Comparative radius of curvature measurement by non-contact Newton's rings

A non-contact interferometric method is presented in which interference takes place at the real images of an object and reference surfaces with a magnification of unity. A theoretical approach has been used to explain and prove the method. Six spherical, convex and concave, mirrors with radii ranging from 964 mm to 2221 mm have been measured. The values of the measurements are compared with those obtained by contact Newton's rings.