Liquid refractive index real-time measuring device based on displacement sensor

Abstract

The utility model provides a liquid refractive index real-time measuring device based on a displacement sensor, which is used for solving the problem that the liquid refractive index cannot be accurately measured in real time in the prior art and can capture and monitor the tiny change of the liquid refractive index in real time. A circular container is selected as a sample container, so that the measurement accuracy is improved; traditional refraction angle measurement is converted into laser beam transverse displacement measurement, and the innovative method not only improves the measurement precision, but also effectively avoids interference of ambient light; the instrument can provide more accurate refractive index data by accurately measuring the displacement change of the laser beam after penetrating through the liquid.

Description

Technical Field

[0001] The utility model belongs to the technical field of optical measurement of liquid refractive index, and in particular relates to a real-time measurement device for liquid refractive index based on a displacement sensor. Background Art

[0002] Refractive index is an important optical property parameter of matter, which can often reflect the state and changes of relevant physical properties of matter, such as concentration and temperature. Accurate measurement of refractive index is crucial in fields such as optics, chemistry and materials science. Measuring the refractive index of liquids is crucial to advancing scientific exploration and plays a core role in industrial manufacturing and environmental monitoring. Because the refractive index of liquids is extremely sensitive to changes in factors such as temperature and concentration, it has become an extremely valuable physical indicator that can help us accurately monitor and control various states of liquids. Traditional methods of measuring refractive index, such as Abbe refractometry, total reflection technology, and Michelson interferometry, have limitations in accuracy and ease of use, and cannot accurately observe changes in the refractive index of liquids in real time. Therefore, a reliable and user-friendly method is needed to measure the refractive index of liquids.

[0003] In scientific research, the real-time liquid refractive index measurement device can be used to study the refractive index variations of optical materials under different conditions and states, explore the optical properties of new materials, and provide important data support for materials science research. In engineering applications, the real-time liquid refractive index measurement device can be used to monitor the refractive index variations of products on the production line in real time, helping to optimize product production and design, and improve product performance and stability. In medical diagnostics, the real-time liquid refractive index measurement device can be used to detect refractive index variations in biological tissues or drugs, enabling precise diagnosis and treatment.

[0004] The patent publication number CN 114062318 A provides a device and method for measuring the refractive index of liquid using a linear array CCD (schematic diagram as shown in FIG. Figure 1 As shown in the figure, light is first passed through a liquid and the radius of the resulting beam is observed. Refraction within the liquid causes the radius of the beam to change. By measuring this radius with a high-precision linear array CCD camera, information about the liquid's refractive index can be indirectly obtained.

[0005] Existing technologies cannot measure the refractive index of liquids in real time, especially for situations where the refractive index of liquids changes rapidly, such as in industrial production processes. The device cannot achieve real-time and fast dynamic measurement;

[0006] Existing technologies have limitations in terms of accuracy and applicability, and are unable to accurately observe the measurement of liquid refractive index in real time;

[0007] Existing technology can only use rectangular containers, which have a weak refractive ability for liquids, resulting in low accuracy of the final measurement results; the measurement of beam radius by linear array CCD may be affected by interference from ambient light, which will affect its measurement accuracy.

[0008] Due to the limitations of its principles, existing technologies are only applicable to measuring certain aspects of liquids, such as concentration or refractive index, and have a narrow scope of application. Utility Model Content

[0009] In light of this, the purpose of this utility model is to provide a real-time liquid refractive index measurement device based on a displacement sensor. Based on the principle of a displacement sensor, this device leverages its high sensitivity and rapid response to capture refractive index changes in optical materials in real time, enabling precise monitoring of optical properties. Compared to traditional refractive index measurement devices, this device offers advantages such as fast measurement speed, high accuracy, and non-contact measurement. It can operate stably in a variety of complex environments, providing important technical support for research and application in related fields.

[0010] A real-time liquid refractive index measuring device based on a displacement sensor comprises a laser light source (3), a reflector (1), a sample container (2), a displacement sensor (4), a base (5), and a data acquisition and processing unit;

[0011] The reflective plate (1) is vertically fixed on the base (5), the sample container (2) is placed in front of the reflective plate (1), and the laser light source (3) is placed in front of the sample container (2);

[0012] The sample container (2) is a transparent cylindrical glass container;

[0013] The laser light emitted by the laser light source (3) is parallel to the surface of the base (5), passes through the sample container and is emitted to the reflector (1); after being reflected by the reflector (1), it enters and passes through the sample container (2) again, and the light is received by the CCD of the displacement sensor (4);

[0014] The data acquisition and processing unit converts the optical signal received on the CCD into an electrical signal, and calculates the displacement Δd of the receiving light spot caused by the change of the refractive index in the sample container (2). The refractive index in the sample container (2) is obtained in real time based on the relationship between the displacement Δd and the refractive index curve pre-stored in the data acquisition and processing unit.

