Patent ID: 7623247

Claim:
A measuring device for measuring a wavefront aberration of an optical system, the measuring device comprising: a first mask for defining light that enters the optical system; a second mask including a first opening and a plurality of further openings, the first opening transmitting a component of the light passing through the optical system including information about the wavefront aberration of the optical system, and the further openings transmitting components of the light passing through the optical system having the information about the wavefront aberration of the optical system removed; a detector for detecting a first interference pattern formed by interference between the light component passing through the first opening and the light component passing through one of the plurality of further openings and detecting a second interference pattern formed by interference between the light components passing through two of the plurality of further openings; and a controller for correcting a wavefront aberration calculated from the detected first interference pattern using a wavefront aberration calculated from the detected second interference pattern; wherein the second mask includes second and third openings as the further openings, and wherein the detector detects the first interference pattern formed by interference between the light component passing through the first opening and the light component passing through second opening and detects the second interference pattern formed by interference between the light component passing through the second opening and the light component passing through the third opening.