基于激光自混合干涉调频信号的位移测量实验

Displacement measurement experiment based on laser self-mixing interference frequency modulation signal

激光自混合干涉在高精度测量领域发挥着越来越重要的作用,微位移测量已应用于大型土木结构、航空航天、健康监测等。传统测量以调幅信号为主,但随着噪声加强,测量误差越来越大,甚至难以测量。为此,采用马赫-曾德尔干涉仪,实现了调幅/调频信号转换。针对大噪声环境下的调频信号,利用多次希尔伯特变换进行相位解卷,实现了原始信号的重构。数值仿真结果证明了该方法的有效性,在10 dB白噪声环境中,系统的信噪比为10.0614 dB,估计误差为0.0614 dB。实验结果表明,微位移重构的误差在100 nm以内,且调频信号的信噪比远高于调幅信号。该方法适用于超精密测量,且在大噪声环境下仍具有较高的信噪比。

Laser self-mixing interferometry plays an increasingly important role in the field of high precision measurement.Micro-displacement measurement has been used in large civil structures,aerospace,health monitoring and so on.The traditional measurement is based on the amplitude modulation signal,but with the enhancement of noise,the measurement error is bigger and bigger,and even difficult to measure.For this reason,the amplitude modulation/frequency modulation(AM)signal conversion is realized by using the Mach–Zehnder interferometer.In this paper,the phase unwinding of frequency modulation signal in high noise environment is carried out by using multiple Hilbert transform,and the original signal is reconstructed.Numerical simulation results demonstrate the effectiveness of the proposed method.The SNR of the system is 10.0614 dB and the estimated error is 0.0614 dB in a 10 dB white noise environment.The experimental results show that the error of micro-displacement reconstruction is within 100 nm,and the SNR of FM signal is much higher than that of AM signal.This method is suitable for ultra-precision measurement and has a high signal-to-noise ratio in high noise environment.