High-precision detection device and method for liquid meniscus contour in capillary tube

Abstract

The invention belongs to the field of image spectrum detection, and particularly relates to a high-precision detection device and method for a liquid meniscus contour in a capillary tube. Comprising a telecentric lens, an industrial camera, a displacement platform, a light source, a capillary tube and a culture dish, the industrial camera, the capillary tube and the culture dish are installed on different displacement platforms respectively, the light source is provided with a rotary telescopic rod and can move in all directions, when the liquid meniscus contour in the capillary tube is shot, the light source, the meniscus of the capillary tube and the industrial camera are adjusted to be aligned to the same horizontal plane, and on the basis of the telecentric imaging principle, according to the light refraction principle, the liquid meniscus contour in the capillary tube is obtained. And deriving a distortion correction function of the meniscus contour in the capillary tube. According to the invention, the industrial camera and the telecentric lens are matched for use, the problem of shape distortion caused by object distance change is avoided, and the difficulty of image distortion correction is reduced. The meniscus contour distortion correction function derived based on the telecentric imaging principle can accurately calculate the actual value of the meniscus contour and restore the actual meniscus contour.

Description

Technical Field

[0001] The invention belongs to the field of image spectrum detection, and in particular relates to a high-precision detection device and method for the contour of a liquid meniscus in a capillary. Background Art

[0002] Capillary action is widely used in geology, petroleum engineering, bioengineering and other fields. Accurately describing the process of capillary phenomena can help us better understand the dynamic behavior of liquids in capillary tubes, which is inseparable from the support of reliable measurement technology.

[0003] In the prior art, the liquid column in the cylindrical capillary is usually used as the object for related research. However, due to the refraction of light, the meniscus profile of the liquid column directly collected has optical distortion. There are usually two ways to weaken or correct the distortion. Method 1: One is to place the capillary in a box filled with a specific liquid, and minimize the optical distortion by matching the refractive index of the liquid and the tube wall; Method 2: Considering that the capillary does not distort in the vertical direction, the curvature radius of the meniscus profile is calculated by the height of the liquid under the meniscus in the capillary;

[0004] For method 1: Since there is air in the middle of the meniscus, light will still refract from liquid to air, and the direction of light propagation will still shift, making it difficult to completely eliminate optical distortion. For method 2: The formula for the radius of curvature is obtained under the premise that the contour of the meniscus is an arc, so this correction method has a systematic error. In order to obtain accurate measurement results, X-ray measurement technology can also be used to measure the contour of the meniscus, but the cost of using this technology is high and X-rays are harmful to the human body to a certain extent, which is not conducive to long-term experiments. Therefore, it is urgent for technicians in this field to solve the above technical problems. Summary of the invention

[0005] The technical problem to be solved by the present invention is that in the above-mentioned prior art, since there is air in the middle of the meniscus, light will still refract from liquid to air, the direction of light propagation will still shift, and optical distortion is difficult to completely eliminate; the meniscus is approximated as an arc, and the formula for the radius of curvature of the meniscus is obtained to correct the meniscus profile, and the correction method has systematic errors; using X-rays to measure the meniscus profile is harmful to the human body and is not conducive to long-term experiments.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A high-precision detection device for the contour of a liquid meniscus in a capillary comprises a telecentric lens, an industrial camera, a displacement platform, a light source, a capillary and a culture dish; the industrial camera, the capillary and the culture dish are respectively mounted on the displacement platform, a rotating telescopic rod is further provided on the optical platform, the light source is mounted on the rotating telescopic rod, the capillary is fixed directly above the culture dish by a V-shaped serrated clamp, and the light source, the liquid meniscus in the capillary and the industrial camera are aligned on the same horizontal plane.

