High-precision liquid refractive index detection system and its detection method

Abstract

This invention discloses a high-precision liquid refractive index detection system and method, comprising a laser, a transparent substrate, a convex lens, a prism sample cell, and a spot detection unit. The laser emits visible light in parallel beams. The transparent substrate is used for photolithographic printing of a computational hologram, the original image of which is a pure black background containing a one-pixel-wide white vertical line. The convex lens images the object light wave reconstructed from the obtained computational hologram, resulting in a line spot optical reconstruction image. The prism sample cell holds the liquid to be tested. The spot detection unit is positioned on the image plane of the convex lens and is used to detect the pixel position at the center of the line spot reconstruction image. By analyzing the pixel position at the center of the line spot reconstruction image detected by the spot detection unit, the refractive index of the liquid to be tested in the prism sample cell can be measured. This application features a simple structure, convenient operation, low cost, and high detection sensitivity and accuracy.

Description

Technical Field

[0001] This application relates to the field of precision detection technology for liquid refractive index, and in particular to a high-precision detection system and method for liquid refractive index. Background Technology

[0002] Refractive index is one of the important optical properties of a medium. In many fields such as automobile manufacturing, daily chemical industry, food industry, pharmaceutical manufacturing and petrochemical industry, the refractive index measurement of related liquids has become a common process control standard.

[0003] Currently, there are various methods for detecting the refractive index of liquids. Based on the detection principle, they can be categorized into geometrical optics, interferometry, and spectroscopic methods. The critical angle method for total internal reflection (also known as the Abbe method) is a typical geometrical optics method for measuring the refractive index of liquids. A mature commercial instrument, the Abbe refractometer, has been developed. However, the Abbe refractometer's detection accuracy is generally in the range of 0.001 to 0.0001, making it difficult to achieve higher precision in liquid refractive index measurement. Interferometry and spectroscopic methods can measure liquid refractive index with higher precision, but these methods are often complex and expensive. Summary of the Invention

[0004] Therefore, it is necessary to provide a high-precision liquid refractive index detection system. The high-precision liquid refractive index detection system of the present invention has advantages such as simple structure, convenient operation, low cost, and high detection sensitivity and accuracy.

[0005] One embodiment of this application provides a high-precision liquid refractive index detection system.

[0006] A high-precision liquid refractive index detection system includes a laser, a transparent substrate, a convex lens, a prism sample cell, and a spot detection unit;

[0007] The laser is used to emit visible light in a parallel laser beam;

[0008] A computational hologram is disposed on the transparent substrate, wherein the original image of the computational hologram is a pure black background containing a white vertical line with a width of one pixel;

[0009] The convex lens is used to image the object light wave reproduced by the computational hologram on the transparent substrate to obtain a line spot with an imaging width of 80μm~120μm.

[0010] The prism sample cell is used to hold the liquid to be tested.

[0011] The spot detection unit is disposed on the image plane of the convex lens. The spot detection unit is used to detect the pixel position of the center of the line spot reconstructed image. By analyzing the pixel position of the center of the line spot reconstructed image detected by the spot detection unit, the refractive index of the liquid to be tested in the sample cell of the prism can be measured.

[0012] In some embodiments, the spot of a parallel laser beam emitted by the laser covers the computational hologram.

[0013] In some embodiments, the center of the computational hologram is located on the optical axis of the convex lens.

[0014] In some embodiments, the prism sample cell has an inverted trapezoidal structure.

[0015] In some embodiments, the prism sample cell has a capacity of less than 1 mL.

[0016] In some embodiments, the prism sample cell is transparent, the bottom surface of the prism sample cell is horizontal, the two sidewalls of the prism sample cell for incident light and outgoing light are inclined, and the two sidewalls gradually move away from the bottom to the top, and the thickness of the two sidewalls is no more than 0.5 mm.

[0017] In some embodiments, the pixel arrangement direction of the linear array detection surface of the spot detection unit is perpendicular to the length direction of the reconstructed linear spot image.

