The task of this Joint Research Project is to improve the form metrology urgently needed for modern optical surface production. The surfaces of optical systems have very particular properties as they are polished and consequently very smooth. These surfaces can be flat, spherical, aspherical or even a free-form type. Mainly the measurement uncertainty and also the lateral resolution will be improved.



By improving flatness metrology, uncertainties at the (sub-)nanometre level will be reached for surfaces of some hundred millimetres. Additionally, the lateral resolution will be improved to tens of micrometres. This is for example important for reference surfaces of high end metrology setups.

For aspheres and free-form surfaces, a special interferometer will be realized applying a combination of the so called Tilted Wave Interferometer and the Traceable Multi Sensor technique. For this, the accuracy will be analysed and optimised by thorough mathematical modelling. General guidelines for improving interferometric measurement concepts with special focus on error separation techniques will be an additional result. Parallel, form measurement accuracy in tactile scanning methods will be investigated and a task-dependent uncertainty evaluation will be performed by numerical simulation using the virtual CMM concept.

These two fundamentally different measuring methods will be compared. Guidelines of their strengths and weaknesses in relation to the specific industrial applications will be established.



Demonstrator setups and calibration standards will be developed and new algorithms for the handling of a large number of data points to produce a comprehensive characterisation of the measured objects will be evaluated.

This project brings together the experts from different communities, including optical (imaging) metrology and (single point) coordinate measuring technique. The interdisciplinary research will enable to resolve error influences of the particular techniques and thus help to improve the measurement accuracy. The expertise to conduct this project exists in Europe, but not in the industry and not in any single NMI alone. The joint project will facilitate a significant advancement in form metrology of optical surfaces.