System and method for measuring concentration of solution based on refractive index

Abstract

The invention discloses a system and a method for measuring solution concentration based on refractive index, relates to the technical field of solution concentration measurement, and aims to solve the problems that test errors are easily generated due to non-uniform distribution of solute concentration in a solution due to lack of a control test in direct measurement in the existing measurement mode; the device comprises a light emitting module, the light emitting module is connected with a liquid storage system and is used for emitting light to the liquid storage system, the liquid storage system is used for carrying out storage test on a solution, and the liquid storage system is connected with a light spot display module which is used for displaying light spots after the light passes through the liquid storage system. The light spot display module is connected with an image acquisition module used for acquiring light spot images, and the image acquisition module is connected with an image processing module used for processing the acquired light spot images. The method has the advantage of comparing and verifying the accuracy of concentration measurement of the to-be-measured solution.

Description

Technical Field

[0001] The present invention relates to the technical field of solution concentration measurement, and more particularly to a system and method for measuring solution concentration based on refractive index. Background Art

[0002] The concentration of a solution is an important parameter commonly used in the fields of chemistry, biology, and pharmaceuticals. Traditional methods for measuring solution concentration include gravimetric method, titration method, conductivity method, etc. Although these methods are accurate, they are complex to operate, time-consuming, and may be affected by many factors. In recent years, with the development of optical technology, the refractive index measurement method has gradually become one of the important means of measuring solution concentration due to its advantages such as fast, accurate, and non-contact.

[0003] At present, when configuring a solution, the refractive index measurement method is generally used to measure the concentration of the solution. The light is directly passed through the container containing the liquid to be tested, and a light spot is formed on the back display backboard after being refracted by the liquid to be tested. At the same time, the light is passed through an empty container to form a second light spot on the display backboard. Then, the concentration of the liquid to be tested is obtained by measuring the emission distance of the light and the distance between the two light spots, and calculating the concentration through a function. However, due to the lack of a control experiment in direct measurement, experimental errors are easily generated due to the uneven distribution of the solute concentration in the solution, resulting in inaccurate measurement of the solution concentration. In view of this, we propose a system and method for measuring the concentration of a solution based on the refractive index. Summary of the invention

[0004] The purpose of the present invention is to provide a system and method for measuring solution concentration based on refractive index, so as to solve the technical problem that the current existing measurement method is prone to experimental errors due to the lack of control experiments in direct measurement and the uneven distribution of solute concentration in the solution, resulting in inaccurate measurement of solution concentration.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a system for measuring solution concentration based on refractive index, comprising a light emitting module:

[0006] The light emitting module is connected to a liquid storage system and is used to emit light to the liquid storage system. The liquid storage system is used to perform storage tests on solutions, and the liquid storage system is connected to a light spot display module for displaying light spots after the light passes through the liquid storage system. The light spot display module is connected to an image acquisition module for acquiring light spot images. The image acquisition module is connected to an image processing module for processing the acquired light spot images. The image processing module is connected to an image analysis module for analyzing the processed light spot images. The image analysis module is connected to a data processing module for combing and calculating data. The data processing module is connected to a data output module for outputting data results. The data output module is connected to a result display module for displaying data results.

[0007] Preferably, the light emitting module is used to generate light of a specific wavelength, stability and adjustable intensity, the liquid storage system includes a right-angled triangle container, and the light spot display module includes a scale plate for reading the light spot coordinates.

[0008] Preferably, the image acquisition module includes an autofocus module and an exposure adjustment module for performing autofocus and exposure adjustment during the spot image acquisition process; the image processing module includes a denoising module for denoising the acquired spot image, a contrast enhancement module for enhancing the image contrast, and an edge detection module for detecting the edge of the spot image; the image analysis module includes a spot positioning module for positioning the spot in the spot image processed in the image processing module, a brightness analysis module for analyzing the brightness of pixels in the spot, and an interference removal module for removing interfering pixels in the spot.

[0009] Preferably, the data processing module is used to calculate the solution concentration based on the spot coordinates, spacing and light emission length parameters, and the data processing module includes a digitization module for digitizing the calculation results, a filtering module for filtering the data, an amplification module for amplifying the data and a data storage module for storing the data.

[0010] Preferably, the result display module includes a display form module for displaying the data processed by the data processing module in tables and charts, a history record module for recording the data, a statistical analysis module for performing statistical analysis on the data, and a user interface module for user operations.

