Facet mirror for e.g. extreme UV (EUV) projection exposure system used in lighting system, has mirror facet unit that varies radius of curvature of mirror facet from specific radius of curvature to another radius of curvature

摘要

The facet mirror (6) has several mirror facets that are provided with an optical surface with specific radius of curvature. A mirror facet unit varies the radius of curvature of the mirror facet from a specific radius of curvature to another radius of curvature. The mirror facet unit has an actuator that changes the radius of curvature of the mirror facet by mechanical force. The actuator is provided with piezo element. The mirror facet comprises a shape memory alloy or bimetal. Independent claims are included for the following: (1) a projection exposure system; and (2) a method for operating facet mirror.