Fig. 1. Experimental setup for the orthogonal dual interferometer.

Fig. 2. (a) Two quadrature signals generated; (b) Lissajous graph.

Fig. 3. (a) Interference signal received by PD1; (b) interference signal received by PD2; (c) interference signal variation diagram when the displacement direction is changed; (d) Lissajous figure when moving along the x direction; (e) Lissajous figure when moving along the −x direction.

Fig. 4. (a) Conventional interferometer single-channel data acquisition; (b) phase difference resulting from each displacement; (c) orthogonal dual-interferometer two-way data acquisition; (d) 20 nm step displacement measurement results; (e) 10 nm step displacement measurement results; (f) 5 nm step displacement measurement results.

Fig. 5. (a) Schematic diagram of cosine error; (b) two interference signals when the target is stationary.