Contents I. INTRODUCTION
In last decade optical 3-D shape measurement systems have been gaining an increasing importance in numerous fields of activities. In fact, we have witnessed their widespread from the first applications to reverse engineering problems requiring canonical surfaces to be reconstructed, to other areas as diverse as industrial, medical, space exploration and cultural heritage to name a few. The industry is today very attracted by the possibilities given by the inspection of products performed by the optical measurement systems [1]–[3], that capture shape data from surfaces in the form of a cloud of points. Traditional areas where they have been successful are the contact-less inspection of manufactured goods such as automobiles, semiconductor chips, food and pharmaceuticals, with the goal to reduce production costs due to manual labour or defective parts and ensure consistent product quality. Then optical 3-D shape measurement systems can automate manufacturing processes by controlling manufacturing equipment such as industrial robotic arms. They may also allow manufacturers to cut down the spending on defective goods since they are useful to check goods (silicon wafer, semiconductor chips or the surface of painted vehicles) for defects one by one with the aim to correct the parameters of the industrial process as soon as a defect is found. On the other hand the current tendency evolves towards the use of scanners in the reconstruction of human faces, sculptures, paintings, pre-historical footprints, and so on. The key to their success can be found in their distinctive attributes. In particular flexibility, reliability, higher operating speeds, consistency and objectivity have made them competitive with respect to traditional measurement systems.
