Method and system for simultaneously measuring liquid refractive index and turbidity and device

Abstract

The present application relates to the field of liquid refractive index and turbidity measurement, and discloses a method, system and device for simultaneously measuring liquid refractive index and turbidity, wherein the method comprises the following steps: S1, measuring the liquid to be measured by using a reflection type refractometer, a photoelectric sensor in the refractometer collecting a brightness image, the refractometer having a prism, the prism being in contact with the liquid to be measured to form a contact interface, the brightness image including a reflected light spot formed by light directly reflected by the contact interface and a scattering factor formed by light reaching the photoelectric sensor after passing through the contact interface into the prism after being scattered by the liquid to be measured; S2, obtaining the refractive index of the liquid to be measured through the position of the brightness change boundary line of the reflected light spot, and obtaining the turbidity of the liquid to be measured through the scattering factor. The present application can simultaneously measure the liquid refractive index and turbidity by using a refractometer, and the measurement is simple and low in cost.

Description

Technical Field

[0001] This invention belongs to the field of liquid refractive index and turbidity measurement, and specifically relates to a method, system and apparatus for simultaneously measuring liquid refractive index and turbidity. Background Technology

[0002] In daily life, we often need to measure both the refractive index and turbidity of liquids. For example, in addition to water, beverages contain soluble and insoluble solids. Soluble solids, such as sugar, increase the refractive index of the liquid. The amount of these substances can be quantified by measuring the refractive index with a refractometer, thus determining their content. Insoluble solids are typically small particles, such as small protein and fat particles in milk, or fruit pulp in fruit juice. The amount of these substances can be quantified by measuring the turbidity with a turbidimeter, thus determining their content.

[0003] Turbidity measurements generally rely on the scattering and transmission of light. For example... Figure 1 As shown, scattering occurs when a beam of light is struck into a liquid. Small particles in the liquid scatter the light in different directions, categorized by particle size into Rayleigh scattering, Mie scattering, and refraction. Each type has different angular components. If we can measure the angular components of all light rays in space, we can infer the size and properties of the scattering particles based on the distribution of light intensity in space. Besides scattering, directly measuring the attenuation of transmitted light can also determine how much light is scattered, thus revealing the particle concentration.

[0004] The current method for measuring the refractive index and turbidity of liquids requires two separate measurements using a refractometer and a turbidimeter. This is not only cumbersome and inefficient, but also requires two separate sets of equipment, which takes up a lot of space, is difficult to manage, and is costly. Summary of the Invention

[0005] One of the objectives of this invention is to provide a method and system for simultaneously measuring the refractive index and turbidity of a liquid to solve the aforementioned technical problems.

[0006] The second objective of this invention is to provide an apparatus equipped with a system for simultaneously measuring the refractive index and turbidity of a liquid.

[0007] To achieve one of the above objectives, the present invention provides a method for simultaneously measuring the refractive index and turbidity of a liquid, comprising the following steps:

[0008] S1, a reflective refractometer is used to measure the liquid to be tested. The photoelectric sensor in the refractometer collects the brightness image. The refractometer has a prism. The prism and the liquid to be tested form a contact interface. The brightness image includes the reflected light spot formed by the light directly reflected from the contact interface and the scattering factor formed by the light that passes through the contact interface after being scattered by the liquid to be tested and enters the prism and reaches the photoelectric sensor.

[0009] S2, the refractive index of the liquid under test is obtained by the position of the boundary line of the brightness change of the reflected light spot, and the turbidity of the liquid under test is obtained by the scattering factor.

[0010] Furthermore, in step S1, the scattering factor is the fuzzy size of the brightness change boundary line.

[0011] Furthermore, in step S2, the turbidity of the liquid to be tested is obtained by using the scattering factor as follows: the brightness value distribution curve of the reflected light spot along the direction perpendicular to the brightness change boundary line is differentiated to obtain a peak value, and the turbidity of the liquid to be tested is obtained by the width of the peak value.

[0012] Furthermore, in step S1, the scattering factor is the brightness value of the scattered light spot formed by the light that passes through the contact interface and enters the prism after being scattered by the liquid to be tested and reaches the photoelectric sensor.

[0013] Furthermore, in step S1, the scattering factor includes the brightness value of the scattered light spot formed by the light that passes through the contact interface and enters the prism after being scattered by the liquid to be tested and reaches the photoelectric sensor, and the blurring size of the brightness change boundary line.

[0014] Furthermore, the brightness value of the scattered light spot is specifically calculated as follows: the average value of the brightness values ​​of multiple pixels of the scattered light spot located outside the reflected light spot is taken as the brightness value of the scattered light spot.

