Laser vibrometer series reciprocating optical frequency modulation calibration method and device

Abstract

A laser vibration measuring instrument series reciprocating optical frequency modulation calibration method and device belong to the field of photoelectric measurement. The calibration device is mainly composed of a calibrated laser vibration measuring instrument, a first acousto-optic modulator, a second acousto-optic modulator, a lens, a first sinusoidal signal source, a second sinusoidal signal source, an FM signal source and a plane mirror. For the laser signal emitted by the laser vibration measuring instrument, the reversibility of the optical path is used, the "I" type optical path structure is used, the output frequency translation and modulation control of the laser vibration measuring instrument are realized by using the twice optical frequency modulation mode of the same group of optical devices combined with twice optical frequency translation, the laser Doppler effect caused by different vibration waveform values is simulated, the modulated laser is completely returned to the calibrated laser vibration measuring instrument along the original path, the change waveform of the frequency value is replaced by the change waveform of the vibration speed value, and the calibration of the laser vibration measuring instrument is realized. The present application has the advantages of portability, wide frequency range, wide amplitude range calibration, high precision and good stability.

Description

TECHNICAL FIELD

[0001] The application relates to a laser vibration measuring instrument series reciprocating optical frequency modulation calibration method and device, and belongs to the technical field of photoelectric measurement. BACKGROUND

[0002] The laser vibration measuring instrument is a general and basic vibration and impact measuring instrument, has a wide frequency range, a wide amplitude range, high precision, is non-contact, has no additional interference and influence on a measured object, and can give a speed, acceleration and displacement change waveform changing with time.

[0003] The metrological calibration of the laser vibration measuring instrument has been an industry difficulty problem, and main reasons are as follows: 1) the excitation is a motion value, the measuring principle is through the laser Doppler effect, the physical motion speed is perceived through the optical frequency change, the output is in the form of an electric signal collecting data, and different aspects such as mechanical motion, optical frequency control and electronic measurement are involved; 2) due to the fact that the frequency range, amplitude range and accuracy of photoelectric measurement are far higher than those of the mechanical motion value, a suitable excitation source required for metrological calibration and performance evaluation is always lacked, and it is difficult to find a device and equipment meeting the requirements; 3) the metrological calibration is usually carried out through the excitation of a "standard vibration table", the value is measured by a "standard laser vibration measuring instrument", and other laser vibration measuring instruments are calibrated. Since the vibration table is a physical motion device of a mechanical and electrical structure, is limited by physical principles and mechanical principles, and is limited by materials and machining capacity, compared with the laser vibration measuring instrument, the stability is not easy to be high, the frequency band is narrow, the amplitude can reach a relatively large value at low frequency, the amplitude can only achieve a very small value at high frequency, the accuracy is low, and the technical requirements of metrological traceability for the laser speed are not easy to be met. Although the standard laser vibration measuring instrument is used for metrological calibration, the uncertainty caused by the vibration table characteristics and the limitation of the amplitude and frequency range are still main problems existing in the metrological calibration of the laser vibration measuring instrument. 4) on the other hand, the other laser vibration measuring instruments are still subjected to the logical problem of the metrological traceability of the standard laser vibration measuring instrument itself, and the metrological calibration problem of the standard laser vibration measuring instrument itself cannot be solved.

[0004] In view of the problems, the patent "optical frequency type metrological testing device of a laser interference vibration measuring instrument (patent number: ZL201110053568.6)" proposes a scheme of using optical frequency regulation to carry out metrological calibration, so as to solve the metrological problem of the laser vibration measuring instrument. The experimental results show that the system composed of the scheme can realize optical frequency regulation, but the returned light is unstable in intensity, and the system cannot be stably and reliably operated and applied. SUMMARY

[0005] In view of the calibration requirement of the laser Doppler principle laser vibration meter and the problems in the above-mentioned optical frequency regulation method for measuring the laser vibration meter, the purpose of the present application is to provide a laser vibration meter tandem reciprocating optical frequency modulation calibration method and device, which uses the reversibility of the optical path, uses a "one" type optical path structure, and realizes the output frequency translation and modulation control of the laser vibration meter by combining the secondary optical frequency modulation mode with the secondary optical frequency translation of the same set of optical devices, so as to simulate the laser Doppler effect caused by different vibration waveform values, return the modulated laser to the calibrated laser vibration meter in the original path, realize the effect of simulating the laser Doppler effect of vibration in the best way, and further realize the calibration of the laser Doppler speed principle laser vibration meter, and trace the vibration value to the time frequency value. The present application can realize portable, wide frequency range, wide amplitude range calibration, and can realize the calibration of the laser vibration meter with high precision and stability.

