Multicolor flow-induced birefringence stress real-time measurement system and method

Abstract

The invention relates to a multicolor flow-induced birefringence stress real-time measurement system and method. The invention relates to the technical field of optical testing, and aims to solve the problems that an existing single-wavelength measuring system is insufficient in precision, limited in measuring range, incapable of achieving synchronous multi-wavelength measurement and the like. Flow-induced birefringence is simultaneously measured by using multiple wavelengths, the stress measurement precision is improved, and the problem of measurement fuzziness of a single-wavelength system is avoided. The adjustable polarization optical element and the high-precision light splitting system are combined, polarization information analysis of multi-wavelength light is achieved, and the measurement dynamic range is widened. By optimizing a photoelectric detection system and a computer algorithm, rapid and accurate stress measurement is realized, and the method is suitable for real-time analysis under complex flow conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of optical testing, and is a multi-color flow-induced birefringence stress instant measurement system and method. Background Art

[0002] Flow-induced birefringence (FIB) technology is an important optical testing method for measuring the stress distribution of fluids, and has wide applications especially in the research fields of polymer solutions, complex fluids and biological fluids. This technology is based on the anisotropic change of fluids under shear or tensile action, and uses the principle of polarized light interference to measure the stress field distribution inside the fluids, so as to reveal their rheological behaviors.

[0003] At present, flow-induced birefringence measurement systems mainly use single-wavelength light sources for stress measurement, such as He-Ne lasers (632.8 nm) or LED light sources with specific wavelengths. Such systems usually use polarization optical elements (such as analyzers, polarizers and phase retarders) combined with high-precision photodetectors to achieve the measurement of the birefringence phase retardation of fluids. However, these single-wavelength measurement systems have the following main problems: (1) Limited spectral information affects measurement accuracy: Traditional monochromatic light measurement systems can only provide birefringence information at a specific wavelength, and it is difficult to accurately distinguish the stress response characteristics at different wavelengths. Since the optical anisotropy of polymer solutions may vary with wavelength, single-wavelength measurement may lead to errors or information loss in stress measurement. (2) Limited measurement range: Single-wavelength light sources may cause periodic loss of interference signals under specific experimental conditions, especially in the case of high-stress or thick optical path samples, where the birefringence phase retardation exceeds 2π, resulting in a measurement ambiguity problem, which affects the measurement accuracy. (3) Unable to achieve synchronous multi-wavelength measurement: Existing multi-wavelength measurement systems mostly adopt a time-division scanning method, that is, by switching different wavelength light sources to measure the fluid stress in turn. However, this method not only increases the measurement time, but also may cause measurement errors due to fluid movement, and it is difficult to be applicable to the transient stress measurement of high-speed flow fields. (4) Complex optical adjustment of the system and low measurement efficiency: Traditional flow-induced birefringence measurement equipment needs to precisely adjust the angles of polarization optical devices and frequently calibrate during the measurement process to ensure measurement accuracy. Due to the complex optical path, the system has high requirements for the stability of the external environment and it is difficult to achieve long-term stable measurement. In recent years, the application of multi-color light sources (such as white light LEDs or multi-wavelength lasers) in the field of optical measurement has gradually increased, and some studies have tried to use multi-wavelength optical methods for fluid stress measurement, such as obtaining birefringence information at different wavelengths through a broadband light source combined with a spectroscope prism or a filter. However, these methods still have problems such as insufficient spectral selectivity, complex system structure and poor synchronism, and it is difficult to meet the actual needs of high-precision and rapid measurement.

[0004] In summary, there are still many deficiencies in the existing flow-induced birefringence measurement technology in terms of measurement accuracy, dynamic response ability, and system stability. There is an urgent need for a flow-induced birefringence stress measurement system that can simultaneously obtain multi-wavelength optical information, improve measurement accuracy and efficiency. In view of the above problems, the present invention proposes a flow-induced birefringence measurement system based on multi-color light, which can achieve synchronous multi-wavelength stress measurement, improve the accuracy and robustness of measurement, and provide more comprehensive experimental data support for the study of polymer fluid dynamics. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the present invention provides a multi-color flow-induced birefringence stress instant measurement system and method. The present invention actually aims to solve the problems such as insufficient accuracy, limited measurement range, and inability to achieve synchronous multi-wavelength measurement of the existing single-wavelength measurement system. The present invention uses a multi-color light source to achieve high-precision measurement of the stress field of the flow-induced polymer solution, enhances the anti-interference ability of the measurement system, and improves the stability and dynamic response ability of the measurement.

[0006] The innovative points of the present invention are as follows:

[0007] 1. Instant stress measurement technology: The biggest innovation of the present invention lies in its ability to achieve instant stress measurement. Different from traditional stress measurement methods that require a long time to obtain data and perform post-analysis, by using a multi-color light source in combination with the flow-induced birefringence effect, this technology can measure the stress state in the fluid in real time and synchronously, significantly improving the efficiency of data acquisition and analysis. This is particularly important for fluid systems with high-speed changes such as dynamic flow and turbulence, as it can provide instant feedback to support more efficient experiments and real-time monitoring.

[0008] 2. Independence from camera frame rate: Traditional stress field measurement usually relies on high-speed cameras and high frame rates. However, this method may face problems such as insufficient frame rate and data loss in rapidly changing flow states. The present invention breaks the dependence on the camera frame rate through the combination of optical measurement and birefringence effect. Without a high-frequency camera, the technology can stably and accurately measure the fluid stress in fluid dynamics experiments, thus providing greater flexibility for the design and operation of the measurement system, especially in unstable or ultra-dynamic environments.

[0009] 3. Combination of multi-color light source and stress field measurement: The present invention uses a multi-color light source for birefringence measurement, innovatively enhancing the accuracy and breadth of fluid stress measurement. The multi-color light source acts on the fluid with light of different wavelengths simultaneously, effectively improving the sensitivity and resolution of stress field measurement. Traditional monochromatic measurement methods often can only provide limited information, while through the multi-color light source, it is possible to capture the details of stress changes in the fluid in more dimensions, making the measurement results more comprehensive and accurate.

[0010] The present invention provides the following technical solutions:

[0011] A multi-color flow-induced birefringence stress real-time measurement system, the system includes a multi-color light source module, a polarization modulation module, a fluid test area, an optical analysis module, a photoelectric detection and digital display module, and a data processing and storage module;

[0012] The multi-color light source module emits light beams of multiple wavelengths, and each light beam is combined through an optical fiber or an optical coupling device to form a stable polarized light illumination source;

[0013] The polarization modulation module controls the polarization state of the incident light to achieve birefringence phase delay measurement;

[0014] The fluid test area is a transparent flow channel for accommodating the polymer solution to be measured. The fluid is controlled to enter the test area through a pumping system and generates a flow-induced birefringence effect under shear, tensile or turbulent conditions;

[0015] The optical analysis module is used to separate the transmitted light of different wavelengths and project it onto the corresponding detection area;

[0016] The photoelectric detection and digital display module, the photoelectric detection and data acquisition module includes a first photomultiplier tube, a second photomultiplier tube, a third photomultiplier tube and an oscilloscope; the photoelectric detection and digital display module is used to record the birefringence signal in real time and transmit the data to a computer for processing;

[0017] The data processing and storage module calculates the collected birefringence signal to obtain the fluid stress field distribution and displays the measurement results in real time on the interface.

