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

Abstract

The invention discloses a liquid refractive index high-precision detection system and method. The system comprises a laser, a transparent substrate, a convex lens, a prism sample pool and a light spot detection unit, the laser is used for emitting visible light of parallel laser beams; the transparent substrate is used for photoetching and printing the computer-generated hologram, and an original image of the computer-generated hologram is a white vertical line with a pixel width in a pure black background; the convex lens is used for imaging object light waves reproduced by the obtained computer-generated hologram to obtain a linear light spot optical reproduced image; the prism sample pool is used for containing to-be-detected liquid; the light spot detection unit is arranged on the image plane of the convex lens and used for detecting the pixel position of the center of the line light spot reproductive image, and the refractive index of the liquid to be detected in the prism sample pool can be detected by analyzing the pixel position, detected by the light spot detection unit, of the center of the line light spot reproductive image. The device is simple in structure, convenient to operate, low in price and high in detection sensitivity and precision.

Description

Technical Field

[0001] The present application relates to the technical field of precise detection of liquid refractive index, and in particular to a high-precision detection system and detection method of liquid refractive index. Background Art

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

[0003] At present, there are many methods for detecting the refractive index of liquids. According to the detection principle, it can be divided into geometric optics, interference and spectroscopy. The total reflection critical angle method (also known as the Abbe method) is a typical method of measuring the refractive index of liquids using geometric optics. A mature commercial instrument, the Abbe refractometer, has been developed. However, the detection accuracy of the Abbe refractometer is generally in the range of 0.001~0.0001, which makes it difficult to achieve higher-precision liquid refractive index measurement. Interference and spectroscopy can measure the refractive index of liquids with higher precision, but these detection methods are often complex and expensive. Summary of the invention

[0004] Based on this, it is necessary to provide a high-precision detection system for liquid refractive index. The high-precision detection system for liquid refractive index of the present invention has the advantages of simple structure, convenient operation, low price, high detection sensitivity and accuracy, etc.

[0005] An embodiment of the present application provides a high-precision detection system for liquid refractive index.

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

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

[0008] A computer-generated hologram is arranged on the transparent substrate, wherein the original image of the computer-generated hologram is a white vertical line with a width of one pixel in a pure black background;

[0009] The convex lens is used to image the object light wave reconstructed by the computer generated hologram on the transparent substrate to obtain a line spot with an imaging width of 80 μm to 120 μm;

[0010] The prism sample pool is used to contain the liquid to be tested;

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

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

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

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

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

[0016] In some of the embodiments, the prism sample pool is transparent, the bottom surface of the prism sample pool is horizontally arranged, the two side walls of the prism sample pool for incident light and outgoing light are inclined, and the two side walls gradually move away from the bottom to the top, and the thickness of the two side walls is not more than 0.5 mm.

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

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

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

[0020] An embodiment of the present application also provides a method for high-precision detection of liquid refractive index.

[0021] A method for high-precision detection of liquid refractive index, using the above-mentioned high-precision detection system for liquid refractive index, comprises the following steps:

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

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

[0024] A computer generated hologram is disposed on the transparent substrate;

[0025] The diffracted light field of the computer generated hologram is imaged through a convex lens to obtain an optical reconstruction image of a line spot with an imaging width of 80 μm to 120 μm;

[0026] The light spot detection unit is controlled to detect the pixel position of the center of the line light spot reconstruction image, the pixel position of the center of the line light spot reconstruction image detected by the light spot detection unit is analyzed, and the refractive index of the liquid to be tested is obtained based on the standard curve.

[0027] In some embodiments, the CGH is calculated by using a calculation method of a modified off-axis interferometric CGH based on the Bouch coding method, and the calculation formula (1) is:

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

[0029] Among them, ℎ(x, y) is the transmittance function of the calculated hologram at the (x, y) coordinate, α is the carrier frequency of the off-axis reference light, and φ(x, y) is the phase distribution of the object light wave of the original image at the (x, y) coordinate.

