Laser vibration meter series reciprocating type optical frequency modulation calibration method and device

Abstract

The invention discloses a laser vibration meter series reciprocating type optical frequency modulation calibration method and device, and belongs to the field of photoelectric measurement. The calibration device is mainly composed of a calibrated laser vibration meter, 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. Aiming at a laser signal emitted by the laser vibration meter, the reversibility characteristic of a light path is utilized, a straight-line-shaped light path structure is used, a secondary light frequency modulation mode of the same group of optical devices is combined with secondary light frequency translation to realize output frequency translation and modulation control of the laser vibration meter, and a laser Doppler effect caused by different vibration waveform magnitude values is simulated. And the modulated laser is completely returned to the calibrated laser vibration meter in the original path, so that the change waveform of the vibration velocity value is replaced by the change waveform of the frequency value, and the calibration of the laser vibration meter is realized. The device has the advantages of portability, wide frequency range, wide amplitude range calibration, high precision and good stability.

Description

Technical Field

[0001] The invention relates to a laser vibrometer serial reciprocating optical frequency modulation calibration method and device, belonging to the technical field of photoelectric measurement. Background Art

[0002] Laser vibrometer is a universal, basic vibration and shock measuring instrument with wide frequency range, wide amplitude range, high precision, non-contact, no additional interference and influence on the measured object, and can provide velocity, acceleration, displacement change waveforms over time.

[0003] The metrological calibration of laser vibrometers has always been a difficult problem in the industry. The main reasons are: 1) Its excitation is the value of motion, and the measurement principle used is based on the laser Doppler effect. It is necessary to perceive the physical motion speed through the change of light frequency, and the output is given in the form of electrical signal acquisition data, involving different aspects such as mechanical motion, light frequency control, and electronic measurement. 2) Since the frequency range, amplitude range and accuracy of photoelectric measurement are much higher than the frequency range, amplitude range and accuracy of mechanical motion values, there has been a lack of suitable excitation sources for its metrological calibration and performance evaluation, and it is difficult to find devices and equipment that meet the requirements. 3) Usually, its metrological calibration is carried out through the excitation of a "standard vibration table", and the value measurement is carried out with a "standard laser vibrometer", and other laser vibrometers are metrologically calibrated. Since the vibration table is a physical motion device of electromechanical structure, it is limited by the limitations of physical and mechanical principles, as well as the limitations of materials and mechanical processing capabilities. Compared with photoelectric measuring instruments such as laser vibrometers, its stability is not easy to achieve very high, the frequency band is narrow, and the amplitude can reach a relatively large value at low frequency, while at high frequency, the amplitude can only achieve a very small value, and the accuracy is also low, which is not easy to meet the technical requirements for metrological traceability of laser velocity measurement. Although people have been using standard laser vibrometers for metrological calibration, the uncertainty caused by the characteristics of the vibration table and the limitations caused by its amplitude and frequency range are still the main problems in the metrological calibration of laser vibrometers. 4) On the other hand, using standard laser vibrometers to trace other laser vibrometers for metrological traceability itself still has a logical problem that the metrological calibration problem of the standard laser vibrometer itself cannot be solved.

[0004] In response to these problems, the patent "An optical frequency metrology test device for a laser interferometer vibrometer (patent number: ZL201110053568.6)" proposes a solution for metrology calibration using optical frequency regulation to solve the metrology problems of laser vibrometers. Experimental results show that although the system composed of this solution can achieve optical frequency regulation, the returned light from its measurement is sometimes strong and sometimes weak, which is very unstable, resulting in the system being unable to operate and apply stably and reliably. Summary of the invention

