| 摘要 |
In a lithographic apparatus, a measurement of the position of an object in an ambient space by an object position measuring system which is influenced by pressure variations in the ambient space, is corrected by an accurate measurement of the pressure in the ambient space. A reference pressure volume may be provided, having a fluid connection with predetermined flow characteristics to the ambient space. A pressure difference is measured between a pressure in the reference pressure volume and an ambient pressure in the ambient space. The absolute pressure in the reference pressure volume is added to the pressure difference to determine a change of pressure in the ambient space. Alternatively, the pressure difference is integrated over time for determining a change of pressure in the reference pressure volume, and this change of pressure in the reference pressure volume is added to the pressure difference to determine a change of pressure in the ambient space. The fluid connection may also be a valve which can be opened and closed.
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