Three-dimensional laser Doppler blood flow velocity measuring system and method based on optical fiber sensing

Abstract

The invention relates to the technical field of blood flow velocity measurement, in particular to a three-dimensional laser Doppler blood flow velocity measurement system and method based on optical fiber sensing. The method comprises the following steps: adjusting the probe to enable a convergent point of five paths of incident light to irradiate a measured target point; red blood cells in a blood vessel move and interact with three groups of detection light through a target point to generate scattered light containing three wavelengths, a probe receives the scattered light, the scattered light is amplified and filtered and then output to three photoelectric detectors respectively, and the photoelectric detectors convert received optical signals into current signals; performing current-voltage conversion and analog-to-digital conversion on the current signal to obtain different digital signals, obtaining Doppler frequency shift through fast Fourier transform, and calculating velocity components in three independent directions based on the Doppler frequency shift; and obtaining the flow velocity of the blood in the blood vessel according to all the velocity components. The human body blood flow velocity can be accurately monitored.

Description

Technical Field

[0001] The present invention relates to the technical field of blood flow velocity measurement, and in particular to a three-dimensional laser Doppler blood flow velocity measurement system and method based on optical fiber sensing. Background Art

[0002] At present, commonly used health testing equipment pays more attention to the patient's blood pressure, pulse and other parameters, and to a certain extent ignores the real-time monitoring of blood flow velocity. The blood flow information of the human circulatory system is also closely related to the health of the human body. The quality of blood circulation function is an important factor affecting the structure, function and metabolism of cardiovascular tissues. Measuring the flow rate of blood microcirculation can monitor and diagnose the growth of tumors, help doctors qualitatively diagnose the severity of patients' burns, assist in the diagnosis of retinal diseases such as glaucoma and macular degeneration in ophthalmology, and play an important role in postoperative monitoring of free flap transplantation. Measuring intravascular blood flow parameters can also understand blood flow disorders and their degree, determine heart function, arteriosclerosis, and determine the effect of treatment and drug effects.

[0003] Laser Doppler velocimetry technology is widely used in the medical field to monitor blood flow velocity in blood vessels due to its advantages of high measurement accuracy, high spatial resolution, fast dynamic response, wide measurement range, and non-contact measurement. At present, laser Doppler velocimetry systems include traditional spatial light Doppler velocimetry and fiber optic Doppler velocimetry. Although one-dimensional or two-dimensional laser Doppler velocimetry systems based on fiber optic sensing have achieved non-invasive and continuous monitoring, they can only obtain the velocity component of blood vessels in a specific direction, and cannot accurately obtain the blood flow velocity of blood vessels in unknown spatial directions in the human body. Summary of the invention

[0004] In order to solve the problem of inaccurate detection results in the existing methods when detecting the blood flow velocity of the human body, the purpose of the present invention is to provide a three-dimensional laser Doppler blood flow velocity measurement system and method based on optical fiber sensing. The technical solutions adopted are as follows:

[0005] In the first aspect, the present invention provides a three-dimensional laser Doppler blood flow velocity measurement system based on fiber optic sensing, the system comprising a laser, a fiber optic coupler, an optical wavelength division multiplexer, an optical circulator, a probe, a fiber optic amplifier, a wavelength division multiplexer, a narrowband filter, a photodetector, and a signal processing component, each laser being connected to a fiber optic coupler; the narrowband filter and the photodetector and the signal processing component being connected by optical fiber, and the photodetector and the signal processing component being electrically connected.

