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为了提高激光自混合干涉仪在位移测量中的精度,将相位调制技术引入激光自混合干涉系统中,通过在激光器的外腔中放置的电光调制器对光束进行正弦相位调制,采用傅里叶变换在频域中重构自混合干涉信号的相位。采用截止阶数的方法对系统的动态测量范围上限进行了理论分析,获得了正确解调相位所需的电光晶体的最低调制频率与被测振动的频率和振幅的关系。将系统应用于高精度商用压电陶瓷的振动过程的测量,测量数据与Agilent 5529A动态校准仪的同步测量结果进行比对,结果表明,相位调制型激光自混合干涉仪适合于动态信号的实时测量,位移测量精度可达20nm。
In order to improve the accuracy of the laser self-mixing interferometer in displacement measurement, the phase modulation technique is introduced into the laser self-mixing interference system, and the light beam is sinusoidally phase-modulated by the electro-optical modulator placed in the outer cavity of the laser. The Fourier transform Reconstruct the phase of the self-mixing interference signal in the frequency domain. By using the cut-off order method, the upper limit of the dynamic range of the system is theoretically analyzed. The relationship between the minimum modulation frequency of the electro-optic crystal and the frequency and amplitude of the measured vibration is obtained. The system is applied to the vibration measurement of high-precision commercial piezoelectric ceramics. The measured data are compared with those of the Agilent 5529A dynamic calibrator. The results show that the phase modulated laser self-mixing interferometer is suitable for real-time measurement of dynamic signals , Displacement measurement accuracy up to 20nm.