| 1. |
- Abrahamsson, Christoffer, et al.
(author)
-
Scatter correction of transmission NIR spectra by photon migration data - Quantitative analysis of solids
- 2005
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In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 1996-756X .- 0277-786X. ; 6009, s. 60090-60090
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Conference paper (peer-reviewed)abstract
- The scope of this presentation is a new methodology to correct conventional NIR data for scattering effects. The technique aims at measuring the absorption coefficient of the samples rather than the total attenuation, measured by conventional NIR spectroscopy. The main advantage of this is that the absorption coefficient is independent of the path length of the light inside the sample, and therefore independent of the scattering effects. The measurements in this work were made using a novel system for time-resolved measurements, based on short light continuum pulses generated in an index-guided crystal fibre and a spectrometer-equipped streak camera. The system enables spectral recordings in the wavelength range 500 - 1200 nm with a spectral resolution of 5 nm and a temporal resolution of 30 ps. The evaluation scheme is based on modeling of light transport by diffusion theory, that provides an independent measure of the scattering properties of the samples, that later is used to correct conventional NIR data. This yields a clear advantage over other pre-processing techniques, where scattering effects are estimated and corrected for by using the shape of the measured spectrum only. PLS calibration models shows that, by using the proposed evaluation scheme, the predictive ability is improved by 50% as compared to models based on conventional NIR data. The method also makes it possible to predict the concentration of active substance in samples with physical properties different from those of the samples included in the calibration model.
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| 2. |
- Afanasiev, Sergey V., et al.
(author)
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Experimental apparatus to study crystal channeling in an external SPS beamline
- 2007
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6634
-
Journal article (peer-reviewed)abstract
- For the new generation of high intensity hadronic machines as, for instance, LHC, halo collimation is a necessary issue for the accelerator to operate at the highest possible luminosity and to prevent the damage of superconductor magnets.1 We propose an experiment aimed to systematic study of the channeling phenomenology and of the newly observed "volume reflection" effect. This experiment will be performed for an external SPS beamline and will make use of a primary proton beam with 400 GeV/c momentum and very small (∼ 3 μrad) divergence. The advantage of a proposed experiment is precise tracking of particles that interacted with a crystal, so that to determine the single-pass efficiency for all the processes involved. For this purpose, a telescope equipped with high-resolution silicon microstrip detectors will be used. New generation silicon crystals and an extra-precise goniometer are mandatory issues. Main goal of the experiment is to get the precise information on channeling of relativistic particles and, ultimately, on the feasibility of such technique for halo collimation at LHC. In this contribution we review the status of the setting-up of experimental apparatus and its future development in sight of the planned run in September 2006.
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| 3. |
- Andersen, Torben, et al.
(author)
-
A new concept for large deformable mirrors for extremely large telescopes
- 2006
-
In: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 1996-756X .- 0277-786X. ; 6272:1, s. 324-331
-
Conference paper (peer-reviewed)abstract
- For extremely large telescopes, there is strong need for thin deformable mirrors in the 3-4 m class. So far, feasibility of such mirrors has not been demonstrated. Extrapolation from existing techniques suggests that the mirrors could be highly expensive. We give a progress report on a study of an approach for construction of large deformable mirrors with a moderate cost. We have developed low-cost actuators and deflection sensors that can absorb mounting tolerances in the millimeter range, and we have tested prototypes in the laboratory. Studies of control laws for mirrors with thousands of sensors and actuators are in good progress and simulations have been carried out. Manufacturing of thin, glass mirror blanks is being studied and first prototypes have been produced by a slumping technique. Development of polishing procedures for thin mirrors is in progress
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| 4. |
- Andersen, Torben, et al.
(author)
-
An Integrated Model of the European Extremely Large Telescope
- 2008
-
In: MODELLING, SYSTEMS ENGINEERING, AND PROJECT MANAGEMENT FOR ASTRONOMY III. - : SPIE. - 1996-756X .- 0277-786X. ; 7017, s. 216-227
-
Conference paper (peer-reviewed)abstract
- Integrated models including optics, structures, control systems, and disturbances are important design tools for Extremely Large Telescopes (ELTs). An integrated model has keen formulated for the European ELT and it includes telescope structure, main servos, primary mirror segment control system, wind, optics, wavefront sensor, deformable mirror, and an AO reconstructor and controller. There are three model phases: Initialization, execution of a solver to determine time responses, and post-processing. In near future, the model will be applied for performance studies and design trade-offs for the European ELT.
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| 5. |
- Ardeberg, Arne, et al.
(author)
-
ELTs, adaptive optics and wavelengths - art. no. 698608
- 2008
-
In: Extremely Large Telescopes: Which Wavelengths? Retirement Symposium for Arne Ardeberg. - : SPIE. - 1996-756X .- 0277-786X. ; 6986, s. 98608-98608
-
Conference paper (peer-reviewed)abstract
- A number of Extremely Large Telescopes for visual-infrared and adjacent wavelengths are in various degrees of progress. All have primary mirrors with equivalent diameters larger than 20 m and are intended for operation with adaptive optics systems. We discuss several ELT observing parameters as functions of wavelength. Stellar energy distributions and atomic line spectra are inspected as are the transmission of the Earth's atmosphere, the emissivity of the sky and telescope and instruments as well as detector sensitivity, resolution and signal-to-noise ratio. The spatial resolution depending on the size of the diffraction limited adaptive optics point spread function is discussed. We have evaluated the ELT efficiency in terms of Johnson V to N band photometry, simulating diffraction-limited ELT images of a stellar field at 4 Mpc and 4 kpc, respectively. We conclude that the information content at shorter wavelengths is of dominant nature and that there is every reason to do the utmost to include shorter wavelengths in the AO regime. We propose to adopt a short-wave length goal of 1 000 nm for first light AO with later updates reaching down to visual wavelengths.
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| 6. |
- Ardeberg, Ame, et al.
(author)
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ELTs, AO wavelengths and science output
- 2008
-
In: GROUND-BASED AND AIRBORNE TELESCOPES II, PTS 1-3. - 0277-786X .- 1996-756X. ; 7012, s. 121-121
-
Conference paper (peer-reviewed)abstract
- A study is presented of the impact on science data from extremely large telescopes of a transformation of wavelength base for optimization of actuator architecture from 2 200 to 1250 nm. From the optical path difference (OPD) data for Euro50, we transform to E-ELT OPDs. We compute the corresponding power spectrum, in which we simulate a higher actuator density via high-pass filtering to convert from K to J band actuator-pitch optimization. From the modified power spectrum we derive the correspondingly modified OPDs, PSFs and Strehl ratios. A massive improvement is demonstrated resulting from converting from AO@K to AO@J. This result is followed up by model-based E-ELT imaging in a field in a galactic disc at a distance of 4 Mpc. The improvements in image quality, background and limiting magnitude are very large as are the increases in photometric precision derived from the field imaging. Further, the great science benefit and large opportunities provided by partial AO is demonstrated. In conclusion, while admittedly challenging, pushing AO optimization to wavelengths as short as possible is of prime concern for the science output of ELTs.
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| 7. |
- Ardeberg, Arne, et al.