[0005] In view of the calibration requirements of laser vibrometers using the laser Doppler principle and the problems of the above-mentioned optical frequency control method for measuring laser vibrometers, the purpose of the present invention is to provide a laser vibrometer serial reciprocating optical frequency modulation calibration method and device, which utilizes the reversibility of the optical path, uses a "one"-shaped optical path structure, and uses the secondary optical frequency modulation method of the same set of optical devices combined with the secondary optical frequency translation to achieve output frequency translation and modulation control of the laser vibrometer, thereby simulating the laser Doppler effect caused by different vibration waveform values, and returning the modulated laser to the calibrated laser vibrometer in its original path, so as to achieve the effect of simulating the laser Doppler effect of vibration in the best way, thereby achieving the calibration of the laser vibrometer based on the laser Doppler velocity measurement principle, and tracing its vibration value to the time frequency value. The present invention can achieve portable, wide frequency range, wide amplitude range calibration, and can achieve laser vibrometer calibration with high accuracy and stability.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] The present invention discloses a laser vibrometer serial reciprocating optical frequency modulation calibration method. The method utilizes the reversibility of an optical path, uses an I-shaped optical path structure, and combines a "secondary optical frequency modulation method" of a same set of optical devices with a "secondary optical frequency translation" to realize output frequency translation and modulation control of the laser vibrometer, thereby simulating the laser Doppler effect caused by different vibration waveform values, and returns the modulated laser to the calibrated laser vibrometer in its original path, thereby simulating the laser Doppler effect of vibration in the best way, and further realizing the calibration of the laser vibrometer based on the laser Doppler velocity measurement principle.

[0008] Furthermore, for the laser signal emitted by the calibrated laser vibrometer, the output frequency of the first sinusoidal signal source is f B The sinusoidal signal controls the first AOM to work at the -1 diffraction order, generating -f B The frequency offset of

[0009] For the laser signal emitted by the calibrated laser vibrometer, the second sinusoidal signal source outputs a sinusoidal signal with a frequency of Ω, and controls the FM signal source to generate a carrier frequency of f B , a frequency deviation of Δf, and a modulation frequency of Ω, controls the second AOM to work at the +1 diffraction order, and generates +f for the laser passing through the second AOM B +f d The laser frequency shift;

[0010] The laser with a frequency of f1 generated by the calibrated laser vibrometer passes through the first acousto-optic modulator and becomes a laser with a frequency of f1-f BThe laser then passes through the second acousto-optic modulator and becomes a laser with a frequency of f1+f d The fan-shaped space scanning shape-changing path laser is transformed into a translational space scanning shape-changing path laser through a lens; the translational space scanning shape-changing path laser is then reflected by a plane reflector, passes through the lens again, converges to the second acousto-optic modulator, passes through the second acousto-optic modulator, and becomes a frequency of f1+f B +2f d The laser passes through the first acousto-optic modulator and becomes a frequency of f1+2f d The laser is returned to the calibrated laser vibrometer for measurement and analysis, giving the vibration velocity peak value v m The vibration velocity peak value v m The measurement results are consistent with the vibration velocity peak value v determined by the modulation frequency deviation Δf using the Doppler frequency shift formula m By comparison, the calibration of the calibrated laser vibrometer is achieved.

[0011] Furthermore, two acousto-optic modulators of the same model and specification are connected in series to perform a series reciprocating optical frequency modulation calibration;

[0012] The incident light emitted by the calibrated laser vibrometer is firstly frequency-shifted by the first acousto-optic modulator working in the -1 diffraction order, and then optically frequency-modulated by the second acousto-optic modulator working in the +1 diffraction order;

[0013] The reflected light reflected by the plane reflector is firstly subjected to optical frequency modulation by the second acousto-optic modulator working at the +1 diffraction order, and then frequency-shifted again by the first acousto-optic modulator working at the -1 diffraction order;

[0014] Use the frequency signal to generate a laser Doppler effect signal waveform that simulates the vibration waveform, and complete the frequency translation and modulation control of the measurement laser;

[0015] The first acousto-optic modulator is always performing frequency translation of the incident light and frequency translation of the reflected light at the same time; the second acousto-optic modulator is always performing frequency modulation of the incident light and frequency modulation of the reflected light at the same time.

