Chlorophyll and backscatter sensors

Abstract

The present invention relates to a chlorophyll and backscattering sensor, comprising: a housing, a first end of which is connected to an end cap; an optical lens assembly, provided with a signal light path and a reference light path, the signal light path is composed of two exit windows, a receiving window, a fluorescence excitation light source, a backscattered exit light source, a filter, and a photodetector, and is used to detect chlorophyll fluorescence signals and backscattered light signals; the reference light path is composed of an exit window, a receiving window, a reference light source, a filter, and a photodetector, and is used to detect reference signals; a control module is installed in the housing, comprising a light source modulation module, a signal demodulation module, and a main control module, the main control module receives a demodulation signal sent by the signal demodulation module and generates a light source modulation signal and sends it to the light source modulation module, and obtains the light intensity to be measured according to the demodulation signal; a power supply module is connected to the main control module to power the sensor. The present invention can effectively improve the accuracy and long-term working stability of the sensor, and the power consumption is less than 1W.

Description

Technical Field

[0001] The invention belongs to the technical field of underwater detection, and relates to a detection device, in particular to a chlorophyll and backscattering sensor. Background Art

[0002] Today, marine pollution is becoming more and more serious, and people's demand for marine environmental monitoring is becoming more and more urgent. Biogeochemical Argo profiling float (English: Biogeochemical-Argo, referred to as: BGC-Argo) is a new oceanographic integrated observation platform. By loading various sensors on the traditional temperature and salinity Argo float, it automatically observes the profile distribution and temporal changes of marine biogeochemical and marine ecological parameters for a long time. The in-situ sensors carried on the BGC-Argo float are the core of the in-situ observation of biogeochemical variables, including bio-optical parameter sensors such as chlorophyll concentration, particle backscattering, and downlink irradiance, as well as chemical parameter sensors such as dissolved oxygen, pH value, and nitrate. At present, various ecological sensors carried by BGC-Argo have begun to develop in the direction of multi-band, miniaturization, low power consumption, and high stability. Among them, chlorophyll and backscatter sensors with the same receiving wavelength and time-sharing multiplexing of the same physical receiving channel are the most common integrated combinations.

[0003] The components of the signals to be measured in bright field seawater are relatively complex, such as Figure 1 As shown, it mainly includes natural light, non-co-frequency background light, co-frequency background light, detector and circuit dark noise, LED pulse drive crosstalk, long-term working LED light source fluctuations and chlorophyll fluorescence / backscattered light signals. The common practice of existing sensors is to use bandpass filters and bandpass filter circuits to weaken and filter out natural light and non-co-frequency background light; and to eliminate dark noise and co-frequency background light by using a differential algorithm that regularly measures the signal when the LED is off and subtracts it from the signal when the LED is on. However, due to the difference in measurement time, the differential method leads to larger errors in environments with drastic fluctuations in background light or complex electromagnetic environments in the water, and even the situation where the measured signal when the LED is off is greater than the measured signal when the LED is on.

[0004] The chlorophyll and backscatter sensors that have been successfully used in the BGC-Argo program are the ECO series of WetLab, a subsidiary of Seabird in the United States. Taking ECO FLBB (FLBBRT-5543) as an example, it adopts a single optical path design, with 470nmLED and 700nm LED exciting fluorescence signals or backscatter signals. The single-channel receiving circuit receives the fluorescence signal and the backscatter signal respectively through time-division multiplexing. However, it lacks the suppression of co-frequency noise (such as the co-frequency components in the drastic changes in natural light caused by waves, the crosstalk of LED pulse driving signals, and the co-frequency components of electromagnetic noise in the water body caused by ships, etc.), and performs poorly in specific scenarios. At the same time, due to the lack of light source monitoring and response measures for biological attachment to the light window, the long-term working stability and accuracy of the sensor are reduced.

[0005] The document “Design of Bright-field Seawater Chlorophyll Sensor Based on Fluorescence Method, Jing Chao et al., Journal of Sensor Technology” records a bright-field seawater chlorophyll sensor based on an orthogonal digital phase-locked amplifier. However, this sensor also fails to consider the influence of co-frequency noise on the extraction of weak fluorescence signals by the orthogonal digital phase-locked amplifier technology and the attenuation of the LED light source during long-term operation, which reduces the long-term working stability and accuracy of the sensor. Its design based on mechanical brushes to clean the optical window is also not suitable for the environmental requirements of BGC-Argo working in a 0-2000m water depth profile. Summary of the invention

[0006] In view of the above-mentioned problems of poor sensor accuracy and long-term working stability in the prior art, the present invention provides a chlorophyll and backscattering sensor, which can effectively improve the accuracy and long-term working stability of the sensor while keeping the sensor power consumption less than 1W.

[0007] In order to achieve the above object, the present invention provides a chlorophyll and backscatter sensor, comprising:

[0008] a housing having a first end connected to the end cover;

[0009] Optical lens assembly, including:

[0010] The first exit window is arranged on the surface of the end cover, and a fluorescent excitation light source is arranged in the end cover channel inside the first exit window;

[0011] The second exit window is arranged on the surface of the end cover, symmetrically arranged with the first exit window, and a rear-scattering exit light source is arranged in the end cover channel inside the second exit window;

[0012] A first receiving window is provided on the surface of the end cover and is located between the first exit window and the second exit window, and a first filter and a first photodetector are sequentially installed in the end cover channel on the inner side thereof from the outside to the inside;

[0013] The third exit window is arranged on the surface of the end cover, symmetrically arranged with the second exit window, and a reference light source is arranged in the end cover channel inside the third exit window;

[0014] The second receiving window is arranged on the surface of the end cover, symmetrically arranged with the first receiving window, and the second filter and the second photoelectric detector are installed in the end cover channel inside the second receiving window in sequence from outside to inside;

[0015] The first exit window, the second exit window, the first receiving window, the fluorescence excitation light source, the backscattered light source, the first filter, and the first photodetector form a signal light path to detect the chlorophyll fluorescence signal and the backscattered light signal;

[0016] The third exit window, the second receiving window, the reference light source, the second filter, and the second photodetector form a reference light path to detect a reference signal;

[0017] The control module is installed in the housing and includes:

[0018] A light source modulation module is used to drive the fluorescence excitation light source, the backscattered emission light source, and the reference light source;

[0019] A signal demodulation module, which demodulates the signals detected by the first photodetector and the second photodetector;

[0020] The main control module receives the demodulation signal sent by the signal demodulation module, generates a light source modulation signal and sends it to the light source modulation module, and obtains the light intensity to be measured according to the demodulation signal;

[0021] The power module is connected to the main control module to provide power for the sensor.

[0022] Furthermore, the optical lens assembly also includes a third photodetector for monitoring the fluorescent excitation light source, which is arranged in the end cover channel inside the fluorescent excitation light source. The signal detected by the third light source detector is transmitted to the signal demodulation module and demodulated by the signal demodulation module.

[0023] Preferably, the signal demodulation module includes three signal acquisition circuits, namely, an optical signal acquisition circuit connected to the first photodetector, a reference signal acquisition circuit connected to the second photodetector, and a light source monitoring signal acquisition circuit connected to the third photodetector; each signal acquisition circuit includes:

[0024] An IV conversion circuit converts the current signal output by the photodetector into a voltage signal;

[0025] Active second-order high-pass filtering and amplifying circuit, which performs high-pass filtering and one-time amplification processing on the converted voltage signal;

[0026] The programmable gain amplifier performs a second amplification on the voltage signal after the first amplification, and adjusts the quadratic multiplier according to the strength of the signal to be measured;

[0027] The AD conversion circuit converts the voltage signal after the second amplification of the programmable gain amplifier into a digital voltage signal.

[0028] Furthermore, it also includes a temperature sensor, which is installed in the end cover, and the probe of the temperature sensor extends out of the end cover, and the temperature sensor is connected to the main control module.

[0029] Preferably, the main control module includes an FPGA, which is connected to the light source modulation module and the signal demodulation module respectively, receives the demodulation signal of the signal demodulation module and generates a light source modulation signal and sends it to the light source modulation module, and controls and drives the fluorescence excitation light source, the backscattered emission light source, and the reference light source to work through the light source modulation module; the FPGA is equipped with:

[0030] The orthogonal digital phase-locked amplifier module is connected to the signal demodulation module, and processes and calculates the demodulated signal received from the signal demodulation module to obtain the light intensity to be measured;

[0031] A first power management module is connected to the power module and manages the power module;

[0032] Communication interface module, communicates with external buoy.

[0033] Furthermore, an extreme ultraviolet decontamination module is also included, and the extreme ultraviolet decontamination module includes:

[0034] An extreme ultraviolet light source is disposed in the end cover channel below the third exit window and is located on one side of the reference light source;

[0035] The driving module is connected between the main control module and the extreme ultraviolet light source, and is used to drive the extreme ultraviolet light source to work.

