为了实现对纳米级微振动的高精度测量，在传统光外差干涉系统的基础上，设计了一种新型共线光外差干涉系统。该系统利用双声光调制器设计成结构对称的双光路，大幅削弱了环境噪声的干扰；在声光调制器后加入精密光阑滤除杂散光，消除了光学噪声；在测量光路中使用法拉第旋光器改变光的偏振态，既减少了光学器件，也使光路更易于调节。采用压电陶瓷模拟振动进行验证试验，试验结果表明，两路探测信号的幅值分别为936 mV和1.1 V，相比传统的外差干涉测量信号幅值提高约15倍，其频率均为30.12 MHz，信号波形稳定且无失真，抗噪性能大幅提升，系统分辨率为2.1 nm。

In order to realize the high-precision measurement of nanoscale micro-vibration, a new type of collinear optical heterodyne interference system is designed based on the traditional optical heterodyne interference system. The symmetrical dual optical path is designed by using dual acoustoptic modulator, which greatly reduces the interference of environmental noise. A precision diaphragm is added behind the acoustooptic modulator to filter out stray light and eliminate optical noise. The Faraday polarimeter is used to change the polarization state of the light in measuring the optical path, which not only reduces the optical components, but also makes the optical path easier to adjust. The experimental verification is carried out by simulating vibration of piezoelectric ceramics. The experimental results show that the amplitudes of the two detection signals are 936 mV and 1.1 V respectively, which is about 15 times higher than that of the traditional heterodyne interferometry, and the frequency is 30.12 MHz. The signal waveform is stable and of no distortion, and the anti-noise performance is greatly improved, and the system resolution is 2.1 nm.