[0030] The above-mentioned high-precision detection system for liquid refractive index includes a laser, a transparent substrate, a convex lens, a prism sample pool and a light spot detection unit. The detection system has a simple structure, low price, convenient operation, high detection sensitivity and accuracy, and can be used for precise detection of liquid refractive index. The parallel laser beam emitted by the laser irradiates the computer hologram on the transparent substrate, and the diffracted light wave is imaged by the convex lens. The imaging beam passes through a prism sample pool containing the liquid to be tested and is imaged on the light spot detection unit. Since the prism sample pool has the characteristics of strong dispersion, and the width of the optical reconstruction image of the line light spot imaged on the light spot detection unit is only in the micrometer range, the refractive index of the liquid to be tested can be measured by reading the pixel position information of the center of the line light spot reconstruction image collected by the light spot detection unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0032] In order to more completely understand the present application and its beneficial effects, the following description will be given in conjunction with the accompanying drawings. In the following description, the same reference numerals represent the same parts.

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

[0034] Figure 2 is an original image of a computer generated hologram in one embodiment of the present invention;

[0035] Figure 3For photolithography on transparent substrates Figure 2 The computer generated hologram of the original image shown;

[0036] Figure 4 for Figure 3 The +1-level optical reconstruction image of the computer generated hologram shown;

[0037] Figure 5 For Figure 3 The CGH after directional filtering;

[0038] Figure 6 For the general Figure 5 CGH Figure 2 The CGI image printed on a transparent substrate at a ratio of 1:1 after valuating. The linear area in the figure is the CGI image.

[0039] Figure 7 for Figure 6 The +1-level optical reconstruction image of the computer generated hologram shown;

[0040] Figure 8 for Figure 6 The 0th-order optical reconstruction image of the computer generated hologram shown;

[0041] Fig. 9 A physical picture of a prism sample cell in one embodiment of the present invention;

[0042] Fig.10 It is the relationship between the pixel position of the center of the line spot reconstruction image collected by the spot detection unit in one embodiment of the present invention and the refractive index of the NaCl solution.

[0043] Description of Reference Numerals

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

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0046] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0047] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed 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 the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0048] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0049] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0050] In this article, "optionally", "optional", "optional" means optional, that is, it means to be selected from any of the two parallel solutions of "yes" or "no". If there are multiple "optional" in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent. In this application, the descriptions such as "optionally contain" and "optionally include" mean "contain or not contain".

[0051] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for a broad range of quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

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

[0054] The liquid refractive index high-precision detection system provided in the embodiments of the present application is illustrative, see Figure 1 As shown, Figure 1 The schematic diagram of the structure of the high-precision liquid refractive index detection system provided in the embodiment of the present application. The high-precision liquid refractive index detection system of the present application can be used for high-precision liquid refractive index detection, and has a small size, simple equipment and high detection accuracy.

[0055] In order to more clearly illustrate the structure of the high-precision liquid refractive index detection system, the high-precision liquid refractive index detection system will be introduced below with reference to the accompanying drawings.

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

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

[0058] A computer-generated hologram is arranged on the transparent substrate, wherein the original image of the computer-generated hologram is a white vertical line with a width of one pixel in a pure black background;

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

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

[0061] The spot detection unit is arranged 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 reconstruction image. By analyzing the pixel position of 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 pool can be measured.

[0062] In some of the embodiments, the computer generated hologram disposed on the transparent substrate is calculated using the Bodge encoding method and is printed on the transparent substrate through photolithography.

[0063] It should be noted that the Burch encoding method is to add a DC bias in the transmittance function of the off-axis optical hologram to replace the bias term composed of the intensity distribution of the reference light and the intensity distribution of the object light wave. This operation can not only reduce the bandwidth requirements of the hologram, but also improve the calculation efficiency and the accuracy of the reproduced 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 not difficult 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 ranges between any two of the above values.

[0065] In some of these embodiments, a spot of a parallel laser beam emitted by a laser overlays a hologram calculation map.