[0018] In some embodiments, the spot detection unit is a line CCD.

[0019] In some embodiments, the angle between the spot detection unit and the horizontal direction is adjustable.

[0020] One embodiment of this application also provides a method for high-precision detection of liquid refractive index.

[0021] A high-precision method for detecting the refractive index of a liquid, employing the aforementioned high-precision liquid refractive index detection system, includes the following steps:

[0022] Place the liquid to be tested into the prism sample cell;

[0023] Control the laser to emit visible light in a parallel laser beam;

[0024] A computational hologram is set on a transparent substrate;

[0025] The diffraction field of the computational hologram is imaged by a convex lens to obtain a line spot optical reconstruction image with an imaging width of 80μm~120μm.

[0026] The system controls the spot detection unit to detect the pixel position at the center of the reconstructed image of the line spot, analyzes the pixel position at the center of the reconstructed image of the line spot detected by the spot detection unit, and obtains the refractive index of the liquid under test based on the standard curve.

[0027] In some embodiments, the computational hologram is calculated using a method for calculating a modified off-axis interferometric computational hologram based on the Bocchi coding method, and the calculation formula (1) is:

[0028] ℎ(x, y) = 0.5{1 + cos[2παx - φ(x, y)]} (1)

[0029] Where ℎ(x, y) is the transmittance function for calculating the (x, y) coordinates of the hologram, α is the carrier frequency of the off-axis reference light, and φ(x, y) is the phase distribution of the object wave in the original image at the (x, y) coordinates.

[0030] The aforementioned high-precision liquid refractive index detection system includes a laser, a transparent substrate, a convex lens, a prism sample cell, and a spot detection unit. This system is simple in structure, low in cost, easy to operate, and offers high sensitivity and accuracy, making it suitable for precise detection of liquid refractive index. A parallel laser beam emitted by the laser illuminates a computational hologram on the transparent substrate. The diffracted light wave is imaged by the convex lens, and the imaged beam passes through a prism sample cell containing the liquid to be tested, before being imaged onto the spot detection unit. Due to the strong dispersion characteristics of the prism sample cell and the fact that the width of the linear optically reconstructed image on the spot detection unit is only on the order of micrometers, the refractive index of the liquid can be measured by reading the pixel position information at the center of the linear optically reconstructed image acquired by the spot detection unit. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings. In the following description, the same reference numerals denote the same parts.

[0033] Figure 1 This is a high-precision liquid refractive index detection system according to an embodiment of the present invention;

[0034] Figure 2 This is the original image of the computational hologram in one embodiment of the present invention;

[0035] Figure 3Photolithography on a transparent substrate Figure 2 The computational hologram of the original image shown;

[0036] Figure 4 for Figure 3 The calculation shows the +1 order optical reconstruction of the hologram;

[0037] Figure 5 To Figure 3 Calculated hologram after directional filtering;

[0038] Figure 6 To be Figure 5 The calculation of holography is shown. Figure 2 A computational hologram 1:1 photolithographically printed onto a transparent substrate after valueization; the line areas in the figure represent the computational hologram.

[0039] Figure 7 for Figure 6 The calculation shows the +1 order optical reconstruction of the hologram;

[0040] Figure 8 for Figure 6 The calculation shows the 0th-order optical reconstruction of the hologram;

[0041] Figure 9 This is a physical image of the prism sample cell in one embodiment of the present invention;

[0042] Figure 10 This illustrates the relationship between the pixel position at the center of the line spot reconstructed image acquired by the spot detection unit in one embodiment of the present invention and the refractive index of the NaCl solution.

[0043] Explanation of reference numerals in the attached figures

[0044] 10. High-precision liquid refractive index detection system; 100. Laser; 200. Transparent substrate; 300. Convex lens; 400. Prism sample cell; 500. Spot detection unit. Detailed Implementation

[0045] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0046] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" 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 this invention and 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 this invention.

[0047] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0048] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0049] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0050] In this document, "optionally," "optionally," and "optional" mean that something is optional, that is, it is selected from either "with" or "without." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. In this application, descriptions such as "optionally contains" and "optionally includes" indicate "contains or does not contain."