[0006] The purpose of the present application is realized by the following technical solutions:

[0007] The laser vibration meter tandem reciprocating optical frequency modulation calibration method disclosed by the present application uses the reversibility of the optical path, uses a "one" type optical path structure, and realizes the output frequency translation and modulation control of the laser vibration meter by combining the secondary optical frequency modulation mode with the secondary optical frequency translation of the same set of optical devices, so as to simulate the laser Doppler effect caused by different vibration waveform values, return the modulated laser to the calibrated laser vibration meter in the original path, realize the effect of simulating the laser Doppler effect of vibration in the best way, and further realize the calibration of the laser Doppler speed principle laser vibration meter.

[0008] Further, for the laser signal emitted by the calibrated laser vibration meter, the first sinusoidal signal source outputs a sinusoidal signal with a frequency of f B , and controls the first acousto-optic modulator to work on the-1 order diffraction level, so as to produce a frequency offset of-f B for the laser passing through the first acousto-optic modulator;

[0009] For the laser signal emitted by the calibrated laser vibration meter, the second sinusoidal signal source outputs a sinusoidal signal with a frequency of Ω, and controls the FM signal source to generate an FM voltage signal with a carrier frequency of f B , a frequency offset of Δf, and a modulation frequency of Ω, and controls the second acousto-optic modulator to work on the+1 order diffraction level, so as to produce a laser frequency offset of+f B +f d for the laser passing through the second acousto-optic modulator;

[0010] The laser with a frequency of f1 generated by the calibrated laser vibration meter passes through the first acousto-optic modulator, and becomes a laser with a frequency of f1-f Blaser with frequency f1+f d laser with frequency f1+f B +2f d laser with frequency f1+2f d laser with frequency f1+2f m laser with frequency f1+2f m laser with frequency f1+2f m laser with frequency f1+2f

[0011] Further, the two same type and size of acousto-optic modulator is used in series to carry out the series reciprocating light frequency modulation calibration.

[0012] The incident light emitted by the laser Doppler vibrometer to be calibrated is first frequency shifted by the first acousto-optic modulator working at-1 order diffraction level, and then modulated by the second acousto-optic modulator working at+1 order diffraction level.

[0013] The reflected light reflected by the plane mirror is first modulated by the second acousto-optic modulator working at+1 order diffraction level, and then frequency shifted by the first acousto-optic modulator working at-1 order diffraction level.

[0014] The frequency signal is used to generate the laser Doppler effect signal waveform of the analog vibration waveform, and the frequency shift and modulation control of the measurement laser are completed.

[0015] The first acousto-optic modulator is always frequency shifting the incident light and the reflected light; the second acousto-optic modulator is always frequency modulating the incident light and the reflected light.

[0016] Further, the lens is used to convert the fan-shaped spatial scanning light into parallel shift spatial scanning light to realize stable and reliable plane reflection; the diffraction angle vertex of the second acousto-optic modulator output light is located at the focal length position of the lens.

[0017] Further, the first acousto-optic modulator and the second acousto-optic modulator are respectively working at-2 and+2, -3 and+3 or other diffraction levels to realize the series reciprocating light frequency modulation calibration.

