FIZEAU INTERFEROMETER AND MEASUREMENT METHOD FOR FIZEAU INTERFEROMETER

摘要

PPROBLEM TO BE SOLVED: To provide a Fizeau interferometer properly measuring the form of a spherical surface to be measured even in the case where a phase shift method is used. PSOLUTION: The Fizeau interferometer 1 is equipped with: an interferometer body 2; and a measuring apparatus 3. The interferometer body 2 is equipped with an optical system 22 comprising a reference spherical surface or the like. The measuring apparatus 3 includes an intensity obtaining section 31 and a form calculating section 32. The intensity obtaining section 31 obtains the intensities of interference light in n positions at equal intervals while the position of the reference spherical surface at the time when the focal point of the reference spherical surface is aligned with the focal point of the spherical surface to be measured is set as the center position and the two positions equidistant from the center position are set as the start position and the end position, respectively. The form calculating section 32 measures the form of the spherical surface to be measured using an algorithm of a phase shift method, wherein a coefficient of the intensity of the interference light in an i-th position and a coefficient of the intensity of interference light in an (n-i+1)th position have the same value. PCOPYRIGHT: (C)2011,JPO&INPIT