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  • 1.
    Benckert, Lars
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Jonsson, Mikael
    Molin, Nils-Erik
    Measuring true in-plane displacements of a surface by stereoscopic white-light speckle photography1987Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 26, nr 2, s. 167-169Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When in-plane surface deformations are measured using white-light speckle photography, errors arise if an out-of-plane displacement is present. Stereoscopic photography resolves this problem and makes possible the measurement of true in-plane displacements. A rigid-body translation is introduced to determine unambiguously the direction of the displacement

  • 2.
    Bergström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Michael, Fergusson
    Viospatia AB.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Virtual projective shape matching in targetless CAD-based close-range photogrammetry for efficient estimation of specific deviations2018Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 57, nr 5, artikkel-id 053110Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A concept for targetless, computer-aided design (CAD)-based, close-range photogrammetry for online shape inspection is introduced. The shape of an object, which is arbitrarily located on a conveyor belt, is to be measured and compared with its nominal shape as defined by a CAD model. For most manufactured objects, deviations are only measured at a few given comparison points. These deviations can be estimated using local photogrammetry based on a priori geometrical information given by the CAD model and the comparison points. Our method results in faster output with higher precision, because we do not generate a shape representation of the entire measured object using typical photogrammetric methods. Images depicting the object from convergent angles are captured by an array of cameras in a precalibrated network, and the CAD model is matched and aligned, within the projective geometry of the camera network, to the depicted object in the images without the use of targets. An algorithm for solving this virtual projective targetless shape matching problem is presented.

  • 3.
    Bergström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Rosendahl, Sara
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Shape verification using dual-wavelength holographic interferometry2011Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 50, nr 10, artikkel-id 101503Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In automotive industry there is an interest of controlling the shape of a large number of identical components on-line in the manufacturing process. We propose a method to do this by capturing a digital hologram of the object and then using information from its computer aided design (CAD) model to calculate the shape and determine the agreement between the manufactured object and the CAD-model. The holographic recording of the object is done using dual wavelengths with a synthetic wavelength of approximately 400 μm. The optical measurement results in a wrapped phase map with the phase values in the interval [−π, π]. Each phase interval represents a depth distance on the object of about 0.2 mm. The phase unwrapping is done iteratively using information from the CADmodel. This implies that it is possible to measure large discontinuities on the surface of the measured object. The method also gives a point-to-point correspondence between the measurement and the CAD-model which is vital for tolerance control.

  • 4.
    Brunnström, K
    et al.
    Acreo AB, Stockholm, Sweden.
    Schenkman, B
    Jacobsen, B
    Object Detection in Cluttered Infrared Images.2003Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 42, nr 2, s. 388-399Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Implementation of the Johnson criteria for infrared images is the probabilities of a discrimination technique. The inputs to the model are the size of the target, the range to it, and the temperature difference against the background. The temperature difference is calculated without taking the background structure into consideration, but it may have a strong influence on the visibility of the target. We investigated whether a perceptually based temperature difference should be used as input. Four different models are discussed: 1. a probability of discrimination model largely based on the Johnson criteria for infrared images, 2. a peak signal-to-noise ratio model, 3. a signal-to-clutter ratio model, and 4. two versions of an image discrimination model based on how human vision analyzes spatial information. The models differ as to how much they try to simulate human perception. To test the models, a psychophysical experiment was carried out with ten test persons, measuring contrast threshold detection in five different infrared backgrounds using a method based on a two-alternative forced-choice methodology. Predictions of thresholds in contrast energy were calculated for the different models and compared to the empirical values. Thresholds depend on the background, and these can be predicted well by the image discrimination models, and better than the other models. Future extensions are discussed.

  • 5.
    Brunnström, K
    et al.
    Acreo AB, Stockholm, Sweden.
    Schenkman, B.N
    Acreo AB, Stockholm, Sweden.
    Comparison of the predictions of a spatio-temporal model with the detection of distortion in small moving images2002Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 41, nr 3, s. 711-722Artikkel i tidsskrift (Fagfellevurdert)
  • 6. Carlsson, C.
    et al.
    Modh, P.
    Halonen, J.
    Schatz, Richard
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Larsson, A.
    High-frequency analog modulation of oxide confined 670-nm vertical-cavity surface-emitting lasers2004Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 43, nr 12, s. 3138-3141Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the bandwidth limitations and the analog modulation characteristics at microwave frequencies (0.1 to 10 GHz)of a low-capacitance oxide-confined 670-nm InGaAIP vertical-cavity surface-emitting laser (VCSEL). A maximum modulation bandwidth of 6.3 GHz, limited by thermal effects, is achieved. From measurements of distortion and noise, a spurious free dynamic range (SFDR) of 100 dB Hz(2/3) is obtained at frequencies up to 2 GHz, rendering such VCSELs useful for transmission of analog signals. At higher frequencies, the SFDR drops due to the thermally limited resonance frequency.

  • 7.
    Carlsson, Torgny E.
    et al.
    KTH, Tidigare Institutioner                               , Industriell produktion.
    Nilsson, B.
    Gustafsson, J.
    System for acquisition of three-dimensional shape and movement using digital Light-in-Flight holography2001Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 40, nr 1, s. 67-75Artikkel i tidsskrift (Fagfellevurdert)
  • 8.
    Dong, Hui
    et al.
    Nanyang Techbological University, Singapore.
    Shum, Ping
    Nanyang Techbological University, Singapore.
    Gong, Yandong
    Yan, Min
    Nanyang Techbological University, Singapore.
    Zhou, Junqiang
    Wu, Chongqing
    Measurement of polarization mode dispersion vectors in optical fibers using a virtual Mueller matrix method2007Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 46, nr 3, s. 035007-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A virtual Mueller matrix method is proposed to measure the first- and second-order polarization mode dispersion (PMD) vectors in optical fibers. This method not only can use a large frequency step to attain low-noise PMD vector data, but also does not require knowledge of the input polarization states. Our measurement method has a simpler setup and is more accurate than the traditional Mueller matrix method.