(author)
-
From Euro50 towards a European ELT
- 2006
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6267 II, s. 26725-26725
-
Conference paper (peer-reviewed)abstract
- With Euro50 as a convenient telescope laboratory, the Euro50 team has continued development aiming at a European extremely large telescope (ELT). Here, we give a progress report. The needs of science and instrumentation are briefly discussed as is the importance of photometric stability and precision. Results are reported from work on integrated modelling. Details are given concerning point-spread functions (PSFs) obtained with and without adaptive optics (AO). Our results are rather encouraging concerning AO photometry and compensation of edge sensor noise as well as regarding seeing-limited ELT operation. The current status of our development of large deformable mirrors is shown. Low-cost actuators and deflection sensors have been developed as have hierarchic control algorithms. Fabrication of large thin mirror blanks as well as polishing and handling of thin mirrors has been studied experimentally. Regarding adaptive optics, we discuss differential refraction and the limitations imposed by dispersive optical path differences (OPDs) and dispersive anisoplanatism. We report on progress in laser guide star (LGS) performance and a real-time online experiment in multi-conjugate AO (MCAO). We discuss ELTs, high-resolution spectroscopy and pupil slicing with and without use of AO. Finally, we present some recent studies of ELT enclosure options.
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| 8. |
- Batista, P.D., et al.
(author)
-
Acousto-electric single-photon detector
- 2007
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6583, s. 658304-
-
Journal article (peer-reviewed)abstract
- We propose a novel concept for a semiconductor-based single-photon detector for quantum information processing, which is capable of discriminating the number of photons in a light pulse. The detector exploits the charge transport by a surface acoustic wave (SAW) in order to combine a large photon absorption area (thus providing high photon collection efficiency) with a microscopic charge detection area, where the photo generated charge is detected with resolution at the single electron level using single electron transistors (SETs). We present preliminary results on acoustic transport measured in a prototype for the detector as well as on the fabrication of radio-frequency single-electron transistors (RFSETs) for charge detection. The photon detector is a particular example of acousto-electric nanocircuits that are expected to be able to control both the spatial and the spin degrees of freedom of single electrons. If realized, these circuits will contribute substantially to a scalable quantum information technology.
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| 9. |
- Bjorstrom, Cecilia M., et al.
(author)
-
Influence of solvents and substrates on the morphology and the performance of low-bandgap polyfluorene: PCBM photovoltaic devices - art. no. 61921X
- 2006
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : International Society for Optical Engineering; 1999. - 0277-786X .- 1996-756X. ; 6192, s. X1921-X1921
-
Journal article (peer-reviewed)abstract
- Spin-coated thin films of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4,7-di-2-thienyl-2,1,3-benzothiadiazole)] (APFO-3) blended with [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) are used as the active material in polymer photovoltaic cells. Such blends are known for their tendency to phase separate during film formation. Tuning the morphology of the blend in a controlled way is one possible road towards higher efficiency. We studied the effect of adding chlorobenzene to chloroform-based blend solutions before spin-coating on the conversion efficiency of APFO-3:PCBM photodiodes, and related that to the lateral and vertical morphology of thin films of the blend. The lateral morphology is imaged by atomic force microscopy (AFM) and the vertical compositional profile is obtained by dynamic secondary ion mass spectrometry (SIMS). The profiles reveal compositional variations consisting of multilayers of alternating polymer-rich and PCBM-rich domains in the blend film spin-coated from chloroform. The vertical compositional variations are caused by surface-directed spinodal waves and are frozen in during the rapid evaporation of a highly volatile solvent. With addition of the low-vapour pressure solvent chlorobenzene, a more homogeneous vertical composition is found. The conversion efficiency for solar cells of this blend was found to be optimal for chloroform: chlorobenzene mixtures with a volume-ratio of 80:1. We have also investigated the role of the substrate on the morphology. We found that blend films spin-coated from chloroform solutions on PEDOT:PSS-coated ITO show a similar compositional structure as the films on silicon, and that changing the substrate from silicon to gold only affects the vertical phase separation in a region close to the substrate interface.
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| 10. |
- Björström, Cecilia M., et al.
(author)
-
Influence of solvents and substrates on the morphology and the performance of low-bandgap polyfluorene:PCBM photovoltaic devices
- 2006
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - Cardiff : SPIE - International Society for Optical Engineering. - 0277-786X .- 1996-756X. ; 6192, s. 61921X-
-
Journal article (peer-reviewed)abstract
- Spin-coated thin films of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (APFO-3) blended with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are used as the active material in polymer photovoltaic cells. Such blends are known for their tendency to phase separate during film formation. Tuning the morphology of the blend in a controlled way is one possible road towards higher efficiency. We studied the effect of adding chlorobenzene to chloroform-based blend solutions before spin-coating on the conversion efficiency of APFO-3:PCBM photodiodes, and related that to the lateral and vertical morphology of thin films of the blend. The lateral morphology is imaged by atomic force microscopy (AFM) and the vertical compositional profile is obtained by dynamic secondary ion mass spectrometry (SIMS). The profiles reveal compositional variations consisting of multilayers of alternating polymer-rich and PCBM-rich domains in the blend film spin-coated from chloroform. The vertical compositional variations are caused by surface-directed spinodal waves and are frozen in during the rapid evaporation of a highly volatile solvent. With addition of the low-vapour pressure solvent chlorobenzene, a more homogeneous vertical composition is found. The conversion efficiency for solar cells of this blend was found to be optimal for chloroform:chlorobenzene mixtures with a volume-ratio of 80:1. We have also investigated the role of the substrate on the morphology. We found that blend films spin-coated from chloroform solutions on PEDOT:PSS-coated ITO show a similar compositional structure as the films on silicon, and that changing the substrate from silicon to gold only affects the vertical phase separation in a region close to the substrate interface
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| 11. |
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| 12. |
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| 13. |
- Chen, Daru, et al.
(author)
-
Some switchable dual-wavelength fibre lasers based on fibre Bragg grating feedback
- 2006
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6351, s. U864-U872
-
Journal article (peer-reviewed)abstract
- Two methods to achieve dual-wavelength switching in a fibre laser are proposed and two corresponding switchable dual-wavelength fibre lasers based on fibre Bragg grating (FBG) feedback are demonstrated in this paper. In one proposed fibre laser, both Raman and Erbium-doped fibre (EDF) pumps are employed and the dual-wavelength switching is achieved by controlling the power of the Raman pump. In the other proposed fibre laser, an injection technique is used and the dual-wavelength switching is realized by controlling the power of the injection laser. The detailed behavior of the dual-wavelength switching in the two fibre lasers is experimentally studied and the principle is explained physically.
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| 14. |
- Chen, Jiajia, et al.
(author)
-
A Novel Joint Scheduling Algorithm for Multiple Services in 10G EPON
- 2008
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 7137
-
Journal article (other academic/artistic)abstract
- In this paper, we propose and evaluate a novel joint scheduling algorithm for multiple services which can support differentiated services and bandwidth allocation with global priority of different traffic such as Triple-play: voice, video and Internet services. Simulation results show that for the higher priority traffic better delay and jitter performance can be achieved compared with the lower priority traffic.
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| 15. |
- Dravins, Dainis, et al.
