Patent ID: 6538749
Filing Date: 2003-03-25
Classification: G01M

Abstract:
A method for evaluating an aberration of an optical element, said method comprising:transmitting light through the optical element; guiding the light from the optical element into a diffraction grating substantially perpendicular to a predetermined axis to obtain a first diffracted light and a second diffracted light; overlapping the first and second diffracted lights to form a sharing image shared by the first and second diffracted lights; changing a light intensity at first and second points in the shared image while detecting the light intensity at the first and second points in the shared image; determining a phase difference in the light intensity between the first and second points; rotating the diffraction grating about the predetermined axis; repeating said transmitting operation, said guiding operation, said overlapping operation, said changing operation, and said determining operation; and evaluating the aberration of the optical element by using the determined phase differences.