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

[0017] Furthermore, the first AOM and the second AOM used respectively work at -2 and +2, -3 and +3 or other diffraction orders to implement serial reciprocating optical frequency modulation calibration.

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

[0019]

[0020] Where A is the amplitude; Ω is the vibration frequency; is the initial phase of vibration

[0021] Vibration speed:

[0022]

[0023] Peak vibration velocity:

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

[0030]

[0031] Doppler frequency shift f d :

[0032]

[0033]

[0034] The peak value of the vibration velocity v is determined by the modulation frequency deviation Δf using the Doppler frequency shift formula m :

[0035]

[0036] Where Δf is the modulation frequency deviation, c is the speed of light, and λ is the wavelength of the incident laser.

[0037] Outgoing light phase:

[0038]

[0039] Where θ0 is the initial phase

[0040] Emerging light:

[0041]

[0042] The frequency f2(t) of the outgoing light E2(t) is obtained by superimposing a cosine-law-varying FM light portion with a frequency deviation of Δf and a modulation frequency of Ω on the frequency f1 of the incident light E1(t).

[0043] According to equations (6), (7), (8), and (9), optical frequency modulation calibration of the laser vibrometer is achieved through optical frequency modulation.

[0044] The present invention also discloses a laser vibrometer serial reciprocating optical frequency modulation calibration device, which is used to implement the laser vibrometer serial reciprocating optical frequency modulation calibration method. A laser vibrometer serial reciprocating optical frequency modulation calibration device mainly consists of a calibrated laser vibrometer, 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 reflector. The calibrated laser vibrometer, the first acousto-optic modulator, the second acousto-optic modulator, the lens, and the plane reflector form an "I"-shaped optical path structure. The first acousto-optic modulator is always performing frequency translation of the incident light and the frequency translation of the reflected light at the same time, and the value of the frequency translation is determined by the control of the first sinusoidal signal source; the second acousto-optic modulator is always performing frequency modulation of the incident light and the frequency modulation of the reflected light at the same time, the modulation frequency deviation and the carrier frequency are determined by the control of the FM signal source, and the modulation frequency is determined by the control of the second sinusoidal signal source; the vertex of the diffraction angle of the output light of the second acousto-optic modulator is located at the focal length position of the lens; the plane reflector is used to reflect the translational spatial scanning shape-changing path laser transmitted by the lens.

[0045] Beneficial effects:

[0046] 1. The present invention discloses a laser vibrometer serial reciprocating optical frequency modulation calibration method and device. Based on the laser frequency emitted by the laser vibrometer to be calibrated, the reversible characteristics of the optical path are utilized, and a "one"-shaped optical path structure is used. The secondary optical frequency modulation method of the same set of optical devices is combined with the secondary optical frequency shift to realize the output frequency shift and modulation control of the laser vibrometer, thereby simulating the laser Doppler effect caused by different vibration waveform values, and returning the modulated laser to the laser vibrometer to be calibrated in its original path, thereby realizing the effect of simulating the laser Doppler effect of vibration in the best way.

[0047] 2. The present invention discloses a laser vibrometer serial reciprocating optical frequency modulation calibration method and device, which uses an acousto-optic modulator to perform frequency shift control, performs optical frequency modulation according to vibration waveform parameters, and feeds back to the calibrated laser vibrometer, so as to replace the changing waveform of the vibration velocity value with the changing waveform of the frequency value, thereby realizing the calibration of the laser vibrometer.

[0048] 3. The present invention discloses a laser vibrometer serial reciprocating optical frequency modulation calibration method and device, which realizes the mechanical motion speed value by equivalently realizing the mechanical motion speed value with the frequency value of the electrical signal source, and can overcome the problems of large size, unstable performance, and non-portability that are difficult to avoid when providing an excitation source for the calibrated equipment in a mechanical motion manner, and can also take into account portability and high precision, and realize on-site measurement and calibration conveniently and quickly.

