A microalgae density measurement system based on light detection and a microalgae density measurement and correction method

Abstract

The invention discloses a microalgae density measurement system based on light detection and a microalgae density measurement and correction method. The method comprises: using a standard LED lighting device based on light conversion materials to penetrate known microalgae solutions of different densities, and using a micro photodetector behind the solution to obtain the light power that changes in real time, and using a high-precision source meter to display and store the photocurrent obtained by testing the light power; changing the light conversion material or the LED chip for excitation of the standard LED lighting device as needed, reassembling the light source, and then using the non-standard LED lighting device to test the density of the microalgae solution; then using a calibration formula to calculate and correct the density of the microalgae solution tested under non-standard light source conditions; finally calculating the accuracy of the microalgae density corrected under different non-standard light source conditions, and comparing the accuracy influencing factors under different test conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical testing, and particularly relates to a microalgae density measurement system based on light detection, as well as a microalgae density measurement and correction method. Background Art

[0002] In the field of microalgae cultivation, in order to accurately and quickly detect the content of microalgae particles, current traditional detection methods include dry weight method, ultrasonic detection method, counting method, electrode method, etc. The dry weight method is to place a certain volume of suspension in a high-speed centrifuge for solid-liquid centrifugal separation. The separated precipitate is washed several times and then centrifuged again. Then the centrifuged particles are dried at a high temperature. Next, the dried particles are put into a weighing bottle with constant weight and dryness, and the mass of the separated particles is weighed. Finally, the content of the particles is calculated. The counting method is often used to detect the number of cells. Using a cell counter or staining with methylene blue, this method requires observation and counting under a microscope and multiple dilutions of the sample, which may lead to large errors. The working principle of the ultrasonic method for detecting concentration is that when ultrasonic waves pass through the suspension, due to the absorption of sound waves by particles, the ultrasonic energy decays and the amplitude decreases. The sound intensity, sound velocity or acoustic impedance before and after the incidence of ultrasonic waves will change, and there is a certain specific relationship between the concentration and the change of ultrasonic waves. According to this principle, the density of suspended particles can be measured. However, such instruments are easily affected by changes in the composition of the fermentation broth, bubbles, temperature changes, and viscosity. The electrode method is a standard electrochemistry detection method that measures the concentration of particles in the suspension by using the change in capacitance between electrodes. However, this method is usually used to detect the number of live cells, and there are still certain limitations in the detection of all types of particulate suspended microalgae.

[0003] With the rapid development of optoelectronic technology, the application of optoelectronic methods in detecting the concentration of suspensions has become increasingly widespread. In the development of optoelectronic technology, advanced light sources with good performance have emerged continuously, such as light-emitting diodes (LEDs), infrared light-emitting diodes, lasers, and infrared lasers. These light sources have stable working states and long lifetimes, and can provide stable incident light for a long time during concentration detection, thus simplifying the detection process of optical signals and greatly improving the detection accuracy. In addition, the improvement of the performance of photodetectors, such as quantum efficiency, light amplification effect, and thermoelectric stability, also provides a reliable guarantee for the accuracy of optoelectronic detection technology.

[0004] At present, microalgae density detection technologies based on optoelectronic technologies include methods such as photometer detection and optical fiber detection. However, there are several limitations in the research on measuring microalgae density by optical methods: (1) Long test process. The traditional steps for testing microalgae density include multiple links such as sampling, detection, calculation, information transmission, and information storage. When testing a large number of samples, it is easy to cause data confusion, and the process is complex. (2) Low adjustability of the light source. Researchers often use commercial light-emitting diodes, and rarely adjust or calibrate the illuminance characteristics of the light source used for optical measurement. Factors such as the brightness, wavelength, optical power, emission angle, and emission color of the light source are not fully considered. (3) Insufficient research on influencing factors. There is little in-depth research on the factors affecting the accuracy of microalgae density measurement, and the analysis of improving measurement accuracy is also insufficient. (4) Ignoring the optical performance differences. The optical performance differences between different microalgae species are easily overlooked. Therefore, existing evaluation methods may not be applicable to various test environments. (5) Limited culture density range. Many studies do not cover the range of common culture densities of microalgae; on the contrary, they are more likely to focus on one of the ranges of common culture densities of microalgae, lacking representativeness. Therefore, many aspects of microalgae density measurement have not been fully studied, such as the influence of different light wavelengths on the optical measurement results of specific microalgae species. In summary, developing a flexible and reliable microalgae density test method plays an important role in large-scale microalgae cultivation, real-time measurement, and monitoring. Summary of the Invention

[0005] The present invention provides a microalgae density measurement system and a microalgae density measurement and correction method based on light detection, which can solve the problems of unconsidered light source adjustability and test accuracy in the existing microalgae density measurement methods. This method detects the change in optical power passing through the microalgae solution by a photodetector, and uses the photocurrent generated by the photodetector to evaluate the change in microalgae density in real time, thus simplifying the detection process; in addition, the present invention also adopts a newly proposed calibration method and calibration formula to calculate and correct the density of the microalgae solution tested under non-standard light source conditions, and evaluate the calculation accuracy; the present invention establishes a direct conversion relationship between the photocurrent and the microalgae density, and the test and calculation are simple and reliable, ensuring the stability of long-term monitoring.

[0006] To solve the above problems, the technical solutions provided by the present invention are as follows:

[0007] An embodiment of the present invention provides a microalgae density measurement system based on optical detection, which includes a lifting platform (7). A rotating turntable (8) is arranged on the lifting platform (7). A transparent microalgae solution container (1) is arranged at the middle position of the rotating turntable (8). A first bracket (6-1) and a second bracket (6-2) are symmetrically arranged on both sides of the rotating turntable (8). An LED lighting device is arranged on the first bracket (6-1). The LED lighting device includes an LED chip (2), a reflector cup (4) docked with the LED chip (2), and a light conversion material layer (3) located on the light-emitting surface of the reflector cup (4). The LED chip (2) is electrically connected to a DC power supply (9). A photodetector (5) is arranged on the second bracket (6-2). The photodetector (5) is electrically connected to a source meter (10), and the source meter (10) is electrically connected to an information processor (11).