[0051] In this application, when numerical intervals (i.e., numerical ranges) are mentioned, unless otherwise specified, the distribution of selectable numerical values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every numerical value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, etc.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0053] This application provides a high-precision liquid refractive index detection system to address at least one of the following problems in the prior art for liquid refractive index detection: (1) the detection accuracy of Abbe refractometers based on the total internal reflection critical angle method is generally in the range of 0.001 to 0.0001, making it difficult to achieve higher precision liquid refractive index measurement; (2) interferometry and spectroscopy systems are complex and expensive. The high-precision liquid refractive index detection system will be described below with reference to the accompanying drawings.

[0054] The high-precision liquid refractive index detection system provided in this application is exemplary; please refer to [link to example]. Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of the high-precision liquid refractive index detection system provided in this application. The high-precision liquid refractive index detection system of this application can be used for high-precision liquid refractive index detection, and it is small in size, simple in equipment, and has high detection accuracy.

[0055] To more clearly illustrate the structure of the high-precision liquid refractive index detection system, the following description, in conjunction with the accompanying drawings, will be provided.

[0056] For example, please refer to Figure 1As shown, a high-precision liquid refractive index detection system includes a laser, a transparent substrate, a convex lens, a prism sample cell, and a spot detection unit.

[0057] The laser is used to emit visible light in a parallel laser beam.

[0058] A computational hologram is disposed on the transparent substrate, wherein the original image of the computational hologram is a pure black background containing a white vertical line with a width of one pixel;

[0059] The convex lens is used to image the object light wave reproduced by the computational hologram on the transparent substrate, and obtain a line spot with an imaging width of 80μm~120μm.

[0060] The prism sample cell is used to hold the liquid to be tested.

[0061] The spot detection unit is positioned on the image plane of the convex lens. The spot detection unit is used to detect the pixel position at the center of the reconstructed image of the line spot. By analyzing the pixel position at the center of the reconstructed image of the line spot detected by the spot detection unit, the refractive index of the liquid to be tested, contained in the prism sample cell, can be measured.

[0062] In some embodiments, the computational hologram disposed on the transparent substrate is calculated using the Borg coding method and then printed onto the transparent substrate using photolithography.

[0063] It should be noted that the Burch coding method replaces the bias term composed of the intensity distribution of the reference light and the intensity distribution of the object light wave in the transmittance function of the off-axis optical hologram by adding a DC bias. This operation can not only reduce the bandwidth requirement of the hologram, but also improve the computational efficiency and the accuracy of the reconstructed image.

[0064] In one embodiment, the imaging width of the line spot is 80 μm, and in another embodiment, the imaging width of the line spot is 120 μm. It is easy to understand that in other examples, the imaging width of the line spot can also be 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, or other values ​​and any range between any two of the above values.

[0065] In some embodiments, the spot of a parallel laser beam emitted by a laser covers the holographic computation map.

[0066] In some embodiments, the laser is a semiconductor laser. A semiconductor laser, also known as a diode laser, is a laser emitting device that uses semiconductor materials as the working medium. The working principle of a semiconductor laser is based on stimulated emission, that is, when electrons in a semiconductor material transition from a high energy level to a low energy level, they release photons. These photons further stimulate more electron transitions, generating coherent light radiation and forming a laser. The advantages of using a semiconductor laser in this application include: (1) High efficiency conversion: Compared with other types of lasers, semiconductor lasers have higher electro-optic conversion efficiency. (2) Miniaturization: Due to the use of microelectronics manufacturing technology, semiconductor lasers can be made into very small sizes. (3) Long lifespan: Under appropriate operating conditions, the lifespan of a semiconductor laser can be very long. (4) Wide wavelength range: By selecting different semiconductor materials, laser output of different wavelengths from ultraviolet to infrared can be obtained. (5) High modulation speed: The injected current can be directly modulated at high speed, which is suitable for fields such as communications that require fast signal processing. (6) Cost-effectiveness: With the development of technology and large-scale production, the cost of semiconductor lasers has gradually decreased, making their widespread application possible.

