Patent ID: 6208424
Filing Date: 2001-03-27
Classification: G01B

Abstract:
An interferometric apparatus for measuring the translation of a body while being insensitive to changes in pitch and yaw of the body as the body translates in mutually orthogonal directions, said interferometric apparatus comprising:beam redirecting means adapted to be fixedly mounted to a body for translation therewith in at least two orthogonal directions; andoptical means for:(a) forming a reference path for a reference beam;(b) in combination with said beam redirecting means, forming a measurement path for a measurement beam having at least two pairs of incoming and outgoing segments where each incoming and outgoing segment in each pair travels, respectively, to and from said redirecting means along different paths that are vertically separated one from the other in a first direction while each pair of segments is laterally separated from one another in a direction orthogonal to said first direction, said measurement path changing in length as the body moves along a select one of said two orthogonal directions and being spatially separated from said reference path;(c) introducing reference and measurement beams for travel along said reference and measurement paths, respectively; and(d) combining said reference and said measurement beams so that they are coextensive and have a predetermined angle between them to generate an interference signal that varies in accordance with changes in said measurement path, said redirecting means being configured and arranged with respect to said optical means so that said reference and measurement beams remain substantially coextensive with said predetermined angle between them as the body moves both along said select direction and orthogonal to said select direction whereby said interference signal is insensitive to changes in pitch and yaw of said body as it moves in said two orthogonal directions.