Vector speed measuring method and measuring device based on single optical fiber probe

Abstract

The invention discloses a vector velocity measurement method and device based on a single optical fiber probe, and relates to the technical field of laser velocity measurement. According to the invention, one probe is used for realizing the functions of three probes, so that a measurement system and optical path debugging are simplified, and the problems of measurement error increase and short measurement depth of field caused by the fact that the three probes are not aligned with one point along with longitudinal movement of the target are solved. The single-probe vector velocity measuring device is composed of a three-frequency laser illumination light source, an optical fiber probe, a reference laser light source and a signal generation and data processing system. Three beams of single-frequency laser are utilized to illuminate a to-be-measured target, an optical fiber probe collects reflected laser, the reflected laser and reference laser interfere with each other to generate three groups of interference light intensity signals, and the vector velocity of the to-be-measured target is obtained through data processing.

Description

Technical Field

[0001] The present invention relates to the technical field of laser velocity measurement, and in particular to a vector velocity measurement method and a measurement device based on a single optical fiber probe. Background Art

[0002] In the field of dynamic high-pressure physics and material mechanics research, measuring the vector velocity of materials under dynamic high-pressure loading is an indispensable means to obtain the mechanical properties of materials.

[0003] In order to measure the vector velocity of a point on the target, two methods are generally used. The first method uses three integrated transceiver probes to measure the velocity components of the same point from three directions, and then calculates the vector velocity; the second method uses a laser beam to illuminate a point, and then uses three receiving probes to measure the Doppler frequency shift of the reflected light from the same point from three directions, and then calculates the vector velocity. Regardless of which method is used, in order to measure the vector velocity of a point, three probes need to be aimed at one point at the same time, which complicates the measurement system and the optical path debugging, and as the distance from the target to the probe changes, the three probes are no longer aimed at one point, resulting in a shorter measurable depth of field and increased measurement errors. Summary of the invention

[0004] The present invention provides a vector velocity measurement method and a measuring device based on a single optical fiber probe, so as to solve the problems that the existing velocity measurement scheme requires three probes to be simultaneously aimed at the same measuring point, resulting in complex optical path debugging and short measurement depth of field, and the measurement error increases as the distance from the measurement target to the probe changes.

[0005] A first aspect of the present invention provides a vector velocity measurement method based on a single optical fiber probe, comprising:

[0006] S1, emitting three non-coplanar illumination laser beams from different angles to the same measuring point on the target to be measured, and the frequencies of the three illumination laser beams are different;

[0007] S2, receiving the reflected light of the measuring point through a single optical fiber probe;

[0008] S3, obtaining a reference laser and interfering it with the reflected light to generate an interference light intensity signal;

[0009] S4, calculating and obtaining the vector velocity of the measuring point according to the interference light intensity signal.

[0010] The present invention is based on a single-probe vector velocity measurement method, which only requires one fiber optic probe to achieve vector velocity laser interferometry measurement that previously required three fiber optic probes, thereby simplifying the measurement system and optical path debugging. Since the fiber optic probe is always aligned with the measurement point, the measurement depth of field is increased, and the problem of increased measurement error as the distance from the target to be measured to the fiber optic probe changes is solved.

[0011] Furthermore, the three illumination laser beams are all conical lasers.

[0012] Furthermore, the three illumination laser beams are all parallel laser beams.

[0013] Furthermore, the reference laser satisfies: the values ​​of |v0-v1|, |v0-v2|, and |v0-v3| are different from each other and are all greater than the maximum absolute value of the Doppler frequency shift of the reflected light caused by the movement of the measuring point; wherein v0 is the frequency of the reference laser, v1, v2, and v3 are the frequencies of the three illumination lasers, respectively, and |·| represents the absolute value.

[0014] Furthermore, among the reflected lights of the reference laser and the three illumination lasers participating in the interference, the following conditions are satisfied: the light intensity of the reference laser is much greater than the reflected light intensity of any one of the three illumination lasers, so as to highlight the interference light intensity signal between the reference laser and the reflected light and suppress the cross-interference light intensity signal between the three reflected lights.