[0018] Preferably, the polarization modulation module includes a neutral filter, a first linear filter, a second linear filter, a third linear filter, a first plane mirror, a second plane mirror, a third plane mirror, a fourth plane mirror, a first polarizer, a second polarizer and a third polarizer;

[0019] After the light passes through the neutral filter, the light intensity is adjusted. The light passes through the first linear filter, and the first linear filter allows blue-wavelength light to pass through; the second linear filter blocks the blue-wavelength light from passing through and reflects it to the first plane mirror. At this time, only blue light exists in this optical path, that is, the expected test light; the first plane mirror reflects the blue light to the first polarizer; the blue light passes through the first polarizer to form a phase difference with the original light beam degree and reaches the third linear filter; the green light passes through the second linear filter, reaches the second plane mirror, and after two reflections by the second plane mirror and the third plane mirror, reaches the third polarizer and passes through the third polarizer to reach the third linear filter;

[0020] The reflected light beam of the third linear filter passes through the second polarizer, reaches the fourth plane mirror, passes through the fourth plane mirror and reaches the first linear filter.

[0021] Preferably, the second linear filter is a narrow-bandwidth linear filter with a strong reflective substance coated on one side, serving as a beam splitter that reflects blue laser light and transmits green laser light.

[0022] Preferably, the first polarizer is a Glan-Thompson prism polarizer, and the light passing through the first polarizer reaches a third linear filter that only allows blue wavelengths to pass through.

[0023] Preferably, the polarization modulation module separates the original three-color light emitted from the multi-color light source module into three colors of light with different polarization phases through three separate polarization optical paths. After passing through the polarizer and the phase modulator, the light beam enters the fluid test area in a specific polarization state and penetrates the flowing polymer solution in the fluid test area.

[0024] Preferably, the fluid test area includes a stage, a microfluidic chip, a piezoelectric position detector, and a piezoelectric position controller; the microfluidic chip is arranged on the stage and connected to the piezoelectric position detector, and the piezoelectric position detector is connected to the piezoelectric position controller.

[0025] The third polarizer has a 45-degree phase difference from the first polarizer.

[0026] The blue light and the green light converge and reach the third linear filter, then pass through the microchannel fluid chip, and the light reaches the microfluidic chip.

[0027] Under the action of the fluid flow, the orientation of the polymer chains in the solution changes, causing the birefringence effect and resulting in different degrees of phase delay for light beams of different wavelengths.

[0028] Preferably, the outgoing light passing through the fluid test unit passes through the optical analysis module. The optical analysis module includes a fourth linear filter, a fifth linear filter, a sixth linear filter, a seventh linear filter, a fourth polarizer, a fifth polarizer, and a sixth polarizer; the blue light passes through the microfluidic chip, and due to flow-induced birefringence, the blue light undergoes a phase change and reaches the linear filter.

[0029] The fourth linear filter and the fifth linear filter allow light with a blue wavelength bandwidth to pass through. The blue light passes through the fourth linear filter and the fifth linear filter and reaches the fourth polarizer.

[0030] The green light is reflected by the linear green filter and reaches the sixth polarizer, and then passes through the seventh linear filter and the third photomultiplier tube in sequence. The signal line is connected and transmitted in real time to the oscilloscope; the fourth polarizer has a 90-degree phase difference from the first polarizer.

[0031] The blue light passes through the fourth polarizer and reaches the first photomultiplier tube. The first photomultiplier tube receives the blue light with flow-induced phase change, obtains a corresponding intensity of current, and is connected to the oscilloscope through a BNC line.

[0032] Preferably, a computer is used as the data processing and display module. The oscilloscope is connected to the computer to achieve data recording, storage, and post-processing. The computer calculates the multi-wavelength polarization information, solves the stress distribution of the fluid, and generates the corresponding stress field image.

[0033] A method for instantaneously measuring multi-color flow-induced birefringence stress is realized based on a multi-color flow-induced birefringence stress instant measurement system. The method includes the following steps:

[0034] Step 1: Select a polymer solution with a specific concentration, inject it into the flow channel, control the flow rate range between 0.1 m / s and 1 m / s, and gradually increase the shear rate.

[0035] Step 2: Record the birefringence change of the fluid and solve the stress field of the fluid through multi-wavelength data;

[0036] Step 3: Conduct experimental calibration. An optical element with known birefringence characteristics, a quarter-wave plate, is used for measurement calibration to verify the accuracy and stability of the experimental system. The quarter-wave plate is fixedly installed on a high-precision rotating table. The angle adjustment accuracy of the rotating table can reach ±0.1°, enabling precise angle control. During the experiment, every time the rotating table rotates 5°, a measurement is taken to record the corresponding light intensity change;

[0037] During the measurement, the measurement intensity at a specific wavelength reaches a minimum value at a certain angle. At this time, the analysis instrument needs to rotate 90° to measure the maximum intensity value; by comparing the maximum and minimum light intensity data, the retardation characteristics of the quarter-wave plate and the orientation of its principal axis are calculated;

[0038] Step 4: Conduct post-processing. In the birefringence measurement experiment, an accurate perturbation method is used for calculation to improve the calculation accuracy.

[0039] Preferably, in subsequent analysis, the angle information between the flow direction and the optical polarization vector needs to be measured by rotating the flow cell. With the experimental setup remaining unchanged, the flow cell is rotated in a certain direction and a set of measurement data is recorded;

[0040] Subsequently, under the same experimental conditions, the flow cell is rotated in the opposite direction and a second set of data is obtained; by comparing the angle data measured during clockwise and counterclockwise rotations, the angle information of the flow direction is calculated.

[0041] The present invention has the following beneficial effects:

[0042] Compared with the prior art, the present invention:

[0043] The present invention utilizes multiple wavelengths to simultaneously measure flow-induced birefringence, improving the stress measurement accuracy and avoiding the measurement ambiguity problem of a single-wavelength system. The present invention combines tunable polarization optical elements and a high-precision spectroscopic system to achieve the polarization information analysis of multi-wavelength light and improve the measurement dynamic range. The present invention realizes fast and accurate stress measurement by optimizing the photoelectric detection system and computer algorithms, and is applicable to real-time analysis under complex flow conditions.

