ALL FIBER STRAIN SENSOR BASED ON THE LASER SELF-MIXING EFFECT

We present the development of a no-contact sensor based on the laser-self-mixing effect for the simultaneous measurement of the linear and angular (yaw and pitch) degrees-of-freedom of the motion of a moving stage. The sensor is made up of three laser diodes with integrated monitor photodiodes and a plane mirror target. The measurement principle is described and a series of experiments is performed to test the proposed method by direct comparison with a reference meter system. Finally, the sensor is tested under complex displacement to validate the feasibility of simultaneous measurements of more than one degree-of-freedom. The proposed technique makes the system easier to align with respect to the traditional interferometric systems and no further optical elements are required in the laser head except for the laser chip and its integrated photodiode, thus providing an effective compact and low-cost motion control system.