| 摘要 |
PROBLEM TO BE SOLVED: To measure an aberration of an inspected optical system in high speed with high accuracy.SOLUTION: There is provided an aberration estimation method utilizing a steepest descent method in which when an evaluation function F, which is expressed by a square-sum of a difference between a first image obtained by performing photoelectric conversion to an optical image of a specimen SP formed by an imaging optical system 105 and a second image estimated to be obtained when an aberration is given to the imaging optical system, exhibits a permissible value or less, the aberration is estimated as an aberration of the imaging optical system. Three is provided a step (S209) in which when the evaluation function does not exhibit a permissible value or less, the aberration is updated by a sum of a current aberration and a primary differential of the aberration of evaluation function. The aberration is an aberration of an entire surface of pupil of the imaging optical system. In the step, the primary differential is calculated by Fourier-transforming to the difference instead of conducting integration by coordinates of respective points on an image surface of the imaging optical system. |