  • 9. Eriksson, F.
    et al.
    Johansson, G. A.
    Hertz, Hans M.
    KTH, Tidigare Institutioner                               , Fysik.
    Birch, J.
    Enhanced soft x-ray reflectivity of Cr/Sc multilayers by ion-assisted sputter deposition2002Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 41, nr 11, s. 2903-2909Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cr/Sc multilayers have been grown on Si substrates using dc magnetron sputtering. The multilayers are intended as condenser mirrors in a soft x-ray microscope operating at the wavelength 3.374 nm. They were designed for normal reflection of the first and second orders, with multilayer periods of 1.692 and 3.381 nm, and layer thickness ratios of 0,471 and 0.237, respectively. At-wavelength soft-x-ray reflectivity measurements were carried out using a reflectometer with a compact soft-x-ray laser-plasma source. The multilayers were irradiated during growth with Ar ions, varying both in energy (9 to 113 eV) and flux, in order to stimulate the adatom mobility and improve the interface flatness. It was found that to obtain a maximum soft x-ray reflectivity with a low flux (Cr=0.76, Sc=2.5) of Ar ions a rather high energy of 53 eV was required, Such energy also caused intermixing of the layers. By the use of a solenoid surrounding the substrate, the arriving ion-to-metal flux ratio could be increased 10 times and the required ion energy could be decreased. A high flux (Cr=7.1, Sc=23.1) of low-energy (9 eV) Ar ions yielded the most favorable growth condition, limiting the intermixing with a subsistent good surface flatness.

  • 10.
    Eriksson, Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Johansson, G.A.
    Royal Institute of Technology, Biomedical and X-Ray Physics, S-10044 Stockholm, Sweden.
    Hertz, H.M.
    Royal Institute of Technology, Biomedical and X-Ray Physics, S-10044 Stockholm, Sweden.
    Birch, Jens
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Enhanced soft x-ray reflectivity of Cr/Sc multilayers by ion-assisted sputter deposition2002Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 41, nr 11, s. 2903-2909Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cr/Sc multilayers have been grown on Si substrates using dc magnetron sputtering. The multilayers are intended as condenser mirrors in a soft x-ray microscope operating at the wavelength 3.374 nm. They were designed for normal reflection of the first and second orders, with multilayer periods of 1.692 and 3.381 nm, and layer thickness ratios of 0.471 and 0.237, respectively. At-wavelength soft-x-ray reflectivity measurements were carried out using a reflectometer with a compact soft-x-ray laser-plasma source. The multilayers were irradiated during growth with Ar ions, varying both in energy (9 to 113 eV) and flux, in order to stimulate the adatom mobility and improve the interface flatness. It was found that to obtain a maximum soft x-ray reflectivity with a low flux (Cr=0.76, Sc=2.5) of Ar ions a rather high energy of 53 eV was required. Such energy also caused intermixing of the layers. By the use of a solenoid surrounding the substrate, the arriving ion-to-metal flux ratio could be increased 10 times and the required ion energy could be decreased. A high flux (Cr=7.1, Sc=23.1) of low-energy (9 eV) Ar ions yielded the most favorable growth condition, limiting the intermixing with a subsistent good surface flatness. © 2002 Society of Photo-Optical Instrumentation Engineers.

  • 11.
    Eriksson, Ingemar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    New high-speed photography technique for observation of fluid flow in laser welding2010Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 49, nr 10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent developments in digital high-speed photography allow us to directly observe the surface topology and flow conditions of the melt surface inside a laser evaporated capillary. Such capillaries (known as keyholes) are a central feature of deep penetration laser welding. For the first time, it can be confirmed that the liquid capillary surface has a rippled, complex topology, indicative of subsurface turbulent flow. Manipulation of the raw data also provides quantitative measurements of the vertical fluid flow from the top to the bottom of the keyhole.

  • 12.
    Eriksson, Ingemar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Haglund, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Holographic measurement of thermal distortion during laser spot welding2012Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 51, nr 3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Welding distortion is an important engineering topic for simulation and modeling, and there is a need for experimental verification of such models by experimental studies. High-speed pulsed digital holography is proposed as a measurement technique for out-of-plane welding distortion. To demonstrate the capability of this technique, measurements from a laser spot weld are presented. A complete twodimensional deformation map with submicrometer accuracy was acquired at a rate of 1000 measurements per second. From this map, particular points of interest can be extracted for analysis of the temporal development of the final distortion geometry.

  • 13.
    Fredriksson, Håkan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Hyyppä, Kalevi
    Multisource flash system for retroreflective beacon detection in CMOS cameras2008Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 47, s. 103001-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a method for improving a flash system for retroreflective beacon detection in CMOS cameras. Generally, flash systems are designed in such a manner that makes them suited for beacon detection in a small range interval. We strive to increase the flash system range interval by exploiting the directional properties of the retroreflector. Thus, light sources placed relatively far away from the optical axis of the camera will contribute only when the retroreflector is far away. This fact can be used to compensate for the 1/distance2 dependency of optical power. We present underlying theory and formulae, then describe a flash system consisting of several light-emitting diodes that was designed by considering the presented method. Simulations show that the usable flash range of the improved system can be almost doubled compared to a general flash system. Tests were performed indicating that the presented method works according to theory and simulations.

  • 14. Granberg, H.
    et al.
    Jensen, J.
    Mattsson, Lars
    KTH, Tidigare Institutioner                               , Industriell produktion.
    Forward scattering of fiber-containing surfaces studied by 3-D reflectance distribution simulations and measurements2003Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 42, nr 8, s. 2384-2390Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent studies have shown that the angular distribution of diffuse reflectance, obtained from bidirectional reflectance distribution function (BRDF) measurements, differs strongly between paper sheets with and without fibers present in the top surface layer. For fiber-containing surfaces, in contrast to pigment-coated paper surfaces, there is a distinct forward scattering at angles much larger than the specular reflection angle. In the search for an explanation of this phenomenon, we have made calculations of reflectance distributions of a simulated paper web, containing randomly distributed hollow fibers. We did this on the assumption that fibers present in paper are considerably larger than the wavelength of visible light, and that the surface microroughness of the fibers can be treated as a diffraction broadening superposed on the ray calculated reflectance distribution. We investigate whether the structural shape and distribution of wood fibers can explain some of the observed forward-scattering phenomenon. We also compare these Monte-Carlo ray tracing calculations qualitatively with experimental BRDF measurements of the diffuse reflectance from a fiber-containing surface. From the calculations we found that the reflection at the inner fiber wall of the hollow fibers constituting the topmost layer plays a major role in forming a forward-scattering reflectance distribution. We also found that the Monte-Carlo-calculated bulk scattering distribution, i.e., the distribution of reflected light after a large number of reflections within the web structure, tended to be elongated perpendicular to the sheet plane of the fiber web, rather than being uniform.

