, Jin; Deng, Huaxia; Yu, Liandong

    2016-01-01

    Calibration is the basis of three-dimensional (3D) reconstruction for machine vision technology. Nowadays, the most widely used calibration method among computer vision is the technique for binocular stereo measurement. However, binocular stereo vision has limited view field which is difficult to measure large-scale mechanical components synchronously. Thus, enlarging the view field is urgent in need for the large scale measurement. With the application of multi-camera system, the calibration for cameras with different focal lengths is required. In this paper, a method aiming at calibration problems for multi-camera system of different focal lengths is proposed. An imaging model for multi-camera system with various focal lengths is analyzed. The Harris corner detector is applied to determine the relationship between signal camera and checkerboard. Finally, the external parameters of different cameras can be obtained by the link with the checkerboard. The calibration results indicate that the calculation method used in this work can calibrate multi-camera with various focal lengths.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  15. Optical Link For Readout From Focal-Plane Array

    NASA Technical Reports Server (NTRS)

    Fossum, Eric R.; Larsson, Anders G.; Maserjian, Joseph

    1992-01-01

    Outputs of photodetectors modulate beam of light. Proposed optical link carries analog readout signals from photodetectors in focal-plane array to external signal-processing circuitry. Insensitive to electromagnetic interference at suboptical frequencies, and imposes smaller heat load on cryogenic apparatus because it does not include high-power electronic amplifier or laser transmitter within cold chamber.

  16. 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

  17. 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.

  18. Analysis and modeling of a thermal focal length in a corner-pumped composite slab laser

    NASA Astrophysics Data System (ADS)

    Li, Q. H.; Liu, H.; Gao, S.; Christopher, D. M.; Gong, M. L.

    2013-01-01

    A simulation method was developed to calculate the thermal focal length for corner-pumped composite slab lasers. Traditional methods assume a uniform heat distribution or an exponential decay heat distribution to simplify the calculation, but the results do not agree well with experimental data for the thermal focal length, which affects the laser resonator design. In the current model, the heat distribution is obtained from the ray trace software Tracepro, which can accurately calculate the pump light absorption distribution in the gain medium. The simulation results with this method have a relative error of 4% compared to experimental results, which is much better than traditional methods with relative errors of 14% for corner-pumped composite slab lasers and demonstrates the effectiveness of this method for the development of new lasers.

  19. Three-dimensional fiber probe based on orthogonal micro focal-length collimation for the measurement of micro parts.

    PubMed

    Cui, Jiwen; Li, Junying; Feng, Kunpeng; Tan, Jiubin

    2015-10-01

    A 3-dimensional fiber probe based on orthogonal micro focal-length collimation (MFL-collimation) is proposed for the measurement of micro parts with high aspect ratios. The probe consists of a fiber stylus which acts as a micro focal-length cylindrical lens (MFLC-lens) of the two orthogonal MFL-collimation optical paths and a probe tip fixed on the free end of the fiber stylus for touching the workpiece. The fiber stylus will deflect (deflection mode) or buckle (buckling mode) under contacts, and the deflection or buckling of the fiber stylus will cause corresponding shifts of the fringe images of the two orthogonal MFL-collimation optical paths. Therefore, the 3-dimensional displacements of the probe tip are transformed into the centroid position shifts of the zero-order fringe images. Experimental results indicate that the fiber probe has a measuring capability in 3-dimensional tactility, and a radial and axial resolution of 5 nm and 3 nm can be obtained respectively. The probe is easily applied in the measurement of micro parts because of its high resolution, low cost, high measurable aspect ratio, low probing forces and capability in three-dimensional tactility. PMID:26480152

  20. Composite axilens-axicon diffractive optical elements for generation of ring patterns with high focal depth

    NASA Astrophysics Data System (ADS)

    Dharmavarapu, Raghu; Vijayakumar, A.; Brunner, R.; Bhattacharya, Shanti

    2016-03-01

    A binary Fresnel Zone Axilens (FZA) is designed for the infinite conjugate mode and the phase profile of a refractive axicon is combined with it to generate a composite Diffractive Optical Element (DOE). The FZA designed for two focal lengths generates a line focus along the propagation direction extending between the two focal planes. The ring pattern generated by the axicon is focused through this distance and the radius of the ring depends on the propagation distance. Hence, the radius of the focused ring pattern can be tuned, during the design process, within the two focal planes. The integration of the two functions was carried out by shifting the location of zones of FZA with respect to the phase profile of the refractive axicon resulting in a binary composite DOE. The FZAs and axicons were designed for different focal depth values and base angles respectively, in order to achieve different ring radii within the focal depth of each element. The elements were simulated using scalar diffraction formula and their focusing characteristics were analyzed. The DOEs were fabricated using electron beam direct writing and evaluated using a fiber coupled diode laser. The tunable ring patterns generated by the DOEs have prospective applications in microdrilling as well as microfabrication of circular diffractive and refractive optical elements.

  1. Direct photofabrication of focal-length-controlled microlens array using photoinduced migration mechanisms of photosensitive sol-gel hybrid materials

    NASA Astrophysics Data System (ADS)

    Kang, Dong Jun; Jeong, Jong-Pil; Bae, Byeong-Soo

    2006-09-01

    Photosensitive sol-gel hybrid (SGH) materials exhibited the peculiar photoinduced migration behavior of unreacted molecules from unexposed areas to exposed areas by selective UV exposure. Using the photoinduced migration mechanism of the photosensitive SGH materials, the microlens array (MLA) with a smooth surface was directly photofabricated, and the focal length was controlled by changing the photoinduced migration parameters. The higher photoactive monomer content and the thicker film creating a higher curvature produced a smaller focal length of the MLA. Thus, a simple fabrication and easy control of the focal length can be applicable to a fabrication of an efficient MLA.

  2. Electromagnetic analysis of the IR sensor focal plane arrays of micro-optics

    NASA Astrophysics Data System (ADS)

    Sikorski, Zbigniew

    2000-04-01

    Matrices of binary micro-lenses monolithically integrated with the focal-place-arrays (FPA) of longwave IR uncooled detectors can significantly improve sensor's parameters. Surface relief of the binary micro-lenses is built of annular stair step structures of heights and widths smaller than the radiation length. Scalar diffraction theory cannot correctly describe diffraction on these micro-structures and therefore the rigorous electromagnetic theory should be applied. In this aper, we have applied the electromagnetic eignemode method to study binary micro-optics for the longwave IR FPA of 50 micrometers pixel width. We have shown that binary refractive micro-lenses outperform their diffractive counterparts allowing for detectors of 10 micrometers width. The effective refractive micro-lenses require the 8-level surface relief. Geometrical optics predictions of the focal position agree quite well width electromagnetic calculations.

  3. Three-dimensional fiber probe based on micro focal-length collimation and a fiber Bragg grating for the measurement of micro parts.

    PubMed

    Cui, Jiwen; Li, Junying; Feng, Kunpeng; Tan, Jiubin

    2015-07-15

    A three-dimensional (3D) fiber probe is proposed for the measurement of micro parts. The probe is made of a fiber Bragg grating (FBG) that acts as a micro focal-length cylindrical lens (MFLC-lens) of two mutually orthogonal micro focal-length collimation (MFL-collimation) optical paths. The radial displacement of the probe tip is transformed into the shift of the fringe image collimated by the MFL-collimation optical path; the axial displacement of the probe tip is transformed into the power ratio variation caused by the Bragg wavelength shift. Advantages of the probe are high precision, low cost, high measurable aspect ratio, and capability of decoupling the 3D tactility. PMID:26176466

  4. 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.

  5. Super-oscillatory focusing of circularly polarized light by ultra-long focal length planar lens based on binary amplitude-phase modulation

    PubMed Central

    Chen, Gang; Li, Yuyan; Yu, Anping; Wen, Zhongquan; Dai, Luru; Chen, Li; Zhang, Zhihai; Jiang, Senlin; Zhang, Kun; Wang, Xianyou; Lin, Feng

    2016-01-01

    In traditional optics, the focal spot size of a conventional lens is restricted to the diffraction limit 0.5λ/NA, where λ is the wavelength in vacuum and NA is the numerical aperture of the lens. Recently, various sub-diffraction focusing optical devices have been demonstrated, but they usually have short focal length and high numerical aperture. Moreover, they always suffer the problem of huge sidelobes near the focal spot and small field of view, especially when the focal spot size is less than the super-oscillation criteria 0.38λ/NA. To address the problem, here, we reported a far-field sub-diffraction point-focusing lens based on binary phase and amplitude modulation with ultra-long focal length 252.8 μm (399.5λ) and small numerical aperture 0.78, and experimentally demonstrated a super-oscillatory focusing of circularly polarized light with spot size 287 nm (0.454λ), smaller than the diffraction limit 0.64λ and the super-oscillation criterion 0.487λ. What’s more, on the focal plane, in the measured area within the radius of 142λ, the largest sidelobe intensity is less than 26% of the central lobe intensity. Such ultra-long distance super-oscillatory focusing with small sidelobes and large field of view has great potential applications in far-field super-resolution microscopy, ultra-high-density optical storage and nano-fabrication. PMID:27353239

  6. Super-oscillatory focusing of circularly polarized light by ultra-long focal length planar lens based on binary amplitude-phase modulation.

    PubMed

    Chen, Gang; Li, Yuyan; Yu, Anping; Wen, Zhongquan; Dai, Luru; Chen, Li; Zhang, Zhihai; Jiang, Senlin; Zhang, Kun; Wang, Xianyou; Lin, Feng

    2016-01-01

    In traditional optics, the focal spot size of a conventional lens is restricted to the diffraction limit 0.5λ/NA, where λ is the wavelength in vacuum and NA is the numerical aperture of the lens. Recently, various sub-diffraction focusing optical devices have been demonstrated, but they usually have short focal length and high numerical aperture. Moreover, they always suffer the problem of huge sidelobes near the focal spot and small field of view, especially when the focal spot size is less than the super-oscillation criteria 0.38λ/NA. To address the problem, here, we reported a far-field sub-diffraction point-focusing lens based on binary phase and amplitude modulation with ultra-long focal length 252.8 μm (399.5λ) and small numerical aperture 0.78, and experimentally demonstrated a super-oscillatory focusing of circularly polarized light with spot size 287 nm (0.454λ), smaller than the diffraction limit 0.64λ and the super-oscillation criterion 0.487λ. What's more, on the focal plane, in the measured area within the radius of 142λ, the largest sidelobe intensity is less than 26% of the central lobe intensity. Such ultra-long distance super-oscillatory focusing with small sidelobes and large field of view has great potential applications in far-field super-resolution microscopy, ultra-high-density optical storage and nano-fabrication. PMID:27353239

  7. Super-oscillatory focusing of circularly polarized light by ultra-long focal length planar lens based on binary amplitude-phase modulation

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Li, Yuyan; Yu, Anping; Wen, Zhongquan; Dai, Luru; Chen, Li; Zhang, Zhihai; Jiang, Senlin; Zhang, Kun; Wang, Xianyou; Lin, Feng

    2016-06-01

    In traditional optics, the focal spot size of a conventional lens is restricted to the diffraction limit 0.5λ/NA, where λ is the wavelength in vacuum and NA is the numerical aperture of the lens. Recently, various sub-diffraction focusing optical devices have been demonstrated, but they usually have short focal length and high numerical aperture. Moreover, they always suffer the problem of huge sidelobes near the focal spot and small field of view, especially when the focal spot size is less than the super-oscillation criteria 0.38λ/NA. To address the problem, here, we reported a far-field sub-diffraction point-focusing lens based on binary phase and amplitude modulation with ultra-long focal length 252.8 μm (399.5λ) and small numerical aperture 0.78, and experimentally demonstrated a super-oscillatory focusing of circularly polarized light with spot size 287 nm (0.454λ), smaller than the diffraction limit 0.64λ and the super-oscillation criterion 0.487λ. What’s more, on the focal plane, in the measured area within the radius of 142λ, the largest sidelobe intensity is less than 26% of the central lobe intensity. Such ultra-long distance super-oscillatory focusing with small sidelobes and large field of view has great potential applications in far-field super-resolution microscopy, ultra-high-density optical storage and nano-fabrication.

  8. Optical-based spectral modeling of infrared focal plane arrays

    NASA Astrophysics Data System (ADS)

    Mouzali, Salima; Lefebvre, Sidonie; Rommeluère, Sylvain; Ferrec, Yann; Primot, Jérôme

    2016-07-01

    We adopt an optical approach in order to model and predict the spectral signature of an infrared focal plane array. The modeling is based on a multilayer description of the structure and considers a one-dimensional propagation. It provides a better understanding of the physical phenomena occurring within the pixels, which is useful to perform radiometric measurements, as well as to reliably predict the spectral sensitivity of the detector. An exhaustive model is presented, covering the total spectral range of the pixel response. A heuristic model is also described, depicting a complementary approach that separates the different optical phenomena inside the pixel structure. Promising results are presented, validating the models through comparison with experimental results. Finally, advantages and limitations of this approach are discussed.

  9. 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.

  10. Brain SPECT with short focal-length cone-beam collimation

    SciTech Connect

    Park, Mi-Ae; Moore, Stephen C.; Kijewski, Marie Foley

    2005-07-15

    Single-photon emission-computed tomography (SPECT) imaging of deep brain structures is compromised by loss of photons due to attenuation. We have previously shown that a centrally peaked collimator sensitivity function can compensate for this phenomenon, increasing sensitivity over most of the brain. For dual-head instruments, parallel-hole collimators cannot provide variable sensitivity without simultaneously degrading spatial resolution near the center of the brain; this suggests the use of converging collimators. We have designed collimator pairs for dual-head SPECT systems to increase sensitivity, particularly in the center of the brain, and compared the new collimation approach to existing approaches on the basis of performance in estimating activity concentration of small structures at various locations in the brain. The collimator pairs we evaluated included a cone-beam collimator, for increased sensitivity, and a fan-beam collimator, for data sufficiency. We calculated projections of an ellipsoidal uniform background, with 0.9-cm-radius spherical lesions at several locations in the background. From these, we determined ideal signal-to-noise ratios (SNR{sub CRB}) for estimation of activity concentration within the spheres, based on the Cramer-Rao lower bound on variance. We also reconstructed, by an ordered-subset expectation-maximization (OS-EM) procedure, images of this phantom, as well as of the Zubal brain phantom, to allow visual assessment and to ensure that they were free of artifacts. The best of the collimator pairs evaluated comprised a cone-beam collimator with 20 cm focal length, for which the focal point is inside the brain, and a fan-beam collimator with 40 cm focal length. This pair yielded increased SNR{sub CRB}, compared to the parallel-parallel pair, throughout the imaging volume. The factor by which SNR{sub CRB} increased ranged from 1.1 at the most axially extreme location to 3.5 at the center. The gains in SNR{sub CRB} were relatively

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

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

    SciTech Connect

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

    1998-10-01

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

  17. Influence of the photoinduced focal length of a thin nonlinear material in the Z-scan technique.

    PubMed

    Reynoso Lara, Edmundo; Navarrete Meza, Zulema; Iturbe Castillo, M David; Treviño Palacios, Carlos G; Martí Panameño, Erwín; Arroyo Carrasco, M Luis

    2007-03-01

    In this paper the response purely refractive of a thin nonlinear material, in the z-scan technique experiment, is modeled as a lens with a focal length that is a function of some integer power of the incident beam radius. We demonstrate that different functional dependences of the photoinduced lens of a thin nonlinear material give typical z-scan curves with special features. The analysis is based on the propagation of Gaussian beams in the approximation of thin lens and small distortion for the nonlinear sample. We obtain that the position of the peak and valley, the transmittance near the focus and the transmittance far from the Rayleigh range depend on the functional dependence of the focal length. Special values of the power reproduce the results obtained for some materials under cw excitation. PMID:19532488

  18. Parabolic Capillary Optics with less than 50 {mu}m Focus and Large Focal Distance for Synchrotron Radiation Scattering

    SciTech Connect

    Schell, Norbert; Eichhorn, Frank; Bjeoumikhov, Aniouar; Ollinger, Christoph

    2007-01-19

    We report the design and performance of a unique parabolic focusing optics for a general purpose materials research station at the bending magnet BM20 (ROBL-CRG) at ESRF. The measured gain between 8-12 keV was >1000, the focal spot <40 {mu}m at a focal length of 235 mm (8 keV) and 244 mm (11.5 keV), respectively, which allows the use of special sample environments around the focus spot. The low divergence of <0.15 deg. especially permits the in situ characterization of stress states in copper dual inlaid interconnect micro-structures as well as the measurement of far-field diffraction patterns of planar waveguides. First test results will be shown and the advantages of the parabolic focusing optics discussed.

  19. 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.

  20. 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.

  1. Diffraction limited focal spot in the interaction chamber using phase retrieval adaptive optics

    NASA Astrophysics Data System (ADS)

    Lefaudeux, Nicolas; Lavergne, Emeric; Monchoce, Sylvain; Levecq, Xavier

    2014-03-01

    In order to provide the end user with a diffraction limited collimated beam, adaptive optics phase correction systems are now a standard feature of ultra intense laser facilities. Generally speaking, these systems are based on a deformable mirror controlled in closed loop configuration in order to correct the aberrations of the beam measured by the wavefront sensor. Such implementation corrects for most of the aberrations of the laser. However, the aberrations of the optical elements located downstream of the wavefront sensor are not measured and therefore not corrected by the adaptive optics loop while they are degrading the final focal spot. We present an improved correction strategy and results based on a combination of both usual closed loop and phase retrieval in order to reach the diffraction limit at the focal spot inside the interaction chamber. The off axis parabola alignment camera located at the focal spot is used in combination of the deformable mirror and wavefront sensor to get images of the focal spot. The residual aberrations of the focal spot are measured by a Phase Retrieval algorithm using the acquired focal spot images. Then the adaptive optics loop is run in order to precompensate for these aberrations, which leads to diffraction limited focal spot in the interaction chamber.

  2. 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.

  3. 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%.

  4. Focal ratio degradation and transmission in VIRUS-P optical fibers

    NASA Astrophysics Data System (ADS)

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

    2008-07-01

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

  5. 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

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

    PubMed

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

    2015-08-18

    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

  7. 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.

  8. 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.

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

    NASA Technical Reports Server (NTRS)

    Heyman, Joseph S.; Rogawski, Robert S.

    1988-01-01

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

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. Nonlinear optical microscopy improvement by focal-point axial modulation

    NASA Astrophysics Data System (ADS)

    Dashtabi, Mahdi Mozdoor; Massudi, Reza

    2016-05-01

    Among the most important challenges of microscopy-even more important than the resolution enhancement, especially in biological and neuroscience applications-is noninvasive and label-free imaging deeper into live scattering samples. However, the fundamental limitation on imaging depth is the signal-to-background ratio in scattering biological tissues. Here, using a vibrating microscope objective in conjunction with a lock-in amplifier, we demonstrate the background cancellation in imaging the samples surrounded by turbid and scattering media, which leads to more clear images deeper into the samples. Furthermore, this technique offers the localization and resolution enhancement as well as resolves ambiguities in signal interpretation, using a single-color laser. This technique is applicable to most nonlinear as well as some linear point-scanning optical microscopies.

  17. 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

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

    NASA Astrophysics Data System (ADS)

    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.

  19. 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

  20. 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.

  1. 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.

  2. 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

  3. Extended depth-of-field 3D endoscopy with synthetic aperture integral imaging using an electrically tunable focal-length liquid-crystal lens.

    PubMed

    Wang, Yu-Jen; Shen, Xin; Lin, Yi-Hsin; Javidi, Bahram

    2015-08-01

    Conventional synthetic-aperture integral imaging uses a lens array to sense the three-dimensional (3D) object or scene that can then be reconstructed digitally or optically. However, integral imaging generally suffers from a fixed and limited range of depth of field (DOF). In this Letter, we experimentally demonstrate a 3D integral-imaging endoscopy with tunable DOF by using a single large-aperture focal-length-tunable liquid crystal (LC) lens. The proposed system can provide high spatial resolution and an extended DOF in synthetic-aperture integral imaging 3D endoscope. In our experiments, the image plane in the integral imaging pickup process can be tuned from 18 to 38 mm continuously using a large-aperture LC lens, and the total DOF is extended from 12 to 51 mm. To the best of our knowledge, this is the first report on synthetic aperture integral imaging 3D endoscopy with a large-aperture LC lens that can provide high spatial resolution 3D imaging with an extend DOF. PMID:26258358

  4. Active stabilization of a fiber-optic two-photon interferometer using continuous optical length control.

    PubMed

    Cho, Seok-Beom; Kim, Heonoh

    2016-05-16

    The practical realization of long-distance entanglement-based quantum communication systems strongly rely on the observation of highly stable quantum interference between correlated single photons. This task must accompany active stabilization of the optical path lengths within the single-photon coherence length. Here, we provide two-step interferometer stabilization methods employing continuous optical length control and experimentally demonstrate two-photon quantum interference using an actively stabilized 6-km-long fiber-optic Hong-Ou-Mandel interferometer. The two-step active control techniques are applied for measuring highly stable two-photon interference fringes by scanning the optical path-length difference. The obtained two-photon interference visibilities with and without accidental subtraction are found to be approximately 90.7% and 65.4%, respectively. PMID:27409920

  5. 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.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

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

  8. 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.

  9. Automated alignment of a reconfigurable optical system using focal-plane sensing and Kalman filtering.

    PubMed

    Fang, Joyce; Savransky, Dmitry

    2016-08-01

    Automation of alignment tasks can provide improved efficiency and greatly increase the flexibility of an optical system. Current optical systems with automated alignment capabilities are typically designed to include a dedicated wavefront sensor. Here, we demonstrate a self-aligning method for a reconfigurable system using only focal plane images. We define a two lens optical system with 8 degrees of freedom. Images are simulated given misalignment parameters using ZEMAX software. We perform a principal component analysis on the simulated data set to obtain Karhunen-Loève modes, which form the basis set whose weights are the system measurements. A model function, which maps the state to the measurement, is learned using nonlinear least-squares fitting and serves as the measurement function for the nonlinear estimator (extended and unscented Kalman filters) used to calculate control inputs to align the system. We present and discuss simulated and experimental results of the full system in operation. PMID:27505378

  10. Automated alignment of a reconfigurable optical system using focal-plane sensing and Kalman filtering

    NASA Astrophysics Data System (ADS)

    Fang, Joyce; Savransky, Dmitry

    2016-08-01

    Automation of alignment tasks can provide improved efficiency and greatly increase the flexibility of an optical system. Current optical systems with automated alignment capabilities are typically designed to include a dedicated wavefront sensor. Here, we demonstrate a self-aligning method for a reconfigurable system using only focal plane images. We define a two lens optical system with eight degrees of freedom. Images are simulated given misalignment parameters using ZEMAX software. We perform a principal component analysis (PCA) on the simulated dataset to obtain Karhunen-Lo\\`eve (KL) modes, which form the basis set whose weights are the system measurements. A model function which maps the state to the measurement is learned using nonlinear least squares fitting and serves as the measurement function for the nonlinear estimator (Extended and Unscented Kalman filters) used to calculate control inputs to align the system. We present and discuss both simulated and experimental results of the full system in operation.

  11. Measurement and compensation of wavefront deformations and focal shifts in high-power laser optics

    NASA Astrophysics Data System (ADS)

    Mann, K.; Schäfer, B.; Stubenvoll, M.; Hentschel, K.; Zenz, M.

    2015-11-01

    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.

  12. 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

  13. 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

  14. Optical design of the focal adjustable flashlight based on a power white-LED

    NASA Astrophysics Data System (ADS)

    Cai, Jhih-You; Lo, Yi-Chien; Sun, Ching-Cherng

    2011-10-01

    In the paper, we design a focal adjustable flashlight, which can provide the spotlight and the wide-angle illumination in different modes. For most users, they two request two illumination modes. In such two modes, one is high density energy of the light pattern and the other is the uniform light pattern in a wide view field. In designing the focal adjustable flashlight, we first build a precise optical model for the high-power LED produced by CREE Inc. in mid-field verification to make sure the accuracy of our simulation. Typically, the lens is useful to be the key component of the adjustable flashlight, but the optical efficiency is low. Here, we introduce a concept of so-called total internal refraction (TIR) lens into the design of flashlight. By defocusing the TIR lens, the flashlight can quickly change the beam size and energy density to various applications. We design two segments of the side of the TIR lens so that they can be applied to the two modes, and the flashlight provides a high optical efficiency for each mode. The illuminance of the center of light pattern at a distance of 2 m from the lamp is also higher than using the lens in the spotlight and wide-angle illumination. It provides good lighting functions for users.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. Calibration method for division of focal plane polarimeters in the optical and near-infrared regime

    NASA Astrophysics Data System (ADS)

    York, Timothy; Gruev, Viktor

    2011-06-01

    Advances in nanofabrication allow for the creation of metallic nanowires acting as linear polarizers in the visible and near infrared regime. The monolithic integration of silicon detectors and pixelated nanowire metallic polarization filters allows for an efficient realization of high resolution polarization imaging sensors. These silicon sensors, known as division of focal plane polarimeters, capture polarization information of the imaged environment from ~400nm to 1050nm wavelength. The performance of the polarization sensor can be degraded by both irregularities in the fabrication of the nanowires and possible misalignment errors during the final deposition of the optical nanowire filters on the surface of the imaging sensor. In addition, electronic offsets due to the readout circuitry, electronic crosstalk, and optical crosstalk will also negatively affect the quality of the polarization information. Partial compensation for many of these post-fabrication errors can be accomplished through the use of a camera calibration routine. This paper will describe one such routine, and show how its application can increase the quality of measurements in both the degree of linear polarization and angle of polarization in the visible spectrum. The imaging array of the division of focal plane polarimeter is segmented into two by two blocks of superpixels. The calibration method chooses one of the four pixels as a reference, and then a gain and offset for each of the remaining three is computed based on this reference. The output is a calibration matrix for each pixel in the image array.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. Direct optical measurement of the on-shot incoherent focal spot and intensity contrast on the OMEGA EP laser

    NASA Astrophysics Data System (ADS)

    Dorrer, C.; Consentino, A.; Irwin, D.