[0015] Furthermore, the brightness value of the scattered light spot is specifically calculated as follows: the average brightness value of multiple pixels in the scattered light spot located outside the reflected light spot is subtracted from the brightness value of pixels located outside both the reflected and scattered light spots to obtain the brightness value of the scattered light spot.

[0016] Furthermore, the photoelectric sensor is an area array CMOS image sensor.

[0017] Furthermore, in step S1, during the measurement of the liquid to be measured using a reflective refractometer, a slit is used to limit the lateral dimension of the light directly reflected from the contact interface, and the lateral dimension direction corresponds to the extension direction of the brightness change boundary line.

[0018] Furthermore, in step S2, a lookup table method is used to determine the turbidity of the liquid to be tested.

[0019] The present invention also provides a system for simultaneously measuring the refractive index and turbidity of a liquid, wherein the refractive index and turbidity of the liquid to be tested are measured by the above-described method for simultaneously measuring the refractive index and turbidity of a liquid.

[0020] To achieve the second objective mentioned above, the present invention provides an apparatus comprising the aforementioned system for simultaneously measuring the refractive index and turbidity of a liquid, for measuring the refractive index and turbidity of the liquid within the smart cup.

[0021] Beneficial technical effects of the present invention:

[0022] This invention can simultaneously measure the refractive index and turbidity of a liquid using a refractometer. The measurement is simple, efficient, and requires only one set of equipment, resulting in fewer devices, less space occupation, convenient management, and low cost. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic diagram of light scattering and transmission in existing turbidity measurements;

[0025] Figure 2 This is a flowchart of the method according to Embodiment 1 of the present invention;

[0026] Figure 3 This is a schematic diagram of the refractometer according to Embodiment 1 of the present invention;

[0027] Figure 4 The image is a brightness image acquired by the refractometer in Embodiment 1 of the present invention;

[0028] Figure 5 This is a schematic diagram showing the scattering of a portion of the light source entering the liquid under test according to the present invention;

[0029] Figure 6 A graph showing the change in the boundary line of brightness variation when different amounts of milk are added to coffee in Embodiment 1 of the present invention.

[0030] Figure 7 A graph showing the relationship between the brightness value and the reflection angle of coffee with different amounts of milk added in Embodiment 1 of the present invention;

[0031] Figure 8 To Figure 7 A schematic diagram of the differentiation process;

[0032] Figure 9 This is a graph showing the relationship between the peak width and the milk concentration value in one embodiment of the present invention.

[0033] Figure 10 This is a flowchart of the method in Embodiment 2 of the present invention;

[0034] Figure 11 This is a diagram showing the changes in the scattered light spot when different amounts of milk are added to coffee in Embodiment 2 of the present invention.

[0035] Figure 12 This is a flowchart of the method in Embodiment 3 of the present invention;

[0036] Figure 13 This is a graph showing the relationship between the absolute intensity value of the scattering brightness and the concentration value of milk in this invention. Detailed Implementation

[0037] To further illustrate the various embodiments, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention, primarily used to illustrate the embodiments and to explain the operating principles of the embodiments in conjunction with the relevant descriptions in the specification. With reference to these drawings, those skilled in the art should be able to understand other possible implementations and the advantages of the present invention. Components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0038] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0039] Example 1

[0040] This invention discloses a method for simultaneously measuring the refractive index and turbidity of a liquid, comprising the following steps:

[0041] S1, a reflective refractometer is used to measure the liquid to be tested. The photoelectric sensor in the refractometer collects the brightness image. The refractometer has a prism. The prism and the liquid to be tested form a contact interface. The brightness image includes the reflected light spot formed by the light directly reflected from the contact interface and the scattering factor formed by the light that passes through the contact interface after being scattered by the liquid to be tested and enters the prism and reaches the photoelectric sensor.

[0042] S2, the refractive index of the liquid under test is obtained by the position of the boundary line of the brightness change of the reflected light spot, and the turbidity of the liquid under test is obtained by the scattering factor.

[0043] In this embodiment, the scattering factor is the fuzzy size of the brightness change boundary line, and the specific method is as follows: Figure 2 As shown, it includes the following steps:

[0044] S1, a reflective refractometer is used to measure the liquid to be tested. The photoelectric sensor of the refractometer acquires the brightness image. The refractometer has a prism. The prism and the liquid to be tested form a contact interface. The brightness image includes the reflected light spot formed by the light directly reflected from the contact interface and the scattering factor formed by the light that passes through the contact interface after being scattered by the liquid to be tested and enters the prism and reaches the photoelectric sensor.

