A method for real-time detection of solution refractive index based on a focused spot of a compound lens

Abstract

This application provides a real-time solution refractive index detection method based on a composite lens focusing spot, comprising the following steps: Step A: The laser emitted by the laser diode is collimated into parallel light by a collimating plano-convex cylindrical lens. The parallel light enters a hollow glass block, the interior of which includes a sample flow cell. The parallel light passes through the hollow glass block and enters the sample flow cell, and then exits from the hollow glass block onto an image sensor; Step B: The parallel light is imaged as a spot on the image sensor, and the spot on the image sensor is recorded. The solution refractive index is inverted by the size of the spot. By designing the hollow glass block, the entire hollow glass block can be regarded as a plano-concave glass cylindrical lens, a biconvex solution cylindrical lens, and a biconcave glass cylindrical lens, forming a composite lens structure. By analyzing the spot morphology of the composite lens structure, the solution refractive index is inverted, thereby improving the resolution of low-refractive-index transparent solutions.

Description

Technical Field

[0001] This invention relates to the field of optical detection technology, and in particular to a method for real-time detection of solution refractive index based on a focused spot of a composite lens. Background Technology

[0002] Existing technologies for detecting transparent solutions have significant shortcomings. Contact-type instruments (such as hydrometers) require direct immersion in the solution, making them susceptible to chemical corrosion and difficult to clean. Furthermore, they are prone to evaporation errors when detecting volatile solutions like alcohol. Traditional refractometers, while capable of measuring refractive index, require manual sampling and are highly susceptible to ambient light interference, making them unsuitable for continuous production environments such as winemaking and chemical distillation. Laser interferometry offers high sensitivity to changes in solution refractive index, but its optical path adjustment is complex and its stability is extremely poor under vibration. Moreover, existing technologies have weak resolution for low-refractive-index transparent solutions and are easily affected by temperature fluctuations. Summary of the Invention

[0003] To address the problem of weak resolution of low-refractive-index transparent solutions in existing technologies, this invention provides a real-time solution refractive index detection method based on a focused spot of a composite lens. By analyzing the spot morphology of the composite lens, the refractive index of the solution is inverted, thereby improving the resolution of low-refractive-index transparent solutions and enhancing the detection stability of transparent solutions such as alcohol.

[0004] To address the aforementioned technical problems, this application provides a method for real-time detection of solution refractive index based on a focused spot of a composite lens, employing the following technical solution:

[0005] A method for real-time detection of solution refractive index based on a focused spot of a compound lens, the method comprising the following steps:

[0006] Step A: The laser emitted by the laser diode is collimated into parallel light by a collimating plano-convex cylindrical lens. The parallel light enters the hollow glass block, which contains a sample flow cell. The parallel light enters the sample flow cell through the hollow glass block and then exits onto the image sensor.

[0007] Step B: Parallel light is imaged as a light spot on the image sensor. The light spot on the image sensor is recorded, and the refractive index of the solution is inverted by the size of the light spot.

[0008] In step B, the calculation steps for the refractive index of the inverted solution are as follows:

[0009] Let the width of the laser beam be Let the parameters of the hollow glass block and the sample flow cell be: the refractive index of the hollow glass block is... The refractive index of the test solution in the sample flow cell is The cross-section of the sample flow cell is a circle with a radius of curvature of . Let the distance between the ray and the optical axis at a certain point be ; And the angle between it and the optical axis is ;

[0010] When the laser beam enters the sample flow cell from the hollow glass block, let point B be the incident point of the sample flow cell. At point B, let the ray vector be... Based on the overall geometric relationship of the hollow glass block, the visible light vector is... ;

[0011] According to the law of refraction The refraction matrix of the interface at point B can be obtained as follows: Then the vector of the ray emitted from point B. ;

[0012] Let point C be the exit point of the sample flow cell. The transmission matrix of the light rays emitted from point B to point C is: Then the incident ray vector at point C is... ;

[0013] According to the law of refraction, the refraction matrix of the interface at point C is: Then the vector of the ray emitted from point C is... ;