[0008] By adopting the above technical solution, the industrial camera is installed on the displacement platform and used in conjunction with the telecentric lens to ensure that no matter how the diameter of the capillary tube and the height of the liquid column in the tube change, the captured meniscus profile image can maintain the same proportion and resolution as the actual meniscus profile, thereby avoiding the shape distortion problem caused by the change in the distance of the object. The capillary is fixed just above the culture dish by a V-shaped serrated clamp, which not only provides stable support, but also facilitates the rapid adjustment of the position of the capillary to meet the needs of different experimental conditions. At the same time, the displacement platform allows the height and angle of the industrial camera to be precisely adjusted, further improving the flexibility and operability of the system. The design of the light source alignment industrial camera, combined with appropriate shading measures, can provide uniform and non-interference lighting, fully retain the details of the meniscus profile, reduce the interference of excess light, and make the collected meniscus profile image clearer and more accurate, which is conducive to subsequent data analysis. The entire device has a compact and reasonable structure, and all components are centrally arranged on a platform, which simplifies the experimental setting process and reduces the difficulty of operation. In addition, this integrated design is also conducive to the daily maintenance and calibration of the equipment. Compared with expensive X-ray imaging technology, the solution proposed by the present invention is not only economical but also harmless to the human body. It is suitable for long-term experimental research, which greatly reduces the cost of scientific research and ensures the safety of researchers. Through the above-mentioned carefully designed experimental device, optical distortion can be effectively reduced, and the accuracy of meniscus profile measurement can be improved, providing more reliable data support for the study of the dynamic behavior of liquids in capillaries.

[0009] Furthermore, the telecentric lens includes an object lens, an aperture stop and an image lens; the distance between the object lens and the image lens is the sum of their focal lengths, and the aperture stop is located at the common focus of the object lens and the image lens.

[0010] By adopting the above technical solution, a key feature of the telecentric lens is that it has a large depth of field range and more flexible focusing. This means that for the same object, no matter how far or close the object is from the lens, the image size remains the same. This eliminates the perspective distortion caused by changes in viewing angle, so that the meniscus profile at different distances can be recorded at the same scale, improving the consistency and accuracy of the measurement. By adjusting the camera target surface, the height of the capillary meniscus, and the light source are aligned on the same horizontal plane. The parallel light passing through the capillary meniscus is received by the telecentric lens. After the flat light passes through the lens group in the telecentric lens, it is inverted in the radial direction of the meniscus and proportionally reduced in the circumferential direction of the meniscus, and is received by the camera target surface, thereby reducing the blurring effect caused by the difference in refractive index, improving the overall clarity and detail expression of the image, and maintaining a good focusing effect throughout the range even if the height of the liquid column in the capillary changes. This is particularly important for studies that require observation of dynamic changes in liquid columns, as it allows clear image sequences to be obtained without adjusting the focal length. Since the images produced by the telecentric lens are distortion-free, no complex geometric distortion correction algorithms are required in subsequent data processing, which simplifies the data processing process and speeds up experimental analysis.

[0011] Furthermore, the bottom of the industrial camera also includes an optical platform, and a computer is also arranged on the optical platform; the industrial camera is electrically connected to the computer.

[0012] By adopting the above technical solution, a stable base is provided, which reduces the influence of external vibration on the imaging process, ensures the clarity of the image and the accuracy of the data, and the fixing devices such as the V-shaped sawtooth clamp and the displacement platform further enhance the overall stability of the system. The electrical connection between the industrial camera and the computer enables the collected data to be immediately transmitted to the computer for processing and analysis, thereby improving work efficiency. Through the image acquisition software supporting the camera, the image white balance parameters and exposure time can be set to enhance the light and dark contrast of the meniscus image while ensuring that the image is not overexposed, and quickly and accurately extract the detailed information of the meniscus contour. Due to the special optical path and light source design in the detection device, the contour of the gas-liquid interface in the meniscus grayscale image is clear and distinct, and the contour curve is extracted in MATLAB according to the grayscale difference. The extracted contour curve is subjected to distortion correction according to the distortion correction formula (19) in claim 6. The scale set behind the light source provides a reference for the actual size of the image, which is convenient for converting pixel units into physical units, thereby achieving more accurate measurement. The displacement platform under the culture dish allows the experimenter to adjust the height and horizontal position of the culture dish as needed to adapt to different experimental conditions or research purposes, enhancing the flexibility of the system. The industrial camera is installed on the displacement platform, which can accurately control the position and angle of the camera to ensure the best imaging perspective. All components (including industrial cameras, telecentric lenses, light sources, capillaries, culture dishes and computers) are integrated on one platform, which simplifies the construction and maintenance of the experimental device. The integrated design makes the entire system easier to operate, reduces the experimental preparation time, and also facilitates daily maintenance work.

