Patent ID: 7181089

Claim:
A method of searching for a fiducial mark, by processing image data indicative of images of said fiducial mark and an area surrounding said fiducial mark, said images being taken by an imaging device, said method comprising: a reference-line setting step of setting, by a person practicing the method, at least one two-dimensional reference line each of which corresponds to at least one portion of a profile of said fiducial mark and the number of which is sufficient to specify said fiducial mark, said reference-line setting step comprising selecting said at least one two-dimensional reference line from among a plurality of stored and predetermined two-dimensional candidate reference lines; a profile-data obtaining step of obtaining profile data indicative of profiles of said images taken by said imaging device, each of said profiles of said images consisting of a group of points at which an optical characteristic of the corresponding image abruptly changes; and a searching step of searching for said fiducial mark, on the basis of said profiles represented by the obtained profile data and said at least one two-dimensional reference line.