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  • 1.
    Bergström, Per
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Rosendahl, Sara
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Shape verification using dual-wavelength holographic interferometry2011In: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 50, no 10, article id 101503Article in journal (Refereed)
    Abstract [en]

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

  • 2.
    Bergström, Per
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Rosendahl, Sara
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Shape verification aimed for manufacturing process control2011In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 49, no 3, p. 403-409Article in journal (Refereed)
    Abstract [en]

    We describe a method to verify the shape of manufactured objects by using their design model. A non-contact measuring method that consists of a stereo-camera system and a single projected fringe pattern is used. The method acquires one image from each camera. Additional shape information from the design model is also used. This surface-measurement method gives an accuracy of about 45 µm. Deviations from the design model within ±1.6 mm can be correctly detected. The measured surface representation is matched to the design model using the ICP-method. Fast performance has been considered adapting the method for on-line use.

  • 3.
    Casselgren, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Engström, Niclas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Rosendahl, Sara
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Fransson, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Investigation of ice surface change during vehicle testing2014In: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, E-ISSN 1745-6444, Vol. 9, no 2, p. 137-150Article in journal (Refereed)
    Abstract [en]

    Today, there are a lot of vehicles and tyre testing carried out on lake ice surfaces. Thus, it is important to have knowledge about parameters that affect roadgrip. The thesis within this paper is that the liquid like layer which appears due to increasing temperature can be reduced by manipulating the ice roughness. This in turn should decrease the temperature dependence of the roadgrip in temperatures around 0°C. In order to investigate this, measurements of temperature, surface roughness and hardness and roadgrip were performed on three outdoor ice surfaces using an IR thermometer, an optical sensor with three IR-diodes, a steel ball drop indentation test and an RT3 curve, respectively. Additional ice roughness measurements were also made on two tempered ice surfaces in an ice hall. Results show a clear connection between ice temperature and roadgrip, unfortunately the created ice roughness was too small to influence the change in roadgrip

  • 4.
    Casselgren, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Rosendahl, Sara
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Eliasson, Jens
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Road surface information system2013In: Proceedings of the 16th SIRWEC conference: Helsinki, FInland (23-25th May 2012), Standing International Road Weather Commission , 2013Conference paper (Other academic)
    Abstract [en]

    In order to classify the road condition, dry asphalt and asphalt covered with water, ice and snow a technique using a sensor called Road eye is presented. The Road eye sensor uses three wavelengths and one photo detector to determine the intensities that are reflected from the road surface and is then able to estimate the road condition. By linking the Road eye sensor to a GPS and a Mulle, a miniature wireless Embedded Internet System, the road conditions can be associated with the correct road position, making it possible to use the information in many different applications.

  • 5.
    Casselgren, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Rosendahl, Sara
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Engström, Niclas
    LKAB, SE-981-86 Kiruna, Sweden.
    Grönlund, Ulrika
    Autoliv Sverige AB, Active Saftey Tech Center, Linköping, Sweden.
    Evaluation of velocity and curvature dependence for roadgrip measured by low lateral slip2017In: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, E-ISSN 1745-6444, Vol. 12, no 1/2, p. 1-16Article in journal (Refereed)
    Abstract [en]

    Roadgrip is an important parameter for vehicle testing and road maintenance. Therefore, an evaluation of the velocity and curvature effects on roadgrip measurement was performed on asphalt roads and on two ice tracks using the continuous roadgrip apparatus RT3 Curve. The aim was to find suitable driving patterns for measurements on public roads and test tracks to ensure the repeatability of roadgrip measurements. During the evaluation, it was concluded that in order to achieve a reliable roadgrip value, regardless of road conditions, the radius of curvature should not be less than 20 m. The velocity dependency of the RT3 Curve is different for the two road conditions, with the measurements on ice being much more sensitive to velocity changes than the measurements on the dry asphalt.

  • 6.
    Casselgren, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Rosendahl, Sara
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Jonsson, Patrik
    Combitech AB, Mittuniversitetet, Department of Information Technology and Media, Mid-Sweden University.
    Road condition analysis using NIR illumination and compensating for surrounding light2016In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 77, p. 175-182Article in journal (Refereed)
    Abstract [en]

    An investigation of a NIR camera system for road surface classification has been conducted for several road conditions. The surfaces were illuminated with three wavelengths, 980 nm, 1310 nm and 1550 nm and a halogen lamp, to simulate a real environment application with surrounding light. A measuring scheme to deal with surrounding light has been implemented enabling road condition classification from NIR images in a real environment. The retrieved camera images have been analyzed and an RGB representation of the different surfaces has been created to classify the different road conditions. The investigation shows that it is possible to distinguish between dry, moist, wet, frosty, icy and snowy road surfaces using a NIR camera system in a disturbed environment.

