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  • 51.
    Kohei, Toko
    et al.
    Chuo University, Japan.
    Chao, Jinhui
    Chuo University, Japan.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    On Curvature of Color Spaces and Its Implications2010In: CGIV 2010/MCS'10 5th European Conference on Colour in Graphics, Imaging, and Vision and 12th International Symposium on Multispectral Colour Science / [ed] Jussi Parkkinen, Timo Jääskeläinen, Theo Gevers, Alain Trémeau, Springfield, VA, USA: The Society for Imaging Science and Technology, 2010, p. 393-398Conference paper (Refereed)
    Abstract [en]

    In this paper we discuss the role of curvature in the context of color spaces. Curvature is a differential geometric property of color spaces that has attracted less attention than other properties like the metric or geodesics. In this paper we argue that the curvature of a color space is important since curvature properties are essential in the construction of color coordinate systems. Only color spaces with negative or zero curvature everywhere allow the construction of Munsell-like coordinates with geodesics, shortest paths between two colors, that never intersect. In differential geometry such coordinate systems are known as Riemann coordinates and they are generalizations of the well-known polar coordinates. We investigate the properties of two measurement sets of just-noticeable-difference (jnd) ellipses and color coordinate systems constructed from them. We illustrate the role of curvature by investigating Riemann normal coordinates in CIELUV and CIELAB spaces. An algorithsm is also shown to build multipatch Riemann coordinates for spaces with the positive curvature.

  • 52.
    Korolija, Natascha
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Lundberg, Jonas
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Speaking of human factors: Emergent meanings in interviews with professional accident investigators2010In: Safety Science, ISSN 0925-7535, E-ISSN 1879-1042, Vol. 48, no 2, p. 157-165Article in journal (Refereed)
    Abstract [en]

    This paper presents a qualitative analysis of the human factor concept, more specifically what it means and includes in everyday professional discourse. It is founded on 10 extensive interviews with professional investigators within the road, maritime and rail administration concerning their practical investigative work. General and specific results are generated of interview contributions using a pragmatic communicative approach and discourse analysis.

    Results show that human factors is an expression tied to individual professional experience, sparks dissatisfaction and demands specification due to recurring indexicality problems. It tends to be used for negative matters. The specific results, listing eight different meanings, indicate that there is no such thing as a professional usage of the human factor but a spectrum of meanings. The study concludes that the meanings of the human factor (a) always evolve in the dynamic process of producing and understanding language, (b) are context-dependent, and (c) emerge through talk, as one type of discourse. Contrary to ordinary conceptions, there is no simple matter as a human factor that may be used in a routine manner. A non-specific use of the notion may even obscure a course of events and prevent necessary investigation, for example, if the human factor simply replaces a factor such as ‘fatigue’. Although contemporary interdisciplinary research focuses peripheral factors, the idea of individual humans and their erroneous acts has survived – and lives – in the practical world of professional investigators. Empirically deduced meanings need to be continuously highlighted and problematised if theory is to approach everyday professional practice.

  • 53.
    Kruse, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Simulation Experiments in Turbid Media - The Effect of In-homogeneous Layers2008In: TAGA 2008 proceedings, Sewickley PA, USA: TAGA - Technical Association of the Graphic Arts , 2008, p. 10-26Conference paper (Other academic)
    Abstract [en]

    The optical property of the substrate governs the reproduction characteristics and quality of printed paper. Paper is a very complex substrate that is designed for different application areas. In the simplest case it is a one-layer structure of fibers. In more complex structures the substrate may be build from several layers with different properties. In both situations it is vital to be able to control the manufacturing in order to achieve the desired product. This paper deals with simulation of differently composed structures that is difficult to accomplish in complex cases that goes beyond the Kubelka-Munk original theory. The paper describes qualitative results concerning the reproduction due to inhomogeneities in the layers themselves and the layer structures. More specifically we will study two simple structures, a one-layer substrate with inclusions ( for example recycled paper) and a two-layer substrate in which the coating layer thickness varies. In the second example the optical properties for the coating layer are supposed to be different from the base. The qualitative results show the degradations that can be expected due to inhomogeneities. The simulations will also allow for computation of the tone value increase in the simulated instances.

  • 54.
    Latorre Carmona, Pedro
    et al.
    Depto. Lenguajes y Sistemas Informáticos, Universidad Jaume I, Campus del Riu Sec s/n, Castellón de la Plana, Spain.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Pla, Filiberto
    Depto. Lenguajes y Sistemas Informáticos, Universidad Jaume I, Campus del Riu Sec s/n, Castellón de la Plana, Spain.
    Sotoca, Jose M.
    Depto. Lenguajes y Sistemas Informáticos, Universidad Jaume I, Campus del Riu Sec s/n, Castellón de la Plana, Spain.
    Affine Illumination Compensation for Multispectral Images2007In: Image Analysis: 15th Scandinavian Conference, SCIA 2007, Aalborg, Denmark, June 10-14, 2007 / [ed] Bjarne Kjær Ersbøll, Kim Steenstrup Pedersen, Springer Berlin/Heidelberg, 2007, p. 522-531Conference paper (Refereed)
    Abstract [en]

    We apply a general form of affine transformation model to compensate illumination variations in a series of multispectral images of a static scene and compare it to a particular affine and a diagonal transformation models. These models operate in the original multispectral space or in a lower-dimensional space obtained by Singular Value Decomposition (SVD) of the set of images. We use a system consisting of a multispectral camera and a light dome that allows the measurement of multispectral data under carefully controlled illumination conditions to generate a series of multispectral images of a static scene under varying illumination conditions. We evaluate the compensation performance using the CIELAB colour difference between images. The experiments show that the first 2 models perform satisfactorily in the original and lower dimensional spaces.

  • 55.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Crystal Vision-Applications of Point Groups in Computer Vision2007In: Computer Vision – ACCV 2007: 8th Asian Conference on Computer Vision, Tokyo, Japan, November 18-22, 2007, Proceedings, Part II / [ed] Yasushi Yagi, Sing Bing Kang, In So Kweon, Hongbin Zha, Springer Berlin/Heidelberg, 2007, p. 744-753Conference paper (Refereed)
    Abstract [en]

    Methods from the representation theory of finite groups are used to construct efficient processing methods for the special geometries related to the finite subgroups of the rotation group. We motivate the use of these subgroups in computer vision, summarize the necessary facts from the representation theory and develop the basics of Fourier theory for these geometries. We illustrate its usage for data compression in applications where the processes are (on average) symmetrical with respect to these groups. We use the icosahedral group as an example since it is the largest finite subgroup of the 3D rotation group. Other subgroups with fewer group elements can be studied in exactly the same way.

