Patent ID: 7639367

Claim:
A method, comprising: directing input light to a plurality of interferometers, where each interferometer introduces a first optical path difference (OPD) between two components of the input light to form output light, wherein at least one of the components contacts a first optic and at least one of the components contacts a second optic, the first and second optics being mounted on a first and second object, respectively, the first object being movable with respect to the second object; using an optical cavity remote from the interferometers to provide the input light, wherein providing the input light comprises receiving light from a light source module, introducing a second OPD between a first portion and a second portion of the light where the second OPD is greater than a coherence length of the light source module, modulating a phase between the first and second portions, and combining the first and second portions to provide the input light; detecting the output light from the interferometers; and determining information about a position of the first object based on the detected output light from at least one of the interferometers.