Development of a sinusoidal phase-shifting self-mixing interferometer for real-time displacement measurement with nanometer accuracy

Abstract

By combining the principles of sinusoidal phase-shifting technique and self-mixing interferometry, a novel instrument has been developed for real-time displacement measurement with nanometer accuracy. The sinusoidal phase shifting is introduced by an electro-optic modulator and the displacement of the object is measured by analyzing the harmonic components in the interference signal during each phase-shifting period. Theoretical analysis and simulation results are presented and some error sources are discussed in detail. The displacement measurement experiments by using a high precision nano-positioning stage and a long-range linear stage are performed to verify the performance of the interferometer. The measurement results of the interferometer are in good agreement with the data from a commercial dual-frequency interferometer, showing that the development of the interferometer is feasible for implementation in a real-time displacement sensor with high accuracy.