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  • Xu, Tianhua, et al. (författare)
  • Phase noise mitigation in coherent transmission system using a pilot carrier
  • 2011
  • Ingår i: Optical Transmission Systems, Subsystems, and Technologies IX. - SPIE - International Society for Optical Engineering. - 9780819489579
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we investigate the phase noise elimination employing an optical pilot carrier in the high speed coherent transmission system considering the equalization enhanced phase noise (EEPN). The numerical simulations are performed in a 28-Gsymbol/s quadrature phase shift keying (QPSK) coherent system with a polarization multiplexed pilot carrier. The carrier phase estimation is implemented by the one-tap normalized least mean square (NLMS) filter and the differential phase detection, respectively. Simulation results demonstrate that the application of the optical pilot carrier is very effective for the intrinsic laser phase noise cancellation, while is less efficient for the EEPN mitigation.
  • Ahmad, Naeem, et al. (författare)
  • Cost Optimization of a Sky Surveillance Visual Sensor Network
  • 2012
  • Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - Belgium : SPIE - International Society for Optical Engineering. - 978-0-8194-9129-9 ; s. Art. no. 84370U
  • Konferensbidrag (refereegranskat)abstract
    • A Visual Sensor Network (VSN) is a network of spatially distributed cameras. The primary difference between VSN and other type of sensor network is the nature and volume of information. A VSN generally consists of cameras, communication, storage and central computer, where image data from multiple cameras is processed and fused. In this paper, we use optimization techniques to reduce the cost as derived by a model of a VSN to track large birds, such as Golden Eagle, in the sky. The core idea is to divide a given monitoring range of altitudes into a number of sub-ranges of altitudes. The sub-ranges of altitudes are monitored by individual VSNs, VSN1 monitors lower range, VSN2 monitors next higher and so on, such that a minimum cost is used to monitor a given area. The VSNs may use similar or different types of cameras but different optical components, thus, forming a heterogeneous network.  We have calculated the cost required to cover a given area by considering an altitudes range as single element and also by dividing it into sub-ranges. To cover a given area with given altitudes range, with a single VSN requires 694 camera nodes in comparison to dividing this range into sub-ranges of altitudes, which requires only 96 nodes, which is 86% reduction in the cost.
  • Anders, Åström, et al. (författare)
  • A High Speed 2D Time-to-Impact Algorithm Targeted for Smart Image Sensors
  • 2014
  • Ingår i: Proc. SPIE 9022, Image Sensors and Imaging Systems 2014. - International Society for Optical Engineering; 1999.
  • Konferensbidrag (refereegranskat)abstract
    • In this paper we present a 2D extension of a previously described 1D method for a time-to-impact sensor [5][6]. As in the earlier paper, the approach is based on measuring time instead of the apparent motion of points in the image plane to obtain data similar to the optical flow. The specific properties of the motion field in the time-to-impact application are used, such as using simple feature points which are tracked from frame to frame. Compared to the 1D case, the features will be proportionally fewer which will affect the quality of the estimation. We give a proposal on how to solve this problem. Results obtained are as promising as those obtained from the 1D sensor.
  • Anderson, Sterling J., et al. (författare)
  • Constraint-based semi-autonomy for unmanned ground vehicles using local sensing
  • 2012
  • Ingår i: UNMANNED SYSTEMS TECHNOLOGY XIV. - Bellingham, WA : SPIE - International Society for Optical Engineering. - 978-0-8194-9065-0 ; s. Article no. 83870K
  • Konferensbidrag (refereegranskat)abstract
    • Teleoperated vehicles are playing an increasingly important role in a variety of military functions. While advantageous in many respects over their manned counterparts, these vehicles also pose unique challenges when it comes to safely avoiding obstacles. Not only must operators cope with difficulties inherent to the manned driving task, but they must also perform many of the same functions with a restricted field of view, limited depth perception, potentially disorienting camera viewpoints, and significant time delays. In this work, a constraint-based method for enhancing operator performance by seamlessly coordinating human and controller commands is presented. This method uses onboard LIDAR sensing to identify environmental hazards, designs a collision-free path homotopy traversing that environment, and coordinates the control commands of a driver and an onboard controller to ensure that the vehicle trajectory remains within a safe homotopy. This system's performance is demonstrated via off-road teleoperation of a Kawasaki Mule in an open field among obstacles. In these tests, the system safely avoids collisions and maintains vehicle stability even in the presence of "routine" operator error, loss of operator attention, and complete loss of communications.