[0011] A method for measuring solution concentration based on refractive index, comprising a system for measuring solution concentration based on refractive index as claimed in any one of claims 1 to 5, comprising the following steps:

[0012] S1. Material preparation;

[0013] Prepare a right-angled triangle container made of a specific transparent material. The refractive index of the material of the container to light is recorded as n. c , set to 1.5, the lengths of the right-angle sides of the container are respectively recorded as l A and l B , the length of the hypotenuse is l C , the right angle is 90°, and the other two angles are ∠α and ∠β respectively.

[0014] Prepare a high-precision scale plate with a minimum scale of 0.1 mm. The material of the scale plate will not interfere with the light, and the surface flatness should be within 0.05 mm to ensure the accuracy of the spot position measurement.

[0015] Prepare a high-resolution image acquisition device that has sufficient pixels and dynamic range to clearly capture the image of the light spot on the scale plate and can be connected to a computer for image analysis and processing;

[0016] Prepare a stable light source, which can emit light in a specific wavelength range of 400nm-700nm, with a power stability within 1%, and the light emitted by the light source is incident at an angle perpendicular to the right angle side of the right triangle container;

[0017] S2, empty container light test;

[0018] Let the perpendicular to the right angle side l A After being refracted and reflected in the container, the incident light passes through the container and forms a light spot on the scale plate;

[0019] The image acquisition device is used to collect the spot image on the scale plate in the no-load state and transmit it to the computer;

[0020] By setting up the image analysis module, the brightness distribution of the light spot pixels is analyzed. Assume that the coordinates of the pixels in the light spot image are (x, y), and the brightness value of the pixels is I(x, y). First, the approximate area of ​​the light spot is determined. By setting the brightness threshold T, the pixels with brightness values ​​greater than T form the candidate area of ​​the light spot. Then, the center point of the light spot is determined using the following algorithm:

[0021] Calculate the center coordinates (x c ,y c ), the formula is:

[0022]

[0023] Taking the centroid coordinates as the center, select the pixels within a certain radius for quadratic fitting, using a two-dimensional Gaussian function Fitting is performed, where A is the amplitude, (x0, y0) is the coordinate of the center of the spot, σ x and σ y are the standard deviations in the x and y directions respectively. The fitting parameters are solved by the least square method to obtain the coordinates of the center point of the light spot (x0, y0);

[0024] Use a high-precision measuring tool to measure the distance between the point where the light exits the container and the center of the empty light spot, recorded as L 1空 , L 1空 is the no-load distance;

[0025] S3, deionized water light test;

[0026] Slowly pour deionized water into the right triangle container, making sure there are no bubbles in the water and the liquid surface is flat;

[0027] Repeat the steps of light incident, image acquisition and light spot center point determination in the empty container light test;

[0028] Measure the distance between the point where the light exits the container and the center of the light spot filled with deionized water, recorded as L 1水 ;

[0029] According to Snell's law, the refractive index of light in air is n0 = 1, and the refractive index in deionized water is n w , we have n0 sinθ0=n w sinθ w , where θ0 is the angle at which the light is incident on the container wall in air, which is known to be 90°. By measuring the incident angle θ w , combined with the known n0, calculate n w ;

[0030] S4, injection of test solution and light testing;

[0031] Slowly inject the solution to be tested into the right triangle container, making sure there are no bubbles in the solution and the liquid surface is flat;

[0032] Repeat the steps of light incident, image acquisition and light spot center point determination in the empty container light test;

[0033] Calculate the distance between the light spot in the empty state and the light spot in the solution state, recorded as L2;

[0034] S5, mixed solution light test;

[0035] A certain amount of the test solution is injected into a right triangle container filled with deionized water to form a mixed solution. Let the volume of the injected test solution be V. t , the volume of deionized water is V w The total volume of the mixed solution is V m=V t +V w ;

[0036] Repeat the steps of light incident, image acquisition and light spot center point determination in the empty container light test;

[0037] Measure the distance between the point where the light exits the container and the center of the spot filled with the mixed solution, recorded as L3. At the same time, calculate the position change between the spot filled with the mixed solution and the spot filled with deionized water, recorded as ΔL 混水 =L3-L 1水 ;

[0038] Calculate the concentration of the test solution in the mixed solution. Assume that the concentration of the test solution in the mixed solution is C 混 , calculated according to the following formula:

[0039] First, according to the relationship between the refractive index of the mixed solution and its components, the refractive index of the mixed solution n m It can be expressed as n m =C 混 ·n s +(1-C 混 )·n w , where n s is the refractive index of the solution to be tested, n w is the refractive index of deionized water;

[0040] Combining the refraction angle change and the distance relationship, construct the equation group:

[0041]

[0042] where θ s is the incident angle of the light in the solution to be tested, θ m is the incident angle of the light in the mixed solution,