    2016-06-01

    Characterizing the prepulse temporal contrast of optical pulses is required to understand their interaction with matter. Light with relatively low intensity can interact with the target before the main high-intensity pulse. Estimating the intensity contrast, instead of the spatially averaged power contrast, is important to understand intensity-dependent laser-matter interactions. A direct optical approach to determining the on-shot intensity of the incoherent pedestal on an aberrated high-intensity laser system is presented. The spatially resolved focal spot of the incoherent pedestal preceding the main coherent pulse and the intensity contrast are calculated using experimental data. This technique is experimentally validated on one of the chirped pulse amplification beamlines of the OMEGA EP Laser System. The intensity contrast of a 1-kJ, 10-ps laser pulse is shown to be ~10× higher than the power contrast because of the larger spatial extent of the incoherent focal spot relative to the coherent focal spot.

  7. Probing focal cortical dysplasia in formalin fixed samples using tissue optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Anand, Suresh; Cicchi, Riccardo; Giordano, Flavio; Buccoliero, Anna Maria; Conti, Valerio; Guerrini, Renzo; Pavone, Francesco Saverio

    2016-03-01

    Focal cortical dysplasia (FCD) is one of most common causes of intractable epilepsy in pediatric population and these are often insensitive to anti-epileptic drugs. FCD is characterized by a disarray in localized regions of the cerebral cortex and abnormal neurons which results them to misfire with incorrect signals. Resective neurosurgery to remove or disconnect the affected parts from the rest of the brain seems to be a viable option to treat FCD. Before neurosurgery the subject could undergo imaging studies including magnetic resonance imaging (MRI) or computed tomography (CT) scans. On the downside FCD could be elusive in MRI images and may be practically invisible in CT scans. Furthermore, unnecessary removal of normal tissues is to be taken into consideration as this could lead to neurological defects. In this context, optical spectroscopy have been widely investigated as an alternative technique for the detection of abnormal tissues in different organ sites. Disease progression is accompanied by a number of architectural, biochemical and morphological changes. These variations are reflected in the spectral intensity and line shape. Here, in this proof of concept study we propose to investigate the application of tissue optical spectroscopy based on fluorescence excitation at two wavelength 378 and 445 nm coupled along with Raman spectroscopy for the detection of FCD on formalin fixed tissue specimens from pediatric subjects. For fluorescence at both the excitation wavelengths FCD showed a decreased intensity at longer wavelength when compared to normal tissues. Also, differences exist in the Raman spectral profiles of normal and FCD.

  8. 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.

  9. VLTI focal instrument AMBER: results of laboratory commissioning of the warm optics

    NASA Astrophysics Data System (ADS)

    Robbe-Dubois, Sylvie; Bresson, Yves; Antonelli, Pierre; Bonhomme, S.; Lagarde, Stephane; Martinot-Lagarde, Gregoire; Petrov, Romain G.; Puget, Pascal; Reynaud, Francois; Roussel, Andre; Rousselet-Perraut, Karine; Tassot, Daniel; Vannier, Martin

    2003-02-01

    AMBER, Astronomical Multi BEam combineR, is the near-infrared focal instrument dedicated to the VLTI. It is designed to combine three of the VLTI Telescopes and to work simultaneously in the J, H and K spectral bands (1.1 to 2.4 μm). The instrumental concept and its opto-mechanic specifications were defined in order to reach the ambitious scientific requirements to satisfy the core astrophysical programs. The project passed the Final Design Review in May 2001, phase which marks the acceptation of the instrument final design and the beginning of the construction and tests. After this phase, optics and mechanical systems have been receptioned since February 2002, for the laboratory tests and alignments. The cooled spectrograph and its cryostat is assembled at the Osservatorio di Arcetri in Firenze, Italy and the cooled detector at the Max-Planck-Institut für Radioastronomie in Bonn, Deutschland. The warm optics, including spatial filter in K and artificial sources injection system, have been pre-aligned at the Observatoire de la Côte d'Azur in Nice, France to validate most of the alignment procedure, the required element accuracies and the associated degrees of freedom. The whole instrument is then currently fully assembled and optimized at the Laboratoire d'Astrophysique de l'Observatoire de Grenoble, France. Its sensitivity and final performance will be evaluated in order to reach the Preliminary Acceptance in Europe, scheduled beginning 2003. This paper gives the results of the warm optics laboratory commissioning.

  10. Depth-resolved photothermal optical coherence tomography by local optical path length change measurement (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Makita, Shuichi; Hong, Young-Joo; Li, En; Yasuno, Yoshiaki

    2016-03-01

    Photothermal OCT has been emerged to contrast absorbers in biological tissues. The tissues response to photothermal excitation as change of thermal strain and refractive index. To resolve the depth of absorption agents, the measurements of the local thermal strain change and local refractive index change due to photothermal effect is required. In this study, we developed photothermal OCT for depth-resolved absorption contrast imaging. The phase-resolved OCT can measure the axial strain change and local refractive index change as local optical path length change. A swept-source OCT system is used with a wavelength swept laser at 1310 nm with a scanning rate of 50 kHz. The sensitivity of 110 dB is achieved. At the sample arm, the excitation beam from a fiber-coupled laser diode of 406 nm wavelength is combined with the OCT probe beam co-linearly. The slowly modulated excitation beam around 300 Hz illuminate biological tissues. M-mode scan is applied during one-period modulation duration. The local optical path length change is measured by temporal and axial phase difference. The theoretical prediction of the photothermal response is derived and in good agreement with experimental results. In the case of slow modulation, the delay of photothermal response can be neglected. The local path length changes are averaged over the half period of the excitation modulation, and then demodulated. This method exhibits 3-dB gain in the sensitivity of the local optical path length change measurement over the direct Fourier transform method. In vivo human skin imaging of endogenous absorption agent will be demonstrated.

  11. 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.

  12. 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.

  13. Investigation of focal ratio degradation in optical fibres for astronomical instrumentation

    NASA Astrophysics Data System (ADS)

    Crause, Lisa; Bershady, Matthew; Buckley, David

    2008-07-01

    A differential method was used to investigate the focal ratio degradation (FRD) exhibited by, and throughput of, a selection of current-generation optical fibres. These fibres were tested to establish which would be best suited to feed the High Resolution Spectrograph being built for the Southern African Large Telescope (SALT), as well as for future instruments on WIYN and SALT. The double re-imaging system of Bershady et al. (2004) was substantially modified to improve image quality and measurement efficiency, and to permit a direct FRD-measurement in the far-field. The re-imaging method compares the beam profile produced by light which passes through a fibre to that which does not. Broad and intermediate band-pass filters were used between 400-800 nm to test for wavelength dependence in the observed FRD over a wide range in beam-speeds. Our results continue to be at odds with a mico-bend model for FRD. We conclude that the new Polymicro FBP fibre is the most suitable product for broadband applications.

  14. 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.

  15. 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

  16. 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.

  17. Direct optical measurement of the on-shot incoherent focal spot and intensity contrast on the OMEGA EP laser

    DOE PAGESBeta

    Dorrer, C.; Consentino, A.; Irwin, D.

    2016-05-18

    Characterizing the prepulse temporal contrast of optical pulses is required to understand their interaction with matter. Light with relatively low intensity can interact with the target before the main high-intensity pulse. Estimating the intensity contrast, instead of the spatially averaged power contrast, is important to understand intensity-dependent laser–matter interactions. A direct optical approach to determining the on-shot intensity of the incoherent pedestal on an aberrated high-intensity laser system is presented. The spatially resolved focal spot of the incoherent pedestal preceding the main coherent pulse and the intensity contrast are calculated using experimental data. Furthermore, this technique is experimentally validated onmore » one of the chirped pulse amplification beamlines of the OMEGA EP Laser System. The intensity contrast of a 1-kJ, 10-ps laser pulse is shown to be ~10× higher than the power contrast because of the larger spatial extent of the incoherent focal spot relative to the coherent focal spot.« less

  18. 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.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    Tarbell, T. D.

    2005-05-01

    Solar-B is a space science mission of the Japanese Aerospace Exploration Agency (JAXA) and a NASA Solar Terrestrial Probes mission. It includes the 50-cm aperture Solar Optical Telescope (SOT), with its Focal Plane Package (FPP) designed for high resolution photospheric and chromospheric imaging and spectro-polarimetry. There are also two coronal instruments, the X-Ray Telescope and Extreme-ultraviolet Imaging Spectrometer. Solar-B will be launched into a Sun-synchronous polar orbit in August, 2006. The SOT is provided by JAXA and is being built by the National Astronomical Observatory of Japan (NAOJ) and Mitsubishi Electric Co. A team of Lockheed Martin, High Altitude Observatory (HAO), and NAOJ scientists and engineers have built the FPP instrument. This paper gives an overview of the science goals of the FPP as well as the instrument performance characteristics. The primary goal is to understand the coupling between the fine magnetic structures in the photosphere and dynamic processes and heating in the chromosphere and corona. The FPP consists of a narrow-band tunable birefringent filter imager, broad-band interference filter imager, and spectro-polarimeter (SP), essentially a space version of the HAO Advanced Stokes Polarimeter. The image is stabilized by a correlation tracker and active tilt mirror. The SP makes vector magnetic measurements from Stokes spectra of the Fe I lines 630.1 and 630.2 nm, with 0.16 arcsec pixels and field of view up to 164 x 328 arcsec. The broad-band system takes diffraction-limited images (0.05 arcsec pixels) in the Ca II H line, CN and G bandheads, and continuum bands. The narrow-band system makes filtergrams, magnetograms, Dopplergrams, and Stokes images in several photospheric lines, Mg b, Na D, and H-alpha, similar to the SOUP filter at La Palma. It has 0.08 arcsec pixels and field-of-view same as that of the SP. SOT and FPP have been calibrated in great detail and have observed the sun in two end-to-end tests at NAOJ. Sample

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

    NASA Astrophysics Data System (ADS)

    Tarbell, T.

    2001-05-01

    Solar-B is a Japanese space science mission of the Institute of Space and Astronautical Sciences (ISAS), with major participation of US and UK research groups. The mission includes the 50-cm aperture Solar Optical Telescope (SOT), with its Focal Plane Package (FPP) designed for high resolution photospheric and chromospheric imaging and spectro-polarimetry. There are also two coronal instruments, the X-Ray Telescope and Extreme-ultraviolet Imaging Spectrometer. Solar-B will be launched into a Sun-synchronous polar orbit in August, 2005. The SOT is provided by ISAS and is being built by the National Astronomical Observatory of Japan (NAOJ) and Mitsubishi Electric Co. A team of Lockheed Martin, High Altitude Observatory (HAO), and NAOJ scientists and engineers are designing the FPP instrument. This talk gives an overview of the science goals of the FPP as well as the current instrument design and performance characteristics. The primary goal is to understand the coupling between the fine magnetic structures in the photosphere and dynamic processes and heating in the chromosphere and corona. The FPP consists of a narrow-band tunable birefringent filter imager, broad-band interference filter imager, and spectro-polarimeter (SP), essentially a space version of the HAO Advanced Stokes Polarimeter. The image is stabilized by a correlation tracker and active tilt mirror. The SP makes vector magnetic measurements from Stokes spectra of the Fe I lines 630.1 and 630.2 nm, with 0.16 arcsec pixels and field of view up to 164 x 328 arcsec. The broad-band system takes diffraction-limited images (0.05 arcsec pixels) in the Ca II H line, CN and G bandheads, and continuum bands. The narrow-band system makes filtergrams, magnetograms, Dopplergrams, and Stokes images in several photospheric lines, Mg b, and H-alpha. It has 0.08 arcsec pixels and field-of-view same as that of the SP. The SP and filter imagers will usually observe simultaneously on the same target region. High

  2. 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

  3. Optical study of thin-film photovoltaic cells with apparent optical path length

    NASA Astrophysics Data System (ADS)

    Cho, Changsoon; Jeong, Seonju; Lee, Jung-Yong

    2016-09-01

    Extending the insufficient optical path length (OPL) in thin-film photovoltaic cells (PVs) is the key to achieving a high power conversion efficiency (PCE) in devices. Here, we introduce the apparent OPL (AOPL) as a figure of merit for light absorbing capability in thin-film PVs. The optical characteristics such as the structural effects and angular responses in thin-film PVs were analyzed in terms of the AOPL. Although the Lambertian scattering surface yields a broadband absorption enhancement in thin-film PVs, the enhancement is not as effective as in thick-film PVs. On the other hand, nanophotonic schemes are introduced as an approach to increasing the single-pass AOPL by inducing surface plasmon resonance. The scheme using periodic metal gratings is proved to increase the AOPL in a narrow wavelength range and specific polarization, overcoming the Yablonovitch limit. The AOPL calculation can be also adopted in the experimental analysis and a maximum AOPL of 4.15d (where d is the active layer thickness) is exhibited in the absorption band edge region of PTB7:PC70BM-based polymer PVs.

  4. Scanning metallic nanosphere microscopy for vectorial profiling of optical focal spots.

    PubMed

    Yi, Hui; Long, Jing; Li, Hongquan; He, Xiaolong; Yang, Tian

    2015-04-01

    Recent years have witnessed fast progress in the development of spatially variant states of polarization under high numerical aperture focusing, and intensive exploration of their applications. We report a vectorial, broadband, high contrast and subwavelength resolution method for focal spot profiling. In this experiment, a 100 nm diameter gold nanosphere on a silica aerogel substrate is raster scanned across the focal spots, and the orthogonal polarization components can be obtained simultaneously by measuring the scattering far field in a confocal manner. The metallic-nanosphere-on-aerogel structure ensures negligible distortion to the focal spots, low crosstalk between orthogonal polarization components (1/39 in experiment), and a low level background noise (1/80 of peak intensity in experiment), while high contrast imaging is not limited by the resonance bandwidth. PMID:25968672

  5. Nonblocking optical planar switching matrices of short length

    NASA Astrophysics Data System (ADS)

    Giglmayr, Josef

    2001-05-01

    Planar switching matrices of parallel waveguides (WGs) have reduced loss due to the absence of tapering but require some confinement of wave propagation reported from Kerr nonlinearities (NL). Parallel switching matrices are fed by the multiple splitting of the input WGs, an appropriate network model is the parallel version of the Spanke-Benes (PSB) network and the reduction of the number of stages (NSs) below N (for N i/o) is analyzed. However, in the parallel case, regarding WGs and SB networks, the location of switches can no longer be fixed but must be a moving location (ML). From the several parallel paths through the PSB network the shortest path is chosen either at the end by path selection switches (PS-SWs) or at the beginning of the switching matrix, respectively. It turns out that the reduction of NS of the switching matrix and in turn the saving of the number of switches (NSWs) is compensated by the number of PS-SWs at the end or at the beginning of the matrix. The replacement of the PS-SWs by combiners at the output (i) restores the energy balance but (ii) causes phase mismatch (iii) provides redundant paths (iv) restricts the overall NS to the NS of the SB network for each copy but (v) improves the nonblocking (NB) characteristic. The routing of the switching matrices and their optical implementation is also briefly discussed.

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

    NASA Technical Reports Server (NTRS)

    Wyman, C. L.

    1974-01-01

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

  7. Spatial modeling of optical crosstalk in InGaAsP Geiger-mode APD focal plane arrays.

    PubMed

    Piccione, Brian; Jiang, Xudong; Itzler, Mark A

    2016-05-16

    We report a spatial model of optical crosstalk in InGaAsP Geiger-mode APD focal plane arrays created via non-sequential ray tracing. Using twenty-four equivalent experimental data sets as a baseline, we show that experimental results can be reproduced to a high degree of accuracy by incorporating secondary crosstalk effects, with reasonable assumptions of material and emission source properties. We use this model to categorize crosstalk according to source and path, showing that the majority of crosstalk in the immediate neighborhood of avalanching pixels in the present devices can be attributed to direct line-of-sight emissions. PMID:27409885

  8. 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

  9. 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

  10. An inversion formula for the exponential Radon transform in spatial domain with variable focal-length fan-beam collimation geometry

    SciTech Connect

    Wen Junhai; Liang Zhengrong

    2006-03-15

    Inverting the exponential Radon transform has a potential use for SPECT (single photon emission computed tomography) imaging in cases where a uniform attenuation can be approximated, such as in brain and abdominal imaging. Tretiak and Metz derived in the frequency domain an explicit inversion formula for the exponential Radon transform in two dimensions for parallel-beam collimator geometry. Progress has been made to extend the inversion formula for fan-beam and varying focal-length fan-beam (VFF) collimator geometries. These previous fan-beam and VFF inversion formulas require a spatially variant filtering operation, which complicates the implementation and imposes a heavy computing burden. In this paper, we present an explicit inversion formula, in which a spatially invariant filter is involved. The formula is derived and implemented in the spatial domain for VFF geometry (where parallel-beam and fan-beam geometries are two special cases). Phantom simulations mimicking SPECT studies demonstrate its accuracy in reconstructing the phantom images and efficiency in computation for the considered collimator geometries.

  11. Analytical solution to 3D SPECT reconstruction with non-uniform attenuation, scatter, and spatially-variant resolution variation for variable focal-length fan-beam collimators

    NASA Astrophysics Data System (ADS)

    Wen, Junhai; Lu, Hongbing; Li, Tianfang; Liang, Zhengrong

    2003-05-01

    In the past decades, analytical (non-iterative) methods have been extensively investigated and developed for the reconstruction of three-dimensional (3D) single-photon emission computed tomography (SPECT). However, it becomes possible only recently when the exact analytic non-uniform attenuation reconstruction algorithm was derived. Based on the explicit inversion formula for the attenuated Radon transform discovered by Novikov (2000), we extended the previous researches of inverting the attenuated Radon transform of parallel-beam collimation geometry to fan-beam and variable focal-length fan-beam (VFF) collimators and proposed an efficient, analytical solution to 3D SPECT reconstruction with VFF collimators, which compensates simultaneously for non-uniform attenuation, scatter, and spatially-variant or distance-dependent resolution variation (DDRV), as well as suppression of signal-dependent non-stationary Poisson noise. In this procedure, to avoid the reconstructed images being corrupted by the presence of severe noise, we apply a Karhune-Loève (K-L) domain adaptive Wiener filter, which accurately treats the non-stationary Poisson noise. The scatter is then removed by our scatter estimation method, which is based on the energy spectrum and modified from the triple-energy-window acquisition protocol. For the correction of DDRV, a distance-dependent deconvolution is adapted to provide a solution that realistically characterizes the resolution kernel in a real SPECT system. Finally image is reconstructed using our VFF non-uniform attenuation inversion formula.

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

    NASA Astrophysics Data System (ADS)

    Bonora, Stefano; Villoresi, Paolo

    2006-04-01

    ) the maximum optical efficiency in the beam shaping process, 2) the optimal equalization of the beam parameter product for the two axes, 3) the use of few optical elements and 4) a very compact size. These goals are addressed by a scheme that splits the collimated beam from the laser diode into different portions while the length of the optical paths of each sub element is kept constant, and by the subsequent use of short focal length aspheric lenses for the focalization of the transformed beam. Each sub-beam is deflected by a couple of plane parallel mirrors, whose normal is directed to equalize the BPP without any mutual shadowing. An optimal solution can be easily envisaged for a laser source of common size of 0.7 x 10 mm. The condition on equal optical path length has the noticeable property of placing the virtual position of the individual portions into which the original beam is split at the same distance with respect to target. Thanks to this, their subsequent focusing is unaffected by the axial displacement of the common solution by the stepped mirrors. In fact, to correct this effect, this latter technique requires the use of a prism pair, involving complexity, size enlargement and higher costs. In this work both an extensive ray tracing and optical analysis is presented as well as the experimental characterization of an experimental model. Moreover, we also report on the technique for the realization of th tilted-face plane mirrors of which is composed our beam shaping device. The scheme of beam shaping here reported can be extended to higher power beam by means of the technique of the beam combination by polarization coupling or that of the optical beam compression. Examples of theses developments are discussed in the paper, and experimental results presented. The most direct applications of the class of optical devices here reported are the high power diode laser direct application in material processing or manufacturing, the coupling into multimode optical

  13. 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

  14. Evaluation the development of focal cerebral ischemia in rats by optical imaging based on the spreading depression signals

    NASA Astrophysics Data System (ADS)

    Chen, Shangbin; Feng, Zhe; Zeng, Shaoqun; Luo, Qingming; Li, Pengcheng

    2007-02-01

    Spreading depression (SD) has been found involved in focal cerebral ischemia which may result in severe or lethal neurological deficits. Electrical recording of SD has been used for acute and long term monitoring of focal cerebral ischemia but with an inherently low resolution. Here, we presented optical intrinsic signal imaging (OISI) to characterize the spontaneous SD waves following permanent middle cerebral artery occlusion (MCAO) in rats with high spatial resolution. During each SD episode, the measured optical reflectance varied regionally: decreased (-12.5+/-2.8%) in the area near the midline, remained flat (3.1+/-2.5%) in the lateral region, and increased (12.1+/-3.6%) in the intermediate cortex. The three types of changes yielded identifications for three biological relevant zones: nonischemic cortex, penumbra and infarct core. Accompanying recurrent SD waves, the suggested penumbral area reduced by about 6.4+/-2.5% of the whole imaged area per SD event, indicating a growth of the infracted area. Staining with 2% 2,3,5-triphenyltetrazolium chloride (TTC) 4 h post-occlusion proved the infarct cortex to be consistent with the lateral region where the final SD wave did not invade (r=0.86+/-0.10). The results suggest that OISI based on SD can effectively used to distinguish nonischemic cortex, penumbra and infarct core in the ischemic hemisphere and monitor the development of ischemia with high spatial resolution.

  15. Study the efficacy of neuroprotective drugs on brain physiological properties during focal head injury using optical spectroscopy data analysis

    NASA Astrophysics Data System (ADS)

    Abookasis, David; Shochat, Ariel

    2016-03-01

    We present a comparative evaluation of five different neuroprotective drugs in the early phase following focal traumatic brain injury (TBI) in mouse intact head. The effectiveness of these drugs in terms of changes in brain tissue morphology and hemodynamic properties was experimentally evaluated through analysis of the optical absorption coefficient and spectral reduced scattering parameters in the range of 650-1000 nm. Anesthetized male mice (n=50 and n=10 control) were subjected to weight drop model mimics real life focal head trauma. Monitoring the effect of injury and neuroprotective drugs was obtained by using a diffuse reflectance spectroscopy system utilizing independent source-detector separation and location. Result indicates that administration of minocycline improve hemodynamic and reduced the level of tissue injury at an early phase post-injury while hypertonic saline treatment decrease brain water content. These findings highlight the heterogeneity between neuroprotective drugs and the ongoing controversy among researchers regarding which drug therapy is preferred for treatment of TBI. On the other hand, our results show the capability of optical spectroscopy technique to noninvasively study brain function following injury and drug therapy.

  16. 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.

  17. Speckle reduction in optical coherence tomography by "path length encoded" angular compounding.

    PubMed

    Iftimia, N; Bouma, B E; Tearney, G J

    2003-04-01

    Speckle, the dominant factor reducing image quality in optical coherence tomography (OCT), limits the ability to identify cellular structures that are essential for diagnosis of a variety of diseases. We describe a new high-speed method for implementing angular compounding by path length encoding (ACPE) for reducing speckle in OCT images. By averaging images obtained at different incident angles, with each image encoded by path length, ACPE maintains high-speed image acquisition and requires minimal modifications to OCT probe optics. ACPE images obtained from tissue phantoms and human skin in vivo demonstrate a qualitative improvement over traditional OCT and an increased SNR that correlates well with theory. PMID:12683852

  18. 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.

  19. Length-adaptive graph search for automatic segmentation of pathological features in optical coherence tomography images

    NASA Astrophysics Data System (ADS)

    Keller, Brenton; Cunefare, David; Grewal, Dilraj S.; Mahmoud, Tamer H.; Izatt, Joseph A.; Farsiu, Sina

    2016-07-01

    We introduce a metric in graph search and demonstrate its application for segmenting retinal optical coherence tomography (OCT) images of macular pathology. Our proposed "adjusted mean arc length" (AMAL) metric is an adaptation of the lowest mean arc length search technique for automated OCT segmentation. We compare this method to Dijkstra's shortest path algorithm, which we utilized previously in our popular graph theory and dynamic programming segmentation technique. As an illustrative example, we show that AMAL-based length-adaptive segmentation outperforms the shortest path in delineating the retina/vitreous boundary of patients with full-thickness macular holes when compared with expert manual grading.

  20. The measurement of the optical cavity length for the Infrared Free-Electron Laser

    SciTech Connect

    C.J. Curtis; J.C. Dahlberg; W.A. Oren; K.J. Tremblay

    1999-10-01

    One of the final tasks involved in the alignment of the newly constructed Free Electron Laser at the Thomas Jefferson National Accelerator Facility was to accurately measure the length between two mirrors which make up the optical cavity. This presentation examines the survey techniques and equipment assembled in order to complete these measurements, together with the possible sources of error, and the accuracy achieved.

  1. 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.