(author)
-
Toward a diffraction-limited square-kilometer optical telescope: Digital revival of intensity interferometry - art. no. 698609
- 2008
-
In: Extremely Large Telescopes: Which Wavelengths? Retirement Symposium for Arne Ardeberg. - : SPIE. - 0277-786X .- 1996-756X. ; 6986, s. 98609-98609
-
Conference paper (peer-reviewed)abstract
- Much of the progress in astronomy follows imaging with improved resolution. In observing stars, current capabilities are only marginal in beginning to image the disks of a few, although many stars will appear as surface objects for baselines of hundreds of meters. Since atmospheric turbulence makes ground-based phase interferometry challenging for such long baselines, kilometric space telescope clusters have been proposed for imaging stellar surface details. The realization of such projects remains uncertain, but comparable imaging could be realized by ground-based intensity interferometry. While insensitive to atmospheric turbulence and imperfections in telescope optics, the method requires large flux collectors, such as being set up as arrays of atmospheric Cherenkov telescopes for studying energetic gamma rays. High-speed detectors and digital signal handling enable very many baselines to be synthesized between pairs of telescopes, while stars may be tracked across the sky by electronic time delays. First observations with digitally combined optical instruments have now been made with pairs of 12-meter telescopes of the VERITAS array in Arizona. Observing at short wavelengths adds no problems, and similar techniques on an extremely large telescope could achieve diffraction-limited imaging down to the atmospheric cutoff, achieving a spatial resolution significantly superior by that feasible by adaptive optics operating in the red or near-infrared.
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| 16. |
- Eastham, D. A., et al.
(author)
-
Construction of a new type of low-energy, scanning electron microscope with atomic resolution
- 2009
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - Monterey : SPIE. - 0277-786X .- 1996-756X. - 9780819476548 ; 7378, s. 73781S-73781S
-
Conference paper (peer-reviewed)abstract
- We describe a new type of scanning electron microscope which works by directly imaging the electron field-emission sites on a nanotip. Electrons are extracted from the nanotip through a nanoscale aperture, accelerated in a high electric field and focussed to a spot using a microscale einzel lens. If the whole microscope (accelerating section and lens) and the focal length are both restricted in size to below 10 microns, then computer simulations show that the effects of aberration are extremely small and it is possible to have a system with approximately unit magnification, at electron energies as low as 300 eV. Thus a typical emission site of 1 nm diameter will produce an image of the same size and an atomic emission site with give a resolution of 0.1-0.2 nm (1-2 Å), and because the beam is not allowed to expand beyond 100nm in diameter the depth of field is large and the contribution to the beam spot size from chromatic aberrations is less than 0.02 nm (0.2 Å) for 500 eV electrons. Since it is now entirely possible to make stable atomic sized emitters (nanopyramids) it is expected that this instrument will have atomic resolution. Furthermore the brightness of the beam is determined only by the field-emission and can be up to a million times larger than in a typical (high-energy) electron microscope. The construction of this microscope, based on using a nanotip electron source which is mounted on a nanopositioner so that it can be positioned at the correct point adjacent to the microscope, entrance aperture, is described. In this geometry the scanning is achieved by moving the sample using piezos. Two methods for the construction of the microscope column are reviewed and the results of preliminary tests are described. The advantages of this low energy, bright-beam, electron microscope with atomic resolution are described. It can be used in either scanning mode or diffraction mode. The major advantage over existing microscopes is that because it works at very low energies the elastic backscatteri g is sensitive to the atomic species and so these can be identified directly without any energy discrimination on the detector. Furthermore it is also possible to use the microscope to do low energy electron diffraction which, because the scattering cross-section is large, can be carried out on single molecules. If these are biological samples such as DNA, proteins and viruses then the low energy means that the radiation damage is minimised. Some possibilities for mounting these samples, which can reduce radiation damage, are discussed. Finally we show a system for producing holograms of single protein molecules.
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| 17. |
- Engström, David, 1976, et al.
(author)
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Steering accuracy of a spatial light modulator-based single beam steerer: guidelines and limitations
- 2008
-
In: SPIE Proceedings. - : SPIE. - 0277-786X .- 1996-756X. - 9780819472588
-
Conference paper (peer-reviewed)abstract
- The positioning accuracy when a phase-only one dimensional spatial light modulator (SLM) is used for beam steering is limited by the number of pixels and their quantized phase modulation. Optimizing the setting of the SLM pixels individually can lead to the inaccuracy being a significant fraction of the diffraction limited spot size. This anomalous behaviour was simulated numerically, and experiments showed the same phenomena with very good agreement. However, by including an extra degree of freedom in the optimization of the SLM setting, we show that the accuracy can be improved by a factor proportional to the number of pixels in the SLM.
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| 18. |
- Enmark, Anita, et al.
(author)
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Architecture of the integrated model of the Euro50
- 2006
-
In: Modeling, Systems Engineering, and Project Management for Astronomy II. - : SPIE. - 0277-786X .- 1996-756X. ; 6271, s. 27114-27114
-
Conference paper (peer-reviewed)abstract
- The Euro50 is a proposed 50m extremely large telescope for optical and infrared wavelengths. To study and predict the performance of the complete telescope system, an integrated model combining the structural model of the telescope, optics models, the control systems and the adaptive optics has been established. Wind and atmospheric disturbances are also included in the model. The model is written in MATLAB and C. It is general and modular and built around dedicated ordinary differential equation solvers. The difference in time constants between subsystems is exploited to speed up calculations. The solvers can handle discontinuities and subsystem mode changes. The high degree of modularity allows different telescope designs to be modelled by rearranging subsystem blocks. Certain subsystems, for instance adaptive optics, can also run in a standalone fashion. Parts of the model are parallelized for execution on a large shared memory machine. The resulting architecture of the integrated model and sample results using the code for different telescope models are presented.
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| 19. |
- Enmark, Anita, et al.
(author)
-
Modeling ELTs at different wavelengths
- 2008
-
In: Extremely Large Telescopes: Which Wavelengths? Retirement Symposium for Arne Ardeberg. - : SPIE. - 0277-786X .- 1996-756X. ; 6986, s. 9860-9860
-
Conference paper (peer-reviewed)abstract
- The next generation of telescopes, the Extremely Large Telescopes (ELTs), will have a multitude Of control loops to maintain nearly diffraction-limited performance in the presence of atmospheric turbulence and external disturbances, for instance from wind. Integrated simulation models combining structural and optical modeling together with control system modeling are efficient tools for prediction of performance of ELTs. Such models include submodels of structures, adaptive optics, atmosphere, wind load, deformable mirrors and a segmented primary mirror. So far the models applied have been applicable to observations in the K-band. However, there is a desire to also operate the ELTs with adaptive optics at wavelengths in the visible range. We here give estimates of the feasibility of performing such simulations. We set up scaling laws for the design parameters as a function of wavelength of operation and we show that the execution time for an integrated model of an ELT depends dramatically on the operation wavelength. We also discuss the consequences of different choices of model refinement. Finally we present estimates of the execution time for integrated models of ELTs. We show that accurate modeling in the K-band calls for long execution times, even with parallel computers. For wavelengths in the visible range, only the very simplest models are feasible due to execution time limitations, thereby precluding many interesting studies related to noise sensitivity and limiting magnitude for guide stars.
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| 20. |
- Enmark, Anita, et al.
