Patent ID: 7362445

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 beam splitter splitting the first and second light beams into a first path and a second path; a first detector path receiving the first and the second light beams from the first path, the first detector path generating a first beat signal in response to the first and the second light beams; a second detector path receiving the first and the second light beams from the second path, the second detector path generating a second beat signal in response to the first and the second light beams; an amplitude detector receiving the first and second beat signals, the amplitude detector generating an amplitude signal derived from the first and second beat signals; and a controller receiving the amplitude signal, the controller generating a plurality of control signals for controlling the at least two degrees of polarization control in response to the amplitude signal.