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15 December 1992 Moire based optical surface profiler for the minting industry
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An Optical Surface Profiler (OSP130) has been developed for the metrology of master tooling used in the coin stamping process. The OSP130 measure, in a non-contacting manner, the surface relief of tools ranging in diameter from 10 mm to 300 mm. Rapid measurements are performed simultaneously on a large grid of equispaced points across the surface of the tool. From the relief data, many parameters such as the location of high and low features, volume of impression, background curvatures and various diameters can be quickly evaluated. The technique used is phase-shifting moire profilometry. A white light projector illuminates a periodic transmission grating which is then imaged onto the object surface. The light pattern on the object is viewed by a high resolution TV camera connected to a computer. The grating is shifted under computer control to a number of positions and corresponding intensity images of the deformed pattern on the object surface are stored in the computer. From the intensity images a phase map, representing the deformation of the periodic grating by the surface relief, is evaluated and compared with an undeformed pattern. This results in an accurate contour map of the surface relief with an uncertainty less than 1% of the relief excursion on the object. Details of the instrument and its use at the Royal Australian Mint are presented.
© (1992) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Bozenko F. Oreb, Kieran G. Larkin, Philip S. Fairman, and M. Ghaffari "Moire based optical surface profiler for the minting industry", Proc. SPIE 1776, Interferometry: Surface Characterization and Testing, (15 December 1992);

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