  • 15.
    Grönwall, Christina
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Steinvall, Ove
    Swedish Defence Research Agency, Sweden.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Chevalier, Tomas
    Swedish Defence Research Agency, Sweden.
    Influence of Laser Radar Sensor Parameters on Range Measurement and Shape Fitting Uncertainties2007Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 46, nr 10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Inobject/target reconstruction and recognition based on laser radar data, the range value's accuracy is important. The range data accuracy depends on the accuracy in the laser radar's detector, especially the algorithm used for time-of-flight estimation. In this paper, a general direct-detection laser radar system applicable for hard-target measurements is modeled. The time- and range-dependent laser radar cross sections are derived for some simple geometric shapes (plane, cone, sphere, and paraboloid). The cross-section models are used, in simulations, to find the proper statistical distribution of uncertainties in time-of-flight range estimations. Three time-of-flight estimation algorithms are analyzed: peak detection, constant-fraction detection, and matched filter. The detection performance for various shape conditions and signal-to-noise ratios is analyzed. Two simple shape reconstruction examples are shown, and the detectors' performance is compared with the Cramér-Raolower bound. The performance of the peak detection and the constant-fraction detection is more dependent on the shape and noise level than that of the matched filter. For line fitting the matched filter performs close to the Cramér-Rao lower bound.

  • 16.
    Grönwall, Christina
    et al.
    FIO.
    Tolt, Gustav
    FOI.
    Chevalier, tomas
    FOI.
    Larsson, Håkan
    FOI.
    Spatial filtering for detection of partly occluded targets2011Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 50, nr 4, s. 047201-1-047201-13Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A Bayesian approach for data reduction based on spatial filtering is proposed that enables detection of targets partly occluded by natural forest. The framework aims at creating a synergy between terrain mapping and target detection. It is demonstrates how spatial features can be extracted and combined in order to detect target samples in cluttered environments. In particular, it is illustrated how a priori scene information and assumptions about targets can be translated into algorithms for feature extraction. We also analyze the coupling between features and assumptions because it gives knowledge about which features are general enough to be useful in other environments and which are tailored for a specific situation. Two types of features are identified, nontarget indicators and target indicators. The filtering approach is based on a combination of several features. A theoretical framework for combining the features into a maximum likelihood classification scheme is presented. The approach is evaluated using data collected with a laser-based 3-D sensor in various forest environments with vehicles as targets. Over 70% of the target points are detected at a false-alarm rate of <1%. We also demonstrate how selecting different feature subsets influence the results.

  • 17.
    Hansson, Göran
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Yt- och Halvledarfysik.
    Solid state multiple-beam laser with tunable wavelength difference between beams2000Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 39, nr 10, s. 2700-2704Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A diode laser pumped solid state laser design capable of generating several simultaneously emitted spatially separate and wavelength tunable beams is presented. The laser design was demonstrated in a dual-beam configuration using Tm,Ho:YLF as laser material. Laser oscillation in two TEM00, longitudinal multimode cw beams of 80-mW maximum output power was demonstrated. The wavelength difference between the beams was tuned over a 15-nm-wide range using one solid etalon as a tuning element.

  • 18.
    Hemberg, Oskar
    et al.
    KTH, Tidigare Institutioner, Fysik.
    Otendal, Mikael
    KTH, Tidigare Institutioner, Fysik.
    Hertz, Hans M.
    KTH, Tidigare Institutioner, Fysik.
    A Liquid-Metal-Jet Anode X-Ray Tube2004Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 43, nr 7, s. 1682-1688Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe a novel electron-impact x-ray source based on a high-speed liquid-metal-jet anode. Thermal power load calculations indicate that this new anode concept potentially could increase the achievable brightness in compact electron-impact x-ray sources by more than a factor 100 compared to current state-of-the-art rotating-anode or microfocus sources. A first, successful, low-power proof-of-principle experiment is described and the feasibility of scaling to high-brightness and high-power operation is discussed. Some possible applications that would benefit from such an increase in brightness are also briefly

  • 19. Hermann, D. S.
    et al.
    Scalia, G.
    Pitois, C.
    De Marco, F.
    D'Have, K.
    Abbate, G.
    Lindgren, M.
    Hult, Anders
    KTH, Tidigare Institutioner                               , Polymerteknologi.
    Novel passive polymer waveguides integrated with electro-optically active ferroelectric liquid crystals2001Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 40, nr 10, s. 2188-2198Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report the preparation and characterization of novel isotropic polymer slab waveguides made by photochemical crosslinking, and their integration with a ferroelectric liquid crystal in an integrated electro-optic modulator. The refractive index of the passive copolymer material in the device was controlled by the copolymer composition, and good agreement between measured and calculated effective indices for the guided modes of polymer films was obtained. The active ferroelectric liquid crystal exhibited a refractive index change of Deltan approximate to0.10 upon application of an ac voltage of +/- 30 V, giving an electro-optic modulation of the input TE0-mode with a contrast ratio of 11:1 and only a small polarization conversion into TM output light.