[0014] Let point D be the exit point of the hollow glass block, and let the center thickness of the double concave cylindrical lens structure be... Then the transmission matrix of the light ray emitted from point C to point D is: The incident ray vector at point D can be obtained. ;

[0015] Then the refraction matrix of the interface where point D is located is The vector of the ray emitted from point D can be obtained. ;

[0016] Let point E be the incident point of the image sensor, and let the distance between the center of the light exit surface of the double concave cylindrical lens structure and the center of the image sensor be . Then the transmission matrix of the light ray emitted from point D to point E is: The incident ray vector at point E can be obtained. ;

[0017] The results obtained from the above formula are as follows: ; This is the radius of the light spot formed on the image sensor.

[0018] In a preferred embodiment, a solution refractive index measuring device is included for the detection method. The solution refractive index measuring device includes a laser diode, a collimating plano-convex cylindrical lens, a hollow glass block containing a cylindrical sample flow cell, and an image sensor arranged sequentially along the optical path.

[0019] The side of the hollow glass block facing the collimating plano-convex cylindrical lens is the light incident surface, and the side facing the image sensor is the light exit surface. The light incident surface is a plane, and the light exit surface is a concave surface.

[0020] In a preferred embodiment, the light incident surface of the hollow glass block and the inner cylindrical sample flow cell and the arc surface of its adjacent side form a plano-concave glass column lens structure, the light emitting surface of the hollow glass block and the inner cylindrical sample flow cell and the arc surface of its adjacent side form a biconcave glass column lens, and the inner cylindrical sample flow cell is a biconvex solution column lens structure.

[0021] The plano-concave glass cylindrical lens structure, the biconvex solution cylindrical lens structure, and the biconcave glass cylindrical lens constitute a composite lens structure.

[0022] In a preferred embodiment, the laser emitted by the laser diode is collimated into parallel light by the collimating plano-convex cylindrical lens, and the parallel light enters the sample flow cell through the plano-concave cylindrical lens structure, and then exits onto the image sensor by the biconcave cylindrical lens structure.

[0023] In a preferred embodiment, a laser diode driver circuit board is disposed on the back of the laser diode for controlling the laser diode to emit laser light.

[0024] In a preferred embodiment, the image sensor is a CMOS image sensor.

[0025] In a preferred embodiment, the , , .

[0026] In summary, this application has the following beneficial effects:

[0027] 1. This invention introduces a composite lens structure design and analyzes the spot morphology of the composite lens structure to invert the refractive index of the solution, thereby improving the resolution of transparent solutions with low refractive index. The spot analysis method realizes refractive index detection by analyzing the difference in the spot morphology after the beam is transmitted. It has the advantages of being non-contact and having a fast response. There are no moving parts, and the response is fast. It can directly measure the increase and decrease of the refractive index of the solution without back-and-forth movement, which significantly improves the detection stability of transparent solutions such as alcohol.

[0028] 2. This invention provides a method for real-time detection of the refractive index of a solution. The laser emitted by the laser diode is collimated into parallel light by a collimating plano-convex cylindrical lens. The parallel light passes through a plano-concave cylindrical lens structure and enters the sample flow cell. Then, it is emitted by a double concave cylindrical lens structure onto an image sensor and imaged as a light spot. The refractive index of the solution is inverted by analyzing the change in the size of the light spot. The entire process is optical measurement without contact with the solution, which is suitable for non-contact rapid measurement of the refractive index of liquids, especially for the refractive index detection of transparent to semi-transparent liquids such as alcohol and sugar solutions.

