针对外差干涉的微振动测量存在稳定性低、严重受环境噪声影响等缺点，提出了对光路的改进方案。根据差分原理将其改为双光路，消除环境噪声的干扰；通过偏振分光棱镜（PBS）将椭圆偏振光变为线偏光，提高干涉信号幅值；改进频移装置（AOM），抑制频率漂移；增加光阑，滤除杂散光，提高系统信噪比。通过探测5kHz压电陶瓷振动信号，以及2．5MHz高频激光超声信号进行实验验证，结果表明：信号稳定且无纹波，系统分辨率为2．3nm，信噪比提高16．7倍。两路干涉信号幅值分别为552mV和736mV，较传统外差干涉信号幅值提高近10倍，有利于纳米量级微振动信号的检测。%Aiming at the problem that the micro-vibration based on heterodyne interference has low stability and is easily impacted by environmental noise ,the ideas of optical path improve-ment were given .According to the difference principle ,the single optical path was converted to a double optical path ,in which the environmental noise was eliminated ;The elliptically po-larized light was changed into linearly polarized light to improve the interference signal ampli-tude by the polarization splitting prism (PBS);The acousto-optic modulator(AOM ) was im-proved to inhibit frequency drift ;The stray light was suppressed by using diaphragm filters so as to improve the system signal-noise ratio (SNR) .The verification experiments were conduc-ted through detecting 5 kHz piezoelectric vibration signal and 2 .5 M Hz laser ultrasonic signal . Experimental results indicate that signal is stable and has no ripple ,the resolution is 2 .3 nm and the SNR has improved by 16 .7 times .The amplitudes of double-channel heterodyne inter-ferometer signal is 552 mV and 736 mV ,respectively ,which are larger than traditional one nearly 10 times ,it is advantageous to measure nanometer micro-vibration signals .
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