Algae classification detector

Abstract

The invention provides an algae classification detector, comprising: a body provided with a detection cavity; the light shield is arranged on the water inlet side of the detection cavity and comprises a water permeable part and a light shielding part; the shading part and the water permeable part are arranged in a layered mode in the incident direction of the background ambient light, and the projection of the shading part in the incident direction covers at least one part of an opening area, used for water circulation, of the water permeable part so as to form a zigzag flow channel allowing the water to enter and blocking linear incidence of the ambient light; the multi-channel excitation light source is suitable for emitting excitation light with at least two different wavelengths to the water body; the optical receiving assembly comprises a detector and a spectrum selector; the spectrum selector is used for limiting an optical signal entering the detector in a preset emission wave band of a fluorescence emission peak of a to-be-detected substance in a water body so as to inhibit an interference optical signal not in the preset emission wave band from entering the detector; and the signal processing module is configured to obtain detection signals corresponding to different exciting lights and output a detection result of the to-be-detected substance based on the detection signals.

Description

Technical Field

[0001] This invention relates to the field of environmental water body detection technology, and in particular to an algae classification and detection instrument. Background Technology

[0002] In modern aquatic ecological monitoring, algal parameters (such as chlorophyll a concentration and taxa-related pigments) are often used as important biological indicators to characterize the state of aquatic ecosystems. To achieve dynamic monitoring of algal biomass, photosynthetic activity, and community changes, it is usually necessary to continuously or frequently measure relevant parameters under in-situ conditions, thereby providing data support for algal bloom early warning and aquatic ecological health assessment.

[0003] In existing in-situ detection methods, chlorophyll a fluorescence assay is widely used due to its high sensitivity and fast response. However, the chlorophyll a fluorescence signal is relatively weak, and the detection process is easily affected by background light interference. The effectiveness of background light suppression directly affects the precision and accuracy of the measurement results, and further affects the assessment error of indicators such as algal density and biomass. To improve the response to weak fluorescence signals, existing equipment often uses high-sensitivity photodetectors (such as photomultiplier tubes). However, high-sensitivity detectors amplify the background light signal along with the target signal, leading to increased measurement error.

[0004] Background light interference in in-situ aquatic environment detection typically falls into two categories: firstly, light radiation from the external environment (type I background light); and secondly, substances in the water that can be excited and produce fluorescence (type II background light), such as colored dissolved organic matter (CDOM). To address type I background light, some devices employ black cylindrical light shields under strong light conditions to reduce the amount of external light entering the detection area. However, this type of fully enclosed light-shielding structure often hinders the exchange between the detection chamber and the external water body, preventing timely updates of the sample and making it difficult to accurately reflect the temporal changes of the indicators. Without a light-shielding structure, it may be necessary to reduce the detector sensitivity to avoid background light saturation or overexposure, which in turn leads to an increase in the chlorophyll a detection limit.

[0005] For the second type of background light, some related technologies introduce interference terms into the signal processing / fitting model to separate the CDOM fluorescence contribution, but the increased model complexity may lead to parameter instability, limited applicability, and data overfitting; other technologies reduce interference signals by reducing the excitation light radiation intensity and / or reducing detector sensitivity, but this will also weaken the chlorophyll a signal, thereby raising the detection limit.

[0006] Therefore, how to effectively suppress the first and second types of background light interference under in-situ flow measurement conditions without significantly affecting water exchange, while simultaneously meeting the low detection limit requirements of parameters such as chlorophyll a, so as to achieve sensitive and reliable detection, is a technical problem that needs to be solved by existing technologies. Summary of the Invention

[0007] This invention provides an algae classification and detection instrument to solve the problem of insufficient accuracy and stability in measuring fluorescence signals such as chlorophyll a due to background light interference in in-situ aquatic ecological detection scenarios in the prior art.