(author)
-
Status of the Integrated Model of the Euro50
- 2006
-
In: Modeling, Systems Engineering, and Project Management for Astronomy II. - : SPIE. - 0277-786X .- 1996-756X. ; 6271, s. 27102-27102
-
Conference paper (peer-reviewed)abstract
- The Euro50 is a proposed 50m extremely large telescope for optical and infrared wavelengths. To study and predict the performance of the complete telescope system, an integrated model combining the structural model of the telescope, optics models, the control systems and the adaptive optics has been established. Wind and atmospheric disturbances are also included in the model. The integrated model is written in MATLAB and C. To satisfy memory demands and to achieve acceptable execution times, 64-bit MATLAB is used and part of the model is run on a shared memory machine using OpenMP. We present results from simulations with a complete integrated single conjugate adaptive optics model. Various sensor and actuator geometries are evaluated. A comparison of wind loading and atmospheric turbulence effects is also presented. The model shows that the telescope will be essentially seeing limited under wind load and no AO correction.
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| 21. |
- Enochsson, Ola, et al.
(author)
-
Structural health monitoring of a concrete bridge in Sweden
- 2006
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6176:18
-
Journal article (peer-reviewed)abstract
- Over the past decade the interests in upgrading, assessment and maintenance of our ageing infrastructure has grown avalanche-like. The main reason is economical aspects but also reasons due to accessibility environmental consideration play a vital role. Recently the Swedish and Norwegian Railway Association decided to upgrade the Iron Ore Line "Malmbanan", a railway line for transportation of iron from northern Sweden to the coasts of Norway and Sweden. Here the owner wanted to increase the axle loads from 25 to 30 tons to reduce the transportation costs. In one of the cases, the Luossajokk Bridge, a recalculation according to design codes showed that the increased axle loads would exceed the yield limit in the reinforcement. Before any decision was taken regarding strengthening or replacing the bridge an assessment with probabilistic methods was used. It appeared that the bridge could carry the higher load with a safety index β ≥ 4.7 for reasonable assumptions of the load distributions. A measurement system was installed to check the real worst placement of the new iron ore locomotive (IORE), and the actually level of strains in the reinforcement for the worst load case1. It was shown that the strain level was far from critical and that the evaluated worst placement of the locomotive was almost correct2. To assure a reliable transportation a long term monitoring program was arranged to check the development of strains with time. Examples from the probabilistic evaluation and the monitoring of the bridge are given and discussed.
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| 22. |
- Fang, Wen Hai, et al.
(author)
-
Power-driven FPGA to ASIC conversion
- 2007
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 1996-756X .- 0277-786X. - 9780819467188 ; 6590
-
Conference paper (peer-reviewed)abstract
- Gate arrays are often presented as a convenient means for ASIC prototyping. Obviously, they can both perform the same function and therefore be built from the same behavioral description. Design development implies a process of subsequent parameter bindings, leaving steadily less freedom for the remaining implementation choices. On the other hand, the ASIC offers more place & route freedom than the gate array. Hence it is commonly suggested that an optimal prototype will always have an acceptable ASIC realization. But this does not make the gate array an easy stepping-stone in ASIC development. Differences in platform technology induce a different structural sugaring to achieve a reasonable implementation. This cannot easily be ported, unless the implementation is developed while keeping the restrictions for the other technology in mind. Such implies a number of scaling rules to be the foundation of the design transformation process. This paper looks into the platform commonalities of Field-Programmable Gate-arrays and standard-cell ASICs from fundamental physical principles. These basic considerations are then related to show how the area and speed restrictions in the logic synthesis can be applied to carry power efficient designs efficiently from prototype to realization. This is illustrated in the design of the SNOW-2 encryption core, where a consistent 38% power reduction is achieved.
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| 23. |
- Fredriksson, Ingemar, et al.
(author)
-
Absolute flow velocity components in laser Doppler flowmetry
- 2006
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : IEEE. - 0277-786X .- 1996-756X. ; 6094, s. 60940A-
-
Journal article (peer-reviewed)abstract
- A method to separate a Doppler power spectrum into a number of flow velocity components, measured in absolute units (mm/s), is presented. A Monte Carlo software was developed to track each individual Doppler shift, to determine the probability, p(n), for a photon to undergo n Doppler shifts. Given this shift distribution, a mathematical relationship was developed and used to calculate a Doppler power spectrum originating from a certain combination of velocity components. The non linear Levenberg-Marquardt optimization method could thus be used to fit the calculated and measured Doppler power spectra, giving the true set of velocity components in the measured sample. The method was evaluated using a multi tube flow phantom perfused with either polystyrene microspheres or undiluted/diluted human blood (hct = 0.45). It estimated the velocity components in the flow phantom well, during both low and high concentrations of moving scatterers (microspheres or blood). Thus, further development of the method could prove to be a valuable clinical tool to differentiate capillary blood flow.
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| 24. |
- Gorpas, Dimitris, et al.
(author)
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Data fitting and image fine-tuning approach to solve the inverse problem in fluorescence molecular imaging
- 2008
-
In: IMAGING, MANIPULATION, AND ANALYSIS OF BIOMOLECULES, CELLS, AND TISSUES VI. - : SPIE. - 0277-786X .- 1996-756X. - 9780819470348 ; 6859
-
Conference paper (peer-reviewed)abstract
- One of the most challenging problems in medical imaging is to ``see{''} a tumour embedded into tissue, which is a turbid medium, by using fluorescent probes for tumour labeling. This problem, despite the efforts made during the last years, has not been fully encountered yet, due to the non-linear nature of the inverse problem and the convergence failures of many optimization techniques. This paper describes a robust solution of the inverse problem, based on data fitting and image fine-tuning techniques. As a forward solver the coupled radiative transfer equation and diffusion approximation model is proposed and compromised via a finite element method, enhanced with adaptive multi-grids for faster and more accurate convergence. A database is constructed by application of the forward model on virtual tumours with known geometry, and thus fluorophore distribution, embedded into simulated tissues. The fitting procedure produces the best matching between the real and virtual data, and thus provides the initial estimation of the fluorophore distribution. Using this information, the coupled radiative transfer equation and diffusion approximation model has the required initial values for a computational reasonable and successful convergence during the image fine-tuning application.
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| 25. |
- Grönlund, Rasmus, et al.
(author)
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Laser-induced fluorescence imaging for studies of cultural heritage - art. no. 66180P
- 2007
-
In: O3A: Optics for Arts, Architecture, and Archaeology. - : SPIE. - 1996-756X .- 0277-786X. - 9780819467607 ; 6618, s. 6180-6180
-
Conference paper (peer-reviewed)abstract
- Laser-induced fluorescence for remote imaging of historical monuments is an established technique, which in this work has been used in measurement campaigns at the Coliseum and the Baptistery of San Giovanni in Laterano in Rome, Italy. The results presented here are examples that show that biodeteriogens can be monitored and that. materials can be identified. Also, cleaned and soiled areas on the stone can be localized and differences between soiling can be found, which may be useful in the sustainable conservation for mapping and evaluation.
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| 26. |
- Güsten, R., et al.
(author)
-
APEX - The Atacama Pathfinder Experiment
- 2006
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6267 I
-
Conference paper (peer-reviewed)abstract
- APEX, the Atacama Pathfinder Experiment, has been successfully commissioned and is in operation now. This novel submillimeter telescope is located at 5107 m altitude on Llano de Chajnantor in the Chilean High Andes, on what is considered one of the world's outstanding sites for submillimeter astronomy. The primary reflector with 12 m diameter has been carefully adjusted by means of holography. Its surface smoothness of 17-18 μm makes APEX suitable for observations up to 200 μm, through all atmospheric submm windows accessible from the ground.
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| 27. |
- Haj-Hosseini, Neda, 1980-, et al.
