Patent ID: 7769556

Claim:
A method for correcting the measuring errors caused by a lens distortion of an objective comprising the following steps: using the objective of a coordinate measuring machine to measure structures on a surface of a mask, the mask being inserted in a measuring stage moveable in a X coordinate direction and a Y coordinate direction, so that different areas of the mask are traversed into an image window of the objective; determining the lens distortion caused by the objective for a plurality of different types of structures on the mask in the image window of the objective; measuring one structure of one type each time within the image window of the objective successively in different locations within the image window to measure the position of the structure, the position of the structure of one type being determined with a measuring window of a detector successively within the image window of the objective; storing the lens distortion obtained for each type of the structure in a database; determining the position of the structure of one type with the measuring window in the image window of the objective; retrieving, in dependence on the type of structure measured, the correction of the lens distortion required for the type of structure, from the database; and correcting the position of the structure measured through the measuring window in the image window of the objective by the lens distortion at the position.