[0015] Further, the vector velocity of the measuring point is calculated based on the interference light intensity signal of the reflected light and the reference laser, including:

[0016] S4-1, using short-time Fourier transform or wavelet transform to process the interference light intensity signal, and obtain f 01 (t), f 02 (t) and f 03 (t);

[0017] Among them, f 01 (t) is the time-frequency signal of the interference light intensity signal formed by the interference of the reflected light of the illumination laser 1 and the reference laser, f 02 (t) is the time-frequency signal of the interference light intensity signal formed by the interference of the reflected light of the illumination laser 2 and the reference laser, f 03 (t) is the time-frequency signal of the interference light intensity signal formed by the interference of the reflected light of the illumination laser 3 and the reference laser;

[0018] S4-2, according to f 01 (t), f 02 (t) and f 03 (t) Calculate the vector velocity of the measurement point:

[0019]

[0020] Among them, α1, β1, γ1 are the angles between the reverse incident direction of the incident light of the illumination laser 1 pointing to the measurement point and the x, y, z axes respectively;

[0021] α2, β2, γ2 are the angles between the reverse incident direction of the incident light of the illumination laser 2 pointing to the measurement point and the x, y, z axes respectively;

[0022] α3, β3, γ3 are the angles between the reverse incident direction of the incident light of the illumination laser 3 pointing to the measurement point and the x, y, z axes respectively;

[0023] The z axis coincides with the optical axis of the fiber optic probe and points to the fiber optic probe, and the x, y, and z axes satisfy the right-hand rule;

[0024] v0 is the frequency of the reference laser, v1 is the frequency of the illumination laser 1, v2 is the frequency of the illumination laser 2, and v3 is the frequency of the illumination laser 3;

[0025] c is the speed of light, and A is the maximum absolute value of the Doppler frequency shift of the reflected light.

[0026] A second aspect of the present invention provides a vector velocity measurement device based on a single optical fiber probe, comprising:

[0027] A three-frequency laser illumination light source is used to emit three non-coplanar illumination laser beams from different angles to the same measuring point on the target to be measured, and the frequencies of the three illumination laser beams are different;

[0028] a single optical fiber probe for receiving reflected light from the measurement point;

[0029] A reference laser light source, used for providing a reference laser;

[0030] The signal generation and data processing system is used to generate an interference light intensity signal of the reflected light and the reference laser, and calculate the vector velocity of the measurement point according to the interference light intensity signal.

[0031] Furthermore, the triple-frequency laser illumination light source includes three single-frequency lasers and three illumination optical fibers; each of the single-frequency lasers is coupled to the illumination optical fiber, so that the illumination laser emitted by each single-frequency laser is emitted in a cone shape from the end face of the illumination optical fiber.

[0032] Furthermore, the triple-frequency laser illumination light source includes three single-frequency lasers and a laser beam expansion device connected to each of the single-frequency lasers, so that the illumination laser emitted by each of the single-frequency lasers is expanded into parallel light by the laser beam expansion device.

[0033] Further, the signal generation and data processing system includes a fiber coupler, a fast response photodetector and a data processor;

[0034] The optical fiber coupler is used to receive the reflected light and the reference laser, and output an interference light intensity signal of the reflected light and the reference laser;

[0035] The fast response photoelectric detector is used to perform photoelectric conversion on the interference light intensity signal;

[0036] The data processor is used to calculate the vector velocity of the measuring point according to the converted interference light intensity signal.

[0037] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0038] Only one optical fiber probe is needed to realize vector velocity laser interferometry measurement, which simplifies the measurement system and optical path debugging.

[0039] Since the fiber optic probe is always aligned with the measuring point, the measuring depth of field is increased, and the problem of increasing measurement error as the distance from the target to be measured to the fiber optic probe changes is solved.