  • 20.
    Hermann, DS
    et al.
    Univ Naples Federico II, Ist Nazl Fis Nucl, I-80126 Naples, Italy Univ Naples Federico II, Dipartimento Sci Fis, I-80126 Naples, Italy Chalmers Univ Technol, Dept Microelect & Nanosci, S-41296 Gothenburg, Sweden Royal Inst Technol, Dept Polymer Technol, S-10044 Stockholm, Sweden Swedish Def Res Agcy FOI, Dept Laser Syst FOI 32, S-58111 Linkoping, Sweden.
    Scalia, G
    Univ Naples Federico II, Ist Nazl Fis Nucl, I-80126 Naples, Italy Univ Naples Federico II, Dipartimento Sci Fis, I-80126 Naples, Italy Chalmers Univ Technol, Dept Microelect & Nanosci, S-41296 Gothenburg, Sweden Royal Inst Technol, Dept Polymer Technol, S-10044 Stockholm, Sweden Swedish Def Res Agcy FOI, Dept Laser Syst FOI 32, S-58111 Linkoping, Sweden.
    Pitois, C
    Univ Naples Federico II, Ist Nazl Fis Nucl, I-80126 Naples, Italy Univ Naples Federico II, Dipartimento Sci Fis, I-80126 Naples, Italy Chalmers Univ Technol, Dept Microelect & Nanosci, S-41296 Gothenburg, Sweden Royal Inst Technol, Dept Polymer Technol, S-10044 Stockholm, Sweden Swedish Def Res Agcy FOI, Dept Laser Syst FOI 32, S-58111 Linkoping, Sweden.
    De Marco, F
    Univ Naples Federico II, Ist Nazl Fis Nucl, I-80126 Naples, Italy Univ Naples Federico II, Dipartimento Sci Fis, I-80126 Naples, Italy Chalmers Univ Technol, Dept Microelect & Nanosci, S-41296 Gothenburg, Sweden Royal Inst Technol, Dept Polymer Technol, S-10044 Stockholm, Sweden Swedish Def Res Agcy FOI, Dept Laser Syst FOI 32, S-58111 Linkoping, Sweden.
    D'have, K
    Univ Naples Federico II, Ist Nazl Fis Nucl, I-80126 Naples, Italy Univ Naples Federico II, Dipartimento Sci Fis, I-80126 Naples, Italy Chalmers Univ Technol, Dept Microelect & Nanosci, S-41296 Gothenburg, Sweden Royal Inst Technol, Dept Polymer Technol, S-10044 Stockholm, Sweden Swedish Def Res Agcy FOI, Dept Laser Syst FOI 32, S-58111 Linkoping, Sweden.
    Abbate, G
    Univ Naples Federico II, Ist Nazl Fis Nucl, I-80126 Naples, Italy Univ Naples Federico II, Dipartimento Sci Fis, I-80126 Naples, Italy Chalmers Univ Technol, Dept Microelect & Nanosci, S-41296 Gothenburg, Sweden Royal Inst Technol, Dept Polymer Technol, S-10044 Stockholm, Sweden Swedish Def Res Agcy FOI, Dept Laser Syst FOI 32, S-58111 Linkoping, Sweden.
    Lindgren, M
    Hult, A
    Univ Naples Federico II, Ist Nazl Fis Nucl, I-80126 Naples, Italy Univ Naples Federico II, Dipartimento Sci Fis, I-80126 Naples, Italy Chalmers Univ Technol, Dept Microelect & Nanosci, S-41296 Gothenburg, Sweden Royal Inst Technol, Dept Polymer Technol, S-10044 Stockholm, Sweden Swedish Def Res Agcy FOI, Dept Laser Syst FOI 32, S-58111 Linkoping, Sweden.
    Novel passive polymer waveguides integrated with electro-optically active ferroelectric liquid crystals2001Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 40, nr 10, s. 2188-2198Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report the preparation and characterization of novel isotropic polymer slab waveguides made by photochemical crosslinking, and their integration with a ferroelectric liquid crystal in an integrated electro-optic modulator. The refractive index of the passive copolymer material in the device was controlled by the copolymer composition, and good agreement between measured and calculated effective indices for the guided modes of polymer films was obtained. The active ferroelectric liquid crystal exhibited a refractive index change of Deltan approximate to0.10 upon application of an ac voltage of +/- 30 V, giving an electro-optic modulation of the input TE0-mode with a contrast ratio of 11:1 and only a small polarization conversion into TM output light. (C) 2001 Society of Photo-Optical Instrumentation Engineers.

  • 21.
    Hyyppä, Kalevi
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Signal response of a laser beam scanner1994Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 33, nr 8, s. 2770-2776Artikkel i tidsskrift (Fagfellevurdert)
  • 22.
    Hällstig, Emil
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen, Kvantkemi.
    Öhgren, Johan
    Allard, Lars
    Sjöqvist, Lars
    Engström, David
    Hård, Sverker
    Ågren, Daniel
    Junique, Stephane
    Wang, Qin
    Noharet, Bertrand
    Retrocommunication utilizing electroabsorption modulators and non-mechanical beam steering2005Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 44, nr 4, s. 045001-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel retrocommunication link utilizing reflective multiplequantum well (MQW) optical modulators and nonmechanical beamsteering and tracking is demonstrated. Large aperture reflective MQWmodulators using AlGaAs/GaAs are optimized and manufactured. Themodulators exhibit a contrast ratio larger than 4:1 and a modulationbandwidth of 10 MHz. Nonmechanical beam steering and tracking arestudied using nematic liquid crystal (NLC) spatial light modulators(SLMs). The communication link is comprised of a retromodulating arraywith four MQW modulators and a transceiver using a NLC SLM for beamsteering and tracking. Transfer of audio, real-time image data and pseudorandombit sequences over 100-m range while tracking the movingretromodulator is shown. The link is capable of transferring data at approximately8 Mbps.

  • 23.
    Jonsson, Magnus
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Inbyggda system (CERES).
    Two fiber-ribbon ring networks for parallel and distributed computing systems1998Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 37, nr 12, s. 3196-3204Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ring networks made of fiber-ribbon point-to-point links are proposed. The first network is a control-channel based network in which one fiber in each link joins with others to form a control-channel ring. This ring improves performance of the network by sending medium access control information immediately before the data transmissions. High throughputs can be achieved in the network due to pipelining, i.e., several packets can travel through the network simultaneously but in different segments of the ring. The network can meet tough performance demands in, e.g., massively parallel signal processing systems, which is shown by example. Also, real-time demands can be met using slot reserving. The network, called CC-FPR (control-channel based fiber-ribbon pipeline ring), can be built today using off-the-shelf fiber optic components. The increasingly good price/performance ratio for fiber-ribbon links indicates a high potential for the success of the proposed kind of networks; a prototype is currently under development. The second network is similar to first except that it divides the network into two subnetworks, one for packet-switched traffic and one for circuit-switched traffic. When the main data flow in the network does not change rapidly, this is a good choice for a simple but powerful network.