[0036] Preferably, the main control module includes:

[0037] FPGA, connected to the light source modulation module and the signal demodulation module respectively, receives the demodulation signal of the signal demodulation module and generates a light source modulation signal and sends it to the light source modulation module, and controls and drives the fluorescence excitation light source, the backscattered emission light source, and the reference light source to work through the light source modulation module;

[0038] The single chip microcomputer is connected to the driving module, and controls and drives the extreme ultraviolet light source through the driving module;

[0039] Lithium battery, to power the microcontroller and driver module;

[0040] A charging module, connected to the power module, for charging the lithium battery;

[0041] FPGA internal features:

[0042] The orthogonal digital phase-locked amplifier module is connected to the signal adjustment module, and processes the demodulated signal received from the signal demodulation module to obtain the light intensity to be measured;

[0043] A first power management module is connected to the power module and the charging module respectively, and manages the power module and the charging module;

[0044] a communication interface module for communicating with an external buoy;

[0045] A second power management module is arranged inside the single chip microcomputer, and the second power management module is respectively connected to the power module and the charging module to manage the power module and the charging module.

[0046] Preferably, the orthogonal digital phase-locked amplifier module includes a first orthogonal digital phase-locked amplifier module and a second orthogonal digital phase-locked amplifier module working simultaneously; when the concentration of the substance to be measured is high, that is, when the output of the first orthogonal digital phase-locked amplifier module is greater than the output of the second orthogonal digital phase-locked amplifier module, the first orthogonal digital phase-locked amplifier module is used to process the demodulated signal to obtain the light intensity to be measured. At this time, the general expression of the demodulated signal is S=S I +S Z +C, where S I =Asin(ft+ψ) is the light signal to be measured, A is the light amplitude to be measured, i.e., the light intensity to be measured, f is the modulation frequency, ψ is the phase of the light signal to be measured; S Z is a specific frequency noise known in the working environment, such as power frequency noise; C is a DC signal component; when the concentration of the substance to be measured is low, that is, when the output of the first orthogonal digital phase-locked amplifier module is less than or equal to the output of the second orthogonal digital phase-locked amplifier module, the second orthogonal digital phase-locked amplifier module is used to process the demodulated signal to obtain the light intensity to be measured. At this time, the general expression of the demodulated signal is S = S I +S Z1 +S Z2 +C, where S I The demodulated signal of the reference signal acquisition circuit is 0, and the demodulated signal of the optical signal acquisition circuit is Asin(ft+ψ), which is the optical signal to be measured. is n groups of non-co-frequency noise signals, N1(x) is the amplitude of the x-th group of non-co-frequency noise, f′(x) is the frequency of the x-th group of non-co-frequency noise, θ1(x) is the phase of the x-th group of non-co-frequency noise; is the mth group of same-frequency noise signals, N2(y) is the amplitude of the yth group of same-frequency noise, θ2(y) is the phase of the yth group of same-frequency noise;

[0047] The first orthogonal digital phase-locked amplifier module includes:

[0048] A subtractor for eliminating a DC component in a demodulated signal;

[0049] Notch filter, used to eliminate known specific frequency noise components in known working environment;

[0050] The multiplier multiplies the two reference signals with a phase difference of 90° with the output of the notch filter. The optical signal acquisition circuit obtains two signals V1 and V2. The frequencies of the two reference signals are the same as the frequency of the optical signal to be measured. The first reference signal is Bsin(ft+φ), and the second reference signal is Bcos(ft+φ), where B is the known reference signal amplitude and φ is the phase.

[0051] FIR type low-pass filter, with a cutoff frequency of F, F = f, eliminates the signals with a frequency higher than f in the signals V1 and V2 obtained by the multiplier to obtain intermediate signals V1′ and V2′;

[0052] The calculation module performs square, sum, and square root operations on the intermediate signals V1′ and V2′ obtained by the FIR low-pass filter to obtain the signal V OUT1 ;

[0053] The window smoothing module calculates the output signal V OUT1 Perform low-pass filtering and window smoothing to obtain the sensor output signal V corresponding to the amplitude A of the light signal to be measured. OUT1 ′;

[0054] The second orthogonal digital phase-locked amplifier module includes:

[0055] The FIR type high-order bandpass filter is used to eliminate the DC signal component and the non-co-frequency noise signal component in the demodulated signal, and to amplify the optical signal to be measured by cutting the output bit width;

[0056] A multiplier multiplies two reference signals with a phase difference of 90° with the output of the FIR type high-order bandpass filter. The optical signal acquisition circuit obtains two signals V3 and V4, and the reference signal acquisition circuit obtains two signals U3 and U4. The frequencies of the two reference signals are the same as the frequency of the optical signal to be measured. The first reference signal is Bsin(ft+φ), and the second reference signal is Bcos(ft+φ), where B is the known reference signal amplitude and φ is the phase;

[0057] FIR type low pass filter, with a cut-off frequency of F, F = f, eliminates the signals with a frequency higher than f in the signals V3, V4 and U3, U4 obtained by the multiplier to obtain intermediate signals V3', V4' and U3', U4';

[0058] The subtractor subtracts V3′ and U3′ calculated by the FIR low-pass filter, and V4′ and U4′ to obtain intermediate signals V1″ and V2″ respectively, eliminating the same-frequency noise in the demodulated signal of the optical signal acquisition circuit;

[0059] The calculation module performs square, sum, and square root operations on the intermediate signals V1" and V2" obtained by the subtractor to obtain the signal V OUT2 ;

[0060] The window smoothing module calculates the output signal V OUT2 Perform low-pass filtering and window smoothing to obtain the sensor output signal V corresponding to the amplitude A of the light signal to be measured. OUT2 ′.

[0061] Preferably, the light source modulation module comprises:

[0062] DA conversion module, receives the digital modulation signal sent by FPGA and converts it into an analog modulation signal;

[0063] The constant current driving module is respectively connected to the fluorescent excitation light source, the backscattered emission light source and the reference light source, and drives the fluorescent excitation light source, the backscattered emission light source and the reference light source to work according to the modulation signal.

[0064] Preferably, the fluorescent excitation light source and the rear scattered emission light source are time-division multiplexed in the optical signal acquisition circuit.

[0065] Compared with the prior art, the advantages and positive effects of the present invention are:

[0066] (1) The chlorophyll and backscattering sensor of the present invention adopts a dual optical signal light path design of a signal light path and a reference light path, which can effectively suppress co-frequency noise, reduce the influence of co-frequency noise and the attenuation of a long-term working LED light source on the detection of weak fluorescence signals, and improve the long-term working stability and accuracy of the sensor.

[0067] (2) The chlorophyll and backscatter sensor of the present invention is provided with an extreme ultraviolet decontamination module, which plays a role in preventing biological attachment to the optical window (i.e., the third exit window). The present invention applies extreme ultraviolet light anti-biological attachment technology to the chlorophyll and backscatter sensor, which solves the defect that the sensor cannot use the traditional built-in mechanical brush to clean the optical window in the application scenario of large water depth span, and further improves the stability and accuracy of the sensor in long-term operation.

[0068] (3) The chlorophyll and backscatter sensor of the present invention is provided with an orthogonal digital phase-locked amplifier module, which uses an orthogonal digital phase-locked amplifier technology to extract the light signal to be measured. The orthogonal digital phase-locked amplifier module adopts a dual-channel heterogeneous structure and can simultaneously output two channels of high and low gain data. The user can choose which data to use based on the comparative analysis of the two channels of data. The present invention can improve the sensitivity and detection limit of the sensor at low concentrations and increase the dynamic range of the sensor at high concentrations without changing the circuit through the orthogonal digital phase-locked amplifier module.

[0069] (4) The chlorophyll and backscatter sensor of the present invention adopts a dual-master control design and uses the high parallel computing capability of FPGA to realize the modulation of multiple light sources and the digital filtering and orthogonal digital phase-locked amplification of multiple signals; and uses a low-power single-chip microcomputer to realize the control of the extreme ultraviolet decontamination module and the low power consumption requirements.

[0070] (5) The chlorophyll and backscattering sensor of the present invention can effectively improve the accuracy and long-term working stability of the chlorophyll and backscattering sensor while keeping the sensor power consumption less than 1W. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 The schematic diagram of the existing signal composition to be tested and the noise removal and background light of the same frequency by differential method;

[0072] Figure 2 This is a schematic diagram of the three-dimensional structure of the chlorophyll and backscattering sensor according to an embodiment of the present invention;

[0073] Figure 3 It is a cross-sectional view of the chlorophyll and backscattering sensor described in Example 1 of the present invention;

[0074] Figure 4 This is a schematic diagram of the end cover structure of the chlorophyll and backscatter sensor according to an embodiment of the present invention;

[0075] Figure 5 for Figure 4 AA section view;

[0076] Figure 6 for Figure 4 BB cross-sectional view;

[0077] Figure 7 for Figure 4 CC section view;

[0078] Figure 8 This is a circuit schematic diagram of the chlorophyll and backscatter sensor described in Example 1 of the present invention;

[0079] Fig. 9 It is a structural block diagram of the orthogonal digital phase-locked amplifier module according to an embodiment of the present invention;

[0080] Fig.10 A cross-sectional view of the chlorophyll and backscatter sensor according to Example 2 of the present invention;

[0081] Fig.11 This is a circuit schematic diagram of the chlorophyll and backscatter sensor described in Example 2 of the present invention.

