Wavefront aberration measuring apparatus

Abstract

An aberration measuring apparatus capable of measuring wavefront aberration at a high degree of accuracy regardless of the magnitude of aberration of an optical system is disclosed. This aberration measuring apparatus includes a first mask which generates a wavefront including wavefront aberration of the optical system and a reference wavefront not including wavefront aberration of the optical system with respect to a predetermined direction, a second mask which generates two wavefronts, both of which include wavefront aberration of the optical system and a detector placed at a position where the two wavefronts generated by the first mask or the two wavefronts generated by the second mask form an interference pattern. Wavefront aberration of the optical system is calculated based on the interference pattern detected by this detector. Then, the aberration measuring apparatus can switch between a mode for measuring wavefront aberration of the optical system using the first mask and a mode for measuring wavefront aberration of the optical system using the second mask.

Dependencies are inferred from the claim text.