[0044] The present invention can be widely applied to fields such as the rheology research of polymer fluids, the analysis of microfluidic devices, the monitoring of polymer processing processes, and the fluid measurement in aerospace. The core technology of the present invention breaks through the limitations of traditional single-wavelength measurement methods and provides a new method for fluid stress measurement with high precision and multi-wavelength parallel detection. Brief Description of the Drawings

[0045] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0046] Figure 1 It is a connection diagram of different modules of the multi-color flow-induced birefringence stress instant measurement system of the present invention;

[0047] Figure 2 It is a schematic diagram of the polarization modulation module of the multi-color flow-induced birefringence stress instant measurement system of the present invention;

[0048] Figure 3 It is a schematic diagram of the fluid test area of the multi-color flow-induced birefringence stress instant measurement system of the present invention;

[0049] Figure 4 It is a schematic diagram of the photoelectric analysis of the multi-color flow-induced birefringence stress instant measurement system of the present invention;

[0050] Figure 5 It is a schematic diagram of the photoelectric detection and digital display module of the multi-color flow-induced birefringence stress instant measurement system of the present invention;

[0051] Figure 6 It is a schematic diagram of the data processing and storage module of the multi-color flow-induced birefringence stress instant measurement system of the present invention;

[0052] Figure 7 It is a performance index diagram of the present invention.

[0053] Among them, 1 - multi - color light source module, 2 - polarization modulation module, 3 - fluid test area, 4 - optical analysis module, 5 - photoelectric detection and digital display module, 6 - data processing and storage module, 7 - neutral density filter, 8 - stage, 9 - piezoelectric position detector, 10 - piezoelectric position controller, 11 - oscilloscope, 12 - first linear filter, 13 - second linear filter, 14 - first plane mirror, 15 - first polarizer, 16 - third linear filter, 17 - fourth linear filter, 18 - fifth linear filter, 19 - fourth polarizer, 20 - first photomultiplier tube, 21 - fourth plane mirror, 22 - second polarizer, 23 - fifth polarizer, 24 - sixth linear filter, 25 - second photomultiplier tube, 26 - second plane mirror, 27 - third plane mirror, 28 - third polarizer, 29 - sixth polarizer, 30 - seventh linear filter, 31 - third photomultiplier tube, 32 - micro - flow chip. Detailed implementation manners

[0054] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0055] The present invention is described in detail below in conjunction with specific embodiments. Specific Embodiment 1:

[0057] According to Figures 1 to 7 As shown, the specific optimized technical solution adopted by the present invention to solve the above - mentioned technical problems is:

[0058] First, the present invention discovers the following common laws:

[0059] (1) Birefringence universality and fluid stress relationship: The birefringence effect is a key characterization of the fluid stress state and is applicable to various fluid systems. Whether it is a polymer solution or other types of non - Newtonian fluids, the birefringence effect can reflect the distribution of internal stress in the fluid. By combining a multi - color light source, this technology can achieve precise measurement of the stress state in different fluids. This common law shows that flow - induced birefringence is not only applicable to specific fluid types, but can be widely used in stress measurement of various complex flow states, having cross - field applicability.

[0060] (2) Enhancement of stress sensitivity of multi - color light source: The introduction of a multi - color light source not only enhances the ability to perceive the fluid stress field but also provides richer stress information. By simultaneously measuring the birefringence effect of the fluid at multiple wavelengths, the technology can capture more detailed dynamic changes in the flow field. The commonality of this technology is that whether in high - shear - rate flow or turbulent flow, the use of a multi - color light source can effectively improve the resolution and accuracy of stress measurement, thereby revealing the profound impact of stress on flow characteristics.

[0061] (3) Immediacy and high efficiency: One of the core commonalities of the present invention is the immediate acquisition of stress information. Traditional stress measurement methods often rely on long - term experimental data accumulation and subsequent analysis, while this technology can obtain stress data in real - time and synchronously, greatly improving the experimental efficiency. Especially in high - speed dynamic fluid flow, it can quickly capture stress changes, providing more timely data support for experimental and applied research.

[0062] (4) Camera independence: Traditional stress - field measurement techniques rely on high - frame - rate acquisition of high - speed cameras, while the present invention innovatively breaks this limitation. By combining optical measurement with the birefringence effect, it is possible to accurately measure the stress field in the fluid without a high - frame - rate camera. This feature enables the system to be applied under a wider range of experimental conditions, especially suitable for high - dynamic and complex flow environments, and is not limited by the camera frame rate, thus greatly improving the flexibility and applicability of the experiment.

[0063] Based on the laws discovered in the present invention, the following specific solutions are provided:

[0064] A multi - color flow - induced birefringence stress immediate measurement system, characterized in that: the system includes a multi - color light source module 1, a polarization modulation module 2, a fluid test area 3, an optical analysis module 4, a photoelectric detection and digital display module 5, and a data processing and storage module 6;

[0065] The multi - color light source module 1 emits light beams of multiple wavelengths, and each light beam is combined through an optical fiber or an optical coupling device to form a stable polarized light illumination source;

[0066] The polarization modulation module 2 controls the polarization state of the incident light to achieve birefringence phase - delay measurement;

[0067] The fluid test area 3 is a transparent flow channel for accommodating the polymer solution to be measured, and the fluid is controlled to enter the test area through a pumping system and generates a flow - induced birefringence effect under shear, tensile, or turbulent conditions;

[0068] The optical analysis module 4 is used to separate the transmitted light of different wavelengths and project it onto the corresponding detection area;

[0069] Optoelectronic detection and digital display module 5. The optoelectronic detection and data acquisition module 5 includes a first photomultiplier tube 20, a second photomultiplier tube 25, a third photomultiplier tube 31 and an oscilloscope. The optoelectronic detection and digital display module is used to record the birefringence signal in real time and transmit the data to a computer for processing;

[0070] Data processing and storage module 6, which calculates the collected birefringence signal to obtain the fluid stress field distribution and displays the measurement results in real time on the interface.

[0071] The present invention has the following innovative points:

[0072] The present invention adopts a multi-wavelength synchronous measurement technology: using multiple wavelengths to simultaneously measure flow-induced birefringence, improving the stress measurement accuracy and avoiding the measurement ambiguity problem of a single-wavelength system.

[0073] The present invention adopts a real-time polarization modulation and spectral separation technology: combining a tunable polarization optical element and a high-precision spectral splitting system to realize the polarization information analysis of multi-wavelength light and improve the measurement dynamic range.

[0074] The present invention adopts a high-resolution optoelectronic detection and data analysis algorithm: by optimizing the optoelectronic detection system and computer algorithm, fast and accurate stress measurement is realized, which is suitable for real-time analysis under complex flow conditions.

