A Study on Distance Measurement System Based on Low -Coherence Interferometry

A fiber-optic low-coherence interferometry system capable of absolute distance measurement is proposed. Light emitted from a broadband light source is split by a fiber-optic Michelson interferometer. When the optical path difference between the measurement arm and the reference arm falls within the coherence length of the light source, interference occurs. By demodulating the interference signal, the zero optical path difference (ZOPD) position can be obtained. The reference mirror is mounted on a reference arm translation stage to scan and locate the ZOPD positions of different measurement surfaces. By extracting the ZOPD position of each measurement surface, the absolute distance value can be obtained. The designed system features a simple structure, fast measurement speed, and high measurement accuracy. The measurement repeatability is better than 1 μm, and the measurement range exceeds 6 mm.