[0067] In some of these embodiments, the photolithography process is performed at a 1:1 scale.

[0068] In some embodiments, the transparent substrate is soda glass.

[0069] In some embodiments, the center of the computed hologram is located on the optical axis of the convex lens.

[0070] In some embodiments, the prism sample cell has an inverted trapezoidal structure.

[0071] In some embodiments, the prism sample cell has a capacity of less than 1 mL.

[0072] In some embodiments, the prism sample cell is transparent. The bottom surface of the prism sample cell is horizontal. Both sidewalls of the prism sample cell, used for incident and outgoing light, are inclined, and gradually move away from each other from the bottom to the top. The thickness of the two sidewalls is no greater than 0.5 mm.

[0073] In this application, the prism sample cell adopts an inverted trapezoidal structure design to facilitate leakage, prevent air bubbles from being generated when the liquid to be tested is injected into the prism sample cell, and reduce the capacity of the prism sample cell. The top of the prism sample cell is designed with an inclination. In order to reduce aberrations, the left inclined surface (i.e., the light-incident surface) and the right inclined surface (i.e., the light-exit surface) are both made of transparent acrylic with the thinnest possible thickness. In this embodiment, the sidewall of the prism sample cell is made of 0.5mm thick transparent acrylic.

[0074] In some embodiments, the pixel arrangement direction of the linear array detection surface of the spot detection unit is perpendicular to the length direction of the reconstructed linear spot image.

[0075] In some embodiments, the spot detection unit is a linear CCD. A linear CCD (Linear CCD) is a type of photosensitive sensor, consisting of a series of closely packed photosensitive elements (pixels). These elements convert received light signals into electrical signals, which are then processed by subsequent circuitry to form image information. A key characteristic of linear CCDs is that they typically have only one or a few rows of photosensitive units, unlike area CCDs, which have a two-dimensional array of photosensitive units and can capture an entire scene at once. Linear CCDs are primarily used in applications requiring high resolution and high precision. When using a linear CCD for imaging, a mechanical motion system is generally required to move the scanned object relative to the linear CCD at a constant speed, or the linear CCD itself moves relative to the scanned object, thereby completing the scanning of the entire surface.

[0076] In some embodiments, the angle between the spot detection unit and the horizontal direction is adjustable.

[0077] One embodiment of this application also provides a method for high-precision detection of liquid refractive index.

[0078] In this document, unless otherwise stated, the reaction steps may be performed in the order described herein or not. For example, other steps may be included between reaction steps, and the order of reaction steps may be appropriately interchanged. This is something that those skilled in the art can determine based on conventional knowledge and experience. Preferably, the reaction methods described herein are performed sequentially.

[0079] A high-precision method for detecting the refractive index of a liquid, employing the aforementioned high-precision liquid refractive index detection system, includes the following steps:

[0080] The liquid to be tested is placed in the prism sample cell.

[0081] Control the laser to emit visible light in a parallel laser beam.

[0082] A computational hologram is set on a transparent substrate;

[0083] The diffraction field of the computational hologram is imaged by a convex lens to obtain a line spot optical reconstruction image with an imaging width of 80μm~120μm.

[0084] The control spot detection unit detects the pixel position of the center of the reconstructed image of the line spot, analyzes the pixel position of the center of the reconstructed image of the line spot detected by the spot detection unit, and obtains the refractive index of the liquid under test based on the standard curve.

[0085] In some embodiments, the original computational hologram is calculated using a method for calculating a modified off-axis interferometric computational hologram based on the Bocchi coding method, and the calculation formula (1) is:

[0086] ℎ(x, y) = 0.5{1 + cos[2παx - φ(x, y)]} (1)

[0087] Where ℎ(x, y) is the transmittance function for calculating the (x, y) coordinates of the hologram, α is the carrier frequency of the off-axis reference light, and φ(x, y) is the phase distribution of the object wave in the original image at the (x, y) coordinates.