  • 56.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Estimation of illumination characteristics2001In: IEEE Transactions on Image Processing, ISSN 1057-7149, E-ISSN 1941-0042, Vol. 10, no 7, p. 1031-1038Article in journal (Refereed)
    Abstract [en]

    The description of the relation between the one-parameter subgroups of a group and the differential operators in the Lie-algebra of the group is one of the major topics in Lie-theory. In this paper, we use this framework to derive a partial differential equation which describes the relation between the time-change of the spectral characteristics of the illumination source and the change of the color pixels in an image. In the first part of the paper, we introduce and justify the usage of conical coordinate systems in color space. In the second part we derive the differential equation describing the illumination change and in the last part we illustrate the algorithm with some simulation examples.

  • 57.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Lie Methods for Color Robot Vision2008In: Robotica (Cambridge. Print), ISSN 0263-5747, E-ISSN 1469-8668, Vol. 26, no 04, p. 453-464Article in journal (Refereed)
    Abstract [en]

    We describe how Lie-theoretical methods can be used to analyze color related problems in machine vision. The basic observation is that the non-negative nature of spectral color signals restricts these unctions to be members of a limited, conical section of the larger Hilbert space of square-integrable functions. From this observation we conclude that the space of color signals can be equipped with a coordinate system consisting of a half-axis and a unit ball with the Lorentz groups as natural trans-formation group. We introduce the theory of the Lorentz group SU(1; 1) as a natural tool for analyzing color image processing problems and derive some descriptions and algorithms that are useful in the investigation of dynamical color changes. We illustrate the usage of these results by describing how to use compress, interpolate, extrapolate and compensate image sequences generated by dynamical color changes.

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  • 58.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Octahedral Filters for 3D Image Processing2009In: Proceedings SSBA 2009, 2009, p. 109-112Conference paper (Other academic)
  • 59.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Spectral Color Spaces: Their Structure and Transformations2005In: Advances in imaging and electron physics / [ed] P.W. Hawkes, Amsterdam: Elsevier , 2005, p. -333Chapter in book (Other academic)
    Abstract [en]

    "Advances in Imaging and Electron Physics" merges two long-running serials-"Advances in Electronics and Electron Physics" and "Advances in Optical and Electron Microscopy". This series features extended articles on the physics of electron devices (especially semiconductor devices), particle optics at high and low energies, microlithography, image science and digital image processing, electromagnetic wave propagation, electron microscopy, and the computing methods used in all these domains.

  • 60.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Spectral color spaces: Their structure and transformations2005In: Advances in Imaging and Electron Physics, ISSN 1076-5670, Vol. 138Article in journal (Refereed)
    Abstract [en]

    The structure and transformations of spectral color spaces are described. The approach applied for the spectral color spaces is data driven in the sense that the properties of the illumination sources and the reflectance properties of objects are of primary interest. Mainly three types of objects are considered in this approach including illumination spectra, reflectance spectra, and sensor sensitivity functions. It is found that under low-intensity illumination, a different definition has to be used. In the new coordinate system, one finds a good similarity between the Euclidean distance between two CIELAB vectors and the perceptual color difference between the corresponding colors for an average human observer.

  • 61.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media.
    Structures in Spaces of RGB Histograms2008Conference paper (Refereed)
    Abstract [en]

    We introduce the theory of group representations as a tool to investigate the structure of spaces related to RGB vectors. Our basic assumption is that for many sources of RGB vectors we can assume that the three channels R, G and B are interchangeable. This means that vectors (RGB) and their permutations such as (GRB) appear approximately with the same probability. We introduce the wide-sense-stationary processes as processes whose matrix of second-order moments commute with the permutations of the channels. For such processes the theory of group representations provides the tools to construct a coordinate transformation that block-diagonalizes the corresponding matrices of second-order moments. This coordinate transformation defines therefore a partial principal component analysis. We implemented the transform and investigated its properties with the help of two large databases together containing over one million images. We also introduce a new parametrization of the coefficient space and show that this parametrization can be used to provide information about the internal structure of the RGB histogram space. We also sketch a generalization taking into account the effect of the reducing the number of bins used.

  • 62.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Time-frequency analysis of color spectra2004In: 2nd European Conference on Color in Graphics, Imaging and Vision,2004, Springfield, VA, USA: IST: The Society for Imaging Science and Technology , 2004, p. 499-Conference paper (Refereed)
  • 63.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Two stage principal component analysis of color2002In: IEEE Transactions on Image Processing, ISSN 1057-7149, E-ISSN 1941-0042, Vol. 11, no 6, p. 630-635Article in journal (Refereed)
    Abstract [en]

    We introduce a two-stage analysis of color spectra. In the first processing stage, correlation with the first eigenvector of a spectral database is used to measure the intensity of a color spectrum. In the second step, a perspective projection is used to map the color spectrum to the hyperspace of spectra with first eigenvector coefficient equal to unity. The location in this hyperspace describes the chromaticity of the color spectrum. In this new projection space, a second basis of eigenvectors is computed and the projected spectrum is described by the expansion in this chromaticity basis. This description is possible since the space of color spectra as conical. We compare this two-stage process with traditional principal component analysis and find that the results of the new structure are closer to the structure of traditional chromaticity descriptors than traditional principal component analysis.

