A solution refractive index real-time detection method based on polarization beam splitting differential measurement

Abstract

The application provides a solution refractive index real-time detection method based on polarization beam splitting differential measurement, which comprises the following steps: step A, emitting laser light through a laser, adjusting the component proportion of s-polarized light and p-polarized light in the laser beam through a half-wave plate, and then passing the laser through a first polarization beam splitting prism to divide the laser into s-polarized light and p-polarized light; the p-polarized light is transmitted by the first polarization beam splitting prism, and then irradiates onto an image sensor after passing through a hollow glass block; the s-polarized light is refracted by the first polarization beam splitting prism to a second polarization beam splitting prism, and then irradiates onto the image sensor after being refracted by the second polarization beam splitting prism and passing through the hollow glass block; the hollow glass block is internally hollow to form a sample flow cell; step B, the s-polarized light and the p-polarized light are imaged as two light spots on the image sensor, the distance x of the two light spots on the image sensor is recorded, and the solution refractive index is inversed through the distance x of the two light spots.

Description

Technical Field

[0001] This application relates to the field of optical detection technology, and in particular to a method for real-time detection of the refractive index of a solution based on polarization beam splitting differential measurement. Background Technology

[0002] Current online concentration detection technologies for solutions face fundamental technical bottlenecks. Contact sensors (such as conductivity meters) are susceptible to corrosion and contamination by the measured medium and are only effective for electrolyte solutions, limiting their application scenarios. Traditional refractometers rely on complex optical structures and precise displacement adjustment mechanisms, resulting in high equipment costs and maintenance expenses. While spectral analysis offers high precision, its complex systems and poor environmental adaptability make it difficult to effectively deploy in dynamic industrial environments such as pharmaceutical reaction vessels and food fermentation tanks. These factors collectively restrict the industrial application of non-contact real-time detection technologies.

[0003] Spot analysis, which measures concentration by tracking changes in the size of a focused beam and using a CMOS sensor for automatic focusing, offers significant advantages such as simple system structure and low hardware cost. However, its detection sensitivity is relatively low and its temperature drift is significant, limiting its practical application. Summary of the Invention

[0004] To address the aforementioned practical problems and the shortcomings of existing technologies, the main technical problem to be solved by this invention is to provide a real-time solution refractive index detection method based on polarization beam splitting differential measurement. By introducing a polarization beam splitting differential optical path amplification mechanism and utilizing optical differential operations to enhance the detection capability of weak signals, the detection sensitivity is improved by orders of magnitude, providing a reliable technical solution for industrial online monitoring.

[0005] To address the aforementioned technical problems, this application provides a real-time solution refractive index detection method based on polarization beam splitting differential measurement, employing the following technical solution:

[0006] The method includes the following steps:

[0007] Step A: A laser beam is emitted by a laser source. The ratio of s-polarized to p-polarized components in the laser beam is adjusted by a half-wave plate. The laser beam is then split into s-polarized and p-polarized light by a first polarizing beam splitter. The p-polarized light is transmitted through the first polarizing beam splitter and then shines onto the image sensor after passing through a hollow glass block. The s-polarized light is refracted by the first polarizing beam splitter to a second polarizing beam splitter, and then refracted by the second polarizing beam splitter to shine onto the image sensor after passing through the hollow glass block. The hollow interior of the hollow glass block forms a sample flow cell.

[0008] Step B: The s-polarized light and p-polarized light are imaged as two spots on the image sensor. The distance x between the two spots on the image sensor is recorded. The refractive index of the solution is inverted using the distance x between the two spots. The calculation steps are as follows:

[0009] Let the parameters of the insulating glass and the solution sample be , and the glass refractive index be . The sample flow cell has an axisymmetric polygonal cross-section, and the thickness at the axis of symmetry of the sample flow cell is... The angle of vertex D on the axis of symmetry is Let the center distance between the first polarizing beam splitter and the second polarizing beam splitter be . The refractive index of the solution to be tested is ;

[0010] p-polarized light enters the sample flow cell from the hollow glass block at point A. The first refraction of the p-polarized light occurs at point A. Let the angle of incidence at point A be θ. The calculation formula is: ;

[0011] According to the law of refraction: ;in, The angle of refraction is ; the angle between the refracted ray of p-polarized light and the incident ray in the solution is . ;

[0012] The p-polarized light exits the sample flow cell at point B into the hollow glass block. The second refraction of the p-polarized light occurs at point B. Due to symmetry, the angle of incidence at point B is... The angle of refraction is The light rays emitted from point B are parallel to the light rays in front of point A, and the p-polarized light finally illuminates point C on the image sensor.

[0013] Point A is the first intersection of the incident p-polarized light ray and the sample cell. The second intersection of the extended incident light ray and the sample cell is point F. Connecting points A, B, and F forms triangle ABF.

