Patent ID: 7554675

Claim:
A light wavefront measuring apparatus comprising: a separating element separating a flux of incident light into a first beam and a second beam; a first interference fringe display section being placed in the first beam and displaying an interference fringe formed from the first beam; a second interference fringe display section having the same structure as a structure of the first interference fringe display section, the second interference fringe display section being placed in the second beam and displaying an interference fringe formed from the second beam; and a wavefront rotating element being placed at least one of between the separating element and the first interference fringe display section and between the separating element and the second interference fringe display section, the wavefront rotating element rotating at least one of wavefronts of the first beam and of the second beam around an optical axis thereof, wherein the first interference fringe display section comprises: a first diffraction grating being placed in the first beam; a second diffraction grating being placed in a beam which passed through the first diffraction grating; and a first display section displaying the interference fringe formed by a beam which passed through the second diffraction grating; wherein the second interference fringe display section comprises: a third diffraction grating having the same structure as a structure of the first diffraction grating and being placed in the second beam; a fourth diffraction grating having the same structure as a structure of the second diffraction grating and being placed in a beam which passed through the third diffraction grating; and a second display section displaying the interference fringe formed by a beam which passed through the fourth diffraction grating wherein the first display section and the second display section are disposed side by side and face in the same direction; wherein a grating vector of the first diffraction grating and a grating vector of the third diffraction grating are identical and the first and third diffraction gratings move unitarily in a direction of the grating vectors.