A method and apparatus for measuring the transmittance of liquids using a time-of-flight camera.

Abstract

This invention relates to the field of liquid transmittance, and particularly to a method and apparatus for measuring liquid transmittance using a time-of-flight camera, comprising: step 1) irradiating the liquid to be tested in a transparent container with a near-infrared light source, and taking a picture of the liquid to be tested in the transparent container with a time-of-flight camera to obtain a transparent image of the liquid to be tested; step 2) wrapping the outer surface of the transparent container containing the liquid to be tested with a light-shielding sheet, and returning it to its original position; taking a picture of the transparent container wrapped with the light-shielding sheet with a time-of-flight camera to obtain an opaque image of the liquid to be tested; step 3) extracting the grayscale values ​​of the transparent image and the opaque image of the liquid to be tested respectively, and calculating the transmittance of the liquid to be tested, thus eliminating measurement errors caused by temperature changes and changes in lighting conditions.

Description

Technical Field

[0001] This invention relates to the field of liquid transmittance, and in particular to a method and apparatus for measuring liquid transmittance using a time-of-flight camera. Background Technology

[0002] Transmittance, also known as percentage transmittance, is expressed as T%. It refers to the ratio of the remaining light intensity to the original infrared light intensity when infrared light passes through a sample, since a certain amount of light is inevitably absorbed by the sample. To indicate the degree of light absorption by a liquid, the ratio of the transmitted light flux to the incident light flux is usually used to characterize the light transmission property of an object, and this is called transmittance.

[0003] Current methods for measuring liquid transmittance typically use two cuvettes: one containing purified water and the other containing the solution to be tested. The transmittance of the solution is then measured using a spectrophotometer. This method is complex and requires strict environmental control, including temperature and light conditions. Changes in temperature and light conditions can lead to errors in the results.

[0004] In Wang Biyi's article "Research on a Laser Atmospheric Transmittance Measurement Method", a new method is introduced to measure the total gray value before and after laser transmission using a CCD detector, thereby accurately and conveniently obtaining the laser atmospheric transmission characteristics. The test results are compared with the traditional transmittance experimental measurement results and simulation calculation results to verify the feasibility of the method and eliminate the measurement error introduced by temperature changes.

[0005] Although the principle of measuring atmospheric transmittance by using a CCD detector to measure the total gray value before and after laser transmission can also be applied to liquid transmittance, a strictly dark room environment is required if a CCD detector is used for measurement, because changes in ambient light will alter the gray value and affect the measurement results. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of complex operation and high requirements for the measurement environment in existing technologies, thereby providing a method and apparatus for measuring the transmittance of liquids using a time-of-flight camera. This invention uses a time-of-flight camera for measurement, and the camera has a built-in near-infrared light source, which can avoid measurement errors caused by changes in ambient light.

[0007] To solve the above-mentioned technical problems, the present invention provides a method for measuring the transmittance of a liquid using a time-of-flight camera, comprising the following steps:

[0008] Step 1) Illuminate the liquid to be tested in a transparent container with a near-infrared light source and take a picture of the liquid to be tested in the transparent container with a time-of-flight camera to obtain a transparent image of the liquid to be tested;

[0009] Step 2) Wrap a light-shielding sheet around the outer surface of the light-transmitting container containing the liquid to be tested, making it a completely opaque liquid corresponding to the liquid to be tested, and return the light-transmitting container containing the liquid to be tested, wrapped with the light-shielding sheet, to its original position; take a picture of the light-transmitting container wrapped with the light-shielding sheet using the time-of-flight camera to obtain an opaque image of the liquid to be tested;

[0010] Step 3) Using the data processing module, extract the grayscale values ​​of the transparent image and the opaque image of the liquid to be tested, respectively, and use the sum N of the grayscale values ​​of the transparent image of the liquid to be tested. C The sum of the gray values ​​N of the opaque image of the liquid under test B The transmittance of the liquid to be tested was calculated.

[0011] Because the liquid under test is not completely transparent, photons in the opaque parts are reflected back and received by the time-of-flight camera's sensor, while photons in the transparent parts are not reflected and are not received by the sensor. Using this principle, the opacity T can be calculated by the ratio of the total grayscale value of the completely opaque liquid (the transparent container enclosed by the light-blocking sheet) to the total grayscale value of the liquid under test (the liquid under test in the transparent container without the light-blocking sheet). B This allows us to further obtain the transmittance of the liquid being tested.

[0012] As an improvement to the above method, the sum of the grayscale values ​​N of the transparent image of the liquid to be tested is... C for:

[0013] N C =∑ 待测液体 a(i,j);

[0014] The sum of grayscale values ​​N of the opaque image of the liquid under test B for:

[0015] N B =∑ 不透明 a(i,j);

[0016] Where a(i,j) are pixel coordinates, i is the x-coordinate and j is the y-coordinate.