[0015] Preferably, the laser light source (3) is a laser of any wavelength.

[0016] Preferably, the sample container (2) is a cylindrical glass container with a wall thickness of 0.1 mm.

[0017] Furthermore, the data acquisition and processing unit is also used for:

[0018] For a certain solution to be tested, the corresponding relationship between the refractive index and displacement Δd of the solution at different temperatures and / or different concentrations is pre-stored. After the displacement Δd is calculated based on the laser signal received on the CCD of the displacement sensor (4), the refractive index of the current solution to be tested is obtained.

[0019] Furthermore, the data acquisition and processing unit is also used for:

[0020] For a certain solution to be tested, when it is placed in a fixed temperature environment, after calculating the displacement Δd based on the laser signal received on the CCD of the displacement sensor (4), the refractive index of the current solution to be tested is obtained, and the concentration of the solution is determined based on a pre-stored concentration-refractive index relationship curve of the solution to be tested.

[0021] Furthermore, the data acquisition and processing unit is also used for:

[0022] For a certain solution to be tested, when its concentration is fixed, after calculating the displacement Δd based on the laser signal received on the CCD of the displacement sensor (4), the refractive index of the current solution to be tested is obtained, and the temperature of the solution is determined based on the pre-stored temperature and refractive index relationship curve of the solution to be tested.

[0023] The utility model has the following beneficial effects:

[0024] This new technology addresses the existing problem of being unable to accurately measure the refractive index of liquids in real time. It can capture and monitor minute changes in the liquid's refractive index in real time. Through high-speed data processing and analysis, the instrument can rapidly respond to changes in the liquid's refractive index, providing continuous, real-time measurement data.

[0025] The technical solution of the utility model is used to solve the problem in the prior art that the rectangular container has an unclear light beam refraction ability, and a circular container is selected as the sample container to improve the measurement accuracy.

[0026] This innovative approach converts traditional refraction angle measurements into measurements of the lateral displacement of the laser beam. This innovative approach not only improves measurement accuracy but also effectively avoids interference from ambient light. By precisely measuring the displacement of the laser beam after it passes through the liquid, the instrument can provide more accurate refractive index data. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of a device for real-time measurement of liquid refractive index;

[0028] FIG2( a ) and FIG2( b ) are three-dimensional views of the device for real-time measurement of liquid refractive index from two viewing angles, respectively;

[0029] Figure 3(a) and Figure 3(b) are schematic diagrams of the lateral displacement of the laser landing point before and after the addition of the test liquid;

[0030] Figure 4 This is the refraction light path diagram of the utility model;

[0031] Figure 5 The laser landing point displacement-refractive index curves of the two containers;

[0032] Figure 6 is the laser landing point displacement-salt water concentration;

[0033] Figure 7 is the refractive index-laser landing point displacement fitting curve.

[0034] Among them, 1-reflector, 2-sample container, 3-laser source, 4-displacement measuring instrument, 5-base. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0036] 1. Measuring device

[0037] The schematic diagram of the real-time liquid refractive index measurement device proposed in the utility model is as follows Figure 1 As shown in the figure, it consists of several key components: laser light source, reflector, sample container, displacement sensor, base and data acquisition and processing unit.

[0038] The reflector is fixed vertically to the base, the sample container is placed in front of the reflector, and the laser light source is placed in front of the sample container. The laser light source emits laser light parallel to the base surface, passes through the sample container, and is directed toward the reflector. After being reflected by the reflector, the light enters and passes through the sample container again, and is received by the CCD of the displacement sensor. The sample container is a cylindrical glass container with a thickness of 0.1mm and high light transmittance, which contains the liquid to be tested. When the sample container is empty and when it is filled with the liquid to be tested, the returning laser light is received by the CCD of the displacement sensor due to the refraction of the liquid. The data acquisition and processing unit converts the optical signal received on the CCD into an electrical signal and calculates the displacement Δd of the received light spot caused by the change in the refractive index in the sample container. Based on the relationship between the displacement Δd and the refractive index curve pre-stored in the data acquisition and processing unit, the refractive index in the sample container can be obtained in real time.

