Apparatus for measuring refractive index of liquid on the basis of transmission optical path, and measurement method therefor

Abstract

Disclosed in the present invention are an apparatus for measuring the refractive index of a liquid on the basis of a transmission optical path, and a measurement method therefor. The apparatus comprises a laser, a sample cell, a thermostatic bath, a photoelectric imaging device, a control unit and a PC, wherein the sample cell is light-transmissive at the front and rear, and one or both of walls of a light-transmissive face is / are of a right-trapezoidal wedge-shaped structure; the thermostatic bath can perform temperature control on a liquid sample; and laser light emitted by the laser penetrates the liquid sample in the sample cell, and finally forms an image on the photoelectric imaging device placed in a transmission direction. The method comprises: when laser light passes through a sample in a sample cell, the laser light being refracted at an interface between different media, such that the direction of an emergent optical path changes, wherein the variable of the change is related to the refractive index of the sample; the laser light forming an image on a photoelectric imaging device after penetrating the sample; and calculating the refractive index of the sample on the basis of the relationship between the position of an imaging point and the refractive index. The present invention achieves measurement of the refractive index of a liquid with an accuracy better than 0.05%.

Description

Device for detecting refractive index of liquid based on transmission light path and detection method thereof TECHNICAL FIELD

[0001] The present application relates to a device for detecting refractive index of liquid and a detection method thereof, in particular to a device for detecting refractive index of liquid based on transmission light path and a detection method thereof. BACKGROUND

[0002] The refractive index of liquid is also known as refractivity or refractive power, which is an important optical physical parameter of liquid and affects the scattering vector of the test system, and the scattering vector is a parameter required for calculation in several test processes, such as particle size test technology based on dynamic light scattering theory and Zeta potential test technology based on electrophoretic light scattering theory. The accuracy of the refractive index of liquid has an important influence on the accuracy of the result. According to theoretical calculation, in the dynamic light scattering technology, 1% error of the refractive index will lead to 2.4% error of the particle size calculation.

[0003] The traditional refractive index detection method based on transmission light path uses a laser beam to be incident on a long rectangular sample pool filled with liquid, wherein the front wall and the rear wall of the long rectangular sample pool are parallel glass plates or quartz plates. The light is refracted in the air and the pool wall interface and the liquid medium and the pool wall interface during the process of passing through the sample pool, wherein the refraction angle meets the refraction law. The emergent light after the light passing through the sample pool is parallel to the direction of the incident light, and a certain offset is generated in the height, and the offset is related to the refractive index of the liquid in the sample pool. The refractive index value of the liquid can be obtained through the relationship between the offset and the refractive index of the liquid. Although this method is simple, the sample pool needs to be inclined at a large angle, the light travels a long distance in the liquid to ensure sufficient offset, and the required sample amount is usually 1 mL or more, which cannot meet the testing demand of micro sample amount. Taking a commonly used glass cuvette with an inner diameter of 10 mm x 10 mm and a wall thickness of 1.2 mm as an example, when the sample pool is inclined by 5°, the light path height offset corresponding to the increase of the refractive index of the liquid from 1.33 to 1.49 is about 0.072 mm; when the sample pool is inclined by 10°, the light path height offset corresponding to the increase of the refractive index of the liquid from 1.33 to 1.49 is about 0.14 mm. Considering that the laser spot size is usually above 100 microns, and the accuracy of the detection offset is in the range of 4-6 microns, the smaller light path offset increases the difficulty of detecting the refractive index of the liquid, and the accuracy of the refractive index detection of this kind of structure is about 1-2%. TECHNICAL PROBLEM

[0004] In view of the problem that the accuracy of the existing refractive index detection method based on transmission light path is low, the present application aims to provide a device for detecting refractive index of liquid based on transmission light path and a detection method thereof, which can provide liquid refractive index detection with an accuracy better than 0.05%. Technical solutions

[0005] A detection device for detecting the refractive index of a liquid based on optical path refraction includes a laser, a sample cell, a constant temperature bath, a photoelectric imaging device, a control unit, and a PC;

[0006] The sample cell contains the liquid sample to be tested.

