Design and simulation of velocity and displacement measurement system with subnanometer uncertainty based on a new stabilized laser Doppler-Interferometer

In this paper, a new velocity and displacement measurement system with subnanometer uncertainty based on the Doppler-interferometric method is presented. Because the instability of the laser frequency directly affects the accuracy of the displacement measurement, a three-longitudinal-mode He-Ne laser at 632.8 nm wavelength is stabilized by combination of frequency-pulling and power-balanced systems. By modeling the stabilized three-longitudinal-mode laser, the resolution of displacement measurement reaches about 90 pm and the synthetic wavelength, ignoring the coherence length, is equal to I km.