Parallel laser vibration measurement method and system based on microcavity type laser frequency comb

Abstract

The invention discloses a parallel laser vibration measurement method and system based on a micro-cavity type laser frequency comb, and the method comprises the steps: employing a micro-cavity type laser frequency beam as a light source, and enabling the light source to provide a large-scale number of narrow-linewidth laser elements; large-scale parallel laser elements are superposed and then combined into one beam to irradiate a vibration target; the vibration target comprises the same position of the measured object or a plurality of positions of the measured object; collecting laser elements after the vibration target is irradiated, and solving frequency deviation and phase change of the optical frequency comb caused by object vibration; and calculating vibration speed information of the object according to the frequency deviation and the phase change. According to the technical scheme, due to the fact that the spectrum distribution of the microcavity optical frequency comb is wide, the microcavity optical frequency comb can be applied to various measurement environments, and damage to objects sensitive to high-power laser is avoided while the measurement precision is improved; according to the invention, the optical frequency comb light source is integrated on the millimeter-level silicon nitride micro-ring chip, and due to the size advantage of the chip microcavity, the technical scheme has the advantages of integration and portability.

Description

Technical Field

[0001] The present invention relates to the field of vibration measurement devices, and in particular to a parallel laser vibration measurement method and system based on a microcavity laser frequency comb. Background Art

[0002] As a non-contact vibration measurement technology, Doppler vibrometer technology has been widely used in many fields such as structural health monitoring, material characterization, and biomedical diagnosis due to its high precision and high sensitivity. This technology irradiates the target surface with a laser beam and detects the slight changes in the frequency of the reflected light caused by the target vibration to accurately measure the vibration characteristics of the target. In order to improve the resolution of the laser Doppler vibrometer system, conventional methods include increasing the output power of the laser or using a shorter wavelength laser. However, these methods face many limitations in practical applications: for some materials, such as photosensitive polymers, biological tissues, and volatile substances, using high-power lasers to irradiate their surfaces may cause thermal damage, photodegradation, or other forms of physical and chemical changes in the samples, thereby destroying the integrity of the samples and even affecting the accuracy of the measurement results. Especially in the biomedical field, because biological tissues are sensitive to light absorption and thermal effects, excessive laser power may cause irreversible tissue damage, which is particularly prominent in affecting the accuracy of the measurement results; in addition, in material characterization, high-power lasers may also cause microstructural changes on the surface of the material, thereby affecting the accuracy of the measurement. On the other hand, the application scenarios of equipment related to high-power laser technology are greatly limited due to its size and weight.

[0003] Therefore, a technical solution is needed that can be applied in a variety of application environments without affecting the integrity of the sample, and that guarantees the resolution of the measurement system and the accuracy of the measurement results. Summary of the invention

[0004] To achieve the above objectives, the present invention provides a parallel laser vibration measurement method based on a microcavity laser frequency comb, comprising the following steps:

[0005] A microcavity laser frequency beam is used as a light source, which provides a large number of narrow linewidth laser elements, the frequencies of which are evenly spaced and have relatively consistent linewidth and frequency noise;

[0006] Large-scale parallel laser elements are superimposed to form a beam to illuminate a vibrating target; the vibrating target includes: the same position of the object to be measured or multiple positions of the object to be measured; when the vibrating target is the same position of the object to be measured, the laser elements after irradiating the vibrating target all carry the vibration information of the target position; when the vibrating target is multiple positions of the object to be measured, the laser elements after irradiating the vibrating target carry the multi-directional vibration information of the vibrating object;

[0007] Collect the laser elements after irradiating the vibrating target to solve the frequency shift and phase change of the optical frequency comb caused by the object's vibration;

[0008] The vibration velocity information of the object is calculated according to the frequency shift and phase change.

[0009] Among them, the number of large-scale parallel laser elements is greater than one hundred, and the interval between laser elements with high repetition frequency is greater than 100 GHz; the laser elements are generated in different optical bands, and the optical bands include: O, C, and L.

[0010] In another aspect, the present invention provides a parallel laser vibrometer system based on a microcavity laser frequency comb, comprising:

[0011] Microcavity frequency comb source: used to output frequency comb stably; in the microcavity frequency comb source, laser passes through the microcavity of silicon nitride chip to excite a large number of narrow linewidth laser elements at one time. The frequencies of the laser elements are equally spaced and have relatively consistent linewidth and frequency noise.

