Setup of a new form measurement system for flat and slightly curved optics with diameters up to 1.5 metres

Abstract

Large optics with diameters of up to 1.5 m are being used more and more in industry and science. Flatness measurements of these optics are needed with uncertainties down to a few ten nanometres. For slightly curved specimens with radii of curvature down to 10 m uncertainties in the sub-micrometre range are required. We are currently building a new form measurement system which aims to fulfil these requirements. It will be set up in 2020 and the first measurements will be carried out in 2021. The setup can be operated with different sensor heads which use deflectometric- or interferometricbased methods. We plan, amongst other things, to use Fizeau interferometers with aperture sizes of 10 mm, 100 mm and 150 mm. The mechanical and optical setup of this new system is presented and simulation results of conventional subaperture stitching methods for this system with an aperture of 100 mm are shown. We also discuss the different measurement methods for the absolute form measurement of these optics.