Nine-point phase demodulation for interferometric measurement

Pure high frequency periodic triangle phase shift is introduced into optical interference, calculates nine data points in each period and obtains discrete phase values. This paper proposes a novel phase demodulation technology analyzing phase information with a symmetric linear method for depressing sampling error. Traditional low finesse Fabry–Perot interferometer produces typical cosine interference signal, performance of which is greatly improved by proposed technology. In experimental configuration we situate an electro-optics crystal to induce phase shift. The variation of Fabry-Perot cavity length is measured with a resolution much higher than the fringe counting or frequency modulation techniques. Simulation and experimentation both demonstrate feasibility and robustness of proposed algorithm. Reconstructed deviation and noise sources are discussed in detail. Various vibration formats are measured as deeper verification.