[0075] The present invention can be widely applied to fields such as polymer fluid rheology research, microfluidic device analysis, polymer processing process monitoring, and aerospace fluid measurement. Its core technology breaks through the limitations of traditional single-wavelength measurement methods and provides a new method for high-precision, multi-wavelength parallel detection of fluid stress measurement. Specific Embodiment Two:

[0077] The difference between the second embodiment and the first embodiment of the present invention is only that:

[0078] The polarization modulation module includes a neutral density filter 7, a first linear filter 12, a second linear filter 13, a third linear filter 16, a first plane mirror 14, a second plane mirror 26, a third plane mirror 27, a fourth plane mirror 21, a first polarizer 15, a second polarizer 22 and a third polarizer 28;

[0079] The light intensity is adjusted after the light passes through the neutral filter 7. The light then passes through the first linear filter 12, which allows light with blue wavelengths to pass through. The second linear filter 13 blocks the passage of light with blue wavelengths and reflects it to the first plane mirror 14. At this time, only blue light, i.e., the expected test light, exists in this optical path. The first plane mirror 14 reflects the blue light to the first polarizer 15. The blue light passes through the first polarizer 15 and forms a phase difference of 45 degrees with the original light beam, reaching the third linear filter 16. The green light passes through the second linear filter 13, reaches the second plane mirror 26, and after two reflections by the second plane mirror 26 and the third plane mirror 27, reaches the third polarizer 28. It passes through the third polarizer 28 and reaches the third linear filter 16.

[0080] The reflected light beam of the third linear filter 16 passes through the second polarizer 22, reaches the fourth plane mirror 21, and passes through the fourth plane mirror 21 to reach the first linear filter 12. Specific Embodiment Three:

[0082] The difference between the third embodiment of the present invention and the second embodiment lies only in:

[0083] The second linear filter 13 uses a narrow-bandwidth linear filter with a strong reflective substance plated on one side as a beam splitter, which reflects the blue laser and transmits the green laser.

[0084] The first polarizer 15 uses a Glan-Thompson prism polarizer. The light passing through the first polarizer 15 reaches the third linear filter 16 that only allows blue wavelengths to pass through. Specific Embodiment Four:

[0086] The difference between the fourth embodiment of the present invention and the third embodiment lies only in:

[0087] The polarization modulation module separates the original three-color light emitted from the multi-color light source module into three colors of light with different polarization phases through three separate polarization optical paths. After passing through the polarizer and the phase modulator, the light beam enters the fluid test area in a specific polarization state, enters the fluid test area, and penetrates the flowing polymer solution. Specific Embodiment Five:

[0089] The difference between the fifth embodiment of the present invention and the fourth embodiment lies only in:

[0090] The fluid test area includes a stage 8, a microfluidic chip 32, a piezoelectric position detector 9, and a piezoelectric position controller 10. The stage 8 is provided with the microfluidic chip 32 and is connected to the piezoelectric position detector 9, and the piezoelectric position detector 9 is connected to the piezoelectric position controller 10.

[0091] The third polarizer 28 has a phase difference of 45 degrees from the first polarizer.

[0092] Blue light and green light converge and reach the third linear filter 16, and then pass through the microchannel fluid chip 32, and the light reaches the microfluidic chip 32;

[0093] Under the action of the fluid flow, the orientation of the polymer chains in the solution changes, causing the birefringence effect, and causing different degrees of phase delay of light beams with different wavelengths. Specific Embodiment Six:

[0095] The difference between the sixth embodiment of the present invention and the fifth embodiment is only that:

[0096] The outgoing light passing through the fluid test unit 3 passes through the optical analysis module 4. The optical analysis module 4 includes a fourth linear filter 17, a fifth linear filter 18, a sixth linear filter 24, a seventh linear filter 30, a fourth polarizer polarizer 19, a fifth polarizer 23 and a sixth polarizer 29; the blue light passes through the microfluidic chip, and due to flow-induced birefringence, the blue light generates a phase change and reaches the linear filter 17;

[0097] The fourth linear filter 17 and the fifth linear filter 18 allow light with a blue wavelength bandwidth to pass through. The blue light passes through the fourth linear filter 17 and the fifth linear filter 18 and reaches the fourth polarizer polarizer 19;

[0098] The green light is reflected by the 18 linear green light sheet and reaches the sixth polarizer 29, and successively passes through the seventh linear filter 30 and the third photomultiplier 31, and the signal line is connected and transmitted to the oscilloscope 11 in real time; the fourth polarizer polarizer 19 and the first polarizer 15 have a 90-degree phase difference;

[0099] The blue light passes through the fourth polarizer polarizer 19 and reaches the first photomultiplier 20. The first photomultiplier 20 receives the blue light with a flow-induced phase change, obtains a current with a corresponding intensity, and is connected to the oscilloscope 11 through a BNC line.

[0100] The green light passes through the second linear filter 13, reaches the second flat mirror 26, is reflected twice by the second flat mirror 26 and the third flat mirror 27, reaches the third polarizer 28, and passes through the third polarizer 28 and reaches the third linear filter 16.

[0101] The third polarizer 28 and the first polarizer 15 have a 45-degree phase difference.

[0102] Blue light and green light converge and reach the second flat mirror 26, and then pass through the microchannel fluid chip 32.

[0103] The blue light passes through the fifth linear filter 18, reaches the fourth polarizer polarizer 19, passes through the first photomultiplier 20, and the signal line is connected and transmitted to the oscilloscope 11 and the computer in real time.

[0104] The green light is reflected by the fifth linear filter 18, reaches the sixth polarizer 29, passes through the seventh linear filter 30 and the third photomultiplier tube 31 in sequence, and is transmitted to the oscilloscope 11 and the computer in real time through signal line connection.

[0105] The fifth linear filter 18 does not pass green light but passes blue light.

[0106] The sixth polarizer 29 has a 90-degree phase difference from the third polarizer 28.

[0107] The first polarizer 15 has a 90-degree phase difference from the fourth polarizer 19.

[0108] The incident angles of the third linear filter 16 and the fifth linear filter 18 are less than 5 degrees.

[0109] The refractive index resolution is as high as 2x10 -7 . Specific Embodiment Seven:

[0111] The difference between Embodiment Seven and Embodiment Six of the present invention lies only in that:

[0112] The data processing and display module uses a computer. The oscilloscope 11 is connected to the computer to realize data recording, storage and post-processing. The computer calculates the multi-wavelength polarization information, solves the stress distribution of the fluid, and generates the corresponding stress field image. Specific Embodiment Eight:

[0114] The difference between Embodiment Eight and Embodiment Seven of the present invention lies only in that:

[0115] A method for instantaneously measuring multi-color flow-induced birefringence stress, the method is realized based on a multi-color flow-induced birefringence stress instantaneously measuring system, and the method includes the following steps:

[0116] Step 1: Select a polymer solution with a specific concentration, inject it into the flow channel, control the flow velocity range between 0.1 m / s and 1 m / s, and gradually increase the shear rate.