[0007] The sample cell is transparent from front to back, and one or both walls of the transparent surface are wedge-shaped glass with right-angled trapezoids. The laser emitted by the laser passes through the liquid sample in the sample cell and is finally imaged on the photoelectric imaging device placed in the transmission direction. The control unit is used to receive instructions from the PC and output control signals to control the temperature of the constant temperature bath to control the temperature of the sample and avoid the influence of temperature deviation on the refractive index measurement.

[0008] The preferred embodiment of the detection device for detecting the refractive index of a liquid based on optical path refraction is that the sample cell has a double-sided light-transmitting design, is made of quartz glass or K9 glass, and is resistant to aqueous and organic samples by a melting process. The two light-transmitting surfaces of the sample cell adopt two designs. One design of the sample cell is that one side of the light-transmitting surface of the sample cell is a parallel glass plate, and the other side of the light-transmitting surface is a right-angled trapezoidal wedge-shaped glass, with its inclined waist side located inside the sample cell.

[0009] Sample cell design two uses wedge-shaped glass with right-angled trapezoids on both sides of the transparent surface, with the sloping side of each wedge located inside the sample cell. Both designs require a sample volume of less than 350 microliters.

[0010] The preferred embodiment of the detection device for detecting the refractive index of a liquid based on optical path refraction is as follows: a wedge-shaped glass is designed with the angle between the inclined waist and the right-angle waist on one side being between 5° and 12°, and two wedge-shaped glasses are designed with the sum of the angles between the inclined waist and the right-angle waist on both sides being between 5° and 12°.

[0011] The preferred embodiment of the detection device for detecting the refractive index of a liquid based on optical path refraction is as follows: when the laser beam passes through the sample cell, it sequentially passes through four interfaces: the interface between air and the outer wall of the glass cell on the laser incidence side, the interface between the inner wall of the glass cell on the laser incidence side and the liquid, the interface between the liquid and the inner wall of the glass cell on the laser emission side, and the interface between the outer wall of the glass cell on the laser emission side and the air. After the laser beam passes through the sample cell, the direction of its emitted laser beam changes, and the variable of this change in direction is related to the refractive index of the sample.

[0012] The preferred embodiment of the detection device for detecting the refractive index of a liquid based on optical path refraction is that the sample cell can be placed vertically or tilted, with a tilt angle of less than 10°, and the direction of the laser emission path is changed in both cases.

[0013] The preferred scheme of the detection device for detecting the refractive index of liquid based on light path refraction is that the laser beam profile of the laser is circular, and the spot projection is circular.

[0014] The preferred scheme of the detection device for detecting the refractive index of liquid based on light path refraction is that the laser beam profile of the laser is circular, and the spot projection is circular.

[0015] The preferred scheme of the detection device for detecting the refractive index of liquid based on light path refraction is that the laser beam profile of the laser is circular, and the spot projection is circular.

[0016] The preferred scheme of the detection device for detecting the refractive index of liquid based on light path refraction is that the laser beam profile of the laser is circular, and the spot projection is circular.

[0017] The preferred scheme of the detection device for detecting the refractive index of liquid based on light path refraction is that the laser beam profile of the laser is circular, and the spot projection is circular.

[0018] The detection method using the detection device for detecting the refractive index of liquid based on light path refraction comprises the following steps:

[0019] 1) Inject a liquid sample with a known refractive index into a sample cell, then place the sample cell in a thermostat for constant temperature operation to make the sample reach a target temperature;

[0020] 2) Obtain the position of the spot imaging center point in the vertical direction coordinate by analyzing the spot projection on the photoelectric imaging device;

[0021] 3) Repeat steps 1) to 2) to detect the positions of the spot center points of 2-5 liquid samples with known refractive indices in the vertical direction;

[0022] 4) Draw a correction curve using the refractive indices of the samples and the positions in the vertical direction;

[0023] 5) Inject a liquid sample with an unknown refractive index, repeat steps 1) to 2) to detect the position of the spot center point of the liquid sample with an unknown refractive index in the vertical direction, and then find the corresponding refractive index on the correction curve.