  • 64.
    Lenz, Reiner
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Bui, Hai Thanh
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Recognition of non-negative patterns2004In: 17th International Conference on Pattern Recognition,2004, Surrey, UK: University of Surrey Press , 2004, p. 498-Conference paper (Refereed)
  • 65.
    Lenz, Reiner
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Bui, Hai Thanh
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Statistical properties of color-signal spaces2005In: Journal of the Optical Society of America A: Optics and Image Science, and Vision, ISSN 1084-7529, Vol. 22, no 5, p. 820-827Article in journal (Refereed)
    Abstract [en]

    In applications of principal component analysis (PCA) it has often been observed that the eigenvector with the largest eigenvalue has only nonnegative entries when the vectors of the underlying stochastic process have only nonnegative values. This has been used to show that the coordinate vectors in PCA are all located in a cone. We prove that the nonnegativity of the first eigenvector follows from the Perron-Frobenius (and Krein-Rutman theory). Experiments show also that for stochastic processes with nonnegative signals the mean vector is often very similar to the first eigenvector. This is not true in general, but we first give a heuristical explanation why we can expect such a similarity. We then derive a connection between the dominance of the first eigenvalue and the similarity between the mean and the first eigenvector and show how to check the relative size of the first eigenvalue without actually computing it. In the last part of the paper we discuss the implication of theoretical results for multispectral color processing. © 2005 Optical Society of America.

  • 66.
    Lenz, Reiner
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Bui, Hai Thanh
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Hernandez-Andres, Javier
    Department of Optics University of Granada.
    Group theoretical structure of spectral spaces2005In: Journal of Mathematical Imaging and Vision, ISSN 0924-9907, E-ISSN 1573-7683, Vol. 23, no 3, p. 297-313Article in journal (Refereed)
    Abstract [en]

    It is known that for every selection of illumination spectra there is a coordinate system such that all coordinate vectors of these illumination spectra are located in a cone. A natural set of transformations of this cone are the Lorentz transformations. In this paper we investigate if sequences of illumination spectra can be described by one-parameter subgroups of Lorentz-transformations. We present two methods to estimate the parameters of such a curve from a set of coordinate points. We also use an optimization technique to approximate a given set of points by a one-parameter curve with a minimum approximation error. In the experimental part of the paper we investigate series of blackbody radiators and sequences of measured daylight spectra and show that one-parameter curves provide good approximations for large sequences of illumination spectra. © 2005 Springer Science + Business Media, Inc.

  • 67.
    Lenz, Reiner
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Bui, Hai Thanh
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Takase, Koichi
    Graduate School of Science and Technology Chiba University.
    A group theoretical toolbox for color image operators2005In: International Conference on Image Processing,2005, Piscataway, NJ: IEEE Image Processing Society , 2005, p. 557-Conference paper (Refereed)
  • 68.
    Lenz, Reiner
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Bui, T.H.
    Hernande-Andres, J.
    Hernánde-Andrés, J., Department of Optics, Sciences Faculty, University of Granada, 18071 Granada, Spain.
    One-parameter subgroups and the chromaticity properties of time-changing illumination spectra2003Conference paper (Other academic)
    Abstract [en]

    Understanding the properties of time-varying illumination spectra is of importance in all applications where dynamical color changes due to changes in illumination characteristics have to be analyzed or synthesized. Examples are (dynamical) color constancy and the creation of realistic animations. In this article we show how group theoretical methods can be used to describe sequences of time changing illumination spectra with only few parameters. From the description we can also derive a differential equation that describes the illumination changes. We illustrate the method with investigations of black-body radiation and measured sequences of daylight spectra.

  • 69.
    Lenz, Reiner
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Granlund, Gösta
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    If I had a fisheye I would not need SO(1,n) or, Is hyperbolic geometry useful in image processing?1998In: Proceedings from the SSAB Symposium on Image Analysis, 1998Conference paper (Refereed)
  • 70.
    Lenz, Reiner
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Hernandez-Andres, Javier
    University of Granada.
    Time-frequency analysis for multi-channel color pattern recognition2004In: 2nd European Conference on Color in Graphics, Imaging and Vision,2004, Springfield, VA, USA: IST: The Society for Imaging Science and Technology , 2004, p. 509-Conference paper (Refereed)
  • 71.
    Lenz, Reiner
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Latorre Carmona, Pedro
    Departamento de Lenguajes y Sistemas Informaticos.
    Octahedral Transforms for 3-D Image Processing2009In: IEEE Transactions on Image Processing, ISSN 1057-7149, E-ISSN 1941-0042, Vol. 18, no 12, p. 2618-2628Article in journal (Refereed)
    Abstract [en]

    The octahedral group is one of the finite subgroups of the rotation group in 3-D Euclidean space and a symmetry group of the cubic grid. Compression and filtering of 3-D volumes are given as application examples of its representation theory. We give an overview over the finite subgroups of the 3-D rotation group and their classification. We summarize properties of the octahedral group and basic results from its representation theory. Wide-sense stationary processes are processes with group theoretical symmetries whose principal components are closely related to the representation theory of their symmetry group. Linear filter systems are defined as projection operators and symmetry-based filter systems are generalizations of the Fourier transforms. The algorithms are implemented in Maple/Matlab functions and worksheets. In the experimental part, we use two publicly available MRI volumes. It is shown that the assumption of wide-sense stationarity is realistic and the true principal components of the correlation matrix are very well approximated by the group theoretically predicted structure. We illustrate the nature of the different types of filter systems, their invariance and transformation properties. Finally, we show how thresholding in the transform domain can be used in 3-D signal processing.

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  • 72.
    Lenz, Reiner
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Latorre Carmona, Pedro
    Universidad Jaume I, Castellon de la Plana, Spain.
    Transform Coding of RGB-Histograms2009In: VISAPP 2009 - Proceedings of the Fourth International Conference on Computer Vision Theory and Applications, Setúbal: Institute for Systems and Technologies of Information, Control and Communication , 2009, , p. 117-124p. 117-124Conference paper (Refereed)
    Abstract [en]

    In this paper we introduce the representation theory of the symmetric group S(3) as a tool to investigate thestructure of the space of RGB-histograms. We show that the theory reveals that typical histogram spaces arehighly structured and that these structures originate partly in group theoretically defined symmetries. Thealgorithms exploit this structure and constructs a PCA like decomposition without the need to construct correlationor covariance matrices and their eigenvectors. We implemented these algorithms and investigate theirproperties with the help of two real-world databases (one from an image provider and one from a image searchengine company) containing over one million images.