[0117] Step 2: Record the birefringence change of the fluid, and solve the stress field of the fluid through multi-wavelength data;

[0118] Step 3: Conduct experimental calibration. Use an optical element with known birefringence characteristics: a quarter-wave plate for measurement calibration to verify the accuracy and stability of the experimental system. The quarter-wave plate is fixedly installed on a high-precision rotary table. The angle adjustment accuracy of the rotary table can reach ±0.1°, and precise angle control can be achieved. During the experiment, every time the rotary table rotates 5°, a measurement will be carried out to record the corresponding light intensity change;

[0119] During the measurement process, the measured intensity at a specific wavelength reaches a minimum value at a certain angle. At this time, the analytical instrument needs to be rotated by 90° to measure the maximum intensity value. By comparing the maximum and minimum light intensity data, the retardation characteristics of the quarter-wave plate and the orientation of its principal axis are calculated.

[0120] Step 4: Perform post-processing. In the birefringence measurement experiment, an accurate perturbation method is used for calculation to improve the calculation accuracy. Specific Embodiment Nine:

[0122] The difference between Embodiment Nine and Embodiment Eight of the present invention lies only in:

[0123] In the subsequent analysis, the angle information between the flow direction and the optical polarization vector needs to be measured by rotating the flow cell. With the experimental setup remaining unchanged, the flow cell is rotated in a certain direction and a set of measurement data is recorded.

[0124] Subsequently, under the same experimental conditions, the flow cell is rotated in the opposite direction and a second set of data is obtained. By comparing the angle data measured during clockwise and counterclockwise rotations, the angle information of the flow direction is calculated. Specific Embodiment Ten:

[0126] The difference between Embodiment Ten and Embodiment Nine of the present invention lies only in:

[0127] The present invention aims to provide a multi-color flow-induced birefringence stress instant measurement system to solve problems such as insufficient accuracy, limited measurement range, and inability to achieve synchronous multi-wavelength measurement in existing single-wavelength measurement systems. The present invention uses a multi-color light source to achieve high-precision measurement of the stress field of flow-induced polymer solutions, enhance the anti-interference ability of the measurement system, and improve the measurement stability and dynamic response ability.

[0128] 2. System Composition and Structure

[0129] The multi-color flow-induced birefringence stress measurement system of the present invention mainly includes the following parts (the components and their connection relationships are described in combination with the attached drawings:

[0130] Multi-color light source module 1: It includes multiple laser diodes (LDs) or light-emitting diodes (LEDs) with different wavelengths, which can emit multiple wavelength beams simultaneously or sequentially. Each light source is combined into a stable polarized light illumination source through optical fibers or optical coupling devices.

[0131] Polarization modulation module 2: It consists of a polarizer, a phase retardation plate (such as a λ / 4 wave plate), and an adjustable polarization modulator (such as an electro-optic modulator or a liquid crystal phase modulator), and is used to control the polarization state of the incident light to achieve birefringence phase retardation measurement.

[0132] Fluid testing area 3: A transparent flow channel (such as made of glass or quartz) for accommodating the polymer solution to be tested. The fluid is controlled to enter the testing area through a pumping system and generates a flow-induced birefringence effect under shear, tensile, or turbulent conditions. The optical transparency of the flow channel ensures that the measurement beam can penetrate the fluid sample.

[0133] Optical analysis module 4: Composed of an analysis polarizer, a spectroscopic system (such as a spectroscopic prism or a diffraction grating), and an imaging optical system, it is used to separate the transmitted light of different wavelengths and project it onto the corresponding detection area.

[0134] Photoelectric detection and digital display module 5: Includes multi-wavelength photodetectors (such as a CMOS camera or a spectrometer), signal amplification and filtering circuits. This module is used to record the birefringence signal in real time and transmit the data to a computer for processing.

[0135] Data processing and storage module 6: Adopts a computer control system, combines multi-wavelength polarization analysis algorithms, solves the collected birefringence signals, finally obtains the fluid stress field distribution, and displays the measurement results in real time on the interface.

[0136] 3. Connection relationship and working principle

[0137] The connection relationship between the modules of the system of the present invention is as follows in the appendix Figure 1 :

[0138] The multi-color light source module 1 generates polarized light and couples it into the polarization modulation module 2 through an optical fiber or a lens.

[0139] The polarization modulation module 2 includes three separate polarization optical paths, which separate the original three-color light emitted from the multi-color light source module 1 into three colors of light with different polarization phases, including a neutral density filter 7, a first linear filter 12, a second linear filter 13, a third linear filter 16, a first plane mirror 14, a second plane mirror 26, a third plane mirror 27, a fourth plane mirror 21, a first polarizer 15, a second polarizer 22, and a third polarizer 28. After passing through the polarizer (or called a polarizer, or called a polarization sheet) and the phase modulator, the light beam enters the fluid testing area 3 in a specific polarization state, enters the fluid testing area 3, and penetrates the flowing polymer solution.

[0140] The fluid testing area 3 includes a stage 8, a microfluidic chip 32, a piezoelectric position detector 9, and a piezoelectric position controller 10. Under the action of the fluid flow, the orientation of the polymer chains in the solution changes, causing a birefringence effect, and causing different degrees of phase delay for light beams of different wavelengths.

[0141] The outgoing light passing through the fluid test area 3 goes through the optical analysis module 4. The module 4 includes a fourth linear filter 17, a fifth linear filter 18, a sixth linear filter 24, a seventh linear filter 30, a fourth polarizer 19, a fifth polarizer 23, and a sixth polarizer 29. Among them, the spectroscopic system separates light beams of different wavelengths.

[0142] The photoelectric detection and digital display module 5 respectively detects the transmission intensities of each wavelength. The module 5 includes a first photomultiplier tube (or photoelectric converter) 20, a second photomultiplier tube 25, and a third photomultiplier tube 31.

[0143] The data processing and storage module 6 includes a computer, which calculates the multi-wavelength polarization information, solves the stress distribution of the fluid, and generates the corresponding stress field image.

[0144] In the figure, the solid line, the dashed line, and the dotted line are respectively used as schematic diagrams of three different colors. Taking the solid line (blue light) as an example, the optical principle is described as follows:

[0145] Turn on the laser. The light passes through the neutral filter 7, and the light intensity is adjusted to the expected value.

[0146] The light passes through the first linear filter 12, and the first linear filter 12 allows light of blue wavelength to pass through.

[0147] The light reaches the first linear filter 12. The second linear filter 13 blocks the passage of blue-wavelength light and reflects it to the first plane mirror 14. At this time, only blue light, that is, the expected test light, exists in this optical path.

[0148] The first plane mirror 14 reflects the blue light to the first polarizer 15.

[0149] The blue light passes through the first polarizer 15 to form a phase difference of 45 degrees with the original light beam and reaches the third linear filter 16.

[0150] The linear filter allows blue light within the blue-wavelength bandwidth to pass through, and the light reaches the microfluidic chip 32.

[0151] The blue light passes through the microfluidic chip 32. Due to flow-induced birefringence, the phase of the blue light changes and reaches the linear filter 17.

[0152] The fourth linear filter 17 and the fifth linear filter 18 allow light within the blue-wavelength bandwidth to pass through. The blue light passes through 17 and 18 and reaches the polarizer 19.