[0024] The application of a detection method of a detection device for detecting the refractive index of a liquid based on light path refraction, preferably, in step 4), the correction curve is drawn, the position data points of the sample with known refractive index are linearly fitted, and the linear correlation coefficient R 2 The correction curve extension line can still be used for effective detection of the unknown refractive index sample when the linear correlation coefficient R

[0025] The detection accuracy of the refractive index of the liquid is better than 0.05%.

[0026] A detection method of a detection device for detecting the refractive index of a liquid based on light path refraction, which can be integrated into a nanoparticle size and Zeta potential instrument based on dynamic light scattering technology and electrophoretic light scattering technology, uses the nanoparticle size and Zeta potential instrument constant temperature tank to constant temperature for the sample, uses the nanoparticle size and Zeta potential instrument laser light source to test the refractive index, can obtain the refractive index of the liquid at this wavelength and this temperature, and is used for particle size and Zeta potential calculation, avoiding the influence of different wavelengths and different temperatures on the refractive index of the liquid. Advantages

[0027] 1. The application utilizes the refraction behavior of laser in different refractive index media in the transmission light path to realize the test of the refractive index of the liquid. The device can be integrated into a nanoparticle size and Zeta potential instrument based on dynamic light scattering technology and electrophoretic light scattering technology, uses the laser light source of the nanoparticle size and Zeta potential instrument as the detection light source of the refractive index, uses the constant temperature tank to constant temperature for the sample, and uses the detected refractive index of the liquid for particle size and Zeta potential calculation of the nanoparticle size and Zeta potential instrument, eliminates the influence of different wavelengths and different temperatures on the detection result of the refractive index of the liquid, and further increases the accuracy of the particle size and Zeta potential detection. The device has good popularization and practical value, and will produce good economic benefits and social benefits after wide popularization and application;

[0028] 2. In the application, the sample is accurately controlled to have a temperature control accuracy of ±0.1℃, avoiding the influence of temperature deviation on the refractive index determination;

[0029] 3. In the application, the sample cell is designed as follows: in design one, the side wall of the sample cell on the light transmission surface is a parallel glass plate, and the side wall of the sample cell on the other side of the light transmission surface is a glass with a straight angle trapezoidal section, and the inclined waist on one side is located in the sample cell; in design two, the side walls on both sides of the light transmission surface of the sample cell are glasses with a straight angle trapezoidal section, and the inclined waists on one side are located in the sample cell. After the laser passes through the sample cell, the direction of the outgoing light path changes, and the variable of the direction change is related to the refractive index of the sample. When the refractive index of the sample is between 1.2 and 1.6, the position of the imaging center point of the light spot and the refractive index are in a linear relationship.

[0030] 4. The present invention adopts a transmission optical path structure, and the position offset of the center point of the light spot imaging is at the millimeter level when the sample refractive index is between 1.2 and 1.6. This can effectively reduce the error caused by the uncertainty of the confirmed center position of the light spot on the detection result, and the detection accuracy of the liquid refractive index is better than 0.05%.

[0031] 5. The two sample cell design used in this invention requires a sample volume of less than 350 microliters each, which can meet the requirements for micro-sample volume testing.

[0032] 6. This invention employs a high-resolution photoelectric imaging device, the photosensitive surface of which is perpendicular to the laser incident direction. The photoelectric imaging device includes a CCD and a CMOS, which can meet the requirements for high-precision refractive index testing.

[0033] 7. This invention is widely used in precision electrical, electronic, instrumentation and other products, and is mainly applied in research and application fields such as medical and health care, biopharmaceuticals, agricultural research, and environmental protection. Attached Figure Description

[0034] Figure 1 is an electrical principle block diagram of a device for detecting the refractive index of a liquid based on a transmission optical path;

[0035] Figure 2A shows a schematic diagram of the design of a sample cell; Figure 2B shows a schematic diagram of the design of a sample cell.