[0082] In the figure, 1, housing, 2, end cover, 311, first exit window, 312, second exit window, 313, third exit window, 321, first receiving window, 322, second receiving window, 331, first filter, 332, second filter, 341, first photodetector, 342, second photodetector, 351, first filter ring, 352, second filter ring, 361, first detector ring, 362, second detector ring, 41, fluorescence excitation light source, 42, rear scattered exit light source, 43, reference light source, 5, light source modulation module, 51, DA conversion module, 52, constant current drive module, 6, signal demodulation module, 61, IV conversion circuit, 62, active second order low Pass filter and secondary amplifier circuit, 63, programmable gain amplifier, 64, AD conversion circuit, 7, main control module, 71, FPGA, 711, orthogonal digital phase-locked amplifier module, 7111, first orthogonal digital phase-locked amplifier module, 7112, second orthogonal digital phase-locked amplifier module, 712, first power management module, 713, communication interface module, 714, light source modulation signal generation module, 72, single-chip microcomputer, 721, second power management module, 73, lithium battery, 74, charging module, 8, power module, 9, temperature sensor, 10, extreme ultraviolet decontamination module, 101, extreme ultraviolet light source, 102, drive module, 11, circuit control board, 12, lithium battery bracket, 13, water sealing plug-in. DETAILED DESCRIPTION

[0083] The present invention is described in detail below by way of exemplary embodiments. However, it should be understood that elements, structures, and features in one embodiment may also be beneficially combined in other embodiments without further description.

[0084] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", etc. are based on the positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0085] Example 1: See Figures 2 to 8 , an embodiment of the present invention provides a chlorophyll and backscatter sensor, including:

[0086] A shell 1, a first end of which is connected to an end cover 2;

[0087] Optical lens assembly, including:

[0088] The first emission window 311 is provided on the surface of the end cover 2, and a fluorescent excitation light source 41 is provided in the end cover channel inside the first emission window 311;

[0089] The second exit window 312 is provided on the surface of the end cover 2, symmetrically arranged with the first exit window 311, and a rear-scattering exit light source 42 is provided in the end cover channel inside the second exit window 312;

[0090] The first receiving window 321 is provided on the surface of the end cover 2, and is located between the first exit window 311 and the second exit window 312. The first filter 331 and the first photodetector 341 are sequentially installed in the inner end cover channel from outside to inside;

[0091] The third exit window 313 is provided on the surface of the end cover 2, symmetrically arranged with the second exit window 312, and a reference light source 43 is provided in the inner end cover channel;

[0092] The second receiving window 322 is provided on the surface of the end cover 2, and is symmetrically arranged with the first receiving window 321. The second filter 332 and the second photodetector 342 are sequentially installed in the end cover channel on the inner side thereof from the outside to the inside;

[0093] The third photodetector 343 is used to monitor the fluorescence excitation light source 41 and is disposed in the end cover channel inside the fluorescence excitation light source 41;

[0094] The first exit window 311, the second exit window 312, the first receiving window 321, the fluorescence excitation light source 41, the backscattered light source 42, the first filter 331, and the first photodetector 341 form a signal light path to detect the chlorophyll fluorescence signal and the backscattered light signal;

[0095] The third exit window 313, the second receiving window 312, the reference light source 43, the second filter 332, and the second photodetector 342 form a reference light path to detect a reference signal;

[0096] The control module is installed in the housing and includes:

[0097] The light source modulation module 5 is used to drive the fluorescence excitation light source 41, the backscattered emission light source 42, and the reference light source 43 to work;

[0098] A signal demodulation module 6 demodulates the signals detected by the first photodetector 341, the second photodetector 342 and the third photodetector 343;

[0099] The main control module 7 receives the demodulation signal sent by the signal demodulation module 6 and generates a light source modulation signal and sends it to the light source modulation module 5, and obtains the light intensity to be measured according to the demodulation signal;

[0100] The power module 8 is connected to the main control module 7 to supply power to the sensor.

[0101] Specifically, see Figures 5 to 7 , the first filter 331 is fixed by the first filter pressing ring 351, and the second filter 332 is fixed by the second filter pressing ring 361. The first filter pressing ring 351 is sleeved on the upper part of the first photodetector 341, and the first filter pressing ring 351 and the first detector pressing ring 361 sleeved on the middle part of the first photodetector 341 separate the first photodetector 341 from the end cover 2, which plays an insulating role. At the same time, the first detector pressing ring 361 fixes the first photodetector 341. The second filter pressing ring 352 is sleeved on the upper part of the second photodetector 342, and the second filter pressing ring 352 and the second detector pressing ring 362 sleeved on the middle part of the second photodetector 342 separate the second photodetector 342 from the end cover 2, which plays an insulating role. At the same time, the second detector pressing ring 362 fixes the detector. It should be noted that both the filter pressing ring and the detector pressing ring are made of non-metallic POM material.

[0102] Continue to see Figure 8 The main control module 7 includes an FPGA 71, which is connected to the light source modulation module 5 and the signal demodulation module 6 respectively, receives the demodulation signal of the signal demodulation module 6 and generates a light source modulation signal and sends it to the light source modulation module 5, and controls and drives the fluorescence excitation light source 41, the backscattered emission light source 42, and the reference light source 43 to work through the light source modulation module 5.

[0103] Continue to see Figure 8 FPGA 71 has:

[0104] The orthogonal digital phase-locked amplifier module 711 is connected to the signal demodulation module 6, and processes and calculates the demodulated signal received from the signal demodulation module 6 to obtain a sensor output signal corresponding to the amplitude of the optical signal to be measured;

[0105] A first power management module 712, connected to the power module 8, manages the power module 8;

[0106] A communication interface module 713, for communicating with an external buoy;

[0107] The light source modulation signal generating module 714 is used to generate a light source modulation signal and send it to the light source modulation module 5 .

[0108] See also Fig. 9The orthogonal digital phase-locked amplifier module includes a first orthogonal digital phase-locked amplifier module 7111 and a second orthogonal digital phase-locked amplifier module 7112 that work simultaneously. When the concentration of the substance to be measured is high, that is, when the output of the first orthogonal digital phase-locked amplifier module is greater than the output of the second orthogonal digital phase-locked amplifier module, the first orthogonal digital phase-locked amplifier module is used to process the demodulated signal to obtain the light intensity to be measured. At this time, the general expression of the demodulated signal is S=S I +S Z +C, where S I =Asin(ft+ψ) is the light signal to be measured, A is the amplitude of the light to be measured, i.e., the light intensity to be measured, f is the modulation frequency, ψ is the phase of the light signal to be measured, S Z is the specific frequency noise known in the working environment (such as power frequency noise, etc.); C is the DC signal component. When the concentration of the substance to be measured is low, that is, when the output of the first orthogonal digital phase-locked amplifier module is less than or equal to the output of the second orthogonal digital phase-locked amplifier module, the second orthogonal digital phase-locked amplifier module is used to process the demodulated signal to obtain the light intensity to be measured. At this time, the general expression of the demodulated signal is S = S I +S Z1 +S Z2 +C, where S I The demodulated signal of the reference signal acquisition circuit is 0, and the demodulated signal of the optical signal acquisition circuit is Asin(ft+ψ) for the optical signal to be measured, A is the amplitude of the optical signal to be measured that needs to be calculated, that is, the intensity of the optical signal to be measured, f is the modulation frequency, and ψ is the phase of the optical signal to be measured; is n groups of non-co-frequency noise signals, N1(x) is the amplitude of the x-th group of non-co-frequency noise, f′(x) is the frequency of the x-th group of non-co-frequency noise, θ1(x) is the phase of the x-th group of non-co-frequency noise; are m groups of same-frequency noise signals, N2(y) is the amplitude of the y-th group of same-frequency noise, θ2(y) is the phase of the y-th group of same-frequency noise; C is the DC signal component.

[0109] Specifically, see Fig. 9 , the first orthogonal digital phase-locked amplifier module 7111 includes:

[0110] A first subtractor, used to eliminate a DC component in the demodulated signal;

[0111] Notch filter, used to eliminate known specific frequency noise components in known working environment;

[0112] The multiplier multiplies the two reference signals with a phase difference of 90° with the output of the notch filter. The optical signal acquisition circuit obtains two signals V1 and V2. The frequencies of the two reference signals are the same as the frequency of the optical signal to be measured. The first reference signal is Bsin(ft+φ), and the second reference signal is Bcos(ft+φ), where B is the known reference signal amplitude and φ is the phase.

[0113] FIR type low-pass filter, with a cutoff frequency of F, F = f, eliminates the signals with a frequency higher than f in the signals V1 and V2 obtained by the multiplier to obtain intermediate signals V1′ and V2′;

[0114] The first calculation module performs square, sum, and square root operations on the intermediate signals V1′ and V2′ obtained by the FIR low-pass filter to obtain a signal V OUT1 ;

[0115] The first window smoothing module calculates the output signal V OUT1 Perform low-pass filtering and window smoothing to obtain the sensor output signal V corresponding to the amplitude A of the light signal to be measured. OUT1 ′.

[0116] Continue to see Fig. 9 In the first orthogonal digital phase-locked amplifier module, the multiplier includes a first multiplier and a second multiplier, the first multiplier and the second multiplier are respectively connected to the notch filter, the first multiplier multiplies the first reference signal Bsin(ft+φ) with the output of the notch filter to obtain a signal V1, and the second multiplier multiplies the second reference signal Bcos(ft+φ) with the output of the notch filter to obtain a signal V2.

