Non-contact liquid concentration on-line fast measuring device based on michelson interference

Abstract

The present application belongs to the technical field of optical interference measurement, non-contact liquid concentration measurement and signal processing, and particularly relates to a non-contact liquid concentration online rapid measurement device based on Michelson interference, which comprises two parts of an optical module and a measurement module; the optical module mainly comprises a main laser, a beam expander, a beam splitter, a mirror, a sample to be measured, a rotating table, a reference laser, a position detector, a variable diaphragm and the like; and the measurement module comprises a photoelectric detector, a data acquisition module and an upper computer data processing module. The initial angle and position of the sample to be measured are fed back in real time to realize accurate calibration of the optical path difference, and then the rapid and accurate measurement of the liquid concentration of the sample to be measured is realized, the random error in the measurement process can be greatly inhibited, and the accuracy and repeatability of the measurement are improved. The present application effectively combines the advantages of light folding reflection, Michelson interference, feedback control, signal acquisition and processing and the like, and the whole device is simple, compact in structure and convenient to operate.

Description

Technical Field

[0001] This invention belongs to the field of optical interferometry and non-contact liquid concentration measurement and signal processing technology, specifically relating to a non-contact online rapid liquid concentration measurement device based on Michelson interferometry. Background Technology

[0002] Liquid concentration measurement has wide applications in scientific research and daily life, such as alcohol concentration, drug concentration, and juice concentration. For example, in the actual production process of a winery, it is necessary to detect the specific alcohol concentration of each bottle of wine produced in a timely manner without contacting the liquid product. This requires a non-contact alcohol concentration rapid measurement device.

[0003] First, non-contact measurement allows for measurement without touching the sample, avoiding the risks of sample contamination and cross-contamination. Second, it can quickly and accurately measure liquid concentration, eliminating the time required for sample reaction in traditional methods. Finally, it enables online measurement, allowing real-time monitoring of liquid concentration changes during production, thus enabling timely adjustments to the production process and ensuring product quality.

[0004] The Michelson interferometry is also an important part of university physics experimental teaching. When using the Michelson interferometry to measure liquid concentration, the need to frequently change different liquid containers for measurement results in variations in the position and angle of the liquid container each time, leading to significant deviations in the measured concentration. Summary of the Invention

[0005] To address the technical problem mentioned above, where frequent changes to different liquid containers for measurement result in variations in the position and angle of the liquid container each time, leading to significant deviations in measured concentration, this invention provides a non-contact online rapid liquid concentration measurement device based on Michelson interferometry. This device precisely positions the cuvette for the sample, reducing the accumulation of measurement errors. It provides non-contact rapid liquid concentration measurement with good repeatability, is simple, and has a compact structure, effectively combining the advantages of optical refraction and reflection, Michelson interferometry, and signal acquisition and processing technologies.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A non-contact online rapid liquid concentration measurement device based on Michelson interferometry includes a main laser, a beam expander, a beam splitter, a first reflecting mirror, a liquid to be measured, a first rotating stage, a second rotating stage, a second reflecting mirror, a reference laser, a position detector, a drive, a first rotating stage controller, a second rotating stage controller, a variable aperture, a photodetector, a data acquisition module, and a host computer data processing module. The light emitted from the main laser passes through the beam expander and is split into transmitted and reflected beams by the beam splitter. The transmitted light enters the liquid to be measured, returns via the second reflecting mirror, passes through the liquid a second time, is reflected by the beam splitter, and then passes through the variable aperture. The light emitted from the beam splitter is received by the photodetector after passing through the variable aperture. The light reflected by the beam splitter returns along its original path after being reflected by the first mirror, then passes through the beam splitter again and is received by the photodetector. The light emitted from the reference laser enters the position detector after passing through the surface of the liquid glass under test. The first rotary stage controller is connected to the first rotary stage via a serial port, and the second rotary stage controller is connected to the second rotary stage via a serial port. The output of the position detector is connected to the drive input of the first rotary stage. The output of the photodetector is connected to the input of the data acquisition module, and the output of the data acquisition module is connected to the host computer data processing module to process the acquired data.

