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12 October 2010 Determining the chronological order of crossing lines using 3D imaging techniques
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The chronological order of creation of crossing lines scratched into a copper surface was determined using 3D profiles measured with SWLI and CM. As the methods used are based only on the deformations of the surface and since the imaging techniques can be used for different materials, the proposed methods are potentially effective also on other materials. Determining the chronological order of orthogonally crossing lines is studied in forensic science. The order of creation of such lines allows in some cases determination of the history of an object without comparing it to other objects.. Methods based on two dimensional (2D) imaging have been used for this task, but such methods are ineffective if the lines are made with a similar tool. We apply Scanning White Light Interferometry (SWLI) and Confocal Microscopy (CM) to study crossing lines on a copper surface scratched with a scratching device. Both SWLI and CM quantitatively measure the 3D surface profiles with sufficient accuracy for forensic applications. 3D image processing allows removing unimportant features, such as surface form and roughness, as well as measurement noise from the measured profiles. Separating inherent features in the crossing area, from other surface characteristics allows one to determine the sequence of creation of the lines even on a rough and wavy surface.
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V. Heikkinen, C. Barbeau, I. Kassamakov, S. Lehto, T. Reinikainen, J. Aaltonen, and E. Hæggström "Determining the chronological order of crossing lines using 3D imaging techniques", Proc. SPIE 7838, Optics and Photonics for Counterterrorism and Crime Fighting VI and Optical Materials in Defence Systems Technology VII, 78380T (12 October 2010);

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