[0049] 4. The present invention discloses a laser vibrometer serial reciprocating optical frequency modulation calibration method and device, which can use different diffraction orders to calibrate different speed value intervals. Each laser diffraction order has a certain spectrum width, and frequency modulation and control are performed within the spectrum width range.

[0050] 5. The present invention discloses a laser vibrometer serial reciprocating optical frequency modulation calibration method and device, which uses a lens to convert the fan-shaped spatial scanning light output by the acousto-optic modulator into a parallel moving spatial scanning light, and then reflects it through a plane reflector, thereby overcoming the problems of unstable optical path, fluctuating intensity, light loss, and lock loss of the reflected light caused by the fan-shaped spatial scanning light output by the acousto-optic modulator, and obtaining stable, reliable, and reproducible optical characteristics, thereby realizing the optical frequency regulation method to calibrate the laser vibrometer. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0052] Figure 2 It is a structural schematic diagram of a laser vibrometer serial reciprocating optical frequency modulation calibration device of the present invention;

[0053] Among them: 1 is the calibrated laser vibrometer, 2 is the first acousto-optic modulator, 3 is the second acousto-optic modulator, 4 is the lens, 5 is the first sinusoidal signal source, 7 is the second sinusoidal signal source, 6 is the FM signal source, and 8 is the plane reflector. DETAILED DESCRIPTION

[0054] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below with reference to the accompanying drawings and examples.

[0055] Embodiment 1:

[0056] This embodiment discloses a laser vibrometer serial reciprocating optical frequency modulation calibration method, such as Figure 2As shown, by utilizing the reversibility of the optical path and using an “I”-shaped optical path structure, the incident light successively passes through the laser vibrometer 1 to be calibrated, the first acousto-optic modulator 2, the second acousto-optic modulator 3, the lens 4, and the plane reflector 8, and the “secondary optical frequency modulation method” and “secondary optical frequency shift” of the same set of optical devices are combined to realize the output frequency shift and modulation control of the laser vibrometer, thereby simulating the laser Doppler effect caused by different vibration waveform values, and returning the modulated laser to the laser vibrometer in its original path, so as to realize the effect of simulating the laser Doppler effect of vibration in the best way, thereby realizing the calibration of the laser vibrometer based on the laser Doppler velocity measurement principle.

[0057] Furthermore, for the laser signal with wavelength λ=632.8nm and frequency f1=c / λ emitted by the calibrated laser vibrometer 1, the first sinusoidal signal source 5 outputs a frequency f B =40MHz sinusoidal signal, controls the first AOM 2 to work at the -1st diffraction order, and generates -f for the laser passing through the first AOM 2. B = -40MHz frequency deviation.

[0058] For the laser signal emitted by the calibrated laser vibrometer 1, the second sinusoidal signal source 7 outputs a sinusoidal signal with a frequency of Ω=100kHz, and controls the FM signal source 6 to generate a carrier frequency of f B =40MHz, frequency deviation Δf=2MHz, modulation frequency ΩFM voltage signal, control the second acousto-optic modulator 3 to work at the +1 diffraction order, and generate +f for the laser passing through the second acousto-optic modulator 3 B +f d =40MHz+f d The laser frequency shift.

[0059] The laser light with a frequency of f1 generated by the calibrated laser vibrometer 1 is converted to a frequency of f1-f by the first acousto-optic modulator 2. B = f1-40MHz laser; then passes through the second acousto-optic modulator 3 and becomes a laser with a frequency of f1+f d The fan-shaped space scanning shape-changing path laser passes through the lens 4 and becomes the translational space scanning shape-changing path laser; the translational space scanning shape-changing path laser is then reflected by the plane reflector 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 the frequency f1+f B +2f d =f1+40MHz+2f d The laser passes through the first acousto-optic modulator 2 and becomes a frequency of f1+2f d The laser is returned to the calibrated laser vibrometer 1 for measurement and analysis, giving the vibration velocity v m The measurement results of the vibration speed v mThe measurement results are consistent with the vibration velocity peak value v determined by the modulation frequency deviation Δf using the Doppler frequency shift formula m By comparison, the calibration of the calibrated laser vibrometer 1 is achieved.

