CN110702210A - Nonlinear Error Correction Method of Fiber-optic Michelson Interferometer Vibrometer - Google Patents
- ️Fri Jan 17 2020
技术领域technical field
本发明属于光纤干涉测量技术领域，主要涉及一种光纤迈克尔逊干涉测振仪非线性误差修正方法。The invention belongs to the technical field of optical fiber interferometric measurement, and mainly relates to a nonlinear error correction method of an optical fiber Michelson interferometric vibrometer.
背景技术Background technique
随着科学研究的快速发展和工业生产水平飞速提高，科研和工业领域对位移测量也提出了更高的要求，振动测量的最小变化量也正朝着纳米量级方向发展。光纤迈克尔逊干涉测振仪是利用激光干涉原理进行高精度位移测量的仪器，具有非接触、高精度等优点。一个光纤迈克尔逊干涉测振仪包含一个激光波长可调制光源；所述激光波长可调制光源进行波长的正弦调制；一个将波长可调制光源分为参考光束和测量光束的光纤耦合器；一个能够反射参考光束的第一反射镜；一个能够反射测量光束的第二反射镜，所述第二反射镜通常被固定于被测物体上，随被测物体一同运动；一个能够检测干涉信号的光电探测器，所述干涉信号是经过所述第一反射镜反射得到的参考光束与所述第二反射镜反射得到的测量光束干涉形成的；以及信号处理单元，耦接所述光电探测器，适于采集所述光电探测器输出的干涉信号。相比于其他激光干涉仪，由于其具有结构简单、电路处理容易、对环境的要求较低等诸多优点，因而更加广泛的应用于位移测量领域。然而，在实际应用中，非线性误差的存在却一直成为光纤迈克尔逊干涉测振仪实现高精度测量的关键问题。With the rapid development of scientific research and the rapid improvement of the level of industrial production, the scientific research and industrial fields have also put forward higher requirements for displacement measurement, and the minimum change in vibration measurement is also developing towards the nanometer level. Fiber Michelson interferometer vibrometer is an instrument for high-precision displacement measurement using the principle of laser interference. It has the advantages of non-contact and high precision. A fiber Michelson interferometer vibrometer includes a laser wavelength modulated light source; the laser wavelength modulated light source performs sinusoidal modulation of wavelength; a fiber coupler that divides the wavelength modulated light source into a reference beam and a measurement beam; a reflective A first mirror for the reference beam; a second mirror capable of reflecting the measurement beam, the second mirror is usually fixed on the object to be measured and moves with the object to be measured; a photodetector capable of detecting interference signals , the interference signal is formed by the interference of the reference beam reflected by the first mirror and the measurement beam reflected by the second mirror; and a signal processing unit, coupled to the photodetector, suitable for collecting The interference signal output by the photodetector. Compared with other laser interferometers, it is more widely used in the field of displacement measurement due to its simple structure, easy circuit processing, and lower requirements for the environment. However, in practical applications, the existence of nonlinear errors has always been a key issue in the realization of high-precision measurement of fiber-optic Michelson interferometry.
