基于激光自混合干涉法的微振动测量

Measurement of Micro-Vibration Based on Laser Self-Mixing Interference

激光自混合干涉法由于其测量精度高、光路简单、准直性好等优点,十分适合于微小振动的测量.然而在测量微振动时,由于被测目标振幅微小且大多情况下其表面反射系数很低,造成测量信号的幅值较小以及光反馈导致的信号波形倾斜不明显,给测量信号解调带来了很大难度.在自混合干涉光路中添加一个预反馈镜,构成带预反馈的干涉光路系统,可将测量信号增强2~4倍.同时,推导"基频-极值点判定算法"的频率幅值解调公式,建立了模型算法,实现自混合干涉信号的解调.理论分析和实验表明,频率测量的误差小于2.5%,振幅测量的误差小于5%.

Laser self-mixing method is very suitable for the measurement of small vibration because of its high precision, simple optical path and better collimation. However, in the measurement of micro-vibration, because of the small amplitude of the object, the low coefficient of the surface and the small amplitude of the measured signal, it caused a great difficulty for the demodulation of the signal with the unobvious inclination of the signal waveform due to the optical feedback. A pre-feedback mirror was added in the self-mixing interference light path to form a feedback optical path system, which could enhance the measurement signal to 2-4 times. At the same time, the frequency and amplitude demodulation algorithm named ＂fundamental formula-extreme point＂ was derived and a model was built to realize the demodulation of the signal. The theoretical analysis and experimental results show that the error of the frequency is less than 2.5%, and the error of the amplitude is less than 5%.