[0060] Furthermore, two acousto-optic modulators of the same model and specification are connected in series to perform a series reciprocating optical frequency modulation calibration;

[0061] The incident light emitted by the calibrated laser vibrometer is firstly frequency-shifted by the first acousto-optic modulator working in the -1 diffraction order, and then optically frequency-modulated by the second acousto-optic modulator working in the +1 diffraction order;

[0062] The reflected light reflected by the plane reflector is firstly subjected to optical frequency modulation by the second acousto-optic modulator working at the +1 diffraction order, and then frequency-shifted again by the first acousto-optic modulator working at the -1 diffraction order;

[0063] Use the frequency signal to generate a laser Doppler effect signal waveform that simulates the vibration waveform, and complete the frequency translation and modulation control of the measurement laser;

[0064] The first acousto-optic modulator is always performing frequency translation of the incident light and frequency translation of the reflected light at the same time; the second acousto-optic modulator is always performing frequency modulation of the incident light and frequency modulation of the reflected light at the same time.

[0065] Furthermore, a lens is used to convert the fan-shaped spatial scanning light into a parallel shifted spatial scanning light to achieve stable and reliable plane reflection; the vertex of the diffraction angle of the output light of the second acousto-optic modulator is located at the focal length position of the lens.

[0066] Furthermore, the first AOM and the second AOM used respectively work at -2 and +2, -3 and +3 or other diffraction orders to implement serial reciprocating optical frequency modulation calibration.

[0067] Furthermore, P is a laser vibrometer 1 in a stationary state, Q is a vibrating object in relative motion with P and with a velocity v(t), and the vibration displacement equation is:

[0068]

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

[0070] Vibration speed:

[0071]

[0072] Peak vibration velocity:

[0073] v m=2πΩA (3)

[0074] The incident light emitted by P is:

[0075] E1(t)=E0 sin(2πf1t) (4)

[0076] The outgoing light reflected by Q is:

[0077] E2(t)=E0 sin(2πf2t+θ0) (5)

[0078] Among them, E0 is the incident light amplitude; f1 is the incident light frequency; f2 is the outgoing light frequency; θ0 is the initial phase of the outgoing light. According to the laser Doppler effect, the outgoing light frequency is:

[0079]

[0080] Doppler frequency shift f d :

[0081]

[0082] The peak value of the vibration velocity v is determined by the modulation frequency deviation Δf using the Doppler frequency shift formula m :

[0083]

[0084] Where Δf is the modulation frequency deviation, c is the speed of light, and λ is the wavelength of the incident laser.

[0085] Outgoing light phase:

[0086]

[0087] Where θ0 is the initial phase

[0088] Emerging light:

[0089]

[0090] The frequency f2(t) of the outgoing light E2(t) is obtained by superimposing a cosine-law-varying FM light portion with a frequency deviation of Δf and a modulation frequency of Ω on the frequency f1 of the incident light E1(t).

[0091] According to equations (6), (7), (8), and (9), optical frequency modulation calibration of the laser vibrometer is achieved through optical frequency modulation.

[0092] The invention also discloses a laser vibrometer serial reciprocating optical frequency modulation calibration device, which is used to implement the laser vibrometer serial reciprocating optical frequency modulation calibration method. A laser vibrometer serial reciprocating optical frequency modulation calibration device is mainly composed of a calibrated laser vibrometer 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 reflector 8. The calibrated laser vibrometer 1, the first acousto-optic modulator 2, the second acousto-optic modulator 3, the lens 4, and the plane reflector 8 form an "I"-shaped optical path structure; the first acousto-optic modulator 2 is always performing frequency translation of incident light and frequency translation of reflected light at the same time, and the value of the frequency translation is controlled and determined by the first sinusoidal signal source 5; the second acousto-optic modulator 3 is always performing frequency modulation of incident light and frequency modulation of reflected light at the same time, and the modulation frequency deviation 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 vertex of the diffraction angle 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 reflector 8 is used to reflect the translational spatial scanning shape-changing path laser transmitted by the lens.