[0014] The angle of triangle ABF at point A is The length of side AF is According to the triangle relationship , The distance from point A to point B. Let F be the distance between point A and point F. , Let F be the angle. ; Angle B is the angle. , can be obtained ;

[0015] Point B is the intersection of the p-polarized light ray and the sample cell. A perpendicular line is drawn from point B to the extension of the incident light ray, intersecting at point G. The line segment BG represents the offset distance of the light ray. According to geometric relationships, we can obtain That is, ;

[0016] Based on the characteristic that the sample flow cell has an axisymmetric polygonal cross-section, the propagation paths of s-polarized light and p-polarized light within the hollow glass block are completely symmetrical. Therefore, the distances from which s-polarized light and p-polarized light illuminate the image sensor can be calculated as follows: The distance between the two light spots on the image sensor is The refractive index of the solution can be obtained by measuring the distance x between two light spots on the image sensor. .

[0017] In a preferred embodiment, a solution concentration measuring device for implementing the method is included. The solution concentration measuring device includes a laser, a half-wave plate, a first polarizing beam splitter, a second polarizing beam splitter, a hollow glass block, and an image sensor. The hollow portion of the hollow glass block forms a sample flow cell, and the sample flow cell contains the solution to be tested.

[0018] In a preferred embodiment, the sample flow cell has an axisymmetric polygonal cross-section; the first polarizing beam splitter and the second polarizing beam splitter are arranged vertically and are cemented together; the two polarizing beam splitters are cemented together on the side of the hollow glass block facing the laser, and the image sensor is cemented together on the side of the hollow glass block away from the laser.

[0019] In a preferred embodiment, the half-wave plate is disposed between the laser and the first polarizing beam splitter prism.

[0020] In a preferred embodiment, the half-wave plate is used to adjust the component ratio of s-polarized light and p-polarized light in the laser beam; the half-wave plate adjusts the laser components at a ratio of 50:50.

[0021] In a preferred embodiment, the laser is connected to a laser driving circuit, which drives the laser to emit laser light.

[0022] In summary, this application has the following beneficial effects:

[0023] 1. This invention provides a real-time solution refractive index detection method based on polarization beam splitting differential measurement. By introducing a polarization beam splitting prism and a half-wave plate, and using a dual-spot polarization beam splitting differential optical path, the sample cell is built into a hollow glass block, so that the laser only contacts the glass wall and not directly contacts the solution, realizing full optical non-contact measurement. This completely eliminates the corrosion and contamination risks of traditional conductivity or refractive probes, and is especially suitable for online sterile concentration monitoring of easily contaminated or high-value liquids such as alcohol and sugar solutions.

[0024] 2. Introduction of polarization beam splitting-differential amplification mechanism: S-beam and p-beam form coplanar dual light spots on the same image sensor. The distance between the two light spots generates a differential amplification response to changes in refractive index, which significantly improves sensitivity and accuracy.

[0025] 3. The present invention adopts an axisymmetric polygonal cross-section structure, which makes the incident light rays parallel to the outgoing light rays. Compared with the conventional triangular prism structure, which relies too much on precise angle adjustment and is easily affected by mechanical vibration or installation errors, making it unsuitable for dynamic online systems, the technical solution of the present invention has the advantages of structural symmetry, optical path self-stabilization, and strong anti-interference ability, making it more suitable for industrial field deployment. Attached Figure Description

[0026] Figure 1 This is a structural distribution diagram of the solution concentration measuring device in a preferred embodiment of the present invention;

[0027] Figure 2 This is a diagram of the laser beams refracted for the first and second times inside the hollow glass block in a preferred embodiment of the present invention;

[0028] Figure 3 This is a diagram showing the relationship between the distance between the two light spots and the refractive index in a preferred embodiment of the present invention.

[0029] Figure labeling: 1. Laser driver circuit; 2. Laser; 3. Half-wave plate; 4. First polarizing beam splitter prism; 5. Glass block; 6. Sample flow cell; 7. Second polarizing beam splitter prism; 8. Image sensor. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed", "equipped", "sleeved / connected", "connected", etc., should be interpreted broadly. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0033] The following is in conjunction with the appendix Figures 1-3 This application will be described in further detail.

[0034] This embodiment provides a method for real-time detection of solution refractive index based on polarization beam splitting differential measurement. Based on the implementation of this method, a solution concentration measuring device is provided. The solution concentration measuring device includes a laser 2, a half-wave plate 3, a first polarization beam splitter prism 4, a second polarization beam splitter prism 7, a hollow glass block 5, and an image sensor 8. The hollow part of the hollow glass block 5 forms a sample flow cell 6, and the sample flow cell 6 contains the solution to be measured.

