Fig. 1. Diagram of principle of measurement system

Fig. 2. Photo of experimental system

Fig. 3. Reference signal from mixer and signals from PD1 and PD2 when object is moved linearly

Fig. 4. Variations of OPD of reference interferometer and measurement interferometer during displacement measurement process. (a) Variation of OPD of reference interferometer; (b) variation of OPD of measurement interferometer

Fig. 5. Optical path difference measurement results after environmental disturbances are compensated