  2. 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

  3. Quasi-optical verification of the focal plane optics of the heterodyne instrument for the far-infrared (HIFI)

    NASA Astrophysics Data System (ADS)

    Candotti, Massimo; Cahill, Gary A.; Finn, Timothy J.; Jellema, Willem; Lavelle, John; Murphy, J. Anthony; O'Sullivan, Creidhe; Trappe, Neil A.

    2004-09-01

    HIFI is one of the three instruments for the Herschel Space Observatory, an ESA cornerstone mission. HIFI is a high resolution spectrometer operating at wavelengths between 157 and 625 µm. The need for a compact layout reducing the volume and mass as much as possible has important consequences for the optical design. Many mirrors are located in the near-field of the propagating beam. Especially in the long wavelength limit diffraction effects might therefore introduce significant amplitude and phase distortions. A classical geometrical optical approach is consequently inadequate. In this paper we present a rigorous quasi-optical analysis of the entire optical system including the signal path, local oscillator path and onboard calibration source optical layout. In order to verify the results of the front-to-end coherent propagation of the detector beams, near-field measurement facilities capable of measuring both amplitude and phase have beam developed. A remarkable feature of these facilities is that the absolute coordinates of the measured field components are known to within fractions of a wavelength. Both measured and simulated fields can therefore compared directly since they are referenced to one single absolute position. We present a comparison of experimental data with software predictions obtained from the following packages: GRASP (Physical Optics Analysis) and GLAD (Plane Wave Decomposition). We also present preliminary results for a method to correct for phase aberrations and optimize the mirror surfaces without changing the predesigned mechanical layout of the optical system.

  4. Depth-encoded synthetic aperture optical coherence tomography of biological tissues with extended focal depth.

    PubMed

    Mo, Jianhua; de Groot, Mattijs; de Boer, Johannes F

    2015-02-23

    Optical coherence tomography (OCT) has proven to be able to provide three-dimensional (3D) volumetric images of scattering biological tissues for in vivo medical diagnostics. Unlike conventional optical microscopy, its depth-resolving ability (axial resolution) is exclusively determined by the laser source and therefore invariant over the full imaging depth. In contrast, its transverse resolution is determined by the objective's numerical aperture and the wavelength which is only approximately maintained over twice the Rayleigh range. However, the prevailing laser sources for OCT allow image depths of more than 5 mm which is considerably longer than the Rayleigh range. This limits high transverse resolution imaging with OCT. Previously, we reported a novel method to extend the depth-of-focus (DOF) of OCT imaging in Mo et al.Opt. Express 21, 10048 (2013)]. The approach is to create three different optical apertures via pupil segmentation with an annular phase plate. These three optical apertures produce three OCT images from the same sample, which are encoded to different depth positions in a single OCT B-scan. This allows for correcting the defocus-induced curvature of wave front in the pupil so as to improve the focus. As a consequence, the three images originating from those three optical apertures can be used to reconstruct a new image with an extended DOF. In this study, we successfully applied this method for the first time to both an artificial phantom and biological tissues over a four times larger depth range. The results demonstrate a significant DOF improvement, paving the way for 3D high resolution OCT imaging beyond the conventional Rayleigh range. PMID:25836528

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  6. 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.

  7. Integrated measurements of acoustical and optical thin layers II: Horizontal length scales

    NASA Astrophysics Data System (ADS)

    Moline, Mark A.; Benoit-Bird, Kelly J.; Robbins, Ian C.; Schroth-Miller, Maddie; Waluk, Chad M.; Zelenke, Brian

    2010-01-01

    The degree of layered organization of planktonic organisms in coastal systems impacts trophic interactions, the vertical availability of nutrients, and many biological rate processes. While there is reasonable characterization of the vertical structure of these phenomena, the extent and horizontal length scale of variation has rarely been addressed. Here we extend the examination of the vertical scale in the first paper of the series to the horizontal scale with combined shipboard acoustic measurements and bio-optic measurements taken on an autonomous underwater vehicle. Measurements were made in Monterey Bay, CA from 2002 to 2008 for the bio-optical parameters and during 2006 for acoustic scattering measurements. The combined data set was used to evaluate the horizontal decorrelation length scales of the bio-optical and acoustic scattering layers themselves. Because biological layers are often decoupled from the physical structure of the water column, assessment of the variance within identified layers was appropriate. This differs from other studies in that physical parameters were not used as a basis for the layer definition. There was a significant diel pattern to the decorrelation length scale for acoustic layers with the more abundant nighttime layers showing less horizontal variability despite their smaller horizontal extent. A significant decrease in the decorrelation length scale was found in bio-optical parameters over six years of study, coinciding with a documented shift in the plankton community. Results highlight the importance of considering plankton behavior and time of day with respect to scale when studying layers, and the challenges of sampling these phenomena.

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

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

    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.

  9. High precision optical cavity length and width measurements using double modulation.

    PubMed

    Staley, A; Hoak, D; Effler, A; Izumi, K; Dwyer, S; Kawabe, K; King, E J; Rakhmanov, M; Savage, R L; Sigg, D

    2015-07-27

    We use doubly phase modulated light to measure both the length and the linewidth of an optical resonator with high precision. The first modulation is at RF frequencies and is set near a multiple of the free spectral range, whereas the second modulation is at audio frequencies to eliminate offset errors at DC. The light in transmission or in reflection of the optical resonator is demodulated while sweeping the RF frequency over the optical resonance. We derive expressions for the demodulated power in transmission, and show that the zero crossings of the demodulated signal in transmission serve as a precise measure of the cavity linewidth at half maximum intensity. We demonstrate the technique on two resonant cavities, with lengths 16 m and a 4 km, and achieve an absolute length accuracy as low as 70 ppb. The cavity width for the 16 m cavity was determined with an accuracy of approximately 6000 ppm. Through an analysis of the systematic errors we show that this result could be substantially improved with the reduction of technical sources of uncertainty. PMID:26367601

  10. 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.

  11. Remote acute demyelination after focal proton radiation therapy for optic nerve meningioma.

    PubMed

    Redjal, Navid; Agarwalla, Pankaj K; Dietrich, Jorg; Dinevski, Nikolaj; Stemmer-Rachamimov, Anat; Nahed, Brian V; Loeffler, Jay S

    2015-08-01

    We present a unique patient with delayed onset, acute demyelination that occurred distant to the effective field of radiation after proton beam radiotherapy for an optic nerve sheath meningioma. The use of stereotactic radiotherapy as an effective treatment modality for some brain tumors is increasing, given technological advances which allow for improved targeting precision. Proton beam radiotherapy improves the precision further by reducing unnecessary radiation to surrounding tissues. A 42-year-old woman was diagnosed with an optic nerve sheath meningioma after initially presenting with vision loss. After biopsy of the lesion to establish diagnosis, the patient underwent stereotactic proton beam radiotherapy to a small area localized to the tumor. Subsequently, the patient developed a large enhancing mass-like lesion with edema in a region outside of the effective radiation field in the ipsilateral frontal lobe. Given imaging features suggestive of possible primary malignant brain tumor, biopsy of this new lesion was performed and revealed an acute demyelinating process. This patient illustrates the importance of considering delayed onset acute demyelination in the differential diagnosis of enhancing lesions in patients previously treated with radiation. PMID:25937571

  12. 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.

  13. 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.

  14. Simultaneous measurement of the root-mean-square roughness and autocorrelation length by optical method

    NASA Astrophysics Data System (ADS)

    Kim, Dalwoo; Oh, Ki-Jang; Lim, Choong-Soo

    1998-12-01

    We developed an on-line measurement system for the simultaneous measurement of the root-mean-square roughness and autocorrelation length which are the parameters of surface roughness. The measurement is based on the scattering theory of light on the rough surface. Computer simulation shows that the measurement range depends on the wavelength of the light source, and this is verified with the experiment. We installed the measurement system at the finishing line of a cold-rolling steel work, and measured the two parameters in situ. The rms roughness and autocorrelation length are measured and transformed in the average surface roughness and then umber of peaks per inch, respectively. The measured data for both of the parameters are compared with those of stylus method, an the optical method is well coincided with the conventional stylus method.

  15. Quantification of choroidal neovascularization vessel length using optical coherence tomography angiography

    NASA Astrophysics Data System (ADS)

    Gao, Simon S.; Liu, Li; Bailey, Steven T.; Flaxel, Christina J.; Huang, David; Li, Dengwang; Jia, Yali

    2016-07-01

    Quantification of choroidal neovascularization (CNV) as visualized by optical coherence tomography angiography (OCTA) may have importance clinically when diagnosing or tracking disease. Here, we present an automated algorithm to quantify the vessel skeleton of CNV as vessel length. Initial segmentation of the CNV on en face angiograms was achieved using saliency-based detection and thresholding. A level set method was then used to refine vessel edges. Finally, a skeleton algorithm was applied to identify vessel centerlines. The algorithm was tested on nine OCTA scans from participants with CNV and comparisons of the algorithm's output to manual delineation showed good agreement.

  16. The optical length effect, diffraction pattern and thermal lensing of Disperse Orange 25

    NASA Astrophysics Data System (ADS)

    Salmani, S.; Ara, M. H. Majles

    2016-08-01

    The nonlinear responses of an azo dye, Disperse Orange 25 (DO25), are investigated under two irradiation of continuous Lasers at 532 and 632 nm wavelengths and the third order refractive index is measured by use of Z-scan technique. At 632 nm wavelength (far from the absorption peak), the close z-scan plots show that this material has a very good nonlinear response with negative sign indicating self-defocusing. The effect of optical length and concentration of samples in nonlinear responses have been investigated experimentally. Also, the radius variation at far field observed due to thermal lens effect. Finally, at other wavelength, 532 nm (near from the absorption peak), the nonlinear optical responses increase sharply so the diffraction rings appear and the numbers of rings increase with the incident laser power.

  17. Effects of varying surfactant chain lengths on the magnetic, optical and hyperthermia properties of ferrofluids

    NASA Astrophysics Data System (ADS)

    Rablau, Corneliu; Vaishnava, Prem; Regmi, Rajesh; Sudakar, Chandran; Black, Correy; Lawes, Gavin; Naik, Ratna; Lavoie, Melissa; Kahn, David

    2009-03-01

    We report studies of the structural, magnetic, magneto-thermal and magneto-optic properties of dextran, oleic acid, lauric acid and myristic acid surfacted Fe3O4 nanoparticles of hydrodynamic sizes ranging from 32 nm to 92 nm. All the samples showed saturation magnetization of ˜50 emu/g, significantly smaller than the bulk value for Fe3O4, together with superparamagnetic behavior. The ac magnetization measurements on the dextran coated nanoparticles showed frequency dependent blocking temperature, consistent with superparamgnetic blocking. The ferrofluid heating rates in a 250 Gauss, 100 kHz ac magnetic field varied with the chain lengths of the surfactants, with higher heating rates for longer chains. DC-magnetic-field-induced light scattering patterns produced by two orthogonal He-Ne laser beams passing through the ferrofluid sample revealed different optical signatures for different surfactants.

  18. Correlation of Retinal Nerve Fiber Layer Thickness and Axial Length on Fourier Domain Optical Coherence Tomography

    PubMed Central

    Dhasmana, Renu; Nagpal, R.C.

    2016-01-01

    Introduction The assessment of the peripapillary Retinal Nerve Fiber Layer (RNFL) thickness has been an important tool for evaluating and diagnosing glaucoma and its progression. Literature suggests that myopic eyes are at an increased risk for developing glaucoma. This study gives an insight into the relationship of RNFL thickness to the axial length in normal population. Aim To correlate the RNFL thickness and the axial length in normal individuals with Fourier domain Optical Coherence Tomography (OCT). Materials and Methods In the current study, 298 eyes of 149 normal individuals (10 years or older) with or without refractive error were recruited. The RNFL thickness was measured using Optovue (RTVue) three-dimensional Fourier domain OCT. Results We observed an inverse relationship between average RNFL thickness and increasing axial length(p=0.003). Maximum RNFL thickness was seen in the Infero-Temporal (IT) quadrant and minimum in the Supero-Nasal (SN) quadrant. RNFL thickness did not show any tendency to decline with age using the Pearsons correlation (r=0.07). Females had an increased RNFL thickness in the Supero-Temporal (ST) and Infero-Nasal (IN) quadrant (p-value 0.046 and 0.02) in comparison to males. There was a statistically significant thinning in Ganglion Cell Complex (GCC) with increasing axial length (p-value 0.000) Conclusion The current study suggests that the average RNFL thickness does not decrease with age. The RNFL and GCC thickness shows an inverse correlation with axial length of the eyeball hence observations have to be carefully interpreted in myopic eyes. Clinicians need to keep the anatomical variations in RNFL for better patient management. PMID:27190850

  19. 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

  20. 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

  1. Modelling and implementation of a fixed-length-extension to measure fluorescent intensity in bioprocesses using an optical sensor

    NASA Astrophysics Data System (ADS)

    Sardesai, Neha; Al-Adhami, Mustafa; Rao, Govind; Kostov, Yordan

    2016-05-01

    Fluorescent proteins are often used as reporters of protein concentration in biology and biomedicine applications. They can be detected using a fluorimeter equipped with fiber optics for ease of access. However, small changes in the path length due to change in the position, or immersion depth of the optical fiber results in large changes in readings. To alleviate the situation, the fiber is equipped with a fixed-length-extension that provides constant path length. The operation of the fiber equipped fluorimeter is theoretically modelled and practically verified in this paper.

  2. DIC image reconstruction using an energy minimization framework to visualize optical path length distribution

    PubMed Central

    Koos, Krisztian; Molnár, József; Kelemen, Lóránd; Tamás, Gábor; Horvath, Peter

    2016-01-01

    Label-free microscopy techniques have numerous advantages such as low phototoxicity, simple setup and no need for fluorophores or other contrast materials. Despite their advantages, most label-free techniques cannot visualize specific cellular compartments or the location of proteins and the image formation limits quantitative evaluation. Differential interference contrast (DIC) is a qualitative microscopy technique that shows the optical path length differences within a specimen. We propose a variational framework for DIC image reconstruction. The proposed method largely outperforms state-of-the-art methods on synthetic, artificial and real tests and turns DIC microscopy into an automated high-content imaging tool. Image sets and the source code of the examined algorithms are made publicly available. PMID:27453091

  3. 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.

  4. Influence of the word length and input power on nonlinear crosstalk induced by hybrid optical amplifiers

    NASA Astrophysics Data System (ADS)

    Singh, Simranjit; Kaler, R. S.

    2013-10-01

    In this paper, the influence of the word length (WL) of a pseudo-random bit sequence (PRBS) and the input laser power on nonlinear crosstalk induced by the different hybrid optical amplifiers (HOAs) has been examined. It is found that the crosstalk is strongly dependent on the WL and very sensitive to the relative powers of the input signals at 0.2 nm and 0.4 nm of the channel spacing. It is shown that the proposed hybrid Raman-EDFA induces lesser crosstalk as compared to other HOAs. The performance of Raman-EDFA HOA is also investigated for 16 × 10 Gbps dense wavelength division multiplexed (DWDM) system at 0.2 nm of channel spacing.

  5. DIC image reconstruction using an energy minimization framework to visualize optical path length distribution.

    PubMed

    Koos, Krisztian; Molnár, József; Kelemen, Lóránd; Tamás, Gábor; Horvath, Peter

    2016-01-01

    Label-free microscopy techniques have numerous advantages such as low phototoxicity, simple setup and no need for fluorophores or other contrast materials. Despite their advantages, most label-free techniques cannot visualize specific cellular compartments or the location of proteins and the image formation limits quantitative evaluation. Differential interference contrast (DIC) is a qualitative microscopy technique that shows the optical path length differences within a specimen. We propose a variational framework for DIC image reconstruction. The proposed method largely outperforms state-of-the-art methods on synthetic, artificial and real tests and turns DIC microscopy into an automated high-content imaging tool. Image sets and the source code of the examined algorithms are made publicly available. PMID:27453091

  6. Revisiting binary sequence length requirements to accurately emulate optical transmission systems in highly dispersive regime

    NASA Astrophysics Data System (ADS)

    Grellier, Edouard; Antona, Jean-Christophe; Bononi, Alberto; Bigo, Sébastien

    2008-11-01

    When increasing channel bit rate beyond 10Gb/s or when operating over fiber lines with sparse or no in-line dispersion compensation, Kerr-like non-linear effects can be considered as second order with respect to dispersive effects, because pulse broadening can expand over numerous neighbor pulses, before optical non-linear effects imprint their signature noticeably. To accurately emulate the interactions between pulses in this case, a few studies emphasized that Pseudo- Random Binary Sequences (PRBS) should be used, with exponential dependence of the required PRBS length on bit rate and accumulated dispersion. In this paper, we explain our strategy to numerically estimate the required number of random, noisy bits for Monte-Carlo simulations, and show that it weakly increases in presence of pulse to pulse correlations and commonly tolerated levels of non-linearities (i.e. leading to transmission penalties as high as 1.5dB, for reference BERs of 10-2, 10-3 or 10-5) . Then we determine the actual required PRBS length that yields the same (sufficient) BER accuracy as the MC method. We demonstrate its actual dependence on BER, and show that MC theory provides a reliable upper bound in FEC-assisted, highly dispersive systems.

  7. High power coatings for line beam laser optics of up to 2-meter in length

    NASA Astrophysics Data System (ADS)

    Mende, Mathias; Kohlhaas, Jürgen; Ebert, Wolfgang

    2016-03-01

    Laser material processing plays an important role in the fabrication of the crucial parts for state-of-the-art smartphones and tablets. With industrial line beam systems a line shaped beam with a length above one meter and an average power of several thousand watts can be realized. To ensure excellent long axis beam homogeneity, demanding specifications regarding the substrate surface form tolerances and the coating uniformity have to be achieved for each line beam optic. In addition, a high laser damage threshold and a low defect density are required for the coatings. In order to meet these requirements, the MAXIMA ion beam sputtering machine was developed and built by LASEROPTIK. This contribution describes the functional principle of MAXIMA deposition machine, which adapts the ion beam sputtering technology with its highest coating quality to the field of large area deposition. Furthermore, recent developments regarding the process control by optical broadband monitoring are discussed. Finally experimental results on different thin film characteristics as for example the coating uniformity, the microstructure and the laser damage resistance of multilayers are presented.

  8. 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.

  9. 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

  10. 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; Moroté, Fabien; Jaillet, Christèle; 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.

  11. Power and length requirements for all-optical switching in semiconductor-doped glass waveguides

    NASA Astrophysics Data System (ADS)

    Mayweather, Derek T.; Digonnet, Michel J. F.; Pantell, Richard H.; Shaw, H. J.

    1994-10-01

    We present a theoretical model that computes the nonlinear index (n2) of semiconductor- doped glasses (SDG), based on the material's properties, and predicts the power and length requirements, as well as the optimum operating wavelengths, for an all-optical SDG waveguide switch. The main conclusions are that (1) n2 depends strongly on pump intensity, which partly explains the large disparity in reported values of n2, (2) the pump and signal wavelengths should be in specific and different ranges to minimize switching power and signal loss, (3) for CdSSe- and CdTe-doped glasses, n2 is relatively small, and the switching power requirement for these two SDGs is consequently quite high (2 - 16 W). We provide evidence that this weak nonlinearity, compared to that of similar semiconductors in bulk, is due to the strong nonradiative recombination of carriers arising from the small size of the semiconductor microcrystallites. Projections indicate that the switching power would be reduced by up to three orders of magnitude by increasing the microcrystallite size, thus producing a slower (ns) but more power-efficient switch.

  12. Determination of the diffusion length and the optical self absorption coefficient using EBIC model

    NASA Astrophysics Data System (ADS)

    Guermazi, S.; Guermazi, H.; Mlik, Y.; El Jani, B.; Grill, C.; Toureille, A.

    2001-10-01

    We have developed a model of calculation of the induced current due to an electron beam. The expression for the electron beam induced current (EBIC) with an extended generation profile is obtained via the resolution of a steady state continuity equation by the Green function method, satisfying appropriated boundary conditions to the physical model. The generation profile takes into account the lateral diffusion, the effect of defects, dislocations and recombination surfaces besides the number of absorbed electrons and that of diffuse electrons as a function of the depth. In the case of a Schottky diode Au/GaAs obtained by metalorganic vapour phase epitaxy (MOVPE) method, the theoretical induced current profile is compared to the experimental one and to theoretical profiles whose analytical expressions are given by van Roosbroeck and Bresse. The minority carriers diffusion length L_n = 2 μm and the optical self-absorption coefficient a=0.034 μm^{-1} can be deduced from the experimental current profile, measured by scanning electron microscopy. The theoretical curve, obtained from the proposed model is in a good agreement with the experimental one for surface recombination velocity 10^6 cm s^{-1} except for distances far from the depletion layer (x_0 > 2.3 μm) where the photocurrent produced by the multiple process of the reabsorbed recombination radiation is preponderant. Our results are in agreement with those obtained by other experimental techniques on the same samples.

  13. 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

  14. 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.

  15. 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

  16. 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

  17. CO2 laser beam propagation with ZnSe optics

    NASA Astrophysics Data System (ADS)

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

    Beam propagation characteristics of ZnSe optics used in kiloWatt power CO2 laser aided material processing applications are determined using the Prometec Laser Beam Analyzer. The laser used was a Rofin Sinar RS6000 CO2 laser with mode aperturing. Beam power varied from 500W to 6300W and beam modes used were TEM(sub 00), TEM(sub 01), TEM(sub 10), and TEM(sub 20). Both transmissive and reflective optics were examined. The ZnSe lenses tested included meniscus, diffractive, and cylindrical lenses of 5 in. focal length and a 10 in. focal length integrating lens. Reflective optics included an integrator and a 5 in. focal length parabolic mirror for welding. Parameters obtained included beam propagation profiles, intensity profiles, depth of focus, spot size, and back focal length. A subset of the data obtained is presented here. Details of the work will appear in a full length paper.

  18. 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

  19. 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.

  20. 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.

  1. Optical pressure/acoustic sensor with precise Fabry-Perot cavity length control using angle polished fiber.

    PubMed

    Wang, Wenhui; Wu, Nan; Tian, Ye; Wang, Xingwei; Niezrecki, Christopher; Chen, Julie

    2009-09-14

    This paper presents a novel Fabry-Perot (FP) optical fiber pressure/acoustic sensor. It consists of two V-shaped grooves having different sized widths, a diaphragm on the surface of the larger V-groove, and a 45 degrees angle-polished fiber. The precision of FP cavity length is determined by the fabrication process of photolithography and anisotropic etching of a silicon crystal. Therefore, the cavity length can be controlled on the order of ten nm. Sensors were fabricated and tested. Test results indicate that the sensors' cavity lengths have been controlled precisely. The packaged sensor has demonstrated very good static and dynamic responses compared to a commercially available pressure sensor and a microphone. PMID:19770876

  2. 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.

  3. Compact color schlieren optical system

    NASA Technical Reports Server (NTRS)

    Buchele, Donald R.; Griffin, Devon W.

    1993-01-01

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

  4. Integration of advanced optical functions on the focal plane array for very compact MCT-based micro cameras

    NASA Astrophysics Data System (ADS)

    Fendler, Manuel; Lasfargues, Gilles; Bernabé, S.; Druart, Guillaume A.; de La Barriere, Florence; Rommeluere, Sylvain; Guérineau, Nicolas; Lhermet, Nicolas; Ribot, Hervé

    2010-04-01

    Over the past decade, several technological breakthroughs have been achieved in the field of optical detection, in terms of spatial and thermal resolutions. The actual trend leads to the integration of new functions at the vicinity of the detector. This paper presents two types of integrated optics in the cryo-cooler, close to the MCT (CdHgTe) infrared detector array. The first one, for spectro-imaging applications, is a Fourier-transform microspectrometer on chip (MICROSPOC), developed for very fast acquisition of spectral signatures. Experimental results will be presented. The second one, for large field of view applications, illustrates the high potentiality of the integration of advanced optical functions in the Dewar of MCT detectors.

  5. Synthesis and Optical Properties of PbSe Nanorods with Controlled Diameter and Length.

    PubMed

    Placencia, Diogenes; Boercker, Janice E; Foos, Edward E; Tischler, Joseph G

    2015-09-01

    The synthesis of PbSe nanorods with low branching (<1%), high aspect ratios (up to ∼16), and controlled lengths and diameters was demonstrated via the removal of water and oleic acid from the synthesis precursors. It was determined that the proper combination of reaction time and temperature allows for the control of PbSe nanorod length and diameter and therefore control over their electronic states, as probed through absorbance and photoluminescence measurements. Similar to PbSe nanowires, nanorods display higher Stokes shifts than for spherical nanocrystals due to intrananorod diameter fluctuations. PMID:26267558

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-06-01

    Two optical techniques for the determination of a bipolar diffusion length LD of optically excited carriers in GaN epitaxial layers, namely a time-resolved picosecond four-wave mixing (FWM) on free carrier grating and time-integrated photoluminescence (PL) are presented and examined. The PL technique is based on time-integrated photoluminescence (PL) spectra measurements from the front and back sides of the sample under cw and nanosecond pulsed laser excitation. The another method utilizes time-resolved picosecond four-wave mixing (FWM) at various light-induced grating periods to extract diffusion coefficient and carrier recombination lifetime. The value of the diffusion length derived by means of FWM decreases with GaN layer thickness from LD = 260 nm (for 1.7 m-thick layer) to LD = 100 nm (for 0.3 m-thick layer). The integral PL measurements give the value of LD = 120-130 nm for the 620 nm layer under pulsed excitation intensities up to 200 kW/cm2. It increases to 150-170 nm at the excitation intensity enhancement to 1 MW/cm2. These values are close to the value of the diffusion length equal to 160 nm obtained using FWM for this layer thickness evidencing the compatibility of both methods. The changes in the value of LD are discussed in terms of the defect distribution in the epitaxial GaN layer.

