Patent ID: 7821648

Claim:
A measurement method for measuring a shape of a target using an interference pattern formed by reference light from a reference surface and light from the target by light from a light source, the measurement method comprising the steps of: converting a first interference pattern into a first shape of the target after obtaining the first interference pattern of the target; obtaining a second interference pattern at a position where the target moves in an optical axis direction of the reference surface; unwrapping the second interference pattern after aligning a phase at a reference point of the first interference pattern with a phase at a reference point of the second interference pattern; converting the unwrapped second interference pattern into a second shape of the target; determining whether or not the first shape of the target coincides with the second shape of the target; and calculating the shape of the target by adding the integral multiple of a wavelength of the light source to the unwrapped second interference pattern in a case where it is determined that the first shape of the target does not coincide with the second shape of the target in the determining step.