[0013] The present invention also includes a high-precision detection method for the contour of a meniscus of liquid in a capillary, wherein the contour of a meniscus of liquid in a capillary is detected by the high-precision detection device for the contour of a meniscus of liquid in a capillary, including the industrial camera being fixed on the optical platform via the displacement platform, the industrial camera being adjusted to be horizontal according to a spirit level before the experiment, the capillary being fixed and suspended in the culture dish filled with liquid via the V-shaped serrated clamp, the tail of the V-shaped serrated clamp being connected to the displacement platform, the displacement platform being adjusted so that the capillary is perpendicular to a horizontal plane, the light source being arranged on the right side of the capillary, the light source being a diffuse reflection surface light source, and a shielding member being used to limit the axial width of the light source to reduce the light reaching the imaging system through the air in the meniscus.

[0014] By adopting the above technical solution, the capillary is adjusted to be perpendicular to the horizontal plane through the displacement platform, which helps to accurately capture the contour of the meniscus and avoid measurement errors caused by tilt. The use of a diffuse surface light source can provide soft and uniform lighting, reduce highlights and shadows caused by direct illumination, and thus improve the overall clarity and contrast of the image. By limiting the axial width of the light source through the shielding piece, the light refracted from the air in the meniscus can be effectively reduced, reducing noise interference and making the imaging clearer. The displacement platform is not only used to fix the industrial camera, but is also connected to a V-shaped serrated clamp, allowing precise fine-tuning of the position of the capillary, further enhancing the stability of the entire system. All key components (such as industrial cameras, capillaries, light sources, etc.) are integrated on one platform, simplifying the construction process of the experimental device and facilitating quick setup and start of experiments. The design of the displacement platform and the V-shaped serrated clamp makes it simple and quick to adjust the position of the capillary and the industrial camera, and convenient for experimenters to flexibly adjust according to needs.

[0015] Furthermore, the displacement platform is adjusted so that the liquid in the culture dish is in full contact with the lower end of the capillary, and after the height of the liquid column in the capillary is stabilized, the position of the light source is adjusted and the meniscus image is captured using the industrial camera.

[0016] By adopting the above technical solution, the displacement platform adjusts the height of the culture dish to ensure that the liquid column in the capillary starts to rise from the same initial height in each experiment, thereby ensuring the consistency of the experimental conditions and allowing the liquid column to reach a stable state before the experiment begins, avoiding measurement errors caused by the instability of the liquid column. After the height of the liquid column is stable, the position of the light source is adjusted to ensure that the light is evenly irradiated on the meniscus, avoiding uneven illumination caused by changes in the liquid column, thereby improving the quality of the image. Imaging when the liquid column is stable reduces image blur or distortion caused by liquid column fluctuations, making the collected meniscus contour clearer. Only when the height of the liquid column is stable can the true shape of the meniscus be accurately captured, which is crucial for subsequent data analysis. By ensuring the stability of the liquid column and uniform illumination, the system errors caused by external factors can be minimized, thereby improving the reliability of the measurement results.