[0012] Michelson interferometer structure: used to use laser interference to solve the frequency offset and phase change of the optical frequency comb caused by the vibration of the object; an acousto-optic frequency shifter is introduced on the interferometer arm of the Michelson interferometer structure, and the acousto-optic frequency shifter shifts the interference signal to 100MHz;

[0013] Signal detection unit and signal demodulation unit: used to calculate the vibration speed information of the object based on the frequency offset and phase change.

[0014] The components that make up the microcavity optical frequency comb light source include: DFB laser, silicon nitride chip and tapered optical fiber. The silicon nitride chip and tapered optical fiber are packaged together on a base with temperature control. The size of the silicon nitride chip is in the millimeter range.

[0015] Furthermore, the microcavity frequency comb light source provides more than one hundred high repetition frequency laser elements with intervals greater than or equal to 100 GHz in different optical bands, and the optical bands include: O, C, and L.

[0016] The microcavity optical frequency comb light source uses DFB lasers of different bands to generate optical frequency combs of different bands. Through microcavities of different radii, frequency combs of different repetition frequencies can be generated.

[0017] Among them, the components of the Michelson interferometer structure also include a beam splitter and a vibrating target;

[0018] The beam splitter is used to divide the frequency comb light source into a detection arm and a reference arm. The multiple parallel lasers of the detection arm and the reference arm are combined into one beam in space to measure the same position on the vibrating target. After the laser elements irradiate the vibrating target, they all carry the vibration information of the target position.

[0019] On the other hand, the Michelson interference structure uses a spectroscopic element to separate lasers of different elements for measuring different positions of an object; the laser elements of different elements carry different vibration information, which is used to quickly obtain vibration information at different positions.

[0020] Furthermore, the signal detection unit and the signal demodulation unit obtain the vibration amplitude and vibration frequency of the object according to the frequency offset and phase change multiplied by the coefficient related to the detection wavelength to form a vibration trajectory; and the vibration trajectory is differentiated to obtain the vibration speed information of the object.

[0021] The calculation method of the vibration velocity information includes:

[0022] The collected signal is subjected to DC removal and bandpass filtering to obtain the in-phase, and the Hilbert transform is performed to obtain the quadrature phase;

[0023] Solve for the Doppler phase shift caused by the vibration of the object;

[0024] Calculate the amplitude of an object's vibration;

[0025] Calculate the vibration velocity of the object by taking the first derivative of the displacement.

[0026] The parallel laser vibration measurement method and system based on the microcavity laser frequency comb provided by the present invention adopts the microcavity laser frequency comb as the detection light and reference light signal, and utilizes the concurrent advantages of multiple frequency elements of the microcavity frequency comb to realize multi-frequency detection of the same object or multi-channel simultaneous detection of multiple objects; wherein the microcavity frequency comb adopts photon integration technology, is compatible with modern CMOS technology, can be freely designed to realize laser frequency combs of any band and repetition frequency, and has the potential for miniaturization. When the multi-channel elements of the frequency comb are used to simultaneously measure the same position of the object, the hundreds of dense comb teeth of the frequency comb are used to superimpose multiple laser beams when measuring at the same position. When measuring the same position of the object to be measured, all laser elements carry the vibration information of the target position after irradiating the vibration target. Due to its wide spectrum characteristics, the power of a single laser element can be greatly reduced to protect power-sensitive materials during detection. When multiple frequency elements are used to measure different objects in a distributed manner, the parallel capability of the frequency comb can be used to simultaneously detect the vibration information of different positions of the object. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A structural diagram of a parallel laser precision vibration measurement system based on a microcavity laser frequency comb according to an embodiment of the present invention;

[0028] Figure 2 A microcavity optical frequency comb light source and a Michelson interference structure are used in a parallel laser precision vibration measurement system based on a microcavity laser frequency comb according to an embodiment of the present invention;

[0029] Figure 3 A partial spectrum of a frequency comb with a repetition frequency of 100 GHz used in a parallel laser precision vibration measurement system based on a microcavity laser frequency comb provided in accordance with an embodiment of the present invention;

[0030] Figure 4 A schematic diagram showing the influence of different numbers of frequency comb teeth states on system accuracy when an object is stationary according to an embodiment of the present invention;

[0031] Figure 5 A schematic diagram of the effect of different numbers of frequency comb tooth states on system accuracy when an object is in a dynamic state according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The present invention realizes parallel laser precision vibration measurement through soliton microcomb technology: soliton microcomb is generated by laser pumping high Q value microcavity resonator. Its core principle is to use nonlinear optical effects to generate stable optical soliton pulses in the microcavity. These soliton pulses appear as a series of equally spaced frequency comb lines in the frequency domain, with extremely high spectral purity, coherence and broadband characteristics.

