Vector speed measuring method and device based on dense array optical fiber probe

Abstract

The invention discloses a vector velocity measurement method and device based on dense array optical fiber probes, 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, and the problems that the measurement error is increased and the measurement depth of field is relatively short due to the fact that three probes in each group are not aligned with one point along with the longitudinal movement of the target are solved. The dense array probe vector velocity measuring device consists of a group of three-frequency laser illumination light sources, a dense array optical fiber probe, a set of multi-point PDV system and a data processing system. According to the invention, the measurement of the dense array vector speed can be realized.

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 device based on a dense array optical fiber probe. Background Art

[0002] In the field of dynamic high-pressure physics and material mechanics research, by measuring the vector velocity surface array or line array distribution in the area of ​​interest of flying pieces, structural parts, etc. under dynamic high-pressure loading, more precise performance parameters of the measured target and dynamic high-pressure loading characteristics can be obtained compared to measuring only the longitudinal velocity distribution.

[0003] In the prior art, to measure the vector velocity of a certain measuring point, generally three probes are required to be aimed at the point at the same time for measurement. If the array vector velocity of N measuring points is to be measured, three probes are required in N times the number, and each group of three probes needs to be aimed at the same measuring point, which complicates the measurement system and brings difficulties to the optical path debugging. In addition, since three probes are required for each measuring point, and the three probes need to be aimed at the same measuring point at different angles, the space occupied by the arranged probes is further increased, so it is difficult to achieve dense array probe arrangement with multiple groups of three probes. Furthermore, as the distance of the target to be measured relative to the probe changes, the three probes originally aimed at the same point are no longer aimed at the same point, but at three different points, resulting in increased measurement errors and a shorter measurable depth of field. Summary of the invention

[0004] The present invention provides a vector velocity measurement method and device based on dense array fiber optic probes, so as to solve the problems that the existing velocity measurement scheme requires a large number of probes, it is difficult to realize dense array probe arrangement, and since every three probes need to be aimed at the same measurement point at the same time, the optical path debugging is complicated and the measurement depth of field is short, and the measurement error increases due to the change in the distance of the measurement target relative to the probe.

[0005] The present invention is achieved through the following technical solutions:

[0006] A first aspect of the present invention provides a vector velocity measurement method based on a dense array optical fiber probe, comprising:

[0007] S1, emitting three non-coplanar illumination laser beams from different angles to the same measurement area on the target to be measured, wherein the frequencies of the three illumination laser beams are different;

[0008] S2, receiving reflected light from a corresponding measuring point in the measuring area through each sub-probe of the dense array optical fiber probe, wherein each sub-probe is aligned with a measuring point in the measuring area;

[0009] S3, obtaining a reference laser and interfering it with the reflected light collected by each sub-probe to generate an interference light intensity signal for each measuring point;

[0010] S4, calculating the vector velocity of each measuring point according to the interference light intensity signal of each measuring point.

[0011] The present invention is based on a vector velocity measurement method of a dense array fiber optic probe, and replaces three fiber optic probes required for measuring one measurement point in the prior art with one fiber optic probe. When measuring multiple points, the number of fiber optic probes required is reduced by 2 / 3, simplifying the measurement system. The reflected light of three illumination lasers with different frequencies and different incident angles at the measurement point is collected by one fiber optic probe, and then a plurality of groups of signals with different frequency characteristics superimposed on a time series are generated by interference of the reflected light and the reference light, and then the vector velocity of the measurement point is obtained by signal extraction and data processing, thereby avoiding the complex optical path debugging of aligning each three probes with one point, and at the same time ensuring that when the distance of the target to be measured relative to the fiber optic probe changes, the measurement point aligned with the fiber optic probe will not change, thereby improving the accuracy of the measurement result.

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

[0013] Furthermore, the three illumination laser beams are all parallel laser beams.

[0014] Furthermore, the reference laser satisfies: |v 0 -v 1 |、|v 0 -v 2 |、|v 0 -v 3 | has different values, and all of them are greater than the maximum absolute value of the Doppler frequency shift of the reflected light caused by the motion of the measurement point; where v 0 is the frequency of the reference laser, v 1 、v 2 、v 3 are the frequencies of the three illumination laser beams, and |·| represents the absolute value.

[0015] Furthermore, among the reference laser and the reflected light of the three illumination lasers participating in the interference, the light intensity of the reference laser is much greater than the reflected light intensity of any illumination laser, 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.

