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Fast error simulation of optical 3D measurements at translucent objects

: Lutzke, Peter; Kühmstedt, Peter; Notni, Gunther


Schmit, J. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Interferometry XVI: Techniques and Analysis : 12.-16.8.2012, San Diego, CA, USA
Bellingham, WA: SPIE, 2012 (SPIE Proceedings Series 8493)
ISBN: 978-0-8194-9210-4
Paper 84930U
Conference "Interferometry" <16, 2012, San Diego/Calif.>
Fraunhofer IOF ()
optical; 3D measurement; translucent; error simulation; raytracing

The scan results of optical 3D measurement at translucent objects deviate from the real objects surface. This error is caused by the fact that light is scattered in the objetcs volume and is not exclusively reflected at its surface. A few approaches were made to separate the surface reflected light from the volume scattered. For smooth objects the surface reflected light is dominantly concentrated in specular direction and could only be observed from a point in this direction. Thus the separation either leads to measurement results only creating data for near specular directions or provides data from not well separated areas.
To ensure the flexibility and precision of optical 3D measurement systems for translucent materials it is necessary to enhance the understanding of the error forming process. For this purpose a technique for simulating the 3D measurement at translucent objects is presented. A simple error model is shortly outlined and extended to an efficient simulation environment based upon ordinary raytracing methods. In comparison the results of a Monte-Carlo simulation are presented. Only a few material and object parameters are needed for the raytracing simulation approach. The attempt of in-system collection of these material and object specific parameters is illustrated. The main concept of developing an error-compensation method based on the simulation environment and the collected parameters is described. The complete procedure is using both, the surface reflected and the volume scattered light for further processing.