[0117] Continue to see Fig. 9 In the first orthogonal digital phase-locked amplifier module, the FIR type low-pass filter includes a first FIR type low-pass filter and a second FIR type low-pass filter. The first FIR type low-pass filter is connected to the first multiplier to eliminate the signal with a frequency higher than f in the signal V1 obtained by the first multiplier to obtain the intermediate signal V1′. The second FIR type low-pass filter is connected to the second multiplier to eliminate the signal with a frequency higher than f in the signal V2 obtained by the second multiplier to obtain the intermediate signal V2′.

[0118] Specifically, see Fig. 9 , the second orthogonal digital phase-locked amplifier module 7112 includes:

[0119] The FIR type high-order bandpass filter is used to eliminate the DC signal component and the non-co-frequency noise signal component in the demodulated signal of the optical signal acquisition circuit, and to amplify the optical signal to be measured by cutting the output bit width;

[0120] A multiplier multiplies two reference signals with a phase difference of 90° with the output of the FIR type high-order bandpass filter. The optical signal acquisition circuit obtains two signals V3 and V4, and the reference signal acquisition circuit obtains two signals U3 and U4. The frequencies of the two reference signals are the same as the frequency of the optical signal to be measured. The first reference signal is Bsin(ft+φ), and the second reference signal is Bcos(ft+φ), where B is the known reference signal amplitude and φ is the phase;

[0121] FIR type low pass filter, with a cut-off frequency of F, F = f, eliminates the signals with a frequency higher than f in the signals V3, V4 and U3, U4 obtained by the multiplier to obtain intermediate signals V3', V4' and U3', U4';

[0122] The subtractor subtracts V3′ and U3′ calculated by the FIR low-pass filter, and V4′ and U4′ to obtain intermediate signals V1″ and V2″ respectively, eliminating the same-frequency noise in the demodulated signal of the optical signal acquisition circuit;

[0123] The second calculation module performs square, sum, and square root operations on the intermediate signals V1" and V2" obtained by the subtractor to obtain the signal V OUT2 ;

[0124] The second window smoothing module calculates the output signal V OUT2 Perform low-pass filtering and window smoothing to obtain the sensor output signal V corresponding to the amplitude A of the light signal to be measured. OUT2 ′.

[0125] Continue to see Fig. 9 In the second orthogonal digital phase-locked amplifier module, the FIR type high-order bandpass filter includes a first FIR type high-order bandpass filter and a second FIR type high-order bandpass filter. The first FIR type high-order bandpass filter is used to eliminate the DC signal component and the non-co-frequency noise signal component in the demodulation signal of the optical signal acquisition circuit, and amplify the optical signal to be measured by intercepting the output bit width. The second FIR type high-order bandpass filter is used to eliminate the DC signal component and the non-co-frequency noise signal component in the demodulation signal of the reference signal acquisition circuit, and amplify the optical signal to be measured by intercepting the output bit width.

[0126] Continue to see Fig. 9 In the second orthogonal digital phase-locked amplifier module, the multipliers include a third multiplier, a fourth multiplier, a fifth multiplier, and a sixth multiplier. The third multiplier and the fourth multiplier are respectively connected to the first FIR type high-order bandpass filter, the third multiplier multiplies the first reference signal Bsin(ft+φ) with the output of the first FIR type high-order bandpass filter to obtain a signal V3, and the fourth multiplier multiplies the second reference signal Bcos(ft+φ) with the output of the first FIR type high-order bandpass filter to obtain a signal V4. The fifth multiplier and the sixth multiplier are respectively connected to the second FIR type high-order bandpass filter, the fifth multiplier multiplies the first reference signal Bsin(ft+φ) with the output of the second FIR type high-order bandpass filter to obtain a signal U3, and the sixth multiplier multiplies the second reference signal Bcos(ft+φ) with the output of the second FIR type high-order bandpass filter to obtain a signal U4.

[0127] Continue to see Fig. 9In the second orthogonal digital phase-locked amplifier module, the FIR type low-pass filter includes a third FIR type low-pass filter, a fourth FIR type low-pass filter, a fifth FIR type low-pass filter, and a sixth FIR type low-pass filter. The third FIR type low-pass filter is connected to the third multiplier to eliminate the signal with a frequency higher than f in the signal V3 obtained by the third multiplier to obtain the intermediate signal V3′. The fourth FIR type low-pass filter is connected to the fourth multiplier to eliminate the signal with a frequency higher than f in the signal V4 obtained by the fourth multiplier to obtain the intermediate signal V4′. The fifth FIR type low-pass filter is connected to the fifth multiplier to eliminate the signal with a frequency higher than f in the signal U3 obtained by the fifth multiplier to obtain the intermediate signal U3′. The sixth FIR type low-pass filter is connected to the sixth multiplier to eliminate the signal with a frequency higher than f in the signal U4 obtained by the sixth multiplier to obtain the intermediate signal U4′.

[0128] Continue to see Fig. 9 In the second orthogonal digital phase-locked amplifier module, the subtractor includes a second subtractor and a third subtractor. The second subtractor is respectively connected to the third FIR type low-pass filter and the fifth FIR type low-pass filter, and V3′ calculated by the third FIR type low-pass filter is subtracted from U3′ calculated by the fifth FIR type low-pass filter to obtain an intermediate signal V1″, thereby eliminating the same-frequency noise in the demodulated signal of the optical signal acquisition circuit; the third subtractor is respectively connected to the fourth FIR type low-pass filter and the sixth FIR type low-pass filter, and V4′ calculated by the fourth FIR type low-pass filter is subtracted from U4′ calculated by the sixth FIR type low-pass filter to obtain an intermediate signal V2″, thereby eliminating the same-frequency noise in the demodulated signal of the optical signal acquisition circuit.

[0129] Specifically, when the concentration of the substance to be measured is high, the intensity of the light signal to be measured is much stronger than the noise. Ignoring the noise term (such as the interference noise of a certain frequency in the working environment is eliminated by a notch filter), the specific steps for calculating the sensor output signal corresponding to the amplitude A of the light signal to be measured are as follows:

[0130] 1. If the demodulated signal amplitude does not exceed the voltage range of the op amp, then the demodulated signal is S = Asin(ft + ψ) + S z +C.

[0131] The first subtractor eliminates the DC signal component in the demodulated signal, and the notch filter eliminates the specific frequency noise. At this time, the demodulated signal only has the optical signal to be measured, that is, S = Asin (ft + ψ). The first multiplier and the second multiplier respectively multiply the two reference signals with a phase difference of 90° with the optical signal to be measured to obtain two signals V1 and V2. The two signals V1 and V2 are expressed as:

[0132] V1=Asin(ft+ψ)*Bsin(ft+φ)=AB[cos(ψ-φ)-cos(2ft+φ+ψ)] / 2

[0133] V2=Asin(ft+ψ)*Bcos(ft+φ)=AB[sin(2ft+φ+ψ)-sin(ψ-φ)] / 2

[0134] The first FIR type low pass filter eliminates the signal with a frequency higher than f in the signal V1 obtained by the first multiplier to obtain an intermediate signal V1′, and the second FIR type low pass filter eliminates the signal with a frequency higher than f in the signal V2 obtained by the second multiplier to obtain an intermediate signal V2′. The intermediate signals V1′ and V2′ are expressed as:

[0135] V1′=ABcos(ψ-φ) / 2

[0136] V2′=-ABsin(ψ-φ) / 2

[0137] The first calculation module performs square, sum, and square root operations on the intermediate signals V1′ and V2′ output by the FIR low-pass filter to obtain an intermediate output signal V OUT1 It is expressed as:

[0138] The first window smoothing module outputs the sensor signal V OUT1 Perform low-pass filtering and window smoothing to obtain the sensor output signal V corresponding to the amplitude A of the light signal to be measured. OUT1 ′.

[0139] 2. If the demodulated signal amplitude exceeds the voltage range of the op amp, the demodulated signal Among them, t1-t5 is a cycle of the signal.

[0140] The first subtractor eliminates the DC signal component in the demodulated signal, and the notch filter eliminates the known specific frequency noise component. At this time, the demodulated signal only has the optical signal to be measured. The first multiplier and the second multiplier respectively multiply the two reference signals with a phase difference of 90° with the optical signal to be measured to obtain two signals V1 and V2. The two signals V1 and V2 are expressed as:

[0141]

[0142]

[0143] The first FIR type low pass filter eliminates the signal with a frequency higher than f in the signal V1 obtained by the first multiplier to obtain an intermediate signal V1′, and the second FIR type low pass filter eliminates the signal with a frequency higher than f in the signal V2 obtained by the second multiplier to obtain an intermediate signal V2′. The intermediate signals V1′ and V2′ are expressed as:

[0144]

[0145]

[0146] The first calculation module performs square, sum, and square root operations on the intermediate signal V1′ output by the first FIR type low-pass filter and the intermediate signal V2′ output by the second FIR type low-pass filter to obtain an intermediate output signal V OUT1 It is expressed as:

[0147]

[0148] The first window smoothing module outputs the sensor signal V OUT1 Perform low-pass filtering and window smoothing to obtain the sensor output signal V corresponding to the amplitude A of the light signal to be measured. OUT1 ′.

