Patent ID: 6961129

Claim:
A polarization control system for heterodyne interferometry, comprising: a light source generating a first light beam with a first polarization state and a first frequency, and a second light beam with a second polarization state and a second frequency; a polarization state modulator (PSM) receiving the first and the second light beams from the light source, the PSM having at least two degrees of polarization control, the PSM changing the first and the second polarization states; a first detector path receiving the first and the second light beams from the PSM, the first detector path generating a first beat signal in response to the first and the second light beams; an amplitude detector receiving the first beat signal, the amplitude detector generating a beat amplitude signal; and a controller receiving the beat amplitude signal, the controller generating a plurality of control signals for controlling the at least two degrees of polarization control in response to the beat amplitude signal.