[0018] Further, P is a laser vibrometer 1 in a static state, and Q is a vibrating object with relative motion to P and a velocity v(t), and the vibration displacement equation of Q is:

[0019]

[0020] wherein A is the amplitude, Ω is the vibration frequency, and is the initial phase of vibration

[0021] Vibration velocity:

[0022]

[0023] Vibration velocity peak:

[0024] v m = 2πΩA (3)

[0025] The incident light emitted by P is:

[0026] E1(t) = E0 sin(2πf1t) (4)

[0027] The outgoing light reflected by Q is:

[0028] E2(t) = E0 sin(2πf2t + θ0) (5)

[0029] wherein E0 is the amplitude of the incident light, f1 is the frequency of the incident light, f2 is the frequency of the outgoing light, and θ0 is the initial phase of the outgoing light. According to the laser Doppler effect, the frequency of the outgoing light is:

[0030]

[0031] Doppler shift f d :

[0032]

[0033]

[0034] The vibration velocity peak v m determined by the Doppler shift formula according to the modulation frequency offset Δf:

[0035]

[0036] wherein Δf is the modulation frequency offset, c is the speed of light, and λ is the wavelength of the incident laser

[0037] Outgoing light phase:

[0038]

[0039] wherein θ0 is the initial phase

[0040] Emission light:

[0041]

[0042] The emission light E2(t) frequency f2(t) is an FM light with a frequency offset of Delta f and a cosine law change part with a modulation frequency of Omega superimposed on the basis of the incident light E1(t) frequency f1.

[0043] According to formula (6) (7) (8) (9), the laser vibration tester is calibrated by light frequency modulation.

[0044] The application also discloses a laser vibration tester series reciprocating light frequency modulation calibration device for realizing the laser vibration tester series reciprocating light frequency modulation calibration method. The laser vibration tester series reciprocating light frequency modulation calibration device is mainly composed of a calibrated laser vibration tester, a first acousto-optic modulator, a second acousto-optic modulator, a lens, a first sinusoidal signal source, a second sinusoidal signal source, an FM signal source and a plane mirror. The calibrated laser vibration tester, the first acousto-optic modulator, the second acousto-optic modulator, the lens and the plane mirror form a "one" type optical path structure. The first acousto-optic modulator simultaneously performs frequency translation of incident light and frequency translation of reflected light at all times, and the value of frequency translation is determined by the first sinusoidal signal source; the second acousto-optic modulator simultaneously performs frequency modulation of incident light and frequency modulation of reflected light at all times, and the modulation frequency offset and the carrier frequency are determined by the FM signal source, and the modulation frequency is determined by the second sinusoidal signal source; the diffraction angle vertex of the output light of the second acousto-optic modulator is located at the focal length position of the lens; and the plane mirror is used for reflecting the translational space scanning variable path laser transmitted by the lens.

[0045] Advantages:

[0046] 1. The laser vibration tester series reciprocating light frequency modulation calibration method and device disclosed by the application use the reversibility of an optical path, use a "one" type optical path structure, and realize output frequency translation and modulation control of a laser vibration tester by combining secondary light frequency modulation with secondary light frequency translation of the same set of optical devices on the basis of the laser frequency of the calibrated laser vibration tester, thereby simulating the laser Doppler effect caused by different vibration waveform values and returning the modulated laser to the calibrated laser vibration tester along the original path, and the effect of simulating the laser Doppler effect of vibration in an optimal manner is achieved.

[0047] 2. The laser vibration tester series reciprocating light frequency modulation calibration method and device disclosed by the application perform frequency shift control by using an acousto-optic modulator, perform light frequency modulation according to vibration waveform parameters, feed back to the calibrated laser vibration tester, replace the vibration speed value change waveform with the frequency value change waveform, and realize calibration of the laser vibration tester.

[0048] 3. The laser vibration meter series-connection reciprocating light frequency modulation calibration method and device can overcome the problems of large size, unstable performance, and inability to be portable when a mechanical movement is used to provide an excitation source for the device to be calibrated, and can balance portability and high precision, and conveniently and quickly realize on-site measurement and calibration.

[0049] 4. The laser vibration meter series-connection reciprocating light frequency modulation calibration method and device can use different diffraction orders to calibrate different speed value intervals, and each laser diffraction order has a certain frequency spectrum width, and frequency modulation and control are performed within the frequency spectrum width range.

