Patent ID: 8351050
Filing Date: 2013-01-08
Classification: G01J,G03F

Abstract:
1. A wavefront-aberration-measuring device arranged to measure wavefront aberration of a to-be-tested optical system, the device comprising: a diffraction grating arranged to split light transmitted through the to-be-tested optical system; a detecting unit arranged to detect interference fringes produced by interference between beams of the light split by the diffraction grating; an arithmetic unit arranged to calculate the wavefront aberration from information on the interference fringes detected by the detecting unit; an image-side mask insertable into and retractable from an image plane of the to-be-tested optical system; and an illuminating unit arranged to incoherently illuminate the image-side mask, wherein the image-side mask has an aperture with a diameter larger than λ/2NA, where λ denotes a wavelength of the illuminating unit and NA denotes a numerical aperture of the to-be-tested optical system, wherein the arithmetic unit calculates the wavefront aberration of the to-be-tested optical system from information on the interference fringes detected by the detecting unit with the image-side mask being retracted from the image plane and information on the interference fringes produced by beams of the light transmitted through the aperture of the image-side mask and split by the diffraction grating, the interference fringes being detected by the detecting unit with the image-side mask being in the image plane, wherein the illuminating unit includes wherein the illuminating unit illuminates the image-side mask through the to-be-tested optical system, wherein the object-side light-radiating portion has in a surface thereof a pattern of depressions and projections whose maximum slope is at least as large as a difference between an incidence-side numerical aperture of the to-be-tested optical system and a numerical aperture of the object-side illuminator, and wherein the object-side mask is moved within a plane by a length at least as large as a period of the pattern during an integration time of the detecting unit.