[0149] It should be noted that the larger the saturation duty cycle (the ratio of t2-t3, t4-t5 to t1-t5) in the demodulated signal, the larger the sensor output signal V OUT1 ’ is bigger.

[0150] When the concentration of the substance to be measured is low, the intensity of the light signal to be measured is close to the noise and the noise term cannot be ignored. The specific steps for calculating the amplitude A of the light signal to be measured are as follows:

[0151] If the demodulated signal amplitude exceeds the voltage range of the op amp, the FIR type high-order bandpass filter will filter out the DC signal of the saturated duty cycle part, so this situation does not need to be considered. The demodulated signal is expressed as

[0152] The first FIR type high-order bandpass filter filters out the DC signal component and n groups of non-co-frequency noise signals in the demodulated signal of the optical signal acquisition circuit, and the second FIR type high-order bandpass filter filters out the DC signal component and n groups of non-co-frequency noise signals in the demodulated signal of the reference signal acquisition circuit. At this time, only the optical signal to be measured and m groups of co-frequency noise components remain in the demodulated signal of the optical signal acquisition circuit and the demodulated signal of the reference signal acquisition circuit. The demodulated signal of the optical signal acquisition circuit and the demodulated signal of the reference signal acquisition circuit are amplified by intercepting the output bit width of the first FIR type high-order bandpass filter and the second FIR type high-order bandpass filter. At this time, the demodulated signal of the optical signal acquisition circuit Reference signal acquisition circuit demodulation signal α is the magnification of the center frequency signal by the FIR type high-order bandpass filter. The third multiplier and the fourth multiplier respectively multiply the two reference signals with a phase difference of 90° with the demodulated signal to obtain two signals V3 and V4. The fifth multiplier and the sixth multiplier respectively multiply the two reference signals with a phase difference of 90° with the demodulated signal to obtain two signals U3 and U4, which are respectively expressed as:

[0153]

[0154]

[0155]

[0156]

[0157]

[0158] The third FIR type low pass filter eliminates the signal with a frequency higher than f in the signal V3 obtained by the third multiplier to obtain an intermediate signal V3′, the fourth FIR type low pass filter eliminates the signal with a frequency higher than f in the signal V4 obtained by the fourth multiplier to obtain an intermediate signal V4′, the fifth FIR type low pass filter eliminates the signal with a frequency higher than f in the signal U3 obtained by the fifth multiplier to obtain an intermediate signal U3′, and the sixth FIR type low pass filter eliminates the signal with a frequency higher than f in the signal U4 obtained by the sixth multiplier to obtain an intermediate signal U4′, which are respectively expressed as:

[0159]

[0160]

[0161]

[0162] The second subtractor subtracts V3′ from U3′ to eliminate the same-frequency noise component in V3′ and obtain the intermediate signal V1",

[0163] The third subtractor subtracts V4′ and U4′ to eliminate the same-frequency noise component in V4′ and obtain the intermediate signal V2″, which are respectively expressed as:

[0164] V1"=αABcos(ψ-φ) / 2

[0165] V2"=-αABsin(ψ-φ) / 2

[0166] The second calculation module performs square, sum, and square root operations on the intermediate signal V1" output by the second subtractor and the intermediate signal V2" output by the third subtractor to obtain an intermediate output signal V OUT2 It is expressed as:

[0167]

[0168] The second window smoothing module performs a smoothing operation on the intermediate output signal V OUT2 Perform low-pass filtering and window smoothing to obtain the sensor output signal V corresponding to the amplitude A of the light signal to be measured. OUT2 '.

[0169] It should be noted that since the above calculation process will be performed hundreds to thousands of times in one sampling cycle, the intermediate output signal V OUT (ie output signal V OUT1 ' and the output signal V OUT2 ') to perform window smoothing calculation.

[0170] In this embodiment, the orthogonal digital phase-locked amplifier module can simultaneously output V OUT1 ' and V OUT2 ', users can output V OUT1 ' and V OUT2 The orthogonal digital lock-in amplifier module can improve the sensitivity and detection limit of the sensor at low concentrations and the dynamic range of the sensor at high concentrations without changing the circuit.

[0171] Continue to see Figure 8 , the light source modulation module 5 comprises:

[0172] The DA conversion module 51 receives the digital modulation signal sent by the FPGA 71 and converts it into an analog modulation signal;

[0173] The constant current driving module 52 is connected to the fluorescent excitation light source 41, the backscattered emission light source 42, and the reference light source 43 respectively, and drives the fluorescent excitation light source 41, the backscattered emission light source 42, and the reference light source 43 to work according to the analog modulation signal.

[0174] Specifically, see Figure 8 The signal demodulation module 6 includes three signal acquisition circuits, which are respectively connected to the first photodetector 341, the second photodetector 342 and the third photodetector 343; each signal acquisition circuit includes:

[0175] IV conversion circuit 61, converting the current signal output by the photodetector into a voltage signal;

[0176] An active second-order high-pass filter and amplifier circuit 62 performs high-pass filtering and primary amplification processing on the converted voltage signal;

[0177] A programmable gain amplifier 63 performs secondary amplification processing on the voltage signal after the primary amplification;

[0178] The AD conversion circuit 64 converts the voltage signal after the second amplification by the programmable gain amplifier 63 into a digital voltage signal.

[0179] In this embodiment, the IV conversion circuit, the active second-order high-pass filter and amplifier circuit, the programmable gain amplifier and the AD conversion circuit all use existing circuits or devices on the market.

[0180] Specifically, the fluorescence excitation light source and the rear scattered emission light source are time-division multiplexed in the optical signal collection circuit.

[0181] In a specific embodiment, see Figure 8 The above also includes a temperature sensor 9, which is installed in the end cover 2, and the probe of the temperature sensor 9 extends out of the end cover, and the temperature sensor 9 is connected to the FPGA 71. The ambient temperature of the chlorophyll and the backscattering sensor is monitored by the temperature sensor, and the monitored ambient temperature signal is transmitted to the FPGA to realize the monitoring of the ambient temperature.

[0182] Continue to see Figure 3 The chlorophyll and backscatter sensor further comprises a circuit control board 11 mounted on the housing 1 , and the main control module 7 , the signal demodulation module 6 , the light source modulation module 5 , and the power supply module 8 are all mounted on the circuit control board 11 .

[0183] Continue to see Figure 3 The chlorophyll and backscatter sensor is connected to an external device through a watertight connector 13 provided at the end of the housing 1.

[0184] The chlorophyll and backscattering sensor in this embodiment adopts a dual optical signal light path design of a signal light path and a reference light path, which can effectively suppress co-frequency noise, reduce the impact of co-frequency noise on weak fluorescence signals and the attenuation of long-term working LED light sources, and improve the long-term working stability and accuracy of the sensor.

[0185] Example 2: See Figure 2 , Figures 4 to 7 , Fig.10 , Fig.11 , this embodiment provides a chlorophyll and backscatter sensor, including:

[0186] A shell 1, a first end of which is connected to an end cover 2;

[0187] The optical lens assembly 3 comprises:

[0188] The first emission window 311 is provided on the surface of the end cover 2, and a fluorescent excitation light source 41 is provided in the end cover channel inside the first emission window 311;

[0189] The second exit window 312 is provided on the surface of the end cover 2, symmetrically arranged with the first exit window 311, and a rear-scattering exit light source 42 is provided in the end cover channel inside the second exit window 312;

[0190] The first receiving window 321 is provided on the surface of the end cover 2, and is located between the first exit window 311 and the second exit window 312. The first filter 331 and the first photodetector 341 are sequentially installed in the inner end cover channel from outside to inside;

[0191] The third exit window 313 is provided on the surface of the end cover 2, symmetrically arranged with the second exit window 312, and a reference light source 43 is provided in the inner end cover channel;

[0192] The second receiving window 322 is provided on the surface of the end cover 2, and is symmetrically arranged with the first receiving window 321. The second filter 332 and the second photodetector 342 are sequentially installed in the end cover channel on the inner side thereof from the outside to the inside;

[0193] The first exit window 311, the second exit window 312, the first receiving window 321, the fluorescence excitation light source 41, the backscattered light source 42, the first filter 331, and the first photodetector 341 form a signal light path to detect the chlorophyll fluorescence signal and the backscattered light signal;

[0194] The third exit window 313, the second receiving window 312, the reference light source 43, the second filter 332, and the second photodetector 342 form a reference light path to detect a reference signal;

[0195] The control module is installed in the housing and includes:

[0196] The light source modulation module 5 is used to drive the fluorescence excitation light source 41, the backscattered emission light source 42, and the reference light source 43 to work;

[0197] A signal demodulation module 6, which demodulates the signals detected by the first photodetector 341 and the second photodetector 342;

[0198] The main control module 7 receives the demodulation signal sent by the signal demodulation module 6 and generates a light source modulation signal and sends it to the light source modulation module 5, and obtains the light intensity to be measured according to the demodulation signal;

[0199] A power module 8 is connected to the main control module 7 to supply power to the sensor;

[0200] The extreme ultraviolet decontamination module 10 is connected to the main control module 7 and is used to prevent biological attachment to the third exit window 313 .

