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).
The development of a contactless sensor based on the Laser-Self-Mixing effect for the simultaneous measurement of
linear and transverse degrees-of-freedom (DOFs) of a moving target is described in this paper. The sensor is made of
three laser diodes with integrated monitor photodiodes, and a properly designed reflective target attached to the moving
object. The proposed technique exploits the differential measurement of linear displacements by two identical self-mixing
interferometers (SMIs) and makes the system more compact and easier to align with respect to traditional
interferometric systems, thus providing an effective low-cost motion control system. The feasibility of the proposed
sensor is experimentally demonstrated over a range of 1 m for linear motion and ± 6 mm for transverse displacements,
with resolutions of 0.7 μm and 20 μm, respectively.
A new fiber strain sensor based on the Laser-Self-Mixing effect in Distributed Feedback Laser diodes is presented.
Compared with existing fiber strain sensors based on Fiber Bragg Gratings, that are sensitive to local strain, our device
achieves comparable sensitivity (~ 1 με) <i>distributed along the whole fiber length</i> and requires a <i>much simpler
electronics</i>. The sensor is based on the interferometric principle of the laser-self-mixing in the moderate feedback
regime, whereby the fiber strain results in a variation of the optical path-length seen by the radiation reflected by the end
facet of the fiber itself. Increasing or decreasing strain recognition is directly provided by the sign of the sawtooth-like