Projection objectives, as well as related components, systems and methods, are disclosed. In general, a projection objective is configured to image radiation from an object plane to an image plane. A projection objective can include a plurality of optical elements along the optical axis. The plurality of optical elements can include a group of optical elements and a last optical element which is closest to the image plane, and a positioning device configured to move the last optical element relative to the image plane. Typically, a projection objective is configured to be used in a microlithography projection exposure machine.