  • 73.
    Lenz, Reiner
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Latorre Carmona, Pedro
    Comp. Languages and Systems, Ja ume I University, Castell ́ on, Spain.
    Meer, Peter
    Electrical and Computer Eng., Rut gers University, Piscataway, USA.
    The Hyperbolic Geometry of Illumination-Induced Chromaticity Changes2007In: IEEE Conference on Computer Vision and Pattern Recognition, CVPR '07., IEEE Computer Society, 2007, p. 1-6Conference paper (Refereed)
    Abstract [en]

    The non-negativity of color signals implies that they span a conical space with a hyperbolic geometry. We use perspective projections to separate intensity from chromaticity, and for 3-D color descriptors the chromatic properties are represented by points on the unit disk. Descriptors derived from the same object point but under different imaging conditions can be joined by a hyperbolic geodesic. The properties of this model are investigated using multichannel images of natural scenes and black body illuminants of different temperatures. We show, over a series of static scenes with different illuminants, how illumination changes influence the hyperbolic distances and the geodesics. Descriptors derived from conventional RGB images are also addressed.

  • 74.
    Lenz, Reiner
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Oshima, Satoshi
    Chuo-University Tokyo Japan.
    Mochizuki, Rika
    Chuo-University Tokyo Japan.
    Chao, Jinhui
    Chuo-University Tokyo Japan.
    An Invariant Metric on the Manifold of Second Order Moments2009In: IEEE Color and Reflectance in Imaging and Computer Vision Workshop 2009 - CRICV 2009, IEEE-Computer Society , 2009, p. 1923-1930Conference paper (Refereed)
    Abstract [en]

    We introduce an invariant metric in the space of symmetric,positive definite matrices and illustrate the usage of thisspace together with this metric in color processing. For thismetric closed-form expressions for the distances and thegeodesics, (ie. the straight lines in this metric) are availableand we show how to implement them in the case of matricesof size 2x2. In the first illustration we use the framework toinvestigate an interpolation problem related to the ellipsesobtained in the measurements of just-noticeable-distances.For two such ellipses we use the metric to construct an interpolatingsequence of ellipses between them. In the secondapplication construct a texture descriptor for chromaticitydistributions. We describe the probability distributions ofchromaticity vectors by their matrices of second order moments.The distance between these matrices is independentunder linear changes of the coordinate system in the chromaticityspace and can therefore be used to define a distancebetween probability distributions that is independentof the coordinate system used. We illustrate this invariance,by way of an example, in the case of different white pointcorrections.

  • 75.
    Lenz, Reiner
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    Solli, Martin
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    Lie Methods in Color Signal Processing: Illumination Effects2006In: 18th International Conference on Pattern Recognition (ICPR'06), Los Alamitos, CA, USA: IEEEPress , 2006, , p. 738-741p. 738-741Conference paper (Refereed)
    Abstract [en]

    In this paper we describe illumination changes with the help of elements in the Lorentz group SU(1,1). We show how Lie-theoretical methods can be applied to solve problems related to illumination changes. We derive partial differential equations that describe the changes in the space of color signals. We show how these changes effect the induced variations in the space of RGB vectors. We illustrate the application of these methods with two examples: In the first example we derive a simple linear equation system that links the pointwise pixel changes to the parameters of the illumination change. In the second example we construct operators in the RGB space that either compensate illumination changes or predict the effects of illumination changes.

  • 76.
    Lindstrand, Mikael
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology. GonioLabs, Åkroken Science Park, Sundsvall Sweden.
    Forensic DOVID reader, bridging 1st, 2nd and 3rd line inspection2010In: Optical Document Security II: Conference on Optical Security and Counterfeit Deterrence 2010, Reconnaissance International , 2010, p. 347-356Conference paper (Refereed)
    Abstract [en]

    GonioLabs’ DOVID Reader (GDR) provides a spatially resolved trichromatic goniophotometric characterization. The present work discusses how the GDR quantifies optical features and differences between them (defects), as appreciated by perceptual evaluation. GDR advantages are a) evaluating different DOVID suppliers, b) gaining more detailed understanding of deterioration due to circulation, c) forensic evaluation of different groups of counterfeits potentially originating from the same production equipment

  • 77.
    Lindstrand, Mikael
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology. Skogsindustrins tekniska forskningsinstitut.
    Kruse, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Information Capacity Revisited - Reflections on Print Quality2000In: Advances in Printing Science and Technology / [ed] J. A. Bristow, Leatherhead, UK: Pira International , 2000, Vol. 26, p. 175-184Conference paper (Refereed)
    Abstract [en]

    The advent of digital printing stresses the importance of quality measurement. Print quality measures that give an objective value have long been sought. The aim is 10 be able to dcscrihe objectively the properties of print on paper so that conclusions regarding the apparent quality can be drawn. In this paper, we discuss the measures proposed in the literature and relate them to the subjective quality. Several years ago, the concept of ‘information capacity’ was proposed as such a measure. Some reflections are made in the light of coding. and telecommunication theory. areas in which in information capacity is a vital tool. On the other hand. for the print quality applications. the interest in in formation capacity has in fact been decreasing. An obvious question therefore arises and is treated in this work: Why have we seen so few applications of this theory for practical applications in the area of print? Is the area of print quality so very different from the areas or image compression and telecommunication?

  • 78.
    Ljung, Patric
    et al.
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Lundström, Claes
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Ynnerman, Anders
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Transfer Function Based Adaptive Decompresion for Volume Rendering of Large Medical Data Sets2004In: Proceedings of IEEE/ACM Symposium on Volume Visualization 2004, Austin, USA, IEEE , 2004, p. 25-32Conference paper (Refereed)
    Abstract [en]

    The size of standard volumetric data sets in medical imaging is rapidly increasing causing severe performance limitations in direct volume rendering pipelines. The methods presented in this paper exploit the medical knowledge embedded in the transfer function to reduce the required bandwidth in the pipeline. Typically, medical transfer functions cause large subsets of the volume to give little or no contribution to the rendered image. Thus, parts of the volume can be represented at low resolution while retaining overall visual quality. This paper introduces the use of transfer functions at decompression time to guide a level-of-detail selection scheme. The method may be used in combination with traditional lossy or lossless compression schemes. We base our current implementation on a multi-resolution data representation using compressed wavelet transformed blocks. The presented results using the adaptive decompression demonstrate a significant reduction in the required amount of data while maintaining rendering quality. Even though the focus of this paper is medical imaging, the results are applicable to volume rendering in many other domains.