[0033] Soliton microcombs can provide high power density and broadband light sources under low power consumption conditions, which can significantly improve the resolution of laser Doppler vibrometer systems without increasing the risk of sample damage, thereby achieving technical effects that traditional lasers cannot achieve. In addition, soliton microcombs have the characteristics of miniaturization and can be integrated into chip microcavities. Chip microcavities are compatible with the current mainstream photon integration process and are easy to integrate into portable or wearable devices, further broadening their scenarios in practical applications.

[0034] The parallel laser precision vibration measurement method based on a microcavity laser frequency comb provided by the present invention comprises the following steps:

[0035] A microcavity laser frequency beam is used as a light source, which provides a large number of narrow-linewidth laser elements, the frequencies of which are evenly spaced and have relatively consistent linewidth and frequency noise; specifically, the number of large-scale parallel laser elements is greater than one hundred, and the intervals between laser elements with high repetition frequencies are greater than 100 GHz; the laser elements are generated in different optical bands, which include: O, C, and L.

[0036] Large-scale parallel laser elements are superimposed to form a beam to illuminate a vibrating target; the vibrating target includes: the same position of the object to be measured or multiple positions of the object to be measured; when the vibrating target is the same position of the object to be measured, the laser elements after irradiating the vibrating target all carry the vibration information of the target position; when the vibrating target is multiple positions of the object to be measured, the laser elements after irradiating the vibrating target carry the multi-directional vibration information of the vibrating object;

[0037] Collect the laser elements after irradiating the vibrating target to solve the frequency shift and phase change of the optical frequency comb caused by the object's vibration;

[0038] The vibration velocity information of the object is calculated according to the frequency shift and phase change.

[0039] In order to realize the parallel laser precision vibration measurement method, the present invention also provides a parallel laser precision vibration measurement system based on a microcavity laser frequency comb, which adopts a microcavity laser frequency beam as a light source, provides large-scale parallel laser elements, and obtains accurate object vibration information after one measurement. It includes two measurement modes: one is to measure multiple laser elements superimposed at the same position, and the other is to use multiple laser elements for distributed measurement in space.

[0040] Specifically, its structure is as follows Figure 1 As shown, including:

[0041] P100 microcavity optical frequency comb light source: In the present invention, the microcavity optical frequency comb is used as the light source of the parallel laser vibrometer system. Figure 2 The P200 part is shown in the figure, including: DFB laser, polarization controller, signal generator, servo controller, EDFA amplifier, silicon nitride chip, band stop filter, photodetector, and tapered optical fiber.

[0042] In the present invention, a silicon nitride microcavity chip and a tapered optical fiber are packaged together on a base with temperature control. The chip size is in the millimeter range, wherein the radius of the microring cavity is 228um. Due to the size advantage of the chip microcavity, it has the characteristics of integration and portability.

[0043] In the present invention, a signal generator is used to change the DFB laser current to tune the laser wavelength to generate a frequency comb. The free spectrum range of the frequency comb is about 100 GHz, corresponding to the 228 um radius of the microring. The residual pump in the cavity is filtered out by using a fiber Bragg grating. At the same time, the power fluctuation in the cavity is detected by a photodetector and fed back to the laser through a servo controller to achieve stable control of the detuning amount between the laser and the microcavity. Through the above closed-loop control, the optical frequency comb is stably output from P200. The frequency comb spectrum is as follows: Figure 3 shown.

[0044] Specifically, the generation of the optical frequency comb mainly relies on the use of EDFA amplifiers to amplify the DFB laser to pump the silicon nitride microcavity chip, and the use of a fiber polarization controller to adjust the polarization state of the laser to align it with the TE mode of the microcavity; the signal generator is used to quickly adjust the frequency of the DFB laser to overcome the accumulation of thermal effects in the cavity during the generation of the optical frequency comb; after the frequency comb is generated, a band-stop filter is used to filter out the residual pump laser in the cavity, and a photodetector is used to detect the fluctuation of the power in the cavity and feed it back to the DFB laser to maintain the long-term stable operation of the optical frequency comb.

