An established measurement system in asphere production, which is a promising approach in high precision freeform manufacturing as-well, is given by a scanning point interferometer based on a multi-wavelength approach. The scanning principle enables for a great flexibility, reduces setup time and costs, and has almost no limitations in spherical departure. Due to the absolute measurement capability, the utilized multi-wavelength approach is beneficial for segmented and interrupted surfaces, which are common apertures of modern application’s optical elements. A new metrology system has recently been developed, based on the before-mentioned multi-wavelength scanning approach, to allow for large surface measurements of up to 850 mm in diameter (part size up to 1 m) with highest accuracy of down to 150 nm peak-to-valley on the max. aperture. The combination of an optimized metrology frame setup with a unique anti-vibration system improves long-term stability, enabling a 3σ RMSi repeatability on a 400 mm surface over 8 hours without recalibration of less than 1 nm.
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