  • 24.
    Kaestner, Anders P.
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE).
    Nilsson, Carl Magnus
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Laboratoriet för intelligenta system.
    Estimating the relative shrinkage profile of newsprint2003Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 42, nr 5, s. 1467-1475Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When water is removed from the paper during paper making, a dimensional change occurs in which the paper shrinks in the direction perpendicular to the direction of processing. The dimensional changes vary across the web and influence, e.g., the surface and compression properties of the paper; they also complicate the control of the paper machine. In this article, a robust method for estimating the relative shrinkage profile is presented. The method is based on a one-dimensional recording of the imprints from the forming fabric, using a fluorescence technique. The recording is transformed into a time-frequency spectrum, on which three different frequency estimators have been evaluated. In simulations on synthetic data and measurements on paper profiles the estimator that maximizes the correlation energy showed the most robust and accurate performance of the methods evaluated, even at a low signal-to-noise ratio.

  • 25.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Analysis and modeling of a high-power Yb:fiber laser beam profile2011Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 50, nr 5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recently the fiber and the disk laser have been developed as advanced high power lasers of continuous wave type. Their beams are fiber-guided. Their low beam parameter product determines the focused beam as a high power density tool for laser materials processing. The lateral and axial power density distribution is crucial for the process. The measurement of a focused Yb:fiber laser beam is compared with its theoretical profile. While a Gauss beam describes the real beam in the far field, in the vicinity of the focus the beam is similar to a top-hat profile. In particular, the peak power density is lower around the focus than for a Gaussian beam. This provides a flatter, less varying optical tool along a certain axial range. A suitable model of the focused laser beam is achieved by superposition of a Gauss beam with a second but negative Gauss beam, each with matched parameters for power, spot diameter, and Rayleigh length. Owing to its much better accuracy with less than a 20% error, the model beam is applicable, e. g., for simulation of the welding process

  • 26. Kazmierczak, Andrzej
    et al.
    Dortu, Fabian
    Schrevens, Olivier
    Giannone, Domenico
    Vivien, Laurent
    Marris-Morini, Delphine
    Bouville, David
    Cassan, Eric
    Gylfason, Kristinn B.
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik.
    Sohlström, Hans
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik.
    Sanchez, Benito
    Griol, Amadeu
    Hill, Daniel
    Light coupling and distribution for Si3N4/SiO2 integrated multichannel single-mode sensing system2009Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 48, nr 1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present an efficient and highly alignment-tolerant light coupling and distribution system for a multichannel Si3N4/SiO2 single-mode photonics sensing chip. The design of the input and output couplers and the distribution splitters is discussed. Examples of multichannel data obtained with the system are given.

  • 27.
    Khodadad, Davood
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Hallstig, Emil J.
    Optronic, Skellefteå, Sweden.
    Sjödahl, Mikael
    Luleå University of Technology, Luleå, Sweden.
    Dual-wavelength digital holographic shape measurement using speckle movements and phase gradients2013Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 52, nr 10, artikkel-id 101912Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new method to measure shape by analyzing the speckle movements in images generated by numerical propagation from dual-wavelength holograms is presented. The relationship of the speckle movements at different focal distances is formulated, and it is shown how this carries information about the surface position as well as the local slope of the object. It is experimentally verified that dual-wavelength holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve the object shape. From a measurement on a cylindrical test object, the method is demonstrated to have a random error in the order of a few micrometers.

  • 28.
    Khodadad, Davood
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hällstig, Emil
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Dual-wavelength digital holographic shape measurement using speckle movements and phase gradients2013Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 52, nr 10, artikkel-id 101912Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new method to measure shape by analyzing the speckle movements in images generated by numerical propagation from dual-wavelength holograms is presented. The relationship of the speckle movements at different focal distances is formulated, and it is shown how this carries information about the surface position as well as the local slope of the object. It is experimentally verified that dual-wavelength holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve the object shape. From a measurement on a cylindrical test object, the method is demonstrated to have a random error in the order of a few micrometers.

  • 29.
    Khodadad, Davood
    et al.
    Luleå University of Technology.
    Hällstig, Emil
    Optronic Partner dp AB.
    Sjödahl, Mikael
    Luleå University of Technology.
    Dual-wavelength digital holographic shape measurement using speckle movements and phase gradients2013Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 52, nr 10, s. 101912-101912Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new method to measure shape by analyzing the speckle movements in images generated by numerical propagation from dual-wavelength holograms is presented. The relationship of the speckle movements at different focal distances is formulated, and it is shown how this carries information about the surface position as well as the local slope of the object. It is experimentally verified that dual-wavelength holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve the object shape. From a measurement on a cylindrical test object, the method is demonstrated to have a random error in the order of a few micrometers.

  • 30.
    Khrennikov, Andrei
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Role of detectors and their proper calibration in inter-relation between classical and quantum optics2012Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 51, nr 6, s. Article ID: 069001-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe quantum theory by using a complex valued random signal, which is (coherently) averaged over a time window, and a photon click is defined as the energy of this averaged signal surpassing a detector threshold. The random signal is modeled as white noise but grows over time s (proportional to s). Eventually this random signal will lead to a detector “click” defined by a detector threshold condition, at which point the random signal is reset. Further we proceed by analysing correlations and finally by modeling the quantum state of an entangled pair by a complex valued correlation function.

  • 31. Li, J. S.
    et al.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Electro-optic modulator based on Si2N2O substrate2006Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 45, nr 1Artikkel i tidsskrift (Fagfellevurdert)
  • 32.
    Li, Yanzeng
    et al.
    Univ N Carolina, NC 28223 USA.
    Park, Serang
    Univ N Carolina, NC 28223 USA.
    Fullager, Daniel B.
    Lasertel North Amer, AZ USA.
    Childers, Darrell
    US CONEC, NC USA.
    Poutous, Menelaos K.
    Univ N Carolina, NC 28223 USA.
    Aggarwal, Ishwar D.
    Univ N Carolina, NC 28223 USA.
    Boreman, Glenn
    Univ N Carolina, NC 28223 USA.
    Hofmann, Tino
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Univ N Carolina, NC 28223 USA.
    Near-infrared transmittance enhancement using fully conformal antireflective structured surfaces on microlenses fabricated by direct laser writing2019Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 58, nr 1, artikkel-id 010501Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Structured surfaces composed of subwavelength-sized features offer multifunctional properties including antireflective characteristics that are increasingly important for the development of micro-optical components. Here, three-dimensional (3-D) direct laser writing, via two-photon polymerization, is used to fabricate planoconvex spherical microlenses with antireflective structured surfaces. The surfaces are composed of subwavelength-sized conicoid structures, which are arranged fully conformal to the convex surface of the microlenses. The dimensions of the conicoid structures are optimized to effectively reduce Fresnel reflection loss over a wide band in the near-infrared spectral range from 1.4 to 2.2 mu m, with a maximum reduction at 1.55 mu m. Infrared reflection and transmission measurements are used, in combination with 3-D finite element calculations, to investigate the performance of the microlenses. The experimental results reveal that in the spectral range from 1.4 to 2.2 mu m an effective suppression of the Fresnel reflection loss at the convex surface of spherical microlenses can be achieved. The transmittance enhancement is ranging from 1% to 3% for spherical microlenses with antireflective structured surfaces, in comparison to an uncoated reference. (C) 2019 Society of Photo-Optical Instrumentation Engineers (SPIE)

