Laser heterodyne interferometry nano-displacement measurement based on electro-optic modulation double-sideband

We propose a novel, to our knowledge, dual-frequency laser heterodyne interferometry nano-displacement measurement method utilizing electro-optic modulation (EOM) to generate double-sideband signals. Unlike conventional dual-frequency laser techniques, the proposed EOM based approach produces strictly symmetric double sidebands with suppressed polarization aliasing errors. By integrating optical digital coherent detection with an all-phase FFT (apFFT) fringe counting algorithm, we achieve nanoscale displacement estimation. The experimental results demonstrate that the proposed method has a resolution better than 3 nm with a microdisplacement measurement accuracy of 3 nm, and maintaining an excellent linearity of 0.0015% during high-speed displacement measurements at 0.1 m/s across 100 mm measurement range. These features suggest broad applicability across high-speed and ultra-precision measurement scenarios, indicating strong potential for industrial metrology and nanotechnology applications.