Patent ID: 7463365

Claim:
A measurement apparatus for measuring an optical characteristic of a target optical system, said measurement apparatus comprising: an object side measurement mark having an object side slit located at an object side of the target optical system, the object side slit having a width in a shorter direction equal to or less than a diffraction limit of the target optical system; an image side measurement mark having a first image side slit located at an image side of the target optical system, and formed in the same direction as that of the object side slit, said image side measurement mark having a first image side slit that has, in a shorter direction, a width equal to or smaller than the diffraction limit of the target optical system, and a second image side slit that has, in a shorter direction, a width greater than the diffraction limit of the target optical system; and a detector for detecting an interference pattern formed by lights from said first and second image side slits, wherein the object side slit includes an object side 0° slit having a longer direction of 0°, an object side 45° slit having a longer direction of 45°, an object side 90° slit having a longer direction of 90° and an object side 135° slit having a longer direction of 135°, with respect to a reference direction, wherein said first image side slit includes an image side 0° slit having a longer direction of 0°, an image side 45° slit having a longer direction of 45°, an image side 90° slit having a longer direction of 90° and an image side 135° slit having a longer direction of 135°, with respect to the reference direction, wherein said measurement apparatus calculates a first wavefront based on a detecting result of an interference fringe formed by light from the image side 0° slit and said second image side slit and a detecting result of an interference fringe formed by light from the image side 90° slit and said second image side slit, and calculates a second wavefront based on a detecting result of an interference fringe formed by light from the image side 45° slit and said second image side slit and a detecting result of an interference fringe formed by light from the image side 135° slit and said second image side slit, and wherein said measurement apparatus calculates a wavefront of the target optical system based on the calculated first and second wavefronts.