  • 33.
    Lindstrom, T
    et al.
    Department of Materials Science, Ångström Laboratory, Uppspla University, Uppsala, Sweden.
    Rönnow, Daniel
    ACREO AB, Kista, Sweden.
    Total integrated scattering from transparent substrates in the infrared region: validity of scalar theory2000Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 39, nr 2, s. 478-487Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Integrated light scattering, from thin, transparent silicon wafers with different front and backside surface roughness is investigated. The measurements are made at near normal incidence in the IR wavelength region 5 to 20 μm using an integrating sphere. A method to separate the scattering contribution from each interface for measurements on transparent samples is introduced. Scalar scattering theory is used to calculate the effective root mean square roughness from reflectance and transmittance measurements, and these values are compared to profilometer data, correcting for the different bandwidth limits. Scattering measurements are performed with both the rough and the smooth surface of the wafer oriented toward the light source, which results in additional knowledge. The maximum ratio between the root mean square roughness and the wavelength of the light, to be used in scalar theory, is found to be considerably higher for the transmittance case than for the reflectance case. In agreement with theory, the calculated root mean square roughness is found to be proportional to the refractive index of incident medium in reflectance, and to the difference in refractive indices of incident and refracting medium for the transmittance case.

  • 34. Lofdahl, M. G.
    et al.
    Eriksson, Henrik
    KTH, Tidigare Institutioner                               , Numerisk analys och datalogi, NADA.
    Algorithm for resolving 2 pi ambiguities in interferometric measurements by use of multiple wavelengths2001Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 40, nr 6, s. 984-990Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Measurement of differences in optical path length in monochromatic light with any interferometric method is insensitive to errors that are whole numbers of waves. If measurements are performed in several wavelengths, this ambiguity can be resolved. We present a general algorithm for finding the correct distance post facto, given multiple measurements in different wavelengths. Applied to piston measurements of a segmented mirror, the capture range of a wavefront sensor can be extended from +/- half a wave to several waves. The extended capture range can be calculated and depends on the selection of wavelengths used for measurements and the expected accuracy of the method used.

  • 35.
    Lundén, Hampus
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    Glimsdal, Eirik
    Norwegian Def Res Estab FFI, Norway; Norwegian Univ Sci and Technol NTNU, Norway.
    Lindgren, Mikael
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten. Norwegian Univ Sci and Technol NTNU, Norway.
    Lopes, Cesar
    Swedish Def Res Agcy, FOI, Linkoping, Sweden.
    How to assess good candidate molecules for self-activated optical power limiting2018Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 57, nr 3, artikkel-id 030802Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reverse saturable absorbers have shown great potential to attenuate laser radiation. Good candidate molecules and various particles have successfully been incorporated into different glass matrices, enabling the creation of self-activated filters against damaging laser radiation. Although the performance of such filters has been impressive, work is still ongoing to improve the performance in a wider range of wavelengths and pulse widths. The purpose of this tutorial is, from an optical engineering perspective, to give an understanding of the strengths and weaknesses of this class of smart materials, how relevant photophysical parameters are measured and influence system performance and comment on the pitfalls in experimental evaluation of materials. A numerical population model in combination with simple physical formulas is used to demonstrate system behavior from a performance standpoint. Geometrical reasoning shows the advantage of reverse saturable absorption over nonlinear scattering due to a fraction of scattered light being recollected by imaging system optics. The numerical population model illustrates the importance of the optical power limiting performance during the leading edge of a nanosecond pulse, which is most strongly influenced by changes in the two-photon absorption cross section and the triplet linear absorption cross section for a modeled Pt-acetylide. This tutorial not only targets optical engineers evaluating reverse saturable absorbing materials but also aims to assist researchers with a chemistry background working on optical power limiting materials. We also present photophysical data for a series of coumarins that can be useful for the determination of quantum yields and two-photon cross sections and show examples of characterization of molecules with excited triplet states. (c) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE).

  • 36.
    Marklund, Olov
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Huntley, Jonathan M.
    Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University.
    Cusack, Rhodri
    MRC Cognition and Brain Sciences Unit, 15 Chaucer Road, Cambridge.
    Robust unwrapping algorithm for three-dimensional phase volumes of arbitrary shape containing knotted phase singularity loops2007Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 46, nr 8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The extension of path-independent 2-D phase unwrapping algorithms, based on placement of branch cut lines between phase singularities of opposite sign, was recently proposed for phase volumes in a paper by Huntley. In 3-D, the singularities were shown to form closed loops, and path independence was achieved by placing branch cut surfaces across the loops. In the current work, we describe in detail an optimized and extended version of Huntley's algorithm. It deals in particular with two aspects that are essential for practical phase volumes: 1. how to close partial loops that pass through arbitrary boundaries separating valid and invalid phase data, and 2. how to select the set of loops having the shortest length. The second algorithm is necessary to deal with ambiguous cases that can arise when the singularities form knots, i. e., two loops pass through a single phase volume element. The performance of the algorithm is demonstrated on 3-D phase maps from two types of medical imaging data: medical resonance imaging (MRI) and x-ray interferometry.