[0201] It should be noted that the working modes of the reference light path are divided into two types: during normal measurement, the reference light source is extinguished, and the second photodetector of the reference light path works synchronously with the first photodetector of the signal light path to eliminate the same-frequency noise in the measured signal, including the same-frequency component of the background light and the crosstalk of the LED driving pulse; during the light window pollution correction, the reference light source and the backscattered light source are synchronously pulse driven, which are received by the second photodetector and the first photodetector respectively to calculate the light window pollution coefficient. The specific calculation process is as follows:

[0202] It is necessary to assume that the transmittance of the light window with the same end face and the same material but not irradiated by the extreme ultraviolet light source after biological attachment is c, the transmittance of the third output light window decontaminated by the extreme ultraviolet light source is a during the same period, and the true value of the backscattering coefficient of the signal light path and the reference light path at the same time is the same, which is bb.

[0203] For the signal optical path, the measured backscatter coefficient observation value is bb1 = 1 × bb × c 2 , where I1 is the outgoing light intensity of the backscattered light source; for the reference light path, the measured backscatter coefficient observation value is bb2 = 2×bb×a×c, where I2 is the outgoing light intensity of the reference light source; dividing the two equations yields The calculation results can be used to correct the light window contamination, which can reduce the error caused by biological adhesion to the light window during long-term operation of the sensor to a certain extent.

[0204] Specifically, see Figures 5 to 7 , the first filter 331 is fixed by the first filter pressing ring 351, and the second filter 332 is fixed by the second filter pressing ring 361. The first filter pressing ring 351 is sleeved on the upper part of the first photodetector 341, and the first filter pressing ring 351 and the first detector pressing ring 361 sleeved on the middle part of the first photodetector 341 separate the first photodetector 341 from the end cover 2, which plays an insulating role. At the same time, the first detector pressing ring 361 fixes the first photodetector 341. The second filter pressing ring 352 is sleeved on the upper part of the second photodetector 342, and the second filter pressing ring 352 and the second detector pressing ring 362 sleeved on the middle part of the second photodetector 342 separate the second photodetector 342 from the end cover 2, which plays an insulating role. At the same time, the second detector pressing ring 362 fixes the detector. It should be noted that both the filter pressing ring and the detector pressing ring are made of non-metallic POM material.

[0205] Specifically, see Fig.11 , the extreme ultraviolet decontamination module 10 comprises:

[0206] The extreme ultraviolet light source 101 is disposed in the end cover channel below the third exit window and is located on the side of the reference light source;

[0207] The driving module 102 is connected between the main control module 7 and the extreme ultraviolet light source 101 , and is used to drive the extreme ultraviolet light source 101 to work.

[0208] Specifically, see Fig.11 , the main control module 7 includes:

[0209] FPGA 71 is connected to the light source modulation module 5 and the signal demodulation module 6 respectively, receives the demodulation signal of the signal demodulation module 6 and generates a light source modulation signal and sends it to the light source modulation module 5, and controls and drives the fluorescence excitation light source 41, the backscattered emission light source 42, and the reference light source 43 to work through the light source modulation module 5;

[0210] The single chip microcomputer 72 is connected to the driving module 102, and controls and drives the extreme ultraviolet light source 101 through the driving module 102;

[0211] The lithium battery 73 supplies power to the single-chip microcomputer 72 and the driving module 102;

[0212] A charging module 74, connected to the power module 8, for charging the lithium battery 73;

[0213] FPGA internal features:

[0214] The orthogonal digital phase-locked amplifier module 711 is connected to the signal demodulation module 6, and processes the demodulated signal received from the signal demodulation module 6 to obtain the light intensity to be measured;

[0215] A first power management module 712 is connected to the power module 8 and the charging module 74 respectively, and manages the power module 8 and the charging module 71;

[0216] A communication interface module 713, for communicating with an external buoy;

[0217] A light source modulation signal generating module 714 is used to generate a light source modulation signal and send it to the light source modulation module 5;

[0218] The single chip microcomputer 72 has a second power management module 721 therein. The second power management module 721 is connected to the power module 8 and the charging module 74 respectively to manage the power module 8 and the charging module 74 .

[0219] See also Fig. 9 The orthogonal digital phase-locked amplifier module includes a first orthogonal digital phase-locked amplifier module 7111 and a second orthogonal digital phase-locked amplifier module 7112 that work simultaneously. When the concentration of the substance to be measured is high, that is, when the output of the first orthogonal digital phase-locked amplifier module is greater than the output of the second orthogonal digital phase-locked amplifier module, the first orthogonal digital phase-locked amplifier module is used to process the demodulated signal to obtain the light intensity to be measured. At this time, the general expression of the demodulated signal is S=S I +S Z +C, where S I =Asin(ft+ψ) is the light signal to be measured, A is the amplitude of the light to be measured, i.e., the light intensity to be measured, f is the modulation frequency, ψ is the phase of the light signal to be measured, S Zis the specific frequency noise known in the working environment (such as power frequency noise, etc.); C is the DC signal component. When the concentration of the substance to be measured is low, that is, when the output of the first orthogonal digital phase-locked amplifier module is less than or equal to the output of the second orthogonal digital phase-locked amplifier module, the second orthogonal digital phase-locked amplifier module is used to process the demodulated signal to obtain the light intensity to be measured. At this time, the general expression of the demodulated signal is S = S I +S Z1 +S Z2 +C, where S I The demodulated signal of the reference signal acquisition circuit is 0, and the demodulated signal of the optical signal acquisition circuit is Asin(ft+ψ) for the optical signal to be measured, A is the amplitude of the optical signal to be measured that needs to be calculated, that is, the intensity of the optical signal to be measured, f is the modulation frequency, and ψ is the phase of the optical signal to be measured; is n groups of non-co-frequency noise signals, N1(x) is the amplitude of the x-th group of non-co-frequency noise, f'(x) is the frequency of the x-th group of non-co-frequency noise, θ1(x) is the phase of the x-th group of non-co-frequency noise; are m groups of same-frequency noise signals, N2(y) is the amplitude of the y-th group of same-frequency noise, θ2(y) is the phase of the y-th group of same-frequency noise; C is the DC signal component.

[0220] Specifically, see Fig. 9 , the first orthogonal digital phase-locked amplifier module 7111 includes:

[0221] A first subtractor, used to eliminate a DC component in the demodulated signal;

[0222] Notch filter, used to eliminate known specific frequency noise components in known working environment;

[0223] The multiplier multiplies the two reference signals with a phase difference of 90° with the output of the notch filter. The optical signal acquisition circuit obtains two signals V1 and V2. The frequencies of the two reference signals are the same as the frequency of the optical signal to be measured. The first reference signal is Bsin(ft+φ), and the second reference signal is Bcos(ft+φ), where B is the known reference signal amplitude and φ is the phase.

[0224] FIR type low-pass filter, with a cutoff frequency of F, F = f, eliminates the signals with a frequency higher than f in the signals V1 and V2 obtained by the multiplier to obtain intermediate signals V1' and V2';

[0225] The first calculation module performs square, sum, and square root operations on the intermediate signals V1′ and V2′ obtained by the FIR low-pass filter to obtain a signal V OUT1 ;

[0226] The first window smoothing module calculates the output signal V OUT1 Perform low-pass filtering and window smoothing to obtain the sensor output signal V corresponding to the amplitude A of the light signal to be measured.OUT1 '.

[0227] Continue to see Fig. 9 In the first orthogonal digital phase-locked amplifier module, the multiplier includes a first multiplier and a second multiplier, the first multiplier and the second multiplier are respectively connected to the notch filter, the first multiplier multiplies the first reference signal Bsin(ft+φ) with the output of the notch filter to obtain a signal V1, and the second multiplier multiplies the second reference signal Bcos(ft+φ) with the output of the notch filter to obtain a signal V2.

[0228] Continue to see Fig. 9 In the first orthogonal digital phase-locked amplifier module, the FIR type low-pass filter includes a first FIR type low-pass filter and a second FIR type low-pass filter. The first FIR type low-pass filter is connected to the first multiplier to eliminate the signal with a frequency higher than f in the signal V1 obtained by the first multiplier to obtain the intermediate signal V1'. The second FIR type low-pass filter is connected to the second multiplier to eliminate the signal with a frequency higher than f in the signal V2 obtained by the second multiplier to obtain the intermediate signal V2'.