[0008] The reference laser beam is at a 45-degree angle to the surface of the liquid container under test, and the position detector is at a 45-degree angle to the surface of the liquid container under test, while being perpendicular to the reference laser beam. The two surfaces of the liquid container under test have good light transmittance. The first rotating stage determines the initial position of the liquid under test. The second rotating stage changes the optical path difference of the beam passing through the liquid under test. The first rotating stage and the second rotating stage rotate relatively independently.

[0009] The variable aperture is a planar aperture with adjustable aperture, which is adjusted according to the width of the generated Michelson interference fringes.

[0010] The main laser is a semiconductor laser with a wavelength of 635nm, an output power of approximately 15mW, a power stability of 0.2%, and a divergence angle of <1.0mrad.

[0011] The reference laser is a helium-neon laser with a wavelength of 632.8 nm, an output power of 3 mW, strong power stability, and a divergence angle of 1.3 mrad.

[0012] The photodetector has a photosensitive area of ​​3.6×3.6mm, a response band of 320-1100mm, a power measurement range of 10~25mW, a bandwidth of <500KHz, and a maximum voltage of 10V.

[0013] The data acquisition module has a resolution of 12 bits, a sampling rate of 500 kSa / s, and 16 single-ended and 8 differential analog input channels.

[0014] The position detector has a photosensitive area of ​​9.0×9.0mm, a spectral response range of 320-1100nm, a sensitivity of 0.6A / W, a spot diameter of 0.2mm or more, and a detection accuracy of 1.5μm.

[0015] The second rotary table controller is set to a step size of 3° and automatically returns to the initial zero position after each experiment.

[0016] The measurement method based on the Michelson interferometer, a non-contact online rapid liquid concentration measurement device, includes the following steps:

[0017] S1. Turn on the main laser and adjust the initial orientation of the liquid to be tested so that the main laser beam can completely pass through the liquid to be tested device. The beams reflected by the beam splitter and transmitted beams coincide at the variable aperture.

[0018] S2. Turn on the reference laser, adjust the beam direction and fix the relative position so that it is incident on the light-transmitting surface of the liquid container under test at a 45-degree angle. The beam reflected by the surface of the liquid container under test is incident on the position detector at a 45-degree angle. The output signal of the position detector is used as the control feedback signal of the first rotary stage. The first rotary stage is adjusted and calibrated according to the coordinate deviation value output by the position detector, thereby realizing the precise adjustment of the position and angle of the liquid under test, ensuring the accuracy and consistency of the test data. Adjusting the reflector makes the interference fringes clearer and more stable.

[0019] S3. Control the second rotary stage controller to rotate the second rotary stage, causing the liquid to be tested to rotate, and the rotation angle is the same each time; the light emitted from the main laser is split into two beams, a transmitted beam and a reflected beam, after being reflected by the first and second reflecting mirrors, and then rejoined by the beam splitter to form a circular interference fringe on the surface of the variable aperture; the optical path difference between the two beams at the central bright fringe is:

[0020] δ=kλ

[0021] The optical path difference of the central dark fringe is:

[0022]

[0023] Where k represents the wave number and λ corresponds to the laser wavelength;

[0024] Differentiating the two equations above, we get dδ=λdk, which is the change in optical path difference. After rotating the second rotating stage and causing the liquid to be measured to rotate, the change in optical path difference caused by the change in distance ΔL between the liquid to be measured and the second reflecting mirror is 2nΔL, where n is the refractive index of the liquid; dk is the number of changes in the interference fringes, denoted by Δk. Therefore, we have 2nΔL=λΔk, that is, n=λΔk / (2ΔL).