[0040] Compared with the parallel light illumination method, the fiber optic illumination method requires fewer devices and the lighting layout is more flexible. Compared with the parallel light illumination method, the incident direction of the light reaching the measuring point does not change with the movement of the target to be measured. There is no need to correct the incident direction of the light during data processing, and the measurement error is smaller. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0042] Figure 1 is a flow chart of a vector velocity measurement method based on a single optical fiber probe according to an embodiment of the present invention;

[0043] Figure 2 This is a schematic diagram of a conical laser beam incident on a target surface to be measured according to an embodiment of the present invention;

[0044] Figure 3 is a schematic diagram of a rectangular coordinate system of a laser incident orientation and an optical fiber probe according to an embodiment of the present invention;

[0045] Figure 4 This is a schematic diagram of a parallel laser beam incident on a target surface to be measured according to an embodiment of the present invention;

[0046] Figure 5It is a schematic structural diagram of a vector velocity measurement device based on a single optical fiber probe according to an embodiment of the present invention.

[0047] The following are the descriptions of the reference numerals:

[0048] 1-illumination laser, 2-illumination laser, 3-illumination laser, 4-target to be measured, 5-measuring point, 6-illumination spot, 7-illumination spot,

[0049] 8-illumination spot, 9-illumination spot, 10-fiber optic probe, 11-illumination fiber, 12-illumination fiber, 13-illumination fiber, 14-reference laser light source, 15-signal fiber, 20-triple-frequency laser illumination light source, 21-illumination laser 1, 22-illumination laser 2, 23-illumination laser 3, 30-signal generation and data processing system, 31-fiber optic coupler, 32-fast response photodetector, 33-data processor. DETAILED DESCRIPTION

[0050] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0051] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to or inherent to other steps or units of the device.

[0052] The terms used in the various embodiments of the application are only used to describe the purpose of specific embodiments and are not intended to limit the various embodiments of the application. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise limited, all terms used here (including technical terms and scientific terms) have the same meaning as the meanings commonly understood by ordinary technicians in the field of the various embodiments of the application. The terms (such as the terms defined in the dictionary generally used) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly defined in the various embodiments of the application.

[0053] The embodiment of the present invention provides a vector velocity measurement method and a measurement device based on a single optical fiber probe, which is suitable for measuring the vector velocity of a point on a target under dynamic high voltage loading, which is beneficial to reducing the complexity of the test system and optical path debugging, increasing the measurement depth of field, and reducing measurement errors.

[0054] In a first aspect, the present invention provides a vector velocity measurement method based on a single optical fiber probe, which is used to measure the vector velocity of a measurement point on a target under dynamic high voltage loading. Figure 1 FIG. 1 is a flow chart of a vector velocity measurement method based on a single optical fiber probe of the present invention, comprising the following steps:

[0055] S1, emitting three non-coplanar illumination laser beams from different angles to the same measuring point on the target to be measured, and the frequencies of the three illumination laser beams are different;

[0056] S2, receives the reflected light from the measurement point through a single fiber optic probe;

[0057] S3, obtaining a reference laser and interfering it with the reflected light to generate an interference light intensity signal;

[0058] S4, calculating the vector velocity of the measuring point according to the interference light intensity signal.

[0059] The three illumination laser beams can be realized by three single-frequency lasers, and the three single-frequency lasers constitute a triple-frequency laser illumination light source.

[0060] like Figure 2 The figure shows a schematic diagram of a conical laser beam incident on the surface of a target to be measured. Three illumination laser beams (illumination laser 1, illumination laser 2, and illumination laser 3) are emitted from illumination optical fibers 11, 12, and 13 to illuminate the same measurement point 5 on the target 4 to be measured from three different directions. The illumination spot covers a large area centered on the measurement point, and diffuse reflection occurs in the covered area. The three incident light beams are not in the same plane. There are slight differences between the optical frequencies v1, v2, and v3 of illumination laser 1, illumination laser 2, and illumination laser 3.

[0061] The fiber optic probe 10 receives the reflected laser light from the three incident illumination laser beams at the measuring point, transmits the reflected laser light collected by the fiber optic probe to one input end of a fiber optic coupler (such as a 2×2 coupler), inputs a reference laser light at the other input end of the fiber optic coupler, and outputs an interference light intensity signal from any output end of the fiber optic coupler.

[0062] The reference laser can be provided by a single-frequency laser, and the optical frequency ν0 of the reference laser must satisfy the following requirements: the values ​​of |v0-v1|, |v0-v2|, and |v0-v3| are different, and are all greater than the maximum value A of the absolute value of the Doppler frequency shift of the reflected light caused by the motion of the measurement point. Since the exact value of A cannot be obtained before measurement, in actual operation, A can take an empirical value or an estimated value given by calculation based on specific physical models and parameters. A can also take a value slightly larger than the empirical value or the estimated value.