(author)
-
Photobleaching behavior of protoporphyrin IX during 5-aminolevulinic acid marked glioblastoma detection
- 2009
-
In: PHOTONIC THERAPEUTICS AND DIAGNOSTICS V. - : SPIE. - 0277-786X .- 1996-756X. - 9780819474070 ; 7161
-
Conference paper (peer-reviewed)abstract
- The highly malignant brain tumor, glioblastoma multiforme (GBM), is difficult to fully delineate during surgical resection due to its infiltrative ingrowth and morphological similarities to surrounding functioning brain tissue. Selectiveness of GBM to 5-aminolevulinic acid (5-ALA) induced protoporphyrin IX (PpIX) is reported by other researchers to visualize tumor margins under blue light microscopy. To allow objective detection of GBM, a compact and portable fiber optic based fluorescence spectroscopy system is developed. This system is able to deliver excitation laser light (405 nm) in both the continuous and pulsed mode. PpIX fluorescence peaks are detected at 635 and 704 nm, using a fiber-coupled spectrometer. It is necessary to optimize the detection efficiency of the system as the PpIX quickly photobleaches during the laser illumination. A light dose of 2.5 mJ (fluence rate = 9 mJ/mm(2)) is experimentally approved to excite an acceptable level of fluourescence signal arising from glioblastoma. In pulsed illumination mode, an excitation dose of 2.5 mJ, with a dark interval of 0.5 s (duty cycle 50\%) shows a significantly shorter photobleaching time in comparison to the continuous illumination mode with the same laser power (p < 0.05). To avoid photobleaching (the remaining signal is more than 90\% of its initial value) when measuring with 2.5 mJ delivered energy, the time for continuous and pulsed illumination should be restricted to 2.5 and 1.1 s, respectively.
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| 28. |
- Heimsten, Rikard, et al.
(author)
-
Modeling large deformable mirrors
- 2008
-
In: SPIE Proceedings. - 1996-756X .- 0277-786X. ; 7017, s. 516-523
-
Conference paper (peer-reviewed)abstract
- Planned Extremely Large Telescopes will rely oil availability of large Deformable Mirror in the 2-3m class. Design and construction of such mirrors are challenging and call for powerful simulation tools. We present an evaluation model which is used to study performance of a large deformable mirror for three: actuator topologies. Back sensors topologies are discussed from the point of view of sensor noise propagation. Two methods for estimating the deflection at the actuator locations on the basis of sensor signal are presented and comapred regarding the computational power needed.
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| 29. |
- Hejll, Arvid, et al.
(author)
-
Structural health monitoring of the Gröndals bridge in Sweden : the behaviour of CFRP strengthening in cold temperature
- 2006
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6176:17
-
Journal article (peer-reviewed)abstract
- To obtain a better knowledge of existing structures behaviour monitoring can be used. The use of monitoring in bridge structures by the use of instruments to assess the integrity of structures is not new and there are reports from structures tested as early as in the 19th century according to ISIS Canada1 However, the term SHM (Structural Health Monitoring) is relatively new to civil engineering and the driving force to implement SHM comes from recognising the limitations of conventional visual inspections and evaluations using conservative codes of practice. The possibilities to monitor existing structures with help of the rapidly evolving Information Technology are to day carried out. The objective of SHM is to monitor the in-situ behaviour of a structure accurately and efficiently, to assess its performance under various service conditions, to detect damage or deterioration, and to determine the health or condition of the structure1. In Sweden strengthening and periodic monitoring of a large freivorbau bridge (pre-stresed concrete box girder bridge) has been carried out, the Gröndals Bridge. The bridge is located in Stockholm and is approximately 400 m in length with a free span of 120 m. It was opened to tram traffic in year 2000. Just after opening cracks were noticed in the webs, these cracks have then increased, the size of the largest cracks exceeded 0.5 mm, and at the end of year 2001 the bridge was temporarily strengthened. This was carried out with externally placed prestressed steel stays. The reason for cracking is quite clear but the responsibility is still debated. Nevertheless, it was evidently that the bridge needed to be strengthened. The strengthening methods used were CFRP plates in the Service Limit State (SLS) and prestressed dywidag stays in the Ultimate Limit State (ULS). The strengthening was carried out during year 2002. At the same time monitoring of the bridge commenced, using LVDT crack gauges as well as optical fibre sensors. This monitoring was carried out during the summer period. In addition to this a winter monitoring was carried out in the beginning of 2005. This paper presents the background to strengthening and a comparison between summer and winter monitoring where the strengthening behaviour between the two seasons is enlightened. The result from the monitoring is very interesting; it would have been preferable to strengthen the bridge during the winter.
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| 30. |
- Henriksson, Markus, et al.
(author)
-
Experimental study of mid-IR laser beam wander close to a jet engine exhaust
- 2006
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 0819464953 - 9780819464958 ; 6397
-
Journal article (peer-reviewed)abstract
- An increasing interest in lasers placed on aircrafts for active countermeasures and active imaging is observed. There remain unsolved issues regarding the propagation effects close to the jet engine exhaust and the possibilities of compensating them with adaptive optics. Laser beam propagation experiments parallel to the exhaust of a downscaled jet engine test rig have been performed. The experiments were carried out with nanosecond laser pulses at 1.6 and 3.5 μm wavelength. The laser spots were projected on a screen and the centroid motion were imaged by cameras. Root mean square magnitudes of the beam wander between 50 and 150 μrad were observed for different engine conditions and geometries. The 3.5 μm system had a frame rate of 607 Hz and could partly resolve the time variation of the beam wander. A correlation time (50 %) of 3.5 ms was observed for the beam wander. Deflections of several hundred μrad due to the average gradients in temperature and pressure were also found when the engine was turned on. In addition to beam wander intensity scintillations has been studied.
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| 31. |
- Henriksson, Markus, et al.
(author)
-
Tandem PPKTP and ZGP OPO for mid-infrared generation
- 2008
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - USA : SPIE - International Society for Optical Engineering. - 0277-786X .- 1996-756X. ; 7115, s. 71150O1-10
-
Journal article (peer-reviewed)abstract
- Efficient laser sources in the 3-5 μrn wavelength range are needed for directed infrared countermeasures, but also have applications in remote-sensing, medicine and spectroscopy. We present new results on our tandem optical parametric oscillator (OPO) scheme for converting the radiation from a 1.06 μm Nd3+-laser to the mid-infrared. Multi Watt level output power in the 3-5 μm range at 20 kHz pulse repetition frequency is reported. Our setup uses a type I quasi phasematched PPKTP crystal in a near degenerate OPO to generate 2.13 μm radiation. A volume Bragg grating resonant close to, but not exactly at the degenerate wavelength, is used as a cavity mirror to reduce the bandwidth and ensure singly resonant operation. Both signal and idler from the PPKTP OPO are used to pump a ZGP OPO generating high power radiation in the 3-5μm region. Using this scheme for each pump photon it is possible to generate four photons for each pump photon, all in the interesting wavelength range, thus enabling high efficiency conversion.
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| 32. |
- Holm, Jesper, et al.