  8. 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.

  9. 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

  10. 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.

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

    PubMed Central

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

    2012-01-01

    Abstract: An optical switch was implemented in the reference arm of an extended depth SD-OCT system to sequentially acquire OCT images at different depths into the eye ranging from the cornea to the retina. A custom-made accommodation module was coupled with the delivery of the OCT system to provide controlled step stimuli of accommodation and disaccommodation that preserve ocular alignment. The changes in the lens shape were imaged and ocular distances were dynamically measured during accommodation and disaccommodation. The system is capable of dynamic in vivo imaging of the entire anterior segment and eye-length measurement during accommodation in real-time. PMID:22808424

  12. Design of an Airborne Scanning Lidar Using a Holographic Optical Element

    NASA Technical Reports Server (NTRS)

    Schwemmer, Geary K.; Hopf, Dan; Neuman, Mark; Kubalak, David; Christhilif, Ellen; Hasselbrack, William; Ranganayakamma, Belthur; Kim, Jin; Hwang, I. H.

    1998-01-01

    An aerosol and cloud backscatter lidar system has been built using a one meter focal length transmission holographic optical element that functions as a scanning telescope. Rotating the disk about the center line normal effects a 45 degree conical scan.

  13. On the path length of an excess electron interacted with optical phonons in a molecular chain

    NASA Astrophysics Data System (ADS)

    Lakhno, V. D.

    2008-08-01

    We show that in a molecular chain with dispersionless phonons at zero temperature, a “quasistationary” moving soliton state of an excess electron is possible. As the soliton velocity vanishes, the path length of the excess electron exponentially tends to infinity. It is demonstrated that in the presence of dispersion, when the soliton initial velocity exceeds the maximum group velocity of the chain, the soliton slows down until it reaches the maximum group velocity and then moves stationarily at this maximum group velocity. A conclusion is made of the fallacy of some works were the existence of moving polarons in a dispersionless medium is considered infeasible.

  14. 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

  15. 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.

  16. Location of Tessellations in Ocular Fundus and Their Associations with Optic Disc Tilt, Optic Disc Area, and Axial Length in Young Healthy Eyes

    PubMed Central

    Terasaki, Hiroto; Yamashita, Takehiro; Yoshihara, Naoya; Kii, Yuya; Tanaka, Minoru; Nakao, Kumiko; Sakamoto, Taiji

    2016-01-01

    Tessellated fundus is found as common and early-phase characteristic of myopic eyes and their locations are varied among patients. However, the relationship between their locations and morphological parameters of the eyes is still unknown. The purpose is this study is to determine the locations of the tessellations in the ocular fundus of young healthy eyes, and to determine relationships between their locations and morphological parameters of the eyes. This is a prospective observational cross sectional study of 126 eyes of 126 healthy volunteers (mean age 26.0±4.1 years). The eyes were classified into eight groups based on the location of the tessellations; no tessellation, temporal, infra-temporal, inferior, nasal, peripapillary, whole retina, and unclassified tessellations. The degree of optic disc tilt was quantified using a sine curve fitting program on the optical coherence tomographic circle scan images. The correlations between each tessellation location and the axial length, area of the optic disc plus conus (AOC), and optic disc tilt were determined. Forty-four eyes were place in the no tessellation group, 12 eyes in the temporal, 21 eyes in the infra-temporal, 9 eyes in the inferior, 8 eyes in the nasal, 15 eyes in the peripapillary, 11 eyes in the whole, and 6 eyes in the unclassified groups. The differences in the axial lengths between the no tessellation group and the infra-temporal groups were significant. A significant difference was found in the AOC between the no tessellation and the inferior, infra-temporal, and peripapilalry groups. A significant difference was found in the optic disc tilt between the no tessellation and infra-temporal groups (P<0.05). The tessellations are located at specific sites in the fundus of young healthy eyes with the infra-temporal location most frequent. It was correlated with some parameters associated with myopia. PMID:27275584

  17. Location of Tessellations in Ocular Fundus and Their Associations with Optic Disc Tilt, Optic Disc Area, and Axial Length in Young Healthy Eyes.

    PubMed

    Terasaki, Hiroto; Yamashita, Takehiro; Yoshihara, Naoya; Kii, Yuya; Tanaka, Minoru; Nakao, Kumiko; Sakamoto, Taiji

    2016-01-01

    Tessellated fundus is found as common and early-phase characteristic of myopic eyes and their locations are varied among patients. However, the relationship between their locations and morphological parameters of the eyes is still unknown. The purpose is this study is to determine the locations of the tessellations in the ocular fundus of young healthy eyes, and to determine relationships between their locations and morphological parameters of the eyes. This is a prospective observational cross sectional study of 126 eyes of 126 healthy volunteers (mean age 26.0±4.1 years). The eyes were classified into eight groups based on the location of the tessellations; no tessellation, temporal, infra-temporal, inferior, nasal, peripapillary, whole retina, and unclassified tessellations. The degree of optic disc tilt was quantified using a sine curve fitting program on the optical coherence tomographic circle scan images. The correlations between each tessellation location and the axial length, area of the optic disc plus conus (AOC), and optic disc tilt were determined. Forty-four eyes were place in the no tessellation group, 12 eyes in the temporal, 21 eyes in the infra-temporal, 9 eyes in the inferior, 8 eyes in the nasal, 15 eyes in the peripapillary, 11 eyes in the whole, and 6 eyes in the unclassified groups. The differences in the axial lengths between the no tessellation group and the infra-temporal groups were significant. A significant difference was found in the AOC between the no tessellation and the inferior, infra-temporal, and peripapilalry groups. A significant difference was found in the optic disc tilt between the no tessellation and infra-temporal groups (P<0.05). The tessellations are located at specific sites in the fundus of young healthy eyes with the infra-temporal location most frequent. It was correlated with some parameters associated with myopia. PMID:27275584

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. Fourier transform-limited optical frequency-modulated continuous-wave interferometry over several tens of laser coherence lengths.

    PubMed

    Xie, Weilin; Zhou, Qian; Bretenaker, Fabien; Xia, Zongyang; Shi, Hongxiao; Qin, Jie; Dong, Yi; Hu, Weisheng

    2016-07-01

    We report on a versatile optical frequency-modulated continuous-wave interferometry technique that exploits wideband phase locking for generating highly coherent linear laser frequency chirps. This technique is based on an ultra-short delay-unbalanced interferometer, which leads to a large bandwidth, short lock time, and robust operation even in the absence of any isolation from environmental perturbations. In combination with a digital delay-matched phase error compensation, this permits the achievement of a range window about 60 times larger than the intrinsic laser coherence length with a 1.25 mm Fourier transform-limited spatial resolution. The demonstrated configuration can be easily applied to virtually any semiconductor laser. PMID:27367076

  5. 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.

  6. Carrier diffusion length measured by optical method in GaN epilayers grown by MOCVD on sapphire substrates

    NASA Astrophysics Data System (ADS)

    Yablonskii, G. P.; Gurskii, A. L.; Pavlovskii, V. N.; Lutsenko, E. V.; Zubialevich, V. Z.; Shulga, T. S.; Stognij, A. I.; Kalisch, H.; Szymakowski, A.; Jansen, R. H.; Alam, A.; Schineller, B.; Heuken, M.

    2005-02-01

    The carrier ambipolar diffusion length L of optically excited carriers in GaN epitaxial layers grown on sapphire substrate was estimated by an optical method using fitting of the experimental photoluminescence spectra recorded from the front and back sides of the samples by the theoretical equation describing light reflection, light absorption and carrier profile in the medium. The estimations were carried out in the range of excitation intensities from 5 W/cm 2 CW up to 1 MW/cm 2 (pulsed), using excitation at the wavelengths of 325, and 337.1 nm in order to vary the excited layer depth. It has been found that in the samples under study the value of L is about 120-130 nm and does not depend significantly on the excitation intensity up to 200 kW/cm 2. Further increase of excitation level leads to higher values of L about 150-170 nm, probably because of the electron-hole plasma expansion.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

    Mehrabian, Masood; Mirabbaszadeh, Kavoos; Afarideh, Hossein

    2013-12-01

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

  9. 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

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

    PubMed

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

    2014-02-15

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

  11. Application of optical design software in the analysis of "unknown" optical systems

    NASA Astrophysics Data System (ADS)

    Roudnicky, Dunja S.

    1998-08-01

    Optical design software is not very usable in designing new optical systems only, but also in analysis of `unknown' systems. When measurements of radii of curvature, focal lengths and axial thickness of elements are done, we use SIGMA 2100 Optical design software (Kidger Optics). We determine which optical glass fits the nearest measured focal length of each element. We also get aberration curves of elements and the whole system. In such a way we analyze elements of an eyepiece which is the part of a compound panoramic sight. Since we now have all specifications of this eyepiece, it is possible to optimize glasses and radii to the more convenient ones, without a risk to change the performance of the whole optical system. This method gives us a possibility of reparation and adaptation of `unknown' optical systems with a high yield.

  12. Dynamic photophoresis-based optical trapping using a spatial light modulator

    NASA Astrophysics Data System (ADS)

    Porfirev, Aleksey P.; Skidanov, Roman V.

    2016-04-01

    We investigate optical trapping light-absorbing particles in the air employing photophoretic forces with optical tweezers generated by a spatial light modulator (SLM). SLM gives us the opportunity to form optical tweezers for multiple trapping in several planes. We investigate the possibility of using lenses with various focal lengths for trapping light-absorbing microparticles with the SLM. We used lenses with a large focal length and a large depth of focus. The results shown in this paper could be useful in various applications of optics and biology.

  13. Axial length measurements before and after removal of silicone oil: a new method to correct the axial length of silicone-filled eyes for optical biometry.

    PubMed

    Wang, Kai; Yuan, Meng-Ke; Jiang, Yan-Rong; Bao, Yong-Zhen; Li, Xiao-Xin

    2009-07-01

    A total of 67 eyes of 67 patients that have undergone vitrectomy and silicone oil tamponade for rhegmatogenous retinal detachment were included in this prospective clinical study. We measured the axial length (AL) and the anterior chamber depth (ACD) with A-mode ultrasonography and IOL Master before and after removal of silicone oil. Phase refractive indices of silicone oil at different wavelengths from 400 nm to 1000 nm were measured with an Abbe refractometer and a series of equations were derived to adjust the AL values obtained with the IOL Master in silicone-filled eyes. The instruments showed good agreement between the AL values measured before and after removal of silicone oil. The ACD values obtained with A-mode ultrasonography were lower than the values obtained with the IOL Master (p < 0.01). The AL values obtained with the IOL Master after removal of silicone oil were lower than the values obtained preoperatively (p < 0.01). The AL values obtained with the IOL Master after adjustment are more accurate than A-mode ultrasonography in silicone-filled eyes. PMID:19523089

  14. Compact color schlieren optical system.

    PubMed

    Buchele, D R; Griffin, D W

    1993-08-01

    A compact optical system for use with rainbow schlieren deflectometry is described. Both halves of the optical system consist of well-corrected telescopes whose refractive elements are all from manufacturer's stock catalogs, with the reflective primary being a spherical surface. As a result, the system is relatively easy to construct and meets the requirement of long focal length for quantitative rainbow schlieren measurements. PMID:20830072

  15. 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.

  16. Mosaic Focal Plane Development

    NASA Astrophysics Data System (ADS)

    Mason, David L.; Horner, Scott D.; Aamodt, Earl K.

    2002-12-01

    Advances in systems engineering, applied sciences, and manufacturing technologies have enabled the development of large ground based and spaced based astronomical instruments having a large Field of View (FOV) to capture a large portion of the universe in a single image. A larger FOV can be accomplished using light weighted optical elements, improved support structures, and the development of mosaic Focal Plane Assemblies (mFPA). A mFPA designed for astronomy can use multiple Charged Coupled Devices (CCD) mounted onto a single camera baseplate integrated at the instrument plane of focus. Examples of current, or proposed, missions utilizing mFPA technology include FAME, GEST, Kepler, GAIA, LSST, and SNAP. The development of a mFPA mandates tighter control on the design trades, component development, CCD characterization, component integration, and performance verification testing. This paper addresses the capability Lockheed Martin Space Systems Company's (LMSSC) Advanced Technology Center (ATC) has developed to perform CCD characterization, mFPA assembly and alignment, and mFPA system level testing.

  17. Mosaic Focal Plane Development

    NASA Astrophysics Data System (ADS)

    Mason, D.; Horner, S.; Aamodt, E.

    Advances in manufacturing and applied sciences have enabled the development of large ground and spaced based astronomical instruments having a Field of View (FOV) large enough to capture a large portion of the universe in a single image. A large FOV can be accomplished using light weighted optics, improved structures, and the development of mosaic Focal Plane Assemblies (mFPAs). A mFPA comprises multiple Charged Coupled Devices (CCD) mounted onto a single baseplate integrated at the focus plane of the instrument. Examples of current, or proposed, missions utilizing mFPA technology include FAME, GEST, Kepler, GAIA, LSST, and SNAP. The development of a mFPA mandates tight control on the design trades of component development, CCD definition and characterization, component integration, and performance verification testing. This paper addresses the results of the Lockheed Martin Space Systems Company (LMSSC), Advanced Technology Center (ATC) developed mFPA. The design trades and performance characterization are services provided by the LMSSC ATC but not detailed in this paper.

  18. Hybrid Extrinsic Silicon Focal Plane Architecture

    NASA Astrophysics Data System (ADS)

    Pommerrenig, D. H.; Meinhardt, T.; Lowe, J.

    1981-02-01

    Large-area focal planes require mechanical assembly techniques which must be compatible with optical alignment, minimum deadspace, and cryogenic requirements in order to achieve optimum performance. Hybrid extrinsic silicon has been found particularly suitable for such an application. It will be shown that by choosing a large-area extrinsic silicon detector array which is hybrid-mated to a multiplicity of multiplexers a very cost-effective and high-density focal plane module can be assembled. Other advantages of this approach are inherent optical alignment and excellent performance.

  19. 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.

  20. Making the ATHENA optics using silicon pore optics

    NASA Astrophysics Data System (ADS)

    Collon, Maximilien J.; Ackermann, Marcelo; Günther, Ramses; Chatbi, Abdelhakim; Vacanti, Giuseppe; Vervest, Mark; Yanson, Alex; Beijersbergen, Marco W.; Bavdaz, Marcos; Wille, Eric; Haneveld, Jeroen; Olde Riekerink, Mark; Koelewijn, Arenda; van Baren, Coen; Müller, Peter; Krumrey, Michael; Burwitz, Vadim; Sironi, Giorgia; Ghigo, Mauro

    2014-07-01

    Silicon Pore Optics, after 10 years of development, forms now the basis for future large (L) class astrophysics Xray observatories, such as the ATHENA mission to study the hot and energetic universe, matching the L2 science theme recently selected by ESA for launch in 2028. The scientific requirements result in an optical design that demands high angular resolution (5") and large effective area (2 m2 at a few keV) of an X-ray lens with a focal length of 12 to14 m. Silicon Pore Optics was initially based on long (25 to 50 m) focal length telescope designs, which could achieve several arc second angular resolution by curving the silicon mirror in only one direction (conical approximation). With the advent of shorter focal length missions we started to develop mirrors having a secondary curvature, allowing the production of Wolter-I type optics, which are on axis aberration-free. In this paper we will present the new manufacturing process, discuss the impact of the ATHENA optics design on the technology development and present the results of the latest X-ray test campaigns.

  1. Focal neurological deficits

    MedlinePlus

    A focal neurologic deficit is a problem with nerve, spinal cord, or brain function. It affects a specific ... of the back, neck, or head Electromyogram (EMG)/ nerve conduction velocities (NCV) MRI of the back, neck, or head Spinal tap

  2. 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. ...

  3. 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 ... Practice . 7th ed. Philadelphia, PA: Elsevier; 2016:chap 101. ...

  4. 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

  5. Quantitative measurement of acoustic pressure in the focal zone of acoustic lens-line focusing using the Schlieren method.

    PubMed

    Jiang, Xueping; Cheng, Qian; Xu, Zheng; Qian, Menglu; Han, Qingbang

    2016-04-01

    This paper proposes a theory and method for quantitative measurement of the acoustic lens-line focusing ultrasonic (ALLFU) field in its focal spot size and acoustic pressure using the Schlieren imaging technique. Using Fourier transformation, the relationship between the brightness of the Schlieren image and the acoustic pressure was introduced. The ALLFU field was simulated using finite element method and compared with the Schlieren acoustic field image. The measurement of the focal spot size was performed using the Schlieren method. The acoustic pressure in the focal zone of the ALLFU field and the transducer-transmitting voltage response were quantitatively determined by measuring the diffraction light fringe intensity. The results show that the brightness of the Schlieren image is a linear function of the acoustic intensity when the acousto-optic interaction length remains constant and the acoustic field is weak. PMID:27139646

  6. 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.

  7. Joint FDTD-Optical/FEM-Electrical Numerical Simulation of Reflection-Type Subwavelength-Microstructure InSb Infrared Focal-Plane Arrays

    NASA Astrophysics Data System (ADS)

    He, J. L.; Hu, W. D.; Ye, Z. H.; Lv, Y. Q.; Chen, X. S.; Lu, W.

    2016-09-01

    The design of a reflection-type subwavelength microstructure has been numerically investigated to concentrate incident light onto pixels for improved photoresponse of InSb infrared focal-plane arrays. Compared with traditional microlenses placed on top of the detector substrate, this reflection-type microstructure is better suited for extremely small pixel pitches. The structure is simulated using a joint numerical method combining the finite-difference time-domain method based on Maxwell's curl equations and the finite-element method based on the Poisson and continuity equations. The results show that this advanced design could effectively improve device response without sacrificing crosstalk. The optimal structure parameters are obtained theoretically, with response increase of approximately 100%.

  8. Joint FDTD-Optical/FEM-Electrical Numerical Simulation of Reflection-Type Subwavelength-Microstructure InSb Infrared Focal-Plane Arrays

    NASA Astrophysics Data System (ADS)

    He, J. L.; Hu, W. D.; Ye, Z. H.; Lv, Y. Q.; Chen, X. S.; Lu, W.

    2016-05-01

    The design of a reflection-type subwavelength microstructure has been numerically investigated to concentrate incident light onto pixels for improved photoresponse of InSb infrared focal-plane arrays. Compared with traditional microlenses placed on top of the detector substrate, this reflection-type microstructure is better suited for extremely small pixel pitches. The structure is simulated using a joint numerical method combining the finite-difference time-domain method based on Maxwell's curl equations and the finite-element method based on the Poisson and continuity equations. The results show that this advanced design could effectively improve device response without sacrificing crosstalk. The optimal structure parameters are obtained theoretically, with response increase of approximately 100%.

  9. 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.

  10. 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.

  11. Size effects on the structural, electronic, and optical properties of (5,0) finite-length carbon nanotube: An ab-initio electronic structure study

    NASA Astrophysics Data System (ADS)

    Tarighi Ahmadpour, Mahdi; Hashemifar, S. Javad; Rostamnejadi, Ali

    2016-07-01

    We use density functional computations to study the zero temperature structural, electronic, magnetic, and optical properties of (5,0) finite carbon nanotubes (FCNT), with length in the range of 4-44 Å. It is found that the structural and electronic properties of (5,0) FCNTs, in the ground state, converge at a length of about 30 Å, while the excited state properties exhibit long-range edge effects. We discuss that curvature effects enhance energy gap of FCNTs, in contrast to the known trend in the periodic limit. It is seen that compensation of curvature effects in two special small sizes may give rise to spontaneous magnetization. The obtained cohesive energies provide some insights into the effects of environment on the growth of FCNTs. The second-order difference of the total energies reveals an important magic size of about 15 Å. The optical and dynamical magnetic responses of the FCNTs to polarized electromagnetic pulses are studied by time dependent density functional theory. The results show that the static and dynamic magnetic properties mainly come from the edge carbon atoms. The optical absorption properties are described in terms of local field effects and characterized by Casida linear response method.

  12. 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.

  13. 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.

  14. SNAP focal plane

    SciTech Connect

    Lampton, Michael L.; Kim, A.; Akerlof, C.W.; Aldering, G.; Amanullah, R.; Astier, P.; Barrelet, E.; Bebek, C.; Bergstrom, L.; Berkovitz, J.; Bernstein, G.; Bester, M.; Bonissent, A.; Bower, C.; Carithers Jr., W.C.; Commins, E.D.; Day, C.; Deustua, S.E.; DiGennaro,R.; Ealet, A.; Ellis, R.S.; Eriksson, M.; Fruchter, A.; Genat, J.-F.; Goldhaber, G.; Goobar, A.; Groom, D.; Harris, S.E.; Harvey, P.R.; Heetderks, H.D.; Holland, S.E.; Huterer, D.; Karcher, A.; Kolbe, W.; Krieger, B.; Lafever, R.; Lamoureux, J.; Levi, M.E.; Levin, D.S.; Linder,E.V.; Loken, S.C.; Malina, R.; Massey, R.; McKay, T.; McKee, S.P.; Miquel, R.; Mortsell, E.; Mostek, N.; Mufson, S.; Musser, J.; Nugent, P.; Oluseyi, H.; Pain, R.; Palaio, N.; Pankow, D.; Perlmutter, S.; Pratt, R.; Prieto, E.; Refregier, A.; Rhodes, J.; Robinson, K.; Roe, N.; Sholl, M.; Schubnell, M.; Smadja, G.; Smoot, G.; Spadafora, A.; Tarle, G.; Tomasch,A.; von der Lippe, H.; Vincent, R.; Walder, J.-P.; Wang, G.

    2002-07-29

    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 sensitive in the visible and near-infrared wavelength regime. We describe the requirements for the instrument suite and the evolution of the focal plane design to the present concept in which all the instrumentation--visible and near-infrared imagers, spectrograph, and star guiders--share one common focal plane.

  15. 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

  16. Beam control for LINC-NIRVANA: from the binocular entrance pupil to the combined focal plane

    NASA Astrophysics Data System (ADS)

    Bertram, T.; Trowitzsch, J.; Herbst, T. M.; Ragazzoni, R.

    2012-07-01

    LINC-NIRVANA is the near-infrared interferometric imaging camera for the Large Binocular Telescope. Once operational, it will provide an unprecedented combination of angular resolution, sensitivity and field of view. To meet the tight requirements that result from long exposure interferometric imaging over a large field of view, active control beyond fringe tracking and adaptive optics has to be in place in the telescope and in the instrument domain. The incoming beams of the binocular telescope have to be controlled along the entire optical path, from the entrance pupil to the combined focal plane. The beams have to coincide in the focal plane of the science detector, their pointing origins, offsets, orientations, plate scales, and distortions have to match each other and must not change during the observation. Non-common path effects between AO and science channel, flexure and thermal effects have to be compensated and offioading requests from the adaptive optics and fringe tracking systems have to be arbitrated without introducing unwanted optical path length differences or changes in the geometry of the binocular entrance pupil. Beam Control aspects include pointing, co-pointing and field derotation, active optics and collimation control. In this presentation, the constraints for coherent imaging over a 1.5 arcminute field of view are discussed together with a concept for a distributed control scheme.

  17. Hemodynamics of focal choroidal excavations.

    PubMed

    Soma, Ryoko; Moriyama, Muka; Ohno-Matsui, Kyoko

    2015-04-01

    The purpose of this study was to investigate the hemodynamics of focal choroidal excavations (FCEs). Four eyes of four patients with a FCE were studied. Indocyanine green angiography (ICGA), laser speckle flowgraphy (LSFG), optical coherence tomography (OCT), and multi-focal electroretinography (mfERG) were performed to investigate the choroidal hemodynamics and the morphological and functional changes. The mean depth of the FCE determined by OCT was 222.5 ± 49.5 μm with a range of 164-272 μm. In one case, subretinal fluid was observed in the excavation, and in three cases, subretinal fluid was not observed. ICGA showed hypofluorescence, and laser flowgraphy (LSFG) showed decreased choroidal blood flow at the excavation in all cases. Three cases were symptomatic, and the amplitudes of the mfERGs were reduced. FCEs cause a decrease of choroidal blood flow. In three of four cases, the mfERGs were depressed over the FCEs leading to symptoms. PMID:25626897

  18. 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.

  19. Controlling the thermally induced focal shift in laser processing heads

    NASA Astrophysics Data System (ADS)

    Negel, Jan-Philipp; Abt, Felix; Blázquez-Sánchez, David; Austerschulte, Armin; Hafner, Margit; Liebig, Thomas; von Strobl-Albeg, Philipp; Weber, Rudolf; Abdou Ahmed, Marwan; Voss, Andreas; Graf, Thomas

    2012-03-01

    A system being able to in situ measure and control not simply the distance between the workpiece and the focusing optics, but the true focal position on the workpiece including the thermally induced focal shift in a laser processing head is presented. In order to achieve this, a bundle of astigmatic measurement beams is used following the same optical path as the welding beam. A camera and a software algorithm allow to keep the focal position constant within a range of 4 mm and with a resolution between 150 μm and 500 μm.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. MWIR and LWIR Megapixel QWIP Focal Plane Arrays

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  6. Optical mode engineering and high power density per facet length (>8.4 kW/cm) in tilted wave laser diodes

    NASA Astrophysics Data System (ADS)

    Ledentsov, N. N.; Shchukin, V. A.; Maximov, M. V.; Gordeev, N. Y.; Kaluzhniy, N. A.; Mintairov, S. A.; Payusov, A. S.; Shernyakov, Yu. M.