[0029] 3. This invention designs a hollow glass block, which can be viewed as a composite lens consisting of a plano-concave glass cylindrical lens, a biconvex solution cylindrical lens, and a biconcave glass cylindrical lens. This composite lens structure facilitates the fabrication of the hollow glass block, ensuring stability, robustness, and reliability. The final biconcave glass cylindrical lens diffuses light and then amplifies it, significantly improving the system's detection sensitivity and resolving power for low-refractive-index transparent solutions. The entire optical assembly is integrated, preventing optical path misalignment and greatly enhancing system reliability, particularly improving the detection stability for transparent solutions such as alcohol. Because the composite lens structure is a single, integrated device, rather than separate components, vibration interference is avoided, improving vibration resistance. Attached Figure Description

[0030] Figure 1 This is a structural distribution diagram of the solution refractive index measuring device in a preferred embodiment of the present invention;

[0031] Figure 2 This is a diagram showing the light spot morphology analysis of the composite lens in a preferred embodiment of the present invention.

[0032] Figure 3 This is a graph showing the relationship between the solution refractive index and the image sensor spot radius in a preferred embodiment of the present invention.

[0033] Explanation of reference numerals in the attached figures: 1. Laser diode driver circuit board; 2. Laser diode; 3. Collimating plano-convex cylindrical lens; 4. Plano-concave cylindrical lens structure; 5. Sample flow cell; 6. Biconcave cylindrical lens structure; 7. Image sensor. Detailed Implementation

[0034] 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.

[0035] 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.

[0036] 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.

[0037] The following is in conjunction with the appendix Figures 1-3 This application will be described in further detail.

[0038] This embodiment provides a method for real-time detection of solution refractive index based on a composite lens focusing spot, which is used for non-contact rapid measurement of liquid refractive index, and is especially suitable for the detection and real-time monitoring of refractive index of transparent to semi-transparent liquids such as alcohol, sugar solution and electrolyte solution.

[0039] refer to Figure 1 This embodiment also provides a solution refractive index measuring device based on the detection method. The device includes a laser diode, a collimating plano-convex cylindrical lens, a hollow glass block containing a sample flow cell, and an image sensor arranged sequentially along the optical path. A laser diode driver circuit board is disposed on the back of the laser diode to control the laser diode to emit laser light. The image sensor is a CMOS image sensor.

[0040] The hollow glass block has a cylindrical sample flow cell in its center, which serves as the channel for the solution to be tested, containing the solution to be tested. The side of the hollow glass block facing the collimating plano-convex cylindrical lens is the light incident surface, and the side facing the image sensor is the light exit surface. The light incident surface is planar, and the light exit surface is concave. The light incident surface of the hollow glass block, the internal cylindrical sample flow cell, and the adjacent arc surface together form a plano-concave glass cylindrical lens structure. The light exit surface of the hollow glass block, the internal cylindrical sample flow cell, and the adjacent arc surface together form a biconcave glass cylindrical lens. The internal cylindrical sample flow cell can be considered as a biconvex solution cylindrical lens structure. Therefore, the hollow glass block as a whole can be viewed as a three-close-fitting lens system consisting of a plano-concave glass cylindrical lens, a biconvex solution cylindrical lens, and a biconcave glass cylindrical lens. The overall structure of the hollow glass block and the sample flow cell constitute a composite lens structure.

[0041] The laser light emitted by the laser diode passes sequentially through the collimating plano-convex cylindrical lens and the hollow glass block, and is finally imaged as a light spot on the image sensor. The refractive index of the solution is inverted by the morphology of the light spot on the image sensor. Specifically, the laser light emitted by the laser diode is collimated into parallel light by the collimating plano-convex cylindrical lens, the parallel light passes through the plano-concave cylindrical lens structure and enters the sample flow cell, and then exits through the biconcave cylindrical lens structure onto the image sensor. The solution refractive index measurement device provided in this embodiment achieves solution refractive index measurement by detecting changes in the light spot morphology.

[0042] refer to Figure 2 Based on the solution refractive index measuring device provided above, the detection method provided in this embodiment includes the following steps:

[0043] Step A: The laser emitted by the laser diode is collimated into parallel light by a collimating plano-convex cylindrical lens. The parallel light passes through a plano-concave cylindrical lens structure and enters the sample flow cell, and then exits through a double concave cylindrical lens structure onto the image sensor.

[0044] Step B: Parallel light is imaged as a light spot on the image sensor. The light spot on the image sensor is recorded, and the refractive index of the solution is inverted by the size of the light spot.