[0036] Figure 3A shows a schematic diagram of laser refraction in a vertically placed sample cell.

[0037] B is a schematic diagram of a laser refraction in a sample cell with one sample cell placed at an angle; C is a schematic diagram of a laser refraction in a sample cell with two sample cells placed vertically; D is a schematic diagram of a laser refraction in a sample cell with two sample cells placed at an angle.

[0038] Figure 4 shows: A is a schematic diagram of the distance between the axis of a vertically placed sample cell and the photoelectric imaging device; B is a schematic diagram of the distance between the axis of a tilted sample cell and the photoelectric imaging device; C is a schematic diagram of the distance between the axis of a vertically placed sample cell and the photoelectric imaging device; D is a schematic diagram of the distance between the axis of a tilted sample cell and the photoelectric imaging device.

[0039] Figure 5 is a schematic diagram showing the imaging of the laser spot on the optoelectronic imaging device and the confirmation of the vertical position of the center point of the spot.

[0040] Figure 6 is a schematic diagram of the method of the present invention for plotting the calibration curve and calculating the light index of the unknown sample;

[0041] A is an example of the vertical position of the center of the light spot in the range of 1.2 to 1.6 of the refractive index caused by the distance between the different photoelectric imaging devices and the central axis of the sample cell in the sample cell design one of the application; B is an example of the imaging position of the light spot in the range of 1.2 to 1.6 of the refractive index caused by the different angles between the inclined waist and the right-angle waist in the sample cell design one of the application; C is an example of the imaging position of the light spot in the range of 1.2 to 1.6 of the refractive index caused by the different sample cell inclination angles in the sample cell design one of the application;

[0042] Figure 8 is an example of the imaging position of the light spot in the range of 1.2 to 1.6 of the refractive index caused by the same angle between the inclined waist and the right-angle waist under the condition of the sample cell design one and the sample cell design two of the application.

[0043] 1 is the sample cell design one, 2 is the sample cell design two, 3 is the sample, 4 is the parallel plate glass, 5 is the wedge-shaped glass, 6 is the right-angle waist, 7 is the inclined waist, 8 is the angle between the inclined waist and the right-angle waist, 9 is the incident laser, 10 is the outgoing laser, 11 is the extension line of the incident laser, 12 is the photoelectric imaging device, 13 is the air-glass pool wall laser incident one side outer wall interface, 14 is the glass pool wall laser incident one side inner wall and liquid interface, 15 is the liquid-glass pool wall laser emission one side inner wall interface, 16 is the glass pool wall laser emission one side outer wall and air interface, 17 is the sample cell inclination angle, 18 is the central axis of the sample cell, 19 is the distance between the photoelectric imaging device and the central axis of the sample cell, 20 is the light spot, 21 is the center of the light spot imaging, 22 is the vertical position of the center of the light spot imaging, 23 is the vertical coordinate, 24 is the correction curve, 25 is the extension line of the correction curve, 26 is the vertical position of the center of the light spot of the known refractive index liquid sample, 27 is the refractive index of the known refractive index liquid, 28 is the vertical position of the center of the light spot of the unknown refractive index liquid sample, 29 is the refractive index of the unknown refractive index liquid. Best mode of the application

[0044] As shown in Figures 1-8, the application provides a device for detecting the refractive index of liquid based on the transmission light path, which is characterized by comprising a laser, a sample cell, a constant temperature tank, a photoelectric imaging device 12, a control unit and a PC; the sample cell is transparent in front and back, and one wall or both walls of the transparent surface is a wedge-shaped glass 5 with a right-angle trapezoidal shape;

[0045] The laser 9 emitted by the laser penetrates through the liquid sample 3 in the sample cell, and finally images on the photoelectric imaging device 12 placed in the transmission direction;

[0046] The control unit is used for receiving the PC end instruction, outputting the control signal to control the temperature of the constant temperature tank to control the temperature of the sample 3, so as to avoid the influence of temperature deviation on the determination of the refractive index.

[0047] As shown in Fig. 2, the sample cell is designed with two light-transmitting surfaces, made of quartz glass or K9 glass, and can resist aqueous and organic samples by fusion process.