[0066] In some of the 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 working media. 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, photons are released, and 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 a higher electro-optical conversion efficiency. (2) Miniaturization: Due to the use of microelectronics manufacturing technology, semiconductor lasers can be made very small in size. (3) Long life: Under appropriate conditions of use, the life of a semiconductor laser can be very long. (4) Wide wavelength range: By selecting different semiconductor materials, laser outputs of different wavelengths from ultraviolet to infrared can be obtained. (5) Fast 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 photolithographic process is printed at a 1:1 scale.

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

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

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

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

[0072] In some embodiments, the prism sample pool is transparent. The bottom surface of the prism sample pool is horizontally arranged. The two side walls of the prism sample pool for incident light and outgoing light are both inclined. The two side walls gradually move away from the bottom to the top. The thickness of the two side walls is not greater than 0.5 mm.

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

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

[0075] In some of the embodiments, the light spot detection unit is a line CCD. Linear CCD refers to a linear charge coupled device, which is a type of photosensor. Linear CCD consists of a series of closely arranged photosensitive elements (pixels), which can convert the received light signals into electrical signals, and then form image information through subsequent circuit processing. The characteristic of line CCD is that it usually has only one or a few rows of photosensitive units, which is different from area CCD (Area CCD), which has a two-dimensional array of photosensitive units and can capture the entire scene at one time. Line CCD is mainly used in applications that require high resolution and high precision. When using line CCD for imaging, it is generally necessary to cooperate with a mechanical motion system so that the scanned object moves at a uniform speed relative to the line CCD, or the line CCD itself moves relative to the scanned object, thereby completing the scanning of the entire surface.

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

[0077] An embodiment of the present application also provides a method for high-precision detection of liquid refractive index.

[0078] In this article, unless otherwise stated, each reaction step may be carried out in the order described herein or may not be carried out in the order described herein. For example, other steps may be included between each reaction step, and the order of the reaction steps may also be appropriately swapped. This can be determined by the technician based on common knowledge and experience. Preferably, the reaction method herein is carried out sequentially.

[0079] A method for high-precision detection of liquid refractive index, using the above-mentioned high-precision detection system for liquid refractive index, comprises the following steps:

[0080] Place the liquid to be tested in the prism sample cell.

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

[0082] A computer generated hologram is disposed on the transparent substrate;

[0083] The diffracted light field of the computer-generated hologram is imaged through a convex lens to obtain an optically reproduced image of a line spot with an imaging width of 80 μm to 120 μm.

[0084] The light spot detection unit is controlled to detect the pixel position of the center of the line light spot reconstruction image, the pixel position of the center of the line light spot reconstruction image detected by the light spot detection unit is analyzed, and the refractive index of the liquid to be tested is obtained based on the standard curve.

[0085] In some embodiments, the CGH original image is calculated using a calculation method of a modified off-axis interferometric CGH based on the Bouch coding method, and the calculation formula (1) is:

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

[0087] Among them, ℎ(x, y) is the transmittance function of the calculated hologram at the (x, y) coordinate, α is the carrier frequency of the off-axis reference light, and φ(x, y) is the phase distribution of the object light wave of the original image at the (x, y) coordinate.

[0088] The above-mentioned high-precision detection system for liquid refractive index includes a laser, a transparent substrate, a convex lens, a prism sample pool and a light spot detection unit. The detection system has a simple structure, low price, convenient operation, high detection sensitivity and accuracy, and can be used for precise detection of liquid refractive index. The parallel laser beam emitted by the laser irradiates the computer hologram on the transparent substrate, and the diffracted light wave is imaged by the convex lens. The imaging beam passes through a prism sample pool containing the liquid to be tested and is imaged on the light spot detection unit. Since the prism sample pool has a strong dispersion characteristic, and the width of the optical reconstructed image of the line light spot imaged on the light spot detection unit is only in the micrometer range, the refractive index of the liquid to be tested can be measured by reading the pixel position information of the center of the line light spot collected by the light spot detection unit.

[0089] Example 1

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

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

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

[0093] The CGI calculated by the Boch coding method is printed on a transparent substrate by 1:1 photolithography. The center of the CGI is located on the optical axis of the convex lens. The original image of the CGI is a white vertical line with a pixel width in a pure black background.

