A microalgae density detection system and method based on visible light communication

Abstract

The present invention provides a microalgae density detection system and method based on visible light communication, the method comprising: using known microalgae solutions with different communication rates and different densities to test communication bit error rates respectively, and obtaining discrete data sets of communication bit error rates; then a signal processor uses a preset curve fitting algorithm to perform discrete data fitting, and obtains the variation law of the communication bit error rate with the microalgae density under different communication rate conditions; the variation law is a linear relationship or a nonlinear relationship; finally, under different conditions, the unknown microalgae density is tested using the linear variation interval of the variation law; the present invention performs signal transmission while monitoring the microalgae density, and decodes the information after receiving it to obtain the microalgae density, thereby simplifying the detection process; in addition, the present invention directly establishes a conversion relationship between the bit error rate obtained from the visible light communication test and the microalgae density, which is completely unaffected by the bit error interference in the communication system, and ensures the stability of monitoring.

Description

Technical Field

[0001] The present invention relates to the field of optical testing technology, and more specifically, to a microalgae density detection system and method based on visible light communication. Background Art

[0002] In the field of microalgae cultivation, if the content of microalgae particles needs to be accurately and quickly detected, the current traditional detection methods include dry weight method, ultrasonic detection method, counting method and electrode method. The dry weight method is to centrifuge a certain volume of suspension on a high-speed centrifuge for solid-liquid separation, wash the separated precipitate several times, centrifuge it again, and then dry the particles after centrifugation at high temperature, put it into a constant weight and dry weighing bottle, weigh the mass of the separated particles, and then calculate the content of the particles. 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 with a microscope, and requires multiple dilutions, which easily lead to large errors. The working principle of ultrasonic method for detecting concentration is that when ultrasonic waves pass through the suspension, the particles absorb the sound waves, the ultrasonic energy is attenuated, the amplitude is reduced, and the sound intensity, sound velocity or acoustic resistance before and after the ultrasonic wave is incident changes. 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. This type of instrument is susceptible to changes in fermentation broth composition, bubbles, temperature changes and viscosity. The electrode method uses a standard electrochemical detection method to measure the concentration of particles in the suspension by using the change in the capacitance between electrodes. However, this method is often used to detect the number of living cells and has limitations for the detection of all granular suspended microalgae.

[0003] With the rapid development of optoelectronic technology, the photoelectric method for detecting the concentration of suspensions has been widely used. In the development of optoelectronic technology, advanced light sources with good performance continue to emerge, such as light-emitting diodes, infrared light-emitting diodes, lasers, infrared lasers, etc. These light sources have stable working conditions and long lifespans. They can provide stable incident light for a long time during concentration detection, which greatly facilitates the detection of optical signals and improves the accuracy of detection. In addition, the improvement of the performance of photodetectors such as quantum efficiency, light amplification effect, and thermoelectric stability provides a reliable guarantee for the accuracy of photoelectric detection technology.

[0004] At present, the microalgae density detection technology based on photoelectric technology includes photometer detection, optical fiber detection and other methods. The traditional steps of testing microalgae density include sampling, detection, calculation, information transmission, information storage and other links. Testing a large number of samples is prone to data confusion and the process is complicated. In addition, the traditional method still needs to be based on communication methods for data transmission. However, bit errors may occur during the communication process, resulting in the failure of the transmission of test results. At present, there is no system that integrates the real-time monitoring and transmission functions of microalgae density in the relevant technologies of microalgae density detection. Summary of the invention

[0005] In order to overcome the defects of the above-mentioned prior art that the microalgae density detection steps are complicated and data transmission and communication are easily affected by bit errors, the present invention provides a microalgae density detection system and method based on visible light communication, which transmits signals while monitoring the microalgae density, and decodes the information after receiving it to obtain the microalgae density, thereby simplifying the detection process; in addition, the present invention directly establishes a conversion relationship between the bit error rate obtained by the visible light communication test and the microalgae density, which is completely unaffected by the bit error interference in the communication system, thereby ensuring the stability of monitoring.

[0006] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0007] A microalgae density detection system based on visible light communication, comprising: a transparent microalgae solution container, a light source, a photodetector, a DC power supply, a waveform generator, a coupler, an oscilloscope and a signal processor;

[0008] The microalgae solution container is used to contain microalgae solutions of different densities and varieties;

[0009] The waveform generator is electrically connected to one input end of the coupler, the DC power supply is electrically connected to the other input end of the coupler, and the output end of the coupler is electrically connected to the control end of the light source; the waveform generator is used to transmit a signal of a preset type, communication rate and voltage;

[0010] The DC power supply is also electrically connected to the photodetector; the output end of the photodetector is connected to an oscilloscope and a signal processor in sequence;

[0011] The light emitted by the light source passes through the microalgae solution container and is input into the photodetector, and the photodetector converts the received light signal into an electrical signal and then inputs it into the oscilloscope; the optical power fluctuation frequency of the light signal is the same as the emission signal frequency of the waveform generator;

[0012] The oscilloscope inputs the collected signal data into the signal processor; the signal processor obtains the communication bit error rate according to the signal data input by the oscilloscope, and calculates the microalgae density in the microalgae solution container in real time according to the communication bit error rate;

[0013] There is currently no integrated method and technology for real-time monitoring and transmission of microalgae density at home and abroad. Compared with the traditional microalgae density monitoring solution that involves multiple steps such as collecting microalgae samples, testing, calculating, storing, transmitting, and decoding, this system transmits signals while monitoring the microalgae density, and decodes the information after receiving it to obtain the microalgae density, with a simple process.

[0014] Preferably, the light source comprises: any one of a laser diode, a light emitting diode (LED), a micro-LED and a mini-LED.

[0015] Preferably, the system further comprises: a light attenuator, an aperture and a bandpass filter; the light attenuator is arranged between the light source and the microalgae solution container; the aperture and the bandpass filter are respectively arranged in front of the receiving surface of the photodetector;

[0016] During the test, if the test optical power is higher than the rated optical power of the photodetector, it may cause signal saturation and inaccurate test. Therefore, the optical attenuator is placed in front of the light source to adjust the strength of the optical signal to ensure that the optical power meets the test range of the photodetector; the bandpass filter can be used to filter out stray light in the surrounding environment; the aperture is used to adjust the spatial range of the incident light on the receiving surface of the photodetector.

[0017] Preferably, when the light source is any one of a light emitting diode (LED), a micro-LED and a mini-LED, the system further comprises a light conversion device, which is arranged between the light source and the microalgae solution container and is used to convert the color of the light emitted by the light source to obtain visible light of different wavelengths;

[0018] The solution of adding a light conversion device in front of the LED can be used for monitoring the density of microalgae under different monochromatic light conditions. The light conversion device can be a light conversion film or a light conversion solution.

[0019] Preferably, when the light source is a laser diode, the system further comprises a temperature controller, and the temperature controller is electrically connected to the light source and the DC power supply respectively;

[0020] When using a laser diode as a light source, since the laser diode has a high current density and generates heat quickly, a temperature controller needs to be connected to ensure the heat dissipation of the laser diode and monitor the heat dissipation process.

