A portable nondestructive detection device and method for leaf chlorophyll a and b content

Abstract

The present invention discloses a portable nondestructive detection device and method for leaf chlorophyll a and b content. The device comprises a housing, a control module and a leaf detection module. The leaf detection module comprises a clamping seat, a pressing sheet, a control switch, a light source assembly and a light intensity sensor. The clamping seat is arranged on the housing. A light-transmitting window is provided on the side of the clamping seat, and a control switch is installed. The control switch adopts a self-resetting button switch. The light intensity sensor is installed in the clamping seat and faces the light-transmitting window. The light source assembly comprises three light-emitting units. Each light-emitting unit comprises an LED lamp, a filter and a light guide. The LED lamp is installed in the housing. A filter is installed on the light-emitting part of the LED lamp; the light guide is used to transmit the light emitted by the LED lamp after filtering by the filter to the light-transmitting window for output. The present invention uses an LED lamp, a filter with a bandwidth of 16nm and a light intensity sensor in combination to achieve nondestructive and separate detection of leaf chlorophyll a and b.

Description

Technical Field

[0001] The invention belongs to the technical field of leaf chlorophyll nondestructive detection, and in particular relates to a portable nondestructive detection device and method for leaf chlorophyll a and b content. Background Art

[0002] The content of chlorophyll a and b is an important evaluation index of plant physiological and ecological characteristics. Measuring the content of chlorophyll a and b in plant leaves can understand the growth status of plants, predict crop yields, and evaluate the drought resistance and cold resistance of plants, which is of great significance for production and life. At present, the detection and analysis of chlorophyll a and b content are mainly carried out by chemical destructive detection and analysis, and these methods require time-consuming and labor-intensive processing of leaves, and also use some toxic solutions such as propanol. Chemical detection methods can no longer meet the needs of ecological monitoring of plants. At present, common chlorophyll meters can only detect total chlorophyll content, and there are no reports on instruments for detecting chlorophyll a and b separately. A low-cost portable chlorophyll a and b content detector is needed to achieve rapid detection of chlorophyll a and b in leaves.

[0003] The photosynthetic pigments of plants include carotenoids and chlorophyll, and chlorophyll plays a core role in photosynthesis. Chlorophyll a and b are the main components of photosynthetic pigments in green plant leaves. The organic matter in the dry matter of fruit yield and crop yield of higher plants is mainly formed by chlorophyll a and b. Chlorophyll a and b play different roles in plants. Chlorophyll a plays a leading role in photosynthesis, playing a dual role in absorbing light and converting light energy into chemical energy. Chlorophyll b is an auxiliary pigment of photosynthesis, and its main function is to increase the absorption of light by plants under low illumination environments. Therefore, plants can adapt to different light environments by adjusting the content and ratio of chlorophyll a and b. Therefore, plants can adjust the content and ratio of chlorophyll a and b to adapt to different light environments. For example, shade plants and sun plants, the chlorophyll a and b content of sun plants are higher than those of shade plants, and the chlorophyll a / b value of shade plants is smaller than that of sun plants. The chlorophyll a / b value in plant leaves will change to meet the needs of plants in different growth stages. The chlorophyll a:b ratio in common mature leaves is stable at around 3:1, while the chlorophyll a / b in young leaves, old leaves or leaves under stress is less than or much less than 3:1.

[0004] Chlorophyll content plays a guiding role in crop selection. Rice is the main food crop in my country. Breeding varieties with high chlorophyll content and low chlorophyll a / b value is of great significance for increasing rice yield. Wheat is the most important food crop in the world today. The germination rate of wheat seeds is positively correlated with the chlorophyll content of wheat.