  • Andler, Sten F, et al. (författare)
  • SMARTracIn : a concept for spoof resistant tracking of vessels and detection of adverse intentions
  • 2009
  • Ingår i: Sensors, and Command, Control, Communications, and Intelligence (C3I) Technologies for Homeland Security and Homeland Defense VIII. - SPIE - International Society for Optical Engineering. - 9780819475718 ; s. 73050G-1-73050G-9
  • Konferensbidrag (refereegranskat)abstract
    • The aim of maritime surveillance systems is to detect threats earlyenough to take appropriate actions. We present the results ofa study on maritime domain awareness performed during the fallof 2008. We analyze an identified capability gap of worldwidesurveillance in the maritime domain, and report from a userworkshop addressing the identified gap. We describe a SMARTracIn conceptsystem that integrates information from surveillance systems with background knowledgeon normal conditions to help users detect and visualize anomaliesin vessel traffic. Land-based systems that cover the coastal watersas well as airborne, space-borne and ships covering open seaare considered. Sensor data are combined with intelligence information fromship reporting systems and databases. We describe how information fusion,anomaly detection and semantic technology can be used to helpusers achieve more detailed maritime domain awareness. Human operators area vital part of this system and should be activecomponents in the fusion process. We focus on the problemof detecting anomalous behavior in ocean-going traffic, and a roomand door segmentation concept to achieve this. This requires theability to identify vessels that enter into areas covered bysensors as well as the use of information management systemsthat allow us to quickly find all relevant information.
  • Berrier, Audrey, et al. (författare)
  • Impact of dry-etching induced damage in InP-based photonic crystals
  • 2008
  • Konferensbidrag (refereegranskat)abstract
    • In this work variations of the carrier lifetime in a GaInAsP/InP quantum well in two-dimensional PhC structures etched by Ar/Cl-2 chemically assisted ion beam etching as a function of the processing parameters is investigated. It is shown that the deposition conditions of the SiO2 mask material and its coverage as well as other process steps such as annealing affect the carrier lifetimes. However the impact of patterning the semiconductor on the carrier lifetime is dominant, showing over an order of magnitude reduction. For given PhC lattice parameters, the sidewall damage is shown to be directly related to the measured carrier lifetimes. A simple qualitative model based on sputtering theory and assuming a conical hole-shape development during etching is used to explain the experimental results.
  • Bianco, L., et al. (författare)
  • The AGIPD System for the European XFEL
  • 2013
  • Ingår i: ADVANCES IN X-RAY FREE-ELECTRON LASERS II : INSTRUMENTATION. - 978-0-8194-9580-8 ; s. Art. no. UNSP 87780V
  • Konferensbidrag (refereegranskat)abstract
    • The European XFEL will generate extremely brilliant pulses of X-rays organized in pulse trains consisting of 2700 pulses <100 fs long, with >10(12) photons, and with a 220 ns spacing. The pulse trains are running at a 10Hz repetition rate. The detector to be used under these conditions will have to face several challenges: the dynamic range has to cover the detection of single photons and extend up to >10(4) photons/pixel/pulse in the same image, framing rates of 4.5 MHz (220 ns) are required in order to record one image per pulse, and as many images as possible have to be recorded during the pulse trains. Due to the high flux, the detector will have to withstand a dose up to 1GGy integrated over 3 years. To meet these challenges a consortium, consisting of Deutsches Elektronensynchrotron (DESY), Paul-Scherrer-Institut (PSI), University of Hamburg and University of Bonn, is developing the Adaptive Gain Integrating Pixel Detector (AGIPD). It is a hybrid-pixel detector, featuring a charge integrating amplifier with dynamic gain switching to cope with the extended dynamic range, and an analogue on-pixel memory for image storage at the required 4.5 MHz frame rate. The readout chip consists of 64x64 pixels of (200 mu m)(2), 8x2 of these readout chips are bump-bonded to a monolithic silicon sensor to form the basic module with 512 x 128 pixels. 4 of these modules are stacked to form a quadrant of the 1k x 1k detector system. Each quadrant is independently moveable in order to adjust a central hole, needed for the direct beam to pass through. Special designs are employed for both the sensor and the readout chip to withstand the integrated dose for 3 years.