[0021] Preferably, the system further comprises: a reflector, wherein the light emitted by the light source passes through the microalgae solution container, is reflected by the reflector, passes through the microalgae solution container for a second time, and is then input into the photoelectric detector;

[0022] When a laser diode with higher collimation is selected as the light source, a thinner light beam can be obtained due to its higher collimation to pass through the microalgae solution bottle; therefore, when using a laser diode, the light can be reflected by the reflector to achieve the process of passing through the microalgae multiple times. This solution can be used for monitoring the density of microalgae under different optical path conditions.

[0023] Preferably, the modulation bandwidth of the coupler is greater than the modulation bandwidth of the light source;

[0024] When selecting a coupler, it is necessary to consider the modulation bandwidth range of the coupler, because the modulation bandwidth range of the coupler affects the test rate during the communication process; if the modulation bandwidth of the coupler is much lower than the modulation bandwidth of the light source, the modulation rate of the light source will be limited by the coupler.

[0025] The present invention also provides a microalgae density detection method based on visible light communication, based on the above-mentioned microalgae density detection system based on visible light communication, comprising the following steps:

[0026] The communication bit error rate is tested under known conditions of different communication rates and different densities of microalgae solutions to obtain a discrete data set of the communication bit error rate;

[0027] The signal processor uses a preset curve fitting algorithm to perform discrete data fitting on the discrete data set of the communication bit error rate to obtain the variation law of the communication bit error rate with the density of microalgae under different communication rate conditions. f BER (B, D); where B is the communication rate and D is the density of microalgae; the change rule f BER (B, D) is a linear or nonlinear relationship;

[0028] By comparing the changing rules under different communication rate conditions f BER (B, D), obtain the changing rules f BER (B, D) The linear change interval is used as the optimal test interval of microalgae density;

[0029] Under the preset test conditions, using the change law f BER (B, D) The linear change interval was used to test the unknown microalgae density;

[0030] The traditional method requires the transmission of test results through communication. However, bit errors may occur during the communication process, resulting in failure to transmit the test results. With this method, even if the communication bit error rate during the test is higher than the rated communication threshold, the size of the microalgae density obtained by the test can be directly reflected.

[0031] Preferably, the discrete data set of the communication bit error rate is expressed as:

[0032]

[0033] in, is the mth communication rate, is the density of the nth microalgae, m and n are the first and second positive integers respectively; is the communication bit error rate obtained by testing under the conditions of the mth communication rate and the nth microalgae density; This is the relationship between the communication rate and the density of microalgae.

[0034] Preferably, the preset test conditions include: general conditions and specific conditions;

[0035] The general conditions include: the modulation bandwidth of each hardware in the detection system is higher than the bandwidth required by the communication rate used in the test; the microalgae solution with unknown microalgae density is ensured to be evenly distributed; and the incident angle of the light source is kept unchanged during the test;

[0036] The specific conditions include: any one of: visible light of different wavelengths, different types of light sources, different algae species, different optical paths, and detecting microalgae density distribution;

[0037] When the specific conditions are changed, all steps in the microalgae density detection method are re-executed.

[0038] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0039] The present invention provides a microalgae density detection system and method based on visible light communication. First, the communication bit error rate is tested respectively by using known microalgae solutions of different communication rates and different densities to obtain a discrete data set of the communication bit error rate. Then, a signal processor performs discrete data fitting on the discrete data set of the communication bit error rate by using a preset curve fitting algorithm to obtain the variation law of the communication bit error rate with the microalgae density under different communication rate conditions. f BER (B, D); Change rules f BER (B, D) is a linear relationship or a nonlinear relationship; finally, the change law is used under different preset conditions f BER (B, D) The linear change interval was used to test the unknown microalgae density;

[0040] The beneficial effects of the present invention are as follows:

[0041] 1) The present invention realizes the real-time calculation of microalgae density by converting the real-time measurement data of the bit error rate in visible light communication into the real-time data of microalgae density. At the same time, this method facilitates the calculation of density-related parameters such as concentration and extinction coefficient;

[0042] 2) The present invention provides a test solution integrating sensing and communication, which transmits signals while monitoring the density of microalgae, decodes the information after receiving it, and obtains the density of microalgae, thus simplifying the detection process;

[0043] 3) The monitoring scheme of the present invention uses light as a medium, is contactless and environmentally friendly, does not require frequent sampling, and only requires a mobile testing device to monitor the density of the microalgae solution at different parts of the microalgae cultivation container, thereby avoiding the contamination of the microalgae solution caused by frequent sampling;

[0044] 4) The present invention directly uses the bit error rate obtained from the visible light communication test as the monitoring object, which has the advantages of being simple and easy to test. There is no need to worry about the problem of too high a bit error rate, and it is completely unaffected by the bit error interference in the communication system, thus ensuring the stability of monitoring;

[0045] 5) The present invention has certain commercial value. Whether from the aspects of marine sewage treatment, microalgae solution culture monitoring, or breakthroughs in key technologies of marine visible light communications, the present invention can support its technical needs and effectively assist in the realization of the "carbon neutrality and carbon peak" goals. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a connection diagram of the microalgae density monitoring system based on LED light source provided in Example 1.

[0047] Figure 2 This is a connection diagram of the microalgae density monitoring system based on LD light source provided in Example 2.

[0048] Figure 3 This is a connection diagram of a microalgae density monitoring system based on an LD light source and a reflector provided in Example 2.

[0049] Figure 4 This is a microalgae density distribution diagram of the bit error rate of green algae measured by red light at different communication rates provided in Example 3.

[0050] Figure 5 This is a microalgae density distribution diagram of the bit error rate of brown algae measured by red light at different communication rates provided in Example 3.

[0051] Figure 6 This is a microalgae density distribution diagram of the bit error rate of green algae measured by blue light at different communication rates provided in Example 3.

[0052] Figure 7This is a microalgae density distribution diagram of the bit error rate of brown algae measured by blue light at different communication rates provided in Example 3.

[0053] Figure 8 This is a distribution diagram of the decreasing trend of light power of different colors of light passing through green algae solutions of different densities provided in Example 3.

[0054] Fig. 9 This is a distribution diagram of the decreasing trend of light power of different colors of light passing through brown algae solutions of different densities provided in Example 3.

[0055] Fig.10 This is a distribution diagram of the accuracy of measuring different microalgae densities using yellow light provided in Example 3 at communication rates of 70 MHz, 80 MHz, and 90 MHz. DETAILED DESCRIPTION

[0056] The drawings are for illustrative purposes only and should not be construed as limiting the present patent;

[0057] In order to better illustrate the present embodiment, some parts in the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product;

[0058] It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0059] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0060] Example 1

[0061] This embodiment provides a microalgae density detection system based on visible light communication, comprising: a transparent microalgae solution container 1, a non-collimated light source 2, a photodetector 7, a DC power supply 15, a waveform generator 16, a coupler 6, an oscilloscope 17, a signal converter 18 and a signal processor 19;

[0062] The microalgae solution container 1 is used to hold microalgae solutions of different densities and varieties. In this embodiment, a small opening is opened on the top of the microalgae solution container 1, and a spiral cover is provided. The small opening is used to quantitatively place the microalgae solution therein, and the spiral cover is used to isolate the microalgae solution from the external environment. The material of the microalgae solution container 1 can be a transparent acrylic plate, glass, quartz stone, etc.; and the shape is preferably a square or a long strip, so that the light beam is incident vertically to reduce the impact on the monitoring results.

