OPL-3D: A novel, portable optical digitizer for fast acquisition of free-form surfaces

The paper presents OPL-3D, a novel, powerful three-dimensional optical digitizer based on structured, incoherent light illumination, developed in our laboratory for noncontact acquisition and digitization of free forms in space. The system exploits active stereovision using time multiplexing based on a combination of Gray code and phase-shifting techniques. The system has been specifically designed for applications to reverse engineering and rapid prototyping of free-form shapes, as well as for applications to measurement and quality control. Suitable estimation of the measurement parameters, as well as specifically developed two-dimensional image analysis, allows us to retrieve very dense point clouds in a few seconds. Special care has been devoted to the implementation of easy-to-use fast calibration procedures, and to enhancement of the flexibility of the system to the measuring problem as well as its portability. A kernel for elaboration of the views and for their alignment is provided. OPL-3D exhibits low-measurement uncertainty (120 μm) over large measurement areas $\text{(450\hspace{0.17em}}\mathrm{mm}\text{×340\hspace{0.17em}}\mathrm{mm}\mathrm{),}$ linearly scalable in the case of smaller areas. The output formats of the data files are fully compatible with the formats commonly used by elaboration environments dedicated to the production of polygonal models and to computer-aided design models of the shapes. The performance of OPL-3D has been tested in a number of applications, ranging from industry to biomedicine and virtual reality.