Patent ID: 7446883
Filing Date: 2008-11-04
Classification: G01B

Abstract:
1. A method for profiling optical flats, said method comprising the steps of: mounting a test flat having rotationally invariant (RI) and variant (RV) terms in an first interferometer having a transmission flat (TF) so that the test flat can be precisely tilted, rotated and translated; adjusting the tilt between the test flat and the first interferometer transmission flat of the first interferometer to be nominally zero; in-situ calibrating an external angle measurement system developing a functional relationship, (Z1=f(High Stability Plane Mirror Interferometer, HSPMI)) between a tilt measured by the first interferometer and an externally induced mechanical tilt; introducing a shear between the test flat and the first interferometer transmission flat and measuring the mechanical tilt during shearing between the test flat and first interferometers transmission flat to generate sheared data; and using the function (Z1=f(HSPMI), correcting the sheared data and then computing the rotationally invariant (RI) terms of the test flat.