    2016-03-01

    Tilted Wave Lasers (TWLs) based on optically coupled thin active waveguide and thick passive waveguide offer an ultimate solution for thick-waveguide diode laser, preventing catastrophic optical mirror damage and thermal smile in laser bars, providing robust operation in external cavity modules thus enabling wavelength division multiplexing and further increase in brightness enabling direct applications of laser diodes in the mainstream material processing. We show that by proper engineering of the waveguide one can realize high performance laser diodes at different tilt angles of the vertical lobes. Two vertical lobes directed at various angles (namely, +/-27° or +/-9°) to the junction plane are experimentally realized by adjusting the compositions and the thicknesses of the active and the passive waveguide sections. The vertical far field of a TWL with the two +/-9° vertical beams allows above 95% of all the power to be concentrated within a vertical angle below 25°, the fact which is important for laser stack applications using conventional optical coupling schemes. The full width at half maximum of each beam of the value of 1.7° evidences diffraction- limited operation. The broad area (50 μm) TWL chips at the cavity length of 1.5 mm reveal a high differential efficiency ~90% and a current-source limited pulsed power >42W for as-cleaved TWL device. Thus the power per facet length in a laser bar in excess of 8.4 kW/cm can be realized. Further, an ultimate solution for the smallest tilt angle is that where the two vertical lobes merge forming a single lobe directed at the zero angle is proposed.

  7. 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

  8. 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.

  9. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

  11. 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

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. Imaging (NIRI) and quantitation (NIRS) in tissue using time-resolved spectrophotometry: the impact of statistically and dynamically variable optical path lengths

    NASA Astrophysics Data System (ADS)

    Benaron, David A.; Ho, David C.; Rubinsky, Boris; Shannon, Mark

    1993-09-01

    Near-infrared spectroscopy (NIRS) and near-infrared optical imaging (NIRI) are two medical techniques under development, respectively offering the ability to use light to noninvasively quantitate metabolite concentration and to image structure within the human body. Due to the dual effects of scattering and absorbance, quantitative measurement using NIRS and reconstruction of deep-tissue structure using NIRI have been problematic. Significant advances have occurred, however, over the past few years that have brought these measurements closer to reality. In this paper, we present several of the areas in which our laboratory has made progress, and discuss the relevance of these contributions in the light of work by other laboratories. With regard to NIR spectroscopy, it now appears both practical and necessary to take into account the length of the paths taken by light in order to derive deep-tissue estimates of pigment concentrations such as hemoglobin. With regard to NIR imaging, path corrected approaches offer improved resolution, and have been used successfully by our group and others to image phantoms, animals, and now humans. Different simplifications have been used in order to accomplish separately spectroscopy and imaging, but it is hoped that a common method will allow combination of the two techniques in order to achieve spatially resolved quantitative optical measurements.

  17. Variable-focal lens using electroactive polymer actuator

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  18. 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.

  19. 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.

  20. Teal Amber Visible Focal Plane Technology

    NASA Astrophysics Data System (ADS)

    Johnson, Charles R.; Burczewski, Ron

    1981-12-01

    Deep-space surveillance missions have imposed severe demands on existing technology and simulated the search for new, advanced technology developments to provide higher performance. Defense Advanced Research Projects Agency (DARPA) sponsored Teal Amber as a visible charge-coupled device (CCD) and associated focal plane signal processing technology development and demonstration program. This paper describes this large-scale, staring-array-sensor concept. The current state of art in the resulting visibled CCD imagers is specified, along with the focal plane signal processor implementation in low power-weight-volume large-scale integrated (LSI) circuitry. Performance requirements and analytic predictions are compared to demonstration system results from an electro-optical test site in White Sands, New Mexico.

  1. 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.

  2. 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.

  3. Megapixel Multi-band QWIP Focal Plane Arrays

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  4. 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.

  5. 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.

  6. Diffraction optics for terahertz waves

    NASA Astrophysics Data System (ADS)

    Wiltse, James C.

    2004-09-01

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

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

    PubMed

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

    2015-10-21

    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. PMID:26395150

  8. Near-infrared optical-absorption behavior in high-beta nonlinear optical chromophore-polymer guest-host materials. II. Dye spacer length effects in an amorphous polycarbonate copolymer host

    NASA Astrophysics Data System (ADS)

    Barto, Richard R.; Frank, Curtis W.; Bedworth, Peter V.; Ermer, Susan; Taylor, Rebecca E.

    2005-06-01

    In the second of a three-part series, spectral absorption behavior of nonlinear optical (NLO) dyes incorporated into amorphous polycarbonate, comprised of a homologous series of dialkyl spacer groups extending from the midsection of the dye molecule, is characterized by UV-Vis and photothermal deflection spectroscopy. The dyes are structural analogs of the NLO dye FTC [2-(3-cyano-4-{2-[5-(2-{4-[ethyl-(2-methoxyethyl)amino]phenyl}vinyl)-3,4-diethylthiophen-2-yl]vinyl}-5,5-dimethyl-5H-furan-2-ylidene)malononitrile]. Previous Monte Carlo calculations [B. H. Robinson and L. R. Dalton, J. Phys. Chem. A 104, 4785 (2000)] predict a strong dependence of the macroscopic nonlinear optical susceptibility on the chromophore waist: length aspect ratio in electric-field-poled films arising from interactions between chromophores. It is expected that these interactions will play a role in the absorption characteristics of unpoled films, as well. The spacer groups range in length from diethyl to dihexyl, and each dye is studied over a wide range of concentrations. Among the four dyes studied, a universal dependence of near-IR loss on inhomogeneous broadening of the dye main absorption peak is found. The inhomogeneous width and its concentration dependence are seen to vary with spacer length in a manner characteristic of the near-IR loss-concentration slope at transmission wavelengths of 1.06 and 1.3μm, but not at 1.55μm. The lower wavelength loss behavior is assigned to purely Gaussian broadening, and is described by classical mixing thermodynamic quantities based on the Marcus theory of inhomogeneous broadening [R. A. Marcus, J. Chem. Phys. 43, 1261 (1965)], modeled as a convolution of dye-dye dipole broadening and dye-polymer van der Waals broadening. The Gaussian dipole interactions follow a Loring dipole-broadening description [R. F. Loring, J. Phys. Chem. 94, 513 (1990)] dominated by the excited-state dipole moment, and have a correlated homogeneous broadening contribution

  9. Experimental determination of diffusion length in SWIR HgCdTe photodiodes

    NASA Astrophysics Data System (ADS)

    Jia, Jia; Chen, Guibin; Li, Xiangyang; Gong, Haimei

    2005-01-01

    Minority carrier diffusion length is a key parameter of material quality and gives an indication of diode performance. It is also one important parameter when considering the increase of the effective optical sensitive area caused by the lateral diffusion and the crosstalk between individual detectors on a focal plane array (FPA). In this paper, we perform diffusion length measurements with two methods on short wavelength infrared (SWIR) HgCdTe photovoltaic devices. One method is based on the different behaviors of electrons and holes in a variation magnetic field B and their effects on the saturation current density J0. The other method is an optical characterization technique called Laser Beam Induced Current (LBIC). The results were in good agreement with each other.

  10. 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

  11. "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.

  12. Infrared focal plane array crosstalk measurement

    NASA Astrophysics Data System (ADS)

    Dang, Khoa V.; Kauffman, Christopher L.; Derzko, Zenon I.

    1992-07-01

    Crosstalk between two neighboring elements in a focal plane array (FPA) occurs when signal incident on one element in the array is seen on another. This undesired effect can occur due to both the electrical and optical properties of the FPA. An effort is underway at the U.S. Army's Night Vision and Electro-Optics Directorate to develop a capability to measure crosstalk on both mid-wave infrared and long-wave infrared FPAs. A single detector in an array is illuminated using a laser source coupled with a beam expander, collimating lens, and focusing lens. The relative response of that detector to that of its neighboring detectors is measured to calculate crosstalk. The various components of the test station, the methodology for implementing the crosstalk measurement, and a model of the laser spot size are discussed.

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

    SciTech Connect

    1996-05-01

    This progress report describes work done on the Extra Focal Convective Suppressing Solar Collector. The topics of the report include sensor refinement for the tracking electronics, tracking controller refinement, system optics evaluation, absorber system material evaluation and performance, tracking hardware evaluation and refinement, and full scale prototype construction and testing.

  14. Focal spot calibration in a digital breast tomosynthesis system

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

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

  15. Evaluation of focal fields and radiation characteristics of a dual-offset reflector antenna

    NASA Astrophysics Data System (ADS)

    Bird, T. S.; Boomars, J. L.

    1980-08-01

    A receive-mode analysis of a dual-offset reflector antenna consisting of an offset paraboloid and an offset hyperboloid is presented. In this analysis the field scattered from the offset paraboloid is determined using a GTD formulation involving two edge points and a reflection point, if one exists. A method is described for deciding whether there is a reflection point from the gradient of the path length at the edge points. The focal-region fields and the radiation characteristics are computed by numerical integration of the physical optics current on the offset hyperboloid. An experimental antenna operating at 35 GHz is described. Results of measurements of radiation patterns and of the power coupled into a circular waveguide array feed are compared with theory. In each case reasonable agreement is achieved for copolarized directed components. However, the experimental antenna produced higher crosspolarization than expected.

  16. Simple tools for simulating phased array focal laws on 3D solids

    NASA Astrophysics Data System (ADS)

    Weber, Walter H.; Mair, H. Douglas; Frazer, Leigh

    2001-04-01

    This paper reports our progress on the development of a three-dimensional raytracing program that can simulate the focal laws of a phased array system. The modeled transducer is divided into elements of a given length, width and inter-element gap distance. Each focal law to be modeled requires a steering angle, focal length and selection of which groups of elements are transmitting and receiving. Electronic scanning is simulated by stepping through a series of predefined focal laws. The program phase shifts and sums the received rays at each element based on the properties of the currently-active focal law. Simulated A-scans are constructed from the received rays which appear animated as the beam is swept. Beam profiles can also be generated that show the primary forward beam and energy in the side lobes. The work is based on Imagine3D ultrasonic simulation software and the dedicated efforts of Doug Mair and Leigh Frazer.

  17. Fractal vector optical fields.

    PubMed

    Pan, Yue; Gao, Xu-Zhen; Cai, Meng-Qiang; Zhang, Guan-Lin; Li, Yongnan; Tu, Chenghou; Wang, Hui-Tian

    2016-07-15

    We introduce the concept of a fractal, which provides an alternative approach for flexibly engineering the optical fields and their focal fields. We propose, design, and create a new family of optical fields-fractal vector optical fields, which build a bridge between the fractal and vector optical fields. The fractal vector optical fields have polarization states exhibiting fractal geometry, and may also involve the phase and/or amplitude simultaneously. The results reveal that the focal fields exhibit self-similarity, and the hierarchy of the fractal has the "weeding" role. The fractal can be used to engineer the focal field. PMID:27420485

  18. Optical system for an astrometric survey from space

    NASA Astrophysics Data System (ADS)

    Phillips, James D.; Reasenberg, Robert D.

    1998-08-01

    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.

  19. Behavior of asymmetric Bessel beam in focal plane of high numerical aperture objective

    NASA Astrophysics Data System (ADS)

    Stafeev, Sergey S.; Kotlyar, Victor V.; Porfirev, Alexey P.

    2016-04-01

    Tight focusing of a linearly-polarized asymmetric Bessel beam, which has a crescent profile, was investigated numerically and experimentally. FDTD calculations show that a binary zone plate of numerical aperture NA = 0.995 forms a crescent in the focal plane, which is rotated clockwise around the optical axis, moving away from the focal plane. Using the Debye formulae it was shown that a direction of polarization of incident light has a significant influence on intensity distribution in focal plane. The crescent in the focal plane was also observed experimentally by focusing of the asymmetric Bessel beam using an immersive objective (NA = 1.25).

  20. 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

  1. Sex prevalence of focal dystonias.

    PubMed Central

    Soland, V L; Bhatia, K P; Marsden, C D

    1996-01-01

    The sex prevalence of idiopathic focal dystonia is reported from a data base review of all patients seen at the National Hospital of Neurology, Queen Square and King's College, London up to 1993. There was a higher prevalence of females to males in all categories of focal dystonia involving the craniocervical region. The female to male ratio for cranial dystonia was 1.92:1 (P < 0.01) and 1.6:1 (P < 0.001) for spasmodic torticollis. On the other hand, twice as many men than women had writer's cramp (M:F = 2.0:1, P < 0.01). At present, there is no clear explanation to account for this differences in the sex prevalence of different types of focal dystonia. PMID:8708656

  2. Infrared transmission measurements of highly curved optical components

    NASA Astrophysics Data System (ADS)

    Tiszauer, Detlev H.; Morrow, Howard E.

    Fourier Transform Infrared Spectrometer (FTIR) measurements on flat witness samples are combined with ray trace results of transmission through a 1/8 inch, 12 mill focal length lens to estimate the net transmission of that lens as it is used in the Geostationary Operational Environmental Satellite (GOES I) Sounder optical train. The ray trace code uses a 'double random' ray method allowing radiometry to be done with a standard ray propagation algorithm.

  3. Directional design of optical lens based on metallic nano-slits with variant widths

    NASA Astrophysics Data System (ADS)

    Zhu, Qiaofen; Zhang, Yan

    2010-08-01

    The lens constructed with slits perforated on the thin metallic film is designed by simulated annealing algorithm. And two demonstrates are carried out to validate the directional design algorithm. First, the lens with one focal spot is considered. After the width of each slit is obtained, the finite-difference time-domain method is used to check the performance of the designed lens. It is found that the focal length is 800nm and the full-width at half-maximum of the focal spot is 252nm, which corresponds to the preset objective well. Then, the lens with three focal spots is also designed by this algorithm and the performance of the designed lens is quite close to the objective. This is the first work to introduce directional algorithm into design SPP lens. It may pave the way for the design sub-wavelength optic devices.

  4. 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

  5. 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.

  6. Programmable axicon for variable inclination of the focal segment

    NASA Astrophysics Data System (ADS)

    Jaroszewicz, Z.; Climent, V.; Duran, V.; Lancis, J.; Kolodziejczyk, A.; Burvall, A.; Friberg, A. T.

    An axicon creates a long and narrow focal segment along its optical axis and therefore it is widely recognized as a cornerstone element in metrology and alignment techniques. In oblique incidence the shape of the axicon can be designed such that its sharp focal line is retained. However, when an elliptical or circular axicon is illuminated at an angle different from the nominal angle, the focal segment suffers from astigmatism and broadens significantly. The use of a spatial light modulator is proposed for real-time compensation of the ensuing aberration. The result is a diffractive axicon with its degree of ellipticity adjusted to the inclination angle of the incident light, thus producing a diffraction-limited Bessel beam for a wide range of illumination angles.

  7. Focal weakness following herpes zoster.

    PubMed Central

    Cockerell, O C; Ormerod, I E

    1993-01-01

    Three patients presented with focal weakness of an arm which followed segmental herpes zoster affecting the same limb. Neurophysiological investigations suggest that the site of the lesion lay at the root, plexus, or peripheral nerve level. This reflects the various ways in which the virus may affect the peripheral nervous system. PMID:8410022

  8. 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

  9. Shaping the focal field of radially/azimuthally polarized phase vortex with Zernike polynomials

    NASA Astrophysics Data System (ADS)

    Wei, Lei; Urbach, H. Paul

    2016-06-01

    The focal field properties of radially/azimuthally polarized Zernike polynomials are studied. A method to design the pupil field in order to shape the focal field of radially or azimuthally polarized phase vortex is introduced. With this method, we are able to obtain a pupil field to achieve a longitudinally polarized hollow spot with a depth of focus up to 12λ and 0.28λ lateral resolution (FWHM) for an optical system with numerical aperture 0.99; a pupil field to generate eight focal spots along the optical axis is also obtained with this method.

  10. 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.

  11. Influence of the ester chain length on the mesogenic behavior and optical anisotropy of 4-[[4-(butoxy)phenyl]diazenyl]phenyl alkanoates

    NASA Astrophysics Data System (ADS)

    Niezgoda, Izabela; Szypszak, Ewelina; Dardas, Dorota; Galewski, Zbigniew

    2016-04-01

    In this manuscript, we report synthesis and physico-chemical characterization of 4-[[4-(butoxy)phenyl]diazenyl]phenyl alkanoates homologous series. For the first time, nineteen derivatives are described here. The enantiotropic nematic phase is typically observed among all members of this series. However, in the case of 4-[[4-(butoxy)phenyl]diazenyl]phenyl stearate, the nematic phase shows a monotropic character. In addition to liquid-crystalline polymorphism, a second crystalline form was observed in some homologs. Furthermore, using a photoelastic modulator, the optical anisotropy in the nematic phase was determined in the first nine compounds of this series. Temperature dependence of optical anisotropy at significantly lower values of reduced temperature is relatively weak. In contrast, optical anisotropy shows a strong temperature effect near isotropization. Moreover, the influence of the ester chain elongation on liquid crystalline and optical properties was established.

  12. Compensation for displacement of the focal point in cone beam single photon emission computed tomography reconstruction.

    PubMed

    Cao, Z; Qian, L

    1997-04-01

    This study examined the effects of focal point displacement on image quality in cone beam single photon emission computed tomography (SPECT). A new image reconstruction algorithm that accounts for the focal point shift was derived and three shift geometries were investigated. The geometries included a lateral shift with a fixed focal length but off-center focusing, a linear axial shift with a variable focal length that depends linearly on the distance between a bin of the detector and the center of the detector, and a random axial shift with a randomly varying focal length. Computer simulation was conducted to evaluate the shift effects with a phantom that was composed of 118 small spherical sources. The results demonstrated that the lateral shift of the focal point was more critical to image quality than was the axial shift. With a 0.64 cm (1 pixel) lateral shift, noticeable artifacts was observed, while an axial shift resulted in minimal changes in image quality until it reached 8 cm (12.5 pixels). The derived reconstruction algorithm eliminated most of the artifacts caused by a fixed lateral shift or a linear axial shift of the focal point, but failed to do so for a random axial shift since the linear distribution assumed in image reconstruction did not match the random shift occurred in acquisition of the data. PMID:9291002

  13. Dither Cavity Length Controller with Iodine Locking

    NASA Astrophysics Data System (ADS)

    Lawson, Marty; Eloranta, Ed

    2016-06-01

    A cavity length controller for a seeded Q-switched frequency doubled Nd:YAG laser is constructed. The cavity length controller uses a piezo-mirror dither voltage to find the optimum length for the seeded cavity. The piezo-mirror dither also dithers the optical frequency of the output pulse. [1]. This dither in optical frequency is then used to lock to an Iodine absorption line.

  14. MRI of Focal Liver Lesions.

    PubMed

    Albiin, Nils

    2012-05-01

    Magnetic resonance imaging, MRI has more advantages than ultrasound, computed tomography, CT, positron emission tomography, PET, or any other imaging modality in diagnosing focal hepatic masses. With a combination of basic T1 and T2 weighted sequences, diffusion weighted imaging, DWI, and hepatobiliary gadolinium contrast agents, that is gadobenate dimeglumine (Gd-BOPTA) and gadoxetic acid (Gd-EOB), most liver lesions can be adequately diagnosed. Benign lesions, as cyst, hemangioma, focal nodular hyperplasia, FNH or adenoma, can be distinguished from malignant lesions. In a non-cirrhotic liver, the most common malignant lesions are metastases which may be hypovascular or hypervascular. In the cirrhotic liver hepatocellular carcinoma, HCC, is of considerable importance. Besides, intrahepatic cholangiocarcinoma and other less common malignancies has to be assessed. In this review, the techniques and typical MRI features are presented as well as the new algorithm issued by American Association for the Study of the Liver Diseases (AASLD). PMID:23049491

  15. 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.

  16. [Focal liver lesion, incidental finding].

    PubMed

    Dietrich, C F; Jenssen, C

    2012-10-01

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

  17. 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…

  18. 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.

  19. 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.

  20. Back focal plane imaging spectroscopy of photonic crystals

    NASA Astrophysics Data System (ADS)

    Wagner, Rebecca; Heerklotz, Lars; Kortenbruck, Nikolai; Cichos, Frank

    2012-08-01

    Back focal plane imaging spectroscopy is introduced to record angle resolved emission spectra of 3-dimensional colloidal photonic crystals. The auto-fluorescence of the colloids is used to quickly map the photonic band structure up to 72 % of the solid angle of a semisphere with the help of a high numerical aperture objective. Local excitation provides spatially resolved information on the photonic crystal's optical properties. The obtained fractional density of states allows direct conclusions on the crystal's stacking faults or defects.

  1. 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.

  2. Slope sensitivities for optical surfaces

    NASA Astrophysics Data System (ADS)

    Rogers, John R.

    2015-09-01

    Setting a tolerance for the slope errors of an optical surface (e.g., surface form errors of the "mid-spatial-frequencies") requires some knowledge of how those surface errors affect the final image of the system. While excellent tools exist for simulating those effects on a surface-by-surface basis, considerable insight may be gained by examining, for each surface, a simple sensitivity parameter that relates the slope error on the surface to the ray displacement at the final image plane. Snell's law gives a relationship between the slope errors of a surface and the angular deviations of the rays emerging from the surface. For a singlet or thin doublet acting by itself, these angular deviations are related to ray deviations at the image plane by the focal length of the lens. However, for optical surfaces inside an optical system having a substantial axial extent, the focal length of the system is not the correct multiplier, as the sensitivity is influenced by the optical surfaces that follow. In this paper, a simple expression is derived that relates the slope errors at an arbitrary optical surface to the ray deviation at the image plane. This expression is experimentally verified by comparison to a real-ray perturbation analysis. The sensitivity parameter relates the RMS slope errors to the RMS spot radius, and also relates the peak slope error to the 100% spot radius, and may be used to create an RSS error budget for slope error. Application to various types of system are shown and discussed.

  3. Fish Tank Optics.

    ERIC Educational Resources Information Center

    McCausland, Stuart; Allard, Brian

    1997-01-01

    Describes procedures for a demonstration of the focal length of spherical lenses and mirrors using an aquarium, a flashlight, and nondairy creamer. Enables nonquantitative three-dimensional observation of these phenomena. (DDR)

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  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. 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.

  10. Rewritable photochromic focal plane masks

    NASA Astrophysics Data System (ADS)

    Molinari, Emilio; Bertarelli, Chiara; Bianco, Andrea; Bortoletto, Fabio; Conconi, Paolo; Crimi, Giuseppe; Gallazzi, Maria C.; Giro, Enrico; Lucotti, Andrea; Pernechele, Claudio; Zerbi, Filippo M.; Zerbi, Giuseppe

    2003-02-01

    The application of organic photochromic materials in astronomy is opening new possibilities which we are investigating in order to design innovative devices for future instrumentation. The photochromic property of transparent/opaque transition (although in a limited wavelength range) and the changes in intrinsic refractive index have led our studies to application in astronomic spectrographs, both as focal plane mask (for MOS application) and as dispersive elements (volume phase holographic gratings, VPHG), respectively. In both cases the possibility to write and erase devices with suitable irradiation has revealed a new perspective for non-disposable and fully customizable items for spectroscopy. Pursuing this goal we have synthesized a series of novel photochromic materials belonging to the diarylethenes. They fulfill the requirements of thermal stability and fatigue resistance necessary to build functional devices. Prototypes of high contrast focal plane mask working in the H-alpha spectral region have been manufactured and characterized both in laboratory and with the AFOSC camera at Asiago telescope (1.8 m). A custom writing robot (ARATRO) which, taking imaging frames and with the aid of interactive mask design software and ad hoc control electronics, is able to write MOS masks, has been constructed. The design of the MOS masks allow the fitting in the AFOSC slit wheel. The overall set-up is ready for the sky tests.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Investigating the Influence of Alkyl Chain Length in Poly(3-alkylthiophene)s Over the Thin Film Morphology by Optical and Electrical Characterization.

    PubMed

    Bhargava, Kshitij; Bilgaiyan, Anubha; Mohan, S Raj; Itoop, M O; Joshi, Mukesh P; Kukreja, L M; Singh, Vipul

    2016-04-01

    This paper studies the influence of alkyl-chain length in poly(3-alkylthiophene)s over the morphology of thin films and electrical parameters of the devices based on it. Regioregular poly(3-hexylthiophene) and poly(3-octylthiophene) were chosen as the semiconducting materials for the study. The morphological variations were studied by absorption spectroscopy, photoluminescence spectroscopy and X-ray diffraction study. The absorption and photoluminescence showed decreased coplanarity of main chain in poly(3-octylthiophene) over poly(3-hexylthiophene) and which was later confirmed using X-ray diffraction studies which clearly showed increased interchain spacing in case of poly(3-octylthiophene). The schottky diodes fabricated using these materials showed decreased mobility in poly(3-octylthiophene) based diodes as measured by space-charge limiting current method and photo-induced charge carrier extraction by linearly increasing voltage technique. Moreover, we observed a negative field dependence of mobility at room temperature in both the devices and attributed this to the presence of dominant positional disorder in poly(3-alkylthiophene)s. Furthermore, the photocurrent dependence on electric field too showed inferior mobility of poly(3-octylthiophene) based diodes. PMID:27451611

  19. The formation of optical membrane reflector surfaces using uniform pressure loading

    SciTech Connect

    Murphy, L.M.; Tuan, C.

    1987-08-01

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

  20. 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.

  1. Digital scanner infrared focal plane technology

    NASA Astrophysics Data System (ADS)

    Ortiz, M. A.; Malone, N. R.; Harris, M.; Shin, J.; Byers, S.; Price, D.; Vampola, J.