[0153] The polarizer 19 (or analyzer) has a phase difference of 90 degrees with the original polarizer 15. The blue light passes through 19 and reaches the first photomultiplier tube 20.

[0154] The first photomultiplier tube 20 receives blue light with flow-induced phase change, obtains a current of corresponding intensity, and is connected to the oscilloscope 11 through a BNC cable.

[0155] By adjusting the oscilloscope 11, the current signal received and amplified by the photomultiplier tube is correctly displayed.

[0156] The oscilloscope 11 is connected to a computer to achieve data recording, storage, and post-processing.

[0157] Compared with the existing single-wavelength measurement method, the multi-color flow-induced birefringence stress measurement system of the present invention has significant advantages in terms of measurement accuracy and data acquisition efficiency.

[0158] 1. Main advantages and technical features

[0159] (1) Improvement in measurement accuracy: The traditional single-wavelength system is prone to phase ambiguity problems in high-stress regions, resulting in increased measurement uncertainty. The present invention uses a multi-color light source and performs joint calculation through the birefringence phase delay information of different wavelengths, increasing the measurement accuracy by more than 30% and effectively reducing the phase ambiguity error.

[0160] (2) Expansion of the measurement range and improvement of the dynamic response ability: The measurement range of the traditional system is limited by the phase delay change range of a single wavelength (generally 0 - 2π), while the present invention uses a multi-wavelength information fusion algorithm to expand the measurement range to 2 - 3 times the original, suitable for a wider range of flow field stress measurement environments, including high shear rates and complex flow conditions.

[0161] (3) Realization of multi-wavelength synchronous measurement and improvement of measurement efficiency: The traditional system relies on gradually switching the single-wavelength light source for measurement, with a large time delay and difficulty in adapting to high-speed flow systems. The present invention uses synchronous multi-wavelength measurement technology to obtain polarization information of multiple wavelengths in a single exposure, increasing the measurement speed by more than 3 times and being suitable for real-time measurement of transient flow fields and dynamic stress changes.

[0162] (4) Improvement of anti-interference ability and enhancement of measurement stability: Since the single-wavelength system is easily affected by ambient light fluctuations, polarization errors, and equipment drift, the measurement error is large. The present invention uses spectral analysis technology and polarization modulation optimization algorithms to improve the anti-interference ability of the system, increasing the signal-to-noise ratio by more than 50% and reducing the long-term measurement drift by about 40%, thus ensuring the stability and reliability of long-term measurement.

[0163] (5) Optimization of the optical design and reduction of the system adjustment difficulty: The traditional system requires precise adjustment of the angles of polarization optical devices and regular calibration to ensure measurement accuracy. The present invention uses a full-spectrum calibration method to automatically correct polarization errors at different wavelengths by computer, greatly reducing the need for manual adjustment and increasing the operation simplicity by more than 50%, suitable for industrial on-line detection and long-term experimental monitoring.

[0164] 2. The main performance indicators can be seen Figure 7

[0165] In summary, through the multi-wavelength flow-induced birefringence measurement method, the present invention breaks through the technical bottleneck of the traditional single-wavelength system, and has achieved significant improvements in accuracy, measurement range, stability, dynamic response, and application adaptability. It can be widely applied to polymer rheology, high-speed fluid mechanics research, and industrial on-line stress monitoring. Specific Embodiment XI:

[0167] To better illustrate the implementation method of the multi-color flow-induced birefringence stress measurement system of the present invention, several specific implementation schemes are provided below, covering optical system design, data processing methods, and replaceable structure schemes.

[0168] Laboratory fluid stress measurement system

[0169] 1. Equipment construction

[0170] This embodiment is applicable to the flow-induced birefringence experiment of polymer solutions in a laboratory environment and can be used to study the fluid stress distribution and rheological properties. The optical path schematic diagram is as Figure 3 shown.

[0171] Multi-color light source module: An argon ion laser light source (blue 488 nm, green 514.5 nm) is adopted. After the light beam passes through the lens and is coupled and synthesized into a coaxial light beam, it enters the polarization modulation module.

[0172] Polarization modulation module: It includes a neutral density filter, a plane mirror, a polarizer, and a linear filter, which are used to control the polarization state of light and perform fast polarization modulation during the measurement process.

[0173] Fluid test area: A transparent quartz flow channel (10 cm long, 2 cm wide, 1 cm thick) is used, which is filled with a high molecular polymer solution, and the fluid is driven to move at different flow rates by an injection pump.

[0174] Optical analysis module: It includes a plane mirror, a polarizer, and a linear filter assembly, which separates the transmitted light by wavelength and projects it onto the photoelectric detection module.

[0175] Photoelectric detection module: A high-sensitivity photomultiplier tube and an oscilloscope are adopted to collect the intensity information of light with different wavelengths.

[0176] Data processing module: The computer control system combines the multi-wavelength polarization analysis algorithm to calculate the stress distribution in the fluid and generate a real-time stress distribution map. The computer controls the piezoelectric platform to realize the scanning of the flow-induced birefringence stress field and form a cloud map.

[0177] 2. Measurement process

[0178] Select a polymer solution with a specific concentration (such as a 1000 ppm polyacrylamide solution) and inject it into the flow channel.

[0179] Control the flow rate within the range of 0.1 m / s to 1 m / s and gradually increase the shear rate.

[0180] Record the change in birefringence of the fluid and resolve the fluid stress field through multi-wavelength data.

[0181] The results show that the system can clearly resolve the stress distribution under a high-shear flow field, with an error lower than 3%, and the measurement range is extended to 2.5 times that of the traditional single-wavelength system.

[0182] 3. Experimental calibration

[0183] The calibration process of the experiment is crucial to ensure the accuracy and reliability of the measurement results. A quarter-wave plate, an optical element with known birefringence characteristics, is used for measurement calibration to verify the accuracy and stability of the experimental system. In the experiment, the quarter-wave plate is fixedly installed on a high-precision rotary table, and the angle adjustment accuracy of the rotary table can reach ±0.1°, enabling precise angle control. During the experiment, a measurement is taken every time the rotary table rotates 5° to record the corresponding change in light intensity.

[0184] During the measurement process, the measured intensity at a specific wavelength reaches a minimum value at a certain angle. At this time, the analysis instrument needs to rotate 90° to measure the maximum intensity value. By comparing the maximum and minimum light intensity data, the retardation characteristics of the quarter-wave plate and the orientation of its principal axis can be further calculated. The experimental data show that the measured retardation values in different directions are basically consistent with the theoretical calculation results. Among them, cross symbols are used to represent the experimental data in different measurement directions, while the theoretical curve is used to represent the retardation of the quarter-wave plate under ideal conditions. The results show that the average retardation error obtained through the birefringence device is only 2.2% of the expected value, and the standard deviation of the measurement is controlled within 1%.

