Non-contact low-cost fiber distance sensor with compensation of target reflectivity

This paper presents a non-contact and low-cost distance sensor aimed at applications where displacements up to few millimeters in micromechanics or in localized spots have to be measured. The proposed sensor is based on plastic optical fibers (POF), a choice that allows obtaining the required operating range without the necessity of complex fiber bundles, as with glass fibers. Moreover, the choice of POF accounts for a simplification of the setup and of the connections. The sensing head is made with two fibers: one is used both for illuminating the target and for collecting the reflected light, and the other for collecting only. This way, by proper analysis of the two received signals it is possible to measure the distance while compensating for target surface reflectivity variations. Several experiments have validated the effectiveness of the proposed approach, highlighting the device performances and limitations.