[0093] Compared with the electromechanical vibration table excitation method, the calibration device of this embodiment can be portable, have a wide frequency range, a wide amplitude range, and can calibrate the laser vibrometer with high accuracy and stability, because it does not require a mechanically moving vibration table and a standard laser vibrometer, as well as additional auxiliary facilities such as a vibration isolation foundation. Compared with the method described in the patent "An optical frequency measurement test device for a laser interferometer vibrometer (patent number: ZL201110053568.6)", due to the use of a "one"-shaped reciprocating optical path, the reversibility of the optical path is effectively utilized, the optical components used in the calibration device of this embodiment are significantly reduced, the light quality is extremely stable and reliable, the waveform and parameter reproducibility are extremely strong, and the stability problem in the optical frequency regulation process can be completely overcome, making it easier to promote and apply. Due to the use of secondary modulation and secondary frequency shift, the simulated vibration amplitude range obtained by the present invention has a doubling effect, expanding the amplitude range, and has important significance and value for large-range vibration amplitude calibration.

[0094] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A laser vibrometer serial reciprocating optical frequency modulation calibration method, characterized in that: By utilizing the reversibility of the optical path and using a "I"-shaped optical path structure, the output frequency shift and modulation control of the laser vibrometer are realized by combining the "secondary optical frequency modulation method" and "secondary optical frequency shift" of the same set of optical devices, thereby simulating the laser Doppler effect caused by different vibration waveform values, and returning the modulated laser to the calibrated laser vibrometer along its original path, simulating the laser Doppler effect of vibration in the best way, and then realizing the calibration of the laser vibrometer based on the laser Doppler velocity measurement principle.

2. A laser vibrometer serial reciprocating optical frequency modulation calibration method as claimed in claim 1, characterized in that: For the laser signal emitted by the calibrated laser vibrometer (1), the first sinusoidal signal source (5) has an output frequency of f B The sine signal controls the first acousto-optic modulator (2) to work at the -1 diffraction order, and generates -f for the laser passing through the first acousto-optic modulator (2). B The frequency offset of In response to the laser signal emitted by the calibrated laser vibrometer (1), the second sinusoidal signal source (7) outputs a sinusoidal signal with a frequency of Ω, and controls the FM signal source (6) to generate a carrier frequency of f B , a frequency deviation of Δf, and a modulation frequency of Ω, controls the second acousto-optic modulator (3) to work at the +1 diffraction order, and generates +f for the laser passing through the second acousto-optic modulator (3). B +f d The laser frequency shift; The laser light with a frequency of f1 generated by the calibrated laser vibrometer (1) is converted into a laser light with a frequency of f1-f1 by passing through the first acousto-optic modulator (2). B The laser then passes through the second acousto-optic modulator (3) and becomes a laser with a frequency of f1+f d The fan-shaped space scanning shape-changing path laser is converted into a translational space scanning shape-changing path laser through lens 4; the translational space scanning shape-changing path laser is then reflected by the plane reflector 8, passes through lens 4 again, converges to the second acousto-optic modulator (3), passes through the second acousto-optic modulator (3), and becomes a frequency of f1+f B +2f d The laser light passes through the first acousto-optic modulator (2) and becomes a laser with a frequency of f1+2f d The laser is returned to the calibrated laser vibrometer (1) for measurement and analysis, giving the vibration velocity v m The measurement results of the vibration speed v m The measurement results are consistent with the vibration velocity peak value v determined by the modulation frequency deviation Δf using the Doppler frequency shift formula m By comparison, the calibration of the laser vibrometer (1) to be calibrated is achieved.

