Patent ID: 7692799

Claim:
A measurement apparatus which measures a wavefront aberration of an optical system to be measured, the apparatus comprising: a measurement mask which is inserted on an object plane of the optical system to be measured, and includes a plurality of reflection units configured to generate spherical waves by reflecting light; a diffractive optical element configured to diffract the light having passed through said measurement mask and the optical system to be measured; and a detection unit configured to detect an interference pattern formed by interference of the light diffracted by said diffractive optical element, said measurement mask including: a reflection layer configured to reflect the light, a first layer which is stacked on said reflection layer, has a plurality of openings, and is made of a first substance, and a second layer which is stacked on said first layer, has a window configured to expose a region in which said plurality of openings are arrayed, and is made of a second substance different from said first substance, wherein said plurality of reflection units are formed by portions of said reflection layer, which are exposed through said plurality of openings.