激光二极管自混合干涉实验仪和微振动研究

用振动激励信号做频率电压变换的倒相触发信号,可以从激光二极管自混合干涉信号还原扬声器谐振时的振动波形,输出信号的振幅与扬声器的振幅成正比. 用正弦波、方波和三角波信号分别激励扬声器,利用自制的激光二极管自混合干涉实验仪观测了的扬声器振动特性,测量了扬声器的谐振曲线.     

用激光自混合干涉测量扬声器的Q值

用激光自混合干涉方法测量扬声器振动,从扬声器振动引起的自混合干涉信号测量扬声器振动速率.由正弦波激振扬声器测量振速的幅频特性曲线,谐波中包含扬声器谐振频率的方波激振扬声器测量振速衰减曲线,分别按谐振法和衰减法测量得到扬声器的品质因数约13.3和10.2.由于方波激励时扬声器有谐波振动成分,由方波激励获得的衰减曲线测量得...     

基于适度光反馈自混合干涉技术的振动测量

光反馈自混合干涉技术是一种新浮现的有别于传统双光束干涉的一类新的测试技术。为了在适度光反馈下进行振动的精密测量,提出了一种基于适度光反馈自混合干涉技术的振动测量方法。经对光反馈自混合干涉信号条纹分析,发现通过选定合适的光反馈水平及激光器线宽展宽因数,可以得到锯齿干涉条纹。这种干涉信号不仅包含振动幅度信息也包含振动方向信息。该振动测量方法利用锯齿干涉条纹的特点,首先通过条纹记数实现大范围振幅粗测,具有半波长位移分辨力;然后基于适度光反馈下小数条纹的特点,给出了小于半波长位移测量的线性表达式,从而实现位移的精测。仿真计算表明,该方法可以实现大量程高分辨力振动位移测量,在叠加20 dB的噪声下,振幅测量相对误差平均为0.5%。     

两重外腔的自混合干涉及其信号分析

提出了具有两重外腔的自混合干涉。根据半导体激光器的自混合干涉理论，研究了两重外腔自混合干涉模型，及其信号的调制和解调方法。该方法用一个附加的参考反射镜在半导体激光器(LD)和目标间形成两重外腔，参考外腔用于补偿光学频率涨落引入的相位误差。用快速傅立叶变换相位探测技术(FFT)分析自混合干涉信号。运用这些方法，可提高相位测量精度，在微光机电系统、光学工程和其他工程应用上有潜在的实用价值。     

简易次声振动及监测实验装置设计

本装置利用低频扬声器作为模拟次声振源,并基于光反馈自混合干涉原理,将次声信号转换为自混合干涉信号,利用快速傅里叶变换进行分析,进而得到次声波的频率和强度.实验结果表明,该装置能够准确地测量出次声振动频率,并对其幅度进行监测.装置光路简单,结构紧凑、易实现,可推广应用于次声波检测的实验教学和监测实践.     

激光自混合干涉测振仪的硬件系统设计

基于激光自混合干涉技术的特点,设计了一种新型半导体激光自混合干涉测振仪系统。系统将频率调制引入自混合干涉中,实现对振动物体的非接触式测量。介绍了激光自混合干涉测振仪的原理、仪器系统的光路系统设计、信号的调制模块设计、解调模块设计以及DSP系统的采集处理模块设计。该仪器体积小、成本低、易于准直、可以非接触式测量,能够测量振动频率在50kHz内的物体,其中包括非周期性振动。可以测量出振动物体的振动频率、振幅以及还原振动波形,振动幅度测量精度可以达到0．325μm,频率精度为1Hz。     

音叉受迫振动的干涉测量

通过干涉测量法得到音叉振动的幅频特性曲线,同时测量位移振幅和速度振幅.实验中使用高品质因子音叉,激励信号的电压也降到了mV量级,既可以让音叉经过较长时间消除暂态过程,又可以减缓音叉由于长时间激励所带来的升温现象.使用干涉测量法测量音叉受迫振动振幅,并给出2种数据处理方式.该方法具有驱动功率小,测量精度高,直接测量位移量,同时测量两方面信号的优点.     

基于数字全息干涉的实时微振动检测

基于数字全息理论的方法,构建了一套微振动实时测量的实验系统。通过运用基于全息干涉图像的振动快速解算算法,直接从记录的全息图中提取振动信息,实现对振动物体振幅值进行实时测量。该系统的接收光为散射光,使得测量角度不受被测物体结构的影响。通过测量由标准正弦波驱动的被测物微振动情况,对该实验系统进行了实验验证,实验结果表明,该系统能够实时测量微振动的振幅值（算法处理时间约为0.11 ms）,在550～2700 Hz频段内被测物的振幅较为稳定,系统稳定性误差为1.66%,真实地反映了其振动情况。     

电磁谐振水波干涉演示仪的设计研究

本文介绍了一种自制的水波干涉衍射演示实验装置.装置利用低频信号源输出低频正弦信号,经电磁转换驱动振子做简谐振动,振子作为波源在水槽中激发水波观察水波干涉衍射现象.本文定量地分析了装置中最重要的驱动部分和振动部分的物理学原理,给出了控制演示实验效果的有效途径.装置结构简单,易于控制,成本低,实验效果明显.还可演示两列频率、振幅不相等的水波的相遇情况.     