[0050] 5. The laser vibration meter series-connection reciprocating light frequency modulation calibration method and device uses a lens to convert the fan-shaped spatial scanning light output by the acousto-optic modulator into parallel moving spatial scanning light, and then reflects the light through a plane mirror, thereby overcoming the problems of unstable light path of reflected light, strong and weak light, light loss, and lock loss caused by the fan-shaped spatial scanning light output by the acousto-optic modulator, and obtaining stable and reliable optical characteristics and excellent reproducibility, and thus the light frequency modulation method can be used to calibrate the laser vibration meter. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 is a schematic diagram of the laser Doppler effect;

[0052] Figure 2 is a structural schematic diagram of a laser vibration meter series-connection reciprocating light frequency modulation calibration device of the present application;

[0053] 1 - the laser vibration meter to be calibrated, 2 - the first acousto-optic modulator, 3 - the second acousto-optic modulator, 4 - the lens, 5 - the first sinusoidal signal source, 7 - the second sinusoidal signal source, 6 - the FM signal source, and 8 - the plane mirror. DETAILED DESCRIPTION

[0054] In order to better illustrate the purpose and advantages of the present application, the content of the application will be further described below in combination with the drawings and examples.

[0055] Example 1

[0056] The laser vibration meter series-connection reciprocating light frequency modulation calibration method disclosed in this example is as follows: Figure 2As shown, using the reversible characteristics of the light path, using the "one" type light path structure, the incident light passes through the calibrated laser Doppler vibrometer 1, the first acousto-optic modulator 2, the second acousto-optic modulator 3, the lens 4, the plane mirror 8 in turn, to realize the output frequency shift and modulation control of the laser Doppler vibrometer in the "two times optical frequency modulation mode" combined with "two times optical frequency shift", so as to simulate the laser Doppler effect caused by different vibration waveform values, and return the modulated laser to the calibrated laser Doppler vibrometer in the original path, realize the effect of simulating the laser Doppler effect of vibration in the best way, and then realize the calibration of the laser Doppler vibrometer based on the principle of laser Doppler velocimetry.

[0057] Further, for the laser signal with wavelength λ = 632.8 nm and frequency f1 = c / λ emitted by the calibrated laser Doppler vibrometer 1, the first sinusoidal signal source 5 outputs a sinusoidal signal with frequency f B = 40 MHz, and controls the first acousto-optic modulator 2 to work on the -1 order diffraction level, so as to produce a frequency offset of -f B = -40 MHz for the laser passing through the first acousto-optic modulator 2.

[0058] For the laser signal emitted by the calibrated laser Doppler vibrometer 1, the second sinusoidal signal source 7 outputs a sinusoidal signal with frequency Ω = 100 kHz, and the FM signal source 6 generates an FM voltage signal with carrier frequency f B = 40 MHz, frequency offset Δf = 2 MHz, and modulation frequency Ω, and controls the second acousto-optic modulator 3 to work on the +1 order diffraction level, so as to produce a laser frequency offset of +f B +f d = 40 MHz + f d .

[0059] The laser with frequency f1 generated by the calibrated laser Doppler vibrometer 1 passes through the first acousto-optic modulator 2 and becomes laser with frequency f1-f B = f1-40 MHz; then passes through the second acousto-optic modulator 3 and becomes fan-shaped spatial scanning variable path laser with frequency f1+f d ; the fan-shaped spatial scanning variable path laser passes through the lens 4 and becomes translational spatial scanning variable path laser; the translational spatial scanning variable path laser is then reflected by the plane mirror 8, passes through the lens 4 again, converges to the second acousto-optic modulator 3, passes through the second acousto-optic modulator 3, and becomes laser with frequency f1+f B +2f d = f1+40 MHz + 2f d ; the laser passes through the first acousto-optic modulator 2 and becomes laser with frequency f1+2f d ; returns to the calibrated laser Doppler vibrometer 1 for measurement and analysis, and gives the measurement result of the vibration speed v m ; the vibration speed v mThe measurement result is compared with the vibration velocity peak value v determined by the Doppler frequency shift formula according to the modulation frequency deviation Δf m In comparison, the calibration of the calibrated laser vibration measuring instrument 1 is further realized.