[0017] Further, the parallel light rays are received by the target surface of the industrial camera;

[0018] Wherein, F'C' is the incident light, θ4' is the incident angle of F'C', θ3' is the refraction angle of F'C', θ2' is the incident angle of C'B', θ1' is the refraction angle of C'B', θ1 is the incident angle of B'B, θ2 is the refraction angle of B'B, θ3 is the incident angle of BC, θ4 is the refraction angle of BC, the point of tangency of the light path of CF with the meniscus when passing through the liquid is point P, the distance P0 from point P to the center of the circle O is the radial distance on the object side, point A" is the midpoint of the length of the reverse extension line of CF in the capillary, the distance A"O from point A" to the center of the circle O is the radial distance on the image side, and the refractive indices of the liquid, capillary wall and air in the capillary are n1, n2 and n3 respectively;

[0019] According to Snell's law:

[0020] n1sinθ1=n2sinθ2 (2)

[0021] n1sinθ1'=n2sinθ2' (3);

[0022] In ΔB'OB, |OB'|=|OB|, so θ1=θ1', that is: θ2=θ2';

[0023] A is the intersection of the extended line BC and OA". According to the sine theorem, in ΔOAB:

[0024] ∠OBA=θ2

[0025]

[0026] In ΔOAC:

[0027]

[0028] Right now:

[0029]

[0030] D is the intersection of the extended line of B'C' and the inner diameter. According to the sine theorem, in ΔODB':

[0031] ∠OB'D=θ2'

[0032]

[0033] In ΔODC':

[0034]

[0035] Right now:

[0036]

[0037] According to equations (3), (6), and (9), we can obtain: θ3 = θ3';

[0038] According to Snell's law:

[0039] n2sinθ3=n3sinθ4 (10);

[0040] n2sinθ3'=n3sinθ4'(11);

[0041] have to

[0042] θ4=θ4′(12);

[0043] In ΔB'PO

[0044] |OP|=sinθ1'·R i (13);

[0045] From formula (2) and formula (11), we can get:

[0046]

[0047] and:

[0048]

[0049] Substituting formula (9) into (14) we get:

[0050]

[0051] In ΔOA”C:

[0052]

[0053] Substituting equation (17) into equation (16), we get

[0054]

[0055] Substituting formula (17) into formula (13) yields:

[0056]

[0057] When the refractive index of air (n3) is 1, the above formula is:

[0058] |OP=|A”O / n1 (19);

[0059] That is: image radial distance = object radial distance × liquid refractive index;

[0060] In the shooting of the capillary meniscus profile image, the ratio of the outer diameter to the inner diameter of the capillary is greater than the refractive index of the liquid in the capillary.

[0061] By adopting the above technical solution, the refraction path of light in different media (liquid, capillary wall, air) is analyzed in detail, and Snell's law is used for calculation, so that the image distortion caused by light refraction can be accurately corrected. According to formula (19), the image radial distance is equal to the object radial distance multiplied by the liquid refractive index. This provides a direct and accurate method to correct the radial size in the image. The corrected image data is more consistent, reducing the systematic error caused by optical distortion and improving the repeatability and reliability of the measurement. The corrected image radial distance can be directly converted into the actual object radial distance, which simplifies the subsequent data processing and analysis process and does not require repeated measurement. The complex geometric correction algorithm is unnecessary because the telecentric lens has provided an image with almost no distortion, which further simplifies the data analysis process. The entire correction process is based on known physical laws and simple mathematical operations, which is easy to program and implement, and convenient for researchers to quickly apply. Through clear physical models and mathematical formulas, researchers can more intuitively understand the formation mechanism of the meniscus profile and the cause of its distortion, so as to better optimize the experimental design. This method is not only applicable to water, but also to other liquids with different refractive indices, which enhances the versatility of the method. As long as the ratio of the outer diameter to the inner diameter of the capillary is greater than the refractive index of the liquid, this method can be used for capillaries of various specifications and has strong adaptability.