[0088] The aforementioned high-precision liquid refractive index detection system includes a laser, a transparent substrate, a convex lens, a prism sample cell, and a spot detection unit. This system is simple in structure, low in cost, easy to operate, and offers high sensitivity and accuracy, making it suitable for precise detection of liquid refractive index. A parallel laser beam emitted by the laser illuminates a computational hologram on the transparent substrate. The diffracted light wave is imaged by the convex lens, and the imaged beam passes through a prism sample cell containing the liquid to be tested, before being imaged onto the spot detection unit. Due to the strong dispersion characteristics of the prism sample cell and the fact that the width of the optically reconstructed line spot image on the spot detection unit is only on the order of micrometers, the refractive index of the liquid can be measured by reading the pixel position information at the center of the line spot acquired by the spot detection unit.

[0089] Example 1

[0090] This embodiment provides a high-precision liquid refractive index detection system.

[0091] The high-precision liquid refractive index detection system includes a laser, a transparent substrate, a convex lens, a prism sample cell, and a spot detection unit.

[0092] A laser is used to emit visible light in parallel beams. The spot of the parallel laser beam emitted by the laser covers a computational hologram on a transparent substrate. The laser is a semiconductor laser.

[0093] The computational hologram, calculated using the Burch coding method, was printed onto a transparent substrate using 1:1 photolithography. The center of the computational hologram is located on the optical axis of the convex lens. The original image of the computational hologram consisted of a pure black background containing a one-pixel-wide white vertical line.

[0094] A convex lens is used to image the object light wave reconstructed from the computational hologram, obtaining a line spot optical reconstruction image with an imaging width of about 100 μm.

[0095] The prism sample cell is used to hold the liquid to be tested. The capacity of the prism sample cell is less than 1 mL. The prism sample cell has an inverted trapezoidal structure. The prism sample cell is transparent. The bottom surface of the prism sample cell is horizontal. Both the incident and exit light rays of the prism sample cell have inclined sidewalls, which gradually move away from each other from the bottom to the top. The thickness of the two sidewalls is 0.5 mm.

[0096] The spot detection unit is a line CCD.

[0097] The spot detection unit is positioned on the image plane of the convex lens. The pixel arrangement direction of the linear array detection surface of the spot detection unit is perpendicular to the length direction of the reconstructed linear spot image. The spot detection unit is used to detect the pixel position at the center of the reconstructed linear spot image. By analyzing the pixel position at the center of the reconstructed linear spot image detected by the spot detection unit, the refractive index of the liquid to be tested in the prism sample cell can be measured.

[0098] Example 2

[0099] This embodiment provides a high-precision liquid refractive index detection system for detecting the refractive index of NaCl solution.

[0100] This embodiment uses the high-precision liquid refractive index detection system from Embodiment 1.

[0101] See Figure 1 As shown, Figure 1 This invention provides a high-precision liquid refractive index detection system according to an embodiment of the present invention.

[0102] In this embodiment, the laser is a semiconductor laser, which emits a laser with a wavelength of 654.2nm and a circular spot shape with a diameter of 1cm; the focal length of the convex lens is 40cm.

[0103] A high-precision method for detecting the refractive index of liquids includes the following steps:

[0104] (1) Place the liquid to be tested in the prism sample cell.

[0105] (2) Control the laser to emit visible light in a parallel laser beam.

[0106] (3) The computational hologram obtained by the Boch coding method is printed on a transparent substrate by 1:1 photolithography.

[0107] (4) Calculate the object light wave reproduced by the hologram and image it by the convex lens to obtain a line spot optical reproduction image with an imaging width of about 100 μm.

[0108] (5) Control the pixel position of the center of the line spot reconstructed image detected by the spot detection unit, analyze the pixel position of the center of the line spot detected by the spot detection unit, and obtain the refractive index of the liquid to be tested based on the standard curve.