[0060] Further, the tandem reciprocating optical frequency modulation calibration is realized by using two acousto-optic modulators of the same model and specification in series.

[0061] The incident light emitted by the calibrated laser vibration measuring instrument is first frequency-shifted by the first acousto-optic modulator working at the-1 order diffraction level, and then modulated in optical frequency by the second acousto-optic modulator working at the+1 order diffraction level.

[0062] The reflected light reflected by the plane mirror is first modulated in optical frequency by the second acousto-optic modulator working at the+1 order diffraction level, and then frequency-shifted by the first acousto-optic modulator working at the-1 order diffraction level.

[0063] The laser Doppler effect signal waveform of the frequency signal is used to generate an analog vibration waveform, and the frequency shift and modulation control of the measurement laser are completed.

[0064] The first acousto-optic modulator is always frequency-shifting the incident light and the reflected light at the same time; the second acousto-optic modulator is always modulating the incident light and the reflected light in frequency at the same time.

[0065] Further, the fan-shaped space scanning light is converted into parallelly shifted space scanning light by using a lens mode to realize stable and reliable plane reflection; the vertex of the diffraction angle of the second acousto-optic modulator output light is located at the focal length position of the lens.

[0066] Further, the first acousto-optic modulator and the second acousto-optic modulator are respectively working at-2 and+2, -3 and+3 or other diffraction levels to realize the tandem reciprocating optical frequency modulation calibration.

[0067] Further, P is a laser vibration measuring instrument 1 in a stationary state, Q is a vibrating object with a relative motion with respect to P and a speed v(t), and the vibration displacement equation of Q is:

[0068]

[0069] Wherein, A is the amplitude; Ω is the vibration frequency; is the initial phase of vibration

[0070] Vibration velocity:

[0071]

[0072] Vibration velocity peak value:

[0073] v m= 2pA (3)

[0074] The incident light emitted by P is:

[0075] E1(t) = E0 sin(2pft) (4)

[0076] The outgoing light reflected by Q is:

[0077] E2(t) = E0 sin(2pf2t + 0o) (5)

[0078] Wherein, E0 is the amplitude of incident light; f1 is the frequency of incident light; f2 is the frequency of outgoing light; 0o is the initial phase of outgoing light. According to the laser Doppler effect, the outgoing light frequency is:

[0079]

[0080] Doppler shift f d :

[0081]

[0082] The vibration speed peak value v m determined by the Doppler shift formula according to the modulation frequency offset Af

[0083]

[0084] Wherein, Af is the modulation frequency offset, c is the speed of light, and l is the wavelength of incident laser

[0085] The outgoing light phase is:

[0086]

[0087] Wherein, 0o is the initial phase

[0088] The outgoing light is:

[0089]

[0090] The outgoing light E2(t) frequency f2(t) is an FM light which is based on the frequency f1 of the incident light E1(t) and superimposes a cosine law change part with a frequency offset Af and a modulation frequency of

[0091] According to formula (6) (7) (8) (9), the optical frequency modulation calibration of the laser vibration tester is realized by optical frequency modulation.

[0092] The application further discloses a laser vibration measuring instrument series reciprocating optical frequency modulation calibration device used for realizing the laser vibration measuring instrument series reciprocating optical frequency modulation calibration method. The laser vibration measuring instrument series reciprocating optical frequency modulation calibration device is mainly composed of a calibrated laser vibration measuring instrument 1, a first acousto-optic modulator 2, a second acousto-optic modulator 3, a lens 4, a first sinusoidal signal source 5, a second sinusoidal signal source 7, an FM signal source 6 and a plane mirror 8; the calibrated laser vibration measuring instrument 1, the first acousto-optic modulator 2, the second acousto-optic modulator 3, the lens 4 and the plane mirror 8 form a “-” type optical path structure; the first acousto-optic modulator 2 simultaneously performs frequency translation of incident light and frequency translation of reflected light at all times, and the value of frequency translation is determined by the first sinusoidal signal source 5; the second acousto-optic modulator 3 simultaneously performs frequency modulation of incident light and frequency modulation of reflected light at all times, and the modulation frequency offset and the carrier frequency are determined by the FM signal source 6, and the modulation frequency is determined by the second sinusoidal signal source 7; the diffraction angle vertex of the output light of the second acousto-optic modulator 3 is located at the focal length position of the lens 4; and the plane mirror 8 is used for reflecting the translational spatial scanning variable path laser transmitted by the lens.