    2011-09-01

    Advancements in finer geometry and technology advancements in circuit design now allow placement of digital architecture on cryogenic focal planes while using less power than heritage analog designs. These advances in technology reduce the size, weight, and power of modern focal planes. In addition, the interface to the focal plane is significantly simplified and is more immune to Electromagnetic Interference (EMI). The cost of the customer's instrument after integration with the digital scanning Focal Plane Array (FPA) has been significantly reduced by placing digital architecture such as Analog to digital convertors and Low Voltage Differential Signaling (LVDS) Inputs and Outputs (I/O) on the Read Out Integrated Circuit (ROIC).

  2. Neurocysticercosis presenting as focal hydrocephalus

    PubMed Central

    Malik, Azharuddin Mohammed; Shamim, Md Dilawez; Ahmad, Mehtab; Abdali, Nasar

    2014-01-01

    A 40-year-old man presented with a 2-month history of headache, nausea and vomiting, with generalised seizures for the past 15 days. On examination he had bilateral papilloedema, visual acuity was 6/6 in both eyes but perimetry showed right homonymous inferior quadrantanopia. His MRI showed numerous small cystic lesions with eccentric nodules, diffusely distributed in bilateral cerebral and cerebellar hemispheres. There was also focal hydrocephalus involving occipital and temporal horns of the left lateral ventricle leading to its selective dilation. Stool examination showed ova of Taenia solium. He was treated with albendazole, prednisone and sustained release sodium valproate for 1 month. His headache resolved and he is free of seizures. Repeat perimetry at 1 month also showed resolution of visual field defect. PMID:24962486

  3. Optimal focal-plane restoration

    NASA Technical Reports Server (NTRS)

    Reichenbach, Stephen E.; Park, Stephen K.

    1989-01-01

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

  4. 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.

  5. 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

  6. SOI diode uncooled infrared focal plane arrays

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

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

  7. 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.

  8. 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

  9. Focal Molography: Coherent Microscopic Detection of Biomolecular Interaction

    NASA Astrophysics Data System (ADS)

    Fattinger, Christof

    2014-07-01

    We introduce and theoretically investigate here a novel analytical method that we have called focal molography, in which molecular interactions are made visible through scattering of coherent light by a coherent pattern of molecules. The scattered light quantifies the presence of molecules at molecular interaction sites. It is separated from noncoherent background scatter by a combination of local dark-field illumination, interference enhancement, and spatial filtering. The latter is achieved by holographic focusing of the wave field generated by the coherently assembled molecules onto an Airy disk and by subtraction of the noncoherent irradiance in the focal plane outside the disk from the irradiance in the disk. This new microscopic method allows distinct detection of low-refractive-index contrast in the nanoenvironment of biomolecules from which information on the interaction of the coherently assembled molecules with molecules in a liquid or gaseous sample may be deduced. The noncoherent surroundings of the coherently assembled molecules consist of freely diffusing solvent and solute molecules. The surroundings, as well as changes in temperature, do not contribute to the coherent signal in the diffraction focus. Interference lithography or high-resolution-imaging lithography can be used to synthesize the coherent pattern of molecules on a monolithic substrate. The coherent pattern of molecules constitutes a synthetic phase hologram that creates a diffraction-limited light wave. We suggest the term "mologram" for the coherent assembly of functional nanostructures and the term "focal molography" for label-free or labeled analysis of molecular interactions through the measurement of the properties of light in the focus of the mologram. We derive analytical formulas that express the detection signal and the sensitivity of focal molography on the surface of a high-refractive-index thin-film optical waveguide in terms of known parameters. We discuss the

  10. 256 x 256 PACE-1 PV HgCdTe focal plane arrays for medium and short wavelength infrared applications

    NASA Technical Reports Server (NTRS)

    Kozlowski, L. J.; Vural, K.; Johnson, V. H.; Chen, J. K.; Bailey, R. B.

    1990-01-01

    The development of two 256 by 256 hybrid HgCdTe focal plane array (FPA) families is described, and their performance is discussed. The hybrid FPAs employ a PV HgCdTe detector array and custom Si CMOS readouts. The PACE-1 process was used to fabricate the detectors, whereby the liquid phase epitaxial growth of HgCdTe occurs on sapphire substrates buffered by a layer of CdTe. The performance characteristics of the detector arrays are given. A tactical 256 by 256 CMOS readout is tested, in which a high functional yield was achieved. Updated test results are given for a 256 by 256 readout circuit developed for use in an orbital replacement instrument for the Hubble Space Telescope. The characterizations of several MWIR and SWIR FPAs were thorough and shown to be reliable. The pixel yield, maximum FPA responsivity nonuniformity, and SWIR FPA read noise for the tests are given. The high contrast and insignificant fixed pattern noise of the imagery from the MWIR 256 by 256 FPA are emphasized. These qualities were obtained when the device was operating at 80 k and utilizing f/2 optics with an 8-in. focal length and a 4.4 micron high pass filter.

  11. 256 X 256 PACE-1 PV HgCdTe focal plane arrays for medium and short wavelength infrared applications

    NASA Astrophysics Data System (ADS)

    Kozlowski, L. J.; Vural, K.; Johnson, V. H.; Chen, J. K.; Bailey, R. B.

    1990-09-01

    The development of two 256 by 256 hybrid HgCdTe focal plane array (FPA) families is described, and their performance is discussed. The hybrid FPAs employ a PV HgCdTe detector array and custom Si CMOS readouts. The PACE-1 process was used to fabricate the detectors, whereby the liquid phase epitaxial growth of HgCdTe occurs on sapphire substrates buffered by a layer of CdTe. The performance characteristics of the detector arrays are given. A tactical 256 by 256 CMOS readout is tested, in which a high functional yield was achieved. Updated test results are given for a 256 by 256 readout circuit developed for use in an orbital replacement instrument for the Hubble Space Telescope. The characterizations of several MWIR and SWIR FPAs were thorough and shown to be reliable. The pixel yield, maximum FPA responsivity nonuniformity, and SWIR FPA read noise for the tests are given. The high contrast and insignificant fixed pattern noise of the imagery from the MWIR 256 by 256 FPA are emphasized. These qualities were obtained when the device was operating at 80 k and utilizing f/2 optics with an 8-in. focal length and a 4.4 micron high pass filter.

  12. 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.

  13. The AIRES Optical Design

    NASA Technical Reports Server (NTRS)

    Haas, Michael R.; DeVincenzi, Donald L. (Technical Monitor)

    2001-01-01

    AIRES (Airborne InfraRed Echelle Spectrometer) is the facility spectrometer for SOFIA (Stratospheric Observatory For Infrared Astronomy). AIRES is a long-slit (approximately 160 in) spectrometer designed to cover the 17 to 210-micron range with good sensitivity using three spectroscopic arrays. Initially, only the 30-130 micron, mid-wavelength array will be available. The instrument has a cryogenic K-mirror to perform field rotation and a slit-viewing camera (lambda < 28 microns, FOV = 160 in diameter) to image source morphology and verify telescope pointing. AIRES employs a large echelle grating to achieve a spectral resolving power (lambda/delta lambda) of approximately 1.0 x 10(exp 6)/lambda (sub mu), where lambda (sub mu) is the wavelength in microns. Hyperfine, Inc. has ruled and tested the AIRES' echelle; its wave-front error is 0.028 waves RMS (root mean square) at 10.6 microns. The instrument is housed in a liquid-helium cryostat which is constrained in diameter (approximately 1 m) and length (approximately 2 m) by the observatory. Hence, the length of the echelle (approximately 1.1 m) and the focal length of its collimator (approximately 5.2 m) severely drive the optical design and packaging. The final design uses diamond-turned aluminum optics and has up to 19 reflections inside the cryostat, depending on the optical path. This design was generated, optimized, and toleranced using Code V. The predicted performance is nearly diffraction-limited at 17 microns; the error budget is dominated by design residuals. Light loss due to slit rotation and slit curvature has been minimized. A thorough diffraction analysis with GLAD (G-Level Analysis Drawer) was used to size the mirrors and baffles; the internal light loss is shown to be a strong function of slit width.

  14. 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.

  15. GABAergic networks jump-start focal seizures.

    PubMed

    de Curtis, Marco; Avoli, Massimo

    2016-05-01

    Abnormally enhanced glutamatergic excitation is commonly believed to mark the onset of a focal seizure. This notion, however, is not supported by firm evidence, and it will be challenged here. A general reduction of unit firing has been indeed observed in association with low-voltage fast activity at the onset of seizures recorded during presurgical intracranial monitoring in patients with focal, drug-resistant epilepsies. Moreover, focal seizures in animal models start with increased γ-aminobutyric acid (GABA)ergic interneuronal activity that silences principal cells. In vitro studies have shown that synchronous activation of GABAA receptors occurs at seizure onset and causes sizeable elevations in extracellular potassium, thus facilitating neuronal recruitment and seizure progression. A paradoxical involvement of GABAergic networks is required for the initiation of focal seizures characterized by low-voltage fast activity, which represents the most common seizure-onset pattern in focal epilepsies. PMID:27061793

  16. 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.

  17. Assessment of Macular Function during Vitrectomy: New Approach Using Intraoperative Focal Macular Electroretinograms

    PubMed Central

    Matsumoto, Celso Soiti; Shinoda, Kei; Terauchi, Gaku; Matsumoto, Harue; Mizota, Atsushi; Miyake, Yozo

    2015-01-01

    Purpose To describe a new technique to record focal macular electroretinograms (FMERGs) during vitrectomy to assess macular function. Methods Intraoperative FMERGs (iFMERGs) were recorded in ten patients (10 eyes) who undergo vitrectomy. iFMERGs were elicited by focal macular stimulation. The stimulus light was directed to the macular area through a 25 gauge (25G) glass fiber optic bundle. Background light was delivered through a dual chandelier-type light fiber probe. Focal macular responses elicited with combinations of stimulus and background luminances were analyzed. Results A stimulus luminance that was approximately 1.75 log units brighter than the background light was able to elicit focal macular responses that were not contaminated by stray light responses. Thus, a stimulus luminance of 160 cd/m2 delivered on a background of 3 cd/m2 elicited iFMEGs from only the stimulated area. This combination of stimulus and background luminances did not elicit a response when the stimulus was projected onto the optic nerve head. The iFMERGs elicited by a 10° stimulus with a duration of 100 ms and an interstimulus interval of 150 ms consisted of an a-, b-, and d-waves, the oscillatory potentials, and the photopic negative response (PhNR). Conclusions Focal ERGs with all components can be recorded from the macula and other retinal areas during vitreous surgery. This new technique will allow surgeons to assess the function of focal areas of the retina intraoperatively. PMID:26658489

  18. 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.

  19. Report on SEQUAL/FOCAL

    NASA Astrophysics Data System (ADS)

    Katz, E. J.; Philander, S. G. H.; Richardson, P. L.

    In Eos (April 6, 1982), United States plans for a program to study the dynamic response of the equatorial Atlantic to seasonally varying surface winds were described. Now, 6 years later, we report on progress toward our goal “to describe accurately, and to model correctly” the changes in the currents and density field of the upper equatorial Atlantic Ocean during a 2-year period. A major effort toward this goal was the field phase of SEQUAL (Seasonal Response of the Equatorial Atlantic) and the closely coordinated French program FOCAL (Français Océan et Climat dans l'Atlantique Equatorial).Between February 1983 and September 1984 changes in the surface winds and in oceanic conditions in the equatorial Atlantic were monitored continuously with a variety of instruments. Figure 1 shows key deployments and sections. The resulting data include six current meter moorings, 15 inverted echo sounders and island tide gauges, 57 near-surface drifters, and 18 French and five U.S. cruises that made 1200 hydrographic stations and 800 current profiles. All these data, as well as nearly 10,000 expendable bathythermographs (XBTs) (from the cruises, from air-dropped expendable bathythermograph (AXBT) programs, and from repeated ship of opportunity lines run between 1980 and 1985) were combined and documented by George Heimerdinger, of the National Oceanographic Data Center, and are available from NODC on request.

  20. 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

  1. 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.

  2. The optical system for JASMINE and the CCD centroiding experiment

    NASA Astrophysics Data System (ADS)

    Yano, Taihei; Gouda, Naoteru; Kobayashi, Yukiyasu; Tsujimoto, Takuji; Nakajima, Tadashi; Hanada, Hideo; Yamada, Yoshiyuki; Araki, Hiroshi; Tazawa, Seiichi; Asari, Kazuyoshi; Tsuruta, Seiitsu; Kawano, Nobuyuki; Takato, Naruhisa

    2005-04-01

    We have investigated the optical design for the Japan astrometry satellite mission (JASMINE). In order to accomplish measurements of astrometric parameters with high accuracy, optics with a long focal length and a wide focal plane for astrometry are required. In 1977 Korsch proposed a three mirror system with a long focal length and a wide focal plane. The Korsch system is one of the convincing models. However, the center of the field is totally vignetted because of the fold mirror. Therefore we consider an improved Korsch system in which the center of the field is not vignetted. Finally, we obtain the diffraction limited optical design with small distortion. Our project needs a common astrometric technique to obtain precise positions of star images on solid state detectors to accomplish its objectives. In order to determine the centers of stars, an image of the point source must be focused onto the CCD array with a spread of a few pixels. The distribution of photons (photoelectrons) over a set of pixels enables us to estimate positions of stars with sub-pixel accuracy. We modify the algorithm to estimate the real positions of stars from the photon weighted mean, which was originally developed by the FAME (Full-Sky Astrometric Mapping Explorer) group. Finally, we obtain the results from the experiment that the accuracy of estimation of distance between two stars has a variance of about 1/300 pixel; that is, the error for one measurement is about 1/300 pixel, which is almost an ideal result given by Poisson photon noise. We also investigate the accuracy of estimation of positions with a different size of PSF. In this case also, we find that the accuracy of estimation has a variance of about 1/300 pixel.

  3. Optical design for large depth of field

    NASA Astrophysics Data System (ADS)

    Shen, Yang; Wang, Hu; Yue, Pan; Xue, Yaoke; Liu, Jie; Ye, Shuifu

    2016-01-01

    Optical system with large depth of field and large field of view has been designed. To enforce optical system with focal length of 6 mm to imaging the object with object length of 200mmm-1200mm, accord to the equation of depth of field, in case of the CCD sensor with pixel of 5.5umx 5.5um square area, the entrance pupil diameter to ideal imaging will be 0.423mm. To enlarge the modulation transfer function (MTF) at spatial frequency of 90 lp/mm, the entrance pupil diameter is enlarged to 1mm.After design and optimization, with field of view of 80°, within object length of 200mm - 1200mm, the optical system can imaging well, the modulation transfer function (MTF) at spatial frequency of 90lp/mm is larger than 0.1, the distortion of full field of viewed is less than 3%.The optical system can be widely used in machine vision, surveillance cameras, etc.

  4. 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

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

    PubMed Central

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

    2015-01-01

    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

  6. 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.

  7. Multiplicative and subtractive focal volume engineering in coherent Raman microscopy

    PubMed Central

    Raghunathan, Varun; Potma, Eric Olaf

    2012-01-01

    Rigorous calculations are performed to study the effective reduction of the nonlinear excitation volumes when using phase-only masks to condition the pump and Stokes driving fields. Focal volume reduction was achieved using both a multiplicative operation of the excitation fields as well as a subtractive operation. Using a tunable optical bottle beam for the Stokes field, an effective reduction of the width of the excitation volume by a factor of 1.5 can be achieved in the focal plane. Further reduction of the focal volume introduces a rapid growth of sidelobes, which renders such volumes unsuitable for imaging applications. In addition, phase sensitive detection was found to provide information from selective sub-divisions of the engineered coherent anti-Stokes Raman scattering excitation volume. In the case of isolated nanoparticles, an apparent resolution improvement by a factor of 3 is demonstrated, and it is shown that the size of sub-diffraction-limited particles can be accurately determined using phase sensitive detection. PMID:21045900

  8. Spatial optical phase-modulating metadevice with subwavelength pixelation.

    PubMed

    Cencillo-Abad, Pablo; Plum, Eric; Rogers, Edward T F; Zheludev, Nikolay I

    2016-08-01

    Dynamic control over optical wavefronts enables focusing, diffraction and redirection of light on demand, however, sub-wavelength resolution is required to avoid unwanted diffracted beams that are present in commercial spatial light modulators. Here we propose a realistic metadevice that dynamically controls the optical phase of reflected beams with sub-wavelength pixelation in one dimension. Based on reconfigurable metamaterials and nanomembrane technology, it consists of individually moveable metallic nanowire actuators that control the phase of reflected light by modulating the optical path length. We demonstrate that the metadevice can provide on-demand optical wavefront shaping functionalities of diffraction gratings, beam splitters, phase-gradient metasurfaces, cylindrical mirrors and mirror arrays - with variable focal distance and numerical aperture - without unwanted diffraction. PMID:27505842

  9. 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

  10. Electrically tunable microlens arrays based on polarization-independent optical phase of nano liquid crystal droplets dispersed in polymer matrix.

    PubMed

    Yu, Ji Hoon; Chen, Hung-Shan; Chen, Po-Ju; Song, Ki Hoon; Noh, Seong Cheol; Lee, Jae Myeong; Ren, Hongwen; Lin, Yi-Hsin; Lee, Seung Hee

    2015-06-29

    Electrically tunable focusing microlens arrays based on polarization independent optical phase of nano liquid crystal droplets dispersed in polymer matrix are demonstrated. Such an optical medium is optically isotropic which is so-called an optically isotropic liquid crystals (OILC). We not only discuss the optical theory of OILC, but also demonstrate polarization independent optical phase modulation based on the OILC. The experimental results and analytical discussion show that the optical phase of OILC microlens arrays results from mainly orientational birefringence which is much larger than the electric-field-induced birefringence (or Kerr effect). The response time of OILC microlens arrays is fast~5.3ms and the tunable focal length ranges from 3.4 mm to 3.8 mm. The potential applications are light field imaging systems, 3D integrating imaging systems and devices for augment reality. PMID:26191743

  11. 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

  12. 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.

  13. 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

  14. 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…

  15. Deep ultraviolet (254 nm) focal plane array

    NASA Astrophysics Data System (ADS)

    Cicek, Erdem; Vashaei, Zahra; McClintock, Ryan; Razeghi, Manijeh

    2011-10-01

    We report the synthesis, fabrication and testing of a 320 × 256 focal plane array (FPA) of back-illuminated, solarblind, p-i-n, AlxGa1-xN-based detectors, fully realized within our research laboratory. We implemented a novel pulsed atomic layer deposition technique for the metalorganic chemical vapor deposition (MOCVD) growth of crackfree, thick, and high Al composition AlxGa1-xN layers. Following the growth, the wafer was processed into a 320 × 256 array of 25 μm × 25 μm pixels on a 30 μm pixel-pitch and surrounding mini-arrays. A diagnostic mini-array was hybridized to a silicon fan-out chip to allow the study of electrical and optical characteristics of discrete pixels of the FPA. At a reverse bias of 1 V, an average photodetector exhibited a low dark current density of 1.12×10-8 A/cm2. Solar-blind operation is observed throughout the array with peak detection occurring at wavelengths of 256 nm and lower and falling off three orders of magnitude by 285 nm. After indium bump deposition and dicing, the FPA is hybridized to a matching ISC 9809 readout integrated circuit (ROIC). By developing a novel masking technology, we significantly reduced the visible response of the ROIC and thus the need for external filtering to achieve solar- and visible-blind operation is eliminated. This allowed the FPA to achieve high external quantum efficiency (EQE): at 254 nm, average pixels showed unbiased peak responsivity of 75 mA/W, which corresponds to an EQE of ~37%. Finally, the uniformity of the FPA and imaging properties are investigated.

  16. Measuring Thermodynamic Length

    SciTech Connect

    Crooks, Gavin E

    2007-09-07

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

  17. 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.

  18. DIVA optical telescope

    NASA Astrophysics Data System (ADS)

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

    2003-02-01

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

  19. 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.

  20. 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.

  1. Photonic processing with polylithic integrated optical devices

    NASA Astrophysics Data System (ADS)

    Bechtel, James H.; Morrison, Charles B.; Shi, Yongqiang

    1998-07-01

    Recent developments in nonlinear optical polymer materials and devices combined with epitaxial liftoff (ELO) and grafting of semiconductor materials are leading to dramatic new possibilities in devices for photonic signal processing. For example, the development of new device architectures is leading to electro-optic modulators that have halfwave voltages of approximately 1V. Applications include very large bandwidth (greater than 100 GHz) electro-optic modulators and high speed (less than 1 ns) switches for programmable optical delay lines for use in phased array systems. Also, with the increase in operating frequency and angular scan resolution, the delay length accuracy can reach magnitudes of micrometers for millimeter wave frequencies. With micro fabrication methods, integrated delay line/switch networks can achieve superior delay performance with a single integrated optic chip that is compact, light weight, and has low optical insertion loss. The use of ELO allows electronic device driver circuits to be integrated with the polymer chip to provide further miniaturization. Also, ELO methods can be used to fabricate very high speed metal-semiconductor-metal (MSM) photodetectors for optical signal detection and monitoring. Here ELO methods can find applications in the fabrication of multispectral detectors and focal plane arrays. Yet other applications include very high speed analog-to-digital converters.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Near-Field Imaging Based on High Resolution Focal Spot Properties

    NASA Astrophysics Data System (ADS)

    Hillers, G.; Campillo, M.; Ben-Zion, Y.; Roux, P.; Lecointre, A.; Vernon, F.

    2015-12-01

    The dense spatial wavefield sampling provided by modern seismological acquisitions allows the resolution of the near-field focal spot. The large-amplitude focal spot emerges from the superposition of a collapsing, time reversed wavefront. We discuss an imaging method that is based on high resolution reconstructions of the focal spot that is obtained from cross correlation. This approach exploits the dependence of the spot's shape on local properties of the propagation medium, i.e., the distance of the first zero crossing is proportional to the wave length. We construct noise correlation functions from data collected by a highly-dense Nodal array centered on the San Jacinto fault zone south of Anza. The focal spot can be obtained from the amplitude distributions at zero lag time. We repeat this analysis using each geophone location as the collapsing point to which the wave length estimate is related. The anisotropic intensity of the converging wavefields leads to distorted focal spots. In addition, strong body and fault zone waves that are associated with the complex fault zone structure prohibit the straightforward analysis of the spatially variable zero-lag time distributions. We discuss strategies to mute the influence of the wavefield anisotropy and the removal of the body and fault zone wave components for improved reconstructions of the symmetric surface wave focal spot. The overall consistency of the local wave speed estimates from the zero crossing and images obtained with more traditional far-field travel time inversions validates the near-field approach. We discuss causes for the remaining inconsistencies and compare limits of the resolution in both cases. At higher frequencies (>3 Hz) both methods reveal a heterogeneous velocity structure that exhibits pronounced low-velocity zones. In addition, near-field based images obtained at wave lengths that are too large for the application of far-field methods suggest a strong velocity contrast across the fault.

  7. Thermal and mechanical architecture for the SAFARI focal plane assembly

    NASA Astrophysics Data System (ADS)

    Martignac, J.

    2010-07-01

    The very challenging SPICA/SAFARI scientific goals imply to cool most detector solutions below 100 mK. This implies to find reliable solutions providing not only very efficient thermal insulation between the different temperature stages, but also keeping the stray light level well below the foreseen astronomical background (20 aW/pixel !). The main constraint is the available power budget (1-2μW) this value includes optical, electrical and parasitic power loads. This poster describes how the Herschel/PACS Bolometer Focal Plane thermo-mechanical design can be adapted to the new thermal and optical needs, while keeping a sufficiently stiff structure to withstand launch vibrations. We give the first results on the thermal and mechanical behaviour obtained with a prototype.

  8. 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

  9. 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.

  10. 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.

  11. Focal Mechanism determination of local M

    NASA Astrophysics Data System (ADS)

    Vales, Dina; Custório, 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) (Fojtíková 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 Zahradník, 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 Português 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.

  12. 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

  13. Collimated focal ratio degradation testing for highly multiplexed fiber systems-an improvement to a standard test.

    PubMed

    Finstad, Daniel; Wishnow, Edward; Poppett, Claire; Sirk, Martin; Edelstein, Jerry; Gibson, Steve; Marcy, Geoff; Howard, Andrew

    2016-09-01

    A simple method for determining the focal ratio degradation of optical fibers has been developed. The method involves splitting the light from the test fiber and recording ring patterns that have traveled over two different, and known, optical paths. This new method will be valuable for testing many fibers as will be needed for new multiobject astronomical spectrographs. PMID:27607255

  14. 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.

  15. 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

  16. 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

  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. 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).

  19. 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

  20. 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.

  1. New multiband IR imaging optics

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  2. 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.

  3. 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.

  4. 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.

  5. Multipass optical system equipped with thin films for the study of the spectra of cryogenic solids: measurement of the infrared spectrum of solid H(2).