[0109] in, Figure 2 The original image of the computational hologram in Embodiment 2 of the present invention is 350×350 pixels in size. The original image is a pure black background containing only a white vertical line with a width of one pixel.

[0110] Figure 3 for Figure 2 The computational hologram of the original image shown is 350×350 pixels in size. It is calculated using the method of corrected off-axis interferometric computational hologram based on the Bocchi coding method. The calculation formula (1) is as follows:

[0111] ℎ(x, y) = 0.5{1 + cos[2παx - φ(x, y)]} (1)

[0112] Where ℎ(x, y) is the transmittance function for calculating the (x, y) coordinates of the hologram, α is the carrier frequency of the off-axis reference light, and φ(x, y) is the phase distribution of the object wave in the original image at the (x, y) coordinates.

[0113] Figure 4 for Figure 3 The calculation of the +1 order optical reconstruction image of the hologram is shown, from... Figure 4 As can be seen, because the computer performs discrete calculations, the reconstructed image has obvious discontinuities in the length direction. In order to make the discontinuities in the length direction of the reconstructed image disappear and become uniform, the hologram needs to be processed by directional filtering, which involves cutting off the high-frequency information in the vertical direction.

[0114] Figure 5 To Figure 3 The calculated hologram after directional filtering is a hologram that retains only the 8 rows of pixels at the center in the vertical direction.

[0115] In this embodiment, the calculated computational hologram needs to be photolithographically printed out for use. Figure 6 To be Figure 5 The calculation of holography is shown. Figure 2 The computational hologram is printed at a 1:1 scale using photolithography after value-enhancing. The linear areas in the image represent the computational hologram, with each pixel measuring 16 μm. The printing medium is a transparent substrate.

[0116] Figure 7 for Figure 6 The image shown is a +1 order optical reconstruction of the hologram with a width of 77 μm.

[0117] Figure 8 for Figure 6The 0th-order optical reconstruction image of the computational hologram shown has a width of 118 μm. Since the 0th-order optical reconstruction image has the strongest intensity and is affected by the 0-frequency diffraction light of the computational hologram, its width is larger than that of the +1st-order optical reconstruction image.

[0118] In this embodiment, Figure 7 +1 level optical reconstruction image and Figure 8 The 0th-order optical reconstruction image in the image was captured using a CCD array under the condition of a parallel beam of the same power emitted by the laser.

[0119] In this embodiment, due to Figure 8 The 0th-order optical reconstruction image shown has the strongest intensity, so this spot is used as the target tracking spot for refractive index detection and is received and detected by the linear CCD.

[0120] Figure 9 This is a physical image of a prism sample cell according to one embodiment of the present invention. The cell wall is made of transparent acrylic sheet, and the capacity of the prism sample cell is 0.8 mL. To facilitate leakage, it is designed as an inverted trapezoid. To prevent air bubbles from forming when the liquid to be tested is injected and to reduce the capacity of the prism sample cell, the top is designed with an inclination. To reduce aberrations, both the left inclined surface (i.e., the side facing the incident light) and the right inclined surface (i.e., the side facing the outgoing light) are made of transparent acrylic with the thinnest possible thickness. In this embodiment, the prism sample cell is made of 0.5 mm thick transparent acrylic.

[0121] In this embodiment, the linear CCD has 10,500 linear pixels, and the pixel size is 4 μm. The angle between the linear CCD and the horizontal direction is 9.2°. This is because when the refractive index of the solution in the prism sample cell is high, the imaging beam is positioned closer to the prism and at a lower height.

