Research On Laser Coherent Vibration Measurement Technology And Signal Demodulation And Enhancement Algorithms

The laser coherent detection system has the characteristics of non-contact,strong concealment,good anti-interference ability,and good detection ability for weak signals,so it is widely used in the field of interception.However,in the process of laser coherent detection,in order to achieve long-distance and high-quality signal detection,it is necessary to conduct more in-depth exploration in aspects such as optical path structure design,target selection,and signal processing.So this article focuses on these three aspects of research,and conducts a more in-depth analysis of laser coherent vibration measurement technology to improve the quality of detection signals.Firstly,the advantages and disadvantages of three laser vibration measurement technologies(speckle image measurement,light reflection vibration measurement,and laser coherent vibration measurement),as well as their adaptation scenarios,were discussed.Laser coherent technology was determined to be used as a micro vibration and speech signal detection scheme.Analyzed the impact of laser linewidth,detector radius,aberration,and demodulation algorithm on signal quality.The broadening of laser linewidth caused by the change of laser phase increases the phase noise during the detection process,resulting in corresponding noise in the demodulated signal,leading to a decrease in signal quality;An increase in detector radius will result in a decrease in signal detection quality;The presence of aberrations reduces the carrier to noise ratio of the signal;The introduction of nonlinearity in demodulation algorithms due to the influence of modulation depth will cause serious distortion of the signal.Secondly,the impact of target selection on signal quality was analyzed.Based on the analysis of acoustic braking loss and signal noise,a model of acoustic braking loss was established,and a surface roughness model of the target was established using Monte Carlo algorithm.Through experimental verification,a more suitable measurement target was selected,and glass medium was determined as the target.Then,the influence of modulation depth on the signal was compared between two traditional demodulation algorithms(differential cross multiplication and arctangent algorithm),and an optical path was constructed for laser coherent vibration measurement experiments.The experimental results show that the vibration measurement system has poor anti-interference ability and is vulnerable to environmental interference when the silent light modulation is used.Due to the influence of the modulation depth,the single optical path signal added with the Acousto-optic modulator will introduce harmonic signals,which will cause nonlinear distortion of the detection signal.Based on theoretical simulation and experimental analysis,a dual optical path heterodyne detection system is proposed,which can effectively eliminate the influence of modulation depth,avoid nonlinear distortion of the signal,and effectively restore the original signal.Prove the feasibility and development potential of dual detection coherent systems in the field of interception through comparative experiments.Finally,based on the wavelet threshold denoising theory,three threshold function methods are used to denoise the signal.Through experimental verification,wavelet threshold denoising has a good denoising effect in laser coherent vibration measurement systems,improving the signal-to-noise ratio of the signal and obtaining clear original signals.