Method of and system for measurement of direction of surface and refractive index variations using interference fringes

摘要

A main measuring light having a first wavelength is projected onto a work and a reference surface to produce first interference fringes and a determination light having a second wavelength slightly different from the first wavelength is projected onto the work and the reference surface to produce second interference fringes. Whether the surface of the work is concave or convex, in which direction the surface inclines or the refractive index distribution of the work is determined on the basis of the relative positions of the first and second interference fringes.