Tilted wave interferometry for testing large surfaces

Abstract

Measuring large surfaces interferometrically is a straight forward established technology, as long as they are concave and spherical. The situation chnages completely if aspheres and freeforms have to be measured. The application of a Tilted Wave Interferometer opens up possibilities to measure large concave surfaces of any shape without compensation optics. For the investigation of large convex aspheres, it is necessary to make use of stitching methods. Due to the freeform capability of the Tilted Wave Interefrometer, it is possible to acquire larger subapertures compared to null interferometers. Therefore measurement and computation time are reduced.