For a variety of UV optical coatings, surface roughness was measured by use of an atomic-force microscope (AFM) to study its dependence on the film material and thickness, coating design, and deposition process. After analyzing the corresponding power spectral density functions, we propose a simple classification model for coatings according to the contributions of substrate roughness and intrinsic film roughness to the scattering. Results of scattering measurements on different types of coatings are presented and are found to be in good agreement with predictions based on the AFM data. Consequences for a scatter reduction strategy are discussed.

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The roughness of a number of uncoated glass substrates with different surface qualities and of surfaces of fluoride films is investigated by various characterization techniques. The influence of bandwidth limitation and the dependence on the examined sample area become obvious. It is shown that the results obtained from the different measuring methods complement each other appropriately.

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