[0016] Furthermore, the vector velocity of each measuring point is calculated based on the interference light intensity signal of each measuring point, including:

[0017] S4-1, using short-time Fourier transform or wavelet transform to process the interference light intensity signal, and obtain f m01 (t), f m02 (t) and f m03 (t);

[0018] Among them, f m01 (t) is the time-frequency signal of the interference light intensity signal formed by the reflected light of the illumination laser 1 reflected by the mth measurement point and the interference with the reference laser, f m02 (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 reflected by the mth measurement point and the reference laser, f m03 (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 reflected by the mth measurement point and the reference laser;

[0019] S4-2, according to f m01 (t), f m02 (t) and f m03 (t) Calculate the vector velocity of the mth measurement point:

[0020]

[0021]

[0022] Among them, α m1 , β m1 , γ m1 are the angles between the reverse incident direction of the incident light of the illumination laser 1 pointing to the mth measurement point and the x, y, and z axes respectively;

[0023] α m2 , β m2 , γ m2 are the angles between the reverse incident direction of the incident light of the illumination laser 2 pointing to the mth measurement point and the x, y, and z axes respectively;

[0024] α m3 , β m3 , γ m3 are the angles between the reverse incident direction of the incident light of the illumination laser 3 pointing to the mth measurement point and the x, y, and z axes respectively;

[0025] The z-axis coincides with the sub-probe optical axis and points to the sub-probe, and the x-, y-, and z-axes satisfy the right-hand rule;

[0026] v 0 is the frequency of the reference laser, v 1 is the frequency of illumination laser 1, v 2 is the frequency of illumination laser 2, v 3 is the frequency of the illumination laser 3;

[0027] c is the speed of light, and A is the maximum absolute value of the Doppler frequency shift of the reflected light.

[0028] Furthermore, if the laser frequency is not stable enough, the optical frequency ν of the three illumination lasers and the reference laser can be simultaneously monitored. 1 , ν 2 , ν 3 and ν 0 , or simultaneously monitor ν 0 -ν 1 , ν 0 -ν 2 , ν 0 -ν 3 , substituting the monitoring value into the vector velocity calculation formula can eliminate the influence of laser frequency instability.

[0029] A second aspect of the present invention provides a vector velocity measurement device based on a dense array optical fiber probe, comprising:

[0030] A triple-frequency laser illumination light source, used to emit three non-coplanar illumination laser beams from different angles to the same measurement area on the target to be measured, wherein the frequencies of the three illumination laser beams are different;

[0031] A dense array fiber optic probe, comprising a plurality of closely arranged sub-probes, each of the sub-probes being used to receive reflected light from a corresponding measuring point in the measuring area, wherein each sub-probe is aligned with a measuring point in the measuring area;

[0032] A multi-point PDV system, comprising multiple receiving channels, each of which is used to mix the reflected light received by each sub-probe with the reference laser to generate an interference light intensity signal, wherein each receiving channel corresponds to a sub-probe;

[0033] The multi-point PDV system is also used to provide a reference laser;

[0034] The data processing system is used to calculate the vector velocity of each measuring point according to the interference light intensity signal of each measuring point.

[0035] Furthermore, the triple-frequency laser illumination light source includes three single-frequency lasers, three circulators and three illumination optical fibers. The illumination laser emitted by each single-frequency laser is coupled to the illumination optical fiber through the circulator and emitted from the end face of the illumination optical fiber. A small amount of illumination laser reflected from the end faces of the three illumination optical fibers is coupled to the three receiving channels of the multi-point PDV system through the circulator for monitoring v 0 -ν 1 , ν 0 -ν 2 , ν 0 -ν 3 real-time data.

[0036] 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, and the illumination laser emitted by each of the single-frequency lasers is expanded into parallel light by the laser beam expansion device.

[0037] Furthermore, the multi-point PDV system is a single light source system; during measurement, the laser inside the multi-point PDV system is disconnected from the optical fiber input and output ports of the multi-point PDV system, and the reference laser is provided by the laser.

[0038] Furthermore, the multi-point PDV system is a dual-light source system; during measurement, the detection laser inside the multi-point PDV system is turned off, and the reference laser is provided by the reference laser inside the multi-point PDV system.

