Optisches Element mit einer reflektierenden Beschichtung

An optical element comprising a reflective coating is specified, wherein the reflective coating comprises at least: an adhesion layer (1), an at least partly reflective metal layer (2) disposed downstream of the adhesion layer (1), and a protective layer system (3) disposed downstream of the metal layer (2) and containing at least five dielectric layers (31, 32), wherein the dielectric layers (31, 32) comprise at least one first layer (31) and at least one second layer (32), wherein the first layer (31) and the second layer (32) have a different resistance toward at least two different contamination substances, and wherein the dielectric layers (31, 32) of the protective layer system (3) have a thickness of not more than 30 nm