[0017] As an improvement to the above method, the calculation of the transmittance of the liquid to be tested specifically includes:

[0018] The sum of the grayscale values ​​N of the opaque image of the liquid under test. B The sum of the grayscale values ​​N of the transparent image of the liquid to be tested C The opacity T of the liquid under test is obtained by the ratio of the two values. B :

[0019]

[0020] If it is completely opaque, with an opacity of 1, then the opacity T of the liquid being tested is... B Transmittance T of the liquid being tested T :

[0021] T T =1-T B .

[0022] As an improvement to the above method, the area of ​​grayscale values ​​extracted from the transparent image of the liquid under test by the data processing module is equal to the area of ​​grayscale values ​​extracted from the opaque image of the liquid under test, and both are greater than or equal to the area occupied by the transparent container. If the area occupied by the transparent container is relatively small in the two images, the data processing module only extracts the grayscale values ​​of the part of interest (including the transparent container) from the two images. Following the above process, the liquid transmittance can be obtained.

[0023] To achieve another objective of the present invention, the present invention provides an apparatus for measuring the light transmittance of a liquid using a time-of-flight camera, used in the aforementioned method for measuring the light transmittance of a liquid using a time-of-flight camera. The apparatus includes: a light source component, a light-transmitting container, a data processing module, a time-of-flight camera, and a light-shielding plate; wherein,

[0024] The light source component is used to generate a near-infrared light source and irradiate it onto the light-transmitting container;

[0025] The light-shielding sheet is used to wrap the light-transmitting container and reflect the near-infrared light source, so that the near-infrared light source cannot pass through the light-transmitting container.

[0026] The time-of-flight camera is used to photograph the liquid to be tested placed in the light-transmitting container to obtain a transparent image of the liquid to be tested; and to photograph the light-transmitting container wrapped by the light-blocking sheet to obtain an opaque image of the liquid to be tested.

[0027] The data processing module is used to extract the grayscale values ​​of the transparent image and the opaque image of the liquid to be tested, and to use the sum N of the grayscale values ​​of the transparent image of the liquid to be tested. C The sum of the gray values ​​N of the opaque image of the liquid under test B The transmittance of the liquid to be tested was calculated.

[0028] As an improvement to the above-mentioned device, the light source component adopts the light source component that is integrated into the time-of-flight camera.

[0029] As an improvement to the above-mentioned device, the light-shielding sheet includes: white paper or plastic material.

[0030] The method and apparatus for measuring the transmittance of liquids using a time-of-flight camera provided by this invention have the following advantages:

[0031] 1) It can be easily measured using simple equipment based on the existing environment, and the operation is simple.

[0032] 2) No strict control of measurement conditions, such as temperature and light conditions, is required. The measurement environment will not affect the measurement results. Compared with the traditional method of measuring the transmittance of liquids using a spectrophotometer, the limitations caused by the environment are reduced.

[0033] 3) It can measure the transmittance of the same solution at different distances, and it can also measure the transmittance of different solutions at the same distance, with a wide range of applications.

[0034] 4) In traditional measurement methods, changes in the size and thickness of the container holding the liquid to be tested will change the overall light transmittance of the liquid. The method and apparatus provided by this invention can directly obtain the overall light transmittance of the liquid to be tested in containers of different shapes and sizes, without being limited by the size and shape of the container. Attached Figure Description

[0035] Figure 1 A structural diagram of the device for measuring the transmittance of a liquid using a time-of-flight camera provided by the present invention;

[0036] Figure 2 Transparent images of the liquid under test captured by a time-of-flight camera;

[0037] Figure 3 Corresponding to the time-of-flight camera Figure 2 An opaque image of the liquid to be tested;

[0038] Figure 4 To preserve the portion of interest in the opaque image of the liquid under test captured by the time-of-flight camera;

[0039] Figure 5 For preservation of time-of-flight camera captures corresponding Figure 4 The part of interest in the image of the liquid to be tested;

[0040] Figures 6(a)-6(l) Transparent images of the liquid under test, taken by a time-of-flight camera, showing the concentration of the liquid under test gradually increasing.

[0041] Figure 7 A graph showing the experimental results of measuring the transmittance of liquid using a time-of-flight camera.

[0042] Attached Figure Labels

[0043] 1. Data processing module; 2. USB data cable; 3. Time-of-flight camera

[0044] 4. Emitted light 5. Reflected light 6. Test liquid Detailed Implementation

[0045] The technical solutions provided by the present invention will be further illustrated below with reference to the embodiments.