[0063] The interference light intensity signal output by the fiber coupler can be expressed as:

[0064] I(t)=I01 (t)+I 02 (t)+I 03 (t)+I 12 (t)+I 13 (t)+I 23 (t)

[0065] In the formula, t represents time;

[0066] I 01 (t) is defined as the interference light intensity signal formed by the interference of the reflected light of the illumination laser 1 reflected by the measurement point and the reference laser, and its corresponding time-frequency signal is f 01 (t);

[0067] I 02 (t) is defined as the interference light intensity signal formed by the interference of the reflected light of the illumination laser 2 reflected by the measurement point and the reference laser, and its corresponding time-frequency signal is f 02 (t);

[0068] I 03 (t) is defined as the interference light intensity signal formed by the interference of the reflected light of the illumination laser 3 reflected by the measurement point and the reference laser, and its corresponding time-frequency signal is f 03 (t);

[0069] I 12 (t) is defined as the interference light intensity signal formed by the interference of the reflected light reflected by the illumination laser 1 and the illumination laser 2 at the measurement point, and its corresponding time-frequency signal is f 12 (t);

[0070] I 13 (t) is defined as the interference light intensity signal formed by the interference of the reflected light reflected by the illumination laser 1 and the illumination laser 3 at the measurement point, and its corresponding time-frequency signal is f 13 (t);

[0071] I 23 (t) is defined as the interference light intensity signal formed by the interference of the reflected light reflected by the illumination laser 2 and the illumination laser 3 at the measurement point, and its corresponding time-frequency signal is f 23 (t).

[0072] In step S4, the method for calculating the vector velocity of the measuring point is specifically as follows:

[0073] S4-1, using short-time Fourier transform or wavelet transform and other data processing algorithms to process the collected light intensity signal, and obtain f 01 (t), f 02 (t) and f 03 (t) Information.

[0074] S4-2, from f 01 (t), f02 (t) and f 03 (t) Calculate the vector velocity V of the measurement point, where V x is the velocity component of the vector velocity along the x-axis, V y is the velocity component of the vector velocity along the y-axis, V z is the velocity component of the vector velocity along the z-axis.

[0075] When calculating, establish a rectangular coordinate system with the optical axis of the fiber optic probe as the z-axis, such as Figure 3 The figure shows a schematic diagram of the rectangular coordinate system of the laser incident orientation and the optical fiber probe. The z-axis coincides with the optical axis of the probe and points to the probe. The x-, y-, and z-axes satisfy the right-hand rule.

[0076] The vector velocity calculation formula is as follows:

[0077]

[0078] in,

[0079]

[0080] α1, β1, γ1 are the angles between the reverse incident direction of the incident light of the illumination laser 1 pointing to the measurement point and the x, y, z axes respectively;

[0081] α2, β2, γ2 are the angles between the reverse incident direction of the incident light of the illumination laser 2 pointing to the measurement point and the x, y, z axes respectively;

[0082] α3, β3, γ3 are the angles between the reverse incident direction of the incident light of the illumination laser 3 pointing to the measurement point and the x, y, z axes respectively;

[0083] v0 is the frequency of the reference laser, v1 is the frequency of the illumination laser 1, v2 is the frequency of the illumination laser 2, and v3 is the frequency of the illumination laser 3;

[0084] c is the speed of light, and A is the maximum absolute value of the Doppler frequency shift of the reflected light.

[0085] Divide the right side of the above vector velocity calculation formula by f 01 、f 02 and f 03 The outside is a known parameter. By substituting the data of the measuring point into the formula, the vector velocity of the measuring point can be obtained.

[0086] In actual measurement, the optical frequency differences between illumination laser 1, illumination laser 2, and illumination laser 3 must have sufficient margin to satisfy the following two conditions at any time:

[0087] (1)f 01 (t), f 02 (t) and f 03(t) There is no overlap between the three;

[0088] (2)f 01 (t), f 02 (t), f 03 Any of (t) does not correspond to f 12 (t), f 13 (t), f 23 (t) overlaps with any of them.