[0006] Preferably, the first detection light emitted by the first laser is divided into two incident lights with equal light intensities through the first optical fiber coupler, and the first incident light of the first laser enters the input port of the optical wavelength division multiplexer through the output port of the first optical fiber coupler; the second incident light of the first laser enters the first optical fiber collimator of the probe through the output port of the first optical fiber coupler and enters the target point;

[0007] The second detection light emitted by the second laser is divided into two incident lights with equal light intensities through the second optical fiber coupler, wherein the first incident light of the second laser enters the input port of the optical wavelength division multiplexer through the output port of the second optical fiber coupler; the second incident light of the second laser enters the second optical fiber collimator of the probe through the output port of the second optical fiber coupler and enters the target point;

[0008] The third detection light emitted by the third laser is divided into two incident lights with equal light intensities through the third fiber coupler, wherein the first incident light of the third laser enters the fifth fiber collimator incident target point of the probe through the output port of the third fiber coupler; the second incident light of the third laser enters the fourth fiber collimator incident target point of the probe through the output port of the third fiber coupler.

[0009] Preferably, the output end of the optical wavelength division multiplexer combines and outputs mixed output light to the first port of the optical circulator, and the mixed output light is output to the incident target point of the third optical fiber collimator of the probe through the second port of the optical circulator; the mixed output light includes two lights of different wavelengths.

[0010] Preferably, when red blood cells in a blood vessel pass through a target point, scattered light containing different wavelengths is generated, and a third optical fiber collimator receives the backscattered light. The backscattered light enters the second port of the optical circulator, is output from the third port of the optical circulator to the input port of the optical fiber amplifier, is amplified by the optical fiber amplifier, and is output to a wavelength division multiplexer. The wavelength division multiplexer separates the scattered light containing the different wavelengths and then outputs them.

[0011] The scattered lights of different wavelengths enter corresponding narrowband filters through different output ports of the wavelength division multiplexer respectively, and enter different photodetectors after being filtered by the narrowband filters;

[0012] Each photodetector converts the corresponding scattered light into a current signal and transmits it to the signal processing component.

[0013] Preferably, the signal processing component performs current-voltage conversion and analog-to-digital conversion on the current signal to obtain different digital signals, which are then transmitted to the host computer;

[0014] The host computer calculates each independent velocity component of the blood in the blood vessels based on different digital signals, and calculates the flow rate of the blood in the blood vessels by integrating all independent velocity components.

[0015] In a second aspect, the present invention provides a three-dimensional laser Doppler blood flow velocity measurement method based on optical fiber sensing, the method comprising:

[0016] Adjust the probe so that the convergence point of the five incident lights shines on the target point to be measured;

[0017] The movement of red blood cells in the blood vessels interacts with the three groups of detection lights through the target point to generate scattered light containing three wavelengths. The probe receives the scattered light, amplifies and filters it, and outputs it to three photodetectors respectively. The photodetectors convert the received light signals into current signals.

[0018] The current signal is converted into current-to-voltage and analog-to-digital to obtain different digital signals. The Doppler frequency shift is obtained by fast Fourier transform. The velocity components in three independent directions are calculated based on the Doppler frequency shift. The blood flow velocity in the blood vessel is obtained based on all the velocity components.

[0019] The present invention has at least the following beneficial effects:

[0020] 1. The three-dimensional laser Doppler blood flow velocity measurement system based on optical fiber sensing provided by the present invention is composed of components such as lasers, optical fiber couplers, optical wavelength division multiplexers, probes, optical fiber amplifiers, demultiplexers, narrowband filters, photodetectors, and signal processing components. Optical fiber sensing technology is used to use lasers of different wavelengths to irradiate target points in blood vessels to obtain scattered light in different directions, thereby determining blood flow velocity. The system provided by the present invention can obtain the blood flow velocity of blood vessels in unknown spatial directions in the human body.

[0021] 2. The fiber-optic sensing three-dimensional laser Doppler blood flow velocity measurement method provided by the present invention utilizes multiple groups of double-beam-double-scattering light paths constructed by lasers of multiple different wavelengths to irradiate target points of human tissues. After the detection light is irradiated to the red blood cells moving in the blood vessels, scattered light is generated. The scattered light is received and three different Doppler frequency shifts can be obtained through spectrum analysis. The velocity components of the blood in the blood vessels in three independent directions are calculated, and then the magnitude of the blood flow velocity in the blood vessels is obtained, thereby realizing accurate monitoring of the blood flow velocity of the human body. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1A flowchart of a method for measuring blood flow velocity using three-dimensional laser Doppler blood flow rate based on optical fiber sensing provided by an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of a three-dimensional laser Doppler blood flow velocity measurement system based on optical fiber sensing provided by an embodiment of the present invention;

