Patent ID: 7701589

Claim:
A three-dimensional shape measuring method for measuring a three-dimensional shape of an object to be measured by changing an optical path length from a light source generating an illumination light having a broadband spectrum to the object to be measured or an optical path length from the light source to a reference mirror and by detecting a position where the optical path lengths are set equal, the method comprising the steps of: finding an approximate position including a position where an envelope of the amplitude of white light fringes takes a maximum value, the fringes being caused by interference between a return light of the illumination light from the reference mirror and a return light of the illumination light from the object to be measured; extracting interference fringes of at least two spectral band components different from each other, which are included in the white light fringes; and determining a position, near the approximate position, where the optical path length from the light source to the object to be measured is set equal to the optical path length from the light source to the reference mirror by finding a position where phases of the interference fringes of the spectral band components different from each other take values equal to each other.