| 摘要 |
<p>PURPOSE:To enable an XY stage to be precisely positioned even if an optical path is changed in temperature distribution and an ambient pressure varies by a method wherein the XY stage is corrected in position based on a change in oscillation frequency to lessen the influence of a change in oscillation frequency from a first laser interferometer. CONSTITUTION:A first temperature measuring means 11 measures a temperature distribution in an optical path which extends from a mirror 9 to a laser interferometer 8 and is located near an optical axis 10. A second temperature measuring means 16 measures a temperature distribution in an optical path which extends from a mirror 14 to a laser interferometer 14 and is located near an optical axis 15. A measuring means 18 measures the change in the oscillation wavelength of a laser taking advantage of a second laser interferometer. A control means 26 calculates the effect of oscillation frequency contained in the signals obtained from the first laser interferometers 8 and 13 taking advantage of a change in oscillation frequency from the second laser interferometer and signals outputted from the first temperature measuring means 11, and XY stages 3 and 5 are corrected in position based on the calculation results to lessen the effect of a change in oscillation frequency from the first laser interferometers 8 and 13.</p> |