[0045] In a specific implementation, the microcavity frequency comb light source can provide more than one hundred high-repetition-frequency laser elements with an interval of 100 GHz or higher in different bands of light. The supported optical bands include: O, C, and L, thereby avoiding the absorption of certain materials in specific bands. At the same time, a power balancing module can be added after the output of the optical frequency comb to achieve power balancing of the microcavity frequency elements, and whether to amplify the frequency comb light source can be selected according to detection needs. At this time, multiple lasers are generated by high-quality factor, nonlinear optical micro-resonant cavities. A large number of narrow-linewidth laser elements can be generated in the microcavity through one-time excitation. The frequencies of each laser element are equally spaced, with relatively consistent linewidth and frequency noise. The number of narrow-linewidth laser elements is usually between fifty and two hundred.

[0046] Microcavity optical frequency comb light source uses DFB lasers of different wavelengths to generate optical frequency combs of different wavelengths. Usually, the 3dB bandwidth of a frequency comb with a 100G repetition rate can reach 50nm. By designing microcavities with different radii, frequency combs with different repetition rates can also be generated. The use of a beamformer can balance the power of the frequency comb teeth to maintain consistent measurement accuracy at different wavelengths.

[0047] P110 Michelson interferometer structure: The present invention adopts the Michelson interferometer structure, and uses the interference of laser to solve the phase shift of the frequency comb signal from the microcavity optical frequency comb light source. The main components of the Michelson interferometer include a collimating lens, a 50:50 beam splitter, an acousto-optic frequency shifter, a reflector, a 100MHz frequency source and a sample to be tested.

[0048] Among them, an acousto-optic frequency shifter is introduced on one of the Michelson interferometer arms. The acousto-optic frequency shifter shifts the frequency of the interference signal to 100 MHz, which can avoid low-frequency noise in the interference signal.

[0049] The Michelson interferometer structure obtains the phase change of the signal of the multi-channel light source emitted by the microcavity optical frequency comb due to the vibration of the object through the interference of lasers, and then obtains the vibration information of the object. Therefore, when multiple laser elements measure the same object at the same time, there is no need to adjust the optical path structure to apply the interference of any multi-channel frequency elements.

[0050] On the other hand, the Michelson interferometer structure can be used for the interference of multi-wavelength lasers: for multi-laser distributed measurement, a spectroscopic element can be additionally introduced to spatially separate lasers of different elements and measure different positions of the object.

[0051] During the application process, the optical frequency comb generated by the frequency comb light source passes through a collimating lens from the optical fiber into space. The beam splitter divides the frequency comb light source into two parts. One part is used as a reference light source through a 100MHz spatial acousto-optic frequency shift and returns through a reflector to become a reference arm. The comb teeth of each optical frequency comb on the reference arm are shifted by 100MHz. The other part is used as a detection light as a detection arm to illuminate the object to be measured.

[0052] The multiple parallel lasers of the detection arm and the reference arm are combined into one beam in space to measure the same position on the vibrating target. At this time, after all laser elements irradiate the vibrating target, they carry the vibration information of the target position, which greatly enhances the detection accuracy compared with a single frequency element.

[0053] When a frequency comb multi-channel coherent light source is used to detect different positions of an object in parallel, the laser elements of different frequencies of the frequency comb carry different vibration information, and the vibration information of different positions can be quickly obtained.

[0054] P120: Signal detection unit and signal demodulation unit: used to obtain the Doppler frequency shift of light caused by the vibration of the object and then obtain the frequency offset and phase change, multiply the frequency offset and phase change by the coefficient related to the detection wavelength to obtain the vibration amplitude and vibration frequency of the object, and derive the vibration trajectory to obtain the vibration velocity information of the object.

[0055] In the present invention, a data acquisition device is used to collect the interference signal between the detection light frequency comb and the signal light frequency comb, obtain the Doppler frequency shift of the detection light signal caused by the vibration of the object, and perform phase demodulation to obtain the object vibration information.