  • Björk, Gunnar, et al. (författare)
  • Schrödinger-cat states : size classification based on evolution or dissipation
  • 2004
  • Ingår i: Proceedings of SPIE - The International Society for Optical Engineering : Vol. 5468. - 0-8194-5391-9 ; s. 335-343
  • Konferensbidrag (refereegranskat)abstract
    • The issue of estimating how "macroscopic" a superposition state is, can be addressed by analysing the rapidity of the state's evolution under a preferred observable, compared to that of the states forming the superposition. This fast evolution. which arises from the larger dispersion of the superposition state for the preferred operator, also represents a useful characteristic for interferometric applications. This approach can be compared to others in which a superposition's macroscopality is estimated in terms of the fragility to dissipation.
  • Bornefalk, Hans (författare)
  • Use of phase and certainty information in automatic detection of stellate patterns in mammograms : IMAGE PROCESSING, PTS 1-3
  • 2004
  • Konferensbidrag (refereegranskat)abstract
    • Detection of stellate patterns is a very important step in computer-aided detection schemes designed for mammography. We introduce a new way of finding these regions based on the use of quadrature filters. The method allows extraction of a certainty measure for each orientation estimate. This makes the method of finding the areas the spicules seem to emanate from more robust than simply basing it on the orientation estimates themselves. The local phase extracted from the filter outputs allows us to discriminate between orientation estimates from edges and dark lines from those generated by bright line structures, i.e. spicules. This makes the method more specific. We also show how the method can be modified for finding non-spiculated masses in digitized mammograms.
  • Brunnström, Kjell, et al. (författare)
  • Simulator Sickness analysis of 3D video viewing on passive 3D TV
  • 2013
  • Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - 978-0-8194-9421-4 ; s. Art. no. 864802
  • Konferensbidrag (refereegranskat)abstract
    • The MPEG 3DV project is working on the next generation video encoding standard and in this process a call for proposal of encoding algorithms was issued. To evaluate these algorithm a large scale subjective test was performed involving Laboratories all over the world. For the participating Labs it was optional to administer a slightly modified Simulator Sickness Questionnaire (SSQ) from Kennedy et al (1993) before and after the test. Here we report the results from one Lab (Acreo) located in Sweden. The videos were shown on a 46 inch film pattern retarder 3D TV, where the viewers were using polarized passive eye-glasses to view the stereoscopic 3D video content. There were 68 viewers participating in this investigation in ages ranges from 16 to 72, with one third females. The questionnaire was filled in before and after the test, with a viewing time ranging between 30 min to about one and half hour, which is comparable to a feature length movie. The SSQ consists of 16 different symptoms that have been identified as important for indicating simulator sickness. When analyzing the individual symptoms it was found that Fatigue, Eye-strain, Difficulty Focusing and Difficulty Concentrating were significantly worse after than before. SSQ was also analyzed according to the model suggested by Kennedy et al (1993). All in all this investigation shows a statistically significant increase in symptoms after viewing 3D video especially related to visual or Oculomotor system.
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