[0043] f2(n s , n m ,θ s ,θ m )=n m -C 混 ·n s -(1-C 混 )·n w =0;

[0044] The equations are solved simultaneously by numerical solution method to obtain the concentration C of the test solution in the mixed solution. 混 ;

[0045] S6, correction and concentration calculation;

[0046] Use L 1水 For L 1空Correction is made, and the correction formula is L 1修正 =L 1空 +k×(L 1水 -L 1空 ), where the correction coefficient k is determined by taking the average value of multiple experiments and is set to 0.8;

[0047] According to the corrected distance L 1修正 , spacing L2 and position change ΔL 混水 , and the known angles ∠α and ∠β of the right triangle container, the concentration C of the solution to be tested can be calculated using the following formula:

[0048] First, according to the law of refraction of light, combined with the above measurement data, the change in the refraction angle of the light in the empty container, the container filled with deionized water, the container filled with the solution to be tested, and the container filled with the mixed solution is calculated. Assume that the refractive index of the light in the solution to be tested is n s , the refractive index in the mixed solution is n m , we have n0 sinθ0=n s sinθ s and n0 sinθ0 = n m sinθ m , where θ s and θ m are the angles of incidence of the light in the solution to be tested and the mixed solution respectively. n is calculated by measuring the angle of incidence and combining it with the known n0. s and n m , the refraction angle changes are Δθ s =θ s -θ0, Δθ m =θ m -θ0;

[0049] Then, perform complex formula integration and derivation:

[0050] According to the volume ratio and concentration relationship of the mixed solution,

[0051] Combining the refraction angle change and the distance relationship, the following complex equations are constructed:

[0052]

[0053] f2(n s , n m ,θ s ,θ m )=n m -C 混 ·n s -(1-C 混 )·n w =0;

[0054] By numerically solving the equations simultaneously, we can obtain n s Relationship with C, assuming that the refractive index n of the solution is known s There is a specific functional relationship between g(n s )=C, and the concentration C of the solution to be tested is calculated through this functional relationship;

[0055] By comparing C 混 By comparing it with C and calculating the average value, the density of the solution can be obtained.

[0056] The present invention forms a mixed solution by injecting a certain amount of the solution to be tested into a right-angled triangle container filled with deionized water, and comprehensively calculates the concentration of the solution to be tested in the mixed solution through the volume change of the solutions after mixing and the change of the refraction position of the light spot, thereby forming a control group with the direct measurement of the concentration of the solution to be tested, which is beneficial to comparing and verifying the accuracy of the concentration measurement of the solution to be tested.

[0057] Preferably, during the measurement, the ambient temperature is maintained between 20° C. and 25° C. to reduce the effect of temperature on the refractive index of the solution and the size of the container.

[0058] Preferably, in order to improve the accuracy and reliability of the measurement, multiple measurements can be performed and the average value can be taken. For the empty container, the container filled with deionized water, the container filled with the solution and the container filled with the mixed solution, at least 5 steps of light testing, image acquisition and spot center point determination are performed respectively, and then the average empty distance L is calculated. 1ɑvg Empty and filled with deionized water distance L 1ɑvg水 , Spacing L 2ɑvg And the position change ΔL ɑvg混水 , and then make corrections and concentration calculations.

[0059] Preferably, in order to verify the accuracy of the measurement method, a standard solution of known concentration can be used for a comparative test. The standard solution of known concentration is injected into a right triangle container, and the test is performed according to the above measurement steps. The calculated concentration is compared with the known concentration of the standard solution. The measurement method is considered accurate if the error is within 5%.

[0060] Preferably, the method can be applied to different types of solutions, including but not limited to transparent solutions, colored solutions and turbid solutions, but for turbid solutions, the image analysis algorithm needs to be properly adjusted to accurately determine the center point of the light spot.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] 1. The present invention injects a certain amount of the solution to be tested into a right-angled triangle container filled with deionized water to form a mixed solution, and comprehensively calculates the concentration of the solution to be tested in the mixed solution by the volume change of the solution after mixing and the change of the refraction position of the light spot, thereby forming a control group with the direct measurement of the concentration of the solution to be tested, which is conducive to comparing and verifying the accuracy of the measurement of the concentration of the solution to be tested, and solves the problem that the existing measurement method lacks a control test in direct measurement, is prone to experimental errors due to the uneven distribution of the solute concentration in the solution, resulting in inaccurate measurement of the solution concentration.