[0005] In recent years, with the development of spectral technology, the SPAD-501 chlorophyll meter was developed by Japan in the 1980s. The second-generation SPAD-502 is widely used throughout the world to guide nitrogen management of crops. Its working principle is to emit light through 650nm and 940nm light sources, measure the transmittance of the light source through the leaves, calculate the SPAD value, and invert the chlorophyll content. Other chlorophyll meters that also use the transmission method include the American CM-1000 chlorophyll meter, the American CCM200, and the British Lufthansa CL-01 chlorophyll meter. Domestic ones include Zhejiang University's TYS-3N and Shanghai Dianjiang's ECa-051. However, it can only measure the overall chlorophyll content and cannot meet the needs of plant ecological testing. Most instruments that can detect chlorophyll a and b separately can only be used in laboratories, which are expensive and complicated to operate.

[0006] The application number is "2021112943641", and the name is "Leaf Chlorophyll A and B Content Inversion Method Based on Spectral Band Overlap Separation", which provides a method for independent detection of leaf chlorophyll a and b by relying on hyperspectral equipment; however, it relies on hyperspectral equipment with a band error of 1nm, which makes the detection cost of this method very high. In summary, there is currently no low-cost, easy-to-use non-destructive detection instrument for leaf chlorophyll a and b content, so it has great development prospects. Summary of the invention

[0007] Aiming at the shortcomings that the nondestructive detection method of leaf chlorophyll a and b content has not been realized and some existing spectral detection instruments are expensive and not easy to carry, the present invention designs a portable nondestructive detection device for leaf chlorophyll a and b content.

[0008] A portable nondestructive detection device for leaf chlorophyll a and b content comprises a housing, a control module and a leaf detection module. The leaf detection module comprises a clamping seat, a pressing plate, a control switch, a light source assembly and a light intensity sensor. The clamping seat is arranged on the housing. A light-transmitting window is provided on the side of the clamping seat and a control switch is installed. The control switch adopts a self-reset button switch. The light intensity sensor is installed in the clamping seat and faces the light-transmitting window. The light source assembly comprises three light-emitting units. Each light-emitting unit comprises an LED lamp, a filter and a light guide. The LED lamp is installed in the housing. A filter is installed on the light-emitting part of the LED lamp; the light guide is used to transmit the light emitted by the LED lamp after being filtered by the filter to the light-transmitting window for output. The central wavelengths of each filter are 650nm, 700nm and 900nm respectively, and the bandwidth is 16nm. The pressing plate is rotatably connected to the side of the clamping seat where the light-transmitting window is provided. The pressing plate can be rotated to cover the light-transmitting window and press the position of the control switch. The control module is used to control the light emission of each LED and receive the reflected light intensity signal detected by the light intensity sensor.

[0009] Preferably, the portable non-destructive detection device for leaf chlorophyll a and b content further comprises a display module. The display module is installed on the side of the housing and is used to display the detection result of leaf chlorophyll a and b content.

[0010] Preferably, the pressing sheet and the display module are located on the same side of the housing.

[0011] Preferably, the LED lamp is driven by an LED driving circuit capable of outputting a constant current to emit light.

[0012] Preferably, the light guide line is a black optical fiber.

[0013] Preferably, a torsion spring is installed between the pressing sheet and the clamping seat, and the torsion spring applies an elastic force to the pressing sheet to move away from the clamping seat.

[0014] Preferably, the detection starts when the control switch is pressed.

[0015] The detection method of the portable non-destructive detection device for leaf chlorophyll a and b content is as follows:

[0016] Step 1: Use the pressing piece and the clamping seat to clamp the blade to be tested, and the blade to be tested completely covers the light-transmitting window on the clamping seat. Press the control switch with the pressing piece.

[0017] Step 2: The control module controls the three LED lights to emit light in sequence, and the light intensity sensor detects the reflected light intensity of three different bands reflected by the measured blade respectively; and then obtains the reflectivity of the measured blade to 650nm, 700nm, and 900nm light.

[0018] Step 4: Calculate the content of chlorophyll a as follows:

[0019] C a =33.99*ln(R 900 / R 700 )-3.41*ln(R 900 / R 650 )-7.54;

[0020] Calculate the content of chlorophyll b C b The content is as follows:

[0021] C b =3.86*ln(R 900 / R 650 )-1.32*10 -8 *ln(R 900 / R 700 )+3.47

[0022] Among them, C a and C bThe unit is ug / cm 2 .

