Measuring Methods And Experiment Study Of Low Frequency Small Vibration With The Method Of Laser Interference

In recent years, it has attached importance to the study of low frequency testing technique. Especially with the rapid development of the modern engineering technique, high precision low frequency vibration measurement has been regarded as the needed be solved problem with the development of industry and science. Based on considering most of the high precision measurement technique, this paper proposed an improved structure of Michelson interferometer which is used to measure the low frequency vibration.In this paper, an alternating modulation phase tracking technique demodulation scheme is designed. And a cat's eye moving mirror and the PZT phase modulation tracking structure is added. The working principle and the structure of the interferometer are analyzed. The signal's frequency spectrum convert is achieved, the low-frequency noise jamming is abated, the signal-to-noise of the system is improved and the measuring resolution is enhanced according to the alternating modulation scheme; Phase tracking technique effectively suppress the low-frequency noise which is caused by outside environment factors such as temperature turbulence, vibration, and the stability of the system is enhanced. Quasi cat's eye moving mirror not only eliminate the backtracked beam which may cause optic source fluctuate influence the interferometer, but also avoid the polarization rate change of the beam, reduce the system error, and improve the system measurement precision, compared with corner cube prism.It constructs a testing platform, and dose simulations according to the laser interferometer proposed by this paper. The experiment results indicate that for the signal with the frequency of 100Hz, the output signal-to-noise is 30dB and the measuring resolution is 1nm. The interferometer can achieve the low frequency vibration measurement.