[0093] Compared with the electromechanical vibration table excitation method, the calibration device can realize portability, wide frequency range and wide amplitude range, and can realize calibration of the laser vibration measuring instrument with high precision and stability without the need of a mechanical motion vibration table, a standard laser vibration measuring instrument and auxiliary facilities such as an additional vibration isolation foundation. Compared with the method described in the patent “Optical frequency type measurement testing device of a laser interference vibration measuring instrument (Patent No. ZL201110053568.6)”, the calibration device uses a “-” type reciprocating optical path, effectively utilizes the reversibility of the optical path, significantly reduces the optical components used, and has extremely stable and reliable light quality, strong waveform and parameter reproducibility, and can completely overcome the stability problem in the optical frequency regulation process, so that the calibration device can be more easily popularized and applied. Since the secondary modulation mode and the secondary frequency shift are used, the analog vibration amplitude range obtained by the calibration device has a doubling effect, the amplitude range is expanded, and the calibration device has important significance and value for calibration of a large-range vibration amplitude.

[0094] The above description is only specific embodiments of the application, and is not used to limit the protection scope of the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A laser vibrometer serially reciprocating optical frequency modulation calibration method, characterized by: Using the reversible characteristics of the optical path, using the "one" type optical path structure, using the "two times optical frequency modulation method" of the same group of optical devices to realize the output frequency translation and modulation control of the laser vibration meter, so as to simulate the laser Doppler effect caused by different vibration waveform values, and return the modulated laser to the original path to the calibrated laser vibration meter; The device for realizing the method is composed of a calibrated laser vibration meter (1), a first acousto-optic modulator (2), a second acousto-optic modulator (3), a lens (4), a first sinusoidal signal source (5), a second sinusoidal signal source (7), an FM signal source (6), and a plane mirror (8); the calibrated laser vibration meter (1), the first acousto-optic modulator (2), the second acousto-optic modulator (3), the lens (4), and the plane mirror (8) form a "one" type optical path structure; the first acousto-optic modulator (2) is always simultaneously performing frequency translation of incident light and frequency translation of reflected light, and the frequency translation value is controlled and determined by the first sinusoidal signal source (5); the second acousto-optic modulator (3) is always simultaneously performing frequency modulation of incident light and frequency modulation of reflected light, and the modulation frequency offset and carrier frequency are controlled and determined by the FM signal source (6), and the modulation frequency is controlled and determined by the second sinusoidal signal source (7); the diffraction angle vertex of the output light of the second acousto-optic modulator (3) is located at the focal length position of the lens (4); the plane mirror (8) is used to reflect the translational spatial scanning path laser transmitted by the lens (4).

2. The method of claim 1, wherein the laser vibrometer series-connection reciprocating optical frequency modulation calibration method is characterized by: A first sinusoidal signal source (5) outputs a sinusoidal signal with a frequency of f B , and controls the first acousto-optic modulator (2) to work on the -1 order diffraction order, so that the laser passing through the first acousto-optic modulator (2) has a frequency offset of -f B ; The second sinusoidal signal source (7) outputs a sinusoidal signal with frequency Ω in response to the laser signal emitted by the laser vibration measuring instrument (1) under calibration, and controls the FM signal source (6) to generate an FM voltage signal with carrier frequency f B , frequency deviation Δf and modulation frequency Ω, and controls the second acousto-optic modulator (3) to work on the +1 order diffraction level, so as to produce a laser frequency offset of +f B +f d for the laser passing through the second acousto-optic modulator (3). The laser with frequency f1 generated by the laser vibrometer under test (1) is converted into a laser with frequency f1-f after passing through the first acousto-optic modulator (2). B The laser light then passes through the second acousto-optic modulator (3) and becomes a laser with a frequency of f1+f. d The fan-shaped spatial scanning variable path laser is transformed into a translational spatial scanning variable path laser after passing through lens 4. The translational spatial scanning variable path laser is then reflected by plane mirror 8, passes through lens 4 again, and converges to the second acousto-optic modulator (3). After passing through the second acousto-optic modulator (3), it becomes a laser with a frequency of f1+f B +2f d The laser light, after passing through the first acousto-optic modulator (2), is converted into a frequency of f1+2f. d The laser beam is returned to the laser vibration meter (1) under calibration for measurement and analysis, and the vibration velocity v is given. m The measurement results indicate that the vibration velocity v m The measurement results are compared with the peak vibration velocity v determined by the Doppler frequency shift formula according to the modulation frequency deviation Δf. m In comparison, this allows for the calibration of the laser vibration meter (1) being calibrated.

