Patent ID: 7426790
Filing Date: 2008-09-23
Classification: G01D

Abstract:
1. A method for initializing a position-measuring system for an object movable in at least two degrees of freedom relative to a measuring frame, the position-measuring system including at least one position-measuring device per degree of freedom, each position-measuring device having a scale including an incremental track for measuring a relative position and an absolute track for measuring an absolute position and scanning heads, corresponding to the scales, for reading the incremental track and absolute track, comprising: an initialization step in which at least one of the incremental tracks and the absolute tracks are evaluated with a first evaluation procedure to form an evaluation result; an alignment step in which the movable object is aligned relative to the measuring frame based on the evaluation result; and an acquisition step in which the absolute tracks are evaluated with a second evaluation procedure having a small tolerance with respect to alignment of scanning head and the corresponding scale to determine a precise absolute position for each degree of freedom.