[0056] In the present invention, the combined light beams of the reference arm and the detection arm in the Michelson interference structure are detected by a high-speed photodetector; that is, multiple comb teeth are measured in parallel through multiple channels; then the frequency offset and phase change of the frequency comb caused by the movement of the object are solved by a signal detection unit and a signal demodulation unit, and then the vibration amplitude and vibration frequency information are obtained by multiplying by a fixed coefficient, and then the vibration trajectory is derived to obtain the vibration speed. The key steps of demodulation include the following

[0057] 1) Remove DC and perform bandpass filtering on the collected signal to obtain the same phase, and perform Hilbert transform to obtain the orthogonal phase:

[0058] The calculation process is expressed as:

[0059] Where η is the detector's responsivity, μ is the effective reflectivity of the detected object, a and b are the field amplitudes of the reference beam and the detection beam, respectively, and θ0, θ1, and θ(t) are the system constant phase, the reference light phase, and the phase disturbance caused by the Doppler frequency shift that carries the object's motion information.

[0060] After removing DC and bandpass filtering, we get the same phase i I (t) = ημ|ab|cos[-2πf ofs t+θ(t)+θ0-θ1], Hilbert transform to orthogonal phase: i Q (t) = ημ|ab|sin[-2πf ofs t+θ(t)+θ0-θ1].

[0061] 2) Solve the Doppler phase shift caused by the vibration of the object:

[0062] The phase angle of the complex signal is solved by the in-phase term and the orthogonal term, which is expressed as:

[0063]

[0064] Furthermore, the constant term 2πf is removed by performing a first-order fit on θ(t) ofs t.

[0065] 3) Calculate the vibration amplitude of the object: The specific implementation can be obtained by multiplying θ(t) by a fixed coefficient, expressed as: λ is the average wavelength of the optical frequency comb.

[0066] 4) Calculate the vibration velocity of the object by taking the first derivative of the displacement, v(t) = (λ / 4π) * dθ(t) / dt.

[0067] Figure 4 Part (a) of the paper provides a description of the effect of different numbers of frequency comb teeth on the improvement of system accuracy when the object is stationary; gradually increase the frequency comb teeth to obtain standard deviation data in the prohibited state. Figure 4 part (b) of the

[0068] On the other hand, when the object is in motion, the influence of different comb teeth numbers on the motion resolution accuracy can be seen in Figure 5 .

[0069] The present invention uses a microcavity laser frequency comb as a detection light and a reference light signal, and utilizes the concurrent advantages of multiple frequency elements of the microcavity frequency comb to realize multi-frequency detection of the same object or multi-channel simultaneous detection of multiple objects. The microcavity frequency comb adopts photon integration technology, is compatible with modern CMOS technology, can be freely designed to realize a laser frequency comb of any band and repetition frequency, and has the potential for miniaturization. When the multi-channel elements of the frequency comb are used to simultaneously measure the same position of an object, the hundreds of dense comb teeth of the frequency comb are used to superimpose multiple laser beams when measuring at the same position. When measuring the same position of the object to be measured, all laser elements carry the vibration information of the target position after irradiating the vibrating target, which can greatly reduce the power of a single laser element to protect power-sensitive materials during detection. When multiple frequency elements are used to distribute measurements of different objects, the parallel capability of the frequency comb can be used to simultaneously detect the vibration information of different positions of the object.

[0070] The Kerr frequency comb used in the present invention as a detection light source can realize simultaneous measurement of multiple lasers, and different numbers of comb teeth can be selected for vibration measurement as needed. The laser power is dispersed over multiple frequencies, which improves the measurement accuracy while avoiding damage to objects sensitive to high-power lasers. On the other hand, the present invention integrates the optical frequency comb light source on a millimeter-scale silicon nitride microring chip. Due to the size advantage of the chip microcavity, the technical solution of the present invention has the advantage of being integrated and portable.

[0071] In summary, the introduction of soliton microcomb technology has created new space for the development of laser Doppler vibrometer technology in terms of portability and accuracy. By utilizing the low-power, high-resolution light source generated by the soliton microcomb, the performance of the Doppler vibrometer system can be significantly improved without damaging the sample. This technology is not only expected to solve the challenges currently faced by laser Doppler vibrometer technology in high-precision measurement, but also promote its application in a wider range of fields.

