Fiber optical interferometric sensor based on a piezo-driven oscillation

We established an interferometric sensor for optical precision measurement of distance changes. A fiber-coupled micro-optical probe with an integrated reference surface is mounted on a bending beam. A piezoelectric actuator deflects the beam. Besides focus scanning this deflection modulates the optical path length of the measuring arm of the interferometer, while the reference path remains unchanged. If the distance between optical probe and measuring object changes, characteristic phase shifts of the corresponding interference signals appear. This enables us to achieve an interferometric resolution. The problem of λ/2 ambiguity is solved by using the signal envelope resulting from confocal focus scanning.