Browsing by Author "Kivi, Miikka"

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  • RF-tehovahvistimet
    (2011) Kivi, Miikka
     Sähkötekniikan korkeakoulu | Bachelor's thesis
  • Sample Alignment for Diffuse Reflectance Measurements
    (2014-12-15) Kivi, Miikka
     Sähkötekniikan korkeakoulu | Master's thesis
    Accurate measurements of material reflectance rely heavily on the accurate placement and alignment of the sample. Majority of currently existing sample alignment methods utilize an alignment laser in some way, but the roughness of diffusely reflecting surfaces prevent the use of such methods directly with that kind of sample, and a separate reflective piece must often be used. In this master’s thesis, a new camera based sample alignment method designed for diffuse reflectance measurements is introduced. The method described in this work consists of a set of procedures for detecting the sample’s linear and angular displacement from a reference point in the goniometric system. The method relies on detection of rigid features in the scene. Sample edges are observed to detect rotational angle of the sample, and sample holder corners are observed to calculate the center of rotation. The performance of this method is studied in an effort to learn about the various sources of error. Cases that were studied include scene lighting conditions and reliability of the different parts of the detection algorithm. The testing was done on modest equipment and an overall accuracy of 230µm for center localization and 0.01° for rotational angle was achieved. The system is, however, inherently limited by the physical characteristics of the camera, as well as the size and distance to the sample. On the other hand, this also means that the alignment method is versatile and scalable, as the details of the detection algorithm can be modified to meet the requirements of a given project, and higher quality cameras can be purchased.