  • 79.
    Lundberg, Jonas
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Rollenhagen, C.
    Royal Institute of Technology.
    Hollnagel, Erik
    Linköping University, Department of Computer and Information Science, CSELAB - Cognitive Systems Engineering Laboratory. Linköping University, The Institute of Technology.
    What-You-Look-For-Is-What-You-Find - The consequences of underlying accident models in eight accident investigation manuals2009In: Safety Science, ISSN 0925-7535, Vol. 47, no 10, p. 1297-1311Article in journal (Refereed)
    Abstract [en]

    Accident investigation manuals are influential documents on various levels in a safety management system, and it is therefore important to appraise them in the light of what we currently know - or assume - about the nature of accidents. Investigation manuals necessarily embody or represent an accident model, i.e., a set of assumptions about how accidents happen and what the important factors are. In this paper we examine three aspects of accident investigation as described in a number of investigation manuals. Firstly, we focus on accident models and in particular the assumptions about how different factors interact to cause - or prevent - accidents, i.e., the accident "mechanisms". Secondly, we focus on the scope in the sense of the factors (or factor domains) that are considered in the models - for instance (hu)man, technology, and organization (MTO). Thirdly, we focus on the system of investigation or the activities that together constitute an accident investigation project/process. We found that the manuals all used complex linear models. The factors considered were in general (hu)man, technology, organization, and information. The causes found during an investigation reflect the assumptions of the accident model, following the What-You-Look-For-Is-What-You-Find or WYLFIWYF principle. The identified causes typically became specific problems to be fixed during an implementation of solutions. This follows what can be called What-You-Find-Is-What-You-Fix or WYFIWYF principle.

    Download full text (pdf)
    fulltext
  • 80.
    Lundberg, Jonas
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Rollenhagen, Carl
    KTH.
    Hollnagel, Erik
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    What you find is not always what you fix-How other aspects than causes of accidents decide recommendations for remedial actions2010In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 42, no 6, p. 2132-2139Article in journal (Refereed)
    Abstract [en]

    In accident investigation, the ideal is often to follow the principle "what-you-find-is-what-you-fix", an ideal reflecting that the investigation should be a rational process of first identifying causes, and then implement remedial actions to fix them. Previous research has however identified cognitive and political biases leading away from this ideal. Somewhat surprisingly, however, the same factors that often are highlighted in modern accident models are not perceived in a recursive manner to reflect how they influence the process of accident investigation in itself. Those factors are more extensive than the cognitive and political biases that are often highlighted in theory. Our purpose in this study was to reveal constraints affecting accident investigation practices that lead the investigation towards or away from the ideal of "what-you-find-is-what-you-fix". We conducted a qualitative interview study with 22 accident investigators from different domains in Sweden. We found a wide range of factors that led investigations away from the ideal, most which more resembled factors involved in organizational accidents, rather than reflecting flawed thinking. One particular limitation of investigation was that many investigations stop the analysis at the level of "preventable causes", the level where remedies that were currently practical to implement could be found. This could potentially limit the usefulness of using investigations to get a view on the "big picture" of causes of accidents as a basis for further remedial actions.

    Download full text (pdf)
    fulltext
  • 81.
    Lundblad, Karin
    et al.
    LiU KogVet, currently Relcon Scandpower AB.
    Speziali, Josephine
    LiU KogVet, currently Vattenfall Power Consultant AB.
    Woltjer, Rogier
    Linköping University, Department of Computer and Information Science, CSELAB - Cognitive Systems Engineering Laboratory. Linköping University, The Institute of Technology.
    Lundberg, Jonas
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    FRAM as a risk assessment method for nuclear fuel transportation2008In: International Confererence Working on Safety,2008, 2008Conference paper (Other academic)
    Abstract [en]

    This paper gives an overview and evaluation of the predictive use of the Functional Resonance Accident Model, FRAM (Hollnagel, 2004), a method that is under development and in line with the theoretical framework of Resilience Engineering (Hollnagel et al. 2006). FRAM is based on the premise that both negative and positive events can result from (expected and unexpected) combinations of the variability in the normal performance of complex socio-technical systems. FRAM was used as a qualitative risk assessment method in a nuclear power plant. The process assessed was the transportation of an 80 ton heavy metal cylinder for transportation of used fuel. The study focused on the transportation of the cylinder inside the power plant and in particular the 40 meter lift that is needed to get the cylinder up into the reactor hall. The FRAM analysis was used to propose recommendations at different levels, such as how to improve human-machine interface issues, procedures, information dissemination within the organization, and government guidelines. 

  • 82.
    Lundin (Palmerius), Karljohan
    et al.
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Gudmundsson, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Ynnerman, Anders
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    General Proxy-based Haptics for Volume Visualization2005In: Eurohaptics Conference, 2005 and Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems, 2005., 2005, p. 557-560Conference paper (Refereed)
    Abstract [en]

    We present a general, proxy-based approach to volume haptics founded upon the notion of 'haptic primitives'. Haptic modes each representing a different aspect of volumetric data, are created by defining sets of haptic primitives which reflect the local properties of the data. The proxy position for every time-frame in the haptic loop is found by balancing the force feedback in the haptic instrument with the force from the haptic primitives involved. The presented general framework allows for rapid development of haptic feedback modes for volumetric data. The approach also allows, in contrast to previous work on proxy-based volume haptics, combination of non-orthogonal constraints and thus allows free combination of various modes in haptic exploration of multivariate data. We demonstrate the effectiveness of our approach through the implementation of five different haptic modes.

  • 83.
    Lundin Palmerius, Karljohan
    et al.
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Ynnerman, Anders
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Gudmundsson, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Proxy-based Haptic Feedback from Volumetric Density Data2002In: Proceedings of the Eurohaptics Conference, 2002, p. 104-109Conference paper (Refereed)
    Abstract [en]

    In this paper a new approach to volume haptics is presented. The developed method makes use of a proxy that is constrained by ‘virtual surfaces’, defined by the local gradient at the proxy position, and not by iso-values as in other approaches to volume haptics. By using a proxy, material properties like friction, stiffness and surface penetrability can be implemented. These material properties are controlled by user defined transfer functions. At the same time, using the gradient to define surfaces, rendering of infinitesimally close virtual surfaces that can be penetrated, is made possible. The algorithm exhibits very high stability, is fast and represents fine details accurately. Compared to earlier techniques, less artifacts occur and higher configurability is provided.