[0008] Among them, the microalgae solution container (1) is used to hold microalgae solutions with different densities and different varieties. The LED chip (2) is used as an excitation light source for the light conversion material and to adjust the light-emitting brightness of the LED lighting device during the test. The light conversion material layer (3) is used to convert the short wavelength of the LED chip into different long wavelengths within the visible light range. The reflector cup (4) is used to collect the light generated by the LED chip and pass through the light conversion material to excite the light conversion material layer (3) to emit light. The edge of the reflector cup (4) is used to fix the light conversion material layer (3). The photodetector (5) is used to receive the optical signal emitted by the light source. The lifting platform (7) is used to adjust the vertical height at which the microalgae solution container (1) is placed during the test. The rotating turntable (8) is used to control the rotation angle of the microalgae solution container (1) and the LED lighting device relative to the photodetector (5). The DC power supply (9) is used to adjust the parameters of the driving voltage and driving current of the LED chip (2). The source meter (10) is used to be electrically connected to the photodetector (5) and feedback the change in the real-time photocurrent detected by the photodetector (5). The information processor (11) is used to obtain the information of the photocurrent obtained by the source meter (10) and perform data analysis and calculation.

[0009] In an optional embodiment of the present invention, the LED chip (2) is any one of short-wave light sources such as deep ultraviolet LED, ultraviolet LED, and blue light LED. The power of the LED chip (2) is selected according to the thickness of the tested microalgae solution container (1). If the thickness of the microalgae solution container (1) is relatively thick, a larger power LED chip can be selected to emit light to ensure higher light penetration. If the thickness of the microalgae solution container (1) is relatively thin, a smaller power LED chip can be selected to emit light to ensure that the test optical power is within the test range.

[0010] In an optional embodiment of the present invention, the material of the light conversion material layer (3) is any one of light conversion materials such as phosphor, quantum dot, perovskite, and organic dye.

[0011] In an alternative embodiment of the present invention, the reflecting cup (4) is made of aluminum or acrylic material.

[0012] In an alternative embodiment of the present invention, the information processor (11) employs an operating terminal device such as a computer or a tablet.

[0013] An embodiment of the present invention provides a method for measuring and correcting the density of microalgae based on light detection, which is implemented by using a light detection-based microalgae density measurement system as described in the above embodiment. The method includes the following steps:

[0014] Step 1: Characterize the light-emitting properties of the light conversion material and the LED chip, and conduct a biological characterization of the microalgae solution. Measure the parameters of the microalgae morphology, the density of the microalgae solution, and the color of the microalgae in the microalgae solution by using traditional testing methods; characterize the light response properties of the photodetector at different wavelengths; store all the measured parameters in the information processor for convenient subsequent calling.

[0015] Step 2: Use a standard LED lighting device composed of a specific light conversion material and an LED chip to test the microalgae solution, obtain the real-time changing photocurrent, and conduct an analysis.

[0016] Step 3: Use a non-standard LED lighting device composed of any light conversion material and an LED chip to test the microalgae solution, obtain the real-time changing photocurrent, and conduct an analysis.

[0017] Step 4: Calculate and correct the density of the microalgae solution tested under the conditions of the non-standard LED lighting device in Step 3 by using a calibration formula.

[0018] Step 5: Evaluate the calculated density of the microalgae solution to obtain the accuracy rate under different test conditions.

[0019] In an alternative embodiment of the present invention, Step 2 specifically includes: Select a fixed light conversion material and an LED chip, combine them to generate an LED lighting device, and define this LED lighting device as a standard LED lighting device; Use this standard LED lighting device to test marine microalgae samples with different concentrations, and obtain the photocurrent through a photodetector; Conduct a linear regression analysis on the photocurrent data obtained under the test conditions of marine microalgae with different densities, and fit the data to obtain the changing trend of the photocurrent under different marine microalgae density conditions; Analyze the changing relationship between the photocurrent and the density of marine microalgae, and obtain the following formula:

[0020] D M = α·P S (1); where D M is the density of marine microalgae, α is the proportionality coefficient, and P S is the magnitude of the photocurrent.

[0021] Among them, the test conditions include: general conditions and specific conditions; the general conditions include: the detection system can operate normally and remain stable, ensuring that the microalgae solution with unknown microalgae density is evenly distributed; the incident angle of the light source remains unchanged during the test; the specific conditions include any one of visible lights with different wavelengths, light sources of different types, different algal species, different optical paths, and detecting the microalgae density distribution.

[0022] In an alternative embodiment of the present invention, step 3 specifically includes: a non-standard test link: since the LED lighting device based on the light conversion material has the characteristic of flexible regulation, the standard LED lighting device can be changed into a non-standard LED lighting device by changing the light conversion material and the LED chip, and the test in step 1 is carried out.

[0023] In an alternative embodiment of the present invention, step 4 specifically includes: the non-standard LED lighting device is characterized in that the light conversion material and the LED chip are adjustable. Therefore, when the standard LED lighting device is changed into a non-standard LED lighting device, the parameters of α and P in formula (1) S will fluctuate. Therefore, it is necessary to recalibrate the relationship between D M and P S through density correction; the calibration takes into account the light conversion efficiency of different light conversion materials, the influence of color change on the photosensitivity of the photodetector, and the absorption of different colors by microalgae; in this case, the calibrated photocurrent is defined as P C , the ratio of the light conversion efficiency of the new light conversion material to the old light conversion material is LE, the ratio of the sensitivity of the photodetector to the new light conversion material to the sensitivity of the photodetector to the old light conversion material is S R , the light absorption rate of microalgae under the old light conversion material is A S , and the light absorption rate of microalgae under the new light conversion material is A C ; the above factors are all used to calibrate the photocurrent P C to ensure that the calibrated photocurrent P C is consistent with the original photocurrent P S and maintains an obvious correlation with D M ;

[0024] The calibrated photocurrent P C can be calculated using the following calibration formula:

[0025] P C = P S ·LE·S R ·(1 - A C ) / (1 - A S ) (2);

[0026] Equation (2) takes into account all the changes to the microalgae solution and the photodetector during the replacement with a non-standard LED lighting device; therefore, Equation (2) is general and can be applied not only to the changes in different light conversion materials but also to the conditions of different LED chips; this adaptability benefits from the fact that any possible changes caused by the changes in the light conversion material or the LED chip have been considered in the calculation of LE; therefore, Equation (2) ensures that the system can adapt to different configurations while maintaining the accuracy of density measurement;

[0027] Calibrated microalgae density D MC is described by the following Equation (3), which includes the calibrated photocurrent P C , D MC = α·P C (3).