[0025] Figure 3 A schematic diagram of the structure of a probe provided by an embodiment of the present invention;

[0026] Figure 4 A schematic diagram of an optical path for measuring blood flow velocity using three-dimensional laser Doppler provided in an embodiment of the present invention;

[0027] In the figure: 1 is a first laser; 2 is a second laser; 3 is a third laser; 4 is a first fiber coupler; 5 is a second fiber coupler; 6 is a third fiber coupler; 7 is an optical wavelength division multiplexer; 8 is an optical circulator; 9 is a probe; 10 is an optical fiber amplifier; 11 is a wavelength division multiplexer; 12 is a first narrowband filter; 13 is a second narrowband filter; 14 is a third narrowband filter; 15 is a first photodetector; 16 is a second photodetector; 17 is a third photodetector; 18 is a signal processing component; 4- 1 and 4-2 are output ports of the first fiber coupler 4; 5-1 and 5-2 are output ports of the second fiber coupler 5; 6-1 and 6-2 are output ports of the third fiber coupler 6; 7-1 and 7-2 are input ports of the optical wavelength division multiplexer 7; 9-1 is a first fiber collimator; 9-2 is a second fiber collimator; 9-3 is a third fiber collimator; 9-4 is a fourth fiber collimator; 9-5 is a fifth fiber collimator; 11-1, 11-2 and 11-3 are output ports of the wavelength division multiplexer 11; 1 , 2 and λ 3 are the incident light of three wavelengths, P is the target point, θ is the angle between the x-axis and the y-axis, represents the velocity component of the blood flow velocity in the blood vessel in the direction perpendicular to the bisector of the angle of the first group of detection lights; represents the velocity component of the blood flow velocity in the blood vessel in the direction perpendicular to the bisector of the angle of the second group of detection lights; It represents the velocity component of the blood flow velocity in the blood vessel in the direction perpendicular to the bisector of the angle of the third group of detection lights. x represents the horizontal axis of the coordinate system; y represents the vertical axis of the coordinate system; and z represents the vertical axis of the coordinate system. DETAILED DESCRIPTION

[0028] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the three-dimensional laser Doppler blood flow velocity measurement system and method based on optical fiber sensing proposed by the present invention are described in detail as follows in conjunction with the accompanying drawings and preferred embodiments.

[0029] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0030] The specific scheme of the three-dimensional laser Doppler blood flow velocity measurement system and method based on optical fiber sensing provided by the present invention is described in detail below with reference to the accompanying drawings.

[0031] An embodiment of a three-dimensional laser Doppler blood flow velocity measurement system based on optical fiber sensing:

[0032] This embodiment proposes a three-dimensional laser Doppler blood flow velocity measurement system based on optical fiber sensing. Figure 2 As shown, a three-dimensional laser Doppler blood flow velocity measurement system based on optical fiber sensing in this embodiment includes a first laser 1, a second laser 2, a third laser 3, a first optical fiber coupler 4, a second optical fiber coupler 5, a third optical fiber coupler 6, an optical wavelength division multiplexer 7, an optical circulator 8, a probe 9, an optical fiber amplifier 10, a wavelength division multiplexer 11, a first narrowband filter 12, a second narrowband filter 13, a third narrowband filter 14, a first photodetector 15, a second photodetector 16, a third photodetector 17, and a signal processing component 18, wherein In the embodiment, optical devices are connected by optical fiber, and electrical devices are connected by electrical connection. Specifically, the first narrowband filter 12 is connected to the first photodetector 15 by optical fiber, and the first photodetector 15 is electrically connected to the signal processing component 18. The second narrowband filter 13 is connected to the second photodetector 16 by optical fiber, and the second photodetector 16 is electrically connected to the signal processing component 18. The third narrowband filter 14 is connected to the third photodetector 17 by optical fiber, and the third photodetector 17 is electrically connected to the signal processing component 18.

