Patent Document ID: 20090207422
Application ID: 12426713
Patent Status: 0

Claim One:
1. A measurement system configured to measure a position of an object in a lithographic apparatus, the measurement system comprising: at least three position detectors configured to detect the position of the object, the at least three position detectors each including a single or multi-dimensional optical encoder to provide at least six position values, the optical encoders being coupled to the object at different locations within a three dimensional coordinate system, wherein at least one position value is provided for each dimension of the three dimensional coordinate system, wherein the measurement system is configured to calculate the position of the object within the three dimensional coordinate system from a subset of at least three of the six position values and to calculate an orientation of the object with respect to the three dimensional coordinate system from another subset of at least three of the six position values, and wherein one of the at least three position detectors comprises a two-dimensional optical encoder, the two-dimensional optical encoder including two separate one-dimensional gratings or a two-dimensional dot grid that are arranged on a side of the object or a measurement frame of the lithographic apparatus.