WO2021082707A1 - Procédé de correction d'erreur non linéaire pour interféromètre de michelson à fibres optiques - Google Patents

Procédé de correction d'erreur non linéaire pour interféromètre de michelson à fibres optiques Download PDF

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Publication number
WO2021082707A1
WO2021082707A1 PCT/CN2020/112417 CN2020112417W WO2021082707A1 WO 2021082707 A1 WO2021082707 A1 WO 2021082707A1 CN 2020112417 W CN2020112417 W CN 2020112417W WO 2021082707 A1 WO2021082707 A1 WO 2021082707A1
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Prior art keywords
michelson interferometer
fiber
measurement
fiber michelson
interference signal
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PCT/CN2020/112417
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English (en)
Chinese (zh)
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胡鹏程
董祎嗣
杨睿韬
乐志涛
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哈尔滨工业大学
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Publication of WO2021082707A1 publication Critical patent/WO2021082707A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02055—Reduction or prevention of errors; Testing; Calibration
    • G01B9/0207—Error reduction by correction of the measurement signal based on independently determined error sources, e.g. using a reference interferometer
    • G01B9/02072—Error reduction by correction of the measurement signal based on independently determined error sources, e.g. using a reference interferometer by calibration or testing of interferometer

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  • the invention belongs to the technical field of optical fiber interferometry, and mainly relates to a method for correcting nonlinear errors of an optical fiber Michelson interferometer.
  • Fiber Michelson interferometer is an instrument that uses the principle of laser interference for high-precision displacement measurement. It has the advantages of non-contact, high-precision, etc.
  • a fiber Michelson interferometer includes a laser wavelength modulated light source; the laser wavelength modulated light source performs wavelength sinusoidal modulation; a fiber coupler that divides the wavelength modulated light source into a reference beam and a measurement beam; and a reference beam capable of reflecting The first reflector; a second reflector that can reflect the measuring beam, the second reflector is usually fixed on the measured object and moves with the measured object; a photodetector that can detect interference signals, so The interference signal is formed by the interference of the reference beam reflected by the first mirror and the measuring beam reflected by the second mirror; and a signal processing unit, coupled to the photodetector, is suitable for collecting the The interference signal output by the photodetector.
  • FIG. 1 shows the structure of a typical light source modulated fiber Michelson interferometer.
  • the sinusoidal signal generator 1 generates a sinusoidal signal and sends it to the wavelength-modulated laser 2.
  • the output laser wavelength of the wavelength-modulated laser 2 is sinusoidally modulated, and the wavelength-modulated laser 2 emits a sinusoidal signal.
  • the laser beam is split into a reference beam and a measurement beam by a fiber coupler 3; the reference beam is collimated by the first collimator 4, reflected by the first mirror 5, and the measurement beam is collimated by the second collimator 6, and the second reflected beam After being reflected by the mirror 7, the reference beam and the measuring beam return to the fiber coupler 3 to interfere, and are output from the other end of the fiber coupler 3 and enter the photodetector 8.
  • the ideal form of the output signal of the photodetector 8 is as follows:
  • the signal performs phase generation, the carrier demodulation unit 9 obtains U m1 and U m2 signals; in an ideal state, U m1 and U m2 can be expressed as:
  • B is the AC amplitude of the interference signal
  • C is the phase modulation depth sum
  • J 1 (C) and J 2 (C) are Bessel functions, with It is a double frequency carrier and a double frequency carrier, and its expression form is:
  • U m1 and U m2 can be expressed as: (Kai Wang, Min Zhang, Fajie Duan, Shangran Xie, and Yanbiao Liao, "Measurement of the phase shift between intensity and frequency modulations within DFB-LD and its influences on PGC demodulation in a fiber-optic sensor system,"Appl.Opt,52(29),7194-7199(2013).)
  • a x and A y are DC offset errors
  • B x and B y are unequal amplitude errors
  • ⁇ is non-orthogonal error. It can be seen from the formula that U m1 and U m2 actually behave as sine and cosine functions with the above three differences. When the above two interference signals with three differences are directly used for displacement calculation, periodic non-linear errors will be generated, which will affect the measurement accuracy. Therefore, U m1 and U m2 must be corrected by obtaining the characteristic parameters A x , A y , B x , By y and ⁇ of the interference signal to obtain an ideal quadrature interference signal, thereby realizing the correction of nonlinear errors.
  • the Heydemann correction method Dai of the German Federal Institute of Physics detects the maximum and minimum values of each interference signal in one cycle, 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 ), which is called the extreme value correction method.
  • the precondition for their normal operation is that the phase change of the interference signal is not less than one cycle.
  • the phase of the interference signal change not less than one period (2 ⁇ ), that is, the change in the optical path difference between the reference optical path and the measurement optical path is not less than the laser wavelength.
  • the method usually used in practice is to move the first mirror or the second mirror to change the optical path of the measuring beam or the reference beam to realize the phase change of the interference signal.
  • 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.
  • the method of moving the first mirror is generally by adding additional piezoelectric ceramics or other motion control elements to drive the first mirror, which also causes it to produce a displacement greater than half the wavelength of the laser, because the displacement is relatively controllable , So it can usually meet the above prerequisites.
  • additional motion control elements increase the complexity of the system and control, and inevitably affect the position stability of the first reflector, thereby introducing measurement errors.
  • Zhu et al. proposed a method of using optical switches for nonlinear error correction. This method is equipped with one optical switch in the reference and measurement optical path. Through the combination of two optical switches “on” and “off", it can be tested Obtain some of the nonlinear error parameters in the interference signal when the object is in a static state, (J.Zhu,P.Hu,J.Tan,Homodyne,laser,vibrometer,capable of detecting,nanometer,displacements,accurately, by using optical shutters.Appl.Opt.2015,54 :10196–10199).
  • this method also has certain shortcomings: this method can only be used with a specific single-frequency interferometer optical path, and is not suitable for fiber Michelson interferometers, and this method can only obtain the DC offset in the triple difference of the characteristic parameters of the interference signal. Setting error and unequal amplitude error parameters are not available for non-orthogonal error parameters, so they are not universal.
