Range-resolved interferometry for metrological measurements using retroreflective microspheres

Optical interferometry is a commonly used method for precision length measurement, particularly in scientific and industrial contexts. While interferometers are effective for maintaining measurement accuracy over large distances, they are often complex and expensive systems. However, the use of pseudo-heterodyne interferometers, specifically those employing range-resolved interferometry (RRI), offers a more cost-effective solution with sub-nanometer-resolved relative length measurement capabilities. This contribution focuses on the application of retroreflective microspheres for metrological measurements using RRI technology. Interference between the back reflection of a focused beam reflected by the microspheres and the fiber tip reflection generates an optical signal that can be evaluated. The retroreflector then forms a novel kind of position encoder with nanometer readout precision where the measurement location is laterally well defined by the position of the microsphere. Various measurements using RRI with different angles of incidence will be shown as well as a comparison of different microspheres.