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Hier finden Sie wissenschaftliche Publikationen aus den FraunhoferInstituten. Measurement of optical freeform surfaces with fringe projection
 Huang, P.S. ; Society of PhotoOptical Instrumentation Engineers SPIE, Bellingham/Wash.: Two and ThreeDimensional Methods for Inspection and Metrology VI : 1011 August 2008, San Diego, California, USA Bellingham, WA: SPIE, 2008 (SPIE Proceedings Series 7066) ISBN: 9780819472861 ISBN: 0819472867 ISSN: 0277786X Paper 706605 
 Conference "Two and ThreeDimensional Methods for Inspection and Metrology" <6, 2008, San Diego/Calif.> 

 English 
 Conference Paper 
 Fraunhofer IOF () 
 distortion correction; optical free form surface; fringe projection; 3D measurement; wavelet filter 
Abstract
Complex optical freeform surfaces are very common optical components for the use in modern illumination and lighting systems. In this paper we describe the use of high accurate fringe projection for the measurement of optical freeform surfaces with a resolution in the subµmrange. To achieve the required high accuracy the method of uniform measurement scale in fringe projection, proposed by the authors some years ago, is used 1. The basic idea is the exclusive use of phase values for the 3Ddata calculation. Because of that, the accuracy of such a measurement setup is mainly restricted by the lens distortion of the projection system. In order to compensate this we introduce a new method for a 3Dcorrection of the distortion of the projection lens taking into account spatial dependent distortion parameters. The distortion of the projection lens is determined by a measurement of reference planes which will be used to calculate a 3Dcorrection matrix. This matrix covers the whole measurement volume (lateral and vertical) and contains the determined distortion of the projection system. As a result the accuracy of the correction improved the absolute accuracy by a factor of four. Furthermore, the data quality is enhanced by a further factor of two using a wavelet filtering for noise reduction. The realized measurement setup has a measurement field of up to 180 mm in diameter. It will be shown that the measurement of optical free form surfaces with medium range accuracy will be possible where we have reached a limit of 0.5 µm RMS error in a measuring field of 70 mm diameter.