Dual axes interferometer

Claim 1

A dual axes interferometer for measuring movement of an instrument along coordinate axes in a machine having x- and ycoordinate axes carriages movable on a base including a light source and interference fringe detector means fixedly mounted on said base and an integral block mounted on one of said carriages, said block consisting of a first beam-splitting surface oriented at 45* to an input beam and splitting said input beam into transmitted and reflected components, a second beam-splitting surface parallel to said first beamsplitting surface receiving said reflected component and splitting it into a first pair of transmitted and reflected subcomponents, a first reference reflecting surface positioned on said block to reflect said first transmitted subcomponent back to said second beam-splitting surface and a first relatively moving reflector for returning said first reflected subcomponent along one of said carriages coordinate axes back to said second beamsplitting surface thereby producing interference fringes at said detector means indicative of movement along said one axis. a second reflecting surface on said block parallEl to said first beam-splitting surface, a third beam-splitting surface coextensive with said second beam-splitting surface receiving said transmitted component from said second reflecting surface and splitting it into a second pair of transmitted and reflected subcomponents, a second reference reflecting surface receiving said second reflected subcomponent and reflecting it back to said third beam-splitting surface and a second relatively moving reflector for returning said second transmitted subcomponent back along the other of said carriage coordinate axis to said third beamsplitting surface thereby producing interference fringes at said detector means indicative of movement along the other of said coordinate axes.