Patent ID: 8134715

Claim:
An interferometer, comprising: a first cavity including a pair of mirrors, at least one of which being movable, defining a first cavity length; a second cavity including a pair of mirrors, at least one of which being movable, defining a second cavity length; a first beam splitter for directing a first polarized input beam into the first cavity through a first phase shift element; a second beam splitter for directing a first polarized reference beam into the first cavity through a second phase shift element; a third beam splitter for directing a second polarized input beam into the second cavity through a third phase shift element; a fourth beam splitter for directing a second polarized reference beam into the second cavity through a fourth phase shift element; a first optical detector for receiving from the first beam splitter a first and a second output beam, the first and second output beams being generated responsive to the respective first polarized input beam and the first polarized reference beam, the first optical detector generating a first signal responsive to the first output beam and to the second output beam; a second optical detector for receiving from the second beam splitter a third and a fourth output beam, the third and fourth output beams being generated responsive to the respective first polarized input beam and the first polarized reference beam, the second optical detector generating a second signal responsive to the third output beam and the fourth output beam; a third optical detector for receiving from the third beam splitter a fifth and a sixth output beam, the fifth and sixth output beams being generated responsive to the respective second polarized input beam and the second polarized reference beam, the third optical detector generating a third signal responsive to the fifth output beam and to the sixth output beam; a fourth optical detector for receiving from the fourth beam splitter a seventh and an eighth output beam, the seventh and eighth output beams being generated responsive to the respective second polarized input beam and the second polarized reference beam, the fourth optical detector generating a fourth signal responsive to the seventh output beam and to the eighth output beam; a first feedback control system for receiving the first and second signals and in response to at least one of the first and second signals generating a first feedback control signal for adjusting the first cavity length; and a second feedback control system for receiving the third and fourth signals and in response to at least one of the third and fourth signals generating a second feedback control signal for adjusting the second cavity length.