[0028] In an alternative embodiment of the present invention, step 5 specifically includes: an accuracy calculation and analysis step: In order to verify the accuracy of D M after using a non-standard LED lighting device, the accuracy rate A obtained from the test can be calculated using the following equation in the accuracy rate evaluation step 5 C ,

[0029] Compared with the prior art, the embodiment of the present invention provides a microalgae density measurement system and a microalgae density measurement and correction method based on light detection, having the following beneficial effects:

[0030] (1) The present invention proposes a simple test method for the density of marine microalgae based on optical signals. This method uses light as the medium, is non-contact and environmentally friendly, and does not have the problem of frequent sampling. It only needs to move the test device to monitor the density of the microalgae solution at different parts of the microalgae cultivation container, avoiding the pollution of the microalgae solution caused by frequent sampling.

[0031] (2) The present invention can directly use an inexpensive LED lighting device as the light source and use the photocurrent obtained by the photodetector as the monitoring object. It has the advantages of simplicity and easy testing. The test system is portable and can be widely applied to signal testing in various occasions.

[0032] (3) The present invention assembles the light source required for microalgae density testing by combining a light conversion material with a reflector cup and an LED chip, which has flexible adjustability in microalgae density testing. Moreover, it can select a suitable combination from any assembled LED lighting device for testing and result correction. Compared with the traditional single LED lighting device, the present invention is more suitable for microalgae density research in various occasions.

[0033] (4) The present invention proposes a method for correcting the measurement results of microalgae density under non-standard LED lighting device conditions, which can ensure that the measured microalgae density still maintains a high accuracy under different combinations of light conversion materials and LED chips.

[0034] (5) The present invention proposes a method for calculating the accuracy rate of the corrected microalgae density, and evaluates the applicability of the present invention through the calculation of the accuracy rate. The present invention has certain commercial value. Whether in the fields of marine sewage detection, microalgae solution culture monitoring, or breakthroughs in key technologies for marine visible light sensing, the present invention can support their technical requirements and effectively assist in the realization of the goals of "carbon neutrality and carbon peak". BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0036] Figure 1 It is a schematic structural diagram of a microalgae density measurement system based on light detection provided by an embodiment of the present application.

[0037] Figure 2 It is an implementation flowchart of a method for measuring and correcting microalgae density based on light detection provided by an embodiment of the present application.

[0038] Figure 3 It is a photocurrent distribution diagram obtained by a method for measuring and correcting microalgae density based on light detection provided by an embodiment of the present application under 7 different angle test conditions.

[0039] Figure 4 It is a photocurrent change diagram obtained by a method for measuring and correcting microalgae density based on light detection provided by an embodiment of the present application under different microalgae density conditions.

[0040] Figure 5 It is the calculation accuracy rate of green algae density by a method for measuring and correcting microalgae density based on light detection provided by an embodiment of the present application under different voltages.

[0041] Figure 6 It is the calculation accuracy rate of green algae density by a method for measuring and correcting microalgae density based on light detection provided by an embodiment of the present application under different test angles.

[0042] Figure 7 It is the calculation accuracy rate of golden algae density by a method for measuring and correcting microalgae density based on light detection provided by an embodiment of the present application under different voltages.

[0043] Figure 8 The calculation accuracy of the density of Chrysochromulina under different test angles for a microalgae density measurement and correction method based on light detection provided by the embodiments of the present application.

[0044] Figure 9 The calculation accuracy of the density of Chlorella under different LED chip excitation conditions for a microalgae density measurement and correction method based on light detection provided by the embodiments of the present application.

[0045] Figure 10 The calculation accuracy of the density of Chrysochromulina under different LED chip excitation conditions for a microalgae density measurement and correction method based on light detection provided by the embodiments of the present application.

[0046] Figure 11 The accuracy of the calculation of the density of Chlorella by orange light under different LED chip excitation conditions for a microalgae density measurement and correction method based on light detection provided by the embodiments of the present application.

[0047] Figure 12 The accuracy of the calculation of the density of Chlorella by red light under different LED chip excitation conditions for a microalgae density measurement and correction method based on light detection provided by the embodiments of the present application. Detailed implementation manners

[0048] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present application.

[0049] As Figure 1 shown, an embodiment of the present invention provides a microalgae density measurement system based on light detection, including a lifting platform 7. A rotating turntable 8 is arranged on the lifting platform 7. A transparent microalgae solution container 1 is arranged at the middle position of the rotating turntable 8. A first bracket 6-1 and a second bracket 6-2 are symmetrically arranged on both sides of the rotating turntable 8, that is, the first bracket 6-1 is arranged on the left side of the microalgae solution container 1, and the second bracket 6-2 is arranged on the right side of the microalgae solution container 1. An LED lighting device is arranged on the first bracket (6-1). The LED lighting device includes an LED chip 2, a reflector cup 4 docked with the LED chip 2, and a light conversion material layer 3 on the light-emitting surface of the reflector cup 4; the LED chip 2, the light conversion material 3, and the reflector cup 4 together form an LED lighting device with adjustable color and adjustable brightness. The LED chip 2 is electrically connected to a DC power supply 9; a photodetector 5 is arranged on the second bracket 6-2. The photodetector 5 is electrically connected to a source meter 10, and the source meter 10 is electrically connected to an information processor 11.

