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251st PTB Seminar "New Trends in Optical Flatness Measurement Techniques"


On the occasion of a PTB seminar in October 2009 new trends in optical flatness measurement techniques were presented and discussed. Colleagues from universities, research centers, national metrology institutes and industry reported on their current approaches.

It was demonstrated that linear scanning deflectometry at almost perpendicular incidence of light on the specimen is capable to measure optical surfaces with an accuracy in the sub-nanometer range and a lateral resolution of a few millimeters. These techniques are, e.g., applied for the characterization of ultra-precise synchrotron optics. Deflectometry is also applied by using a broad spectrum of incidence angles thereby reaching height resolutions in the nanometer range.

For almost perpendicular incidence of light, methods from interferometry also yield accuracies in the sub-nanometer range. Some of these methods enable at the same time high lateral resolution of some ten micrometers, as for example the Traceable-Multi-Sensor method of PTB. In contrast to conventional interferometry, this method does not rely on a reference surface which is an important advantage. Similarly to deflectometry, some methods of interferometry are employed with non-perpendicular incidence of light. These methods are applied to also measure technical surfaces at a somewhat reduced accuracy.

The seminar was considered to be a valuable forum for optical measurement techniques and it was suggested that similar events be organized again in future.



M. Schulz, AG 4.21
C. Elster, AG 8.42

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