图1为典型的光源调制式光纤迈克尔逊干涉测振仪结构，正弦信号发生装置1产生正弦信号给到波长可调制激光器2，对波长可调制激光器2输出激光波长进行正弦调制，波长可调制激光器2发出的激光通过光纤耦合器3分光为参考光束和测量光束；其中参考光束经过第一准直器4准直，第一反射镜5反射，测量光束经过第二准直器6准直，第二反射镜7反射后，参考光束和测量光束原路返回到光纤耦合器3中发生干涉，并由光纤耦合器3另一端输出并入射光电探测器8，光电探测器8的输出信号理想形式如下：Figure 1 shows the structure of a typical light source-modulated fiber Michelson interferometric vibrometer. A sine signal generator 1 generates a sine signal and sends it to a wavelength-modulated laser 2. The wavelength of the output laser from the wavelength-modulated laser 2 is sinusoidally modulated. The wavelength-modulated laser The laser light emitted by 2 is split into a reference beam and a measurement beam by a fiber coupler 3; wherein the reference beam is collimated by the first collimator 4, the first reflecting mirror 5 is reflected, the measurement beam is collimated by the second collimator 6, and the first After being reflected by the two mirrors 7, the reference beam and the measuring beam return to the fiber coupler 3 to interfere, and the other end of the fiber coupler 3 outputs and enters the photodetector 8. The ideal form of the output signal of the photodetector 8 is as follows :
信号进行相位生成载波解调单元9得到Um1和Um2信号；理想状态下，Um1和Um2可以表示为：The signal is phase-generated and the carrier demodulation unit 9 obtains U m1 and U m2 signals; ideally, U m1 and U m2 can be expressed as:
其中，B为干涉信号的交流幅值，C为相位调制深度和，J1(C)和J2(C)为贝塞尔函数， 
理想情况下，调节相位载波的幅值，使得J1(C)＝J2(C)，并设定乘法器中载波基频信号和倍频信号的幅值相同即K1＝K2，为参考光路与测量光路之间的相位差。由此可以看出，Um1和Um2表现为关于 
其中m为光强调制系数，P1、P2、θ1和θ2表达式如下：where m is the intensity modulation coefficient, and the expressions of P 1 , P 2 , θ 1 and θ 2 are as follows:
以上式子可以简化整理为：The above formula can be simplified as:
其中，Ax、Ay分别为直流偏置误差，Bx、By分别为不等幅误差，δ为非正交误差。由公式可以看出，Um1和Um2实际表现为含有上述三差的正余弦函数。将上述两路含有三差的干涉信号直接用于位移解算时，会产生周期性的非线性误差，影响测量精度。因此必须通过获取干涉信号的特征参数Ax、Ay、Bx、By和δ对Um1和Um2进行修正，得到理想的正交干涉信号，从而实现对非线性误差修正。Among them, A x and A y are the DC bias errors respectively, B x and By are the unequal amplitude errors, respectively, and δ is the non-orthogonal error. It can be seen from the formula that U m1 and U m2 actually behave as sine and cosine functions containing the above three differences. When the above-mentioned two interference signals with three differences are directly used for displacement calculation, periodic nonlinear errors will be generated, which will affect the measurement accuracy. Therefore, it is necessary to correct U m1 and U m2 by obtaining the characteristic parameters A x , A y , B x , By and δ of the interference signal to obtain an ideal orthogonal interference signal, thereby realizing the correction of nonlinear errors.
非线性误差的修正方法，最早由Heydemann在1981年提出，他利用最小二乘法对大于一个周期的干涉信号进行椭圆拟合，从而获取干涉信号的特征参数，从而实现对非线性误差的修正(P.L.M.Heydemann,Determination and correction of quadrature fringemeasurement errors in interferometers.Appl.Opt.1981,20:3382-3384)，该方法为非线性误差修正的经典方法，研究人员根据该方法提出了多种改进方法，均可以称之为Heydemann修正法；德国联邦物理研究院的Dai通过检测各路干涉信号一个周期内的极大值和极小值，实时的提取非线性误差参数，实现对非线性误差的实时修正(G.-L.Dai,F.Pohlenz,H.-U.Danzebrink,K.Hasche,G.Wilkening,Improving the performance ofinterferometers in metrological scanning probe microscopes.Meas.Sci.Technol.2004,15:444-450)，称之为极值修正方法。以上两种方法虽然实现了非线性误差的修正，但其能够正常工作的前提条件为：干涉信号的相位变化不小于一个周期。The nonlinear error correction method was first proposed by Heydemann in 1981. He used the least squares method to perform ellipse fitting on the interference signal greater than one period, so as to obtain the characteristic parameters of the interference signal, so as to realize the correction of the nonlinear error (P.L.M. Heydemann, Determination and correction of quadrature fringemeasurement errors in interferometers.Appl.Opt.1981,20:3382-3384), this method is a classic method for nonlinear error correction, and researchers have proposed a variety of improved methods based on this method, all of which can be It is called the Heydemann correction method; Dai of the German Federal Institute of Physics detects the maximum and minimum values of each interference signal in a period, extracts the nonlinear error parameters in real time, and realizes the real-time correction of the nonlinear error (G .-L. Dai, F. Pohlenz, H.-U. Danzebrink, K. Hasche, G. Wilkening, Improving the performance of interferometers in metrological scanning probe microscopes. Meas. Sci. Technol. 2004, 15:444-450), It is called the extreme value correction method. Although the above two methods realize the correction of nonlinear errors, the precondition for their normal operation is that the phase change of the interference signal is not less than one cycle.