  • 84. Order onlineBuy this publication >>
    Läthén, Gunnar
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Segmentation Methods for Medical Image Analysis: Blood vessels, multi-scale filtering and level set methods2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Image segmentation is the problem of partitioning an image into meaningful parts, often consisting of an object and background. As an important part of many imaging applications, e.g. face recognition, tracking of moving cars and people etc, it is of general interest to design robust and fast segmentation algorithms. However, it is well accepted that there is no general method for solving all segmentation problems. Instead, the algorithms have to be highly adapted to the application in order to achieve good performance. In this thesis, we will study segmentation methods for blood vessels in medical images. The need for accurate segmentation tools in medical applications is driven by the increased capacity of the imaging devices. Common modalities such as CT and MRI generate images which simply cannot be examined manually, due to high resolutions and a large number of image slices. Furthermore, it is very difficult to visualize complex structures in three-dimensional image volumes without cutting away large portions of, perhaps important, data. Tools, such as segmentation, can aid the medical staff in browsing through such large images by highlighting objects of particular importance. In addition, segmentation in particular can output models of organs, tumors, and other structures for further analysis, quantification or simulation.

    We have divided the segmentation of blood vessels into two parts. First, we model the vessels as a collection of lines and edges (linear structures) and use filtering techniques to detect such structures in an image. Second, the output from this filtering is used as input for segmentation tools. Our contributions mainly lie in the design of a multi-scale filtering and integration scheme for de- tecting vessels of varying widths and the modification of optimization schemes for finding better segmentations than traditional methods do. We validate our ideas on synthetical images mimicking typical blood vessel structures, and show proof-of-concept results on real medical images.

    List of papers
    1. Flexible and Topologically Localized Segmentation
    Open this publication in new window or tab >>Flexible and Topologically Localized Segmentation
    2007 (English)In: EuroVis07 Joint Eurographics: IEEE VGTC Symposium on Visualization / [ed] Ken Museth, Torsten Möller, and Anders Ynnerman, Aire-la-Ville, Switzerland: Eurographics Association , 2007, , p. 179-186p. 179-186Conference paper, Published paper (Refereed)
    Abstract [en]

    One of the most common visualization tasks is the extraction of significant boundaries, often performed with iso- surfaces or level set segmentation. Isosurface extraction is simple and can be guided by geometric and topological analysis, yet frequently does not extract the desired boundary. Level set segmentation is better at boundary extrac- tion, but either leads to global segmentation without edges, [CV01], that scales unfavorably in 3D or requires an initial estimate of the boundary from which to locally solve segmentation with edges. We propose a hybrid system in which topological analysis is used for semi-automatic initialization of a level set segmentation, and geometric information bounded topologically is used to guide and accelerate an iterative segmentation algorithm that com- bines several state-of-the-art level set terms. We thus combine and improve both the flexible isosurface interface and level set segmentation without edges.

    Place, publisher, year, edition, pages
    Aire-la-Ville, Switzerland: Eurographics Association, 2007. p. 179-186
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-40841 (URN)54293 (Local ID)978-3-905673-45-6 (ISBN)54293 (Archive number)54293 (OAI)
    Conference
    Eurographics/ IEEE-VGTC Symposium on Visualization, 23-25 May, Norrköping, Sweden
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2013-09-19
    2. Phase Based Level Set Segmentation of Blood Vessels
    Open this publication in new window or tab >>Phase Based Level Set Segmentation of Blood Vessels
    2008 (English)In: Proceedings of 19th International Conference on Pattern Recognition, IEEE Computer Society , 2008, p. 1-4Conference paper, Published paper (Refereed)
    Abstract [en]

    The segmentation and analysis of blood vessels hasreceived much attention in the research community. Theresults aid numerous applications for diagnosis andtreatment of vascular diseases. Here we use level setpropagation with local phase information to capture theboundaries of vessels. The basic notion is that localphase, extracted using quadrature filters, allows us todistinguish between lines and edges in an image. Notingthat vessels appear either as lines or edge pairs, weintegrate multiple scales and capture information aboutvessels of varying width. The outcome is a “global”phase which can be used to drive a contour robustly towardsthe vessel edges. We show promising results in2D and 3D. Comparison with a related method givessimilar or even better results and at a computationalcost several orders of magnitude less. Even with verysparse initializations, our method captures a large portionof the vessel tree.

    Place, publisher, year, edition, pages
    IEEE Computer Society, 2008
    Series
    International Conference on Pattern Recognition, ISSN 1051-4651
    National Category
    Medical Laboratory and Measurements Technologies
    Identifiers
    urn:nbn:se:liu:diva-21054 (URN)10.1109/ICPR.2008.4760970 (DOI)000264729000023 ()978-1-4244-2175-6 (ISBN)978-1-4244-2174-9 (ISBN)
    Conference
    19th International Conference on Pattern Recognition (ICPR 2008), 8-11 December 2008, Tampa, Finland
    Note

    ©2009 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE: Gunnar Läthén, Jimmy Jonasson and Magnus Borga, Phase Based Level Set Segmentation of Blood Vessels, 2008, Proceedings of 19th International Conference on Pattern Recognition. http://dx.doi.org/10.1109/ICPR.2008.4760970

    Available from: 2009-09-28 Created: 2009-09-28 Last updated: 2015-10-09
    3. Momentum Based Optimization Methods for Level Set Segmentation
    Open this publication in new window or tab >>Momentum Based Optimization Methods for Level Set Segmentation
    2009 (English)In: Momentum Based Optimization Methods for Level Set Segmentation: Second International Conference, SSVM 2009, Voss, Norway, June 1-5, 2009. Proceedings / [ed] Gerhard Goos, Juris Hartmanis, and Jan van Leeuwen, Berlin: Springer Berlin/Heidelberg, 2009, p. 124-136Conference paper, Published paper (Refereed)
    Abstract [en]

    Segmentation of images is often posed as a variational problem. As such, it is solved by formulating an energy functional depending on a contour and other image derived terms. The solution of the segmentation problem is the contour which extremizes this functional. The standard way of solving this optimization problem is by gradient descent search in the solution space, which typically suffers from many unwanted local optima and poor convergence. Classically, these problems have been circumvented by modifying the energy functional. In contrast, the focus of this paper is on alternative methods for optimization. Inspired by ideas from the machine learning community, we propose segmentation based on gradient descent with momentum. Our results show that typical models hampered by local optima solutions can be further improved by this approach. We illustrate the performance improvements using the level set framework.