[0050] Among them, the microalgae solution container 1 is used to hold microalgae solutions with different densities and different varieties; the LED chip 2 serves as an excitation light source for the light conversion material and adjusts the light emission brightness of the LED lighting device during the test; the light conversion material layer 3 is used to convert the short wavelength of the LED chip into different long wavelengths within the visible light range; the reflector cup 4 is used to collect the light generated by the LED chip and pass through the light conversion material to excite the light conversion material layer 3 to emit light; the edge of the reflector cup 4 is used to fix the light conversion material layer 3; the photodetector 5 is used to receive the optical signal emitted by the light source; the lifting platform 7 is used to adjust the vertical height at which the microalgae solution container 1 is placed during the test; the rotary turntable 8 is used to control the rotation angles of the microalgae solution container 1 and the LED lighting device relative to the photodetector 5; the DC power supply 9 is used to adjust the parameters of the driving voltage and driving current of the LED chip 2; the source meter 10 is electrically connected to the photodetector 5 and feeds back the change in the real-time photocurrent detected by the photodetector 5; the information processor 11 is used to obtain the information of the photocurrent obtained by the source meter 10 and perform data analysis and calculation. The first bracket 6-1, the lifting platform 7, the rotary turntable 8 and the second bracket 6-2 can be fixed on the optical platform for experimental testing.

[0051] The LED chip 2 is any one of the short-wave light sources of deep ultraviolet LED, ultraviolet LED, and blue LED; the power of the LED chip 2 is selected according to the thickness of the microalgae solution container 1 to be tested. If the thickness of the microalgae solution container 1 is relatively thick, a LED chip with a larger power can be selected to emit light to ensure a higher light penetration; if the thickness of the microalgae solution container 1 is relatively thin, a LED chip with a smaller power can be selected to emit light to ensure that the test optical power is within the test range. The material of the light conversion material layer 3 is any one of the light conversion materials of phosphor, quantum dot, perovskite, and organic dye. However, considering the film-forming characteristics, light-emitting characteristics, and response characteristics of the light conversion material, in the present invention, quantum dots with stability, narrow spectrum, and adjustable color are preferably used as the light conversion material; preferably, the thickness of the light conversion material is relatively thick to ensure that it only transmits the long-wavelength monochromatic light after light conversion. The reflector cup 4 is made of aluminum or acrylic material. The photodetector 5 can be a PIN or APD diode. Among them, the APD diode has higher sensitivity and is suitable for test scenarios with fast response; the source meter 10 is a high-precision source meter, so it can test the change in photocurrent at the picoampere level and has higher applicability for testing different microalgae densities. The information processor 11 uses an operating terminal device such as a computer or a tablet.

[0052] In the specific implementation process, the LED chip 2 is fixed on the substrate, and the reflector cup 4 is fixed on the LED chip 2, while the light conversion material layer 3 is fixed on the edge of the reflector cup 4. The LED chip 2, the light conversion material layer 3, and the reflector cup 4 are assembled together into an LED lighting device and fixed with the first bracket 6-1. The microalgae solution container 1 is placed on the lifting platform 7. When it is necessary to test data at different angles, a rotating turntable 8 can be placed between the microalgae solution container 1 and the lifting platform 7 to control the rotation of the LED lighting device and the microalgae solution container 1. The photodetector 5 is fixed on the second bracket 6-2, and the LED lighting device, the microalgae solution container 1, and the photodetector 5 are placed at the same horizontal height. The LED lighting device is aligned with the microalgae solution container 1, and the photodetector 5 is used to receive the optical signal emitted by the LED lighting device. The DC power supply 9 is connected to the positive and negative electrodes of the LED chip 2 to excite the LED chip 2 to emit light. The short-wavelength light emitted by the LED chip 2 is collected by the reflector cup 4, passes through the light conversion material layer 3, and the short-wavelength light is converted into long-wavelength light. The converted light passes through the microalgae solution container 1 and reaches the photodetector 5. The photodetector 5 is connected to the source meter 10, and the source meter 10 can display and capture the photocurrent captured by the photodetector 5 in real time. The source meter 10 stores the photocurrent data and transfers it to the information processor 11 through the data line. Finally, the information processor 11 processes the obtained photocurrent signal, and through calculation, obtains the microalgae solution density and the test accuracy rate.

[0053] In this embodiment, the light conversion material layer 3 is in the shape of a thin sheet, which is convenient for light to pass through the light conversion material; the thickness of the light conversion material layer is usually about 3 mm. On the one hand, it ensures a certain light transmittance, and on the other hand, it ensures a relatively high purity of the emitted light color; at the same time, when selecting the light conversion material, it is necessary to consider its optical properties such as emission color, quantum efficiency, and emission power, as well as its conversion rate and related response speed in the light conversion process and other attributes related to detection and sensing.

[0054] Among various light conversion materials such as commercial phosphors, organic dyes, perovskites, carbon dots, and quantum dots for lighting and display, quantum dot materials with high quantum efficiency, good monochromaticity, stable emission, and fast modulation rate can be selected; taking cadmium selenide quantum dots as an example, it can generate most emission wavelengths in the visible light range under blue light or ultraviolet light excitation, and can achieve stable emission under high-temperature conditions, meeting the requirements for testing the microalgae density at multiple different light conversion wavelengths in this embodiment.

[0055] The use of quantum dots as light conversion materials provides great support for the realization of their effects. Compared with other light conversion materials, the technical advantages of quantum dots include: 1. The emission peak of quantum dots is relatively narrow, with a full width at half maximum (FWHM) ranging from about 20 nanometers to 40 nanometers. This helps to avoid the influence of inconsistent absorption coefficients of different wavelength bands in the microalgae solution on the experiment. 2. The internal quantum yield of quantum dots can be as high as 90%, with a relatively high emission intensity, thus ensuring the stability of the total emission intensity. 3. The response speed of quantum dots is higher than that of ordinary commercial phosphors. Their fluorescence lifetime is usually on the order of about 10 nanoseconds, while the fluorescence lifetime of commercial phosphors is up to the microsecond level, which limits their response speed in light detection. Therefore, when using quantum dots for testing, it can meet the test requirements of fast response. 4. The emission color of quantum dots can be easily adjusted by controlling methods such as quantum dot size and element ratio. Therefore, in the experiment, continuously variable monochromatic light can be used to measure the microalgae density, and this continuously variable test effect cannot be achieved by traditional semiconductor devices with discrete emission peaks such as laser diodes and high-power light-emitting diodes. 5. The emission properties of quantum dots are relatively stable in a water-oxygen environment, can withstand high temperatures, and can be paired with high-power LEDs and lasers to produce stable light output, thus supporting the implementation of the experiment. 6. Compared with materials such as perovskite that have high requirements for a non-polar environment and have poor film-forming properties, the manufacturing process of quantum dot films made of silica gel material can support quantum dots to be made into various flexible shapes to meet the requirements of co-packaging with high-power light-emitting diodes in the experiment.

