Abstract

The Foucault test (referred to as the knife edge or wire test) was invented by L. M. Foucault in 1858. In its most basic form only a white light point source and a knife edge are necessary to qualitatively detect small errors on an optical surface. It has been shown that under ideal conditions, errors on the surface as small as λ/600 can be detected. Thus this is one of the most sensitive yet economical tests and should always be considered as an option when one has a limited testing budget.

© 1980 Optical Society of America