半导体激光微小振动实时干涉测量仪

设计了一种半导体激光干涉测量仪,可以实时测量物体的微小振动。通过信号处理电路对干涉信号进行分析,得到实际振动的振幅和频率。给出了具体的理论分析,实验结果验证了该干涉仪的实用性。     

Displacement measurement method based on laser self-mixing interference in the presence of speckle

In order to achieve the accurate measurement of displacement, this Letter presents a self-mixing interference displacement measurement method suitable for the speckle effect. Because of the speckle effect, the amplitude of the self-mixing interference signal fluctuates greatly, which will affect the measurement accuracy of displacement. The ensemble empirical mode decomposition is used to process the interference signal, which can filter out high-frequency noise and low-frequency noise at the same time. The envelope of the self-mixing interference signal is extracted by Hilbert transform, and it is used to realize the normalization of the signal. Through a series of signal processing, the influence of speckle can be effectively reduced, and the self-mixing interference signal can be transformed into standard form. The displacement can be reconstructed by fringe counting and the interpolation method. The experimental results show that the method is successfully applied to the displacement measurement in the presence of speckle, which verifies the effectiveness and feasibility of the method.     

仿真分析测量参数对光反馈自混合信号的影响

针对含有光反馈的半导体激光器,在外腔波动条件下,研究其光反馈干涉自混合信号模型。经计算仿真分析,得到了外腔运动参数及激光器本身参数的变化对光反馈自混合信号波形的影响规律。结果表明,利用光反馈自混合干涉效应可以进行多参数传感测量。     

大气颗粒物多参数激光自混合传感的数值模拟与特性分析

基于颗粒物米氏散射特性、激光自混合三镜腔理论和激光器稳态条件,推导出在大气颗粒物光反馈下激光器频率、功率、线宽的理论表达式,建立了大气颗粒物光反馈下的激光自混合理论模型。同时,数值模拟和分析了大气颗粒物物理参数对激光自混合干涉信号的影响。结果表明,在一定粒径范围内,激光自混合反馈强度随大气颗粒物粒径增大先增大后减小,且反馈强度峰值出现的位置随颗粒物折射率实部的增大、虚部的减小向粒径较大处移动;自混合系统的外腔长度影响自混合干涉信号的波动深度,激光器输出光信号的幅值随外腔长度增大呈指数衰减;自混合干涉信号波动频率与大气颗粒物运动速度呈线性关系。分析结果对基于激光自混合效应的大气颗粒物多物理参数传感具有重要作用。     

Absolute small-angle measurement based on optical feedback interferometry

We present a simple but effective method for small-angle measurement based on optical feedback interferometry （or laser self-mixing interferometry）. The absolute zero angle can be defined at the biggest fringe amplitude point, so this method can also achieve absolute angle measurement. In order to verify the method, we construct an angle measurement system. The Fourier-transform method is used to analysis the interference signal. Rotation angles are experimentally measured with a resolution of 10^-6 rad and a measurement range of approximately from -0.0007 to ＋0.0007 rad.     

基于光反馈自混合干涉效应波形转折点的智能识别

对光反馈自混合干涉信号波形转折点的智能识别进行了理论分析和实验研究。首先经对光反馈自混合干涉信号特点的分析，发现其波形转折点可以作为外部物体运动位移实时测量的依据。通过对信号波形的逐步处理可以获得波形转折点的位置，以此为基准点可以实现位移的精测。实验测试结果同理论分析吻合较好。若系统进入较复杂状态，识别出的位置与其实际位置出现偏差，不再是单一值，可以对转折点位置的所有值取平均，从而得到其对应的精确位置。     

The study of laser self-mixing vibrometer employing different feedback regime using a VCSELS

Laser interferometry based on self-mixing effect widely used to measure displacement, velocity, vibration and distance due to compactness, non-contact, as well as low cost. An important use of the self-mixing effect inside a laser diode is in optical self-mixing vibrometer. We have experimentally investigated self-mixing interference produced by the feedback of light from a vibrated target into a vertical-cavity surface-emitting laser for sensing applications. In this paper, the self-mixing vibrometer employing different feedback regime is discussed and a theoretical analysis is also proposed. Numerical analysis focused on the distortion self-mixing waveform. Numerical analysis and experimental results show that mode-hop occurs when the laser self-mixing vibrometer employing at high feedback level.     

Measurement of the velocity inside an all-fiber DBR laser by self-mixing technique

The self-mixing interference for optical velocity sensing is experimentally investigated in an all-fiber configuration distributed Bragg reflector laser. Simultaneously, theory model of self-mixing interference laser Doppler velocimeter based on quasi-analytical method. The experimental results show Doppler shift frequency is linearly proportional to the value of the velocity which agrees well with theory analysis. The results preserve an enough signal-to-noise ratio around 40 dB in the range from 39.3–317.0 mm/s (measurement range depending on bandwidth of circuit) for velocity measurement. Additionally, the cutoff circuit is used in our system to get a stable Doppler signal and reduces the error rate to 0.136 % in practical measurement.