[0008] This invention provides an algae classification and detection instrument, comprising: a main body, configured with a detection chamber suitable for containing water; a light shield disposed on the water inlet side of the detection chamber, including a water-permeable portion and configured to allow the water to enter the detection chamber; and a light shield disposed layered with the water-permeable portion along the incident direction of ambient light, wherein the projection of the light shield in the incident direction covers at least a portion of the opening area of ​​the water-permeable portion for water flow, thereby forming a tortuous flow channel for water to enter and blocking the straight-line incident ambient light; and a multi-channel excitation light source optically connected to the detection chamber, suitable for excitation of the detection chamber. The water body emits excitation light of at least two different excitation wavelengths; an optical receiving component, optically connected to the detection cavity, includes a detector and a spectral selector disposed on the incident light side of the detector; wherein the spectral selector is used to limit the light signal entering the detector to a preset emission band of the fluorescence emission peak of the analyte in the water body, so as to suppress interfering light signals outside the preset emission band from entering the detector; a signal processing module, electrically connected to the detector, is configured to acquire detection signals corresponding to different excitation lights, and output the detection result of the analyte based on the detection signals.

[0009] According to the algae classification and detection instrument provided by the present invention, the light shield includes a housing; the water-permeable part includes a flow hole array, comprising a plurality of flow holes opened on the housing and arranged along the length direction of the algae classification and detection instrument.

[0010] According to the algae classification detector provided by the present invention, the light-shielding part includes: a first light-shielding plate disposed on a first side of the flow hole array and a second light-shielding plate disposed on a second side opposite to the first side, wherein the end faces of the two light-shielding plates in the length direction are flush with the end face of the shell; the first light-shielding plate includes a first extension extending from the shell in a direction away from the shell, the end of the first extension having a curved portion biased towards the second side; the second light-shielding plate includes a second extension extending from the shell in a direction away from the shell and having a length greater than the first extension; a third extension extending from the end of the second extension toward the first side and beyond the root of the first extension; and a fourth extension extending from the end of the third extension toward the shell; wherein, in a projection perpendicular to the normal of the fourth extension, the fourth extension at least partially overlaps with the curved portion.

[0011] According to the algae classification and detection instrument provided by the present invention, the upper part of the shell is further provided with a vent hole, which is suitable for removing air bubbles in the detection chamber.

[0012] According to the algae classification detector provided by the present invention, the detection window of the detector is disposed in the upper part of the detection cavity; the detection window is constructed as a stepped structure, and the lower surface of the detection window extends downward relative to the upper edge of the detection cavity.

[0013] According to the algae classification detector provided by the present invention, the signal processing module is configured to: acquire the background signal of the detector as a dark background reference value when the multi-channel excitation light source is turned off, and subtract the dark background reference value from the detection signal acquired when the multi-channel excitation light source is turned on, so as to suppress the interference of dark current in the algae classification detector.

[0014] According to the algae classification detector provided by the present invention, the signal processing module is configured to acquire dark background reference values ​​for different excitation wavelengths, and to subtract the corresponding dark background reference values ​​from the detection signals corresponding to different excitation wavelengths.

[0015] According to the algae classification and detection instrument provided by the present invention, the multi-channel excitation light source includes at least six groups of light-emitting units with different center wavelengths; the algae classification and detection instrument further includes a driving and acquisition circuit, which is configured to drive each light-emitting unit to emit light according to a preset rule, and to enable the detector to acquire corresponding detection signals during the emission of each light-emitting unit, so as to form a group of detection signals corresponding to different excitation wavelengths.

[0016] According to the algae classification detector provided by the present invention, the excitation optical axis of the multi-channel excitation light source is set at a preset angle with the receiving optical axis of the detector, and they intersect in the detection cavity to form the optical measurement area.

[0017] According to the algae classification and detection instrument provided by the present invention, the window of the detector and the window of the multi-channel excitation light source are coated sapphire quartz sheets.

[0018] The algae classification detector provided by this invention reduces the amount of ambient light entering the detection chamber by setting a light shield that forms a non-direct light-shielding path on the water inlet side of the detection chamber, thus reducing the influence of external background light while ensuring water entry and exchange. A spectral selector is also set on the light-inlet side of the detector to limit the received light signal to a preset emission band near the fluorescence emission peak of the analyte, thereby suppressing interference signals from water fluorescence outside the preset emission band from entering the detector. A multi-channel excitation light source is used to acquire detection signals under different excitation conditions, and the signal processing module outputs the detection results, thereby improving the accuracy and stability of algae classification detection under in-situ flow conditions. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of an algae classification and detection instrument according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a light shield according to an embodiment of the present invention; Figure 3 This is a top view of a light shield according to an embodiment of the present invention.