(author)
-
Novel low-loss 3-element ring resonator for second-harmonic generation of 808nm into 404nm using periodically poled KTP
- 2007
-
In: Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications VI. - : SPIE. - 1996-756X .- 0277-786X. - 9780819465689 ; 6455
-
Conference paper (peer-reviewed)abstract
- We present a novel ring resonator for second harmonic generation consisting of only two spherical mirrors and a refractive element. In our work we use periodically poled KTP as a nonlinear material for generating the second harmonic using an 808nm tapered grating stabilized external cavity laser as pump source. With 286mW of fundamental 808nm radiation coupled into the resonator, we generate 130mW blue light at 404nm, resulting in a power conversion efficiency of 45\%.
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| 33. |
- Ilias, Michail, 1971-, et al.
(author)
-
Evaluation of a Fiber-Optic Fluorescence Spectroscopy System to Assist Neurosurgical Tumor Resections
- 2007
-
In: Novel Optical Instrumentation for Biomedical Applications III (Proceedings Volume). - Bellingham, Washington, USA : SPIE - International Society for Optical Engineering. - 0277-786X .- 1996-756X. - 9780819467751 ; , s. 66310W-1-66310W-8
-
Conference paper (other academic/artistic)abstract
- The highly malignant brain tumor, glioblastoma multiforme, is difficult to totally resect without aid due to its infiltrative way of growing and its morphological similarities to surrounding functioning brain under direct vision in the operating field. The need for an inexpensive and robust real-time visualizing system for resection guiding in neurosurgery has been formulated by research groups all over the world. The main goal is to develop a system that helps the neurosurgeon to make decisions during the surgical procedure. A compact fiber optic system using fluorescence spectroscopy has been developed for guiding neurosurgical resections. The system is based on a high power light emitting diode at 395 nm and a spectrometer. A fiber bundle arrangement is used to guide the excitation light and fluorescence light between the instrument and the tissue target. The system is controlled through a computer interface and software package especially developed for the application. This robust and simple instrument has been evaluated in vivo both on healthy skin but also during a neurosurgical resection procedure. Before surgery the patient received orally a low dose of 5-aminolevulinic acid, converted to the fluorescence tumor marker protoporphyrin IX in the malignant cells. Preliminary results indicate that PpIX fluorescence and brain tissue autofluorescence can be recorded with the help of the developed system intraoperatively during resection of glioblastoma multiforme.
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| 34. |
- Johansson, Ann, et al.
(author)
-
mTHPC pharmacokinetics following topical administration
- 2006
-
In: Optical Diagnostics and Sensing VI. - : SPIE. - 1996-756X .- 0277-786X. ; 6094, s. 940-940
-
Conference paper (peer-reviewed)abstract
- Measurements of concentration of sensitizers for photodynamic therapy can provide important information in the dosimetry planning and can also give input to the optimal time for treatment. There has been skepticism towards fluorescence techniques for this purpose, as the signal depends on the fluorescence yield and optical properties of the tissue. Absorption based techniques, lack on the other hand, often the sensitivity required for many sensitizers with relative weak absorption in a wavelength region where hemoglobin absorption is dominant. A direct comparison between absorption and fluorescence techniques for measuring mTHPC concentration after topical application on hairless SKH-1 mice bearing skin carcinomas has been performed. 20 μl/cm2 of m-THPC thermogel (0.5 mg m-THPC/ml) were applied on normal and tumor area and the concentration of mTHPC was measured at 4 and 6 hours after drug application by two methods: 1. A fluorescence imaging system capturing images at two wavelengths (500 and 650 nm) following 405 nm excitation. Signals from different regions of interest were averaged and the intensity ratio at 650 to 500 was calculated. 2. A diffuse reflectance spectroscopy system with a fiber separation of 2 mm, providing the absorbance at 652 nm. Both systems provided consistent results related to the photosensitizer concentration. The methods show a remarkable difference in the concentration of photosensitizer in normal skin and tumor. No significant difference in mTHPC concentration in tumor could be observed between the 4 and 6h groups after drug application.
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| 35. |
- Johansson, Ann, et al.
(author)
-
Pre-treatment dosimetry for interstitial photodynamic therapy
- 2005
-
In: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 1996-756X .- 0277-786X. ; 5863:1, s. 1-58630
-
Conference paper (peer-reviewed)abstract
- A genetic algorithm for optimal placement of optical fibers in arbitrary geometries for interstitial photodynamic therapy has been developed. Based on calculated fiber positions, the diffuse light distribution is simulated by solving the diffusion equation by means of the finite element method and the treatment time is calculated. Utilizing an instrument for interstitial photodynamic therapy that is capable of both delivering the therapeutic irradiation and measuring parameters of relevance to treatment monitoring, knowledge has been gained on temporal variations of tissue light absorption, sensitizer photobleaching and tissue oxygenation status. We speculate on how variations in these three parameters can be implemented in a crude pre-treatment dosimetry model for photodynamic therapy
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| 36. |
- Johansson, Ann, et al.
(author)
-
System for integrated interstitial photodynamic therapy and dosimetric monitoring
- 2005
-
In: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5689:1, s. 130-140
-
Conference paper (peer-reviewed)abstract
- Photodynamic therapy for the treatment of cancer relies on the presence of light, sensitizer and oxygen. By monitoring these three parameters during the treatment a better understanding and treatment control could possibly be achieved. Here we present data from in vivo treatments of solid skin tumors using an instrument for interstitial photodynamic therapy with integrated dosimetric monitoring. By using intra-tumoral ALA-administration and interstitial light delivery solid tumors are targeted. The same fibers are used for measuring the fluence rate at the treatment wavelength, the sensitizer fluorescence and the local blood oxygen saturation during the treatment. The data presented is based on 10 treatments in 8 patients with thick basal cell carcinomas. The fluence rate measurements at 635 nm indicate a major treatment induced absorption increase, leading to a limited light penetration at the treatment wavelength. This leads to a far from optimal treatment since the absorption increase prevents peripheral tumor regions from being fully treated. An interactive treatment has been implemented assisting the physician in delivering the correct light dose. The absorption increase can be compensated for by either prolonging the treatment time or increasing the output power of each individual treatment fiber. The other parameters of importance, i.e. the sensitizer fluorescence at 705 nm and the local blood oxygen saturation, are monitored in order to get an estimate of the amount of photobleaching and oxygen consumption. Based on the oxygen saturation signal, a fractionized irradiation can be introduced in order to allow for a re-oxygenation of the tissue
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| 37. |
- Jonsson, P., et al.
(author)
-
Spectral detection of ultraviolet laser induced fluorescence from individual bioaerosol particles
- 2006
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 0819464961 - 9780819464965 ; 6398
-
Journal article (peer-reviewed)abstract
- We present results of a measurement system designed for detecting the fluorescence spectrum of individual aerosol particles of biological warfare agents excited with laser pulses at wavelengths around 290 or 340 nm. The biological aerosol is prepared and directed into a narrow air beam. A red laser is focused on the aerosol beam and a trigger photomultiplier tube monitor the presence of individual particles by measuring the scattered light. When a particle is present in the detection volume, a laser pulse is triggered from an ultraviolet laser and the fluorescence spectrum is acquired with a spectrometer based on a diffraction grating and a 32 channels photomultiplier tube array with single-photon sensitivity. The spectrometer measures the fluorescence spectra in the wavelength region from 300 to 800 nm. In the experiment we used different simulants of biological warfare agents. These bioaerosol particles were excited by a commercial available gas laser (337 nm), or a laser (290 nm) that we have developed based on an optical parametric oscillator with intracavity sum-frequency mixing. In the analysis of the experiments we compare the measured signals (fluorescence spectra, total fluorescence energy and the scattered energy) from the individual bioaerosol particles excited with the two different ultraviolet wavelengths.