为了实现上述的前提条件，需要使干涉信号的相位产生不小于一个周期(2π)的变化，即参考光路和测量光路之间的光程差变化不小于激光波长。实际中通常采用的方法为移动第一反射镜或第二反射镜，通过改变测量光束或参考光束的光程，实现干涉信号的相位变化。但是这两种方法在实际中都存在一定的缺陷。移动第二反射镜的方法一般是通过控制被测对象的运动，使得第二反射镜产生大于激光半波长的位移，从而获取相位变化大于一个周期的干涉信号。然而实际情况中，有时被测对象能够运动的位移小于上述的位移大小甚至不能随意运动，因此无法满足上述的前提条件。相比而言，移动第一反射镜的方法一般是通过增加额外的压电陶瓷或其他运动控制元件驱动第一反射镜，同样使其产生大于激光半波长的位移，由于该位移大小相对可控，因此通常能够满足上述的前提条件。但该方法也存在一定的问题：额外增加的运动控制元件，增加系统和控制的复杂度，并且不可避免的影响了第一反射镜的位置稳定性，从而引入了测量误差。In order to realize the above preconditions, it is necessary to make the phase of the interference signal change not less than one period (2π), that is, the change of the optical path difference between the reference optical path and the measurement optical path is not less than the laser wavelength. The method usually adopted in practice is to move the first mirror or the second mirror, and realize the phase change of the interference signal by changing the optical path of the measurement beam or the reference beam. However, these two methods have certain defects in practice. The method of moving the second mirror is generally to control the movement of the object to be measured, so that the second mirror produces a displacement greater than half the wavelength of the laser, so as to obtain an interference signal with a phase change greater than one period. However, in actual situations, sometimes the displacement of the measured object that can be moved is smaller than the above-mentioned displacement and even cannot move at will, so the above-mentioned preconditions cannot be satisfied. In contrast, the method of moving the first mirror is generally to drive the first mirror by adding additional piezoelectric ceramics or other motion control elements, which also generates a displacement greater than half the wavelength of the laser, because the displacement is relatively controllable. , so the above preconditions can usually be met. However, this method also has certain problems: additional motion control elements increase the complexity of the system and control, and inevitably affect the positional stability of the first mirror, thereby introducing measurement errors.
2015年，Zhu等提出了利用光开关进行非线性误差修正的方法，该方法在参考和测量光路各配置一路光开关，通过两路光开关“开”、“关”的组合，可以在被测物处于静止状态时获取干涉信号中的部分非线性误差参数，(J.Zhu,P.Hu,J.Tan,Homodyne laservibrometer capable of detecting nanometer displacements accurately by usingoptical shutters.Appl.Opt.2015,54:10196–10199)。但是，该方法也存在一定的缺陷：该方法只能配合特定的单频干涉仪光路，并不适用于光纤迈克尔逊干涉测振仪，并且该方法只能获取干涉信号特征参数的三差中的直流偏置误差和不等幅误差参数，而对非正交误差参数则无法获取，因此不具有普遍性。In 2015, Zhu et al. proposed a method for nonlinear error correction using optical switches. This method configures an optical switch in each of the reference and measurement optical paths. Part of the nonlinear error parameters in the interference signal obtained when the object is at rest, (J.Zhu,P.Hu,J.Tan,Homodyne laservibrometer capable of detecting nanometer displacements accurately by usingoptical shutters.Appl.Opt.2015,54:10196 –10199). However, this method also has certain defects: this method can only be matched with a specific single-frequency interferometer optical path, and is not suitable for fiber Michelson interferometric vibrometers, and this method can only obtain the three differences of the characteristic parameters of the interference signal. DC offset error and unequal amplitude error parameters are not available for non-quadrature error parameters, so they are not universal.