[0021] Figure label: 1-Ontology; 2-Sunshade; 21-Shell; 22-Flow hole; 23-First sunshade; 231-First extension; 232 - Bending section; 241 - Second extension; 242 - Third extension; 243 - Fourth Extension; 24 - Second light-shielding plate; 25 - Ventilation holes; 3-Multi-channel excitation light source; 4-Optical receiving components. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] In existing in-situ fluorescence detection, a fully opaque structure is typically used to suppress ambient light, but this affects water exchange. Conversely, ensuring water exchange introduces strong background light, causing high-sensitivity detectors (such as PMTs) to experience background light spikes / saturation. This necessitates reducing detection sensitivity or excitation intensity, thus raising the detection limit for target fluorescence such as chlorophyll a. Therefore, there is an urgent need for an in-situ detector that can suppress background light interference while ensuring water exchange, thereby allowing for high-sensitivity detection and helping to lower the detection limit for chlorophyll a.

[0024] In view of this, the present invention provides an algae classification and detection instrument.

[0025] Figure 1 This is a schematic diagram of an algae classification and detection instrument according to an embodiment of the present invention.

[0026] The algae classification and detection instrument includes a main body 1, a light shield 2, a multi-channel excitation light source 3, an optical receiving component 4, and a signal processing module.

[0027] The main body 1 is equipped with a detection chamber suitable for containing water.

[0028] A light shield 2 is disposed on the water inlet side of the detection chamber. The light shield includes a water-permeable portion and a light-shielding portion. The water-permeable portion is configured to allow water to enter the detection chamber. The light-shielding portion and the water-permeable portion are arranged in layers along the incident direction of the ambient light, and the projection of the light-shielding portion in the incident direction covers at least a portion of the opening area of ​​the water-permeable portion for water flow, thereby forming a tortuous flow channel that allows water to enter while blocking the straight-line incident ambient light.

[0029] The multi-channel excitation light source 3 is optically connected to the detection cavity, and is suitable for emitting excitation light of at least six different excitation wavelengths into the water in the detection cavity.

[0030] The optical receiving component 4 is optically connected to the detection cavity and includes a detector and a spectral selector disposed on the light-incident side of the detector. The spectral selector is used to limit the light signal entering the detector to a preset emission band of the fluorescence emission peak of the analyte in the water, so as to suppress interference light signals from non-preset emission bands from entering the detector.

[0031] The signal processing module is electrically connected to the detector and is configured to acquire detection signals corresponding to different excitation lights, and output the detection results of the analyte based on the detection signals.

[0032] According to an embodiment of the present invention, the light shield 2 can be assembled onto the body by means of snap-fit ​​or bolt connection, wherein the light shield 2 and the body 1 together form an opaque detection cavity to eliminate the influence of background ambient light.

[0033] According to an embodiment of the present invention, the water-permeable part may be a plurality of through holes or slots provided on the light shield 2 to form an opening area for the water supply to enter and exit the detection chamber.

[0034] According to an embodiment of the present invention, the light-shielding part and the water-permeable part are arranged in layers. Exemplarily, the light-shielding part is arranged on the inner side of the detection cavity closer to the water-permeable part, and is arranged to surround the water-permeable part, so that the background ambient light incident along the opening area of ​​the water-permeable part is blocked in each projection direction, so as to form a dark chamber in the detection cavity as much as possible.

[0035] According to an embodiment of the present invention, the multi-channel excitation light source 3 has at least two sets of light-emitting units, each set of light-emitting units being used to send excitation light with different excitation wavelengths. The excitation wavelength of the excitation light can be configured and changed according to the excitation characteristics of the substance to be tested (e.g., algal pigments).

[0036] For example, based on the biochemical characteristics of the algal pigment to be tested (such as chlorophyll a), the center wavelength of its emitted fluorescence (such as 680 nm) is preset as a fixed monitoring window; then, the sample is excited and scanned in a continuous band using a fluorescence spectrophotometer to obtain the corresponding excitation spectrum.

[0037] Based on the obtained excitation spectrum, several characteristic peaks with the highest signal intensity are selected, and the excitation wavelengths of the path emission units of the multi-channel excitation light source are configured to the corresponding characteristic peak wavelengths to ensure that the maximum signal gain is obtained under a fixed emission detection window, thereby improving the sensitivity of the detector.