[0025] S4. Adjust the variable aperture before the photodetector so that the photodetector receives the light intensity corresponding to a single stripe at a time, thereby detecting the number of stripe movements when the second rotating stage is rotated; connect the photodetector to the data acquisition module, send the acquired data to the host computer data processing module, draw a waveform and read out the stripe change, record the experimental data, and read out the number of peaks in the waveform from the waveform graph, which is the number of stripe changes Δk.

[0026] S5. Correlate the number of stripe changes produced by liquids of different concentrations with their concentrations, establish a functional relationship curve between liquid concentration and the number of stripes, and obtain the liquid concentration at the same time by linear fitting when the number of stripe changes of an unknown concentration of liquid is obtained.

[0027] Compared with the prior art, the beneficial effects of this invention are:

[0028] 1. This invention employs a non-contact online rapid liquid concentration measurement device based on Michelson interferometry, which provides both non-contact rapid detection of liquid concentration and ensures the repeatability of each measurement. This invention utilizes purely optical components, resulting in a compact optical path.

[0029] 2. This invention introduces a reference optical path, and uses a high-precision position detector to provide online feedback and calibrate the turntable position, thereby achieving accurate positioning of the initial position of the sample under test, determining the accuracy and repeatability of the optical path difference, and realizing accurate measurement of interference fringes.

[0030] 3. In this invention, the main laser and the reference laser do not interfere with each other. One beam forms changes in the Michelson interference fringes, and the concentration of the liquid can be accurately and quickly obtained based on the changes in the number of interference fringes. The other beam ensures that the cuvette is placed at the same position and angle each time, thereby ensuring the repeatability of each Michelson interference experiment, eliminating external interference, and making the operation convenient. Attached Figure Description

[0031] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0032] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0033] Figure 1 Schematic block diagram of the present invention;

[0034] Figure 2 This is a flowchart of the method steps of the present invention.

[0035] Wherein: 1 is the main laser, 2 is the beam expander, 3 is the beam splitter, 4 is the first reflector, 5 is the liquid to be tested, 6 is the first rotating stage, 7 is the second rotating stage, 8 is the second reflector, 9 is the reference laser, 10 is the position detector, 11 is the driver, 12 is the first rotating stage controller, 13 is the second rotating stage controller, 14 is the variable aperture, 15 is the photodetector, 16 is the data acquisition module, and 17 is the host computer data processing module. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. These descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the claims of the present invention. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0038] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0039] In this embodiment, as Figure 1As shown, the device for high repeatability and rapid measurement of liquid concentration consists of a main laser 1, a beam expander 2, a beam splitter 3, a first reflector 4, the liquid to be measured 5, a first rotating stage 6, a second rotating stage 7, a second reflector 8, a reference laser 9, a position detector 10, a drive 11, a first rotating stage controller 12, a second rotating stage controller 13, a variable aperture 14, a photodetector 15, a data acquisition module 16, and a host computer data processing module 17; wherein, the beam emitted from the main laser 1 travels in the direction of the beam expander 2, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 10, 19 ... A beam splitter 3 splits the light beam into two paths. One path passes sequentially through the liquid under test 5, the second reflector 8, the beam splitter 3, the variable aperture 14, and the photodetector 15. The other path passes sequentially through the first reflector 4, the beam splitter 3, the variable aperture 14, and the photodetector 15. The laser emitted from the reference laser 9 passes sequentially through the liquid under test 5 and the position detector 10. The optical signal received by the photodetector 15 is converted into an electrical signal and transmitted to the data acquisition module 16, and then to the host computer data processing module 17.