[0039] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0040] Replacing a group of three probes with one probe reduces the number of required fiber optic probes by 2 / 3. At the same time, the number of required photodetectors (in a multi-point PDV system) is also reduced by 2 / 3, saving components and simplifying the measurement system.

[0041] By measuring the vector velocity of one measurement point with one probe, the complex optical path debugging that requires three probes to be aligned at one point is avoided, thus simplifying the measurement process.

[0042] By reducing the space occupied by the probe and realizing dense array probe arrangement, vector velocity measurement can be performed on densely arranged measurement points. There is no situation where the probe cannot be aligned with a point as the distance of the target to be measured relative to the probe changes, which reduces the measurement error and increases the measurement depth of field.

[0043] The existing multi-point PDV system and dense array fiber optic probes can be used to realize the dense array vector velocity measurement function. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] 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:

[0045] Figure 1 is a flow chart of a dense array vector velocity measurement method according to an embodiment of the present invention;

[0046] Figure 2It is a schematic diagram of a rectangular coordinate system of a laser incident orientation and a dense array optical fiber probe according to an embodiment of the present invention;

[0047] Figure 3 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;

[0048] 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;

[0049] Figure 5 It is a schematic structural diagram of a vector velocity measurement device based on a dense array optical fiber probe according to an embodiment of the present invention.

[0050] The following are the descriptions of the reference numerals:

[0051] 1-illumination laser 1, 2-illumination laser 2, 3-illumination laser 3, 4-circulator, 5-circulator, 6-circulator, 7-illumination optical fiber, 8-illumination optical fiber, 9-illumination optical fiber, 10-target to be measured, 11-dense array optical fiber probe, 12-signal optical cable, 13-multi-point PDV system, 14-data processing system, 20-triple-frequency laser illumination light source, 21-single-frequency laser, 22-single-frequency laser, 23-single-frequency laser. DETAILED DESCRIPTION

[0052] 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.

[0053] 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.

[0054] 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.

[0055] The embodiments of the present invention provide a vector velocity measurement method and a measurement device, which are suitable for measuring the vector velocity array or line array distribution of a target to be measured under dynamic high voltage loading, which is beneficial to reducing the complexity of optical path debugging and improving the measurement depth of field.

[0056] A first aspect of the present invention provides a vector velocity measurement method based on a dense array optical fiber probe, which is used to measure the vector velocity distribution of a target under dynamic high pressure loading. Figure 1 The flowchart of the dense array vector velocity measurement method of the present invention is shown, which includes the following steps:

[0057] S1, emitting three non-coplanar illumination laser beams from different angles to the same measurement area on the target to be measured, wherein the frequencies of the three illumination laser beams are different;

[0058] S2, receiving reflected light from a corresponding measuring point in the measuring area through each sub-probe of the dense array optical fiber probe, wherein each sub-probe is aligned with a measuring point in the measuring area;

[0059] S3, obtaining a reference laser and interfering it with the reflected light collected by each sub-probe to generate an interference light intensity signal at each measurement point;

[0060] S4, calculating the vector velocity of each measuring point according to the interference light intensity signal of each measuring point.

[0061] 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.

[0062] After beam expansion, three illumination laser beams (illumination laser 1, illumination laser 2, and illumination laser 3) illuminate the same area to be measured on the target 10 from three different directions and produce diffuse reflection. For any measuring point in the area to be measured, the three incident light beams illuminating the measuring point are not in the same plane. The optical frequencies v of illumination laser 1, illumination laser 2, and illumination laser 3 are 1 、v 2 、v 3 There are slight differences between them.

[0063] The dense array fiber optic probe 11 is composed of a group of closely arranged sub-probes, each sub-probe receives the laser reflected by the corresponding measurement point, that is, one sub-probe corresponds to one measurement point, so that the reflected laser at different positions in the measurement area is collected by multiple sub-probes to obtain the vector velocity distribution of the measurement area.

[0064] Where, the optical frequency ν of the reference laser 0 Need to meet: ν 0 -ν 1 , ν 0 -ν 2 , ν0 -ν 3 The absolute values ​​of are different from each other, 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 the specific physical model and parameters. A can also take a value slightly larger than the empirical value or estimated value.