[0039] The measurement device is based on the law of light refraction. When a laser beam is directed at a liquid interface at a preset angle, the degree of its refraction varies depending on the liquid's refractive index. This change in the liquid's refractive index deflects the laser beam's path through the liquid, causing the position of the laser's landing point at the detection end to change (as shown in Figure 3). By precisely measuring the horizontal displacement of the laser's landing point, the liquid's refractive index can be calculated.

[0040] 2. Optical Path Analysis

[0041] In order to calculate the specific relationship between the laser landing point and the refractive index, a detailed optical path analysis was carried out.

[0042] The optical path diagram is as follows Figure 4 As shown in the figure, after the laser light source emits laser light, it first passes through the sample container wall and enters the liquid to be measured. It then passes through the sample container a second time, striking the reflector. After being reflected by the reflector, it passes through the sample container wall a third time, propagates through the liquid, and passes through the sample container wall a fourth time before exiting and entering the CCD of the displacement sensor. This indicates that this optical path undergoes four refractions and one reflection. Because the sample container wall is very thin, its effect on distance measurement is negligible. Therefore, refraction at the container wall is not considered in this analysis.

[0043] right Figure 4 The parameters are set as follows:

[0044] The origin is the center of the bottom disk of the sample container, the diameter of the bottom disk parallel to the CCD surface is the x-axis, and the y-axis is perpendicular to the x-axis; R: radius of the cylindrical glass container; no: refractive index of air; ns: refractive index of the liquid; h: distance between the displacement sensor CCD screen plane and the sample container; xn: x-axis coordinate of the light at the intersection of the two media during the nth refraction; yn: y-axis coordinate of the light at the intersection of the two media during the nth refraction; θin-n: incident angle of the nth refraction; θout-n: exit angle of the nth refraction; θn-n: normal direction of the nth refraction; θrn: direction of the laser light during the nth refraction; x5: x-axis coordinate of the spot when the laser is projected onto the CCD screen. d: distance d from the y-axis when the laser light is emitted parallel to the y-axis; Δd represents the x-axis displacement between the laser light exiting and returning to the CCD screen after five refractions.

[0045] For the first refraction:

[0046] x1=d

[0047] For the second refraction:

[0048]

[0049] For the third refraction:

[0050] In the optical path design, the reflector C is actually close to the disk, so the displacement deviation caused by 2 to 3 is ignored in the optical path analysis. Therefore, it can be known that:

[0051]

[0052] For the fourth refraction:

[0053] The fourth refraction is the key refraction that affects the CCD receiving position:

[0054]

[0055] For the fifth refraction:

[0056]

[0057] Δd=x5-x1.

[0058] We therefore established a mathematical relationship between the horizontal displacement of the laser spot and the refractive index of the liquid. Using this relationship, we can calculate the correspondence between changes in the liquid's refractive index and changes in the value measured by the displacement sensor. Using pre-calibrated liquid refractive index data, we can plot a calibration curve between the laser spot position and the refractive index. To further improve measurement accuracy, we can compare the measured values ​​with the fitted curve to optimize the precision of the measurement results. The real-time data obtained during the measurement process can be rapidly processed by the computer system and displayed instantly, allowing the user to keep abreast of the latest changes in the liquid's refractive index. Through these steps, we have successfully developed a device capable of measuring changes in the refractive index of liquids in real time.

[0059] 3. Computer simulation:

[0060] Based on the optical path, we derived the relationship between the liquid refractive index ns and the horizontal distance Δd of the laser landing point on the CCD display, and simulated and fitted the curve fitting diagram of the liquid laser landing point displacement and refractive index. Figure 5 As shown, the slope can be used to determine the sensitivity of the change in laser landing point displacement relative to the change in refractive index. We define measurement sensitivity as unit laser position change / unit refractive index change. Calculation shows the average sensitivity between refractive indices of 1 and 2: the average sensitivity of cylindrical sample containers is 2.8935; the average sensitivity of rectangular containers is 0.2994. This shows that the refraction measurement method using cylindrical sample containers is more accurate than that using rectangular containers, and the sensitivity is about an order of magnitude higher. This conclusion can also be seen directly from the image. This shows that the method of selecting cylindrical sample containers to carry liquids can improve measurement accuracy.

