Patent ID: 7898670
Filing Date: 2011-03-01
Classification: G01B,G01N,G02B,G02F

Abstract:
1. A method of measuring distortion comprising the steps of: (a) positioning a first substrate having a first focal plane and a plurality of first markings containing position information in contact with a second substrate having a second focal plane and a plurality of second markings containing position information; (b) directing incident light at the first focal plane and the second focal plane so that the incident light reflects from the first focal plane to produce a first beam of light and the second focal plane to produce a second beam of light, the first and second beams of light being coincident and having orthogonal polarization; (c) passing the coincident first and second beams of light having orthogonal polarization through a common optical path; (d) focusing the coincident first and second beams of light having orthogonal polarization separately on a single image plane; (e) simultaneously detecting the first and second beams of light having orthogonal polarization at the single image plane; and (f) reproducing the position information contained in the first markings and the second markings from the detected first and second beams of light, respectively, on the single image plane.