[0056] An embodiment of the present invention provides a method for measuring and correcting microalgae density based on light detection, which is implemented by using a microalgae density measurement system based on light detection as described in the above embodiment. The method includes: using a standard LED lighting device based on a light conversion material to transmit through microalgae solutions with known different densities, and using a micro-photodetector behind the solution to obtain the real-time changing optical power. At the same time, a high-precision source meter is used to display and store the photocurrent obtained by measuring the optical power. According to the need, change the light conversion material of the standard LED lighting device or the excitation LED chip, reassemble the light source, and then use this non-standard LED lighting device to measure the density of the microalgae solution. Then, use the proposed calibration method and calibration formula to calculate and correct the density of the microalgae solution measured under non-standard light source conditions. Finally, calculate the accuracy of the microalgae density corrected under different non-standard light source conditions, and compare the accuracy influencing factors under different test conditions. The present invention uses a method with lower cost to monitor the change of microalgae density, simplifies the test process, and at the same time, the present invention can also predict the microalgae density obtained by testing with different combinations of light sources, improving the applicability of different light-emitting light sources as test light sources.

[0057] Specifically, a method for measuring and correcting microalgae density based on light detection includes the following steps:

[0058] Step 1, characterize the light-emitting properties of the light conversion material and the LED chip, and conduct biological characterization of the microalgae solution. Use traditional testing methods to measure parameters such as the morphology of microalgae in the microalgae solution, the density of the microalgae solution, and the color of the microalgae. Characterize the light response properties of the photodetector at different wavelengths. Store all the measured parameters in the information processor for convenient subsequent retrieval.

[0059] Step 2, use a standard LED lighting device composed of a specific light conversion material and an LED chip to test the microalgae solution, obtain the real-time changing photocurrent, and conduct analysis.

[0060] Step 3, use a non-standard LED lighting device composed of any light conversion material and an LED chip to test the microalgae solution, obtain the real-time changing photocurrent, and conduct analysis.

[0061] Step 4, use a calibration formula to calculate and correct the density of the microalgae solution tested under the conditions of the non-standard LED lighting device in Step 3.

[0062] Step 5, evaluate the calculated density of the microalgae solution to obtain the accuracy rates under different test conditions.

[0063] Specifically, Step 1 includes: Characterization process: Select cadmium selenide quantum dots as the light conversion material and mix the cadmium selenide quantum dots with silica gel solution. By means of conventional methods such as high-temperature curing, cooling, and demolding, make light conversion material layer 3 films of 3 mm in size from green, orange, and red cadmium selenide quantum dots for light conversion. Prepare LED chips with emission wavelengths of 273 nm, 305 nm, 274 nm, 405 nm, and 450 nm respectively. This emission range covers short wavelength ranges such as deep ultraviolet, ultraviolet, and blue light, and is used to test the light conversion effects of different emission wavelengths on the cadmium selenide quantum dot films. Characterize the luminescence performance of the above quantum dot films, and measure parameters such as the emission spectrum, emission peak wavelength, full width at half maximum, and light conversion efficiency under different excitation light source conditions of the light conversion material.

[0064] Characterize the luminescence performance of the LED chips, and measure parameters such as the emission spectrum, emission peak wavelength, full width at half maximum, and emission power of the LED chips under the operating voltage. Conduct biological characterization of two microalgae solutions, namely green algae and golden algae with different colors. Use traditional testing methods to measure parameters such as the morphology of microalgae in the microalgae solution, the density of the microalgae solution, and the color of the microalgae. Use a PIN diode as the photodetector to characterize the light response properties of the photodetector at different wavelengths from 300 nm to 800 nm. Use a computer as the information processor, and store all the measured parameters in the information processor for convenient subsequent retrieval.

[0065] Step 2 specifically includes: Standard test session: Select a fixed light conversion material and an LED chip, combine them to produce an LED lighting device, and define this LED lighting device as the standard LED lighting device; Use this standard LED lighting device to test marine microalgae samples with different concentrations, and obtain photocurrents through a photodetector; Conduct a linear regression analysis on the photocurrent data obtained under different densities of marine microalgae test conditions, and fit the data to obtain the change trend of photocurrent under different marine microalgae density conditions; Analyze the change relationship between photocurrent and marine microalgae density to obtain the following formula:

[0066] D M = α·P S (1); where, D M is the marine microalgae density, α is the proportionality coefficient, and P S is the magnitude of the photocurrent.

[0067] Among them, the test conditions include: General conditions and specific conditions; The general conditions include: The detection system can operate normally and remain stable, ensuring that the microalgae solution with unknown microalgae density is evenly distributed; Keep the incident angle of the light source unchanged during the test; The specific conditions include any one of visible lights with different wavelengths, different types of light sources, different algal species, different optical paths, and detection of microalgae density distribution.

[0068] In this embodiment, a green quantum dot film and a 450nm blue LED chip are combined to produce an LED lighting device, and this LED lighting device is defined as the standard LED lighting device. Use this standard LED lighting device to test green algae samples with densities of 2.04×10 8 、3.06×10 8 、4.09×10 8 、5.11×10 8 、8.17×10 8 cells / L, and test golden algae samples with densities of 1.20×10 9 、3.45×10 9 、4.79×10 9 、5.98×10 9 、9.57×10 9 cells / L, and obtain the corresponding photocurrents through a photodetector. Conduct a linear regression analysis on the photocurrent data obtained under different densities of marine microalgae test conditions, and fit the data to obtain the change trend of photocurrent under different marine microalgae density conditions.