[0065] The reference laser can be provided by a multi-point PDV system (Photonic Doppler Velocimeter), which can be a single light source system or a dual light source system. Specifically, when it is a single light source system, while maintaining the state that the reflected light of the three illumination lasers collected by the dense array fiber optic probe can reach the photodetector inside the PDV, the connection between the PDV internal laser and the dense array fiber optic probe is disconnected, and the PDV internal laser is used as the reference laser of the vector velocity measurement device. When the multi-point PDV system is a dual light source system, the laser used as the detection light source inside the PDV system is turned off, and the reference laser inside the PDV system is used as the reference laser of the vector velocity measurement device.

[0066] The reflected laser collected by each sub-probe can be input into one receiving channel of the multi-point PDV system respectively, and the interference light intensity signal of each receiving channel can be collected by the multi-point PDV system. The interference light intensity signal can be expressed as:

[0067] I m (t) = I m01 (t)+I m02 (t)+I m03 (t)+I m12 (t)+I m13 (t)+I m23 (t)

[0068] In the formula, t represents time, I m (t) represents the interference light intensity signal at the mth measurement point;

[0069] I m01 (t) is defined as the interference light intensity signal formed by the interference of the reflected light of the illumination laser 1 at the mth measurement point and the reference laser, and its corresponding time-frequency signal is f m01 (t);

[0070] I m02 (t) is defined as the interference light intensity signal formed by the interference of the reflected light of the illumination laser 2 at the mth measurement point and the reference laser, and its corresponding time-frequency signal is f m02 (t);

[0071] I m03(t) is defined as the interference light intensity signal formed by the interference of the reflected light of the illumination laser 3 at the mth measurement point and the reference laser, and its corresponding time-frequency signal is f m03 (t);

[0072] I m12 (t) is defined as the interference light intensity signal formed by the interference of the reflected light of illumination laser 1 and illumination laser 2 at the mth measurement point, and its corresponding time-frequency signal is f m12 (t);

[0073] I m13 (t) is defined as the interference light intensity signal formed by the interference of the reflected light of illumination laser 1 and illumination laser 3 at the mth measurement point, and its corresponding time-frequency signal is f m13 (t);

[0074] I m23 (t) is defined as the interference light intensity signal formed by the interference of the reflected light of illumination laser 2 and illumination laser 3 at the mth measurement point, and its corresponding time-frequency signal is f m23 (t).

[0075] 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:

[0076] (1)f m01 (t), f m02 (t) and f m03 (t) There is no overlap between the three;

[0077] (2)f m01 (t), f m02 (t), f m03 Any of (t) does not correspond to f m12 (t), f m13 (t), f m23 (t) overlaps with any of them.

[0078] If the light intensity of the reference laser participating in the interference is much greater than the light intensity of the reflected light of the illumination laser participating in the interference, then only the above item (1) needs to be satisfied.

[0079] In step S4, the method for calculating the vector velocity of each measurement point is specifically as follows:

[0080] S4-1, use short-time Fourier transform or wavelet transform and other data processing algorithms to process the collected interference light intensity signal and obtain the f of each measurement point. m01 (t), f m02 (t) and f m03 (t) Information.

[0081] S4-2, from f m01 、f m02 and f m03 Calculate the vector velocity V of the mth measurement point m , where V mx is the velocity component of the vector velocity along the x-axis, V my is the velocity component of the vector velocity along the y-axis, V mz is the velocity component of the vector velocity along the z-axis.

[0082] When calculating, set up an independent rectangular coordinate system for each sub-probe, such as Figure 2 The figure shows a schematic diagram of the rectangular coordinate system of the sub-probe. For the mth sub-probe, the z-axis coincides with the optical axis of the sub-probe and points to the sub-probe, and the x-, y-, and z-axes satisfy the right-hand rule.

[0083] The vector velocity calculation formula is as follows:

[0084]

[0085] in,

[0086]

[0087] α m1 , β m1 , γ m1 are the angles between the reverse incident direction of the incident light from the illumination laser 1 pointing to the mth measurement point and the x, y, and z axes respectively;

[0088] α m2 , β m2 , γ m2 are the angles between the reverse incident direction of the incident light from the illumination laser 2 pointing to the mth measurement point and the x, y, and z axes respectively;

[0089] α m3 , β m3 , γ m3 are the angles between the reverse incident direction of the incident light of the illumination laser 3 pointing to the mth measurement point and the x, y, and z axes respectively;

[0090] The z-axis coincides with the sub-probe optical axis and points to the sub-probe, and the x-, y-, and z-axes satisfy the right-hand rule;

[0091] v 0 is the frequency of the reference laser, v 1 is the frequency of illumination laser 1, v 2 is the frequency of illumination laser 2, v 3 is the frequency of the illumination laser 3;

[0092] c is the speed of light, and A is the maximum absolute value of the Doppler frequency shift of the reflected light.