[0072] The above disclosures are only several specific embodiments of the present invention; however, the present invention is not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A parallel laser vibration measurement method based on a microcavity laser frequency comb, characterized in that: The following steps are involved: A microcavity laser frequency beam is used as a light source, the light source provides a large number of narrow line width laser elements, the frequencies of the laser elements are equally spaced, and have relatively consistent line width and frequency noise; The massively parallel laser elements are superimposed and synthesized into a beam to illuminate a vibrating target; the vibrating target includes: the same position of the object to be measured or multiple positions of the object to be measured; when the vibrating target is the same position of the object to be measured, the laser elements after irradiating the vibrating target all carry the vibration information of the target position; when the vibrating target is multiple positions of the object to be measured, the laser elements after irradiating the vibrating target carry the multi-directional vibration information of the vibrating object; Collecting the laser elements after irradiating the vibrating target, and solving the frequency shift and phase change of the optical frequency comb caused by the vibration of the object; The vibration velocity information of the object is calculated according to the frequency shift and phase change.

2. The parallel laser vibrometer method according to claim 1, characterized in that: The number of the massively parallel laser elements is greater than one hundred, and the interval between the laser elements is greater than 100 GHz with a high repetition rate; The laser elements are generated in different optical bands, and the optical bands include: O, C, and L.

3. A parallel laser vibrometer system based on a microcavity laser frequency comb, characterized in that: include: Microcavity optical frequency comb light source: used for stably outputting an optical frequency comb; in the microcavity optical frequency comb light source, laser light passes through the microcavity of the silicon nitride chip to excite and generate a large number of narrow linewidth laser elements at one time, and the frequencies of the laser elements are distributed at equal intervals, with relatively consistent linewidth and frequency noise; Michelson interference structure: used to solve the frequency shift and phase change of the optical frequency comb caused by the vibration of the object by using the interference of lasers; an acousto-optic frequency shifter is introduced on the interference arm of the Michelson interference structure, and the acousto-optic frequency shifter shifts the interference signal to 100 MHz; The signal detection unit and the signal demodulation unit are used to calculate the vibration speed information of the object according to the frequency offset and phase change.

4. The parallel laser vibrometer system according to claim 3, characterized in that: The components constituting the microcavity optical frequency comb light source include: a DFB laser, a silicon nitride chip and a tapered optical fiber. The silicon nitride chip and the tapered optical fiber are packaged together on a base with temperature control. The size of the silicon nitride chip is in the millimeter order.

5. The parallel laser vibrometer system according to claim 3, characterized in that: The microcavity frequency comb light source provides more than one hundred high repetition frequency laser elements with intervals greater than or equal to 100 GHz in different optical bands, and the optical bands include: O, C, and L.

6. The parallel laser vibrometer system according to claim 4, characterized in that: The elements of the Michelson interference structure also include a beam splitter and a vibrating target; The beam splitter is used to divide the frequency comb light source into a detection arm and a reference arm. The multiple parallel lasers of the detection arm and the reference arm are combined into one beam in space to measure the same position on the vibrating target. After irradiating the vibrating target, the laser elements all carry the vibration information of the target position.

7. The parallel laser vibrometer system according to claim 6, characterized in that: The Michelson interference structure uses a spectroscopic element to separate lasers of different elements for measuring different positions of an object; the laser elements of different elements carry different vibration information for quickly obtaining vibration information of different positions.

8. The parallel laser vibrometer system according to claim 3, characterized in that: The signal detection unit and the signal demodulation unit obtain the vibration amplitude and vibration frequency of the object according to the frequency offset and phase change multiplied by the coefficient related to the detection wavelength to form a vibration trajectory; The vibration trajectory is derived to obtain the vibration velocity information of the object.

9. The parallel laser vibrometer system according to claim 8, characterized in that: The method for calculating the vibration velocity information includes: The collected signal is subjected to DC removal and bandpass filtering to obtain the in-phase, and the Hilbert transform is performed to obtain the quadrature phase; Solve for the Doppler phase shift caused by the vibration of the object; Calculate the amplitude of an object's vibration; Calculate the vibration velocity of the object by taking the first derivative of the displacement.

10. The parallel laser vibrometer system according to claim 3, characterized in that: The microcavity optical frequency comb light source uses DFB lasers of different wavelength bands to generate optical frequency combs of different wavelength bands, and can generate frequency combs of different repetition frequencies through microcavities of different radii.

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