[0048] The two light-transmitting surfaces of the sample cell can be designed in two ways. In the first design, the cell wall on one side of the light-transmitting surface is a parallel glass plate 4, and the cell wall on the other side is a right-trapezoidal glass 5 with one side of the inclined waist 7 located inside the sample cell.

[0049] In the second design, the cell wall on both sides of the light-transmitting surface is a right-trapezoidal glass 5 with one side of the inclined waist 7 located inside the sample cell. The sample volume required by both designs is less than 350 microliters.

[0050] In the first design, the angle 8 between one side of the inclined waist 7 and the right angle waist 6 of the right-trapezoidal glass 5 is between 5° and 12°, and in the second design, the sum of the angles 8 between the inclined waist 7 and the right angle waist 6 of the right-trapezoidal glass 5 on both sides is between 5° and 12°.

[0051] As shown in Fig. 3, when the laser 9 of the laser passes through the sample cell, it passes through four interfaces in turn, namely the air and glass cell wall laser incident side outer wall interface 13, the glass cell wall laser incident side inner wall and liquid interface 14, the liquid and glass cell wall laser emission side inner wall interface 15, and the glass cell wall laser emission side outer wall and air interface 16. After the laser passes through the sample cell, the direction of the emitted laser 10 changes, and the variable of the direction change is related to the refractive index of the sample.

[0052] As shown in Fig. 3, the sample cell can be placed vertically or inclined at an angle 17 of less than 10°, and the direction of the laser emission path 10 changes.

[0053] As shown in Fig. 5, the laser beam profile of the laser is circular, and the spot 20 is projected as a circle.

[0054] After the laser passes through the sample, the spot 20 is imaged on the photoelectric imaging device 12, which can detect the position 22 of the spot imaging center point 21 with high precision. Since the laser is refracted after passing through the sample cell 1 and 2, the spot imaging position deviates from the direction of the incident laser 9. The refractive index 29 of the sample is calculated by the relationship between the position 22 of the spot imaging center point and the refractive index.

[0055] The distance between the photoelectric imaging device 12 and the central axis 18 of the sample cell is set to be within the range of 25mm-75mm. The position 22 of the spot imaging center point is related to the distance 19 from the sample cell to the photoelectric imaging device, and the farther the distance, the greater the imaging position offset.

[0056] A high-resolution photoelectric imaging device is used, and the photosensitive surface of the photoelectric imaging device 12 is perpendicular to the direction of the laser incident 9. The photoelectric imaging device includes CCD and CMOS.

[0057] As shown in Figure 6, the position of the imaging center point 22 of the light spot and the refractive index of the sample within the range of 1.2 to 1.6 are linearly related.

[0058] As shown in Figure 6, the correction curve is drawn by 2-5 known refractive index samples and the refractive index of the unknown refractive index sample is calculated, and the specific steps include the following steps:

[0059] 1) Inject the liquid sample with known refractive index 27 into the sample cell, then put the sample cell into the thermostat, and perform constant temperature operation to make the sample reach the target temperature;

[0060] 2) The position 22 of the imaging center point of the light spot 20 in the vertical direction coordinate 23 is obtained by analyzing the projection of the light spot 20 on the photoelectric imaging device 12;

[0061] 3) Repeat steps 1)-2) to detect the vertical position 26 of the light spot center point of 2-5 known refractive index liquid samples;

[0062] 4) Draw the correction curve 24 using the refractive index and the vertical position of the sample;

[0063] 5) Inject the liquid sample with unknown refractive index, repeat steps 1)-2) to detect the vertical position 28 of the light spot center point of the liquid sample with unknown refractive index, and then find the corresponding refractive index 29 on the correction curve 24.

