Comparative study of different digitization techniques and their accuracy

The various manufacturers of digitization systems speak of the effectiveness and accuracy of their tools under optimal conditions, but actual experimentation with simple or complex objects and different materials yields results that on occasions refute the effectiveness of those systems. In order to help choose a digitization system on the basis of its accuracy and the quality of the distribution of points and triangular meshes, in the field of reverse engineering, we compared five digitization techniques (three versions of the laser scanner, a fringe projection version and an X-ray version): (1) an ordered point cloud obtained with a laser incorporated in a CMM, (2) a disordered point cloud obtained with a manual laser the position of which is determined with a Krypton Camera, (3) an Exascan manual laser with targets, (4) an ordered point cloud obtained by high precision Computerized Tomography (CT) and (5) an Atos fringe projection scanner with targets. Each of the three calibrated pieces (a sphere, a cylinder and a gauge block) was measured five times by the five digitization systems to confirm the accuracy of the measurement. A comparison was also made of the meshes generated by the five software packages (Focus-Inspection, Metris, VxScan, Mimics and Atos) of the five digitization systems for the three calibrated pieces and two more complex pieces (a bone and an automobile window winder pulley) to determine meshing quality. Finally, all the pieces were meshed by triangulation in the Catia V5 DSE (Digitized Shape Editor) module in order to test the quality of the points distribution.

Research highlights
► Expanded uncertainty (mm): MMC = 0.040, Camera = 0.104, Exascan = 0.230, CT = 0.295 and Atos = 0.025.
► The digitization system that produces the least noise is Atos, followed by CMM laser scan.
► The distribution of the mesh in the digitization is better in CT.
► The system with greater accuracy is Atos, and the CT system digitizes all parts of the pieces.