Patent ID: 7995213

Claim:
A measurement apparatus which measures a wavefront aberration of an optical system to be measured, comprising: a condensing optical system inserted on a side of an object plane of the optical system to be measured, the condensing optical system configured to converge a certain component of light from a light source located on the object plane of the optical system to be measured so as to guide the certain component to the optical system to be measured, and to reflect a remaining component of the light from the light source without guiding the remaining component to the optical system to be measured; a catoptric system which is inserted on a side of an image plane of the optical system to be measured, the catoptric system configured to reflect the certain component of the light from the light source, which is guided to the optical system to be measured by said condensing optical system and has passed through the optical system to be measured, to guide the certain component to the optical system to be measured; a detection unit configured to detect an interference pattern obtained upon interference between the certain light component reflected by said condensing optical system and the light component which is guided to the optical system to be measured by said catoptric optical system and has passed through the optical system to be measured; a polarization changing unit which is inserted between said condensing optical system and the light source, the polarization changing unit having an optical member which is rotatable to change a polarization state of light incident thereon, and is configured to change a polarization state of the light which enters said condensing optical system by rotating the optical member; and a control unit, wherein said control unit: controls said polarization changing unit to generate linearly polarized light beams along at least three different azimuths, as the polarization state of the light which enters said condensing optical system, obtains wavefronts of the optical system to be measured with respect to the linearly polarized light beams along the at least three different azimuths, which are calculated based on the interference pattern detected by said detection unit, calculates a wavefront of the optical system to be measured with respect to non-polarized light and a birefringent characteristic of the optical system to be measured, based on the obtained wavefronts of the optical system to be measured, and calculates a wavefront of the optical system to be measured with respect to arbitrary polarized light, based on the wavefront with respect to non-polarized light and a birefringent characteristic of the optical system to be measured.