[0093] Divide the right side of the above vector velocity calculation formula by f m01 、f m02 and f m03 The outside is a known parameter. The data of each measuring point can be substituted into the formula to calculate the vector velocity of each measuring point.

[0094] If the output laser frequencies of the triple-frequency laser illumination source and the reference laser may not be stable enough due to the application environment and may drift over time, affecting the measurement accuracy, the optical frequencies ν of the three illumination lasers and the reference laser can be simultaneously monitored. 1 , ν 2 , ν 3 , ν 0 , or simultaneously monitor ν 0 -ν 1 , ν 0 -ν 2 , ν 0 -ν 3 By substituting the monitored values ​​into the vector velocity calculation formula, the influence of unstable laser frequency can be eliminated.

[0095] Furthermore, when the optical axes of the sub-probes of the dense array fiber optic probe are not parallel to each other, a rectangular coordinate system is established with the optical axis of each sub-probe as the z-axis to obtain the vector velocities of different measuring points. The vector velocities of different measuring points are then converted to the same coordinate system as needed to obtain the multi-point vector velocity distribution of the measurement area in the same coordinate system.

[0096] When the optical axes of the sub-probes of the dense array fiber optic probe are parallel to each other, it is only necessary to set a rectangular coordinate system for any one of the sub-probes, calculate the vector velocity, and then translate the rectangular coordinate system so that the z-axis coincides with the optical axis of another sub-probe, and then calculate the vector velocity. The vector velocities of different measurement points obtained in this way are equivalent to the vector velocities of different measurement points in a rectangular coordinate system.

[0097] In one embodiment, the above-mentioned illumination laser for measurement is a conical laser, that is, an optical fiber illumination method is adopted. Figure 3 As shown, the illumination laser gradually diffuses from the end face of the optical fiber to the surface of the target to be measured, forming an approximately elliptical spot in the area to be measured, and three conical laser beams overlap in the same area to be measured.

[0098] The target to be measured is illuminated in a cone-shaped beam, which is very convenient to implement. As the target moves, the overlapping area of ​​the illumination spots of the three laser beams on the target becomes smaller, but as long as the area still covers each 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 target is always perpendicular to the optical axis of the probe) 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-shaped beam illumination method will increase as the target moves, and the measurement depth of field of the cone-shaped beam illumination method needs to be limited to a smaller range.

[0099] An optional implementation of the fiber optic illumination method is: three illumination laser beams emitted by three single-frequency lasers are coupled into three circulators respectively, and then emitted through the end face of the illumination fiber coupled to each circulator to illuminate the same measurement area on the target to be measured.

[0100] In one embodiment, the illumination laser is a parallel laser, that is, a parallel light illumination method is adopted. The three laser beams can be expanded into parallel light by a laser beam expansion device and then illuminate the target to be measured.

[0101] like Figure 4 The figure shows a schematic diagram of a parallel laser beam incident on the surface of the target to be measured. 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 to be measured. There is no need to correct the incident direction of the light during data processing, and the measurement error does not increase with the movement of the target. Therefore, this illumination method can obtain a larger measurement depth of field than the conical beam illumination method.

[0102] A second aspect of the present invention provides a vector velocity measurement device based on a dense array optical fiber probe corresponding to the above-mentioned vector velocity measurement method, such as Figure 5 The figure is a schematic diagram of the structure of the vector velocity measurement device of the present invention, comprising:

[0103] A triple-frequency laser illumination light source 20 is used to emit three non-coplanar illumination laser beams from different angles to the same measurement area on the target 10 to be measured, and the frequencies of the three illumination laser beams are different;

[0104] A dense array fiber optic probe 11, comprising a plurality of closely arranged sub-probes, each sub-probe being used to receive reflected light from a corresponding measuring point in a measuring area, wherein each sub-probe is aligned with a measuring point in the measuring area;

[0105] The multi-point PDV system 13 includes multiple receiving channels, each receiving channel is used to mix the reflected light received by each sub-probe with the reference light inside the multi-point PDV system to obtain an interference light intensity signal corresponding to each measuring point, wherein each receiving channel corresponds to one sub-probe;

[0106] The data processing system 14 is used to calculate the vector velocity of each measuring point according to the interference light intensity signal of each measuring point.

