Fig. 1. Schematic diagram of the system configuration. C, collimator.

Fig. 2. Schematic diagram of signal processing module.

Fig. 3. Measurement system; (a) schematic diagram of the measurement system; (b) picture of the prototype of the measurement system. HPI, Hewlett Packard interferometer; LS, laser source; PC, personal computer.

Fig. 4. Grating images; (a) by Zygo New View 700; (b) by SEM.

Fig. 5. Output of three interference signals.

Fig. 6. Comparison measurement result of the 10 mm round-trip; (a) original displacement difference; (b) linear fitting and residual error for the forward movement; (c) linear fitting and residual error for the backward movement. Disp, displacement.

Fig. 7. Comparison measurement result of 200 μm movement; (a) original displacement difference; (b) linear fitting and residual error for the movement.

Fig. 8. Stability test results; (a) the system stability measurement results for our system and HP5530 for 300 s; (b) Allan deviation analysis of the measurement data.