Patent ID: 7443516

Claim:
An apparatus for correcting optical distortion, in an optical image that is caused due to distortion in an optical system imaging the optical image comprising: a distortion detecting mirror; a reference mirror that generates an interfering light interfering with light reflected from the distortion detecting mirror by reflecting the light from the light source; a mirror control unit that controls a relative angle between an imaginary plane substantially perpendicular to a surface of the reference mirror and a surface of the distortion detecting mirror; a reference surface determining unit that determines a reference surface corresponding to a height of the distortion detecting mirror when the mirror control unit sets the relative angle to zero in substance; a distortion detecting unit that detects the optical distortion corresponding to a measurement height of the surface of the distortion detecting mirror by measuring relative heights of respective lattice points on the surface of the distortion detecting mirror from the reference surface determined by the reference surface determining unit, based on interference between the light reflected from the distortion detecting mirror and the interfering light generated by the reference mirror when the mirror control unit sets the relative angle to an angle other than zero; and a correcting unit that corrects the optical distortion detected by the distortion detecting unit.