[0185] In addition, for the measurement of the principal axis direction, the experimental results are in good agreement with the theoretical values. During the data processing, the maximum deviation between the actually measured angle and the theoretical value does not exceed 0.15°, indicating that the experimental system can measure the birefringence characteristics of the optical element more precisely. The above calibration results show that the measurement accuracy of the experimental device is relatively high and can be used for further birefringence measurement experiments.

[0186] 4. Post-processing method

[0187] In the birefringence measurement experiment, the post-processing of data is crucial for ensuring the accuracy of measurement results. Due to the close relationship between the delay characteristics of light and wavelength, in a birefringence measurement system, the measured value of light intensity needs to be related to the birefringence and angle information. For light of different wavelengths, the variation law of delay follows a certain mathematical relationship. Therefore, through the known light intensity ratio, the birefringence and its corresponding angle information can be solved.

[0188] During the data processing, due to the small wavelength difference, an accurate perturbation method can be used for calculation to improve the calculation accuracy. By introducing appropriate mathematical methods, a high-precision numerical solution can be obtained, making the final calculation error controlled within the experimental accuracy range. The experimental results show that the accuracy of this calculation method can reach 0.5%, which is much higher than the measurement accuracy required by the experiment, thus ensuring the reliability of experimental data.

[0189] Throughout the data analysis process, it is assumed that the birefringence does not change significantly within the used wavelength range. For most polymer solutions, since the selected light wavelength is far from the main absorption band and the wavelength difference is small, the birefringence dispersion effect can be ignored. However, to ensure the measurement accuracy, each experimental system still needs to be specifically verified to confirm that the dispersion effect can be ignored within the experimental wavelength range.

[0190] In the subsequent analysis, angle measurement is also an important part of the experiment. The angle information between the flow direction and the optical polarization vector needs to be measured by rotating the flow cell. First, with the experimental setup unchanged, rotate the flow cell in a certain direction and record a set of measurement data. Subsequently, under the same experimental conditions, rotate the flow cell in the opposite direction and obtain the second set of data. By comparing the angle data measured by clockwise and counterclockwise rotations, the angle information of the flow direction can be further calculated.

[0191] Experimental data show that the measurement system can stably obtain the light intensity change information under different rotation directions and accurately calculate the angle of the flow direction based on this. For a flow field at a specific speed, once the angle measurement is completed, the calculation of the extinction angle can be completed with only one experimental run. This measurement method improves the efficiency of the experiment, reduces experimental errors at the same time, and ensures the accuracy of data analysis. Overall, this post-processing method can meet the requirements of high-precision birefringence measurement and provides reliable technical support for further optical measurement research. Specific implementation method twelve:

[0193] High-pressure pipeline fluid monitoring system

[0194] 1. Equipment improvement points

[0195] This embodiment is applicable to industrial application scenarios, such as the flow stress monitoring of polymer flooding agents in oil pipelines. In a high-pressure pipeline environment, the flow-induced birefringence signal is weak. Therefore, the system has been optimized as follows:

[0196] Light source optimization: Use a high-power multi-wavelength laser (such as 473nm, 532nm, 808nm) to replace the LED to increase the light intensity to penetrate the high-concentration polymer solution.

[0197] Fluid test area: Adopt a high-pressure-resistant sapphire window (tolerating 10MPa), and add a temperature control system to the outer layer of the flow channel to adapt to different temperature environments (-10°C to 80°C).

[0198] Optical analysis module: Adopt a high-resolution spectrometer and combine it with polarization imaging technology to enhance the spatial resolution of the birefringence signal.

[0199] 2. Measurement process

[0200] Add polymer flooding agent to the high-pressure pipeline and control the flow rate from 0.5m / s to 3m / s.

[0201] Real-time monitor the fluid stress distribution in the pipeline through the multi-wavelength birefringence measurement system and analyze its rheological properties.

[0202] The results show that the system can still maintain a signal-to-noise ratio of more than 85dB in an extreme pressure environment, improving the measurement stability by 40% compared with traditional methods. Specific implementation method thirteen:

[0204] High-resolution microfluidic measurement system

[0205] 1. Equipment improvement points

[0206] This embodiment is applicable to the measurement of flow-induced birefringence stress in microfluidic devices and can be used for biological fluid or micro-scale flow research.

[0207] Light source optimization: Adopt a supercontinuum light source to achieve a wider wavelength coverage (450 - 800nm).

[0208] Fluid test area: The microchannel is made of PDMS material, and the channel size is 100μm × 50μm, which is suitable for micro-scale flow research.

[0209] Detection system: Adopt a high-speed polarization camera to improve the time resolution, which is suitable for transient flow research (the highest frame rate is 1000fps).

[0210] 2. Measurement process

[0211] Inject a low-concentration DNA solution through a microfluidic chip and observe the flow-induced birefringence phenomenon.

[0212] Record the transient flow field stress changes and analyze the molecular orientation of the fluid by combining polarization resolution techniques.

[0213] The results show that the system can detect stress fluctuations with nanosecond-level time resolution, providing a new method for biophysical rheology research.

[0214] Replaceable structural solutions

[0215] Some key components of the present invention can be replaced with different technical solutions to adapt to different application scenarios:

[0216] Light source selection

[0217] Solution 1: LED light source (low cost, suitable for laboratory research).

[0218] Solution 2: Laser light source (high power, suitable for industrial high-pressure pipelines).

[0219] Solution 3: Supercontinuum light source (broad spectrum, suitable for high-resolution microfluidic research).

[0220] Polarization modulation method

[0221] Solution 1: Liquid crystal modulator (low power consumption, suitable for laboratory environment).

[0222] Solution 2: Electro-optic modulator (high-speed modulation, suitable for industrial on-line detection).

[0223] Detection system

[0224] Solution 1: CMOS camera (high cost performance, suitable for general experiments).

[0225] Solution 2: Spectrometer + polarization detector (high resolution, suitable for precision measurement).

[0226] Solution 3: High-speed polarization camera (suitable for transient flow field research).

[0227] The above different embodiments demonstrate the applicability of the present invention in aspects such as laboratory basic research, industrial applications, and microscale flow measurement. The multi-color flow-induced birefringence measurement system of the present invention breaks through the limitations of traditional methods through core technologies such as multi-wavelength light sources, polarization modulation, and high-resolution detection, and has achieved significant improvements in measurement accuracy, dynamic range, measurement speed, etc., and can be widely applied in fields such as polymer rheology, microfluidics, and high-speed fluid mechanics.

[0228] In summary, by combining multi-color light sources with the flow-induced birefringence effect, the technology of the present invention not only improves the accuracy of fluid stress measurement but also breaks through the dependence of traditional measurement methods on high-speed cameras and frame rates. Its innovative real-time stress measurement ability demonstrates significant advantages in both static flows and complex turbulent flows. Compared with traditional technologies, the present invention has higher flexibility and applicability and can be widely applied to various types of fluid stress measurements, especially in high-dynamic and rapidly changing flow environments, where it can provide timely and accurate stress information.

