Optical-distortion correcting apparatus and optical-distortion correcting method

A method of correcting optical distortion, comprising:

• controlling a relative angle between optical axes of a distortion detecting mirror and a reference mirror;
• detecting a measurement height of a surface of the distortion detecting mirror by measuring positions of respective lattice points on the surface, the measurement height from a reference surface that is a surface substantially parallel to the reference mirror, wherein the positions are measured at a plurality of relative values;
• and
• correcting the optical distortion based on the measurement height.

A computer-readable recording medium that stores therein a computer program for correcting optical distortion, the computer program making a computer execute:

• controlling a relative angle between optical axes of a distortion detecting mirror and a reference mirror;
• detecting a measurement height of a surface of the distortion detecting mirror by measuring positions of respective lattice points on the surface, the measurement height from a reference surface that is a surface substantially parallel to the reference mirror, wherein the positions are measured at a plurality of relative values;
• and
• correcting the optical distortion based on the measurement height.