[0062] The present invention has the following beneficial effects:

[0063] 1. The present invention effectively eliminates image distortion caused by light refraction by using a telecentric lens and an optical distortion correction method based on Snell's law. The image radial distance is equal to the object radial distance multiplied by the liquid refractive index, thereby achieving accurate radial dimension correction. This method ensures high consistency and accuracy of the imaging results and significantly improves the accuracy of meniscus profile measurement.

[0064] 2. The present invention optimizes the experimental device design, including the integrated layout of industrial camera, displacement platform, light source and displacement platform, so that the experimental setting is simpler and faster. The correction method based on physical laws and mathematical formulas simplifies the data processing process and reduces the need for complex geometric correction algorithms, which not only improves the experimental efficiency, but also enhances the intuitiveness and operability of data processing;

[0065] 3. The present invention is applicable to a variety of liquids with different refractive indices and can be used for capillaries of various specifications. Compared with the expensive and harmful X-ray imaging technology, the conventional optical elements and computer software used in the present invention greatly reduce the experimental cost, are suitable for long-term and frequent experimental operations, and provide an economical and efficient solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a schematic diagram of the structure of the telecentric lens of the present invention;

[0067] Figure 2 It is a schematic diagram of the meniscus profile curve distortion correction principle of the present invention;

[0068] Figure 3 It is a lower edge contour extraction and correction diagram of the steel ball used for inspection of the present invention;

[0069] Figure 4 It is a comparison diagram between the measured value and the actual value of the steel ball profile of the present invention;

[0070] Figure 5 is a liquid surface image of ultrapure water in the capillary of the present invention;

[0071] Figure 6 It is a comparison of the ultrapure water meniscus profile before and after correction of the present invention. DETAILED DESCRIPTION

[0072] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

[0073] In the description of the present invention, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second" and the like do not indicate the importance of the components, and therefore cannot be understood as limiting the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution, and do not limit the scope of protection of the present invention.

[0074] like Figure 1 and Figure 2 As shown, a high-precision detection device for the contour of a liquid meniscus in a capillary tube, an optical platform is located at the bottom of the device, a computer and an industrial camera are respectively arranged on the optical platform, the industrial camera is mounted on a displacement platform, a telecentric lens is also mounted on the displacement platform, the industrial camera is electrically connected to the computer, the displacement platform is used to adjust the position of the industrial camera to ensure horizontal alignment, a V-shaped sawtooth clamp is mounted on the displacement platform to fix the capillary tube to ensure that it is perpendicular to the horizontal plane, the capillary tube is located directly above a culture dish to observe the liquid meniscus and hold the liquid, the height is adjusted by the displacement platform, the displacement platform is arranged below the culture dish to adjust the height of the culture dish and control the height of the liquid column, the light source provides uniform illumination, the telecentric lens includes an object lens, an aperture diaphragm and an image lens, the distance between the object lens and the image lens is the sum of their focal lengths, the aperture diaphragm is located at the common focus of the object lens and the image lens, a black tape is used as a shield to limit the axial width of the light source to minimize the light reaching the imaging system through the air in the meniscus;

[0075] When the aperture diaphragm is small enough, almost only parallel light can pass through the entire imaging system to reach the target surface. The shape of the curved liquid surface in the capillary is equivalent to being scaled to the imaging target surface at a certain ratio, avoiding the problem of the object shape changing with the imaging distance in high-speed cameras, high-magnification lenses, etc., and improving the accuracy of the image data. The scaling ratio can be calculated by the following formula:

[0076]

[0077] Where: H1 is the actual meniscus height, H2 is the photographed meniscus height. f1 is the focal length of the object lens, and f2 is the focal length of the image lens;