[0040] The preferred embodiment of the present invention is shown in the diagram below. Figure 1 As shown, its specific structure is as follows: The main laser 1 is a semiconductor laser with a wavelength of 635nm, an output power of approximately 15mW, a power stability of 0.2%, and a divergence angle <1.0mrad; the reference laser 9 is a helium-neon laser with a wavelength of 632.8nm, an output power of 3mW, strong power stability, and a divergence angle of 1.3mrad; the photodetector 15 has a photosensitive area of ​​3.6×3.6mm, a response band of 320-1100mm, a power measurement range of 10~25mW, and a bandwidth of [missing information]. <500KHz, maximum voltage is 10V; data acquisition module 16 has a resolution of 12bit, a sampling rate of 500kSa / s, 16 single-ended analog input channels, and 8 differential input channels; position detector 10 has a photosensitive area of ​​9.0×9.0mm, a spectral response range of 320-1100nm, a sensitivity of 0.6A / W, a spot diameter of 0.2mm or more, and a detection accuracy of 1.5μm; the second rotary stage controller 13 is set with a step size of 3° and automatically returns to the initial zero position after each experiment.

[0041] The method for measuring liquid concentration using the aforementioned non-contact, highly repeatable, and rapid liquid concentration measurement device based on the Michelson interferometry principle includes the following steps:

[0042] Step 1: After building the interference device according to the Michelson interference principle, turn on the main laser 1 and adjust the initial orientation of the liquid to be tested 5 so that the main laser beam can completely pass through the liquid to be tested device. The beams reflected by the beam splitter 3 and transmitted beams coincide at the variable aperture.

[0043] Step 2: Turn on the reference laser 9, adjust the beam direction and fix its relative position so that it is incident on the light-transmitting surface of the container of the liquid to be tested 5 at a 45-degree angle. The beam reflected by the surface of the container of the liquid to be tested 5 is incident on the position detector 10 at a 45-degree angle. The output signal of the position detector 10 serves as the control feedback signal of the first rotating stage 6. The first rotating stage 6 is adjusted and calibrated according to the coordinate deviation value output by the position detector 10, thereby achieving precise adjustment of the position and angle of the liquid to be tested 5, ensuring the accuracy and consistency of the test data. Adjusting the reflector makes the interference fringes clearer and more stable.

[0044] Step 3: Control the second rotary stage controller 13 to rotate the second rotary stage 7, causing the liquid to be tested 5 to rotate, thereby changing the optical path difference transmitted through the liquid. Each time the second rotary stage 7 rotates by the same angle, the light emitted from the main laser 1 is split into two beams, a transmitted beam and a reflected beam, after passing through the beam splitter 3. The transmitted beam passes through the liquid to be tested 5 and then enters the second reflecting mirror 8, while the reflected beam is reflected by the beam splitter 3 and then enters the first reflecting mirror 4. The two beams, after being reflected by the first reflecting mirror 4 and the second reflecting mirror 8, rejoin after passing through the beam splitter 3 to form a circular interference fringe. The optical path difference between these two beams at the central bright fringe is:

[0045] δ=kλ (1)

[0047] The optical path difference of the central dark fringe is:

[0048]

[0049] Where k represents the wave number and λ corresponds to the laser wavelength;

[0050] Differentiating the two equations above, we get dδ=λdk, which is the change in optical path difference. After rotating the second rotating stage 7 to rotate the liquid 5 to be tested, the change in optical path difference caused by the change in distance ΔL between the liquid 5 to be tested and the second reflecting mirror 8 is 2nΔL, where n is the refractive index of the liquid; dk is the number of changes in the interference fringes, denoted by Δk. Therefore, we have 2nΔL=λΔk, that is, n=λΔk / (2ΔL).

[0051] Step 4: Adjust the aperture of the variable aperture 14 before the photodetector 15 so that the photodetector 15 receives the light intensity corresponding to only a single fringe at a time, thereby detecting the number of fringe movements when the second rotary table 7 is rotated. The photodetector 15 is connected to the data acquisition module 14, which sends the acquired data to the host computer data processing module 17 to plot a waveform and read the fringe change. The experimental data is recorded, and the number of waveform peaks read from the waveform is the number of fringe changes, Δk.

[0052] Step 5: Correlate the number of stripe changes produced by liquids of different concentrations with their concentrations, establish a functional relationship curve between liquid concentration and the number of stripes, and obtain the liquid concentration at the same time by linear fitting when the number of stripe changes of an unknown concentration of liquid is obtained.

