Patent ID: 7113261

Claim:
A radiation system, comprising: a radiation generator configured to generate radiation, the radiation generator comprising a radiation source; and an illumination system configured to receive the radiation and provide a beam of radiation, the illumination system comprising a beam measuring system configured to measure at least one of position and tilt of the beam of radiation relative to the illumination system; and a projecting device arranged to direct part of the beam of radiation to the beam measuring system wherein the part of the beam of radiation is a part of a cross section of the beam of radiation, wherein the radiation generator further comprises a collector configured to collect the radiation from the source and to form an intermediate focus in the radiation between the radiation generator and the illumination system; a first diaphragm configured to pass the radiation from a first peripheral part of a cross section of the radiation; and a second diaphragm configured to the pass radiation from a second peripheral part of a cross section of the radiation; the beam measuring system further comprises a first position sensor; and a second position sensor; and the projecting device further comprises a first optical element configured to receive the radiation passed by the first diaphragm and to generate a far field image of the intermediate focus on the first position sensor; and a second optical element configured to receive the radiation passed by the second diaphragm and to generate a far field image of the intermediate focus on the second position sensor.