[0033] In terms of the optical path, the first detection light emitted by the first laser 1 is divided into two incident lights with equal light intensities through the first optical fiber coupler 4, wherein the first incident light of the first laser 1 enters the input port 7-1 of the optical wavelength division multiplexer 7 through the output port 4-1 of the first optical fiber coupler 4; the second incident light of the first laser 1 enters the first optical fiber collimator 9-1 of the probe 9 through the output port 4-2 of the first optical fiber coupler 4 and enters the incident target point P; the wavelength of the first detection light emitted by the first laser 1 is λ 1 .

[0034] The second detection light emitted by the second laser 2 is divided into two incident lights with equal light intensities through the second fiber coupler 5, wherein the first incident light of the second laser 2 enters the input port 7-2 of the optical wavelength division multiplexer 7 through the output port 5-1 of the second fiber coupler 5; the second incident light of the second laser 2 enters the second fiber collimator 9-2 of the probe 9 through the output port 5-2 of the second fiber coupler 5 and enters the incident target point P; the wavelength of the second detection light emitted by the second laser 2 is λ 2 .

[0035] The third detection light emitted by the third laser 3 is divided into two incident lights with equal light intensities through the third fiber coupler 6, wherein the first incident light of the third laser 3 enters the fifth fiber collimator 9-5 of the probe 9 through the output port 6-1 of the third fiber coupler 6 and enters the incident target point P; the second incident light of the third laser 3 enters the fourth fiber collimator 9-4 of the probe 9 through the output port 6-2 of the third fiber coupler 6 and enters the incident target point P; the wavelength of the third detection light emitted by the third laser 3 is λ 3 .

[0036] The output end of the optical wavelength division multiplexer 7 combines and outputs the mixed output light to the first port of the optical circulator 8, and the mixed output light is output to the third optical fiber collimator 9-3 of the probe 9 through the second port of the optical circulator 8 and enters the target point P; the mixed output light includes λ and λ 2 Two wavelengths, λ 1 ≠λ 2 ≠λ 3 .

[0037] In the probe 9, the output light of the third optical fiber collimator 9-3 includes λ 1 and λ 2 The wavelength of the mixed output light of the two wavelengths is λ 1 , the wavelength of the output light of the second optical fiber collimator 9-2 is λ 2 The wavelength of the output light of the fourth optical fiber collimator 9-4 and the fifth optical fiber collimator 9-5 is λ 3 .

[0038] The red blood cells in the blood vessels generate a process containing λ when passing through the target point P. 1 , 2 and λ 3 The backscattered light of three wavelengths is received by the third optical fiber collimator 9-3, and the backscattered light enters the second port of the optical circulator 8, and is output from the third port of the optical circulator 8 to the input port of the optical fiber amplifier 10, and is amplified by the optical fiber amplifier 10 and output to the wavelength division multiplexer 11, which divides the wavelengths containing λ into 1 , 2 and λ 3The scattered light of three wavelengths is separated and output; the wavelength is λ 1 The scattered light enters the input port of the first narrowband filter 12 through the output port 11-1 of the wavelength division multiplexer 11, and the wavelength after being filtered by the first narrowband filter 12 is λ 1 The scattered light enters the first photodetector 15; the wavelength is λ 2 The scattered light enters the input port of the second narrowband filter 13 through the output port 11-2 of the wavelength division multiplexer 11, and the wavelength after filtering by the second narrowband filter 13 is λ 2 The scattered light with a wavelength of 3 enters the second photodetector 16; the scattered light with a wavelength of 3 enters the input port of the third narrowband filter 14 through the output port 11-3 of the wavelength division multiplexer 11, and the wavelength after filtering by the third narrowband filter 14 is λ 3 The scattered light enters the third photodetector 17.

