Patent ID: 7567699

Claim:
A method for determining the center of a rotationally symmetrical alignment mark thereby using an image recognition software, comprising the following steps: (a) recognizing the alignment mark (J) by means of the image recognition software and determining the position of a first reference point (R 1 ) in the area of the alignment mark (J); (b) rotating the image (J) of the alignment mark around a symmetry angle with respect to which the alignment mark is rotationally symmetrical; (c) recognizing the rotated image (J′) of the alignment mark by means of the image recognition software and determining the position of a second reference point (R 2 ) in the rotated image (J′) of the alignment mark whose position with respect to the rotated image (J′) of the alignment mark corresponds to the position of the first reference point (R 1 ) with respect to the non-rotated image (J) of the alignment mark; (d) determining the center of rotation of the rotated image (J′) of the alignment mark on the basis of the rotated first reference point (R 1 ′) and the second reference point (R 2 ); and wherein steps (a)-(d) above are performed by a computer.