发明内容SUMMARY OF THE INVENTION
针对上述非线性修正方法存在的问题，本发明提出和研发了一种光纤迈克尔逊干涉测振仪非线性误差修正方法及装置，本发明在不需要改变第一反射镜和第二反射镜位置的前提下，通过给激光波长可调制光源进行波长预扫描，利用输出激光波长的连续变化使干涉仪的参考光束与测量光束之间的光程差产生连续的变化，使得探测器得到的干涉信号产生至少一个周期的相位变化，实现干涉信号特征参数的预提取，并利用预提取的特征参数在测量过程中实现非线性误差修正的目的。In view of the problems existing in the above nonlinear correction methods, the present invention proposes and develops a method and device for correcting nonlinear errors of an optical fiber Michelson interferometer vibrometer. The present invention does not need to change the positions of the first and second mirrors. Under the premise, by pre-scanning the wavelength of the laser wavelength modulated light source, the optical path difference between the reference beam and the measurement beam of the interferometer can be continuously changed by the continuous change of the output laser wavelength, so that the interference signal obtained by the detector can be generated. The phase change of at least one cycle realizes the pre-extraction of the characteristic parameters of the interference signal, and uses the pre-extracted characteristic parameters to realize the purpose of nonlinear error correction in the measurement process.
本发明的目的通过以下技术方案实现：The object of the present invention is achieved through the following technical solutions:
1.光纤迈克尔逊干涉测振仪非线性误差修正方法，光纤迈克尔逊干涉仪中包含：1. The nonlinear error correction method of the fiber-optic Michelson interferometer vibrometer. The fiber-optic Michelson interferometer includes:
一个激光波长可调制的光源；A light source whose laser wavelength can be modulated;
光路结构，所述光路结构中包括：分束装置、第一反射装置和第二反射装置，其中，所述分束装置用于将所述光源发出的激光分离为参考光束和测量光束，所述第一反射装置用于反射所述参考光束，所述第二反射装置用于反射所述测量光束；an optical path structure, the optical path structure includes: a beam splitting device, a first reflection device and a second reflection device, wherein the beam splitting device is used to separate the laser light emitted by the light source into a reference beam and a measurement beam, the the first reflection device is used for reflecting the reference beam, and the second reflection device is used for reflecting the measurement beam;
一个能够检测干涉信号的光电探测器，所述干涉信号是经过所述第一反射装置反射得到的参考光束与所述第二反射装置反射得到的测量光束干涉形成的；a photodetector capable of detecting an interference signal, the interference signal is formed by the interference of the reference beam reflected by the first reflection device and the measurement beam reflected by the second reflection device;
其特征在于，所述方法包括：It is characterised in that the method includes:
步骤一：打开所述光纤迈克尔逊干涉测振仪，连续改变所述光源的输出激光波长，进而改变所述参考光束与所述测量光束之间的相位差，使得所述相位差产生至少一个周期的连续变化；Step 1: Turn on the fiber Michelson interferometric vibrometer, continuously change the output laser wavelength of the light source, and then change the phase difference between the reference beam and the measurement beam, so that the phase difference generates at least one cycle continuous change;
步骤二：提取所述干涉信号的特征参数；Step 2: extracting characteristic parameters of the interference signal;
步骤三：利用所提取到的特征参数，对光纤迈克尔逊干涉测振仪位移测量过程中的非线性误差进行修正。Step 3: Correct the nonlinear error in the displacement measurement process of the optical fiber Michelson interferometer vibrometer by using the extracted characteristic parameters.
步骤四：对得到的位移—时间图进行分析，获得振动目标的振动幅度和频率。Step 4: Analyze the obtained displacement-time diagram to obtain the vibration amplitude and frequency of the vibration target.
2.根据权利要求1所述的光纤迈克尔逊干涉测振仪非线性误差修正方法，其特征在于：所述分束装置可以是：光纤耦合器、非偏振分光镜。2 . The nonlinear error correction method for a fiber Michelson interferometer vibrometer according to claim 1 , wherein the beam splitting device can be an optical fiber coupler or a non-polarized beam splitter. 3 .
