Patent ID: 7733500

Claim:
A wavefront sensor that splits an optical wavefront to be measured into two optical paths, displaces the split optical wavefronts from each other, and mixes the wavefronts together again to measure a configuration of the optical wavefronts from an interference fringe formed on an interference measurement plane, comprising: optical path difference compensation members, which are arranged on the two optical paths respectively, for imaging each of the wavefronts that once have been split into the two optical paths, and again collimating the imaged wavefronts to remove an optical path difference that occurs depending on an incident angle of the optical wavefront to be measured, wherein a propagation optical path difference between the two optical paths up to the interference measurement plane is kept constant regardless of the incident angle of the optical wavefront to be measured; wherein each of the optical path difference compensation members have at least one lens, each lens being inclined with respect to a corresponding optical path by a predetermined angle; and wherein both of the optical path difference compensation members are arranged so that the respective lenses are inclined with respect to their own optical path of the two optical paths in opposite directions.