[0053] The working principle of this invention is as follows:

[0054] If the number of interference fringes changing between the container holding the liquid to be tested 5 and the empty container when rotated by the same angle is N1 and N2, then ΔN = N1 - N2 represents the optical path difference caused by the liquid in the container at a certain angle. The refractive index of the liquid can be calculated through ΔN.

[0055] The formula for calculating the refractive index n of a transparent solution is:

[0056]

[0057] In the formula, λ0 is the laser wavelength; t is the length from the inner surface of the front wall to the inner surface of the rear wall of the cuvette, i.e., the inner diameter of the cuvette, t = 10 mm; θ is the incident angle of the light, i.e., the rotation angle of the cuvette.

[0058] According to the optical path calculation formula δ=nd0 (d0 is the path length of the light beam), when the path length d0 of the light beam changes after the liquid 5 under test rotates by a certain angle, the corresponding optical path will change. To accurately calculate the effect of the liquid under test on the optical path difference, the optical path difference caused by the air during the rotation of the container under no-load conditions needs to be eliminated. Treating the air in the container as a glass with a relative refractive index n=1, and substituting it into formula (1), we obtain the number of fringe shifts caused by the change in optical path after the rotation angle θ as N′. Adding this as a correction quantity to ΔN, we get ΔN′=ΔN+N′.

[0059]

[0060] The corrected formula for calculating the refractive index n of a liquid is as follows:

[0061]

[0062] At a certain temperature, changing the concentration of the solution in a container will change the refractive index, causing the concentric ring fringes of the Michelson interferometer to shift. When the refractive index increases, the optical path length increases, and the interference fringes emerge one by one from the center outwards; when the refractive index decreases, the optical path length decreases, the fringes indent, and they disappear one by one from the center. Therefore, by measuring the change in the fringes and determining its direction of movement, the changes in parameters such as solution concentration and refractive index can be obtained. The thickness of the container containing the liquid 5 is d, and the internal optical path length is d. Changing the concentration of the liquid changes the refractive index, which will change the optical path length, thus allowing the observation of the corresponding change in the interference fringes. According to the interference condition of the Michelson interferometer, 2nd = kλ, when the concentration of the liquid 5 in the container changes, its refractive index also changes, causing a change in the interferometer fringes. According to the interference condition, the relationship is 2Δnd = Δkλ, that is...

[0063]

[0064] When the refractive index of the liquid in the container changes by Δn, the number of interference fringes changes by Δk accordingly. By counting Δk and the number of droplets Δv, the functional relationship between the change in the liquid's refractive index Δn and the change in solution concentration c Δc can be determined. Integrating this functional relationship yields the relationship between the refractive index n and the concentration c.

[0065] Based on the Michelson interference principle, a liquid to be tested 5 and a second rotating stage 7 are added to the main optical path of the device. The light beam, after passing through a beam expander 2 and a beam splitter 3 (50% transmittance), is split into two beams: a reflected beam and a transmitted beam. The transmitted beam passes through the liquid to be tested 5 and then enters the second reflecting mirror 8; the reflected beam is reflected by the beam splitter 3 (50% transmittance) to the first reflecting mirror 4. The two beams converge after reflection by the first reflecting mirror 4 and the second reflecting mirror 8, forming a circular interference fringe at the variable aperture 14. The optical path difference between the two beams at the central bright fringe is:

[0066] δ=kλ (1)

[0068] The optical path difference of the central dark fringe is:

[0069]

[0070] Differentiating the two equations respectively, we get dδ = λdk. The change in optical path difference dδ is the change in distance ΔL between the liquid 5 and the mirror 2 caused by rotating the first rotating stage 6, which rotates the liquid 5 under test. The resulting change in optical path difference is 2nΔL. Here, n is the refractive index of the liquid; dk is the number of changes in the interference fringes, denoted by Δk. Therefore, 2nΔL = λΔk, i.e., n = λΔk / (2ΔL).