  • the present invention proposes and develops a method and device for nonlinear error correction of a fiber Michelson interferometer.
  • the present invention does not need to change the positions of the first mirror and the second mirror.
  • the continuous change of the output laser wavelength is used to continuously change the optical path difference between the reference beam and the measuring beam of the interferometer, so that the interference signal obtained by the detector generates at least one
  • the periodic phase change realizes the pre-extraction of the characteristic parameters of the interference signal, and uses the pre-extracted characteristic parameters to realize the purpose of non-linear error correction in the measurement process.
  • Non-linear error correction method of fiber Michelson interferometer includes:
  • a light source whose laser wavelength can be modulated
  • the optical path structure includes: a beam splitting device, a first reflecting device and a second reflecting device, wherein the beam splitting device is used to separate the laser light emitted by the light source into a reference beam and a measuring beam, the The first reflecting device is used for reflecting the reference beam, and the second reflecting device is used for reflecting the measuring beam;
  • a photodetector capable of detecting interference signals, the interference signal being formed by the interference of the reference beam reflected by the first reflecting device and the measuring beam reflected by the second reflecting device;
  • Step 1 Turn on the fiber Michelson interferometer, 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 produces at least one cycle of continuous Variety;
  • Step 2 Extract the characteristic parameters of the interference signal
  • Step 3 Use the extracted characteristic parameters to correct the nonlinear error in the displacement measurement process of the fiber Michelson interferometer.
  • the beam splitting device can be a fiber coupler or a non-polarizing beam splitter.
  • this method can pre-scan the wavelength of the wavelength modulated light source without changing the position of the first mirror and the second mirror, and utilize the continuous change of the output laser wavelength.
  • the optical path difference between the reference beam and the measuring beam of the interferometer is continuously changed, so that the interference signal obtained by the detector has at least one period 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 non-linear error correction during the measurement process and provides measurement accuracy.
  • the technical solution of the present invention particularly 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.
  • this method does not need to increase the complexity of the optical path. It only adds a signal generating device for wavelength pre-scanning to the wavelength modulated laser, and is suitable for fiber Michelson interferometers.
  • Figure 1 is a schematic diagram of the structure of a typical light source modulated fiber Michelson interferometer composed of a fiber coupler;
  • FIG. 2 is a schematic diagram of the overall configuration structure of the present invention when it is applied to the typical light source modulated fiber Michelson interferometer in FIG. 1 as an example;
  • Figure 3 is a schematic diagram of the structure of a compact light source modulated fiber Michelson interferometer composed of a non-polarizing beam splitter;
  • FIG. 4 is a schematic diagram of the overall configuration structure when the present invention is applied to the compact light source modulated fiber Michelson interferometer in FIG. 3 as an example;
  • the fiber Michelson interferometer itself has different forms of optical path structures, the following takes the typical fiber Michelson interferometer composed of the fiber coupler shown in FIG. 2 as an example to describe the embodiments of the present invention in detail.
  • a non-linear error correction device for Michelson fiber interferometer based on laser wavelength pre-scanning includes a sinusoidal signal generating device 11, a pre-scanning signal generating device 12, a laser wavelength modulated light source 13, a fiber coupler 14, and a first standard.
  • the output end of the device 11 is equipped with a laser wavelength modulated light source 13
  • the output end of the pre-scan signal generating device 12 is equipped with a laser wavelength modulated light source 13
  • the wavelength modulated single-frequency laser 13 is equipped with a fiber coupler 14, a fiber coupler 14.
  • the output ends are respectively equipped with a first collimator 15 and a 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, fiber-coupled
  • the input end of the device 14 is equipped with a photodetector 19, the output end of the photodetector 19 is equipped with a phase generating carrier demodulation unit 20, and the output end of the phase generating carrier demodulation unit 20 is equipped with a non-linear correction unit 21 and a non-linear correction unit 21.
  • the output terminal is configured with the host computer 22.
  • the sine signal generator generates a sine wave to the laser wavelength modulated light source, so that the output wavelength of the light source is sine modulated, and the light source emits a beam of laser light, which first enters the fiber coupler and then passes through
  • the fiber coupler separates the laser into the measurement beam and the reference beam; the reference beam passes through the collimator, and then returns to the original path after being reflected by the reflector; at the same time, the measurement beam passes through the collimator and irradiates the measured target (such as a flat mirror, The corner cube, the surface of the object under test) is reflected and returned 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.
  • the electrical signal enters the phase to generate the carrier unit Perform processing to obtain two interference signals U m1 and U m2 with three differences;
  • the pre-scan signal generating device is turned on, and the pre-scan signal generating device generates a scan signal to the wavelength modulated single-frequency laser, so that the laser output wavelength is continuously scanned and changed. Therefore, in the process, the reference optical path and the measurement optical path are separated from each other.
  • the amount of change in the optical path difference is
  • the phase change of the corresponding two interference signals U m1 and U m2 is also Store the two interference signals U m1 and U m2 during the change; when That is, when the change of the optical path difference is greater than the laser wavelength ⁇ , the phase change of the two interference signals U m1 and U m2 exceeds one cycle, and the Lissajous figure is a complete ellipse pattern;
  • step (3) According to the two-channel interference signal 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 channels of interference signal U m1 and U m2 can be obtained.
  • the triple difference in the interference signal can be eliminated, that is, the ideal orthogonal interference signal sin( ⁇ ) and cos( ⁇ ) can be obtained, so as to realize the correction of the nonlinear error in the interferometric measurement process and improve the accuracy of the measurement.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Instruments For Measurement Of Length By Optical Means (AREA)