[0045] S2, the total internal reflection angle is obtained by measuring the position of the boundary line of the brightness change of the reflected light spot, and then the refractive index of the liquid to be tested is obtained. At the same time, the turbidity of the liquid to be tested is obtained by measuring the fuzzy size of the boundary line of the brightness change.

[0046] In this specific embodiment, the reflective refractometer structure is as follows: Figure 3 As shown, the refractometer includes a light source 1, a prism 2, a lens unit 3, and a photoelectric sensor 4. The prism 1 has a contact interface 21 that contacts the liquid 5 to be measured. Light emitted from the light source 1 enters the prism 2 through the incident surface 22 and illuminates the contact interface 21. The photoelectric sensor 4 is located on the image-side focal plane of the lens unit 3, meaning the lens unit 3 is in an infinity-focusing mode. Light reflected from the contact interface 21 exits the prism 2 through the exit surface 23 and is imaged onto the photoelectric sensor 4 by the lens unit 3 using infinity-focusing. The photoelectric sensor 4 is a planar array photoelectric sensor, preferably a planar array CMOS image sensor, which is low in cost. Using this refractometer, the light source 1 does not need to use a point light source, making the size smaller, but it is not limited to this. In some embodiments, the refractometer can also use other existing reflective refractometers, such as the refractometer disclosed in US Patent: US7492447B2.

[0047] After measuring the liquid under test using the above refractometer, the results are as follows: Figure 4 The brightness image contains a reflected light spot formed by the light directly reflected from the contact interface 21. The reflected light spot has a clear brightness change boundary line near the critical angle corresponding to the total reflection angle. By measuring the position of this brightness change boundary line, the total reflection angle can be obtained, and then the refractive index of the liquid under test can be obtained. For details, refer to the refractive index measurement principle of the existing reflective refractometer. This is a very mature technology and will not be discussed in detail.

[0048] At the same time, such as Figure 5 As shown, a portion of the light from light source 1 (the part that is not totally internally reflected) is transmitted into the liquid 5 being tested. This portion of light is scattered when it encounters suspended particles in the liquid 5. The scattered light (the dotted lines in the figure) returns to prism 2 after passing through contact interface 21 and is finally received by photoelectric sensor 4. Because of the scattering, the brightness change boundary line of total internal reflection is blurred by scattering from many particles close to contact interface 21. Figure 6 The diagram shows the blurring of the boundary lines as 0%, 5%, 20%, and 50% milk are added to pure coffee, respectively. Figure 7 As shown, a graph depicting the brightness values ​​of the reflected light spot with varying reflection angles (corresponding to the horizontal axis direction in the image, i.e., along the direction perpendicular to the brightness change boundary line) reveals that the brightness change boundary line is more blurred in highly turbid liquids. Here, for each horizontal axis position, a vertical axis average is calculated at the box location to reduce noise, and this average value is plotted along the horizontal axis position. Therefore, by measuring the blur size of this brightness change boundary line, the corresponding turbidity (particle concentration) can be obtained.

[0049] To extract the brightness change boundary line, this specific embodiment uses a differential method, such as... Figure 8 As shown, when the turbidity is very low (0% milk), the differential of this brightness change boundary line has a very narrow peak; while at 50% milk, this peak becomes relatively wider. Figure 9 The graph showing the relationship between peak width and milk concentration is shown. It can be seen that the differential peak width of this brightness change boundary line is highly correlated with the milk concentration, especially in the high turbidity stage. Therefore, by measuring this peak width, the corresponding turbidity can be obtained. For example, a known turbidity can be used for calibration to obtain a table showing the relationship between turbidity and peak width, as shown in Table 1. Then, during measurement, the turbidity can be obtained by looking up the table, but it is not limited to this.

[0050] Table 1. Relationship between turbidity and peak width

[0051]

[0052] Implementation 2

[0053] The main difference between this embodiment and Embodiment 1 is that the scattering factor is the brightness value of the scattered light spot formed by the light that passes through the contact interface and enters the prism after being scattered by the liquid to be tested, reaching the photoelectric sensor. The specific method is as follows: Figure 10 As shown, it includes the following steps:

[0054] S1, a reflective refractometer is used to measure the liquid to be tested. The photoelectric sensor in the refractometer collects the brightness image. The refractometer has a prism. The prism and the liquid to be tested form a contact interface. The brightness image includes the reflected light spot formed by the light directly reflected from the contact interface and the scattering factor formed by the light that passes through the contact interface after being scattered by the liquid to be tested and enters the prism and reaches the photoelectric sensor.

