In one aspect, the invention features an angle-measuring interferometry system
that includes an interferometer which during operation directs a measurement beam
to contact a measurement object, the interferometer comprising a beam steering
assembly having a beam steering element positioned to contact and direct the measurement
beam and an electronic positioning system to selectively orient the beam steering
element within the interferometer. The angle-measuring interferometry system also
includes an angle measurement system which during operation calculates a change
in angular orientation of the measurement object based on a measurement signal
derived from the measurement beam, wherein the measurement signal is derived from
at least one interferometric signal produced by combining at least a portion of
the measurement beam with a second beam after the measurement beam contacts the
measurement object.
