High-dynamical-range angular measurement based on Heterodyne Phase Shifting Interferometry

A novel Heterodyne Phase Shifting Interferometer (HPSI) with nano-radians resolution and tens of milli-radians measurement range is developed. Instead of using a PZT-driven mirror to generate phase shift, the interferometer uses the heterodyne scheme. Such that the non-linearity and hysteresis effects of PZT are overcome. The non-linearity within the full range is less than 0.0005. Applying an intensity-modulated beam to test the angular measurement performance, the angular measurement noise level is 1.5nrad/Hz1/2. Due to the large dynamical range and good linearity, this HPSI is a good choice for precision angular metrology.