Highly sensitive displacement measurement utilizing the wavelength interrogation

Spectral interferometric methods utilizing the interference of two beams in a Michelson interferometer to measure the displacement are analyzed theoretically and experimentally. First we consider an experimental setup comprising a white-light source, a dispersion balanced Michelson interferometer and a spectrometer. The position of one of the interferometer mirrors is controlled via a piezo positioning system and the displacement measurement is based on the wavelength interrogation, i.e., the position of a selected interference fringe in the resultant channeled spectrum is measured as a function of the mirror displacement. Second we consider a setup with another interferometer, included in the Michelson interferometer, to increase the sensitivity of the displacement measurement. In this setup, the resultant channeled spectrum is with envelope which shifts with the displacement of the interferometer mirror. We analyze the new measurement method theoretically and show that the displacement measurement is once again possible by using the wavelength interrogation and the sensitivity is substantially increased. We also realized the new measurement setup in which the position of the interferometer mirror is controlled via a closed-loop piezo positioning system and confirmed the theoretical results.