    PubMed

    Steinhoff, R; Apparao, K V; Ferguson, D W; Narahari Rao, K; Winnewisser, B P; Winnewisser, M

    1993-11-20

    A multipass optical system external to the optical head of a cryostat has been designed for use with a Bruker IFS 120 HR interferometer. A White cell using mirrors with a focal length of 10 cm is the central feature of the system. Nearly all optical elements, including those in the cryostat, have been optimized with thin-film technology for maximum signal throughput in the 6000 to 7000 cm(-1) range. The extension of the path length of the sample, in a cell limited to 3.8 cm in length, is illustrated with spectra of solid para-H(2) at 12 K. The cell was limited to four passes in this application because of refraction of the infrared radiation at the sample surface. Twelve to 20 passes are possible for a sample with an index of refraction close to 1 and with smaller aperture settings. PMID:20856500

  6. Actinic Granuloma with Focal Segmental Glomerulosclerosis

    PubMed Central

    Phasukthaworn, Ruedee; Chanprapaph, Kumutnart; Vachiramon, Vasanop

    2016-01-01

    Actinic granuloma is an uncommon granulomatous disease, characterized by annular erythematous plaque with central clearing predominately located on sun-damaged skin. The pathogenesis is not well understood, ultraviolet radiation is recognized as precipitating factor. We report a case of a 52-year-old woman who presented with asymptomatic annular erythematous plaques on the forehead and both cheeks persisting for 2 years. The clinical presentation and histopathologic findings support the diagnosis of actinic granuloma. During that period of time, she also developed focal segmental glomerulosclerosis. The association between actinic granuloma and focal segmental glomerulosclerosis needs to be clarified by further studies. PMID:27293392

  7. 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

  8. [Liver ultrasound: focal lesions and diffuse diseases].

    PubMed

    Segura Grau, A; Valero López, I; Díaz Rodríguez, N; Segura Cabral, J M

    2016-01-01

    Liver ultrasound is frequently used as a first-line technique for the detection and characterization of the most common liver lesions, especially those incidentally found focal liver lesions, and for monitoring of chronic liver diseases. Ultrasound is not only used in the Bmode, but also with Doppler and, more recently, contrast-enhanced ultrasound. It is mainly used in the diagnosis of diffuse liver diseases, such as steatosis or cirrhosis. This article presents a practical approach for diagnosis workup, in which the different characteristics of the main focal liver lesions and diffuse liver diseases are reviewed. PMID:25523277

  9. 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.

  10. Close Range Calibration of Long Focal Length Lenses in a Changing Environment

    NASA Astrophysics Data System (ADS)

    Robson, Stuart; MacDonald, Lindsay; Kyle, Stephen; Shortis, Mark R.

    2016-06-01

    University College London is currently developing a large-scale multi-camera system for dimensional control tasks in manufacturing, including part machining, assembly and tracking, as part of the Light Controlled Factory project funded by the UK Engineering and Physical Science Research Council. In parallel, as part of the EU LUMINAR project funded by the European Association of National Metrology Institutes, refraction models of the atmosphere in factory environments are being developed with the intent of modelling and eliminating the effects of temperature and other variations. The accuracy requirements for both projects are extremely demanding, so accordingly improvements in the modelling of both camera imaging and the measurement environment are essential. At the junction of these two projects lies close range camera calibration. The accurate and reliable calibration of cameras across a realistic range of atmospheric conditions in the factory environment is vital in order to eliminate systematic errors. This paper demonstrates the challenge of experimentally isolating environmental effects at the level of a few tens of microns. Longer lines of sight promote the use and calibration of a near perfect perspective projection from a Kern 75mm lens with maximum radial distortion of the order of 0.5m. Coordination of a reference target array, representing a manufactured part, is achieved to better than 0.1mm at a standoff of 8m. More widely, results contribute to better sensor understanding, improved mathematical modelling of factory environments and more reliable coordination of targets to 0.1mm and better over large volumes.

  11. 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)

  12. 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)

  13. [Sonographic leg length measurement].

    PubMed

    Holst, A; Thomas, W

    1989-03-01

    After brief presentation of the clinical and radiological methods to measure the leg length and the leg length difference the authors outline the new diagnostic method for measuring the leg length and the leg length difference by means of real time sonography. Postmortem tests and clinical examples show that ultrasound is ideal to determine exactly the length of femur and tibia. The joint gaps on the hip, knee and upper ankle joint can be demonstrated by means of a 5 MHz linear scanner. A 1 mm strong metal bar on the skin and under the scanner is placed at right angles to the longitudinal axis of the body so that the bar can be seen in the centre. A measuring device gives the distances of the joint gaps in cm so that the difference correspond to the real length of femur and tibia. This standardised measuring is done by a particularly developed bearing and measuring device. The results of the sonographical measurements on 20 corpses and checking after consecutive dissections showed in 75% of cases a 100% sonographic measuring accuracy of the total leg length. The separately considered results for femur (85%) and tibia (90) were even better. The maximum sonographic measuring fault was 1.0 cm for the femur (in one case) and 0.5 cm for the tibia, respectively. All sonographic measurements were performed with the Sonoline SL-1 of the Siemens Company (Erlangen, W-Germany). Thus, sonographical measuring of the leg length offers a reliable, non-invasive method that can be repeated as often as necessary and is simply executed.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2652268

  14. Optically coupled focal plane arrays using lenslets and multiplexers

    DOEpatents

    Veldkamp, Wilfrid B.

    1991-01-01

    A detector array including a substrate having an array of diffractive lenses formed on the top side of the substrate and an array of sensor elements formed on the backside of the substrate. The sensor elements within the sensor array are oriented on the backside so that each sensor is aligned to receive light from a corresponding diffractive lens of the lens array. The detector array may also include a second substrate having an array of diffractive elements formed on one of its surfaces, the second substrate being disposed above and in proximity to the top side of the other substrate so that the elements on the second substrate are substantially aligned with corresponding sensor elements and diffractive lenses on the other substrate.

  15. 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.

  16. 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

  17. Performance characterization of a PIAA complex focal plane mask

    NASA Astrophysics Data System (ADS)

    Newman, Kevin; Belikov, Ruslan; Guyon, Olivier; Pluzhnik, Eugene

    2015-01-01

    The Phase Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC) is an architecture for directly observing extrasolar planets, and can achieve performance near the theoretical limits for any direct-detection instrument. PIAACMC can be designed for centrally-obscured and segmented apertures, which is particularly useful for next-generation telescopes. The PIAACMC architecture includes aspheric PIAA optics, and a complex phase-shifting focal plane mask that provides a pi phase shift to a portion of the on-axis starlight. The phase-shifted starlight is forced to interfere destructively with the un-shifted starlight, causing the starlight to be eliminated, and allowing a region for high-contrast imaging near the star.The main challenge in designing the complex focal plane mask is to achieve deep contrast over a wide spectral band. Another challenge for the mask design is to avoid sharp features, which can be difficult to manufacture. We present a solution to the design challenge by dividing the mask into sections and optimizing the phase shift produced by each section. We also demonstrate a method to design the mask with a smooth profile. One remaining challenge is to measure the performance of the mask. We present a method to compute the phase profile of the mask based on measurements of the diffraction pattern. The computed phase profile is used to simulate the expected coronagraph performance.

  18. 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.

  19. 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.

  20. Reduction of effective terahertz focal spot size by means of nested concentric parabolic reflectors

    SciTech Connect

    Neumann, V. A.; Laurita, N. J.; Pan, LiDong; Armitage, N. P.

    2015-09-15

    An ongoing limitation of terahertz spectroscopy is that the technique is generally limited to the study of relatively large samples of order 4 mm across due to the generally large size of the focal beam spot. We present a nested concentric parabolic reflector design which can reduce the terahertz focal spot size. This parabolic reflector design takes advantage of the feature that reflected rays experience a relative time delay which is the same for all paths. The increase in effective optical path for reflected light is equivalent to the aperture diameter itself. We have shown that the light throughput of an aperture of 2 mm can be increased by a factor 15 as compared to a regular aperture of the same size at low frequencies. This technique can potentially be used to reduce the focal spot size in terahertz spectroscopy and enable the study of smaller samples.

  1. Design, fabrication and characterization of a polarization-sensitive focal plane array

    NASA Astrophysics Data System (ADS)

    Vorobiev, Dmitry; Ninkov, Zoran

    2015-03-01

    Measurement of polarization is a powerful yet underutilized technique, with potential applications in remote sensing, astronomy, biomedical imaging and optical metrology. We present the design, fabrication and characterization of a CCD-based polarization-sensitive focal plane array (FPA). These devices are compact permanently aligned detectors capable of determining the degree and angle of linear polarization in a scene, with a single exposure, over a broad spectral range. To derive the polarization properties, we employ a variation of the division-of-focal plane modulation strategy. The devices are fabricated by hybridizing a micropolarizer array (MPA) with a CCD. The result is a "general-purpose" polarization-sensitive imaging sensor, which can be placed at the focal plane of a wide number of imaging systems (and even spectrographs). We present our efforts to date in developing this technology and examine the factors that fundamentally limit the performance of these devices.

  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. 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

  5. Focal Dermal Hypoplasia: A Rare Case Report

    PubMed Central

    Srinivas, Sahana M; Hiremagalore, Ravi

    2015-01-01

    Focal dermal hypoplasia (Goltz syndrome) is a rare genetic multisystem disorder primarily involving the skin, skeletal system, eyes, and face. We report the case of an eight-month-old female child who presented with multiple hypopigmented atrophic macules along the lines of blaschko, skeletal anomalies, umbilical hernia, developmental delay, hypoplastic nails, syndactyly, and lobster claw deformity characteristic of Goltz syndrome. PMID:25657436

  6. Focal dermal hypoplasia: a rare case report.

    PubMed

    Srinivas, Sahana M; Hiremagalore, Ravi

    2015-01-01

    Focal dermal hypoplasia (Goltz syndrome) is a rare genetic multisystem disorder primarily involving the skin, skeletal system, eyes, and face. We report the case of an eight-month-old female child who presented with multiple hypopigmented atrophic macules along the lines of blaschko, skeletal anomalies, umbilical hernia, developmental delay, hypoplastic nails, syndactyly, and lobster claw deformity characteristic of Goltz syndrome. PMID:25657436

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. Demonstration Telescopes Using "Dollar Optics"

    NASA Astrophysics Data System (ADS)

    Ross, Paul

    2008-05-01

    I propose a poster that illustrates the use of "dollar optics” for experimentation and for the creation of demonstration telescopes. Handling a variety of lenses and mirrors provides an opportunity for discovering practical optics. Some part of this path of exploration must have been traveled by Galileo as he experimented with spectacle lenses. "Dollar optics” include reading glasses (positive meniscus lenses), convex and concave mirrors, Fresnel sheets, magnifying lenses, and eye loupes. Unwanted distance spectacles (negative meniscus lenses) are available at second-hand stores. Galileo telescopes, "long” 17th century telescopes, and useful demonstration models of Newtonian reflectors can be made with "dollar” optics. The poster will illustrate practical information about "dollar optics” and telescopes: magnification, focal length, and "diopters” disassembling spectacles; creating cheap mounts for spectacle lenses; the importance of optical axes and alignment; eyepieces; and focusing. (A table would be useful with the poster to set out a hands-on display of "dollar optic” telescopes.) Educators, experimenters, and those concerned with astronomy outreach might be interested in this poster. Working with "dollar optics” requires facility with simple tools, interest in planning projects, patience, imagination, and the willingness to invest some time and effort. "Dollar optics” may help to foster creativity and hands-on enthusiasm - as did Galileo's work with simple lenses 400 years ago. "Oh! When will there be an end put to the new observations and discoveries of this admirable instrument?” - Galileo Galilei as quoted by Henry C. King, The History of the Telescope.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. Document Length Normalization.

    ERIC Educational Resources Information Center

    Singhal, Amit; And Others

    1996-01-01

    Describes a study that investigated document retrieval relevance based on document length in an experimental text collection. Topics include term weighting and document ranking, retrieval strategies such as the vector-space cosine match, and a modified technique called the pivoted cosine normalization. (LRW)

  2. Pleiades HR in Flight Geometrical Calibration : Location and Mapping of the Focal Plane

    NASA Astrophysics Data System (ADS)

    de Lussy, F.; Greslou, D.; Dechoz, C.; Amberg, V.; Delvit, J. M.; Lebegue, L.; Blanchet, G.; Fourest, S.

    2012-07-01

    The Pleiades system, ORFEO system optical component (Optical and Radar Federated Earth Observation) consists of a constellation of two satellites for very High Resolution panchromatic and multispectral optical observation of the Earth. Its mission is to cover all European civilian needs (mapping, tracking floods and fires) and defence in the category of metric resolution: 0.7m Nadir. The first Pleiades satellite was launched at the end of last year. One of the key objectives of the Pleiades HR (PHR) project is to achieve a location accuracy that will allow the use of images in GIS (Geographical Information System) without geometrical model improvement by refining on ground control points. The image location without refined model was specified with the precision of the most commonly used tool ie the civil GPS. So the location accuracy has been specified at less than 12m for 90% of the images on a nominal satellite configuration. Very special care has been taken all along the PHR project realization to achieve this very good location accuracy. The final touch is given during the in-orbit commissioning phase which lasts until June 2012. The geometric quality implies to tune the parameters involved in the geolocation model (geometric calibration): besides attitude and orbit restitution tuning (not considered here), it consists in estimating the biases between the instrument orientation and the AOCS reference frame, and also the sight line of each detector in the focal plane. This is called static geometrical model. The analysis of dynamic perturbations outside of the model are the second most important image quality objective of in-flight commissioning, not described in this paper. Finally "image quality assessment" consists in evaluating the image quality obtained in the final products. For geolocation model, it is quantified by the absolute geolocation and the pointing accuracies, and it is a main contributor in length alteration and planimetric and altimetric

  3. Optimum optical structures for active control

    NASA Astrophysics Data System (ADS)

    Shannon, R. R.; Richard, R. M.; Hansen, J. G. R.

    1980-01-01

    A NASTRAN structural analysis of a lightweight mirror structure has been completed and is compared with previous experimental measurements. A preliminary design for a 4 meter aperture, 6 meter focal length primary mirror is presented.

  4. 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

  5. Talin determines the nanoscale architecture of focal adhesions.

    PubMed

    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

    2015-09-01

    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

  6. 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

  7. 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

  8. Chest pain in focal musculoskeletal disorders.

    PubMed

    Stochkendahl, Mette Jensen; Christensen, Henrik Wulff

    2010-03-01

    The musculoskeletal system is a recognized source of chest pain. However, despite the apparently benign origin, patients with musculoskeletal chest pain remain under-diagnosed, untreated, and potentially continuously disabled in terms of anxiety, depression, and activities of daily living. Several overlapping conditions and syndromes of focal disorders, including Tietze syndrome, costochondritis, chest wall syndrome, muscle tenderness, slipping rib, cervical angina, and segmental dysfunction of the cervical and thoracic spine, have been reported to cause pain. For most of these syndromes, evidence arises mainly from case stories and empiric knowledge. For segmental dysfunction, clinical features of musculoskeletal chest pain have been characterized in a few clinical trials. This article summarizes the most commonly encountered syndromes of focal musculoskeletal disorders in clinical practice. PMID:20380955

  9. Focal tracer uptake in the jaw.

    PubMed

    El-Zahry, Mai R; Sinzinger, Helmut

    2014-01-01

    Focal tracer uptake in the jaw during conventional bone scintigraphy is a quite frequent finding usually due to dental disease and seldom to other diseases including malignant disease. Methylene diphosphonate-technetium-99m ((99m)Tc-MDP) 3-phase bone scan is considered the most sensitive imaging method for the detection of jaw osteonecrosis at an early stage. This finding can also but seldom be seen in patients undergoing palliative radionuclide treatment for bone metastases. In conclusion, focal jaw lesions are usually benign and of dental origin. In a small percentage of cancer patients of about 4.3%, jaw lesions as diagnosed among 347 cases of various carcinomas may be due to malignancy. Unfortunately, the number of studies is small, most of them are retrospective and few show biopsy results. PMID:25397621

  10. Extensive Focal Epithelial Hyperplasia: A Case Report

    PubMed Central

    Mansouri, Zahra; Bakhtiari, Sedigheh; Noormohamadi, Robab

    2015-01-01

    Focal epithelial hyperplasia (FEH) or Heck’s disease is a rare viral infection of the oral mucosa caused by human papilloma virus especially subtypes 13 or 32. The frequency of this disease varies widely from one geographic region and ethnic groups to another. This paper reports an Iranian case of extensive focal epithelial hyperplasia. A 35-year-old man with FEH is described, in whom the lesions had persisted for more than 25 years. The lesion was diagnosed according to both clinical and histopathological features. Dental practitioner should be aware of these types of lesions and histopathological examination together and a careful clinical observation should be carried out for a definitive diagnosis. PMID:26351501

  11. 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

  12. Focal adhesions, stress fibers and mechanical tension

    PubMed Central

    Burridge, Keith; Guilluy, Christophe

    2016-01-01

    Stress fibers and focal adhesions are complex protein arrays that produce, transmit and sense mechanical tension. Evidence accumulated over many years led to the conclusion that mechanical tension generated within stress fibers contributes to the assembly of both stress fibers themselves and their associated focal adhesions. However, several lines of evidence have recently been presented against this model. Here we discuss the evidence for and against the role of mechanical tension in driving the assembly of these structures. We also consider how their assembly is influenced by the rigidity of the substratum to which cells are adhering. Finally, we discuss the recently identified connections between stress fibers and the nucleus, and the roles that these may play, both in cell migration and regulating nuclear function. PMID:26519907

  13. 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; /Fermilab

    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.

  14. [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

  15. 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

  16. The Focal Surface of EUSO Telescope

    NASA Technical Reports Server (NTRS)

    Shimizu, H. M.; Kawasaki, Y.; Takizawa, Y.; Sakaki, N.; Teshima, M.; Ebisuzaki, T.; Takahashi, Y.; Adams, J.; Catalano, O.; Scarisi, L.; Six, N. Frank (Technical Monitor)

    2002-01-01

    The Extreme Universe Space Observatory (EUSO) is a science mission under conceptual design for the detection of extremely high energy cosmic rays and neutrinos by the observation of time-resolved images of atmospheric fluorescence photons generated along the extensive air shower, in the near ultraviolet wavelength region. A refractive telescope with double-sided double Fresnel lens will be employed to achieve a large field of view of 60 degrees. The energy and arrival direction of the primary particles will be determined by observing the time evolution of the airshower. The focal surface of the EUSO telescope will be segmented to a few hundred thousand pixels to resolve the entire field of view with the angular resolution of the order of 0.1 degree. The time evolution will be observed with the time resolution of 0.8 microsecond. A large scale array of multianode photomultiplier (MAPMT) is being studied as the EUSO focal surface. The MAPMT array is capable of detecting near ultraviolet photons at single photoelectron level. In this contribution, we will report the present status of the focal surface design including the optimization of anode segmentation and the minimization of the dead area and discuss overall experimental performance in detecting extensive airshowers.

  17. Mechanism of Focal Adhesion Kinase Mechanosensing

    PubMed Central

    Sturm, Sebastian; Bullerjahn, Jakob Tómas; Bronowska, Agnieszka; Gräter, 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

  18. Multispectral linear array (MLA) focal plane mechanical and thermal design

    NASA Technical Reports Server (NTRS)

    Mitchell, A. S.; Kaminski, E. F.

    1982-01-01

    The mechanical and thermal design of an integrated focal plane subsystem of a Multispectral Linear Array (MLA) instrument is discussed in terms of focal-plane alignment, thermoelastic performance, and thermal requirements. The modular construction and thermal control of the focal plane array are discussed.

  19. 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…

  20. Focus in Grade 2: Teaching with Curriculum Focal Points

    ERIC Educational Resources Information Center

    National Council of Teachers of Mathematics, 2011

    2011-01-01

    "Focus in Grade 2: Teaching with Curriculum Focal Points" describes and illustrates learning paths for the mathematical concepts and skills of each grade 2 Focal Point as presented in 'Curriculum Focal Points for Prekindergarten through Grade 8 Mathematics". It includes representational supports for teaching and learning that can facilitate…

  1. Molded, wafer level optics for long wave infra-red applications

    NASA Astrophysics Data System (ADS)

    Franks, John

    2016-05-01

    For many years, the Thermal Imaging market has been driven by the high volume consumer market. The first signs of this came with the launch of night vision systems for cars, first by Cadillac and Honda and then, more successfully by BMW, Daimler and Audi. For the first time, simple thermal imaging systems were being manufactured at the rate of more than 10,000 units a year. This step change in volumes enabled a step change in system costs, with thermal imaging moving into the consumer's price range. Today we see that the consumer awareness and the consumer market continues to increase with the launch of a number of consumer focused smart phone add-ons. This has brought a further step change in system costs, with the possibility to turn your mobile phone into a thermal imager for under $250. As the detector technology has matured, the pixel pitches have dropped from 50μm in 2002 to 12 μm or even 10μm in today's detectors. This dramatic shrinkage in size has had an equally dramatic effect on the optics required to produce the image on the detector. A moderate field of view that would have required a focal length of 40mm in 2002 now requires a focal length of 8mm. For wide field of view applications and small detector formats, focal lengths in the range 1mm to 5mm are becoming common. For lenses, the quantity manufactured, quality and costs will require a new approach to high volume Infra-Red (IR) manufacturing to meet customer expectations. This, taken with the SwaP-C requirements and the emerging requirement for very small lenses driven by the new detectors, suggests that wafer scale optics are part of the solution. Umicore can now present initial results from an intensive research and development program to mold and coat wafer level optics, using its chalcogenide glass, GASIR®.

  2. A new method of focal plane mosaic for space remote sensing camera

    NASA Astrophysics Data System (ADS)

    Sun, Guangwei; Li, Lin

    2011-08-01

    With the development of space remote sensors, the urgent needs of large area array optical detectors increase strongly. To address the conflict between the resolution and the detector size, the most straightforward approach is to use a larger CCD chip, but a single small area array CCD chip cannot meet the needs of the focal plane, therefore, the method of CCD mosaic must be used. This paper presents a new method of splicing, it's a twice-imaging scheme. The first image is formed on an imaging plate of intercepting optical component, and then four separate CCD cameras are used to produce the segmented images on the final image plane. So a CCD focal plane mosaic can be achieved.

  3. Progress on the development of active micro-structured optical arrays for x-ray optics

    NASA Astrophysics Data System (ADS)

    Rodriguez Sanmartin, Daniel; Zhang, Dou; Button, Tim; Atkins, Carolyn; Doel, Peter; Wang, Hongchang; Brooks, David; Feldman, Charlotte; Willingale, Richard; Michette, Alan; Pfauntsch, Slawka; Sahraei, Shahin; Shand, Matthew; James, Ady; Dunare, Camelia; Stevenson, Tom; Parkes, William; Smith, Andy

    2009-08-01

    The Smart X-Ray Optics (SXO) project comprises a U.K.-based consortium developing active/adaptive micro-structured optical arrays (MOAs). These devices are designed to focus X-rays using grazing incidence reflection through consecutive aligned arrays of microscopic channels etched in silicon. The silicon channels have been produced both by dry and wet etching, the latter providing smoother channel walls. Adaptability is achieved using piezoelectric actuators, which bend the device and therefore change its focal distance. We aim to achieve a 5 cm radius of curvature which can provide a suitable focal length using a tandem pair MOA configuration. Finite Element Analysis (FEA) modelling has been carried out for the optimization of the MOA device design, consider different types of actuators (unimorph, bimorph and active fibre composites), and different Si/piezoelectric absolute and relative thicknesses. Prototype devices have been manufactured using a Viscous Plastic Processing Process for the piezoelectric actuators and dry etched silicon channels, bonded together using a low shrinkage adhesive. Characterisation techniques have been developed in order to evaluate the device performance in terms of the bending of the MOA channels produced by the actuators. This paper evaluates the progress to date on the actuation of the MOAs, comparing FEA modelling with the results obtained for different prototype structures.

  4. Hemispherical infrared focal plane arrays: a new design parameter for the instruments

    NASA Astrophysics Data System (ADS)

    Fendler, M.; Dumas, D.; Chemla, F.; Cohen, M.; Laporte, P.; Tekaya, K.; Le Coarer, E.; Primot, J.; Ribot, H.

    2012-07-01

    In ground based astronomy, mainly all designs of sky survey telescopes are limited by the requirement that the detecting surface is flat whereas the focal surface is curved. Two kinds of solution have been investigated up to now. The first one consists in adding optical systems to flatten the image surface; however this solution complicates the design and increases the system size. Somehow, this solution increases, in the same time, the weight and price of the instrument. The second solution consists in curving artificially the focal surface by using a mosaic of several detectors, which are positioned in a spherical shape. However, this attempt is dedicated to low curvature and is limited by the technical difficulty to control the detectors alignment and tilt between each others. Today we would like to propose an ideal solution which is to curve the focal plane array in a spherical shape, thanks to our monolithic process developed at CEA-LETI based on thinned silicon substrates which allows a 100% optical fill factor. Two infrared uncooled cameras have been performed, using 320 x 256 pixels and 25 μm pitch micro-bolometer arrays curved at a bending radius of 80 mm. These two micro-cameras illustrate the optical system simplification and miniaturization involved by curved focal plane arrays. Moreover, the advantages of curved detectors on the optical performances (Point Spreading Function), as well as on volume and cost savings have been highlighted by the simulation of the opto-mechanical architecture of the spectrometer OptiMOS-EVE for the European Extremely Large Telescope (E-ELT).

  5. HST Cycle 21 Focus and Optical Monitor

    NASA Astrophysics Data System (ADS)

    Cox, Colin

    2013-10-01

    This program is the Cycle 21 implementation of the HST Optical Monitoring Program. The 9 orbits comprising this proposal will utilize ACS {Wide Field channel} and WFC3 {UVIS channel} to observe stellar cluster members in parallel with multiple exposures over an orbit. Phase retrieval performed on the PSF in each image will be used to measure primarily focus, with the ability to explore apparent coma, astigmatism, and third order spherical changes in WFC3. The goals of this program are to:1.} monitor the overall OTA focal length for the purposes of maintaining focus within science tolerances.2.} gain experience with the relative effectiveness of phase retrieval on WFC3/UVIS PSFs.3.} determine focus offset between the imagers and identify any SI-specific focus behavior and dependencies.If need is determined, future visits will be modified to interleave WFC3/IR channel and STIS/CCD focii measurements.