[0107] 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 the three single-frequency lasers simultaneously emit three illumination lasers: illumination laser 1, illumination laser 2, and illumination laser 3. Illumination laser 1, illumination laser 2, and illumination laser 3 should satisfy the following requirements: they are incident on the same measurement area on the target to be measured from different angles and are not in the same plane.

[0108] In one embodiment, the triple-frequency laser illumination light source 20 includes three single-frequency lasers, and the three lasers are respectively coupled to three illumination optical fibers. The illumination laser 1, illumination laser 2, and illumination laser 3 emitted by the three single-frequency lasers are respectively coupled to the illumination optical fibers 7-9 via the circulator 4, the circulator 5, and the circulator 6. That is, the illumination laser 1 is coupled to the illumination optical fiber 7 via the circulator 4, and is emitted from the end face of the illumination optical fiber 7; the illumination laser 2 is coupled to the illumination optical fiber 8 via the circulator 5, and is emitted from the end face of the illumination optical fiber 8; the illumination laser 3 is coupled to the illumination optical fiber 9 via the circulator 6, and is emitted from the end face of the illumination optical fiber 9. The three laser beams form a conical laser to irradiate the same measurement area on the target to be measured. A small amount of laser light reflected by the illumination laser 1, the illumination laser 2, and the illumination laser 3 at the end face of the illumination optical fiber returns to the circulator and is respectively coupled into the three receiving channels of the multi-point PDV system (for monitoring ν 0 -ν 1 , ν 0 -ν 2 , ν 0 -ν 3 real-time data).

[0109] In one embodiment, the illumination laser 1, the illumination laser 2, and the illumination laser 3 emitted by the triple-frequency laser illumination light source 20 are respectively expanded into parallel light by a laser beam expansion device and then irradiated to the same measurement area on the target to be measured. At the same time, a small amount of illumination laser 1, illumination laser 2, and illumination laser 3 are respectively coupled into the three receiving channels of the multi-point PDV system (for monitoring v 0 -ν 1 , ν 0 -ν 2 , ν 0 -ν 3 real-time data).

[0110] The multi-point PDV system includes multiple receiving channels, and each sub-probe of the dense array fiber optic probe 11 is connected to each receiving channel of the multi-point PDV system through a signal optical cable to perform one-to-one signal transmission. The multi-point PDV system collects the light intensity signal of each channel, and the light intensity signal includes the interference light intensity signal formed by the interference of the reflected light of the illumination laser 1 and the reference laser, the interference light intensity signal formed by the interference of the reflected light of the illumination laser 2 and the reference laser, the interference light intensity signal formed by the interference of the reflected light of the illumination laser 3 and the reference laser, the interference light intensity signal formed by the interference of the reflected light of the illumination laser 1 and the illumination laser 2, the interference light intensity signal formed by the interference of the reflected light of the illumination laser 1 and the illumination laser 3, and the interference light intensity signal formed by the interference of the reflected light of the illumination laser 2 and the illumination laser 3.

[0111] In one embodiment, the multi-point PDV system 13 is a single light source system. During measurement, the laser inside the multi-point PDV system is disconnected from the optical fiber input and output ports of the multi-point PDV system, and the reference laser is provided by the laser.

[0112] In one embodiment, the multi-point PDV system is a dual-light source system. During measurement, the detection laser inside the multi-point PDV system is turned off, and a reference laser signal is provided by a reference laser inside the multi-point PDV system.

[0113] In the data processing system, the process of calculating the vector velocity of each measuring point according to the interference light intensity signal of each measuring point refers to the embodiment of the first aspect of the present invention.

[0114] 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 dense array optical fiber probe, characterized in that: include: S1, emitting three non-coplanar illumination laser beams from different angles to the same measurement area on the target to be measured, and the frequencies of the three illumination laser beams are different; S2, receiving reflected light from a corresponding measuring point in the measuring area through each sub-probe of the dense array optical fiber probe, wherein each sub-probe is aligned with a measuring point in the measuring area; S3, obtaining a reference laser and interfering it with the reflected light collected by each sub-probe to generate an interference light intensity signal for each measuring point; S4, calculating the vector velocity of each measuring point according to the interference light intensity signal of each measuring point.

