Measuring the 3D shape of semi-transparent surfaces with projector-camera 3D scanners is a difficult task because these surfaces weakly reflect light in a diffuse manner, and transmit a large part of the incident light. The task is even harder in the presence of participating background surfaces. The two methods proposed in this paper use sinusoidal patterns, each with a frequency chosen in the frequency range allowed by the projection optics of the projector-camera system. They differ in the way in which the camera-projector correspondence map is established, as well as in the number of patterns and the processing time required. The first method utilizes the discrete Fourier transform, performed on the intensity signal measured at a camera pixel, to inventory projector columns illuminating directly and indirectly the scene point imaged by that pixel. The second method goes beyond discrete Fourier transform and achieves the same goal by fitting a proposed analytical model to the measured intensity signal. Once the one (camera pixel) to many (projector columns) correspondence is established, a surface continuity constraint is applied to extract the one to one correspondence map linked to the semi-transparent surface. This map is used to determine the 3D point cloud of the surface by triangulation. Experimental results demonstrate the performance (accuracy, reliability) achieved by the proposed methods.

Phase-shift profilometry (PSP) is a technique for acquiring non-contact three-dimensional measurements using a projector and a camera. The technique can be used to measure 3D surfaces with high accuracy. However, it can be sensitive to motion because phase images are sequentially captured. We propose a new technique that uses residual phase errors to minimize the influence of motion on the recovered phases (and 3D points). The method minimizes residual phase error with respect to apparent phase offset variations caused by motion. Furthermore, a total variation scheme is used to minimize spatial variations of apparent phase offset variations. We demonstrate the method with different moving objects, and we also study the effect of the magnitude of the motion on the accuracy of the recovered phases. Visual artefacts as well as accuracy loss associated with motion are found to be significantly decreased.

ABSTRACT This paper presents three process assessments that took place in Luxembourg in 2012. It depicts the TIPA® process assessment framework and reports on its usage in three different partially outsourced contexts: a telecommunication service provider, a European institution, and a bank. Finally, this paper presents the lessons learned from these experimentations and some improvement perspectives. Copyright © 2014 John Wiley & Sons, Ltd.

This paper describes an environment to automatically or semi-automatically compute the precise mapping between a set of 2D images and a triangulated 3D model built from high-resolution 3D range data. This environment is part of our Atelier3D framework for the modeling, visualization and analysis of large sensor-based datasets. This work was done to initially support three cultural heritage application projects: the modeling of the Grotta dei Cervi in Italy, of the Erechtheion in Athens, Greece, and of Leonardo's Mona Lisa. The proposed method combines image-based registration, feature matching, robust estimation techniques and advanced multi-resolution rendering with a powerful user interface.