[0045] In step B, the calculation steps for the refractive index of the inverted solution are as follows:

[0046] Let the width of the laser (parallel light) beam be... Let the parameters of the hollow glass block and the sample flow cell be: the refractive index of the hollow glass block is... The refractive index of the test solution in the sample flow cell is The cross-section of the sample flow cell is a circle with a radius of curvature of . Let the distance between the ray and the optical axis at a certain point be ; And the angle between it and the optical axis is ;

[0047] When the laser (parallel light) enters the sample flow cell through the plano-concave cylindrical lens structure, let point B be the incident point of the sample flow cell. At point B, let the light vector be... ,vector That is, the position vector of the light ray, where This represents the distance between the incident ray and the optical axis at point B. This represents the angle (in radians) between the incident ray and the optical axis at point B; based on the overall geometry of the hollow glass block, the visible ray vector is... ;

[0048] According to the law of refraction The refraction matrix of the interface at point B can be obtained as follows: ,in, Let be the radius of curvature; then the vector of the ray emitted from point B (the ray emitted from point B is the ray that enters the solution from point B) is... ,in This represents the distance between the emitted ray and the optical axis at point B. This represents the angle (in radians) between the emitted ray and the optical axis at point B; as shown in the figure, ; This represents the angle between the emitted ray at point B and the optical axis (in radians).

[0049] Let point C be the exit point of the sample flow cell, based on the radius of curvature of the sample flow cell. The transmission matrix of the light ray emitted from point B to point C can be obtained as follows: Then the incident ray vector at point C Wherein, the incident ray at point C is the ray that enters from point B and travels to point C. This represents the distance between the incident ray and the optical axis at point C. This represents the angle between the incident ray and the optical axis at point C (in radians).

[0050] Similarly, according to the law of refraction, the refraction matrix of the interface at point C is: Then the vector of the ray emitted from point C is... Wherein, the ray emitted from point C is the ray emitted from point C to point D. This represents the distance between the emitted ray and the optical axis at point C. This represents the angle (in radians) between the emitted ray at point C and the optical axis. As shown in the diagram, ;

[0051] Let point D be the exit point of the hollow glass block, and let the center thickness of the double concave cylindrical lens structure be... Then the transmission matrix of the light ray emitted from point C to point D is: The incident ray vector at point D can be obtained. ,in, This represents the distance between the incident ray and the optical axis at point D. This represents the angle between the incident ray and the optical axis at point D (in radians).

[0052] Assume the refractive index of air is At normal temperature and pressure, the refractive index of air Approximately 1, the refraction matrix of the interface where point D is located can be obtained as follows: Then the vector of the ray emitted from point D. In this context, the ray emitted from point D is the same ray that enters the air from point D. This represents the distance between the emitted ray and the optical axis at point D. This represents the angle (in radians) between the emitted ray and the optical axis at point D; as shown in the figure, ;

[0053] Let point E be the incident point of the image sensor, and let the distance between the center of the light exit surface of the double concave cylindrical lens structure and the center of the image sensor be . Then the transmission matrix of the light ray emitted from point D to point E is: The incident ray vector at point E can be obtained. ,in This represents the distance between the incident ray and the optical axis at point E. This represents the angle between the incident ray and the optical axis at point E (in radians).

[0054] The results obtained from the above formula are as follows: ;

[0055] That is, we can derive the following: ;

[0056] Since light is imaged as a spot on the image sensor, then This can represent the radius of the light spot formed by the image sensor. Based on symmetry, the diameter of the light spot imaged on the image sensor is... Then based on the spot radius and solution refractive index The refractive index of the solution can be calculated by inversion based on the size of the light spot. The relationship between solution refractive index and image sensor spot radius is shown in the diagram. Figure 3 .