[0064] The correction curve 24 in step 4) is drawn, and the position data points of the known refractive index samples are linearly fitted, and the linear correlation coefficient R 2 The correction curve extension line 25 can still be used for effective detection of unknown refractive index samples when the linear correlation coefficient R

[0065] As shown in Figure 7A, the sample cell design 1, the fixed angle between the inclined waist and the right angle waist is 5°, the fixed sample cell inclination angle is 0°, the distance between the photoelectric imaging device and the sample cell axis is 25mm, 50mm and 70mm respectively, the refractive index is within the range of 1.2 to 1.6, the refractive index and the vertical position of the light spot center point are linearly related, the farther the distance, the greater the linear relationship slope, and the incident laser extension line 11 is at the vertical position of the photoelectric imaging device 12 0;

[0066] As shown in B of FIG. 7, the sample cell design one 1 has a fixed sample cell tilt angle of 0°, a fixed distance between the photoelectric imaging device and the central axis of the sample cell of 75 mm, and an angle between the oblique waist and the right-angle waist of 5°, 7°, 10°, and 12°. The refractive index is in a range of 1.2 to 1.6, and the refractive index has a linear relationship with the position of the center of the light spot in the vertical direction. The larger the angle between the oblique waist and the right-angle waist, the larger the slope of the linear relationship. The position of the incident laser extension line 11 in the vertical direction of the photoelectric imaging device 12 is 0.

[0067] As shown in C of FIG. 7, the sample cell design one 1 has a fixed angle between the oblique waist and the right-angle waist of 5°, a fixed distance between the photoelectric imaging device and the central axis of the sample cell of 25 mm, and a sample cell tilt angle of 0°, 5°, and 10°. The refractive index is in a range of 1.2 to 1.6, and the refractive index has a linear relationship with the position of the center of the light spot in the vertical direction. The larger the sample cell tilt angle, the larger the slope of the linear relationship. The position of the incident laser extension line 11 in the vertical direction of the photoelectric imaging device 12 is 0.

[0068] As shown in FIG. 8, the sample cell tilt angle is fixed at 5°, and the distance between the photoelectric imaging device and the central axis of the sample cell is fixed at 50 mm. The sample cell design one 1 has an angle between the oblique waist and the right-angle waist of 10°, and the sample cell design two 2 has an angle between the oblique waist and the right-angle waist of 5° on both sides and a total angle of 10°. The refractive index is in a range of 1.2 to 1.6, and the refractive index has a linear relationship with the position of the center of the light spot in the vertical direction. Under the condition that the total angle between the oblique waist and the right-angle waist is the same, the position of the center of the light spot in the vertical direction is basically the same, and the slope of the linear relationship is basically the same.

[0069] A detection method of a device for detecting the refractive index of a liquid based on a transmission light path. The method and device can be integrated into a nanoparticle size and Zeta potential instrument based on dynamic light scattering technology and electrophoretic light scattering technology. The nanoparticle size and Zeta potential instrument constant temperature tank is used to heat the sample, and the nanoparticle size and Zeta potential instrument laser light source is used to test the refractive index. The refractive index of the liquid at the wavelength and temperature can be obtained, and is used for particle size and Zeta potential calculation, avoiding the influence of different wavelengths and temperatures on the refractive index of the liquid.

Claims

1. A device for detecting the refractive index of a liquid based on a transmitted light path, characterized by: The device comprises a laser, a sample cell, a thermostat, a photoelectric imaging device, a control unit and a PC. The sample cell contains the liquid sample to be measured. The sample cell is transparent in front and back, and one or both walls of the transparent surface is a right trapezoidal glass. The laser emitted by the laser passes through the liquid sample in the sample cell and finally forms an image on the photoelectric imaging device placed in the transmission direction. The control unit receives instructions from the PC and outputs control signals to control the temperature of the thermostat to control the temperature of the sample, avoiding the influence of temperature deviation on the determination of refractive index.

2. The device for detecting the refractive index of a liquid based on a transmission light path according to claim 1, characterized in that: The sample cell is designed with two transparent surfaces, made of quartz glass or K9 glass material, and uses a melting process to resist water-based and organic samples. The two transparent surfaces of the sample cell use two designs. In the first design, one side of the sample cell is a parallel glass plate, and the other side is a right trapezoidal glass with one side of the inclined waist inside the sample cell. In the second design, both sides of the sample cell are right trapezoidal glasses with one side of the inclined waist inside the sample cell. The sample volume required by the above two designs is less than 350 microliters.