[0038] According to an embodiment of the present invention, the light-emitting unit may be implemented using an LED, a laser diode or other narrow-band light source, and shall be installed in a position that is optically connected to the detection cavity, so that the excitation light emitted by it can illuminate the optical measurement area inside the detection cavity.

[0039] According to an embodiment of the present invention, the multi-channel excitation light source 3 can employ a time-division multiplexing driving algorithm to control each channel to emit excitation light. For example, during the detection period T1, only the first channel is activated, at which time the detector synchronously acquires the fluorescence signal at that wavelength; while during the detection period T2, the first channel is deactivated, and the second channel is activated. This sequential pulse excitation method avoids spectral cross-interference between different excitation lights and reduces the impact of light source heating on measurement stability.

[0040] According to embodiments of the present invention, the detector may be a photomultiplier tube (PMT), a silicon photodiode, an avalanche photodiode (APD), or other photodetector devices. Its output terminal is electrically connected to a signal processing module to convert the received optical signal into an electrical signal for further processing. To improve the detection capability of weak fluorescence signals, the detector preferably employs a high-sensitivity detector device and can be used in conjunction with a preamplifier circuit to meet the range and noise requirements. According to an embodiment of the present invention, the spectral selector may include a bandpass filter, which may be directly mounted or fixedly installed at the incident light window of the detector. The center wavelength of the bandpass filter is set to match the fluorescence emission peak of the analyte, and its passband covers a preset emission band; its stopband is used to suppress light signals outside the preset emission band from entering the detector.

[0041] For example, if the analyte is chlorophyll a in water, its fluorescence emission peak is located near 680 nm. In this case, the spectral selector is configured as a bandpass filter with a center wavelength of 680 nm and a bandwidth of 10-20 nm. With this configuration, the spectral selector has high transmittance in the band near 680 nm, while having a high cutoff depth for light signals outside this band (especially excitation light generated by multi-channel excitation sources, background ambient light, and non-target band fluorescence generated by other fluorophores in the water). This allows the detector to primarily receive fluorescence signals near the emission peak of the analyte, while significantly attenuating background fluorescence signals outside this band, thereby improving the signal-to-noise ratio of the target fluorescence signal and enhancing detection stability.

[0042] In some embodiments, the spectral selector may be a filter wheel composed of multiple channels of different wavelengths, or a continuous spectral selector composed of a grating spectral dispersive mechanism. By rotating the filter wheel or adjusting the grating angle, it can adapt to the fluorescence detection needs of different substances to be tested (such as chlorophyll, phycocyanin, phycoerythrin, dissolved organic matter or polycyclic aromatic hydrocarbons).

[0043] Through the above-described configuration, the non-direct-path light-blocking path formed by the light-shielding cover reduces the incident intensity of ambient light entering the detection cavity without hindering water entry and exchange. This avoids relying solely on reducing detection sensitivity or excitation intensity to suppress background ambient light saturation. Simultaneously, the spectral selector on the light-incident side of the detector confines the received light signal to a preset emission band near the fluorescence emission peak of the analyte, suppressing interference signals from water fluorescence outside the preset emission band from entering the detector. This structural combination allows the algae classification detection device to stably acquire weak target fluorescence signals even under in-situ flow measurement conditions. This improves measurement stability and lowers the detection limit requirements for algal pigments such as chlorophyll a, phycocyanin, and phycoerythrin, thus providing a more reliable signal basis for algae classification output.

[0044] Figure 2 This is a schematic diagram of a light shield according to an embodiment of the present invention.

[0045] like Figure 2 As shown, the light shield includes a housing 21, and the water-permeable part includes an array of flow holes, which includes a plurality of flow holes 22 opened on the housing and arranged along the length direction of the algae classification detector.

[0046] According to an embodiment of the present invention, the shell 21 can be a planar structure, which is relatively simple to process. Water in the water body enters the detection chamber through the array of flow holes to complete the detection of algae in the water body.

[0047] According to an embodiment of the present invention, the housing 21 can also be configured as a three-panel structure, including a front and two opposite sides, each side having an array of flow holes. When performing water body detection, especially for water bodies with relatively fixed flow, such as in rivers or streams, the side with the array of flow holes can be oriented towards the direction of water flow, thereby enabling water body detection while ensuring water flow as much as possible.

