Lithographic apparatus and device manufacturing method

摘要

Optical system, especially an illumination objective for semiconductor lithography has a number of optical elements (2), at least one load bearing structure (3) that serves to deflect forces, including weight forces, away from the optical elements and a measurement structure (5) that is independent of the load bearing structure. The invention also relates to a corresponding method for changed the position of an object or an image in the inventive optical system, whereby the position of the optical elements is changed relative to the measurement structure, at least for known positions of the object and target positioning of the image in relation to the measurement structure.