Patent ID: 8472030

Claim:
A surface profile measuring apparatus in which a profile of a target surface is measured on the basis of an interference pattern formed by interference between a measuring beam reflected by the target surface and a reference beam, the apparatus comprising: a first image pickup device configured to pick up an image of the interference pattern; an optical system configured to guide the measuring beam and the reference beam to the first image pickup device; a second image pickup device with which a distribution of light quantity of a beam of the light from the light source traveling thereto avoiding the optical system is measured; and an arithmetic unit configured to calculate a profile of the target surface on the basis of the image of the interference pattern picked up by the first image pickup device, wherein a distribution of light quantity of a beam of the light from the light source transmitted through the optical system is measured with the first image pickup device, and wherein the arithmetic unit is configured to obtain the profile of the target surface by calculating distortion of the optical system on the basis of the distribution of light quantity measured with the first image pickup device and the distribution of light quantity measured with the second image pickup device, and correcting, on the basis of the distortion, the profile of the target surface calculated on the basis of the interference pattern.