[0229] Specifically, see Fig. 9 , the second orthogonal digital phase-locked amplifier module 7112 includes:

[0230] The FIR type high-order bandpass filter is used to eliminate the DC signal component and the non-co-frequency noise signal component in the demodulated signal of the optical signal acquisition circuit, and to amplify the optical signal to be measured by cutting the output bit width;

[0231] A multiplier multiplies two reference signals with a phase difference of 90° with the output of the FIR type high-order bandpass filter. The optical signal acquisition circuit obtains two signals V3 and V4, and the reference signal acquisition circuit obtains two signals U3 and U4. The frequencies of the two reference signals are the same as the frequency of the optical signal to be measured. The first reference signal is Bsin(ft+φ), and the second reference signal is Bcos(ft+φ), where B is the known reference signal amplitude and φ is the phase;

[0232] FIR type low pass filter, with a cut-off frequency of F, F = f, eliminates the signals with a frequency higher than f in the signals V3, V4 and U3, U4 obtained by the multiplier to obtain intermediate signals V3', V4' and U3', U4';

[0233] The subtractor subtracts V3' and U3' calculated by the FIR low-pass filter, and V4' and U4' to obtain intermediate signals V3" and V4", respectively, to eliminate the same-frequency noise in the demodulated signal of the optical signal acquisition circuit;

[0234] The second calculation module performs square, sum, and square root operations on the intermediate signals V1" and V2" obtained by the subtractor to obtain the signal V OUT2;

[0235] The second window smoothing module calculates the output signal V OUT2 Perform low-pass filtering and window smoothing to obtain the sensor output signal V corresponding to the amplitude A of the light signal to be measured. OUT2 ′.

[0236] Continue to see Fig. 9 In the second orthogonal digital phase-locked amplifier module, the FIR type high-order bandpass filter includes a first FIR type high-order bandpass filter and a second FIR type high-order bandpass filter. The first FIR type high-order bandpass filter is used to eliminate the DC signal component and the non-co-frequency noise signal component in the demodulation signal of the optical signal acquisition circuit, and amplify the optical signal to be measured by intercepting the output bit width. The second FIR type high-order bandpass filter is used to eliminate the DC signal component and the non-co-frequency noise signal component in the demodulation signal of the reference signal acquisition circuit, and amplify the optical signal to be measured by intercepting the output bit width.

[0237] Continue to see Fig. 9 In the second orthogonal digital phase-locked amplifier module, the multipliers include a third multiplier, a fourth multiplier, a fifth multiplier, and a sixth multiplier. The third multiplier and the fourth multiplier are respectively connected to the first FIR type high-order bandpass filter, the third multiplier multiplies the first reference signal Bsin(ft+φ) with the output of the first FIR type high-order bandpass filter to obtain a signal V3, and the fourth multiplier multiplies the second reference signal Bcos(ft+φ) with the output of the first FIR type high-order bandpass filter to obtain a signal V4. The fifth multiplier and the sixth multiplier are respectively connected to the second FIR type high-order bandpass filter, the fifth multiplier multiplies the first reference signal Bsin(ft+φ) with the output of the second FIR type high-order bandpass filter to obtain a signal U3, and the sixth multiplier multiplies the second reference signal Bcos(ft+φ) with the output of the second FIR type high-order bandpass filter to obtain a signal U4.

[0238] Continue to see Fig. 9In the second orthogonal digital phase-locked amplifier module, the FIR type low-pass filter includes a third FIR type low-pass filter, a fourth FIR type low-pass filter, a fifth FIR type low-pass filter, and a sixth FIR type low-pass filter. The third FIR type low-pass filter is connected to the third multiplier to eliminate the signal with a frequency higher than f in the signal V3 obtained by the third multiplier to obtain the intermediate signal V3′. The fourth FIR type low-pass filter is connected to the fourth multiplier to eliminate the signal with a frequency higher than f in the signal V4 obtained by the fourth multiplier to obtain the intermediate signal V4′. The fifth FIR type low-pass filter is connected to the fifth multiplier to eliminate the signal with a frequency higher than f in the signal U3 obtained by the fifth multiplier to obtain the intermediate signal U3′. The sixth FIR type low-pass filter is connected to the sixth multiplier to eliminate the signal with a frequency higher than f in the signal U4 obtained by the sixth multiplier to obtain the intermediate signal U4′.

[0239] Continue to see Fig. 9 In the second orthogonal digital phase-locked amplifier module, the subtractor includes a second subtractor and a third subtractor. The second subtractor is respectively connected to the third FIR type low-pass filter and the fifth FIR type low-pass filter, and V3′ calculated by the third FIR type low-pass filter is subtracted from U3′ calculated by the fifth FIR type low-pass filter to obtain an intermediate signal V3″, thereby eliminating the same-frequency noise in the demodulated signal of the optical signal acquisition circuit; the third subtractor is respectively connected to the fourth FIR type low-pass filter and the sixth FIR type low-pass filter, and V4′ calculated by the fourth FIR type low-pass filter is subtracted from U4′ calculated by the sixth FIR type low-pass filter to obtain an intermediate signal V4″, thereby eliminating the same-frequency noise in the demodulated signal of the optical signal acquisition circuit.

[0240] It should be noted that, in this embodiment, the specific steps of calculating the sensor output signal corresponding to the amplitude A of the light signal to be measured when the light concentration to be measured is high and calculating the sensor output signal corresponding to the amplitude A of the light signal to be measured when the light concentration to be measured is low are the same as those in Embodiment 1 and will not be repeated here.

[0241] It should also be noted that since the above calculation process is performed hundreds to thousands of times in one sampling cycle, the intermediate output signal V is smoothed by the window smoothing module. OUT (ie output signal V OUT1 ′ and output signal V OUT2 ') to perform window smoothing calculation.

[0242] In this embodiment, the orthogonal digital phase-locked amplifier module can simultaneously output V OUT1 ' and V OUT2 ', users can output V OUT1 ' and V OUT2The orthogonal digital lock-in amplifier module can improve the sensitivity and detection limit of the sensor at low concentrations and the dynamic range of the sensor at high concentrations without changing the circuit.

[0243] Continue to see Fig.11 , the light source modulation module 5 comprises:

[0244] The DA conversion module 51 receives the digital modulation signal sent by the FPGA 71 and converts it into an analog modulation signal;

[0245] The constant current driving module 52 is connected to the fluorescent excitation light source 41, the backscattered emission light source 42, and the reference light source 43 respectively, and drives the fluorescent excitation light source 41, the backscattered emission light source 42, and the reference light source 43 to work according to the analog modulation signal.

[0246] Specifically, see Fig.11 The signal demodulation module 6 includes three signal acquisition circuits, namely, an optical signal acquisition circuit connected to the first photodetector 341, a reference signal acquisition circuit connected to the second photodetector 342, and a light source monitoring signal acquisition circuit connected to the third photodetector 343; each signal acquisition circuit includes:

[0247] IV conversion circuit 61, converting the current signal output by the photodetector into a voltage signal;

[0248] An active second-order high-pass filter and amplifier circuit 62 performs high-pass filtering and primary amplification processing on the converted voltage signal;

[0249] The programmable gain amplifier 63 performs a second amplification process on the voltage signal after the first amplification, and adjusts the second power multiple according to the strength of the signal to be measured;

[0250] The AD conversion circuit 64 converts the voltage signal after the second amplification by the programmable gain amplifier 63 into a digital voltage signal.

[0251] In this embodiment, the IV conversion circuit, the active second-order high-pass filter and amplifier circuit, the programmable gain amplifier and the AD conversion circuit all adopt existing circuits on the market.

[0252] Specifically, the fluorescence excitation light source and the rear scattered emission light source are time-division multiplexed in the optical signal collection circuit.

[0253] In a specific embodiment, see Fig.11The above also includes a temperature sensor 9, which is installed in the end cover 2, and the probe of the temperature sensor 9 extends out of the end cover, and the temperature sensors 9 and 9 are connected to the FPGA 71. The ambient temperature of the chlorophyll and the backscattering sensor is monitored by the temperature sensor, and the monitored ambient temperature signal is transmitted to the FPGA to realize the monitoring of the ambient temperature.

[0254] Continue to see Fig.10 The chlorophyll and backscatter sensor further includes a circuit control board 11 mounted on the housing 1 , and the light source modulation module 5 , the signal demodulation module 6 , the power module 8 , and the charging module 74 are all mounted on the circuit control board 11 .

[0255] Continue to see Fig.10 The lithium battery 73 is installed on the housing 1 through a lithium battery bracket 12.

[0256] Continue to see Fig.10 The chlorophyll and backscatter sensor is connected to an external device through a watertight connector 13 provided at the end of the housing 1.

[0257] The chlorophyll and backscattering sensor in this embodiment adopts a dual optical signal light path design of a signal light path and a reference light path, which can effectively suppress co-frequency noise, reduce the impact of co-frequency noise on weak fluorescence signals and the attenuation of long-term working LED light sources, and improve the long-term working stability and accuracy of the sensor.

[0258] Compared with Example 1, the chlorophyll and backscatter sensor in this embodiment is further provided with an extreme ultraviolet decontamination module, which plays a role in preventing biological attachment to the optical window (i.e., the third exit window). The present invention applies extreme ultraviolet light anti-biological attachment technology to chlorophyll and backscatter sensors, which solves the defect that traditional sensors in large water depth span application scenarios cannot use mechanical brushes to clean the optical window, and further improves the stability and accuracy of the sensor in long-term operation.