[0061] At room temperature of 20°C, the laser landing point of salt water with different concentrations was measured. The measurement data are as follows Figure 6 As shown:

[0062] according to Figure 6 It can be seen that the laser point displacement is nearly linearly related to the concentration of NaCl solution. According to the literature, the refractive index and concentration of sodium chloride solution are nearly linearly related. Therefore, the relationship between the refractive index and displacement can be normalized according to the known data to obtain the relationship between the refractive index and the laser point ( Figure 7 ). As can be clearly seen from the figure, as the refractive index increases, the laser landing point position also increases accordingly. Therefore, as long as the laser landing point position is measured, compared with the laser landing point position of pure water (i.e., 0% NaCl solution), the displacement distance of the laser landing point is calculated, and then the refractive index of the liquid to be measured can be easily determined by referring to the change curve. We have established a fitting curve between the refractive index and the laser landing point position through curve fitting. Using this curve and the real-time collected laser landing point data, the refractive index value of the liquid can be obtained in real time.

[0063] According to this method, the refractive index of a series of NaCl solutions with different concentrations was measured and shown in Table 1.

[0064] Table 1: Refractive index and laser landing point displacement of NaCl solutions with different concentrations

[0065]

[0066] In terms of measuring accuracy, the accuracy of the refractive index measuring instrument developed in the present invention mainly depends on the measurement accuracy of the laser landing position. According to experimental results, the measurement accuracy of the laser landing position of the instrument has reached 0.01 mm. This level of accuracy corresponds to a refractive index measurement accuracy of 0.0001, indicating that the instrument can sensitively capture small changes in the refractive index. The measurement accuracy of the laser landing point is a key factor affecting the refractive index measurement results. Therefore, if the measurement accuracy of the laser landing point can be improved through technical improvements, the measurement accuracy of the refractive index is expected to be significantly improved. For example, the use of higher-resolution displacement sensors may push the measurement accuracy to a higher level. It should also be noted that the laser light source in the present invention is a laser of any wavelength.

[0067] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A real-time measurement device for liquid refractive index based on a displacement sensor, characterized in that: It comprises a laser light source (3), a reflector (1), a sample container (2), a displacement sensor (4), a base (5) and a data acquisition and processing unit; The reflective plate (1) is vertically fixed on the base (5), the sample container (2) is placed in front of the reflective plate (1), and the laser light source (3) is placed in front of the sample container (2); The sample container (2) is a transparent cylindrical glass container; The laser light emitted by the laser light source (3) is parallel to the surface of the base (5), passes through the sample container and is emitted to the reflector (1); after being reflected by the reflector (1), it enters and passes through the sample container (2) again, and the light is received by the CCD of the displacement sensor (4); The data acquisition and processing unit converts the optical signal received on the CCD into an electrical signal, and calculates the displacement Δd of the receiving light spot caused by the change of the refractive index in the sample container (2). The refractive index in the sample container (2) is obtained in real time based on the relationship between the displacement Δd and the refractive index curve pre-stored in the data acquisition and processing unit.

2. The device for real-time measurement of liquid refractive index based on a displacement sensor according to claim 1, characterized in that: The laser light source (3) is a laser of any wavelength.

3. The device for real-time measurement of liquid refractive index based on a displacement sensor according to claim 1, characterized in that: The sample container (2) is a cylindrical glass container with a wall thickness of 0.1 mm.

4. The device for real-time measurement of liquid refractive index based on a displacement sensor according to claim 1, wherein: The data acquisition and processing unit is further used for: For a certain solution to be tested, the corresponding relationship between the refractive index and displacement Δd of the solution at different temperatures and / or different concentrations is pre-stored. After the displacement Δd is calculated based on the laser signal received on the CCD of the displacement sensor (4), the refractive index of the current solution to be tested is obtained.

5. The real-time liquid refractive index measuring device based on a displacement sensor according to claim 1, characterized in that: The data acquisition and processing unit is further used for: For a certain solution to be tested, when it is placed in a fixed temperature environment, after calculating the displacement Δd based on the laser signal received on the CCD of the displacement sensor (4), the refractive index of the current solution to be tested is obtained, and the concentration of the solution is determined based on a pre-stored concentration-refractive index relationship curve of the solution to be tested.

6. The device for real-time measurement of liquid refractive index based on a displacement sensor according to claim 1, characterized in that: The data acquisition and processing unit is further used for: For a certain solution to be tested, when its concentration is fixed, after calculating the displacement Δd based on the laser signal received on the CCD of the displacement sensor (4), the refractive index of the current solution to be tested is obtained, and the temperature of the solution is determined based on the pre-stored temperature and refractive index relationship curve of the solution to be tested.

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