2. The vector velocity measurement method based on dense array 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 dense array 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 dense array 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 dense array optical fiber probe according to claim 1, characterized in that: Among the reference laser participating in the interference and the reflected light of the three illumination lasers collected by each of the sub-probes, the following conditions are satisfied: the light intensity of the reference laser is much greater than the reflected light intensity of any illumination laser, 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 method for measuring vector velocity based on dense array optical fiber probe according to claim 1, characterized in that: The step of calculating the vector velocity of each measuring point according to the interference light intensity signal of each measuring point comprises: S4-1, using short-time Fourier transform or wavelet transform to process the interference light intensity signal, and obtain f m01 (t), f m02 (t) and f m03 (t); Among them, f m01 (t) is the time-frequency signal of the interference light intensity signal formed by the reflected light of the illumination laser 1 reflected by the mth measurement point and the interference with the reference laser, f m02 (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 reflected by the mth measurement point and the reference laser, f m03 (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 reflected by the mth measurement point and the reference laser; S4-2, according to f m01 (t), f m02 (t) and f m03 (t) Calculate the vector velocity of the mth measurement point: Among them, α m1 , β m1 , γ m1 are the angles between the reverse incident direction of the incident light of the illumination laser 1 pointing to the mth measurement point and the x, y, and z axes respectively; α m2 , β m2 , γ m2 are the angles between the reverse incident direction of the incident light of the illumination laser 2 pointing to the mth measurement point and the x, y, and z axes respectively; α m3 , β m3 , γ m3 are the angles between the reverse incident direction of the incident light of the illumination laser 3 pointing to the mth measurement point and the x, y, and z axes respectively; The z-axis coincides with the sub-probe optical axis and points to the sub-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. The method for measuring vector velocity based on dense array optical fiber probe according to claim 1, characterized in that: By simultaneously monitoring the optical frequencies ν1, ν2, ν3 and ν0 of the three illumination lasers and the reference laser, or simultaneously monitoring ν0-ν1, ν0-ν2, ν0-ν3, and substituting the monitored values ​​into the vector velocity calculation formula, the influence of laser frequency instability can be eliminated.

8. A vector velocity measurement device based on a dense array optical fiber probe, characterized in that: include: A triple-frequency laser illumination light source, used to emit three non-coplanar illumination laser beams from different angles to the same measurement area on the target to be measured, wherein the frequencies of the three illumination laser beams are different; A dense array fiber optic probe, comprising a plurality of closely arranged sub-probes, each of the sub-probes being used to receive reflected light from a corresponding measuring point in the measuring area, wherein each sub-probe is aligned with a measuring point in the measuring area; A multi-point PDV system, comprising multiple receiving channels, each of which is used to mix the reflected light received by each sub-probe with the reference laser to generate an interference light intensity signal, wherein each receiving channel corresponds to a sub-probe; The multi-point PDV system is also used to provide a reference laser; The data processing system is used to calculate the vector velocity of each measuring point according to the interference light intensity signal of each measuring point.

9. The vector velocity measurement device based on dense array optical fiber probe according to claim 8, characterized in that: The triple-frequency laser illumination light source includes three single-frequency lasers, three circulators and three illumination optical fibers; each of the single-frequency lasers is coupled to the illumination optical fiber through the circulator, so that the illumination laser emitted by each single-frequency laser is emitted in a cone from the end face of the illumination optical fiber; a small amount of illumination laser reflected from the end faces of the three illumination optical fibers is coupled to the three receiving channels of the multi-point PDV system through the circulator.

10. The vector velocity measurement device based on dense array optical fiber probe according to claim 8, 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.

11. The vector velocity measurement device based on dense array optical fiber probe according to claim 8, characterized in that: The multi-point PDV system is a single light source system; during measurement, the laser inside the multi-point PDV system is disconnected from the optical fiber input and output ports of the multi-point PDV system, and the reference laser is provided by the laser.

12. The vector velocity measurement device based on dense array optical fiber probe according to claim 8, characterized in that: The multi-point PDV system is a dual-light source system; during measurement, the detection laser inside the multi-point PDV system is turned off, and the reference laser is provided by the reference laser inside the multi-point PDV system.

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