Patent ID: 7428059

Claim:
A measurement method for measuring a wavefront aberration of a target optical system using a first interference pattern formed by a light from a first image side slit, and a light from a second image side slit, and a second interference pattern formed by a light from a third image side slit that has a longitudinal direction orthogonal to that of the first image side slit, and a light from a fourth image side slit that has a longitudinal direction orthogonal to that of the second image side slit, the first, second, third, and fourth image side slits being located at an image side of the target optical system, the first and third image side slits having, in a shorter direction, a width equal to or smaller than a diffraction limit of the target optical system, and the second and fourth image side slits having, in a shorter direction, a width greater than the diffraction limit of the target optical system, said measurement method comprising the steps of: obtaining a first wavefront from the first interference pattern, the first and second image side slits inclining by +45° to a polarization direction of a linearly polarized light incident upon the first and second image side slits; obtaining a second wavefront from the second interference pattern, the third and fourth image side slits inclining by −45° to the polarization direction of a linearly polarized light upon the third and fourth image side slits; and calculating wavefront aberration of the target optical system based on the first and second wavefronts of the target optical system obtained by said obtaining step.