Patent ID: 8704199

Claim:
A lithographic apparatus, comprising: a radiation source configured to provide radiation; a radiation collector including a first region and a second region, the first region comprising a first optical characteristic and the second region comprising a second optical characteristic the first and second optical characteristics being different from each other, wherein the first region and the second region each is configured to collect at least a portion of the radiation from the radiation source; an illumination system configured to condition radiation collected by the first region of the radiation collector and to provide a radiation beam, wherein the radiation collector is configured to be aligned with a part of the illumination system; and a detector configured to be in a fixed positional relationship with the part of the illumination system and to detect a change of a characteristic of radiation collected by the second region of the radiation collector, wherein the detected change is indicative of a change in a position or orientation of the radiation collector relative to the part of the illumination system with respect to which the radiation collector is configured to be aligned.