3. The device for detecting the refractive index of a liquid based on a transmission light path according to claim 2, characterized in that: The angle between the inclined waist and the right angle waist of the glass in the first design is between 5° and 12°, and the sum of the angles between the inclined waist and the right angle waist of the two glasses in the second design is between 5° and 12°.

4. The device for detecting the refractive index of a liquid based on a transmission light path according to claim 1, characterized in that: The laser emitted by the laser passes through the sample cell through four interfaces in turn. They are the air and glass cell wall laser incident side outer wall interface, the glass cell wall laser incident side inner wall and liquid interface, the liquid and glass cell wall laser emission side inner wall interface, and the glass cell wall laser emission side outer wall and air interface. After the laser passes through the sample cell, the direction of the outgoing laser beam changes, and the variable of the direction change is related to the refractive index of the sample.

5. The device for detecting the refractive index of a liquid based on a transmission light path according to claim 1, characterized in that: The sample cell is placed vertically or at an angle of less than 10°, and the direction of the laser beam changes. The laser beam profile of the laser is circular, and the spot projection is circular.

6. The device for detecting the refractive index of a liquid based on a transmission light path according to claim 1, characterized in that: After the laser passes through the sample, the spot is imaged on the photoelectric imaging device, which can detect the position of the spot imaging center point with high precision. Since the laser refracts after passing through the sample cell, the spot imaging position deviates from the incident laser direction. The refractive index of the sample is calculated by the relationship between the spot imaging center point position and the refractive index. When the refractive index of the sample is in the range of 1.2 to 1.6, there is a linear relationship between the spot imaging center point position and the refractive index.

7. The device for detecting the refractive index of a liquid based on a transmission light path according to claim 1, characterized in that: The distance between the photoelectric imaging device and the central axis of the sample cell is set to be within the range of 25mm-75mm; the distance between the sample cell and the photoelectric imaging device is related to the position of the spot imaging center point; the farther the distance, the greater the imaging position offset. A high-resolution photoelectric imaging device is used, and the photosensitive surface of the photoelectric imaging device is perpendicular to the laser incident direction. The photoelectric imaging device includes CCD and CMOS.

8. The method according to any one of claims 1 to 7, wherein the method is characterized by: The device comprises the following steps: 1) Inject a liquid sample with a known refractive index into the sample cell, then place the sample cell in the thermostat, and perform constant temperature operation to make the sample reach the target temperature; 2) Analyze the spot projection on the photoelectric imaging device to obtain the position of the spot imaging center point in the vertical direction coordinate. 3) Repeat steps 1)-2) to detect the vertical position of the light spot center of 2-5 samples with known refractive index; 4) Draw a correction curve using the refractive index and the vertical position of the samples; 5) Inject a sample with unknown refractive index, repeat steps 1)-2) to detect the vertical position of the light spot center of the sample with unknown refractive index, and then find its corresponding refractive index on the correction curve.

9. The detection method of claim 8, wherein the device is used to detect the refractive index of the liquid. The correction curve in Step 4) is drawn by linear fitting the position data points of the sample with known refractive index, the linear correlation coefficient R 2 The correction curve extension line is still used for effective detection of unknown refractive index samples when the linear correlation coefficient R is better than 0.

99.

10. The detection method of claim 8, wherein the device for detecting the refractive index of a liquid based on a transmission light path can be integrated into a nanoparticle size and Zeta potential instrument based on dynamic light scattering technology and electrophoretic light scattering technology, the sample is kept at a constant temperature by using a constant temperature tank of the nanoparticle size and Zeta potential instrument, and the refractive index is tested by using a laser light source of the nanoparticle size and Zeta potential instrument, so that the refractive index of the liquid at the wavelength and the temperature can be obtained and used for calculating the particle size and the Zeta potential, thereby avoiding the influence of different wavelengths and different temperatures on the refractive index of the liquid.

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