[0063] 2. The present invention also analyzes the brightness distribution of the light spot pixels by setting an image analysis module, and by setting a brightness threshold T, the pixels with brightness values ​​greater than T form a candidate area of ​​the light spot, and then calculates the center coordinates of the candidate area of ​​the light spot, thereby improving the accuracy of the reading of the light spot on the scale plate, which is beneficial to reduce the problem of blurred light spot readings due to heat dissipation after the light passes through the solution, affecting the accuracy of solution concentration calculation.

[0064] 3. The present invention also injects deionized water into the container and corrects the distance of the container in an unloaded state by the distance after the light passes through the deionized water, thereby improving the accuracy of the length between the light exiting point in the container and the light spot on the scale plate in the unloaded state, thereby overcoming the measurement error and further improving the accuracy of the solution concentration calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a schematic diagram of the system framework of the present invention;

[0066] Figure 2 A schematic diagram of the system framework of the image processing module of the present invention;

[0067] Figure 3 Schematic diagram of the system framework of the image analysis module of the present invention;

[0068] Figure 4 It is a schematic diagram of the system framework of the data processing module of the present invention;

[0069] Figure 5 It is a schematic diagram of the system framework of the result display module of the present invention.

[0070] Description of the numbers in the figure:

[0071] 1. Light emission module; 2. Liquid storage system; 3. Light spot display module; 301. Scale plate; 4. Image acquisition module; 401. Autofocus module; 402. Exposure adjustment module; 5. Image processing module; 501. De-noising module; 502. Contrast enhancement module; 503. Edge detection module; 6. Image analysis module; 601. Brightness analysis module; 602. Light spot positioning module; 603. Interference removal module; 7. Data processing module; 701. Digitization module; 702. Filtering module; 703. Amplification module; 704. Data storage module; 8. Data output module; 9. Result display module; 901. Display form module; 902. History module; 903. Statistical analysis module; 904. User interface module. DETAILED DESCRIPTION

[0072] In order to facilitate those skilled in the art to understand the technical solution of the present invention, the technical solution of the present invention is further described in conjunction with the accompanying drawings of the specification.

[0073] Example 1

[0074] like Figures 1 to 4 As shown, the present invention provides a system for measuring solution concentration based on refractive index, including a light emitting module 1:

[0075] The light emitting module 1 is connected to a liquid storage system 2 and is used to emit light to the liquid storage system 2. The liquid storage system 2 is used to perform storage tests on solutions, and the liquid storage system 2 is connected to a light spot display module 3 for displaying light spots after the light passes through the liquid storage system 2. The light spot display module 3 is connected to an image acquisition module 4 for acquiring light spot images. The image acquisition module 4 is connected to an image processing module 5 for processing the acquired light spot images. The image processing module 5 is connected to an image analysis module 6 for analyzing the processed light spot images. The image analysis module 6 is connected to a data processing module 7 for combing and calculating data. The data processing module 7 is connected to a data output module 8 for outputting data results. The data output module 8 is connected to a result display module 9 for displaying data results.

[0076] like Figures 1 to 4As shown, the light emitting module 1 is used to generate light of a specific wavelength, stable and adjustable intensity, the liquid storage system 2 includes a right triangle container, the light spot display module 3 includes a scale plate 301 for reading the light spot coordinates, the image acquisition module 4 includes an autofocus module 401 and an exposure adjustment module 402 for performing automatic focusing and exposure adjustment during the light spot image acquisition process, the image processing module 5 includes a denoising module 501 for denoising the acquired light spot image, a contrast enhancement module 502 for enhancing the image contrast, and an edge detection module 503 for detecting the edge of the light spot image, the image analysis module 6 includes a light spot positioning module 602 for positioning the light spot in the light spot image processed in the image processing module 5, a brightness analysis module 601 for analyzing the brightness of the pixels in the light spot, and an interference removal module 603 for removing interfering pixels in the light spot.

[0077] like Figures 1 to 4 As shown, the data processing module 7 is used to calculate the solution concentration according to the spot coordinates, spacing and light emission length parameters, and the data processing module 7 includes a digitization module 701 for digitizing the calculation results, a filtering module 702 for filtering the data, an amplification module 703 for amplifying the data and a data storage module 704 for storing the data, and the result display module 9 includes a display form module 901 for displaying the data processed by the data processing module 7 in tables and charts, a history record module 902 for recording the data, a statistical analysis module 903 for statistical analysis of the data and a user interface module 904 for user operation.

[0078] Example 2

[0079] The present invention provides a method for measuring solution concentration based on refractive index according to embodiment 1, comprising the following steps:

[0080] S1. Material preparation;

[0081] Prepare a right-angled triangle container made of a specific transparent material. The refractive index of the material of the container to light is recorded as n. c , set to 1.5, the lengths of the right-angle sides of the container are respectively recorded as l A and l B , the length of the hypotenuse is l C , the right angle is 90°, and the other two angles are ∠α and ∠β respectively.