[0046] The present invention is a method for measuring the light transmittance of a liquid using a time-of-flight camera 3. The main idea is to use the time-of-flight camera 3 to obtain two images: one is a transparent image of the liquid to be tested, and the other is an opaque image of the liquid to be tested in the same container. The light transmittance of the liquid to be tested is calculated by the difference in grayscale values ​​between the two images.

[0047] Example 1

[0048] like Figure 1 As shown, in the device for measuring the transmittance of a liquid using a time-of-flight camera provided by the technical solution of the present invention, the light source component and the time-of-flight camera 3 are positioned relatively fixed. The laser light source of the time-of-flight camera 3 emits emitted light 4, i.e., near-infrared light, which illuminates the liquid 6 to be tested. Since the liquid 6 to be tested is a semi-transparent object, it can be understood as having opaque particles suspended in a transparent liquid. Ideally, the near-infrared light emitted by the light source of the time-of-flight camera 3 will be reflected back when it encounters the suspended particles, forming reflected light 5 which is received by the sensor of the time-of-flight camera 3. The sensor has a built-in filter (830nm-865nm), while the transparent part without suspended particles will be directly transmitted through and will not be received by the sensor.

[0049] Specifically, the device for measuring the light transmittance of a liquid using a time-of-flight camera provided by the technical solution of the present invention includes: a light source component, a light-transmitting container, a data processing module 1, a time-of-flight camera 3, and a light-shielding plate; in this embodiment, the function of the data processing module is executed by a host computer.

[0050] The light source component of the time-of-flight camera 3 is used to generate a near-infrared light source and illuminate the light-transmitting container.

[0051] Wrap the translucent container with white paper to reflect the near-infrared light source, so that the near-infrared light source cannot pass through the translucent container;

[0052] The time-of-flight camera 3 is used to photograph the liquid to be tested placed in the light-transmitting container to obtain a transparent image of the liquid to be tested; it is also used to photograph the light-transmitting container wrapped by the light-blocking sheet to obtain an opaque image of the liquid to be tested, and the transparent image and the opaque image of the liquid to be tested are transmitted to the data processing module 1 via the USB data cable 2.

[0053] The data processing module 1 obtains the light transmittance of the liquid under test by using the sum of gray values ​​of the transparent image of the liquid under test and the sum of gray values ​​of the opaque image of the liquid under test.

[0054] Example 2:

[0055] This embodiment will further illustrate the method for measuring the light transmittance of a liquid using a time-of-flight camera provided by the present invention, in conjunction with the accompanying drawings.

[0056] The device is attached Figure 1 As shown in the diagram, the light emitted by the time-of-flight camera 3 shines onto the liquid to be tested 6. Part of the light is reflected by the liquid to be tested 6, and part of it passes through the liquid to be tested 6 and is emitted out.

[0057] The time-of-flight camera 3 takes an image of the liquid under test 6, and the acquired transparent image of the liquid is transferred to the PC via USB data cable 2 through control software. Figure 2 As shown, the sum of its grayscale values ​​is calculated and denoted as N. C :

[0058] N C =∑ 待测液体 a(i,j)

[0059] Then, cover the container of the test liquid 6 with a layer of white paper as a complete correspondence. Figure 2 The completely opaque liquid was captured using a time-of-flight camera 3. The acquired images of the opaque liquid were then transferred to a PC via a USB data cable 2 using control software, as shown in the attached image. Figure 3 As shown, the sum of its grayscale values ​​is calculated and denoted as N. B :

[0060] N B =∑ 不透明 a(i,j)

[0061] Because the liquid under test is not completely transparent, photons in the opaque parts are reflected back and received by the time-of-flight camera's sensor, while photons in the transparent parts are not reflected and are not received by the sensor. Using this principle, the opacity T can be calculated by the ratio of the sum of the grayscale values ​​of the opaque image of the liquid to the sum of the grayscale values ​​of the transparent image of the liquid. B :

[0062]

[0063] If it is completely opaque, the opacity is 1. If it is a semi-transparent object, and the opacity T has already been calculated... B Then the transmittance is:

[0064] T T =1-T B

[0065] Right now:

[0066]

[0067] Appendix Figures 6(a)-6(l) The image shows the results of an experiment using a time-of-flight camera 3 to measure the transmittance of a liquid. The concentration of the liquid being tested increases sequentially. Figures 6(a)-6(k) The test liquids are transparent and are divided into 11 levels. Figure 6(l) shows a completely opaque liquid, i.e., level 12. Figure 7 To and Figures 6(a)-6(k) The corresponding transmittance curve of the liquid being tested.