[0039] The first photodetector 15 emits a signal with a wavelength of λ 1 The scattered light of wavelength λ is converted into a first current signal and transmitted to the signal processing component 18. The second photodetector 16 2 The scattered light of wavelength λ is converted into a second current signal and transmitted to the signal processing component 18. 3 The scattered light is converted into a third current signal and transmitted to the signal processing component 18.

[0040] The signal processing component 18 performs current-to-voltage conversion and analog-to-digital conversion on the three current signals to obtain a first digital signal, a second digital signal and a third digital signal, and then transmits them to the host computer. The host computer calculates the magnitudes v of the three independent velocity components of the blood in the blood vessel according to the first digital signal, the second digital signal and the third digital signal. x 、v y and v z , and finally the blood flow velocity v in the blood vessels is calculated based on the magnitude of the three velocity components.

[0041] like Figure 3 As shown in the figure, it is a schematic diagram of the structure of the probe, the probe 9 is composed of a circular ring bracket and five fiber collimators, wherein the first fiber collimator 9-1, the second fiber collimator 9-2, the fourth fiber collimator 9-4 and the fifth fiber collimator 9-5 are fixed at the vertices of two diameters on the circular ring, and the two diameters are perpendicular to each other, and the third fiber collimator 9-3 is located at the center of the two perpendicular diameters, i.e., the center of the circular ring.

[0042] The outgoing light of the third fiber optic collimator 9-3 is vertically directed toward the target point P, the outgoing light of the first fiber optic collimator 9-1 and the outgoing light of the third fiber optic collimator 9-3 form an angle θ, the outgoing light of the second fiber optic collimator 9-2 and the outgoing light of the third fiber optic collimator 9-3 form an angle θ, the outgoing light beam of the fourth fiber optic collimator 9-4 and the outgoing light of the fifth fiber optic collimator 9-5 form an angle 2θ, wherein the three outgoing lights of the first fiber optic collimator 9-1, the second fiber optic collimator 9-2 and the third fiber optic collimator 9-3 are located in the same plane, and the three outgoing lights of the fourth fiber optic collimator 9-4, the fifth fiber optic collimator 9-5 and the third fiber optic collimator 9-3 are located in the same plane, and the two planes are perpendicular to each other.

[0043] An embodiment of a three-dimensional laser Doppler blood flow velocity measurement method based on optical fiber sensing:

[0044] This embodiment proposes a three-dimensional laser Doppler blood flow velocity measurement method based on optical fiber sensing. Figure 1 As shown, the method comprises the following steps:

[0045] Step S1, adjusting the probe so that the convergence point of five incident lights irradiates the measured target point;

[0046] Step S2, the red blood cells in the blood vessels move through the target point and interact with the three groups of detection lights to generate scattered light containing three wavelengths, the probe receives the scattered light, amplifies and filters it, and outputs it to three photodetectors respectively, and the photodetectors convert the received light signals into current signals;

[0047] Step S3, performing current-to-voltage conversion and analog-to-digital conversion on the current signal to obtain different digital signals, obtaining Doppler frequency shift through fast Fourier transform, and calculating velocity components in three independent directions based on the Doppler frequency shift; and obtaining the blood flow velocity in the blood vessel based on all the velocity components.

[0048] This embodiment will use the three-dimensional laser Doppler blood flow velocity measurement system provided in the previous embodiment to detect blood flow velocity. Considering that when using multiple wavelengths of light to detect human blood information, one or more wavelengths are usually located in the near-infrared light band that is invisible to the human eye, when debugging the position of the probe fiber collimator, you can first use the light in the visible light band to adjust it, and then install it into the system for measurement after determining the angles of the five fiber collimators.

[0049] When selecting a laser, at least one laser with a wavelength in the visible light range is selected. When the system is working, the visible light source can serve as a detection light and also as an indicator light source. After adjusting the angle of the fiber collimator in the probe, the three groups of light paths illuminate the same target point P, so the visible detection light can be used to ensure that all detection lights can illuminate the point to be measured.