[0078] The imaging system is mainly composed of an industrial camera and a telecentric lens. The industrial camera model is AVT Prosilica GT1290C, which is fixed on the optical platform through a high-precision displacement platform. Before the experiment, the industrial camera is adjusted to a horizontal level according to the level. The cleaned and dried capillary is fixed by a V-shaped serrated clamp and suspended in a culture dish filled with liquid. The tail of the V-shaped serrated clamp is connected to the high-precision displacement platform. The displacement platform is adjusted to make the capillary perpendicular to the horizontal plane. A diffuse reflection surface light source is arranged on the right side of the capillary. Under the premise of ensuring that the light source covers the contour of the meniscus, it is necessary to use black tape to limit the axial width of the light source to minimize the light reaching the imaging system through the air in the meniscus. During the experiment, the displacement platform under the culture dish is adjusted to make the liquid in the culture dish fully contact with the lower end of the capillary. After the height of the liquid column in the capillary is stable, the light source, the capillary meniscus, and the camera target surface are adjusted to be aligned on the same horizontal plane. Use an industrial camera to collect meniscus images. When collecting meniscus images, the exposure time of the industrial camera should be set to ensure that the image has a high signal-to-noise ratio without overexposure, and that the meniscus has enough details.

[0079] When light propagates in two different media, it will be refracted at the interface of the media, and the propagation direction of the light will change. When collecting the contour of the meniscus of the liquid column in a cylindrical capillary, the light will have two propagation paths. The first: the light passes through the external air-tube wall-liquid under the meniscus-air inside the meniscus-liquid under the meniscus-tube wall-external air to the imaging system. The second: the light passes through the external air-tube wall-liquid under the meniscus-tube wall-external air to the imaging system. For the first case, the direction of the light changes in both the radial and axial directions. When the light source is narrow in the axial direction, the telecentric imaging system cannot receive the light that passes through the air inside the meniscus, and the corresponding area in the grayscale image appears black. In the second case, the direction of the light only changes in the radial direction and can be received by the telecentric imaging system, but the distortion caused by the change in the radial direction of the light needs to be corrected;

[0080] The telecentric lens used in the experiment only receives parallel light. Assuming that CF is a beam of parallel light received by the target surface of the industrial camera, the optical path diagram of CF in the capillary can be inferred based on the principle of light refraction. Figure 2 The red arrowhead line is shown in the figure. The light passes through points C', B', B, and C and is received by point F on the target surface of the industrial camera. F'C' is the incident light, θ4' is the incident angle of F'C', and θ3' is the refraction angle of F'C'. θ2' is the incident angle of C'B', and θ1' is the refraction angle of C'B'. θ1 is the incident angle of B'B, and θ2 is the refraction angle of B'B. θ3 is the incident angle of BC, and θ4 is the refraction angle of BC. The point of tangency between the light path of CF and the meniscus when passing through the liquid is point P. The distance from point P to the center of the circle, point O, is the radial distance on the object side, point A” is the midpoint of the length of the reverse extension line of CF in the capillary, and the distance from point A” to the center of the circle, point O, is the radial distance on the image side. The refractive indices of the liquid, capillary wall, and air in the capillary are n1, n2, and n3, respectively.

[0081] According to Snell's law:

[0082] n1sinθ1=n2sinθ2 (2)

[0083] n1sinθ1'=n2sinθ2' (3)

[0084] In ΔB'OB, |OB'|=|OB|, so θ1=θ1', that is: θ2=θ2'

[0085] A is the intersection of the extended line BC and OA". According to the sine theorem, in ΔOAB:

[0086] ∠OBA=θ2

[0087]

[0088] In ΔOAC:

[0089]

[0090] Right now:

[0091]

[0092] D is the intersection of the extended line of B'C' and the inner diameter. According to the sine theorem, in ΔODB':

[0093] ∠OB'D=θ2'

[0094]

[0095] In ΔODC':

[0096]

[0097] Right now:

[0098]

[0099] According to equations (3), (6), and (9), we can obtain: θ3 = θ3'

[0100] According to Snell's law:

[0101] n2sinθ3=n3sinθ4 (10)

[0102] n2sinθ3'=n3sinθ4'(11)

