| 摘要 |
<p>A lithographic apparatus includes a displacement measuring system to measure a position of a moveable object with respect to a reference frame of the lithographic apparatus, in at least three coplanar degrees of freedom (x,y,Rz) of an orthogonal x-y-z coordinate system centred in the center of the moveable object. The moveable object includes a support structure configured to support a patterning device or a substrate table (2) configured to support a substrate. The displacement measuring system includes at least three sensor heads (4,5,6,7), each sensor head being positioned with a measuring direction (54...57) substantially coplanar with the x-y plane of the coordinate system and each sensor head being furthermore positioned with the measuring direction substantially perpendicular to a connection line (10,11) connecting the sensor head with the center of the movable object and extending coplanar with the x-y plane.</p> |