[0071] Before measurement, pre-adjustment is performed. After adjusting the interference fringes, measurements are taken for solutions with different concentration gradients. After data acquisition, the data is processed by a host computer, and the corresponding fringe change number Δk is read in MATLAB software. A correlation table between the fringe change number and the solution concentration is established and fitted into a curve. Then, the same measurement operation as the pre-experiment is performed on the unknown solution to obtain the number of interference fringes of the unknown solution. By comparing this value with the curve fitted from the pre-experiment data, the measured value of the refractive index n of the liquid under test can be obtained.

[0072] The above description only illustrates the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention, and all such changes should be included within the protection scope of the present invention.

Claims

1. A non-contact online rapid liquid concentration measurement device based on Michelson interferometry, characterized in that: The system includes a main laser (1), a beam expander (2), a beam splitter (3), a first reflector (4), a liquid to be tested (5), a first rotating stage (6), a second rotating stage (7), a second reflector (8), a reference laser (9), a position detector (10), a driver (11), a first rotating stage controller (12), a second rotating stage controller (13), a variable aperture (14), a photodetector (15), a data acquisition module (16), and a host computer data processing module (17). The light emitted from the main laser (1) passes through the beam expander (2) and enters the beam splitter (3), where it is split into two beams: a transmitted beam and a reflected beam. The transmitted beam enters the liquid to be tested (5), returns via the second reflector (8), passes through the liquid to be tested a second time, is reflected by the beam splitter (3), and then passes through the variable aperture (14) before being detected by the photodetector. The beam splitter (15) receives the light; the light reflected by the beam splitter is reflected by the first reflector (4) and returns along the original optical path, then passes through the beam splitter (3) and the variable aperture (14) before being received by the photodetector (15); the light emitted from the reference laser (9) passes through the glass surface of the liquid to be tested (5) and enters the position detector (10); the first rotary stage controller (12) is connected to the first rotary stage (6) via a serial port, the second rotary stage controller (13) is connected to the second rotary stage (7) via a serial port, the output of the position detector (10) is connected to the input of the drive (11) of the first rotary stage (6); the output of the photodetector (15) is connected to the input of the data acquisition module (16), and the output of the data acquisition module (16) is connected to the host computer data processing module (17) to perform calculation and processing on the acquired data.

2. The non-contact online rapid liquid concentration measurement device based on Michelson interferometry according to claim 1, characterized in that: The reference laser (9) emits a beam at a 45-degree angle to the surface of the liquid (5) container, and the position detector (10) also forms a 45-degree angle with the surface of the liquid (5) container and is perpendicular to the beam emitted by the reference laser (9). The two surfaces of the liquid (5) container have good light transmittance. The first rotating stage (6) determines the initial position of the liquid (5). The second rotating stage (7) changes the optical path difference of the beam passing through the liquid (5). The first rotating stage (6) and the second rotating stage (7) rotate relatively independently.

3. The non-contact online rapid liquid concentration measurement device based on Michelson interferometry according to claim 1, characterized in that: The variable aperture (14) is a planar aperture with adjustable aperture, which is adjusted according to the width of the generated Michelson interference fringes.

4. The non-contact online rapid liquid concentration measurement device based on Michelson interferometry according to claim 1, characterized in that: The main laser (1) is a semiconductor laser with a wavelength of 635nm, an output power of about 15mW, a power stability of 0.2%, and a divergence angle of <1.0mrad.

5. The non-contact online rapid liquid concentration measurement device based on Michelson interferometry according to claim 1, characterized in that: The reference laser (9) is a helium-neon laser with a wavelength of 632.8 nm, an output power of 3 mW, strong power stability, and a divergence angle of 1.3 mrad.