[0122] Figure 10 This is a schematic diagram showing the relationship between the pixel position of the center of the line spot acquired by the spot detection unit in one embodiment of the present invention and the refractive index of the NaCl solution. The vertical axis represents the pixel position of the center of the line spot, and the horizontal axis represents the refractive index of the NaCl solution. The refractive index of the NaCl solution is measured in the range of 1.333076 to 1.361575. Within this refractive index range, the pixel position of the center of the line spot acquired by the line CCD moves by 9167 pixels. Figure 10 In the model, the pixel position at the center of the linear spot exhibits a near-linear relationship with the refractive index of the NaCl solution, with a linearity as high as 0.9988. The calculated sensitivity is 321660 pixels per refractive index unit, and the accuracy can reach 3.1 × 10⁻⁶. -6 .according to Figure 10The linear relationship between the pixel positions of the centers of multiple line spots acquired by the line CCD and the refractive index of the NaCl solution is shown in the figure. A standard curve is plotted based on this standard curve. The refractive index of any liquid in the range of 1.333076 to 1.361575 can be measured.

[0123] In summary, the high-precision liquid refractive index detection system of the present invention has the advantages of simple structure, convenient operation, low price, and high detection sensitivity and accuracy.

[0124] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0125] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0126] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A liquid refractive index high-precision detection system, characterized in that, The system comprises a laser, a transparent substrate, a convex lens, a prism sample cell and a light spot detection unit. The laser is used to emit visible light of parallel laser beams. The transparent substrate is provided with a computer hologram, and an original drawing of the computer hologram comprises a white vertical line with a pixel width in a pure black background. The convex lens is used to image object light waves reproduced by the computer hologram on the transparent substrate, so as to obtain a line light spot with an imaging width of 80-120 μm. The prism sample cell is used to contain a liquid to be measured. The light spot detection unit is arranged on an image plane of the convex lens, and is used to detect a pixel position of a center of a line light spot reproduction image.

2. The liquid refractive index high-precision detection system according to claim 1, characterized in that, The laser emits visible light of parallel laser beams, and a light spot of the visible light covers the computer hologram on the transparent substrate.

3. The liquid refractive index high-precision detection system according to claim 1, characterized in that, A center of the computer hologram on the transparent substrate is located on an optical axis of the convex lens.

4. The liquid refractive index high-precision detection system according to claim 1, characterized in that, The prism sample cell has an inverted trapezoidal structure. The prism sample cell has a capacity of less than 1 mL.

5. The liquid refractive index high-precision detection system according to any one of claims 1-4, characterized in that, The prism sample cell is transparent, a bottom surface of the prism sample cell is horizontally arranged, two side walls of the prism sample cell for incident light and emergent light are inclined, and the two side walls gradually move away from each other from the bottom to the top, and a thickness of the two side walls is not greater than 0.5 mm.

6. The liquid refractive index high-precision detection system according to any one of claims 1-4, characterized in that, A pixel arrangement direction of a line array detection surface of the light spot detection unit is perpendicular to a length direction of a line light spot reproduction image.

7. The liquid refractive index high-precision detection system according to any one of claims 1-4, characterized in that, The light spot detection unit is a line CCD.

8. The liquid refractive index high-precision detection system according to claim 7, characterized in that, An angle between the light spot detection unit and a horizontal direction is adjustable.

9. A method for high-precision detection of the refractive index of a liquid, characterized in that The liquid refractive index high-precision detection system comprises the following steps: The liquid to be measured is placed in the prism sample cell. The laser is controlled to emit visible light of parallel laser beams. The transparent substrate is provided with the computer hologram. A diffraction light field of the computer hologram is imaged by the convex lens to obtain a line light spot optical reproduction image with an imaging width of 80-120 μm. The light spot detection unit is controlled to detect a pixel position of a center of the line light spot reproduction image, the pixel position of the center of the line light spot reproduction image detected by the light spot detection unit is analyzed, and a refractive index of the liquid to be measured is obtained based on a standard curve.

10. The liquid refractive index high-precision detection method according to claim 9, characterized in that, The computer hologram is calculated by a modified off-axis interference type computer hologram calculation method based on a Bogachev encoding method, and a calculation formula (1) is as follows: h(x, y) = 0.5{1 + cos[2παx - φ(x, y)]} (1) wherein h(x, y) is a transmittance function of the computer hologram at an (x, y) coordinate, α is a carrier frequency of off-axis reference light, and φ(x, y) is a phase distribution of object light waves of an original drawing at the (x, y) coordinate.

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