[0035] The laser beam is divided into components 3 in a 50:50 ratio by a half-wave plate. The sample flow cell 6 has an axisymmetric polygonal cross-section. The first polarizing beam splitter prism 4 and the second polarizing beam splitter prism 7 are arranged vertically and are cemented together. The two polarizing beam splitters are cemented together on the side of the hollow glass block 5 facing the laser 2. The image sensor 8 is cemented together on the side of the hollow glass block 5 away from the laser 2. The laser 2 is connected to a laser driving circuit 1, which drives the laser 2 to emit laser light.

[0036] The first polarizing beam splitter 4, the second polarizing beam splitter 7, and the hollow glass block 5 constitute an optical system. The laser emitted by the laser 2 passes through the half-wave plate 3 to adjust the ratio of the s-polarized light and p-polarized light components in the beam, and then passes through the first polarizing beam splitter 4 to split the light into s-polarized light and p-polarized light. The p-polarized light is transmitted through the first polarizing beam splitter 4 and then shines on the image sensor 8 after passing through the hollow glass block 5. The s-polarized light is refracted by the first polarizing beam splitter 4 to the second polarizing beam splitter 7, and then refracted by the second polarizing beam splitter 7 to the hollow glass block 5 before shining on the image sensor 8. Since the first polarizing beam splitter 4 and the second polarizing beam splitter 7 are arranged vertically, and the sample flow cell 6 has an axisymmetric polygonal cross-section, forming a symmetrical design, the propagation paths of the s-polarized light and p-polarized light in the sample flow cell 6 are completely symmetrical.

[0037] This embodiment provides a method for real-time detection of the refractive index of a solution based on polarization beam splitting differential measurement, including the following steps:

[0038] Step A: A laser beam is emitted by a laser source. The ratio of s-polarized to p-polarized components in the laser beam is adjusted by a half-wave plate. Then, the laser beam is split into two beams by a first polarizing beam splitter, one of which is s-polarized and the other is p-polarized. The p-polarized beam is transmitted through the first polarizing beam splitter and then shines on the image sensor after passing through a hollow glass block. The s-polarized beam is refracted by the first polarizing beam splitter to a second polarizing beam splitter, and then refracted by the second polarizing beam splitter to shine on the image sensor after passing through the hollow glass block. The hollow interior of the hollow glass block forms a sample flow cell with an axisymmetric polygonal cross-section.

[0039] Step B: The s-polarized light and p-polarized light are imaged as two spots on the image sensor. The distance x between the two spots on the image sensor is recorded. The refractive index of the solution is inverted using the distance x between the two spots. The calculation steps are as follows:

[0040] Let the parameters of the insulating glass and the solution sample be , and the glass refractive index be . The thickness at the axis of symmetry of the sample flow cell is ,Right now Figure 2 The length of segment DE is The angle of vertex D on the axis of symmetry is Let the center distance between the first polarizing beam splitter and the second polarizing beam splitter be . The refractive index of the solution to be tested is ;

[0041] p-polarized light enters the sample flow cell from the hollow glass block at point A. The first refraction of the p-polarized light occurs at point A. Let the angle of incidence at point A be θ. ,like Figure 2 The calculation formula is: ;

[0042] According to the law of refraction: ;in, For the refractive index of glass, The refractive index of the solution to be tested is... The angle of refraction is ; the angle between the refracted ray of p-polarized light and the incident ray in the solution is . ;

[0043] The p-polarized light exits the sample flow cell to the hollow glass block at point B. The second refraction of the p-polarized light occurs at point B. Figure 2 Based on symmetry, the angle of incidence at point B is... The angle of refraction is The light rays emitted from point B are parallel to the light rays in front of point A, and the p-polarized light finally illuminates point C on the image sensor.

[0044] like Figure 2 Point A is the first intersection of the incident p-polarized light ray and the sample cell. The second intersection of the extension of the incident light ray and the sample cell is point F. Connecting points A, B, and F forms triangle ABF.

[0045] The angle of triangle ABF at point A is The length of side AF is According to the triangle relationship , This represents the distance (length) from point A to point B. The distance (length) from point A to point F. , Let F be the angle. ; Angle B is the angle. , can be obtained ;

[0046] Point B is the intersection of the p-polarized light ray and the sample cell. A perpendicular line is drawn from point B to the extension of the incident light ray, intersecting at point G. The line segment BG represents the offset distance of the light ray. According to geometric relationships, we can obtain That is, ;

[0047] p-polarized light enters from point A, refracts at point A, illuminates point B, refracts again at point B, and exits at point C. The exiting ray is parallel to the ray direction on the incident side at point A, following the BC direction. Due to the symmetrical design of the measuring device, the propagation paths of s-polarized and p-polarized light are completely symmetrical. Therefore, the distances between the s-polarized and p-polarized light illuminating the image sensor are... The distance between the two light spots on the image sensor is ;

[0048] Therefore, by measuring the distance x between the two light spots on the image sensor, the refractive index of the solution can be obtained by inversion. , (like Figure 3 ).