[0082] Prepare a high-precision scale plate with a minimum scale of 0.1 mm. The material of the scale plate will not interfere with the light, and the surface flatness should be within 0.05 mm to ensure the accuracy of the spot position measurement.

[0083] Prepare a high-resolution image acquisition device that has sufficient pixels and dynamic range to clearly capture the image of the light spot on the scale plate and can be connected to a computer for image analysis and processing;

[0084] Prepare a stable light source, which can emit light in a specific wavelength range of 400nm-700nm, with a power stability within 1%, and the light emitted by the light source is incident at an angle perpendicular to the right angle side of the right triangle container;

[0085] S2, empty container light test;

[0086] Let the perpendicular to the right angle side l A After being refracted and reflected in the container, the incident light passes through the container and forms a light spot on the scale plate;

[0087] The image acquisition device is used to collect the spot image on the scale plate in the no-load state and transmit it to the computer;

[0088] By setting up the image analysis module, the brightness distribution of the light spot pixels is analyzed. Assume that the coordinates of the pixels in the light spot image are (x, y), and the brightness value of the pixels is I(x, y). First, the approximate area of ​​the light spot is determined. By setting the brightness threshold T, the pixels with brightness values ​​greater than T form the candidate area of ​​the light spot. Then, the center point of the light spot is determined using the following algorithm:

[0089] Calculate the center coordinates (x c ,y c ), the formula is:

[0090]

[0091] Taking the centroid coordinates as the center, select the pixels within a certain radius for quadratic fitting, using a two-dimensional Gaussian function Fitting is performed, where A is the amplitude, (x0, y0) is the coordinate of the center of the spot, σ x and σ y are the standard deviations in the x and y directions respectively. The fitting parameters are solved by the least square method to obtain the coordinates of the center point of the light spot (x0, y0);

[0092] Use a high-precision measuring tool to measure the distance between the point where the light exits the container and the center of the empty light spot, recorded as L 1空 , L 1空 is the no-load distance;

[0093] S3, deionized water light test;

[0094] Slowly pour deionized water into the right triangle container, making sure there are no bubbles in the water and the liquid surface is flat;

[0095] Repeat the steps of light incident, image acquisition and light spot center point determination in the empty container light test;

[0096] Measure the distance between the point where the light exits the container and the center of the light spot filled with deionized water, recorded as L 1水 ;

[0097] According to Snell's law, the refractive index of light in air is n0 = 1, and the refractive index in deionized water is n w , we have n0 sinθ0=n w sinθ w , where θ0 is the angle at which the light is incident on the container wall in air, which is known to be 90°. By measuring the incident angle θ w , combined with the known n0, calculate n w ;

[0098] S4, injection of test solution and light testing;

[0099] Slowly inject the solution to be tested into the right triangle container, making sure there are no bubbles in the solution and the liquid surface is flat;

[0100] Repeat the steps of light incident, image acquisition and light spot center point determination in the empty container light test;

[0101] Calculate the distance between the light spot in the empty state and the light spot in the solution state, recorded as L2;

[0102] S5, mixed solution light test;

[0103] A certain amount of the test solution is injected into a right triangle container filled with deionized water to form a mixed solution. Let the volume of the injected test solution be V. t , the volume of deionized water is V w The total volume of the mixed solution is V m =V t +V w ;

[0104] Repeat the steps of light incident, image acquisition and light spot center point determination in the empty container light test;

[0105] Measure the distance between the point where the light exits the container and the center of the spot filled with the mixed solution, recorded as L3. At the same time, calculate the position change between the spot filled with the mixed solution and the spot filled with deionized water, recorded as ΔL 混水 =L3-L1水 ;

[0106] Calculate the concentration of the test solution in the mixed solution. Assume that the concentration of the test solution in the mixed solution is C 混 , calculated according to the following formula:

[0107] First, according to the relationship between the refractive index of the mixed solution and its components, the refractive index of the mixed solution n m It can be expressed as n m =C 混 ·n s +(1-C 混 )·n w , where n s is the refractive index of the solution to be tested, n w is the refractive index of deionized water;

[0108] Combining the refraction angle change and the distance relationship, construct the equation group:

[0109]

[0110] where θ s is the incident angle of the light in the solution to be tested, θ m is the incident angle of the light in the mixed solution,

[0111] f2(n s , n m ,θ s ,θ m )=n m -C 混 ·n s -(1-C 混 )·n w =0;

