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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Image-based 3D metrology of non-collaborative surfaces

Karami, Ali 11 April 2023 (has links)
Image-based 3D reconstruction has been employed in industrial metrology for micro measurements and quality control purposes. However, generating a highly-detailed and reliable 3D reconstruction of non-collaborative surfaces (textureless, shiny, and transparent) is still an open issue. This thesis presents various methodologies to successfully generate a highly-detailed and reliable 3D reconstruction of non-collaborative objects using the proposed photometric stereo image acquisition system. The first proposed method employs geometric construction to integrate photogrammetry and photometric stereo in order to overcome each technique's limitations and to leverage each technique's strengths in order to reconstruct an accurate and high-resolution topography of non-collaborative surfaces. This method uses accurate photogrammetric 3D measurements to rectify the global shape deviation of photometric stereo meanwhile uses photometric stereo to recover the high detailed topography of the object. The second method combines the high spatial frequencies of photometric stereo depth map with the low frequencies of photogrammetric depth map in frequency domain to produce accurate low frequencies while retaining high frequencies. For the third approach, we utilize light directionality to improve texture quality by leveraging shade and shadow phenomena using the proposed image-capturing system that employs several light sources for highlighting roughness and microstructures on the surface. And finally, we present two methods that effectively orient images by leveraging the low-contrast textures highlighted on object surfaces (roughness and 3D microstructures) using proper lighting system. Various objects with different surface characteristics including textureless, reflective, and transparent are used to evaluate different proposed approaches. To assess the accuracy of each approach, a comprehensive comparison between reference data and generated 3D points is provided.
2

Inspection dimensionnelle - Une approche multi-capteurs pour la vérification des spécifications géométriques / Dimensional inspection - Multi-sensor approach for geometrical specification verification

Sadaoui, Sif Eddine 09 July 2019 (has links)
L'inspection dimensionnelle, qui consiste à vérifier la conformité géométrique des pièces vis-à-vis des spécifications, est une étape essentielle dans le cycle de vie des produits. Elle s’appuie de plus en plus sur la mesure multi-capteurs qui permet un gain de temps certain. Néanmoins, le gain de temps n'a de sens que si la qualité des résultats respecte le besoin métrologique. En effet, la mise en œuvre combinée de capteurs de technologie et de caractéristiques différentes engendre un certain nombre de problèmes qui affectent directement la qualité de la mesure. Dans ce travail, une approche d'inspection automatique utilisant un scanner combinant un capteur à contact avec un capteur laser-plan monté sur une MMT est proposée. Cette approche cherche à utiliser au mieux les capacités de chacun des capteurs, en privilégiant la mesure avec le capteur laser-plan dès lors que la qualité requise est obtenue pour un gain de temps. L’approche consiste à définir une séquence d’opérations de mesure de surfaces qui portent des spécifications, appelées entités d’inspection.Partant d'un ensemble d'orientations du scanner, la séquence d'opérations est établie pour chaque orientation par évaluation de l'aptitude du capteur laser puis celle du palpeur à mesurer les surfaces avec la qualité nécessaire. La gamme d'inspection est complétée par la définition optimale de la trajectoire du capteur laser-plan et celle du palpeur pour chaque orientation. La trajectoire finale exécutée sur machine MMT est obtenue par transformation et assemblage des deux trajectoires. À l'issue de l'exécution, la mesure avec les deux capteurs conduit à deux nuages de points hétérogènes qu’il convient de traiter avant l’évaluation finale des spécifications. / Dimensional inspection, which consists in verifying the geometric conformity of parts in terms of specifications, is an essential step in the product life cycle. Recently, dimensional inspection has been increasingly based on multi-sensor measurement that allows a significant time saving. However, time saving is only meaningful if the quality of the results respects the metrological requirements. Indeed, the combined use of sensors of different technologies and characteristics generates issues that affect the measurement quality. In this work, an automatic inspection approach using a scanner combining a contact sensor with a laser-plane sensor mounted on a CMM is proposed. This approach aims to best use the abilities of each of the sensors, giving priority to measurement with the laser-plan sensor as soon as the required quality is obtained for time saving. The approach consists in defining a sequence of surface measurement operations that have specifications, called inspection features.Starting from a set of scanner orientations, the sequence of operations is established for each orientation by evaluating the ability of the laser sensor and then that of the probe to measure surfaces with the required quality. The inspection plan is completed by the optimal definition of the laser-plane sensor path and the probe path for each orientation. The final path executed on the CMM machine is obtained by transforming and assembling the two paths. At the end of the execution, the measurement with the two sensors leads to two heterogeneous point clouds that must be processed before the final evaluation of the specifications.

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