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Ein hybrides Meßsystem zur Kalibrierung von Strichteilungen / O. Freide (2000)

Public Titre : Ein hybrides Meßsystem zur Kalibrierung von Strichteilungen Titre original : [Un système de mesure hybride pour l'étalonnage de division de traits] Type de document : Thèse/HDR Auteurs : O. Freide, Auteur Mention d'édition : 1 Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2000 Collection : DGK - C Sous-collection : Dissertationen num. 521 Importance : 70 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-9560-1 Langues : Allemand (ger) Descripteur : [Vedettes matières IGN] Acquisition d'image(s) et de donnée(s) [Termes IGN] chambre DTC [Termes IGN] détection de contours [Termes IGN] erreur systématique [Termes IGN] étalonnage d'instrument [Termes IGN] étalonnage de capteur (imagerie) [Termes IGN] filtrage du bruit [Termes IGN] filtre de Canny [Termes IGN] filtre de Deriche [Termes IGN] interféromètre au laser [Termes IGN] pixel [Termes IGN] précision millimétrique Index. décimale : 35.11 Géométrie et qualité des prises de vues Résumé : (Auteur) This thesis presents a new system for the calibration of scales of random code and length. For this purpose, a laser interferometer and a CCD-array camera are combined to form a hybrid measuring system with an accuracy better than ±5 µm. Laserbeam and longitudinal axis of the scale are arranged colinearly. The camera is positioned perpendicular to this axis and observes a 1 cm2 large window of the scale. As the distance between the two edges of a line of a bar code scale may be wider than the size of the window, they are observed separately one after the other. The center of a line, used by definition for the calibration, can be derived from the two images. Measurement is possible under both static and dynamic conditions. The difference is that, as both gauges are read out simultaneously, the scale stands still or moves in longitudinal direction. For static measurements, the edge positions are approximately adjusted by means of their nominal value, which automatically reduces the number of observations to a minimum. Of course, dynamic measurement is faster, but the technical demands are higher due to the steady read out of both gauges. In order to reduce the amount of data, only those images with at least one visible edge of the bar code are stored. Therefore, after grabbing, each image is immediately scanned for edges by a simple but imprecise method. The precise determination of the distance between the edge and the origin of the image coordinate system is done off-line after the measurement, using their entire width in the radiometrically corrected image. The distance between the edge and the origin of the coordinate system is transformed by a previously determined scale factor into the metric system of the laser. After meteorological correction, the laser value determines the shift relative to the arbitrarily chosen start position yielding the geometric relation between the images. After describing the physical principles and their technical realisation, the errors of both sensors are presented in a systematic manner to give an estimate of the accuracy of the system. Especially for the camera, practical research results concerning lens distortion, system noise, sensor sensitivity, and lighting effects are presented. To extract the edges in an image reliably and with sub-pixel accuracy, different algorithms for edge detection are explained in detail and compared with regard to their performance. This includes the Difference-of-Boxes, Laplacian-of-Gaussian, Difference-of-Gaussians and the shen, canny, deriche filter group. With these algorithms, sub-pixel accuracy can already be achieved by the proposed evaluation stra-tegy in the twodimensional image. Special sub-pixel precise algorithms are only summarized because they merely reduce noise as demonstrated by the “STEGER-Filter”. Finally, the results of the practical application of the measurement system with respect to the calibration of Invar-Barcode staffs are presented. Numéro de notice : 27822 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Thèse étrangère Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=56446

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27822-01	35.11	Livre	Centre de documentation	En réserve M-103	Disponible