Scalable Fizeau Interferometer

For the production of ASML lithography systems, optically smooth surfaces of various sizes must be measured interferometrically for their flatness and local gradients. In addition, depending on the product type, different requirements are placed on imaging quality, distortion and image field curvature. We would like to present our design for a Fizeau interferometer based on a scalable plano-convex lens. The optimisation was carried out for an aperture of 350mm, although the system also meets the constraints on the relevant parameters for diameters of 250mm to 600mm. This offers the possibility to build interferometers of different measurement apertures with a single design and to use plano-convex lenses that are relatively easy and therefore cheap to produce. Only distances have to be adjusted in the system. We will also show our laboratory setup and the first measurement results with an aperture of 350mm.