Fluorides and oxides are classical materials for optical coatings. At present, fundamental improvements of film properties are necessary, especially for optical components of high power excimer lasers and other applications in the UV spectral region. The optical properties and the laser damage threshold of the films are determined by the thin film microstructure and by contamination inside the films. Strong connections between optical losses and laser stability, on the one hand, and the film microstructure, on the other hand, have been shown. Therefore, sensitive optical characterization techniques in the UV region have to be used. We report first results of deep UV spectroscopic ellipsometric measurement of fluoride and oxide films.