Method and device for measuring wavefront using light-exit section causing light amount distribution in at least one direction

A wavefront measuring device configured to obtain wavefront information of an optical system to be measured, the device comprising:

• a light-exit section configured to allow a light beam to exit therefrom, the light beam having a light amount distribution, in a first direction and a second direction crossing the first direction, corresponding at least to one period of periodicity;
• a diffraction grating into which the light beam allowed to exit from the light-exit section and having passed via the optical system comes, and which has periodicity in directions corresponding to the first direction and the second direction;
• a detector configured to detect intensity distribution of an interference fringe formed by a plurality of light beams generated from the diffraction grating;
• and
• an arithmetic unit configured to obtain the wavefront information of the optical system, by using a result of detection by the detector,
• wherein the light-exit section comprises:
• first, second and third light-passing portions each allowing a light to pass therethrough, the first and second light-passing portions being arranged adjacently in the first direction, and the first and third light-passing portions being arranged adjacently in the second direction;
• and
• first and second light-shielding portions each shielding the light, the first light-shielding portion being arranged between the first and second light-passing portions such that each of the first and second light-passing portions is in contact with the first light-shielding portion, and the second light-shielding portion being arranged between the first and third light-passing portions such that each of the first and third light-passing portions is in contact with the second light-shielding portion, wherein
• widths, in the first direction, of the first and second light-passing portions are different from each other, and widths, in the second direction, of the first and third light-passing portions are different from each other, and
• the third light-passing portion has a width in the first direction equal to the width of the first light-passing portion in the first direction.