Patent ID: 6552804
Filing Date: 2003-04-22
Classification: G01B

Abstract:
Apparatus for interferometrically measuring at least one of the position and angular orientation of a plane object mirror, said apparatus comprising:an interferometer having reference and measurements paths and including a plane mirror in said measurement path, said interferometer being structured and arranged to generate a reference and measurement beam for travel along said reference and measurement paths, respectively, where the measurement beam travels to said plane object mirror at least twice, contacting it at two spatially separate locations in the process, and thereafter is mixed with said reference beam to provide a signal having a property that varies in accordance with changes in the location to said plane object mirror such that said signal is substantially independent of angular changes in said plane mirror about at least one axis orthogonal to the measurement path thereof; optical means arranged to intercept at least said measurement beam after one transit to said plane object mirror to generate an optical signal containing information that varies in at least one plane in accordance with the angular orientation of said plane object mirror; and means for receiving said optical signal, converting it to an electrical signal, determining said information therefrom, and converting said information to said angular orientation of said plane object mirror.