Versatile, fast, non-contact and accurate characterization of form and mid-spatial errors on large freeform surfaces

The dimensions of optics for scientific and industrial applications are growing. Moreover, aspherical and freeform surface shapes are increasingly applied, both in centred and off-axis apertures. Measuring these optics in conventional interferometric setups is challenging: tall interferometric test towers are used and for cases other than off-axis parabolas, a CGH has to be used and setup size grows with the off-axis distance and radius of curvature. Measuring large convex surfaces is particularly difficult. High point density is necessary for measuring mid-spatial frequencies, which rules out coordinate measuring machines. Measurements of theses surfaces using the DUI NMF range of cylindrical non-contact measurement machines will be demonstrated, showing flexibility, high point density, short measurement times and no setup cost.