[0023] Preferably, the reflectivity of the measured blade to the 650nm, 700nm, and 900nm light is obtained by dividing the reflected light intensity of the measured blade to the 650nm, 700nm, and 900nm band light by the incident light intensity. The incident light intensity is detected by the light intensity sensor by covering the light-transmitting window with a standard white board and then emitting light in sequence from three LED lights.

[0024] The beneficial effects of the present invention are:

[0025] 1. The present invention uses LED lights, 16nm bandwidth filters and light intensity sensors to achieve non-destructive and separate detection of leaf chlorophyll a and b. Compared with the high-spectrum solution with 1nm accuracy in the prior art, the present application greatly reduces the cost of the detection equipment. And through actual measurement, for the reflectivity of the 650nm, 700nm, and 900nm band spectra on the leaves, the spectral information of the characteristic band of 16nm bandwidth and the spectral information of the characteristic band of 1nm bandwidth show a high consistency, so that the present invention achieves a high detection accuracy while reducing costs.

[0026] 2. The present invention arranges the LED lamp away from the light-transmitting window and uses light-guiding materials to guide the filtered light to the leaves for reflection, thereby avoiding interference with the light intensity sensor when the LED lamp emits light, thereby improving the detection accuracy of chlorophyll a and b.

[0027] 3. The present invention uses a pressing sheet and a clamping seat to clamp the blade for detection, which eliminates the interference of external ambient light on the detection and improves the accuracy of the detection; at the same time, the present invention installs the control switch on the clamping seat, and automatically sends a detection start signal by using the action of the pressing sheet clamping the blade, thereby simplifying the complexity of the detection operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0029] Figure 2 It is a structural schematic diagram of the leaf detection module in the present invention;

[0030] Figure 3 It is a schematic diagram of the internal structure of the present invention;

[0031] Figure 4 A flow chart of leaf chlorophyll a and b detection for the present invention;

[0032] Figure 5It is a comparison chart of the spectrum of the leaf in the 650nm, 700nm and 900nm bands with its average spectrum at 642-658nm, 692-708nm and 892-908nm (Part a is a comparison chart of the 650nm spectrum and the 642-658nm average spectrum; Part b is a comparison chart of the 700nm spectrum and the 692-708nm average spectrum; Part c is a comparison chart of the 900nm spectrum and the 892-908nm average spectrum);

[0033] Figure 6 The comparison chart of chlorophyll a and b contents of leaves measured at 1nm bandwidth of characteristic band and 16nm bandwidth of characteristic band (part a is the comparison chart of chlorophyll a content; part b is the comparison chart of chlorophyll b);

[0034] Figure 7 This is a comparison chart of the inversion results of the chlorophyll a and b contents measured by the present invention and the measured values ​​(part a corresponds to the chlorophyll a content; part b corresponds to the chlorophyll b content). DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the accompanying drawings.

[0036] Example 1

[0037] like Figure 1 , 2 As shown in Figure 3, a portable non-destructive detection device for leaf chlorophyll a and b content includes a housing 3, a display module 1, a control module 7 and a leaf detection module. The leaf detection module is installed on the housing 3, and is used to clamp the leaf to be tested, and emit test light to the leaf to be tested and receive light reflected by the leaf to be tested. The control module 7 is used to receive the light signal output by the leaf detection module, and calculate the chlorophyll a and b content of the leaf to be tested respectively. The display module 1 is installed on the side of the housing 3, and is used to display the detection results of the leaf chlorophyll a and b content.