3.根据权利要求1所述的光纤迈克尔逊干涉测振仪非线性误差修正方法，其特征在于：所述第一反射装置和第二反射装置可以是：平面镜、角锥棱镜、法拉第旋转镜。3 . The method for correcting nonlinear errors of an optical fiber Michelson interferometer vibrometer according to claim 1 , wherein the first reflecting device and the second reflecting device can be: a plane mirror, a corner prism, and a Faraday rotating mirror. 4 .
本发明具有以下特点及良好效果：The present invention has the following characteristics and good effects:
相比于Heydemann或者极值修正的方法，本方法可以在不需要改变第一反射镜和第二反射镜位置的前提下，通过给波长可调制光源进行波长预扫描，利用输出激光波长的连续变化使干涉仪的参考光束与测量光束之间的光程差产生连续的变化，使得探测器得到的干涉信号产生至少一个周期的相位变化，实现干涉信号特征参数的预提取，并利用预提取的特征参数在测量过程中实现非线性误差修正的目的，提供测量精度。相比于以上两种方法，本发明技术方案尤其解决了被测位移小于激光半波长时非线性误差无法有效补偿的问题，提高了位移测量的精度。相比于利用光开关进行非线性误差修正的方法，该方法无需增加光路的复杂程度，仅仅在波长可调制激光器加入一个用于波长预扫描的信号发生装置，并且适用于光纤迈克尔逊干涉测振仪。Compared with the Heydemann or extreme value correction method, this method can pre-scan the wavelength of the wavelength-modulated light source without changing the positions of the first and second mirrors, and utilize the continuous change of the output laser wavelength. The optical path difference between the reference beam and the measurement beam of the interferometer is continuously changed, so that the interference signal obtained by the detector produces at least one cycle of phase change, so as to realize the pre-extraction of the characteristic parameters of the interference signal, and use the pre-extracted features The parameter realizes the purpose of nonlinear error correction in the measurement process and provides measurement accuracy. Compared with the above two methods, the technical solution of the present invention especially solves the problem that the nonlinear error cannot be effectively compensated when the measured displacement is less than the half wavelength of the laser, and improves the accuracy of displacement measurement. Compared with the method of nonlinear error correction using optical switches, this method does not need to increase the complexity of the optical path, only adds a signal generating device for wavelength pre-scanning to the wavelength-modulated laser, and is suitable for fiber Michelson interferometric vibration measurement. instrument.
附图说明Description of drawings
图1是由光纤耦合器构成的典型光源调制式光纤迈克尔逊干涉测振仪结构示意图；Figure 1 is a schematic structural diagram of a typical light source modulated fiber Michelson interferometric vibrometer composed of fiber couplers;
图2是本发明以应用于图1中典型光源调制式光纤迈克尔逊干涉测振仪为例时的总体配置结构示意图；2 is a schematic diagram of the overall configuration structure when the present invention is applied to the typical light source modulated fiber Michelson interferometric vibrometer in FIG. 1 as an example;
图3是由非偏振分光镜构成的紧凑型光源调制式光纤迈克尔逊干涉测振仪结构示意图；Figure 3 is a schematic structural diagram of a compact light source modulated fiber Michelson interferometry vibrometer composed of a non-polarizing beam splitter;
图4是本发明以应用于图3中紧凑型光源调制式光纤迈克尔逊干涉测振仪为例时的总体配置结构示意图；FIG. 4 is a schematic diagram of the overall configuration structure when the present invention is applied to the compact light source modulated optical fiber Michelson interferometric vibrometer in FIG. 3 as an example;
图1中件号说明：1正弦信号发生装置、2激光波长可调制光源、3光纤耦合器、4第一准直器、5第二准直器、6第一反射镜、7第二反射镜、8光电探测器、9相位生成载波解调单元、10上位机。Description of part numbers in Figure 1: 1. Sine signal generator, 2. Laser wavelength modulated light source, 3. Fiber coupler, 4. First collimator, 5. Second collimator, 6. First mirror, 7. Second mirror , 8 photodetectors, 9 phase generation carrier demodulation units, 10 upper computer.