[0063] The microalgae solution container 1 in this embodiment is placed above the lifting platform 11 to adjust the horizontal height of the microalgae solution container 1 to ensure that the light beam passes through the center of the microalgae solution;

[0064] The waveform generator 16 is electrically connected to one input end of the coupler 6, the DC power supply 15 (the output is 0-30V in this embodiment) is electrically connected to the other input end of the coupler 6, and the output end of the coupler 6 is electrically connected to the control end of the non-collimated light source 2; the waveform generator 16 is used to transmit a signal of a preset type, communication rate and voltage;

[0065] The DC power supply 15 is also electrically connected to the photodetector 7; the output end of the photodetector 7 is connected to an oscilloscope 17, a signal converter 18 and a signal processor 19 in sequence;

[0066] The light emitted by the non-collimated light source 2 passes through the microalgae solution container 1 and is input into the photodetector 7. The photodetector 7 converts the received light signal into an electrical signal and then inputs it into the oscilloscope 17. The optical power fluctuation frequency of the light signal is the same as the emission signal frequency of the waveform generator 16.

[0067] The oscilloscope 17 inputs the collected signal data into the signal processor 19; the signal processor 19 obtains the communication bit error rate according to the signal data input by the oscilloscope 17, and calculates the microalgae density in the microalgae solution container 1 in real time according to the communication bit error rate;

[0068] The system further comprises: a light attenuator 8, an aperture 9 and a bandpass filter 10; the light attenuator 8 is arranged between the non-collimated light source 2 and the microalgae solution container 1; the aperture 9 and the bandpass filter 10 are respectively arranged in front of the receiving surface of the photodetector 7;

[0069] The non-collimated light source 2 is specifically any one of a light emitting diode LED, a micro-LED and a mini-LED. The system further comprises a light conversion device 4, which is arranged between the non-collimated light source 2 and the microalgae solution container 1, and is used to convert the color of the light emitted by the light source to obtain visible light of different wavelengths. When the non-collimated light source 2 adopts an ordinary light emitting diode, a temperature controller is usually not required under the condition of maintaining the heat dissipation of the base.

[0070] The modulation bandwidth of the coupler 6 is greater than the modulation bandwidth of the non-collimated light source 2;

[0071] When selecting a coupler, it is necessary to consider the modulation bandwidth range of the coupler, because the modulation bandwidth range of the coupler affects the test rate during the communication process; if the modulation bandwidth of the coupler is much lower than the modulation bandwidth of the light source, the modulation rate of the light source will be limited by the coupler. Therefore, in this embodiment, the coupler modulation bandwidth is up to 4 GHz, which is much higher than the modulation bandwidth of the LED light source.

[0072] In the specific implementation process, Figure 1As shown, the light conversion device 4 is fixed in front of the LED non-collimated light source 2, and the light source composed of the LED non-collimated light source 2 and the light conversion device 4 is placed in front of the microalgae solution container 1, and the light attenuator 8 is placed between the microalgae solution container 1 and the LED non-collimated light source 2 to adjust the light power; the LED non-collimated light source 2 is aligned with the central part of the microalgae solution container 1, so that the light passes vertically through the microalgae solution container 1 and reaches the position of the photodetector 7; wherein, the photodetector 7 is fixed with an aperture 9 and a bandpass filter 10; the height of the microalgae solution container 1 is adjusted by a lifting platform 11, The height of other components can be adjusted by the bracket 5; the DC signal provided by the DC power supply 15 and the AC signal generated by the waveform generator 16 are coupled through the coupler 6, and transmitted to the LED non-collimated light source 2 through the high-speed communication line 14 to make it emit light and emit a modulated signal at the same time; the photodetector 7 receives the light signal and displays the obtained signal change law on the oscilloscope 17, and the signal obtained by the oscilloscope 17 is converted into digital by the signal converter 18, and finally calculated and processed on the signal processor 19; the signal processor 19 can be a mobile terminal device such as a mobile phone, a tablet, or a computer;

[0073] In this embodiment, the light conversion device 4 is a light conversion film, which is generally in the form of a thin sheet to facilitate light to pass through the light conversion material; under the condition of designing a suitable light conversion material device, the light conversion film is also replaced by a light conversion solution; the thickness of the light conversion film is usually not more than 3 mm, otherwise the light transmittance will be greatly reduced, and the initial light intensity is too weak, which may affect the accuracy of the test results; at the same time, the selection of the light conversion film needs to consider its optical properties such as luminous color, quantum efficiency, luminous power, and its conversion rate and related modulation rate in the light conversion process. Communication properties;

[0074] Among the various light conversion materials used for lighting and display, such as commercial phosphors, organic dyes, perovskites, carbon dots, and quantum dots, quantum dot materials with high quantum efficiency, good monochromaticity, stable luminescence, and fast modulation rate are preferred when preparing light conversion films; taking cadmium selenide quantum dots as an example, it can produce most of the luminescent wavelengths in the visible light range under the excitation of blue light or ultraviolet light, and can achieve stable luminescence under high temperature conditions of more than 100 degrees, which meets the requirements of realizing multiple different light conversion wavelengths to test the density of microalgae in this embodiment;

[0075] The use of quantum dots as light conversion films has a great supporting role in achieving its effect. Compared with other light conversion materials, the technical advantages of quantum dots include: 1) The luminescence peak of quantum dots is narrow, and the half-peak width ranges from about 20 nanometers to 40 nanometers, which helps to avoid the influence of inconsistent absorption coefficients of different bands in microalgae solutions on the experiment; 2) The internal quantum yield of quantum dots can be as high as 90%, with high luminescence intensity, thus ensuring the stability of the total luminescence intensity; 3) The modulation bandwidth of quantum dots is higher than that of ordinary commercial phosphors, usually within 20MHz, while the modulation bandwidth of commercial phosphors is only within 3MHz. Therefore, when using quantum dots for testing, it can meet the test requirements of microalgae density under higher transmission rate conditions; 4) The luminescence color of quantum dots can be conveniently adjusted by controlling the size of quantum dots, element ratio, etc., so in the experiment The density of microalgae can be tested by using continuously changing monochromatic light, which cannot be achieved by using traditional semiconductor devices with discrete light emission peaks, such as laser diodes and high-power light-emitting diodes. 5) The luminescence properties of quantum dots are relatively stable in water and oxygen environments, can withstand high temperatures, and can be used with high-power LEDs and lasers to produce stable light output, thereby supporting the implementation of the experiment. 6) Compared with materials such as perovskites that have high requirements for non-polar environments, the manufacturing process of quantum dot membranes based on silicone materials can support quantum dots to be made into various flexible shapes to meet the needs of co-packaging with high-power light-emitting diodes in experiments.

