All-interferometric six-degrees-of-freedom sensor based on laser self-mixing

We report on the development of an all-interferometric sensor based on the laser-self-mixing for the simultaneous detection of multi-degrees-of-freedom displacement of a remote target. The prototype system consists only of a laser head, equipped with 6 diode lasers and a properly designed reflective target. Information on a single degree-of-freedom motion is extracted by the differential measurement of two linear displacements by means of two nominally identical self-mixing interferometers. The sensor has been experimentally tested to measure yaw, pitch, roll, straightness and flatness corrections over a continuous linear range of 1 m, with resolutions of 0.7 μm (longitudinal), 20 μm (straightness and flatness), 0.001° (yaw and pitch) and 0.015 °(roll).