info:eu-repo/semantics/doctoralThesis
NEW OPTICAL SETUPS FOCUSED ON THE MEASUREMENT OF THE SHAPE AND DISPLACEMENT FIELDS
Autor
Víctor Hugo Flores Muñoz
Institución
Resumen
"This thesis presents the advances and achievements obtained during the PhD work.
The focus of the work was to propose and create new implementations of well-known 3D shape recovery techniques such as Stereo Vision (SV), Digital Image Correlation (DIC) and Fringe Projection (FP) along with their algorithms. Since all these techniques are based on the capture of an image by a camera, a calibration process is needed in order to create a relationship between the image coordinates and the real world coordinates.
In this thesis, the two utilized calibration methods are presented, Direct Linear Transformation (DLT) and Tsai's Method. Once the system is calibrated, it is possible to guarantee that the performed measurements correspond to a real coordinate system. The main advantage of the optical metrology techniques is that they are contact-free so there is no alteration of the sample due to the measurement device. From there several applications come to mind: measurement of displacement fields, deformation, spatial location and topography.
The proposals of this thesis are aimed to improve and simplify these tasks using the techniques mentioned before. DIC is utilized to measure in-plane deformations using one camera, while a Stereo-DIC system is able to obtain the 3D shape and displacement fields of a sample, but its main disadvantage is the need of twin cameras in order to obtain a good correlation. In order to solve that problem we propose two possible solutions.
The first consist of the use of a biprism to create the two perspectives of a scene using a single camera, with this change, we create an emulated SV system with twin cameras, since we utilized the same camera for both perspectives; the only inconvenient is the distortion induced by the biprism but this can be fixed by calibration, as it is presented in this thesis. The second improvement is the use of FP with DIC because it has great sensibility to out-ofplane displacement, so when using both techniques together is possible to calculate 3D displacements fields of a deformed sample. If the area of interest of a sample is not a full-field view, but instead is only a point, we introduce a tracking system based in the detection of centroids of reflective markers which are utilized as points of interest to be located in a real world coordinate system."
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