[0055] S2, by measuring the position of the boundary line of the brightness change of the reflected light spot, the total reflection angle is obtained, and then the refractive index of the liquid to be tested is obtained. At the same time, the turbidity of the liquid to be tested is obtained by measuring the brightness value of the scattered light spot.

[0056] The reflective refractometer used in this specific embodiment is the same as that in Embodiment 1. Figure 5 As shown, because a portion of the light from light source 1 (the part that is not totally internally reflected) is transmitted into the liquid 5 to be tested, this portion of light is scattered when it encounters the suspended particles in the liquid 5. The scattered light returns to the prism 2 after passing through the contact interface 21 and is finally received by the photoelectric sensor 4. Therefore, the brightness image acquired by the photoelectric sensor 4 includes not only the reflected light spot but also the scattered light spot, such as... Figure 11As shown in the solid-line box, and as can be seen from the figure, the brightness of the scattered light spot changes significantly when 0%, 5%, 20%, and 50% milk are added to pure coffee, respectively. Therefore, turbidity (milk concentration) can be obtained from these changes.

[0057] Since the liquid can only re-enter the prism at an angle within the total internal reflection angle at the contact interface, scattered light spots will only appear in the corresponding areas (i.e., the darker sides of the reflected light spots) in the brightness image, and their brightness value is denoted as I. 透射区域 Therefore, the corresponding part of the region with a larger than total reflection angle (i.e., the side of the brighter part of the reflected spot, such as...) can be utilized. Figure 11 The brightness value I at the dashed box in the image. 全反射区域 As a reference value (theoretically, this part has no scattered light), the absolute brightness value I of the scattered light spot is obtained. 散射强度 This is used to counteract the effects of sensor noise or background, as shown in the following formula:

[0058] Liquid particle concentration ∝ I 散射强度 =I 透射区域 -I 全反射区域

[0059] To reduce errors, the brightness intensity values ​​of N pixels in these areas can be averaged to obtain a more accurate average value. Therefore, by averaging the brightness values ​​of N pixels, the error can be significantly reduced.

[0060] The turbidity of the liquid to be tested can be determined by measuring the brightness value of the scattered light spot. A known turbidity can be used for calibration to obtain a table showing the relationship between turbidity and the brightness value of the scattered light spot, as shown in Figure 2. Then, during measurement, the turbidity can be obtained by looking up the table, but it is not limited to this.

[0061] Table 2 Relationship between turbidity and the brightness of the scattered light spot

[0062]

[0063] To better measure turbidity, a clear boundary must be established between the scattered light spot area and the reflected light spot area. Therefore, in this specific embodiment, a slit is used to limit the lateral dimension of the light directly reflected from the contact interface. The lateral dimension direction corresponds to the extension direction of the brightness change boundary line. In this specific embodiment, the slit can be attached to the lens, reducing the effective size of the lens in this direction; alternatively, a slit can be attached to the light source or the incident surface of a prism, strictly defining the aperture. This confines the area of ​​direct light reflection to a relatively small width, making the light in the scattered area more accurate and unaffected by reflection.

[0064] Example 3

[0065] The absolute brightness value I of the scattered light spot in Example 2 散射强度 Plot the curve corresponding to the milk concentration value, such as... Figure 13 As shown, the absolute brightness value I can be seen. 散射强度 It increases with increasing turbidity, but begins to saturate at around 5%. This means that when the turbidity intensity is very high, this absolute brightness value I... 散射强度 The slope becomes very gradual, leading to increased errors in turbidity measurement. As shown in Example 1, its measurement method is more suitable for high turbidity levels. Therefore, this embodiment proposes a measurement method combining the methods of Example 1 and Example 2, which can more accurately measure turbidity values ​​across the entire range. Specifically, the scattering factor in this embodiment includes the brightness value of the scattered light spot formed by the light scattered by the liquid to be measured, passing through the contact interface, entering the prism, and reaching the photoelectric sensor, as well as the blurring size of the brightness change boundary line. The specific method is as follows... Figure 12 As shown, it includes the following steps:

[0066] S1, a reflective refractometer is used to measure the liquid to be tested. The photoelectric sensor in the refractometer collects the brightness image. The refractometer has a prism. The prism and the liquid to be tested form a contact interface. The brightness image includes the reflected light spot formed by the light directly reflected from the contact interface and the scattering factor formed by the light that passes through the contact interface after being scattered by the liquid to be tested and enters the prism and reaches the photoelectric sensor.