[0048] Figure 3 This is a top view of a light shield according to an embodiment of the present invention.

[0049] like Figure 3 As shown, the light-shielding portion includes: a first light-shielding plate 23 disposed on a first side of the flow-through hole array and a second light-shielding plate 24 disposed on a second side opposite to the first side, wherein the end faces of the two light-shielding plates in the length direction are flush with the end faces of the housing. The first light-shielding plate 23 includes a first extension 231 extending from the housing 21 in a direction away from the housing, and the end of the first extension 231 has a curved portion 232 biased towards the second side. The second light-shielding plate 24 includes a second extension 241 extending from the housing 21 in a direction away from the housing and having a length greater than that of the first extension 231; a third extension 242 extending from the end of the second extension 241 toward the first side and exceeding the root of the first extension 231; and a fourth extension 243 extending from the end of the third extension 242 toward the housing 21. Wherein, in a projection perpendicular to the normal of the fourth extension 243, the fourth extension 243 and the curved portion 232 at least partially overlap.

[0050] According to an embodiment of the present invention, the light-shielding part may be made of materials such as stainless steel or titanium alloy, and the surface of the light-shielding part may be anodized or sprayed with black to increase the light-shielding effect.

[0051] According to another embodiment of the present invention, the light-shielding part may also be made of black plastic or composite material.

[0052] With the light shield provided by the present invention, due to the staggered arrangement of the first and second light shields, and the fact that the ends of the fourth extension and the curved portion can overlap in projection perpendicular to the normal of the fourth extension, a space that is basically sealed off from ambient light is formed inside the flow hole. Most of the ambient light is directly reflected or absorbed by the first and second light shields. Only a small portion of the incident light can enter the space between the fourth extension and the curved portion, and it must undergo repeated reflections by the fourth extension and the curved portion before it can pass through the light shield and enter the detection cavity. This arrangement can greatly reduce the influence of background ambient light on the detection results.

[0053] In outdoor testing, if the algae classification detector releases too quickly or the water flow in the water is too fast, some bubbles may be generated in the detection chamber. These bubbles accumulate in the detection chamber, which on the one hand will cause some refraction of the excitation light and emission light, thus interfering with the detection results; on the other hand, the accumulation of these bubbles will also affect the pressure balance inside and outside the detection chamber, hindering the flow of water samples.

[0054] In one illustrative embodiment, the upper part of the housing 21 is also provided with a vent 25, which is suitable for removing air bubbles in the detection chamber.

[0055] According to an embodiment of the present invention, the vent hole can be set within the range blocked by the light-shielding part to prevent background ambient light from entering the detection cavity through the vent hole.

[0056] In one illustrative embodiment, the detector's detection window is disposed at the upper part of the detection cavity. The detection window is configured with a stepped structure, and its lower surface extends downward relative to the upper edge of the detection cavity.

[0057] According to an embodiment of the present invention, since the density of the bubbles in the detection chamber is relatively low, the detection window is constructed as a downwardly protruding stepped structure. After the bubbles rise to the lower surface of the detection window, they can rise further, thereby avoiding the bubbles from adhering to the detection window and affecting the detection results.

[0058] Besides the two types of background interference—ambient light and fluorescence produced by colored dissolved organic matter in water under the influence of excitation light—dark currents in the electronic circuitry of the equipment and detectors can also interfere with the measurement.

[0059] Therefore, in one illustrative embodiment, the signal processing module is configured to: acquire the background signal of the detector as a dark background reference value when the multi-channel excitation light source is off, and subtract the dark background reference value from the detection signal acquired when the multi-channel excitation light source is on, so as to suppress the interference of dark current and background ambient light in the algae classification detector.

[0060] According to an embodiment of the present invention, when the multi-channel excitation light source is turned off, the detector acquires the background signal within a preset sampling time window to obtain a dark background reference value V. dark The dark background reference value is used to characterize the output baseline caused by factors such as detector dark current, amplifier circuit background noise, and ambient stray light under conditions without excitation light illumination.

