RADIATION BEAM POSITION SENSOR

摘要

PCT No. PCT/GB95/00735 Sec. 371 Date Nov. 13, 1996 Sec. 102(e) Date Nov. 13, 1996 PCT Filed Mar. 31, 1995 PCT Pub. No. WO95/27188 PCT Pub. Date Oct. 12, 1995An apparatus for detecting the position of a primary beam of electromagnetic radiation, the apparatus including a leaky mirror for reflecting the primary beam and for extracting from the primary beam a secondary beam and a position sensitive detector for detecting the spatial position of the secondary beam, wherein the leaky mirror comprises a material which has a transmissivity of less than 0.2 for the radiation of the primary beam and the position sensitive detector is arranged in the path of the secondary beam after transmission by the leaky mirror, the position of the secondary beam providing a measure of the position of the primary beam.