Patent ID: 6184994
Filing Date: 2001-02-06
Classification: G01B

Abstract:
A method for absolute surface testing of planar or spherical surfaces including the steps of:employing a phase shifting interferometer with a reference surface position and a test surface position;placing a first test piece A in the reference surface position;placing a second test piece C in the test surface position;using the interferometer to produce a measured difference map m.sub.1 of the first and second test pieces;replacing the first test piece A with a third test piece B in the reference position and using the interferometer to produce a measured difference map m.sub.a, of the third and second test pieces;the second test piece C with the first test piece A in the test surface position and using the interferometer to produce a measured difference map m.sub.3, of the third (B) and first (A) test pieces;rotating the test piece (A) at the test surface position by at least two additional different predetermined angular amounts and using the interferometer to produce measured difference maps m.sub.4. . . m.sub.m-3, of the third (B) and first (A) test pieces at the positions of each of the at least two different predetermined angular amounts positions;Calculating rotationally sheared surface maps of the first test piece A; andusing the measured difference maps and the rotationally sheared surface maps to produce absolute surface maps of the first (A), second (B) and third (C) test pieces.