[0076] In this embodiment, the photodetector 7 may be a PIN diode or an APD diode, etc. The APD diode has a high sensitivity and is suitable for high-speed communication scenarios;

[0077] In the present embodiment, the waveform generator 16 is an arbitrary waveform generator. The small voltage signal emitted by the arbitrary waveform generator is coupled with the DC voltage signal provided by the DC power supply through a coupler and transmitted to the positive and negative electrodes of the light source. Driven by the voltage, the light source starts to emit light and emits a light signal. The light power fluctuation frequency in the light signal is consistent with the emission signal frequency set by the arbitrary waveform generator. The small alternating current signal generated by the arbitrary waveform generator is used to characterize the density of microalgae. This can more sensitively feedback the changes in light power caused by the density of microalgae than the test method powered by DC current, and can solve the problem that the light power may be unstable when the traditional light source powered by DC power supplies tests the density of microalgae.

[0078] Example 2

[0079] This embodiment provides a microalgae density detection system based on visible light communication, comprising: a transparent microalgae solution container 1, a collimated light source 3, a photodetector 7, a DC power supply 15, a waveform generator 16, a coupler 6, an oscilloscope 17, a signal converter 18 and a signal processor 19;

[0080] The microalgae solution container 1 is used to contain microalgae solutions of different densities and species;

[0081] The microalgae solution container 1 in this embodiment is placed above the lifting platform 11 to adjust the horizontal height of the microalgae solution container 1 to ensure that the light beam passes through the center of the microalgae solution;

[0082] The waveform generator 16 is electrically connected to one input end of the coupler 6, the DC power supply 15 is electrically connected to the other input end of the coupler 6, and the output end of the coupler 6 is electrically connected to the control end of the collimated light source 3; the waveform generator 16 is used to transmit a signal of a preset type, communication rate and voltage;

[0083] The DC power supply 15 is also electrically connected to the photodetector 7; the output end of the photodetector 7 is connected to an oscilloscope 17, a signal converter 18 and a signal processor 19 in sequence;

[0084] The light emitted by the collimated light source 3 passes through the microalgae solution container 1 and is input into the photodetector 7. The photodetector 7 converts the received light signal into an electrical signal and then inputs it into the oscilloscope 17. The optical power fluctuation frequency of the light signal is the same as the emission signal frequency of the waveform generator 16.

[0085] The oscilloscope 17 inputs the collected signal data into the signal processor 19; the signal processor 19 obtains the communication bit error rate according to the signal data input by the oscilloscope 17, and calculates the microalgae density in the microalgae solution container 1 in real time according to the communication bit error rate;

[0086] The system further comprises: an optical attenuator 8, an aperture 9 and a bandpass filter 10; the optical attenuator 8 is arranged between the collimated light source 3 and the microalgae solution container 1; the aperture 9 and the bandpass filter 10 are respectively arranged in front of the receiving surface of the photodetector 7;

[0087] The collimated light source 3 is specifically a laser diode, and the system further comprises a temperature controller 13, wherein the temperature controller 13 is electrically connected to the collimated light source 3 and the DC power supply 15 respectively;

[0088] When using a laser diode as a light source, since the laser diode has a high current density and generates heat quickly, a temperature controller needs to be connected to ensure the heat dissipation of the laser diode and monitor the heat dissipation process;

[0089] The system further comprises: a reflector 12, after the light emitted by the collimated light source 3 passes through the microalgae solution container 1, it is reflected by the reflector 12 and then passes through the microalgae solution container 1 twice, and then is input into the photoelectric detector 7;

[0090] When a laser diode with high collimation is selected as the light source, a thinner light beam can be obtained due to its high collimation to pass through the microalgae solution bottle; therefore, when using a laser diode, the light can be reflected by the reflector to achieve a process of passing through the microalgae multiple times. This solution can be used for microalgae density monitoring under different optical path conditions;

[0091] The modulation bandwidth of the coupler 6 is greater than the modulation bandwidth of the collimated light source 3;

[0092] When selecting a coupler, it is necessary to consider the modulation bandwidth range of the coupler, because the modulation bandwidth range of the coupler affects the test rate during the communication process; if the modulation bandwidth of the coupler is much lower than the modulation bandwidth of the light source, the modulation rate of the light source will be limited by the coupler. Therefore, in this embodiment, the coupler modulation bandwidth is up to 4 GHz, which is much higher than the modulation bandwidth of the laser diode.

[0093] In the specific implementation process, Figure 2 The figure shows an implementation method of selecting a collimated light source, wherein the LD collimated light source 3 is placed in front of the microalgae solution container 1, and an optical attenuator 8 is placed between the microalgae solution container 1 and the LD collimated light source 3 to adjust the optical power; the LD collimated light source 3 is aligned with the central part of the microalgae solution container 1, so that the light passes vertically through the microalgae solution container 1 and reaches the position of the photodetector 7, wherein an aperture 9 and a bandpass filter 10 are fixed in front of the photodetector 7; the height of the microalgae solution container 1 is adjusted by a lifting platform 11, and the heights of other devices can be adjusted by a bracket 5; the DC signal provided by the DC power supply 15 and the AC signal generated by the arbitrary waveform generator 16 are coupled through a coupler 6, and transmitted to the LD collimated light source 3 through a high-speed communication line 14, so that it emits light while emitting a modulated signal; at the same time, the DC power supply 15 provides the current required by the temperature controller 13, so that the temperature controller 13 can continuously provide a temperature control function for the LD collimated light source 3; the photodetector 7 receives the optical signal and displays the obtained signal change law on the oscilloscope 17, and the signal obtained by the oscilloscope 17 is converted into analog to digital through a signal converter 18, and finally calculated and processed on a signal processor 19;

[0094] like Figure 3The figure shows an implementation method of selecting a collimated light source, wherein a reflector 12 is placed in front of a microalgae solution container 1, an LD collimated light source 3 and a photodetector 7 are placed behind the microalgae solution container 1, and an optical attenuator 8 is placed between the microalgae solution container 1 and the LD collimated light source 3 to adjust the optical power; the LD collimated light source 3 is aligned with one side of the microalgae solution container 1, and the light is allowed to vertically pass through the microalgae solution container 1 and reach one of the mirror surfaces of the reflector 12, and the light is reflected back to the microalgae solution container 1 by another optical path through two vertical mirror surfaces of the reflector 12, and vertically passes through the microalgae solution container 1 to reach the position of the photodetector 7, wherein an aperture 9 and a bandpass filter 10 are fixed in front of the photodetector 7; the microalgae solution container 1 is adjusted by the lifting platform 11, and the heights of other devices can be adjusted by the bracket 5; the DC signal provided by the DC power supply 15 is coupled with the AC signal generated by the arbitrary waveform generator 16 through the coupler 6, and is transmitted to the LD collimated light source 3 through the high-speed communication line 14, so that it emits a modulated signal while emitting light; at the same time, the DC power supply 15 provides the current required by the temperature controller 13, so that the temperature controller 13 can continuously provide the temperature control function for the LD collimated light source 3; the photodetector 7 receives the light signal and displays the obtained signal change law on the oscilloscope 17; the signal obtained by the oscilloscope 17 is converted into digital form by the signal converter 18, and finally calculated and processed on the signal processor 19.