[0094] The convex lens is used to image the object light wave reconstructed by the computer generated hologram to obtain an optically reconstructed image of a line spot with an imaging width of about 100μm.

[0095] The prism sample pool is used to hold the liquid to be tested. The capacity of the prism sample pool is less than 1mL. The prism sample pool is an inverted trapezoidal structure. The prism sample pool is transparent. The bottom surface of the prism sample pool is set horizontally. The two side walls of the prism sample pool for incident light and outgoing light are both inclined, and the two side walls gradually move away from the bottom to the top. The thickness of the two side walls is 0.5mm.

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

[0097] The spot detection unit is arranged 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 linear spot reconstruction image. The spot detection unit is used to detect the pixel position of the center of the linear spot reconstruction image. By analyzing the pixel position of the center of the linear spot reconstruction image detected by the spot detection unit, the refractive index of the liquid to be tested in the prism sample pool can be measured.

[0098] Example 2

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

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

[0101] See also Figure 1 As shown, Figure 1 A high-precision liquid refractive index detection system according to an embodiment of the present invention is provided.

[0102] In this embodiment, the laser is a semiconductor laser, the wavelength of the laser light emitted by the laser is 654.2 nm, the spot shape of the emitted parallel laser beam is circular, and the spot diameter is 1 cm; the focal length of the convex lens is 40 cm.

[0103] A high-precision detection method for liquid refractive index comprises the following steps:

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

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

[0106] (3) The computer generated hologram calculated by the Bodge coding method is printed on a transparent substrate via 1:1 photolithography.

[0107] (4) The object light wave reconstructed by the CGH is imaged by a convex lens to obtain an optically reconstructed image of a line spot with an imaging width of about 100 μm.

[0108] (5) Control the spot detection unit to detect the pixel position of the center of the line spot reconstruction image, 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 This is the original image of the computer-generated hologram in Example 2 of the present invention, which has a size of 350×350 pixels and is a white vertical line with a width of only one pixel in a pure black background.

[0110] Figure 3 for Figure 2 The computer generated hologram of the original image shown in the figure has a size of 350×350 pixels and is calculated using a modified off-axis interferometric computer generated hologram calculation method based on the Bouch coding method. The calculation formula (1) is:

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

[0112] Among them, ℎ(x, y) is the transmittance function of the calculated hologram at the (x, y) coordinate, α is the carrier frequency of the off-axis reference light, and φ(x, y) is the phase distribution of the object light wave of the original image at the (x, y) coordinate.

[0113] Figure 4 for Figure 3 The +1-level optical reconstruction image of the computer generated hologram shown is Figure 4 It can be seen that since the computer performs discrete calculations, the reconstructed image has obvious discontinuity in the length direction. In order to make the discontinuity of the reconstructed image in the length direction disappear and become uniform, the hologram needs to be directional filtered, which is done by cutting off the high-frequency information in the vertical direction.

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

[0115] In this embodiment, the calculated computer-generated hologram needs to be printed out for use. Figure 6 For the general Figure 5 CGH Figure 2 The computer-generated hologram printed by 1:1 lithography after valueization. The linear area in the figure is the computer-generated hologram. The size of each pixel is 16μm, and the printing medium is a transparent substrate.

[0116] Figure 7 for Figure 6 The +1st order optical reconstruction image of the computer generated hologram shown has a width of 77 μm.

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

[0118] In this embodiment, Figure 7 The +1 optical reproduction image and Figure 8 The 0th-order optical reconstruction image is taken by an area array CCD under the condition of a parallel beam of the same power emitted by the laser.

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

[0120] Fig. 9 This is a physical picture of a prism sample pool in an embodiment of the present invention. The pool wall of the prism sample pool is a transparent acrylic sheet, and the capacity of the prism sample pool is 0.8mL. In order to facilitate leakage, it is designed as an inverted trapezoid; in order to prevent bubbles from being generated when injecting the liquid to be tested and to reduce the capacity of the prism sample pool, the top is inclined; in order to reduce aberration, the left inclined surface (i.e., the side of the incident light) and the right inclined surface (i.e., the side of the outgoing light) are made of transparent acrylic with the thinnest thickness possible. In this embodiment, the prism sample pool is made of 0.5mm thick transparent acrylic.

