Patent ID: 7616330

Claim:
A method of determining at least one geometric characteristic of an object having a first surface and a second surface, where at least one of the first and second surfaces passes a substantial amount of light therethrough, the method comprising: (a) adjusting a positional relationship between a first surface of the object and a light source to illuminate a subregion of the first surface of the object, whereby a portion of light illuminating the subregion of the first surface of the object passes through the object to the second surface of the object; (b) delivering light from the subregion of the first surface of the object to a wavefront sensor while blocking a majority of light from the second surface of the object from reaching the wavefront sensor; (c) determining a wavefront of light received from the subregion of the first surface with a wavefront sensor; (d) repeating steps (a) through (c) for a plurality of different subregions spanning a measurement region for the first surface of the object, where adjacent subregions have an overlapping portion; (e) stitching together the wavefronts determined in each execution of step (c) including derivatives of the wavefronts in the overlapping portions, to construct a wavefront of light received from the measurement region of the first surface of the object; and (f) determining at least one shape parameter of the first surface of the object from the constructed wavefront.