[0038] The blade detection module includes a clamping seat 9, a pressing sheet 2, a control switch 4, a light source assembly and a light intensity sensor 6. The clamping seat 9 is integrally formed on the housing 3. A light-transmitting window is provided on the detection surface of the side of the clamping seat 9, and a control switch 4 is installed. The control switch 4 adopts a self-reset button switch. The light intensity sensor 6 is installed in the clamping seat 9 and faces the light-transmitting window. The light source assembly includes three light-emitting units. Each light-emitting unit includes an LED lamp 5, an LED driving circuit 8, a filter and a light guide. The LED lamp 5 and the LED driving circuit 8 are both fixed in the housing. The LED driving circuit 8 can output a constant current; the LED lamp 5 is driven by the LED driving circuit 8 to emit light. The light emitting part of the LED lamp is equipped with a filter; the light guide adopts a black optical fiber. One end of the light guide is connected to the side of the filter away from the LED lamp. The other end of the light guide is connected to the light-transmitting window. The LED lamp 5 is arranged away from the light intensity sensor 6, which can prevent the light scattered from the LED lamp 5 from affecting the detection accuracy of the light intensity sensor. The pressing sheet 2 and the display module 1 are located on the same side of the housing to facilitate the user to read data.

[0039] The central wavelengths of the filters are 650nm, 700nm, and 900nm, respectively, and the bandwidths are all 16nm. The light emitted by the LED lamps corresponding to the 650nm and 700nm bands is used to provide illumination information for detecting the chlorophyll a and b content of the leaves, respectively. The light emitted by the LED lamp corresponding to the 900nm band is used to normalize the reflection signal of the light emitted by the first LED lamp and the second LED lamp. The reason is that the light of the specific bands emitted by the first LED lamp and the second LED lamp is scattered when passing through the leaves, resulting in an increase in the path of the light passing through the leaves, but the path is not increased in the near-infrared, so the near-infrared light is selected for normalization.

[0040] The pressing piece 2 is obtained by 3D printing; one side edge of the pressing piece 2 is rotatably connected to the edge of the detection surface of the clamping seat 9. When the pressing piece 2 is rotated to the clamping seat 9 to the extreme position, the pressing piece 2 covers the light-transmitting window and presses the control switch 4 downward to send a signal to the control module 7 to start the detection. A torsion spring is installed between the pressing piece 2 and the clamping seat 9. The torsion spring applies an elastic force to the pressing piece 2 away from the detection surface of the clamping seat 9, so that the pressing piece 2 automatically releases the blade being tested after the detection is completed. The pressing piece 2 has two functions, namely, pressing the control switch 4 and removing the influence of ambient light.

[0041] The main controller of the control module 7 is a single chip microcomputer, which is used to control the LED drive circuits 8 to work in sequence, and to process the light signal detected by the light intensity sensor 6 to obtain the content of chlorophyll a and b. The display module is an OLED liquid crystal display screen, which is used to visualize some relevant information and test results of the test.

[0042] like Figure 4As shown, the detection method of the portable non-destructive detection device for leaf chlorophyll a and b content is as follows:

[0043] Step 1: The user presses the pressing sheet 2 with his fingers, so that the pressing sheet 2 and the clamping seat 9 clamp the blade to be tested, and the light-transmitting window on the clamping seat 9 is completely covered by the blade to be tested. The pressing sheet 2 presses the control switch 4, and the test starts.

[0044] Step 2: The control module 7 controls the three LED lights 5 to light up in sequence, and the light intensity sensor 6 detects the light intensity reflected by the measured blade when the three LED lights light up, and transmits it to the control module 7. The control module 7 calculates the reflectivity R of the measured blade to the light of 650nm, 700nm, and 900nm bands based on the reflected light intensity and the incident light intensity. 650 , R 700 , R 900 (Reflected light intensity divided by incident light intensity). The average of ten detection values ​​of the light intensity sensor 6 is taken as the final reflected light intensity. The incident light intensity is measured by using a standard white plate ( After the white panel covers the light-transmitting window, the three LED lights 5 emit light in sequence, which is detected by the light intensity sensor 6.

[0045] Step 4: Calculate the chlorophyll a and b content.