[0069] Figure 3 is the test density of 2.04×10 8 、3.06×108 、4.09×10 8 、5.11×10 8 8.17×10 8 Photocurrent distribution diagram obtained from a solution of green algae per liter. The distribution of photocurrent presents a dome-shaped distribution centered at an angle of 0 degrees. Among them, the orange light with the highest luminous efficiency showed the highest photocurrent at any test angle, while the red light with the lowest luminous efficiency showed the lowest photocurrent. When light passes through the microalgae solution instead of the air, the photocurrent decreases, which is from Figure 2 It can be seen from the comparison between the solid and dotted curves that the increase in the receiving angle significantly reduces the photocurrent obtained by the photodetector, which indicates that the receiving angle has an important influence on the measurement of microalgae density.

[0070] Figure 4 The test density provided in this embodiment is 2.04×10 8 、3.06×10 8 、4.09×10 8 、5.11×10 8 8.17×10 8 When the green algae solution of 1000 micrograms / liter is matched with a green quantum dot film and a 450nm blue light LED to form a standard LED lighting device, the photocurrent change trend and its fitting diagram are obtained under the conditions of LED driving voltage of 3.0V, 3.2V, and 3.5V. The results show that under different LED driving voltages, the relationship between the tested photocurrent and the microalgae density is linear, that is, the photocurrent can better reflect the changes in the microalgae density and establish a relationship with the real-time changes in the microalgae density.

[0071] Step 3 specifically includes: Non-standard test link: Since LED lighting devices based on light conversion materials have the characteristics of flexible regulation, the standard LED lighting device can be changed to a non-standard LED lighting device by changing the light conversion material and LED chip, and the test of step 1 can be carried out.

[0072] In this embodiment, since the LED lighting device based on light conversion materials has the characteristics of flexible regulation, the standard LED lighting device can be changed into a non-standard LED lighting device by changing the light conversion materials and LED chips, and the test in step 1 is performed. In step 3, the green light quantum dot film is changed into an orange or red quantum dot film, and the 450nm blue light LED chip is changed into a 273nm, 305nm, 274nm, 405nm deep ultraviolet and ultraviolet chip, and the test in step 2 is repeated to obtain the photocurrent P S .

[0073] ​​​​Step 4 specifically includes: Calibration process: The characteristics of the non-standard LED lighting device are that the light conversion material and the LED chip are adjustable. Therefore, when the standard LED lighting device is changed to a non-standard LED lighting device, the parameters of α and P in formula (1) will fluctuate. Therefore, it is necessary to recalibrate the relationship between D and P through density calibration; the calibration takes into account the light conversion efficiency of different light conversion materials, the influence of color changes on the photosensitivity of the photodetector, and the absorption of different colors by microalgae; in this case, the calibrated photocurrent is defined as P, the ratio of the light conversion efficiency of the new light conversion material to that of the old light conversion material is LE, the ratio of the sensitivity of the photodetector to the new light conversion material to the sensitivity of the photodetector to the old light conversion material is S, the light absorption rate of microalgae under the old light conversion material is A, and the light absorption rate of microalgae under the new light conversion material is A; the above factors are all used to calibrate the photocurrent P to ensure that the calibrated photocurrent P is consistent with the original photocurrent P and maintains an obvious correlation with D; S The parameters of will fluctuate. Therefore, it is necessary to recalibrate D M and P S ; the calibration takes into account the light conversion efficiency of different light conversion materials, the influence of color changes on the photosensitivity of the photodetector, and the absorption of different colors by microalgae; in this case, the calibrated photocurrent is defined as P C , the ratio of the light conversion efficiency of the new light conversion material to that of the old light conversion material is LE, the ratio of the sensitivity of the photodetector to the new light conversion material to the sensitivity of the photodetector to the old light conversion material is S R , the light absorption rate of microalgae under the old light conversion material is A S , the light absorption rate of microalgae under the new light conversion material is A C ; the above factors are all used to calibrate the photocurrent P C to ensure that the calibrated photocurrent P C is consistent with the original photocurrent P S and maintains an obvious correlation with D M ;

[0074] The calibrated photocurrent P C can be calculated using the following calibration formula:

[0075] P C =P S ·LE·S R ·(1 - A C ) / (1 - A S ) (2);

[0076] Formula (2) takes into account all the changes to the microalgae solution and the photodetector during the replacement with the non-standard LED lighting device; therefore, formula (2) is general and can be applied not only to the changes in different light conversion materials but also to the conditions of different LED chips; this adaptability benefits from the fact that any possible changes caused by the changes in the light conversion material or the LED chip have been considered in the calculation of LE; therefore, formula (2) ensures that the system can adapt to different configurations while maintaining the accuracy of density measurement.

[0077] The calibrated microalgae density D MC can be described by the following formula (3), which includes the calibrated photocurrent P C , D MC =α·P C (3).

[0078] Step 5 specifically includes: accuracy rate calculation and analysis session: In order to verify D M accuracy, the following equation can be used to calculate the accuracy rate A obtained from the test in the accuracy rate evaluation step 5 C ,

[0079] In this embodiment, the influencing factors of the accuracy rate are analyzed in eight aspects.

[0080] As Figure 5 shown, a green algae solution is selected as the observation object, and a standard LED lighting device composed of a green light quantum dot film and a 450 nm blue light LED chip is used for testing. The accuracy rate of microalgae density calculation of a non-standard LED lighting device composed of a corrected red quantum dot film and a 450 nm blue light LED chip under the conditions of LED chip drive voltages of 3.0 V, 3.2 V, and 3.5 V is analyzed under the above standard test conditions. Figure 5 The average accuracy rate is higher than 0.93.

[0081] As Figure 6 shown, a green algae solution is selected as the observation object, and a standard LED lighting device composed of a green light quantum dot film and a 450 nm blue light LED chip is used for testing. The accuracy rate of microalgae density calculation of a non-standard LED lighting device composed of a corrected red quantum dot film and a 450 nm blue light LED chip under the conditions of a photodetector receiving angle of 10 degrees, 20 degrees, and 30 degrees is analyzed. The photodetector receiving angle is defined as the included angle between the perpendicular line of the photodetector receiving interface and the light emitting angle of the LED chip. Figure 6 The average accuracy rate is higher than 0.87.