[0050] Specifically, the device is first started, and the probe is adjusted so that the convergence point of the incident light is irradiated on the target point to be measured.

[0051] When the red blood cells in the blood vessels move through the target point, they interact with the three sets of detection light and stimulate the 1 , 2 and λ 3 The backscattered light of three wavelengths is divided into three types with wavelength λ by amplification and filtering. 1 The scattered light with wavelength λ 2 The scattered light with wavelength λ 3 The scattered light is further converted into current signals by three photodetectors.

[0052] After the signal processing component performs current-to-voltage conversion and analog-to-digital conversion on the current signal, the wavelength is obtained. 1 The first digital signal corresponding to the scattered light with a wavelength of λ 2 The second digital signal corresponding to the scattered light and the wavelength is λ 3 The host computer calculates the velocity v of the blood in the blood vessel according to the first digital signal, the second digital signal and the third digital signal.

[0053] In the receiving optical path, the third optical fiber collimator 9-3 is used as a medium for receiving scattered light.

[0054] Five fiber collimators are fixed on a circular ring bracket at a specific angle. The first fiber collimator 9-1, the second fiber collimator 9-2, the fourth fiber collimator 9-4, and the fifth fiber collimator 9-5 are fixed at the four vertices of the two vertical diameters of the circular ring, and the third fiber collimator 9-3 is fixed at the center of the circular ring bracket, so as to ensure that the first fiber collimator 9-1, the second fiber collimator 9-2 and the third fiber collimator 9-3 are in the same plane, the fourth fiber collimator 9-4, the fifth fiber collimator 9-5 and the third fiber collimator 9-3 are in the same plane, and the two planes are perpendicular to each other. The specific angles of each of the five optical fiber collimators are such that the outgoing light of the third optical fiber collimator 9-3 is directed vertically toward the target point P, the angle between the outgoing light of the first optical fiber collimator 9-1 and the outgoing light of the third optical fiber collimator 9-3 is θ, the angle between the outgoing light of the second optical fiber collimator 9-2 and the outgoing light of the third optical fiber collimator 9-3 is θ, and the angle between the outgoing light beam of the fourth optical fiber collimator 9-4 and the outgoing light of the fifth optical fiber collimator 9-5 is 2θ.

[0055] like Figure 4 As shown in the optical path principle diagram of the three-dimensional laser Doppler blood flow velocity measurement in this embodiment, the wavelength is λ 1 The incident light with wavelength λ 1 and λ2 The mixed incident light of the first double beam-double scattered light path is formed. The angle between the two beams is θ, and the direction perpendicular to the bisector of the angle is the x-axis, and the wavelength is λ. 2 The incident light with wavelength λ 1 and λ 2 The mixed incident light of the second double beam-double scattered light path is formed. The angle between the two beams is θ, and the direction perpendicular to the bisector of the angle is the y-axis, and the wavelength is λ 3 The two incident lights form the third set of double beams - double scattered light paths. The angle between the two beams is 2θ, and the z axis is perpendicular to the bisector of the angle. Using common sense in geometry, we know that the angle between the x-axis and the y-axis is θ, and the z axis is perpendicular to the plane where the x-axis and the y-axis are located. That is, the directions of the three coordinate axes are independent of each other, forming a non-standard three-dimensional coordinate system. The three Doppler frequency shifts f of the three detection light paths are obtained. D1 、f D2 and f D3 After that, the velocity components of the blood vessel at the target point P on the x-axis, y-axis, and z-axis of the coordinate system can be obtained respectively. and The size of v x 、v y and v z , further, under the premise of unknown blood vessel direction, the blood flow velocity v in the blood vessel in this coordinate system can be obtained.

[0056] The calculation formula of Doppler frequency shift can be obtained from the double beam-double scattering system, which can be specifically expressed as:

[0057]

[0058] Among them, f D is the Doppler frequency shift, v is the velocity component of the target velocity in the direction perpendicular to the bisector of the angle between the two beams, λ i is the wavelength of the incident light, θ is the angle between the two light beams, and sin is the sine function.