[0046] Chlorophyll a content a As shown in the formula:

[0047] C a =33.99*ln(R 900 / R 700 )-3.41*ln(R 900 / R 650 )-7.54

[0048] Chlorophyll b content C b As shown in the formula:

[0049] C b =3.86*ln(R 900 / R 650 )-1.32*10 -8 *ln(R 900 / R 700 )+3.47

[0050] Among them, C a and C b The unit is ug / cm^2.

[0051] In order to verify the accuracy of the instrument in the present invention, a detection accuracy verification test was carried out:

[0052] The nondestructive detection instrument for leaf chlorophyll a and b content in the present invention was used to detect the chlorophyll a and b content of 40 leaves. The multiple test results of each leaf sample were averaged to reduce the detection error. The averaged chlorophyll a and b content was used as the predicted chlorophyll a and b content value of the sample. The true value of chlorophyll a and b content was measured by UV3600 as the measured chlorophyll a and b content value of the sample. The results are as follows: Figure 7 By comparing the predicted and true values ​​of the chlorophyll a and b contents of the samples, the standard deviation and accuracy of the data are calculated, and the accuracy of the instrument is analyzed as shown in equations 4 and 5.

[0053] Absolute deviation = |predicted value - true value|

[0054]

[0055] The verification results of this embodiment are shown in Table 1.

[0056] Table 1 Leaf chlorophyll accuracy verification table

[0057]

[0058] It can be seen from Table 1 that the nondestructive detection instrument for leaf chlorophyll a and b content provided by the present invention has detection accuracy of chlorophyll a and b of 93.8% and 92.3% respectively, which has very high precision.

[0059] Example 2

[0060] The chlorophyll a and b content detection equipment provided in Example 1 realizes comprehensive verification of low-cost and accurate detection of chlorophyll a and b. The specific process is as follows:

[0061] Based on the characteristic band (1nm bandwidth) with high spectral resolution determined by the hyperspectral equipment, the characteristic band is used as the central wavelength, and the wavelength is extended to both sides by 8nm as the extended spectral resolution (16nm), namely 642-658nm, 692-708nm, and 892-908nm characteristic bands. According to the spectral response characteristics of different leaves, several sample spectra are selected from the corresponding spectral data sets, and the average spectra in the range of 642-658nm, 692-708nm, and 892-908nm are extracted, and compared with the characteristic spectra of 650nm, 700nm, and 900nm. The spectral data obtained are as follows: Figure 5 .

[0062] from Figure 5It can be seen that the characteristic band 16nm bandwidth spectrum of different leaf samples has a high consistency with the characteristic band spectrum, and the spectral reflectance of each sample is relatively close; the RMSE between the 650nm and 700nm characteristic bands is 0.0023 and 0.0021 respectively, and the RMSE of the normalized infrared 900nm is 0.00043, which meets the accuracy requirements, indicating that the spectral response of the leaf has a high consistency near the two characteristic spectra. Therefore, it is feasible to use the spectral information of the 16nm bandwidth to replace the characteristic spectrum.

[0063] The characteristic bands of different spectral resolutions have relatively consistent spectral information, but there are still some differences. These differences will bring certain errors to the inversion of chlorophyll a and b content. Therefore, it is necessary to compare the results of inverting chlorophyll a and b content of different bandwidth characteristic spectra of each sample to analyze whether the final error meets the accuracy requirements. According to the chlorophyll a and b inversion model, the different inversion results of each sample are as follows: Figure 6 shown.

[0064] Similarly, the inversion results of characteristic spectra with different spectral resolutions are also relatively consistent, indicating that the inversion error caused by the error between spectra will not affect the inversion of related chemical components. The RMSE of the inversion accuracy of the chlorophyll a and b contents are 1.96ug / cm^2 and 0.079ug / cm^2, respectively, meeting the accuracy requirements. Therefore, the characteristic bands of 650nm and 700nm of leaf chlorophyll a and b contents based on spectral images can be expanded to 642-658nm and 692-708nm, respectively, and the normalized 900nm is expanded to 892-908nm. The spectral information with different bandwidths has a high consistency in inverting the chlorophyll a and b contents.