[0082] As Figure 7 shown, a chrysophyceae solution is selected as the observation object, and a standard LED lighting device composed of a green light quantum dot film and a 450 nm blue light LED chip is used for testing. The accuracy rate of microalgae density calculation of a non-standard LED lighting device composed of a corrected red quantum dot film and a 450 nm blue light LED chip under the conditions of LED chip drive voltages of 3.0 V, 3.2 V, and 3.5 V is analyzed under the above standard test conditions. Figure 7 The average accuracy rate is higher than 0.90.

[0083] As Figure 8 ​​​As shown in the figure, the chrysophyceae solution was selected as the observation object, and a standard LED lighting device composed of a green quantum dot film and a 450 nm blue LED chip was used for testing. The calculation accuracy of microalgae density of a non-standard LED lighting device composed of a corrected red quantum dot film and a 450 nm blue LED chip was analyzed under the condition that the receiving angle of the photodetector was 10 degrees, 20 degrees, and 30 degrees under the above standard test conditions. Figure 8 The average accuracy rate is higher than 0.96.

[0084] As Figure 9 shown, the green algae solution was selected as the observation object, and standard LED lighting devices composed of a green quantum dot film and deep ultraviolet and ultraviolet LED chips of 273 nm, 305 nm, 274 nm, and 405 nm were used for testing respectively. The calculation accuracy of microalgae density after a non-standard LED lighting device composed of a corrected orange quantum dot film and deep ultraviolet and ultraviolet LED chips of 273 nm, 305 nm, 274 nm, and 405 nm was analyzed under the above standard test conditions. Figure 9 The average accuracy rate is higher than 0.93.

[0085] As Figure 10 shown, the chrysophyceae solution was selected as the observation object, and standard LED lighting devices composed of a green quantum dot film and deep ultraviolet and ultraviolet LED chips of 273 nm, 305 nm, 274 nm, and 405 nm were used for testing respectively. The calculation accuracy of microalgae density after a non-standard LED lighting device composed of a corrected orange quantum dot film and deep ultraviolet and ultraviolet LED chips of 273 nm, 305 nm, 274 nm, and 405 nm was analyzed under the above standard test conditions. Figure 10 The average accuracy rate is higher than 0.91.

[0086] As Figure 11 shown, the green algae solution was selected as the observation object, and a standard LED lighting device composed of an orange quantum dot film and a 400 nm ultraviolet LED chip was used for testing. The accuracy rate of a non-standard LED lighting device composed of a corrected orange quantum dot film and deep ultraviolet and ultraviolet LED chips of 273 nm, 305 nm, 274 nm, and 405 nm in the calculation of microalgae density was analyzed under the above standard test conditions. Figure 11 The average accuracy rate is higher than 0.94.

[0087] As Figure 12As shown, the green algae solution was selected as the observation object, and a standard LED lighting device composed of a red quantum dot film and a 400 nm ultraviolet LED chip was used for testing. The accuracy rates of the non-standard LED lighting devices composed of the corrected red quantum dot film and deep ultraviolet and ultraviolet LED chips of 273 nm, 305 nm, 274 nm, and 405 nm in microalgae density calculation were analyzed under the above standard test conditions. Figure 12 The average accuracy rate is higher than 0.90.

[0088] Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the protection scope of the present invention. Many specific details are set forth in the following description to facilitate a thorough understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed.

[0089] The technical effects and advantages of the present invention are as follows: (1) Technically, the present invention uses conventional materials such as quantum dots and phosphors to prepare a light conversion material with the support of the existing technology, which has the characteristics of high stability and easy preparation. (2) Technically, the present invention uses photocurrent as the monitoring object for feedback of microalgae density, which has the advantages of simple operation and high accuracy. There is a linear positive correlation between photocurrent and optical power, and the optical power is affected by the real-time microalgae density. Therefore, the photocurrent can directly reflect the dynamic change of microalgae density without sampling, with convenient observation and high accuracy. (3) Theoretically, this embodiment proposes a five-step implementation method. After characterizing the light conversion material, LED chip, microalgae solution, etc., the photocurrent under different microalgae density conditions is tested under the conditions of a standard LED lighting device, and the photocurrent obtained under non-standard LED lighting device conditions is corrected to deduce and calculate the microalgae density, and finally the accuracy of the present invention under different conditions is calculated. (4) Theoretically, this embodiment proposes a correction algorithm to correct the photocurrent obtained under non-standard LED lighting device conditions by using the photocurrent obtained under standard LED lighting device conditions, so as to calculate the microalgae density under non-standard LED lighting device conditions. (5) Theoretically, this embodiment proposes an algorithm for calculating the accuracy of the microalgae density calculated by the present invention, and evaluates the universality of the present invention under different conditions such as LED chip drive voltage, receiving angle size of the photodetector, light conversion material type, LED chip type, etc. (6) The present invention is technically feasible, and after the technology of the present invention matures, it can be used for marine environmental monitoring; under outdoor test conditions, all the test instruments involved in the present invention can be used for underwater detection after waterproof design; (7) The function of the present invention is not only applicable to monitoring the density of a single type of microalgae, but also applicable to monitoring the density of multiple types of microalgae;

[0090] In addition, as auxiliary evidence of the novelty of the present invention, it is also reflected in the following important aspects:

[0091] The expected benefits and commercial value after the transformation of the present invention are as follows: a. In the treatment of marine sewage, it is usually necessary to analyze the components and characteristics of microalgae suspensions in marine sewage samples. By combining the correlations between microalgae spectra, scattering characteristics, transmission characteristics, etc. and microalgae concentration and composition, the seawater quality can be effectively evaluated from the perspective of their optical characteristics. b. At present, the cultivation of functional microalgae has occupied a certain market share nationwide. At the same time, the cultivation and monitoring of microalgae are also developing towards the direction of intelligent suspension solution monitoring and evaluation. The microalgae optical property evaluation mechanism proposed by the present invention can provide convenient technical support for this process. c. The current key technical bottleneck of marine visible light communication lies in that the transmission distance is easily restricted by water quality characteristics. Therefore, by evaluating the optical properties of microalgae suspension seawater solution, the communication quality of underwater visible light communication under different water quality conditions can be dynamically monitored, which plays an important role in improving the communication rate, signal-to-noise ratio, etc. of marine visible light communication. In summary, whether it is from aspects such as marine sewage treatment, microalgae solution cultivation monitoring, or the breakthrough of key technologies of marine visible light communication, the present invention can effectively meet the technical requirements and provide support for achieving the goals of "carbon neutrality and carbon peak".