[0112] The equations are solved simultaneously by numerical solution method to obtain the concentration C of the test solution in the mixed solution. 混 ;

[0113] S6, correction and concentration calculation;

[0114] Use L 1水 For L 1空 Correction is made, and the correction formula is L 1修正 =L 1空 +k×(L 1水 -L 1空 ), where the correction coefficient k is determined by taking the average value of multiple experiments and is set to 0.8;

[0115] According to the corrected distance L 1修正 , spacing L2 and position change ΔL 混水, and the known angles ∠α and ∠β of the right triangle container, the concentration C of the solution to be tested can be calculated using the following formula:

[0116] First, according to the law of refraction of light, combined with the above measurement data, the change in the refraction angle of the light in the empty container, the container filled with deionized water, the container filled with the solution to be tested, and the container filled with the mixed solution is calculated. Assume that the refractive index of the light in the solution to be tested is n s , the refractive index in the mixed solution is n m , we have n0 sinθ0=n s sinθ s and n0 sinθ0 = n m sinθ m , where θ s and θ m are the angles of incidence of the light in the solution to be tested and the mixed solution respectively. n is calculated by measuring the angle of incidence and combining it with the known n0. s and n m , the refraction angle changes are Δθ s =θ s -θ0, Δθ m =θ m -θ0;

[0117] Then, perform complex formula integration and derivation:

[0118] According to the volume ratio and concentration relationship of the mixed solution,

[0119] Combining the refraction angle change and the distance relationship, the following complex equations are constructed:

[0120]

[0121] f2(n s , n m ,θ s ,θ m )=n m -C 混 ·n s -(1-C 混 )·n w =0;

[0122] By numerically solving the equations simultaneously, we can obtain n s Relationship with C, assuming that the refractive index n of the solution is known s There is a specific functional relationship between g(n s )=C, and the concentration C of the solution to be tested is calculated through this functional relationship;

[0123] By comparing C 混By comparing it with C and calculating the average value, the density of the solution can be obtained.

[0124] In the embodiment of the present invention, during the measurement process, the ambient temperature is maintained between 20°C and 25°C to reduce the influence of temperature on the refractive index of the solution and the size of the container. In order to improve the accuracy and reliability of the measurement, multiple measurements can be performed and the average value can be taken. For the empty container, the container filled with deionized water, the container filled with the solution and the container filled with the mixed solution, at least 5 light test, image acquisition and spot center point determination steps are performed respectively, and then the average empty distance L is calculated. 1αvg空 , the distance L after filling with deionized water 1αvg水 , Spacing L 2αvg And the position change ΔL αvg混水 , and then make corrections and concentration calculations. In order to verify the accuracy of the measurement method, a standard solution of known concentration can be used for comparative testing. The standard solution of known concentration is injected into a right triangle container, and the test is performed according to the above measurement steps. The calculated concentration is compared with the known concentration of the standard solution. The error is within 5%, which is considered to be accurate. This method can be applied to different types of solutions, including but not limited to transparent solutions, colored solutions, and turbid solutions. However, for turbid solutions, the image analysis algorithm needs to be appropriately adjusted to accurately determine the center point of the light spot. As another embodiment of the present invention,

[0125] The embodiments of the present invention disclose preferred embodiments, but are not limited thereto. A person skilled in the art can easily understand the spirit of the present invention based on the above embodiments and make different extensions and changes. However, as long as they do not deviate from the spirit of the present invention, they are all within the protection scope of the present invention.

Claims

1. A system for measuring solution concentration based on refractive index, characterized in that: The light emitting module (1) comprises: The light emitting module (1) is connected to a liquid storage system (2) and is used to emit light to the liquid storage system (2); the liquid storage system (2) is used to perform storage testing on a solution; the liquid storage system (2) is connected to a light spot display module (3) for displaying a light spot after the light passes through the liquid storage system (2); the light spot display module (3) is connected to an image acquisition module (4) for acquiring a light spot image; the image acquisition module (4) is connected to an image processing module (5) for processing the acquired light spot image; the image processing module (5) is connected to an image analysis module (6) for analyzing the processed light spot image; the image analysis module (6) is connected to a data processing module (7) for combing and calculating data; the data processing module (7) is connected to a data output module (8) for outputting data results; the data output module (8) is connected to a result display module (9) for displaying the data results.

2. The method for measuring solution concentration based on refractive index according to claim 1, characterized in that: The light emitting module (1) is used to generate light of a specific wavelength, stability and adjustable intensity; the liquid storage system (2) comprises a right-angled triangle container; and the light spot display module (3) comprises a scale plate (301) for reading the light spot coordinates.