图2中件号说明：11正弦信号发生装置、12预扫描信号发生装置、13激光波长可调制光源、14光纤耦合器、15第一准直器、16第二准直器、17第一反射镜、18第二反射镜、19光电探测器、20相位生成载波解调单元、21非线性校正单元、22上位机。Description of part numbers in Fig. 2: 11 sinusoidal signal generator, 12 pre-scan signal generator, 13 laser wavelength modulated light source, 14 fiber coupler, 15 first collimator, 16 second collimator, 17 first reflector Mirror, 18 second mirror, 19 photodetector, 20 phase generation carrier demodulation unit, 21 nonlinear correction unit, 22 upper computer.
图3中件号说明：1正弦信号发生装置、2激光波长可调制光源、3光纤环形器、4准直器、5非偏振分光镜、6第一反射镜、7第二反射镜、8光电探测器、9相位生成载波解调单元、10上位机。Description of the part number in Figure 3: 1. Sine signal generator, 2. Laser wavelength modulated light source, 3. Optical fiber circulator, 4. Collimator, 5. Non-polarizing beam splitter, 6. First reflector, 7. Second reflector, 8. Photoelectric Detector, 9 phase generation carrier demodulation unit, 10 upper computer.
图4中件号说明：11正弦信号发生装置、12预扫描信号发生装置、13激光波长可调制光源、14光纤环形器、15准直器、16非偏振分光镜、17第一反射镜、18第二反射镜、19光电探测器、20相位生成载波解调单元、21非线性校正单元、22上位机。Description of part numbers in Figure 4: 11 sinusoidal signal generator, 12 pre-scan signal generator, 13 laser wavelength modulated light source, 14 fiber circulator, 15 collimator, 16 non-polarizing beam splitter, 17 first reflector, 18 The second mirror, 19 photodetectors, 20 phase generation carrier demodulation unit, 21 nonlinear correction unit, 22 upper computer.
具体实施方式Detailed ways
由于光纤迈克尔逊干涉测振仪本身具有不同形式的光路结构，下面以图2中所示的由光纤耦合器构成的典型光纤迈克尔逊干涉仪为例，对本发明实施例进行详细描述。Since the fiber Michelson interferometer vibrometer itself has different forms of optical path structures, the following takes the typical fiber Michelson interferometer composed of fiber couplers shown in FIG. 2 as an example to describe the embodiments of the present invention in detail.
一种光纤迈克尔逊干涉测振仪非线性误差修正装置，该装置包括正弦信号发生装置11、预扫描信号发生装置12、激光波长可调制光源13、光纤耦合器14、第一准直器15、第二准直器16、第一反射镜17、第二反射镜18、光电探测器19、相位生成载波解调单元20、非线性校正单元21、上位机22；在正弦信号发生装置11输出端配置有激光波长可调制光源13，在预扫描信号发生装置12输出端配置有激光波长可调制光源13，波长可调制单频激光器13输出端配置光纤耦合器14，光纤耦合器14输出端分别配置第一准直器15和第二准直器16，第一准直器15输出端配置第一反射镜17，第二准直器16输出端配置第二反射镜18，光纤耦合器14的输入端配置有光电探测器19，光电探测器19输出端配置有相位生成载波解调单元20，相位生成载波解调单元20输出端配置有非线性校正单元21，非线性校正单元21输出端配置上位机22。An optical fiber Michelson interferometric vibrometer nonlinear error correction device, the device comprises a sinusoidal signal generating device 11, a pre-scanning signal generating device 12, a laser wavelength modulated light source 13, a fiber coupler 14, a first collimator 15, The second collimator 16 , the first mirror 17 , the second mirror 18 , the photodetector 19 , the phase generation carrier demodulation unit 20 , the nonlinear correction unit 21 , and the upper computer 22 ; at the output end of the sine signal generator 11 A laser wavelength modulated light source 13 is configured, a laser wavelength modulated light source 13 is configured at the output end of the pre-scanning signal generating device 12, a fiber coupler 14 is configured at the output end of the wavelength modulated single-frequency laser 13, and the output end of the fiber coupler 14 is configured respectively The first collimator 15 and the second collimator 16, the output end of the first collimator 15 is equipped with a first reflector 17, the output end of the second collimator 16 is equipped with a second reflector 18, the input of the fiber coupler 14 A photodetector 19 is arranged at the output end of the photodetector 19, a phase generation carrier demodulation unit 20 is arranged at the output end of the photodetector 19, a nonlinear correction unit 21 is arranged at the output end of the phase generation carrier wave demodulation unit 20, and the upper position is arranged at the output end of the nonlinear correction unit 21 Machine 22.