[0089] If the intensity of the reference laser participating in the interference is much greater than the intensity of the illumination laser participating in the interference, the interference intensity signal of the reference laser and the reflected light can be highlighted while suppressing the cross-interference intensity signal between the three reflected lights. In this case, only the above-mentioned item (1) needs to be satisfied. If the output laser frequencies of the three-frequency laser illumination light source and the reference laser light source are not stable enough due to the application environment and drift over time, affecting the measurement accuracy, the influence of the unstable laser frequency can be eliminated by simultaneously monitoring the optical frequencies ν1, ν2, ν3, and ν0 of the three illumination lasers and the reference laser, or by simultaneously monitoring the real-time data of ν0-ν1, ν0-ν2, and ν0-ν3.

[0090] In one embodiment, the above-mentioned illumination laser for measurement adopts optical fiber illumination. Figure 2 As shown, the illumination laser is emitted from the end face of the optical fiber and diffuses in a cone shape to the surface of the target to be measured, forming an approximately elliptical light spot at the measuring point, covering a large area centered on the measuring point.

[0091] Three laser beams illuminate the target 4 to be measured. As the target moves, the overlapping area of ​​the illumination spots of the three laser beams on the target changes from illumination spot 6 to the overlapping area of ​​illumination spots 7, 8, and 9. The overlapping area becomes smaller, but as long as the area still covers the measurement point, the vector velocity measurement can continue. Therefore, this illumination method can obtain a larger measurement depth of field. As the target moves, the incident direction of the light reaching the measurement point from the end face of the illumination fiber may change. When processing data, it is necessary to calculate the distance from the measurement point to the fiber probe based on the longitudinal velocity history of the measurement point (the longitudinal velocity must be much greater than the transverse velocity or the target surface must always be perpendicular to the probe optical axis) and continuously correct the incident direction of the light reaching the measurement point accordingly. If the incident direction of the light reaching the measurement point cannot be corrected, the measurement error of the cone beam illumination method will increase as the target moves, and the measurement depth of field of the cone beam illumination method needs to be limited to a smaller range.

[0092] In one embodiment, the illumination laser is a parallel laser, that is, a parallel light illumination method is adopted. Compared with the optical fiber illumination method, a laser beam expander (not shown) is added, and the laser beam expander expands the three laser beams into parallel light before illuminating the target to be measured.

[0093] like Figure 4 The figure shows a schematic diagram of parallel laser beams incident on the surface of the target to be measured. As the target to be measured moves longitudinally, the distance from the measuring point to the fiber optic probe changes, and the size of the illumination spot of the three parallel beams on the target to be measured remains unchanged. As the target to be measured moves longitudinally, the overlapping area changes from spot 6 to the overlapping area of ​​spots 7, 8, and 9, and the overlapping area becomes smaller. However, as long as the measuring point is located in the overlapping area, the vector velocity measurement can continue. Due to the use of parallel light illumination, the incident direction of the light reaching the measuring point does not change with the movement of the target, and the incident direction of the light does not need to be corrected during data processing. The measurement error will not increase with the movement of the target, so this illumination method can obtain a larger measurement depth of field than the cone beam illumination method.

[0094] Since the fiber optic probe only receives reflected laser light incident along its optical axis, the single-probe measurement method of the present invention allows the collected data to come from a point where the optical axis of the probe intersects the surface of the target at any time during the entire measurement process. The problem of the three probes no longer being aimed at the same point as the target moves longitudinally in the conventional three-probe measurement method does not exist. This solves the problem of increased measurement error and short measurement depth of field caused by the three probes not being aimed at one point.

[0095] A second aspect of the present invention provides a vector velocity measurement device corresponding to the above-mentioned vector velocity measurement method, such as Figure 5 The figure is a schematic structural diagram of a vector velocity measurement device based on a single optical fiber probe of the present invention, comprising:

[0096] The triple-frequency laser illumination light source 20 is composed of three single-frequency lasers (single-frequency laser 21, single-frequency laser 22, single-frequency laser 23), and is used to emit three non-coplanar illumination laser beams (illumination laser 1, illumination laser 2, illumination laser 3) from different angles to the same measurement point on the target 4 to be measured, and the frequencies of the three illumination laser beams are different;

[0097] The optical fiber probe 10 is used to receive the reflected light from the measuring point;

[0098] A reference laser light source 14, used to provide a reference laser;

[0099] The signal generation and data processing system 30 is used to generate an interference light intensity signal between the reflected light and the reference laser, and then calculate the vector velocity of the measurement point based on the interference light intensity signal.