Claims

1. A portable non-destructive detection device for leaf chlorophyll a and b content, comprising a housing (3), a control module (7) and a leaf detection module; characterized in that: The blade detection module comprises a clamping seat (9), a pressing plate (2), a control switch (4), a light source assembly and a light intensity sensor (6); the clamping seat (9) is arranged on a housing (3); a light-transmitting window is provided on the side of the clamping seat (9) and a control switch (4) is installed; the control switch (4) adopts a self-resetting button switch; the light intensity sensor (6) is installed in the clamping seat (9) and faces the light-transmitting window; the light source assembly comprises three light-emitting units; each of the light-emitting units comprises an LED lamp (5), a filter and a light guide; the LED lamp (5) is installed in the housing; The light emitting part of the lamp is equipped with a filter; the light guide is used to transmit the light emitted by the LED lamp after being filtered by the filter to the light-transmitting window for output; the central wavelengths of the filters are 650nm, 700nm and 900nm respectively, and the bandwidths are all 16nm; the pressing plate (2) is rotatably connected to the side of the clamping seat (9) where the light-transmitting window is opened; the pressing plate (2) can be rotated to cover the light-transmitting window and press the control switch (4); the control module (7) is used to control the light emission of each LED and receive the reflected light intensity signal detected by the light intensity sensor (6).

2. A portable non-destructive detection device for leaf chlorophyll a and b content according to claim 1, characterized in that: It also includes a display module (1); the display module (1) is installed on the side of the housing (3) and is used to display the detection results of the chlorophyll a and b contents in the leaves.

3. A portable non-destructive detection device for leaf chlorophyll a and b content according to claim 2, characterized in that: The pressing sheet (2) and the display module (1) are located on the same side of the housing.

4. A portable non-destructive detection device for leaf chlorophyll a and b content according to claim 1, characterized in that: The LED lamp (5) is driven by an LED driving circuit (8) capable of outputting a constant current to emit light.

5. A portable non-destructive detection device for leaf chlorophyll a and b content according to claim 1, characterized in that: The light guide line is a black optical fiber line.

6. A portable non-destructive detection device for leaf chlorophyll a and b content according to claim 1, characterized in that: A torsion spring is installed between the pressing sheet (2) and the clamping seat (9); the torsion spring applies an elastic force to the pressing sheet (2) to move away from the clamping seat (9).

7. A portable non-destructive detection device for leaf chlorophyll a and b content according to claim 1, characterized in that: When the control switch (4) is pressed, detection begins.

8. A portable non-destructive detection method for leaf chlorophyll a and b content according to any one of claims 1 to 7, characterized in that: Using the detection device as claimed in claim 1; the method comprises the following steps: Step 1: Use the pressing sheet (2) and the clamping seat (9) to clamp the blade to be measured, and the blade to be measured completely covers the light-transmitting window on the clamping seat (9); the pressing sheet (2) presses the control switch (4); Step 2: The control module (7) controls the three LED lights (5) to emit light in sequence, and the light intensity sensor (6) respectively detects the reflected light intensity of three different bands reflected by the measured blade; and then obtains the reflectivity of the measured blade to 650nm, 700nm, and 900nm light; Step 4: Calculate the content of chlorophyll a as follows: C a =33.99*ln(R 900 / R 700 )-3.41*ln(R 900 / R 650 )-7.54; Calculate the content of chlorophyll b C b The content is as follows: C b =3.86*ln(R 900 / R 650 )-1.32*10 -8 *ln(R 900 / R 700 )+3.47 Among them, C a and C b The unit is ug / cm 2 .

9. A portable non-destructive detection method for leaf chlorophyll a and b content according to claim 8, characterized in that: The reflectivity of the measured blade to the light of 650nm, 700nm and 900nm is obtained by dividing the reflected light intensity of the measured blade to the light of 650nm, 700nm and 900nm by the incident light intensity; the incident light intensity is detected by the light intensity sensor (6) by covering the light-transmitting window with a standard white board and then emitting light in sequence by three LED lights (5).

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