    Place, publisher, year, edition, pages
    Berlin: Springer Berlin/Heidelberg, 2009
    Series
    Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349 ; 5567
    National Category
    Medical Laboratory and Measurements Technologies
    Identifiers
    urn:nbn:se:liu:diva-21037 (URN)10.1007/978-3-642-02256-2_11 (DOI)000270543900011 ()3-642-02255-3 (ISBN)978-3-642-02255-5 (ISBN)978-3-642-02256-2 (ISBN)
    Conference
    Second International Conference, SSVM 2009, June 1-5, Voss, Norway
    Note

    Original Publication: Gunnar Läthén, Thord Andersson, Reiner Lenz and Magnus Borga, Momentum Based Optimization Methods for Level Set Segmentation, 2009, Lecture Notes in Computer Science 5567: Scale Space and Variational Methods in Computer Vision, 124-136. http://dx.doi.org/10.1007/978-3-642-02256-2_11 Copyright: Springer http://www.springerlink.com/

    Available from: 2009-09-28 Created: 2009-09-28 Last updated: 2018-02-19Bibliographically approved
    4. A Fast Optimization Method for Level Set Segmentation
    Open this publication in new window or tab >>A Fast Optimization Method for Level Set Segmentation
    2009 (English)In: Image Analysis: 16th Scandinavian Conference, SCIA 2009, Oslo, Norway, June 15-18, 2009. Proceedings / [ed] A.-B. Salberg, J.Y. Hardeberg, and R. Jenssen, Springer Berlin/Heidelberg, 2009, p. 400-409Conference paper, Published paper (Refereed)
    Abstract [en]

    Level set methods are a popular way to solve the image segmentation problem in computer image analysis. A contour is implicitly represented by the zero level of a signed distance function, and evolved according to a motion equation in order to minimize a cost function. This function defines the objective of the segmentation problem and also includes regularization constraints. Gradient descent search is the de facto method used to solve this optimization problem. Basic gradient descent methods, however, are sensitive for local optima and often display slow convergence. Traditionally, the cost functions have been modified to avoid these problems. In this work, we instead propose using a modified gradient descent search based on resilient propagation (Rprop), a method commonly used in the machine learning community. Our results show faster convergence and less sensitivity to local optima, compared to traditional gradient descent.

    Place, publisher, year, edition, pages
    Springer Berlin/Heidelberg, 2009
    Series
    Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349 ; 5575
    Keywords
    Image segmentation - level set method - optimization - gradient descent - Rprop - variational problems - active contours
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-19313 (URN)10.1007/978-3-642-02230-2_41 (DOI)000268661000041 ()978-3-642-02229-6 (ISBN)978-3-642-02230-2 (ISBN)
    Conference
    16th Scandinavian Conference on Image Analysis, June 15-18 2009, Oslo, Norway
    Available from: 2009-07-09 Created: 2009-06-17 Last updated: 2018-01-23Bibliographically approved
    5. Blood vessel segmentation using multi-scale quadrature filtering
    Open this publication in new window or tab >>Blood vessel segmentation using multi-scale quadrature filtering
    2010 (English)In: Pattern Recognition Letters, ISSN 0167-8655, E-ISSN 1872-7344, Vol. 31, no 8, p. 762-767Article in journal (Refereed) Published
    Abstract [en]

    The segmentation of blood vessels is a common problem in medical imagingand various applications are found in diagnostics, surgical planning, trainingand more. Among many dierent techniques, the use of multiple scales andline detectors is a popular approach. However, the typical line lters usedare sensitive to intensity variations and do not target the detection of vesselwalls explicitly. In this article, we combine both line and edge detection usingquadrature lters across multiple scales. The lter result gives well denedvessels as linear structures, while distinct edges facilitate a robust segmentation.We apply the lter output to energy optimization techniques for segmentationand show promising results in 2D and 3D to illustrate the behavior of ourmethod. The conference version of this article received the best paper award inthe bioinformatics and biomedical applications track at ICPR 2008.

    Place, publisher, year, edition, pages
    Elsevier, 2010
    Keywords
    Image segmentation, Blood vessels, Medical imaging, Multi-scale, Quadrature filter, Level set method
    National Category
    Medical Laboratory and Measurements Technologies
    Identifiers
    urn:nbn:se:liu:diva-21046 (URN)10.1016/j.patrec.2009.09.020 (DOI)000277552600014 ()
    Note
    Original Publication: Gunnar Läthén, Jimmy Jonasson and Magnus Borga, Blood vessel segmentation using multi-scale quadrature filtering, 2010, Pattern Recognition Letters, (31), 8, 762-767. http://dx.doi.org/10.1016/j.patrec.2009.09.020 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Available from: 2009-09-28 Created: 2009-09-28 Last updated: 2017-12-13
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    Segmentation Methods for Medical Image Analysis : Blood vessels, multi-scale filtering and level set methods
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    Cover
  • 85.
    Läthén, Gunnar
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Andersson, Thord
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Medical Informatics.
    Lenz, Reiner
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Borga, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Level set based segmentation using gradient descent with momentum2009In: SSBA 2009, Symposium on image analysis,2009, Halmstad, Sweden: Halmstad University , 2009Conference paper (Other academic)
  • 86.
    Läthén, Gunnar
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Andersson, Thord
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Lenz, Reiner
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Borga, Magnus
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Momentum Based Optimization Methods for Level Set Segmentation2009In: Momentum Based Optimization Methods for Level Set Segmentation: Second International Conference, SSVM 2009, Voss, Norway, June 1-5, 2009. Proceedings / [ed] Gerhard Goos, Juris Hartmanis, and Jan van Leeuwen, Berlin: Springer Berlin/Heidelberg, 2009, p. 124-136Conference paper (Refereed)
    Abstract [en]

    Segmentation of images is often posed as a variational problem. As such, it is solved by formulating an energy functional depending on a contour and other image derived terms. The solution of the segmentation problem is the contour which extremizes this functional. The standard way of solving this optimization problem is by gradient descent search in the solution space, which typically suffers from many unwanted local optima and poor convergence. Classically, these problems have been circumvented by modifying the energy functional. In contrast, the focus of this paper is on alternative methods for optimization. Inspired by ideas from the machine learning community, we propose segmentation based on gradient descent with momentum. Our results show that typical models hampered by local optima solutions can be further improved by this approach. We illustrate the performance improvements using the level set framework.