[0057] 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 solution refractive index based on a focused spot of a compound lens, characterized in that: The detection method includes the following steps: Step A: The laser emitted by the laser diode is collimated into parallel light by a collimating plano-convex cylindrical lens. The parallel light enters the hollow glass block, which contains a sample flow cell. The parallel light enters the sample flow cell through the hollow glass block and then exits onto the image sensor. Step B: Parallel light is imaged as a light spot on the image sensor. The light spot on the image sensor is recorded, and the refractive index of the solution is inverted by the size of the light spot. In step B, the calculation steps for the refractive index of the inverted solution are as follows: Let the width of the laser beam be Let the parameters of the hollow glass block and the sample flow cell be: the refractive index of the hollow glass block is... The refractive index of the test solution in the sample flow cell is The cross-section of the sample flow cell is a circle, and the radius of curvature of the circle of the sample flow cell is... Let the distance between the ray and the optical axis at a certain point be ; And the angle between it and the optical axis is ; When the laser beam enters the sample flow cell from the hollow glass block, let point B be the incident point of the sample flow cell. At point B, let the ray vector be... Based on the overall geometric relationship of the hollow glass block, the visible light vector is... ; According to the law of refraction The refraction matrix of the interface at point B can be obtained as follows: Then the vector of the ray emitted from point B. ; Let point C be the exit point of the sample flow cell. The transmission matrix of the light rays emitted from point B to point C is: Then the incident ray vector at point C is... ; According to the law of refraction, the refraction matrix of the interface at point C is: Then the vector of the ray emitted from point C is... ; Let point D be the exit point of the hollow glass block, and let the center thickness of the double concave cylindrical lens structure be... Then the transmission matrix of the light ray emitted from point C to point D is: The incident ray vector at point D can be obtained. ; Then the refraction matrix of the interface where point D is located is The vector of the ray emitted from point D can be obtained. ; Let point E be the incident point of the image sensor, and let the distance between the center of the light exit surface of the double concave cylindrical lens structure and the center of the image sensor be . Then the transmission matrix of the light ray emitted from point D to point E is: The incident ray vector at point E can be obtained. ; Calculation results: ; This is the radius of the light spot formed on the image sensor.

2. The method for real-time detection of solution refractive index based on a focused spot using a compound lens according to claim 1, characterized in that: The invention includes a solution refractive index measuring device for the detection method, the solution refractive index measuring device comprising a laser diode, a collimating plano-convex cylindrical lens, a hollow glass block containing a cylindrical sample flow cell, and an image sensor arranged sequentially along the optical path; The side of the hollow glass block facing the collimating plano-convex cylindrical lens is the light incident surface, and the side facing the image sensor is the light exit surface. The light incident surface is a plane, and the light exit surface is a concave surface.

3. The method for real-time detection of solution refractive index based on a focused spot using a composite lens according to claim 2, characterized in that: The light incident surface of the hollow glass block and the inner cylindrical sample flow cell and the arc surface on its adjacent side form a plano-concave glass column lens structure. The light exit surface of the hollow glass block and the inner cylindrical sample flow cell and the arc surface on its adjacent side form a biconcave glass column lens. The inner cylindrical sample flow cell is a biconvex solution column lens structure. The plano-concave glass cylindrical lens structure, the biconvex solution cylindrical lens structure, and the biconcave glass cylindrical lens constitute a composite lens structure.

4. The method for real-time detection of solution refractive index based on a focused spot using a composite lens according to claim 3, characterized in that: The laser emitted by the laser diode is collimated into parallel light by the collimating plano-convex cylindrical lens. The parallel light passes through the plano-concave glass cylindrical lens structure and enters the sample flow cell, and then exits through the biconcave cylindrical lens structure onto the image sensor.

5. The method for real-time detection of solution refractive index based on a focused spot of a compound lens according to claim 2, characterized in that: A laser diode driver circuit board is disposed on the back of the laser diode for controlling the laser diode to emit laser light.

6. The method for real-time detection of solution refractive index based on a focused spot using a composite lens according to claim 2, characterized in that: The image sensor is a CMOS image sensor.

7. The method for real-time detection of solution refractive index based on a focused spot using a compound lens according to claim 1, characterized in that: The , , .

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