Acoustic Signal Receiving And Processing Display Based On Laser Interference

For the acoustic signal detection, seismometers and pressure hydrophones have been used in the traditional methods. However, these detectors usually have lower sensitivity. Focusing on the demand of high sensitivity, the laser interference measurement techniques are researched in this thesis.Firstly, the development status and prospects of laser interference technique for acoustic signal detection are introduced. The theory of laser interference and interference requirement are researched. Principle of different type laser interferometers, the selection and testing methods of optical components are studied in this thesis.Secondly, the laser interferometer modulation and demodulation technique and the methods of signal eliminating have been analyzed, the principle and software implementation of the phase generated carrier (PGC) algorithm have been studied particularly. Improve the PGC algorithm to deduct the contrast of interference stripes effect, so the detection performance of laser interferometer can be enhanced. With the requirements of the low frequency and weak acoustic signal detection, eliminating trend methods are used to eliminate low frequency random signal after the process of PGC algorithm.Then, LabVIEW programming language is used to write a software in this thesis, which can control data acquisition card and read the GPS information to achieve real-time demodulation, process and display of laser interference signal. The software can also eliminate trend signal and improve the algorithm.Finally, the laser interferometer is constructed to research techniques of alignment and measurement about the laser interferometer. Test the laser interferometer and the software. The results have shown that the laser interferometer can detect certain low frequency and weak acoustic vibration signals, the software runs normally.This thesis researches on the optical design of interferometer, optical signal modulation and demodulation algorithm and real time display software of laser interferometer. A laser interferometer system is constructed initially, which can be used to detect low frequency acoustic signal.