[0059] The three Doppler frequency shifts f are obtained by the above calculation formula. D1 、f D2 and f D3 Then, the velocity components of the blood flow velocity in the blood vessels in the unknown direction on the x-axis, y-axis and z-axis are calculated according to the Doppler frequency shift. and Size:

[0060]

[0061] Among them, v x Indicates the velocity of blood flow in the blood vessel in the direction perpendicular to the bisector of the angle of the first group of detection light The size of vy The velocity component of the blood flow velocity in the blood vessel in the direction perpendicular to the bisector of the angle of the second group of detection light The size of v z Represents the velocity component of the blood flow velocity in the blood vessel in the direction perpendicular to the bisector of the angle of the third group of detection light The size of f D1 represents the frequency difference of the scattered light of the two incident lights of the first detection light path, that is, the first Doppler frequency shift; f D2 represents the frequency difference of the scattered light of the two incident lights of the second detection light path, that is, the second Doppler frequency shift; f D3 It represents the frequency difference of the scattered light of the two incident lights of the third detection light path, that is, the third Doppler frequency shift; 1 represents the wavelength of the first detection light emitted by the first laser; 2 represents the wavelength of the second detection light emitted by the second laser; 3 Represents the wavelength of the third detection light emitted by the third laser.

[0062] Thus, the blood flow velocity in the blood vessel can be obtained in a non-standard three-dimensional coordinate system composed of three directions perpendicular to the bisectors of the angles of the three sets of detection lights:

[0063]

[0064] in, represents the velocity component of the blood flow velocity in the blood vessel in the direction perpendicular to the bisector of the angle of the first group of detection lights; represents the velocity component of the blood flow velocity in the blood vessel in the direction perpendicular to the bisector of the angle of the second group of detection lights; Represents the velocity component of the blood flow velocity in the blood vessel in the direction perpendicular to the bisector of the angle of the third group of detection lights.

[0065] Therefore, the flow rate of blood in the blood vessels can be expressed as:

[0066]

[0067] Where θ is the angle between the x-axis and the y-axis;

[0068] Furthermore, substituting into v x 、v y and v z Then simplify the formula to get:

[0069]

[0070] Where v represents the flow rate of blood in the blood vessels.

[0071] Thus, the present embodiment can monitor the blood flow rate in the blood vessels.

[0072] This embodiment uses three lasers with different wavelengths to construct three sets of double-beam-double-scattering light paths to irradiate target points of human tissue. After the detection light is irradiated to the red blood cells moving in the blood vessels, scattered light is generated. The scattered light is received and three different Doppler frequency shifts can be obtained through spectrum analysis. The velocity components of the blood in the blood vessels in three independent directions are calculated, and then the size of the blood flow velocity in the blood vessels is obtained, thereby realizing accurate monitoring of the blood flow velocity of the human body.

[0073] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A three-dimensional laser Doppler blood flow velocity measurement system based on optical fiber sensing, characterized in that: The system comprises a laser, an optical fiber coupler, an optical wavelength division multiplexer (7), an optical circulator (8), a probe (9), an optical fiber amplifier (10), a wavelength division multiplexer (11), a narrowband filter, a photodetector, and a signal processing component (18). Each laser is connected to an optical fiber coupler; the narrowband filter and the photodetector and the signal processing component (18) are connected by optical fibers, and the photodetector and the signal processing component (18) are electrically connected.

2. The three-dimensional laser Doppler blood flow velocity measurement system based on optical fiber sensing according to claim 1, characterized in that: The probe (9) is composed of a circular ring support and five optical fiber collimators, wherein the first optical fiber collimator (9-1), the second optical fiber collimator (9-2), the fourth optical fiber collimator (9-4) and the fifth optical fiber collimator (9-5) are fixed at two vertical diameter vertices on the circular ring, and another optical fiber collimator is located at the center of the circular ring.

