| 摘要 |
An apparatus for measuring the positions of marks on a mask is provided, said apparatus comprising a mask holder for holding the mask, a recording unit for recording the marks of the mask held by the mask holder, an actuating module for moving the mask holder and the recording unit relative to each other, and an evaluating module, which numerically calculates the gravity-induced sagging of the mask in the mask holder and determines the positions of the marks on the mask, based on the calculated sagging, the recordings made by the recording unit and the relative movement between the mask holder and the recording unit, wherein, prior to calculating said sagging, the present position of the mask in the mask holder is determined and is taken into consideration in said numerical calculation, and/or the geometrical dimensions of the mask are taken into consideration in said numerical calculation of sagging.
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