[0049] The above description is merely a preferred embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention by those skilled in the art within the scope of the technology disclosed in the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A method for real-time detection of the refractive index of a solution based on polarization beam splitting differential measurement, characterized in that: The method includes a solution concentration measuring device for implementing the method, the solution concentration measuring device including a laser, a half-wave plate, a first polarizing beam splitter prism, a second polarizing beam splitter prism, a hollow glass block, and an image sensor, wherein the hollow portion of the hollow glass block forms a sample flow cell, and the sample flow cell contains the solution to be tested. The sample flow cell has an axisymmetric polygonal cross-section; the first polarizing beam splitter and the second polarizing beam splitter are arranged vertically and are glued together; the two polarizing beam splitters are glued together on the side of the hollow glass block facing the laser, and the image sensor is glued together on the side of the hollow glass block away from the laser. The half-wave plate is disposed between the laser and the first polarizing beam splitter; the half-wave plate is used to adjust the component ratio of s-polarized light and p-polarized light in the laser beam; the half-wave plate adjusts the laser components at a ratio of 50:

50. The method includes the following steps: Step A: A laser beam is emitted by a laser source. The ratio of s-polarized to p-polarized components in the laser beam is adjusted by a half-wave plate. The laser beam is then split into s-polarized and p-polarized light by a first polarizing beam splitter. The p-polarized light is transmitted through the first polarizing beam splitter and then shines onto the image sensor after passing through a hollow glass block. The s-polarized light is refracted by the first polarizing beam splitter to a second polarizing beam splitter, and then refracted by the second polarizing beam splitter to shine onto the image sensor after passing through the hollow glass block. The hollow interior of the hollow glass block forms a sample flow cell. Step B: The s-polarized light and p-polarized light are imaged as two light spots on the image sensor. The distance x between the two light spots on the image sensor is recorded, and the refractive index of the solution is inverted through the distance x between the two light spots. The sample flow cell has an axisymmetric polygonal cross-section structure, which makes the propagation paths of the s-polarized light and p-polarized light in the sample flow cell symmetrical, and the outgoing light rays are parallel to the direction of the incident light rays.

2. The method for real-time detection of solution refractive index based on polarization beam splitting differential measurement according to claim 1, characterized in that: The specific calculation steps in step B are as follows: Let the parameters of the insulating glass and the solution sample be , and the glass refractive index be . The sample flow cell has an axisymmetric polygonal cross-section, and the thickness at the axis of symmetry of the sample flow cell is... The angle of vertex D on the axis of symmetry is Let the center distance between the first polarizing beam splitter and the second polarizing beam splitter be . The refractive index of the solution to be tested is ; p-polarized light enters the sample flow cell from the hollow glass block at point A. The first refraction of the p-polarized light occurs at point A. Let the angle of incidence at point A be θ. The calculation formula is: ; According to the law of refraction: ;in, The angle of refraction is ; the angle between the refracted ray of p-polarized light and the incident ray in the solution is . ; The p-polarized light exits the sample flow cell at point B into the hollow glass block. The second refraction of the p-polarized light occurs at point B. Due to symmetry, the angle of incidence at point B is... The angle of refraction is The light rays emitted from point B are parallel to the light rays in front of point A, and the p-polarized light finally illuminates point C on the image sensor. Point A is the first intersection of the incident p-polarized light ray and the sample cell. The second intersection of the extended incident light ray and the sample cell is point F. Connecting points A, B, and F forms triangle ABF. The angle of triangle ABF at point A is The length of side AF is According to the triangle relationship , The distance from point A to point B. Let F be the distance between point A and point F. , Let F be the angle. ; Angle B is the angle. , can be obtained ; Point B is the intersection of the p-polarized light ray and the sample cell. A perpendicular line is drawn from point B to the extension of the incident light ray, intersecting at point G. The line segment BG represents the offset distance of the light ray. According to geometric relationships, we can obtain That is, ; Based on the characteristic that the sample flow cell has an axisymmetric polygonal cross-section, the propagation paths of s-polarized light and p-polarized light within the hollow glass block are completely symmetrical. Therefore, the distances from which s-polarized light and p-polarized light illuminate the image sensor can be calculated as follows: The distance between the two light spots on the image sensor is The refractive index of the solution can be obtained by measuring the distance x between two light spots on the image sensor. .

3. The method for real-time detection of solution refractive index based on polarization beam splitting differential measurement according to claim 1, characterized in that: The laser is connected to a laser driving circuit, which is used to drive the laser to emit laser light.

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