18 June 2007 Measurement errors of mirrorlike, tilted objects in white light interferometry
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White-light interferometry is an absolute 3D-measurement technique, used for the inspection of structured silicon and other materials with high quality surfaces. In this technique, each pixel of the camera detects a separate interference signal, which correlates with the height of the corresponding object point. Different signal processing algorithms are used, which extract the height from the interference signal by using the coherence or the phase information of the signal. However, measurement errors can occur if there are chromatic aberrations in the interferometer system. Then the phase information correlates with the height information in an unexpected manner and there are often disturbing 2&pgr; phase jumps in the numerical evaluation process, although the topography of the object is continuous and a light source with a short coherence length is used. We examined a Mirau type white-light interferometer with chromatic aberrations and explain how mirrorlike, tilted objects cause a correlation of the phase and the height information in each interference signal. We also show that this measurement error depends on both the slope of the object point and its field position. A comparison of measurements and a simulation, which shows the described correlation effect, is given.
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Reinhard Berger, Reinhard Berger, Thomas Sure, Thomas Sure, Wolfgang Osten, Wolfgang Osten, } "Measurement errors of mirrorlike, tilted objects in white light interferometry", Proc. SPIE 6616, Optical Measurement Systems for Industrial Inspection V, 66162E (18 June 2007); doi: 10.1117/12.726142; https://doi.org/10.1117/12.726142

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