Patent ID: 8373866
Filing Date: 2013-02-12
Classification: G03F

Abstract:
1. A wavefront aberration measuring apparatus configured to measure wavefront aberration of an optical system, the wavefront aberration measuring apparatus comprising: a first mask arranged in an object plane of the optical system and having a plurality of openings; an illumination optical system configured to illuminate the plurality of openings of the first mask by using light from a light source; a second mask arranged in an image plane of the optical system and having an opening allowing passage of light containing aberration of the optical system and one of a pinhole and a slit; an image pickup unit configured to take an image of interference fringe generated by light having passed through the optical system and said one of the pinhole and the slit of the second mask and the light having passed through the optical system and the opening of the second mask; an evaluation value calculating unit configured to calculate an evaluation value to evaluate a state of the interference fringe by using image data of the image; a determining unit configured to determine, based on the calculated evaluation value, whether the wavefront aberration of the optical system is to be calculated; and a wavefront aberration calculating unit configured to calculate, in accordance with a determination result of the determining unit, the wavefront aberration of the optical system from the image data, wherein the evaluation value calculating unit sets a processing direction in which the evaluation value is calculated in a plurality of local regions in the image differently for each of the local regions and calculates evaluation values in the plurality of local regions, and wherein the determining unit determines whether the wavefront aberration is to be calculated based on the evaluation values in the plurality of local regions.