  6. Limits of spectral resolution in optical measurements

    NASA Astrophysics Data System (ADS)

    Marques, Manuel B.

    2014-08-01

    Nowadays a growing number of scientists relies on optical spectral measurements for their research. The market is full of new plug-and-play equipment for spectral analysis that take the fuss out of the measurements. As with other instruments (computers, lasers, etc.) the researcher doesńt need any longer to work with someone with a post-graduate formation on the technology to be able to do excellent research. But, as in every instrument, there are limitations on the instrument use that affect its precision and resolution. Currently there is in the market a large variety of equipment for spectral measurements. They range from the huge long focal length double pass monochromators to the small pocket size USB connected array spectrometers. The different configurations have different sensitivities on the light input system, light intensity, coherence, polarization, etc. In this talk we will discuss a few of the limitations in spectral measurements that can be found in experimental setups.

  7. Increasing the penetration depth for ultrafast laser tissue ablation using glycerol based optical clearing

    NASA Astrophysics Data System (ADS)

    Gabay, Ilan; Subramanian, Kaushik G.; Martin, Chris; Yildirim, Murat; Tuchin, Valery V.; Ben-Yakar, Adela

    2016-03-01

    Background: Deep tissue ablation is the next challenge in ultrafast laser microsurgery. By focusing ultrafast pulses below the tissue surface one can create an ablation void confined to the focal volume. However, as the ablation depth increases in a scattering tissue, increase in the required power can trigger undesired nonlinear phenomena out of focus that restricts our ability to ablate beyond a maximum ablation depth of few scattering lengths. Optical clearing (OC) might reduce the intensity and increase the maximal ablation depth by lowering the refractive index mismatch, and therefore reducing scattering. Some efforts to ablate deeper showed out of focus damage, while others used brutal mechanical methods for clearing. Our clinical goal is to create voids in the scarred vocal folds and inject a biomaterial to bring back the tissue elasticity and restore phonation. Materials and methods: Fresh porcine vocal folds were excised and applied a biocompatible OC agent (75% glycerol). Collimated transmittance was monitored. The tissue was optically cleared and put under the microscope for ablation threshold measurements at different depths. Results: The time after which the tissue was optically cleared was roughly two hours. Fitting the threshold measurements to an exponential decay graph indicated that the scattering length of the tissue increased to 83+/-16 μm, which is more than doubling the known scattering length for normal tissue. Conclusion: Optical clearing with Glycerol increases the tissue scattering length and therefore reduces the energy for ablation and increases the maximal ablation depth. This technique can potentially improve clinical microsurgery.

  8. Optical implementation of the generalized Hough transform with totally incoherent light.

    PubMed

    Fernández, Ariel; Alonso, Julia R; Ayubi, Gastón A; Osorio, Matías; Ferrari, José A

    2015-08-15

    The generalized Hough transform is a well-established technique for detecting complex shapes in images containing noisy or missing data. We present an efficient optical implementation of this transform using an electrical lens with variable focal length and a rotating pupil mask matching the pattern to be found. The proposed setup works under fully (i.e., both spatially and temporally) incoherent illumination and can handle orientation changes or scale variations in the pattern. Validation experiments showing its real-time application are presented. PMID:26274689

  9. 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

  10. Foveated optics

    NASA Astrophysics Data System (ADS)

    Bryant, Kyle R.

    2016-05-01

    Foveated imaging can deliver two different resolutions on a single focal plane, which might inexpensively allow more capability for military systems. The following design study results provide starting examples, lessons learned, and helpful setup equations and pointers to aid the lens designer in any foveated lens design effort. Our goal is to put robust sensor in a small package with no moving parts, but still be able to perform some of the functions of a sensor in a moving gimbal. All of the elegant solutions are out (for various reasons). This study is an attempt to see if lens designs can solve this problem and realize some gains in performance versus cost for airborne sensors. We determined a series of design concepts to simultaneously deliver wide field of view and high foveal resolution without scanning or gimbals. Separate sensors for each field of view are easy and relatively inexpensive, but lead to bulky detectors and electronics. Folding and beam-combining of separate optical channels reduces sensor footprint, but induces image inversions and reduced transmission. Entirely common optics provide good resolution, but cannot provide a significant magnification increase in the foveal region. Offsetting the foveal region from the wide field center may not be physically realizable, but may be required for some applications. The design study revealed good general guidance for foveated optics designs with a cold stop. Key lessons learned involve managing distortion, telecentric imagers, matching image inversions and numerical apertures between channels, reimaging lenses, and creating clean resolution zone splits near internal focal planes.

  11. Electron-Focus Adjustment for Photo-Optical Imagers

    NASA Technical Reports Server (NTRS)

    Fowler, Walter B.; Flemming, Keith; Ziegler, Michael M.

    1987-01-01

    Internal electron focus made independent of optical focus. Procedure enables fine tuning of internal electron-focusing system of photo-optical imager, without complication by imperfections of associated external optics. Applicable to imager in which electrons emitted from photocathode in optical focal plane, then electrostatically and/or magnetically focused to replica of image in second focal plane containing photodiodes, phototransistorss, charge-coupled devices, multiple-anode outputs, or other detectors.

  12. Focal damage to macaque photoreceptors produces persistent visual loss

    PubMed Central

    Strazzeri, Jennifer M.; Hunter, Jennifer J.; Masella, Benjamin D.; Yin, Lu; Fischer, William S.; DiLoreto, David A.; Libby, Richard T.; Williams, David R.; Merigan, William H.

    2014-01-01

    Insertion of light-gated channels into inner retina neurons restores neural light responses, light evoked potentials, visual optomotor responses and visually-guided maze behavior in mice blinded by retinal degeneration. This method of vision restoration bypasses damaged outer retina, providing stimulation directly to retinal ganglion cells in inner retina. The approach is similar to that of electronic visual protheses, but may offer some advantages, such as avoidance of complex surgery and direct targeting of many thousands of neurons. However, the promise of this technique for restoring human vision remains uncertain because rodent animal models, in which it has been largely developed, are not ideal for evaluating visual perception. On the other hand, psychophysical vision studies in macaque can be used to evaluate different approaches to vision restoration in humans. Furthermore, it has not been possible to test vision restoration in macaques, the optimal model for human-like vision, because there has been no macaque model of outer retina degeneration. In this study, we describe development of a macaque model of photoreceptor degeneration that can in future studies be used to test restoration of perception by visual prostheses. Our results show that perceptual deficits caused by focal light damage are restricted to locations at which photoreceptors are damaged, that optical coherence tomography (OCT) can be used to track such lesions, and that adaptive optics retinal imaging, which we recently used for in vivo recording of ganglion cell function, can be used in future studies to examine these lesions. PMID:24316158

  13. Focal damage to macaque photoreceptors produces persistent visual loss.

    PubMed

    Strazzeri, Jennifer M; Hunter, Jennifer J; Masella, Benjamin D; Yin, Lu; Fischer, William S; DiLoreto, David A; Libby, Richard T; Williams, David R; Merigan, William H

    2014-02-01

    Insertion of light-gated channels into inner retina neurons restores neural light responses, light evoked potentials, visual optomotor responses and visually-guided maze behavior in mice blinded by retinal degeneration. This method of vision restoration bypasses damaged outer retina, providing stimulation directly to retinal ganglion cells in inner retina. The approach is similar to that of electronic visual protheses, but may offer some advantages, such as avoidance of complex surgery and direct targeting of many thousands of neurons. However, the promise of this technique for restoring human vision remains uncertain because rodent animal models, in which it has been largely developed, are not ideal for evaluating visual perception. On the other hand, psychophysical vision studies in macaque can be used to evaluate different approaches to vision restoration in humans. Furthermore, it has not been possible to test vision restoration in macaques, the optimal model for human-like vision, because there has been no macaque model of outer retina degeneration. In this study, we describe development of a macaque model of photoreceptor degeneration that can in future studies be used to test restoration of perception by visual prostheses. Our results show that perceptual deficits caused by focal light damage are restricted to locations at which photoreceptors are damaged, that optical coherence tomography (OCT) can be used to track such lesions, and that adaptive optics retinal imaging, which we recently used for in vivo recording of ganglion cell function, can be used in future studies to examine these lesions. PMID:24316158

  14. 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.

  15. Optical instruments

    NASA Technical Reports Server (NTRS)

    Abel, I. R. (Inventor)

    1974-01-01

    A wide angle, low focal ratio, high resolution, catoptric, image plane scanner is described. The scanner includes the following features: (1) a reflective improvement on the Schmidt principle, (2) a polar line scanner in which all field elements are brought to and corrected on axis, and (3) a scanner arrangement in which the aperture stop of the system is imaged at the center of curvature of a spherical primary mirror. The system scans are a large radial angle and an extremely high rate of speed with relatively small scanning mirrors. Because the system is symmetrical about the optical axis, the obscuration is independent of the scan angle.

  16. Optical coupling

    NASA Astrophysics Data System (ADS)

    Bock, J. J.; Gundersen, J.; Lee, A. T.; Richards, P. L.; Wollack, E.

    2009-03-01

    This paper describes contributions to the CMBpol Technology Study Workshop concerning optical coupling structures. These are structures in or near the focal plane which convert the free space wave to a superconducting microstrip on a SI wafer, or to the waveguide input to a HEMT receiver. In addition to an introduction and conclusions by the editor, this paper includes independent contributions by Bock on 'Planar Antenna-Coupled Bolometers for CMB Polarimetry', by Gunderson and Wollack on 'Millimeter-Wave Platlet Feeds', and by Lee on 'Multi-band Dual-Polarization Lens-coupled Planar Antennas for Bolometric CMB polarimetry.'

  17. Dynamic focal spots registration algorithm for freeform surface measurement

    NASA Astrophysics Data System (ADS)

    Guo, Wenjiang; Zhao, Liping; Chen, I.-Ming

    2013-06-01

    In a wavefront sensing system, the raw data for surface reconstruction, either the slope matrix or curvature matrix, is obtained through centroiding on the focal spot images. Centroiding is to calculate the first moment within a certain area of interest, which encloses the focal spot. As the distribution of focal spots is correlated to the surface sampling condition, while a uniform rectangular grid is good enough to register all the focal spots of a uniformly sampled near flat surface, the focal spots of aspherical or freeform surfaces have varying shapes and sizes depending on the surface geometry. In this case, the normal registration method is not applicable. This paper proposed a dynamic focal spots registration algorithm to automatically analyze the image, identify and register every focal spot for centroiding at one go. Through experiment on a freeform surface with polynomial coefficients up to 10th order, the feasibility and effectiveness of the proposed algorithm is proved.

  18. 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

  19. The impact of domestication on the chicken optical apparatus.

    PubMed

    Roth, Lina S V; Lind, Olle

    2013-01-01

    Domestication processes tend to release animals from natural selection and favour traits desired by humans, such as food-production and co-operative behaviour. A side effect of such selective breeding is the alteration of unintended traits. In this paper, we investigate how active selection for egg production in chickens has affected the visual system, in particular the optical sensitivity that relates to the ability of chickens to see in dim light. We measured eye dimensions as well as the pupil diameter at different light intensities (the steady state pupil dynamics), in adult male and female White Leghorns and the closest relatives to their ancestor, the Red Junglefowls. With this information, we calculated the focal length and optical sensitivity (f-number) of the eyes. Males have larger eyes than females in both breeds and White Leghorn eyes are larger than those of Red Junglefowls in both sexes. The steady state pupil dynamics is less variable, however, the combination of pupil dynamics and eye size gives a higher optical sensitivity in Red Junglefowl eyes than in White Leghorns at light intensities below approximately 10 cd/m(2). While eye size and focal length match the larger body size in White Leghorns compared to Red Junglefowls, the steady state pupil dynamics do not. The reason for this is likely to be that eye morphology and the neuro-muscular control of the pupil have been affected differently by the strong selection for egg production and the simultaneous release of the selection pressure for high performing vision. This study is the first description of how optical sensitivity has changed in a domesticated species and our results demonstrate important considerations regarding domestication processes and sensory ability. PMID:23776492

  20. Optical design of solar blind ultraviolet warning system

    NASA Astrophysics Data System (ADS)

    Li, Quanyong; Xu, Chunyun; Dong, Jianing

    2012-11-01

    Ultraviolet warning technology is one of the important methods for missile warning. "Solar blind region" provides a very effective way to detect the target for missile approaching alarm. In order to find the target by detecting the ultraviolet radiation of missile efflux plasma, ultraviolet optical system design of large field of view and large relative aperture is the key for the technology of ultraviolet detection. From the academic point of view, the structure parameters are determined for 2048×2048 ultraviolet CCD detector according to the requirements of ultraviolet warning system. The refractive ultraviolet warning optical system is designed for 0.24μm ~0.28μm wave band with ZEMAX optical design software. The focal length is 41mm, the field of view is 46°and the relative aperture is 1:3.5. In order to ensure the detected energy, aspherical and binary surface are adopted to reduce the aberration and spot size of the system. Within the 0.8 field of view RMS of spot diagram is less than 13μm. It is smaller than the pixel size 13.5μm of ultraviolet CCD. The energy concentration is more than 80%. This optical system has long focal length and large relative aperture that meet the energy requirements of warning system. Large field of view can satisfy the range of searching targets. The spot diagram RMS of each field of view is so small that can meet the requirement of image quality. In addition, the system is composed of six lenses. The structure of it is simple, the volume is small and the application is very convenient.

  1. 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

  2. Wave statistics in a coastal focal zone

    NASA Astrophysics Data System (ADS)

    Janssen, T. T.; Herbers, T. H. C.; Pearman, D. W.; Van Ettinger, E.; Smit, P. B.

    2014-12-01

    Wave-current dynamics in wave focal zones in exposed coastal inlets and river mouths are still poorly understood. This is in part due to lack of observations, which are complicated due to the presence of energetic waves, strong (tidal) currents, dynamic seabed morphology, and often busy ship traffic. Conventional (fixed) instruments, such as buoys and bottom-mounted current or pressure sensors, are difficult to maintain in such areas, and the spatial variability of the wave field is difficult to capture with single point measurements, or even arrays of fixed measurements. In addition to the observational difficulties, the effects of e.g. current shear, wave blocking, statistical inhomogeneity [see Smit & Janssen, 2013, J. Phys. Ocean., 43, pp 1741-1758], and nonlinearity [see Janssen & Herbers, 2009, J. Phys Ocean., 39, pp 1948-1964] on wave statistics are not fully understood, not accounted for in operational stochastic wave models, and - as a consequence - often ignored. In this paper, we consider new observational data of waves approaching the Mouth of the Columbia River undergoing bottom refraction and strong wave-current interaction. The data were collected during the 2013 ONR RIVET experiment using an array of free drifting wave-current buoys. The Lagrangian instruments capture the spatial variability of the wave field in the inlet and, by deploying them in large ensembles, resolve the (inhomogeneous and nonlinear) wave statistics in the focal zone. We discuss the use of free-drifting instruments to measure wave statistics in a coastal wave focal zone, consider the observed effects of wave inhomogeneity, and show that non-Gaussian effects are important and affect extreme wave occurrences in the Mouth of the Columbia River.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Accurate Fiber Length Measurement Using Time-of-Flight Technique

    NASA Astrophysics Data System (ADS)

    Terra, Osama; Hussein, Hatem

    2016-06-01

    Fiber artifacts of very well-measured length are required for the calibration of optical time domain reflectometers (OTDR). In this paper accurate length measurement of different fiber lengths using the time-of-flight technique is performed. A setup is proposed to measure accurately lengths from 1 to 40 km at 1,550 and 1,310 nm using high-speed electro-optic modulator and photodetector. This setup offers traceability to the SI unit of time, the second (and hence to meter by definition), by locking the time interval counter to the Global Positioning System (GPS)-disciplined quartz oscillator. Additionally, the length of a recirculating loop artifact is measured and compared with the measurement made for the same fiber by the National Physical Laboratory of United Kingdom (NPL). Finally, a method is proposed to relatively correct the fiber refractive index to allow accurate fiber length measurement.

  8. Holographic lens for optical correlator

    NASA Astrophysics Data System (ADS)

    Semenov, G. B.; Koreshev, S. N.; Pavlov, A. V.; Shubnikov, Y. I.

    1984-08-01

    Aberrations in holographic optics place limitations on the information capacity of the data that can be processed by holographic optical correlators. Nonetheless, the aberrations can be reduced sufficiently for an extensive class of devices such as those for real time data input using space-time light modulators and a TV channel. This paper analyzes the aberrations of holographic lenses, demonstrating the feasibility of an off-axis lens for correlation image analysis with aberrations similar to an axial lens. A requirement that the wave aberrations not exceed a quarter-wavelength was placed on the lens. Equations are solved for coma and astigmatism, and used to plot the maximum wave aberrations as a function of the spatial frequency of the proposed signal for three cases: (1) normal propagation of a diverging beam and oblique propagation of a plane beam; (2) oblique propagation of diverging and parallel beams, symmetrical with respect to the normal to the photographic plate; (3) oblique propagation of the diverging beam and normal propagation of the parallel beam. The angle between the beam axes was 45 deg in all cases, with a lens focal length of 350 mm and an operture of 32 mm.

  9. 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.

  10. 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.

  11. 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.

  12. Numerically bridging lamellipodial and filopodial activity during cell spreading reveals a potentially novel trigger of focal adhesion maturation.

    PubMed

    Loosli, Y; Vianay, B; Luginbuehl, R; Snedeker, J G

    2012-05-01

    We present a novel approach to modeling cell spreading, and use it to reveal a potentially central mechanism regulating focal adhesion maturation in various cell phenotypes. Actin bundles that span neighboring focal complexes at the lamellipodium-lamellum interface were assumed to be loaded by intracellular forces in proportion to bundle length. We hypothesized that the length of an actin bundle (with the corresponding accumulated force at its adhesions) may thus regulate adhesion maturation to ensure cell mechanical stability and morphological integrity. We developed a model to test this hypothesis, implementing a "top-down" approach to simplify certain cellular processes while explicitly incorporating complexity of other key subcellular mechanisms. Filopodial and lamellipodial activities were treated as modular processes with functional spatiotemporal interactions coordinated by rules regarding focal adhesion turnover and actin bundle dynamics. This theoretical framework was able to robustly predict temporal evolution of cell area and cytoskeletal organization as reported from a wide range of cell spreading experiments using micropatterned substrates. We conclude that a geometric/temporal modeling framework can capture the key functional aspects of the rapid spreading phase and resultant cytoskeletal complexity. Hence the model is used to reveal mechanistic insight into basic cell behavior essential for spreading. It demonstrates that actin bundles spanning nascent focal adhesions such that they are aligned to the leading edge may accumulate centripetal endogenous forces along their length, and could thus trigger focal adhesion maturation in a force-length dependent fashion. We suggest that this mechanism could be a central "integrating" factor that effectively coordinates force-mediated adhesion maturation at the lamellipodium-lamellum interface. PMID:22453759

  13. Focal Ca2+ transient detection in smooth muscle.

    PubMed

    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

  14. Characterization of the KATRIN Focal Plane Detector

    NASA Astrophysics Data System (ADS)

    Bodine, Laura; Leber, Michelle; Myers, Allan; Tolich, Kazumi; Vandevender, Brent; Wall, Brandon

    2008-10-01

    The Karlsruhe Tritium Neutrino (KATRIN) Experiment is a next generation tritium beta decay experiment designed to measure directly the electron neutrino mass with a sensitivity of 0.2 eV. In the experiment, electrons from tritium decay of a gaseous source are magnetically guided through analyzing solenoidal retarding electrostatic spectrometers and detected via a focal plane detector. The focal plane detector is a 90mm diameter, 500 micron thick monolithic silicon pin-diode array with 148 pixels. The diode contacts have a titanium nitride overlayer and are connected to preamplifiers via an array of spring-loaded pogo pins. This novel connection scheme minimizes backgrounds from radioactive materials near the detector, facilitates characterization and replacement of the detector wafer, but requires a unique mounting design. The force of the pins strains the silicon, possibly altering the detector properties and performance. Results on the mechanical, thermal and electrical performance of a prototype detector under stress from pogo pin readouts will be presented.

  15. Visual function and perinatal focal cerebral infarction.

    PubMed Central

    Mercuri, E; Atkinson, J; Braddick, O; Anker, S; Nokes, L; Cowan, F; Rutherford, M; Pennock, J; Dubowitz, L

    1996-01-01

    AIMS: To evaluate the visual function of infants with perinatal cerebral infarction in whom the site and size of the lesion has been determined using magnetic resonance imaging (MRI). METHODS: Twelve infants with cerebral infarction on MRI were studied with a battery of tests specifically designed to evaluate visual function in infancy. This included tests: for visual attention (fixation shifts); of cerebral asymmetry (optokinetic nystagmus, visual fields); for assessment of acuity (forced choice preferential looking); and neurophysiological measures of vision (phase reversal and orientation reversal visual evoked potential). RESULTS: A considerable incidence of abnormalities on at least one of the tests for visual function used was observed. The presence or severity of visual abnormalities could not always be predicted by the site and extent of the lesion seen on imaging. CONCLUSIONS: Early focal lesions affecting the visual pathway can, to some extent, be compensated for by the immature developing brain. These data suggest that all the infants presenting with focal lesions need to be investigated with a detailed assessment of various aspects of vision. Images PMID:8949687

  16. 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

  17. Idiopathic focal epilepsies: the "lost tribe".

    PubMed

    Pal, Deb K; Ferrie, Colin; Addis, Laura; Akiyama, Tomoyuki; Capovilla, Giuseppe; Caraballo, Roberto; de Saint-Martin, Anne; Fejerman, Natalio; Guerrini, Renzo; Hamandi, Khalid; Helbig, Ingo; Ioannides, Andreas A; Kobayashi, Katsuhiro; Lal, Dennis; Lesca, Gaetan; Muhle, Hiltrud; Neubauer, Bernd A; Pisano, Tiziana; Rudolf, Gabrielle; Seegmuller, Caroline; Shibata, Takashi; Smith, Anna; Striano, Pasquale; Strug, Lisa J; Szepetowski, Pierre; Valeta, Thalia; Yoshinaga, Harumi; Koutroumanidis, Michalis

    2016-09-01

    The term idiopathic focal epilepsies of childhood (IFE) is not formally recognised by the ILAE in its 2010 revision (Berg et al., 2010), nor are its members and boundaries precisely delineated. The IFEs are amongst the most commonly encountered epilepsy syndromes affecting children. They are fascinating disorders that hold many "treats" for both clinicians and researchers. For example, the IFEs pose many of the most interesting questions central to epileptology: how are functional brain networks involved in the manifestation of epilepsy? What are the shared mechanisms of comorbidity between epilepsy and neurodevelopmental disorders? How do focal EEG discharges impact cognitive functioning? What explains the age-related expression of these syndromes? Why are EEG discharges and seizures so tightly locked to slow-wave sleep? In the last few decades, the clinical symptomatology and the respective courses of many IFEs have been described, although they are still not widely appreciated beyond the specialist community. Most neurologists would recognise the core syndromes of IFE to comprise: benign epilepsy of childhood with centro-temporal spikes or Rolandic epilepsy (BECTS/RE); Panayiotopoulos syndrome; and the idiopathic occipital epilepsies (Gastaut and photosensitive types). The Landau-Kleffner syndrome and the related (idiopathic) epilepsy with continuous spikes and waves in sleep (CSWS or ESES) are also often included, both as a consequence of the shared morphology of the interictal discharges and their potential evolution from core syndromes, for example, CSWS from BECTS. Atypical benign focal epilepsy of childhood also has shared electro-clinical features warranting inclusion. In addition, a number of less well-defined syndromes of IFE have been proposed, including benign childhood seizures with affective symptoms, benign childhood epilepsy with parietal spikes, benign childhood seizures with frontal or midline spikes, and benign focal seizures of adolescence. The

  18. 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

  19. Posttraumatic focal dystonia of the shoulder.

    PubMed

    Vasileiadis, Georgios I; Sakellariou, Vasileios I; Papagelopoulos, Panayiotis J; Zoubos, Aristeides B

    2012-06-01

    Focal posttraumatic shoulder dystonia is a rare and not easily identifiable entity. Its true pathophysiologic nature, predisposing factors, and disease course remain debatable.This article describes a rare case of a 40-year-old man with late symptoms of focal shoulder dystonia after peripheral trauma of his left shoulder girdle. The shoulder was indirectly injured from the impact of a fall off his motorbike 3 years earlier. He was referred to the authors' institution because remarkable reduction of arm abduction, muscle spasms, and circumscribed hypertrophy of the trapezius muscle were noted while his head and neck were in neutral position and had a full range of motion. The left shoulder had a fixed elevated posture compared with the contralateral shoulder. A continuous burning pain was localized over the area of the hypertrophied trapezius muscle, radiating to the ipsilateral side of the head and neck. Dystonic movements of the trapezius, rhomboid, and supraspinatus muscles were observed. The abduction of the shoulder was significantly decreased, and any repetitive effort for arm abduction induced an exaggeration of his movement disorder, leading to a more pronounced shoulder elevation.Plain radiographs and magnetic resonance imaging of the left shoulder revealed a suprascapular tendinitis with no other abnormalities. Repeated needle electromyography of the left trapezius muscle and neurography of the accessory nerve on both sides were normal. Injections of botulinum toxin A were effective in the resolution of muscle hypertrophy and abnormal posture. PMID:22691679

  20. 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