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Influence of the pixel size of the camera on 3D-measurements with fringe projection

: Brakhage, P.; Heinze, M.; Notni, G.; Kowarschik, R.

Osten, W. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Optical measurement systems for industrial inspection III : 23 - 26 June 2003, Munich, Germany
Bellingham/Wash.: SPIE, 2003 (SPIE Proceedings Series 5144)
ISBN: 0-8194-5014-6
Conference "Optical Measurement Systems for Industrial Inspection" <2003, München>
Conference Paper
Fraunhofer IOF ()
3D-measurement; fringe projection; error; pixel size; stage

The projection of fringes onto objects in some 3D-measurement systems has two main reasons: First, to solve the problem of homologous points for the camera images and second, to create a continuous metric in the object space. The second effect leads to the well-known sub-pixeling accuracy. The accuracy of such measurement systems is not limited the pixel size of the camera. But, depending on some surface-discontinuities (i.e. steps) and the viewing direction of camera, this principle is not valid for a certain number of pixels. When a camera is viewing " downstairs", these pi? get the phase information from the upper and the lower step. By using our very precise measurement system kolibri TM his effect is evident on most complex technical surfaces and is clearly distinguished from statistical noise. We disc the different circumstances of this effect and give a well-adapted algorithm for eliminating these errors.