Knowing the limits: surface deviation in the mid-spatial-frequency range by deflectometric measurements

Deflectometric measurements using V-SPOT technology has been proven to achieve accurate surface profiles for aspheres at moderate cost and low preparation effort. In order to extend the resolution limit, the optical and mechanical device has been improved to provide on the one side topography information in the slope domain at high accuracy (< 5 μrad) and an improved lateral resolution (< 0,2 mm) to cover surface profile errors in the mid-spatial-frequency range from 1 to 10 mm-1. Within this publication we are providing the experimental setup and the measurement procedures to achieve production relevant information about the surface quality. Slope deviations of aspheric samples (glass and metal) are analyzed in angular spectral components and the surface profile is compared with interferometric data to proof accuracy and lateral resolution of our device. As final conclusion we outlook for further improvements of the proposed device to allow full control of form deviation and mid-spatial frequency errors.