[0103] have to

[0104] θ4=θ4'(12)

[0105] In ΔB'PO

[0106] |OP|=sinθ1'·R i (13)

[0107] From formula (2) and formula (11), we can get:

[0108]

[0109] and:

[0110]

[0111] Substituting formula (9) into (14) we get:

[0112]

[0113] In ΔOA”C:

[0114]

[0115] Substituting equation (17) into equation (16), we get

[0116]

[0117] Substituting formula (17) into formula (13) yields:

[0118]

[0119] When the refractive index of air (n3) is 1, the above formula is:

[0120] |OP=|A”O / n1 (19)

[0121] That is: image radial distance = object radial distance × liquid refractive index.

[0122] In the capture of the capillary meniscus profile image, the ratio of the outer diameter to the inner diameter of the selected capillary must be greater than the refractive index of the liquid in the capillary, otherwise the complete meniscus image cannot be captured.

[0123] like Figure 3 and Figure 4 As shown, the accuracy of the measurement method is verified by measuring the profile of a standard spherical steel ball in a capillary. In order to simulate the imaging conditions of the meniscus, the experiment needs to use a steel ball with a diameter that is the same as the inner diameter of the capillary as much as possible. Limited by the specifications of the steel ball and the capillary, the present invention uses a standard spherical steel ball with a diameter of 1.400mm and a capillary with an inner diameter of 1.402mm to carry out the accuracy verification experiment. It should be noted that the inner diameter of the selected capillary is 0.14% larger than the diameter of the steel ball, which is conducive to easily placing the steel ball into the capillary, and the resulting measurement error is acceptable.

[0124] In the experiment, the steel ball was immersed in the pure water column of the capillary. The image of the steel ball in the pure water was photographed using the measurement method proposed in the present invention, and the contour of the steel ball was extracted and corrected successively. The contour curves of the steel ball before and after correction are shown in FIG. Figure 3 shown. Figure 4 A comparison between the corrected steel ball contour curve in the capillary and the actual contour of the steel ball is given, and it can be seen that the two are almost completely consistent, with a relative root mean square error of only 1.34%. The sources of this error are two-fold: on the one hand, the inner diameter of the selected capillary is larger than the diameter of the steel ball; on the other hand, due to the limitation of pixel density, the extracted steel ball contour is stepped. The error caused by limited pixel density also exists in the measurement of the meniscus contour of the liquid column, and is also the only source of error in the measurement method proposed in the present invention. The accuracy of the measurement method of the meniscus contour of the liquid column in the capillary proposed in the present invention has been verified;

[0125] The meniscus images of ultrapure water in four sizes of quartz capillaries were obtained in the experiment. Figure 5 Each meniscus image is scaled to the same scale as shown in the figure. Figure 5 It can be seen that the meniscus of the capillary liquid column under all experimental conditions is complete. This is attributed to the fact that the ratio of the outer diameter to the inner diameter of the capillary selected in the experiment is greater than the refractive index of the liquid. Due to the special optical path and light source design in the experiment, the contour of the gas-liquid interface in the meniscus grayscale image is clear and distinct, and the contour curve can be easily extracted based on the grayscale difference. According to formula (19), the meniscus contour is corrected in the radial direction. The meniscus contour curves before and after correction are shown in Figure 6 shown.

[0126] The preferred embodiments of the present invention are described in detail above; however, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.

Claims

1. A high-precision detection device for the meniscus profile of a liquid in a capillary, characterized in that: It includes a telecentric lens, an industrial camera, a displacement platform, a light source, a capillary and a culture dish; the industrial camera, the capillary and the culture dish are respectively installed on the displacement platform, a rotating telescopic rod is also provided on the optical platform, the light source is installed on the rotating telescopic rod, the capillary is fixed directly above the culture dish by a V-shaped serrated clamp, and the light source, the meniscus of the liquid in the capillary and the industrial camera are aligned on the same horizontal plane.