3. A serially connected reciprocating optical frequency modulation calibration method for a laser vibrometer as recited in claim 2, characterized by: The working mode of using two acousto-optic modulators of the same model and specification in series is used to perform serial reciprocating optical frequency modulation calibration. For the incident light emitted by the calibrated laser vibration meter (1), first, the first acousto-optic modulator (2) working at the -1 order diffraction level performs frequency translation, and then the second acousto-optic modulator (3) working at the +1 order diffraction level performs optical frequency modulation. For the reflected light reflected back by the plane mirror (8), first, the second acousto-optic modulator (3) working at the +1 order diffraction level performs optical frequency modulation, and then the first acousto-optic modulator (2) working at the -1 order diffraction level performs frequency translation again. The frequency signal is used to generate the laser Doppler effect signal waveform of the analog vibration waveform, and the frequency translation and modulation control of the measurement laser are completed. The first acousto-optic modulator (2) is always simultaneously performing frequency translation of incident light and frequency translation of reflected light; the second acousto-optic modulator (3) is always simultaneously performing frequency modulation of incident light and frequency modulation of reflected light.

4. The method of claim 2, wherein the laser vibrometer series-connection reciprocating optical frequency modulation calibration method is characterized by: The lens mode is used to convert the fan-shaped spatial scanning light into parallel shift spatial scanning light, and stable and reliable plane reflection is realized; the diffraction angle vertex of the output light of the second acousto-optic modulator (3) is located at the focal length position of the lens (4).

5. The method of claim 2, wherein the laser vibrometer series-connection reciprocating optical frequency modulation calibration method is characterized by: The first acousto-optic modulator (2) and the second acousto-optic modulator (3) used respectively work at -2 and +2, -3 and +3 or other diffraction levels to realize serial reciprocating optical frequency modulation calibration.

6. A serially connected reciprocating optical frequency modulation calibration method for a laser vibrometer as recited in claim 2, characterized by: P is a laser vibration meter (1) in a static state, Q is a vibrating object with relative motion with P and a speed v(t), and the vibration displacement equation of Q is: where A is the amplitude; Ω is the oscillation frequency; is the initial phase of the oscillation Vibration speed: Vibration speed peak: v m = 2πΩA (3) The incident light emitted by P is: E1(t) = E0 sin(2πf1t) (4) The outgoing light reflected by Q is: E2(t) = E0 sin(2πf2t + θ0) (5) Wherein, E0 is the amplitude of the incident light; f1 is the frequency of the incident light; f2 is the frequency of the outgoing light; θ0 is the initial phase of the outgoing light The outgoing light frequency is modulated by the laser Doppler effect: Doppler shift f d : The peak vibration velocity v determined from the Doppler shift formula in terms of the modulation frequency deviation Δf m : Wherein, Δf is the modulation frequency offset, c is the speed of light, and λ is the wavelength of the incident laser Outgoing light phase: Wherein, θ0 is the initial phase Outgoing light: The outgoing light E2(t) frequency f2(t) is an FM light with a frequency offset of Δf and a cosine law change part with a modulation frequency of Ω, which is superimposed on the basis of the incident light E1(t) frequency f1; According to formula (6) (7) (8) (9), the optical frequency modulation calibration of the laser vibration tester is realized by optical frequency modulation.

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