Interferometric methods for assessment of toroidal diffraction grating performance

The measurement of the shape and optical performance of toroidal mirrors has always presented a challenge to the manufacturer and user of these types of optical elements. This report presents a technique for evaluating the complex shape and optical performance of long radius toroidal mirrors that are to be used in the EUV. The measurement techniques will be discussed and examples given. Interferometric analysis will be presented. Performance spot diagrams and MTF analysis will be discussed. Manufacturing techniques will be evaluated with respect to the application of more definitive measurement technology.