[0095] Example 3

[0096] This embodiment provides a microalgae density detection method based on visible light communication, based on the microalgae density detection system based on visible light communication described in Embodiments 1 and 2, comprising the following steps:

[0097] The communication bit error rate is tested under known conditions of different communication rates and different densities of microalgae solutions to obtain a discrete data set of the communication bit error rate;

[0098] The discrete data set of the communication bit error rate is expressed as:

[0099]

[0100] in, is the mth communication rate, is the density of the nth microalgae, m and n are the first and second positive integers respectively; is the communication bit error rate obtained by testing under the conditions of the mth communication rate and the nth microalgae density; is the relationship between communication rate and microalgae density;

[0101] The signal processor uses a preset curve fitting algorithm to perform discrete data fitting on the discrete data set of the communication bit error rate to obtain the variation law of the communication bit error rate with the density of microalgae under different communication rate conditions. f BER (B, D); where B is the communication rate and D is the density of microalgae; the change rule f BER (B, D) is a linear or nonlinear relationship;

[0102] By comparing the changing rules under different communication rate conditions f BER (B, D), obtain the changing rules f BER (B, D) The linear change interval is used as the optimal test interval of microalgae density;

[0103] Under the preset test conditions, using the change law f BER (B, D) The linear change interval was used to test the unknown microalgae density;

[0104] The preset test conditions include: general conditions and specific conditions;

[0105] The general conditions include: the modulation bandwidth of each hardware in the detection system is higher than the bandwidth required by the communication rate used in the test; the microalgae solution with unknown microalgae density is ensured to be evenly distributed; and the incident angle of the light source is kept unchanged during the test;

[0106] The specific conditions include: any one of: visible light of different wavelengths, different types of light sources, different algae species, different optical paths, and detecting microalgae density distribution;

[0107] When the specific conditions are changed, all steps in the microalgae density detection method are re-executed.

[0108] In the specific implementation process, the microalgae density test first needs to determine the mapping relationship between the microalgae density and the communication bit error rate of the test; under the condition of setting different communication rates, the communication bit error rate obtained by the test will be different; therefore, at different communication rates ( , where m = 1, 2, 3 and other integers), the communication bit error rate corresponding to different densities of microalgae can be obtained ( , where n = 1, 2, 3 and other integers), the mapping relationship can be expressed as the following formula:

[0109]

[0110] in, , , , is the density of microalgae with a certain density gradient; The symbols represent the effect relationship between communication rate and microalgae density;

[0111] During the test, we first tested a microalgae solution with a known communication rate and concentration to obtain a data set of communication bit error rate. Then, we fitted the discrete data of the data set to obtain the variation law of the communication bit error rate with the density of the microalgae solution under different communication rate conditions. f BER (B, D); where the communication rate B and the microalgae density D are both bit error rate related functions f BER The variable of (B, D); the law of change f BER (B, D) The curve equations fitted by the data can be linear or nonlinear. The variation law of the communication bit error rate with the density of the microalgae solution under different communication rate conditions is obtained. f BER (B, D) After comparing the different communication rate B conditions, f BER (D) can be determined f BER (D) The linear variation interval is the optimal test interval for the microalgae solution;

[0112] If it is necessary to test the density of a new microalgae solution of the same species, the sample can be tested at the communication rate corresponding to the optimal test interval to obtain a certain communication bit error rate, and then the known f BER (B, D) Determine the density value of the microalgae solution corresponding to the communication bit error rate;

[0113] The above method can be used for microalgae density detection under different test conditions, specifically:

[0114] 1) Different algae species: Due to different light absorption characteristics of different microalgae, such as brown algae and green algae have different absorption of red light. Therefore, when the microalgae species are changed, it is necessary to find out the mapping relationship between the microalgae density and the tested communication bit error rate and the change law, and then test the solution density of different varieties of microalgae solutions;

[0115] 2) Different light sources and different wavelengths of visible light: The test light source can be replaced in the above test process, but due to the different light absorption characteristics of different microalgae, such as the large difference in the absorption of green light and red light by brown algae, when the test light source is changed, it is necessary to find out the mapping relationship and change law between the microalgae density and the communication bit error rate of the test, and then test the solution density of different varieties of microalgae solutions;

[0116] 3) Different optical paths: For microalgae solutions with low density (less than a certain value), a multi-optical path (with a reflector) test method can be used to ensure that the test results are clear and visible; similarly, for microalgae solutions with high density (greater than a certain value), a single optical path test method can be selected to avoid the impact caused by rapid light decay;

[0117] 4) Detection of microalgae density distribution: The above test method can also be used to test the density distribution of a large area of ​​microalgae solution. Under the condition of ensuring the consistency of the optical path, different communication bit error rates can be obtained by performing visible light communication in different areas of the microalgae solution. Therefore, the communication bit error rate based on the regional distribution characteristics can be used to indirectly reflect the density of the microalgae solution. It is also necessary to find out the change law again and then detect the density distribution of the microalgae.

[0118] The accuracy of this method can be verified by comparing the calculated density of the microalgae solution with the data of the density of the microalgae solution obtained by the traditional counting method;

[0119] In addition, for the tests under the above-mentioned specific conditions, some general conditions need to be met:

[0120] Ensuring that the modulation bandwidth of each hardware in the communication system is higher than the bandwidth required by the communication rate used in the test is the key to ensuring the accuracy of this method. All test equipment constitutes the detection system. The overall bandwidth of the system depends on the bandwidth of any device. For example, if the system bandwidth needs to be greater than 100, then the bandwidth of any device must be greater than 100. Hardware refers to all electronic components of the required test system.

[0121] According to Shannon's theorem:

[0122]

[0123] Where, C is the communication capacity, BW is the communication system bandwidth, and S / N is the signal-to-noise ratio. If the modulation bandwidth of the communication system hardware is lower than the bandwidth required for the communication rate used in the test, then under the communication rate test conditions, all communication bit error rate limitations will come from the system bandwidth limitations, rather than the optical power limitations. When the modulation bandwidth of the communication system hardware is high enough, all bit error rate limitations in this test will come from the optical power passing through the microalgae solution. Therefore, the communication bit error rate obtained by the test can indirectly reflect the change in optical power affected by the density of the microalgae solution.