[0067] S2, the total internal reflection angle is obtained by measuring the position of the boundary line of the brightness change of the reflected light spot, and then the refractive index of the liquid to be tested is obtained. At the same time, the turbidity of the liquid to be tested is obtained by measuring the brightness value of the scattered light spot and the blur size of the boundary line of the brightness change.

[0068] More specific details regarding the measurement of the brightness value of the scattered light spot and the blur size of the boundary line of the brightness change can be found in Examples 1 and 2, and will not be elaborated here.

[0069] The turbidity of the liquid under test can be determined by measuring the brightness value of the scattered light spot and the fuzzy size of the boundary line of the brightness change. The turbidity can be calibrated using known turbidity, and the relationship table between turbidity and the brightness value and peak width of the scattered light spot is obtained, as shown in Table 3. Then, during measurement, the turbidity can be obtained by looking up the table, but it is not limited to this. In some embodiments, other methods such as machine learning can also be used to achieve this.

[0070] Table 3. Relationship between turbidity and the brightness and peak width of the scattered light spot.

[0071]

[0072] Example 4

[0073] The present invention also provides a system for simultaneously measuring the refractive index and turbidity of a liquid, wherein the refractive index and turbidity of the liquid to be tested are measured by the above-described method for simultaneously measuring the refractive index and turbidity of a liquid.

[0074] Example 5

[0075] The present invention also provides an apparatus comprising the above-described system for simultaneously measuring the refractive index and turbidity of a liquid. In this embodiment, the apparatus may be a smart cup, a benchtop measuring instrument, a portable measuring instrument, etc.

[0076] When this invention is used to measure coffee, it can simultaneously measure the refractive index and turbidity of the coffee, and determine the sugar content and milk content of the coffee.

[0077] When this invention is used to measure fruit juice, it can simultaneously measure the refractive index and turbidity of the juice, and determine the sugar content and pulp content of the juice.

[0078] When this invention is used to measure a known clear liquid, it can simultaneously measure the refractive index and turbidity of the known clear liquid, and determine whether the sensor is dirty and needs to be cleaned.

[0079] This invention can simultaneously measure the refractive index and turbidity of a liquid using a refractometer. The measurement is simple, efficient, and requires only one set of equipment, resulting in fewer devices, less space occupation, convenient management, and low cost.

[0080] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art will understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A method for simultaneously measuring the refractive index and turbidity of a liquid, characterized in that, Includes the following steps: S1, a reflective refractometer is used to measure the liquid to be tested. The photoelectric sensor in the refractometer collects the brightness image. The refractometer has a prism. The prism and the liquid to be tested form a contact interface. The brightness image includes the reflected light spot formed by the light directly reflected from the contact interface and the scattering factor formed by the light that passes through the contact interface after being scattered by the liquid to be tested and enters the prism and reaches the photoelectric sensor. S2, the refractive index of the liquid under test is obtained by the position of the boundary line of the brightness change of the reflected light spot, and the turbidity of the liquid under test is obtained by the scattering factor. In step S1, the scattering factor includes the brightness value of the scattered light spot formed by the light after being scattered by the liquid to be tested, passing through the contact interface, entering the prism, and reaching the photoelectric sensor, and the blurring size of the brightness change boundary line; the photoelectric sensor is a CMOS image sensor. In step S2, the turbidity of the liquid to be tested is obtained by using the scattering factor as follows: the brightness value distribution curve of the reflected light spot along the direction perpendicular to the brightness change boundary line is differentiated to obtain a peak value, and the turbidity of the liquid to be tested is obtained by the width of the peak value.

2. The method for simultaneously measuring the refractive index and turbidity of a liquid according to claim 1, characterized in that, The brightness value of the scattered light spot is specifically calculated by taking the average of the brightness values ​​of multiple pixels of the scattered light spot located outside the reflected light spot.

3. The method for simultaneously measuring the refractive index and turbidity of a liquid according to claim 1, characterized in that: In step S1, during the measurement of the liquid to be tested using a reflective refractometer, a slit is used to limit the lateral dimension of the light directly reflected from the contact interface, and the lateral dimension direction corresponds to the extension direction of the brightness change boundary line.

4. The method for simultaneously measuring the refractive index and turbidity of a liquid according to claim 1, characterized in that: In step S2, the turbidity of the liquid to be tested is obtained by looking up a table.

5. A system for simultaneously measuring the refractive index and turbidity of a liquid, characterized in that, The refractive index and turbidity of the liquid to be tested are measured using the method for simultaneously measuring the refractive index and turbidity of a liquid as described in any one of claims 1-4.

6. An apparatus, characterized in that: A system for simultaneously measuring the refractive index and turbidity of a liquid, as described in claim 5, is provided.

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