Reach On The Method Of Weak Sound Signal Detection Based On Laser Interference

Seismometers and hydrophones are the common tools for the acoustic signal detection.However, weak and low-frequency acoustic signal can not be effectively detected due to their lower sensitivity limitation. Derivation of theory and experimental verification have been done based on laser interference technology ,which could detect the weak and low frequency vibrational signal.Firstly, this paper introduces the some laser interferometer and different kinds of the measuring device briefly,and also lists their respective characteristics and parameters.Then several optical calculation methods have been researched, especially Jones matrix.This article analyzed the polarization properties of various optical components. The interferometer modulation and demodulation algorithm are studied, especially principle of the algorithm Phase Generated Carrier. In order to improve the signal-to-noise ratio and the effect of demodulation, the parameter of PGC algorithm has been optimized and selected.According to the actual situation, a set of interference measurement system is designed and manufactured,then the materials and parameters of the optical components are researched.For technical requirement, the parameters and the performance of PZT piezoelectric ceramics,amplifying circuit and photoelectric detector were studied, and the design of the acquisition and transmission and processing system were always done.Finally, the performance of the optical components were tested. The precision and frequency accuracy of the measuring system were verified by nano-displacement table and accelerometer. The noise was analyzed from the result of measuring and sources of interference in the process was found out. At last, improvement suggestions were put forward.This thesis researches the calculation method of laser interferometer theory, modulation and demodulation and the design of the measuring equipment. A laser interferometer measuring system is constructed,which could detect the low-frequency and weak acoustic signal.Resolution and dynamic range meet the design requirements, the system works well with stable performance.