[0124] In addition, the test accuracy can be further improved by ensuring the stability of the microalgae solution, removing stray light, and ensuring the stability of the test environment;

[0125] The test results of this method may have certain errors; the source of the error may be factors such as the instability of the test optical path, the change of the incident angle of light on the surface of the microalgae solution, and the current fluctuation; therefore, the key to improving the accuracy of this method is to ensure the uniformity of the microalgae solution before the test and to keep the incident angle of the test light source consistent;

[0126] The detection of microalgae density is mainly divided into the following parts:

[0127] 1) Calibration of microalgae solutions with different densities: Since the sizes and culture concentrations of different algae vary, a solution concentration gradient of approximately 1.5×10 8 cells / L of green algae solution, and a concentration gradient of about 1.5×10 9 8 portions of brown algae solution with 10 cells / L were used as comparison; at the same time, green, yellow and red quantum dot light conversion films were prepared to obtain monochromatic light sources of different colors; under the conditions of different communication rates, green light, yellow light, red light and blue light (original LED chip emission) were used as communication light to test the optical communication bit error rate;

[0128] The visible light communication bit error rate under different microalgae densities is tested to obtain discrete points of the optical communication bit error rate under different microalgae densities; a curve fitting algorithm is used to fit the gradient curve of the visible light communication bit error rate under different microalgae densities to obtain the nonlinear relationship between the microalgae density and the visible light communication bit error rate; through the nonlinear relationship, under the same communication test conditions, the communication bit error rate of the unknown microalgae density is continued to be tested, and it is compared with the obtained nonlinear curve, the density of the unknown microalgae solution is obtained from the comparison result, and it is compared with the microalgae density obtained by the traditional method to evaluate the accuracy of the algorithm proposed in this embodiment;

[0129] 2) Testing of microalgae density under different monochromatic light conditions: First, after obtaining the nonlinear relationship between microalgae density and visible light communication bit error rate under specific monochromatic light conditions, the nonlinear relationship between microalgae density and visible light communication bit error rate obtained under different monochromatic light conditions is compared, thereby obtaining a nonlinear relationship data set between microalgae density and visible light communication bit error rate under different monochromatic light conditions; combined with the absorption characteristic curves of microalgae solutions at different wavelengths, the mapping relationship between microalgae density and test monochromatic light under different color light conditions is established; finally, based on the absorption characteristic curves of microalgae solutions at different wavelengths, a nonlinear relationship between microalgae density and visible light communication bit error rate of monochromatic light within the visible light range is established;

[0130] 3) Testing of microalgae density under different optical path conditions: Under the condition that the microalgae container remains unchanged and the light is incident vertically, the optical path of the emitted light through the microalgae solution remains unchanged; under the condition of using a thinner laser beam for testing, the laser beam can be made to pass through the container of the microalgae solution and then irradiate the reflector at an angle of 45 degrees; then through another reflector perpendicular to the above reflector, the light beam is emitted again at an angle of 45 degrees, returns to the container of the microalgae solution, and vertically incident on the container of the microalgae solution to reach the photodetector; in the above test, the light source and the photodetector are located on the same side, and the distance between the light source and the photodetector is less than the width of the container of the microalgae solution to ensure that the light can vertically pass through the microalgae solution twice; the above method can obtain the test curve of the microalgae density obtained by testing under different optical path conditions;

[0131] 4) Microalgae density test of different algae species: After obtaining the nonlinear relationship between microalgae density and visible light communication bit error rate under specific monochromatic light conditions, the nonlinear relationship between microalgae density and visible light communication bit error rate of different algae species is compared to obtain a data set of nonlinear relationship between microalgae density and visible light communication bit error rate under different algae species conditions; then, the two algae can be mixed in proportion and the ratio coefficient of the two algae can be set; the communication bit error rate corresponding to the mixed microalgae solution can be obtained by the same method; the above communication bit error rate is compared with the bit error rate obtained by testing the solutions of the two algae separately, and the density of the mixed algae solution under the proportion condition can be obtained;

[0132] 5) Distributed test of microalgae density: In view of the uneven distribution of microalgae density, the microalgae density distribution can be tested; first, in order to prevent the influence of beam diffusion on the test results, a laser with collimation characteristics is required as the light source required for distributed testing; secondly, the laser can perform penetrating tests on various parts of the microalgae solution container and record the container position corresponding to the bit error rate of the test; finally, the microalgae density at each position of the microalgae solution container is calculated to obtain the density distribution image of the microalgae solution at different positions;

[0133] 6) Statistics on the accuracy of microalgae density calculation: In order to measure the accuracy of the microalgae density calculated by this method, this example compares the microalgae density calculated by this method with the microalgae density obtained by the traditional counting method, and the accuracy is defined as follows:

[0134]

[0135] That is, the accuracy rate is the microalgae density obtained by the counting method minus the absolute value of the microalgae density obtained by the present method divided by the microalgae density obtained by the counting method; if the accuracy rate is higher than 0 and lower than 1, it means that the error is small if it is close to 1;

[0136] The monitoring results of this method are as follows:

[0137] like Figure 4 As shown in the figure, when green algae is used as the monitoring object under green light communication conditions, the bit error rate shows a relatively obvious linear increasing trend with the increase of microalgae density; this increasing trend is mainly due to the influence of optical effects such as light reflection and absorption caused by the increase of microalgae density, which leads to a decrease in optical power and ultimately causes an increase in the bit error rate; although this linear trend is irregular under high and low communication rates, it shows quite regular characteristics at different communication rates when the communication rate is moderate; the constraint of this communication rate is due to the limited bandwidth of the quantum dots themselves, so it cannot support the system to run at a high communication rate; taking the linear trend of the bit error rate under 100MHz test conditions as an example: this trend can be fitted with BER=aX D +b formula, where X D represents the change in microalgae density, a and b represent the slope of the curve and the intersection with the y-axis respectively; under different communication rates, the b value of the formula shows almost linear changes, and the slope is almost unchanged, indicating that this method has good stability under different bit error rate test conditions and is applicable to a wide range of communication rates; however, when the communication rate is lower than 30MHz or higher than 90MHz, the formula has a large error and is not recommended for use; this is due to the fact that the bit error rate is too low and the change is not sensitive when measuring under low communication rate conditions, and the bit error rate is too high and cannot be measured under high communication rate conditions;

[0138] like Figure 5 As shown, Figure 5 The results are the variation rules of the communication bit error rate of brown algae under the same red light test conditions. Figure 4 The pattern of the results shown is similar;

[0139] like Figure 6 and Figure 7 As shown in Figure 2, when blue LEDs were used as communication light sources for testing green algae and brown algae, the bit error rate remained the same as that of the control algae when the density of the microalgae increased. Figure 4 , Figure 5 The similar increasing trend has the same principle; however, the test results under blue light communication conditions have two major drawbacks; first, the relationship between the bit error rate and the microalgae density is a nonlinear relationship, which is difficult to fit with a simple linear formula; second, under different communication rate conditions, the slope of the nonlinear curve shows a changing trend, which further increases the difficulty of using a formula to describe the relationship between the bit error rate and the microalgae density under different communication rate conditions; this phenomenon is due to the fact that when blue light is used as a communication light source, the microalgae's absorption rate of blue light is much higher than that of red light and other colors of light, resulting in the nonlinear characteristics; it can be inferred that the blue light in this method is not suitable for detecting the density change of the green algae solution;

[0140] also, Figure 8 and Fig. 9 The light power of green algae and brown algae with different concentrations was tested respectively. Among them, the blue light had the largest light power. After light conversion, the light power of orange light was higher than that of other lights, that is, its luminous efficiency was excellent. When the light passed through a low-concentration microalgae solution, its light power showed a cliff-like downward trend, such as Figure 8 and 9 As shown in the figure, as the concentration of microalgae increases, the light power shows a linear decreasing trend. In addition, it is found that under the condition of different color light transmission, the light power attenuation trend of green algae and brown algae is also inconsistent. Therefore, this also shows that different color light has a great influence on the test results of green algae and brown algae.

