The surface functional properties of a material can be changed by adding a thin evaporated or sputtered layer of a different appropriate element. For example, optical properties of lenses such as light transmission, reflectivity or polarization can be changed by deposition of a suitable layer of a thin film. This finds application either in high tech scientific experiments where light has to be properly manipulated or in commonly used  glasses for eye ware. Also in this case, as the coating process is carried out in a vacuum environment, vacuum chambers with suitable cleanliness and vacuum integrity are required to ensure product reproducibility and quality.