US Patent 7515275 Optical apparatus and method for distance measuring

An optical sensor for determining a distance between a target and a probe head is described. The optical sensor comprises a light source delivering a broadband spectrum; a fiber-optic Michelson interferometer (FOMI) for creating an interferogram; and an analyzer unit for receiving the interferogram from an output of the FOMI and for determining the distance of the target by finding a position corresponding to a maximum in a Fourier transform of the spectral distribution of the interferogram. The FOMI comprises a probing optical fiber terminated by the probe head and a reference optical fiber, the reference optical fiber having a fixed optical path length.