2. The high-precision detection device and method for the meniscus profile of liquid in a capillary according to claim 1, characterized in that: The telecentric lens comprises an object lens, an aperture stop and an image lens; the distance between the object lens and the image lens is the sum of their focal lengths, and the aperture stop is located at the common focus of the object lens and the image lens.

3. The high-precision detection device for the meniscus profile of liquid in a capillary according to claim 1, characterized in that: The bottom of the industrial camera also includes an optical platform, and a computer is also arranged on the optical platform; the industrial camera is electrically connected to the computer.

4. A high-precision detection method for the meniscus profile of a liquid in a capillary, comprising any one of the above-mentioned high-precision detection devices for the meniscus profile of a liquid in a capillary, characterized in that: The industrial camera is fixed on the optical platform through the displacement platform. Before the experiment, the industrial camera is adjusted to be horizontal according to the spirit level. The capillary is fixed by the V-shaped serrated clamp and suspended in the culture dish filled with liquid. The tail of the V-shaped serrated clamp is connected to the displacement platform. The displacement platform is adjusted to make the capillary perpendicular to the horizontal plane. The light source is arranged on the right side of the capillary. The light source adopts a diffuse reflection surface light source. A shielding member is used to limit the axial width of the light source to reduce the light reaching the imaging system through the air in the meniscus.

5. The high-precision detection method of the meniscus profile of liquid in a capillary according to claim 4, characterized in that: The displacement platform is adjusted to make the liquid in the culture dish fully contact with the lower end of the capillary, and after the height of the liquid column in the capillary is stabilized, the position of the light source is adjusted and the meniscus image is collected using the industrial camera.

6. The high-precision detection method of the meniscus profile of liquid in a capillary according to claim 4, characterized in that: The parallel light rays are received by the target surface of the industrial camera; Wherein, F'C' is the incident light, θ4' is the incident angle of F'C', θ3' is the refraction angle of F'C', θ2' is the incident angle of C'B', θ1' is the refraction angle of C'B', θ1 is the incident angle of B'B, θ2 is the refraction angle of B'B, θ3 is the incident angle of BC, θ4 is the refraction angle of BC, the point of tangency of the light path of CF with the meniscus when passing through the liquid is point P, the distance P0 from point P to the center of the circle O is the radial distance on the object side, point A" is the midpoint of the length of the reverse extension line of CF in the capillary, the distance A"O from point A" to the center of the circle O is the radial distance on the image side, and the refractive indices of the liquid, capillary wall and air in the capillary are n1, n2 and n3 respectively; According to Snell's law: n1sinθ1=n2sinθ2 (2) n1sinθ1'=n2sinθ2' (3); In ΔB'OB, |OB'|=|OB|, so θ1=θ1', that is: θ2=θ2'; A is the intersection of the extended line BC and OA". According to the sine theorem, in ΔOAB: ∠OBA=θ2 In ΔOAC: Right now: D is the intersection of the extended line of B'C' and the inner diameter. According to the sine theorem, in ΔODB': ∠OB'D=θ2' In ΔODC': Right now: According to equations (3), (6), and (9), we can obtain: θ3 = θ3'; According to Snell's law: n2sinθ3=n3sinθ4 (10); n2sinθ3'=n3sinθ4'(11); have to θ4=θ4′(12); In ΔB'PO |OP|=sinθ1'·R i (13); From formula (2) and formula (11), we can get: and: Substituting formula (9) into (14) we get: In ΔOA”C: Substituting equation (17) into equation (16), we get Substituting formula (17) into formula (13) yields: When the refractive index of air (n3) is 1, the above formula is: OP = |A"O / n1 (19); That is: image radial distance = object radial distance × liquid refractive index; In the shooting of the capillary meniscus profile image, the ratio of the outer diameter to the inner diameter of the capillary is greater than the refractive index of the liquid in the capillary.

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