Abstract

La présente invention a trait au domaine technique de l'interférométrie par fibres optiques et concerne un procédé de correction d'erreur non linéaire pour un interféromètre de Michelson à fibres optiques. Selon l'invention, sans avoir besoin de modifier la position d'un premier réflecteur et d'un deuxième réflecteur, un pré-balayage de longueur d'onde est réalisé sur une source de lumière modulée en longueur d'onde laser; une variation continue de la différence de trajet optique entre un faisceau de référence et un faisceau de mesure de l'interféromètre est générée au moyen de la variation de longueur d'onde laser de sortie continue afin de générer au moins un cycle de changement de phase dans un signal d'interférence obtenu par un détecteur, de sorte à mettre en oeuvre la pré-extraction de paramètres caractéristiques du signal d'interférence; et les paramètres caractéristiques pré-extraits sont utilisés pour mettre en oeuvre la correction d'erreur non linéaire et réaliser une mesure de déplacement à haute précision pendant le processus de mesure. La présente invention réalise la pré-extraction des paramètres caractéristiques du signal d'interférence de l'interféromètre de Michelson à fibres optiques, permet de résoudre efficacement le problème de correction d'erreur non linéaire en interférométrie, en particulier dans les mesures de micro-déplacement, et présente des avantages techniques significatifs dans le domaine de la mesure de précision.
PCT/CN2020/112417 2019-10-28 2020-08-31 Procédé de correction d'erreur non linéaire pour interféromètre de michelson à fibres optiques WO2021082707A1 (fr)

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CN110701998A (zh) * 2019-10-28 2020-01-17 哈尔滨工业大学 光纤迈克尔逊干涉仪非线性误差修正方法
CN112857210B (zh) * 2021-03-09 2023-03-17 哈尔滨工业大学 基于阵列式探测器的单光束三自由度外差激光干涉仪
CN112857208B (zh) * 2021-03-09 2022-12-16 哈尔滨工业大学 基于高速相机的单光束三自由度激光干涉仪
CN112857207B (zh) 2021-03-09 2022-12-16 哈尔滨工业大学 基于阵列式探测器的单光束三自由度零差激光干涉仪
CN113108710B (zh) * 2021-04-14 2022-05-03 安徽大学 基于椭圆拟合的光学低频应变检测系统与检测方法

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