3. A system for measuring solution concentration based on refractive index according to claim 2, characterized in that: The image acquisition module (4) comprises an autofocus module (401) and an exposure adjustment module (402) for performing autofocus and exposure adjustment during the process of spot image acquisition; the image processing module (5) comprises a denoising module (501) for performing denoising on the acquired spot image, a contrast enhancement module (502) for enhancing the image contrast, and an edge detection module (503) for detecting the edge of the spot image; the image analysis module (6) comprises a spot positioning module (602) for positioning the spot in the spot image processed in the image processing module (5), a brightness analysis module (601) for analyzing the brightness of pixels in the spot, and an interference removal module (603) for removing interfering pixels in the spot.

4. A system for measuring solution concentration based on refractive index according to claim 3, characterized in that: The data processing module (7) is used to calculate the solution concentration according to the light spot coordinates, the spacing and the light emission length parameters, and the data processing module (7) comprises a digitization module (701) for digitizing the calculation results, a filtering module (702) for filtering the data, an amplification module (703) for amplifying the data and a data storage module (704) for storing the data.

5. A system for measuring solution concentration based on refractive index according to claim 4, characterized in that: The result display module (9) comprises a display form module (901) for displaying the data processed by the data processing module (7) in tables and charts, a history record module (902) for recording the data, a statistical analysis module (903) for performing statistical analysis on the data, and a user interface module (904) for users to operate.