[0061] With the multi-channel excitation light source activated and the water in the detection chamber excited, the detector acquires the corresponding detection signal V. light Next, the signal processing module subtracts the dark background reference value from the detection signal to obtain the effective fluorescence signal V after dark background correction. correct ,Right now:

[0062] The above process effectively suppresses dark current interference and circuit noise in the algae classification and detection instrument. This is achieved when an effective fluorescence signal V is obtained. correct Then, by using the non-negative least squares method for spectral decoupling analysis, the component contents of cyanobacteria, green algae, diatoms / dinoflagellates and cryptophytes in the water body can be accurately retrieved and further converted into corresponding algal density and biomass indicators.

[0063] According to embodiments of the present invention, the dark background reference value can be updated according to a preset period or before each measurement begins to adapt to changes in dark current caused by factors such as temperature variations and device drift. In multi-channel excitation applications, the dark background reference value can also be obtained separately for the sampling periods of different excitation channels and used to perform dark background subtraction on the detection signals of the corresponding channels to further improve the consistency and comparability of the multi-channel detection signal group.

[0064] In one illustrative embodiment, the signal processing module is further configured to acquire dark background reference values ​​for different excitation wavelengths, and to subtract the corresponding dark background reference values ​​from the detection signals corresponding to different excitation wavelengths.

[0065] Since the driving power, heating characteristics and transient response of each channel of the multi-channel excitation light source are different, by collecting and subtracting the corresponding dark background reference value for each excitation wavelength, the dynamic electrical drift and local thermal drift caused by the switching of the light-emitting unit can be eliminated, ensuring that the signals of each channel participating in the classification fitting have a high degree of linear consistency, thereby improving the accuracy of algal component identification in complex water samples.

[0066] In one illustrative embodiment, the multi-channel excitation light source includes at least two sets of luminescent units with different center wavelengths. The algae classification detector also includes a driving and acquisition circuit configured to drive each luminescent unit to emit light according to a preset rule, and to enable the detector to acquire corresponding detection signals during the luminescence of each luminescent unit, thereby forming a set of detection signals corresponding to different excitation wavelengths.

[0067] According to embodiments of the present invention, the driving and acquisition circuit can switch between different light-emitting units according to preset rules, such as using time-division driving or polling driving: at any given time, a group of light-emitting units is driven to emit light, and the detector acquires the corresponding detection signal during the illumination period of that light-emitting unit; then, the process is repeated with another group of light-emitting units, thereby forming a detection signal group corresponding one-to-one with different excitation wavelengths. The preset rules may include the lighting sequence of each channel, the lighting duration, the sampling time window, and the channel switching interval, etc., which can be specifically set according to the detector response speed and water flow conditions.

[0068] In one illustrative embodiment, the excitation optical axis of the multi-channel excitation light source is set at a preset angle to the receiving optical axis of the detector, and they intersect within the detection cavity to form an optical measurement area. This allows the receiving path of the detector to avoid the direct irradiation path of the excitation light, thereby reducing background noise and preventing premature photoelectric saturation of the high-sensitivity detector.

[0069] In one illustrative embodiment, the spectral selector is a bandpass filter.

[0070] In one illustrative embodiment, the detector window and the multi-channel excitation light source window are coated sapphire quartz sheets to prevent light flux and inhibit microbial growth.

[0071] In one illustrative embodiment, in order to characterize the fluorescence signal generated by the analyte (e.g., chlorophyll a) in the water under different excitation conditions, and to reduce the influence of background noise of electronic circuits, dark current of detectors, and fluorescence interference substances in the water on the measurement results, the signal processing module can normalize / correct and calculate the detection signal based on the fluorescence intensity model.

[0072] For example, at an excitation wavelength of λ ex The emission wavelength is λ em Under these conditions, the fluorescence intensity of a single fluorophore can be expressed by the following formula:

[0073] in, This is represented as the excitation wavelength being λ. ex The emission wavelength is λ em Fluorescence intensity under the given conditions; kThese are system constants related to the device's optical path structure, detector response, and gain of amplification and acquisition circuits. This indicates the emission spectrum of the analyte at the emission wavelength. The relative emission contribution in the vicinity; This indicates that the excitation light source is in The effective irradiance or equivalent excitation intensity at the location; Indicates the substance to be tested in The absorbance value of the fluorophore at the excitation wavelength.