[0121] In this embodiment, the number of linear array pixels of the line CCD is 10500, and the pixel size is 4 μm. The angle between the line CCD and the horizontal direction is 9.2°, because when the refractive index of the solution in the prism sample pool is high, the imaging beam is closer to the prism and at a lower height.

[0122] Fig.10 The figure is a schematic diagram of the relationship between the pixel position of the center of the line spot collected by the spot detection unit in an embodiment of the present invention and the refractive index of the NaCl solution, wherein the ordinate is the pixel position of the center of the line spot, the abscissa is the refractive index of the NaCl solution, and the measurement range of the refractive index of the NaCl solution is 1.333076~1.361575. Within this refractive index range, the movement amount of the pixel position of the center of the line spot collected by the line CCD is 9167 pixels. Fig.10 In the figure, there is a basic linear relationship between the pixel position of the center of the line spot and the refractive index of the NaCl solution, with a linearity of up to 0.9988. The calculated sensitivity is 321660 pixels / refractive index unit, and the accuracy can reach 3.1×10 -6 .according to Fig.10The linear relationship between the pixel position of the center of multiple line spots collected by the line CCD and the refractive index of the NaCl solution is plotted to form a standard curve. Based on the standard curve, the refractive index of any liquid in the refractive index range of 1.333076~1.361575 can be measured.

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

[0124] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0125] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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 above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A high-precision liquid refractive index detection system, characterized in that: It includes a laser, a transparent substrate, a convex lens, a prism sample pool and a light spot detection unit; The laser is used to emit a parallel laser beam of visible light; A computer-generated hologram is arranged on the transparent substrate, wherein the original image of the computer-generated hologram is a white vertical line with a width of one pixel in a pure black background; The convex lens is used to image the object light wave reconstructed by the computer generated hologram on the transparent substrate to obtain a line spot with an imaging width of 80 μm to 120 μm; The prism sample pool is used to contain the liquid to be tested; The light spot detection unit is arranged on the image plane of the convex lens, and is used to detect the pixel position of the center of the line spot reconstruction image. The refractive index of the liquid to be tested in the prism sample pool can be measured by analyzing the pixel position of the center of the line spot reconstruction image detected by the light spot detection unit.

2. The high-precision liquid refractive index detection system according to claim 1, characterized in that: The spot of the parallel laser beam emitted by the laser covers the computer hologram on the transparent substrate.

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

4. The high-precision liquid refractive index detection system according to claim 1, characterized in that: The prism sample pool is an inverted trapezoidal structure; And / or, the capacity of the prism sample cell is less than 1 mL.

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

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

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

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

9. A high-precision detection method for liquid refractive index, characterized in that: The high-precision liquid refractive index detection system according to any one of claims 1 to 8 comprises the following steps: Place the liquid to be tested in the prism sample cell; Control the laser to emit a parallel laser beam of visible light; A computer generated hologram is disposed on the transparent substrate; The diffracted light field of the computer generated hologram is imaged through a convex lens to obtain an optical reconstruction image of a line spot with an imaging width of 80 μm to 120 μm; The light spot detection unit is controlled to detect the pixel position of the center of the line light spot reconstruction image, the pixel position of the center of the line light spot reconstruction image detected by the light spot detection unit is analyzed, and the refractive index of the liquid to be tested is obtained based on the standard curve.

10. The high-precision detection method for liquid refractive index according to claim 9, characterized in that: The computer generated hologram is calculated by using a calculation method of a modified off-axis interferometric computer generated hologram based on the Bouch coding method, and the calculation formula (1) is: ℎ(x, y) = 0.5{1 + cos[2παx - φ(x, y)]} (1) Among them, ℎ(x, y) is the transmittance function of the calculated hologram at the (x, y) coordinate, α is the carrier frequency of the off-axis reference light, and φ(x, y) is the phase distribution of the object light wave of the original image at the (x, y) coordinate.

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