| 摘要 |
The X, Y and Rx positions of a mask stage (MT) are measured using optical encoder-reading heads (10,11) measuring displacements of respective grid gratings (12,13) mounted on the mask stage. The grid gratings are preferably provided on cut-away portions of the mask table so as to be co-planar with the pattern on the mask itself. Measurements of the table position in the other degrees of freedom can be measured with capacitative or optical height sensors.
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