[0100] In one embodiment, the triple-frequency laser illumination light source 20 includes three single-frequency lasers and three illumination optical fibers. The three lasers are respectively coupled to the three illumination optical fibers 11-13. The illumination laser 1 is emitted through the end face of the illumination optical fiber 11, the illumination laser 2 is emitted through the end face of the illumination optical fiber 12, and the illumination laser 3 is emitted through the end face of the illumination optical fiber 13, forming three conical laser beams that irradiate the same measuring point on the target to be measured.

[0101] In one embodiment, the triple-frequency laser illumination light source 20 includes three single-frequency lasers and a laser beam expansion device connected to each single-frequency laser. The illumination laser 1, illumination laser 2, and illumination laser 3 emitted by the three single-frequency lasers are respectively expanded into parallel light by the laser beam expansion device (not shown) and then irradiated to the same measurement area on the target to be measured.

[0102] The reference laser light source 14 adopts a single-frequency laser, and the optical frequency ν0 of the reference laser must satisfy: the absolute values ​​of ν0-ν1, ν0-ν2, and ν0-ν3 are different from each other, and are all greater than the maximum absolute value of the Doppler frequency shift of the reflected light caused by the movement of the measuring point.

[0103] The signal generation and data processing system 30 includes a fiber coupler 31, a fast response photodetector 32 and a data processor 33. The fiber probe 10 is connected to one input end of the fiber coupler 31 through a signal fiber 15, and the signal output end of the reference laser light source 14 is connected to the other input end of the fiber coupler 31. Any output end of the fiber coupler 31 outputs an interference light intensity signal of the reflected light and the reference laser, and then the interference light intensity signal is input into the fast response photodetector 32 for photoelectric conversion, and the converted signal is input into the data processor 33 for vector velocity calculation.

[0104] The light intensity signal outputted from any output end of the fiber coupler 31 includes an interference light intensity signal formed by the interference of the reflected light of the illumination laser 1 and the reference laser, an interference light intensity signal formed by the interference of the reflected light of the illumination laser 2 and the reference laser, an interference light intensity signal formed by the interference of the reflected light of the illumination laser 3 and the reference laser, an interference light intensity signal formed by the interference of the reflected light of the illumination laser 1 and the illumination laser 2, an interference light intensity signal formed by the interference of the reflected light of the illumination laser 1 and the illumination laser 3, and an interference light intensity signal formed by the interference of the reflected light of the illumination laser 2 and the illumination laser 3. When the reference laser intensity is much greater than the intensity of the reflected light received by the fiber probe, the last three groups of interference light intensity signals can be ignored.

[0105] In the data processor 33, the process of calculating the vector velocity of the measuring point according to the interference light intensity signal refers to the embodiment of the first aspect of the present invention.

[0106] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 vector velocity measurement method based on a single optical fiber probe, characterized in that: include: S1, emitting three non-coplanar illumination laser beams from different angles to the same measuring point on the target to be measured, and the frequencies of the three illumination laser beams are different; S2, receiving the reflected light of the measuring point through a single optical fiber probe; S3, obtaining a reference laser and interfering it with the reflected light to generate an interference light intensity signal; S4, calculating and obtaining the vector velocity of the measuring point according to the interference light intensity signal.

2. The vector velocity measurement method based on a single optical fiber probe according to claim 1, characterized in that: The three illumination laser beams are all conical lasers.

3. The vector velocity measurement method based on a single optical fiber probe according to claim 1, characterized in that: The three illumination laser beams are all parallel lasers.