6. The non-contact online rapid liquid concentration measurement device based on Michelson interferometry according to claim 1, characterized in that: The photodetector (15) has a photosensitive area of ​​3.6×3.6mm, a response band of 320-1100mm, a power measurement range of 10~25mW, a bandwidth of <500KHz, and a maximum voltage of 10V.

7. The non-contact online rapid liquid concentration measurement device based on Michelson interferometry according to claim 1, characterized in that: The data acquisition module (16) has a resolution of 12 bits, a sampling rate of 500 kSa / s, and 16 single-ended and 8 differential analog input channels.

8. The non-contact online rapid liquid concentration measurement device based on Michelson interferometry according to claim 1, characterized in that: The position detector (10) has a photosensitive area of ​​9.0×9.0mm, a spectral response range of 320-1100nm, a sensitivity of 0.6A / W, a spot diameter of 0.2mm or more, and a detection accuracy of 1.5μm.

9. The non-contact online rapid liquid concentration measurement device based on Michelson interferometry according to claim 1, characterized in that: The second rotary table controller (13) is set to a step size of 3° and automatically returns to the initial zero position after each experiment.

10. The measurement method of the non-contact online rapid liquid concentration measurement device based on Michelson interferometry according to any one of claims 1-9, characterized in that: Includes the following steps: S1. Turn on the main laser (1) and adjust the initial orientation of the liquid to be tested (5) so that the main laser can completely pass through the liquid to be tested (5) device. The beams reflected and transmitted by the beam splitter (3) coincide at the variable aperture (14). S2. Turn on the reference laser (9), adjust the output direction and fix the relative position so that it is incident on the light-transmitting surface of the container of the liquid to be tested (5) at a 45-degree angle. The beam reflected by the surface of the container of the liquid to be tested (5) is incident on the position detector (10) at a 45-degree angle. The output signal of the position detector (10) is used as the control feedback signal of the first rotating stage (6). The first rotating stage is adjusted and calibrated according to the coordinate deviation value output by the position detector (10), thereby realizing the precise adjustment of the position and angle of the liquid to be tested (5), ensuring the accuracy and consistency of the test data. Adjusting the reflector makes the interference fringes clearer and more stable. S3. Control the second rotary stage controller (13) to rotate the second rotary stage (7), causing the liquid to be tested (5) to rotate, and the rotation angle is the same each time; the light emitted from the main laser (1) is split into two beams, one transmitted and one reflected, after passing through the beam splitter (3). The two beams are reflected by the first mirror (4) and the second mirror (8), and then rejoined on the surface of the variable aperture (14) after passing through the beam splitter (3) to form a ring-shaped interference fringe; the optical path difference between the two beams in the central bright fringe is: δ=kλ The optical path difference of the central dark fringe is: Where k represents the wave number and λ corresponds to the laser wavelength; Differentiating the two equations above, we get dδ=λdk, which is the change in optical path difference. After rotating the second rotating stage (7) to rotate the liquid to be tested (5), the change in optical path difference caused by the change in distance ΔL between the liquid to be tested (5) and the second reflecting mirror (8) is 2nΔL, where n is the refractive index of the liquid; dk is the number of changes in the interference fringes, denoted by Δk. Therefore, we have 2nΔL=λΔk, i.e., n=λΔk / (2ΔL). S4. Adjust the aperture of the variable aperture (14) before the photodetector (15) so that the photodetector (15) receives the light intensity corresponding to a single stripe at a time, thereby detecting the number of stripe movements when rotating the second rotary table (7); the photodetector (15) is connected to the data acquisition module (16), which sends the acquired data to the host computer data processing module (17), plots the waveform and reads out the amount of stripe change, records the experimental data, and reads out the number of peaks in the waveform from the waveform, which is the number of stripe changes Δk; S5. Correlate the number of stripe changes produced by liquids of different concentrations with their concentrations, establish a functional relationship curve between liquid concentration and the number of stripes, and obtain the liquid concentration at the same time by linear fitting when the number of stripe changes of an unknown concentration of liquid is obtained.

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