Flatness

Abstract

Because flatness is one of the most important parameters that characterize optical properties of optical devices such as plane mirrors and prisms, a wide variety of measuring techniques has been invented so far. The simplest method is observing the curvature of the interference fringes formed between the sample and an optical flat. This method, however, is capable of measuring only λ/20 of the curvature, and it is not always sufficient for current applications.