4. The vector velocity measurement method based on a single optical fiber probe according to claim 1, characterized in that: The reference laser satisfies: the values ​​of |v0-v1|, |v0-v2|, and |v0-v3| are different from each other and are all greater than the maximum value of the absolute value of the Doppler frequency shift of the reflected light caused by the movement of the measuring point; Wherein, v0 is the frequency of the reference laser, v1, v2, and v3 are the frequencies of the three illumination lasers, and |·| represents the absolute value.

5. The vector velocity measurement method based on a single optical fiber probe according to claim 1, characterized in that: Among the reflected lights of the reference laser and three illumination lasers participating in the interference, the following conditions are satisfied: the light intensity of the reference laser is much greater than the reflected light intensity of any one of the three illumination lasers, so as to highlight the interference light intensity signal between the reference laser and the reflected light and suppress the cross-interference light intensity signal between the three reflected lights.

6. The vector velocity measurement method based on a single optical fiber probe according to claim 1, characterized in that: The step of calculating the vector velocity of the measuring point according to the interference light intensity signal comprises: S4-1, using short-time Fourier transform or wavelet transform to process the interference light intensity signal, and obtain f 01 (t), f 02 (t) and f 03 (t); Among them, f 01 (t) is the time-frequency signal of the interference light intensity signal formed by the interference of the reflected light of the illumination laser 1 and the reference laser, f 02 (t) is the time-frequency signal of the interference light intensity signal formed by the interference of the reflected light of the illumination laser 2 and the reference laser, f 03 (t) is the time-frequency signal of the interference light intensity signal formed by the interference of the reflected light of the illumination laser 3 and the reference laser; S4-2, according to f 01 (t), f 02 (t) and f 03 (t) Calculate the vector velocity of the measurement point: Among them, α1, β1, γ1 are the angles between the reverse incident direction of the incident light of the illumination laser 1 pointing to the measurement point and the x, y, z axes respectively; α2, β2, γ2 are the angles between the reverse incident direction of the incident light of the illumination laser 2 pointing to the measurement point and the x, y, z axes respectively; α3, β3, γ3 are the angles between the reverse incident direction of the incident light of the illumination laser 3 pointing to the measurement point and the x, y, z axes respectively; The z axis coincides with the optical axis of the fiber optic probe and points to the fiber optic probe, and the x, y, and z axes satisfy the right-hand rule; v0 is the frequency of the reference laser, v1 is the frequency of the illumination laser 1, v2 is the frequency of the illumination laser 2, and v3 is the frequency of the illumination laser 3; c is the speed of light, and A is the maximum absolute value of the Doppler frequency shift of the reflected light.

7. A vector velocity measurement device based on a single optical fiber probe, characterized in that: include: A three-frequency laser illumination light source is used to emit three non-coplanar illumination laser beams from different angles to the same measuring point on the target to be measured, and the frequencies of the three illumination laser beams are different; a single optical fiber probe for receiving reflected light from the measurement point; A reference laser light source, used for providing a reference laser; The signal generation and data processing system is used to generate an interference light intensity signal of the reflected light and the reference laser, and calculate the vector velocity of the measurement point according to the interference light intensity signal.

8. The vector velocity measurement device based on a single optical fiber probe according to claim 7, characterized in that: The triple-frequency laser illumination light source includes three single-frequency lasers and three illumination optical fibers; each of the single-frequency lasers is coupled to the illumination optical fiber, so that the illumination laser emitted by each single-frequency laser is emitted in a cone shape from the end face of the illumination optical fiber.

9. The vector velocity measurement device based on a single optical fiber probe according to claim 7, characterized in that: The triple-frequency laser illumination light source comprises three single-frequency lasers and a laser beam expansion device connected to each of the single-frequency lasers. The illumination laser emitted by each of the single-frequency lasers is expanded into parallel light by the laser beam expansion device.

10. The vector velocity measurement device based on a single optical fiber probe according to claim 7, characterized in that: The signal generation and data processing system includes a fiber coupler, a fast response photoelectric detector and a data processor; The optical fiber coupler is used to receive the reflected light and the reference laser, and output an interference light intensity signal of the reflected light and the reference laser; The fast response photoelectric detector is used to perform photoelectric conversion on the interference light intensity signal; The data processor is used to calculate the vector velocity of the measuring point according to the converted interference light intensity signal.

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