[0074] Because algae produce relatively weak fluorescence, photomultiplier tubes (PMTs) with high sensitivity are typically used as detectors for detecting low concentrations of chlorophyll a. A typical PMT has a radiosensitivity of 150 V / nW. In this case, if the first and second types of background light are not reduced or eliminated, the background signal value (dark background reference value V) will be... dark The detector easily reaches its saturation value, making detection impossible. Simply reducing the detector's radiation sensitivity can lower the dark background reference value V. dark However, it cannot distinguish V at low algal concentrations. dark and V light .

[0075] According to embodiments of the present invention, a light shield with a tortuous flow channel that allows water to enter while blocking straight-line incident ambient light can be formed. This significantly reduces the likelihood of external ambient light entering the detection chamber along a straight path, while ensuring water entry and exchange within the detection chamber, thereby suppressing the influence of the first type of background light on weak fluorescence measurements. Secondly, by limiting the emission band to a preset wavelength on the light-incident side of the detector and setting multi-channel excitation conditions, the effective response of target pigments such as chlorophyll a within the preset emission band is kept within a range suitable for detection. Simultaneously, the contribution of fluorescent interfering substances in the water to the detection signal under non-target conditions is reduced, thereby suppressing the second type of background light. Finally, based on the reduction of background light interference, a dark background reference value is acquired under excitation light-off conditions and subtracted from the detection signal to reduce the residual background influence caused by detector dark current and electronic circuit background noise. Through the above settings, the combined suppression of external ambient light, water fluorescence interference, and system background noise is achieved, thereby improving the stability and reliability of algae classification detection under in-situ flow conditions.

[0076] Based on the above-described solution, the present invention also provides the following embodiments to illustrate the technical effects that the present invention can achieve.

[0077] Example 1 When the detector's radiation sensitivity is 80 mV / nW at 700 nm and the excitation source power is 0.75 W, the unfiltered water sample #1 has a radiation sensitivity of 80 mV / nW at 580 nm, 525 nm, and 460 nm. lightThe values ​​were 0.035±0.001 V, 0.044±0.001 V, and 0.091±0.001 V, respectively; the V values ​​for filtered water sample 1# (total organic carbon content of 6.8 mg C / L) were... light The values ​​are all equal to 0.0016 V. The in-situ detection of chlorophyll a concentration by the equipment is 39 μg / L, and the detection of chlorophyll a concentration according to national standard HJ 897-2017 is 42 μg / L, with an absolute deviation of 7%.

[0078] Example 2 When the detector's radiation sensitivity is 100 mV / nW at 700 nm and the excitation source power is 0.75 W, the unfiltered water sample #2 shows V0 at 580 nm, 525 nm, and 460 nm. light The values ​​were 0.018±0.001 V, 0.055±0.002 V, and 0.095±0.003 V, respectively; the V (light) values ​​for filtered water sample 2# (total organic carbon content of 2.4 mg C / L) were all 0.000 V. The in-situ chlorophyll a concentration detected by the equipment was 20 μg / L, and the chlorophyll a concentration detected according to the national standard HJ 897-2017 was 21 μg / L, with an absolute deviation of 5%.

[0079] Example 3 When the detector's radiation sensitivity is 50 mV / nW at 700 nm and the excitation source power is 0.50 W, the unfiltered water sample #3 shows Vt values ​​at 580 nm, 525 nm, and 460 nm. light The values ​​were 0.0021±0.0002 V, 0.0072±0.0004 V, and 0.0150±0.0007 V, respectively; the V values ​​for filtered water sample #3 (total organic carbon content of 4.3 mg C / L) were... light All values ​​were below 0.0004 V. The in-situ chlorophyll a concentration detected by the equipment was 7 μg / L, while the concentration detected according to the national standard HJ 897-2017 was 8 μg / L, with an absolute deviation of 12%.