    Download full text (pdf)
    FULLTEXT02
  • 87.
    Läthén, Gunnar
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Jonasson, Jimmy
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Borga, Magnus
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Blood vessel segmentation using multi-scale quadrature filtering2010In: Pattern Recognition Letters, ISSN 0167-8655, E-ISSN 1872-7344, Vol. 31, no 8, p. 762-767Article in journal (Refereed)
    Abstract [en]

    The segmentation of blood vessels is a common problem in medical imagingand various applications are found in diagnostics, surgical planning, trainingand more. Among many dierent techniques, the use of multiple scales andline detectors is a popular approach. However, the typical line lters usedare sensitive to intensity variations and do not target the detection of vesselwalls explicitly. In this article, we combine both line and edge detection usingquadrature lters across multiple scales. The lter result gives well denedvessels as linear structures, while distinct edges facilitate a robust segmentation.We apply the lter output to energy optimization techniques for segmentationand show promising results in 2D and 3D to illustrate the behavior of ourmethod. The conference version of this article received the best paper award inthe bioinformatics and biomedical applications track at ICPR 2008.

    Download full text (pdf)
    FULLTEXT01
  • 88.
    Läthén, Gunnar
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Jonasson, Jimmy
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Borga, Magnus
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    Phase Based Level Set Segmentation of Blood Vessels2008In: Proceedings of 19th International Conference on Pattern Recognition, IEEE Computer Society , 2008, p. 1-4Conference paper (Refereed)
    Abstract [en]

    The segmentation and analysis of blood vessels hasreceived much attention in the research community. Theresults aid numerous applications for diagnosis andtreatment of vascular diseases. Here we use level setpropagation with local phase information to capture theboundaries of vessels. The basic notion is that localphase, extracted using quadrature filters, allows us todistinguish between lines and edges in an image. Notingthat vessels appear either as lines or edge pairs, weintegrate multiple scales and capture information aboutvessels of varying width. The outcome is a “global”phase which can be used to drive a contour robustly towardsthe vessel edges. We show promising results in2D and 3D. Comparison with a related method givessimilar or even better results and at a computationalcost several orders of magnitude less. Even with verysparse initializations, our method captures a large portionof the vessel tree.

    Download full text (pdf)
    FULLTEXT01
  • 89.
    Läthén, Gunnar
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Carr, Hamish
    School of Computer Science and Informatics University College Dublin.
    Topologically Localized Level Set Segmentation2007In: Symposium on Image Analysis,2007, 2007, p. 89-92Conference paper (Other academic)
  • 90. Marker, J
    et al.
    Braude, I
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Breen, David
    Contour-Based Surface Reconstruction using Implicit Curve Fitting, and Distance Field Filtering2006In: IEEE Volume Graphics,2006, 2006, p. 95-Conference paper (Refereed)
  • 91.
    Mochizuki, Rika
    et al.
    Chuo University.
    Nakamura, Tatsuya
    Chuo University.
    Chao, Jinhui
    Chuo University.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Correction of Color-Weakness by Matching of Discrimination Thresholds2008In: Proc. CGIV 2008, 7003 Kilworth Lane, Springfield, VA 22151 USA: The Society for Imaging Science and Technology , 2008, , p. 208-213p. 208-213Conference paper (Refereed)
    Abstract [en]

    The correction of the effects of color-weakness is difficultif not impossible. One of the reasons is that are no objectivecriterions available to evaluate corrections since it is difficult toquantify the color perception of an individual. Also the degreeand the character of color-weakness vary widely among individualsand different color stimuli. In this paper, we use Riemanngeometry to construct a new method for color-weakness correction.The basic mechanism is the matching between the discriminationthresholds of color-weak and of color-normal observers.The goal is to provide the same color perception of color-normalobservers to the color-weak observer: it takes into account theindividual differences between observers and since it defines aglobal deformation of the whole color space it is applicable forcorrection of complex visual inputs such as natural images.

  • 92.
    Museth, Ken
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Breen, David
    Whitaker, Ross
    Barr, A
    Level Set Surface Editing Operators2002In: ACM Transactions on Graphics, ISSN 0730-0301, E-ISSN 1557-7368, Vol. 21, no 3, p. 330-338Article in journal (Refereed)
  • 93.
    Museth, Ken
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Breen, David
    Zhukov, L
    Whitaker, Ross
    Level Set Segmentation from Multiple Non-Uniform Volume Datasets2002In: IEEE Visualization 02,2002, 2002, p. 179-Conference paper (Refereed)
  • 94.
    Museth, Ken
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Breen, D.E.
    Drexel University.
    Whitaker, R.T.
    University of Utah.
    Mauch, S.
    California Institute of Technology.
    Johnson, D.
    University of Utah.
    Algorithms for interactive editing of level set models2005In: Computer graphics forum (Print), ISSN 0167-7055, E-ISSN 1467-8659, Vol. 24, no 4, p. 821-841Article in journal (Refereed)
    Abstract [en]

    Level set models combine a low-level volumetric representation, the mathematics of deformable implicit surfaces and powerful, robust numerical techniques to produce a novel approach to shape design. While these models offer many benefits, their large-scale representation and numerical requirements create significant challenges when developing an interactive system. This paper describes the collection of techniques and algorithms (some new, some pre-existing) needed to overcome these challenges and to create an interactive editing system for this new type of geometric model. We summarize the algorithms for producing level set input models and, more importantly, for localizingminimizing computation during the editing process. These algorithms include distance calculations, scan conversion, closest point determination, fast marching methods, bounding box creation, fast and incremental mesh extraction, numerical integration and narrow band techniques. Together these algorithms provide the capabilities required for interactive editing of level set models. © The Eurographics Association and Blackwell Publishing Ltd 2005.

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