| 摘要 |
For interferometrically determining the X and Y coordinates of a stage, for instance for photolithography equipment, three mirrors are provided in the configuration of two independent rigid bodies. There are two extended main mirrors M1, M2 lying perpendicular to the axis of interest, and a third smaller calibration mirror M3 which is fabricated or fixed at a right angle at the end surface of one of the long mirrors. The orthogonality error between the calibration mirror M3 and the mirror to which it is attached is calibrated, the departure of parallelism with the other mirror is determined. |
