Forensic graphic research using Conoscopic Holography technology
A scientific contribution to the interpretation of superposed graphic elements, i.e. micro residues of toner and handwriting tracks.
The investigation of the so-called "determination of the application history" between graphic features, both homogeneous and heterogeneous, is an extremely delicate matter and partly still debated in the scientific and forensic community. On this specific subject, a decades-long research in close collaboration with the Laboratory of the Faculty of Engineering, University of Rome, 3D analysis performed by Conoscopic Holography (Laser profilometry, better known as "interferential method") and, subsequently, through the use of opto-electronic microscopy.
Preliminary Study on the 3D Digitization of Millimeter Scale Products by Means of Photogrammetry
Photogrammetry is a passive 3D digitization technique, mainly oriented to large sized objects, since its origins are in architectural and civil engineering. With the continues development of digital imaging hardware and software, photogrammetric applications are involving smaller and smaller fields of view, with some critical aspects such as the depth of field getting narrower. In this conditions the lack of focus becomes important and affects heavily the possibility of accurately calibrate cameras. Bi-dimensional calibration patterns are affected by this problem when the camera principal axis has an angle with the pattern plane higher than a critical value. Moreover, the accuracy of the pattern, in terms of both shape and 3D positions of the targets, becomes critical decreasing the size of the pattern. In this paper the authors address these problems through a comparison of several calibration patterns included into the open source computer vision software library called OpenCV. 3D digitization of a small object is presented to test the best resulting calibration, using a consumer reflex camera equipped with macro lens and extension tube.
Multistack Close Range Photogrammetry for Low Cost Submillimeter Metrology
Considerable research effort has been focused on evaluating the accuracy of meso- and macroscale digital close range photogrammetry. However, evaluations of accuracy and applications in the submillimeter scale are rare. In this paper the authors propose the development of a three-dimensional (3D) photogrammetric scanner, based on macrolens cameras, able to reconstruct the three-dimensional surface topography of objects with submillimeter features. The system exploits multifocal image composition and has been designed for installation on all types of Numerical Controlled or Robotic systems. The approach is exploitable for digitizing submillimeter features at mesoscale as well as macroscale objects.