[0259] The above embodiments are used to explain the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A chlorophyll and backscatter sensor, characterized in that: include: a housing having a first end connected to the end cover; Optical lens assembly, including: A first exit window is provided on the surface of the end cover, and a fluorescent excitation light source is provided in the end cover channel inside the first exit window; The second exit window is arranged on the surface of the end cover, symmetrically arranged with the first exit window, and a rear-scattering exit light source is arranged in the end cover channel inside the second exit window; A first receiving window is provided on the surface of the end cover and is located between the first exit window and the second exit window, and a first filter and a first photodetector are sequentially installed in the end cover channel on the inner side thereof from the outside to the inside; The third exit window is arranged on the surface of the end cover, symmetrically arranged with the second exit window, and a reference light source is arranged in the end cover channel inside the third exit window; The second receiving window is arranged on the surface of the end cover, symmetrically arranged with the first receiving window, and the second filter and the second photoelectric detector are installed in the end cover channel inside the second receiving window in sequence from outside to inside; The first exit window, the second exit window, the first receiving window, the fluorescence excitation light source, the backscattered light source, the first filter, and the first photodetector form a signal light path to detect the chlorophyll fluorescence signal and the backscattered light signal; The third exit window, the second receiving window, the reference light source, the second filter, and the second photodetector form a reference light path to detect a reference signal; The control module is installed in the housing and includes: A light source modulation module is used to drive the fluorescence excitation light source, the backscattered emission light source, and the reference light source; The signal demodulation module demodulates the signals detected by the first photodetector and the second photodetector; the main control module receives the demodulation signal sent by the signal demodulation module and generates a light source modulation signal to send to the light source modulation module, and obtains the light intensity to be measured according to the demodulation signal; the main control module includes an FPGA, which is connected to the light source modulation module and the signal demodulation module respectively, receives the demodulation signal of the signal demodulation module and generates a light source modulation signal to send to the light source modulation module, and controls and drives the fluorescence excitation light source, the backscattered light source, and the reference light source to work through the light source modulation module; the FPGA is provided with an orthogonal digital phase-locked amplifier module, which is connected to the signal demodulation module, and processes and calculates the demodulation signal received from the signal demodulation module to obtain the light intensity to be measured; the orthogonal digital phase-locked amplifier module includes a first orthogonal digital phase-locked amplifier module and a second orthogonal digital phase-locked amplifier module working simultaneously; when the concentration of the substance to be measured is high, that is, when the output of the first orthogonal digital phase-locked amplifier module is greater than the output of the second orthogonal digital phase-locked amplifier module, the first orthogonal digital phase-locked amplifier module is used to process the demodulation signal to obtain the light intensity to be measured, and the general expression of the demodulated signal at this time is S=S I +S Z +C, where S I =Asin(ft+ψ) is the light signal to be measured, A is the light amplitude to be measured, i.e., the light intensity to be measured, f is the modulation frequency, ψ is the phase of the light signal to be measured; S Z is the specific frequency noise known in the working environment, C is the DC signal component; when the concentration of the substance to be measured is low, that is, when the output of the first orthogonal digital phase-locked amplifier module is less than or equal to the output of the second orthogonal digital phase-locked amplifier module, the second orthogonal digital phase-locked amplifier module is used to process the demodulated signal to obtain the light intensity to be measured. At this time, the general expression of the demodulated signal is S=S I +S Z1 +S Z2 +C, where S I The demodulated signal of the reference signal acquisition circuit is 0, and the demodulated signal of the optical signal acquisition circuit is Asin(ft+ψ), which is the optical signal to be measured. is n groups of non-co-frequency noise signals, N1(x) is the amplitude of the x-th group of non-co-frequency noise, f'(x) is the frequency of the x-th group of non-co-frequency noise, θ1(x) is the phase of the x-th group of non-co-frequency noise; is the mth group of same-frequency noise signals, N2(y) is the amplitude of the yth group of same-frequency noise, θ2(y) is the phase of the yth group of same-frequency noise; The power module is connected to the main control module to provide power for the sensor.

2. The chlorophyll and backscatter sensor according to claim 1, characterized in that: The optical lens assembly also includes a third photodetector for monitoring the fluorescent excitation light source, which is arranged in the end cover channel inside the fluorescent excitation light source. The signal detected by the third light source detector is transmitted to the signal demodulation module and demodulated by the signal demodulation module.

3. The chlorophyll and backscatter sensor according to claim 2, characterized in that: The signal demodulation module includes three signal acquisition circuits, namely, an optical signal acquisition circuit connected to the first photodetector, a reference signal acquisition circuit connected to the second photodetector, and a light source monitoring signal acquisition circuit connected to the third photodetector; Each signal acquisition circuit includes: An IV conversion circuit converts the current signal output by the photodetector into a voltage signal; Active second-order high-pass filtering and amplifying circuit, which performs high-pass filtering and one-time amplification processing on the converted voltage signal; The programmable gain amplifier performs a second amplification on the voltage signal after the first amplification, and adjusts the quadratic multiplier according to the strength of the signal to be measured; The AD conversion circuit converts the voltage signal after the second amplification of the programmable gain amplifier into a digital voltage signal.

4. The chlorophyll and backscatter sensor according to claim 3, characterized in that: It also includes a temperature sensor, which is installed in the end cover. The probe of the temperature sensor extends out of the end cover, and the temperature sensor is connected to the main control module.

5. The chlorophyll and backscatter sensor according to claim 3, characterized in that: The FPGA is also provided with: a first power management module connected to the power module to manage the power module; Communication interface module, communicates with external buoy.

6. The chlorophyll and backscatter sensor according to claim 3, characterized in that: Also included is an extreme ultraviolet decontamination module, the extreme ultraviolet decontamination module comprising: An extreme ultraviolet light source is disposed in the end cover channel below the third exit window and is located on one side of the reference light source; The driving module is connected between the main control module and the extreme ultraviolet light source, and is used to drive the extreme ultraviolet light source to work.

7. The chlorophyll and backscatter sensor according to claim 6, characterized in that: The main control module also includes: The single chip microcomputer is connected to the driving module, and controls and drives the extreme ultraviolet light source through the driving module; Lithium battery, to power the microcontroller and driver module; A charging module, connected to the power module, for charging the lithium battery; FPGA internal features: A first power management module is connected to the power module and the charging module respectively, and manages the power module and the charging module; a communication interface module for communicating with an external buoy; A second power management module is arranged inside the single chip microcomputer. The second power management module is respectively connected to the power module and the charging module to manage the power module and the charging module.

8. The chlorophyll and backscatter sensor according to claim 5 or 7, characterized in that: The first orthogonal digital phase-locked amplifier module includes: A subtractor for eliminating a DC component in a demodulated signal; Notch filter, used to eliminate known specific frequency noise components in known working environment; The multiplier multiplies the two reference signals with a phase difference of 90° with the output of the notch filter. The optical signal acquisition circuit obtains two signals V1 and V2. The frequencies of the two reference signals are the same as the frequency of the optical signal to be measured. The first reference signal is Bsin(ft+φ), and the second reference signal is Bcos(ft+φ), where B is the known reference signal amplitude and φ is the phase. FIR type low-pass filter, with a cutoff frequency of F, F = f, eliminates the signals with a frequency higher than f in the signals V1 and V2 obtained by the multiplier to obtain intermediate signals V1' and V2'; The calculation module performs square, sum, and square root operations on the intermediate signals V1' and V2' obtained by the FIR low-pass filter to obtain the signal V OUT1 ; The window smoothing module calculates the output signal V OUT1 Perform low-pass filtering and window smoothing to obtain the sensor output signal V corresponding to the amplitude A of the light signal to be measured. OUT1 '; The second orthogonal digital phase-locked amplifier module includes: The FIR type high-order bandpass filter is used to eliminate the DC signal component and the non-co-frequency noise signal component in the demodulated signal, and to amplify the optical signal to be measured by cutting the output bit width; A multiplier multiplies two reference signals with a phase difference of 90° with the output of the FIR type high-order bandpass filter. The optical signal acquisition circuit obtains two signals V3 and V4, and the reference signal acquisition circuit obtains two signals U3 and U4. The frequencies of the two reference signals are the same as the frequency of the optical signal to be measured. The first reference signal is Bsin(ft+φ), and the second reference signal is Bcos(ft+φ), where B is the known reference signal amplitude and φ is the phase; FIR type low pass filter, with a cut-off frequency of F, F = f, eliminates the signals with a frequency higher than f in the signals V3, V4 and U3, U4 obtained by the multiplier to obtain intermediate signals V3', V4' and U3', U4'; The subtractor subtracts V3' and U3' calculated by the FIR low-pass filter, and V4' and U4' to obtain intermediate signals V1" and V2", respectively, to eliminate the same-frequency noise in the demodulated signal of the optical signal acquisition circuit; The calculation module performs square, sum, and square root operations on the intermediate signals V1" and V2" obtained by the subtractor to obtain the signal V OUT2 ; The window smoothing module calculates the output signal V OUT2 Perform low-pass filtering and window smoothing to obtain the sensor output signal V corresponding to the amplitude A of the light signal to be measured. OUT2 '.

9. The chlorophyll and backscatter sensor according to claim 8, characterized in that: The light source modulation module comprises: The DA conversion module receives the digital modulation signal sent by the FPGA and converts it into an analog modulation signal; the constant current driving module is connected to the fluorescent excitation light source, the backscattered emission light source, and the reference light source respectively, and drives the fluorescent excitation light source, the backscattered emission light source, and the reference light source to work according to the modulation signal.

10. The chlorophyll and backscatter sensor according to claim 3, characterized in that: A fluorescence excitation light source and a backscattered emission light source are time-division multiplexed optical signal acquisition circuit.

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