On-machine separation and compensation of target mirror’s surface shape errors in multidimensional interferometric measurement system

In multi-dimensional nanopositioning and nanomeasuring devices, interference measurement is widely used. The three-dimensional (3D) target mirror serves as the spatial reference plane to achieve multidimensional interference measurements. However, the surface shape errors of the target mirror are superimposed on the geometric dimensions of the measured workpiece, which limits the system's overall measurement accuracy. This paper proposes a method for on-machine separation and compensation of the target mirror's surface shape errors based on the micro-nano-coordinate measuring machine (MNCMM) that employs interference measurement. This method provides the model for the separation and compensation of the surface shape errors. The MNCMM employs a home-made resonant probe and a reference flat crystal to achieve the separation experiment. Subsequently, an interpolation algorithm is used to compensate for the surface shape errors at any point in space according to the compensation model. By comparing the flatness measurement results of a standard flat crystal with a flatness of 50 nm before and after compensation, the flatness is reduced from 175 to 77 nm. It demonstrates the reliability of the method. This method can be widely applied to on-machine compensation for surface shape errors in multidimensional interference measurement systems.