Patent ID: 6999181

Claim:
A method, comprising: tracking a fringe line disturbance that has breached its field of reference on a reference field by reference field basis by: reading image data for a first reference field, said image data comprising pixel locations of one or more detected fringe lines within said first reference field, said fringe line disturbance's fringe line being one of said one or more detected fringe lines; starting at a pixel location that corresponds to an intercept of said fringe line with a border of said first reference field, following each pixel location of said fringe line in a direction away from said border; reading image data for a second reference field, said image data for said second reference field comprising pixel locations of one or more detected fringe lines within said second reference field, said fringe line being one of said one or more detected fringe lines within said second reference field, said second reference field adjacent to said first reference field; starting at a pixel location that corresponds to an intercept of said fringe line with a border of said second reference field, following each pixel location of said fringe line in a direction away from said border of said second reference field; translating each pixel location of said tracked fringe line disturbance being followed to an x,y,z s data point, where x and y represent a position on the plane of an interferometer's sample stage, and where z s represents the height of a sample above said x,y position, said sample placed upon the sample stage of an inteferometer so as to create said fringe line disturbance, said fringe line disturbance observed on said interferometer's detector.