  • 7.
    Rosendahl, Sara
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    On-line shape inspection using a projected fringe pattern2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    A stereo camera system together with a single projected fringe pattern and one image recording is used to measure 3D-shape. The idea is to make the measurement quick enough to be able to use the method when testing quality on-line in manufacturing industry. For this to be possible the digital master (e.g. the CAD model) of the object is used to find homologous points, i.e. points corresponding to the same object point, in the cameras. Given the homologous points the shape can be calculated using optical triangulation. In the results of the shape measurement it can be seen that as long as the object has approximately the same shape as expected (the same shape as the digital master) the method works. For the setup used in these measurements the accuracy was ≈± 40 µm. However, large deviation from the digital master will be incorrectly detected due to the fact that the phase in the images is wrapped. An analytical expression for the maximum detectable deviation is calculated and for the setup used it became ≈± 1.6 mm. Since the accuracy in the shape measurement depends on the phase error an analytical expression for this is derived. It is seen that the phase error becomes large if the fringe modulation is low and the speckle contrast in the fringe pattern is high. The phase in the fringes is determined using a Fourier filter method which gives that the phase error also depends on the size of the filter in the Fourier spectrum. To reduce the phase error focus has been put on suppressing the speckles by moving the aperture. It is verified by simulations and experiments that this method reduces both the speckle contrast and the phase error by 60 % for a movement of three aperture diameters.

  • 8.
    Rosendahl, Sara
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Shape and surface characterization using diffused light2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Diffuse reflection from various surfaces have been studied using several different methods in order to draw conclusions about the surfaces. First of all the aim was to perform fast and accurate shape measurements of molded steel objects on-line in a production system. Two measurement methods were used, stereoscopic imaging with projected fringes and dual wavelength digital holography. Information from the CAD model of the object was used to speed up the shape determination, mainly by enhancing the performance of the phase unwrapping. The uncertainty of the shape result was between 3.5 µm and 40 µm depending on the measurement method. The request on conformity between the object and the CAD model varied between 0.1 mm and 1.6 mm. To overcome the influence of speckles in the case of using interference fringes in the stereoscopic imaging an investigation of speckle reduction using a moving aperture was performed. The technique resulted in a decrease in the speckle contrast of about 60%.Secondly, diffuse reflections that come not only from the surface, but also from beneath it were studied. Measurements were done both on ice surfaces with the aim to identify changes in the surface structure and on glass spheres and sand grains with the aim to detect different moist content in granular material. The ice measurements showed an increase in the back reflection and a decrease in the specular reflection when the surface went from being smooth to being rough, a fact that can be useful when considering the roadgrip of icy roads. Depending on the water content in the granular materials the moist measurements when illuminating the surfaces with white light showed differences in the shape of the reflection distribution in the plane of incidence. Given these differences a simple model describing the water content was proposed.All experiments, except the ones on ice, have been performed in the laboratory. The results have been analyzed and compared to simulations, model estimations, and in the case of the shape measurements with the corresponding CAD models, all with relatively good outcome.In this thesis the work is presented in six papers. One about the speckle reduction method, three about the shape measurements and two about the ice surface structure and the moist in granular material, respectively.

  • 9.
    Rosendahl, Sara
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Bergström, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Dual-wavelength holographic shape measurement with iterative phase unwrapping2011In: Optical Measurement Systems for Industrial Inspection VII / [ed] Peter H. Lehmann; Wolfgang Osten; Kay Gastinger, Bellingham, Wash.: SPIE - International Society for Optical Engineering, 2011, p. 80820B-Conference paper (Refereed)
    Abstract [en]

    In order to measure the shape of a large number of identical components in a manufacturing industry we propose a method where digital holography is used to capture an image of the object and then the shape of the object is achieved by using information from the CAD-model. The holographic recording of the object is done using dual wavelengths giving a synthetic wavelength of about 400 μm. This gives a phase map where the phase intervals represent a depth distance on the object of about 0.2 mm. To find the shape of the object the phase map has to be unwrapped. Since the surface contains discontinuities we use information from the CAD-model of the measured object and unwrap the phase iteratively. The result becomes a digital point representation of the measured surface that can either be used just as a description of the object shape or as a way to describe how well the object has been manufactured compared to the CAD-model. The measurement process that is proposed is adapted for on-line purposes; hence it is fast and reliable.

