Patent ID: 7042576

Claim:
A positioning stage device comprising: a movable stage; positioning measurement means for measuring the position of the stage, the position measurement means comprising first means for measuring the position of the stage and second means for measuring the position of the stage, wherein the first means comprises (i) a plane mirror, which is an object to be measured, mounted to the stage, and (ii) a first interferometer, wherein the second means comprises (i) the same plane mirror and (ii) a second interferometer and wherein each of the first and second interferometers directs light onto the plane mirror; correction means for correcting measurement errors of said first and second interferometers caused by the atmosphere of the interferometers and for handing a corrected measuring result from the first interferometer to the second interferometer when the interferometers are switched; and calibration means for calibrating an absolute position of said stage after switching a plural number of times.