[0068] Example 3:

[0069] Based on the time-of-flight method for measuring liquid transmittance in Example 2, when calculating the grayscale values ​​of the liquid to be tested and its corresponding completely opaque object, only the region of interest, i.e., the area where the liquid to be tested is located, can be extracted, as shown in the attached figure. Figure 4 , 5 Then calculate the sum of their grayscale values.

[0070] N C ′=∑ 待测液体 a(i,j)

[0071] N B ′=∑ 不透明 a(i,j)

[0072] "

[0073] Where, N C ′ represents the sum of gray values ​​in the region of interest of the transparent image of the liquid to be tested, N. B ′ represents the sum of gray values ​​in the region of interest of the opaque image of the liquid to be tested.

[0074] Based on the principle that photons are reflected back from opaque parts and thus received by the TOF camera sensor, while photons from transparent parts are not reflected and are not received by the sensor, the opacity T of the liquid being tested can be calculated. B ′;

[0075]

[0076] Thus, the transmittance T of the liquid can be calculated. T ′:

[0077]

[0078] This yields the transmittance result T. T It avoids errors caused by background changes and is relatively accurate.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A device for measuring the transmittance of a liquid using a time-of-flight camera, characterized in that, The device comprises a light source component, a light-transmitting container, a data processing module, a time-of-flight camera and a light shield; wherein, The light source component is used to generate a near-infrared light source and irradiate it to the light-transmitting container; The light shield is used to wrap the light-transmitting container and reflect the near-infrared light source, so that the near-infrared light source cannot penetrate the light-transmitting container; The time-of-flight camera is used to take a picture of the liquid to be tested placed in the light-transmitting container to obtain a transparent image of the liquid to be tested, and to take a picture of the light-transmitting container wrapped by the light shield to obtain an opaque image of the liquid to be tested; The data processing module is used to extract the grayscale values ​​of the transparent image and the opaque image of the liquid to be tested, and to use the sum N of the grayscale values ​​of the transparent image of the liquid to be tested. C The sum of the gray values ​​N of the opaque image of the liquid under test B The transmittance of the liquid to be tested is calculated. The light source component uses the light source component of the time-of-flight camera.

2. The device for measuring the light transmittance of a liquid using a time-of-flight camera according to claim 1, wherein, The light shield comprises white paper or plastic material.

3. A method for measuring the light transmittance of a liquid using a time-of-flight camera, implemented based on the device for measuring the light transmittance of a liquid using a time-of-flight camera according to claim 1, characterized in that, The method comprises the following steps: Step 1) irradiate the liquid to be tested placed in the light-transmitting container by a near-infrared light source, and take a picture of the liquid to be tested placed in the light-transmitting container by a time-of-flight camera to obtain a transparent image of the liquid to be tested; Step 2) wrap the outer surface of the light-transmitting container where the liquid to be tested is placed with a light shield and put it back to the original position; take a picture of the light-transmitting container wrapped by the light shield by the time-of-flight camera to obtain an opaque image of the liquid to be tested; Step 3) Extracting the gray value of the transparent image of the liquid to be tested and the gray value of the opaque image of the liquid to be tested respectively by the data processing module, and calculating the total sum N of the gray value of the transparent image of the liquid to be tested and the total sum N of the gray value of the opaque image of the liquid to be tested C B , and the light transmittance of the liquid to be tested is calculated.​ 4. The method of measuring liquid transmittance with a time-of-flight camera according to claim 3, wherein, The sum of the gray values of the liquid transparent image to be measured N C is: N C =∑ 待测液体 a(i,j) The sum of the gray scale values N of the liquid non-transparent image to be measured B is: N B =∑ 不透明 a(i,j) Wherein, a(i,j) is the pixel coordinate, i is the horizontal coordinate, and j is the vertical coordinate.

5. The method of measuring liquid transmittance using a time-of-flight camera according to claim 3, wherein, The calculation of the light transmittance of the liquid to be tested specifically comprises: The light transmittance T of the liquid to be measured is obtained from the ratio of the sum N of the gray scale values of the non-transparent image of the liquid to be measured B and the sum N of the gray scale values of the transparent image of the liquid to be measured C B :​ The optical density T of the liquid to be measured is converted into the transmittance T of the liquid to be measured B The optical density T of the liquid to be measured is converted into the transmittance T of the liquid to be measured T : T T = 1 - T B .

6. The method of measuring liquid transmittance with a time-of-flight camera according to claim 3, wherein, The data processing module extracts the area of the gray value of the transparent image of the liquid to be tested and the area of the gray value of the opaque image of the liquid to be tested, and both are greater than or equal to the area occupied by the light-transmitting container.

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