下面同样以图2中所示的由光纤耦合器构成的典型光纤迈克尔逊干涉测振仪为例，阐述该方法的步骤如下：The following also takes the typical fiber Michelson interferometer vibrometer composed of fiber couplers shown in FIG. 2 as an example, and the steps of the method are described as follows:
(1)打开光纤迈克尔逊干涉测振仪，正弦信号发生装置产生正弦波给到激光波长可调制光源，使光源输出波长被正弦调制，光源发出一束激光，该激光首先入射光纤耦合器中，之后通过光纤耦合器将激光分离为测量光束和参考光束；参考光束通过准直器，再经反射镜反射后原路返回；同时，测量光束经过准直器，照射到被测目标(如平面反射镜、角锥棱镜、被测物体表面)后反射，沿原路返回；参考光束和测量光束返回光纤耦合器发生干涉，由光纤耦合器出射进入光电探测器转换成电信号，电信号输入相位生成载波单元进行处理得到两路含有三差的干涉信号Um1和Um2；(1) Turn on the optical fiber Michelson interferometric vibrometer, the sinusoidal signal generating device generates a sinusoidal wave to the laser wavelength modulated light source, so that the output wavelength of the light source is sinusoidally modulated, and the light source emits a beam of laser, which is first incident into the fiber coupler, After that, the laser is separated into a measurement beam and a reference beam by a fiber coupler; the reference beam passes through the collimator, and is reflected by the mirror to return to the original path; at the same time, the measurement beam passes through the collimator and irradiates the measured target (such as plane reflection). mirror, corner prism, the surface of the object to be measured), and then reflect and return along the original path; the reference beam and the measuring beam return to the fiber coupler to interfere, and the fiber coupler exits into the photodetector and converts it into an electrical signal, and the electrical signal input phase generates The carrier unit is processed to obtain two channels of interference signals U m1 and U m2 containing three differences;
(2)预扫描信号发生装置开启，预扫描信号发生装置产生扫描信号给到波长可调制单频激光器，使激光器输出波长连续的扫描变化，因此在该过程中，参考光路与测量光路之间的光程差的变化量为 
(3)根据步骤(2)中存储的两路干涉信号Um1和Um2，并利用三差参数提取方法，如椭圆拟合法和极值检测法，可以得到两路干涉信号Um1和Um2的三差参数，即干涉信号的特征参数：Ax、Bx、Ay、By和δ；(3) According to the two interference signals U m1 and U m2 stored in step (2), and using three-difference parameter extraction methods, such as ellipse fitting method and extreme value detection method, two interference signals U m1 and U m2 can be obtained The three difference parameters of , namely the characteristic parameters of the interference signal: A x , B x , A y , By y and δ;
(4)在迈克尔逊光纤干涉测振仪位移测量过程中保持预扫描信号发生装置给到激光器信号不变，并使用步骤(3)中获取的干涉信号的特征参数，进行如下操作：(4) During the displacement measurement process of the Michelson fiber interferometer vibrometer, keep the laser signal given by the pre-scan signal generator unchanged, and use the characteristic parameters of the interference signal obtained in step (3) to perform the following operations:
可以消除干涉信号中的三差，即得到理想的正交干涉信号sin(φ)和cos(φ)，从而实现干涉测量过程中非线性误差的修正，提高测量的准确性，并利用反正切运算得到位移量。The three differences in the interference signal can be eliminated, that is, the ideal orthogonal interference signals sin(φ) and cos(φ) can be obtained, so as to realize the correction of nonlinear errors in the interferometric measurement process, improve the measurement accuracy, and use the arctangent operation. get the displacement.
(5)对得到的位移—时间图进行分析，获得振动目标的振动幅度和频率。(5) Analyze the obtained displacement-time diagram to obtain the vibration amplitude and frequency of the vibration target.