In situ and ex situ characterization of optical surfaces by light scattering techniques

The continuous development of optical technologies and the accompanying requirements on the manufacturing process place challenging demands on metrology. In addition to highly sensitive and robust measurement techniques, the inspection tools should be fast and capable of characterizing large and complex-shaped surfaces. These aspects can be addressed by light-scattering-based characterization techniques, which also enable a large flexibility for the measurement conditions because of the noncontact data acquisition and are, thus, suited not only for ex situ but also in situ characterization scenarios. Application examples ranging from the roughness characterization of magneto-rheological finished substrates to polished extreme ultraviolet mirror substrates with diameters of more than 600 mm by compact as well as laboratory-based instruments are presented.