| 摘要 |
PROBLEM TO BE SOLVED: To prevent a sensitivity correction data of an image sensor from being changed by a foreign matter deposited onto a calibration mirror piece. SOLUTION: A foreign matter deposition detecting part 17 comprises a memory 18 and a comparison processing part 19. The memory 18 stores a sensor output when scanning the mirror piece 3 for calibration just mounted now and not deposited with the foreign matter, by the image sensor 11. A synchronization signal of the image sensor 11 is prepared in a synchronization signal generator 20, based on an encoder signal used for controlling a moving stage 1 by a stage controller 21. Processing for storing the data in the memory 18 is enough to be executed once just after the mirror piece 3 for the calibration is replaced. The comparison processing part 19 compares the sensor output obtained by scanning the mirror piece 3 for the calibration when obtaining the correction data, with the sensor output stored in the memory 18 just after the mirror piece 3 for the calibration is replaced by the processing, so as to determine the presence of deposited foreign matter in the mirror piece 3 for the calibration. COPYRIGHT: (C)2006,JPO&NCIPI
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