[0229] The above description is only a preferred embodiment of a multi-color flow-induced birefringence stress real-time measurement system and method. The protection scope of a multi-color flow-induced birefringence stress real-time measurement system and method is not limited to the above embodiments. All technical solutions falling within this concept belong to the protection scope of the present invention. It should be noted that for those skilled in the art, several improvements and changes made without departing from the principle of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A multi-color flow-induced birefringence stress instant measurement system, characterized by: The system includes a multicolor light source module, a polarization modulation module, a fluid testing area, an optical analysis module, a photoelectric detection and digital display module, and a data processing and storage module; The multi-color light source module emits light beams of multiple wavelengths, and each light beam is combined through an optical fiber or an optical coupling device to form a stable polarized light illumination source; The polarization modulation module controls the polarization state of the incident light to achieve birefringence phase delay measurement; The fluid testing area is a transparent flow channel for containing the polymer solution to be tested. The fluid is controlled to enter the testing area through a pumping system and generates a flow-induced birefringence effect under shear, stretch or turbulence conditions. The optical analysis module is used to separate the transmitted light of different wavelengths and project them to the corresponding detection area; The photoelectric detection and data display module includes a first photomultiplier tube, a second photomultiplier tube, a third photomultiplier tube and an oscilloscope; the photoelectric detection and data display module is used to record the birefringence signal in real time and transmit the data to a computer for processing; The data processing and storage module solves the collected birefringence signals to obtain the fluid stress field distribution and displays the measurement results in real time on the interface.

2. The system according to claim 1, characterized in that: The polarization modulation module includes a neutral filter, a first linear filter, a second linear filter, a third linear filter, a first plane mirror, a second plane mirror, a third plane mirror, a fourth plane mirror, a first polarizer, a second polarizer and a third polarizer; After the light passes through the neutral filter, the light intensity is adjusted. The light passes through the first linear filter, which allows blue wavelength light to pass through. The second linear filter blocks the blue wavelength light from passing through and reflects it to the first plane mirror. At this time, there is only blue light in the optical path, that is, the expected test light. The first plane mirror reflects the blue light to the first polarizer. The blue light passes through the first polarizer to form a phase difference with the original light beam intensity and reaches the third linear filter. The green light passes through the second linear filter and reaches the second plane mirror. After being reflected twice by the second plane mirror and the third plane mirror, it reaches the third polarizer and passes through the third polarizer to reach the third linear filter. The light beam reflected by the third linear filter passes through the second polarizer, reaches the fourth plane mirror, and then passes through the fourth plane mirror to reach the first linear filter.

3. The system according to claim 2, characterized in that: The second linear filter adopts a narrow bandwidth linear filter, one side of which is coated with a strong reflective material, and acts as a beam splitter to reflect the blue laser and transmit the green laser.

4. The system according to claim 3, characterized in that: The first polarizer is a Glan-Thompson prism polarizer, and light passes through the first polarizer to reach the third linear filter that only allows blue wavelengths to pass through.

5. The system according to claim 4, characterized in that: The polarization modulation module separates the original three-color light emitted from the multi-color light source module into three colors of light with different polarization phases through three separate polarization light paths. After passing through the polarizer and phase modulator, the light beam enters the fluid test area in a specific polarization state and penetrates the flowing polymer solution.

6. The system according to claim 5, characterized in that: The fluid testing area includes a stage, a microfluidic chip, a piezoelectric position detector and a piezoelectric position controller; the stage is provided with a microfluidic chip and connected to the piezoelectric position detector, and the piezoelectric position detector is connected to the piezoelectric position controller; The third polarizer has a phase difference of 45 degrees with the first polarizer; The blue light and green light converge to reach the third linear filter, and then transmit through the microchannel fluid chip, and the light reaches the microfluidic chip; Under the action of fluid flow, the orientation of polymer chains in the solution changes, causing a birefringence effect, which causes light beams of different wavelengths to have different degrees of phase delay.

7. The system according to claim 6, characterized in that: The outgoing light passing through the fluid testing unit passes through the optical analysis module, which includes a fourth linear filter, a fifth linear filter, a sixth linear filter, a seventh linear filter, a fourth polarizer, a fifth polarizer, and a sixth polarizer; the blue light passes through the microfluidic chip, and due to the flow-induced birefringence, the blue light undergoes a phase change and reaches the linear filter; The fourth linear filter and the fifth linear filter allow the blue wavelength broadband light to pass through, and the blue light passes through the fourth linear filter and the fifth linear filter and reaches the fourth polarizer polarizer; The green light is reflected by the linear filter and reaches the sixth polarizer, and then passes through the seventh linear filter and the third photomultiplier tube. The signal line is connected and transmitted to the oscilloscope in real time. The fourth polarizer has a 90-degree phase difference with the first polarizer. The blue light passes through the fourth polarizer to reach the first photomultiplier tube. The first photomultiplier tube receives the blue light with flow-induced phase change, obtains a current of corresponding intensity, and is connected to an oscilloscope through a BNC line.

8. The system according to claim 7, characterized in that: The data processing and display module uses a computer, and the oscilloscope is connected to the computer to realize data recording, storage and post-processing. The computer calculates the multi-wavelength polarization information, solves the stress distribution of the fluid, and generates the corresponding stress field image.

9. A method for real-time measurement of multi-color flow-induced birefringence stress, the method being implemented based on the system of claim 1, characterized in that: The method comprises the following steps: Step 1: Select a polymer solution of a specific concentration, inject it into the flow channel, control the flow rate range between 0.1m / s and 1m / s, and gradually increase the shear rate; Step 2: Record the birefringence changes of the fluid and solve the fluid stress field through multi-wavelength data; Step 3: Conduct experimental calibration, using an optical element with known birefringence properties: a quarter-wave plate for measurement calibration to verify the accuracy and stability of the experimental system. The quarter-wave plate is fixedly mounted on a high-precision rotating stage with an angle adjustment accuracy of ±0.1°, which can achieve precise angle control. During the experiment, every time the rotating stage rotates 5°, a measurement is performed to record the corresponding light intensity change; During the measurement process, the measured intensity of a specific wavelength reaches a minimum at a certain angle, at which point the analyzer needs to be rotated 90° in order to measure the maximum intensity value. By comparing the maximum and minimum light intensity data, the delay characteristics of the quarter-wave plate and the orientation of its main axis are calculated. Step 4: Post-processing: In the birefringence measurement experiment, an accurate perturbation method is used to perform calculations to improve the calculation accuracy.

10. The method according to claim 9, characterized in that: In the subsequent analysis, the angle information between the flow direction and the optical polarization vector needs to be measured by rotating the flow cell. When the experimental setup remains unchanged, the flow cell is rotated in a certain direction and a set of measurement data is recorded. Subsequently, under the same experimental conditions, the flow cell was rotated in the opposite direction and a second set of data was obtained; by comparing the angle data measured by clockwise and counterclockwise rotations, the angle information of the flow direction was calculated.

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