  • 37.
    Melin, L. Gunnar
    Luleå tekniska universitet.
    High-speed moire photography for studying dynamic properties in carbon fiber composites1998Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 37, nr 2, s. 642-649Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the experiments reported here, a moire technique for measuring in-plane displacements was applied to the study of carbon/epoxy composite specimens deformed at high strain rates. The moire fringes were analyzed using the Fourier transform method. The measurements show that the material behaves in a linearly elastic manner up to fracture. Crack propagation rates of about 2000 m/s in the grating plane were observed. The optical aspects of the experiment are discussed

  • 38.
    Metaferia, Wondwosen
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Halvledarmaterial, HMA.
    Simozrag, Bouzid
    Junesand, Carl
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Halvledarmaterial, HMA. Epiclarus AB, Sweden.
    Sun, Yanting
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Halvledarmaterial, HMA.
    Carras, Mathieu
    Blanchard, Romain
    Capasso, Federico
    Lourdudoss, Sebastian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Halvledarmaterial, HMA.
    Demonstration of a quick process to achieve buried heterostructure quantum cascade laser leading to high power and wall plug efficiency2014Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 53, nr 8, s. 087104-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Together with the optimal basic design, buried heterostructure quantum cascade laser (BH-QCL) with semi-insulating regrowth offers a unique possibility to achieve an effective thermal dissipation and lateral single mode. We demonstrate here the realization of BH-QCLs with a single-step regrowth of highly resistive (>1 x 10(8) ohm . cm) semi-insulating InP: Fe in <45 min for the first time in a flexible hydride vapor phase epitaxy process for burying ridges etched down to 10 to 15 mu m depth, both with and without mask overhang. The fabricated BH-QCLs emitting at similar to 4.7 and similar to 5.5 mu m were characterized. 2-mm-long 5.5-mu m lasers with a ridge width of 17 to 22 mu m, regrown with mask overhang, exhibited no leakage current. Large width and high doping in the structure did not permit high current density for continuous wave (CW) operation. 5-mm-long 4.7-mu m BH-QCLs of ridge widths varying from 6 to 14 mu m regrown without mu mask overhang, besides being spatially monomode, TM00, exhibited wall plug efficiency (WPE) of similar to 8 to 9% with an output power of 1.5 to 2.5 W at room temperature and under CW operation. Thus, we demonstrate a quick, flexible, and single-step regrowth process with good planarization for realizing buried QCLs leading to monomode, high power, and high WPE.

  • 39.
    Mohan, N.K.
    et al.
    Indian Institute of Technology.
    Svanbro, Angelica
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Molin, Nils-Erik
    Dual-beam symmetric illumination-observation TV holography system for measurements2001Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 40, nr 12, s. 2780-2787Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Leendertz dual-beam symmetric illumination-normal observation arrangement is widely employed for real time evaluation of in-plane displacement components as well as surface shape. Instead of observing along the optical axis, we have examined the Leendertz arrangement by observing the scattered light along the direction of the illumination beams, and imaged it as two separate images onto the photo sensor of a CCD camera. The interferometer is a combination of two channels, each of which measures independently and simultaneously the information pertaining to either the in-plane displacement component of a deformation vector, or the surface relief variation of a three-dimensional object. In addition, a summary of possible measurements that can be carried out from the present arrangement is also highlighted. Experimental results using a four-frame phase shifting technique are illustrated

  • 40. Nilsson, B.
    et al.
    Carlsson, Torgny E.
    KTH, Tidigare Institutioner                               , Industriell produktion.
    Simultaneous measurement of shape and deformation using digital light-in-flight recording by holography2000Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 39, nr 1, s. 244-253Artikkel i tidsskrift (Fagfellevurdert)
  • 41.
    Nilsson, C M
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Malmqvist, L.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Carlsson, J.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Red fluorescence sensor for noncontact on-line measurements in paper production2001Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 40, nr 8, s. 1674-1681Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A robust sensor is developed for on-line measurements in paper production. The sensor is designed for optimal response to lignin in paper. A diode laser operating at 630 nm is used for excitation and fluorescence light in the wavelength region 660 to 740 nm is detected. A compact photomultiplier tube is used for fast detection with a high SNR. The measuring spot is 90 mum in diameter. All optical and electronics components are housed in a small 250X140X90 mm(3) box. Because the system can make up to 1.2 million measurements/s the distance between adjacent measuring points can be as short as about 20 mum, even at a paper speed of 25 m/s, as is common with a modern newsprint paper machine. The recording system can store data continuously for 45 min at this sampling rate and data from three more sensors can be recorded simultaneously with the same resolution. This high-capacity sensor system can monitor the behavior of a paper machine at much higher time and space resolution than has traditionally been possible. From test runs on four different newsprint paper machines we observed the existence of small spots of high fluorescence in the paper from one machine, characteristic behavior with a significantly lower level of fluorescence in periodical sections of about 200 m in another machine, and that wire marks and periodical patterns could be very well identified from the fluorescence recordings. Such data have proven to contain important information for the papermaker concerning, for example the relative shrinkage of the paper web in the drying section of the paper machine. © 2001 Society of Photo-Optical Instrumentation Engineers.

  • 42.
    Nordin, Daniel
    et al.
    Luleå tekniska universitet.
    Hyyppä, Kalevi
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Advantages of a new modulation scheme in an optical self mixing FMCW system2002Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 41, nr 5, s. 1128-1133Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new frequency-modulated continuous wave modulation scheme, which gives correct results even when the Doppler shift is larger than the frequency difference associated with the range, is presented and tested with a tunable laser diode and fiber-based system. By inserting a constant frequency region in the modulation scheme, both the magnitude and the sign of all beat frequencies can be determined. When they are known, the correct frequency difference as a result of the range can be calculated. This new scheme gives more freedom when choosing the modulation parameters of the laser, because increasing the modulation frequency, and/or the frequency sweep, to avoid ambiguities resulting from a large Doppler shift no longer becomes necessary. This is especially useful when using a somewhat cheaper laser diode source, since the maximum obtainable modulation frequency and frequency sweep can be somewhat limited. The suggested modulation scheme makes it possible to use some laser diodes in an application they otherwise would not be suited for.

