摘要
为了提取固体表面的微振动信息,本文提出了一种基于正弦相位调制干涉仪和实时归一化PGC-DCM算法的探测方法。采用归一化PGC-DCM算法实现载波相位调制深度和载波相位延迟的计算,然后对正交干涉信号分量进行预归一化,再经过运算消去干涉信号条纹的对比度系数,实现正交干涉信号分量的完全归一化,最后利用微分交叉相乘原理实现干涉信号相位的解调。利用数值仿真证明了解调算法的有效性,并在光学暗室环境中搭建了一套正弦相位调制干涉系统,对多种不同频谱特征的固体表面微振动进行探测实验和信息解调;实验结果表明,所提方法能够准确探测固体表面的微振动信息,在3 kHz的被测微振动频率范围内,干涉信号相位解调的平均信噪失真比为33.0956 dB,动态范围优于22.75 dB。
Objective Vibration is a periodic reciprocating displacement change.It is one of the most common physical phenomena.Sensing of many physical quantities can be achieved through microvibration measurements.For example,when sound waves are incident on a gas-solid surface,surface microvibration will be generated on the gassolid surface owing to the large difference in acoustic impedance between air and solid materials.Detecting the microvibration of solid surface excited via acoustic radiation can realize acoustic information extraction.Laser interferometry is the main technology for detecting weak vibrations.Because the amplitude of microvibration on a solid surface is only several nanometers,it is necessary to demodulate the interference signal phase.The phasegeneration carrier-demodulation algorithm has been widely used as a method to realize the phase demodulation of the interference signal.However,the traditional PGC-DCM algorithm is considerably affected by the optical intensity fluctuation and interference signal visibility.Further,the disturbance of a measurement light echo often results in a large nonlinear error in phase demodulation.To achieve an accurate measurement of weak vibration excited via acoustic radiation,a detection method is proposed based on a sinusoidal phase modulating interferometer and an improved PGC-DCM demodulation algorithm.Methods A sinusoidal phase modulating laser Doppler interferometer was used to detect the gas-solid surface radiated by sound waves,and a microvibration detection signal was obtained.An improved PGC-DCM algorithm based on real-time normalization was used to restore the microvibration on the solid surface.In this algorithm,the amplitude of each frequency component of the interference signal was achieved using the fast Fourier transform.Additionally,the effective interference signal components were extracted based on the spectrum threshold.Then,the amplitude sum of the low-frequency components and that of the components with a carrier frequency shift were calculated.There was a functional relationship between the ratio of the two amplitude sums and phase-modulation depth.The phase-modulation depth could be determined from the function table.The in-phase carrier and quadrature carrier signals were mixed with the interference detection signal.After filtering using a low-pass filter,the two orthogonal signals,which were mathematical,were obtained by the carrier phase delay functions.The carrier phase delay could be obtained by taking the ratio of the two signals and arctangent operation.The algorithm realized the real-time calculation of the phase-modulation depth and carrier phase delay and the prenormalization of the orthogonal interference signal components using the phase-modulation depth and carrier phase delay.Then,the algorithm was used to calculate the sum of the squares of the orthogonal interference signal components.And the interference signal visibility coefficient could be calculated using the square root of the sum signal.Thus,the complete normalization of the orthogonal interference signal components could be realized.After normalizing the orthogonal interference signal components,the phase demodulation of the interference signal was realized using the principle of differential cross multiplication.Finally,the microvibration excited via acoustic radiation was extracted through filtering.Results and Discussions To detect the solid surface microvibration excited via acoustic radiation,this paper proposes a detection method based on a sinusoidal phase modulating interferometer and an improved PGC-DCM signal demodulation algorithm based on real-time normalization.A numerical simulation of the proposed method is conducted,and a set of partial optical fiber sinusoidal phase modulating interference system is built in the darkroom environment to detect the microvibration of the solid surface excited via actual acoustic radiation.The simulated and experimental results show that the proposed improved PGC-DCM demodulation algorithm can accurately calculate the phase-modulation depth and carrier phase delay of the interference signal(Figs.4 and 5).Moreover,it can eliminate the influence of the interference signal fringe contrast coefficient and realize the normalization of the orthogonal interference signal components(Fig.8).Furthermore,the proposed method can effectively demodulate the measured microvibration.For the signal demodulation algorithm,the conventional PGC-DCM demodulation algorithm usually produces large nonlinear errors due to the fluctuation of phase-modulation depth,change in the carrier phase delay,and fluctuation of the interference signal visibility.The proposed improved PGC-DCM algorithm can effectively eliminate these nonlinear errors(Fig.10).The demodulation result of the improved PGC-DCM algorithm can effectively retain the intensity information of the measured microvibration.Conclusions The proposed algorithm and interferometric system can effectively detect the microvibration of the gas-solid interface excited via acoustic radiation.The improved PGC-DCM algorithm can accurately calculate the phase-modulation depth and carrier phase delay.Additionally,the orthogonal interference signal components can be completely normalized,thereby considerably reducing the nonlinear errors caused by the fluctuation of the phasemodulation depth and change in the carrier phase delay.The improved PGC-DCM algorithm eliminates the influence of interference signal visibility on the demodulation results.Furthermore,it realizes the complete normalization of orthogonal interference signal components of the sinusoidal phase modulating interferometer and improves the stability of the PGC-demodulation algorithm.The proposed method can detect the microvibration information of the solid surface.In the frequency range of 3 kHz,the average signal-to-noise distortion ratio of phase demodulation is 33.0956 dB and the dynamic range is 22.75 dB.
作者
张烈山
李荣森
兰益成
袁鹏哲
王嘉炜
Zhang Lieshan;Li Rongsen;Lan Yicheng;Yuan Pengzhe;Wang Jiawei(Faculty of Mechanical Engineering and Automation,Zhejiang Sci-Tech University,Hangzhou,Zhejiang 310018,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2022年第3期37-49,共13页
Chinese Journal of Lasers
基金
国家自然科学基金青年项目(61905220)
浙江省基础公益研究计划项目(LGF21F050004)。
关键词
测量
正弦相位调制
表面微振动
调制深度
载波相位延迟
归一化
measurement
sinusoidal phase modulation
surface microvibration
modulation depth
carrier phase delay
normalization