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| 38. |
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| 39. |
- Kasai, Y., et al.
(author)
-
JEM/SMILES observation capability
- 2009
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9780819477798 ; 7474
-
Conference paper (peer-reviewed)abstract
- A new generation of sub-millimeter-wave receivers employing sensitive SIS (Superconductor-Insulator- Superconductor) detector technology will provide new opportunities for precise passive remote sensing observation of minor constituents in atmosphere. Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) was designed to be onbord the Japanese Experiment Module (JEM) on the International Space Station (ISS) as a collaboration project of National Institute of Information and Communications Technology (NICT) and Japan Aerospace Exploration Agency (JAXA). SMILES scheduled to be launch in September 11, 2009 by the H-II Transfer Vehicle (HTV). Mission Objectives are: i) Space demonstration of superconductive mixer and 4-K mechanical cooler for the submillimeter limb emission sounding, and ii) global observations of atmospheric minor constituents. JEM/SMILES will allow to observe the atmospheric species such as O3, H35Cl, H37 Cl, ClO, BrO, HOCl, HO2, and HNO3, CH3CN, and Ozone isotope species with the precisions in a few to several tens percents from upper troposphere to the mesosphere. We have estimated the observation capabilities of JEM/SMILES. This new technology may allow us to open new issues in atmospheric science.
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| 40. |
- Khrennikov, Andrei
(author)
-
Can the mathematical formalism of quantum mechanics be applied to psychology?
- 2008
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 7023:Article ID: 702308
-
Journal article (peer-reviewed)abstract
- We show that (in contrast to rather common opinion) the domain of applications of the mathematical formalism of quantum mechanics is not restricted to physics. This formalism can be applied to the description of various quantum-like (QL) information processing. In particular, the calculus of quantum (and more general QL) probabilities can be used to explain some paradoxical statistical data which was obtained in psychology and cognitive science. We consider the QL description of prisoners dilemma (PD) and so called disjunction effect (violation of Savage's sure thing principle which plays the fundamental role in modern economics).
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| 41. |
- Khrennikov, Andrei
(author)
-
Quantum averages from Gaussian random fields at the Planck length scale
- 2008
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 7023:Article ID: 702309
-
Journal article (peer-reviewed)abstract
- We show that the mathematical formalism of quantum mechanics can be interpreted as a method for approximation of classical (measure-theoretic) averages of functions f : L 2(R3) → R. These are classical physical variables in our model with hidden variables - Prequantum Classical Statistical Field Theory (PCSFT). In this paper we provide a simple stochastic picture of such a quantum approximation procedure. In the probabilistic terms this is nothing else than the approximative method for computation of averages for functions of random variables. Since in PCSFT the space of hidden variables is L 2(R3), the role of a classical random variable is played by a random field. In PCSFT we consider Gaussian random fields representing random fluctuations at the prequantum length scale. Quantum mechanical expression for the average (given by the von Neumann trace formula) is obtained through moving from the prequantum length scale to the quantum one (the scale at that we are able to perform measurements).
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| 42. |
- Kotilahti, K, et al.
(author)
-
Near-infrared spectroscopic imaging of stimulus-related hemodynamic responses on the neonatal auditory cortices.
- 2005
-
In: Optical tomography and spectroscopy of tissue VI. - : SPIE. - 1996-756X .- 0277-786X. - 9780819456670 ; 5693, s. 388-395
-
Conference paper (peer-reviewed)abstract
- We have used near-infrared spectroscopy (NIRS) to study hemodynamic auditory evoked responses on 7 full-term neonates. Measurements were done simultaneously above both auditory cortices to study the distribution of speech and music processing between hemispheres using a 16-channel frequency-domain instrument. The stimulation consisted of 5-second samples of music and speech with a 25-second silent interval. In response to stimulation, a significant increase in the concentration of oxygenated hemoglobin ([HbO2]) was detected in 6 out of 7 subjects. The strongest responses in [HbO2] were seen near the measurement location above the ear on both hemispheres. The mean latency of the maximum responses was 9.42±1.51 s. On the left hemisphere (LH), the maximum amplitude of the average [HbO2] response to the music stimuli was 0.76± 0.38 μ M (mean±std.) and to the speech stimuli 1.00± 0.45 μ± μM. On the right hemisphere (RH), the maximum amplitude of the average [HbO2] response was 1.29± 0.85 μM to the music stimuli and 1.23± 0.93 μM to the speech stimuli. The results indicate that auditory information is processed on both auditory cortices, but LH is more concentrated to process speech than music information. No significant differences in the locations and the latencies of the maximum responses relative to the stimulus type were found.
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| 43. |
- Kuzmin, Leonid, 1946
(author)
-
A Parallel/Series Array of Cold-Electron Bolometers with SIN Tunnel Junctions for Cosmology Experiments
- 2008
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9780819472304 ; 7020:3, s. 1-9
-
Conference paper (peer-reviewed)abstract
- A novel concept of the parallel/series array of Cold-Electron Bolometers (CEB) with Superconductor-Insulator-Normal (SIN) Tunnel Junctions has been proposed for matching with JFET readout. The current-biased CEBs are connected in series for DC and in parallel for HF signal. A signal is concentrated to the absorber through the capacitance of tunnel junctions and additional capacitance for coupling of superconducting islands. Due to dividing power between CEBs in the array and increasing responsivity, the noise matching could be effectively optimized and the photon Noise Equivalent Power could be easily achieved at 300 mK with a room temperature JFET readout.
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| 44. |
- Lindbergh, Tobias, et al.
(author)
-
Reduced scattering coefficient determination by non-contact oblique angle illumination: methodological considerations
- 2007
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6435, s. 64350I-1-64350I-12
-
Journal article (peer-reviewed)abstract
- The reduced scattering coefficient, µs, was determined using oblique angle illumination and imaging backscattered light intensity. The distance r between the point of light incidence (hot-spot) and the circular symmetric diffuse reflectance centre, is ~1/µ. Previously, r was obtained analyzing a 1D strip aligned with the laser beam. We improved this method by calculating a 2D intensity image with extended dynamic range by assessing camera linearity, superimposing images with multiple integration times, and compensating for lens vignetting. The hot-spot algorithm utilises several images to minimize speckle variations and account for laser beam shape. Diffuse centre position is obtained by filtering the superimposed image with decreasing thresholds using momentum analysis to determine circular symmetry. The method was evaluated on 18 optical liquid phantoms with µs[1.5, 3.0] mm-1 and µs[0.01, 0.16] mm-1. The 2D method had better linearity with µs and smaller variations due to more stable hot-spot detection, than the 1D method. The anisotropy factor g was obtained by fitting measured and Monte Carlo simulated spatially resolved intensity decays and verified with a laser Doppler flowmetry technique. With an optimal compensation for the µa dependence, the rms error in µ estimation was 2.9%.
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| 45. |
- Magesacher, Thomas, et al.