  • 43.
    Nordin, Daniel
    et al.
    Luleå University of Technology.
    Hyyppä, Kalevi
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Using a discrete thermal model to obtain a linear frequency ramping in a frequency-modulated continuous-wave system2005Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 44, nr 7, s. 74202-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The lasing wavelength of a single-section distributed feedback (DFB) laser diode can be modulated by modulating the drive current. This makes it possible to utilize the DFB laser diode in a frequency-modulated continuous wave (FMCW) range and velocity measuring system. In FMCW, the frequency of the laser is ramped, and the frequency difference between the reflected wave and a local-oscillator wave is monitored. For maximum performance the frequency ramping should be linear. Due to thermal phenomena, a linear ramping of the current seldom results in a linear ramping of the optical frequency. We have derived a discrete thermal model, using resistors and capacitors, of our laser module. The thermal model was then used as a starting point to model the frequency behavior of the laser and to derive modulation currents that resulted in a linear frequency ramping at some different modulation frequencies.

  • 44.
    Nyberg, S
    et al.
    Swedish Def Res Agcy, Div Sensor Technol, S-58111 Linkoping, Sweden.
    Bohman, L
    Swedish Def Res Agcy, Div Sensor Technol, S-58111 Linkoping, Sweden.
    Assessing camouflage methods using textural features2001Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 40, nr 9, s. 1869-1876Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Developments in the area of signature suppression make it progressively more difficult to recognize targets. The emphasis has been on the reduction of distinct features, like hot spots in the infrared band. Thus, to obtain a low false alarm rate, threat sensors have to utilize more information, i.e., spatial and spectral properties. The purpose of our work is to develop a general tool for camouflage assessment. The approach proposed applies texture descriptors to quantify the similarity between different parts of an image. In addition, other descriptors are used to distinguish man-made object characteristics. The selection of an appropriate set of features is discussed. The assumption is that an area containing observable targets has different statistics than other areas. Statistical properties along with detected target specific features have to be combined with methods used in data fusion. An experiment with a dataset of 44 reference images has been carried out, using a recently developed computer program called Terrtex. High correlation with perception experiments is achieved using only one or two texture features. The importance of a careful selection of background area size is finally discussed. (C) 2001 Society of Photo-optical instrumentation Engineers.

  • 45.
    Olsson, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Selective imaging of sound sources in air using phase-calibrated multiwavelength digital holographic reconstructions2007Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 46, s. 75801-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method for selective imaging using multiwavelength digital holographic reconstructions and the phase response of a sound source is demonstrated. Several sound measurements, using laser vibrometry, and digital reconstructions are made for several frequencies of the sound field emitted from two ultrasound transducers with different phase characteristics. Adding the reconstructed complex amplitudes together and applying a filter derived from the standard deviation over the phases for the different reconstructions makes possible a selective imaging of primary sources. When the imaging method is calibrated for a certain phase response, only primary sources with that particular phase response are imaged. Other sources and unwanted speckles are efficiently suppressed. The depth resolution obtained is 3 wavelengths.

  • 46.
    Olsson, Erik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Forsberg, Fredrik
    Three-dimensional selective imaging of sound sources2009Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 48, nr 3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A technique for 3-D selective imaging of sound sources is described analytically and demonstrated experimentally. One-dimensional recordings of the acoustic field is measured using laser vibrometry. By applying digital holographic and tomographic algorithms to the acquired 1-D data, the full 3-D complex amplitude is reconstructed. The use of multiple frequencies in the spectral content of the acoustic field gives a number of advantages: higher spatial resolution, less noise in the reconstructed image, less sensitivity to noise in the measurements, and the possibility to perform selective imaging. Theory for all three steps-the measurement of sound using light, numerical propagation of waves, and finally the tomographic reconstruction in the process are given. In the experiment, the positions of three ultrasound sources are accurately determined and two different types of transducers are distinguished from each other. This multiwavelength technique could show to be a useful addition to optoacoustic imaging.

  • 47. Olsson, Erik
    et al.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Zipser, Lothar
    HTW, Hochschule für Technik und Wirtschaft, Dresden.
    Locating primary sound sources in scattering media using multifrequency digital holographic reconstruction2006Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 45, nr 1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Multifrequency digital holographic reconstructions of primary sound sources embedded in scattering media are demonstrated. The sound field is measured with a scanning laser Doppler vibrometer (LDV) and broadening of the spectral content of the sound source is achieved by tuning the primary ultrasound (US) transducer around its resonance frequency. The results show that combining the complex amplitudes from the different frequency reconstructions results in a reduced susceptibility to multiple scattered sound and makes possible a quite thorough localization of the primary sound source. The depth resolution obtained is 11 US frequencies. This depth sensitivity is improved even further to only 2.8 wavelengths by applying a filter determined from the standard deviation over the phases

  • 48.
    Pang, Xiaodan
    et al.
    Technical University of Denmark, Denmark.
    Yu, Xianbin
    Zhao, Ying
    Deng, Lei
    Zibar, Darko
    Monroy, Idelfonso Tafur
    Experimental characterization of a hybrid fiber-wireless transmission link in the 75 to 110 GHz band2012Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 51, nr 4, artikkel-id 045004Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a detailed experimental investigation of a hybrid optical-fiber wireless communication system operating at the 75 to 110 GHz (W-band) for meeting the emerging demands in short-range wireless applications. Measured W-band wireless channel properties such as channel loss, frequency response, phase noise, and capacity are reported. Our proposed system performs a sextuple frequency up-conversion after 20 km of fiber transmission, followed by a W-band wireless link. A 500 Mbit/s amplitude shift keying signal transmission is experimentally demonstrated for performance analysis purposes.

  • 49.
    Rönnow, Daniel
    Department of Technology, Uppsala University, Uppsala, Sweden; Max-Planck-Institut für , Stuttgart, Germany.
    Interface roughness statistics of thin films from angle-resolved light scattering at three wavelengths1998Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 37, nr 2, s. 696-704Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The possibility of determining interface roughness and cross-correlation statistics of the two interfaces of a thin film from angle-resolved light scattering data at three wavelengths is investigated. It is shown that angle-resolved light scattering measurements at three wavelengths are not sufficient to determine the three power spectral density functions describing the thin film roughness. An attempt to combine reflectance and transmittance scattering to determine the roughness of a thin film on a transparent substrate appears to work and provides encouraging results.

  • 50.
    Saldner, Henrik
    et al.
    Luleå tekniska universitet.
    Mohan, Nandigana K.
    Luleå tekniska universitet.
    Molin, Nils-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Comparative TV holography for vibration analysis1995Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 34, nr 2, s. 486-492Artikkel i tidsskrift (Fagfellevurdert)
12 1 - 50 of 61
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