Micro-vibration measuring technology based on heterodyne interference

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 improvement 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 polarized light was changed into linearly polarized light to improve the interference signal amplitude by the polarization splitting prism (PBS); The acoustooptic modulator(AOM) was improved 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 conducted through detecting 5 kHz piezoelectric vibration signal and 2.5 MHz 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 interferometer 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.