Absolute form-interferometry for aspheres and freeform surfaces (AbsoForm)

The new DFG-research project “Absolute form-interferometry for aspheres and freeform surfaces (AbsoForm)” in cooperation with Institute of Technical Optics (ITO) of the University of Stuttgart, PTB WG 8.42, PTB WG 5.56 and PTB WG 4.24 is set to start on January 1st 2023 for a three-year funding period. The accurate measurement of aspheres or freeform surfaces is challenging. The so-called "reference-free" form interferometry is a measurement technique where no physical reference surface exists. It is far more demanding than classical reference surface-based form measurement techniques as used, e.g., for flatness or sphere measurements. While it has many advantages, the absolute form accuracy reached by “reference-free” form interferometry is still limited. In this project the tilted-wave interferometer (TWI) is considered which is a promising “reference-free” technique for optical form measurement. The goal is to explore if and how additional absolute methods can be used to improve the accuracy of the absolute form measurements of such measurement systems. Virtual modeling of the experimental scenarios to be considered plays a crucial role to find the optimal methods that are finally realized in the experimental setup and verified by means of special test objects. More information can be found here.