(author)
-
Measurement and modeling of short copper cables for ultra-wideband communication
- 2006
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6390, s. 39006-39006
-
Conference paper (peer-reviewed)abstract
- High-speed communication using the copper network, originally installed for telephony, is one of the dominant Internet access techniques. Several variants of a technology referred to as digital subscriber line (DSL) have been developed, standardized and installed during the last two decades. Essentially, DSL achieves high rates by exploiting wide bands of the copper cable channel. The shorter the cable, the wider the band that can be used efficiently for communication. Current DSL standards foresee the use of bands up to 30MHz. Cable properties have been studied by means of measurements, characterization and modeling up to frequencies of 30MHz. Recent investigations have shown that it is feasible both from technical and from economical point of view to exploit very short cables (up to 200m) even further and use bands above 30MHz. A prerequisite for further evaluation and the design of such ultra-wideband copper (UWBC) systems is the extension of existing cable models to higher frequencies. This paper presents wideband measurement results of insertion loss and crosstalk coupling in a 10-pair cable of various length values for frequencies up to 200MHz. We compare the results with extrapolations of cable models that are established in the 30MHz-range.
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| 46. |
- Malki, Suleyman, et al.
(author)
-
ISO/OSI compliant network-on-chip implementation for CNN applications
- 2005
-
In: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5839:1, s. 341-352
-
Conference paper (peer-reviewed)abstract
- The paper investigates the potential for a packet switching network for real-time image processing by a Cellular Neural Network (CNN) implemented on a Field-Programmable Gate-Array (FPGA). The implementation of a CNN requires several parameter restrictions with respect to the universal concept. For instance, the number representation and the cloning template are often confined to respectively 8 bits and a neighborhood of 1. It has been shown that optimal (i.e. minimal level) CNN architectures as derived from a morphological specification of the desired operation lead to arbitrarily large templates. A subsequent transformation step can turn this into a sequence of smaller templates for a specified hardware platform. The existence of a generic platform that can already handle the universal CNN architecture for prototyping and verification eliminates this need for technology-driven performance degradation. The proposed packet switcher consists of a physical layer where the CNN nodal function is performed, a data-link layer where the nodal data are maintained, a network layer with the packet receiver and sender and the actual switch as element of the transport layer. This ISO/OSI compliant level-wise structure monitors the network parameters and autonomously adjusts for the size of the neighborhood. It separates the broadcast of the network variables from the actual computation, allowing each to be executed at its own speed. The concept is tested on a re-design of the ILVA architecture and has been shown to handle arbitrary neighborhoods and precision at a comparable size and speed (1 node per BlockRAM / multiplier module @220 MHz clock)
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| 47. |
- Malki, Suleyman, et al.
(author)
-
Veins feature extraction using DT-CNNS - art. no. 65900N
- 2007
-
In: VLSI Circuits and Systems III. - : SPIE. - 1996-756X .- 0277-786X. ; 6590, s. 5900-5900
-
Conference paper (peer-reviewed)abstract
- As the identification process is based on the unique patterns of the users, biometrics technologies are expected to provide highly secure authentication systems. The existing systems using fingerprints or retina patterns are, however, very vulnerable. One's fingerprints are accessible as soon as the person touches a surface, while a high resolution camera easily captures the retina pattern. Thus, both patterns can easily be "stolen" and forged. Beside, technical considerations decrease the usability for these methods. Due to the direct contact with the finger, the sensor gets dirty, which decreases the authentication success ratio. Aligning the eye with a camera to capture the retina pattern gives uncomfortable feeling. On the other hand, vein patterns of either a palm of the hand or a single finger offer stable, unique and repeatable biometrics features. A fingerprint-based identification system using Cellular Neural Networks has already been proposed by Gao. His system covers all stages of a typical fingerprint verification procedure from Image Preprocessing to Feature Matching. This paper performs a critical review of the individual algorithmic steps. Notably, the operation of False Feature Elimination is applied only once instead of 3 times. Furthermore, the number of iterations is limited to I for all used templates. Hence, the computational need of the feedback contribution is removed. Consequently the computational effort is drastically reduced without a notable chance in quality. This allows a full integration of the detection mechanism. The system is prototyped on a Xilinx Virtex II Pro P30 FPGA.
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| 48. |
- Nyström, Marcus, et al.
(author)
-
Variable resolution images and their effects on eye-movements during free-viewing
- 2007
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6492, s. 49216-49216
-
Conference paper (peer-reviewed)abstract
- Earlier studies have shown that while free-viewing images people tend to gaze at regions with a high local density of bottom up features such as contrast and edge density. In particular, this tendency seems to be more emphasized during the first few fixations after image onset. In this paper, we present a new method to investigate how gaze locations are chosen by introducing varying image resolution, and measure how it affects eye-movement behavior during free viewing. Results show that gaze density overall is shifted toward regions presented in high resolution over those degraded in resolution. However, certain image regions seem to attract early fixations regardless of display resolution. These results suggest that top-down control of gaze guidance may be the dominant factor early in visual processing. © 2007 SPIE-IS and T.
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| 49. |
- Owner-Petersen, Mette
(author)
-
Effects of atmospheric dispersion on the PSF background level
- 2006
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 1996-756X .- 0277-786X. ; 6272 II, s. 839-846
-
Conference paper (peer-reviewed)abstract
- Atmospheric dispersion represents a relatively overlooked problem in connection with the ultimate quality of ELT images corrected by adaptive optics (AO). The aim of this paper is to evaluate the contribution from atmospheric dispersion to the background level of the point-spread function (PSF). Since proper suppression of this level is important for the prospects for direct exo-planet observation, it is necessary to quantify the contributions from all possible sources to it. Atmospheric dispersion will in principle result in three different kinds of contributions. The first one is related to the fact that two rays of different color following the same path through the atmosphere to the telescope do not have the same optical path-length difference (OPD). The second one is related to the fact that two coinciding rays of different color entering the atmosphere at a non zero zenith angle will be separated due to refraction before they reach the telescope. The third one is related to the fact that rays are diffracted by inhomogeneities in the atmosphere and that the diffraction angle is dependent on color. This last effect is small[2] and will not be treated here. As a consequence of dispersion phase fluctuations can, in principle, only be compensated at a single wavelength by AO systems with deformable mirrors (DMs). Hence looking for an exo-planet in a certain spectral bandwidth there will be a contribution from the parent star uncorrected background level. Hence it will be crucial to perform observations in a narrow spectral bandwidth and to ensure that the wavefront measurements used for AO correction are performed within the same narrow bandwidth. The last point affects the needed magnitude of the parent star, which is used for wavefront measurements.
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| 50. |
- Owner-Petersen, Mette, et al.
(author)
-
Polychromatic AO: Wavefront sensing and observing at different wavelengths
- 2008
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In: Extremely Large Telescopes: Which Wavelengths? Retirement Symposium for Arne Ardeberg. - : SPIE. - 1996-756X .- 0277-786X. ; 6986, s. 9860-9860
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Conference paper (peer-reviewed)abstract
- When performing adaptive optics (AO) correction for the effect of atmospheric fluctuations, different effects, related to measuring the wavefront at one wavelength and observing at another one, may show up. Some of these effects are related to the dispersive properties of the atmosphere. Others are related to diffraction, both regarding light propagation through the turbulent atmosphere to the entrance pupil of the telescope and regarding the inevitable Fraunhofer diffraction taking place for light propagating from the exit pupil to the image plane of the telescope. In this paper some of these effects are revised and discussed, in particular the way in which uncorrected wavefront errors in the point spread function (PSF) will scale with color, and the way in which dispersion affects the Strehl ratio and the background level of the AO corrected PSF. Also discussed is the trade-off between AO spectral bandwidth and Poisson noise.
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