3. A laser vibrometer serial reciprocating optical frequency modulation calibration method as claimed in claim 2, characterized in that: Use two acousto-optic modulators of the same model and specification to connect in series to perform series reciprocating optical frequency modulation calibration; The incident light emitted by the calibrated laser vibrometer (1) is firstly frequency-shifted by a first acousto-optic modulator (2) working at the -1st diffraction order, and then optically frequency-modulated by a second acousto-optic modulator (3) working at the +1st diffraction order; The reflected light reflected by the plane reflector (8) is firstly subjected to optical frequency modulation by the second acousto-optic modulator (3) working at the +1st diffraction order, and then frequency-shifted again by the first acousto-optic modulator (2) working at the -1st diffraction order; Use the frequency signal to generate a laser Doppler effect signal waveform that simulates the vibration waveform, and complete the frequency translation and modulation control of the measurement laser; The first acousto-optic modulator (2) is always performing frequency translation of the incident light and frequency translation of the reflected light at the same time; the second acousto-optic modulator (3) is always performing frequency modulation of the incident light and frequency modulation of the reflected light at the same time.

4. A laser vibrometer serial reciprocating optical frequency modulation calibration method as claimed in claim 2, characterized in that: The fan-shaped spatial scanning light is converted into parallel shifted spatial scanning light by using a lens method, thereby realizing stable and reliable plane reflection; the vertex of the diffraction angle of the output light of the second acousto-optic modulator (3) is located at the focal length position of the lens (4).

5. A laser vibrometer serial reciprocating optical frequency modulation calibration method as claimed in claim 2, characterized in that: 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 orders to realize serial reciprocating optical frequency modulation calibration.

6. A laser vibrometer serial reciprocating optical frequency modulation calibration method as claimed in claim 2, characterized in that: P is a laser vibrometer (1) in a stationary state, Q is a vibrating object in relative motion with P and with a velocity v(t), and its vibration displacement equation is: Where A is the amplitude; Ω is the vibration frequency; is the initial phase of vibration Vibration speed: Peak vibration velocity: 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) Among them, E0 is the incident light amplitude; f1 is the incident light frequency; f2 is the outgoing light frequency; θ0 is the initial phase of the outgoing light. According to the laser Doppler effect, the outgoing light frequency is: Doppler frequency shift f d : The vibration velocity peak value v is determined by the modulation frequency deviation Δf using the Doppler frequency shift formula m : Where Δf is the modulation frequency deviation, c is the speed of light, and λ is the wavelength of the incident laser. Outgoing light phase: Where θ0 is the initial phase Emerging light: The frequency f2(t) of the outgoing light E2(t) is the frequency f1 of the incident light E1(t), with a cosine-law-varying FM light part superimposed on it with a frequency deviation of Δf and a modulation frequency of Ω. According to equations (6), (7), (8), and (9), optical frequency modulation calibration of the laser vibrometer is achieved through optical frequency modulation.

7. A laser vibrometer serial reciprocating optical frequency modulation calibration device, used to implement a laser vibrometer serial reciprocating optical frequency modulation calibration method as claimed in claim 2, 3, 4, 5 or 6, characterized in that: The invention mainly comprises a calibrated laser vibrometer (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 reflector (8); the calibrated laser vibrometer (1), the first acousto-optic modulator (2), the second acousto-optic modulator (3), the lens (4), and the plane reflector (8) form a "one"-shaped optical path structure; the first acousto-optic modulator (2) performs frequency translation and reflection of incident light at the same time. The frequency of light is shifted, and the value of the frequency shift is controlled and determined by the first sinusoidal signal source (5); the second acousto-optic modulator (3) is always performing frequency modulation of the incident light and the frequency modulation of the reflected light at the same time, the modulation frequency deviation and the 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 vertex of the diffraction angle of the output light of the second acousto-optic modulator (3) is located at the focal length position of the lens (4); the plane reflector (8) is used to reflect the translational spatial scanning shape-changing path laser transmitted by the lens (4).

Images