[0080] Example 4 When the detector's radiation sensitivity is 60 mV / nW at 700 nm and the excitation source power is 0.8 W, the unfiltered water sample #4 has a radiation sensitivity of 60 mV / nW at 590 nm, 520 nm, 460 nm, and 420 nm. light The values ​​were 0.0185±0.0012 V, 0.0882±0.0037 V, 0.1442±0.0082 V, and 0.0882±0.0035 V, respectively; the V values ​​for filtered water sample 1# (total organic carbon content of 3.1 mg C / L) were... lightBoth values ​​were 0.0024 V. The total chlorophyll a concentration detected in situ by the equipment was 10 μg / L, while the chlorophyll a concentration detected according to the national standard HJ 897-2017 was 9 μg / L, with an absolute deviation of 11%. After treatment, the chlorophyll a contents of green algae, cyanobacteria, diatoms, and cryptophytes were 4.1, 0.40, 3.9, and 0.60 μg / L, respectively.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An algae classification and detection instrument, characterized in that, include: The main body is equipped with a detection chamber suitable for containing water. A light shield, disposed on the water inlet side of the detection chamber, includes a water-permeable portion configured to allow water to enter the detection chamber; and a light-shielding portion, which is disposed in layers with the water-permeable portion along the incident direction of ambient light, and the projection of the light-shielding portion in the incident direction covers at least a portion of the opening area of ​​the water-permeable portion for water flow, so as to form a tortuous flow channel for water to enter and block the straight incident of ambient light; A multi-channel excitation light source, optically connected to the detection cavity, is suitable for emitting excitation light of at least two different excitation wavelengths into the water in the detection cavity; An optical receiving component, optically connected to the detection cavity, includes a detector and a spectral selector disposed on the incident light side of the detector; wherein the spectral selector is used to limit the light signal entering the detector to a preset emission band of the fluorescence emission peak of the analyte in the water body, so as to suppress interfering light signals outside the preset emission band from entering the detector. The signal processing module, electrically connected to the detector, is configured to acquire detection signals corresponding to different excitation lights and output the detection results of the analyte based on the detection signals.

2. The algae classification and detection instrument according to claim 1, characterized in that, The light shield includes: case; The permeable part includes: an array of flow holes, comprising multiple flow holes opened on the shell and arranged along the length direction of the algae classification and detection instrument.

3. The algae classification and detection instrument according to claim 2, characterized in that, The light-shielding part includes: A first light-shielding plate is disposed on a first side of the flow hole array and a second light-shielding plate is disposed on a second side opposite to the first side, wherein the end faces of the two light-shielding plates in the length direction are flush with the end face of the housing; The first light-shielding plate includes a first extension extending from the housing in a direction away from the housing, and the end of the first extension has a curved portion biased towards the second side; The second light shield includes a second extension that extends from the housing away from the housing and has a length greater than the first extension; a third extension that extends from the end of the second extension toward the first side and beyond the root of the first extension; and a fourth extension that extends from the end of the third extension toward the housing. In a projection perpendicular to the normal of the fourth extension, the fourth extension at least partially overlaps with the curved portion.

4. The algae classification and detection instrument according to claim 2, characterized in that, The upper part of the housing is also provided with a vent hole, which is suitable for removing air bubbles in the detection chamber.

5. The algae classification and detection instrument according to claim 4, characterized in that, The detector's detection window is located at the upper part of the detection cavity; The detection window is constructed in a stepped structure, with the lower surface of the detection window extending downward relative to the upper edge of the detection cavity.

6. The algae classification and detection instrument according to claim 1, characterized in that, The signal processing module is configured as follows: When the multi-channel excitation light source is turned off, the background signal of the detector is collected as a dark background reference value, and the dark background reference value is subtracted from the detection signal collected when the multi-channel excitation light source is turned on, so as to suppress the interference of dark current and background ambient light in the algae classification detector.

7. The algae classification and detection instrument according to claim 6, characterized in that, The signal processing module is configured to acquire dark background reference values ​​for different excitation wavelengths and subtract the corresponding dark background reference values ​​from the detection signals corresponding to different excitation wavelengths.

8. The algae classification and detection instrument according to claim 1, characterized in that, The multi-channel excitation light source includes at least two sets of light-emitting units with different center wavelengths; The algae classification detector also includes a driving and acquisition circuit, which is configured to drive each light-emitting unit to emit light according to a preset rule, and to enable the detector to acquire the corresponding detection signal during the emission of each light-emitting unit, so as to form a group of detection signals corresponding to different excitation wavelengths.

9. The algae classification and detection instrument according to claim 1, characterized in that, The excitation optical axis of the multi-channel excitation light source is set at a preset angle to the receiving optical axis of the detector, and they intersect within the detection cavity to form the optical measurement area.

10. The algae classification and detection instrument according to claim 1, characterized in that, The detector window and the multi-channel excitation light source window are coated sapphire quartz sheets.

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