  • 10.
    Rosendahl, Sara
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Bergström, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Hällstig, Emil
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Optisk formmätning för användning on-line i tillverkningsprocesser2009In: Svenska mekanikdagarna: Södertälje 2009, Stockholm: Svenska nationalkommittén för mekanik , 2009, p. 88-Conference paper (Other academic)
  • 11.
    Rosendahl, Sara
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Casselgren, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Simplified model for light scattering from granular materials with varying moisture content2013In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 52, no 17, p. 4006-4012Article in journal (Refereed)
    Abstract [en]

    Reflection measurements were performed on dry and moistened sand grains and glass spheres, respectively. A simple model for determining the water content is proposed from looking at the reflection distribution in the plane of incidence. The model is a combination of two sheared cosine-functions and consists of only two parameters. One parameter controls whether the reflection is mainly in the forward or backward direction. The former is true when the water content is high and the latter is true when the material is dry. The other parameter gives an idea of the homogeneity of the material.

  • 12.
    Rosendahl, Sara
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Hällstig, Emil
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Phase errors due to speckles in laser fringe projection2010In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 49, no 11, p. 2047-2053Article in journal (Refereed)
    Abstract [en]

    When measuring a three-dimensional shape with triangulation and projected interference fringes it is of interest to reduce speckle contrast without destroying the coherence of the projected light. A moving aperture is used to suppress the speckles and thereby reduce the phase error in the fringe image. It is shown that the phase error depends linearly on the ratio between the speckle contrast and the modulation of the fringes. In this investigation the spatial carrier method was used to extract the phase, where the phase error also depends on filtering the Fourier spectrum. An analytical expression for the phase error is derived. Both the speckle reduction and the theoretical expressions for the phase error are verified by simulations and experiments. It was concluded that a movement of the aperture by three aperture diameters during exposure of the image reduces the speckle contrast and hence the phase error by 60%. In the experiments, a phase error of 0.2 rad was obtained.

  • 13.
    Rosendahl, Sara
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Hällstig, Emil
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Sjödahl, Mikael
    Phase errors in speckle reduced laser fringe projection2010In: Speckle 2010: optical metrology : 13 - 15 September 2010, Florianópolis, Brazil / [ed] Armando Albertazzi Gonçalves, Bellingham, Wash: SPIE - International Society for Optical Engineering, 2010, p. 73871E-Conference paper (Refereed)
    Abstract [en]

    When measuring 3D-shape with triangulation and projected interference fringes it is of interest to reduce the phase error in the fringe pattern. A study has been carried out concerning parameters that will affect the phase error and an analytical expression has been derived. It is concluded that the phase error depends on the speckle contrast, C, and the modulation, M, of the fringes and since the phase in this investigation is determined using the spatial carrier method the phase error also depends on the filtering of the Fourier spectrum. To reduce the phase error this work has been focusing on suppressing the speckle contrast. For this the method with a moving aperture is used; a disk with several apertures is rotated in the aperture plane of the camera lens. To verify the derived expression for the phase error and the method to suppress speckles both numerical simulations and experiments have been performed. In the measurements made it was concluded that after an aperture movement of three aperture diameters the speckle contrast and hence the phase error was reduced by 60 %. A phase error of 0.15 radians was obtained in the experiments, thus approximately 1/40 of a fringe period

  • 14.
    Rosendahl, Sara
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Hällstig, Emil
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Sjödahl, Mikael
    Shape measurement with one fringe pattern recording including a digital master2010In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 49, no 14, p. 2622-2629Article in journal (Refereed)
    Abstract [en]

    We present a method in which the 3D shape of an object can be measured and compared to the shape of the digital master of the object, e.g., the computer-aided design model. The measurement is done using a stereo camera system and a single projected fringe pattern. Because the digital master is available, i.e., the expected shape is known, only one projection and image recording is necessary; thus, the method becomes fast. The idea in this work is to find homologous points in the cameras, i.e., points corresponding to the same object point, using the object information. An algorithm to find the homologous points is presented and a method to calculate shape is described. Given the ambiguity due to the fact that the phase in the images is wrapped, there is a maximum deviation from the master that can be correctly detected. An analytical expression for this deviation is derived. Results from the shape measurement of an object both with and without deviations from the digital master are also presented. In these measurements, where the measurement volume is approximately 1 dm3 and the fringe period on the object plane is about 1 mm, the accuracy is ≈± 40 μm, and a deviation of max ≈± 1.6mm can be correctly detected.

  • 15.
    Rosendahl, Sara
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Hällstig, Emil
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Incoherent imaging of coherent projection2007Conference paper (Other academic)
1 - 15 of 15
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