Browsing by Author "Vargas, R."

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Camera-projector calibration methods with compensation of geometric distortions in fringe projection profilometry: A comparative study
(Sociedad Espanola de Optica, 2018) Vargas, R.; Marrugo Hernández, Andrés Guillermo; Pineda, J.; Meneses, J.; Romero, L.A.
The calibration methods most used in fringe projection profilometry are based on models of least squares adjustment and stereo vision techniques. However, the geometric distortions of the projector and camera lenses introduce imprecision in certain regions of the 3D reconstruction. In this paper, we perform a comparative study between the second order polynomial adjustment method and the stereo calibration method applying lens distortion compensation. The experimental results show that in the stereo calibration the incidence of the distortions in the 3D reconstruction is significant. In contrast, in the proposed polynomial calibration, reconstruction errors are associated with the calibrated volume, typically low within the calibration volume. © Sociedad Española de óptica.Los métodos de calibración más usados en perfilometría por proyección de franjas están basados en modelos de ajustes por mínimos cuadrados y técnicas de visión estéreo. Sin embargo, las distorsiones geométricas de los lentes del proyector y de la cámara introducen imprecisión en ciertas regiones de la reconstrucción 3D. En este trabajo realizamos un estudio comparativo entre el método de ajuste polinomial de segundo orden y el método de calibración estéreo aplicando compensación de distorsiones. Los resultados experimentales muestran que en la calibración estéreo la incidencia de las distorsiones en la reconstrucción 3D es significativa. En cambio, en la calibración polinomial propuesta, los errores de reconstrucción están asociados al volumen calibrado. © Sociedad Española de óptica.
Fringe quality map for fringe projection profilometry in LabVIEW
(Sociedad Espanola de Optica, 2018) Pineda, J.; Vargas, R.; Romero, L.A.; Meneses, J.; Marrugo Hernández, Andrés Guillermo
The phase retrieval process is mainly affected by local shadows, irregular surface brightness and fringe discontinuities. To overcome these problems, image-processing strategies are carried out such as binary masks, interpolation techniques, and filtering. Similarly, many unwrapping algorithms have been developed to handle phase unwrapping errors in two-dimensional regions. The presence of error-prone areas can be visualized during the acquisition stage avoiding the use of image processing strategies and sophisticated phase unwrapping algorithms, which in many cases represent high computational costs and long execution times. To help overcome these problems, we propose a Fringe Quality Map based on a phase residue analysis to estimate error-prone areas during acquisition. The software was fully implemented in LabVIEW, and we provide the software as supplementary material. Experimental results demonstrate that the proposed method estimates areas with poor contrast, which lead to unwrapping errors, as well as phase errors in a more complex 3D shape. © Sociedad Española de Óptica.