Compact fiber-coupled three degree-of-freedom displacement interferometry for nanopositioning stage calibration

Heterodyne displacement interferometry is a widely accepted methodology capable of measuring displacements with sub-nanometer resolution in many applications. We present a compact heterodyne system capable of simultaneously measuring Z-displacement along with changes in pitch and yaw using a single measurement beam incident on a plane mirror target. The interferometer's measurement detector utilizes differential wavefront sensing to decouple and measure these three degrees of freedom. Reliable rotational measurements typically require calibration; however, two analytical models are discussed which predict the readout of rotational scaling factors.