3. The three-dimensional laser Doppler blood flow velocity measurement system based on optical fiber sensing according to claim 1, characterized in that: The first detection light emitted by the first laser (1) is divided into two incident lights of equal light intensity via the first optical fiber coupler (4). A first path of incident light from a first laser (1) enters an input port (7-1) of an optical wavelength division multiplexer (7) via an output port (4-1) of a first optical fiber coupler (4); a second path of incident light from the first laser (1) enters a first optical fiber collimator (9-1) of a probe (9) via an output port (4-2) of the first optical fiber coupler (4) and enters a target point; The second detection light emitted by the second laser (2) is divided into two incident lights with equal light intensities via the second optical fiber coupler (5), wherein the first incident light of the second laser (2) enters the input port (7-2) of the optical wavelength division multiplexer (7) via the output port (5-1) of the second optical fiber coupler (5); the second incident light of the second laser (2) enters the second optical fiber collimator (9-2) of the probe (9) via the output port (5-2) of the second optical fiber coupler (5) to enter the target point; The third detection light emitted by the third laser (3) is divided into two incident lights with equal light intensities via the third optical fiber coupler (6), wherein the first incident light of the third laser (3) enters the fifth optical fiber collimator (9-5) of the probe (9) via the output port (6-1) of the third optical fiber coupler (6) and enters the incident target point; and the second incident light of the third laser (3) enters the fourth optical fiber collimator (9-4) of the probe (9) via the output port (6-2) of the third optical fiber coupler (6) and enters the incident target point.

4. The three-dimensional laser Doppler blood flow velocity measurement system based on optical fiber sensing according to claim 1, characterized in that: The output end of the optical wavelength division multiplexer (7) combines and outputs mixed output light to the first port of the optical circulator (8), and the mixed output light is output to the incident target point of the third optical fiber collimator (9-3) of the probe (9) through the second port of the optical circulator (8); the mixed output light includes two lights of different wavelengths.

5. The three-dimensional laser Doppler blood flow velocity measurement system based on optical fiber sensing according to claim 4, characterized in that: When red blood cells in a blood vessel pass through a target point, scattered light containing different wavelengths is generated. A third optical fiber collimator (9-3) receives the backscattered light. The backscattered light enters the second port of the optical circulator (8), is output from the third port of the optical circulator (8) to the input port of the optical fiber amplifier (10), is amplified by the optical fiber amplifier (10), and is output to the wavelength division multiplexer (11). The wavelength division multiplexer (11) separates the scattered light containing the different wavelengths and outputs them. The scattered lights of different wavelengths enter corresponding narrowband filters through different output ports of the wavelength division multiplexer respectively, and enter different photodetectors after being filtered by the narrowband filters; Each photodetector converts the corresponding scattered light into a current signal and transmits it to the signal processing component (18).

6. The three-dimensional laser Doppler blood flow velocity measurement system based on optical fiber sensing according to claim 5, characterized in that: The signal processing component (18) performs current-voltage conversion and analog-to-digital conversion on the current signal to obtain different digital signals, which are then transmitted to the host computer; The host computer calculates each independent velocity component of the blood in the blood vessels based on different digital signals, and calculates the flow rate of the blood in the blood vessels by integrating all independent velocity components.

7. The method for measuring blood flow velocity using three-dimensional laser Doppler blood flow rate based on optical fiber sensing according to claim 1, characterized in that: The method includes: Adjust the probe so that the convergence point of the five incident lights shines on the target point to be measured; The movement of red blood cells in the blood vessels interacts with the three groups of detection lights through the target point to generate scattered light containing three wavelengths. The probe receives the scattered light, amplifies and filters it, and outputs it to three photodetectors respectively. The photodetectors convert the received light signals into current signals. The current signal is converted into current-to-voltage and analog-to-digital to obtain different digital signals. The Doppler frequency shift is obtained by fast Fourier transform. The velocity components in three independent directions are calculated based on the Doppler frequency shift. The blood flow velocity in the blood vessel is obtained based on all the velocity components.

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