6. A method for measuring solution concentration based on refractive index, comprising the system for measuring solution concentration based on refractive index according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Material preparation; Prepare a right-angled triangle container made of a specific transparent material. The refractive index of the material of the container to light is recorded as n. c , set to 1.5, the lengths of the right-angle sides of the container are respectively recorded as l A and l B , the length of the hypotenuse is l C , the right angle is 90°, and the other two angles are ∠α and ∠β respectively. Prepare a high-precision scale plate with a minimum scale of 0.1 mm. The material of the scale plate will not interfere with the light, and the surface flatness should be within 0.05 mm to ensure the accuracy of the spot position measurement. Prepare a high-resolution image acquisition device that has sufficient pixels and dynamic range to clearly capture the image of the light spot on the scale plate and can be connected to a computer for image analysis and processing; Prepare a stable light source, which can emit light in a specific wavelength range of 400nm-700nm, with a power stability within 1%, and the light emitted by the light source is incident at an angle perpendicular to the right angle side of the right triangle container; S2, empty container light test; Let the perpendicular to the right angle side l A After being refracted and reflected in the container, the incident light passes through the container and forms a light spot on the scale plate; The image acquisition device is used to collect the spot image on the scale plate in the no-load state and transmit it to the computer; By setting up the image analysis module, the brightness distribution of the light spot pixels is analyzed. Assume that the coordinates of the pixels in the light spot image are (x, y), and the brightness value of the pixels is I(x, y). First, the approximate area of ​​the light spot is determined. By setting the brightness threshold T, the pixels with brightness values ​​greater than T form the candidate area of ​​the light spot. Then, the center point of the light spot is determined using the following algorithm: Calculate the center coordinates (x c ,y c ), the formula is: Taking the centroid coordinates as the center, select the pixels within a certain radius for quadratic fitting, using a two-dimensional Gaussian function Fitting is performed, where A is the amplitude, (x0, y0) is the coordinate of the center of the spot, σ x and σ y are the standard deviations in the x and y directions respectively. The fitting parameters are solved by the least square method to obtain the coordinates of the center point of the light spot (x0, y0); Use a high-precision measuring tool to measure the distance between the point where the light exits the container and the center of the empty light spot, recorded as L 1空 , L 1空 is the no-load distance; S3, deionized water light test; Slowly pour deionized water into the right triangle container, making sure there are no bubbles in the water and the liquid surface is flat; Repeat the steps of light incident, image acquisition and light spot center point determination in the empty container light test; Measure the distance between the point where the light exits the container and the center of the light spot filled with deionized water, recorded as L 1水 ; According to Snell's law, the refractive index of light in air is n0 = 1, and the refractive index in deionized water is n w , we have n0sinθ0=n w sinθ w , where θ0 is the angle at which the light is incident on the container wall in air, which is known to be 90°. By measuring the incident angle θ w , combined with the known n0, calculate n w ; S4, injection of test solution and light testing; Slowly inject the solution to be tested into the right triangle container, making sure there are no bubbles in the solution and the liquid surface is flat; Repeat the steps of light incident, image acquisition and light spot center point determination in the empty container light test; Calculate the distance between the light spot in the empty case and the light spot in the solution case, and record it as L2; S5, mixed solution light test; A certain amount of the test solution is injected into a right triangle container filled with deionized water to form a mixed solution. Let the volume of the injected test solution be V. t , the volume of deionized water is V w The total volume of the mixed solution is V m =V t +V w ; Repeat the steps of light incident, image acquisition and light spot center point determination in the empty container light test; Measure the distance between the point where the light exits the container and the center of the spot filled with the mixed solution, recorded as L3. At the same time, calculate the position change between the spot filled with the mixed solution and the spot filled with deionized water, recorded as ΔL 混水 =L3-L 1水 ; Calculate the concentration of the test solution in the mixed solution. Assume that the concentration of the test solution in the mixed solution is C 混 , calculated according to the following formula: First, according to the relationship between the refractive index of the mixed solution and its components, the refractive index of the mixed solution n m It can be expressed as n m =C 混 ·n s +(1-C 混 )·n w , where n s is the refractive index of the solution to be tested, n w is the refractive index of deionized water; Combining the refraction angle change and the distance relationship, construct the equation group: where θ s is the incident angle of the light in the solution to be tested, θ m is the incident angle of the light in the mixed solution, f2(n s ,n m ,θ s ,θ m )=n m -C 混 ·n s -(1-C 混 )·n w =0; The equations are solved simultaneously by numerical solution method to obtain the concentration C of the test solution in the mixed solution. 混 ; S6, correction and concentration calculation; Use L 1水 For L 1空 Correction is made, and the correction formula is L 1修正 =L 1空 +k×(L 1水 -L 1空 ), where the correction coefficient k is determined by taking the average value of multiple experiments and is set to 0.8; According to the corrected distance L 1修正 , spacing L2 and position change ΔL 混水 , and the known angles ∠α and ∠β of the right triangle container, the concentration C of the solution to be tested can be calculated using the following formula: First, according to the law of refraction of light, combined with the above measurement data, the change in the refraction angle of the light in the empty container, the container filled with deionized water, the container filled with the solution to be tested, and the container filled with the mixed solution is calculated. Assume that the refractive index of the light in the solution to be tested is n s , the refractive index in the mixed solution is n m , we have n0sinθ0=n s sinθ s and n0sinθ0=n m sinθ m ,in… s and… m are the angles of incidence of the light in the solution to be tested and the mixed solution respectively. n is calculated by measuring the angle of incidence and combining it with the known n0. s and n m , the refraction angle changes are Δ… s =… s -…0,Δθ m =θ m -…0; Then, perform complex formula integration and derivation: According to the volume ratio and concentration relationship of the mixed solution, Combining the refraction angle change and the distance relationship, the following complex equations are constructed: f2(n s ,n m ,… s ,θ m )=n m -C 混 ·n s -(1-C 混 )·n w =0; By solving the equations simultaneously through numerical solution methods, we can get n s Relationship with C, assuming that the refractive index n of the solution is known s There is a specific functional relationship between g(n s )=C, and the concentration C of the solution to be tested is calculated through this functional relationship; By comparing C 混 By comparing it with C and calculating the average value, the density of the solution can be obtained.

7. The method for measuring solution concentration based on refractive index according to claim 6, characterized in that: During the measurement, the ambient temperature was maintained between 20°C and 25°C to reduce the effect of temperature on the refractive index of the solution and the size of the container.

8. The method for measuring solution concentration based on refractive index according to claim 7, characterized in that: In order to improve the accuracy and reliability of the measurement, multiple measurements can be performed and the average value can be taken. For the empty container, the container filled with deionized water, the container filled with solution and the container filled with mixed solution, at least 5 steps of light testing, image acquisition and spot center point determination are performed respectively, and then the average empty distance L is calculated. 1αvg Empty and filled with deionized water distance L 1αvg Water, spacing L 2αvg And the position change ΔL αvg混水 , and then make corrections and concentration calculations.

9. The method for measuring solution concentration based on refractive index according to claim 8, characterized in that: In order to verify the accuracy of the measurement method, a standard solution of known concentration can be used for a comparative test. The standard solution of known concentration is injected into a right triangle container, and the test is performed according to the above measurement steps. The calculated concentration is compared with the known concentration of the standard solution. If the error is within 5%, the measurement method is considered accurate.

10. The method for measuring solution concentration based on refractive index according to claim 9, characterized in that: This method can be applied to different types of solutions, including but not limited to transparent solutions, colored solutions and turbid solutions. However, for turbid solutions, the image analysis algorithm needs to be properly adjusted to accurately determine the center point of the light spot.

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