[0141] Fig.10 The results show that regardless of the communication rate of 70 MHz, 80 MHz or 90 MHz, the method proposed in this embodiment can provide a higher accuracy under the conditions of different unknown densities of microalgae, with an average accuracy of about 0.8, a maximum accuracy of about 0.98, and a minimum accuracy of about 0.68;

[0142] This method has many advantages, as follows:

[0143] 1) This method realizes the real-time calculation of the density of the microalgae solution by converting the real-time measurement data of the bit error rate in the wireless visible light communication into the real-time data of the density of the microalgae solution. At the same time, this method facilitates the calculation of density-related parameters such as concentration and extinction coefficient. This embodiment provides a test method integrating sensing and communication. The optical wireless communication process includes the transmission of information obtained from the optical sensing test.

[0144] 2) This embodiment provides a conversion algorithm for visible light communication bit error rate and microalgae solution density. The algorithm converts the bit error rate obtained from the visible light communication test into the density of the microalgae solution, thereby realizing a sensing-communication integrated algorithm.

[0145] 3) This embodiment studies and optimizes the conversion algorithm between the visible light communication bit error rate and the density of the microalgae solution. During the optimization process, the type of light source, the bandwidth of the light source communication system, the color of the light source, the absorption curve of the microalgae solution for different colors, the actual communication conditions, etc. are taken into consideration. Under different conditions, the parameters of the conversion algorithm are adjusted to ensure the accuracy of the results.

[0146] 4) Compared with the traditional dry weight method, ultrasonic detection method, counting method and electrode method, the process of this method is simpler; the traditional method of testing the concentration of microalgae solution requires multiple steps, including sampling, detection, calculation, information transmission, information storage and other links, and the testing of a large number of samples is prone to data confusion; while the testing steps of this method include preparing microalgae solution samples and testing to obtain experimental results. In special cases, the preparation steps of microalgae solution samples can even be omitted, such as dynamically monitoring the density of microalgae solution in a microalgae photobioreactor;

[0147] 5) The traditional method of sampling microalgae solution has the disadvantage of frequent sampling, which may lead to the introduction of new bacterial flora into the original microalgae solution, causing damage to the growth of microalgae. This method does not require frequent sampling, and only requires moving the test device to monitor the density of the microalgae solution at different parts of the microalgae culture container;

[0148] 6) This method uses light as the sensing and transmission medium, which will not affect the growth of the microalgae solution, nor cause contamination of the microalgae solution. It is a non-contact and environmentally friendly testing method;

[0149] 7) In addition to the monitoring function, this method also has scientific research value: Different from other technologies, this method can use different light conversion devices to obtain monochromatic light of different colors after conversion; by replacing different light conversion devices, the accuracy of the test of microalgae density under different monochromatic light conditions and their differences can be studied, and the differences in the test results of microalgae density of different microalgae solutions under different monochromatic light conditions and their causes can also be studied;

[0150] 8) By changing the type of light source, the density range of microalgae solution that can be tested by this method is larger; if a single light source, such as a laser diode, is used, the test results may be accurate within a certain microalgae density range; however, once the microalgae density increases, the power of the laser diode is at the milliwatt level, so it attenuates significantly, resulting in insensitivity to the density of high-concentration microalgae solution, thereby making the testable range of microalgae solution density smaller; on the contrary, when the density of the microalgae solution is high, using a high-power light-emitting diode for testing may obtain more accurate test results;

[0151] 9) This method has many adjustable parameters, including light source, light conversion device, type of microalgae solution, density of microalgae solution, transmission path of communication signal in microalgae, spatial position of microalgae solution test, photodetector, etc., which greatly meets the requirements of test accuracy and diversity;

[0152] The technical effects and advantages of this method are as follows:

[0153] 1) Technically, this method can realize visible light communication testing in a wide range of visible light communication rates from 5 MHz to about 1 GHz under conventional visible light communication test conditions. The communication rate range depends on the bandwidth of the entire communication system. Within this communication rate range, this method can realize accurate calculation of the density of microalgae solution under conventional aquaculture conditions;

[0154] 2) Technically, this method uses bit error rate as the monitoring object of the visible light communication system, because the bit error rate under a certain communication rate condition is easier to monitor than the communication rate under a certain bit error rate condition; therefore, this method selects the bit error rate of the visible light communication system as the test object, which has the advantages of simplicity and easy testing;

[0155] 3) In theory, this embodiment proposes an algorithm, after calibrating the density of the microalgae solution, the visible light communication bit error rate under different microalgae densities is tested, and the gradient curve of the visible light communication bit error rate under different microalgae densities is obtained by curve fitting method to obtain the variation law of microalgae density and visible light communication bit error rate; through this variation law, under the same test conditions, an unknown microalgae density is tested, and the test results are compared with the traditional microalgae solution density test results to evaluate the accuracy of this method;

[0156] 4) In theory, this embodiment proposes an algorithm. After obtaining the nonlinear relationship between the microalgae density and the visible light communication bit error rate under specific monochromatic light conditions, the nonlinear relationship between the microalgae density and the visible light communication bit error rate obtained under different monochromatic light conditions is compared, and combined with the absorption characteristic curves of the microalgae solution at different wavelengths, a universal nonlinear relationship between the microalgae density and the visible light communication bit error rate for monochromatic light in all visible light ranges is finally obtained;

[0157] 5) This method clarifies the density range of microalgae solutions that can be tested under different light sources and different luminous colors, as well as the communication rate range that can be used for testing, which provides guidance for microalgae density testing in different scenarios;

[0158] 6) This method is technically feasible and can be used for marine environment monitoring after the method is mature. Under outdoor test conditions, all test instruments involved in this method can be used for underwater detection after waterproof design.

