A linear/angular interferometer capable of measuring large angular motion

A novel linear and angular interferometric heterodyne system, capable of measuring large angular motion, is proposed. The interferometric system has a high linear-displacement resolution of 1.24 nm while the angular-displacement resolution can reach 0.0025 arcsec. By combining the advantages of the interferometer with a retroreflector and the interferometer with a plane-mirror reflector, the proposed interferometric measurement system allows a desirable transverse motion and rotational motion along any of the three orthogonal directions. Using a retroreflector with a diameter of 38.1 mm, the translational range in the transverse directions is no less than 20 mm × 10 mm while the angular range along any axis is no less than 10°. The angular readings can be used to compensate the linear outputs in real time when the Abbe error occurs. This ability has been demonstrated by the experiments.