[0092] The present invention fills the technical gaps in the domestic and international industries: Current research mainly focuses on fields such as microscopic measurement of microalgae density and remote sensing measurement of microalgae distribution density. There is less research on measuring microalgae density by optical methods under the condition of near-field light field distribution. Compared with the traditional microalgae density measurement methods in multiple links such as microalgae sample collection, testing, calculation, and storage, the present invention has the characteristics of simplicity, high efficiency, and flexible light source replacement when monitoring microalgae density.

[0093] Does the technical solution of the present invention solve the current technical problems? All along, people have hoped to obtain a reliable marine microalgae density monitoring device applicable to different test light sources for fields such as seawater monitoring and microalgae cultivation monitoring. In the present invention, this problem is solved.

[0094] Does the technical solution of the present invention overcome the technical prejudice? Traditionally, microalgae density measurement relies on specific instruments such as microscopes and photometers. However, the present invention proposes a portable and flexibly assembled microalgae density measurement device and method, which can adjust the test distance, test angle, etc. according to the thickness of the microalgae solution container. Compared with the existing methods, it has a more perfect test system.

[0095] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A method for measuring and correcting microalgae density based on light detection, which is implemented by a microalgae density measurement system based on light detection, characterized in that: The following steps are involved: Step 1, characterize the various luminous properties of the light conversion material and the LED chip, perform biological characterization on the microalgae solution, and use traditional testing methods to measure the parameters of the microalgae morphology, microalgae solution density, and microalgae color in the microalgae solution; Characterize the light response properties of the photodetector at different wavelengths; store all the parameters obtained from the test in the information processor for subsequent retrieval; Step 2, using a standard LED lighting device composed of a specific light conversion material and an LED chip to test the microalgae solution, obtain a real-time photocurrent, and perform analysis; Step 3, using a non-standard LED lighting device composed of any light conversion material and LED chip to test the microalgae solution, obtain a real-time photocurrent, and perform analysis; Step 4, using a calibration formula to calculate and correct the density of the microalgae solution tested under the non-standard LED lighting device conditions in step 3; Step 5, evaluating the calculated density of the microalgae solution to obtain the accuracy under different test conditions.

2. A method for measuring and correcting microalgae density based on light detection according to claim 1, characterized in that: Step 2 specifically includes: selecting a fixed light conversion material and LED chip, combining to produce an LED lighting device, and defining the LED lighting device as a standard LED lighting device; using the standard LED lighting device to test marine microalgae samples of different concentrations, and obtaining photocurrent through a photodetector; performing linear regression analysis on the photocurrent data obtained under the test conditions of marine microalgae of different densities, and fitting the data to obtain the change trend of the photocurrent under different marine microalgae densities; analyzing the relationship between the change of photocurrent and the density of marine microalgae, and obtaining the following formula: D M =α·P S (1); where D M is the density of marine microalgae, α is the proportionality coefficient, P S is the magnitude of the photocurrent; Among them, the test conditions include: general conditions and specific conditions; the general conditions include: the detection system can operate normally and remain stable to ensure that the microalgae solution with unknown microalgae density is evenly distributed; the incident angle of the light source is kept unchanged during the test; the specific conditions include: visible light of different wavelengths, different types of light sources, different algae species, different optical paths and any one of detecting microalgae density distribution.

3. A method for measuring and correcting microalgae density based on light detection according to claim 2, characterized in that: Step 3 specifically includes: Non-standard test phase: Since LED lighting devices based on light conversion materials have the characteristics of flexible regulation, the standard LED lighting device can be changed into a non-standard LED lighting device by changing the light conversion material and the LED chip, and the test of step 1 can be carried out.

4. A method for measuring and correcting microalgae density based on light detection according to claim 3, characterized in that: Step 4 specifically includes: the non-standard LED lighting device is characterized by adjustable light conversion materials and LED chips. Therefore, when the standard LED lighting device is changed to a non-standard LED lighting device, α and P in formula (1) are S The parameters will fluctuate, so it is necessary to recalibrate D through density correction. M With P S The calibration takes into account the photoconversion efficiency of different photoconversion materials, the effect of color change on the photosensitivity of the photodetector, and the absorption of different colors by microalgae; in this case, the calibrated photocurrent is defined as P C The ratio of the light conversion efficiency of the new light conversion material to the old light conversion material is LE, and the ratio of the sensitivity of the photodetector to the new light conversion material to the sensitivity of the photodetector to the old light conversion material is S R The light absorption rate of microalgae under the old light conversion material is A S The light absorption rate of microalgae under the new light conversion material is A C ; The above factors are used to calibrate the photocurrent P C To ensure that the calibrated photocurrent P C With the original photocurrent P S Consistent with D M Maintain clear relevance; Calibrated photocurrent P C This can be calculated using the following calibration formula: P C =P S ·THE R ·(1-A C ) / (1-A S ) (2); Formula (2) takes into account all changes to the microalgae solution and the photodetector in the process of replacing the non-standard LED lighting device; therefore, formula (2) is universal and can be applied not only to changes in different light conversion materials, but also to use under conditions of different LED chips; this adaptability is due to the fact that any changes that may be caused by changes in light conversion materials or LED chips have been taken into account in the calculation of LE; therefore, formula (2) ensures that the system can adapt to different configurations while maintaining the accuracy of density measurement; Calibrated microalgae density D MC It is described by the following formula (3), which includes the calibrated photocurrent P C , D MC =α·P C (3).

5. A method for measuring and correcting microalgae density based on light detection according to claim 4, characterized in that: Step 5 specifically includes: Accuracy calculation and analysis: In order to verify the accuracy of the LED lighting device after using it, M In the accuracy evaluation step 5, the following equation is used to calculate the test accuracy A C ,

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