[0159] 7) To ensure the calculation accuracy, this embodiment provides a calibration method for calculating the density of microalgae; if the calculation result of the density of microalgae is inaccurate, the density of microalgae can be recalibrated to improve the calculation accuracy;

[0160] 8) The role of this method is not limited to monitoring the single parameter of microalgae density, but can also provide a variety of test results for the test environment, such as the test results of communication bit error rate in different types of transmission media, the test results of communication bit error rate in transmission media with different concentrations, the test results of communication bit error rate under conditions of uneven medium concentration distribution, the extinction coefficient of monochromatic light of different colors in microalgae solutions, the extinction coefficient of monochromatic light in different types of microalgae solutions, the microalgae density tested at different optical communication rates, the microalgae density tested under different communication optical path conditions, etc.;

[0161] In addition, the novelty of this method is also supported by the following important aspects:

[0162] 1) The expected benefits and commercial value of this method after transformation are:

[0163] a. In marine sewage treatment, it is necessary to analyze the composition and characteristics of microalgae suspended matter in marine sewage sample suspensions. Combining the correlation between microalgae spectrum, scattering characteristics, transmission characteristics, etc. and microalgae concentration and composition, the seawater quality can be effectively evaluated from the perspective of its optical properties;

[0164] b. Currently, the cultivation of functional microalgae has occupied a certain market share nationwide, and the cultivation and monitoring process of microalgae is also increasingly tending to realize intelligent monitoring and evaluation of suspended solutions. The microalgae optical property evaluation mechanism proposed in this project can provide convenient technical support for it;

[0165] c. The current key technical bottleneck of marine visible light communication is that the transmission distance is easily limited by water quality characteristics. Therefore, by evaluating the optical properties of microalgae suspended seawater solution, the communication quality of underwater visible light communication under different water quality conditions can be dynamically grasped, which plays an important role in improving the communication rate and signal-to-noise ratio of marine visible light communication;

[0166] In summary, whether from the perspectives of marine sewage treatment, microalgae solution culture monitoring, or breakthroughs in key technologies for marine visible light communications, this method can support their technical needs and effectively assist in achieving the goals of “carbon neutrality and carbon peak”.

[0167] 2) This method fills the technical gap in the industry at home and abroad:

[0168] There are currently no integrated methods and technologies for real-time monitoring and transmission of microalgae density at home and abroad. Compared with the traditional microalgae density test method that involves multiple steps such as collecting microalgae samples, testing, calculating, storing, transmitting, and decoding, this method transmits signals while monitoring the microalgae density, and decodes the information to obtain the microalgae density after receiving it. The traditional method requires the test results to be transmitted through communication, but bit errors may occur during the communication process, resulting in failure to transmit the test results. With this method, even if the communication bit error rate during the test is higher than the rated communication threshold, the size of the microalgae density obtained from the test can be directly reflected.

[0169] 3) Does the technical solution of this method solve the technical problems that people have been eager to solve but have never been able to solve successfully?

[0170] People have always hoped to obtain a monitoring device that integrates sensing and communication, and use it in the fields of seawater monitoring, microalgae cultivation monitoring, etc. In this method, this problem is solved;

[0171] 4) Whether the technical solution of this method overcomes technical bias:

[0172] Traditionally, it is believed that when the communication bit error rate is higher than the hard decision value (i.e. 3.8 10 -3 ), it is determined that the error of the transmission signal is too large and the data is unreliable; however, by directly measuring the communication bit error rate to infer the density of the microalgae solution, there is no need to worry about the problem of too high a communication bit error rate. Even if the communication bit error rate is higher than the hard decision value, this method can be successfully implemented, which can solve the two major problems of data monitoring and transmission at the same time.

[0173] The same or similar reference numerals correspond to the same or similar components;

[0174] The terms used in the drawings to describe positional relationships are only used for illustrative purposes and should not be construed as limiting this patent;

[0175] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled 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 list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A microalgae density detection system based on visible light communication, characterized in that: include: a transparent microalgae solution container, a light source, a photodetector, a DC power supply, a waveform generator, a coupler, an oscilloscope, and a signal processor; The microalgae solution container is used to contain microalgae solutions of different densities and varieties; The waveform generator is electrically connected to one input end of the coupler, the DC power supply is electrically connected to the other input end of the coupler, and the output end of the coupler is electrically connected to the control end of the light source; the waveform generator is used to transmit a signal of a preset type, communication rate and voltage; The DC power supply is also electrically connected to the photodetector; the output end of the photodetector is connected to an oscilloscope and a signal processor in sequence; The light emitted by the light source passes through the microalgae solution container and is input into the photodetector, and the photodetector converts the received light signal into an electrical signal and then inputs it into the oscilloscope; The optical power fluctuation frequency of the optical signal is the same as the transmission signal frequency of the waveform generator; The light source includes: any one of a laser diode, a light emitting diode LED, a micro-LED and a mini-LED; When the light source is any one of a light emitting diode (LED), a micro-LED and a mini-LED, the system further comprises a light conversion device, which is disposed between the light source and the microalgae solution container and is used to convert the color of the light emitted by the light source to obtain visible light of different wavelengths; When the light source is a laser diode, the system further comprises a temperature controller, which is electrically connected to the light source and the DC power supply respectively; The oscilloscope inputs the collected signal data into the signal processor; the signal processor obtains the communication bit error rate according to the signal data input by the oscilloscope, and calculates the microalgae density in the microalgae solution container in real time according to the communication bit error rate.

2. A microalgae density detection system based on visible light communication according to claim 1, characterized in that: The system further comprises: a light attenuator, an aperture and a bandpass filter; the light attenuator is arranged between the light source and the microalgae solution container; the aperture and the bandpass filter are respectively arranged in front of the receiving surface of the photoelectric detector.

3. The microalgae density detection system based on visible light communication according to claim 1, characterized in that: The system further comprises a reflector. After the light emitted by the light source passes through the microalgae solution container, it is reflected by the reflector and then passes through the microalgae solution container for a second time, and then is input into the photoelectric detector.

4. A microalgae density detection system based on visible light communication according to any one of claims 1 to 3, characterized in that: The modulation bandwidth of the coupler is greater than the modulation bandwidth of the light source.

5. A method for detecting microalgae density based on visible light communication, based on the microalgae density detection system based on visible light communication as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: The communication bit error rate is tested under known conditions of different communication rates and different densities of microalgae solutions to obtain a discrete data set of the communication bit error rate; The discrete data set of the communication bit error rate is expressed as: Among them, B m is the mth communication rate, D n is the density of the nth microalgae, m and n are the first and second positive integers respectively; BER mn is the communication bit error rate obtained under the conditions of the mth communication rate and the nth microalgae density; ⊙ is the relationship between the communication rate and the microalgae density; The signal processor performs discrete data fitting on the discrete data set of the communication bit error rate using a preset curve fitting algorithm to obtain the variation law of the communication bit error rate with the density of microalgae under different communication rate conditions. BER (B, D); where B is the communication rate and D is the density of microalgae; the change law f BER (B, D) is a linear relationship or a nonlinear relationship; By comparing the changing rules under different communication rate conditions, BER (B,D), obtain the change law f BER (B, D) linear change interval, and used as the optimal test interval of microalgae density; Under the preset test conditions, using the variation law f BER (B, D) The linear change interval was used to test the unknown microalgae density; The preset test conditions include: general conditions and specific conditions; The general conditions include: the modulation bandwidth of each hardware in the detection system is higher than the bandwidth required by the communication rate used in the test; the microalgae solution with unknown microalgae density is ensured to be evenly distributed; and the incident angle of the light source is kept unchanged during the test; The specific conditions include: any one of: visible light of different wavelengths, different types of light sources, different algae species, different optical paths, and detecting microalgae density distribution; When the specific conditions are changed, all steps in the microalgae density detection method are re-executed.

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